Abatement Of Contaminants Research Articles

Enhanced Ozonation of Trace Organic Contaminants in Municipal Wastewater Plant Effluent by Adding a Preceding Filtration Step: Comparison and Prediction of Removal Efficiency

Ozonation is an efficient method for removing trace organic contaminants (TrOCs) and improving the quality of municipal wastewater plant effluents. Nevertheless, the wide application of ozonation is still challenging because of various wastewater matrices, ozone dose design, and ozone-refractory compounds. An enhanced ozonation supported by adding an additional filtration step was studied to overcome these limitations. A municipal wastewater plant effluent spiked with 6 structurally different TrOCs was employed to investigate the efficiency of TrOCs elimination and water quality improvement when combining ozonation with filtration. A kinetic approach, based on ozone and hydroxyl radicals (•OH) exposure, was used to predict TrOCs abatement and to evaluate ozone dose demand. A significantly more efficient removal of dissolved organic carbon (DOC) was observed when combining ozonation with filtration. Furthermore, the •OH scavenging rate of the effluent matrix was decreased from 6.4 × 10–⁴ s–¹ for conventional ozonation to 1.2 × 10–⁴ s–¹ when combining anion resin filtration (ARF) with ozonation. An improved removal (38% removal at 0.1 g O₃/g DOC) of atrazine (which is a typical ozone-refractory compound) was achieved by combining granular activated carbon filtration (GAF) with ozonation compared to stand-alone ozonation (8% removal at 0.5 g O₃/g DOC). The measured and predicted elimination demonstrated that the kinetic approach was reliable to predict target contaminants abatement in effluent by use of combined filtration–ozonation systems.

Advances in contaminants abatement by ferrate(VI)

Ferrate(VI) (FeVIO42−, Fe(VI)) has received increasing attention as a potential water treatment chemical since it possesses oxidation, disinfection, and coagulation properties, which can be used in simultaneously remediating organic contaminants (e.g., endocrine disruptors and pharmaceuticals), inactivating microorganisms (e.g., Escherichia coli and bacteriophage MS2), and removing toxic metals (e.g., Cu(II) and As(III)) in water. This paper introduces the properties of Fe(VI) and its oxidation mechanisms, then reviews the research on Fe(VI)-based water treatment technologies in recent years. The benefits of using Fe(VI) as an oxidizing agent are that it produces an environmentally benign byproduct (Fe(III)) while exhibiting high efficiency in abating pollutants in water, although Fe(VI) oxidation efficiency is limited to its stability and selectivity. The recent research results on the degradation of emerging organic contaminants by enhanced Fe(VI) oxidation technologies are presented. The induction of Fe(V) and Fe(IV) species generation in organic contaminants oxidation by Fe(VI) is the most effective method that may contribute to enhanced oxidation of organic contaminants that are less reactive with Fe(VI). Because Fe(V) and Fe(IV) have their higher oxidation reactivity than Fe(VI), and the rate constants of the reactions of Fe(IV) and Fe(V) with compounds are 2–4 orders of magnitude higher than that of Fe(VI) with compounds. It is generally accepted that no harmful byproducts such as halogenated organics and bromate would be formed during Fe(VI) oxidation. However, some recent studies have shown that disinfection by-products (DBPs) might be generated during Fe(VI) oxidation in the presence of Br– or I–. Under environmentally relevant conditions, the formation of bromate and DBPs would not be a problem for Fe(VI) application as their concentration levels are quite low. Meanwhile, the characteristics of newly formed iron(III) oxides/hydroxide during Fe(VI) oxidation and self-decomposition, and the mechanisms for metals removal by newly formed iron(III) oxides/hydroxide are summarized in this paper. Besides Fe(VI) oxidation, adsorption of organic pollutants and metals with Fe(VI) resultant nanoparticles could also be an effective method for water treatment and environmental remediation. Finally, the current knowledge gaps and future research needs are proposed. The economic synthesis method for ferrate remains a major challenge. The mechanism of the oxidation of organic pollutants by Fe(VI), especially the involvement of Fe(V) and Fe(IV), remains to be further clarified. The oxidation performance of Fe(VI) should be improved by greener and more efficient activation means. The oxidation and adsorption/coagulation synergetic effect of Fe(VI) should also be explored to promote the application of Fe(VI) in water pollution control. We believe that this review could inspire scientists, inventors, researchers, and engineers in this field.

