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Dynamics of Nitrification in the Activated Sludge Process RICHARD A. PODUSKA, Environmental Engineer Tennessee Eastman Company Kingsport, Tennessee 37662 JOHN F. ANDREWS, Professor Civil and Environmental Engineering University of Houston Houston. Texas 77004 INTRODUCTION Renewed interest in the problems created by the discharge of nitrogen compounds to receiving waters has focused attention on the form and concentration of nitrogen in wastewater treatment plant effluents. Most wastewater treatment plants are designed, operated and evaluated based on the reduction of carbonaceous 5-day biochemical oxygen demand (BOD) rather than on the total BOD of the effluent (carbonaceous and nitrogenous). As a result, ammonium is the primary form of nitrogen in most wastewater treatment plant effluents. Since ammonium may be biologically oxidized to nitrate in a receiving water, the nitrogenous oxygen demand can represent a major portion of the total oxygen demand for a treatment plant effluent. Assuming a theoretical oxygen requirement for nitrification of 4.5 mg oxygen per mg ammonium nitrogen oxidized to nitrate, an effluent with 20 mg NH+4-N per liter has a nitrogenous oxygen demand (NOD) of 90 mg/1. This is considerably greater than that contributed by the ultimate carbonaceous oxygen demand of normal domestic biological treatment plant effluents (20-40 mg/1). The conversion of ammonium to nitrate within a biological treatment plant would represent a significant improvement in effluent quality through a reduced ultimate BOD. Additionally, the oxidation of ammonium to nitrate in a treatment plant offers the advantage of reducing the amount of chlorine required to obtain effective disinfection. This results from the decreased formation of chloramines which are less effective disinfectants than free residual chlorine. Nitrification can be accomplished in the activated sludge process if conditions suitable for the retention and accumulation of the nitrifying bacteria are maintained. Since the autotrophic nitrifiers have lower yields and growth rates, and are more sensitive to environmental conditions than heterotrophic organisms, it is possible to obtain high degrees of carbonaceous BOD removal and little, if any ammonium oxidation. Efficient nitrification of industrial wastes is often difficult due to the presence of growth inhibiting chemicals (1) and adverse pH conditions. The conditions necessary for nitrification in the activated sludge process may be expressed in terms of sludge age (SA), pH, temperature and dissolved oxygen concentration. The concentration of nitrifying bacteria will depend on their specific growth rate and on the rate at which they are discharged from the system through the effluent and waste sludge streams. Several laboratory, pilot and full-scale investigations have been conducted with nitrifying activated sludge systems and have demonstrated that high efficiencies of nitrification are obtained at sludge ages of approximately 4 days or greater (2,3,4,5,6,7). It is important to note, however, that at temperatures less than 20 C the sludge age required to maintain a high nitrification efficiency increases substantially. In the past, the design and modeling of biological wastewater treatment processes has been based on steady state models even though the inputs to these processes are usually far 1005
Object Description
Purdue Identification Number | ETRIWC197491 |
Title | Dynamics of nitrification in the activated sludge process |
Author |
Poduska, Richard A. Andrews, John F. |
Date of Original | 1974 |
Conference Title | Proceedings of the 29th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,24462 |
Extent of Original | p. 1005-1025 |
Series | Engineering extension series no. 145 |
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 | 2009-06-05 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page1005 |
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 | Dynamics of Nitrification in the Activated Sludge Process RICHARD A. PODUSKA, Environmental Engineer Tennessee Eastman Company Kingsport, Tennessee 37662 JOHN F. ANDREWS, Professor Civil and Environmental Engineering University of Houston Houston. Texas 77004 INTRODUCTION Renewed interest in the problems created by the discharge of nitrogen compounds to receiving waters has focused attention on the form and concentration of nitrogen in wastewater treatment plant effluents. Most wastewater treatment plants are designed, operated and evaluated based on the reduction of carbonaceous 5-day biochemical oxygen demand (BOD) rather than on the total BOD of the effluent (carbonaceous and nitrogenous). As a result, ammonium is the primary form of nitrogen in most wastewater treatment plant effluents. Since ammonium may be biologically oxidized to nitrate in a receiving water, the nitrogenous oxygen demand can represent a major portion of the total oxygen demand for a treatment plant effluent. Assuming a theoretical oxygen requirement for nitrification of 4.5 mg oxygen per mg ammonium nitrogen oxidized to nitrate, an effluent with 20 mg NH+4-N per liter has a nitrogenous oxygen demand (NOD) of 90 mg/1. This is considerably greater than that contributed by the ultimate carbonaceous oxygen demand of normal domestic biological treatment plant effluents (20-40 mg/1). The conversion of ammonium to nitrate within a biological treatment plant would represent a significant improvement in effluent quality through a reduced ultimate BOD. Additionally, the oxidation of ammonium to nitrate in a treatment plant offers the advantage of reducing the amount of chlorine required to obtain effective disinfection. This results from the decreased formation of chloramines which are less effective disinfectants than free residual chlorine. Nitrification can be accomplished in the activated sludge process if conditions suitable for the retention and accumulation of the nitrifying bacteria are maintained. Since the autotrophic nitrifiers have lower yields and growth rates, and are more sensitive to environmental conditions than heterotrophic organisms, it is possible to obtain high degrees of carbonaceous BOD removal and little, if any ammonium oxidation. Efficient nitrification of industrial wastes is often difficult due to the presence of growth inhibiting chemicals (1) and adverse pH conditions. The conditions necessary for nitrification in the activated sludge process may be expressed in terms of sludge age (SA), pH, temperature and dissolved oxygen concentration. The concentration of nitrifying bacteria will depend on their specific growth rate and on the rate at which they are discharged from the system through the effluent and waste sludge streams. Several laboratory, pilot and full-scale investigations have been conducted with nitrifying activated sludge systems and have demonstrated that high efficiencies of nitrification are obtained at sludge ages of approximately 4 days or greater (2,3,4,5,6,7). It is important to note, however, that at temperatures less than 20 C the sludge age required to maintain a high nitrification efficiency increases substantially. In the past, the design and modeling of biological wastewater treatment processes has been based on steady state models even though the inputs to these processes are usually far 1005 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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