Wastewater treatment performance of a filtration bio-reactor equipped with a mesh as a filter material

The mesh filtration bio-reactor (MFBR) was equipped with a nylon mesh as filter material instead of a microfiltration membrane in a membrane bio-reactor. Laboratory scale MFBRs were used for the experiments. We have observed that a mesh having a pore size of 100 mum effectively rejected activated sludge and that the reactor retained SS of up to 9000 mg.l(-1) with a flux of 0.5-0.76 m.day(-1) at very low pressure (5-10 mm-H2O). The study also revealed that the sludge layer formed at the mesh surface plays an essential role in separating activated sludge. The synthetic wastewater (BOD:200 mg.l(-1), T-N:50 mg.l(-1). T-P:5.7 mg.l(-1)) was fed to the reactor under the following conditions: HRT of 4-8 h, continuous feeding, continuous filtration, and continuous or intermittent aeration. Under these conditions, SS and BOD of the effluent were less than 1.5 mg.l(-1) and 5.0 mg.l(-1), respectively. Under intermittent aeration conditions T-N removal attained 80 %, although the mesh filter was clogged in 1-2 weeks. In addition, when the filtration bio-reactor was applied to an A2O process, effective T-N removal was obtained without clogging of the mesh filter for 2 months. These results show that a MFBR can be of use as an alternative advanced wastewater treatment system. (C) 2000 Elsevier Science Ltd. All rights reserved.