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Hendricks, D.(2006). Water treatment unit processes: physical and chemical. Boca Raton, Florida: CRC Press. Available from <http://books.google.com/books>. Accessed 2009 February 25.
Expansion of Granular Water Filters During Backwash
Granular media filtration is a crucial unit operation in water treatment plants because of its high effluent quality standards. This paper studied the mathematical models for graded filter media with uniform and irregular sieve diameters. It points out that an increase in flow rate causes the bed to expand and accommodate the increased flow while maintaining the same pressure drop. It has been found that the log-log plot of the backwash velocity against bed porosity is linear for a fluidized bed of uniform grain size. Once the porosity of the media is known, the expanded bed height can be calculated with the formula given in the paper. From the paper, it reconfirmed that sand media with a size of 0.52 mm and uniformity coefficient of 1.43 results an effective backwashing at an expansion of 50% at 2.75 cm/s backwash velocity.
Akkoyunlu, A. (2003). "Expansion of Granular Water Filters During Backwash."Environmental Engineering Science. 20(6): 655-665, 2003. Available from <http://www.liebertonline.com/doi/pdf/10.1089/109287503770736168>. Accessed 2009 February 27.