Phosphates.....are they worth removing??

[Saturn94]

Hayward manual says pH 7.2-7.8. You're desired level is well within that range.

 

[JoyfulNoise]

Swampwoman,

Now that you will be running an SWG, you are going to want to actively monitor your CSI as an important parameter for cell health. SWGs work best when your CSI is a bit negative. I keep my CSI near -0.1 to help keep the cell scale free. Operating at a lower pH like you do is a good thing.

 

[AUSpool]

As for Hanna, the calibration standards are for checking the meter INDEPENDENT of your pool water to make sure the LED light source and photodiode are working properly. Your pool water, tap water, etc, would be unreliable for that process.

The pool water isn't for calibration but rather 'optical zeroing' for want of a better term. Hanna sell 'Calibration checking set point' standards but it doesn't say if they can be used to calibrate the meter or just check it. I've since tossed my old low range checker and instructions with it but my guess is it's just to check it to ensure the LED and photodiode are working properly over time.


Same as my old ColourQ every time it's used it needs to be 'zeroed' with untreated pool water. A baseline reading prior to reading the same water with the reagents?

The HI 713 and HI 717 Checker®HC’s are extremely simple to use. First, zero the instrument with your water sample. Next, add the reagents. Last, place the vial into the Checker®HC, press the button and read the results. It’s that easy.


REAGENTS AND STANDARDS
HI 717-11 Calibration checking set (0.0 and 15.0 ppm phosphate)

Swampwoman,


Now that you will be running an SWG, you are going to want to actively monitor your CSI as an important parameter for cell health. SWGs work best when your CSI is a bit negative. I keep my CSI near -0.1 to help keep the cell scale free. Operating at a lower pH like you do is a good thing.

I used to get calcium scale on the cell and in the pool but not anymore. I've added a new cell, added borates, raised my CYA to 70ppm. I don't know if it's any one thing but I have adopted the TFP levels for a SWCG pool and my CSI is now near -0.1. I should go back to my historical data a see what my SCI was pre TFP.

 

[AUSpool]

SW, It's good your FC is holding.

Theory 1. - Without explanation it's just interesting to know, I could copy the extract word for word when I get home if your interested. I'd put my money on the FC in favour of any high PO4 level.

Theory 3. - Antifreeze is also a carbon source which in theory would give any bacteria (bacteria would utilize a carbon source quicker than algae would) a growth boost but with the FC present I doubt it.

 

[Swampwoman]

UPDATE: MAXXED THE HIGH LIMIT ON HANNA METER.

Not kidding. After a few trial flights to manage to not spill the powder, zeroing out against un-reagent ed water, getting the time set right (exactly 5 min) I read the whopping high limit of 30,000 ppb orthophosphates.

Tomorrow, I will get out the vinegar, distilled water, etc. and do a 1:2 dilution a few times to see where I'm really at here. But its certainly looking more and more like our initial crazy tests were in fact true or true-ish.

My buddy didnt give me the lab info yet so I'll have to stalk him, but I am not only confounded at this point, I'm also not sure what to do next.

BECAUSE I'm not sure I can even get my "old pool" back at this point - notwithstanding the imminent wiring of the swg box.

This a.m. FC was as ridiculously low 1.5 ppm after completely holding overnight at 10 ppm on Thurs. a.m.

The Seaklear tech wrote back to me yesterday confirming there's no alum in the commercial phosphate remover and theorizing that the addition of salt and resultant increase in TDS was what spiked my chlorine use, and that the sooner I started up the SWG, the sooner that salt would be put into production.

Whether I intended to or not, I suppose I might as well just SEE whether or not the phos-monster eats the cell. That way I can at least serve as some kind of cautionary tale in TFP lore

Water, of course, looks innocent and clear as a bell

Hi ho.

 

[JoyfulNoise]

Very strange results indeed. It's hard to know where you started off at, if you were indeed over 60,000ppb PO4 or if the SeaKlear failed to work properly at cold water temperatures.

I forgot, did SeaKlear give you any indication that temperature would affect the removal process? My water was in the low 70's when I performed the removal process and I got what I consider excellent results (a 10X reduction).

 

[Swampwoman]

^Seaklear said cold water would slow the reaction down...which is why I heated the water first to 72. But Terry had also said not to run heater during treatment...so the temp dropped by 10 degrees. He and I both believe the treatment indeed did something based on the milkiness and floc formation of the lathanum. So its more likely that he levels were higher than previously read.

EXPERIMENT UPDATE:

Careful rinse with vinegar, then distilled water, zeroed calibration with pool water un-reagent ed, diluted 5ml distilled water and 5 ml pool water, got a consistent

40,000 ppb phosphate

UNEXPECTED CONSEQUENCES?

