water treatment - harvard universitywilsonweb.physics.harvard.edu/arsenic/remediation/... ·...

106 AUGUST 2008 | JOURNAL AWWA • 100:8 | PEER-REVIEWED | LANTAGNE

Point-of-use (POU) water treatment with sodium hypochlorite (NaOCl) has

been proven to reduce diarrheal disease in developing countries. However,

program implementation is complicated by unclear free chlorine residual

guidelines for POU water treatment and difficulties in determining appropriate

dosage recommendations. The author presents evidence supporting proposed

criteria for household water treatment for free chlorine residuals of < 2.0 mg/L

1 h after NaOCl addition and > 0.2 mg/L after 24 h of storage. In testing of 106

drinking water sources from 13 countries, free chlorine residual was measured

for 24 h after treatment with different NaOCl doses. For most unchlorinated water

(with turbidity < 10 ntu or from an improved source), the NaOCl dose necessary

to meet the proposed criteria was 1.875 mg/L. For most unimproved sources with

turbidity of 10–100 ntu, the required dose was 3.75 mg/L. POU chlorination is not

recommended in waters with turbidity > 100 ntu. The article also discusses the

applicability of POU water treatment with NaOCl to emergency water treatment.

BY DANIELE S. LANTAGNE

Villagers draw water from an open well in Malawi,

one of 13 countries studied to determine whether

point-of-use drinking water treatment and safe storage

options can help reduce the incidence of disease

and death in these countries.

Sodium hypochlorite dosage for household and emergency

water treatmentn estimated 1.1 billion people lack access to improvedwater supplies, and 2.6 billion people are without ade-quate sanitation (WHO/UNICEF, 2004). The healthconsequences of inadequate water and sanitation servicesinclude an estimated 4 billion cases of diarrhea and 2.2

million deaths each year, mostly among young children in devel-oping countries (WHO/UNICEF, 2000). In addition, waterbornediarrheal diseases lead to decreased food intake and nutrientabsorption, malnutrition, reduced resistance to infection (Baquiet al, 1993), and impaired physical growth and cognitive devel-opment (Guerrant et al, 1999). Recently point-of-use (POU)drinking water treatment and safe storage options have beenrecognized as approaches that can accelerate the health gainsassociated with improved water until the longer-term goal ofuniversal access to piped, treated water can be attained (Fewtrell& Colford, 2005). Household water treatment and storage prac-tices can prevent disease and thereby support poverty alleviationand development goals.

A

2008 © American Water Works Association

LANTAGNE | 100:8 • JOURNAL AWWA | PEER-REVIEWED | AUGUST 2008 107

BACKGROUNDHousehold water treatment and the Safe Water System

(SWS). Chlorination was first used for disinfection ofpublic water supplies in the early 1900s and is one factorthat contributed to dramatic reductions in waterbornedisease in cities in the United States (Cutler & Miller,2005). Although small trials of POU chlorination hadbeen implemented in the past (Mintz et al, 1995), larger-scale trials began in the 1990s, as part of the Pan Amer-ican Health Organization (PAHO) and the US Centersfor Disease Control and Prevention (CDC) response to epi-demic cholera in Latin America (Tauxe et al, 1995). TheSWS strategy that was devised by the CDC and PAHOincluded three elements:

• water treatment with dilute sodium hypochlorite(NaOCl) at the POU location,

• storage of water in a safe container, and• communication to effect behavioral change to

improve hygiene and water and food-handling practices.In seven randomized, controlled trials, the SWS resulted

in reductions in diarrheal disease incidence ranging from25 to 84% (Chiller et al, 2006; Crump et al, 2005; Lubyet al, 2004; Reller et al, 2003; Quick et al, 2002; 1999;Semenza et al, 1998).

Chlorine residual standards and NaOCl dosing recom-mendations. The World Health Organization (WHO) andthe US Environmental Protection Agency (USEPA) havedeveloped guidelines for free chlorine residual in treateddrinking water and for use of NaOCl for water treat-ment in emergency situations. The WHO health-basedguideline value for maximum free chlorine residual in

drinking water is 5 mg/L (WHO, 2004). According toWHO, this “guideline value is conservative, as no adverseeffect level was identified in the critical study.” The orga-nization also noted that in infrastructure systems, the freechlorine residual ranges from 0.2 to 1.0 mg/L, and the“minimum target concentrations for chlorine at the pointof delivery are 0.2 mg/litre in normal circumstances and0.5 mg/litre in high-risk circumstances” (WHO, 2004).

These recommendations did not refer to an appropri-ate chlorine residual for household water treatment withNaOCl, although an overall minimum appropriate freechlorine residual of 0.2 mg/L and a maximum of 5 mg/Lhas been established. In addition, the guidelines recom-mended a maximum pH of 8.0 and ideal median turbid-ity of < 0.1 ntu before chlorination to ensure effectivedisinfection. The guidelines noted that most consumersfind water of < 5 ntu acceptable and local conditionsdetermine appropriate turbidity guidelines.

Public drinking water providers in the United States arerequired to meet minimum standards for water quality andremoval of bacteria, viruses, and protozoa. The maxi-mum turbidity allowed postfiltration before chlorinationis 1 ntu (USEPA, 2002).

The USEPA maximum contaminant level (MCL) forfree chlorine in drinking water is 4 mg/L (USEPA, 2006a).Many treatment plant operators aim for a free chlorineresidual of 0.2–0.5 mg/L at the distal ends of the distri-bution system.

In emergency situations, WHO recommends that “theconcentration of free chlorine should be increased to > 0.5mg/litre throughout the system as a minimum immediate

response” and that the “ap-propriateness of householdlevel treatment should beevaluated” (WHO, 2004).For household treatment,WHO recommends thattrained personnel prepare astock 1% NaOCl solutionand test to determine thedosage necessary to leave afree chlorine residual of0.4–0.5 mg/L 30 min afterthis solution is added tosource water (WHO, 2005).This is a modification of thesecond edition of the WHOguidelines for drinking waterquality, which recommendedadding 3 drops/L of 1% stockNaOCl solution in emergencysituations rather than deter-mining the dosage for eachsituation (WHO, 1997).

For emergency situationsin the United States such asChildren gather around a community well in Malawi.


hurricanes, the USEPA recommends the addition of eightdrops or one eighth of a teaspoon of 4–6% NaOCl solu-tion to 1 gal of clear water (USEPA, 2006b). Doublethat dose is recommended for “cloudy, murky, or col-ored” water. Because the majority of household bleachesavailable in the United States are 5.25% NaOCl, 5.25%is the concentration used to convert the dose in drops tomg/L in this article.

Inexactness of the term “drop” as a measurement. Acomplication of using drops for NaOCl dosing is that a“drop” is an inconsistently defined measurement. Sci-entifically, one drop is defined as 0.0821 mL, which isequivalent to 12.2 drops/mL (Young & Glover, 2002). Apharmacist’s drop is 0.05 mL, equivalent to 20 drops/mL;in cooking, 24 drops is defined as one fourth of a tea-spoon, equivalent to 19.6 drops/mL (Rowlett, 2000).Laboratory supply companies often specify the dropsper millilitre of their dropper bottles. Simple laboratorylow-density polyethylene plastic dropper bottles com-

monly used by international organizations for NaOCldosing have a range between 16 and 24 drops/mL.Because of this variation in drop size, conversions fromdosage regimes expressed in drops are presented in thisarticle using three conversion factors: 15 drops/mL, 20drops/mL, and 25 drops/mL.

