sulphur denitrator Questions

[epicfatigue]

Hey Guys,

I currently have a sulphur denitrator connected to a Kamoer FX-STP2.

I originally started with 1 L of media for my 450L tank nitrates at 22ppm, it pulled them down fast so i stopped it and halved it.
Same thing again, so i removed more and now i am currently running maybe 2 to 2 1/2 Cups of media and a flow rate of 16ml/s.

The Question i have here is how to peg this to my desired nitrate level.

The way i have been told to use this is once nitrate hits 0 you have to increase it, otherwise you will get H2S, and eventually you will get 0.X nitrate comming out and the system will stay that way.

So i have been testing every 3 days and increasing it by 2mls each time and every time i get 0 nitrate. I forgot about it last week and was expecting rotten eggs but no nothing still 0.

So my question is to achieve my desired nitrate do i stay on this path keep tuning up until it reads 0.X ? (Will have to remove more media to achieve this)
Do i turn the flow back down and if i do not smell rotten eggs just peg the ml/s to what my tank needs?
Do i just crank the flow so the reactor just shuts off and the bacteria goes to sleep?

Sorry there is just no clear cut information on this

 

[tzabor10]

Try running it on a timer.

 

[Randy Holmes-Farley]

I’ve never used one and the various ways to control them are not usually discussed much since they are not that common.

Reducing flow sounds best to me. A timer would work too, but the interval needs to be short enough that the water doesn’t become anaerobic.

 

[epicfatigue]

I’ve never used one and the various ways to control them are not usually discussed much since they are not that common.

Reducing flow sounds best to me. A timer would work too, but the interval needs to be short enough that the water doesn’t become anaerobic.

My Question is if i reduce flow which to me sounds like the way to go, how do i prevent the bacteria from creating H2S as they will use the media. Or should the Bacteria just starve off and it should balance?

As i have had it running fast will this mean i will get a rotten egg smell when i dial it back?

 

[Lasse]

A timer would work too, but the interval needs to be short enough that the water doesn’t become anaerobic.

I´m confused. In my world - a sulphur denitrator needs to be anoxic/anaerobic in order to work as a denitrator. However - the NO3 levels is important in a long run because organisms that need NO3 in the metabolism (Waste N2 and CO2) dominate over the ones that use S compounds (Waste H2S)

I would recommend that you rise the flow till you read around 2 ppm NO3 in the outlet - when you get that - try to balance the flow around that (2-3 ppm NO3) You read right - you should rise the flow, hence get the system i little more ineffective as a denitrator. If it is possible try to filtrate the inflow from organic matter - in order to form H2S in the filter - you need anaerobic conditions, lack of NO3 + organic matter

When you dial in the filter - have an eye on NO2

Sincerely Lasse

 

[epicfatigue]

@Lasse So you would recommend speeding up the flow rather fast ??
I have been doing is super slow and found the reactor would always catch up.

For example i would only increase the flow by 2mls each time should i go for 10mls

 

[Randy Holmes-Farley]

My intent was slow, but not too slow.

 

[epicfatigue]

My intent was slow, but not too slow.

Yeah i think this is where i am going wrong, since i have been using a Kamoer FX-STP2 i have been able to creep the speed up very slowly and really give the bacteria a chance of growing.
I have been upping the flow by about 33% every 3 days what would you aim for as a Guess randy 50%?

 

[Lasse]

Because that the denitrification process (even with the sulphur method) depends on the level of how anoxic the media is - a slower flow will do the process as effective as possible - which means lower to zero NO3 in the effluent. I understand why every one want it slower because if the "consumption" of NO3 per time unit in the reactor will be lesser than the aquariums production of NO3 in the same time span - the concentration will rise.

However - and this is strictly IMO - I´ll think that this is a logical somersault.

In all anaerobic situations there is always a danger of hydrogen sulphide formation. In salt water the normal sulphide concentration is around 10 000 mg/L - it means that there is enough of S available regardless of whether the media is sulfur or not. However - IMO - there is 3 main factors for the rate of hydrogen sulphide formation.
1 level of anoxic/anaerobic environment
2 level of NO3 in the water
3 level of organic carbon in the water - either in the form of DOC (Dissolved Organic Carbon) or POC (Particulate Organic Carbon)

Even if a sulphur denitrator is build on strains of autotrophic sulphur bacteria there is always heterotrophic bacteria present in the water and media

1) Higher flow - less anoxic/anaerobic environment - lesser NO3 "consumption" - lesser hydrogen sulphide formation

