CCA 3100
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1.0 COAGULANT CHARGE ANALYSIS
1.1 INTRODUCTION
The Coagulant Charge Analyzer (CCA) can provide valuable data concerning charge demand
and coagulation for water treatment systems. The CCA’s output is the
STREAMING
CURRENT VALUE (SCV)
, a term which is commonly interchanged with “charge” or
“charge measurement.” A voltage and current is generated by electrically charged particles in
the sample that are momentarily attached to the cylinder walls within the probe. A
reciprocating piston causes fluid motion, which shears the loosely bound counter-ions away
from the particles attached to the cylinder walls. Electrodes in the cylinder measure this current
generated by the sheared counter-ions. The signal is electronically processed and the output is
the SCV.
The loosely bound counter-ions, mentioned above, are a component of the “double layer.” This
concept is described in Section 1.3. Both streaming current and zeta potential are based upon
the double layer principle. Therefore, the streaming current value produced by the CCA is
comparable to the well known zeta potential.
1.2 BACKGROUND
As originally developed, the streaming potential measurement utilized a capillary passage or
porous plug of the material of concern, through which the bulk fluid can be forced by an
applied pressure. Counter-ions in the diffuse layer surrounding the material then migrate with
the fluid, creating an electrical potential or current, either of which can be measured. If the
current is measured, it is termed the “streaming current.” The CCA 3100 measures the
streaming current without the need for a capillary passage or porous plug. Rather, the
laboratory unit employs a piston and probe assembly, which is completely described in the
following sections.
Summary of Contents for CCA3100
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