My new sulphur denitrator setup

[Delphinus]

Ask away! (Not speaking for Psyire of course, but I'm hoping he doesn't mind).

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?

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.

2) Do you add CO2 to the Ca reaction chamber?

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.

3) Is the Ca reaction chamber recirculated? Is the Nitrate reaction chamber recirculated? Both?

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.

4) Do you have an additional Ca reactor, or is this your only Ca reactor?

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.

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?

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.

6) Do you attempt to vent the N2 produced?...

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..

[Delphinus]

If you want more reading, try these:

http://www.canreef.com/vbulletin/sho...d.php?t=28791&
http://www.canreef.com/vbulletin/sho...d.php?t=26299&
http://www.canreef.com/vbulletin/sho...d.php?t=26313&

[Psyire]

Tony answered the above questions well, but I can definately add some info regarding ORP.

The denitrification process taking place in the sulphur media is one of reduction and requires an anerobic condition. An ORP value of -50 to -300 is perfect for the stabilization of these anerobic bacteria. Higher than -50 and you get too much oxidization or oxygen present, and lower than -300 and you get a byproduct of Hydrogen sulfide. (H2S) The ORP probe is in there to monitor ORP so I am better able to adjust my 'flow, or drip rate' through the reactor. This will inable me to have the best possible environment for these anerobic bacteria at all times. Atleast that is the theory behind it...

[Psyire]

So I now have the unit running on around 15g of water I just pulled from my tank during a water change. I have the drip rate set at about 3 per/second and I plan to leave it that way until the effluent tests zero for nitrate. The water is currently reading about 30 ppm of nitrate.

Here is a picture of the setup:


note* Probe ports and flow meter will not be used until unit is cycled.

[Delphinus]

What test kit are you planning to use to test the effluent?

FWIW I can't get my effluent to zero nitrates yet. It's been steady at 13ppm for the last week so I slowed it down a bit last night and will retest after 24 hours again. Actually before I hijack this thread any worse I'll go update my own with the latest results because there are some headaches there again.

[Psyire]

Great News!

(The following tests were performed by the same nitrate kit that I used above and in the same manner. Salifert)

I have just tested the effluent and it's reading ZERO nitrate! (3 drops per second roughly)

This is after roughly 1 week of operation.

Now for the really amazing part... the source water in the red bucket is reading around 0.2 nitrate. (just barely see a pink tint when viewing from the side)

So this unit reduced the nitrate in 15g of water from 30 to 0.2 in the same time frame. Very cool.

The one thing that I did that I believe made a big difference was after I had it running I fed a dropper full of bacteria straight into the reactor. I used the bacteria that comes in the Polyplab Reef-resh system and it apparently contains 6 different strains of anerobic bacteria. So I believe this helped it establish a culture, quickly. I'm sure you could use bacteria that comes with any of the zeovit type systems as well.

[Delphinus]

Cool idea to seed it. Seems to have made a huge difference. Awesome results..

For comparison I'm still not reading zero on my output after 6 weeks (although output < input). And weird that your Salifert doesn't have interference whereas mine did. I dont understand why I'm always the statistical anomaly...