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As a Hanovia Dealer:
I just wanted to point out that the proliferation of THM's can occur when chlorine levels are higher than the recommended levels. When UV is used as a supplemental Sanitizer, it is recommended that the Free Chlorine Levels are to be kept at the low spectrum of the Health Dept. Regulations.
DPB's can also be created when a pool that isnt on UV maintains over 2.0 ppm chlorine.
High Capacity Feed Chlorination is a solution that is rapidly becoming an option... Addressing the FUNDAMENTAL Issue in Pool Chlorination is the answer...
If one were to use a Free Chlorine (FC) level that is around 20% of the Cyanuric Acid (CYA) level, then that is roughly equivalent to 0.2 ppm FC with no CYA and would significantly lower the amount of disinfection by-products IF the organic precursors to such by-products were destroyed/oxidized/modified by a supplemental system to the point where chlorine will no longer create the chlorinated by-products. Also, even if such a system did not do anything to some precursors, a low active chlorine level would still result in cumulatively lower disinfection by-products if those by-products themselves were destroyed/oxidized/modified by supplemental systems.
Unfortunately, there isn't a lot of detailed data on the main supplemental systems of ozone, UV and MPS to know the fate of the large variety of possible disinfection by-products, both chlorinated and brominated.
There's no way I'd want a pool with 2 ppm FC and no CYA as is often the requirement for U.S. indoor pools, as compared to DIN 19643 in Europe where 0.3 to 0.6 ppm FC is used (0.2 to 0.5 ppm if ozonation is part of the process). Not only is the active chlorine level much higher with 2 ppm FC and no CYA resulting in faster chlorine reactions in general to create disinfection by-products (as well as oxidizing bather waste), but it also has chlorine react with skin, swimsuits and hair that much faster as well as react with some pool materials to corrode metal or degrade some plastics and fibers (e.g. pool covers). My wife has personal experience with this difference between an indoor commercial pool at around 1-2 ppm FC with no CYA vs. our own residential outdoor pool with an FC of 3-6 ppm with 40 ppm CYA and the difference is night and day -- her swimsuits degrade in just one season at the commercial pool and her skin is flakier and hair frizzier while in our own pool the swimsuits last for years and the effects on skin and hair are far less noticeable.
The much better scenario is to have the bulk of the overall oxidation and/or removal of bather waste and related chemicals (e.g. suntan lotion) to be via coagulation/filtration and supplemental oxidation (or UV break-up) while having the active chlorine level be low to provide the necessary bulk water disinfection.
Wow, how to resurrect a thread! Good topic though.
What I try to get done is first an auto feed system, and I love liquid chlorine and Muriatic acid for their ease of control. Then Ozone, but properly dosed and contacted. The little units that get used to pump ozone directly into the water can be construed as useful but to get the benefits that Ozone is touted for you need to use a system and you need to drop some buckage.
THM's and DBP's in general will be created when oxidizing with chlorine but not so with Ozone, or for naysayers, at least not anywhere near the extent as chlorine. So a good Ozone system will oxidize most everything meaning the chlorine will be the free residual we want and wont be creating DBP's. Even with a good Ozone system I like to start them at 2ppm FC and drop it over time until they see combined starting to get created.
Now that said, another system I am not all that excited about using is salt. I would love to get a pool going I can monitor that uses liquid chlorine and some salt added just so you get some of that salt "feel" that people want. I would like to see this operate for a few years to see the results.
What I do have now is a new pool with salt and Ozone and CO2. When I have used CO2 before, which was mostly commercially, I ended up switching it back to acid because the CO2 cost was too high. However I am currently marveling at the stability of the chemistry in this pool and wondering if the Ozone is actually oxidizing any of the salt. It seems I can elevate the chlorine level simply by upping the Ozone dose. And the alkalinity level seem to hang on forever.
And yes, I do like UV and people seem to finally get it that the flows and doses need to be right. Before with the "lo" pressure UV I think most systems had way to much water flow through them to be useful.
Rick:
http://www.up.ethz.ch/education/term_paper/termpaper_hs07/RIEDER_re...
Mentions that Ozone also produces DPB's - I just wanted to point that out, because the US model for Ozone treatment has ALWAYS been criticized...
I am still trying to find the link to the US study mentioning the relationship between UV and DPB's...The study is not completed yet - FYI...
Yes, Ozone and Bromine combinations were and probably still are used, especially in spa chemistry. About 30 years ago I thought Bromine was a great system, by reading about it. Not long after I started to realize that it was too easy for people to amass huge bromine banks in their water. (might be part 1, depends on what you use I guess) Instead of adding the part 2 oxidizer only they would add both again. Hence the bad odors associated with Bromine systems. Along came Ozone and you could then apparently dispose of part 2 as the Ozone was doing things like oxidizing the bromamines back into the bromine.
