"Coolant waste is classified as HW09 oily wastewater and is considered hazardous waste in the non-specific industry. According to the "People's Republic of China Law on the Prevention and Control of Solid Waste Pollution" and the "Guidelines for the Formulation of Management Plans for Hazardous Waste Generators," it is strictly regulated nationwide, which has a significant impact on the coolant industry. This article briefly explores two technical approaches for the treatment of coolant waste."
Cutting fluid wastewater generated from machining processes is classified as HW09 oily wastewater and falls under the category of hazardous waste in the non-specific industry. According to the "Law of the People's Republic of China on the Prevention and Control of Solid Waste Pollution" and the "Guidelines for the Development of Hazardous Waste Management Plans for Waste Generators," it is strictly regulated nationwide, significantly impacting the cutting fluid industry and the operations of mechanical manufacturing companies, thereby driving the upgrade of technology and management.
Firstly, let's consider the development process of cutting fluids. The transition from using pure oil to oil-water emulsions was primarily driven by cost considerations. Using pure cutting oil offers advantages such as long-term usability and excellent machining finish. However, a major drawback is the increased risk of fire due to the desire for faster production. To ensure the safety of the company's assets, the industry shifted towards using oil-water emulsions, which is the current mainstream in the market.
Given the environmental pressures, it is not feasible to revert to using pure oil cutting fluids from a process feasibility standpoint. Moreover, even when using pure oil, the problem of volatile organic compounds (VOCs) still exists, and the challenges associated with their control are not much different from those of oily wastewater. Therefore, it is essential to approach the treatment of oily wastewater with a scientific and correct method, which demonstrates a responsible scientific attitude towards history and the environment. Avoiding the issue will not lead to development, nor will it contribute to the progress and optimization of technology and management.
Currently, the environmental pressures have stimulated the emergence of many enterprises selling environmental protection equipment to address the challenges posed by HW09 oily wastewater. Based on market visits and research, there are mainly two technical approaches: distillation and membrane filtration.
Low-temperature distillation involves exploiting the differences in boiling points and boiling ranges of the various components in cutting fluid solutions. Given that cutting fluid is a dilute solution consisting mainly of organic compounds dissolved in water, with water accounting for over 95% of the solution, distillation utilizes different pressures, temperatures, stirring characteristics, and the addition of azeotropic agents to achieve cost-controlled separation of different substances. Ultimately, hazardous substances are sent to hazardous waste stations, while water is separated for recycling or discharge into the environment.
Membrane filtration, on the other hand, utilizes the "semi-permeable membrane effect" between different substances in a solution. It refers to the ability of a certain semi-permeable membrane material to allow the passage of solutes while preventing the passage of solvents. Membrane filtration can effectively separate acids, alkalis, salts, and other chemical substances. By using a systematic approach and conducting in-depth studies on the characteristics of HW09 wastewater, high-quality semi-permeable membrane materials can be selected. Employing various physical and catalytic methods, it is possible to reduce the oily wastewater to below 10% of its original volume.
Overall, the treatment of cutting fluid wastewater generated from machining processes involves two main technical approaches: low-temperature distillation and membrane filtration. These methods address the challenges associated with HW09 oily wastewater and align with the principles of scientific responsibility, promoting development, and facilitating the progress and optimization of technology and management.
| Method | Advantages | Disadvantages |
|---|---|---|
| Low-Temperature Distillation | Thorough separation, high production efficiency | Higher initial investment |
| Membrane Filtration | Purely physical method, safer, lower separation cost | Higher maintenance cost (including labor), higher technological investment |
