Two types of filter media in groundwater treatment were conducted for a comparative study of surface structure and catalytic performance. Natural filter media was adopted from a conventional aeration–filtration groun...Two types of filter media in groundwater treatment were conducted for a comparative study of surface structure and catalytic performance. Natural filter media was adopted from a conventional aeration–filtration groundwater treatment plant, and active filter media as a novel and promising filter media was also adopted. The physicochemical properties of these two kinds of filter media were characterized using numerous analytical techniques,such as X-Ray diffraction（XRD）, scanning electron microscope（SEM）, energy dispersive X-ray（EDX）, X-ray photoelectron spectroscopy（XPS） and Zeta potential. The catalytic activities of these filter media were evaluated for ammonium and manganese oxidation.XRD data showed that both active filter media and natural filter media belonged to birnessite family. A new manganese dioxide（Mn O2） phase（PDF#72-1982） was found in the structure of natural filter media. The SEM micrograph of natural filter media showed honeycomb structures and the active filter media presented plate structures and consisted of stacked particle. These natural filter media presented lower level of some trace elements such as calcium and magnesium, lower degree of crystallinity, lower Mn（III） content and lattice oxygen content than that of active filter media, which were associated with its poor ammonium and manganese catalytic activities. In addition, some γ-Fe2 O3 and Mn CO3 were found in the coating which may hinder the ammonium and manganese catalytic oxidation. This study provides a thorough and comprehensive understanding about the most commonly used filter media in water treatment, which can provide a theoretical guide to practical applications.展开更多
Comparisons of microbial community structure, in eight filter media of zeolites, anthracite, shale, vermiculite, ceramic filter media, gravel, steel slag and bio-ceramic, were undertaken by analyzing the phospholipid ...Comparisons of microbial community structure, in eight filter media of zeolites, anthracite, shale, vermiculite, ceramic filter media, gravel, steel slag and bio-ceramic, were undertaken by analyzing the phospholipid fatty acid （PLFA） composition. A total of 20 fatty acids in the range of C18to C20 were determined but only 13 PLFAs were detected in steel slag. They consist of saturated fatty acids, branched fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. The variation of fatty acids was revealed in the relative proportions of these fatty acids in different media. The aerobic prokaryotes were the predominant group in all media. The PLFA composition showed significant differences among the eight different media by Tukey＇s honestly test. It was found that steel slag was significantly different in the microbial community as compared to other filter media, probably due to its alkaline effluent. Steel slag alone is probably not a good choice of substratum in constructed wetlands. The principle components analysis （PCA） showed that zeolites, bio-ceramic, shale and vermiculite had a similar microbial community structure while steel slag and ceramic filter media were distinct from other media.展开更多
A novel kind of filter media has been studied using in biological aerated filter process which is produced by waste coal fly ash and coal gangues.The specific surface area and sum of braking and ware rate are viewed a...A novel kind of filter media has been studied using in biological aerated filter process which is produced by waste coal fly ash and coal gangues.The specific surface area and sum of braking and ware rate are viewed as the main factor for determining preparation conditions,including calcination temperature (in the range of 900 ℃ to 1250 ℃),proportion of coal gangue (in the range of 0 to 25%) and soaking time (in the range of 0 to 40 min).The effects of sintering conditions on the main property parameters are researched and the reasons have been analyzed.Considered with all factors,the optimum technological conditions are chosen as follows:the calcination temperature is 1050 ℃ ;the soaking time is 10 min and the proportion of coal gangue is 5%.When at these condition,the main property parameters of the filter media in the technological conditions are 1.6 m 2 /g for the specific surface area and 2.96 % for sum of braking and are rate respectively.Finally,a scanning electron microscope is used for analyzing the microstructure of the filter media.展开更多
Passive cooling techniques are cost effective and reliable methods of cooling remote radio heads (RRH). This paper investigates the plausibility of a passive cooling technique involving exchanging warm air, from the i...Passive cooling techniques are cost effective and reliable methods of cooling remote radio heads (RRH). This paper investigates the plausibility of a passive cooling technique involving exchanging warm air, from the internal cavity of RRHs, with fresh ambient air, to reduce the operating temperature using natural convection across air filters. The results indicate that, an internal air filter tube structure, with width of the enclosure, running vertically up the middle of an RRH, along with 4 pleat filter sides (2.0 ± 0.5 cm separation) provides the most effective outdoor suitable setup out of those examined. This provides a reduction in temperature of 3.9°K ± 0.4°K in the PA and 4.0°K ± 0.4°K in the radio, and a reduction in mass of 0.45 ± 0.05 kg, and is capable of withstanding water ingress and corrosive conditions including wind driven rain and salt fog.展开更多
