Drinking Water Reservoir - Wilmington, OH - Case Study
The dominant blue-green algae were Cylindrospermopsin and Microcystis, requiring frequent use of Copper Sulfate treatments to reduce the algae prior to the treatment plant.
- Ultrasound just as effective in controlling the algae
- Reservoir is clearer than it has been historically
- Overall lower cyanobacteria count
Background and Problem
Historically, the City of Wilmington, OH Water Department experienced both Blue-Green (Cyanobacteria) and Green algae in two drinking water reservoirs – Res 1 and Res 2. The dominant blue-green algae were Cylindrospermopsin and Microcystis, requiring frequent use of Copper Sulfate treatments to reduce the algae prior to the treatment plant.
The goal of using ultrasound was to Reduce Chemical usage, saving on chemical costs and labor costs.
After 60 days, the reports showed that there were no algae in the actual water column, however there was still evidence of toxins along the rock-bed sides and in the silt at the bottom. It was concluded that past residual algae toxins were embedded in the bottom, causing it to show up in reports, but there were no new algae growing. They also concluded that ultrasound was just as effective as Copper Sulphate for controlling the algae in the reservoir.
Rick Schaffer, superintendent of the Wilmington Water Treatment Plant states: “The reservoir with the ultrasonic unit is certainly clearer than it has been historically, and it has an overall lower cyanobacteria count…The Smaller Reservoir (Res 2) is almost tropical, it looks so clear. It looks as good as it does the night after a copper treatment”.
At the end of the 90-day trial, the City of Wilmington purchased a second 360° ultrasound unit to treat the larger Reservoir 2.
Advantages And Disadvantages To Ultrasound Technology For Algae Control
Ultrasound has been a proven technology in the US for Blue-Green and Green algae types for the past 17 years. There are significant cost savings in labor and chemical costs, and requires minimum electricity or can run on solar, which can add to the cost savings. Ultrasound can be used in both small and large applications, can cover 120 acres with a single 360° unit, and shows no effect on other wildlife or plant life.
Ultrasound is, however, limited in that it does not treat all blue-green and green algae. It is recommended that an algae genus identification be obtained prior to installation. The technology is line-of-sight, therefore if there are any obstructions (islands) or coves in the reservoir, then multiple units may need to be added for full coverage.