Engineering models of combined chemical and biological processes

Steady-state models of biological degradation, representative of situations found in the treatment of difficult to degrade wastes, are studied in conjunction with chemical pretreatment. Multiple reactor configurations and inhibitory biological kinetic regimes are utilized to study a reaction network where a nonbiodegradable compound is chemically oxidized to yield biodegradable intermediates. The simulations show that the combined reactor system can achieve higher mineralization efficiencies than either reactor alone and demonstrate specific cases and operating regions where enhancement of mineralization occurs. Optimal operating regions are identified under given design constraints. Overall efficiency and achievement of process treatment objectives are functions of the waste characteristics, kinetic regimes present, and the reactor configurations used. A key element in effectively mineralizing the waste is operation in regions not subject to biomass washout. Pretreatment of inhibitory compounds in the chemical reactor or biomass recycling can stabilize the bioculture and lead to increased mineralization and a broader range of high-conversion operating regions.