CONTROL OF CRYPTOSPORIDIUM - FROM RESERVOIRS TO CLARIFIERS TO FILTERS

Control of Cryptosporidium in potable waters requires an integrated mu ltiple barrier approach of source water protection of water supply res ervoirs and treatment technology through clarification, filtration, an d disinfection. Pristine lakes and protected reservoirs have far lower concentrations of oocysts (mean values less than 10 oocysts/100 L) th an unprotected supplies. Coagulation is critical to the effective cont rol of Cryptosporidium by clarification and filtration. Coagulation co nditions that produce filtered waters of low turbidities, particle cou nts, and effectively remove natural organic matter also produce high r emovals of Cryptosporidium. Dissolved air flotation (DAF) can achieve oocyst removals of 3 log compared to about 1 log by sedimentation. DAF and filtration provide two effective barriers to Cryptosporidium with cumulative log removals of 4 to 5 compared to log removals of 3 to 4 by sedimentation and filtration. (C) 1998 IAWQ. Published by Elsevier Science Ltd.