Ten organisms per cubic meter.
That number is why an industry rebuilt its engine rooms. An independent laboratory has run the nanobubble ozone approach against the same duty and published the result.
A vessel takes on ballast water in one port for stability and discharges it in another, and whatever was living in the first port travels with it.
Zebra and quagga mussels reached the Great Lakes from Europe in the 1980s and spread through the eastern waterways from there. Once a population establishes, it does not get removed. It gets managed, annually, forever, by somebody who had no part in bringing it.
That permanence is why the regulation is so strict. No remediation budget buys the water back.
The convention, in five lines
| What | Detail |
|---|---|
| Ratification threshold met | 8 September 2016 — 30 states representing 35 percent of world merchant shipping tonnage |
| Entry into force | 8 September 2017 |
| D-2 standard, ≥50 µm organisms | Fewer than 10 viable organisms per cubic meter of discharge |
| D-2 standard, 10–50 µm organisms | Fewer than 10 viable organisms per milliliter of discharge |
| Phase-in for existing ships | Completed 8 September 2024 |
Source: IMO — Ballast Water Management Convention and IMO — implementing the BWM Convention.
Where a single pass stops
The microbial indicators and the smaller organism class are within reach of a contained oxidation stage, against a stated worst-case influent load. The largest class is not. Resting cysts and big zooplankton are the most oxidant-resistant things in a ballast tank, and a type-approved shipboard unit reaches them by holding the water in the ship's tanks for the length of a voyage. The reactor is high-flow and holds nothing back, so the resistant class stays out of scope, named in the scope document in writing before anyone signs.
None of this is a compliance figure. The standard in the table binds a ship and its own ballast water management system, and a service hull is neither. When ballast has already gone over the side, from a failed unit, a violation or a quarantine berth, the obligation stays with the vessel that discharged it. The work is judged by whether the water in the basin is better afterward.
What NOAA's centers found
On 1 July 2020, NOAA's National Centers for Coastal Ocean Science published that NCCOS-affiliated testing, carried out under a cooperative research and development agreement, had evaluated a commercial nanobubble ozone system on ship ballast water. The system was highly effective at controlling algae, bacteria and motile zooplankton. There was no statistically significant adverse residual-toxicity effect on organisms in the receiving water.
Killing what is in the tank is easy if you will discharge something unpleasant. Killing it and discharging water the harbor can live with is the engineering port states inspect for.
What the release establishes
The NOAA release names other technology and other partners. It does not name ChemSlayer, SeaBreather or Alarivean. It establishes that a nanobubble ozone approach can meet this duty without a residual-toxicity penalty. It does not establish this system.
The system under test is called Nanobubble Ozone Technology — NBOT, the same abbreviation Sophia Delta uses for Nano Bubble Oxidation Technology; the two belong to different companies. The cooperative agreement covering that work is theirs as well. Alarivean completed the term of one of its own with NOAA, entered via AMURI and private in the ordinary way of such agreements. Its subject was toxin chemistry: disable the groups on a molecule that do the harm and the harm stops, with every atom still accounted for. That term is over and no CRADA is in force today. Dr Peter Moeller carries the relationship on as an advisor.
Why the same stage rides on a service hull
Type-approved systems live aboard the vessel and treat on uptake or on discharge, the right architecture for routine trading. It leaves open what happens once the routine stops.
A ship arrives with a failed treatment unit and a port state that will not accept the discharge. A ship sits in quarantine with tank water nobody wants moved. A basin has an established invasion that no individual ship caused and no individual ship will solve. A terminal wants to know what is entering its water, which no certificate issued in another port can answer. In each case the problem now belongs to the basin, and a treatment stage brought to the water beats a second retrofit.
The treatment train sits inside the service hull, so nothing is cut into your engine room. Water is drawn in, worked on as it moves through and released against the standard into the same berth or basin it came from. Nothing accumulates on the treatment side of the intake, and nothing leaves the area in a hold. Where a residual oxidant has to be knocked down before release, hydrogen peroxide does that job. A sulfur reductant would exert an oxygen demand of its own and eat the enrichment the discharge exists to deliver.
