Elucidating the fate of a mixed toluene, DHM, methanol, and i-propanol plume during in situ bioremediation

Zinc and copper supplements enhance trichloroethylene removal by Pseudomonas plecoglossicida in water

The effects of two microelements, zinc and copper, on the aerobic co-metabolic removal of trichloroethylene (10 mg/L) by the isolate Pseudomonas plecoglossicida were investigated. The strain was previously isolated from a petroleum-contaminated site using toluene (150 mg/L) as substrate. Different concentrations (1, 10 and 100 mg/L) of microelements provided with SO42- and Cl- were tested. The results showed the supplement of Zn2+ and Cu2+ at the low concentration (1 mg/L) significantly enhanced cell growth. The removal efficiencies for toluene and trichloroethylene were also enhanced at the low concentration (1 mg/L) of Zn2+ and Cu2+. Compared to the control without zinc supplement, higher concentrations of zinc (10 and 100 mg/L) enhanced the removal efficiencies for both toluene and trichloroethylene in the first three days but showed some inhibitory effect afterward. However, the higher concentrations of Cu2+ (10 and 100 mg/L) always showed inhibitory to the toluene removal while showing inhibitory to the TCE removal after three days. For both Zn2+ and Cu2+, the anions SO42- and Cl- did not show significant difference in their effects on the toluene removal. A possible mechanism for Zn2+ and Cu2+ to enhance the removal of toluene and trichloroethylene would be their involvement in toluene oxygenase-based transformation processes. In addition, high concentrations of Zn2+ and Cu2+ ions could be removed from the liquid by the cells accordingly. The results imply a potential of supplementing low concentrations of zinc and copper to enhance bioremediation of the sites co-contaminated with toluene and trichloroethylene.

Critical factors for enhancing the bioremediation of a toxic pollutant at high concentrations in groundwater: Toxicity evaluation, degrader tolerance, and microbial community

Groundwater near refinery and natural gas plants often contain elevated concentrations of toxic sulfolane. Studies on any concentration of sulfolane are limited. Column experiment was conducted to investigate the effects of adding a low dose of H₂O₂ and nutrient on bioremediation. Vibrio fischeri light inhibition test was used evaluate the toxicity of effluents. The continuous column experiment conditions were sulfolane at 100 mg L^-1, dissolved oxygen at 7 mg L^-1, absence of phosphorus, and very short hydraulic retention time (7.9 h). A low dose of H₂O₂ (5.88 mM) enhanced the sulfolane (27.1%) and COD removal (11.8%) in comparison with the control set. Adding nutrient increased bicinchoninic acid protein assay levels, sulfolane removal (99.6%) and COD removal (80.3%). Addition of both H₂O₂ and nutrient further improved COD removal (90.3%) and COD/sulfolane ratio (0.90) and toxicity removal (Vibrio fischeri light inhibition ratio < 1%). Batch experiment indicated the degraders tolerated sulfolane up to 400 mg L^-1. The DGGE method and dendrogram analysis were utilized to investigate the changes of degrader community structure.

Process-based modeling of electrokinetic-enhanced bioremediation of chlorinated ethenes

This study presents a process-based modeling analysis of electrokinetic-enhanced bioremediation (EK-Bio) to illuminate the complex interactions between physical, electrostatic and biogeochemical processes occurring during the application of this remediation technique. The features of the proposed model include: (i) multidimensional electrokinetic transport in saturated porous media by electromigration and electroosmosis, (ii) charge interactions, (iii) degradation kinetics, (iv) microbial populations dynamics of indigenous and specialized exogenous degraders, (v) mass transfer limitations, and (vi) geochemical reactions. A scenario modeling investigation is presented, which was inspired by an EK-Bio pilot application conducted in a clayey aquitard at the Skuldelev site (Denmark) contaminated by chlorinated ethenes. Lactate and specialized degraders are delivered under conservative and reactive transport conditions. In the considered setup, transport of lactate using electrokinetics results in more than fourfold increase in the distribution efficiency with respect to a diffusion-only scenario. Moreover, EK transport by electromigration and electroosmosis yields fluxes at least two orders of magnitude larger than diffusive fluxes. Quantitative metrics are also defined and used to assess the amendment distribution and the enhanced contaminant biodegradation in the different conservative and reactive transport scenarios.