Essential Cleaning Practices for Quartz Sand Filters

 
In modern swimming pool water treatment systems, quartz sand filters play a crucial role. They are responsible for removing impurities and contaminants from the water, ensuring that users enjoy clear and safe water quality. However, as time goes on, the filters can gradually accumulate human lipids and other organic substances, posing challenges to water quality maintenance. Therefore, regular cleaning of quartz sand filters, particularly effective backwashing and forward washing, is essential for maintaining filter performance and stable water quality. This article will delve into the necessity of cleaning quartz sand filters and the methods involved, helping users understand how to better maintain this critical equipment.

The Importance of Cleaning Quartz Sand Filters

 
Quartz sand filters are vital in the water treatment process of swimming pools, and their cleaning is primarily aimed at removing the buildup of lipids rather than addressing sand layer calcification. Swimming pools and spas contain significant amounts of suspended human lipids. If these fats are not adequately treated, they can accumulate on the surface of the quartz sand particles. This buildup not only increases the sand's rejection of lipids but also allows the lipids to penetrate deeper into the filter layer, eventually saturating it completely. When this occurs, the lipids cannot be captured by the filter due to the overall repulsion from the saturated filter layer, resulting in cloudy pool water with a greenish to yellowish tint. Even with backwashing, the water quality may not significantly improve, often necessitating a change of water source or filter media.
However, such conditions typically do not persist; they can recur frequently, especially in high-temperature pool environments. Consequently, commercially available filter cleaning agents have been developed specifically to remove organic lipids adhering to the filter media's surface, helping to restore the filter's normal functionality.

Backwashing Quartz Sand Filters

 
Backwashing is an indispensable step in the maintenance of quartz sand filters, primarily aimed at removing accumulated contaminants from the filter layer to restore its filtering efficiency. The best time to perform backwashing is when the filter pressure rises or the circulation flow rate decreases. This process not only reduces the pressure in the filter but also increases the water flow rate, ensuring the continued cleanliness of the pool water. Below, we outline the backwashing procedure and its importance in maintaining the filtration system.

1. The Necessity of Backwashing

 
The backwashing operation of quartz sand filters is a critical aspect of assessing filter efficiency. The timing for backwashing is primarily based on changes in the flow rate of the circulation system, typically monitored through an increase in filter pressure, known as differential pressure or head loss. As contaminants gradually accumulate on the quartz sand filter layer during water circulation, the surface of the filter layer thickens, impeding water flow and increasing filter pressure. At this point, backwashing can effectively eliminate the accumulated contaminants, lower the pressure, and enhance the filtering flow rate.

2. Control of Head Loss

 
The swimming pool filtration system employs a circulation design that must balance filtering efficiency with water flow capability. It is generally recommended to control head loss within an appropriate range. While exceeding this range may improve water quality, it can reduce output flow, leading to decreased circulation efficiency and potential filtration dead zones. Conversely, maintaining head loss below this range may increase water circulation frequency, but the filtering quality might suffer. Additionally, frequent backwashing can waste water resources. Therefore, when performing backwashing, it is essential to add the initial pressure after backwashing to the required differential pressure to determine a reasonable backwashing pressure.

Forward Washing of Quartz Sand Filters

 
Forward washing is another crucial step in maintaining quartz sand filters, aimed at effectively removing residual impurities from the surface of the filter media. By directing water flow downward, forward washing cleans the filter layer, preventing unremoved contaminants from re-entering the pool during subsequent filtration. Here, we will discuss the significance of forward washing and its comparison with backwashing.

1. The Importance of Forward Washing

 
The filtering media of quartz sand filters can be reused; therefore, during backwashing, the filter layer expands upwards by 1.2 to 1.3 times. The upward water flow causes collisions between the filter media particles, scraping off the impurities adhering to their surfaces. However, due to the uniform hardness of the filter media, smaller particles may break during backwashing, and some heavier small particles may not be washed away and could settle at the bottom, potentially re-entering the pool through the collection pipes. This scenario necessitates forward washing to ensure that impurities within the filter are thoroughly removed.

2. Comparison of Forward Washing and Backwashing

 
In practice, the importance of forward washing is often underestimated. Especially under water-scarce conditions, the amount of water and time for backwashing may be insufficient, leading to incomplete removal of impurities from the quartz sand surface. As a result, during downstream filtration, these remaining impurities may enter the pool, rapidly degrading water quality and even leaving behind black water streaks, known as "malformations." Therefore, the draining action of forward washing is critical in effectively preventing such situations.

Conclusion

 
Quartz sand filters play an indispensable role in maintaining water quality in swimming pools. Regular backwashing and forward washing not only remove contaminants and keep the water clean but also enhance the overall efficiency of the filtration system. By properly controlling head loss and the frequency of backwashing, the system can operate normally, providing users with a safe and hygienic water environment. These measures are vital for enhancing the swimming pool experience and safeguarding user health.