This paper presents the results of a study on mercury distribution in urban wells from the town of Almadén (central Spain), a site that not only hosted the world’s largest mercury mine but also a large roasting plant for cinnabar (HgS). The study includes data on Hg contents in the underground waters and also quality and physical-chemical parameters such as pH, conductivity, oxidation-reduction potential (ORP), dissolved oxygen, and water temperature from 27 wells and 2 monitoring drill holes. An important proportion of the wells (16 %) display Hg concentrations above the European Union Commission (EUC) and Spanish threshold (at 1 μg L⁻¹) and only 10 % exceeded the US EPA recommendation (at 2 μg L⁻¹). As expected, the highest concentrations of dissolved and total Hg are found in wells near to the mine. Hydrochemical water types depend on geogenic and anthropogenic factors, for example, higher mercury concentrations are linked to water-rock interactions (e.g., oxidation, leaching) in sectors where soluble mercury compounds have formed. Hg concentrations show a decrease from 2013 to 2015, a fact that may be due to the encapsulation of the main calcines waste dump or to dilution effects related to strong rainfall events previous to the sampling survey.

In this study, the fruit of Catalpa bignonioides was used as the raw material to obtain low-cost activated carbon. The activation process was carried out by using chemical activation method with zinc chloride. Catalpa activated carbon (CAC) was characterized using elemental analyzer, Brunauer-Emmet-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and the point of zero charge (pHZPC). The BET surface area of CAC prepared by the impregnation ratio of 30 % ZnCl₂ (w/w) was found to be 896.02 m²/g. The efficiency in the process of the removal of methylene blue (MB) from aqueous solution by CAC was searched with different factors, such as temperature, pH, adsorbent concentration, dye concentration, and contact time. From the experimental data obtained, the studies related to adsorption isotherm, kinetics, and thermodynamics were performed. Langmuir model provided the best fit, and the adsorption capacity for the removal of methylene blue from aqueous solution by CAC was calculated to be 271.00 mg/g at 25 °C. The adsorption follows a pseudo-second-order kinetic model. Moreover, the thermodynamic parameters such as ΔG°, ΔH°, and ΔS° presented that the adsorption was spontaneous and endothermic.

The Rio Santiago in the Cordillera Negra of Peru is severely contaminated by acid mine drainage in its headwaters. In a strongly acid stream, at about 3800 m above sea level (masl), microterraces were found with terrace walls built up of dead moss, with encrustations and interstitial fine, creamy sediment. The stream water was turbid due to the presence of similar suspended sediment, which also occurred as a thin basal layer in inter-rim basins. The moss was identified as the rare bryophyte Anomobryum prostratum (Müll. Hal.) Besch. Chemical and mineralogical analyses show that green, living parts of the moss are gradually coated by Al/Fe (hydr)oxides, inducing their senescence and death. The necromass is covered by creamy crusts through precipitation of schwertmannite-type material from the stream water and simultaneous ‘capture’ of fine sediment. The latter consists of a mixture of precipitate and fine detrital primary minerals. These processes are held responsible for the formation of the microterraces, which regarding their composition and environment seem to be unique. Remarkable is the high As content of the creamy crusts and sediment, attributed to strong sorption of As, whereas its solute concentration is relatively low. This calls for more attention to suspended fine sediment in the assessment of environmental risks of stream water use. Lastly, the results raise serious doubts about the use of aquatic bryophytes as bioindicator for chemical pollution in acid mine drainage-polluted streams.

Sugarcane molasses, which is a kind of microbial carbon source, is a viscous by-product of the refining of sugarcane into sugar. However, experiments were designed to ascertain the mechanism and kinetics of Cr(VI) reduction with sugarcane molasses without adding microbes in aqueous solution. Results indicated that sugarcane molasses can reduce Cr(VI) to Cr(III) at pH values that range from 2.0 to 6.1 when no bioreduction occurs in the reaction. Furthermore, the reaction mechanism was proven to be that Cr(VI) acts as an electrophile that readily accepts electrons from the phenolic hydroxyl group of plant polyphenol, and it is then reduced to Cr(III) and in the process oxidizes the phenolic hydroxyl group to a quinone. Meanwhile, the reaction could be described by the pseudo-first-order kinetic model with respect to Cr(VI) concentration. The reaction rate constants were 324.2, 65.9, 21.9, and 14.4 h⁻¹ when pH values were 2.0, 3.5, 5.0, and 6.1, respectively, at 20 °C. The k ₒbₛ increased 3.36, 7.02, and 13.48 times with the temperature adjusted from 5 to 10, 20, and 30 °C.

