Biogas production and reactor performance of a pilot scale anaerobic biofilm digester treating food waste

This study investigated the performance of a 1167L anaerobic biofilm single stage reactor in treating food waste. The reactor was operated at different hydraulic retention times (HRTs) of 120, 90, 60, 30 and 15 days under mesophilic conditions. The optimum hydraulic retention time in this study was 60 days with biogas and methane production obtained were 69L/day and 36L/day, respectively and removal efficiencies of 81.62 % (total solid), 83.62 % (volatile solid) and 91.68 % (chemical oxygen demand). It was observed when HRT decreased, the volatile fatty acid and ammonia accumulation increased rapidly whereas pH decreased continuously. The decline in biogas production (HRT 15 days) was likely due to over loading, which resulted drop of pH and alkalinity and increase of volatile fatty acid. The kinetic study showed that the modified Gompertz model had the best fit with the experimental data compared to First Order and Logistic Function kinetic models. This study demonstrates that the stability and performance of the anaerobic digestion process, such as biogas production rate, methane yield and removal efficiency and bacterial community were significantly affected by HRTs.