CA1070864A - Sludge dewatering process - Google Patents
Sludge dewatering processInfo
- Publication number
- CA1070864A CA1070864A CA280,273A CA280273A CA1070864A CA 1070864 A CA1070864 A CA 1070864A CA 280273 A CA280273 A CA 280273A CA 1070864 A CA1070864 A CA 1070864A
- Authority
- CA
- Canada
- Prior art keywords
- sludge
- solids
- dewatering
- percent
- filter cake
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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- Treatment Of Sludge (AREA)
- Separation Of Suspended Particles By Flocculating Agents (AREA)
Abstract
SLUDGE DEWATERING PROCESS
ABSTRACT OF THE DISCLOSURE
Sewage sludges of the waste-activated, raw and digested types are dewatered for yielding a product having a sufficiently high heat value to support autogenous combustion. The process in-cludes the addition of a polymeric flocculent to the sludge, mixing the flocculated sludge with a slurry containing a small percentage of newsprint pulp, thereafter dewatering the mixed flocculated sludge until a firm filter cake is obtained containing up to 25 percent dry solids and a clear filtrate is obtained, and lastly dewatering the filter cake to yield a final product containing up to 49 per-cent dry solids.
ABSTRACT OF THE DISCLOSURE
Sewage sludges of the waste-activated, raw and digested types are dewatered for yielding a product having a sufficiently high heat value to support autogenous combustion. The process in-cludes the addition of a polymeric flocculent to the sludge, mixing the flocculated sludge with a slurry containing a small percentage of newsprint pulp, thereafter dewatering the mixed flocculated sludge until a firm filter cake is obtained containing up to 25 percent dry solids and a clear filtrate is obtained, and lastly dewatering the filter cake to yield a final product containing up to 49 per-cent dry solids.
Description
~07()864 BACKGROUND OF THE INVENTION
This invention relates generally to a process of dewatering sewage sludge, and more particularly to such a process which yields a product having a sufficiently high heat value required for auto-genous incineration.
Suitable disposal of domestic sewage sludge is becoming an increasing problem due to the use of large, centralized treatment plants and the shortage of suitable landfill sites. Presently, disposal of sewage sludges by incineration has proven practical, but expensive, because of the additional heat required. Ordinarily, the additional heat is required to evaporate the water remaining in the dewatered sludge, i.e., the filter cakes, in order to success-fully complete the incineration process. With the rising costs of fuel, however, there is great interest in feeding sludge to an in-cinerator that would have a high enough solids concentration so that little or no additional fuel would be needed. Presently, sludge is dewatered prior to incineration using either ferric chloride and lime or some suitable polymer as conditioning agents. However, the resulting sludge is normally too low in combustible solids to be autogenously incinerated so that excess heat, usually by burning natural gas or oil, must be supplied for incineration. Also, if ferric chloride and lime are utilized, a greater percentage of ash ~r .. , :. :
... ..... . . .
~0'7V1~6~
results thereby compounding the disposal problem.
What is needed is a conditioning agent which is inexpensive and is readily available and which permits the sludge to be de-watered to a higher solid concentration without the handling pro-blems common to the use of ferric chloride and lime. Such a con-ditioning agent should have a high heat value thus reducing the final solids concentration required for autogenous incineration, should be capable of combining with sludge to permit the mixture to give up its water with relative ease, and should not be hazardous to prepare or use.
A material which has been found to fulfill each of these requirements is waste newsprint, a material which is abundant and, because of its relatively low market value, is presently being hauled to landfill sites for disposal. It is known that fibrous paper sludge is readily dewaterable in a two-stage process of vacuum dewatering followed by squeezing in a mechanical rotary press or the like to achieve a high solids concentration.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a dewatered polymer coagulated sewage sludge having a furnace feed solids concentration which is higher than that presently achievable and at a sufficiently high heat value required for autogenous incin-eration.
An autogenous sludge is produced for combustion in accordance with the present invention by flocculating the sewage sludge with the use of a suitable polymer, mixing the flocculated sludge with a slurry containing a small percentage of paper fibers, and dewatering the mixed flocculated sludge in a two-stage process of vacuum de-watering followed by compression dewatering.
