Eloy García-Calvo

Occurrence of emerging pollutants in urban wastewater and their removal through biological treatment followed by ozonation

This work reports a systematic survey of over seventy individual pollutants in a Sewage Treatment Plant (STP) receiving urban wastewater. The compounds include mainly pharmaceuticals and personal care products, as well as some metabolites. The quantification in the ng/L range was performed by Liquid Chromatography-QTRAP-Mass Spectrometry and Gas Chromatography coupled to Mass Spectrometry. The results showed that paraxanthine, caffeine and acetaminophen were the main individual pollutants usually found in concentrations over 20 ppb. N-formyl-4-amino-antipiryne and galaxolide were also detected in the ppb level. A group of compounds including the beta-blockers atenolol, metoprolol and propanolol; the lipid regulators bezafibrate and fenofibric acid; the antibiotics erythromycin, sulfamethoxazole and trimethoprim, the antiinflammatories diclofenac, indomethacin, ketoprofen and mefenamic acid, the antiepileptic carbamazepine and the antiacid omeprazole exhibited removal efficiencies below 20% in the STP treatment. Ozonation with doses lower than 90 microM allowed the removal of many individual pollutants including some of those more refractory to biological treatment. A kinetic model allowed the determination of second order kinetic constants for the ozonation of bezafibrate, cotinine, diuron and metronidazole. The results show that the hydroxyl radical reaction was the major pathway for the oxidative transformation of these compounds.

Physicochemical Characterization and Ecotoxicological Assessment of CeO2 Nanoparticles Using Two Aquatic Microorganisms

The physicochemical properties of nanoparticles determine their interaction with living organisms. Four different cerium oxide nanoparticles, including commercial materials, were characterized and compared with a micron-sized ceria. The formation of aggregates as well as ζ-potential, surface area, and chemical composition were determined. The formation of primary particle aggregates was a slow process that led to different particle sizes depending on the composition of the medium. In this paper, we describe the toxicity of cerium oxide for the self-luminescent cyanobacterial recombinant strain Anabaena CPB4337 and the green alga Pseudokirchneriella subcapitata. The toxicity for Anabaena exposed to nanoparticles in pure water for 24 h ranged from 0.27 to 6.3 mg/l; P. subcapitata EC(50) (yielded effective concentration of nanoparticles that inhibits the cellular function of interest by 50%) values in the 2.4-29.6 mg/l range. Images of both organisms showed membrane disruption and highly damaged cells. Free cerium was highly toxic for both organisms, but the negligible amount found dissolved in the nanoparticle suspensions could not explain the observed toxic effect of nanoceria on the aquatic organisms; the dissolution of zinc could contribute to the toxicity of bulk material but could not explain the toxic effect of nanoceria either. We found no evidence of nanoparticle uptake by cells, but our observations suggested that their toxic mode of action required direct contact between nanoparticles and cells; in the case of the cyanobacterium, cells completely coated by layers of ceria nanoparticles were observed. Cell damage most probably took place by cell wall and membrane disruption; further research is needed to find out whether the oxidative activity of ceria could be responsible.

Removal of pharmaceuticals and kinetics of mineralization by O3/H2O2 in a biotreated municipal wastewater

The ozonation of an effluent from the secondary clarifier of two Municipal Wastewater Treatment Plants was performed by using alkaline ozone and a combination of ozone and hydrogen peroxide. Alkaline ozonation achieved only a moderate degree of mineralization, essentially concentrated during the first few minutes; but the addition of hydrogen peroxide eventually led to a complete mineralization. The evolution of total organic carbon (TOC) as a measure of the extent of mineralization and the concentration of dissolved ozone were analyzed and linked in a kinetic model whose parameter represented the product of the exposure to hydroxyl radicals and the kinetic constant of indirect ozonation. This rate parameter yielded the highest values during the first part of O(3)/H(2)O(2) runs. The kinetic constant for the decomposition of ozone at the end of the run was also measured and computed for the non-oxidizable water matrix and yielded essentially the same values regardless of whether or not hydrogen peroxide was used. A group of 33 organic compounds, mainly pharmaceuticals and some relevant metabolites present in the wastewater effluents, were evaluated before and after the ozonation process using a liquid chromatography-hybrid triple-quadrupole linear ion trap system (LC-QqLIT-MS). The results demonstrate that the ozonation degrades these compounds with efficiencies of over 99% in most cases, even under low mineralization conditions in alkaline ozonation.

