High Phosphorous in RODI

[Todd31]

Hello,

My ATI water lab test for my RODI came back telling me my Phosphorous was high:

Phosphorus 3.59 µg/l

I have a 4 stage RODI system from BRS. Very recently changed my sediment filter and carbon block. DI Resin looks to be about 3/4 of the way color changed, and I still get a reading of 0.00 on the TDS meter.

What should I be doing?

 

[Randy Holmes-Farley]

Do nothing at all. This is a perfect example of unguided info from an icp test of RO water being more trouble than benefit.

That amount of phosphate, when used for top off, is hundreds, maybe even thousands of times less than you add each day in foods. It has no significant effect on the phosphate balance in the tank. I show that in an article that I’ll link in the next post.

 

[Randy Holmes-Farley]

Here it is. Note that you have far less than 0.05 ppm (50 ug/L) phosphate


http://www.advancedaquarist.com/2012/3/chemistry

From it:

Comparison of Food Sources of Phosphate to Other Sources
What about other sources of phosphate, like the "crappy" RO/DI water containing 0.05 ppm phosphate? A similar analysis will show it equally unimportant relative to foods.

Let's assume that the aquarist in question adds 1% of the total tank volume each day with RO/DI to replace evaporation. Simple math shows that the 0.05 ppm in the RO/DI becomes 0.0005 ppm added each day to the phosphate concentration in the aquarium. That dilution step is critical, taking a scary number like 0.05 ppm down to an almost meaningless 0.0005 ppm daily addition. Since that 0.0005 ppm is 40-600 times lower than the amount added each day in foods (Table 4), it does not seem worthy of the angst many aquarists put on such measurements. That said, tap water could have as much as 5 ppm phosphate, and that value could then become a dominating source of phosphate and would be quite problematic. Purifying tap water is important for this and many other reasons.

 

[Todd31]

thanks for your feedback... I was concerned because they have a separate phosphorous and phosphate measurement... and I'm not savvy enough to know the difference

Phosphorus 3.59 µg/l 0.02 µg/l +3.57 µg/l

Phosphate 0.01 mg/l 0 mg/l +0.01 mg/l

 

[Randy Holmes-Farley]

thanks for your feedback... I was concerned because they have a separate phosphorous and phosphate measurement... and I'm not savvy enough to know the difference

Phosphorus 3.59 µg/l 0.02 µg/l +3.57 µg/l

Phosphate 0.01 mg/l 0 mg/l +0.01 mg/l

They likely only measured total P (phosphorus) by ICP (can't actually measure phosphate separately with that technique), assumed it was all phosphate, and calculated it mathematically from the molecular weight of phosphate. That's what Triton does for aquarium water. The values are quite low.