ABSTRACT
An essential component of any bioremediation program is the evaluation of its success. Evaluation is not as readily accomplished as might be assumed for a number of reasons (Madsen 1991; Heitzer and Sayler 1993; Macdonald and Rittman 1993; Shannon and Unterman 1993). A valuable and critical review (Dott et al. 1995) discussed the need for an assessment that takes into account all the phases involved, and suggested that the diffi culty of demonstrating in situ bioremediation may require long-term studies. An illustrative example is provided by bioremediation of an aquifer in Switzerland, which was contaminated with diesel fuel. Oxidants were provided in the form of O2 and NO3
–, but measurements of carbon and nitrogen balance were not suffi ciently precise to assess the spatial effectiveness of the treatment. A laboratory microcosm using material from the aquifer was constructed: the use of gene probes revealed that bacteria belonging to different phylogenetic groups were present, and bacteria able to degrade toluene and 1,3-dimethylbenzene were isolated (Hess et al. 1997). It was, however, pointed out that, because of the greater diversity of organisms in the aquifer, there were limitations in the extent to which the results of the laboratory experiments could be extrapolated to the fi eld situation.
