Volatile organic compounds(VOCs) are typical pollutants that affect air quality.Discharge plasma is thought to be a potential method that can remove VOCs from flue gas.In this experiment,pulsed corona discharge plasma...Volatile organic compounds(VOCs) are typical pollutants that affect air quality.Discharge plasma is thought to be a potential method that can remove VOCs from flue gas.In this experiment,pulsed corona discharge plasma combined with a biological tower was carried out to remove the benzene series,and toluene was selected as the typical VOC.The results indicated that the removal efficiency of toluene by pulsed corona plasma was slightly higher than that of direct current(DC) corona plasma,while its energy efficiency was much higher than DC corona plasma.Under the optimal experimental conditions of pulse voltage 8.5 kV,initial toluene concentration 1400 mg m^(-3),and toluene flow rate of 121h^(-1),the toluene removal efficiency reached 77.11% by the single method of pulsed corona discharge plasma,and the energy efficiency was up to 1.515 g/(kW·h) under the pulse voltage of 4.0 kV.The trickling biofilter was constructed by using the screened and domesticated Acinetobacter baumannii,and the highest toluene removal efficiency by the pulsed corona discharge plasma combined with the trickling biofilter rose up to 97.84%.Part of the toluene was degraded into CO_(2),H_(2)O,and some intermediate products such as o-diphenol under the influence of Acinetobacter baumannii.When the remaining waste gas passed through the discharge plasma reactor,the benzene ring structure could be directly destroyed by the collision between toluene and plasma.Meanwhile,O·,OH·,and some other oxidizing radicals generated by the discharge also join into the oxidative decomposition of toluene and its intermediate products,thereby further improving the removal efficiency of toluene.Therefore,the two-stage plasma-biofilter system not only showed a high toluene removal efficiency,but also had a good energy efficiency.The results of this study will provide theoretical support and technical reference for industrial VOC treatment.展开更多
Bacteria play a major role in metabolizing ammonia and other metabolites in recirculating aquaculture systems(RASs).To characterize and compare the bacterial communities in the biofilters of two full-scale RASs for th...Bacteria play a major role in metabolizing ammonia and other metabolites in recirculating aquaculture systems(RASs).To characterize and compare the bacterial communities in the biofilters of two full-scale RASs for the culture of puffer fish,Takifugu rubripes,at different ages and densities were studied.In overall,47807 optimized reads of the 16 S rRNA gene with V4-V5 region were obtained from four biofilm samples collected after biofilm maturation.At 97%cut-off level,these sequences were clustered into 500 operational taxonomic units,and were classified into 19 bacterial phyla and 138 genera.At the phylum level,Proteobacteria and Bacteroidetes were the most abundant,followed by Nitrospirae and Planctomycetes.At the genus level,Colwellia,Marinifilum,Oceanospirillum,Lutibacter,Winogradskyella,Pseudoalteromonas,Arcobacter,and Phaeobacter were the top members.Nitrosomonas and Nitrospira were main ammonia-and nitrite-oxidizing bacteria.Differences in bacterial communities at different sampling dates and similarities of both biofilters were revealed in the Venn diagram and cluster analysis.Maintaining a good water quality and health offarmed fish in RASs depended on the correct management of the bacterial communities.This study provides more accurate information on the bacterial communities associated with the bifilters of both RASs.展开更多
Biofiltration is emerging as a promising cost effective technique for the Volatile Organic Compounds (VOCs) removal from industrial waste gases. In the present investigation a comparative modeling study has been carri...Biofiltration is emerging as a promising cost effective technique for the Volatile Organic Compounds (VOCs) removal from industrial waste gases. In the present investigation a comparative modeling study has been carried out using Radial Basis Function Neural Network (RBFN) and Response Surface Methodology (RSM) to predict and optimize the performance of a biofilter system treating toluene (a model VOC). Experimental biofilter system performance data collected over a time period by daily measurement of inlet VOC concentration, retention time, pH, temperature and packing moisture content was used to develop the mathematical model. These independent variables acted as the inputs to the mathematical model developed using RSM and RBFN, while the VOC removal efficiency was the biofilter system performance parameter to be predicted. The data set was divided into two parts: 60% of data was used for training phase and remaining 40% of data was used for the testing phase. The average % error for RSM and RBFN were 7.76% and 3.03%, and R2 value obtained were 0.8826 and 0.9755 respectively. The results indicated the superiority of RBFN in the prediction capability due to its ability to approximate higher degree of nonlinearity between the input and output variables. The optimization of biofilter parameters was also done using RSM to optimize the biofilter performance. RSM being structured in nature enabled the study of interaction effect between the independent variables on biofilter performance.展开更多
Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the act...Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the activated sludge and toluene degrading bacteria, and the packing material consisted of different mixing ratios of peat and wood chips. A final toluene load of 21.2 g/(m3·h) was attained step by step in four parallel biofilters. A shortest start-up time of 15 days and a highest EC of 17.0 g/(m3·h) were observed in the biofilter B-4, which was inoculated with a special microbial consortium consisting of three strains of toluene degrading bacteria and was packed with the mixture of peat and wood chips at a ratio of 80:20 (w/w). These results indicated that inoculating pre-acclimatized microbes dramatically shortened the start-up time, and such a composition of packing material could maintain an appropriate environment (with the bed porosity and water content equating to 0.45 and 1.96, respectively) for the growth of dominant toluene degrading bacteria in the biofilter.展开更多
Mathematical models of steady-state biofilteration are discussed. The theoretical results are much useful for the design of biofilters. This model is based on the system of non-linear reaction/diffusion equations cont...Mathematical models of steady-state biofilteration are discussed. The theoretical results are much useful for the design of biofilters. This model is based on the system of non-linear reaction/diffusion equations contains a non-linear term related to Monod kinetics, Andrews kinetics, interactive model from Monod kinetics and Andrews kinetics. Analytical expression of concentration of VOC (Volatile organic compounds) and oxygen are derived by solving the system of non-linear equations using Adomian decomposition method (ADM) method. Our analytical results are also compared with the simulation results. Satisfactory agreement is noted.展开更多
In this paper, mathematical models of biofilm mixtures of n-butanol biofilters were discussed. The model is based on the mass transfer in the biofilm interface and chemical oxidation in the biofilm phase and gas phase...In this paper, mathematical models of biofilm mixtures of n-butanol biofilters were discussed. The model is based on the mass transfer in the biofilm interface and chemical oxidation in the biofilm phase and gas phase. An approximate analytical expression of concentration profiles of n-butanol in the biofilm phase and gas phase has been derived using the homotopy perturbation method and hyperbolic function method for all possible values of parameters. Furthermore, in this work, the numerical simulation of the problem is also reported using the Matlab program. Good agreement between the analytical and numerical results is noted. Graphical results are presented and discussed quantitatively to illustrate the solution. The analytical results will be useful in finding the yields of biomass and oxygen consumption, the specific biomass surface area, activation energy and saturation constant for the Michaelis-Menten kinetics.展开更多
This paper investigates and provides a critical analysis of the toluene biofilter model developed by Li and De Visscher. The model simulation results have been reproduced and compared with several sets of experimental...This paper investigates and provides a critical analysis of the toluene biofilter model developed by Li and De Visscher. The model simulation results have been reproduced and compared with several sets of experimental data from literature. Three different model variations are considered: model with no substrate inhibition, with substrate inhibition, and with air flow rate modification. A sensitivity analysis has been performed on model to study the effect of important parameters on the removal efficiency. Model limitations and improvements have been highlighted.展开更多
Biofiltration has become a widely accepted technology for the removal of hydrogen sulfide (H2S) which is one of the major odor causing gases present in the air streams of municipal wastewater treatment facilities. In ...Biofiltration has become a widely accepted technology for the removal of hydrogen sulfide (H2S) which is one of the major odor causing gases present in the air streams of municipal wastewater treatment facilities. In addition to odorous nature, H2S is toxic and corrosive. In this study, a biofilter which uses a novel media was employed in a pumping station which is closely located at the University City, Sharjah, UAE. The H2S removal performance data were collected and subsequently used in the determination of kinetics and modeling of H2S. The data were best represented by a first order biofilter model. Based on the first order kinetic constant, a correlation is developed to predict concentrations at the biofilter outlet. Based on the predicted outlet concentrations and dispersion (gaussian and US-EPA AERMOD) models, a study on H2S dispersion is conducted. The dispersion study confirmed a biofilter installation at the pumping station site would significantly reduce H2S levels in the University community and would provide cleaner air.展开更多
