AWWA ACE69057

Results from a series of bench-scale experiments and sampling of full-scale slow sand filters (SSFs) confirmed a relationship between increased ripening time and increased biomass, protistan abundance, and E.coli removals. Additionally, several protist feeding experiments were conducted and a bench-scale "seeding" to assess improvement of SSF performance was performed. Protistan predation studies showed that the percentage of ingested bacteria per protist experiences a spike 0-2 hours after bacteria are introduced to protists from a SSF. The time of year, water temperature, and type of bacteria used in the study, whether indigenous or lab-cultured, have minor effects on predation. The seeding study showed increased protistan populations in some seeded filters and minor improvements to E.coli removal performance in filters that were initially unripened. Includes 14 references, tables, figures.