Wastewater treatment system

Abstract

The utility model relates to a wastewater treatment system which comprises an adjusting tank, a first-stage reaction unit, a second-stage reaction unit, a third-stage reaction unit and a filtering unit which are connected in sequence, wherein the adjusting tank is used for mixing evaporative crystallization mother liquor with waste acid to obtain mixed liquor; the first-stage reaction unit is used for adding lime milk into the mixed liquid for neutralization reaction to obtain first supernate; the second-stage reaction unit is used for removing chloride ions in the first supernate by using an ultrahigh lime aluminum method to obtain second supernate; the third-stage reaction unit is used for performing hardness removal treatment on the second supernate to obtain third supernate; the filtering unit is used for filtering the third supernate and then sending the filtered third supernate to the front end of the wastewater zero discharge system for retreatment. The evaporative crystallization mother liquor and the waste acid are synchronously treated by adopting the technologies of neutralization reaction, ultrahigh lime aluminum method, hardness removal, filtration and the like, so that components such as COD (Chemical Oxygen Demand), sulfate radicals, chloride ions and the like in the evaporative crystallization mother liquor and the waste acid can be removed in a sludge form.

Description

Technical Field

[0001] The utility model relates to the technical field of water treatment, in particular to a wastewater treatment system. Background Art

[0002] The zero liquid discharge technology for wastewater is to further concentrate and purify the treated industrial wastewater, evaporate and refine the dissolved substances in the water. During the evaporation and crystallization process, in addition to producing finished salts, some concentrated mother liquor will also be generated.

[0003] At present, the main components of the evaporation and crystallization mother liquor of zero liquid discharge in the steel industry are the enrichment of sulfate ions, chloride ions, COD and other ions. Generally, single-effect evaporation + drum drying is used to produce miscellaneous salts. Although the amount of miscellaneous salts is small, they cannot be consumed in the steel plant and need to be outsourced for treatment. The drying cost and outsourcing disposal cost are both relatively high. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a wastewater treatment system to solve the problem of treating the evaporation and crystallization mother liquor of zero liquid discharge of wastewater.

[0005] To achieve the above purpose, the utility model provides a wastewater treatment system, which includes a regulating tank, a first-stage reaction unit, a second-stage reaction unit, a third-stage reaction unit and a filtering unit connected in sequence; wherein,

[0006] The regulating tank is used to mix the evaporation and crystallization mother liquor produced by the zero liquid discharge system of wastewater with waste acid to obtain a mixed solution;

[0007] The first-stage reaction unit is used to add lime milk to the mixed solution for neutralization reaction, and then perform solid-liquid separation to obtain a first supernatant;

[0008] The second-stage reaction unit is used to remove chloride ions in the first supernatant by the ultra-high lime-aluminum method, and then perform solid-liquid separation to obtain a second supernatant;

[0009] The third-stage reaction unit is used to remove hardness from the second supernatant, and then perform solid-liquid separation to obtain a third supernatant;

[0010] The filtering unit is used to filter the third supernatant and send it to the front end of the zero liquid discharge system of wastewater for re-treatment.

[0011] Optionally, the waste acid is waste hydrochloric acid or waste sulfuric acid produced by the factory.

[0012] Optionally, the primary reaction unit includes a primary reaction tank, a primary sedimentation tank, and a first chemical dosing device. The water inlet end of the primary reaction tank is connected to the conditioning tank, the water outlet end of the primary reaction tank is connected to the water inlet end of the primary sedimentation tank, the water outlet end of the primary sedimentation tank serves as the water outlet end of the primary reaction unit, and the first chemical dosing device is used to add lime milk into the primary reaction tank.

[0013] Optionally, the pH of the neutralization reaction is between 8 and 9.

[0014] Optionally, the secondary reaction unit includes a secondary reaction tank, a secondary sedimentation tank, and a second chemical dosing device. The water inlet end of the secondary reaction tank serves as the water inlet end of the secondary reaction unit, the water outlet end of the secondary reaction tank is connected to the water inlet end of the secondary sedimentation tank, the water outlet end of the secondary sedimentation tank serves as the water outlet end of the secondary reaction unit, and the second chemical dosing device is used to add lime milk and sodium aluminate into the secondary reaction tank.

[0015] Optionally, the pH in the secondary reaction tank is between 12 and 13.

