The expanded Bed Biofilm reactor (EBBR) – an innovative Biofilm approach for tertiary nitrification
The expanded bed biofilm reactor (EBBR) was developed by Advanced Bioprocess Development Ltd. (ABD) to provide a compact tertiary nitrification process. In terms of performance, the EBBR can meet an NH3-N discharge of less than 1 mg/L at high volumetric loading rates (1.0 kg NH3-N/m3 expanded bed /day). This high rate results from a predominance of nitrifying bacteria immobilized as thin biofilms on small particles of a novel support medium, glassy coke. The resulting bed of biofilm-particles are fluidized by the upward flow of wastewater in the reactor column, thus forming an expanded bed. The continuous-flow expanded bed does not require periodic backwashing. The immobilization of biomass and lack of backwashing means that the system offers a long biofilm retention time (equivalent to an activated sludge age of > 30 days). This long residence time allows formation of a complex community of heterotrophic microbes, which includes bacteria, protozoa, rotifers, nematodes and oligochaetes. While providing tertiary nitrification treatment to activated sludge settled effluent at a pilot-scale, this heterotrophic community provided collateral removal of roughly 50 percent of the incoming biochemical oxygen demand (BOD) and total suspended solids (TSS). A reduction of bacteria counts was also observed. An engineering analysis was conducted to compare EBBR with proven-effective submerged biofilm technologies, namely the moving bed biofilm reactor (MBBR) and biological aerated filter (BAF), for a small municipal wastewater treatment case at a design daily average flow of
5,490 m3/day (1.45 mgd). For this case, the analysis suggested that EBBR could be competitive with established submerged biofilm treatment technologies in terms of overall system footprint, construction and capital cost. The EBBR technology is now being considered for demonstration scale testing and full-scale applications in the North American market.