This study evaluated the role of physical and biological filter characteristics on the removal of MS2 bacteriophage in biosand filters (BSFs). Three full-scale BSFs reached 4-log10 removal of MS2 within 43 days of operation. MS2 removal between 4-log10 to 7-log10 was measured for up to 294 days. Core sand samples from one filter were taken for protein, carbohydrate, and genomic extraction. Higher MS2 removal in the top 5 cm of the sand media coincided with greater diversity of microbial communities and increased concentrations of carbohydrates. Ammonia-oxidizing archaea (AOA) �Candidatus Nitrosopumilus maritimus� and nitrite-oxidizing bacteria (NOB) �Ca. Nitrospira defluvii� were dominant populations in the upper layers, and Thiobacillus-related operational taxonomic units (OTUs) were dominant in the lower layers. Proteolytic bacterial populations such as the classes Sphingobacteria and Clostridia were observed over the entire filter depth. A conceptual model for physical and biological interactions with MS2 as a function of filter depth is illustrated in the figure below.   Overall, besides media ripening and physical removal mechanisms of filter depth and long residence time, chemolithotrophs and proteolytic bacteria can also influence MS2 removal. The insight on the mechanism of virus removal can be used to improve the design and efficacy of future BSFs, ultimately leading to improved performance and reduced disease incidence in areas where clean potable water is unavailable.

Role of diverse microbial communities in MS2 bacteriophage removal in biosand filters

248th National Meeting (2014)

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