This paper studied the characteristics of the carbon emission of an industrial wastewater treatment plant (IWWTP) and a domestic WWTP (DWWTP) located in a high-tech industrial park of Shaanxi Province, China. The results showed that the total carbon emissions of the IWWTP and DWWTP were 10.13 kg/t and 1.84 kg/t in 2020, respectively. Indirect carbon emissions play a dominant role in the total carbon emission of the IWWTP, which accounts for about 97.6% of the total amount. The direct carbon emissions of greenhouse gases (e.g., CH₄, N₂O) account for about 62% of the total carbon emissions in the DWWTP, followed by the indirect carbon emissions generated by electricity consumption (31.06%) and chemical consumption (6.94%). Additionally, the centralized recycling and re-utilization of the wastewater could achieve 1.06 kg/t and 1.16 kg/t of carbon emission reduction in the IWWTP and DWWTP, respectively, while the carbon emissions of the DWWTP are inversely proportional to the treatment capacity. Therefore, it is of great value to collect and utilize intensively the recycled water to achieve the goal of regional carbon emission reduction and carbon neutralization of WWTPs in industrial parks.

Industrial wastewater containing refractory organic compounds, heavy metals, and emerging contaminants poses a significant challenge to conventional treatment methods due to their high chemical stability and toxicity. This review systematically summarizes recent advances in Fenton-based advanced oxidation processes (AOPs) for industrial wastewater treatment, with a particular focus on the paradigm shift from homogeneous to heterogeneous catalytic systems. Homogeneous Fenton processes, which rely on Fe²⁺/H₂O₂ reactions, exhibit rapid reaction kinetics but are severely limited by a narrow operational pH range (2–4) and the generation of substantial iron sludge. In contrast, heterogeneous Fenton systems employing immobilized or supported catalysts—such as iron-loaded zeolites, metal–organic frameworks, and carbon-based composites—broaden the applicable pH range to near-neutral conditions (4–8), enable catalyst recovery and reuse over multiple cycles, and enhance process sustainability by reducing iron leaching and sludge production. Integration with external energy inputs—such as photo, electricity, or ultrasound—can further promote radical generation and mass transfer, improving degradation efficiency while reducing chemical consumption. Practical applications in treating wastewater from textile, pharmaceutical, and electroplating industries have demonstrated effective contaminant removal and enhanced biodegradability. However, most current research remains at the laboratory scale, with long-term catalyst stability, operational costs, and scalability representing major barriers to large-scale implementation. Future research should focus on developing stable and regenerable catalysts, advancing pilot-scale studies of integrated systems, and conducting long-term evaluations under real wastewater conditions to promote the development of efficient, low-carbon, and sustainable solutions for industrial wastewater treatment.