I work at a water bottling plant and I'm just trying to figure out how to test our mineral solutions. I'd appreciate it if anyone can help me with this one.

One blend of water uses a sodium sulfate/sodium bicarbonate solution which is injected in RO water at a rate of .75ml per 1 gallon. The mineral solution is made of 96 gallons RO water, 30.72 lbs sodium sulfate and 50 lbs sodium bicarbonate. TDS on RO averages approx 0.8 ppm and the desired TDS on finished product is 12 - 18 ppm. What should the TDS on the mineral solution be to give me the desired result on finished product.

Hi Mr H

O.k you have 96 gallon mix ro water with 80.72 lbs solids or 36.6139761064kg

Your ppm for that mixture are 83863.3ppm(a correction they are 83895.3)

You are then adding 75ml of that to another RO Gallon and seeking a 12-18ppm

96 gallons into litres is 4.54 x 96 = 435.84 litres with a 83863.3ppm

435,840ml / 75ml = 5811.2 doses. say 5811

83863.3ppm / 5811 = 14.43ppm and lots of other 1s and 3s and such.

So I think what your asking is "why am I only getting 0.8ppm? Because the 75ml solution I add should have about 14.43ppm in it"

Except that's going into a Gallon.

Your 75ml soultion has about .00108grams inside it.

So if I put that in a gallon(uk) I get a ppm of 0.237567ppm

You claim you're getting 0.8ppm, which to me suggest that the concentration is slightly higher than .00108grams probably around .0037grams per 75ml you add, giving you around 0.8ppm.

If I'm right.

You need to increase the 96 RO gallon mixture you use for the 75ml soultion.

By well lets think about it,

To get a ppm in gallon(uk) of 16ppm you need your 75ml solution to have 0.073grams or 73mg in it.

73mg times by 5811.2 = 424217.6 which is 424.2176KG

I believe your ratios are 62% Sodium bicarbonate and 38% sodium sulfate

so 424.2176 / 100 = 4.242176 x 62 = 263.014912kg or 263kg of sodium Bicarbonate

424.2176 / 100 = 4.242176 x 38 = 161.202668 or 161.2kg of Sodium Sulfate.

So if that is what you are doing.

Your current 36.6kg of sodiums, in the 96 Gallons RO mixture for the 75ml solution is way too small.

What you need to do is put in 161.2kg of sodium sulfate to the 96 gallons and 263kg of sodium bicarbonate. Then your 75ml solution from that should have a concentration high enought for 75ml to increase the ppm in a gallon of RO water to 16ppm.

It's 424.KG of solids in 436.litres roughly.

That mixture should give you a solution where 75ml of it will cause a Gallon(uk)of RO water to get a ppm of arround 16ppm.

**If that's what you are doing.**Rosy or Bored Chemist if that is what he wants, to make up a 96 gallon Ro solution of two different sodiums, then to use 75ml of that solution to make another Gallon have a ppm of between 12-18ppm is that right?

From what you have shown me I think it is.

What should the TDS on the mineral solution be to give me the desired result on finished product.

TDS on the 75ml solution 73mg. ppm on 75ml solution 973.333ppm

TDS On RO 96 gallons for the 75ml solution 424.203Kg and you should get around 5811- 75ml solutions from it.

TDS on a Gallon RO for a 16ppm 0.073grams

73mg / 100 = 730 micrograms x 62 = 45.26mg sodium bicarbonate 62%

73mg / 100 = 730 micrograms x 38 = 27.73mg sodium sulfate 38%