Anaerobic digestion of waste activated sludge at psychrophilic temperatures with ozonation to reduce biosolids production and enhance energy recovery

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The wastewater treatment industry is undergoing a major transformation by increasingly focusing on wastewater resource recovery instead of simply wastewater treatment. Energy is an important resource that can be recovered from wastewater, and several facilities aim at operating energy neutral processes. At the same time, biosolids disposal is a major operational expense as it can use up to 60% of a facilities yearly budget. The current proposal aims at tackling this combined problem by both minimizing biosolids production and by maximizing biomethane yields. This will be accomplished though treating waste activated sludge (WAS) with ozone to enhance it degradability in anaerobic digestion, and though operating the anaerobic digesters at psychrophilic (20 °C and lower) temperatures. The ozone treatment will allow the operation of the psychrophilic anaerobic digester at high rates, which corresponds to solids retention time (SRT) equal or lower than 20 days. Thus, beside the decrease in operation temperate, the operation of the digesters will not be modified substantially from the typical conditions. The enhanced degradability of the WAS will also potentially create additional process capacity, which may reduce capital investments for the water resource recovery facilities (WRRF). This new process will be the first of its kind by which the hydrolysis action of ozone will be used to reduce the digester operation temperature and directly increase the biogas output while maintaining a relatively low SRT. The current NSERC-CRD proposal is joint with an NSERC-ARD proposal presented by the Centre National en Électrochimie et en Technologies Environnementales (CNETE; affiliated with the Collège Shawinigan). The new process developed through the proposed project, which will be commercialized by Air Liquide and its partners, will likely provide important economic and environmental benefits to the Canadian wastewater resource recovery industry. It will also generate employment within Air Liquide and its partners for commercializing, manufacturing, and installing the new processes.********