The paper presents the results of studies on increasing the efficiency of wastewater treatment from nitrogen compounds during the re-engineering of sludge bioreactors with the use of contact carriers for biomass immobilization. To assess the contribution of the indicative species of microorganisms involved in the processes of nitrification and denitrification, an analysis of the indices of species diversity by functional zones was carried out. The results of the operation of the bioreactor are given when using reticulate contact carriers in the form of partitions to separate the functional zones. It was noted that the oxidation-reduction potential of the bioreactor in nitrogen increased 1.7 times after re-engineering.