Information and Frequently Asked Questions about HAA5
Information and Frequently Asked Questions about HAA5

Disinfection Byproducts Update - January 2021

Drinking water supplied by the Springfield Water and Sewer Commission to retail customers in Springfield and Ludlow is currently in compliance for disinfection byproducts (including haloacetic acids, or HAA5).

This means there are no violations of drinking water standards at this time. This follows seven quarters of non-compliance due to elevated HAA5 (see the archive). Information about HAA5 and the Commission's continued efforts to permanently resolve any future issues with HAA5 is below.

December 2020 Sampling Results

The Commission conducts sampling for HAA5 quarterly, in accordance with MassDEP and EPA regulations. Test results from December 1, 2020, indicated that HAA5 levels were below regulatory limits at all eight sample locations.

While this is good news, it has been observed that HAA5 levels can fluctuate due to a variety of factors. Therefore it is possible that HAA5 levels could elevate above the regulatory limit again due to environmental conditions or other factors. The next round of sampling will be conducted in March 2021. Customers will receive notice if the regulatory limit is exceeded at any sampling site.

Solutions - January 2021 Update

A year-long pilot study concluded in November 2020 (more information here). Results of the pilot study were promising and offered both potential short-term and permanent solutions.

Short-Term Solutions: The pilot study identified a different coagulant that is effective at removing more dissolved natural organic matter (NOM), one of the main causes of elevated HAA5 (see below), from the raw water. Though the coagulant is new to the Commission, it is approved by the American Water Works Association (AWWA) and is regularly used by water systems around the country. MassDEP approved a trial of the new coagulant in half of the West Parish Filters Water Treatment Plant. The trial will take place in January 2021. Pending successful results, full-scale utilization of the coagulant as a short-term solution to HAA5 may proceed with approval from MassDEP.

What is HAA5 and how does it get into the water?

HAA5 is an organic compound that forms 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 is considered a “disinfection byproduct.”

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 HAA5 in the treated water. The issue of elevated HAA5 first arose in late 2018 when above-average rainfall in increased the amount of dissolved NOM in the reservoir water by approximately 50%.

The graphic below summarizes how HAA5 forms:

Why is HAA5 regulated?

Some studies have shown that long-term exposure to HAA5 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 Maximum Contaminant Level (MCL) is set at a level intended to maintain a large margin of protection against health effects.

More information about the potential health risks of HAA5 is available from MassDEP, which regulates drinking water quality, at 617-292-5770 or at

Additional information on why HAA5 is 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 HAA5 is set at a level that balances the immediate health risk presented by waterborne pathogens, and the potential health risks presented by HAA5 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 HAA5?

The Commission does not advocate the need to purchase a home water filter to remove HAA5, 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 HAA5

Commission customers with questions about HAA5 should call 413-310-3501 or email