FACTORS AFFECTING THE BIODEGRADATION OF PHENANTHRENE INITIALLY DISSOLVED IN DIFFERENT NONAQUEOUS-PHASE LIQUIDS

A study was conducted of the importance of measured partitioning rate, the nonaqueous-phase liquid (NAPL)-water interfacial area, and the to xicity of NAPLs to the biodegradation of constituents of NAPLs. Bacter ial mineralization of phenanthrene was slower if the compound was init ially dissolved in phthalate eaters than in aliphatic hydrocarbons wit h several NAPL-water interfacial areas. The differences were not the r esult of toxicity of the test NAPLs. The rates of partitioning of phen anthrene from NAPLs to water were faster with larger interfacial areas , but a consistent influence of interfacial area on the rate of minera lization was not evident. The measured rates of partitioning from NAPL s to water under sterile conditions varied among the NAPLs, the mass t ransfer rates being slower with phthalate esters than with alkanes. Th e rates of mineralization of phenanthrene initially in NAPLs were corr elated with measured partitioning rates, but the rates of biodegradati on were sometimes faster than the partitioning rates measured under st erile conditions. Although the rates of biodegradation of a constituen t of nontoxic NAPLs are generally related to rates of mass transfer de termined under sterile conditions, we suggest that the partitioning ra te determined in the absence of microorganisms is not an adequate pred ictor of the maximum rate of biodegradation of such constituents.