CN111762953A - Wastewater pretreatment method - Google Patents
Wastewater pretreatment method Download PDFInfo
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- CN111762953A CN111762953A CN202010562248.2A CN202010562248A CN111762953A CN 111762953 A CN111762953 A CN 111762953A CN 202010562248 A CN202010562248 A CN 202010562248A CN 111762953 A CN111762953 A CN 111762953A
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- water
- clear liquid
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- raw water
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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
- C02F9/00—Multistage treatment of water, waste water or sewage
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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
- C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
-
- 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
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- 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
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
- C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
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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
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- 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
- C02F2001/007—Processes including a sedimentation step
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
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- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
Abstract
The invention relates to the technical field of water treatment, in particular to a wastewater pretreatment method, which pre-regulates untreated raw water to be alkaline, then adds a chelating agent to eliminate heavy metal ions in the raw water and softens the raw water to obtain a first clear liquid and a solid-liquid mixture; carrying out solid-liquid separation on the solid-liquid mixture to obtain a second clear liquid and solid waste; and performing reverse osmosis on the first clear liquid and the second clear liquid to obtain primary fresh water and primary concentrated water, performing homogeneous membrane electrodialysis on the primary concentrated water to obtain secondary fresh water and concentrated solution, performing crystallization separation on the concentrated solution to obtain crystal salt and secondary concentrated water, and pumping the secondary concentrated water into the raw water for circulating dialysis. The invention can effectively soften hard water, and the raw water softened by the invention has the hardness of below 10ppm, breaks through the barrier of the prior art and has better softening effect. Meanwhile, the invention effectively utilizes the secondary concentrated water and the solid waste after pretreatment, thereby realizing zero discharge.
Description
Technical Field
The invention relates to the technical field of water treatment, in particular to a wastewater pretreatment method.
Background
In modern production, the bipolar membrane electrodialysis method is usually an economic and reliable means for desalting wastewater, however, due to the excessively high hardness of wastewater, when the wastewater circulates through the bipolar membrane, damage is inevitably caused to the bipolar membrane, and generally, if the softened wastewater is circulated for desalting, the bipolar membrane needs to be replaced once every circulation, so that the economic benefit is poor.
Therefore, in wastewater treatment processes, wastewater is usually pretreated, and the purpose of pretreatment is to reduce the hardness of wastewater. The traditional method for reducing the hardness of the wastewater is generally a 'double-alkali method' hardness reduction, namely sodium hydroxide and sodium carbonate are adopted to replace calcium and magnesium ions in the wastewater, and the calcium and magnesium ions actually become precipitate and are separated out.
The method for reducing the hardness of the wastewater by adopting a 'double-alkali method' can only reduce the hardness of the wastewater to 50ppm generally, the wastewater with the hardness entering a bipolar membrane for electrodialysis can only circulate twice in the bipolar membrane, namely the bipolar membrane is replaced, and the actual use effect is not ideal.
Meanwhile, the traditional wastewater pretreatment mode is simple, the effect is single, heavy metal ions in the wastewater cannot be removed, the COD concentration is high, and the pretreatment effect is not ideal.
Disclosure of Invention
The invention aims to provide a wastewater pretreatment method for reducing damage to an electrodialysis membrane.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a method of wastewater pretreatment comprising the steps of:
the method comprises the following steps: adding an alkaline substance into untreated raw water to make the pH value of the raw water alkaline;
step two: adding a chelating agent into the alkaline raw water obtained in the first step, stirring for reaction, standing for precipitation for a period of time to obtain a first clear liquid and a solid-liquid mixture, pumping the first clear liquid into a buffer pool, and waiting for use;
step three: carrying out solid-liquid separation on the solid-liquid mixture to obtain a solid phase and a second clear liquid, pumping the clear liquid into a buffer pool for waiting use, and simultaneously discharging the solid phase, pressing into a mud cake and conveying away;
step four: pumping the first clear liquid and the second clear liquid into a first-stage low-pressure reverse osmosis membrane for first-stage reverse osmosis treatment to obtain first-stage fresh water and first-stage concentrated water;
step five: performing homogeneous membrane electrodialysis on the primary concentrated water to obtain secondary fresh water and a concentrated solution;
step six: and collecting and recycling the primary fresh water and the secondary fresh water.