Expressing doses in milligrams per litre facilitates com-parison and highlights the disparities among existing rec-ommendations. The WHO 1997 recommendation of 3drops/L of 1% NaOCl is equivalent to NaOCl doses of2, 1.5, and 1.2 mg/L at 15, 20, and 25 drops/mL, respec-tively. The USEPA recommendation of 8 drops/gal of5.25% NaOCl is equivalent to doses of 7.41, 5.56, and4.44 mg/L at 15, 20, and 25 drops/mL, respectively, anddouble these doses for turbid water. The USEPA recom-mendation of one eighth of a teaspoon is equivalent to0.625 mL, using a conversion of 5 mL per teaspoon.Adding 0.625 mL of 5.25% NaOCl solution to 1 galresults in a dose of 8.69 mg/L of NaOCl. The authorreviewed recommendations by 18 nongovernmental orga-nizations (NGOs) and emergency agencies in the UnitedStates and identified variations in NaOCl dose from0.2–27.78 mg/L.

Chlorine dosage in the SWS program. The SWS NaOClsolution is packaged in a bottle with directions instruct-ing users to add one full bottle cap of the solution toclear water (or two capfuls to turbid water) in a stan-dard-sized (generally 20-L) storage container, agitate, andwait 30 min before drinking. The variables that deter-mine the NaOCl dosage in this packaging are the con-centration of NaOCl solution (%), the size of the cap(mL), and the size of the storage the container (L).

Between 1993 and 2003, the CDC helped establishSWS programs in 14 countries. In each country, the bestpackaging option was selected from existing plastic bot-tles and caps, or a specialized bottle design was devel-oped to fit an available cap. A dosing strategy was devel-oped after nonstandardized chlorine residual testing andin accordance with the cap size availability in the coun-try. This strategy led to widely varying SWS products.

To compare doses across these varying products, themg/L of NaOCl dose was calculated according to Eq 1

NaOCl Dose (mg/LW) = (1)

NaOCl Concentration (mg/LCl)× Amount Added (mLCl)× 1 L�1,000 mL

Litres of water treated (LW)

in which LW is litres of water and Cl is chlorine. A dosevariation from 0.8 to 4.0 mg/L of NaOCl was seen in theinitial SWS products. However, medians of 1.75–2.0mg/L for clear water and 3.5–4.0 mg/L for turbid waterwere identified. Data collected by the author betweenSeptember 2003 and January 2004 in Madagascar,


This Haitian family uses chlorine to disinfect water.

A tap water source is used to fill containers.


Kenya, Uzbekistan, and Tajikistan confirmed these medi-ans as the doses necessary to maintain free chlorineresidual in water stored in closed and open containersfor 24 h. Dosage testing in these four countries was notconducted with consistent methodology and is notincluded in this study. Thereafter, a consistent method-ology to conduct dosage testing for SWS implementationwas developed and has since been completed in 13 coun-tries by the author and in additional countries by CDCstaff and implementing partners.

METHODSSetting. The data presented in this study were collected

from March 2004 through April 2006. During that period,the author completed or assisted with the water quality test-ing, product development, government approval processes,and training necessary to begin large-scale SWS programsin 13 countries. Twelve of these programs were establishedwith the social marketing NGO Population Services Inter-national (PSI) and one was planned with the NGO AbtAssociates. Countries were selected on the basis of theNGOs’ strategic plan and the availability of funding fortechnical assistance and project initiation.

Study design. In each country, water sources used fordrinking by the local population were identified by con-sulting local NGO staff, water experts, and nationalstatistics. A minimum of five and a maximum of twelverepresentative sources were selected for sampling. Waterfrom each source was collected in multiple clean, locallypurchased containers. Plastic, recycled vegetable oil con-tainers of 20 L or 10 L are used throughout Africa aswater storage containers (called jerry cans). In mostcountries, these cans were used to collect water and asthe storage container during the analysis. In some coun-tries, ceramic water storage pots obtained from localpotters were used because these are the locally preferredstorage containers. In Nepal, both plastic containersand locally used metal tapered containers (gagris) wereused in the testing. Analysis occurred within 24 h ofcollection of each sample. For all water quality para-meters, a minimum of 7% of samples were duplicatedfor quality control.

Each source water sample was analyzed for turbid-ity, pH, conductivity, and free and total chlorine beforeNaOCl addition to characterize the source water andprovide appropriate data for regression analysis. Tur-bidity was measured after agitation of the sample waterwith a turbidimeter,1 calibrated weekly with nonexpiredstock calibration solutions. The pH and conductivitywere measured with a multimeter,2 calibrated weeklywith nonexpired stock calibration solutions. Free andtotal chlorine were measured immediately after samplecollection using a single-wavelength chlorine colorimeter3

and DPD-1 and DPD-3 tablets.3 The colorimeter wascalibrated daily using nonexpired stock calibration solu-tions at 0, 0.1, 1.0, and 2.65 mg/L.

After the source water samples were characterized, aknown NaOCl dose was added with a pipette to a singlecontainer of each of the source waters. NaOCl solution,as commercially available bleach, was purchased locally.The NaOCl concentration was measured using a portableiodimetric titration method for high-range (20–70,000mg/L) total chlorine.4

Free and total chlorine residual levels were measuredover a period of 24 h in each container at 1, 2, 4, 8, and24 h after chlorine addition. However, constraints suchas access to the containers at certain time periods didnot allow for measurements at these exact times in everylocation. The time intervals were selected because it is rec-ommended to all SWS users that they drink the water aminimum of 30 min after treatment to allow sufficientcontact time and a maximum of 24 h after treatmentbecause of decay of the chlorine residual over time. In thedosage testing, 1 h was used rather than 30 min becauseof laboratory time and equipment constraints. Testing formicrobial indicators was not conducted because the pres-ence of chlorine residual is strongly associated with theabsence of field-testable microbial indicators such astotal coliform and Escherichia coli (Quick, 2002; 1999).In Cameroon, water samples were collected for metalsanalysis in a glass container, acidified to a pH below2.0, and stored on ice below 6oC for later analysis inthe United States. Method 200.7 (USEPA, 1994) wasused to analyze the samples,5 and all laboratory qualitycontrol guidelines were met.

Data analysis. All data were entered into a spreadsheetprogram,6 and supplemental add-in programs7 were usedfor analysis. For analysis, turbidity was divided into fiveranges: 0–1 ntu (to account for the USEPA recommen-dation of 1 ntu as the maximum turbidity for chlorinat-ing water), 1–5 ntu (to account for the WHO recom-


In Ethiopia, a woman draws water from an open source.



mendation of 5 ntu as the maximum turbidity accept-able to users), 5–10 ntu, 10–100 ntu, and > 100 ntu.

