Discussing nitrate reduction

[Lasse]

Again, I expect crushed coral media in such a reactor will not accomplish much. If you try to make the whole reactor anoxic it will be extraordinarily tricky to keep it from becoming anaerobic and producing hydrogen sulfide. Special media with interior anoxic regions rarely solve elevated nitrate problems.

As long as you have around 2 mg/L NO3 in the outlet - you will have a low production of hydrogen sulfide. My experiences is also that even if the effluent is lower than 2 mg/L NO3 - the hydrogen sulphide production is low and will be fast oxidized in the aquarium water. Could be a good idea if the outlet of the reactor is situated near the skimmer intake - in that case you do not need to worry about hydrogen sulphide.

There’s not enough organic around.

True - therefore you need to have a little overspill of labile DOC to maintain the denitrification process. IME the amount of overspill will be the mechanism you use in order to control the denitrification process.

I measure my NO3 once a week and adjust the dosing regime with these result as guiding tools.

Sincerely Lasse

 

[GARRIGA]

If you try to make the whole reactor anoxic it will be extraordinarily tricky to keep it from becoming anaerobic and producing hydrogen sulfide.

Hydrogen sulfide was something I came to fear after learning more about denitrification.

Would adding a skimmer post perhaps resolve this issue by gassing out or perhaps algae solve it? I'm not well versed in hydrogen sulfide other than concluding hydroxyl radicals can remove it. I've been told.

 

[GARRIGA]

If you dose into the media - the right way and with the right dose/waterflow ratio - the DOC will only affect the bacteria population in the media - not in the DT, rocks, sump, corals or whatever. It will be consumed and converted into mainly CO2 in the media. These bacteria is not primary bacteria plankton - they are bacteria that attach to something. You need to create a anaerobic environment in the media - it means that the aerobic bacteria metabolism needs to be very high in the first layer of the media (consume all free oxygen in the incoming water) and you need a little "spill" over of DOC in the other layers of the media in order to have the denitrification process going on. You can theoretical get a anaerobic filter media with help of a very slow flow through the media but the second part - free DOC for the denitrification process will take a very long time to get. You can get it with help of internal production (in the filter) of carbohydrates, alcohols or other labile DOC but it will take a long time before this happens. This is the reason why passive DSB works but have a "starting" time of months, or even years. The flow in these beds is done by equilibrium processes between water in the aquarium and the porewater in the media (in the DSB). The needed labile DOC is produced by breakdown processes in the media (sediments)

You can also get some conversion of ammonium directly to N2 with nitrite as electron acceptor. This process is autotroph - do not need DOC with other words. this process - Anammox - was discovered back in 1990:ties and can be responsible for more than 50 % of the N2 production in sediments around the world. As I know - it has not been shown in aquariums even if I suspect it can take place in my reversed flow DSB cause around 0.4 mg L NH3/NH4 is normally disappearing from my water that flow through my DSB - but I´m not sure because my NO3 will rise in the system if I do not dose enough of DOC. However - anammox can be responsible for the N loss in static DSB - but as I know it - it has not been shown.

I can´t explain exactly whats happens in my reversed flow DSB but it consume N - I can totally control excess nitrate - the end product of the oxygen-dependent nitrification in my aquarium with help of ethanol dosing.

Sincerely Lasse

I grasp the denitrification process and removal of DO by nitrification to create an environment of bound oxygen such as nitrate.

What I still don't understand being why be concerned with DOC into the main display. Would some not eventually make it to the denitrification filter or do we need to avoid putting DOC into the display? I get it's easier to control as you execute but all may not have that option or means to properly calibrate and test influent and effluent.

Seems to me in the most simplified manner that key being an environment devoid of DO and containing bound oxygen plus a carbon source. Depending on who you speak to this can be called anaerobic or anoxic. I call it anoxic with anaerobic being devoid of all oxygen. Both dissolved and bound.

 

[malacoda]

If you already have zeolite media, the first thing I would do is put in a reactor (zeolite 'branded' or otherwise).

