Nonpoint stormwater runoff remains a major threat to surface water quality in the USA. More effective stormwater control measures can be designed by understanding patterns in pollutant export with respect to the runoff hydrograph. In particular, nutrient concentrations in urban stormwater can cause deleterious effects in sensitive watersheds in the Southeast and Mid-Atlantic USA. A year-long study captured stormwater samples from 36 storm events at two catchments (one primarily impermeable and the other substantially wooded) and analyzed for total suspended solids and various nutrient species. Using these data, the first flush effect (the assumption that the initial portion of a rainfall-runoff event is more polluted than the later portions) was evaluated based on several published methods and definitions. Based on an analysis of multiple methodologies, the ranking of first flush strength among the pollutants was total suspended solids (TSS) > ammonia (NH₃) > total Kjeldahl nitrogen > NO₂-NO₃ > total phosphorus > orthophosphate (O-PO₄). Nitrogen species generally displayed a stronger first flush than phosphorus species, with O-PO₄ showing the weakest first flush effect. Various relationships ° climate, land use, and the first flush strength were also explored. Of the rainfall characteristics analyzed, total rainfall and runoff volume each inversely affected the first flush strength of TSS on the more impervious catchment. Although orthophosphate did not have a strong first flush effect, the relative first flush strength for O-PO₄ increased with increasing rainfall or runoff. Land use did not influence the first flush strength of the pollutants. On average, most pollutants exhibited a slight first flush effect, but substantial pollutant loading still occurred in the latter portion of the storm’s total runoff volume. Thus, treating the majority of a storm’s total pollutant load requires capturing a commensurate fraction of runoff volume.

Three novel composite adsorbents, sulfate-coated zeolite (SCZ), hydrotalcite (SCH), and activated alumina (SCAA), were characterized and employed for the removal of phosphate from aqueous solution using equilibrium and kinetic batch experiments. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectrum were used to study the surface characteristics of the coated layer. Equilibrium tests showed that the adsorption of phosphate followed both Langmuir and Freundlich isotherms. The powder-type SCZ was better for phosphate removal (maximum binding energy, β = 111.49 mg g−1) compared to hydrotalcite and activated alumina. The adsorption of phosphate was considered to take place mainly by ion exchange. The kinetic data followed a pseudo-second-order kinetic model. The initial adsorption of phosphate onto the sulfate-coated adsorbents was fast, indicating that the sulfate-coated materials developed in this study can be used as promising adsorbents for the removal of phosphate from wastewater or sewage.

This study presents the application of multivariate statistical tools for the evaluation of spatial variations and the interpretation of water quality data obtained in a monitoring program of Lis river basin surface water, Portugal. Twenty-seven physicochemical and microbiological parameters were determined in six water sampling campaigns at 16 monitoring sites during the period from September 2003 to November 2006. Correlation analysis, principal component analysis, and cluster analysis were performed to evaluate the main water pollution sources and to characterize the spatial distribution of water pollution profiles in river basin. The results achieved with the statistical methodologies led to distinguish natural and anthropogenic pollution sources. Additionally, monitoring sites with similar water pollution profile were identified, indicating that some monitoring locations can be changed to improve the spatial characterization of water quality in the river basin. CBO, CQO, P, and N were identified as significant variables affecting spatial variations, namely in the Lis river middle reach. Besides the identification of main pollution sources, the applied statistical tools were able to identify spatial patterns of water pollution in Lis river basin, which further helps in the reassessment of the number and location of monitoring sites.

The photocatalytic degradation of dyes under sunlight irradiation has received much attention not only because the attempt is aimed at decomposition of pollutants but also at finding methods of making use of solar energy. Following this line, zinc oxide nano-particles were prepared using solvent thermal method in order to decompose Naphthol Green B in presence of sunlight. Complete mineralization and decolorization of Naphthol Green B were achieved in 14 h. In order to reduce the band gap of zinc oxide and increase its photocatalytic activity in sunlight, it was doped with different concentrations of aluminum (1 %, 3 %, 5 %, and 10 %). The obtained band gap energy of the Al-doped ZnO nanoparticles was investigated as a function of Al content. Reduction of band gap energy for the heavily doped ZnO nanoparticles (10 % Al) was observed from 3.29 to 3.23 eV leading to fast transfer for electron from the excited state of dye to conduction band of ZnO. Therefore, by using the 10 % Al-doped ZnO nanoparticles, the complete mineralization and decolorization of Naphthol Green B were achieved in 6 h under sunlight. These results suggested that the heavily doped ZnO nanoparticles with aluminum has a positive effect towards photocatalytic reactions with dye under solar energy.

A rapid, simple, sensitive and cost-effective analytical method has been standardised to determine the residues of imidacloprid and thiamethoxam in soil. This method does not require any cleanup with costly sorbents. The recoveries of imidacloprid and thiamethoxam obtained in this no-cleanup method were on par with the protocol involving primary–secondary amine-based cleanup. This method requires less volume of solvent (20 mL of acetonitrile/sample) and is suitable for high throughput analyses involving large number of samples. The limit of quantification of the method was 0.01 μg/g. Dissipation kinetics of imidacloprid and thiamethoxam in the soils of sugarcane ecosystem was studied by adopting this rapid method. The half-life of imidacloprid and thiamethoxam was 9.07 and 6.22 days when applied at 70 and 100 g a.i./ha, respectively. The dissipation of both the neonicotinoids followed first-order kinetics with good fit.

