Sediment Removal Efficiency Research Articles

A NEW RELATIONSHIP FOR SEDIMENT REMOVAL EFFICIENCY OF VORTEX CHAMBER TYPE SEDIMENT EXTRACTOR

ABSTRACT A new relationship for estimating the sediment removal efficiency of vortex chamber type sediment extractor is developed using the data from literature. The procedure for design of vortex chamber extractor is listed and illustrated through examples. Data from laboratories and field have been analysed for validation of the existing relationships on its sediment removal efficiency.

Gate and Vacuum Flushing of Sewer Sediment: Laboratory Testing

The objective of this study was to test the performance of a traditional gate-flushing device and a newly designed vacuum-flushing device in removing sediment from combined sewers and CSO storage tanks. A laboratory hydraulic flume was used to simulate a reach of sewer or storage tank. The flushing device was fabricated and installed at upstream end of the flume. The removed sediment was collected at downstream end of the flume and weighed. The test results indicate that the weight of flushed sediment increases with increasing initial water depth in the flushing device; the weight of flushed sediment decreases with increasing initial water depth in the flume; the weight of flushed sediment only changes slightly with changing height of flushing device opening for water release and does not necessarily increase with increasing opening height. Water is held up by vacuum and is released upon dissipation of the vacuum in the vacuum-flushing device rather than through closing and opening of a mechanical gate in the gate-flushing device. The test results indicate that sediment removal efficiency of the vacuum-flushing device is practically the same as the gate-flushing device.

Clay Translocation in the Artificial Recharge of a Groundwater System in the Southern Zagros Mountains, Iran

The shortage of water in Iran and most countries in the arid and semiarid zones is approaching the critical stage. Because about 60% of the water used in Iran is supplied by underground resources and natural recharge cannot replace the amount of water exploited, artificial recharge of groundwater (ARG) is actively pursued in this country. Desiltation of turbid floodwaters in sedimentation basins is a prerequisite for ARG. It is executed close to the heads of alluvial fans on an extensive area in Iran. Because the sediment removal efficiency of sedimentation basins is not 100%, downward migration of some clay particles, both in sedimentation basins and recharge ponds, causes the gradual impermeability and eventual clogging of the vadose zone and reduces the economic life of the recharge systems. Coarse-grained alluvium beneath 2 sedimentation basins, one in operation for 13 years and the other for 11 years, was sampled down to a depth of 7.5 m. Sampling was repeated in a control area outside and adjacent to the ARG system. X-ray diffraction patterns clearly show the presence of illite, chlorite, kaolinite, smectite, and sepiolite. Single laths and bundles of laths of palygorskite–sepiolite, a well-formed 6-sided and a pseudohexagonal flake of kaolinite, and smectite particles with smooth, wavy edges are clearly seen in the transmission electron micrograph. The order of clay mineral accumulation at a depth of 7.5 m was as follows: sepiolite > palygorskite > chlorite. The relatively high concentration of sepiolite may indicate its neoformation in the rooting zone of river red gum (Eucalyptus camaldulensis Dehnh.).

Sediment Removal Efficiency of Vortex Chamber Type Sediment Extractor

Experimental results on sediment removal efficiency of vortex chamber type sediment extractors are reported. A geometric configuration of the extractor is identified that is able to remove even the fine sediment (0.055⩽d⩽0.22 mm) from flow with high efficiency. For the purpose of analysis, the experimental data of present study are compiled with the data from other laboratories and the field that were collected previously by other investigators. Since the existing relations are not found to produce satisfactory results, a new relationship is developed for determination of the sediment removal efficiency of the vortex chamber type sediment extractors.

STUDIES ON VORTEX CHAMBER TYPE SEDIMENT EXTRACTOR

ABSTRACT The sediment removal efficiency of vortex chamber type sediment extractors is studied in detail. The procedure for design of vortex chamber type sediment extractor is listed and illustrated through an example. Data from laboratories and field have been analysed for validation of the existing relationships on its sediment removal efficiency. Since the existing relations are not found to produce satisfactory results, a new relationship is developed for determination of the efficiency.

Modelling of water and sediment transport over grassed areas

Grassed areas, such as grass filter strips (GFS) and grassed swales, have been used extensively for the protection of surface water against erosion and polluted runoffs. A mathematical model of sediment transport in runoff over grass has been developed, allowing an assessment of the sediment removal efficiency of GFS and swales for non-submerged flow conditions. The model is one-dimensional and simulates two main processes: (1) generation of runoff and (2) sediment transport. The modified Green–Ampt model is used for assessment of infiltration, while a kinematic wave model is used for simulation of overland flow. A transport equation is used for modelling of sediment movement through grass, where sediment deposition is assessed by the method developed at the University of Aberdeen. The model does not simulate particle trapping in a pond (which may develop upstream from a GFS), re-suspension of particles already deposited, or infiltration of particles into soil. For a known particle size distribution of inflow sediment, the model is capable of predicting the particle size distribution of the outflow sediment. The model was developed for modelling single rain events. However, it could be also applied for a sequence of rain events assuming that the initial soil wetness is constant. An example of model application in an urban area is presented in the paper, along with sensitivity analysis of the main model results.

