Nitrate addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H2S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect of four different concentrations of nitrate (0.12, 0.24, 0.50, and 1.00 mM) was investigated for a period of 3 days in relation to sulfide concentration in two bioreactors set up at Guadalete wastewater treatment plant (Jerez de la Frontera, Spain). Physicochemical variables were measured in water and air, and the activity of bacteria implicated in the sulfur and nitrogen cycles was analyzed in the biofilms and in the water phase of the bioreactors. Biofilms were a net source of sulfide for the water and gas phases (7.22±5.3 μmol S-1) in the absence of nitrate dosing. Addition of nitrate resulted in a quick (within 3 h) decrease of sulfide both in the water and atmospheric phases. Sulfide elimination efficiency in the water phase increased with nitrate concentrations following the Michaelis-Menten kinetics (Ks=0.63 mM NO3-). The end of nitrate addition resulted in a recovery or increase of initial net sulfide production in about 3 h. Addition of nitrate increased the activity of NR-SOB and decreased the activity of sulfate-reducing bacteria. Results confirmed the role of NR-SOB on hydrogen sulfide consumption coupled with nitrate reduction and sulfate recycling, revealing Sulfurimonas denitrificans and Paracoccus denitrificans as NR-SOB of great importance in this process. © Springer Science+Business Media Dordrecht 2013.

The use of aqueous suspension of nanoparticles of titanium dioxide for photocatalytic removal of pollutants is not suitable for industrial applications due to the inconvenient and expensive separation of nanoparticles of titanium dioxide for reuse. The nanosized titanium dioxide needs to be immobilized on the support for improving the efficiency and economics of the photocatalytic process. In the present paper, nanoparticles of titanium dioxide have been immobilized on the surface of the support using three different techniques. The immobilized films of titanium dioxide have been characterized using X-ray diffraction and scanning electron microscopy to notice any change in the phase composition and photocatalytic properties of the titanium dioxide after immobilization on the support. A photocatalytic test has been performed under similar reaction conditions to compare the photocatalytic performance of the films of immobilized titanium dioxide prepared using different techniques.

This study investigates the potential impact of OSPW (oil sands processed water) in terms of naphthenic acids (NAs) in the event that OSPW which contain NAs were discharged to a stretch of the Athabasca River of Alberta, Canada. A one-dimensional model WASP7 (water quality analysis simulation programme) was hydro-dynamically calibrated and validated for the data 1999-2008. The model represented the field data quite well except frozen seasons. The sensitivity analysis showed that the concentrations of NAs in the Athabasca River due to OSPW discharged to the river will be most sensitive to changes in the discharge rate of OSPW and concentrations of NAs in the OSPW. The WASP7 was applied to investigate how to achieve acceptable concentrations of NAs (≤0.15 mg/L) along the river, assuming NAs are degraded by natural dilution, biodegradation, sorption, photodegradation or combinations of these processes. If only the dilution effect is considered for an OSPW discharged at 1.5, 3.0 and 4.5 m 3/s (initial NAs concentration of 120 mg/L) to the river, respectively, all the NAs concentrations simulated would exceed an allowable limit of ≤0.15 mg/L, which indicates that dilution effect alone is not sufficient to decrease the concentration of NAs in the river. Similarly, by only considering a photodegradation rate of 0.005/day, the concentrations of NAs would decrease by approximately 0.1-3 %. However, by only considering a maximum biodegradation rate of 0.4/day, NAs discharged to the river can be decreased by 5-90 %. If a more moderate biodegradation rate of 0.2/day is assumed but photodegradation is also considered at 0.0025/day, then for the same three discharge rates of OSPW to the river, the allowable OSPW NAs have to be limited to 8.02, 4.09 and 2.77 mg/L to limit NAs at 0.15 mg/L. This implies that high biodegradation itself is more effective than a combination of moderate biodegradation and photodegradation in degrading NAs. Through multiple numerical experiments with WASP7, it seems that to limit the concentrations of the final NAs in the Athabasca River within 0.15 mg/L, it will be crucial to limit the OSPW NAs and the OSPW discharge rate to the river. © 2013 Springer Science+Business Media Dordrecht.

