Groundwater Contamination Prevention and Advanced Remedial Techniques

Preventive Measures and Remedial Techniques For Groundwater Contamination

ContentsIntroduction

Importance of Groundwater

Sources of Groundwater Contamination

Prevention from Groundwater Pollution

Participation of Industries and Community

Groundwater Remediation

Conventional and Innovative Remediation Techniques

Typical Groundwater Contaminants

Practical Remediation Technologies

Royal Commission Environmental Regulations for Groundwater Prevention

Conclusion

Introduction

Groundwater is water present below the ground surface that saturates the pore space in the subsurface.

At least 50% of the world population depends on groundwater as a source of drinking water.

Other uses of groundwater includes Irrigation of crops, Industrial uses etc.

Groundwater is a part of natural water cycle therefore, it can spread throughout the cycle and if contaminated, can cause damage to other entities ( Sea life, lakes, human health etc)

Groundwater can be polluted / contaminated as a result of HUMAN activity and Natural conditions.

Contaminations found in the groundwater cover a broad range of physical, chemical (Organic & Inorganic), bacteriological and radioactive parameters.

Sources of Groundwater Pollution

Improper use of contaminated waterLeaking Fuel and Chemical TanksExtensive use of Pesticides, Herbicides and fertilizersDrainage of house hold chemicalsIndustrial Chemical spills Badly Managed Landfill

Industrial Emissions

Prevention of Groundwater Contamination

Once Groundwater gets contaminated, it may be difficult and expensive to clean it up, therefore,

The best way to deal with groundwater contamination is not to contaminate it in the first place

Prevention of Groundwater Contamination

Participation of Industries:

Minimize use of Toxic / Hazardous Raw Materials

Maintain Integrity of the Storage Tanks, Pipelines, surface impoundments

Adopt Good Engineering Practices for selecting proper material for tanks and pipes.

Implement monitoring programs: Leak Detection and repair program, spill detection, spill control, emergency response plan etc.

Manage Properly: Waste materials, their transport and disposal.

Install Monitoring Wells

Monitor Periodically: Groundwater quality

Prevention of Groundwater Contamination

Participation of Community:

Minimize use of house hold chemicals containing Hazardous substances.

Avoid draining chemicals, motor oil, insecticides in community areas.

Reduce pesticide application

Use proper procedures for handling chemicals (Paints, Pesticides, Insecticides, polishing materials, cleaning chemicals and detergents).

Immediately clean any spills and report any leakages to concerned department.

Groundwater RemediationGroundwater remediation is the process that is used to remove pollution from groundwater.

Pollutants and contaminants can be removed from groundwater by applying various techniques thereby making the groundwater safe for use.

Groundwater remediation techniques are mainly divided into two technologies: Ex-Situ Technology and In-Situ Technology

Ex-Situ Technology involves treatment of groundwater by de-watering the polluted aquifer (pumping out), then treating the water on surface by Physical, chemical or biological technology and finally re-injecting the treated water to the aquifer.

In-Situ Technology involves treatment of groundwater within the aquifer (in the sub-surface) by using thermal, chemical and biological treatment technology.

Remediation Techniques

Ex-Situ Technology: Extraction of groundwater from aquifer , treat above ground. and return the treated water to the aquifer. Extraction is done by pumping groundwater from the well or trench and treat them with a variety of techniques such as :

Stream strippingInvolves treatment by introducing steam which extract the contaminants from the pumped out groundwater. The extracted steam (along with contaminants can be recovered from the condensate or treated further by incineration.

Oxygen SpargingInvolves introduction of oxidizing/reducing agents ( O3, H2O2, Hypochlorite) to chemically convert the toxic contaminants to less toxic compounds.

BioremediationInvolves treatment of pumped up groundwater by air (biodegradation) with careful control of moisture, heat nutrients, oxygen and pH.

Carbon AdsorptionInvolves passing the contaminated pumped up groundwater through activated carbon column in which contaminants gets adsorbed.

Remediation TechniquesEx-Situ Technology

Remediation TechniquesIn-Situ Remediation Technology:Involves treatment of groundwater (in-place) without extracting the water from aquifer. There are several treatment techniques used for in-situ groundwater treatment such as:Air Sparging:Involves the injection of contaminant-free air into the subsurface saturated zone, enabling a phase transfer of hydrocarbons from a dissolved state to a vapor phase.

