The Experts below are selected from a list of 3579 Experts worldwide ranked by ideXlab platform
Xingzhi Du - One of the best experts on this subject based on the ideXlab platform.
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floc destruction and its impact on dewatering properties in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of waste activated sludge
Bioresource Technology, 2009Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:Floc destruction and its impacts on the dewatering properties in terms of capillary suction time (CST) in the process of using Flat-Sheet Membrane for simultaneous thickening and digestion (MSTD) of waste activated sludge were investigated. A pilot-scale MSTD reactor was used to treat waste activated sludge, and extracellular polymeric substances (EPS), soluble biopolymers, dissolved cations and the dewatering properties were measured. The results indicated that the destruction mechanisms of the MSTD process could be divided into two phases due to the variation of dissolved oxygen (DO). Polysaccharides and proteins were released in both phases, but the release patterns were different. The concentration of polysaccharides was much greater than that of proteins in Phase 1, while the ratio of proteins to polysaccharides ranged from 1.5 to 1.7. The divalent cations in supernatant significantly increased in Phase 1, while the monovalent cations in supernatant rose in Phase 2. The dewatering properties in terms of CST significantly increased in the MSTD process, and the mixed liquor suspended solids (MLSS), particle size, and biopolymers in supernatant had significant effects on the dewatering properties.
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Membrane fouling mechanisms in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of activated sludge
Separation and Purification Technology, 2008Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for simultaneous thickening and digestion of activated sludge (MSTD) was studied in this paper, and the Membrane fouling mechanisms of this process under high and changing mixed liquor suspended solids (MLSSs) were investigated. About 30 g/L concentrated sludge and 45% mixed liquor volatile suspended solids (MLVSSs) destruction efficiency were achieved at the end of each period of sludge treatment. Test results showed that viscosity, capillary suction time (CST), soluble microbial products (SMPs) and chemical oxygen demand concentrations of colloids (CODc) had significant influences on Membrane fouling among various sludge variables. CST was then chosen as an indicated parameter, and the empirical relationship between CST and Membrane permeability was established. It was also found that the filtration cake and the irreversible foulants consisted of large numbers of carbohydrate and protein, and Membrane fouling of Membrane modules was not homogeneous.
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application of Flat Sheet Membrane to thickening and digestion of waste activated sludge was
Journal of Hazardous Materials, 2008Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:Abstract The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 μm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5–1.5 mg/L, temperature 20–28 °C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.
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Application of Flat-Sheet Membrane to thickening and digestion of waste activated sludge (WAS).
Journal of hazardous materials, 2007Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 microm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5-1.5 mg/L, temperature 20-28 degrees C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.
Fenglin Yang - One of the best experts on this subject based on the ideXlab platform.
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preparation of a nano mno2 surface modified reduced graphene oxide pvdf Flat Sheet Membrane for adsorptive removal of aqueous ni ii
RSC Advances, 2016Co-Authors: Renjie Li, Yuehua Zhang, Fenglin YangAbstract:In this paper, nanoscale MnO2 particles were attached onto the surface of a PVDF Flat Sheet Membrane, step by step, first through dispersion of graphene oxide (GO) in the PVDF Membrane, then reduction of immobilized GO by hydroiodic acid and further micro-wave assisted oxidation of RGO (reduced graphene oxide) by KMnO4 and formation of MnO2 on GO. The SEM observation revealed an asymmetric structure with a finger-like transition layer dominating the Membrane of PVDF/MnO2. The uniform distribution of MnO2 on the Membrane is revealed by EDX and XPS analysis. The attached MnO2 endowed the Membrane with high adsorption capacity for aqueous Ni(II). The adsorption was spontaneous and endothermic, fitting a pseudo-first-order kinetic model and Freundlich isotherm model well. The pure water flux and stable permeation flux of the PVDF/MnO2 Membrane reached 31.2 L m−2 h−1 and 9.0 L m−2 h−1 under 0.1 MPa, which were 2.3 and 2.6 times those of the PVDF Membrane. The analysis of the fouling resistance and flux recovery ratio indicated that the PVDF/MnO2 Membrane had better antifouling properties than the PVDF Membrane, attributed to the changes of Membrane morphologies and surface hydrophilicity. The PVDF/MnO2 Membrane had a high removal ratio (≥87.4%) of Ni2+ in dynamic adsorption. Meanwhile the Ni(II) adsorbed Membrane could be easily regenerated by a 0.1 M HNO3 solution.
