After building my water for a long time, I am entertaining using my municipal water. I have reviewed the last 10 years of WQRs and the values are consistent based on the source, which in my case is 90% from Lake Ontario and 10% from Lake Otisco. I had the water tested a while back and it corresponded almost exactly with the WQR averages for a ten year period. So it’s stable:
Ca = 33.9
Mg = 9.2
SO4 = 22.9
Cl = 27.7
Na = 8.9
My question relates to the phenomenon by which Carbonate Hardness = Carbonate Alkalinity for Water pH < 8.5.
Since the CO3 component of the alkalinity will generally be a small percentage of the HCO3 concentration when Water pH is < 8.5, is it fair to say that Carbonate Hardness = Carbonate Alkalinity in that scenario?
If so, it would seem that, for my water at least, HCO3 can be calculated as follows:
Hardness as CaCO3 = (2.49733.9)+(4.1649.2) = ~ 123
My local WQR quotes my Water pH as being between 7.1-8.5 (which i’ll verify by measuring of course) so let’s assume the median of 7.8. Assuming an Alkalinity value equal to the Hardness value:
Carbonate hardness will be zero at beer pH. It will all be bicarbonate. The h in hco3 becomes unbound to the co3 and binds to an OH to form a water molecule at 8.3 and above. Bicarbonate can only exist if there isn’t a bunch of hydroxide ions, which there aren’t any at beer pH. That’s part of the reason for using the caco3 equivalent and why lime softening works.
Why are you assuming hardness is equal to alkalinity? That’s only the case if Residual alkalinity is zero and rare for source water. If the pH is in the high 7 to low 8 range you provided, then your RA is a positive value, which means there is more alkalinity as CaCO3, then hardness as CaCO3.
I’m trying to correlate the hardness as CaCO3 to Alkalinity as CaCO3 because my WQRs have stable Ca and Mg numbers but variable hardness and alkalinity. Over the last 10 years or so, the major brewing ions have not changed, but the WQRs quote ranges of 85-150 ppm as CaCO3 for alkalinity and 100-190 as CaCO3 for hardness. The alkalinity values I am calculating using the above equations seem to jive with the ranges in my WQR and I am just trying to get a sanity check.
I’m not trying to making any sweeping statement but rather just presenting my calculations for critique.
Well I don’t have the formula in front of me, but isn’t hardness 7(Ca) + 3.5(Mg)?
I’m sorry I don’t really follow the rest… the hardness as CaCO3 is already correlated to alkalinity as CaCO3. That’s why they use the correlation.
The thing about hardness and alkalinity staying the same while calcium and magnesium fluctuate can’t be absolutely true as those minerals are the primary constituents of the hardness component.
So what I’m getting out of all this is that you’re trying to derive your bicarbonate value, but it’s not stated on your published water report (which is kinda unusual), and you haven’t had it lab tested. Is that correct?
If that’s the case; you can’t derive the alkalinity AFAIK. It must be measured. Hardness can be derived from Ca and MG. You can measure alkalinity at home pretty cheaply, with a total alkalinity kit. Which is usually bromocresol green/ methyl red, titrated with sulfuric n/50 (that’s from memory someone correct me if I’m wrong). I think it’s 25ml water couple drops of the indicator titrate from green to red. ML’s used multiplied by 20 will give you your total alkalinity as CaCO3. You could also send it out to ward labs, or call your water supplier, they’ll have the data. These are just snapshots in time though, measuring the water coming out of your tap on the day you use it is far more accurate. That goes for hardness as well. It’s easier to measure it, then go by averages. If this for your spreadsheet I’d suggest putting in an input device for the titrations for those who want to measure on the day. There really is no substitute for measuring those variables, if you want your pH model to be accurate, as fluctuations in those parameter assumptions will change the residual alkalinity. The model will then generate an incorrect output.
Yes, that approach would work…if all the hardness was carbonate hardness (aka: temporary hardness). In the case of this water, a significant portion of the hardness is permanent hardness (aka: paired with SO4 and Cl ions).
So the bicarbonate ion content is not 149 ppm. Its more like 96 ppm.
