Examination of monodispersed artificial particles similar to C. parvum oocysts in size as the removal surrogate of Cryptosporidium

This study investigated the feasibility of using artificial particles, MX-500 and SX-500, similar to Cryptosporidium parvum oocysts in size, as surrogate tracers of Cryptosporidium removal in water treatment. For this purpose, coagulation-filtration experiments were conducted for the two kinds of artificial particles and C. parvum oocysts under such conditions as coagulant (polyaluminium chloride) concentration of 8 mg l⁻¹, influent of 1,000 counts ml⁻¹ and kaolin turbidity of 10 units. The results showed that the turbidity removals were almost same for the three cases at 95%, while the particle removals differed: 1.92, 1.74 and 2.00 log₁₀ units for MX-500, SX-500 and Cryptosporidium oocysts, respectively. The un-coagulated particle counts in the coagulation chamber were 300 counts ml⁻¹ for SX-500 and 240 counts ml⁻¹ for MX-500 and C. parvum oocysts, which indicated that the coagulation efficiency of the three kinds of particle was similar. In the examination of the filtrate counts, similar filtration behaviour was found between both artificial particles and C. parvum oocysts over the filtration running time with correlation coefficients (R²) over 85%. These similarities in the coagulation and filtration characteristics of the artificial particles and C. parvum oocysts suggest that the particles of similar size to C. parvum would be reliable removal surrogates of C. parvum oocysts for the evaluation of C. parvum oocyst removal in water treatment processes.