title: Novel application of oxygen-transferring membranes to improve anaerobic wastewater treatment.
abstract: Anaerobic biological wastewater treatment has numerous advantages over conventional aerobic processes; anaerobic biotechnologies, however, still have a reputation for low-quality effluents and operational instabilities. In this study, anaerobic bioreactors were augmented with an oxygen-transferring membrane to improve treatment performance. Two anaerobic bioreactors were fed a synthetic high-strength wastewater (chemical oxygen demand, or COD, of 11,000 mg l(-1)) and concurrently operated until biomass concentrations and effluent quality stabilized. Membrane aeration was then initiated in one of these bioreactors, leading to substantially improved COD removal efficiency (> 95%) compared to the unaerated control bioreactor (approximately 65%). The membrane-augmented anaerobic bioreactor required substantially less base addition to maintain circumneutral pH and exhibited 75% lower volatile fatty acid concentrations compared to the unaerated control bioreactor. The membrane-aerated bioreactor, however, failed to improve nitrogenous removal efficiency and produced 80% less biogas than the control bioreactor. A third membrane-augmented anaerobic bioreactor was operated to investigate the impact of start-up procedure on nitrogenous pollutant removal. In this bioreactor, excellent COD (>90%) and nitrogenous (>95%) pollutant removal efficiencies were observed at an intermediate COD concentration (5,500 mg l(-1)). Once the organic content of the influent wastewater was increased to full strength (COD = 11,000 mg l(-1)), however, nitrogenous pollutant removal stopped. This research demonstrates that partial aeration of anaerobic bioreactors using oxygen-transferring membranes is a novel approach to improve treatment performance. Additional research, however, is needed to optimize membrane surface area versus the organic loading rate to achieve the desired effluent quality.
authors.affiliation: Department of Civil Engineering, University of Minnesota, 122 Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA.
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Kappell
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Semmens
authors.forename: Paige J
authors.initials: PJ
authors.lastname: Novak
authors.forename: Timothy M
authors.initials: TM
authors.lastname: LaPara
mesh_terms: D000693:Anaerobiosis; D019149:Bioreactors; D007220:Industrial Waste / Q000517:prevention & control; D008567:Membranes, Artificial; D010100:Oxygen / Q000737:chemistry*; D014873:Water Pollutants; D018508:Water Purification / Q000379:methods*
chemical_list: D007220:Industrial Waste; D008567:Membranes, Artificial; D014873:Water Pollutants; D010100:Oxygen