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Construction principles and design parameters of horizontal flow sedimentation tanks. The figure below shows a horizontal flow sedimentation tank equipped with a skid-mounted sludge scraper. http://www.gy*anweiqiu.com/images/image/20150624185899099909.jpg To ensure a uniform and steady flow of wastewater into the sedimentation tank, rectification measures should be in place in the water inlet area. The baffle at the flow outlet is generally set 0.1–0.15 m above the water surface of the tank; the immersion depth of the baffle should be no less than 0.25 m, with values of 0.5–1.0 m being typical. The baffle is located 0.5–1.0 m away from the water inlet. The outlet weir not only controls the water level in the sedimentation tank but also has a direct impact on the uniform distribution of water flow within it. The overflow rate per unit length along the entire outflow weir in sedimentation tanks should be equal; for primary sedimentation tanks, it is generally 250 m3/m·day, while for secondary sedimentation tanks, it ranges from 130 to 250 m3/m·day. The toothed triangular weir is the most commonly used, and the water surface should be at 1/2 of the tooth height. To adapt to changes in water flow or uneven settlement of structures, an adjusting mechanism that allows the weir plate to move up and down must be installed at the weir opening, in order to keep the outlet weir as level as possible. A baffle should be installed in front of the weir to prevent floating debris, or a scum collection and removal device should be provided. The baffle should be 0.1–0.15 m above the water surface, 0.3–0.4 m submerged under the water surface, and 0.25–0.5 m away from the outlet. Multi-bin sedimentation tanks do not require mechanical sludge scraping equipment. Each sludge storage bin is equipped with its own sludge discharge pipe, allowing for independent sludge discharge without interference between them, thus ensuring the proper concentration of the settled sludge. In the width direction of the tank, there are generally no more than two rows of sludge hoppers. http://www.gy*anweiqiu.com/images/image/20150624185823762376.jpg Design of horizontal sedimentation tanks: The aspects related to the functional design of sedimentation tanks include the number of tanks, the dimensions of the sedimentation area, and the dimensions of the sludge area. How to design and construct vertical sedimentation tanks and the principle parameters involved. Working principle of vertical sedimentation tanks: In a vertical sedimentation tank, wastewater flows vertically from bottom to top at a velocity of v. The suspended particles in the wastewater can be in one of three states of motion: ① When the settling velocity of the particles is u > v, the particles will settle downward at a rate of u – v, thereby allowing them to be removed ； ②When u=v, the particle is in a random state, neither sinking nor rising ； ③It can be seen from this that when the settleable particles belong to the free sedimentation type, under the same surface hydraulic load conditions, the removal efficiency of vertical sedimentation tanks is lower than that of horizontal sedimentation tanks. However, when the sedimentable particles are of the flocculent precipitation type, the situation becomes more complex. On the one hand, due to the opposing flow states within the pool, there are particles rising and particles falling. At the same time, there is contact and collision between rising particles and between falling particles, which causes the diameter of the particles to gradually increase, facilitating their sedimentation. Features of vertical sedimentation tanks: The plan view of vertical sedimentation tanks can be circular, square, or polygonal. The diameter of the pool or the side length of its edges is generally not more than 8 meters, usually ranging from 4 to 7 meters, though there are also pools with dimensions exceeding 10 meters. To reduce the total height of the tank, multiple sludge hoppers can be used in the sludge area. The depth-to-width (diameter) ratio of vertical sedimentation tanks is generally not greater than 3, with 2 being the usual value.