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Many water and wastewater treatment plants (WWTPs) are fitted with a UV system that provides post treatment disinfection before the water is released to receiving water. This paper presents a study on expected removal for the pharmaceutical venlafaxine (VEN) in a typical UV unit at a municipal WWTP with analysis of removal rates of an advanced oxidation process using UV irradiation with injection of H2O2. The study is supported by bench scale degradation experiments on VEN. Results demonstrated that UV can completely degrade VEN, but the addition of H2O2 increased pseudo first order rate constant by up to 2.5 times. Extrapolations of the lab data indicated that removal rates of VEN at the UV disinfection unit of a typical municipal WWTP are approximately 0.4% at standard operating conditions. With the addition of 10 mg/L of H2O2, degradation of VEN can be increased by ten times over existing UV treatment. By studying the impact of adjusting parameters such as UV intensity, UV dosage, and H2O2 dosage, a framework is set to allow researchers and engineers to move forward with developing UV/H2O2 systems that meet their future design needs for pharmaceutical removal. [ABSTRACT FROM AUTHOR]

Environmental context: The correlation of physicochemical characteristics of humic substances with their function is crucial to our understanding of how environmental pollutants interact with humic substances. We have developed an approach that models emergent functions of fulvic and humic acids depending on sample characteristics. The results will be useful for predicting the sequestration of organic contaminants in soil under various conditions. The structural organisation of humic substances (HS) has been a central question of earth sciences for several decades. The latest experimental results have led to the recognition of HS as complex mixtures of small molecules and oligomers. We investigate the correlation between the chemical composition of HS, perceived as labile aggregates, and the emergent functions. Computational modelling was used to help to understand the processes and mechanisms on the molecular scale that occur in different fractions of the HS, fulvic acids (FA) and humic acids (HA), as they interact with metal ions and organic pollutants. The importance of non-covalent interactions in the emergent functions of HS is highlighted. H-bonding, hydrophilic/hydrophobic surface areas and π-stacking interactions play a significant role in aggregation processes as well as in the sorption of environmental pollutants. In a highly hydrophilic system with small molecules (the SRFA-22 model), H-bonding is the main force that drives the aggregation process. However, in a highly aromatic and hydrophobic model with larger molecular fragments (SRHA-6), hydrophobic and π-stacking interactions dominate in the aggregation process. The chemical properties of contaminants significantly affect their mechanisms of sorption by HS. The interaction of a polar pollutant, phenol, with HS occurs through H-bonding, whereas non-polar benzene interacts through hydrophobic and π-stacking interactions. The non-polar pollutant results in a much stronger sorption by HS and causes an additional structural rearrangement of the aggregates, which make it more stable in the environment. Environmental context. The correlation of physicochemical characteristics of humic substances with their function is crucial to our understanding of how environmental pollutants interact with humic substances. We have developed an approach that models emergent functions of fulvic and humic acids depending on sample characteristics. The results will be useful for predicting the sequestration of organic contaminants in soil under various conditions. [ABSTRACT FROM AUTHOR]

This study evaluates the influence of UV dose on degradation of carbamazepine (CBZ) in wastewater under UV-C (λ = 254 nm) photolysis with and without H2O2. The rate of degradation of CBZ exhibited a direct dependence on the intensity of incident UV irradiation as the rate of degradation was observed to increase linearly (R2 = 0.98) with UV intensity between 1.67 and 8.95 × 1017 photons/s. More than 95% of the CBZ that spiked in wastewater rapidly degraded within 4 min with a first-order rate constant of 1.2 min−1 for an optimum H2O2 dose of 100 mg/L. Bench-scale continuous flow reactor experiments also showed that CBZ degraded with first-order kinetics at a rate constant of 1.02 min−1. The kinetic parameters obtained for a continuous bench-scale reactor were in good agreement with the relationships developed through batch experiments with only a marginal deviation of ± 6.5%. The relationship between UV intensity and CBZ degradation rate obtained in this study was extrapolated to the UV disinfection unit of a wastewater treatment plant to predict possible degradation of CBZ during UV disinfection. The addition of 100 mg/L of H2O2 to the secondary-treated effluent entering the UV disinfection unit is predicted to achieve over 60% degradation of CBZ. Abbreviations: CBZ carbamazepine; AOPs advanced oxidation processes; UV ultraviolet radiation; UV-C ultraviolet C (λ = 254 nm) radiation; NZVI non-zerovalent iron; WWTP wastewater treatment plant; HPLC high-performance liquid chromatography [ABSTRACT FROM AUTHOR]

