From the Evening Leader‘s Mike Burkholder:

An Ohio EPA spokesperson says the results of an alum pilot project last month on Grand Lake St. Marys should be known by the end of the year. On Sept. 23 and 24, state officials directed a pilot project to dose portions of the lake with alum — a compound that bonds with phosphorus in the water column and renders it unusable as a source of food for algae. A lower phosphorus level in the lake should result in fewer algae blooms, including blooms containing the cyanobacteria that dominated this summer. 

“The plan is to monitor it every couple of weeks for 60 days,” Ohio EPA spokesperson Dina Pierce said. “Primarily we are checking the phosphorus levels. The goal is to take the phosphorus out of the water column by 60 to 80 percent. That in turn, if successful, would remove that from the water column and as a food source for cyanobacteria.”
That raw data will be forwarded to consultants at Tetra Tech, who will then compile the data in a complete report. That report is expected approximately a month after the 60-day period — putting its release near the end of the year.

“There is a lot of data gathering,” Pierce said. “If it is successful, it would help in determining a dosing level for the entire lake, if that is something we are able to do next year. What we are doing now is a science project to see if it works.”

The alum dosing would not be a cure to the lake’s algae blooms. Pierce said the alum, if successful, should help reduce the frequency and strength of the blooms in the future.

“It doesn’t mean there never would be a bloom,” Pierce said. “But if it works, as we expect and hope, it would make it to where it wouldn’t be a nuisance and wouldn’t be like what we had this past summer.”
During the applications, water clarity improved in the lake where alum was introduced. Pierce said clarity is not the goal of the alum dosing.

“It’s not going to make the lake crystal clear,” Pierce said. “The whole goal is to remove phosphorus from the water column and make it if not impossible, difficult for blue-green algae to create a significant outbreak. Less phosphorus in the water column should help make it easier for other biomasses to flourish.”

Pierce said any additional water clarity as a result of the alum applications would be a side benefit of the project.