Reduction of NOx in Fe-EDTA and Fe-NTA solutions by an enriched bacterial population

► An enriched biomass with Streptomyces sp., Enterobcater sp. and Citrobacter sp. was developed. ► The biomass utilized NOx & FeIIIEDTA/NTA as terminal e− acceptors simultaneously. ► Being an electron donor, ethanol concentration affected the NOx reduction rates. ► Both FeIINTA and FeIIEDTA enhanced the NOx reduction rates using the biomass. ► Higher growth and NOx reduction rates achieved in Fe-NTA media than Fe-EDTA media. 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 0.047mMolesL−1d−1mg−1 biomass, respectively while in Ferric EDTA and Ferric NTA solutions were 0.022 and 0.024mMolesL−1d−1mg−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 0.0026mMolesL−1d−1mg−1 biomass. The significance of these observations are presented and discussed in this paper.