Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession...Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession mechanisms and their association with the N removal performance of bioreactors.The laboratory woodchip bioreactors were continuously operated for 360 days under three influent N level treatments,and the results showed that the average removal rate of TN was 45.80 g N/(m^(3)·day)when the influent N level was 100 mg N/L,which was better than 10 mg N/L and 50 mg N/L.Dynamic succession of bacterial communities in response to influent N levels and DOM characteristics was an important driver of TN removal rates.Medium to high N levels enriched a copiotroph bacterial module(Module 1)detected by network analysis,including Phenylobacterium,Xanthobacteraceae,Burkholderiaceae,Pseudomonas,and Magnetospirillaceae,carrying N-cycle related genes for denitrification and ammonia assimilation by the rapid consumption of DOM.Such a process can increase carbon limitation to stimulate local organic carbon decomposition to enrich oligotrophswith fewer N-cycle potentials(Module 2).Together,this study reveals that the compositional change ofDOMand bacterial community succession are closely related to N removal performance,providing an ecological basis for developing techniques for N-rich effluent treatment.展开更多
The effects of tourmaline on nitrogen removal performance and biofilm structures were comparatively investigated in two identical laboratory-scale sequencing batch biofilm reactors（SBBRs）（denoted SBBR1 and SBBR2） ...The effects of tourmaline on nitrogen removal performance and biofilm structures were comparatively investigated in two identical laboratory-scale sequencing batch biofilm reactors（SBBRs）（denoted SBBR1 and SBBR2） at different nitrogen loading rates（NLRs） varying from（0.24 ± 0.01） to（1.26 ± 0.02） g N/（L·day）. SBBR1 was operated in parallel with SBBR2, but SBBR1 was filled with polyurethane foam loaded tourmaline（TPU） carriers and another（SBBR2） filled with polyurethane foam（PU） carriers. Results obtained from this study showed that the excellent and stable performance of SBBR1 was obtained. Ammonia nitrogen removal and total nitrogen removal were higher in SBBR1 than that in SBBR2 with increase of NLR. At an NLR of（0.24 ± 0.01） g N/（L·day）, the majority of the spherical and elliptical bacteria were surrounded by the extracellular polymeric substance（EPS） and bacillus or filamentous bacteria in two SBBRs biofilms. When NLR increased to（1.26 ± 0.02） g N/（L·day）, the clusters were more obvious in the SBBR1 biofilm than that in the SBBR2 biofilm. Bacteria in SBBR1 were inclined to synthesis more EPS, and the formed EPS could protect the bacteria from free ammonia（FA） under extreme condition NLR（1.26 ± 0.02） g N/（L·day）. The results of polymerase chain reaction-denaturing gradient gel electrophoresis analysis showed that the microbial community similarity in SBBR2 decreased more obviously than that in SBBR1 with the increase of NLR, which the microbial community in SBBR1 was relatively stable.展开更多
In this study, the water budget in the treatment of high salinity landfill-leachate was estimated and the influence of evapotranspiration （ET） on treatment performance was investigated. The salinity of the inside of...In this study, the water budget in the treatment of high salinity landfill-leachate was estimated and the influence of evapotranspiration （ET） on treatment performance was investigated. The salinity of the inside of horizontal subsurface flow constructed wetland （HSF） of the raw leachate inflow was 15.0± 3.4 g.Cl/L which was in the level of the salinity of the survival limit of reed, and that of the double diluted leachate inflow was 9.3 ± 1.9 g.CI7L. There were large differences in the vegetation between HSF of the raw leachate inflow and that of the double diluted leachate inflow. The dense vegetation bed of double diluted leachate inflow during the growing season （April-October） provided a high ET and a large water loss, which made great contributions to the reduction of the outflow load of COD and T-N. The HSF with die-back reeds in the non-growing season （November-March） provided a slight ET and a small water loss and made less of a contribution to pollutant removal compared to the HSF with dense vegetation bed during the growing season. However, the HSF with die-back reeds during the non-growing season exhibited higher removal performance than the unplanted HSF.展开更多
