Aluminium based flocculants

[Retep]

In short, no we don't recommend either floc or clarifier. Make sure that you have enough FC for your CYA level, run the pump, brush, and clean the filter cartridges as needed. Lastly, be patient. It will clear if you follow what we suggest to do in Pool School.

Aluminium based flocculants are excellent. IMHO this is essential for proper water treatment,in order to capture colloids.
A sand filter is able to filter about 20 microns - colloids are 0.001 - 0.1 microns .The problem with non commercial filters is the filtration speed , which is usually between 15 - 20 gpm/ft2. If you were to add the flocculant slowly into your skimmer it does not have the time to form a proper floc. Filter channeling will happen and the floc will pass through the filter and finally ending up in the pool.
Now you'll have aluminium residuals in your pool, which may cause itchiness on the skin.
Another method for flocculation in private pools is to broadcast the aluminium sulfate over the pool surface . Turn off your pump, wait till the floc settles at the bottom of the pool and vacuum to waste.

 

[chem geek]

Re: Flocculant

Retep, welcome to TFP!

If you have a sand filter and need finer filtration then one can Add DE to a Sand Filter. Proper circulation/filtration with elevated chlorine levels is usually done and usually works without resorting to clarifiers or flocculants. If one is in a hurry and doesn't mind spending more money with the possibility of the product not working, then those are options. As for colloids, phosphate removers producing lanthanum phosphate and lanthanum carbonate precipitate can severely cloud water and take a long time to clear which is why some phosphate remover products contain clarifiers in them. However, we don't recommend using phosphate removers and most cloudy water is caused either by algae or by over-saturation with calcium carbonate so can be cleared (or fixed) without using clarifiers or flocculants.

 

[Retep]

Re: Flocculant

Thanks for welcoming me ,Chem Geek,
By adding DE to a sand filter you may get some filter blocking.
Don't forget that a typical DE Filter has a filtration speed of about 2gpm/ft2 compared to the speed of a sand filer which could be anywhere between 15-20 gpm/ft2.
Also DE is organic based , therefore it will react with the chlorine
by creating more combined chlorine. For this reason Perlite should be used instead of DE.
You are correct in saying that with elevated chlorine levels you could achieve clear water, however - the higher your chlorine levels are , the more
DBP you'll create.
With a proper flocculation process we are trying to capture those small organic impurities (bacteria, viruses), which are mostly introduced to the pool by the bather. By taking out those beforehand we have to disinfect / oxidise less afterwards ,allowing us to run at lower chlorine levels.

The NSPF recommends a FC residual of 2 - 4 ppm in public swimming pools. IMHO this is way too high, since with those high doses of FC ,we also create high doses of DBP. I guess the reason behind NSPF's guidelines is that the microbiological aspect is being met, which I am certain it does. With 2-4 ppm it's no surprise. . :lol: .
It seems in North America we forget about the byproducts of chlorination. In Germany very strict guidelines apply - max. THM's in the pool water is
20 ppb (microgram/liter) . I wonder how many public swimming pools in North America had their water tested on THM (80% or so being Chloroform) and TOC.
The NSPF Pool Operator Handbook ( CPO) mentiones very little about it ( page 46) , except it says that "Currently the risk to human health due to THM is relatively low". . Hard to believe no guidelines are being set, since there is so much research out there clearly demonstrating that THM's are linked to cancer. Link -> http://www.ncbi.nlm.nih.gov/pmc/article ... 8-0088.pdf
This article was published in 1994 - at the end it says that UV radiation should be considered. Meanwhile research has shown that UV radiation should not be used in chlorinated pools, since it raises THM levels up to 300 %. . .Something we did not know back in 1994. This is something which should be mentioned in the NSPF Pool Operator Handbook as well.
Links on UV radiation in swimming pools ->(written in french with some english) ->
http://www.inrs.fr/inrs-pub/inrs01.nsf/ ... nd2237.pdf
And another one ( french and english just below ) ->
http://www.water-quality-journal.org/in ... er/2009009

The German approach is to run with as little as possible FC by still maintaining microbiological safe and healthy water.
You will find this article very interesting - it clearly demonstrates that it is achievable to run a public pool between 0.3 - 0.6 ppm by still maintaining proper sanitation -> http://www.lims.hu/media/furdokonf/Engl ... ger3_p.pdf

 

[dmanb2b]

Re: Flocculant

Also DE is organic based , therefore it will react with the chlorine by creating more combined chlorine. For this reason Perlite should be used instead of DE.

