Description of Remedial Action Technologies

nunGEOSCIENCE CORR12 METRO PARK RD. •ALBANY, NEW YORK 1220551S/45B-1313FAX 518/453-2472

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APPENDICESTO THE

FEASIBILITY STUDYFOR THE

DELAWARE SAND AND GRAVEL LANDFILL

FINAL

Prepared by

Dunn Geoscience Corporation12 Metro Park Road

Albany, New York 12205

Prepared for

State of DelawareDepartment of Natural Resources

and Environmental ControlDover, Delaware

Date

December 1987

DUNN GEOSCIENCE CORPORATION R3025I3

APPENDIX A

SUMMARIES AND DESCRIPTIONOF

REMEDIAL ACTION TECHNOLOGIES

December 1987

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Table of ContentsDescription of Remedial Action Technologies

1. NO ACTION l-l

2. CONTAINMENT 2-1

2a. Capping 2-1

2a.l Synthetic membrane 2-12a.2 Clay 2-22a.3 Asphalt 2-22a.4 Concrete 2-32a.5 Floating covers 2-32a.6 Multi-media 2-4

2b. Dust Control . 2-4

2b.l Polymers 2-52b.2 Water 2-52b.3 Wind fences and screens 2-5

2c. Containment Barriers 2-6

2c.l Slurry walls 2-62c.2 Grout curtains - 2-7

2c.2a Stage-up method 2-82c.2b Stage-down method 2-82c.2c Grout port method 2-82c.2d Vibrating beam method 2-8

2c.3 Sheet piling 2-92c.4 Bottom sealing .2-9

3. GROUNDWATER AND FLUID COLLECTION 3-1

3a. Groundwater Pumping 3-1

3a.I Discharge wells 3-13a.2 Injection wells 3-1

3b. Liquid Removal 3-2

3b.l Pumps 3-2

3b.la Centrifugal pumps 3-23b.lb Reciprocating pumps 3-33b.lc Displacement pumps 3-33b.ld Immersion pumps 3-4

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3b.Ie Submersible pumps 3-4

3b.2 Industrial vacuum loaders 3-5

3c. Subsurface Collection Drains 3-5

3c.l French drains 3-63c.2 Tube drains 3-6

4. GAS COLLECTION 4-1

4a. Passive Gas Control Systems 4-1

4a.l High permeability 4-14a.2 Low permeability 4-2

4b. Active Gas Collection/Recovery . 4-2

5, DIVERSION 5-1

5a. Grading 5-1

5a.l Scarification 5-15a.2 Tracking . 5-25a.3 Contour furrowing 5-2

5b. Revegctation . 5-2

5b.l Grasses 5-35b.2 Legumes 5-35b.3 Shrubs 5-45b.4 Trees 5-4

5c. Surface Water Controls 5-4

5c.I Dikes and berms 5-55c.2 Channels, ditches, trenches, diversions,

and waterways 5-65c.3 Terraces and benches 5-75c.4 Chutes and downpipes 5-75c.5 Seepage basins 5-85c.6 Levees and floodwalls 5-85c.7 Addition of freeboard 5-9

5d. Sedimentation Basins and Ponds 5-9

5c. Sediment Turbidity Controls and Containment 5-10

5e.l Silt curtains " 5-105e.2 Cofferdams 5-115e.3 Surface sealing 5-115e.4 In-situ grouting 5-12

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6. REMOVAL 6-1

6a. Excavation and/or Drum Removal 6-1

6a.l Loading and casting 6-1

6a.la Backhoes 6-26a.lb Cranes and attachments 6-26a.lc Dozers and loaders 6-3

6a.2 Hauling excavation 6-3

6a.2a Scrapers 6-36a.2b Haulers 6-4

6a.3 Drum moving and loading 6-4

6a.3a Drum grapplers 6-46a.3b Fork lifts and attachments 6-4

6b. Surface Debris Removal 6-5

6b.I Cranes 6-56b.2 Flatbeds 6-56b.3 Haulers/dump trucks 6-5

6c. Stream Sediment Removal 6-5

6c.l Mechanical dredging 6-5

6c.la Clamshell dredge 6-66c.lb Dragline dredge 6-66c.Ic Backhoe 6-7

6c.2 Hydraulic dredging 6-7

6c.2a Plain suction dredge 6-86c.2b Cutterhead dredge 6-86c.2c Dust pan dredge 6-9

6c.3 Pneumatic dredging 6-9

6c.3a Airlift dredge 6-106c.3b Pneuma dredge 6-106c.3c Oozer dredge 6-11

6d. Removal and Replacement or Relocation of Waterand Sewer Lines _ 6-12

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7. TREATMENT 7-1

7a. Groundwatcr/Liouid Waste Treatment 7-1

7a.l Biological treatment 7-1

7a.la Activated sludge . 7-27a.lb Trickling filters 7-27a.Ic Aerated lagoons/Aerobic-Anaerobic

lagoons 7-37a.ld Waste stabilization ponds 7-47a.le Rotating biological discs 7-47a,If Fluidized bed bioreactor 7-57a.Ig Enzyme treatment 7-57a.Ih Anaerobic biological treatment 7-57a.li Spray irrigation 7-67a.lj Bioreclamation 7-67a.lk Equalization 7-7

7a.2 Chemical treatment 7-7

7a.2a Immobilization 7-8

7a.2a.l Precipitation 7-87a.2a.2 Polymerization 7-9

7a.2b Detoxification 7-9

7a.2b.l Neutralization 7-97a.2b.2 Hydrolysis 7-107a.2b.3 Oxidation/reduction 7-10

7a.2b.3a Hydrogen peroxideoxidation 7-11

7a.2b.3b Hypochlorite oxidation 7-117a.2b.3c Ozonation 7-127a.2b.3d Wet air oxidation 7-127a.2b.3e Supercritical water

oxidation 7-137a.2b.3f Electrolytic oxidation 7-13

7a.2b.4 Chemical dechlorination 7-147a.2b.5 Ultraviolet photolysis 7-147a.2b.6 Liquid-liquid solvent

extraction 7-157a.2b.7 Alkaline chlorination 7-157a.2b.S Chlorinolysis s 7-167a.2b.9 Chloroiodides 7-167a.2b.10 Hydroraetaliurgy 7-167a.2b.ll Ion exchange 7-17

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7a.3 Physical treatment 7-17

7a.3a Flow equalization 7-18,7a.3b Flocculation/coagulation/sedimentation 7-187a.3c Carbon adsorption 7-197a.3d Powdered activated carbon systems 7-207a.3e Sorbents ' 7-207a.3f Screening 7-217a.3g Reverse osmosis 7-217a.3h Distillation 7-227a.3i Steam distillation/stripping 7-227a.3j Air stripping 7-237a.3k Filtration 7-247a.31 Flotation 7-247a.3m Supercritical extraction 7-257a.3n Dialysis 7-257a.3o Electrodialysis 7-267a.3p Electrophoresis 7-267a.3q Freeze-crystallization 7-277a.3r High gradient magnetic separation 7-277a.3s Ultrafiltration _ 7-287a.3t Zone refining 7-287a.3u Gamma-ray radiolysis 7-297a.3v Permeable treatment bed 7-29

7b. Sludge/Solids Treatment 7-30

7b.l Biological treatment 7-30

7b.la Composting/Land treatment 7-307b.lb Membrane aerobic reactor systems 7-317b.lc Fluidized bed bioreactors 7-317b.ld Enzyme treatment 7-31

7b.2 Chemical treatment: chemical dechlorination 7-317b.3 Physical treatment 7-31

7b.3a Screens, hydraulic classifiers 7-317b.3b Dewatering/thickening 7-32

7b.3b.l Centrifugation 7-32

7b.3b.la Solid bowl centrifuge 7-337b.3b.lb Basket centrifuge 7-337b.3b.lc Disc centrifuge 7-34

7b.3b.2 Gravity thickening 7-347b.3b.3 Filtration 7-35

7b.3b.3a Belt press filter 7-357b.3b.3b Vacuum filter 7-367b.3b.3c Pressure filter 7-36

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7b.3b.4 Dewatcring lagoons 7-37

7b.3b.4a Gravity underdrainage 7-377b.3fo.4b Vacuum pumping 7-377b.3b.4c Vacuum-assisted

drying beds 7-387b.3b.4d Electroosmosis 7-38

7b.3b.5 Freeze-drying 7-397b.3b.6 Suspension freezing 7-397b.3b.7 Evaporation 7-40

7b.3c Zone refining 7-40

7b.3d Solidification, stabilization,fixation 7-40

7b.3d.l Cement-based solidification(cement pozzolan) 7-41

7b.3d.2 Silicate-based solidification 7-4 17b.3d.3 Vitrification 7-427b.3d.4 Thermoplastic solidification 7-437b.3d.5 Organic polymer solidification 7-447b.3d.6 Self-cementing techniques 7-447b.3d.7 Surface encapsulation 7-457b.3d.8 Freezing (temporary

immobilization) 7-457b.3d.9 Sorbents 7-46

7b.4 Water and Sewer Line Treatment 7-46

7c. Soils Treatment 7-47

7c.l Biological treatment: bioreclamation 7-477c.2 Chemical treatment 7-47

7c.2a Immobilization 7-47

7c.2a.l Precipitation 7-487c.2a.2 Chelation 7-48

7c.2b Hydrogen peroxide oxidation 7-49

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7c.3 Physical treatment 7-49

7c.3a Soil washing/soil flushing 7-497c.3b Air stripping 7-497c.3c Supercritical extraction 7-497c.3d Solidification, stabilization,

fixation . 7-49

7d. Gaseous waste treatment 7-49

7d.l Flaring 7-507d.2 Adsorption 7-51

7d.2a Activated carbon 7-517d.2b Resin 7-51

7d.3 Afterburners 7-52

7d.3a Direct flame afterburner 7-527d.3b Thermal afterburner 7-537d.3c Catalytic afterburner 7-53

7e. Thermal destruction _ _ ... 7-54

7e.l Incineration 7-54

7e.la Molten glass incinerator 7-547e.lb Molten salt incinerator 7-557e.lc Rotary kiln 7-557e.ld Industrial kilns 7-567e.le Fluidized bed incinerator 7-577e.lf Circulating bed incinerator 7-577e.lg Multiple hearth incinerator 7-587e.lh Liquid injection incinerator 7-597e.li Fume incinerator 7-607e.lj Multiple-chamber incinerator 7-607e.lk Cyclonic incinerator 7-617e.ll Auger combustor incinerator 7-617e.lm .Ship-mounted incinerator /ocean

incineration 7-617e.ln Catalytic incineration 7-627e.lo Oxygen incineration 7-627e.lp Infrared incineration 7-637e.lq Open pit incineration 7-637e.lr Sulfur regeneration 7-647e.ls Fuel blending/coincineration 7-647e.lt Boilers 7-647e.lu Blast furnaces 7-65

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7e.2 Pyrolysis 7-66

7e.2a Plasma arc pyrolysis 7-667e.2b High temperature electric reactor 7-677c.5c High temperature fluid wall reactor 7-67

7e,3 Starved air combustion 7-687e.4 Calcination 7-687c.5 Sintering 7-697e.6 Radio frequency (RF) heating 7-697e.7 Wet oxidation 7-70

7f. Thermal destruction peripheral systems 7-70

7f.I Heat recovery systems 7-717f.2 By-product recovery 7-71

7f.2a Acid recovery 7-717f.2b Salt and metal recovery 7-72

7f.3 Air pollution control 7-72

7f.3a Gaseous pollutant removal systems 7-72

7f.3a.l Wet spray towers 7-737f.3a.2 Dry spray towers 7-737f.3a.3 Packed-bed scrubbers 7-747f.3a.4 Plate scrubbers 7-74

7f.3b Particulate pollution removal systems 7-75

7f.3b.l Electrostatic prccipitators , 7-757f.3b.2 Baghouse filters 7-767f.3b.3 Venturi scrubbers 7-767f.3b.4 Orifice scrubbers 7-777f.3b.5 Ionizing wet scrubbers 7-777f.3b.6 Wet electrostatic precipitators 7-77

7f.4 Nitrogen oxides removal 7-787f,5 Steam plume control 7-78

7f.5a Cooling stack gases 7-797f.5b Heating stack gases 7-797f.5c Dilution of stack gases 7-80

7f.6 Mist elimination 7-80

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8. STORAGE 8-1

9. DISPOSAL 9-1

9a. On-sitc disposal 9-1

9a.l Landfills 9-1

9a.la Trench landfills 9-29a.lb Area landfills 9-2

9a.2 Waste Piles 9-39a.3 Surface Impoundments 9-39a.4 Land Treatment 9-4

9b. Off-Site Disposal 9-4

9b.l Landfills 9-4

9b.la Trench landfills 9-49b.lb Area landfills 9-4

9b.2 Waste Piles 9-49b.3 Surface Impoundments 9-49b.4 Land Treatment 9-4

10. ALTERNATIVE WATER SUPPLY 10-1

lOa. Water Supply Replacement 10-1

lOa.l Replacement of contaminated central watersupplies 10-1

lOa.la Municipal water systems 10-1lOa.lb New surface water intake 10-2lOa.lc Deeper or upgradient wells 10-2

IOa.2 Point-of-use water supplies 10-2

10a.2a Bottled and bulk water 10-210a.2b Point-of-use wells ' 10-210a.2c Rainwater collection 10-3

lOb, Treatment 10-3

lOb.l Central treatment 10-310b.2 Point-of-use treatment 10-4

11. PERMANENT RELOCATION OF RESIDENTS, BUSINESSES, ANDCOMMUNITY FACILITIES 11-1

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1. NO ACTION

Description of Technology

"No action" implies maintaining a status quo at a particular site. Thoughenvironmental monitoring may be continued as an option, no initial oradditional remedial actions are taken. At those sites where an initialremedial action has been implemented, cessation of that activity wouldeffectively be defined as an action and would fall under its respective GRA.

Applications

This alternative is applicable in any situation. It is often applied when thecontaminants are organics that will degrade naturally before they can adverselyaffect an area or where a site is determined to pose no environmental or healthrisks.

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2. CONTAINMENT

2 a . Capping _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _


Capping is a process used to cover buried waste materials to prevent theirexposure at the surface by enhancing runoff and to minimize recharge toground water. The designs of modern caps usually conform to the performancestandards in 40 CFR 264.310 which addresses RCRA landfill closurerequirements. These standards include minimum liquid migration through thewastes, low cover maintenance requirements, efficient site drainage, highresistance to damage by settling or subsidence, and a permeability lower thanor equal to the underlying liner system or natural soils. These performancestandards may not always be appropriate, particularly in instances where thecap is intended to be temporary, where there is very low precipitation, andwhen the capped waste is not leached by infiltrating rainwater. (Note:Subpart G of 40 CFR 264 may also be applicable.)

Applications

Capping is necessary whenever contaminated materials are to be buried or leftin place at a site. In general, capping is performed when extensive subsurfacecontamination at a site precludes excavation and removal of wastes because ofpotential hazards and/or unrealistic costs. _, Capping is often performedtogether with the groundwater extraction or containment technologies to preventor significantly reduce further plume development, thus, reducing the timeneeded to complete groundwater cleanup operations. In addition, groundwatermonitoring wells are often used in conjunction with caps to detect anyunexpected migration of the capped wastes. A gas collection system shouldalways be incorporated into a cap when wastes may generate gases such asmethane. Capping is also associated with surface water control technologies,such as ditches, dikes, and berms, because these structures are often designedto accept rainwater drainage from the cap. Two other surface water controltechnologies, grading and revegetation, are incorporated into multi-layeredcaps.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C.

2a.l synthetic membrane


Flexible, synthetic membranes are made of polyvinyl chloride (PVC), chlorinatedpolyethylene (CPE), ethylene propylene rubber, butyl rubber, Hypalon andneoprene (synthetic rubbers), and elasticized polyolefin. Synthetic liners

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require special field installation methods to ensure proper sealing of seams.(Note: High Density Polyethylene, HOPE, is the currently preferred syntheticliner material.)

Application

Synthetic membranes arc most often used in combination with soil as the lowpermeability layer of a multi-layer cap. It is overlain by a vegetative layerand a drainage layer.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/OQ6, Washington, D.C.

2a.2 clay


When sufficient fine-grained soils are not available to achieve the desiredpermeability, clay material can be brought in. Bentonite, a natural clay withhigh swelling properties, is often transported to a site and mixed with on-sitesoil and water to produce the low permeability layer of the cap.

Applications

Clays, such as montmoriUonite and bentonite, should be mixed with the soil ofa cap's low permeability layer if the soils permeability is greater than 10cm/3.

Reference


2a.3 asphalt


Emulsified asphalt or tar may be mixed with relatively small amounts of on-sitesoils to create stronger and less permeable surface sealants. Asphalt issuitable for mixing with sandy soils for stabilization and waterproofing.

Applications

Asphalt resists water and some acids and bases. Most organic compounds inconcentrated form, however, can weaken and permeate this type of cover.Asphalt caps, therefore, should not be used for petroleum-derived wastes andsolvents. Asphalt can be mixed with sandy soils to form, the low permeabilitylayer of a multi-layer cap or used as a single layer cap.

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References

Martin, E.J., and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Company, New York, N.Y., 520 p.


2a.4 concrete


This alternative is very similar to asphalt in terms of application. Portlandcement is mixed with in-situ sandy soils to create a less permeable surfacecover.

Applications

Cement, like asphalt, can be used for a single layer cap or can be mixed withsoil to form the low permeability layer of a multi-layer cap. Soil cements canresist moderate amounts of alkali, organics, and inorganic salts.

Reference

Martin, EJ. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Company, New York, N.Y., 520. p.


2a.5 floating covers


Floating covers consist of a synthetic lining placed, in one piece, over animpoundment with proper anchoring at the edges and with floats to prevent thelining from submerging. This technology is used mainly to cover drinking watersupply reservoirs, but it can be used temporarily to prevent overtopping of awaste lagoon prior to final closure.

Applications

Floating covers cannot be considered as a final remedial action at a site, butthey can be more cost-effective than pumpdown and treatment to preventovertopping of lagoon wastes. Covers are especially advantageous when a yearor more will elapse before final closure of the lagoon. Floating covers shouldnot be considered on lagoons with weak berms or those located in areas thatcannot support the weight of heavy construction equipment. Also, availablecover materials may not always be compatible with the lagoon wastes.

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Reference _ __ _...

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C

2a.6 multi-layered


The design of multi-layered caps generally conforms to EPA's guidance under IRCRA which recommends a three-layered system consisting of an upper vegetative -'layer underlain by a drainage layer over a low permeability layer. The capfunctions by diverting infiltrating liquids from the vegetative layer through "1the drainage layer and away from the underlying waste materials. '

Applications

The EPA recommends a multi-layer cap, instead of a single layer cap, whenevercapping is used.

Reference


2b. Dust Controls


Commonly used measures for controlling fugitive dusts from inactive waste pilesand active clean-up sites include use of chemical dust suppressants, windscreens, water spraying, and other dust control measures commonly used duringconstruction.

Applications

Dust controls should be applied where inactive waste piles are exposed to thewind and at active clean-up sites.

Reference


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2b.l polymers


Dust suppressants include a -wide range of natural and synthetic materialswhich strengthen bonds between soil particles and hold this strengthenedcondition for an appreciable period of time. A wide variety of resins,bituminous materials, and polymers are marketed as dust suppressants.

Applications

Dust suppressants are primarily used to temporarily bind soil particles andreduce fugitive dust emissions from inactive waste piles. They are lesseffective for active work areas.

Reference


2b.2 water


The most commonly used method for control of dust emissions is spraying wateron the exposed surface areas. ., . .„ _..__._.. _... .

Applications

Water spraying is most commonly used as dust control on roads and excavationsites and in truck boxes. Water is applied with a water wagon or spray bars asoften as needed. The amount and frequency depend on the weather, traffic, androad surface material. Spray nozzles can be installed in truck beds, and thecontaminated soils can be sprayed during loading and dumping. Water sprayingworks best for large grain-size particles.

Reference


2b.3 wind fences and screens


A wind fence is a porous screen which takes up or deflects a sufficient amountof wind so that the wind velocity is lowered below the threshold required forinitiation of soil movement. Wind screens are typically 4 to 10 feet high andare composed of polyester or other high strength materials.


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Applications

Wind screens can be used to control particulates greater than 10 micrometers indiameter by reducing wind velocity. Wind velocity is reduced for a distance of1 to 5 fence heights downwind from the fence.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C. \

2c. Containment Barriers


Containment barriers represent a technology for encapsulating an area torestrict the movement of contaminated groundwater. Barriers are installedupgradient, downgradient, or around a suspected contaminant source.

Applications

Containment barriers arc useful whenever it is necessary to contain, capture,or redirect groundwater flow in the vicinity of a site.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington,D.C.

2c.l slurry walls


A slurry wall is a low-permeability, subsurface barrier that is constructed ina vertical trench excavated under a slurry. This slurry, usually a mixture ofbentonite and water, acts like a drilling fluid. It hydraulically shores thetrench to prevent collapse and, at the same time, forms a filter cake on thetrench walls to prevent high fluid losses into the surrounding ground. Slurrywall types are differentiated by the materials used to backfill the slurrytrench. Most commonly, an engineered soil mixture is blended with thebentonite slurry and placed in the trench to form a soil-bentonite slurrywall. la some cases, the trench is excavated under a slurry of Portlandcement, bentonite, and water, and this mixture is left in the trench to hardeninto a ccment-bentonite slurry wall. In the rare case where great strength isrequired of a subsurface barrier, prc-cast or cast-in-place concrete- panels areconstructed in the trench to form a diaphragm wall, (see 2c.3 sheet piling).


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Applications

The applications of a slurry wall depend on its construction, itsconfiguration, and the composition of the slurry.

Most slurry walls are keyed-in; they are constructed in a trench that has beenexcavated into a confining layer that forms the bottom of the contained site.Hanging slurry walls that extend below the water table and are not tied to aconfining layer are useful for containing floating contaminants and migratinggases and for causing a drop in the water level on the downgradient side of thebarrier.

Circumferential installations are useful for reducing the amount of leachateproduced and reducing the amount and the fraction of the total producedleachate leaving the site. Upgradient slurry walls can divert cleangroundwater around a site and slow the leachate generation. Downgradient wallscan be used to capture floating contaminants, gases, and leachate.

The compatibility of the slurry and the site contaminants determines theapplicability of a slurry wall. Soil-bentonite slurries are unsatisfactory forstrong acids and bases, strong salt solutions, and some organic chemicals.Cement-bentonite slurry walls are even more susceptible to chemical attack thansoil-bentonite mixtures. They are not suitable for sulfates, strong acids andbases, and other highly ionic substances. Because a cement-bentonite slurrysets to a semi-rigid solid, it can accommodate topographical variations. Itsstrength makes cement-bentonite more suitable than soil-bentonite for wallsadjacent to buildings or roads. Finally, because the cement-bentoniteexcavation slurry is the backfill, too, this type of slurry wall can beconstructed in restricted areas where there is no room to mix soil-bentonitebackfill.

Reference


2c.2 grout curtains


Grout (cement and bentonite) curtains are subsurface barriers created inunconsolidated materials by pressure injection. Grout barriers can be manytimes more costly than slurry walls and are generally incapable of attainingtruly low permeabilities in unconsolidated materials.

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Applications

Like other barriers, grout curtains can have any of a number ofconfigurations. Regardless of the configuration, though, grout does not alwayspenetrate and set and is not always compatible with the chemicals in thewaste. Conventional injection grouting is fairly unreliable as a groundwatercontrol method and is not recommended over slurry walls and other barriers inany situation.

Reference


2c.2a stage-up method

In the stage-up method, the borehole is drilled to the full depth of the wallprior to grout injection. The drill is withdrawn one "stage" leaving severalfeet of borehole exposed. Grout is then injected into this length of openborehole until the desired volume has been injected. When injection iscomplete, the drill is withdrawn further, and the next stage is injected.

