OCCURRENCE OF CRYPTOSPORIDIUM SPP OOCYSTS AND GIARDIA SPP CYSTS IN SEWAGE INFLUENTS AND EFFLUENTS FROM TREATMENT PLANTS IN ENGLAND

Cryptosporidium parvum and Giardia duodenalis can cause severe diarrho ea in infected individuals and their transmissive stages, oocysts and cysts, are voided in large numbers with the faeces of infected hosts. Contaminated sewage effluents are recognised as a potential source of waterborne (oo)cysts. In this investigation methods optimised for the recovery of both from a range of wastewaters were used to determine th e occurrence of these organisms in influents, effluents and sludges fr om seven sewage treatment works in England. The data indicated the pre sence of small numbers of oocysts both in sewage influent and effluent samples whereas cysts were detected more frequently and at higher con centrations in both influents and effluents. Whilst sludge samples fro m 1/5 sites contained oocysts, cysts were detected from all five sites . These investigations indicate that discharge of sewage effluents int o a watercourse, which may be used for potable water abstraction, can contaminate that watercourse with potentially infectious oocysts. In a ddition, the application of sludge to land can be responsible for cont aminating watercourses with (oo)cysts following run-off or leaching. ( C) 1997 IAWQ. Published by Elsevier Science Ltd.