A low-permeability locality with heterogeneous geology contaminated primarily by tetrachloroethene (PCE) present partially in the free phase in the unsaturated zone was treated on a pilot scale via direct push pneumatic fracturing combined with the hydraulic delivery of a remediation suspension consisting of milled iron, sulphidated nanosized zerovalent iron and sand in guar gum solution. Afterwards, a whey solution was injected into the fractures as a carbon source for bacteria. The unsaturated and saturated zones were treated. Long-term monitoring of the groundwater revealed that the abiotic reduction of PCE and trichloroethene was the dominant remediation processes for several months after the injections. A complex microbial consortium was developed that was capable of effective, long-term chlorinated ethenes (ClE) dechlorination. The consortium consisted mainly of Dehalococcoides but also of other anaerobic bacterial strains capable of partial dechlorination of ClE, including the sulphate-reducing bacteria; Geobacter and Desulfitobacterium. The average chlorine number in the groundwater decreased from 3.65 to 1.38 within 2.5 years after the injections, while the average ClE concentration increased from 13.5 to 31.5 mgL-1 because of the substantial acceleration of the ClE mass-transfer to the groundwater caused by the treatment. The remediation processes remained fully active for 2.5 years.

DEKONTA a s Volutová 2523 CZ 158 00 Prague 5 Czech Republic

Institute for Environmental Studies Faculty of Science Charles University Benátská 2 CZ 128 01 Prague 2 Czech Republic

Institute of Microbiology Academy of Sciences of the Czech Republic v v i Vídeňská 1083 CZ 142 20 Prague 4 Czech Republic

NANO IRON s r o Topolová 933 CZ 667 01 Židlochovice Czech Republic

Technical University of Liberec Studentská 2 CZ 461 17 Liberec Czech Republic

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