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

[needsajet]

So I'm volunteering two pools for the season, provided I can get experimental design help from mas985 or joyfulnoise.

The strongest I can get is 200 g/L (~20%) 'rare earth salts' Phosphate remover (listed as 'lanthanum salt derivative' on the MSDS). Or I can get 15% that says simply 'lanthanum chloride'

I can use last year's FC/day as a baseline, which I have records for. The third pool, while not to be described as a control, might show up a material seasonal difference.

Two more data points, to add to the existing one. If we're up for the quest to rule phosphate reduction in or out, some number of years from now.

 

[Swampwoman]

Maybe compare the lanthanum chloride to the composition of Seakleer (lanathum chloride) which reports removal of 9,000 ppb per 32 oz in 10,000 gallons to get an idea of strength. Seakleer also recommends the addition of chitosan clarifier to help address any cloudiness caused by the lanathum.

Does the lanathum chloride you can access report a removal rate?

And do you already have a phosphate test kit? Taylor's only goes to 1000 ppb. All of them pretty much require dilution with distilled water to give much of an accurate read. Pool stores are def inaccurate, likely goes without saying

I use Hanna Instrments high range test, which is colorimetric. Here's a link n case you want to go that route: High Range Phosphate Colorimeter – Checker® HC HI717 - Hanna Instruments

One other consideration before you undertake the quest...check about your glass filter media. The lanathum chloride is meant to collect in your filter after being broadcast over pool for backwashing based on pressure rise a few days later. I don't know if glass media is contraindicated at all. Might be fine.

If the glass media is ok with that, a cheaper removal route for small quantities might be to add a very small amount of Alum to the filter instead, which will also collect and remove phosphates. Pool Alum mfgs post rates for this on the product. But any technical grade Alum works for this purpose. This might be more readily available in AU as its popular abroad for metal removal. Note - this is not like floccing where you add 4-12 lbs per 10k, which is also a hi po4 removal strategy I just tried and got a removal rate of 15,900 ppb on the rate of 8 lbs per 10k.

Keep us posted!

 

[needsajet]

Thanks for those suggestions, though I'm feeling a bit over-whelmed!

I found SeaKlear Phosphate Remover MSDS and it says '25% to 65% lanthanum chloride hydrate'. Yep, the phosphate removers here provide the removal rate and dosages recommended and their usage sheets also recommend a clarifier used in conjunction. I compared with your rate (32 oz per 10K gals to remove 9000 ppb) and the product I'm looking at here (20% lanthanum chloride) shows a rate about 4 times higher. Before I found TFP, I used a bottle of lanthanum chloride phosphate remover without any drawbacks. I looked back at my notes and I used way more than needed - around triple. That said, I make a good guinea pig for glass vs. sand because one of the two pools is on conventional sand filtration.

Incidentally, I noticed a question earlier about what threshold might be indicated, in the event that we found that phosphate removers were cost-effective. I've read a lot of labels lately, and I've seen a range of 125 to 200 ppb as the threshold for treatment. I'm not mentioning this because I believe it's right; it's just chem co. numbers after all, probably pulled out of thin air, but maybe it gives us a rough indicator or starting point.

I'm concerned about test kit cost because I'd like to try a method that would be do-able for most people at a cost commensurate with the potential savings. We're OK with pool store tests for iron and copper, and I know their accuracy isn't great on those either. Do you think they're better, worse, or much the same at testing phosphates vs. iron and copper? I suppose all over the map, haha

So what are the risks of using too much lanthanum chloride? For example, I have two test results from different pool stores, both at 200 ppb. So I was thinking of adding enough lanthanum chloride to remove 500 ppb. That's quite affordable for me. I'd like to stick to a method that's easily available to average pool owners. If helpful, I could take water to a few more pool stores for the added entertainment! Like most pool owners, I have no call for chelates, so I don't have huge ongoing inputs of phosphates. Likely just fertilizer blow-in and a bit in the fill water contributing to what I'm seeing in pool store tests (after the 'Start-up Tech' contribution when the pool was first filled).

