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

Respirometric techniques have been used for the on-line and off-line a ssessment of toxic effects of substances. A model-based method to desc ribe toxic effects on the biodegradation kinetics based on a respirome tric 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 automa ted method will be presented which allows us to perform the RIKA test within 3 hours by using an activated sludge based respirographic biose nsor (RODTOX, Rapid Oxygen Demand and TOXicity tester). These results could be achieved because a respirogram obtained from this biosensor g ives rise to a degradation rate versus substrate concentration data-se t that covers the whole substrate concentration range required by me R IKA test. Starting from an initial concentration of 20 mg COD/l in the ARIKA procedure, the biogenic substrate is degraded completely in les s than 30 minutes. Using a model-based approach coupled to a non-linea r parameter estimation algorithm, the kinetic parameters of the biodeg radation process can be obtained. Performing batch tests with differen t toxicant concentrations (usually 4) men allows us to deduce the depe ndence of the kinetic parameters on the toxicant concentrations. Since the method is automated, the procedure is fast and labour-saving.