Photovoltaic wastewater advanced treatment device and wastewater treatment method

Abstract

The invention discloses a photovoltaic wastewater advanced treatment device and a wastewater treatment method. Comprising a first-stage defluorination device, a second-stage defluorination device, an A / O biological membrane denitrification device, a third-stage defluorination device, an ozone oxidation-biological contact oxidation coupling device, a fourth-stage defluorination device, a defluorination agent adding system and an intelligent acid-base device, a sludge external reflux device, a fluorine removal agent adding system and an acid-base intelligent device are arranged in the device, so that the wastewater treatment effect is further improved, and the labor cost is saved; according to the invention, the photovoltaic wastewater is effectively treated, and all indexes simultaneously reach the pollutant discharge standard of a municipal sewage treatment plant under the conditions of 200-600mg / L of fluoride, 80-200mg / L of COD (Chemical Oxygen Demand), 5-30mg / L of NH3-N and 10-50mg / L of TN (Town Nitrogen), namely, the fluoride is less than or equal to 1.5 mg / L, the COD is less than 40mg / L, the NH3-N is less than 1.0 mg / L and the TN is less than 10mg / L, so that the treated wastewater can be directly discharged without being further treated by a comprehensive sewage treatment plant.

Description

Technical Field

[0001] The invention relates to a wastewater treatment device and a treatment method thereof, and in particular to a photovoltaic wastewater deep treatment device and a wastewater treatment method. Background Art

[0002] In the context of carbon peak and carbon neutrality, the rapid development of the photovoltaic industry has led to a sharp increase in the demand for photovoltaic cells. The preparation process of photovoltaic cells produces a large amount of acid-base wastewater, high-fluorine wastewater and ammonia nitrogen wastewater. According to statistics, the amount of wastewater generated by photovoltaic cells per GW is 150,000-200,000m 3 In 2023, China's photovoltaic cell production will be 545GW, and the annual discharge of photovoltaic wastewater will be about 81.75-109 million m 3 , which poses a severe challenge to environmental quality. In response to the rapid development of the photovoltaic industry, various regions have formulated strict emission standards, such as requiring fluoride emission standards to be lower than 1.5mg / L or lower than 1.0mg / L, and the existing process only focuses on reducing the concentration of fluoride ions. This has, to a certain extent, led to a large increase in sludge volume and secondary pollution of the environment. While paying attention to the fluoride ion concentration in photovoltaic wastewater, it is also necessary to pay attention to the pollution caused by COD, NH3-N, TN, etc. in the wastewater. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a deep treatment device that can reduce the fluoride ion concentration in photovoltaic wastewater and reduce the content of other substances in the wastewater such as COD, NH3-N, TN, etc.; The second purpose of the present invention is to provide a wastewater treatment method that utilizes a device to reduce the fluoride ion concentration in photovoltaic wastewater and reduce the content of other substances in the wastewater such as COD, NH3-N, TN, etc.

[0004] Technical solution: The photovoltaic wastewater deep treatment device described in the present invention includes a first-stage defluorination device, a second-stage defluorination device, an A / O biofilm denitrification device, a third-stage defluorination device, an ozone oxidation-biological contact oxidation coupling device and a fourth-stage defluorination device connected in sequence, as well as a defluorination agent dosing system and an acid-base intelligent device; wherein, a sludge external reflux device is provided between the first-stage defluorination device and the second-stage defluorination device and between the third-stage defluorination device and the fourth-stage defluorination device, and a defluorination agent dosing system and an acid-base intelligent device are provided in the first defluorination device and the second defluorination device and are intelligently controlled through a control system.

[0005] Preferably, the first-stage defluorination device includes a first-level first coagulation zone, a second-level coagulation zone, a first-level flocculation zone, a first-level sedimentation zone, and a sludge internal reflux device is provided between the first-level sedimentation zone and the first-level first coagulation zone; the second-stage defluorination device includes a second-level coagulation zone, a second-level flocculation zone, a second-level sedimentation zone, and a sludge external reflux device is provided between the second-level sedimentation zone and the first-level first coagulation zone; the third-stage defluorination device includes a third-level first coagulation zone, a third-level second coagulation zone, a third-level flocculation zone, a third-level sedimentation zone, and a sludge internal reflux device is provided between the third-level sedimentation zone and the third-level first coagulation zone; the fourth-stage defluorination device includes a fourth-level coagulation zone, a fourth-level flocculation zone, a fourth-level sedimentation zone, and a sludge external reflux device between the fourth-level sedimentation zone and the third-level first coagulation zone; wherein the first-level sedimentation zone, the second-level sedimentation zone, the third-level sedimentation zone and the fourth-level sedimentation zone are all provided with a sump for diverting wastewater supernatant and a sludge hopper for discharging sludge.

