Influence of Temperature on MBBR Denitrification for Advanced Nitrogen Removal of Wastewater Treatment Plant Effluent

High total nitrogen content is an urgent issue for the reuse of Wastewater Treatment Plant (WWTP) effluent. Moving Bed Biofilm Reactor (MBBR) was selected for advanced denitrification of WWTP effluent, and the influence of temperature on the nitrate removal performance was studied. Under 12 h hydrautic retention time (HRT) and 13°C, 19°C, 25°C and 30°C conditions, the NO3 -N removal and denitrification rate were not influenced obviously by the temperature variation. The NO3 -N removal were 82.9±26.7%, 80.1±27.2%, 85.0±22.3% and 82.9±13.3% respectively; and the denitrification rate achieved 35.5±2.4 mg NO3 -N •(L•d) -1 ), 36.4±1.5mg NO3 -N •(L•d) -1 ,38.3±16.5 NO3 -N •(L•d) -1 and 39.2±21.2 NO3 -N •(L•d) -1 accordingly. The similar nitrate removal and denitrification rate might have resulted from the long HRT compensation for the denitrification deficiency at low temperature. Three-dimensional fluorescence spectra showed that the dissolved organic matter (DOM) removal were 47.6%, 49.0%, 50.5% and 52.5%, and they were slightly influenced by the temperature. The amount of denitrification narG, nirS and nosZ genes at 13°C and 19°C conditions were higher than those under 25°C and 30°C, and the narG and nirS gene content of 13°C were the highest, which were 2.04×10 and 1.63×10copies/g-SS respectively. Considering the pollutant removal efficiency and the denitrification genes abundance as a whole, 25°C was the optimum choice for nitrogen removal of WWTP effluent by denitrification MBBR.