Direct detection of the triphenylpyrylium-derived short-lived intermediates in the photocatalyzed degradation of acetaminophen, acetamiprid, caffeine and carbamazepine

Advanced oxidation processes are useful methodologies to accomplish abatement of contaminants; however, elucidation of the reaction mechanisms is hampered by the difficult detection of the short-lived primary key species involved in the photocatalytic processes. Nevertheless, herein the combined use of an organic photocatalyst such as triphenylpyrylium (TPP+) and photophysical techniques based on emission and absorption spectroscopy allowed monitoring the photocatalyst-derived short-lived intermediates. This methodology has been applied to the photocatalyzed degradation of different pollutants, such as acetaminophen, acetamiprid, caffeine and carbamazepine. First, photocatalytic degradation of a mixture of the pollutants showed that acetaminophen was the most easily photodegraded, followed by carbamazepine and caffeine, being the abatement of acetamiprid almost negligible. This process was accompanied by mineralization, as demonstrated by trapping of carbon dioxide using barium hydroxide. Then, emission spectroscopy measurements (steady-state and time-resolved fluorescence) allowed demonstrating quenching of the singlet excited state of TPP+. Laser flash photolysis experiments with absorption detection showed that oxidation of contaminants is accompanied by TPP+ reduction, with formation of a pyranyl radical (TPP), that constituted a fingerprint of the redox nature of the occurring process. The relative amounts of TPP detected was also correlated with the efficiency of the photodegradation process.

Isolation, Characterization, and Environmental Application of Bio-Based Materials as Auxiliaries in Photocatalytic Processes

Sustainable alternative substrates for advanced applications represent an increasing field of research that attracts the attention of worldwide experts (in accordance with green chemistry principles). In this context, bio-based substances (BBS) isolated from urban composted biowaste were purified and characterized. Additionally, these materials were tested as auxiliaries in advanced oxidizing photocatalytic processes for the abatement of organic contaminants in aqueous medium. Results highlighted the capability of these substances to enhance efficiency in water remediation treatments under mild conditions, favoring the entire light-driven photocatalytic process.

Improved dye removal and simultaneous electricity production in a photocatalytic fuel cell coupling with persulfate activation

A coupling method introducing persulfate (PS) into a photocatalytic fuel cell (PFC) was investigated to improve the decoloration of methyl orange (MO) and simultaneous electricity production. The TiO2 nanotube arrays (TNAs) were fabricated successfully on the titanium sheet as the photoanode, which was confirmed by the characterizations of X-ray diffraction and scanning electron microscopy. Due to the characteristics of inorganic sacrificial agent and strong oxidant for PS, the proposed PFC/PS system could improve the photocatalytic reaction and extend the range of active species reaction from the solid electrodes surface to the total liquid phase through the formation of sulfate radical (SO4−) and hydroxyl radical (HO) for MO removal. Hence, PFC/PS exhibited remarkable cell performance, increasing the MO decomposition by 40.36% and electricity generation by 44.97% relative to the PFC system without adding PS. Besides, the pollutant removal ability of the PFC/PS system was systematically assessed at different operation parameters, such as PS concentration, initial MO concentration, initial pH, and UV light intensity. Furthermore, the underlying mechanism of MO elimination was elucidated by the radicals quenching tests and hydrogen peroxide (H2O2) quantitative determination, and these results confirmed that the formation of reactive species, including SO4−, HO, H2O2 and even photogenerated holes, were responsibility for contaminant abatement in the PFC/PS system.

Cadmium uptake kinetics in parts of the seagrass Cymodocea nodosa at high exposure concentrations

