[Randy Holmes-Farley]

Maybe something to do with the NO3 depletion leading to PO4 release as first discussed in:

My understanding is that the phosphate release discussed there comes from phosphorus in the organics consumed by nitrate-based oxidation. If the carbon source driving the reaction has no phosphorus (as in vodka), then I don't see any phosphate being released. Perhaps I am misunderstanding where they claim the phosphorus comes from, however.