INFLUENCE OF HYDRODYNAMIC CONDITIONS ON NAPHTHALENE DISSOLUTION AND SUBSEQUENT BIODEGRADATION

The influence of hydrodynamic conditions on the dissolution rate of cr ystalline naphthalene as a model polycyclic aromatic hydrocarbon (PAH) was studied in stirred batch reactors with varying impeller speeds. M ass transfer from naphthalene melts of different surface areas to the aqueous phase was measured and results were modeled according to the f ilm theory. Results were generalized using dimensionless numbers (Reyn olds, Schmidt, and Sherwood). In combined mass transfer and biodegrada tion experiments, the effect of hydrodynamic conditions on the degrada tion rate of naphthalene by Pseudomonas 8909N was studied. Experimenta l results were mathematically described using mass-transfer and microb iological models. The experiments allowed determination of mass-transf er and microbiological parameters separately in a single run. The biom ass formation rate under mass transfer limited conditions, which is re lated to the naphthalene biodegradation rate, was correlated to the di mensionless Reynolds number, indicating increased bioavailability at i ncreased mixing in the reactor liquid. The methodology presented in wh ich mass transfer processes are quantified under sterile conditions fo llowed by a biodegradation experiment can also be adapted to more comp lex and realistic systems, such as particulate, suspended PAH solids o r soils with intrapartically sorbed contaminants when the appropriate mass-transfer equations are incorporated. (C) 1998 John Wiley & Sons, Inc.