Arsenic Treatment Technology Evaluation Handbook for Small Systems

151 Pages·2003·1.84 MB·English

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