The efficiency of advanced membranes towards removal of general and specific microbes from wastewater was investigated. The treatment included a subsequent system of activated sludge, ultrafiltration （hollow fibre me...The efficiency of advanced membranes towards removal of general and specific microbes from wastewater was investigated. The treatment included a subsequent system of activated sludge, ultrafiltration （hollow fibre membranes with 100 kDa cut-off, and spiral wound membranes with 20 kDa cut-off）, and RO （reverse osmosis）. The removal evaluation of screened microbes present in treated wastewater showed that hollow fibre membrane rejected only 1 log （90% rejection） of the TPC （total microbial count）, TC （total coliforms）, and FC （faecal coliforms）. A higher effectiveness was observed with spiral wound, removing 2-3 logs （99%-99.9%） of TPC and complete rejection of TC and FC. The RO system was successful in total rejection of all received bacteria. The removal evaluation of inoculated specific types of bacteria showed that the hollow membranes removed 2 logs （99%） of inoculated E. coli （10^7-10^8 cfu/mL inoculum）, 2-3 logs （99%-99.9%） of Enterococus spp. （10^7-10^10 cfu/mL inoculum）, 1-2 logs （90%-99%） of Salmonella （10^8-10^10 cfu/mL inoculum） and 1-2 logs （90%-99%） of Shigella （10^5-10^6 cfu/mL inoculum）. The spiral wound was significantly efficient in rejecting further 3 logs of E. coil, 5 logs of Enterococus spp., 4 logs of Salmonella, and a complete rejection of all received bacteria was accomplished by RO membrane. The results indicate that Gram positive bacteria were removed much more efficiently compared to the Gram negative ones, the rationale behind such behaviour is based on cell walls elasticity.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
文摘The efficiency of advanced membranes towards removal of general and specific microbes from wastewater was investigated. The treatment included a subsequent system of activated sludge, ultrafiltration （hollow fibre membranes with 100 kDa cut-off, and spiral wound membranes with 20 kDa cut-off）, and RO （reverse osmosis）. The removal evaluation of screened microbes present in treated wastewater showed that hollow fibre membrane rejected only 1 log （90% rejection） of the TPC （total microbial count）, TC （total coliforms）, and FC （faecal coliforms）. A higher effectiveness was observed with spiral wound, removing 2-3 logs （99%-99.9%） of TPC and complete rejection of TC and FC. The RO system was successful in total rejection of all received bacteria. The removal evaluation of inoculated specific types of bacteria showed that the hollow membranes removed 2 logs （99%） of inoculated E. coli （10^7-10^8 cfu/mL inoculum）, 2-3 logs （99%-99.9%） of Enterococus spp. （10^7-10^10 cfu/mL inoculum）, 1-2 logs （90%-99%） of Salmonella （10^8-10^10 cfu/mL inoculum） and 1-2 logs （90%-99%） of Shigella （10^5-10^6 cfu/mL inoculum）. The spiral wound was significantly efficient in rejecting further 3 logs of E. coil, 5 logs of Enterococus spp., 4 logs of Salmonella, and a complete rejection of all received bacteria was accomplished by RO membrane. The results indicate that Gram positive bacteria were removed much more efficiently compared to the Gram negative ones, the rationale behind such behaviour is based on cell walls elasticity.
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.
