Fate of methanol in an anaerobic digester

This paper mill was concerned with the anaerobic biodegradability of methanol, its by-products and the potential for gas stripping the system. A series of laboratory-scale experiments were conducted to evaluate the fate of methanol during anaerobic treatment. According to our research result, more than 99% of methanol contained in the condensate was biodegraded during anaerobic digestion. From an anaerobic digester batch test, the second order bio-degradation rate constant,k _b2 , was estimated to range from 3.97×10⁻³ m³/g·day (when only condensate was fed) to 4.06×l0⁻² m³/g·day (when condensate was fed at a proposed rate). The by-products from methanol degradation such as acetaldehyde, and methyl ethyl ketone, were degraded completely in 32 hours. Since the anaerobic treatment process has a retention time of 5 days, condensate by-products are believed to be completely biodegraded. The introduction of condensate into the existing anaerobic pretreatment process appears to improve the treatment efficiency, leading to a more stable anaerobic treatment as well as a reduced sludge generation in the aerobic wastewater treatment process due to the reduced organic loading.