China 
Africa 
Explore chapters and articles related to this topic
Conventional Biological Treatment
Published in David H.F. Liu, Béla G. Lipták, Wastewater Treatment, 2020
Robert D. Buchanan, LeRoy H. Reuter
A sand filter usually consists of 3 to 4 in of sand laid over 6 to 12 in of gravel. Tile underdrains collect the effluent, which is discharged to the receiving waters. A uniform flow distribution to sand filters is important and is usually achieved by trough distribution or a rotary-arm distribution device.
Impact of Urbanization on Flooding
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Structural BMPs are classified as the infiltration BMPs, filtration BMPs, volume-storage and reuse BMPs, and conveyance and pretreatment BMPs (Dorman et al., 2013). Design guidance of structural BMPs is available at different local agencies.Infiltration BMPs including bioretention, bioswale, and permeable pavement are designed to encourage percolation and groundwater recharge and can provide volume reduction to prevent flooding. Bioretention areas are landscaped, shallow depressions to mimic predevelopment hydrologic conditions and enhance biodiversity and water quality. Bioswales are shallow, narrow, vegetated channels, often referred to as linear bioretention, that are designed to treat runoff primarily by vertical filtration of runoff through soil media and infiltration into underlying soils. Permeable pavement is a highly versatile stormwater BMP because it can effectively reduce pollutants and can be integrated into site plans with various configurations and components.Filtration BMPs including planter boxes, green roofs, and sand filters have been used widely because they can be incorporated into a wide range of landscapes including roadway corridors, rights-of-way, sidewalks, and areas with limited space due to their versatility. A planter box is a concrete box containing soil media and vegetation that functions similarly to a small bioretention area but is completely lined and must have an underdrain. Green roofs reduce the runoff volume and rates by intercepting rainfall in a layer of rooftop growing media. A sand filter is a treatment system used to remove the particulates and solids from stormwater runoff by facilitating physical filtration.Volume-storage and reuse BMPs include cisterns/rain and stormwater wetlands, which reduce the total runoff volume washed into the traditional stormwater conveyance system from smaller storm events. Stormwater wetlands can be effectively implemented in open space areas to temporarily capture and store runoff where infiltration is limited or not feasible. Cisterns and rain barrels reduce runoff washed from buildings and are intended to maximize the rainfall interception and minimize pollutant introduction into stormwater.Conveyance and pretreatment BMPs are vegetated filter strips and vegetated swale. Vegetated filter strips are bands of dense, permanent vegetation with a uniform slope, designed to provide pretreatment of runoff generated from impervious areas before flowing into another BMP as part of a treatment train. Vegetated swales are shallow, open grass channels that are the LID alternatives to traditional curbs and gutters. Compared with other LID practices, vegetated swales have a relatively low construction cost, a moderate maintenance burden, and require only a moderate amount of surface area.
Experimental study on the lateral distribution of the sidewall friction of large and deep-water caissons
Published in Marine Georesources & Geotechnology, 2022
Wenlong Chen, Jianlin Ma, Qinke Wang, Bingnan Jiang
In order to simulate the dynamic sinking process of the caisson in a more realistic way, a “solid-liquid circulation system” was designed for this test. Its schematic diagram is shown in Figure 6. The “solid-liquid circulation system” was composed of two pumps, a frequency converter, a water tank, pipes, and so on. First, the sand-water mixture was pumped from the borehole into the water tank through the sand outlet pipe, and the sand filter in the water tank separated the sand and water. Then, the water pump pumped the separated water into the borehole through the water inlet pipe. There were scales on the inner and outer sidewalls of the caisson. The test staff on the operating floor observed the height difference between the inner and outer liquid levels and then adjusted the frequency converter to maintain a dynamic balance of the solid-liquid circulation system.