[0016] Optionally, the tertiary reaction unit includes a tertiary reaction tank, a tertiary sedimentation tank, and a third chemical dosing device. The water inlet end of the tertiary reaction tank serves as the water inlet end of the tertiary reaction unit, the water outlet end of the tertiary reaction tank is connected to the water inlet end of the tertiary sedimentation tank, the water outlet end of the tertiary sedimentation tank serves as the water outlet end of the tertiary reaction unit, and the third chemical dosing device is used to add sodium carbonate into the tertiary reaction tank.

[0017] Optionally, the filtration unit includes an intermediate water tank, an activated carbon filter, and a clean water tank. The water inlet end of the intermediate water tank serves as the water inlet end of the filtration unit, the water outlet end of the intermediate water tank is connected to the water inlet end of the activated carbon filter, the water outlet end of the activated carbon filter is connected to the water inlet end of the clean water tank, and the water outlet end of the clean water tank is connected to the front end of the zero liquid discharge system for wastewater.

[0018] In the wastewater treatment system provided by the present utility model, there are at least one of the following beneficial effects:

[0019] 1) By adopting technologies such as neutralization reaction, ultra-high lime-aluminum method, hardness removal, and filtration to treat the evaporation crystallization mother liquor and waste acid, components such as COD, sulfate, and chloride ions in them can be effectively removed, and the final clear liquid can be refluxed to the front end of the zero liquid discharge system for wastewater for re-treatment. Moreover, the main pollutants in the evaporation crystallization mother liquor are removed in the form of sludge, and the sintering unit of the steel mill can be used to dispose of the sludge, reducing the generation amount of miscellaneous salts, achieving waste treatment with waste, and greatly reducing the disposal cost;

[0020] 2) Since sludge is generated during the treatment process of the waste acid itself, the introduction of the evaporation crystallization mother liquor only increases the sludge production to a certain extent. Therefore, the entire treatment process is relatively environmentally friendly and does not produce other additional pollutants.

[0021] 3) Utilize the waste acid in the steel mill to synchronously treat the evaporation crystallization mother liquor, treating waste with waste, which effectively reduces the treatment cost.

[0022] 4) The process equipment adopted by the system operates stably and is easy to operate. For the regulation and control involved, PLC or DCS automatic control can be used to complete it. Description of the Drawings

[0023] Those of ordinary skill in the art should understand that the provided drawings are used to better understand the present utility model and do not constitute any limitation to the scope of the present utility model. Among them:

[0024] Figure 1 is the structural block diagram of the wastewater treatment system provided by an embodiment of the present utility model;

[0025] Figure 2 is the flow chart of the wastewater treatment system provided by an embodiment of the present utility model.

[0026] Among them:

[0027] 101 - Regulation tank; 201 - First reaction tank; 202 - First sedimentation tank; 203 - First dosing device; 301 - Second reaction tank; 302 - Second sedimentation tank; 303 - Second dosing device; 401 - Third reaction tank; 402 - Third sedimentation tank; 403 - Third dosing device; 501 - Intermediate water tank; 502 - Activated carbon filter; 503 - Clean water tank. Detailed Embodiments

[0028] As described in the background art, currently, for the zero - discharge evaporation crystallization mother liquor of wastewater in the steel industry, its main components are the enrichment of sulfate ions, chloride ions, COD, and other ions. Generally, single - effect evaporation + drum drying is used to produce miscellaneous salts. Although the amount of miscellaneous salts is small, they cannot be consumed within the steel mill and need to be outsourced for treatment. The drying cost and the outsourcing disposal cost are both relatively high. At the same time, there is waste acid (waste hydrochloric acid or waste sulfuric acid) in the steel industry that needs to be treated, and generally, lime is added for neutralization precipitation to remove heavy metal and other pollutants.

[0029] Based on this, the present utility model considers co - treating the waste acid in the steel mill with the evaporation crystallization mother liquor, and improving on the original treatment process to reduce the production of miscellaneous salts, thereby reducing the disposal cost.

[0030] To make the objectives, advantages and features of the present utility model more clear, the following further describes the present utility model in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the objectives of the embodiments of the present utility model. To make the objectives, features and advantages of the present utility model more obvious and understandable, please refer to the accompanying drawings. It should be noted that the structures, scales, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present utility model. Any modification of the structure, change of the proportional relationship or adjustment of the size, in the case of being the same or similar to the effects that the present utility model can produce and the objectives that can be achieved, should still fall within the scope covered by the technical content disclosed by the present utility model.

