Factors affecting microbiological quality of household drinking water supplied by small-scale ultrafiltration systems: A field study.

Small scale ultrafiltration (UF) systems have been increasingly used in rural areas for drinking water supply, but their effectiveness in guarantying microbiological water safety at household level has rarely been assessed. Therefore, this study surveyed six representative villages where UF was utilized for full-scale drinking water supply for at least four years. At each village, the influent and the effluent from every stages of the treatment, as well as household tap water, were sampled and analyzed for microbiological indicating parameters, including total coliform count, Escherichia coli count, and heterotrophic plate count. The results were further assessed against current drinking water quality guidelines and standards. It was found that: (1) the qualification rate of household tap water samples varied substantially in the studied villages (0-75%), mainly due to the lack of post-disinfection and the occurrence of fecal contamination during water distribution; (2) UF appeared to be effective in controlling microbial contamination for small-scale systems with high-quality source water, while for systems using inferior source water, fecal contamination during water distribution necessitated continuous post-disinfection; and, (3) existing monitoring of membrane operational parameters cannot ensure microbial quality of treated water, and therefore, routine monitoring of microbial indicators in household water is recommended.