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Haiqing Chang - One of the best experts on this subject based on the ideXlab platform.
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Smart ultrafiltration membrane fouling control as desalination pretreatment of shale gas fracturing wasteWater: The effects of Backwash Water.
Environment international, 2019Co-Authors: Haiqing Chang, Baicang Liu, Chen Chen, John C. CrittendenAbstract:Abstract Background Increasing attention is being paid to the treatment of shale gas fracturing wasteWater, including flowback and produced Water (FPW). Energy-efficient pretreatment technologies suitable for desalinating and reusing FPW are of paramount importance. Objectives This work focused on enhanced fouling alleviation of ultrafiltration (UF) as a pretreatment for desalinating shale gas FPW in Sichuan Basin, China. The UF fouling behaviors under various Backwash Water sources or coagulant dosages were evaluated, and membrane surface characteristics were correlated with UF fouling. The feasibility of Fourier transform infrared (FTIR) microscope mapping technique in quantifying UF fouling was also assessed. Methods Various Backwash Water sources, including UF permeate, ultrapure Water, nanofiltration (NF) permeate, reverse osmosis (RO) permeate, RO concentrate and forward osmosis (FO) draw solution, were used to clean UF membranes fouled by shale gas FPW. The UF fouling behaviors were characterized by total and non-Backwashable fouling rates. Membrane surface characteristics were analyzed by scanning electron microscopy (SEM), total tension surface and FTIR spectra. Results Protein-like substances in terms of fluorescence intensity in the Backwash Water decreased with the order of UF permeate, RO concentrate, NF permeate, RO permeate and FO draw solution. Compared with UF permeate Backwashing, alleviated UF fouling was observed by using demineralized Backwash Water including ultrapure Water and RO permeate, irrespective of hollow fiber and flat-sheet membranes. NF permeate and RO concentrate after NF used as Backwash Water resulted in low and comparable membrane fouling with that in integrated coagulation-UF process under optimal dosage. Among the Backwash Water tested, FO draw solution Backwashing corresponded to the lowest UF fouling rates, which were even lower than that in the presence of coagulant under optimal dosage. The superiority of these Backwash Water sources to UF permeate was further confirmed by SEM images and FTIR spectra. The residual foulant mass on membrane surface and the total surface tension correlated well with non-Backwashable and total fouling rates, respectively. Conclusions FTIR microscopy was a powerful surface mapping technique to characterize UF membrane fouling caused by shale gas FPW. Backwash Water sources significantly influenced the fouling of UF membranes. In the integrated UF-NF-RO or UF-FO process, RO concentrate or FO draw solution were proposed as Backwash Water to enhance UF fouling control and decrease waste discharge simultaneously.
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Effect of filtration mode and Backwash Water on hydraulically irreversible fouling of ultrafiltration membrane
Chemosphere, 2017Co-Authors: Haiqing Chang, Baicang Liu, Heng Liang, Senlin ShaoAbstract:To investigate the effect of filtration mode and Backwash Water on ultrafiltration (UF) membrane performance, total fouling index (TFI) and hydraulic irreversible fouling index (HIFI) for constant pressure (CP) filtration and constant flux (CF) filtration were compared. Kaolin, humic acid (HA) and sodium alginate (SA) solutions were used as feed solutions, and then the fouled membranes were Backwashed with UF permeate or ultrapure Water. Results showed that when the kaolin solution was filtrated, the filtration mode had a limited effect on the membrane fouling, and low TFI and HIFI were observed. When HA and SA solutions were filtrated, the TFI of UF under CP mode was comparable to or slightly higher than that under CF mode. Higher TFI was observed at a hydrophobic membrane, a high filtration strength, a high feed concentration, a low pH, a high ionic strength, and a low Ca2+ concentration. When the UF permeate was used as the Backwash Water, the HIFI for the UF operated under CF mode was significantly less than that under CP mode. Low irreversible fouling was obtained when the ultrapure Water was used for Backwashing, and the HIFI for the UF under different filtration modes was almost identical.