1. Taylor salt test continues to produce "globs" in test when silver nitrate is added. Even when stirred with lab stick, looks like curdled milk. Reads way way higher than test strips (eg 2680 vs 6600) Clearly something is now wrong with this test that wasn't wrong before Monday.

2. FC zeroed out from 5 to zero by end of day yesterday. Re dosed to 10 today. Temporarily out of chlorine. CYA is still 40. The chlorine phenom is driving me crazy. I just can't explain it. Water looks clear. No signs of algae. FC was rock solid, even through phosphate treatment, at about 2 ppm per day with residual f about 5 each morning until Monday when sand was changed, 25lb calcium added, 50 lb salt and 11 lb boric acid. Now I don't recognize this pool in terms of conduct

3. All other tests appear normal, (ph 7.6, TA 80, CH 100 ) though calcium is lower today than yesterday by 10 -- I get metal interference so maybe I just have trouble between purple and blue.

4. Iron is back at stable .3

5. Borates still reading 50. I also tested a spoonful of the boric acid in distilled water and tested with strip to confirm in my own mind that its boric acid, not AA shipped by mistake.

Electrician in on his way.

Once I add that cya, there's no going back...but should decide that this a.m.

If swg fails and I switch back to chlorine, I'll be stuck with high cya as this well could not handle even a 50% dilution. So I might as well just go for it and see what happens.

 

[JoyfulNoise]

SW,

Re: the salt test

It's supposed to look like curdled milk and a little clumpy. That's the silver chloride (solid precipitate) coming out of solution. It's a white solid that is almost completely insoluble in water. If you post a picture of the test I can confirm it.

What water sample size are you using for the salt test?

Re: Phosphates

Wow, 40ppm PO4! That is a lot of phosphates. Does that number make sense based on past historical usage of sequestrants?

 

[Swampwoman]

Actually, yes, if the theory worked up with the Jack's technician is true and it's possible to build up 1200 ppb po4 after 4-6 weeks treatment at 12 oz. and I have applied same (more actually, in early years) over 4 summers at about 24 weeks that alone would account for total polyphoshate additions of at least 28,800 - notwithstanding converting 23,000 gallons of blackwater swamp with 20+ wheelbarrows of leaves that sat for 2 years back to clear water via cholorination in spring 2012 -- which is guaranteed to produce enormous amounts of orthophosphates.

So, we know that cholorine breaks down polyphosphates over time, and that the baseline is orthophosphate. We know that without much calcium in the water (per Jack's) that the polyphosphate isn't necessarily getting filtered out by combining with calcium. We know that apart from evaporation and backwashing, I don't lower my water level much or do water changes due to water table and well. Formula for a perfect phosphate storm

Also, I just found this - CG's quote from Taylor on the salt test -- this MUST be happening here, I suspect:

Orthophosphate at concentrations greater than 25 ppm will precipitate as silver phosphate to cause positive interference. This can be prevented by diluting orthophosphate concentrations below 25 ppm with DI water. Bromide, iodide, and cyanide at all levels titrate as equivalent chloride concentrations. Sulfide, thiosulfate, and sulfite interfere but can be removed by treatment with hydrogen peroxide.

-- Next time I test, I will do a 50/50 dilution with Distilled water to see what happens.

Well, I'm certainly over 25 ppm (25,000 ppb) at the moment and I believe the test.

But what's weird is that the test seemed to have worked correctly BEFORE the sand change, calcium, boric acid and extra salt. As if the phosphate treatment did in fact remove orthophosphates to a lower level...but now something has broken more down, which is entirely possible, since the remover doesn't touch POLYphosphates and there's no question I'd have an abundance of old poly...

One emerging idea from all this is that perhaps people with SWG who recover a swamp should consider trash pump instead of slam alone for conversion for the water dilution alone -- I'd be real interested in knowing what kind of PO4 level is produced from a blackwater slam but I am betting it is quite high. Something for future experiments but hopefully not in MY pool

Update with pic from salt test: clumpier than I suspect it should be? When I wiped out the phial there was also lots of silver powder clinging to sides.

 

[JoyfulNoise]

While it is probably advisable to dilute your sample, I don't think the positive interference from your phosphates will make a huge difference. It takes 3 moles of silver ions (Ag+) to react with 1 mol of phosphate (PO4[3-]) to form silver phosphate (Ag3PO4). At 40ppm phosphates, that would take 120ppm AgNO3 to react which would yield an equivalent sodium chloride concentration of

120ppm (58.44 / 169.87) = 41ppm in NaCl units.

So the positive error from your phosphate level alone is not really significant. Polyphosphates from sequestrants would complicate the matters a bit more because the sequestrant would act on silver ions in similar way to other metals.

Back to my original question - did you use the correct sample size of water when doing the NaCl test?

People often think the sample size is 25mL for the K-1766. It is not. It is 10mL. If you use 25mL of pool water, it takes 2.5 times as many drops to titrate a sample.

