Introduction to Established Disinfection Technologies

Disinfection is typically the last step in the wastewater treatment process. The performance of the disinfection process greatly depends on the performance of the upstream treatment processes (i.e., primary treatment, biological treatment, secondary sedimentation, and tertiary filtration). The purpose of disinfection in the wastewater treatment is the destruction or inactivation of disease causing pathogens (e.g., protozoan, bacteria, and viruses) to protect public health and the environment. As part of the Water Environment Research Foundation Project 04-HHE-4, a survey of the disinfection processes of 4450 publically owned treatment works (POTWs) was conducted. As a result of this study, it was determined that 75.3 percent of the POTWs in the United States utilized chlorine disinfection as the main disinfection process. The authors of this study also found that 20.6 and 0.2 percent of the POTWs located in the United States utilized ultraviolet light (UV) disinfection and ozone disinfection, respectively. It was determined that 3.9 percent of the POTWs did not disinfect the treatment plant effluent at all. This paper will provide a brief description of the three established groups of disinfection technologies used to disinfect wastewater (i.e., chlorine, UV, and ozone). A brief description of each disinfection technology as well as the mechanisms of pathogen inactivation of chlorine, UV, and ozone disinfection will be described in the presentation. The advantages and disadvantages of using each type of disinfection technology will be discussed. Pictures of the disinfection equipment utilized in each system as well as a comparison of the effectiveness of each technology will be presented.