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

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I say try the pond water. Just grab a sample from a swampy green part of the pond. Should be enough.

You will need to mark water levels and keep the buckets level. I suggest topping off with bottled water. It has a pH in the 7-8 range with some alkalinity and no chlorine. So it should be good.

You might see if you can just buy some phosphate only fertilizer as opposed to using general fertilizer or else I think you might wind up crashing your pH again. Sometimes garden stores sell a phosphorous only treatment for stimulating flowering.


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I've never seen a phosphate only liquid fertilizer. I do have some MG Bloom Booster 15-30-15 that I can use. I already have the buckets marked in gallon increments. My next plan is to wait until the FC goes to 0 (probably a couple more days), add the fertilizer to the bucket and mix, then readjust that water to the same as the other bucket, then dose both buckets with algae water and mix. How does this sound?

I know I'll have to raise the pH in the fertilizer bucket, then raise the TA a little in the other bucket so they both match.

How many ppm of P do you think I should add? Originally I was going to add 120 ppm P but that seems like overkill and would like to add a realistic amount.
 
Sounds like a plan. Why not look for some monopotassium phosphate (potassium isn't really a big deal)?

Amazon.com : 5 Pounds Monopotassium Phosphate Fertilizer Garden

It's 52% P2O5 and 34% K2O. No nitrogen. It's mildly acidic with a pKa of about 6.8 so it shouldn't drop the pH too much if you add in a small quantity (120ppm is definitely overkill). I'd shoot for a phosphate level of maybe 3-5ppm, that should be more than adequate for what is considered "high" phosphate levels. I don't put much stock in test strips but, if that's all you have for testing phosphates then so be it. Also, grab your lake water sample and let it get good and green before you inoculate. You want to be sure that it is a source of algae first (add some organic debris to the pond water sample when you capture it so that your inoculant "broth" stays healthy). You shouldn't need to add too much, so I would take a sample of your water with no fertilizer in it, say one cup, and add to it no more than a few drops (say, 1mL) of the pond water. Mix that up well and then add a few drops of that dilution (again, no more than 1mL) to each of your buckets. That should dilute the innoculant down quite a bit and create a solution with some algae that closely matches the water in the buckets. You want the algae from the pond water but you don't want the chemistry of the pond water shifting anything in your buckets.

Keep the buckets out of direct sunlight (indirect light will be fine) and keep the tops covered with a damp cloth to reduce evaporation effects and to keep birds and other creatures from sampling the soup. But do uncover them a bit each day to let the samples "breath". Take pictures or setup a web camera to capture the cloudiness.

A better experimental setup would be allowing someone else to setup the fertilizer in the water without you know which is which (label the buckets A and B). This way your obvious bias doesn't skew the results :D

Good luck.


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While you're at it, make a third bucket up with bottled water (no nitrates) but add phosphates to it to simulate a nitrogen deficient environment as well.

You could also make a fourth bucket up with bottled water and your general purpose fertilizer (N-P-K) to use as a nutrient rich control solution. Techically speaking, you probably want to create a duplicate set of control buckets each with similar solutions but NO algae innoculant to rule out environmental contamination...

I think we're up to 8 buckets now ... :hammer:


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I'm thinking I should just ship smackdab 5 gallons of MY water ;)

Update: o.k. I just put 5 gal of my pool water unadulterated out back by the kayak (which regularly gets algae if I leave it too long without a rinse and rain collects - it hangs on a fence.)

I'm just gonna leave it there and take a peek every day. I live across from a river so im guessing there'll be algae spores floating around. I'll let you know when it goes green ;)
 
Well, apparently I can't keep the kids out of the buckets so I guess I'm not going to be able to do it without the question of contamination. I've looked for a place to hide them and have none. I vote for Joyfulnoise to take a crack at it. I guess I'll use my new fertilizer in the garden so not a total loss.
 
If they hadn't seen me messing with the buckets, they would have never even noticed them. "What's in there?" "What are you doing?" "Let me see?" is what I hear. I knew right then it was over. Oh well. I get a laugh out of them most days.
 
I've been sidelined a bit and forgot about te pail I set out June 26.

Well I hobbled over today and darned if its not crystal clear still.

The spot its sitting in is where I get algae stains on the concrete from the kayak.

When I test pool today, I will test to see if chlorine has zeroed out yet. Certainly not reactive considering my po4 level ;)

Update: still had 1.5 ppm FC, that's why. Boy, the higher (swg) cya sure make a difference!
 

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Update: Test bucket is def at zero FC now. Still clear and no algae...so that's 22 days now at 50,000+ ppb. Not terribly reactive, eh?

Could be the trace copper from my old heat exchanger that just bit the dust or the borates or could just be that an algae spore hasn't happened along.

