Superior methylparaben removal by anaerobic fluidized bed ceramic membrane bioreactor with PVDF tubular fluidized biocarrier : Reactor performance and microbial community

An anaerobic fluidized bed ceramic membrane bioreactor (AFCMBR) was operated with fluidized tubular biocarrier consisting of polyvinylidene difluoride (PVDF) for treating synthetic low-strength wastewater containing high dosage of methylparaben. The AFCMBR was run over 150 d to investigate the effect of hydraulic retention time (HRT) on the removal efficiency of methylparaben and any potential adverse impact of the addition of methylparaben on methane content in the biogas produced by AFCMBR. The fluidization of the PVDF biocarrier along the membrane surface played a key role in cleaning the membrane by maintaining the transmembrane pressure below 0.05 bar at 10.4 L/m2·h (LMH) of permeate flux (corresponding to 8 h of HRT). The fouling rate was also effectively reduced by conducting intermittent backwashing with the permeate produced by AFCMBR. Continuous feeding of methylparaben into the AFCMBR did not deteriorate microbial activity during the entire operational period applied in this study. Biodegradation through the biofilm formed on PVDF media was thought to be the dominant pathway to remove methylparaben. Microbial analysis of the biofilm community revealed the presence of aromatic-compound-degrading syntrophs (Syntrophorhabdus and Longilinea), propionate-oxidizing syntrophs (Syntrophobacter and Smithella), acetoclastic Methanothrix, and hydrogenotrophic methanogens (Methanobacterium, Methanolinea, and Methanoregula), indicating a syntrophic partnership for metabolizing methylparaben and propionate in the feed wastewater.