Vacuum Bubble® Technology Science
Advanced Aeration Inc. 's Vacuum Bubble® Aerators are built upon sound scientific principles and engineering practices. The bubbles are created under a partial vacuum and consequently, as they enter the water, the higher water pressure surrounding them causes them to collapse further. There are no other, documented aerators with bubbles as small as 0.25mm in diameter.
This technology addresses biochemical oxygen demand (BOD) and waste treatment problems by improving the performance of aerobic bacteria. As the aerobic bacteria oxidize waste and consume oxygen, the Vacuum Bubble® Technology Aerator makes additional oxygen readily available by producing very large populations of micro Vacuum Bubbles®. The process is proven to be highly energy-and cost-efficient across a wide range of applications.
Most aeration equipment in use today utilizes compressed air systems. These introduce bubbles of air into the water by forcing the compressed air through a fine pore diffuser, similar to the aerators commonly found in most home fish tanks. Experimental results with these systems have shown that the minimum bubble sizes generated are greater than 3 to 4 millimeters in diameter. Bubbles of this size quickly rise to the surface and are lost to the atmosphere. They do not remain in the water long enough to transfer an appreciable amount of oxygen.
The Vacuum Bubble® Technology Aerator, instead of using the compressed air/fine pore system, uses a patented process to create bubbles in a partial vacuum. The micro Vacuum Bubbles® created in this process average 0.25 mm in diameter. The small size of the bubble and the low-pressure gas it holds create a small buoyancy force (The phenomenon which makes bubbles rise in a liquid). This buoyancy force is so small that it is less than the surrounding surface tension of the water. The bubble, in fact, does not rise to the surface, but remains suspended in the fluid. This makes all of the oxygen in the bubble available to be dissolved in the liquid as needed.
Figure 1: Photograph of actual bubbles produced by Vacuum Bubble® Technology in a small demonstration tank
Determining the Average Size of a Micro Vacuum Bubble®
A VBT™ 100 Aerator was installed in a 55 gallon glass tank with 50 gallons of tap water. A watertight plastic rectangle large enough to hold a Polaroid camera was mounted with a clear plastic grid of 9 mm squares. The aerator was placed 24 inches below the surface of the water. The aerator plate was 2 inches in diameter and had ten 2.38 mm orifices.
Figure 2: Vacuum Bubble® photographed using
Polaroid PN665 film/negative back lighted with
As the propeller withdrew water from the 12 inch column, a partial vacuum interface formed between the plate and propeller causing water to collapse in the partial vacuum, thus forming the micro Vacuum Bubbles®. The aerator was activated for 60 seconds, shut-off and a Polaroid negative taken of the bubbles accumulated on the surface of the submerged 9 mm square grids.
This image was enlarged 3.1X from 3" X 4" film to an 8" X 11" photograph which was examined using a Bausch and Lomb dissecting microscope at 60X magnification. A micrometer slide with 0.01 mm scales was used to measure the diameters of 15 randomly chosen bubbles in three randomly chosen grid squares for each of three one-minute sample periods (See Figure 1).
Figure 2 shows the vacuum bubble diameters on the 9 mm scale of the sample grid. An average of 75.8 bubbles per square had a 0.25 mm mean diameter delivering a volume of 0.0082 mm3 per bubble. Oxygen exchange surface area per bubble was 0.1962 mm2.
The Importance of Bubble Size in Aeration
As the total surface area of a population of bubbles increases, oxygen transfer efficiency (OTE) increases. For the same volume of air, many small bubbles have a greater surface area than fewer large bubbles.
Common compressed air diffusers, which are found in many municipal and industrial waste treatment processes, frequently produce bubbles 20 mm or greater in diameter. Not only do these bubbles have a small total surface area for a given volume pumped, they also rise to the surface quickly, and are lost to the atmosphere. Advances in fine-pore diffusers have led to the development of aeration systems producing bubbles averaging 3 to 4 mm in diameter. This represents the state of the art in compressed air systems.
Advantages of Bubbles Created by VBT™
Figure 3: Relative size of
bubbles commonly produced
by various aeration methods.
- Compressed air diffusers produce bubbles 20mm or greater in diameter.
- Fine-pore diffusers produce bubbles between 2mm and 4mm in diameter.
- VBT™ creates bubbles 0.25mm in diameter.
One 20mm Bubble:
Surface Area 12.6cm2
300 3mm Bubbles
Total Surface Area: 84cm2
6X Greater than 20mm Bubble
500,000 0.25mm Bubbles
Total Surface Area: 1000cm2
80X Greater than 20mm Bubble
12X Greater than 3mm Bubble
Vacuum Bubble® Technology and Aerobic Bacteria
Conventional Waste Treatment
It is expected that in the conventional septic tank or waste lagoon the organic waste contained in them is digested. This is not the case - the organic waste builds up over time and the tanks and lagoons are nothing more than containers for sedimentation and sludge storage. The bacteria in normal septic digestion are anaerobic and are accompanied by odorous gases and groundwater contaminating pathogens.
By supplying enough oxygen, an aerobic condition is developed. Bacteria that obtain their energy aerobically are much more efficient. The same organic waste food supply supports a much larger bacterial flora by aerobiosis than anaerobiosis, and therefore, aerobic decomposition of organic matter is much more rapid. Aerobiosis in activated sludge is substantially complete in six to eight hours, whereas conventional septic digestion of sewage sludge requires about 60 days.
The usual end products from anaerobic decomposition are carbon dioxide, methane, ammonia, and hydrogen sulfide. The end products of aerobic bacteria are carbon dioxide, ammonia, water, and sulfates. The ammonia is not given off as a gas, and is nitrified by the aerobs Nitrosomonas - oxidizing the ammonia into nitrite, and Nitrobacter - oxidizing the nitrite into non-toxic nitrate. Nitrates are directly plant usable and will not harm fish. The only gas given off by aerobic bacteria is odorless carbon dioxide, thereby eliminating any offensive odor
Advanced Aeration, Inc., treatment systems are permitted through the Florida Department of Environmental Protection and the Florida Department of Health. Please call SWS at 813-785-0500 for design assistance or to schedule a presentation.
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