In many parts of the world, fluoride in drinking water is responsible for notable public health issues. The present study is aimed to prepare a new adsorbent magnesia-hydroxyapatite (Mg-HAP) that can serve as a valuable defluoridating agent. Characterization of the synthesized adsorbent was done by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscope (TEM), and Scanning electron microscope (SEM)/Energy-dispersive X-ray spectroscopy (EDX) analysis to reveal the bonding patterns, phase characteristics, and microstructural and morphological details. The influences of pH, adsorbent dose, contact time, and initial fluoride concentration and the effect of interfering anions were studied. The defluoridation capacity was evaluated to be 1.4 mg/g, and the adsorbent showed very good capability to remove fluoride from contaminated water over a wide range of pH. Equilibrium modeling was done, and the experimental data was fitted into Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms. Study of the kinetic data for the adsorption process revealed that it follows pseudo-second-order reaction. It also indicated that the intraparticle diffusion contributes to the rate-determining step in the process. The quality of treated water was analyzed for total dissolved solids (TDS), turbidity, residual calcium, residual phosphorus content, electrical conductivity, hardness, and total alkalinity. The results obtained were very promising and confirmed the prospects of usage of Mg-HAP in defluoridation of drinking water.

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 aim of this study is to use a range of statistical tools to assess particulate matter less than 10 μm (PM₁₀) in the atmosphere that has been measured daily at five locations in South Australia over a 7-year period. We consider a wind rose model to provide a graphical display of the frequency distribution of wind speed to explore the role of PM₁₀ accumulation over time. A generalised least squares technique with a first-order autoregressive model was applied to the realisation of average changes in PM₁₀, and these were assessed at the 5 % significance level. This study found the change in variability of PM₁₀ concentration over time. The pre-whitened PM₁₀ series were considered as realisations of white noise using correlogram plots. Furthermore, a robust regression technique involving wet (>0.5-mm rainfall) and dry properties (<0.5-mm rainfall) was used to assess the influence of rainfall on PM₁₀ distributions for the city of Adelaide.

The levels and composition of particulate matter in Ash Meadows National Wildlife Refuge (NWR) that hosts the only population of the endangered Devil’s Hole pupfish (Cyprinodon diabolis) were examined to obtain baseline air quality information. PM₁₀ and PM₂.₅ mass concentrations were measured using continuous monitors over a period of 12 months. In addition, integrated PM₁₀ and PM₂.₅ filter samples were collected and a subset chemically analyzed for elements, ions, elemental carbon, and organic carbon. The average filter-based PM₁₀ (10.9 μg m⁻³) and PM₂.₅ (5.1 μg m⁻³) levels at Ash Meadows NWR are similar to those previously measured at rural and continental background sites in the southwestern USA. Mineral dust accounted for the largest percentage of aerosol mass, with the highest concentrations being measured during fall months of 2009. Elemental and organic carbon levels were generally low, except for August 29, 2009. During this event, transport of wildfire smoke was suggested, by the passage of air masses over wildfires in California, Utah, and Arizona. Ammonium sulfate varied with season, with the highest concentrations in spring and the lowest in fall and winter. Halite (NaCl) quantities were very low, except for the filter samples collected during a windy period on October 4, 2009 indicating the possible contribution of alkaline playa dust upwind of the site. Above average concentrations of crustal calcium compounds, including carbonates and gypsum, were measured in the PM₁₀ sample collected on November 9, 2009 as well as the two preceding months, ascribed to wind-driven dusty conditions prevailing throughout the late summer and fall of 2009.

Nutrient enrichment is considered one of the most important causes for summer hypoxic conditions in the northern Gulf of Mexico (NGOM) off the Louisiana coast. While many studies on nutrient inputs from the large Mississippi-Atchafalaya River System have been conducted, little is known about nutrient inputs from other coastal rivers in Louisiana. In this study, we utilized long-term (1980–2009) records on river discharge and nutrient concentrations of four major Louisiana coastal rivers—the Sabine, Calcasieu, Mermentau, and Vermilion—to estimate daily, monthly, and annual inflows of nitrate and nitrite nitrogen (NO₃ + NO₂), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) into the NGOM. The three-decade-long nutrient inflows from these rivers were analyzed for their seasonal fluctuations, interannual variabilities, and decadal trends. Fluxes of NO₃ + NO₂, TKN, and TP for these river basins were estimated to assess land use effects on riverine nutrients. Our study found that the four coastal rivers discharged each year a considerably large amount of NO₃ + NO₂ (total of 1755 t), TKN (12,208 t), and TP (1833 t) into the NGOM, with a peak input of nitrogen during the spring. The Mermentau and Vermilion Rivers, which drain intensive agriculture areas, had significantly higher NO₃ + NO₂, TKN, and TP concentrations when compared with the Sabine and Calcasieu Rivers, which drain forest-pasture-dominated lands. The fluxes of NO₃ + NO₂, TKN, and TP from the Mermentau River Basin (156 kg km⁻² year⁻¹ NO₃ + NO₂, 942 kg km⁻² year⁻¹ TKN, and 206 kg km⁻² year⁻¹ TP) and the Vermilion River Basin (374, 1078, and 360) were much higher than those combined from the Sabine and Calcasieu River Basins (66, 710, and 62). These findings fill a major knowledge gap concerning the quantity and characteristics of nitrogen and phosphorus transport from coastal watersheds to North America’s largest hypoxic zone.

