Gravity-driven membrane filtration(GDM)has increasingly captured researchers'attention due to its low energy consumption and operation&maintenance.However,severe membrane fouling and permeate DOC increase rest...Gravity-driven membrane filtration(GDM)has increasingly captured researchers'attention due to its low energy consumption and operation&maintenance.However,severe membrane fouling and permeate DOC increase restricted GDM's widespread application.This study combined granular active carbon(GAC)and magnetic particles to address this issue and results suggested that GDM3 achieved highly effective pollutant removals(85%COD_(Mn),95% UV_(254),and 65% DOC)and significant flux improvement(96%)than GDM itself.GAC pretreatment before the membrane mainly helped to reduce pollutant load and improve permeated quality while magnetic particles in situ on the membrane surface contributed to engineering more open and connected structures with less extracellular polymeric substance(EPS)and soluble microbial products(SMP)than other GDM groups due to their bioeffect.GDM3 was cost-effective and had the lowest total cost with a decrease of 7.5%and 5.7%to GDM1 and GDM2.The findings provided a deep insight into the combined GAC and magnetic particles in GDM performance improvement and played a fundamental role in developing sustainable and environmentally friendly GDM processes.展开更多
A gravity-driven membrane(GDM)system is a cleaning-free ultrafiltration(UF)process for decentralized water purification.However,GDM has a poor permeate quality and low stable flux when the feed water contains high lev...A gravity-driven membrane(GDM)system is a cleaning-free ultrafiltration(UF)process for decentralized water purification.However,GDM has a poor permeate quality and low stable flux when the feed water contains high levels of particulates,organic matter,and micropollutants.To address these challenges,this study used riverbank filtration(BF)as a pretreatment for GDM.The experimental results showed that BF could effectively reduce turbidity and particulate organic matter,and preferentially remove biopolymers and protein-like fluorescent components from natural organic matter.The removal efficiencies of micropollutants(diclofenac,carbamazepine,acetamidophenol,and bisphenol A)increased by 15.2%-65.3% in the presence of BF.Moreover,BF-GDM improved the removal of assimilable organic carbon(AOC)by 42%,thereby enhancing the biological stability of the permeate.Despite a modest increase of approximately 20%in the removal of dissolved organic matter,the BF significantly improved the stable flux from 2.8 to 7.3 L·m^(-2)·h^(-1).This remarkable improvement is attributed to the effective removal of key foulants,including particulate substances,biopolymers,and protein-like fluorescent substances,which leads to a thinner bio-cake layer with a higher density of microorganisms.Additionally,because of the high microbial diversity of the soil,BF pretreatment enriched the microbial diversity of the biocake layer,thereby enriching functional microorganisms capable of degrading pollutants in BF-GDM,such as Nitrospirota and Ascomycota.Overall,BF is a highly effective pretreatment for GDM,which potentially broadens its application to polluted source water.展开更多
This study proposed a novel membrane filtration and dissolved ozone flotation integrated(MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and req...This study proposed a novel membrane filtration and dissolved ozone flotation integrated(MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and required no backwashing, flushing, or chemical cleaning. Because ozone was added in the MDOF process, ozonation, coagulation, and membrane filtration could occur in a single reactor. Moreover, in situ ozonation occurred in the MDOF process, which differs from the conventional pre-ozonation membrane filtration process. Significant enhancement of turbidity removal was further achieved through the addition of membrane filtration. Membrane fouling was mitigated in the MDOF process compared to the MDAF process. In situ ozonation in the MDOF process decreased the fluorescence intensity and transformed the high MW dissolved organics into small MW compounds. For the fouling layer, the extracellular polymeric substance(EPS) contents and cake layer morphology were analyzed. The results indicated that the contents of EPS decreased. Furthermore, a thinner and more loosely structured cake layer formed in the MDOF process. Because coagulation and ozonation occurred simultaneously in a single reactor, the generation of hydroxyl radicals was enhanced through the catalytic effect of Al-based coagulants on ozone decomposition, which further alleviated membrane fouling in the MDOF process.展开更多
Chlorine is usually applied in the urban water treatment process to deactivate pathogens and prevent waterborne diseases.As a pre-treatment,it remains unclear whether chlorinated water can effectively alleviate membra...Chlorine is usually applied in the urban water treatment process to deactivate pathogens and prevent waterborne diseases.As a pre-treatment,it remains unclear whether chlorinated water can effectively alleviate membrane fouling during ultrafiltration(UF).In this study,tap water was investigated for its effect on biofilm formation and biofouling in a gravity-driven membrane(GDM)filtration system.For comparison,biofilm/biofouling with untreated surface(lake)water was studied in parallel.It was found that more severe membrane fouling occurred with the filtration of tap water than lake water,and larger quantities of polysaccharide and extracellular DNA(eDNA)were present in the tap-water biofilm than in the lake-water biofilm.The tap-water biofilm had a densely compact morphology.In contrast,a porous,spider-like structure was observed for the lake-water biofilm,which was assumed to be associated with the bacteria in the biofilm.This hypothesis was verified by 16S ribosomal RNA(rRNA)sequencing,which demonstrated that Xanthobacter was the dominant taxon in the tap-water biofilm.Additionally,membrane hydrophobicity/hydrophilicity played a minor role in affecting the membrane fouling properties and microbial community.This study revealed the significant role of chlorine-resistant bacteria in biofouling formation and provides a deeper understanding of membrane fouling,which can potentially aid in searching for effective ways of controlling membrane fouling.展开更多
