HAB had a productive day today at Fish Lake! 30,000 gallons of alum were applied to bring the total to date to 50,000 gallons. The project plan calls for a total application of 95,000 gallons. The key to a successful alum application is the formation of the floc and the precise placement of the floc on the lakebed. The floc is formed when the liquid alum mixes with lake water immediately after application. It is a whitish-green precipitant, is more dense than water and sinks through the water column at a rate of 1 foot every 2.5 minutes. Once it reaches the bottom, the floc’s active binding sites are in place to intercept phosphorus as it leaches from the lakebed.
HAB’s application technology maximizes the floc formation and settling by applying the alum through drop hoses that extend 18-24 inches into the lake. There are jet nozzles at the end of each hose and the alum is applied under the pressure created from the onboard pumps. This setup effectively injects a stream of alum that flash mixes with lake water below the surface. Floc immediately forms at a depth of 2-3 feet. Forming the floc below the lake surface bypasses any interference in settling by avoiding the surface tension of the water and algal scums on the surface. It also forms the floc at a depth where it is less susceptible to wave action. All of this results in rapid settling in the target application zone, reduces drift and ensures that lake sediments receive the prescribed dose without gaps in coverage. In addition, HAB determines it’s daily application zones based on wind speeds and direction to work in the more sheltered areas of the lake (less wave action). This also reduces drift and maximizes the precision of the operation.