We study the adsorption and desorption of chromium on two soils (a forest soil and a vineyard soil), both individually or after being combined with ground mussel shell, and on various materials (mussel shell, pyritic material from a dump site, and slate processing fines). The adsorption capacity depends mainly on the initial Cr concentration, on the pH, and on the abundance of noncrystalline Fe. The highest adsorption percentage (94 %) corresponds to the pyritic material, which also shows very low desorption rates (1.4 %), has the lowest pH, and has the highest concentration of noncrystalline Fe. The adsorption isotherms in most cases fit the Freundlich and Lineal models, rather than the Langmuir model, with no easily predictable maximum for chromium adsorption.

Tobacco (Nicotiana tabacum L.) stem ash (TSA) was evaluated as an adsorbent for removal of methylene blue (MB) from aqueous solution by batch adsorption method. MB adsorption increased with increase in contact time, initial solution pH, and adsorbent dose. Contact time for adsorption equilibrium was 180 min. The MB adsorption per unit mass of adsorbent (in milligram per gram) increased with the increasing initial dye concentration. Adsorption of MB onto TSA followed the pseudo-second-order kinetic model with a rate constant (k ₂) of 0.017 g mg⁻¹ min⁻¹. The mechanism of adsorption was described with intra-particle diffusion model. It was found that the intra-particle diffusion was not a sole rate-controlling step. Equilibrium adsorption was investigated by the Freundlich, Langmuir, Temkin, and Jovanoic isotherms. On the basis of coefficient of determination, the order of isotherm fit was Langmuir (R ² = 0.974) > Freundlich (R ² = 0.957) = Temkin (R ² = 0.957) > Jovanoic (R ² = 0.764) isotherm. The maximum monolayer adsorption capacity of TSA was 35.7 mg g⁻¹. The dimensionless separation factor (R L) was low (0.137), indicating favorable adsorption of MB onto TSA. The results clearly demonstrate the potential of TSA as a low-cost and an easily available adsorbent for sequestering MB from wastewater.

An experimental design methodology was applied for response surface modeling and optimization of diethyl phthalate (DEP) removal from synthetic wastewater by continuous-flow ozonation. The five independent variables considered were the initial concentration of DEP, initial solution pH, liquid flow rate, gas flow rate, and ozone concentration in the inlet gas. Using the Box–Behnken design, two quadratic models were developed as a functional relationship between respectively DEP removal efficiency and ozone mass transfer and the independent variables considered. It was found that all the factors considered have a significant effect on the removal efficiency response, except for the gas flow rate which did not influence DEP removal in the ranges considered. The results show that the ozonation efficiency can be predicted and are in very good agreement with the experimental data. Optimal conditions for two different sets of constraints were determined.

Alpine ecosystems, representing a large proportion of the land area in Europe, are under pressure from changes in climate and land-use. This may also impact the quality of drainage waters. Here, we assess effects of plant communities (snowbed, dwarf shrub heath, and tall herb meadow) on concentrations of dissolved organic carbon and nitrogen (DOC and DON), ammonium (NH₄-N), nitrate (NO₃-N), and phosphorus (tot-P and PO₄-P) in locally derived seepage water in a non-fertilized sub-alpine area of southern Norway. In addition, we investigated effects of two density levels of sheep (no sheep and 80 sheep km⁻²) on infiltration capacity, pore size distribution and concentrations of nutrients and bacteria in surface runoff. Concentrations of NO₃-N (<0.02–0.03 mg l⁻¹) and NH₄-N (<0.02–0.03 mg l⁻¹) were low in seepage waters with no significant differences associated with plant community. Also, concentrations of DOC and DON were low, in particular in snowbeds, probably due to low productivity and small soil carbon pools. Infiltration rates, which were significantly smaller in snowbeds than in tall herb meadow, were further reduced by grazing. In turn, this caused increased runoff of coliform bacteria, whereas no effect of grazing on NH₄-N, NO₃-N and PO₄-P was observed. Grazing may significantly alter biological water quality but is not likely to affect the productivity of surface waters in non-fertilized alpine areas.

There is a pollution risk when disposing of post-remediation biomass from chelate-assisted metal phytoremediation. To assess this risk, we measured water extractable lead (Pb) in Brassica rapa tissues with ICP-MS, determined if chelated Pb was present with HPLC-MS, and identified Pb storage locations using electron microscopy with x-ray microanalysis. Ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS) were used to enhance Pb movement from contaminated soil to above ground B. rapa tissues. With Pb-EDTA, 92 % (5) of Pb was water extractable from dried tissues and complexed as Pb-EDTA. Electron microscopy and x-ray microanalysis showed Pb stored in xylem vessels. After composting of plant tissues, 79 % (2) of Pb was water extractable and complexed as Pb-EDTA. Total plant Pb accumulation was lower from soils amended with EDDS, but only 6.7 % (0.3) of Pb was water extractable from dried tissues and 55 % (25) from wet tissues of plants grown in EDDS-amended soils. Pb-EDDS was detected in tissues but not at quantifiable levels. This work emphasizes the need for proper treatment and disposal of contaminated post-remediation plant tissues, especially when using EDTA. Composting of plant tissues containing Pb-EDTA was shown to significantly reduce waste material volume and slightly reduce the water extractable fraction, but further immobilization of Pb would be necessary to minimize transport risk. Amending Pb-contaminated soils with EDDS can result in plant biomass with a lower potential to leach Pb into groundwater, but the lower Pb accumulation with EDDS would require longer phytoremediation time compared with EDTA. © 2013 Springer Science Media Dordrecht.

