GB2496723A - Sludge treatment process using hydrolysis and pasteurisation - Google Patents
Sludge treatment process using hydrolysis and pasteurisation Download PDFInfo
- Publication number
- GB2496723A GB2496723A GB1218016.2A GB201218016A GB2496723A GB 2496723 A GB2496723 A GB 2496723A GB 201218016 A GB201218016 A GB 201218016A GB 2496723 A GB2496723 A GB 2496723A
- Authority
- GB
- United Kingdom
- Prior art keywords
- sludge
- text
- temperature
- hydrolysis
- time
- 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.)
- Granted
Links
- 239000010802 sludge Substances 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 45
- 230000007062 hydrolysis Effects 0.000 title claims abstract description 19
- 238000006460 hydrolysis reaction Methods 0.000 title claims abstract description 19
- 238000009928 pasteurization Methods 0.000 title claims abstract description 12
- 230000008569 process Effects 0.000 title description 30
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 230000003247 decreasing effect Effects 0.000 claims abstract description 4
- 230000029087 digestion Effects 0.000 description 7
- 238000002203 pretreatment Methods 0.000 description 7
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 244000052769 pathogen Species 0.000 description 6
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000001717 pathogenic effect Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 235000014113 dietary fatty acids Nutrition 0.000 description 3
- 229930195729 fatty acid Natural products 0.000 description 3
- 239000000194 fatty acid Substances 0.000 description 3
- 150000004665 fatty acids Chemical class 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000011368 organic material Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000010801 sewage sludge Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 238000004065 wastewater treatment Methods 0.000 description 2
- 241000894006 Bacteria Species 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 241000588724 Escherichia coli Species 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000001580 bacterial effect Effects 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000013270 controlled release Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/02—Biological treatment
- C02F11/04—Anaerobic treatment; Production of methane by such processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/18—Treatment of sludge; Devices therefor by thermal conditioning
- C02F11/185—Treatment of sludge; Devices therefor by thermal conditioning by pasteurisation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Hydrology & Water Resources (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Health & Medical Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Molecular Biology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Treatment Of Sludge (AREA)
Abstract
A method for treating sludge comprises: (i) heating the sludge, for a predetermined amount of time, to a temperature sufficient to enable hydrolysis of the sludge to begin; (ii) heating the sludge, for a second predetermined period of time, to increase the temperature and enable pasteurisation of the sludge to occur; and (iii) allowing the temperature of the sludge to decrease and holding the sludge at the decreased temperature for a third predetermined period of time, to enable further hydrolysis of the sludge to occur. Preferably, the temperature in steps (i) and (iii) is from 30 to 52°C, whilst the temperature in step (ii) can be greater than 55 °C. The predetermined amount of time in steps (i) and (ii) may be from 12 to 24 hours, whilst the predetermined amount of time in step (iii) is suitably from 2 to 4 days.
Description
SLUDGE TREATMENT PROCESS
Field of the Invention
This invention relates to the treatment of sludge, i.e., the solid waste resulting from waste-water treatment.
Background of the Invention
Waste-water treatment leads to the production of sludge. In industry, this sludge is treated by mesophilic anaerobic digestion (MAD). The MAD process converts sludge to biogas, which can be used to generate heat and electricity.
However, this process is inefficient, and not all the sludge can be converted.
This sludge must be disposed of correctly, which creates an environmental burden.
MAD reduces the organic content of sewage sludge by conversion to methane through the actions of micro-organisms. The processes which occur in a traditional MAD process are well documented. Essentially the digestion process is considered to involve three steps: a first step of solubilisation of solids by enzymes; a second step of bacterial synthesis of fatty acids (acidogenesis); and finally a third step of gasification by the methane bacteria. A temperature of 30°-35°C provides the best rate of conversion and stability with a typical retention time of at least 12 days and typically of the order of 18-20 days.
It was previously thought that sufficient pathogen reduction could be achieved by treating the sludge in a MAD process at a temperature of around 30°-35°C. However, in more recent times, particularly due to increasing concern over well-known sewage-borne diseases such as E.coli, the level of pathogen reduction that can be achieved in such MAD processes alone is no longer considered sufficient to meet health requirements.