DETAILED DESCRIPTION OF THE INVENTION
Experimentation has been performed to determine the effects on sludge dewaterability of the addition of various quantities of pulp newsprint. The sewage sludge first used was thickened waste-activated sludge from a municipal treatment plant. This was selected 107~6~
because waste-activated sludge is probably the most difficult sludge from a domestic sewage treatment plant to dewater. Activated sludge as referred to herein refers to a sewage sludge resulting from a sequential biological oxidation of raw sewage, which may have been subjected to a primary clarification treatment prior to oxidation, followed by settling operations to recover the oxidized organic solids as an underflow sludge.
The process used and the results obtained on thickened waste-activated sludge (WAS) with the addition of pulp newsprint is set forth in the table below.
~ E
O N ~ ~ ~
o~P O Vl ~1 ~
O O O ~
O
'4 ~ W CO
O t ~ ~ w ~ ~ ~
~0 ~ ", ," ~D
~P o O m O ~n oO o ~
u~
I_ ~ u~
~9 ~ ~ 1--~D
~ U~
I,n Ul O
dP O g g ~ ~
d~ O O ~0 .P ~n ~
_3_ ~ ~ ~
~07~ ;4 The experimentation showed that the process for dewatering sludge to yield a product having a sufficiently high heat value required for autogenous incineration must be subjected to a two-stage process consisting of vacuum filtration followed by compression filtration. Upon vacuum filtration a filter cake is obtained having 13 to 15 percent dry solids concentration which translates into a heat value of 950 BTU/lb. of filter cake. The compression dewatering step yields a final product containing approximately 25 to 30 percent solids which translates into a final product having a heat value of 1780 BTU/lb. of pressed filter cake.
The addition of pulp newsprint was not in itself sufficient to adequately dewater the sludge. A chemical agent, such as a water soluble, cationic organic polymer, must be added to flocculate the sludge prior to dewatering. Also, the sludge should be flocculated prior to mixing with the pulp newsprint. A much higher concentra-tion of solids in the filter cake (13.5 percent versus 9.6 percent of polymer treated sludge only) was obtained in this matter. Since the paper pulp itself exhibits a demand for the polymer, it requires less chemical conditioner if the sludge, polymer and paper pulp are mixed in this sequence.
Both the filter yield and the final so]ids concentration of the product depend upon the relative amount of newsprint pulp added to the flocculated waste-activated sludge. The addition of pulp at a ratio of 2-1/2 to 4 parts fiber pulp to 10 parts sludge solids produced satisfactory results. And, it should be pointed out that the concentration of solids in the pressed filter cake of 24 to 25 percent for the mixture used during one of the tests can be increased to 30 to 35 percent solids using higher compressive pressures than that carried out.
Further tests with raw primary and digested sludges produced similar results. The digested sludge as herein used is any sewage sludge which has been subjected to anaerobic conditions for an ex-tended period whereby the sludge solids are partially decomposed.
~07086~
A raw sewage sludge is produced by subjecting a raw sewage stream to a settling operation, with or without previo~s flocculation of the sewage. And, the settled raw sewage solids are withdrawn as the `
underflow from the settling operation.
In the case of raw primary sludge, vacuum filtration follow-ed conditioning with newsprint pulp and polymer yielded a filter cake of 18 to 20 percent dry solids. The compression dewatering stage yielded a final product with 30 to 35 percent solids. For this, a filter yield of 5 to 7 pounds dry solids/square foot/hour was used as a design estimate with 4 percent primary solids, 1 per-cent paper solids and 10 to 15 pounds polymer per ton of dry primary solids.
With digested primary sludges, vacuum filtration yielded a filter cake of 16 to 18 percent solids. The compression dewatering stage produced a final product with 30 to 35 percent solids content.
A filter yield of 5 to 6 pounds of dry solids/square foot/hour was used with 3 percent sludge solids, 0.9 percent paper solids and 12 to 15 pounds of polymer/ton of dry digested solids.