2c.2b stage-down method

Stage-down grouting differs from stage-up grouting in that the injections aremade from the top down. Thus, the borehole is drilled through the first zonethat is to be grouted, the drill is withdrawn, and the grout injected. Uponcompletion of the injection, the borehole is redrilled through the groutedlayer into the next zone to be grouted, and the process is repeated.

2c.2c grout port method

The grout port method utilizes a slotted injection pipe that has been sealedinto the borehole with a brittle Portland cement and clay mortar jacket.Rubber sleeves cover the outside of each slit (or port) permitting grout toflow only out of the pipe. The injection process begins by isolating the groutport in the zone to be injected using a double packer. A brief pulse of highpressure water is injected into the port to rupture the mortar jacket. Groutis pumped between the double packers, passes through the ports in the pipe,under the rubber sleeve, and out through the cracked mortar jacket into thesoil.

2c.2d vibrating beam method

The vibrating beam method is not an injection technique as described above, butinstead is a way of placing grout so as to generate a wall. In this method, anI-beam is vibrated into the soil to the desired depth and then raised at acontrolled rate. As the beam is raised, grout is pumped through a set ofnozzles mounted In the beam's base filling the newly formed cavity. When thecavity is completely filled, the beam is moved less than one beam width alongthe wall, leaving a suitable overlap to ensure continuity.

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» 2c.3 sheet piling

j Description of Technologyj

In addition to slurry wall and grouted cut-offs, sheet piling can be used to; form a groundwater barrier. Sheet piles can be made of wood, pre-castj concrete, or steel.a.

Applications

I . Steel sheet piling can be employed as a groundwater barrier, but because ofcosts and unpredictable wall integrity, it is seldom used. It is suitable fortemporary dewatering for other construction or as erosion protection where someother barrier, such as a slurry wall, intersects flowing surface water. Sheetpiling is not recommended in rocky soils, Damage to and deflection of the

, piles result in an ineffective barrier.

1 Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):ill EPA/625/6-85/006, Washington, D.C.

2c.4 bottom sealing


Bottom sealing refers to techniques used to place a horizontal barrier beneathan existing site to act as a floor and prevent downward migration ofcontaminants. Most of these techniques involve variations of grouting or otherconstruction support techniques.

Applications

Bottom sealing techniques are developmental, so no detailed analysis ofapplications is possible.

Reference



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3. GROUNDWATER AND FLUID COLLECTION

3a. Groundwater Pumping


Groundwater pumping techniques involve the active manipulation and managementof groundwater to contain or remove a plume or to adjust groundwater levels toprevent formation of a plume.

Applications

Well systems are very versatile and can be used to contain, remove, divert, orprevent development of plumes under a variety of site conditions. Pumping ismost effective at sites where underlying aquifers have high intergranularhydraulic conductivity. It has been used with some effectiveness at sites withmoderate hydraulic conductivities and where pollutant movement is occuringalong fractured or jointed bedrock. In fractured bedrock, the fracturepatterns must be traced in detail to ensure proper well placement.

3a.l discharge wells


Discharge wells are wells where water and contaminants are pumped out of theground.

Applications

Use of discharge wells alone is best suited to situations where contaminantsare miscible and move readily with water, where the hydraulic gradient is steepand hydraulic conductivity is high, and where quick removal is not necessary.Discharge wells are frequently used in combination with slurry walls to preventgroundwater from overtopping the wall and to minimize contact of the leachatewith the wall to prevent wall degradation. Slurry walls also reduce the amountof contaminated water that requires removal, so costs and pumping time arereduced. Where the water table intercepts disposal wastes, discharge wells canbe used to control plume development by lowering the water table.

Reference


3a.2 injection wells


Injection wells re-introduce water (generally treated groundwater) into thesubsurface.

DUNN GEOSCIENCE CORPORATION ft it 3 0 2 5 3 H

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Applications

Injecting water into the ground can change a plume's direction and slow itsmigration speed, thus, creating a groundwater barrier. This technique isapplicable for short-term diversion and when diversion will provide time forthe plume to degrade.

Discharge and injection wells can be used in combination to contain or remove aplume where the hydraulic gradient is relatively flat and conductivities arcmoderate. The injection wells direct contaminants to the discharge wells.

Reference


3b. Liquid Removal

3b.l pumps


Pumping is required to remove liquids and sludges from ponds, waste lagoons,and surface impoundments. Liquid wastes pumped from these sites must bemanaged to prevent degradation of the surrounding environment. The liquidwastes may be pumped to a treatment system or a tank truck for transportoff-site to a commercially operated treatment facility.

Applications

Pumping Is necessary whenever liquids and sludges must be moved.

Reference

USEPA, 1985, Handbook -Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-S5/006, Washington, D.C.

3b.la centrifugal pumps

Description of Technology/Applications

Centrifugal pumps are suited for pumping large volumes against small heads andcan handle liquids with high solids content. They operate at rates of 2 gpmto 10,000 gpm and are inexpensive, simple, and easy to repair and maintain.Centrifugal pumps must be primed.

DUNN GEOSCIENCE CORPORATION S83G2535

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Reference


3b.lb reciprocating pumps


Reciprocating pumps can deliver fluids against high pressures and operate withhigh efficiencies over a wide range of operating conditions. The capability ofachieving high pressures at low velocities is important when pumping abrasiveslurries or other high viscosity fluids. Additionally, total costs, includinginitial, power, and maintenance, are lower than comparable pumps. Compared tocentrifugal and displacement pumps, the reciprocating pump is the leastsensitive to changes in capacity when the discharge pressure varies. Thecapacity of a reciprocating pump can be accurately adjusted with the aid of ametering device. These pumps are incompatible with some treatment processes,because the effluent stream pulsates.

Diaphragm reciprocating pumps can handle fluid mixtures with higher solidcontents than centrifugal pumps can handle. This pump is leak-free, so itprevents cross-contamination. It can produce pressures up to 150 psi.

Bellow reciprocating pumps can be used to produce pressures of up to 50 psi.Applications of bellow pumps are more restricted than diaphragm pumps, butbecause these pumps have no seals and special nonclogging valves are availablefor them, abrasive or particulate mixtures can be pumped.

Piston reciprocating pumps are not recommended for use with abrasive fluids,because these pumps require a packing seal to prevent leaks. Since, in somepiston pumps, the piston and cylinder are open to the fluid being pumped, theyare not recommended for use with corrosive chemicals. Piston pumps maintainhigh volumetric efficiency at any desired flow rate. They are used wherepressures of 600 to 10,000 psi are necessary.

Reference


3b.lc displacement pumps


Generally, displacement pumps should not be used with abrasives, and theyshould never be run dry.


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Gear displacement pumps can be used for a wide range of fluids, including somecorrosive chemicals, but they should not be used for abrasives. Gear pumpsproduce pressures up to 100 psi.

Flexible impeller displacement pumps are applicable for pressures up to 30psi. They cannot handle abrasives but are self-priming and require no checkvalves. They are nearly as efficient as gear and centrifugal pumps.

Flying vane displacement pumps have the same applications and limitations asflexible impeller pumps.

Reference


3b.ld immersion pumps


Immersion pumps arc designed so the inlet port is immersed in liquid, but themotor and electrical components remain dry. They are virtuallymaintenance-free and very versatile.

Applications

Parts of this pump can be constructed of materials suitable to the liquid beingpumped, so they are applicable for use with hard-to-handle chemicals, such assulfuric acid, sodium hydroxide, and ferric chloride. These pumps areself-priming and can pump liquids with temperatures up to 260°.

Reference


3b.le submersible pumps


Submersible pumps operate only when totally submersed in the fluid beingpumped. They contain liquid-proof electrical connections and use a motor whichis cooled by the liquid. These pumps are economical and energy efficient.

Applications

Submersible pumps can be used for industrial process wastewater, flood water,and most clean or dirty waters. Some submersible pumps are built to pump

DUNN GEOSCIENCE CORPORATION ftR302537

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mildly corrosive solutions and kerosene-based solutions. Certain types ofsubmersible pumps can work in as little as 3/16 inches of liquid, and some canpump semi-solids of appreciable size.

Reference


3b.2 industrial vacuum loaders


Both vehicle-mounted and portable skid-mounted vacuum units are available.Industrial vacuum loaders can be used in large-scale clean-ups to removeliquids and almost any solid that can fit through a 7-inch hose and transportthe material to treatment or disposal. A boom and 500-foot hose allow a vacuumloader to remove materials from otherwise inaccessible areas. Loadercapacities range from 500 to 6000 gallons. The wastes removed must bechemically compatible with the vacuum loader's construction materials.

Reference


3c, Subsurface Collection Drains


Subsurface drains include any type of buried conduit used to convey and collectaqueous discharges by gravity flow. Subsurface drains essentially functionlike an infinite line of extraction wells. They create a continuous zone ofinfluence in which groundwater within this zone flows towards the drain.

Applications

Since drains essentially function like an infinite line of extraction wells,they can perform many of the same functions as wells. They can be used tocontain or remove a plume or to lower the groundwater table to prevent contactof water with the waste material. The decision to use drains or pumping isgenerally based on a cost-effectiveness analysis. For shallow contaminationproblems, drains can be more cost-effective than pumping, particularly instrata with low or variable hydraulic conductivity. Subsurface drains may alsobe preferred over pumping where groundwater removal is required over a periodof several years, because the operation and maintenance costs associated withpumping are substantially higher.

DUNN GEOSCIENCE CORPORATION B H U 0 -C 5 3 8

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Reference


3c.l french drainsi


French drains are ditches filled with gravel which capture groundwater and Idivert it to collection locations (i.e., pumping wells, sumps). - '

Applications j

French or gravel drains can be used where the amount of water to be drained issmall and flow velocities are low. If used to handle high volumes or rapid :iflows, these drains are likely to fail due to excessive siltation, particularlyin fine-grained soils.

An innovative adaptation of the french drain concept can be applied at sites :where bedrock contamination hinders the implementation of normal remedial 'measures. Enhanced bedrock fracturing through controlled blasting can create a"french drain effect" without requiring excavation and backfilling. Initialresults of this action are very promising.

Reference


3c.2 tube drains


This includes pipe and tile drains where piping composed of PVC, steel,concrete, baked clay, vitrified clay, etc., are set in the gravel-filledditch. This application is necessary where higher flow velocities exist.

Applications

For hazardous waste site applications, pipe drains are most frequently used.They handle large flow volumes and high flow velocities better than otherdrains. Tile drains have not been widely used in hazardous waste siteapplications.

Reference



4-1

4. GAS COLLECTION


Methane and other gases generated by biodegradation in landfills often pose aserious risk and must be controlled. This involves either passive barrier orventing systems or active gas collection systems.

Applications

Any landfill containing organic material should have a gas control system.

4a. Passive Gas Control Systems .............


These systems are used to prevent the subsurface migration oflandfill-generated gases beyond the landfill property line or other appropriatelimit Passive gas control systems control subsurface gas movement by alteringthe paths of flow without the use of mechanical components.

Applications

Passive gas control systems can be used at virtually any site where there iscapability to trench or drill an excavation to at least the same depth as thelandfill. Limiting factors could include the presence of a perched water tableor rock strata. Passive vents should generally be expected to be lesseffective in areas of high rainfall or prolonged freezing temperatures.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPAa/625/6-85/006, Washington, D.C.

4a.l . high permeability


High-permeability systems entail the installation of highly permeable (relativeto the surrounding soil) trenches or wells between the landfill and the area tobe protected. Since the permeable material offers conditions more conducive togas flow than the surrounding soil, paths of flow to points of controlledrelease are established. High-permeability systems generally take the form oftrenches or wells excavated outside of the landfill limit and backfilled with ahighly permeable medium such as a coarse crushed stone. As well spacingdecreases, the design and function of well vents approaches that of trenchvents.

DUNN GEOSCIENCE CORPORATION flfl3Q25liG

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Applications

High permeability systems should be used (with or without low permeabilitysystems) when controlled gas venting is desired.

Reference


4a,2 low permeability


Low-permeability systems block gas flow into areas of concern by the use ofbarriers (such as synthetic membranes or natural clays) between the landfilland the area to be protected. With low-permeability systems, gases are notcollected and, therefore, cannot be conveyed to a point of controlled releaseor treatment. The purpose of the system is to prevent or reduce gas migrationinto areas that are to be protected.

Applications

Low permeability systems should be used (with or without high permeabilitysystems) when the goal is to block gas flow into areas of concern.

Reference _ .


4b. Active Gas Collection/Recovery


An active gas collection system alters the pressure gradients and paths of gasmigration by mechanical means. It typically consists of four components: gasextraction wells, gas collection headers, vacuum blowers or compressors, and atreatment system.

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Applications

Active gas collection/recovery systems are applicable to landfill sites wheregaseous emissions through the surface are to be controlled. This method can beused to supplement landfill capping and to prevent resulting lateral gasmigration. They can be used at virtually any site where it is possible todrill or excavate through landfilled material to the required depth. Limitingfactors could include the presence of free-standing leachate (i.e., saturation)or impenetrable materials within the landfill.

Reference


ri ,

DUNN GEOSCIENCE CORPORATION ^

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5. DIVERSION

5a. Grading


Grading is the general term for techniques used to reshape the surface ofcovered landfills to manage surface water infiltration and run-off whilecontrolling erosion. The spreading and compaction steps used in grading aretechniques practiced routinely at sanitary landfills. The equipment andmethods used in grading are essentially the same for all landfill surfaces, butapplications of grading technology will vary by site. Grading is oftenperformed in conjunction with surface sealing practices and revegetation aspart of an integrated landfill closure plan.

Applications

Grading is typically part of landfill closure. It minimizes infiltration,differential settling, ponding, leaching, and soil erosion and prepares thesoil for revegetation. Grading is not always economically attractive if coversoil is not readily available.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):-EPA/625/6-85/006, Washington, D.C.

5a.l scarification

Description off* Technology

Scarification is the shallow grooving of the land surface along surfacecontours by harrowing or by dragging the bucket teeth of a front-end loaderover the ground. Specially-equipped crawler tractors can also performscarification.

Applications

Scarification is applicable whenever slopes are not too steep to move along thesurface contouir. It reduces run-off velocities and minimizes erosion.

Reference



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5a.2 tracking


Tracking, like scarification, is the shallow grooving of the land surfaceparallel to the contour, but itis accomplished using a cleated crawler tractorrunning perpendicular to the contour.

Applications _,

Tracking is used on steep slopes where scarification and terracing are not 'possible, because the slope is too steep to move along the contour. It helpsreduce run-off velocities and erosion. r j

Reference


5a.3 contour furrowing j


Contour terracing or furrowing is used on long slopes in conjunction with otherroughening techniques to disrupt and slow surface runoff. This effect isaccomplished by running a bulldozer parallel to the contour. Dirt is allowedto dribble off the blade end, creating small depressions that interruptdownslope surface water flow.

Applications

Contour furrowing or terracing can be used wherever slopes are not too steep tomove along the surface contour. Terracing is necessary where surface waterrun-off is high.

Reference


5b. Reveggtation


The establishment of a vegetative cover is a cost-effective method to stabilizethe surface of hazardous waste disposal sites, especially when preceded bycapping and grading.


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Revegetation decreases erosion by wind -and water and contributes to thedevelopment of a naturally fertile and stable surface environment. Also, thetechnique can be used to upgrade the appearance of disposal sites that arebeing considered for various re-use options.

Applications

Revegetation may be part of a long-term site reclamation project, or it may beused on a temporary or seasonal basis to stabilize intermediate cover surfacesat waste disposal sites. Revegetation may not be feasible at disposal siteswith high cover soil concentrations of phytotoxic chemicals, unless these sitesare properly sealed, vented, and recovered with suitable topsoil.

Reference


5b.l grasses,


Grasses, such as fescue and lovegrass, are quick-growing and durable and havedense root systems.

Applications

Grasses should be planted where a quick, lasting ground cover is desired. Thedense root system of a grass adequately anchors soil and increases infiltrationby disrupting run-off.

Reference -- —'•—


5b.2 legumes


Legumes (lespedeza, vetch, clover, etc.) are vegetation that can store nitrogenand that are readily established on steep slopes.

Applications

When steep slopes need to be stabilized or the cover soil needs fertilizationto grow other vegetation, legumes are a good candidate for revegetation. Theycan be readily established on steep slopes, and legumes store nitrogen in theirroots. _


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Reference


5b.3 shrubs


Shrubs such as bristly locust and autumn olive, are dense, tolerant, durablevegetation,

Applications

Shrubs are appropriate where soils are acidic and disposal site conditions areharsh. They provide a dense cover.

Reference


5b,4 trees


Trees provide a long-term protective cover and a fertile layer of decayingleaves and branches.

Applications

Trees are long-term protection and are generally planted after grasses andlegumes have stabilized the cover.

Reference


5c. Surface Water Controls


Diversion and collection systems control the movement of water either bychanneling or by keeping water from encroaching upon a site.


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Applications"

Diversion and collection systems are necessary when there is run-off from awaste site that must be treated, when excessive erosion of a disposal site isoccurring, or when there is a threat of surface water encroaching upon a site.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EEA/625/6-85/006, Washington, D.C

5c.l dikes and berms


Dikes and berms are well-compacted earthen ridges or ledges constructedimmediately up-slope from or along the perimeter- of disturbed areas (e.g.,disposal sites). These structures are generally designed to provide short-termprotection of critical areas by intercepting storm run-off and diverting theflow to natural or manmade drainageways, to stabilized outlets, or to sedimenttraps. The two terms, dikes and berms, are generally used interchangeably;however, dikes may also have applications as flood containment levees.

Applications

Dikes and berms may be used to prevent excessive erosion of newly constructedslopes until more permanent drainage structures are installed or until theslope is stabilized with vegetation. They are widely used to provide temporaryisolation of wastes until they can be removed or effectively contained. Theyhave particularly widespread use during excavation and removal operations whereit is necessary to isolate drums or contaminated soils which have beentemporarily staged on-site. The dikes not only prevent run-off, but can alsoprevent mixing of incompatible wastes. These temporary structures are designedto handle relatively small amounts of runoff; they are not recommended fordrainage areas larger than 5 acres. Diversion of storm run-off will decreasethe amount of water available to infiltrate the soil cover, thereby reducingthe amount of leachate production.

Reference


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5c.2 channels, ditches, trenches, diversions, arid waterways


Channels are excavated ditches that are generally wide and shallow withtrapezoidal, triangular, or parabolic cross sections. Diversion channels areused primarily to intercept run-off or reduce slope length. They may or maynot be stabilized. Channels stabilized with vegetation or stone rip- rap(waterways) are used to collect and transfer diverted water off site or to -,on-site storage or treatment. ]

ApplicationsI'T

The applications of channels, waterways, and ditches depend on the specificdesign. Earthen channels can be used on the perimeter of a disposal site todivert run-off from entering the area of waste disposal. They are usuallytemporary, since they are inadequately stabilized to resist erosion. Adiversion has the same application as an earthen channel, but is used on gradedslopes. Swales placed along the perimeter of the site are used to keepoff-site runoff from entering the site and to carry surface runoff fromlandfills. Swales are more permanent than earthen channels, because their sideslopes are less steep and are stabilized by vegetative cover. Half-round pipechannels may be constructed on the perimeter of a waste site and moved asneeded to protect other portions of the waste site. They can also be usedsuccessfully to carry storm water run-off over a filled area where it is notpractical to carry the run-off around the fill. Sodded waterways are usedprimarily In situations where the flow quantities and velocities arcsignificant, and a full growth of grass is required to prevent erosion.Typically, five acres is often considered to be a large enough area to warrantsod. The maximum allowable velocities for sodded waterways are dependent onthe type of grass. Where the tributary drainage area is relatively small andthe quantity of run-off and velocity of flow is low, grass-seeded waterways canbe effectively used. Stone waterways provide added protection againsterosion. If the waterway is intended to carry large quantities of run-offand/or the flow velocities are excessive, the stone may be grouted in place. Astone channel is a permanent means of diverting off-site drainage around thedisposal site and carrying surface run-off from landfills.

Reference



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5c.3 terraces and benches


Terraces and benches are embankments constructed along the contour of very longor very steep slopes to intercept and divert flow and to control erosion byreducing slope length. These structures are classified as bench terraces ordrainage benches. Bench terraces are used primarily to reduce land slope whiledrainage benches on broad-based terraces act to remove or retain water onsloping land.

Applications

Benches and terraces may be used to break up steeply graded slopes of covereddisposal sites into less credible segments. Upslope of disposal sites, theyact to slow and divert storm run-off around the site, thereby minimizingerosion. Downslope of landfill areas, they act to intercept and divertsediment-laden run-off to traps or basins. Hence, they function tohydrologically isolate sites where remedial actions have not yet beencompleted, to control erosion of cover materials on sites which have beencapped, or to collect contaminated sediments eroded from disposal areas. Fordisposal sites undergoing final grading (after capping and prior torevegetation), construction of benches or terraces may be included as part ofthe integrated site closure plan.

5c.4 chutes and downpipes


Chutes and downpipes are structures used to carry concentrated flows of surfacerun-off from one level to a lower level without erosive damage. They generallyextend downslope from earthen embankments (dikes or berms) and convey water tostabilized outlets located at the base of terraced slopes.

Chutes (or flumes) are open channels, normally lined with bituminous concrete,Portland cement^concrete, grouted rip-rap, or similar non-erodible material.

Downpipes (downdrains; pipe slope drains) are temporary structures constructedof rigid piping (such as corrugated metal) or flexible tubing of heavy-dutyfabric. They are installed with standard prefabricated entrance sections.

Applications

Chutes and downpipes often represent key elements in combined surface controlsystems. They are especially effective in preventing erosion on long, steepslopes, and can be used to channel storm run-off to sediment traps, drainagebasins, or stabilized waterways for off-site transport. However, they provideonly temporary erosion control while slopes are stabilized with vegetativegrowth. Chutes are limited to heads of about 18 feet or less. Also, downpipesare limited to drainage areas five acres in size.


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Reference


5c.5 seepage basins


Seepage or recharge basins and ditches are used to discharge water collectedfrom surface water diversions, groundwater pumping, or leachate treatment togroundwater. They may also be used in in-situ treatment to force treatmentreagents into the subsurface.

Applications

Seepage basins and ditches are most effective in highly permeable soils so thatrecharge can be performed. They are not applicable at sites where collectedrun-off or groundwatcr is contaminated. Many basins and ditches are used inareas with shallow groundwatcr tables.

Reference


5c.6 levees and floodwalls


Levees are earthen embankments that function as flood protection structures inareas subject to inundation from tidal flow or river flooding. Levees create abarrier to confine flood waters to a floodway and to protect structures behindthe barrier. Floodwalls perform much the same function as levees, but areconstructed of concrete.

For hazardous waste sites, levees and floodwalls help to control major lossesof waste and cover material and prevent massive leachate production andsubsequent contamination from river or tidal flooding.

Applications

Flood containment levees are most suitable for installation in flood fringeareas or areas subject to storm tide flooding, but not for areas directlywithin open floodways. They may be constructed as perimeter embankmentssurrounding disposal sites located in floodplain fringe areas or installed atthe base of landfills along slope faces that are subject to periodicinundation. Levees serve to protect land disposal sites from flood waters,which may erode cover materials and transport waste materials off-site, orwhich may add water to waste materials, thus increasing hazardous leachateproduction.


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Because of the relatively long, flat side slopes of levees, an embankment ofany considerable height requires a very large base width. For locations withlimited space and fill material or excessive real estate costs, the use ofconcrete floodwalls is preferred as an alternative to levee construction.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPa/625/6-85/006, Washington, D.C

5c.7 addition of freeboard


Adding freeboard to a levee, floodwall, or dike means increasing its heightabove the liquid level. This increases the storing and diversion capabilitiesof the structure.

Applications

Freeboard should be added to any levee, floodwall, or dike that is notsufficiently tall to hold or divert expected floodwater volumes away fromdisposal sites.

