I work at a sturgeon farm and we use denitrifiers on our large growout systems. Although the research is about 10 years old, we found that out of sucrose, vinegar, methanol, and molasses, the latter was the cheapest to use over time.
So we add molasses to our DN reactors constantly using a dosing pump. Every week we set the rate based on the nitrates. We put about 30gal/min of water through the reactor that's about 4' in diameter and 8' tall for each 100,000 gallon system. The molasses (carbon source) is mixed with the water as it enters the reactor. I think that's about all I can say without disclosing any intellectual property.
And they work. Nitrate levels going into the DNs ranges between 100 and 200ppm. Coming out: less than 50ppm. Usually more like 20. The trick is getting your water flow slow enough so that heterotrophic bacteria consume the oxygen before it passes through most of the media. The denitrifying bacteria are anoxic and will not do their job if the O2 is too high. Also, if your NO3 drops to 0 then the bacteria will begin to produce hydrogen sulfide, which is toxic and smelly. Also, make sure you have adequate nitrfying bacteria because some of the NO3 will bounce back as NH3 and NO2. Overall the process gains you back the pH lost during nitrification.
The major con of molasses: it stains the water brown. For your application I'd look into using sugars or vinegars. They also make non-toxic carbon sources that you can buy for the marine aquarium, but I haven't tried them in freshwater.
I often suggest denitrifiers on this site, but I usually get drowned out by the pothos people. All of my tanks are planted at home, and my reef tanks don't run denitrifiers either. My nitrates are typically 0 but I attribute some of that to my deeper substrates. But if I had a constant issue with nitrate I'd build a DN. They sell such reactors in stores but you can build one for cheap out of PVC. Who knows, maybe you have some bioavailable carbon in your tank already and the bacteria might just need a proper home!
I hope this helps
So we add molasses to our DN reactors constantly using a dosing pump. Every week we set the rate based on the nitrates. We put about 30gal/min of water through the reactor that's about 4' in diameter and 8' tall for each 100,000 gallon system. The molasses (carbon source) is mixed with the water as it enters the reactor. I think that's about all I can say without disclosing any intellectual property.
And they work. Nitrate levels going into the DNs ranges between 100 and 200ppm. Coming out: less than 50ppm. Usually more like 20. The trick is getting your water flow slow enough so that heterotrophic bacteria consume the oxygen before it passes through most of the media. The denitrifying bacteria are anoxic and will not do their job if the O2 is too high. Also, if your NO3 drops to 0 then the bacteria will begin to produce hydrogen sulfide, which is toxic and smelly. Also, make sure you have adequate nitrfying bacteria because some of the NO3 will bounce back as NH3 and NO2. Overall the process gains you back the pH lost during nitrification.
The major con of molasses: it stains the water brown. For your application I'd look into using sugars or vinegars. They also make non-toxic carbon sources that you can buy for the marine aquarium, but I haven't tried them in freshwater.
I often suggest denitrifiers on this site, but I usually get drowned out by the pothos people. All of my tanks are planted at home, and my reef tanks don't run denitrifiers either. My nitrates are typically 0 but I attribute some of that to my deeper substrates. But if I had a constant issue with nitrate I'd build a DN. They sell such reactors in stores but you can build one for cheap out of PVC. Who knows, maybe you have some bioavailable carbon in your tank already and the bacteria might just need a proper home!
I hope this helps
