New water report

[roblanderson]

I spoke with someone at our city water department and she sent me the numbers I need to enter into Bru n water. See the attached screenshot for the details.

When I enter this into the Bru'n Water spreadsheet I'm told that the Cation/Anion difference is showing an unbalanced report. They should be within 0.5 of each other and instead it is 4.84 - quite a difference.

Have I misinterpreted the numbers I was given? Do they need to be converted first maybe?

 

[stpug]

That water report just looks wacky. Fairly high mineralization with fairly low alkalinity, and a 9 (unit) pH. Maybe my bumping this will garner the attention of AJ or Martin.

^Bump^

 

[mabrungard]

I'm a little concerned that the Ca and Mg levels are expressed in "as CaCO3" terms. The 40 ppm Mg level would make this water questionable for brewing use. But if that is in as CaCO3 terms, then the true concentration is only 9.7 ppm. The Ca concentration would also be lower if it was expressed as CaCO3.

Use the conversion calculator to convert those Ca and Mg values and see how the balance works then. Of course, you could always check with the City and see if they are reporting those values as CaCO3.

 

[passedpawn]

[moved to brew science]

 

[ajdelange]

They are quite clear (footnote) that all the ion concentrations are in mg/L even going into the distinction between NO3 as nitrogen and NO3 as the ion. OTOH alkalinity has to be in ppm as CaCO3 so why not the hardnesses? Interpreting the hardnesses as the metals leads to pretty wild imbalance so I think we have to assume they are 'as CaCO3'. Expressing them as such has long traditional standing. It was only fairly recently that laboratories using ICP and ACS started reporting Ca++ and Mg++ as the metals.

An alkalinity of 55 at pH 9 implies bicarbonate of 59.9 and carbonate of 2.5 as compared to the values of 43 and 12 given in the report. Bobbling this computation is fairly common. There is a caveat with the method that says something to the effect that the numbers do not represent ion concentrations in the usual sense. I don't know what sense they do represent ion concentrations in but even Ward Labs was doing this until it was pointed out to them that it was throwing balance calculations off (the only thing one really needs bicarbonate and carbonate concentration data for). Fixing this and interpreting the metal 'as CaCO3' gets this report down to a balance of 3.425/3.095 - as close as many Ward Lab reports (after they corrected the carbonate/bicarbonate). The rest of the imbalance is very probably attributable to the fact that data was accumulated from samples taken on four different dates. Mineral contents of sources change over time. Any sample of water will balance but you can't expect sodium measured in January to balance with calcium measured in March.

What to do? Put in the corrections indicated above and live with 3.2/3.1 (2.4% imbalance). The only place where imbalance is important is where you are trying to synthesize a given profile. You cannot synthesize an imbalanced profile because nature does not allow them. This is not intended to diminish the significance of the imbalance numbers as a quality control check!

The other thing to do, of course, is to send a sample off to Ward Labs and see how it compares to the corrected data from the utility. That's probably a good investment.

 

[roblanderson]

Thanks for the input everyone! I made these adjustments:

Converted Calcium from 80 -> 32.1
Converted Magnesium from 40 -> 9.7
Converted Bicarbonate from 43 -> 52.5
Converted Carbonate from 12 -> 7.2

These changes give me a very close to balanced Cation/Anion ratio. I've got a follow up email to the person who gave me the original numbers. Depending on what I hear back I may go ahead and send in a sample to Ward Labs as well.

 

[ajdelange]

Converted Bicarbonate from 43 -> 52.5
Converted Carbonate from 12 -> 7.2

How did you get those numbers? Alkalinity (defined to end point 4.4) of 55 and pH 9 gives bicarbonate of 59.89 and carbonate of 2.48 assuming ideally dilute solution chemistry. Making the usual corrections for finite ionic strength gives 58.68 and 3.02. Assuming alkalinity is defined to end point 4.5 (ISO) the numbers are 60.51 and 2.51 for ideally dilute chemistry and 59.33 and 3.06 when the other ions are accounted for.

There's a simple check you can do on carbonate and bicarbonate numbers. Take their molar ratio. Using the values you propose that ratio is (7.2/60)/(52.5/61) = 0.139429. The ratio (ideally dilute chemistry) should be 10^(pH - 10.376) = 10^(9 - 10.376) = 0.0420727 so clearly 52 and 7.2 cannot be the right numbers. Wonder how you got those.

These changes give me a very close to balanced Cation/Anion ratio. I've got a follow up email to the person who gave me the original numbers. Depending on what I hear back I may go ahead and send in a sample to Ward Labs as well.

Did you intentionally distort the bicarb and carb to get better balance?

The lab should be able to tell you what the end point of the alkalinity titration was and will certainly confirm that the hardnesses were reported 'as CaCO3' but won't know what you are talking about with respect to the carbo corrections. They'll just say "Well we use Standard Methods {whatever the method number is}".

 

[roblanderson]

I used the conversion calculator on the Bru'n Water spreadsheet.

You are way over my head of course, but thanks for the explanation! If I use 58.7 for bicarbonate and 3.0 for carbonate then it perfectly balances.

 

[ajdelange]

Did you enter alkalinity and pH? I thought that if you did that it would come up with close to the 'right' answer (as #7 shows there can be some variability depending on how you assume the lab measured the alkalinity) as I think I remember some posts where people did that and got the right answer. Maybe I don't remember correctly. Perhaps you have an old version of the spreadsheet?

 

[roblanderson]

First I just used the Ion Concentration Conversion Calculator at the bottom. I entered 43 and 12 and used the results. Now I see that when I enter the alkalinity as 55 and ph as 9 that I get a different estimate. Screenshot attached.

 

[ajdelange]

That's better. I thought it worked that way. It apparently assumes alkalinity endpoint of 4.5 which is probably reasonable as that is what the ISO method uses though Ward Labs used 4.4.