The Experts below are selected from a list of 13614 Experts worldwide ranked by ideXlab platform
Wladyslaw Kowalski - One of the best experts on this subject based on the ideXlab platform.
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Pulsed UV Systems
Ultraviolet Germicidal Irradiation Handbook, 2009Co-Authors: Wladyslaw KowalskiAbstract:Pulsed light systems using ultraviolet wavelengths have been shown to rapidly produce high levels of Disinfection. The rate of Disinfection is high due to the extreme UV power levels produced by pulsed UV lamps. The Disinfection effect of pulsed light is primarily due to the UV content and can be modeled using the same basic UV rate constants previously presented for UV exposure. One exception exists – pulsed light induces a secondary effect, rapid heating due to the UVA content that can rupture microbial cells. This new Disinfection Process will also be addressed here after the basics of pulsed UV Disinfection are covered.
Liqiu Zhang - One of the best experts on this subject based on the ideXlab platform.
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Disinfection by-products formation and acute toxicity variation of hospital wastewater under different Disinfection Processes
Separation and Purification Technology, 2020Co-Authors: Luo Yuchen, Li Feng, Yongze Liu, Liqiu ZhangAbstract:Abstract Hospital wastewater (HWW) contains a large number of pathogenic microorganisms; therefore Disinfection is an indispensable unit for its treatment. This study compared the formation and formation potential of Disinfection by-products (DBPs) and assessed the variations of acute toxicity for both of first physical treatment effluent (FPTE) and second biological treatment effluent (SBTE) of HWW under five different Disinfection Processes, including free chlorine (Cl2), chlorine dioxide (ClO2), ozone (O3), ultraviolet (UV) and ultraviolet/chlorine (UV/Cl2). Firstly, the optimal parameters of each Disinfection Process for FPTE and SBTE were determined respectively based on the required Disinfection efficiency (i.e., controlling the concentration of fecal coliforms). The amounts of total DBPs in different Disinfection Processes under the optimal disinfectants dosage followed the order of Cl2 > UV/Cl2 > ClO2 > UV ≈ O3, which demonstrated that the amount of DBPs formation was closely related to the dosage of chlorine. Meanwhile, the amounts of total Disinfection by-products formation potential (DBPFP) under the optimal disinfectants dosage followed the order of UV/Cl2 > UV ≈ Cl2 > O3 > ClO2. Besides, it was found that with the reduction of chlorine dosage, the formed DBPs in UV/Cl2 Disinfection Process decreased. However, UV/Cl2 Disinfection Process might degrade organic compounds into more DBPs precursors, leading to higher DBPFP than that in Cl2 Disinfection Process. Significantly, some specific DBPFPs such as haloketones-FP (HKFP), chloral hydrate-FP (CHFP) and trichloronitromethane-FP (TCNMFP) in O3 Disinfection Process were found higher than that in Cl2 Disinfection Process, which could be attributed to the formation of O3 oxidation by-products, for instance aldehydes, methyl ketones and trivalent nitrogen compounds. Additionally, apart from O3, the growth inhibition rate of Chlorella vulgaris increased in all the other Disinfection Processes and the order of the acute toxicity in each disinfected effluent was consistent with that of DBPs formation.