Validation of a vegetated filter strip model (VFSMOD)

AbstractVegetated filter strips (VFS) are designed to reduce sediment load and other pollutants into water bodies. However, adaptation of VFS in the field has been limited owing to lack of data about their efficiency and performance under natural field conditions. A number of models are available that simulate sediment transport and trapping in VFS, but there is a general lack of confidence in VFS models owing to limited validation studies and model limitations that prevent correct application of these models under field conditions. The objective of this study is to test and validate a process‐based model (VFSMOD) that simulates sediment trapping in VFS. This model links three submodels: modified Green–Ampt's infiltration, Quadratic overland flow submodel based on kinematic wave approximation and University of Kentucky sediment filtration model. A total of 20 VFS, 2, 5, 10 and 15 m long and with various vegetation covers, were tested under simulated sediment and runoff conditions. The results of these field experiments were used to validate the VFS model. The model requires 25 input parameters distributed over five input files. All input parameters were either measured or calculated using experimental data. The observed sediment trapping efficiencies varied from 65% in the 2‐m long VFS to 92% in the 10‐m long filters. No increase in sediment removal efficiency was observed at higher VFS length. Application of the VFS model to experimental data was satisfactory under the condition that actual flow widths are used in the model instead of the total filter width. Predicted and observed sediment trapping efficiencies and infiltration volume fitted very well, with a coefficient of determination (R2) of 0·9 and 0·95, respectively. Regression analyses revealed that the slope and intercept of the regression lines between predicted versus observed infiltration volume and trapping efficiency were not significantly different than the line of perfect agreement with a slope of 1·0 and intercept of 0·0. Copyright © 2001 John Wiley & Sons, Ltd.

Sediment Removal Efficiency of Settling Basins

Experimental investigations have been carried out on the sediment removal efficiency of settling basins. Laboratory data on removal efficiency from the present and earlier studies were first used for checking the accuracy of the existing empirical and analytical methods for determination of the sediment removal efficiency of settling basins. The existing relationships were not found to yield satisfactory results over the whole range of data. Therefore, reanalysis of these data was done and a new relationship developed. The effect of continuous flushing of a sediment-water mixture from the settling basin on its removal efficiency was also studied through analysis of experimental data.

Effect of Filter Media Particle Size Distribution on Filtration Efficiency

Abstract The results of an experimental study of a sand filter water quality model are presented. The model is built to represent an underground confined water quality sand filter structure. Three types of sands, namely fine, medium and coarse, were used to study the effect of filter media particle size distribution on sediment removal efficiency. The results indicated that the sediment removal efficiency for all sand types decreased with time. The use of medium sand provided the scale model filter with the highest sediment removal efficiency. The finding of this study indicates that the media grain size has a measurable effect on the efficiency of the sand filter water quality structure.

Effect of Filter Thickness on Efficiency of Sand Filter Water Quality Structure

Abstract The primary objective of this study is to determine the relationship between the thickness of a sand filter and its effectiveness in removing fine particles suspended in water. To accomplish this objective, a physical model of a sand filter was built and designed to represent an underground confined water quality sand filter structure. Three types of sands, namely fine, medium and coarse, were used. The results indicated that the sediment removal efficiency for all sand thicknesses decreased with time. Within the range of variables studied, a thicker sand bed resulted in a more effective sand filter water quality structure.

A MODELING APPROACH FOR OPTIMUM SEDIMENT DETENTION POND DESIGN1

ABSTRACT: A design procedure to determine optimum size for a sediment detention pond is presented. The procedure is based on simulating the sediment removal efficiency of the pond in conjunction with temporal variations in rainfall and potential land use and/or management options. The simulation procedure is based on a combined probabilistic‐deterministic modeling approach. The probabilistic model generates daily rainfall with hourly increments for a selected site. The deterministic model simulates sediment yield and concentration for drainage area (pond inflow) and sediment trapping efficiency of the pond. The sediment yield and concentration in pond effluent is estimated from the difference between sediment inflow to the pond and sediment trapped by the pond. As an example, the procedure is applied to determine optimum design for a sediment detention pond in a surface mined area using several pond design options and alternative mining operation/land reclamation strategies.

