Slaked lime and calcium chloride

[Aquaticus]

I live near Madison, Wisconsin, where the water is very hard. We've got a lot of temporary hardness, and several of the local brewers (another hobby) use slaked lime with additional calcium salts to remove. Typical water parameters are:

IonAverage(ppm)
Calcium (Ca+2) 70
Magnesium (Mg+2) 41
Sodium (Na+1) 9
Chloride (Cl-1) 19
Sulfate (SO4-2) 21
Total Hardness 344
Bicarbonate (HCO3-1) 364
Alkalinity 298
Residual Alkalinity 224

I'm wondering if any of you out there with similar water profiles are pretreating your water with slaked lime and calcium chloride to remove the temporary hardness? According to my brewing/water geek friend, the addition of 1 gram of slaked lime and .5 gram of calcium chloride per gallon will reduce the bicarbonate to about 50 ppm.

Yes, I know I could use RO water (I even have an unused RO unit in my attic), but even with 50% RO, we still have pretty hard water. Plus, RO creates a lot of waste water. Slaked lime and calcium chloride are dirt cheap, and I wouldn't need much to treat 50 gallons at a time.

Thoughts appreciated,

Eric

[danielt]

Your buddy doesn't know much about water chemistry. Sorry to say that but slack lime and Calcium Chloride raise the water hardness (gH).

The brewers use lime (CaCO3) to increase the waters buffering capacity as the fermentation produces CO2 which acidifies the water and kills the yeast. They need to buffer the acidifying effect of CO2 by adding lime to increase the water's kH (carbonate hardness or alkalinity). The effect of a high kH is high pH as well.

Bicarbonate is not reduced by increasing the gH of the water. You can use peat, blackwater extract or RO water to remove water hardness. RO water will lower kH and gH as well. peat and other organic acids in the blackwater extract will put a dent in kH but will do little against gH.

[Aquaticus]

Are we sure we are talking about the same thing? Slaked lime, calcium hydroxide, will react with bicarbonate (which I have a lot of in my water) to form water and calcium carbonate, which drops out of solution as a white residue. It would reduce the hardness of my water, not increase it. Right? Adding the calcium chloride will provide some extra calcium to ensure that the reaction completes, because my water doesn't have all that much free calcium to begin with.

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + 2H2O

[danielt]

[sarcastic]So Calcium Carbonate does not increase kH and gH? [/sarcastic]

I don't know exactly which substance is "slaked lime" as English is not my native language. Your reaction will decompose the Calcium Bicarbonate into Calcium Carbonate which, in the end, will raise kH if it does not dissolve further by itself. Now, if we're talking about an acidic pH it will dissolve, if the pH is alkaline it will precipitate. But we're talking about a pH in the 8-9 range.

Calcium Chloride does not do anything to kH.

Slaked lime will raise pH and gH. If it were to remove kH from water it will also cause the pH to bounce, HEAVILY.

[Aquaticus]

I think what I may have forgot to add (importantly) is that I would treat the water in a container and decant off the precipitated calcium carbonate thereby removing it. In testing, the pH does increase a little, but not a whole lot. I'm still waiting to see what the pH is going to be after resting.

[danielt]

I remember reading somewhere about this reaction but it involves CO2 for the carbonate to precipitate and also boiling. I might be way over my head with this as I read the chemistry bits concerning aquariums. Also, the process you're describing don't think it lowers kH just gH. I'm stopping here as I'm sensing it's all gibberish what I'm typing