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Arsenic Treatment Technology Evaluation Handbook for Small PDF

151 Pages·2003·1.84 MB·English
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Arsenic Treatment Technology Evaluation Handbook for Small Systems Office of Water (4606M) EPA 816-R-03-014 July 2003 www.epa.gov/safewater Printed on Recycled Paper The decision trees contained in this document were current when the handbook was published in 2003. They are still relevant and can provide a simple guide for selecting an arsenic treatment. However, EPA has slightly modified the trees since publication to reflect changes in regulation and arsenic treatment technologies. To visit the revised trees, visit http://www.arsenictradeshow.com The trees are intended for use as an iterative tool. Users can work their way through the trees a number of times, modifying preferences and system specific circumstances. There may not be a single solution. Further cost evaluation and assessment of other considerations such as labor commitments, residual disposal, and available space, may be necessary. Disclaimer The information in this document has been subjected to the Agency’s peer and administrative re- views and has been approved for publication as an EPA document. Mention of trade names or commercial products does not constitute an endorsement or recommendation of use. This page intentionally left blank. Executive Summary In January 2001, the U.S. Environmental Protection Agency (USEPA) published a final Arsenic Rule in the Federal Register. This rule established a revised maximum contaminant level (MCL) for arsenic at 0.010 mg/L. All community and non-transient, non-community (NTNC) water sys- tems, regardless of size, will be required to achieve compliance with this rule by January 2006. This technical handbook is intended to help small drinking water systems make treatment decisions to comply with the revised arsenic rule. A “small” system is defined as a system serving 10,000 or fewer people. Average water demand for these size systems is normally less than 1.4 million gallons per day (MGD). Provided below is a checklist of activities that should normally take place in order to comply with the new Arsenic Rule. Many of the items on this checklist refer to a section in this handbook that may help in completing the activities. Arsenic Mitigation Checklist 1. Monitor arsenic concentration at each entry point to the distribution system (see Section 1.3.2). 2. Determine compliance status. This may require quarterly monitoring. See Section 1.3.2 for details on Arsenic Rule compliance. 3. Determine if a non-treatment mitigation strategy such as source abandonment or blending can be implemented. See Sections 2.1.1 through 2.1.3 for more detail and Decision Tree 1, Non- Treatment Alternatives. 4. Measure water quality parameters. See Section 3.1.1 for more detail on water quality param- eters that are used in selecting a treatment method. (cid:122) Arsenic, Total (cid:122) Nitrite (cid:122) Arsenate [As(V)] (cid:122) Orthophosphate (cid:122) Arsenite [As(III)] (cid:122) pH (cid:122) Chloride (cid:122) Silica (cid:122) Fluoride (cid:122) Sulfate (cid:122) Iron (cid:122) Total Dissolved Solids (TDS) (cid:122) Manganese (cid:122) Total Organic Carbon (TOC) (cid:122) Nitrate 5. Determine the treatment evaluation criteria. See Section 3.1.2 for more detail on parameters that are used in selecting a treatment method. (cid:122) Existing Treatment Processes (cid:122) Target Finished Water Arsenic Concentration Arsenic Treatment Technology Evaluation Handbook for Small Systems i (cid:122) Technically Based Local Limits (TBLLs) for Arsenic and TDS (cid:122) Domestic Waste Discharge Method (cid:122) Land Availability (cid:122) Labor Commitment (cid:122) Acceptable Percent Water Loss (cid:122) Maximum Source Flowrate (cid:122) Average Source Flowrate (cid:122) State or primacy agency requirements that are more stringent than those of the USEPA. 6. Select a mitigation strategy using the decision trees provided in Section 3.2. These trees lead to the following mitigation strategies. (cid:122) Non-Treatment & Treatment Minimization Strategies (cid:129) Source Abandonment (cid:129) Seasonal Use (cid:129) Blending Before Entry to Distribution System (cid:129) Sidestream Treatment (cid:122) Enhance Existing Treatment Processes (cid:129) Enhanced Coagulation/Filtration (cid:129) Enhanced Lime Softening (cid:129) Iron/Manganese Filtration (cid:122) Treatment (Full Stream or Sidestream) (cid:129) Ion Exchange (cid:129) Activated Alumina (cid:129) Iron Based Sorbents (cid:129) Coagulation-Assisted Microfiltration (CMF) (cid:129) Coagulation-Assisted Direct Filtration (CADF) (cid:129) Oxidation/Filtration (cid:122) Point-of-Use Treatment Program (cid:129) Activated Alumina (cid:129) Iron Based Sorbent (cid:129) Reverse Osmosis 7. Estimate planning-level capital and operations and maintenance (O&M) costs for the mitiga- tion strategy using the costs curves provided in Section 4. Include costs for arsenic removal and waste handling. If this planning level cost is not within a range that is financially possible, consider using different preferences in the decision trees. 