Reducing alkalinity with slaked lime

[Yooper]

The real beauty of Hubert's method is that you don't have to calculate or weigh out anything. Just add lime, gradually, to 1/3 of the water until pH reaches 11+ (but don't go too far). Add some chalk before adding the lime and stir well to get it in suspension and keep it there as you add the lime. Also add any supplemental calcium salts.The chalk doesn't do anything but serve as precipitation sites for the chalk which is to precipitate. Let it sit and settle and then decant.

Now add some more chalk to the decanted water, stir and start to add untreated tap water. Stir and monitor the pH. When the pH gets to around 8.5 you are finished. The bicarbonate in the added untreated water is neutralizing the excess OH- from the extra lime you added to get to pH 11+

Ca++(from water) +2HCO3- + Ca++(from lime) +2(OH-) ---> CaCO3 + H2O
As the reaction takes place OH- is consumed and you can see the pH drop. This neutralization of the OH- is very important. At pH 11 the OH- contributes alkalinity of 50 ppm as CaCO3. At pH 10 it contributes 5 and at pH 9 only 0.5 so once the pH has pulled back below 9 you should be OK.

Or the other thing you can do without measuring chemicals is add lime (plus chalk and extra calcium) until pH 11+ is reached, allow time for precipitation, decant and then bubble air through for a few days or until the pH falls back to the pH you want. This is better than neutralizing with another acid in the sense that you don't get any of the anion of the other acid.

I just followed these directions for the first time.

I don't have any vessels handy larger than 10 gallons, so I thought I'd treat 10 gallons at a time, and brew on Wednesday or Thursday.

I used the above info and Kai's spreadsheet, and found that I could use 2 grams gypsum and 4 grams calcium chloride to get my calcium up and I used a pinch of chalk. I stirred well, and had it at 66 degrees.

I saw that Kai's spreadsheet called for 52.6 grams of lime so I weighed that out, but only planned to use as much as I needed according to the above directions.

I had 3.30 gallons of water and after the first lime addition the pH shot up. I added a bit more, but by then the pH was 12.8! I stopped, since I was WAY over 11+. I measured what was left and found that I used a total of 37 grams of lime.

I'm letting it sit now, and will decant later.

Then I see that I will add untreated tap water until my pH gets to around 8.5.

Aside from not liking lifting all that water, it seems easy enough. At least at this point! My aquarium test kit didn't come today, so I will test tomorrow when it does come for the GH and KH.

 

[Yooper]

Oh, I have another question for any body who can help! When I did the treatment of 1/3 of the water first, it was to drop magnesium.

I assume this happens quickly? And then approximately how much does it drop? If that's been answered already, I do apologize. My brain is pretty full right now.

 

[Nateo]

I assume this happens quickly? And then approximately how much does it drop? If that's been answered already, I do apologize. My brain is pretty full right now.

I believe if you raise the pH over 12 you'll drop nearly all of the Mg in that portion. It takes about 8-12 hours for my water to drop clear after treatment.

 

[ajdelange]

The reaction is fast but the settling time may be appreciable. That's one of the advantages of adding the chalk. The magensium hydroxide is a gel which will entrap some of the chalk you added as nucelation sites and the calcium carbonate which is also precipitated in thiis phase (of treatment) and you should see a layer at the bottom after some time.

 

[Yooper]

Thank you both!

When this is finished, and I want to guess my final results, the majority of the Mg will be gone out of this 3.3 gallons, and the other 6.6 gallons will not drop since it's added later (but the alkalinity WILL drop) I should expect that the total Mg in all water (which is 26 ppm out of the tap) would be about 17 ppm.

The aquarium kit did come, so I can measure the GH and KH when finished.

I'm assuming that this is almost necessarily a two-day process. Doing 1/3 of the water to drop the Mg, and waiting, and then doing the rest of the water, and waiting, means that in all practicality that it would have to be over a couple of days. I think I can do two 10 gallon "batches" at the same time, to have enough water for a 10 gallon batch until I find/figure out a bigger vessel.

