he article presents the results of evaluating the ability of activated sludge, saturated with anammox bacteria, to adapt to mesophilic and lower temperature operating conditions. As the main temperature regimes, temperatures of 30, 25, 15, and 13 ° C were selected. The system showed stable operation at temperatures up to 15 ° С with the highest degree of purification with respect to ammonium nitrogen - 0.33 mg / dm3. At the same time, the concentration of nitrites taking into account forced nitritation reached 0.07 mg / dm3. An additional increase in the efficiency of the system requires structural changes in the adopted technological scheme of the bioreactor, however, the introduction of an internal recirculation system of attached biomass (with load) inside the anammox department is considered as an essential element of the system that ensures stability

Keywords: nitrification, denitrification, activated sludge, aeration tank, anammox, biological treatment, domestic wastewater, low-oxygen treatment method, energy saving, resource saving, ecology