rss

WaterOperator.org Blog

Articles in support of small community water and wastewater operators.

Featured Video: Disinfection Byproducts in Tap Water: 5 Things To Know

Featured Video: Disinfection Byproducts in Tap Water: 5 Things To Know

The challenge of disinfection byproduct (DBP) control in drinking water lies in balancing the varying health risks of over 600 known DBPs with the benefits of microbial waterborne illnesses prevented via disinfection. While DBPs can originate from industrial sources, they generally form in water treatment systems when natural organic matter reacts with a disinfectant, usually chlorine-based. Ongoing studies have suggested that the toxicity for any given DBP can range from having no known health effects to exhibiting links between exposure and cancer, birth defects, or reproductive disorders. Disinfectant type and dose, residual chlorine, inorganic and organic precursor concentrations, pH, temperature, and water age can impact DBP formation.

The management of DBPs in drinking water is enforced through the Stage 1 and Stage 2 Disinfection Byproduct Rule (DBPR). Collectively, the rules set maximum contaminant levels (MCLs) for total trihalomethanes (TTHM), 5 haloacetic acids (HAA5), bromate, chlorite, chlorine/chloramines, chlorine dioxide, and DBP precursors.

According to a 2019 report by the U.S. Environmental Protection Agency (EPA), the Stage 2 DBPR invoked the largest number of community water system violations between 2017 and 2018, accounting for approximately 30% of all drinking water violations. Consecutive water systems, those with surface water sources, and systems serving populations of 501 to 10,000 people experienced violations more frequently. A greater compliance challenge is experienced by consecutive systems because they have little control over the water that they receive. While treated water may have achieved compliance at the system’s interconnection, DBP concentrations can rise through the receiving distribution system.

Non-consecutive utilities experiencing compliance challenges for the Stage 1 or 2 DBPR can start by troubleshooting the system using our previous blog post on The Disinfection By-Product Challenge. Consecutive systems should coordinate with their wholesale system following the approaches suggested in the 2019 report discussed above. The preferable methods of control often lie in prevention and optimization. As your system troubleshoots the cause of high DBP concentrations, keep the community informed on your efforts as well as some basic information on the health effects and sources of DBPs. Operators can find a general overview on DBP challenges in this week’s featured video. We recommend using this video to provide customers with answers to the following questions:

  • What are disinfection byproducts?
  • How are DBPs regulated?
  • How do I know if my water has high levels of DBPs?
  • How are people exposed to DBPs?
  • How do I remove DBPs from my home’s water?

The Disinfection By-Product Challenge

The Disinfection By-Product Challenge

Staying in compliance with Stage II DBP testing can be a challenge for many small systems. Moreover, when preventing DBP formation becomes a pressing need, it is easy to get overwhelmed by the range and cost of options out there, especially if you are trying to keep up with new technologies. Then there is the fact that solutions to DBP problems often involve several different actions or multiple steps, giving the situation an extra level of challenge.

However, before planning a remediation strategy it might be valuable to initiate a DBP profile study - testing from the source water through the treatment process, and continuing into the distribution system. Why? Because, as Justin Spears in a recent H2Outlook (Kentucky Water & Wastewater Operator's Association) article found out, sometimes the problem isn't where you think it is!

According to his article, he was all set to add a mixer to his storage tank when results from his DBP profile study showed that most of his DBPs were forming in the plant's clearwell. His problem was at the treatment plant, not in the tank! In the end, Justin solved his DBP problem quickly by using chlorine dioxide, made on site by mixing chlorine gas, which he had already in place, with sodium chlorite. However, every treatment plant and source water is different, and what worked for him might not be the best for you.

Interested in finding out more about options for DBP control? Check out this video or this website or this manual. In addition, you can choose Disinfection and Disinfection By-Products as a category in WaterOperator's document or event database to find all sorts of resources.