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Role of Backwash Water composition in alleviating ultrafiltration membrane fouling by sodium alginate and the effectiveness of salt Backwashing
Journal of Membrane Science, 2016Co-Authors: Haiqing Chang, Senlin Shao, Heng Liang, Bin Liu, Wei GaoAbstract:Abstract To obtain a better hydraulic cleaning strategy for ultrafiltration (UF) membranes fouled by sodium alginate (SA), various types of Backwash Water, including UF permeate, ultrapure Water, NaCl solution, CaCl 2 solution and SA solution, were compared with respect to hydraulic cleaning efficiency (HCE), hydraulically irreversible fouling index, Fourier transform infrared spectra analysis, normalized transmembrane streaming potential coefficient and foulant release. The results indicated that UF permeate Backwash or CaCl 2 solution Backwash significantly decreased the HCE. On the contrary, NaCl solution Backwash greatly alleviated the SA fouling, and Backwashing with ultrapure Water or organic compounds was also efficient when both Na + and Ca 2+ were present in feed Water. Moreover, the amount of released SA from the fouling layer during Backwashing was closely related to that of released Ca 2+ . Electric double layer release involved in Backwashing with ultrapure Water and SA solution, and ion exchange played significant roles in the effective hydraulic cleaning associated with Na + . Further, monovalent salt Backwashing was quite effective for a wide range of salt concentrations, and the approach was effective irrespective of monovalent salt types. Moreover, the results obtained from natural organic matter (NOM) and effluent organic matter (EfOM) further proved the efficiency of NaCl solution Backwash.
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Towards a better hydraulic cleaning strategy for ultrafiltration membrane fouling by humic acid: Effect of Backwash Water composition.
Journal of environmental sciences (China), 2015Co-Authors: Haiqing Chang, Heng Liang, Nanqi RenAbstract:As a routine measurement to alleviate membrane fouling, hydraulic cleaning is of great significance for the steady operation of ultrafiltration (UF) systems in Water treatment processes. In this work, a comparative study was performed to investigate the effects of the composition of Backwash Water on the hydraulic cleaning performance of UF membranes fouled by humic acid (HA). Various types of Backwash Water, including UF permeate, Milli-Q Water, NaCl solution, CaCl2 solution and HA solution, were compared in terms of hydraulically irreversible fouling index, total surface tension and residual HA. The results indicated that Milli-Q Water Backwash was superior to UF permeate Backwash in cleaning HA-fouled membranes, and the Backwash Water containing Na(+) or HA outperformed Milli-Q Water in alleviating HA fouling. On the contrary, the presence of Ca(2+) in Backwash Water significantly decreased the Backwash efficiency. Moreover, Ca(2+) played an important role in foulant removal, and the residual HA content closely related to the residual Ca(2+) content. Mechanism analysis suggested that the Backwash process may involve fouling layer swelling, ion exchange, electric double layer release and competitive complexation. Ion exchange and competitive complexation played significant roles in the efficient hydraulic cleaning associated with Na(+) and HA, respectively.
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hydraulic irreversibility of ultrafiltration membrane fouling by humic acid effects of membrane properties and Backwash Water composition
Journal of Membrane Science, 2015Co-Authors: Haiqing Chang, Fangshu Qu, Huarong Yu, Kai Li, Senlin Shao, Guibai Li, Heng LiangAbstract:Abstract Five commercially available ultrafiltration (UF) membranes: polyethersulfone (PES, 100 kDa), polyvinylidene fluoride (PVDF, 100 kDa) and cellulose acetate (CA, 100, 30 and 10 kDa), were fouled with humic acid (HA) solutions and cleaned using various compositions of Backwash Water including ultrapure Water, monovalent cations (Na + ), divalent cations (Ca 2+ ), an organic compound (HA) and UF permeate. The hydraulically irreversible fouling and the hydraulic cleaning efficiency (HCE) for each combination of membrane and Backwash Water composition were analyzed. In summary, both the membrane properties and the Backwash Water composition affected hydraulically irreversible fouling. The membrane properties significantly affected the total fouling, and the HCE was primarily affected by the Backwash Water composition. Further, the adhesive free energy between HA and the membranes correlated well with the total fouling. Ultrapure Water was superior to UF permeate for Backwashing, and the presence of appropriate components (e.g., Na + or HA) further improved the HCE; however, Ca 2+ exerted detrimental impacts on the HCE. In addition, the removal of the deposited HA was consistent with the amount of Ca 2+ released from the fouling layer during Backwashing. Mechanistic analysis suggested that the Backwashing process involves fouling layer swelling, ion exchange, electric double layer release and competitive complexation.