 

[Yooper]

I had some issues (leaking ball valve) so I ended up starting over.

but now I really need some advice!

I started with 3.5 gallons of my tap water, stirred in a pinch of chalk and 2 grams CaS04 and 4 grams CaCl2. I started stirring in the lime, but by the time I stopped at only 30 grams, the pH was 12.7!

The precipitates dropped out right away, but I waited for it to settle. I racked off, and started stirring in my tap water, following the instructions to do so until my pH read 8.5. I was planning on a total of 10 gallons.

I must have really screwed up, because I have 25 gallons of water at 8.5, but I still have about 9 gallons in the first vessel that has a pH of 9 and I don't have any more buckets to dilute further!

I guess my questions are: did this happen because of the pH being too high at 12.7? I assume it did, but according to calculations on Kai's spreadsheet, I'd need like 57 grams of lime to drop the alkalinity (in 10 gallons) and I've only used 30 grams for 34 gallons of water.

My next question- now what? do I start over, keep diluting, stop?

 

[afr0byte]

I had some issues (leaking ball valve) so I ended up starting over.

but now I really need some advice!

I started with 3.5 gallons of my tap water, stirred in a pinch of chalk and 2 grams CaS04 and 4 grams CaCl2. I started stirring in the lime, but by the time I stopped at only 30 grams, the pH was 12.7!

The precipitates dropped out right away, but I waited for it to settle. I racked off, and started stirring in my tap water, following the instructions to do so until my pH read 8.5. I was planning on a total of 10 gallons.

I must have really screwed up, because I have 25 gallons of water at 8.5, but I still have about 9 gallons in the first vessel that has a pH of 9 and I don't have any more buckets to dilute further!

I guess my questions are: did this happen because of the pH being too high at 12.7? I assume it did, but according to calculations on Kai's spreadsheet, I'd need like 57 grams of lime to drop the alkalinity (in 10 gallons) and I've only used 30 grams for 34 gallons of water.

My next question- now what? do I start over, keep diluting, stop?

I usually only need about 6 or so grams for ~9 gallons of water. So, 30 grams is a lot! I'm guessing you have a number entered wrong in the spreadsheet.

 

[Yooper]

I usually only need about 6 or so grams for ~9 gallons of water. So, 30 grams is a lot! I'm guessing you have a number entered wrong in the spreadsheet.

So, use the water I have that is 8.5, after decanting?

 

[Nateo]

I've never tried the split method, so I can't really say. Did you check the hardness with your test kit? As long as your hardness and RA are where you want them to be, and you have as much water as you need, you'll be fine.

 

[pjj2ba]

I usually only need about 6 or so grams for ~9 gallons of water. So, 30 grams is a lot! I'm guessing you have a number entered wrong in the spreadsheet.

Seems like a lot to me as well. I'm using around 3-4 grams for 10 gal. Perhaps a decimal point error?


I use my boil pot sans pickup tube to do my water treating. After it settles I pump it over the my HLT and mash tun. There is about 1.5 gal that I cannot drain with the pump since I took the pickup off. Then I just slowly tip the pot and drain it into jugs being careful to leave the precipitate behind.

 

[Yooper]

I just did the GH/KH test on one of the buckets of water. Apparently I diluted too much or something because the KH was 161, while the GH was 196.9!

so I think I'm back to the drawing board.

I assume it's because I didn't add enough CaCl2 and CaSo4 for the amount of water I started with since I figured it for 10 gallons.

 

[Nateo]

I just did the GH/KH test on one of the buckets of water. Apparently I diluted too much or something because the KH was 161, while the GH was 196.9!

so I think I'm back to the drawing board.

Is that ppm? My test kit gives me German degrees. I usually end up with about 7* GH and 2-3* KH. I do use a bunch of lime in my way, but I think I mentioned that already.

 

[Yooper]

Is that ppm? My test kit gives me German degrees. I usually end up with about 7* GH and 2-3* KH. I do use a bunch of lime in my way, but I think I mentioned that already.

