What type of filtration system involves both gravity and pressure in its operation?

The type of filtration system that involves both gravity and pressure in its operation is direct filtration. In direct filtration, water is passed through a filter medium under pressure, typically aided by gravity as well. This process allows for effective removal of solids and impurities directly from the water before it continues through the treatment process.

The combination of pressure and gravity increases the efficiency of the filtration, enabling it to manage larger volumes of water while maintaining quality. This method is commonly used in water treatment facilities because it can produce high-quality effluent while minimizing the residuals produced during the filtration process.

Other filtration types typically do not utilize both forces in conjunction. Indirect filtration primarily relies on gravity, while sedimentation filtration uses gravity but does not apply pressure in the same manner. Coagulation is a separate step in the treatment process that prepares the water for filtration but does not describe a filtration system itself.