Enrichment and characterization of Anammox bacteria in a non-woven membrane reactor

Abstract

An upflow column reactor packed with nonwoven fabric carrier was used to enrich anaerobic ammonium oxidation (Anammox) sludge. After 101 days, the reactor Anammox sludge concentration increased from 470 to 3,118 mg·L1. In the stable operating stage, the average total nitrogen (TN) volume loading rate was 818.3 mg·L1, and the maximum removal efficiencies of NH+4-N, NO2-N and TN were 65.9, 81.2 and 63.8%, respectively. Scanning electron microscopy (SEM) showed that the cultivated sludge was dominated by a mix of short rod-shaped and spherical bacteria, which accumulated to the typical cauliflower-like aggre-gates assumed to be the Anammox culture. Fluorescence in situ hybridization (FISH) analysis using 16S rRNA showed that the dominant population developed in the reactor when hybridized with both PLA46 and Amx820 gene probes. This indicates that the cultivated biomass may comprise Planctomycetes bacteria. The results of real-time quantitative PCR (qPCR) showed that these bacteria formed 45 to 60% of the total bacteria in the Anammox sludge. The study demonstrated successful detection and enrichment of Anammox bacteria in wastewater.