[0031] As used in the present utility model, the singular forms "a", "an" and "the" include plural objects unless the context clearly indicates otherwise. As used in the present utility model, the term "or" is generally used in the sense of including "and / or" unless the context clearly indicates otherwise. As used in the present utility model, the term "several" is generally used in the sense of including "at least one" unless the context clearly indicates otherwise. As used in the present utility model, the term "at least two" is generally used in the sense of including "two or more" unless the context clearly indicates otherwise. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third" may explicitly or implicitly include one or at least two of such features.

[0032] In the description of the present utility model, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected to", "fixed" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0033] Please refer to Figure 1 , this embodiment provides a wastewater treatment system, including a regulating tank 101, a primary reaction unit, a secondary reaction unit, a tertiary reaction unit and a filtering unit connected in sequence; wherein,

[0034] Adjusting groove 101, which is used to mix the evaporation crystallization mother liquor produced by the zero liquid discharge system for wastewater with waste acid to obtain a mixed liquid;

[0035] The first-stage reaction unit is used to add lime milk to the mixed liquid for neutralization reaction, and then perform solid-liquid separation to obtain the first supernatant;

[0036] The second-stage reaction unit is used to remove chloride ions in the first supernatant by the ultra-high lime-aluminum method, and then perform solid-liquid separation to obtain the second supernatant;

[0037] The third-stage reaction unit is used to remove hardness from the second supernatant, and then perform solid-liquid separation to obtain the third supernatant;

[0038] The filtration unit is used to filter the third supernatant and send it to the front end of the zero liquid discharge system for wastewater for re-treatment.

[0039] By treating the evaporation crystallization mother liquor and waste acid by adopting technologies such as neutralization reaction, ultra-high lime-aluminum method, hardness removal, and filtration, components such as COD, sulfate radical, and chloride ions in them can be effectively removed, and the final clear liquid can be refluxed to the front end of the zero liquid discharge system for wastewater for re-treatment. Moreover, the main pollutants in the evaporation crystallization mother liquor are removed in the form of sludge, and the sintering unit of the steel plant can be used to dispose of the sludge, reducing the generation amount of miscellaneous salts, realizing treating waste with waste, and greatly reducing the disposal cost. Since sludge will be generated during the treatment process of waste acid itself, the introduction of the evaporation crystallization mother liquor only increases the sludge production by a certain amount, so the entire treatment process is relatively friendly to the environment and does not generate other additional pollutants.

[0040] In this embodiment, the waste acid is, for example, waste hydrochloric acid or waste sulfuric acid produced by a steel plant.

[0041] Furthermore, the first-stage reaction unit includes a first-stage reaction tank 201, a first-stage sedimentation tank 202, and a first chemical dosing device 203. The water inlet end of the first-stage reaction tank 201 is connected to the adjusting groove 101, the water outlet end of the first-stage reaction tank 201 is connected to the water inlet end of the first-stage sedimentation tank 202, the water outlet end of the first-stage sedimentation tank 202 serves as the water outlet end of the first-stage reaction unit, and the first chemical dosing device 203 is used to add lime milk into the first-stage reaction tank 201. In this embodiment, after the evaporation crystallization mother liquor produced by the zero liquid discharge system for wastewater is mixed with the waste acid, it can be sent into the first-stage reaction tank 201 through a pressure pump, and then lime milk is added into the first-stage reaction tank 201 through the first chemical dosing device 203. The lime milk reacts with the mixed liquid for neutralization reaction. During the neutralization reaction, a large amount of sulfate radical can be precipitated, and at the same time, under the clarification effect of lime, part of the COD in the mixed liquid can be precipitated synchronously. After solid-liquid separation by the first-stage sedimentation tank 202, the first supernatant is obtained.

[0042] Preferably, the pH of the neutralization reaction is between 8 and 9, and this pH can be adjusted by controlling the dosage of lime milk to optimize the effect of the neutralization reaction.

