Analysis on Landscape Characteristics of Agricultural Ditches in Lake Dianchi Basin

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.

Design of Stubble-breaking Ditching Colter Based on SolidWorks and Its Strength Analysis

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.

Design of Shallow Dish Roadside Ditch in Arid Area——Taking Highway 304 Line from Yanchi to Hongjing in Ningxia Province as an Example

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.

Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system

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.

An innovative integrated oxidation ditch with vertical circle(IODVC) for wastewater treatment

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.

Numerical simulation of a combined oxidation ditch flow using 3D k-ε turbulence model

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.

Seasonal Dynamics of Nitrogen and Phosphorus in Water and Sediment of A Multi-level Ditch System in Sanjiang Plain,Northeast China

The multi-level ditch system developed in the Sanjiang Plain,Northeast China has sped up water drainage process hence transferred more pollutants from farmlands into the rivers of this region.Understanding the seasonal dynamics of nitrogen (N) and phosphorus (P) transportation in the ditch system and the role of different ditch size is thus crucial for water pollution control of the rivers in the Sanjiang Plain.In this study,an investigation was conducted in the Nongjiang watershed of the Sanjiang Plain to study the nutrient variation and the correlation between water and sediments in the ditch system in terms of ditch level.Water and sediments samples were collected in each ditch level in growing season at regular intervals (once per month),and TN,NO 3--N,NH 4+-N,TP,and PO 4 3--P were analyzed.The results show that nutrient contents in water were higher in June and July,especially in July,the contents of TN and TP were 3.21mg/L and 0.84mg/L in field ditch,4.04mg/L and 1.06mg/L in lateral ditch,2.46mg/L and 0.70mg/L in branch ditch,1.92mg/L and 0.63mg/L in main ditch,respectively.In August and September,the nutrient contents in the water were relatively lower.The peak value of nutrient in ditch water had been moving from the field ditch to the main ditch over time,showing a remarkable impact of ditch system on river water environment.The nutrient transfer in ditch sediments could only be found in rainfall season.Nutrient contents in ditch sediment had effect on that in ditch water,but nutrients in ditch water and sediments had different origination.Ditch management in terms of the key fac-tors is hence very important for protecting river water environment.

Enhanced biological nutrients removal using an integrated oxidation ditch with vertical circle from wastewater by adding an anaerobic column

Compared to conventional oxidation ditches, an integrated oxidation ditch with vertical circle （IODVC） has the characters of concise configuration, simple operation and maintenance, land saving and automatical sludge returning. By the utilization of vertical circulation, an aerobic zone and an anoxic zone can be unaffectedly formed in the IODVC. Therefore, COD and nitrogen can be efficiently removed. However, the removal efficiency of phosphorus was low in the IODVC. In the experiment described, a laboratory scale system to add an anaerobic column to the IODVC has been tested to investigate the removal of phosphorus from wastewater. The experimental results showed that the removal efficiency of TP with the anaerobic column was increased to 54.0% from 22.3% without the anaerobic column. After the acetic sodium was added into the influent as carbon sources, the mean TP removal efficency of 77. 5 % was obtained. At the same time, the mean removal efficiencies of COD, TN and NH3-N were 92.2%, 81.6% and 98.1%, respectively, at 12 h of HRT and 21-25 d of SRT. The optimal operational conditions in this study were as follows： recycle rate = 1.5-2.0, COD/TN 〉 6, COD/TP 〉 40, COD loading rate = 0.26-0.32 kgCOD/（kgSS· d）, TN loading rate = 0. 028-0. 034 kgTN/（ kgSS·d） and TP loading rate = 0.003-0.005 kgTP/（kgSS· d）, respectively.

Addition of anaerobic tanks to an oxidation ditch system to enhance removal of phosphorus from wastewater

The oxidation ditch has been used for many years all over the world as an economic and efficient wastewater treatment technology. It can remove COD, nitrogen and a part of phosphorus efficiently. In the experiment described, a pilot scale Pasveer oxidation ditch system has been tested to investigate the removal of phosphorus from wastewater. The experimental results showed that influent total phosphorus(TP) was removed for 35%-50%. After this, two anaerobic tanks with total volume of 11 m 3 were added to the system to release phosphorus. As a result, the TP removal efficiency increased by about 20%. At an anaerobic HRT of about 6 hours, a TP removal efficiency of 71% was achieved.

