EFFECTS OF REDUCING SUBSTRATES ADDITION ON CONTAMINATED AQUIFER MICROBIAL POPULATION AND THE DECHLORINATION ACTIVITY

Tetrachloroethene (PCE) and trichloroethene (TCE) (chloroethenes) are intensively used in industrial sector due to their physical and chemical characteristics (low inflammability) that makes them excellent solvents. These compounds are hardly degraded through physical and chemical remediation techniques; but some bacteria can transform them. In anaerobic and reductive conditions, chloroethenes can be dechlorinated through organohalide respiration (OHR) where one atom of chlorine was substituted with a hydrogen atom. This pathway is efficient in dechlorination of highly chlorinated compounds (PCE and TCE), but their daughter compounds (dichloroethene, DCE, and vinyl chloride, VC) are hardly transformed creating an accumulation of these compounds. They are oxidated in aerobic conditions. Chloroethenes are toxic for human being and TCE and VC are carcinogenic. In anaerobic conditions, fermentable substrates can be added to increase reducing power available for OHR bacteria (biostimulation). In the prospective of a more sustainable bioremediation techniques, chose of reducing substrates are focused on food industrial waste that are no longer used with food purposes. In this study two reducing substrates (engineering molasses and tomato peels) were tested to determine their effects on enhancement of OHR activity at laboratory scale. The microcosms were analyzed through monitoring of chloroethenes transformation by GC-MS, and chemical and physical parameters. In addition, through monitoring of dechlorination rate of chloroethenes (GC-MS analysis), and phylogenetic and functional biomarkers (qPCR analysis), the addition of engineering molasses was analyzed at filed scale. The addition of the two substrates effected OHR activity with an increase of dechlorination highly chloroethenes. In the aquifer, biomarkers characteristic of dechlorination pathways were present in high amount (105-106 gene copies L-1). The research was supported by Inail (National Institute for Insurance against Accidents at Work) in BRIC research funding