AWWA WQTC58866

This study examined the impacts of oocyst preservation method and age on the removal of seeded Cryptosporidium oocysts by in-line filtration. An existing study has investigated the infectivity of Cryptosporidium parvum as a function of preservation method and oocyst age. However, similar studies have not been performed to investigate the impacts of preservation method and oocyst age on the physical removal of Cryptosporidium. Previous pilot scale seeding studies have used fresh oocysts stored under controlled conditions. However, full-scale drinking water treatment plants encounter oocysts of widely different ages on a daily basis. Differences in age and environment may affect Cryptosporidium removal efficiency through water treatment. As a result, the data from this study may help drinking water utilities better evaluate and apply other published data to their situation. In the current study, oocysts from the same production lot were divided and preserved using different methods. Oocysts from each preservation method were then seeded into pilot-scale in-line filters at 2, 8 and 17 weeks of age. No statistically significant (95% confidence level) differences in removals as a function of age or preservation method were observed. Depending on the preservation method and age, observed average Cryptosporidium removals ranged from 3.5 to 4.0 log. Includes 15 references, tables, figures.