Further, in the first step, the alkaline substances added into the raw water are sodium hydroxide and sodium carbonate, and the pH value ranges from 9 to 11.
Further, the solid-liquid separation method in the third step is to filter out solid particles by using a micro-filter, so that the precision of particles in the clear liquid is less than 10 μm.
The invention also discloses a chelating agent in the step two, which comprises the following components in percentage by mass:
1-3 parts of polyaluminum chloride;
4-6 parts of sodium ethylene diamine tetracetate;
6-8 parts of sodium carbonate;
1-3 parts of sodium sulfite;
1-3 parts of gelatin;
40-60 parts of desalted water.
In summary, compared with the conventional technical means, the technical means adopted by the invention has the following beneficial effects:
the invention can effectively soften hard water, the softening limit of the traditional 'double alkali method' is 50ppm after hard water softening, and the raw water softened by the invention has the hardness of below 10ppm, thus breaking through the barrier of the prior art and having better softening effect. According to the invention, hard water is softened to below 10ppm, if the concentrated water of the homogeneous membrane is subjected to acid-base conversion treatment by using the bipolar membrane, the damage to the bipolar membrane in the subsequent process is extremely small, and under the condition of using the same bipolar membrane, the bipolar membrane consumed in the process is at most one fifth of the bipolar membrane consumed by the traditional double-alkali method. Meanwhile, the chelating agent disclosed by the invention not only can remove hardness, but also can remove heavy metal ions in the wastewater, and can also reduce the COD concentration in the wastewater, so that the loss of the bipolar membrane is further reduced when the bipolar membrane electrodialysis is carried out, and the economic benefit is relatively high. Finally, the secondary concentrated water in the pretreatment method can still flow back to enter the original water for circulation, no discharge is caused, the solid waste is effectively utilized, and zero discharge is really realized.
Detailed Description
In light of the foregoing, it is intended that the following description be read in connection with the accompanying drawings and that the appended claims be construed as broadly as possible and that various changes and modifications may be made therein without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
The first embodiment is as follows:
a method of wastewater pretreatment comprising the steps of:
the method comprises the following steps: adding alkaline substance into untreated raw water to adjust pH value of the raw water to 9.
Step two: and (3) adding a chelating agent into the raw water with the pH value of 9 in the first step, stirring for reaction, standing for precipitation for 0.5h to obtain a first clear liquid and a solid-liquid mixture, pumping the first clear liquid into a buffer pool, and waiting for use.
Step three: and pumping the solid-liquid mixture into a micro-filter to filter solid particles to obtain a solid phase and a second clear liquid, wherein the precision of particles in the second clear liquid is smaller than 10 mu m. Pumping the second clear liquid into a buffer pool for waiting use, and simultaneously discharging the solid phase, pressing the solid phase into mud cakes and transporting the mud cakes.
Step four: pumping the first clear liquid and the second clear liquid into a first-stage low-pressure reverse osmosis membrane for first-stage reverse osmosis treatment to obtain first-stage fresh water and first-stage concentrated water;
step five: performing homogeneous membrane electrodialysis on the primary concentrated water to obtain secondary fresh water and a concentrated solution;
step six: and collecting the primary fresh water and the secondary fresh water for later use.
In addition, the concentrated solution can be crystallized and separated to obtain mother liquor and crystal salt, the crystal salt is collected, and the mother liquor is pumped back to the raw water in the first step for circulation treatment.
The crystallization separation specifically comprises the following steps:
1. introducing deep well water into the jacket of the jacketed crystallizer for circulating cooling in the jacketed crystallizer for the concentrated solution;
2. stirring the concentrated solution in the jacketed crystallizer to separate out crystal salt and mother liquor;
3. and (3) putting the mixture containing the crystal salt and the mother liquor into a centrifugal machine for separation to obtain the crystal salt and the mother liquor, and pumping the mother liquor back to the raw water in the first step for circular treatment.
