Industrial wastewater resource utilization: from meeting discharge standards to turning waste into treasure.

Environmental regulation continues to tighten, coupled with the continuous rise in water resource costs, a transformation is taking place in domestic industrial water treatment. For a long time, the only goal for factories building sewage treatment facilities was to meet discharge standards and smoothly pass environmental. However, with tightening water resource constraints and the advancement of the dual carbon goals, simple end-of-pipe treatment is no longer sufficient to support long- business operations, and **wastewater resource utilization** is gradually becoming the core lever for the green transformation of industrial enterprises.

Industrial wastewater sources are complex, and industries such chemical, printing and dyeing, electroplating, and food processing have huge differences in water quality and pollutant components. After biochemical and sedimentation treatment, the sewage of many is directly discharged into the pipe network, and the residual salts, thermal energy, and recyclable materials in the water are taken away together, completely wasting the value of the resources. In water-scarce areas, the procurement price of production water rises year by year, and the fresh water intake quota is becoming increasingly tight. Relying on purchasing fresh water to maintain production not only drives up production costs but also directly affects production capacity once the water intake quota is restricted. Against this background, resource solutions such as reclaimed water reuse, concentrated water reduction, salt recovery, and waste heat recovery are being adopted by a large number of industrial projects.

Wastewater resource is not simply filtering and reusing sewage; it has extremely high requirements for process combinations. Conventional biochemical treatment can only degrade organic matter. For high-salinity wastewater recalcitrant organic wastewater, it needs to be paired with membrane methods and advanced treatment processes such as ultrafiltration, reverse osmosis, nanofiltration, and advanced oxidation Many enterprises easily fall into the trap of directly copying the reuse solutions of other factories, ignoring their own water quality fluctuations and material impurities, which leads to frequent fouling membrane elements, a significant increase in cleaning frequency, and an increase in chemicals and energy consumption instead of a decrease, making it difficult for the project to operate stably shortly commissioning. The success or failure of a resource utilization project depends on full-cycle monitoring of water quality and pollutant tracing in the early stages, matching the process route with water needs, rather than blindly pursuing high recovery rates.

Resource utilization transformation also needs to take into account the disposal problems of sludge and concentrated liquid. Increasing the water rate will inevitably produce concentrated liquid. If the concentrated water disposal plan is not planned synchronously, it will only transfer pollutants from the water to the concentrated liquid, creating new waste pressure and increasing the overall cost. Mature resource utilization projects will coordinate the entire chain: source reduction at the front end, reducing the amount of wastewater generated through production optimization; deep treatment in the middle stage to achieve water circulation; and reduction and stabilization disposal of concentrated liquid and sludge at the end, with some scenarios achieving the of materials such as salt, acid, and alkali, truly achieving closed-loop management of pollutants.

From an economic perspective, resource utilization projects involve a certain amount initial equipment investment, with short-term investment higher than traditional sewage stations, but the long-term benefits are obvious. Many manufacturing enterprises have reduced their fresh water consumption more than 40% through reclaimed water reuse, significantly reducing water fees and water intake pressure. At the same time, the recovered products can be reused in processes, reducing raw material procurement. Supported by green finance policies, compliant water-saving and emission-reduction projects can also apply for green credit and energy-saving subsidies improving the ESG level of enterprises and gainin advantages in bidding and customer audits.

Looking ahead, the core logic of industrial water treatment will continue to shift from "pollution" to "resource circulation". At the policy level, local governments' requirements for the reuse rate of industrial