Evolution des caractéristiques chimiques et biologiques des sédiments en circuit clos - III. Bilan azoté de systèmes polytrophes

The evolution of nitrogen content in experimental closed circuit Sand filters was followed, each tank being fed with different quantities of soluble organic matter. According to the trophic conditions, two types of metabolism could be observed : - a loss of nitrogen (denitrification), reaching almost 90% of the nitrogen input in eutrophic conditions, and close to 35% in mesotrophic conditions. - a gain in nitrogen (fixation), a predominant metabolism in oligotrophic and eutrophic conditions.