Alk & Nielsen reactor

[Osama]

I have a large (8" X 30") reeator. I place 2 cups of Kalk that would last 2 weeks in my setup. the reactor's output looses potency after 5 days & lots of kalk remains unrdissolved. pH of output drops to below 11 while it was above 12 when the solution was freshly made. Any idea as to what is wrong with the kalk solution & what to do to remedy this situation.

 

[rabagley]

First possible problem, how often does your mixing pump run? Are you sure it's starting properly? Is the impeller still in good shape?

Second possible problem, could there be any CO2 in your water supply? Is your supply water ever exposed to the atmosphere between the RO filter and the reactor?

The way to examine the state of your reactor is to take what's sitting in the bottom of the reactor and try to make regular kalkwasser in another container. If it mixes, then it's still calcium hydroxide and you're not correctly circulating the reactor contents. If it doesn't, the calcium hydroxide has been turned into calcium carbonate and you've got CO2 entering your reactor somehow.

Regards,
Ross

 

[Len]

I hate chemistry but perhaps this article might help:
http://www.reefscapes.net/articles/bree ... asser.html

Perhaps mix less, use vinegar, or make sure there isn't too much CO2?

 

[Osama]

Thanks Ross & Len. First description of my system. When I mix a fresh batch I clean the container & fill with RO water from the RO storage tank. RO storage tank has a lid. Tthe reactor is fed from the RO storage tank directly via a liter meter pump. So only time the water is in contact with the air is when it is inside the storage tank & when I fill the reactor.
My reactor has a magnetic motor outside the cylinder with a stirring bar inside the cylinder. After an initial mixing continuously for 2-4 hrs I stir for 5 minutes every hour. Any comments on the system or how I am operating it is welcome. thanks.

 

[Fastmarc]

I guess it might be difficult to introduce vinegar while using a Neilsen reactor. That's the reason I didn't bother building one. I use vinegar and couldn't imagine how to accomplish that.

 

[rabagley]

When I mix a fresh batch I clean the container & fill with RO water from the RO storage tank. RO storage tank has a lid. Tthe reactor is fed from the RO storage tank directly via a liter meter pump. So only time the water is in contact with the air is when it is inside the storage tank & when I fill the reactor.

From this description, it sounds like the water is exposed to the air while it sits in the storage tank after being filtered. If so, that's my first guess. The water put into a Nilsen reactor should come directly from the filter or as near to that as possible. Exposure to air will cause atmospheric levels of CO2 to build up in the supply water. The CO2 will react with the dissolved lime and in the high pH of the reactor, it will form insoluble calcium carbonate.

My reactor has a magnetic motor outside the cylinder with a stirring bar inside the cylinder. After an initial mixing continuously for 2-4 hrs I stir for 5 minutes every hour. Any comments on the system or how I am operating it is welcome. thanks.

I tend to like the reactors that use pumps better than the ones that use stirrers but that's just me. In any case, this isn't the problem. If you've observed it stirring and it's doing the same job it was a week ago, then your kalk is being stirred. As such, it's almost certainly CO2 contamination of the supply water. Try to dissolve what's left in the reactor in some fresh RO/DI water. I'll bet that it won't dissolve at all and that what's in there is now calcium carbonate.

To fix it, you'll need to talk to someone who knows more about RO/DI systems than I do. I have a 3 gallon bladder tank on mine that keeps the water completely sealed away from the air, but that required a bit of installation and may not be what you need in your personal situation. I'm sure that something can be made to work, but you need to limit the amount of time your water spends in contact with air to minutes at most.

I guess it might be difficult to introduce vinegar while using a Neilsen reactor. That's the reason I didn't bother building one. I use vinegar and couldn't imagine how to accomplish that.

You can use vinegar with a kalk reactor, but you need to dose it separately. It's impractical to add it to the reactor, so don't bother. Just set up a separate drip/pump with the vinegar dripping right beside the reactor output line and you'll have the same effect. As long as the vinegar gets mixed into the tank water slowly enough, your inhabitants will have no problem converting it to CO2 for the kalk to convert into HCO3-.

Regards,
Ross