Technology Evaluation and Membrane Pilot Study to Achieve Low-Level Phosphorus Limits for Barrie, Ontario

Lake Simcoe is the second largest lake in Southern Ontario, Canada and plays an important role in the surrounding area. The 76 ML/d (20.1 mgd) Barrie Water Pollution Control Centre (WPCC), discharges to Lake Simcoe and will be required to meet strict effluent phosphorus load limits set forth by the Lake Simcoe Phosphorus Reduction Strategy. The strategy imposes annual mass load limits on the effluent total phosphorus (TP) that become increasingly more stringent in the future. Depending on the design capacity of the Barrie WPCC, the TP limit can vary from 0.04 mg/L to ultimately 0.02 mg/L. The purpose of the project is to identify the most reliable and cost effective technology to achieve the required effluent TP limits.A total of seven different types of treatment technologies were evaluated during a preliminary and detailed screening of alternatives. The technologies which were considered included Aqua Aerobic AquaDiamond® Cloth Filters, IDI Densadeg and Kruger Actiflo high-rate flocculated settling systems, CoMag® High Rate Ballasted Settling Process, Parkson D2® Continuously Backwashing Upflow Sand Filters (CBSFs), Blue Pro® (CBSFs) Filters and Tertiary Membrane Filtration. Based on the detailed evaluation of the phosphorus removal technologies, the City selected a tertiary membrane filtration system for the Barrie WPCC. Due to the difficulty of consistently achieving an effluent TP concentration at or below 0.05 mg/L, the City completed a low-level phosphorus removal pilot study utilizing a single membrane supplier. The objectives of the pilot study were to evaluate the phosphorus removal capabilities, the coagulant dose requirements and the impact to pH and alkalinity, and the solids generated. During the study, which was completed in December 2011, both alum and ferric were tested and the membranes were challenged tested with increased flow and phosphorus loads. This paper will present a brief discussion of the alternative technologies evaluated and the reason for selecting membranes and then focus on the results of the pilot tests and the lessons learned.