For Rousselle (1990), nitrogen was present in
wastewater in two main organic forms (proteins, amino
acids) and mineral (NH4
+, NO3
-
). The organic form will
therefore undergo ammonification followed by
nitrification. According to Ouazzani et al. (1996)
ammonium ions were largely eliminated by absorption
onto the sand particles and organic particles, before
undergoing nitrification if the conditions of aerationallow them. Nitrification was the biological
phenomenon of oxidation of ammonia to nitrate by
autotrophic microorganisms (Pochon et al., 1958). The
bacterium responsible of this reaction was Nitrosomas
(Pochon & De Barjac, 1958; Dommergues & Mangenot,
1970). Nitrification was influenced by temperature and
pH. The optimum area of the porous medium of pH for
nitrification was ranged between 6.6 and 9. The Fig 5b