Wei Chen - One of the best experts on this subject based on the ideXlab platform.
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micro flocculation sedimentation and ozonation for controlling ultrafiltration membrane fouling in recycling of activated carbon filter Backwash Water
Chemical Engineering Journal, 2017Co-Authors: Jianan Zhang, Tao Lin, Wei ChenAbstract:Abstract The reuse of activated carbon filter Backwash Water (ACFBW) was performed using an ultrafiltration (UF) system. The feed Water was pretreated by the micro-flocculation/sedimentation, followed by ozonation, prior to its entry into the UF system. The dose of 2 mg/L PACl and subsequent 10 min sedimentation were involved in the pretreatment, which resulted in the removal of most particles and bacteria in ACFBW, causing a decrease of transmembrane pressure (TMP) and the mitigation of membrane fouling. In the parallel experiment with or without preozonation, the influence of dosing ozone at 0.15 mg/L on membrane fouling was investigated. The results showed that the preozonation restrained bacteria breeding on the membrane surface and maintained the membrane permeability. The preozonation reduced the hydrophobic organic matters and changed the molecular weight distribution of organics in the influent ACFBW, reflecting macromolecular organic compounds to form small fractions. In addition, the preozonation narrowed the pore size of membrane, the virgin membrane varying from 2.1 to 26.3 nm compared with the used membrane with preozonation from 1.5 to 23.6 nm. The preozonation improved the hydrophobicity of membrane material in a long-running filtration, which could aggravate the membrane fouling. However, the preozonation enhanced UF performance due to the characteristics change of organic matters, which was dominant in alleviating membrane fouling compared with the adverse influence of the increased hydrophobicity of membrane material.
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The shadow of dichloroacetonitrile (DCAN), a typical nitrogenous disinfection by-product (N-DBP), in the Waterworks and its Backwash Water reuse.
Chemosphere, 2017Co-Authors: Tan Yiwen, Tao Lin, Fuchun Jiang, Jian Dong, Wei Chen, Dongju ZhouAbstract:Dichloroacetonitrile (DCAN) is one of nitrogenous disinfection by-products (N-DBPs) with strong cytotoxicity and genotoxicity. In this study, the formation potential (FP) of DCAN was investigated in the samples of six important Water sources located in the Yangtze River Delta. The highest formation concentration of DCAN was 9.05 μg/L in the Water sample taken from Taihu Lake with the lowest SUVA value. After the NOM fractionation, the conversion rate of hydrophilic fraction to DCAN was found the highest. Subsequently, a Waterworks using Taihu Lake as Water source was chosen to research the FP variations of DCAN in the treatment process and Backwash Water. The results showed that, compared to the conventional treatment process, O/biological activated carbon (BAC) process increased the removal efficiency of DCAN from 21.89% to 50.58% by removing aromatic protein and soluble biological by-products as main precursors of DCAN. The DCAN FP in the effluent of BAC filters using old granular activated carbon was higher than that in the influent and the DCAN FP of its Backwash Water was lower than that in raw Water. In the Backwash Water of sand filters, the DCAN FP higher than raw Water required the recycle ratio less than 5% to avoid the accumulation of DCAN.
