A NOVEL APPROACH TO SUBSTRATE FORMULATION FOR ENHANCED REDUCTIVE DECHLORINATION

The most common method for the bioremediation of chlorinated solvents involves the reductive dechlorination of the constituent of concern through the addition of a carbon substrate. This process has been shown to be successful using both complex substrates like molasses or vegetable oil as well as using simple substrates such as sodium, potassium, or ethyl lactate or engineered compounds comprised of a single volatile fatty acid (VFA).  While the substrates to date have been demonstrated to be effective in promoting completed degradation of chlorinated compounds, there has been a push to lower costs by increasing the efficiency and kinetics of the microbial populations through the addition of nutrients or microbial cultures.  One area not well investigated is simultaneous optimization of the biological systems responsible for the entire process using a single substrate.

In order to investigate this theory, JRW compared the efficiency and kinetics of a system fed with a blend of VFAs and nutrients to a system fed with sodium lactate and nutrients alone.  Results show that the blended system exhibited atypical results with 99% complete reduction of PCE to ethene in 24 days under controlled conditions.  Systems fed sodium lactate and nutrient and sodium lactate alone exhibited much slower classical degradation patterns for DCE, VC, and ethene.  When compared with VFA and biological field data, the VFA profile from the blended substrate suggests that multiple microbial communities became active almost simultaneously thereby promoting the degradation of the contaminant much more quickly than typically observed.