FATE OF METHANOL IN AN ANAEROBIC TREATMENT SYSTEM IN A PAPER MILL
Abstract:A paper mill has recently proposed the treatment of methanol-containing condensate in an existing anaerobic pretreatment system as an alternative control of hazardous air pollutants (HAPs) 40 CFR Part 63 Subpart S – Maximum Achievable Control Technology. There was a concern on the anaerobic biodegradability of methanol and byproducts and the potential for gas stripping from the system. A series of laboratory-scale experiments was conducted and a mathematical model was developed to evaluate the fate of methanol during anaerobic treatment. More than 99% of methanol contained in the condensate was biodegraded during anaerobic digestion. From an anaerobic digester batch test, the second order biodegradation rate constant, kb2, was estimated to range from 3.97 × 10-3 m3/g·day (when only condensate was fed) to 4.06 × 10-2 m3/g·day (when condensate was fed at the proposed rate). The losses of methanol through the Styrofoam™ cover system and volatilization were estimated to be almost zero (< 0.01%). Byproducts from methanol degradation such as acetaldehyde and methyl ethyl ketone were degraded completely in 32 hours. Since the anaerobic treatment process has the detention time of 5 days, condensate byproducts are believed to be completely biodegraded. Since acetaldehyde and methyl ethyl ketone have one order of magnitude smaller Henry's law constants than methanol, the release of these byproducts to the atmosphere is expected to be much smaller than methanol, which was found to have almost zero loss through volatilization. The introduction of condensate into the existing anaerobic pretreatment process appears to improve the treatment efficiency, leading to more stable anaerobic treatment as well as reduced sludge generation in the aerobic wastewater treatment process due to reduced organic loading.
Document Type: Research Article
Publication date: January 1, 2001
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