Algae blooms are a regular occurrence at the Canoe Brook Water Treatment Plant in Short Hills, New Jersey. Over the past five years, the plant team has tried various methods to control the growth, which typically persists for weeks or months during late spring and summer.

Contributing to the problem is a fairly shallow reservoir that allows sunlight to penetrate to the bottom of the lake, and high levels of organics pumped in from the nutrient-rich Passaic River. Looking to attack the algae at its source, the plant historically applied copper sulfate at the first sign of blooms. Although a short-term fix, the chemical created long-term problems.

The Canoe Brook plant tested and deployed in one of its reservoirs a chemical-free remedy in a new device that attacks algae cells using high-frequency sound waves.

Drawbacks of chemicals 

Copper sulfate treatments at Canoe Brook failed to pass the cost-benefit test. “The first treatment of the year would go great, but the rest would have no effect whatsoever,” says Scott Brezinski, water quality supervisor for New Jersey American Water at Canoe Brook, which serves 126,000 customers in 25 municipalities. “Copper had lost its effectiveness for us.”

Dying algae cells sank to the bottom of the reservoir and degraded, further increasing organic carbon and decreasing dissolved oxygen. Copper sulfate also had the potential to lyse algae cells, releasing taste and odor compounds and possibly algal toxins. The treatments were also expensive: Material and labor costs for application and monitoring were about $85,000 a year.

“When the plant was reconstructed in 2012, we included ozone and granular activated carbon, so there never were any tastes or odors released out of the plant,” Brezinski says. “It was more treatment challenges. In the past, before the plant was redesigned, there would be periodic taste and odor complaints. The new plant eliminated that, but the plant wasn’t performing as well as it could have been because of the high algae levels.” In particular, the algae led to short filter runs.  

Sonic solution 

Seeking a less costly and more environmentally friendly alternative, Canoe Brook learned about LG Sonic algae treatment technology through American Water’s Innovation Development Program in September 2013. The program, launched in 2009, seeks out innovations and brings them to the water industry. To date, the program has examined more than 600 technologies.

“Isle Utilities, an independent technology and innovation consultancy that brings together technical and commercial specialists, held a seminar for American Water where a number of technologies were presented, and this was one of them,” says Dr. Orren Schneider, water technology manager with American Water.

Manufactured in The Netherlands by LG Sound, the underwater device uses high-frequency sound waves to attack algae cells. The treatment is widely used in commercial and residential applications but is relatively new for municipal drinking water reservoirs, Schneider says.

In May 2014, four solar-powered ultrasonic algae control buoys were assembled and placed in Canoe Brook’s Reservoir No. 1. The purchase price was about $150,000, and Schneider estimates a payback period of 1.8 years.

Designed to eliminate up to 90 percent of algae, the chemical-free system is safe for fish and plants. It prevents growth by transmitting ultrasonic waves that target gas vesicles in the algae, causing them to become less buoyant and sink to the bottom of the reservoir. The sonic treatment thus helps prevent algae and blooms from forming; less algae means less decay. Copper sulfate is used to kill blooms if they form.

LG Sonic’s Chameleon Technology makes it possible to adjust the program according to water conditions, algae type and application, enabling the device to treat cyanobacteria (blue-green algae), green algae, diatoms and other unwanted growth.

Deployed in spring and retrieved in November, each buoy has three ultrasonic transducers that cover about 50 acres. One main buoy also monitors factors such as turbidity, dissolved oxygen, pH and temperature. Data linked through a cellphone card to an LG Sonic server can be tracked in real time.

“We used data received from the sensor package on the buoy and collected samples on a daily or weekly basis to look at algae, organic matter, and taste and odor compounds,” Schneider says. “Toward the end of the project, we analyzed the economic and operational data and assessed how much it cost or saved.”

Positive outcome

Test data showed a 20 percent reduction in chemical usage in 2014, allowing for 83 percent longer filter runs, despite pumping 20 percent more water than the previous year. Annual savings are estimated at $78,000 ($18,000 in copper sulfate and $60,000 in monitoring costs).

Water turbidity and total organic carbon also declined, reducing the concentration of taste- and odor-causing compounds in raw water. Concentrations of geosmin (one taste and odor compound) in Reservoir No. 1 were less than 5 ng/L, compared to 55 ng/L at one point in untreated Reservoir No. 2.

Based on the initial results, American Water is looking to install ultrasonic systems at several plants in Kentucky and Hawaii. “This was the first time the LG Sonic units had been used in drinking water in the U.S.,” Schneider says. “We were surprisingly pleased with the results and how fast we saw the impact.”