Good candidate for lime softening?

[thecebruery]

So I got my water report back the other day, and my magnesium in particular is wayyyy higher than I'd like for it to be. To wit:

Calcium: 61.4
Magnesium: 54.4
Sodium: Not reported
Chloride: 27.5
Sulfate: 21.1
Alkalinity (as CaCO3): 286

So does my relatively high alkalinity and temporary hardness make me a good candidate for lime treatment? I'm brewing on a 1.5bbl system, and I could dilute w/ 75% distilled water every batch (some of my lighter styles are going to need at least that to get the magnesium down to where it should be) or shell out a few hundred for a good RO system, but if I can achieve reproducible results with lime, I'd rather do that - cheaper, and lets me use the money I'd spend on an expensive RO system elsewhere.

Anyone smarter than me have any thoughts?

 

[ajdelange]

You have 3 mEq/L calcium and 5.72 mEq/L alkalinity but also 4.48 mEq/L magnesium so it is quite possible that you can do something with lime to include removing perhaps half the magnesium. Exactly what you can do would have to be determined by experimentation and this implies that you have good means for measuring calcium and magnesium hardnesses and alkalinity plus pH.

Another question to ponder is as to how variable these parameters you have posted may be varying over time. If they change much then you would have to develop treatment protocols to cover all the variations you may encounter. Certainly can be done but dilution with RO water is definitely an easier approach if you can take the pain of the capital expense.

 

[mabrungard]

The lime softening treatment is a viable alternative, but as AJ implies, the level of permanent hardness is going to limit how low you can get the magnesium. I haven't performed the calculations on your water, but I wouldn't be surprised with an ending Mg level of half the original.

To precipitate the magnesium hydroxide, you will have to bring the pH up to around 12 to conduct the process in a timely manner. Decant the clear water off the precipitate and then you will have to neutralize the excess hydroxyl. Bubbling air or CO2 through the water will take out some of it, but an acid addition will probably be needed to take it the rest of the way down.

If you want really low Mg, you will probably need to go the RO route.

 

[ajdelange]

In the traditional 'split' treatment only about half the water is subjected to the high pH regimen and the 'acid' is bicarbonate ion from the other half. That's why you can only get rid of about half the magnesium. If you treat the whole volume to high pH you should be able to get more of the magnesium but then might need an external acid to re balance pH. What you are able to do depends on how you go about things and that's why I can't tell you exactly what to expect.