Drinking Water Program Fact Sheet Recommendations for Arsenic Removal from Private Drinking - PDF document

1 Drinking Water Program Fact Sheet:Recommendations for Arsenic Removal from PrivateDrinking Water Wells in Oregon IntroductionArsenic is a naturally occurring element foundin soils and groundwater. Arsenic ��2 &#x/MCI; 0 ;&#x/MCI; 0 ;lead, chromium and manganese. As statedabove, when operated under ideal conditionsRO can remove over 95% of As (V).2) RO requires very little maintenance and addition of chemicals.Disadvantages:Smaller RO pointuse systems produceonly a few gallons of treated water per day.The supply of drinkable water is limited andnormally available only in the kitchen area the home.2) If you have As (III) in your drinking water,you’ll need to preoxidize it to As (V), whichwill increase the complexity and cost of yoursystem.3) ROtreated water may taste bland becausethe inorganic materials removed in thetreatment process also imparttaste to drinkingwater.4) If you have significant amounts of iron ormanganese in your water, you’ll probablyneed additional pretreatment equipment toremove those prior to RO treatment.5) Larger RO systems called pointentrysystems can treat water for the entire house.However, these are much more expensive.More importantly, RO pointentry systemscan cause corrosion control problems in houseplumbing, which can elevate the levels of leadand copper found in your drinking water.Anionic Exchange SystemsAnionic exchange systems use aphysical/chemical process to exchange ionsbetween a resin bed and water passingthrough. These systems soften water,removeiron and manganese, and lower nitrate andarsenic levels. Specific contaminant removalis determined by the composition of theresin bed used. Anionic exchange systemsare typically pointentry systems,meaning that they treat all water cominginto the home.These systems work by passing waterthrough the resin bed, which is chargedwith chloride ions from dissolved salt.Arsenic molecules in the water replacethese chloride ions by knocking them offand taking their place. This processcontinues until all of the sites on the resinare full. The resin is then backwashedwith water that is supersaturated withdissolved salt. The chlorine ions in thisbackwash water strip the embeddedarsenic molecules out of the resin and intothe backwash wastewater. New chlorineions replace the arsenic molecules, fullyrecharging the resin bed so that the processcan be performed again.Pros and Cons of Anionic ExchangeAdvantages:1) Anionic exchange requires littlemaintenance; additional salt is added everyfew weeks.2) Systems are typically installed to treatan entire house.Disadvantages:1) Other constituents in water can competewith arsenic for the resin sites reducing thesystems effectiveness. EPA recommendsthe influent water have less than 500 mg/Lof total dissolved solids (TDS) and lessthan 25 mg/L of sulfate.Treated water can have a very low(acidic) pH and high levels of chloride, ��3 &#x/MCI; 0 ;&#x/MCI; 0 ;which can cause corrosion controlproblems and high levels of lead and copperthe treated water.3) If the system fails, all of the arseniccaptured on the resin at that time can bereleased at once causing a large concentrationof arsenic in the treated water.Iron Oxide Filter SystemsIron oxide filters are a relatively new andpromising method for lowering arsenic levelsin private drinking water systems. Likeactivated carbon, these granular filters havelarge amounts of surface area and an affinityfor arsenic to adhere to its surface. Althoughthese filters are fairly new to the hometreatment market, the principals behind themhave been used by public water suppliers formany years.Iron oxide media can be housed in small inlinefilter cartridges (pointuse) or in largertanks like the ones used for ion exchangesystems (pointentry). These filters can beused to enhance the performance of reverseosmosis systems that are not effectivelyremoving As (III). The media can be disposedof as nonhazardous waste.Pros and Cons of Iron Oxide FiltersAdvantages1) They are effective for both As (III) and (V) removal.2) They can be used as pointuse or pointentry systems.3) They remove other inorganicconstituents.4) They are simple to use and install.5) They are disposable as nonhazardouswaste.Disadvantages1) The media must be replaced on regularbasis.2) The presence of iron, manganese,sulfate, silica or organic carbon can reduceeffectiveness.Arsenic Treatment Checklist:1) Have I had my water tested at a statecertified laboratory?2) Have I done a retest to confirm theresults?3) Have I also tested for iron andmanganese?4) Have I contacted a water treatmentprofessional to aid in the analysis andselection of an adequate solution?5) Have I checked references for the watertreatment professional that I’ve selected?6) Are there other problems with mydrinking water that should also beaddressed?Where can I find additional information?For more information regarding the health effects of arsenic, contact one of the toxicologists at (673 ��4 &#x/MCI; 0 ;&#x/MCI; 0 ; &#x/MCI; 1 ;&#x/MCI; 1 ;A list of Oregon certified drinking water laboratoriescan be received by calling theDrinking Water Program at (, or by utilizing the web address listed below.Information on the Web:Oregon certified drinking water laboratories list: http://public.health.oregon.gov/LaboratoryServices/EnvironmentalLaboratoryAccreditatio n/Documents/AllLabsDWMatrix.pd f EPA’s private wells page: http://water.epa.gov/drink/info/well/ The State of Maine has an excellent web page devoted to private wells, with a largesection devoted to arsenic removal. Much of this fact sheet was derived from theirsite.State of Maine information: http://www.maine.gov/dhhs/eng/water/Templates/PrivateWells/privatewells.htm