In this study, the three-dimensional physical model of pleated air filtration media was simplified to porous media model, and the calculation parameters of porous media were obtained based on experimental data. The mo...In this study, the three-dimensional physical model of pleated air filtration media was simplified to porous media model, and the calculation parameters of porous media were obtained based on experimental data. The model of V-shaped pleated air filter media is constructed, the height of the media pleat is 50 mm and the pleat thickness is 4 mm, the pleat angle is 3.7°. The Hertz-Mindlin contact model was modified by Johnson Kendall Roberts (JKR) adhesion contact model. The deposition process of particles in media was simulated based on computational fluid dynamics (CFD) theory and discrete element method (DEM). Results show that the CFD–DEM coupling method can be effectively applied to the macro research of pleated air filter media. The particles will form dust layer and dendrite structure on the fiber surface, and the dust layer will affect the subsequent air flow organization, and the dendrite structure will eventually form a “particle wall”. The formation of the “particle wall” will prevent the particles from moving further in the fluid domain, which makes area of pleated angle become the “low efficiency” part about the particle deposition. Compared with area of pleated angle, the particles are concentrated in the opening area and the middle area of the pleated to agglomerate and deposit.展开更多
Reusable PM_(2.5) filter media and their regeneration techniques have attracted widespread attention and shown significant prospect for application in air purification.In this study,we reviewed the recent research pro...Reusable PM_(2.5) filter media and their regeneration techniques have attracted widespread attention and shown significant prospect for application in air purification.In this study,we reviewed the recent research progress on the cleaning and regeneration of indoor PM_(2.5) filters considering two methods,namely,dry and wet cleaning.The principles,application status,and limitations of air back-blow and air pulse-jet dry-cleaning techniques were analyzed.The wet-cleaning characteristics and regeneration performance of novel washable PM_(2.5) filters,including superhydrophobic,electrostatically enhanced,metal-organic framework composite,and microchannel monolith filters,were evaluated and summarized.Maintaining the structural stability and chemical resistance of the filter media during the cleaning process was determined to be key to filter regeneration.Therefore,cleaning and regeneration characteristics should be integrated into the design of high-efficiency and low-resistance filter materials to develop more practical reusable PM_(2.5) filter media.展开更多
The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil deconta...The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil decontamination,and no need for excavation.During the last three decades,enhanced and hybrid EK systems were developed and tested for improving the efficiency of contaminants removal from soils.Chemically enhanced-EK processes exhibited excellent efficiency in removing contaminants by controlling the soil pH or the chemical reaction of contaminants.EK hybrid systems were tested to overcome environmental hurdles or technical drawbacks of decontamination technologies.Hybridization of the EK process with phytoremediation,bioremediation,or reactive filtermedia(RFM)improved the remediation process performance by capturing contaminants or facilitating biological agents’movement in the soil.Also,EK process coupling with solar energy was proposed to treat off-grid contaminated soils or reduce the EK energy requirements.This study reviews recent advancements in the enhancement and hybrid EK systems for soil remediation and the type of contaminants targeted by the process.The study also covered the impact of operating parameters,imperfect pollution separation,and differences in the physicochemical characteristics and microstructure of soil/sediment on the EK performance.Finally,a comparison between various remediation processes was presented to highlight the pros and cons of these technologies.展开更多
