Paper industry is a raw material industry with circular economy characteristics. Paper industry can not only drive the development of upstream industries such as forestry, chemical industry, machinery manufacturing and logistics, but also promote the development of downstream industries such as packaging, publishing, cultural communication and medical & health care. However, the bleaching process of pulp will produce a large amount of medium wastewater containing cellulose, resinate and other ingredients difficult to biodegrade. At the same time, there will be organic halides, dioxins and other carcinogens in the waste water after bleaching, which will cause serious environmental pollution. With the increasingly strict requirements of environmental protection in the world, chlorine-free bleaching has been the trend in the world. In chlorine-free

Cooling towers use water as a circulating coolant, which absorbs heat from a system and releases it into the atmosphere to have the system cooled. The cooling water in a cooling tower will be recycled through the system. However, the circulating cooling water provides suitable temperature and humidity conditions for the growth of bacteria and microorganisms. And microbial growth can lead to problems such as sediment attachment, equipment corrosion, and algae blooms. This will lead to blockages in pipes and, more troubling, to bacteria such as Legionella, which can cause serious health concerns. The good news is that cooling tower ozone sterilization is now the best solution for the problem. For the treatment of circulating water in cooling towers, chlorine