Textile wastewater was treated by adsorption in batch and column systems using electrochemically modified montmorillonite clay and activated carbon. Textile wastewater was obtained from a denim manufacturing process; according to the characterization of wastewater, non-biodegradable organic matter was found and it limits the application of biological treatments, and then an alternative method was evaluated. The adsorption process was performed with natural and modified materials; iron-modified montmorillonite was prepared at pH 7 using iron electrodes and activated carbon was treated with copper electrodes at pH 2, and 10–12 % of iron and copper respectively were found in the modified materials. Adsorption kinetics and isotherms of chemical oxygen demand (COD), color, and total organic carbon (TOC) were evaluated; the adsorption capacities for color were 50, 37, and 44 U PtCo/g for natural clay, activated carbon, and iron-modified clay, respectively. Adsorption kinetics of COD, color, and TOC data were best adjusted to Elovich model and isotherms data to Freundlich model, indicating chemisorption on heterogeneous materials. The regeneration of materials was performed in the presence and absence of hydrogen peroxide. Continuous systems were evaluated for color and TOC. Fe-modified clay was the best adsorbent, and data were best adjusted to Thomas and Yoon-Nelson models.

Rhodamine B (RhB) is one of synthetic dyes with good stability. Treatment of wastewater containing synthetic dyes has attracted much attention. Heterogeneous activation of peroxymonosulfate (PMS) has been found to be a promising wastewater treatment technology through the activation with metal oxides for the generation of sulfate radicals. In this study, α-MnO₂ was prepared by a simple hydrothermal method and used as the catalyst to activate PMS. The degradation of RhB was studied by the α-MnO₂/PMS system. It was found that the prepared α-MnO₂ exhibited high catalytic activity on the activation of PMS for the degradation of RhB. The degradation of RhB could be well described by the first-order kinetic model. Influences of PMS concentration and α-MnO₂ dose on the degradation of RhB were examined. The chemical oxygen demand (COD) was determined to evaluate the mineralization capability of the α-MnO₂/PMS system. The stability of α-MnO₂ was also investigated through reusability experiments. Quenching tests of radicals were applied to differentiate the contribution of major reactive species for the degradation of RhB by the α-MnO₂/PMS system.

Sorption and desorption of heavy metals (Cd, Cu, Pb, and Zn) was evaluated in biochars derived from sugarcane bagasse (SB), eucalyptus forest residues (CE), castor meal (CM), green coconut pericarp (PC), and water hyacinth (WH) as candidate materials for the treatment of contaminated waters and soils. Solid–liquid distribution coefficients depended strongly on the initial metal concentration, with K d,ₘₐₓ values mostly within the range 10³–10⁴ L kg⁻¹. For all biochars, up to 95 % removal of all the target metals from water was achieved. The WH biochar showed the highest K d,ₘₐₓ values for all the metals, especially Cd and Zn, followed by CE (for Cd and Pb) and PC (for Cd, Pb, and Zn). Sorption data were fitted satisfactorily with Freundlich and linear models (in the latter case, for the low concentration range). The sorption appeared to be controlled by cationic exchange, together with specific surface complexation at low metal concentrations. The low desorption yields, generally less than 5 %, confirmed that the sorption process was largely irreversible and that the biochars could potentially be used in decontamination applications.

Municipal landfill soils are not able to retain heavy metals indefinitely, and these metals can migrate into the groundwater. Environmental contamination induced by toxic metals creates a societal health risk. The objective of this work is to study the ability of landfill soil to retain metals (Pb, Cd, Cu, Fe and Zn). The soil came from the municipal solid waste dump of the City of Yamoussoukro (Côte d’Ivoire). Operating parameters such as thickness of soil, metal concentration and filtered volume were investigated. A factorial experimental design was used to determine which parameters influence the metal retention rate. Thickness of soil and metal concentration were the most important factors influencing metal retention. Using a 2³ factorial matrix, the best performances for metal retention (99.8–100 % removal) were obtained by selecting a thickness of soil of 2.0 cm, an initial metal concentration of 50 mg L⁻¹ and 200 mL of metallic solution. The optimal experimental conditions for metal retention were then investigated using the Excel Solver program. Between 98.9 and 99.9 % of the metals were retained in subsequent experiments using these optimal conditions (soil thickness ranging between 10 and 14 cm and metal concentration of up to 300 mg L⁻¹ in 400 mL of metallic solution).

Nutrition and pollution stress stimulate genetic adaptation in microorganisms and assist in evolution of diverse metabolic pathways for their survival on several complex organic compounds. Persistent organic pollutants (POPs) are highly lipophilic in nature and cause adverse effects to the environment and human health by biomagnification through the food chain. Diverse microorganisms, harboring numerous plasmids and catabolic genes, acclimatize to these environmentally unfavorable conditions by gene duplication, mutational drift, hypermutation, and recombination. Genetic aspects of some major POP catabolic genes such as biphenyl dioxygenase (bph), DDT 2,3-dioxygenase, and angular dioxygenase assist in degradation of biphenyl, organochlorine pesticides, and dioxins/furans, respectively. Microbial metagenome constitutes the largest genetic reservoir with miscellaneous enzymatic activities implicated in degradation. To tap the metabolic potential of microorganisms, recent techniques like sequence and function-based screening and substrate-induced gene expression are proficient in tracing out novel catabolic genes from the entire metagenome for utilization in enhanced biodegradation. The major endeavor of today’s scientific world is to characterize the exact genetic mechanisms of microbes for bioremediation of these toxic compounds by excavating into the uncultured plethora. This review entails the effect of POPs on the environment and involvement of microbial catabolic genes for their removal with the advanced techniques of bioremediation.

