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The City of Danville has received confirmation that the taste and odor issues in the city’s drinking water are due to the presence of algal blooms in the Dan River, the source of the city’s drinking water.
These blooms now have passed. City water treatment plant operators have not noticed abnormal odor in the raw water for nearly one week. They are still feeding carbon as a precautionary measure.
“We are running odor tests on the raw and treated water and taste tests on the treated water multiple times each day,” Interim Director of Utilities Jason Grey said. “It still may take more days yet for the taste and odor to be purged out of the system due to the long detention time that the water has in the storage tanks and distribution system.”
He added that when the taste and odor are no longer present from the cold water, customers still may notice odor in their hot water due to the trapped gases in the hot water heater.
“It will take a little longer for the hot water heater to purge the odor out,” Grey said.
The city continues testing the treated water leaving the plant for regulated contaminants. Those tests continue to show the water is safe to drink.
Raw water samples collected and analyzed last week showed the presence of algae. These samples were analyzed at Old Dominion University.
“Although the algae population in the samples was low, several species that can cause taste and odor were present,” Grey said.
The species identified were Synura, Asterionella and Synedra.
“The population was low because the algal blooms had already passed,” Grey said.
Algal blooms are common in water systems fed by reservoirs such as lakes, but uncommon in river sources. Plant operators say the city has not experienced an issue with algal blooms in the river in more than 15 years.
The city began receiving calls on Feb. 9 of an odd taste and odor coming from the taps of customers. Initially, plant operators believed the problem was related to the large Ballou Park reservoir being taken out of service for repairs.
When no connection could be made to the reservoir repairs, plant operators suspected algal blooms as the cause. On Feb. 13, plant operators began adding carbon to the treatment process. Since then, the odd taste and odor in the treated drinking water leaving the plant has diminished.
The city’s testing has included water samples taken from various points of the city’s water distribution system and from the homes of some customers who notified the city of the odd taste and odor. From the beginning, the drinking water in the system has been through all of the treatment processes, and all tests for regulated contaminants has showed the water is safe to drink.
Danville Utilities provides natural gas, water, wastewater and telecommunications services in Danville and distributes electricity to approximately 42,000 customer locations in a 500-square-mile service territory covering Danville, the southern third of Pittsylvania County, and small portions of Henry and Halifax counties.