Polyformaldehyde wastewater treatment device

Abstract

The utility model discloses a polyformaldehyde wastewater treatment device which comprises a first treatment pond, a second treatment pond, a third treatment pond and a fourth treatment pond, the first treatment pond is communicated to the second treatment pond through a second pipeline, and the second treatment pond is communicated to the third treatment pond through a third pipeline; the third treatment pond is communicated to a fourth treatment pond through a fourth pipeline, and the fourth treatment pond is connected with a fifth pipeline. According to the polyformaldehyde wastewater treatment device disclosed by the utility model, the polyformaldehyde wastewater is removed by adopting two-stage biochemistry, the concentration of formaldehyde is reduced through enrichment, adsorption, degradation and precipitation of special sludge in the first-stage biological selection enhanced reaction tank, and the stable operation of a second-stage biochemical system is ensured; the method has the advantages of no need of adding a large amount of chemicals, good treatment effect, low investment, simple process flow, high automation degree, simple operation, low operation cost, high treatment efficiency and the like.

Description

TECHNICAL FIELD

[0001] The utility model relates to a wastewater treatment device, especially to a polyformaldehyde wastewater treatment device. BACKGROUND

[0002] Polyformaldehyde (POM), also known as acetal resin, polyoxymethylene, polyacetal, is a thermoplastic crystalline polymer, known as "super steel" or "race steel". Polyformaldehyde is one of the new products of coal chemical industry. As a kind of thermoplastic engineering plastic with excellent comprehensive performance, polyformaldehyde has excellent properties such as high hardness, wear resistance, fatigue resistance and good dimensional stability, and its application field is extremely wide, especially in replacing non-ferrous metal materials such as copper, aluminum and zinc. Therefore, it is widely used in automobile industry, medical equipment, agricultural machinery and military industry.

[0003] Generally, the wastewater discharged in polyformaldehyde production is acidic, with a pH value of about 3-4, and the organic pollutants include formaldehyde, methanol, benzene, trioxymethylene and dioxolane. Formaldehyde can directly react with the protein, DNA and RNA of microorganisms, resulting in the death of microorganisms or the inhibition of biological activity. When the concentration of formaldehyde is less than 5 mg / L, the biochemical system is relatively stable; when the concentration of formaldehyde is more than 100 mg / L, the microorganisms will be inhibited. Polyformaldehyde wastewater has the following characteristics: high COD, high formaldehyde concentration, strong biological toxicity; high concentration of formaldehyde polymers such as trioxymethylene (TOX) and dioxolane (DOX); high water temperature and low pH value, which belongs to industrial wastewater with strong biological toxicity, complex composition, difficult biodegradation, large fluctuation of water quality and quantity, and difficult treatment, and has great harm to the environment. The polymers of formaldehyde such as trioxymethylene and dioxolane are relatively stable organic matters, which are difficult to be utilized by microorganisms. These characteristics determine that the treatment of polyformaldehyde wastewater is difficult, and the COD of the effluent is difficult to meet the discharge standard, and it is impossible to realize reuse.

[0004] For the treatment of polyformaldehyde wastewater, the commonly used processes include lime pretreatment method, Fenton method, iron-carbon micro-electrolysis method and electrochemical method.

[0005] The lime pretreatment method is to add lime to polyformaldehyde wastewater to adjust the alkalinity, heat to about 70 DEG C, make polyformaldehyde substances occur polymerization reaction, generate sugar substances which are easy to be utilized by microorganisms, and then remove by anaerobic and aerobic. Due to the incomplete saccharification reaction, only part of the formaldehyde can be removed by using this method, resulting in unstable operation of the subsequent biochemical system; at the same time, the wastewater is heated and then cooled, a large amount of alkali is added, and then acid is added for readjustment, which consumes a lot of energy and reagent. Therefore, this method is widely used in the early stage of polyformaldehyde development, and then gradually replaced by other methods.

