Wastewater treatment plants are important as normal water contains impurities that can be

harmful to humans, animals, and the environment.

Media filtration is a mechanical process used by waste water treatment plants in India. Both

chemical and physical absorption process are used here. The four crucial stages in media filtration

are straining, sedimentation, interception, and diffusion. The last stage is inertial compaction.

Application of dual media filters is a good solution for contaminated water. It is considered to be

excellent for the removal of turbidity, organic matter, and many other impurities. However,

dissolved solids are partially removed by this process.

The dual media filter technology is used in various water treatment plants. Mainly, it is because

of its effective construction and dual filtration procedure.

Water in a dual media filter passes through media with moderately smaller pores. Anthracite

exudes out the largest molecules. Next layer removes particles with the help of adhesion and

straining combination feature of sand and garnet. Filters do not block as fast as they do in a single

filtration process. It is basically due to multiple depths or filters in dual media filter process.

An automatic back washing technique is used in dual media filters that helps maintaining unit

efficiency.

Different Types of Dual Media Filters

Three, most common, types of dual media filters are mentioned here:

• Calcite Filters

Calcite is a compound that is naturally found in the environment. Therefore, it is cost effective.

Calcite filters help to enhance the pH levels in water. They also neutralize water. Straining of pipes

can be avoided because of this.

• Anthracite Filters

This filter is used with sand in dual media filters. It’s gravity is lighter than sand and this feature

makes it more suitable. Moreover, it can resists more chemicals as it has high carbon content. It

is considered as one of the best options to remove suspended solid and turbidity. In bio=film

treatment, anthracite is used as a carrier. It also helps in the growth of micro-flocks.

• Activated Charcoal Filters

Charcoal, in other words carbon, is treated with oxygen. Small pores are opened between the

carbon atoms resulting in absorption of impurities from liquid and gases.

Organic matters, chlorine, and disinfectants are removed from water with the help of activated

charcoal filters. They are also known to enhance the taste of water. Using this process before any

other filtration process such as reverse osmosis, saves oxidation.

Application of Dual Media Filters

Dual media filters are mostly applicable where water is contaminated with turbidity, iron,

suspended solids, etc. They are one of the most effective ways to remove impurities under various

conditions.

Common uses of dual media filters are in these filtration processes:

• Drinking Water Treatment

• Removes

• Pre-treatment in RO process

• Pre-treatment in desalination process

• Swimming Pool Water Treatment

• Removes

• Turbidity

Suspended solids

• Wastewater Treatment

• Removes

• Ground Water Treatment

• Removes

• Process Water Treatment

• Removes

• Used in full stream filter

• Used in side stream filter

Features of Dual Media Filters

• Simple design

• Multi-layer filters

• 20-30 micron filtration rating

• Standard and persuasive quartz sand media

• Air cleaning for high flow pressure vessel

• Low pressure drop across the vessel

• Vessels like MSRL, SS, DRP, and MSEP

• Manual, semi-automatic, and automatic features

• For safety, structural steel legs are designed which provide strong support

• Takes care of occasional fluctuations in flow rate

• Filter cycles between backwashing are long

Benefits of Dual Media Filters

Dual filters are more efficient than the normal sand media filters in attracting large amount of

particles present in water. This happens because of the many filter layers with different levels of

pores.

Another difference noted when compared with the sand media filters is that dual media filters

last longer. This is because of the complete utilization of the dual media filter bed. Some more

benefits are mentioned below:

• Removes turbidity and TSS effectively

• High quality output

• Hand holes and two elliptical manholes

• High dirt removal capacity

• Filtration rate is high

• Easy operation

• Easy to maintain

• Easy to install

• Low installation cost

• Reliable and efficient

• Low energy requirement

• Minimal start-up time

• Loss of pressure is less

• Cost effective

Dual media filters are much more efficient in removing dirt as compared to pressure filters.

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