Microbial domestication and response of low C/N ammonia nitrogen wastewater treated by zonal influent micro-pressure internal circulation reactor

Abstract

In this study, by distributing the influent in a micro-pressure internal circulation reactor (MPR) at a flow rate ratio of 1:2:1 to the anaerobic zone, anoxic zone, and aerobic zone, efficient denitrification of low C/N ammonia nitrogen wastewater was successfully achieved without the need for additional carbon sources or nitrified liquid reflux. Compared with the traditional treatment method of adding carbon sources, the treatment cost was reduced. By regulating the dissolved oxygen (DO) content in the growth environment of microbial flora, the nitrifying flora was first enriched, followed by the denitrifying and simultaneous nitrification-denitrification (SND) bacteria flora. During this process, the diversity of microbial populations decreased with the increase of DO concentration. The removal efficiency of COD, NH₄⁺ -N and TN reached 95 %, 85 % and 80 % respectively. The 16S rRNA amplicon sequencing showed that the increase of dissolved oxygen during domestication promoted the proliferation of nitrifying bacteria, the relative abundance of nitrifying genes increased, while the secretion of extracellular polymers increased, and the activities of dehydrogenase activity and specific aerobic rate increased. Then, with the decrease of DO concentration, the relative abundance of nitrifying bacteria at the genus level wasn′t affected. However, the denitrifying functional bacteria increased significantly, especially the abundance of bacteria with SND functions, and the TN removal amount in the aerobic zone reached 21.24 % of the total removal amount.