Annacis Island Co-Digestion Facility & Energy Recovery
Metro Vancouver (Metro) is a regional government agency that operates several wastewater treatment plants in the Vancouver metropolitan area. The Annacis Island Wastewater Treatment Plant (AIWWTP) processes sewage flows of approximately 131 MGD and the treated effluent is discharged into the Fraser River. Approximately 12,000 dry tonnes of biosolids are produced from an thermophilic anaerobic digestion process and centrifuge dewatering at 24-34 percent solids concentration.
Recovering energy from liquid waste and biosolids is one of Metro Vancouver's goals for managing liquid wastes affordably and effectively. Co-digestion has several merits for Metro, including increasing biogas production, reducing greenhouse gas emissions, reducing untreated discharges, and mitigation for other WWTPs.
The objective of the co-digestion facility project is to design and construct a facility at the AIWWTP to test a variety of available feedstocks for direct feeding into the anaerobic digesters. The co-digestion facility is a full-scale pilot facility that will confirm the feasibility of the technology and can be expanded in the future.
HDR developed the process design, including process flow diagrams, of a co-digestion facility at Metro's 500 ML/day (130 MGD) Annacis Island WWTP. The facility includes a receiving station, screening, grit removal, a heated storage tank, a storage tank mixing pump, a digester feed pump, and other support facilities. Wastes to be accepted include fats, oils, and grease (FOG) from grease trap haulers, spoiled milk, crude glycerin, industrial DAFT float, deicing fluid, chicken processing waste, and thickened primary sludge from other Metro wastewater treatment plants.