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Recycling of activated carbon filter Backwash Water using ultrafiltration: membrane fouling caused by different dominant interfacial forces
Journal of Membrane Science, 2017Co-Authors: Tao Lin, Zhang Jianan, Wei ChenAbstract:Abstract The reuse of activated carbon filter Backwash Water was performed using an ultrafiltration (UF) system and the membrane fouling mechanism was investigated using a model involving XDLVO theory and hydrodynamic interaction. Pretreatment by micro-flocculation/sedimentation removed most particulate pollutants; thus, residual organic colloids determined the details of the UF membrane fouling. The membrane fouling was divided into two periods. Membrane fouling in the initial period was determined by interfacial forces between the membrane and colloids. The calculated interfacial forces showed that permeation drag (PD) force dominated the total interfacial force at long-range, while London-van der Waals and short-range Lewis acid-base (AB) forces governed membrane fouling at short-range (
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Micro-flocculation/sedimentation and ozonation for controlling ultrafiltration membrane fouling in recycling of activated carbon filter Backwash Water
Chemical Engineering Journal, 2017Co-Authors: Zhang Jianan, Tao Lin, Wei ChenAbstract:Abstract The reuse of activated carbon filter Backwash Water (ACFBW) was performed using an ultrafiltration (UF) system. The feed Water was pretreated by the micro-flocculation/sedimentation, followed by ozonation, prior to its entry into the UF system. The dose of 2 mg/L PACl and subsequent 10 min sedimentation were involved in the pretreatment, which resulted in the removal of most particles and bacteria in ACFBW, causing a decrease of transmembrane pressure (TMP) and the mitigation of membrane fouling. In the parallel experiment with or without preozonation, the influence of dosing ozone at 0.15 mg/L on membrane fouling was investigated. The results showed that the preozonation restrained bacteria breeding on the membrane surface and maintained the membrane permeability. The preozonation reduced the hydrophobic organic matters and changed the molecular weight distribution of organics in the influent ACFBW, reflecting macromolecular organic compounds to form small fractions. In addition, the preozonation narrowed the pore size of membrane, the virgin membrane varying from 2.1 to 26.3 nm compared with the used membrane with preozonation from 1.5 to 23.6 nm. The preozonation improved the hydrophobicity of membrane material in a long-running filtration, which could aggravate the membrane fouling. However, the preozonation enhanced UF performance due to the characteristics change of organic matters, which was dominant in alleviating membrane fouling compared with the adverse influence of the increased hydrophobicity of membrane material.
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Evaluation of a drinking Water treatment process involving directly recycling filter Backwash Water using physico-chemical analysis and toxicity assay
RSC Advances, 2016Co-Authors: Bingwei Hou, Tao Lin, Wei ChenAbstract:Recycling the filter Backwash Water of a drinking Water treatment plant (DWTP) was considered as a feasible method to enhance the efficiencies of pollutant removal and Water conservation. In this study, the purification efficiency and Water quality evaluation were investigated in a DWTP with a direct recycling of sand filters Backwash Water (SFBW) at recycling rates of 0–30%. The concentrations of dissolved organic carbon and dissolved nitrogen matters, and the formation potentials of carbonated or nitrogenous disinfection by-products did not obviously increase or were even lower than that without recycling when the recycling rate of SFBW was less than 20%. The di-haloacetamides (DCAcAm) accounted for the majority of HAcAms formed during chlorination in all Water extracts, followed by tri-HAcAms and, to a much lower extent, mono-HAcAms. The immobilization of Daphnia magna (D. magna) increased with the increasing exposure concentration of Water extracts during a 48 h period. The immobilization of D. magna exposed to Water treated by recycling SFBW at a recycling rate below 20% was nearly equivalent to that without a recycling process. When the recycling rate was more than 20%, there was a significant increase in the superoxide dismutase (SOD) activity of D. magna, whereas a significant inhibition observed in the catalase (CAT) activity, which reflected a damaged defense chain caused by the toxic substances including chlorinated and nitrogenous disinfection by-products such as DCAcAm. When the recycling rate was more than 20%, there was a statistically significant difference (p > 0.05) between the recycling rate of SFBW and the toxicity effect of Water sample extracts during the recycling trial. It was also identified that the main precursors of DCAcAm were hydrophilic and low molecular weight fractions of dissolved organic nitrogen.
S.g.j. Heijman - One of the best experts on this subject based on the ideXlab platform.
