Disinfection
(PDF Version)
Adopted by the WEF Board of Trustees: June 16, 2010
The Water Environment Federation (WEF) supports the continued responsible use of chlorine-based disinfectants such as chlorine gas, calcium hypochlorite, and sodium hypochlorite, in addition to alternative disinfection methods, including ultraviolet (UV) radiation and ozonation. Wastewater disinfection requirements are site-specific, depending on treated wastewater characteristics, applicable water quality and disinfection standards, and treatment process configuration and constraints. Therefore, all current disinfection options should remain available to allow a comparative evaluation of scientific, environmental, engineering, and economic benefits at each site. WEF believes that a proposal to ban the use of any specific disinfectant, such as chlorine-based chemicals, is inappropriate unless justified through scientific studies. WEF will continue to support disinfection-related research, advances in technology, and improvements in current methods to enhance process effectiveness and efficiency, safety, and beneficial effects on human health and the environment.
Background
Wastewater treatment facilities are designed to meet effluent standards established to protect the quality of receiving waters. These receiving waters may support a variety of beneficial uses, including habitat for aquatic species, contact and non-contact recreation, or potable water supply. Both the receiving water quality and the effectiveness of wastewater treatment processes are influenced by factors that are unique to each facility. Therefore, all disinfection processes should be evaluated relative to site-specific objectives and implemented, as necessary, to meet these objectives, while protecting the environment with minimal or no adverse impacts.
Disinfection is used to reduce the risk of water-borne disease transmission. Since 1976, the US EPA has encouraged site-specific evaluations to determine whether disinfection of wastewater effluents is necessary. Although disinfection is often beneficial, seasonal-only disinfection or no disinfection at all may be acceptable at sites where the use of the receiving water does not pose a hazard to public health or the environment.
Options for Disinfection
Historically, the most commonly and widely-used disinfectants have been chlorine-based chemicals. Chlorine disinfection has been identified as one of the top 10 advances in public health protection in the 20th century and has reliably and cost-effectively met bacteriological water quality standards. Overall, the public health benefits associated with chlorine disinfection far outweigh concerns regarding residual chlorine, chlorination byproducts (which can be mitigated through the use of a dechlorination process after disinfection), and/or public exposure to possible chlorine gas releases (either inadvertent or from terrorism-related incidents).
In addition to chlorine-based disinfectants, the use of alternative disinfection processes such as UV radiation and ozonation has been expanding. UV disinfection system installations have grown in both number and size over the past 20 years, due to the development of higher-efficiency UV lamps, improvements in reactor design and automation, and the absence of byproducts in the disinfected effluent. Interest in ozone disinfection has also increased due to advances in ozone generation systems and contactors, as well as its strong reactivity and potential to improve water quality. These alternatives provide additional options for effectively and efficiently meeting water quality objectives at wastewater treatment facilities.
Rationale
Current disinfection practices have reduced risks to public health while cost-effectively meeting water quality objectives. Based on current knowledge, the known benefits of these disinfection practices far outweigh the known risks. Maintaining the availability of all disinfection alternatives, including the use of chlorine-based chemicals, allows facilities to effectively disinfect wastewater effluents while balancing scientific, environmental, engineering, and economic considerations.
The suitability of any disinfectant depends on site-specific factors, such as treated wastewater characteristics, process effectiveness and reliability, applicable water quality standards, current and anticipated uses of the receiving water, treatment process configuration and constraints, safety, and cost. As our understanding of any disinfection technology with respect to these factors will never be complete, WEF will support continued study and research to further enhance our knowledge.
About the Water Environment Federation
Founded in 1928, the Water Environment Federation (WEF) is a not-for-profit technical and educational organization with 36,000 individual members and 75 affiliated Member Associations representing water quality professionals around the world. WEF members, Member Associations and staff proudly work to our mission to provide bold leadership, champion innovation, connect water professionals, and leverage knowledge to support clean and safe water worldwide. To learn more, visit www.wef.org.
Reference
Leong, L.Y.C.; Tang, C.C.; Kuo, J. Disinfection of Wastewater Effluent – Comparison of Alternative Technologies, Project 04-HHE-4; Water Environment Research Foundation: Alexandria, VA, 2008.