Development Of Remediation Technologies Research Articles

ENHANCEMENT OF DECONTAMINATION OF PETROLEUM HYDROCARBONS IN CRUDE OIL POLLUTED SOIL BY USING CYCLODEXTRINS

Soil contaminated by total petroleum hydrocarbons is a well-recognized worldwide problem because of its strong persistence in the environment and its potentially toxic effects on human beings, animals and microorganisms. During the past three decades, the research and development of remediation technology for petroleum hydrocarbons-contaminated soil have been systematically studied such as the physical, chemical and bioremediation technologies. To address the associated environmental concerns, innovative remediation technologies are urgently needed. Cyclodextrins are nonhazardous and environmentally acceptable organic substances that have been shown to be biodegradable in soil and water after their introduction into an environmental system. The decontamination technique based in cyclodextrin extraction has been developed to eliminate petroleum hydrocarbons. Cyclodextrins have successfully been used in soil cleaning technologies as solubiliser–carrier molecules. These molecules can transfer continuously the insoluble contaminants from the soil surface to the aqueous phase by complex formation. In the aqueous phase the microorganisms can degrade the contaminants much easier partly because these molecules become available for the microbial cells, partly because the entrapment of contaminants by cyclodextrins reduces their toxicity.

ВЫДЕЛЕНИЕ ДЕГАЛОГЕНАЗ ПЕРФТОРКАРБОНОВЫХ КИСЛОТ ШТАММОВ PSEUDOMONAS PLECOGLOSSICIDA 2,4 Д И PSEUDOMONAS MOSSELII 5(3)

The aim of this study was to isolate and investigate enzymes involved in the biodegradation of perfluorocarboxylic acids (PFCAs) in Pseudomonas plecoglossicida strain 2,4-D and Pseudomonas mosselii strain 5(3). In this research, enzymes from these strains were concentrated from the culture medium by ultrafiltration and ammonium sulfate precipitation, followed by purification through size-exclusion chromatography. The enzyme activity after ultrafiltration was higher Enzymes from strain 2,4-D released 2 ppm of fluoride ions after 24 hours, increasing to 40,7 ppm after 48 hours. For strain 5(3), fluoride release reached 3 ppm at 24 hours and 46 ppm at 48 hours, confirming the activity of the isolated dehalogenases and their ability to degrade PFCAs. Size-exclusion chromatography revealed that the molecular weight of enzymes from strain 5(3) is approximately 80 kDa, while for strain 2,4-D, it is 76 kDa. The study of these enzymes holds both applied significance for environmental remediation technology development and fundamental importance. Understanding the molecular structure and mechanisms of dehalogenase activity not only provides insights into the cleavage of robust C-F bonds but also sheds light on enzyme evolution as a whole.

Impact of Fibrous Microplastic Pollution on Commercial Seafood and Consumer Health: A Review.

The omnipresence of microfibers in marine environments has raised concerns about their availability to aquatic biota, including commercial fish species. Due to their tiny size and wide distribution, microfibers may be ingested by wild-captured pelagic or benthic fish and farmed species. Humans are exposed via seafood consumption. Despite the fact that research on the impact of microfibers on marine biota is increasing, knowledge on their role in food security and safety is limited. The present review aims to examine the current knowledge about microfiber contamination in commercially relevant fish species, their impact on the marine food chain, and their probable threat to consumer health. The available information suggests that among the marine biota, edible species are also contaminated, but there is an urgent need to standardize data collection methods to assess the extent of microfiber occurrence in seafood. In this context, natural microfibers should also be investigated. A multidisciplinary approach to the microfiber issue that recognizes the interrelationship and connection of environmental health with that of animals and humans should be used, leading to the application of strategies to reduce microfiber pollution through the control of the sources and the development of remediation technologies.

