Print Email Facebook Twitter Unravelling the reasons for disproportion in the ratio of AOB and NOB in aerobic granular sludge Title Unravelling the reasons for disproportion in the ratio of AOB and NOB in aerobic granular sludge Author Winkler, M.K.H. Bassin, J.P. Kleerebezem, R. Sorokin, D.Y. Van Loosdrecht, M.C.M. Faculty Applied Sciences Department Biotechnology Date 2012-05-11 Abstract In this study, we analysed the nitrifying microbial community (ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB)) within three different aerobic granular sludge treatment systems as well as within one flocculent sludge system. Granular samples were taken from one pilot plant run on municipal wastewater as well as from two lab-scale reactors. Fluorescent in situ hybridization (FISH) and quantitative PCR (qPCR) showed that Nitrobacter was the dominant NOB in acetate-fed aerobic granules. In the conventional system, both Nitrospira and Nitrobacter were present in similar amounts. Remarkably, the NOB/AOB ratio in aerobic granular sludge was elevated but not in the conventional treatment plant suggesting that the growth of Nitrobacter within aerobic granular sludge, in particular, was partly uncoupled from the lithotrophic nitrite supply from AOB. This was supported by activity measurements which showed an approximately threefold higher nitrite oxidizing capacity than ammonium oxidizing capacity. Based on these findings, two hypotheses were considered: either Nitrobacter grew mixotrophically by acetate-dependent dissimilatory nitrate reduction (ping-pong effect) or a nitrite oxidation/nitrate reduction loop (nitrite loop) occurred in which denitrifiers reduced nitrate to nitrite supplying additional nitrite for the NOB apart from the AOB. Subject aerobic granular sludge . mixotrophic . nitrite loop . AOB . NOB . PHA To reference this document use: http://resolver.tudelft.nl/uuid:902d419e-70e7-4295-8081-dbd14afe079d DOI https://doi.org/10.1007/s00253-012-4126-9 Publisher Springer Source http://link.springer.com/article/10.1007/s00253-012-4126-9 Source Applied microbiology and biotechnology, 94(6)2012 Part of collection Institutional Repository Document type journal article Rights (c)2012 The Authors and Springer Files PDF Winkler.pdf 416.96 KB Close viewer /islandora/object/uuid:902d419e-70e7-4295-8081-dbd14afe079d/datastream/OBJ/view