By Maggie Reilly
Did you know that all water bodies contain algae, and that some algae are indicators of healthy aquatic ecosystems? Other organisms rely on them for energy and oxygen.
But algae can cause major problems in our lakes when they grow excessively or become a harmful bloom that produces cyanotoxins.
“An out-of-control algal bloom, whether it has toxins or not, is bad,” said Isabel Escobar, a professor of chemical engineering at the University of Kentucky. “With harmful algal blooms, once they die, it’s not just a decaying organism. It’s now a decaying organism along with the presence of a harmful toxin.”
Escobar saw the effects of cyanotoxins in summer 2014, when a major algal bloom on Lake Erie made international news. When the blue-green algae, technically called cyanobacteria, reached water treatment plants, oxidants would cause the cells to burst and the toxins inside to release into the water.
If not adequately removed, the toxins could contaminate drinking water. Escobar helped in the public response and served on the Blue Ribbon Panel that suggested alternative water treatments during the crisis. She now works to improve membrane filters for water treatment, which filter out contaminants such as nutrients, PFAS and algal toxins.
The Division of Water spoke with Escobar to gain a better understanding of algal blooms and what we can do to keep our waters and ourselves safe.
What makes algae go “bad?”
“We mainly associate the causes of harmful algal blooms with warm temperatures, sunlight, presence of high amounts of nutrients — specifically phosphorus and nitrogen — and the lack of species that graze on algae. These factors all contribute to rapid algal growth and bloom formation.
We all add fertilizers that contain phosphorus. We are often quick to blame farmers for the excess of phosphorus in our waters, but we may all be playing a part.
Furthermore, research that is currently being performed … to determine if the type of nitrogen — such as ammonium, urea, nitrite and nitrate — present in the water might be a key parameter in the toxicity of algal blooms.”
How do harmful algal blooms impact the dissolved oxygen in water bodies?
“That is part of eutrophication. Eutrophication is a natural aging process for lakes and reservoirs but is accelerated by human impact. It occurs when algal species grow in excess with the presence of nutrients, resulting in bloom formation.
If there is a significant increase of algae in a body of water, they will start using the oxygen (whether or not the algae contains toxins). This will lead to fish kills and other organism kills. When those start to die and decay, you get the death of the body of water.”
How are water treatment facilities able to filter out the toxins?
“Surface water treatment often starts with the addition of an oxidant, which kills algae upon contact. The problem here is that once the algal cells are killed, the toxin is released. Now the toxins get to the water treatment plant, where they are often put in contact with powdered activated carbon, a very old and common form of water treatment because organic matter attaches to it for easy removal.
The toxicity of some algal toxins, like mycrocystin, the one present in Lake Erie, are even harmful at levels as low as one part per billion, or the equivalent of one blade of grass in a football field. For a toxin to be harmful at this low of a concentration, the process of removing it must be very thorough. The difficulty is that to determine the correct amount of activated carbon to be added to adsorb the toxin often depends on trying multiple different concentrations and then waiting possibly four to six hours to obtain efficiency results. This must be done continuously until they show results in an acceptable concentration. This was the short-term solution that a water treatment plant in Ohio came up with for the toxin removal of the household water coming from Lake Erie.
The long-term solution decided on was ozonation (a process where a reactive form of oxygen attacks both organic and inorganic materials present in the water) which is a very energy intensive and expensive method of treating water, but once that ozone is in contact with the toxin it breaks it down.”
Since you’ve been in Kentucky what kind of harmful algae issues have you encountered?
“I have been involved in studying how to best design membrane materials for the removal of microcystin. So instead of working in a water treatment plant or (on a certain) body of water, I am more involved with the theoretical work to make better filters that could be used in the future.”
Why not boil the water when there is a fear of algal toxin presence?
“That’s a really common misconception. When there is algae or bacteria that get in the water, immediately what you get is a boil water advisory. However, the toxin is not alive. It is not something you can kill by boiling because it’s just a chemical. So, when you boil the water, what you are actually doing is evaporating the water and concentrating the toxin in the water that’s left. Now, the water you may be drinking actually has a more concentrated toxin level than before.”
What should people know about water filtration systems used inside their homes?
“The use of point-of-use filters, such as the ones attached to refrigerators, sinks, and houses, is effective for only as long as the recommended time provided by the manufacturer. After that, they must be disposed of because if they are kept in use, bacteria start growing on them because of all of the “food,” such as organic matter, that accumulates on them.
The one beautiful thing about all bacteria is they are such brilliant organisms that if they stay long enough in contact with something and they get hungry, they’ll figure out a way to eat it.”
For more information, visit the Kentucky Division of Water’s Harmful Algal Blooms webpage.
This interview has been edited for length and clarity.
Maggie Reilly served as an intern with the Kentucky Division of Water and the North American Lake Management Society from June through December 2020.