In accordance with further experimentation, thickened waste-activated sludge was pumped to a vacuum filter at a concentrationof 5.6 percent suspended solids and, after flocculation with a water-soluble, cationic organic polymer, was mixed with a slurry contain-ing approximately 2 percent of recycled waste fiber. The mixture was dewatered on the vacuum filter and yielded a firm filter cake containing 22 percent dry solids. It likewise yielded a clear filtrate containing approximately 200 ppm suspended solids at a sludge dewatering rate of 5 to 6 pounds dry sludge solids per square foot per hour.
The filter cake was thereafter dewatered using a compression filter and yielded a product with a final concentration of approxi-mately 30 percent solids.
In yet another experiment, flocculated digested sewage sludge at 7.3 percent concentration of solids was mixed with dilute pulp slurry and dewatered on a vacuum filter to yield a firm filter cake ~V7~6~
containing 24.9 percent solids and a clear filtrate containing 2000 ppm total solids (approximately 600 ppm suspended solids) at a sludge dewatering rate of 4.5 to 5 pounds dry sludge solids per square foot per hour. The filter cake was then pressed in a com-pression filter to a final solids concentration of 40 to 49 percent solids with a discharge liquid phase containing approximately 8000 ppm total solids.
The proportion of fiber required for optimum treatment of the sludge during the last two aforementioned tests was 2-1/2 to 4 parts fiber to 10 parts sludge solids. And, one of the side bene-fits of the addition of fiber to the filter feed sludge is the vastly improved clean quality of the filtrate effecting a clean operation of the vacuum filter. Without the addition of fiber to the filter feed sludge, the filtrate was found to contain a heavy solids load of 1. 5 to 2.5 percent which, when recycled to the front end of the treatment plant, adds an additional load on all the equipment in-stalled. Filtrate solids during the test period on both the last two aforementioned sludges and thickened secondary sludge only were reduced to a range from 200 to 500 ppm, thus virtually eliminating any recycle load on the treatment plant.
The furnace feed solids required for autogenous sludge com-bustion of polymer and paper conditioning of primary sludge was compared to ferric chloride and lime conditioning of primary sludge. The addition of 30 pounds of paper solids, having a heat value of 8000 BTU/lb., to 100 pounds flocculated sludge solids, having 8200 BTU/lb., yields 130 pounds of furnace feed solids having 8150 BTU/lb. At this heat value per pound of dry solids it has been calculated that autogenous combustion requires a furnace feed of 32 percent dry solids. On the other hand, the addition of 20 pounds of lime solids having no heat value to 100 pounds sludge solids having a heat value of 8200 Btu/lb., yields 120 pounds fur-nace feed solids having a heat value of 6830 BTU/lb. At this heat value per pound of dry solids it has been calculated that autogenous combustion requires a furnace feed of 37 percent. The fiber addition 1~7()~6~
to flocculated sewage sludge in accordance with the present inven-tion therefore produces a sufficiently high heat value per pound of dry solids required for autogenous combustion wherein the percent of dry solids required for furnace feed is 5 percent less than that requlred using ferric chloride and lime conditioning of primary sludge. Also, use in accordance with the invention of polymer and newsprint pulp as conditioning agents for the sludge produces a sludge amenable to autogenous incineration with less ash, and a cleaner filtrate. And, tne waste fiber filter aid improves the calorific value of the filter cake and imparts sufficient strength to the filter cake to allow pressing during dewatering without extrusion.
Obviously, many modifications and variations of the invention are made possible in the light of the above teachings. It is there-fore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.
This invention relates generally to a process of dewatering sewage sludge, and more particularly to such a process which yields a product having a sufficiently high heat value required for auto-genous incineration.
Suitable disposal of domestic sewage sludge is becoming an increasing problem due to the use of large, centralized treatment plants and the shortage of suitable landfill sites. Presently, disposal of sewage sludges by incineration has proven practical, but expensive, because of the additional heat required. Ordinarily, the additional heat is required to evaporate the water remaining in the dewatered sludge, i.e., the filter cakes, in order to success-fully complete the incineration process. With the rising costs of fuel, however, there is great interest in feeding sludge to an in-cinerator that would have a high enough solids concentration so that little or no additional fuel would be needed. Presently, sludge is dewatered prior to incineration using either ferric chloride and lime or some suitable polymer as conditioning agents. However, the resulting sludge is normally too low in combustible solids to be autogenously incinerated so that excess heat, usually by burning natural gas or oil, must be supplied for incineration. Also, if ferric chloride and lime are utilized, a greater percentage of ash ~r .. , :. :
... ..... . . .
