Because of emissions of coal-fired electricity production and other industrial emissions, acid rain has been a common problem in the United States, particularly in the Northeast. Acid rain negatively affects most aquatic ecosystems. It reduces the pH of water, altering its basic chemistry and making it more difficult for native organisms to thrive. It also effects hardness in ways that can be both beneficial and harmful.
Water hardness is a measure of its dissolved mineral content. It is important because of its ability to limit dramatic changes in pH, and for its ability to precipitate phosphorous--an essential nutrient--and make it unavailable to plants and algae. Because nutrient pollution has become common in most waterbodies due to development, the ability to process and remove phosphorous is critical for ecosystems to maintain a healthy nutrient-oxygen balance. A surplus of nutrients and depletion of dissolved oxygen leads to a process known as eutrophication, which accelerates the growth of algae and weeds at the expense of zooplankton and fish.
Unfortunately, the benefit of increasing hardness by acid rain is offset by more aggressive acidification. When lake bottoms acidify, anaerobic (oxygen-depleted) conditions arise, in which gases such as hydrogen sulfide and methane are produced. These contribute to higher acidity as well as the accumulation of foul-smelling organic muck. Finally, anaerobic processes on the bottom contribute to the release of phosphorous from organic sediment, stimulating the growth of undesirable algae and weeds.
Is Liming a Solution for Acid Lakes?
Adding lime (calcium carbonate) to acid lakes is a common solution to offsetting declining pH. However, it is only a temporary, and expensive, fix. It is like taking an aspirin tablet to cure a headache when the real problem is a brain tumor. CLEAN-FLO International has engineered and developed a complete lake restoration program designed to reverse the acidification of lakes. This process not only removes the acids as they come into the acid lakes from rain and groundwater but also prevents the production of acids at the bottom of lakes.
Clean-Flo’s Solutions for Acidic Lakes
Acid lakes are the result of depositions by rain of carbonic acid, nitric acid, and sulfuric acid. The CLEAN-FLO process of acid lake restoration first neutralizes the acidity of the lakes through a technology called Continuous Laminar Flow Inversion and Oxygenation, a process of continuous lake inversion and lake aeration from surface to bottom. In this process, carbonic acid is converted into carbon dioxide and is released to the atmosphere. Nitric acid is converted to nitrogen gas, and similarly released to the atmosphere. Sulfuric acid can be reduced to elemental sulfur by aerobic bacteria stimulated by inversion oxygenation and precipitates and settles into the bottom sediment.
Oxygenation as a Solution for Acidic Lakes
The present condition of acid lakes in the northwestern United States perpetuates an environment which is neither favorable for aquatic plants nor aquatic animals. Continuous Laminar Flow Inversion and Oxygenation reverses these effects by exposing every drop of water in the lake to the atmosphere several times a week. By oxygenating the bottom water and getting rid of anaerobes and the toxic gases that they produce, the acids at the acid lake bottom are eliminated, an environment favorable for aquatic fish and insect life results, and aquatic plant growth is limited.
It is absolutely impossible for hypolimnetic aeration to perform either of these tasks. In addition to the sulfur deposition from aerobic digestion of sulfates, once the inversion and oxygenation has conditioned the water so that larger aquatic fauna can live, sulfate becomes an important food source for these faunas.
We consistently get sulfate, nitrogen and carbonic acid reductions and increases in pH in acid lakes, even without lime. It is crucial however, that high dissolved oxygen levels be maintained at the sediment water interface and this has only been accomplished via Continuous Laminar Flow Inversion and Oxygenation. Acid lake neutralization cannot be obtained by liming alone, or by hypolimnetic aeration of acid lakes.