Innovative evaluation methods for bioremediation

Bioremediation is a potentially powerful technique for remediating environmental contamination by NAPLs; however, performance evaluation of bioremediation, especially in situ bioremediation, in the field is difficult due to the uncertainty created by matrix and contaminant heterogeneity, inaccessibility to observation, expense of sampling, and limitations of some measurements. The objective of this research is to provide a prototype for conversion of the NRC's (NRC, 1993) general guidelines for evaluating bioremediation into practical protocols by: (1) integrating routine chemical analyses with innovative techniques from molecular biology and geochemistry into a rational evaluation strategy; and (2) demonstrating the strategy's application in laboratory-scale mesocosms simulating bioremediation of NAPL contaminated soils. The importance of using a comprehensive, coordinated suite of tests to evaluate bioremediation is demonstrated by data for several analyses from a laboratory-scale slurry-phase bioremediation of a top-soil contaminated with a synthetic NAPL of phenanthrene dissolved in dodecane. These data provide four key pieces of evidence indicative of successful bioremediation: (1) documentation of the loss of phenanthrene, (2) an increase in aqueous-phase TIC, (3) a decrease in the δ¹³C of the dissolved inorganic pool, and (4) a correlation between the phenanthrene removal and the increase in the number of phenanthrene-degrading bacteria.