~0'7V1~6~
results thereby compounding the disposal problem.
What is needed is a conditioning agent which is inexpensive and is readily available and which permits the sludge to be de-watered to a higher solid concentration without the handling pro-blems common to the use of ferric chloride and lime. Such a con-ditioning agent should have a high heat value thus reducing the final solids concentration required for autogenous incineration, should be capable of combining with sludge to permit the mixture to give up its water with relative ease, and should not be hazardous to prepare or use.
A material which has been found to fulfill each of these requirements is waste newsprint, a material which is abundant and, because of its relatively low market value, is presently being hauled to landfill sites for disposal. It is known that fibrous paper sludge is readily dewaterable in a two-stage process of vacuum dewatering followed by squeezing in a mechanical rotary press or the like to achieve a high solids concentration.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a dewatered polymer coagulated sewage sludge having a furnace feed solids concentration which is higher than that presently achievable and at a sufficiently high heat value required for autogenous incin-eration.
An autogenous sludge is produced for combustion in accordance with the present invention by flocculating the sewage sludge with the use of a suitable polymer, mixing the flocculated sludge with a slurry containing a small percentage of paper fibers, and dewatering the mixed flocculated sludge in a two-stage process of vacuum de-watering followed by compression dewatering.
DETAILED DESCRIPTION OF THE INVENTION
Experimentation has been performed to determine the effects on sludge dewaterability of the addition of various quantities of pulp newsprint. The sewage sludge first used was thickened waste-activated sludge from a municipal treatment plant. This was selected 107~6~
because waste-activated sludge is probably the most difficult sludge from a domestic sewage treatment plant to dewater. Activated sludge as referred to herein refers to a sewage sludge resulting from a sequential biological oxidation of raw sewage, which may have been subjected to a primary clarification treatment prior to oxidation, followed by settling operations to recover the oxidized organic solids as an underflow sludge.
The process used and the results obtained on thickened waste-activated sludge (WAS) with the addition of pulp newsprint is set forth in the table below.
~ E
O N ~ ~ ~
o~P O Vl ~1 ~
O O O ~
O
'4 ~ W CO
O t ~ ~ w ~ ~ ~
~0 ~ ", ," ~D
~P o O m O ~n oO o ~
u~
I_ ~ u~
~9 ~ ~ 1--~D
~ U~
I,n Ul O
dP O g g ~ ~
d~ O O ~0 .P ~n ~
_3_ ~ ~ ~
~07~ ;4 The experimentation showed that the process for dewatering sludge to yield a product having a sufficiently high heat value required for autogenous incineration must be subjected to a two-stage process consisting of vacuum filtration followed by compression filtration. Upon vacuum filtration a filter cake is obtained having 13 to 15 percent dry solids concentration which translates into a heat value of 950 BTU/lb. of filter cake. The compression dewatering step yields a final product containing approximately 25 to 30 percent solids which translates into a final product having a heat value of 1780 BTU/lb. of pressed filter cake.
The addition of pulp newsprint was not in itself sufficient to adequately dewater the sludge. A chemical agent, such as a water soluble, cationic organic polymer, must be added to flocculate the sludge prior to dewatering. Also, the sludge should be flocculated prior to mixing with the pulp newsprint. A much higher concentra-tion of solids in the filter cake (13.5 percent versus 9.6 percent of polymer treated sludge only) was obtained in this matter. Since the paper pulp itself exhibits a demand for the polymer, it requires less chemical conditioner if the sludge, polymer and paper pulp are mixed in this sequence.