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Influence of Ca and Na ions in Backwash Water on ultrafiltration fouling control
Desalination, 2010Co-Authors: S.g.j. Heijman, J.q.j.c. Verberk, J.c. Van DijkAbstract:The effect of calcium and sodium in Backwash Water on the fouling control of ultrafiltration is investigated on a bench scale. Besides permeate of ultrafiltration and demineralized Water, solutions with different calcium or sodium concentrations were used for Backwash. The results show that Backwashing with demineralized Water is better than with permeate of ultrafiltration. The Backwash efficiency decreases when calcium and sodium are added in demineralized Water for Backwash. That is probably because the presence of calcium and sodium in Backwash Water increases the Ca-bridging effect between the negatively charged membrane and the negatively charged NOM, and compresses the double layer of the membrane and the NOM, leading to a strong adhesion force on the membrane.
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Impact of Backwash Water composition on ultrafiltration fouling control
Journal of Membrane Science, 2009Co-Authors: S.g.j. Heijman, J.q.j.c. Verberk, Arne Verliefde, Antonius J.b. Kemperman, J.c. Van Dijk, Gary AmyAbstract:This paper investigates the impacts of different components in Backwash Water on ultrafiltration (UF) fouling control. Natural surface Water was used as feed Water, different Backwash Waters with different Ca2+ and Na+ concentrations were prepared by dosing CaCl2 and NaCl into demineralized Water. Furthermore, UF permeate containing mainly natural organic matter (NOM) with minimal cations (Ca2+ and Na+) was produced by dialysis and used for Backwashing as well. Thus, the efficiency of different Backwash Waters on UF fouling control was evaluated. Results show that the presence of both divalent (Ca2+) and monovalent cations (Na+) in Backwash Water reduces the fouling control efficiency. Since the negative charges of UF membranes and NOM compounds are screened by the cations during filtration, NOM can easily deposit on the surface of the UF membrane, causing fouling. When the mono- and divalent cations are absent in the Backwash Water, the charge-screening effect around the negatively charged UF membrane and NOM is reduced, increasing the repulsion force between them. In addition to the charge-screening effect, the absence of calcium in Backwash Water can also reduce the calcium-bridging effect between the membrane and NOM, increasing the fouling control efficiency of the Backwash. Measurements of the streaming potential indicate that Backwashing with demineralized Water can maintain the negative charge of the membrane. Organic compounds in the Backwash Water do not influence the fouling control efficiency of the Backwash.
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Removal of divalent cations reduces fouling of ultrafiltration membranes
Journal of Membrane Science, 2008Co-Authors: A.j. Abrahamse, C. Lipreau, S.g.j. HeijmanAbstract:Abstract The effect of divalent ions on hydraulic irreversible fouling of ultrafiltration membranes was studied. Not only the effect of removing divalent ions by pretreatment of raw Water with ion exchange is quantitatively studied, but also the effects of different types of Backwash Water are considered. By replacing divalent ions with sodium in cation exchange, the amount of hydraulic irreversible fouling (remaining fouling after Backwashing) is reduced by at least 60%. When adding either calcium or magnesium to Water treated with cation exchange, a linear relation is found between the ion concentration and the irreversible fouling rate. The effects of calcium and magnesium are identical when the concentrations are expressed in mol/L. Removing divalent ions from the Backwash Water does not affect irreversible fouling, but when using MilliQ Water as Backwash Water, irreversible fouling can (almost) completely be prevented.
Heng Liang - One of the best experts on this subject based on the ideXlab platform.
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Effect of filtration mode and Backwash Water on hydraulically irreversible fouling of ultrafiltration membrane
Chemosphere, 2017Co-Authors: Haiqing Chang, Baicang Liu, Heng Liang, Senlin ShaoAbstract:To investigate the effect of filtration mode and Backwash Water on ultrafiltration (UF) membrane performance, total fouling index (TFI) and hydraulic irreversible fouling index (HIFI) for constant pressure (CP) filtration and constant flux (CF) filtration were compared. Kaolin, humic acid (HA) and sodium alginate (SA) solutions were used as feed solutions, and then the fouled membranes were Backwashed with UF permeate or ultrapure Water. Results showed that when the kaolin solution was filtrated, the filtration mode had a limited effect on the membrane fouling, and low TFI and HIFI were observed. When HA and SA solutions were filtrated, the TFI of UF under CP mode was comparable to or slightly higher than that under CF mode. Higher TFI was observed at a hydrophobic membrane, a high filtration strength, a high feed concentration, a low pH, a high ionic strength, and a low Ca2+ concentration. When the UF permeate was used as the Backwash Water, the HIFI for the UF operated under CF mode was significantly less than that under CP mode. Low irreversible fouling was obtained when the ultrapure Water was used for Backwashing, and the HIFI for the UF under different filtration modes was almost identical.
