Do sulfer denitrators work long term and more info

[chrisk500]

I am looking at getting a denitrator as I am trying to automate everything with my tank. Are these proven to work over a long period or only drop nitrates down for a short while? Are there any articles out there that discuss how they work?
Thanks!
chris

[tmz]

Here is a thread on it. It is very comprehiensive and long. There are many links to articles throughout. I just buil;t one and I am in the process of cycling it. My understanding is that the sulfur media lasts about 2 years and the flow can be addjusted to suit you aquariums nitrate production for short and longterm applications.

http://reefcentral.com/forums/showthread.php?s=&threadid=1288082&perpage=25&pagenumber=1

[chrisk500]

Thanks for the VERRRRY lengthy thread. I will get on it today. From just glancing it over the denitrator looks promising. Is there a reason people choose vodka/carbon sources vs denitrators?

[Randy Holmes-Farley]

Sulfur denitrators do not reduce phosphate while carbon dosing can. Also, sulfur denitrators will deplete alkalinity while carbon dosing will not. Carbon dosing is also cheaper, but has its own concerns (which include potentially reduced O2, possibly driving nutrients too low, and maybe causing unsightly bacterial mats).

[packer]

I have been running mine for over four years now. The only maintenance I do is replace the intake and outflow lines about every 45 days as they start to build up algae inside and restrict the flow. I have had great luck with it. Takes patience and a little work in the beginning, but once you achieve a stable beneficial rate ( Nitrates produced to Nitrates removed) it just sits and does its thing.

[chrisk500]

<a href=showthread.php?s=&postid=14108041#post14108041 target=_blank>Originally posted</a> by Randy Holmes-Farley
Sulfur denitrators do not reduce phosphate while carbon dosing can. Also, sulfur denitrators will deplete alkalinity while carbon dosing will not. Carbon dosing is also cheaper, but has its own concerns (which include potentially reduced O2, possibly driving nutrients too low, and maybe causing unsightly bacterial mats).

You can make up for the alkalinity by increasing your dosing and most people already run GFO for PO4 so are these potential negatives to sulfur denitrators a concern are just something to keep in mind?

[tmz]

Randy,

Could you help me understand how the alkalinity depletion occurs when using a sufur denitrator.?Will running the effluent through argonite minimize it?

Thanks

[Randy Holmes-Farley]

That could reduce the alkalinity drop, but will then boost calcium.

i discuss it here:

Nitrate in the Reef Aquarium
http://www.advancedaquarist.com/issues/august2003/chem.htm

from it:

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

2 H2O + 5 S + 6 NO3- ---> 3 N2 + 5 SO4-- + 4 H+

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+ ---> Ca++ + 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 Ca++ per week

since calcium weighs 40 mg/mmol, that's

4.3 ppm Ca++ 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 and alkalinity levels. On the other hand, the acid produced will have a long term lowering effect on the alkalinity, so if you use it, watch the alkalinity.

As to its actual ability to reduce nitrate, I cannot say for sure. I expect that it can be made to work, but the only aquarist that I have spoken to that uses one has had considerable difficulty with it.

[note that this was written more than five years ago, many people use them now OK]

[packer]

Just something to keep in mind. I test and dose Alk and run GFO.

The bad of a sulphur denitrator could be the reaction and addition of SO2, rotten egg smelling water, that is a very bad thing and can crash a tank fast. It is produced when the flow is too slow or no nitrates are in the incoming water. It started to produce that a one point and thats when I discovered the algae restricted lines. Now I keep that issue in check and no problems. The other issue is the PH on the outflow will be low due to the anarobic process used to consume the nitrate. I run my output in an area prior to the protien skimmer and the air increases the ph. so it really has no affect on my overall tank ph level.