Applicability and Extraction Characteristics of Aluminum Sulfate as Extractant of Harmful Heavy Metals for On-Site Treatment of Deep-Sea Mining Tailings

This research was focused on the eco-friendly treatment of deep-sea mining tailings in the sea areas and mainly dealt with evaluating the optimal conditions by comparing aluminum sulfate (AS), which had been proven recently to have an effect as a heavy metal extractant, with ethylenediaminetetraacetic acid (EDTA) in terms of environmental and economic feasibility. Harmful heavy metals in the manganese nodules (2%, w/v) were chemically washed by mixing with each EDTA and AS concentration for 16 elapsed times. Copper, zinc, nickel, and cadmium, which could have a fatal effect due to their high total content or high bioavailable content, were selected as the primary treatment target materials. The content of harmful heavy metals was 293.2 times more for nickel when compared with environmental standards of various countries. When 1% AS was used as the extractant, the removal efficiency of harmful heavy metals compared to the bioavailable content was 32.77% on average. It has been verified that multi-stage treatment could be necessary, and the short treatment time could be an important factor. Within a short elapsed time (3 h), the remediation efficiency of zinc and nickel under the 1% AS condition was higher than with 0.1 M EDTA. In terms of environmental and economic feasibility, it was verified that the use of 1% AS would be reasonable. The results of this research could be valuably applied to process design and optimization as basic data presented before the development of remediation technologies in the future.Graphical

Global Warming: A study of erratic fluctuations in land and oceanic temperature as influenced by heightening industrial activity and population growth

Tackling the global climate crisis is a daunting task. Excessive greenhouse gas emissions lead to rising temperatures and sea levels, stratospheric ozone depletion and a greater occurrence of intense, sporadic natural disasters. In order to commence the development of remedial technologies to subdue the adverse effects of global warming, it is essential to understand the range of anthropogenic and industrial activities that cause global land and oceanic temperatures to fluctuate beyond their expected statistical range. The following paper employs a myriad of machine learning algorithms in the development of deep neural networks (DNNs) that are used to forecast land and oceanic temperatures. Data input during the model’s training process, (covering an overall sample period of 28 years from 1990 - 2018), consists of sectoral carbon emission values of the top 20 contributors to the climate crisis worldwide—as well as additional correlated factors, such as population growth rate and gross domestic product (GDP) growth per capita, incorporated to create a comprehensive and versatile predictive tool. Results indicate high predictive accuracy of the model, with a low mean square error (MSE) of 0.208 and a high coefficient of determination (r²) of 98.7%, implying a high degree of explainability regarding variations in predictions.

Nanogravimetric Monitoring of Electrochemically Driven Fluoride Ion Extraction from Water By Aniline-Based Copolymer Films

Sustainable access to safe drinking water is a global societal goal [1]. Accordingly, much attention has been given to the development of technologies for remediation of the unintended effects of agricultural practices and industrial processes. The case of fluoride in water is an interesting case in two respects: its desirability up to a point and its natural origins. The beneficial effects of fluoride on dental health are recognized: in some countries drinking water is routinely fluoridated. However, high levels of fluoride can have detrimental effects on teeth, bones and internal organs; the recommended upper limit is 1.5 mg/L. The fluoride concentration in natural waters - the source of most drinking water - is dictated by the presence of calcium ions, through the solubility product of calcium fluoride. Dependent on the local geology, the calcium ion concentration may be relatively low or high, such that either the beneficial effects of fluoride may not be realized or its injurious effects may dominate. Determination of fluoride concentration using ion selective electrodes is well-established. The question then is how to remedy high fluoride levels. Existing methods for removal of excess fluoride from drinking water and wastewater include precipitation (as Ca or Al salts), membrane technologies and adsorption. Each of these has limitations, e.g. high costs, toxic by-products and slow or complex processes.Here we explore electrochemically controlled fluoride ion extraction by electroactive polymer films. This approach has been studied for water softening (using polypyrrole [2]) and perchlorate removal (using polypyrrole composites [3] and polyaniline-based copolymers [4]). Here we explore the feasibility of using a range of polyaniline-based materials in an electrochemically switched ion exchange system for fluoride removal from water [5]. The concept is based on F- ion uptake as counter ions in the oxidation (p-doping) of the conducting polymer film. Upon oxidation, the film will “capture” F- ions from solution. After separation of the purified water, the F- ions would then be ejected into a concentrated waste stream by reduction (un-doping) of the oxidized polymer.In this presentation we compare the characteristics and performance of polyaniline, poly(o-aminophenol) and poly(o-toluidine) homopolymer films with each other and with those of their copolymers of various composition. Film deposition is controlled electrochemically and monitored nanogravimetrically using the EQCM. Acoustic impedance enables distinction between gravimetric and viscoelastic interpretation of the response [8]. The extent of redox-driven fluoride uptake is then determined upon exposure to solutions of varying fluoride (and in some cases chloride) concentration. Correlation of EQCM-derived film mass and charge responses is used to assay fluoride and solvent uptake during film oxidation and reduction. Comparison with the total redox site population (from the response in fluoride-free media) yields the efficiency. Observations for these aniline-based homopolymers and copolymers reveal behavior that is quite different to that seen for typical small anionic dopants, such as chloride, nitrate and perchlorate. Further, there are surprisingly diverse responses to fluoride for these relatively similar polymeric materials, notably the extent of film solvation change during fluoride uptake. Use of different electrochemical control functions and timescales reveals differences in fluoride ion uptake and release rates. The relevance of these data to defluoridation will be discussed.

