DIY sulphur denitrator

[robert]

Thought I would share the sulphur denitrator I built today out of junk I had laying around.

The body is an old odyssea canister filiter -

On the inlet side I have valve to control flow and a pipe which takes water to the very bottom of the canister. Its hard to see, but at the bottom of the inlet pipe is a small powerhead. It sits in the sump water.

The outlet side takes allows water to flow out of the very top of the canister. So inlet goes deep, outlet returns shallow.

Media is coral chunks which I sprinkle with sulphur and melt in the oven...you don't have to melt it but I do...This time I added GFO. If I had raw Iron I would have used it - but you never know how the irons been alloyed so unless your certain - stick to GFO. I added the better part of a three pound container....

I let it run in a tub of rodi to let any fines wash out and then just set it in my sump. Tomorrw I'll cut back the flow to let it go anerobic...in a week or two it will begin stripping the water of nitrate and phosphate very efficiently.

 

[robert]

Oh yes - based on what I've run in the past - this should handle 500 gallons of water but we'll see. Its better to be smaller than oversized.

 

[robert]

So I guess if you've read this far your asking "why a sulphur denitrator?" What are the advantages?

A sulphur denitrator esentially operates like a remote deep sandbed and like a remote deep sand bed it can't crash your tank if the power fails. I prefer to have no anerobic zones "in" my system.

It doesn't need to be fed. Set it up, dial it in and it can run for a year or more off the excess nutrients in your system - no dosing - no pellets.

It doesn't add a bacterial load to the water column like carbon dosing does. So what is that bacteria your feeding with your carbon sources? - don't know...most of the time its not a problem until it is....gonna happen...The bacteria in the sulphur denitrator need an oxygen depleted environment to do their job...the don't live in an oxygenated environment.

Cheato and algae scrubbers are organics in the water...You have to harvest continually. Stop or get behind and they will die and add nutrients back into the system. The worst hair algae outbreak I've ever had was due to a cheato die off...

A sulphur denitrator is tunable by controlling flow...an ideal denitrator is one that runs slightly slower than you nutrients build, thereby increasing the interval between water changes - not eliminating them.

Little known - sulphur denitrators also sequester phosphates - but you have to mix up the coral with the sulphur to get the desired results. The ones you buy don't do this for some reason. I guess they didn't read the studies.

The sulphur iron reactors are even better, GFO is way, way more efficient at binding phosphate in a low ph environment like the inside of a sulphur denitrator.

A sulphur denitrator adds calcium to the tank - but it will consume alk.

Theres more ... what are the downsides?

These can produce hydrogen sulphide gas if run too slowly. This scares most people away...but then so can your sand bed or any other filter. I once lost the flow to a bio-pellet reactor once and didn't notice it for a while...it smelled so bad I pitched it.

Why aren't they more popular?

I think it might be because most commercial versions of this run with aqualifter pumps through 1/4 inch tubing...they clog and are generally a pain in the posterior.

Sorry for all the typos..anything you don't follow - ask.

 

[Synodontis]

Hi Robert,

I'm a fan of sulphur reactors to reduce & control nitrates. At the moment I'm also building a reactor. Can I ask what the logic is behind melting sulphur over the coral bones? Something I have not seen / heard about before. I take it you use sulphur powder?
Thanks

 

[robert]

The sulphur in contact with the coral facilitates the removal of phosphates.

Its based on a study I read out of china on water treatment.

I used fairly small coral bits and I don't coat the coral completely with sulphur - I just melt the sulphur onto one side so that 50 percent is exposed and 50 percent of each piece is covered.

Search :
"Nitrate and phosphate removal in sulphur-coral stone autotrophic denitrification packed-bed reactors"
-Recirculating Aquaculture Engineering Laboratory, Shanghai Ocean University, Shanghai 2009, China

 

[Oceansize]

I'm a big fan of sulphur denitrators. Mine works so well, I don't think I'll ever build a saltwater tank again without one. Mine is store-bought (the Korallin) so I guess I'm not binding phosphate, but my phosphate has never registered above 0.25 ppm in the entire time the tank has been up & running so I'm not concerned about that.

I've only had one episode where the drip rate got so low that hydrogen sulfide was evident. I merely increased the drip rate without changing anything else and the smell was gone within minutes. My only complaint is, as you say, the tubing tends to increasingly restrict flow so every morning I make sure to check the drip rate and usually have to open the valve just a little bit more to maintain the desired drip rate.

I don't know why they aren't more popular, my only guess is the time, tweaking, & testing necessary to get them up & running initially, and also the fact that they were first invented only about 10 years ago, which is a short time to adopt a relatively radical new approach to nitrate export.

The aragonite in the chamber is maintaining my Calcium perfectly, but as expected, my Alk depletion rate is a little higher than it was without the denitrator. I've been thinking about taking the aragonite out of the chamber, replacing it with even more sulphur, and then running the output through a separate Calcium reactor to keep my Alk stable. If you have an opinion about that strategy, I'd love to hear it.

