Abstract
Alcohol stillage wastewater consists of high-strength suspended solids and organic matters, is best treated effectively by anaerobic digestion. To develop more efficient systems for treating alcohol stillage wastewater, a mesophilic submerged anaerobic membrane bioreactor was operated for 4 months by changing the hydraulic retention time and CODCr loading rate. The performances of the anaerobic treatment and membrane operation were investigated experimentally. The maximum organic loading rate obtained in this study was 12.4 kgCOD·m-3·d-1 and the removal efficiency was 97.8%. Furthermore, the CODCr concentration of water that permeated the membrane was under 1,000 mgCOD·L-1 when the organic loading rate was lower than 6.0 kgCOD·m-3·d-1. The addition of trace elements (i.e., Fe, Co and Ni) was necessary to maintain stable operation for this wastewater treatment at a high organic loading rate. The operation was successfully carried out for over 4 months by controlling the on/off time of the suction pump and by recirculating of biogas, without backflushing or chemical cleaning. No significant decrease in flux and the recovered amount of membrane pressure during the off period of filtration was observed in the initial 50 days of continuous operation at sludge concentrations of 10-16 gSS·L-1; however, both parameters gradually decreased to approximately 30% of their initial values after 4 months of continuous operation.
