70
SEWAGE TREATMENT AND INDUSTRIAL WASTES
Don E. Bloodgood
Associate Professor of Sanitary Engineering
Purdue University
You who are in attendance at this conference have heard papers
and discussions on the utilization of industrial wastes. If industrial
wastes are discharged into a sewer system that takes them to a sewage
treatment plant, they will have some effect upon the operation of
that plant. I would like to impress upon you the need for taking
steps in the utilization of industrial wastes which will materially
assist in the more satisfactory operation of the sewage treatment
plants in cities where industries are located.
The capacity of a sewage treatment works is often measured
in terms of the number of persons that it can serve; thus, you can
see the value for the rating of the waste from an industrial plant
in terms of population equivalent. A manufacturing plant may
employ one hundred people yet the waste material discharged to the
sewer may be equivalent in strength and perhaps, also in volume, to
the waste that would be expected from 10,000 persons. If such a
manufacturing plant were located in a city whose population was
2,000, a plant designed to handle the waste from the city would be
entirely too small, in fact, it might be % as large as would be needed.
Though the cost for sewage disposal is relatively small, multiplying
it by five times increases the cost per person to somewhat of a burden.
This situation is most often apparent in cities of smaller size, though
not infrequently the large industries are in the large cities and conse¬
quently the effects of industrial wastes on their sewage treatment
plants are also serious.
If industrial wastes caused no difficulty in sewage treatment
other than making necessary a larger treatment works, the problem
might be considered relatively simple, but most industrial wastes
interfere with the proper functioning of a particular part of the treat¬
ment works.
The effect of industrial wastes which have not been given pre-
treatment before discharge into the sewerage system have been ob¬
served, and I will attempt to illustrate these effects upon the several
parts of a sewage treatment plant.
Grit Chambers
The flume water from a sugar beet factory contains great quanti¬
ties of inert solids washed from the sugar beets before they are pro-