Study on influencing factors of denitrification by a step-feed multistage biofilm reactor

Experiments have been carried out to investigate the effect of biological factors such as organic loading, dissolved oxygen (DO) and temperature on performance of denitrification in a step-feed multi-stage biofilm reactor ,for municipal wastewater treatment in small cities and towns.lt was found that organic loading, DO and temperature had significant influences on performance of denitrification in the reactor. Under the conditions of the temperature of 20~25°C, DO of 5 mg/L, organic loading of 1.0 kgCOD/m3·d, biofilm density of 30%, nitrogen loading of 0.22 kgTN/m3·d, with wastewater fed in the 1st, 3rd and 6th stages , and flow distribution ratio of 2:2:1, SND process was successfully constructed in the reactor , the effluent concentration of COD, NH₄⁺-N and TN are 33 mg/L, 2.6 mg/L and 29.4 mg/L respectively, the removal efficiencies of COD· NH₄⁺ -N and TN are 90.1%., 96.0% and 63.9% respectively. When the water temperature is below 15°C, nitrification rate is affected by the temperature notably.