8. Evaluate design considerations for the mitigation strategy. See Section 2.5 for enhancing exist- ing treatment processes and Sections 6 through 8 for the design of new treatment processes. Arsenic Treatment Technology Evaluation Handbook for Small Systems ii 9. Pilot the mitigation strategy. Although not explicitly discussed in this Handbook, piloting the mitigation strategy is a normal procedure to optimize treatment variables and avoid implement- ing a strategy that will not work for unforeseen reasons. For many small systems, piloting may be performed by the vendor and result in a guarantee from the vendor that the system will perform. 10.Develop a construction-level cost estimate and plan. 11. Implement the mitigation strategy. 12.Monitor arsenic concentration at each entry point to the distribution system to ensure that the arsenic levels are now in compliance with the Arsenic Rule – assumes centralized treatment approach, not point-of-use treatment. Table ES-1 provides a summary of information about the different alternatives for arsenic mitigation found in this Handbook. Please note that systems are not limited to using these technologies. Arsenic Treatment Technology Evaluation Handbook for Small Systems iii Table ES-1. Arsenic Treatment Technologies Summary Comparison. (1 of 2) Membrane SorptionProcesses Processes Factors IronBased Reverse IonExchange ActivatedAlumina A Sorbents Osmosis IX AA IBS RO USEPABATB Yes Yes NoC Yes USEPASSCTB Yes Yes NoC Yes SystemSizeB,D 25-10,000 25-10,000 25-10,000 501-10,000 SSCTforPOUB No Yes NoC Yes POUSystemSizeB,D - 25-10,000 25-10,000 25-10,000 RemovalEfficiency 95%E 95%E upto98%E >95%E TotalWaterLoss 1-2% 1-2% 1-2% 15-75% Pre-OxidationRequiredF Yes Yes YesG LikelyH pH5.5-6 I pH6-8.3L <250mg/LCl-I pH6.5-9E <2mg/LF-I <5mg/LNO-I <360mg/LSO2-K pH6-8.5 OptimalWater 3 4 <50mg/LSO2-J <30mg/LSilicaM <1mg/LPO-3N NoParticulates QualityConditions 4 4 <500mg/LTDSK <0.5mg/LFe+3I <0.3NTUTurbidity <0.3NTUTurbidity <0.05mg/LMn+2I <1,000mg/LTDSK <4mg/LTOCK <0.3NTUTurbidity OperatorSkillRequired High LowA Low Medium SpentResin,SpentBrine, SpentMedia,Backwash SpentMedia,Backwash WasteGenerated RejectWater BackwashWater Water Water Possiblepre&postpH adjustment. Possiblepre&postpH Mediamaybevery Pre-filtrationrequired. adjustment. expensive.O Highwaterloss(15- OtherConsiderations Potentiallyhazardousbrine Pre-filtrationmaybe Pre-filtrationmaybe 75%offeedwater) waste. required. required. Nitratepeaking. ModifiedAAavailable. CarbonatepeakingaffectspH. CentralizedCost Medium Medium Medium High POUCost - Medium Medium Medium AActivatedaluminaisassumedtooperateinanon-regeneratedmode. BUSEPA,2002a. CIBS'strackrecordintheUSwasnotestablishedenoughtobeconsideredasBestAvailableTechnology(BAT)orSmallSystemCompliance Technology(SSCT)atthetimetherulewaspromulgated. DAffordableforsystemswiththegivennumberofpeopleserved. EUSEPA,2000. FPre-oxidationonlyrequiredforAs(III). GSomeironbasedsorbentsmaycatalyzetheAs(III)toAs(V)oxidationandthereforewouldnotrequireapre-oxidationstep. HROwillremoveAs(III),butitsefficiencyisnotconsistentand pre-oxidationwillincreaseremovalefficiency. IAwwaRF,2002. JKempic,2002. KWang,2000. LAAcanbeusedeconomicallyathigherpHs,butwithasignificantdecreaseinthecapacityofthemedia. MClifford,2001. NTumalo,2002. OWithincreaseddomesticuse,IBScostwillsignificantlydecrease. Arsenic Treatment Technology Evaluation Handbook for Small Systems iv Table ES-1. Arsenic Treatment Technologies Summary Comparison. (2 of 2) Precipitative Processes Enhanced Coagulation-- Coagulation- Factors EnhancedLime (Conventional) Assisted Oxidation AssistedDirect Softening Coagulation Micro- Filtration Filtration Filtration Filtration LS CF CMF CADF OxFilt USEPABATB Yes Yes No Yes Yes USEPASSCTB No No Yes Yes Yes SystemSizeB,D 25-10,000 25-10,000 500-10,000 500-10,000 25-10,000 SSCTforPOUB No No No No No POUSystemSizeB,D - - - - - 95%(w/FeCl)E RemovalEfficiency 90%E 3 90%E 90%E 50-90%E <90%(w/Alum)E TotalWaterLoss 0% 0% 5% 1-2% 1-2% Pre-OxidationRequiredF Yes Yes Yes Yes Yes pH5.5-8.5 OptimalWater pH10.5-11I pH5.5-8.5P pH5.5-8.5P pH5.5-8.5P >0.3mg/LFe QualityConditions >5mg/LFe+3I Fe:AsRatio>20:1 OperatorSkillRequired High High High High Medium BackwashWater, BackwashWater, BackwashWater, BackwashWater, BackwashWater, WasteGenerated Sludge(highvolume) Sludge Sludge Sludge Sludge Possiblepre& TreatedwaterrequirespH Possiblepre&post Possiblepre&post OtherConsiderations postpH None. adjustment. pHadjustment. pHadjustment. adjustment. CentralizedCost LowQ LowQ High Medium Medium POUCost N/A N/A N/A N/A N/A BUSEPA,2002a. DAffordableforsystemswiththegivennumberofpeopleserved. EDependsonarsenicandironconcentrations. FPre-oxidationonlyrequiredforAs(III). IAwwaRF,2002. PFields,etal.,2002a. QCostsforenhancedLSandenhancedCFarebasedonmodificationofanexisitngtechnology.Mostsmallsystemswillnothavethistechnologyin place. Arsenic Treatment Technology Evaluation Handbook for Small Systems v

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Arsenic Treatment Technology Evaluation Handbook for Small Systems iii 9. Pilot the mitigation strategy. Although not explicitly discussed in this Handbook, piloting the
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