Alum floc is also easy to come by. I'll go look at some products and see if they have any instructions for a filter method. Whatever might be easy for an average pool owner is something I'd like to try. It seems that lanthanum chloride is the common, simple, easy to buy, method.

If there's an opportunity to save people money, even if it's years in the future, I think it's a worthwhile exploration. No one got to 7.5%/4.5% FC/CYA without looking at lots of results, but it had to start somewhere

 

[JoyfulNoise]

Don't focus so much on daily FC loss, but keep an eye on total chlorine usage. Are these both SWG pools? If so, keep your CYA on high end (80-90ppm) and try to maintain your FC between 2.5-3ppm. See how that shows up as pump run time and SWG output.

Also, don't bother with alum flocc (no offense Swampwoman...), just find a source (commercial grade is best) of nothing but lanthanum chloride, no other additives. The SeaKlear Commercial Phosphate Remover is LaCl3 only. If these pools are sand filter pools, then I would only use a clarifier IF using DE in the sand filter doesn't help. So start by dosing the pool as recommended by the instructions and circulate for 48 hours straight. Add DE to the sand filter after dosing BUT DON'T BACKWASH right away. You typically want the system to run for 2 days in order to get the proper conversion of lanthanum carbonate to lanthanum phosphate. If the DE does not help, then try a simple polymeric clarifer (GLB Clear Blue is one but any locally available product will do).

200 ppb is really on the very lowest end of the scale. Honestly, that's practically zero in my book when it comes to algae nutrients. You're only going to need a few ounces of the phosphate remover to lower that and you may not even experience any cloudiness as a result. In my pool that had a little over 1000ppb, the water was more "hazy" than cloudy after treatment and the haziness cleared up in about 5 to 8 hours (I have a DE filter so no need for a clarifier). That was a dose of about 8oz of the SeaKlear PR.

Above all - KEEP GOOD RECORDS! When I was doing my tests, I had to construct a spreadsheet (pre PoolMath App days) and I tested daily or every other day. If you want to test that frequently, getting a K-1001 or K-1004 test kit to supplement what you have with a reliable DPD color matching cell is key for quick daily measurements.

 

[Swampwoman]

- At your small doses, no real worries about excess lanthanum. In larges doses it tends to floc (eg 2 gallons=flocc galore).

- if your po4 is likely under 1,000, pool store testing will be fine...ish. But for those using chelants/sequestrant at all, they will be inaccurate. I did an experiment last year going to 3 different pool stores. None were correct. Two under-reported dramatically, eg 1 at "750" and another at "1000" and a 3rd at "2500" -- The first two were both well under the limits of their strips (1000 and 2500 respectively)..,the 3rd at least was accurate in that he could tell it exceeded the limit of his 2500 strip

So you're vulnerable to their interpretation of "blue." Some can see intensity, others can't.

- with low #s, a quarter pound of alum added to filter via skimmer would theoretically remove your ppb...but i agree with Joyful to use lanthanum for posterity and experimental purposes as we don't want to have to support future alum done wrong by newbs

eg max application as filter aid would be a pound or all heck would break loose re gumming up the works. Also, alum at large doses increases sulphates, not ideal for swg. If it were used habitually, over time the concentration could reach problematic proportions. Not in single treatments done sparingly.

 

[AusJohn]

Hi Swampwoman,

I have come into this thread very late, I haven't read it all the way through. I just wasn't sure if you had found a resolution to your analytical problems but have a couple of comments. Based on your readings in your testing going back around the middle of the thread, you had astronomically high readings for phosphate that didn't seem to be coming down and you were wondering if the whole phosphate test involved some black magic of some sort.

There are, I think a couple of key points here. 1) you had been using phosphonate based sequestrants for an extended period, that can give you high phosphate levels. 2) you were mainly trying to control iron.

