Interpreting drinking water quality samples: understanding contamination pathways at the point of collection

Katrina J. Charles , Saskia Nowicki , Li Ann Ong , Dara Johnston , Zahid Hayat Mahmud

2.2 billion people lack access to safely managed drinking water, with microbiological water quality the major barrier to the achievement of SDG target 6.1. Microbiological water quality is strongly influenced by environmental and hand hygiene. We demonstrate the significant contribution of contamination from hygiene at water collection point localities and at the household level to drinking water quality. Comparison of water quality samples from 5,080 water systems at the ‘point of delivery’ (PoD) to those from the ‘point of collection’ (PoC) demonstrated that 60% of the E. coli positive results at the PoC were caused by contamination from local hygiene-related pathways, with seasonal variability. Additionally, household hygiene contamination pathways contributed a further 5% to 70% of E. coli positive detections in samples from the ‘point of use’ (PoU) based on analysis of 38 Multiple Indicator Cluster Survey (MICS) datasets. Better reporting of PoC and PoD methods is required to recognise this contribution from poor hygiene and ensure data are interpreted appropriately, thereby enabling more efficient targeting and prioritisation of interventions. Further revisions to drinking water quality sampling protocols are required to reflect the increase in (unchlorinated) piped water systems with potential for considerable biofilm growth, with implications for release of Pseudomonas and other opportunistic pathogens during sampling. There is immediate benefit to be gained from expanding communication and hygiene education to encourage cleaning of taps and spouts for drinking water.