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A Critical Review of UOD Analysis Using Respirometer Techniques EDWIN L. BARNHART, Vice President GEORGE J. KEHRBERGER, Senior Engineer Hydroscience, Inc. Leonia, New Jersey INTRODUCTION The oxygen consumption equivalent of a waste is usually expressed in terms of its Biochemical Oxygen Demand (BOD). This test is performed by mixing bacteria with the waste in a dilute solution and observing the amount of oxygen consumed during a specific time intervaL For convenience, a group of British scientists in the late nineteenth century decided to adopt the five-day value of oxygen consumption as their standard test. Their reasoning was influenced to a large degree by their belief that all streams in England reached the ocean in five days. The acceptance of the five-day value of BOD was also based on the acceptance of biological oxidation as a one-phase, first-order reaction. This manner of thinking has, until just recently, remained prevalent in pollution control analysis, despite continuous evidence that the actual reactions follow a significantly different path. Ideally, the first stage of the BOD reaction is the result of the oxidation of organics to carbon dioxide and water, while the second stage reaction involves the oxidation of ammonia to nitrate. It must be noted that the rate of reaction observed in the BOD test is a function of the measurement environment and will change with experimental conditions. Two techniques are available for measuring oxygen utilization: the dilute bottle technique, called the BOD test, and a respirometer type test, commonly called a Warburg study (1). In the bottle testj very dilute samples of the substrate are mixed with suitable bacterial seed and are incubated under stagnant conditions for five-days, or another period of interest. The DO in the bottle at the beginning and end of the experiment is noted and the difference is the BOD of the system. The principle limitations of the test result from the very dilute solution which must be studied (less than six mg/l of BOD, since any greater value would deplete the available oxygen to an unacceptable level), and the lack of mixing in the system. The measurement of oxygen consumption in a respirometer is accomplished by measuring pressure differences in the system. As oxygen from the atmosphere over the liquid passes into solution to replace the oxygen used in oxidation, the carbon dioxide produced during oxidation is adsorbed in a potassium hydroxide well, causing a measurable pressure change. Mixing, seed concentration, sample concentration and sampling interval is left to the discretion of the experimenter. This method of testing has rarely been applied outside of the research laboratory, because of the complexity of performance and data interpretation. Today, large involved computer models of the national river systems are being constructed to provide information on the steps required to achieve the desired levels -1385-
Object Description
Purdue Identification Number | ETRIWC1969097 |
Title | Critical review of UOD analysis using respirometer techniques |
Author |
Barnhart, Edwin L. Kehrberger, G. J. (George J.) |
Date of Original | 1969 |
Conference Title | Proceedings of the 24th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,16392 |
Extent of Original | p. 1385-1397 |
Series | Engineering extension series no. 135 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-05-21 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 1385 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | A Critical Review of UOD Analysis Using Respirometer Techniques EDWIN L. BARNHART, Vice President GEORGE J. KEHRBERGER, Senior Engineer Hydroscience, Inc. Leonia, New Jersey INTRODUCTION The oxygen consumption equivalent of a waste is usually expressed in terms of its Biochemical Oxygen Demand (BOD). This test is performed by mixing bacteria with the waste in a dilute solution and observing the amount of oxygen consumed during a specific time intervaL For convenience, a group of British scientists in the late nineteenth century decided to adopt the five-day value of oxygen consumption as their standard test. Their reasoning was influenced to a large degree by their belief that all streams in England reached the ocean in five days. The acceptance of the five-day value of BOD was also based on the acceptance of biological oxidation as a one-phase, first-order reaction. This manner of thinking has, until just recently, remained prevalent in pollution control analysis, despite continuous evidence that the actual reactions follow a significantly different path. Ideally, the first stage of the BOD reaction is the result of the oxidation of organics to carbon dioxide and water, while the second stage reaction involves the oxidation of ammonia to nitrate. It must be noted that the rate of reaction observed in the BOD test is a function of the measurement environment and will change with experimental conditions. Two techniques are available for measuring oxygen utilization: the dilute bottle technique, called the BOD test, and a respirometer type test, commonly called a Warburg study (1). In the bottle testj very dilute samples of the substrate are mixed with suitable bacterial seed and are incubated under stagnant conditions for five-days, or another period of interest. The DO in the bottle at the beginning and end of the experiment is noted and the difference is the BOD of the system. The principle limitations of the test result from the very dilute solution which must be studied (less than six mg/l of BOD, since any greater value would deplete the available oxygen to an unacceptable level), and the lack of mixing in the system. The measurement of oxygen consumption in a respirometer is accomplished by measuring pressure differences in the system. As oxygen from the atmosphere over the liquid passes into solution to replace the oxygen used in oxidation, the carbon dioxide produced during oxidation is adsorbed in a potassium hydroxide well, causing a measurable pressure change. Mixing, seed concentration, sample concentration and sampling interval is left to the discretion of the experimenter. This method of testing has rarely been applied outside of the research laboratory, because of the complexity of performance and data interpretation. Today, large involved computer models of the national river systems are being constructed to provide information on the steps required to achieve the desired levels -1385- |
Resolution | 300 ppi |
Color Depth | 8 bit |
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