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Role of Backwash Water composition in alleviating ultrafiltration membrane fouling by sodium alginate and the effectiveness of salt Backwashing
Journal of Membrane Science, 2016Co-Authors: Haiqing Chang, Senlin Shao, Heng Liang, Bin Liu, Wei GaoAbstract:Abstract To obtain a better hydraulic cleaning strategy for ultrafiltration (UF) membranes fouled by sodium alginate (SA), various types of Backwash Water, including UF permeate, ultrapure Water, NaCl solution, CaCl 2 solution and SA solution, were compared with respect to hydraulic cleaning efficiency (HCE), hydraulically irreversible fouling index, Fourier transform infrared spectra analysis, normalized transmembrane streaming potential coefficient and foulant release. The results indicated that UF permeate Backwash or CaCl 2 solution Backwash significantly decreased the HCE. On the contrary, NaCl solution Backwash greatly alleviated the SA fouling, and Backwashing with ultrapure Water or organic compounds was also efficient when both Na + and Ca 2+ were present in feed Water. Moreover, the amount of released SA from the fouling layer during Backwashing was closely related to that of released Ca 2+ . Electric double layer release involved in Backwashing with ultrapure Water and SA solution, and ion exchange played significant roles in the effective hydraulic cleaning associated with Na + . Further, monovalent salt Backwashing was quite effective for a wide range of salt concentrations, and the approach was effective irrespective of monovalent salt types. Moreover, the results obtained from natural organic matter (NOM) and effluent organic matter (EfOM) further proved the efficiency of NaCl solution Backwash.
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Towards a better hydraulic cleaning strategy for ultrafiltration membrane fouling by humic acid: Effect of Backwash Water composition.
Journal of environmental sciences (China), 2015Co-Authors: Haiqing Chang, Heng Liang, Nanqi RenAbstract:As a routine measurement to alleviate membrane fouling, hydraulic cleaning is of great significance for the steady operation of ultrafiltration (UF) systems in Water treatment processes. In this work, a comparative study was performed to investigate the effects of the composition of Backwash Water on the hydraulic cleaning performance of UF membranes fouled by humic acid (HA). Various types of Backwash Water, including UF permeate, Milli-Q Water, NaCl solution, CaCl2 solution and HA solution, were compared in terms of hydraulically irreversible fouling index, total surface tension and residual HA. The results indicated that Milli-Q Water Backwash was superior to UF permeate Backwash in cleaning HA-fouled membranes, and the Backwash Water containing Na(+) or HA outperformed Milli-Q Water in alleviating HA fouling. On the contrary, the presence of Ca(2+) in Backwash Water significantly decreased the Backwash efficiency. Moreover, Ca(2+) played an important role in foulant removal, and the residual HA content closely related to the residual Ca(2+) content. Mechanism analysis suggested that the Backwash process may involve fouling layer swelling, ion exchange, electric double layer release and competitive complexation. Ion exchange and competitive complexation played significant roles in the efficient hydraulic cleaning associated with Na(+) and HA, respectively.
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hydraulic irreversibility of ultrafiltration membrane fouling by humic acid effects of membrane properties and Backwash Water composition
Journal of Membrane Science, 2015Co-Authors: Haiqing Chang, Fangshu Qu, Huarong Yu, Kai Li, Senlin Shao, Guibai Li, Heng LiangAbstract:Abstract Five commercially available ultrafiltration (UF) membranes: polyethersulfone (PES, 100 kDa), polyvinylidene fluoride (PVDF, 100 kDa) and cellulose acetate (CA, 100, 30 and 10 kDa), were fouled with humic acid (HA) solutions and cleaned using various compositions of Backwash Water including ultrapure Water, monovalent cations (Na + ), divalent cations (Ca 2+ ), an organic compound (HA) and UF permeate. The hydraulically irreversible fouling and the hydraulic cleaning efficiency (HCE) for each combination of membrane and Backwash Water composition were analyzed. In summary, both the membrane properties and the Backwash Water composition affected hydraulically irreversible fouling. The membrane properties significantly affected the total fouling, and the HCE was primarily affected by the Backwash Water composition. Further, the adhesive free energy between HA and the membranes correlated well with the total fouling. Ultrapure Water was superior to UF permeate for Backwashing, and the presence of appropriate components (e.g., Na + or HA) further improved the HCE; however, Ca 2+ exerted detrimental impacts on the HCE. In addition, the removal of the deposited HA was consistent with the amount of Ca 2+ released from the fouling layer during Backwashing. Mechanistic analysis suggested that the Backwashing process involves fouling layer swelling, ion exchange, electric double layer release and competitive complexation.
