Chemical phosphorus removal

[1] One method of eutrophication remediation is the application of aluminum sulfate, a salt commonly used in the coagulation process of drinking water treatment.

Aluminum sulfate, or "alum" as it is commonly referred, has been found to be an effective lake management tool by reducing the phosphorus load.

Phosphorus is most effectively removed at the neutral pH range, when the insoluble aluminum hydroxide is present.

This hydroxide functions as a Lewis acid,[5] creating a flocculation environment similar to conventional wastewater treatment.

When applied to the epilimnion, boats powered by an outboard motor are deployed onto a lake carrying aluminum sulfate.

After determining the necessary dosage and location of the application, the aluminum sulfate is added to the surface of the lake near the wake of the outboard motor.

[8] Therefore, alum treatment is most effectively applied to shallow lakes with primarily internally loaded phosphorus.

[8] The necessity of repeated treatment requires continuous management and phosphorus monitoring to ensure optimal effectiveness.

Lakes with benthic feeding fish such as carp tend to have lower success at removing phosphorus.

[4] An additional concern is that aluminum salts can acidify lakes, making them potentially toxic to aquatic organisms.

[8] To reduce negative biological effects, the accepted limit for dissolved aluminum concentrations in a water body is 50 μg Al/L and pH should be restricted to a range of 5.5-9.