How does one test for organic phosphates?

[09659]

It should also be noted that the phosphate tests only test for inorganic phosphate (aka orthophosphate).

How does one test for organic phosphates?

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XXX XXXXX® Phosphate Remover is a highly concentrated solution formulated to react with phosphates in pool water.

Apply XXX XXXXX® Phosphate Remover evenly into the water around the perimeter. Please use reference chart for complete dosing information, after checking Ortho-phosphate level with a test kit. Do not apply more than 8 ounces in an average residential pool per treatment. Clouding will occur upon addition and increase filter pressure, so backwash and/or clean the filter as necessary. Recheck phosphate level after application and treat accordingly. Also test phosphate levels monthly to ensure proper maintenance. Be aware that phosphate testing is subjective and is influenced by existing algae. Algae in a pool will result in a false reading. Additionally, polo-phosphorus & other chemicals are added by municipalities to control infrastructure piping. Poly-phosphorus does not show up on the test kit, therefore will also distort true phosphate loading.

Dosing chart* is based on treating 10,000 gallons of water.
Ortho-phosphate level..........Ounces to add
0-500ppb............................2 ounces
500-1000ppb.......................4 ounces
1000ppb-2000ppb................8 ounces
2000ppb +..........................10 ounces plus

Handling & Storage:
XXX XXXXX® Phosphate Remover is inherently stable with an indefinite shelf life under normal storage temperatures less than 120 F (48.9 C). Prevent freezing to avoid container damage and product loss.

Though XXX XXXXX® Phosphate Remover is non-toxic and non-hazardous, gloves and appropriate eye protection should be worn when handling and using the product. Review the product MSDS before using.

*Competing impurities in water, including but not limited to fluoride, arsenic, poly-phosphorus as well as variances in source water quality interfere in testing and removal rates. The goal of this product is to remove phosphorus and improve overall water quality and efficiency with the use of sanitizers. The use of this product is assuming proper filtration, circulation, and industry standard water chemistry.

* XXX XXXXX® Phosphate Remover is not an algaecide and does not kill algae.

Be aware that phosphate testing is subjective and is influenced by existing algae. Algae in a pool will result in a false reading. Additionally, poly-phosphorus & other chemicals are added by municipalities to control infrastructure piping. Poly-phosphorus does not show up on the test kit, therefore will also distort true phosphate loading.

*Competing impurities in water, including but not limited to fluoride, arsenic, poly-phosphorus as well as variances in source water quality interfere in testing and removal rates.

Could you please comment on these two sections?

Thanks

 

[JasonLion]

How does one test for organic phosphates?

There is no practical way to do so. There are lab tests, but I don't know of anything affordable that will do it.

Phosphates bound up in algae won't show on the test, but will appear in the water eventually when the algae dies.

Your second quote should be obvious. Some chemicals will interfere with the test and some chemicals will interfere with the removal process. Both are fairly rare, they are just covering themselves legally.

I don't understand where you are going with this. Answers to these questions are not going to help you take care of pools.

 

[09659]

I am a subcontractor for someone who, perhaps, over-values phosphate removers.

I'm trying to give him a, perhaps, more realistic view of phosphate removers.

Is poly-phosphorus organic phosphates?

I'm trying to show someone that it says right on the bottle that phosphate tests do not include organic phosphates.

Answers to these questions are not going to help you take care of pools.

Not directly, but indirectly it will. I'm hoping to convince him that there are better ways to manage pools than with phosphate removers. If I succeed, it will make taking care of pools easier for me.

 

[chem geek]

Polyphosphate is inorganic, not organic phosphate, but won't show up in orthophosphate tests. The organic phosphates will also not show up in the orthophosphate test. The organic phosphate found in algae as well as the organic phosphate found in HEDP metal sequestrant will break down slowly from chlorine to form orthophosphate so you may think you have no phosphates now but they will show up later after these compounds break down.

