Denitrification rates determination in the process of removing nitrogen from wastewater

Abstract

The purpose of the study was to determine denitrification rates during aeration tanks converting to the aero-mode of the nitri-denitrifier with the nitrate recycling. Studies were conducted on an experimental facility with wastewater and activated sludge from one of the sewage treatment facilities of the Udmurt Republic. At the beginning of the experiment, the activated sludge was under anoxic conditions (the mixture was mechanically mixed without aeration), while periodically the mixture was analyzed for nitrate content. Thus, the rate of denitrification during endogenous respiration was determined. Further, waste water was added to the sludge (anoxic conditions were preserved) - simulation of nitrate recycling. According to the results of experimental studies, the calculated denitrification rates were r_ds = 0.71 ± 0.04 mg N-NO₃ / mg of active heterotrophic microorganisms per day on easily oxidizable substrate, on endogenous respiration r_de = 0.12 ± 0.02 mg N-NO₃ / mg of active heterotrophic microorganisms per day, on difficult oxidizable substrate r_dp = 0.12 ± 0.01 mg N-NO₃ / mg of active heterotrophic microorganisms per day.