For analysis, each source was categorized according tothe WHO (2000) classification as improved or notimproved. Improved sources included household connec-tions, public standpipes, boreholes and protected dug wells,protected springs, and rainwater collection. Unimprovedsources included unprotected wells, unprotected springs,vendor-provided water, bottled water, and tanker truckwater. These categories were slightly modified to reflectthe types of drinking water sources people used in the 13countries studied. Urban and rural standpipes were dif-ferentiated because of the large number of these samplestaken, and a collapsed category termed “open water” wascreated. Open water included lakes, rivers, created pondsused as reservoirs, unprotected springs, rainwater stored increated ponds, and tanked river water. Before collectingwater from any source, the author confirmed that thesource was used for drinking by local populations.

RESULTSWater quality. A total of 106 drinking water sources

from 13 countries were analyzed using a consistentmethodology (Table 1). Of these sources, 67 (63%) wereimproved (Table 1). These included urban standpipes(21%), rural standpipes (11%), protected wells (19%),and springs (12%). The remaining 39 sources (37%) wereunimproved and included open wells (16%), open water(19%), and vendor water (2%).

As shown in Table 1, the drinking water sources sam-pled varied considerably from country to country. For

example, no wells were sampled in Burundi; wells arenot common because there is no local well-drilling com-pany. In Angola, where the target population for the SWSproject is within the major cities of Luanda and Huambo,the majority of the samples taken were from urban stand-pipes. Overall, a variety of drinking water was sampledacross the 13 countries.

Table 2 shows water quality testing results by sourcetype. The mean turbidity was lower in improved sourcesthan in unimproved sources. Of the 106 samples, 35(33%) exceeded a turbidity value of 5 ntu (range of5.4–551.0 ntu), and 68 (64%) exceeded 1 ntu. The pHand conductivity had no relation to source type. Eleven(10.4%) of the 106 sources exceeded a pH value of 8.0(range of 8.1–9.4).

Free chlorine residual levels were measured in each ofthe 106 sources, with only five samples (4.7%) of thesources having detectable free chlorine residual. All fivesamples with chlorine residual came from urban stand-pipes—one that was located in Malawi (chlorine residualof 0.2 mg/L), one in Mozambique (0.3 mg/L), one inAngola (1.4 mg/L), and two in Ethiopia (0.5 and 1.3mg/L). Of the 22 total urban standpipes, which could beexpected to be chlorinated, only 5 (22.7%) had chlorineresidual present at the time of testing.

Quality control. Duplicate sampling was conductedfor each water quality parameter tested. All data methigh quality control standards (Table 3). The relativepercent difference of duplicated samples was 7.09% forfree chlorine, 7.85% for turbidity, 1.39% for pH, and6.68% for conductivity.

Improved Sources—n Unimproved Sources—n

Urban Rural Protected Protected Open Open VendorCountry Standpipe Standpipe Well Spring Well Water Water

Angola 5 2 1 1 3

Burundi 6 3 3

Cameroon 2 3 3 2 2

Democratic Republic 1 1 3of the Congo

Ethiopia 2 1 1 2

Guinea 2 3 1 3 1

Malawi 1 1 1 1 1

Mozambique 3 1 3 1

Nepal 2 1 4 2 3

Nigeria 1 1 3 1 1 2

Tanzania 2 1 1 1

Yemen 1 3 1

Zambia 2 1 1 1

Total—n (%) 22 (21) 12 (11) 20 (19) 13 (12) 17 (16) 20 (19) 2 (2)

n—number of samples

TABLE 1 Sources analyzed by country



Dosage testing results: analysis. After chlorine addition,a sample was considered to meet the guidelines for freechlorine residual if the value was < 2.0 mg/L 1 h afterNaOCl addition and > 0.2 mg/L 24 h after NaOCl addi-tion. This free chlorine residual range was selectedbecause of user acceptability concerns above 2.0 mg/Lfree chlorine, because < 0.2 mg/L chlorine may not ade-quately protect water from recontamination, and becausethis range met the WHO and USEPA guidelines for freechlorine in drinking water. This dosage regime has beenspecifically approved as “consistent with the Third Edi-tion of the Guidelines” in correspondence from theWHO Water, Sanitation, and Health Coordinator (Bar-tram, 2005).

These criteria were also consistent with taste accept-ability studies. The author and the NGO PSI conductedfocus group testing on taste perception at different chlo-rine residual levels in Ethiopia and Zambia. In Ethiopia,focus group participants did not taste the chlorine resid-ual at 1.0 mg/L, noticed the chlorine residual at 2.0 mg/L,found the taste objectionable at 3.0 mg/L, and found thewater unsuitable for drinking at 4.0 mg/L. In Zambia,participants did not notice a taste at 0.2 mg/L, tasted theresidual at 1.0 mg/L but did not find it objectionable,found the 2.0 mg/L residual too strong and bitter, andrefused to taste the water at 3.0 mg/L.

Dosage testing results for the 1.875-mg/L dose in safe stor-age containers. A dose of 1.875 mg/Lof NaOCl was added to 100 (94%)of the total 106 source water sam-ples in safe storage containers. Thesix sources for which the 1.875-mg/Ldose was not tested had turbidity > 5ntu; logistics prevented the samplingof multiple doses for the same source,and a double dose of 3.75 mg/L wasthe only dose tested. In this case, asafe storage container was defined asa jerry can. Analyses comparing jerry

cans with unsafe storage containers are provided in asubsequent section.

Five of the 100 sources dosed with 1.875 mg/L ofNaOCl had free chlorine residual present before dosing.The 1.875-mg/L dose caused all five samples to exceed 2.0mg/L of free chlorine residual 1 h after chlorine addition.A half dose of 0.94 mg/L NaOCl led to free chlorineresiduals that met the criteria in two of these sources.No sample at either the 0.94-mg/L or 1.875-mg/L dose atany time exceeded the WHO guideline value of 5 mg/L orthe USEPA MCL of 4 mg/L for free chlorine residual.

Because these five urban standpipe sources werealready chlorinated, they were excluded from furtheranalysis. Of the 95 remaining sources tested at the 1.875-mg/L NaOCl dose, 74 sources (77.9%) had free chlorineresiduals no greater than 2.0 mg/L 1 h after chlorineaddition and no less than 0.2 mg/L for 24 h after chlo-rine addition, in accordance with the proposed criteria.These results were correlated with both turbidity andsource type.