Both the filter yield and the final so]ids concentration of the product depend upon the relative amount of newsprint pulp added to the flocculated waste-activated sludge. The addition of pulp at a ratio of 2-1/2 to 4 parts fiber pulp to 10 parts sludge solids produced satisfactory results. And, it should be pointed out that the concentration of solids in the pressed filter cake of 24 to 25 percent for the mixture used during one of the tests can be increased to 30 to 35 percent solids using higher compressive pressures than that carried out.
Further tests with raw primary and digested sludges produced similar results. The digested sludge as herein used is any sewage sludge which has been subjected to anaerobic conditions for an ex-tended period whereby the sludge solids are partially decomposed.
~07086~
A raw sewage sludge is produced by subjecting a raw sewage stream to a settling operation, with or without previo~s flocculation of the sewage. And, the settled raw sewage solids are withdrawn as the `
underflow from the settling operation.
In the case of raw primary sludge, vacuum filtration follow-ed conditioning with newsprint pulp and polymer yielded a filter cake of 18 to 20 percent dry solids. The compression dewatering stage yielded a final product with 30 to 35 percent solids. For this, a filter yield of 5 to 7 pounds dry solids/square foot/hour was used as a design estimate with 4 percent primary solids, 1 per-cent paper solids and 10 to 15 pounds polymer per ton of dry primary solids.
With digested primary sludges, vacuum filtration yielded a filter cake of 16 to 18 percent solids. The compression dewatering stage produced a final product with 30 to 35 percent solids content.
A filter yield of 5 to 6 pounds of dry solids/square foot/hour was used with 3 percent sludge solids, 0.9 percent paper solids and 12 to 15 pounds of polymer/ton of dry digested solids.
In accordance with further experimentation, thickened waste-activated sludge was pumped to a vacuum filter at a concentrationof 5.6 percent suspended solids and, after flocculation with a water-soluble, cationic organic polymer, was mixed with a slurry contain-ing approximately 2 percent of recycled waste fiber. The mixture was dewatered on the vacuum filter and yielded a firm filter cake containing 22 percent dry solids. It likewise yielded a clear filtrate containing approximately 200 ppm suspended solids at a sludge dewatering rate of 5 to 6 pounds dry sludge solids per square foot per hour.
The filter cake was thereafter dewatered using a compression filter and yielded a product with a final concentration of approxi-mately 30 percent solids.
In yet another experiment, flocculated digested sewage sludge at 7.3 percent concentration of solids was mixed with dilute pulp slurry and dewatered on a vacuum filter to yield a firm filter cake ~V7~6~
containing 24.9 percent solids and a clear filtrate containing 2000 ppm total solids (approximately 600 ppm suspended solids) at a sludge dewatering rate of 4.5 to 5 pounds dry sludge solids per square foot per hour. The filter cake was then pressed in a com-pression filter to a final solids concentration of 40 to 49 percent solids with a discharge liquid phase containing approximately 8000 ppm total solids.
The proportion of fiber required for optimum treatment of the sludge during the last two aforementioned tests was 2-1/2 to 4 parts fiber to 10 parts sludge solids. And, one of the side bene-fits of the addition of fiber to the filter feed sludge is the vastly improved clean quality of the filtrate effecting a clean operation of the vacuum filter. Without the addition of fiber to the filter feed sludge, the filtrate was found to contain a heavy solids load of 1. 5 to 2.5 percent which, when recycled to the front end of the treatment plant, adds an additional load on all the equipment in-stalled. Filtrate solids during the test period on both the last two aforementioned sludges and thickened secondary sludge only were reduced to a range from 200 to 500 ppm, thus virtually eliminating any recycle load on the treatment plant.