[0006] Fenton method is to use the low pH of wastewater, adding hydrogen peroxide and ferrous sulfate to wastewater, using the hydroxyl radical generated by Fenton reaction to treat wastewater, but Fenton oxidation method needs to add a large amount of reagent, and the sludge quantity is large, so the comprehensive treatment cost is high.

[0007] Iron-carbon micro-electrolysis method is to use iron filings to reduce formaldehyde in wastewater into methanol and other easily degradable organic matter, but the conversion rate of formaldehyde is not high, and there is still a high concentration of formaldehyde after treatment, and the toxicity problem of wastewater still exists.

[0008] Electrochemical technology uses the electrochemical reaction of organic matter on the anode to remove pollutants in wastewater. Since no additional flocculating agent needs to be added, the electrochemical method has the advantages of high efficiency, wide application range, economic and environmental protection, simple operation and the like. However, for the treatment of polyformaldehyde wastewater, the unit energy consumption is high, the equipment investment is large, and the treatment effect is poor, so this method only exists in the development and research of laboratory, and has not been applied in actual engineering.

[0009] Compared with the physical and chemical treatment process, the biological method is favored due to its mature process, good treatment effect, low running cost, convenient operation management and the like. However, the inhibition of formaldehyde and TOX to microorganisms increases the difficulty of biological treatment of polyformaldehyde wastewater, and the existing treatment scheme cannot well reduce the toxicity of formaldehyde, especially the biological treatment scheme; moreover, the existing biological treatment scheme has high cost and complex operation. SUMMARY

[0010] The technical problem to be solved by the utility model lies in: providing a polyformaldehyde wastewater treatment device, which solves the problem that the existing biological polyformaldehyde wastewater treatment cannot well reduce the toxicity of formaldehyde.

[0011] The technical problem to be solved by the utility model is solved by the following technical scheme:

[0012] The utility model provides a polyformaldehyde wastewater treatment device, including first treatment pool, second treatment pool, third treatment pool and fourth treatment pool, wherein,

[0013] The first treatment pool is communicated to the second treatment pool through the second pipeline, and the second treatment pool is communicated to the third treatment pool through the third pipeline;

[0014] The third treatment pool is communicated to the fourth treatment pool through the fourth pipeline, wherein,

[0015] The fourth treatment pool is connected with the fifth pipeline.

[0016] As a preferred technical scheme of the utility model, the first treatment pool is a biological selection enhancement reaction tank, wherein,

[0017] The outlet of the first treatment tank is communicated to the second treatment tank through a second pipeline;

[0018] The second treatment tank is a sedimentation tank, and the outlet thereof is communicated to the third treatment tank through the third pipeline;

[0019] The third treatment tank is a hydrolysis / aerobic circulating biochemical tank, wherein the third treatment tank is provided with a fourth reflux pipeline;

[0020] The fourth treatment tank is a secondary sedimentation tank, and the outlet thereof is communicated to the first treatment tank through a second reflux pipeline.

[0021] As a preferred technical scheme of the present application, the second reflux pipeline is further connected with a third reflux pipeline, and the third reflux pipeline is connected to the third treatment tank;

[0022] The second treatment tank is communicated to the first treatment tank through a first reflux pipeline.

[0023] As a preferred technical scheme of the present application, the first treatment tank is connected with a first pipeline for introducing polyformaldehyde wastewater.

[0024] As a preferred technical scheme of the present application, the first treatment tank is a biological selection enhanced reaction tank in the form of a gallery type reaction tank, wherein,

[0025] The ratio of the total length of the gallery to the width is 6-20:1;

[0026] The first treatment tank is further provided with linearly arranged aerators.

[0027] As a preferred technical scheme of the present application, the third treatment tank is a hydrolysis / aerobic circulating biochemical tank in the form of a gallery type reaction tank, wherein,

[0028] The ratio of the total length of the gallery to the width is 20-40:1;

[0029] The third treatment tank is further provided with linearly arranged aerators.

