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The Role of Nitrate Nitrogen in Bio-Oxidation E. D. SCHROEDER, Assistant Professor Civil Engineering Department University of California Davis, California A. W. BUSCH, Professor Environmental Engineering Department Rice University Houston, Texas INTRODUCTION Bacterial reduction of nitrate has been a subject of importance to engineers since the early part of the century. Reduction of nitrate ion has been known to be related to substrate oxidation, and nitrate has been referred to as a "chemical source of oxygen." Nitrate has been added to oxygen-starved treatment systems and streams with the purpose of keeping them aerobic. Results of nitrate addition have been unpredictable and generally less than expected. The objectives of this paper are the explanation of reported results and the discussion of the role of nitrate metabolism in bio-oxidation. INORGANIC NITRATE METABOLISM Nitrate reduction by micro-organisms may be divided into two general categories, assimilatory and dissimilatory (1). The term, denitrification, has often been used to describe the nitrate reduction process, however, the term will be used here only in cases where the gaseous end products NO, N2O and N2 are formed. Assimilatory nitrate reduction occurs in bacterial systems in which nitrate is a source of nitrogen for synthesis. Micro-organisms in general, and also many higher plants, have the ability to reduce nitrate (N+5) to ammonia (N-3). Nitrogen must be in the ammonia state for incorporation into cellular material (2,3). Thus, microbial systems would be expected to utilize ammonia nitrogen preferentially over more oxidized forms such as nitrite or nitrate. Inhibition of nitrate reduction by ammonia has been demonstrated with several microorganisms (2,4, 5). Examples have also been found in which nitrate assimilation was not inhibited by ammonia, however (2,6). Dissimilatory nitrate reduction has been defined as reduction of nitrate in which nitrate serves as the essential hydrogen acceptor which enables an organism to grow(l). A slightly broader definition will be used here which defines dissimilatory nitrate reduction as occurring where nitrate serves as the terminal exogenous hydrogen acceptor for the oxidation of a substrate. The difference between the two definitions may be explained by a brief discussion of bacterial metabolism. Terminal oxidation of organic compounds by bacteria centers around the Krebs cycle, a bio-chemical reaction system with carbon dioxide and reduced pyrimidine nucleotides as primary products. A schematic diagram of the Krebs - 263 -
Object Description
Purdue Identification Number | ETRIWC196724 |
Title | Role of nitrate nitrogen in bio-oxidation |
Author |
Schroeder, Edward D. Busch, Arthur Winston, 1926- |
Date of Original | 1967 |
Conference Title | Proceedings of the 22nd Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,14179 |
Extent of Original | p. 263-278 |
Series |
Engineering extension series no. 129 Engineering bulletin v. 52, no. 3 |
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 | 2009-05-20 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 263 |
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 | The Role of Nitrate Nitrogen in Bio-Oxidation E. D. SCHROEDER, Assistant Professor Civil Engineering Department University of California Davis, California A. W. BUSCH, Professor Environmental Engineering Department Rice University Houston, Texas INTRODUCTION Bacterial reduction of nitrate has been a subject of importance to engineers since the early part of the century. Reduction of nitrate ion has been known to be related to substrate oxidation, and nitrate has been referred to as a "chemical source of oxygen." Nitrate has been added to oxygen-starved treatment systems and streams with the purpose of keeping them aerobic. Results of nitrate addition have been unpredictable and generally less than expected. The objectives of this paper are the explanation of reported results and the discussion of the role of nitrate metabolism in bio-oxidation. INORGANIC NITRATE METABOLISM Nitrate reduction by micro-organisms may be divided into two general categories, assimilatory and dissimilatory (1). The term, denitrification, has often been used to describe the nitrate reduction process, however, the term will be used here only in cases where the gaseous end products NO, N2O and N2 are formed. Assimilatory nitrate reduction occurs in bacterial systems in which nitrate is a source of nitrogen for synthesis. Micro-organisms in general, and also many higher plants, have the ability to reduce nitrate (N+5) to ammonia (N-3). Nitrogen must be in the ammonia state for incorporation into cellular material (2,3). Thus, microbial systems would be expected to utilize ammonia nitrogen preferentially over more oxidized forms such as nitrite or nitrate. Inhibition of nitrate reduction by ammonia has been demonstrated with several microorganisms (2,4, 5). Examples have also been found in which nitrate assimilation was not inhibited by ammonia, however (2,6). Dissimilatory nitrate reduction has been defined as reduction of nitrate in which nitrate serves as the essential hydrogen acceptor which enables an organism to grow(l). A slightly broader definition will be used here which defines dissimilatory nitrate reduction as occurring where nitrate serves as the terminal exogenous hydrogen acceptor for the oxidation of a substrate. The difference between the two definitions may be explained by a brief discussion of bacterial metabolism. Terminal oxidation of organic compounds by bacteria centers around the Krebs cycle, a bio-chemical reaction system with carbon dioxide and reduced pyrimidine nucleotides as primary products. A schematic diagram of the Krebs - 263 - |
Resolution | 300 ppi |
Color Depth | 8 bit |
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