Simultaneous determination of inhibition kinetics of carbon oxidation and nitrification with a respirometer

This paper presents a new method for the simultaneous determination of inhibition kinetics of both carbon oxidation and nitrification with the RODTOX (Rapid Oxygen Demand and TOXicity tester) respirometric biosensor. The biokinetic parameters of carbon oxidation and nitrification are estimated on the basis of respirometric data obtained from batch experiments with pulse injection of a mixture of a readily biodegradable carbon (acetic acid) and nitrogen (ammonium chloride) source. This estimation is based on a Double Monod mathematical model and a nonlinear parameter estimation algorithm. Performing batch tests with six to eight different concentrations of a toxic compound allows the deduction of the dependence of the kinetic parameters on the toxicant concentrations. The time necessary for a complete determination of the inhibition kinetics is approx. 8 h. Practical applications of the developed method are given.