The presence of macrolide antibiotics in aquatic environments causes serious antibiotic resistance propagation in microorganisms. In this study, the use of porous resins as adsorbents for the removal of tylosin from aqueous solutions was evaluated. The effectiveness of the resins (macroporous resin XAD-4, hypercross-linked resin MN-202, and aminated polystyrene resin MN-150) was compared with commercial hydroxylated multiwall carbon nanotubes (H-MWCNTs). Similar patterns of pH-dependent adsorption were observed despite the different surface properties and pore structures of the three resins, implying the importance of the tylosin molecular form in the adsorption process. Tylosin adsorption onto the four adsorbents showed different ionic strengths and temperature dependence consistent with the tylosin speciation and corresponding adsorption mechanism. The adsorption of tylosin onto the XAD-4 and MN-202 is mainly controlled by the intermolecular interactions between the matrix of the adsorbents and the tylosin molecule, whereas specific bonds among multiple surface functional groups are the predominant contributors to MN-150 and H-MWCNTs. The pore size is the key parameter in tylosin adsorption onto the surface of the adsorbents. The adsorption kinetics of the four adsorbents followed the pseudo-second-order model. The adsorption isotherm data well fit the Langmuir models, indicating surface coverage by a monomolecular layer.

Coal mine methane is a significant greenhouse gas source as well as a potential lost energy resource if not effectively used. In recent years, mine ventilation air (MVA) capture and use has become a key element of research and development due to comparatively larger methane emissions by MVA than other coal mine sources. Technologies have been evaluated to treat the low methane concentrations in MVA such as thermal-based technologies or processing by biofiltration. This review initially considers the techniques available for treating the low methane concentrations encountered in MVA, after which it focuses on developments in biofiltration systems. Biofiltration represents a simple, energy-efficient, and cheap alternative to oxidize methane from MVA. Major factors influencing biofilter performance along with knowledge gaps in relation to its application to MVA are identified and discussed.

In this study, 11 plants (legumes, grasses, and crops) were screened for their ability to grow and survive in soil contaminated with 1 % diesel/oil mix (aliphatic hydrocarbons) or 1 % crude oil. Based on emergence, shoot length, root length, and root/shoot biomass ratio in contaminated soil, maize and wheat which showed the highest growth were selected for further investigation: a long-term phytoremediation study to evaluate the effect of maize and wheat on the microbial removal of hydrocarbons (1 % diesel/oil mix). The results showed that the presence of both maize and wheat in hydrocarbon-contaminated soil led to a significant increase in the utilization of total petroleum hydrocarbon (TPH), from 57 % in the control soil to 72 and 66 % in soil planted with maize and wheat, respectively. Microbial community analysis using denaturing gradient gel electrophoresis (DGGE) showed that the presence of a plant rhizosphere resulted in changes in the structure of the soil microbial community. Sequencing of prominent bands revealed the presence of a few hydrocarbonoclastic fungi only in the contaminated soil planted with maize and wheat. In terms of specific hydrocarbonoclastic activity, DGGE analysis based on alkB genes showed that soils with maize and wheat had similar rates of hydrocarbonoclastic activity but distinct microbial communities in some instances. Most probable number quantitative polymerase chain reaction (MPN-qPCR) confirmed that the number of alkB gene copies in soil planted with maize and wheat increased about 20- and 16-fold, respectively, relative to the control soil. This study showed that fungal and alkB bacterial communities contribute to the rhizoremediation of petrogenic hydrocarbons.

Colistin is a peptide antibiotic widely used as a food additive in animal farming, specially swine and poultry, and also has recently been applied in human medicine to treat infections caused by multiresistant gram-negative bacteria strains. When orally administered, colistin is eliminated in feces virtually unaltered; thus, it may reach water bodies and wastewater treatment facilities in its active form. Apart from the risks associated with development of antimicrobial resistance and environmental toxicity issues, the presence of antimicrobials in wastewater can, additionally, interfere in biological processes commonly used to treat them. Nitrifying bacteria are among the most sensitive microorganisms to inhibitory compounds, including pharmaceuticals, and are useful as biosensors to access contaminant toxicity information in wastewater treatment plants. Therefore, in order to assess the colistin acute toxicity to the microorganisms involved in the nitrification processes, the nitritation and nitratation kinetics were monitored under different colistin concentrations. The results showed that only ammonia-oxidizing bacteria are sensitive to the antibiotic, presenting an IC50 of 10.8 mg L⁻¹ of colistin when used as a commercial formulation and 67.0 mg L⁻¹ when used as raw colistin sulfate. For nitrite-oxidizing bacteria, even the highest colistin concentration used in the assays (316 mg L⁻¹) was not sufficient to inhibit the process. According to these results, the colistin concentrations expected in animal farming wastewater, when its dosage is used as a growth promoter, would not be enough to keep nitrification from taking place. Nevertheless, when used in higher concentrations, such as for therapeutic purposes, it could endanger the maintenance of the process.

The purpose of this study was to determine the effect of soil contamination with tri- and hexavalent chromium and soil application of compost, zeolite, and CaO on the mass of oats and content of nitrogen compounds in different organs of oats. The oats mass and content of nitrogen compounds in the crop depended on the type and dose of chromium and alleviating substances incorporated to soil. In the series without neutralizing substances, Cr(VI), unlike Cr(III), had a negative effect on the growth and development of oats. The highest doses of Cr(VI) and Cr(III) stimulated the accumulation of total nitrogen but depressed the content of N-NO₃ ⁻ in most of organs of oats. Among the substances added to soil in order to alleviate the negative impact of Cr (VI) on the mass of plants, compost had a particularly beneficial effect on the growth and development of oats. The application of compost, zeolite, and CaO to soil had a stronger effect on the content of nitrogen compounds in grain and straw than in roots. Soil enrichment with either of the above substances usually raised the content of nitrogen compounds in oats grain and straw, but decreased it in roots.