[Objectives]To explore the control mode of farmland drainage pollutants and investigate the effects of ecological ditch and wetland on reducing farmland drainage pollutants in Hetao Irrigation District.[Methods]Based ...[Objectives]To explore the control mode of farmland drainage pollutants and investigate the effects of ecological ditch and wetland on reducing farmland drainage pollutants in Hetao Irrigation District.[Methods]Based on the demonstration construction project of the ecological ditch-constructed wetland system in the Hetao Irrigation District,an experimental study was conducted from July to September 2023 to investigate the interception and purification effects of ecological ditches,constructed wetlands,and the combined ecological ditch-constructed wetland system on farmland drainage pollutants.Key water quality parameters measured included total nitrogen(TN)concentration and total phosphorus(TP)concentration.[Results]Different treatment modes of ecological ditches and constructed wetlands have a certain removal effect on nitrogen and phosphorus pollutants in water bodies.The ecological ditches treated with Astragalus laxmannii,Melilotus officinalis,Medicago sativa,bio-ball substrate,and bio-sheet substrate showed reduction efficiencies for TN and TP of 21.09% and 23.84%,12.06% and 26.67%,20.08% and 34.15%,23.65% and 20.56%,and 19.92% and 25.83%,respectively.The emergent plant area showed reduction efficiencies of 24.28%for TN and 17.89%for TP,while the submerged plant area achieved a reduction efficiency of 10.21%for both TN and TP.Among the different treatment modes,the ecological ditch with M.sativa performed better in TP removal,whereas the bio-ball substrate treatment mode showed higher effectiveness in TN removal.In addition,the emergent plant area exhibited better TP removal performance,while the submerged plant area was more effective in TN removal.The combined system of ecological ditch and constructed wetland achieved removal rates of 37.55% for TN and 11.47% for TP.It effectively facilitates the step-by-step interception and adsorption purification of pollutants,thereby showing significant removal and purification effects on nitrogen and phosphorus contaminants.This contributes to mitigating agricultural non-point source pollution.[Conclusions]The combined ecological ditch-constructed wetland system serves dual functions of agricultural drainage and pollutant interception and purification.It reduces the pollution load of farmland drainage on receiving water bodies to some extent and mitigates agricultural non-point source pollution.Therefore,it is a relatively suitable technology for managing agricultural non-point source pollution in the Hetao Irrigation District.展开更多
A series of scaled model aircraft ditching tests are performed by launch facility system in Hydraulics Laboratory.According to the measured pitch angle,acceleration and pressure history,research on the impact characte...A series of scaled model aircraft ditching tests are performed by launch facility system in Hydraulics Laboratory.According to the measured pitch angle,acceleration and pressure history,research on the impact characteristic of ditching is conducted.To solve the problem of cavitation effect which may occur in full scale aircraft,the action mechanism and effect of cavitation are studied,and an innovative experimental simulation measure is taken.It is shown that the cavitation bar directly and effectively separates aircraft bottom from water surface and therefore reduces negative pressure,thus enhancing the authenticity of the test results.The dynamic responses including stability and overload after impacting water at different initial pitch angles are analyzed to find the optimum one,which turns out to be heavily dependent on the bottom curvature of fuselage,and rebound phenomenon occurs when pitch angle exceeds a certain value because of the huge positive pressure acting at the spray root on rear fuselage.In addition,the influences of descent rate and horizontal velocity are analyzed.The results show that the descent rate mainly affects the overall load,which is of higher level of importance,while the horizontal velocity mainly affects the load of local structure.展开更多
Agricultural drainage ditches(ADDs)are widespread and serve as critical zones,playing a vital role in mitigating non-point source nitrogen(N)and phosphorus(P)pollution in farmland.However,limited information is known ...Agricultural drainage ditches(ADDs)are widespread and serve as critical zones,playing a vital role in mitigating non-point source nitrogen(N)and phosphorus(P)pollution in farmland.However,limited information is known about the interaction relationship between multiple factors and nutrient release in multistage ADDs.Here,a comprehensive five-level agricultural drainage system(comprising field,sublateral,head,branch,and trunk ditches)was selected as the study model.We developed a simulation setup and applied the Box-Behnken Design(BBD)model to systematically examine the influence of various environmental factors on nutrient release dynamics.The results demonstrated that the developed regression model(p<0.0001)reliably predicted total nitrogen(TN)and total phosphorus(TP)concentrations in multistage ADDs.Based on the response surface plots and contour lines,optimal release conditions for nutrients in multistage ADDs(5 days,296 K,1.03 mg/L N,0.10 mg/L P)were determined through multi-objective optimization.We found that nutrient application exerted the most substantial influence on the release conditions.As field water was discharged into the ditches,the nutrient levels were decreased progressively.Overall,the N and P release processes in multistage ADDs were jointly influenced by environmental factors and ditch scale.These findings offer a solid theory for studying nutrient release and deposition in multistage ADDs,providing key insights for managing farmland ditches to reduce agricultural pollution.展开更多