Constructed Wetlands for River Water Quality Improvement

The Des Plaines River Wetlands Demonstration Project has reconstructed four wetlands in Wadsworth, Illinois, USA. The river drains an agricultural and urban watershed, and carries a non-point source contaminant load of sediment, nutrients and agricultural chemicals. Up to 40% of the average stream flow is pumped to the wetlands, and allowed to return from the wetlands to the river through control structures followed by vegetated channels. Native wetland plant species have been established, ranging from cattail, bulrushes, water lilies, and arrowhead to duckweed and algae. Pumping began in the summer of 1989, and has continued during the ensuing spring, summer and fall periods. The experimental design provides for different hydraulic loading rates, ranging from 5 to 60 cm/week. Intensive wetland research began in late summer 1989, and continues to present. Detailed hydrology is measured for each wetland. Sediment removal efficiencies ranged from 86–100% for the four cells during summer, and from 38–95% during winter. Phosphorus removal efficiencies ranged from 60–100% in summer and 27–100% in winter. The river contains both old, persistent and modem, degradable agricultural chemicals. The principal modem pollutant is atrazine, of which the wetlands remove approximately half. The project is successfully illustrating the potential of constructed wetlands for controlling non-point source pollution at an intermediate position in the watershed.

Design of Perforated Risers to Control Dewatering of Sedimentation Basins

Sedimentation basins intercept and detain storm runoff from earth disturbance sites to facilitate gravitational settling of suspended sediment. Designing sedimentation basins to control the period of dewatering is an important sediment removal efficiency consideration. A design and analysis procedure is derived which evaluates dewatering of perforated-riser controlled sedimentation basins. This development assumes the basins stage-storage relationship can be assumed to be linear in the water-storage zone. The theory is applied to three specific sedimentation basins, each with different degrees of nonlinearity of the stage-storage relationship. Actual dewatering of basins with linear or nearly linear stage-storage relationships is very well represented by the theory developed. Actual dewatering of basins with non-linear stage-storage relationships is slightly faster (up to 11% for the basin evaluated) than predicted using the theory developed herein.

Ponding Surface Drainage Water for Sediment and Phosphorus Removal

ABSTRACT SEDIMENT and phosphorus (P) removal efficencies of a sediment-retention pond with a capacity of about 3400 m3 receiving surface water runoff from 4050 ha of irrigated land, were measured for five years. Average daily flow through the pond, during the irrigation runoff period, was 347 L/s, with a pond retention time of 2.7 h. The pond removed 65 to 76 percent of the sediment, and 25 to 33 percent of the total P entering the pond. Sedi-ment and phosphorus removal efficiencies depended upon the flow rate and the sediment concentration of surface return flow entering the pond. Sediment and phosphorus were most efficiently removed when the stream flow was 340 to 453 L/s and the sediment concen-tration was in the range of 20 to 750 mg/L. Sediment removed from the pond was used to cover protruding basalt to improve and expand a golf course.

Stormwater Detention in Developing Watersheds

A method for evaluating the effects of subdivision scale detention storage basins on watershed hydrologic and water quality response is identified and applied to a developing watershed in Houston, Tex. Data used in the modeling efforts were obtained from historic flow records and measured storm pollutant concentrations. Reductions in peak flows and sediment export provided by various sizes of detention basins are analyzed by the model STOREME for 200-acre (80-ha) developed areas. The results indicate that storage volumes on the order of 30%-60% of the runoff volumes can reduce flood peaks to predevelopment levels. Sediment removal efficiencies in the basins are between 90% and 100%. Analysis of various levels of storage controls on different frequency storms suggests that an optimum control level exists. The results are extended to define the overall watershed response for different land uses in Keegans Bayou.

Irrigation Water Salt Concentration Influences on Sediment Removal by Ponds

AbstractIrrigation water salt concentration effects on sediment pond efficiency were investigated to demonstrate the necessity of considering the salt concentration in the irrigation waters when designing sediment retention ponds. The influence of dissolved salt was determined by adding concentrated CaCl2 solutions to three ponds and then measuring electrical conductivities and sediment concentrations at the pond outlets. Increasing the salt concentration increased the sediment removal efficiencies when the retention time in the pond exceeded 1 hour or the inflow sediment concentration exceeded 500 ppm for the three soils studied. Adding salt to laboratory soil sample suspensions increased the settling rates for the two soils studied. That data indicate that the salt concentration in irrigation water is an important factor in determining sediment pond size and retention time. Using pond design criteria obtained from sediment ponds receiving water of a given salt concentration to design ponds that will receive water with a different salt concentration should include adjustments for salt concentration differences. A simple laboratory test is suggested to predict which soils will respond to irrigation water salt concentration changes that are likely to result in sediment pond efficiency changes.