Phase B - Evaluation of a combined anaerobic/aerobic/anoxic sludge digestion system for Annacis Island wastewater treatment plant

点击翻译按钮获取中文摘要

In Canada, medium-to-large scale municipal wastewater treatment plants (WWTPs) have been adapting anaerobic (AN) digestion technologies to generate energy in the form of biogas (60-75% methane) from wastewater sludge. Other benefits of AN digestion are diversion of organic waste from landfills, reduction of pathogens and odour, production of organic fertilizer, and reduction of greenhouse emissions. While AN digestion process is effective for reducing pathogens and destroying organic matter, solids reduction above 50% is often difficult to achieve. Therefore, advanced AN digestion processes with pretreatments and different digestion combinations (i.e. stage digestion) have gained interest in recent years. Furthermore, substantial ammonia and phosphate are released in AN digesters through hydrolysis of waste sludge which can degrade the final effluent quality of a WWTP. Therefore, sequential AN/ aerobic (AERO) sludge digestion process has been recommended due to many additional advantages (e.g. higher solids/pathogen destruction, ammonia removal, odour reduction and better dewaterability) over the single-stage AN digestion. Metro Vancouver and UBC Bioreactor Technology Group have recently completed an NSERC ENGAGE project (Phase A) that pointed out significant advantages of the sequential AN/AERO combination over the current AN digester configuration at Annacis. The main objective of this proposal (Phase B) is to verify these beneficial effects in larger-scale automated fermenters with automated air flow control valves for dissolved oxygen (DO) set-point control. If results from Phase B confirm the advantages, Metro Vancouver will have the option to convert some of the existing flow-through AN vessels to AERO/ANOX sludge digesters to operate a combined AN/AERO/ANOX system at Annacis. In addition to conventional digestion performance parameters, Phase B will also evaluate the fate of a group selected pharmaceuticals in digesters. The knowledge gained will lead to other biosolids-to-energy conversion and waste minimization opportunities at WWTPs in BC (e.g. Northwest Langley) and Canada. It will train highly qualified personnel (HQP) in a specialized field.