Biologically active carbon （BAC） system was set up in a water plant of South China during January to December 2007,to study the invertebrate community characteristics of BAC filter.Thirty-seven invertebrate species ...Biologically active carbon （BAC） system was set up in a water plant of South China during January to December 2007,to study the invertebrate community characteristics of BAC filter.Thirty-seven invertebrate species were found,of which 28 belonging to rotifers.Filter operation could lead to an output of invertebrates in high abundances with the filtrate,and the maximum density could reach 5608 individuals/m 3.Average abundances in the effluent water increased in 27-33 folds in comparison to the influent water during the sampling period.Invertebrate community succession had the following trend：filter-feeding animals → small benthic invertebrates → large benthic and resistant invertebrates.Abundances of large-sized invertebrates （copepod adult and oligochaete） at bigger-media column were significantly higher than that at small-media column.The results implied the abundant species diversity of invertebrate in BAC filter.The relationship between invertebrate and biofilm still remain to be studied in detail.展开更多
Filtration of aerosol particles using non-woven fibrous media is a common practice for air cleaning. It has found wide applications in industries and our daily lives. This paper overviews some of these applications an...Filtration of aerosol particles using non-woven fibrous media is a common practice for air cleaning. It has found wide applications in industries and our daily lives. This paper overviews some of these applications and provides an industrial perspective. It starts from discussing aerosol filtration theory, followed by a brief review on the advancement of filtration media. After that, filtration applications in respiratory protection, dust collection, and engine in-take air cleaning are elaborated. These are the areas that the author sees as the typical needed ones in China's fast pace economical development endeavor, where air filtration enables the protection of human health, environment and equipment for sustainability.展开更多
Nutrient pollution still remains one of the greatest challenges to water quality contributing to harmful contaminations water sources,and costly impacts on the economy.This review considers the development of the biof...Nutrient pollution still remains one of the greatest challenges to water quality contributing to harmful contaminations water sources,and costly impacts on the economy.This review considers the development of the biofilters,focusing on the design features that have the most influence on their technical and economic performance.Modern biofilters,based on SAF technology,are particularly suitable for sewage treatment works with throughput rates up to 1,000m^3/d.The main advantages of SAF plants include high quality effluent,low power usage and small footprint.A wide range of filter media are available for different designs,which could be configured for both aerobic and anaerobic treatment in BOD and/or ammonia reduction applications.The two most important parameters for filter media are their Specific Surface Area(SSA,m^2/m^3)and Void Fraction(percentage of void volume or porosity).However,due to the risk of clogging by suspended solids or excess sludge the media used for this application should be limited to about 500m^2/m^3.In tertiary treatment or river restoration applications where the influents tend lack any readily biodegradable substrates,SAF design provides the most appropriate choice for further development to produce effluents with very low nutrient levels.展开更多
The filter paper and activated carbon which filled inside the gas filter have porous media characteristics. In order to study the flow field structure in the filter layer and the activated carbon layer, Computational ...The filter paper and activated carbon which filled inside the gas filter have porous media characteristics. In order to study the flow field structure in the filter layer and the activated carbon layer, Computational Fluid Dynamics method is used to simulate the aerodynamic characteristics of a simplified gas filter. The inertial and viscosity parameters of porous media are solved by Forchheimer equation. The three-dimensional N-S equation and the modified low Reynolds number k-ε turbulence model are adopted to analyze the influence of the explosion-proof plate on the gas filter’s aerodynamic characteristics. The results showed that the air age in the upstream of the activated carbon plates was small, which easily caused the rapid penetration of the Poisonous gas. And in the downstream and around of the activated carbon plates, the air age is larger, formed dead zone, the utilization rate of activated carbon is lower. The explosion-proof plate increases the pressure drop of the gas filter, the air age distribution in the filter layer is more uniform and the utilization rate of filter paper is improved. However, the explosion-proof plate has little influence on the flow field structure of the activated carbon layer.展开更多
In this paper, a new type of resonant Brewster filters （RBF） with surface relief structure for the multiple channels is first presented by using the rigorous coupled-wave analysis and the S-matrix method. By tuning ...In this paper, a new type of resonant Brewster filters （RBF） with surface relief structure for the multiple channels is first presented by using the rigorous coupled-wave analysis and the S-matrix method. By tuning the depth of homogeneous layer which is under the surface relief structure, the multiple channels phenomenon is obtained. Long range, extremely low sidebands and multiple channels are found when the RBF with surface relief structure is illuminated with Transverse Magnetic incident polarization light near the Brewster angle calculated with the effective media theory of sub wavelength grating. Moreover, the wavelengths of RBF with surface relief structure can be easily shifted by changing the depth of homogeneous layer while its optical properties such as low sideband reflection and narrow band are not spoiled when the depth is changed. Furthermore, the variation of the grating thickness does not effectively change the resonant wavelength of RBF, but have a remarkable effect on its line width, which is very useful for designing such filters with different line widths at desired wavelength.展开更多
