Treatment of alkalinity with phosphoric then boiling - cloudy?

[Mer-man]

I have very hard water, 130ppm Ca 320ppm bicarbonate.

I use 75% phosphoric to neutralize alkalinity buffering and my mash pH consistently falls approximately where I expect it to.

My process is: fill kettle, add acid and stir, then pre-boil (to reduce dissolved O2).

After the boiling, the water gets cloudy. I would expect this otherwise, but can someone explain why the water is apparently cloudy with carbonate after I have dosed it with acid?

 

[Silver_Is_Money]

If you were to do roughly 5-10 minutes of boiling before the acid addition, by my calculations you would have at that juncture (after cooling, settling, and decanting) right close to 51 ppm Ca++ and 65 ppm alkalinity.

Then from there you can add phosphoric acid (as necessary, and recipe dependent) to remove the remaining alkalinity, and you will be left with water that has a beneficial ~51 ppm of Ca++.

 

[Mer-man]

Yeah, that's pretty close to what I previously titrated boiling my water to yield.

But how about the appearance of persisting carbonate after acid treatment? From a mash pH perspective, the alkalinity seems neutralised and to yield the desired residual alkalinity, but visually . . . not.

 

[z-bob]

Maybe the cloudiness is calcium phosphate?

 

[ajdelange]

It's most likely apatite. Your alkalinity is about 5 mEq/L and your calcium about 6.5. Thus boiling should, using DeClerck's rule of thumb, remove about 4 each of alkalinity and calcium leaving the calcium level at 2.5 or 50 mg/L and the alkalinity at 1 mEq/L (50 ppm as CaCO3). If you have decanted off the precipitate you shouldn't require much phosphoric to get the mash pH (is that what you are trying to do?) and you shouldn't have apatite precipitation. But you are adding the acid first. That will reduce the alkalinity (remove bicarbonate) but if you don't take the pH down far enough there will be quite a bit of PO4--- in there and with all that calcium the precipitate will form. At this point boiling won't likely drop any chalk. What i don' understand is why the precipitate doesn't form until after the boil. In any case I think you'll solve the problem by boiling and decanting first. You'll use less acid that way (and minimize the liklihood of apatite precipitation).

You might want to try collecting some of the precipitate, drying it and dropping a bit of vinegar onto it. If it fizzes it's chalk. If it doesn't its appatite. If it's a mix it will fizz somewhat but not as vigorously as straigth chalk so you might try a comparison fizz test with some chalk to get a rough idea as to how much chalk is in the mix.

 

[Mer-man]

I acidify to reduce alkalinity to hit mash pH. I boil to drive off dissolved oxygen.

What's the consequence of apatite precipitation? I cannot find anything about it being problematic. I give my wort a 45minute settling for trub before transfer, so if the apatite is still around would it not settle then?

 

[ajdelange]

You have a lot of alkalinity to dispose of thus you need a lot of acid to dispose of it and as every mEq of alkali removed by acid is replaced by a mmol of the anions of that acid wind up with a lot of phosphate anions - so many in fact that it appears that apatite is being precipitated.

There are no consequences of having apatite in your mash that I am aware of. In fact some is precipitated in the mash if calcium is present in the mash water in any case.

It just seems foolish to decarbonate with acid and then boil when boiling decarbonates water like thusthis leaving less of an acid requirement. In fact, depending on the beer, it might eliminate it entirely.

 

[z-bob]

I acidify to reduce alkalinity to hit mash pH. I boil to drive off dissolved oxygen.

What's the consequence of apatite precipitation? I cannot find anything about it being problematic. I give my wort a 45minute settling for trub before transfer, so if the apatite is still around would it not settle then?

It's not a problem, but you are using more acid than necessary because boiling (w/o acid) also decarbonates the water -- although I think you need to let the chalk settle out and decant the water off to get the full affect (because adding acid will redissolve the chalk), and that might oxygenate it.

I have water like yours. I don't boil it just because of the energy required -- which is probably a foolish false economy.

 

[ajdelange]

You can get the same level of decarbonation with lime in the cold.

 

[Silver_Is_Money]

You can get the same level of decarbonation with lime in the cold.

Yes, but then you would need to add even more acid.

 

[z-bob]

Yes, but then you would need to add even more acid.

Actually you don't, it takes less acid. You just have to decant the softened decarbonated water off the chalk that precipitates out. I haven't tried it yet; need to get food-grade Rubbermaid trashcan and a place to set it up.

 

[ajdelange]

Now that I can trivially calculate such things let's recall that he has about 5 mEq/L alkalinity. He didn't tell us pH or alkalinity so the 5 is a guess from the bicarbonate. Just a note in passing: I need water pH and alkalinity to solve problems like this. I can guess at the alkalinity from the bicarbonate and the guess is pretty good most of the time depending on pH. I'm guessing here. Assuming that he can get DeClerks nominal reduction to 1 mEq/L presumably at pH 8.4 he would require 0.89 mEq acid per liter of the water decarbonated with lime (or boiling) to reach a mash pH of 5.4. Were he to acidify the untreated water to pH 5.4 with acid without lime it would require 4.57 mEq/L = right around 5 times as much.

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

There's nothing in that to suggest that additional acid would be needed. Quite the opposite in fact. The HCO3- is removed.

 

[Silver_Is_Money]

Actually you don't, it takes less acid. You just have to decant the softened decarbonated water off the chalk that precipitates out. I haven't tried it yet; need to get food-grade Rubbermaid trashcan and a place to set it up.

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

There's nothing in that to suggest that additional acid would be needed. Quite the opposite in fact. The HCO3- is removed.

Thanks for correcting me, z-bob and A.J.

