Disinfection of wastewater using ultraviolet radiation

The disadvantages associated with the use of chlorine for disinfection, in conjunction with improvements in ultraviolet radiation disinfection technologies have led to the recent increased use of ultraviolet radiation to provide disinfection of effluents from wastewater treatment plants. The theory of ultraviolet radiation and the engineering design of the ultraviolet disinfection system are discussed in depth. The operational history and records of two wastewater treatment plants that use ultraviolet radiation for disinfection were analyzed in an attempt to develop correlations on the factors that affect ultraviolet radiation disinfection efficiency and to investigate as to whether disinfection with ultraviolet radiation is a legitimate alternative to disinfection with chlorine. One facility is a tertiary wastewater treatment plant while the other is a secondary facility. A high level of disinfection was consistently observed at the tertiary case study facility under the range of operating conditions encountered since the ultraviolet radiation system was put on-line in January 1991. The ultraviolet disinfection system at the secondary case study facility in general provided a satisfactory level of disinfection; however, it was subject to poor disinfection efficiencies upon high plant flows. Based on the performance of the two case study facilities, ultraviolet radiation disinfection systems can be successfully used to disinfect treated wastewater effluents from both secondary and tertiary facilities. Ultraviolet radiation does represent a reliable, safe and practical alternative to disinfection with chlorine