AWWA WQTC52998

Although numerous investigations have examined the removal of Cryptosporidiumparvum and other pathogens through filtration processes, those studies have generally been conducted under steady-state conditions with optimized pretreatment. Adequate chemical pretreatment during coagulation and flocculation is critical for maintaining good particle removal during filtration. Furthermore, several studies have indicated the importance of coagulation processes for improving filter removal efficiencies of Cryptosporidium parvum and Giardia. In this investigation, Cryptosporidium passage through filters under benchmark stable operating conditions was compared to removals during periods of suboptimal coagulation, as well as during filter ripening, breakthrough and hydraulic surges. The removal of Cryptosporidium was compared to the removal of particles and turbidity. Additional pilot scale investigations examined ways of mitigating filter operation effects. Bench-scale investigations contributed additional understanding and pilot-scale results were evaluated in terms of filtration robustness. This paper presents selected key study results, summarizes the main conclusions, briefly discusses regulatory implications of the results, and presents guidance to utilities. Includes 12 references, table, figures.