page 463 |
Previous | 1 of 6 | Next |
|
|
Loading content ...
Section Four BIOLOGICAL SYSTEMS - D. SLUDGE TREATMENT 53 IMPROVED SLUDGE DEWATERING Edwin R. Hendricks, Senior Engineer BBS Corporation Columbus, Ohio 43229 INTRODUCTION Overview of Solids Disposal Ultimate disposal of wastewater sludge is and has been an increasingly complex and expensive proposition for the City of Columbus, Ohio. Sludge incinerators have been in operation for over thirty years. The incineration capacity is initially limited by the amount of water contained in the sludge. Historically, the two multihearth incinerators at the Southerly WWTP have been limited to about 5.5 wt/hr. Two new incinerators have recently come on line and they provide about 7.0 wt/hr each. Total incineration capacity at the SoWWTP is about 25 wt/hr and, allowing 3 of 4 units on line continuously, the reliable capacity is about 430 wt/d. When it is possible to obtain sludge cake dry enough such that minimal auxiliary fuel is required to sustain burning, the condition is described as autogenous combustion. Analysis of the incinerators indicates that autogenous combustion will be obtained when the sludge cake is about 24% to 28% solids. At that point, fuel requirements necessary to maintain control of the incinerators should fall to less than 0.10 gallon, per wt. of sludge burned. The projection of changes in incinerator performance as feed sludge cake dryness is increased from 18% to 30% solids is inexact due to the number of critical variables. However, the projection of near autogenous combustion is reliable. Recent operations where 26-28% cake was burned with greatly reduced fuel indicates verification of the projections. Contrarily, projection of quantitative changes in composting performance as feed sludge cake is varied from 18% to 30% is not practical, given the limited scope of studies and time allotted. However, initial surveys of the composting situation clearly indicate that the impact of improved cake solids would be even greater on composting than on incineration. For instance, it is projected that doubling the cake solids would result in using about 70% less wood chips. The combined effect of decreased wood chip addition, improved mixing and reduced handling are expected to combine synergistically to provide significant improvements at composting. There does not seem to be any overwhelming advantages or disadvantages to ongoing land application programs vis-a-vis cake solids improvement. The City currently practices surface application of cake, and injection of thickened sludge is being piloted on a full scale basis. Analysis to date indicates similar costs for both methods. In other works, the reduced cost of hauling sludge cake is offset by dewatering costs. However, there may be some advantage to the drier filter press sludge in that handling and storing the 28% cake is expected to be much easier than the 18%cake. Systematic Analysis In order to provide guidance for selection of new solids handling facilities and/or expansion of existing facilities, a systematic cost comparison of selected solids handling models was undertaken. Key assumptions of that analysis were as follows: 1. Incinerator capital costs was treated as sunk cost (capital cost not included in the analysis). 45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118. Primed in U.S.A. 463
Object Description
Purdue Identification Number | ETRIWC199053 |
Title | Improved sludge dewatering |
Author | Hendricks, Edwin R. |
Date of Original | 1990 |
Conference Title | Proceedings of the 45th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,41605 |
Extent of Original | p. 463-468 |
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 | 2009-08-20 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 463 |
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 | Section Four BIOLOGICAL SYSTEMS - D. SLUDGE TREATMENT 53 IMPROVED SLUDGE DEWATERING Edwin R. Hendricks, Senior Engineer BBS Corporation Columbus, Ohio 43229 INTRODUCTION Overview of Solids Disposal Ultimate disposal of wastewater sludge is and has been an increasingly complex and expensive proposition for the City of Columbus, Ohio. Sludge incinerators have been in operation for over thirty years. The incineration capacity is initially limited by the amount of water contained in the sludge. Historically, the two multihearth incinerators at the Southerly WWTP have been limited to about 5.5 wt/hr. Two new incinerators have recently come on line and they provide about 7.0 wt/hr each. Total incineration capacity at the SoWWTP is about 25 wt/hr and, allowing 3 of 4 units on line continuously, the reliable capacity is about 430 wt/d. When it is possible to obtain sludge cake dry enough such that minimal auxiliary fuel is required to sustain burning, the condition is described as autogenous combustion. Analysis of the incinerators indicates that autogenous combustion will be obtained when the sludge cake is about 24% to 28% solids. At that point, fuel requirements necessary to maintain control of the incinerators should fall to less than 0.10 gallon, per wt. of sludge burned. The projection of changes in incinerator performance as feed sludge cake dryness is increased from 18% to 30% solids is inexact due to the number of critical variables. However, the projection of near autogenous combustion is reliable. Recent operations where 26-28% cake was burned with greatly reduced fuel indicates verification of the projections. Contrarily, projection of quantitative changes in composting performance as feed sludge cake is varied from 18% to 30% is not practical, given the limited scope of studies and time allotted. However, initial surveys of the composting situation clearly indicate that the impact of improved cake solids would be even greater on composting than on incineration. For instance, it is projected that doubling the cake solids would result in using about 70% less wood chips. The combined effect of decreased wood chip addition, improved mixing and reduced handling are expected to combine synergistically to provide significant improvements at composting. There does not seem to be any overwhelming advantages or disadvantages to ongoing land application programs vis-a-vis cake solids improvement. The City currently practices surface application of cake, and injection of thickened sludge is being piloted on a full scale basis. Analysis to date indicates similar costs for both methods. In other works, the reduced cost of hauling sludge cake is offset by dewatering costs. However, there may be some advantage to the drier filter press sludge in that handling and storing the 28% cake is expected to be much easier than the 18%cake. Systematic Analysis In order to provide guidance for selection of new solids handling facilities and/or expansion of existing facilities, a systematic cost comparison of selected solids handling models was undertaken. Key assumptions of that analysis were as follows: 1. Incinerator capital costs was treated as sunk cost (capital cost not included in the analysis). 45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118. Primed in U.S.A. 463 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Tags
Comments
Post a Comment for page 463