Kinetics of anaerobic purification of industrial wastewater

As a part of the development of an integral mathematical model describing the up-flow anaerobic sludge blanket (UASB) reactor, the kinetics of the conversion of organic wastes has to be known. We compared the Monod model with the model proposed by Andrews et al. Together with the assumption that the substrate for the anaerobic bacteria is formed by nonionized, volatile fatty acids, the Andrews model is able to describe substrate inhibition and reactor failure due to pH changes.From four batch experiments, with different concentrations of microorganisms, it could be concluded with a reliability of over 95% that the monod model was inadequate and Andrews' model was adequate to describe the measurements. Standard statistical techniques like the X2- and the F-test were used for this purpose. From a parameter sensitivity analysis for the Andrews model it followed that the maximum specific growth rate microAmax of the bacteria and the inhibition constant K1 are the parameters which influence the system most. Thus, these parameter were determined experimentally and most accurately. The results are: microAmax =16*10-4h-1+/-2% and K1 = 0.0158 g HAc/L+/-2.5%The other parameters were taken from literature. From calculation of the Thiele modulus for the particles it follows that transport limitation of the substrate in the flocs is not significant. The efficiency is 0.85 in the worst case..