Sediment Floc Reduction, Nuisance Algae Reduction, Water Quality Improvements, and Other Observed Ecological Benefits, in Lake Apopka, Florida

03 Mar

Excerpt from: Overall Trends in the Efficacy of Allied Group/CleanFlo’s Laminar Flow Aeration and Bioaugmentation as a Treatment for Sediment Floc Reduction, Nuisance Algae Reduction, Water Quality Improvements, and Other Observed Ecological Benefits, in Lake Apopka, Florida January, 2016

Prepared by: Restorative Lake Sciences Jennifer L. Jermalowicz-Jones, Ph.D. Candidate Water Resources Director

“INTRODUCTION AND SUMMARY:

Lake Apopka is a 12,500 ha (30,888 acre) hypereutrophic lake located in central Florida approximately 32 km (20 miles) northwest of Orlando, Florida. The lake has an approximate mean depth of 1.6 meters (5.2 feet) and has been the focus of intense restoration efforts over the past few decades due to 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.

The most prominent phytoplankton communities consist of blue-green algae (cyanobacteria) such as Planktolyngbya spp., among others. These blue-green algae are capable of secreting neurotoxins which are known saxotoxins. In addition to the turbidity issue caused by the high density of phytoplankton, there is an overabundance of soft organic flocculent muck on the lake bottom. This material becomes easily suspended during wave activity or when boats make contact with the lake bottom. As a result of these factors, the dissolved oxygen concentration of the lake water is often compromised due to the lack of light penetration into the water column and the high water temperatures that are increased both by seasonality and the high amount of suspended solids that are continually circulated throughout the water column.

1.1 Introduction to Laminar Flow Aeration and Bioaugmentation (In General):

Allied Group/CleanFlo laminar flow aeration systems are retrofitted to a particular site and account for variables such as water depth and volume, contours, water flow rates, and thickness and composition of lake sediment. The systems are designed to completely mix the surrounding waters and evenly distribute dissolved oxygen throughout the lake sediments for efficient microbial utilization.

An Allied Group/CleanFlo laminar flow aeration system utilizes diffusers which are powered by onshore air compressors. The diffusers are connected via extensive self-sinking airlines which help to purge gasses such as H2S from the sediments. In addition to the placement of the diffuser units, the concomitant use of bacteria and enzymatic treatments to facilitate the microbial breakdown of organic sedimentary constituents is also used as a component of the treatment.

Beutel (2006) found that lake oxygenation eliminates release of (ammonia) NH3+ from sediments through oxygenation of the sediment-water interface. Allen (2009) demonstrated that NH3+ oxidation in aerated sediments was significantly higher than that of control mesocosms with a relative mean of 2.6 ± 0.80 mg N g dry wt. day-1 for aerated mesocosms and 0.48 ± 0.20 mg N g dry wt. day-1 in controls.

Although this is a relatively new area of research, recent case studies have shown promise on the positive impacts of laminar flow aeration systems on aquatic ecosystem management with respect to organic matter degradation and increase in water depth and rooted aquatic plant management in eutrophic ecosystems (Restorative Lake Sciences, 2009-present).”

View Lake Apopka Interim Report