Optimal redox for denitrification

[pedersen]

Hi

I have just bought a denitrifier filter (AquaMedic NitrateReductor 400) together with a mv controller an a redox probe to measure the redox potential in the filter. The manual says, that the redox value in the filter should be between -50 and -300 for the dinitrification proces to take place. That is a very broad range !

Can anyone tell me, what the optimal redox value in a denitrifier is ? That is, what redox value should I aim for, if I want to achieve the maximum nitrate reduction ?

 

[Mihai]

Until you get an official to do it: WELCOME to REEFS.ORG!

Now to your question: sorry, I have no idea . I use a DSB instead .

M.

 

[Anonymous]

Thanx, Mihai, for welcoming the member.

As far as the optimal redox potential for the denit, it is a difficult question.

First of all, this is not *real* science since a lot of the parameter is empirically derived, that is, someone kept the redox at -120mV, for example, and it worked well. Another did it at -25mV, and it works pretty well too. etc..

Second is that the redox value and the bacterial activity level interacts with each others. Don't remember off hand rather the mechanism is negative feedback or positive feedback, but either way it is not going to be easy to maintain.

third, other parameters such as dissolved oxygen (if I remember correctly) also affect the redox to some extend.

Overally, redox is a very difficult subject , and as far as I know, large portion of people who use denitr. got disappointed. In majority of the cases, there are other alternatives that can replace denitr, such as DSB or other proper water parameter management technique, such as appropriate skimmer, feeding adjustment, and regular water change.

 

[pedersen]

Thank you for the warm welcome

 

[Anonymous]

The point I want you to get from my comment is that if you can keep the redox within the range, you are in good shape. A good "optimal" value to start is the middle of the range, that is, -175mV., unless someone can give you a better, justified value. Good luck.