Analysis of bacterial communities by metagenome sequencing in a partial nitritation fixed bed reactor at low ammonium concentration

Biological nitrogen removal from wastewater via partial nitritation (partial nitrite oxidation) is an interesting practice as it reduces the energy demand for aeration for subsequent denitrification or anammox processes. Nitrogen removal via nitrite is mainly used for treating wastewaters (WW) with high ammonium concentrations and low C/N ratios. In last the decade the researches targeting the application of partial nitrification anammox processes (PN/A) to diluted WW (low ammonium concentration). The key factor for application of all the PN/A processes in wastewater is the control over PN. Understanding the effect of the different conditions and substrate concentrations on the nitrifier communities can lead to the development of stable technologies for PN.

In this study, a shotgun metagenome sequencing was performed for the biofilm of a partial nitrification up-flow fixed bed reactor, which operated with mainstream ammonium concentration (50mg/L as N) for 230 days. The biomass in the reactor was sourced from nitrifying activated sludge. Taxonomic profiling at phylum through species levels for Prokaryotes was performed. A comparison between the phylum and the specie level longwise the reactor and the source biomass was conducted. The effect of dissolved oxygen and nitrogen compounds profile along the reactor on the different nitrifying communities was studied. The dominant phylum in the reactor was Proteobacteria, the dominant ammonia oxidizer specie was Nitrosomonas europaea and the dominant specie of nitrite oxidizing bacteria was Nitrospira defluvii. The reactor`s conditions were suitable also for Planctomycetes community growth. DO and N-compounds concentration profiles had a noticeable effect on the bacterial groups` composition along the reactor.