Separation and Materials Balance of
Solids Fractions in Sewage
J. V. HUNTER, Lecturer
H. HEUKELEKIAN, Professor and Chairman
Department of Sanitation
Rutgers, the State University
New Brunswick, New Jersey
It has been long recognized that a more complete knowledge of the organic constituents of sewage would be of considerable value both in the study
of the various biological treatment processes and in understanding the pollu-
tional characteristics of sewage. Up to 1959, however, no comprehensive
studies of the organic composition of sewage had been reported in the literature.
Most of the work reported up to this time involved either determination
of welldefined groups such as the nitrogenous compounds (2) with special reference to the amino acids (8) (7), and the volatile fatty acids (7), or of compounds of particular interest, such as Indole and Skatole (6) and more recently,
the presence of surface active agents (4). Two comprehensive analyses of
sewage were reported in 1959, giving the organic constituents of an English
domestic sewage (5), and the mineral and organic constituents of the particular matter in an American domestic sewage (3). Both outlined methods for
the separation of sewage physically into three particulate and one soluble
fraction, involving settling, centrification, and filtration. Unfortunately, in
neither case was there any estimation as to the nature and the extent of the
losses encountered during the processing of the sewage, except for losses involved in the concentration of the soluble fraction (5), and such information
is necessary if the results obtained by such comprehensive analyses are to be
validly interpreted.
It is the purpose of these authors to extend the organic analyses of the
particulate fractions (31, to include the soluble material, and to study simultaneously the nature and extent of the losses involved. The estimation of
these losses and the information obtained on the general organic nature of the
sewages studied are the subject of this report.
SAMPLING AND PROCESSING
The sampling procedure was arranged so that the material collected for
analysis was as representative as possible of the sewage organics. To this end,
24-hr automatically composited samples were obtained from a predominantly
domestic sewage source. Samples were obtained over two periods, the first
representing the winter and spring of 1959; the second the fall and winter o f
1959-60. Sampling was so arranged that each day of the week received equal
representation. The adequacy of the sampling procedure is apparent from examination of Table I. The similarity of characteristics revealed by examination of the composite sewages before processing reflects not only the fact that
the sewage utilized over both periods were notably similar in nature, but also
that the sampling procedure used was capable of revealing this similarity.
The particulate sewage material was removed and dried according to the
method of Heukelekian and Balmat (3).   These particulates are divided into
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