Overview
The shallow sand filter is a filtration device commonly used in the water treatment field. With its unique structure and working principle, it plays a significant role in raw water pretreatment, circulating water filtration, and reclaimed water reuse in numerous industries. It can effectively remove impurities such as suspended solids, particles, and colloids in water, improve water quality, ensure the smooth progress of subsequent water treatment processes, and guarantee the normal operation of water-using equipment. It is widely applied in industries, municipalities, agriculture, landscape architecture, and many other fields.
Working Principle
I. Water Inflow Process:
The water to be filtered enters the top water inlet of the shallow sand filter through the water inlet pipe, relying on its own gravity or external pumping pressure. Subsequently, the water flow evenly spreads over the surface of the sand filter layer inside the filter. During this process, there is usually a water distribution device to rationally distribute the incoming water, ensuring that the water flow can evenly cover the entire sand filter layer and avoiding situations where the local water flow is too fast or too slow, which could affect the filtering effect.
II. Filtration Stage:
The core of the shallow sand filter lies in its sand filter layer. This layer is typically filled with high-quality filter materials like quartz sand. These filter materials possess appropriate particle sizes and pore structures. When the water flow passes through the sand filter layer, suspended solids, particles, and other impurities in the water with particle sizes larger than the pores of the sand filter material will be intercepted on the upper part of the sand filter layer. Meanwhile, the clean water can permeate through the pores of the filter material and continue to infiltrate downward. Eventually, it gathers in the water collection area at the bottom of the filter and then flows out from the water outlet, thus realizing the separation of impurities from the water and achieving the purpose of filtration and purification.
III. Backwashing Process:
As the filtration continues, more and more impurities will accumulate on the surface of the sand filter layer, resulting in an increase in the filtration resistance and a decrease in the filtration efficiency. When certain conditions are met (such as when the water pressure difference between the inlet and outlet reaches the set value or the filtration flow rate drops significantly), it becomes necessary to conduct backwashing operations on the sand filter layer. During backwashing, reverse water flow is introduced from the water collection area at the bottom of the filter, causing the water to flow through the sand filter layer from bottom to top. By leveraging the impact force of the water flow and the mutual friction between the filter material particles, the impurities attached to the surface and within the pores of the sand filter material are washed away. The washed-down impurities are then discharged out of the filter through the sewage outlet at the top along with the backwashing water, thereby restoring the filtering capacity of the sand filter layer.
IV. Operation and Maintenance Stage:
During daily operation, in addition to regularly performing backwashing based on the filtering situation, it is also essential to monitor the loss of sand filter materials and replenish new filter materials in a timely manner to ensure that the sand filter layer always maintains good filtering performance. At the same time, it is necessary to regularly check whether each component of the equipment, including the water inlet pipe, water outlet pipe, valves, and water distribution device, is functioning properly and whether the sealing is in good condition. This enables the timely detection and handling of potential failure risks, ensuring the long-term stable operation of the equipment.
Performance Characteristics
I. Obvious Filtration Effect:
It has a strong interception ability for suspended solids, particles, and other impurities of different particle sizes in water. It can effectively reduce the content of impurities in water, making the filtered water clearer and more transparent and meeting the water quality requirements of various water use scenarios. For example, in the industrial circulating water system, it can significantly reduce problems such as equipment scaling and blockage caused by impurities in water.
II. Stable and Reliable Operation:
The overall structural design of the shallow sand filter is reasonable. The core sand filter layer has relatively stable properties. As long as it is used and maintained in accordance with the normal operation procedures, the equipment can operate stably for a long time under normal working conditions without easily breaking down. This provides a solid guarantee for continuous and stable water treatment and reduces the occurrence of situations like production interruption or water use inconvenience caused by equipment failures.
III. Wide Adaptability:
It can handle water of different types and qualities. Whether it is surface water, groundwater, or sewage that has undergone a certain degree of pretreatment, as long as there are suspended solids, particles, and other impurities in the water that need to be removed, the shallow sand filter can be applied. Moreover, under different working conditions such as temperature and pressure, as long as they are within a reasonable range, it can normally perform its filtering function, demonstrating strong adaptability.
IV. Simple Operation and Easy Maintenance:
The operation of the equipment is relatively straightforward. Operators can master basic operation processes such as starting, stopping, adjusting the flow rate, and conducting backwashing after simple training. The daily maintenance work mainly focuses on regular backwashing, replenishing filter materials, and routine inspections of equipment components. It does not require complex professional skills or tools, which is convenient for enterprises or relevant user units to manage and maintain, effectively reducing the operation and maintenance costs of the equipment.
