Zeolite

[chem geek]

This thread discusses some technical attributes of Zeolite. There are quite a few posts regarding zeolite, but a couple that distill some of the pros/cons are one from waterbear and one from JasonLion.

I've done a search of posts on multiple forums on zeolite and it appears that it does usually filter very well, similar to DE, for a clear water look even at night with lights and has a polished look as well. The fine pores could clog and cause the filter to behave more like regular sand, but I haven't seen reports of that -- perhaps regular backwashing prevents that from occurring. There are reports of the filter material getting into the water, presumably from it getting crushed into finer dust that escapes the filter. As noted, using a sand filter with some added DE has the benefits of finer filtration (though not as good as DE itself) with the ease-of-use of backwashed sand.

One claim that the zeolite manufacturers make (see Zeobest, ZeoSand, Zeobrite, Zelbrite, Zel-Eau, Zeoclere) is that the zeolite prevents or reduces chloramine formation, most saying that this is due to the ammonia adsorption. This simply isn't true! Ammonia combines with chlorine very quickly where at normal pool chlorine concentrations (FC around 10% of CYA) the formation of monochloramine happens with 90% completion in around 40 seconds. So there is no way that the ammonia will get to the zeolite filter before it combines with chlorine (unless someone urinates directly into the skimmer!).

A detailed analysis follows. First, let's look at the rate of formation of monochloramine.

See this link for one of many sources for the rate constant of 3.07x10⁶ for hypochlorous acid combining with ammonia. The Wei & Morris model used a rate constant of 6.13x10⁶ as did Selleck & Saunier. The latest full breakpoint chlorination model is from Jafvert & Valentine (1992) that gives 4.17x10⁶ and one can purchase the paper describing this model here.

0.1 ppm FC equivalent with no CYA (using a larger FC would just make the reaction even faster) is the following (all chlorine "ppm" is relative to chlorine gas)
(0.1 mg/L) / (1000 mg/g) / (70.9064 g/mole) = 1.4x10^-6 moles/liter
at a pH near 7.5, half of this is hypochlorous acid, so 7.0x10^-7 moles/liter

So the rate of the reaction of chlorine combining with ammonia to form monochloramine is
Rate = Rate Constant * [HOCl] * [NH₃] = 3.07x10⁶ * 7.0x10^-7 * [Ammonia] = 2.1 * [Ammonia]
and this result is in moles/liter/second

From the above it is seen that ammonia itself combines with hypochlorous acid in under a second (since the net rate factor of 2.1 is >1), but we now need to see how much ammonia there is at a pH of 7.5 since most of it will be ammonium ion and as the ammonia is depleted, ammonium ion will rapidly convert to ammonia so the reaction will continue (with exponential decay).

0.1 ppm total ammonia is the following (all ammonia "ppm" is relative to atomic nitrogen)
(0.1 mg/L) / (1000 mg/g) / (14.0067 g/mole) = 7.1x10^-6 moles/liter

There are many sources for the Ka or Kb of ammonium/ammonia, but this link is a pretty clear one. I'll use the Ka constant of 5.6x10^-10.

[H⁺] * [NH₃] / [NH₄⁺] = 5.6x10^-10
at a pH of 7.5, [NH₃] / [NH₄⁺] = 5.6x10^-10 / 10^-7.5 = 1.8x10^-2
so it is clear that most of the total ammonia is in the form of ammonium ion, NH₄⁺.
Total Ammonia = [NH₃] + [NH₄⁺] = [NH₃] + ([NH₃] / 1.8x10^-2) so
[NH₃] = Total Ammonia / (1 + 1/1.8x10^-2) = 7.1x10^-6 / 56.55 = 1.3x10^-7

so the rate is 2.1 * 1.3x10^-7 = 2.6x10^-7 moles/liter/second

If I ignore the slowdown as the ammonium ion level drops, I get 7.1x10^-6 / 2.6x10^-7 = 27 seconds. The 40 seconds for 90% completion I referred to earlier in this post used the accurate exponential decay formulas and used the Jafvert & Valentine rate constant.

Now, let's look at how quickly monochloramine might be removed via ammonia adsorption through multiple turnovers through the zeolite filter. There is an equilibrium between monochloramine and ammonia, though the reaction is very much favored towards monochloramine.

The equilibrium constant for the reaction of chlorine with ammonia to make monochloramine is 2.0x10¹¹ (ratio of 4.17x10⁶ / 2.11x10^-5 rate constants from Jafvert & Valentine cited above). In case one thinks that there will be a lot of ammonia left for the filter to remove at equilibrium, the amount would be:

[NH₃] = [NH₂Cl] / [HOCl] / K = 7.1x10^-6 / 7.0x10^-7 / 2.0x10¹¹ = 5.1x10^-11
[NH₄⁺] = [H⁺] * [NH₃] / 5.6x10^-10 = 10^-7.5 * 5.1x10^-11 / 5.6x10^-10 = 2.9x10^-9

this is 2.9x10^-9 / 7.1x10^-6 = 0.04% of the total initial ammonia or resulting monochloramine amount. Even if it were completely removed during each pass of water through the filter, it would take thousands of turnovers to remove the monochloramine via ammonium ion adsorption. However, the removal will have more ammonia replenished from monochloramine while going through the filter so we need to look at that rate.

