Article courtesy of Denice Thibodeau | Aug 25, 2015 | GoDanRiver |Shared as Educational Material
Keeping contaminants out of the Dan River — while being ready to quickly treat any that might appear — was the goal of an exhaustive study recently completed for the Danville Utilities water plant.
The study was discussed at the Danville Utility Commission meeting Monday.
Environmental Engineering & Technology Inc. gathered information about:
» various local, state and federal agencies’ reports following the coal ash spill at the shuttered Duke Energy Dan River Steam Plant in Eden, North Carolina, in 2014;
» algae blooms, like the ones that occurred earlier this year and led to numerous complaints about the smell and taste of treated water; and
» about 2,500 businesses, farms and industries along the watershed that have the potential — no matter how slight — for releasing any contaminants into the river and exactly what those contaminants would be.
Barry Dunkley, director of water and wastewater treatment, said he did not believe all of this information had been collected in a single study before, and the evaluation of the information has offered the utility a number of ways it can improve its ability to respond to potential problems.
Dunkley said that while some companies along the river have permits to discharge water into the river, there are also several who simply store potential contaminants on-site.
Nancy McTigue, of EE&T, said one of the most important steps is to have open lines of communication with the various companies, people and officials along the watershed so warnings of any problems could be heard as quickly as possible.
McTigue pointed out that while Danville’s drinking water was never affected by the coal ash spill, the delay by Duke Energy and North Carolina officials in warning water treatments plans downstream about the problem on the way should not have happened.
Dunkley said the plant is going to install “an early warning system” near the planned industrial park on Berry Hill Road that will take constant water readings and warn of coming problems about a half-day before the water gets to the treatment plant.
That project is underway, but requires going through a permitting process that can take some time getting approvals from the Virginia Marine Resource Commission, the Army Corps of Engineers and other state and federal agencies before it can be installed.
Dunkley said he is particularly pleased that water heading to Danville would have pH balances checked earlier.
“We would see fluctuations that would indicate the presence of algae blooms sooner,” Dunkley said. “That would help tremendously.”
McTigue also recommended a full plant audit of the treatment facility, which would involve inspecting every piece of equipment, making sure there are back-ups for necessary systems during any emergencies — and storage space for extra supplies needed in an emergency, such as the additional carbon used to treat the algae blooms. She said the last audit was done 15 years ago, and equipment that was 10 years old and in good shape then is now 25 years old and due for a thorough inspection.
Filters in particular need to be checked to make sure they didn’t lose any of their usual lifespan while filtering out coal ash last year, McTigue said.
Dunkley said the plant has 18 very large filters, with filtering media at least 30 inches deep. The filters trap any solids — sand, plant matter and other particulates — and run about 100 hours continuously before they require cleaning.
“We can take two at a time out of service without impacting plant capacity,” Dunkley said.
McTigue said having automatic sludge removal system would eliminate the need to shut filters down that often — because more of the particulates would be trapped and removed as water came into the storage basins at the plant, before it hit any filters — but Dunkley pointed out that installing the system to do that would cost up to $2 million, something not currently in the budget.
Cost also was a factor for other possible ways to improve the water treatment plant, such as having a large raw water storage pond or lake that could store a three-day water supply that would allow the plant to stop taking water directly from the river during a “contamination event.”
But the cost — estimated at $16 million — coupled with a lack of appropriate locations and highly restrictive permitting rules, forced the study researchers to put this idea on a “not recommended at this time” basis.