AUTOMATED RESPIRATION INHIBITION KINETICS ANALYSIS (ARIKA) WITH A RESPIROGRAPHIC BIOSENSOR

Abstract

Respirometric techniques have been used for the on-line and off-line assessment of toxic effects of substances. A model-hased method to describe toxic effects on the biodegradation kinetics based on a respirometric technique has been developed by Volskay and Grady, However. this so-called RIKA-procedure (Respiration Inhibition Kinetics Analysis) is rather laborious and time consuming. In this paper, a fast and automated method will be presented which allows us to perform the RIKA test within 3 hours by using an activated sludge based respirographic biosensor (RODTOX, Rapid Oxygen Demand and TOXicity tester). These results could be achieved because a respirogram obtained from this biosensor gives rise to a degradation rate versus substrate concentration data-set that covers the whole substrate concentration range required by the RIKA test. Starting from an initial concentration of 20 mg COD/1 in the ARIKA procedure, the biogenic substrate is degraded completely in less than 30 minutes. Using a model-based approach coupled to a non-linear parameter estimation algorithm. the kinetic parameters of the biodegradation process can be obtained. Performing batch tests with different toxicant concentrations (usually 4) then allows us to deduce the dependence of the kinetic parameters on the toxicant concentrations. Since the method is automated, the procedure is fast and labour-saving.