The reaction rate of replenishing ammonia that is removed has a rate constant of 2.11x10^-5 so the rate is:

k * [NH₂Cl] = 2.11x10^-5 * 7.1x10^-6 = 1.5x10^-10 moles/liter/second

[EDIT] I've modified the analysis that follows correcting some errors I originally had -- the errors I had made zeolite look better at removing monochloramine via ammonia absorption than would actually occur. [END-EDIT]

Even if we were to assume that the entire pool's amount of monochloramine were exposed to zeolite and that the ammonia were instantly absorbed by the zeolite, then this implies a half-life for monochloramine of -ln(.5)/2.11x10^-5 = 32851 seconds or 9.1 hours. Of course, only a fraction of the pool's water is in the filter at any time so even if we assume that the water in the filter is there for 2 minutes, compared to even a quick 3 hour turnover this is a factor of 90 so monochloramine reduction would take over a month assuming 24/7 running of the filter.

Of course, there may be some direct absorption of monochloramine into zeolite, though this has yet to be shown to take place.

The bottom line is that the process of zeolite removing ammonium ion from the water would likely result in a negligible reduction in monochloramine and that in any event it would certainly not prevent it's rapid formation so long as there was chlorine in the water.

The only practical way that zeolite could reduce the amount of chloramine production in the bulk pool water would be by filtering out precursors of such production (i.e. small particles), but it couldn't filter out the ammonia quickly enough if there is chlorine in the water (as demonstrated above) and it has not been shown to filter out urea which is the largest component of sweat and urine that upon oxidation most likely produces dichloramine and trichloramine.

I believe what has happened is that someone used two true facts to draw an incorrect conclusion as follows:

TRUE: Zeolite removes ammonia (via ammonium ion) from water that is filtered
TRUE: Chlorine (hypochlorous acid) combines with ammonia to form monochloramine
FALSE: Therefore, Zeolite prevents or reduces chloramine formation in pools

The reason that the conclusion is false is that it requires the ammonia to persist in the presence of chlorine long enough to be able to be filtered out by the Zeolite and that simply doesn't happen. I'm guessing that one manufacturer posted the claim and then everyone else followed suit, just assuming it was correct.

There is a task force on Zeolites as part of NSF International so I've contacted them to see if I can get more info on where this claim came from. I've also contacted the manufacturers noted above. Hopefully, that will clear things up. [EDIT] I am now a member of the NSF Zeolite task force and am giving input to ensure that the experiments are being done properly so we can finally get some real results with these filters to see if they do reduce monochloramine or other chloramines via any means. [END-EDIT]

Richard

 

[Aquaclear-NZ]

i am an absolute believer in Zeolite having sold it for the last 6 years, and use it as our standard media

Here are some of the things i have found

1 - Water Clarity, outperforms DE with research from the university of Adelaide (australia) claiming filtration to 2 mircons. this does however depend on the size/ grade of the Zeolite, there are a couple of manufacturers , if your particle size is the same as pool sand, you do not get the benefit of this fine filtration, for this reason i only carry the particle size of 0.5mm - 2.7mm (you may have to do the math to work this out in inches im afraid)

2) Media return to the pool - this is common at the beginning, the problem can be overcome by giving it at least 3 good backwashes on startup of 8 - 10 minutes each. Zeolite is mined and blasted and during the screening process can accumulate dust

3) Cost - the cost of zeolite is nearly double that of sand - however it has a life expectancy of 10 - 12 years, so over the life of the media it is no more expensive, however it does require a regeneration treatment every 12 - 18 months, remove the top from the filter and pour in a bag of pool salt, let it soak over night, then backwash ( i will cover the reason for this shortly )

4) Requires less backwashing - the media works better as it traps fine particles (like any filter media), this saves water,chemical and heating costs

5) Indoor pools - removes the odour of ammonium/chloramines from the air, i have several written references from both commercial and domestic pools commenting on this. this is much the same reason why zeolites are commonly used as kitty litter

I have attached a small spec sheet that i worte a couple of years ago for our industry professionals

 

[JasonLion]

Aquaclear-NZ,

2) In the majority of cases doing a proper startup backwash keeps any crushed Zeolite from getting into the pool. But there are people who have ongoing problems with crushed Zeolite getting into the pool that can not be solved by any amount of backwashing. Zeolite can be great, and problems are fairly rare, but it still gets too many complaints for me to rate it as a trouble free solution.

3 & 4) The cost and water saving differences are not normally significant enough to be worth worrying about. Neither sand or Zeolite is a significant percentage of the cost of operating a pool and the difference in frequency of backwashing is far smaller than the difference between a normal size filter and an oversized filter.

5) This I simply don't believe. Even if you ignore Chem Geeks reasoning above, which alone is enough to rule this out, the amount of Zeolite used in a filter can't trap any significant amounts of ammonium/chloramines without being regenerated several times per day. A couple of hours after the Zeolite is regenerated it's ability to absorb dissolved impurities will be saturated and won't have any further effect on the water quality till the next regeneration.