[0030] The polyformaldehyde wastewater treatment device of the present application adopts two-stage biochemical treatment to remove polyformaldehyde wastewater, and the concentration of formaldehyde is reduced in the first-stage biological selection enhanced reaction tank through the enrichment, adsorption, degradation and sedimentation of special sludge, thereby ensuring the stable operation of the second-stage biochemical system; a large amount of chemical agents does not need to be added, the treatment effect is good, the BOD of the effluent from the secondary sedimentation tank can be reduced to below 5 mg / L, the tail water quality can be stably brought up to the requirements of the discharge standard, and the device has the advantages of low investment, simple process flow, high automation degree, simple operation, low operation cost and high treatment efficiency. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of this utility model;

[0032] In the diagram: 100, First treatment tank; 200, Second treatment tank; 300, Third treatment tank; 400, Fourth treatment tank; 001, First pipeline; 002, Second pipeline; 003, Third pipeline; 004, Fourth pipeline; 005, Fifth pipeline; 006, First return pipe; 007, Second return pipe; 008, Third return pipe; 009, Fourth return pipe. Detailed Implementation

[0033] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] Example

[0035] like Figure 1 As shown, this embodiment provides a polyoxymethylene wastewater treatment device, including a first treatment tank 100, a second treatment tank 200, a third treatment tank 300, and a fourth treatment tank 400. The first treatment tank 100 is connected to the second treatment tank 200 through a second pipe 002, and the second treatment tank 200 is connected to the third treatment tank 300 through a third pipe 003. The third treatment tank 300 is connected to the fourth treatment tank 400 through a fourth pipe 004. The fourth treatment tank 400 is connected to a fifth pipe 005.

[0036] Specifically, in this embodiment, the first treatment tank 100 is a biological selection enhanced reaction tank, wherein the outlet of the first treatment tank 100 is connected to the second treatment tank 200 through the second pipe 002; the second treatment tank 200 is a sedimentation tank, wherein its outlet is connected to the third treatment tank 300 through the third pipe 003; the third treatment tank 300 is a hydrolysis / aerobic circulating biochemical tank, wherein the third treatment tank 300 has a fourth return pipe 009; the fourth treatment tank 400 is a secondary sedimentation tank, wherein it is connected to the first treatment tank 100 through the second return pipe 007.

[0037] In this embodiment, the dissolved oxygen at the end of the hydrolysis / aerobic circulating biological tank is controlled at 3-5 mg / L, and the pH is controlled at 6-8; the surface loading of the secondary sedimentation tank is 0.5-1.0 m3 / (m2·h).

[0038] The second return pipe 007 is also connected to a third return pipe 008, which is connected to the third treatment tank 300; the second treatment tank 200 is connected to the first treatment tank 100 through the first return pipe 006. The first treatment tank 100 is connected to a first pipe 001 for introducing polyoxymethylene wastewater.

[0039] The polyformaldehyde wastewater is treated by using a two-stage biochemical treatment process. The first-stage biological selection and reinforcement reaction tank (i.e., the first treatment tank 100) selects growth of formaldehyde-degrading bacteria, reduces the toxicity of the wastewater, reduces the impact of toxic substances on the second-stage biochemical tank (i.e., the third treatment tank 300), and ensures stable operation of the second-stage biochemical tank.

[0040] More specifically, regarding the first treatment tank 100 and the third treatment tank 300, the first treatment tank 100 is a biological selection and reinforcement reaction tank in the form of a gallery-type reaction tank, wherein the ratio of the total length to the width of the gallery is 6-20:1, preferably 8-12:1; the residence time is 24-48 hours; the first treatment tank 100 also has linearly arranged aerators, such as HS strong-cut aerators, in the embodiment, the aeration air volume is 0.6-1.8 m3 / h / m3 (tank capacity), preferably 0.9-1.5 m3 / h / m3 (tank capacity); and the dissolved oxygen at the end thereof is controlled to be 0.5-1.5 mg / L, and the pH is controlled to be 6-7.