Bioremediation:Involves injection of oxygen to enhance the biodegradation. This treatment also combines injection of degrading bacteria and nutrients into aquifer to stimulate biodegradation. In-well air stripping:Involves injection of air in double screened well, lifting the water up the well and force it out in upper screen. VOCs in the contaminated water are transferred from dissolved phase to vapor phase in air bubbles and drawn off and treated.

Chemical Oxidation:Involves Reduction-Oxidation reactions that chemically converts hazardous contaminants to less toxic compounds. Cyanide oxidation and de-chlorination are the typical examples of chemical oxidation.

Thermal Treatment:Involves increase in temperature of the source zone to increase the mobility of the pollutants. The mobility facilitate removal of pollutants and can also results in In-Situ destruction of contaminants. PhythoremediationIt involves the use of macroscopic plants to destroy, remove, immobilize and treat contaminants. This process does not use microorganisms.

Remediation Techniques

In-Situ Bioremediation

Selection of Remedial TechnologyThe selection of the remedial technology depends upon several parameters such as:

Contaminant Profile:Types of compounds ( DNAPL, LNAPL, Ammonia, Virus, Bacteria)Quantity and Solubility ( Solubility in Water)Toxicity and volatility ( VOCs , SVOCs, Metals, etc)Biodegradability

Aquifer Profile:Soil Type (permeability, homogeneity, chemistry, confined or open, etc)Groundwater Flow directionWater Table locationRecharge location ( seasonal Rainfall)

Feasibility Profile:Cost of technologyTime of completion

Groundwater ContaminantsSeveral man made chemicals are referred to as Groundwater contaminants because of their extensive use, accidental spills and leaks, mismanagement and illegal dumping. Some of the popular contaminants are the following:

DNAPL (Dense Non Aqueous Phase Liquids )

LNAPL (Light Non Aqueous Phase Liquids)

Inorganic Chemicals ( Ammonia, Cyanide, Fluoride)

Metals

Bacteria and Viruses

Groundwater ContaminantsDNAPL :Dense Non Aqueous Phase Liquids are organic compounds heavier than water and having less absolute solubility. These compounds include chlorinated solvents (EDC) and halogenated aromatics (TCB) DNAPLs migrate very fast through the soil formation and reach water table because of their high density and low viscosity. They sink steeply to the bottom of the aquifer till they reach the impermeable bed rock.

Treatment of DNAPLThe following types of technologies are increasingly being used to treat DNAPLs:

In situ thermal treatment In situ chemical oxidation Surfactant/co-solvent flushing In situ bioremediation Ground water extraction (P&T or recirculation) ExcavationContainment (Engineered caps and slurry walls).

DNAPL Dense Non Aqueous Phase Liquid Migration Pattern

Groundwater ContaminantsLNAPL Light Non Aqueous Phase Liquids are organic compounds lighter than water and having low solubility. These liquids include Gasoline, fuel oil and other petroleum products.LNAPL Remediation:Remediation may require the use of more than one technology. It is likely that several remediation techniques, used in series and/or parallel applications, will be required for maximum contaminant removal. This collaborative effort may be referred to as a treatment train approach. A conceptual example of a treatment train which might be effective at an LNAPL site includes:

Pump and Treat for mobile LNAPL removal followed by vapor extraction for removal of residual LNAPL .

Additional technologies such as bioremediation might be used to further reduce contaminant concentrations.

LNAPL Light Non Aqueous Phase Liquid Migration Pattern

Typical Groundwater Contaminants And Their Treatment OptionsContaminantMain SourceTreatment TechnologyTrichloroethylene(TCE)Degreasing of Metal and Electronic parts, Extract for oil and waxes, fumigant, carries in paints and adhesivesPump and Treat Activated CarbonThermal and BiologicalMTBEMTBE can be released to groundwater by leaking underground storage tanks and piping, atmospheric deposition, spills during transportation, and leaks at refineriesAir SpargingIn-Situ oxidation ( H2O2 and Fe)Bioremediation/BioaugmentationPump and Treat.EDC (DNAPL)From EDC and VCM Plants, storage tanks, pipelines etc.In-situ Bioremediation.Gasoline (LNAPL)Gasoline and other petroleum fuels tanks, petrol stations, storage tanks and pipelines.In-situ BioremediationVapor extractionAmmoniaAmmonia Storage Tanks, Landfill leaks, Waste stockpile, etc.Pump and TreatCombination of Air Stripping, Nitrification, Ion Exchange.

