Wellboat Oxygenation and Disinfection with Nanobubbles

Why treat oxygen and disinfection as two separate jobs?

Because they happen at different times, to different water, with different risks. Mixing them up is how suppliers end up promising one box that does everything, and how operators end up with equipment that does neither job well.

• With fish on board — oxygen. The wells are loaded, the fish are consuming oxygen, and demand moves with every stage of the trip. The task is to hold dissolved oxygen stable. This is the ABAN-20.
• With the wells empty — disinfection. After unloading and before the next loading, the wells, piping and associated equipment are washed, disinfected and verified. The task is biosecurity between assignments, done fast enough that the vessel gets back to work. This is the ARVAND-O3, the skid form of the NanoOzone approach.

ARVAND-O3 is not a treatment for water with fish in it. It runs on isolated, empty wells in a closed loop. ABAN-20 is an oxygenation module, not a disinfection system. What they share is the vessel: the same hull, the same crew, the same seawater pump room and the same pressure on time.

Why is oxygen hard to hold stable in a loaded wellboat?

A loaded well is a closed volume carrying a high biomass, and the fish do not consume oxygen at a steady rate. Operators describe the same set of problems:

• Demand changes quickly during loading, transport and unloading. Crowding, handling and temperature all move it.
• Welfare drops fast when dissolved oxygen becomes unstable. There is little margin and little time to correct.
• Retrofit space is limited. A wellboat pump room was not drawn with a new skid in mind.
• Hydraulic capacity and pressure drop must stay manageable. The vessel's pumps already have a job.
• Operating cost and maintenance need to be predictable, because the crew has to live with the equipment at sea.

How does wellboat oxygenation with ABAN-20 work?

ABAN-20 treats a sidestream, not the full well flow. The logic runs in four steps:

1. A sidestream of seawater is taken from the vessel's recirculation loop, using the vessel's own seawater pump. No pump is included in NanoSWIM's scope.
2. Low-pressure oxygen from the vessel's oxygen supply is fed in where mixing is strongest.
3. Twenty passive, hydrodynamic generators create the nanobubbles. No electrical power is used inside the generators to make them.
4. The oxygen-rich water returns to the well.

In NanoSWIM's internal tests, nanoparticle tracking analysis measured mean bubble sizes of about 100–122 nm and concentrations in the order of 10⁸ particles per millilitre. These are internal laboratory measurements, not results from a vessel. For the physics of why bubbles that small behave differently, see how nanobubbles work.

How does ABAN-20 fit on a vessel?

The design philosophy is low pressure, low hydraulic demand and a compact footprint that can be retrofitted. The module is 1.5 × 0.6 × 2.0 m on a stainless-steel frame, with PVC / UPVC piping and manifolds. Because the vessel's seawater pump does the hydraulic work, the electrical load is controls and instrumentation only — approximately 1.5–3 kW. Control is by PLC with an HMI.

On a multi-well vessel, one ABAN-20 per well is recommended, each fed from a common vessel oxygen header. One module per well gives each well its own distribution and adds redundancy, so that a fault on one skid is less likely to affect oxygen in the other wells.

The skid carries the instrumentation the crew needs to see what it is doing: an inlet isolation valve, a water flow meter, an oxygen flow meter, pressure gauges before and after the generator banks, an outlet riser / vent, and sample and sensor points.

ABAN-20 is also membrane-ready: an optional sidestream membrane polishing or disinfection module can be added later without changing the core oxygenation skid. The module carries a 2-year warranty. Full specifications are on the ABAN-20 product page, and the wider transport context is on live fish transport.

How many ABAN-20 modules does a wellboat need?

The table below is a calculation from published oxygen-consumption models, not a measurement. It takes a two-well vessel with 2 × 1,500 m³ wells at a maximum stocking density of 150 kg/m³ — 225,000 kg of fish per well — at 8 °C.

For salmon it uses O₂ = 82.9 × W^−0.2 × 1.07^T, and for cod O₂ = 80.1 × (1 − e^(−0.185 × T^0.79)), both in mg O₂ per kg fish per hour, with W the fish weight in kg and T the temperature in °C. Flow per well follows from the module's hydraulic design ratio of 10 m³/h per kg O₂/h.

Even the most demanding case, 1 kg salmon at 32.05 kg O₂/h per well, sits well inside one module's design basis of 100 kg O₂/h. One module per well is still recommended — for distribution and for redundancy, not because one well needs more.

Species	Fish size	Specific O₂ demand	O₂ per well	Flow per well	ABAN-20 per well
Salmon	1 kg	142.4 mg/kg/h	32.05 kg/h	320.5 m³/h	1
Salmon	5 kg	103.2 mg/kg/h	23.23 kg/h	232.3 m³/h	1
Cod	1 kg	49.3 mg/kg/h	11.09 kg/h	110.9 m³/h	1
Cod	5 kg	49.3 mg/kg/h	11.09 kg/h	110.9 m³/h	1

Calculated from published models, not measured on a vessel. Assumptions: 2 × 1,500 m³ wells, 150 kg/m³, 225,000 kg per well, 8 °C. The cod model has no weight term, which is why both cod rows are identical. Your own vessel is sized against its own wells, species, densities and temperatures.

Why does wellboat disinfection take so long between assignments?

The second job starts when the fish are off. Between one assignment and the next, the operator has to show that nothing is carried from one load, farm or region to the next — and every hour spent proving it is an hour the vessel is not earning.

