Water Treatment > Quality Water Solutions > Coagulation Control > Streaming Current

Streaming current detectors monitor charge on-line. They detect changes in coagulant demand and either adjust dosage automatically or call for manual adjustment. On-line charge analyzers are especially important in reacting to the many compounds that cause coagulants to fluctuate but do not appear as visible turbidity or color.

These detectors receive raw-water samples just after coagulant addition (and other treatment chemicals as needed). Visible floc need not be present in the sample; only the charge environment of the particle or colloid is important, not size. The device shears the floc apart with pistons and uses precious-metal electrodes to look at the minute changes in voltage imparted to the contaminant by the coagulant.

The sample point is critical. It must be far enough from the addition point so the coagulant has enough time to neutralize the charge present. But if it is too far from the addition point, too much time will go by and large floc will have formed. The shear forces measured will then include those associated with the contaminants and those needed to break the larger floc apart. Each site has a unique set point control, so it is best to experiment with the sample point before installing these detectors permanently.