Search

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]

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]

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 study, the relative efficiency of four forms of supported titanium dioxide (TiO2) as a photocatalyst to degrade 2,4-dichlorophenoxyacetic acid (2,4-D) in Killex®, a commercially available herbicide was studied. Coated glass spheres, anodized plate, anodized mesh, and electro-photocatalysis using the anodized mesh were evaluated under an ultraviolet – light-emitting diode (UV-LED) light source at λ = 365 nm in a semi-passive mode. Energy consumption of the system was used to compare the efficiency of the photocatalysts. The results showed both photospheres and mesh consumed approximately 80 J/cm3 energy followed by electro-photocatalysis (112.2 J/cm3), and the anodized plate (114.5 J/cm3). Although electro-photocatalysis showed the fastest degradation rate (K = 5.04 mg L−1 h−1), its energy consumption was at the same level as the anodized plate with a lower degradation rate constant of 3.07 mg L−1 h−1. The results demonstrated that three-dimensional nanotubes of TiO2 surrounding the mesh provide superior degradation compared to one-dimensional arrays on the planar surface of the anodized plate. With limited broad-scale comparative studies between varieties of different TiO2 supports, this study provides a comparative analysis of relative degradation efficiencies between the four photocatalytic configurations. [ABSTRACT FROM AUTHOR]

Correction for ‘Facile synthesis of NiS2 nanoparticles ingrained in a sulfur-doped carbon nitride framework with enhanced visible light photocatalytic activity: two functional roles of thiourea’ by Milad Jourshabani et al., J. Mater. Chem. A, 2018, 6, 13448–13466. [ABSTRACT FROM AUTHOR]

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 H 2 O 2 . The study is supported by bench scale degradation experiments on VEN. Results demonstrated that UV can completely degrade VEN, but the addition of H 2 O 2 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 H 2 O 2 , 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 H 2 O 2 dosage, a framework is set to allow researchers and engineers to move forward with developing UV/H 2 O 2 systems that meet their future design needs for pharmaceutical removal.

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 H 2 O 2 . 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 ( R 2  = 0.98) with UV intensity between 1.67 and 8.95 × 10 17 for an optimum H -1 for an optimum H 2 O 2 . 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 H -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 H 2 O 2 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.