Tao Lin - One of the best experts on this subject based on the ideXlab platform.
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micro flocculation sedimentation and ozonation for controlling ultrafiltration membrane fouling in recycling of activated carbon filter Backwash Water
Chemical Engineering Journal, 2017Co-Authors: Jianan Zhang, Tao Lin, Wei ChenAbstract:Abstract The reuse of activated carbon filter Backwash Water (ACFBW) was performed using an ultrafiltration (UF) system. The feed Water was pretreated by the micro-flocculation/sedimentation, followed by ozonation, prior to its entry into the UF system. The dose of 2 mg/L PACl and subsequent 10 min sedimentation were involved in the pretreatment, which resulted in the removal of most particles and bacteria in ACFBW, causing a decrease of transmembrane pressure (TMP) and the mitigation of membrane fouling. In the parallel experiment with or without preozonation, the influence of dosing ozone at 0.15 mg/L on membrane fouling was investigated. The results showed that the preozonation restrained bacteria breeding on the membrane surface and maintained the membrane permeability. The preozonation reduced the hydrophobic organic matters and changed the molecular weight distribution of organics in the influent ACFBW, reflecting macromolecular organic compounds to form small fractions. In addition, the preozonation narrowed the pore size of membrane, the virgin membrane varying from 2.1 to 26.3 nm compared with the used membrane with preozonation from 1.5 to 23.6 nm. The preozonation improved the hydrophobicity of membrane material in a long-running filtration, which could aggravate the membrane fouling. However, the preozonation enhanced UF performance due to the characteristics change of organic matters, which was dominant in alleviating membrane fouling compared with the adverse influence of the increased hydrophobicity of membrane material.
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The shadow of dichloroacetonitrile (DCAN), a typical nitrogenous disinfection by-product (N-DBP), in the Waterworks and its Backwash Water reuse.
Chemosphere, 2017Co-Authors: Tan Yiwen, Tao Lin, Fuchun Jiang, Jian Dong, Wei Chen, Dongju ZhouAbstract:Dichloroacetonitrile (DCAN) is one of nitrogenous disinfection by-products (N-DBPs) with strong cytotoxicity and genotoxicity. In this study, the formation potential (FP) of DCAN was investigated in the samples of six important Water sources located in the Yangtze River Delta. The highest formation concentration of DCAN was 9.05 μg/L in the Water sample taken from Taihu Lake with the lowest SUVA value. After the NOM fractionation, the conversion rate of hydrophilic fraction to DCAN was found the highest. Subsequently, a Waterworks using Taihu Lake as Water source was chosen to research the FP variations of DCAN in the treatment process and Backwash Water. The results showed that, compared to the conventional treatment process, O/biological activated carbon (BAC) process increased the removal efficiency of DCAN from 21.89% to 50.58% by removing aromatic protein and soluble biological by-products as main precursors of DCAN. The DCAN FP in the effluent of BAC filters using old granular activated carbon was higher than that in the influent and the DCAN FP of its Backwash Water was lower than that in raw Water. In the Backwash Water of sand filters, the DCAN FP higher than raw Water required the recycle ratio less than 5% to avoid the accumulation of DCAN.
