Removal of
Organic Colloids by Microflotation
E. ALAN CASSELL,  Associate Professor
Civil Engineering Department
Clarkson College
Potsdam, New York
ALAN J. RUBIN, Assistant Professor
Civil Engineering Department
University of Cincinnati
Cincinnati, Ohio
HOWARD B. LAFEVER, Senior Student
Civil Engineering Department
EGON MATUEVIC, Professor
Department of Chemistry
Clarkson College
Potsdam, New York
INTRODUCTION
Microflotation is a foam separation process recently introduced on an experimental basis to the field of water renovation (1). This technique is suitable for
the removal of colloidal particles and has been successfully applied to the separation of bacteria and algae (2, 3, 4,  5),  and organic color'from water.
Several characteristics distinguish microflotation from conventional foam
separation techniques. Efficient separations by conventional procedures frequently
require tall reflux columns (because of wet and voluminous foam), high flow rates
of gas, and large bubbles. As in conventional foam separations, microflotation
requires the addition of a collector and a frother. However, under optimum conditions, microflotation produces a thin, relatively dry foam on which the colloids
are collected.    In addition,  very low gas flow rates of fine bubbles are required.
Two important advantages of microflotation should permit its eventual widespread adoption to engineering use as a solid-liquid separation technique. First,
high rates of solids separation are indicated by data on bacteria and materials
which cause organic color in water. Efficient removals were obtained in one to
five mins. Second, low degree of specificity is found with regard to the nature
of the dispersed substances. Various materials can be successfully removed using
similar experimental conditions. This is in contrast to conventional foam separations which tend to be specific (6, 7, 8).
Reviews of the application of foam separation to the separation of microorganisms have been presented by Rubin, et al (2) and Dobias and Vinter (9).
This paper is an attempt to elucidate the conditions controlling efficient
microflotation. Specifically, effects of pH and aluminum salts (coagulants) on
the foam separation by microflotation of several species of bacteria and materials
which cause organic color in water are outlined.
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