Manganese Oxidation Thru Clo2

8/6/2019 Manganese Oxidation Thru Clo2

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East Meets West:Treatment and Blending Considerations in UsingCarrizo-Wilcox Groundwater in Central Texas

By: Thomas E. Caponi, P.E.Bury+Partners, Inc.

221 West Sixth Street, Suite 600Austin, Texas 78701

INTRODUCTION

Many communities within Central Texas along the IH 35 corridor have experienced double digit

growth rates over the last 10 years, and this rate of growth is expected to continue within manycommunities of the region. The ability of the region to sustain this growth is largely dependenton our ability to provide adequate water supplies. The expansion of surface water supplies islimited as these sources are largely developed and committed to serve existing demand. Thegroundwater supplies within Central Texas, such as the Edwards Aquifer, are used extensivelybut water level decreases have resulted in limitations on water withdrawals imposed byregulatory agencies.

CARRIZO-WILCOX AQUIFER OVERVIEW

The Carrizo-Wilcox Aquifer has been identified as a potential groundwater source to servegrowing demands along the IH 35 corridor. The aquifer extends from the Rio Grande inSouth Texas northeastward into Arkansas and Louisiana generally parallel to and east of IH 35(see Figure 1). The aquifer is a hydrologically connected system consisting of theWilcox Group and the overlying Carrizo Formation of the Claiborne Group. The Carrizo Sandand Wilcox Group outcrop out along a narrow band that parallels the Gulf Coast and dipsbeneath the land surface toward the coast (see outcrop zone in Figure 1).


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Figure 1. Major Aquifers of Texas

Source: TWDB, 2010a

The aquifer is predominantly composed of sand locally interbedded with gravel, silt, clay, andlignite deposited during the Tertiary Period. South of the Trinity River and north of theColorado River, the Wilcox Group is divided into three distinct formations: the Hooper,Simsboro, and Calvert Bluff (see Figure 2). Of the three formations, the Simsboro typicallycontains the most massive water-bearing sands. This division cannot be made south of theColorado River or north of the Trinity River due to the absence of the Simsboro as a distinct unit.Aquifer thickness in the downdip portion ranges from less than 200 feet to more than 3,000 feet(Ashworth, 1995).

Well yields are commonly 500 gallons per minute (gpm), and some may reach 3,000 gpm.

Yields greater than 500 gpm are produced from the Carrizo Sand in the southern orWinter Garden area of the aquifer, and are also obtained from the Carrizo and Simsboroformations in the central region (Ashworth, 1995).


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Locally, the Carrizo-Wilcox Aquifer may have elevated levels of dissolved carbon dioxide, iron,manganese, hydrogen sulfide andmethane with high iron contentcommon throughout much of thenortheastern part of the aquifer

(Ashworth, 1995). Groundwaterextracted from deeper downdipportions of the aquifer may havewater temperatures exceeding 90 F.However, total hardness levelsmostly fall within a range that wouldgenerally classify the water as softwater, with corresponding low levelsof dissolved solids and alkalinity.While treatment techniques havebeen available and practiced for

some time in addressing waterquality concerns with respectto individual constituents foundin Carrizo-Wilcox Aquifergroundwater, some treatmentconsiderations are often overlookedespecially when considering treatment appropriate to address all of the various constituents ofconcern found in this groundwater.

Figure 2. Carrizo-Wilcox Aquifer and Cross-Section atLeon County, Texas

Source: TWDB, 2010b

The quality characteristics found in Carrizo-Wilcox Aquifer groundwater are also in sharpcontrast to other more commonly used surface and groundwater supplies in Central Texas thatare generally high hardness and high alkalinity waters, whose quality characteristics areprincipally derived from the limestone of the Texas Hill Country. The differences in waterquality and water chemistry between the Carrizo-Wilcox and Central Texas aquifers createconsiderable challenges in the design and operation of water supply systems where both watersources are blended or intermixed in the distribution system.

