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Sludge Conditioning with Incinerator Ash J. E. SMITH, JR., Research Sanitary Engineer S. W. HATHAWAY, Research Chemist J. B. FARRELL, Research Chemical Engineer R. B. DEAN, Chief Ultimate Disposal Research Program Advanced Waste Treatment Research Laboratory National Environmental Research Center, EPA Cincinnati, Ohio INTRODUCTION Sewage sludge handling and disposal can account for as much as 50 percent of the total cost of treating sewage. A substantial portion of this cost is incurred in a filtration step which converts a low solids liquid sludge into a filter cake which can be disposed of by incineration or landfill. Biological sludges generated by secondary treatment such as the activated sludge or trickling filter processes are low in solids and are exceptionally difficult to dewater. The use of secondary treatment is increasing at a rapid rate; consequently, the prospect is for generation of more sludges which will be more difficult to dewater. Traditionally, sludges have been conditioned for vacuum filtration by the addition of either ferric chloride alone or combined with lime. In recent years, polymeric sludge conditioning agents have been developed. These materials have been adopted by many treatment plants, where they have improved the filter yield and reduced overall operating cost. However, these polymers are expensive chemicals and do not work on all sludges. Some sludges, such as waste activated sludge, do not respond well to polymeric conditioners, nor to inorganic chemical conditioners. Mixing them with primary sludge makes it possible to dewater them, but increases the unit cost of conditioning in proportion to the amount of waste activated sludge present. Continued need to develop better ways of dewatering sludge is thus evident. In Germany, addition of from one to five parts of sludge incinerator ash for every part sludge solids has successfully aided sludge dewatering by both rotary vacuum filtration and pressure filtration (1,2). Vater at Stuttgart reported vacuum filter yields as high as 8.5#/ft2/hr when using 2.5 parts ash for each part sludge solids (3). The Beloit-Passavant "Sludge All" process employs ash as a conditioning agent in the filter pressing of sludge (4). Busse patented a process using ash as a filter aid (5) which states that for the process to be effective, the ash particle size must be below 0.1 mm. Most published work in the U.S. has only been done on a laboratory scale, with the buchner Funnel test, using fly ash from coal combustion (6,7). A plant scale pressure filtration study is now getting underway at Cedar Rapids, Iowa (8). The design of this plant is based on unpublished pilot scale pressure and rotary vacuum filtration studies using fly ash. All of the rotary vacuum filter work was done with fly ash in combination with chemical coagulants. No work was done with fly ash alone, or at levels of addition greater than 2 parts ash per part sludge solids. Tenney (9) in working with fly ash found that suitable dosage levels for successful sludge conditioning were from 1 to 1.5 parts ash for each part sludge solids for digested sludge, and from 5 to 7 parts ash for dilute activated sludge. LaRocca and Eckenfelder (10) used fly ash to successfully dewater chemical sludges. Tenney (9) noted that fly ash also helps to improve filtrate quality, by lowering the phosphorus and COD content. Fly ash is said to give the cake a more rigid structure; however, the cake may be higher in moisture on an ash-free basis (11). Most of the work on ash-conditioning of sludge has been directed toward finding a beneficial use for fly ash in the wastewater treatment industry, since it is an abundant waste product. Little has been done in this country with the ash from sludge incineration. For 911
Object Description
Purdue Identification Number | ETRIWC197281 |
Title | Sludge conditioning with incinerator ash |
Author |
Smith, J. E. Hathaway, S. W. Farrell, J. B. Dean, R. B. |
Date of Original | 1972 |
Conference Title | Proceedings of the 27th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,20246 |
Extent of Original | p. 911-925 |
Series | Engineering extension series no. 141 |
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 | 2009-06-08 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page0911 |
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 | Sludge Conditioning with Incinerator Ash J. E. SMITH, JR., Research Sanitary Engineer S. W. HATHAWAY, Research Chemist J. B. FARRELL, Research Chemical Engineer R. B. DEAN, Chief Ultimate Disposal Research Program Advanced Waste Treatment Research Laboratory National Environmental Research Center, EPA Cincinnati, Ohio INTRODUCTION Sewage sludge handling and disposal can account for as much as 50 percent of the total cost of treating sewage. A substantial portion of this cost is incurred in a filtration step which converts a low solids liquid sludge into a filter cake which can be disposed of by incineration or landfill. Biological sludges generated by secondary treatment such as the activated sludge or trickling filter processes are low in solids and are exceptionally difficult to dewater. The use of secondary treatment is increasing at a rapid rate; consequently, the prospect is for generation of more sludges which will be more difficult to dewater. Traditionally, sludges have been conditioned for vacuum filtration by the addition of either ferric chloride alone or combined with lime. In recent years, polymeric sludge conditioning agents have been developed. These materials have been adopted by many treatment plants, where they have improved the filter yield and reduced overall operating cost. However, these polymers are expensive chemicals and do not work on all sludges. Some sludges, such as waste activated sludge, do not respond well to polymeric conditioners, nor to inorganic chemical conditioners. Mixing them with primary sludge makes it possible to dewater them, but increases the unit cost of conditioning in proportion to the amount of waste activated sludge present. Continued need to develop better ways of dewatering sludge is thus evident. In Germany, addition of from one to five parts of sludge incinerator ash for every part sludge solids has successfully aided sludge dewatering by both rotary vacuum filtration and pressure filtration (1,2). Vater at Stuttgart reported vacuum filter yields as high as 8.5#/ft2/hr when using 2.5 parts ash for each part sludge solids (3). The Beloit-Passavant "Sludge All" process employs ash as a conditioning agent in the filter pressing of sludge (4). Busse patented a process using ash as a filter aid (5) which states that for the process to be effective, the ash particle size must be below 0.1 mm. Most published work in the U.S. has only been done on a laboratory scale, with the buchner Funnel test, using fly ash from coal combustion (6,7). A plant scale pressure filtration study is now getting underway at Cedar Rapids, Iowa (8). The design of this plant is based on unpublished pilot scale pressure and rotary vacuum filtration studies using fly ash. All of the rotary vacuum filter work was done with fly ash in combination with chemical coagulants. No work was done with fly ash alone, or at levels of addition greater than 2 parts ash per part sludge solids. Tenney (9) in working with fly ash found that suitable dosage levels for successful sludge conditioning were from 1 to 1.5 parts ash for each part sludge solids for digested sludge, and from 5 to 7 parts ash for dilute activated sludge. LaRocca and Eckenfelder (10) used fly ash to successfully dewater chemical sludges. Tenney (9) noted that fly ash also helps to improve filtrate quality, by lowering the phosphorus and COD content. Fly ash is said to give the cake a more rigid structure; however, the cake may be higher in moisture on an ash-free basis (11). Most of the work on ash-conditioning of sludge has been directed toward finding a beneficial use for fly ash in the wastewater treatment industry, since it is an abundant waste product. Little has been done in this country with the ash from sludge incineration. For 911 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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