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

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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 μm 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-H 2O). 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.