SOURCE WATER CHARACTERIZATION

In order to properly assess the need for groundwater treatment and any potential consequences ofblending groundwater with other supplies, accurate groundwater characterization data isessential. Issues often overlooked in obtaining accurate groundwater characterization datainclude:

Purging of the well Field vs. laboratory parameters Sample collection procedures


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A. Well PurgingChemical characteristics of stagnant groundwater that has resided in the well borebetween pumping cycles may differ significantly from groundwater within the aquifer.Therefore, this stagnant water must be removed from the well prior to field analyses andsample collection to obtain a representative sample of in-situ groundwater.

The amount of water to be pumped before collection of water samples depends upon anumber of factors. There is no set number of well bore volumes to be pumped that fits allsituations. However, it is generally agreed that a minimum of three (3) well borevolumes of water should be evacuated in addition to attaining the stabilization of pH,temperature and electrical conductivity of the discharging water (Boghici, 2003). It isrecommended that at least three (3) readings for these parameters be taken at 3 to 5minute intervals. These parameters are deemed to have stabilized when three successivemeasurements are within the following ranges:

pH: 0.1 pH units

Temperature: 3% Specific Conductance: 3%Detailed well purging procedures are provided in the Texas Water Development BoardsField Manual for Groundwater Sampling (Boghici, 2003) and other standard groundwatertexts.

B. Field ParametersSeveral analyses must be made in the field at the time of sampling (Boghici, 2003).These parameters include the following:

pH

Temperature Specific conductance Alkalinity Dissolved gases (carbon dioxide, oxygen and hydrogen sulfide)Measurements of pH, temperature, and specific conductance are used to establish that thewell has stabilized before sampling may begin. Other parameters, such as oxidationreduction potential, alkalinity, and dissolved gases, are measured at the time of samplingbecause chemical reactions may occur during the holding time. These reactions change

the chemical composition of the water, thus making any laboratory analysis at a later timeinaccurate. Since carbon dioxide is part of the carbonate system, an accuratemeasurement of pH and alkalinity in the field can be used to estimate the dissolvedcarbon dioxide concentration in the water (Sawyer and McCarty, 1978, pg 373).


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C. Sample Collection ProceduresIt is critical that the collection of samples from the well for field parameter analysis beconducted to minimize chemical changes to the sample from oxidation and release of

dissolved gases. Therefore, sampling andanalytical techniques should be employed thatminimize sample aeration and that can conductanalyses rapidly. Figure 3 illustrates a simplemethod of sample collection that minimizessample aeration and dissolved gas release. Ashort length of hose is connected to the sampletap on the well that directs the sample to anarrow-mouth container. A low rate of flowcan be maintained during sample analysis forpH, temperature, and specific conductance,while fixed volume samples are required wherereagents are added.

WATER QUALITY CHARACTERISTICS

Table 1 provides data from Carrizo-Wilcox wells in Gonzales and Guadalupe County, alongwith analyses of surface water from the Guadalupe River and groundwater from theEdwards Aquifer. These data tend to illustrate the contrast between Carrizo-Wilcoxgroundwater and surface water and groundwater supplies commonly used in Central Texas.

While groundwater quality of the Carrizo-Wilcox aquifer varies locally and across the aquiferand these data represent a localized set of conditions, they are useful to highlight some of thepotential problems and challenges in using this aquifer for water supply in Central Texas.

Table 1 illustrates the low pH, hardness and alkalinity levels of the Carrizo-Wilcox groundwaterfrom these locations. Hardness averages about 70 mg/L, which is characteristic of watergenerally considered soft (Sawyer and McCarty, 1978). Concentrations of iron and manganeseare generally above the secondary maximum contaminant level (MCL). Corrosion indicescalculated from these data indicate the aggressive nature of the raw groundwater.

Also shown in Table 1 are analyses of surface water samples from the Guadalupe River and

samples of Edwards Aquifer groundwater. These waters are considerably higher in pH,hardness and alkalinity than the Carrizo-Wilcox groundwater. Hardness levels areapproximately 250 mg/L which is considered a hard water. Corrosion indices indicate that thewater is non-aggressive and slightly scale forming.