Ranking potential impacts of priority and emerging pollutants in urban wastewater through life cycle impact assessment

Life cycle impact assessment (LCIA), a feature of the Life cycle assessment (LCA) methodology, is used in this work outside the LCA framework, as a means to quantify the potential environmental impacts on ecotoxicity and human toxicity of wastewater containing priority and emerging pollutants. In order to do this, so-called characterisation factors are obtained for 98 frequently detected pollutants, using two characterisation models, EDIP97 and USES-LCA. The applicability of this methodology is shown in a case study in which wastewater influent and effluent samples from a Spanish wastewater treatment plant located in the Mediterranean coast were analysed. Characterisation factors were applied to the average concentration of each pollutant, obtaining impact scores for different scenarios: discharging wastewater to aquatic recipient, and using it for crop irrigation. The results show that treated wastewater involves a substantially lower environmental impact when compared to the influent, and pharmaceuticals and personal care products (PPCPs) are very important contributors to toxicity in this wastewater. Ciprofloxacin, fluoxetine, and nicotine constitute the main PPCPs of concern in this case study, while 2,3,7,8-TCDD, Nickel, and hexachlorobenzene are the priority pollutants with highest contribution. Nevertheless, it must be stressed that the new characterisation factors are based on very limited data, especially with regard to toxicology, and therefore they must be seen as a first screening to be improved in the future when more and higher quality data is available.

Automatic Searching and Evaluation of Priority and Emerging Contaminants in Wastewater and River Water by Stir Bar Sorptive Extraction followed by Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry

A new analytical method based on stir bar sorptive extraction (SBSE), followed by comprehensive two-dimensional gas chromatography (GCxGC-TOF-MS), has been developed for the automatic searching and evaluation of nonpolar or semipolar contaminants in wastewater and river water. The target compounds selected were 13 personal care products (PCPs), 15 polycyclic aromatic hydrocarbons (PAHs) and 27 pesticides. Excellent results have been obtained in terms of separation efficiency and also in terms of compound identification. Exceptional method detection limits were achieved applying the optimized method, at or below 1 ng/L for most of the compounds in real samples. The reliable confirmation of analyte identity was possible at this low concentration level, even for typically troublesome compounds such as the PAHs. The other validation parameters were good. In addition to obtaining analytical information such as identification and quantification of target analytes, it is also possible to screen for nontarget compounds or unknowns. New contaminants have been identified in the wastewater effluents and river water samples, such as cholesterol and its degradation products, pharmaceuticals, industrial products, other pesticides, and PCPs. The multidimensional information generated by the instrument can also be used by the researchers for contrasting samples and identifying, much more easily, the major differences between samples. We have used this feature to propose studies of comparison between the fingerprinting of different water samples, such as the contamination variation along a river affected by the discharge of urban wastewaters and also the contamination variation over a period of time in the effluent. Results show that the most frequently detected contaminants (and the contaminants detected at higher concentrations) were the PCPs. The musk fragrances galaxolide and tonalid were the most concentrated compounds in the samples. The pesticides and PAHs were present at much lower concentration than PCPs.

Identification of intermediates and assessment of ecotoxicity in the oxidation products generated during the ozonation of clofibric acid.

The degradation of an aqueous solution of clofibric acid was investigated during catalytic and non-catalytic ozonation. The catalyst, TiO(2), enhanced the production of hydroxyl radicals from ozone and raised the fraction or clofibric acid degraded by hydroxyl radicals. The rate constant for the reaction of clofibric acid and hydroxyl radicals was not affected by the presence of the catalyst. The toxicity of the oxidation products obtained during the reaction was assessed by means of Vibrio fischeri and Daphnia magna tests in order to evaluate the potential formation of toxic by-products. The results showed that the ozonation was enhanced by the presence of TiO(2,) the clofibric acid being removed completely after 15 min at pH 5. The evolution of dissolved organic carbon, specific ultraviolet absorption at 254 nm and the concentration of carboxylic acids monitored the degradation process. The formation of 4-chlorophenol, hydroquinone, 4-chlorocatechol, 2-hydroxyisobutyric acid and three non-aromatic compounds identified as a product of the ring-opening reaction was assessed by exact mass measurements performed by liquid chromatography coupled to time-of-flight mass spectrometry (LC-TOF-MS). The bioassays showed a significant increase in toxicity during the initial stages of ozonation following a toxicity pattern closely related to the formation of ring-opening by-products.