For ship operators
Variance between port states is what the standard actually costs.
A convention is one document. Its enforcement is dozens of port states with different sampling regimes, tolerances and appetites for detention.
A service capability covers the cases an engine room cannot answer. A shipboard unit down at the wrong berth. A port state reading the convention harder than the last one. Tank water that has to be treated where it sits and put back into the same berth. Rare per vessel, constant per fleet.
Pricing is an ongoing subscription against the water outcome agreed for a defined port zone, held with a licensed service operator. You are not renting the hull or buying its hours. It runs continuously, so it is there when your rare case turns up.
It ends on two grounds. Performance outside the specification written into the agreement, whenever that happens. Or, once the minimum subscription period has been served, a fleet that is not satisfied, with no cause to argue and no fault to establish.
For port and terminal authorities
You inherit the basin decisions anyone else makes.
A port authority does not control what arrives. It answers for the water afterward — to a regulator, a fishing community, a city that can see the basin from its waterfront.
Ballast is one input into that basin. Discharge, spills and heat are others. They arrive separately and compound, so a port program is usually scoped as one service zone carrying several capabilities — characterized once, consented once, contracted once. The same hull can run a ballast quarantine duty on Monday, work a sheen on Wednesday and hold dissolved oxygen through an August week when the basin goes still. One contract, one crew.
The contract runs continuously because the loading does. Ballast arrives on every tide, the outfall never pauses and the heat comes back on schedule. A program that turns up only for the worst of it inherits everything the quiet months put there.
Reporting is written for the body that will ask — method, dose, position, time, result, per pass.
Questions from the compliance desk
Five compliance questions
Does ChemSlayer replace a type-approved ballast water management system?
No. Where a flag or port state requires a type-approved system aboard the vessel, that requirement stands, and the scope says so in writing.
ChemSlayer is a service capability used alongside it: for tank water that cannot be discharged, for quarantine situations, and for basins where the problem belongs to the authority and no single ship can be sent the bill.
What exactly did NOAA validate?
NCCOS-affiliated testing under a cooperative research and development agreement evaluated a commercial nanobubble ozone system on ship ballast water. It was highly effective against algae, bacteria and motile zooplankton, with no statistically significant adverse residual-toxicity effect on receiving-water organisms.
It names other technology and other partners. Not this one.
Source: NOAA NCCOS, 1 July 2020
Does treating ballast water with ozone create bromate?
It can. Bromide takes ozone about eighty-three times more readily than chloride does, and what comes off that reaction can go on to become bromate.
Bromate is stable and cannot be quenched back out, so the stage runs enclosed and instrumented. Formation needs bromide over a threshold that salt and brackish harbor water does not reliably reach, and dissolved carbon competes for the ozone. Both are assessed for the basin before a hull is committed.
The limit is whatever governs your receiving water, fixed when the port's regulator consents the duty and written into the service level agreement before a hull sails. If no regulation covers that harbor, the discharge is held to the known safety limits for marine life. No fixed number is published. Bromate runs on its own near-real-time analytical channel with independent laboratory confirmation on an agreed cadence, because inline probes cannot see a stable end-product. The port authority can halt an active deployment on any suspected infraction until it is cleared.
Source: Ozone: Science & Engineering · discharge standard supplied by Alarivean
What does one pass reach in ballast water?
The microbial indicators and the smaller organism class, on a single pass, against a stated worst-case influent load. That is never a D-2 compliance figure.
The largest class, resting cysts and big zooplankton, is excluded in writing. A shipboard unit reaches it by holding the water for a whole voyage; this reactor is high-flow and stores nothing.
Can you certify compliance for us?
No. Certification is the business of the flag state, the port state and the recognized organizations they appoint, and a service operator is not one of them.
What the operator provides is treatment, instrumentation and a record of what was done — in a format an inspector can read without an interpreter.
Next step
Start with the basin and the traffic.
Send the basin, the traffic, your discharge regime and the failure mode that worries you. Alarivean returns a read on whether this belongs in your port.