P erchlorate is a chemical compound com-posed of one chlorine atom and four oxygenatoms. Perchlorate found in water systems

can be either naturally occurring or the result ofhuman activity. Perchlorate moves easily throughwater systems and can last for many decades undertypical groundwater and surface water conditions.Sources of perchlorate contamination resulting fromhuman activity include chemical fertilizers and vari-ous other chemical and industrial activities, such asthe manufacture of ammonium perchlorate, an oxidecomponent and the primary ingredient in solid propel-lant for rockets, missiles and fireworks. Perchloratesalts also are used on a large scale as a component ofautomobile airbag inflators.Perchlorate was discovered at various manufacturingsites and in well-water and drinking-water supplieswithin several months following the April 1997development of a low-level (4 ppb) detection method.Perchlorate releases have been confirmed in at least25 states throughout the United States. The UnitedStates Environmental Protection Agency (EPA), otherfederal agencies, states, water suppliers and industryalready are actively addressing perchlorate contami-nation through monitoring for its presence in drink-ing water and in source water. The full extent of per-chlorate contamination is not known at this time.Figure 1 shows the results of a water-well samplingstudy Texas Tech University conducted on the TexasHigh Plains to identify perchlorate concentrations ingroundwater (Figure 1).

Drinking Water Problems: Perchlorate

Monty C. Dozier, Assistant Professor and Extension Specialist,Rebecca H. Melton, Extension Assistant, Texas Cooperative Extension,

The Texas A&M University SystemMichael F. Hare, Senior Natural Resources Specialist, Pesticide Programs Division,

Texas Department of AgricultureDana O. Porter, Associate Professor and Extension Agricultural Engineer,

Bruce J. Lesikar, Professor and Extension Agricultural Engineer, Texas Cooperative Extension,The Texas A&M University System

L-54688/07

Figure 1. Distribution of perchlorate detections in waterwells (Jackson, et. al. 2004).

LegendPerchlorate (ppb)

ND (< 0.5 ppb)

0.5 - 4.0

4.0 - 10.0

10.0 - 20.0

> 20.0

Studies of thyroid health of both newborns andadults have concluded that present perchlorate envi-ronmental exposures levels do not appear to pro-duce harmful effects. Regulatory agencies and othergroups are now trying to determine a safe level ofperchlorate in water. Following recommendations inthe NRC (2005 report) report, the EnvironmentalProtection Agency (EPA) has set a reference dose(RfD) of 0.0007 mg/kg per day. An RfD is an esti-mate of the maximum daily oral exposure that islikely to be without risk of adverse health effects toan individual during that individual’s lifespan. Theperchlorate RfD was derived from a study in whicha maximum daily perchlorate dose of 0.007mg/kg/day given to human volunteers did not inhib-it iodide uptake. An uncertainty factor of 10 isapplied to the dose to account for varying effects onsensitive population, resulting in a final RfD of0.0007 mg/kg/day. This RfD could be used to figureaction levels. For example, a person weighing 154pounds (70 Kg) who drinks 2 liters of water per daycould consume water containing up to 24.5 micro-grams/L (ppb) of perchlorate without adverseeffects. Texas’ perchlorate advisory level was revisedin 2005 to 17 ppb, although the prior advisory levelof 4 ppb still is being used for public water systems.For more information on this topic, seehttp://www.epa.gov/safewater/ccl

How can you remove perchlorate from well water?

Well owners can treat their water to remove per-chlorate using reverse osmosis or ion exchangeprocesses.

Reverse Osmosis (RO)A reverse osmosis (RO) unit operates by passingwater under pressure though a semi-permeablemembrane. The membrane allows water to passthrough but prevents perchlorate from doing so.Most RO units will have

• A prefilter to remove solids and extend mem-brane life;

• An activated carbon filter to remove odors,taste and chlorine;

• A semi-permeable membrane through whichwater flows under pressure;

• A tank to hold treated water; and • A drain connection for discharging reject water

produced.