There are two primary phosphate tests that work essentially in the same way. The Taylor K-1106 test first adds an R-0980 reagent with sodium molybdate (Na₂MoO₄) and sulfuric acid which when mixed with a sample containing phosphate produces PMo₁₂O₄₀³⁻. A reducing agent is then added, such as the Taylor R-0981 reagent stannous chloride with glycerol (and R-0007 thiosulfate is also added to remove chlorine) to form the blue ion PMo₁₂O₄₀⁷⁻. The Taylor K-8005 test adds an R-8005A reagent with ammonium molybdate tetrahydrate, antimony(III) potassium tartrate, and sulfuric acid while the R-8005B reagent adds the reducing agent ascorbic acid.

This link describes the different kinds of phosphates and says:

Orthophosphates are relatively easy to measure and will usually give a rough indication of the total level of phosphates in the water. Orthophosphate concentration is determined by means of a chemical reaction resulting in a color change dependent on the concentration of orthophosphates present. The intensity of the color is then measured with a Vernier Colorimeter.

The test for total phosphates involves digesting, or treating the sample with an acid and an oxidizer, and boiling for 30 minutes to convert all the phosphates into orthophosphates. The orthophosphate test is then conducted on the sample. The results are reported as total phosphates. This test is more involved than the orthophosphate test, but it is the form of phosphates most commonly reported.

The pool store tests are the same as the Taylor ones and test only for orthophosphate since, as you know, the pool store employees aren't adding an acid and an oxidizer to the sample and boiling for 30 minutes!

 

[09659]

First of all, unless you live in an older city such as New York, Chicago, or St. Louis, less than 15% of municipal cities still add polyphosphates (SHMP) to reduce pipe corrosion.

Inorganic phosphates include, but are not limited to, SHMP (Sodium Hexametaphosphate) and TKPP (Tetra-Potassium Pyrophosphate). There are numerous other inorganic phosphates that will also serve as suitable secondary inhibitors. Organic phosphates or phosphonates include, but are not limited to, HEDP (1-Hydroxyethylidine-1,1-diphosphonic acid; also known as ethanol diphosphonate, acetodiphosphonic acid, or etidronic acid), ATMP or AMP (aminotri(methylenephosphonic acid)), PBTC (Phosphonobutane tricarboxylic acid), DETPMP (Diethylenetriaminepenta(methylene phosphonic acid)), and HPA (hydroxyphosphono acetic acid).

This agrees with what you said.

 

[chem geek]

My water district north of San Francisco uses orthophosphate for corrosion control and it of course shows up in the standard phosphate test. It's roughly 300-500 ppb phosphate.

Algae and bacteria can use organic phosphates as nutrients, but it's slower uptake since they must be broken down into orthophosphate for use. It is orthophosphate that is the most bio-available so contributes to faster algae growth -- of course only if the active chlorine level isn't high enough to kill the algae faster than this growth. Even in the presence of an abundance of phosphates and nitrates, algae are ultimately limited in their growth rates by sunlight and temperature.

The links to your sources are the following (one should normally include those when possible) where the first one is from Phosphate_Facts_and_Myths.pdf from mcgrayel.com while your second source is from patent application US 20030230742 A1. These are not authoritative scientific sources, especially the patent application. That doesn't mean the information is incorrect, just that you need to be careful. The mcgrayel file says that phosphates aren't a problem unless very high above 1000 ppb, but I have had 3000 ppb in my pool and others have had 5000 ppb and one over 20,000 ppb and yet in every case algae growth was prevented by maintaining a proper FC/CYA ratio. There is no question that a pool high in algae nutrients is quite "reactive" so a phosphate remover should be seen in the same vein as an algaecide, namely as insurance if one does not expect to be able to maintain a proper FC/CYA level.

So as a pool service you should compare the price of a weekly dose of Polyquat algaecide vs. regular phosphate remover if you have to have something to control algae and also consider whether the water supply is going to continue to add phosphates to the water in which case the Polyquat might be more economical.