 

[Randy Holmes-Farley]

It doesn't add a bacterial load to the water column like carbon dosing does. So what is that bacteria your feeding with your carbon sources? - don't know...most of the time its not a problem until it is....gonna happen...The bacteria in the sulphur denitrator need an oxygen depleted environment to do their job...the don't live in an oxygenated environment..

Where do you think the bacteria that do grow end up if not in the water column?

 

[Randy Holmes-Farley]

The aragonite in the chamber is maintaining my Calcium perfectly, but as expected, my Alk depletion rate is a little higher than it was without the denitrator. I've been thinking about taking the aragonite out of the chamber, replacing it with even more sulphur, and then running the output through a separate Calcium reactor to keep my Alk stable. If you have an opinion about that strategy, I'd love to hear it.

It just depends on whether you want the combination to end up with slowly rising calcium or slowly depleting alkalinity. Each can be dealt with, as long as folks recognize the issue.

That said, I can't see how it matters if you run the output of the denitrator directly to the alk reactor, or just run the CaO3/CO2 reactor as usual on its own.

 

[Oceansize]

It just depends on whether you want the combination to end up with slowly rising calcium or slowly depleting alkalinity. Each can be dealt with, as long as folks recognize the issue.

That said, I can't see how it matters if you run the output of the denitrator directly to the alk reactor, or just run the CaO3/CO2 reactor as usual on its own.

To your first point, yes I do recognize the issue, thanks largely to you sir and previous articles you have written on the subject! I think I'd rather have alk too low than calcium too high, since it is easier to add Alk than it is to remove calcium (is that even possible aside from adding more coral?), but I'm nevertheless in the mood to experiment and see what rate my calcium increases by in order to maintain stable alkalinity, knowing full well that I may prefer my current setup and revert back to it. Right now I have very little calcium-consuming critters (a tiny Acan frag, a tiny Duncan frag, and coralline algae) so I'm assuming my calcium depletion rate will increase from where it is now since I'm a long way from being done stocking, hence the experimental attitude.

To your second point, I recognize it may not make a difference, however I surmised that the effluent coming from the denitrator has a more profound need to be buffered than does the tank water in general, so I figured the buffering effect would be more efficient if I ran directly to the CA reactor from the denitrator. If I'm off-base with that assumption, I'd love to know the science behind it!

 

[robert]

Where do you think the bacteria that do grow end up if not in the water column?

The vast majority of bacteria in our systems is in attached bio-films. This is the case in the sulphur denitrator. The bacteria is growing on the media - not in the water column. The flow is slow, meaning very little of the bacterial film is ever dislodged.

 

[Randy Holmes-Farley]

To your second point, I recognize it may not make a difference, however I surmised that the effluent coming from the denitrator has a more profound need to be buffered than does the tank water in general, so I figured the buffering effect would be more efficient if I ran directly to the CA reactor from the denitrator. If I'm off-base with that assumption, I'd love to know the science behind it!

That is correct, but I expect the difference is small.

FWIW, folks using limewater as I do have a similar issue since limewater adds very slightly more calcium than is needed relative to the alkalinity (because it adds exactly the equivalent of calcium carbonate, but magnesium gets into the coral skeletons in place of some of the calcium. In my case, I just let the calcium drift up, but water changes limit the rise. Mine ends up in the upper 400's despite the fact that the Instant Ocean I use does not supply that much.

 

[Randy Holmes-Farley]

To your first point, yes I do recognize the issue, thanks largely to you sir and previous articles you have written on the subject! !

Thanks, I'm glad they were helpful!

 

[Randy Holmes-Farley]

The vast majority of bacteria in our systems is in attached bio-films. This is the case in the sulphur denitrator. The bacteria is growing on the media - not in the water column. The flow is slow, meaning very little of the bacterial film is ever dislodged.

Yes, I agree. But they do not endlessly accumulate in the denitrator. The must be sloughed off, just as they are from the rock surfaces and pores that they grow on when dosing organic carbon. Or from the surfaces of biopellets when using those.

 

[robert]

Yes, I agree. But they do not endlessly accumulate in the denitrator. The must be sloughed off, just as they are from the rock surfaces and pores that they grow on when dosing organic carbon. Or from the surfaces of biopellets when using those.

Sure - they accumulate in the denitrator...the denitrator does ocassionally need to be flushed, but I've gone well over a year before it became necessary.

 

[Oceansize]

Speaking of slouging off biofilm: An interesting thing happened while breaking in my denitrator: on two separate occasions I ended up increasing the drip rate too much, and the next day the tank had quite a bit of white cloudiness (that's how I knew it got too high, heh). I'm assuming the white cloudiness was due to the anaerobic bacteria getting too much oxygen and dying off? Since I've got the attention of some experts here, I'm curious if you guys have a guess as to the cause of the cloudiness. It had no observable/detectable adverse effect on the health of the tank.