As the concentration of the concentrated water of the homogeneous membrane increases, the hardness also increases, when the concentration exceeds the upper limit of the water inlet requirement of the homogeneous membrane and the concentrated water does not reach the concentration index, the concentrated water needs to be circulated to the front-end pretreatment working section to continuously remove the hardness, and enters the homogeneous membrane for concentration after reaching the standard, and finally enters the next working procedure after reaching the index. Therefore, the obtained concentrated solution can be selected to be continuously returned to the step for hardness removal.
If the high-concentration wastewater produced by the homogeneous membrane is subjected to evaporative crystallization treatment, deep hardness removal is also necessary, so that the scaling of an evaporation device can be effectively prevented, and the safety accident rate of the device can be reduced.
Meanwhile, the invention also discloses a chelating agent in the step two, which comprises the following components in percentage by mass:
1 part of polyaluminum chloride; 4 parts of sodium ethylene diamine tetracetate; 6 parts of sodium carbonate; 1 part of sodium sulfite; 2 parts of gelatin; 50 parts of demineralized water.
The chelating agent disclosed by the invention has the effect of directionally capturing heavy metal ions and calcium and magnesium ions in wastewater to form flocculation sedimentation, can effectively reduce the hardness of the wastewater to be lower than 10ppm, and can only reduce the hardness of the wastewater to be 50ppm by using a traditional 'double-alkali method' hard water softening method.
Meanwhile, because the content of free chlorine in the wastewater is high, the free chlorine corrodes metal materials, and the bipolar membrane does not contain the free chlorine when entering water, the chelating agent can not only reduce the hardness of the wastewater, but also remove the free chlorine in the wastewater and reduce the damage to the bipolar membrane.
Example two:
a method of wastewater pretreatment comprising the steps of:
the method comprises the following steps: adding alkaline substance into untreated raw water to adjust pH value of the raw water to 11.
Step two: and (3) adding a chelating agent into the raw water with the pH value of 11 in the first step, stirring for reaction, standing for precipitation for 1h to obtain a first clear liquid and a solid-liquid mixture, pumping the first clear liquid into a buffer pool, and waiting for use.
Step three: and pumping the solid-liquid mixture into a micro-filter to filter solid particles to obtain a solid phase and a second clear liquid, wherein the precision of particles in the second clear liquid is smaller than 10 mu m. Pumping the second clear liquid into a buffer pool for waiting use, and simultaneously discharging the solid phase, pressing the solid phase into mud cakes and transporting the mud cakes.
Step four: pumping the first clear liquid and the second clear liquid into a first-stage low-pressure reverse osmosis membrane for first-stage reverse osmosis treatment to obtain first-stage fresh water and first-stage concentrated water;
step five: performing homogeneous membrane electrodialysis on the primary concentrated water to obtain secondary fresh water and a concentrated solution;
step six: and collecting the primary fresh water and the secondary fresh water for reuse.
In addition, the concentrated solution can be crystallized and separated to obtain mother liquor and crystal salt, the crystal salt is collected, and the mother liquor is pumped back to the raw water in the first step for circulation treatment.
1. Introducing deep well water into the jacket of the jacketed crystallizer for circulating cooling in the jacketed crystallizer for the concentrated solution;
2. stirring the concentrated solution in the jacketed crystallizer to separate out crystal salt and mother liquor;
3. and (3) putting the mixture containing the crystal salt and the mother liquor into a centrifugal machine for separation to obtain the crystal salt and the mother liquor, and pumping the mother liquor back to the raw water in the first step for circular treatment.
As the concentration of the concentrated water of the homogeneous membrane increases, the hardness also increases, when the concentration exceeds the upper limit of the water inlet requirement of the homogeneous membrane and the concentrated water does not reach the concentration index, the concentrated water needs to be circulated to the front-end pretreatment working section to continuously remove the hardness, and enters the homogeneous membrane for concentration after reaching the standard, and finally enters the next working procedure after reaching the index. Therefore, the obtained concentrated solution can be selected to be continuously returned to the step for hardness removal.
If the high-concentration wastewater produced by the homogeneous membrane is subjected to evaporative crystallization treatment, deep hardness removal is also necessary, so that the scaling of an evaporation device can be effectively prevented, and the safety accident rate of the device can be reduced.