5d. Sedimentation Basins and Ponds


Sedimentation basins are used to control suspended solids entrained in surfaceflows. A sedimentation basin is constructed by placing an earthen dam across awaterway ornatural depression, by excavation, or by a combination of both. The purpose ofinstalling a sedimentation basin is to impede surface run-off carrying solids,thus allowing sufficient time for the particulate matter to settle.

Applications

Sedimentation basins are usually the final step in control of diverted,uncontaminated, surface run-off prior to discharge. They are especially usefulif the surface run-off has a high silt or sand content and are essential to agood surface flow control system.

Reference



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5e. Sediment Turbidity Controls and Containment


Removal of contaminated sediments in open water often generates turbiditycaused by resuspension of fine-grained particles. Low turbidity dredgingequipment and turbidity minimizing techniques control and contain sedimentturbidity. For example, dredging upstream forces generated turbidity to passaround the dredge, thus increasing flocculation and settling. Schedulingdredging for periods of low flow and dry, calm weather also aids turbidityreduction.

Applications

When removing sediments in open water, especially where flow velocities andnatural turbulence are high, turbidity control is important. Turbidity spreadscontamination and slows dredging operations.

5c.l silt curtains


Silt curtains are low-permeability, floating barriers that extend verticallyfrom the surface of the water to a specified depth. A silt curtain must bedesigned to meet specific site conditions, including water depth and changes inwater depth due to tides, type of bottom sediment, and current velocity.

Applications

Silt curtains are used to control near-surface turbidity in the vicinity ofsmall dredging and capping operations. Silt curtains arc not recommended foruse in open oceans, in currents that exceed 1 knot, in areas frequently exposedto high tides and large waves, or around hopper or cutterhead dredges wherefrequent curtain movement is necessary. Tides and wave actions cause thecurtain to flair, thereby reducing its effective depth. In areas characterizedby tidal currents, the use of this method may actually result in higherturbidity levels outside the curtain than inside because of the sweeping motionof the curtain. A single curtain is adaptable to many situations, because itsconfiguration is flexible. A U-shaped configuration is suitable on a river andalong shores. Circular and elliptical configurations are acceptable in openwaters and in tide-influenced waters. The maze configuration is generally notrecommended because of the potential for direct flow between the separatecurtain sections.

References

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C,


5-il

5e.2 cofferdams


Cofferdams can be built around a contaminated area in a waterbody to isolatethat area from stream flow. The area can then be dredged, dewatered, andexcavated or capped with low permeability material. Cofferdams may beconstructed of many materials, such as soil, sheet piling, earth-filled sheetpile cells, and sand bags (for short duration structures).

Applications

Cofferdams are most easily constructed for flow containment of shallow ports,streams, and rivers or waters with low flow velocities. Where flow velocityexceeds 2 feet per second, cofferdam construction is not recommended because ofthe difficulty of driving sheet piling. Cofferdam construction is feasible forsome relatively wide and deep rivers (to about 10. feet), providing that thevelocity of flow is not excessive. Single wall cofferdams are best suited toshallow waters. For depths greater than 5 feet, cellular cofferdams (circularsheet pile cells filled with earth) are recommended.

Cofferdams can be installed across streams, in pairs, to isolate contaminatedsediment deposition and to allow dewatering and excavation access where thereis contamination across the entire channel width. This set-up requires streamdiversion. Alternatively, a single curved or rectangular cofferdam may beconstructed to isolate an area along one bank of a stream or river.

5e.3 surface sealing


Cement, quicklime, or other grouting materials can be applied to the surface ofor mixed with bottom sediments to create a seal which minimizes leaching anderosive transport of contaminated sediments.

There are essentially two approaches to sealing or stabilizing bottom sedimentsfollowing stream diversion. The first is to pneumatically apply a layer ofconcrete or grout to form a surface seal. The second method is to mixconcrete, quicklime, or grout with the contaminated sediments to stabilize thesediments. The stabilizing agent is applied to the surface and mixed with thecontaminated sediments using rubber-tire or crawler-type rotor or trenchermixing equipment.

Methods that have been used for applying concrete under water (without streamdiversion) include: pumping concrete and grouting preplaced aggregate. Mobileconcrete pumps, which may be barge-mounted or used on shore, are widely usedfor placing concrete under water. Grouting of preplaced aggregate is a methodwhich may be used in flowing streams. A coarse aggregate or combination ofseveral types of aggregate are preplaced in forms. Grout made of cement, sand,and water can then be forced through pipes to fill the voids in the aggregate.

DUNN GEOSCIENCE CORPORATTON

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Applications

Surface sealing methods which involve the use of stream diversion are limitedto shallow waters with low flow velocities, where diversion can be accomplishedcost-effectively. The major advantage of this method is that it is unlikely tostir up the sediments and create downstream contamination. Stream diversionalso simplifies the application of grouts or sealant materials.

Sealing methods which do not employ diversion are applicable to deep, open -,water, where bottom currents are not sufficient to erode the cap. Thesemethods will provide less resuspension of bottom sediments than in-situ -'injection methods. Also, sealing methods such as concrete pumps canpotentially be used in confined areas not accessible to barge-mounted injectionsystems. However, the grout or sealant may impact the water column duringapplication; application methods would be slow, and it maybe difficult toobtain complete coverage.

Reference


5e.4 in-situ grouting


Injection of clay-cement or quicklime stabilizes contaminated sediments. Onegrout injection system consists of barge-mounted injection pipes connected tomixing pipes that enter the sediments. The process includes lowering theoperating-mixing apparatus (mixing blades are located within the individualshafts) to the required depth and injecting a cement or lime- based slurry intothe sediments. The mixing blades are then reversed and the shafts are removedand relocated. Continuous mixing apparatus that eliminates removal andrelocation arc also available.

Applications

Theoretically, ia-situ grouting is applicable for depths of 80 to 130 feetbelow the sea floor, but the method's reliability has not been proven. In-situgrouting is applicable only in calm waters in good weather.

Reference


DUNN GEOSCIENCE CORPORATION A R 3 0 2 5 5

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6. REMOVAL


Remedial techniques for contaminated soils, sludges, sediments, and liquids andsolid wastes often involve removal and subsequent treatment and disposal.Excavation, removal, and hauling are generally accomplished with conventionalheavy construction equipment.

Reference


6a. Excavation and/or Drum Removal


Excavation and removal followed by land disposal or treatment are performedextensively in hazardous waste site remediation. There are no absolutelimitations on the types of waste which can be excavated and removed.

Applications

Almost all hazardous wastes can be excavated and removed for disposal ortreatment regardless of the site conditions, but it may be cost-prohibitive atgreat depths or in complex hydrogeologic environments. Also, worker health andsafety, waste mobility, the feasibility of on-site containment or in-situtreatment, and the disposal or treatment costs are considerations in thedecision to excavate. Often, excavation and removal are employed for only themost contaminated areas within a hazardous waste site.

Reference


6a.l loading and casting


Loading and casting is the actual excavation and transportation of the materialto be removed from the ground to the hauling trucks or to a dumping area.Loading and casting can be accomplished by a wide variety of conventionalequipment, but only the equipment acceptable for use at hazardous waste sitesis discussed here.

DUNN GEOSCfENCE CORPORATION H302555

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All of the loading and casting equipment described below is suitable forexcavating cover materials, excavating at depths, and precisely excavatingaround buried objects.

6a.la backhoes


Backhoes are mechanically or hydraulically operated in a drag and hoistmaneuver. They are usually crawler-mounted, although they can bebarge-mounted. The lateral and vertical reach of a backhoe is limited by thelength of the boom.

Applications

Backhoes arc generally used for trenching and subsurface excavation where it isexpedient to keep the excavator at the original ground level. Where it isnecessary for the backhoe to excavate beyond the maximum depth of the boom anddipper assembly, however, a "working bench" can be excavated for the backhoenext to the trench so that the vehicle can excavate to the desired depth. Thebackhoe unit can also be adapted with various attachments, such as grapples fordrum excavation work.

Reference


6a.lb cranes and attachments


The crane equipped with a clamshell or orange-peel bucket is rarely used forloading or casting excavation in the sense of high production. Its uses are insubaqueous excavation and in the rehandling of materials. For instance,cable-operated cranes fitted with the clamshell buckets, drum grapples,magnets, hoists, slings, and lifters are ideal for large-scale drum excavation,lifting, and staging at sites with unrestricted working space.

Cranes can also be adapted for use as dragline excavators for deeperexcavations. Draglines are very suitable for excavating large land areas withloosely compacted soil. Dragline excavation of landfill sites containingexplosive materials or very toxic chemicals is unsafe.

Cranes have very limited mobility, are slow, and cannot be used for backfillingand compacting. Also, it is difficult to spot the bucket attachments whenscraping and dumping.

DUNN GEOSCIENCE CORPORATION * 0 On £ C C £

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Reference - . . . _ . .


6a.lc dozers and loaders


Dozers and loaders can be crawler- or tire-mounted. Crawlers are ideal forexcavating rough, unstable surfaces. Tire-mounted vehicles are faster and moremobile than crawlers on level terrain. Crawler dozers are excellent gradersand earth movers. Dozers can remove soil overburden and can push earth anddrums to more accessible areas for loading.

Front-end loaders are used for digging, lifting, hauling, and dumping. In drumexcavation work, loader use is limited to lifting and loading structurallysound drums, as manual assistance is required. Crawler loaders can carryexcavated material 300 feet. Loader capacity ranges from 5 to 20 cubic yards.

Dozers and loaders are limited in speed and mobility in marshy and swampy areasand must be used in combination with other excavation equipment, such asbackhoes.

Reference


6a.2 hauling excavation


Hauling excavation is the removal and on-site and off-site transportation ofwastes and contaminated materials.

6a.2a scrapers


Scrapers can be used to remove and haul surface cover material, where there areno drums buried near the surface, and to respread and compact cover soil.Working with soft- to medium- density material requires a self-propelled,self-loading scraper, while a push-loaded scraper works best for medium to hardrock and soil. Scraper capacities range from 2 to 40 cubic yards, and scraperscan economically haul material more than 1000 feet. They must be usedsimultaneously with other excavation equipment, such as loaders and dozers.

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Reference


6a.2b haulers


Haulers are large, rubber-tired vehicles. They can be 2- or 3-axle vehicles or jdouble-trailer, multiple-axle vehicles. Haulers are available as bottom-dump, Jrear-dump, and side dump, and their capacities range from 1 to 100 tons.

f •Applications

Haulers are most useful for hauling soils and damaged and undamaged drums tooff-site disposal sites.

Reference


6a.3 drum moving and loading

Description of Technology/Applications ..r

Moving damaged and undamaged drums to off-site secure landfills or selecteddrum reburial sites is often part of the remedial plan for drum disposalsites. The equipment described above can be used for drum excavation, moving,and loading. In addition, drum or barrel grapplers and forklifts are alsoapplicable.

6a.3a drum grapplers j

Description of Technology/Applications - ,

Drum or barrel grapplers can be used to move, load, and unload drums without *the manual assistance required when doing this job with other equipment. Thisis the safest way for workers to handle drums containing hazardous substances.

6a.3b fork lifts and attachments


Forklift trucks can be used to move, load, and unload drums, but manualassistance is required.

DUNN QEOSC1ENCE CORPORATION 4R302558

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6b. Surface Debris Removal _

6b.l cranes - See 6a.lb

6b.2 flatbeds


Flatbeds are convenient for transporting large wastes that are difficult toload and unload from haulers and for contained wastes, sediments, soils,sludges, and liquids that do not need trailer walls for support. Forklifts,dozers, and other loading equipment can drive onto the flatbed to load andunload it.

6b.3 haulers/dump trucks - See 6a.2b

6c. Stream Sediment Removal


Dredging is the process of removing bottom sediments from a water body. Inrecent years, dredging has been employed in the removal of sediments that havebeen contaminated by hazardous substances.

Applications

Removing sediment from a water body and treating it is an alternative toin-situ treatment whenever sediments are contaminated.

6c.l mechanical dredging


The main advantage of mechanical dredging is removal of sediments at nearlyin-situ densities, therefore maximizing solids content and minimizing the scaleof facilities required for dredged material transport, treatment, anddisposal. On the other hand, because mechanical dredging removes bottomsedimentthrough direct application of mechanical force to dislodge the material,sediment resuspension (and therefore turbidity) is often high. Additionally,mechanical dredging has a characteristically low production rate.

Applications

Mechanical dredging generally has application in streams and rivers that arerelatively shallow and whose flow velocities are relatively low. It is alsoused for removing contaminated sediments deposited on dry river banks or infloodplains. Mechanical dredging is ineffective for removing unabsorbed liquidcontaminants.

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Reference


6c.la clamshell dredge


Clamshell (or grab) dredges are crane-operated devices. Most are equipped withone crane, but multiple crane configurations are not uncommon. The crane isnormally mounted on a flat- bottomed barge or pontoon but may also becrawler-mounted.

Applications

Clamshell dredges are adaptable to either land-based or barge-mountedoperation. They are capable of excavating materials at nearly in-situdensities and of excavating almost any type of material, except the mostcohesive consolidated sediment and solid rock. Clamshell dredges are easilycontrolled and maneuvered in small and very confined areas. The working depthof the clamshell is limited, theoretically, only by the length of the cable.In practice, most clamshell dredges operate at depths of up to 100 feet. Thesedredges bite into the sediment and hoist it out of the water. Clamshelldredges cause turbidity, though, so operation is typically limited to shallowstreams and rivers with low flow velocity.

Reference


6c.lb dragline dredge


The primary difference between the dragline and the clamshell is in the controlcable arrangement. The dragline bucket is loaded by being pulled by a dragcable through the material being excavated and toward the crane. By thisarrangement, the dragline offers a longer reach than the clamshell.

Applications

Draglines are adaptable to either land-based or barge-mounted operation. Theyarc capable of excavating material at nearly in-situ densities and are easilycontrolled and maneuvered in small and confined areas, although somewhat lessthan the clamshell. Like clamshell dredges, draglines generate turbidity andare limited to shallow streams and rivers with low flow velocity. Draglinesare ineffective against free or unabsorbed liquid contaminants.

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Reference


6c.lc backhoe


Backhoes are mechanically or hydraulically operated in a drag and hoistmaneuver. They are usually crawler-mounted, although they can bebarge-mounted. The lateral and vertical reach of a backhoe is limited by thelength of the boom.

Applications

Backhoes are normally used for trenching and for other subsurface excavationwhere it is expedient to keep the excavator at original ground level. Becauseof the limited lateral and vertical reach of backhoes, however, they are notoften used for the removal of contaminated sediments. They are capable ofexcavating almost any type of material, and are easily controlled andmaneuvered in small and confined areas. Conventional backhoes are capable ofdigging to a depth of about 40 feet. Extended backhoes are capable of diggingto a depth of up to 80 feet. Backhoes share the limitations of othermechanical dredging techniques, such as low production rate and requirementsfor separate disposal vessels and , equipment, but backhoe availability isexcellent.

Reference


6c.2 hydraulic dredging


Hydraulic dredges remove and transport sediment in liquid slurry form.Slurries of 10 to 20 percent solids by wet weight are common in standardhydraulic dredging operations. The slurries may be pumped many thousands offeet through floating or pontoon-supported pipeline to a dredged materialtreatment/ storage area. Hydraulic dredges are usually barge-mounted and carrydiesel or electric-powered centrifugal pumps with discharge pipes ranging insize from 6 to 48 inches in diameter.

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Applications

Hydraulic dredges are not limited to use in waters with low flow velocity, buttheir use requires large areas for settling and dewatering dredged slurries.

Reference


6c.2a plain suction dredge


The plain suction dredge is the simplest of all hydraulic dredges. It reliessolely on the suction generated by the centrifugal pump to dislodge, capture,and transport the excavated slurry. The dredge head is attached to the end ofa ladder, and its position is controlled vertically and horizontally by themovement of cables attached to the ladder.

00 2 0

Applications

ilPlain suction dredges are a good choice for removing relatively free-flowingsands, gravels, and unconsolidated material. They have a relatively highproduction rate in deep water and can discharge directly to disposal areas.The dredged material, however, does require extensive dewatering andconsolidation. These dredges are ineffective in removing hard and cohesivematerials and should not be operated in rough waters, in heavy river traffic,or in areas where there is extensive debris that may block or damage suctionlines.

Reference


6c.2b cuttcrhead dredge


The cutterhead is probably the most efficient and versatile dredge of all. Itsconfiguration is similar to the plain suction dredge, except that it isequipped with a rotating cutter apparatus surrounding the intake end of thesuction pipe. This device, known as the cutterhead, rotates to dislodgesediment and allows transport of sediment by suction to the suction pipe.

DUNN GEOSCiENCE CORPORATION &R3Q2562

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Applications

The cutterhead can efficiently dig and pump all types of alluvial materials orcompacted deposits, such as clay or hardpan. The larger and more powerfulmachines are used to dredge rock-like formations such as coral, and the softertype of basalt and limestone without blasting. The cutterhead is capable ofconstructing level bottoms and finishing slopes efficiently.

Reference


6c.2c dustpan dredge


The dustpan dredge is a hydraulic suction dredge which features a widely-flareddredging head with high-pressure water jets. These jets loosen and agitate thesediments which are captured in the dustpan head as the dredge itself iswinched forward into the excavation.

Applications

The dustpan dredge works best in free-flowing, granular material. The highpressure jetting action may improve efficiency slightly by loosening cohesivedeposits. Production rates for dustpan dredges are high, about the same as forplain suction dredges.

Reference


6c.3 pneumatic dredging


Pneumatic dredges feature a pump that operates on compressed air andhydrostatic pressure to draw sediments to the collection head and through thetransport piping. Otherwise, they are no different than hydraulic dredges.

Applications

Pneumatic dredges are operable in shallow or deep water with no theoreticalmaximum depth. They are easily dismantled and transported and can yield denserslurries with less turbidity than hydraulic dredges.

R302563

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Reference


6c.3a airlift dredge


Airlift dredges use compressed air to dislodge and transport sediments.Compressed air is introduced into the bottom of an open vertical pipe, usuallycontrolled and supported by a barge-mounted crane. As the air is released, itexpands and rises, creating upward currents which carry both water and sedimentup the pipe. Air can also be introduced through a special transport head whichcan be vibrated or rotated to further dislodge more cohesive sediments.

Applications

Airlift dredges require at least 20 feet of water to operate economically. Itsprimary advantage is that it continuously transports material, thus maximizingits production rate.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006,. Washington, D.C

6c.3b Pneuma dredge


The Pneuma dredge consists of a pump which is lowered by a crane into thesediments being dredged. The pump is driven by compressed air and operates bypositive displacement. The body of the pump contains three cylindricalvessels, each with an intake opening on the bottom and an air port and adischarge outlet on top. Pneuma dredges are normally suspended from a cranecable and pulled ahead into the sediments being dredged by a second cable. Thedredge head is essentially fixed relative to the vessel so that lateralmanipulation of the dredge is limited to the positioning and movement of thevessel.

Applications

Though Pneuma dredges are most applicable to loosely consolidated sediments,the intake openings can be fitted with shovel attachments to aid in penetrationof sediments. Extremely deep applications are possible, limited by verticaland lateral control ability and air pressure requirements. They are capable ofdelivering a slurry of high solids content with , minimal turbidity generation.


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Tests show that the Pneuma pump is able to dredge at almost in-situ density ina loosely-compacted, silty clay typical of many estuarine sediments whilegenerating a low level of turbidity. Though not small, Pneuema dredges arerelatively easily dismantled and transported by truck or air. The operation ofthe Pneuma is partially dependent upon hydrostatic pressure, and this may limitits effectiveness in shallow water. Production rates for Pneuma dredges aremoderate, and the set up can be obstructive to navigation.

Reference _ _ _ _ _ _ _ _ _ _=


6c.3c Oozer dredge ___ . ..... _


The Oozer dredge consists of a pump similar in concept to the Pneuma. It usesvacuum pressure in the filling chambers and atmospheric pressure when dredgingin the shallow waterways. The pump is usually mounted at the end of a ladder.The pump body consists of two cylinders to which a vacuum is applied toincrease the differential pressure and flow between the sediment and thecylinders. Sediment thickness detectors, underwater television cameras, and aturbidimeter are attached near the suction mouth for monitoring. Oozer dredgesare normally pulled along a straight line fixed by a cable-and-wincharrangement anchored on land or on the bottom of the water course. The dredgevessel moves along the line of the cable, and the cable is repositioned toestablish a new line as dredging progresses.

Applications

The Oozer dredge is capable of operating at depths up to 60 feet. Slurries of30 to 70 percent solids content can be achieved without significantlyincreasing turbidity or causing resuspension. Suspended oil can be collectedby an attached hood, and cutters can be attached for dislodging hard soils.Moderate production rates and obstruction of waterway traffic are limitingfactors of Oozer dredges. In addition, they have no capability of lateralmanipulation beyond the positioning and movement of the dredge vessel.

Reference



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6d. Removal and Replacement or Relocation of Water and Sewer Lines


When damage to lines is unrepairable or repair is uneconomical, the old lineshould be removed and replaced. If contamination of the area is extensive, theline should be relocated as a safeguard.

Applications

Pipeline replacement is applicable to virtually all cases of pipelinecontamination. Excavation and replacement of defective sewer pipe segments isnormally undertaken when the structural integrity of the pipe has deterioratedseverely, for example, when pieces of pipe are missing, pipe is crushed orcollapsed, or the pipe has large cracks (especially longitudinal cracks) andalternative rehabilitative techniques are not feasible. In addition, pipelinereplacement is often required when the pipe is significantly misaligned.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-S5/006, Washington, D.C.

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7. TREATMENT

7a. Groundwater/Liouid Waste Treatment


Aqueous and liquid wastes include leachate, contaminated water from dredging,contaminated run-off, contaminated water from clean-up, aqueous waste fromdewatering sludges and other treatment processes. These wastes must be treatedbefore disposal.

Applications

Aqueous and liquid waste streams have a wide range of characteristics. Thediversity in volume, type, and concentration of contaminants necessitates avariety of treatment processes, all with different applications.

7a.l biological treatment


Biological treatment processes involve placing a waste stream in contact with amixture of microorganisms. The microorganisms decompose the organic compoundsin waste streams. Typically, the microorganisms used in the process arepresent in the influent waste stream. _ The process just optimizes the microbialenvironment; thus, natural degradation is enhanced. Methods of optimizing theenvironment include controlling the dissolved oxygen level, adding nutrients,increasing the concentration of microorganisms, and slowly increasing influentwaste concentrations to develop the microbial population within the process.

Applications

Biological treatment is applicable when the waste stream contains organics.Aerobic systems destroy all organics. Anaerobic systems are effective only onsimple organics (carbohydrates, proteins, alcohols, and acids).

.Biological processes should generally be preceded by neutralization andequalization of the influent to make it uniform. Soluble inorganics shouldalso be removed, because they inhibit microbial activity.

Reference

Arthur D. Little, Inc., 1977, Physical, Chemical and Biological TreatmentTechniques for Industrial Wastes. Volume I: USEPA Contract No. 68-01-3554

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7a.la activated sludge


The activated sludge process uses microorganisms in suspension to oxidizesoluble and colloidal organics with molecular oxygen. The two basic componentsof such a system are the aeration basin and the final settling tanks orclarifiers. A mixture of wastewater and microorganisms is aerated and mixed inthe aeration basin. A portion of the settled sludge is then pumped from thesecondary clarifier back to the aeration basin to maintain a sufficient number jof microorganisms. The effluent from the final settling tank is then 1discharged.

There are several modifications to the activated sludge process. The treatmentprocess modifications include shorter or longer detention periods, equipmentsubstitutes or system modifications, etc.