Resorcinol-based carbon xerogel/ZnO composite for solar-light-induced photodegradation of sulfamerazine

Recently, the release of antibiotics, such as sulfonamides, into the environment has raised significant concern due to the potential creation of antibiotic-resistant bacteria. Thus, the development of remediation technologies for effluents containing such compounds is of utmost urgency. In this context, this work evaluated the creation of a resorcinol-based carbon xerogel/zinc oxide photocatalyst (XC/ZnO) to efficiently promote the photodegradation of the antibiotic known as sulfamerazine in aqueous media. The employment of this carbonaceous structure as a co-catalyst is justified by its high surface area and electrical conductivity. The methodology used in the synthesis of the composites was a simple one-pot reaction, combining the simultaneous precipitation of zinc oxide and polycondensation of the resorcinol-based carbon gel. Regarding the composites' characterization, X-ray diffractometry confirms that the composites have the Wurtzite structure of the zinc oxide, whereas the carbon xerogel formation is evidenced by the infrared, diffuse reflectance, and X-ray photoelectron spectroscopies. Morphology-wise, the XC/ZnO is arranged as nodular particle agglomerates, with particles between 500 nm and 50 nm. The photocatalytic tests under simulated solar radiation show that the composites developed are superior to the pure oxide in the photodegradation of sulfamerazine, as all XC/ZnO materials developed achieved higher apparent reaction rate constants (kapp) than pure zinc oxide, with the XC/ZnO 0.5 material obtaining a kapp 75% higher than the one observed for the ZnO sample. Furthermore, the chronoamperometry tests confirmed that the optimized composite (XC/ZnO 0.5) has a greater capacity for photocurrent generation when compared to pure zinc oxide. Therefore, the modification proposed was successful to enhance the photodegradation of sulfamerazine in aqueous media, highlighting the viability of the composites developed for photocatalytic applications.

PFAS Experts Symposium 2: PFAS Remediation research – Evolution from past to present, current efforts, and potential futures

AbstractDue to the diverse chemistries of per‐ and polyfluoroalkyl substances (PFAS) and their apparent recalcitrance to natural biological and abiotic transformation processes, remediation of this class of compounds in groundwater environments is much more challenging than that of other common contaminants such as chlorinated solvents, hydrocarbons, methyl tert‐butyl ether, and 1,4‐dioxane. Overall, the groundwater remediation community is faced with substantial challenges that will require both continued enhancement of existing technologies and development of new technologies and strategies to manage PFAS‐impacted sites. Fortunately, an extraordinary breadth and depth of ongoing research in PFAS remediation is funded through a variety of different agencies and organizations. This research can be organized into three main categories: (1) nondestructive approaches that remove PFAS from water and other matrices; (2) destructive technologies that break carbon–fluorine and carbon–carbon bonds to create nontoxic products; and (3) coupled systems that concentrate and then destroy PFAS. As with previous groundwater contaminants, an initial focus on ex situ PFAS treatment is now slowly evolving to include more in situ research. However, as of 2021, there are no practical groundwater remediation technologies that have been shown to destroy target PFAS (i.e., mineralize and/or create nontoxic products) in situ at full‐scale field application. While the historical goal of in situ treatment for most contaminants has been destruction, practitioners, facility owners, and regulators may need to alter their expectations and objectives for PFAS, at least in the short term, to management strategies that include treatment at receptor locations to avoid exposures and adsorption‐based attenuation strategies for some plumes. These approaches can be used as practical alternatives to PFAS destruction or to buy time until promising technologies become both commercially available and accepted by the industry. The success of any remedial effort typically depends upon meeting regulatory criteria, which in the case of PFAS, are currently in flux at the federal level and differ by orders of magnitude among state regulatory bodies. While this is understandable given the uncertainty and complexity of this issue, setting firm, consistent, and attainable regulatory standards is necessary to provide researchers and practitioners with necessary benchmarks for remediation technology development and commercialization.