The textile industry creates environmental problems due to the release of highly polluting effluents containing substances from different stages of dyeing that are resistant to light, water, and various chemicals, and most of them are difficult to decolorize because of its synthetic origin. The biological degradation of dyes is an economical and environmentally friendly alternative. The aim of this work was to use biofilms of basidiomycete fungi isolated from the Peruvian rainforest for the decolorization of synthetic reactive dyes, considering the advantages of these systems which include better contact with the surrounding medium, resistance to chemical and physical stress, and higher metabolic activity. Among several isolates, two were selected for their capacity of rapid decolorization of several dyes and their biofilm-forming ability. These strains were molecularly identified as Trametes polyzona LMB-TM5 and Ceriporia sp. LMB-TM1 and used in biofilm cultivation for the decolorization of six reactive dyes and textile effluents. Azo dyes were moderately decolorized by both strains, but Remazol Brilliant Blue R (anthraquinone) and Synozol Turquoise Blue HF-G (phthalocyanine) were highly decolorized (97 and 80 %, respectively) by T. polyzona LMB-TM5. Degradation products were found by HPLC analysis. Simulated effluents made of a mixture of six dyes were moderately decolorized by both strains, but a real textile effluent was highly (93 %) decolorized by T. polyzona LMB-TM5. In summary, T. polyzona LMB-TM5 was more efficient than Ceriporia sp. LMB-TM1 for the decolorization of textile dyes and effluents at high initial rates enabling the development of in-plant continuous biofilm processes.

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.

The aim of this study was to investigate the synergistic effects of the process of iron-carbon microelectrolysis (ICME) followed by struvite (MAP) crystallization on treating antibiotic wastewater. Characteristics of ICME effluent depended mainly on the iron to carbon mass ratio (Fe/C). The optimum reaction conditions of Fe/C ratio of 2:1 and reaction time of 90 min were observed. The ICME effluent was further treated by MAP crystallization using Na₂HPO₄·12H₂O and MgCl₂·6H₂O as precipitation agents. The results showed that, the Mg²⁺/NH₄ ⁺-N/PO₄ ³⁻-P molar ratio of 1:1:1 and pH 8.5, were suitable for the crystallization process, which could obtain high-quality MAP containing 5.18 % N,10.23 % Mg, and 13.83 % P. Optimal total removal rate of COD and NH₄ ⁺-N removal rate achieved 84.6 and 89.9 %, respectively. The economic evaluation of NH₄ ⁺-N recovery by the synergistic process was also conducted, indicating that the synergistic process had the potential to benefit COD emission reduction and nitrogen recovery. Graphical Abstract The aim of this study was to investigate the effects of treating antibiotic wastewater using iron and carbon combined process of microelectrolysis and struvite (MAP) crystallization. The MAP was of high purity and good crystal morphology, which could be used as a slow-release fertilizer.

After alkaline hydrothermal conversion of volcanic tephra to zeolite (VT-Z) particles, calcium ion cross-linked alginate-zeolite composites (VT-Z/CA) were subsequently fabricated as sorbents for enhancing removal of Cu(II) ions from aqueous solution. The naturally occurring VT minerals were used as silica and alumina sources for zeolite crystallization. The conversion conditions were optimized by altering the alkaline concentration, conversion time, temperature and addition of ethanol. After the synthesized VT-Z particles were entrapped into CA biopolymer template, the developed VT-Z/CA composites not only make full use of the excellent adsorption capabilities of zeolites but also prevent the major problems of mobility/agglomeration for zeolite particles in aqueous media. The VT-Z/CA composites were characterized and studied for aqueous removal of Cu(II) ions in a batch mode. Solution pH 5.5 was found to be the best choice. The kinetic data were evaluated by the pseudo-first, pseudo-second order, and Elovich model. The adsorption kinetics followed the pseudo-first model. Langmuir isotherm best described the adsorption behavior with the maximum adsorption capacity for Cu(II) at 121.1 mg g⁻¹ (45 °C). The composites were successfully explored for treatment of Cu(II)-bearing livestock farm wastewater in China. The VT-Z/CA composites offer a highly attractive alternative for remediating heavy metal contaminated water with advantages of being easy to operate, cost-effective, biodegradable, and environmentally benign.

We have conducted an interlaboratory comparison study for total mercury and methylmercury analysis in natural (unspiked) water samples annually for the past 4 years. The samples were primarily freshwater, with the exception of one coastal seawater sample in 2014. The study provided participants with an opportunity to assess the quality of their measurements and the intercomparability of their data with their peers. Data on analytical methods used were collected and used to determine whether any methods yield biased results and should be discontinued. The majority of participants received performance scores of 3 or higher, indicating satisfactory performance and results close to the consensus means. However, the coefficients of variation between labs were greater than 20 % in most cases, which may not be sufficiently precise for multilaboratory environmental research, where the processes being studied may vary by 20 % or less. Total mercury analysis methods that do not use gold amalgamation were shown to be underperforming relative to those that do. No significant correlation was observed between sample storage time or temperature and total mercury recovery. Methylmercury analysis methods that do not use distillation performed poorly relative to those that use distillation.