Biofilters are typical biofilm reactors, and they usually have poor biofilm formation resulting in limited reactor performance. Exogenous acylated homoserine lactones (AHLs) can enhance biofilm formation in many biore...Biofilters are typical biofilm reactors, and they usually have poor biofilm formation resulting in limited reactor performance. Exogenous acylated homoserine lactones (AHLs) can enhance biofilm formation in many bioreactors based on quorum sensing regulation. However, their effect on biofilm in biofilters utilized for volatile organic compound (VOC) removal is unknown and needs to be investigated. In this study, the effects of the exogenous AHLs on biofilters for gaseous toluene removal were investigated. Analysis of biofilms in biofilters showed that the addition of exogenous AHLs considerably enhanced biofilm growth;the average biofilm concentration increased by 18%. Furthermore, the average biofilm coverage proportions in biofilters with and without exogenous AHLs were 17 % and 13 %, respectively, demonstrating the positive effect of exogenous AHLs on biofilm coverage. In particular, exogenous AHLs promoted the production of extracellular polymeric substances and the microbial adhesive strength of the biofilm. In addition, the exogenous AHLs showed no significant effect on the gaseous toluene removal efficiency of the biofilter. These results show that exogenous AHLs can enhance biofilm formation and can guide the application of exogenous AHLs in VOC biofilters.展开更多
This paper presents an analytical model for predicting VOC waste gas degradation in a trickling biofilter. To facilitate the analysis, the packed bed is simplified into a series of straight capillary tubes covered by ...This paper presents an analytical model for predicting VOC waste gas degradation in a trickling biofilter. To facilitate the analysis, the packed bed is simplified into a series of straight capillary tubes covered by the biofilm. The gas-liquid flow field through the tube is divided into the liquid film flow on the biofilm and the gas core flow in the center. The biofilm consists of a reaction free zone close to solid wall and a reaction zone beneath the liquid film. The capillary tube model accounts for the effect of mass transport resistance in the liquid film and the biofilm, the gas-liquid interfacial mass transport resistance, the biochemical reaction, and the limitation of oxygen to biochemical reaction. The liquid film thickness in the capillary tube is obtained by simultaneously solving a set of hydrodynamic equations representing the momentum transport behaviors of the gas-liquid two-phase flow. The mass transport equations are established for gas core, liquid film, and biofilm combined with biochemical kinetics equations. An iterative computation process is employed to solve the discrete equations. The predicted purification efficiencies of VOC waste gas in trickling biofilter are found to be in good agreement with the experimental data. It has been revealed that for a fixed inlet concentration of toluene, the purification efficiency of trickling biofilter decreases with the increase in gas flow rate and liquid flow rate. The purification efficiency of VOC waste gas is dominated by mass transport resistance in liquid film and biofilm. The highest biodegradation rate occurs at the inlet of waste gas in trickling biofilter.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
Antibiotic micro-pollution is usually found at the ng/L–level in drinking water sources or discharge water of wastewater treatment plants. In this study, a novel approach mediated by manganese oxidizing bacteria(Mn O...Antibiotic micro-pollution is usually found at the ng/L–level in drinking water sources or discharge water of wastewater treatment plants. In this study, a novel approach mediated by manganese oxidizing bacteria(Mn OB) in a biofilter was developed to control the pollution. The results indicated that the biogenic manganese oxide(Mn O x) produced during the oxidation of the feeding manganese ions could coat the surface of the filtering sand effecting the simultaneous removal of antibiotics. It was found that the removal of antibiotics is insured as long as the feeding manganese was well removed and was not influenced by the hydraulic loading. The growth rate of the Mn OB group revealed that the antibiotic concentration at 50 and 100 ng/L promoted their activity, but it was inhibited at 500 and 1000 ng/L. The structure of the bacterial community was stable in the presence of antibiotics(50 ng/L), but their extracellular processes changed. The removal performance of the feeding manganese seemed to relate to the extracellular processes of the dominant bacterial genus. Moreover, the freshly formed Mn O x was a buserite-like material that was rich in Mn(III) and Mn(IV)(94.1%), favoring the degradation. The biofilter did not generate additional antibiotic resistant genes in the presence of antibiotics.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
