State Water Resources Research Institute Program

Project ID: 2009RI82B
Title: Sequential Inactivation of Microorganisms in Drinking Water using Ultraviolet Radiation and Residual Chlorine
Project Type: Research
Start Date: 4/01/2009
End Date: 3/31/2010
Congressional District: 1st
Focus Categories: Water Supply, Water Use
Keywords: Disinfection, Ultraviolet Radiation, Chlorine, Sequential Inactivation
Principal Investigator: Pennell, Kelly G.
Federal Funds: $ 15,263
Non-Federal Matching Funds: $ 30,537
Abstract: Water disinfection is commonly practiced throughout the United States to prevent disease outbreak from consumption of microbial-contaminated drinking water. The most common disinfection technique applied is chlorine. Concern over chlorination has been rising over the past several years due to the formation of disinfection byproducts, which include chloroform, other trihalomethanes (THMs), and haloacetic acids (HAAs), as well as Cryptosporidium parvum's reported resistance to chlorine-based disinfectants.

As an alternative to chlorine disinfection, some water and wastewater treatment systems are incorporating ultraviolet (UV) radiation. UV radiation is a broad spectrum antimicrobial agent that has limited potential for DBP formation. Over 400 UV disinfection facilities exist worldwide, including several large UV installations being constructed and/or designed for municipalities such as Seattle, WA (180-mgd) and New York City (2,200 mgd). One reason for interest in UV radiation for water disinfection is its effectiveness at inactivating Crypotosporidum, which has recently been targeted in water treatment regulations. Despite the promise of UV radiation as a disinfectant, there are some concerns over its use, for instance, it does not provide a residual disinfectant.

Sequential disinfection processes use two or more disinfectants with fundamentally different mechanisms of inactivation and have the potential to target a wider range of microorganisms than either disinfectant alone. They are often considered when the primary disinfectant is not capable of providing a long-lasting residual (such as the case with UV radiation, ozone, etc.), or when a synergistic response is developed through the combined application of disinfectants. Sequential disinfection may also be employed as a means of broadening antimicrobial behavior in a treatment setting, relative to the application of a single disinfectant.

The proposed research will focus on evaluating the effectiveness of UV radiation followed by chlorination. This application is appropriate for not only large water treatment systems that may have long distribution times, thereby requiring a residual disinfectant, but also for smaller scale systems where UV treatment can be practiced on a routine basis and augmented with residual chlorine, as needed. Better understanding of disinfection systems, especially those that have potential to target a broader microorganism population, while being inherently less susceptible for DBP formation due to a decrease in chemical use, is beneficial to virtually any water supply system.

The proposed research has the following research objectives:

Progress/Completion Report, 2009, PDF

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