High Speed Dewatering of Ultra-Fine Sediments
Type:
Presented during:
WODCON XX: "The Art of Dredging" - 2013, Brussels, Belgium
Authors:
Hodges M, Shobrook C
Abstract: A historic bottleneck for the dredging industry has been high speed dewatering of fine grained sediment, such as clays, silts, and organics. The use of clarifiers and belt presses or other batch treatments typically achieves a 1:3 ratio of dredging time to dewatering time for ultra-fine material. The premise of the technology behind the Rapid Dewatering System (RDS) is to dewater dredged material down to 0.0007 micron in real time, keeping a 1:1 pace with any dredge flow rate. The primary unit of the RDS, the AquaScreen, was introduced commercially by Genesis Water in 2003, and the secondary dewatering unit, the TerraCore, was introduced commercially in 2011.
The RDS uses a patented dispersion system to achieve continuous, instant removal of the free water phase from flocculated sediment going over the AquaScreen. Relieved of its hydraulic load, the flocculated mass on the AquaScreen is gravity fed to the TerraCore units, where secondary, or capillary, dewatering occurs. The resulting cake removed from the TerraCores is stackable and ready for trucking or other types of transport. The clear water discharge from the system is typically <10-20ppm TSS. Each AquaScreen is paired with several TerraCores to achieve a continuous dewatering operation for flow rates up to 9,500 l/min (2,500gpm). An additional AquaScreen and TerraCore train doubles capacity, due to the modular design of the system.
The RDS process begins with delivery of slurry from a hydraulic dredge to an innovative coarse debris screening unit, followed by sand separation. The remaining fine slurry is flocculated with polymer and pumped to the AquaScreen.
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Keywords: Dewatering, flocculation, hydraulic, sediment