If its still clear in another week, I'm gonna add a bucket of well water beside it to see if the well water turns ;)
 
Ok, bucket now has got algae starting. Today is the 23nd, darn near a month ;) Don't know how long FC was at zero, because I didn't notice and test again til Monday, at which point it was zero.

My fountain was refilled with pool water before a party on July 9th and with the health stuff going on I also forgot to give it any chlorine. It just started to turn also (added FC this a.m.)

Not scientific, but my hunch is (broadly, not precisely) that my particular combo of extremely high phosphates, metals (incl a bit of residual copper), cya at 70 etc isn't in fact any more "reactive" in terms of algae than the average pool. I would have to work pretty hard on the negligence front to cause a bloom if a pail of my water can sit in the sun for nearly a month with no treatment before it starts to turn green ;)

Just tested the pail for copper: barely changed color at all, would say .1

An earlier poster had read somewhere that extremely high phosphates could somehow limit growth...perhaps in this case that's what's happening.

So, my two concerns about phosphate levels this high were function of swg due to phosphate scaling (has now run since April flawlessly) and reactive water (water not reactive.)

My 15 year old heater DID develop a leak in the heat exchanger and showed signs of corrosion -- blue oxidized copper. But my salt level isn't actually much higher than it was last year (I've only added 2 bags since start up) even though I've switched to swg so this may be the outcome of age plus high salt wear down and possibly phosphate scaling. My ph has been allowed to be higher this year with swg since my metal level is lower...negative csi but not super aggressive. Either way, new heater is cupro so should be a better fit for swg and this time I'm having a zinc anode plumbed into the system just as a precaution.

I've contracted a new liner and ergo water change and will be trucking in new water next month so my only real phosphate consideration going forward will be whether or not I treat annually/periodically to offset my sequestrant usage...which will be much lower than historical. With some sequestrant use, a fairly new swg and brand new heater and liner, may well choose to go that route to avoid building up to a level in another five years where its untreatable ;)

image.jpg
 
[h=2]Hi All,[/h]

Very informative thread. I am considering phosphate removers because I fall in the class of people who might benefit, per this from Chem_Geek (Orenda PR-10000 versus cheap Lanthanum Chloride salt crystal

So the real question for pool owners who do what is practiced here at this forum is whether a product such as a phosphate remover savesthem cost in the long run. For that to occur several things need to be true: 1) theirlevel of phosphates needs to be somewhat low (500 ppb or lower; not 3000 ppb, forexample) and needs to be introduced at a low rate, 2) they need to maintain a lowerFC/CYA level to lose less and therefore use less chlorine and 3) they still need to makesure they don't get to a near-zero FC or else bacteria can convert organic phosphatesto orthophosphates and an algae bloom with subsequent required shocking would stillbe needed.





I believe that my pool has very low phosphates, but I want to make sure I haven't overlooked an obvious non-trivial source. I contacted my water utility and found that phosphates in the water supply are below detectable levels (13 ppb). No metal sequestrates added to source water or to my pool. No agriculture or industry nearby (I live in Berkeley, at the foot of the hills, about 1.5 miles from the bay). Pool is covered 18 hours/day. Very little organic debris in the pool. Swimmers are clean. Clothes washer detergent has no phosphates, so no residue there. Small amounts of phosphate presumably from soil, organic matter blow in. Had algae once when FC went to zero by mistake. So I'm thinking I have very little phosphate, and it is a limiting nutrient.

Question #1: Is there some potentially non-trivial source of phosphate that I could be overlooking?


Question #2: If my phosphates are as low as I suspect, can i use less than the recommended amount of Orenda PR10000 (to save money) without reducing its effectiveness?​
 
szmad,

I am currently running a phosphate remover experiment on my pool. I have lots of data collected so far but I will not share it until the end of the season when I have a full set to analyze and make proper conclusions from.

My PO4 levels started at 1000ppb in late March. I lowered them to ~100ppb using SeaKlear commercial phosphate remover (9000ppb/10,000gal removed per quart). I just measured phosphate levels yesterday and I am back up to 250ppb. So in my pool, they increase at a rate of roughly 37.5ppb per month. I have no PO4 in my fill water (municipal supply) and my pool is left open day & night. I use no metal sequestrants. There is no fertilizers used on my property or anywhere near me. So the only source of PO4 is bather load and organic debris.

I will update this thread with my chlorine usage at the end of the season.

As for product use - follow the directions on the correct amount to use. In my pool, I only had to use 8oz in a 32oz (1 quart) bottle. The SeaKlear product cost me $40. So I have plenty left to use over the coming seasons.
 
swampwoman,

re: zinc anode

Unless properly engineered into your existing setup, a zinc anode attached to the bonding wire and buried in dirt will do absolutely nothing for you.

