Inversion Oxygenation and Bioaugmentation Quickly Reduces Organic Sediments

22 Feb

The Challenge

Lake Apopka is a 30,888 acre hyper-eutrophic lake located in central Florida. Once known for fantastic fishing, the lake had 28 fishing camps located around it. Decades of fertilizer and chemical use in adjoining parcels have contributed excessive nutrient inputs that have devastated the aquatic ecosystem and have transitioned the lake from a clear macrophyte-dominated system to a turbid phytoplankton-dominated system. Large quantities of organic sediment have accumulated throughout the lake bottom, destroying fishing and ultimately ending the operation of all the fishing camps.

The Solution

The State of Florida contracted our distributor Allied Group for implementing our inversion oxygenation and bioaugmentation in a 250 acre pilot area. The system was installed in August 2015. Prior to installation, comprehensive baseline water and sediment sampling was undertaken in May 2015, and then followed up with monthly sampling once the system was started. In December 2015, after only 4 months of operation, the data was gathered and analyzed by an independent consultant to determine if progress was being made.

The Results

There is no separating barrier between the pilot area and the rest of the lake, so constant mixing occurs. Even with this mixing, the results showed a 12.5% decrease in blue green algae, increased water column depth and significantly reduced water column ammonia, sediment phosphorous and organic matter. The following photos show the water behind a boat before the system was installed and 4 months later

Lake Apopka- 1Lake Apopka Restored

 

 

 

 

 

 

The contour maps shown below represent the increase in water depth that has occurred between May and December. You will see an increase in depth where the muck has been consumed by the microbes. Each line in these scans represents an increase of one foot in depth from the surface of the lake with the dark blue being the deepest points in the treatment area. The scale at the right shows the feet depth associated with each color. In December, we see some areas that are five feet or deeper forming as well as expansion of the 2, 3 and 4 foot depths.

Lake Restoration Stage 1Lake Restoration Stage 2Chart

The maps below show the changes from red (dense vegetation growth) to blue (no vegetation growth) after 4 months. Additionally the table below the maps quantifies the changes in aquatic vegetation biovolume. There has been a substantial reduction in the highest percent cover categories (60-80%) from May to December of 2015. This is due to the ability of the laminar flow aeration system to affect the sediment pore water chemistry and drive the denitrification process which limits sediment nutrients (such as ammonia) to many rooted macrophytes.
Vegetation GrowthVegetation Growth Map 2Chart

 

 

 

 

% Aquatic Plant Bio-VolumeMay 2015December 2015Net Loss or Gain
0%-5% 26.09%85.93%59.84%
5%-20% 8.69%10.87%2.18%
20%-40% 12.64%1.29%(11.35%)
40%-60% 17.76%0.99%(16.77%)
60%-80% 19.34%0.55%(18.79%)
>80% 15.48%0.37%(15.11%)

 

Overall the project has been a tremendous success to date. The amount of visual fish activity in the treatment has increased substantially, and it will only get better with more time.