Correlation with turbidity. Sources with lower turbiditieswere more likely to meet the criteria at an NaOCl dose of1.875 mg/L than were sources with higher turbidities.The majority (91.4%) of the 35 samples in the turbidityrange of 0 to < 1 ntu met the criteria at a dose of 1.875mg/L NaOCl (Table 4). The three samples that did notmeet the criteria included two spring sources in Douala,

Number Turbidity—ntu pH Conductivity—µmhos/cmSource Type of Sources Average (Range) Average (Range) Average (Range)

Urban tap 22 2.9 (0.14–9.31) 7.4 (6.5–9.4) 236 (10–780)

Rural tap 12 3.0 (0.0–17.6) 6.8 (4.8–9.0) 167 (50–610)

Protected well 20 11.9 (0.0–87.1) 6.6 (5.0–8.5) 338 (10–1,130)

Spring 13 0.5 (0.0–1.38) 6.3 (4.3–8.5) 435 (0 to > 2,000)

Open well 17 21.9 (0.7–135.5) 6.8 (4.1–8.4) 455 (0–960)

Open water 20 47.3 (0.0–551.0) 7.3 (5.1–8.8) 235 (0–880)

Vendor water 2 1.1 (0.5–1.7) 7.3 (7.3–7.3) 480 (120–840)

Total 106 15.7 (0.0–551.0) 6.9 (4.1–9.4) 311 (0 to > 2,000)

All 106 samples were analyzed for turbidity. However, because of meter dysfunction, only 98 samples were analyzed for pH and 93 for conductivity. The pH was notmeasured in Malawi samples, and conductivity was not measured in the Malawi and Mozambique samples.

TABLE 2 Source water physical and chemical characteristics by source type

Samples Duplicated Relative PercentParameter Collected—n Samples—n (%) Difference

Free chlorine 1,393 99 (7.1) 7.09

Turbidity 106 22 (20.8) 7.85

pH 98 15 (15.3) 1.39

Conductivity 91 13 (14.3) 6.68

n—number

TABLE 3 Quality control for water quality parameters



Cameroon, and one urban tap in Zambia. Similarly, themajority of the sources in the turbidity ranges of 1 to < 5ntu (81.3%) and 5 to < 10 ntu (81.8%) also met the cri-teria after addition of 1.875 mg/L of NaOCl, and no dif-ference was seen in the percentage of sources meeting thecriteria in the two turbidity ranges. Of the eight sourcesin the combined turbidity range of 1 to < 10 ntu that didnot meet the criteria, five were from Cameroon. Althoughfour of these five sources met the criteria at 1 h, all fourdegraded rapidly in 24 h to 0.04, 0.05, 0.14, and 0.14mg/L of free chlorine residual, indicating high chlorinedemand. The remaining three samples, which met thecriteria, came from two open water sources in Mozam-bique and Zambia and one spring in Yemen.

In the range of 10 to < 100 ntu, only seven (46.7%) ofthe fifteen samples tested met the criteria after addition of

1.875 mg/L of NaOCl. All of the eight sources that didnot meet the criteria were either open well or open watersources. Of the seven sources that met the criteria, threewere protected well sources, one was a rural tap source, twowere open well sources, and one was an open water source.Neither of the two sources tested that had turbidity � 100ntu met the criteria after addition of 1.875 mg/L of NaOCl.

Correlation by source type. Compared with improvedsources, unimproved sources were statistically less likely(p = 0.001) to meet the criteria at a dose of 1.875 mg/L.Of the 61 improved sources tested, 54 (88.5%) met thecriteria versus 20 (58.8%) of 34 unimproved sources(Table 5). The seven improved sources that did not meetthe criteria included an urban tap in Zambia, five sources(two springs, two rural taps, and a protected well) inCameroon, and a spring in Yemen.

Unchlorinated UnchlorinatedSources With Free Sources (> 10 ntu)

Unchlorinated Chlorine Residual Unchlorinated With Free Chlorine Unchlorinated Sources Tested of 0.2–2.0 mg/L for Sources (>10 ntu) Residual of 0.2–3.5

Turbidity Sources at 1.875-mg/L 24 h at 1.875-mg/L Tested at 3.75-mg/L mg/L for 24 h at Range in Study NaOCl Dose NaOCl Dose NaOCl Dose 3.75-mg/L NaOCl Dose

ntu n n (%) n (%) n (%) n (%)

0 to < 1 35 35 (100) 32 (91.4)

1 to < 5 32 32 (100) 26 (81.3)

5 to < 10 12 11 (92) 9 (81.8)

10 to < 100 19 15 (79) 7 (46.7) 15 (78.9) 10 (66.7)

� 100 3 2 (67) 0 (0) 3 (100) 1 (33.3)

Total 101 95 (94) 74 (77.9)

n—number, NaOCl—sodium hypochlorite

TABLE 4 Unchlorinated sources meeting free chlorine residual criteria, categorized by turbidity

Unchlorinated UnchlorinatedSources With Free Sources With

Unchlorinated Chlorine Residual Unchlorinated Free Chlorine Unchlorinated Sources Tested of 0.2–2.0 mg/L for Sources Tested Residual of 0.2–3.5

Sources at 1.875-mg/L 24 h at 1.875-mg/L at 3.75-mg/L mg/L for 24 h at Source in Study NaOCl Dose NaOCl Dose NaOCl Dose 3.75-mg/L NaOCl DoseType n n (%) n (%) n (%) n (%)

Urban tap 17 17 (100) 16 (94.1)

Rural tap 12 12 (100) 10 (83.3)

Protected well 20 19 (95) 18 (94.7)

Spring 13 13 (100) 10 (76.9)

Open well 17 15 (88) 9 (60.0) 14 (82.4) 10 (71.4)

Open water 20 17 (85) 9 (52.9) 20 (100) 14 (70)

Vendor water 2 2 (100) 2 (100.0) 2 (100) 2 (100)

Total improved 62 61 (98) 54 (88.5)

Total unimproved 39 34 (87) 20 (58.8) 36(92.3) 26 (72.2)

Total sources 101 95 (94) 74 (77.9)

n—number, NaOCl—sodium hypochlorite

TABLE 5 Unchlorinated sources meeting criteria for free chlorine residual, categorized by source



Correlation by turbidity and source type. Because of theindividual correlations seen between turbidity and dosageand between source type and dosage, a combined corre-lation between turbidity and source type with dosagewas analyzed. A total of 84 of the 101 nonchlorinatedsources analyzed were improved and/or had turbidity <10 ntu. Of the 84 improved or low-turbidity sources, 82were analyzed at the 1.875-mg/L dose of NaOCl, and 71of these (86.6%) met the free chlorine residual criteria.Of the 11 samples that did not meet the guidelines, 7were from Cameroon. The remaining four samples camefrom an urban tap and an open water source in Zambia,an open well in Mozambique, and a spring in Yemen.When the Cameroon samples are removed from theanalysis, the addition of 1.875 mg/L of NaOCl tononchlorinated waters from an improved source or withturbidity < 10 ntu met the free chlorine residual criteriain 94.7% of samples tested. Further analysis in this arti-cle references this correlation of the 1.875-mg/L dosewith both source type and turbidity.

Dosage testing results for unimproved waters with turbid-ity > 10 ntu. As described previously, 84 of the 101 nonchlo-rinated sources analyzed either had a turbidity < 10 ntuand/or were from an improved source. Of the remaining 17samples, 14 samples (13.9%) came from unimprovedsources with turbidity of 10–100 ntu and 3 samples werefrom unimproved sources with turbidity > 100 ntu.

