SOLUBLE MICROBIAL PRODUCTS (SMP) IN ANAEROBIC CHEMOSTATS

The production of soluble microbial products (SMP) in anaerobic system s was evaluated using chemostat reactors. Results from steady-state an d tracer experiments with C-14-glucose and C-14-acetate showed that si gnificant amounts of SMP were produced during the acidogenesis of gluc ose, but that SMP did not accumulate during methanogenesis from acetat e. In addition, at a retention time of 40 days, SMP comprised almost a ll of the effluent COD from the glucose-fed chemostat. For shorter ret ention times, as low as 10 days, the SMP concentration remained almost constant, but its significance in the effluent COD was reduced due to the accumulation of intermediate volatile fatty acids. The results fr om a C-14- tracer experiment in the glucose-fed chemostat were used to evaluate the importance of including SMP formation and degradation in kinetic modeling of the methanogenic chemostats. Three models were ev aluated: a model without SMP production, a model with SMP production b ut no degradation, and a model with SMP production and degradation. Th e results of this kinetic analysis indicate that the model that includ es SMP production and degradation was the only one able to adequately represent the fate of C-14 in the tracer experiment. The kinetic param eters obtained from fitting the model to the tracer experiment were su ccessfully used to predict steady-state concentrations of SMP and to c haracterize the formation and degradation characteristics of the SMP. (C) 1994 John Wiley & Sons, Inc.