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The City of Danville has installed an automated monitoring station upstream on the Dan River to collect real-time data on water quality that could provide early detection of contamination of river water.
If the parameters indicate possible contamination, water treatment plant operators would conduct water sampling, and if necessary, shut down the raw water intake until the contaminated water has passed.
“This station is great for the operators because they can see what is coming from upstream,” Alan Johnson, Danville Utilities water treatment manager, said Friday. “With this information, they can adjust chemical treatments before it gets here. They also could speed up treatment and increase the amount of water storage in case they need to shut down the intake.”
An example would be an organic contamination if there were a large raw sewage spill upstream. Johnson said the upstream location of the station provides a lead-time of up to half a day depending on river’s rate of flow.
“The station’s sensors continuously monitor several parameters, including turbidity,” Johnson said. “The measurement of turbidity is a key test of water quality. When we have high turbidity, then we have more particles to remove during the water treatment process.”
Turbidity is the cloudiness or haziness of water caused by the presence of suspended particulates. The more total suspended solids in the water, the murkier it seems and the higher the turbidity. High turbidity can be caused by heavy rainfall or snowmelt.
The station also monitors parameters for conductivity, pH levels, depth and temperature. Conductivity is a measure of the salts in the water, while the pH of river water is the measure of how acidic or basic the water is on a scale of 0-14.
“Conductivity and pH levels are good parameters to alert us to possible contaminants,” Johnson said. “The level of pH also can be an indicator of algae growth, which we have had problems with.”
Johnson said plans are being made to add sensors for algae and dissolved oxygen. Dissolved oxygen is a measure of how much oxygen is dissolved in the water. “This measurement can tell us a lot about water quality,” Johnson said.
The water treatment plant is located at 279 Park Ave. and provides drinking water to 18,000 households and businesses in the city as well as the Pittsylvania County Service Authority.