Ceramic membrane bioreactor for low carbon source wastewater treatment: process design performance and membrane fouling

Abstract

In this study, the ceramic flat membrane bioreactor (MBR) process was combined with the anaerobic/aerobic/anoxic (AOA) process, providing a theoretical basis for the combined application of these two processes, as well as for the treatment of typical urban domestic wastewater (low C/N wastewater). The results showed that the AOA–MBR achieved 94.31%, 98.82%, 88.40% and 98.61% removal of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen (TN) and total phosphorus (TP) from the target effluent, respectively, while the control AOA process achieved 93.27%, 96.48%, 79.79% and 89.52% removal of COD, ammonia nitrogen, TN and TP, respectively. The coupled AOA–MBR process was significantly more efficient in utilizing the internal carbon source in the endogenous denitrification stage than the AOA process. Two process parameters, dissolved oxygen in the aerobic zone and the sludge recycle ratio, were optimized for both reactors in terms of optimizing denitrification, phosphorus removal performance and decreasing operating costs, and the optimum operating conditions were determined. The membrane fouling resistance was mainly caused by the filter cake layer, and the changes in the content and composition of the main membrane contaminants, soluble microbial product (SMP) and extracellular polymer substance (EPS), during the process operation were identified. The addition of polymeric aluminium chloride had a certain adsorption effect on the SMP, which increased the average particle size of the activated sludge from 122.1 μm to 161.1 μm. Thus, the cake layer was loosened, which could slow down the rate of membrane fouling and prolong the membrane fouling cycle to 19–20 days.