 

[chem geek]

Kitty litter absorbs ammonia and so does zeolite. But kitty litter does not have chlorine in it while pools do. This means that in pools the ammonia from sweat and urine combine with chlorine very, very quickly to form monochloramine. So any claim to the contrary is patently false. What you wrote in your write-up is similar to what some manufacturers have claimed and it is completely incorrect to say that monochloramine formation is prevented, at least from the ammonia from bather sweat/urine.

The only question is whether zeolite absorbs monochloramine itself so that chloramines are reduced via multiple turnovers and it is not clear that it does. If you have any links to research data that it does, then please post them so we can follow up on them.

Some manufacturers claimed that because the filter media absorbed ammonia and since ammonia is in equilibrium with monochloramine (both true statements) that the filter removed monochloramine. However, as shown in my lead post in this thread, the reaction rate of monochoramine forming ammonia is far too slow for even an ideal filter instantaneously removing ammonia from being able to remove monochloramine from the water faster than it would get oxidized anyway from chlorine (as shown above, it would take over a month).

I suspect that if there is any reduction in chloramine formation, and therefore smell from chloramines, it is due to the filter removing particulate matter that contains organic precursors that could form volatile disinfection products (organic chloramines). However, a DE filter would likely provide the same benefit. In other words, it's the finer filtration capability that may be of primary benefit, but this is speculation at this point. Of the manufacturer reports of happy users of indoor pools that I've seen, they have all switched to zeolite from sand so it's not clear that switching to DE wouldn't have accomplished the same thing. Hopefully, the work that will be done by the Zeolite task force at NSF International will help settle this issue by seeing how the zeolite filter does with monochloramine and with simulated bather load. If these do not show a benefit, then simulating organic particulate matter could be tried next.

Richard

 

[Guest]

i am an absolute believer in Zeolite having sold it for the last 6 years, and use it as our standard media

Here are some of the things i have found

1 - Water Clarity, outperforms DE with research from the university of Adelaide (australia) claiming filtration to 2 mircons. this does however depend on the size/ grade of the Zeolite, there are a couple of manufacturers , if your particle size is the same as pool sand, you do not get the benefit of this fine filtration, for this reason i only carry the particle size of 0.5mm - 2.7mm (you may have to do the math to work this out in inches im afraid)
Once again I say hogwash. In a high rate sand filter the chamber is pressurized so the water is going to take the path of least resistance, this will be between the grains and not through the pores so even with a .5mm grain size you will NOT be getting micron filtration. Granted it might be somewhat better than sand because of the smaller particle size and less smooth surface in some zeolites (however, most have a very mixed grain size so this might be moot.)

2) Media return to the pool - this is common at the beginning, the problem can be overcome by giving it at least 3 good backwashes on startup of 8 - 10 minutes each. Zeolite is mined and blasted and during the screening process can accumulate dust

3) Cost - the cost of zeolite is nearly double that of sand - however it has a life expectancy of 10 - 12 years, so over the life of the media it is no more expensive, however it does require a regeneration treatment every 12 - 18 months, remove the top from the filter and pour in a bag of pool salt, let it soak over night, then backwash ( i will cover the reason for this shortly )
You are forgetting the acid needed to bring it to the proper pH range also!
You then have an acidic brine to deal with.

4) Requires less backwashing - the media works better as it traps fine particles (like any filter media), this saves water,chemical and heating costs
This makes no sense. If it is more effective at trapping particles it will need more frequent backwashing since the more particulate matter trapped the more backpressure created. An ineffective media would need less backwashing, not a more effective one

5) Indoor pools - removes the odour of ammonium/chloramines from the air, i have several written references from both commercial and domestic pools commenting on this. this is much the same reason why zeolites are commonly used as kitty litter
Zeolite has been used as a filter medium in fresh water aquaira for years for this ammonia scavaging ability. However, in the presence of chloirne this falls apart, as Chemgeek has illustrated! Most of the ammonia scavaging claims come from zeolites use in other water filtration applications and has not been substantiated except in manufacturers literature!
I have attached a small spec sheet that i worte a couple of years ago for our industry professionals

Your brochure reads like a sales brochure. Marketing often has no basis in reality. You will find that a good majority of the membership in this forum (even those not in the industry) are far more sophisticated and informed about swimming pool water chemistry than most manufacturer's reps!

 

[Aquaclear-NZ]

Wow - pretty brutal reaction to someone else's opinion and experiences

the "brochure" is a sales referal and outline for shops and service people

just because someone has a different line of thought to what you subscribe to does not make it rubbish or Crud. you guys are happy to pour litres of bleach into a pool, but shudder at the thought of adding acid (which i have yet to see zeolite raise pH)

There are many manufacturers of Zeolites around the world - and like anything is of varying qualities and mineral makeup, any zeolite that requires loads of acid has a problem. I sell around two tonne of this every month for both new pools and to existing filters, so after around 400+ ton sold and not had any negative feedback, i am fairly confident that it works.
The north American market is really keen on DE, even though as far as most the research goes, handling it will probably give you lung cancer, yet advice is doled out about throwing handfuls into the skimmer to top up filters.