The furnace feed solids required for autogenous sludge com-bustion of polymer and paper conditioning of primary sludge was compared to ferric chloride and lime conditioning of primary sludge. The addition of 30 pounds of paper solids, having a heat value of 8000 BTU/lb., to 100 pounds flocculated sludge solids, having 8200 BTU/lb., yields 130 pounds of furnace feed solids having 8150 BTU/lb. At this heat value per pound of dry solids it has been calculated that autogenous combustion requires a furnace feed of 32 percent dry solids. On the other hand, the addition of 20 pounds of lime solids having no heat value to 100 pounds sludge solids having a heat value of 8200 Btu/lb., yields 120 pounds fur-nace feed solids having a heat value of 6830 BTU/lb. At this heat value per pound of dry solids it has been calculated that autogenous combustion requires a furnace feed of 37 percent. The fiber addition 1~7()~6~
to flocculated sewage sludge in accordance with the present inven-tion therefore produces a sufficiently high heat value per pound of dry solids required for autogenous combustion wherein the percent of dry solids required for furnace feed is 5 percent less than that requlred using ferric chloride and lime conditioning of primary sludge. Also, use in accordance with the invention of polymer and newsprint pulp as conditioning agents for the sludge produces a sludge amenable to autogenous incineration with less ash, and a cleaner filtrate. And, tne waste fiber filter aid improves the calorific value of the filter cake and imparts sufficient strength to the filter cake to allow pressing during dewatering without extrusion.
Obviously, many modifications and variations of the invention are made possible in the light of the above teachings. It is there-fore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.
Claims (6)
1. A process of sludge dewatering, comprises:
first adding a water-soluble, organic polymeric flocculent to a quantity of thickened waste-activated sewage sludge having a concentration of suspended sludge solids of approximately 3 to 6 percent;
then mixing the flocculated sludge with a slurry containing approximately 2 to 3 percent of paper fibers, the ratio of the fibers to the sludge solids being 2.5 to 4:10;
thereafter dewatering the mixed flocculated sludge until a firm filter cake is obtained containing approximately 14 to 22 percent dry solids and a clean filtrate is obtained containing approximately 200 to 650 ppm suspended solids; and finally dewatering the filter cake to yield a final product containing approximately 30 percent dry solids, said product having a sufficiently high heat value required for autogenous combustion.
first adding a water-soluble, organic polymeric flocculent to a quantity of thickened waste-activated sewage sludge having a concentration of suspended sludge solids of approximately 3 to 6 percent;
then mixing the flocculated sludge with a slurry containing approximately 2 to 3 percent of paper fibers, the ratio of the fibers to the sludge solids being 2.5 to 4:10;
thereafter dewatering the mixed flocculated sludge until a firm filter cake is obtained containing approximately 14 to 22 percent dry solids and a clean filtrate is obtained containing approximately 200 to 650 ppm suspended solids; and finally dewatering the filter cake to yield a final product containing approximately 30 percent dry solids, said product having a sufficiently high heat value required for autogenous combustion.
2. The process according to claim 1, wherein said dewater-ing of said mixed flocculated sludge is carried out by vacuum filtering, and said dewatering of said filter cake is carried out by compression filtering.
3. A process of sludge dewatering, comprising:
first adding a water-soluble, anionic organic polymeric flocculent to a quantity of digested sewage sludge having a con-centration of suspended sludge solids of approximately 3 to 7 per-cent;
then mixing the flocculated sludge with a slurry containing less than 3.0 percent fibers, the ratio of the fiber to the sludge solids being 2.5 to 4:10;
thereafter dewatering the mixed flocculated sludge, at a rate of approximately 4.5 to 6 pounds dry sludge solids per square foot per hour, until a firm filter cake is obtained containing approximately 16 to 25 percent dry solids; and finally dewatering the filter cake to yield a final product containing approximately 30 to 49 percent dry solids, said product having a sufficiently high heat value required for autogenous com-bustion.
first adding a water-soluble, anionic organic polymeric flocculent to a quantity of digested sewage sludge having a con-centration of suspended sludge solids of approximately 3 to 7 per-cent;
then mixing the flocculated sludge with a slurry containing less than 3.0 percent fibers, the ratio of the fiber to the sludge solids being 2.5 to 4:10;
thereafter dewatering the mixed flocculated sludge, at a rate of approximately 4.5 to 6 pounds dry sludge solids per square foot per hour, until a firm filter cake is obtained containing approximately 16 to 25 percent dry solids; and finally dewatering the filter cake to yield a final product containing approximately 30 to 49 percent dry solids, said product having a sufficiently high heat value required for autogenous com-bustion.
4. The process according to claim 3, wherein said dewatering of said mixed flocculated sludge is carried out by vacuum filtering, and said dewatering of said filter cake is carried out by compres-sion filtering.
