CN112608005B - Method for recovering struvite from municipal sludge - Google Patents
Method for recovering struvite from municipal sludge Download PDFInfo
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- CN112608005B CN112608005B CN202011337412.6A CN202011337412A CN112608005B CN 112608005 B CN112608005 B CN 112608005B CN 202011337412 A CN202011337412 A CN 202011337412A CN 112608005 B CN112608005 B CN 112608005B
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- 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
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/15—Treatment of sludge; Devices therefor by de-watering, drying or thickening by treatment with electric, magnetic or electromagnetic fields; by treatment with ultrasonic waves
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
- C01B25/451—Phosphates containing plural metal, or metal and ammonium containing metal and ammonium
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
- C02F1/56—Macromolecular compounds
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- 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
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/122—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using filter presses
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B9/00—Fertilisers based essentially on phosphates or double phosphates of magnesium
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
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- Environmental & Geological Engineering (AREA)
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- Inorganic Chemistry (AREA)
- Treatment Of Sludge (AREA)
Abstract
The invention provides a method for recovering struvite from municipal sludge, which can firstly carry out ultrasonic treatment on the municipal sludge, break the sludge and simultaneously cause cell rupture, thereby promoting intracellular moisture and PO 4 3‑ Releasing into the liquid phase; secondly, the solid TP in the sludge can be promoted to be mostly PO 4 3‑ The form is transferred to the liquid phase, so that the phosphorus content in the liquid phase after solid-liquid separation of the sludge can be improved, and the subsequent improvement of the struvite extraction recovery rate is facilitated; thirdly, the municipal sludge is subjected to ultrasonic treatment, no additional reagent is required to be added, the treatment cost is low, the process is simple, no expensive equipment investment is required, the capital construction and equipment investment are saved, and the popularization and the application are facilitated.
Description
Technical Field
The invention belongs to the technical field of struvite recovery and treatment, and particularly relates to a method for recovering struvite from municipal sludge.
Background
Struvite has the chemical name of magnesium ammonium phosphate and the chemical formula of MgNH 4 PO 4 ·6H 2 O, 12% of N and 52% of P 2 O 5 . The plant availability of the struvite is as high as 70-100%, which is superior to most mineral phosphate fertilizers, and the struvite is a slow release fertilizer with excellent effect, is insoluble in water, has small leaching property, is not easy to run off, and has small influence on water environment.
Phosphorus is a nutrient substance necessary for organisms, currently, available phosphorus ores are few due to rapid increase of global population, and in addition, the discharge of phosphorus-containing waste can cause eutrophication of water bodies. Therefore, the recovery of phosphorus resources from various phosphorus-rich wastes is an important way to solve the shortage of phosphorus resources.
In general, 1g of struvite can be crystallized from 0.1 cubic meter of wastewater. If the world population is 70 hundred million, 2.5gPO is discharged by everyone 4 3- Calculated as/d, 62kt of phosphorus (in P) can be discharged in one year 2 O 5 Measured), the exploitation amount of the phosphorite can be reduced by 6.8 percent. Therefore, the struvite phosphorus is recovered from the municipal sludge, so that the influence of nitrogen and phosphorus on water pollution can be reduced, the phosphorite resource is saved, and the key effect on the continuous development strategy of a sewage treatment plant is achieved.
The method for recovering phosphorus from the sludge liquid phase in a struvite precipitation mode has the characteristics of high stability, simple operation method, high plant availability and low economic cost compared with other recovery modes, but the recovery rate of struvite phosphorus from the sludge liquid phase is only about 40-60 percent at present, and meanwhile, the recovery purity of struvite is greatly influenced by metal ions such as Ca, mg, fe, al and the like in the sludge. Therefore, how to avoid the ineffective combination of the metal forest and phosphorus in the struvite phosphorus recovery process and improve the recovery efficiency and the recovery purity of struvite become the key of sludge phosphorus recovery.
Disclosure of Invention
The present invention is directed to solving at least one of the above problems in the prior art. Therefore, the invention provides a method for recovering struvite from municipal sludge, so as to improve the recovery efficiency and recovery purity of the struvite.
In a first aspect of the invention, there is provided a process for recovering struvite from municipal sludge comprising the steps of:
s1: carrying out solid-liquid separation on the municipal sludge to obtain filtrate and filter residue;
s2: carrying out secondary filtration on the filtrate obtained in the step S1 to obtain secondary filtrate;
s3: and (3) mixing the secondary filtrate obtained in the step (S2) with a magnesium source and a composite metal complexing agent, and carrying out struvite reaction treatment to obtain struvite particles.