[0006] Preferably, the defluoridation agent dosing system consists of a defluoridation agent dosing device, an online fluoride monitoring device arranged at the water outlet of the first defluoridation device, and an online fluoride monitoring device arranged at the water outlet of the second defluoridation device; the acid-base intelligent device consists of a liquid alkali dosing device, an online pH meter arranged in the first-level second coagulation zone, and an online pH meter arranged in the second-level coagulation zone; the defluoridation agent dosing system and the acid-base intelligent device are both centrally controlled by a control system.

[0007] Preferably, the A / O biofilm device is composed of a first anoxic biofilm zone, a first aerobic biofilm zone, a second anoxic biofilm zone, and a second aerobic biofilm zone in sequence, and also includes a first nitrification liquid reflux device from the first aerobic biofilm zone to the first anoxic biofilm zone, and a second nitrification liquid reflux device from the second aerobic biofilm zone to the second anoxic biofilm zone.

[0008] Preferably, agitators are provided in the first anoxic biofilm zone and the second anoxic biofilm zone, and aerators are provided in the first aerobic biofilm zone 302 and the second aerobic biofilm zone 304 .

[0009] Preferably, the ozone oxidation-biological contact oxidation coupling device comprises an ozone oxidation tank, a degassing tank and a biological contact oxidation tank for removing ozone, and a micro-nano gas dissolving device for adding ozone.

[0010] The photovoltaic wastewater deep treatment method using the system described in the present invention comprises the following steps:

[0011] S1: adding lime or calcium chloride and liquid alkali into the first coagulation zone and the second coagulation zone; adding aluminum salt or mixed defluoridant and liquid alkali into the first coagulation zone and the fourth coagulation zone, and adding flocculant into the first flocculation zone, the second flocculation zone, the third flocculation zone and the fourth flocculation zone;

[0012] S2: The wastewater shall stay in the first coagulation zone of the first level for no less than 15 minutes, in the second coagulation zone of the first level for no less than 10 minutes, and in the first flocculation zone for no less than 5 minutes; in the first coagulation zone of the second level for no less than 20 minutes, and in the second flocculation zone for no less than 5 minutes; in the first coagulation zone of the third level for no less than 15 minutes, in the second coagulation zone of the third level for no less than 10 minutes, and in the third flocculation zone for no less than 5 minutes; in the first coagulation zone of the fourth level for no less than 20 minutes, and in the fourth flocculation zone for no less than 5 minutes;

[0013] S3: The ratio of the residence time of the wastewater in the first anoxic biofilm zone, the first aerobic biofilm zone, the second anoxic biofilm zone, and the second aerobic biofilm zone is 4:4:3:1, and the total residence time of the wastewater in the A / O biofilm denitrification device is 10-15h;

[0014] S4: The wastewater stays in the ozone oxidation tank for 0.5-3 hours and in the biological contact oxidation tank for 2-5 hours.

[0015] Preferably, step S3 maintains the dissolved oxygen concentration in the first anoxic biofilm zone and the second anoxic biofilm zone at 0.2-0.5 mg / L.

[0016] Preferably, in step S3, the dissolved oxygen in the first aerobic biofilm zone and the second aerobic biofilm zone is maintained at 2-4 mg / L.

[0017] Preferably, in step S3, part of the nitrification liquid in the first aerobic biofilm zone flows back to the first anoxic biofilm zone, and part of the nitrification liquid in the second aerobic biofilm zone flows back to the second anoxic biofilm zone.

