Micro-Bubble Aeration Solution

*** In June 2020, this type of aeration diffuser were added to the lake. The design/placement were not explained despite requests. At this time, the design appears inefficient / not-optimized based on input loading analysis, lake morphology, and the extent of blue-green algae dominance. The City/Contractor have declined to comment on these considerations and requests emailed to them. Please continue reading to understand how this system works and its benefits.***

The City of St. Pete said they were considering micro-bubble aeration for Harbor Isle Lake Remediation in their June 2019 statement. However, it was not included in their July 2019 bid request, or pursued in 2019.

The City still has not explained their choice for the current nano-bubble aeration system despite multiple written requests. The money spent on this nano-bubble system, recent chemical treatments because of the system's ineffectiveness, and the city infrastructure endeavors in 2019 (like the reclaimed water flow-meter) -- has likely surpassed the cost of a proven correctly designed micro-bubble aeration system to be installed.

Submersed micro-bubble aeration is a type of aeration that is placed at the lake’s bottom and directly addresses the no dissolved oxygen at Harbor Isle Lake's bottom effectively and in a timely manner. Refer to Figure 1, below:

Figure 1

Illustration of a diffuser (purple-black circle) at bottom of lake and its air hose (black line) running to on-shore compressor unit (gray cube). This methodology provides oxygen to the bottom of the lake and circulates its water through laminar flow inversion, as shown via the arrows.

Comparison Chart: Nano-bubble vs. Micro-bubble Aeration System

Micro-bubble Aeration Proven Benefits

A properly designed submersed micro-bubble aeration system, immediately and over time:

• Oxygenates the bottom water, via air diffusers, allowing the process to start immediately at reducing and/or eliminating nutrients in the water column

• Provides circulation of the water column, immediately, preventing stagnant water that cyanobacteria prefers

• Overtime this provides an environment where other safe organism types can become dominant and for good (aerobic) bacteria to grow, which reduces bad (anaerobic) bacteria and organic muck (nutrient source)

Many historical micro-bubble aeration case studies can be found online, from various companies, including the City's contractor: Solitude Lake Management, which show reduction of nutrients, algae blooms, increased water clarity and dissolved oxygen within 1-3 months of a proper system being implemented in lakes Harbor Isle’s size or larger.

Local Renaissance Lake Install Example

Renaissance Neighborhood Lake’s micro-bubble aeration system, which the City provided funds to install, had visibly improved results within 3 months of running.

RENAISSANCE #1 – (Left Photo) “Lake with severe planktonic algae bloom.”

RENAISSANCE #2 – (Right Photo) “Same lake 3 months after bottom aeration system was installed. No chemicals were used.”

Ask the City why micro-bubble aeration, the less costly, proven to be successful, permanent solution was being ignored as an option even though substantial data and evidence support it?

Figure 2: Example of what the surface of the water looks like with a micro-bubble diffuser placed at lake's bottom

Submersed Aeration Basic Principle

"[Submersed] aeration is based on the principle that ponds restore themselves using natural processes already in the water. A water restoration process, using pond aeration duplicates those natural processes and accelerates them to keep up with today’s pollutants. A properly designed system can help increase fish growth and health, reduce odors, nutrients, and muck, increase clarity and create a healthier aquatic ecosystem."

Adding beneficial biological augmentation (e.g. non-toxic bacteria or enzymes) in conjunction with this type of system can further improve results.

Micro-bubble Aeration Reduces Blue-Green Algae

This excerpt is from a testimonial on CLEAN-FLO International's website. They are a 50 year old company who designs/installs submersed micro-bubble aeration systems, who have handled cases for blue-green algae reduction.

"Our firm has studied Clean-Flo technologies since 2009 and has noted several consistent results among sites which include: - - Statistically significant reductions in Microcystis colonies in inland lakes that contain whole-lake aeration and utilize bio augmentation with C-Flo® bacteria and ceramic diffuser designs.

• Statistically significant reductions in lake bottom “muck” with whole-lake aeration systems.

• Statistically significant increases in Secchi Transparency and water clarity (on average, a 2-3 meter increase in water transparency)

• Statistically significant shifts in algal genera composition from a blue-green algal dominated state to a diatom and single-celled green algae dominated state. "

Micro-bubble Aeration Detailed Proven Benefits

A Properly Designed Submersed Micro-Bubble Aeration System:

• Increases dissolved oxygen throughout the water column, most importantly at lower depths

-- This encourages aerobic beneficial bacteria to decompose non-living organic matter. This reduces nutrients and/ or muck (organic sediment) at the lake bottom

-- This also increases the process of oxidizing or eliminating pollution, e.g. high nutrient levels that currently exists and that could occur in the future

• Creates circulation of the water column

-- This allows algae cells to be mixed into deeper water, reducing sunlight and its availability to grow

-- This disturbs cyanobacteria(blue-green algae) buoyancy

-- This prevents stagnant water which cyanobacteria scums and other invasive pond weeds (e.g. duckweed) prefer to grow and reside

• Allows for an environment to have a beneficial organisms be dominant

• Improves water clarity, or reduces turbidity of the water

• Prevents thermal stratification