Estimation of pollutant partition in sandy soils with different water contents

Biological synthesis of iron nanoparticles using hydrolysates from a waste-based biorefinery

The purpose of this work was to produce iron nanoparticles (Fe-NP) by microbial pathway from anaerobic bacteria grown in anaerobic fluidized bed reactors (AnFBRs) that constitute a new stage of a waste-based biorefinery. Bioparticles from biological fluidized bed reactors from a biorefinery of organic fraction of municipal solid wastes (that produces hydrolysates rich in reducing sugars) were nanodecorated (embedded nanobioparticle or nanodecorated bioparticle, ENBP) by biological reduction of iron salts. Factors "origin of bioparticles" (either from hydrogenogenic or methanogenic fluidized bed reactor) and "type of iron precursor salt" (iron chloride or iron citrate) were explored. SEM and high-resolution transmission electron microscopy (HRTEM) showed amorphous distribution of nanoparticles (NP) on the bioparticles surface, although small structures that are nanoparticle-like could be seen in the SEM micrographs. Some agglomeration of NPs was confirmed by DLS. Average NP size was lower in general for NP in ENBP-M than ENBP-H according to HRTEM. The factors did not have a significant influence on the specific surface area of NPs, which was high and in the range 490 to 650 m² g^-1. Analysis by EDS displayed consistent iron concentration 60-65% iron in nanoparticles present in ENBP-M (bioparticles previously grown in methanogenic bioreactor), whereas the iron concentration in NPs present in ENBP-H (bioparticles previously grown in hydrogenogenic bioreactor) was more variable in a range from 8.5 to 62%, depending on the iron salt. X-ray diffraction patterns showed the typical peaks for magnetite at 35° (3 1 1), 43° (4 0 0), and 62° (4 0 0); moreover, siderite diffraction pattern was found at 26° (0 1 2), 38° (1 1 0), and 42° (1 1 3). Results of infrared analysis of ENBP in our work were congruent with presence of magnetite and occasionally siderite determined by XRD analysis as well as presence of both Fe⁺² and F⁺³ (and selected satellite signal peaks) observed by XPS. Our results on the ENBPs hold promise for water treatment, since iron NPs are commonly used in wastewater technologies that treat a wide variety of pollutants. Finally, the biological production of ENBP coupled to a biorefinery could become an environmentally friendly platform for nanomaterial biosynthesis as well as an additional source of revenues for a waste-based biorefinery.

Benzene homologues contaminants in a former herbicide factory site: distribution, attenuation, risk, and remediation implication

Benzene homologues often used as organic raw materials or as detergents in chemical industry are prone to accidental release into the environment which can cause serious long-term soil pollutions. In a large former herbicide factory site, we investigated 43 locations for benzene homologues contaminations in soil, soil gas, and groundwater and studied the hydrogeological conditions. An inverse distance weighted interpolation method was employed to determine the pollutants three-dimensional spatial distribution in the soils. Results showed that benzene homologues residues were mainly originated from the herbicide production workshop and that the pollution had horizontally expanded at the deeper soil layer. Contaminants had already migrated 15 m downward from ground surface. Contaminant phase distribution study showed that NAPL was the primary phase (> 99%) for the pollutants accumulated in the unsaturated zone, while it had not migrated to groundwater. The primary mechanism for contaminant transport and attenuation included dissolution of "occluded" NAPL into pore water and pollutant volatilization into soil pore space. Risk assessment revealed that the pollutants brought unacceptable high carcinogenic and non-carcinogenic risks to public health. In order to convert this former chemical processing factory site into a residential area, a remediation to the polluted production workshop sites is urgently required.

Butylbenzene and tert-Butylbenzene-Sorption on Sand Particles and Biodegradation in the Presence of Plant Natural Surfactants

The effects of hydrocarbons sorption on sand and saponins presence in the system on butylbenzene and tert-butylbenzene biological degradation was investigated. Additionally, the impact of saponins-containing plant extracts on environmental microorganisms was studied. Results of cell surface property measurements in samples with saponins only revealed changes in cell surface hydrophobicity, electrokinetic potential and membrane permeability when compared to corresponding values for glucose-grown microbes. Subsequently, in sorption experiments, the hydrocarbon adsorption kinetics in bacteria-free samples were better explained with the pseudo-second order kinetic model as compared to the pseudo-first order and intraparticular diffusion models. Moreover, the equilibrium data fitted better to the Freundlich isotherm for both benzene derivatives. In the samples combining hydrocarbons sorption and biological degradation in the presence of saponins, alkane-substituted hydrocarbons removal was accelerated from 40% to 90% after 14 days and the best surfactant in this aspect was S. officinalis extract.