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Degradation behaviors and genetic toxicity variations of pyrazolone pharmaceuticals during chlorine dioxide Disinfection Process
Chemical Engineering Journal, 2018Co-Authors: Xing-hua Jia, Li Feng, Yongze Liu, Liqiu ZhangAbstract:Abstract Pyrazolone pharmaceuticals such as isopropylphenazone (PRP) and aminopyrine (AMP) were commonly used as antipyretic analgesics, and their frequently detection in aquatic environment has become a major concern in recent years. Chlorine dioxide (ClO2) Disinfection Process has been proved to be a feasible way to degrade antipyrine (ANT), which is the first synthetic pyrazolone pharmaceutical. In this work, the reaction kinetics, degradation pathways and genetic toxicity of PRP and AMP during ClO2 Disinfection Process were investigated. Experimental results demonstrated that the reaction of both PRP and AMP with ClO2 followed second-order kinetics, the second-order rate constants were calculated to be kapp(PRP) = 11.0 M−1 s−1 and kapp(AMP) = 1.30 × 105 M−1 s−1 at neutral pH. Slightly alkaline environment (pH = 9) was in favor of the reaction. C C double bond and C N bond on pyrazolone ring were main active groups under ClO2 electrophilic attack. The degradation pathways of pyrazolone pharmaceuticals could be concluded as C C cleavage, ring-opening reaction and de-carbonyl reaction. Pyrazolone contaminated water exhibited genetic toxicity according to micronucleus test of Viciafaba root tip, however, the toxicity could be reduced through ClO2 Disinfection Process.
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degradation of clofibric acid in uv chlorine Disinfection Process kinetics reactive species contribution and pathways
Royal Society Open Science, 2018Co-Authors: Yuqing Tang, Li Feng, Yongze Liu, Xueting Shi, Liqiu ZhangAbstract:As a potential endocrine disruptor, clofibric acid (CA) was investigated in this study for its degradation kinetics and pathways in UV/chlorine Process. The results showed that CA in both UV photolysis and UV/chlorine Processes could be degraded via pseudo-first-order kinetics, while it almost could not be degraded in the dark chlorination Process. The observed rate constant ( k obs ) in UV photolysis was 0.0078 min −1, and increased to 0.0107 min −1 combining with 0.1 mM chlorine. The k obs increased to 0.0447 min −1 with further increasing the chlorine dosage from 0.1 to 1.0 mM, and reached a plateau at higher dosage (greater than 1.0 mM). The higher k obs was obtained at acid solution rather than basic solution. Moreover, the calculated contributions of radical species to k obs indicated that the HO• contributed significantly to CA degradation in acidic conditions, while the reactive chlorine species and UV direct photolysis dominated in neutral and basic solution. The degradation of CA was slightly inhibited in the presence of HC O 3 − (1 ∼ 50 mM), barely affected by the presence of Cl − (1 ∼ 200 mM) and greatly suppressed by humic acid (0 ∼ 5 mg l −1 ). Thirteen main degradation intermediates and three degradation pathways of CA were identified during UV/chlorine Process.
Chris Douville - One of the best experts on this subject based on the ideXlab platform.
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impact of wastewater infrastructure upgrades on the urban water cycle reduction in halogenated reaction byproducts following conversion from chlorine gas to ultraviolet light Disinfection
Science of The Total Environment, 2015Co-Authors: Larry B Barber, Michelle L Hladik, Alan M Vajda, Kevin C Fitzgerald, Chris DouvilleAbstract:The municipal wastewater treatment facility (WWTF) infrastructure of the United States is being upgraded to expand capacity and improve treatment, which provides opportunities to assess the impact of full-scale operational changes on water quality. Many WWTFs disinfect their effluent prior to discharge using chlorine gas, which reacts with natural and synthetic organic matter to form halogenated Disinfection byproducts (HDBPs). Because HDBPs are ubiquitous in chlorine-disinfected drinking water and have adverse human health implications, their concentrations are regulated in potable water supplies. Less is known about the formation and occurrence of HDBPs in disinfected WWTF effluents that are discharged to surface waters and become part of the de facto wastewater reuse cycle. This study investigated HDBPs in the urban water cycle from the stream source of the chlorinated municipal tap water that comprises the WWTF inflow, to the final WWTF effluent Disinfection Process before discharge back to the stream. The impact of conversion from chlorine-gas to low-pressure ultraviolet light (UV) Disinfection at a full-scale (68,000 m3 d− 1 design flow) WWTF on HDBP concentrations in the final effluent was assessed, as was transport and attenuation in the receiving stream. Nutrients and trace elements (boron, copper, and uranium) were used to characterize the different urban source waters, and indicated that the pre-upgrade and post-upgrade water chemistry was similar and insensitive to the Disinfection Process. Chlorinated tap water during the pre-upgrade and post-upgrade samplings contained 11 (mean total concentration = 2.7 μg L− 1; n = 5) and 10 HDBPs (mean total concentration = 4.5 μg L− 1), respectively. Under chlorine-gas Disinfection conditions 13 HDBPs (mean total concentration = 1.4 μg L− 1) were detected in the WWTF effluent, whereas under UV Disinfection conditions, only one HDBP was detected. The chlorinated WWTF effluent had greater relative proportions of nitrogenous, brominated, and iodinated HDBPs than the chlorinated tap water. Conversion of the WWTF to UV Disinfection reduced the loading of HDBPs to the receiving stream by > 90%.