Denitrification coupled to anaerobic methane oxidation is a recently discovered process performed by bacteria affiliated to the NC10 phylum. These microorganisms could play important roles in the energy-efficient way of anaerobic wastewater treatment where residual dissolved methane might be removed at the expense of nitrate or nitrite. The difficulty to enrich these microorganisms due to a slow growth rate, especially at low temperatures, limited its application in engineering field. In this study, an NC10 bacteria community was enriched from Taihu sediments by a membrane biofilm bioreactor at ambient temperature of 10–25 °C. After 13 months enrichment, the maximum denitrification rate of the enriched culture reached 0.54 mM day⁻¹ for nitrate and 1.06 mM day⁻¹ for nitrite. Anaerobic methane oxidation coupled denitrification was estimated from the ¹³C-labeled CO₂ (¹³CO₂) production during batch incubations with ¹³CH₄. Furthermore, analysis of 16S rRNA genes clone library confirmed the presence of NC10 phylum bacteria and fluorescence in situ hybridization showed that NC10 bacteria dominated the reactor. All of the results indicated the NC10 bacteria community was competitive in terms of treating nitrate-contaminated water or wastewater under natural conditions.

The degradation of two pesticides, carbofuran (CBF) and ioprodine (IPR), was studied by the photolytic decomposition of hydrogen peroxide (UV/H₂O₂). The influence of two experimental parameters, H₂O₂ concentration and initial pH, as well as their interactions, was investigated. Optimization was carried out where experimental parameters were determined for the treatment of each pesticide. Both pesticides were totally eliminated by UV/H₂O₂ system under optimal conditions. However, significant differences were found: CBF degradation was influenced by both parameters and their interactions, while IPR degradation was not statistically affected by initial pH. Interestingly, analysis of degradation pathways showed a major influence of photolysis process and oxidation due to hydrogen peroxide for the CBF degradation, while the synergistic combination between both of them played the most relevant role during IPR degradation. A mixture of both pesticides was also submitted to UV/H₂O₂ action in which a lower rate was observed for IPR elimination while CBF was not affected. A 90 % of chemical oxygen demand (COD) was removed and 75 % of mineralization was achieved after the treatment of the mixture. Almost 92 % of the toxicity was eliminated making this technique a promising process to treat toxic mixtures of these pesticides.

Information on the phytotoxicity of nanoparticles (NPs) at low concentrations (e.g., ppb to low ppm) is scarce. Therefore, this study was conducted to assess the effects of laboratory-prepared Cu, Zn, Mn, and Fe oxide NPs in low concentrations (<50 ppm) on the germination of lettuce (Lactuca sativa) seeds in a water medium. The data showed that CuO NPs were slightly more toxic than Cu ions while the toxicity of ZnO NPs was similar to that of Zn ions, and MnOx NPs and FeOx NPs were not only less toxic than their ionic counterparts but also significantly stimulated the growth of lettuce seedlings by 12–54 %. This study showed that manufactured NPs were not always more toxic than other chemical species containing the same elements. Instead, Mn or Fe NPs can significantly enhance plant growth and have the potential to be effective nanofertilizers for increasing agronomic productivity.

Triclosan is an antimicrobial agent which is frequently found in the aquatic environment. Photolysis is an important transformation pathway for triclosan in surface water. Though a lot of studies have been conducted on the toxicity of triclosan, few of them focused on the ecological risk of the mixture after sunlight irradiation. The aim of the present study was to investigate the potential toxicity of triclosan under light irradiation and the influence of the coexisting humic acid by bioassay. Photo-induced acute toxicity and genetic toxicity were observed in the triclosan solutions after 24 h of light irradiation. The addition of humic acid at the concentration of 1 and 5 mg/L both resulted in a significant decrease (p < 0.05) in the photo-induced toxicity of triclosan. It is suggested that the photo-transformation process and the influence of humic acid should be considered for the ecological risk assessment of triclosan in surface water since humic acid is ubiquitous in natural water.

The study of the time series from the township of Campo Grande in the State of Mato Grosso do Sul (from January 2004 to 31 December 2010) is presented. Various statistical methods were used for the data analysis. Using robust statistics, very pronounced skewness of the ozone volume part distribution during each month of the year was obtained. The variability in data is the largest during a month of September. The average annual values have asymmetrical distribution of the ozone volume fraction. Within the measured period, these averages are between 15 and 20 ppb. Particularly pronounced ozone distribution asymmetry throughout the year 2007 could be explained by observing meteorological parameters. Principal component analysis (PCA) presented here clearly shows that air temperature and wind speed are contributing factors in ozone formation, while relative humidity and atmospheric pressure cause the decrease in the ozone volume fraction in the air. Further, the hierarchical cluster analysis (CA) was performed for meteorological and ozone data using the Ward’s methods. The correlation between ozone and the effective temperature index (TEv) showed a development of the ozone with high temperature of air. From the Pearson’s correlation coefficients, it is clear that the relative humidity and the air temperature have a negative effect on respiratory system, causing respiratory illnesses.