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SPECIAL PUBLICATION SJ2008-SP11 - page 18 / 48





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Literature Review & Summary Report Design Basis Memorandum

BCI Project No. 19-15089 September 2007

St. Johns River Water Management District Contract # SK940AA

Page 10

centrate (liquid phase) can be achieved on almost any type of sludge by expert operation of quality equipment.

Centrifuge dewatering units (Figure 5) are available in capacities of approximately 800 gallons per minute of a pre-thickened sludge.

Figure 5 Solid Bowl Centrifuge

2.3.2 Equipment Type – Hydrocyclone

A hydrocyclone (Figure 6) is a high-throughput, particle-size classifier that can accurately separate sediments into coarse and fine-grained portions. The typical hydrocyclone is a cone-shaped vessel with a cylindrical section containing a tangential feed entry port and axial overflow port on top and an open apex at the bottom (the underflow). A slurry of the particles to be separated enters at high velocity and pressure through the feed port and swirls downward toward the apex. Near the apex, the flow reverses into an upward direction and leaves the hydrocyclone through the overflow. Coarse particles settle rapidly toward the walls and exit at the apex through a nozzle. Fine particles are carried with the fluid flow to the axial overflow port.

Hydrocyclones are best suited for removing sand particles greater than 150 mesh. In this application, cyclones are used to remove dredge over-cut from the sediment prior to dewatering. Sand is discharged from the cyclone at around 65 % solids and is suitable for immediate reuse.

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