Tapas K Das - One of the best experts on this subject based on the ideXlab platform.
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Evaluating the life cycle environmental performance of chlorine Disinfection and ultraviolet technologies
Clean Technologies and Environmental Policy, 2002Co-Authors: Tapas K DasAbstract:With increasing emphasis on promoting a sustainable ecological future and concern over introducing a toxic chemical in the water, the design of the Disinfection Process is increasingly leaning toward technologies that destroy the pathogens while balancing the effects of this disinfected wastewater on the population of aquatic biota or a drinking water supply. Since ultraviolet (UV) irradiation is not a chemical additive, it does not leave or produce any by-product toxic compounds in the wastewater, like traditional chlorination and de-chlorination Processes do. Therefore, the use of UV does not affect a drinking water supply or the aquatic biota in receiving waters. Life cycle assessment or analysis (LCA) is used to quantify the environmental benefits of using UV Disinfection technology (as well as better protecting public health), instead of chlorination and de-chlorination methods. LCA tools are being used to evaluate the short and long term environmental effects of both Processes, and to select the best sustainable Process. The approach here combines environmental LCA with these Disinfection Processes incorporating economic criteria and all aspects of the environment: chemical use, electricity use, and releases to water, air, and land. The environmental, health, and economic benefits and other effects show the greater sustainability of UV technology (a "clean" ecological Disinfection Process) in comparison to that of traditional Disinfection with chlorine.
Yuqing Tang - One of the best experts on this subject based on the ideXlab platform.
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degradation of clofibric acid in uv chlorine Disinfection Process kinetics reactive species contribution and pathways
Royal Society Open Science, 2018Co-Authors: Yuqing Tang, Li Feng, Yongze Liu, Xueting Shi, Liqiu ZhangAbstract:As a potential endocrine disruptor, clofibric acid (CA) was investigated in this study for its degradation kinetics and pathways in UV/chlorine Process. The results showed that CA in both UV photolysis and UV/chlorine Processes could be degraded via pseudo-first-order kinetics, while it almost could not be degraded in the dark chlorination Process. The observed rate constant ( k obs ) in UV photolysis was 0.0078 min −1, and increased to 0.0107 min −1 combining with 0.1 mM chlorine. The k obs increased to 0.0447 min −1 with further increasing the chlorine dosage from 0.1 to 1.0 mM, and reached a plateau at higher dosage (greater than 1.0 mM). The higher k obs was obtained at acid solution rather than basic solution. Moreover, the calculated contributions of radical species to k obs indicated that the HO• contributed significantly to CA degradation in acidic conditions, while the reactive chlorine species and UV direct photolysis dominated in neutral and basic solution. The degradation of CA was slightly inhibited in the presence of HC O 3 − (1 ∼ 50 mM), barely affected by the presence of Cl − (1 ∼ 200 mM) and greatly suppressed by humic acid (0 ∼ 5 mg l −1 ). Thirteen main degradation intermediates and three degradation pathways of CA were identified during UV/chlorine Process.