Treatment of a synthetic Nylon production wastewater under denitrifying conditions in an anoxic sequencing batch reactor

A synthetic Nylon production wastewater high in nitrate (400–800 mg/L NO3‐N), total organic carbon (TOC=2000 mg/L), and chemical oxygen demand (COD=5450 mg/L) was treated in a laboratory‐scale, anoxic Sequencing Batch Reactor (AxSBR). The purpose was to determine the extent of organic carbon removal with different nitrate doses and the feasibility of achieving complete removal of oxidized forms of nitrogen (NOx) and organic carbon. The organic carbon consisted of 27 different alcohols, acids, aldehydes, and ketones. A concentration of 400 mg/L NO3‐N (NOx‐N/C=0.2) in the AxSBR resulted in removal of 33% TOC and 35% COD. Doubling the concentration to 800 mg/L NO3‐N (NOx‐N/C=0.4) increased removal of TOC and COD to 46% and 44%, respectively. An equivalent of 5000 mg/L NO3‐N (NOx‐N/C=2.5) was required to achieve 92% removal of TOC and COD. Under nitrate‐limiting conditions the readily degraded organics included: n‐butanol, methanol, ethanol, n‐propanol, l‐pentanol, cyclopentanol, picric acid, formic acid, acetone, n‐butyraldehyde, and propionaldehyde; and less readily degraded were s‐and t‐butanol, isopropanol, cyclohexanol, MEK, and cyclohexanone.