During bio-ethanol production from sugarcane molasses, large amounts of vinasse, which is strongly acidic with high COD and BOD, is produced as a by-product. Disposal of vinasse is one restrictive problem for sustainable bio-ethanol production. In this study, possible application of vinasse to farmland was investigated. First, the staple characteristics of vinasse were determined. Second, availability of nutrients such as nitrogen and potassium to crops and dynamics in the soil environment were studied in the laboratory, and crop growth experiments were carried out in the field. Farmland application of vinasse as a substitute for one third of the potassium showed no significant damage to the growth of red-radishes and tomatoes. When large amounts of vinasse are applied to farmland as a substitution for the nitrogen in traditional chemical fertilizers, nitrogen-hunger especially immediately after application is expected. In addition, it is necessary to take into consideration the leaching of ions and the dark material in the vinasse for proper timing of application and soil conditions.
An improved numerical model for the accurate prediction of the fault rupture mechanism through the overlying soil gives confidence to the engineers in sitting the structures near or above faults. In this work, a sophisticated numerical model incorporating a hardening-softening constitutive model with shear band effect is calibrated from the direct shear model test results and validated for the prediction of the behavior of medium dense Fontainebleau sand bed due to quasi-static normal movement of the bed rock of fault with dip angle equals to 60°. The numerical results show satisfactory agreement with the experimental data from centrifuge (115g) and 1g model tests in terms of normalized vertical displacements profile of the ground surface, minimum relative vertical base displacement for the rupture to reach the ground, the average dip angle propagated into the soil as well as the horizontal extent of the deformed surface ground. The effect of the very low stress fields in the 1g tests (scale effect) is discussed.
Due to the growing concern for natural environment conservation in Japan, agricultural channels have recently been required to provide structures for an aquatic habitat. Following such request, an irrigation channel running in To-on, Ehime, was reconstructed for aiming to create the aquatic habitat by widening a part of the channel. This paper deals with the flow and material transport in the channel with a side-cavity, by means of field observation and numerical experiment. The field observation revealed a clock-wise eddy in the cavity. The average velocity in the cavity was less than 10 cm/s and flow in the cavity was always calm, not so depend on the discharge in the channel. To simulate the flow and then investigate the material transport in the channel, a horizontally 2-D shallow water flow model combined with quadtree numerical grids was used. The materials were modeled to be transported horizontally with the same speed as water flow. At the same time, however, they settle down following the Stokes law of resistance. The computed result showed that the material having small settling velocity is easy to be transported into inner part of the cavity.
A multiobjective optimization model is developed for controlling TN (Total Nitrogen) load discharged from field plots in an agricultural watershed. In optimization, maximizations of allowable TN discharge per unit area and total yield of rice are intended while complying with an effluent limitation standard prescribed for river water quality management. The discharge from a field plot is separated into two components, i.e., direct runoff and baseflow. As discharged TN from a plot travels with these components toward an outlet of the watershed, the amount of TN is assumed to decrease due to distance-related self-purification occurring in subsurface zone, drainage canal and river. Locations of field plots and traveling routes of TN are identified or predicted by a GIS (Geographic Information System) with a digital elevation model and by field surveys. The model developed is applied to an agricultural watershed bordering with Lake Biwa in Shiga Prefecture, Japan. The result demonstrates that the optimal allocation of maximum allowable discharged TN load among field plots is helpful in prioritizing plots where fertilization should be reduced.
In bends of pressure pipelines, thrust forces generated due to internal pressure. Thrust forces act on the bends outward and tend to move the bends. In our previous study, a lightweight thrust restraint using geogrids and an anchor plate was proposed. In addition, the advantage of the proposed thrust restraint was verified by laboratory model tests and full-scale tests and the resistance mechanism was revealed by numerical analyses. Based on the failure mechanism, the maximum lateral resistance was evaluated by solving equations for the force equilibrium. In the present study, the lateral resistance of the proposed method was formulated considering the tensile characteristics of the geogrid. In addition, the calculated results were compared with the experimental results in order to verify the accuracy of the proposed formula. As results, it was revealed that the lateral resistance can be evaluated by the proposed formula. Furthermore the design method for the lightweight thrust restraint was suggested.
Effect of the adsorption of humic acid on the capture of kaolinite particles flowing through the column packed with Toyorua sand were analyzed on the basis of electrophoretic mobility of kaolinite particles coated with humic acid. Electrophoretic mobility of the bare particles and the particles coated with humic acid indicated that adsorption of humic acid increased negative charge of particles and this tendency became more significant with pH decreasing. Column experiments were performed for bare particles and the particles coated with humic acid as a function of pH under ionic strength of 1.0 ×1.0-3 mol/L. It was found that initial capture rate decreases by adsorption of humic acid. It was also found that adsorption of humic acid reduced the tendency of capture rate to increase with elapse time under acidic condition and enhanced capture rate to decrease with elapse time under alkali condition. This result was consistent to the result of electrophoretic mobility, indicating that adsorption of humic acid increases the double layer repulsion by providing negative charge to particles.
To solve the problem of diffuse pollution brought about of eutrophication in lakes, an investigation was conducted in lotus paddy fields, at which little research had been conducted. The study area consisted of low-land lotus paddy fields around the Lake Kasumigaura watershed in Ibaraki Prefecture. The area is well known as the largest production center of lotus roots in Japan. The results of the study show that the mass balance loads of total nitrogen(T-N), total phosphorus(T-P), chemical oxygen demand(COD), and suspended solids from the lotus paddy fields were -3.22 , 1.87, 75.36 and 552 kg·km-2·d-1, respectively. Comparing these values to the unit reported in "The Fifth Plan for Water Quality Conservation in the Lakes and Ponds related to Lake Kasumigaura", it was found that T-N was purified, T-P was 2.1 times higher and COD was 4.8 times higher. It was found that the major cause of the effluent loads was the outflow of suspended matters during puddling and lotus planting. The dissolved matter was influenced by the increase of discharge. The suspended matter discharge from the lotus paddy fields temporarily accumulated at the end of the drainage canals and flowed out when there was a rainfall.
It is important to evaluate the salt tolerance of native plants in order to utilize them for improving halomorphic soil in arid regions. Tamarix austromongolica, a dominant species in Inner Mongolia, China, has the property of salt absorption and expected soil desalinization. The effect of salt concentration in groundwater on the growth of stock diameter and shoot length were evaluated by cultivation experiments, growing the plants from cuttings for two years. Though the plants grew well in 1% salt concentration of groundwater, the evapotranspiration in the second year was reduced because of the growth of the root system. The growth of the plants and evapotranspiration were reduced with increasing groundwater salinity of 3 to 5%, but most plants did not die. In contrast, the plants which were supplied with groundwater of 7% salt concentration in the second year started to die in about a month, and two thirds of them died within five months. Thus the results showed that the tolerant limit of salinity of the plants in groundwater was 7%, and the growth was constrained with groundwater salinity of 3 to 5% concentration. The plants that survived with 7% salinity in the second year, however, were grown in groundwater salt concentration of 3% to 5% in the first year. This result indicated that saline stress might have changed the characteristic of salinity tolerance of the plant.