Denitrification occurs through the respiration of specialist bacteria using nitrate as an oxygen source, they need carbon and phosphate for food to grow and multiply.
So we are talking about removing nitrate (phospate and carbon) using bacteria and then skimming off any excess bacterial biomass that leaves the reactor via your skimmer.
Ok i thought the denitrification in rice/biopellet/vodka systems was a byproduct of the creation of new bacterial cells which are soon exported, not denitrification as a byproduct of anaerobic respiration (if that's a term).