A novel application of automatic vacuum membrane bioreactor in wastewater reclamation

An automatic vacuum membrane bioreactor (AVMBR) equipped with an on-line air–water–chemicals backwashing system was developed for a purpose of the reclamation of domestic wastewater (300–800 mg-COD/L) and traditional Chinese medicine (TCM) wastewater (259–12775 mg-COD/L). The experimental setups were operated in pilot scale at hydraulic retention times (HRTs) of 3, 1 and 0.5 h for domestic wastewater, and at HRTs of 1, 3, 5 and 8 h for TCM wastewater. Experimental results indicated that membrane flux was able to resume as the fouled membrane modules being operated for 150 days were repeatedly subject to an air–water–chemicals backwashing procedure. Compared to a new membrane module, the contaminated membrane fluxes were resumed to 94.7% after the first cleaning, to 82.7% after the second cleaning and to 70.0% after the third cleaning at a vacuum value of 0.02 MPa. To meet reuse standard (effluent COD, less than 30 mg/L), the minimum HRT required by the AVMBR system was 1 h for domestic wastewater reclamation, and 1 h for less than 1000 mg-COD/L, 3.0 h for 1000–3000 mg-COD/L, and 5.0 h for 3000–6000 mg-COD/L TCM wastewater reclamation.However, when the TCM wastewater COD was larger than 6000 mg/L, an 8-h HRT operation of the AVMBR system failed to produce an effluent having a COD concentration less than 30 mg/L. It is concluded that the pilot-scale AVMBR system developed is feasible for the reclamation of domestic wastewater and TCM wastewater with a COD concentration less than 6000 mg/L.