That's with the "conversion table" they give.

It was 9 kH and 11 Gh before the conversion.

I have one 10 gallon batch sitting there, with the pH just up over 9 since I couldn't add any more water but it really looks like I'm getting a lot of precipitation out of that one.

I think when I added more water to bring the pH down to 8.5 that I didn't have enough calcium to encourage more precipitation. I could run and add some to the buckets now, but I'm about ready to think I'm not smart enough to do this.

On the bright side, Bob saw me messing with water, my pH meter, chemicals, and said, "OK- that's it! We're going to look at RO systems". So there is a silver lining!

In the meantime, I have about 35 gallons of water sitting in my brewery, and I want to brew tomorrow. I might end up putting 14 gallons in my BK and boiling it to precipitate out the alkalinity at this point.

 

[Nateo]

You might want to try the way Martin recommended (that I use) at least once before you buy an RO system. I got to the same point you're at, and about gave up. The way I do it now requires very little calculating.

 

[Nateo]

I'm working on some recipes right now for my brew day tomorrow. I'll be up another half hour or so if you want me to help with your water tonight. It'll be tight, but you should have enough time to try my water treatment and still brew tomorrow.

 

[Yooper]

I'm working on some recipes right now for my brew day tomorrow. I'll be up another half hour or so if you want me to help with your water tonight. It'll be tight, but you should have enough time to try my water treatment and still brew tomorrow.

Well, sure, if you have time!

I have vessels of water all over the place with a pH of 8.5. I don't know if I can start there or not, but if you can give me your "Ten Steps for Morons", I'd be thrilled!

 

[Nateo]

So here's what I do, in only 6 steps:
1) Add lime until you hit 12. (like, a bunch of lime ~ several tbsp)
2) Let precipitate settle out (overnight usually)
3) Decant
4) Add phosphoric acid until pH drops under 8
5) Let precipitate settle out (apatite, looks like jelly)
6) Enjoy

That's the quick and dirty method I use, but I end up with reasonably soft water, and "some" amount of excess phosphate. Since malt contains a lot of phosphate, I don't worry too much about it.

You have to lower the pH and let the apatite precipitate off before you test it, otherwise there will still be way too much calcium left over from the large amount of lime. My GH is like 27* before it precipitates.

It takes a few hours for the apatite to precipitate, so I'd add the acid first thing in the morning. Sometimes I rush it a little too much, and end up using brewing water with a small amount of apatite still in suspension. I haven't noticed any ill-effects, but it's probably not ideal. It's probably better to wait until it drops clear.

When I add the acid (I use 10% phosphoric) it takes a few tbsp to get the pH to drop from 12 to 10, then only maybe 1 tsp to drop from 10 to 8. So if you add acid and it doesn't drop right away, don't go too crazy with it.

Let me know if you have any questions.

 

[Yooper]

Ok, so you decant twice?

I just went in and decided to give it another try. There was some precipitate in the buckets, but not really all that much. so I dumped those and used my two cooler MLTs, with 9 gallons in each one.

I added some CaCl2 and CaSo4 (a total of 4 grams CaSo4 and 8 grams CaCl2 because I'm low in calcium and my understanding is that I need the calcium to precipitate the alkalinity). I added about a TBS of lime, and stirred like crazy. The pH in one is 11.89 (close enough, I thought) and the pH in the other is right at 12. I see stuff already "forming" and falling out.

So, in the morning, I should decant, adjust down to 8, and then decant?

That is doable, but decanting means lifting, which I hate! But I promise to give it my best shot.

Edit- oh, and THANK YOU. I have an IQ of 172, believe it or not. But I feel like an imbecile with this stuff.

I hope I have enough phosphoric acid.

 

[Nateo]

I decant after step 2. The next morning I'll add acid, then after the apatite settles, I'll pump the water off the top, straight into my BK to heat for strike liquor. Just try to leave as much of the jelly behind as you can.

