Hillsborough's Drinking Water Returns to Compliance

10/23/08 — The Town of Hillsborough has returned to compliance with the level of total trihalomethanes in its water system.

Water samples taken in late September to verify earlier test results showed a lower level of the contaminant, reducing the town’s running annual average of TTHMs in its water supply to .079 milligrams per liter. Compliance with EPA standards is based on an annual average. The maximum level of TTHMs allowed by the EPA is .080 mg/L.

Test results from the original water samples taken in August for the town’s third-quarter testing period increased the town’s annual average to .083 mg/L.

The higher third-quarter level of TTHMs may be attributed to the extended drought over the past year. The drought reduced water levels in the town’s reservoirs, which can increase organics in the water. These organics can lead to the formation of TTHMs.

The contaminant also can form when water is chlorinated for too long. The Utilities Department has determined that it can change one of the locations for applying chlorine to the town’s water, allowing the disinfectant to be added later in the treatment process. The project can be completed under the department’s current budget.

The Utilities Department had considered expediting a project planned for Fiscal Year 2010 to allow ammonia to be applied earlier in the treatment process. Instead it plans to relocate the feed point for permanganate, an oxidizer, from the water treatment plant to the raw water pump station as well changing the water system’s chlorination point. The permanganate helps remove organics from the water and would be more effective if added to the raw water earlier.

The Utilities Department believes these changes will keep the town in compliance with TTHM levels during the fourth quarter.

Trihalomethanes are byproducts of the disinfection process for water and have been linked to an increase in cancer at high levels of exposure.

However, a person would have to drink 2 liters of water every day with levels above the state and federal standards for a lifetime for a one-in-a-million chance of developing a risk of cancer or problems with the liver, kidneys or central nervous system, states the EPA and the Public Water Supply Section of the N.C. Department of Environment and Natural Resources.