Fact Sheet: Disinfection Alternatives

Disinfection of wastewater protects the public from potential exposure to pathogenic microorganisms that would otherwise be present in wastewater effluent that is discharged into waterbodies that may be used for recreation or drinking water. Wastewater disinfection has traditionally been accomplished using some form of chlorination. In fact, more than 60% of the 20,000 municipal wastewater treatment plants in North America use chlorination as the primary method of disinfecting effluent. Although an effective disinfectant, chlorine (and related compounds) has come under increased scrutiny because of regulatory, safety, and security issues. Many treatment facilities are now considering disinfection alternatives to be used either solely or in combination with traditional chlorination for the treatment of effluent into sensitive receiving waters.

For treatment facilities in search of an alternative to liquid chlorine disinfection, there are a few technologies from which to choose. One such technology gaining acceptance in many treatment facilities is ultraviolet (UV) disinfection. WERF has funded several projects looking at various aspects of UV disinfection methods. Our research has shown it to be a cost-effective alternative, as well as an effective disinfection method for such resistant pathogens as Cryptosporidium. Other options for disinfection, such as ultrasonic and ozonation disinfection, show a good deal of promise, as well. These technologies, however, are particularly energy-intensive and are not yet cost effective for most facilities. WERF also is examining new technologies, including the use of tin oxide anodes to electrochemically generate disinfectants in situ.

Research Highlights

Fate and Persistence of Pathogens Subjected to Disinfection (stock no. 98HHE2) Investigates the fate and persistence of bacteria, viruses, and protozoan pathogens subjected to disinfection to determine how each responds to various disinfection techniques and to provide guidance on the disinfection processes most likely to result in optimal wastewater effluent.

Identifying and Communicating the Benefits and Risks of Disinfecting Wet Weather Flows (stock no. 00HHE6) Improves the understanding and communication of the benefits and risks of wet weather flow disinfection related to aquatic life and human health. Also defines effective disinfection control programs.

Oxidation Reduction Potential vs. Residual Control of Chlorine (stock no. 99WWF6) Compiles results of a literature review on oxidation reduction potential (ORP) sensors, membrane sensors, and automatic chemistry systems. Side by side tests of all three technologies were conducted to identify the drawbacks, advantages, and overall strengths and weaknesses of both ORP and residual chlorine technologies.

Disinfection of Wastewater Effluent: Pros and Cons of Technologies (project no. 04-HHE-4, ongoing) Will develop a single document that presents the pros and cons and costs of various technical options for wastewater disinfection that can be used by wastewater professionals to evaluate and select the appropriate technology for their application.  

Additional Research

Impacts of Disinfectant Selection on Health Risk From Pathogens in Effluent (stock no. 99HHE1) Provides a detailed characterization of the effects of disinfectants on common wastewater bacteria, in terms of their initial response to disinfectant exposure, changes in bacterial community post-exposure, and nature and extent of bacterial physiological damage resulting from exposure to disinfectants. Also provides a quantitative assessment of risks of viral infection associated with application or omission of disinfection as part of municipal wastewater treatment and offers recommendations regarding the circumstances under which wastewater disinfection should be practiced.

Numerical and Experimental Characterizations of Dose Distributions in UV Disinfection Systems (stock no. 99CTS2UR) Applies newly developed tools for estimation of the dose distribution in UV disinfection systems. The results of this research should enable the regulatory community to develop a rational, scientifically based protocol for design and regulation of these disinfection systems. WERF can only provide limited information on this project to protect patent potential.

The Effect of Upstream Treatment Processes on UV Disinfection Performance (stock no. D93012) This report is a comprehensive document evaluating the effect of a wide variety of upstream treatment processes on UV disinfection efficiency. It provides information for operators, consultants, and design engineers on process changes for enhancement of UV disinfection, and also provides guidance for new process design.

Understanding Viability of Pathogens During Disinfection (stock no. 00HHE1) Improves the fundamental understanding of disinfectant reactivity on pathogen and indicator organism viability and clarifies the species-specific response to chlorination. This will lead to improvements in disinfection processes to protect public health. WERF can only provide limited information on this project to protect patent potential

Comparison of UV Irradiation to Chlorination: Guidance for Achieving Optimal UV Performance (stock no. D43008) Compares the biocidal efficiencies of UV irradiation and chlorination using secondary effluents of varying quality, assesses the efficiency of UV inactivation of total and fecal coliforms, investigates the effect of suspended solids and particle size distribution on UV disinfection of secondary wastewater effluent, evaluates existing UV disinfection models and presents a newly developed model, and compares the economic feasibility of UV irradiation with that of chlorination/dechlorination.

Optimization of Vortex Separator Removal Efficiencies for CSO Treatment (stock no. D41002) Investigates the degree of contaminant removal achievable through the modification of vortex combined sewer overflow (CSO) control devices. This research specifically uses dissolved air flotation, UV disinfection, and chemical addition.

Inactivation of Pathogens by UV Technologies (stock no. 00CTS9CO) Determines whether design parameters currently used for low UV irradiation disinfection systems are applicable for high intensity and pulsed UV systems.

Phase II: Development and Implementation of a Pilot-Scale Tin Oxide Disinfection System (project no. 02-CTS-6, ongoing) Evaluates the effect of common water quality parameters on tin oxide anode effectiveness, evaluates the specific mechanisms of oxidation and disinfection with tin oxide anode systems, and characterizes the impact of reactor configuration and anode processing techniques on the type and kinetics of production of reactive species.

A Risk-Based Approach to Optimize Filtration and Disinfection Systems (project no. 04-HHE-5, ongoing) Will develop risk-based criteria for the design and operation of wastewater filtration and disinfection systems that will minimize health risks posed by pathogens occluded in effluent particles.