Approved December 1, 2000, by the WEF Executive Committee

Use of Chlorine-Based Disinfectants For Wastewater Effluent Disinfection

The Water Environment Federation (WEF) supports the continued use of chlorine-based disinfectants among the available alternatives for wastewater effluent disinfection. Chlorine-based disinfectants include chlorine gas, calcium hypochlorite, sodium hypochlorite and similar chlorine-based chemicals. Since any requirement for wastewater disinfection is site-specific, all options should remain available for comparative evaluation including economic, scientific, environmental and engineering considerations. The options include chlorine-based disinfectants and other disinfectants such as ultraviolet light and ozone. WEF will continue to support disinfection-related research, advancements in technology and improvements in the use of current methods to improve their effectiveness and efficiency with the resultant benefits of improvement in human health and the environment. It is the strong and considered opinion of WEF that any proposal to ban the use of chlorine-based disinfectants is inappropriate and unjustified.

Background
Wastewater treatment facilities are designed and operated to meet effluent standards that are compatible with the maintenance of a desired water quality in the receiving waters. The factors that influence both the designation of the desired receiving water quality and the selection of the treatment processes that produce the compatible effluent quality can be highly site-specific. To allow for the most efficient and flexible control of water quality, a variety of processes are available including the use of chlorine-based disinfectants.

Wastewater disinfection is used frequently to maintain the quality of receiving water that supports aquatic species, contact and non-contact recreation, or serves as a source of potable water. The objective of wastewater disinfection is to reduce the risk of disease transmission through wastewater effluents while minimizing adverse side effects.

Chlorine-based disinfectants have historically been the most frequently used wastewater effluent disinfectants. Chlorine disinfection has been identified as one of the top 10 public health advances of the 20th century. These disinfectants have been proven to reliably meet bacteriological water quality standards. The health concerns raised regarding the use of chlorine based disinfectants are far outweighed by the cost effectiveness of pathogen reduction achieved. When used with a dechlorination process after disinfection, chlorine compounds have demonstrated their effectiveness and alleviated concerns of the impact of chlorine residuals and chlorination byproducts on aquatic biota.

The use of any wastewater treatment process must be evaluated with respect to the required water quality objectives. Disinfection remains one necessary tool to achieve certain water quality objectives and should only be practiced to the extent necessary to achieve these objectives.

Disinfection of wastewater effluents may not be necessary in all circumstances. The options of seasonal disinfection or no disinfection may be acceptable, particularly where the uses of receiving water are not adversely affected by the presence of pathogens. Since 1976, such site-specific evaluations have been encouraged by the U.S. Environmental Protection Agency.

The application of specific disinfection technologies must also be judged with respect to the other processes in a wastewater treatment plant. Unit processes used at a waste water treatment facility prior to and after the disinfection process can have an impact on the effectiveness and environmental acceptability of a disinfectant. These processes and the use of the receiving water or the effluent, are highly site-specific. Any assessment of a wastewater treatment practice such as disinfection must be done on a site-specific basis.

Rationale
The appropriateness of a particular disinfection technology at a given site may best be judged by evaluating specific factors. Among these are the safety of the technology, current and anticipated uses of the receiving water and the water quality standards necessary to maintain these uses, the potential impacts on public health, the effectiveness of the technology against pathogens, the potential for and significance of disinfection byproduct formation and the costs of the alternatives. Our knowledge of the performance of any disinfection technology with respect to any or all of these factors can never be complete. WEF continues to support advancement of knowledge in these areas.

Current disinfection practices have succeeded in reducing public health risks and in meeting water quality objectives in a cost effective manner. Based on our current knowledge, the known benefits of chlorine-based disinfection of wastewater effluents outweigh the known risks, when chlorine-based disinfection is chosen and responsibly practiced to meet receiving water standards.