Influence of operating conditions on microbial consortia in a continous flow submerged bichamber membrane bioreactor

Abstract

Influence of operating conditions on nitrogen related bacterial abundance was investigated in a lab-scale anoxic/oxic membrane bioreactor (A/O MBR) and the full-scale conventional activated sludge (CAS), where the seed for the A/O MBR was collected from, using 16S rDNA clone library and fluorescent in-situ hybridization (FISH) techniques. To increase a C/N ratio from 0.5 (in the CAS) to 3.0, the A/O MBR's sewage feed was supplemented with sodium acetate. Nitrification performance achievable by the A/O MBR biomass (> 99% removal) was consistently greater than the CAS (74% removal). The average total nitrogen removal efficiency of the CAS was 41% which was also lower than the 86% attained by the A/O MBR. 16S rDNA clone library and FISH results showed that Nitrosospira spp. and Nitrospira spp. were the predominant ammonia and nitrite oxidizing bacteria, respectively, in both systems despite the differences in operating conditions. The search for a denitrifying candidate led to the identification of Dechloromonas spp. in the A/O MBR. This observation suggested that a nitrate reducing bacteria community could be established in an MBR designed for nitrogen removal.