基金supported by the National Key Research and Development Program of China(No.2016YFC00400706)the National Natural Science Foundation of China(No.51778521)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2017JQ2014)
文摘Two types of filter media in groundwater treatment were conducted for a comparative study of surface structure and catalytic performance. Natural filter media was adopted from a conventional aeration–filtration groundwater treatment plant, and active filter media as a novel and promising filter media was also adopted. The physicochemical properties of these two kinds of filter media were characterized using numerous analytical techniques,such as X-Ray diffraction（XRD）, scanning electron microscope（SEM）, energy dispersive X-ray（EDX）, X-ray photoelectron spectroscopy（XPS） and Zeta potential. The catalytic activities of these filter media were evaluated for ammonium and manganese oxidation.XRD data showed that both active filter media and natural filter media belonged to birnessite family. A new manganese dioxide（Mn O2） phase（PDF#72-1982） was found in the structure of natural filter media. The SEM micrograph of natural filter media showed honeycomb structures and the active filter media presented plate structures and consisted of stacked particle. These natural filter media presented lower level of some trace elements such as calcium and magnesium, lower degree of crystallinity, lower Mn（III） content and lattice oxygen content than that of active filter media, which were associated with its poor ammonium and manganese catalytic activities. In addition, some γ-Fe2 O3 and Mn CO3 were found in the coating which may hinder the ammonium and manganese catalytic oxidation. This study provides a thorough and comprehensive understanding about the most commonly used filter media in water treatment, which can provide a theoretical guide to practical applications.
基金supported by the National Natural Science Foundation of China (No.30870221,20877093,50808172)the High Technology Research and Development Program (863) of China (No.2009X207209-004)
文摘Comparisons of microbial community structure, in eight filter media of zeolites, anthracite, shale, vermiculite, ceramic filter media, gravel, steel slag and bio-ceramic, were undertaken by analyzing the phospholipid fatty acid （PLFA） composition. A total of 20 fatty acids in the range of C18to C20 were determined but only 13 PLFAs were detected in steel slag. They consist of saturated fatty acids, branched fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. The variation of fatty acids was revealed in the relative proportions of these fatty acids in different media. The aerobic prokaryotes were the predominant group in all media. The PLFA composition showed significant differences among the eight different media by Tukey＇s honestly test. It was found that steel slag was significantly different in the microbial community as compared to other filter media, probably due to its alkaline effluent. Steel slag alone is probably not a good choice of substratum in constructed wetlands. The principle components analysis （PCA） showed that zeolites, bio-ceramic, shale and vermiculite had a similar microbial community structure while steel slag and ceramic filter media were distinct from other media.
基金Sponsored by the National High Technology Research Development Plan(863)of China(Grant No.2007AA06411)State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(Grant No.2010DX05)the Critical Patented Projects in the Control and Management of the National Polluted Water Bodies(Grant No.2008ZX07207)
文摘A novel kind of filter media has been studied using in biological aerated filter process which is produced by waste coal fly ash and coal gangues.The specific surface area and sum of braking and ware rate are viewed as the main factor for determining preparation conditions,including calcination temperature (in the range of 900 ℃ to 1250 ℃),proportion of coal gangue (in the range of 0 to 25%) and soaking time (in the range of 0 to 40 min).The effects of sintering conditions on the main property parameters are researched and the reasons have been analyzed.Considered with all factors,the optimum technological conditions are chosen as follows:the calcination temperature is 1050 ℃ ;the soaking time is 10 min and the proportion of coal gangue is 5%.When at these condition,the main property parameters of the filter media in the technological conditions are 1.6 m 2 /g for the specific surface area and 2.96 % for sum of braking and are rate respectively.Finally,a scanning electron microscope is used for analyzing the microstructure of the filter media.
