Intrinsic bioremediation of trichloroethylene and chlorobenzene: field and laboratory studies.

Activities at a former fire training area at Robins Air Force Base in Georgia, USA resulted in contamination of groundwater with a mixture of trichloroethylene (TCE) and chlorobenzene (CB). Results from the field investigation suggest that intrinsic bioremediation process is occurring, which caused the decrease in TCE and CB concentrations, and increase in TCE degradation byproducts [e.g., dichloroethylene isomers (DCEs), vinyl chloride (VC)] concentrations. Contaminated groundwater samples collected from this site were used to conduct microbial enumeration tests, and used as the inocula for microcosm establishment. Results from the microbial enumeration study indicate that methanogenesis was the dominant biodegradation pattern within the source and mid-plume areas, and the aerobic biodegradation process dominated the downgradient area. Laboratory microcosm experiments were conducted to evaluate the feasibility of using CB as the primary substrate to enhance the intrinsic biodegradation of TCE. Microcosm results suggest that CB can serve as the primary substrate (electron donor), and enhance TCE biodegradation to less-chlorinated compounds under both aerobic cometabolism and reductive dechlorination conditions.     

Technological prospecting: Patent mapping of bioremediation of soil contaminated with agrochemicals using fungi

The purpose of this study was to investigate the development of biotechnologies related to the bioremediation of soil contaminated by agrochemicals using fungi through technological prospecting with patent mapping and analysis of scientific products. Due to the high complexity of biotechnologies involving microorganisms, it is observed that the state of the art is still in development, with several technological advantages already elucidated and important challenges to be overcome. Patent mapping revealed that the number of granted or pending patents showed a positive trend. In this context, a high number of patent documents were observed that describe processes and methods aimed at the preparation and application of fungi in soil bioremediation, as well as biotechnologies that use consortia of different strains of fungi or fungi and bacteria and advanced approaches involving genetic engineering. In short, it was found that inventions related to the investigated biotechnology have been protected mainly in China, the USA, Japan, and the European Union, with emphasis on the technological impact of patents in India. Finally, the findings indicated that soil bioremediation with the use of fungi presents a potential for development due to a series of technological and environmental aspects.     

Feasibility study for the remediation of groundwater contaminated by organolead compounds

The aim of this research was to assess the effectiveness of chemical oxidation, Advanced Oxidation Processes (AOPs) and adsorption on granular activated carbon (GAC) for the ex situ remediation of a groundwater contaminated by organolead compounds, including tetraethyl lead (TEL), triethyl lead (TREL) and diethyl lead (DEL). The groundwater of concern was collected from the site of a former tetraalkyllead producing company in Trento (Italy), and showed an average total organic lead (TOL) content about 95.1 microg/L (TEL 0.5 microg/L, TREL 86.4 microg/L, DEL 8.3 microg/L). The main target of the study was to find out which method was more effective in reducing the pollutant content. For this purpose, several laboratory tests were performed, including chemical oxidation tests with different reactants (hydrogen peroxide, modified Fenton's reagent, potassium permanganate, activated potassium persulfate, oxygen and combinations of potassium permanganate and modified Fenton's reagent), AOPs with ozone, UV radiation and hydrogen peroxide and filtration on granular activated carbon. A combination of chemical and physical treatments was also tested, with GAC filtration followed by chemical oxidation. According to the results achieved, the treatments which showed the best remediation performances were: chemical oxidation with modified Fenton's reagent, AOPs with hydrogen peroxide and ozone (perozone), AOPs with hydrogen peroxide and UV radiation, and the combined treatment with activated carbon filtration followed by chemical oxidation with perozone. All these treatments showed a 90% TOL removal, with excellent removals of both TEL and TREL, and final DEL concentrations below 5 microg/L.     

