Trichloroethylene (TCE) is a toxic and recalcitrant groundwater pollutant. An innovative technology using microbial produced Pd(0) nanoparticles for the remediation of TCE contaminated groundwater was developed. The nanoscale bio-Pd particles were precipitated on the biomass of Shewanella oneidensis and hydrogen gas, formate, or formic acid were used as hydrogen donors. Ethane turned out to be the only organic degradation product and no intermediate chlorinated reaction products were detected. Subsequently bio-Pd was implemented in a plate membrane reactor (MR) for the treatment of water containing TCE. In a continuous MR system, containing 50 mg L(-1) bio-Pd, removal rates up to 2,515 mg TCE day(-1) g(-1) Pd were achieved with H(2) gas as hydrogen donor. The measured chloride mass balance confirmed the removal rates. This work shows that a complete, efficient and rapid removal of TCE was achieved with bio-Pd and that a MR system containing bio-Pd and supplied with hydrogen gas offers an alternative for the current remediation technologies of water contaminated with TCE.

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Lindane (gamma-hexachlorocyclohexane, gamma-HCH) is a recalcitrant and toxic organochlorine insecticide. Due to its non-selective production process and widespread use, HCH isomers and their degradation products have been detected frequently in soils and groundwater. An innovative technology using microbial produced Pd(0) nanoparticles, i.e. bio-Pd, was developed to treat groundwater containing a mixture of HCHs and chlorobenzenes. In a first step, the groundwater was de-ironized and most of the chlorobenzenes were removed in a biological trickling filter. The mu g L(-1) levels of HCHs and chlorobenzenes were removed in a second step by the bio-Pd-based technology. Therefore, a 200-L pilot scale reactor was developed with 100 mg L(-1) bio-Pd encapsulated in alginate beads. Hydrogen gas was bubbled at the bottom of the reactor and served to charge the bio-Pd catalyst. The reactor influent contained 5.2 mu g L(-1) HCHs and 51.1 mu g L(-1) chlorobenzenes. During a test period of 10 days, 29% of the HCH isomers and 63% of the chlorobenzenes were removed applying a nominal hydraulic residence time of 4 h. These removal percentages could be increased to 75 and 68% by doubling the nominal hydraulic residence time to 8 h. This study demonstrated that biologically produced nanoparticles of Pd can be applied for the large-scale remediation of groundwater contaminated with HCHs