tailieunhanh - PHYSICAL - CHEMICAL TREATMENT OF WATER AND WASTEWATER - CHAPTER 17 (END)

hử trùng là một quá trình đơn vị liên quan đến các phản ứng làm cho sinh vật gây bệnh vô hại. Một quá trình đơn vị đồng hành là khử trùng. Khử trùng liên quan đến việc giết hại tất cả các sinh vật. Tiệt trùng là không thường xuyên thực hành trong điều trị nước và nước thải. Vì vậy, chương này sẽ chỉ thảo luận về các quá trình đơn vị khử trùng. Thảo luận này sẽ bao gồm các phương pháp khử trùng, các yếu tố ảnh hưởng đến khử trùng, và các chất khử trùng. | 17 Disinfection Disinfection is a unit process involving reactions that render pathogenic organisms harmless. A companion unit process is sterilization. Sterilization refers to the killing of all organisms. Sterilization is not often practiced in the treatment of water and wastewater. Thus this chapter will only discuss the unit process of disinfection. This discussion will include methods of disinfection factors affecting disinfection and the various disinfectants that have been used. Because chlorine is the most widely used disinfectant its chemistry will be discussed at length. The design of chlorination unit operations equipment will also be discussed. The following disinfectants will also be specifically addressed ozone and ultraviolet light. METHODS OF DISINFECTION AND DISINFECTANT AGENTS USED Generally two methods of disinfection are used chemical and physical. The chemical methods of course use chemical agents and the physical methods use physical agents. Historically the most widely used chemical agent is chlorine. Other chemical agents that have been used include ozone ClO2 the halogens bromine and iodine and bromine chloride the metals copper and silver KMnO4 phenol and phenolic compounds alcohols soaps and detergents quaternary ammonium salts hydrogen peroxide and various alkalis and acids. As a strong oxidant ClO2 is similar to ozone. Ozone will be discussed specifically later in this chapter. It does not form trihalomethanes that are disinfection by-products and suspected to be carcinogens. Also ClO2 is particularly effective in destroying phenolic compounds that often cause severe taste and odor problems when reacted with chlorine. Similar to the use of chlorine it produces measurable residual disinfectants. ClO2 is a gas and its contact with light causes it to photooxidize however. Thus it must be generated on-site. Although its principal application has been in wastewater disinfection chlorine dioxide has been used in potable water treatment .