Enhanced degradation of perfluorooctanoic acid by heat-activated persulfate in the presence of zeolites

The treatment of contaminations with perfluorooctanoic acid (PFOA) is a huge challenge due to its environmental persistence and global distribution. A combination of adsorption and degradation processes is considered as a promising approach for removing PFOA traces from water. In the present study, we developed a novel treatment strategy for PFOA using heat-activated persulfate in the presence of BEA35 - a BEA-structure type zeolite. Our experimental results show for the first time that BEA35 not only removes PFOA by adsorption, but also accelerates its degradation by means of heat-activated persulfate until complete mineralization. The presence of zeolite (50 g L-1) increases PFOA degradation up to 99.8% compared with 58% in homogeneous solution under the same reaction conditions (C0,persulfate = 100 mM, 90 min, 70 °C). The influence of reaction conditions such as pH value, zeolite dosage and type were investigated, and possible reaction mechanisms were considered. The applicability of the zeolite-based treatment system was verified with real groundwater samples. A first cost estimation was provided for the application case of a zeolite fixed-bed adsorber with intermittent regeneration by heat-activated persulfate. The presented approach has the potential to overcome several shortcomings of the existing PFOA degradation technologies, such as high energy demands, vulnerability in complex water matrices, and inefficiency at trace concentration levels. Our findings provide an effective and efficient strategy for treatment of water containing traces of PFOA, which can also inspire the development of remediation technologies for water contaminated by other micropollutants.

Pollution in the interflow from a simple landfill in a mountainous and hilly area in Southwest China

Simple landfills lack pollution prevention measures and therefore continuously release pollutants into the surrounding environment. There are a large number of simple landfills in the mountainous and hilly areas in China, and the interflow accounts for a large proportion of runoff. However, the pollution in the interflow stemming from the simple landfill has not been extensively studied. Here, the pollution of the interflow caused by the simple landfill near the Yunxi Town Landfill in the mountainous and hilly region in Southwest China was studied. The composition and pollution release potential of aged refuse in the landfill were determined, and the water quality of interflow around the landfill was monitored for five months. Seasonal changes in water quality of the interflow were observed, and the concentration of pollutants in the interflow around the simple landfill greatly exceeded the water quality standard for the local water function zoning throughout the sampling period. Specifically, the chemical oxygen demand concentrations of the interflow were 247.90 ± 81.57 mg/L, and more than 50 types of refractory organics were detected, with as many as 10 types of polycyclic aromatic hydrocarbons and Environmental Protection Agency priority pollutants. The total nitrogen concentration of the interflow was 132.45 ± 108.68 mg/L; organic nitrogen (53.27%) was the main component, followed by nitrate nitrogen (32.28%) and nitrous nitrogen and ammonia nitrogen (14.45%). The results highlight the need for the remediation of interflow around simple landfills in mountainous and hilly areas. Generally, the basic data could be used to aid the development of remediation technology.