We investigated the changes in communities of bacteria,ammonia-oxidizing bacteria,and Nitrospira during the operation of a pufferfish Takifugu rubripes recirculating aquaculture system by using high-throughput DNA seq...We investigated the changes in communities of bacteria,ammonia-oxidizing bacteria,and Nitrospira during the operation of a pufferfish Takifugu rubripes recirculating aquaculture system by using high-throughput DNA sequencing.Differences in bacterial communities were observed at days 1-32,47-62 and 78-93 of biofilm development by using 16S rRNA gene pyrosequencing.The relative abundance of Proteobacteria(Gammaproteobacteria)increased,while that of Bacteroidetes(Flavobacteria)decreased.The proportions of Nitrosomonas and Nitrospina ranged from 0.02%to 0.30%and from 0.02%to 0.83%,respectively.Ammonia monooxygenase gene pyrosequencing revealed that the top three operational taxonomic units were related to Nitrosomonas aestuarii(17.5%-61.1%),uncultured beta proteobacterium clone B67S-54(1.9%-45.2%),and uncultured bacterium clone AZPa8(3.6%-24.7%).Nitrite oxidoreductase gene pyrosequencing revealed that the relative abundance of the dominant strain Nitrospira sp.Ecomares 2.1 increased,but that of the abundant species Nitrospira marina decreased.Our results demonstrated that the communities of bacteria,ammonia-oxidizing bacteria,and Nitrospira were changing during the operation of the pufferfish recirculating aquaculture system.展开更多
As all other forms of livestock production, fish farming has numerous environmental impacts. Water pollution is one of the most significant outcomes, since aquaculture effluents contain non-ingested food and fish dreg...As all other forms of livestock production, fish farming has numerous environmental impacts. Water pollution is one of the most significant outcomes, since aquaculture effluents contain non-ingested food and fish dregs that affect the receiving water bodies when discharged without any treatment. Conventional pollutants (suspended solids, dissolved organic matter and nutrients), as well as pesticides, heavy metals and emerging pollutants (as antibiotics and hormones), are commonly found in these effluents. Recirculating aquaculture systems (RAS, systems that integrate the treatment and the reuse of water in the process) are an invaluable alternative for preventing water pollution by diminishing both the volume and the eutrophication potential of the effluents. Based on our review of the extant literature in the field, we conclude that activated carbon-based biofilters are a favorable technology to achieve a level of water quality that is compatible with environmentally-sound aquaculture practices.展开更多
The aim of this research is to develop a representative model which simulates the performance of a biofilter used to treat drinking water.A steady-sate model is applied.The Monod-type substrate utilization is used,and...The aim of this research is to develop a representative model which simulates the performance of a biofilter used to treat drinking water.A steady-sate model is applied.The Monod-type substrate utilization is used,and the external and the internal mass transfer are neglected in this model.The model describes the process of substrate biodegradation,bacterial attachment onto filter media,and detachment of suspended bacteria.It simulates the natural organic matter (NOM) and biomass profiles in a biofilter as a function of filter depth and filtration velocity.The key biokinetic parameters k and KS are estimated through a special experiment.The results of the model testing show that the model prediction agrees well with the experimental展开更多
In recent years, rural tourism has developed a lot and especially in the Souss Massa Draa region, in the South West of Morocco. The need to implement an eco-friendly sewage treatment has grown accordingly to resolve t...In recent years, rural tourism has developed a lot and especially in the Souss Massa Draa region, in the South West of Morocco. The need to implement an eco-friendly sewage treatment has grown accordingly to resolve the wastewater issue. In this context, a pilot project of planted filters has been achieved in the Atlas Kasbah Ecolodge. During 3 years, the water purification performance and its compliance with the requirements of environmental management were assessed. The objective was to find an eco-friendly and affordable alternative to noncompliant ditches and sumps found in the rural areas of Morocco. The monitoring of physicochemical parameters of treated wastewater has revealed a perfect adaptation of the system to the needs of rural tourism facilities both in terms of efficiency and in terms of integration into the natural environment. Thus, such a technique could be spread in remote areas.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
