What Is Rapid Sand Filter?

Oct. 25, 2010 - PRLog -- From SHubham : www.shubhamindia.com

Rapid Sand Filter are usually built open with the water passing down the filter but by gravity. It has a filter rate of 4 – 8 m3/m2/hr. The tank is made of concrete with a depth of 3.0 to 3.5m. Coarse sand of size 0.4 to 1.5mm is used as the filter medium.
Rapid Sand Filter use relatively coarse sand and other granular media to remove particles and impurities that have been trapped in a floc through the use of flocculation chemicals--typically salts of aluminium or iron. Water and flocs flows through the filter medium under gravity or under pumped pressure and the flocculated material is trapped in the sand matrix.
Mixing, flocculation and sedimentation processes are typical treatment stages that precede filtration. Chemical additives, such as coagulants, are often used in conjunction with the filtration system.

rapid gravity sand filter are typically designed as part of multi-stage treatment systems used by large municipalities. These systems are complex and expensive to operate and maintain, and therefore less suitable for small communities and developing nations.
Advantages
Much higher flow rate than a slow sand filter; about 150 to 200 million gallons of water per acre per day
Requires relatively small land area
Less sensitive to changes in raw water quality, e.g. turbidity
Disadvantages
Requires greater maintenance than a slow sand filter. For this reason, it is not usually classed as an "appropriate technology," as the term is applied in less-developed countries.
Generally ineffective against taste and odour problems.
Produces large volumes of sludge for disposal.
Requires on-going investment in costly flocculation reagents.

For More Details : www.shubhamindia.com

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