Efficient organic carbon utilization for combined nutrient removal and biogas production in hybrid biofilm activated sludge system

Abstract

Moving bed biofilm technology is a successful and promising biological treatment process considered for cost-effective management of wastewaters. In this study, a hybrid moving bed biofilm pilot plant was operated and obtained results were compared with simulation results of two biological processes: a conventional Biological Nutrient Removal (BNR) system and a novel hybrid activated sludge configuration implemented with Moving Bed Biofilm Reactor (MBBR) and a reactive primary clarifier (RPC). An efficient organic carbon entrapment (87%) was obtained in reactive primary clarifier where the major component (95%) of the total Chemical Oxygen Demand (COD) was determined as slowly hydrolysable (XS1), according to respirometric tests. Pilot plant and simulation studies exhibited that an improved nitrogen and phosphorus removal performance, as well as higher biogas production (47%) were obtained by organic carbon redirection in proposed hybrid configurations, securing a 40% less reactor volume. Investigation of the economic aspects indicated that hybrid system has a lower operating cost (i.e., 23% less air requirement, 40% less mixing energy requirement), does not require internal recirculation pumps, and produces more energy through anaerobic digestion compared to conventional BNR. Therefore, proposed novel hybrid configuration is more efficient for the treatment of municipal wastewater in terms of Capital Expenditures (CAPEX) and Operational Expenditures (OPEX) within the energy self-sufficient treatment plant approach and sustainable treatment plant operation.