Media like Zeolite and De*Nitrate work best under constant, diffuse low flow — the kind of thorough, diffuse flow you rarely get by placing it passively in a bag in the sump.

I used Seachem De*Nitrate in a mesh bag by the baffle of my sump (e.g. where I thought it would be appropriate flow) and it didn't do much for my NO3.

Then, per the instructions, I put it in a reactor (DIY) with a flow rate of ~50g/h through the reactor ... and my NO3 went from 25 down to 2 within 48 hours and stayed there for as long as I ran the reactor.

KZ recommends no more than 400 l/h (100 g/h) for zeolite. Seachem recommends no more than 50 g/h for De*Nitrate.

Once you get the zeolite working the way it's meant to, if needed, you can target dose a carbon source into the reactor as mentioned by Randy Holmes-Farley and Lasse...

Just add it at the intake of the reactor's pump.

But with the levels you're currently at, I doubt you'll need to dose carbon once the zeolite is getting the proper amount of flow.

 

[GARRIGA]

My assumption is that the anaerobic bacteria in the media would consume most of the carbon before it exits the reactor.

Understood but how's that differ from direct injection vs general dosing the display. Excess from the display would eventually make it to the media and one can increase display dosage to ensure enough make it to where needed. Plus why would it all need to be removed first pass through the media?

 

[GARRIGA]

If you already have zeolite media, the first thing I would do is put in a reactor (zeolite 'branded' or otherwise).

Media like Zeolite and De*Nitrate work best in under constant, diffuse low flow — the kind of thorough, diffuse flow you rarely get by placing it passively in a bag in the sump.

I used Seachem De*Nitrate in a mesh bag by the baffle of my sump (e.g. where I thought it would be appropriate flow) in a 20g and it didn't do much for my NO3.

Then, per the instructions, I put it in a reactor (DIY) with a flow rate of ~50g/h through the reactor ... and my NO3 went from 25 down to 2 within 48 hours and stayed there for as long as I ran the reactor.

Then, once you get the zeolite working the way it's meant to, if it's still not enough to keep your NO3 where you want it, you can target dose a carbon source into the reactor (just add it at the intake of the reactor's pump) as mentioned by Randy Holmes-Farley and Lasse.

Used pumice sized same as Seachem Denitrtate. Same core product. Regardless how slow flow was there came a point where nitrates couldn't be resolved without dosing carbon or algae. My media represented 25% of tank volume therefore one can't argue enough wasn't used. Seems that without the carbon source in tank denitrification not very feasible and just marketing by Seachem.

Having said that, not sure if my carbon dosing was assisted by a large slow flowing media or it would have had the same results had I dosed carbon in a tank with nothing fancier than live rock, sump and skimmer. Perhaps one day I'll do a Berlin carbon dosing experiment although at the moment my success tells me likely just wasted effort. Solution might be as simple as having a large amount of media and carbon since I later increased the flow beyond recommendation and was able to resolve nitrates as effectively with what now likely purely aerobic media. Key being the carbon since nothing else changed other than flow.

 

[Mels_Reef]

Understood but how's that differ from direct injection vs general dosing the display. Excess from the display would eventually make it to the media and one can increase display dosage to ensure enough make it to where needed. Plus why would it all need to be removed first pass through the media?

If you look back at the first couple of posts in this thread, I am extremely leary of dosing carbon. I have had bad experiences both times I tried it. Even at 30% if the recommended dose.

I am looking for an alternative no3 export system similar to a sulfur denitrator because I already have that reactor but I don’t want to use the sulfur.

 

[GARRIGA]

If you look back at the first couple of posts in this thread, I am extremely leary of dosing carbon. I have had bad experiences both times I tried it. Even at 30% if the recommended dose.

I am looking for an alternative no3 export system similar to a sulfur denitrator but I don’t want to use the sulfur.

You also asked for different forms of carbon to exclude NoPox as that may have been the culprit vs dosing carbon in general. My point here strictly about the function of carbon in resolving nitrates.

What I know of sulfur reactors (which is not lots) is that you will need the sulfur otherwise back to the attempt at creating an environment where DO is removed leaving behind bound oxygen which can't be solved without a carbon source.