The emission of air pollutants from various industries is a major contributor to environmental pollution.The removal of these pollutants before they are discharged into the environment has become an important means of...The emission of air pollutants from various industries is a major contributor to environmental pollution.The removal of these pollutants before they are discharged into the environment has become an important means of controlling air pollution.Biochar has attracted increasing attention because of its low cost,high porosity,large specific surface area,abundant surface functional groups,and high removal capacity.The physicochemical properties of biochar are greatly affected by feedstock types,preparation,and modification conditions.For this reason,the capacity and propensity of biochar for removing air pollutants are rather variable.To understand the existing research status and grasp the latest research progress,a systematic review on the removal of different air pollutants by biochar is highly needed.Based on the recent research,this paper systematically analyzes and summarizes the preparation and modification methods of biochar commonly used for the removal of six air pollutants(SO_(2),H_(2)S,CO_(2),Hg0,VOCs,and NH_(3)),as well as the removal performance and mechanisms.Then,the potential influencing factors(preparation parameters,physicochemical characteristics of biochar,and removal conditions)are discussed.Finally,the regeneration of biochar,suggestions,and future perspectives are proposed.展开更多
Microplastics(MPs),as a new category of environmental pollutant,have been the hotspot of eco-friendly issues nowadays.Studies based on the aging process,the migration pattern of MPs in runoff rainwater,and the use of ...Microplastics(MPs),as a new category of environmental pollutant,have been the hotspot of eco-friendly issues nowadays.Studies based on the aging process,the migration pattern of MPs in runoff rainwater,and the use of bioretention cells to remove MPs from runoff rainwater are beginning to attract widespread attention.This review analyses the migration patterns of MPs in rainwater runoff through their sources,structure and characteristics.The mechanism of removing MPs from runoff stormwater,the purification efficiency of different fillers and their influencing factors,and the accumulation,fate,and aging of MPs in bioretention cells are described.Furthermore,the hazards of MP accumulation on the performance of bioretention cells are summarised.Future directions for removing MPs in bioretention cells are proposed:(1)research on MPs smaller than 100μm;(2)influence of MPs aging process on bioretention cells;(3)exploration of more effective fillers to enhance their removal efficiency;(4)research on synergistic removal mechanism of MPs and other pollution.展开更多
The layout of the buckets for tunnel boring machine(TBM)directly affects the muck removal efficiency of cutterhead during excavation.In order to improve the muck removal performance for TBM,the optimal design of bucke...The layout of the buckets for tunnel boring machine(TBM)directly affects the muck removal efficiency of cutterhead during excavation.In order to improve the muck removal performance for TBM,the optimal design of bucket layout was investigated.The whole muck transfer process was simulated by discrete-element method(DEM),including the muck falling,colliding,pilling up,shoveling and transferring into the hopper.The muck model was established based on size distribution analysis of muck samples from the water-supply tunnel project in Jilin Province,China.Then,the influence of the bucket number and the interval angle between buckets on muck removal performance was investigated.The results indicated that,as the number of buckets increased from four to eight,the removed muck increased by 29%and the residual volume decreased by 40.5%,and the process became steadier.Different interval angles between buckets were corresponding to different removed muck irregularly,but the residual muck number increased generally with the angles.The optimal layout of buckets for the cutterhead in this tunnel project was obtained based on the simulation results,and the muck removal performance of the TBM was verified by the actual data in the engineering construction.展开更多
