The Virginia Department of Environmental Quality said Thursday that initial test results of raw water samples collected from the Dan River and tributaries are inconclusive in determining the source of the odd taste and odor in the city’s drinking water.
The agency is testing for the presence of nutrients that would feed the growth of algae, which is believed to have led to the re-emergence of an earthy, musty taste and odor in the city’s drinking water.
“We have not seen anything out of the ordinary,” said Bill Hayden, public affairs director for the state agency.
Hayden said the North Carolina Department of Environment and Natural Resources also is reporting that initial test results show nutrient levels within normal ranges.
Field teams from both agencies surveyed the Dan River and its major tributaries, including the Smith River, to observe the water and river banks and to collect water samples. The teams did not find the presence of algal blooms or unusual sources of nutrients that would stimulate blooms. They did detect higher than normal pH levels in the Smith River, but speculate that the cause may be the growth of water plants in the lower Smith watershed.
“There is no specific culprit in the river that we have been able to identify,” Hayden said. “We are waiting for more sample results and we will analyze those results as they come in.”
When the odd taste and odor first emerged in February, raw water samples analyzed at Old Dominion University confirmed the presence of algae species. The species identified were Synura, Asterionella and Synedra.
Jason Grey, interim director of utilities, said Thursday, “While we are disappointed that the initial findings are inconclusive, the process is not over, and we will continue to work with state authorities who have jurisdiction over the river quality.
“We understand that our water customers are frustrated and angry. We do not take this situation lightly. No one involved in treating our drinking water will stop working on the taste and odor problems until they are resolved.”
While test results from samples collected last week are inconclusive, Jeffrey Wells, engineering field director for the Danville office of the Virginia Department of Health’s Office of Drinking Water, said Thursday it is well documented that taste and odor events similar to what the city is experiencing are caused by biological activity in reservoirs and rivers.
“The biological activity can produce non-toxic, non-regulated taste- and odor-causing compounds that can be detected by humans in levels as low as one part per trillion,” Wells said.
To remove the bad taste and odor, the city’s water plant operators continue to add powdered activated carbon to the treatment process. At the recommendation of the Office of Drinking Water, the city will begin feeding a higher dosage of carbon.
In addition, the city is flushing out water storage tanks across the city as recommended by the Office of Drinking Water to remove in them any water with a bad taste and smell.
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 the Office of Drinking Water confirms that all tests for regulated contaminants show the water is safe to drink.
The city also has arranged for the assistance of an outside consulting firm that has expertise in taste and odor treatment control. The firm will evaluate current operations and make recommendations.