Nitrous oxide (N2O) gas is a fourth contributor in the greenhouse effect after CO2, CH4, and water vapor. Although its concentration is relatively low, but very difficult to be decomposed in the atmosphere. A laborato...Nitrous oxide (N2O) gas is a fourth contributor in the greenhouse effect after CO2, CH4, and water vapor. Although its concentration is relatively low, but very difficult to be decomposed in the atmosphere. A laboratory-scale biofilter was used to evaluate the effects of flow rate, medium depth, and water content of filter medium on the N2O removal efficiency and the growth of microorganisms in the compost. The biofilter was operated using cow-manure based compost medium with husk and coco peat as bulking agent. Research was carried out by batch flow system for 9 hours. The result indicates that the highest N2O removal efficiency is obtained under flow rate of 88 cm3/min with a depth of 50 cm and water content 50% (w/w) by 61%, and elimination capacity for 14078 g/(m3·h) was achieved.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2019YFC0214303)the Applied Basic Research Program of Wuhan,China(No.2015060101010068)
文摘Volatile organic compounds(VOCs) are typical pollutants that affect air quality.Discharge plasma is thought to be a potential method that can remove VOCs from flue gas.In this experiment,pulsed corona discharge plasma combined with a biological tower was carried out to remove the benzene series,and toluene was selected as the typical VOC.The results indicated that the removal efficiency of toluene by pulsed corona plasma was slightly higher than that of direct current(DC) corona plasma,while its energy efficiency was much higher than DC corona plasma.Under the optimal experimental conditions of pulse voltage 8.5 kV,initial toluene concentration 1400 mg m^(-3),and toluene flow rate of 121h^(-1),the toluene removal efficiency reached 77.11% by the single method of pulsed corona discharge plasma,and the energy efficiency was up to 1.515 g/(kW·h) under the pulse voltage of 4.0 kV.The trickling biofilter was constructed by using the screened and domesticated Acinetobacter baumannii,and the highest toluene removal efficiency by the pulsed corona discharge plasma combined with the trickling biofilter rose up to 97.84%.Part of the toluene was degraded into CO_(2),H_(2)O,and some intermediate products such as o-diphenol under the influence of Acinetobacter baumannii.When the remaining waste gas passed through the discharge plasma reactor,the benzene ring structure could be directly destroyed by the collision between toluene and plasma.Meanwhile,O·,OH·,and some other oxidizing radicals generated by the discharge also join into the oxidative decomposition of toluene and its intermediate products,thereby further improving the removal efficiency of toluene.Therefore,the two-stage plasma-biofilter system not only showed a high toluene removal efficiency,but also had a good energy efficiency.The results of this study will provide theoretical support and technical reference for industrial VOC treatment.
基金Supported by the National Key R&D Program of China(No.2017YFD0701700)National Natural Science Foundation of China(Nos.31472312,31672673)。
文摘Bacteria play a major role in metabolizing ammonia and other metabolites in recirculating aquaculture systems(RASs).To characterize and compare the bacterial communities in the biofilters of two full-scale RASs for the culture of puffer fish,Takifugu rubripes,at different ages and densities were studied.In overall,47807 optimized reads of the 16 S rRNA gene with V4-V5 region were obtained from four biofilm samples collected after biofilm maturation.At 97%cut-off level,these sequences were clustered into 500 operational taxonomic units,and were classified into 19 bacterial phyla and 138 genera.At the phylum level,Proteobacteria and Bacteroidetes were the most abundant,followed by Nitrospirae and Planctomycetes.At the genus level,Colwellia,Marinifilum,Oceanospirillum,Lutibacter,Winogradskyella,Pseudoalteromonas,Arcobacter,and Phaeobacter were the top members.Nitrosomonas and Nitrospira were main ammonia-and nitrite-oxidizing bacteria.Differences in bacterial communities at different sampling dates and similarities of both biofilters were revealed in the Venn diagram and cluster analysis.Maintaining a good water quality and health offarmed fish in RASs depended on the correct management of the bacterial communities.This study provides more accurate information on the bacterial communities associated with the bifilters of both RASs.