In recent years,the ecological quality of ditches became worse and worse with the degradation of its ecological functioning.It was necessary to apply a multi-disciplinary and multi-scale approach to study ditches base...In recent years,the ecological quality of ditches became worse and worse with the degradation of its ecological functioning.It was necessary to apply a multi-disciplinary and multi-scale approach to study ditches based on landscape ecology theory.Spatial and network features of agricultural ditches in Lake Dianchi Basin were analyzed by geographic information system technology.The results indicated that the ditches at high level were made by concrete or block stones,the coverage of vegetation of buffer zones and width ratio between ditch sections and vegetation zones were very low;The network of agricultural ditches in Lake Dianchi basin had similar characteristics,the connectivity and circuitry were low,and the fractal dimension index of ditch network were larger in southeastern and southern banks.展开更多
Stubble-breaking device is a key working part of no-tillage seeder in stub land,and directly affects planting quality of seeder.Based on the current domestic used stubble-breaking device,a new kind of stubble-breaking...Stubble-breaking device is a key working part of no-tillage seeder in stub land,and directly affects planting quality of seeder.Based on the current domestic used stubble-breaking device,a new kind of stubble-breaking ditching colter was designed.To study its strength property and reduce trouble in work,the three-dimensional model of stubble-breaking ditching colter was established based on SolidWorks.By using Cosmos,it was carried out the finite element analysis.The distortion and stress of stubble-breaking ditching colter in work were obtained,and the weak link of strength was found.The result showed that the maximum stress of stubble-breaking ditching colter was 5.862×108 N/m2,and the maximum twisted displacement was 2.648 mm.The stubble-breaking ditching colter was carried out improved design.Based on Cosmos,the static analysis was carried out.It showed that the strength and rigidity of improved stubble-breaking ditching colter were obviously improved.The research provided reference basis for optimal design of the stubble-breaking ditching colter.展开更多
In this study, the shallow dish cross-section roadside ditch was designed, based on highway 304 line from Yanchi to Hongjing of Ningxia Province. The hy- draulic calculation of the shallow ditch obtained the correspon...In this study, the shallow dish cross-section roadside ditch was designed, based on highway 304 line from Yanchi to Hongjing of Ningxia Province. The hy- draulic calculation of the shallow ditch obtained the corresponding water outlet dis- tance of the ditch with the width of 1.5 m or 2 m suitable for local use under dif- ferent groove longitudinal slope conditions. And the key roadside ditch construction techniques and suitable grass species were introduced.展开更多
The oxidation ditch process is economic and efficient for wastewater treatment, but its application is limited in case where land is costly due to its large land area required. An innovative integrated oxidation ditch...The oxidation ditch process is economic and efficient for wastewater treatment, but its application is limited in case where land is costly due to its large land area required. An innovative integrated oxidation ditch with vertical circle(IODVC) system was developed to treat domestic and industrial wastewater aiming to save land area. The new system consists of a single channel divided into two ditches(the top one and the bottom one by a plate), a brush, and an innovative integral clarifier. Different from the horizontal circle of the conventional oxidation ditch, the flow of IODVC system recycles from the top zone to the bottom zone in the vertical circle as the brush is running, and then the IODVC saved land area required by about 50% compared with a conventional oxidation ditch with an intrachannel clarifier. The innovative integral clarifier is effective for separation of liquid and solids, and is preferably positioned at the opposite end of the brush in the ditch. It does not affect the hydrodynamic characteristics of the mixed liquor in the ditch, and the sludge can automatically return to the down ditch without any pump. In this study, experiments of domestic and dye wastewater treatment were carried out in bench scale and in full scale, respectively. Results clearly showed that the IODVC efficiently removed pollutants in the wastewaters, i.e., the average of COD removals for domestic and dye wastewater treatment were 95% and 90%, respectively, and that the IODVC process may provide a cost effective way for full scale dye wastewater treatment.展开更多
