APPLICATION OF EXPERIMENTAL RESEARCH METHODOLOGY TO THE STUDY OF NITRIFICATION IN MIXED CULTURE

Nitrification is an aerobic process formed by two consecutive reaction s: nitritation and nitratation. Using an experimental research methodo logy, we have studied the specific effects and the possible interactio ns between initial ammonia concentration, pH and temperature on these two reactions as well as on the experimental conditions leading to a n itrite build-up. In the experimental field studied (35 < [N-NH4+](o) m g.l(-1) < 90, 15 < T degrees C < 25 and 7 < pH < 8.5), the statistic i nterpretation of the results shows that only temperature and pH have a significant positive effect on ammonia removal. Moreover, the effect of these two parameters is linear. As for nitrite accumulation, the te mperature effect is negligible and a strong interaction between [N-NH4 ](o) and pH is revealed. When the values of these two variables are hi gh, nitratation is inhibited and 50% of the nitrogen introduced at the beginning accumulates temporarily in the Form of nitrites. The result s clearly show that a high NH3 concentration inhibits Nitrobacter, sta rting from between 6.6 and 8.9 mg N-NH3.l(-1). This research enables a better understanding of the nitrite build-up phenomena which can be t hus minimized or maximized in the case of new process of nitrogen trea tment. Copyright (C) 1996 IAWQ.