In the present study, response surface methodology (RSM) was applied to maximize As(V) removal from aqueous solutions by using modified magnetic nanoparticles with ascorbic acid (AA-MNPs). The structural features of the produced material were characterized by means of X-ray diffraction (XRD), N₂ adsorption–desorption, Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). More specifically, the effects of pH, temperature, arsenic ion concentration, and sorbent dosage were investigated on the arsenic adsorption. A total of 20 sets of experiments were designed by the software to achieve maximum adsorption capacity (q ₑ) and removal efficiency (R). Analysis of variance (ANOVA) of the two-factor interaction (2FI) model suggested that the predicted values were in good agreement with experimental data. The best local maximum values for pH, arsenic concentration, and sorbent dosage were found to be 2, 5 mg L⁻¹, and 0.1 g L⁻¹, respectively, that yielding maximum q ₑ of 44.99 mg g⁻¹ and a maximum R of 42.69 %. Additionally, the obtained value for desirability was equal to 0.862. The results indicated that the Langmuir model provided the best correlation of the equilibrium data. Moreover, the obtained results revealed that the pseudo-second-order kinetic model could best describe the adsorption kinetics.

This study investigates the importance of the organic matter characteristics of several organic amendments (i.e., buffalo manure, food and kitchen waste, fruit and vegetables waste, and activated sewage sludge) and their influence in the bioremediation of a polycyclic aromatic hydrocarbons (PAH)-contaminated soil. The removal of low molecular weights (LMW) and high molecular weights (HMW) PAHs was monitored in four bioremediation reactors and used as an indicator of the role of organic amendments in contaminant removal. The total initial concentration of LMW PAHs was 234 mg kg⁻¹ soil (dry weight), while the amount for HMW PAHs was 422 mg kg⁻¹ soil (dry weight). Monitoring of operational parameters and chemical analysis was performed during 20 weeks. The concentrations of LMW PAH residues in soil were significantly lower in reactors that displayed a mesophilic phase, i.e., 11 and 15 %, compared to reactors that displayed a thermophilic phase, i.e., 29 and 31 %. Residual HMW PAHs were up to five times higher compared to residual LMW PAHs, depending on the reactor. This demonstrated that the amount of added organic matter and macronutrients such as nitrogen and phosphorus, the biochemical organic compound classes (mostly soluble fraction and proteins), and the operational temperature are important factors affecting the overall efficiency of bioremediation. On that basis, this study shows that characterization of biochemical families could contribute to a better understanding of the effects of organic amendments and clarify their different efficiency during a bioremediation process of PAH-contaminated soil.

In the present work, the synthesized calcium carbonate (CaCO₃) identified as fusiform aragonite was obtained through the biomimetic mineralization process for possible recovery of high concentration of phosphorus (P) within the wide range of pH. It was characterized before/after phosphate sorption by the combination of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray absorption near-edge structure (XANES) at molecular level. By batch experiments, the sorption isotherms and envelopes of the fusiform aragonite to phosphate were explored. The experimental data showed that the fusiform aragonite at pH ≥6.0 has a steep raising sorption capacity with increasing initial P (>9.0 mM) due to its unique crystalline structure and morphology. The likely mechanism is that the occurrence of fast nucleation growth of Ca-P phases (including amorphous calcium phosphate (ACP), dibasic calcium phosphate (DCP), and hydroxyapatite (HAP)) is triggered upon attainment of the stabilized crystal morphology of aragonite in solution due to phosphate sorption. These features may contribute to the fusiform aragonite as an idea adsorbent for high phosphate removal from wastewater even independent of pH.

