Trihalomethanes (THMs) in the Mon River Basin
Targeted Study
WV Water Research Institute
What are trihalomethanes?
Trihalomethanes (THMs), a family of halogenated disinfection byproducts, are ubiquitously present in finished drinking water. They form as a result of the interaction between organic matter and chlorination in the disinfection process.
Regulation of THMs
Trihalomethanes are known carcinogens and have negative effects on reproduction (Hood, 2005).
Out of concern for public health, the EPA has established a regulatory standard for total trihalomethane (TTHM) in finished drinking water of 80 μg/L.
Bromide and THM
While the relationship between intake bromide levels and TTHM in finished water is not clear, high bromide levels at the water authority’s intake increase the risk of exceeding TTHM limits.
Increasing Bromide Levels
Our 3RQ data have shown increasing bromide levels in the Mon downstream of Masontown, PA. We have identified high bromide levels issuing from Whitely Creek which enters the Mon downstream of Masontown.
Beginning of the THM Targeted Study
In November 2015, a THM exceedance was found at the Beth Center Elementary School near Fredericktown, Pennsylvania. This sparked a study of THM levels in the surrounding areas with emergency funding provided by Colcom Foundation.
Sampling Locations
WVWRI collected samples at five participating water authorities (Charleroi, East Dunkard, PA American Brownsville, Southwest, and TriCounty) in Southwestern Pennsylvania over a four week period in February 2016.
Results (2016)
No findings of any exceedances for TTHM were reported at any of the sample locations over the four week study period.
Results (2016)
In addition to TTHM, we also analyzed for bromide. Concentrations were low at all stations (non-detect shown as 1⁄2 the minimum detection limit (e.g. 0.010 mg/l).
Findings
There were no sites that reported an excess of the 80 microgram limit. In addition to that, the data showed no correlation between either bromide or chloride levels at the river intakes and TTHM.
Scroll down to learn about the 2018-2019 extension of our original project.
Citation
Hood E. (2005). Tap Water and Trihalomethanes: Flow of Concerns Continues. Environmental Health Perspectives, 113(7), A474.
Project Extension
With funding from the United States Geological Survey (USGS), an extension of this targeted study was completed from 2018 through 2019.
Goals
1) Develop a statistical model for predicting TTHM levels using source water quality data.
2) Examine the effects of water treatment and distribution on TTHMs formation.
Sampling Locations
Samples were collected from the Borough of Charleroi Water Authority (CH), TriCounty Joint Municipal Authority (TC), and Southwestern Pennsylvania Water Authority (SW).
Click the points on the map to view results.
Results (2019)
Chloroform was the most dominant THM species in all the finished water samples.
Results (2019)
There was a positive correlation between TTHM formation and the intake water's total organic carbon (TOC) level.
Findings
1. The concentration of TOC increased with higher temperatures. As this occurred, TTHM levels also increased and reached above 80 μg/L.
2. Chloroform was the most dominant THM species in all of the finished water samples. The low levels of brominated THM species can be confirmed by the low bromide levels reported, typically below the limit of 0.01 mg/L.
Linear Regression Model for TTHM
Based on the model, TTHM can be calculated from the following equation:
TTHM (µg/L)= -2.95*chloride (mg/L) +16.15*TOC (mg/L) +4.65*Temp (in C) -10.52