Treatment of EDC (Ethylene Dichloride) & ChloroformGroundwater contaminated by Ethylene Dichloride and Chloroform can be treated through in-situ bio remediation by using certain types of Enzymes under proper conversion parameters.

This In-Situ process is applicable to both fresh and brackish waters.

50 to 80 percent biodegradation can be achieved by injecting Enzymes in the aquifer within 5 to 10weeks.

Applicability:EDC (1.3 g/cc), Chloroform (1.5 g/cc) , Chlorobenzene, Vinyl Chloride, VOCs.

Limitations:Permeability of the groundAquifer Matrix

Practical ExecutionThis In-Situ Bio remediation is practically implemented by two industrial facilities in Jubail to reduce EDC and other chlorinated compounds from the groundwater.

Treatment of MTBE (Methyl Tertiary Butyl Ether )MTBE is broadly used as Gasoline additive and is one of the popular contaminant of the groundwater.

The solubility in water is as high as 4.3% comparing to Solubility of benzene and toluene 0.18% and 0.05% respectively.

MTBE is very mobile and can spread to very large subsurface area very quickly.

Groundwater contaminated with MTBE can be treated by : In-Situ Oxidation

Bioremediation (Enhanced by Oxygen and Nutrients injection)

Pump and Treat by Air Stripping & Activated Carbon Adsorption

Combination of Catalytic Chemical Oxidation with UV Presence.

Treatment of AmmoniaAmmonia is one of the major pollutants which contaminates groundwater. Ammonia contamination could lead to Sea Water Pollution. Being Toxic to Aquatic Organism, Remediation of Ammonia is very important.

US Department of Energy has successfully conducted pilot studies on the Innovative Remedial Techniques on an Aquifer near Moab, Utah, USA. Which shows that technologies are available for treating groundwater contaminated with high levels of Ammonia to a safe level of 3 mg/L

These technologies includes:

Pump and Treat by Ammonia Stripping

Pump and Treat by Air Stripping and further Nitrification

Pump and Treat by Ion Exchange

Limitation: Needs pH Adjustments,

RCER-2010 Royal Commission Environmental Regulation on Groundwater PreventionRoyal Commission has always been concerned about Public Health and Environment including Surface and Subsurface groundwater.

At Royal Commission Environmental Control Department(RC-EPCD), we believe in Prevention from groundwater contamination as the very first rule of remediation. Therefore, Royal Commission Environmental Regulation (RCER) has made it obligatory for all industries to stringently follow RCER Groundwater Regulation such as:At least 3 Groundwater Monitoring Wells in each industrial facility.

Periodical Monitoring Groundwater Quality.Periodical Reports to RC.

Mandatory use of Impervious Liner (1.5 mm thick HDPE liners) for : Tank foundations, Secondary Containments(Dikes) and Storm Water Pond

Storage Tank Regulations: Spill Control Devices, Leak Detection and Overfill System Containments and Double Walls, Material of Construction

Implementation of Leak Detection and Repair System to ensure the integrity of the pipelines and components.

Separate Location for Landfills: Inert Waste Non Hazardous Waste Hazardous Industrial Wastes Sanitary Wastes.

Landfill Design Double Liners Groundwater Monitoring wells Near Landfill Leachate Collection System

Monitoring Groundwater Quality from 60 Monitoring Wells outside industrial facilities in Jubail Industrial City.

Reviewing Groundwater Quality Reports submitted by Individual Industries from over 500 Wells in the Jubail Industrial City.

Checking Quality of Groundwater used for Re-mineralization of drinking water which is supplied in Royal Commission Area.RCER-2010 Royal Commission Environmental Regulation on Groundwater Prevention

ConclusionPrevention from groundwater contamination is the best Remedial Option.

2. Mostly, groundwater contaminants are of industrial origin.

3. Royal Commission is closely monitoring the quality of Groundwater through out the Jubail Industrial City and also have implemented strict regulation for the prevention of groundwater pollution.

4. Environmental Awareness Programs Including groundwater prevention should be Implemented for Community.

5. Innovative Technologies are available for the groundwater remediation, for several common contaminants including EDC and Other Chlorinated Compounds, MTBE and Ammonia.

Thank youPrevention Pays - Remedy Costsand The Prevention is in Our Hands