Gas dispersion in a set of three different porous materials with similar particle size, as a function of material tortuosity and anisotropy ratio, was investigated. The materials were packed with different spatial orientations of the individual particles so as to create media with different tortuosity and anisotropy ratios. Three different media (slate chips, wood chips, and pebbles) and four particle orientations have been used to generate a total of nine different porous media mimicking single porosity, dual porosity isotropic, anisotropic, aggregated, or granular materials. Resulting values of tortuosity and anisotropy ratio for each medium were determined via measurements of gas permeability and molecular gas diffusion coefficient. These values were then compared to measured values of gas dispersivity for each medium. The results showed that dispersivity is inversely proportional to tortuosity but directly proportional to anisotropy ratio and that the relations were approximately linear within the range of tortuosities and anisotropy ratios investigated. Wood chips (dual porosity material) yielded higher values of gas dispersivity compared to slate chips (single porosity material). A likely reason is in part the difference in pore structure between the materials and in part a difference in particle surface roughness (which was highest for wood chips) both of which affects dispersion.

Safe drinking water is a luxury to approximately 800 million people worldwide. The number of people without access to clean water has been reduced, thanks to technologies like the biosand filter (BSF), an intermittently operated household scale slow sand filter. The BSF outlet (control diameter 0.5″) was modified in this study by reducing the outlet diameter (0.37″ and 0.25″) to determine the effects of hydraulic retention time on removal rates. Filters were dosed with 20 L of spiked lake water daily and observed for pH, dissolved oxygen (DO), fecal coliforms (FC), turbidity, nitrate, nitrite, sulfate, and ammonia until initial flow rates dropped below 0.2 L/min. Consistent with previous studies, the average turbidity was reduced to below 1 NTU; the average DO was reduced by 45 %. No significant difference was observed between the modified BSFs and the control BSF. Removal efficiency of FC was not significantly different between the modified BSFs (93.3 % and 91.9 %) and the control BSF (89.6 %). Mean FC reduction during the startup period (17 days) was significantly greater in the modified 0.25″ BSF when compared with the control during the same time period. After the first 17 days of the experiment, the average reduction efficiency of all filters was >97 %. While source water was below guideline values for nitrate, nitrite, ammonia, and sulfate during the course of the experiment, total nitrogen reduction was observed. The reduction indicates that the plastic BSF is capable of accomplishing limited denitrification during the filtering process.

In the present investigation, we report the immobilization of the enzyme tyrosinase on mesoporous silica material, i.e. MCM-41 to serve as a tool for the detection of phenol. The enzyme immobilized onto the MCM-41 matrix has shown to retain its activity and is quite stable. The immobilization of enzyme has been discussed, and the various factors that affect the loading of enzyme onto MCM-41 were studied and optimized. The applicability of tyrosinase-immobilized MCM-41 was then demonstrated for the detection of phenol. The lowest detectable concentration of phenol by tyrosinase-immobilized MCM-41 was observed to be 1 mg l−1. The factors influencing the detection of phenol were then studied in detail.

The presence of synthetic dyes in industrial wastewaters may create serious environmental problems due to their mutagenicity and toxicity to aquatic life and humans. In this study, the decolourization and degradation of methylene blue (MB) by a Sphingomonas paucimobilis strain isolated from industrial wastewater was investigated under aerobic conditions. Decolourization extent of MB in medium was over 85 % when the bacterium was grown on a high concentration of the dye (1,000 mg/L) after a retention time of 5 days, while reduction in COD was 92.99 % suggesting mineralization of dyes as a result of microbial activities. The bacterium retained decolourizing activity over a wide range of pH (2–10), with peak activity obtained at pH 9. Analysis of samples extracted from decolourized culture flasks at pH 9 using UV–visible and Fourier transform infrared (FTIR) spectroscopy confirmed that the mechanism of colour removal was due to biodegradation rather than adsorption of dye on cells. Scanning and transmission electron microscopy revealed the secretion of exopolysaccharides (EPS) by S. paucimobilis cells on exposure to MB—a probable physiological defence mechanism to ensure controlled diffusion of dye molecules into cellular structures. Biokinetic coefficients, namely, growth yield, Y; specific biomass decay, K d; maximum specific substrate rate, k; saturation constant for substrate, K ₛ; and maximum specific biomass growth rate, μ ₘₐₓ, were determined by the Monod type kinetic equation. Results indicate that S. paucimobilis holds a promise as a good candidate for the biological treatment of industrial effluent containing high concentrations of synthetic dyes.

Arsenic mobility around mining districts is primarily controlled by distribution and abundance of iron minerals. Arsenite-rich mine waters although frequently reported, the interaction of which with schwertmannite is poorly understood despite its high toxicity and mobility. We examined three synthetic schwertmannite types distinguished by surface area (19.9–227.5 m2/g), Fe/S molar fractions (4.7–6.6), and saturation index (−1.6–0.8) towards arsenite retention through controlled batch equilibrium studies at 22 ± 2°C and 1 atmospheric pressure in oxic conditions. Sorption isotherms were investigated as a function of dissolved arsenite concentrations (0.13–1.33 mmol/L) at constant sediment load (10 g/L) and pH (3.0) in order to understand the role of synthesis pathway and physicochemical properties on arsenite immobilization. Multilayer surface coverage with more than one process governs arsenite uptake. X-ray diffractograms, infrared spectroscopy, and high resolution electron microscopic examination revealed new phase formation where schwertmannite underwent morphological and structural degradation. Ionic exchange between schwertmannite SO 4 2− and aqueous arsenite has resulted in an elevated aqueous SO 4 2− that varied according to dissolved arsenite concentrations. Stoichiometric calculations showed that 1 mol of dissolved arsenite can effectively replace 0.12–0.19 mol of schwertmannite SO 4 2− . This study implies that schwertmannites can be used as potential adsorbents for arsenite treatment where the total uptake will be strongly controlled by both ion exchange and surface precipitation.