Might find that an ATS best solves your issue yet now being told that algae produce a form of DOC (also something I know little about and little time to read all the research papers provided) yet there's also a plausible solution to that by using sponges which also crave DOC including that produced by algae.

Reefing one big you know what rabbit hole. I'm going to start going by Alice at some point

 

[UMALUM]

I appreciate your experience, but for me NoPox is absolutely not an option for me again. I can’t speak for all SPS keepers, just myself.

Your not alone, it did the same thing to my system. I'm not sure why it's toxic to some systems but after talking to a couple people and two of my vendors it happens more frequent than some think. It was like a very slow stn leaving a dark beige/brown skeleton behind. Fragging the price didn't help once it was infected the whole thing was toast.

I ended up going the ATS route. No mess no poison.

 

[malacoda]

Used pumice sized same as Seachem Denitrtate. Same core product. Regardless how slow flow was there came a point where nitrates couldn't be resolved without dosing carbon or algae. My media represented 25% of tank volume therefore one can't argue enough wasn't used. Seems that without the carbon source in tank denitrification not very feasible and just marketing by Seachem.

Having said that, not sure if my carbon dosing was assisted by a large slow flowing media or it would have had the same results had I dosed carbon in a tank with nothing fancier than live rock, sump and skimmer. Perhaps one day I'll do a Berlin carbon dosing experiment although at the moment my success tells me likely just wasted effort. Solution might be as simple as having a large amount of media and carbon since I later increased the flow beyond recommendation and was able to resolve nitrates as effectively with what now likely purely aerobic media. Key being the carbon since nothing else changed other than flow.

My response was intended for the OP.

That said, @GARRIGA, you don't mention if you had your pumice in a reactor. Is it possible there was not enough low flow for all "25% of tank volume" worth of pumice to effectively come in contact with, and 'treat,' your nitrates?

 

[Mels_Reef]

If you already have zeolite media, the first thing I would do is put in a reactor (zeolite 'branded' or otherwise).

Media like Zeolite and De*Nitrate work best under constant, diffuse low flow — the kind of thorough, diffuse flow you rarely get by placing it passively in a bag in the sump.

I used Seachem De*Nitrate in a mesh bag by the baffle of my sump (e.g. where I thought it would be appropriate flow) and it didn't do much for my NO3.

Then, per the instructions, I put it in a reactor (DIY) with a flow rate of ~50g/h through the reactor ... and my NO3 went from 25 down to 2 within 48 hours and stayed there for as long as I ran the reactor.

KZ recommends no more than 400 l/h (100 g/h) for zeolite. Seachem recommends no more than 50 g/h for De*Nitrate.

Once you get the zeolite working the way it's meant to, if needed, you can target dose a carbon source into the reactor as mentioned by Randy Holmes-Farley and Lasse...

Just add it at the intake of the reactor's pump.

But with the levels you're currently at, I doubt you'll need to dose carbon once the zeolite is getting the proper amount of flow.

Current nitrate levels are my sweet spot but the trend is heading upward and I am also trying to cut back on weekly WC’s. So I am preparing for intervention with this thread.

My plan is to fill the recirculating reactor with mostly small ceramic rings, some CaRx ARM, and a bit of zeolites. I can control the feed rate via a manifold with a gate valve and I can also control the output (effluent) via a gate valve. So I will have no problems with experimenting with different flow rates. Thanks for your input!

 

[GARRIGA]

My response was intended for the OP.

That said, @GARRIGA, you don't mention if you had your pumice in a reactor. Is it possible there was not enough low flow for all "25% of tank volume" worth of pumice to effectively come in contact with, and 'treat,' your nitrates?

My tank had a plate with 25% of tank volume under it and entrance of water on one end therefore all water had to go through the media. This was in a 20G test tank therefore the plate covered the bottom and water flow was forced to travel minimum 20" end to end with four inches of depth. Goal was to have water travel an extended period to allow nitrification time to strip DO then pumped back into the aquarium via a Tidal 75 to hopefully gas off any hydrogen sulfide formed.