[0043] Furthermore, the secondary reaction unit includes a secondary reaction tank 301, a secondary sedimentation tank 302, and a second chemical dosing device 303. The water inlet end of the secondary reaction tank 301 serves as the water inlet end of the secondary reaction unit. The water outlet end of the secondary reaction tank 301 is connected to the water inlet end of the secondary sedimentation tank 302, and the water outlet end of the secondary sedimentation tank 302 serves as the water outlet end of the secondary reaction unit. The second chemical dosing device 303 is used to add lime milk and sodium aluminate into the secondary reaction tank 301. In this embodiment, the water inlet end of the secondary reaction tank 301 is connected to the water outlet end of the primary sedimentation tank 202 to receive the first supernatant after solid-liquid separation in the primary sedimentation tank 202. Then, lime milk and sodium aluminate are added into the secondary reaction tank 301 through the second chemical dosing device 303 to remove chloride ions in the first supernatant by the ultra-high lime-aluminum method. The ultra-high lime-aluminum method is an effective method for removing chloride ions. By adding lime milk and sodium aluminate into the chloride-ion-containing solution, calcium-aluminum chloride compounds (a kind of Friedel's salt) with extremely low solubility are generated to achieve the effect of removing chloride ions. After solid-liquid separation in the secondary sedimentation tank 302, a second supernatant is obtained.

[0044] Preferably, the pH in the secondary reaction tank 301 is between 12 and 13, and this pH can be adjusted by controlling the dosage of lime milk.

[0045] Furthermore, the tertiary reaction unit includes a tertiary reaction tank 401, a tertiary sedimentation tank 402, and a third chemical dosing device 403. The water inlet end of the tertiary reaction tank 401 serves as the water inlet end of the tertiary reaction unit. The water outlet end of the tertiary reaction tank 401 is connected to the water inlet end of the tertiary sedimentation tank 402, and the water outlet end of the tertiary sedimentation tank 402 serves as the water outlet end of the tertiary reaction unit. The third chemical dosing device is used to add sodium carbonate into the tertiary reaction tank 401. In this embodiment, the water inlet end of the tertiary reaction tank 401 is connected to the water outlet end of the secondary sedimentation tank 302 to receive the second supernatant. Then, sodium carbonate is added into the tertiary reaction tank 401 through the third chemical dosing device 403 to generate calcium carbonate precipitate, which is subjected to solid-liquid separation in the tertiary sedimentation tank 402.

[0046] Further, the filtration unit includes an intermediate water tank 501, an activated carbon filter 502, and a clean water tank 503. The water inlet end of the intermediate water tank 501 serves as the water inlet end of the filtration unit. The water outlet end of the intermediate water tank 501 is connected to the water inlet end of the activated carbon filter 502. The water outlet end of the activated carbon filter 502 is connected to the water inlet end of the clean water tank 503. The water outlet end of the clean water tank 503 is connected to the front end of the zero liquid discharge system. In this embodiment, the water inlet end of the intermediate water tank 501 is connected to the water outlet end of the tertiary reaction tank 401 to receive the third supernatant. The third supernatant is sent into the activated carbon filter 502 by a lift pump to further reduce the COD therein, and then enters the clean water tank 503. At this time, most of the pollutants such as sulfate ions, chloride ions, and COD in the waste liquid are removed, meeting the conditions for the front-end pretreatment of the zero liquid discharge system. Finally, it is sent back to the front-end pretreatment device of the zero liquid discharge system by a lift pump for further treatment.

[0047] During the treatment process, the sludge generated by reaction precipitation is dehydrated and can be consumed by the sintering unit in the steel plant. Since sludge will be generated during the treatment process of the waste acid itself, the introduction of the evaporation crystallization mother liquor only increases the sludge production by a certain amount. Therefore, the entire treatment process is relatively friendly to the environment and does not produce other additional pollutants.

[0048] Based on the same inventive concept, please refer to Figure 2 , this embodiment of the utility model further provides a wastewater treatment method, including the following steps:

[0049] S1. Mix the evaporation crystallization mother liquor produced by the zero liquid discharge system with the waste acid to obtain a mixed liquid;

[0050] S2. Add lime milk to the mixed liquid for neutralization reaction, and then perform solid-liquid separation to obtain a first supernatant;

[0051] S3. Use the ultra-high lime-aluminum method to remove chloride ions in the first supernatant, and then perform solid-liquid separation to obtain a second supernatant;

[0052] S4. Perform hardness removal treatment on the second supernatant, and then perform solid-liquid separation to obtain a third supernatant;

[0053] S5. Filter the third supernatant and send it to the front end of the zero liquid discharge system for further treatment.

[0054] Preferably, the waste acid is waste hydrochloric acid or waste sulfuric acid produced by the factory.

[0055] Preferably, the adjustment and control involved in the entire wastewater treatment process can be automatically controlled and completed by PLC or DCS.