As for the differing rate of algae growth for orthophosphate vs. organic phosphates, this paper indicates that bacteria utilize organic phosphates much more than algae (i.e. the fastest algae growth comes from orthophosphate). This paper has similar conclusions where essentially it is the more efficient bacterial conversion of organic phosphates and excretion of orthophosphate that can provide this faster-uptake nutrient to algae. In a pool, however, bacteria are killed very quickly with chlorine so this mechanism isn't readily available -- that is, bacteria aren't converting organic phosphates rapidly to orthophosphate so algae are left to do that on their own, much more slowly.

 

[09659]

Wholesale prices:
Minimum maintenance doses:

Polyquat 60 Algaecide Equivalent:
2 fluid ounces = $0.87 / week / 10,000 gallons

Ortho-Phosphate Remover:
2 fluid ounces = $1.22 / week / 10,000 gallons

Polyquat 60 Algaecide Equivalent:
-Lower Cost
-More consistent dosage requirements
-Clarifies water
-Does not cloud water
-Does not clog filter
-Works regardless of inorganic phosphate levels (inorganic phosphates are food for algae, also known as orthophosphates)
-Works regardless of organic phosphate levels (organic phosphates turn into inorganic phosphates over time)
-Works regardless of nitrate levels (nitrates are food for algae)

Ortho-Phosphate Remover:
-Higher Cost
-Less consistent dosage requirements
-Does not clarify water
-Clouds water temporarily
-Clogs up filter
-Lowers only inorganic phosphate levels (inorganic phosphates are food for algae, also known as orthophosphates)
-Does not lower organic phosphate levels (organic phosphates turn into inorganic phosphates over time)
-Does not lower nitrate levels (nitrates are food for algae)

Am I missing anything?

 

[jblizzle]

Yeah, the fact that with adequate chlorine you don't need any of that stuff. And that they are just bandaids trying to cover the underlying problem.

 

[chem geek]

Nope, you've pretty much summed it up and is why we recommend Polyquat if one has to have an algaecide for some insurance such as with only visiting a pool to dose once a week. The only time the phosphate would be cheaper is if you didn't need to do as much weekly maintenance if the water supply didn't add phosphates and you didn't use phosphate-based metal sequestrants or have blown-in fertilizer.

Perhaps the only caveat would be if one had yellow/mustard algae since neither Polyquat nor borates seem to keep that in check. That's one case where if not eradicated the use of a phosphate remover can help, but the downsides of a phosphate remover remain. There are other approaches for yellow/mustard algae, but they have other long-term side effects such as turning the pool effectively into a bromine pool or having to maintain a higher chlorine level (FC that is at least 15% of the CYA level).

 

[09659]

Yeah, the fact that with adequate chlorine you don't need any of that stuff. And that they are just bandaids trying to cover the underlying problem.

The prime-contractor won't let me have the Free Chlorine go above 5 ppm and he won't dilute the water because of high cyanuric acid levels. I cannot maintain the proper FC/CYA ratio.

I don't have much choice.

 

[chem geek]

When I first got my pool 11 years ago I followed the advice from my pool builder and pool store so was using Trichlor tabs and all kinds of other products including Polyquat algaecide, clarifier, enzyme, and metal sequestrant. My pool started to get dull/cloudy after a year and a half when the CYA hit around 150 ppm and I was trying to maintain 3 ppm FC. However, I only used the Polyquat every other week so perhaps using it weekly would have let me get the CYA to 200 or 250 ppm. So if you are able to have the FC up to 5 ppm, then perhaps with Polyquat the CYA could get to 400 ppm before you run into trouble with algae, depending on other factors like algae nutrients.

Such a low FC/CYA level will oxidize bather waste more slowly so won't do so well with pool parties, but for low bather-load it may still be OK especially for an outdoor pool.