6600ppm / 2.5 = 2640ppm

Which looks a lot like the numbers you're getting from your strips.

 

[Swampwoman]

Ooooo, good catch Matt! I was using 25 ml.

I'm betting that's what was different between last Saturday's concordance and tests this week! Doh!

In other news, the swg, while not yet giving average readings, gave the "instant" reading when prompted of 2700 ppm...pretty much exactly as strips said.

I've now added another bag of salt and 6 lbs of cya. I stocked up on a couple of carboys of 12% just in case, so well see what happens next.

 

[Saturn94]

In my experience the strips correlate closely, within a couple hundred ppm, with my SWCG readings. Once in a great while I'll have a bad strip that's way off, but it's easy enough to retest to confirm. I've never felt the need to use anything more accurate for salt.

 

[JoyfulNoise]

SW,

Then that explains it because a 25mL sample would give you 2.5X as many drops. For a 25mL sample size, the drop count sensitivity is 80ppm/drop.

All tests have varying tolerances. Strips are usually only good to within +/-400ppm, the K-1766 is +/-200ppm. But at the end of the day what matters is the SWG. It needs to be satisfied.

My preference is always for the K-1766 results because that is a true chemical measure of chloride concentration as opposed to other measures which are only proxies for chloride.

It's good to know that, even with phosphate interference, the K-1766 still came out close to your other tests.

 

[Swampwoman]

This saga is really something ;( But so goes experimental pool chemistry.

For about half of today, I was quite excited because the swg was chugging along nicely. Now I am getting "low salt" (not true) and more concerning, "check cell."

I did the manual/diagnostic salt check again (read at 3100 - i added salt earlier, just 1 bag) and that temporarily cleared the codes, but they came back again less than alf an hour later.

Should I shut it down and start a phosphate treatment tomorrow, or should I give it a day to see if it changes its mind? Clearly it s not happy with its current working conditions...which using chemgeek's formula, I could have actually predicted.

I was simply hoping for a miracle

 

[JoyfulNoise]

Typically you don't want to add salt and run the cell right away. In cold water it takes 24-48hrs for the salt to dissolve and the water to homogenize. I'm surprised you haven't gotten a high-salt alarm too.

Post the diagnostic codes and JamesW can tell you if it's working or not.

I think you might want to consider a new thread for your SWG saga...technically this thread is supposed to be about phosphates. I might have to report you for high-jacking

 

[Swampwoman]

Lol. Except of course the only reason I'm bothering to attempt to read and remove phosphates at all is because I was given cause for concern about switching to swg....so whether or not a brand new cell fouls is def germane to the phosphate question

My water is 77 via heater; I reset the average salt reading per a diagnostic manual I dug up (troubleshooting guide at into pools) and its back into production mode for the moment..held for a few hours now.

So Im gonna keep running until it won't, and call Natural Chemistry mom a.m. to ask how much their "high" phos floc product removes. If I do a second phosphate removal run, I want to vacuum it all to waste and keep it off the cll pâté if possible. But the Seaklear might work just as well on circulate, ten shut down overnight.

I promised my mother a heated pool for her visit next weekend. So I might attempt to get by without more treatments til after

 

[AUSpool]

40,000ppb PO4, someone's been on the phosphate merry-go-round!

This quote had me thinking;

But in reality, these units ( ref to SWG) are more like small chlorine factories that take in salty pool water and output chlorine. Inside the factory, however, work proceeds under some rather extreme conditions. At some points inside the generator, chlorine concentrations can reach 50 ppm (the normal recommended level for pool water is a maximum of 4 ppm), pH can be either close to 14 or 0 (normal levels are between 7.2 and 7.8) and temperatures can exceed 120 degrees.

I'm not sure about the two extremes of pH but if scale is going to happen it will occur on the plate at the greatest pH extreme, the cathode. So I thought it would be interesting to put a few pH values into here:

PO4 = 10^[11.755 - log(375) - 2log(26.67) - (0.65 * 7.5)] = 28.44 ppm = 28,440 ppb phosphate.

At a pH of 14 it's 0.00169ppm of PO4 and at 0 it's 2,133,044ppm of PO4. And for a minute I was thinking that at 2,133,044ppm of PO4 there's nothing to worry about but I had the cathode and anode mixed up where at the cathode it's 0.00169ppm PO4. So why don't we all have a PO4 scale issue and mixing up the cathode and anode is one answer as in a self cleaning cell the cathode and anode are interchangeable. ie. constantly switching. I have know idea what the frequency is.

So maybe the PO4 concentration won't matter that much for a self cleaning cell.

Just for interest here's the full quote for high PO4 inhibiting microbial growth that I had referred to.

