Nitrate removal in a packed bed reactor using volatile fatty acids from anaerobic acidogenesis of food wastes

Abstract

A packed bed reactor (PBR) was fed with nitrate containing synthetic wastewater or effluent from a sequencing batch reactor used for nitrification. The C source introduced into the PBR consisted of volatile fatty acids (VFAs) produced from anaerobic acidogenesis of food wastes. When nitrate loading rates ranged from 0.50 to 1.01 kg N/m(3.)d, the PBR exhibited 100 similar to 98.8% NO3--N removal efficiencies and nitrite concentrations in the effluent ranged from 0 to 0.6 NO2--N mg/L. When the PBR was further investigated to determine nitrate removal activity along the bed height using a nitrate loading rate less than 1.01 kg N/m(3.)d, 100% nitrate removal efficiency was observed. Approximately 83.2% nitrate removal efficiency was observed in the lower 50% of the packed-bed height. When reactor performance at a C/N ratio of 4 and a C/N ratio of 5 was compared, the PBR showed better removal efficiency (96.5%) of nitrate and less nitrite concentration in the effluent at the C/N ratio of 5. VFAs were found to be a good alternative to methanol as a carbon source for denitrification of a municipal wastewater containing 40 mg-N/L.