Concentrating Organic Matters in Sewage using Forward Osmosis Membrane Treatment for Energy Production by Methane Fermentation

摘要

The activated sludge process is widely used for sewage treatment, and the power consumption for aeration and the disposal of excess sludge are inevitable problems. The methane fermentation process is anaerobic process that requires no aeration, can produce energy and generate less excess sludge. However, sewage treatment using methane fermentation is difficult due to too low concentration of organic matters in sewage. Application of forward osmosis (FO) membrane treatment has been examined as the concentrating method of sewage. In this study, the effects of the operating pressure to the water permeate flux, reverse salt passage ratio of NaCl, and concentration ratio of organic matter were evaluated in concentrating of sewage using seawater. The water permeate flux was increased from 0.05 to 0.75 m/d as the operating pressure increased from 0 to 1.0 MPa, the operating pressure was effective factor for improvement of the flux. Moreover, increase of the pressure made the concentration ratio of organic matter increased and made the reverse salt passage ratio from seawater to sewage decreased. It became clear that the inhibition of methane fermentation by NaCl is suppressed by pressurization in concentrating of sewage using FO membrane treatment.