Figure 3. Sample collection technique formeasurement of field parameters


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Table 1

Summary of Raw Water QualityCarrizo-Wilcox Aquifer Wells in Gonzales and Guadalupe Counties

Guadalupe River Surface WaterEdwards Aquifer Groundwater

Gonzales Co. WellsParameter Units

RegulatoryLimits

Average Range

GuadalupeCo. Well

GuaRiver

WaSe

pH (field) s.u. 6.5-8.5 6.2 5.83 6.87 5.45 8

Temp (field) C N/A 27.8 26.7 29.1 24

CO2 (field) mg/L N/A 58.7 44.0 64.7 57.7

Total hardness as CaCO3 mg/L N/A 70.9 30.3 164 31 Total alkalinity as CaCO3 mg/L N/A 32.6 17.5 67.5 37

Total Iron mg/L 0.30* 1.24 0.875 2.14 2.31

Total Manganese mg/L 0.05* 0.0875 0.0467 0.14 0.0423

Calculated CorrosionIndices

Recommended Average Range

Aggressive Index (AI) >12 9.3 8.40 10.70 8.3

Ryznar Index (RI) 6.5-7.0 11.0 8.8 12.4 12.18 6

Langelier Index (LI) >0 -2.4 -3.3 -1.0 -3.36 0

Larson's Ratio >5.0 0.6 0.3 1.2 1.0

* indicates Secondary MCL


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POTENTIAL WATER QUALITY AND TREATMENT ISSUES

Water quality data shown in Table 1 indicates that elevated levels of iron and manganese, andthe corrosivity of the raw water need to be addressed. In addition, operating facilities haveexperienced the following problems:

Corrosion of metallic well and WTP components Deterioration of greensand filter media Filter loading rates less than design Excess chemical consumption for pH adjustment

A. Iron and Manganese

Table 1 shows that iron and manganese levels were consistently above the MaximumContaminant Levels (MCLs). Elevated levels of iron in the raw groundwater areillustrated in Figure 4 which shows heavy iron staining at a well discharge pad from aGonzales County well.

B. Corrosion Issues

Corrosion of well andtreatment system componentshave been experienced at somefacilities. This corrosion ismost likely the result of low pHand high levels of dissolvedcarbon dioxide in the wellwater. Figures 5 and 6 showthe corrosion of mild steelcolumn pipe from a verticalturbine well pump from aGonzales County well afterapproximately four (4) years ofservice. Figures 7 and 8 showthe corrosion of the cast ironvertical turbine pump impellerand pump housing flange.Downhole camera inspection ofthe casing and stainless steelpipe based well screen at theselocations did not indicate anysignificant corrosion. Columnpipe and pump bowls have since been replaced with stainless steel at these locations.

Figure 5. Corrosion of mild steel column pipe.

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Figure 6. Vertical turbine well pump column pipe corrosion.

Figure 7. Corrosion of pump impeller.



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Figure 8. Corrosion of pump impeller and pump housing flange.

The Gonzales County groundwater is treated for iron and manganese removal usingpressure filters without atmospheric aeration, and manganese greensand filtrationwith permanganate addition. The epoxy coated mild steel pressure filter internalcomponents showed considerable damage within three years of service. Figures 9and 10 illustrate corrosion of the internal wall and underdrain plate of the pressure filter.Figures 11 and 12 show pitting near the underdrain nozzle, and fine media thatapparently migrated through the filter to the underdrain.



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Figure 9. Corrosion and pitting of the internal top wall of the pressure filter

Figure 10. Corrosion and pitting of underdrain plate.



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Figure 11. Underdrain plate and nozzle. Note fine media particles.

Figure 12. Below underdrain plate with accumulation of fine media.



