Wake County

March 19, 2014

Floating islands and eco-manipulation: Nine technologies to clean Jordan Lake?

Floating SolarBee pumps are only the beginning. As North Carolina tries to fix Jordan Lake with technology, it could explore everything from man-made islands to dredging.

The state’s current plan to clean the water at Jordan Lake is pretty straightforward: Deploy a fleet of water-circulating, solar-powered pumps and see if they kill algae. But that’s only the beginning of the “technological” solutions that the legislature might consider for the regional water supply.

Tom Reeder, head of the Division of Water Quality, briefed lawmakers Wednesday on a range of technologies, from ecosystem manipulation to man-made floating islands. It could be a good idea to test two or three more of these ideas as it tries to clear Jordan Lake’s waters, according to Reeder.

All this is happening, by the way, because legislators and developers from the Triad don’t want to pay for existing rules to control nutrient pollution in the eight counties upstream of the lake. That program is on delay for three years while the legislature explores a cleanup “pilot program.”

So, first, there’s the option that’s already set to go:

1. SolarBee: This is the machine that the legislature has agreed to test, starting in the next month, at a cost of $1.44 million. They’ll suck water up from below and pump it out across the surface. In the pilot, 36 big pumps will float in the Morgan Creek and Haw River arms of the lake. One theory is that they confuse algae – which is degrading the water – by confusing the microorganisms.

Then there are these alternatives, which Reeder researched for the new legislative committee on Jordan Lake. He wasn’t endorsing them, but he did offer his thoughts on each option.

2. Make islands: Put plants and microbes on floating manmade mats, which supposedly would take in the nutrients that are harming the lake. This is an emerging technology used in some wastewater lagoons around the state, but it could cost something like $30 million, and might attract geese or provide a foothold for invasive species, and it would take ongoing maintenance, Reeder said. Even so, it’s potentially promising, he said.

3. Change the ecosystem: “Food-web manipulation,” as it’s called, is not a popular option. Theoretically, the state could encourage water-cleaning species. “Once you start manipulating the ecosystem, people are not going to be very happy about that,” Reeder said.

4. Grow algae: Run water over a lakeside surface seeded with algae, called an algal turf scrubber. The algae growing on the surface would remove nutrients from the water, but it might need to be 1,000 to 2,000 acres in size. The state also could use “algae wheels,” Reeder said.

5. Add stuff: Add aluminum salts to the water, hoping they “bind” to phosphorous, a pollutant common in lawn fertilizer which feeds algal blooms. This tactic has worked in smaller lakes, but it could be toxic and costly, Reeder said.

6. Dredge the lake: Basically, the state could scoop out underwater sediment. This option requires a lot of permits, and it’s the least viable, Reeder said.

7. Remove water: Pump out the lake’s deepest waters in an effort to reduce algae. This technique, called hypolimnetic withdrawal, hasn’t worked often, and it’s not very viable, Reeder said.

8. Add water: Allow more “low-nutrient” water into the lake, diluting the high-nutrient water that feeds algae. This has only been tried a few times, Reeder said.

9 AquaLutions: A proprietary technology that removes nutrients from the water. It’s being tested in Florida, Reeder said, and Durham has explored a pilot program, according to the city’s website.

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