Sodium hypochlorite dosage for household and emergency water treatment - Response

For the 1.1 billion people worldwide who do not have access to improved drinking water supply, point-of-use (POU) water treatment with sodium hypochlorite (NaOCl) is proven to reduce the incidence of diarrheal disease. However, NaOQ dosage recommendations for both household water treatment and disaster response water treatment vary significantly. In this study, 106 water samples front a variety of unproved and unimproved sources in 16 countries were tested ep ascertain whether a standardized NaOCl dosage regime could be developed. Results indicated that for household water treatment with NaOCl alone, a dose of 1.875 mg/L NaOCl proved effective in 86.6% of samples with turbidity < 10 ntu and a dose of 3.75 mg/L NaOCl was effective in 91.7% of unimproved sources with turbidity of 10-100 ntu. On the basis of test results, it is also recommended that POU chlorination programs adopt a proposed criteria for a free chlorine residual of < 2.0 mg/L 1 hour after NaOCl addition and > 0.2 mg/L after 24 hours of storage.