Tertiary Treatment of Secondary
Industrial Effluents by Activated Carbon
NED K. BURLESON, Research Engineer
Center for Research in Water Resources
W. WESLEY ECKENFELDER, JR., Professor
JOSEPH F. MALINA, JR., Associate Professor
Department of Civil Engineering
University of Texas
Austin, Texas
INTRODUCTION
The increasing water needs for industrial and municipal use combined with
the growing demand for more aesthetic waters for recreational purposes have
made the reduction of organic pollutants imposed upon our natural waters a matter
of national concern. The rapidly increasing number of pollution sources along our
waterways has moved regulatory bodies to place more stringent restrictions on the
qualities of wastewater discharges returned to the natural system. These restrictions and the rising cost of industrial water have caused an emphasis to be placed
on the development of wastewater treatment systems producing a high quality
effluent.
Many studies have been directed to a solution to this problem. Tertiary
treatment of biologically treated wastewater is being considered as a practical solution. Adsorption of biologically resistant materials from secondary effluents is
being investigated and of the adsorbent materials thus far evaluated, activated
carbon has shown the most promise in this application.
Activated carbon is a general term applied to carbonaceous material with
certain adsorptive and catalytic properties. Activated carbon is generally manufactured from raw materials such as wood, coal, lignite, sugar, vegetation, petroleum hydrocarbons, and other organic materials. These raw materials are
charred in the presence of catalytic agents such as magnesium chloride or zinc
chloride, then activated by treatment with oxidizing gases, which dissipate the
more readily oxidizible portions of the char. The resulting carbon is highly porous containing internal surface areas as great as 2500 square meters per gram.
Variations in the raw material, temperatures, additives and procedures used, result in activated carbons with widely diverse adsorptive properties (1).
The treatment of water and wastewaters followed two basic schemes. Some
applications include the addition of powdered activated carbon to raw water with
subsequent separation of the carbon by coagulation and settling. The passage of
raw water through a bed of activated carbon in a downward direction or in a
countercurrent fashion has also been applied.
The batch mixing scheme which has been primarily used in municipal water
treatment for removal of tastes and odors, has the advantage of allowing a very
small activated carbon particle to be used, which results in nigh adsorption rates
and allows a closer control of the effluent quality.   The practice is not favored
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