Applications

The activated sludge process treats aqueous organic waste streams having less \than 1% suspended solids content In general, the process is unsuited for Islurries, solids, tars, or viscous waste streams. The activated sludgetreatment system is best suited for industrial wastes with organicconstituents. This system is the most compact biological treatment system andallows the greatest control of dissolved oxygen levels to accommodate variableorganic loadings. The activated sludge process has been widely used for ...municipal waste water treatment and for industries, including canneries; paper j'ljand pulp mills; refineries; and steel, textile, petrochemical, pharmaceutical, 'and timber processing plants. Pretreatment with lime is necessary to removeheavy metals. 1

Reference

Arthur D. Little, Inc., 1977, Physical, Chemical, and Biological TreatmentTechniques for Industrial Wastes. Volume I: USEPA Contract No. 68-01-3554

7a.ib trickling filters J

Description of Technology *With a trickling filter, wastewater is sprinkled over stones or another !suitable substance and is allowed to trickle through the bed. The filter is abed of highly permeable media to which microorganisms attach and therebydegrade the waste as it percolates through. The filtered water is then settledin a clarifier. A portion of the water may be recycled. Recirculation helpsin seeding the filter as well as diluting strong influent wastes. There are

DUNN GEOSCIENCE CORPORATION 4 f? 3 0 2 5 S 8

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several variations to standard-rate trickling filters. Trickling filters areclassified according to the applied hydraulic and organic loadings. Tricklingfilters have the advantage over other systems of being able to recover rapidlyfrom shock hydraulic and organic loads.

Applications

Trickling filters are used extensively in the treatment of sanitary sewage andrefinery waste waters containing oil, phenol, and sulfide. They are applicableto the same industrial wastes that the activated sludge treatment process canhandle, but the trickling filter can accept variable hydraulic and organicloadings and provide a fairly uniform effluent stream for treatment by anotherprocess.

Reference


7a.lc aerated lagoqns/aerobic-anaerobic lagoons


An aerated lagoon is a basin in which water is treated on a flow-throughbasis. Wastewater is aerated by means of surface aerators. The lagoon iscompletely mixed; hence settling does not occur. The solids must be settledprior to discharge.

Lagoons are classified as aerobic-anaerobic when little mixing occurs and whena large portion of the incoming solids and biological solids produced fromwaste conversion settle to the bottom of the basin.

Applications

The aerated lagoon biological treatment process can be used on the same typesof waste streams and organic species as the activated sludge treatment process,but the aerated lagoon does not circulate microorganisms to allow the microbialstrains to acclimatize. Aerated lagoon treatment requires longer retentiontimes and much larger land areas than activated sludge treatment does.

Reference

Arthur D. Little, Inc., 1977, Physical, Chemical and Biological TreatmentTechniques for Industrial Wastes. Volume I; USEPA Contract No. 68-01-3554

DUNN GEOSCIENCE CORPORATIONH302569-

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7a.ld waste stabilization ponds


Waste stabilization ponds are large shallow basins which provide aerobic andfacultative anaerobic decomposition of organics in aqueous waste streams. Theponds rely on long retention periods and natural aeration for the aerobicmicroorganisms to decompose organics to carbon dioxide and water. Naturalaeration is encouraged by wind action and algal photosynthesis. The -.facultative anaerobic decomposition, which sometimes occurs in the ponds, takes Jplace at the benthic sediment-water interface. '

Applications [ 1

Waste stabilization ponds can be used for first order biodegradation or finaleffluent polishing. They are used to treat sanitary sewage and industrialwastes from meat and poultry packing, cannery, and dairy plants; iron and steelworks; paper, pulp, and textile mills; oil refineries; and petrochemicalplants. These wastes are mostly carbohydrates, proteins, organic acids, and ,alcohols.

Reference


7a.le rotating biological discs


This sytem consists of a series of rotating discs mounted on a horizontal shaftwhich is placed in a basin or tank. As the contaminated water flows throughthe basin, the media rotates with approximately 40 percent of the discs plasticmedia immersed. This enables contact with the wastcwater for removal oforganic matter by the biological film that develops in the media. Aeration isachieved as the drum rotates. RBD's advantage over other similar processes isits energy savings due to reduced effluent recycle costs.

A rotating biological disc can handle considerable flow variations and highorganic shock loads. The system is modular, so it is flexible to meetincreases and decreases in treatment needs.

Reference


DUNN GEOSCIENCE CORPORATION &H3Q25

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7a.lf fluidized bed bioreactor


Soluble solids are introduced into a fluidized bed of suspended sand andoxygen. This suspension creates a large surface area to improve aerobicmicrobial degradation.

Applications

Aerobic fluidized bed bioreactors require predeveloped microbes to be added totreatment systems.

Reference

USEPA, 1986, Treatment Technology Briefs - Alternatives to Hazardous WasteLandfills: EPA/600/8-86/017, Cincinnati, Ohio, 31 p.

7a.Ig enzyme treatment -


Enzymes are chemical catalysts derived from organisms. They lower theactivation energy needed for chemical reactions to occur. Enzymes catalyzespecific reactions and, therefore, cannot adapt well to the varying compositionof typical waste streams.

Applications

Because an enzyme's catalytic reaction is very specific, enzyme treatment isimpractical for full-scale industrial or municipal waste treatment processesthat treat inhomogeneous and varying wastes.

Reference


7a.lh anaerobic biological treatment


The anaerobic biological treatment process encompasses the reduction of organicmatter in an oxygen-free environment to methane, carbon dioxide and smallquantities of hydrogen sulfide and hydrogen. It comprises two stages, acidfermentation and methane fermentation. Anaerobic treatment can occur invarious types of anaerobic reactors ranging from continuous feed packed columnsto batch digesters.


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Applications

Anaerobic biological treatment is used to treat aqueous wastes with low tomoderate levels of organics and can handle some halogenated organics betterthan aerobic treatment. Anaerobic treatment is effective for acetaldehyde,acetic anhydride, acetone, acrylic acid, aniline, benzoic acid, butanol,crcsol, ethyl acrylate, methyl ethyl ketone, phenol, and vinyl acetate. Theprocess is primarily used with wastes that are high in soluble BOD.

Reference

Ramalho, R.S., 1977, Introduction to Wastewater Treatment Processes: AcademicPress, Inc., New York, NY, 409 p.

USEPA, 1986, Treatment Technology Briefs - Alternatives to Hazardous WasteLandfills: EPA/600-8-86/017, Cincinnati, Ohio, 31 p.

7a.li spray irrigation


This action involves the application of aerated water to a waste mass toenhance biodegradation and infiltration. This alternative assumes that sometype of active groundwater capture system is operating simultaneously tocollect the induced leachate. Recirculating the water through the wastes inthis manner leads to decreasing concentrations.

Applications

Spray irrigation is applicable in shallow water level areas where the leachatecan easily be captured. The contaminants present must be organics which arereadily biodegraded into harmless or less toxic transformation products. Thisis a cost-effective procedure with fewer health and safety considerations thanexcavation of the waste mass.

7a.Ij bioreclamation


Bioreclamation utilizes microorganisms to metabolize organic contaminantsresulting in the breakdown and subsequent detoxification of thesecontaminants. There are three processes through which this can occur: I.aerobic respiration in which oxygen is required as an electron acceptor; 2.anaerobic in which sulfate or nitrate ions serve as electron acceptors; and 3.interactive fermentation/methanogenic processes using reductive dehalogenation.


7-7

The process can be used to treat soils and groundwater. In soils the rate ofbiodegradation can be influenced by a number of factors. The major factors arepH, temperature, soil moisture content, soil oxygen content and nutrientconcentrations. In soils, as it is with groundwater, indigenous bacteria arestimulated by the optimization of such factors. Lab studies would be necessaryto determine optimal conditions and nutrient requirements. Site specificstudies are also essential to accurately predict not only the treatability of aspecific contaminant, but also substrate removal rates.

Nutrients and oxygen (generally in the form of hydrogen peroxide) are generallyadded through injection wells for deep applications. Seepage basins or sprayirrigation can be applied in shallow water table conditions.

Applications

There are several factors affecting the viability of this technique. The mostimportant is the relative biodegradability of the contaminants. Groundwatertemperature is also a key consideration. Optimal organism growth occurs from68°F to 99°F. Site geology and soil types are also important factors.Moderate to high "hydraulic conductivities are necessary so that the nutrientsand water can be added throughout the contaminated area.

Reference

Tetra Tech Richardson, 1987, personal communication

7a.lk equalization

Description of Technology/Application

This technology involves the flow of waste water streams into an equalizationbasin. BOD variations may be smoothed out prior to emission to a treatmentplant.

Reference

Ramalho, R.S., 1977, Introduction to Wastewater Treatment Processes: AcademicPress Inc., New York, NY, 409 p. . . . . . . _ _ . -

7a.2 chemical treatment


Chemical treatment includes processes that change the chemical form of a wasteto degrade it, stabilize it, or prepare it for further treatment.

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Applications

Typically, chemical treatment can be used for any organic or inorganiccontaminant. The applicability depends on the specific chemical process, themix of wastes, the contaminant concentrations, the treatment agent, the removalefficiencies, and the cost.

7a.2a immobilization


Immobilization methods arc designed to render contaminants insoluble and toremove contaminants from waste water. Little is currently known about theeffectiveness and reliability of immobilization techniques as applied tohazardous waste streams.

Applications

Immobilization can be effective for organics and inorganics.

7a.2a.I precipitation


Precipitation, is a well-known process in which the chemical equilibrium of awaste is changed to reduce the solubility of the contaminant The contaminantsthen precipitate out of solution. The precipitation is commonly used to treatheavy metals-containing wastes.

Applications

Precipitation is the most promising method for immobilizing dissolved metalssuch as lead, cadmium, zinc, and iron. Some forms of arsenic, chromium, andmercury and some organic fatty acids can also be treated by precipitation. Allof the divalent metal cations can be precipitated using sulfide, phosphate,hydroxide, or carbonate. However, the solubility product and the stability ofthe metal complexes vary. Because of the low solubility product of sulfidesand the stability of the metal sulfide over a broad pH range, sulfideprecipitation looks most promising.

Reference


DUNN GEOSCIENCE CORPORATION H tt 3 0 2 5 7 ty

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7a.2a.2 polymerization


Polymerization involves injection of a catalyst into a groundwater plume toconvert an organic monomer (e.g., styrene, vinyl chloride, isoprene, methylmethacrylate, and acrylonitrile) to a larger chemical multiple of itself withdifferent properties. The process transforms a fluid-like substance into agel-like, nonmobile mass.

Applications

Polymerization is suited for groundwater clean-up after a land spill orunderground leak of a pure organic monomer. Applications for uncontrolledhazardous waste sites are limited by the difficulty of initiating sufficientcontact between the polymerizing catalyst and the monomer, and the long-termeffectiveness of polymerization is unknown.

Reference


7a.2b detoxification


Treatment techniques discussed in this section are those which serve todestroy, degrade, or otherwise reduce the toxicity of contaminants.

Applications

Detoxification is applicable to a number of chemical contaminants, but specificapplicability depends on the detoxification method.

Reference


7a.2b.l neutralization


This process involves introducing dilute acids and bases into liquid wastes tobring the pH to 7. Typically, a multiple compartment concrete equalizationbasin lined with material resistant to the expected waste streams is used forneutralization. Mixers make the process more efficient and influent andeffluent baffles control flow distribution.


7-10

Applications

Neutralization is commonly used prior to biological treatment since bacteriaarc sensitive to such changes. It can also be used as pretreatment for severalchemical treatment processes such as: carbon adsorption, ion exchange, airstripping, and chemical oxidation/reduction. Neutralization can adjust the pHof acidic or basic plumes and can act as a final treatment for groundwatereffluent from another treatment. It can prevent the formation of toxic gasesduring oxidation, reduction, or precipitation and can increase the hydrolysisrate of certain organics.

Reference


Ramalho, R.S., 1977, Introduction to Wastewater Treatment Processes: AcademicPress, New York, NY, 409 p.

7a.2b,2 hydrolysis


Hydrolysis enhances cleavage rates of organic molecules by acceleration ofacid- or base-catalyzed hydrolysis rates through adjustment ofsoil/groundwater/sludge pH.

Applications

Hydrolysis may be applicable with in situ treatment of certain organics.Esters, amides, carbonates, phosphoric and phosphonic acid esters, andpesticides can be degraded by hydrolysis. Hydrolysis products, however, may bemore toxic than the initial compound, so the reaction should be studiedcarefully before applying hydrolysis. For sites where there is heavy metalcontamination, acid hydrolysis is not recommended because of potentialmobilization of heavy metals.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-S5/006, Washington, D.C.

7a.2b,3 oxidation/reduction


Oxidation and reduction reactions serve to alter the oxidation state of acompound through loss or gain of electrons, respectively.


7-11

Applications

Oxidation and reduction can precipitate, detoxify, or solubilize inorganics anddecompose, detoxify, or solubilize organics. Oxidation can be a pretreatmentfor organics before biodegradation. These techniques are widely used forwastewater treatment but are largely conceptual for in-situ treatment.Oxidizing inorganics in soils is limited to arsenic and some lead compounds.

Reduction is less applicable than oxidation for the treatment of organics.Reduction is applicable, however, for the treatment of chromium and selenium insoils.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C " . _ .

7a.2b.3a hydrogen peroxide oxidation


This treatment process involves the addition of hydrogen peroxide to oxidizeorganic compounds.

Applications

Hydrogen peroxide oxidation is routinely used to control the biologicaltreatment of municipal wastewater and to detoxify cyanide and organicpollutants in industrial waste. Hydrogen peroxide has served as a subsurfaceoxygen source for several bioreclamation projects.

Reference


7a.2b.3b hypochlorite oxidation


This treatment process involves the addition of sodium or calcium hypochlorite(bleaching agents) to oxidize organic wastes.

Applications

Hypochlorite oxidation is used to treat drinking water, municipal wastewater,and industrial waste, but it is not used to treat contaminated groundwater orsoil. Hypochlorite oxidation must be performed under controlled conditions(not in-situ), because toxic chlorinated organics could be formed.

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References

USEPA, 1986, Treatment Technology Briefs - Alternatives to Hazardous WasteLandfills: EP A/600/8-86/017, Cincinnati, Ohio, 31 p.


L

7a.2b.3c ozonation

Description of Technology '

Ozonation is a chemical oxidation process using ozone, an extremely reactive ' ]gas, as the oxidizing agent. i

Applications \

Ozonation is appropriate for liquid, aqueous, and gaseous waste streams withless than 1.0 percent oxidizable compounds. Ozonation is used to treatdrinking water, municipal wastewater, and industrial waste. Ozone can be used ;to pretreat wastes to breakdown refractory organics or as a polishing step . Jafter biological or other treatment processes to oxidize untreated organics.Ozone is currently used for treatment of hazardous wastes to destroy cyanideand phenolic compounds.

References m

Kiang, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: Ann ! 'Arbor Science Publishers, Inc., Ann Arbor, Michigan, 549 p.

USEPA, 1986, Treatment Technology Briefs - Alternatives to Hazardous Waste : 'Landfills: EP A/600/8-86/017, Cincinnati, Ohio, 31 p.

7a.2b.3d wet air oxidation


Wet air oxidation uses elevated temperature and pressure to oxidize organics. -JThe oxidation products and the inorganics stay in liquid form. The off-gas islow in nitrogen oxides, sulfur oxides, and particulates. Off-gas treatment may •be necessary for hydrocarbon emissions. The process is thermally ;self-sustaining.

Applications

Wet air oxidation has been used to treat aqueous waste streams with less than 5percent organics and with some pesticides, phenolics and organic sulfur,cyanide wastewaters. It is not recommended for aromatic halogenated organics.This technology is not economical for dilute or concentrated wastes, and it isnot appropriate for solids or viscous liquids.

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Reference


7a.2b.3e supercritical water oxidation


The supercritical water oxidation process is basically a high- temperature,high-pressure wet air oxidation. The unique properties of water above 500°Cor 705°F (supercritical region) cause it to act as an excellent non-polarsolvent for nearly all organic materials. Aqueous solutions or slurries(organic content >5 percent) are mixed with high-pressure oxygen (3200 to 3600psi or >218 atms) to chemically oxidize wastes in less than one minute with>99.99 percent efficiency. The process is an emerging technology which may beless expensive than high-temperature incineration for destruction oforganically contaminated aqueous wastes.

Applications

Supercritical water oxidation is used to treat aqueous organic solutions andslurries and mixed organic and inorganic wastes.

Reference


7a.2b.3f electrolytic oxidation


In this process, cathodes and anodes are immersed in a tank containing a wasteto be oxidized, and a direct electrical current is imposed on the system. Theprocess is particularly applicable to cyanide-bearing waste. The products ofdecomposition for cyanide waste are ammonia, urea, and carbon dioxide. Duringthe decomposition, metals present are plated out on a cathode.

Applications

Electrolytic oxidation is used to treat wastes with up to 10 percent cyanideand to separate metals to allow for their potential recovery.

Reference

USEPA, 1986, Treatment Technology Briefs - Alternatives to Hazardous WasteLandfills: EPA/600-8-86/017, Cincinnati, Ohio, 31 p.


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7a.2b.4 chemical dechlorination


All chemical dcchlorination processes use chemical reagents to remove thechlorine atoms (by substitution) from biphenyls. The molecule is thenrearranged to form less harmful chemical compounds. Most chemicaldcchlorination processes use a sodium reagent to remove the chlorine atoms frombiphenyls.

Applications 1

Chemical dechlorination is used to treat chlorinated hydrocarbons, acids,thiols, chlorides, and dioxins. Research is being done by several companies onthe technology to dechlorinate PCB's. However, it is still an experimentalprocess. Dewatering before dechlorination increases the reaction rate.

Reference

USEPA, 1986, Treatment Technology Briefs - Alternatives to Hazardous WasteLandfills: EPA/600/8-86/017, Cincinnati, Ohio, 31 p. 'I

7a.2b.5 ultraviolet photolysis


Ultraviolet photolysis is a process that destroys or detoxifies hazardouschemicals in aqueous solutions utilizing ultraviolet irradiation.

Applications

Ultraviolet photolysis has been used to degrade dioxins in waste sludge. Theprocess has been used on a laboratory scale to reduce dioxin levels on a sitefor an overall destruction efficiency of 99.94 percent. The process has beenused for conventional wastewater treatment in lieu of chlorination, but has notbeen widely used at hazardous waste sites. Ultraviolet light cannot penetratepollutants in soil or opaque solutions. Introducing ozone can enhanceultraviolet photolysis.

Reference


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7a.2b.6 liquid-liquid solvent extraction


Liquid-liquid solvent extraction is a process for separating liquids by mixingthe stream with a solvent which is immiscible with part of the waste but whichwill extract other components of the waste stream. The extracted componentsare then removed from the immiscible solvent for reuse or disposal.

Applications

Solvent extraction is effective when the contaminated wastewater contains onlya few compounds that need to be extracted. It is most often encountered as atreatment method when the waste stream contains valuable organics.Consequently, it is not often used in conventional industrial waste treatment.While, theoretically, solvent extraction can be used to extract organics in anyconcentration, it is most effective for extracting organics in lowconcentrations. Two applications are the removal of up to 5% phenol from cokeindustry wastes, and the removal and recovery of toxic dyes. This technologyis most useful for removing organics that cannot be degraded biologically.

Reference

State of California, 1981, Alternatives to the Land Disposal of HazardousWastes, 288 p.

7a.2b.7 alkaline chlorination


In this process, chlorine gas (with caustic), chlorine dioxide, andhypochlorite (sodium or calcium) are routinely used to destroy cyanide which isconverted to nitrogen gas and carbon dioxide gas.

Applications

Alkaline chlorination is used to treat free and complex cyanides. pH controlis required to avoid toxic volatiles release.

Reference


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7a.2b.8 chlorinolysis


At temperatures around 500°C in the presence of excess chlorine, thecarbon-carbon bonds of hydrocarbons can be broken, and the molecular fragmentscan react with chlorine to form chlorinated hydrocarbons of shorter chainlength.

Applications ~i

Chiorinolysis can produce salable carbon tetrachloride from waste chlorinationhydrocarbons. Chlorinolysis has been used to reduce agent orange ,concentrations by converting part to carbon tetrachloride. Chlorinolysis can •'!be used on wastes from the production of pesticides, vinyl chloride,herbicides, solvents, and other wastes. Wastes should contain only hydrogen,carbon, and chlorine and less than 5% aromatic compounds, so pretreatment isoften necessary.

Reference

Metcalf & Eddy, Inc., 1985, Briefing: Technologies Applicable to HazardousWaste: prepared for USEPA, Cincinati, Ohio.

7a.2b.9 chloroiodidcs


Chemical degradation using chloroiodides requires that the chloroiodides bedissolved in a micellar solution. Contaminated materials are then contactedwith the chloroiodides in micellar solution at ambient temperatures.Degradation occurs by the breaking of bonds.

Applications

In laboratory tests, chloroiodides have been used to degrade dioxins and otherorganics from wastes. Chemical degradation has also been used on contaminatedsoils at a laboratory scale.

7a.2b,10 hydrometallurgy


This is the combined application of solvent extraction, electrowinning,chemical precipitaion, and filtration to the recovery of pure metals fromhydroxide sludges. The attraction of these approaches to treatment is thatthey can be used to either selectively remove a single toxic compound (like

•l

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cadmium) prior to disposal or to actually produce a useful product. Tests havedemonstrated that acid extraction at a pH of approximately 1 will solubilizeover 95% of the metals in a sludge, thereby making them available forsubsequent treatment.

Reference

Martin, EJ. and Metry, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Co., New York, N.Y., p. 152.

7a.2b.ll ion exchange


Ion exchange removes toxic metal ions from solution to recover concentratedmetal solutions for recycling by exchanging one ion, electrostatically attachedto a solid resin material, for a dissolved toxic ion. The resulting residualsinclude spent resins and spent regenerants such as acid, caustic, or brine.

Applications

Ion exchange is a practical treatment for hazardous compounds in groundwater.It has been used to remove heavy metals, toxic ions, inorganics, and organicsfrom industrial and domestic wastewaters.

Reference


7a.3 physical treatment


Physical treatment technologies include processes which separate components ofa waste stream or change the physical form of the waste without altering thechemical structure of the constituent materials. Physical treatment techniquesare often used to separate the materials within the waste stream so they can bereused or detoxified by chemical or biological treatment or destroyed byhigh-temperature incineration.

Applications

Physical treatment technologies are useful for separating hazardous materialsfrom an otherwise non-hazardous waste stream, for separating various hazardouscomponents for different treatment processes, and as a pretreatment forultimate destruction in a biological, chemical, or thermal treatment process.

Reference


(DUNN GEOSCIENCE CORPORATION ftR3 02583

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7a.3a flow equalization


Ponds arc often constructed to regulate the flow into a treatment center.These equalization ponds buffer high recharge events (such as rainfalls in thecase of surface water treatment).

Applications

A basin is often constructed as part of the headworks of a treatment facilityto regulate flow into a process that will become upset (i.e. overloaded) byhydraulic fluctuations. It is typically used in wastewater treatment plantswhich have an infiltration/inflow problem which would result in excessive flowsafter rain events.

Reference

Ramalho, R.S., 1977, Introduction to Wastewater Treatment Processes, AcademicPress, NY, 409 p.

7a.3b flocculation, coagulation, sedimentation


Flocculation is the process by which small, unsettleable particles suspended ina liquid medium are made to agglomerate into larger, more settleableparticles. The mechanisms by which flocculation occurs involve surfacechemistry and particle change phenomena. In simple terms, these variousphenomena can be grouped into two sequential mechanisms.

o chemically induced destabilization of the requisite surface-relatedforces, thus allowing particles to stick together when they touch and

o chemical bridging and physical enmeshment between the now nonrepellingparticles, allowing for the formation of large particles.

Sedimentation is part of the precipitation process for removing suspended solidparticles from a waste stream. Sedimentation is usually accomplished byproviding sufficient time and space in special tanks or holding ponds forsettling. Chemical coagulating agents are often added to encourage thesettling of fine particles.