[0018] Beneficial effect: Compared with the prior art, the present invention has the following significant effects: the present invention can make photovoltaic wastewater reach the pollutant discharge standard of urban sewage treatment plants under the conditions of influent fluoride of 200-600mg / L, COD of 80-200mg / L, NH3-N of 5-30mg / L, and TN of 10-50mg / L, that is, fluoride ≤1.5mg / L, COD <40mg / L, NH3-N <1.0mg / L, and TN <10mg / L, so that the treated wastewater can be directly discharged without further treatment in a comprehensive sewage treatment plant, and while reducing the fluoride ion concentration in the wastewater, it can further avoid the large increase in sludge volume and the secondary pollution of the environment by other pollutants in the wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the connection between various devices in the present invention;

[0020] Figure 2 It is a connection diagram of the internal modules of each device in the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below in conjunction with the embodiments and drawings.

[0022] Examples 1-3 provide the effects of opening or closing the sludge external reflow device between the first defluorination device 100 and the second defluorination device 200 and between the third defluorination device 400 and the fourth defluorination device 600 on the defluorination effect.

[0023] Example 1

[0024] The defluorination effect is provided when the sludge external reflow device between the first defluorination device 100 and the second defluorination device 200 and between the third defluorination device 400 and the fourth defluorination device 600 is turned on.

[0025] Photovoltaic wastewater enters the first-stage defluorination device 100 and first flows into the first-stage coagulation zone 101, where lime or calcium chloride and liquid alkali are added. Through rapid stirring, the residence time is not less than 15 minutes, so that the agent and wastewater are fully mixed and a preliminary chemical reaction occurs, preparing for subsequent defluorination. Then the wastewater enters the second-stage coagulation zone 102, with a residence time of not less than 10 minutes, to further enhance the coagulation effect and make the fluoride and other impurities in the water better condensed. Then the wastewater comes to the first-stage flocculation zone 103, where a flocculant preferably PAM is added, and the residence time is not less than 5 minutes, so that small particles are condensed into larger flocs. Finally, the wastewater flows into the first-stage sedimentation zone 104. Under the action of gravity and the scraper, the flocs settle to the bottom sludge hopper, and the supernatant continues to flow to the sump and then flows to the second-stage defluorination device 200 by gravity. Part of the sludge in the primary sedimentation zone is returned to the primary first coagulation zone 101 through the sludge internal return device to increase the sludge concentration and enhance the defluorination effect. The fluoride concentration of the effluent from the first-stage defluorination device 100 is not higher than 50 mg / L.

[0026] The wastewater from the first-stage defluorination device 100 enters the second-stage defluorination device 200: the wastewater also undergoes coagulation reaction in the secondary coagulation zone 201 of the second-stage defluorination device, with a residence time of not less than 20 minutes, to further remove impurities such as fluoride in the water. Then it enters the secondary flocculation zone 202, with a residence time of not less than 5 minutes, to make the flocs more compact. Finally, it is precipitated in the secondary sedimentation zone 203, and the treated wastewater flows to the A / O biofilm denitrification device 300. Part of the sludge in the secondary sedimentation zone 203 is returned to the first coagulation zone 101 of the first-stage defluorination device 100 through the sludge external return device to supplement the sludge amount in the first-stage defluorination device 100 and improve the defluorination efficiency. The fluoride concentration of the effluent from the second-stage defluorination device 200 is 8-15 mg / L and the pH is 6.0-8.0.

[0027] The wastewater treated by the second-stage defluorination device 200 enters the A / O biofilm denitrification device 300, and passes through the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm zone 303, and the second aerobic biofilm zone 304 in sequence. Agitators are arranged in the first anoxic biofilm zone 301 and the second anoxic biofilm zone 303 to maintain the dissolved oxygen concentration in the pool at 0.2-0.5 mg / L. Aerators are arranged in the first aerobic biofilm zone 302 and the second aerobic biofilm zone 304 to ensure the sewage treatment effect and operation efficiency. The dissolved oxygen in the pool is controlled at 2-4 mg / L. Part of the nitrification liquid in the first aerobic biofilm zone 302 flows back to the first anoxic biofilm zone 301 to provide nitrate nitrogen substrate and alkalinity for the first anoxic biofilm zone 301, thereby promoting system denitrification. Part of the nitrification liquid in the second aerobic biofilm zone 304 also flows back to the second anoxic biofilm zone 303 to effectively remove organic matter and total nitrogen in the photovoltaic wastewater. The total residence time of the A / O biofilm denitrification device 300 is 10-15 hours, and the ratio of the residence time of the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm zone 303, and the second aerobic biofilm zone 304 is preferably 4:4:3:1.

