Sometimes Green Is Not Good. Here's a Remedy for Algal Problems in Surface Source Waters

A liquid formulation of ionic copper enables an Ohio city to eliminate harmful algae blooms and microcystin in its drinking water reservoir

Sometimes Green Is Not Good. Here's a Remedy for Algal Problems in Surface Source Waters

EarthTec algaecide (Earth Science Labs) is placed in a tank mounted in a boat and delivered by an electric pump to two simple pipe manifolds towed at boatside.

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In late of 2017 the City of Marysville in north-central Ohio experienced its first harmful algae bloom in its surface water reservoir.

After evaluating various alternatives with its engineer, the city selected a treatment with a liquid formulation of ionic copper to control microcystin issues resulting from algae growth. Since the proactive treatment program began in 2018, the city has not experienced another HAB.

The city continued the chemical treatment to combat algae while preparing for a new water treatment plant commissioned in 2022.

Issues with microcystin

In 2017, Marysville was operating a nearly 100-year-old conventional lime-softening water treatment plant with an average daily flow of 20 mgd. With the ability to select either groundwater or surface water, the city has significant flexibility to address water quality and treatment issues. Whenever possible, the city prefers surface water from its reservoir due to the simpler operation and lower cost of collecting and treating the water.

After completing improvements to the reservoir in mid- to late 2017, the city for the first time experienced an algae bloom, with microcystin concentrations above 1.6 ug/L. The event triggered enhanced monitoring requirements and a review of treatment alternatives under Ohio EPA rules.

Raw water microcystin concentration continued to climb, eventually reaching 2.69 ug/L in October. Problems persisted into winter, as December testing found detectable concentrations of microcystin in the finished water, requiring a complete switch to groundwater.

Choosing a remedy

In February 2018 the city completed a treatment optimization plan and a cyanotoxin general plan to address the HAB issues. As part of the plan, the city evaluated the full spectrum of chemical and mechanical treatment options for controlling algae in its reservoir.

The city had used traditional copper sulfate in 2011-12 to control filamentous algae growth in the reservoir. However, its limited solubility caused undissolved copper sulfate to accumulate with dead algae on the bottom of the lake. When this occurs, the algae releases phosphorus, nitrogen and other nutrients which tend to fuel additional algae growth.

Beyond the copper accumulation, the city found traditional copper sulfate somewhat cumbersome to handle and apply. City personnel also investigated various ultrasonic technologies, but found those options cost-prohibitive.

After further review, the water plant team investigated EarthTec algaecide (Earth Science Labs), containing only 5% copper in purely ionic form. As a liquid, the product is manufactured with a formulation that enables easy application and extremely rapid dispersion.

The purely ionic copper reacts quickly to kill algae without causing cell lysis or other issues. Further, the lower concentration of copper, already in a fully dissolved state, reduces concerns about copper exposure and eliminates accumulation within the reservoir.

Simple treatment

After reviewing the product with the Arcadis engineering firm, the city began treatment in spring 2018. The treatment is easily applied by boat. The product is transferred to a 60-gallon tank mounted in the boat and delivered by a 12-volt electric pump to two simple pipe manifolds towed at boatside.

The submerged manifolds deliver the product, which disperses in the water. Treatment of the 110-acre reservoir can be completed within one to two hours by a two-person crew. The treatment is applied every two to three weeks, starting as soon as the water temperature climbs above 50 degrees F and continuing as needed through the summer and into early fall.

Since the proactive treatments began in spring 2018, the city has not detected microcystin in more than 100 samples collected in more than four years of monitoring. The treatment is affordable, with an annual cost of less than $15,000.

Based on the good results, the city continued its treatment program to protect its investment in the new water treatment plant, commissioned in late 2022.

About the author

Louis LeBrun, P.E., (llebrun@earthScienceLabs.com) is a civil and environmental engineer with more than 20 years’ experience in the application and commercialization of water and wastewater technology.



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