Soil biofiltration, also known as soil bed reactor (SBR), technology was originally developed in Germany to take advantage of the diversity in microbial mechanisms to control gases producing malodor in industrial proc...Soil biofiltration, also known as soil bed reactor (SBR), technology was originally developed in Germany to take advantage of the diversity in microbial mechanisms to control gases producing malodor in industrial processes. The approach has since gained wider international acceptance and continues to see improvements to maximize microbial and process efficiency and extend the range of problematical gases for which the technology can be an effective control. We review the basic mechanisms which underlay microbial soil processes involved in air purification, advantages and limitations of the technology and the current research status of the approach. Soil biofiltration has lower capital and operating/energetic costs than conventional technologies and is well adapted to handle contaminants in moderate concentrations. The systems can be engineered to optimize efficiency though manipulation of temperature, pH, moisture content, soil organic matter and airflow rates. Soil air biofiltration technology was modified for application in the Biosphere 2 project, which demonstrated in preparatory research with a number of closed system testbeds that soil could also support crop plants while also serving as soil filters with airpumps to push air through the soil. This Biosphere 2 research demonstrated in several closed system testbeds that a number of important trace gases could be kept under control and led to the engineering of the entire agricultural soil of Biosphere 2 to serve as a soil filtration unit for the facility. Soil biofiltration, coupled with food crop production, as a component of bioregenerative space life support systems has the advantages of lower energy use and avoidance of the consumables required for other air purification approaches. Expanding use of soil biofiltration can aid a number of environmental applications, from the mitigation of indoor air pollution, as a method of reducing global warming impact of methane (biogas), improvement of industrial air emissions and prevention of accidental release of toxic gases.展开更多
The biofiltration of n-hexane is studied to optimize determinants factors of hydrophobic VOC filtration efficiency. Four trickle-bed air biofilters (TBABs) were employed;two of which were supplied with nutrients buffe...The biofiltration of n-hexane is studied to optimize determinants factors of hydrophobic VOC filtration efficiency. Four trickle-bed air biofilters (TBABs) were employed;two of which were supplied with nutrients buffered at a neutral pH, while another two at an acidic pH of 4 to induce and enhance fungal growth. The loading rate of n-hexane was kept constant in all TBABs at 13 g/m3/h. At each pH levels studied, the biomass of the TBABs was pre-acclimated using different ratios of n-hexane and methanol. The fungal biomass responsible for the degradation of n-hexane was then examined and quantified. Dichloran Rose Bengal Chloramphenicol agar was used for fungi quantification, and optical microscopy for classification. Effluent biomass was validated by measuring volatile suspended solids. Fungal counts resulting from n-hexane biodegradation were related to nitrate and carbon consumption. It was found that n-hexane elimination capacity closely followed biomass growth, and reached a steady-state at an optimum biomass density of roughly 3000 cfu/ml. Major shifts in fungal species were observed in all TBABs. Dominant fungal species grew slowly to become the most numerous, and were found to provide maximum elimination capacity, although TBABs pre-acclimated to higher methanol concentrations took less time to reach this steady-state. It was concluded, therefore, that steady and monitored growth of TBAB biomass is an essential factor in maximizing fungi’s ability to metabolize VOCs and that a new ecological biofiltration model may be the most effective at VOC purification.展开更多
The bacterial antibiotic resistome(BAR)is one of the most serious contemporary medical challenges.The BAR problem in drinking water is receiving growing attention.In this study,we focused on the distribution,changes,a...The bacterial antibiotic resistome(BAR)is one of the most serious contemporary medical challenges.The BAR problem in drinking water is receiving growing attention.In this study,we focused on the distribution,changes,and health risks of the BAR throughout the drinking water treatment system.We extracted the antibiotic resistance gene(ARG)data from recent publications and analyzed ARG profiles based on diversity,absolute abundance,and relative abundance.The absolute abundance of ARG was found to decrease with water treatment processes and was positively correlated with the abundance of 16S rRNA(r=0.963,/?<0.001),indicating that the reduction of ARG concentration was accompanied by decreasing biomass.Among treatment processes,biofiltration and chlorination were discovered to play important roles in shaping the bacterial antibiotic resistome.Chlorination exhibited positive effects in controlling the diversity of ARG,while biofiltration,especially granular activated carbon filtration,increased the diversity of ARG.Both biofiltration and chlorination altered the structure of the resistome by affecting relative ARG abundance.In addition,we analyzed the mechanism behind the impact of biofiltration and chlorination on the bacterial antibiotic resistome.By intercepting influent ARG-carrying bacteria,biofilters can enrich various ARGs and maintain ARGs in biofilm.Chlorination further selects bacteria co-resistant to chlorine and antibiotics.Finally,we proposed the BAR health risks caused by biofiltration and chlorination in water treatment.To reduce potential BAR risk in drinking water,membrane filtration technology and water boiling are recommended at the point of use.展开更多
