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EVALUATION OF UNIT PROCESSES FOR MECHANICAL DEWATERING OF ANAEROBICALLY DIGESTED SLUDGE AT METRO CHICAGO'S WEST-SOUTHWEST SEWAGE TREATMENT PLANT Bernard Sawyer, Research Chemist I Robert Watkins, Research Chemist I Cecil Lue-Hing, Director Research and Development Department The Metropolitan Sanitary District of Greater Chicago Cicero, Illinois 60650 INTRODUCTION The Metropolitan Sanitary District of Greater Chicago (District) collects and treats the wastewater from Chicago and over 120 surrounding suburbs. It serves an area of 852 square miles inhabited by 6 million people plus an equivalent industrial and nonindustrial waste load of 4 million people for a total population of about 10 million. The district's West-Southwest Sewage Treatment Works (W-SW STW) has a design capacity of 1200 mgd and currently utilizes its solids via the following: heat drying and sale as dry fertilizer, high-rate anaerobic digestion and application to land, and Imhoff digestion followed by sand bed dewatering, long-term storage, and distribution to the general public. The last method of solids utilization has been an extremely successful one for the district in the past two years. The general public has been so willing to utilize the solids generated ("NU-EARTH") that the district currently cannot fill the demand. It is believed that the success of this program is due to the fertilizer value of the solids and its relatively dry state (>30% total solids). The district has determined that this "NU-EARTH" program could be expanded by including a portion of its liquid digested sludge. This would require that the liquid slurry (approximately 4-5% solids) from the digesters would have to be dewatered before long- term storage to achieve a final solids concentration greater than 30%. Preliminary studies, however, indicated that sludge dewatering to a solids concentration of 15% would be required to avoid overly long storage times to achieve this level of dryness of Nu-Earth. The engineering department of the district conducted a desk-top study to determine the most cost-effective dewatering processes to be used in a testing program whereby a single dewatering process would be selected for processing anaerobically digested sludge produced at its W-SW STW. As a result of this study, three processes were chosen for study via pilot plant testing. These were vacuum filtration, centrifugation and belt filter pressing. The R&D department of the district, therefore, was charged with the responsibility of testing these processes on a pilot scale at the W-SW STW. This report details the results and conclusions of that testing program. Vacuum filtration has been used since the 1920s to dewater sewage sludges, with solid bowl centrifuges coming into prominence in the 1960s, and belt filter presses in the 1970s. Reviews of the performances of various mechanical dewatering devices have been prepared by the Water Pollution Control Federation [1] and the U.S. EPA [2]. However, much of this work concerns the dewatering of primary sludge, trickling filter humus, undigested waste-activated sludge or combinations of the above, with limited information available on the dewatering characteristics of an anaerobically digested primary and waste-activated sludge mixture. Mudgett [3] obtained a 28% cake and a 6.2 lb/ft2/hr yield, conditioning digested sludge with 60 lb FeCl3/dry ton and 160 lb CaO/dry ton. Schepman and Cornell [4] achieved a 21% cake and a 3.0 lb/ft2 /hr yield using 160 lb FeCl3/ton and 240 lb/ton CaO. 537
Object Description
Purdue Identification Number | ETRIWC197648 |
Title | Evaluation of unit processes for mechanical dewatering of anaerobically digested sludge at Metro Chicago's west-southwest sewage treatment plant |
Author |
Sawyer, Bernard M. Watkins, Robert Lue-Hing, Cecil |
Date of Original | 1976 |
Conference Title | Proceedings of the 31st Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,27048 |
Extent of Original | p. 537-553 |
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 | 2009-07-08 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 537 |
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 | EVALUATION OF UNIT PROCESSES FOR MECHANICAL DEWATERING OF ANAEROBICALLY DIGESTED SLUDGE AT METRO CHICAGO'S WEST-SOUTHWEST SEWAGE TREATMENT PLANT Bernard Sawyer, Research Chemist I Robert Watkins, Research Chemist I Cecil Lue-Hing, Director Research and Development Department The Metropolitan Sanitary District of Greater Chicago Cicero, Illinois 60650 INTRODUCTION The Metropolitan Sanitary District of Greater Chicago (District) collects and treats the wastewater from Chicago and over 120 surrounding suburbs. It serves an area of 852 square miles inhabited by 6 million people plus an equivalent industrial and nonindustrial waste load of 4 million people for a total population of about 10 million. The district's West-Southwest Sewage Treatment Works (W-SW STW) has a design capacity of 1200 mgd and currently utilizes its solids via the following: heat drying and sale as dry fertilizer, high-rate anaerobic digestion and application to land, and Imhoff digestion followed by sand bed dewatering, long-term storage, and distribution to the general public. The last method of solids utilization has been an extremely successful one for the district in the past two years. The general public has been so willing to utilize the solids generated ("NU-EARTH") that the district currently cannot fill the demand. It is believed that the success of this program is due to the fertilizer value of the solids and its relatively dry state (>30% total solids). The district has determined that this "NU-EARTH" program could be expanded by including a portion of its liquid digested sludge. This would require that the liquid slurry (approximately 4-5% solids) from the digesters would have to be dewatered before long- term storage to achieve a final solids concentration greater than 30%. Preliminary studies, however, indicated that sludge dewatering to a solids concentration of 15% would be required to avoid overly long storage times to achieve this level of dryness of Nu-Earth. The engineering department of the district conducted a desk-top study to determine the most cost-effective dewatering processes to be used in a testing program whereby a single dewatering process would be selected for processing anaerobically digested sludge produced at its W-SW STW. As a result of this study, three processes were chosen for study via pilot plant testing. These were vacuum filtration, centrifugation and belt filter pressing. The R&D department of the district, therefore, was charged with the responsibility of testing these processes on a pilot scale at the W-SW STW. This report details the results and conclusions of that testing program. Vacuum filtration has been used since the 1920s to dewater sewage sludges, with solid bowl centrifuges coming into prominence in the 1960s, and belt filter presses in the 1970s. Reviews of the performances of various mechanical dewatering devices have been prepared by the Water Pollution Control Federation [1] and the U.S. EPA [2]. However, much of this work concerns the dewatering of primary sludge, trickling filter humus, undigested waste-activated sludge or combinations of the above, with limited information available on the dewatering characteristics of an anaerobically digested primary and waste-activated sludge mixture. Mudgett [3] obtained a 28% cake and a 6.2 lb/ft2/hr yield, conditioning digested sludge with 60 lb FeCl3/dry ton and 160 lb CaO/dry ton. Schepman and Cornell [4] achieved a 21% cake and a 3.0 lb/ft2 /hr yield using 160 lb FeCl3/ton and 240 lb/ton CaO. 537 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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