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5 PRINCIPLE OF OPERATION
5.1 Description of Operation
The STORM™ Settling Rate Monitor is a stand‐alone Flocculant and Coagulant dosing control
system for use in Thickener applications. The device measures the settling time of Thickener
feed samples withdrawn from the Thickener centre-well.
A sample is drawn from the Thickener centre-well into the Settling Cylinder. When the Settling
Cylinder is full, the flocculated particles will start to settle, passing the optical sensor.
5.2 Settling Rate – Flocculant Dose Control
Turbidity monitoring is used to determine the settlement rate. The settling rate is used to
control Flocculant addition. When the flocculated material is draw into the Settling Cylinder it
will begin to settle, with an interface between the flocculated solids and the clear supernatant.
When this interface passes the optical sensor, the time is recorded. Should the sample settle
too quickly, the Flocculant dose rate will be reduced. If the sample settles too slowly, the
Flocculant dose rate will be increased.
5.3 Supernatant Turbidity – Coagulant Dose Control
The final supernatant turbidity can be used to control Coagulant addition. When all the
particles have settled, the supernatant turbidity is measured. This reading controls the
Coagulant dose rate. If the residual turbidity is too high, the Coagulant dose rate will be
increased. If the residual turbidity is low, the Coagulant dose rate will be decreased.
5.4 Sampling Sequence
Air pressure is directed to a venturi vacuum generator to draw the
centre-well sample into the Settling Cylinder. Conductivity level sensors
in the Settling Cylinder stop the sample when the cylinder is full.
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