Household water storage compromises drinking water safety in a “safely managed” system

Yarrow Linden , Erin Kowalsky, Kevin Zhu, Christine Fagnant-Sperati , Sandy McGunegill, Arnaldo Cumbana, Magalhães Mangamela, Rassul Nalá, Matthew C. Freeman, Karen Levy , Joe Brown

While nearly three-quarters of the globe use safely managed drinking water services, water quality can deteriorate between the point of service provision and point of consumption due to intermittent supply and the need to store water at the household level. To test if water storage contributes to waterborne pathogen hazards, we estimated prevalence and concentration of enteric pathogens in piped and stored drinking water samples in Beira, Mozambique, using large-volume sampling methods. We assessed water sample concentrates for microbial contamination from bacterial, protozoan, viral, helminthic, antimicrobial resistance (AMR), and microbial source tracking targets with RT-qPCR using a custom TaqMan Array Card. We found that enteric pathogens, AMR targets, and human mtDNA were more prevalent in stored drinking water compared to household tap water. We also detected enteric pathogens— including Cryptosporidium, Giardia, pathogenic Escherichia coli, and rotavirus— directly from 13% (11/87) of piped sources connected to a well-managed, but intermittent, water supply system, albeit less frequently than in stored water. These findings suggest that without continuity in service delivery combined with effective filtration treatment in piped supplies and safe storage microbial contamination of drinking water at the point of use may continue to occur.