Sulfur denitrators can be a little difficult to operate; I’ve found that as sold, they usually require some modification to allow easier use by the hobbyist.
If I understand you correctly, your denitrator was working as expected (i.e., you were getting zero nitrate out for a given flow), then something happened, and then your denitrator was not working at all (I.e., the effluent nitrate concentration was maybe even the same as the nitrate concentration in your tank).
This happens, and it doesn’t mean you killed your resident microbial population as suspected.
The bacteria that perform sulfur denigration are anaerobes that need anoxic (without air) conditions. Now you didn’t open the reactor and expose the bacteria inside to air. But if the flow rate changed (increased), or the dissolved oxygen in your tank water increased, the ORP inside the reactor might have risen just high enough that these anaerobes turned off (they stopped working) and went to sleep.
Thats what they do.
We tend to run our sulfur denitrators right at the edge. We want to push the most amount of flow through them they can handle. Sure, you could send much less flow through the reactor than it can handle, but we’d all have giant underutilized reactors.
As a result of we run our reactors, the ORP (think of it as a measure of how much oxygen is in the water) in the reactor is typically right below the level where the bacteria will shut off. This is like driving your car to do errands with the tachometer always right below the red zone.
I run a Korallin S3002. There’s a couple of things I do to prevent the bacteria shutting off. First, I use a metering pump to precisely send the water through the reactor. Using a valve to modulate flow from a regular pump or power head is prone to variations in flow. I’ve also replaced the valves with higher quality John guest fittings, and especially the purge valve to keep the headspace free of gas build up.
If you get high ORP shutdown of your denitration, simply back the reactor way down (I use 5mL/min - your reactor might have a different startup flow), then increase it by 5mL/min every 24-48 hours testing the effluent, until I get a trace of nitrate. That’s my holding flow.
Whatever you do, though, don’t open up the reactor, wash the media, etc. your bacteria are still in there. They’re just sleeping.
Matt