A one-step, simple and low-cost strategy toward production of novel NiS2/S-doped g-C3N4 (NiS2/CNS) composites was successfully accomplished. The hybrid photocatalyst materials with different amounts of NiS2 nanoparticles (NPs) were successfully in situ synthesized via thermal condensation of a mixture containing thiourea and nickel(ii) nitrate. Interestingly, thiourea showed two very important roles: (i) thiourea not only acted as a precursor to in situ produce sulfur-doped carbon nitride materials, but also (ii) the sulfur atmosphere that originated from polycondensation of thiourea provided a sulfur source for in situ production of NiS2 nanoparticles as a non-noble metal sulfide on the CNS sheets during the synthesis. Density functional theory (DFT) computations were carried out to estimate the preferred position of S atoms within the backbone of the CNS framework as well as to compare the band gaps and partial density of states (PDOS) spectra. The NiS2 NPs ingrained in the CNS phase increased the efficient charge transport via a heterojunction interface and obviously decreased the recombination of electron–hole pairs evidenced by photoelectrochemical and photoluminescence measurements. Moreover, the band structures of NiS2 as a Mott insulator were studied through electrochemical methods. It was also found that the optimal NiS2 loading value in the NiS2/CNS composites was 5.9 wt% having a reaction rate constant equal to 0.011 min−1, which was about 3.1 and 26.1 times faster compared with those of the CNS (0.0035 min−1) and bulk g-C3N4 (0.00042 min−1) toward degradation of Rhodamine B (RhB) under visible light irradiation. The optimized photocatalyst was capable of showing a high efficiency for phenol photodegradation as a light insensitive pollutant. Hence, the synergistic effects originating from combining sulfur doping and in situ growing of NiS2 NPs in one material enhanced the physicochemical properties of carbon nitride materials. Our results might offer new insight into the cost-effective and simple designing of a photocatalyst using a bi-functional precursor such as thiourea so that it could easily be used on a large scale and even in industrial catalyst production. [ABSTRACT FROM AUTHOR]

This article presents the results of an investigation into the function of UV in a photo-assisted ozonation process for treatment of carbamazepine (CBZ) in treated domestic wastewaters. Experiments were conducted on synthetic spiked water and secondary treated municipal wastewater. Degradation of CBZ was studied for various combination of O3 dosage ranging from 4.8 to 14.4 mg/h and UV intensities with varying intensity and wavelength (UVC: λ = 254 nm and UVA: 352 nm). In synthetic spiked water, CBZ was degraded to below detectable limits within 0.5 min for ozone dose of 14.4 mg/h. The rate of degradation of CBZ increased exponentially with increase in ozone dose following a zero-order rate at each dose level. The degradation rate of CBZ in wastewater was slower compared to deionized water (DI) water by 40-75% for various doses of ozone, presumably due to the presence of organic matter remaining in treated wastewater. Optimal UV intensities for UVA and UVC were obtained as 0.62 and 0.82 mW/cm2 for all doses of ozone in synthetic spiked water samples and UV intensities beyond this resulted in lower rates of degradation of CBZ. For photo-assisted ozonation with ozone doses of 9.6 and 14.4 mg/L, rate constants were two times higher for UVA irradiations as compared to UVC irradiation. Contrary to observations in DI water, experiments in wastewater showed increase in rate of degradation with higher UV intensities. Overall, photo-assisted ozonation was found to be appropriate for both water and wastewater treatment by exploiting the benefit of direct attack of ozone and of produced .OH radicals to yield a greater extent of mineralization of CBZ. [ABSTRACT FROM AUTHOR]