文摘Passive cooling techniques are cost effective and reliable methods of cooling remote radio heads (RRH). This paper investigates the plausibility of a passive cooling technique involving exchanging warm air, from the internal cavity of RRHs, with fresh ambient air, to reduce the operating temperature using natural convection across air filters. The results indicate that, an internal air filter tube structure, with width of the enclosure, running vertically up the middle of an RRH, along with 4 pleat filter sides (2.0 ± 0.5 cm separation) provides the most effective outdoor suitable setup out of those examined. This provides a reduction in temperature of 3.9°K ± 0.4°K in the PA and 4.0°K ± 0.4°K in the radio, and a reduction in mass of 0.45 ± 0.05 kg, and is capable of withstanding water ingress and corrosive conditions including wind driven rain and salt fog.
文摘In this study, the three-dimensional physical model of pleated air filtration media was simplified to porous media model, and the calculation parameters of porous media were obtained based on experimental data. The model of V-shaped pleated air filter media is constructed, the height of the media pleat is 50 mm and the pleat thickness is 4 mm, the pleat angle is 3.7°. The Hertz-Mindlin contact model was modified by Johnson Kendall Roberts (JKR) adhesion contact model. The deposition process of particles in media was simulated based on computational fluid dynamics (CFD) theory and discrete element method (DEM). Results show that the CFD–DEM coupling method can be effectively applied to the macro research of pleated air filter media. The particles will form dust layer and dendrite structure on the fiber surface, and the dust layer will affect the subsequent air flow organization, and the dendrite structure will eventually form a “particle wall”. The formation of the “particle wall” will prevent the particles from moving further in the fluid domain, which makes area of pleated angle become the “low efficiency” part about the particle deposition. Compared with area of pleated angle, the particles are concentrated in the opening area and the middle area of the pleated to agglomerate and deposit.
基金This project was supported by the Natural Science Foundation of China(grant No.51936005)It was also supported by the Natural Science Foundation of Guangdong Province,China(grant No.2019A1515010648).
文摘Reusable PM_(2.5) filter media and their regeneration techniques have attracted widespread attention and shown significant prospect for application in air purification.In this study,we reviewed the recent research progress on the cleaning and regeneration of indoor PM_(2.5) filters considering two methods,namely,dry and wet cleaning.The principles,application status,and limitations of air back-blow and air pulse-jet dry-cleaning techniques were analyzed.The wet-cleaning characteristics and regeneration performance of novel washable PM_(2.5) filters,including superhydrophobic,electrostatically enhanced,metal-organic framework composite,and microchannel monolith filters,were evaluated and summarized.Maintaining the structural stability and chemical resistance of the filter media during the cleaning process was determined to be key to filter regeneration.Therefore,cleaning and regeneration characteristics should be integrated into the design of high-efficiency and low-resistance filter materials to develop more practical reusable PM_(2.5) filter media.
文摘The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil decontamination,and no need for excavation.During the last three decades,enhanced and hybrid EK systems were developed and tested for improving the efficiency of contaminants removal from soils.Chemically enhanced-EK processes exhibited excellent efficiency in removing contaminants by controlling the soil pH or the chemical reaction of contaminants.EK hybrid systems were tested to overcome environmental hurdles or technical drawbacks of decontamination technologies.Hybridization of the EK process with phytoremediation,bioremediation,or reactive filtermedia(RFM)improved the remediation process performance by capturing contaminants or facilitating biological agents’movement in the soil.Also,EK process coupling with solar energy was proposed to treat off-grid contaminated soils or reduce the EK energy requirements.This study reviews recent advancements in the enhancement and hybrid EK systems for soil remediation and the type of contaminants targeted by the process.The study also covered the impact of operating parameters,imperfect pollution separation,and differences in the physicochemical characteristics and microstructure of soil/sediment on the EK performance.Finally,a comparison between various remediation processes was presented to highlight the pros and cons of these technologies.
