Anaerobic digestion of brewery effluent: two-year operating experiences

In this paper we discuss two years operational experiences of an AD wastewater treatment plant to treat brewery waste. The plant uses a 900 m3 expanded granular sludge blanket (EGSB) bioreactor, at 35oC. The variation in effluent composition was balanced in a buffer tank and the EGSB reactor included recycle to provide further buffering. The average waste flow was 250 m3/day which corresponded to a daily load of 6000 kg COD/day. The digester’s performance was assessed based on COD, suspended solids, Ripley’s ratio, volatile fatty acids, and biogas production. The initial COD concentration in effluent of 15000 mg/l was reduced to 120 mg/l in waste sent to sewer, resulting in about 99.2% COD reduction. Suspended solids concentrations were reduced from 2400 mg/l in the effluent to 55 mg/l being released to sewer. The plant has recovered the initial capital expenditure in five years. The wastewater effluent has a high treatability with 86% COD present as soluble COD. This results in a quality of gas which exceeded the expected methane to CO2 ratio of 60% to 40%. An average of 80 m3 of biogas is produced every hour, but the variance in gas flow remains an issue.