Of these 14 unimproved sources with turbidity of10–100 ntu, 12 were analyzed at a dose of 3.75 mg/L ofNaOCl. Five (41.7%) of these 12 sources met the crite-ria for free chlorine residual after chlorine addition atthe 3.75-mg/L dose. Of the three unimproved sourceswith turbidity > 100 ntu, none had chlorine residual pre-sent 24 h after addition of 3.75 mg/L of NaOCl andthus did not meet the criteria established in this research.

Results for dosage testing in unsafe storage containers.The SWS program promotes the addition of NaOCl at thehousehold level into a safe storage container, defined asa closed ceramic, plastic, or metal container into whichusers cannot dip their hands. However, not all SWS usershave access to such a container, and therefore dosagetesting was also conducted in the laboratory using uncov-ered storage containers with large openings.

Test results for these unsafe storage containers wereinconsistent. In Malawi, the decay of free chlorine resid-ual in open ceramic receptacles occurred significantlyfaster than in the closed plastic containers (Figure 1).Because the locally made ceramic receptacles were firedat a low temperature, the clay was crumbling. Scrubbingthe ceramic receptacles to remove loose organic mate-rial significantly reduced free chlorine residual decay. InKenya, the author did not note additional chlorinedemand in open ceramic containers that were well madeand fired at a high temperature (Figure 2). However,previous researchers in Kenya did observe additionalchlorine demand in ceramic pots (Ogutu et al, 2001). In

Nepal, a spring sample with turbidity of 0.08 ntu, pHof 5.9, and conductivity of 340 µmhos/cm was ana-lyzed at NaOCl doses of 1.44 mg/L and 1.875 mg/L inplastic jerry cans and open metal gagris. As shown inFigure 3, at both doses, the chlorine residual decayedmore rapidly in the gagris. Nonetheless, the samplesanalyzed in nonsafe storage containers in Nepal, Kenya,and Malawi met the criteria for free chlorine residualproposed in the current research.

DISCUSSIONOn the basis of these data, it is recommended that

the proposed criteria for a free chlorine residual of no

0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

0 4 8 12 16 20 24 Time—h

Fre

e C

hlo

rin

e R

esid

ual

—m

g/L

Plastic jerry can Ceramic pot

FIGURE 1 Comparison of chlorine residual decay at a double NaOCl dose (4 mg/L) in open ceramic and closed plastic containers in Malawi

NaOCl—sodium hypochlorite

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Time—h

Fre

e C

hlo

rin

e R

esid

ual

—m

g/L

Plastic jerry can Ceramic container

FIGURE 2 Comparison of chlorine residual decay at a double NaOCl dose (4 mg/L) in open ceramic and closed plastic containers in Kenya



more than 2.0 mg/L 1 h after NaOCl addition and no lessthan 0.2 mg/L 24 h after treatment be adopted by house-hold and emergency POU chlorination programs. Thesecriteria are consistent with WHO and USEPA recom-mendations for free chlorine residual in treated waterand are compatible with taste-testing results from twodeveloping countries.

Current results clearly indicated that a NaOCl dose of1.875 mg/L is appropriate for use in unchlorinated waterwith turbidity < 10 ntu or from an improved source. Ofthe 82 samples tested at this dose, 71 (86.6%) met theproposed free chlorine residual criteria. The 1.875-mg/LNaOCl dose for clear water is consistent with 3 drops/Lof 1% solution (a 1.5-mg/L dose at a conversion factorof 20 drops/mL) established by the WHO in 1997. Thisdose provides a maximum concentration × time (C × T)factor of 56.25 mg-min/L and a minimum of 6 mg-min/Lif users wait 30 min before drinking. A C × T factor of

6–56.25 mg-min/L is sufficient to inactivate many bac-teria, viruses, and some protozoa that cause waterbornediseases, although inactivation effectiveness is also depen-dent on pH and temperature (CDC, 2006). It will notinactivate Cryptosporidium, however, and populations atrisk for Cryptosporidium infection should consider a fil-tration step before chlorination in order to remove theoocysts. This dose is significantly less than the USEPAemergency recommendation of 8 drops of 5.25%NaOCl/gal of clear water, which leads to a dose between4.44 mg/L and 7.41 mg/L, depending on the size of thedrops used (USEPA, 2006b).

Of the 11 unchlorinated water sources with turbid-ity < 10 ntu or from an improved source that did notmeet the criteria at the 1.875-mg/L dose, 7 (63.6%)were from Cameroon. In Cameroon, the containers usedfor collection and testing were more difficult to cleanthan those in other countries, and vegetable oil residuemay have increased the chlorine demand of the sam-ples. Unfortunately, it was not possible to retest theCameroon samples in clean containers. This observa-tion highlights the need for users to be educated aboutcleaning containers before using POU chlorination. Ifthe Cameroon samples are removed from the analysis,the percentage of unchlorinated water samples with tur-bidity < 10 ntu or from an improved source that met thefree chlorine residual criteria at the 1.875-mg/L NaOCldose increases from 86.6% to 94.7%.

Of the 101 nonchlorinated sources analyzed for thisstudy, 14 (13.2%) came from unimproved source waterswith turbidity of 10–100 ntu. The results of dosage test-ing in these sources were not as consistent: only 3 (27.3%)of the 11 sources analyzed at the 1.875-mg/L dose had freechlorine residuals that met the criteria, and only 5 (41.7%)of the 12 sources analyzed at the 3.75-mg/L dose hadfree chlorine residuals that met the criteria. However, ifthe free chlorine residual criteria established in this arti-cle were relaxed to < 3.5 mg/L at 1 h after NaOCl addi-tion, then 8 (66.7%) of the 12 sources analyzed wouldmeet this criterion; if the criterion were further relaxed to> 0.1 mg/L after 24 h of storage, then 11 (91.7%) of the12 sources analyzed at the 3.75-mg/L dose would meetthis relaxed criterion. This relaxation of the criteriaallowed some sources that met the criteria at a 1.875-mg/L dose to also meet the criteria at a dose of 3.75-mg/L NaOCl and allowed sources that showed signifi-cant decay of the chlorine residual over the 24 h to 0.1mg/L to meet the criteria. The subsequent section high-lights some concerns about raw chlorination of turbidwater and this relaxation of criteria.

Concerns associated with direct chlorination of turbidwater. One concern with directly chlorinating turbid wateris whether the free chlorine residual will effectively inac-tivate disease-causing organisms and thus reduce theincidence of diarrheal disease. Data from two studiessuggest that it will. In 30 sources in western Kenya with


0

0.4

0.8

1.2

1.6

2.0

0 4 8 12 16 20 24

Time—h

Fre

e C

hlo

rin

e R

esid

ual

—m

g/L

Plastic container Open gagri

0

0.4

0.8

1.2

1.6

2.0

0 4 8 12 16 20 24

Time—h

Fre

e C

hlo

rin

e R

esid

ual

—m

g/L

FIGURE 3 Comparison of chlorine residual decay at NaOCl doses of 1.44 mg/L (A) and 1.875 mg/L (B) in open gagris and closed plastic containers in Nepal


A

B



turbidity values of 0.3–1,724.0 ntu, researchers foundthat 9 of 10 sources with turbidity of 0–10 ntu, all 10sources with turbidity of 10–100 ntu, and 6 of 10 sourceswith turbidity > 100 ntu had E. coli concentrations of <1 cfu/100 mL 30 min after NaOCl addition (Crump et al,2004). In a further study, the same researchers foundthat household chlorination of stored drinking waterfrom these highly turbid sources (mean turbidity of 55ntu, range of 0–1,000 ntu) effectively reduced diarrhealdisease incidence in this population (Crump et al, 2005).Users of household chlorination had a 26% reduction ofdiarrheal disease incidence compared with controls, andusers of a combined flocculant/disinfectant product8

showed a similar (19%) reduction of diarrheal diseaseincidence compared with controls.