A decision support system (DSS) is developed to optimise the performance of different operations of small water treatment systems to improve day-to-day decisions. The support system includes a data management system, knowledge-based system, performance assessment of different unit processes, fault tree analyses, preventive and corrective actions and event tree analysis (ETA). Performance assessment identifies the critical events (failures) and fault tree analysis identifies the interrelationships between the critical events and the root causes. Fault trees are developed based on the information obtained from events of waterborne outbreaks, responses to questionnaires by the participating smaller utilities, state-of-the-art literature review and personal communication with the operators. ETA is used to identify the potential health outcomes which are further integrated with the quantitative microbial risk assessment. The developed DSS is advanced to an automated user friendly program that can be used by treatment plant operators to assess system performance. [ABSTRACT FROM AUTHOR]

In this paper, degradation of bisphenol S (BPS) in spiked water and postsecondary-treated wastewater by a variety of oxidation processes was investigated in a flow-through reactor. Kinetics of degradation in O3, ultraviolet ðUVÞ=O3, UV=H2O2, and UV=O3=H2O2 were determined and reported. The degradation of BPS by O3 alone was competitive with the UV-promoted methods. An increase in BPS loss with O3 was observed in postsecondary-treated wastewater, demonstrating its potential application as a treatment method for BPS. Total organic carbon (TOC) as an indicator of the extent of organic compound mineralization and sulfate as a by-product produced during degradation were measured. It was noted that although the loss of BPS was similar in the UV=O3=H2O2 and the O3 processes, the overall mineralization rate was different, indicating that the combination technique offers a more efficient system in terms of overall mineralization rate. The UV=O3=H2O2 process was the most effective and led to complete mineralization of 50 mg=L BPS within 90 min in both spiked water and postsecondary-treated wastewater. [ABSTRACT FROM AUTHOR]

A bench-scale flow-through photocatalytic reactor using light emitting diodes (LED) as light source and a TiO2 nanotube array (TN) as immobilized catalyst has been designed, fabricated and tested on commonly studied contaminants. The photoreactor is comprised of 144, 365-nm UV-LED lamps mounted along the inner periphery of an annular cylinder. An ordered array of TN, as catalyst, was immobilized by electrochemical anodization of a titanium cylinder and placed in the center of the reactor. Synthesized TN was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Laboratory investigations were conducted on the photoreactor to treat 4-chlorophenol (4-CP), atrazine and methylene blue. The performance of the photoreactor at different flow rates and at varying distances of photocatalyst from the light source was monitored. The photocatalytic reaction rates increased with bubbling oxygen into the reservoir. Significant improvement was observed when H2O2 was added and degradation to detection limits was observed. [ABSTRACT FROM AUTHOR]

In this paper, light-emitting diodes (LEDs), a novel light source, is reported for the photocatalytic degradation of four known pesticides [2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP)] in aqueous solution. 2,4-Dichlorophenoxyacetic acid was further chosen to evaluate the impact of photocatalyst loading and light intensity on the degradation rate. The degradation of 2,4-D under LED irradiation (365 nm) was compared with that using mercury discharge lamp irradiation (350 nm). Irradiation of the different pesticides with a 365-nm LED light source led to their complete mineralization upon prolonged exposure. The degradation rate was slower when mixtures of pesticides were used because of competition between pesticide molecules for adsorption sites, hydroxyl radicals, and holes. A suitable photocatalyst loading was determined to be of ; a linear relationship between the first-order kinetic rate and light intensity (2.7 to approximately 46.5 mW) was observed. A comparison between LEDs and conventional mercury discharge lamps indicated that the former was more energy-efficient. [ABSTRACT FROM AUTHOR]

This study investigates a cross-section of TiO2 compositions for which existing evidence suggests the prospect of improved performance compared to standard Degussa P25. In the context of a program aimed toward a 365 nm LED based photo-reactor, the question is whether a distinctly superior photocatalyst composition for drinking water treatment is now available that would shape design choices. An answer was sought by synthesizing several photocatalysts with reported high reactivity in some context in the literature, and by performing photocatalysts reactivity tests using common pollutants of water system including Natural Organic Matter (NOM) and Emerging Contaminants (ECs) from the pesticide and pharmaceutical classes. 365 nm Light Emitting Diodes (LEDs) were used as the irradiation source. Since LEDs are now available in the UV, we did not examine the TiO2 modifications that bring band gap excitation into the region beyond 400 nm. The results suggest that the choice of the photocatalyst should be best made to fit the reactor design and photocatalyst mounting constraints such as mass transport, reactive surface, and light field. No photocatalyst composition overall, superior for all classes emerged. [ABSTRACT FROM AUTHOR]