[0028] The wastewater treated by the A / O biofilm denitrification device 300 enters the third-stage defluorination device 400: the wastewater passes through the third-stage first coagulation zone 401 and the third-stage second coagulation zone 402 of the third-stage defluorination device in turn. Aluminum salt or mixed defluoridation agent and liquid alkali are added to these two areas to react with fluoride in the water. The residence time in the third-stage first coagulation zone 401 is not less than 15 minutes, and the residence time in the third-stage second coagulation zone 402 is not less than 10 minutes. The wastewater then enters the third-stage flocculation zone 403, and PAM is added to the third-stage flocculation zone 403 to promote floc formation. The residence time is not less than 5 minutes. Finally, it is precipitated in the third-stage sedimentation zone 404. The supernatant after precipitation continues to flow to the subsequent treatment link. Part of the sludge in the third-stage sedimentation zone 404 is returned to the third-stage first coagulation zone 401 through the sludge internal reflux device to keep the sludge concentration in the device stable. The fluoride concentration of the effluent from the third-stage defluorination device 400 is 1.5-2.5 mg / L and the pH is 6.0-7.0.

[0029] The wastewater from the third-stage defluorination device 400 enters the ozone oxidation-biological contact oxidation coupling device 500: first, ozone oxidation treatment is carried out in the ozone oxidation tank 501, and ozone is added by a micro-nano gas dissolving device 504. The residence time in the ozone oxidation tank is preferably 1 hour, so that ozone is fully in contact with the wastewater and oxidatively decomposes the difficult-to-degrade organic matter in the water. The residual ozone in the wastewater is removed through the degassing tank 502, and then enters the biological contact oxidation tank 503, and the residence time is preferably 3 hours. The biofilm in the tank is fully in contact with the wastewater to further remove pollutants such as organic matter and ammonia nitrogen.

[0030] Finally, the wastewater enters the fourth-stage defluorination device 600: the wastewater undergoes the final defluorination treatment in the fourth-stage coagulation zone 601, the fourth-stage flocculation zone 602 and the fourth-stage sedimentation zone 603 of the fourth-stage defluorination device 400. Here, aluminum salt or mixed defluoridation agent and liquid alkali are also added to the fourth-stage coagulation zone 601 to react with the fluoride in the water, and PAM is added to the fourth-stage flocculation zone 602 to promote floc formation. The residence time in the first coagulation zone is not less than 20 minutes, and the residence time in the flocculation zone is not less than 5 minutes to ensure that the fluoride content in the wastewater meets the discharge standard. Part of the sludge in the fourth-stage sedimentation zone 603 is returned to the third-stage first coagulation zone 401 of the third-stage defluorination device 400 through the sludge external return device to supplement the sludge amount in the third-stage defluorination device 400, improve the defluorination efficiency, and ensure that the fluoride in the wastewater meets the standard. The fluoride concentration of the effluent from the fourth-stage defluorination device 600 stably reaches 0.5-1.5 mg / L and the pH is 6.0-7.0.

[0031] Example 2

[0032] The defluorination effect is provided when the sludge external reflow device between the first defluorination device 100 and the second defluorination device 200 is closed and the sludge external reflow device between the third defluorination device 400 and the fourth defluorination device 600 is opened.