Variation of biological and hydrological parameters and nitrogen removal optimization of modified Carrousel oxidation ditch process

To enhance the nitrogen removal,a systemic monitoring of the biological and hydrological parameters of Carrousel oxidation ditch in Chongqing Jingkou Wastewater Treatment Plant was carried out to study the feasibility of simultaneous nitrification and denitrification(SND).The variation and distribution of parameters such as flow velocity,concentration of dissolved oxygen(DO) and mixed liquor suspended solids(MLSS) in oxidation ditch were monitored and analyzed,which were major control factors for SND.The results showed that,the dimensional distribution of flow velocity,DO and MLSS were affected significantly by the operation condition of the aeration wheels.With all the four aeration wheels being in operation,DO and flow velocity were higher and the mixing of MLSS was sufficient.With three aeration wheels being in operation,the flow velocity in most of the bottom areas was enough to meet the basic requirements of no deposition,and the anaerobic region and aerobic region could exist simultaneously in one oxidation ditch,which was helpful to the process of SND.According to spatial distribution characteristics of the flow velocity,DO and soluble components under optimized condition,different functional zones of biochemical reaction in the Carrousel oxidation ditch system were defined,which might contribute to the optimization control and SND of Carrousel oxidation ditch.

Nitrogen and Phosphorus Pollutants Removal from Rice Field Drainage with Ecological Agriculture Ditch: A Field Case

Excessive nitrogen and phosphorus in agricultural drainage can cause a series of water environmental problems such as eutrophication of water bodies and non-point source pollution.By monitoring the water purification effect of a paddy ditch wetland in Gaochun,Nanjing,Jiangsu Province,we investigated the spatial and temporal distribution patterns of N and P pollutants in paddy drains during the whole reproductive period of rice.Then,the dynamic changes of nitrogen and phosphorus in time and space during the two processes of rainfall after basal fertilization and topdressing were analyzed after comparison.At last,the effect of the ditch wetland on nutrient purification and treatment mechanism,along with changing flow and concentration in paddy drains,was clarified.The results of this study showed that the concentrations of various nitrogen and phosphorus in the ditch basically reached the peak on the second and third days after the rainfall(5.98 mg/L for TN and 0.21 mg/L for TP),which provided a response time for effective control of nitrogen and phosphorus loss.The drainage can be purified by the ecological ditch,about 89.61%,89.03%,89.61%,98.14%,and 79.05%of TN,NH4+-N,NO3−-N,NO2−-N,and TP decline.It is more effective than natural ditches for water purification with 80.59%,40%,12.07%,91.06%and 18.42%removal rates,respectively.The results of the study can provide a theoretical basis for controlling agricultural non-point source pollution and improving the water environment of rivers and lakes scientifically.

Effect of Return Sludge Pre-concentration on Biological Phosphorus Removal in a Novel Oxidation Ditch

A pilot-scale,pre-anoxic-anaerobic oxidation ditch was used in this study to treat municipal wastewater with limited carbon source.A novel return activated sludge(RAS) pre-concentration tank was adopted for improv-ing the phosphorus removal efficiency and the effects of RAS pre-concentration ratio were studied.Under the opti-mal operational condition,the suspended total phosphorus(STP) and the total phosphorus(TP) removal efficiencies were around 58.9% and 63.9% respectively and the effluent-P was lower than 0.8 mg·L-1.The reason is that with the optimal RAS pre-concentration ratio,nitrate is completely removed with endogenous carbon source and the secondary phosphorus release is strictly restrained in the pre-anoxic tank.Therefore,the anaerobic phosphorus release and the carbon source uptake by phosphorus accumulation organisms(PAOs) in the sludge,which are ex-tremely important to the phosphorus removal process,can be fully satisfied.Furthermore,the oxidation-reduction potential is proved to be suitable for controlling the RAS pre-concentration ratio due to influent fluctuation and varied conditions.The novel modified system is also beneficial for PAO accumulation.

