Nitrogen Removal Performance in Biological Decomposition on N, N－Dimethylformamide under Acidic Conditions

Abstract

N, N－Dimethylformamide (DMF) is ranked as the largest discharged organic material in PRTR (2007). Nitrogen removal is an important subject for biological DMF treatment processes. In this work, the performances of nitrogen removal for DMF, N-methylformamide (MF) and formamide (FA) were examined under acidic conditions with bench-scale mesh-filtration bioreactors, because the mesh filtration was conducted successfully under acidic condition. The reactors were operated at HRT=10 days and at 0.0192 kg－N?(m³?d)^–1 of volumetric nitrogen loading rate. The pH was not controlled and, therefore, the mixed liquors in the reactors were kept at around pH=3. The removals of total organic carbon (TOC) were more than 95%, but nitrogen removals were affected by the substrate: Kj－N removals were 95% for DMF and 70% for MF and FA; total nitrogen removals were 55% for DMF, 20% for MF and 10% for FA. In the process fed DMF as a substrate, the production of N₂O was observed even under oxic condition. Nitrate reduction was observed even at pH=3, but the nitrate reduction performance decreased rather under neutral pH condition. However, the reduction from N₂O to N₂ was suppressed under wide range of pH conditions.