Settlement Velocity Research Articles

Identification of Coastal Problem and Prediction of Coastal Erosion Sedimentation in South Sulawesi

Dynamic processes that occur on the coast and the development of coastal areas can cause problems in coastal areas such as erosion and sedimentation. To solve these issues, some types of coastal protection can be applied. On the other hand, to determine the right choice of protection, it must be known in advance whether the erosion or sedimentation would be issued. Incidence of erosion or sedimentation on the coast can be predicted by using the wave parameters for instance wave height and wave period. For the case of grain sediment, the parameters are performed such as diameter and settlement velocity of sediment grain. To predict the erosion and sedimentation, the Kraus's equation is used. It is predicted that erosion and coastal sedimentation in South Sulawesi shows the sedimentation occurs on the Pare-Pare Mattirotasi Beach with the small wave conditions (normal), while the big wave conditions at several points along the eroding shoreline. For the case of Tanjung Bayang, te erosion takes place either in small wave or big wave. On the other hand, the wave height in Tanjung Bira obtained from the wave forecasting results based on the wind data BMKG Selayar waters relatively large yield is 0.89∼1.64 m. So that the sediment grain size is relatively large will experience sedimentation and the smaller grains will easily carried away by the waves and currents that occur so easily eroded.

Foundation Pit Deformation during the Excavation and Simulation

Based on the background of foundation pit excavation of a village, the process of excavation is simulated by FLAC3D .And the calculation and analysis is combined with the engineering practice. The results show that the deformation of foundation pit is mainly composed of ground surface settlement, and the maximum deformation occurred in the middle of the pit wall at the top of the part. The surface subsidence with the ongoing of the excavation, the general surface subsidence trend is rising. When it comes to the foundation pit, when the settlement velocity is very large, the foundation turns to be unstable, which need supporting methods. Flac3D program applied on the excavation of rock and soil deformation law study is feasible. The result of the study to further relevant basis are provided for the practical engineering and have certain practical application value to the rock and soil deformation in the process of excavation research.

紫茎泽兰种子形态特征和萌发特性与其入侵性的关系

Ageratina adenophora is a noxious invasive weed worldwide. However, the mechanisms underlying its invasiveness are still not well elucidated. To explore the effects of seed characteristics on invasiveness of this invader,A.adenophora was compared with three native species in terms of seeds morphological traits and germination responses to environmental factors including temperatures,water,and salt. The invader was significantly lower in seed weight,length,width,and pappus length than three phylogenetically closely related native plant species. Seed settlement velocity was lower for the invader although the difference between the invader and two natives( E. japonicum and E. chinense) was not significant. Small seeds facilitated spread of the invader. Compared with the seeds of two natives( E. japonicum and E.chinense),seeds of the invader germinated in a wider range of temperature. In sublow temperature( 15 and 20 ℃),germination ratio and germination index were higher for the invader than for two natives( E. japonicum and E.stoechadosmum). Responses of seed germination to water and salt stress were stronger for the invader relative to three natives. At suitable conditions( without water and salt stress),however,germination ratio and germination index were higher for the invader than for three natives. These traits mentioned above may facilitate successful invasion of A.adenophora.

Bench‐Scaled Nano‐Fe0 Permeable Reactive Barrier for Nitrate Removal

There are many fundamental problems with the injection of nano‐zero‐valent iron (NZVI) particles to create permeable reactive barrier (PRB) treatment zone. Among them the loss of medium porosity or pore blocking over time can be considered which leads to reduction of permeability and bypass of the flow and contaminant plume up‐gradient of the PRB. Present study provides a solution for such problems by confining the target zone for injection to the gate in a funnel‐and‐gate configuration. A laboratory‐scale experimental setup is used in this work. In the designed PRB gate, no additional material from porous media exists. NZVI (d50 = 52 ± 5 nm) particles are synthesized in water mixed with ethanol solvent system. A steady‐state condition is considered for the design of PRB size based on the concept of required contact time to obtain optimum width of PRB gate. Batch experiment is carried out and the results are used in the design of PRB gate width (~50 mm). Effect of high initial NO3–‐N concentration, NZVI concentration, and pore velocity of water in the range of laminar groundwater flow through porous media are evaluated on nitrate‐N reduction in PRB system. Results of PRB indicate that increasing the initial NO3–‐N concentration and pore velocity has inhibitor effect—against the effect of NZVI concentration—on the process of NO3–‐N removal. Settlement velocity (S.V.) of injected NZVI with different concentrations in the PRB is also investigated. Results indicate that the proposed PRB can solve the low permeability of medium in down‐gradient but increasing of the S.V. especially at higher concentration is one of the problems with this system that needs further investigations.

