Reactor performance of static magnetic field membrane bioreactor for treating actual high-salt textile dyeing wastewater and possible mechanism on magnetically enhanced membrane fouling control

Abstract

Performance of the static magnetic field membrane bioreactor (SMFMBR) for treating actual high-salt textile dyeing wastewater was evaluated. Membrane fouling behavior and possible mechanisms were investigated using multiple methods including chemical composition analysis, microbial community analysis, and four-dimensional label-free quantification metaproteomic analysis. The results showed that three SMFMBRs equipped with the SMFs of 97.2 mT (1#), 202.3 mT (2#) and 303.4 mT (3#) possessed higher removal efficiency of color, chemical oxygen demand (COD) and acute toxicity, as well as higher activity of key enzymes than the conventional MBR (0#). Treatment efficiency of 3# SMFMBR was the highest among all the four groups. Potentially effective bacterial and fungal species were selectively enriched in the suspended sludge of three SMFMBRs according to the results of both high-throughput sequencing and quantitative real-time polymerase chain reaction (QRT-PCR). Membrane fouling rate of 3# SMFMBR was the lowest among all the groups, followed by that of 2#, 0# and 1# reactors. SMF of higher intensity (in 2# and 3# SMFMBRs) mitigated membrane fouling by inhibiting the production of microbial products (mainly consisting of proteins) and the growth of potential fouling-causing microbes on the membrane surface. By contrast, SMF of lower intensity (in 1# SMFMBR) aggravated membrane fouling by improving the yield of fouling-causing microbial products and the growth of biofilm on the membrane surface. Furthermore, the down-regulated porin and the up-regulated Ca2+-binding protein in biocake EPS were also responsible for the mitigation of membrane fouling in 3# SMFMBR.