To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal （SNDPR）, a whole course of SNDPR damage and recovery was...To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal （SNDPR）, a whole course of SNDPR damage and recovery was studied in a pilot-scale, anaerobicanoxic oxidation ditch （OD）, where the volumes of anaerobic zone, anoxic zone, and ditches zone of the OD system were 7, 21, and 280 L, respectively. The reactor was fed with municipal wastewater with a flow rate of 336 L/d. The concept of simultaneous nitrification and denitrification （SND） rate （rSND） was put forward to quantify SND. The results indicate that： （1） high nitrogen and phosphorus removal efficiencies were achieved during the stable SND phase, total nitrogen （TN） and total phosphate （TP） removal rates were 80% and 85%, respectively; （2） when the system was aerated excessively, the stability of SND was damaged, and rSND dropped from 80% to 20% or less; （3） the natural logarithm of the ratio of NOx to NH4^＋ in the effluent had a linear correlation to oxidation-reduction potential （ORP）; （4） when NO3^- was less than 6 mg/L, high phosphorus removal efficiency could be achieved; （5） denitrifying phosphorus removal （DNPR） could take place in the anaerobic-anoxic OD system. The major innovation was that the SND rate was devised and quantified.展开更多
Bioaerosol emissions from wastewater and wastewater treatment processes are a significant subgroup of atmospheric aerosols. Most previous work has focused on the evaluation of their biological risks. In this study, ho...Bioaerosol emissions from wastewater and wastewater treatment processes are a significant subgroup of atmospheric aerosols. Most previous work has focused on the evaluation of their biological risks. In this study, however, the adsorption method was applied to reduce airborne microorganisms generated from a pilot scale wastewater treatment facility with oxidation ditch. Results showed adsorption on granule activated carbon （GAC） was an efficient method for the purification of airborne microorganisms. The GAC itself had a maximum adsorption capacity of 2217 CFU/g for airborne bacteria and 225 CFU/g for fungi with a flow rate of 1.50 m^3/hr. Over 85% of airborne bacteria and fungi emitted from the oxidation ditch were adsorbed within 80 hr of continuous operation mode. Most of them had a particle size of 0.65-4.7 μm. Those airborne microorganisms with small particle size were apt to be adsorbed. The SEM/EDAX, BET and Boehm＇s titration methods were applied to analyse the physicochemical characteristics of the GAC. Relationships between GAC surface characteristics and its adsorption performance demonstrated that porous structure, large surface area, and hydrophobicity rendered GAC an effective absorber of airborne microorganisms. Two regenerate methods, ultraviolet irradiation and high pressure vapor, were compared for the regeneration of used activated carbon. High pressure vapor was an effective technique as it totally destroyed the microorganisms adhered to the activated carbon. Microscopic observation was also carried out to investigate original and used adsorbents.展开更多
The standard three dimensional（3D） k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Compariso...The standard three dimensional（3D） k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.展开更多
基金Supported by Special Fund Project for the Transformation of Scientific and Technological Achievements in Inner Mongolia Autonomous Region(2021CG0013)Bayannur City Science and Technology Plan Project(K202014)+1 种基金Inner Mongolia Autonomous Region Science and Technology Plan Project(2022YFHH0088)Research Special Project of the Education Department of Inner Mongolia Autonomous Region(STAQZX202320).
文摘[Objectives]To explore the control mode of farmland drainage pollutants and investigate the effects of ecological ditch and wetland on reducing farmland drainage pollutants in Hetao Irrigation District.[Methods]Based on the demonstration construction project of the ecological ditch-constructed wetland system in the Hetao Irrigation District,an experimental study was conducted from July to September 2023 to investigate the interception and purification effects of ecological ditches,constructed wetlands,and the combined ecological ditch-constructed wetland system on farmland drainage pollutants.Key water quality parameters measured included total nitrogen(TN)concentration and total phosphorus(TP)concentration.[Results]Different treatment modes of ecological ditches and constructed wetlands have a certain removal effect on nitrogen and phosphorus pollutants in water bodies.The ecological ditches treated with Astragalus laxmannii,Melilotus officinalis,Medicago sativa,bio-ball substrate,and bio-sheet substrate showed reduction efficiencies for TN and TP of 21.09% and 23.84%,12.06% and 26.67%,20.08% and 34.15%,23.65% and 20.56%,and 19.92% and 25.83%,respectively.The emergent plant area showed reduction efficiencies of 24.28%for TN and 17.89%for TP,while the submerged plant area achieved a reduction efficiency of 10.21%for both TN and TP.Among the different treatment modes,the ecological ditch with M.sativa performed better in TP removal,whereas the bio-ball substrate treatment mode showed higher effectiveness in TN removal.In addition,the emergent plant area exhibited better TP removal performance,while the submerged plant area was more effective in TN removal.The combined system of ecological ditch and constructed wetland achieved removal rates of 37.55% for TN and 11.47% for TP.It effectively facilitates the step-by-step interception and adsorption purification of pollutants,thereby showing significant removal and purification effects on nitrogen and phosphorus contaminants.This contributes to mitigating agricultural non-point source pollution.[Conclusions]The combined ecological ditch-constructed wetland system serves dual functions of agricultural drainage and pollutant interception and purification.It reduces the pollution load of farmland drainage on receiving water bodies to some extent and mitigates agricultural non-point source pollution.Therefore,it is a relatively suitable technology for managing agricultural non-point source pollution in the Hetao Irrigation District.
