Design of Settling Units for Removal
of Inert Suspended Solids
r. w. simpson and william garlow
Chief Sanitary Engineer, Sanitary Engineer
Gilbert Associates, Inc.
Reading, Pennsylvania
Many industries throughout the country have been, or will be faced
with construction of industrial waste treatment facilities, for the removal
of inert solids from waste discharges. Industry, for the most part, has
looked upon construction of waste treatment plants with misgivings,
expecting costly construction and operating charges, which would
increase production costs. Since many benefits may result from intelligent design and construction of sedimentation basins for removal of
inert suspended solids, the cost is not always a liability.
According to a survey of industrial waste treatment made by Industry and Power (1), 45 of the 48 states have laws or a program for
regulating stream pollution. Of the 45 states, 11 arbitrarily require
primary treatment; 18 states are presently in the process of classifying
streams, for the development of standards. Action by the U. S. Public
Health Service, in studying drainage basins and providing financial
help to state authorities, has prompted state action. The time will come
when all industry must face the reality of waste treatment.
It is difficult for management in many industrial plants to realize
that inert solids, which have no detrimental bacterial or oxygen absorbing effect, are classified as pollutants; however, such materials may
cause silt or sludge deposits, or discolor the streams into which they
are discharged.
Without prompting by state authorities, there are some plants which
have constructed treatment units, in order to recover water for reuse
in the plant.The reuse of water may pay dividends to management in
many ways.
First of all, it is not always possible to obtain the full supply of
raw water needed by industry. The average steel mill requires approximately 65,000 gallons per ton of steel produced and purchased water
is expensive. Surface water also usually requires treatment. Ground
water may be corrosive, scale forming, or may contain undesirable
metallic ions.   A good supply of ground water is becoming increas-
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