No, he was right. The bacteria consume oxygen, thus reducing nitrate to
nitrogen. A lot of other things get reduced of oxygen as well.

No he is wrong. O2 is NOT produced. The oxygen's that are removed from
NO2- end up as H2O. NOT free O2. It is a VERY complex series of events.
Never is O2 produced along the way.

Look into denitrification. It is an ENZYMATIC process in anaerobic bacteria
involving more than one enzyme.

SEE: http://www.reefscapes.net/articles/a...ogencycle.html

(Look at the part that refers to denitrification and anaerobic bacteria)