基金supported by the National Project for Large Aircraft of China。
文摘A series of scaled model aircraft ditching tests are performed by launch facility system in Hydraulics Laboratory.According to the measured pitch angle,acceleration and pressure history,research on the impact characteristic of ditching is conducted.To solve the problem of cavitation effect which may occur in full scale aircraft,the action mechanism and effect of cavitation are studied,and an innovative experimental simulation measure is taken.It is shown that the cavitation bar directly and effectively separates aircraft bottom from water surface and therefore reduces negative pressure,thus enhancing the authenticity of the test results.The dynamic responses including stability and overload after impacting water at different initial pitch angles are analyzed to find the optimum one,which turns out to be heavily dependent on the bottom curvature of fuselage,and rebound phenomenon occurs when pitch angle exceeds a certain value because of the huge positive pressure acting at the spray root on rear fuselage.In addition,the influences of descent rate and horizontal velocity are analyzed.The results show that the descent rate mainly affects the overall load,which is of higher level of importance,while the horizontal velocity mainly affects the load of local structure.
基金supported by the National Science Funds for Creative Research Groups of China(No.51421006)the National Key Research and Development Program of China(No.2021YFD1700600)the National Major Projects of Water Pollution Control and Management Technology(No.2017ZX07204003)。
文摘Agricultural drainage ditches(ADDs)are widespread and serve as critical zones,playing a vital role in mitigating non-point source nitrogen(N)and phosphorus(P)pollution in farmland.However,limited information is known about the interaction relationship between multiple factors and nutrient release in multistage ADDs.Here,a comprehensive five-level agricultural drainage system(comprising field,sublateral,head,branch,and trunk ditches)was selected as the study model.We developed a simulation setup and applied the Box-Behnken Design(BBD)model to systematically examine the influence of various environmental factors on nutrient release dynamics.The results demonstrated that the developed regression model(p<0.0001)reliably predicted total nitrogen(TN)and total phosphorus(TP)concentrations in multistage ADDs.Based on the response surface plots and contour lines,optimal release conditions for nutrients in multistage ADDs(5 days,296 K,1.03 mg/L N,0.10 mg/L P)were determined through multi-objective optimization.We found that nutrient application exerted the most substantial influence on the release conditions.As field water was discharged into the ditches,the nutrient levels were decreased progressively.Overall,the N and P release processes in multistage ADDs were jointly influenced by environmental factors and ditch scale.These findings offer a solid theory for studying nutrient release and deposition in multistage ADDs,providing key insights for managing farmland ditches to reduce agricultural pollution.
基金Supported by National Key Sciences and Technology Program for Water Solutions (2008ZX07102-004) ~~
文摘In recent years,the ecological quality of ditches became worse and worse with the degradation of its ecological functioning.It was necessary to apply a multi-disciplinary and multi-scale approach to study ditches based on landscape ecology theory.Spatial and network features of agricultural ditches in Lake Dianchi Basin were analyzed by geographic information system technology.The results indicated that the ditches at high level were made by concrete or block stones,the coverage of vegetation of buffer zones and width ratio between ditch sections and vegetation zones were very low;The network of agricultural ditches in Lake Dianchi basin had similar characteristics,the connectivity and circuitry were low,and the fractal dimension index of ditch network were larger in southeastern and southern banks.
基金Supported by National Science and Technology Support Plan of China(2011BAF07B01)~~
文摘Stubble-breaking device is a key working part of no-tillage seeder in stub land,and directly affects planting quality of seeder.Based on the current domestic used stubble-breaking device,a new kind of stubble-breaking ditching colter was designed.To study its strength property and reduce trouble in work,the three-dimensional model of stubble-breaking ditching colter was established based on SolidWorks.By using Cosmos,it was carried out the finite element analysis.The distortion and stress of stubble-breaking ditching colter in work were obtained,and the weak link of strength was found.The result showed that the maximum stress of stubble-breaking ditching colter was 5.862×108 N/m2,and the maximum twisted displacement was 2.648 mm.The stubble-breaking ditching colter was carried out improved design.Based on Cosmos,the static analysis was carried out.It showed that the strength and rigidity of improved stubble-breaking ditching colter were obviously improved.The research provided reference basis for optimal design of the stubble-breaking ditching colter.
