Point-of-use chlorination of turbid water: results from a field study in Tanzania

Abstract

Household-based chlorine disinfection is widely effective against waterborne bacteria and viruses, and may be among the most inexpensive and accessible options for household water treatment. The microbiological effectiveness of chlorine is limited, however, by turbidity. In Tanzania, there are no guidelines on water chlorination at household level, and limited data on whether dosing guidelines for higher turbidity waters are sufficient to produce potable water. This study was designed to assess the effectiveness of chlorination across a range of turbidities found in rural water sources, following local dosing guidelines that recommend a 'double dose' for water that is visibly turbid. We chlorinated water from 43 sources representing a range of turbidities using two locally available chlorine-based disinfectants: WaterGuard and Aquatabs. We determined free available chlorine at 30 min and 24 h contact time. Our data suggest that water chlorination with WaterGuard or Aquatabs can be effective using both single and double doses up to 20 nephelometric turbidity units (NTU), or using a double dose of Aquatabs up to 100 NTU, but neither was effective at turbidities greater than 100 NTU.

Microbiological effectiveness of household water treatment technologies under field use conditions in rural Tanzania

“…In this study, the effectiveness of both Waterguard and Aquatabs in Kisarawe district was lower than that in Geita district, probably because of the overall much higher turbidity observed in Kisarawe both in source and household drinking water samples [37]. Turbidity is known to negatively affect water disinfection by chlorine [37][38][39][40] by exerting chlorine demand. Because highly turbid source waters are common across rural Tanzania [37], chlorination-only technologies may not be as widely effective as other HWTS options.…”

“…The physical-chemical properties of untreated water have been observed to limit in situ microbial reductions by HWTS methods, including chlorination [21,36,37]. In this study, the effectiveness of both Waterguard and Aquatabs in Kisarawe district was lower than that in Geita district, probably because of the overall much higher turbidity observed in Kisarawe both in source and household drinking water samples [37]. Turbidity is known to negatively affect water disinfection by chlorine [37][38][39][40] by exerting chlorine demand.…”

User preferences and willingness to pay for safe drinking water: Experimental evidence from rural Tanzania

“…The durables were ceramic pot filters (Safe Water Now, n.d.), and ceramic siphon filters (Basic Water Needs India Pvt Ltd, n. d.-a). All these options significantly reduce E. coli concentrations in the laboratory (LeChevallier and Au, 2004;Brown and Sobsey, 2010;Basic Water Needs India Pvt Ltd, n. d.-b), and in the field (Mohamed et al, 2015;Clasen et al, 2007;Souter et al, 2003;Ziff, 2008;Brown et al, 2008). Boiling served as a comparison for the HWTS retail products; it has been shown to significantly reduce E. coli in field conditions (Brown and Sobsey, 2012).…”

Evaluation of the international standardized 24-h dietary recall methodology (GloboDiet) for potential application in research and surveillance within African settings

“…However, as in any preparation of a GloboDiet version, typical African foods will need to be included in GloboDiet databases and combined implicit and explicit descriptions will be applied to each food and recipe during data collection. Additional descriptive pieces of information that may be deemed necessary to collect are sources of drinking water [32, 33] and water treatment methods [34, 35] because drinking water is still a vector of microbial infections and chemical hazards in Africa. Other examples of description consideration details that might be interesting to consider are application of treatments to decrease cyanogenic agents in cassava [36], or the covering of street-vended foods.…”