Reducing Disinfection Byproduct Violations
Disinfecting drinking water ensures that harmful contaminants such as bacteria, viruses, and other microbial pathogens will not exist in the finished water. However, the disinfectant itself can react with naturally-occurring materials in the water to form unintended byproducts that may pose health risks. This means that one operational goal for drinking water systems is maximizing disinfection efficiency while limiting the formation of disinfection byproducts.There are many types of unregulated disinfection byproducts. For regulated disinfection byproducts, the EPA lists possible health effects that include an increased risk of cancer, liver and kidney problems, anemia, and nervous system problems—especially in fetuses, infants, and children. The EPA also lists possible reproductive and developmental health concerns.
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Figure 1. Number of Disinfection Byproduct Violations by Year
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Violations by year
Since 2010, the department has issued the following violations for disinfection byproducts:
- 86 total haloacetic acids drinking water violations
- 208 total trihalomethanes drinking water violations
It appears that after falling from 2010 to 2014, the number of violations increased from 2015 through 2018 before declining again in 2019. The department is not certain of the exact reason this occurred as disinfection byproduct formation may be impacted by numerous factors (e.g., organic content in the source water, water age, disinfectant dose, etc.).
Minimizing disinfection byproduct formation
Because numerous factors can impact byproduct formation, we provide detailed resources on the Disinfectant and disinfection Byproduct rules webpage. Below are several ways systems can minimize disinfection byproduct formation.
Managing disinfectant dosage. Overfeeding disinfectant can increase disinfection byproducts formation. Eliminating pre-treatment disinfection may help reduce disinfection byproducts formation. Any change in disinfection practices must not sacrifice adequate disinfection for consumers’ protection. Operators that can reduce disinfectant demand can reduce disinfectant dosage without sacrificing water potability. Surface water systems should conduct a disinfection profile before changing disinfection practices. (Reminder: changes in treatment must go through a design review, so please contact the department before changing treatment to discuss.)
Managing water age. The longer finished water sits in storage or in the distribution system, the more total trihalomethanes and haloacetic acids will form. Operators should pay close attention to storage tank turnover and water use and should flush tanks and lines if necessary.
Removing disinfection byproducts precursors prior to disinfection. Naturally occurring organic matter (NOM) reacts with disinfectants to create disinfection byproducts. Operators should understand raw water quality and how it changes. Algae blooms, spring run-off, and human/wildlife impacts in the source water area are examples of activities that contribute NOM to source water. Operators may want to test raw and finished water for various precursors, including total organic carbon (TOC), dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA) or bromide, to assess if the treatment plant removes disinfection byproducts precursors effectively.
Managing pH. Changing the pH can affect disinfection byproducts formation. Different disinfection byproducts will either increase or decrease as the pH changes.
Being aware. Higher water temperatures can increase disinfection byproducts formation. While operators may not be able to control temperatures, they can carefully manage other factors that form disinfection byproducts while temperatures are high.
Asking for help! Hire an expert to evaluate possible solutions for controlling your water system’s disinfection byproducts formation. Water systems can use disinfection byproducts formation potential tests or pilots to predict the success of a proposed solution.
➽ Emily Clark, Nicole Grazianio and Bryan Pilson, drinking water compliance assurance section
