The performance and microbial community of anaerobic membrane bioreactor for high calcium papermaking wastewater treatment

High calcium papermaking wastewater challenges anaerobic biological technology applications, leading to sludge calcification and unstable reactor operation. This study employed an anaerobic membrane bioreactor (AnMBR) to treat high-calcium papermaking wastewater (1000 mg/L) and achieved an average chemical oxygen demand removal efficiency of 90.1%. No significant accumulation of volatile fatty acids was observed during the entire experimental period. The methane production capacity decreased with the increasing inlet calcium ion concentration, and the maximum methane production rate in Stage 4 was 115.4 mL·(gVSS·d)−1. The maximum transmembrane pressure reached was 4.33 kPa, and the sludge was primarily present in the form of flocs due to the hydraulic shear effects. Anaerolineaceae, Bacteroidetes_vadinHA17, Methanosaetaceae and Methanobacteriaceae were identified as the dominant bacterial species in Stage 4, correlating with the robust anaerobic digestion performance. In conclusion, the AnMBR exhibited a reliable and effective treatment method for high calcium papermaking wastewater.