Upstream treatment of the sludge before MAD is therefore advisable.
One known method is to hydrolyse then pasteurise the raw sludge before MAD.
This is known as "Enhanced Enzymic Hydrolysis" ("EEH") as shown in Figure 2.
Another method is pasteurisation of the sludge. A third method is hydrolysis of the sludge, which is known as acid-phase digestion. These pre-treatment processes have two main advantages. Firstly, a "safe sludge" can be produced, which is safe to use in agriculture as it is free of harmful pathogens. Secondly, the pre1reatment results in increased biogas production and therefore a reduced amount of sludge requiring disposal. However, even with this pre-treatment, conversion to biogas is still reasonably inefficient, and there is still a relatively large amount of sludge requiring disposal. Therefore, there exists a need for an alternative MAD pre-treatment process.
Summary of the Invention
It has surprisingly been found that a pre-treatment process comprising an initial hydrolysis step followed by pasteurisation and then a further hydrolysis step, results in high amounts of biogas production, high amounts volatile solids destruction and efficient heat balance of the process. This results in low amounts of waste, and therefore has environmental benefits.
The present invention therefore comprises a method for treating sludge, corn pri sing: (i) heating the sludge, for a predetermined amount of time, to a temperature sufficient to enable hydrolysis of the sludge to begin and preheat sludge prior to pasteurisation; (ii) heating the sludge, for a second predetermined period of time, to increase the temperature and enable pasteurisation of the sludge to occur; and (iii) allowing the temperature of the sludge to decrease and holding the sludge at the decreased temperature for a third predetermined period of time, to enable further hydrolysis of the sludge to occur.
Description of the Drawing
Figure 1 illustrates a process of the invention.
Figure 2 illustrates EEH, a process of the prior art.
Description of the Invention
As used herein, raw sludge means sewage sludge having a high organic content, which has not previously been subject to a treatment process to reduce the organic content/pathogen content. Typically this will be sludge having a total Chemical Oxygen Demand (COD) greater than about 1O,000mg/L, more preferably 30,000. The raw sludge should have a BOD (5 day) in the range 8,000 to 250,000 mg/I (the BOD indicating the biodegradability of the sludge).
The method of the invention is a method for treating sludge, prior to sludge digestion, preferably prior to mesophilic anaerobic digestion.
In stage (I), the raw sludge is heated to start the hydrolysis process.
Preferably, the raw sludge is heated to a temperature of 30-52t, more preferably, 40-42t. In a preferred embodiment, this step is carried out for a period of 12 to 24 hours. This raises the temperature of the sludge, via hot water, for efficient heat balance. It also begins to hydrolyse the sludge, and therefore starts to increase volatile fatty acid (VFA) concentration. Preferably, the heating is carried out using low grade heat recovered from the CHP engine, to ensure energy efficiency.
In stage (ii), the sludge is further heated, preferably with steam, in order to increase the temperature and therefore thermally condition and pasteurise the organic material. Preferably, the temperature of this step is greater than 55CC, more preferably from 55 to GOt. In a preferred embodiment, stage (H) comprises of 6 hours of filling and heating of the sludge, followed by 5 hours of further heating of sludge and subsequent emptying of the tank. The steam is added on the feed to stage (H) such that at the end of the filling and heating cycle the desired temperature is achieved. This ensures pathogens are killed and causes an increase in VFA concentration. Pasteurisation also acts as a pre-treatment stage for stage (iii).
In stage (Hi), the sludge is cooled in order to further hydrolyse the organic material and produce volatile acids. Preferably, the temperature of this step is from 30-5TC, more preferably from 40-42t. The retention period within this stage is preferably from 2 to 4 days. This ensures hydrolysis is carried out, and also acidogenesis and acetogenesis, to increase the VFA concentration, prior to optional methanogensis.
Each of the stages should be carried out in separate tanks. Stage (ii), i.e. the pasteurisation stage, may be carried out in two separate tanks in parallel.
Optionally, the pre-treated sludge is then transferred to a conventional anaerobic digester, with a retention time of 12-25 days, and an operating temperature of 33-41 t. These operating conditions allow optimum anaerobic biological digestion of readily degradable organic material, producing the useful by-product of biogas. This gas is typically 60-70% methane, with the balance mainly carbon dioxide, and is a suitable fuel for combined heat and power units and boilers.
