Nitrate Reactors

[jakub]

I recently gained some interest in different nitrate/phosphate reduction methods. sure carbon,bio pellets and gfo works but i just want something different and more controllable. from what I have heard and read a nitrate reactor (sulfur reactor) is kanda like a nitrate/phosphate rodi unit. It's sed that the media lasts a long time a nice perk. I know their is vary limited information on this subject.

I know the ketch phrase don't fix it if it,s not broken but i want to try something new. I would appreciate some input: experience, opinions or advice.

thanks jakub

 

[biom]

I dont think sulfur reactor is more controllable than biopellets, vodka, vinegar or others. The main advantage of sulfur reactor over the others is its capability to reduce nitrates not limited by the presence of phosphates in the water. That's why sulfur reactor is perfect if you have very high levels of nitrate and very low phosphates levels, in this situation the other organic carbon methods are not working because they need phosphates to reduce nitrates. But if you want to use sulfur reactor continuously then you should consider that it has noting to do with phosphates and you will need another method to remove them (GFO for example).

 

[Randy Holmes-Farley Verified Community Expert]

As noted, it does not do much for phosphate. It also depletes alkalinity. A few people really like them, but they are not super popular.

Here's my commentary on these reactors and their pros and cons as well as most other methods:

Nitrate in the Reef Aquarium - REEFEDITION
https://www.reef2reef.com/blog/nitrate-in-the-reef-aquarium

Sulfur Denitrators

In these systems, bacteria use elemental sulfur and produce N2 from the sulfur and nitrate according the following equation (or something similar):

2 H2O + 5 S + 6 NO3– → 3 N2 + 5 SO42- + 4 H+

The production of acid (H+) in this reactor can tend to reduce the aquarium alkalinity. It has also been suggested to pass the effluent of such a reactor through a bed of aragonite to use the acid (H+) produced to dissolve the calcium carbonate, and thereby provide calcium and alkalinity to the aquarium. While that is a fine idea, it doesn’t add much calcium and alkalinity to most aquaria.

To estimate the magnitude of the effect, we start with a liberal estimate of how much nitrate might be removed. Say 10 ppm of nitrate per week.

10 ppm nitrate = 0.16 mmole/L of nitrate

Since 4 moles of H+ are produced for every 6 moles of nitrate consumed, this will produce

0.107 mmoles/L of H+ per week

How much calcium this could produce?

Assume that it takes one proton to dissolve one calcium carbonate:

CaCO3 + H+ → Ca2+ + HCO3–

Clearly, this is a substantial overestimate because much of the acid will be used up driving the pH down to the point where CaCO3 can even begin to dissolve. Consequently, we have an upside limit of 0.107 mmoles of Ca2+per week. Since calcium weighs 40 mg/mmol, that’s 4.3 ppm Ca2+ per week.

For comparison, an aquarist adding 2% of the tank volume in saturated limewater daily is adding on the order of 16 ppm of calcium per day. Consequently, this method may not be especially useful for maintaining calcium. Additionally, the acid produced will have a long term lowering effect on the alkalinity. In fact, it is double dipping on the alkalinity depletion since alkalinity is consumed when the nitrate is produced, and again when it is removed in the denitrator. So if you use a sulfur denitrator, be sure to monitor the alkalinity in the aquarium.

 

[jakub]

Let's say I don't mind adding more alk and watching my ph more closely,would this be a efficient nitrate remover?

 

[cope413]

All the methods listed and used can be "efficient". You would need to be more specific.

Perhaps it's better to say what your nitrates are at (as well as how big your system is and other relevant params), what method you're currently using, and what you don't like about it. "Different and more controllable" is oddly vague/ambiguous. Carbon dosing (vinegar, vodka, etc) is easily "controllable". As is growing/harvesting macroalgae. I've seen a few detailed threads with sulfur denitrators. I'll dig around, but if you provide more info, you may get more help.

 

[Randy Holmes-Farley Verified Community Expert]

Let's say I don't mind adding more alk and watching my ph more closely,would this be a efficient nitrate remover?

It certainly can work well. I agree that "efficient" isn't really a term with a clear meaning, so I'm not sure I understand the question. It is not "better" than some of the other methods, IMO. methods that also export phosphate (macroalgae, ATS, organic carbon dosing to a lesser extent) have pluses, and while you certainly can add extra alkalinity, it makes using a balanced additives system a bit more complicated.