Novel Respirometry Measurement and Comparison of Monod Kinetic Constants and Methanogen Concentrations for 27 Full-Scale Anaerobic Bioreactors.

Monod kinetic coefficient values (k and K) as well as methanogen concentrations (X and X) for various anaerobic bioreactors are required to gain a deeper understanding of anaerobic biotechnology. However, there are no existing, practical methods to measure or estimate these parameters or variables in typical anaerobic digester biomass that contains mixed cultures with inert organic solids. Current measurement methods rely on pure cultures developed in the laboratory. In this work, a novel respirometric method was developed and used to determine methanogen Monod parameters and active biomass concentration for samples from 27 full-scale anaerobic reactors. Differences (one to three orders of magnitude) were observed among acetate and H k values and active biomass fractions for the different biomass microbial communities. Average k values for acetate and H were 14.6- and 48-g COD/g COD-d, whereas average K values were 21.9- and 0.32-mg COD/L, respectively. Average X as a fraction of total VSS was 0.80% and ranged from 0.02% to 2.49%, whereas average X was 1.16% and ranged from 0.04% to 8.23%. Granular biomass k values were approximately three times greater than flocculant biomass values, indicating significant fundamental differences ostensibly exist in methanogenesis between the two process configurations. In the future, relationships may be developed to predict kinetic constant values based on microbial community composition.