Information and Frequently Asked Questions about Disinfection Byproducts
Information and Frequently Asked Questions about Disinfection Byproducts

Disinfection Byproducts Update – January 2023

On January 6, 2023, The Springfield Water and Sewer Commission (Commission) is notifying its customers of an exceedance of the maximum contaminant level (MCL) for the disinfection byproducts (DBPs) haloacetic acids (HAA5) and total trihalomethanes (TTHM) in the drinking water. Sample results taken on December 1, 2022, indicated that our system exceeded the standard or maximum contaminant level (MCL) established by drinking water regulations for HAA5 at 8 sample locations and for TTHM at 3 sample locations.

The MCL for HAA5 is 60 parts per billion (ppb) and for TTHM is 80 ppb, with both respectively calculated as the average of the results from the past four quarters at an individual sample site. The Commission has experienced elevated levels of HAA5 in the finished drinking water since Fall 2018, when it first reported an exceedance. There have also been exceedances of the MCL for TTHM, which is another category of DBP regulated by the Stage 2 Disinfection Byproduct Rule, since March 2022.

The exceedance was not an immediate health hazard and customers may continue consuming and using their water as normal. If this had been a public health emergency, customers would have been notified within 24 hours.

To address exceedances for DBPs and replace end-of-life infrastructure the Commission is building a new West Parish Filters Water Treatment Plant.  Design of the treatment plant is currently underway.


The Commission has been actively working to reduce HAA5 in the drinking water since 2015, when it initiated a comprehensive planning process to modernize the West Parish Filters Water Treatment Plant. While the Commission has regularly optimized existing plant processes to meet regulatory changes over the years, the plant’s last substantial upgrade was in 1974. 

The planning process determined that construction of a new water treatment plant at West Parish Filters is the most effective long-term solution to address regulatory compliance for disinfection byproducts.

Design of the new treatment plant is currently underway, and construction is anticipated to begin in 2024. Click here to learn more about the new drinking water treatment plant construction and project schedule.

Water and Wastewater Infrastructure Renewal Program Interactive Map - Learn more about the new water treatment plant and other water and sewer improvement projects planned throughout our region over the next several years.

What are DBPs and how do they get into the water?

HAA5 are five haloacetic acid compounds and TTHM are four volatile organic chemicals that form when chlorine, which is used for disinfection, reacts with dissolved natural organic matter (NOM) found in surface water supplies, such as Cobble Mountain Reservoir. Therefore HAA5 and TTHMs are considered “disinfection byproducts.”

Dissolved NOM enters the reservoir from rain and snow melt from the surrounding forest. Both the amount and types of NOM in the reservoir impact the levels of DBPs in the treated water. The issue of elevated DBPs (specifically HAA5) first arose in late 2018 when above-average rainfall increased the amount of dissolved NOM in the reservoir water by approximately 50%. Since then the amount of NOM has continued to fluctuate and is impacted by changing weather patters and more intense, severe storms.

The graphic below summarizes how DBPs form:

Why are DBPs regulated?

Some studies have shown that long-term exposure to DBPs at elevated levels above the regulatory limit over many years (i.e. decades or a lifetime) may increase the risk of developing health problems. The MCL is set at a level intended to maintain a large margin of protection against health effects.

The Massachusetts Department of Environmental Protection (MassDEP) regulates public drinking water supplies in accordance with Safe Drinking Water Act standards, which include the Stage 2 Disinfection Byproduct Rule under which HAA5 and TTHMs are regulated.

More information about the potential health risks of DBPs is available from MassDEP at 617-292-5770, or on their website.

HAA5 information:

TTHM information:

Additional information on why DBPs are regulated is discussed by UMass Professor Dr. David Reckow, a national expert on disinfection byproducts, on Connecting Point (Feb. 12, 2019):  See the video

Why is chlorine added to drinking water?

Chlorine has been used in drinking water since the early 1900s to prevent waterborne illness caused by pathogens (bacteria) such as cholera, typhoid, and E. coli. Such pathogens are considered the most widespread and immediate risk to public health associated with drinking water. Treatment with chlorine also eliminates viruses such as the coronavirus. Chlorine dosage levels are traditionally higher in summer months due to increased water temperatures that promote bacteria growth.

The regulatory limit for DBPs is set at a level that balances the immediate health risk presented by waterborne pathogens, and the potential health risks presented by DBPs after long-term (decades or a lifetime) exposure to elevated levels. While the Commission is committed to complying with all drinking water regulations, preventing the immediate health risk of waterborne illness through proper disinfection is its foremost priority.

Should I install a filter if I'm concerned about DBPs?

The Commission does not advocate the need to purchase a home water filter to remove DBPs, and does not recommend any particular models or brands.

For customers that still wish to install a home treatment device, it is advised to thoroughly research whether the filter they choose performs as advertised. According to the American Water Works Association, some home filters can be used to reduce some chemical compounds that form due to chlorination, but not all. Customers should inquire if the device they choose is certified by an independent third party. NSF International, the Water Quality Association, and Underwriters Laboratories all certify home filter products.

Questions About DBPs

Commission customers with questions about DBPs should call 413-310-3501 or email