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Preparation of a nano-MnO2 surface-modified reduced graphene oxide/PVDF Flat Sheet Membrane for adsorptive removal of aqueous Ni(II)
RSC Advances, 2016Co-Authors: Lifen Liu, Yuehua Zhang, Fenglin YangAbstract:In this paper, nanoscale MnO2 particles were attached onto the surface of a PVDF Flat Sheet Membrane, step by step, first through dispersion of graphene oxide (GO) in the PVDF Membrane, then reduction of immobilized GO by hydroiodic acid and further micro-wave assisted oxidation of RGO (reduced graphene oxide) by KMnO4 and formation of MnO2 on GO. The SEM observation revealed an asymmetric structure with a finger-like transition layer dominating the Membrane of PVDF/MnO2. The uniform distribution of MnO2 on the Membrane is revealed by EDX and XPS analysis. The attached MnO2 endowed the Membrane with high adsorption capacity for aqueous Ni(II). The adsorption was spontaneous and endothermic, fitting a pseudo-first-order kinetic model and Freundlich isotherm model well. The pure water flux and stable permeation flux of the PVDF/MnO2 Membrane reached 31.2 L m−2 h−1 and 9.0 L m−2 h−1 under 0.1 MPa, which were 2.3 and 2.6 times those of the PVDF Membrane. The analysis of the fouling resistance and flux recovery ratio indicated that the PVDF/MnO2 Membrane had better antifouling properties than the PVDF Membrane, attributed to the changes of Membrane morphologies and surface hydrophilicity. The PVDF/MnO2 Membrane had a high removal ratio (≥87.4%) of Ni2+ in dynamic adsorption. Meanwhile the Ni(II) adsorbed Membrane could be easily regenerated by a 0.1 M HNO3 solution.
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preparation of a nano mno2 surface modified reduced graphene oxide pvdf Flat Sheet Membrane for adsorptive removal of aqueous ni ii
RSC Advances, 2016Co-Authors: Lifen Liu, Yuehua Zhang, Fenglin YangAbstract:In this paper, nanoscale MnO2 particles were attached onto the surface of a PVDF Flat Sheet Membrane, step by step, first through dispersion of graphene oxide (GO) in the PVDF Membrane, then reduction of immobilized GO by hydroiodic acid and further micro-wave assisted oxidation of RGO (reduced graphene oxide) by KMnO4 and formation of MnO2 on GO. The SEM observation revealed an asymmetric structure with a finger-like transition layer dominating the Membrane of PVDF/MnO2. The uniform distribution of MnO2 on the Membrane is revealed by EDX and XPS analysis. The attached MnO2 endowed the Membrane with high adsorption capacity for aqueous Ni(II). The adsorption was spontaneous and endothermic, fitting a pseudo-first-order kinetic model and Freundlich isotherm model well. The pure water flux and stable permeation flux of the PVDF/MnO2 Membrane reached 31.2 L m−2 h−1 and 9.0 L m−2 h−1 under 0.1 MPa, which were 2.3 and 2.6 times those of the PVDF Membrane. The analysis of the fouling resistance and flux recovery ratio indicated that the PVDF/MnO2 Membrane had better antifouling properties than the PVDF Membrane, attributed to the changes of Membrane morphologies and surface hydrophilicity. The PVDF/MnO2 Membrane had a high removal ratio (≥87.4%) of Ni2+ in dynamic adsorption. Meanwhile the Ni(II) adsorbed Membrane could be easily regenerated by a 0.1 M HNO3 solution.
Xinhua Wang - One of the best experts on this subject based on the ideXlab platform.