It gained a lot of popularity even into the commercial world but seems to have fallen by the wayside now. Could be because of the DBP info that has been coming out
However, in the chlorination world it isnt the issue as in the Bromine salts world. I find myself wonder about the salt world in general now tho as it pertains to the topic.
In general, the brominated disinfection by-products are more harmful than the chlorinated ones. Any strong oxidizer, be it chlorine, ozone or MPS, will oxidize bromide to bromine which can then react with organics to produce brominated DBPs. So not only will bromine probably eventually fall by the wayside, but finding a way to remove bromide from fill water would also be helpful. The higher mutagenic/genotoxic rates in some of the Barcelona papers were due to the relatively high bromide levels in the fill water of that city:
http://link.springer.com/content/pdf/10.1007%2FBF01636483
though such bromide levels were "only" 2-3.7 ppm, but that was enough to have >> 100 ppb brominated THM levels.
Hi Scott and Matt,
Could you back up that some European countries banned the use of UV, especially in Austria?
Howard,
As a UV manufacturer, running an R&D dep, I follow up very closely all development about UV treatment especially in Aquatics. I would like to make a few comments about your post.
First, I would conclude that THM appears in chlorinated water, UV or not.
About France, the THM reduction and data collection is made by regional agencies on a volunteered basis. We will see what the AFSSET says about all those datas.
In fact there is a study that shows that UV reduces 2 THMs out of 4. To avoid any confusion, I would precise that UV & THM issue refers only to medium pressure systems and has nothing to see with low pressure.
By reading Al,
I would like to correct that I've never seen any claim such as "99,99% reduction of chloramines". For chloramines reduction, please refer to Delta's presentation at the 2010 WAHC in Colorado Springs. On the other side, we claim 99,99% of bugs eradication which is certified by 1/3rd party bodies such as NSF, O NOrm, DVGW, etc.
There are numerous surveys, studies around the world showing the bad effect (I am not talking about UV) of chlorinated pool (France recognized as a professional desease, 100% reimbursed byt the health car system, a long exposition to chloramines).
Researchers are working on UV water treatment, and as of now, I am not sure that I ve seen something that says something totally against treating water in Aquatics, or which would endangered the swimmers. Unfortunately, what I see is some lobbying trying to ban UVs.
The future seems even to be brighter on the UV side: Many studies are currently being conducted that should reveal additional benefits of UV in water treatment. There could also be some interesting results regarding the reduction of Nitrosamines (which are highly carcinogenic). Last, while not related to pools, it’s interesting that some recent research indicates that with UV there may be a reduction of pharmaceutical residue in water.
Thanks for the conversation Gents. Rex Richard's recommended this article during a Pool Genius Academy webinar this week. Thanks Howard for your forthright position. Alan Lewis' article;
http://www.allchlor.com.au/newsview/chloramines-in-your-swimming-po...
At Dryden Aqua we manufacture UVc low pressure systems and we purchase medium pressure units for resale to our clients. However we do not use UVc for swimming pool water treatment on ethical grounds, given that we know the technology has the potential to harm the public and pool staff.
There are many variables involved in the equation such as UV irradiation level, light spectrum, concentration of precursors etc etc. Given the right conditions, UV irradiation will reduce the size of organ-chloramine molecules to produce a higher concentration of more volatile smaller molecules. The main THM is the smallest molecule which is chloroform, other volatile molecules such as cyanogen chloride will also increase after UV and may reach concentrations as high as 0.14 mg/l in the water. A proportion of the volatile molecules will escape the water and enter the gas phase above the water. The maximum 15 minute exposure level for cyanogen in the atmosphere is 0.77 mg in 1000 litres of air, so it just takes 6 litres of water in the pool to degas and you reach the maximum level in 1 cubic meter of air.
Given that the small molecules are lipid soluble, they will pass through your skin and lung tissue and enter your blood. The blood brain barrier does not stop their passage and we know for sure they are implicated in causing neurological harm. We also suspect that if young children under the age of 2 are exposed to lipid soluble chlorinated chemicals they impact on the development of children and may cause spinal deformities such as scoliosis 10 to 15 years after the initial exposure. The German Environment Agency now suggests that perhaps it is not a good idea for children under 2 use a chlorinated pool.
It will be many years before the dangers are fully analysed and quantified, so at the moment we really do not know what is happening, all we know is that there is a cause and an effect. As opposed to waiting for the next 10 to 20 years for the laboratories to analyse the problem and quantify the dangers, we have taken the position to avoid the issues by not using UV.
The French authorities have a decree relating to UV, and require the atmosphere to be monitored for THM`s. An update is due for release in a few weeks, I will post the report as soon as it enters the public domain. I do not expect UV to be banned but the THM level may be reduced to a concentration that may make it very difficult to continue to use UV irradiation of chlorinated water.
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