Water & Energy: Water

Water treatment plant

By KEVIN KILBANE | The Municipal

Raleigh Water in Raleigh, N.C., is throwing a curve at algae and bacteria that can cause taste and odor issues in residents’ drinking water.

In early 2019 it launched a pilot project testing use of shade balls in the west reservoir at its E.M. Johnson Water Treatment Plant. The hollow, dark-colored, 4-inch diameter plastic balls float on the surface of a body of water, blocking most sunlight from reaching the water. Sunlight can spur growth of algae and bacteria that give drinking water a bad taste.

The plant is one of two water treatment facilities Raleigh Water operates as it provides water and sanitary sewer services to about 610,000 people in the city and several nearby communities. The utility stores raw water from Falls Lake in the plant’s west and east reservoirs before treating it for use as drinking water.

Raleigh Water needed about 5 million shade balls to cover the west reservoir surface.

“In short, our main water source has had various taste and odor issues over the years due to high algal counts, MIB, geosmin, etc., although in general these issues have been pretty rare, thankfully,” Ed Buchan, Raleigh Water’s senior communications analyst, said in an email. “Thus, we decided to try the shade balls out in one of our terminal reservoirs to see how they worked.”

MIB, which is 2-Methylisoborneol, and geosmin are natural substances that result from the presence of algae and bacteria in water.

Staff members learned about shade balls at an American Water Works Association Annual Conference and Exposition, Buchan said.

The utility has limited data on the shade balls’ effectiveness because weather conditions haven’t created algae problems the last few years. However, for the first few weeks the shade balls covered the west reservoir, they reduced MIB and geosmin levels significantly — while the east reservoir showed large increases in both readings, water test data provided by Buchan showed.

“Also, our (water plant) manager did say the shade balls have been very effective in dissuading geese and other waterfowl from taking up residence around the reservoir and loitering in the water,” Buchan said. It had been common to have 30 to 50 geese on the west reservoir, but shade balls have nearly eliminated the problem.

Shade balls also can be useful in other public utility settings, according to Bryan Stuck, general manager at Environmental Control Company LLC in Wilmington, N.C. The firm makes shade balls

hits a home run with shade balls

ABOVE: Plastic shade balls cover the surface of the west reservoir at Raleigh Water’s E.M. Johnson Water Treatment Plant in Raleigh, N.C. Raleigh Water tried shade balls to prevent sunlight from sparking the algae and bacteria growth that can cause taste and odor problems in drinking water. Officials also found the shade balls keep geese out of the reservoir. (Photo provided by Raleigh Water) Use of plastic shade balls such as these helps Raleigh Water and water and wastewater utilities in other communities reduce algae and bacteria growth, wildlife deaths and the amount of chemicals needed to treat or disinfect water or wastewater. (Photo provided by Environmental Control Company)

for customers in the United States and Canada, including the ones used by Raleigh Water.

For example, shade balls can be used on wastewater lagoons to keep waterfowl and animals out of water that may contain toxins that could kill them. Blocking sunlight from water, keeping water temperature cooler and preventing algae and bacteria growth also can minimize accumulations of organic matter that can disrupt the treatment process, ECC says on its website, https://eccllc.us.

Use of shade balls also can reduce the amount of chemicals needed to disinfect or treat drinking water or wastewater. In addition, they can limit evaporation losses on water bodies and block sunlight from sparking the formation of the carcinogen bromate in disinfected water.

ECC’s Stuck said use of shade balls has become fairly common among municipal utilities and some industries, such as foundries and plating businesses.

It typically takes 10 shade balls per square foot of water surface being covered, Stuck said. Total cost for shade balls varies based on location and other factors.

“We usually guarantee them for 10 years,” he said of the balls’ longevity. “But we’ve had customers that have had them longer than that.”

When the balls appear ready for replacement, they can be recycled as with any other high-density polyethylene plastic. Stuck’s company also will help with redeploying shade balls to a new location.

Raleigh Water has had only one slight issue with its shade balls.

“I can also say that while they seem to be effective, high winds can cause them to bunch together and kind of pile up on themselves,” Buchan said.

Based on the shade balls’ success, Raleigh Water officials are exploring the possibility of covering the surface of the E.M. Johnson’s east reservoir. Buchan said one option could be a floating solar-energy array, which would help prevent taste and odor problems and also generate electricity to power the water treatment plant.

Learn more

To see a video report on Raleigh Water’s use of shade balls, go to https://archive.org/details/ crnc-Shade_Balls_Pilot_Project.