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new insight into sludge digestion mechanism for simultaneous sludge thickening and reduction using Flat Sheet Membrane coupled aerobic digesters
Chemical Engineering Journal, 2017Co-Authors: Wen Yi Yuan, Zhichao Wu, Xinhua Wang, Xuedong ZhangAbstract:Abstract Three identical pilot-scale Flat-Sheet Membrane-coupled aerobic digesters for simultaneous sludge thickening and reduction (MSTR) were performed in parallel under a hydraulic retention time (HRT) of 14.6 h for 15 days. In the first 8 days, the stepwise destruction of waste activated sludge (WAS) flocs, i.e., dispersion from the outer to inner part, was observed likely due to the variation of dissolved oxygen concentration (Step 1: from 7.0 to 2.5 mg/L, Step 2: from 2.5 to 0.5 mg/L). During the process, the concentration of extracellular polymeric substances (EPS) first decreased from about 170.0 to 140.8 mg/g volatile suspended solids (VSS), then from 140.8 to 67.7 mg/g VSS, resulting in the much higher concentration of soluble organic matters and small particles (1–20 μm) in Step 2. Meanwhile, the ratio of protein like substances to humic acids in the EPS first increased from 0.5 to 0.7, then decreased from 0.7 to 0.4. After 8 days, the regroupment of sludge fraction and successive increase in fine particle could also correspond to the slight change of EPS concentration. Moreover, the degree of humification of the supernatant could well correspond to the reduction degree of the sludge.
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floc destruction and its impact on dewatering properties in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of waste activated sludge
Bioresource Technology, 2009Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:Floc destruction and its impacts on the dewatering properties in terms of capillary suction time (CST) in the process of using Flat-Sheet Membrane for simultaneous thickening and digestion (MSTD) of waste activated sludge were investigated. A pilot-scale MSTD reactor was used to treat waste activated sludge, and extracellular polymeric substances (EPS), soluble biopolymers, dissolved cations and the dewatering properties were measured. The results indicated that the destruction mechanisms of the MSTD process could be divided into two phases due to the variation of dissolved oxygen (DO). Polysaccharides and proteins were released in both phases, but the release patterns were different. The concentration of polysaccharides was much greater than that of proteins in Phase 1, while the ratio of proteins to polysaccharides ranged from 1.5 to 1.7. The divalent cations in supernatant significantly increased in Phase 1, while the monovalent cations in supernatant rose in Phase 2. The dewatering properties in terms of CST significantly increased in the MSTD process, and the mixed liquor suspended solids (MLSS), particle size, and biopolymers in supernatant had significant effects on the dewatering properties.
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Membrane fouling mechanisms in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of activated sludge
Separation and Purification Technology, 2008Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for simultaneous thickening and digestion of activated sludge (MSTD) was studied in this paper, and the Membrane fouling mechanisms of this process under high and changing mixed liquor suspended solids (MLSSs) were investigated. About 30 g/L concentrated sludge and 45% mixed liquor volatile suspended solids (MLVSSs) destruction efficiency were achieved at the end of each period of sludge treatment. Test results showed that viscosity, capillary suction time (CST), soluble microbial products (SMPs) and chemical oxygen demand concentrations of colloids (CODc) had significant influences on Membrane fouling among various sludge variables. CST was then chosen as an indicated parameter, and the empirical relationship between CST and Membrane permeability was established. It was also found that the filtration cake and the irreversible foulants consisted of large numbers of carbohydrate and protein, and Membrane fouling of Membrane modules was not homogeneous.
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application of Flat Sheet Membrane to thickening and digestion of waste activated sludge was
Journal of Hazardous Materials, 2008Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:Abstract The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 μm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5–1.5 mg/L, temperature 20–28 °C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.
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Application of Flat-Sheet Membrane to thickening and digestion of waste activated sludge (WAS).
Journal of hazardous materials, 2007Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 microm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5-1.5 mg/L, temperature 20-28 degrees C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.
Zhiwei Wang - One of the best experts on this subject based on the ideXlab platform.
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study on the Membrane fouling of the process of using two layer Flat Sheet Membrane for sludge thickening and water reuse
Applied Mechanics and Materials, 2015Co-Authors: Ming Yuan Zhou, Wen Yi Yuan, Zhiwei Wang, Jie GuanAbstract:In this paper, the critical flux was applied to represent the tendency of Membrane fouling. The response surface model was used to study different factors, such as sludge concentration, space between Membranes and aeration rate, affecting Membrane fouling of the upper and lower layer Membrane module. It was found that the model is fitting and significant, moreover, the sludge concentration, space between Membranes and aeration rate has a significant impact on the upper and lower Membrane fouling. Meanwhile, it was also observed that the critical flux of both upper and lower layer Membrane module sharply decreased with the increase of sludge concentration. However, the different variation tendency of Membrane fouling between upper and lower layer Membrane module was detected due to the change of space between Membranes and aeration rate, when it was under different sludge concentrations. Finally, optimum operating parameters under different sludge concentration simulated by response surface model were successfully applied to the process of using Flat-Sheet Membrane for four-stage sludge thickening.
