Modeling biofilm kinetics for a low-loaded expanded-bed anaerobic reactor

The effect of surface coverage of biomass on biofilm kinetics in an expanded-bed, granular activated carbon an aerobic reactor was evaluated. Acetate was used as the sole organic carbon source. An assumption of 10% surface coverage of biofilm was examined and compared to 100% coverage. Best estimated values of k(a) and K(sa) did not differ significantly from one case to the other. The confidence region analysis also showed that the biofilm was fully penetrated in the expanded-bed reactor for the case of 10% coverage, as well as when 100% coverage was assumed. Because the biofilm was fully penetrated, a model having no internal diffusion resistance and using the best estimates of k(a) and K(sa) obtained from the 10 and 100% coverage assumptions was capable of giving good predictions of effluent acetate concentrations for an in dependent experiment having a reduced liquid detention time. Consideration of biofilm surface-loading criteria demonstrated how the results can be applied to other reactors for the purpose of predicting when the extent of surface coverage and internal diffusion resistance are not significant factors in biofilm modeling.