Which filtration method is often required to prepare water for drinking?

The correct choice is membrane filtration because this method specifically involves passing water through a semi-permeable membrane that allows water molecules to pass while blocking larger contaminants such as bacteria, viruses, and particles. This is especially important in preparing water for drinking purposes, as it ensures the removal of harmful microorganisms and impurities, making the water safe for consumption.

Membrane filtration techniques can vary in pore size, which allows for targeted filtration based on specific contaminants that need to be removed. This precision is essential in water treatment processes, making membrane filtration a reliable and widely used method for producing clean drinking water.

In contrast, centrifugation is primarily used for separating substances based on density and is not effective for filtering dissolved contaminants from water. Flotation, meanwhile, involves the separation of solids based on their buoyancy and is not focused on purifying water for drinking. Absorption refers to the process where one substance permeates another; while it can be involved in water purification processes, it is not specifically a primary filtration method for preparing drinking water.