"Another recent study conducted in Belgium has suggested a link between chlorinated swimming pool water and children's asthma. The link is based on the existence of an irritant in the water known as trichloramine, which is produced when chlorinated water comes into contact with organic matter" and infact the link below "swimming pool issues includes research from a variety of sources about what a horrible product chlorine is - and yet do you hear me bagging it - no

there are 3 things what will continue to cause media coming out of a filter to a pool, valve problem, lateral problem (or incompatibility, i have seen this with 20+year old filters) or overfilling

I have never seen or heard of Zeollite causing a rising pH, even in a direct replacement of sand in a pressure filter. New Zealand might not be the biggest market in the world, however i do deal with over 200 service staff, 50+ pool builders and 50 - 60 shops on a regular basis. While not all of them use zeolite - there are enough of them spread around the country that i would be notified of an issue like that. We also supply product to upgrade at least 2 commercial centres per year, this work is gained through work of mouth between pool operators and managers, not as a result of advertising

The chamber is pressurised in a filter - yes, however there are major structural differences between silica sand which is essentially a smooth pebble, relying on trapping the impurities between particles. Zeolite is a lattice of tiny crystals that will trap the fine impurities rather than relying on getting trapped between particles. Without a sanitiser of some description this would become a breeding ground for bugs

DE is not common in commercial applications due to its high maintenance costs

it does require less backwashing - it is also well documented that a filter with zeolite media will gain pressure at a slower rate to the same filter with sand as a media. There are plenty of docs avilable via a google search regarding this. So a 5 min backwash will generally send around 1500L of water down the drain, and depending on your method of heating this can cust $4 - 6$ to reheat. If you are saving 2 backwashes a month - this can be upwards of $72/yr. The chemical cost on the BBB method may be cheap, but even at a couple of dollars a time, this still brings the total savings to $100 annually. Without thinking for a minute that you are also dumping 1500L of what will one day be the worlds most precious resource down the drain

While i understand your logic behind the ammonium absorbtion claims and look forward to seeing the results of the experiments, there is a large amount of feedback from rec centre and aquatic centre managers regarding not just an improvement in water clarity, but also in the odour in the complex.

I look forward to getting to work tomorrow and sending through the rest of the UofA reseach pdf on particle size and filteration rate obtained through Zeolite, DE and sand media filters

in the meantime though - heres a bit more reading
http://watercarenaturally.co.nz/assets/2007/10/15/SwimmingPoolIssues_1.pdf
http://www.watertechonline.com/article.asp?IndexID=6635473
http://www.afm.eu/biological_aspects/afm_sand_or_zeolites.htm
http://www.encyclopedia.com/doc/1G2-3400900551.html

btw - i do quite enjoy what i do and this forum - so this is not intended to inflame...... but there is more than one way to skin a cat

 

[spishex]

The filtration claims in this link are pretty impressive, but all the anecdotes seem to involve switching out old systems (mostly cartridge) with new zeolite filters.

And then the third link says basically what's been stated here:

When zeolites are used for ion exchange filtration, a regeneration cycle is normally implemented on 48 hour cycles. If zeolites are used as a replacement for sand in pressure sand filters, we find that they perform extremely well during the first few days and possibly up to several weeks in swimming pool applications.

They're very interesting particles, but as with many things in life the marketing for them in the pool segment gets overblown.

Just to throw some anecdotes of my own in as "evidence", I've probably switched 50 or so filters from sand to zeolite and every benefit that I ever saw was for my employer (higher profit margins, less storage space) and myself (only had to lug half the weight from my truck to the filter!!). None of those customers ever came back to us to say what a difference it made, and I can think of one in particular that switched the whole filter out within a year for a cartridge because he was still unsatisfied with the filtration. I heard from him about his problems probably half a dozen times while he had Zeolite in his filter, but haven't heard from him since he switched to cartridge. Hardly solid evidence, but that's my experience. Since going into business for myself I've had no compelling reason to use it.

For what it's worth I've had basically the same experience with Borates

 

[PaulR]

4) Requires less backwashing - the media works better as it traps fine particles (like any filter media), this saves water,chemical and heating costs
This makes no sense. If it is more effective at trapping particles it will need more frequent backwashing since the more particulate matter trapped the more backpressure created. An ineffective media would need less backwashing, not a more effective one

Hang on... my impression is that the frequency of backwashing goes: sand (highest), DE, cartridge (which you don't actually backwash, but cleaning the cartridges is the equivalent). So you're arguing that sand is the most effective media, and cartidge is the least? That doesn't sound right.
--paulr

 

[spishex]

The amount of time a cartridge can take between cleanings is because of the square footage of filtration. If you only had 3-4 square feet of cartridge area as you do in a sand filter you'd be cleaning much more. Instead you have something more in the 50 - 500 sq ft range. The finer the filtration, the faster the media will clog up per square foot.

If you look at the second link in NZ's post you'll see the claims that he's referring to. I guess because the particles are "hollow" they're supposed to be able to hold more than a solid grain of sand.

