Nord Carolina: eutrofizzazione del lago Jordan

By Rachel Nash,  December 16, 2013

Jordan Lake eutrophication

North Carolina Jordan Lake

CHAPEL HILL – As the state prepares to move forward with a trial method to reduce nutrient pollution flowing into Jordan Lake, some are questioning the logic behind the costly technology. WCHL’s Resident science expert Jeff Danner says the aerator pumps will not be an adequate solution, but rather a temporary fix instead of managing stormwater run-off upstream.

“If we really want to have good water here over the next several decades, we just need to manage our stormwater and just not let pollutants reach our drinking source,” Danner says.

North Carolina’s Department of Environment and Natural Resources is preparing to sign a $1.3 million contract with the Medora Corporation, the maker of the SolarBee, according to WRAL News.

SolarBees are solar-powered pumps that circulate the water near a lake’s surface, intended to reduce blue-green algae blooms.

About three-dozen of the pumps will be place in the lake by April 1.

Danner says that though there are positive aspects to the pumps, he believes that pollution controls upstream are the best way to prevent phosphorus and other nutrients from reaching Jordan Lake, the source of drinking water for much of the Triangle.

“By circulating the water, you can add some oxygen back in, and also by mixing the water, you shift the algae population from the surface. It’s not as though the circulation is without benefit, but what you need to do is compare that to what our plan was in the first place, which was to stop the stormwater run-off and not get the nutrients in the water.”

Environmental advocates have argued for years that Jordan Lake has problems with pollution because it’s fed by streams and tributaries that carry contaminants from urban areas.

Danner explains that warm water in combination with contaminants, particularly those which contain phosphorus, can cause algae blooms.

When a lake accumulates too much blue/green algae on the surface, it can make the water smell or taste badly. It can also create toxicity in the water that can cause people to become ill.

“The only reason that algae is bad for a lake is when you have a lot of algae, it will die and fall to the bottom of the lake where it fuels the population boom in bacteria that eat the dead algae, and that will use up the oxygen in the lake,” he says.

When the dissolved oxygen drops, fish populations begin to die.

Danner says the pumps will likely make Jordan Lake look better for a short period of time but will not be the most viable option.

“Consider the irony of this plan—we would allow the nutrients to get to the lake and then we would be treating it with circulating pumps. Well, that is exactly what happens in a waste water treatment plant and I am not so sure people want their drinking source to be set up like a waste water treatment plant.”

Recently there’s been a debate raging between those who champion environmental protection standards to limit run-off into Jordan Lake, and those who say the rules are too stringent and will negatively impact developers.

“One thing that is missing from the plans with pumps is that all of those stormwater control systems that would prevent the nutrient run-off would also limit the amount of other pollutants that would get into out water supply, like oils and other pollution on the ground that gets washed into our lake,” Danner says. “The same systems that would stop the phosphorus from getting there would stop these other pollutants from reaching the lake, which is another net benefit for your water source.”

The contract between North Carolina’s Department of Environment and Natural Resources and Medora is for a two-year lease on the pumps with an option to buy them later, as reported by multiple news outlets. If the SolarBees prove to be successful, the State will consider purchasing additional devices.

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