If the pH is over 11, that's enough to get the hardness to drop out, it just drops faster at 12 than 11, so I shoot a little high. Have you made cheese? If you add enough lime, it looks like milk does when it breaks. If you add a little too much acid and the pH drops below 8, that's OK too, as long your mash pH is correct.

My way would probably work better if I added calcium, but figuring out how much to add sounds like math, so I skip it, and just treat my water as-is. I'll add any flavor minerals during the boil. Any acid will work, you'll just end up with the ion the acid leaves behind after the H+ leaves. So lactic leaves lactate, sulfuric leaves sulfate, phosphoric leaves phosphate, etc. I'm sure a small amount of lactic would be OK, if necessary.

 

[Yooper]

Have you made cheese? If you add enough lime, it looks like milk does when it breaks.

Actually, YES- that's exactly what my water looked like just now! It was like milk, long before the clean break!

I get it, I think! I wondered about decanting twice but I can actually pump so that is helpful. I don't really have big enough vessels for more than about 9 gallons of water (and of course lose some to the precipitate) so it's still sort of a PITA.

 

[Yooper]

Ok, all decanted and pH adjusted down to 8. I'm just waiting for the apatite to settle and then I'll check the GH/KH.

I got TONS of sediment. Like the bottom 1.5 gallons of both vessels was all precipitate.

I'm still not convinced that this is easier than an RO system, but so far so good.

 

[Nateo]

I'm still not convinced that this is easier than an RO system, but so far so good.

I wouldn't claim it's easier. It's cheaper and more convenient for me. YMMV, but hey, at least you gave it a shot, even if you decide it's not for you. It did take me doing it a few times before I hit my stride.

 

[pjj2ba]

I don't add extra Ca when I treat with lime. I also don't add enough lime to get the pH up to near 12 (~ 3 gm/10 gal). I can't recall my exact #'s but we have fairly high Ca in our water (I need to look it up to refresh my memory) After pumping off the ppt., I never get any extra precipitate when I use phosphoric acid to bring the pH down.

I'm a bit fuzzy my recollections on the reaction between Ca and PO4, (other than the product is really insoluble) but I recall the formation of a ppt. was not something that always happened. I used to make a lot of media for growing plants on defined media in petri plates or for mineral nutrition experiments (with lots of Ca and PO4). If you mixed the components in the wrong order, the Ca and PO4 would combine, but if you did it the other way, then it didn't. I can't recall the details though.

I keep meaning to try added some extra Ca when I add the lime, but haven't yet. Maybe for this next batch and I'll see if the extra Ca reacts with the phosphoric acid when I add it

 

[Nateo]

I don't add extra Ca when I treat with lime. I also don't add enough lime to get the pH up to near 12. . . I never get any extra precipitate when I use phosphoric acid to bring the pH down.

If I understand AJ's explanation correctly, you'll only get extra precipitate if you add a whole bunch of lime. If I only raise the pH to 11 I don't get much extra precipitate, but it takes much longer for it to drop clear. At 12 it drops clear much quicker, but I get a fair amount of extra precipitate when I add the acid.

 

[Yooper]

I don't add extra Ca when I treat with lime. I also don't add enough lime to get the pH up to near 12 (~ 3 gm/10 gal). I can't recall my exact #'s but we have fairly high Ca in our water (I need to look it up to refresh my memory) After pumping off the ppt., I never get any extra precipitate when I use phosphoric acid to bring the pH down.

I'm a bit fuzzy my recollections on the reaction between Ca and PO4, (other than the product is really insoluble) but I recall the formation of a ppt. was not something that always happened. I used to make a lot of media for growing plants on defined media in petri plates or for mineral nutrition experiments (with lots of Ca and PO4). If you mixed the components in the wrong order, the Ca and PO4 would combine, but if you did it the other way, then it didn't. I can't recall the details though.