[0033] Photovoltaic wastewater enters the first-stage defluorination device 100 and first flows into the first-stage coagulation zone 101, where lime or calcium chloride and liquid alkali are added. Through rapid stirring, the residence time is not less than 15 minutes, so that the agent and wastewater are fully mixed and a preliminary chemical reaction occurs, preparing for subsequent defluorination. Then the wastewater enters the second-stage coagulation zone 102, with a residence time of not less than 10 minutes, to further enhance the coagulation effect and make the fluoride and other impurities in the water better condensed. Then the wastewater comes to the first-stage flocculation zone 103, where a flocculant preferably PAM is added, and the residence time is not less than 5 minutes, so that small particles are condensed into larger flocs. Finally, the wastewater flows into the first-stage sedimentation zone 104. Under the action of gravity and the scraper, the flocs settle to the bottom sludge hopper, and the supernatant continues to flow to the sump, and then flows to the second-stage defluorination device 200 by gravity. Part of the sludge in the primary sedimentation zone 104 is returned to the primary first coagulation zone 101 through the sludge internal return device to increase the sludge concentration and enhance the defluorination effect. The fluoride concentration of the effluent from the first-stage defluorination device 100 is not higher than 50 mg / L.

[0034] The wastewater from the first-stage defluorination device 100 enters the second-stage defluorination device 200: the wastewater also undergoes coagulation reaction in the secondary coagulation zone 201 of the second-stage defluorination device, with a residence time of not less than 20 minutes, to further remove impurities such as fluoride in the water. Then it enters the secondary flocculation zone 202, with a residence time of not less than 5 minutes, to make the flocs more compact. Finally, it is precipitated in the secondary sedimentation zone 203, and the treated wastewater flows to the A / O biofilm denitrification device 300. The external reflux device is closed, and part of the sludge in the secondary sedimentation zone 203 is returned to the secondary coagulation zone 201 through the sludge internal reflux device to supplement the sludge volume in the secondary coagulation zone 201 and improve the defluorination efficiency. The fluoride concentration of the effluent from the second-stage defluorination device 200 is 10-20 mg / L and the pH is 6.0-8.0.

[0035] The wastewater treated by the second-stage defluorination device 200 enters the A / O biofilm denitrification device 300, and passes through the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm zone 303, and the second aerobic biofilm zone 304 in sequence. Agitators are arranged in the first anoxic biofilm zone 301 and the second anoxic biofilm zone 303 to maintain the dissolved oxygen concentration in the pool at 0.2-0.5 mg / L. Aeration is arranged in the first aerobic biofilm zone 302 and the second aerobic biofilm zone 304, and the dissolved oxygen in the pool is controlled at 2-4 mg / L. Part of the nitrification liquid in the first aerobic biofilm zone 302 flows back to the first anoxic biofilm zone 301 to provide nitrate nitrogen substrate and alkalinity for the first anoxic biofilm zone 301, thereby promoting system denitrification. Part of the nitrification liquid in the second aerobic biofilm zone 304 also flows back to the second anoxic biofilm zone 303, thereby effectively removing organic matter and total nitrogen in the photovoltaic wastewater. The total residence time of the A / O biofilm denitrification device 300 is 12 hours, and the ratio of the residence time of the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm zone 303, and the second aerobic biofilm zone 304 is 4:4:3:1.

[0036] The wastewater treated by the A / O biofilm denitrification device 300 enters the third-stage defluorination device 400: the wastewater passes through the third-stage first coagulation zone 401 and the third-stage second coagulation zone 402 of the third-stage defluorination device 400 in turn. Aluminum salt or mixed defluoridation agent and liquid alkali are added to these two areas to react with fluoride in the water. The residence time in the third-stage first coagulation zone 401 is not less than 15 minutes, and the residence time in the third-stage second coagulation zone 402 is not less than 10 minutes. Then it enters the third-stage flocculation zone 403, and PAM is added to promote floc formation. The residence time is not less than 5 minutes. Finally, it is precipitated in the third-stage sedimentation zone 404. The supernatant after the third-stage sedimentation continues to flow to the subsequent treatment link. Part of the sludge in the third-stage sedimentation zone 404 is returned to the third-stage first coagulation zone 401 through the sludge internal reflux device to keep the sludge concentration in the device stable. The fluoride concentration of the effluent from the third-stage defluorination device 400 is 2.0-3.0 mg / L and the pH is 6.0-7.0.

[0037] The wastewater from the third-stage defluorination device 400 enters the ozone oxidation-biological contact oxidation coupling device 500: first, ozone oxidation treatment is carried out in the ozone oxidation tank 501. Ozone is added by a micro-nano gas dissolving device 504. The residence time in the ozone oxidation tank is 1 hour, so that ozone is fully in contact with the wastewater and oxidatively decomposes the difficult-to-degrade organic matter in the water. The residual ozone in the wastewater is removed by the degassing tank 502, and then enters the biological contact oxidation tank 503. The residence time is 3 hours. The biofilm in the tank is fully in contact with the wastewater to further remove pollutants such as organic matter and ammonia nitrogen.