Another concern associated with directly chlorinatingturbid waters is chlorination by-products formed by thereaction of NaOCl with organic material. The CDC hasmeasured trihalomethane levels in waters (with turbidi-ties of 0–325 ntu) that had been treated with NaOCldoses of up to 12 mg/L, in both plastic and ceramic stor-age containers, and found that no sample exceeded WHOguideline values for individual or combined THM con-centrations (Lantagne et al, 2008).

A final concern in implementing chlorination pro-grams is user acceptance of the taste and smell of chlo-rine. Taste-testing results showed that users accept upto a chlorine residual of 2.0 mg/L. In the event that usersobject to the taste of the chlorine at a lower residualthan 2.0 mg/L, dosage testing can be completed to deter-mine whether lower dosages will maintain the appro-priate residual.

In many areas of the world, the diarrheal disease bur-den can be reduced by directly chlorinating turbid waters.Although pretreatment flocculation or filtration beforechlorination yields higher quality water, it often is not eco-nomically feasible. In unimproved source waters withturbidities of 10–100 ntu, a 3.75-mg/L dose of NaOClcan provide adequate chlorine residuals to reduce diar-rheal disease until improved sources can be provided(Crump et al, 2005; 2004). On the basis of results fromthe current research and other studies, POU chlorina-tion alone is not recommended for source waters with tur-bidity > 100 ntu.

IMPLEMENTATION EXAMPLESThe CDC provides extensive technical support for

implementation of household-based chlorination pro-grams. Often institutions that implement these programsfind the NaOCl dosage and product design aspects ofthe program daunting. Since the time of the testingdescribed in this research, the dosage testing methodologydescribed here has been completed by CDC staff, NGOstaff, or in-country laboratories in seven additional coun-tries, with consistent results. It is recommended that localdosage testing be completed before initiation of a POU A water vendor in Angola fills customers’ containers with water.

In Africa, women may need to walk miles to obtain drinking water.



chlorination project. If local dosage testing cannot becompleted, however, programs can use as a guidelineNaOCl doses of 1.875 mg/L for unchlorinated, improvedsources or sources with turbidity < 10 ntu and 3.75 mg/Lfor unimproved sources with turbidity of 10–100 ntu.The amount of NaOCl to be added for a dose of 1.875 or3.75 mg/L can be calculated using Eq 2 in which Cl ischlorine and LW is litres of water. Useful conversion fac-tors for this equation include

• 15 to 25 drops is generally equal to 1 mL,• 3.78 L is equal to 1 gal, and• 1% NaOCl is equal to 10,000 mg/L NaOCl.

Volume NaOCl (mLCl) = (2)

The following section provides examples of howdosage testing affects SWS program implementation.

Recommended implementation strategy for national-scale programming. PSI is a social marketing NGO thatsells health products in developing countries at anaffordable cost by distributing them through wholesaleand retail commercial networks and generating demandthrough behavior change communications. Currently,PSI sells NaOCl solution in 16 countries. Through June2006, PSI had sold more than 21 million bottles ofsolution worldwide, potentially treating more than 24billion litres of water.

In each PSI program country, dosage testing has beencompleted, and many of those results are included here.These results have led to the development of a regionalproduct, a solution of 1.25% NaOCl packaged in a 150-mL bottle with a 3-mL cap. One bottle is sufficient totreat fifty 20-L containers (1,000 L) of clear water usinga dosing regime of one capful per 20 L (a dose of 1.875mg/L). On the assumption that a family uses 20 L of high-quality water for drinking, cooking, and washing per day,a single bottle will last a family of 5–6 people approxi-

mately 50 days. In addition toproviding the correct dosage,the product is easy to use andtransportable and has enoughspace on the bottle for instruc-tions. Compared with the orig-inal designs shown in the pho-tograph on page 116, theregional product has signifi-cantly reduced product cost,simplified project initiation,and facilitated the importationof product from neighboringcountries in emergencies.

PSI has implemented theregional product concept byinvesting in a specialized 3-mLvolume cap mold.9 Programcountries import the easilytransportable caps from Kenyaand import a bottle mold toproduce bottles at a local plas-tics company. Ten of the 16PSI program countries havebegun with or converted to theregional bottle. An additionaltwo countries have designsvery similar to the regionalbottles but use locally avail-able caps with a different vol-ume (2.5 mL and 4 mL) and adifferent NaOCl concentra-tion. Dosage testing in eachnew country is still recom-mended, and if a higher orlower dosage is needed, the

NaOCl Dosage (mg/LW) × LW��NaOCl Concentration (mg/LCl)× 1 L�1,000 mL

These containers were used for dosage testing in the study.

These bottles illustrate the range of initial sodium hypochlorite water treatment products for

programs in Bolivia, Peru, Zambia, Uganda, Kenya, India, and Madagascar.



NaOCl concentration is modified, and the bottle and capsize are conserved. For example, to account for theceramic pots with high chlorine demand in Malawi, theconcentration of the solution was increased to 1.6% (onecap for clear water then results in a dose of 2.4 mg/L).

Recommended implementation strategy for community-based programs. The SWS is also implemented in smallerscale community-based projects by different imple-menting partners. Although product standardization isnot as feasible across these projects, it remains impor-tant to ensure that the chlorine dosage is appropriate.It is recommended that an available, nonleaking bottle-and-cap combination be identified and that NaOCl beobtained from a private company or by using an elec-trolytic generator. The NaOCl solution should be man-ufactured to a concentration that results in chlorineresidual levels that meet the criteria when one cap of thesolution is added to the volume of water in the local safestorage container.

In the Jolivert Safe Water for Families program in ruralnorthern Haiti, a 250-mL bottle with a 5-mL cap isimported from the United States and labeled for the pro-ject. The 0.7% NaOCl solution is produced locally usingan electrolytic generator. This dose, equivalent to 1.75mg/L in 20 L of water, meets proposed free chlorine resid-ual criteria established in the current research. A doubledose is not needed because turbid water is not used fordrinking in Haiti.

Recommended implementation strategy for emergencyresponse. POU chlorination has been recommended as adrinking water treatment option in many diverse emer-gency situations, such as pipe breakages in developedcountries, hurricane season in the United States (includ-ing the response to Hurricane Katrina in 2005), the2004 tsunami in Asia, refugee camps, and cholera out-breaks. CDC staff has provided assistance to relief orga-nizations in these circumstances to identify sources ofchlorination products, determine appropriate dosagerequirements, develop educational messages, and mon-itor and evaluate programs.