I keep meaning to try added some extra Ca when I add the lime, but haven't yet. Maybe for this next batch and I'll see if the extra Ca reacts with the phosphoric acid when I add it

I added the extra Ca because of AJ's explanation that I can only drop the alkalinity as much as I can drop the calcium. I'm paraphrasing, of course! But the jist of it was that my calcium is relatively low, so I'd be limited to dropping less alkalinity. Since I use CaSo4 and CaCl2 anyway in the beer as additions, I just added them prior to the lime treatment. Calcium will drop some, but the chloride and sulfate will remain and I'll have enough calcium in the brewing water. At least, that was the way I understood it!

I just checked the GH/KH. The KH was 3*- which should be around 56 ppm if I read the conversion correctly. That's a huge reduction. But I must not be ready yet, as the GH was off the charts!

 

[mabrungard]

I'm still not convinced that this is easier than an RO system, but so far so good.

Definitely NOT easier, but orders of magnitude cheaper if you don't count your labor. If your water is suited to it, lime softening is excellent for brewing and potentially better for brewing than RO. That last statement is really dependent upon the concentrations of other ions (Na, SO4, and Cl) being modest or low.

Lime cost...$6 to treat thousands of gallons of water
Treatment vessel costs...depends, but I like Nate's garbage can idea

RO unit purchase...$100 to $200
Membrane and filter costs...maybe $10 per 1000 gals, but it depends on the water
Tank or vessel to hold RO water...depends. Garbage can is still looking good!

When the water is suitable, the selection of treatment method will boil down to your desired level of effort. RO is almost effortless and you will have to work with lime softening.

 

[Nateo]

I bought my phosphoric from dudadiesel. 1L of 85% was about $18 with shipping. That diluted out to about 9L of 10%, which will probably last me forever.

 

[afr0byte]

Ahh, I love beer geekery.

 

[Borisfa]

Sorry for reborn this threat.

My water has Alkalinity 186,5 mgCaCo3/L and 63,6 mg/L of Ca and 3,41 mg/L of Mg. Am I candidate to use slaked lime to reduce alkalinity?

I try do a simulation on Braukaiser spreadsheet and I have a result that I would like to share with you, because I intent to use next weekend and I would like to be "sure" to use without to do a mistake.

I see that I should do:

Add 150 ppm of Gypsym
Add 50 ppm of CaCl2 - my water Cl content is 2,12 mg/L
Add 160 ppm of Slacked Lime - Ca surpluss=38ppm

This water is for a American IPA and SO4/Cl=3,3/1 (SO4 is zero on my water).

Are they correct my additions as reported above?

Thanks,

Fabiano da Mata

P.S.: Sorry for my English

 

[ajdelange]

Your alkalinity is 185,5 ppm as CaCO3 or 3,71 mEq/L. You calcium is 63,6 mg/L equivalent to 3,18 mEq/L. The reaction by which lime decarbonates is

Ca++ + 2HCO3- + Ca++ + 2(OH)- ---> 2CaCO3 + 2H2O.

Thus for each mEq of alkalinity (bicarbonate) or calcium to be removed you will need a mEq of calcium (half a mmol) and a mEq of (OH)- (1 mmol) from 1/2 mmol of Ca(OH2). As a general rule you can decarbonate down to 1 mEq/L of whichever is the less of Ca++ or alkalinity. Here that is calcium so you should be able to get it down to around 1 mEq meaning removing 2,18 mEq. The same amount of alkalinity will be removed so that there will be 3,71 - 2,18 = 1,53 mEq/L alkalinity left. To remove 2,18 mEq of calcium and alkalinity requires 1,09 mmol/L Ca(OH)2 or 80 mg/L.

To remove more alkalinity in a case like this one add supplemental calcium until the calcium hardness and alkalinity are at least equal. If you add 3,71 - 3,18 = 0,53 mEq/L calcium then you should be able to reduce both calcium and alkalinity to 1 mEq/L i.e. both are reduced by 2,71. This would require 1,35 mEq/L or 100 mg/L.

With precipitation reactions like this reactions often aren't as expected. It is best to make several trial solutions, add different amounts of lime and see which dose gives the best reduction.