A strain Pandoraea pnomenusa LX-1 that uses dichloromethane （DCM） as sole carbon and energy source has been isolated and identified in our laboratory. The optimum aerobic biodegradation of DCM in batch culture was e...A strain Pandoraea pnomenusa LX-1 that uses dichloromethane （DCM） as sole carbon and energy source has been isolated and identified in our laboratory. The optimum aerobic biodegradation of DCM in batch culture was evaluated by response surface methodology. Maximum biodegradation （5.35 mg/（L.hr）） was achieved under cultivation at 32.8℃, pH 7.3, and 0.66% NaC1. The growth and biodegradation processes were well fitted by Haldane＇s kinetic model, yielding maximum specific growth and degradation rates of 0.133 hr^-1 and 0.856 hr^-1, respectively. The microorganism efficiently degraded a mixture of DCM and coexisting components （benzene, toluene and chlorobenzene）. The carbon recovery （52.80%-94.59%） indicated that the targets were predominantly mineralized and incorporated into cell materials. Electron acceptors increased the DCM biodegradation rate in the following order： mixed 〉 oxygen 〉 iron 〉 sulfate 〉 nitrate. The highest dechlorination rate was 0.365 mg C1-/（hr.mg biomass）, obtained in the presence of mixed electron acceptors. Removal was achieved in a continuous biotrickling filter at 56%-85% efficiency, with a mineralization rate of 75.2%. Molecular biology techniques revealed the predominant strain as P. pnomenusa LX-1. These results clearly demonstrated the effectiveness of strain LX-1 in treating DCM-containing industrial effluents. As such, the strain is a strong candidate for remediation of DCM coexisting with other organic compounds.展开更多
In this work,a novel nitrogen-doped biochar-supported nanoscale ferrous sulfide composite(nFeS@NBC)was fabricated by pyrolyzing corn straw pretreated with Mohr’s salt through a one-step carbothermic reduction process...In this work,a novel nitrogen-doped biochar-supported nanoscale ferrous sulfide composite(nFeS@NBC)was fabricated by pyrolyzing corn straw pretreated with Mohr’s salt through a one-step carbothermic reduction process,which was applied in the efficient disposal of hexavalent chromium(Cr(VI))-containing wastewater.The key effects of impregnation ratio and pyrolysis temperature on the properties and removal performance of nFeS@NBC for Cr(VI)were subsequently investigated.The properties of nFeS@NBC were characterized through a series of techniques.It indicated that FeS nanoparticles were successfully loaded and–NH2 functional groups effectively formed on the biochar surface,which enhanced the removal performance of nFeS@NBC for Cr(VI)from wastewater.The removal performance of nFeS@NBC for Cr(VI)was systemically evaluated at different experimental conditions and in the presence of major co-existing ions.Adsorption kinetics was best suited to the pseudo-second-order model.Additionally,Langmuir isotherms model could well explain the adsorption experiment data for the removal of Cr(VI)by nFeS@NBC with the highest adsorption capacity of 373.85 mg·g^(–1).According to the thermodyna-mic study,nFeS@NBC dominated the adsorption of Cr(VI)through an endothermic and spontaneous process.The adsorption and reduction served as the main removal mechanisms of nFeS@NBC for aqueous Cr(VI).nFeS@NBC could be used repetitively for its regeneration.Thus,the above results showed that it was feasible and efficient to remove Cr(VI)by nFeS@NBC,providing a potential green material for environmental remediation.展开更多
This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam re...This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.展开更多
In the present research, a submerged membrane bioreactor was tested to treat domestic wastewater. Three experimental runs were conducted all with a hydraulic retention time of 5h and sludge retention times (SRTs) of 5...In the present research, a submerged membrane bioreactor was tested to treat domestic wastewater. Three experimental runs were conducted all with a hydraulic retention time of 5h and sludge retention times (SRTs) of 5, 10, and 20 d. The pollutant removal performance of the membrane bioreactor, the membrane effluent quality, and a kinetic model for sludge growth in the bioreactor were investigated. The combined process was capable of removing over 90% of both COD (chemical oxygen demand) and NH 3 N on the average. The total removal for COD was almost independent of SRT, but that for NH 3 N improved with increasing SRT. Membrane effluent quality meets the water quality standard for reuse issued by the Ministry of Construction of China. Increasing SRT causes the concentrations of suspended solids (SS) and volatile suspended solids (VSS) in the bioreactor to increase. However, the ratio of VSS/SS did not change much. Kinetic analysis showed that the sludge yield coefficient (kg VSS·kg COD -1 ) and the endogenous coefficient of microorganisms were 0.25 and 0.04d -1 , which are similar to those of the conventional activated sludge process.展开更多
基金supported by the National Key Research and Development Program of China (Nos.2018YFE0105600 and 2020YFC1806803)the New Zealand MBIE Catalyst Fund (No.92846082).
