Direct sewage filtration for concentration of organic matters by dynamic membrane
Sewage treatment is experiencing a paradigm shift whereby sewage should be treated as a resource with maximum reuse of water, nutrients and energy. Concentration of sewage for organic matter enrichment is essential for improved energy recovery. In this study, the concentrating performance of direct sewage filtration by a dynamic membrane was investigated. A novel double-layer cloth-media membrane module was developed. A 50 μm Daron cloth was selected as inner layer and a 1 μm propene polymer cloth as outer layer. Quick formation of the dynamic membrane was observed and it agreed with the complete blocking model. The results of continuous-flow experiments showed that chemical oxygen demand (COD) was concentrated to about 4500 mg/L within nine operation cycles in 70 hours. Trans-membrane pressure increased quickly to 80 kPa at the end of each cycle. Theoretical concentrating efficiency (η) was 77% and the carbon balance calculation showed 70.7% COD was retained in the reactor during the concentrating process. Scanning electron microscopy analysis showed that the cake layer was almost completely removed after physical cleaning and the gel layer was not remarkable. A sequencing sewage concentrating process was proposed for long-term operation.