The combined fouling during ultrafiltration（UF） of surface water pretreated to different extents was investigated to disclose the roles of polysaccharides, proteins, and inorganic particles in UF membrane fouling. B...The combined fouling during ultrafiltration（UF） of surface water pretreated to different extents was investigated to disclose the roles of polysaccharides, proteins, and inorganic particles in UF membrane fouling. Both reversible and irreversible fouling decreased with enhanced pretreatment（biologically active carbon（BAC） treatment and sand filtration）. The sand filter effluent fouled the membrane very slowly. The UF membrane removed turbidity to less than 0.1 nephelometric turbidity unit（NTU）, reduced polysaccharides by 25.4%–29.9%, but rejected few proteins. Both polysaccharides and inorganic particles were detected on the fouled membranes, but inorganic particles could be effectively removed by backwashing. The increase of turbidity in the sand filter effluent to 3.05 NTU did not significantly increase the fouling rate, but an increase in the turbidity in the BAC effluent to6.11 NTU increased the fouling rate by more than 100%. The results demonstrated that the polysaccharide, not the protein, constituents of biopolymers were responsible for membrane fouling. Membrane fouling was closely associated with a small fraction of polysaccharides in the feed water. Inorganic particles exacerbated membrane fouling only when the concentration of fouling–inducing polysaccharides in the feed water was relatively high. The combined fouling was largely reversible, and polysaccharides were the predominant substances responsible for irreversible fouling.展开更多
Extensive research efforts are currently devoted to developing and improving conventional technologies for water treatment. Membrane-based water treatment technologies are among the most preferred options due to their...Extensive research efforts are currently devoted to developing and improving conventional technologies for water treatment. Membrane-based water treatment technologies are among the most preferred options due to their commercial success, simple operation, low energy and space requirements, and high separation efficiency. Despite the advances made in membrane-based technologies, fouling remains a critical challenge. Fouling occurs upon the accumulation of unwanted impurities on the membrane surface and within the membrane pores which results in a significant decline in the membrane permeate flux. To alleviate the operational challenges from fouling, surface modification to develop antifouling membranes appears to be an effective technique. A comprehensive review of the surface modification techniques for the development of antifouling membranes is provided in this paper. Chemical surface modification techniques (grafting and plasma treatment), physical modification techniques (blending, coating, adsorption, and thermal treatment), and combined physical and chemical modification techniques have been discussed. Moreover, the challenges related to surface modification and the future research directions are addressed.展开更多
Antibiotic resistance genes(ARGs)have been detected in various atmospheric environments.Airborne ARGs transmission presents the public health threat.However,it is very difficult to quantify airborne ARGs because of th...Antibiotic resistance genes(ARGs)have been detected in various atmospheric environments.Airborne ARGs transmission presents the public health threat.However,it is very difficult to quantify airborne ARGs because of the limited availability of collectable airborne particulate matter and the low biological content of samples.In this study,an optimized protocol for collecting and detecting airborne ARGs was presented.Experimental results showed that recovery efficiency tended to increase initially and then declined over time,and a range of 550-780 copies/mmz of capture loading was recommended to ensure that the recovery efficiency is greater than 75%.As the cell walls were mechanically disrupted and nucleic acids were released,the buffer wash protects ARGs dissolution.Three ratios of buffer volume to membrane area in buffer wash were compared.The highest concentrations of airborne ARGs were detected with 1.4μL/mm^2 buffer wash.Furthermore,the majority of the cells were disrupted by an ultrasonication pretreatment(5 min),allowing the efficiency ARGs detection of airborne samples.While,extending the ultrasonication can disrupt cell structures and gene sequence was broken down into fragments.Therefore,this study could provide a theoretical basis for the efficient filter collection of airborne ARGs in different environments.An optimized sampling method was proposed that the buffer wash was 1.4 nL/mm and the ultrasonication duration was 5 min.The indoor airborne ARGs were examined in accordance with the improved protocol in two laboratories.The result demonstrated that airborne ARGs in an indoor laboratory atmosphere could pose the considerable health risk to inhabitants and we should pay attention to some complicated indoor air environment.展开更多