Welcome to TFP

Can you clarify your above statement? I am by far no where near the knowledge level of Chem Geek when it comes to chemistry, but if what you have stated above is correct, how could DE filters be so popular?

 

[Retep]

Re: Flocculant

Hello dmanb and thanks for the welcome.
DE is ( was ) popular since it allowed to capture smaller impurities much better than a sand filter.(from 1-4 micrometers on a DE Filter)
compared to about 20 micrometer on a sand filtration.
Recently DE is getting more and more replaced with Perlite for the following reasons:
When DE is inhaled it will stay in your lungs - something to be avoided.
Another reason is that while DE is excellent for filtration, it does contain organics which will react with oxidisers such as chlorine or chlorine dioxide.
This will lead to higher combined chlorine levels in the pool water - by using Perlite instead, this can be avoided.
Practical tests in swimming pools have confirmed this.
To my knowledge DE is still being used for other applications where there is no chlorine residuals in the water and it does a good job.
Here is a link I just found : DE vs. Perlite -> ( disclaimer : I do not have any commercial interests in either products)
http://www.texasaquaticsupply.com/docs/ ... 0Earth.pdf

IMHO nothing beats a well engineered sand filter - much easier in terms of maintenance and with the right technology the same clarity
can be achieved as in DE or Perlite Filters.

 

[JasonLion]

Levels of colloids in the typical residential swimming pool are low and essentially irrelevant to water quality except in very unusual situations.

Pool DE is heat treated crystalline silicate. There is no measurable organic content and no creation of CC from using DE, nor does it react with chlorine in any meaningful way.

Disinfection byproducts are far lower in outdoor pools then they are in indoor pools, and byproducts are also far lower when using CYA compared to not using CYA. Levels in the typical outdoor pool are far below the relevant thresholds. There are some interesting debates about the idea approach in an indoor pool, but that is largely irrelevant here where we deal almost exclusively with outdoor pools.

Retep, it is very difficult to keep track of what you are trying to say. You keep switching topics and mentioning unrelated technical facts in what appears to be the same stream of thought.

 

[chem geek]

There are many residential pools with DE filters and we've never seen higher than normal chlorine demand in such pools including carefully measured overnight chlorine loss tests. That simply does not seem to be a problem in practice.

As for FC levels, the FC number alone is meaningless with respect to the active chlorine (hypochlorous acid) level and it is the active chlorine level that determines the rate of disinfection, oxidation and creation of disinfection by-products. In pools with Cyanuric Acid (CYA), the active chlorine level is far, far lower. Roughly speaking, at a pH near 7.5 the active chlorine level in a pool with CYA is the same as in a pool with an FC that is FC/CYA. So a pool with an FC that is 10% of the CYA level has roughly the same active chlorine level as a pool with 0.1 ppm FC with no CYA. So while I would agree that 2-3 ppm FC with no CYA is too high, 2-3 ppm FC with 20-30 ppm CYA is not high at all. There is a difference in active chlorine level of 20-30 times.

My wife has personally experienced this difference in active chlorine levels between an indoor community center pool with 1-2 ppm FC and no CYA vs. our outdoor pool with 3-6 ppm FC with 40 ppm CYA. Her swimsuits degrade (elasticity gets shot) in just one winter season at the indoor pool and her skin is flakier and hair frizzier after swimming. In our pool even after multiple summer swim seasons the swimsuits show little sign of wear and her skin and hair are not as affected. I attribute this to the 10-20 times higher active chlorine level in the indoor pool compared to our outdoor pool.

The German DIN 19643 standard that uses 0.3-0.6 ppm FC with no CYA (or 0.2-0.5 ppm FC if ozone is used) uses coagulation/filtration to remove organic precursors, but also uses granulated active carbon to remove all chlorine and choramines as well. Chlorine is reintroduced into the water stream after filtration. Trying to maintain a consistent low FC level in a pool is challenging since localized chlorine demand can wipe out the low FC while in pools with CYA one gets a low active chlorine level, but plenty of FC to satisfy local chlorine demand. CYA is a hypochlorous acid buffer holding most of the chlorine in reserve that is released quickly as needed.

