Nutrient removal using anaerobically fermented leachate of food waste in the BNR process

Abstract

Nutrients removal efficiencies highly depend on the presence of biodegradable organic carbon in the biological nutrient removal (BNR) process but most domestic wastewater in Korea has shown a low C/N ratio and has a small amount of biodegradable COD (chemical oxygen demand). On the other hand, about 11,577 tons of food waste that contains a lot of organic material has been produced in Korea per day. The feasibility and applicability of anaerobically fermented leachate of food waste (AFLFW) as an external carbon source was examined in the laboratory-scale BNR process at different operation conditions with synthetic wastewater and domestic sewage. As the addition of AFLFW increased, the average removal efficiencies of SCOD, T-N, T-P changed from 96%, 60%, and 2% to 90%, 77%, and 67%, respectively. From anoxic nitrate utilization tests, it was observed that once the readily biodegradable COD (especially VFAs) was depleted, the denitrification rate reduced from 8.2 mg NO3-N/g VSS/hr to 0.7 mg NO3-N/g VSS/hr. From the molecular size distribution test, it was concluded that about 60% of soluble COD in effluent, which was considered to originate from AFLFW, had a large molecular size (> 30kDa) that was not used by microorganisms.