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.

There are significant concerns about the impact of heavy metal contamination in soils as a consequence of urbanisation and industrialisation in developing countries. Routine chemical analysis of soils is used to measure the total concentration of metals from point source or diffuse activities, but this fails to put in context the bioavailability of the analyte or the potential toxicity of multiple contaminants. Bacterial biosensors provide a useful tool for assessing the toxicity of the bioavailable fraction of heavy metals in soils and for complementing chemical analysis. There are few examples of genuine environmental applications of biosensors for pollutant diagnosis. This study applied constitutively marked biosensors (which were comprehensively characterised) to soils collected from across Northern China (60,000 km²). The biosensors were responsive to soils impacted by As, Cd, Cr, Cu, Hg, Pb, and Zn when compared to ‘uncontaminated controls’. The response of the biosensor correlated with individual (or groups of) metals related to their concentration and source. The geo-accumulation index (I gₑₒ) assisted in explaining the biosensor response. The constitutively marked biosensors offered a focussed understanding of analyte bioavailability and placed in a relevant context the elemental analysis. When matrix-matched control samples can be collected, then such a biosensor procedure (as adopted here) is applicable to contrasting soils exposed to a wide range of contaminants. Biosensor applications complemented routine soil chemical analysis for this regional-scale study.

In this paper, we report on a field experiment being carried out in a Typic Eutrorthox. The experiment was initiated in the 1997–98 agricultural season as a randomized block design with four treatments (0, 5, 10, and 20 t ha⁻¹) of sewage sludge and five replicates. Compound soil samples were obtained from 20 subsamples collected at depths of 0–0.1 and 0.1–0.2 m. Cu, Fe, Mn, and Zn concentrations were extracted with DTPA pH 7.3; 0.1 mol L⁻¹ HCl, Mehlich-I, Mehlich-III, and 0.01 mol L⁻¹ CaCl₂. Metal concentrations were determined via atomic absorption spectrometry. Diagnostic leaves and the whole above-ground portion of plants were collected to determine Cu, Fe, Mn, and Zn concentrations extracted by nitric–perchloric digestion and later determined via atomic absorption spectrometry. Sewage sludge application caused increases in the concentrations of soil Cu, Fe, and Mn in samples taken from the 0–0.1 m depth evaluated by the extractants Mehlich-I, Mehlich-III, 0.01 mol L⁻¹ HCl and DTPA pH 7.3. None of the extractants provided efficient estimates of changes in Mn concentrations. The acid extractants extracted more Cu, Fe, Mn, and Zn than the saline and chelating solutions. The highest concentrations of Cu, Fe, and Zn were obtained with Mehlich-III, while the highest concentrations of Mn were obtained with HCl. We did not observe a correlation between the extractants and the concentrations of elements in the diagnostic leaves nor in the tissues of the whole maize plant (Zea mays L.).

Although aluminum (Al) is considered innocuous to living beings, exposure to high concentrations can elicit damage. Al has been found to cause liver pathologies in various animal models. Its mechanisms of toxicity are unclear; presumably, it interacts with protein sulfhydryl groups and promotes reactive oxygen species formation causing oxidative stress. Lipid peroxidation, protein carbonyl content, and activity of superoxide dismutase, catalase, and caspase-3 were determined in liver of Cyprinus carpio exposed to 0.05, 120, and 239.42 mg Al L⁻¹ for 12, 24, 48, 72, and 96 h. Al induced increased lipid peroxidation and protein carbonyl content as well as changes in enzymatic activity, indicating it elicits oxidative stress and apoptosis in common carp liver.

Japan has been receiving increasing levels of atmospheric nitrogenous pollutants from the East Asian continent over the last few decades, so it is critical to evaluate the impact of this increased atmospheric nitrogen (N) deposition on N cycling even in rural forests. This study evaluated the contribution of the current level of atmospheric N deposition to N cycling in a rural forested area. Bulk precipitation and stream water were collected during 2007-2011 at the Shiiba Research Forest (SRF) located in the central Kyushu mountain range of southern Japan. Litterfall was also collected to investigate the contribution of atmospheric N deposition to total N input (litterfall N + atmospheric N deposition). The results showed that atmospheric depositions of both nitrate (NO3 -) and ammonium (NH4 +) were a few times higher during 2009-2011 than in 1991. This could be the result of additional N deposition from the increased long-range transport of nitrogenous pollutants from the East Asian continent. The current level of annual N deposition (9.7 kg N ha-1 year-1) at the SRF was comparable with that at many urban sites and was close to the reported threshold values causing N saturation in forest ecosystems. Although current atmospheric N deposition was an important component (23 %) of total N input (43 kg N ha -1 year-1) at the SRF, the concentrations of NO 3 - in stream water were consistently low (<10 μmol L-1). These results indicate that atmospheric N deposition is currently largely incorporated into forest ecosystems without excess N export from forested watersheds. © 2013 Springer Science+Business Media Dordrecht.