Also, as previously mentioned, I'm usually having to open the valve a little bit more each day to maintain a constant drip rate; I'm assuming that bacteria is increasing in the tube, constricting flow. But one day after being gone for three days, I discovered the water was POURING out of the effluent tube as fast as it could (and became one of the two white-cloudiness episodes I just mentioned). It was as if whatever was constricting the flow had become completely dislodged while I was out of town. IF my previous theory is correct (flow that is too high will not only reduce the denitrification rate, but actually kill significant amounts of anaerobic bacteria), then could that be the explanation for why my effluent tube completely unclogged itself? (My recollection is that, since I knew I was going to be out of town a few days, I opened up the valve a little more than I normally would just before leaving to prevent the flow from completely stopping while I was gone, and therefore I suppose it's possible that I over did it and ironically prompted the opposite effect)

 

[Randy Holmes-Farley]

Sure - they accumulate in the denitrator...the denitrator does ocassionally need to be flushed, but I've gone well over a year before it became necessary.

I don't see why you think the bacteria stay there. Obviously the must grow in mass in proportion to the amount of nitrate they are consuming.

 

[Randy Holmes-Farley]

Speaking of slouging off biofilm: An interesting thing happened while breaking in my denitrator: on two separate occasions I ended up increasing the drip rate too much, and the next day the tank had quite a bit of white cloudiness (that's how I knew it got too high, heh). I'm assuming the white cloudiness was due to the anaerobic bacteria getting too much oxygen and dying off? Since I've got the attention of some experts here, I'm curious if you guys have a guess as to the cause of the cloudiness. It had no observable/detectable adverse effect on the health of the tank.

Also, as previously mentioned, I'm usually having to open the valve a little bit more each day to maintain a constant drip rate; I'm assuming that bacteria is increasing in the tube, constricting flow. But one day after being gone for three days, I discovered the water was POURING out of the effluent tube as fast as it could (and became one of the two white-cloudiness episodes I just mentioned). It was as if whatever was constricting the flow had become completely dislodged while I was out of town. IF my previous theory is correct (flow that is too high will not only reduce the denitrification rate, but actually kill significant amounts of anaerobic bacteria), then could that be the explanation for why my effluent tube completely unclogged itself? (My recollection is that, since I knew I was going to be out of town a few days, I opened up the valve a little more than I normally would just before leaving to prevent the flow from completely stopping while I was gone, and therefore I suppose it's possible that I over did it and ironically prompted the opposite effect)

I'm not sure what the cloudiness was, but bacteria is a reasonable guess, alive or dead.

FWIW, bacteria in the water are generally desirable as food, unless somehow you drive the growth of a pathogenic species (which has, perhaps, happened in a few isolated cases with organic carbon dosing).

 

[Triggreef]

Yes, I agree. But they do not endlessly accumulate in the denitrator. The must be sloughed off, just as they are from the rock surfaces and pores that they grow on when dosing organic carbon. Or from the surfaces of biopellets when using those.

But being since the bacteria in question are anaerobic, wouldn't they die when reintroduced to oxygenated water? Really not affecting much if anything?

Also as far as the effluent coming dislodged and then running much faster than wanted, this is why you should periodically open the valve to flush it for a few seconds then readjust the flow. Other wise you eventually end up with to much pressure which pushes the slough out and end up flowing to fast.

 

[Randy Holmes-Farley]

Sulfur eating bacteria won't find any food in the tank, if that is all they eat, so yes, they will likely die if not skimmed or eaten first.

I'm not suggesting there's any problem at all with them in the main tank. They may be great food for filter feeders. I just wouldn't claim they are not released.

 

[robert]

I don't see why you think the bacteria stay there. Obviously the must grow in mass in proportion to the amount of nitrate they are consuming.

Specifically, I said they don't add to the bacterial load in the water column like carbon dosing does.

I'm sure you would agree that the two systems, carbon dosing and sulphur denitrators are fundamentally different in that carbon dosing is an "export" system whereas a sulphu denitrators is a "sequestration" system.

Carbon dosing ultimately depends on the skimmer for export of excess nutrients, where the sulphur denitrator stores the excess nutrients untill a flush.

Further carbon dosing by itself takes nothing out of the system, but instead dumps bacteria into the water column for the skimmer to take care of. I can run a sulphur denitrator without a skimmer as the consuming bacteria and excess nutrients they hold remain in the denitrator.

It is possible to flush a sulphur denitrator into your system, but by design your not supposed to.

One of the advantages of the design that I showed in the DYI over commercially avalable product, is that the DIY presented is flushable in-situ through 1/2' fittings where the purchased products only provide 1/4 ports. Anyone who has flushed one of these would appreciate this.

In closing - a sulphur denitrator can function without any other form of export for up to a year and still maintain reduced nutrient levels.
A carbon system cannot.