Pre-treatment Strategies for Anaerobic Digestion

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With increasing quantity of municipal sewage sludge, the quality and level of treatment are of serious concern in Canada and many parts of the world, specifically, about 660,000 tons are produced annually in Canada. With the implementation of strict regulations on sludge disposal and closure of more landfills, sludge management is becoming increasingly challenging. Many municipalities across Canada have already set aggressive waste diversion goals to reduce the environmental footprint of current waste management practices. Thus, there has been growing attention to developing advanced and reliable technologies for bioenergy and value-added resources from waste, which can provide dual benefits of waste diversion and revenue generation. Anaerobic digestion is by far the most widely implemented waste-to-bioenergy technology for converting waste to methane-rich biogas. On the other hand, the possibilities of terminating the process after the fermentation stage and recovering volatile organic acids have received particular attention. These volatile organic acids can be used as a feedstock for various high value-added products, including bioplastics, bioenergy, liquid hydrocarbons, lipids for biodiesel production, electron donors for biological nutrient removal. Currently, not only the volatile solids stabilization efficiency of most existing anaerobic digesters is modest and relatively low but also the biosolids are difficult to dewater requiring high chemical conditioning doses. The main goal of this research proposal is to develop a novel sludge combined chemical and mechanical pre-treatment process to enhance the digestion efficiency and increase the organic loading rate. Furthermore, this research project aims to understand the feasibility of combining the hydrothermal pretreatment with the vacuum fermentation process for higher volatile fatty acids production.