Applications

Flocculation and coagulation are applicable to any aqueous waste stream orsurface impoundment containing prccipitable or suspended material,


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Flocculation is typically preceded by precipitation and used in conjunctionwith a solid-liquid separation process, such as sedimentation. It may be apretreatment for another treatment, such as activated carbon adsorption.

Sedimentation is applicable to aqueous wastes with high suspended solidloadings, including surface run-off, collected leachate or landfill toeseepage, dredge slurries, effluents from biological treatment andprecipitation/flocculation treatment, and industrial wastewaters. Also, it canbe used as a pretreatment for chemical processes.

References

Kiang, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers, Inc., Ann Arbor, Michigan, 549 p.

Martin, E.J. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Co., New York, New York, 520 p.


USEPA, 1985, Handbook - Remedial Action Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C.

7a.3c carbon adsorption


Carbon adsorption uses the surface attachment between organic solutes and thelarge internal pore surface area of activated carbon grains to remove organicsfrom aqueous and gaseous waste streams. The residuals are spent carbon andsteam or solvent regenerant.

Applications

Adsorption is an effective and practical treatment for contaminated groundwaterand wastewater. It has been used to remove mixed organics and selectinorganics from wastewater and to recover select organics and inorganics fromaqueous solution. The applicability of adsorption depends on the solventhaving a high molecular weight, a low water solubility, a low- polarity, and alow degree of ionization.

Reference


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7a.3d powdered activated carbon systems


The powdered activated carbon (PAC) system combines physical adsorption withbiologial treatment. This process achieves a higher degree of treatment thanis possible by either method alone. The system consists of adding powderedactivated carbon to the aeration basin of an activated sludge system. Themixture of contaminated water, activated sludge, and powdered carbon is aerated —for a hydraulic detention time adequate for complete biological treatment. JAfter aeration, the mixture flows to a clarifier. Settled solids are fed back -*to the aeration tank to maintain the necessary concentration of microorganismsand carbon, and the treated water is discharged. Carbon is added to the ' |aeration basin at a rate dependent upon influent characteristics and desired |effluent quality.

Applications

The PAC system has been proven effective for wastewaters containing highconcentrations of nonbiodcgradable compounds or substances potentially toxic to jbiological growth. It is more effective than either adsorption of biological itreatment alone.

Reference

Tetra Tech Richardson, Inc., 1987, personal communication

7a.3e sorfaents


Sorbents are natural and synthetic solid materials which eliminate freeliquid. Natural sorfaents include flyash, bentonite, vermiculite, and kilndust

Applications

Sorbents are widely used to remove free liquid and improve waste handling.Some sorbents have been used to limit the escape of volatile organiccompounds. They may also be useful in waste containment when they modify thechemical environment and maintain the pH and redox potential to limit thesolubility of wastes. ** Although sorbents prevent drainage of free water, theydo not necessarily prevent leaching of waste constituents, and secondarycontainment is generally required.

Reference


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7a.3f screening


Screening removes large particles from waste streams by passing the streamthrough a rotating drum, vibrating, or stationary screen.

Applications

Screening is used to remove large particles from wastewater primarily as apretreatment before other solid-liquid separation processes or to protectmechanical equipment.

Reference


7a.3g reverse osmosis

Description of Technology _ _ _ _ _ _

Reverse osmosis is a process for separating components in a liquid stream byapplying external pressure to one side of a membrane so that solvent will flowin the opposite direction.

Applications

Reverse osmosis is generally capable of separating dissolved ionic andnon-ionic components from water solutions by transporting the water through themembrane. Solutions containing up to 10% of the dissolved component can beprocessed, buit normal feeds range from 500 ppm to about 20,000 ppm.

Aqueous streams with dissolved organics may be processed by reverse osmosis,but pure organics usually deform plastic membranes. Strong acids and basescannot be fed to reverse osmosis systems, but many other ionic compounds,including heavy metal solutions, may be treated by this process.

Reverse osmosis has been widely used to produce drinking water from brackishgroundwater and sea water. It is also used in processes in the food processingand textile industries. Uses for treatment of industrial wastes include therecovery of electroplating chemicals from plating rinse waters and removal ofsulfites from paper industry wastewaters.

References•S


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7a.3h distillation


Distillation is a process for separating liquids with different boilingpoints. The mixed-liquid stream is exposed to increasing amounts of heat, andthe various components of the mixture are vaporized and recovered. The vapormay be recovered and reboiled several times to effect a complete separation ofcomponents.

Applications

Distillation is applicable to virtually any aqueous-organic or organic-organicliquid mixture. It is most important as a solvent recovery technique; impurewaste organic solvent mixtures can be separated and purified by distillationfor reuse.

Reference


7a.3i steam distillation/stripping


There are two types of distillation: batch and continuous fractional. Thedistillation process uses steam to remove organics from aqueous wastes.

Steam stripping uses steam to remove organics from aqueous wastes. Steamstripping is essentially a continuous fractional distillation process carriedout in a packed or tray tower. Clean steam rather than reboiled bottoms,provides direct heat to the tower. The resulting residuals are contaminatedsteam condensate, recovered solvent, and "stripped" effluent.

Applications

Steam distillation is used to treat primarily spent solvents, eitherhalogenated or nonhaiogenated.

Steam stripping is generally used in place of distillation only when organiccomponents and water cannot mix. It is most applicable to the removal oflow-boiling-point organics contained in water at dilute concentrations.Solvent recovery is its most important application, but steam stripping canalso remove organics from wastewater prior to discharge to surface waters orother treatments.

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References



7a.3j air stripping


Air stripping is a well-known technology that works on the principle ofcounter-current flow. Wastewater flows down through the packing while air isforced upward and exhausted at the top. There are various configurationsranging from a packed column to a diffused air basin, or a cross-flow tower orcoke tray aerator. The theory for all configurations is the same. Volatileorganics have an affinity for the gas phase and will leave the aqueous phasefor the gas phase.

Applications

Air stripping is used to remove volatile organics from aqueous waste streams orsoils. Generally components with Henry's Law constants of greater than 0.003can be effectively removed by air stripping. This includes such components as1,1,1-trichloroethane, trichloroethylene, chlorobenzene, vinyl chloride, anddichlorbethylcne. The feed stream must be low in suspended solids and mayrequire pH adjustment of hydrogen sulfide, phenol, ammonia, and other organicacids or bases to reduce solubility and improve transfer to the gas phase.Stripping is often only partially effective and must be followed by anotherprocess, such as biological treatment or carbon adsorption. Combined use ofair stripping and activated carbon can be an effective way of removingcontaminants from groundwater. The air stripper removes the more volatilecompounds not removed by activated carbon and reduces the organic load on thecarbon, thus reducing the frequency (and expense) of carbon regeneration.

References




7-24

7a.3k filtration


Filtration is a process for separating liquids and solids using various typesof porous materials. There are many types of filters designed to achievevarious levels of separation. Many of these filter types are described insection 7b.3d. The granular media filter is another type that can be used inthe physical treatment of aqueous and liquid wastes.

A granular media filter uses gravity to remove solids from a fluid passed -1through a bed of granular material. Removal mechanisms include straining,physical adsorption, and coagulation-flocculation. Such mechanisms aid in f~|removing particles much smaller than the void size of the media. j

Applications!

Filters can economically handle streams containing less than 100 to 200 'nig/liter suspended solids, depending on the required effluent level.Filtration is typically used after gravity separation processes for additional |removal of suspended solids and oils, prior to the other treatment processes, !and as a polishing step for treated wastes to reduce suspended solids andassociated contaminants to low levels. Pretreatment by filtration isappropriate for membrane separation processes, ion exchange, and carbonadsorption to prevent plugging or overloading of these processes.

References



7a.31 flotation


Flotation is a process for removing solids from liquids by floating theparticles to the surface using tiny air bubbles. Flotation is useful forremoving particles too small to be removed by sedimentation.

Applications

Dissolved air flotation is used in conjunction with precipitation for theremoval of suspended solids, oils, and greases from wastes and is particularlyeffective in removing finely divided particles that settle too slowly forsedimentation. It is widely used in refining, meat packing, paint, poultryprocessing, paper milling, and baking industries to achieve 80-99% removal ofsuspended and floating materials.

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References


7a.3m supercritical extraction


At a certain combination of temperature and pressure, fluids reach theircritical point, beyond which their solvent properties are greatly altered.These properties make extraction more rapid and efficient than processes usingdistillation and conventional solvent extraction methods.

Applications

Presently, the use of supercritical carbon dioxide to extract hazardousorganics from aqueous streams is being investigated. Supercritical extractionis used to remove hazardous waste from the soil, but its application is limiteddue to its newness and its high capital cost.

Reference


7a.3n dialysis


Dialysis is a process for separating components in a liquid stream using amembrane. Components of a liquid stream will diffuse through the membrane if astream with a greater concentration is on the other side of the membrane. Theprocess is used to extract pure process solutions from mixed waste streams.

Applications

Dialysis application is limited to_ Jiquids containing high concentrations oflow-molecular-weight dissolved compounds. The process can recover caustics,acids, and cyanides from aqueous wastes, but is not used on a large scale totreat groundwater. Dialysis is rarely preferred over newer processes; it hasa low flow rate, is unsuitable to treat dilute solutions, and has outputstreams that are more dilute than the feed. This process is capital-intensiveand requires extensive maintenance and constant operator supervision.

Reference


DUNN GEOSCIENCE CORPORAT[ON ftR 302591

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7a.3o electrodialysis


A later development of dialysis, this process is used to separate thecomponents of an ionic solution by applying an electrical current to thesolution which causes ions to move through the dialysis membrane.

Applications

Electrodialysis can recover inorganic acids, bases, and salts containing zinc, -Icoper, iron, and other metals from solutions. This process, however, is notused on a large scale to treat groundwater. It is capital-intensive and r 1requires extensive maintenance and constant operator supervision. |

Reference ,!

State of California, 1981, Alternatives to the Land Disposal of HazardousWastes, 288 p. i7a.3p electrophoresis I


Electrophoresis is the transport of electrically charged particles under theinfluence of the D.C. electric field. The particles may be complexmacromolecules and colloids or particulate matter and either living cells (suchas bacteria or crythrocytes) or inert material (such as oil emulsion dropletsor clay). Almost any particulate can be made to electrophoresc.

Applications

Electrophoresis is used extensively as a laboratory tool in the analysis andseparation of proteins, polysaccharides, and nucleic acids. It has also beenused commercially for creaming rubber latex and for fractionation of animalsera for veterinary vaccines. Numerous proposed applications have beenresearched and shown to be technically feasible, including deposition ofpaints, polymers, ceramics, and metals. The process has also been consideredfor water purification (e.g., for separation of emulsions and fpr color, virus,and algae removal).

References


KSang, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers, Inc., Ann Arbor, Michigan, 549 p.

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7a.3q freeze-crystallization


Freeze-crystallization involves the formation of "pure" ice crystals from asolution and the concentration of dissolved solutes in a residual brine. Theice crystals may be separated mechanically from the brine, then washed andmelted to yield fresh water (or solvent).

Applications

A number of freeze-crystallization processes have been developed fordesalination, but none have become commercial. Waste treatment applicationstested in the laboratory include: sulfite liquors; plating liquors; paper millbleach solutions; arsenal redwater; solutions containing acetic acid, methanol,and aromatic acids; ammonium nitrate wastes; and cooling tower blowdown.

Reference


7a.3r high gradient magnetic separation


High gradient magnetic separators use fine ferromagnetic filament materialcontaining 95% void space (felted or woven steel fabric, compressed steel wool,expanded metal, etc.) and magnets capable of generating high-intensity fields,up to 20,000 gauss, in large spaces. The impurities are collected in thefilter by magnetic attraction as the feed stream passes through the unit. Whenthe magnet is turned off, the filter matrix may be washed clean.

Applications

Current applications include clay whitening (removal of a small, colored,magnetic fraction) and upgrading of low-grade iron ore. Applications currentlybeing investigated but not yet commercial include: beneficiation of otherores, coal desulfurization, removal of flue dust in air streams from blastfurnaces, and wastewater treatment (including municipal wastes and steel millwastewaters).

Reference

Kiang, Y.H. and Metry, A.A., Hazardous Waste Processing Technology: Ann ArborScience Publishers, Inc., Ann Arbor Michigan, 549 p.

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7a.3s ultrafiltration


Ultrafiltration is similar to reverse osmosis, but the separation begins athigher molecular weights. The result is that dissolved components with a lowmolecular weight will pass through the membrane with the bulk liquid while the , thigher molecular weight components become concentrated through the loss of *solvent. Ultrafiltration systems can handle much more corrosive fluids thanreverse-osmosis units. ~]

Applications

Ultrafiltration is used for electrocoat _ paint rejuvenation, rinse-water jrecovery, protein recovery from cheese whey, and metal machining oil emulsiontreatment, with capacity to handle _100 x 10 gal/yr for .each application.There are also smaller plants (on the order of 10 x 10 gal/yr) for treatmentof textile sizing waste and wash water from electronic component manufacturingand for production of sterile water for pharmaceutical manufacturing.

Kiang, Y.H. and Metry, A.A., Hazardous Waste Processing Technology: Ann ArborScience Publishers, Inc., Ann Arbor, Michigan, 549 p.


7a.3t zone refining


Zone refining is a fractional crystallization technique in which a rod ofimpure material is purified by heating so as to cause a molten zone to passalong its length. Basic equipment consists of a material support or ingotholder to contain the sample, a feed or travel mechanism, and a source ofheat. The process may include a cooling step.

Applications

Zone refining is applicable to solids, liquids, and slurries. Presently,however, it is only useful for processing small quantities (up to 10 kg) ofrelatively pure material. Processing rates arc <10 cm/hr. The process is notpractical for the complex mixtures that characterize most waste streams. Evenfor specialized applications, the process is only operationally feasible if thedistribution coefficients permit segregation of impurities.

Reference



7-29

7a.3u gamma-ray radiolysis


In this process, toxic organics are exposed to radiation from a gamma raysource after dissolving the organics in a suitable organic solvent.

Applications

Gamma ray radiolysis can be used to destroy toxic organics. It has been usedon a laboratory scale but has been proven inefficient and prohibitively costlyfor large-scale use.

7a.3v permeable treatment bed


Permeable treatment beds are essentially excavated trenches placedperpendicular to groundwater flow and filled with an appropriate material totreat the plume as it flows through the material. Some of the materials thatmay be used in the treatment bed are limestone, crushed shell, activatedcarbon, glauconitic green sands, and synthetic ion exchange resins. Permeabletreatment beds have the potential to reduce the quantities of contaminantspresent in leachate plumes. The system is applicable to relatively shallowgroundwater tables containing a plume. To date, the application of permeabletreatment beds at hazardous waste sites has not been performed.

Applications

A permeable treatment bed system is applicable to relatively shallowgroundwater tables containing a plume. To date, the application of permeabletreatment beds at hazardous waste sites has not been performed. However,bench- and pilot-scale testing has provided preliminary quantification oftreatment bed effectiveness. Potentially numerous problems exist in using apermeable treatment bed. These include the saturation of bed material,plugging of the bed with precipitates, and the short life of treatmentmaterials. Therefore, permeable treatment should probably be considered as atemporary remedial action rather than a permanent one.

Reference _ . _ = _ = = . -..-_,_..__-, . -



7-30

7b. Sludge/Solids Trgatment

7b,l biological treatment - Sec 7a.l

7b.la coinposting/land treatment


Land treatment involves the controlled application of a waste onto orincorporated into the soil surface. The objectives of land treatment are the "jbiological and chemical degradation of organic waste constituents and the _1immobilization of inorganic waste constituents. Land treatment also is adisposal process, because some of the original waste and certain waste '"]by-products remain at the site at closure.

Composting is essentially aerobic digestion of organics. It may take placewithin a structure (a silo or aerobic digestor), or it may be conducted on theland. Adequate mixing and aeration of waste is provided so that aerobicmicroorganisms perform decomposition on organics. When composting occurs onthe land, the soil houses the microorganisms and performs an added function of (adsorbing metals and refractory organics. Sequential mixing and turning of the jsoil mass maintains aerobic conditions.

Applications

When used for hazardous waste treatment, the basic philosophy of land treatmentis that it is a waste-management practice for wastes treatable in a soilsystem. Hazardous waste should not be placed in or on a land treatment siteunless the waste can be made less hazardous by the reactions occurring in or onthe soil.

Land treatment can result in the neutralization of wastes with high and low pHvalues and in the conversion of inorganic constituents to a less mobile ortoxic form. However, land treatment is best used for those wastes that arebiologically degraded or chemically stabilized. The greater the degree oftreatment a waste undergoes in a soil, the more acceptable the waste is forland treatment. A waste that contains components that are degraded,neutralized, made less mobile, and/or made less toxic in the soil is an idealcandidate for land treatment.

Although filtration and dilution occur when wastes arc land applied, suchmechanisms are not acceptable for the treatment of hazardous wastes if they arethe only or primary mechanisms that occur. Filtration and dilution providelittle net reduction of hazards if they do not alter the chemical state of thewaste.

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Composting requires long retention periods and limestone and nutrientaddition. Composting leachate requires biological treatment for decompositionof solvent organics. Composting has been applied to combinations of municipalrefuse, animal manure, vegetative matter, and sewage sludge. Petroleum wasteshave also been treated in this manner.

Reference


Martin, E.J. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Co. New York, N.Y., 520 p.

7b.lb membrane aerobic reactor system


A membrane of aerobic microorganisms Is used to prevent loss of cell mass and,thereby, provide high concentrations of ceils to destroy pollutants.

Applications

This system requires predeveloped microbes to be added. It has been provensuccessful for the treatment of paint sludges.

Reference


7b.lc fluidized bed bioreactor -(See 7a.lf)

7b.ld enzyme treatment - (See 7a.lg)

7b.2 chemical treatment: chemical dechlorination - (See 7a.2b.4)

7b.3 physical treatment - See 7a.3

7b.3a screens, hydraulic classifiers


Screens consist of bars, woven wire, or perforated plate surfaces which retainparticles of a desired size range while allowing smaller particles and thecarrying liquid to pass through the openings in the screening surface. Severaltypes of screens and sieves have application for solids separation at hazardouswaste sites.


7-32

Hydraulic classifiers are commonly used to separate sand and gravel fromslurries and classify them according to grain size. These units consist ofelevated rectangular tanks with v-shaped bottoms to collect the material.Discharge valves which are located along the bottom of the tank are activatedby motor-driven vanes that sense the level of solids as they accumulate. Theprincipal of operation is simple. The slurry is introduced into the feed endof the tank. As the slurry flows to the opposite end, solids settle outaccording to particle size as a result of differences in settling velocity.Coarse materials settle out first near the feed end and materials areprogressively finer along the length of the tank. Manually adjusted splitter |gates below the discharge valves can be used to selectively direct materials of -Ispecific grain sizes to subsequent handling and treatment.

1Application |

Hydraulic classifiers are used to remove sand and gravel size particles fromslurries and to classify the removed materials according to grain size.Materials arc recovered from the classifier at about 30 percent moisturecontent. They are capable of removing and classifying materials within thesize range of 3/8 inch down to about 150 to 200 mesh (105 to 74 microns). Theupper limitation of 3/8 inch is handled by prescreening the wastes to remove • Jall large materials. Other solids separation techniques are required toclassify the fine- grained materials (<200 mesh).

Reference


7b.3b dewatering/thickening


Volume reduction is one of the primary goals in sludge treatment. This isnormally achieved by reducing the water content of the sludge by variousmethods. Among these are centrifugation, gravity thickening, filtration,dewatering lagoons, evaporation, and several freezing technologies.

7b.3b.l ccntrifugation


Centrifugal dewatering uses the force developed by fast rotation of acylindrical drum or bowl to separate solids and liquids by density differencesunder the influence of centrifugal force. Dewatering is usually accomplishedusing solid bowl or basket centrifuges. Disc centrifuges are also availableand are mainly used for clarification and thickening.


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Applications

Centrifuges can be used to dewater material with grain sizes anywhere from siltto fine gravel. Solids concentrations achieved typically range from 15 to 40percent.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C. .

7b.3b.la solid bowl centrifuge


The solid bowl centrifuge consists of a long bowl, normally mountedhorizontally and tapered at one end. Sludge is introduced into the unitcontinuously, and the solids concentrate on the periphery. A helical scrollwithin the bowl, spinning at a slightly different speed, moves the accumulatedsludge towards the tapered end where additional solids concentration occursprior to discharging the solids.

Applications

The solid bowl centrifuge is better suited for large-scale dewateringoperations than other centrifuges, because it can handle a higher feed rate.It can also handle temporary increases in hydraulic loading or solidsconcentrations. This centrifuge dewaters more completely than the others.

Reference


7b.3b.Ib basket centrifuge


In the basket centrifuge, flow enters the machine at the bottom and is directedtoward the outer wall of the basket. Solids continually cake on the outer wallof the basket. A skimmer removes the liquid, and a knife removes the dewateredcake.

Applications

Basket centrifuges can handle hard-to-dewater sludges better and requires lessmaintenance than the others. It must, however, be operated on a batch basis.

Reference



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7b.3b.Ic disc centrifuge


In the disc centrifuge, the incoming stream is distributed between a multitudeof narrow channels formed by staked conical discs. Suspended particles haveonly a short distance to settle, so small and low density particles are readily • .collected and discharged continuously through fairly small orifices in the bowl "wall.

Applications ~ -»

The disc centrifuge has more limited application at hazardous waste sites than [ Ithe other types of centrifuges. Although it can yield a highly clarifiedccntrate even without the use of chemicals, the percent solids concentration islow, maintenance requirements are relatively high, and pretreatmentrequirements (grit and fibrous material removal) are extensive. The |clarification capability and throughput range are high, but sludge !concentration is limited by the necessity of discharging through orifices of0.05 inches to 0.1 inches in diameter. Therefore, the disc centrifuge isgenerally considered a thickener rather than a dewatering device.

7b.3b.2 gravity thickening

Description of TechnologyfFB1

design to a conventional clarifier. The slurry enters the thickener through a 'center feedwell designed to dissipate the velocity and stabilize the densitycurrents of the incoming stream. The feed sludge is allowed to thicken andcompact by gravity settling. A sludge blanket is maintained on the bottom tohelp concentrate the sludge. The clarified liquid overflows the tank and theunderflow solids are raked to the center of the tank and withdrawn by gravity j idischarge or pumping. Flocculants are often added to the feed stream to !enhance agglomeration of the solids and promote quicker or more effectivesettling. Tanks are usually constructed of concrete or steel.

Applications -J

Because gravity thickening typically achieves a solids concentration of only 2 1to 15 percent, thickeners are most often used to reduce a slurry's hydraulic [load before feeding it to a more efficient dewaterer. They also provide sludgestorage. Gravity thickeners are not applicable where space is restricted. i

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7b.3b.3 filtration


Filtration is a physical process whereby particles suspended in a fluid areseparated from it or sludges are dewatered by forcing the fluid or sludgethrough a porous medium or by simple compression.

Applications _ _ _

Filtration is applicable for a wide range of solids concentrations and particlesizes and is the most effective dewatering method.

Reference


7b.3b.3a belt press filter


Belt filter presses employ single or double moving belts to continuouslydewater sludges. The belt press filtration process includes three stages:chemical conditioning of the feed, gravity drainage to a nonfluid consistency,and dewatering. A flocculant is added prior to feeding the slurry to the beltpress. In the next step, free water drains from the conditioned sludge. Thesludge then enters a two-belt contact zone where the sludge cake is dewateredby compression.

Applications

Belt press filters use less energy than other filters, but they are verysensitive to feed characteristics and chemical conditioning. This method,then, is not applicable where sensing and prescreening devices are notavailable. Belt press filters can achieve 70 to 80 percent solids.