That Tidal 75 could be adjusted from 10% flow at it's lowest to maximum of 300 gph. At it's lowest flow it would meet Seachem's requirements. This worked on it's own in the beginning but short lived.

I'll post a few pics in a moment. Very similar to Lasse's reverse DSB except mine was lateral flow. In the end should cause the same environment except I dosed carbon into the display.

 

[GARRIGA]

Here’s the final product. Water entered on the right which will be clear in further pics and drawn by the HOB to the left end. You can see the standpipe under the HOB

 

[GARRIGA]

Here’s an example of the bottom layer filled with pumice.

 

[GARRIGA]

Here’s the completed plate. You can see how water entered on one end.

 

[GARRIGA]

Here’s a better view showing the thickness of the media under the plate tank is 16” high and 4” dedicated to pumice there’s Reborn on top of the plate but likely zero impact on what’s happening under the plate beyond further nitrification

 

[Mels_Reef]

My tank had a plate with 25% of tank volume under it and entrance of water on one end therefore all water had to go through the media. This was in a 20G test tank therefore the plate covered the bottom and water flow was forced to travel minimum 20" end to end with four inches of depth. Goal was to have water travel an extended period to allow nitrification time to strip DO then pumped back into the aquarium via a Tidal 75 to hopefully gas off any hydrogen sulfide formed.

That Tidal 75 could be adjusted from 10% flow at it's lowest to maximum of 300 gph. At it's lowest flow it would meet Seachem's requirements. This worked on it's own in the beginning but short lived.

I'll post a few pics in a moment. Very similar to Lasse's reverse DSB except mine was lateral flow. In the end should cause the same environment except I dosed carbon into the display.

How do you test for hydrogen sulfide?

 

[GARRIGA]

How do you test for hydrogen sulfide?

I don't. Just assume it's a potential and built the flow effluent to hopefully solve it. Another reason once I confirmed carbon dosing at high flows worked I abandoned the need to go slow. Why take the chance.

Later on I added Pom Pom algae and turned the HOB into a diy Fuge to solve for excess co2 as well as end the need for carbon dosing which was lowering my pH to unmanageable.

Next iteration replacing the bottom plate with a canister (reactor) then fed to a larger AquaClear 500 diy ATS or Fuge with goal to allow media to capture and decompose detritus then allow algae to remove inorganics. Not a fan of cleaning socks or any type of mechanical filtration and prefer letting nature solve it. Thinking about how to incorporate sponges into the canister to solve DOC I wasn't aware previously needed solving. All in an attempt to design my main to be as stress free as possible as I'd rather spend time viewing my living art, family, traveling and fishing. Plus wife likely not a fan of stinking socks or skimmate. Noise another problem being this will be in the family room where watching movies are a priority. Last I need is an unhappy wife (life).

 

[ronsonb]

Definitely worth a read and trying out.
https://www.reef2reef.com/threads/poor-mans-nutrients-control-donovans-nitrate-destroyer.302685/

I would make some slight modifications, like using a versa dosing pump (or any continuous duty pump) to control the flow through the reactor.

It sounds like the denitrator reactor with the sulfur component.

Can second this. I built one and I made some slight modifications to be able to auto dose and connect its own small water pump. I dose minimal carbon into it only when nitrates start to climb and find it effective even without dosing vinegar.

It can drive nitrates down real fast, I actually have it off currently because my nitrates were 3.5 the other day when I tested. The trick is getting the drip to be as slow as possible without creating hydrogen sulfide. Once dialed in tho it is VERY effective.

 

[Mels_Reef]

Can second this. I built one and I made some slight modifications to be able to auto dose and connect its own small water pump. I dose minimal carbon into it only when nitrates start to climb and find it effective even without dosing vinegar.

It can drive nitrates down real fast, I actually have it off currently because my nitrates were 3.5 the other day when I tested. The trick is getting the drip to be as slow as possible without creating hydrogen sulfide. Once dialed in tho it is VERY effective.

That’s kind of my plan I think. I already have the recirculating reactor so I will be doing my own experimental version of Donovans reactor

With the gate valves on both ends of the reactor it’s very easy to control