 

[JasonLion]

I am sorry if you find it "brutal". That is not our intention. Our goal is to cut through the marketing hype to find out what is actually going on. There are a tremendous number of things that "everyone" in the pool industry says that are just plain wrong. Obviously Zeolite works for pool water filtering for a great number of people, the filter doesn't explode, the water stays clean. On the other hand, that doesn't mean that the marketing claims made for Zeolite are all true or that Zeolite is the best choice in any specific situation.

I want to be very clear that our primary focus here is on residential pools (unless a particular posts states otherwise). The cost tradeoff issues are quite different between residential pools and commercial pools. For a residential pool the cost differences between sand and Zeolite are irrelevant, lost in the noise. For a commercial pool the situation is very different, the quantities are far larger and even relatively small cost differences require careful consideration.

If a residential pool owner follows our advice, they will purchase an oversized filter that requires backwashing less than once a month (under normal conditions). Whatever the backwashing differences between sand and Zeolite, they will not make any practical difference in this situation.

DE is a known carcinogen, but only when the airborne DE dust is breathed in. Even minimal precautions can prevent this from happening. If there is any significant amount of humidity the DE will not normally become airborne. In dry conditions a standard dust mask, sold at every hardware store, will protect you from any DE that becomes airborne. In commercial applications a more expensive professional grade dust mask would be appropriate and completely sufficient.

Saying things like "handling it (DE) will probably give you lung cancer" is misleading at best (which is being very charitable). Statements like that do not contribute to the conversation and reduce the credibility of the other things you say.

 

[JasonLion]

If you look at the second link in NZ's post you'll see the claims that he's referring to. I guess because the particles are "hollow" they're supposed to be able to hold more than a solid grain of sand.

It is quite plausible to me that the variable size of the Zeolite particles, and thus variable water channel size, allows debris to penetrate deeper into the Zeolite bed than it would into a sand bed. That could allow the debris to be spread over a greater volume, which would reduce the water resistance compared to sand, given some fixed amount of debris. Of course, the superior filtering of Zeolite will increase the total amount of debris that must be contained. It is difficult to theorize how these two effects balance out.

 

[spishex]

Good point. That would make more sense then packing up the particles like little suitcases which would require you to line up the debris shortest to tallest and filter in that order. :-D

 

[Guest]

Wow - pretty brutal reaction to someone else's opinion and experiences

the "brochure" is a sales referal and outline for shops and service people
As I said, it's marketing hype.
just because someone has a different line of thought to what you subscribe to does not make it rubbish or Crud. you guys are happy to pour litres of bleach into a pool, but shudder at the thought of adding acid (which i have yet to see zeolite raise pH)
Where do you get the idea that we shudder at the thought of adding acid to a pool? I was referring to the acidic brine needed to recharge zeolite, which then has to be disposed of.
http://www.zeobrite.com/PDF/Zeobrite%20 ... cedure.pdf
If the cleaner is left out there is still the problem of the concentrated brine, which cannot be discharged into normal waste channels in many areas.



There are many manufacturers of Zeolites around the world - and like anything is of varying qualities and mineral makeup, any zeolite that requires loads of acid has a problem. I sell around two tonne of this every month for both new pools and to existing filters, so after around 400+ ton sold and not had any negative feedback, i am fairly confident that it works.
The north American market is really keen on DE, even though as far as most the research goes, handling it will probably give you lung cancer, yet advice is doled out about throwing handfuls into the skimmer to top up filters.
Actually, cartridges are more common that DE filters here and DE, if handled properly, is no more dangerous than handling any other pool chemical. In fact, in many localities in the US carts are the only kind of filter allowed. Some localities only allow DE with a separation tank.
"Another recent study conducted in Belgium has suggested a link between chlorinated swimming pool water and children's asthma. The link is based on the existence of an irritant in the water known as trichloramine, which is produced when chlorinated water comes into contact with organic matter" and infact the link below "swimming pool issues includes research from a variety of sources about what a horrible product chlorine is - and yet do you hear me bagging it - no
We have has numerous discussions on here about indoor pool air quality, which the study the study tyou are referring to is discussing. Search the forum and you will see.
there are 3 things what will continue to cause media coming out of a filter to a pool, valve problem, lateral problem (or incompatibility, i have seen this with 20+year old filters) or overfilling

I have never seen or heard of Zeollite causing a rising pH, even in a direct replacement of sand in a pressure filter. New Zealand might not be the biggest market in the world, however i do deal with over 200 service staff, 50+ pool builders and 50 - 60 shops on a regular basis. While not all of them use zeolite - there are enough of them spread around the country that i would be notified of an issue like that. We also supply product to upgrade at least 2 commercial centres per year, this work is gained through work of mouth between pool operators and managers, not as a result of advertising

The chamber is pressurized in a filter - yes, however there are major structural differences between silica sand which is essentially a smooth pebble, relying on trapping the impurities between particles. Zeolite is a lattice of tiny crystals that will trap the fine impurities rather than relying on getting trapped between particles. Without a sanitiser of some description this would become a breeding ground for bugs

