Passive Sulfur for Nitrate control

[victoly]

I put in 500g of sulfur prills in a filter sock in my sump. Not under the overflow, but just passively sitting in the first chamber. One side effect of this is that alkalinity is consumed, so I measure alkalinity every 30 minutes until i get a better handle. My nitrates are not very high atm (10 ppm), and I also have some gfo in a bag in my sump as well to deal with po4. Should be interesting!

 

Most sulfur denitrator reactors run in combination with limestone media to buffer the h+ released (lowers pH) and release some bicarb (alkalinity) which is consumed by bacteria to change nitrate to nitrogen gas. I'm not doing that, because over time you get increase in Ca, which is consumed relatively proportionally to alk. So I monitor the alk and dose accordingly. I really dont have any idea how much the consumption will change, because right now my tank is consuming zero. 

 

The basic theory here can be read in detail here ;

 

http://www.baharini.eu/baharini/lib/exe/fetch.php?media=badess:182.pdf

 

2 H2O + 5 S + 6 NO3– → 3 N2 + 5 SO42- + 4 H+

 

Sulfur + nitrate are used by bacteria to produce nitrogen gas, sulfate (abundant in saltwater, probably not an issue) and protons (which are an issue). Protons decrease pH and combine with carbonate and reduce alkalinity. 

 

SCIENCE

 

 

[Gig 'em @ NDstructible]

How funny, I was just researching sulfur denitrators this morning. It's like I could sense what you were about to say...... SCIENCE!!

[victoly]

This is it. nothing crazy.





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[fourdrachma]

The way I understand it is, the sulfur media eventually harbors bacteria that reduces phosphates. Your method will only grow anaerobic bacteria, which is beneficial too.. but it could be used more efficiently inside a reactor.


Sulfur nitrate reactors use small beads of elemental sulfur in a contact chamber. Water is introduced very slowly. As the water is dripped in and dripped out slowly, all oxygen is removed, making the water anaerobic in the contact chamber. At this point, bacteria will use nitrate in the absence of oxygen and by the time the water exits the reactor, most of the nitrate has been removed. The reactor can be outfitted with a circulation pump that keeps the water circulating inside the reactor without introducing any oxygen. The downside to this chemical reaction is that hydrogen ions are released, which makes the seawater more acidic. Most sulfur reactors pass water over crushed coral before returning it to the tank, as the acidic water dissolves the crushed coral and replenishes ph and calcium. Since sulfate is another bi-product of the chemical reaction within the reactor, crushed coral also absorbs this and removes it before water re-enters the aquarium.
The plus-side to sulfur based reactors is that they are almost maintenance free. The sulfur beads last a long time, with some systems advertising that they never need replaced. The crushed coral media will dissolve over time and need replaced, but even that can last for extended periods. They are much easier to use and maintain, and don’t carry the risks associated with traditional nitrate reactors, or bio-pellets.

Here’s a pic of mine, with a protein skimmer taking in the water exiting the sulfur reactor, it’s eliminated all algae and cyanobacteria. It’s well worth the cost. It requires a lift pump to supply the slow drip of water from the sump.


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[Sierra Bravo]

Your link does not work for me to read the theory, but fourdrachma is dead-on in his summation that the specific bacteria a sulfur denitrator uses requires the exhaustion of oxygen for the bacteria to switch to nitrates in order to continue to oxidize sulfur.  The flow through rate is only 1-3 drops per second, and generally takes months to get your nitrates down.  If your drip rate is too high, not enough nitrates will be processed.  Too slow, and they consume too much sulfur.   I'm not sure that a passive bag of sulfur will create the same effect.  Nice thing is once you get everything balanced it takes care of itself and is almost maintenance free.

For what it's worth, I've been running one for 9 months or so and could not be happier with the results.

[victoly]

So the idea here is instead of forcing a chamber to become anaerobic, that the center of the passive columns become anaerobic on their own, both from outside the column to inside, as well as from the surface of the media to the inner layers of media. 

So far I am relatively sure that its functioning well, as I'm only limited by my ability to accurately test nitrate. Its dropped me from 10-5 ppm, and there is definitely some alk consumption going on specifically from the sulfur media. 

I honestly think that the possibility exists that we are over-mechanizing this process, at the behest of those who wish to sell us reactors

[Timfish]

A description of sulpher denitrification's use at the Aquarium de Musée national de Arts ď Afrique et ď Océanie can be found on page 9 of Seascope V 17pdf here:

 

spectrum-sitecore-spectrumbrands.netdna-ssl.com/~/media/UPG/Files/Instant%20Ocean/SeaScope/Volume%2017_2000.pdf

 

All the issues of Seascope and an index of topics can be found here

http://www.instantocean.com/Ocean-of-Knowledge/SeaScope/SeaScope-Index-by-Subject.aspx

 

Delbeek and Sprung have a detailed discussion of the chemistry and effects on seawater of sulfer reactors starting on pg 277 of "The Reef Aquarium" Vol III.