Each layer of media is designed to filter out specific types and sizes of particles, allowing for more efficient and effective removal of contaminants.
In multi-media filters, the layers in the media re-stratify due to density differences prior to resuming normal filtration.
Nut shell filters are commonly used as a tertiary oil removal step for treatment of produced water.
Sand filters are often used to remove fine solids following biological treatment and clarification of oil refinery wastewater.
Nalco Water Handbook, Fourth Edition (McGraw-Hill Education: New York, Chicago, San Francisco, Athens, London, Madrid, Mexico City, Milan, New Delhi, Singapore, Sydney, Toronto, 2018).