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C. Deterioration of Filter Media

Filter media in this application consists of 1.0 foot of anthracite, 1.5 feet of manganese

greensand and approximately 1.0 foot of support gravel. It was suspected that the

manganese greensand was deteriorating and samples of this media were collected. Thissampling indicated a significant deterioration in the effective size (size decrease) of the

media. The effective size, often abbreviated as d10, is defined as that size for which 10%

of the grains are smaller by weight and is read from a sieve analysis curve at the 10%

passing point. The uniformity coefficient is a measure of the size range of the media and

is defined as the ratio of d60/d10, with d60 being the size for which 60% of the media are

smaller by weight (AWWA, 1990). The media size data from this filter indicated that the

effective size was less than 0.2 mm, which means that greater than 10% by weight of the

media sample passed the 0.2 mm sieve. Note that sieve sizes smaller than 0.2 mm were

not used in the sieve analysis. The manufacturer specifies the effective size of the

original media is to be within a range from 0.3 to 0.35 mm. The filter sample was greater

than 33% less than the manufacturers original product specification, indicatingsignificant media deterioration.

The manganese greensand supplied for this filter is a natural glauconitic greensand.

Under certain conditions, this type greensand media can deteriorate, with grains softening

and the manganese oxide coating dissolving or flaking from the surface. According

manufacturer, factors to consider if media deterioration is noted include the following:

Water temperature a maximum water temperature of 27 C is recommended. Silica and total dissolved solids concentration (TDS) waters with silica levels below

10 mg/L or TDS levels less than 100 mg/L have been shown to contribute to media

failure and softening.

pH the minimum allowable pH is 6.2.Data from well sampling indicate that water temperature at the well head ranged from26.7 to 29.1 C. Silica and TDS levels were greater than 15 mg/L and 115 mg/L,respectively. The pH of filter influent (5.8 to 6.8) can be below the minimum pHrecommended for greensand media (6.2). Therefore, while silica and TDS levels in theinfluent water do not appear to be factors contributing to media deterioration, watertemperature could be a factor, particularly if during summer months water temperature atthe filters is higher than measured at the well head. However, it appears that influent pH

was the major cause of the media deterioration.


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D. Pressure Filter Loadings

While the maximum design filtration rate for the pressure filters typically is limited to5 gpm/ft2 of filter area, operators have reported they generally operate the filters at amaximum rate of 3.25 to 3.5 gpm/ft2. The manufacturer of the conventional greensand

media requires that the differential pressure across the filter be limited to 10 psi, asdamage to the media is possible at greater pressures. Operators have set filters tobackwash when a differential pressure of 8 psi is reached. Operators report that whenoperating at filter loading rates of 4 gpm/ft2 or greater filter run times are too short to bepractical.

E. Chemical Consumption

Chemical addition is required in order to a produce a less aggressive more stable waterand to adjust chemical parameters as required for blending. With Carrizo-Wilcox aquifergroundwater, pH increase is generally desirable and is accomplished with either alkali

addition or removal of dissolved CO2. With alkali addition, the form of chemical andfeed point is an important consideration. With the low hardness water typically found inCarrizo-Wilcox groundwater, there is opportunity to stabilize the water with lime withoutresulting in final hardness levels that are unacceptable, particularly in Central Texaswhere high hardness levels are typical. Since treatment processes using pressure filtersresult in groundwater remaining under pressure from the well head through the treatmentprocess and to storage with no atmospheric exposure, excess CO2 is never allowed toescape to the atmosphere. When caustic is added for pH adjustment, the caustic mustfirst neutralize dissolved CO2 resulting in more caustic consumption than would occur ifexcess CO2 were allowed to escape to the atmosphere prior to caustic addition.

TREATMENT AND BLENDING CONSIDERATIONS

Characterization data and operational experience indicate that treatment may be required toaddress the following water quality issues:

Iron and manganese removal Corrosion control Water chemistry modifications for blending

As illustrated in the previous section, generally accepted treatment techniques for iron andmanganese removal may result in operational problems such as excessive corrosion and media

degradation when treating Carrizo-Wilcox aquifer groundwater. In addition, the uniquecharacteristics of this groundwater offer opportunities for lower cost methods for waterchemistry adjustments required to control corrosivity and to facilitate blending with other watersupplies.