5. A process of sludge dewatering, comprising:
first adding a water-soluble, anionic organic polymeric flocculent to a quantity of raw primary sewage sludge having a concentration of suspended sludge solids of approximately 4 percent;
then mixing the flocculated sludge with a slurry containing approximately 3.0 percent paper fibers, the ratio of the fiber to the sludge solids being 2.5 to 4:10;
thereafter dewatering the mixed flocculated sludge, at a rate of approximately 5 to 7 dry sludge solids per square foot per hour, until a firm filter cake is obtained containing approximately 18 to 20 percent dry solids; and finally dewatering the filter cake to yield a final product containing approximately 30 to 35 percent dry solids, said product having a sufficiently high heat value required for autogenous com-bustion.
first adding a water-soluble, anionic organic polymeric flocculent to a quantity of raw primary sewage sludge having a concentration of suspended sludge solids of approximately 4 percent;
then mixing the flocculated sludge with a slurry containing approximately 3.0 percent paper fibers, the ratio of the fiber to the sludge solids being 2.5 to 4:10;
thereafter dewatering the mixed flocculated sludge, at a rate of approximately 5 to 7 dry sludge solids per square foot per hour, until a firm filter cake is obtained containing approximately 18 to 20 percent dry solids; and finally dewatering the filter cake to yield a final product containing approximately 30 to 35 percent dry solids, said product having a sufficiently high heat value required for autogenous com-bustion.
6. The process according to claim 5, wherein said dewatering of said mixed flocculated sludge is carried out by vacuum filtering, and said dewatering of said filter cake is carried out by compression filtering.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA280,273A CA1070864A (en) | 1977-06-10 | 1977-06-10 | Sludge dewatering process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA280,273A CA1070864A (en) | 1977-06-10 | 1977-06-10 | Sludge dewatering process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070864A true CA1070864A (en) | 1980-01-29 |
Family
ID=4108865
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,273A Expired CA1070864A (en) | 1977-06-10 | 1977-06-10 | Sludge dewatering process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1070864A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4961862A (en) * | 1988-03-22 | 1990-10-09 | Baker Hughes | Amendment addition system and method for twin belt press filter |
| DE3919001A1 (en) * | 1989-06-10 | 1990-12-13 | Utap Ges Fuer Umwelttechnnisch | Solidifying and utilising sewage sludge as soil improver - by mixing with absorbent fibrous waste material, pressing into blocks and drying |
| WO2010104440A1 (en) * | 2009-03-10 | 2010-09-16 | Arne Lindahl | Recovery of energy from organic wastes |
| US9068776B2 (en) | 2009-10-30 | 2015-06-30 | Suncor Energy Inc. | Depositing and farming methods for drying oil sand mature fine tailings |
| US9404686B2 (en) | 2009-09-15 | 2016-08-02 | Suncor Energy Inc. | Process for dying oil sand mature fine tailings |
| US9909070B2 (en) | 2009-09-15 | 2018-03-06 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
-
1977
- 1977-06-10 CA CA280,273A patent/CA1070864A/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4961862A (en) * | 1988-03-22 | 1990-10-09 | Baker Hughes | Amendment addition system and method for twin belt press filter |
| DE3919001A1 (en) * | 1989-06-10 | 1990-12-13 | Utap Ges Fuer Umwelttechnnisch | Solidifying and utilising sewage sludge as soil improver - by mixing with absorbent fibrous waste material, pressing into blocks and drying |
| WO2010104440A1 (en) * | 2009-03-10 | 2010-09-16 | Arne Lindahl | Recovery of energy from organic wastes |
| US9404686B2 (en) | 2009-09-15 | 2016-08-02 | Suncor Energy Inc. | Process for dying oil sand mature fine tailings |
| US9909070B2 (en) | 2009-09-15 | 2018-03-06 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
| US10590347B2 (en) | 2009-09-15 | 2020-03-17 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
| US9068776B2 (en) | 2009-10-30 | 2015-06-30 | Suncor Energy Inc. | Depositing and farming methods for drying oil sand mature fine tailings |
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