Water Treatment for Public Pools and Aquatic Centres

The challenges in a public aquatic facility

A municipal swim hall is two buildings in one: a public leisure space upstairs and a chemical process in the plant room below. Almost everything a pool operator is judged on — water quality, hall air, energy use, complaints, the budget line — comes out of how those two are balanced.

The problems are remarkably similar from one facility to the next:

• Bather load swings hard. A Tuesday morning with two aqua classes and a Saturday with four hundred children are not the same water. Dosing set for the average is wrong twice a day.
• Chloramines accumulate in the hall. Combined chlorine leaves the water surface and collects exactly where people breathe.
• Ventilation compensates. Air handling is often the largest energy line in a swim hall, and part of that capacity exists purely to carry away what the water gives off.
• The building pays. Chloramine-laden air is aggressive towards ductwork, fixings and untreated metal. Corrosion in a pool hall is slow, expensive and invisible until something has to be replaced.
• Staff are exposed for a full shift. Lifeguards, swim instructors and cleaners are at the water’s edge for hours, at the height where the worst of the air sits.
• Documentation is constant, and chemical prices only move one way while a municipal budget is agreed a year in advance.

None of this is a reason to abandon chlorine. It is a reason to make the pool need far less of it.

Chloramines, air quality and staff health

Free chlorine is not the problem. What free chlorine produces is. When it meets sweat, urine, skin cells, sunscreen and cosmetics it forms chloramines — combined chlorine — and the volatile fraction leaves the water and settles in a layer above the surface.

This is why the smell test misleads people. A hall with a sharp chlorine smell almost always has a combined chlorine problem, not an excess of free chlorine. A well-run pool smells of very little.

For a facility with an instructor corps, indoor air quality is not only a comfort question. Swim teachers, lifeguards and cleaning staff spend a whole working day at the water’s edge, and unlike the public they are there every day. Competitive swimmers in daily training, small children and guests with asthma feel it next. It shows up as complaints, as swim clubs booking elsewhere, and sometimes as sick leave.

Water treatment is one of three levers. The other two are ventilation design and pre-swim showering discipline. If the air handling is undersized or the shower routine has slipped, no treatment system rescues the hall on its own — and we would rather say that at the site visit than after the invoice.

How nanobubbles cut chemical use

A nanobubble generator sits in the circulation loop after filtration. It dissolves oxygen or ozone into the passing water as bubbles under roughly 200 nanometres across. They are far too small for buoyancy to lift them out, so instead of rising and bursting they stay in suspension, and their enormous combined surface area transfers gas into the water far more completely than coarse injection manages. The underlying science is on How nanobubbles work.

What that changes in a commercial pool water treatment loop is straightforward:

• Organic load is oxidised as it passes through the system, so there is less material left in the basin for free chlorine to react with. Fewer chloramines form in the first place, rather than being destroyed after the fact.
• Chlorine demand falls, so the same disinfection result holds at a much lower dose.
• Fine particles and biofilm lift off surfaces and reach the filter, which is why operators usually notice the clarity before the log sheet confirms anything.
• Combined chlorine in the basin falls, and the hall air follows it down.

What it does not do

It is a loop technology. It treats the water that passes through it, at the turnover rate your plant already runs, so it cannot act on contamination in the basin the instant a bather introduces it. It does not replace filtration, pH control or coagulation, and it does not remove the residual requirement in a public basin. It also will not fix a hygiene problem: showers, hair and body-oil load are still yours to manage.

And if your facility is small and your chemical spend is already modest, the payback period is long. That is a legitimate reason not to buy this. The system built for high commercial bather loads is NanoSWIM Pro; the application-level explanation for basins of every kind is under swimming pool water treatment.

Retrofitting into an existing plant room

Practically every public installation is a retrofit. The basin, the pipework, the filters and the dosing equipment stay where they are; the generator is plumbed into the existing loop. What we check before quoting anything:

1. Flow and turnover. Circulation rate, filter capacity and the basin volumes on your permit. This decides which unit fits, and whether it runs full-flow or on a side stream.
2. Plant room space and access. Where the unit can stand, how the pipework routes to it, and whether it fits through the door — a real obstacle in older municipal buildings, and better found now than on delivery day.
3. Power supply. Available circuits, and the kW draw at the flow rate you actually run rather than the one on the nameplate.
4. Gas handling. Where ozone is part of the specification, off-gas destruction and plant room ventilation belong in the design, not in a later accessory order.
5. Control and logging. How the unit is monitored, what it writes into your existing log routine, and who receives an alarm at 03:00.
6. Commissioning window. Installation normally fits inside a planned maintenance shutdown, so tell us your shutdown weeks early.

A retrofit does not strip out your dosing plant. It stays, it doses far less, and it is still there if you ever need to lift the residual quickly.

