A Procedure for Continuous
Nitrifications Corrections During Warburg
Respirometer Studies
JAMES M. SYMONS, Research Public Health Engineer
Engineering Section
Division of Water Supply and Pollution Control
Robert A. Taft Sanitary Engineering Center
Cincinnati, Ohio
ROGER LABONTE, Assistant Professor of Sanitary Engineering
Ecole Polytechnique
Montreal,  Canada
The Warburg Respirometer, a constant-volume manometer, permits the direct and continuous measurement of the oxygen utilization of an organic solution
-- microorganism mixture in a closed system under conditions of constant temperature and agitation (1,2,3,4). One of the common uses of the Warburg
Respirometer is for biodegradation studies. In general, these studies involve the
mixing of a microorganism seed of specified origin with an organic solution in a
Warburg Respirometer flask and measuring the rate and extent of oxygen uptake
over a desired time period. Often, this oxygen uptake is compared with the oxygen uptake of a similar microorganism seed suspended in water. The rate of oxygen uptake, time lag to the beginning of metabolism, and the extent of total
oxygen uptake of the fed sample, as compared to the control (unfed) sample, are
used to evaluate the ease and extent of biodegradation of the organic matter under study (5,6,7,8). There are several problems associated with this technique;
one of the major ones is the inability of the test to distinguish between oxygen
taken up for the oxidation of organic matter to carbon dioxide and water and oxygen taken up for the oxidation of reduced nitrogen, i.e., nitrification.
NITRIFICATION PROBLEM
The nitrification reactions, as carried out by the autotrophic nitrifying bacteria, can be summarized by use of the following three equations. The reacting
weights are given below each equation as well as oxygen taken up per unit of
nitrogen converted.
NOs + 2H+ + H20 (1)
+
wu.    ,    i_1/9   On
•»-
14 as N          48
1                3.43
\l/~>        .     i /n    /~i                                                    ».
"«2 T ■"* * v2
.^-
14 as N         16
1                1.14
- 498 -
N03 (2)