Activation of persulfate and removal of ethyl-parathion from soil: Effect of microwave irradiation

Advanced persulfate oxidation technology is widely used in organic pollution control of super fund sites. In recent years, microwave radiation has been proven a promising method for persulfate activation. However, most of the prior works were focused on the treatment of polluted water, but there are few reports aiming at contaminated sites, especially the knowledge of using microwave activated persulfate technology to repair pesticide-contaminated sites. In this study, an effective activation/oxidation method for the remediation of pesticide-contaminated soil, i.e., microwave/persulfate, was developed to treat soil containing ethyl-parathion. The concentration of persulfate, reaction temperature, and time were optimised. The results showed that up to 77.32% of ethyl-parathion was removed with the addition of 0.1 mmol·persulfate·g−1 soil under the microwave temperature of 60 °C. In comparison, 19.43% of ethyl-parathion was removed at the same reaction temperature under the condition of water bath activated persulfate. Electron paramagnetic resonance (EPR) spectroscopy combined with spin-trapping technology was used to detect reactive oxidation species, and OH and SO4− were observed in the microwave/persulfate system. Quenching experiments suggested that ethyl-parathion was degraded by the generated OH and SO4−. Paraoxon, phenylphosphoric acid, 4-nitrophenol, dimethyl ester phosphate, and some alkanes were the dominant oxidative products identified by gas chromatography–mass spectrometry (GC-MS) analysis. A possible pathway for ethyl-parathion degradation was proposed in this study. The results obtained serve as the guidance to the development of remediation technologies involving persulfate and microwave for soil contaminated by organic contaminants such as pesticides.

Benchtop 19 F NMR spectroscopy as a practical tool for testing of remedial technologies for the degradation of perfluorooctanoic acid, a persistent organic pollutant.

The development of effective remedial technologies for the destruction of environmental pollutants requires the ability to clearly monitor degradation processes. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for understanding reaction progress; however, practical considerations often restrict the application of NMR spectroscopy as a tool to better understand the degradation of environmental pollutants. Chief among these restrictions is the limited access smaller environmental research labs and remediation companies have to suitable NMR facilities. Benchtop NMR spectroscopy is a low-cost and user-friendly approach to acquire much of the same information as conventional nuclear magnetic resonance (NMR) spectroscopy, albeit with reduced sensitivity and resolution. This paper explores the practical application of benchtop NMR spectroscopy to understand the degradation of perfluorooctanoic acid using sodium persulfate, a common reagent for the destruction of groundwater contaminants. It is found that Benchtop 19 F NMR spectroscopy is able to monitor the complete degradation of perfluorooctanoic acid into fluoride; however, the observation of intermediate degradation products formed, which can be observed using a conventional NMR spectrometer, cannot be readily distinguished from the parent compound when measurements are performed using the benchtop instrument. Under certain reaction conditions, the formation of fluorinated structures that are resistant to further degradation is readily observed. Overall, it is shown that benchtop 19 F NMR spectroscopy has potential as a quick and reliable tool to assist in the development of remedial technologies for the degradation of fluorinated contaminants.

Activate persulfate for catalytic degradation of adsorbed anthracene on coking residues: Role of persistent free radicals

Carbonaceous residues and polycyclic aromatic hydrocarbons (PAHs) are discharged simultaneously during the coke production. Chemical-structural properties of coking residues, such as coke powder, tar slag, and fly ash, were characterized by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area, scanning electron microscopy (SEM), and electron paramagnetic resonance (EPR) techniques. Highly disorder amorphous structures with abundant of oxygen functionalities and persistent free radicals were observed for coke powder and tar slag. The potential activation of persistent free radicals (PFRs) on persulfate to generate reactive oxygen species (ROS) and induce the degradation of anthracene (ANT) was studied. The formation of H2O2 and decay rate of ANT highly correlate with the spin densities of bounded PFRs in coking residues. EPR technique combined with different radical scavengers was applied to investigate the generation of ROS. The results suggest that PFRs provide the electron to persulfate or/and O2, inducing the formation of SO4−, H2O2, and OH. The produced ROS then back-reacts with adsorbed organic compounds, such as ANT, resulting in its oxidation and/or complete mineralization. The obtained results are relevant to the fate of adsorbed pollutants in coke-polluted soil environments and shed light on the development of remediation technologies for solid waste released during the coke production.