• Pathogen transfer between loads and between regions is the risk the whole procedure exists to control.
• Downtime. Washing, disinfection and verification take hours to a day or more of vessel time per turnaround.
• Chemical handling and discharge add handling complexity, crew-safety exposure and environmental pressure.
• Uneven treatment. UV or standard loop treatment often disinfects the circuit but not the full water body inside the well.

How does wellboat disinfection with ARVAND-O3 work?

ARVAND-O3 is a closed-loop system for planned technical disinfection of the wells, piping and associated equipment between transfer operations. Ozone is made on board, delivered into the water as nanobubbles, circulated through the wells and controlled by measurement. The process chain runs: ozone generator → nanobubble generator → recirculation loop → wellboat tanks → ORP / TRO monitoring → off-gas control.

On board, the operating workflow has five steps:

1. Prepare and isolate the system.
2. Start closed-loop circulation.
3. Activate NanoOzone treatment.
4. Monitor ORP / TRO and contact time.
5. Verify safe conditions before reuse.

The control parameters are ORP monitoring, TRO monitoring in seawater, a defined exposure (contact) time, off-gas management and automatic safety shutdown. ARVAND-O3 has no published capacity, ozone output or flow figure: it is sized per vessel, from the well volumes and the circulation loop.

How is the ozone kept under control on board?

Ozone is hazardous to breathe. That is the starting point of the ARVAND-O3 design, not a footnote to it. The skid is built around keeping ozone where it is meant to be and removing it before anything leaves the system.

• Ozone generation: an oxygen feed to three ozone generators on a common ozone gas manifold.
• Water side: a seawater inlet with strainer, a duty pump and a standby pump, a nanobubble reactor and a static mixer.
• Off-gas: a degassing separator and an ozone destruct unit on the vent, so off-gas is destroyed rather than released.
• Before discharge: a deozonation cartridge, so treated water leaves without residual ozone.
• Safety: an ozone gas detector, a PLC / HMI control cabinet, an emergency stop and a stack light. Gas detection and automatic safety shutdown are both part of the design.

Ozone reverts to oxygen. Residual ozone is removed before discharge and off-gas is destroyed at the vent. The whole skid sits on a stainless-steel frame with a footprint of about 2.0 × 2.0 m.

Why nanobubbles instead of UV, chemical dosing or standard ozone?

Each existing method does part of the job. UV treats water only as it passes the unit, with no residual effect inside the well and limited effect in dead zones and complex piping. Chemical dosing brings a handling and safety burden, chemical cost, discharge concerns, potential corrosion and more work for the crew. Standard ozone delivered as macro-bubbles has lower gas-transfer efficiency, more off-gassing and wasted ozone, and a longer time to reach the target ORP / TRO.

The reasoning behind delivering ozone as nanobubbles is a design rationale, and we present it as one. Bubbles under 200 nm stay suspended instead of rising and bursting. The aim is higher gas-transfer efficiency, so less ozone is wasted and less off-gas is produced; a longer effective contact time; better reach into tanks, piping and hard-to-reach zones; and an oxidative effect in the water body inside the well, not only in the technical room. Reactive oxygen species formed when the bubbles collapse can enhance microbial inactivation and attack on biofilm. How much of that shows up on a given vessel is exactly what a pilot measures. The longer comparisons are on nanobubbles vs ozone and nanobubbles vs UV.

What gets measured, and what can you show an auditor?

Biosecurity is only as good as the record behind it. ARVAND-O3 logs ORP and TRO continuously, against a defined contact time, and ends every cycle with verification of safe conditions before the wells are reused. That log is the document: what was treated, for how long, and what the measurements showed when the cycle ended.

The same logic applies to the turnaround itself. A pilot records how long the disinfection and verification actually take on your vessel, so the before-and-after comparison rests on your own clock, not ours. On the oxygen side, the ABAN-20's water and oxygen flow meters, pressure gauges and sample points give the crew a direct reading of what each module is delivering. How this fits the wider framework of standards and documentation is covered on standards and compliance.

What can NanoSWIM claim today — and what not yet?

This is the section to read before anything else is quoted in a board paper or a tender.

• Design basis is not a vessel result. The ABAN-20 figures — 100 kg O₂/h, 1,000 m³/h, 5 kg O₂/h per generator — are the design basis. They have not yet been verified on a vessel.
• Bubble measurements are internal. The size and concentration figures come from NanoSWIM's internal laboratory tests.
• The sizing table is a calculation from published models, not a measurement.
• The 50 % figure is a target. The pilot aims to cut disinfection turnaround by at least 50 % while improving biosecurity control. It is a goal to be measured against, not a result.
• Development status. A prototype has been built and lab-tested, and testing of the system's two treatment stages is completed. The wellboat systems are offered through a pilot programme.
• What it does not replace. ARVAND-O3 is not presented as a substitute for washing out the wells or for the vessel's hygiene protocol. It is the disinfection and verification step inside that protocol. ABAN-20 does not disinfect, and it does not include a pump.

NanoSWIM's technology is patent pending: UK patent application GB2507053.3, "Method and apparatus for water cleaning", filed 8 May 2025 and owned by NanoSWIM AS.

How do you put a value on a shorter turnaround?

We do not publish an example with someone else's day rate, because yours is the only one that matters. The logic is simple enough to fill in yourself:

1. Value per turnaround = hours saved ÷ 24 × your vessel's day rate.
2. Annual value = value per turnaround × turnarounds per year, plus any saving on chemicals and handling.

Use the hours actually saved during a pilot, not the 50 % target. If the measured saving is small on your vessel, the formula will say so — and that is worth knowing before a fleet decision, not after. Send us your turnaround numbers and we will work through them with you.