Treatment of Chinese traditional medicine wastewater in a submerged membrane bioreactor

A pilot scale test was conducted in a submerged membrane bioreactor SMBR with capacity of 10.0 m³/d for 120 days to treat high-strength Chinese traditional medicine wastewater. Performance of the SMBR was investigated with a sludge retention time (T_SR) of 50 days, a hydraulic retention time (T_HH) of 8.0 h, membrane flux of 8.0 L/(m²·h) and dissolved oxygen (DO) concentration of 2.0-3.0 mg/L, respectively. It was observed that the SMBR had high capacity of COD and suspended solid (SS) removal. The influent COD concentration was fluctuated between 1000 and 5000 mg/L, while the averaged effluent COD concentration was only 44.6 mg/L. The influent SS concentration was fluctuated between 1000 and 1600 mg/L, while little effluent SS was detected. It was found that the COD remove rate increased with mixed liquor suspended solids (MLSS) and organic loading rate (R_OL). In order to obtain good-quality effluent, the operational conditions of the SMBR were suggested as follows: the temperature was controlled above 10°C, MLSS about 7000 mg/L, R_OL under 24.76 kg/(m³·d), low vacuum value and constant water flux.