In response to United Nations Sustainable Development Goal 6 - Clean Water and Sanitation, TSMC is committed to enhancing sustainable water resource management. In addition to modifying high-gravity rotating packed beds to achieve a 70% reduction in chemical oxygen demand (COD), TSMC also strives to reduce the use of chemicals in treating wastewater pollutants and continuously improving the quality of discharged water. Further innovation and development of the "Hypochlorous Acid (HOCI) Conversion System" has been achieved by converting sodium hypochlorite (NaOCI) into hypochlorous acid water. This effectively reduces residual chlorine in discharge water by 99% while maintaining the same sterilization and ammonia nitrogen removal effect. At the same time, it reduces the amount of sodium hypochlorite used and optimizes equipment operating efficiency. This system has been successfully implemented at Fab 15B, and as of November 2023, 6,029 tons of sodium hypochlorite have been reduced, resulting in a reduction of 752 tons of carbon emissions and a total green benefit of NT$31.7 million, in line with TSMC’s Environmental Policy.
Optimal Mixing Ratio for Modulating Concentration, Reducing Usage and Protecting the Environment
As semiconductor technologies continue to evolve, the consumption of sodium hypochlorite (NaOCI) to treat pollutants in wastewater has increased. Sodium hypochlorite is mainly used for disinfection and ammonia nitrogen removal. Sodium hypochlorite dissolves in water and produces hypochlorous acid at a pH of 5.5-6.5, which has an oxidation and disinfection ability more than 80 times that of sodium hypochlorite. To practice green manufacturing, TSMC launched the NaOCl reduction project in 2022. It added waste sulfuric acid recycled from the manufacturing process and combined it with deionized water (DI Water). After repeated testing, the optimal ratio of the three was formulated and the HOCl Conversion System was successfully developed. This reduced residual chlorine and increased the value of sulfuric acid waste reuse, promoting environmental friendliness. At the same time, in order to overcome the unstable nature of chlorine dioxide, the system innovatively adopts a design without storage devices. After analyzing the concentration data of pollutants in the water through monitoring instruments, the programmable logic controller calculates and issues instructions for precise adjustment. This not only ensures stable production and real-time application of chlorine dioxide, but also enhances the efficiency of wastewater treatment equipment operation.
Developing prevention and control technologies is an important strategy for TSMC's sustainable water management. The HOCI Conversion System is expected to be introduced into Fab 18 in the fourth quarter of 2023, resulting in a total annual reduction of 7,387 tons of sodium hypochlorite and 922 tons of carbon emissions. It will also reduce the outsourced transportation of sulfuric acid waste by 954 tons. The annual green benefits will reach NT$38.84 million and it will also be included in the standard design of new manufacturing facilities, moving towards the goal of net zero emissions by 2050.
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