Biocomplementation of SVE to achieve clean-up goals in soils contaminated with toluene and xylene

Soil vapor extraction (SVE) and bioremediation (BR) are two of the most common soil remediation technologies. Their application is widespread; however, both present limitations, namely related to the efficiencies of SVE on organic soils and to the remediation times of some BR processes. This work aimed to study the combination of these two technologies in order to verify the achievement of the legal clean-up goals in soil remediation projects involving seven different simulated soils separately contaminated with toluene and xylene. The remediations consisted of the application of SVE followed by biostimulation. The results show that the combination of these two technologies is effective and manages to achieve the clean-up goals imposed by the Spanish Legislation. Under the experimental conditions used in this work, SVE is sufficient for the remediation of soils, contaminated separately with toluene and xylene, with organic matter contents (OMC) below 4 %. In soils with higher OMC, the use of BR, as a complementary technology, and when the concentration of contaminant in the gas phase of the soil reaches values near 1 mg/L, allows the achievement of the clean-up goals. The OMC was a key parameter because it hindered SVE due to adsorption phenomena but enhanced the BR process because it acted as a microorganism and nutrient source.

Modeling perchloroethylene degradation under ultrasonic irradiation and photochemical oxidation in aqueous solution

Sonolysis and photochemical degradation of different compounds such as chlorinated aliphatic hydrocarbons are among the recent advanced oxidation processes. Perchloroethylene is one of these compounds that has been mainly used as a solvent and degreaser. In this work, elimination of perchloroethylene in aqueous solution by ultrasonic irradiation, andphotochemical oxidation by ultra violet ray and hydrogen peroxide were investigated. Three different initial concentrations of perchloroethylene at different pH values, detention periods, and concentrations of hydrogen peroxide were investigated. Head space gas chromatography with FID detector was used for analyses of perchloroethylene. This research was performed in 9 months from April through December 2011.

Results showed that perchloroethylene could be effectively and rapidly degraded by ultrasonic irradiation, photochemical oxidation by ultra violet ray, hydrogen peroxide and a combination of these methods. Kinetics of perchloroethylene was strongly influenced by time, initial concentration and pH value. Degradation of Perchloroethylene increased with decrease in the initial concentration of perchloroethylene from 0.3 to 10 mg/L at all initial pH. The results showed an optimum degradation condition achieved at pH = 5 but did not affect significantly the perchloroethylene destruction in the various pH values. Kinetic modeling applied for the obtained results showed that the degradation of perchloroethylene by ultrasound and photo-oxidation followed first order and second order model. The percentage of removal in the hybrids reactor was higher than each of the reactors alone, the reason being the role of hydroxyl radical induced by ultrasound and photochemical reaction.

Survey of hazardous organic compounds in the groundwater, air and wastewater effluents near the Tehran automobile industry

Potential of wastewater treatment in car industry and groundwater contamination by volatile organic compounds include perchloroethylene (PCE), trichloroethylene (TCE) and dichloromethane (DCM) near car industry was conducted in this study. Samples were collected in September through December 2011 from automobile industry. Head-space Gas chromatography with FID detector is used for analysis. Mean PCE levels in groundwater ranged from 0 to 63.56 μg L(-1) with maximum level of 89.1 μg L(-1). Mean TCE from 0 to 76.63 μg L(-1) with maximum level of 112 μg L(-1). Due to the data obtained from pre treatment of car staining site and conventional wastewater treatment in car factory, the most of TCE, PCE and DCM removed by pre aeration. Therefor this materials entry from liquid phase to air phase and by precipitation leak out to the groundwater. As a consequence these pollutants have a many negative health effect on the workers by air and groundwater.

Remediation of sandy soils contaminated with hydrocarbons and halogenated hydrocarbons by soil vapour extraction

This paper presents the study of the remediation of sandy soils containing six of the most common contaminants (benzene, toluene, ethylbenzene, xylene, trichloroethylene and perchloroethylene) using soil vapour extraction (SVE). The influence of soil water content on the process efficiency was evaluated considering the soil type and the contaminant. For artificially contaminated soils with negligible clay contents and natural organic matter it was concluded that: (i) all the remediation processes presented efficiencies above 92%; (ii) an increase of the soil water content led to a more time-consuming remediation; (iii) longer remediation periods were observed for contaminants with lower vapour pressures and lower water solubilities due to mass transfer limitations. Based on these results an easy and relatively fast procedure was developed for the prediction of the remediation times of real soils; 83% of the remediation times were predicted with relative deviations below 14%.