Although the potential for perchlorate contaminationhas been estimated to affect drinking-water suppliesof at least 12 million people in the United States, theeffect of low-level, chronic exposure still is not fullyunderstood. Currently, there is no National PrimaryDrinking Water Regulation (NPDWR) for perchlo-rate. Perchlorate was placed on the Office of WaterConta-minants’ Candidate List in March 1998, witha note that additional research and information arerequired before regulatory determinations can bemade.

What are the potential healtheffects of perchlorate?

Most people are exposed to perchlorate via theirdiets, because perchlorate is found in many agricul-tural products. For instance, the Food and DrugAdministration (FDA) found iceberg lettuce grownin Belle Glade, Florida, to have 71.6 ppb of per-chlorate. Some red leaf lettuce grown in Californiawas found to contain 52 ppb of perchlorate.Because some controversy surrounds the environ-mental and health effects of perchlorate, theNational Research Council (NRC) was asked toassess potential adverse health effects of perchlo-rate ingestion. In a 2004 report, the NRC con-firmed that perchlorate blocks iodide uptake by thethyroid. Iodide is an essential component in twohormones produced by the thyroid. These hor-mones are influential for growth and developmentin fetuses, infants and young children. This makesfetuses and newborns especially sensitive to per-chlorate ingestion. People with compromised thy-roid function resulting from conditions that reducethyroid hormone production and people withiodide deficiencies also are considered to be popu-lations potentially sensitive to perchlorate inges-tion. Long-term change in the production of thyroidhormones can result in thyroid hypertrophy andhyperplasia and possibly in hypothyroidism in indi-viduals who cannot compensate with an increasingthyroid iodide uptake. The NRC (2005) points outthat fortunately the body has an efficient feedback-control mechanism to compensate for iodide defi-ciency, so it would probably take an iodide-uptakereduction of at least 75% for months or longerbefore adverse health effects would result. TheNRC concluded “. . . available epidemiological evi-dence is not consistent with a causal associationbetween perchlorate and congenital hypothyroidism,changes in thyroid function in normal-birthweight, full-term newborns, or hypothyroidism or other thyroid dis-orders in adults.”

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However, RO units result in relatively poor waterrecovery. Most units are designed to recover 20 to 30percent of the water processed. For example, if 100gallons of water are treated, only 20 to 30 gallons willbe useable; the rest of the water will be sent to awastewater treatment system. Homeowners using on-site wastewater treatment should consider the impactthis additional loading may have on their systems.Because of their inefficiency, RO units typically areused to treat only drinking and cooking water. Thus,system size should be based on the number of gallonsto be used for these purposes each day. Typical RO

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and the perchlorate takes its place because the per-chlorate ion is more strongly attracted to the resinexchange site than was the ion it replaced. Once allof the original ions have been replaced, the columnis considered to be saturated and must be replaced.The used resin should be disposed of as a hazardouswaste. It is not practical to attempt to regenerate theresin because it is extremely difficult to remove theperchlorate from it.Resins designed for perchlorate removal are espe-cially effective in ion-exchange units. Nitrate-selec-tive-resins also effectively remove perchlorate.Selective resins can prevent perchlorate “dumping”as the ion-exchange-resin bed reaches saturation.Dumping refers to higher perchlorate concentra-tions being found in the effluent water than in thesource water and occurs especially when sourcewater contains sulfates. Resins developed for pref-erential nitrate exchange prevent sulfates from dis-placing or “dumping” nitrate or perchlorate as aresin bed reaches saturation.For water sources containing large amounts of sul-fates or of total dissolved solids (TDS), ion exchangemay not be a good option for treating perchlorate.Presence of these constituents demands frequentresin replacement, dramatically increasing a system’soperational costs. If source water requires treatmentfor nitrates as well as for perchlorate, a multiple-col-umn system should be used. The first ion-exchangecolumn will remove perchlorate, and the resin usedwill have to be replaced. Columns following the firstin the series will remove nitrate, and these resincolumns can be regenerated.