Phytotoxic effects of a single heavy metal on different crops are widely reported; however, consequences of combined metal toxicity on maize are rarely investigated. In this study, a pot experiment was conducted to assess the phytotoxic effects both Al and Cr on morphophysiological and biochemical traits, photosynthetic gas exchange capacities, metal uptake, and translocation in different plant parts. Plants were exposed to Al³⁺ (100 μM), Cr⁶⁺ (100 μM), and Al³⁺ + Cr⁶⁺ (100 + 100 μM), and data were collected at pre- and post-silking stages while uncontaminated pots were served as control (Ck). Results depicted that both Al and Cr impaired maize growth and yield response and inhibited photosynthesis and gas exchange attributes i.e., transpiration, stomatal conductance, inter-cellular CO₂, as well as water use efficiency (WUE) and intrinsic water use efficiency (WUEi). Moreover, Al and Cr toxicities caused lipid peroxidation and membrane damage while activated antioxidative defense system in terms of superoxide dismutase (SOD), peroxidaes (POD), and catalase (CAT) and mediated reduced glutathione contents (GSH). Increased proline and reduced protein contents were also observed with a combined metal toxicity. Interestingly, Cr proved to be more toxic than Al whereas affects were more apparent where both Al and Cr were applied simultaneously. Plant exposure to both Al and Cr increased metal contents in different plant parts, while maximum metal contents were recorded in roots followed by stem, leaves, corn ear, and grains. Overall severity in phytotoxic effects was observed as Al+Cr > Cr > Al > Ck. Additionally, values of combined application of both Al + Cr were higher than those of the linear sum of Al and Cr alone, suggesting that synergistic effects of Al + Cr were more toxic than their individual effects. Hence, combined metal toxicity proved more damaging for maize than individual metal stress.

An in situ post tsunami study was conducted to assess the effect of water management and rainfalls in soil properties and water quality at a low-lying coastal area of central Chile affected by Mw8.8 Earthquake Tsunami the night of 27 February 2010. Soil samples were taken at two depths (0 to 20 and 20 to 40 cm) during 2010 and late 2012. Water quality in a local shallow well was also monitored in 2010 and 2012. High soil salinity was recorded 2 months later than tsunami occurs, closely associated to water-soluble chloride and cations (Cl⁻ > > Na⁺ > > Ca²⁺ > Mg²⁺ > K⁺), ionic toxicities, and vegetal inhibition (Vasconcellea pubescens) by less available water to plants. An initial reduction in soil pH due to ionic strength and coarse-textured class of soil was observed and the sodium adsorption ratio (SAR) in soil varied between 5.7 and 11.2 (mmol L⁻¹)⁰.⁵ showing to be saline. Although SARw values are very high (>18 (mmol L⁻¹)⁰.⁵), it does not exist risks of reduction on soil infiltration rates according to ECw (>5 dS m⁻¹) obtained. After 2 years, soil salinity was drastically reduced in the affected areas due to high soil permeability and natural attenuation (rainfalls and leaching effects), with sulfate and bicarbonate concentrations showing excessive values. Further, irrigation water quality returned to pre-tsunami situation, with only levels of sodium slightly exceeding desirable range from health point of view. Finally, it is suggested a proper design of irrigation systems before implementing other management practices.

The aim of this 2-year study was to examine the temporal changes in the concentration of microbiological indicators of water contamination and selected physicochemical parameters within the Białka river and its selected tributaries in the vicinity of the largest ski station in Białka Tatrzańska. The study involved 24 series of sampling in eight sites throughout the Białka river and on its selected tributaries. Temperature, pH, and electrical conductivity (EC₂₅ °C) were measured onsite. The microbiological assays included the numbers of mesophilic and psychrophilic bacteria, Staphylococcus spp. and Salmonella spp., as well as coliforms, thermotolerant (fecal) coliforms, Escherichia coli, Enterococcus faecalis, and sulfate-reducing Clostridium. The chemical analyses were conducted to determine the concentration of NH₄ ⁺, NO₂ ⁻, NO₃ ⁻, and PO₄ ³⁻. The analyses showed that contrary to common opinion, waters of the Białka river are strongly polluted in some sections. Seasonal variation in the prevalence of microbial indicators of fecal pollution was found, and the largest numbers of microorganisms were observed in winter ski season, followed by summer holidays. Similar seasonal pattern was observed in the examined chemical parameters. There was also very strong spatial variation within the tested microbial and chemical parameters, indicating the presence of pollution hotspots in the course of the Białka river. The employed principal component analysis revealed the presence of two main pollution sources, mainly affecting the quality of river water, i.e., fecal contamination of human origin and the natural source in the form of surface runoff and soil leaching. These factors, depending on the location of the sampling site, occurred in different configurations.

