In view of the sedimentation is the main unit to remove suspended solids in the water, the progress of the sedimentation process is discussed. The characteristics and merits of the sedimentation tank, the sedimentation tank with honeycomb inclined tube, the high density sedimentation tank and the interception sedimentation tank are introduced. Designed to improve sedimentation tank settling efficiency.

At present, most of the domestic and international water treatment process using precipitation (clarification) filtration and disinfection form, of which the sediment removal of suspended solids in raw water is particularly important. Sedimentation tank as one of the main facilities to remove suspended solids in the water industry has been widely used. Throughout the development of sedimentary structures can be found in the 20th century, mainly used before the 1960s advection, vertical and radial flow sedimentation tanks, 60 years since the various types of clarification pool prevailed, after the 70s, mainly inclined pipe, oblique Plate and composite sedimentation tank. Improvements in the form of precipitation structures increase the efficiency of precipitation separation. Sedimentation tank design and development are all around how to increase the sedimentation area and change the water flow of the two aspects. The design of the sedimentation tank is always aimed at increasing the settling efficiency of the sedimentation tank.

There are two ways to improve settling efficiency:

1) shorten the precipitation distance of particles, increase the sedimentation tank area, inclined tube precipitation belong to this category;

2) increase the sinking speed of alum particles, through the use of efficient flocculant and optimize the flocculation process to achieve.

1 advection settling tank

Stratosphere sedimentation tank is currently the most widely used in China's large and medium-sized water plant pool, with a simple structure, easy management, impact resistance and strong advantages. Stratosphere sedimentation tank is rectangular, the upper part of the sedimentation zone, the lower part of the sludge zone, the water front of the pool area, the pool has a water outlet area. After the coagulated raw water flows into the sedimentation tank, it is evenly distributed along the entire cross section of the influent area, into the sedimentation area, and then slowly flows to the exit area. Water particles sink in the bottom of the pool, the sludge deposited regularly discharged outside the pool.

2 honeycomb inclined plate (tube) sedimentation tank

Cellular Swashplate (Pipe) Precipitation A number of cellular swashplate assemblies positioned at an angle (typically 60 °) to the horizontal are placed in a settling tank. Flow can flow from the bottom up or down, the pellets sink to the bottom, and then automatically slide down. From the analysis of improving the hydraulic conditions of the sedimentation tank, the Froude number is greatly improved as the hydraulic radius of the sedimentation tank is greatly reduced, so that the Reynolds number R is greatly reduced, meeting the requirements of water flow stability and laminar flow. In order to further improve the precipitation efficiency, many improved honeycomb inclined plate (tube) sedimentation tank came into being.

Honeycomb inclined tube packing Features:

Wet big, small hydraulic radius.

2. Laminar flow is good, particle settlement from flocculation interference.

3. When the inclined tube length of 1 meter, the payload by 3-5 tons / m 2 & dot; design. V0 control in the 2.5-3.0 mm / sec range, the best water quality.

4. The honeycomb inclined pipe is adopted at the water intake, and when the pipe length is 2.0-3.0 meters, it can be safely operated and handled in the high turbidity of 50-100 kg / m 3 silt content.

5. Inclined tube sedimentation tank, its processing capacity is 3-5 times the advection settling tank, accelerating the clarification tank and pulsed clarification tank 2-3 times.

Product Specifications: Φ25mm, Φ35m, Φ50mm, Φ80mm

2.1 Labyrinth inclined tube sedimentation tank

Labyrinth inclined plate sedimentation tank is installed in the vertical direction of the inclined plate of ordinary inclined plate sedimentation tank several wing-shaped blades, wing-shaped blades into the mainstream into the water, swirl and circulation area. Located in the mainstream area of ​​flocs, the flow rate and sinking speed of the common role, gradually sinking. The flocs in the swirl zone are forced to the circulation area and trap some flocs after passing through each wing. Into the circulation area of ​​the floc, under the action of the circulation, a spiral movement and sink along the wings to the bottom of the pool. The vortex forced convection in the swirling zone of the labyrinthine sedimentation tank and the efficient sedimentation in the recirculation zone make it have a higher precipitation efficiency.

Particle separation of the labyrinth belongs to the dynamic separation, especially in the vortex zone, which includes the separation process of gravity, fluid resistance and inertial force under the action of the swirling flow, and the mass produced in the main flow zone and the swirling flow zone Exchange also flocs flocculation effect of collisions with each other. Therefore, its treatment effect is superior to ordinary inclined plate precipitation.

2.2 small spacing inclined plate sedimentation tank

In fact, the flow of water in the inclined tube settling tank is pulsating because when the large alum pellets in the inclined tube are separated from the water The relative movement produces a small vortex behind the alum particles, and the movement of these vortices creates a pulsation of the water flow. These pulsations have no effect on the large alum particles, which play a supporting role in the precipitation of incompletely-reacted small particles, thus affecting the water quality of the effluent. In order to overcome this phenomenon, to suppress the pulsation of water flow, a small spacing of inclined plate precipitation equipment came into being.

This device has the following advantages:

1, due to significantly reduced spacing, alum precipitation distance is also significantly reduced, so that more small particles can be precipitated;

2, due to reduced spacing, hydraulic resistance increases, so that the water flow in sedimentation tank in the main part of the flow resistance, so that sedimentation tank flow distribution, compared with the inclined tube, significantly improved the precipitation conditions;

3, mud performance is far superior to other forms of shallow sedimentation tanks, because this device basically no lateral constraints, sedimentation area of ​​equipment and mud area equal.

3, high-density sedimentation tank

High-density sedimentation process is based on the traditional advection settling tank, take full advantage of the dynamic coagulation, accelerated flocculation principle and shallow pool theory, the coagulation, enhanced flocculation, inclined tube precipitation three processes are optimized. Mainly based on four mechanisms: a unique integrated reaction zone design, a lower flow rate change from the reaction zone to the sedimentation zone, a sludge circulation from the sedimentation zone to the reaction zone, and a sedimentation arrangement using a inclined tube. The reaction tank is divided into two parts: rapid coagulation reaction tank and slow coagulation flow reactor. Rapid coagulation reaction tank is the introduction of raw water to the center of the bottom of the reaction tank, the cylinder installed in the middle of an impeller, the role of the impeller is to make the reaction pool water flow evenly mixed and the distribution of flocculation and polyelectrolytes to provide the required kinetic energy . Slowly from the pre-settling tank alum into the clarifier tank, so to avoid alum broken, and produce vortex, so that a large number of suspended solids in the uniform deposition of particles.

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