Saving external carbon source for post-denitrification by deoxygenation of trickling filter effluent

Conference poster, 2007

When the effluent from a nitrifying trickling filter has to be denitrified the high oxygen concentration in the trickling filter effluent will consume considerable amounts of carbon source in the denitrification unit. By controlling the ammonium concentration after the trickling filter by the addition of small amounts of ammonium rich return liquors, oxygen can be consumed in a non-aerated nitrifying reactor. Deoxygenation experiments were carried out in laboratory scale MBBR:s filled with biofilm carriers previously acclimatised to low ammonium concentrations. The experimental results showed that a MBBR operated under low ammonium (0.8 mg NH4+-N/l) and oxygen concentrations (2.5 mg O2/l) achieved nitrification rates of about 0.5 g NH4+-N/m2d. When implemented at a 330 000 m3/d plant this is estimated to give a carbon source saving of about 400 kg of methanol per day.