During the 2004 hurricane season in the United States,Florida officials were interested in providing a POU chlo-rination product because the numerous hurricanes lefthouseholds without the power necessary to boil water,and officials found households did not have tools to dosewater with bleach. The CDC assisted Florida by locatingcommercially available dropper bottles, developing abottle label, creating a survey for users, and assistingwith dosage and chlorine residual testing. Volunteers inhurricane centers were rapidly mobilized to fill bottleswith donated and locally available commercial 5.25%bleach, label the bottles, and distribute them to hurricanecenter visitors. One concern in the project was that thedose of 4 drops/gal (equivalent to 2.78 mg/L using aconversion factor of 20 drops/mL) that had been rec-ommended by the CDC and Florida officials was signif-

icantly less than the USEPA recommendation of 8drops/gal (5.56 mg/L using a conversion factor of 20drops/mL) during emergencies, which could have led toconflicting messages. Nonetheless, Florida officials felt theproject was successful and continued to distribute bottlesthroughout the 2004 hurricane season.

Further research. Although results indicated that appro-priate free chlorine residual levels can be achieved throughPOU chlorination of source waters with turbidities up to100 ntu, user preference for clear water and acceptabletaste and the potential for persistent bacterial contami-nation in highly turbid water highlight the need for fur-ther research. A low-cost method to remove organic mate-rial from turbid water and reduce chlorine demand isneeded to reach populations who rely on the poorestquality water, which may include those who bear thelargest share of the burden of diarrheal disease deaths. Thepotential effect of inexpensive, locally available prechlo-rination treatment products such as alum as a flocculant,sand as a filter, and Moringa oleifera (moringa) seeds as

Chlorine is used to purify water in Kenya.



a coagulant to reduce the chlorine demand of turbidwaters is currently being evaluated. According to unpub-lished data from previous CDC investigations, the fer-rous sulfate in a commercially available combined coag-ulation/chlorination product8 has been proven to reducethe chlorine demand of turbid waters. However, the prod-uct may be too expensive for the poorest to afford, neces-sitating nonmarket-based distribution mechanisms toreach this population.

In addition, further research is warranted to deter-mine what physiochemical properties cause nonchlori-nated source waters from a protected source or of tur-bidity < 10 ntu to not meet the criteria for free chlorineresidual established in this article. Furthermore, manyPOU chlorination users, particularly in rural areas, pre-fer to use ceramic containers. Results are mixed onwhether ceramic containers increase chlorine demand,and further research is needed to quantify the chlorinedemand of different types of ceramic containers.

The applicability of these recommendations to disasterresponse in developed countries should be further stud-ied. The current USEPA guidelines for emergency situa-tions in the United States recommend adding 8 drops of4–6% NaOCl solution to 1 gal of clear water. This dose,using 5.25% NaOCl and a conversion factor of 20drops/mL is equal to 5.56 mg/L. This dose is signifi-cantly higher than what was necessary to achieve free

chlorine residual levels of no greater than 2.0 mg/L 1 hafter chlorine addition and no less than 0.2 mg/L after24 h of storage for nearly all waters in this study. Toaddress these discrepancies, further research is war-ranted to establish NaOCl dosage requirements forwaters likely to be used for drinking in emergency situ-ations in the United States.

CONCLUSIONSDiarrheal diseases often are transmitted by contami-

nated drinking water and result in an estimated 2.2 mil-lion deaths each year. POU chlorination of householddrinking water is proven to reduce diarrheal disease inci-dence and can help prevent these deaths in developingcountries. This research provided a framework to addresstwo technical challenges in the implementation of POUchlorination programs: unclear free chlorine residualguidelines for household water treatment and determi-nation of the NaOCl doses necessary to obtain the desiredfree chlorine residuals in different source waters. It is rec-ommended that POU chlorination programs adopt theproposed criteria for free chlorine residual of < 2.0 mg/L1 h after NaOCl addition and > 0.2 mg/L after 24 h ofstorage for household water treatment. Although POUchlorination projects should conduct dosage testing ofrepresentative sources in the area of intervention, theNaOCl doses of 1.875 mg/L for nonchlorinated, improved

REFERENCES

Baqui, A.H.; Black, R.E.; Sack, R.B.; Chowdhury, H.R.; Yunus, M.; &Siddique, A.K., 1993. Malnutrition, Cell-Mediated Immune Defi-ciency and Diarrhea: A Community-Based Longitudinal Studyin Rural Bangladeshi Children. Amer. Jour. Epidemiol.,137:3:355.

Bartram, J., 2005. Personal communication to Eric Mintz of the Cen-ters for Disease Control and Prevention.

CDC (Centers for Disease Control and Prevention), 2006. Effect ofChlorine in Inactivating Selected Microorganisms.http://www.cdc.gov/safewater/about_pages/chlorinationtable.htm (accessed Sept. 9, 2007).

Chiller, T.M.; Mendoza, C.E.; Lopez, M.B.; Alvarez, M.; Hoekstra, R.M.;Keswick, B.H.; & Luby, S.P., 2006. Reducing Diarrhoea inGuatemalan Children: Randomized Controlled Trial of Floccu-lant–Disinfectant for Drinking Water. Bull. World Health Org.,84:1:28.

Crump, J.A.; Otieno, P.O.; Slutsker, L.; Keswick, B.H.; Rosen, D.H.;Hoekstra, R.M.; Vulule, J.M.; & Luby, S.P, 2005. Household-BasedTreatment of Drinking Water With Flocculant–Disinfection forPreventing Diarrhoea in Areas With Turbid Source Water inRural Western Kenya: Cluster Randomized Controlled Trial. Brit.Med. Jour., 331:7515:478.

Crump, J.A.; Okoth, G.O.; Slutsker, L.; Ogaja, D.O.; Keswick, B.H.; &Luby, S.P., 2004. Effect of Point-of-Use Disinfection, Flocculation,and Combined Flocculation–Disinfection on Drinking WaterQuality in Western Kenya. Jour. Appl. Microbiol., 97:1:225.

Cutler, D. & Miller, G., 2005. Role of Public Health Improvements inHealth Advances: The Twentieth-Century United States. Demog-raphy, 42:1:1.

Fewtrell, L. & Colford, J., 2005. Water, Sanitation, and Hygiene inDeveloping Countries: Interventions and Diarrhoea—A Review.Water Sci. & Technol., 52:8:133.

Guerrant, D.I.; Moore, S.R.; Lima, A.A.; Patrick, P.D.; Schorling, J.B.; &Guerrant, R.L., 1999. Association of Early Childhood Diarrhoeaand Cryptosporidiosis With Impaired Physical Fitness and Cogni-tive Function Four–Seven Years Later in a Poor Urban Commu-nity in Northeast Brazil. Amer. Jour. Trop. Med. & Hyg., 61:5:707.

Lantagne, D.S.; Blount, B.C.; Cardinali, F.; & Quick, R., 2008. Disinfec-tion By-Product Formation and Mitigation Strategies in Point-of-Use Chlorination of Turbid and Non-Turbid Waters in WesternKenya. Jour. Water & Health, 6:1:67.

