Reliability of microbial surrogate Chlorella for determining Cryptosporidium oocysts removal

The green alga, Chlorella, abundant in water sources and similar in size to the Cryptosporidium oocysts, may be a suitable candidate to evaluate the removal capacities of the waterworks for Cryptosporidium oocysts. The zeta potentials of Cryptosporidium oocysts in different water samples were more negative than Chlorella. Although the hydrophobicities of Chlorella were similar to Cryptosporidium oocysts, the experimental collision efficiencies for Cryptosporidium oocysts were higher than for Chlorella. It is indicated that Cryptosporidium oocysts would consume more coagulants during coagulation, with higher removal rate in the filtration process than Chlorella.