DE is not common in commercial applications due to its high maintenance costs
I have worked at a commercial installation that uses DE for it's two swimming pools and have seen several others that do. I cannot comment on how common it is but I know it's not unusual.

it does require less backwashing - it is also well documented that a filter with zeolite media will gain pressure at a slower rate to the same filter with sand as a media. There are plenty of docs avilable via a google search regarding this. So a 5 min backwash will generally send around 1500L of water down the drain, and depending on your method of heating this can cust $4 - 6$ to reheat. If you are saving 2 backwashes a month - this can be upwards of $72/yr. The chemical cost on the BBB method may be cheap, but even at a couple of dollars a time, this still brings the total savings to $100 annually. Without thinking for a minute that you are also dumping 1500L of what will one day be the worlds most precious resource down the drain

While i understand your logic behind the ammonium absorbtion claims and look forward to seeing the results of the experiments, there is a large amount of feedback from rec centre and aquatic centre managers regarding not just an improvement in water clarity, but also in the odour in the complex.

I look forward to getting to work tomorrow and sending through the rest of the UofA reseach pdf on particle size and filteration rate obtained through Zeolite, DE and sand media filters
Don't forget to include cartridges also. I noticed that you do sell them! :?
in the meantime though - heres a bit more reading
http://watercarenaturally.co.nz/assets/2007/10/15/SwimmingPoolIssues_1.pdf
http://www.watertechonline.com/article.asp?IndexID=6635473
http://www.afm.eu/biological_aspects/afm_sand_or_zeolites.htm
http://www.encyclopedia.com/doc/1G2-3400900551.html

Interesting read, the first three discuss zeolite in water filtration for such uses as wastewater and water purification but do not specifially discuss it's use in a chlorinated swimming pool, which is a different environment.
The final one is mostly a discussion on air quality and disinfection byproducts in INDOOR pools and this is a well known problem that is not applicable to outdoor pools. The main difference between the two is the UV light that an outdoor pool is exposed to from the sun.

btw - i do quite enjoy what i do and this forum - so this is not intended to inflame...... but there is more than one way to skin a cat

Sorry if this comes across as harsh. but the use of zeolite in water filtration is not new but it's use in pool filtration is and many claims are being made for it that are not substantiated. Just as the claims for such things as ionizers as 'chemical free', enzymes as a substitute for sanitation, and saltless water 'softeners'/descalers that use magnets and inductive pulses. Many of these have some sort of 'research' to back up their claims also. Here in the USA back in the days of the Old West they peddled a thing called Snake Oil. Sadly, it's still being sold today. Care to buy a pool magnet?

Now, I am not saying that Zeolite is not a viable filter medium, but if you read the various manufacturers claims for it you'd better be wearing tall boots so as not to step in any.

 

[chem geek]

"Another recent study conducted in Belgium has suggested a link between chlorinated swimming pool water and children's asthma. The link is based on the existence of an irritant in the water known as trichloramine, which is produced when chlorinated water comes into contact with organic matter" and infact the link below "swimming pool issues includes research from a variety of sources about what a horrible product chlorine is - and yet do you hear me bagging it - no

Virtually ALL of the reports of asthma, respiratory and ocular problems associated with swimming pools are with INDOOR pools and these almost always have no Cyanuric Acid (CYA) in them. The theoretical models for breakpoint chlorination (oxidation of ammonia by chlorine) actually predict higher nitrogen trichloride production rates when using higher active chlorine (hypochlorous acid) concentrations. This is described technically here. It is also well-known in the water treatment industry that it is better to dose with lower amounts of chlorine for a longer period of time than dosing with high concentrations for a shorter time, even though both have the same disinfection capability (CT value -- chlorine concentration times time). The reason is that higher concentrations of chlorine result in a greater production of disinfection by-products. And, as waterbear pointed out, outdoor pools are exposed to sunlight where UV can break down the more sensitive volatile disinfection by-products and, of course, air exchange is far better as well.

The SwimmingPoolIssues link has incorrect or at least misleading information in it. For example, it says "at pH 8.0 chlorine is only some 15% efficient." This is only true when there is no CYA in the water. As shown in the graphs in this post, CYA acts as a chlorine buffer, something that has been known since at least 1974 as described in the technical paper in this link. At a temperature of 85F, and a pH of 8.0, with no CYA in the water 21.8% of the chlorine is hypochlorous acid compared to 47% at a pH of 7.5 so the drop in concentration with higher pH is more than half. With CYA in the water and the FC being 10% of the CYA level, then at a pH of 8.0, 1.0% of the chlorine is hypochlorous acid compared to 1.2% at a pH of 7.5 so the drop in concentration with higher pH is far less. You can also see that without CYA in the water, one is essentially over-chlorinating their pool with levels of chlorine 40 times higher than necessary (at the same FC level).