An investigation into an extraction of polychlorinated biphenyls (PCBs) from transformer oil (TO) using different solvents and its dechlorination with visible light was conducted. The extraction experiments showed that dimethyl sulfoxide (DMSO) was the preferable solvent for extraction of PCBs from TO, with an average of 88.79% recovery. Multicycle extractions using DMSO led to 87.93, 11.22, and 0.77% PCBs recovery during the first, second, and third cycles, respectively. Optimization studies indicated that for TO with low concentrations of PCBs, a 5-min shaking time, and a DMSO to TO ratio of is optimal. For higher concentrations of PCBs in TO, the optimum conditions were 30 min of shaking time with a DMSO to TO ratio of . Furthermore, water aids in the extraction. PCBs were effectively dechlorinated using visible light in conjunction with sodium borohydride, , as a reducing agent. The presence of DMSO did not seem to interfere with the dechlorination. [ABSTRACT FROM AUTHOR]

A study on dechlorination of PCB138 in transformer oil (TO) and 2-propanol (IPA) using 254 nm ultraviolet (UV) light as well as dye sensitized visible light has been conducted. Studies on dechlorination of polychlorinated biphenyls (PCBs) in TO using visible light in the presence of methylene blue (MB) and triethylamine (TEA) (providing a ‘photocatalytic’ cycle) in both deaerated and aerated conditions have been conducted to determine effects of TO, MB and TEA on reaction rates. The results show that photolytic methods are effective in treating PCBs in TO, and that the oil plays a limited adverse role. Under UV irradiation, PCB 138 can be >99% dechlorinated in the presence 0.06% (w/w) TO in IPA within 1 h with a rate constant of 0.0853 min−1, while 47% of PCB138 can be dechlorinated in 92.1% (w/w) TO in IPA within 2 h with a rate constant of 0.0051 min−1. In the ‘photocatalytic’ system, 94% reduction of PCB 138 was achieved within 30 min with a rate constant of 0.0968 min−1 when the solvent was 60.70% (w/w) TO in IPA, while 71% dechlorination of PCB138 was achieved within 30 min with a rate constant of 0.0382 min−1 when 81.62% (w/w) TO was present. In treatment of 30–73 ppm PCBs in TO, the optimal concentration of MB and TEA were found to be 0.5 g/L and 58.08 g/L respectively. Because of quenching by oxygen, deaeration of the solution is necessary for an efficient reaction. The photocatalytic system is especially adapted for treating lower concentration of PCBs in TO. [ABSTRACT FROM AUTHOR]

A bench-scale process to treat boiler feed water for reuse in steam generation was developed. Industrial water samples from a steam-assisted gravity drainage plant in northern Alberta, Canada, were obtained and samples characterized. The technology, which consists of coagulation-settling to remove oil/grease and particulates followed by an advanced oxidative treatment, led to clean water samples with negligible organic carbon. Coagulation followed by settling removed most particulates and some insoluble organics. The advanced oxidative treatment removed any remaining color in the samples, decreased the organic content to near-zero, and provided water ready for reuse. Water Environ. Res., 84, 725 (2012). [ABSTRACT FROM AUTHOR]

Feasibility of photocatalytic dechlorination of PCB-138 and Aroclor-1254 using platinum loaded TiO2 (P25) in an alkaline 2-propanol medium has been investigated. Experiments were conducted in batch mode using a Rayonet photo-reactor under aerated and deaerated conditions with black lamps emitting around 350 nm as light source. Two forms of platinum deposition were investigated: Photochemically loaded P25 as well as addition of potassium hexachloroplatinate into the reaction medium. Partial dechlorination of PCBs was observed after 7 h of irradiation with pure TiO2 as catalyst when the reaction vessel was kept open to air. Complete dechlorination was observed after 5 h of irradiation in a deaerated environment. Enhanced photocatalytic efficiency was observed when platinum deposited P25 was used as catalyst, with the best result being obtained when aqueous potassium hexachloroplatinate was added into the reaction medium. Lower potassium hexachloroplatinate concentration (0.1 mM) yielded better performance. [ABSTRACT FROM AUTHOR]

