How to dial in a DIY nitrate reactor?

[detroit_fan]

A member on my local board posted this thread on a diy nitrate reactor-

http://michiganreefers.com/forums/showthread.php?t=82666

It looks very simple, just a bulk reef supply dual reactor, some no-no3 media, a feed pump and a needle vavle.

I have 2 questions-

How do you know when the reactor is dialed in?

How do you know when to replace the media?

 

[packer]

I have a Midwest unit. It is very similar to the Korallin unit. Both of these are larger and have a recirc pump on top of the unit. It is important to keep the circulation thru the media and not allow it to clog or form dead spots. This will produce Hydrogen Sulfide, toxic to a reef (smells like rotten eggs).

While in no way can I dispute the homemade versions, I would be concerned with this happening with potantial for more of a channeling effect with only a set low flow. The manufactured versions maintain a low flow (drip) but push/recirc the internal water at a higher flow. Also the sulphur will last a very long time, and can even be rinsed and reused after a few years. The Ca media, be it ARM or crushed coral degrades in a much shorter amount of time. So with the two manufactured units mentioned it is easy to open the unit and remove just the Ca media and replace it leaving the sulphur undisturbed. I would see some issues with the media mixed together, and would feel it necessary to replace it all for fresh Ca media. The sulphur is much more costly so it seems a waste of cash.

Again I cannot dispute the homemade versions and only wanted to bring up a few points. I have had great luck with my unit for over five years. Hydrogen sulfide is not something to mess with.

 

[packer]

Sorry to miss answering your questions.

"Dialed in" is simply the drip rate that allows the unit to consume the nitrate. At first the units must start at only 1 drip per second or less to allow the bacteria to form and build that will consume the nitrates. They are anerobic so the unit also must vent itself of O2, and that happens at the slow drip rate. Once the bacteria forms you can increase the drip rate 1 dps and allow it to cycle again. Depending on your initial tank NO3 this can take a few days to a few weeks, longer time for higher incoming nitrate.

As the unit works it will put out nitrate free water and the plan is to have a unit large enough to reduce the nitrates and allow a drip rate high enough to put out more nitrate free water then is coming in. This will in turn lower the nitrate in your overall system.

One issue with these is that once your units reduce the nitrates away they will also produce Hydrogen sulfide if not getting any incoming nitrates. Or if the drip rate is too slow or the units become clogged or develope dead spots this can also happen.

The dialed in refers to the point where your unit and drip rate are adjusted to the nitrates being produced on a steady basis. So if you have say 25ppm nitrate when you start, it will take awhile to cycle the unit to a 3-4 dps drip rate, and then running like that depending on the size of the units and gallons of total water in the system time to lower the nitrates to zero or near zero. Then the unit needs to adjust to the nitrate load the tank is producing. If it produces low nitrates, then alot of times at that point it helps to open the unit and remove a bit of the sulphur if you find it is producing hydrogen sulfide at a higher drip rate. By messing with it you will get to a point where the unit feeds on the nitrates produced in balance with the amount of bacteria present. I believe the reason the hydrogen sulfide is produced is that if no nitrates are present, the bacteria seeds itself to the sulphur and then consumes it for a food source, putting off the gas.

The sulphur I also believe is a place for the bacteria to reside if I remember right. If consuming nitrates, the sulphur will not be consumed (really what you dont want for aformentioned reasons) and it will last a long time (years). If it becomes clogged simply remove it and rinse in freshwater and reuse it.

The Ca media is used to buffer the units water to help increase the ph as the lack of O2 drops the ph. It also will dissolve slightly and add a very small bit of calcium to the system. You can add more media if/as needed and its a good idea to replace it about every six months with total fresh media.

 

[tmz]

I use a diy reactor ,the diy thread version as shown in Reefkeeeping magazine. This one has a recirculator and is relatively easy to build with pvc. I thik a recircualtion set up with a bit of pressurization is the proper application.

The amount of sulfur you put in it will determine how much nitrate free effluent you can ultimately produce. I use 3 litres of carib sea LSM sulfur and run mine at 15 litres per hour of near 0 nitrate water. It took 4 weeks to get to that level, starting at a drop or two per second and doubling whenever the effluent hit 0 nitrate. This type of cycling allows the the aerobic bacteria feeding on the sulfur to colonize and use up the O2 in the water and then move on to the O in NO3. The unit needs to be degassed during the low flow stages to realease built up nitrogen gas which is left once the bacteria consume the oxygen fromthe water and the nitrate. Once it flows more quickly, most of the nitrogen is pushed out with the effluent water and degassing to avoid blockages is needed less frequently.

Hydrogen sulfide may be formed when the nitrate in the reactor is exhausted as an oxygen source . In this situation the bacteria will fix hydrogen to the sulfide from the sulfur instead of oxygen creating hydrogen sulfide which is toxic instead of sulfate which is not. So if you get a rotten egg smell in the gas the flow needs to be increased to provide more oxygen and nitrate. If the flow is too high,however, the bacteria will just consume the oxygen in the water and perhaps one of the O atoms in the nitrate which would leave NO2 (nitrate).

It is important to monitor ph since the effluent is usually at a ph of about 7.0. It will also use up some alkalinity. Running it through a course of argonite will offset these effects to a degree and give you a bit of calcium and carbonate as a by product. This should be done in a separate canister since th agonite will dissolve much more quickly than the sulfur. Once it's cycled you don't wan't to open the reactor since doing so introcduces oxygen which necessitates an new cycling process.