Salt Electrolysis and UV Lamp for Pool?

UV will destroy the chlorine by reducing it to hydrochloric acid, so this may not work.

What part of it

DVader is correct, UV light will execute your chlorine.

I think what you are wanting is an ozone generator, many of which are marketed for swimming pools. I would suggest considering only the corona-discharge type, because the type that uses UV to generate ozone requires anual bulb replacement (VERY expensive bulbs). Do not look at the low end of the market- for $200 it is unlikely you will get much satisfaction. For your 15,000 gallon pool, there are a number of options that would begin in price around $1200-$2000 (and up, if you really want to get fancy). Generally, corona discharge units are much more expensive initially than UV ozone generators, but last a whole lot longer (some manufacturers claim up to 5 years...). We have been using corona discharge ozone generators in a number of locations, not only for swimming pools, but for pretreatment of potable water as well. For swimming pools with a properly sized ozone generator, no additional chemicals are required (this is in the tropics where it takes less than 24 hours for an algae bloom in untreated water). I haven't tried an ozone generator with a salt water pool, though.

Many thanks to RGO for his detailed answers.

Following the salt system manufacturer´s advice for my outdoor pool I need to add cyanuric acid (best level 30 ppm) to stabilize the chlorine. I am testing this at the beginning of the season and add if needed. I also read about the risks of overdosing the cyanuric acid and "locking" the chlorine. I did not know that urine raises the level.

Regarding the UV system, the previous comments of CR4 users warned from the combination because of the additional oxidation of the chlorine.

The fact that there seem to be installations out there (like the one that RGO is maintaining) that combine both systems, might suggest that the UV can do more good than harm.

The suggestion of RGO to install the UVC lamp upstream from the chlorine generator makes sense to me. I am not sure about his suggestion to have it downstream the filter. I have read though that if installed upstream the filter, UVC helps the retention of algae by the sand filter. That would be very interesting for anyone with algae problems, or not?

Thanks a lot in advance for your contributions.

The suggestion of RGO to install the UVC lamp upstream from the chlorine generator makes sense to me. I am not sure about his suggestion to have it downstream the filter. I have read though that if installed upstream the filter, UVC helps the retention of algae by the sand filter.

Is algae not a pertinent component in the effectiveness of a sand filtration process? I'm thinking so and may it be a reason to implement UV downstream of the sand filter.

Are you sure about the acid you're adding? The commonly used type would be sulfuric or hydrochloric acid, in different stabilized commercial forms.

Cyanuric would form in the water if there are dejects or urine, as far as I know.

Concerning the UV before the filters, if dead cells pass the UV, less radiation will strike the living ones. If you think of radiation as inhibiting cell growth, not destroying them, this will not be correct.

On the other hand, filters will only retain dead organic matter, because it will become more aggregated, after reacting with chlorine (mostly inside the pool). So, it's best to filter before the radiation treatment.

Chlorine locking will occur if pH is outside the 7,5-8,5 range.

As for the UV side effects, if the lamp radiates in the 560 nm wavelength, the chlorine level should not be too affected.

cheers

Thanks mycr4id for your link.

Regarding RGo´s comment:

Cyanuric acid is commonly used as stabilizer/conditioner of salt water pools. It is included in chlorine tablets and long term use of these tablets can bring the cyanuric levels to a level that impedes the chlorine to work. Dilution with fresh water is then the only fix. I know because I am buying this product in powder form for the salt water pool independently of the hydrochloric acid used for pH control.

Hi Urbie

The filter removes particulates, many of which provide food for bacteria, others provide protection and a "home".

The more thoroughly you remove these particulates, the more effective chlorine, ozone and/or UV will be. Any particulates not removed provide shelter for bacteria (and algae spores) from the chlorine, UV and ozone.

UV has no residual effect. Once it has zapped the bugs as they pass beneath the lamp, it's effectiveness ceases. Some of the dead bacteria will provide food for bacteria which were not killed or have re-infected after the UV (from piping, the atmosphere, people, pets etc).

Ozone has a short residence time. While effective, the residual effect is of short duration. To compensate, the flow rate to the pump is sometimes increased, so that any particular bit of water is treated more often.

Chlorine (and bromine) compounds are cheap, have a long lasting effect (good residual) and fairly easy to use. This is why they are so widely used.

During the cold of winter, the reaction rates slow down, but so does the rate of multiplication of bacteria and algae.

UV and ozone are often used together, in fact ozone generation is usually accompanied by UV generation, if UV isn't used to generate the ozone. (The corona generators also generate UV, although that is not their primary purpose.) It supplements chlorine if used before chlorination and can substantially reduce the chlorine required as well as improving the residual effectiveness of the chlorine.

There is no reason ozone and/or UV wouldn't work just as well in salt water as in fresh, although to use them without chlorine you need a proper system, not just one grafted on to a conventional salt water chlorinator.

Even though these people treat fresh water, they developed an excellent pool management system that utilizes, amongst others, uv-treatment of the water - POOLCOP - www.apmi.co.za. Contact them. Even if you don't utilize their system I found them to be quite helpful with general questions on pools like yours.