BackgroundSeagrass species have been recommended as biomonitors of environmental condition and as tools for phytoremediation, due to their ability to concentrate anthropogenic chemicals. This study aims to provide novel information on metal accumulation in seagrasses under laboratory conditions to support their use as a tool in the evaluation and abatement of contamination in the field. We investigated the kinetics of cadmium uptake into adult leaf blades, leaf sheaths, rhizomes and roots of Cymodocea nodosa in exposure concentrations within the range of cadmium levels in industrial wastewater (0.5–40 mg L−1).ResultsA Michaelis–Menten-type equation satisfactorily described cadmium accumulation kinetics in seagrass parts, particularly at 0.5–5 or 10 mg L−1. However, an S equation best described the uptake kinetics in rhizomes at 5 mg L−1 and roots at 10 and 20 mg L−1. Equilibrium concentration and uptake rate tended to increase with the exposure concentration, indicating that seagrass displays a remarkable accumulation capacity of cadmium and reflect high cadmium levels in the surrounding medium. Concerning leaf blades and rhizomes, the bioconcentration factor at equilibrium (range 73.3–404.3 and 14.3–86.3, respectively) was generally lower at higher exposure concentrations, indicating a gradual reduction of available binding sites. Leaf blades and roots accumulated more cadmium with higher rate than sheaths and rhizomes. Uptake kinetics in leaf blades displayed a better fit to the Michaelis–Menten-type equation than those in the remaining plant parts, particularly at 0.5–10 mg L−1. A marked variation in tissue concentrations mainly after the steady state was observed at 20 and 40 mg L−1, indicative of the stress induced on seagrass cells. The maximum concentrations observed in seagrass parts at 5 and 10 mg L−1 were comparatively higher than those previously reported for other seagrasses incubated to similar exposure concentrations.ConclusionsCymodocea nodosa displays a remarkable cadmium accumulation capacity and reflects high cadmium levels in the surrounding medium. Kinetic models satisfactorily describe cadmium uptake in seagrass parts, primarily in adult leaf blades, at high exposure concentrations, permitting to predict cadmium accumulation in field situations. Cymodocea nodosa appeared to be a valuable tool in the evaluation and abatement of cadmium contamination in coastal areas.

Environmental fate and ecotoxicological risk of the antibiotic sulfamethoxazole across the Katari catchment (Bolivian Altiplano): Application of the GREAT-ER model

Antibiotics are emergent contaminants that can induce adverse effects in terrestrial and aquatic organisms. The surface water compartment is of particular concern as it receives direct waste water discharge. Modeling is highlighted as an essential tool to understand the fate and behavior of these compounds and to assess their ecotoxicological risk. This study aims at testing the ability of the GREAT-ER model in simulating sulfamethoxazole (SMX) concentrations in the surface waters of the arid high-altitude Katari catchment (Bolivian Altiplano), assessing the sensitivity of the parameters considered, and evaluating the ecotoxicological risk posed. The model predicted the general spatial pattern of SMX concentrations. No contaminant abatement was observed during the wet season, supporting the idea that non-point sources, such as runoff and remobilization processes, play an important role during that season. During the dry season, the abatement capacity was 91%, suggesting that natural attenuation, particularly photodegradation, is high during low flow. Pharmaceutical consumption was the parameter that influenced the environmental concentrations the most. The ratio of Predicted Environmental Concentrations to predicted no-effect concentrations varied between 0.14 and 26.6 for the wet season and between 0.14 and 7.6 for the dry season depending on the river stretch.

Publisher's note

Advanced oxidation processes are useful methodologies to accomplish abatement of contaminants; however, elucidation of the reaction mechanisms is hampered by the difficult detection of the short-lived primary key species involved in the photocatalytic processes. Nevertheless, herein the combined use of an organic photocatalyst such as triphenylpyrylium (TPP+) and photophysical techniques based on emission and absorption spectroscopy allowed monitoring the photocatalyst-derived short-lived intermediates. This methodology has been applied to the photocatalyzed degradation of different pollutants, such as acetaminophen, acetamiprid, caffeine and carbamazepine. First, photocatalytic degradation of a mixture of the pollutants showed that acetaminophen was the most easily photodegraded, followed by carbamazepine and caffeine, being the abatement of acetamiprid almost negligible. This process was accompanied by mineralization, as demonstrated by trapping of carbon dioxide using barium hydroxide. Then, emission spectroscopy measurements (steady-state and time-resolved fluorescence) allowed demonstrating quenching of the singlet excited state of TPP+. Laser flash photolysis experiments with absorption detection showed that oxidation of contaminants is accompanied by TPP+ reduction, with formation of a pyranyl radical (TPP), that constituted a fingerprint of the redox nature of the occurring process. The relative amounts of TPP detected was also correlated with the efficiency of the photodegradation process.