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A. Iron and Manganese Removal

Treatment techniques for iron and manganese removal are fairly well established, but thespecific characteristics of the Carrizo-Wilcox groundwater need to be considered in theprocess selection. Table 2 provides a summary of the available methods for removal of

iron and manganese. The primary methods include the following: Aeration Permanganate Chlorine, and Chlorine dioxide

Aeration or the injection of air (molecular oxygen) to the raw water may provide somedegree of oxidation of iron and manganese under the proper conditions. Oxidation ofiron by molecular oxygen is considered quite slow at pH 6 and quite rapid at pH 7.5 andabove (AWWA, 1990). Oxidation of manganese by molecular oxygen is generally not

practiced as a pH of 8.5 or higher along with other conditions are required to make theprocess feasible (AWWA, 1990). Since the pH of the raw water is generally 7 or less,aeration by injection of air (without CO2 release) may not contribute significantly to ironremoval without considerable reaction time to allow significant oxidation to occur.Atmospheric aeration with CO2 release may improve the effectiveness of iron oxidationas the post-aeration pH of Carrizo-Wilcox groundwater may be above 7. A supplementaloxidant may be necessary for consistent iron removal and required for effectivemanganese removal.


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Table 2

Potential Treatment Technologies

Treatment

Objective

General

TechnologySpecific Technology

Draft aeratorsAir oxidation

Air injection

Permanganate oxidation

Chlorine oxidation

Chlorine dioxide oxidation

Mixed oxidant oxidation

Chemical oxidation

Ozone oxidation

Biological oxidation Ferazur/Mangazur process

Sodium silicateSequestration Polyphosphates

Zeolite

Iron and ManganeseRemoval/Treatment

SofteningLime/soda ash

Pressure filtrationGranular Media

Gravity filtersFiltration

Membrane Membrane filtration

Chlorine

Chloramines

Chlorine dioxideDisinfection Chemical

Ozone

Aeration Draft aerators

Chlorine

Chlorine dioxideTaste and Odor Control

Chemical

Ozone

Caustic SodaChemical addition

Lime

Soda AshCorrosion Control

AerationDraft aerators


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Permanganate is currently used successfully to remove iron and manganese from Carrizo-Wilcox groundwater. Permanganate is most effectively used with oxide coated filtermedia such as manganese greensand as the greensand enhances the iron and manganeseremoval process and tends to adsorb excess permanganate that can impart a pink color tothe water. As noted previously in this paper, deterioration of natural greensand media has

been observed most likely due to the low pH of the raw groundwater. Greensand Plus,amanufactured manganese greensand, is an available alternative to greensand media.

While Greensand Plus is still detrimentally affected by low pH groundwater, it is not

subject to an 8-psi differential pressure limitation in a pressure filter application that

effectively limits the throughput capacity of the conventional greensand. According to

the Greensand Plus manufacturer, the media has been successfully operated at an 18-psi

pressure differential or a 125% increase over the current pressure limitation. By

increasing the pressure differential across the filters, the maximum flow rate of water

processed by each filter can be significantly increased to the maximum filter loading

typically allowed by TCEQ (5 gpm/ft2).

Free chlorine oxidation of iron is practical; however, alkaline conditions and chlorinedosages well above the stoichiometric requirements are necessary in order to achieveeffective rates of oxidation for manganese (Langlais, 1991). Also, complexed iron is noteffectively removed by free chlorine (Langlais, 1991). While complexed iron is not oftenencountered in Carrizo-Wilcox groundwater as dissolved organic carbon (DOC) levelsare less than 2.0 mg/L oxidation by free chlorine may not be practical as a primaryoxidant due to its inefficiency in oxidizing dissolved manganese (Sommerfeld, 1999).The efficiency of free chlorine for the oxidation of manganese is greatly improved whenused in conjunction with manganese greensand. It has been suggested that chlorineaddition prior to manganese greensand filtration using the Greensand Plus media willprovide effective removal of dissolved manganese without permanganate addition.