Meanwhile, the invention also discloses a chelating agent in the step two, which comprises the following components in percentage by mass:
1 part of polyaluminum chloride; 6 parts of sodium ethylene diamine tetracetate; 8 parts of sodium carbonate; 2 parts of sodium sulfite; 3 parts of gelatin; 60 parts of desalted water.
Claims (4)
1. A method of pre-treating wastewater, comprising the steps of:
the method comprises the following steps: adding an alkaline substance into untreated raw water to make the pH value of the raw water alkaline;
step two: adding a chelating agent into the alkaline raw water obtained in the first step, stirring for reaction, standing for precipitation for a period of time to obtain a first clear liquid and a solid-liquid mixture, pumping the first clear liquid into a buffer pool, and waiting for use;
step three: carrying out solid-liquid separation on the solid-liquid mixture to obtain a solid phase and a second clear liquid, pumping the clear liquid into a buffer pool for waiting use, and simultaneously discharging the solid phase, pressing into a mud cake and conveying away;
step four: pumping the first clear liquid and the second clear liquid into a first-stage low-pressure reverse osmosis membrane for first-stage reverse osmosis treatment to obtain first-stage fresh water and first-stage concentrated water;
step five: performing homogeneous membrane electrodialysis on the primary concentrated water to obtain secondary fresh water and a concentrated solution;
step six: and collecting and recycling the primary fresh water and the secondary fresh water.
2. A method of pre-treating wastewater according to claim 1, characterized in that: in the first step, the alkaline substances added into the raw water are sodium hydroxide and sodium carbonate, and the pH value ranges from 9 to 11.
3. A method of pre-treating wastewater according to claim 1, characterized in that: and the solid-liquid separation method in the third step is to filter out solid particles by adopting a micro-filter, so that the precision of the particles in the clear liquid is less than 10 mu m.
4. The invention also discloses a method for pretreating wastewater according to claim 1, wherein the chelating agent in the second step is characterized by comprising the following components in percentage by mass:
1-3 parts of polyaluminum chloride;
4-6 parts of sodium ethylene diamine tetracetate;
6-8 parts of sodium carbonate;
1-3 parts of sodium sulfite;
1-3 parts of gelatin;
40-60 parts of desalted water.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010562248.2A CN111762953A (en) | 2020-06-18 | 2020-06-18 | Wastewater pretreatment method |
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| CN202010562248.2A CN111762953A (en) | 2020-06-18 | 2020-06-18 | Wastewater pretreatment method |
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Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101357798A (en) * | 2007-07-31 | 2009-02-04 | 深圳市邦友通科技有限公司 | Heavy metal wastewater purificant |
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| CN105858969A (en) * | 2016-06-07 | 2016-08-17 | 韶关市雅鲁环保实业有限公司 | Wastewater treatment process of iron-copper-sulfur polymetallic mine slurry detention reservoir |
| CN106865920A (en) * | 2017-04-18 | 2017-06-20 | 昆明标洁环保科技有限责任公司 | Deep treatment method and reuse technology containing acid waste water containing heavy metal ions |
| CN107445354A (en) * | 2017-09-29 | 2017-12-08 | 楚雄滇中有色金属有限责任公司 | The preprocess method of high rigidity Metallurgical Waste Water reuse |
| CN107585845A (en) * | 2017-10-31 | 2018-01-16 | 四川行之智汇知识产权运营有限公司 | Suitable for the reagent of Industrial Waste Water Treatments |
| CN108059221A (en) * | 2016-11-08 | 2018-05-22 | 青岛市晨昱生化科技有限公司 | Flocculant |
-
2020
- 2020-06-18 CN CN202010562248.2A patent/CN111762953A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101357798A (en) * | 2007-07-31 | 2009-02-04 | 深圳市邦友通科技有限公司 | Heavy metal wastewater purificant |
| CN105417795A (en) * | 2015-12-15 | 2016-03-23 | 江苏肯创环境科技股份有限公司 | Desulfurization waste water zero discharging treatment process for coal-fired power plant |
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| CN108059221A (en) * | 2016-11-08 | 2018-05-22 | 青岛市晨昱生化科技有限公司 | Flocculant |
| CN106865920A (en) * | 2017-04-18 | 2017-06-20 | 昆明标洁环保科技有限责任公司 | Deep treatment method and reuse technology containing acid waste water containing heavy metal ions |
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