title: Evaluation of wastewater treatment in a novel anoxic-aerobic algal-bacterial photobioreactor with biomass recycling through carbon and nitrogen mass balances.
abstract: Algal-bacterial symbiosis, implemented in an innovative anoxic-aerobic photobioreactor configuration with biomass recycling, supported an efficient removal of total organic carbon (86-90%), inorganic carbon (57-98%) and total nitrogen (68-79%) during synthetic wastewater treatment at a hydraulic and sludge retention times of 2 days and 20 days, respectively. The availability of inorganic carbon in the photobioreactor, determined by its supply in the wastewater and microalgae activity, governed the extent of nitrogen removal by assimilation or nitrification-denitrification. Unexpectedly, nitrate production was negligible despite the high dissolved oxygen concentrations, denitrification being only based on nitrite reduction. Biomass recycling resulted in the enrichment of rapidly settling algal flocs, which supported effluent total suspended solid concentrations below the European Union maximum discharge limits. Finally, the maximum nitrous oxide emissions recorded were far below the emission factors reported for wastewater treatment plants, confirming the environmental sustainability of this innovative photobioreactor in terms of global warming impact.
authors.affiliation: Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n, 47011 Valladolid, Spain.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Alcántara
authors.affiliation: Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n, 47011 Valladolid, Spain.
authors.forename: Jesús M
authors.initials: JM
authors.lastname: Domínguez
authors.affiliation: Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n, 47011 Valladolid, Spain.
authors.forename: Dimas
authors.initials: D
authors.lastname: García
authors.affiliation: Department of Biodiversity and Environmental Management, University of León, 24071 León, Spain.
authors.forename: Saúl
authors.initials: S
authors.lastname: Blanco
authors.affiliation: Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n, 47011 Valladolid, Spain.
authors.forename: Rebeca
authors.initials: R
authors.lastname: Pérez
authors.affiliation: Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n, 47011 Valladolid, Spain.
authors.forename: Pedro A
authors.initials: PA
authors.lastname: García-Encina
authors.affiliation: Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n, 47011 Valladolid, Spain. Electronic address: mutora@iq.uva.es.
authors.forename: Raúl
authors.initials: R
authors.lastname: Muñoz
mesh_terms: D000332:Aerobiosis; D018533:Biomass; D019149:Bioreactors; D002244:Carbon / Q000378:metabolism*; D000860:Hypoxia; D009584:Nitrogen / Q000378:metabolism*; D062065:Wastewater
chemical_list: D002244:Carbon; D009584:Nitrogen; D062065:Wastewater
keywords: Algal–bacterial symbiosis; Dissimilatory nitrogen removal; Enhanced sedimentation; Inorganic carbon competition; Nitrous oxide emissions