I would "recycle" the dentrator or build a new one. After 6 days of inactivity, you will have quite the foul smelling "output" from the reactor. Instead of having only a certain portion of the tubing being aerobic/anaerobic, after this long without new O2 infused, it will be primarily anaerobic.
Plug the intake/outport, disconnect it completely and take it outside. Fill a 5 gal pail with SW and run the reactor through that to see how bad it's gotten. Try to do this away from windows. :shock:
My guess is it will stink to high heaven but it's not a lost cause. You can recycle the unit by maintaining an ammonia source in that 5 gal pail. Just change the water daily for the first few days to get rid of the stink. It might just be simpler to build a new one but I leave that up to you.
FWIW, 20 ppm going in and 10 ppm coming out means the unit was not working properly to being with. The denitrator should only be "dripped" at a slower rate while it's new and just cycling to build up the bacteria. It should not be kept at such a slow rate permanently. Once the nitrate reading exiting the unit reach's zero, the flow can be increased to a slow stream/trickle. Otherwise the total water volume of the tank is not being turned over fast enough for the unit to have any possitive effect on the nitrate level as a whole.
My guess is that if you never did get a zero reading from the unit, the tubing amount (length) used was not sufficiently long enough or possibley was not constructed to promote de nitrification.
http://www.aloha.net/~hqf/indexdondenitrator.htm
On a side note, you'd have a much better go of it all 'round if you just swapped out the CC for snad (1-1½") or went BB.
Cheers
Steve
