title: Nitrogen-converting communities in aerobic granules at different hydraulic retention times (HRTs) and operational modes.
abstract: This study determined how the activity and number of nitrogen-converting microorganisms varied with changes in hydraulic retention time (HRT) and the operating regime of aerobic granular sequencing batch reactors (GSBRs) treating high-nitrogen wastewater. Continuously aerated (O-mode) GSBRs were operated at HRTs of 10-, 13- and 19-h. Then the same reactors were operated at identical HRTs but the cycles started with an anoxic phase (A/O mode). To investigate the microbial communities, DNA- and RNA-based relative real-time PCR was used. In all experimental reactors ammonium was fully removed with a removal rate up to 75 mg N-NH4 (+)/(L·h), and nitrification efficiency was above 90 %. The efficiency of the removal of oxidized nitrogen forms decreased with the lengthening of HRT. The study found that variable oxic conditions (A/O mode) in the GSBR cycle stimulated the simultaneous activity of ammonium oxidizing bacteria (AOB), N2O-reducers, and Anammox bacteria in aerobic granules. With both modes, the activity of nitrogen-converting bacteria was highest with a 13-h HRT. Shortening HRT, resulted in higher chemical oxygen demand and nitrogen loadings, which favored the growth of Anammox microorganisms in granules and caused a decrease in the number of AOB. With all HRTs, the number of Anammox microorganisms was about 1.5-times higher in A/O mode than in O mode.
authors.affiliation: Department of Environmental Biotechnology, University of Warmia and Mazury in Olsztyn, Słoneczna 45 G, 10-709, Olsztyn, Poland, agnieszka.cydzik@uwm.edu.pl.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Cydzik-Kwiatkowska
authors.forename: Irena
authors.initials: I
authors.lastname: Wojnowska-Baryła
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology; D059013:Microbial Consortia; D009584:Nitrogen / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D009584:Nitrogen