Residential pools have far lower bather load compared to the commercial/public pools used in most DBP studies and far lower organic precursors as a result. Also, outdoor pools exposed to sunlight tend to have less issues with measured chloramines, especially in low bather-load pools such as residential pools, possibly due to the UV in sunlight breaking down some chlorine to hydroxyl radicals (which can oxidize organics that chlorine is otherwise slow to oxidize, such as urea).

If you want a technical summary of the misconceptions or incomplete information in the pool/spa industry, I suggest you look at the post Certified Pool Operator (CPO) training -- What is not taught.

 

[Retep]

Levels of colloids in the typical residential swimming pool are low and essentially irrelevant to water quality except in very unusual situations.

Pool DE is heat treated crystalline silicate. There is no measurable organic content and no creation of CC from using DE, nor does it react with chlorine in any meaningful way.

Disinfection byproducts are far lower in outdoor pools then they are in indoor pools, and byproducts are also far lower when using CYA compared to not using CYA. Levels in the typical outdoor pool are far below the relevant thresholds. There are some interesting debates about the idea approach in an indoor pool, but that is largely irrelevant here where we deal almost exclusively with outdoor pools.

Retep, it is very difficult to keep track of what you are trying to say. You keep switching topics and mentioning unrelated technical facts in what appears to be the same stream of thought.

Yeps - possible I keep switching topics - I sometimes get carried away :-D
I agree that for a typical residential outdoor pool (due to the mostly light bather load) we can get away with standard filtration where flocculants
are perhaps not really needed.
Quite a different story though in heavily used indoor public pools where I spend most of my time.

 

[Retep]

There are many residential pools with DE filters and we've never seen higher than normal chlorine demand in such pools including carefully measured overnight chlorine loss tests. That simply does not seem to be a problem in practice.

As for FC levels, the FC number alone is meaningless with respect to the active chlorine (hypochlorous acid) level and it is the active chlorine level that determines the rate of disinfection, oxidation and creation of disinfection by-products. In pools with Cyanuric Acid (CYA), the active chlorine level is far, far lower. Roughly speaking, at a pH near 7.5 the active chlorine level in a pool with CYA is the same as in a pool with an FC that is FC/CYA. So a pool with an FC that is 10% of the CYA level has roughly the same active chlorine level as a pool with 0.1 ppm FC with no CYA. So while I would agree that 2-3 ppm FC with no CYA is too high, 2-3 ppm FC with 20-30 ppm CYA is not high at all. There is a difference in active chlorine level of 20-30 times.

My wife has personally experienced this difference in active chlorine levels between an indoor community center pool with 1-2 ppm FC and no CYA vs. our outdoor pool with 3-6 ppm FC with 40 ppm CYA. Her swimsuits degrade (elasticity gets shot) in just one winter season at the indoor pool and her skin is flakier and hair frizzier after swimming. In our pool even after multiple summer swim seasons the swimsuits show little sign of wear and her skin and hair are not as affected. I attribute this to the 10-20 times higher active chlorine level in the indoor pool compared to our outdoor pool.

The German DIN 19643 standard that uses 0.3-0.6 ppm FC with no CYA (or 0.2-0.5 ppm FC if ozone is used) uses coagulation/filtration to remove organic precursors, but also uses granulated active carbon to remove all chlorine and choramines as well. Chlorine is reintroduced into the water stream after filtration. Trying to maintain a consistent low FC level in a pool is challenging since localized chlorine demand can wipe out the low FC while in pools with CYA one gets a low active chlorine level, but plenty of FC to satisfy local chlorine demand. CYA is a hypochlorous acid buffer holding most of the chlorine in reserve that is released quickly as needed.

Residential pools have far lower bather load compared to the commercial/public pools used in most DBP studies and far lower organic precursors as a result. Also, outdoor pools exposed to sunlight tend to have less issues with measured chloramines, especially in low bather-load pools such as residential pools, possibly due to the UV in sunlight breaking down some chlorine to hydroxyl radicals (which can oxidize organics that chlorine is otherwise slow to oxidize, such as urea).

