title: Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations.
abstract: The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.
authors.affiliation: Department of Environmental Biotechnology, University of Warmia and Mazury in Olsztyn, Stoneczna St. 45G, 10-709 Olsztyn, Poland. magdalena.zielinska@uwm.edu.pl
authors.forename: Magdalena
authors.initials: M
authors.lastname: Zielińska
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Bernat
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Cydzik-Kwiatkowska
authors.forename: Joanna
authors.initials: J
authors.lastname: Sobolewska
authors.forename: Irena
authors.initials: I
authors.lastname: Wojnowska-Baryła
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D002244:Carbon / Q000032:analysis; D004269:DNA, Bacterial / Q000235:genetics; D058645:Denaturing Gradient Gel Electrophoresis; D017404:In Situ Hybridization, Fluorescence; D009566:Nitrates / Q000032:analysis / Q000378:metabolism; D009573:Nitrites / Q000032:analysis / Q000378:metabolism; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D010100:Oxygen / Q000032:analysis*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D000644:Quaternary Ammonium Compounds / Q000032:analysis / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000382:microbiology; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000032:analysis; D014873:Water Pollutants / Q000032:analysis / Q000378:metabolism*
chemical_list: D002244:Carbon; D004269:DNA, Bacterial; D009566:Nitrates; D009573:Nitrites; D009584:Nitrogen; D010100:Oxygen; D000644:Quaternary Ammonium Compounds; D012722:Sewage; D062065:Wastewater; D014873:Water Pollutants