Non-woven fabric filter separation activated sludge reactor for domestic wastewater reclamation

A non-woven fabric filter was experimentally evaluated for solid-liquid separation in an activated sludge reactor as an alternative membrane. A polypropylene fabric filter (70, 50 and 35 g/m²) was used for the experiment. The pilot system was operated in A/O (Anaerobic/Oxic) type in which the filter module was submerged into the oxic compartment. The filtration module consists of 10 plate type rectangular filter elements with effective filtration area, 2 m². Gravity filtration was carried out for solid-liquid separation by changing the water head 0.05–0.5 m without backwashing during the system operation. Initial permeate flux was set at 0.4 m/d. C/N ratio of raw wastewater was controlled at 4.5 in terms of BOD/T-N. The fabric filter system showed a good performance enough for domestic wastewater treatment. Effluent solid concentration was 3.2 mg/L (93.5% removal). COD removal efficiency was 91.6% producing an effluent concentration around 13 mg/L. 66% of total nitrogen removal could be obtained at the adjusted C/N ratio of influent wastewater. However phosphorus removal was very low at 23%. It was found that the initial flux of 0.4 m/d should be maintained for stable performance of the system.