Enhancement of cryptosporidium oocyst removal by coagulation and sedimentation with poly-silicate iron (PSI)

The improvement of Cryptosporidium oocysts removals is an urgent need in drinking water treatment and one of the possible solutions is to use high-performance coagulant such as poly-silicate iron coagulant (PSI) instead of conventional coagulants like poly aluminum chloride (PAC). The efficiency of synthetic Cryptosporidium oocysts (S-Crypto) removal using PSI was evaluated by both jar tests and pilot plant experiments. The residual concentration of S-Crypto could be reduced even though the coagulation was operated under the optimum conditions for turbidity removal. The removal efficiencies of S-Crypto using PSI were up to 42-1073766880gher than those using PAC in the pilot plant. The higher performance of PSI is brought about by the presence of ferric species in the coagulant which promotes better sedimentation and not by the higher flocculation performance of the coagulant. In addition, the performance of PSI was independent of temperature, and S-Crypto removal by ferric chloride (FC) was not stable in cold raw water. It was suspected that the bound polymerized silica of PSI increases the stability of coagulation in cold water