In this paper some of the practical issues involved in the development and application of an extraction-photodegradation remediation technology for polychlorinated biphenyl (PCB) impacted weathered soils are addressed. The extraction of PCBs from weathered soils was investigated using the conventional Soxhlet extraction and by shake extraction using different solvents. The shake extraction has the potential for up-scaling to a field technology. The photodegradation of the extracted PCBs was investigated under direct ultraviolet light at 254 nm wavelength as well as under photosensitized light at 350 nm. The production of biphenyl, a by-product of the dechlorination of PCBs was investigated and it was found to degrade in the same ultraviolet system. [ABSTRACT FROM AUTHOR]

A promising photolysis based technology to dechlorinate polychlorinated biphenyls (PCBs), extracted from soils, in alkaline isopropanol (IPA) as reaction medium has been proposed. To be marketable the impact of co-contaminants extracted along with the PCBs, on the photodechlorination process needs investigation. In this paper the effectiveness of the photodeclorination process on PCBs extracted from samples of a representative soil containing co-contaminants is reported. The photodechlorination of PCBs extracted from weathered soils showed promising results of more than 76% dechlorination within the first hour of UV irradiation. Nearly complete dechlorination (96%) was achieved after 2 h of UV irradiation. To provide quantitative controlled appraisal of the effect of co-contaminants and explanation of the effects, dechlorination of neat Aroclor 1254 in the presence of the common co-contaminant, transformer oil, was evaluated. Further, the effect of transformer oil on some of the individual PCB congeners in the Aroclor mixture was also studied. The difference in the maximum percentage dechlorination of PCBs with and without transformer oil is 15%. Une technologie prometteuse basée sur la photolyse est proposée pour déchlorer les BPC extraits des sols dans un milieu de réaction composé d’alcool isopropylique alcalin. Afin d’être commercialisable, il faut examiner l’impact des co-contaminants extraits avec les BPC lors du processus de photo-déchloration. Dans cet article, l’efficacité du processus de photo-déchloration sur les BPC extraits d’échantillons d’un sol représentatif contenant des co-contaminants est présentée. La photo-chloration des BPC extraits de sols altérés a montré des résultats de déchloration prometteurs de plus de 76 % dans la première heure de rayonnement UV. Une déchloration presque complète (96 %) a été réalisée après 2 heures de rayonnement UV. Pour fournir une évaluation quantitative contrôlée de l’effet des co-contaminants et l’explication des effets, la déchloration d’Aroclor 1254 pur en présence du co-contaminant commun, de l’huile de transformateur, a été évaluée. De plus, l’effet de l’huile de transformateur sur certains des congénères individuels des BPC dans le mélange d’Aroclor a également été étudié. La différence dans le pourcentage maximum de déchloration des BPC avec et sans huile de transformateur est de 15 %. [ABSTRACT FROM AUTHOR]

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A novel pilot-scale flow through photoreactor has been designed with the intent to apply it in the field. The photoreactor uses a new plastic coil, instead of the conventional quartz tube. The photoreactor consists of six ultraviolet (UV) lamps with five around the coil and one at the center. Laboratory investigations were conducted using the photoreactor to treat neat Aroclor 1254 in alkaline isopropanol (IPA). The photoreaction is fast and efficient, even though the UV transmittances of the three plastic tubes investigated were lower than that of quartz. The reaction kinetics of the practical mixtures are explored. An analysis of five different constituent congeners of Aroclor 1254 indicated that higher congeners dechlorinate producing some of the lower ones, which are subsequently dechlorinated. The dechlorination of Aroclor 1254 was faster when water was added to the alkaline IPA–Aroclor solution. [ABSTRACT FROM AUTHOR]

