OWASA reports results from additional testing of drinking water for disinfection by-products.

OWASA reported Friday that its additional testing of drinking water for disinfection by products showed improvement.

“Our drinking water continues to be safe to drink and in compliance with the Federal Safe Drinking Water Act and related State standards,” said Kenneth Loflin, Water Supply and Treatment Manager. “However, we are continuing to investigate possible causes and solutions to ensure satisfactory levels of disinfection byproducts.”

On September 4th, OWASA had reported that elevated levels of disinfection by-products called trihalomethanes (THMs) and haloacetic acids (HAAs) were found in several water samples in mid-August. THMs and HAAs form when chlorine used in drinking water treatment reacts chemically with organic matter that is naturally present in water.

Under the Federal Safe Drinking Water Act and related State regulations, THM levels may average up to 80 parts per billion (ppb) in a one-year period. OWASA’s yearly average for THMs is 53.2 ppb.  HAAs may average up to 60 ppb. OWASA’s yearly average for HAA samples is 48.3 ppb.

According to the U.S. Environmental Protection Agency and the N.C. Department of Environment and Natural Resources’ Public Water Supply Section, a person would have to drink 2 liters of water with elevated THM/HAA levels every day for a lifetime to have a one-in-a-million chance of having cancer or certain other health effects. One part per billion is like a penny in $10 million.

On Friday, October 10th, OWASA reported that water samples taken from 28 locations on September 15th and 16th showed acceptable levels of THMs at all 28 locations but HAAs were elevated at 22 locations. (Please see the table below showing test results by location.)

OWASA’s Laboratory staff has reported the test results to customers where the water samples were taken, and to the NC Department of Environment and Natural Resources’ Public Water Supply Section.
 
To address THM and HAA levels, on August 21st OWASA resumed use of wood-based carbon particles instead of coal-based carbon for taste and odor control in drinking water treatment. Since this change, a sample of treated water leaving the Jones Ferry Road Water Treatment Plant in Carrboro met the THM and HAA limits of 80 ppb and 60 ppb.

OWASA also believes that heavy rain from Tropical Storm Hanna affected the September 15 and 16 water samples by carrying organic material into OWASA’s lakes.

OWASA is the community-owned, public non-profit water and sewer agency that serves the Carrboro-Chapel Hill community.

Results from testing water samples taken on September 15 and 16, 2008

Water from all of the Chapel Hill-Carrboro City Schools was sampled on September 15 or 16 as requested by the City Schools.
Locations that were sampled in August and which had satisfactory THM and HAA levels were not resampled September 15-16.