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Recycling of activated carbon filter Backwash Water using ultrafiltration: membrane fouling caused by different dominant interfacial forces
Journal of Membrane Science, 2017Co-Authors: Tao Lin, Zhang Jianan, Wei ChenAbstract:Abstract The reuse of activated carbon filter Backwash Water was performed using an ultrafiltration (UF) system and the membrane fouling mechanism was investigated using a model involving XDLVO theory and hydrodynamic interaction. Pretreatment by micro-flocculation/sedimentation removed most particulate pollutants; thus, residual organic colloids determined the details of the UF membrane fouling. The membrane fouling was divided into two periods. Membrane fouling in the initial period was determined by interfacial forces between the membrane and colloids. The calculated interfacial forces showed that permeation drag (PD) force dominated the total interfacial force at long-range, while London-van der Waals and short-range Lewis acid-base (AB) forces governed membrane fouling at short-range (
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Micro-flocculation/sedimentation and ozonation for controlling ultrafiltration membrane fouling in recycling of activated carbon filter Backwash Water
Chemical Engineering Journal, 2017Co-Authors: Zhang Jianan, Tao Lin, Wei ChenAbstract:Abstract The reuse of activated carbon filter Backwash Water (ACFBW) was performed using an ultrafiltration (UF) system. The feed Water was pretreated by the micro-flocculation/sedimentation, followed by ozonation, prior to its entry into the UF system. The dose of 2 mg/L PACl and subsequent 10 min sedimentation were involved in the pretreatment, which resulted in the removal of most particles and bacteria in ACFBW, causing a decrease of transmembrane pressure (TMP) and the mitigation of membrane fouling. In the parallel experiment with or without preozonation, the influence of dosing ozone at 0.15 mg/L on membrane fouling was investigated. The results showed that the preozonation restrained bacteria breeding on the membrane surface and maintained the membrane permeability. The preozonation reduced the hydrophobic organic matters and changed the molecular weight distribution of organics in the influent ACFBW, reflecting macromolecular organic compounds to form small fractions. In addition, the preozonation narrowed the pore size of membrane, the virgin membrane varying from 2.1 to 26.3 nm compared with the used membrane with preozonation from 1.5 to 23.6 nm. The preozonation improved the hydrophobicity of membrane material in a long-running filtration, which could aggravate the membrane fouling. However, the preozonation enhanced UF performance due to the characteristics change of organic matters, which was dominant in alleviating membrane fouling compared with the adverse influence of the increased hydrophobicity of membrane material.
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Evaluation of a drinking Water treatment process involving directly recycling filter Backwash Water using physico-chemical analysis and toxicity assay
RSC Advances, 2016Co-Authors: Bingwei Hou, Tao Lin, Wei ChenAbstract:Recycling the filter Backwash Water of a drinking Water treatment plant (DWTP) was considered as a feasible method to enhance the efficiencies of pollutant removal and Water conservation. In this study, the purification efficiency and Water quality evaluation were investigated in a DWTP with a direct recycling of sand filters Backwash Water (SFBW) at recycling rates of 0–30%. The concentrations of dissolved organic carbon and dissolved nitrogen matters, and the formation potentials of carbonated or nitrogenous disinfection by-products did not obviously increase or were even lower than that without recycling when the recycling rate of SFBW was less than 20%. The di-haloacetamides (DCAcAm) accounted for the majority of HAcAms formed during chlorination in all Water extracts, followed by tri-HAcAms and, to a much lower extent, mono-HAcAms. The immobilization of Daphnia magna (D. magna) increased with the increasing exposure concentration of Water extracts during a 48 h period. The immobilization of D. magna exposed to Water treated by recycling SFBW at a recycling rate below 20% was nearly equivalent to that without a recycling process. When the recycling rate was more than 20%, there was a significant increase in the superoxide dismutase (SOD) activity of D. magna, whereas a significant inhibition observed in the catalase (CAT) activity, which reflected a damaged defense chain caused by the toxic substances including chlorinated and nitrogenous disinfection by-products such as DCAcAm. When the recycling rate was more than 20%, there was a statistically significant difference (p > 0.05) between the recycling rate of SFBW and the toxicity effect of Water sample extracts during the recycling trial. It was also identified that the main precursors of DCAcAm were hydrophilic and low molecular weight fractions of dissolved organic nitrogen.