Effects of operating parameters on performances of nitrification and denitrification processes

Nitrification and denitrification of synthetic wastewater was studied by using two reactors in series. An activated sludge unit was used for nitrification followed by a downflow biofilter (packed column) for denitrification. A glucose solution was fed to the denitrification column to supply carbon source. Effects of important process variables such as sludge age, hydraulic residence time and feed ammonium concentration on system's performance were investigated. Effluent ammonium-nitrogen (NH4-N) concentration decreased with increasing sludge age and hydraulic residence time and remained constant for sludge age and hydraulic residence times greater than 12 d and 15 h, respectively. Feed ammonium-nitrogen concentration above 200 mg/l resulted in significant levels of NH4-N in the effluent at theta(c) = 15 d and theta(H) = 12 h in nitrification. Performance of denitrification stage was not satisfactory for feed NO3-N concentrations above 150 mg N/l resulting in significant effluent NO3-N levels at hydraulic residence time of theta(H) = 6 h.