Sulfur Denitrator

edosan · May 22, 2015

Hi guys, sorry for my english is a bit rusted (I am from Chile).

I was reading about Sulfurs Denitrators, and got me thinking...correct me if I am wrong.

Sulfur get water, and then you got a light solution of sulfuric acid, then the solution goes to aragonite to dilute calcium and then goes into the tank, to feed bacteria (a very basic resume), is that correct?

If it is, and asuming that I can get my hands on sulfuric acid 9x% pure...can I make a solution with sulfuric acid diluted like 10% (acid to water I know), and then add aragonite to the solucion? (adjusting the PH and concentration ?) and then using a dosing pump, use it direct to the tank/sump?

Maybe my question is dumb...not a chem expert...I will apretiate some pointers ...

Randy Holmes-Farley · May 22, 2015

Sorry, that scheme won't be very useful except as a complicated way to add calcium and lower pH and alkalinity.

Yes, sulfuric acid is produced in a sulfur denitrator, which tends to reduce alkalinity and pH in the aquarium (a drawback of such a denitrator). Running the effluent over aragonite tends to dissolve some calcium carbonate and helps boost the pH somewhat, but it then becomes an unbalanced additive of calcium and somewhat less alkalinity than was depleted by the sulfuric acid. So the net effect is that the sulfur denitrator reduces nitrate, reduces pH (but not as much as without the aragonite), reduces alkalinity, and adds calcium.

The scheme you propose is similar to how a calcium carbonate/carbon dioxide reactor works, with one critical difference. In a CaCO3/CO2 reactor, the carbon dioxide added as the acid to dissolve the calcium carbonate can be blown off to the air (as carbon dioxide). That way the device produces both calcium and alkalinity, and only has a smallish pH lowering effect on the aquarium.

If you use ANY mineral acid (sulfuric, hydrochloric, etc.) then that acid cannot be blown back off to the air after the calcium carbonate is dissolved, so you end up lowering pH and adding calcium, but not adding alkalinity.

In a sense, if you add sulfuric acid to aragonite, you get calcium sulfate. If you add hydrochloric acid you get calcium chloride. Both of those would be easier to just add as a bulk chemical (which people do, most especially calcium chloride since calcium sulfate is not that soluble).

edosan · May 22, 2015

Thanks a lot Randy.! (sorry for the rookie questions

)

I was believing that you feed the bacteria in the tank, with sulfur denitrator you feed bacteria inside the sulfur denitrator, I am correct? and the acid is a drawback as you mention...

Randy Holmes-Farley · May 22, 2015

This is the right place to ask these sorts of questions!

I'm not sure I understand the last question. If you add sulfuric acid to an aquarium, it will dissociate into H+ and sulfate. Sulfate is the third or fourth most abundant ion in seawater (depending on whether you mean by weight or number of ions), so it is already there in large amounts and it is not consumed by bacteria in normal seawater.

edosan · May 22, 2015

What I was trying to say is that I was under the impresion that in a sulfur denitrator, the idea was to produce "food" for the bacteria inside the tank, with that in mind I was thinking about h2so4....but later I read (after this post) that the denitrate bacteria is inside the sulfur reactor, so add h2so4 to the tank make no sense (like you say), since is a not desirable by-product. Is that correct?

Lonelyreef · May 22, 2015

What about a sulfur reactor as a tool to lower nitrates only using sulfur media

Randy Holmes-Farley · May 22, 2015

edosan said:
What I was trying to say is that I was under the impresion that in a sulfur denitrator, the idea was to produce "food" for the bacteria inside the tank, with that in mind I was thinking about h2so4....but later I read (after this post) that the denitrate bacteria is inside the sulfur reactor, so add h2so4 to the tank make no sense (like you say), since is a not desirable by-product. Is that correct?

A sulfur denitrator in normal use produces nothing the the main tank would consume (except possibly the bacteria themselves when they get released from the sulfur and leave the denitrator). Bacteria grow on the sulfur and get energy by essentially using the sulfur to break down nitrate. All that happens inside of the denitrator.

edosan · May 22, 2015

Perfect! Thanks!

Randy Holmes-Farley · May 22, 2015

Lonelyreef said:
What about a sulfur reactor as a tool to lower nitrates only using sulfur media

That's the normal use of a sulfur denitrator. It can work, but there are many other methods as well.

I discuss them all here:

https://www.reef2reef.com/blog/nitrate-in-the-reef-aquarium

rage1199 · May 26, 2015

I use a sulfur denitrator. Once I got it tuned in like a Calcium reactor, which took about a month with constant measuring of parameters. My doser doses 10ml more Alkalinity than Calcium a day with 0 Nitrates and PH at 8.1 with the help ok Kalk in top off.