Predicting Removal of Trace Organic Compounds by Biofilms

Secondary utilization is a concept that describes biodegradation of trace-level organic compounds by the bacteria that are sustained by metabolism of a more plentiful primary substrate. Secondary utilization was tested using five simple organic compounds and laboratory-scale biofilm reactors. The experimental studies showed that secondary utilization is a possible and effective mechanism for removal of trace-level organics in aquatic environments. Individual trace organic compounds can be reduced to very low concentrations when the biofilm is grown through primary substrate utilization. A non-steady-state biofilm model is required to describe secondary utilization, because it does not require the biofilm mass to be sustained by utilization of secondary substrates. Instead, the biofilm mass is an input data parameter determined by uptake of the primary substrate. Experimentally determined steady-state biofilm thickness was based on primary substrate utilization, and independently determined kinetic parameters were obtained for secondary substrates. Biofilm modeling using the non-steady-state biofilm technique successfully explained and predicted removal of secondary substrates. The key concept of successful modeling of secondary utilization is that the primary substrate determines the biofilm mass, and secondary substrates will be utilized according to their own kinetics.