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37 ADAPTATION AND DEADAPTATION KINETICS OF ACTIVATED SLUDGE PR. Senthilnathan, Graduate Student J. J. Ganczarczyk, Professor Department of Civil Engineering University of Toronto Toronto, Ontario, M5S 1A4 INTRODUCTION The microbial populations in the activated sludge are versatile in degrading various organic priority pollutants, if adequate time for acclimation (adaptation) is given.1'2.3 The rate of biodegradation can drastically vary with the extent of adaptation. When sufficient time for adaptation cannot be provided, bioaugmentation or the addition of pre-adapted cultures to activated sludge can be implemented to increase the efficiency of biodegradation. However, in a new environment, when the favored substrates are not available, the adapted cultures may lose their ability (deadaptation) to degrade the specific chemicals to which they were adapted. Also, microorganisms engineered for bioaugmentation, depending on the methods of preservation, may undergo deadaptation during storage and transportation. In fact, an additional period of acclimation was found necessary to initiate biodegradation by some biological supplements.4 The rate of deadaptation and the length of time needed for deadaptation might be an important factor in: 1) predicting the biodegradability of organic pollutants which are discharged intermittently; 2) successful application of bioaugmentation products; and 3) determining the shelf life of such products. This study is a preliminary attempt to determine the effect of deadaptation on phenol acclimated activated sludge when subjected to a new environment with glucose as the sole carbon source. The rate of adaptation of these cultures to glucose was also determined. Phenol was selected for this study since: 1) it is a common pollutant found in many industrial wastewaters; 2) it is known to be toxic or inhibitory to microorganisms; and 3) phenol degrading biological supplements are commercially available. BACKGROUND Adaptation Adaptation or acclimation of microorganisms is a process of physiological, morphological or genetical adjustment to environmental conditions that makes the microorganisms more fit for existence under new habitat. Microbial populations acquire the ability to grow under conditions unfavorable to the original populations by making changes in the pattern of expression of their genes. Microbial adaptation to high and low temperatures, increasing and decreasing salinity, increasing and decreasing pH, ultraviolet radiation, and several toxic chemicals (including antibiotics, 2,4-D, methyl parathion, p-nitrophenol) is well known.2-5~9 Adaptation to one chemical can induce the ability to metabolize a host of other chemicals which are structurally similar.3'9 Adaptation can be induced in two ways: 1) by gradually increasing the intensity of the selection pressure; and 2) by exposing the population to the extreme conditions to allow for the emergence of the surviving organisms. The length of time required for adaptation varies with respect to the type of inoculum (seed), the amount of inoculum, nature of the test compound, physical and chemical conditions prevailing during the exposure, exposure concentration, and duration of exposure. The adaptation time required by activated sludge for degrading various priority pollutants vary from few days to 6 weeks depending on the nature of pollutant.'" Adaptation can be either phenotypic or genotypic. In phenotypic adaptation, the genetic information content of the cells is unchanged; only the degree of expression of genes is altered. Phenotypic adaptation may be common during short-term fluctuations in the environment. Genotypic adaptation 43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 301
Object Description
Purdue Identification Number | ETRIWC198837 |
Title | Adaptation and deadaptation kinetics of activated sludge |
Author |
Senthilnathan, P. R. Ganczarczyk, Jerzy J., 1928- |
Date of Original | 1988 |
Conference Title | Proceedings of the 43rd Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,39828 |
Extent of Original | p. 301-308 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
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Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 301 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | 37 ADAPTATION AND DEADAPTATION KINETICS OF ACTIVATED SLUDGE PR. Senthilnathan, Graduate Student J. J. Ganczarczyk, Professor Department of Civil Engineering University of Toronto Toronto, Ontario, M5S 1A4 INTRODUCTION The microbial populations in the activated sludge are versatile in degrading various organic priority pollutants, if adequate time for acclimation (adaptation) is given.1'2.3 The rate of biodegradation can drastically vary with the extent of adaptation. When sufficient time for adaptation cannot be provided, bioaugmentation or the addition of pre-adapted cultures to activated sludge can be implemented to increase the efficiency of biodegradation. However, in a new environment, when the favored substrates are not available, the adapted cultures may lose their ability (deadaptation) to degrade the specific chemicals to which they were adapted. Also, microorganisms engineered for bioaugmentation, depending on the methods of preservation, may undergo deadaptation during storage and transportation. In fact, an additional period of acclimation was found necessary to initiate biodegradation by some biological supplements.4 The rate of deadaptation and the length of time needed for deadaptation might be an important factor in: 1) predicting the biodegradability of organic pollutants which are discharged intermittently; 2) successful application of bioaugmentation products; and 3) determining the shelf life of such products. This study is a preliminary attempt to determine the effect of deadaptation on phenol acclimated activated sludge when subjected to a new environment with glucose as the sole carbon source. The rate of adaptation of these cultures to glucose was also determined. Phenol was selected for this study since: 1) it is a common pollutant found in many industrial wastewaters; 2) it is known to be toxic or inhibitory to microorganisms; and 3) phenol degrading biological supplements are commercially available. BACKGROUND Adaptation Adaptation or acclimation of microorganisms is a process of physiological, morphological or genetical adjustment to environmental conditions that makes the microorganisms more fit for existence under new habitat. Microbial populations acquire the ability to grow under conditions unfavorable to the original populations by making changes in the pattern of expression of their genes. Microbial adaptation to high and low temperatures, increasing and decreasing salinity, increasing and decreasing pH, ultraviolet radiation, and several toxic chemicals (including antibiotics, 2,4-D, methyl parathion, p-nitrophenol) is well known.2-5~9 Adaptation to one chemical can induce the ability to metabolize a host of other chemicals which are structurally similar.3'9 Adaptation can be induced in two ways: 1) by gradually increasing the intensity of the selection pressure; and 2) by exposing the population to the extreme conditions to allow for the emergence of the surviving organisms. The length of time required for adaptation varies with respect to the type of inoculum (seed), the amount of inoculum, nature of the test compound, physical and chemical conditions prevailing during the exposure, exposure concentration, and duration of exposure. The adaptation time required by activated sludge for degrading various priority pollutants vary from few days to 6 weeks depending on the nature of pollutant.'" Adaptation can be either phenotypic or genotypic. In phenotypic adaptation, the genetic information content of the cells is unchanged; only the degree of expression of genes is altered. Phenotypic adaptation may be common during short-term fluctuations in the environment. Genotypic adaptation 43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 301 |
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