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floc destruction and its impact on dewatering properties in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of waste activated sludge
Bioresource Technology, 2009Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:Floc destruction and its impacts on the dewatering properties in terms of capillary suction time (CST) in the process of using Flat-Sheet Membrane for simultaneous thickening and digestion (MSTD) of waste activated sludge were investigated. A pilot-scale MSTD reactor was used to treat waste activated sludge, and extracellular polymeric substances (EPS), soluble biopolymers, dissolved cations and the dewatering properties were measured. The results indicated that the destruction mechanisms of the MSTD process could be divided into two phases due to the variation of dissolved oxygen (DO). Polysaccharides and proteins were released in both phases, but the release patterns were different. The concentration of polysaccharides was much greater than that of proteins in Phase 1, while the ratio of proteins to polysaccharides ranged from 1.5 to 1.7. The divalent cations in supernatant significantly increased in Phase 1, while the monovalent cations in supernatant rose in Phase 2. The dewatering properties in terms of CST significantly increased in the MSTD process, and the mixed liquor suspended solids (MLSS), particle size, and biopolymers in supernatant had significant effects on the dewatering properties.
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Membrane fouling mechanisms in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of activated sludge
Separation and Purification Technology, 2008Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for simultaneous thickening and digestion of activated sludge (MSTD) was studied in this paper, and the Membrane fouling mechanisms of this process under high and changing mixed liquor suspended solids (MLSSs) were investigated. About 30 g/L concentrated sludge and 45% mixed liquor volatile suspended solids (MLVSSs) destruction efficiency were achieved at the end of each period of sludge treatment. Test results showed that viscosity, capillary suction time (CST), soluble microbial products (SMPs) and chemical oxygen demand concentrations of colloids (CODc) had significant influences on Membrane fouling among various sludge variables. CST was then chosen as an indicated parameter, and the empirical relationship between CST and Membrane permeability was established. It was also found that the filtration cake and the irreversible foulants consisted of large numbers of carbohydrate and protein, and Membrane fouling of Membrane modules was not homogeneous.
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application of Flat Sheet Membrane to thickening and digestion of waste activated sludge was
Journal of Hazardous Materials, 2008Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:Abstract The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 μm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5–1.5 mg/L, temperature 20–28 °C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.
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Application of Flat-Sheet Membrane to thickening and digestion of waste activated sludge (WAS).
Journal of hazardous materials, 2007Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 microm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5-1.5 mg/L, temperature 20-28 degrees C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.
Zhichao Wu - One of the best experts on this subject based on the ideXlab platform.
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new insight into sludge digestion mechanism for simultaneous sludge thickening and reduction using Flat Sheet Membrane coupled aerobic digesters
Chemical Engineering Journal, 2017Co-Authors: Wen Yi Yuan, Zhichao Wu, Xinhua Wang, Xuedong ZhangAbstract:Abstract Three identical pilot-scale Flat-Sheet Membrane-coupled aerobic digesters for simultaneous sludge thickening and reduction (MSTR) were performed in parallel under a hydraulic retention time (HRT) of 14.6 h for 15 days. In the first 8 days, the stepwise destruction of waste activated sludge (WAS) flocs, i.e., dispersion from the outer to inner part, was observed likely due to the variation of dissolved oxygen concentration (Step 1: from 7.0 to 2.5 mg/L, Step 2: from 2.5 to 0.5 mg/L). During the process, the concentration of extracellular polymeric substances (EPS) first decreased from about 170.0 to 140.8 mg/g volatile suspended solids (VSS), then from 140.8 to 67.7 mg/g VSS, resulting in the much higher concentration of soluble organic matters and small particles (1–20 μm) in Step 2. Meanwhile, the ratio of protein like substances to humic acids in the EPS first increased from 0.5 to 0.7, then decreased from 0.7 to 0.4. After 8 days, the regroupment of sludge fraction and successive increase in fine particle could also correspond to the slight change of EPS concentration. Moreover, the degree of humification of the supernatant could well correspond to the reduction degree of the sludge.