According to an embodiment of the present invention, in step S1, the equipment used for solid-liquid separation is a plate-and-frame filter press.
According to an embodiment of the present invention, in step S1, the apparatus used for solid-liquid separation is a membrane filter press.
According to an embodiment of the invention, the method further comprises concentrating the municipal sludge before step S1.
According to an embodiment of the invention, the method further comprises concentrating the municipal sludge until the water content of the sludge is less than 30% before the step S1.
According to one embodiment of the invention, the method further comprises sonicating the municipal sludge prior to subjecting the municipal sludge to the concentration process.
According to one embodiment of the invention, the sonic energy density of the sonication is between 0.8 and 1.2W/mL.
According to one embodiment of the invention, the sonic energy density of the sonication is 1.0W/mL.
According to one embodiment of the invention, the time of the ultrasonic treatment is 30 to 45min.
According to one embodiment of the invention, the time of the sonication is 35min.
According to an embodiment of the invention, in step S2, after the secondary filtration, the content of suspended matters in the secondary filtrate is less than or equal to 5mg/L.
According to one embodiment of the present invention, in step S3, when the secondary filtrate is mixed with a magnesium source, the molar ratio of magnesium to phosphorus is (0.5 to 1): 1.
according to an embodiment of the present invention, in step S3, when the secondary filtrate is mixed with a magnesium source, the molar ratio of magnesium to phosphorus is 0.8:1.
according to one embodiment of the invention, in the step S3, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is (90-100): 1.
According to an embodiment of the present invention, in step S3, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is 95.
According to one embodiment of the invention, the composite metal complexing agent is ethylenediamine tetraacetic acid and humic acid in a mass ratio of (1-3): 1.
According to one embodiment of the present invention, the composite metal complexing agent is an ethylenediaminetetraacetic acid/humic acid mixture in a mass ratio of 2: 1.
The method for recovering struvite from municipal sludge provided by the invention at least has the following technical effects:
the method provided by the invention can firstly carry out ultrasonic treatment on municipal sludge, firstly, the sludge can be broken and simultaneously the cells are broken, thereby promoting the water content and PO in the cells 4 3- Releasing into the liquid phase; secondly, the solid TP in the sludge can be promoted to be mostly PO 4 3- The form is transferred to the liquid phase, so that the phosphorus content in the liquid phase after solid-liquid separation of the sludge can be improved, and the subsequent improvement of the struvite extraction recovery rate is facilitated; thirdly, municipal sludge is super-treatedAnd 3, acoustic treatment is performed, no additional reagent is added, and the treatment cost is low.
And then solid-liquid separation is carried out through plate-frame filter pressing or diaphragm filter pressing, so that filter residues with low water content can be obtained, and sludge reduction can be realized.
And after solid-liquid separation, adding a magnesium source and a composite metal complexing agent into the secondary filtrate obtained after solid-liquid separation to carry out struvite recovery reaction treatment, thereby obtaining struvite particles. In practical application, the phosphorus concentration in the municipal sludge dewatering filtrate can be effectively reduced, and the return load of the sludge water filtrate in a sewage treatment plant is reduced.
The method provided by the invention has the advantages of simple process, no need of expensive equipment investment, capital construction and equipment investment saving and contribution to popularization and application.
According to the method provided by the invention, the composite metal complexing agent is a mixture of ethylenediamine tetraacetic acid and humic acid, so that the scaling problem of equipment and pipelines in the struvite recovery process can be effectively avoided.
Detailed Description
The following are specific examples of the present invention, and the technical solutions of the present invention will be further described with reference to the examples, but the present invention is not limited to the examples.
Example 1
The embodiment provides a method for recovering struvite from municipal sludge, which comprises the following steps:
s1: carrying out solid-liquid separation on the municipal sludge to obtain filtrate and filter residue;
s2: carrying out secondary filtration on the filtrate obtained in the step S1 to obtain secondary filtrate;
s3: and (3) mixing the secondary filtrate obtained in the step (S2) with a magnesium source and a composite metal complexing agent, and carrying out struvite reaction treatment to obtain struvite particles.
In the step S1, the equipment adopted for solid-liquid separation is a diaphragm type filter press.
In the step S2, after the secondary filtration, the content of suspended matters in the secondary filtrate is less than or equal to 5mg/L.
In step S3, when the secondary filtrate is mixed with a magnesium source, the molar ratio of magnesium to phosphorus is 0.8:1.
in step S3, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is 95.