文摘Biofiltration is emerging as a promising cost effective technique for the Volatile Organic Compounds (VOCs) removal from industrial waste gases. In the present investigation a comparative modeling study has been carried out using Radial Basis Function Neural Network (RBFN) and Response Surface Methodology (RSM) to predict and optimize the performance of a biofilter system treating toluene (a model VOC). Experimental biofilter system performance data collected over a time period by daily measurement of inlet VOC concentration, retention time, pH, temperature and packing moisture content was used to develop the mathematical model. These independent variables acted as the inputs to the mathematical model developed using RSM and RBFN, while the VOC removal efficiency was the biofilter system performance parameter to be predicted. The data set was divided into two parts: 60% of data was used for training phase and remaining 40% of data was used for the testing phase. The average % error for RSM and RBFN were 7.76% and 3.03%, and R2 value obtained were 0.8826 and 0.9755 respectively. The results indicated the superiority of RBFN in the prediction capability due to its ability to approximate higher degree of nonlinearity between the input and output variables. The optimization of biofilter parameters was also done using RSM to optimize the biofilter performance. RSM being structured in nature enabled the study of interaction effect between the independent variables on biofilter performance.
基金financial supports by the National Natural Science Foundation of China (Grant No. 21505156)the Fundamental Research Funds for the Central Universities (24720122043)the Scientific Research and Technological Development Projects of PetroChina Co., Ltd. (2013F-2101)
文摘Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the activated sludge and toluene degrading bacteria, and the packing material consisted of different mixing ratios of peat and wood chips. A final toluene load of 21.2 g/(m3·h) was attained step by step in four parallel biofilters. A shortest start-up time of 15 days and a highest EC of 17.0 g/(m3·h) were observed in the biofilter B-4, which was inoculated with a special microbial consortium consisting of three strains of toluene degrading bacteria and was packed with the mixture of peat and wood chips at a ratio of 80:20 (w/w). These results indicated that inoculating pre-acclimatized microbes dramatically shortened the start-up time, and such a composition of packing material could maintain an appropriate environment (with the bed porosity and water content equating to 0.45 and 1.96, respectively) for the growth of dominant toluene degrading bacteria in the biofilter.
文摘Mathematical models of steady-state biofilteration are discussed. The theoretical results are much useful for the design of biofilters. This model is based on the system of non-linear reaction/diffusion equations contains a non-linear term related to Monod kinetics, Andrews kinetics, interactive model from Monod kinetics and Andrews kinetics. Analytical expression of concentration of VOC (Volatile organic compounds) and oxygen are derived by solving the system of non-linear equations using Adomian decomposition method (ADM) method. Our analytical results are also compared with the simulation results. Satisfactory agreement is noted.
文摘In this paper, mathematical models of biofilm mixtures of n-butanol biofilters were discussed. The model is based on the mass transfer in the biofilm interface and chemical oxidation in the biofilm phase and gas phase. An approximate analytical expression of concentration profiles of n-butanol in the biofilm phase and gas phase has been derived using the homotopy perturbation method and hyperbolic function method for all possible values of parameters. Furthermore, in this work, the numerical simulation of the problem is also reported using the Matlab program. Good agreement between the analytical and numerical results is noted. Graphical results are presented and discussed quantitatively to illustrate the solution. The analytical results will be useful in finding the yields of biomass and oxygen consumption, the specific biomass surface area, activation energy and saturation constant for the Michaelis-Menten kinetics.
文摘This paper investigates and provides a critical analysis of the toluene biofilter model developed by Li and De Visscher. The model simulation results have been reproduced and compared with several sets of experimental data from literature. Three different model variations are considered: model with no substrate inhibition, with substrate inhibition, and with air flow rate modification. A sensitivity analysis has been performed on model to study the effect of important parameters on the removal efficiency. Model limitations and improvements have been highlighted.
文摘Biofiltration has become a widely accepted technology for the removal of hydrogen sulfide (H2S) which is one of the major odor causing gases present in the air streams of municipal wastewater treatment facilities. In addition to odorous nature, H2S is toxic and corrosive. In this study, a biofilter which uses a novel media was employed in a pumping station which is closely located at the University City, Sharjah, UAE. The H2S removal performance data were collected and subsequently used in the determination of kinetics and modeling of H2S. The data were best represented by a first order biofilter model. Based on the first order kinetic constant, a correlation is developed to predict concentrations at the biofilter outlet. Based on the predicted outlet concentrations and dispersion (gaussian and US-EPA AERMOD) models, a study on H2S dispersion is conducted. The dispersion study confirmed a biofilter installation at the pumping station site would significantly reduce H2S levels in the University community and would provide cleaner air.
