The Effect of Nitrogen Deficiency on the
Behavior of the Complete-Mixing
Activated Sludge Process
M. HAMDY BECHIR, Lecturer
JAMES M. SYMONS, Assistant Professor of Sanitary Engineering
Civil Engineering Department
Massachusetts Institute of Technology
Cambridge, Massachusetts
INTRODUCTION
The process of biological removal of pollution from waste waters is accomplished primarily by bacteria which use the organic matter as a source of nutrition. Pollutants are often organic carbon which must be oxidized or removed
through a synthesis reaction to eliminate their harmful effects on tne receiving
body of water. The bacteria, in order to keep living, have to reproduce or synthesize new cells and increase both in mass and in number. The bacteria in pursuing their natural course of life use the organic carbon available in the waste for
energy and new cells, and since the waste is the bacterial food it has to be balanced nutritionally if unhindered growth is to be obtained. The general equation
for organic carbon removal (as represented by acetic acid) by bacteria is:
5C2H402   +  4.5 02   +  Nitrogen Source—1> 5OO2 + 6- 5 H20 + C5H7O2N   (1)
C5H7O2N is one chemical formulation for activated sludge (1). This shows that
the nitrogen content of the bacterial masses in an activated sludge amounts to
more than 12 per cent. Nitrogen is a basic element in the protein structure of all
living matter and the protein in turn is of vital importance in the maintenance of
the structural and functional integrity of all biological forms.
Domestic sewage contains all the essential elements needed by the bacteria
and actually contains an abundance of nitrogen. On the other hand, a great variety of industrial wastes are totally void of nitrogen or contain little nitrogen relative to their organic carbon content. If these wastes are to be treated biologically,
then different amounts of nitrogen will have to be supplied artificially. A Knowledge of the exact amount and form of nitrogen which must be added to a biological system treating these wastes is a primary factor and needs to be completely
understood if an economical means of treatment is to be designed.
If the receiving body of water can, withstand and safely assimilate a certain
quantity of organic matter, because of the flow and natural purification processes,
it may be advisable to treat the waste to the extent that the effluent would contain
the above mentioned organic load. Higher degrees of treatment would serve no
purpose, especially if the cost became exceedingly expensive.
LITERATURE REVIEW AND THEORETICAL CONSIDERATIONS
Need for Nitrogen
Researchers,   realizing the importance of the nitrogen role in the synthesis
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