Improvement of phenol separation and biodegradation from saline wastewater in extractive membrane bioreactor (EMBR)

Extractive membrane bioreactor (EMBR) is a promising technology for phenol saline wastewater treatment. In this work, an electrospun polydimethylsiloxane/polymethyl methacrylate/multi-walled carbon nanotubes (PDMS/PMMA/MWCNTs) membrane was firstly used in EMBR. To address low phenol transmembrane mass transfer issue, effects of wastewater condition (1.3–5.5 L/h circulation rate, 1000–4000 mg/L phenol), biomass addition (without/with pre-acclimated activated sludge) and biofilm formation (50.5–120.7 μm) were investigated. Membrane characterizations confirmed that biofilms on membrane surface gradually developed under increasing phenol concentrations, with simultaneously increased thickness and extracellular polymeric substances (EPS) excretion. Results showed phenol transmembrane mass transfer rates with activated sludge and formed biofilm increased 21.6–31.7% compared to those without activated sludge. Finally, 100% removal of permeated phenol and 99.96% rejection of salt were achieved under wastewater circulation rate of 4.4 L/h with 1000–4000 mg/L phenol and 10 g/L sodium chloride. Relevant findings are of significance in promoting the EMBR application in organic-inorganic composite wastewater treatment. • An EMBR with PDMS/PMMA/MWCNTs ENM was set up for the first time. • Phenol saline composite wastewaters were successfully separated and biodegraded. • Thin biofilms of 50.5–120.7 μm developed on membrane surface after sludge addition. • Relationship between biofilm formation and EPS release was discussed. • Phenol transmembrane mass transfer rates increased 21.6–31.7% due to biomass.