Figure 2. Reverse Osmosis Treatment Unit (Adaptedfrom Kneen et al., 1995 and USEPA, 2003.

unit production rates range from 5 to 15 gallons perday.RO devices typically cost between $300 and $1,000.Unit installation takes from 30 to 60 minutes,assuming no significant plumbing modifications arenecessary. The RO unit’s semi-permeable mem-brane must be replaced according to its manufac-turer’s recommended schedule. New membranescost about $150, and a carbon-based pre-filter typi-cally costs between $15 and $50. Depending on thesystem, based on a 10 year life, cost of water pro-duction ranges from 5 to 10 cents/gallon, notaccounting for costs of water wasted or costs, ifany, of treating rejected water.

Ion ExchangeIon (charged atom) exchange removes perchloratefrom a water source by passing the water underpressure through one or more columns packed witha particular exchange resin. As perchlorate movesacross the resin, an ion is released from the resin,

Perchloratecontaminated

waterTreatedwater

Perchlorate

Chloride

Exchange resin

Figure 3. Ion Exchange Process (Adapted fromRobillard et al., 2001).

An ion exchange unit costs between $400 and$1500. Operation and maintenance costs have beenestimated to be $0.02 per gallon of treated water.

How should a well ownerselect a treatment unit?

No single technology will treat all water contami-nants. Before selecting a treatment option, wellowners should test the water source, using a labora-tory qualified to determine water quality. A list oflabs certified by the Texas Commission on Environ-mental Quality (TCEQ) for testing drinking watercan be found at: http://www.tnrcc.state.tx.us/permitting/waterperm/ pdw/chemlabs.pdfOnce you have established the constituents presentin your water supply, research different productsand find one suitable for treating these constituents.If you need multiple water treatment products toremove contaminants from your water, pleaseremember to check how or if these different treat-ment products work together. For example,although the ion exchange process can be used totreat both nitrate and perchlorate, a system must beset up specifically to treat both. Compare initialcosts, operation and maintenance costs and require-ments, contaminant removal efficiency, warranties,life expectancy of the system and company reputa-tion. Before making your final decision, also consid-er quantity of reject water or solid wastes generatedby a system.Home water-treatment systems are not regulated byfederal or state laws, but some national organiza-tions offer product certifications. The Water QualityAssociation (WQA) offers a validation program andadvertising guidelines. Products that receive theWQA’s Gold Seal Product Validations are certifiedas to mechanical performance but not for ability toremove harmful contaminants. The NationalSanitation Foundation (NSF) certifies products’ abil-ity to remove contaminants affecting health. A listof drinking-water treatment units with NSF certifi-cation can be found on the World Wide Web at:http://www.nsf.org /Certified/DWTU/. For questionsregarding a particular product’s certification, con-tact the NSF Consumer Hotline at 877-8-NSF-HELPor info@nsf.org or by writing to NSF International,P.O. Box 130140, 789 N. Dixboro Road, Ann Arbor,MI 48113-0140. An EPA registration number on aproduct indicates merely that the unit is registeredwith the EPA; this registration number does notimply EPA approval or certification.

How can well owners keeptheir systems working?

No matter what treatment technology you use,maintenance is required to keep the system operat-ing properly, and the first step to proper operationand maintenance is proper installation. Qualifiedinstallers

• carry liability insurance for property damageduring installation;

• are accessible for service calls;• accept responsibility for minor adjustments

after installation; and • give a valid estimate of installation costs.

After system installation, water treatment unitsmust be maintained properly. RO membranes andresin in ion exchange units must be replaced as nec-essary. All systems should be operated according tomanufacturer’s specifications. Treating more waterin a certain period of time than a system is designedfor may lower treatment effectiveness and adverselyimpact treated water quality. Water output by treat-ment units should be tested regularly to ensureproper system operation.