Study on Intercepting Method for Nitrogen and Phosphorus in Ecological Ditches and Pond

[Objective] The research aimed to reduce emission load of the farmland runoff by using ecological ditches and pond. [Method] N and P intercepting project construction of the ecological ditches and pond in Zhaiji Village, Xiangcheng District, Suzhou City as research object, by repairing 1 834 m3 of original drainage ditches, newly excavating 6 800 m2 of ecological main ditches and 6 000 m2 of artificial purification ecological pond, etc., runoff emission load in real control area of the project was counted. [Result] Annual net loads of the runoff emission for TN and TP were respectively 2 552.22 and 95.00 kg in 33.3 hm2 of farmland. Annual runoff intercepting loads of TN and TP were respectively 1 225.07 and 50.35 kg in ditches. Annual runoff intercepting loads of TN and TP were respectively 1 327.15 and 44.65 kg in ecological pond. In effluent, TN concentration was 6.32 mg/L and was smaller than 15 mg/L. TP concentration was 0.25 mg/L and was smaller than 0.5 mg/L. They both reached level-one A discharge standard. [Conclusion] The research provided theoretical basis for effective control of the agricultural non-point source pollution in Taihu Lake basin.

Phosphorus Sorption-desorption Characteristics of Ditch Sediments from Different Land Uses in a Small Headwater Catchment in the Central Sichuan Basin of China

Investigation of phosphorus (P) sorption-desorption characteristics of drainage ditch sediments is important for better understanding on sediment P transport behaviors in ditches. Surface ditch sediment samples were collected from headwater sub-catchment of forestland, sloping cropland, paddy field, and residential area in a representative catchment in the central Sichuan Basin. These sediment samples were used for determination of P sorption-desorption characteristics by a batch equilibrium technique. Results showed that the maximum P sorption capacities (Qm) in the sediments ranged from 159.7 to 263.7 mg/kg, while higher Qm were observed in the ditch sediments from the paddy fields. The Qm was significantly and positively correlated with oxalate-extractable Fe and Al oxides (r=0.97 and 0.98, p < 0.01), clay fraction (r = 0.78, p < 0.05) and organic matter (r = 0.95, p < 0.01). Sediment pH, clay and organic matter influenced the P sorption through amorphous Fe and Al oxides. CaCO3 content was negatively correlated with the Qm (r = -0.83, p < 0.05), implying that saturated CaCO3 (> 50 g/kg) would not increase P sorption capacity in the ditch sediments. The ditch sediments featured a linear desorption curve, suggesting that P release risk would be enhanced with the increase of the P adsorption. The P desorption rate was positively correlated with Olsen P (r = 0.94, p < 0.01), but negatively related to the fine particle-size fractions (r = -0.92, p < 0.01), the sum of the amorphous Fe and Al oxides (r = -0.67, p < 0.05) and the P sorption capacity (r = -0.59, p < 0.05). The ditch sediments from residential area had a higher P release risk than that from the other ditches of forestland, sloping cropland and paddy field. The P sorption index (PSI) derived from single-point measurement was significantly correlated with the P sorption capacity (r = 0.99, p < 0.01), and could be used for estimating Qm as 1.64 times PSI plus 24.0 (Qm = 1.64 PSI + 24.0) for similar sediments with highly calcareous soils and sediments. Ditch cleaning and sediment removal for the ditch in residential area were recommended in this area to reduce the P release risk.

Robotic Roof Ditch综合应用技术小结

本文简要介绍了车身顶条自动化涂胶综合新工艺,摒弃了传统手工涂胶加饰条安装,改进了国外机器人自动涂胶系统工艺,减少了先期投资和后期维护,通过自主创新,集成了车内涂胶和车顶涂胶机器人系统,实现了具有外饰性涂胶功能的自动化涂胶系统,在提高柔性化的同时有效降低生产成本,提高汽车制造技术应用水平。

Numerical study on hydraulic performance of submerged propellers in oxidation ditch

The submerged propeller is an efficient diving mix device,which is applicable for oxidation ditch treatment in industry,city and village wastewater-treatment plant. The impeller structure and reasonable rotating speed are important factors that determine flow field distribution and energy conversion efficiency. So it is necessary to use modern design methods to develop new kinds of high efficiency submerged propellers,and research the flow field characteristics of submerged propellers. On the basis of the existing form drawing,three-dimensional model of submerged propellers and unstructured tetrahedral mesh were generated. Based on Navier- Stokes equations and standard k- ε turbulence model,the flow was simulated by using a simple algorithm. Through changing some design parameters of propellers,the corresponding numerical simulation results reveal that for the same impeller diameter and service area of submerged propellers,the power consumption could be reduced effectively by optimizing blade mounting angle,which can determine the best blade mounting angle and most suitable rotational speed under given conditions. The study can provide theoretical and project guidance for submerged propellers design.