Settlement Properties of the Suspended Sediment using Micro Videoscope in the Chikugo River Estuary

Under water micro video scope was developed to measure floc settling velocity and applied to the suspended sediment floc in the Chikugo River estuary. The effective densities of the flocs were measured successfully. The floc density distribution function was proposed from the floc settling speed and their diameters. The floc density distribution function varied with tide. In ebb tide, floc densites were smaller than in flood tide. This fact shows that the flocs in flood tide mainly consists of the mud which was suspended from the river bed. Mass settling flux was also calculated. When suspended sediment contains algae or algal residuals, the settling velocity showed lower value. On the other hand, containing high concentration of extracellular polymeric substances (EPS) made settlement velocity high.

Effective depth, initial head loss and backwashing criteria as the key factors of burned oil palm shell (BOPS) granular filtration

These studies are mainly focused on effective depth, initial head loss and backwashing criteria that have been identified as the key factors in relation to the fundamental parameters and also, indicated possible operation performance. Granular filter media used in this study are limited to burned oil palm shell (BOPS) and sand. The study on the bed depth in relation to effluent over influent turbidities ratio (Ce/Co) has been found to exhibit an exponential relation which showed a strong correlation coefficient (R2 = 0.9) for different effective sizes of BOPS (ES, 1.0–2.5 mm) and sand (ES, 0.4–0.9 mm). By approximating relatively constant Ce/Co for both BOPS and sand at different effective sizes, an exponential equation (R2 = 0.98) is proposed to link all effective bed depths. This enabled a determination of the effective depth of BOPS and sand media which were not executed in the experiment. Initial head loss of single media of BOPS and sand which involved comparison of different models, such as Ergun and modified Kozeny–Carmen equations with experimental results, at different flow rates, showed a good agreement with modified Kozeny-Carmen equation for non-sphere. In backwashing criteria, studies that showed the relation between the difference in granular settlement velocity with backwashing water velocity, confirmed that the best combination of dual-media are sand of ES = 0.5mm with UC of 1.5 and BOPS of ES = 1.0mm with UC of 1.3.

Pile settlement and volume reduction measurement during forced-aeration static composting

In this study, a settlement measurement device was used to track the settlement of different layers in composting piles, and time courses of settlement velocity, bulk density distribution, and effective bulk density were investigated. Settlement is divided into two stages: the physical compressive settlement and the mass loss settlement. At the end of the former stage, bulk density (ρ′) and pile height (h) follow ρ′=AhB, where A is a fitting parameter for the initial bulk density of the composting material, and B is the compression parameter. The physical compressibilities of composting mixtures are night-soil sludge and garden refuse (1:1)>sewage sludge and cornstalks (5:4)>night-soil sludge and garden refuse (2:3)>sewage sludge and bark (1:1). Adding the proportion of bulking agent in the proper extent effectively retarded composting settlement. Bark exhibits a better supporting capability than cornstalk does as a bulking agent.

Preparation of Macromolecular Heavy Metal Coagulant and Treatment of Wastewater Containing Copper

Many treatment technologies for wastewater containing heavy metals have been developed in recent years, but these technologies have some disadvantages, such as poor removing efficiency and complex operation. For this reason, a macromolecular heavy metal coagulant polyethyleneimine-sodium xanthogenate (PEX) was prepared by grafting a xanthogenate group to polyethyleneimine. It was determined that PEX has the function of removing both turbidity and copper ions. It was also determined that copper ions and turbidity have a cooperative removal effect with each other in the process of treating wastewater containing both turbidity and copper ions by PEX. The investigation showed that PEX is an amphoteric polyelectrolyte. At lower pH values, the amino groups of the macromolecule are electrically positive; therefore, turbidity is removed because of electroneutralization coagulation; at higher pH values, both amino groups and xanthogenic radical groups contribute to the removal of heavy metals, as a result of chelation. Compared with traditional chemical precipitation by calcium oxide and coagulation by an ordinary inorganic coagulant, PEX showed obvious advantages, for example, removing both turbidity and copper ions, higher removal efficiency, lower suitable pH value, and higher floc settlement velocity.