That same document, written by "International Non-Toxic Water Treatment Association" is hardly unbiased given that it is promoting ionization systems. Also, as I noted above, every one of the swimming pool venues that could be identified was indoors and likely without CYA. Their studies on ionization do not demonstrate killing of pathogens to prevent person-to-person transmission which is of concern in commercial/public pools. They only demonstrate prevention of uncontrolled bacteria growth and they neglect to mention the slow kill rates and even slower inactivation of viruses. Of course, chlorine is slow to kill protozoan oocysts such as Giardia and especially Cryptosporidium.

The Dryden Aqua link said the following about zeolite: "However zeolites will be absorbing and adsorb biological nutrients, and they have an even rougher macro porous structure than sand, these properties make zeolites a wonderful support for bacteria, but a dreadful mechanical filtration media in sand filters." Of course, they are promoting their own glass-based AFM material.

I don't think zeolite is bad. I am just skeptical of some of the claims since some are clearly wrong (i.e. prevents chloramine formation by removing ammonia). As I mentioned before, I'm hopeful that some careful tests at NSF will determine the effectiveness of zeolite -- both for chloramine removal and for quality of filtration (i.e. particle size). I have no vested interested in the result one way or the other -- I just want to know the truth.

Richard

 

[Aquaclear-NZ]

I know the article was definitly skewed towards ionisers - and personally i am not a beliver in these, however some people swear by them
the point i am making is that there is a different point of view for everything a glass media manufacturer will make their own claims, ozone, mineral, UV makers will all have results skewed in there direction.

btw i have had a fairly busy day and have not had time to upload the study..... its an interesting read

 

[chem geek]

I tend to focus on peer-reviewed scientific papers, when possible, and avoid taking manufacturer's literature too seriously unless they have demonstrated a consistent reputation for accuracy, completeness and balance. Some manufacturers have been pretty good about being forthcoming, to the extent that businesses can, such as Buckman Labs (makers of PolyQuat), Dupont (at least the division that makes Oxone non-chlorine shock), Taylor (makers of test kits) and a few others. I do not consider all points of view to be equal; some are more biased than others and some are just plain wrong or deceitful. Science is validated by experiment and observation, not by points of view. I do not consider the point-of-view that the Earth is flat to be accurate, for example.

This paper talks about an NH₃Cl⁺ cation which isn't found free in water but has been found bound to strong anions so in theory it's possible for monochloramine, NH₂Cl, to briefly form the charged cation and become attached to the zeolite. This paper talks about purification of dichloramine, NHCl₂, solutions by removal of ammonia via ammonium ion, NH₄⁺, and NH₃Cl⁺ by ion exchange (note that this implies NOT removing dichloramine itself). This paper talks about the pKa for monobromammonium ion, NH₃Br⁺, being 6.5 compared to a value of 1.0 for monochlorammonium ion, NH₃Cl⁺ which would explain why it is not found freely in water (the ion is a fairly strong acid so dissociates at normal pool pH). This is just speculation on my part, but there could be a mechanism for zeolite to absorb monochloramine via this monochlorammonium ion, albeit indirectly -- though it could be rate-limited similar to monochloramine->ammonia(->ammonium ion). We'll see if this happens in experiments using zeolite with water containing monochloramine compared to a control using either a regular sand filter or no filter (i.e. just circulation).

Richard

 

[gtm]

Science is validated by experiment and observation, not by points of view.

A colleague of mine once told me, "The average of good science and bad science is NOT good science." As Richard's example of the flat Earth notion implies, we don't progress by taking the concensus of all theories, we proceed by using data to reject the bad ones.

In a similar vein, when I was writing my first paper for publication way back when, my major professor crossed out a place where I'd said, "We believe that ..." and wrote a rather scathing note in the margin that basically said, "No one cares what you believe, only what your data can prove. Stick to that." I torture my own grad students now with both quotes.

One of the great things about this forum is that there are strong links to the hard science via Richard and others, and a healthy degree of skepticism throughout; i.e., a very "scientific" mindset.

One of the rules of science is that you can be, actually ought to be, fairly brutal when assessing theories, data and analysis methods. That's good and healthy, as long as it's addressing the theory and not the theorist, which has been (IMHO) true through this thread.

FWIW ... Gary

 

[chem geek]

1 - Water Clarity, outperforms DE with research from the university of Adelaide (australia) claiming filtration to 2 mircons. this does however depend on the size/ grade of the Zeolite, there are a couple of manufacturers , if your particle size is the same as pool sand, you do not get the benefit of this fine filtration, for this reason i only carry the particle size of 0.5mm - 2.7mm (you may have to do the math to work this out in inches im afraid)

5) Indoor pools - removes the odour of ammonium/chloramines from the air, i have several written references from both commercial and domestic pools commenting on this. this is much the same reason why zeolites are commonly used as kitty litter

Aquaclear-NZ E-mailed me a lot of materials including the following:

• Two testimonials. One indicated a lot of cost savings and improved water clarity from the better filtration compared to their sand filter. The other indicated a marked improvement in water clarity and achieving breakpoint chlorination (presumably they mean able to get the CC lowered) which they were not always able to do in the past.[/*:m:1culwh0l]
• A description of Zelbrite's ability to absorb ammonium ion including capacity, selectivity and equilibrium. Interestingly, this paper included a graph showing the reduced capacity of zeolite to hold ammonium ion when sodium ion is present as well as data indicating the contact time necessary to achieve specific levels of equilibrium.[/*:m:1culwh0l]
• A graph presumably from the "Australian Water Quality Centre" showing sand filtration to 15 microns, D.E. to 5 microns, and Zelbrite to 2 microns.[/*:m:1culwh0l]
• A Zelbrite properties marketing document and a Zelbrite vs. glass media marketing document -- both with technical info including noting a 0.5 to 2 mm Zelbrite particle size (this is equivalent to 500 to 2000 microns in size).[/*:m:1culwh0l]
• Two documents on iron removal by ZELflocc.[/*:m:1culwh0l]
• The same technical info document posted earlier.[/*:m:1culwh0l]

I have received similar, though not identical, documents and testimonials from several zeolite manufacturers/brands. I've also communicated with one of the leading consultants who was the only one with actual scientific paper references. What is common with all of the above is that at most it indicates that 1) some types of zeolite (ones with smaller particle size and rougher harder particles) filters better (i.e. removes smaller particles) than traditional sand and 2) zeolite will remove ammonium ion (and iron, if in ferrous state).

The only information relating to chloramines is the anecdotal evidence from some of the testimonials, but this could be attributed to the better filtration along with backwashing that will remove more particulate matter that could combine with chlorine to form chloramines. That is, D.E. might also show similar benefits compared to sand. Even D.E. added to sand might show significant benefits. Cartridge filters would be expected to be somewhere in between. Also, sand filters can harbor bacteria and such bio-fouling could increase chloramine levels (according to Dryden-Aqua) so it's possible that zeolite is more resistant to such bio-fouling (I have no proof of that; I'm just speculating here).

The information from the consultant is particularly damning (see the report in Page 1 and Page 2). For example, the graph of equilibrium concentrations (on page 2) and capacity of ammonium ion in zeolite at various sodium ion levels was very enlightening. The "maximum" capacity of 17 mg/gm (104 meq / 110 g quoted as ammonium exchange in the "Zelbrite Properties" document) is only achieved either when the sodium concentration is 0.1 mg/L (equivalent to 0.25 ppm salt as mg/L sodium chloride) or very high ammonium ion levels of 10 mgN/L or higher (MUCH higher, if the salt levels are near typical pool levels).

At an ammonium concentration of 1 mgN/L, which for a sense of reference would register as 5 ppm CC if it combined with chlorine to form monochloramine, the capacity of zeolite at 100 mg/L sodium (254 ppm salt) is 1.5 mg/gm (less than 10% of maximum capacity) while at 1000 mg/L sodium (2542 ppm salt) the capacity is around 0.2 mg/gm or less (around 1% of maximum capacity). Basically, the capacity of zeolite in a non-SWG pool is on the order of 1 mg/gm if there were 1 mgN/L of ammonium ion so if we have that concentration in 40,000 liters (10,567 gallons) of water, then that's 40 gN of ammonium ion requiring 40,000 grams of zeolite, or about 88 pounds. This means that if there were really a lot of ammonia in the water, then recharging of the zeolite would be frequent, especially in SWG pools. But of course, there is very little ammonia getting absorbed because ammonia is in extraordinarily small quantities in water that has an excess of chlorine in it.

The consultant further described testing with Zelbrite that showed it took 8 hours contact to get to 1/3rd equilibrium capacity, 24 hours contact to get to 1/2 equilibrium capacity, and 72 hours contact to get to 80-90% equilibrium capacity. I can only assume (generously) that these times are in filtration systems with multi-hour turnovers of the water. Even with this assumption, the absorption of ammonia is slow, but as I've said all along it's a moot point since ammonia will combine with chlorine in the water to form monochloramine with very, very little ammonia left and the rate of monochloramine to produce ammonia is slow.

So far I have seen nothing that demonstrates that zeolite removes monochloramine and it is clear that it cannot prevent monochloramine from getting formed via chlorine combining with ammonia. There is also nothing demonstrating that zeolite removes urea which is the largest nitrogenous component in sweat/urine.

Richard

 

[Guest]

Also, when speaking of sand filters and 'biofouling' it needs to be noted that there are two types of sand filters, high rate (the pressurized type used in pools) and slow sand filters (which are designed to promote bacterial filtration to break down nitrogen to ammonia and are used in aquaria. These are also called 'biological' sand filters. Zeolites have been used in these types of filters for many years to scavange ammonia.

I also find the claims that sand filters to 15 microns, DE to 5 and zeolite to 2 suspect. That would mean sand filters better than a cart and we know that is not the case! Best case with a high rate sand flter that has been reported is perhaps 30 microns.

 

[schrody]

FWIW...I'm about to switch away from zeolite to sand/DE. Yes, I did recharge my zeolite towards the end of last pool season but it is still not filtering well enough to remove what I am identifying as pollen based on pictures in this post:
http://www.troublefreepool.com/algae-i-d-please-t9297.html

I thought about posting this separately but I'm really not trying to start a new discussion...just throwing in my experience with zeolite. If it warrants more discussion or distracts from the science, let me know and I'll move it.