Nitrifying population dynamics in a redox stratifi

Authors: Rongchang Wang Xinmin Zhan Yalei Zhang Jianfu Zhao

Publish Date: 2011/01/22

Volume: 5, Issue: 1, Pages: 48-56

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Abstract

Nitrogen removal performance and nitrifying population dynamics were investigated in a redox stratified membrane biofilm reactor RSMBR under oxygen limited condition to treat ammoniumrich wastewater When the NHt 4 + N loading rate increased from 111±10 to 372 ± 32 gNHt 4 + N·m−2·d−1 the nitrogen removal in the RSMBR system increased from 180±96 mgN·d−1 to 1289±617 mgN·d−1 Shortcut nitrogen removal was achieved with nitrite accumulation of about 223 ± 53 mgNO 2 − N·L−1 Confocal micrographs showed the stratified distributions of nitrifiers and denitrifiers in the membrane aerated biofilms MABs at day 120 ie ammonia and nitrite oxidizing bacteria AOB and NOB were dominant in the region adjacent to the membrane while heterotrophic bacteria propagated at the top of the biofilm Realtime qPCR results showed that the abundance of amoA gene was two orders of magnitude higher than the abundance of nxrA gene in the MABs However the nxrA gene was always detected during the operation time which indicates the difficulty of complete washout of NOB in MABs The growth of heterotrophic bacteria compromised the dominance of nitrifiers in biofilm communities but it enhanced the denitrification performance of the RSMBR system Applying a high ammonia loading together with oxygen limitation was found to be an effective way to start nitrite accumulation in MABs but other approaches were needed to sustain or improve the extent of nitritation in nitrogen conversion in MABs

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