V. Good Cost-Effectiveness:
On the one hand, the purchase cost of the shallow sand filter itself is relatively low compared to some high-end and complicated filtration equipment, giving it an advantage in price and enabling users to save on equipment procurement expenses. On the other hand, the cost of filter materials is also relatively reasonable, and the filter materials can be updated by replenishment, with a relatively long service life. In the long run, on the basis of ensuring a good filtering effect, it has good cost-effectiveness.
Structural Components
I. Tank:
The tank is generally made of materials such as carbon steel or stainless steel and formed through welding, assembly, and other processes. It has excellent sealing properties, effectively preventing water leakage during the filtration process. At the same time, it has sufficient strength to bear the weight of the internal sand filter layer, water, and the pressure generated during the filtration process, preventing the tank from deforming or being damaged. The shape of the tank is commonly cylindrical or square. Its top is equipped with a water inlet and an exhaust port, and its bottom is equipped with a water outlet and a sewage outlet, facilitating the inflow and outflow of water and the discharge of impurities. The appearance of the tank is usually treated with anti-corrosion and anti-rust measures to make it more aesthetically pleasing and durable.
II. Sand Filter Layer:
This is the core part of the shallow sand filter for realizing the filtering function. It is formed by filling filter materials like quartz sand according to a specific particle size range and filling thickness. Different application scenarios will select an appropriate quartz sand particle size based on the required filtering accuracy. When filling, it is necessary to ensure that the sand filter materials are evenly distributed to avoid local accumulation or vacancies, thereby providing favorable conditions for efficient filtering.
III. Water Distribution Device:
The water distribution device is located below the water inlet at the top of the tank. Its function is to evenly disperse the incoming water flow across the entire surface of the sand filter layer, enabling the water flow to evenly pass through the sand filter layer for filtration. Common types of water distribution devices include perforated pipes and nozzles. Through reasonable design and layout, they ensure the even distribution of water flow on the sand filter layer and enhance the filtering effect.
IV. Water Collection Device:
The water collection device is positioned above the water outlet at the bottom of the tank and is responsible for collecting the filtered clean water. It ensures that the water can smoothly flow out from the water outlet and avoids issues such as water flow short-circuiting. Common water collection devices include filter caps and water collection troughs. These can effectively gather the filtered water and guide it to flow out from the water outlet.
V. Backwashing System:
The backwashing system is a crucial part for ensuring that the shallow sand filter can maintain good filtering performance over the long term. It mainly consists of components such as a backwashing water pump, backwashing pipelines, and valves. The backwashing water pump provides the power for the water flow required for backwashing, transporting the water to the bottom of the tank through the backwashing pipelines. The valves are used to control the direction and flow rate of the water flow, ensuring the orderly progress of the backwashing process according to the set procedures and parameters.
Application Cases
I. Industrial Field:
In industrial production, such as in the chemical, electric power, and steel industries, there are relatively high requirements for the quality of production water. In the circulating water system, suspended solids, particles, and other impurities are often mixed in. The long-term accumulation of these impurities can lead to problems like equipment scaling, corrosion, and pipeline blockage. The shallow sand filter is applied in the pretreatment stage of industrial circulating water, effectively removing impurities from the water, ensuring the quality of the circulating water, extending the service life of the equipment, reducing equipment maintenance costs, and improving the efficiency and stability of industrial production.
II. Municipal Water Supply:
In the municipal water supply system, the source water may come from surface water or groundwater, which often contains impurities such as silt and rust. The shallow sand filter can serve as a front-end filter to conduct preliminary filtration on the raw water, removing most of the visible impurities in the water. This reduces the burden on subsequent in-depth treatment processes, improves the water quality of the water supply, and ensures that residents can use clean and safe drinking water.
III. Agricultural Irrigation Field:
For agricultural irrigation water, excessive impurities in the water can clog the irrigation nozzles and affect the irrigation effect. The shallow sand filter can filter the irrigation water to remove suspended solids, particles, and other impurities, making the irrigation water clearer. This ensures the normal operation of the irrigation system, improves the irrigation efficiency, and contributes to the healthy growth of crops.
IV. Landscape Architecture Water:
In landscape architecture, for water features such as lakes and fountains, there are certain requirements regarding the clarity and aesthetics of the water quality. The shallow sand filter can be used to filter the water, removing impurities to maintain the water's clarity and transparency, thereby enhancing the visual appeal of the landscape and creating a more pleasant and comfortable leisure environment for people.
In conclusion, the shallow sand filter occupies an indispensable position in the water treatment processes of many industries due to its unique filtering principle, excellent performance characteristics, and wide applicability. It is an important piece of equipment for ensuring water quality safety, meeting diverse water use requirements, and improving the efficiency of water resource utilization. With the continuous development of water treatment technology and the continuous elevation of water quality requirements, its application prospects will be even broader, and its functions are expected to be further optimized and upgraded.