Evaluation on the performance of triple oxidation ditch system treating municipal wastewater

The oxidation ditch system in Handan WWTP is the biggest triple oxidation ditch system (T O.D.) treating municipal wastewater in China with a service population of 350000. The system can perform three functions, aerobic, anoxic and precipitation process in different ditch by alternating the operation mode, and the simultaneous removal of nitrogen and organic substances can be attained. Statistic analysis of data from past five year operation in the WWTP was presented, and investigations on COD, nitrogen, phosphorus removal in system were carried out in the field. The optimum number of aerated brush to meet satisfied nitrification and denitrification was determined on basis of field experiment. The effluent is reused as cooling water for a electricity power plant, and excess sludge is utilized as fertilizer. The concept of an ecological WWTP is put forward by the example of Handan WWTP.

Dynamics Analysis of Water Ditching of Deformable Helicopter

To understand the effect of attitude angle on helicopter water ditching,a finite element model(FEM)of helicopter water ditching was established via the nonlinear finite element method.Based on the LS-DYNA software,the finite element model of the helicopter was established.Different attitude of helicopter water ditching was simulated and analysed.Three pressure measuring points were arranged in the aircraft belly area.The pressure curves were provided seperately.Finally,the effects of attitude on helicopter water ditching was discussed,particularly the stability and the overload of helicopter.Through the contours of stress,it can be figured out that the maximum pressure locates at the position of aircraft belly where stiffness is larger.Then simulation and experimental results were compared.The difference of peak acceleration along the Z direction was small.Therefore,this method is feasible and helpful for the design of helicopter water ditching.

Effects of environmental factors on <i>Sparganium emersum</i>and <i>Sparganium erectum</i>colonization in two drainage ditches with different maintenance

In the Niheishimizu and Ooshimizu sections of the town of Misato in the Akita Prefecture, Northern Japan, there are many abundant spring water areas. Sparganium (Sparganium emersum and Sparganium erectum) species are widely distributed in the irrigation water that fed by spring water. The irrigation waters were divided the natural type ditch and the maintained ditch that connect with nearby natural ditch to promote environmentally friendly agriculture. This study was conducted in both sections to support the maintenance of the irrigation water fed by the abundant spring water. A vegetation survey was conducted in September of 2005. The survey collected data on the amount of vegetation cover and the stem lengths of the plant species found in selected locations of the study area. The water depths and the flow velocities were also measured in these locations. As for the growth situation of S. emersum and S. erectum, the submerged form of S. emersum was found in water approximately 15 cm deep with a surface flow velocity of approximately 7 cm/s. This species was characterised by a relatively fast flow and relatively shallow water. The emergent and submerged growth forms of S. emersum were found in waters having flow velocities faster than those associated with S. erectum. The emergent form of S. emersum grew in relatively deep water. S. emersum is more capable of adjusting to the conditions of stream habitats than S. erectum.

Simulation of liquid-gas flow in full-scale Caroussel oxidation ditch with surface aeration

A model for liquid-gas flow （MLGF）, considering the flee movement of liquid surface, was built to simulate the wastewater velocity field and gas distribution in a full-scale Caroussel oxidation ditch with surface aeration. It was calibrated and validated by field measurement data, and the calibrated parameters and sections were selected based on both model analysis and numerical computation. The simulated velocities of MLGF were compared to that of a model for wastewater-sludge flow （MWSF）. The results show that the free liquid surface considered in MLGF improves the simulated velocity results of upper layer and surface. Moreover, distribution of gas volume fraction （GVF） simulated by MLGF was compared to dissolved oxygen （DO） measured in the oxidation ditch. It is shown that DO distribution is affected by many factors besides GVF distribution.