AWWA MTC53666

The emergence of the chlorine resistant pathogen Cryptosporidium has meant thatsimple treatment processes that do not employ either a physical or physiochemicalbarrier are no longer adequate to guarantee protection of the public fromwaterborne disease. Following an outbreak of cryptosporidiosis in West Cumbria in1993 associated with the water supply, North West Water (NWW) embarked on a planto provide a robust and reliable barrier to Cryptosporidium. Historically, thewater sources in this part of the North West of England have been classed as highquality, i.e., low turbidity and color. Consequently, only coarse microstrainingfollowed by disinfection with chlorine and pH elevation with lime has beenrequired to comply with the EC drinking water directive. The paper describes theapproach to the project including the: site pilot trials; selection criteria forthe membrane system; operating experience of the system since late 1999; and,performance of the system compared to the pilot trial results. Includes 11 references, tables, figures.