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Water Treatment Calculator for pH Reduction

02/09/2016 7:24 PM

I need some help trying to locate an online calculator or Excel spreadsheet that allows you to calculate the amount of a given acid (say Muriatic Acid...aka Hydrochloric Acid @ 10 degree Baume 15.7% or 20 degree Baume 31.45%) to be injected in order to lower the water pH a certain amount, given a process flow rate (GPM or GPD or mL/minute), with the results in Gallons per hour (etc) in order to size a chemical metering pump.

U.S or Imperial or Metric units are all okay.

I use to have one, but that was a few years ago before my office PC was hacked. Now I can't find one anywhere online.

If none are available, can any of you Chemistry Wiz share an example of as manual calculation?

This is what I have for given data: 8.0 GPM raw water process flow; initial pH = 9.1; desired pH = 7.4; and total Alkalinity = 175 mg/l.

I need to lower the raw water pH to make an Arsenic Adsorption unit more efficient.

It's been a long long time since Water Chemistry class. I'd hate to rummage through roughly 200+ Storage Totes down in the basement trying to find my books and notes.
HELP!

TIA!!!!!!!

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#1

Re: Water Treatment Calculator for pH Reduction.

02/09/2016 10:26 PM
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#2

Re: Water Treatment Calculator for pH Reduction

02/10/2016 6:57 PM

Good try SolarEagle. I've come across all 3 or them, with poolcalculator coming the closest that I need, but you need to work the resulting mass dose of acid fluid ounces back into Gallon per Hour of acid injection, based on the overall water volume to treat, which can be viewed as Gallons per Day sort of..... it's what I've been using currently.

One of them is solely for home brewing brew-ha-ha.

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#3
In reply to #2

Re: Water Treatment Calculator for pH Reduction

02/10/2016 11:29 PM

That's a matter of getting one's priorities straight, of course.

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#4
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Re: Water Treatment Calculator for pH Reduction

02/11/2016 1:57 AM

Well if you ballpark it, you should then be able to tweak it with testing the water....You know if you had a sophisticated enough feed system you should be able to just punch in the desired qualities and have the machine decide the dose rate....

CAT 1000 pH controller

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#7
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Re: Water Treatment Calculator for pH Reduction

02/11/2016 8:04 AM

I really like this controller....a bit pricey though.

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#5

Re: Water Treatment Calculator for pH Reduction

02/11/2016 3:58 AM

I used to run STASOFT on DOS, off a floppy disk, but it may help you. Version 4 is available at:

http://www.wrc.org.za/Pages/Resources_FreeSoftw.aspx

There is a lot of software for water leak management, but just check for Stasoft - 4.

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#9
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Re: Water Treatment Calculator for pH Reduction

02/11/2016 9:10 AM

Thanks, this appears to be what I am looking for!!!

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#6

Re: Water Treatment Calculator for pH Reduction

02/11/2016 7:47 AM

What drift allowance do you have on the output end?

The problem I see is that going between the two points will essentially remove the buffering capacity of the water, especially using a strong acid such as HCl. With the amount of change and finishing so near the neutral point, even a small fluctuation in feedwater pH can cause wide variations in the end flow.

Using a weak acid will reduce this issue somewhat, but a positive feedback controller as suggested by SE is likely the only way to nail it down to your desired level.

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#8
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Re: Water Treatment Calculator for pH Reduction

02/11/2016 8:13 AM

Preliminarily, I'm aiming for below pH = 8.0, because the AdEdge Arsenic Adsorption module is more efficient below that threshold, so I have a little play to work with.

I'm taking care of oxidizing the Fe & Mg with a predosing of Sodium Hypochlorite.....aka Cl2 Demand is taken into account. Yes, I know the raw water will pH will climb somewhat after after the injection of the Na Hypo.

This is a very small seasonal, privately-owned, water system, so $$$ is very tight for the Owner.

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#10

Re: Water Treatment Calculator for pH Reduction

02/11/2016 11:26 AM

The amount required will vary according to water mineral content.

The best way is to titrate a small sample and extrapolate for your volume.

This will give excellent results,and minimize overshoot and expense.

Crude,but very effective.

Experience will dictate your starting point,and as the water condition varies,small adjustments may be required.

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