New Aspects of the Role of Organisms and Detritus in the Detoxification System of the Biosphere

The review covers new aspects of the participation of organisms in the detoxification system of the biosphere. Problems of detoxification of toxic environmental pollutants are analyzed. New author’s experimental data in combination with a large amount of information in the scientific literature gave rise to a new concept of the role of biogenic detritus and related nutrients in environmental detoxification (ex-living matter concept). This may be useful for the development of new technologies for remediation and decontamination of the environment.

Remediation of agrosoddy-podzolic soils contaminated with cadmium

Results of a long-term field experiment on the remediation of agrosoddy-podzolic soils (Retisols) contaminated with cadmium have been analyzed. The solidification/stabilization method (S/S technology) has been used for the development of remediation technology. Different rates of ameliorants and fertilizers (limestone and phosphorite meals, superphosphate, sodium sulfide, peat, and zeolite) have been studied as ameliorating additives. It has been shown that the efficiency of ameliorating additives in decreasing the mobility of cadmium in the soil depends on their type (the dissolution of ameliorant in water and solubility products of the resulting Cd compounds), application rate, and the time elapsed since the application. In the first year of the experiment, the highest efficiency has been observed for water-soluble forms of ameliorating additives: sodium sulfide and superphosphate. Limestone meal and zeolite have showed the longest aftereffect. The application of all ameliorating additives under study has increased the yield of agricultural crops and reduced their cadmium content down to below the MPC level in most cases, which makes this agronomic practice promising for the remediation of agricultural lands with an elevated content of cadmium.

Stability and pH-independence of nano-zero-valent iron intercalated montmorillonite and its application on Cr(VI) removal

Composite of nano-zero-valent iron and montmorillonite (NZVI/MMT) was prepared by inserting NZVI into the interlayer of montmorillonite. The unique structure montmorillonite with isolated exchangeable Fe(III) cations residing near the sites of structural negative charges inhibited the agglomeration of ZVI and result in the formation of ZVI particles in the montmorillonite interlayer regions. NZVI/MMT was demonstrated to possess large specific surface area and outstanding reducibility that encourage rapid and stable reaction with Cr (VI). Besides, the intercalation also makes NZVI well dispersed and more stable in the interlayer, thereby improving the reaction capacity by 16 times. The effects of pH value, initial concentration of Cr (VI) and reaction time on Cr (VI) removal have also been investigated in detail. According to PXRD and XPS characterization, NZVI/Cr (VI) redox reaction occurred in the interlayer of MMT. The study of NZVI/MMT is instrumental to the development of remediation technologies for persistent environmental contaminants.

English

Oil sludge is a thick viscous mixture of sediments, water, oil and hydrocarbons, encountered during crude oil refining, cleaning of oil storage vessels and waste treatment. Polycyclic aromatic hydrocarbons (PAHs), which are components of crude oil sludge, constitute serious environmental concerns, as many of them are cytotoxic, mutagenic and potentially carcinogenic. Improper management and disposal of oil sludge causes environmental pollution. The adverse effects of oil sludge on soil ecology and fertility have been of growing interest among environmental scientist and an important consideration in the development of efficient technologies for remediation of contaminated land, with a view to making such land available for further use. Oil sludge can be treated by several methods such as physical, chemical and biological processes. The biological processes are mostly cost effective and environmentally friendly, as they are easy to design and implement, as such they are more acceptable to the public. Compost, the product of biological breakdown of organic matter is a rich source of hydrocarbon-degrading microorganisms such as bacteria and fungi. These microorganisms can degrade the oil sludge to less toxic compounds such as carbon dioxide, water and salts. Compost bioremediation, the application of composting in remediation of contaminated environment, is beginning to gain popularity among remediation scientists. The success or failure of compost bioremediation depends on a number of factors such as nutrients, pH, moisture, aeration and temperature within the compost pile. The bioavailability and biodegradability of the substrate to the degrading microorganisms also contributes to the success of the bioremediation process. This is a review on the biological remediation technologies employed in the treatment oil sludge. It further assesses the feasibility of using compost technology for the treatment of oil sludge, as a better, faster and more cost effective option. Key words: Biodegradation, bioremediation, composting, oil sludge, polycyclic aromatic hydrocarbons (PAHs).

