What Are Nanobubbles? The Science Behind Nanobubble Technology

What are nanobubbles?

A nanobubble is a gas-filled bubble with a diameter below roughly 200 nanometres — sub-micron bubbles thousands of times smaller than a grain of salt, and small enough that you cannot see them individually. Water full of them looks slightly milky at high concentration and completely clear at working concentrations.

The interesting part is not the size on its own. It is what the size does to the physics.

An ordinary bubble from an air stone is buoyant. It rises, reaches the surface within seconds, and whatever gas has not dissolved on the way up escapes into the room. That is why coarse aeration is inefficient: most of the gas you paid for leaves the water without doing anything.

Below about a micron, buoyancy stops winning. Drag and Brownian motion dominate, so the bubble effectively stops rising and drifts with the water instead. It stays in suspension for days rather than seconds, which gives the gas inside it time to actually dissolve.

Key properties

Four properties do the work. They are worth understanding separately, because different applications lean on different ones.

Enormous combined surface area

Split one large bubble into many small ones and the volume stays the same while the total surface area grows dramatically. Gas transfer happens across that surface, so a given volume of gas delivered as nanobubbles presents vastly more interface to the water than the same volume delivered as coarse bubbles. That is the whole mechanism behind efficient oxygen transfer — and the reason a nanobubble generator can raise dissolved oxygen using much less gas than an equivalent diffuser.

Negative surface charge

Nanobubbles carry a negative charge at the gas–water interface. Two consequences matter in practice. First, the bubbles repel each other, so they do not merge back into large bubbles — this is what makes them stable rather than transient. Second, the charge attracts suspended solids and helps lift biofilm off wetted surfaces so the filter can take it out, which is why operators usually report a visible change in water clarity before they see it in the test results.

Oxidation on collapse

When a nanobubble does eventually collapse, the energy released is concentrated into an extremely small volume. Across billions of bubbles this produces a sustained oxidative environment — advanced oxidation — that disrupts cell membranes of pathogens and breaks down the organic compounds that would otherwise turn into disinfection by-products.

Gas choice

The same generator can carry different gases, and this is the main design decision. Oxygen is used where the goal is oxygenation — aquaculture, wastewater, oxygenation in live fish transport. Ozone is used where the goal is oxidation and disinfection, because ozone is a far stronger oxidiser than chlorine and reverts to plain oxygen afterwards rather than leaving a residue.

The problem with chlorine

Chlorine works. It is cheap, extremely well understood, and it leaves a measurable residual in the basin, which is exactly what a public pool needs. None of that is in dispute, and any page claiming otherwise is selling something.

The problem is what chlorine produces once it meets what swimmers bring with them. Free chlorine reacts with sweat, urine, skin oils, cosmetics and sunscreen to form chloramines — combined chlorine. Chloramines cause the sharp smell in an indoor pool hall, the stinging eyes, the tight skin, and the airway irritation that hits instructors and competitive swimmers hardest. They also accelerate corrosion of fixtures, ductwork and the building fabric.

A counter-intuitive but useful rule: a strong chlorine smell almost always means too little free chlorine relative to the load, not too much. The smell is the by-product, not the disinfectant.

Nanobubble oxidation attacks the organic load that forms chloramines in the first place. That is the whole proposition, and it is covered in buyer terms on chlorine-free pool disinfection.

How it works

In a pool or process installation, the nanobubble generator sits in the circulation loop after filtration. Water is already particle-free at that point, so the oxidative capacity goes into dissolved organics rather than being wasted on debris.

1. Generation. Water passes through the generator, where gas is introduced and sheared into nanobubbles at high density. The unit is inline — it does not need a separate contact tank.
2. Dissolution. Because the bubbles do not surface, the gas has time to dissolve. Transfer efficiency is high compared with injection into an open basin, where much of the gas escapes.
3. Oxidation and disinfection. The oxidative environment disrupts pathogens and breaks down organic load, cutting the precursors that form combined chlorine and other disinfection by-products.
4. Clarity and surface effect. Charged bubbles carry fine particles and lifted biofilm to the filter, which improves clarity and reduces the manual cleaning burden on wetted surfaces.
5. Return. Treated water returns to the basin. Where ozone is used, excess gas is managed as part of the system design so the air above the water stays within safe limits.

Honest limit: this is a treatment-loop technology. It acts on water that passes through the system, exactly like UV and ozone injection. It does not place a persistent disinfectant in the basin, which is why a public pool usually keeps a small chlorine residual for regulatory reasons.