[0041] Regarding the fourth treatment tank 400 (i.e., the secondary sedimentation tank), it is backflowed to the third treatment tank 300 (i.e., the hydrolysis / aerobic circulating biochemical tank) through the second backflow pipe 007 and the third backflow pipe 008. Specifically, the backflow ratio of the mixed liquor at the end to the hydrolysis / aerobic circulating biochemical tank is 4-15:1, preferably 8-10:1; and the sludge backflow ratio of the secondary sedimentation tank to the hydrolysis / aerobic circulating biochemical tank is 1-2:1.

[0042] The third treatment tank 300 is a hydrolysis / aerobic circulating biochemical tank in the form of a gallery-type reaction tank, wherein the ratio of the total length to the width of the gallery is 20-40:1, and in the embodiment, it is preferably 25-35:1; the residence time of the hydrolysis / aerobic circulating biochemical tank is 72-144 hours; the sludge concentration in the hydrolysis / aerobic circulating biochemical tank is 5-12 gVSS / L, preferably 6-8 gVSS / L; and the third treatment tank 300 also has linearly arranged aerators, such as HS strong-cut aerators, in the embodiment, the aeration air volume is 0.6-1.8 m3 / h / m3 (tank capacity), preferably 0.9-1.5 m3 / h / m3 (tank capacity).

[0043] Further, regarding the second treatment tank 200, i.e., the sedimentation tank, in the embodiment, the sludge backflow ratio thereof to the biological selection and reinforcement reaction tank (i.e., the first treatment tank 100) is 1-2:1, the surface load of the sedimentation tank is 0.5-1.0 m3 / (m2·h); and the sludge backflow ratio of the secondary sedimentation tank (i.e., the fourth treatment tank 400) to the biological selection and reinforcement reaction tank is (1-2):1.

[0044] Specifically, the polyformaldehyde wastewater first enters the biological selection and strengthening reaction tank (i.e. the first treatment tank 100), and the sludge backflow of the sedimentation tank (i.e. the second treatment tank 200) and the secondary sedimentation tank (i.e. the fourth treatment tank 400) enters the biological selection and strengthening reaction tank (i.e. the first treatment tank 100). After a large amount of sludge and polyformaldehyde wastewater are contacted, microorganisms suitable for the hydrolysis of formaldehyde are cultivated, and the concentration of formaldehyde is reduced. The outlet of the biological selection and strengthening reaction tank is connected with the sedimentation tank, and the outlet of the sedimentation tank is connected with the third treatment tank 300 (i.e. the hydrolysis / aerobic circulating biochemical tank). Meanwhile, the mixed liquid at the end of the hydrolysis / aerobic circulating biochemical tank is backflowed to the water inlet end of the tank, so that the organic matter in the wastewater is completely degraded. The hydrolysis / aerobic circulating biochemical tank is connected with the secondary sedimentation tank, and the effluent of the secondary sedimentation tank is connected with the effluent pipe. The sludge precipitated in the secondary sedimentation tank can be backflowed to the biological selection and strengthening reaction tank and the hydrolysis / aerobic circulating biochemical tank at the same time.

[0045] The present application utilizes a two-stage biochemical treatment process to treat the polyformaldehyde wastewater. The first-stage biological selection and strengthening reaction tank selects formaldehyde-degrading bacteria to grow, reduces the toxicity of the wastewater, reduces the impact of abnormal drainage on the second-stage biochemical tank, and ensures the stable operation of the second-stage biochemical tank.