Two different functional biofilters were carried out and compared for the treatment of off-gas containing multicomponent odors and volatile organic compounds (VOCs) in this study. The effects of pH values and the empt...Two different functional biofilters were carried out and compared for the treatment of off-gas containing multicomponent odors and volatile organic compounds (VOCs) in this study. The effects of pH values and the empty bed retention time (EBRT) on the performance of the bioreactors were studied; and the characteristics of microbial populations in the two biofilters were also determined. The experimental results indicated that the removal effciencies of hydrophilic compounds such as butyric acid and ammonia were higher in the neutral pH biofilter (NPB) than those in the low pH biofilter (LPB). In contrast, the removal effciencies of the compounds with poor water solubility such as styrene and ethyl mercaptan were higher in the LPB than those in the NPB. The characteristics of microbial population in the two biofilters revealed that the heterotrophic bacteria, nonacidophilic thiobacteria, ammonia oxidizing bacteria, and nitrite oxidizing bacteria were major microorganisms in the NPB, whereas acidophilic thiobacteria and fungi were dominant in the LPB. Therefore, the performance of the biofilter depended on the characteristics of the compound being treated and the type of microorganisms.展开更多
Several on-site greywater treatment systems are under development including biofiltration, whose efficiency is influenced by the filter media. Therefore, the main objective of this study was to evaluate the influence ...Several on-site greywater treatment systems are under development including biofiltration, whose efficiency is influenced by the filter media. Therefore, the main objective of this study was to evaluate the influence of the type of filter media and their grain size in the removal of organic and microbial pollutants from greywater. Hence, three types of local filter media of different grain size were used for the pre-treatment of greywater. Their removal potential and clogging time were evaluated and compared. The results indicated that the type of filter media and the grain size have an influence on the elimination of organic and microbial pollution from greywater. Indeed, sand of 1 - 2 mm in size obtained the highest removal efficiencies of organic pollutants (67.35% and 78.04% for COD and BOD5 respectively) and microbial indicators (2.07, 1.77 and 2.27 log. units for E. coli, fecal coliforms and enterococci respectively). Although media of fine texture enhanced the removal efficiencies, they experienced significant clogging problems. To overcome these limitations while enhancing the removal efficiency, 1) pre-treatment stage with coarse materials followed by a treatment with finer materials or 2) the use of a combination of fine and coarse materials should be considered.展开更多
A novel three-stage integrated biofilter(TSIBF)composed of acidophilic bacteria reaction segment(ABRS),fungal reaction segment(FRS)and heterotrophic bacteria reaction segment(HBRS)was constructed for the treatment of ...A novel three-stage integrated biofilter(TSIBF)composed of acidophilic bacteria reaction segment(ABRS),fungal reaction segment(FRS)and heterotrophic bacteria reaction segment(HBRS)was constructed for the treatment of odors and volatile organic compounds(VOCs)from municipal solid waste(MSW)comprehensive treatment plants.The performance,counts of predominant microorganisms,and bioaerosol emissions of a flill-scale TSIBF system were studied.High and stable removal efficiencies of hydrogen sulfide,ammonia and VOCs could be achieved with the TSIBF system,and the emissions of culturable heterotrophic bacteria,fungi and acidophilic sulfur bacteria were relatively low.The removal efficiencies of different odors and VOCs,emissions of culturable microorganisms,and types of predominant microorganisms were different in the ABRS,FRS and HBRS due to the differences in reaction conditions and mass transfer in each segment.The emissions of bioaerosols from the TSIBF depended on the capture of microorganisms and their volatilization from the packing.The rational segmentation,filling of high-density packings and the accumulation of the predominant functional microorganisms in each segment enhanced the capture effect of the bioaerosols,thus reducing the emissions of microorganisms from the bioreactor.展开更多
Waste gases from oil refining wastewater treatment plants are often characterized by the presence of multicomponent and various concentrations of compounds.An evaluation of the performance and feasibility of removing ...Waste gases from oil refining wastewater treatment plants are often characterized by the presence of multicomponent and various concentrations of compounds.An evaluation of the performance and feasibility of removing multicomponent volatile organic compounds(VOCs)in off-gases from oil refining wastewater treatment plants was conducted in a pilot-scale compost-based biofilter system.This system consists of two identical biofilters packed with compost and polyethylene(PE).This paper investigates the effects of various concentrations of nonmethane hydrocarbon(NMHC)and empty bed residence time(EBRT)on the removal efficiency of NMHC.Based on the experimental results and practical applications,an EBRT of 66 s was applied to the biofilter system.The removal efficiencies of NMHC were within the range of 47%–100%.At an EBRT of 66 s,the average removal efficiency of benzene,toluene,and xylene were more than 99%,99%,and 100%,respectively.The results demonstrated that multicomponent VOCs in off-gases from the oil refining wastewater treatment plant could be successfully removed in the biofilter system,which may provide useful information concerning the design criteria and operation of full-scale biofilters.展开更多