The composite metal complexing agent is prepared from ethylene diamine tetraacetic acid and humic acid according to a mass ratio of 2: 1.
Example 2
The embodiment provides a method for recovering struvite from municipal sludge, which comprises the following steps:
s1: and (3) concentrating the municipal sludge until the water content of the sludge is less than 30%.
S2: carrying out solid-liquid separation on the municipal sludge to obtain filtrate and filter residue;
s3: carrying out secondary filtration on the filtrate obtained in the step S1 to obtain secondary filtrate;
s4: and (3) mixing the secondary filtrate obtained in the step (S2) with a magnesium source and a composite metal complexing agent, and carrying out struvite reaction treatment to obtain struvite particles.
In the step S2, the equipment adopted for solid-liquid separation is a diaphragm type filter press.
In the step S3, after the secondary filtration, the content of suspended matters in the secondary filtrate is less than or equal to 5mg/L.
In step S4, when the secondary filtrate is mixed with a magnesium source, the molar ratio of magnesium to phosphorus is 0.8:1.
in step S4, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is 95.
The composite metal complexing agent is prepared from ethylene diamine tetraacetic acid and humic acid according to the mass ratio of 2: 1.
Example 3
The embodiment provides a method for recovering struvite from municipal sludge, which comprises the following steps:
s1: carrying out ultrasonic treatment on the municipal sludge, wherein the sound energy density of the ultrasonic treatment is 1.0W/mL, and the ultrasonic treatment time is 35min;
s2: and (3) concentrating the municipal sludge until the water content of the sludge is less than 30%.
S3: carrying out solid-liquid separation on municipal sludge to obtain filtrate and filter residue;
s4: carrying out secondary filtration on the filtrate obtained in the step S1 to obtain secondary filtrate;
s5: and (3) mixing the secondary filtrate obtained in the step (S2) with a magnesium source and a composite metal complexing agent, and carrying out struvite reaction treatment to obtain struvite particles.
In step S3, the equipment adopted for solid-liquid separation is a diaphragm type filter press.
In the step S4, after the secondary filtration, the content of suspended matters in the secondary filtrate is less than or equal to 5mg/L.
In step S5, when the secondary filtrate is mixed with a magnesium source, the molar ratio of magnesium to phosphorus is 0.8:1.
in step S5, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is 95.
The composite metal complexing agent is prepared from ethylene diamine tetraacetic acid and humic acid according to a mass ratio of 2: 1.
Comparative example 1
The embodiment provides a method for recovering struvite from municipal sludge, which comprises the following steps:
s1: carrying out solid-liquid separation on municipal sludge to obtain filtrate and filter residue;
s2: carrying out secondary filtration on the filtrate obtained in the step S1 to obtain secondary filtrate;
s3: and (3) mixing the secondary filtrate obtained in the step (S2) with a magnesium source and a composite metal complexing agent, and carrying out struvite reaction treatment to obtain struvite particles.
In the step S1, the equipment adopted for solid-liquid separation is a diaphragm type filter press.
In the step S2, after the secondary filtration, the content of suspended matters in the secondary filtrate is less than or equal to 5mg/L.
In step S3, when the secondary filtrate is mixed with a magnesium source, the molar ratio of magnesium to phosphorus is 0.8:1.
in step S3, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is 95.
The composite metal complexing agent is ethylenediamine tetraacetic acid.
Comparative example 2
The embodiment provides a method for recovering struvite from municipal sludge, which comprises the following steps:
s1: carrying out solid-liquid separation on the municipal sludge to obtain filtrate and filter residue;
s2: carrying out secondary filtration on the filtrate obtained in the step S1 to obtain secondary filtrate;
s3: and (3) mixing the secondary filtrate obtained in the step (S2) with a magnesium source and a composite metal complexing agent, and carrying out struvite reaction treatment to obtain struvite particles.
In the step S1, the equipment adopted for solid-liquid separation is a diaphragm type filter press.
In the step S2, after the secondary filtration, the content of suspended matters in the secondary filtrate is less than or equal to 5mg/L.
In step S3, when the secondary filtrate is mixed with a magnesium source, the molar ratio of magnesium to phosphorus is 0.8:1.
in step S3, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is 95.
The composite metal complexing agent is humic acid.
Example of detection
In this example, the municipal sludge of a sewage treatment plant of Changsha was used as a test object, and struvite was recovered by the methods of examples 1 to 3 and comparative examples 1 and 2, respectively, and the purity of struvite was examined.
