Monica B. Emelko

The Importance of Coagulation for the Removal of Cryptosporidium and Surrogates by Filtration

This investigation examined the removal of Cryptosporidium and several surrogates by granular medium filtration. The study focused on coagulation impacts on removals. Inactivated C. parvum oocysts and non-inactivated Bacillus subtilis were seeded in two pilot plants. The pilot plant locations were chosen to represent different coagulation regimes. Under optimized coagulation conditions (filter effluent turbidity < 0.1 NTU), approximately 5 log10 removal of Crypto. was obtained in one location, and approximately 3 log10 in the other. This difference is likely related at least in part to the difference in coagulation regimes. Suboptimal coagulation produced a substantial deterioration of Crypto. removal in both locations. The trends seen for Bacillus were generally similar to those observed for Crypto.. Although turbidity may be of value for assessing coagulation impacts on Crypto. removal, particle counts may be a more sensitive parameter in this regard.