Reference _ _ _ _ _ _ _ _


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7b.3b.3b vacuum filter


A vacuum filter consists of a horizontal cylindrical drum which rotatespartially submerged in a vat of sludge. The drum is covered with a continuousbelt of fabric or wire mesh. A vacuum is applied to the inside of the drum bymeans of a connection within a central trunion. The vacuum causes liquid inthe vat to be forced through the filter medium leaving wet solids adhering to _the outer surface. As the drum continues to rotate, it passes from the cake Iforming zone to a drying zone, and finally to a cake discharge zone where the 'sludge cake is removed from the media.

Applications j

Vacuum filters are applicable when chemical conditioning is not optimal andwhen a higher hydraulic throughput is important. A vacuum filter'sdisadvantages include its energy inefficiency and its inefficiency as adewaterer compared to other filters. Also, vacuum filtration requires anincoming solids content of at least 3 percent. , i

Reference


7b.3b,3c pressure filter '!

Description of Technologyi

Pressure filtration is used to describe a category of filters in which rigidindividual filtration chambers are operated in parallel under relatively highpressure. The filter press, the most common representative of the group, •consists of vertical plates that are held rigidly in a frame and are pressed !together by a large screw jack or hydraulic cylinder. The liquid to befiltered caters the cavity formed by the frame. Pressed against this hollowframe are perforated metal plates covered with fabric filter medium. The plate Joperates on a cycle which includes filling, pressing, cake removal, media -*washing, and press closing.

Applications

Filter presses are the most effective dewaterers. They require more iconditioning chemicals and space and cost more to operate than other filtrationmethods, though, which limits their applicability.

Reference



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7b.3b.4 dewatering lagoons


Dewatering lagoons use a gravity- or vacuum-assisted underdrainage system toremove water. The base of the lagoon is lined with clay plus a synthetic lineror other appropriate liner material to prevent migration of contaminants intothe underlying soils and groundwater. At a minimum, the liner consists of alow permeability clay layer which is several feet thick. A combinationclay/synthetic liner and a secondary leachate collection system are required insome instances.

Applications

Dewatering lagoons are suitable for large-scale dewatering operations thatwould require many dewatering devices if another method was used. Lagoondewatering is one of the more effective methods but requires large areas andlong set-up times.

Reference


7b.3b.4a gravity underdrainage


This system consists of a filler material (well-graded sand or filter fabric)underlain by a porous free-draining gravel layer. Perforated drainage pipe isembedded in the gravel. The drainage pipe network is designed with flowgradients leading towards a central collection point or sump.

Applications

Gravity drainage . systems can achieve 99 percent solid removal .and a solidsconcentration of 35 to 40 percent after 10 to 15 days. They are the leastexpensive to operate but require more land than other methods, becausedewatering is slower.

7b.3b.4b vacuum pumping


Vacuum pumping systems can use either pumped wells or well points. Pumpedwells with large vacuum pumps may be installed directly in the waste material.Well points may be used, provided they are installed to the depth of anunderlying sand filter.


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Applications

Vacuum pumping can dewater faster and more effectively than gravity draining,but it is more expensive and requires more maintenance.

eference


7b.3b.4c vacuum-assisted drying beds -1

Description of Technology ! r

Vacuum-assisted drying beds use a porous media filter plate set above anaggregate-filled support plenum which drains to a sump. A relatively smallvacuum pump is connected to drain a vacuum from the sump. The vacuum isactivated when the volume of the slurry has been reduced by half due to gravitydrainage. The vacuum holds until the solids crack, allowing air through thebed.

Applications

Vacuum-assisted beds dewater 50 percent faster than gravity drainage systemsbut are more costly to operate and require more maintenance.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006, Washington, D.C - . _._ _

7b.3b.4d electroosmosis


This technique involves a process in which a direct current electricalpotential is set up in the soil by means of electrodes. This electric jpotential induces the flow of water in the pores of the fine-grained sediment -Ior sludge towards the negative pole, or cathode. A line of wells or wellpoints can be installed to intercept and remove the water. 1

Applications

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RElectroosmosis is a very costly technique which would be limited to dewateringof very fine-grained (2 to 10 microns), very hazardous, and difficult todewater solids.

Reference


7b.3b.5 freeze-drying


Freeze-drying is a process for subliming frozen water from a material underhigh vacuum. Basic equipment consists of a vacuum chamber, a vacuum source,and the appropriate refrigeration and heating equipment. Suitable feedsinclude wet solids, sludges, and slurries.

Applications

Freeze-drying has no apparent potential for treating hazardous industrialwastes. Although freeze-drying is used commercially for desiccating biologicaland sensitive materials, it does not appear adaptable to economical wasteprocessing on a large scale. The process is slow, costly, andenergy-intensive, with limited use for removing water. There are no knownapplications to waste treatment, and none are under development. ....__

Reference

Kiang, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers, Inc., Ann Arbor, Michigan 549 p.

7b.3b.6 suspension freezing


It has been shown that freezing a sludge causes the suspended solids toagglomerate and form relatively large floe particles. Upon thawing, these floeparticles settle and occupy significantly less volume than before freezing,leaving a clear supernatant. Filterability is increased. The conditioningeffect can be explained as the result of dehydration and pressure exerted onthe sludge particles by the ice structure, causing agglomeration anddensification.

Applications

No commercial suspension freezing or freeze dewatering applications exist.Freezing alum sludges typical of wastewater treatment plants has been thecenter of interest in the laboratory. Development of freezing for othermaterials has not been advanced.

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References

Kiang, Y.H. and Metry A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers, Inc., Ann Arbor, Michigan, 549 p.

7b.3b.7 evaporation


Evaporation is the phase change of a substance from a liquid to a gas. Natural Ievaporation uses solar energy or diffusion to vaporize liquids. Indirect -'evaporation is done in a system where a heating medium is separated from theliquid by physical barriers. Direct contact evaporation occurs where the )heating medium is in contact with the liquid. ,

Applications i

Evaporation is most widely used for separating water from inorganic solutionsand slurries, though it is also used for concentrating sludges containingorganic solvents. It is currently used in electroplating paper, andfermentation industries to concentrate waste solutions for recovery of valuable 'constituents. It can also be used to remove water from sludge to produceincinerable solids and to reduce slurry volumes prior to land disposal. Solarevaporation ponds are widely used for dewatering hazardous wastes prior to landdisposal.

Reference



7b.3c zone refining - See 7a.3t

7b.3d Solidification, Stabilization, Fixation


Solidification and stabilization are terms which are used to describe treatmentsystems which accomplish one or more of the following objectives:

o Improve waste handling or other physical characteristics of the waste

o Decrease the surface area across which transfer or loss of containedpollutants can occur

o Limit the solubility or toxicity of hazardous waste constituents.


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Applications

These processes are applicable wherever changing physical characteristics ofthe waste would make handling easier using the handling methods available.They can be used to limit a waste's solubility and toxicity, even if the wasteswill not be transported.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised):EPA/625/6-85/006a_ Washington, D.C.

7b.3d.l cement-based solidification (cement pozzolan)


This method involves mixing the wastes directly with Portland cement, a verycommon construction material. The waste is incorporated into the rigid matrixof the hardened concrete. Most solidification is done with Type I Portlandcement, but Types II and V can be used for sulfate or sulfite wastes. Thismethod physically or chemically solidifies the wastes, depending upon wastecharacteristics.

Applications

Cement solidification is not acceptable for organic or inorganic disposalwithout secondary containment. While cement physically bonds wastes, mostwastes are not chemically bound and are subject to leaching. Wastes that willinterfere with cement's set and cure include various salts, organics, somesilts and clays, and coal or lignite. Cement solidification doubles the weightand volume of the wastes, increasing the transportation and disposal costs.

References



7b.3d.2 silicate-based solidification

Description of TechnologyjSilicate-based processes refer to a very broad range ofsolidification/stabilization methods which use a siliceous material togetherwith lime, cement, gypsum, and other suitable setting agents.

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Applications

Silicates used together with lime, cement, or other setting agents canstabilize a wide range of materials including metals, waste oil, and solvents.The feasibility of using silicates for any application, however, must bedetermined on a site-specific basis, particularly in view of the large numberof additives and different sources of silicates which may be used. Solublesilicates, such as sodium and potassium silicate, are generally more effectivethan fly ash, blast furnace slag, etc. Materials such as sodium faorate,calcium sulfate, potassium dichromatc, and carbohydrates can interfere with the |formation of bonds between calcium silicate and aluminum hydrates. Oil and -1grease can also interfere with bonding by coating waste particles, but severaltypes of oily sludges have been stabilized with silicate-based processes. "]

One of the major limitations with silicate-based processes is that a largeamount of water which is not chemically bound will remain in the solid after _solidification. In open air, the liquid will leach until it comes to someequilibrium moisture content with the surrounding soil. Because of this waterloss, the solidified product is likely to require secondary containment.

Reference i


7b.3d.3 vitrification


Large electrodes are inserted into soils containing significant levels ofsilicates. Graphite on the soil surface connects the electrodes. A highcurrent of electricity passes through the electrodes and graphite. The heatcauses a melt that gradually works downward through the soil. Some contaminantorganics are volatilized and escape from the soil surface and may be collectedby a vacuum system. Inorganics and some organics are trapped in the melt thatcools to form obsidian or very strong glass.

Applications

This process is quite costly and so has been restricted to radioactive or veryhighly toxic wastes. To be considered for vitrification, the wastes should beeither stable or totally destroyed at the process temperature.

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Of all the common solidification methods, vitrification offers the greatestdegree of containment. Most resultant solids have an extremely low leachrate. Some glasses, such as borate-based glasses, have high leach rates andexhibit some water solubility. The high energy demand and requirements forspecialized equipment and trained personnel greatly limit the use of thismethod.

References



7b.3d.4 thermoplastic solidification


Thermoplastic solidification involves sealing wastes in a matrix such asasphalt bitumen, paraffin, or polyethylene. The waste is dried, heated, anddispensed through a heated plastic matrix. The mixture is then cooled to forma rigid, but deformable, solid. Bitumen solidification is the most widely usedof the thermoplastic techniques.

Applications ____

Thermoplastic solidification involving the use of an asphalt binder is mostsuitable for heavy metal or electroplating wastes. Relative to the cementsolidification, the increase in volume is significantly less, and the rate ofleaching is significantly lower. Also, thermoplastics are little affected byeither water or microbial attack.

Oxidizers, solvents, grease, xylenes, toluene, salts, cyanides, ammonium, andtetraborates are all incompatible with thermoplastic solidification.Containers are often necessary for transportation and disposal, because thewaste-matrix mixture is too plastic to support itself.

Reference



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7b.3d.5 organic polymer solidification


Organic polymer techniques were developed to solidify waste fortransportation. The polymer is generally formed in a batch process where thewet or dry wastes arc blended with a prepolymer in a waste receptacle (steeldrum) or in a specially designed mixer. When these two components arethoroughly mixed, a catalyst is added and mixing is continued until thecatalyst is thoroughly dispersed. Mixing is terminated before the polymer hasformed, and the resin-waste mixture is transferred to a waste container ifnecessary. The polymerized material does not chemically combine with thewaste; it forms a spongy mass that traps the solid particles. Any liquidassociated with the waste will remain after polymerization. The polymer massmust often be dried before disposal.

Applications

Organic polymer solidification is applicable to acid wastes, sut fates, halides,and radioactive materials. Organics, oxidizers, and heavy metals are often notcompatible with this solidification method. Like other techniques, organicpolymer solidification may result in a waste-matrix mass that requiressecondary containment.

Reference

Martin, E.J. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Co., New York, N.Y., 520 p.

7b.3d.6 self-cementing techniques


Some industrial wastes such as flue-gas cleaning or desulfurization sludgescontain large amounts of calcium sulfate and calcium sulfite. A technology hasbeen developed- to treat these types of wastes so that they becomeself-cementing. Usually a small portion (8-10% by weight) of the dewateredwaste sulfate/sulfite sludge is calcinated under carefully controlledconditions to produce a partially dehydrated cementitious calcium sulfate orsulfite. This calcinated waste is then reintroduced into the bulk of the wastesludge along with other proprietary additives. Fly ash is often added toadjust the moisture content. The finished product is a hard, plaster-likematerial with good handling characteristics and low permeability.

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Applications-

Self-cementing is applicable to sludges with a high calcium sulfate or calciumsulfite content. This technique can not be used for sludges containingorganics, as the result would be a fire hazard. Sludges containing oxidizers,halides, heavy metals, and radioactive materials could be solidified byself-cementing providing that sulfates are also present.

Reference


7b.3d.7 surface encapsulation


This treatment encapsulates large particles in an environmentally securebarrier using lime or cement pozzolan, thermoplastic, or organic polymer. Amatrix is formed from reactive components, but the waste is not uniformlydispersed. The product containing the waste is in nodule form.

Applications

Surface encapsulation can be applied to almost all wastes. Organic solventsand oils must first be absorbed on a solid matrix, and acid wastes should beneutralized before incorporation. Oxidizers sometimes deteriorate theencapsulating materials.

Encapsulation completely isolates the wastes from leaching solutions. Itallows for efficient space use, eliminates the danger of spills, and withstandsthe stresses of various disposal schemes.

References

Martin, E.J, and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Co., New York, N.Y., 520 p.


--- - - ; - '7b.3d.8 freezing (temporary immobilization)


Suspension freezing is a process in which the separation of suspended solids ina liquid can be aided by agglomeration of the solids by freezing. This processhas been demonstrated in a limited way in the dewatering of alum sludges.Natural freezing or freezing by refrigeration and subsequent thawing of sheet

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or bulk sludge can be used. Freezing the sludge causes the suspended particlesto agglomerate and form relatively large floe particles. Upon thawing, thesefloe particles separate rapidly leaving a clear supernatant and occupysignificantly less volume than before freezing. The solids then can beseparated by filtration or decantation and the residual water finally removedby natural drying or evaporation.

Applications

There are no practical permanent applications of freeze suspension. Freezingof hazardous waste streams is sometimes used as a temporary immobilizationmethod, often on an emergency basis.

Reference

Arthur D. Little, Inc., 1977, Physical, Chemical and Biological TreatmentTechniques for Industrial Wastes. Volume II: USEPA Contract No. 68-01-3554.

7b,3d.9 sorbents


Sorbents are natural and synthetic solid materials which eliminate freeliquid. Natural solvents include flyash, bentonite, vermiculite, and kilndust.

Applications

Sorbents are often used in spill clean-ups and the solidification of drummedmaterials. Sorbents are widely used to remove free liquid and improve wastehandling. Some sorbents have been used to limit the escape of volatile organiccompounds. They may also be useful in waste containment when they modify thechemical environment and maintain the pH and redox potential to limit thesolubility of wastes. Although sorbents prevent drainage of free water, theydo not necessarily prevent leaching of waste constituents, and secondarycontainment is generally required.

7b.4 water and sewer line treatment - (in-situ inspection and cleaning ofcontaminated water and sewer lines)


Hazardous substances can enter public water systems through a wide variety ofpathways, contaminating the components of the systems as well as the water.Once contaminated, water systems can serve as secondary sources ofcontamination, and the system's users can be exposed to hazardous substancesover long periods of time.

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Sanitary and storm sewers can become contaminated by infiltration of leachateor contaminated groundwater through cracks, ruptures, or poorly sealed jointsin piping and by direct discharges into the lines. Potable water supply mainscan become contaminated by contact with contaminated water that mayinadvertently flow through them or by infiltration of leachate or contaminatedgroundwater.

Water and sewer lines are generally inspected for groundwater leakage,structural defects, areas that need cleaning, and problems at points ofconnection. Inspection techniques include smoke testing, dye-water flooding,first-hand visual observation, and closed-circuit television visualobservation.

Cleaning lines improves flow conditions and capacity, allows more thoroughvisual inspections, and makes repair easier. Cleaning is done by mechanicalscouring, hydraulic scouring and flushing, bucket dredging, suction cleaningwith pumps or vacuum, chemical absorption, or a combination of these.

Applications

Pipeline inspection is applicable to all visually observable cases of pipelinecontamination or leakage of contaminated water. The methods are well-developedand accepted. Small diameter pipelines (less than 6 inches) cannot beinspected by closed-circuit television, and pipelines less than 48 inches indiameter cannot readily be inspected first-hand by workmen. Televisioninspection offers the advantages of worker safety and a permanent videotaperecord of the inspection. It is common practice to clean pipelines beforeinspection to insure visibility of defects and free access of workmen and/orequipment.

Reference


7c. Soils Treatment

7c.l biological treatment: bioreclamation - See 7a.lj

7c.2 chemical treatment - See 7a.2

7c.2a immobilization


Immobilization methods are designed to render contaminants insoluble, toprevent leaching of the contaminants from the soil matrix, and to prevent theirmovement from the area of contamination. Little is currently known about theeffectiveness and reliability of immobilization techniques.

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Applications

Immobilization can be effective for organics and inorganics, but itsreliability and effectiveness have not been demonstrated.

7c.2a.l precipitation


Precipitation is a well-known process in which the chemical equilibrium of awaste is changed to reduce the solubility of the contaminant. The contaminantsthen precipitate out of solution. The precipitate is removed by any one ofseveral methods. Precipitation is commonly used to treat heavymetals-containing wastes.

Applications

Precipitation is the most promising method for immobilizing dissolved metalssuch as lead, cadmium, zinc, and iron. Some forms of arsenic, chromium, andmercury and some organic fatty acids can also be treated by precipitation. Allof the divalent metal cations can be precipitated using sulfide, phosphate,hydroxide, or carbonate. However, the solubility product and the stability ofthe metal complexes vary. Because of the low solubility product of sulfidesand the stability of the metal sulfide over a broad pH range, sulfideprecipitation looks most promising. In-situ precipitation is most applicableto sites with sand or coarse silt strata. Factors that may effect thismethod's applicability include potential groundwater pollution, potential toxicgas formation (with sulfur treatment), potential soil pore clogging, andpotential precipitate resolubilization.

Reference


7c.2a.2 cheiation


Cheiation occurs when a ligand with more than one donor atom attaches to ametal ion often immobilizing it.

Applications

Chclating agents may be used in soil flushing to remove heavy metals from thesoil. The use of chelating agents may also be a very effective means ofimmobilizing metals. Depending upon the specific chelating agent, stable metalchelatcs may be highly mobile or may be strongly sorbed to the soil.

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Reference


7c.2b hydrogen peroxide oxidation - See 7a.2b.3a

7c.3 physical treatment - See 7a.3

7c.3a soil washing/soil flushing


Soil washing requires excavation and treatment of soils in a soil washer withan extractant solution. Soil flushing, on the other hand, is an in-situtreatment. In this process water or an aqueous extractant solution is injectedinto the area of contamination, and the contaminated elutriate is pumped to thesurface for removal, recirculation, or on-site treatment and reinjection.During washing or flushing, sorbed contaminants are mobilized into solution byreason of solubility, formation of an emulsion, or by chemical reaction withthe flushing solution. These extractant solutions may include water,surfactants, acids or bases, chelating agents, or oxidizing and reducingagents.

Applications

Soil washing and flushing can be used to extract inorganic or organic compoundsfrom soils; however, they have primarily been tested for extracting heavymetals. Soil flushing may be accomplished in conjunction with another in-situprocess, such as microbial degradation.

Reference


7c.3b air stripping - See 7a.3j

7c.3c supercritical extraction - See 7a.3m

7c.3d solidification, stabilization, fixation - See 7b.3d

7d. gaseous waste treatment (methods in addition to incineration)


Gaseous wastes may be present at hazardous waste sites as a result of bulk gasdisposal in containers, volatilization of organic liquids, by-products of wastedecomposition, or by-products of treatment or other on-site processes. Once

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captured and collected, gaseous wastes can be treated thermally to rendercontaminants less hazardous or treated physically or chemically to remove andconcentrate contaminants.

Applications

Gaseous wastes must be treated wherever they pose a health risk. Air qualitystandards must be reviewed to ensure that gas emissions are within allowedconcentrations. —

Reference -'

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised): ' ]EPA/625/6-85/006, Washington, D.C. ;

7d.l flaring


Flaring is a special category of combustion where wastes are exposed to an open ,flame and no special features arc employed to control temperatures or time of Icombustion. Supplementary fuels may be needed to sustain continuouscombustion.

Applications

Flares are commonly used in the oil and gas industry to dispose of waste gasesand fumes at refineries, at sewage treatment plants to dispose of digester gas,and at sanitary landfills to dispose of landfill gas. Although flares providesufficient destruction of contaminants for conventional applications,destruction removal efficiencies (DREs) required by current environmentalregulations for thermal destruction of hazardous wastes arc generally toostringent to be met by flaring. Exceptions may be gaseous waste streamsconsisting of relatively simple hydrocarbons (emissions from fuel tanks,landfill methane gas, etc.).

Supplemental fuel is required to sustain a flame with gases of low heatingvalue. Gases with heating values as low as the low hundreds of Btu's per cubicfoot can sustain a flame. (Natural gas has a heating value of approximately1,000 Btu's per cubic foot.).

Reference


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7d.2 adsorption


Adsorption is the adherence of one substance to the surface of another byphysical and chemical processes. Treatment of waste streams by adsorption isessentially a process of transferring and concentrating contaminants (theadsorbate) from one medium (liquid or gas) to another (the adsorbent).Adsorption gas treatment systems consist of containerized beds of adsorbentwhich the contaminated media pass through.

Applications

Adsorption is widely used in industry for air pollution and odor control, oftenin association with solvent recovery and reuse systems.

Reference


7d.2a activated carbon


Activated carbon is a highly porous material. Adsorption takes place on thewalls of the pores because of an imbalance of forces on the atoms of thewalls. The adsorption of molecules onto the wall surfaces serves to balancethe forces.

Applications

Carbon adsorption is generally accepted for use in controlling volatilehydrocarbons; organic-related emissions; certain sulfur-related emissions, suchas hydrogen-sulfide; mercury; vinyl chloride; most haiogenated organics; andradioactive materials, such as iodine, krypton, and xenon. Carbon adsorptioncan also control oxides of sulfur and nitrogen and carbon monoxide. Generally,GAC acts as an accumulator of organic contaminants until the bed is saturated.Hot gases are passed through the bed to desorb the organics which are condensedand recovered or are incinerated.

Reference

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised);EPA/625/6-85/006, Washington, D.C.

s

7d.2b resin


Resins adsorb contaminants in a way similar to that of activated carbon.

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Applications

Resins are capable of removing most organic contaminants from water and arealso applicable to removal of organics from gaseous streams. However, resinsarc not widely used for gaseous waste treatment.

Reference


7d.3 afterburners


Afterburners are simple combustors employed to destroy (by oxidation) gaseoushydrocarbons not destroyed in the primary incinerator chamber.

Applications

In well-designed and well-operated incinerators incomplete combustion productsare emitted :n insignificant amounts. The primary overall end products ofcombustion are, in most cases, carbon dioxide and water vapor. Afterburnersshould be used whenever products other than carbon dioxide and water areproduced. The incineration of chlorinated hydrocarbons, organic fluorides,organic bromides, sulfur, organophosphorous compounds, or nitrogen compoundsrequires an afterburner.

Reference

Martin, E.J. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Co., New York, N.Y. 520 p.

7d.3a direct flame afterburner


In a direct flame afterburner, a high percentage of the vapors pass directlythrough the flame in a direct flame unit.

Applications

Direct flame afterburners are used where the gaseous wastes are easilycombusted.

Reference


DUNN GEOSCIENCE CORPORATION m n ri n+* r t t+An302618

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7d.3b thermal afterburner


In a thermal unit, the vapors remain in a high temperature oxidizing atmospherelong enough for oxidation reactions to take place.

Applications

Thermal afterburners are usually an integral part of rotary kilns used inhazardous waste incinerators. Thermal afterburners are also used with liquidinjection incinerators in a few instances, with pyrolysis units when chemicalsare not being recycled, and with co-incineration units where the incineratorused normally requires an afterburner. Catalytic afterburners are a proventechnology not yet used extensively on hazardous waste incinerators.