Adsorption together with size exclusion and charge attraction/repulsion has to be taken into account when considering removal of pharmaceuticals as emerging contaminants from water by reverse osmosis and nanofiltration membranes. Glucocorticosteroids (hydrocortisone (HYDRO), dexamethasone (DEXA)), anesthetics (procaine, lidocaine) with relatively weak hydrophobicities (1 < log K O/W < 3), and membranes (XLE, LFC–1, CPA3, SWC1, NF90, and NF270) have been investigated in this study. Adsorption was studied by measuring the concentration of compounds in feed and permeate and by monitoring changes in membrane flux in the batch mode operation during 24 h. A decrease in the feed concentrations for HYDRO and DEXA (log K O/W < 2) was observed. The loss of these compounds in feed was associated with irreversible adsorption onto an NF270 and a CPA3 membrane. Therefore, when considering removal of pharmaceuticals with lower hydrophobicity, adsorption has to be particularly taken into account for membranes with bigger pores in the selective layer. Also, a high dipole moment and low water solubility affected adsorption on the membranes. For smaller and slightly more hydrophobic pharmaceuticals (log K O/W > 2), an increase in the feed concentration was obtained. Firstly, these compounds instantly adsorbed to the membrane. Secondly, the compounds diffused through the polymer matrix and desorbed to the permeate side after equilibrium had been reached.

The present paper examines the phosphate adsorption from aqueous solutions onto goethite, bentonite, and bentonite–goethite system. The properties of the materials were studied by X-ray diffraction (XRD), attenuated total reflectance (ATR), and NMR spectra and by the measurement of the specific surface area, the point of zero charge (p.z.c.) and the pore-specific volume. ATR and NMR spectra of bentonite and bentonite–goethite system show peaks which correspond to tetrahedrally and octahedrally coordinated Al. The specific surface area of the system differs according to the appropriate method used, while system’s p.z.c. is higher than bentonite and lower than goethite. The pore-specific volume of bentonite–goethite system is higher than that of bentonite or goethite. According to XRD spectrum of bentonite–goethite system, goethite coats the (001) spacing of bentonite while the coating of (010) plane of bentonite is limited. The crystallinity of the system decreases and the negative permanent charge increases. Phosphate adsorption experiments took place at different pH (3.8–9.0) and concentrations (40.3–443.5 μmol L⁻¹) and constant capacitance model was applied to describe adsorption. A ligand exchange mechanism characterizes the model because the charge is divided among adsorbate and adsorbent. The constant capacitance model describes the adsorption mechanism in all examined pH. This model can be utilized in such systems using the surface protonation-dissociation constant of goethite and showing the exact shape of the adsorption isotherms for different pH values. Τhe produced low-cost bentonite–goethite system presents the highest adsorption of P per kilogram of goethite.

The degradation of sodium p-cumenesulfonate (SCS) by electrochemical, photochemical, and photoelectrochemical methods in aqueous solution of NaClO4, NaCl, and NaClO has been studied. It was found that as a result of NaClO4 electroreduction and photodecomposition, the ions Cl- and ClO3- are formed. These ions undergo transformations into radicals, mainly Cl-center dot, Cl-2(center dot-), ClO center dot, ClO2 center dot, and ClO3 center dot, due to electrochemical and photochemical reactions. It was shown that the interpretation of results of the studies over mineralization processes carried out in the presence of ClO4-cannot be adequate without taking into consideration the reduction of ClO4 to Cl- and ClO3-. Therefore, previous works presented in the literature should be rediscussed on the basis of the new data. Photoelectrochemical mineralization of substrate in NaCl solution at the concentration of 16 mmol L-1 is comparable with the efficiency of the reaction in NaClO4 solution containing more than 8 mmol L-1 of NaClO. Total SCS mineralization was obtained in the photoelectrochemical reactor with a UV immersion lamp with a power 15 W in the period of 135 min and current intensity of 350 mA. In such conditions, the power consumption was about 1.2 kWh per g of TOC removed.

