ROLE OF PARTITIONING IN BIODEGRADATION OF PHENANTHRENE DISSOLVED IN NONAQUEOUS-PHASE LIQUIDS

A study was conducted to determine whether biodegradation of organic compounds dissolved in nonaqueous-phase liquids (NAPLs) is limited by spontaneous partitioning of the chemical to the aqueous phase. The biodegradation and partitioning rates of phenanthrene from NAPL to water varied with the NAPL and the concentration of the test substrate. The rates of mineralization in 10 of 11 tests with Pseudomonas sp. or an enrichment culture exceeded the rates of spontaneous partitioning with three concentrations of phenanthrene in three NAPLs. However, biodegradation was slow if the partitioning rate was slow. Mineralization by a subsoil slurry was slower than spontaneous partitioning with one phenanthrene concentration in three NAPLs. The maximum rate of biodegradation of pollutants in NAPLs thus cannot be predicted from the rates of their spontaneous partitioning to water.