基金supported by the National Natural Science Foundation of China(No.52070113)the Natural Science Foundation of Jiangsu Province(No.BK20191480)the Open Fund of Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province(No.JBGS005).
文摘Biofilters are typical biofilm reactors, and they usually have poor biofilm formation resulting in limited reactor performance. Exogenous acylated homoserine lactones (AHLs) can enhance biofilm formation in many bioreactors based on quorum sensing regulation. However, their effect on biofilm in biofilters utilized for volatile organic compound (VOC) removal is unknown and needs to be investigated. In this study, the effects of the exogenous AHLs on biofilters for gaseous toluene removal were investigated. Analysis of biofilms in biofilters showed that the addition of exogenous AHLs considerably enhanced biofilm growth;the average biofilm concentration increased by 18%. Furthermore, the average biofilm coverage proportions in biofilters with and without exogenous AHLs were 17 % and 13 %, respectively, demonstrating the positive effect of exogenous AHLs on biofilm coverage. In particular, exogenous AHLs promoted the production of extracellular polymeric substances and the microbial adhesive strength of the biofilm. In addition, the exogenous AHLs showed no significant effect on the gaseous toluene removal efficiency of the biofilter. These results show that exogenous AHLs can enhance biofilm formation and can guide the application of exogenous AHLs in VOC biofilters.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 50006015) the Key Research Project of Chongqing Science and Technology Committee (Grant No. 2001-6681) and the Applied Foundation Research Project of Chongqing Scien
文摘This paper presents an analytical model for predicting VOC waste gas degradation in a trickling biofilter. To facilitate the analysis, the packed bed is simplified into a series of straight capillary tubes covered by the biofilm. The gas-liquid flow field through the tube is divided into the liquid film flow on the biofilm and the gas core flow in the center. The biofilm consists of a reaction free zone close to solid wall and a reaction zone beneath the liquid film. The capillary tube model accounts for the effect of mass transport resistance in the liquid film and the biofilm, the gas-liquid interfacial mass transport resistance, the biochemical reaction, and the limitation of oxygen to biochemical reaction. The liquid film thickness in the capillary tube is obtained by simultaneously solving a set of hydrodynamic equations representing the momentum transport behaviors of the gas-liquid two-phase flow. The mass transport equations are established for gas core, liquid film, and biofilm combined with biochemical kinetics equations. An iterative computation process is employed to solve the discrete equations. The predicted purification efficiencies of VOC waste gas in trickling biofilter are found to be in good agreement with the experimental data. It has been revealed that for a fixed inlet concentration of toluene, the purification efficiency of trickling biofilter decreases with the increase in gas flow rate and liquid flow rate. The purification efficiency of VOC waste gas is dominated by mass transport resistance in liquid film and biofilm. The highest biodegradation rate occurs at the inlet of waste gas in trickling biofilter.
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.
基金supported by the National Key R&D Program of China (No. 2017YFC0403404)the Shandong Provincial Natural Science Foundation (No. ZR2016EEQ30)。
文摘Antibiotic micro-pollution is usually found at the ng/L–level in drinking water sources or discharge water of wastewater treatment plants. In this study, a novel approach mediated by manganese oxidizing bacteria(Mn OB) in a biofilter was developed to control the pollution. The results indicated that the biogenic manganese oxide(Mn O x) produced during the oxidation of the feeding manganese ions could coat the surface of the filtering sand effecting the simultaneous removal of antibiotics. It was found that the removal of antibiotics is insured as long as the feeding manganese was well removed and was not influenced by the hydraulic loading. The growth rate of the Mn OB group revealed that the antibiotic concentration at 50 and 100 ng/L promoted their activity, but it was inhibited at 500 and 1000 ng/L. The structure of the bacterial community was stable in the presence of antibiotics(50 ng/L), but their extracellular processes changed. The removal performance of the feeding manganese seemed to relate to the extracellular processes of the dominant bacterial genus. Moreover, the freshly formed Mn O x was a buserite-like material that was rich in Mn(III) and Mn(IV)(94.1%), favoring the degradation. The biofilter did not generate additional antibiotic resistant genes in the presence of antibiotics.
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.
基金This research was supported by the National Key R&D Program of China(No.2017YFD0701700)the National Natural Science Foundation of China(Nos.31472312 and 31672673).
