DEGRADATION MECHANISMS OF COLLOIDAL ORGANIC-MATTER IN BIOFILM REACTORS

The degradation mechanisms of colloidal organic matter in biofilm reactors have been studied in an idealized laboratory reactor system with soluble starch as a model substrate. Batch tests and experiments with different reactor configurations have shown that for this specific substrate, bulk liquid hydrolysis is the mechanism for transforming non-diffusible organic matter into biofilm diffusible substrate. A simplified mathematical description has led to the identification of the degree of hydrolysis, D-H, as the parameter expressing the major difference between degradation of diffusible and non-diffusible organic matter in a biofilm reactor. D-H depends on the combined volumetric and surface hydraulic loading rate, Q(2)/(AV). In full-scale wastewater treatment plants, the degradation mechanism presented in this paper can explain important differences between the performance of trickling filters and RBC reactors.