Microbial Dynamics of Biosand Filters and Contributions of the Microbial Food Web to Effective Treatment of Wastewater-Impacted Water Sources.

Biosand filtration systems are widely used for drinking water treatment, from household-level, intermittently operated filters to large-scale continuous municipal systems. While it is well-established that microbial activity within the filter is essential for the removal of potential pathogens and other contaminants, the microbial ecology of these systems and how microbial succession relates to their performance remain poorly resolved. We determined how different source waters influence the composition, temporal dynamics, and performance of microbial communities in intermittently operated biosand filters. We operated lab-scale biosand filters, adding daily inputs from two contrasting water sources with differing nutrient concentrations and found that total coliform removal increased and became less variable after 4 weeks, regardless of water source. Total effluent biomass was also lower than total influent biomass for both water sources. Bacterial community composition, assessed via cultivation-independent DNA sequencing, varied by water source, sample type (influent, effluent, or sand), and time. Despite these differences, we identified specific taxa that were consistently removed, including common aquatic and wastewater bacteria. In contrast, taxa consistently more abundant in the sand and effluent included predatory, intracellular, and symbiotic bacteria.