AA Treatment and High Phosphate Levels

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smallpooldad

0
Aug 6, 2008
429
Honolulu
I have been using Jack's Magic "The Purple Stuff" for some months now, some weeks ago the Phosphate reading was over 18,000 ppm.

This has not been a problem as the pool FC reads from 5.0 to 6.0 (normally closer to 5.0 ppm) with a CYA between 70 and 80. The pool looks very clean with virtually no visible iron stains. This is a first as I now maintain a level of 25 to 30 ppm of Jack's "The Purple Stuff". Prior to this I use to maintain about 14 ppm and slowly but surely the stains returned, this is not the case at this higher maintenance level.

I do cover the pool nightly as trade winds blowing anywhere from 16 mph to 38+ mph across the pool can cause up to a 6 F to 8 F drop in temperature overnight. I have read this can also cause staining due to swings in temperature, I think the nightly covering has helped with the stains.

My only concern is that at some point far into the future, I hope, I will need once again to do an AA treatment. If possible without draining the pool but if necessary it can be drained as it is not a large pool being 10,000 gallons. If the FC is dropped to 0 prior to adding the AA at nightime, and utilizing 32 oz of Algaecide the day before but compensating with enough chlorine to bring it back up to 4 ppm on that prior day, will I have an issue with Ammonia when I add back liquid chlorine in the pre-dawn hours. The reason I mention this is that even at the last no-drain AA treatment it took far more Chlorine than it should have based on a lower Phosphate level of say 4,000 ppm. The expected Phosphate levels might exceed 40,000 ppm or even 80,000 ppm in the future.

Are my concerns unfounded or for safety's sake should I just drain the pool? I realize that this question is more targeted to those of you that have a knowledge of chemistry and how these numbers might affect the outcome, so I hope you see the dilemma.
 
I would guess that at such high phosphate levels that the limit to algae and bacteria growth lie elsewhere such as with nitrate levels or with the amount of sunlight (for algae) and temperature.

As for the high chlorine demand, the Polyquat 60 itself reacts with chlorine and 32 ounces in 10,000 gallons would use up around 6 ppm FC though over a period of a couple of weeks (probably somewhat more than half of that the first week and probably more in the first day or two since you are adding a higher than maintenance amount). In addition, an excess of ascorbic acid creates extra chlorine demand. 1 pound of AA in 10,000 gallons uses up 4.8 ppm FC. So between the AA and the Polyquat you're looking at 11 ppm FC of demand. When you say "far more chlorine", how much are you talking about?
 
Chem Geek,

Thank you for the reply.

I added 8 ppm liquid chlorine to compensate for the Algaecide 60, I used 1 1/2 lb of AA and added 8 ppm liquid Chlorine to compensate for that, and I added 5 ppm liquid Chlorine to raise level of chlorine to 5 ppm. In total added 21 ppm of liquid chlorine, using Walmart Chlorine at a rate of 22 ozs per 1 ppm chlorine. All this before sunrise.

I did use Thio-Trine to reduce chlorine from 4 ppm to zero an hour before using the AA but it was dark. I did not compensate for that.

Over the next few days (3 or 4 - I cannot quite remember) the FC kept dropping back to 2.0 or 3.0 every 4 or 5 hours in the daylight hours but no algae or clouding. Kept bringing it back to FC 5 or 6 and in the evening I would up it to 8. CYA was around 70-75 the whole time. So that much liquid chlorine in ppm, this despite the SWG running during the daylight hours at normal levels for 6 hours. Finally on the 3rd or 4th night I set the SWG at power level 3 at 100% from 8pm to 5:30 am and that seemed to do the trick. I think the FC then got up to 10 ppm in the morning. Then let it run at it's normal power level 2 at about 60%, and it settled back to holding at 5 ppm over the next few days.

Brought pH to 7.3 by adding some borax, it was not a lot maybe 8 ppm, but I cannot quite remember and of course thereafter maintained the pH at 7.3 with muriatic acid.

Also the UV Index was very high on those days if I remember correctly.

Questions:

If say the Phosphates are 50 or 80 thousand do you think I should drain even if the pool is still clear?

And can this level of Phosphate have any detrimental affect to ones skin, eyes, respitory system, etc?


Thank you for your help.
 
Smallpooldad, what are you using to measure phosphates to such a high level, or did you mean 18,000 ppb, not ppm? I am curious as I'm on a steady diet of jack's pink and have not yet been able to discern my phosphate level. Then again, I don't have jack's test kit and perhaps I should ( I use 16 ounces weekly as maintenance on a 22,000 gal pool.) I will watch your thread closey as I'm not as far along in stain remediation as you.
 
Swampwoman,

Testing high Phosphates is actually very simple, using Aquatrend's Phosphate Test Kit and diluting the pool sample accordingly by adding sufficient water from the same tube to a small water jug. Then checking the color against the color chart.

As far as stain remediation goes I think Jack's test kit is essential otherwise one really has no idea if one has too little or too much. I find that keeping it in the 25 to 30 ppm, as opposed to 14 to 10 for maintenance and 20 to 16 for cleaning as recommended by Jack's, works much better in my pool. Or to put it more bluntly it really does seem to stop or slow down considerably iron stains at that level of 25 to 30 ppm. I think it is ppm, Chem Geek might know the correct answer. You can also use the diluting sample method for Jack's Test Kit by mixing half pool water and half tap water so long as your tap water contains very little phosphates. I actually do it by eye, no dilution,

Hope this helps.
 
Thanks! Actually, just before you posted, we did a test using our hagen aquarium kit where we diluted ours by a 10:1 drop ratio and came up with 25 ppm/mgL which is 25,000 ppb.

