SIMULTANEOUS NITRIFICATION-DENITRIFICATION IN A ROTATING BIOLOGICAL CONTACTOR

Simultaneous nitrification\aerobic denitrification studies or a high strength synthetic nitrogenous fertilizer wastewater in a single stage were carried out using a rotating biological contactor (RBC). Mixed culture biofilm consisting of Nitrifiers and Thiosphaera pantotropha (a heterotrophic nitrifer and aerobic denitrifier) was acclimated to 1386 mg 1-1 of TKN & 400 mg l-1 of nitrate nitrogen. The effect of different nitrogen loadings and hydraulic retention times (HRTs) on percentage removal of TKN and nitrate nitrogen simultaneously, was investigated. A maximum TKN removal of 95.6 percent could be achieved at a nitrogen loading of 9.36 gN m-2 d-1 and HRT of 2 days. The results showed that the process is zero order with respect to nitrogen removal. The HRT studied were in the range of 0.5-3 days. The corresponding percentage TKN removal ranged from 43.9-93.7. Nitrate removal of 97-98% could also be achieved simultaneously. Nitrite accumulated significantly throughout these studies. Nitrogen loading and hydraulic retention time were found to be important process control parameters. A theoretical estimation of Nitrifiers and T. pantotropha was also carried out based on nitrification and denitrification rates observed during these studies.