Luby, S.P.; Agboatwall, M.; Hoekstra, R.M.; Rahbar, M.H.; Billhimer,W.; & Keswick, B.H., 2004. Delayed Effectiveness of Home-Based Interventions in Reducing Childhood Diarrhea, Karachi,Pakistan. Amer. Jour. Trop. Med. & Hyg., 71:4:420.

Mintz, E.D.; Reiff, F.M.; & Tauxe, R.V., 1995. Safe Water Treatmentand Storage in the Home: A Practical New Strategy to Pre-vent Waterborne Disease. Jour. Amer. Med. Assoc.,273:12:948.

Ogutu, P.; Garrett, V.; Barasa, P.; Ombeki, S.; Mwaki, A.; & Quick, R.E.,2001. Seeking Safe Storage: A Comparison of Drinking WaterQuality in Clay and Plastic Vessels. Amer. Jour. Public Health,91:10:1610.



sources or sources with < 10 ntu turbidity and 3.75 mg/Lfor unimproved sources with turbidity of 10–100 ntu canbe used as a starting point for dosage testing or as a guide-line value when dosage testing is not practical. Address-ing these technical implementation issues will allow expan-sion of household chlorination programs to improvewater quality and prevent disease worldwide.

ACKNOWLEDGMENTThe author thanks Population Services International

staff in Angola, Burundi, Cameroon, Democratic Repub-lic of Congo, Ethiopia, Guinea, Malawi, Mozambique,Nepal, Nigeria, Tanzania, and Zambia as well as Kenya,Madagascar, Tajikistan, and Uzbekistan, plus Abt Asso-ciates staff in Yemen for their invaluable assistance insample collection and logistical coordination.

ABOUT THE AUTHORDaniele S. Lantagne is an environmentalengineer in the Enteric Diseases Epidemi-ology Branch, M/S A-38, Centers forDisease Control and Prevention, 1600Clifton Rd. NE, Atlanta, GA, 30333; e-mail [email protected]. She holds bach-

elor’s and master’s degrees from the MassachusettsInstitute of Technology in Cambridge. She has com-pleted her master’s thesis on trihalomethane formation

in Haiti and since 2001 has worked on water and sani-tation in the developing world. Lantagne has traveledto more than 30 countries in Africa, Asia, and LatinAmerica, where she provided technical assistance, stud-ied and implemented point-of-use water treatment pro-grams, and worked with filtration, chlorination, andmixed-treatment options.

Date of submission: 1/18/07Date of acceptance: 12/4/07

FOOTNOTES12020 turbidimeter, LaMotte Co., Chestertown, Md.2 Hanna Instruments, Bedfordshire, United Kingdom31200 chlorine colorimeter, LaMotte Co., Chestertown, Md.4Method 8209, Hach Co., Loveland, Colo.5Analytical Services Inc., Norcross, Ga.6Microsoft Excel, Microsoft, Redmond, Wash. 7Analysis ToolPak and Pivot Tables, Microsoft Excel, Microsoft,Redmond, Wash.

8PuR®, Procter & Gamble, Cincinnati, Ohio9AMM Engineering, Nairobi, Kenya

If you have a comment about thisarticle, please contact us at

[email protected].

Quick, R.E.; Kimura, A.; Thevos, A.; Tembo, M.; Shamputa, I.; Hutwag-ner, L.; & Mintz, E., 2002. Diarrhea Prevention Through House-hold-Level Water Disinfection and Safe Storage in Zambia.Amer. Jour. Trop. Med. & Hyg., 66:5:584.

Quick, R.E.; Venczel, L.V.; Mintz, E.D.; Soleto, L.; Aparicio, J.; Gironaz,M.; Hutwagner, L.; Greene, K.; Bopp, C.; Maloney, K.; Chavex, D.;Sobsey, M.; & Tauxe, R.V., 1999. Diarrhea Prevention in BoliviaThrough Point-of-Use Disinfection and Safe Storage: A Promis-ing New Strategy. Epidemiol. & Infect., 122:1:83.

Reller, M.E.; Mendoza, C.E.; Lopez, M.B.: Alvarez, M.; Hoekstra,R.M.; Olson, C.A.; Baier, K.G.; Keswick, B.H.; & Luby, S.P.,2003. A Randomized Controlled Trial of Household-BasedFlocculant–Disinfectant Drinking Water Treatment for Diar-rhea Prevention in Rural Guatemala. Amer. Jour. Trop. Med. &Hyg., 69:4:411.

Rowlett, R., 2000. How Many? A Dictionary of Units of Measure-ment. http://www.unc.edu/~rowlett/units/ (accessed Aug. 22,2007).

Semenza, J.C.; Roberts, L.; Henderson, A.; Bogan, J.; & Rubin, C.H.,1998. Water Distribution System and Diarrheal Disease Trans-mission: A Case Study in Uzbekistan. Amer. Jour. Trop. Med. &Hyg., 59:6:941.

Tauxe, R.V.; Mintz, E.D.; & Quick, R.E., 1995. Epidemic Cholera in theNew World: Translating Field Epidemiology Into New PreventionStrategies. Emerg. Infectious Dis., 1:4:141.

USEPA (US Environmental Protection Agency), 2006a. List of DrinkingWater Contaminants and MCLs: National Primary Drinking

Water Regulations. http://www.epa.gov/safewater/mcl.html(accessed Aug. 22, 2007).

USEPA, 2006b. Emergency Disinfection of Drinking Water.http://www.epa.gov/safewater/faq/emerg.html (accessed Aug.22, 2007).

USEPA, 2002. Long-Term 1 Enhanced Surface Water Treatment Rule:A Quick Reference Guide. EPA/816-F-02-001, Washington.

USEPA, 1994. Method 200.7, Determination of Metals and Trace Ele-ments in Water and Wastes by Inductively CoupledPlasma–Atomic Emission Spectrometry. Environmental Monitor-ing Systems Lab., Ofce. of Res. & Devel., Cincinnati.

Young, R. & Glover, T., 2002. Measure for Measure. Sequoia Publ.,Littleton, Colo.

WHO (World Health Organization), 2005. Household Water Treatmentand Safe Storage Following Emergencies and Disasters.http://www.who.int/household_water/resources/emergencies.pdf (accessed Aug. 22, 2007).

WHO, 2004 (3rd ed.). Guidelines for Drinking-Water Quality, Vol. 1: Recommendations. WHO, Geneva.

WHO, 1997 (2nd ed.). Guidelines for Drinking-Water Quality, Vol. 3: Surveillance and Control of Community Supplies. WHO, Geneva.

WHO/UNICEF, 2004. Meeting the MDG Water and Sanitation Target: A Mid-Term Assessment of Progress. WHO, Geneva.

WHO/UNICEF, 2000. Global Water Supply and Sanitation Assessment,2000 Report. WHO, Geneva.


water treatment - harvard universitywilsonweb.physics.harvard.edu/arsenic/remediation/... ·...

Documents