Air & Water Quality Glossary Media / Medium Materials used in filters and softeners to treat water. In the case of a filter, the media will mechanical trap particles as they try to pass from the top of the bed to the bottom of the bed. Some media perform functions beyond just filtration. They can be used to raise the pH as when calcite (limestone,marble chips) is used. They can adsorb VOC(s) and radon as when activated carbon is used. They can oxidize minerals as when birm or greensand is used. In the case of a softener, the media is not designed to do any filtration. The media in a softener consists of small plastic beads that contain sites for the exchange of ions. Media is the plural form of medium and refers to more than one type of material. Previous Page Home | Top of page | Contact © Copyright 2000, Air & Water Quality, Inc. Maine's Water Experts