Filtration of Glycoprotein-Modified Carboxylated Polystyrene Microspheres as <i>Cryptosporidium</i> Oocysts Surrogates: Effects of Flow Rate, Alum, and Humic Acid

Abstract

In this study, a surrogate of Cryptosporidium parvum oocysts was prepared using Cryptosporidium-sized carboxylated polystyrene microspheres and an alpha-1-acid glycoprotein (AGP). The zeta potential of the modified surrogates was found to be similar to that of viable Cryptosporidium parvum. These surrogates were used in laboratory-scale filtration experiments under the effects of flow velocity, alum addition, and humic acid (HA) coating on quartz sand surfaces. Filtration results showed that increased flow rates enhanced the transport of microspheres mostly as a result of increased hydrodynamic force. HA adsorbed on the grain surfaces greatly enhanced the mobility of microspheres in the packed bed, possibly as a result of increased repulsion between microspheres and the media. Alum inhibited the transport of microspheres in the column mostly as a result of the charge neutralization of the microspheres. The transport of microspheres when alum and HA coexisted was almost the same as the condition when alum and HA were absent. Deposition profiles showed a monotonic decline with distance under conditions where no HA was present, while nonmonotonic depositions were observed under conditions where HA was adsorbed on collector surfaces.