page 759 |
Previous | 1 of 11 | Next |
|
|
Loading content ...
NET SLUDGE YIELDS OBTAINED DURING SINGLE-STAGE NITRIFICATION STUDIES AT CHICAGO'S WEST-SOUTHWEST TREATMENT PLANT Alan W. Obayashi, Research Chemist III Booker Washington, Sanitary Chemist II Cecil Lue-Hing, Director Department of Research and Development The Metropolitan Sanitary District of Greater Chicago Chicago, Illinois 60611 INTRODUCTION The Metropolitan Sanitary District of Greater Chicago (MSDGC) has for the past several years conducted full-scale single-stage nitrification studies of each of its three major plants, namely the Calumet, the North Side and the West-Southwest treatment plants. These studies were conducted in order to establish design criteria for the expansion of the major plants, which will have to achieve ammonia removal as well as meet stricter effluent water quality criteria in terms of 5-day biochemical oxygen demand (BOD) and suspended solids (SS). In particular, studies were conducted of the District's West-Southwest (W-SW) treatment plant, the world's largest secondary treatment plant. The results of the study, which will be reported on in a subsequent paper [ 1 ], proved to be quite interesting. In general, provided that there was sufficient dissolved oxygen in the aeration tank, the key to successful nitrification during the winter months at W-SW was found to be the maintenance of a solids retention time (SRT) which was long enough to promote the growth during the colder temperatures of the relatively slow-growing autotrophic bacteria which utilize the ammonia as an energy source. With the assumption that the total mass of suspended solids in the activated sludge system was equal to the suspended solids under aeration, (i.e., no solids in the clarifers), unstable nitrification (30% to 70% removal of NH4-N) was found to occur at SRTs of 3 to 4 days at wastewater temperatures of 11-13 C. In contrast, operation at SRTs in the range of 6 to 10 days at the same temperatures provided NH4-N removals in excess of 90%, with effluent NH4-N values being generally less than 1 mg/1. The above results were not entirely unexpected, since theoretically, in order to maintain a culture of nitrifying bacteria in the activated sludge process, the process must be operated such that the net growth rate (1/SRT), i.e., the discharge of suspended solids per unit time divided by the total SS in the system, must not exceed the maximum growth rate of the nitrifying bacteria, otherwise the bacteria will "wash out" of the system. Since the growth rate is equal to the reciprocal of the SRT of the system, in order to maintain successful nitrification the SRT must be significantly greater than (or growth rate significantly lower than) the SRT at which the growth rate is maximum at a given temperature. This is assuming that dissolved oxygen and pH are not limiting. In order to evaluate how much greater the SRT must be, Lawrence and McCarty [2] have introduced the following concept of the safety factor (SF): 6g SF = — 0m 759
Object Description
Purdue Identification Number | ETRIWC1977077 |
Title | Net sludge yields obtained during single-stage nitrification studies at Chicago's west-southwest treatment plant |
Author |
Obayashi, Alan W., 1946- Washington, Booker Lue-Hing, Cecil |
Date of Original | 1977 |
Conference Title | Proceedings of the 32nd Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,26931 |
Extent of Original | p. 759-769 |
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 | 2009-07-01 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 759 |
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 | NET SLUDGE YIELDS OBTAINED DURING SINGLE-STAGE NITRIFICATION STUDIES AT CHICAGO'S WEST-SOUTHWEST TREATMENT PLANT Alan W. Obayashi, Research Chemist III Booker Washington, Sanitary Chemist II Cecil Lue-Hing, Director Department of Research and Development The Metropolitan Sanitary District of Greater Chicago Chicago, Illinois 60611 INTRODUCTION The Metropolitan Sanitary District of Greater Chicago (MSDGC) has for the past several years conducted full-scale single-stage nitrification studies of each of its three major plants, namely the Calumet, the North Side and the West-Southwest treatment plants. These studies were conducted in order to establish design criteria for the expansion of the major plants, which will have to achieve ammonia removal as well as meet stricter effluent water quality criteria in terms of 5-day biochemical oxygen demand (BOD) and suspended solids (SS). In particular, studies were conducted of the District's West-Southwest (W-SW) treatment plant, the world's largest secondary treatment plant. The results of the study, which will be reported on in a subsequent paper [ 1 ], proved to be quite interesting. In general, provided that there was sufficient dissolved oxygen in the aeration tank, the key to successful nitrification during the winter months at W-SW was found to be the maintenance of a solids retention time (SRT) which was long enough to promote the growth during the colder temperatures of the relatively slow-growing autotrophic bacteria which utilize the ammonia as an energy source. With the assumption that the total mass of suspended solids in the activated sludge system was equal to the suspended solids under aeration, (i.e., no solids in the clarifers), unstable nitrification (30% to 70% removal of NH4-N) was found to occur at SRTs of 3 to 4 days at wastewater temperatures of 11-13 C. In contrast, operation at SRTs in the range of 6 to 10 days at the same temperatures provided NH4-N removals in excess of 90%, with effluent NH4-N values being generally less than 1 mg/1. The above results were not entirely unexpected, since theoretically, in order to maintain a culture of nitrifying bacteria in the activated sludge process, the process must be operated such that the net growth rate (1/SRT), i.e., the discharge of suspended solids per unit time divided by the total SS in the system, must not exceed the maximum growth rate of the nitrifying bacteria, otherwise the bacteria will "wash out" of the system. Since the growth rate is equal to the reciprocal of the SRT of the system, in order to maintain successful nitrification the SRT must be significantly greater than (or growth rate significantly lower than) the SRT at which the growth rate is maximum at a given temperature. This is assuming that dissolved oxygen and pH are not limiting. In order to evaluate how much greater the SRT must be, Lawrence and McCarty [2] have introduced the following concept of the safety factor (SF): 6g SF = — 0m 759 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Tags
Comments
Post a Comment for page 759