Reverse osmosis, UV and ozone do three different jobs, and none of them is a drop-in replacement for another. Reverse osmosis removes dissolved material from water by pushing it through a membrane. UV inactivates organisms as water passes a lamp. Ozone oxidises contamination chemically and then has to be removed again. Choosing between them starts with deciding which problem you actually have.
What Does Reverse Osmosis Actually Do?
Reverse osmosis (RO) is a separation process. Water is forced under pressure through a semi-permeable membrane that lets water through and holds back most dissolved salts and many other dissolved substances. What comes out is a purified stream, and what is left behind is a more concentrated reject stream that has to go somewhere.
That makes RO a tool for changing what the water contains: salt content, hardness, dissolved minerals. It is not a disinfection method. A membrane is not a guarantee against microorganisms, and RO water that is stored or piped onward can pick up contamination again. In swimming pools it is rarely part of the circulation loop. Where it appears at all, it is on the fill-water side, for example when the mains water is very hard or when dissolved solids have built up and part of the volume is being replaced.
The honest limits: RO uses energy to create pressure, it produces a reject stream, the membranes need cleaning and replacing, and it does nothing about the chloramines and organic load that bathers add every day. NanoSWIM does not sell RO, and it would be the wrong answer to a smell or clarity problem.
What Does UV Treatment Do in a Pool?
UV is a light-based disinfection step. Water in the circulation loop passes through a chamber with a lamp, and organisms exposed to enough UV dose are inactivated because their genetic material is damaged. Many UV systems for pools sit after the filter, so the water is as clear as possible when it reaches the lamp. Clear water matters, because particles can shade organisms from the light.
UV is well suited to organisms that are tolerant of chlorine. Some plants also use it to reduce combined chlorine, depending on the lamp type, so the details of the system matter. Read the supplier's documentation rather than assuming.
The limit that surprises buyers: UV leaves no residual. Disinfection happens at the lamp, not in the basin. Once the water has passed the chamber, nothing in it protects against contamination arriving from the next swimmer, so a Norwegian public pool still has to keep a measurable disinfectant residual in the water. The lamp also ages and the quartz sleeve fouls, so output has to be monitored and the lamp replaced on schedule. We compare it in more detail on the UV comparison page.
What Does Ozone Do, and What Do You Have to Deal With Afterwards?
Ozone is a strong oxidant. Dissolved in the water, it attacks pathogens and breaks down organic compounds, which is why it has a long history in pool and drinking-water treatment. It also reverts to oxygen and leaves no residue.
The practical issue is delivery and removal. Ozone is a toxic gas, and conventional installations typically inject it into the water, give it time to react in a contact vessel, and then remove the remaining ozone before the water goes back to the pool. That means more plant-room space, a destruction step, and a gas that has to be monitored for safety. Like UV, it acts on water passing through the system and leaves no persistent residual in the basin. See the ozone comparison page for the longer version.
Where Do Nanobubbles Fit Next to These Three?
Nanobubbles are a way of delivering a gas, not a fourth disinfectant. They are gas-filled bubbles under roughly 200 nanometres in diameter. At that size they do not rise and burst; they stay suspended for days rather than seconds, and their very large combined surface area makes gas transfer far more complete than coarse injection, where most of the gas escapes at the surface. With ozone as the gas, their collapse releases concentrated oxidative energy, which is advanced oxidation: it disrupts pathogens and breaks down organic load.
NanoSWIM installs the treatment inline in the existing circulation loop, after filtration, with no separate contact tank. Our published figure is 99.9% pathogen reduction, for oxidative disinfection in the treatment loop, and up to 90% reduction in chemical use against a conventional chlorine dosing regime on comparable pools. The technology page explains the mechanism in more depth: how nanobubble treatment works.
It shares the limits of the others. It is a treatment-loop technology, it leaves no persistent residual in the basin on its own, and it does not replace correct filtration, sensible pH control or competent operation. Capital cost is higher than dosing pumps and drums.
How Do They Compare Side by Side?
| Method | What it does | Leaves a residual in the basin? | What you have to manage | Wrong tool for |
|---|---|---|---|---|
| Reverse osmosis | Separates dissolved material from water through a membrane | No | Energy, reject stream, membrane cleaning and replacement | Disinfection, chloramines, organic load |
| UV | Inactivates organisms at the lamp | No | Lamp ageing, sleeve fouling, clear water before the lamp | Replacing a residual in a Norwegian public pool |
| Ozone (conventional) | Oxidises contamination, reverts to oxygen | No | Contact vessel, removal of excess ozone, gas safety | Plant rooms with no space or no gas handling |
| Nanobubble ozone or oxygen | Delivers gas efficiently for oxidation inline | No, not on its own | Flow rate and plant-room fit, filtration and pH control | A pool with failing filtration or poor operation |
Which One Should You Ask About First?
Match the method to the problem before you ask for quotes.
- Hard or salty fill water, or dissolved solids creeping up: ask about RO or partial water replacement.
- Chlorine-tolerant organisms or high combined chlorine: ask about UV, and which lamp type.
- Heavy organic load and a smelly hall: ask about oxidation in the loop, with ozone or nanobubble delivery.
- Any of the above: ask what happens to the residual, and what documentation the supplier can show.
Compare against what you already run. A chlorine pool, a salt pool and a loop-treatment system fail in different ways, and our comparison overview lays them out side by side, including conventional chlorine and salt chlorination. For Norwegian public pools, the requirement is set by forskrift om badeanlegg, bassengbad og badstu and enforced by the municipal health authority; Folkehelseinstituttet (FHI) publishes guidance. NanoSWIM does not claim any certificate or approval, so ask every supplier, including us, what documentation they can provide. The standards page lists what the buyer must satisfy.
In my own experience, nobody ever asks me about the chemistry first. They say the water looks sharper, and the operator is usually the first to notice, well before any test result moves. On a job I worked on myself, the technician took me down to the deep end and pointed at the lane lines on the floor tiles, saying he could finally see where the black line stopped and the joint began. I have stopped being surprised by that. Test strips tell you the number; the person who cleans that pool every morning tells you whether it worked.
If you are weighing these methods for a pool, hotel or public facility, contact NanoSWIM in Bergen with your pool volume and flow rate. We will tell you plainly if another method fits your problem better. For flow rates up to 500 m³/h, the NanoSWIM Pool System is where we would start the conversation.