Treatment of Membrane Cleaning Wastewater from Thermal Power Plant Using Membrane Bioreactor

An integrated membrane bioreactor (MBR) with synthetic RO membrane cleaning wastewater from a thermal power plant was used to study the long-term operating characteristics, membrane fouling, and cleaning of membrane fouling. The results show that the MBR had a great removal effect on mainly an organic pollutant (citric acid) with an average of 98.4% rejection, and the concentration of organics in the effluent also achieved "Discharge standard of pollutants for municipal wastewater treatment plant" (GB12/599-2015). The optimal operating conditions were as follows: the membrane flux was 8 L/(m²·h); the hydraulic retention time (HRT) was 4 h; the sludge retention time (SRT) was 15 d, and the pH value was 6~7. A membrane fouling analysis showed that the resistance of the cake layer and the concentration polarization were the main components of membrane fouling. When the specific flux (SF) decreased to 10 L/(h·m² mH₂O), the membrane module was cleaned by tap water and then soaked in 0.05 wt% hydrochloric acid (HCl) and 3000 mg/L sodium hypochlorite (NaOCl) for 1 h and 3 h, respectively. Finally, the membrane flux could be recovered to 84.9% compared to the new membrane.