A TRANSIENT MATHEMATICAL-MODEL FOR MAXIMUM RESPIRATION ACTIVITY AND OXYGEN DIFFUSION-COEFFICIENT ESTIMATION IN NON-STEADY-STATE BIOFILMS

A transient mathematical model was established in order to evaluate ox ygen diffusivity in non-steady-state biofilms. A submerged fixed bed b iofilm system with efficient medium recirculation was investigated for p-toluenesulphonic acid degradation by Comamonas testosteroni T-2 in a multispecies biofilm. Static mixer elements (Sulzer Chemtech Ltd, Sw itzerland) were used as a support matrix for biofilm formation. Biofil m respiration was estimated using the dynamic gassing-out oxygen uptak e method. Based on the dissolved oxygen concentration profiles, the ox ygen diffusion coefficient and the maximum respiration activity were c alculated. The values of the dissolved oxygen diffusion coefficient va ried with biolfilm development and values reported here (2 x 10(-10)-1 .2 x 10(-9) m(2) s(-1))are in good agreement with literature data. Cal culated oxygen consumption rates fit well with values obtained in resp irometry tests with washed out biofilms. The knowledge of diffusivity changes in biofilms is particularly important for removal capacity est imation and appropriate reactor design. (C) 1998 Society of Chemical I ndustry.