 

[Borisfa]

@ajdelange, thanks for your reply. Some doubt:

- How change mg/L to mEq/L?
- After remove the alkalinity, some Ca++ will be consumed to precipitate as CaCO3, and now to other questions:
- Should I remove this precipitate to use this water on mash tun?
- Should I add more Ca++ source to adjust Ca++ on the water?

- How is the procedure (how long should be the settling time, should stir,....?) when I add lime? Should I dilute lime before add (make a solution or add powder)? Alis there a better temperature to do?

Thanks,

Fabiano

 

[afr0byte]

@ajdelange, thanks for your reply. Some doubt:

- How change mg/L to mEq/L?
- After remove the alkalinity, some Ca++ will be consumed to precipitate as CaCO3, and now to other questions:
- Should I remove this precipitate to use this water on mash tun?
- Should I add more Ca++ source to adjust Ca++ on the water?

- How is the procedure (how long should be the settling time, should stir,....?) when I add lime? Should I dilute lime before add (make a solution or add powder)? Alis there a better temperature to do?

Thanks,

Fabiano

I'll let AJ answer to question about converting to mEq/L, as I forget how, but I can answer the other questions.

Yes you should add more Ca++, probably by adding calcium chloride. Calcium sulfate is another option.

Yes you should separate the precipitate from the water. I use an autosiphon.

You may want to add more calcium to the water you separated from the precipitate. It depends on how much is left over (which depends on how much additional calcium you added initially and how much caco3 fell out of solution).

I usually add all my extra calcium and the lime to an empty pot. Then I add the water a gallon (3.78 liters) at a time, stirring a little after each gallon, until I reach my full volume. I do this at room temperature, but I imagine warmer might be better because caco3 is less soluble at higher temps (This is why you can boil water to decarbonate (remove caco3).). After I hit full volume I let the water sit for about 12 hours. It should already be cloudy at this point...that's the caco3 coming out of solution.

 

[ajdelange]

- How change mg/L to mEq/L?

Your alkalinity is expressed in ppm as CaCO3. To convert to mEq/L divide by 50. You calcium content is expressed in mg/L of the ion. To convert to mEq/K divide by 20.

- After remove the alkalinity, some Ca++ will be consumed to precipitate as CaCO3,

Yes

- Should I remove this precipitate to use this water on mash tun?

Yes, you must separate the clear water from the precipitate and use the clear water. If any of the precipitate gets into the mash it will act like chalk (it is chalk) and raise the pH of the mash. You removed it from the water because you do not want the pH raising effect. If you put it back into the mash you have wasted your time and effort.

- Should I add more Ca++ source to adjust Ca++ on the water?

Yes. You can use the numbers I posted in order to estimate what the calcium level will be after decarbonation by this method and then add additional calcium so that the calcium level will be what you want for your beer. If you do this do it before lime treatment as extra calcium before lime addition will allow you to remove more bicarbonate.

How is the procedure (how long should be the settling time, should stir,....?) when I add lime? Should I dilute lime before add (make a solution or add powder)? Alis there a better temperature to do?

Here's the procedure as I laid it out for an article in an old brewing magazine. The whole article is at http://wetnewf.org/pdfs/Brewing_articles/BT_Alkalinity_II/AlkalinityPtII.pdf and this part starts on p14:

1. Add 1 tsp. of chalk for each 5 gallons of water to be treated to the water.
2. Multiply the temporary hardness of the water by 0.74 to get a rough idea of the amount of lime required (in mg) to treat 1 L. Then multiply by the number of liters to be treated and divide by 1000 to get the number of grams required for the entire volume.
3.Increase the result from Step 2 by 20-30% and place this in a small beaker or flask. Add enough water to get this into suspension.
4. Add the slurry from Step 3 to the water in initially large and then smaller increments. Stir thoroughly and check pH after each addition.
5. Continue additions fairly rapidly until a pH between 9.5 and 10 is reached.
6. Monitor pH. As precipitation takes place the pH will fall back (see Figure 3.1)
7. At this point add only small amounts of additional slurry to maintain the pH in the 9.5 - 10 region.
8. pH will continue to drop as CO2 from the air is dissolved but the rate of drop will slow. When it does, stop addition of lime and let the water sit while the precipitate settles.
9. Decant the water from the precipitate and measure hardness and alkalinity.