In a preferred embodiment, each stage has a variable liquid level control, to allow optimum retention time independent of feed rate achieved by incorporating a pump mixing and transfer system. In a further preferred embodiment, the available headspace could be used for the periodic jetting of liquid into the gas space to treat potential foaming in the tank.
The key benefits of this process are that the pre-treatment, in particular the presence of step (ii) of the process, leads to enhanced quality safe sludge" (class A sludge), which is suitable for use in agriculture. The process also means that there is a high rate of solid destruction, and rate of biogas production. This biogas can be used to provide the energy to heat the process, meaning that the whole process is energy self-sufficient. This means that the process is commercially viable and economically attractive, compared to conventional anaerobic digestion and other commercial technologies.
Step (U), i.e. the pasteurisation step, is responsible for reducing the pathogen content of the sludge.
As the process is energy self-sufficient, this leads to the whole process having a lower carbon footprint, which is beneficial to the environment.
Figure 1 illustrates a process according to the invention.
The following examples illustrate the invention.
Example I
A pilot plant was constructed in accordance with the claimed invention to process I m3 of thickened sludge per day in a semi-batch process using two parallel streams. The pilot plant includes 7 m3 of storage capacity for untreated and treated sludge tanks. The filling and emptying of these tanks were manually controlled.
The automated process consists of two parallel streams of two tanks; each tank has a working capacity of 2.5 m3. Sludge was batch fed alternatively between the two streams automatically. The pasteurisation tanks operated at between 55°C and 75°C, with direct steam heating. The third stage hydrolysis tanks were cooled indirectly with final effluent from a hydrant. All tanks included a side stream mixing loop with pump for recirculation, heating or cooling and transfer to the next tank.
Both streams combined and fed into the digester which had a working capacity of 20 m3.
The pasteurisation and hydrolysis tanks continuously produced biogas which was held in a floating gas bell. The controlled release of biogas was vented directly to atmosphere.
Example 2
In the pilot plant of Example 1, a study was conducted to compare the effects of either using a heated first hydrolysis tank according to the invention (i.e. for step (i) according to the invention), or using an unheated buffer tank in place of the first hydrolysis tank (comparative).
The results showed that the use of a heated hydrolysis tank produced sludge with mean volatile fatty acids (VFA) of 4064 mg/L compared with a mean of 3262 mg/L when an unheated buffer tank was used, demonstrating that the heated tank begins the hydrolysis process. This is beneficial to the overall pre-treatment process.
Claims (1)
- <claim-text>CLAIMS1. A method for treating sludge, comprising: (i) heating the sludge, for a predetermined amount of time, to a temperature sufficient to enable hydrolysis of the sludge to begin; (ii) heating the sludge, for a second predetermined period of time, to increase the temperature and enable pasteurisation of the sludge to occur; and (Di) allowing the temperature of the sludge to decrease and holding the sludge at the decreased temperature for a third predetermined period of time, to enable further hydrolysis of the sludge to occur.</claim-text> <claim-text>2. A method according to claim 1, wherein the temperature of step (i) is 30 to 52t.</claim-text> <claim-text>3. A method according to claim 1 or claim 2, wherein the increased temperature of step (ii) is greater than 55'C.</claim-text> <claim-text>4. A method according to any preceding claim, wherein the decreased temperature of step (iii) is 30 to 52t.</claim-text> <claim-text>5. A method according to any preceding claim, comprising a further step (iv): transferring the sludge to an anaerobic digester.</claim-text> <claim-text>6. A method according to any preceding claim, wherein the pre-determined amount of time in step (i) is 12 to 24 hours.</claim-text> <claim-text>7. A method according to any preceding claim, wherein the pre-determined time in step (ii) is from 12 to 24 hours with a minimum of 5 hours.</claim-text> <claim-text>8. A method according to any preceding claim, wherein the pre-determined time in step (Hi) is from 2 to 4 days.</claim-text>