[0038] Finally, the wastewater enters the fourth-stage defluorination device 600: the wastewater undergoes final defluorination treatment in the fourth-stage coagulation zone 601, the fourth-stage flocculation zone 602 and the fourth-stage sedimentation zone 603 of the fourth-stage defluorination device. Here, aluminum salt or mixed defluoridation agent and liquid alkali are also added to the fourth-stage coagulation zone 601 to react with the fluoride in the water, and PAM is added to the fourth-stage flocculation zone 602 to promote floc formation. The residence time of the fourth-stage first coagulation zone 601 is not less than 20 minutes, and the residence time of the fourth-stage flocculation zone 602 is not less than 5 minutes to ensure that the fluoride content in the wastewater meets the discharge standard. Part of the sludge in the fourth-stage sedimentation zone 603 is returned to the third-stage first coagulation zone 401 of the third-stage defluorination device 400 through the sludge external return device to supplement the sludge amount in the third-stage defluorination device 400, improve the defluorination efficiency, and ensure that the fluoride in the wastewater meets the standard. The fluoride concentration of the effluent from the fourth-stage defluorination device 600 stably reaches 1.0-1.5 mg / L and the pH is 6.0-7.0.

[0039] Example 3

[0040] The defluorination effect is provided when the sludge external return device between the first defluorination device 100 and the second defluorination device 200 is turned on and the sludge external return device between the third defluorination device 400 and the fourth defluorination device 600 is turned off.

[0041] Photovoltaic wastewater enters the first-stage defluorination device 100 and first flows into the first coagulation zone 101, where lime or calcium chloride and liquid alkali are added. Through rapid stirring, the residence time is not less than 15 minutes, so that the agent and wastewater are fully mixed, and a preliminary chemical reaction occurs, preparing for subsequent defluorination. Then the wastewater enters the first-stage second coagulation zone 102, with a residence time of not less than 10 minutes, to further enhance the coagulation effect and make the fluoride and other impurities in the water better condensed. Then the wastewater comes to the first-stage flocculation zone 103, where a flocculant preferably PAM is added, and the residence time is not less than 5 minutes, so that small particles are condensed into larger flocs. Finally, the wastewater flows into the first-stage sedimentation zone 104. Under the action of gravity and the scraper, the flocs settle to the bottom sludge hopper, and the supernatant continues to flow to the sump and then flows to the second-stage defluorination device 200 by gravity. Part of the sludge in the secondary sedimentation zone 203 is returned to the primary first coagulation zone 101 through the sludge internal return device to increase the sludge concentration and enhance the defluorination effect. The fluoride concentration of the effluent from the first-stage defluorination device 100 is not higher than 50 mg / L.

[0042] The wastewater from the first-stage defluorination device 100 enters the second-stage defluorination device 200: the wastewater also undergoes coagulation reaction in the secondary coagulation zone 201 of the second-stage defluorination device, with a residence time of not less than 20 minutes, to further remove impurities such as fluoride in the water. Then it enters the secondary flocculation zone 202, with a residence time of not less than 5 minutes, to make the flocs more compact. Finally, it is precipitated in the secondary sedimentation zone 203, and the treated wastewater flows to the A / O biofilm denitrification device 300. Part of the sludge in the secondary sedimentation zone 203 is returned to the first coagulation zone 101 of the first-stage defluorination device 100 through the sludge external return device to supplement the sludge amount in the first-stage defluorination device 100 and improve the defluorination efficiency. The fluoride concentration of the effluent from the second-stage defluorination device 200 is 8-15 mg / L and the pH is 6.0-8.0.

