Impact of Acclimation and Startup on COD Removal and Microbial Communities in Anaerobic Fluidized Bed Membrane Bioreactors. AFMBR

An anaerobic fluidized bed membrane bioreactor (AFMBR) is a new and highly effective method for energy-efficient treatment of low strength wastewater, but the factors that affect performance are not well known. Different inoculation methods of the granular activated carbon (GAC) used in the reactor, and reactor startup conditions, were examined here to determine their impact on AFMBR chemical oxygen demand (COD) removal and microbial communities that developed in the reactor. Acclimation using methanol and a microbiologically diverse bog sediment (M), domestic wastewater (W), or anaerobic digester sludge (D) all achieved 63 ± 12% COD removal for AFMBRs fed diluted wastewater (100 ± 21 mg/L COD). COD removal (67 ± 7%) for reactors acclimated to wastewater and fed with effluent from a microbial fuel cell (MFC) was only slightly greater than that produced by these acclimation procedures. However, acclimation to acetate (A) significantly improved wastewater COD removal to 84 ± 6%. In addition, after feeding M with an acetate medium for one week (MA), COD removal of this reactor increased to 70 ± 6%. Microbial communities enriched on the GAC included Geobacter, sulfur-reducing bacteria, Syntrophaceae, and Chlorobiaceae, with reactor A having the highest relative abundance of Geobacter. These results showed that acetate was the most useful substrate for initial acclimation of GAC communities, a temporary acetate feed can be used to improve AFMBR performance, and GAC harbors unique communities relative to those in the AFMBR influent and solution.