Temperatures ranging from 650 to 1300°C are generally required tosuccessfully operate these devices. Hydrocarbon levels can usually besatisfactorily reduced at temperatures of 760°C, but higher temperatures maybe required to oxidize carbon monoxide.

Reference


7d.3c catalytic afterburner


Catalytic devices incorporate a catalytic surface to accelerate the oxidationreactions.

Applications

Catalytic afterburners are used to destroy combustible materials in lowconcentrations but are readily poisoned by chlorinated hydrocarbons due to theformation of corrosive HC1. Usually, noble metals such as platinum andpalladium are the catalytic agents.

The catalyst must be supported in the hot waste gas stream in a manner thatwill expose the greatest surface area to the waste gas so that the combustionreaction can occur on the surface, producing non-toxic effluent gases of carbondioxide, nitrogen, and water vapor. Most of the combustion occurs during flowthrough the catalyst bed, which operates at maximum temperatures of810-870°C. Catalytic incinerators carry out combustion at relatively lowtemperatures while achieving high destruction efficiencies.

Reference


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7e. thermal destruction


Thermal destruction is the high temperature conversion of a waste to a lessbulky, less toxic, or less noxious material. It can be used to destroy organiccontaminants in liquid, gaseous, and solid waste streams. - .

Applications -.

Thermal destruction is primarily used to destroy liquid, gaseous, and solid *organic hazardous wastes but can also be used to greatly reduce the volume ofother wastes, thus reducing health and environmental hazards and the need for r ]new landfill capacity. I

Reference ii


7e.l incineration I


Incineration is a thermal destruction method using high-temperature oxidation.The principal products of incineration arc carbon dioxide, water vapor, and ,:!,ash. The hazardous products of incineration are compounds containing sulfur, i'Jnitrogen, halogens, and heavy metals (mercury, arsenic, selenium, lead, andcadmium).

Applications I

Incineration is most useful for purely organic wastes. If the peripherals ; jrequired to destroy hazardous incineration products are available, incineration | jcan be used for numerous waste types. Incineration is applicable for liquid,gaseous, and solid waste streams. -,

Reference *

Kiang, Y.H. and Metry, A.A., Hazardous Waste Processing Technology: Ann Arbor 1Science Publishers, Inc., Ann Arbor, Michigan, 549 p. ;

7c.la molten glass incinerator i


Molten glass is a heat transfer mechanism used to destroy organics and tocapture ash and inorganics. Acid gas and particulates are emitted; the glasscontains and stabilizes the residue.


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Applications :

Molten glass incineration can be used to treat most solid or liquid wastes. Itis, however, inappropriate for soils or high ash waste, and off-gas requiresadditional treatment. If sodium sulfates exceed 1 percent of the final glass,subsequent treatment may be necessary.

Reference


7e.lb molten salt incinerator


In molten salt incineration, wastes and air are injected beneath the surface ofa molten salt bath composed of sodium carbonate (90%) and sodium sulfates(10%). Incineration reduces hydrocarbons to carbon dioxide and water vapor-The hot gases rise through the salt which acts as a scrubber to remove any acidgas emissions. The gases then pass through a secondary reaction zone and theoff-gas clean-up system and are discharged. Inorganics are stabilized as newcompounds in the salt. The solid residue is composed of salt and ash.

Applications

Molten salt incineration can destroy hazardous liquids and solids. It is bestsuited to treat wastes with low ash and water contents. The salt bed canentrap heavy metals and neutralize acid in the off-gas and reduce or eliminatethe need for pollution control equipment. The salt and residue can typicallybe disposed without further treatment.

Reference

Kiang, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers Inc., Ann Arbor, Michigan, 549 p.

7e.lc rotary kiln


The rotary kiln incinerator is a cylindrical, refractory-lined shell mountedwith its axis at a slight slope from the horizontal. It can be fueled bynatural gas, oil, or pulverized coal. The kilns usually are very long, so thecombustion zone occupies a small portion of the incinerator. Most of theheating of the waste is heat transfer with the combustion product gases and thewalls of the kiln.


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Wastes are injected into the kiln at the higher end and are passed through thecombustion zone as the kiln rotates. The rotation creates turbulence andimproves combustion. Rotary kilns often employ afterburners to ensure completecombustion. Most rotary kilns are equipped with wet scrubber emissioncontrols.

Applications

Rotary kilns are capable of burning waste in any physical form. They canincinerate solids and liquids independently or in combination and can acceptwaste feed without any preparation. Hazardous wastes which have been treatedin rotary kilns include PCBs, tars, obsolete munitions, poly vinyl chloridewastes, and bottoms from solvent reclamation operations. Incineration inrotary kilns is the preferred treatment for mixed hazardous solids, but kilnsrequire careful maintenance.

Reference


7e.ld industrial kiln


A kiln is an inclined, elongated, 60 to 760-foot, steel cylinder lined withrefractory brick. Kilns provide high temperatures, long residence times, andstrong turbulence that destroy and assimilate some of the most unstable andtoxic wastes. Raw materials enter the kiln at the raised end and move down theincline as the combustion gases produced by burning fuel heat them.

Applications

Cement and other industrial kilns are considered to be a promising disposaloption for many organic wastes. They are considered especially applicable forincinerating chlorinated wastes since the hydrochloric acid produced serves toneutralize the typically alkaline clinker production process. It has beendetermined that hard-to-burn wastes, such as PCBs, can be successfullycombusted in cement kilns. Less hazardous chemicals, such as • waste solventsand still bottoms from solvent reclaiming operations, are already beingpurchased by cement companies and burned on a continuous basis in cement kilns.

Reference

Freeman, H.M., Olexsey, R.A., Oberacker, D.A., and Mournighan, R.E., 1986,Thermal Destruction of Hazardous Waste-A State-of-thc-Art Review:' ElsevierScience Publishers B.V., Amsterdam, the Netherlands, 15 p.

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7e.le fluidized bed incinerator


The fluidized bed incinerator consists of a cylindrical, vertical,refractory-lined vessel containing a bed of inert, granular material, usuallysand, on a perforated metal plate. Combustion air is introduced through aplenum at the bottom of the incinerator and rises vertically, fluidizing thebed and maintaining turbulent mixing of bed particles. Waste material isinjected into the bed, and combustion occurs within the bubbling bed. Heat istransferred from the bed into the injected wastes. Auxiliary fuel is usuallyinjected into the bed. Bed temperatures vary from 1400 to 1600°F. Since themass of the heated, turbulent bed is much greater than the mass of the waste,heat is rapidly transferred to the waste materials; a residence time of a fewseconds for gases and a few minutes for liquids is sufficient for combustion.The residence time is long enough to allow the solid materials to become smalland light enough to be carried off as particulates. Suspended fineparticulates are usually separated in a cyclone when exhaust gases pass throughair pollution control devices before being released into the atmosphere.

Applications

Fluidized bed incinerators are typically used for the disposal of municipalwastewater treatment plant sludges, oil refinery waste, and pulp and paper millwaste. Fluidized beds are particularly well-suited for the incineration ofslurries, sludges, and wastes with a high ash content Some wastes requirepretreatments, such as drying, shredding, and sorting. Exhaust gases are lowin nitrogen oxides, and the bed traps some gases. This reduces the need for apollution control system.

Reference


7e.lf circulating bed incinerator


The circulating bed combustion process is an extension of the fluidized bedtechnology. Unlike a conventional fluidized bed which has a fixed bed depth,high velocity air introduced at the bottom of the refractory-lined combustionchamber circulates the bed throughout the system. This results in entrainmentof wastes and subsequent combustion along the entire height of the combustionsection. Complete destruction can be attained at relatively low temperaturesbecause of this high degree of turbulence. Off-gases pass through a cyclonewhich captures and recycles solids and limestone bed material to the combustionzone through a nonmechanical seal. The combustion gases pass through a heatrecovery sysKem and baghouse filter prior to discharge to a stack. Use of alimestone bed reduces the need for acid gas scrubbing.

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Applications

Circulating bed incinerators can be used to burn organic solids, sludges,slurries, and liquids. Favorable wastes have a heat content greater than 6000Btu/lb and solids less than 1 inch in diameter.

This technology is presently used only at a pilot scale. No commercial-scalefacilities exist, so the application is still considered conceptual.

Reference

CDM, 1986, Capacity and Capability of Alternatives to Land Disposal forSuperfund Wastes; Mobile Treatment Technologies: USEPA Contract No. 68-01-7053

7e.lg multiple hearth incinerator


The multiple hearth incinerator is a cylindrical, steel shell lined withrefractory material. This refractory-lined chamber is divided into smallerzones, " or hearths, which are created by self-supporting refractor arches.Waste is introduced through the top of the furnace. The waste is moved byrabble teeth attached to arms and a vertically-positioned central shaft whichrotates and plows the waste either inward or outward across the hearth floor tothe drop opening where it falls to the next hearth. Ultimately, there is oneperipheral opening at the bottom which connects to the ash removal system.Auxilliary fuel burners are mounted on the furnace walls, and air is introducedthrough the walls.

Applications

The multiple hearth incinerator can be used for the disposal of all forms ofcombustible industrial waste materials, including sludges, tars, solids,liquids, and gases. The incinerator is best suited for hazardous sludgedestruction. Solid waste often requires pretreatment, such as shredding andsorting. The multiple hearth incinerator can treat the same wastes as therotary kiln provided that solid wastes are pretreated. The principaladvantages of multiple hearth incineration include high residence time forsludge and low-volatile materials, ability to handle a variety of sludges,ability to evaporate large amounts of water, high fuel efficiency, andutilization of a variety of fuels. The greatest disadvantages of thetechnology include susceptibility to thermal shock; inability to handle wastescontaining ash, which fuses into large rock-like structures; and wastesrequiring very high temperatures. Also, control of the firing of supplementalfuels is difficult.


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References



7e.lh liquid injection incinerator


A liquid injection incinerator consists of a refractory-lined combustionchamber and a series of atomizing devices, typically rotary cup or pressurenozzles. These devices introduce waste material into the combustion chamber invarious droplet sizes to mix with air. Following combustion, the resultinggases are cooled and treated with air pollution control devices to removeparticulates and to neutralize acid gases. Complete combustion requiresadequate atomization of the waste to provide for efficient mixing with theoxygen source. Therefore, pretreatment, such as blending, may be required forwastes that pose potential atomization problems.

Applications

Liquid injection can be used to destroy virtually any pumpable waste or gas.These units have been used in the destruction of PCBs, solvents, still andreactor bottoms, polymer wastes, and pesticides. Unlikely candidates fordestruction include heavy metal wastes and other wastes high in inorganics. Itdoes not have a need for a continuous ash removal system other than forpollution control.

Liquid incinerators have no moving parts and require the least maintenance ofall types of incinerators. The major limitations of liquid injection are itsability to incinerate only wastes which can be atomized in the burner nozzleand the burner's susceptibility to clogging. It also needs a supplementalfuel. Storage and mixing tanks are required to ensure a steady and homogeneouswaste flow.

References




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7e.Ii fume incinerator


Fume incinerators are similar to liquid injection incinerators in basicprinciples. The only difference is that in the waste injection method, fumesdo not require atomization. Rich fumes (high Btu content fumes) are normallyused in the burner as fuel while dilute fumes are directly introduced into thesecond chamber.

Applications

Fume incinerators can be used to destroy any combustible waste, but a mixingand storage system is necessary to keep composition and flow rate variations ata minimum. Incineration temperature, residence time, and excess air rate mustalso be carefully controlled to insure combustion efficiency.

Reference


7e.lj multiple-chamber incinerator


The combustion process in a multiple-chamber incinerator proceeds in twostages: primary or solid fuel combustion in the ignition chamber, followed bysecondary or gaseous-phase combustion. The secondary combustion zone iscomposed of two parts, a downdraft or mixing chamber and an up-pass expansion jor combustion chamber. j

Applications

Generally, multiple-chamber incinerators are used for solid wastes. Flowablematerials, such as sludges, liquids, and gases, can be used in a multiplechamber incinerator only if a proper burner is used. I

Multiple-chamber incinerators are usually batch-fed. For wastes with a highvolatile content, smaller batches are necessary. ]

Reference


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7e.lk cyclonic incinerator


A cyclonic incinerator is a cylindrical, refractory-lined furnace. Air wastesand fuel are injected through the furnace walls. The result is a cylinder offlame which spirals out of the furnace.

Applications

The cyclonic incinerator can handle gaseous, liquid, and sludge wastes. Theair injection method makes it a staged combustion chamber, that is, the frontend of the incinerator operates fuel-rich and the exhaust end operatesfuel-lean. This feature makes it especially adaptable to wastes containingnitrogen for nitrogen oxide control.

Reference


7e.ll auger combustor incinerator


An auger combustor incinerator uses starved air combustion to partially combustsolid waste that the auger mixes and moves through the primary chamber. Anafterburner completes the combustion of any combustible gases.

Applications

The auger combustor system can be used to dispose of sludge and shredded solidwastes. At the present time, the auger combustor system is used primarily fordisposal of municipal solid waste and recovery of waste energy. However, itsdesign does offer potential for use in the processing of hazardous wastes.

Reference


7e.lm ship-mounted incinerator/ocean incineration


A ship-mounted incinerator is usually a liquid injection unit without airpollution control equipment that destroys hazardous waste far away frompopulated areas. Tests show that ocean incineration is nearly 100% efficient.

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Applications

Ship-mounted incineration presents an attractive alternative to land-basedincineration and is encouraged by the U.S. Environmental Protection Agency as ameans of disposal of toxic substances which could not be disposed of on landdue to public resistance. Questions remaining unanswered about at-seaincineration include: the long-term impact on marine life, the safety and • .health of crew members, and the effect of hydrochloric acid discharge into theatmosphere.

Reference '/

Kiang, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: Ann I'|Arbor Science Publishers, Inc., Ann Arbor, Michigan, 549 p. '• \

7e.ln catalytic incineration


Catalytic incineration uses catalysts to increase the oxidation rate of thewastes, thus requiring a lower oxidation temperature than thermal incinerationto produce the same products and to liberate the same heat of combustion.

Applications

Catalytic incineration applications are primarily in the waste gas treatment.There arc catalytic systems developed for chlorinated liquid waste treatment;however, this type of system has very limited applications. The fouling ofcatalyst is a major concern in the application of catalytic incineration andhas to be studied before the selection of catalytic systems.

Reference

Kiang, Y.H,, and Metry, A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers, Inc., Ann Arbor, Michigan, 549 p.

7e.lo oxygen incineration


Oxygen incineration uses oxygen, instead of air, as an oxidant. It is a highertemperature process than thermal oxidation, making it more efficient. Also,the unit is more compact than thermal incinerators.

Applications

Oxygen incineration is not widely used, as it is relatively new and expensive.It should be used when wastes destruction requires temperatures around5000°F. High temperature materials for the furnace must be available foroxygen incineration.

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7e.lp infrared incineration


Infrared incineration uses pyrolysis and subsequent oxidation fueled byinfrared energy to destroy hazardous waste. Wastes are conveyed under infraredheating elements. The ashes fall into a hopper for disposal, and off-gases aresent to a burner for complete combustion and emission through air pollutioncontrol equipment.

Applications

Infrared incineration is primarily used to treat solids, sludges, andcontaminated soils. Liquid and gaseous injection systems are available. Thisprocess has low particulate and gas emissions and allows a high degree ofcontrol. It is well-suited for materials that need long residence times to becompletely destroyed. *""*

Reference


7e.lq open pit incineration


Open-pit incineration is the burning of waste materials on open land withoutthe use of combustion equipment.

Applications

Open-pit incineration is suited for materials that__ could _explode in a closedincinerator and oversized wastes and plastics that are hard to handle inconventional incinerators. Pit incinerators are most efficient for solidwastes, especially rubber and plastic. This form of incineration is utilizedmainly for the disposal of waste explosives. It is generally unacceptable forthe disposal of other forms of waste because of the associated lack ofcombustion product effluent control. According to federal regulations,hazardous wastes, other than explosive military-type wastes, can not be burnedopenly.

Reference



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7e.lr sulfur regeneration


A sulfuric acid regeneration unit is used to combust high sulfur refinerywaste. Sulfur is recovered from the combustion gases using a doublecontact-double absorption sulfuric acid plant.

Applications

Sulfur regeneration can destroy hazardous waste with high sulfur content. Itis particularly applicable to high sulfur, high Btu refinery wastes.

Reference


7e.ls fuel blending/cotncineration


Fuel blending is a method to reuse waste organics as fuel substitutes. Theobjective is the controlled blending of segregated wastes of knowncharacteristics into a fuel product whose chemical and physical characteristicsmeet the fuel specifications of the fuel user.

Applications

Waste oils, solvents, and organic sludges can be combined to produce a fuel ofgreater than 10,000 Btu/lb. Chlorine wastes cannot be used, and water andsolid content cannot be high. Certain hazardous constituents, such as PCBs,and corrosive wastes should not be used in fuel blending.

Reference


7c. 11 boilers


Boilers can be used to destroy solvent waste by using the waste as a supplementto fossil fuel. The process usually consists of blending the waste materialwith fuel and Injecting the mixture into the modified boiler burner.

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Applications

Alcohols, spent nonhalogenated solvents, and highly volatile by-products can beburned in boilers. For the smaller boilers with only one burner, theconventional practice is to premix the primary fuel (oil) and the wastematerial in a tank prior to introduction into the firebox. For larger boilerswith multiple burners, one or more burner is dedicated to waste introductionwith the remaining burners fired with primary fuel and used for leveling.

Waste may constitute over 50 percent of the fuel to the boiler for particularlyclean, high energy value wastes. However, generally, the waste feed rate isbelow 20 percent of the total fuel to the boiler. For difficult-to-burn wastesand particularly for corrosive, halogenated wastes, feed concentrations below 5percent (on a volume basis) are most common.

Reference

Freeman, H.M., Olexsey, R.A., Oberacker, D.A., and Mournighan, R.E,, 1986,Thermal Destruction of Hazardous Waste—A State-of-the-Art Review: ElsevierScience Publishers B.V., Amsterdam, The Netherlands, 15 p.

ICF Consulting Associates, Inc., 1986, Guide to Solvent Waste ReductionAlternatives: prepared for the Alternative Technology and Policy DevelopmentSection of the California Department of Health Services.

7e.lu blast furnaces


High heat content hazardous wastes can be used to supplement coke and otherfuel requirements for blast furnaces. A blast furnace produces molten ironfrom iron ore and other iron- bearing feed materials.

Applications

Blast furnaces can use only high-heat-content hazardous wastes. The hazardouswaste's trace element composition must be controlled to avoid product qualityproblems.

Reference


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7e,2 pyrolysis


Pyrolysis is generally defined as the thermal decomposition of a compound inthe absence of oxygen. The heart of the pyrolytic waste-conversion process isthe pyrolytic converter. The unit consists of a sealed, air-tight, rotarycylinder inside a heavy, insulating jacket. The gas-dried rotary revolvesslowly on a slight decline from infeed to outfeed. Wastes are injected througha seal area that intermittently opens. A flapper valve seal minimizes oxygen Ientry. -•*

Applications H

Pyrolysis of hazardous wastes is relatively new. It is expected to be limitedto those wastes for which the pyrolyzed product, gas or char, does not containtoxic or hazardous substances. Also, pyrolysis is not very effective onsludge-like or caking material.

Reference " [


7e.2a plasma arc pyrolysis


The principle of plasma arc technology involves breaking the bonds betweenorganic constituents. This is accomplished in an atomization zone whereco-linear electrodes generate a plasma or electric arc which is stabilized byfield coil magnets. As low pressure air passes the arc, the electrical energyis converted to thermal energy by the activation of air molecules into theirionized atomic states. When the excited atoms and molecules relax to lowerenergy states, intense ultraviolet light is emitted. The energy from thedecaying plasma.. Is transferred to the passing waste materials, reducing them totheir elemental constituents. An equilibrium zone is provided for thecontrolled cooling and recombination of the atomic species to form simplemolecules.

Applications

This process can be applied to liquids and sludges that can be fluidized byadding a liquid. Favorable wastes include liquids with a high chlorinecontent.

The advantages of plasma arc pyrolysis include the lack of hazardous combustionproducts, the production of fuel gases, portability, and high efficiency.

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Reference



7e.2b high temperature electric reactor


This process utilizes a vertical reactor heated by electrodes implanted in thewalls to pyrolize organic wastes. The reactor has a core enclosed by porousrefractory material. Carbon electrodes implanted in the wall of the reactorheat the reactor core to radiant temperatures. Heat transfer is accomplishedby radiation coupling from the core by means of a gaseous blanket formed byflowing nitrogen through the walls of the core. In the process, organiccompounds are rapidly heated to temperatures in the range of 3800-4400°F(2090-2430°C) and destroyed.

Applications

The process is designed to pyrolize organics attached to particulates, such ascarbon black or soil. However, the developer claims that recent tests haveshown the process is also effective for liquid refractory waste streams, such

[~ as carbon tetrachloride.

The unit will process from 75 to 125 pounds (34-57 kg) of contaminated solidsper minute. Hard numbers are not available for pure liquids; however, capacitywould be less.

Reference

Freeman, H.M., Olexsey, R.A., Oberacker, D.A., and Mournighan, R.E., 1986,Thermal Destruction of Hazarous Waste-A State-of-the-Art Review: Elsevier

[" Science Publishers B.V., Amsterdam, The Netherlands, 15 p.

7e.2c high temperature fluid wall reactor*


The high temperature fluid wall process quickly reduces organic wastes to theirelemental state in a very high temperature process (about 4000°F). Theprocess is carried out in a patented reactor which consists of a tubular coreof refractor material capable of emitting radiant energy supplied by largeelectrodes in the jacket of the vessel. During the process, an inert gas isinjected to coat the wall of the reactor to prevent destruction from hightemperatures.

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Applications

The high temperature fluid wall process has been used to treat PCB-contaminatedsoils and other wastes. It is highly efficient and eliminates the formation ofintermediate pyrolysis products, but it requires some preparation of the feedand is energy intensive.

Reference


7e,3 starved air combustion


Starved air combustion utilizes equipment and process flows similar to thosefor incineration, but in this process, less than the theoretical amount of airfor complete combustion is supplied. Because the process is neither purelypyrolytic nor purely oxidative, it is called starved air combustion or thermalgasification rather than pyrolysis or incineration. An auxiliary fuel may berequired, depending on the proportion of volatiles in the solids. Hightemperatures decompose and vaporize the waste. The gas-phase reactions arcpyrolytic or oxidative, depending on the concentration of oxygen remaining inthe stream. Under proper control, the gas leaving the vessel is low-Btu gas(up to 130 Btu/ft3) that can be burned in an afterburner, a boiler, oranother furnace. Some processes utilize pure oxygen instead of air and, thus,produce a high-Btu fuel gas. The solid residue is a char with more or lessresidual carbon, depending on how much combustion air has to be supplied toreach the proper operating temperatures. Pollution equipment normallyassociated with the starved air combustion process includes exhaust gasscrubbers and afterburners.

Applications

This process has not been proven with hazardous waste.

Reference

Martin, E.J. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhoid Co., New York, N.Y., 520 p.

7c.4 calcination


Calcination is the conversion by thermal decomposition, at elevatedtemperatures, of aqueous liquids and sludges into solid materials, without any

j

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interaction with the gaseous phase (such as the air oxidation which occursduring incineration). Evaporation, dewatering, and volatilization can all bepart of calcination.

Applications

Calcination processes have been used in the recalcination of lime sludges fromwater treatment plants; coking- of heavy residues and tars from petroleumrefining operations; concentration and volume reduction of liquid radioactivewastes; and treatment of mixed refinery sludges containing hydrocarbons,phosphates and compounds of Ca, Mg, K, Na, S, Fe, and Al.

In general, calcination systems require fairly extensive air pollution controlequipment including particulate-removal devices, wet scrubbers, and possiblyfinal gas adsorption systems

Reference


7e.5 sintering


Sintering can be defined as a limited form of calcination in which the physicalstructure, but not the chemical nature, of the solid is changed. This processsometimes results in volume reduction.