Although recent studies show that the iron oxides do not enter or accumulate in plants, they may preclude the transport of water and nutrients in the plants through/as a consequence of their aggregation on the surface of the roots. The feasibility of using iron oxide nanoparticles to modify the availability of trace elements (TEs) to Helianthus annuus in the soil as well as their interference with the plant response during an imposed water deficiency stress were studied in a pot experiment. Plants were grown in a compost pre-amended contaminated soil with and without nano-maghemite (NM) and later exposed to drought. The nano-amendment promoted the growth of H. annuus (higher (25 %) dry weight than in the same soil without NM), mainly due to the insolubilisation of pore water Zn in the soil and the consequent reduction of its availability to the plants. During the water stress, NM did not cause an increase in the accumulation of proline or total amino acids in the plants, which are normally used as drought stress indicators, compared to the control plants without NM. In conclusion, NM could be useful soil amendments during phytoremediation procedures, since it can immobilise TEs in the soil without disrupting the plant water balance.

Paris conurbation is a heavily urbanized but weakly industrialized catchment. Recently, it has been shown at the scale of Paris that alkylphenols (AP) and phthalates (PAE) are not rejected by the industry, but they originate from domestic wastewater at more than 95 %. However, the contribution of the different types of greywater to the pollution by alkylphenols and phthalates was not addressed. This work aims at providing new insights on this particular point. Hence, the concentration of four phthalates (diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), benzyl butyl phthalate (BBP), and di(2-ethylhexyl)phthalate (DEHP)) and two alkylphenols (octylphenols (OP) and isomers of nonylphenol (NP)) were followed in greywater. For each sample, analyses were carried out on both the dissolved and particulate phases. Moreover, water quality parameters were also monitored, in order to find out whether or not any correlation exists between the concentration of the investigated contaminants and the quality of water. Water quality parameters studied are pH, total suspended solids (TSS), dissolved and particular organic carbon (DOC and POC), chemical and biochemical oxygen demands (COD and BOD5), total Kjeldahl nitrogen (TKN), and anionic detergents (methylene blue active substance or MBAS). This paper presents the methodology used to monitor two greywater with the most important volumes: showers and washing machines. These greywater showed high variability with regard to water quality parameters. Moreover, AP and PAE concentrations are given for the first time for these two types of greywater. All compounds except OP were observed in almost all samples in at least one of the two monitored phases. The concentrations varied between limit of quantification for OP and 102 μg/l for DEHP. The levels measured in washing machines were higher than those for showers for all compounds. For instance, median NP concentration in washing machines was 3.59 μg/l against 1.09 μg/l in showers, DEHP was observed at 102 μg/l in washing machines against 16.6 μg/l in showers. Variability of the results was explained by habits of individuals (shower time, number of products used…) but also by differences in product composition. However, each type of water exhibited the same distribution. NP was the most abundant AP (about 85 % of the total amount) while DEHP represented the two thirds of the PAE compounds. The partition coefficients (Kd in l/kg) were evaluated. The results showed that log Kd ranged between 2.1 (DEP) and 4.8 (DEHP). Log Koc presented similar trends lying in the 2.4 (DEP)-5.0 (DEHP) range. Finally, with regard to greywater quality, the application for greywater reuse is discussed.

Natural zeolitic tuff was modified with FeCl₃solution for the removal of fluoride, and the effect of chloride, nitrate, and sulfate ions was examined on fluoride sorption from solutions and drinking water. The unmodified zeolitic tuff (Z) and the iron-modified zeolitic tuff (Fe(III)-Z) were characterized by scanning electron microscopy and X-ray diffraction analysis. The elemental composition, the specific surface area, and the point of zero charge of the zeolitic material were also determined. The fluoride adsorption was carried out in a batch system considering the effect of contact time, the initial concentration of fluoride ions, and the effect of other anions naturally present in the drinking water. The kinetic and isotherm results were adjusted to the pseudo-second-order and Freundlich models, respectively, which indicated that the sorption mechanism was chemisorption on a heterogeneous material. The fluoride sorption capacity was higher in solutions (2.7 mg/g) than in drinking water (0.41 mg/g), and this could be attributed to the presence of other anions. Overall, the presence of chloride ions significantly diminished the fluoride adsorption capacity, while the presence of nitrate and sulfate ions did not show any significant effect; the anion removal efficiency by Fe(III)-Z followed the order F⁻ > > Cl⁻ > NO₃⁻ > SO₄²⁻.