Evaluation of bioremediation methods for the treatment of soil contaminated with explosives in Louisiana Army Ammunition Plant, Minden, Louisiana

Two bioremediation methods, namely, soil slurry reactor and land farming technique were evaluated for the treatment of soil contaminated with explosives in Louisiana Army Ammunition Plant, Minden, Louisiana. The soil had a high concentration of 2,4,6-trinitrotoluene (TNT) of 10,000 mg/kg of soil and medium level contamination of RDX 1900 mg/kg and HMX 900 mg/kg of soil. The results indicated that soil slurry reactor under co-metabolic condition with molasses as co-substrate removed TNT more efficiently than land farming method. TNT removal efficiency was 99% in soil slurry reactor compared to 82% in land farming after 182 days. HMX and RDX were also removed from the soil in both methods, but the removal efficiency was low. The radiolabeled study showed that soil microbes mineralize TNT. The mass-balance of TNT indicated 23.5% of TNT was mineralized to CO(2), 22.6% was converted to biomass, and 52.3% was converted to various TNT intermediates in the soil slurry reactor. Both methods maintained high bacterial population fairly well. The results of this bench-scale study are promising with regard to transferring the technology to full-scale application at this site.     

Sand bioconsolidation through the precipitation of calcium carbonate by two ureolytic bacteria

Two ureolytic strains, B. sphaericus LMG 22257 and Bacillus sp (I-001), were tested for their ability to consolidate sand by submitting them to two days' treatment using 10⁷ viable cell concentrations of inocula and medium precipitation with calcium ions. The results showed that B. sphaericus LMG 22257 induced greater calcium carbonate formation. Both strains produced calcite and were able to consolidate sand. Tensile strength of consolidated sand was not a function of the amount of precipitated CaCO₃ but a linear function of the ratio bioconsolidation index (BC) defined as the ratio of CaCO₃ volume to initial sand porosity. A simple model to estimate the engineering benefits of consolidation is proposed.     

Detection of ammonia by photoacoustic spectroscopy with semiconductor lasers

Sensitive photoacoustic detection of ammonia with near-infrared diode lasers (1.53 microns) and a novel differential acoustic resonator is described; a sensitivity of 0.2 parts per million volume (signal-to-noise ratio = 1) is attained. To eliminate adsorption-desorption processes of the polar NH3 molecules, a relatively high gas flow of 300 SCCM was used for the ammonia-nitrogen mixture. The results are compared with recent ammonia measurements with a NIR diode and absorption spectroscopy used for detection and photoacoustic experiments performed with an infrared quantum-cascade laser. The performance of the much simpler and more compact setup introduced here was comparable with these previous state-of-the-art measurements.     

Remediation of groundwater contaminated with DNAPLs by biodegradable oil emulsion

Emulsion-based remediation with biodegradable vegetable oils was investigated as an alternative technology for the treatment of subsurface DNAPLs (dense non-aqueous phase liquids) such as TCE (trichloroethylene) and PCE (perchloroethylene). Corn and olive oil emulsions obtained by homogenization at 8000rpm for 15min were used. The emulsion droplets prepared with corn and olive oil gave a similar size distribution (1-10microm) and almost all of initially injected oil, >90%, remained in a dispersed state. In batch experiments, 2% (v/v) oil emulsion could adsorb up to 11,000ppm of TCE or 18,000ppm of PCE without creating a free phase. Results of one-dimensional column flushing studies indicated that contaminants with high aqueous solubility could be efficiently removed by flushing with vegetable oil emulsions. Removal efficiencies exceeded 98% for TCE and PCE with both corn and olive oil emulsions. The results of this study show that flushing with biodegradable oil emulsion can be used for the remediation of groundwater contaminated by DNAPLs.     

Detection of organomercurials with sensor bacteria.

Mercury and its organic compounds, especially methylmercury, are hazardous compounds that concentrate in biota via biomagnification and cause severe neurological disorders in animals. In this paper, a recombinant whole-cell bacterial sensor for the detection of the organic compounds of mercury was constructed. The sensor carries firefly luciferase gene as a reporter under the control of the mercury-inducible regulatory part of broad spectrum mer operon from pDU1358. In addition, a gene-encoding organomercurial lyase (an enzyme necessary for cleavage of the mercury-carbon bond) was coexpressed in the sensor strain. The sensitivity of the sensor was evaluated on some environmentally important organomercurial compounds. The lowest detectable concentrations were 0.2 nM (50 ng/L), 1 nM (0.34 microg/L), and 10 microM (2.3 mg/L) for methylmercury chloride, phenylmercury acetate, and dimethylmercury, respectively. The sensor responded also to inorganic mercury and, therefore, using the sensor described here together with sensor bacteria responding only to inorganic mercury, it should be possible to characterize the mercury contamination, for example, in environmental samples.     