Spatio-temporal evaluation of organic contaminants and their transformation products along a river basin affected by urban, agricultural and industrial pollution

This study aims to assess the occurrence, fate and temporal and spatial distribution of anthropogenic contaminants in a river subjected to different pressures (industrial, agricultural, wastewater discharges). For this purpose, the Henares River basin (central Spain) can be considered a representative basin within a continental Mediterranean climate. As the studied river runs through several residential, industrial and agricultural areas, it would be expected that the chemical water quality is modified along its course. Thereby the selection of sampling points and timing of sample collection are critical factors in the monitoring of a river basin. In this study, six different monitoring campaigns were performed in 2010 and contaminants were measured at the effluent point of the main wastewater treatment plant (WWTP) in the river basin and at five different points upstream and downstream from the WWTP emission point. The target compounds evaluated were personal care products (PCPs), polycyclic aromatic hydrocarbons (PAHs) and pesticides. Results show that the river is clearly influenced by wastewater discharges and also by its proximity to agricultural areas. The contaminants detected at higher concentrations were the PCPs. The spatial distribution of the contaminants indicates that the studied contaminants persist along the river. In the time period studied no great seasonal variations of PCPs at the river collection points were observed. In contrast, a temporal trend of pesticides and PAHs was observed. Besides the target compounds, other new contaminants were identified and evaluated in the water samples, some of them being investigated for the first time in the aquatic environment. The behaviour of three important transformation products was also evaluated: 9,10-anthracenodione, galaxolide-lactone and 4-amino-musk xylene. These were found at higher concentrations than their parent compounds, indicating the significance of including the study of transformation products in the monitoring programmes.

A fluid dynamic model for three-phase airlift reactors

A simple model for the description of flow behavior in three phase (solid–liquid–gas) airlift reactors (TPAL) was developed. Based on an energy balance, which takes into account the dissipation of energy in the phase interfaces, the model predicts liquid, and solid circulation velocities, gas holdup and solid distribution within the reactor. It describes the three flow modes in relation to the solid behavior as the gas flow increases, namely, packed, fluidized and circulating beds and establishes the boundary conditions between the flow modes with accuracy. The hysteresis effect widely described in literature is also predicted, the initial solid holdup distribution (e00s) is the main parameter to describe this effect. Experimental data obtained by various authors for reactors of different shape (internal or external loops) and size (from 0.020 to 284 m3), different solid particles (sizes from 0.1 to 3 mm and solid densities from 2550 to 3700 kg/m3) and different experimental conditions are simulated satisfactorily.

An insight into the mechanisms of nanoceria toxicity in aquatic photosynthetic organisms

The effect of nanoceria on two aquatic photosynthetic organisms of ecological relevance, a green alga and a cyanobacterium, is reported. The main bioenergetic process of these organisms, photosynthesis, was studied by measuring both oxygen evolution and chlorophyll a fluorescence emission parameters. Nanoceria significantly inhibited photosynthesis in the cyanobacterium in the entire range of concentrations tested (0.01-100 mg/L), while a dual effect of nanoceria was found in the green alga with slight stimulation at low concentrations and strong inhibition at the highest concentrations tested. Chlorophyll a fluorescence experiments indicated that nanoceria had a significant impact on the primary photochemical processes of photosystem II. The primary cause of the observed photosynthetic inhibition by nanoceria is an excessive level of ROS formation; the results indicated a strong generation of reactive oxygen species (ROS) which caused oxidative damage, as evidenced by lipid peroxidation in both photosynthetic organisms. It is proposed that nanoceria can increase the production of hydrogen peroxide (a normal ROS by-product of light-driven photosynthesis) in both the green alga and the cyanobacterium; through an oxidative reaction, these ROS cause lipid peroxidation, compromising membrane integrity and also seriously impairing photosynthetic performance, eventually leading to cell death.

Degradation of caffeine and identification of the transformation products generated by ozonation

The ozonation of caffeine in water was performed at different pH values, including acidic conditions. Kinetic experiments were conducted by adding pulses of a concentrated caffeine solution to ozone saturated water. The results showed a rapid decrease of ozone concentration during the first 15s after injection, followed by a gradual decline at a much slower rate. The data were fitted to a second order kinetic model with rate constants increasing from 0.25 to 1.05 M(-1)s(-1) for pH in the 3-10 range. The initial ozone consumption per mol of ozonated caffeine was greater at high pH values, reflecting a higher ozone decomposition rate. The decomposition of ozone was positively affected by the concentration of caffeine, an effect that could be attributed to the presence of a reaction intermediate from the ozonation of caffeine that behaved as a strong promoter of ozone decomposition. A study of the transformation products identified by liquid chromatography in combination with time-of-flight mass spectrometry was carried out, which permitted a tentative degradation pathway to be proposed and several persistent by-products to be identified at both pH 3 and 8. Most transformation products were the result of the opening of the imidazole ring after breaking caffeines N9C8 double bond.