2) It have been shown that higher NO3 in the water will favour the anaerobic heterotrophic bacteria strains that use NO3 as electron acceptor in the absence of Oxygen over the anaerobic heterotrophic bacteria that use sulphur compounds as the electron acceptor in the absence of both O2 and NO3. There is a line of command here: oxygen -> nitrate -> sulphur compounds

3) All heterotrophic bacteria need organic carbon in one or another form. If there is DOC or POC present - the two factors above is critical if you get a hydrogen sulphide formation. Because a sulphur denitrator is build on bacterial processes that are not depended on organic carbon - you can diminish the risks of hydrogen sulphide formation by limit DOC and POC in the media

There is one backslash with using sulphur denitrators and it is that if the process is not total complete - high concentrations of nitrite (NO2) will be formed - hence my warning of NO2 formation. NO2 is not very acute toxic in saltwater but nether the less - it is IMO unwanted

This above is the background why I - if I was in the same situation - probably should rise the flow with my left hand and the NO2 meter in the right.

Another option I would consider is to take out the denitrator from the aquaria and let it to work in a bucket until my NO3 concentration in the aquarium is there it should be or a little higher. During the time in the bucket - I would feed the filter with NaNO3 or KNO3 (you can get it in the grocery shelfs as Chile saltpetre (NaNO3) or salpetre (KNO3). When I reinstall the working filter - I would tune in the speed in a way that I get the wanted NO3 concentration in the effluent of the filter. Needs probably a couple of weeks with testing. I would also test for NO2

I prefer to use Hanna Checkers (or Hanna Marine Master) for these checks. Hi-782 (High NO3 tester 0-75 ppm) and Hi - 764 (0-200 ppb NO2-N) is the methods I use. The high NO3 meter has a accuracy of ± 2 ppm but it is OK for me even in low concentration. If you are very picky with your NO3 measurement - the low NO3 checker can be an alternative but it is much more complicated to use

Sorry for long post but a statement I saw in another thread is is applicable here

Reefing is not rocket science - it is much more complicated

Sincerely Lasse

 

[Randy Holmes-Farley]

So I do not know the perfect answer and I'm only speculating.

But I think that the chance of hydrogen sulfide formation is not the same as in a carbon denitrator. A carbon denitrator, with all its excess organic carbon, is a ticking time bomb if things go too slow. A sulfur denitrator is not. The only carbon available is that in the water coming into the reactor, and the sulfur itself does not generally seem to lead to hydrogen sulfide formation. That gives a much bigger leeway for slow flow, IMO.

 

[Lasse]

So I do not know the perfect answer and I'm only speculating.

But I think that the chance of hydrogen sulfide formation is not the same as in a carbon denitrator. A carbon denitrator, with all its excess organic carbon, is a ticking time bomb if things go too slow. A sulfur denitrator is not. The only carbon available is that in the water coming into the reactor, and the sulfur itself does not generally seem to lead to hydrogen sulfide formation. That gives a much bigger leeway for slow flow, IMO.

I´ll think your right there - it is a lesser risk. But if yo run DOC dosing or have a lot of particles in the water - it will be enough of organic carbon in the media for formation of hydrogen sulphide

Sincerely Lasse

 

[Malum Argenteum]

An anecdotal observation: my sulfur denitrator (I'm using a Geo's CR510 calcium reactor as a denitrator, running for over a decade now) sometimes gets a clogged feed line. It is fed by a Aqualifter pump, so not all that reliable. This has never led to any problems that I can detect other than rising nitrates in the system. So I personally don't worry about running the reactor too slowly, or having it effectively shut off.

 

[Lasse]

I´m not either so worried for toxic concentration of hydrogen sulphide in the DT from a sulphur based denitrification. Especially if the effluent is located in a well oxygenated area. My reversed DSB using heterotopic denitrification is situated as the bottom of my reversed light refugium - around 23 L and with a flow of around 2300 L/H. During nighttime it is we oxygenated by the macroalgae - during daytime well oxygenated by the corals photosynthesis. Oxygen will oxidase the H2S directly.

But is good to know what you are working with - it means that you can design the use in a way to minimize the risks - even if they ar low

Sincerely Lasse

 

[epicfatigue]

thanks guys, i have always worried about having the effluent produce zero nitrates.
Ill now just control the flow to set the display and ignore the output of the reactor and just sniff it once a week to see if i have rotten eggs. if i don't ill ignore it.