Production of bioemulsifiers by Amycolatopsis tucumanensis DSM 45259 and their potential application in remediation technologies for soils contaminated with hexavalent chromium

In recent years, increasing interest has been shown in the use of bioemulsifiers as washing agents that can enhance desorption of soil-bound metals. However, high production costs derived from the use of expensive substrates for formulation of the fermentation media represent the main challenge for full, large-scale implementation of bioemulsifiers. This work reports on a first study of bioemulsifier production by the actinobacterium Amycolatopsis tucumanensis DSM 45259 using different carbon and nitrogen sources. Preliminary results on the potential use of these compounds as washing agents for soils contaminated with Cu(II) and Cr(VI) are also presented. The best specific production was detected using glycerol and urea as carbon and nitrogen substrates, respectively. However, with all of the substrates used during the batch assay, the bioemulsifiers showed high levels of stability at extreme conditions of pH, temperature, and salt concentration. Under the current assay conditions, the bioemulsifiers were not effective in removing Cu(II) from soil. However, they were able to mediate Cr(VI) recovery, with the removal percentage doubled compared to that seen when using deionized water. These findings appear promising for the development of remediation technologies for hexavalent chromium compounds based upon direct use of these microbial emulsifiers.

Iron oxide nanoparticles in geomicrobiology: from biogeochemistry to bioremediation

Iron oxides are important constituents of soils and sediments and microbial iron reduction is considered to be a significant anaerobic respiration process in the subsurface, however low microbial reduction rates of macroparticulate Fe oxides in laboratory studies led to an underestimation of the role of Fe oxides in the global Fe redox cycle. Recent studies show the high potential of nano-sized Fe oxides in the environment as, for example, electron acceptor for microbial respiration, electron shuttle between different microorganisms, and scavenger for heavy metals. Biotic and abiotic reactivity of iron macroparticles differ significantly from nano-sized Fe oxides, which are usually much more reactive. Factors such as particle size, solubility, ferrous iron, crystal structure, and organic molecules were identified to influence the reactivity. This review discusses factors influencing the microbial reactivity of Fe oxides. It highlights the differences between natural and synthetic Fe oxides especially regarding the presence of organic molecules such as humic acids and natural organic matter. Attention is given to the transport behavior of Fe oxides in laboratory systems and in the environment, because of the high affinity of different contaminants to Fe oxide surfaces and associated co-transport of pollutants. The high reactivity of Fe oxides and their potential as adsorbents for different pollutants are discussed with respect to application and development of remediation technologies.

Bioaugmented remediation of high concentration BTEX-contaminated groundwater by permeable reactive barrier with immobilized bead

Ineffective biostimulation requires immediate development of new technologies for remediation of high concentration BTEX-contaminated (benzene, toluene, ethylbenzene and xylene) groundwater. In this study, bioaugmentation with Mycobacterium sp. CHXY119 and Pseudomonas sp. YATO411 immobilized bead was used to remediate BTEX-contaminated groundwater with about 100mgl−1 in total concentration. The batch test results showed that the CHXY119 and YATO411 immobilized bead completely biodegraded each BTEX compound, and the maximum biodegradation rates were 0.790mgl−1h−1 for benzene, 1.113mgl−1h−1 for toluene, 0.992mgl−1h−1 for ethylbenzene and 0.231mgl−1h−1 for p-xylene. The actual mineralization rates were 10.8% for benzene, 10.5% for toluene, 5.8% for ethylbenzene and 11.4% for p-xylene, which indicated that the bioremediation of BTEX by the immobilized bead requires a rather small oxygen supply. Degradation rates achieved by the bioaugmented permeable reactive barrier (Bio-PRB) system of the immobilized bead were 97.8% for benzene, 94.2% for toluene, 84.7% for ethylbenzene and 87.4% for p-xylene; and the toxicity of the groundwater fell by 91.2% after bioremediation by the bioaugmented PRB, which confirmed its great potential for remediating groundwater with high concentrations of contaminants.