In modern water treatment systems, filtration equipment is a key component to ensure that water quality meets standards and that the system operates stably. Among them, the quartz sand filter, as a filtration device with a simple structure, stable operation, and convenient maintenance, is widely used in various fields such as industrial circulating water, domestic water, sewage treatment, and pure water pretreatment. With its efficient ability to remove suspended solids and impurities, the quartz sand filter not only significantly improves water quality but also effectively extends the service life of subsequent filtration equipment and reduces system operating costs. This article will comprehensively introduce the structural principle, usage method, and maintenance essentials of the quartz sand filter to help readers gain an in-depth understanding of this fundamental yet important water treatment equipment.
The quartz sand filter, also known as a mechanical filter, is one of the common filtration methods among multi-media filters. It is usually used together with an activated carbon filter to achieve a more comprehensive water purification effect. The main function of the quartz sand filter is to remove suspended substances, solid particles, suspended solids, and insoluble non-colloidal solid substances in water. The activated carbon filter, on the other hand, is good at removing odor, color, chlorine, organic matter, heavy metals, synthetic detergents, viruses, and radioactive substances. The combination of the two can effectively achieve deep water treatment and is a conventional and efficient water treatment device.
The quartz sand filter is not only used for deep water treatment but is also often used as a pretreatment device for reverse osmosis filters, precision filters, nanofiltration devices, and microfiltration devices. By removing suspended substances and large particles from the water, the quartz sand filter can effectively extend the service life of subsequent filtration equipment, reduce maintenance costs, and improve the operational efficiency of the entire water treatment system.
The working principle of the quartz sand filter mainly relies on the impurity interception capacity of quartz sand. Through the quartz sand filtration layer, suspended substances and solid particles in the water are trapped and adsorbed to achieve water purification. Specifically, the working process of the quartz sand filter can be divided into the following stages.
When the source water enters the quartz sand filter, the water flow passes through the quartz sand filtration layer. The filtration layer consists of quartz sand with different particle sizes, and there are numerous voids between the sand grains. When suspended substances and solid particles in the water pass through the filtration layer, they are trapped and adsorbed on the surface of the sand particles. The impurity interception capacity of the quartz sand layer mainly depends on factors such as sand particle size, filtration rate, and layer thickness. Generally, the smaller the particle size, the slower the filtration rate, and the thicker the filtration layer, the stronger the impurity interception capacity.
To improve the filtration efficiency of the quartz sand filter, a coagulant is usually added to the source water. The coagulant undergoes a cationic hydrolysis reaction and polymerization process in water, producing a large number of positive ions and polymer molecules. These positive ions and polymers adsorb colloidal particles in the water, neutralizing their surface charges and reducing the repulsive forces between them. When the repulsive force decreases, the colloidal particles come closer together and aggregate into larger particles. These larger particles are more easily trapped and adsorbed by the quartz sand layer during filtration, thus enhancing the filtration effect.
After running for a period of time, the quartz sand filtration layer accumulates a large amount of impurities and dirt, resulting in decreased filtration performance. At this time, backwashing is required. The backwashing process uses reverse water flow and compressed air together to loosen the sand layer, flushing away impurities and dirt adsorbed on the sand surface and discharging them through the drainage pipeline. During backwashing, the water flow direction is opposite to normal filtration, moving from the bottom of the filter upward through the sand layer. Meanwhile, compressed air is introduced to form a gas–liquid mixed cleaning process. This gas–liquid cleaning effectively removes impurities and dirt in the sand layer, restores the impurity interception capacity of the quartz sand, and achieves the purpose of cleaning.
Correct usage not only improves filtration efficiency but also extends equipment life and reduces maintenance costs. The detailed steps and precautions for using quartz sand filters are as follows:
Before using the quartz sand filter, an equipment inspection should be carried out. Check whether the valves are functioning properly to ensure there are no leaks or blockages. Also, confirm that the tap water supply meets the demand and that water pressure is stable. Only when the equipment is in normal condition and the water source is sufficient can the filter operate properly.
Start the Equipment: Open the inlet and vent valves while closing other valves. When water flows out of the vent valve, close it, then open the drain valve so that the outflow reaches its maximum. After draining for 3–5 minutes, close the lower inlet valve and upper drain valve.
Forward Washing: Open the lower drain valve and adjust the upper inlet valve so that the filter can perform forward washing. After draining for 10–15 minutes, close the lower drain valve, open the water outlet valve, and start feeding water to the filter.
Add Coagulant: Add an appropriate amount of coagulant to the quartz sand filter. The dosage depends on the conductivity of the water. The coagulant helps aggregate fine particles in the water to improve the filtration effect.
Adjust Valves: Once the equipment is operating normally, adjust the inlet and outlet valves to appropriate positions to ensure smooth water flow and effective filtration.
During operation, regularly inspect the equipment status. Observe the pressure difference between the inlet and outlet to ensure it remains within the normal range. Generally, when the pressure difference reaches 0.07 MPa, backwashing is required. Also, periodically check the effluent quality to ensure it meets requirements. If abnormal water quality is detected, identify and address the cause promptly.
Maintenance is essential to ensure the long-term stable operation of quartz sand filters. The following are common maintenance measures.
Regularly inspect valves and pipelines for leaks, blockages, or damage. Repair or replace damaged components in time to maintain smooth water flow. Additionally, clean the inside of the pipelines regularly to prevent debris buildup that may affect flow and filtration efficiency.
Regularly clean the exterior of the quartz sand filter and maintain the cleanliness of the surrounding area. Remove dust, dirt, and debris from the equipment surface to prevent them from entering the filter and affecting performance. Keeping the environment around the equipment clean also helps prevent contamination.
After long-term operation, the quartz sand filter accumulates a large amount of impurities, reducing its performance. Therefore, regular backwashing is necessary to remove contaminants and restore filtration performance. The specific steps are as follows:
Close Inlet and Outlet Valves: Before backwashing, make sure both valves are closed to prevent water from entering the filter or flowing in the wrong direction.
Open the Drain Valve: Open the drain valve to allow wastewater inside the filter to flow out. Connect the drain pipe to the discharge system to avoid wastewater overflow.
Start the Backwash Pump: Turn on the backwash pump and set the appropriate duration and flow according to the operation manual to ensure thorough cleaning. During backwashing, water flows upward through the sand layer to flush out impurities and dirt, which are then discharged. The process typically lasts 10–15 minutes.
Discharge Wastewater: After backwashing, turn off the pump and continue draining residual water and cleaning fluid to ensure complete discharge and prevent contamination.
Resume Operation: Once the drainage is complete, close the drain valve and confirm that all steps are finished. Open the inlet and outlet valves to resume normal operation. Monitor the post-wash filtration effect to ensure water quality meets the requirements.
Maintain detailed records of operating parameters such as runtime, inlet and outlet pressure difference, coagulant dosage, and backwash time. These records help in understanding the operating condition of the equipment, identifying potential issues early, and providing references for maintenance and servicing.
In general, the quartz sand filter, with its efficient impurity interception performance, stable operating characteristics, and simple maintenance method, occupies an important position in water treatment engineering. Proper operation and regular maintenance not only ensure long-term stable operation but also significantly improve water treatment efficiency and overall system performance. With the continuous development of water treatment technology, the quartz sand filter will continue to play an irreplaceable role as a key pretreatment and filtration device in various industrial and domestic water treatment systems.
