Alum Treatments Harmful to Freshwater Eco Systems

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Treating lakes with alum can initially reduce blue-green algae blooms, but this expensive measure is often harmful to freshwater food chain and the wildlife it supports.

Sufficient water circulation will disrupt the blue-green takeover and eliminate the need for treatments with chemicals.

The notion that alum treatments can provide a sure-fire solution to repugnant blue-green algae blooms in lake waters is proving to be a rampant and expensive misconception. Worse yet, such treatments may draw up inert phosphorous from lake sediments, activating more phosphorous than was present before the treatments and creating the potential for exceptionally abundant blue-green blooms.

Some water treatment specialists used to swear by alum as a harmless remedy for blue-green algae (cynaobacteria). This belief was based on the compound’s ability to convert and essential algae nutrient – phosphorous – to aluminum phosphate, and “trap” it in the lake sediment. However, application is a tricky endeavor, and it is difficult to know how much material to apply to various areas of a lake due to variances in water depths. Also, run-off, a major contributor of phosphorous, is unpredictable. In addition, the pH of lake water can be neither too acidic nor basic; otherwise treatment absorption will not be effective.

“The pH factor is always a moving target due to natural algae cycles,” explains Joel Bleth, president of Pump Systems, Inc. ( of Dickinson, ND, “For that reason many lake managers opt to use acidic aluminum sulfate, because it gets you closer to the recommended pH range. It is more expensive, but hopefully you can save a little money in the long run if you can use less of it.”

Unfortunately, increased pH-absorption latitude does not get users of this treatment around the undesirable “trade-offs” due to variable depths throughout the lake and unexpected runoff. Also, this chemical kills some aquatic organisms that are essential to water clarity, biodiversity and helping to sustain a vigorous fish community. And in some cases these calculations have been far enough off that fish have been killed.

A new, eco-friendly paradigm

When phosphorus is allowed to cause out-of-control blue-green blooms, the lake can develop low oxygen, toxins in the water, odors, and unsightly conditions. But there is a more natural paradigm, a “holistic” method of controlling blue-green blooms without running the risks and expense of applying alum to remove phosphorus. That paradigm is long-distance water circulation.

"If you can create sufficient circulation, blue-green algae problems and other unwanted water conditions can be avoided or even corrected," says Bleth. "Sufficient water circulation will disrupt the blue-green takeover and eliminate the need for treatments with chemicals."

To provide reliable long-distance water circulation, Pump Systems developed SolarBee™, a floating self-contained system used in lakes and reservoirs. Powered by solar modules, a single SolarBee unit can draw up to 10,000 gallons of water per minute and spread it gently across the surface for continuous aeration 24-hours per day. The system's mixing action prevents the takeover of blue-green algae and promotes a good crop of diatoms and green algae ("good algae"), zooplankton and dissolved oxygen.

The ability of this technology to effectively control problematic blue-green algae blooms has been well documented. In numerous applications these circulators virtually eliminated the high costs of alum treatments. Also, water clarity was often greatly improved, sediments firmed up, and fish populations improved.


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