What process involves the removal of additional fluid through a semipermeable membrane using added pressure?

The process of ultrafiltration involves the removal of additional fluid through a semipermeable membrane by applying pressure. During ultrafiltration, a pressure differential is created across the membrane, allowing water and small solutes to pass through while retaining larger molecules and particles. This process is particularly useful in water treatment, where it is employed to separate contaminants from water, ensuring the purity and safety of the final product.

In contrast, osmosis refers to the movement of water across a semipermeable membrane driven by concentration gradients, without the need for applied pressure. Dialysis is a similar but distinct process where solutes move across a membrane to equalize concentration levels, typically relying on diffusion rather than pressure. Filtration is a broader term encompassing various methods of separating solids from liquids but does not specifically refer to the use of semipermeable membranes or applied pressure. Thus, ultrafiltration is the precise answer to the question posed.