REMOVAL AND INACTIVATION OF CRYPTOSPORIDIUM OOCYSTS BY ACTIVATED-SLUDGE TREATMENT AND ANAEROBIC-DIGESTION

To determine the fate of Cryptosporidium parvum oocysts during wastewa ter treatment, a model of an activated sludge treatment plant was desi gned with a flow of 17 ml/min and a detention time of 6 hours. Samples of raw sewage were seeded with oocysts and primary and secondary effl uents were analyzed for C. parvum using an immunofluorescent technique . To compare removal efficiencies of oocysts by various wastewater tre atment processes, raw sewage, activated sludge, trickling filter and b iodisc effluents were seeded with oocysts and settled for 2 hr and for the respective Sludge produced by a wastewater treatment plant and an aerobically digested at 37 degrees C in a laboratory digester was also seeded with C. parvum oocysts. Oocyst inactivation was measured by ex cystation and direct counts. Removal of oocysts In primary and seconda ry sedimentation averaged 83.4% and 90.7% The total oocyst removal in sewage treatment In comparison with other treatment processes, activat ed sludge had the maximum oocyst removal efficiency at 92%, The anaero bic digestion process inactivated 90% of the oocysts within four hours of exposure. 99.9% of the oocysts were eliminated by anaerobic digest ion after 24 hours. This demonstrates that the activated sludge proces s and anaerobic digestion can be effective for the removal and inactiv ation of C. parvum oocysts.