Your water chemistry at this point was atypical for simple tests used in pool or aquarium water and ripe for false positive readings. There are quite a number of phosphate tests where iron can give a blue colour. While your testing said 0.3-0.4 ppm of iron, your test would only be determining iron free in solution. Your levels of total iron are likely much higher as the iron bound to the sequestrant is not free to react and would tend to get ignored but the iron is still there. The bonding for the sequestrants is pH dependant and will be weaker at low pH. Most of the phosphate tests use chemistry that drops the pH quite low, between 1 and 2. This is likely to liberate more iron which also forms a blue colour with the phosphate reagents. Iron and phosphate also tends to stick to glass ware so unless you are acid rinsing and then washing your test tubes in distilled water 2-3 times you are likely to get some positive results for DI water when testing at the ppb level.

Secondly you had a question about the pH dropping due to lanthanum addition this does not relate to hydrolysis of water the way that adding iron or aluminium salts acidify water. The reason for this is very simple. The lanthanum precipitates initially as lanthanum carbonate and the removal of carbonate from solution drops the pH, just as adding carbonate to the water will raise pH.

I'm probably too late to actually help with your original problem but maybe it assists in understanding why you were having problems.

 

[Swampwoman]

Thanks for the info...better late than never.

Per the thread(s) that branched off from this one and by way of update, I was actually able to drop out my high po4 level and fe last fall with an alum floc treatment. My po4 is down to 5000 ppb range and no more scaling...my fe has been at zero and I've stopped using sequestrant entirely for the moment.

However, for reasons still not determined, my heat exchanger failed in subsequent months.

 

[AusJohn]

I'm glad it got resolved, yes alum would work reasonably well, not down to the level that you will get to with the lanthanum, but way cheaper to remove the bulk of it with alum when you have high levels.

My pool gets a lot of debris in it from palms and tree ferns. So phosphate can sneak in there, but it doesn't tend to build up. I have an old cheap SWCG that isn't self cleaning. Periodically I just let the pH drift up a little higher and as the chlorinator scales, it will tend to precipitate out calcium phosphate first or at least a mixture of calcium carbonate and calcium phosphate. Calcium phosphate scaling, like calcite scaling is very pH dependent but it's much less soluble than calcite as the pH rises. Self cleaning chlorinators are a bit more convenient, but there can be advantages to the old fashioned ones too, aside from their being a bit cheaper too.

 

[needsajet]

I'm in the midst of experimenting and Matt or Kate or others... the method is to backwash after 48 hours, and I have two questions.

After 48 hours, is there any risk the phosphates migrate back from the filter into the pool water? Or is it just ">=48 hours"?

Is cold water any impairment, e.g. with cold water should I wait longer before backwashing?

 

[JoyfulNoise]

I'm in the midst of experimenting and Matt or Kate or others... the method is to backwash after 48 hours, and I have two questions.

After 48 hours, is there any risk the phosphates migrate back from the filter into the pool water? Or is it just ">=48 hours"?

Is cold water any impairment, e.g. with cold water should I wait longer before backwashing?

48 hours is just a conservative figure (includes the time for the pool to clear). The conversion of lanthanum carbonate to phosphate is relatively fast and irreversible to a certain extent. So 48 hours gives you a good safety margin. Normally one would use testing to determine the end point and when I did the treatment my pool cleared in under 8 hours and the next day, about 24 hours later, the PO4 levels were zero. Using a time based method simply allows the pool owner to get away without testing.

Cold water shouldn’t be a huge impediment. I waited until my pool water was above 65F but that was because I didn’t want to mess around with my pool filter while the air temps were low.

 

[needsajet]

Thanks, Matt.

I'll write up my notes later and add them here, but my experience was similar... instantly and very slightly foggy water, then all gone after about 12 hours. I've been doing 40 grams lanthanum chloride at a time, but would double that comfortably if I did it again.

 

[JoyfulNoise]

Thanks, Matt.

I'll write up my notes later and add them here, but my experience was similar... instantly and very slightly foggy water, then all gone after about 12 hours. I've been doing 40 grams lanthanum chloride at a time, but would double that comfortably if I did it again.

Sounds good.

