The kinetics of inhibition in methane fermentation of swine manure

Abstract

The microbial kinetics of methane fermentation in anaerobic digestion of organic wastes have been traditionally described using studies of pure substrates, relatively isolated cultures and continuous flow biological reactors. A study involving semi-batch continuously loaded anaerobic digesters using swine waste has demonstrated that the conventional mathematical description of microbial growth kinetics under inhibiting conditions is not sufficient. One inherent problem encountered in mathematical modelling of biological waste treatment processes is sufficient description of the complex organic substrate. Regardless of the composition of this substrate, or the operational mode of the reactor (batch, semi-batch or continuous flow), the microbial kinetics of any system that has the same groups of organisms present must be the same. The difference in these systems is that they are described by different mass balances, not by different microbial kinetics. Conventional kinetics has proved to be totally inaccurate in describing the operation of these semi-batch reactors under inhibited conditions and has led to the development of a new kinetic description that accurately describes both semi-batch and continuous flow reactors in the inhibited and non-inhibited states.