[0046] The following is a typical operating example:

[0047] A certain 80,000 / year polyformaldehyde project, the wastewater mainly comes from the formaldehyde recovery tower bottom sewage wastewater, polymerization unit wastewater, initial rainwater and ground washing wastewater, the water amount is about 2400m3 / d, the COD of the wastewater is 3000-4000mg / L, the formaldehyde concentration is 500-1000mg / L, the pH is 3-5, the wastewater adopts a two-stage biochemical treatment process, i.e. the wastewater treatment device in the embodiment, and the specific process is shown in Figure 1 , wherein:

[0048] The residence time of the biological selection and strengthening reaction tank (the first treatment tank 100) is 48 hours. The biological selection and strengthening reaction tank adopts a gallery type reaction tank form, and the total length to width ratio of the gallery is 11:1.

[0049] The selection of the aeration intensity of the biological selection and strengthening reaction tank needs to comprehensively consider the sludge respiration oxygen demand and the mixed energy consumption oxygen demand of the sludge in suspension. The aeration amount is generally controlled at 1.2m3 / h / m3 (tank capacity). The aerator adopts a HS strong cutting aerator, and the aerator is linearly arranged. The aeration removes some sugar substances in the wastewater, improves the dewatering performance of the sludge, and the dissolved oxygen at the end of the biological selection and strengthening reaction tank is controlled at 0.5-1.5mg / L.

[0050] Another important control parameter of the biological selection and strengthening reaction tank is the pH value. Since there is an acidification step during the degradation of formaldehyde, if the pH is too low, the hydrolysis process of formaldehyde will be inhibited. Generally, the pH of the biological selection and strengthening reaction tank is controlled at 6-7.

[0051] For the treatment of polyformaldehyde wastewater, obtaining a certain number of microorganisms capable of degrading formaldehyde and polyformaldehyde is the key to the effective treatment of the wastewater. Biological selection enhancement is a method of removing specific pollutants in wastewater by obtaining a specific strain through natural screening and controlling suitable growth conditions to make the strain grow and reproduce and gradually become the dominant bacteria in the system. Therefore, the two important points are sludge supplement and prevention of sludge loss.

[0052] The activated sludge of the secondary sedimentation tank is returned as a supplement of the strain, and at the same time, the concentration of formaldehyde in the system can be reduced, and the growth of microorganisms can be utilized, and the activated sludge has good adsorption performance, which can adsorb and treat toxic substances. The sludge return ratio of the secondary sedimentation tank to the biological selection enhancement reaction tank is 1-2:1.

[0053] In order to ensure the sludge concentration of the biological selection enhancement reaction tank, the sludge of the settling tank needs to be returned to the biological selection enhancement reaction tank, and the sludge return ratio of the settling tank is controlled to be 1-2:1.

[0054] The effluent of the biological selection enhancement reaction tank enters the settling tank, and the settling tank is equipped with a mud scraper. The surface load of the settling tank is 0.5 m3 / (m2·h).

[0055] The effluent of the settling tank enters the hydrolysis / aerobic circulating biochemical tank, and the residence time of the hydrolysis / aerobic circulating biochemical tank is 144 hours. The hydrolysis / aerobic circulating biochemical tank adopts a corridor type reaction tank form, and the ratio of the total length of the corridor to the width is 33:1. The biological selection enhancement reaction tank is provided with linearly arranged aerators, and the aerators adopt HS strong cutting aerators. The aeration air volume is 1.2 m3 / h / m3(pool capacity).

[0056] The sludge of the secondary sedimentation tank needs to be returned to the front end of the hydrolysis / aerobic circulating biochemical tank to ensure the sludge concentration of the hydrolysis / aerobic circulating biochemical tank. The sludge return ratio of the secondary sedimentation tank is 1-2:1, and the sludge concentration in the hydrolysis / aerobic circulating biochemical tank is 6-8 gVSS / L.

[0057] At the same time, the mixed liquor at the end of the hydrolysis / aerobic circulating biochemical tank needs to be returned to the front end of the hydrolysis / aerobic circulating biochemical tank, and the return ratio is 10:1.

[0058] At the same time, the dissolved oxygen at the end of the hydrolysis / aerobic circulating biochemical tank is controlled to be 3-5 mg / L, and the pH is controlled to be 6-8.