What Martin Brungard said (not that Ive checked his calculations). There is some confusion in this thread over the term carbonate hardness. It is not the same as water hardness. See Carbonate hardness - Wikipedia for more more info
Can you expand on the 96 ppm result? i.e. how you arrive there?
I guess maybe part of the confusion is my fault. What I really want is to use the known values I have (Ca, Mg, SO4, Cl) to estimate, via calculation, my bicarbonate value in ppm.
Without delving into the actual calculations, assuming the water analysis analyzed for all the significant ions, there are equivalent amounts of anions (Ca++, Mg++, Na+) and cations (HCO3-, Cl-, SO4–). Based on this equivalence it is possible to calculate the bicarbonate concentration, the alkalinity and the residual alkalinity.
Just eyeballing the analysis, your water looks pretty versatile.
Roger said it. I assumed that the concentrations of other ions were correct and represented the vast majority of all dissolved content. I then solved to find the bicarbonate concentration that produces balanced cation/anion totals.
This is still just an estimate though, not an actual calculation, isn’t it? The other ions in the water will have an effect on this balance, and isn’t there a +- .1 meq/l variance between the two typically seen? For the balance to be perfect, wouldn’t the pH have to be 7.00?
So using this method of determination would produce a range of probable results from 90-102ppm (ignoring the other ions in the water, and assuming the pH is 7.0), correct?
1.) I’ll be measuring water pH and estimating off that, so that goes away;
2.) I have all the other ions (K, F, NO3, NO2) to add in to make the estimation a little “sturdier”;
3.) The difference of 10-12 ppm HCO3 isn’t going to impact the estimated pH too dramatically, if at all.
So for me it’s a solid way to get a single value for HCO3 using the rest of the quoted ions, rather than trying to use the ranges for CaCO3 hardness and alkalinity quotes in my WQR.
You are confusing CO3 with HCO3. If we were concerned with CO3, that value you mention would be correct. But Bru’n Water deals with HCO3 since that is the form of carbonate ion that we have at typical brewing pH.
In dealing with CaCO3 additions, isn’t your sheet inherently dealing with CO3 also? And doesn’t the CO3 from the chalk just pick up a H+ becoming the HCO3 species, because of the typical brewing pH (or availability of H+ ions)?
I don’t understand how 158 ppm of CO3 in distilled H2O could become 322 ppm HCO3 without the addition of more carbon or violating some laws of physics.
The reason I ask is because Kai’s water numbers use the 158 number when dealing with CaCO3 additions, which he then lists as HCO3.
If I put his salt additions, RO, and grist into your sheet I get more than double the bicarbonate he quotes, and absurdly high predicted mash pH. Like above 6.
Unfortunately, Kai’s information is incorrect too. There is history behind that value when talking about chalk.
As you may have heard, it takes extraordinary measures to get chalk to dissolve in water. Unfortunately, that also applies to wort since wort doesn’t have much of the ‘strong’ acid content needed to dissolve chalk. Brewers know that chalk doesn’t provide the alkalinity that its chemistry says it adds and therefore the pH doesn’t rise as expected.
With a -2 charge, you could expect carbonate to neutralize twice the acid content that bicarbonate can since it has a -1 charge (on an ion to ion basis). But carbonate does not dissociate completely in water or wort. To help account for that apparent deficiency, users assumed that the 158 ppm value should be applied instead of the 322 ppm value.
But in typical usage, chalk doesn’t even provide the 158 ppm contribution to alkalinity. In fact, there is only a minor strong acid content in wort. Adding chalk to mash or wort typically only raises pH by about 0.1 unit…no matter how much chalk you add. While wort is clearly ‘acidic’ since its pH is below 7, the acids that drive the pH down are very ‘weak’. They don’t have the power to react with the carbonate in chalk.
The bottom line will always be: DON’T USE CHALK IN BREWING…IT DOESN’T WORK AT ALL!!!
Ok, but then why does your sheet give me such a high mash pH (6.2) from the chalk additions, if it doesn’t raise the pH that much (which I agree with)? Is the 322 number there just to keep the mEq/l balance even, but not affecting the predicted mash pH to the extent that 322 ppm HCO3 would (and I guess the Ca contribution would also be different).