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GBGB1117358.0A GB201117358D0 (en) | 2011-10-07 | 2011-10-07 | Method |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB201218016D0 GB201218016D0 (en) | 2012-11-21 |
| GB2496723A true GB2496723A (en) | 2013-05-22 |
| GB2496723B GB2496723B (en) | 2016-07-13 |
Family
ID=45091717
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GBGB1117358.0A Ceased GB201117358D0 (en) | 2011-10-07 | 2011-10-07 | Method |
| GB1218016.2A Active GB2496723B (en) | 2011-10-07 | 2012-10-08 | Sludge treatment process |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GBGB1117358.0A Ceased GB201117358D0 (en) | 2011-10-07 | 2011-10-07 | Method |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB201117358D0 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018208999A1 (en) * | 2017-05-11 | 2018-11-15 | Bl Technologies, Inc. | Method for pre-conditioning sludge |
| EP3683194A1 (en) * | 2019-01-14 | 2020-07-22 | Dünnebeil, Andreas | Method and device for disintegration of organic substrates |
| NL2033778B1 (en) | 2022-12-21 | 2024-06-27 | Haskoningdhv Nederland Bv | Methode voor het produceren van biogas in een anaerobe slibbehandeling |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0179234A2 (en) * | 1984-10-22 | 1986-04-30 | UTB Umwelttechnik Buchs AG | Process and apparatus for the treatment of sewage sludge |
| US4983298A (en) * | 1989-02-21 | 1991-01-08 | Leonhard Fuchs | Process for the disinfection and aerobic stabilization of sewage sludge |
| US20020168288A1 (en) * | 2001-04-27 | 2002-11-14 | Brade Colin Edward | Heating sludge |
| US6521133B1 (en) * | 2000-08-07 | 2003-02-18 | Roediger Pittsburgh, Inc. | Process for thermal sludge disinfection |
| WO2003040047A1 (en) * | 2001-11-09 | 2003-05-15 | United Utilites Plc | Incubation treatment of sludge for pathogen reduction prior to digestion |
| US20070209997A1 (en) * | 2006-03-10 | 2007-09-13 | Poppe John R | Continuous flow biosolids stabilization |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0027001D0 (en) * | 2000-11-04 | 2000-12-20 | Biwater Treat Ltd | Method and apparatus for the treatment of sludge |
-
2011
- 2011-10-07 GB GBGB1117358.0A patent/GB201117358D0/en not_active Ceased
-
2012
- 2012-10-08 GB GB1218016.2A patent/GB2496723B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0179234A2 (en) * | 1984-10-22 | 1986-04-30 | UTB Umwelttechnik Buchs AG | Process and apparatus for the treatment of sewage sludge |
| US4983298A (en) * | 1989-02-21 | 1991-01-08 | Leonhard Fuchs | Process for the disinfection and aerobic stabilization of sewage sludge |
| US6521133B1 (en) * | 2000-08-07 | 2003-02-18 | Roediger Pittsburgh, Inc. | Process for thermal sludge disinfection |
| US20020168288A1 (en) * | 2001-04-27 | 2002-11-14 | Brade Colin Edward | Heating sludge |
| WO2003040047A1 (en) * | 2001-11-09 | 2003-05-15 | United Utilites Plc | Incubation treatment of sludge for pathogen reduction prior to digestion |
| US20070209997A1 (en) * | 2006-03-10 | 2007-09-13 | Poppe John R | Continuous flow biosolids stabilization |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018208999A1 (en) * | 2017-05-11 | 2018-11-15 | Bl Technologies, Inc. | Method for pre-conditioning sludge |
| US11453608B2 (en) | 2017-05-11 | 2022-09-27 | Bl Technologies, Inc. | Method for pre-conditioning sludge |
| EP3683194A1 (en) * | 2019-01-14 | 2020-07-22 | Dünnebeil, Andreas | Method and device for disintegration of organic substrates |
| NL2033778B1 (en) | 2022-12-21 | 2024-06-27 | Haskoningdhv Nederland Bv | Methode voor het produceren van biogas in een anaerobe slibbehandeling |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2496723B (en) | 2016-07-13 |
| GB201117358D0 (en) | 2011-11-23 |
| GB201218016D0 (en) | 2012-11-21 |
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| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) |
Free format text: REGISTERED BETWEEN 20220714 AND 20220720 |