Sulphur Reactor Denitrification

[Jas139]

Hi all, I have previously posted this thread to the beginners forum, but would appreciate any further advice if possible.

I am relatively new to reef keeping (11 months) and have just invested in an aqua medic sulphur reactor in an attempt to reduce my rising nitrate levels (currently 50ppm). Water changes and reduced feeding have so far been unsuccessful. I have recently set the unit up at 1 drop per second flow rate while it matures.

I have, however, noted that the instructions state that you should also pump the water that leaves the filter through a bed of hydrogencarbonate to neutralise the by-product of the process, sulphuric acid. I assume that this has been suggested to avoid a reduction in PH levels?.

I have checked the instructions for other units e.g. Deltec, and have not identified any similiar units which state this as a particular requirement, however, they do state that PH levels of the water leaving the unit will be reduced.

I would be grateful if anyone could advise on whether this is a requirement specific to the aquamedic unit or whether all units require some form of secondary filtering to increase PH.

My initial view was that I would compensate any effect on PH by buffering the water as well as ensuring that the return tube from the filter feeds into a high flow area of the tank.

In addition, does anyone have any idea what the maximum flow rate through the unit is once the reactor has started to work. I assume that you are not limited to 1 drop per second as maximum flow?

Not sure how many other people are using these units and are able to advise further?

Any feedback would be most welcome.

 

[John_Brandt]

Hi Jas,

AquaMedic instructions often contain some oddities because of translations into English.

Sulfuric is not the only acid that denitrifiers of this sort can produce. They will potentially make carbonic, nitric and phosphoric acid.

I'm curious if your nitrate test kit measures nitrate ion or nitrate as total nitrogen.

It is not typical for denitrifier manufacturers to recommend passing the water over carbonate (crushed coral, etc.), but there is nothing wrong with this practice. And if the water is acidic it will act like a calcium reactor. But activated carbon would be a better barrier for potentially harmful forms of acid. Sulfuric acid/hydrogen sulfide is not something you want to be dripping into your aquarium. Passing the effluent through a mixture of carbonate and activated carbon might be the best solution of all.

The drip rate you are using (1 drop per second) is a starting guideline. You will need to establish a balanced flow that brings about complete dentrification, and does not stop the reduction reaction at nitrite. A flow that is too rapid will just convert the nitrate to nitrite (upon which it will be re-oxidized back to nitrate by the aerobic nitrifiers within the aquarium). A flow that is too slow will convert sulfur to hydrogen sulfide (rotten egg smell).

The effluent of an ideally balanced denitrifier may actually smell of methane. It smells a lot like an almost-rotten rutabaga.

You will need to test the effluent for nitrite, and if you find it you begin to slow the flow. High levels of nitrite will confound your nitrate test and may give an erroneously high reading.

 

[wetworx101]

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