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Passive Sulfur for Nitrate control

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I put in 500g of sulfur prills in a filter sock in my sump. Not under the overflow, but just passively sitting in the first chamber. One side effect of this is that alkalinity is consumed, so I measure alkalinity every 30 minutes until i get a better handle. My nitrates are not very high atm (10 ppm), and I also have some gfo in a bag in my sump as well to deal with po4. Should be interesting!


Most sulfur denitrator reactors run in combination with limestone media to buffer the h+ released (lowers pH) and release some bicarb (alkalinity) which is consumed by bacteria to change nitrate to nitrogen gas. I'm not doing that, because over time you get increase in Ca, which is consumed relatively proportionally to alk. So I monitor the alk and dose accordingly. I really dont have any idea how much the consumption will change, because right now my tank is consuming zero. 


The basic theory here can be read in detail here ;




2 H2O + 5 S + 6 NO3– → 3 N2 + 5 SO42- + 4 H+


Sulfur + nitrate are used by bacteria to produce nitrogen gas, sulfate (abundant in saltwater, probably not an issue) and protons (which are an issue). Protons decrease pH and combine with carbonate and reduce alkalinity. 






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