sedimentation tank

Zhengyuan Environmental Protection Manufacturer specializes in the design of sedimentation tanks, which are mainly divided into primary sedimentation tanks, secondary sedimentation tanks, and tertiary sedimentation tanks according to their positions in the wastewater treatment process. A sedimentation tank is a water purification system that utilizes the principle that suspended impurity particles in the water flow can separate from the water flow when their downward settling velocity is greater than the flow velocity of the water, or when their downward settling time is less than the time it takes for the water to flow out of the sedimentation tank.

Sedimentation tank is a treatment structure that uses gravity settling to remove suspended particles with a higher density than water from water. It is one of the most widely used treatment units in wastewater treatment and can be used for wastewater treatment, post-treatment of biological treatment, and deep treatment.

Principle of sedimentation tank:

A sedimentation tank is a water purification system that utilizes the principle that suspended impurity particles in the water flow can separate from the water flow when their downward settling velocity is greater than the flow velocity of the water, or when their downward settling time is less than the time it takes for the water to flow out of the sedimentation tank.

The treatment efficiency of an ideal sedimentation tank is only related to surface load, that is, to the surface area of the sedimentation tank, and is not related to the depth of the sedimentation tank. The depth of the tank is only related to factors such as the time and quantity of sludge storage and the prevention of sludge erosion. In actual continuous operation of sedimentation tanks, the overflow of water from the outlet weir will cause an upward flow velocity of the water flow. Therefore, particles with a sedimentation velocity less than the upward flow velocity will follow the water flow, while particles with a sedimentation velocity equal to the ascending flow velocity will be suspended in the tank. Only particles with a sedimentation velocity greater than the upward flow velocity will settle in the tank. The time for sediment particles to settle to the bottom of the sedimentation tank is related to the hydraulic retention time of the water flow in the sedimentation tank, that is, it is related to the depth of the tank body.

In theory, the shallower the pool body, the easier it is for particles to reach the bottom of the pool, which is the theoretical basis for shallow sedimentation tanks such as inclined tube or inclined plate sedimentation tanks. In order to allow particles slightly larger than the rising flow velocity in the sedimentation tank to settle down and prevent the already settled sludge from being disturbed by the incoming water flow and rebounding, a buffer zone is left between the sedimentation zone and the sludge storage zone to allow particles slightly larger than the rising flow velocity or rebounding particles in these sedimentation tanks to come into contact with each other and then settle down again.

Price of sedimentation tank:Starting from 20000 yuan, please consult customer service for specific prices

The role of sedimentation tank in sewage treatment:

The function of a three-stage sedimentation tank is to separate sludge and water, clarify the biologically treated mixture, and concentrate the sludge in the mixture. The tertiary sedimentation tank is the final stage of sewage biological treatment, playing a decisive role in ensuring the qualified suspended solids content of the effluent water quality.

If the setting of the tertiary sedimentation tank is not reasonable, even if the biological treatment effect is good, the content of dissolved organic matter in the mixed liquid is already very low, and the effect of sludge water separation in the tertiary sedimentation tank is not ideal, the effluent quality may still be unqualified.

If the sludge concentration effect is not good, the amount of microorganisms returning to the aeration tank cannot be guaranteed, and the decrease in the concentration of the aeration mixture will lead to a decrease in the sewage treatment effect, thereby affecting the effluent quality.

Analysis of the advantages and disadvantages of various types of sedimentation tanks:

1、 Advantages and disadvantages of inclined tube (plate) sedimentation tank

Advantages

1. Increase in sedimentation area;

2. High sedimentation efficiency and large water production;

3. Good hydraulic conditions, low Re and high Fr, conducive to sedimentation;

Disadvantages

Due to its short residence time, its buffering capacity is poor;

2. High requirements for coagulation;

3. Maintenance and management are difficult, and the inclined plate (pipe) needs to be replaced after a period of use

Applicable conditions

1. Secondary sedimentation tank suitable for small and medium-sized sewage treatment plants

2. Can be used for potential tapping and renovation of existing horizontal sedimentation tanks

2、 Advantages and disadvantages of horizontal sedimentation tank

Advantages

1. There is no limit to the amount of water processed, and the sedimentation effect is good.

2. Strong adaptability to changes in water volume and temperature.

3. Compact layout, easy construction, and low cost.

Disadvantages

1. It is difficult to distribute water evenly between the inlet and outlet.

2. When discharging multiple buckets of mud, each bucket needs to be equipped with a mud discharge pipe (valve), which is manually operated and the work is complicated. When using mechanical scraping, it is easy to rust.

Horizontal sedimentation tank - applicable scope

1. Suitable for areas with high groundwater levels and poor geological conditions.

2. Large, medium, and small-scale sewage treatment projects can all be adopted.

3、 Advantages and disadvantages of vertical flow sedimentation tank

Advantages

Vertical flow sedimentation tank has good effect, small footprint, and easy sludge discharge

Disadvantages

The depth of the pool is large, construction is difficult, and the cost is high. Commonly used for small sewage treatment plants with a water volume of less than 20000 m3/d.

Applicable conditions

Suitable for small sewage treatment plants

4、 Advantages and disadvantages of radial flow sedimentation tank

Advantages

The advantage of radial flow sedimentation tank is that it uses more mechanical sludge discharge, operates well, has simpler management, and the sludge discharge equipment has become standardized.

Disadvantages

Mechanical sludge discharge equipment is complex and requires high construction quality;

Applicable conditions

1. Suitable for areas with high groundwater levels

2. Suitable for large and medium-sized sewage treatment plants

Structural design of sedimentation tank:

The sedimentation tank consists of five functional zones, namely the inlet zone, sedimentation zone, buffer zone, sludge zone, and outlet zone. The inflow and outflow zones are used for water distribution and collection, ensuring that the water flow is evenly distributed across various flow sections, providing as stable hydraulic conditions as possible for improving volume utilization, coefficient, and solid particle settling.

The settling zone is the area where sediment particles can separate from water.

The sludge area is an area for storing, concentrating, and discharging sludge.

The buffer layer is a water layer that separates the settling zone and the sludge zone, preventing the sludge from being washed away by water flow and re floating.

The above parts are interconnected to form an organic whole, in order to achieve the required processing capacity and settlement efficiency in the design.