CONTRERAS edgardo Martin
congresos y reuniones científicas
Inhibition of the respiration rate of ammonia oxidizing bacteria by nitrite
E.M. CONTRERAS; F. RUIZ; N. BERTOLA
Rio de Janeiro - Brasil
Congreso; ENPROMER 2005; 2005
Abstract. The first step in the biological nitrogen removal process involves the sequential oxidation of ammonia to nitrite and nitrate by ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) respectively. In this paper the effect ammonia, nitrite, and nitrate concentrations on the nitrification rate were studied using respirometric techniques.The nitrifying sludge was obtained from a laboratory scale completely mixed, continuous-flow activated sludge reactor. Synthetic wastewater was used with ammonia as energy source. Open and closed respirometers were used to measure the oxygen uptake rate (OUR) of the biomass under different experimental conditions. A Monod-based model was used to describe the total specific OUR (SOUR) at low dissolved oxygen (DO) concentrations. Experimental results showed that Monod parameters (SOURm, Ko) were not affected by ammonia and nitrate within the tested concentrations. A partial inhibition was observed at high nitrite concentrations due to the increase in the Ko values; however, SOURm values were almost constant showing that nitrite was a competitive inhibitor. Open respirometer experiments showed that the total OUR decreased as the nitrite concentration increased due to the inhibition of AOB; in addition, the ammonia oxidation coefficient was not affected by nitrite within the tested concentrations. The obtained results suggest that nitrite is a competitive inhibitor of the oxygen consumption by AMO via the formation of N2O4.