The gravity-driven membrane bioreactor(MBR)system is promising for decentralized sewage treatment because of its low energy consumption and maintenance requirements.However,the growing sludge not only increases membra...The gravity-driven membrane bioreactor(MBR)system is promising for decentralized sewage treatment because of its low energy consumption and maintenance requirements.However,the growing sludge not only increases membrane fouling,but also augments operational complexities(sludge discharge).We added the metabolic uncoupler 3,3’,4f,5-tetrachlorosalicylanilide(TC$)to the system to deal with the mentioned issues.Based on the results,TCS addition effectively decreased sludge ATP and sludge yield(reduced by 50%).Extracellular polymeric substances(EPS;proteins and polysaccharides)decreased with the addition of TCS and were transformed into dissolved soluble microbial products(SMPs)in the bulk solution,leading to the break of sludge floes into small fragments.Permeability was increased by more than two times,reaching 60-70 L/m2/h bar when 10-30 mg/L TCS were added,because of the reduced suspended sludge and the formation of a thin cake layer with low EPS levels.Resistance analyses confirmed that appropriate dosages of TCS primarily decreased the cake layer and hydraulically reversible resistances.Permeability decreased at high dosage(50 mg/L)due to the release of excess sludge fragments and SMP into the supernatant,with a thin but more compact fouling layer with low bioactivity developing on the membrane surface,causing higher cake layer and pore blocking resistances.Our study provides a fundamental understanding of how a metabolic uncoupler affects the sludge and bio-fouling layers at different dosages,with practical relevance for in situ sludge reduction and membrane fouling alleviation in MBR systems.展开更多
基金supported by the National Key Research and Development Program of China(No.2023YFC3208002)National Natural Science Foundation of China(No.52370007)+1 种基金Excellent Youth Foundation of Hei Long Jiang Province of China(No.YQ2022E034)Anhui Provincial Key Laboratory of Environmental Pollution Control and Resource Reuse(No.2021EPC02)。
文摘Gravity-driven membrane filtration(GDM)has increasingly captured researchers'attention due to its low energy consumption and operation&maintenance.However,severe membrane fouling and permeate DOC increase restricted GDM's widespread application.This study combined granular active carbon(GAC)and magnetic particles to address this issue and results suggested that GDM3 achieved highly effective pollutant removals(85%COD_(Mn),95% UV_(254),and 65% DOC)and significant flux improvement(96%)than GDM itself.GAC pretreatment before the membrane mainly helped to reduce pollutant load and improve permeated quality while magnetic particles in situ on the membrane surface contributed to engineering more open and connected structures with less extracellular polymeric substance(EPS)and soluble microbial products(SMP)than other GDM groups due to their bioeffect.GDM3 was cost-effective and had the lowest total cost with a decrease of 7.5%and 5.7%to GDM1 and GDM2.The findings provided a deep insight into the combined GAC and magnetic particles in GDM performance improvement and played a fundamental role in developing sustainable and environmentally friendly GDM processes.
基金supported by the National Natural Science Foundation of China(52270077 and 52070147)。
文摘A gravity-driven membrane(GDM)system is a cleaning-free ultrafiltration(UF)process for decentralized water purification.However,GDM has a poor permeate quality and low stable flux when the feed water contains high levels of particulates,organic matter,and micropollutants.To address these challenges,this study used riverbank filtration(BF)as a pretreatment for GDM.The experimental results showed that BF could effectively reduce turbidity and particulate organic matter,and preferentially remove biopolymers and protein-like fluorescent components from natural organic matter.The removal efficiencies of micropollutants(diclofenac,carbamazepine,acetamidophenol,and bisphenol A)increased by 15.2%-65.3% in the presence of BF.Moreover,BF-GDM improved the removal of assimilable organic carbon(AOC)by 42%,thereby enhancing the biological stability of the permeate.Despite a modest increase of approximately 20%in the removal of dissolved organic matter,the BF significantly improved the stable flux from 2.8 to 7.3 L·m^(-2)·h^(-1).This remarkable improvement is attributed to the effective removal of key foulants,including particulate substances,biopolymers,and protein-like fluorescent substances,which leads to a thinner bio-cake layer with a higher density of microorganisms.Additionally,because of the high microbial diversity of the soil,BF pretreatment enriched the microbial diversity of the biocake layer,thereby enriching functional microorganisms capable of degrading pollutants in BF-GDM,such as Nitrospirota and Ascomycota.Overall,BF is a highly effective pretreatment for GDM,which potentially broadens its application to polluted source water.