A study was carried out under in vitro conditions to characterize the growth of blue green alga, Spirulina platensis, in standard CFTRI medium containing different nanoparticles of copper oxide (CuO) (50 nm, 10 ppm), zinc oxide (ZnO) (50 nm, 10 ppm), tricalcium phosphate (TCP) (<100 nm, 90 ppm), and hydroxy apatite (HA) (<200 nm, 90 ppm). S. platensis exhibited significant higher growth in standard CFTRI medium containing 90 ppm phosphorus as nanoparticles of TCP and HA. On the other hand, calcium phosphate nanoparticles caused significant reduction in nitrate reductase activity as well as in protein content of the alga. Marked change in chlorophyll-a/b ratio was also noted when phosphorus was supplied through nano tricalcium phosphate and nano hydroxy apatite particles as compared to ionic form (K2HPO 4). The study revealed that the growth of Spirulina in the presence of ZnO nanoparticles was retarded, while no growth was observed with CuO nanoparticles. It was concluded that alga Spirulina showed much sensitivity to nanoparticles of zinc and copper (<50 nm) and was able to tolerate the toxicity of nanophosphate (tricalcium phosphate <100 nm; hydroxy apatite <200 nm). © 2013 Springer Science+Business Media Dordrecht.

A study was undertaken to assess the extent of mercury contamination in the water and sediment in a seasonal wetland, as well as to determine the relationship between environmental parameters and the distribution of the mercury contamination. Water and sediment samples were collected and analysed for methylmercury, inorganic mercury and other physical and chemical variables. One-way analysis of variance and homogeneity of variance were performed, and linear regression analysis was used to determine correlations between mercury and other environmental variables. The highest mercury concentrations were recorded at the sites located closest to the industrial complex. Methylmercury concentrations in the water and sediment were mostly higher during the low flow season, while inorganic mercury concentrations in the water and sediment were higher during the high flow and low flow seasons, respectively. Chromium, manganese, organic carbon and fine sediment particles were found to have significantly positive correlations with mercury concentrations in water and sediment. It was also found that the mercury concentrations decreased within a relatively short distance from the sites closer to the industrial complex to the sites further downstream.

Finding an environmentally safe and cost-effective method which is efficient enough to meet the regulatory standards of potable and industrial wastewater presents unique challenges. In this work, Moringa stenopetala seed powder which had particle size of 300 μm was characterized; ash content 4.7 %, bulk density 0.531/cm3, particle density 0.88 g/cm3, color yellowish, and pH 4.5. Fourier transform infrared spectroscopy analysis showed the multifunctionality of the M. stenopetala seed powder. M. stenopetala seed powder was assessed for percentage chromium removal and milligrams per gram chromium uptake as a function of contact time, pH, and dose of the adsorbent and initial concentration. The maximum percent removal was 99.74 %. Sorption kinetics of chromium adsorption by M. stenopetala seed powder was predicted reliably using a pseudo-second order model. An intra-particle diffusion model revealed that the biosorption of metals proceeds through various processes. Equilibrium uptakes were evaluated using Langmuir, Freundlich, Temkin, and the Dubinin-Radushkevich adsorption isotherm models. Even though the correlation coefficient was not as high as the Langmuir and Freundlich models for Temkin adsorption isotherm model, the metal uptake which was predicted by the model is comparable with the experimental value. Generally, the seed powder of M. stenopetala was found to be effective in the removal of chromium from tannery wastewater. © 2013 Springer Science+Business Media Dordrecht.

Hydrogels based on p(4-VP) of different dimensions were prepared and, after chemical modification, were used in the removal of one of the most potent toxic materials, cyanide. Macro and micron p(4-VP) hydrogel swelling behavior was evaluated in various aquatic environments. HCl, bromoethane, 1-bromobutane, 1-bromohexane, and 2-bromoethylamine were used as quaternizing agents to generate positive charges on both p(4-VP) macrogels and microgels. The modified p(4-VP) macrogels and microgels were used in cyanide ion removal for the first time from aqueous environments. The p(4-VP)-HCl at macro and micro sizes removed almost 49 and 61 mg cyanide ions per gram hydrogel in deionized water after modification, respectively. Moreover, the absorption capacity of the modified p(4-VP) hydrogel did not change significantly in tap, drinking, and creek waters. Parameters that affect the absorption process, such as cyanide concentration, contact time, hydrogel amount, and contaminated water source, were investigated. Additionally, magnetic field responsive macro and micro p(4-VP) hydrogel composites provided many advantages, such as easy handling after cyanide absorption, e.g., ready removal of cyanide-loaded p(4-VP) composites with an externally applied magnetic field. Langmuir and Freundlich adsorption isotherms were applied to the data obtained for cyanide uptake from aqueous environments.