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Pakistan Journal of Biological Sciences
Year: 2006  |  Volume: 9  |  Issue: 1  |  Page No.: 119 - 122

Effect of Stocking Density on Vermistabilization of Waste Activated Sludge

K. Naddafi, M. Zamanzadeh, G. A. Omrani, A. R. Mesdaghinia, A. A. Azimi and E. Mobedi    

Abstract: Sludge disposal has always represented a substantial portion of the costs associated with sewage treatment. In addition, the skilled personnel are not easily available to assure sound maintenance and operation of the conventional sludge treatment systems such as aerobic and anaerobic digestion; therefore, it is necessary to employ low cost and low technology practices in sludge management. Using earthworms in stabilization of sewage sludge, which has been approved by considerable work, can be a good alterative. This research was conducted to study the effect of stocking densities on sludge stabilization and sludge characteristics. In this regard, 40, 80 and 120 g earthworm wet weight were introduced into each of the plastic bins sizing 36 x 25 x 20 cm (length x width x height) to provide the desired stocking densities of 0.45, 0.90 and 1.35 kg worms m-2. Each bin received 2 kg waste activated sludge. The pilot-scale study showed that the highest VS (24.3%) reduction occurred in a stocking density of 1.35 kg Worm m-2 in which TKN and organic to mineral P ratio reduced 58.3 and 93.5 %, respectively.

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