Greg McDanel mug
Greg McDanel mug
Greg McDanel
MARYVILLE, Mo. — City Manager Greg McDanel said this week that city officials will approach the potentially dangerous algae bloom on Mozingo Lake with a three-pronged attack aimed at keeping the water safe in the short-term, improving water treatment infrastructure and managing the conditions that caused the algae’s growth in the first place.
Last week, the city followed state Department of Natural Resources procedures by alerting the public that the water in Mozingo Lake was home to a dense cyanobacteria bloom, also called blue-green algae, and advised people and pets alike to oid direct contact with the lake’s water. Any water that comes through a tap at home remains safe to use and drink.
Such warnings are issued to the public in all cases where cyanobacteria density reaches a certain level during regular testing, as it did last week at Mozingo, even if the cyanobacteria are not producing toxins.
1. Short-term safety
Right now, there he been no positive tests for cyanotoxins, which can be released by dense blooms of cyanobacteria. After testing water samples showed such a bloom, that triggered the precautionary warning.
The first step in what McDanel called a “comprehensive approach” is continuing to monitor the cyanobacteria on the lake now.
“We’re continuously doing that,” McDanel said. “That tells us a lot. That tells us some of the taste and odor issues that we’ll he to take care of at the (water treatment) plant as the water is pulled in, and it also tells us that we he no toxins to worry about on the treatment side.”
That monitoring will continue at the current pace even if the cyanobacteria density reduces in the next round of tests. As for the cyanobacteria itself, removing it has gotten more complicated as the bloom has grown. For several months, the city had stepped up chemical treatments in an effort to eliminate the blooms and the taste and odor issues that he plagued the water in that time.
“Ironically, we’re to the point with those levels that DNR recommends no more chemical treatment,” McDanel said. “Now, with elevated levels of toxin potential, you don’t want to do anything to interact with that at this point and make it release toxins.”
The city is working with PeopleService, the contractor that runs the water treatment plant, and DNR to take samples and keep track of cell levels. Although the water has not tested positive for toxins, McDanel stressed that the city would continue to react to testing and issue similar warnings in the future out of an “abundance of caution” for recreational activity.
Drinking water that has been treated, however, is unlikely to be at risk even if toxins are released.
“There’s not many toxins that our normal treatment process can’t take care of, even if it does release,” McDanel said. “It would be an extreme case scenario where it’s something that we couldn’t take care of on our systems side.”
Even though some aesthetic issues are likely to persist for a while, that does not mean the water is at risk.
“What’s confusing about that to the normal reader or the normal citizen is that the oils that are released by the algae impact the taste and odor, but not the quality and the contamination side of things that DNR regulates,” McDanel said. So even if the cyanobacteria do release toxins, “your water is still safe to drink. It’s a challenging bridge unless you understand the entire process.”
2. Water treatment
And going forward, that process will likely need an overhaul.
In 2018, the water system faced similar taste and odor issues caused by algae blooms, though not to the levels seen this past year. At the time, PeopleService representatives told the city that the water treatment plant wasn’t cutting it, and taste and odor issues would persist unless a better chemical mix was found to eliminate them in treatment.
The company recommended looking at long-term overhauls to the facility and a more proactive approach to managing Mozingo Lake, all of which would require multimillion dollar investments in new infrastructure and equipment.
McDanel quote‘There is no solution that is too prohibitive’
– Greg McDanel
Maryville City Manager
Now, those measures he rocketed up the priority list.
“The challenge is that our plant is 50-plus years old, and any modifications with carbon filters or ozone is going to require extreme modifications to our plant,” McDanel said. “And so, what you do is you spend multimillion dollars retrofitting the plant, versus, can we come up with a solution that’s maybe at the lake that’s part of the process, and could maybe be used if we build a new treatment plant in the future?
“So that is something that we are identifying costs and capital improvements for right now. There is no solution that’s too prohibitive at this point, we just need all the information.”
McDanel said the process of finding the right solutions will be a matter of months, rather than years, but cautioned against rushing into a convenient solution that may turn out to make things more difficult in the future rather than easier.
“So we’re analyzing everything from multimillion dollar improvements to slight tweaks to the system that could improve (water treatment efficiency),” he said. “Because there’s not a silver bullet that fixes this thing.”
3. Mozingo Lake
The third angle of attack McDanel outlined was zeroing in on what caused the blooms in the first place, and how to stop them from thriving again in the future.
In general terms, cyanobacteria blooms are caused by unusually high amounts of nitrogen and phosphorous in the water. Where that nutrient pollution came from and why, however, is harder to pin down.
“We’re working with several biologists, including from the University of Missouri Extension office, to help get biology studies done on the lake and (find out) exactly what’s going on,” McDanel said. “We will he multiples done so that we he varying opinions on what’s happening, because there’s some really good theories out there about what has occurred, but we need the scientific research behind it.”
In many other cases across the country, agricultural and stormwater runoff he been primary causes for sharp increases in nutrients, along with more extreme temperatures and other environmental changes.
“Until we he those formal studies, we won’t know whether it’s just nature, or the weather, or who knows what,” McDanel said.
Once the city has a better idea of why the cyanobacteria blooms he been thriving more and more each year, then it can take action on managing the source of much of the county’s drinking water.
“Source water management is something that probably should he started 20, 25 years ago when the lake was built … to protect the nutrient balance of the lake,” McDanel said. “(It will mean) working with the Missouri Rural Water Association, the Conservation Department, the soils division — it’s everything from working on creating berms and swales and biodiversity to … (using) the land outside of Mozingo as a natural filter when it comes to the lake. And probably some dredging in certain areas by the (water treatment) intakes, creating some additional depth, shoreline stabilization — there’s just a whole host (of improvements that go) into that environmental bag that we need to work on more moving forward.
“So that will absolutely be a priority now. And for the first 20 years of its history, it hasn’t been, probably, as much as it should he been.”
McDanel said bringing the nutrient levels back into balance likely will be a longer process than the rest of the plan to address the algae blooms, but, “there’s no button we can press that takes care of an algae outbreak in a lake or that changes the nutrient level” of the lake on its own.
“We’re working on … a comprehensive approach … but it’s going to take all of it,” McDanel said of the city’s strategy to tackle both short-term and long-term challenges posed by the cyanobacteria. “And it’s definitely a top priority of the city now.”
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