Are you adding granular lanthanum chloride? 40gm in your pool will remove roughly 800ppb PO4

 

[needsajet]

Unfortunately, the best I could find near me is liquid at 200 grams lanthanum chloride per litre (not very good I know, but the others were 15% and just said 'rare earth salts' so at least this way I know what I have, hopefully!). Riley00dog (TFPer in Brisbane) found granular at a pool shop so I tried a few here in Sydney but no such luck. (just responses like "You won't find powdered phosphate remover anywhere. Just buy this.")

Each treatment was 200 mls, so I translated to active ingredient at 40 grams.

 

[JoyfulNoise]

Ok. Sounds good. Best to use whatever you can find that’s designed for pools. As long as it’s just lanthanum chloride and no other “stuff” (clarifier, flocs, etc), then it will still work.

 

[cchaddick]

I'll be the phosphate-level devil's advocate. I don't necessarily disagree with the reasoning of those focusing on the FC/CYA levels and ignoring phosphates. However, after years of attempting to battle the yellow-green algae cycle via chemistry/clean/chemistry alone, I tried a phosphate remover. Notice that I didn't give a brand name or where I bought it - I'm not a salesman. I will say that it was less than $30 for the bottle.

I am not exaggerating when I say that since lowering the phosphates to near 0, I have not had a single spot of yellow-green algae this summer. It has made general chemical maintenance more economical and much less time consuming.

 

[Jimrahbe]

I'll be the phosphate-level devil's advocate. I don't necessarily disagree with the reasoning of those focusing on the FC/CYA levels and ignoring phosphates. However, after years of attempting to battle the yellow-green algae cycle via chemistry/clean/chemistry alone, I tried a phosphate remover. Notice that I didn't give a brand name or where I bought it - I'm not a salesman. I will say that it was less than $30 for the bottle.

I am not exaggerating when I say that since lowering the phosphates to near 0, I have not had a single spot of yellow-green algae this summer. It has made general chemical maintenance more economical and much less time consuming.

c,

Just for interest, where do you normally run your CYA and FC???

Thanks,

Jim R.

 

[Leebo]

As I started this thread a few years ago I did so knowing full well a personal test was in order. I had a few questions in my head that I was interested in seeing for myself and the best way I personally learn is by doing. In the following I hope to share some of what I personally have learned. I hope to write this in a way that leaves opinions out however there will be times I cannot back-up what I say with solid numbers or facts. When I do make comments that can’t be backed up I hope to make sure to express that the statements are opinions or unproven facts.

So let’s start with some background why this topic always interested me. Since we converted from Baquacil I had always kept my CYA level in the 30-40ppm ballpark. This meant that my FC could be as low as 2ppm at times and still be “safe” following the FC/CYA ratio. That said, I commonly struggled with the water when we allowed the FC to stay around 3ppm for more than a day or two. I don’t have numbers or spreadsheets to show you here, but commonly if we allowed the chlorine level to hang around 3-4ppm for a day we’d lose the “TFP Sparkle” I always wanted to keep. It wouldn’t really turn cloudy, but the water looked dull. As soon as we’d bump the chlorine level up towards the top end of the FC Chart the sparkle would reappear. We got to a point where we would keep our FC level at a minimum of around 5 and would try to keep it around 7ppm at all times. Looking back at old PoolMath logs our average FC level from June 1st to Sept 30th

2017 was around 9.5ppm. To maintain this level we would use roughly a gallon of 12.5% liquid chlorine every other day, or about 60 to 65 gallons for June, July, August and September. Unfortunately PoolMath didn’t record chemical additions at this point so all I can say is rough estimates, but I would say an estimated FC loss of 2.5ppm per day was correct.

In early June 2018 I had ordered the Taylor K-1106 phosphate Kit and found that my phosphate level was in the ballpark of 1,000ppb. At that point I also ordered a quart of Orenda’s K-10,000 phosphate remover. Added roughly 10 ounces which removed almost all of the phosphates. Since this addition I’ve rarely needed to add any additional remover. To date I’m still on my initial quart of phosphate remover. After two seasons of removing phosphates I’m only out roughly $60 for a test kit and the chemical itself. I’m crossing my toes I may even have enough left to try to stretch this initial purchase out for a third season. ??

