Application of Combined In Situ Chemical Reduction and Enhanced Bioremediation to Accelerate TCE Treatment in Groundwater

Groundwater at trichloroethylene (TCE)-contaminated sites lacks electron donors, which prolongs TCE’s natural attenuation process and delays treatment. Although adding electron donors, such as emulsified oil, accelerates TCE degradation, it also causes the accumulation of hazardous metabolites such as dichloroethylene (DCE) and vinyl chloride (VC). This study combined in situ chemical reduction using organo-iron compounds with enhanced in situ bioremediation using emulsified oil to accelerate TCE removal and minimize the accumulation of DCE and VC in groundwater. A self-made soybean oil emulsion (SOE) was used as the electron donor and was added to liquid ferrous lactate (FL), the chemical reductant. The combined in situ chemical reduction and enhanced in situ bioremediation achieved favorable results in a laboratory microcosm test and in an in situ biological field pilot test. Both tests revealed that SOE+FL accelerated TCE degradation and minimized the accumulation of DCE and VC to a greater extent than SOE alone after 160 days of observation. When FL was added in the microcosm test, the pH value decreased from 6.0 to 5.5; however, during the in situ biological pilot test, the on-site groundwater pH value did not exhibit obvious changes. Given the geology of the in situ pilot test site, the SOE+FL solution that was injected underground continued to be released for at least 90 days, suggesting that the solution’s radius of influence was at least 5 m.

Water quality assessment of East Kolkata Wetland with a special focus on bioremediation by nitrifying bacteria

East Kolkata Wetlands (EKW) is designated as International Ramsar site and are the hotspot for large-scale wastewater aquaculture practices. However, the continued surveillance of physicochemical properties of water and application of an eco-friendly approach are essential to ensure safe aquaculture practices. In the present study, we assessed the seasonal variation in physicochemical parameters of water across EKW and investigated the role of nitrifying bacteria as probiotics. We statistically analyzed various physicochemical properties of water samples from EKW. Results of the statistical analysis indicated a significant variation in all the physicochemical parameters across the selected water bodies of EKW (p < 0.01). We isolated and enumerated Nitrosomonas sp. and Nitrobacter sp. and assessed their ability to degrade trichloroethylene (TCE). The role of Nitrosomonas and Nitrobacter sp. were further investigated and established through a small-scale experiment. Two microbial isolates, NSW3 and NBW2, displayed superior TCE degradation ability at pH 5, and the application of these strains as probiotics were found to improve the quality of water and survival rate of fishes in the treated experimental tanks. Our findings suggest that the application of the above mixed bacterial cultures in aquaculture could be an effective and environment-friendly approach for safe and productive aquaculture operations.

Biological effects of tourmaline treatment on Dehalococcoides spp. during the reductive dechlorination of trichloroethylene

To explore the application of mineral in bioremediation of contaminated aquifers, this study investigated tourmaline-induced changes in TCE degradation, community structure, cell proliferation and gene expression of dechlorinating bacteria.

Removal mechanism and quantitative control of trichloroethylene in a post-plasma-catalytic system over Mn–Ce/HZSM-5 catalysts

The optimization of the TCE degradation process was achieved and the TCE degradation pathway in the PPC system was proposed.

High Degradation of Trichloroethylene in Water by Nanostructured MeNPs@CALB Biohybrid Catalysts

In this study, a methodology was developed for the rapid degradation of trichloroethylene (TCE) and 1,1-dichloroethylene (1,1-DCE) in distilled water and room temperature without the production of toxic chlorinated by-products. This process was carried out using bionanohybrids of different metals (Pd, Fe, Cu and Zn) obtained by enzyme–metal coordination called MeNPs@CALB, which present different metal species and nanoparticle sizes. The Cu2O@CALB biohybrid, which contained Cu2O nanoparticles, showed excellent catalytic performance in TCE degradation by removing 95% (>125 ppm) in 10 min using 1.5 g/L of catalyst. On the other hand, in the degradation reaction of 1,1-DCE, Cu2O@CALB eliminated 94% (93 ppm) in 1 min. Cu2O@CALB exhibited excellent stability and recyclability under sustainable conditions, maintaining its effectiveness in more than 90% for three cycles.

