Using Anaerobic Co-digestion to Enhance Biogas Production from Municipal Organic Wastes at Wastewater Treatment Plants

摘要

To enhance biogas production and assist in municipal organic waste management, anaerobic co-digestion with the addition of low-cost municipal organic wastes as co-substrates has been considered an effective and commercially flexible approach to reduce digestion limitations and improve methane yields at municipal wastewater treatment plants. As such, low-cost municipal organic wastes including fats, oils and grease (FOG) and kitchen waste (KW) were investigated as potential co-substrates to enhance methane yield from the anaerobic co-digestion using activated sludge and raw sludge as the primary substrates. Economical biochemical methane potential (BMP) tests were applied to select suitable co-substrates. The selected co-substrate FOG was also pre-treated using ultrasonic and thermo-chemical methods. Data were evaluated using linear and advanced non-linear regression models to estimate optimum operating parameters. The ideal co-substrate and pre-treatment were applied in the 15L semi-continuous flow anaerobic digesters under varying conditions with the goal of optimization. Important parameters which would influence biogas production including pH, temperature, total solid (TS), total volatile solid (TVS), chemical oxygen demand (COD), ammonia nitrogen, total kjeldahl nitrogen (TKN), volatile fatty acids (VFA), and long-chain fatty acids (LCFA) were analyzed during the tests. The current results indicate that FOG was the most suitable co-substrate that could achieve enhanced methane production with thermo-chemical pre-treatment. The semi-continuous flow reactors also yielded better methane production with low hydrogen sulfide concentrations. The experimental and estimated parameters are contributing to an on-going series of research efforts centered on the integrated wastewater treatment plant digester upgrade project of the City of Kingston.