[0043] The wastewater treated by the second-stage defluorination device 200 enters the A / O biofilm denitrification device 300, and passes through the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm zone 303, and the second aerobic biofilm zone 304 in sequence. Agitators are arranged in the first anoxic biofilm zone 301 and the second anoxic biofilm zone 303 to maintain the dissolved oxygen concentration in the pool at 0.2-0.5 mg / L. Aeration is arranged in the first aerobic biofilm zone 302 and the second aerobic biofilm zone 304, and the dissolved oxygen in the pool is controlled at 2-4 mg / L. Part of the nitrification liquid in the first aerobic biofilm zone 302 flows back to the first anoxic biofilm zone 301 to provide nitrate nitrogen substrate and alkalinity for the first anoxic biofilm zone 301, thereby promoting system denitrification. Part of the nitrification liquid in the second aerobic biofilm zone 304 also flows back to the second anoxic biofilm zone 303, thereby effectively removing organic matter and total nitrogen in the photovoltaic wastewater. The total residence time of the A / O biofilm denitrification device 300 is 12 hours, and the ratio of the residence time of the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm zone 303, and the second aerobic biofilm zone 304 is 4:4:3:1.

[0044] The wastewater treated by the A / O biofilm denitrification device 300 enters the third-stage defluorination device 400: the wastewater passes through the third-stage first coagulation zone 401 and the third-stage second coagulation zone 402 of the third-stage defluorination device 400 in turn. Aluminum salt or mixed defluoridation agent and liquid alkali are added to these two areas to react with fluoride in the water. The residence time in the third-stage first coagulation zone 401 is not less than 15 minutes, and the residence time in the third-stage second coagulation zone 402 is not less than 10 minutes. Then it enters the third-stage flocculation zone 403, and PAM is added to promote floc formation. The residence time is not less than 5 minutes. Finally, it is precipitated in the third-stage sedimentation zone 404. The supernatant after precipitation continues to flow to the subsequent treatment link. The sludge external reflux device between the third defluorination device 400 and the fourth defluorination device 600 is closed, and part of the sludge in the third-stage sedimentation zone 404 is refluxed to the third-stage first coagulation zone 401 through the sludge internal reflux device to keep the sludge concentration in the device stable. The fluoride concentration of the effluent from the third-stage defluorination device 400 is 1.5-3.0 mg / L and the pH is 6.0-7.0.

[0045] The wastewater from the third-stage defluorination device 400 enters the ozone oxidation-biological contact oxidation coupling device 500: first, ozone oxidation treatment is carried out in the ozone oxidation tank 501. Ozone is added by a micro-nano gas dissolving device 504. The residence time in the ozone oxidation tank is 1 hour, so that ozone is fully in contact with the wastewater and oxidatively decomposes the difficult-to-degrade organic matter in the water. The residual ozone in the wastewater is removed by the degassing tank 502, and then enters the biological contact oxidation tank 503. The residence time is 3 hours. The biofilm in the tank is fully in contact with the wastewater to further remove pollutants such as organic matter and ammonia nitrogen.

[0046] Finally, the wastewater enters the fourth-stage defluorination device 600: the wastewater undergoes final defluorination treatment in the fourth-stage coagulation zone 601, the fourth-stage flocculation zone 602 and the fourth-stage sedimentation zone 603 of the fourth-stage defluorination device 600. Aluminum salt or mixed defluoridation agent, liquid alkali and PAM are also added here. The residence time in the fourth-stage first coagulation zone is not less than 20 minutes, and the residence time in the fourth-stage flocculation zone is not less than 5 minutes to ensure that the fluoride content in the wastewater meets the discharge standard. Part of the sludge in the fourth-stage sedimentation zone 603 is returned to the fourth-stage coagulation zone 601 through the sludge internal reflux device to supplement the amount of sludge in the fourth-stage coagulation zone 601, improve the defluorination efficiency, and ensure that the fluoride content in the wastewater meets the standard. The fluoride concentration of the effluent from the fourth-stage defluorination device 600 stably reaches 1.0-1.5 mg / L and the pH is 6.0-7.0.

[0047] In summary, it can be intuitively seen from Examples 1-3 that when other conditions are the same, turning on the sludge external reflow devices between the first defluorination device 100 and the second defluorination device 200 and between the third defluorination device 400 and the fourth defluorination device 600 can improve the defluorination effect.

