Microbiological performance of novel household water treatment devices in India

Commercial innovation of household-scale water treatment (HWT) devices is rapid in India, where unsafe drinking water contributes to the high burden of disease and death associated with diarrhoeal diseases. Performance testing data for novel devices are not publicly available and there has been no systematic attempt to independently verify manufacturer effectiveness claims. We purchased three gravity-driven HWT devices available on the Indian market to evaluate their performance in reducing bacteria, viruses, and protozoan surrogates in the laboratory according to World Health Organization testing protocols. Results indicated that technologies were moderately effective in reducing Escherichia coli (1.6–2.9 log₁₀) and MS2 (1.4–2.8 log₁₀), and less effective against Bacillus subtilis spores (0.73–2.2 log₁₀) and 3 μm microspheres (0.33–0.56 log₁₀), as means over the testing period (750–4,000 l). Effectiveness declined sharply over the duration of testing for each device, suggesting that the manufacturer-specified effective lifespans were overestimated for all devices. Moderate variability was observed across challenge conditions intended to represent actual use conditions, but performance was not significantly different between challenge waters or ambient testing temperature. Our results suggest that these novel devices do not meet international minimum performance recommendations and that manufacturer effectiveness claims are misleading. Further technological innovation and regulation in this sector may serve to protect public health.