An improved nitrifying
enrichment to remove ammonium and nitrite from freshwater aquaria systems
R.
Grommen, I. Van Hauteghem, M. Van Wambeke, W. Verstraete-2002
Aquaculture, 211(1-4): 115-124
Abstract:
The total ammonium nitrogen (TAN) concentration is
often a key limiting water quality parameter in intensive aquaculture
systems. Removing ammonia (NH3) through biological activity is
thus an important objective in aquaria and aquaculture system designs. In
this study, the performance characteristics of a suspension of nitrifying
cells (named ammonia binding inoculum liquid, ABIL) have been explored. This
aqueous suspension contains a highly active, nitrifying microbial consortium
that can be used to shorten the start-up period of a biofilter.
Tests were performed in freshwater at lab scale (70
l, 20-24 °C). Results showed that the application of the consortium at a
dose of 5 mg volatile suspended solids (VSS) l-1 assures a total
removal of ammonium (NH4+) and nitrite species from 10
mg N l-1 to below the detection limit within a period of 4 days.
Experimentally, at a substrate level of 10 mg TAN l-1, a rate of
biological ammonium and nitrite conversion of the order 0.3-0.5 g TAN g-1
VSS-1 day-1 could be achieved by the consortium in the
freshwater aquaria systems tested. Provided adequate aeration and dissolved
oxygen (DO) levels of 6 mg l-1 or more, no important intermediary
nitrite concentrations were found. Only a small amount of TAN was not
recovered as nitrate and might have been lost through ammonia stripping.
Pre-inoculating the nitrifiers in polyurethane (PU) sponges and installation
of such sponges in the freshwater aquaria did not improve the effect
compared to adding the consortium directly to the water.
After 12 months preservation of the inoculum at 4 °C,
no important decrease in ammonium removal activity and only a minor decrease
in the nitrite removal rate of the consortium were noticed.
(Laboratory of Microbial Ecology and Technology
(LabMET), Ghent University, Coupure Links 653, B-9000 Ghent, Belgium, Tel.:
+32-9-264-59-76; fax: +32-9-264-62-48, e-mail of W. Verstraete: Willy.Verstraete@rug.ac.be;
http://welcome.to/labmet)