Anaerobic Co-digestion of Organic Fraction of Municipal Solid Waste with Municipal Sludge with or without Microwave Pre-treatment

Abstract

Anaerobic co-digestion of organic fraction of municipal solid waste (OFMSW), with thickened waste activated sludge (TWAS) and primary sludge (PS) has the potential to enhance (biodegradation) of solid waste, increase longevity of existing landfills and lead to more sustainable development by improving waste to energy production. This study reports on mesophilic batch anaerobic biological methane potential (BMP) assays carried out with different concentrations and combinations (ratios) of OFMSW, TWAS (microwave (MW) pre-treated and untreated) and PS to assess digester stability and potential improved specific biodegradability and potential increased specific biogas production by digestion of OFMSW with PS and TWAS in various tri-substrate mixtures. Results indicated improvements in specific biogas production with concomitant improvements in COD and volatile solid (VS) removal for co-digestion of OMSW, TWAS and PS vs. controls. In terms of improvements in biogas production and digester stability the OFMSW:TWAS:PS:50:25:25 ratio with or without TWAS MW treatment was deemed best for further continuous digester studies. At a 15d HRT which is the regulatory policy in the province of Ontario for municipal mesophilic anaerobic TWAS:PS treatment, co-digestion of OFMSW:TWAS:PS, and OFMSW:TWASMW:PS resulted in a 1.38 and 1.46 fold relative improvement in biogas production and concomitant waste stabilization when compared to TWAS:PS and TWASMW:PS digestion at the same HRT and volumetric VS loading rate respectively. Treatment of OFMSW with PS and TWAS provides beneficial effects that could be exploited at MWWTP that are being operated at loading rates less than design capacity.