What does filtration pass treated water through, according to the text?

Filtration in water treatment typically involves passing the water through a medium that effectively removes suspended solids and impurities. Sand and anthracite coal are commonly used materials in the filtration process due to their ability to capture particulates and provide effective filtration.

Sand serves as a primary filter medium, trapping large particles, while anthracite coal, a form of carbon, offers better filtration of smaller particles and enhances the overall process by preventing the formation of a muddy water layer. This dual-layer approach improves the quality of the treated water, making it a standard practice in many water treatment facilities.

In contrast, plastic membranes are often used in microfiltration and ultrafiltration processes but do not serve as the primary mechanism for standard filtration in the way that sand and anthracite do. Carbon filters focus on removing specific contaminants and flavors but are not the primary medium in conventional filtration systems. Chlorine tablets are used for disinfection rather than filtration, killing pathogens but not removing physical particles. Thus, sand and anthracite coal is the most accurate answer regarding the filtration process for treated water.