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 for over 150 d to investigate the effect of hydraulic retention time (HRT) on the methylparaben removal efficiency and adverse impact on methane content in the biogas produced. The fluidization of the PVDF biocarrier along the membrane surface played a key role in physically 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 effectively reduced by intermittent backwashing applied with the permeate. Continuous feeding of methylparaben into the AFCMBR did not deteriorate microbial activity during the entire operational period. Biodegradation through the biofilm formed on PVDF media was thought to be the dominant removal pathway. 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.