title: Effect of operating parameters on denitrification in an anoxic rotating biological contactor.
abstract: The presence of nitrate in water and wastewater is a serious environmental problem. Anoxic rotating biological contactors (RBC) are a promising novel technology for nitrate removal. In this study the effect of two carbon/nitrogen (C/N) molar ratios (1.5 and 3.0) on denitrification, using acetate as a carbon source, were investigated in an anoxic bench-scale RBC, treating synthetic wastewater. The effect of different hydraulic retention times (HRTs) and different nitrogen and carbon influent concentrations on the reactor performance, at constant C/N, were also analysed. The average removal efficiency in terms of nitrogen-nitrate was about 90.4% at C/N = 1.5, lowering to 73.7% at C/ N = 3.0. Considering carbon-acetate removal, overall efficiencies of 82.0% and 63.6% were attained at C/N ratios of 1.5 and 3.0, respectively. The increase in nitrogen-nitrate (from 50 to 100 mg N-NO3- L(-1)) and carbon-acetate influent concentrations and the decrease in HRT, keeping C/N constant, had a slight negative effect in terms of substrate removal. It was found that, for the tested conditions, the use of C/N = 1.5 is advantageous to denitrification. The anoxic RBC was significantly effective at reducing nitrate concentrations within a relatively short HRT. These reactors may be a feasible option for the treatment of nitrate-rich wastewaters.
authors.affiliation: IBB - Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Susana
authors.initials: S
authors.lastname: Cortez
authors.forename: Pilar
authors.initials: P
authors.lastname: Teixeira
authors.forename: Rosário
authors.initials: R
authors.lastname: Oliveira
authors.forename: Manuel
authors.initials: M
authors.lastname: Mota
mesh_terms: D000085:Acetates / Q000378:metabolism; D000693:Anaerobiosis; D018441:Biofilms; D056804:Biofuels / Q000032:analysis; D019149:Bioreactors; D002244:Carbon / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D012399:Rotation; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods; D018508:Water Purification / Q000379:methods
chemical_list: D000085:Acetates; D056804:Biofuels; D009566:Nitrates; D002244:Carbon; D009584:Nitrogen