What we have measured

In NanoSWIM's internal tests, nanoparticle tracking analysis (NTA) of three samples gave mean bubble sizes of about 100–122 nm and concentrations in the order of 10⁸ particles per millilitre. These are our own laboratory measurements. They are not independent certification, and they are not readings from a pool or a vessel in service.

• Test A: mean size 100.3 nm, concentration 1.60 × 10⁸ particles/mL.
• Test B: mean size 104.4 nm, concentration 1.47 × 10⁸ particles/mL.
• Test C: mean size 121.9 nm, concentration 7.58 × 10⁷ particles/mL.

In all three samples, 90% of the measured particles were smaller than 184 nm (D90 of 145.5, 147.6 and 183.8 nm).

Size and concentration are the two numbers worth asking any nanobubble supplier for. Bubbles under about 200 nm stay suspended instead of rising and bursting, so size tells you whether the gas stays in the water long enough to dissolve or react. Concentration tells you how much of that gas–water interface is actually there.

Honest limit: NTA sizes and counts particles in a sample. On its own it does not prove that every particle counted is a gas bubble rather than a fine solid, and results depend on the water and on how the sample is handled. Read these as internal test data, and ask us for the test conditions if you are comparing suppliers.

Can a nanobubble generator work without electrical power?

In one product, yes. In the marine ABAN-20 oxygenation module for wellboats, the 20 nanobubble generators are passive and hydrodynamic: no electrical power is used inside the generators to create the nanobubbles. A sidestream of seawater, driven by the vessel's own seawater pump, meets low-pressure oxygen from the vessel's oxygen supply, and the flow through the generators forms the bubbles.

Electricity on the ABAN-20 skid goes to controls and instrumentation only — approximately 1.5–3 kW. The energy that makes the bubbles comes from a pump the vessel already runs. That is why, in a wellboat retrofit, flow and pressure drop are the questions to settle first, more than the electrical supply.

This describes the ABAN-20 specifically. It is not a claim about every NanoSWIM product: the pool and industrial systems are not described as passive, so check the product page for the unit you are considering. How the module fits on board is covered under wellboat solutions.

	Conventional bubbles	Microbubbles	Nanobubbles
Diameter	Above ~1 mm, visible	~1–100 µm	Below ~200 nm
Behaviour in water	Rise fast and burst at the surface	Rise slowly, gradually shrink	Effectively neutrally buoyant, drift with the water
Time in suspension	Seconds	Minutes to hours	Days
Surface area per unit of gas	Low	High	Very high
Surface charge	Negligible	Weak	Strong negative charge
Gas transfer efficiency	Poor — most gas escapes	Moderate	High
Typical use	Coarse aeration, agitation	Flotation, cleaning	Oxygenation, oxidation, disinfection

Boundaries between the categories are conventions rather than hard physical thresholds, and different literature draws the microbubble/nanobubble line at slightly different diameters. The behavioural difference — whether a bubble rises or stays suspended — is the part that matters operationally.

What the benefits are, and where they depend on the site

What this delivers depends on the application, and it is worth separating what is well established from what is site-specific.

• Lower chemical consumption. Up to 90% less chemical use against a conventional dosing regime on comparable pools. The size of the reduction depends on bather load, water temperature and how the plant is run.
• Better air quality indoors. Less combined chlorine means less of the smell, eye irritation and airway irritation that dominate complaints in swim halls.
• Higher dissolved oxygen. Directly useful in aquaculture and wastewater treatment, where oxygen availability is the process bottleneck rather than a comfort issue.
• Improved clarity. Fine particles and biofilm are moved to the filter instead of accumulating on surfaces.
• No persistent residue. Ozone reverts to oxygen; there is no chemical residual left for bathers to react to.

Documented outcomes are collected on our references page — including a reference: 40% higher oxygen at a fish farm. If you want the method compared directly against what you run today, we publish honest head-to-heads: Nanobubbles vs chlorine, Nanobubbles vs UV and Nanobubbles vs ozone, each of which says plainly where the alternative is the better choice.

Where nanobubble technology is not the answer

Being specific about this is more useful than another list of benefits.

• If you need a guaranteed persistent disinfectant residual throughout the basin with no chemical at all, no treatment-loop technology delivers that — not nanobubbles, not UV, not ozone.
• If your problem is particulate rather than organic or microbial, filtration and hydraulics will do more for you than any oxidation step.
• If capital budget is the binding constraint and the facility is small and lightly used, conventional dosing or a salt chlorinator will be cheaper over a short horizon.
• If the plant room has no space or no spare flow capacity, the retrofit conversation has to start with hydraulics, not with the generator.