ReferencesBurge, S., and Halde, R. 1999. Nitrate andPerchlorate Removal from Groundwater by IonExchange. Livermore, CA: Lawrence LivermoreNational Laboratory. Available at: http://www.cluin.org/download/contaminantfocus/perchlorate/LLNL1.pdf.California Environmental Protection Agency (CEPA).2004. Perchlorate Contamination TreatmentAlternatives. Sacramento, CA: Office of PollutionPrevention and Technology Development,Department of Toxic Substances Control, CaliforniaEnvironmental Protection Agency. Available at:http://www.dtsc.ca.gov/ScienceTechnology/TD_REP_Perchlorate-Alternatives.pdf.Greer, M.A., Goodson, G., Pleuss, R.C., Greer, S.E.2002. Health effect assessment for environmentalperchlorate contamination: the dose response forinhibition of thyroidal radioiodide uptake inhumans. Environ. Health Perspect. 110:927-937.Hassinger, E., Doerge, T.A., and Baker, P.B. 1994.Water Facts: Number 7 Choosing Home WaterTreatment Devices. Tucson, AZ: Arizona CooperativeExtension. Available at: http://ag.arizona.edu/pubs/water/az9420.pdf.

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Herman, G.M., and Jennings, G.D. 1996. HomeDrinking Water Treatment Systems. North CarolinaCooperative Extension Service. Available at:http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www2.ncsu.edu/bae/programs/extension/publicat/wqwm/he419.html.Jackson, A. W., Rainwater, K., Anderson, T.,Lehman, T., Tock, R., Rajagopalan, S. and Ridley,M. 2004. Distribution and Potential Sources ofPerchlorate in the High Plains Region of Texas.Lubbock, TX: Texas Tech University WaterResources Center, Lubbock Texas. Available at:http://www.waterresources.ttu.edu/final%20report.pdfKamrin, M., Hayden, N., Christian, B., Bennack, D.,and D’Itri, F. 1990. A Guide to Home WaterTreatment. East Lansing MI: Michigan StateUniversity Extension. Available at: http://www.gem.msu.edu/pubs/msue/wq21p1.html.Kneen, B., Lemley, A., and Wagenet, L. 1995. WaterTreatment Notes: Reverse Osmosis treatment ofDrinking Water. Ithaca, NY: Cornell UniversityCooperative Extension. Available at: http://www.cce.cornell.edu/factsheets/wq-fact sheets/home/FSpdf/Factsheet4.pdf

NRC. 2005. Health implications of PerchlorateIngestion. National Research Council of the NationalAcademies. National Academies Press. Washington,D.C.Lahlou, M.Z. 2003. Point-of-Use/Point-of-Entry Systems.Morgantown, WV: National Drinking WaterClearinghouse. Available at: http://www.nesc.wvu.edu/ndwc/articles/OT/SP03/TB_Point_of_Use.html.Robillard, P.D., Sharpe, W.E., and Swistock, B.R.2001. Water Softening. University Park, PA: PennState Cooperative Extension. Available at: http://www.sfr.cas.psu.edu/water/water%20softening.pdf.United States Environmental Protection Agency(USEPA). 2003. Arsenic Treatment TechnologyEvaluation Handbook for Small Systems. EPA 816-R-03-014. Washington D.C.: USEPA Office of Water.United States Environmental Protection Agency(USEPA). 2005. Perchlorate e-factsheet. WashingtonD.C.: USEPA Office of Water. Available at:http://www.epa.gov/safewater/ccl/perchlorate/perchlorate.html

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This publication was funded by the Rio Grande Basin Initiative administered by the Texas Water Resources Institute ofTexas Cooperative Extension, with funds provided through a grant from the Cooperative State Research, Education, andExtension Service, U.S. Department of Agriculture, under Agreement No. 2005-45049-03209.