Sodium hypochlorite dosage for household and emergency water treatment

Abstract

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.

Effective Use of Household Water Treatment and Safe Storage in Response to the 2010 Haiti Earthquake

“…Only 10 (3.3%) samples were 10 NTU, indicating the need for double chlorine dosage, filtration before disinfection, or more frequent cleaning of filters. 23 The average turbidity of 155 untreated water samples tested in the recovery evaluation was 3.8 NTU (minimum = 0, maximum = 46), with only 15 (9.7%) samples 10 NTU.…”

Chlorination of Household Drinking Water Among Cholera Patients' Households to Prevent Transmission of Toxigenic Vibrio cholerae in Dhaka, Bangladesh: CHoBI7 Trial

“…15 There is an extensive literature demonstrating the efficacy of POU chlorination of household drinking water in reducing the incidence of pediatric diarrheal diseases. 14,16 However, previous studies have also found that the effectiveness of chlorine in reducing microbial contamination can vary based on source-water turbidity, source-water baseline contamination levels, and in-home contamination. 16,17 In rural Ecuador, only 17% of households with high source-water turbidity (> 10 NTU) were able to achieve the World Health Organization guideline for safe drinking water after chlorine treatment with a sodium hypochlorite (NaOCl) solution of 1.875 mg/L.…”

Short-term WASH interventions in emergency response: a systematic review

“…Only two evaluations measured both reported and confirmed use (Lantagne andClasen 2012, Colindres et al 2007) (Table 17). Documents with both measures, reported use ranged between 6-22% and confirmed use ranged [4][5][6][7][8][9][10][11][12].…”

“…The amount of organic content and withdrawn water also impact the amount of chlorine needed for treatment. Ideally, the FCR for water treatment would be greater than or equal to 0.2 mg/L and less than or equal to 2.0 mg/L -which is the range ensuring water treatment but not exceeding taste or guideline thresholds (Lantagne 2008). Six documents were identified in the review evaluating well disinfection.…”

“…Cost may explain the low use in Madagascar (Dunston et al 2001) as the free distribution of the same product had much higher rates in the same area (Mong et al 2001). Excessive dosing was observed in Madagascar (FCR >3.5 mg/L) (Mong et al 2001) and taste was noted as a hindrance to use in Nepal and Philippines (Lantagne andClasen 2012, Plan 2013 Figure 18 ** 'Peak rates' mentioned but suitable for comparison in Figure 18 As noted in the chlorine tablet section above, the effectiveness of liquid chlorine on total and faecal coliforms was measured during a flood in Bangladesh in one document (Sirajul Islam et al 2007). Liquid chlorine was effective eliminating 82% of total coliforms and 77% of faecal coliforms.…”