well! Today, let's talk about the "old buddy" in the sewage treatment industry - sedimentation tanks! This thing may seem ordinary, but it plays a super important role in the sewage treatment process! The suspended impurities and sludge in the sewage are all handled by sedimentation tanks. There are several common sedimentation tanks on the market, each with its own "exclusive trick". Today, we will break them open and crush them, and compare them carefully!
Horizontal sedimentation tank: steady and stable "big brother"
Horizontal sedimentation tank is considered the oldest qualified sedimentation tank, and it is the first choice for many sewage treatment plants when they are built. From its appearance, it looks like a long large sink, with sewage slowly flowing in from one end and then strolling forward in the direction of the sink.
Why is it called 'Big Brother'? Because its working principle is particularly simple and rough, it relies on gravity to naturally sink impurities and sludge in the sewage. When sewage flows in the pool, the speed is relatively slow, so that impurities with higher density than water have enough time to sink to the bottom of the pool. The sludge that sinks to the bottom will be pushed into the sludge hopper by a specialized scraper and then discharged, while the treated clean water will flow away from the overflow weir at the other end of the pool.
It has many advantages! Firstly, the structure is simple and the construction cost is not high. For small-scale sewage treatment plants with limited budgets or places where treatment requirements are not particularly high, it is simply the "king of cost-effectiveness". Moreover, its operation and maintenance are also very convenient, and even if there are problems, it is not complicated to repair. In addition, the treatment effect of the horizontal flow sedimentation tank is very stable, and the anti shock load capacity is strong. Even if the inlet water quality suddenly changes a little, it can also be "as stable as Mount Tai" and work normally.
However, it also has its own shortcomings. The first one is that it occupies a large area, as it is elongated and requires sufficient retention time and sedimentation distance for sewage, so the length is generally relatively long. In places where land resources are scarce and every inch of land is precious, this is not very friendly. Also, its sludge discharge is not very convenient, and the scraper needs regular maintenance. If the maintenance is not in place, it is easy to have problems with poor sludge discharge, which affects the treatment effect.
Vertical flow sedimentation tank: a small and clever "little clever" with a compact body
Compared to the "big brother" horizontal flow sedimentation tank, the vertical flow sedimentation tank is like a "little clever". Its shape is cylindrical, and sewage enters from the inlet pipe in the center of the tank and slowly spreads outwards. Impurities and sludge sink vertically under the action of gravity, while clean water flows out from the overflow weir around the top of the tank.
The biggest advantage of a vertical flow sedimentation tank is its small footprint! Because it develops vertically and does not need to be stretched out like a horizontal sedimentation tank, it is particularly suitable for use in areas with scarce land resources, such as small sewage treatment plants in some cities. Moreover, its sludge discharge method is relatively simple and direct. The sludge can slide directly into the sludge hopper by its own gravity, and the sludge discharge efficiency is quite high.
However, it also has many 'shortcomings'. Due to its large pool depth, the flow of water in the pool is not very uniform, which can easily lead to short flow phenomena, where sewage flows out of the outlet before it has fully settled, which can affect the treatment effect. In addition, the processing capacity of vertical flow sedimentation tanks is limited, and their processing capacity is generally relatively small, making them less suitable for treating high flow sewage. Moreover, its construction difficulty is slightly higher than that of a horizontal sedimentation tank, and the construction cost is also relatively higher.
Radial flow sedimentation tank: a high-performance "big guy"
The radial flow sedimentation tank is a true 'big guy', with a shape resembling a large disk and a diameter that can reach tens or even hundreds of meters! Wastewater enters from the inlet pipe at the center of the pool and flows radially around like spokes of a wheel. Impurities and sludge gradually settle at the bottom of the pool during the flow process, while clean water is discharged from the overflow weir around the pool.
Why is it called a "high-performance" player? Firstly, its processing capability is super strong! Due to the large area of the pool, there is enough space for sewage to settle inside, so it can treat large flow of sewage. Many large sewage treatment plants like to use it. Moreover, its sedimentation effect is very good, and the water flow distribution is relatively uniform, making it less prone to short flow phenomena. Radial flow sedimentation tanks are generally equipped with mechanical scraping equipment, which has a high degree of automation and particularly high sludge discharge efficiency, greatly reducing the workload of manual operation.
However, 'big guys' also have their own troubles. Its construction cost is not low, not only does it occupy a large area, but the construction process is complex and requires high construction technology. In addition, due to its complex mechanical scraping equipment, the maintenance and management costs of the equipment are also relatively high. If the equipment malfunctions, it is also difficult to repair. Also, it is sensitive to changes in the quality and quantity of incoming water. If the concentration of suspended solids in the incoming water suddenly increases or the water volume fluctuates greatly, it may affect the sedimentation effect.
Slant tube (plate) sedimentation tank: an innovative "rising star"
The inclined tube (plate) sedimentation tank is considered a "newcomer" in sedimentation tanks, and its design is particularly creative. Many inclined pipes or plates are installed in the sedimentation tank, and sewage flows between these inclined pipes (plates). Impurities and sludge slide along the surface of the inclined pipes (plates) to the bottom of the tank under the action of gravity, while clean water flows away from above.
What are the benefits of this design? Firstly, it greatly increases the sedimentation area! Because the inclined tube (plate) divides the sedimentation tank into many small sedimentation units, which increases the sedimentation area several times in a limited space, the sedimentation efficiency is particularly high and can treat a large amount of sewage in a short period of time. Moreover, due to the presence of inclined pipes (plates), the distance between impurities and sludge sedimentation in sewage is shortened, and the sedimentation time is greatly reduced, resulting in a much better treatment effect than traditional sedimentation tanks. In addition, the inclined tube (plate) sedimentation tank has a relatively small footprint and is very suitable for use in the renovation of existing sewage treatment plants. It does not require too much expansion of the site to improve treatment capacity.
However, it is not perfect either. Diagonal pipes (plates) are easily clogged. If the concentration of suspended solids in the sewage is relatively high or there are some fibrous impurities, it is easy to get stuck between the inclined pipes (plates), affecting the sedimentation effect. Moreover, the inclined tube (plate) needs to be replaced and cleaned after a period of use, resulting in relatively high maintenance costs. In addition, it requires high uniformity of the inflow. If the inflow distribution is uneven, it will cause excessive load on some inclined pipes (plates), affecting the overall treatment effect.
Summary: Each has its own strengths, choose according to your needs
Having said so much, each of these sedimentation tanks really has its own advantages! A horizontal sedimentation tank is like a steady and reliable old friend. Although it may be a bit cumbersome, its advantage lies in its simplicity and stability; The vertical flow sedimentation tank is like a flexible assistant, suitable for use in small spaces; Radial flow sedimentation tank is an efficient "strongman" that can carry large flow of sewage; The inclined tube (plate) sedimentation tank is a creative "technical flow" with ultra-high sedimentation efficiency.
In practical applications, which sedimentation tank should be chosen? This needs to be comprehensively considered based on various factors such as the scale of the sewage treatment plant, the amount of treated water, the quality of incoming water, site conditions, and budget. If you are planning a sewage treatment project, you must study it carefully and choose the most suitable sedimentation tank for yourself, so as to ensure the treatment effect and control the cost within a reasonable range!
Alright, that's all for today's comparison about sedimentation tanks! If you have any further questions, feel free to chat with me anytime!
