Applicability and Microbial Community Structure of Denitrification Suspended Carriers

In order to investigate the effects of temperature and organic loading on the bioactivity reactivation of anoxic biofilm in suspended carriers, the experiment was carried out under low organic loading, shock loading and low temperature conditions. The experimental results showed that the increase of polysaccharide in extracellular polymeric substance (EPS) was important during bioactivity reactivation process, and polysaccharide content was higher than that of protein under shock loading and low temperature conditions, and the contents of both polysaccharide and protein were much higher under low organic loading condition. Anoxic biofilm achieved excellent applicability in shock loading condition, moreover anoxic biofilm reactivated under low organic loading had lowest denitrication capacity and anoxic biofilm recovered at low temperature was in between. In addition, the relative abundance of Proteobacteria under low organic loading, shock loading and low temperature conditions increased from 72.23%, 78.66% and 76.35% to 83.17%, 84.30% and 80.46% at the end of the reactivation process (25th day), respectively. However, the relative abundance of Proteobacteria under low organic loading was lower than those of other reactors, indicating that the anoxic suspended carriers were less suitable for total nitrogen removal in wastewater treatment plant. The increase in relative abundance of Dechloromonas was significant for enhancing total nitrogen removal, and anoxic biofilm possessed comparatively rich biodiversity when the denitrification capability was recovered. The presence of Flavobacterium could promote the denitrification capacity of biofilm at low temperature.