posted May 15, 2012, 7:40 AM by Kellie Lynch
updated Jan 10, 2013, 10:35 AM
Over the years, dense blooms of algae (i.e. cyanobacteria) due to nutrient loading from a number of man-made and natural sources in Grand Lake St. Marys have resulted in low dissolved oxygen and the production of algal toxins, which are very harmful to the health of marine ecologies.
As a part of efforts to improve the Lake’s water quality, alum treatment has been extensively applied to the Lake region to decrease phosphorus, control algal blooms, and increase the clarity of the water. In 2011, approximately $3.7 million was spent on the alum treatment in the Lake, and an additional $5.1 million is scheduled for this year.
However, ABSMaterials finds this approach very concerning, as alum contains a sulfate that can be converted into sulfide, which is highly toxic to aquatic organisms. Sulfates in alum also allow mercury already deposited in the water to be converted into methyl mercury, the most toxic form of mercury, which can easily enter organisms in the food chain.
Furthermore, alum treatment will be a short-term approach to improve water quality and will not be enough to ensure the long-term sustainability of the Great Lakes region. Dr. Nogaro, a research scientist at Grand Valley State University recently presented
about the effects of Alum application in Grand Lake St. Marys at the Ohio State University ESGP seminar. She concluded that alum treatment was ineffective in reducing phosphorus. She also mentioned that implemented treatments should target non-point sources of nutrients before they enter the lake. These actions can maintain long-term protection of the Lake. In particular, bioretention systems such as vegetated buffer strips, wetlands, rain gardens, and bioswales should be implemented within watersheds to effectively reduce nutrient loading caused by stormwater runoff.
Osorb® rain gardens
are the only rain gardens that capture and remediate non-point source pollution while safely reducing algae-causing nutrients and toxins. No only do they outperform alum treatments in preventing pollution in both surface and groundwater, they have no negative environmental effects such as toxic daughter products. Algal blooms are a particular threat to lakes in 2012
because of a warmer-than-average winter, so bioretention systems for effective runoff management should be a part of every city's water quality planning.