6.5. Denitrification rates
Oxidation of an organic carbon and electron donor
and subsequent reduction of nitrate to elemental
nitrogen yields around 70% of the energy gained with
oxygen as the final electron acceptor (Payne, 1970).
High nitrate removal rates can be accomplished with
this energy efficient process under suitable conditions.
As stated earlier, information on denitrification in
recirculating systems is scarce and nitrate removal rates
by denitrification reactors are reported in only few
studies. In some studies, sufficient information is
provided to allow calculation of these rates, while in
others this information is lacking. Volumetric nitrate
removal rates by different denitrifying reactors used in
aquaculture facilities and in aquariums are summarized
in Table 3. The wide range (1–166 mgNO3-N/l/h) in
rates is most likely due to differences in operational
parameters, such as system configuration, types of
electron donor, reduction states of the reactors, and the
ambient nitrate concentrations at which the various
reactors were operated. No clear differences in
denitrification rates are found between systems in
which external carbon sources are used to fuel