What do oxidizing filters use to treat water?

Oxidizing filters primarily utilize oxidants to treat water, making this the correct choice. These filters function by introducing substances that promote oxidation, which helps in removing dissolved metals such as iron and manganese from water. The oxidants, such as chlorine, potassium permanganate, or air (in some cases, used to oxidize contaminants), convert soluble contaminants into insoluble particles that can then be filtered out. This process is essential in water treatment as it effectively improves water quality by reducing undesirable substances that can affect taste, appearance, and health.

The other options do not properly represent the mechanism used by oxidizing filters. Physical barriers, for instance, are commonly used in filtration systems to remove particulate matter but do not address the chemical changes needed for effective oxidation. Biological treatment involves microorganisms breaking down contaminants, which is different from the direct application of chemical oxidants. While activated carbon is effective in adsorbing impurities and removing odors and tastes, it does not provide the oxidation process inherent in the function of oxidizing filters.