Nitrogen Compounds in Sewage
ARTHUR M. HANSON, Senior Sanitary Chemist
THOMAS F. FLYNN, JR., Sanitary Chemist
Division of Laboratories and Research
New York State Department of Health
Albany, New York
Little is known about specific nitrogen compounds in sewage. That fraction
which volatilizes on boiling at pH 7.4 is reported as ammonia nitrogen while a
number of unspecified nitrogen compounds are determined by the Kjeldahl procedure and are reported as "organic nitrogen." Prior to the eighth edition of Standard Methods of Water Analysis, distillation of ammonia was carried out by making
the sewage alkaline with sodium carbonate. Nichols and Foote (1) found that
sodium carbonate was not an effective buffer, and that a pH of 7.4 had to be
maintained to recover ammonia nitrogen quantitatively from ammonium salts.
The phosphate buffer, however, did not prevent 5. 8 per cent of urea nitrogen and
two per cent peptone nitrogen from being recovered as ammonia-N.
Morgan, Lackey, and Gilcreas (2) demonstrated that mercuric salts were
superior to copper for catalyzing the oxidation of organic matter, and that carbohydrates, lipids, and nitrates in amounts occurring in sewage did not interfere with
rutrogen recovery in the standard procedure for organic nitrogen. However, the
Kjeldahl procedure, without modification, does not quantitatively determine such
refractories as nitro, nitroso, or azo compounds, and compounds containing ring
nitrogen.
Understanding the limitations of existing analytical methods is the first step
toward their improvement. Because of recent developments in analytical biochemistry, such as more sensitive chromogenic reagents, sharper separations, and
improved concentration technics, analytical operations have been extended from
the milligram to the microgram range. Some ofthe more complex nitrogen compounds of sewage, formerly considered together as organic nitrogen, can now be
differentiated and determined in a more specific manner.
This paper presents the results of an investigation of a nitrogen balance at
various sewage plants in the Albany, New York area. Nitrogen balance means
that the sum of individual nitrogen determinations was compared with the values
obtained for "total" or Kjeldahl nitrogen.
In 1927 Neave and Buswell (3) reported three analyses of sewage nitrogen. In
each of these the sum of the urea and ammonia nitrogen was approximately 90
per cent of the total.
Heukelekian and Balmat (4) separated sewage solids into three fractions:
settleable, supracolloidal, and colloidal. Organic nitrogenous material was hydrolyzed, and the amino acids were determined by unspecified paper chromatographic, and spectrophotometric methods. The amino acids accounted for 65 to
81 per cent of the total nitrogenous matter in the different fractions.
Sastry, Subrahmanyam, and Pillai (5) evaporated sewage to dryness at not
over 60 C. The drieci solids were desalted and amino acids were separated by
circular paper chromatography. Proteins or total amino acids were determined
in the same way after acid hydrolysis. Sewage samples collected at the Institute
of Science contained 0.36 to 1.01 mg of free amino acids and 65 to 91.3 mg of
total amino acids per gm of solids.    Samples taken at the outskirts of Bangalore
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