After the Lake Harmony Association received a report indicating their lake was filling with sediment, it began looking for a solution. Conventional dredging would have been very expensive and disruptive, so the Association began considering natural alternatives. Soon after, Clean-Flo International was selected to design and implement a bio-dredging system to address the problem. Below is the story of how Clean-Flo’s custom-designed inversion oxygenation system and bioaugmentation program reduced 48,239 cubic yards of sediment in the first four months of operation.
Getting the System Designed and Installed
The first step in the design process was for Clean-Flo to gain a fuller understanding of the lake conditions at Lake Harmony. To achieve this, a sonar scan of the lake bottom was performed, and bottom sediment samples were taken. The scan used a Lowrance HDS 7 fishfinder/chartplotter with broadband sounder technology, built-in GPS antenna, and high-definition mapping to produce high-resolution bottom contour (bathymetric) and composition maps. The original contour maps for the lake with color-coded scales are shown below. The scale goes from light blue (shallowest) to dark blue (deepest). The contour interval in the maps is one foot. The deepest reading obtained in the initial scan was 14.14 feet. The 14’ contour (14’ or greater but less than 15’) was a very small area in 2017. The deepest contour in the eastern section of the lake was 10’ and it encompassed a small area. The 6’ contour barely reached into the northwestern cove in 2017.
In addition to mapping, sediment samples for collected and analyzed for organic content of the sediment. Sediment is composed of organic matter, inorganic matter and water. The only solution to reducing inorganic matter is dredging. However, if the sediment contains organic matter, it is possible to reduce the sediment without dredging.
Based on the detailed characteristics of the lake, Clean-Flo designed an inversion oxygenation system with two compressors and 24 micro-porous ceramic diffusers. The diffusers were strategically placed using GPS coordinates to maximize the efficiency of the system. The system took three days to install and began operation on June 16th 2018.
Shortly after the system installation, Clean-Flo began a program of bioaugmentation to catalyze the sediment digestion process. The biological additives are an equally important part of the overall restoration and muck reduction strategy. Both of these components of Clean-Flo’s service work in tandem to create the impressive results achieved at Lake Harmony to date.
What happens to the sediment?
To understand what happens to the sediment we must first understand how it gets there in the first place. Organic matter--such as leaves, grass clippings, and animal waste--is added to the lake each year. This waste sinks to the bottom and decomposes to form organic muck and sediment on the bottom. Year-after-year this occurs and the sediment accumulates. During decomposition, organic matter releases nutrients into the water. Organic sediment on the bottom is decomposed in two ways: anaerobic (without oxygen) digestion or aerobic (with oxygen) digestion. If the lake is eutrophic, then anaerobic digestion takes place and releases nutrients in forms that favor the growth of algae and cyanobacteria (toxic blue green algae). Algae blooms in the summer and dies off and sinks to the bottom in winter, where it contributes to the accumulation of organic matter described above. This cycle is called nutrient recycling and accelerates on an exponential scale in eutrophic conditions.
If aerobic digestion takes place and is enhanced by enzymatic digestion--a key component of Clean-Flo's bioaugmentation program--then nutrients are released in forms that favor the growth of life-forms that create the foundations of a productive food chain. Beneficial nutrients are also supplemented by other Clean-Flo biological products to further support these life-forms at the bottom of the food chain. Once the organisms such as zooplankton proliferate, the food chain “blooms” instead of the algae. Fish size and populations increase as do the predators who feed on the fish. The food chain therefore provides a biochemical metabolic pathway for removal of nutrients and this prevents recycling and the worsening of algae blooms each year. Aerobic digestion is much faster than anaerobic digestion which means that we can digest the sediment faster than it forms and therefore achieve a net reduction in organic sediment.
In short, Clean-Flo changes the digestion of the organic material on the bottom of the lake from an anaerobic to an aerobic process. The presence of oxygen breaks the cycle of the sediment buildup by incorporating it into the food chain.
Below is a side by side comparison of the depth profiles of the lake. The initial scan was taken on 9/13/17, nine months prior to installation. The second scan was taken on 10/9/18, approximately four months after the system was installed and started.
After four months there were noticeable increases in depth throughout the lake. The deepest reading increased from 14.1' to 14.9' but this is not the most significant area of depth increase. Whereas the eastern part of the lake had an 8' depth contour before the Clean-Flo system was installed, the same section of the lake now reached up to 10' in depth consistently. As shown in the images below, one can also see how the 8 ft contour line (highlighted with a red line) in the center of the lake crept north and encompassed substantially more area than prior to the program's beginning.
Increasing depth brought corresponding increases in the lake's volume. The initial scan calculated the water body volume to be 910.09 acre-feet (296.5M gallons). The second scan of the lake calculated the water volume to be 940.12 acre-feet (306.3M gallons). The increase in volume is equal to the reduction in bottom sediment through the operation of Clean-Flo's system and biougmentation program. This effectively meant that 29.9 acre-feet, or 48,239 cubic yards of sediment, had been reduced in Lake Harmony over the course of four months.
Additional Benefits of a Clean-Flo System
The Lake Harmony Association contacted Clean-Flo as an alternative to dredging, but the Clean-Flo process has many more benefits than just sediment or muck reduction. Whereas dredging is a one-time event and temporary fix, the Clean-Flo program system and bioaugmentation continues to improve the Lake year-after-year. A secondary benefit of muck reduction is that the lake's bottom composition hardens over time. As organic matter is removed, the bottom consists of increasingly higher proportions of inorganic (sand, silt, clay) sediment. Below is the side by side comparison of Lake Harmony’s bottom hardness before and after Clean-Flo's program began. In these maps, yellow refers to soft bottom, the orange refers to medium bottom, and the red refers to hard bottom. Another way to think about it, the darker the better.
After the first four months of operation, the area consisting of soft bottom decreased by 36%, medium bottom decreased 4%, and hard bottom increased by 35%.
Clean-Flo changes the biological processes on the bottom from anaerobic to aerobic, and this creates a plethora of side benefits. Algae growth is reduced. Water clarity goes up. Delighting fishermen, the fish get healthier and bigger.
After being contacted by the Lake Harmony Association to address sediment accumulation, Clean-Flo performed a preliminary scan of the lake to assess depth, volume, and bottom composition. Samples were also taken to evaluate the organic proportion of bottom sediment. Clean-Flo thereafter installed an inversion oxygenation system and began a bioaugmentation program to address the issues. The system was started and program began on June 16th of 2018. A second scan of the lake bottom was conducted on October 9th of the same year. The second scan showed that Clean-Flo reduced the muck in Lake Harmony by 29.9 acre-feet, or 48,239 cubic yards, in the first four months of service. To put this in perspective, a tri-axle dump truck holds approximately 20 yards of topsoil. That equates to 2,412 dump trucks removing muck from the lake. Not only was the primary issue been dramatically improved, but the overall ecosystem of the lake was also in a much healthier state, and continues to improve. Algae reduction, increasing water quality and clarity, and better fishing are just a few examples of how. We sincerely hope the residents and visitors of Lake Harmony enjoy the healthy lake for many years to come. If you are interested in reading more stories such as this one click here and if your body of water needs help contact us here!