[/QUOTE]

 

[Borisfa]

Thanks @afr0byte and @ajdelange. More some questions:

My Water report is:

- Alkalinity: 186,5 mg CaCo3/L
- Bicarbonate: 225,1 mg/L
- Carbonate: 1,2 mg/L
- Calcium: 63,6 mg/L
- Magnesium: 3,4 mg/L
- Total Sulfate: 0
- Nitrite: 0
- Nitrate: 0,24 mgN/L
- Sodium: 4,8 mg/L
- Iron: 0
- Total Hardness: 172,9 mg/L
- pH: 7,5

My alkalinity: 186,5 mg/L or 3,73 mEq/L.
My Calcium : 63,6 mg/L or 3,18 mEq/L.

1) For a maximum alkalinity removal, Should I add about 0,55 mEq/L ou 11 ppm of some Calcium source (I need, at least, 74,6 ppm of Calcium)?

2) Considering I adjust my water to 74,6+30% = 97 mg/L of Calcium to remove Alkalinity and considering I need more Calcium for my mash (about needed 80 mg/L for mash) of Calcium on my mash, so I need add more 80 mg/L. Resuming, Will I need a initial Calcium content of 177 mg/L (97 ppm for decarbonating +80 ppm for mash) . Is this right?

3) Now about Lime, considering that is right remove 3,73 mEq/L of alkalinity, so I am need about 1,9 mmol/L of Lime, that represent 38 mg/L or 76 mg/L?

Thanks again,

Fabiano da Mata

 

[Borisfa]

@ajdelange, we add chalk to shift reaction to right side?

 

[Borisfa]

Here's the procedure as I laid it out for an article in an old brewing magazine. The whole article is at http://wetnewf.org/pdfs/Brewing_articles/BT_Alkalinity_II/AlkalinityPtII.pdf and this part starts on p14:

@ajdelange, on the article, you said the "As the molecular weight of slaked lime is 74.09 each gram is 135 mM and will treat 27 mEq of bicarbonate or 1350 mg as CaCO3" I think that the right would be "....each gram is 13.5 mM..." and how we have 1 mmol of Lime for 2 mmol of CaCO3, I think that the right would be "... each gram is 13.5 mM and will treat 27 mEq (1648 mg) of bicarbonate or 2700 mg (2 mmol) as CaCO3" because the MW balance we have:

- 122/74 (2HCO3-/1Ca(OH)2) = 1648,6 mg.
- 200/74 (2CaCO3/1Ca(OH)2) = 2702,7 mg.

Are these wrong?

Thanks,

Fabiano

 

[ajdelange]

There is a theoretical limit as to how much calcium and carbonate can simultaneously be in solution: [Ca++][CO3--] < Ks
expresses it mathematically. The reaction with lime is

Ca++ + 2HCO3- + (Ca++ + 2(OH)-) ----> 2CaCO3 + 2H2O

The extent to which this reaction takes place depends on how much reacts to get [Ca++][CO3--] > Ks. Adding calcium in any form pushes the reaction to the right. Adding OH- pushes the reaction to the right. Clearly, then, to maximize the amount of bicarbonate precipitated you should increase the amount of lime and the amount of calcium. If, however, there is excess lime it won't react and lime, being alkaline, will contribute to the alkalinity of the water and your efforts will have been in vain. Thus is why we try to guess what the correct amount of lime to add may be based on the stoichimetry implied by the equation. However, it doesn't tell the whole story. It is possible to have supersaturated solutions of CaCO3, that is, solutions where [Ca++][CO3--] > Ks and precipitation does not occur or does not occur to the point where [Ca++][CO3--] =< Ks. This is why the procedure recommends adding calcium carbonate to the mix before treatment. It is hoped that the crystals will serve as precipitation nuclei and insure that the maximum amount of precipitation forms. This is why DeClerck recommends experiments with different amounts of lime and choice of the dose which gives the best decarbonation. This is why the procedure requires the use of a pH meter for best results. This is why the procedure recommends that hardness and alkalinity be measured for each trial dose (how else would you know which is the most effective).