Study on the Inactivation of Pseudomonas sp and the Degradation of Trichloroethylene by Fenton-Like Reaction

The present work intended to use goethite, one of the main compositions of pipe deposit, to combine with H2O2 to degrade TCE or disinfect drinking water. Goethite exhibited excellent degradation performance for TCE, outstanding inactivation ability for Pseudomonas and the disinfection effect for filter water of water treatment plants. The TCE degradation efficiency could reach 87.4%, while the inactivation efficiency of Pseudomonas and the bacterial mortality rate in filtered water were more than 99.9% in this study. In order to effectively reduce the disinfection by-products (chlorine-resistant bacteria) and conduct permanent disinfection, the Fenton-like and chlorine combined disinfection method was also investigated. Experimental results indicated that the bacteria could be effectively killed by this combined method and the chlorine residual was 0.41m g/L, ensuring sustainable disinfection. This work verified that the pipe deposit from the water distribution network is multifunctional, which is a potential candidate for pollutant removal and sterilization. The results could also offer theoretical support for water quality security in water distribution networks in the future.

Survival, metabolic rates and locomotory activities of a groundwater-obligate copepod species under long-term exposures to tetrachloroethylene

Volatile organic compounds (VOCs) are known to potentially cause a severe change in the respiratory metabolism of freshwater species, however the effect of these contaminants on groundwater-obligate species has not been investigated to date. Tetrachloroethylene (TCE) is a VOC frequently found in the groundwater bodies of industrialized areas, even years after a contamination event because TCE degradation takes several decades to occur. Contamination from TCE is considered persistent and difficult to remediate. Its high density favors a gravity-driven vertical infiltration into groundwater bodies. The TCE threshold value is 1.1 μg/L in groundwater bodies of Italy. TCE concentration in many Italian groundwater bodies is widely over this legal limit. In this study, we investigated the effect of 1.1 μg/L TCE on the survival, oxygen consumption, and locomotory activities of a groundwater-obligate copepod species. The specimens required for the trials were collected in the Antro del Corchia Cave (Tuscany). We measured the individual-based oxygen consumption of this species as a proxy of possible metabolic reactions to long-term (5 days) exposures to TCE at 8.0°C that is the mean annual temperature of groundwater flowing in the cave. To this end, we used a sealed glass microplate equipped with 24-planar oxygen sensor spots with optical isolation glued onto the bottom of 80-μL wells (Loligo Systems, Denmark) integrated with a 24-channel fluorescence-based respirometry system (SDR Sensor Dish Reader, PreSens, Germany). The system allows simultaneous measurement of 20 replicates and 4 controls. Survival and locomotory activity assessments were performed by counting the number of alive individuals and measuring the number of moving animals in 5 mL glass vials each containing 20 individuals. Preliminary results showed a decreasing in oxygen consumption of the organisms exposed to 1.1 μg/L TCE for 5 days at 8°C respect to the control. However, neither survival nor locomotory activities appeared to have been affected by exposure to TCE. See Suppl. material 1.

Preparation of palladized carbon nanotubes encapsulated iron composites: highly efficient dechlorination for trichloroethylene and low corrosion of nanoiron

A method developed based on the capillary effect and capillary condensation theory was used to synthesize an innovative Fe/C/Pd composite in this study. This composite (Fe@CNTs@Pd) consists of carbon nanotubes (CNTs) with nanoscale zerovalent iron (NZVI) on the inner surface and palladium nanoparticles supported on the outer surface of CNTs. This structure successfully addresses the problems of high iron corrosion rate and lower utilization rate of hydrogen in the application of bimetal nanoparticles for trichloroethylene (TCE) removal. TCE degradation experiments and electrochemical tests were conducted to investigate the material properties and reaction mechanisms of the composite. It is found that the prepared composite material contribute a high level of TCE dechlorination rate and substantially reduced hydrogen production during iron corrosion in water compared with the conventional CNTs-supported bimetal materials (Fe/Pd@CNTs). Hydrogen spillover effect helps the reactivity of Fe@CNTs@Pd for TCE degradation and suppressed the galvanic cell effect, which results in a stronger resistance to corrosion. Although the K obs of Fe@CNTs@Pd was 16.87% lower than that of Fe/Pd@CNTs, the hydrogen production rate of Fe@CNTs@Pd was 10 times slower than that of Fe/Pd@CNTs. Therefore, Fe@CNTs@Pd shows a significant reduction in the corrosion rate at a cost of slightly slower degradation of TCE. In sum, the prepared composites demonstrate important characteristics, including alleviating NZVI agglomeration, maintaining high TCE removal efficiency and reducing the corrosion of NZVI.