Chlorine dioxide is effective in the rapid oxidation of uncomplexed iron and manganesewhere the pH is above 5.0 to 5.5 (Langlais, 1991). However, chlorine dioxide has beenshown to be ineffective in the oxidation of iron and manganese when elevated levels ofdissolved organic carbon are present. Reduced iron that has been complexed by humicand fulvic acids is apparently unaffected by chlorine dioxide concentrations in the rangeof 3 to 5 mg/L. Manganese oxidation by chlorine dioxide was impeded by competitiveoxidant demand exerted by the dissolved organic carbon.

The major problem with the use of chlorine dioxide is that chlorite is formed as abyproduct of the oxidation reactions. Chlorite concentration is limited to 1.0 mg/L under

the disinfection byproduct (DPB) regulations. Assuming iron and manganeseconcentrations of 1.2 and 0.9 mg/L, respectively, the chlorine dioxide dosage necessaryfor iron and manganese oxidation based on the theoretical requirements provided inTable 8 is approximately 3.6 mg/L. Assuming that approximately 60 percent of thechlorine dioxide is converted to chlorite (White, 1999, pg 1181), the chloriteconcentration would be approximately 2.2 mg/L, more than twice the allowable chloriteconcentration under the DBP rules. Therefore, chlorine dioxide addition will typicallynot prove to be a practical treatment method for iron and manganese oxidation.


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B. Corrosion Control

Carrizo-Wilcox aquifer groundwater has the potential to cause corrosion of wellcomponents, raw water and treated water piping, treatment system components anddistribution systems. Not all Carrizo-Wilcox groundwater is equally corrosive and, as

discussed previously, proper sampling and characterization is important in assessingcorrosion potential.

Well components consist of the well casing, well screen, and pump components. Wherevertical turbine well pumps are used, basic pump components include the pump bowl andimpeller, column pipe, and pump shaft and pump discharge head. As discussedpreviously, significant corrosion of mild steel column pipe and pump bowls have beenobserved while stainless steel well screen and mild steel casing pipe have not shownsignificant corrosion. While it is possible to provide cathodic protection for the wellscreen, well casing and pump components, experience with corrosive Carrizo-Wilcoxgroundwater has indicated that stainless steel components (column pipe and pump bowls)

have satisfactorily resisted corrosion.

The objective of corrosion control for drinking water generally means the production offinished water that is chemically stable, neutral or slightly scale forming, and which has asufficient buffering system so that slight changes to the water do not result in significantquality characteristic changes. In order to protect treatment system components fromcorrosive attack as shown previously, chemical adjust prior to treatment is recommendedwhere raw groundwater demonstrates corrosive tendencies.

Various methods of water stabilization are available including the following:

Aeration (removal of dissolved carbon dioxide) Caustic soda (sodium hydroxide) addition Lime (calcium hydroxide) addition Soda ash (sodium carbonate) additionWhile aeration and alkali addition are effective methods to adjust pH, the stability of pHonce adjusted must also be considered. When practicing only pH adjustment, the pH ofthe water can decrease to nearly pre-treatment levels given adequate time within thedistribution system. Buffer intensity, which is a measure of a waters ability to resistchange in pH, is determined by measuring the quantity of strong base required to changepH by one unit. Buffer intensity is generally a function of both pH and alkalinity. Given

the low alkalinity levels of the raw Carrizo Wilcox groundwater, alkalinity adjustmentshould also be considered together with pH adjustment in order to form a more stablefinished water. Neutralizing dissolved carbon dioxide by the addition of caustic soda(sodium hydroxide) or lime actually forms additional alkalinity as part of theneutralization process (Stumm & Morgan, 1970); whereas the process of removingdissolved carbon dioxide through aeration or air stripping does not alter alkalinity.Poorly buffered waters can result in low localized pH in distribution systems as a resultof acid-producing biofilms such as nitrifers (Hart, 2009). In one study, alkalinity greaterthan 80 mg/L was shown to reduce red water occurrences (Imran, 2005).


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A comparison of common alkali is provided in Table 3. As indicated in Table 3, lime isthe least expensive alkali however, calcium is a component of lime and lime addition willraise the hardness.