Controlled experiments to predict horseweed (Conyza canadensis) dispersal distances

Abstract Controlled-environment experiments were conducted to predict the dispersal distance of horseweed seed. Seed were released from a fixed height and collected at three distances from the introduction point along a 6-m wind tunnel. Dispersal potential was assessed at wind speeds of 8 and 16 km hr−1 and release heights of 50.8 and 76.2 cm. In separate experiments, settlement velocity was determined to be 0.323 m sec−1 (SD = 0.0687). These data were used to parameterize a mechanistic model and compared to a quantile extrapolation (QE) of wind-tunnel results. The QE method predicted a greater mean dispersal distance than the mechanistic model, with large disparities between maximum dispersal distances. Quantile extrapolation predicted dispersal distances over 100 m, whereas the mechanistic model predicted a maximum distance of approximately 30 m. Air turbulence within the wind tunnel and complex dynamics of seed flight may have contributed to the discrepancy between models. Predicting the mean and numer...

Hysteresis area, a rheological parameter used as a tool to assess the ability of filamentous sludges to settle

The activated sludge process is the most widely used biological wastewater treatment method. The measurement of some physico-chemical parameters in aeration tanks does not allow clarification operation failures to be avoided. This study focuses on the determination of a rheological parameter of filamentous activated sludge at standard concentrations (2–7 g L −1) in order to assess sludge settleability. On filamentous sludges, rheological measurements in shear flow display a hysteresis area (or reduced hysteresis area (rHa) when the volume of sludge considered is 1 mL), which corresponds to the presence of filamentous bacteria in the sludges. In numerous cases of filamentous activated sludges, significant relationships with the zone settlement velocity (ZSV) parameters of settleability point out that hysteresis area could be used to predict the ability of filamentous activated sludges to settle. With the protocol used, a filamentous activated sludge with a rHa >20 Pa s −1 mL −1, always showed a very low or null ability to settle whatever the value of activated sludge total suspended solid (TSS) content over a standard range (2–7 g L −1)

Start-up of EGSB Reactor for Treatment of Wastewater Containing Pentachlorophenol

By using a Lab-scale Expanded Granular Sludge Bed (EGSB) reactor, the strategies of start-up and the changes of characteristics of granular sludge before and after start-up were investigated. In the first stage, the pentachlorophenol (PCP) concentration in wastewater was fixed at 5 mg/L, and the organic loading rate (OLR) gradually increased. The OLR increased to 5.4 kg COD/(m 3 -reactor d) after 25 days. Then began the second stage, OLR was stabilized as 5 kg COD/(m'-reactor d), while the PCP concentration was gradually increased. The PCP loading rate increased to 94.7 mg/(L-reactor d) in 63 days after the second stage start-up, the COD removal and PCP removal were 91.2% and 99.6% respectively. The EGSB reactor has the ability to bear PCP overloading to some extent. After the start-up was finished, the settlement velocity of granular sludge increased, the specific methanogenic activity of sludge and dechlorination rate of PCP were apparently increased. The results show that the two-stage start-up strategy is appropriate.

Blanket development in a malting wastewater anerobic treatment

A 3 m3 pilot UASB reactor was operated with malting wastewater. In order to find the aggregation characteristics, the sludge concentration profile was determined throughout time. Reactor behaviour concerning the physical properties of the sludge can be evaluated using this procedure. Moreover, organic load per VSS can be calculated from this profile. The organic load based per VSS is more accurate as a design parameter than the volumetric load. Under the study conditions imposed the COD removal efficiencies achieved were about 85%. Organic loads of 0.6-0.7 kg COD/(kgVSS.d) were reached. After operating at 30 degrees C, temperatures of 28 degrees C and 15 degrees C were tested, showing no decrease in COD removal efficiency. At week 15 the presence of granules was verified, and after that, sludge concentrations of 30-35 kg VSS/m3 were measured at the bottom of the reactor. The SVI of the granular sludge decreased to values below 20 mL/gVSS. The settlement velocity was 10 m/h, which is much greater than the recommended values for the settlement zone; therefore, no problems are to be expected in the settler regarding the sludge sedimentation. The biomass yield coefficient obtained was 0.10 gVSS/gCOD in agreement with literature values for brewering effluent.