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Originally Posted by StirCrazy
I haven't hear much about sulpher denitrators, do you have any good links on how it works and what is taking place during the process?
Steve
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Steve,
As you can see by Tony's response and Christy's link, (which is an excerpt from Sprung & Delbeek's Vol 3.), their use has been being studied since 1991. They require a break in period while the anoxic bacteria colonize and feed on the sulfur during which nitrites are actually produced. After the initial break in period, they will produce effluent low in nitrates, but rich in sulfate and acidic. This effluent is then run through a calcerous substrate which binds some of the sulfate and consumes some of the acid finally returning to the tank with slightly higher calcium & alkalinity values.
That this system works to consume nitrates isn't in dispute, but there are arguments over how much calcium and alkalinity are replenished. Sulfate is also a byproduct of this system, but I have not been able to find anyone who has noticed this to be a problem. Most people offset sulfate buildup with 20% or so monthly water changes which would be a hell of a lot cheaper than the 25% weekly I have been going through to keep my nitrates down. Most people report that the need for water changes is much less and that the significant nitrate reduction does nothing but promote better system health.
The units themselves are ridiculously expensive for what you get. I was going to DIY until I ran across this one on eBay, but if I was going to need a bigger one I would definitely build one myself. It's simply a reverse flow Calcium reactor you feed from the bottom, the effluent coming out the top. Sulfur beads can be had at a winemaking store for under $5/kg and the calcerous material can be any pebble sized calcium carbonate.
I'm doing another water change tonight to get some nitrate laden water from my tank and get this thing fired up... hopefully when I get back from holidays it will be reading zero and I can put it in the system. I will keep everyone posted.
Oh ya... from what I've read, ZEOvit kinda works on the same principle but sans sulfur and you have to supply a regular carbon based food source... the pros of ZEOvit are that some trace elements are supplied using this method, but I didn't go too far in depth... I think Ruth was using ZEOvit so she may be able to tell us more.....