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What is a Nanobubble?

Nanobubbles are nanoscopic bubbles of non-condensable gases suspended in liquid, that carry remarkable properties with significant benefits.

Types of Bubbles

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Nanobubbles are constantly moving in solution and can stay in suspension indefinitely. This is known as Brownian Motion.

 

The presence of nanobubbles helps destroy biofilm, removes existing deposits and disrupts future growth, allowing particulate to simply flow downstream for easy removal

How does the Nanobubble Generator produce nanobubbles?

The Rapid Water Technologies Nanobubble Generator produces nanobubbles through the principle of shear cavitation.

Shear cavitation occurs when high-shear stresses create a depression of the static fluid pressures below that of the vapor pressure of the fluid.

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When this pressure differential is reached, bubbles spontaneously form from the solubilized, or entrained, gases within the liquid. Cavitation is pressure driven “boiling” at constant temperature

Why do nanobubbles stay in solution?

Nanobubbles are extremely small pockets of non condensable gases that have been entrained in the water. Due to their small size, nanobubbles have reduced buoyancy and stay in solution for extremely long periods of time.

How do nanobubbles impact zeta potential?

Hydroxide ions stabilize the nanobubbles, causing a decrease in the absolute value of the zeta-potential for the solution. The zeta potential, measured in electron-volts (eV), is a measure of electrokinetic potential or electrical potential at the slipping plane, the space between moving fluids and stationary surfaces.

How do nanobubbles remove and prevent scale, as well as improve filtration and separation?

Decreasing the zeta potential, moving toward a zero value, indicates an increase in probability of spontaneous coagulation or agglomeration of like-charged particles. An increase in the magnitude indicates greater difficulty of coagulation. The presence of nanobubbles reduces the magnitude of the solution’s zeta potential by creating an electrostatic lattice within the liquid, produced by the attraction of hydroxide ions to its positively charged bubble core. This, in turn, attracts other positively charged particles.

Bubble Lattice

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This lattice acts as the “cement” (bubbles) to bond the “bricks” (cations) of like particles while preventing such bonding with opposite charge particles; which prevents scale from forming (Ca+ and CO3-) while forming filterable and/or settle-ready floc particulates. The electrostatic lattice principle is aided by the fact that air (bubbles) attracts hydrophobic contaminants, the main reason for air flotation separations. As a result, scale formation is mitigated, pipe and heat transfer surfaces repel deposits and become or remain clean, filtration efficiencies are increased, and density and flotation separations experience greater effectiveness (such as with DAFs and centrifuges).

Do nanobubbles cause corrosion?

Due to the bubble formation, oxygen within the system has not shown to contribute to corrosion of ferrous components and pipes at similar dissolved oxygen levels. The gas, air and/or oxygen remains available for aerobic processes and contributes to oxidation reactions of suspended particles.

Organic corrosion is corrosion attributed to the formation and growth of micro organisms on a metal surface leading to the decomposition of the component. Nanobubbles prevent the formation and attachment of micro organisms to surfaces and thus eliminates organic corrosion.

Rapid Water Technologies has conducted metallurgy testing on the most common metals used in mechanical systems. The results have shown no loss of weight, no corrosion and no pitting. A detailed report is available upon request.

How do nanobubbles prevent biofilm?

Biofilm formation is not possible within systems where both nanobubbles are present and existing biofilm has been removed. Zeta potential prevents the agglomeration, or formation, of the organic colonies. 

 It also prevents any organisms from attaching to surfaces on which they would otherwise grow. Additionally, where organisms manage to attach to a surface and then grow, the scouring effect of the nanobubbles themselves will target their removal

the increase in the gas/liquid interface permits for increased mass transfer of oxygen into the liquid at low relative dissolved oxygen levels. Such oxygenation of the water prohibits algae growth and blooms, which are common organisms in biofilm

Do nanobubbles impact aerobic digestion?

Increased dissolved oxygen encourages aerobic processes and cell growth which is advantageous in systems such as irrigation, aquaponics, and wastewater treatment. Additionally, increased dissolved oxygen levels contribute to improved oxidation-reduction (redox) reaction for remediation of certain contaminants.

Nanobubble gases, while small, are still available for aerobic digestion. This means that organisms within the water that require air for life and growth will still have it available, while organisms that prefer oxygen-depleted systems will starve and die out. If the gas is oxygen, then redox reactions will be encouraged, which are the reactions responsible for remediation of biologic and inorganic contaminants.

Because nanobubbles remain in solution longer, the dissolved gas is available for longer periods when compared to solutions with microbubbles, which float out of solution and have more opportunity to dissolve into the solution. Additionally, Rapid Water Technologies is able to inject and increase dissolved gases above saturation to further encourage the oxygen reduction potential (ORP) for specific purposes

Do nanobubbles impact chemical use?

The formation of nanobubbles increases the concentration of hydroxide ions in a solution. Nanobubbles remove organic and inorganic fouling agents and surfaces and prevents further formation.

Nanobubbles more efficiently disperse and dissolve active compounds in a solution.

These factors, combined with the change in zeta potential, can reduce chemical usage for corrosion inhibitors, biocides, scale inhibitors and clean-in-place applications such as casustics, acids and surfactants

What is the boundary layer and is it impacted by nanobubbles?

Boundary Layer Slip occurs when nanobubbles, which are attracted to hydrophobic surfaces -- such as stainless steel, carbon steel, copper and PVC -- reduce the surface boundary layer of the flow regime.

The surface nanobubbles will also bind with and remove any scale or contamination over time, leading to better surface wettability and thus heat transfer efficiency.

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