Evaluation of Carbon and Nitrogen Removal Performance of the Oxic-Hydrolytic and Denitrification-Oxic Process in Coking Wastewater Treatment

The novel oxic-hydrolytic and denitrification-oxic (O/H/O) process has attracted intensive attention from the industry and academia and has been applied in coking wastewater treatment practice in recent years. However, there has yet been a mechanism model that can systematically guide the design and operation of the O/H/O process in optimization. In this study, a two-step nitrification–denitrification activated sludge model no. 3 for coking wastewater (TCW-ASM3) model was established. The addition of new components and processes enables TCW-ASM3 to accurately simulate the biological reaction processes in the O/H/O system. The simulation results show that the increase in the step feeding ratio (R1) will lead to the increase in biological effluent chemical oxygen demand (COD) and total nitrogen (TN). To meet the TN effluent target (TN < 50 mg/L), R2 > 320% was needed. The energy consumption under this effluent constraint (COD < 200 mg/L, TN < 50 mg/L) was 4.873–5.752 kWh/m3. The foregoing results showed that the O/H/O process could be adjusted in different modes according to the pollutant characteristics and effluent targets. This study is the first report of the O/H/O process model, which is capable of providing strategies of multiple targets for the pollutant removal from industrial wastewaters with high toxicity and high C/N ratio.