Phosphate is required for microbial generation of ATP and for nucleic acid and membrane phospholipid synthesis. High concentrations of phosphate, however, may inhibit microbial growth. Concentrations of available nitrogen and phosphorous often limit both productivity and decomposition in aquatic habitats. Additions of of available nitrogen and phosphorus are often used to increase productivity in aquaculture practices. The elimination of the phosphate limitation is sometimes undesirable, as it can lead to prolific algal or cyanobacterial growth. This growth has occurred following addition of phosphates, in the form of household detergents, to lakes where productivity was phosphate limited.

There was no mention of a level or mode of interaction and since Atlas and Bartha tend to treat PO4 with NO3 I assume that very high nitrates may have the same affect. In an aquatic environment PO4 is considered limiting in favour of carbon or nitrogen because it's generally considered that there's generally plenty of carbon in the carbonate buffer system and many of the primary producers (Cyanobacteria) can fix their own nitrogen. I doubt it makes much difference but in the natrual environment 'limiting' is usually thought of as 'it is or was limiting but not anymore' while in aquarium and pool talk it's applied backwards as 'it's not limiting so how can we limit it'.

 

[Swampwoman]

Aus, I can't remember where I read it now but indeed that "self-cleaning" approach was by design to reduce scaling problems.

Jack' magic purple also has something in it that is supposed to clean the cell.

In a perfect world, I'd get my po4 down to "normal" levels and then add the Jacks that I bought. But right now we're leaning toward just seeing how far we can go as it is -- if the cell continues to be functional, the question becomes how long can it remain functional.

Here's where we're at/What we now know:

1. Since resetting average salt level yesterday, the cell has operated and produced chlorine without further error reading despite 40,000 ppb po4....which has to prove whatever the effects, they're not immediate -- its been about 13 hours of continual running.

2. Even though my chlorine wasn't holding consistently prior to the switch (despite passing the OCLT), with the cell in production at 50% overnight, my FC this a.m. Is 9. I'm now dialing down to 30% to see if it can maintain something closer to in-range.

3.My ph is back to "normal" for this pool at 7.4 without adjustment (acid rain? It did rain

4. This means my csi, with my low calcium reading of 100, is running about -.097 -- a little aggressive water-wise, but I'm vinyl, and while I didn't pay attention to csi previously, I believe I've typically run a little aggressive because I had even less calcium last year, TA in same range, and typically keep ph on low side.

What I'm not sure of is how aggressive is too aggressive...but for the cell, I suspect this should help in terms of PO4 scaling.

I'm thinking my goal now will be to see if I can make it to the 500 hour "check cell" mark without po4 removal.

My reasoning (perhaps insane) is that removing more po4, if it even works, will take at least $250 more worth of product, plus the pita of running the well nonstop plus the 20% chem drop from last time with the increase in iron.

Worst case, a new cell is in the $400 range.

I'm likely changing ALL the water next season with a new liner if I get my way, so it doesn't entirely make sense to drop another chunk on PO4 removal IF the cell will operate this season when the benefit to the water might only be a few months.

Every day that I can get out if the cell despite the po4 readings also will help answer the central question of whether its actually worth removing phosphates.

My hunch is normally, no, but this season might tell a different story

Ps fascinating about the po4 limiting level...wonder what it IS!

 

[AUSpool]

Jack's magic purple also has something in it that is supposed to clean the cell.

The word 'magic' leaves me feeling a bit sceptical. I use a 10% HCl solution - nothing that's not already in my pool.

With a son that is anaphylactic to dairy I'm in the habit of knowing exactly what's in every thing I use. Plus in one of my field trips we visited an old gold mine with a lake affected by acid mine drainage. What a disaster, a lake with a pH of ~4 above a town on level 5 water restrictions so from the start I've been very cautious about what I put in my pool.

Given your circumstances I think I would proceed as you've planed. Maybe put the $250 toward a rain water catchment system.

Ps fascinating about the po4 limiting level...wonder what it IS!

I suspect it has something to do with blocking or interfering with the movement of nutrients across the cell wall.

 

[Saturn94]

SW,

I'd be surprised if you have issues with the salt cell. While I don't have any numbers, my pool has been on a steady diet of Purple Stuff for years (since about 2006?). I recently tested our tap water for phosphates and it was between 500-1000ppb. Given those two factors I'd be shocked if the pool didn't have very high phosphate levels (I'll test the pool once I finish spring opening; just started yesterday).

My last salt cell lasted 7 years. I'd inspect the cell at closing each fall and rarely saw any evidence of scaling; at most a very small white deposit here and there that was easily removed.....certainly nothing that would have affected the function of the cell.

Maybe there is something to the Purple Stuff preventing scaling? I asked the company about the differences between the Pink Stuff, which I understand is higher concentration, and Purple Stuff. All they said was the Purple Stuff was specifically designed to work more efficiently in salt pools.