Applications

Sintering can be used to reduce a waste's volume and improve its handling.


7e.6 radio frequency (RF) heating


The frequencies of interest for in-situ soil heating are between 2 to 45 Mhz,In this frequency range dipole molecules absorb electromagnetic (EM) energywhich appears as heat due to dipole rotation and molecular vibration. Theabsorption of EM energy and conversion to heat occurs throughout the volume ofthe material and is not dependent on the slow process of thermal conduction.The amount of energy dissipated in the heated soil is proportional to thedielectric constant, loss tangent, frequency and field strength of the applied

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electromagnetic energy. The penetration depth of the applied fields isinversely related to frequency and the conductivity of the soil. Thus, for anygiven soil, a frequency may be selected to provide the required penetrationdepth. Penetration of EM energy to a depth of a few to 10 meters can betypically achieved.

Application .jThere are certain sites in the country which contain the lighter chlorinated ._hydrocarbons and aromatic compounds such as tetrachloroethylene, Itrichloroethylene, trichloroethane, chlorobenzene, benzene, toluene, etc. - *These chemicals have relatively high vapor pressure (all boil in the range of74 to I35°C) and can be easily vaporized and recovered from the soil. For ' jsuch chemical contaminants, simple heating should be applicable. Soil |containing high molecular weight polycyclic aromatic hydrocarbons such as PCBs,dioxins, etc, will be more difficult to treat by the thermal mechanisms. This iis due to their high boiling points, low vapor pressure at intermediatetemperatures, and thermal stability. For such chemical contaminants, a priorreaction with a reagent for the removal of the organically bound chlorineappears to be attractive. In-situ application and heating of soil withreagents such as alkoxidcs of polyethylene glycol is one way of treating PCB Iand dioxin contaminants.

Reference

Dev, H. and Condorelli, P., 1986, In Situ Radio Frequency Heating Process forDecontamination of Soil: Presented before the Division of EnvironmentalChemistry, American Chemical Society, New York, NY, Preprint of Abstract.

7e.7 wet oxidation - see 7a.2b.3d and 7a.2b.3e

7f. thermal destruction peripheral systems


Modern incineration systems include not only incinerators for waste disposal,but also energy and by-product recovery systems, as well as air and waterpollution control systems. These peripheral systems are now designed as anintegrated part of incineration systems. Applications are dependent on thesystem and incinerator in question.

Reference


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7f.l heat recovery systems


Incineration is an energy-intensive process in which an appreciable amount ofwaste heat is generated. There are two different approaches in heat recovery.For both rich wastes (wastes that, alone, can be burned like fuel) and leanwastes (wastes that require additional fuel to maintain the incinerationtemperature), heat can be recovered for process plant use. For lean wastes,heat also can be conserved by reducing the fuel required for incineration.

Applications

Because heat is a by-product of incineration, this kinetic energy form can beused for hot water heating, process fluid heating, steam generation, airheating, process gas heating, heat transfer oil heating, and cryogenic fluidvaporization.

Reference


7f.2 by-product recovery


Incineration of some wastes produces usable by-products; technology is nowallowing for the recovery of some of these.

Application

By-product recovery should be practiced whenever the by-products are dangerousto the environment and when recovery of usable by-products is economical.

7f.2a acid recovery


Incineration of various compounds produces commercially usable acids, includinghydrochloric acid, hydrobromic acid, and phosphoric acid. If the acid is in agaseous state, an absorption tower is typically used for acid recovery. Aventuri scrubber can often recover acid in a mist or solid form.

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Applications

Whenever chlorinated hydrocarbons arc incinerated, HCl is emitted as aby-product and can be recovered. Because of the heat content in theincinerator flue gases, it is difficult to recover hydrochloric acid at aconcentration greater than the azeotropic mixture (20% by weight of hydrogenchloride).

Reference


7f.2b salt and metal recovery


Salts and metals can be recovered using evaporators, condensers, scrubbers,towers, and similar equipment.

Applications

This is especially suited as a catalyst recovery method. Organic-contaminatedcatalysts can be combusted in the incinerator; the catalysts, in either elementor oxide form, can then be recovered.

Reference


7f.3 air pollution control


Air pollutants from hazardous waste incinerators include the products ofincomplete combustion of organic constituents and inorganic air pollutants.Gas and particulate pollution control should be part of every wasteincineration system.

7f.3a gaseous pollutant removal systems


Mass transfer devices for gas absorption are used to remove gaseous pollutantsfrom incinerator flue gases.

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7f.3a.l wet spray towers


A spray tower is a vertical chamber in which a scrubbing liquid is atomized byhigh pressure nozzles. Gas passes through the liquid in a countercurrent,cocurrent, or cross flow direction. Gas adsorption by the liquid is increasedby the increased surface area and the increased liquid-to-gas ratio.

Applications

Because of the simple design, wet spray towers are not engineering intensive.Gas absorption and dust removal occur in one step. This process is suitablefor high-temperature, high-moisture, and high-dust loading applications. Theinherent disadvantages are that particulates are collected wet, the spraynozzles are susceptible to plugging, the structure is large and bulky, andoperating at high efficiencies may require pump-discharge pressures. Theparticulate collection efficiency is not as good as a venturi scrubber, andpacked towers have higher absorption efficiencies.

Reference


7f.3a.2 dry spray towers _ _


The dry spray tower is a variation of the spray tower in which the evaporationof the scrubbing solution is controlled. The materials in the tower are a drypowder by the time they reach the tower bottom.

Applications

This system is not extensively used but is effective where direct landfillingof effluent is desired. This process eliminates the need for scrubber-watertreatment.

Reference

Martin, EJ. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhold Co., New York, N.Y., 520 p.

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7f.3a.3 packed-bed scrubbers


Packed-bed scrubbers are vessels filled with randomly-oriented packingmaterial. The scrubbing liquid enters through the top, and gas flows throughthe bed in a countercurrent, cocurrent, or cross flow direction. The wetpacking material provides interfacial surface area for increased gasadsorption.

Applications

Packed-bed scrubbers are a major air-pollution-control device for hazardouswaste incinerators because of their high removal efficiency for gaseousemissions. Designed properly, a packed-bed scrubber will remove 99% of thehalogens from incinerator exhaust gases. The inherent nature of the designdoes not, however, allow for removal of particulates from exhaust gases withhigh particulate loadings. Unless prior treatment is used, this type of wastestream causes clogging in the packed-bed scrubber. This system is often usedin conjunction with liquid injection incinerators.

Reference


7f.3a.4 plate scrubbers


A plate scrubber is a vertical, cylindrical column with plates inside. Thescrubbing liquid enters at the top and flows across the plates as the gasenters at the bottom and is broken up as it passes through holes in theplates. Gas absorption occurs more rapidly if the gas is broken up.

Applications

Plate towers are not as common as packed-bed towers or veaturi scrubbers forthe control of air pollution from hazardous waste incineration. They arecapable of controlling gaseous emissions from liquid injection incinerators.

At hazardous waste incineration facilities, plate towers with two sieve traysare typically used as an absorber-mist eliminator in conjunction with ahigh-energy venturi scrubber.

Reference



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7f.3b particulate pollution removal systems


Incinerator flue gases contain suspended pajticles which must be removed beforeemitting the gases to the atmosphere.

7f.3b.l electrostatic precipitators


Electrostatic precipitation is a process by which particles suspended in a gasare electrically charged and separated from the gas stream. In this process,negatively charged gas ions are formed between emitting and collectingelectrodes by applying a sufficiently high voltage to the emitting electrodesto produce a corona discharge. Suspended particulate matter is charged as aresult of bombardment by the gaseous ions, and electrostatic forces pull ittoward the grounded collecting plates. Particle charge is neutralized at thecollecting electrode, where subsequent removal is effected by periodicallyrapping or rinsing.

Applications

Electrostatic precipitators have been widely used in conjunction with utilityboilers and with municipal and industrial incinerators. Dry ESPs are notcapable of removing acid gases; therefore, facilities burning halogenatedwastes must employ wet scrubbing of acid halides if ESPs are used forparticulate emission control. Electrostatic precipitators effectively collectfine particles [less than 3.9 x 10 in. (I um) in diameter] but are unableto capture noxious gases. They perform poorly on particles with highelectrical resistivity.

Electrostatic precipitators have been employed by European facilities wherehazardous wastes are incinerated, although the wastes generally do not containvery high levels of chlorine. When halogenated wastes are incinerated, carefulwaste blending is employed to protect ESPs from corrosion, so HC1 gasconcentrations do not exceed 1000 ppm and usually average 300 ppm.

References



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7f.3b.2 baghouse filters


A baghouse filter removes particles from a gas stream by passing the streamthrough cloth tubes or bags. Sieving, interception, impingement, gravitationalsettling, electrostatic attraction, and diffusion are mechanisms a baghouse .filter uses.

Applications Ii.l

Baghouse filters usually remove >99% of the entrained particles. The bags mustbe cleaned of this collected material periodically. Methods and frequency of !cleaning differ, depending on the type of baghouse filter. j

Baghouse filters can be cleaned either intermittently or continuously. ..Intermittent baghouses cannot be cleaned while on-line and, thus, are limitedto low-dust loadings or infrequent operation. They have the distinct advantageof being low-priced. Continuous cleaning baghouses are more expensive butoperate continuously and can handle high-dust loadings.

t—tReferences


7f.3b.3 venturi scrubbers


Venturi scrubbers utilize the kinetic energy of a moving gas stream to atomizethe scrubbing liquid into droplets. Liquid is injected into the high-velocitygas stream and is atomized by the formation and shattering of filaments andfilms which have extremely large surface areas.

Applications -»

The venturi scrubber is one of the most predominant air-pollution-control "•devices for hazardous waste incinerators. It is commonly used with rotary kilnand liquid inspection incinerators. Emissions of SC , HF, and HC1 can be ]reduced using this process. i

Reference ]



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7f.3b.4 orifice scrubbers


Orifice scrubbers are similar to venturi scrubbers, but the orifice createsmore turbulence than the venturi provides and also typically introduces highergas pressure drops.

Applications - See Venturi Scrubber - (7f,3b.3)

Reference

Martin, E.J. and Johnson, J.H. Jr., 1987, Hazardous Waste ManagementEngineering: Van Nostrand Reinhoid Co., New York, N.Y., 520 p.

7f.3b.5 ionizing wet scrubbers


An ionizing wet scrubber charges particulates in a gas stream usinghigh-voltage ionization. A packed scrubber section removes the particles byinertial impaction or by attraction to a neutral surface.

Applications

This process is only effective on particles that are easily ionized.

References

Kiaiig, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers, Inc., Ann Arbor, Michigan, 549 p.

7f.3b.6 wet electrostatic precipitators


The wet electrostatic precipitator (WEP) is a variation of the dryelectrostatic precipitator design. The two major added features in a WEPsystem are: (1) a pre-conditioning step, where inlet sprays in the entrysection are provided for cooling, gas absorption, and removal of coarseparticles, and (2) a wetted collection surface, where liquid is used tocontinuously flush away collected materials.


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Applications

The WEP overcomes some of the limitations of the dry electrostaticprccipitator. Its operation is not influenced by the resistivity of theparticles. Further, since the internal components are continuously beingwashed with liquid, build-up of tacky particles is controlled, and there issome capacity for removal of gaseous pollutants. In general, applications ofthe WEP fall into two areas: removal of fine particles and removal ofcondensed organic fumes.

References


7f.4 nitrogen oxides removal


In addition to combustion, nitrogen oxides can be minimized by wet scrubbing.Because of the inert nature and low solubilities of nitrogen oxides, however,mass transfer of nitrogen oxides is slow. Partially or completely oxidizingnitrogen oxide to nitrogen dioxide before scrubbing or using a catalyst topromote the adsorption of nitrogen oxide or to convert the nitrogen oxide tonitrogen-sulfur will improve mass transfer.

Applications

Wet nitrogen oxide scrubbing is not a widely used technology. This is becausethe chemistry of the reaction is not well understood, and mass transfer ratesare too slow.

References

Kiang, Y.H. and Metry, A.A., 1982, Hazardous Waste Processing Technology: AnnArbor Science Publishers, Inc.. Ann Arbor, Michigan, 549 p.

7f.5 steam plume control


The exhaust gases from scrubbers of an incineration system usually aresaturated with water vapor. When mixed with cold air, the saturated gasescause condensation of water vapor; the condensed water vapor then forms a steamplume. Pluming can be controlled by diluting flue gases or by bringing the gastemperature to the critical temperature of the gas at the ambient air

. temperature.


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Applications

Steam plumes are not dangerous, but their appearance is objectionable. Plumecontrol, therefore, should be practiced when desired for aesthetic reasons.

References


7f.5a cooling stack gases


1 Cooling the gases before emission condenses the water vapor until thetemperature reaches the direct contact and indirect heat exchangers can be used

! for cooling.

Applications

Direct contact coolers have low equipment costs and, where water is readilyil! available, low operating costs. Contamination of cooling water by CC>2,

nitrogen oxides, sulfur oxides, and other contaminants lowers the pH. Indirectcontact coolers do not result in the contamination of cooling water but dorequire a larger heat transfer surface and higher water flow. Constructionmaterials may be higher than in the direct contact design.

References


7f.5b heating stack gases


Heating the gas, without increasing its partial pressure, brings the exhaustconditions below the critical line- Direct or indirect heating can be used.

Applications

This process is applicable where an inexpensive form of heat is available orwhere water (for cooling) is not readily available.

References


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7f.5c dilution of stack gases


Diluting the gas drops its partial pressure to bring the conditions below thecritical line. Typically, dilution causes some condensation and a lowering ofthe temperature. Dilution can be performed with a forced or induced draftsystem.

Applications

This system is useful where neither cooling water or an inexpensive fuel sourceis readily available.

References


7f.6 mist elimination


Mist eliminators arc widely used to reduce emissions of liquid droplets fromscrubbers. Mist eliminators are normally installed downstream from, or are anintegral part of, the scrubbing system. The types of mist eliminators mostcommonly used in hazardous waste incineration facilities are cyclonecollectors, simple inertial separators such as baffles, wire mesh misteliminators, and fiber bed mist eliminators.

Applications

Cyclones are used for collecting very heavy liquid loadings of droplets > 10 u,such as those emitted from venturi scrubbers.

In the simple inertial separators, the primary collection mechanisms areinertial impaction and, to a lesser extent, interception.

Wire mesh eliminators are formed from meshes of wire knitted into a cylindricalopen weave which is then crimped to give a stable wire configuration. The cutdiameter for liquid droplet collection is a strong function of the gas velocityand can range from. I to 10 u.

References



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8. STORAGE


When treatment centers are bracked up or an appropriate treatment or disposalplan has not yet been devised, temporary storage in landfills, surfaceimpoundments, waste piles, or tanks may be necessary or preferred to immediatetreatment or disposal.

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9. DISPOSAL


A land-application-disposal site is designed and operated to avoid human healthexposure and to minimize or eliminate migration of contaminants from the site.Emphasis is placed on approaches that reduce the possibility of contaminatingsurface water or groundwater, that control gaseous emissions and wind erosion,and that eliminate adverse food-chain impacts. These approaches normallyinvolve one or more of the following: a natural or man-made impervious linerfor the site, diversion of surface run-on, incorporation of the wastes in thesoil, an impermeable cover, and avoidance of food-chain vegetation on the sitesurface.

Applications

Key components of decisions related to land disposal methods are waste and sitecharacterization, environmental monitoring, relative risk assessment,evaluation of control and remedial action options, operation and managementskills, and public acceptance. Environmental monitoring is needed both beforeand after land disposal is implemented to verify the design assumptions andcriteria and to assure that environmental and human health problems do notoccur. Even though a technically and environmentally sound land disposalmethod can be designed and operated, public opinion and acceptance of themethod frequently is the deciding factor.

Reference


9a. On-site disposal

9a.l Landfills


A "landfill is a disposal facility where hazardous wastes are placed in or onthe land. Landfills for hazardous wastes frequently are considered as atechnology of last resort to be used after approaches to reduce or eliminatethe hazards posed by the wastes have been evaluated or utilized. The intent isto bury or alter the wastes so that they are not an environmental or publichealth hazard. Any soil cover must be greater than the deptK of the plow zoneso that subsequent use of the land will not return the landfilled wastes to thesurface. Landfills are not homogenous and are usually made up of cells inwhich a discrete volume of the hazardous waste is kept isolated from adjacentcells and wastes by a suitable barrier. Barriers, liners, and covers arenecessary to prevent the escape of the waste, its constituents, and leachate.

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Applications

Landfilling relies on containment, rather than treatment or detoxification, forcontrol of hazardous wastes. Technologically, it is an unsophisticated methodof containment. Landfilling is a common method of hazardous waste managementfor both untreated wastes and the residues from treatment technologies.Landfills require careful construction, continuous maintenance and monitoring,and a high degree of management and technical attention.

Reference


9a.la trench landfills

Description of Technology ;

Trench landfills involve cutting, lining, filling, and capping trenches.Relative to other landfill techniques, this is a good one, because the trenchescan be small and capped soon after filling begins, cutting down the time the . 1waste is not secured.

Applications

This approach is taken when no natural depressions in the topography exist orwhen a deeper depression is desired.

9a.lb area landfills


Area landfiliing takes advantage of natural and man-made topography. Theactual landfill construction requires little or no excavation. Quarry-,canyon-, and pit-filling take advantage of earth or rock walls on at least partof the landfill perimeters as a man-made or natural "excavation" is filled withwaste cells from the wall outward. Slope filling is the outward building of aninclined surface via the emplacement of waste cells.

Applications

This approach is taken when a natural or man-created depression exists whichcan be readily secured.

DUNN GEOSCIENCE CORPORATION $R3026&9

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9a.2 Waste Piles


A waste pile is a noncontainerized accumulation of solid, nonflowing hazardouswaste used for storage or from which discharge to the land may occur. Wastepiles are considered land-disposal facilities subject to RCRA regulations,including those relating to groundwater and air-emissions monitoring.Precipitation and surface water run-on, leaching, and wind dispersal must allbe controlled.

Applications

Waste piles are created for temporary storage or treatment of solid waste priorto permanent disposal. They are regulated in the same manner as the landfillitself.

Reference


9a.3 Surface Impoundments


A surface impoundment is a man-made excavation, diked area, or naturaltopographic depression designed to hold an accumulation of liquid wastes orwastes containing free liquids. A surface impoundment must maintain enoughfreeboard to prevent overtopping by wave action, storms, or overfilling. Allearthen dikes must have a protective cover of grass, shale, rock, or comparablematerial to minimize wind and water erosion and to reserve their structuralintegrity. Dikes must have sufficient structural integrity to prevent massivefailure without dependence on any liner system.

Applications

Surface impoundments (i.e., storage, settling, and aeration pits, ponds, orlagoons) are used to contain liquid wastes.

Reference



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9a.4 Land Treatment - See 7b.la

9b. Off-site Disposal

9b,l Landfills - See 9a.l

9b.la trench landfills - See 9a.ia

9b.lb area landfills - See 9a.lb

9b.2 Waste Piles - See 9a.2

9b.3 Surface Impoundments - See 9a.3

9b.4 Land Treatment - See 7b.la

OUNN GEOSCIENCE CORPORATION 5830265 I

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10. ALTERNATIVE WATER SUPPLY


When a water supply is contaminated, a new supply of acceptable quality must beprovided to the community with minimal disruption of service. The contaminatedsupply may be abandoned completely, blended with the new supply to dilute thecontamination, or replaced temporarily.

Reference


lOa. Water Supply Replacement _ __.__. ._._ . . .......

lOa.l replacement of contaminated central water supplies


A contaminated central water supply may be replaced by one new source or bytapping more than one new source concurrently or consecutively. Availablesources may include those listed below.

lOa.la municipal water systems


Using treated water from another supply requires a cross-connection betweensystems. Many such cross-connections exist between neighboring water systemsfor emergencies. Water transmission lines can be installed if there are nocross-connections.

Applications

When an aquifer or surface water supply becomes contaminated, water can oftenbe diverted from municipal supplies on either an emergency or permanent basis.As a permanent approach, municipal water must be compared to water treatmentcosts or relocation of the source of water.

Reference


DUNN GEOSCIENCE CORPORATION flfi302652

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lOa.lb new surface water intake


The intake of surface water may be relocated if the new location ishydraulically isolated from the contaminated surface water. For example, in ariver the intake should be upstream of the source of contamination. Otherfactors to consider include the proximity of the new intake to the supply *system, water quantity available, required treatment of the new supply, and theeffects of the new intake on recreation, industry, and the environment. |

lOa.lc deeper or upgradient wellsI ;


New groundwater wells can be used if aquifer contamination would not be drawn tto the area of influence of the new wells. The new wells would have to be Ihydraulically or geologically isolated from the contaminated supply. !

IOa.2 point-of-use water supplies


If central water supplies are contaminated at the source or in transmissionthrough pipelines, they can be replaced permanently or temporarily at eachusage point. _

10a,2a bottled and bulk water '


The use of bottled and bulk water is common for temporary or semi-temporarywater supplies on an emergency basis until more permanent water supply ; iarrangements can be made. Bulk water can be provided in portable tanks(trailers or tank trucks) by commercial, clean water contractors and by publicemergency service organizations.

Reference . -*

USEPA, 1985, Handbook - Remedial Action at Waste Disposal Sites (Revised): ]EPA/625/6-85/006, Washington, D.C. '

10a.2b point-of-use wells -


Point-of-use wells, individual wells for each user establishment, may befeasible as a permanent alternative to a contaminated central supply, providedthat the available groundwater is and can be expected to remainnon-contaminated.

DUNN GEOSCIENCE CORPORATION M3G2653

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Reference .


10a.2c rainwater collection


For individual users, rainwater running off the roof is led through gutters anddownspouts to a cistern situated on or below the ground. Cistern storageconverts the intermittent rainfall into a continuous supply. For municipalservice, roof water may be combined with water collected from sheds or catcheson impervious ground surfaces.

Applications

Rainwater is rarely the immediate source of municipal water supplies but couldserve as a replacement to a contaminated water supply. The use of rainwater isgenerally confined to farms and towns in semi-arid regions devoid ofsatisfactory groundwater or surface water supplies.

Reference


lOb. Treatment


Treatment or upgrading existing treatment at central facilities or point-of-useunits also provide an alternative to a contaminated water supply. Point-of-useunits include line bypasses for treated water, faucet-mounted treatment units,and whole-house treatment units.

lOb.l central treatment


Central water supplies that are contaminated at the source can be treated toacceptable quality at central treatment systems. For some supplies, such as insmall communities that pump groundwater directly to distribution systemswithout treatment, central treatment may require installation of newfacilities. For other supplies, such as in large communities that alreadytreat surface water before distribution, upgrading of existing treatment withthe installation of polishing units may be necessary.

DUNN GEOSCIENCE CORPORATION AR3Q265U

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Applications

Many of the technologies described for treatment of aqueous wastes also applyto treatment of contaminated water supplies. In general, however, thosetechnologies that are normally associated with "polishing" (i.e., removal oflow concentrations of contaminants), such as activated carbon, ion exchange,and reverse osmosis, are most applicable to treatment for public watersupplies.

Reference


10b.2 point-of-use treatment


Central water supplies that are contaminated at the source or in transmissioncan be treated to acceptable quality at the point- of-use with a variety ofcommercially available systems. Most applications of treatment units arc foraesthetic purposes (taste, odor, and color), although their use is increasingfor removal of organic contaminants from drinking water.

DUNN GEOSCIENCE CORPORATION H ft 3 0 2 6 55

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11. PERMANENT RELOCATION OF RESIDENTS, BUSINESSES, AND COMMUNITY FACILITIES


When adequate, economically feasible, water supply replacement or treatmentplans can not be devised, residents, businesses, and community facilities arerelocated to where an adequate water supply is available. This is clearly alast resort alternative.

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Description of Remedial Action Technologies

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