The photodegradation of trichloroethylene with or without the NAPL by UV irradiation in surfactant solutions

The effect of pH in the range of 3.0–11.0 on anaerobic fermentation of primary sludge (PS) was investigated at room temperature. The experimental results showed that the concentrations of soluble chemical oxygen demands (SCOD), soluble protein and carbohydrate and short-chain fatty acids (SCFAs) under alkaline conditions were significantly higher than those under other pHs. At fermentation time of 5 days, the average SCFAs concentration increased from 968 to 3511 mg COD/L with the increase of pH from 3.0 to 10.0. However, further increasing pH to 11.0 resulted in the decrease of SCFAs. At pH 10.0, acetic, propionic and iso-valeric acids were the three main products, and the volatile suspended solids (VSS) reduction reached 38%. It was also observed that at any pH value investigated, there were obvious ammonia and phosphorus releases during fermentation. According to this study it is obvious that alkaline pH benefited the soluble organic carbon production from PS.     

The photodegradation of trichloroethylene with or without the NAPL by UV irradiation in surfactant solutions

The photodegradation of trichloroethene (TCE) with or without nonaqueous phase liquids (NAPL) by ultraviolet irradiation in surfactant solutions was examined in this study. The photodecay of TCE was studied at monochromatic 254 nm UV lamps. The effects of the type of surfactants, initial surfactant concentrations, pH levels and NAPL concentrations were examined to explore the photodecay of TCE. All the photodegradation of TCE followed pseudo-first-order decay kinetics at various conditions. It was found that Brij 35 overdose and higher initial pH levels may retard or inhibit the photodecay of TCE, mainly due to protons, intermediate generation and change of surfactant structure in the processes. The optimal condition for TCE photodecay was suggested based on the analysis of kinetics data, from which the reaction mechanism of TCE in the presence of NAPL form was also studied. In general, the reactions of TCE in micellar solution and NAPL pool can be considered as independent pathways due to the low molecule diffusion between the two phases.     

Remediation of soils contaminated with polychlorinated biphenyls by microwave-irradiated manganese dioxide

The removal of polychlorinated biphenyls (PCBs) using microwave-irradiated manganese dioxide (MnO₂) in PCB-contaminated soils under different conditions is investigated. The removal of PCB77 in two actual soil samples exhibits strong pH-dependent behavior, and the removal efficiency is higher in acidic soil (Ali-Perudic Ferrosols) than that in neutral soil (Udic Argosols). The removal kinetics of PCB77 using microwave-irradiated MnO₂ under different experimental conditions fits a pseudo-first-order kinetic model well. Both the removal efficiency and the kinetic constant (k) values of PCB77 in Ali-Perudic Ferrosols considerably increase, although in a nonlinear fashion, as the initial amount of MnO₂ is increased, as the treated soil mass is increased, and as the microwave power is increased. The reactivity of three PCBs (PCB28, PCB77, and PCB118) did not present as a function of the degree of chlorination in the reaction with microwave-irradiated MnO₂. The pronounced removal of three PCBs in contaminated soil (all above 95%) indicates that MnO₂ in combination with microwave irradiation is promising for technological applications that seek to remediate sites critically polluted with PCBs.     

MXene介导的近红外光热效应用于快速清除多种耐药菌以及菌膜

随着细菌耐药性的不断出现和加重,针对耐药菌感染和菌膜这类难以用传统抗生素治疗的临床医疗问题,需要发展新型高效快速的杀菌方法.本文采用新型二维材料MXene与近红外激光相结合,实现了在20 min内对细菌以及菌膜的快速高效杀除.为了测试该方案的广谱抗菌性,我们对包括耐药性的耐甲氧西林金黄色葡萄球菌(MRSA)和耐万古霉素...     

