Comparison of mesophilic and thermophilic treatment of pot ale in anaerobic membrane bioreactors

Anaerobic digestion is accepted as a reliable method to treat high strength industrial wastewater for years. Anaerobic membrane bioreactor is a relatively new technology which is becoming more and more attractive to treat wastewaters especially for wastewaters with high COD, TSS and FOG concentrations. Moreover, anaerobic digestion under thermophilic condition seems a promising option for wastewaters which are already warm from the main production process such as distillery products. This thesis focuses on comparing anaerobic digestion of pot ale which is a byproduct of whiskey production, under mesophilic and thermophilic conditions in anaerobic membrane bioreactors. Two reactors with a volume of 10 liters equipped with an ultrafilteration membrane were used for this study. Different parameters were measured to evaluate the biological performance and filtration characteristics of both systems. The reactor performances was studied under thermophilic and mesophilic conditions during the start up period. Ammonia inhibition and VFA accumulation took place in thermophilic reactor. A pH control was implemented in the thermophilic reactor to control the concentration of free ammonia which resulted in an improvement of the reactor performance after a few days. Once steady state was reached, batch tests were performed to compare the both reactors with respect to specific methanogenic activity, biomass COD fractionation, comparison of EPS and SMP, viscosity and filterability. The thermophilic system had a higher biogas production and less sludge production but at the same time higher ammonia concentration which made the system less stable compared to mesophilic. It was observed mesophilic reactor membrane faced more challenges regards to fouling compared to thermophilic. Sludge from mesophilic reactor showed higher EPS, capillary suction time and viscosity than thermophilic sludge. Conversely thermophilic sludge revealed higher SMP than mesophilic. It concluded that thermophilic condition has the potential to be better if the ammonia toxicity is solved