文摘Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession mechanisms and their association with the N removal performance of bioreactors.The laboratory woodchip bioreactors were continuously operated for 360 days under three influent N level treatments,and the results showed that the average removal rate of TN was 45.80 g N/(m^(3)·day)when the influent N level was 100 mg N/L,which was better than 10 mg N/L and 50 mg N/L.Dynamic succession of bacterial communities in response to influent N levels and DOM characteristics was an important driver of TN removal rates.Medium to high N levels enriched a copiotroph bacterial module(Module 1)detected by network analysis,including Phenylobacterium,Xanthobacteraceae,Burkholderiaceae,Pseudomonas,and Magnetospirillaceae,carrying N-cycle related genes for denitrification and ammonia assimilation by the rapid consumption of DOM.Such a process can increase carbon limitation to stimulate local organic carbon decomposition to enrich oligotrophswith fewer N-cycle potentials(Module 2).Together,this study reveals that the compositional change ofDOMand bacterial community succession are closely related to N removal performance,providing an ecological basis for developing techniques for N-rich effluent treatment.
基金supported by the Project of Nature Scientific Foundation of Heilongjiang Province (No. C2017037)the National Natural Science Foundation of China (No. 31501839)
文摘The effects of tourmaline on nitrogen removal performance and biofilm structures were comparatively investigated in two identical laboratory-scale sequencing batch biofilm reactors（SBBRs）（denoted SBBR1 and SBBR2） at different nitrogen loading rates（NLRs） varying from（0.24 ± 0.01） to（1.26 ± 0.02） g N/（L·day）. SBBR1 was operated in parallel with SBBR2, but SBBR1 was filled with polyurethane foam loaded tourmaline（TPU） carriers and another（SBBR2） filled with polyurethane foam（PU） carriers. Results obtained from this study showed that the excellent and stable performance of SBBR1 was obtained. Ammonia nitrogen removal and total nitrogen removal were higher in SBBR1 than that in SBBR2 with increase of NLR. At an NLR of（0.24 ± 0.01） g N/（L·day）, the majority of the spherical and elliptical bacteria were surrounded by the extracellular polymeric substance（EPS） and bacillus or filamentous bacteria in two SBBRs biofilms. When NLR increased to（1.26 ± 0.02） g N/（L·day）, the clusters were more obvious in the SBBR1 biofilm than that in the SBBR2 biofilm. Bacteria in SBBR1 were inclined to synthesis more EPS, and the formed EPS could protect the bacteria from free ammonia（FA） under extreme condition NLR（1.26 ± 0.02） g N/（L·day）. The results of polymerase chain reaction-denaturing gradient gel electrophoresis analysis showed that the microbial community similarity in SBBR2 decreased more obviously than that in SBBR1 with the increase of NLR, which the microbial community in SBBR1 was relatively stable.
文摘In this study, the water budget in the treatment of high salinity landfill-leachate was estimated and the influence of evapotranspiration （ET） on treatment performance was investigated. The salinity of the inside of horizontal subsurface flow constructed wetland （HSF） of the raw leachate inflow was 15.0± 3.4 g.Cl/L which was in the level of the salinity of the survival limit of reed, and that of the double diluted leachate inflow was 9.3 ± 1.9 g.CI7L. There were large differences in the vegetation between HSF of the raw leachate inflow and that of the double diluted leachate inflow. The dense vegetation bed of double diluted leachate inflow during the growing season （April-October） provided a high ET and a large water loss, which made great contributions to the reduction of the outflow load of COD and T-N. The HSF with die-back reeds in the non-growing season （November-March） provided a slight ET and a small water loss and made less of a contribution to pollutant removal compared to the HSF with dense vegetation bed during the growing season. However, the HSF with die-back reeds during the non-growing season exhibited higher removal performance than the unplanted HSF.
基金the National Natural Science Foundation of China(41977297)the Special Research Fund of Natural Science(Special Post)of Guizhou University[(2020)01]the Key Cultivation Program of Guizhou University[2019(08)].
