Opta Industrial Minerals Group is a world-leading supplier of water filtration products, including:

• Garnet – International Garnet (UL Certified)
• Greengrit

Excerpt from “Introduction to Water Treatment – Volume 2” (AWWA)

…Dual- and mixed/multimedia filters have a coarse-to-fine gradation of filter media. By using fine media with a high specific gravity and coarse media with a lower specific gravity, the layers of media approximately maintain their respective positions in the filter bed even after backwashing. Some mixing does occur. Mixing actually makes the filter more effective by providing more contact area for the suspended particles.

In operation, the coarse layer on top removes larger suspended particles. The finer particles pass through this layer and are removed by finer media below. As a result, most of the filter bed is used to remove suspended particles. This allows for longer filter runs and higher filtration rates because head loss does not build up as quickly as with rapid-sand filters. Multi-media filters are becoming popular, because they can greatly increase a water treatment plant’s capacity without loss in water quality…