Test Methods to Determine the Presence of Halorespring Subsuface Bacteria

Chlorinated solvents, such as tetrachloroethene (PCE) and trichloroethene (TCE) are common ground water pollutants. Natural attenuation or the stimulation of halorespiring microorganisms are potentially the most promising and cost-effective technologies for remediating sites contaminated with chlorinated compounds. Central to the successful implementation of these bioremediation technologies is the determination of the presence of halorespiring organisms at the site and of the extent of dechlorination. Halo-respiration is an energy-producing metabolic process and is characterized by (i) high dechlorination rates. (ii) fe values in the range of 0.6-0.7, (iii) hydrogen threshold values below 0.5ppmv. This process is carried out by several diverse groups of bacteria and stimulated by different substrates. Hence, measures of the process , and not of organisms or genera, are currently the only approaches that reliably measure halorespiration. Our primary approach, therefore, is to determine these parameters to establish the presence and activity of halorespriring organisms. These measurements can be performed in microcosms containing solids, and a time consuming enrichment procedure for halorespiring organisms is not required. The research is aimed towards the development of a protocol with general applicability for the evaluation of sediment and aquifer materials for the presence of halorespiring organisms. In addition to the evaluation for the intrinsic bioremediation potential of a certain site, this protocol will also provide valuable information about possible biostimulation strategies.