文摘Soil biofiltration, also known as soil bed reactor (SBR), technology was originally developed in Germany to take advantage of the diversity in microbial mechanisms to control gases producing malodor in industrial processes. The approach has since gained wider international acceptance and continues to see improvements to maximize microbial and process efficiency and extend the range of problematical gases for which the technology can be an effective control. We review the basic mechanisms which underlay microbial soil processes involved in air purification, advantages and limitations of the technology and the current research status of the approach. Soil biofiltration has lower capital and operating/energetic costs than conventional technologies and is well adapted to handle contaminants in moderate concentrations. The systems can be engineered to optimize efficiency though manipulation of temperature, pH, moisture content, soil organic matter and airflow rates. Soil air biofiltration technology was modified for application in the Biosphere 2 project, which demonstrated in preparatory research with a number of closed system testbeds that soil could also support crop plants while also serving as soil filters with airpumps to push air through the soil. This Biosphere 2 research demonstrated in several closed system testbeds that a number of important trace gases could be kept under control and led to the engineering of the entire agricultural soil of Biosphere 2 to serve as a soil filtration unit for the facility. Soil biofiltration, coupled with food crop production, as a component of bioregenerative space life support systems has the advantages of lower energy use and avoidance of the consumables required for other air purification approaches. Expanding use of soil biofiltration can aid a number of environmental applications, from the mitigation of indoor air pollution, as a method of reducing global warming impact of methane (biogas), improvement of industrial air emissions and prevention of accidental release of toxic gases.
文摘The biofiltration of n-hexane is studied to optimize determinants factors of hydrophobic VOC filtration efficiency. Four trickle-bed air biofilters (TBABs) were employed;two of which were supplied with nutrients buffered at a neutral pH, while another two at an acidic pH of 4 to induce and enhance fungal growth. The loading rate of n-hexane was kept constant in all TBABs at 13 g/m3/h. At each pH levels studied, the biomass of the TBABs was pre-acclimated using different ratios of n-hexane and methanol. The fungal biomass responsible for the degradation of n-hexane was then examined and quantified. Dichloran Rose Bengal Chloramphenicol agar was used for fungi quantification, and optical microscopy for classification. Effluent biomass was validated by measuring volatile suspended solids. Fungal counts resulting from n-hexane biodegradation were related to nitrate and carbon consumption. It was found that n-hexane elimination capacity closely followed biomass growth, and reached a steady-state at an optimum biomass density of roughly 3000 cfu/ml. Major shifts in fungal species were observed in all TBABs. Dominant fungal species grew slowly to become the most numerous, and were found to provide maximum elimination capacity, although TBABs pre-acclimated to higher methanol concentrations took less time to reach this steady-state. It was concluded, therefore, that steady and monitored growth of TBAB biomass is an essential factor in maximizing fungi’s ability to metabolize VOCs and that a new ecological biofiltration model may be the most effective at VOC purification.
基金This research was supported by the National Key Research and Development Program of China-International collaborative project from Ministry of Science and Technology(Grant No.2017YFE0107300)the National Science Foundation for Young Scientists of China(Grant No.51708534)+1 种基金the Natural Science Foundation of China(Grant Nos.51678551,51678552 and 41861144023)Xiamen Municipal Bureau of Science and Technology(No.3502Z20171003)and K.C.Wong Education Foundation.
文摘The bacterial antibiotic resistome(BAR)is one of the most serious contemporary medical challenges.The BAR problem in drinking water is receiving growing attention.In this study,we focused on the distribution,changes,and health risks of the BAR throughout the drinking water treatment system.We extracted the antibiotic resistance gene(ARG)data from recent publications and analyzed ARG profiles based on diversity,absolute abundance,and relative abundance.The absolute abundance of ARG was found to decrease with water treatment processes and was positively correlated with the abundance of 16S rRNA(r=0.963,/?<0.001),indicating that the reduction of ARG concentration was accompanied by decreasing biomass.Among treatment processes,biofiltration and chlorination were discovered to play important roles in shaping the bacterial antibiotic resistome.Chlorination exhibited positive effects in controlling the diversity of ARG,while biofiltration,especially granular activated carbon filtration,increased the diversity of ARG.Both biofiltration and chlorination altered the structure of the resistome by affecting relative ARG abundance.In addition,we analyzed the mechanism behind the impact of biofiltration and chlorination on the bacterial antibiotic resistome.By intercepting influent ARG-carrying bacteria,biofilters can enrich various ARGs and maintain ARGs in biofilm.Chlorination further selects bacteria co-resistant to chlorine and antibiotics.Finally,we proposed the BAR health risks caused by biofiltration and chlorination in water treatment.To reduce potential BAR risk in drinking water,membrane filtration technology and water boiling are recommended at the point of use.
