Development of a Mainstream Anaerobic Treatment Process Using a Hybrid UASB-Micro Sieve System

As part of the WERF Project ENER5R12, a 1.8-m3 pilot plant reactor using the upflow anaerobic blanket-sludge bioreactor (UASB) process has been constructed and commissioned at the Luggage Point Innovation Centre at the Luggage Point Wastewater Treatment Plant, Brisbane, Australia. During its start-up, the pilot plant was seeded with 0.8 m3 of granular biomass from a local brewery UASB and has been operational through an initial period of 7 months. The bioreactor has been operated with an average hydraulic retention time of 7 hour treating mainly raw sewage for the entire operational period. Chemical oxygen Demand (COD) removal has averaged approximately 30% with a gas production of roughly 250 L/d at 73% methane (CH4). Biologically, the process is stable with organic acids at less than 75 mg/L and an average pH of 6.8. While the process is stable, performance is dominated by the solids capture, and partly the effluent non-VFA COD of 100 mgCOD/L. An Anaerobic MBR (AnMBR) being operated in parallel is achieving approximately 70% COD removal. Since the process is biologically stable, the research will move into the next phases which focus on a number of aspects, including improving overall performance. This includes application of hybrid UASB process (filter) processes and use of a dynamic micro-sieve system to both remove solids from the influent, and to enable better destruction of solids within the system. Current performance clearly indicates that the ability of UASB systems to treat domestic wastewater is limited by its capacity for solids, and that this should be the focus. Therefore, further work in 2016 will focus on implementation of a rotating belt filter for influent and effluent treatment, implementation of in-UASB filtration as part of the original plan, and further operational optimization.