Application of ozonation for pharmaceuticals and personal care products removal from water

Due to the shortening on natural water resources, reclaimed wastewater will be an important water supply source. However, suitable technologies must be available to guaranty its proper detoxification with special concern for the emerging pharmaceutical and personal care products that are continuously reaching municipal wastewater treatment plants. While conventional biological systems are not suitable to remove these compounds, ozone, due to its interesting features involving molecular ozone oxidation and the possibility of generating unselective hydroxyl radicals, has a wider range of action on micropollutants removal and water disinfection. This paper aims to review the studies dealing with ozone based processes for water reuse by considering municipal wastewater reclamation as well as natural and drinking water treatment. A comparison with alternative technologies is given. The main drawback of ozonation is related with the low mineralization achieved that may lead to the production of reaction intermediates with toxic features. The use of hydrogen peroxide and light aided systems enhance ozone action over pollutants. Moreover, scientific community is focused on the development of solid catalysts able to improve the mineralization level achieved by ozone. Special interest is now being given to solar light catalytic ozonation systems with interesting results both for chemical and biological contaminants abatement. Nowadays the integration between ozonation and sand biofiltration seems to be the most interesting cost effective methodology for water treatment. However, further studies must be performed to optimize this system by understanding the biofiltration mechanisms.

Chelate-modified fenton treatment of sulfidic spent caustic

Spent caustic can be treated by several treatment methods. Among the advanced techniques, Fenton reagent has many advantages. But since spent caustic contains excessive amounts of sulfide compounds, utilizing this technique in treatment of such wastewaters is not economical. The acid neutralization step, which was applied as the pretreatment process, showed an 84% COD abatement at temperature equal to 80 °C and a pH equal to 4.0. The acid neutralized wastewater was then introduced to the chelate-modified Fenton system and oxidized. Using a ratio of tartrate/Fe2+=1.1, reaction time=50min, temperature=95 °C, Fe2+=110mg/l and a ratio of H2O2/COD=1.2 in the chelate-modified Fenton system at an optimum pH value equal to 1.9, total COD abatement of the wastewater reached over 99.4%. Having tartrate added to the Fenton system, a series of photochemical reactions enhanced Fe2+ and hydroxyl radicals’ generation. This method has proved to be the recommended technique for the contamination abatement of spent caustic.

Organic Contaminant Abatement in Reclaimed Water by UV/H2O2 and a Combined Process Consisting of O3/H2O2 Followed by UV/H2O2: Prediction of Abatement Efficiency, Energy Consumption, and Byproduct Formation.

UV/H2O2 processes can be applied to improve the quality of effluents from municipal wastewater treatment plants by attenuating trace organic contaminants (micropollutants). This study presents a kinetic model based on UV photolysis parameters, including UV absorption rate and quantum yield, and hydroxyl radical (·OH) oxidation parameters, including second-order rate constants for ·OH reactions and steady-state ·OH concentrations, that can be used to predict micropollutant abatement in wastewater. The UV/H2O2 kinetic model successfully predicted the abatement efficiencies of 16 target micropollutants in bench-scale UV and UV/H2O2 experiments in 10 secondary wastewater effluents. The model was then used to calculate the electric energies required to achieve specific levels of micropollutant abatement in several advanced wastewater treatment scenarios using various combinations of ozone, UV, and H2O2. UV/H2O2 is more energy-intensive than ozonation for abatement of most micropollutants. Nevertheless, UV/H2O2 is not limited by the formation of N-nitrosodimethylamine (NDMA) and bromate whereas ozonation may produce significant concentrations of these oxidation byproducts, as observed in some of the tested wastewater effluents. The combined process of O3/H2O2 followed by UV/H2O2, which may be warranted in some potable reuse applications, can achieve superior micropollutant abatement with reduced energy consumption compared to UV/H2O2 and reduced oxidation byproduct formation (i.e., NDMA and/or bromate) compared to conventional ozonation.