In general, if you want to get more bicarbonate out you add more calcium in the form of a non alkaline salt such as the sulfate or chloride. Increasing [Ca++] decreased the amount of [CO3--] required to reach [Ca++][CO3--] = Ks. Thus, if you plan to augment calcium, do it before lime treatment.

It is much easier to just boil your water. You should be able to decarbonate it equally effectively and you don't have to worry about correctly adjusting the lime dose. Again, adding supplemental calcium before boiling is a good idea as is an addition of chalk for nucleation.

 

[Borisfa]

@ajdelange, look for these messeges above that were quote below.

My Water report is:

- Alkalinity: 186,5 mg CaCo3/L
- Bicarbonate: 225,1 mg/L
- Carbonate: 1,2 mg/L
- Calcium: 63,6 mg/L
- Magnesium: 3,4 mg/L
- Total Sulfate: 0
- Nitrite: 0
- Nitrate: 0,24 mgN/L
- Sodium: 4,8 mg/L
- Iron: 0
- Total Hardness: 172,9 mg/L
- pH: 7,5

My alkalinity: 186,5 mg/L or 3,73 mEq/L.
My Calcium : 63,6 mg/L or 3,18 mEq/L.

1) For a maximum alkalinity removal, Should I add about 0,55 mEq/L ou 11 ppm of some Calcium source (I need, at least, 74,6 ppm of Calcium)?

2) Considering I adjust my water to 74,6+30% = 97 mg/L of Calcium to remove Alkalinity and considering I need more Calcium for my mash (about needed 80 mg/L for mash) of Calcium on my mash, so I need add more 80 mg/L. Resuming, Will I need a initial Calcium content of 177 mg/L (97 ppm for decarbonating +80 ppm for mash) . Is this right?

3) Now about Lime, considering that is right remove 3,73 mEq/L of alkalinity, so I am need about 1,9 mmol/L of Lime, that represent 38 mg/L or 76 mg/L?

What would be right? on calcs above?

@ajdelange, on the article, you said the "As the molecular weight of slaked lime is 74.09 each gram is 135 mM and will treat 27 mEq of bicarbonate or 1350 mg as CaCO3" I think that the right would be "....each gram is 13.5 mM..." and how we have 1 mmol of Lime for 2 mmol of CaCO3, I think that the right would be "... each gram is 13.5 mM and will treat 27 mEq (1648 mg) of bicarbonate or 2700 mg (2 mmol) as CaCO3" because the MW balance we have:

- 122/74 (2HCO3-/1Ca(OH)2) = 1648,6 mg.
- 200/74 (2CaCO3/1Ca(OH)2) = 2702,7 mg.

Are these wrong?

Are these wrong?

Sorry for reply, but how I sent multiples messeges, some of that could miss.

Thanks again,

Fabiano da Mata

 

[ajdelange]

@ajdelange, on the article, you said the "As the molecular weight of slaked lime is 74.09 each gram is 135 mM and will treat 27 mEq of bicarbonate or 1350 mg as CaCO3" I think that the right would be "....each gram is 13.5 mM..."

I do too! 1000/74.09 =13.49. That's been out there for years and no one ever noticed the mistake before. Guess no one ever read it or maybe it's obvious that I left out the decimal point.

..and how we have 1 mmol of Lime for 2 mmol of CaCO3, I think that the right would be "... each gram is 13.5 mM and will treat 27 mEq (1648 mg) of bicarbonate or 2700 mg (2 mmol) as CaCO3" because the MW balance we have:

It's 1 mmol of Ca(OH)2 treats two mEq of bicarbonate. A mEq of bicarbonate (alkalinity) is approximately 50 ppm as CaCO3 thus 27*100 = 2700 mg as CaCO3.

 

[Borisfa]

Multiple postage. Sorry.