FACTORS AFFECTING TRIHALOMETHANE CONCENTRATIONS WITHIN THE ORONO - VEAZIE WATER DISTRICT, MAINE

Trihalomethanes (THMs) are a chlorination byproduct formed during water purification due to chemical reactions between chlorine and dissolved organic carbon (DOC) in source waters. THMs are a known carcinogen. Recently, the town of Orono, Maine has measured high levels of THMs in drinking water. The EPA’s maximum contaminant level (MCL) for THMs is 80 parts per billion (ppb) and Orono’s yearly average is currently 79.4 ppb; the town was out of compliance with the EPA limit from fall 2011 until mid 2013. In order to try to identify potential factors affecting THM levels in local homes, several University of Maine courses implemented a sampling program testing home water wells. Testing was conducted in March and October of 2015. We tested four hypotheses regarding TTHM formation, including:

1. Residences located farthest from the well source will have higher THM concentrations then those located closest.
2. Residences serviced by dead-end water pipes will have higher THM concentrations due to high residence times.
3. Flushing water pipes before sampling, a common practice when sampling for THMs, decreases THM concentrations which does not accurately represent what the resident consumes.
4. Samples collected in the fall have higher THM concentrations due to higher DOC concentrations in the source water.

In four locations, THM concentrations did surpass the EPA’s MCL during Fall 2015 sampling. Sampling suggests that seasonality and dead-end locations do play a roll in THM concentrations. Dead-end locations have statistically higher THM concentrations then non-dead end locations. Furthermore, samples taken during Fall 2015 have higher THM concentrations then their spring counterparts. Data regarding the other two hypotheses were inconclusive and more sampling will need to be completed.