Struvite has the chemical name of magnesium ammonium phosphate and the chemical formula of MgNH 4 PO 4 ·6H 2 O, mg: n: the ratio of P is 1:1, P and Mg readily produce many impurities other than struvite, such as Mg 3 (PO 4 ) 2 、Ca 3 (PO 4 ) 2 、CaHPO 4 And the like. During struvite crystallization reaction, NH 4+ Only struvite precipitates with P and Mg can be formed, but no other precipitates can be formed. The struvite precipitation purity can thus be converted by determining the ammonium ion concentration in the precipitation product. The formula for calculating the purity of struvite is shown as formula (1).
ш＝(c×a×V×245.41)/(14.007×m)×100％，(1)。
III in the formula (1) is struvite purity in unit%;
c is NH in the substrate solution 4+ -N concentration in mg/L;
a is the dilution multiple of the substrate dissolving solution;
14.007 is the relative atomic mass of nitrogen in g/mol;
245.41 relative molecular mass of struvite in g/mol;
v is the volume of the precipitation solution in L;
m is the mass of the precipitate taken in mg.
The purity test results of struvite are shown in table 1.
TABLE 1
| Numbering | Struvite purity/%) |
| Example 1 | 70.5 |
| Example 2 | 75.3 |
| Example 3 | 80.2 |
| Comparative example 1 | 65.7 |
| Comparative example 2 | 67.8 |
As can be seen from the test results in Table 1, the struvite recovered by the method of example 3 has the highest purity. The method of example 2 and example 1 follows. The ultrasonic treatment of the municipal sludge can break the sludge and cause cell rupture, thereby promoting the water content and PO in the cells 4 3- Released into the liquid phase. Can also promote most of the solid TP in the sludge to be PO 4 3- The form is transferred to the liquid phase, so that the phosphorus content in the liquid phase after solid-liquid separation of the sludge can be improved, and the subsequent improvement of the struvite purity is facilitated.
According to the method provided by the invention, the composite metal complexing agent is a mixture of ethylenediamine tetraacetic acid and humic acid, so that the scaling problem of equipment and pipelines in the struvite recovery process can be effectively avoided.
The present invention has been described in detail with reference to the embodiments, but the present invention is not limited to the embodiments described above, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.
Claims (9)
1. A method for recovering struvite from municipal sludge is characterized by comprising the following steps:
s1: carrying out solid-liquid separation on the municipal sludge to obtain filtrate and filter residue;
s2: carrying out secondary filtration on the filtrate obtained in the step S1 to obtain secondary filtrate;
s3: mixing the secondary filtrate obtained in the step S2 with a magnesium source and a composite metal complexing agent, and carrying out struvite reaction treatment to obtain struvite particles;
the composite metal complexing agent is prepared from ethylene diamine tetraacetic acid and humic acid according to the mass ratio of (1-3): 1.
2. The method according to claim 1, wherein in step S1, the equipment used for solid-liquid separation is a plate-and-frame filter press.
3. The method of claim 1, further comprising concentrating the municipal sludge prior to step S1.
4. The method of claim 3, further comprising sonicating the municipal sludge prior to the thickening.
5. The method of claim 4, wherein the sonication has an acoustic energy density of 0.8 to 1.2W/mL.
6. The method of claim 4, wherein the sonication time is 30-45 min.
7. The method as claimed in claim 1, wherein in step S2, the content of suspended matters in the secondary filtrate after the secondary filtration is less than or equal to 5mg/L.
8. The method according to claim 1, wherein in step S3, the molar ratio of magnesium to phosphorus is (0.5-1): 1.
9. the method according to claim 1, wherein in the step S3, when the secondary filtrate is mixed with the composite metal complexing agent, the volume ratio of the secondary filtrate to the composite metal complexing agent is (90-100): 1.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1712143A (en) * | 2004-06-25 | 2005-12-28 | 上海万森水处理有限公司 | Cleaning method of circulating water system |
| CN105502866A (en) * | 2016-02-05 | 2016-04-20 | 无锡国联环保能源集团有限公司 | Method and system for recycling struvite from sludge |
| CN111484214A (en) * | 2020-06-03 | 2020-08-04 | 华电水务科技股份有限公司 | Phosphorus recycling device and method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1712143A (en) * | 2004-06-25 | 2005-12-28 | 上海万森水处理有限公司 | Cleaning method of circulating water system |
| CN105502866A (en) * | 2016-02-05 | 2016-04-20 | 无锡国联环保能源集团有限公司 | Method and system for recycling struvite from sludge |
| CN111484214A (en) * | 2020-06-03 | 2020-08-04 | 华电水务科技股份有限公司 | Phosphorus recycling device and method |
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