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The sedimentation function is also responsible for calculating the height of the platform for the chemical storage drums. This height is calculated by adding the water depth in the channel and the water depth in the sedimentation tank.
Sedimentation is a basic step of most traditional water treatment processes. In our plant it comes between flocculation and chlorination. It uses gravity to separate water from the particles - particles settle to the bottom of the tank while the clean water rises to the top. Any particle settling faster than the critical velocity of the tank should settle out. Critical velcoty is a function of he flowrate and setting area of the tank. A particle's settling velcotiy depends on its size and density. Larger particles settle faster and therefore are thereby easier to separate from the clean water. Our design employs plate settlers which lessen the distance a particle must fall in order to settle out. This increases the tanks efficiency.
Outlined in CEE 492, the sedimentation algorithm relies on design assumptions and simple geometric relationships to determine the dimensions and number of plate settlers. The width of the tank is determined by the width of the plate settler material and an upward velocity of 100 m/day is set to allow for the formation of a sludge blanket. Additionally, the lamella are installed 5cm apart at an angle of 60° from the horizontal. From these initial conditions, the algorithm determines the tank's length and depth as well as the number of plate settlers. The depth of the tank is divided into three sections - the space above the plate settlers, the space below the plate settlers and the space with the plate settlers. Below the plate settlers the walls are sloped toward the drain pipe to aide drainage. Due to the angle of the lamella, the tank's entire length is not used for sedimentation. Additionally, the channel between the flocculator and sedimentation tanks and the launder pipe diameter decrease the active length of the sedimentation tank and must be accounted for when determining the number of plate settlers. PICTURE. Since the sedimentation tank determines many of the inputs for other functions, it is run at the beginning of the design process. This means that the sedimentation function has no way of knowing the launder pipe diameter. The current design assumes a pipe diameter of 15cm, however in the future, this diameter should be found iteratively after the launder function runs. The effluent launders and sludge drain pipe are also designed in separate functions. Finally, the sedimentation function is also responsible for calculating the #height of the platform for the chemical storage containers. This is based on the water height in the channel and height of the tank.