Evaluation of the benefit of practically operating reverse osmosis system in the factory: taking the recycling of KI solution and water of the screen polarizing plate as an example

In recent years, with the advocacy of the circular economy and the rising awareness of environmental protection, energy saving, water saving and carbon reduction have become important topics for discussion today. The high-tech semiconductor, photoelectric, solar and other electronic industries involve high energy and water consumption. In addition to responding to the energy saving, water saving and carbon reduction, one of the main purposes of this system development is to reduce the use of materials and make the process chemicals reusable. In the practical factory operation, a large amount of water is used in the polarization process, and the wastewater generated in etching and pickling is discharged continuously. In order to recycle the water discharging from the manufacturing process, the reverse osmosis membrane system (RO membrane system) is often used for wastewater recycling. In this study, the KI waste liquid discharging from the process of a polarizing plate factory was concentrated with anti-fouling RO membrane. The quantity and arrangement of RO system membranes were simulated and designed with software, and the results, such as water volumes and pressures of inflow and outflow water for the membrane, changes of membrane pressure difference (ΔP), changes of permeating water quality, chemical cleaning frequency and water collection time, were discussed and the optimal parameters of RO membrane, such as the best water collection volume and time, chemical cleaning frequency, best concentration, time and temperature matching with cleaning in process (CIP) were inferred so as to improve the stability of the RO membrane system, enable RO permeating water to enter the water purifying system for reuse, reduce the treatment cost of wastewater recycle and improve the permeating water output efficiency of treatment equipment, accommodating effective utilization of water resources and economic benefits and to sustainable development of the industry. HIGHLIGHTS The RO membrane system runs stably, the concentration of KI will be relatively stable and the recovered water quality can be purer.; About US$ 670,000 is needed for wastewater treatment and water pollution fees, while US$ 560,000 can be saved per year through the use of the recycling technology according to this study, for which the investment can be recovered in about 1.14 years.