Effects of organics on an ANAMMOX biofilm reactor: nitrogen removal efficiency and microbial community

For the purpose of investigating the effect of different organic concentrations on nitrogen removal efficiency in anammox biofilm reactor, the denitrification efficiency of the reactor under the different concentrations of organic matter was tested after the successful start-up of the anammox bio-film reactor. In this study, MPN (most probable number) method and high-throughput sequencing technology were used to compare and analyze the differences of microbial communities in the bio-film under the influence of different concentrations of organic matter. In comparison with the reactor without any organic matter, the results indicated that the total nitrogen removal rate increases by 5.08% and 10.41% under the influent chemical oxygen demands (COD) of 30 and 60 mg L–1, respectively. While the total nitrogen removal rate only increases by 4.71% when the COD concentration rises to 90 mg L–1. In comparison with the reactor without any organic matter, the MPN method and high-throughput sequencing result showed that the denitrifying bacteria number was increased and the abundance of Planctomycetes and Proteobacteria was increased in the reactor under COD of 60 mg L–1. Under the effect of 90 mg L–1 COD, the abundance of Proteobacteria continued to increase, while the abundance of Planctomycetes decreased sharply. At mentioned point, denitrification played a leading role. The experimental data showed that the denitrifying bacteria and anammox bacteria in the reactor achieved symbiosis and complementary advantages under certain organic concentration, but the growth of anammox bacteria was inhibited under the condition of high organic concentrations. This study can provide a reference value for anammox biofilm reactor to treat wastewater containing organic matter.