Fluorescence techniques have been used to identify humic substances, (e.g. aquatic fulvic acids from different origins). Synchronous scans have proven adequate for distinguishing detail and differentiating samples. As well, fluorescence has often been used to probe humic interactions with metals and xenobiotic organics. In this study, the fluorescence of a well-characterized material, Laurentian fulvic acid (LFA) was compared with that of a simple hydroquinone/quinone (H2Q/Q) model system. Synchronous fluorescence (room 1) and laser-excited fluorescence experiments at 10 °K were carried out to characterize the fluorophore. The synchronous fluorescence behavior of LFA displayed similarities to that of an equilibrated, aerated, H2Q/Q system, but only at higher pH. (Higher pH favours a shift of the redox equilibrium towards quinone.) In contrast, the spectra of LFA suggest the role of "quinone" groups, even at lower pH. A significant feature of these spectra is a lowest energy band. At low temperature this band was more selectively excited at 470 nm, but vibrationally resolved line narrowed spectra were not observed. Fluorescence lifetimes were very short compared to the laser pulse width of ca.10 ns. Under the low condition the spectra of LFA and the model are essentially identical. We suggest that the principal luminophore in LFA is a quinone-hydroquinone type, perhaps a charge transfer complex consistent with the absence of the fluorescence line-narrowing phenomenon. The spectra imply a lowest energy component of LFA emission from a fluorophore very similar to that of the simplest H2Q/Q. The significant similarities of the model system to LFA are underscored by striking parallels in the radicals in the two systems seen in well-resolved electron paramagnetic resonance (EPR) spectra that could be obtained at pH = 6. [ABSTRACT FROM AUTHOR]

Laurentide humic acid has been titrated with paraquat and with selected divalent metal ions. In some cases, the humic acid was spiked with one cation before titration with another one. Several equivalence points were determined for the binding of the divalent cations, including paraquat. Three equivalence points agreed well with values predicted from the acidic properties of the humic acid. Eight independent experiments gave nine replicate values for an equivalence point that corresponds to 79.2 mole % of the total pairs of carboxyl groups. It is postulated that this represents a large molecular weight or structural fraction of the humic acid. The remaining 20.8 mole % can either bind one divalent cation to two carboxylate anions or bind one divalent cation to one carboxylate anion, with another anion providing for charge balance. Aggregation ‐ disaggregation and dissolution ‐precipitation phenomena may determine which case prevails, and they in turn are sensitive to the chemical compositions of samples. It should be possible to develop analytical chemical methods for characterizing the stoichiometric properties of humic acid samples. [ABSTRACT FROM PUBLISHER]

The solution phase complexing equilibria of atrazine by fulvic acid at 25°C±1.° have been investigated over the pH range of 1.3 to 6.0. Experiments with 0.1MKC1 and chelated Cu(II) are compared with those without metal ions. The use of a fulvic acid having calibrated acidic and Cu(II) chelation properties has made it possible to obtain stoicheometricly “exact”; chemical information. This is correlated with previous hydrolysis kinetics work. It is concluded that atrazine is hydrogen bonded in a labile equilibrium, to an identifiable set of protonated carboxyl groups, which act as Brönsted acid catalysts for hydrolysis. 0.1M KC1 changes (1‐αA), the degree of protonation of the carboxyl groups, without otherwise affecting the atrazine complexing. Cu(II) chelation both reduces and weakens the complexing through a combination of carboxyl group blocking, and fulvic acid aggregation. Simple equations are presented for predictive calculations. [ABSTRACT FROM PUBLISHER]

The effects of cocontaminants, such as extractable organics and transformer oil (TO) on the remediation of polychlorinated biphenyl (PCB) impacted soils by hydrogen peroxide (H2O2), have been investigated. Presence of transformer oil is found to adversely affect the PCB degradation. About 20 and 60% of Aroclor 1254 were remediated by 15 and 30% H2O2, respectively, in soils which did not contain TO. When TO was introduced, no Aroclor 1254 degradation was observed with 15% H2O2 and a limited amount of about 20% of Aroclor 1254 degraded with 30% H2O2 treatment. The impact of cocontaminants on major Aroclor 1254 congeners 101, 87, 110, 118, 105, and 138 were also found to be limited in the presence of TO. [ABSTRACT FROM AUTHOR]