The kit specifically measures HPO4, which is orthophosphate.

I suspect your measurement of 18,000 may actually be ppb, but I could be all wet on that. I do know that the level below which algae is not fed (according not just to pool industry, but also according to watershed research etc.) is 100 ppb, which is why I suspect our 18k and 25k readings collectively may be ppb, not ppm, but please chime in ChemGeek if you have the straight of it ;)

I think i'm going to call jack's again tomorrow and see if they can discuss or refer me to info about the accumulation effects of their product. If I get the chance to call, I'll ask if they have any research on human health impact via skin absorption. The only thing I could find was a paper that mentioned no human health impact except to the digestion system at "very high" (but unspecified) levels.

But your concern wasn't the orthophosphate itself, but ammonia that could be created with the introduction of high volumes of chlorine? Did I understand that correctly?
 
Swampwoman,

Well I looked at the side of the plastic tub the Phosphate Test Kit comes in and it does state parts per billion so we have the answer and you are correct.

My concern over Ammonia is that if the the Chlorine is reduced to zero as it is prior to adding AA then it might be possible that such a large amount of Phosphates (Ortho type) in the water could overwhelm the water creating a situation where Ammonia might be produced. If indeed a 40-80 thousand ppb of Phosphates is a large amount and it might not be. I think and hope that Chem Geek can answer that question.

It seems that from Chem Geek's reply that Nitrates are more of an issue, or a combination of both, might be the deciding factor as to whether or not Ammonia might be produced and raise its ugly head.

As I understand it and I could be wrong enough or a lot of Chlorine will eventually get rid of Ammonia. How I do not know, again maybe Chem Geek can enlighten us here. So as I understand it Chlorine does not produce Ammonia but gets rid of it.

As far as I know Nitrates can most easily be removed by draining, again let us wait for Chem Geek to weigh in. Other methods of removing Nitrates are not viable with pool water I believe, but I could be incorrect.

Testing for Nitrates is easily done with an aquarium kit but in the 17 plus years of owning our pool I have only seen them present once and that might be the gardners dropping some fertilizer in the pool inadvertantly. I beleive, but am not sure, large amounts of organic matter, human or animal urine (if your ten 180 lb English Mastiffs play in the pool all afternoon) and others such as plant debris can also cause an increase in Nitrates in the pool.

So let us wait and see what Chem Geek might be kind enough to write.

Finally as regards stains I find that keeping the Calcium on the lower end of the recommended level for type of pool, as Jason Lion has recommended in some posts, also helps a lot in keeping iron and other stains out of the pool if the pH is 7.4 or below, mine is kept at 7.3.
 
Ah, that makes more sense. You fear that by zeroing out the chlorine, you'll get the bacteria that generates the ammonia! Gotcha! I will be curious to see if ChemGeek thinks phosphates exacerbate that possibility!

Btw, I did have ammonia on opening the (foreclosed) swamp, and indeed, if you hammer it hard with chlorine you can eventually clear it. Apparently, that is fairly common in Michigan -- opening to zero cya after winter. In my case, it was also the high volume of organics in the pool -- it smelled absolutely anaerobic!

Thanks for the tip about calcium -- I'm vinyl and at 130, but I'll keep that in mind!
Cheers!
 
If the chlorine gets to zero and bacteria start to grow and convert CYA into ammonia, I don't think it will matter whether the phosphtes are 5000 ppb or 30,000 ppb. The bacteria will likely be limited in their growth by other factors. However, that doesn't mean that lowering phosphates to 150 ppb or less won't slow down bacteria growth -- it likely will. Then again, the Polyquat algaecide inhibits bacteria as well as algae; it's just not enough to be called a disinfectant.

The high phosphate levels aren't high at all as far as health effects. Phosphate buffers are used in all kinds of medical products to control pH. Then again, phosphates are used in bowel preps for colonoscopies and enemas, but that's quite concentrated phosphate.

smallpooldad, you described some extra chlorine demand the last time you tried the AA treatment, but did the CYA drop? I wouldn't assume that you had an ammonia problem. If you had ammonia, you wouldn't be able to hold chlorine at all and it would have been consumed within minutes. The slow drop you saw is from a much slower loss, not from reacting with ammonia.
 
Thanks, ChemGeek! I am thinking there might be benefit in my case to lower my phosphates before I close for the season to reduce the volume of possible algae growth overwintering as we get very wild temp swings here in spring -- so if I elect to do so, it might make sense to do a high phosphate treatment before doing the AA treatment just to be on the safe side in terms of low chlorine and algae. My cover is semi solid, but due to the mesh in the center and comment from the old owner previous to the foreclosed one, I suspect it will still be a black opening...but better just black than black and super green ;)

I suspect smallpooldad does not need to close for the winter having the good fortune to live in Hawaii, so in his case it does not sound as cut and dried!
 

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Just keep in mind that phosphate remover product is quite expensive for reducing high phosphate levels. As for preventing algae over the winter, the easiest way is to close the pool as late as possible in the fall so that the water temp is as cold as possible (preferably below 50ºF) then add Polyquat and chlorine per the directions in this post and then open the pool as early as possible so that the water temp is still cold (preferably below 50ºF) in the spring.
 
Swampwoman and Chem Geek,

All of your recent posts were very interesting although we do not ever have to close the pool in our climate.

Chem Geek as regards a CYA drop, the answer is I am not sure but I think you maybe correct although it only dropped by about 15 or 20 to say 60, the reason for this I do not know.

Also I was glad to learn that the Phosphate level even at say 80,000 ppb is of no issue, so I will proceed with a no drain treatment when I have to and hopefully that will turn out well.

Thank you both for your help and Swampwoman good luck on your closing and opening.
 
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