A pilot scale study of options for the treatment combined sewer overflows is being conducted in Ontario, Canada. The objective is to achieve primary clarification equivalency in simple, high-rate satellite treatment systems. Effluent disinfection will also be required where bathing beaches are to be protected. Long column settling tests conducted with CSO suspensions indicated that approximately 40% of the suspended solids was non-settleable at the test threshold of 0.3 m/h. The use of a cationic polymer as the sole coagulant in a three metre diameter vortex separator achieved at least 50% TSS removal at surface loads up to approximately 40 m/h. The effluents from solid/liquid separation operations using the polymer coagulation strategy were more amenable to UV disinfection than those produced with metal-based coagulants. This document has been updated to include experimental results to mid-1997.

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