Kalkwasser and effects

[The Saltman]

Hi guys,

I'm am going to be running a kalk reactor and am very paranoid about having an accident. Therefore, I limit the amount of water available to the kalk reactor. I will be using a litermeter 3 with the kalk reactor. I know the litermeter is pretty reliable, but I trust nothing. My question has to do with the effects of the kalkwasser on my tank if I were to have an accident. My total system volume is 235 gallons. I am thinking about having a 5 or 10 gallon resevoir. If the litermeter would fail and pump all the 5 or 10 gallons into the tank, would it have enough of effect on the ph to kill all the inhabitants? I understand freshly mixed kalk has a ph of around 12. But, would it be enough to kill everything? Or would it really not the shift the ph a whole lot?

 

[The Saltman]

Looking at another post I seen that Randy said that adding kalkwasser to 1% of the tank volume with raise ph by 0.6. If this is true, by dumping a 10 gallon freshly mixed kalk container it would raise the ph by 2.4? I wouldn't think this would be enough to crash the tank?

 

[Pauper]

I assume you are using a LM pump that has a pressure tube. I have a similar setup using a LM3 with a kalk reactor. What I did was set the dosing rate close to the evap rate so even if the pressure tube fails, it won't keep going.

 

[MCsaxmaster]

Agreed, I think that using sufficiently small tubing or something along those lines to limit the max. rate that kalk can be added is a good option.

Ca(OH)2 has a solubility of about 17.65 mmol/l. If you add 10 gal of saturated kalkwasser to your tank you'll add ~40 l. Since Ca(OH)2 includes 1 equivalent of Ca2+ per mole but 2 eq of alkalinity, you’d add 0.01765 mol/l * 40 l * 2 eq/mol = 1.412 equivalents of alkalinity. If this were added all at once, but actively mixed into the tank water (or pumped in over a few minutesâ€"insufficient time for atmospheric exchange of CO2) you’d add 1.4 eq to a tank of ~940 l (235 gal * 4 l/gal = 940 l), but you’d also increase system volume by 10 gal (~40 l).

Let’s say you start with pH = 8.20 and alk = 2.5 meq/l. If we add 1.4 eq alkalinity and 10 gal volume we’ll have a new alkalinity of 1.4 eq/980 l + 0.0025 eq/l ~ 3.94 meq/l. If this is done rapidly without the possibility for much uptake of atmospheric CO2 the pH will rise from 8.20 to ~ 9.41, which is quite a lot. That is certainly sufficient to cause the spontaneous precipitation of a lot of CaCO3. I’m not sure how likely pH that high is to cause real harm to the tank inhabitants. It’s not something they would experience in nature, and not something that has generally been studied (to the best of my knowledge) so we don’t necessarily have a good baseline. One can envision that it could be problematic though. Folks rarely actually experience mortality or problems like that with big kalk overdoses, IME, but that’s not to say that it’s harmless by any stretch. pH is an important parameter for cellular function. Depending on the ability of critters to regulate their cellular pH, one could imagine this doing bad things indeed.

Edit: Ack, miscalculations--numbers have been corrected above.

 

[The Saltman]

<a href=showthread.php?s=&postid=12564600#post12564600 target=_blank>Originally posted</a> by Pauper
I assume you are using a LM pump that has a pressure tube. I have a similar setup using a LM3 with a kalk reactor. What I did was set the dosing rate close to the evap rate so even if the pressure tube fails, it won't keep going.

I understand what your saying. However, I don't even trust setting a dosing rate. I think all things are prone to fail. I just want to be safe in case in pumps the whole reservoir in the tank.

 

[Pauper]

I'ven been running this setup for two years and never had a problem. The pressure tube seems flimsy but astonishingly, it's never failed. If you are really that worried then you might want to get a spectrapure float valve. I've used two for water containers and they are more solid than my solenoids. I've left water running overnight and never seen a drop of water come out when it got full.

 

[David Grigor]

Depending on the design of the Kalk reactor, it if were to stick on the likelyhood of it actually being fully saturated is quite low because it won't have mixed thoroughly and be pretty diluted.

I use Kalkwasser on all my systems, for redundancy I also use a Aquacontroller to turn it off if reaches > 8.6 to keep from precipitating.