During the last two years I’ve slowly allowed myself to accept the bottom end of the FC/CYA ratio. I’ve slowly started to allow the chlorine levels to stay just above the minimum while keeping water sparkling. While before I was adding a gallon of 12.5% every other day I now find myself adding a gallon of 10% every three days. In 2017 I would commonly maintain an average FC level of around 10 but now I have cut that almost in ½ and maintain an average FC level of around 5. Because I was able to accept the lower end of the FC/CYA ratio I was able to lower my daily chlorine use from almost 2.5ppm down to around 1.5ppm. With these savings I estimate that I paid off the initial $60 price tag in about 2 months and have been saving on chlorine ever since. Additionally I’m able to spend just a hair less time each week carrying jugs of chlorine around and spend more time enjoying the pool.

Now as many who know me will agree, I enjoy a good argument. Debating allows me to really see both sides of the story and make informed decisions. So I’d like to spend a few minutes discrediting my own text above.

First, I did maintain the FC/CYA ratio the entire time. Seldom did I ever allow my chlorine levels to drop below the minimum level, and even less frequent did I allow it to stay for any length of time. Would the water keep its “sparkle” right now if I’d increase my phosphate level and continue to allow the chlorine level to drop down to 2-3ppm? I can’t answer that for sure. While In the past I had struggled while keeping the FC that low, but I can’t say for sure what would happen. Second, I still had to slam each year. These last two July’s has seen us leave for a week with nobody to watch over the pool. Each time we left for around 10 days and each time we returned to a green pool. Part of the reason our average chlorine is as high as it is over the last two years is each year it also includes a week long Slam. It’s my personal opinion that removing phosphates did give me a bit more “wiggle room” to maintain that TFP sparkle, but it didn’t allow me to avoid algae 100%.

 

[JoyfulNoise]

@Leebo

I can sum up your post in one sentence .... for Pete’s sake, would you just get an SWG already ?‍♂?‍?‍

 

[ajw22]

In early June 2018 I had ordered the Taylor K-1106 phosphate Kit and found that my phosphate level was in the ballpark of 1,000ppb.

Lee, it should be pointed out that you acted on phosphates based on your own testing with the K-1106.

I was told by my pool guy that I had high phosphates. He said the office told him to bring a water sample to the office to test for every pool he services. I got a K-1106 test kit when I ordered phosphate remover. But before I used it I did the K-1106 in front of my pool guy. Guess what, negligible phosphates. I still have the unopened bottle.

If you are going to treat phosphates base it on your own testing.

 

[mas985]

@Leebo, I had a very similar experience this year.

My first SWG cell lasted almost 10 years which I know is probably above average to begin with. However, my second cell that I just replaced at the beginning of this year only lasted 4.5 years. The difference? I believe it has to do with phosphates but let me explain.

For the first 10 years of my pool experience, I would replace the pool water every year or every other year because of high CH levels. Unbeknownst to me, I was also keeping phosphate levels down as our fill water has over 200 ppb of phosphates. The year after I replaced my first SWG cell, our area came under drought water restrictions and we were asked to not replace pool water so I didn't for the next 4 years. What I noticed as time went on is that it became harder and harder to keep algae at bay with FC levels near the lower end of the SWG recommendations (5%) as I had done for years. Right before the cell failure, I had to run closer to 10%. After the cell failure, I tested the pool for phosphates thinking that it might be related and sure enough the level had climbed to over 4500 pbb. So a few months ago, I removed the phosphates and now am able to run again at a 5% CYA FC level.

So while it may be true that you can operate a pool just fine with high phosphate levels, it does come at a cost of higher FC levels and in my case, more frequent SWG replacement. The cost of those 4 years of cell life far outweighs the cost of the treatment. So in the future, I will be keeping an eye on phosphate levels.