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The increasing number of cryptosporidiosis outbreaks over the last two decades has led to concerns over the efficiency of conventional water treatment processes to remove Cryptosporidium oocysts. A problem with chemical disinfection is that in many cases the use of disinfectants would create high levels of byproducts because higher dosages and longer contact times than now used would be required for the inactivation of Cryptosporidium. Since Cryptosporidium oocysts are almost completely resistant to chlorine-based disinfectants at the concentrations and contact times practical for water treatment, the physical-chemical removal process including coagulation, clarification and filtration is of great importance, particularly for those utilities using traditional treatment methods. Coagulation is employed in most surface water treatment facilities, and is one of the most important steps for effective removal by clarification and filtration. The parameters that affect coagulation efficiency and, therefore, the optimum coagulant dose, include several raw water quality characteristics. One of the main factors that control coagulation is natural organic matter (NOM). The objective of this study was to evaluate the effects NOM on the removal of Cryptosporidium parvum oocysts during coagulation and sedimentation using bench-scale experiments. The study was done for three initial DOC concentrations and for several pH values and alum dose conditions. Materials and methods discussed include: jar tests; matrix water; natural organic matter; coagulant; cryptosporidium parvum oocysts; cryptosporidium parvum oocyst enumeration; dissolved organic carbon; and, ultraviolet absorbance. Includes 16 references, figures.

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Edition: Vol. - No. Published: 11/01/2002 Number of Pages: 13File Size: 1 file , 300 KB