Electromobility Values of
Particulate Matter in Domestic Wastewaters
SAMUEL D. FAUST, Associate Professor
MARTIN C. MANGER, Research Fellow
Department of Environmental Science,
College of Agriculture,
Rutgers - The State University,
New Brunswick, N. J.
Electrochemical phenomena are presumed to be involved in the removal of
particulate matter from domestic wastewaters by biological and chemical processes. Consequently, several attempts have been made to determine the electrical properties of these particles. Biltz and Krohnke (1) observed in 1904 that dispersed matter accumulated at the anode when sewage liquors were electrolyzed.
In 1931 Baley (2) found that sewage colloids migrated toward the anode (+ pole)
when the pH was 7. 0 or greater, and toward the cathode (- pole) when the pH was
6.0 or less. These observations led Baly to conclude that the esoelectric point of
fresh sewage colloids occurred at pH value of approximately 6.5. In 2934 Mills
(3), who utilized the moving boundary U-tube technique to observe the relative
electrical migration velocities of dispersed matter in sewage, concluded: a) "The
particles ofthe dispersate normally carry a negative charge;" b) "The magnitude
of this charge is greater at reactions more alkaline than normal, and less at reactions more acid;" and c) "At pH 6 the particles of the dispersate still carry a
negative charge, but between pH 6 and 2 this charge is replaced by a relatively
small positive charge."
No data have been published, therefore, that show quantitative electromobility values of particulate matter in domestic wastewater. Such information
would, however, be useful in the evaluation of the electrochemical phenomana
involved in the removal of these substances by various chemical and biological
treatment processes. This study reports on the sign of particle charge and magnitude and distribution of electromobility values of particulate matter in a typical
domestic wastewater.
EXPERIMENTAL PROCEDURES
Grab samples of a nearby domestic wastewater were collected during dry-
weather flows. These samples were settled for two hrs at 4C and filtered through
glass wool in order to obtain the supra-colloidal and colloidal fractions of particulate matter as described by Heukelekian and Balmat (4). No further separation
of these fractions was attempted.
Electromobility values were measured at 20C ±0.5 with the microelectrophoresis cell of Briggs (5) using the techniques of Black and Smith (6). Approximately bu particles were observed in any one sample by repetition ot sequences of
five mobility measurements in one direction, reversal of cell polarity, and five
mobility measurements in the opposite direction. The values of pH and specific
conductance were determined also at 20C ±0.5.
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