If you want a technical summary of the misconceptions or incomplete information in the pool/spa industry, I suggest you look at the post Certified Pool Operator (CPO) training -- What is not taught.

I just posted something on the CPO Thread while you were writing this. .
Back to the topic:
Of course there is a huge difference between private small pools and public ones.
As you stated the FC number is basically meaningless - I agree.
In order to determine if the water is microbiological safe we have to take a look at the ORP's. We reasonally can assume that by obtaining
750mV the water should be safe, regardless how high or how low the FC levels are. Naturally we should aim at a lower FC level by still obtaining those 750mV.
Automated ORP equipment is very slow in taking the readings and there are quite a few variations between manufacturers.
For this reason it is mandatory to have Amperometric controllers in public pools in Germany.

In Germany activated carbon is used only for Pools which uses Ozon. The majority of public pools use standard sand filtration - some of those
have in the sand filter a layer of perhaps 5 inches of either activated carbon or Anthrazit. Most of the pools there have different layers of silica sand, which has to be heat treated in order to burn organic substances which otherwise would lead to higher combined chlorine.
For DE Filters they also used to use Activated Carbon Powder . DE Filters though are nowadays a thing of the past in Germany.

As for CYA in indoor pools : It is very interesting what you write - I never had the chance to try this out in one of the indoor pools which I service,
since my local authorities don't permit the use of CYA in indoor pools.

 

[JasonLion]

Amperometric sensors don't measure ORP, they measure HOCl. HOCl is the number that matters, not ORP, which is why everyone is switching to amperometric sensors. ORP has lots of problems and is best avoided if possible.

Again, the problem with low FC levels is that it is impossible to maintain them across the entire pool. The low levels of FC get used up in local regions of water due to people swimming in that area, and the water is no longer sanitized in that area. If we could somehow maintain a uniform FC level across the pool a low FC level would be perfect. That is why some people have started experimenting with extreme circulation systems that replace the water before the FC level has time to fall very far.

 

[Retep]

Amperometric sensors don't measure ORP, they measure HOCl. HOCl is the number that matters, not ORP, which is why everyone is switching to amperometric sensors. ORP has lots of problems and is best avoided if possible.

Again, the problem with low FC levels is that it is impossible to maintain them across the entire pool. The low levels of FC get used up in local regions of water due to people swimming in that area, and the water is no longer sanitized in that area. If we could somehow maintain a uniform FC level across the pool a low FC level would be perfect. That is why some people have started experimenting with extreme circulation systems that replace the water before the FC level has time to fall very far.

Exactly - I just wrote / explained this in the CPO thread ( before I read your post here).
However - ORP do matter, but it shouldn't be used to "control" the Chlorine level ( I refer to Chlorine instead of Hypochlorous Acid to keep it simple).

ORP should be used as a "helping" parameter when it comes to maintaining a constant residual of Chlorine in the water. Most Amperometric units
have also a display which shows how many ORP's we got, but (of course) it is the Amperometric probes which will stay at a more or less constant Chlorine residual reading.

As to "extreme" circulation : It always depends on the pool - which purpose. Warm-up pool, leisure pool, and so on. . .
The circulation rate should be based that for every bather in the pool 2m3 / bather of circulation water is required.
In other words : 100 people/hour/pool maximum capacity = 2oo m3/ hr pump capacity ( or 880 gpm).
Don't be fooled though - if no proper water treatment is applied that will simply mean that the cloudy water is being turned over more often.
Good filtration will always be the key.

 

[chem geek]

In order to determine if the water is microbiological safe we have to take a look at the ORP's. We reasonally can assume that by obtaining
750mV the water should be safe, regardless how high or how low the FC levels are. Naturally we should aim at a lower FC level by still obtaining those 750mV.

Please see this post I just wrote in the CPO thread. ORP as an absolute measure is next to useless except as a very rough guide; ORP is most useful for process control as a setpoint. Again, please read the first post in the CPO thread including its links since you are still bringing up topics that have already been extensively researched and addressed here on this forum.