基金Supported by the Science and Technology Project of the Communication and Transportation Construction~~
文摘In this study, the shallow dish cross-section roadside ditch was designed, based on highway 304 line from Yanchi to Hongjing of Ningxia Province. The hy- draulic calculation of the shallow ditch obtained the corresponding water outlet dis- tance of the ditch with the width of 1.5 m or 2 m suitable for local use under dif- ferent groove longitudinal slope conditions. And the key roadside ditch construction techniques and suitable grass species were introduced.
文摘The oxidation ditch process is economic and efficient for wastewater treatment, but its application is limited in case where land is costly due to its large land area required. An innovative integrated oxidation ditch with vertical circle(IODVC) system was developed to treat domestic and industrial wastewater aiming to save land area. The new system consists of a single channel divided into two ditches(the top one and the bottom one by a plate), a brush, and an innovative integral clarifier. Different from the horizontal circle of the conventional oxidation ditch, the flow of IODVC system recycles from the top zone to the bottom zone in the vertical circle as the brush is running, and then the IODVC saved land area required by about 50% compared with a conventional oxidation ditch with an intrachannel clarifier. The innovative integral clarifier is effective for separation of liquid and solids, and is preferably positioned at the opposite end of the brush in the ditch. It does not affect the hydrodynamic characteristics of the mixed liquor in the ditch, and the sludge can automatically return to the down ditch without any pump. In this study, experiments of domestic and dye wastewater treatment were carried out in bench scale and in full scale, respectively. Results clearly showed that the IODVC efficiently removed pollutants in the wastewaters, i.e., the average of COD removals for domestic and dye wastewater treatment were 95% and 90%, respectively, and that the IODVC process may provide a cost effective way for full scale dye wastewater treatment.
文摘To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal （SNDPR）, a whole course of SNDPR damage and recovery was studied in a pilot-scale, anaerobicanoxic oxidation ditch （OD）, where the volumes of anaerobic zone, anoxic zone, and ditches zone of the OD system were 7, 21, and 280 L, respectively. The reactor was fed with municipal wastewater with a flow rate of 336 L/d. The concept of simultaneous nitrification and denitrification （SND） rate （rSND） was put forward to quantify SND. The results indicate that： （1） high nitrogen and phosphorus removal efficiencies were achieved during the stable SND phase, total nitrogen （TN） and total phosphate （TP） removal rates were 80% and 85%, respectively; （2） when the system was aerated excessively, the stability of SND was damaged, and rSND dropped from 80% to 20% or less; （3） the natural logarithm of the ratio of NOx to NH4^＋ in the effluent had a linear correlation to oxidation-reduction potential （ORP）; （4） when NO3^- was less than 6 mg/L, high phosphorus removal efficiency could be achieved; （5） denitrifying phosphorus removal （DNPR） could take place in the anaerobic-anoxic OD system. The major innovation was that the SND rate was devised and quantified.
基金supported by the National Natural Science Foundation of China (No.50921064, 50978249)
文摘Bioaerosol emissions from wastewater and wastewater treatment processes are a significant subgroup of atmospheric aerosols. Most previous work has focused on the evaluation of their biological risks. In this study, however, the adsorption method was applied to reduce airborne microorganisms generated from a pilot scale wastewater treatment facility with oxidation ditch. Results showed adsorption on granule activated carbon （GAC） was an efficient method for the purification of airborne microorganisms. The GAC itself had a maximum adsorption capacity of 2217 CFU/g for airborne bacteria and 225 CFU/g for fungi with a flow rate of 1.50 m^3/hr. Over 85% of airborne bacteria and fungi emitted from the oxidation ditch were adsorbed within 80 hr of continuous operation mode. Most of them had a particle size of 0.65-4.7 μm. Those airborne microorganisms with small particle size were apt to be adsorbed. The SEM/EDAX, BET and Boehm＇s titration methods were applied to analyse the physicochemical characteristics of the GAC. Relationships between GAC surface characteristics and its adsorption performance demonstrated that porous structure, large surface area, and hydrophobicity rendered GAC an effective absorber of airborne microorganisms. Two regenerate methods, ultraviolet irradiation and high pressure vapor, were compared for the regeneration of used activated carbon. High pressure vapor was an effective technique as it totally destroyed the microorganisms adhered to the activated carbon. Microscopic observation was also carried out to investigate original and used adsorbents.
基金The Specialized Research Fund for the Doctoral Programof Higher Education(No.20010610023) and the Sino-Finnish Scientific and TechnologicalCooperation Program
文摘The standard three dimensional（3D） k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.