基金supported by the National Hi-Tech Research and Development Program (863) of China(No. 2002AA601120)the National Key TechnologyR &D Program:Shanghai China Expo-Tech Project (No.2007BAK27B05)
文摘Biologically active carbon （BAC） system was set up in a water plant of South China during January to December 2007,to study the invertebrate community characteristics of BAC filter.Thirty-seven invertebrate species were found,of which 28 belonging to rotifers.Filter operation could lead to an output of invertebrates in high abundances with the filtrate,and the maximum density could reach 5608 individuals/m 3.Average abundances in the effluent water increased in 27-33 folds in comparison to the influent water during the sampling period.Invertebrate community succession had the following trend：filter-feeding animals → small benthic invertebrates → large benthic and resistant invertebrates.Abundances of large-sized invertebrates （copepod adult and oligochaete） at bigger-media column were significantly higher than that at small-media column.The results implied the abundant species diversity of invertebrate in BAC filter.The relationship between invertebrate and biofilm still remain to be studied in detail.
文摘Filtration of aerosol particles using non-woven fibrous media is a common practice for air cleaning. It has found wide applications in industries and our daily lives. This paper overviews some of these applications and provides an industrial perspective. It starts from discussing aerosol filtration theory, followed by a brief review on the advancement of filtration media. After that, filtration applications in respiratory protection, dust collection, and engine in-take air cleaning are elaborated. These are the areas that the author sees as the typical needed ones in China's fast pace economical development endeavor, where air filtration enables the protection of human health, environment and equipment for sustainability.
文摘Nutrient pollution still remains one of the greatest challenges to water quality contributing to harmful contaminations water sources,and costly impacts on the economy.This review considers the development of the biofilters,focusing on the design features that have the most influence on their technical and economic performance.Modern biofilters,based on SAF technology,are particularly suitable for sewage treatment works with throughput rates up to 1,000m^3/d.The main advantages of SAF plants include high quality effluent,low power usage and small footprint.A wide range of filter media are available for different designs,which could be configured for both aerobic and anaerobic treatment in BOD and/or ammonia reduction applications.The two most important parameters for filter media are their Specific Surface Area(SSA,m^2/m^3)and Void Fraction(percentage of void volume or porosity).However,due to the risk of clogging by suspended solids or excess sludge the media used for this application should be limited to about 500m^2/m^3.In tertiary treatment or river restoration applications where the influents tend lack any readily biodegradable substrates,SAF design provides the most appropriate choice for further development to produce effluents with very low nutrient levels.
文摘The filter paper and activated carbon which filled inside the gas filter have porous media characteristics. In order to study the flow field structure in the filter layer and the activated carbon layer, Computational Fluid Dynamics method is used to simulate the aerodynamic characteristics of a simplified gas filter. The inertial and viscosity parameters of porous media are solved by Forchheimer equation. The three-dimensional N-S equation and the modified low Reynolds number k-ε turbulence model are adopted to analyze the influence of the explosion-proof plate on the gas filter’s aerodynamic characteristics. The results showed that the air age in the upstream of the activated carbon plates was small, which easily caused the rapid penetration of the Poisonous gas. And in the downstream and around of the activated carbon plates, the air age is larger, formed dead zone, the utilization rate of activated carbon is lower. The explosion-proof plate increases the pressure drop of the gas filter, the air age distribution in the filter layer is more uniform and the utilization rate of filter paper is improved. However, the explosion-proof plate has little influence on the flow field structure of the activated carbon layer.
基金Project supported by the National Natural Science Foundation of China (Grant No 10704079)
文摘In this paper, a new type of resonant Brewster filters （RBF） with surface relief structure for the multiple channels is first presented by using the rigorous coupled-wave analysis and the S-matrix method. By tuning the depth of homogeneous layer which is under the surface relief structure, the multiple channels phenomenon is obtained. Long range, extremely low sidebands and multiple channels are found when the RBF with surface relief structure is illuminated with Transverse Magnetic incident polarization light near the Brewster angle calculated with the effective media theory of sub wavelength grating. Moreover, the wavelengths of RBF with surface relief structure can be easily shifted by changing the depth of homogeneous layer while its optical properties such as low sideband reflection and narrow band are not spoiled when the depth is changed. Furthermore, the variation of the grating thickness does not effectively change the resonant wavelength of RBF, but have a remarkable effect on its line width, which is very useful for designing such filters with different line widths at desired wavelength.