[0059] The effluent of the hydrolysis / aerobic circulating biochemical tank enters the secondary sedimentation tank, and the sludge-water separation is completed in the secondary sedimentation tank. The surface load of the secondary sedimentation tank is 0.5 m3 / (m2·h).

[0060] After being treated by the device, the effluent COD is 100-200 mg / L, the effluent formaldehyde is <0.1 mg / L, and the effluent SS is <100 mg / L.

[0061] The polyformaldehyde wastewater treatment device of the utility model does not need to add a large amount of chemical medicine, the technological process is simple, and the operation cost is low; the treatment process has high automation degree and simple operation; two-stage biochemical treatment is used to remove polyformaldehyde wastewater; through the enrichment, adsorption, degradation and precipitation of special sludge in the first-stage biological selection enhancement reaction tank, the concentration of formaldehyde is reduced, and the stable operation of the second-stage biochemical system is ensured; the treatment effect is good, the BOD of the effluent from the secondary sedimentation tank can be reduced to below 5mg / L, and the tail water quality can stably reach the discharge standard requirement; the utility model has the advantages of low investment, simple technological process, high automation degree, simple operation, low operation cost and high treatment efficiency.

[0062] The basic principle, main features and advantages of the utility model are shown and described above. Those skilled in the art should understand that the utility model is not limited to the above-mentioned embodiments, and various changes and improvements can be made without departing from the spirit and scope of the utility model, and these changes and improvements all fall within the scope of the utility model. The scope of protection of the utility model is defined by the appended claims and their equivalents.

Claims

1. A polyformaldehyde wastewater treatment device, characterized by comprising: It comprises a first treatment tank (100), a second treatment tank (200), a third treatment tank (300) and a fourth treatment tank (400), wherein, The first treatment tank (100) is connected to the second treatment tank (200) through a second pipeline (002), and the second treatment tank (200) is connected to the third treatment tank (300) through a third pipeline (003); The third treatment tank (300) is connected to the fourth treatment tank (400) through a fourth pipeline (004), wherein, The fourth treatment tank (400) is connected with a fifth pipeline (005).

2. A polyformaldehyde wastewater treatment device according to claim 1, characterized in that, The first treatment tank (100) is a biological selection enhanced reaction tank, wherein, The outlet of the first treatment tank (100) is connected to the second treatment tank (200) through a second pipeline (002); The second treatment tank (200) is a sedimentation tank, and its outlet is connected to the third treatment tank (300) through the third pipeline (003); The third treatment tank (300) is a hydrolysis / aerobic circulating biochemical tank, wherein the third treatment tank (300) has a fourth reflux pipe (009); The fourth treatment tank (400) is a secondary sedimentation tank, wherein it is connected to the first treatment tank (100) through a second reflux pipe (007).

3. A polyformaldehyde wastewater treatment device according to claim 2, characterized in that, The second reflux pipe (007) is also connected with a third reflux pipe (008) connected to the third treatment tank (300); The second treatment tank (200) is connected to the first treatment tank (100) through a first reflux pipe (006).

4. A polyformaldehyde wastewater treatment device according to claim 3, characterized in that, The first treatment tank (100) is connected with a first pipeline (001) for introducing polyformaldehyde wastewater.

5. A polyformaldehyde wastewater treatment device according to any one of claims 1 to 4, characterized in that, The first treatment tank (100) is a biological selection enhanced reaction tank in the form of a gallery type reaction tank, wherein, The ratio of total length to width is 6-20:1; The first treatment tank (100) also has linearly arranged aerators.

6. A polyformaldehyde wastewater treatment device according to claim 5, characterized in that, The third treatment tank (300) is a hydrolysis / aerobic circulating biochemical tank in the form of a gallery type reaction tank, wherein, The ratio of total length to width is 20-40:1; The third treatment tank (300) also has linearly arranged aerators.

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