基金supported by the National Natural Sci-ence Foundation of China (No. 50621804).
文摘Two different functional biofilters were carried out and compared for the treatment of off-gas containing multicomponent odors and volatile organic compounds (VOCs) in this study. The effects of pH values and the empty bed retention time (EBRT) on the performance of the bioreactors were studied; and the characteristics of microbial populations in the two biofilters were also determined. The experimental results indicated that the removal effciencies of hydrophilic compounds such as butyric acid and ammonia were higher in the neutral pH biofilter (NPB) than those in the low pH biofilter (LPB). In contrast, the removal effciencies of the compounds with poor water solubility such as styrene and ethyl mercaptan were higher in the LPB than those in the NPB. The characteristics of microbial population in the two biofilters revealed that the heterotrophic bacteria, nonacidophilic thiobacteria, ammonia oxidizing bacteria, and nitrite oxidizing bacteria were major microorganisms in the NPB, whereas acidophilic thiobacteria and fungi were dominant in the LPB. Therefore, the performance of the biofilter depended on the characteristics of the compound being treated and the type of microorganisms.
文摘Several on-site greywater treatment systems are under development including biofiltration, whose efficiency is influenced by the filter media. Therefore, the main objective of this study was to evaluate the influence of the type of filter media and their grain size in the removal of organic and microbial pollutants from greywater. Hence, three types of local filter media of different grain size were used for the pre-treatment of greywater. Their removal potential and clogging time were evaluated and compared. The results indicated that the type of filter media and the grain size have an influence on the elimination of organic and microbial pollution from greywater. Indeed, sand of 1 - 2 mm in size obtained the highest removal efficiencies of organic pollutants (67.35% and 78.04% for COD and BOD5 respectively) and microbial indicators (2.07, 1.77 and 2.27 log. units for E. coli, fecal coliforms and enterococci respectively). Although media of fine texture enhanced the removal efficiencies, they experienced significant clogging problems. To overcome these limitations while enhancing the removal efficiency, 1) pre-treatment stage with coarse materials followed by a treatment with finer materials or 2) the use of a combination of fine and coarse materials should be considered.
基金by the key Projects in the National Science&Technology Pillar Program of China during the Twelfth Five-Year Plan Period(No.2013BAC25B00-004).
文摘A novel three-stage integrated biofilter(TSIBF)composed of acidophilic bacteria reaction segment(ABRS),fungal reaction segment(FRS)and heterotrophic bacteria reaction segment(HBRS)was constructed for the treatment of odors and volatile organic compounds(VOCs)from municipal solid waste(MSW)comprehensive treatment plants.The performance,counts of predominant microorganisms,and bioaerosol emissions of a flill-scale TSIBF system were studied.High and stable removal efficiencies of hydrogen sulfide,ammonia and VOCs could be achieved with the TSIBF system,and the emissions of culturable heterotrophic bacteria,fungi and acidophilic sulfur bacteria were relatively low.The removal efficiencies of different odors and VOCs,emissions of culturable microorganisms,and types of predominant microorganisms were different in the ABRS,FRS and HBRS due to the differences in reaction conditions and mass transfer in each segment.The emissions of bioaerosols from the TSIBF depended on the capture of microorganisms and their volatilization from the packing.The rational segmentation,filling of high-density packings and the accumulation of the predominant functional microorganisms in each segment enhanced the capture effect of the bioaerosols,thus reducing the emissions of microorganisms from the bioreactor.
文摘Waste gases from oil refining wastewater treatment plants are often characterized by the presence of multicomponent and various concentrations of compounds.An evaluation of the performance and feasibility of removing multicomponent volatile organic compounds(VOCs)in off-gases from oil refining wastewater treatment plants was conducted in a pilot-scale compost-based biofilter system.This system consists of two identical biofilters packed with compost and polyethylene(PE).This paper investigates the effects of various concentrations of nonmethane hydrocarbon(NMHC)and empty bed residence time(EBRT)on the removal efficiency of NMHC.Based on the experimental results and practical applications,an EBRT of 66 s was applied to the biofilter system.The removal efficiencies of NMHC were within the range of 47%–100%.At an EBRT of 66 s,the average removal efficiency of benzene,toluene,and xylene were more than 99%,99%,and 100%,respectively.The results demonstrated that multicomponent VOCs in off-gases from the oil refining wastewater treatment plant could be successfully removed in the biofilter system,which may provide useful information concerning the design criteria and operation of full-scale biofilters.