基金supported by the National Natural Science Foundation of China(No.51708443)the National Key Research and Development Program of China(No.2016YFC0400701)+1 种基金the China Postdoctoral Science Foundation(No.2017M623326XB)the Shaanxi Provincial Department of Education Key Laboratory Research Projects(No.18JS057)
文摘This study proposed a novel membrane filtration and dissolved ozone flotation integrated(MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and required no backwashing, flushing, or chemical cleaning. Because ozone was added in the MDOF process, ozonation, coagulation, and membrane filtration could occur in a single reactor. Moreover, in situ ozonation occurred in the MDOF process, which differs from the conventional pre-ozonation membrane filtration process. Significant enhancement of turbidity removal was further achieved through the addition of membrane filtration. Membrane fouling was mitigated in the MDOF process compared to the MDAF process. In situ ozonation in the MDOF process decreased the fluorescence intensity and transformed the high MW dissolved organics into small MW compounds. For the fouling layer, the extracellular polymeric substance(EPS) contents and cake layer morphology were analyzed. The results indicated that the contents of EPS decreased. Furthermore, a thinner and more loosely structured cake layer formed in the MDOF process. Because coagulation and ozonation occurred simultaneously in a single reactor, the generation of hydroxyl radicals was enhanced through the catalytic effect of Al-based coagulants on ozone decomposition, which further alleviated membrane fouling in the MDOF process.
基金financially supported by the Key Research and Development Plan of the Ministry of Science and Technology,China(2019YFD1100104 and 2019YFC1906501)。
文摘Chlorine is usually applied in the urban water treatment process to deactivate pathogens and prevent waterborne diseases.As a pre-treatment,it remains unclear whether chlorinated water can effectively alleviate membrane fouling during ultrafiltration(UF).In this study,tap water was investigated for its effect on biofilm formation and biofouling in a gravity-driven membrane(GDM)filtration system.For comparison,biofilm/biofouling with untreated surface(lake)water was studied in parallel.It was found that more severe membrane fouling occurred with the filtration of tap water than lake water,and larger quantities of polysaccharide and extracellular DNA(eDNA)were present in the tap-water biofilm than in the lake-water biofilm.The tap-water biofilm had a densely compact morphology.In contrast,a porous,spider-like structure was observed for the lake-water biofilm,which was assumed to be associated with the bacteria in the biofilm.This hypothesis was verified by 16S ribosomal RNA(rRNA)sequencing,which demonstrated that Xanthobacter was the dominant taxon in the tap-water biofilm.Additionally,membrane hydrophobicity/hydrophilicity played a minor role in affecting the membrane fouling properties and microbial community.This study revealed the significant role of chlorine-resistant bacteria in biofouling formation and provides a deeper understanding of membrane fouling,which can potentially aid in searching for effective ways of controlling membrane fouling.
基金This work was jointly supported by the National Natural Science Foundation of China(Grant No.51608150)the Open Project of State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(No.ES201810-02)+3 种基金the Natural Science Foundation of Heilongjiang Province(No.E2017042)the Natural Science Foundation of Harbin(No.2017RAQXJ206)special support from the China Postdoctoral Fund(No.2018T110303)special support from the Heilongjiang Postdoctoral Found(No.LBH-TZ14).
文摘The gravity-driven membrane bioreactor(MBR)system is promising for decentralized sewage treatment because of its low energy consumption and maintenance requirements.However,the growing sludge not only increases membrane fouling,but also augments operational complexities(sludge discharge).We added the metabolic uncoupler 3,3’,4f,5-tetrachlorosalicylanilide(TC$)to the system to deal with the mentioned issues.Based on the results,TCS addition effectively decreased sludge ATP and sludge yield(reduced by 50%).Extracellular polymeric substances(EPS;proteins and polysaccharides)decreased with the addition of TCS and were transformed into dissolved soluble microbial products(SMPs)in the bulk solution,leading to the break of sludge floes into small fragments.Permeability was increased by more than two times,reaching 60-70 L/m2/h bar when 10-30 mg/L TCS were added,because of the reduced suspended sludge and the formation of a thin cake layer with low EPS levels.Resistance analyses confirmed that appropriate dosages of TCS primarily decreased the cake layer and hydraulically reversible resistances.Permeability decreased at high dosage(50 mg/L)due to the release of excess sludge fragments and SMP into the supernatant,with a thin but more compact fouling layer with low bioactivity developing on the membrane surface,causing higher cake layer and pore blocking resistances.Our study provides a fundamental understanding of how a metabolic uncoupler affects the sludge and bio-fouling layers at different dosages,with practical relevance for in situ sludge reduction and membrane fouling alleviation in MBR systems.
