Energy Balance Evaluation in Coking Wastewater Treatment: Optimization and Modeling of Integrated Biological and Adsorption Treatment System

The main objective of this study is to develop and assess a novel wastewater treatment system for coking wastewater to enable maximization of net energy gain. Additionally, a new methodology is proposed for evaluation of energy saving. The new combined biotreatment and adsorption system (A2BA1) is designed with two adsorption reactors placed at the input and output of the biotreatment unit. An energy modeling coupled mathematical simulation (EMMS) methodology is proposed for assessment of the energy balance. The optimal operating conditions (OOCs) are achieved and energy saving rates (ESRs) can also be calculated in the proposed methodology. The results showed that the A2BA1 system enabled energy savings in treatment of volume loads of chemical oxygen demand (COD) and NH3-N in the range 0.82–2.96 kg COD/(m3·d) and 0.06–0.15 kg NH3-N/(m3·d), respectively. Using the EMMS methodology, the operating condition sets of Q18(2506.9, 104.2, 0.98), Q33(3008.1, 101.1, 2.00), and Q36(2524.3, 102.6, 2.02) were found to be the OOCs, and the average value of ESRs of the three OOCs reached 48.3%. In this work, Qi stood for the mathematical set of the ith operating condition comprised of the basic variables (i.e., raw wastewater COD (mg/L), biotreated effluent COD (mg/L), and activated carbon dosage (g/L)). Furthermore, in order to realize net energy gain in the coking wastewater treatment, the adsorbent price of activated carbon should be 54% of the current price for the same adsorption performance. It is concluded that the A2BA1 system and EMMS methodology can help decision-makers design and optimize wastewater treatment in terms of energy savings.