文摘We investigated the changes in communities of bacteria,ammonia-oxidizing bacteria,and Nitrospira during the operation of a pufferfish Takifugu rubripes recirculating aquaculture system by using high-throughput DNA sequencing.Differences in bacterial communities were observed at days 1-32,47-62 and 78-93 of biofilm development by using 16S rRNA gene pyrosequencing.The relative abundance of Proteobacteria(Gammaproteobacteria)increased,while that of Bacteroidetes(Flavobacteria)decreased.The proportions of Nitrosomonas and Nitrospina ranged from 0.02%to 0.30%and from 0.02%to 0.83%,respectively.Ammonia monooxygenase gene pyrosequencing revealed that the top three operational taxonomic units were related to Nitrosomonas aestuarii(17.5%-61.1%),uncultured beta proteobacterium clone B67S-54(1.9%-45.2%),and uncultured bacterium clone AZPa8(3.6%-24.7%).Nitrite oxidoreductase gene pyrosequencing revealed that the relative abundance of the dominant strain Nitrospira sp.Ecomares 2.1 increased,but that of the abundant species Nitrospira marina decreased.Our results demonstrated that the communities of bacteria,ammonia-oxidizing bacteria,and Nitrospira were changing during the operation of the pufferfish recirculating aquaculture system.
文摘As all other forms of livestock production, fish farming has numerous environmental impacts. Water pollution is one of the most significant outcomes, since aquaculture effluents contain non-ingested food and fish dregs that affect the receiving water bodies when discharged without any treatment. Conventional pollutants (suspended solids, dissolved organic matter and nutrients), as well as pesticides, heavy metals and emerging pollutants (as antibiotics and hormones), are commonly found in these effluents. Recirculating aquaculture systems (RAS, systems that integrate the treatment and the reuse of water in the process) are an invaluable alternative for preventing water pollution by diminishing both the volume and the eutrophication potential of the effluents. Based on our review of the extant literature in the field, we conclude that activated carbon-based biofilters are a favorable technology to achieve a level of water quality that is compatible with environmentally-sound aquaculture practices.
基金National Natural Science Foundation of China(No.50638020)Science-Technology Creation Plan for Graduate Students of Jiangsu Province of China(No.1061B06013)
文摘The aim of this research is to develop a representative model which simulates the performance of a biofilter used to treat drinking water.A steady-sate model is applied.The Monod-type substrate utilization is used,and the external and the internal mass transfer are neglected in this model.The model describes the process of substrate biodegradation,bacterial attachment onto filter media,and detachment of suspended bacteria.It simulates the natural organic matter (NOM) and biomass profiles in a biofilter as a function of filter depth and filtration velocity.The key biokinetic parameters k and KS are estimated through a special experiment.The results of the model testing show that the model prediction agrees well with the experimental
文摘In recent years, rural tourism has developed a lot and especially in the Souss Massa Draa region, in the South West of Morocco. The need to implement an eco-friendly sewage treatment has grown accordingly to resolve the wastewater issue. In this context, a pilot project of planted filters has been achieved in the Atlas Kasbah Ecolodge. During 3 years, the water purification performance and its compliance with the requirements of environmental management were assessed. The objective was to find an eco-friendly and affordable alternative to noncompliant ditches and sumps found in the rural areas of Morocco. The monitoring of physicochemical parameters of treated wastewater has revealed a perfect adaptation of the system to the needs of rural tourism facilities both in terms of efficiency and in terms of integration into the natural environment. Thus, such a technique could be spread in remote areas.
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.
文摘Nitrous oxide (N2O) gas is a fourth contributor in the greenhouse effect after CO2, CH4, and water vapor. Although its concentration is relatively low, but very difficult to be decomposed in the atmosphere. A laboratory-scale biofilter was used to evaluate the effects of flow rate, medium depth, and water content of filter medium on the N2O removal efficiency and the growth of microorganisms in the compost. The biofilter was operated using cow-manure based compost medium with husk and coco peat as bulking agent. Research was carried out by batch flow system for 9 hours. The result indicates that the highest N2O removal efficiency is obtained under flow rate of 88 cm3/min with a depth of 50 cm and water content 50% (w/w) by 61%, and elimination capacity for 14078 g/(m3·h) was achieved.