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floc destruction and its impact on dewatering properties in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of waste activated sludge
Bioresource Technology, 2009Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:Floc destruction and its impacts on the dewatering properties in terms of capillary suction time (CST) in the process of using Flat-Sheet Membrane for simultaneous thickening and digestion (MSTD) of waste activated sludge were investigated. A pilot-scale MSTD reactor was used to treat waste activated sludge, and extracellular polymeric substances (EPS), soluble biopolymers, dissolved cations and the dewatering properties were measured. The results indicated that the destruction mechanisms of the MSTD process could be divided into two phases due to the variation of dissolved oxygen (DO). Polysaccharides and proteins were released in both phases, but the release patterns were different. The concentration of polysaccharides was much greater than that of proteins in Phase 1, while the ratio of proteins to polysaccharides ranged from 1.5 to 1.7. The divalent cations in supernatant significantly increased in Phase 1, while the monovalent cations in supernatant rose in Phase 2. The dewatering properties in terms of CST significantly increased in the MSTD process, and the mixed liquor suspended solids (MLSS), particle size, and biopolymers in supernatant had significant effects on the dewatering properties.
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Membrane fouling mechanisms in the process of using Flat Sheet Membrane for simultaneous thickening and digestion of activated sludge
Separation and Purification Technology, 2008Co-Authors: Xinhua Wang, Zhichao Wu, Zhiwei Wang, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for simultaneous thickening and digestion of activated sludge (MSTD) was studied in this paper, and the Membrane fouling mechanisms of this process under high and changing mixed liquor suspended solids (MLSSs) were investigated. About 30 g/L concentrated sludge and 45% mixed liquor volatile suspended solids (MLVSSs) destruction efficiency were achieved at the end of each period of sludge treatment. Test results showed that viscosity, capillary suction time (CST), soluble microbial products (SMPs) and chemical oxygen demand concentrations of colloids (CODc) had significant influences on Membrane fouling among various sludge variables. CST was then chosen as an indicated parameter, and the empirical relationship between CST and Membrane permeability was established. It was also found that the filtration cake and the irreversible foulants consisted of large numbers of carbohydrate and protein, and Membrane fouling of Membrane modules was not homogeneous.
-
application of Flat Sheet Membrane to thickening and digestion of waste activated sludge was
Journal of Hazardous Materials, 2008Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:Abstract The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 μm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5–1.5 mg/L, temperature 20–28 °C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.
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Application of Flat-Sheet Membrane to thickening and digestion of waste activated sludge (WAS).
Journal of hazardous materials, 2007Co-Authors: Zhiwei Wang, Xinhua Wang, Zhichao Wu, Xingzhi DuAbstract:The feasibility of using Flat-Sheet Membrane for waste activated sludge (WAS) thickening and digestion was studied in this paper. The characteristics of the processes including the thickening efficiency, effluent water quality and filtration properties of the Membrane for sludge thickening process (MST), digestion efficiency, effluent water quality and Membrane permeability of the Membrane for sludge simultaneous thickening and digestion process (MSTD) were investigated. Test results showed that good sludge thickening efficiency and superior effluent water quality were obtained in the MST process under hydraulic retention time (HRT) 0.26 and 2 d operation of each cycle, and the Membrane fouling was mainly due to the increase of apparent viscosity of mixed liquors and the decrease of the cross-flow velocity (CFV) along Membrane surfaces during one thickening cycle. Membranes were also selected for the processes and M1 Membrane of polyvinylidene fluoride (PVDF) material with pore size 0.2 microm demonstrated better permeability compared with other three Membranes. About 80% MLSS destruction rate and 73% MLVSS destruction rate were achieved under HRT 1 d, dissolved oxygen (DO) concentration 0.5-1.5 mg/L, temperature 20-28 degrees C and 15 d operation for one cycle in MSTD process, and Membrane fouling of MSTD process was attributed to not only the reason of MST process mentioned above, but also the change of sludge properties such as the increase of soluble COD and microbial polymeric substances including EPS, carbohydrate and nucleic acids, etc. of the mixed liquors.