Development of Full-scale Sizing Criteria from Tertiary Pilot Testing Results to Achieve Ultra-low Phosphorus Limits at Innisfil, Ontario

The Town of Innisfil, Ontario, is served by the Lakeshore Water Pollution Control Plant (LWPCP) which has a rated capacity of 14,370 m3/d and a current average flow of about 9,000 m3/d. The plant uses an extended aeration activated sludge system followed by filters. Alum is added to the aeration basin effluent mixed liquor to reduce the effluent total phosphorus (TP) concentration to approximately 0.09 mg/L. As its capacity is expanded, the LWPCP will need to achieve lower effluent TP concentrations. The following tertiary phosphorus removal processes were tested:Alum addition followed by ultra-filtration membranesFerric chloride addition with reactive filtration series systemFerric sulfate and alum addition with series filtrationFerric chloride and polymer addition with ballasted flocculation and filtrationAll of the processes achieved effluent TP concentrations of 0.03 mg/L and lower. This paper documents the performance results and scale-up considerations for each process.