This study evaluated the behavior of a sequencing batch reactor (SBR) at laboratory-scale in removing the emerging contaminants, ibuprofen (IBP) and methylparaben (MPB), at different concentrations. Individual experiments were carried out for each pollutant and they were divided into six stages of operation, which included starting, load variation, and interim periods of system stabilization. The treated wastewater was synthetic, and it included the pollutions MPB or IBP, glucose as a co-substrate, macronutrients, and micronutrients. The inoculum used to start the reactor was an aerobic sludge from an SBR system used in the treatment of domestic wastewater, which presented with high-content organic material and featured good sedimentation characteristics. The removal percentages of the two compounds at concentrations of 300, 500, and 1000 μg/L were not similar. For MPB, high removal percentages (>96 %) were obtained, while for IBP, decreasing removal percentages were found with increases in analyte concentration, exhibiting average values of 51 ± 15.3, 26 ± 16.6, and 16 ± 5.4 %. Following the removal of IBP, this behavior showed pronounced effects in biomass inhibition during exposure to high concentrations of the pollutant.

The anaerobic biodegradability of combined microwave-ultrasonic pretreated thickened excess activated sludge (PTEAS) mixed with raw primary sludge (PS) was investigated in this study. The pretreatment resulted in the enhancement of mesophilic anaerobic digester performance which in turn improved biogas production capacity and quality, total and volatile solid reduction, dewaterability, protein solubilisation and significant reduction of pathogens to produce class A biosolid. This study presented the results of two continuously stirred mesophilic anaerobic digesters charged with various proportions of a mixture of PTEAS and PS similar to the large-scale industrial practice. Digester 1 was charged with 75 % PTEAS and 25 % PS, while digester 2 was fed with 25 % PTEAS and 75 % PS. The methane production was 122 mL CH₄/g total chemical oxygen demand for digester 2 after 20 days of anaerobic digestion. This amount further increased for both digesters with digestion time. The biogas quality in terms of methane to carbondioxide ratio (CH₄/CO₂) was significantly improved for digester 1 compared with digester 2 after 20 days of digestion. Volatile solid reduction of 76 and 57 % was achieved for digester 1 and digester 2 respectively after the same 20 days of digestion. The CH₄/CO₂ ratio reached 2.2:1 and 1.1:1 after 20 days of digestion for digester 1 and digester 2, respectively. Higher percentage of PTEAS increases the digestion kinetics, the methane production capacity and the biogas quality. Furthermore, total coliform reduction of 84 and 44 % was achieved for digester 1 and digester 2 respectively after 22 days of digestion. Hydrolysis rate and biochemical methane production were improved for both digesters based on the results of Gompertz kinetic model and the hydrolysis rate constants as determined by model fitting of the experimental data.

In the European registration procedure for pesticides, microcosm and mesocosm studies are the highest aquatic experimental tier to assess their environmental effects. Evaluations of microcosm/mesocosm studies rely heavily on no observed effect concentrations (NOECs) calculated for different population-level endpoints. Ideally, a power analysis should be reported for the concentration–response relationships underlying these NOECs, as well as for measurement endpoints for which significant effects cannot be demonstrated. An indication of this statistical power can be provided a posteriori by calculated minimum detectable differences (MDDs). The MDD defines the difference between the means of a treatment and the control that must exist to detect a statistically significant effect. The aim of this paper is to expand on the Aquatic Guidance Document recently published by the European Food Safety Authority (EFSA) and to propose a procedure to report and evaluate NOECs and related MDDs in a harmonised way. In addition, decision schemes are provided on how MDDs can be used to assess the reliability of microcosm/mesocosm studies and for the derivation of effect classes used to derive regulatory acceptable concentrations. Furthermore, examples are presented to show how MDDs can be reduced by optimising experimental design and sampling techniques.