Cu amended zero valent iron bimetallic nanoparticles were synthesized by doping Cu on the surface of iron. They were incorporated with granular activated carbon (AC) to prepare supported particles (AC–Fe⁰–Cu), which were used to remove γ-HCH. Cu on the surface of iron enhanced the dechlorination activity of Fe⁰. The dechlorination rate constant (kₒbₛ) increased with the Cu loading on the surface of iron and the maximum was achieved with 6.073% Cu. AC as a support was effective for increasing the dispersion of the nanoparticles and avoiding the agglomeration of the metallic nanoparticles. The simultaneous adsorption of γ-HCH on AC accelerated the degradation rate of γ-HCH by the bimetals. After reaction for 165 min, around 99% of γ-HCH was removed by the solids of AC–Fe⁰–Cu. In addition, AC could adsorb the degradation products. The degradation of γ-HCH was mainly through dehydrochlorination and dichloroelmination based on the intermediate products detected by GC/MS.

The variability of hydrogeochemical conditions can affect groundwater microbial communities and the natural attenuation of organic chemicals in contaminated aquifers. It is suspected that in situ biodegradation in anoxic plumes of chloroethenes depends on the spatial location of the contaminants and the electron donors and acceptors, as well as the patchiness of bacterial populations capable of reductive dechlorination. However, knowledge about the spatial variability of bacterial communities and in situ biodegradation of chloroethenes in aquifers is limited. Here, we show that changes of the bacterial communities, the distribution of putative dechlorinating bacteria and in situ biodegradation at the border of a chloroethenes plume (Bitterfeld, Germany) are related to local hydrogeochemical conditions. Biotic reductive dechlorination occurred along a 50 m vertical gradient, although significant changes of the hydrogeochemistry and contaminant concentrations, bacterial communities and distribution of putative dechlorinating bacteria (Dehalobacter spp., Desulfitobacterium spp., Dehalococcoides spp., and Geobacter spp.) were observed. The occurrence and variability of in situ biodegradation of chloroethenes were revealed by shifts in the isotope compositions of the chloroethenes along the vertical gradient (δ13C ranging from −14.4‰ to −4.4‰). Our results indicate that habitat characteristics were compartmentalized along the vertical gradient and in situ biodegradation occurred with specific reaction conditions at discrete depth. The polyphasic approach that combined geochemical and biomolecular methods with compound-specific analysis enabled to characterize the spatial variability of hydrochemistry, bacterial communities and in situ biodegradation of chloroethenes in a heterogeneous aquifer.

In the last 10 years, the number of field applications of zero-valent iron differing from permeable reactive barrier has grown rapidly and at present are 112. This study analyzes and compares such field applications. By using statistical analysis, especially ANOVA and principal component analysis, this study shows that chlorinated solvent contamination can be treated efficiently by using zero-valent iron material singly or associated with other technologies. In the analyzed sample of case studies, the association with microbial dechlorination increased significantly the performances of nanoscale iron. This is likely due to the synergistic effect between the two processes. Millimetric iron was always used in association with source zone containment; therefore, it is not possible to distinguish the contributions of the two techniques. The comparison also shows that catalyst addition seems to not dramatically improve treatment efficiency and that such improvement is not statistically significant. Finally, the injection technology is correlated to the type of iron and to the soil permeability.

Two greenhouse pot experiments were conducted in Agrinion, Greece, using a randomized block design in four replications, respectively, as follows: The first one included five levels of treated municipal wastewater (TMWW), being used as an irrigation water source. The second one, five levels of applied Cl at a constant soil applied Cd level of 10.36 mg/kg soil, the plants being irrigated with fresh well water. The purpose of these experiments was to study the impact of the Cl × Cd interrelationship on planning TMWW reuse, for the irrigation of Brassica oleracea var. Capitata (cabbage) cv F1 Gloria, ehich was used as test plant, in both of these experiments. It was found that the TMWW Cl content, originating mainly from the procedure of wastewater chlorination, was synergistically interrelated with the toxic heavy metal Cd, increasing its soil availability and cabbage plant leaf uptake (edible plant part). As this increase is directly associated with the consumer's health, it was suggested that the TMWW be subjected to dechlorination process or the disinfection be made by ozonation or UV, which do not include Cl.