[0056] In summary, the embodiment of the present utility model provides a wastewater treatment system. By adopting technologies such as neutralization reaction, ultra-high lime-aluminum method, hardness removal, and filtration to treat the evaporation crystallization mother liquor and waste acid, it can effectively remove components such as COD, sulfate radical, and chloride ion therein. The final clear liquid can be refluxed to the front end of the zero wastewater discharge system for re-treatment. Moreover, the main pollutants in the evaporation crystallization mother liquor are removed in the form of sludge, and the sintering unit of the steel plant can be used to dispose of the sludge, reducing the generation amount of miscellaneous salts, achieving waste treatment with waste, and greatly reducing the disposal cost. Since sludge will be generated during the treatment process of waste acid itself, the introduction of the evaporation crystallization mother liquor only increases the sludge production to a certain extent. Therefore, the entire treatment process is relatively environmentally friendly and does not produce other additional pollutants.

[0057] In addition, it should also be recognized that although the present utility model has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present utility model. For any person skilled in the art, without departing from the scope of the technical solution of the present utility model, many possible changes and modifications can be made to the technical solution of the present utility model by using the technical content disclosed above, or it can be modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present utility model without departing from the content of the technical solution of the present utility model still fall within the scope of protection of the technical solution of the present utility model.

Claims

1. A wastewater treatment system, characterized in that, It includes a regulating tank, a primary reaction unit, a secondary reaction unit, a tertiary reaction unit and a filtration unit connected in sequence; among them, the regulating tank is used to mix the evaporation crystallization mother liquor produced by the zero liquid discharge system of wastewater with waste acid to obtain a mixed solution; the primary reaction unit is used to add lime milk to the mixed solution for neutralization reaction, and then perform solid-liquid separation to obtain a first supernatant; the secondary reaction unit is used to remove chloride ions in the first supernatant by the ultra-high lime-aluminum method, and then perform solid-liquid separation to obtain a second supernatant; the tertiary reaction unit is used to perform hardness removal treatment on the second supernatant, and then perform solid-liquid separation to obtain a third supernatant; the filtration unit is used to filter the third supernatant and send it to the front end of the zero liquid discharge system of wastewater for re-treatment.

2. The wastewater treatment system according to claim 1, wherein, The waste acid is waste hydrochloric acid or waste sulfuric acid produced by the factory.

3. The wastewater treatment system according to claim 1, wherein The primary reaction unit includes a primary reaction tank, a primary sedimentation tank and a first dosing device. The water inlet end of the primary reaction tank is connected to the regulating tank, the water outlet end of the primary reaction tank is connected to the water inlet end of the primary sedimentation tank, and the water outlet end of the primary sedimentation tank serves as the water outlet end of the primary reaction unit. The first dosing device is used to add lime milk into the primary reaction tank.

4. The wastewater treatment system according to claim 3, wherein The pH of the neutralization reaction is between 8 and 9.

5. The wastewater treatment system according to claim 1, wherein The secondary reaction unit includes a secondary reaction tank, a secondary sedimentation tank and a second dosing device. The water inlet end of the secondary reaction tank serves as the water inlet end of the secondary reaction unit, the water outlet end of the secondary reaction tank is connected to the water inlet end of the secondary sedimentation tank, and the water outlet end of the secondary sedimentation tank serves as the water outlet end of the secondary reaction unit. The second dosing device is used to add lime milk and sodium metaaluminate into the secondary reaction tank.

6. The wastewater treatment system according to claim 5, wherein The pH in the secondary reaction tank is between 12 and 13.

7. The wastewater treatment system according to claim 1, wherein The tertiary reaction unit includes a tertiary reaction tank, a tertiary sedimentation tank and a third dosing device. The water inlet end of the tertiary reaction tank serves as the water inlet end of the tertiary reaction unit, the water outlet end of the tertiary reaction tank is connected to the water inlet end of the tertiary sedimentation tank, and the water outlet end of the tertiary sedimentation tank serves as the water outlet end of the tertiary reaction unit. The third dosing device is used to add sodium carbonate into the tertiary reaction tank.

8. The wastewater treatment system according to claim 1, characterized in that, The filtration unit includes an intermediate water tank, an activated carbon filter and a clean water tank. The water inlet end of the intermediate water tank serves as the water inlet end of the filtration unit, the water outlet end of the intermediate water tank is connected to the water inlet end of the activated carbon filter, the water outlet end of the activated carbon filter is connected to the water inlet end of the clean water tank, and the water outlet end of the clean water tank is connected to the front end of the zero liquid discharge system of wastewater.

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