A comprehensive investigation of polybromodiphenyl ethers (PBDEs) in wastewater was conducted in the second largest international metroplex area along the U.S. and Mexico (MX) border. Concentrations of PBDEs in wastewater and sludge were measured in four wastewater treatment plants (WWTPs) in El Paso, Texas and two WWTPs in Cd. Juarez, Chihuahua, MX. A green approach in sample preparation technique, called stir bar sorptive extraction (SBSE) coupled with thermal desorption and gas chromatography and mass spectrometry, was used which requires minimum amount of organic solvents and has good sensitivity at nanogram-per-liter levels for wastewater samples and nanograms per gram for waste sludge solids. Concentrations of PBDEs ranged from 30.2 to 342 ng L⁻¹ in wastewater influents, from not detected to 209 ng L⁻¹ in effluents, and from not detected to 1,303 ng g⁻¹ in sludge. Among 27 PBDEs studied, BDE-47, BDE-99, and BDE-100 were the most commonly detected congeners in all samples. Further evaluation showed that secondary and tertiary treatments are highly effective at removing PBDEs from wastewater with percent removals ranging from 84 % to 100 %, while advanced primary treatment only removed 41–73 % of PBDEs. As a complement, the ambient air temperature change on PBDEs concentrations was evaluated finding that this factor did not have an influence on the PBDEs concentrations in WWTPs. The incomplete removal of PBDEs in WWTPs implicates a potential impact on the environmental and public health as a result of the continuous release of PBDEs from the WWTPs to the Rio Grande River and irrigation canals.

A pot experiment was conducted in order to study the relationships of soil pollution indices to maize (Zea mays L.) growth characteristics and soil and plant heavy metal content, as well as the metal plant uptake. A completely randomized block design was used, including 11 treatments in three replications. The treatments applied were control (freshwater), four levels of inorganic NPK fertilizer combined with treated municipal wastewater and freshwater and three sludge levels (5, 25 and 50 %, respectively) in the presence of treated wastewater and freshwater, respectively. The mean effect of the applied sludge levels independent of the presence of the freshwater or wastewater contributed to the accumulation of heavy metals Cr, Cu, Zn and Mn in soil and in leaves. The soil pollution indices, i.e., pollution load index (PLI), elemental pollution index (EPI), total concentration factor and heavy metal load, showed that the soil had been polluted with heavy metals to a great extent. The application of sludge treatment affected positively the maize plant height, leaf number and the indices PLI and EPI. All pollution indices studied were positively related to plant leaf number and plant height, as well to heavy metal soil content.

In this work, photocatalytic degradation of two reactive dyes, Reactive Yellow 84 (RY 84) and Reactive Black 5 (RB 5), on FeTiO₃/TiO₂ heterojunction in the presence of UV–visible radiation and H₂O₂ has been reported. FeTiO₃/TiO₂ heterojunction has been prepared from ilmenite FeTiO₃ and anatase TiO₂ by employing oxalic acid as an organic linker. FeTiO₃/TiO₂ ratios have been varied from 1 to 5 wt.%, and the materials were characterized by X-ray diffraction, scanning electron microscope and diffused reflectance UV–visible spectroscopic analysis. The photocatalytic activity of FeTiO₃/TiO₂ heterojunction for the degradation of the organic dyes RY 84 and RB 5 in the presence of UV–visible light was found to be higher than that of pure TiO₂. The addition of H₂O₂ increases the rate of degradation of both dyes on FeTiO₃/TiO₂ heterojunction. It facilitates the fast degradation of dye solutions even when their concentration was above 100 mg/l, which is otherwise very slow due to the low transmittance of light by the dye solution. The extent of mineralisation of the reactive dye during photocatalytic degradation was estimated from chemical oxygen demand analysis. FeTiO₃/TiO₂ heterojunction photocatalyst was also found to have good photostability; the material retains almost 97 % of its initial activity even in the fifth cycle.

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.

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.