What material is used to support the filter media in a filtration system?

The use of gravel and sand as supporting materials in a filtration system is essential for effective filtration processes. Gravel typically forms the bottom layer of the filter and provides a sturdy base that allows for proper drainage and support of the upper filter media. It has a larger particle size which facilitates the flow of water through the system while preventing clogging.

Sand serves as the upper layer and works to capture smaller particles and impurities from the water as it passes through. The combination of these materials creates a multi-layered filtration system, enhancing the overall efficiency of particle removal. The gradation from gravel to sand allows for optimal water flow and filtration, ensuring that contaminants are effectively trapped while still achieving the necessary hydraulic performance.

Other materials mentioned, such as clay or coal, may play roles in different filtration or treatment processes but do not serve the same supportive function in a traditional filtration system as gravel and sand do. Plastic beads, while sometimes used in specific types of filtration for biofiltration or other specialized applications, do not provide the foundational support required in standard filtration setups. Thus, gravel and sand are the appropriate choices for supporting filter media effectively.