Compliance: what the regulations actually require

Norwegian public pools operate under the bathing-facility regulation (forskrift om badeanlegg, bassengbad og badstu), enforced locally by the municipal environmental health office. The regulation is written around water quality, control routines and documentation rather than around one approved technology, and that has one consequence every buyer needs to understand before writing a specification:

• A public basin generally has to maintain a measurable disinfectant residual, so that what one bather introduces cannot reach the next before the water has circulated and been treated.
• So a zero-chlorine public pool is not a realistic goal in Norway, and any supplier who offers you one is either mistaken or not talking about a public facility. Municipal pool disinfection with nanobubbles means a strongly reduced chlorine level, not the absence of chlorine. What that reduction buys is still real: the smell goes, the eye irritation goes, the chemical line falls, and the residual on your log stays inside the permit.
• EN 15288 — part 1 for design, part 2 for operation — is frequently referenced in Norwegian tender documents. It is a safety and operating standard for swimming pools, not a product approval, so ask every supplier which standards their documentation actually refers to, and what is certified versus what is merely "designed in accordance with".
• Whatever you install, the health authority’s questions stay the same: what is measured, how often, by whom, and what happens when a sample deviates.

We keep the detail — which rules apply to a Norwegian bathing facility, what documentation to demand, and the questions worth putting to every supplier including us — on regulations and standards.

Operating budget and payback

Nobody signs off aquatic facility water treatment on comfort alone, so here is the honest shape of the numbers.

• Capital. Higher than dosing pumps and drums. It is an equipment purchase, and it belongs in the investment budget rather than the operating one.
• Chemicals. This is the line that moves, and it moves permanently. It is also the easiest saving to verify: twelve months of delivery notes before, twelve months after.
• Energy. Two directions at once. The unit adds a modest continuous load; the air handling can often be turned down once combined chlorine falls. The net result depends on your building, and it should be calculated, not assumed.
• Consumables and service. Ask what wears, how often and at what price — before signing, not after.
• Building maintenance. A less corrosive hall atmosphere slows down what you would otherwise be replacing. Real, but hard to put on an invoice, so treat it as upside rather than as the business case.
• Payback. For a busy facility with a large chemical spend it is short. For a small pool with a modest one it is not. We would rather calculate it with you than publish a generic figure that fits nobody.

Budget line	Conventional dosing	With nanobubbles in the loop	How to verify it
Chemical purchasing	Full dose, all year	Substantially reduced — up to 90% less on comparable pools	Compare twelve months of delivery notes, before and after
Combined chlorine	Rises with bather load	Formation suppressed at source	Your existing log; the parameter is already sampled
Hall air and ventilation	Air handling sized to carry chloramines away	Lower load once combined chlorine falls	Ask your ventilation contractor what the setpoints allow
Building and fixtures	Continuous corrosive load	Reduced	Judge it over years, not months — and budget it as upside
Staff environment	Exposure for a full shift	Tracks combined chlorine downwards	Ask the instructors, and log it as seriously as a water sample
Capital and service	Dosing pumps and chemical storage	Equipment purchase plus a service agreement	Ask for total cost over five years on your own basin volume

These are directions, not promises. Every figure depends on bather load, water temperature, turnover rate and local chemical and energy prices. The only number worth budgeting on is one calculated against your facility — ask us for it, and ask every competing supplier for the same thing on the same basis.

How we deliver in public tenders

Municipal purchasing has its own rules, and a supplier who does not respect them wastes everybody’s time. Two things matter more than the rest.

First: specify function, not brand. A tender that names a product invites a complaint and narrows the field. A tender that states what the water and the air have to achieve lets several suppliers answer, and leaves you with something you can hold the winner to afterwards.

Second: make every claim measurable at handover. A promise that cannot be tested at commissioning is not a requirement, it is a sentiment. Clauses worth writing into a public tender:

1. Water quality parameters and the residual range your permit expects, with the sampling and logging routine that proves them.
2. A target for combined chlorine in the basin, and — if you have ever measured it — for the hall air above the surface.
3. Documented chemical consumption before and after, with the measurement method agreed in advance.
4. Energy draw in kW at your circulation rate, stated by the supplier and verified at commissioning.
5. Total cost of ownership over five years: equipment, installation, consumables, service and energy in one figure.
6. Service response time, spare-part availability, and what happens when the nearest engineer is not in Norway.
7. Documentation: technical description, commissioning report, operating instructions in Norwegian, and training for the operating staff.
8. References from comparable facilities, with a named contact who will actually take the call.

We answer tenders on those terms and we are comfortable being measured against them. If a requirement in your specification rules us out, you will hear it from us at the clarification stage rather than in an answer that stretches.

References

The result we publish with figures attached is a resort pool that cut chlorine consumption by 85%: the reference with measured results. Read it for what it is — a hotel resort, not a municipal facility with a residual written into its permit. A public pool should expect a smaller reduction from the same technology, because it starts from a floor it is not allowed to go below.

Across pools, industrial water treatment and live fish transport, NanoSWIM systems are in use with more than 500 customers in over 35 countries. What we can document, and what we cannot, is set out on our references.

Ask for a reference visit as well. Standing in someone else’s plant room tells you more than any brochure, and it is the normal way this kind of equipment gets bought.

Book a site visit

The first step costs you an hour. We come to the facility, look at the plant room, take the basin volumes, turnover rate, current dosing regime and a year of chemical purchasing, and come back with a written answer: what a system would cost, what it would save, what it would change in the hall, and what it would not touch.

If the numbers do not work for your facility, the answer will say so. Book a site visit and we will bring the calculation rather than a brochure.