Use of a nitrifying culture to shorten the activation time of biofilters for the removal of ammonium and nitrite in freshwater aquaria.
The removal of ammonia (NH3) through nitrification in intensive aquaculture systems is an important process as the total ammonia nitrogen (TAN, compromising NH4+ and NH3) concentration often is the key limiting water quality parameter in these intensive aquaculture systems. In this study, the performance characteristics of a suspension of nitrifying cells (named ABIL) have been explored This aqueous suspension contains a highly active, nitrifying microbial consortium and is stable for several months when preserved at 4 degrees C. Tests were performed in freshwater at lab scale (70 L, 20 - 24 degrees 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 and nitrite species from 10 mg N L(-1) to below the detection limit within a period of four days. Experimentally, at a substrate level of 10 mg TAN L(-1), a rate of biological ammonium and nitrite conversion of the order of 0.3 - 0.5 g TAN g(-1) VSS(-1) d(-1) could be achieved by the consortium in the freshwater aquaria systems tested Provided adequate aeration and dissolved oxygen levels of 6 mg per L or more, no important intermediary nitrite concentrations were noticed Only a small amount of TAN was not found back as nitrate and might have been lost due to ammonia stripping After 12 months preservation of the inoculum at 4 degrees C, no important decrease in ammonium removal activity and only a minor decrease in the nitrite removal rate of the consortium were noticed.