Start another thread and we can discuss it further.
 
Thanks Matt, very interesting. I am looking forward to your results.

The Orenda web site has a dosing calculator but it isn't very informative, and doesn't tell me if the concentration/remediation function is nonlinear. I would expect that as the PO4 concentration declines, the required PR dose declines less than proportionately....

One quick question, which I'm sure is answered on some thread around here, but which I'll ask you since your online: can you recommend an inexpensive, easy to get and use PO4 measurer?
 
I use the K-1106 phosphate test kit from Taylor. It's a color comparison test that goes up to 1000ppb but, admittedly has a very limited color resolution chart. The test kit runs about $20 or so.

I believe swampwoman uses the Hanna Instruments electronic colorimeter tester as found here -

Hanna Instruments HI713 Phosphate Low Range Checker® HC: Science Lab Calorimeters: Amazon.com: Industrial Scientific

It is better in terms of measuring but I would definitely check calibration and accuracy. I believe Hanna also sells standards as well to ensure the device is operating properly. You do pay a premium for it though - $50 for the tester.

I personally think your PO4 levels will be quite low and getting under 100ppb should be easily attainable. So you don't really need a highly sophisticated tester to see that. Drops do fine in my opinion.

I wouldn't get too deep in the weeds trying to reengineer the phosphate remover chemistry. I don't see much utility in trying to use less than the prescribed dose. The chemistry works well as-described. You'll likely only need a dose of a few ounces if your phosphates are low and you're going to have to buy at least a quart (Orenda may only sell gallons at this point). So you're not saving yourself any trouble by trying to find some optimal low dose.
 
Thanks Matt, I'll either go with the K1106 or, as I explain next, just assume I'm low. I rechecked the Orenda web site (Dosing Calculator - Orenda Technologies), put in some different numbers and got a wider dosing range recommendation, which reveals that they assume a linear relationship between PO4 levels and dosing. In case you are interested, below are the dosing results for 1000 gallons of pool: Looks roughly like 0.05 oz per 100 ppb per 1000 gallons. So in the best-case scenario -- you can scale the dosing down linearly and add a small amount every month -- a 10,000 gallon pool that accumulated 50 ppb/month for 8 months of "open" time would need only 2 oz of the product per year, which at approximately $1.50/oz for the product is only ~$3/year. So for pools with low PO4 this is pretty darn cheap insurance. Of course, there might be some lower limit on the frequency or quantity -- they might not scale the way I've assumed -- in which case the cost would be higher. Still, I'm persuading myself to just buy a quart of the stuff and follow the 0-500 ppb dosing recommendations (one time shot plus maintenance). (Also, at such low doses, I presumably don't need to worry about getting a clarifier.)

PO4 quantity of PR1000

​

0-500ppb
0.2​
ounces​

500-1000ppb
0.4​
ounces​

1000-2000ppb
0.8​
ounces​

2000ppb+
1​
ounces​
 
Clarifiers are cheap, I would have one on hand. When I added the phosphate remover to my pool, I did it 4 ounces at a time and I poured it *extremely* slowly (barely a dribble) in through my skimmer with the pump running at high speed. After the first 2 ounces, I could immediately see that my water had lost clarity. It was not bad, I could still see the drain covers in the deep end and make out the screws on them, but the water had a definite fogginess or smoky character to it. By the time all 8 oz went in, it was definitely cloudy. I have a DE filter so there was no need to use a clarifier and the cloudiness cleared in about 5 hours with full restoration of clarity in 8 hours. My filter pressure went up by 3 psi and remained that way until I did my annual tear down and clean which was a few days later (I targeted my phosphate removal with my annual filter clean). I let the product work for 48 hours and it had done its job. I have no experience with sand filters but I do know from reports here that they take a lot longer to clear and may not fully clear away the resulting lanthanum carbonate/phosphate precipitates without help.

If you don't want to buy clarifier then you can also add some DE to your sand filter. We have a procedure in Pool School for doing it. The nice part about DE (pool grade, not food grade!) is that it really improves the filtration performance of sand filter and it get's flushed out with the next backwash so there's little worry about chemical interactions or chemicals remaining in your water. The downside is you have to buy a bag of DE and the smallest quantity I have ever seen for pools is a 5-lb bag. Most sand filters only need about a cup of DE to get the filtration boost so a 5-lb bag will last a looooong time.

Up to you of course. Please post back here when you experiment and let us know how it goes. Pictures are always a plus.

Matt

PS - If you don't want to buy a test kit, let the pool store test it for you. They looooove to test for phosphates and you don't have to buy anything...just tell them you'll think about it....
 

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