Laboratory evaluation of a new coagulant/disinfectant point-of-use water treatment product for emergencies.

Abstract

There is emerging evidence that point-of-use (POU) water treatment can be effective in the improvement of microbial water quality and the decrease in diarrhoeal disease incidence in humanitarian emergencies. Coagulant/disinfection products (CDPs) have the distinct advantage of providing microbial quality improvement, turbidity reductions and a free chlorine residual (FCR). The laboratory treatment performance of a novel CDP, the 'Pureit(®) ' sachet, has been evaluated under different water quality conditions. The CDP performance was evaluated with regard to bacteriological humanitarian water quality objectives as well as the recent World Health Organization recommendations for evaluating POU water treatment options. At least 4 log10 reductions of tested bacterial indicators for a 'highly protective' status were attained in the tested conditions. Treated waters were consistently below 10MPN per 100ml with regard to final Escherichia coli concentrations (i.e. 'low risk') with majority of samples with no detectable E.coli (i.e. 'very low risk'). Attainment of the target FCR levels (at least 0·5 and 0·2mgl(-1) after 0·5 and 24h respectively) was dependant on the test water matrix. FCRs are thought to have been affected by the product's formulation, which contains a quenching agent intended to reduce chlorinous tastes. Treated water turbidity levels were marginally above the nonhealth-based target of five nephelometric turbidity units, partially due to the filtration cloth employed. This study has served to identify the performance envelopes of the CDP under challenging conditions. In particular, initial alkaline pHs negatively affected this product's performance with regard to bacterial log10 reductions. This CDP has the potential to attain humanitarian drinking water quality objectives when not operating under extreme conditions; consistently achieving E.coli log10 reductions between 4·5 and 5·2 resulting in treated water with E.coli concentrations mostly below the <1MPN per 100ml target level.