基金supported by the China Major Science and Technology Program for Water Pollution Control and Treatment (No. 2012ZX07404-002)
文摘The combined fouling during ultrafiltration（UF） of surface water pretreated to different extents was investigated to disclose the roles of polysaccharides, proteins, and inorganic particles in UF membrane fouling. Both reversible and irreversible fouling decreased with enhanced pretreatment（biologically active carbon（BAC） treatment and sand filtration）. The sand filter effluent fouled the membrane very slowly. The UF membrane removed turbidity to less than 0.1 nephelometric turbidity unit（NTU）, reduced polysaccharides by 25.4%–29.9%, but rejected few proteins. Both polysaccharides and inorganic particles were detected on the fouled membranes, but inorganic particles could be effectively removed by backwashing. The increase of turbidity in the sand filter effluent to 3.05 NTU did not significantly increase the fouling rate, but an increase in the turbidity in the BAC effluent to6.11 NTU increased the fouling rate by more than 100%. The results demonstrated that the polysaccharide, not the protein, constituents of biopolymers were responsible for membrane fouling. Membrane fouling was closely associated with a small fraction of polysaccharides in the feed water. Inorganic particles exacerbated membrane fouling only when the concentration of fouling–inducing polysaccharides in the feed water was relatively high. The combined fouling was largely reversible, and polysaccharides were the predominant substances responsible for irreversible fouling.
文摘Extensive research efforts are currently devoted to developing and improving conventional technologies for water treatment. Membrane-based water treatment technologies are among the most preferred options due to their commercial success, simple operation, low energy and space requirements, and high separation efficiency. Despite the advances made in membrane-based technologies, fouling remains a critical challenge. Fouling occurs upon the accumulation of unwanted impurities on the membrane surface and within the membrane pores which results in a significant decline in the membrane permeate flux. To alleviate the operational challenges from fouling, surface modification to develop antifouling membranes appears to be an effective technique. A comprehensive review of the surface modification techniques for the development of antifouling membranes is provided in this paper. Chemical surface modification techniques (grafting and plasma treatment), physical modification techniques (blending, coating, adsorption, and thermal treatment), and combined physical and chemical modification techniques have been discussed. Moreover, the challenges related to surface modification and the future research directions are addressed.
基金This study was supported by the National Natural Science Foundation of China(Grant No.51678402)the key technologies R&D program of Tianjin(No.20ZXGBSY00100).
文摘Antibiotic resistance genes(ARGs)have been detected in various atmospheric environments.Airborne ARGs transmission presents the public health threat.However,it is very difficult to quantify airborne ARGs because of the limited availability of collectable airborne particulate matter and the low biological content of samples.In this study,an optimized protocol for collecting and detecting airborne ARGs was presented.Experimental results showed that recovery efficiency tended to increase initially and then declined over time,and a range of 550-780 copies/mmz of capture loading was recommended to ensure that the recovery efficiency is greater than 75%.As the cell walls were mechanically disrupted and nucleic acids were released,the buffer wash protects ARGs dissolution.Three ratios of buffer volume to membrane area in buffer wash were compared.The highest concentrations of airborne ARGs were detected with 1.4μL/mm^2 buffer wash.Furthermore,the majority of the cells were disrupted by an ultrasonication pretreatment(5 min),allowing the efficiency ARGs detection of airborne samples.While,extending the ultrasonication can disrupt cell structures and gene sequence was broken down into fragments.Therefore,this study could provide a theoretical basis for the efficient filter collection of airborne ARGs in different environments.An optimized sampling method was proposed that the buffer wash was 1.4 nL/mm and the ultrasonication duration was 5 min.The indoor airborne ARGs were examined in accordance with the improved protocol in two laboratories.The result demonstrated that airborne ARGs in an indoor laboratory atmosphere could pose the considerable health risk to inhabitants and we should pay attention to some complicated indoor air environment.
