UPDATE POSTED THURSDAY, MARCH 26: The Virginia Department of Environmental Quality has agreed to survey the Dan River to determine the source of the algae growth that caused the odd taste and odor in the city’s drinking water.
However, David K. Paylor, director of the department, cautions that the cause of algae growth is frequently difficult to determine.
“Virginia Department of Environmental Quality will continue to work closely with the City of Danville and others as we attempt to find the cause of algae resulting in drinking water problems from the Dan River and to identify potential solutions,” Paylor said Wednesday.
The city requested the state agency’s assistance following the re-emergence of an earthy, musty odor and taste in the water on Friday. Since then, city water plant operators have been adding powdered activated carbon to the treatment process. The carbon absorbs the algae and then is removed from the water.
On Wednesday, operators no longer could detect the odor in the raw water and the taste and odor in the treated water. They will continue feeding carbon indefinitely, however, as a precautionary measure.
Customers may continue to notice an odd taste and odor in their tap water until it purges out of the city’s distribution system. The water in the system has been through all of the treatment processes, and all tests for regulated contaminants show the water is safe to drink.
More tests than usual are being conducted. When the odd taste and odor re-emerged, the city -- as it did in early February when the presence of algae first developed -- sent water samples to a private lab in North Carolina to be tested for the presence of volatile organic chemicals such as benzene. These contaminants are both man-made and naturally occurring. In the water samples tested, the amount of each chemical was below detection limits.
Last month, test results for these chemicals also were negative.
The city also has collected water samples to be tested for the presence of pesticides, and on Wednesday, it received the kits needed to collect water samples needed for a lab in Indiana to test for the presence of algae products. Those test results will not be available until next week, at the earliest.
Last month, raw water samples analyzed at Old Dominion University confirmed the presence of algae species. The species identified were Synura, Asterionella and Synedra.
ORIGINAL STORY POSTED SUNDAY, MARCH 22:
City of Danville water treatment plant operators have resumed adding carbon to the treatment process due to the re-emergence of an odd taste and odor in the water.
The feeding of powdered activated carbon began again on Friday after plant operators began detecting odor in the raw water pulled into the plant from the Dan River, the source of the city’s drinking water.
Since Friday, city officials have received a growing number of complaints.
Barry Dunkley, division director of water and wastewater treatment, stressed on Sunday that the water in the system has been through all of the treatment processes, and all tests for regulated contaminants show the water is safe to drink.
As it did when the situation first developed in early February, the city has ordered additional testing. Samples of raw and treated water were sent on Friday to a private lab to be tested for volatile organic compounds. Test results are expected on Monday. Samples tested last month were negative.
The city also plans to send water samples to a lab in Indiana to test for the presence of algae products.
An algal bloom in February created an earthy, musty taste and odor in the water. The city began receiving complaints in early February. At first, the algae were not visible, but it developed into a full bloom. The bloom was the first in more than 15 years. City officials do not know the source of the bloom.
After the bloom passed beyond the city’s water intake above the Schoolfield Dam, the city continued feeding carbon until complaints ceased.
As before, Dunkley said all system water will have to be displaced before the taste and odor will cease. That process will take a number of days.