Novel external extractive membrane bioreactor (EMBR) using electrospun polydimethylsiloxane/polymethyl methacrylate membrane for phenol-laden saline wastewater

Abstract

Phenol-laden saline wastewaters can adversely affect water, groundwater, soil, organisms and ecosystems. Given that frequently-used biodegradation process is generally inhibited by salinity, this work aims to solve the problem through a novel configuration of external extractive membrane bioreactor (EMBR) for the objective of simultaneous phenol permeation, salt rejection and biodegradation. Contact angles of 160.9 ± 2.2° (water) and 0.0° (phenol) were observed on the electrospun polydimethylsiloxane/polymethyl methacrylate (PDMS/PMMA) membrane, suggesting this superhydrophobic/superorganophilic membrane was suitable for separating phenol from water-soluble salt. Phenol ranging from 14.1 ± 2.7 to 290.7 ± 10.4 mg/L (stages 1 to 8) was continuously permeated and completely biodegraded in external EMBR under a hydraulic retention time (HRT) of 24 h, which corresponded with detoxification performance improving from 6.3% to 70.5%. After phenol exposure of 8 stages, Proteobacteria and Saccharibacteria became the main phyla for microorganisms. Enumeration of functional genes (phe, amoA, narG, nirS) confirmed that phenol was mainly consumed by denitrifiers and other heterotrophs as the sole carbon and energy source via oxidation and ring cleavage. As bacterial responses, these genes’ proliferation was promoted under low phenol concentrations but inhibited under high phenol concentrations. Meanwhile, results of extracellular polymeric substances revealed that protein was the key substance in toxicity resistance, phenol adsorption and transfer.