Development of an Integrated Resource Recovery Strategy for the 630 ML/d Duffin Creek Water Pollution Control Plant

The Duffin Creek Water Pollution Control Plant (WPCP) is a conventional activated sludge secondary treatment facility located in Pickering, Ontario that treats municipal wastewater from the Regional Municipality of Durham and York (the Regions). The plant has an average day design capacity of 630 megaliters per day (ML/d). The liquid treatment process consists of headworks, primary and secondary treatment, phosphorus removal via dual-point chemical addition, and chlorine disinfection. Waste activated sludge (WAS) is co-thickened with raw sludge in the primary clarifiers. Solids handling processes include anaerobic digestion (for a portion of the sludge generated), dewatering, and incineration. The plant also receives hauled septage, liquid raw sludge and digested biosolids from wastewater treatment plants in both Regions. Several internal energy sources generated at the plant are being used to offset energy consumption. Heat from the incineration process is recovered to generate steam, which is used to drive turbines to power the fluidizing air blowers, with excess steam to supplement plant heating. Biogas generated from the digestion process is captured to fuel hot water boilers and supplement digester and building heating. Capital upgrades to the incinerators are underway, which will allow heat recovered from incineration to meet plant-wide process and building heating demand, freeing up biogas for alternative utilization. In addition, ongoing upgrades to the digesters will divert imported sludge (largely digested) away from the primary digesters, therefore improving digestion performance and increasing biogas generation. The current solids treatment and energy recovery operations are illustrated in Figure 1. In alignment with Regional goals to advance sustainability and reduce greenhouse gas (GHG) emissions, the Regions initiated an Integrated Resource Recovery (IRR) Study at the Duffin Creek WPCP in 2019. The purpose of this study is to identify feasible opportunities that can be integrated into the plant, including energy efficiency/recovery, material use reduction/recovery, and water conservation/recycling opportunities. This paper presents the review and development of energy use reduction and recovery opportunities associated with solids treatment at the Duffin Creek WPCP.