Development of a differential volume reactor for soil biodegradation studies

A bench scale experimental system was developed for the analysis of polycyclic aromatic hydrocarbon (PAH) degradation by mixed microbial cultures in PAH contaminated Manufactured Gas Plant (MGP) soils and on sand. Operational parameters and reactor design were optimized to reduce dispersion and channeling effects. The effective dispersion coefficient approached optimal values. A plug flow differential volume reactor (DVR) was developed to remove performance effects related to reactor configuration as opposed to system structure. The differential volume assumption allows simplification of the coupled partial differential equations describing unsteady state behavior in soil systems. Unsteady state behavior could be monitored using on-line capillary-column gas chromatography and on-line high performance liquid chromatography. The developed on-line analytical systems were easily maintained, sensitive for PAH and resolved very complex PAH mixtures eluting from weathered contaminated soils. The reactor system was capable of providing a fundamental protocol for evaluation of specific mixed microbial cultures on specific soil systems by elucidating the important system variables and their interactions. The reactor design and peripherals are described. This reactor system could be well represented mathematically. The mathematical models and experimental data are presented for the biodegradation of naphthalene on artificial and MGP soils.