Ask away!
(Not speaking for Psyire of course, but I'm hoping he doesn't mind).
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Originally Posted by untamed
I'm really interested in this.
Sorry for tons of questions...
1) The sulfer based reaction has no need for low pH or CO2 addition, right?
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Errr .. yes and no. No as in you don't inject CO2 to lower the pH, but you DO need a zone of "little to no" oxygen (aka "anoxic zone" or "anaerobic zone") for the anaerobic bacteria that reduces nitrate, to take hold. They metabolise the sulfur, consuming the nitrates and releasing nitrogen gas, and sulphates (see your RHF text you quoted). NSW already has sulfate to some degree and there's nothing in the literature to suggest that it's harmful in any way.
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2) Do you add CO2 to the Ca reaction chamber?
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No - the absence of oxygen plus the metabolic activities reduce the pH in the reactor, so the water entering the Ca reaction chamber is already with depressed pH.
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3) Is the Ca reaction chamber recirculated? Is the Nitrate reaction chamber recirculated? Both?
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The Ca reaction chamber is the second stage of a 2 stage calcium reactor. These are almost always single-pass, otherwise you're basically looking at a complete reactor for the second stage. I imagine there is benefit for recirc on this stage but it's fairly atypical thing, based probably mostly on economics. I've been considering making my 2nd stage recirculation at some point but it's not a priority. The flow-through flowrate is very slow.
The nitrate reducing chamber, or the first stage, is recirculated. This part is basically the same as any calcium reactor.
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4) Do you have an additional Ca reactor, or is this your only Ca reactor?
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Technically I think you're better off not relying on the denitrator to replenish Ca and Alk on a heavy Ca drawing bioload (ie. SPS, clams, etc.). Personally I have several reactors anyhow as I'm a gear nerd and like trying different things so in my case the answer is "yes I have an additional Ca reactor" but at the moment the tank I run my denitrator on has a very low Ca demand as there are no corals in there for now. So no other reactor on THAT tank but that may change one day.
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5) Why the ORP sensor in the Nitrate chamber? Does the sulpher reaction also need to be in the absence of oxygen? If so, how is oxygen removed from this reactor?
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I can't answer the ORP thing, maybe Psyire can chime in on that one. In my opinion, ORP is a useless number to track unless you're running ozone on your system.
The sulfur reaction does need to be in the absence of oxygen.
Oxygen is removed by cycling the reactor and using a very slow flowrate. Thus, once the oxygen is depleted, very little returns into reactor from the feed.
There is a slight caveat. Once the unit has "cycled completely" and after a period of time the tank nitrates will read zero. At this point you need to increase the flowthrough rate through the reactor so that nitrate can be consumed at the rate it is produced.
So technically you don't want an completely oxygen-free zone, as if you do that, you'll have the wrong chemical reaction take place, and produce H2S instead. Apparently the levels are so low as to generally not be a concern other that it will stink your place to high heaven. But you do want a "low" oxygen zone until your tank is reading zero nitrates and then you rely on a smaller population of bacteria with the faster flowrate.
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6) Do you attempt to vent the N2 produced?...
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It is recommended to place the output of the reactor in a high turbulent zone, preferably a sump not the main tank, and above the waterline to aid in gas exchange. Other than that, no special consideration for venting N2 (which is a part of air anyhow), except for that the first stage, i.e. the sulfur stage, should be an upflow so that gas can escape into the second stage (which should also be upflow so gas can escape from there as well). A downflow style will end up with a gas bubble at the top that can't go anywhere.
Hope this helps..