reduction of nox in fe-edta and fe-nta solutions by an enriched bacterial population

an enriched biomass was developed from municipal sewage sludge consisting of three dominant bacteria, representing the genera of enterobacter, citrobacter and streptomyces. the biomass was used in a series of batch experiments in order to determine kinetic constants associated with biomass growth and nox reduction in aqueous ferrous edta/nta solutions and ferric edta/nta solutions using ethanol as organic electron donor. the maximum specific reduction rates of nox in ferrous edta and ferrous nta solutions were 0.037 and 0.047 mmoles l⁻¹ d⁻¹ mg⁻¹ biomass, respectively while in ferric edta and ferric nta solutions were 0.022 and 0.024 mmoles l⁻¹ d⁻¹ mg⁻¹ biomass, respectively. in case of ferric edta/nta solution, the kinetic constants associated with reduction of ferric edta/nta to ferrous edta/nta were also evaluated simultaneously. the maximum specific reduction rates of ferric edta and ferric nta were 0.0021 and 0.0026 mmoles l⁻¹ d⁻¹ mg⁻¹ biomass. the significance of these observations are presented and discussed in this paper.