Impacts of subsurface biogeochemical processes over time have always been a concern for the long-term performance of zero valent iron (Fe⁰)-based permeable reactive barriers (PRBs). To evaluate the biogeochemical impacts, laboratory experiments were performed using flow-through glass columns for 210 days at controlled temperature (20 °C). Two different particle sizes of Fe⁰ were used in the columns, and to simulate indigenous microbial activity, extra carbon source was provided in the two columns (biotic columns) and the remaining two columns were kept abiotic using gamma radiations. Heavy metals (Zn, As) were removed efficiently in all the columns, and no exhaustion of treatment capability or clogging was observed during our experimental duration. Newly formed Fe mineral phases and precipitates were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and micro-XRF techniques in solid phase at the end of the experiment. In addition, 16S rRNA gene extraction was used for microbial community identification in biotic columns. During the incubation, microbial population shifted in favor of Desulfosporosinus species (sulfate-reducing bacteria) from initial dominance of Acidithiobacillus ferrooxidans in sediments. Dominant mineral phases detected in biotic columns were mackinawite (FeS) and sulfate green rust, while in abiotic columns, magnetite/maghemite phases were more prevalent.

It is important to understand the fate of Hg and Sb within the wastewater treatment process so as to examine potential treatment options and to ensure compliance with regulatory standards. The fate of Hg and Sb was investigated for an activated sludge process treatment works in the UK. Relatively high crude values (Hg 0.092 μg/L, Sb 1.73 μg/L) were observed at the works, whilst low removal rates within the primary (Hg 52.2 %, Sb 16.3 %) and secondary treatment stages (Hg 29.5 %, Sb −28.9 %) resulted in final effluent concentrations of 0.031 μg/L for Hg and 2.04 μg/L for Sb. Removal of Hg was positively correlated with suspended solids (SS) and chemical oxygen demand (COD) removal, whilst Sb was negatively correlated. Elevated final effluent Sb concentrations compared with crude values were postulated and were suggested to result from Sb present in returned sludge liquors. Kepner Tregoe (KT) analysis was applied to identify suitable treatment technologies. For Hg, chemical techniques (specifically precipitation) were found to be the most suitable whilst for Sb, adsorption (using granulated ferric hydroxide) was deemed most appropriate. Operational solutions, such as lengthening hydraulic retention time, and treatment technologies deployed on sludge liquors were also reviewed but were not feasible for implementation at the works.

Present technologies for wastewater treatment do not sufficiently address the increasing pollution situation of receiving water bodies, especially with the growing use of personal care products and pharmaceuticals (PPCP) in the private household and health sector. The relevance of addressing this problem of organic pollutants was taken into account by the Directive 2013/39/EU that introduced (i) the quality evaluation of aquatic compartments, (ii) the polluter pays principle, (iii) the need for innovative and affordable wastewater treatment technologies, and (iv) the identification of pollution causes including a list of principal compounds to be monitored. In addition, a watch list of 10 other substances was recently defined by Decision 2015/495 on March 20, 2015. This list contains, among several recalcitrant chemicals, the painkiller diclofenac and the hormones 17β-estradiol and 17α-ethinylestradiol. Although some modern approaches for their removal exist, such as advanced oxidation processes (AOPs), retrofitting most wastewater treatment plants with AOPs will not be acceptable as consistent investment at reasonable operational cost. Additionally, by-product and transformation product formation has to be considered. The same is true for membrane-based technologies (nanofiltration, reversed osmosis) despite of the incredible progress that has been made during recent years, because these systems lead to higher operation costs (mainly due to higher energy consumption) so that the majority of communities will not easily accept them. Advanced technologies in wastewater treatment like membrane bioreactors (MBR) that integrate biological degradation of organic matter with membrane filtration have proven a more complete elimination of emerging pollutants in a rather cost- and labor-intensive technology. Still, most of the presently applied methods are incapable of removing critical compounds completely. In this opinion paper, the state of the art of European WWTPs is reflected, and capacities of single methods are described. Furthermore, the need for analytical standards, risk assessment, and economic planning is stressed. The survey results in the conclusion that combinations of different conventional and advanced technologies including biological and plant-based strategies seem to be most promising to solve the burning problem of polluting our environment with hazardous emerging xenobiotics.