文摘The emission of air pollutants from various industries is a major contributor to environmental pollution.The removal of these pollutants before they are discharged into the environment has become an important means of controlling air pollution.Biochar has attracted increasing attention because of its low cost,high porosity,large specific surface area,abundant surface functional groups,and high removal capacity.The physicochemical properties of biochar are greatly affected by feedstock types,preparation,and modification conditions.For this reason,the capacity and propensity of biochar for removing air pollutants are rather variable.To understand the existing research status and grasp the latest research progress,a systematic review on the removal of different air pollutants by biochar is highly needed.Based on the recent research,this paper systematically analyzes and summarizes the preparation and modification methods of biochar commonly used for the removal of six air pollutants(SO_(2),H_(2)S,CO_(2),Hg0,VOCs,and NH_(3)),as well as the removal performance and mechanisms.Then,the potential influencing factors(preparation parameters,physicochemical characteristics of biochar,and removal conditions)are discussed.Finally,the regeneration of biochar,suggestions,and future perspectives are proposed.
基金supported by the National Natural Science Foundation of China(No.52070152).
文摘Microplastics(MPs),as a new category of environmental pollutant,have been the hotspot of eco-friendly issues nowadays.Studies based on the aging process,the migration pattern of MPs in runoff rainwater,and the use of bioretention cells to remove MPs from runoff rainwater are beginning to attract widespread attention.This review analyses the migration patterns of MPs in rainwater runoff through their sources,structure and characteristics.The mechanism of removing MPs from runoff stormwater,the purification efficiency of different fillers and their influencing factors,and the accumulation,fate,and aging of MPs in bioretention cells are described.Furthermore,the hazards of MP accumulation on the performance of bioretention cells are summarised.Future directions for removing MPs in bioretention cells are proposed:(1)research on MPs smaller than 100μm;(2)influence of MPs aging process on bioretention cells;(3)exploration of more effective fillers to enhance their removal efficiency;(4)research on synergistic removal mechanism of MPs and other pollution.
基金Project(51475478)supported by the National Natural Science Foundation of ChinaProject(2012AA041801)supported by the National High Technology Research and Development Program of China+1 种基金Project(2014FJ1002)supported by the Science and Technology Major Project of Hunan Province,ChinaProject(2013CB035401)supported by the National Basic Research Program of China。
文摘The layout of the buckets for tunnel boring machine(TBM)directly affects the muck removal efficiency of cutterhead during excavation.In order to improve the muck removal performance for TBM,the optimal design of bucket layout was investigated.The whole muck transfer process was simulated by discrete-element method(DEM),including the muck falling,colliding,pilling up,shoveling and transferring into the hopper.The muck model was established based on size distribution analysis of muck samples from the water-supply tunnel project in Jilin Province,China.Then,the influence of the bucket number and the interval angle between buckets on muck removal performance was investigated.The results indicated that,as the number of buckets increased from four to eight,the removed muck increased by 29%and the residual volume decreased by 40.5%,and the process became steadier.Different interval angles between buckets were corresponding to different removed muck irregularly,but the residual muck number increased generally with the angles.The optimal layout of buckets for the cutterhead in this tunnel project was obtained based on the simulation results,and the muck removal performance of the TBM was verified by the actual data in the engineering construction.