Incorporation of Chitosan and Glass Substrate for Improvement on Adsorption, Separation and Stability of Tio2 Photocatalysis

It has been demonstrated that the single TiO2 has high capabilites for photodegradation process for all types pollutants. However, TiO2 are still far from becoming a potential candidate for photocatalytic system due to weakness for the adsorbtion process, separation as well as dissolution during the treatment. Therefore, this study highlights on the highly adsorption, easy separation and promising stability of TiO2(SY) photocatalyst by fabrication of Chitosan-TiO2(SY) supported glass substrate (Cs-TiO2(SY)/Glass substrate) photocatalysts. Cs with abundant R-NH and NH2 groups promotes adsorption sites of synthetic dyes. Meanwhile, present of glass substrate support increase the stability and easy separation of the potocatalysts. The fabrication process Cs- TiO2(SY)/Glass substrate has been done through dip-coating methods. Further analyzed by the adsorption photodegradation with Methyl Orange (MO) as a model of synthetic dyes compound. Approximately, 70% of total removal of MO by optimize 8 layers of photocatalyst analysis has been achieved within 1 hour of UV irradiation. Besides that, the adsorption photocatalyst has been achieved about 50% when no exposure of light for 15 minutes irradiation. It concluded that, a suitable photocatalytic conditions and sample parameters, possessing the Cs-TiO2(SY) gave the benefits of adsorption-photodegradation practice in the abatement of wastewater contaminants.

Emerging investigators series: prediction of trace organic contaminant abatement with UV/H2O2: development and validation of semi-empirical models for municipal wastewater effluents

Recent evaluations of potable reuse treatment trains suggest that the use of UV and UV/H2O2may become increasingly common, particularly in systems employing ozone and/or biofiltration.

Advances in predicting organic contaminant abatement during ozonation of municipal wastewater effluent: reaction kinetics, transformation products, and changes of biological effects

Ozonation of municipal wastewater effluent has been considered in recent years as an enhanced wastewater treatment technology to abate trace organic contaminants (micropollutants).

Bioremediation of diesel contamination at an underground storage tank site: a spatial analysis of the microbial community.

The present study reports on a real case of contamination due to the chronic leakage of diesel fuel from an underground tank at a dismissed service station. Speciation of the microbial community according to both lateral and vertical gradients from the origin of the contaminant release was analyzed by means of the PCR-DGGE technique. Moreover, the effects of a landfarming treatment on both the microbial community structure and the abatement of contamination were analyzed. The concentration of total petrol hydrocarbons (TPHs) decreased along the horizontal gradient (from 7042.2 ± 521.9 to 112.2 ± 24.3 mg kg(-1)), while increased downwards from the position of the tank (from 502.6 ± 43.7 to 4972.5 ± 275.3 mg kg(-1)). PCR-DGGE analyses and further statistical treatment of the data indicated a correlation between structure of the bacterial communities and amount of diesel fuel contamination. On the other hand, level of contamination, soil texture and depth were shown to affect the fungal community. Chloroflexi and Ascomycota were the most abundant microbes ascertained through culture-independent procedures. Landfarming promoted 91.6 % reduction of TPHs in 75 days. Furthermore, PCR-DGGE analyses evidenced that both bacterial and fungal communities of the treated soil were restored to the pristine conditions of uncontaminated topsoil. The present study demonstrated that bacterial and fungal communities were affected differently by soil factors such as level of hydrocarbon contamination as well as soil depth and texture. This report shows that a well-planned landfarming treatment can drive the restoration of the soil in terms of both abatement of the contaminants and resilience of the microbial community structure.

Experimental Investigation of Solid Recovered Fuel (SRF) Gasification: Effect of Temperature and Equivalence Ratio on Process Performance and Release of Minor Contaminants

The growing problem related to municipal solid waste generation has encouraged the development of alternative paths to convert waste to energy. Among the different options, gasification has been proposed as an interesting and efficient technology. In this study the influence of equivalence ratio (ER) and temperature on the performance of the air-gasification process during the gasification of a SRF material has been evaluated. One of the parameters to assess the gasification performance was the tracking of the evolution of some minor contaminants present in the syngas (tar and N, S, and Cl compounds). The results suggest that gasification temperatures around 800–850 °C and ER on the order of 0.30–0.35 could be appropriate conditions during SRF gasification aiming for tar and trace contaminants abatement without compromising to a large extent other gasification performance parameters.

ChemInform Abstract: Heterogeneous Photocatalytic Nanomaterials: Prospects and Challenges in Selective Transformations of Biomass‐Derived Compounds

AbstractReview: 50 refs.