Red mud and fly ash for remediation of mine sites contaminated with As, Cd, Cu, Pb and Zn

The paper presents the results of a laboratory investigation conducted for assessing the feasibility of immobilising the heavy metals (As, Cd, Cu, Pb and Zn) contained in a disused mine tailings dam. Samples of tailings were mixed with relatively small proportions of bauxite red mud and power station fly ash. The sorption capacity of these two materials, already determined for Cd, Cu, Pb and Zn, has been determined here for arsenic by means of batch experiments on purposely prepared solutions. The results of this preliminary investigation show that sorption capacity is strongly influenced by pH. While the red mud performs better at low pH, the ability of fly ash to adsorb As increases with increasing pH. Tests carried out in leach columns containing tailings alone and tailings mixed with 15% by weight neutralized red mud or fly ash demonstrate the heavy metal sorption potential of the two materials, the red mud proving to be the more effective.     

Synthesis of GaN nanowires through Ga2O3 films' reaction with ammonia

GaN nanowires were synthesized by ammoniating Ga₂O₃ films on Ti layers deposited on Si (111) substrates at 950 °C. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM). The XRD, FTIR and HRTEM studies showed that these nanowires were hexagonal GaN single crystals. SEM observation demonstrated that these GaN nanorods with diameters ranging from 50 nm to 100 nm and lengths up to several micrometers intervene with each other on the substrate.     

Simultaneous N-intercalation and N-doping of epitaxial graphene on 6H-SiC(0001) through thermal reactions with ammonia

Surface functionalization of epitaxial graphene overlayers on 6H-SiC(0001) has been attempted through thermal reactions in NH₃. X-ray photoelectron spectroscopy and micro-region low energy electron diffraction results show that a significant amount of N is present at the NH₃-treated graphene surface, which results in strong band bending at the SiC surface as well as decoupling of the graphene overlayers from the substrate. The majority of the surface N species can be removed by annealing in vacuum up to 850 °C, weakening the surface band bending and resuming the strong coupling of graphene with the SiC surface. The desorbed N atoms can be attributed to the intercalated species between graphene and SiC. Low temperature scanning tunneling spectroscopy and density functional theory simulations confirm the presence of N dopants in the graphene lattice, which are in the form of graphitic substitution and can be stable above 850 °C. This is the first report of simultaneous N intercalation and N doping of epitaxial graphene overlayers on SiC, and it may be employed to alter the surface physical and chemical properties of epitaxial graphene overlayers.      

Improving the accuracy of measurement of parts with contaminated surfaces by multichannel optoelectronic systems

A method is proposed for improving the measurement accuracy of multichannel optoelectronic instruments in mechanical engineering. The method involves the suppression of crosstalk and processing of the measurement data in accordance with the resulting transfer function of the detector. An example of practical implementation is given.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 25–27, September, 1995.     

Synthesis and characterization of monodispersed orthorhombic manganese oxide nanoparticles produced by Bacillus sp. cells simultaneous to its bioremediation

A heavy metal resistant strain of Bacillus sp. (MTCC10650) is reported. The strain exhibited the property of bioaccumulating manganese, simultaneous to its remediation. The nanoparticles thus formed were characterized and identified using energy dispersive X-ray analysis (EDAX), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD) and atomic force microscopy (AFM). When the cells were challenged with manganese, the cells effectively synthesized nanoparticles of average size 4.62 ± 0.14 nm. These were mostly spherical and monodispersed. The ex situ enzymatically synthesized nanoparticles exhibited an absorbance maximum at 329 nm. These were more discrete, small and uniform, than the manganese oxide nanoparticles recovered after cell sonication. The use of Bacillus sp. cells seems promising and advantageous approach. Since, it serves dual purposes of (i) remediation and (ii) nanoparticle synthesis. Considering the increasing demand of developing environmental friendly and cost effective technologies for nanoparticle synthesis, these cells can be exploited for the remediation of manganese from the environment in conjunction with development of a greener process for the controlled synthesis of manganese oxide nanoparticles.     

Solidification of radioactively contaminated sludge from industrial water basins by cementing with sorption additives

The possibility of solidification of sludge from industrial water basins by incorporation into Portland cement and slag alkaline binder with sorption additives (Cambrian clay) was examined. The solidified products with respect to their mechanical strength and radionuclide leachability meet the requirements of safe storage both in standard and in the simplest repositories.