 

[ajdelange]

No trouble at all. Literally. All I did was type =Ct(5,7) into cell C56 and =C56*(Qbicarb(5.4) - Qbicarb(7)) into Cell D56 to get the acid required in mEq/L. Want to know how much 85% phosphoric acid that is? Type =D56/PhosNorm(5.4,85) into another cell. That's all there is to it. Pardon my enthusiasm but this Voltmeter thing is incredible. I just really wish I'd done this 20 years ago.

 

[z-bob]

Hopefully this isn't too much of a thread veer. Let's say I want to experiment with lime-softening my water. Is the following reasonable? I'm purposely leaving out most of the numbers, just focusing on the process:

1. Put 25 gallons of water in a 30 gallon food-safe plastic trashcan.
2. Add however much lime the water calculator says I need for 25 gallons (I'm just removing carbonates, not trying drop out magnesium hydroxide)
3. Let it settle for a few days. Obviously I do the above before brew day.
4. Dip my 6 or 7 gallons off the top and brew my beer It will still probably need some acid.
5. Top-up back to the 25 gallon mark and add enough lime to treat the new water. This will stir up the chalk at the bottom; that's a good thing for providing nucleation points.

This ought to be good enough water for the Kurig coffee machine too; we've been buying bottled water for it to keep it from scaling and clogging.

 

[ajdelange]

Put about 10 gallons of water into the barrel and add enough lime to get the pH up to about 10 or 11. Stir in some precipitated chalk to get those nucleation sites you spoke of. You now have some pretty alkaline water. Neutralize it with the bicarbonate from more of your tap water by adding it with lots of stirring until the pH is 8.4. Let it sit for a while and decant as much as you can without disturbing the precipitate. Check the alkalinity of this water.

If you intend to add any calcium salts to this decarbonated water do that before the lime treatment. The extra calcium may get you a bit below 1 mEq/L akalinity after treatment. Check at least alkalinity and preferrably hardness too with a test kit.

 

[z-bob]

Put about 10 gallons of water into the barrel and add enough lime to get the pH up to about 10 or 11. Stir in some precipitated chalk to get those nucleation sites you spoke of. You now have some pretty alkaline water. Neutralize it with the bicarbonate from more of your tap water by adding it with lots of stirring until the pH is 8.4. Let it sit for a while and decant as much as you can without disturbing the precipitate. Check the alkalinity of this water.

If you intend to add any calcium salts to this decarbonated water do that before the lime treatment. The extra calcium may get you a bit below 1 mEq/L akalinity after treatment. Check at least alkalinity and preferrably hardness too with a test kit.

If I use a starting pH of 11 and transfer the water off the first precipitate, that will remove the magnesium too, right? (I'll still have the Mg from the additional water) And what about Fe(ii) iron? The more soluble iron that my water has just enough of to be annoying. But I'll need 2 barrels instead of one...

 

[ajdelange]

Yes, some of it i.e. the part in those first 10 gal. But if you titrate back to pH 8.4 with more tap water with lots of stirring the Mg(OH)2 will redissolve and you won't lose any.

WRT iron - you want to oxidize that to Fe(III). Fe(OH)3 should precipitate at lower pH but a higher pH won't hurt a bit. To get all the clearwater iron converted try pumping out of the barrel and back into it through a shower head or sprinker device. Then add enough Ca(OH)2 to get the pH up to 8.4. Then filter through clean play sand or whatever medium you can kluge up. Now separate pump all but 10 gal into the second barrel. I can't help thinking that an RO machine would make things a lot easier than having to do all this.

 

[z-bob]

I was talking about pH --> 11 for a few days, decant the water off the precipitate, then titrate back to 8.4. The Mg++ from the first batch of water would be in the precipitate.

The Fe(II) is not causing a problem with my beer, I just thought if I could remove half the iron for free that would be good. I hoped it might drop out as ferrous hydroxide. It's not worth setting up an aerator and a sand filter. But thanks, I find this topic fascinating and I hope I'm not wasting your time.

 

[mabrungard]

Soluble iron (Fe(II)) is precipitated to Fe(OH)2 when the pH is increased enough. So you will get that benefit. I've done this at sites where we had iron problems and had to store and treat the water anyhow. But the standard treatment for soluble iron is to oxidize it to Fe(III) with some sort of air contact and then filter out the precipitate.

To produce good Mg reduction, raising the pH to at least 11 is necessary. An even higher pH does accelerate the Mg precipitation reaction. The precipitate (Mg(OH)2) is a gel and its somewhat problematic to deal with. The sludge at the bottom of the vessel can be bulky. You are better off in decanting off the water and disposing of the sludge instead of adding another batch of water on it if you're aiming for Mg reduction.

 

[Mer-man]

Soluble iron (Fe(II)) is precipitated to Fe(OH)2 when the pH is increased enough. So you will get that benefit. I've done this at sites where we had iron problems and had to store and treat the water anyhow. But the standard treatment for soluble iron is to oxidize it to Fe(III) with some sort of air contact and then filter out the precipitate.

To produce good Mg reduction, raising the pH to at least 11 is necessary. An even higher pH does accelerate the Mg precipitation reaction. The precipitate (Mg(OH)2) is a gel and its somewhat problematic to deal with. The sludge at the bottom of the vessel can be bulky. You are better off in decanting off the water and disposing of the sludge instead of adding another batch of water on it if you're aiming for Mg reduction.

Hi Martin, it does not look like 5.3 reflects the reduction in Ca ions after acid additions.

 

[mabrungard]

Hi Martin, it does not look like 5.3 reflects the reduction in Ca ions after acid additions.

What reduction of Ca ions? An acid addition does not necessarily mean that a Ca reduction will occur. Only with phosphoric acid added to a water with high Ca content could a reduction occur and that is not included in Bru'n Water.

 

[Mer-man]

That's what I said. I'll just have to remember it then.