Water plant operators today began feeding a higher dosage of activated carbon in the treatment process after detecting a slight elevation in odor at the city’s raw water intake.
Jason Grey, interim director of utilities, said Tuesday that the higher dosage is a precautionary measure.
“We detected a slight elevation in odor in samples we collected this morning, but we do not know if it signals the start of another event similar to what we experienced earlier this year,” Grey said. “We are increasing the dosage of carbon to get out in front of any reoccurrence.”
The city first experienced issues with an earthy odor and taste in its drinking water in February. Tests conducted then on raw water samples from the Dan River confirmed the presence of three species of algae associated with odor and taste, including a high concentration of Synura.
The problem re-emerged in March. The Virginia Department of Environmental Quality was unable at that time to confirm the presence of algal blooms, but those results were limited to the samples collected on a particular day, and the Virginia Department of Health’s Office of Drinking Water remained confident that biological activity was the culprit.
Algae are naturally present in all surface waters and excessive growths into blooms can cause taste and odor problems. The Office of Drinking Water says carbon is the best solution to remove unpleasant odor and taste caused by biological activity. The treatment plant’s filtration system removes both algae and carbon particles before the water enters the distribution system.
Throughout both odor and taste events, the water in the city’s system went through all of the treatment processes, and the Office of Drinking Water confirmed all tests showed Danville’s drinking water met state and federal regulations.
The city has notified both the Office of Drinking Water and the Virginia Department of Environmental Quality (DEQ) of the slight elevation in odor in the raw water samples collected this morning.
A DEQ environmental monitoring team will collect additional samples Thursday along the Dan River. The team’s river run had been previously scheduled as part of the agency’s ongoing monitoring efforts.
In addition to collecting water samples along the Dan River, the city has requested the agency collect samples along the Smith River. Grey said the city has received reports from citizens of the re-emergence of an odd odor along the Smith River near Martinsville. The Smith River is a tributary to the Dan River.