The media filtration technology is primarily implemented for the removal of suspended impurities, light colour and odour to provide limited polishing to water and wastewater. The media used are mainly sand, anthracite and activated carbon. They are used in a steel pressurized vessel. Water or wastewater is passed through the bed in order to remove these from the water. Basic filtration takes place by means of sieving, adhesion etc.

Types of Products

¤ Sand Filter
In sand filters either single or dual grade sand is filled up in a pressurized vessel. It is equipped with inlet distributor internally and a bottom collecting system. Externally, it is fitted with isolation valves and frontal pipe work. Under the sand bed, gravels and pebbles of uniform size are provided as the bottom layer. It's main function is to support the sand bed. It is used primarily for removing the suspended impurities from the water source. When water having suspended impurities is passed through the sand bed the suspended impurities get trapped within the sand media. Finally the clear water comes out as the product. Backwash of the filter is needed to remove these entrapped impurities from the filter as it reaches to its maximum limits. This limit is governed by differential pressure across the filter.

¤ Dual Media Filter
Dual media filter comprises off sand as filtering media and anthracite as polishing media. It is internally equipped with inlet distributor and a bottom collecting system. Externally, it is fitted with isolation valves and frontal pipe work. Sand removes the suspended particles while anthracite is used for removing the odor and colour to make the water good for a number of applications. Gravels and Pebbles are used to provide support to both the media. Once the solids like suspended solids are accumulated, the filter needs to be backwashed. Prior to the backwash, air scouring is also to be done for loosening of dirt and suspended solids. Limit for the backwash in these filers is governed by differential pressure across the filter.

¤ Carbon Filters
Carbon Filters use a specific grade of carbon as media. It is mainly used for polishing applications, such as removal of the colour and odor. It is externally equipped with frontal pipe work and isolation valves. Internally it is fitted with inlet distributor and a bottom collecting system. Pebbles and gravels are used as support media. At regular intervals, backwash of this filter is needed for the removal of accumulated suspended solids. The collection of such particles over carbon media will reduce the adsorption capacity of carbon. Since the main application is to remove the colour and odour, a sand filter is normally required as pretreatment to this filter in order to avoid the accumulation of suspended particles over the carbon.

¤ Auto Valveless Gravity Filter (AVGF)
Auto valveless gravity filter is a special type of filter, which uses sand as filtering media. It works on the principal of gravity filtration without the help of any valve, rate controllers, gauges, pilot mechanisms and air compressors. It consists of two compartments. One is filtering section and other is wash water storage compartment. In normal filtering operation, water gets filtered while traveling across the sand bed. The suspended solids gets accumulated in the filter bed during normal operation, and differential pressure start increasing which causes the water level to rise in the backwash pipe. As the level of water reaches the top of the loop, siphon action start and backwash begins. From the storage compartment Wash water flows through the sand bed, and is discharged through the back wash pipe. A siphon breaker ends the wash cycle. Primary applications of these filters include raw water clarification, site stream filtration of cooling tower etc i.e. mainly for low turbidity applications.

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