基金supported by the Major Science and Technology Project of Zhejiang Province(No.2011C13023)the Ph.D. Programs Foundation of Ministry of Education of China(No.20093317110003)
文摘A strain Pandoraea pnomenusa LX-1 that uses dichloromethane （DCM） as sole carbon and energy source has been isolated and identified in our laboratory. The optimum aerobic biodegradation of DCM in batch culture was evaluated by response surface methodology. Maximum biodegradation （5.35 mg/（L.hr）） was achieved under cultivation at 32.8℃, pH 7.3, and 0.66% NaC1. The growth and biodegradation processes were well fitted by Haldane＇s kinetic model, yielding maximum specific growth and degradation rates of 0.133 hr^-1 and 0.856 hr^-1, respectively. The microorganism efficiently degraded a mixture of DCM and coexisting components （benzene, toluene and chlorobenzene）. The carbon recovery （52.80%-94.59%） indicated that the targets were predominantly mineralized and incorporated into cell materials. Electron acceptors increased the DCM biodegradation rate in the following order： mixed 〉 oxygen 〉 iron 〉 sulfate 〉 nitrate. The highest dechlorination rate was 0.365 mg C1-/（hr.mg biomass）, obtained in the presence of mixed electron acceptors. Removal was achieved in a continuous biotrickling filter at 56%-85% efficiency, with a mineralization rate of 75.2%. Molecular biology techniques revealed the predominant strain as P. pnomenusa LX-1. These results clearly demonstrated the effectiveness of strain LX-1 in treating DCM-containing industrial effluents. As such, the strain is a strong candidate for remediation of DCM coexisting with other organic compounds.
基金supported by the Shandong Province Young Taishan Scholar,China(Grant No.tsqn202312155)the National Natural Science Foundation of China(Grant No.42471081)+1 种基金the Shandong Provincial Natural Science Foundation(Grant No.ZR2021YQ22)the Shandong Province Colleges and Universities Youth Innovation Science and Technology Teams Support Program(Grant No.2021KJ015).
文摘In this work,a novel nitrogen-doped biochar-supported nanoscale ferrous sulfide composite(nFeS@NBC)was fabricated by pyrolyzing corn straw pretreated with Mohr’s salt through a one-step carbothermic reduction process,which was applied in the efficient disposal of hexavalent chromium(Cr(VI))-containing wastewater.The key effects of impregnation ratio and pyrolysis temperature on the properties and removal performance of nFeS@NBC for Cr(VI)were subsequently investigated.The properties of nFeS@NBC were characterized through a series of techniques.It indicated that FeS nanoparticles were successfully loaded and–NH2 functional groups effectively formed on the biochar surface,which enhanced the removal performance of nFeS@NBC for Cr(VI)from wastewater.The removal performance of nFeS@NBC for Cr(VI)was systemically evaluated at different experimental conditions and in the presence of major co-existing ions.Adsorption kinetics was best suited to the pseudo-second-order model.Additionally,Langmuir isotherms model could well explain the adsorption experiment data for the removal of Cr(VI)by nFeS@NBC with the highest adsorption capacity of 373.85 mg·g^(–1).According to the thermodyna-mic study,nFeS@NBC dominated the adsorption of Cr(VI)through an endothermic and spontaneous process.The adsorption and reduction served as the main removal mechanisms of nFeS@NBC for aqueous Cr(VI).nFeS@NBC could be used repetitively for its regeneration.Thus,the above results showed that it was feasible and efficient to remove Cr(VI)by nFeS@NBC,providing a potential green material for environmental remediation.
基金Supported by the National Natural Science Foundation of China(21606008,21436002)the National Basic Research Foundation of China(2013CB733600)the Fundamental Research Funds for the Central Universities(ZY1630,JD1617,buctrc201616,and buctrc201617)
文摘This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.
文摘In the present research, a submerged membrane bioreactor was tested to treat domestic wastewater. Three experimental runs were conducted all with a hydraulic retention time of 5h and sludge retention times (SRTs) of 5, 10, and 20 d. The pollutant removal performance of the membrane bioreactor, the membrane effluent quality, and a kinetic model for sludge growth in the bioreactor were investigated. The combined process was capable of removing over 90% of both COD (chemical oxygen demand) and NH 3 N on the average. The total removal for COD was almost independent of SRT, but that for NH 3 N improved with increasing SRT. Membrane effluent quality meets the water quality standard for reuse issued by the Ministry of Construction of China. Increasing SRT causes the concentrations of suspended solids (SS) and volatile suspended solids (VSS) in the bioreactor to increase. However, the ratio of VSS/SS did not change much. Kinetic analysis showed that the sludge yield coefficient (kg VSS·kg COD -1 ) and the endogenous coefficient of microorganisms were 0.25 and 0.04d -1 , which are similar to those of the conventional activated sludge process.
