Mixed Media Filtration System – When It Is Used
Ensuring a clean and safe water supply is one of the greatest challenges faced today. Providing potable drinking water to residents or clean water for industrial and commercial use is a critical process. There are 100’s of contaminants that can pollute water sources, even tap water. These impurities can range from naturally occurring to man-made and include bacteria, viruses, mold, metals, volatile organic compounds (VOC), pesticides, and other chemicals. Drinking such water can cause vomiting and diarrhea or even serious health risks as well as affect the taste and smell of water and increase maintenance costs. Using impure water for industrial purposes can cause equipment failure and increased maintenance costs.
Water treatment can help remove pollutants from the water, but with so many different technologies, it can be overwhelming to choose the right water filter.
Choosing a Filter
When choosing the right water filter, there are many factors to consider, the maximum required flow rate, nature of suspended solids, the required quality of treated water, price range, and lifespan of the filter. While there are many different methods for water filtration, the best and most commonly used is a mixed media filtration system.
A mixed-media filtration system consists of three layers of granular media each progressively sized in coarseness and layer depth. The coarsest material lies at the bottom while the finer material sits at the top. Typically the three layers are garnet, sand, and anthracite and used to reduce the SDI (Silt Density Index) and TSS (Total Suspended Solids) of water. Suspended solid contains small particles like silt, clay, organic matter, algae, and microorganisms.
Anthracite is at the top while the Garnet layer is at the bottom and when the water passes through this filtration system the larger contaminants are trapped in the first or top layer with smaller contaminants catching in the lower layers. This results in highly efficient filtering as removal of contaminants takes place throughout the entire bed. A well-operated mixed media filter can remove particulates as small as 20 microns and using a coagulant can remove particulates as small as 10 microns.
When is Mixed Media Filtration Used?
Mixed media filtration systems are used for the pretreatment process for reverse osmosis systems helping guarantee a long life of the membrane elements. Mixed media filters can be cleaned themselves in a process known as backwashing. This system is used where there are a large number of contaminants, reducing the need for replacement filter cartridges and operator efforts. In backwashing water flows in the opposite direction, expelling the collected filtered particles and discarding them through the drain filter thus restoring and extending the filters’ performance. However, it is important to note that backwashing should be performed when:
- Turbidity of the filtered water is more than 10%,
- The pressure gauge of filter reads more than 10psi and
- Water flow is remarkably slow.
For more information on how mixed media filtration systems work, please reach out to us.
