Wastewater treatment system optimization with an industrial symbiosis model: A case study of a Chinese eco-industrial park

In Chinese industrial parks, the centralized wastewater treatment plant (CWWTP) is an essential shared infrastructure to further purify the in-plant pretreated industrial wastewater. Most of the contaminants, such as organic matter, are removed by in-plant wastewater treatment to guarantee the safety and efficiency of the CWWTP. Carbon source shortages are common in the denitrification process in CWWTPs, and such issues are generally solved by adding external carbon sources, such as glucose. Some biodegradable organics that are abundant in industrial wastewater, such as food production wastewater, can be utilized as the external carbon sources for denitrification. This study proposed an industrial symbiosis-based model to optimize the wastewater treatment system in industrial parks by reusing organic matter in food wastewaters as the external carbon source for advanced treatment processes in CWWTPs. A case study of a Chinese eco-industrial park is investigated to verify the technical and economic feasibility of the model. The case study indicates that the overall cost-savings potential of the model is approximately 6.55 million Chinese Yuan (CNY) per year, accounting for approximately 20% of the annual operating cost of the CWWTP. Additionally, the mitigation potential of greenhouse gas (GHG) emissions is 5977 t CO2-eq per year, accounting for 1.7% of the GHG emissions of the original model. Furthermore, potential barriers to implementing the IS model and the relevant policy implications are discussed.