Table 3

Comparison of Common Alkali

ChemicalAlkalinity Added

(mg/L as CaCO3 per mg/L chemical)

Cost, 2009 Dollars

($/ton)

Quicklime 1.35 110

Hydrated Lime 1.35 245

Sodium Hydroxide 1.25 788

Soda Ash 0.94 539

Sodium Bicarbonate 0.60 900

Source: Hart, 2009

In one system treating Carrizo-Wilcox groundwater using manganese greensand pressurefiltration with permanganate addition, a combination of hydrated lime addition (pre-filtration) and caustic addition (post filtration) was demonstrated to be the mosteconomical method of pH adjustment and corrosion control. The lime and caustic feedsystem includes the following:

Roughly split the alkali requirement between lime and caustic (approximately 18mg/L each),

Reduce the caustic dosage and cost by half, Limit the hardness increase in the finished water from approximately 71 mg/L to

95 mg/L,

Raise the pH of the raw water above the minimum recommended for thegreensand media (6.2) helping to prevent further media deterioration,

Raise the pH while lowering the corrosivity of the raw water to lessen thecorrosive effects that the raw water has on the raw water piping, and

Add the lime prior to the filters where any increases in turbidity due to the limeaddition has the potential to be removed by the filters.

The lime and caustic pH adjustment system reduced chemical cost by approximately

$150,000 during the first year of operation compared to the caustic only method of pHadjustment. A hydrated lime slurry feed system was selected for feeding lime. Thecapital cost of the liquid hydrated lime system was approximately $300,000 less than dryhydrated lime feed system and approximately $400,000 less than the quicklime system .Liquid hydrated lime was available for delivery at the plant site at 30 to 35% solution anda 10,000 gallon bulk storage tank was purchased for storage and feeding of the hydratedlime slurry. The bulk storage tank was mounted on load cells which measured the weightof the tank and its contents. Coupled with a microprocessor, the load cells were able to


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monitor the weight of a delivery of hydrated lime. With the lime solution strength asdelivered entered to the processor and the initial solution strength prior to delivery, theweight of water to be added to the tank to attain the desired solution feed strength wascomputed. By monitoring the weight of water added, the microprocessor regulated theaddition of water to attain the desired feed concentration. The lime slurry storage tank is

shown in Figure 14.

Figure 14. Lime Slurry Storage Tank.



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REFERENCES

American Water Works Association (AWWA). 1990. Water Supply and Treatment. 4th Edition,McGraw-Hill.

Ashworth, John B., and Janie Hopkins. 1995. Aquifers of Texas, Report 345. Texas WaterDevelopment Board (TWDB), November.

Boghici, Radu. 2009. Water Quality in the Carrizo-Wilcox Aquifer, 19902006, Report 372.Texas Water Development Board. January.

Boghici, Radu. 2003. A Field Manual for Groundwater Sampling, UM 51. Texas WaterDevelopment Board. March.

Hart, Vincent, Thomas Crowley and Sam Samandi. 2009. Expensive Problem, Inexpensive

Solution, Boost Alkalinity with Carbon Dioxide and Lime. Opflow, American Water Works

Association, September.

Imran, S.J., et. al. 2005. Red Water Release in Drinking Water Distribution Systems.Journal

AWWA, September.

Langlais, Bruno, David A Reckhow and Deborah R Brink. 1991. Ozone in Water Treatment,

Application and Engineering. AWWA Research Foundation, Lewis Publishers.

National Lime Association. 2000. Using Lime for Acid Neutralization.

Sawyer, Clair, N. and Perry L McCarty. 1978. Chemistry for Environmental Engineering, 3rd ed.

McGraw Hill.

Sommerfeld, Elmer O. 1999. Iron and Manganese Removal Handbook. American Water WorksAssociation.

Stumm, W, and James J Morgan. 1970. Aquatic Chemistry. Wiley-Interscience.

White, George Clifford. 1999. Handbook of Chlorination, 4th edition. Wiley Interscience.

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Manganese Oxidation Thru Clo2

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