Heterogeneous photocatalytic nanomaterials: prospects and challenges in selective transformations of biomass-derived compounds

Heterogeneous photocatalysis has become a comprehensively studied area of research during the past three decades due to its practical interest in applications including water-air depollution, cancer therapy, sterilization, artificial photosynthesis (CO2 photoreduction), anti-fogging surfaces, heat transfer and heat dissipation, anticorrosion, lithography, photochromism, solar chemicals production and many others. The utilization of solar irradiation to supply energy or to initiate chemical reactions is already an established idea. Excited electron-hole pairs are generated upon light irradiation of a wide-band gap semiconductor which can be applied to solar cells to generate electricity or in chemical processes to create/degrade specific compounds. While the field of heterogeneous photocatalysis for pollutant abatement and mineralisation of contaminants has been extensively investigated, a new research avenue related to the selective valorisation of residues has recently emerged as a promising alternative to utilise solar light for the production of valuable chemicals and fuels. This tutorial review will focus on the potential and applications of solid photonanocatalysts for the selective transformation of biomass-derived substrates.

Removal of Cr(VI) with Cogeneration of Electricity by an Alkaline Fuel Cell Reactor

Electricity can be harvested directly from an alkaline ethanol fuel cell (AEFC) reactor in which contaminant Cr(VI) is taken as the oxidant. The performance of the AEFC reactor was characterized in terms of power generation, Cr(VI) removal, cathodic efficiency, polarization curves, and Cr(VI) reduction kinetics. The cell potential, Cr(VI) removal, and cathodic efficiency are strongly dependent on pH and Cr(VI) concentration. Using 3.94 mM Cr(VI) in 1 M H2SO4 catholyte and 2.0 M C2H5OH in 0.5 M KOH anolyte, a high open circuit potential of 1.46 V and more than 96.0% Cr(VI) removal efficiency could be achieved, and in case of varying Cr(VI) concentration to 8.65 mM, a power density of 0.19 mW cm–2 at a current density of 0.23 mA cm–2 was observed. The Cr(VI) reduction follows a first-order kinetics. This work shows that the use of fuel cell provides a novel approach for simultaneous electricity generation and contaminant abatement.

Sorption of aqueous organic contaminants onto dodecyl sulfate intercalated magnesium iron layered double hydroxide

Dodecyl sulfate anion (DS−) intercalated magnesium iron layered double hydroxide (DS–Mg–Fe LDH) was firstly prepared by the co-precipitation method, and was characterized by the means of X-ray diffraction (XRD), Fourier infrared (FT-IR), Total Organic Carbon analysis (TOC), themogravimetric and differential thermal analysis (TG-DTA) and surface characteristics analysis (BET-N2). The sorption characteristics and mechanisms of hydrophobic organic contaminants (naphthalene, nitrobenzene, acetophenone) and hydrophilic contaminant (aniline) on DS–Mg–Fe LDH were investigated, and were subsequently compared with that on the inorganic magnesium iron layered double hydroxides (CO3–Mg–Fe LDH and NO3–Mg–Fe LDH). The greater sorption amount of organic contaminants on DS–Mg–Fe LDH than on CO3–Mg–Fe LDH and NO3–Mg–Fe LDH indicated that organic modified LDHs were potential sorbents for the abatement of organic contaminants. Sorption mechanism on DS–Mg–Fe LDH varied with the types of organic contaminants. The uptake curves of naphthalene, nitrobenzene and acetophenone on DS–Mg–Fe LDH were linear, and sorption capacities for three hydrophobic compounds were in the sequence of their hydrophobicity (refers to water solubility or Kow). These results suggested that the sorption mechanism was the partition between water and the organic interlayer phase composed of the alkyl chain of DS−. After eliminating the influence of the hydrophobicity, the polar compounds (nitrobenzene and acetophenone) exhibited higher affinity to DS–Mg–Fe LDH than nonpolar compound (naphthalene), which demonstrated that both the hydrophobicity and polarity benefited the sorption of hydrophobic compounds on organic LDHs. For hydrophilic compound, aniline, its uptake curve was nonlinear. The sorption process of aniline was the cooperation of the adsorption on hydroxide surface through forming the hydrogen bonding and the weak partition to the interlayer organic phase.