Water Authority responds to algae floc photos

The Lake Elsinore & San Jacinto Watersheds Authority said the “floating alum floc” in photos published in last week’s Friday Flyer were the result of significantly high concentrations of algae present in the water column. The authority postponed multiple times the application of alum, which helps reduce the algae in the lake.

“The cause of the floating alum floc shown is most likely due to the significantly high concentrations of algae present in the water column,” the authority said in a statement to The Friday Flyer. “Due to the delayed start on the alum application, a combination of the warming weather, and the abundance of nutrients in the water column from the numerous winter storms, conditions are more conducive for the algae to feed on.”

Algae floats in the lake near Sierra Park early last week as the alum treatment began. The Lake Elsinore & San Jacinto Watersheds Authority, which applies the alum treatment semi-annually in an attempt to mitigate the algae, explained the reason for the “alum floc” and how its alum treatment will help. Photo by Maevin Webster

The alum floc shown in the photos will eventually settle out of the water column in this area as an inert (harmless, non-reactive) compound, but it is uncertain how long this time-period will be. The settling could take as little as a day or as long as several days, the authority said.

“However, a benefit of the extended time that the alum remains suspended in the water column, is that there is greater opportunity for the alum to bind with any remaining phosphorus in the water column and provide for the maximum amount of phosphorus removal, which is used to feed algae,” the water authority said.

On the second day of the alum application, Aquatechnex switched its application technology from a surface spray application to sub-surface injection to reduce the amount of alum floating on the lake surface. This should be most beneficial when it applied alum to the shallower East Bay and North Ski Area above the causeway.

It is not recommended that additional water spraying be done to break up the alum that has concentrated in the narrow coves, as this could result in the floating alum floc spraying onto any nearby boats or docks.




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