[0048] Example 4

[0049] The photovoltaic wastewater has COD198mg / L, ammonia nitrogen30mg / L, TN48mg / L, and fluoride596mg / L. When treated with the device, the wastewater stays in the first-level first coagulation zone 101 for 25min, the second-level second coagulation zone 101 for 20min, and the first-level flocculation zone 103 for 10min; the second-level coagulation zone 201 stays for 25min, and the second-level flocculation zone 201 stays for 10min; the third-level first coagulation zone 401 stays for 20min, the third-level second coagulation zone 402 stays for 15min, and the third-level flocculation zone 403 stays for 5min; the fourth-level first coagulation zone 601 stays for 20min, and the third-level flocculation zone 602 stays for 5min. The total residence time of the A / O biofilm denitrification device 300 is 12 hours, and the residence times of the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm 303, and the second aerobic biofilm zone 304 are 4 hours, 4 hours, 3 hours, and 1 hour, respectively. The residence time of the ozone oxidation tank 501 is 1 hour, and the residence time of the biological contact oxidation device is 3 hours. The fluoride concentration of the effluent of the first-stage defluoridation device 100 is 49 mg / L, the fluoride concentration of the effluent of the second-stage defluoridation device 200 is 20 mg / L and the pH is 7.2, the fluoride concentration of the effluent of the third-stage defluoridation device 400 is 3.0 mg / L and the pH is 6.7, and the fluoride concentration of the effluent of the fourth-stage defluoridation device 600 is 1.5 mg / L and the pH is 7.0.

[0050] Water quality indicators Fluoride mg / L CODmg / L Ammonia nitrogen mg / L TNmg / L pH Influent water quality 596 198 30 48 6-9 Outlet water quality 1.5 38 0.9 10 7.0

[0051] Example 5

[0052] Photovoltaic wastewater has COD152mg / L, ammonia nitrogen21mg / L, TN33mg / L, and fluoride405mg / L. It is treated by the present device. The residence time of the first coagulation zone 101 is 20min, the residence time of the second coagulation zone 102 is 15min, and the residence time of the first flocculation zone 103 is 10min; the residence time of the second coagulation zone 201 is 20min, and the residence time of the second flocculation zone 202 is 10min; the residence time of the third first coagulation zone 401 is 15min, the residence time of the third second coagulation zone 402 is 10min, and the residence time of the third flocculation zone 403 is 5min; the residence time of the fourth coagulation zone 601 is 20min, and the residence time of the fourth flocculation zone 602 is 5min. The total residence time of wastewater in the A / O biofilm denitrification device 300 is 12 hours, and the residence times of the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm 303, and the second aerobic biofilm zone 304 are 4 hours, 4 hours, 3 hours, and 1 hour, respectively. The residence time of wastewater in the ozone oxidation tank 501 is 1 hour, and the residence time of the biological contact oxidation device is 3 hours. The fluoride concentration of the effluent of the first-stage defluoridation device 100 is 45 mg / L, the fluoride concentration of the effluent of the second-stage defluoridation device 200 is 15 mg / L and the pH is 7.3, the fluoride concentration of the effluent of the third-stage defluoridation device 400 is 2.6 mg / L and the pH is 6.8, and the fluoride concentration of the effluent of the fourth-stage defluoridation device 600 is 1.1 mg / L and the pH is 6.7.

[0053] Water quality indicators Fluoride mg / L CODmg / L Ammonia nitrogen mg / L TNmg / L pH Influent water quality 405 152 21 33 6-9 Outlet water quality 1.1 37 0.9 8 6.7

[0054] Example 6

[0055] The photovoltaic wastewater has COD118mg / L, ammonia nitrogen10mg / L, TN21mg / L, and fluoride288mg / L. The device is used to treat the wastewater. The residence time of the first coagulation zone 101 is 15min, the residence time of the second coagulation zone 102 is 10min, and the residence time of the first flocculation zone 103 is 5min; the residence time of the second coagulation zone 201 is 20min, and the residence time of the second flocculation zone 202 is 5min; the residence time of the third first coagulation zone 401 is 15min, the residence time of the third second coagulation zone 402 is 10min, and the residence time of the third flocculation zone 403 is 5min; the residence time of the fourth first coagulation zone 601 is 20min, and the residence time of the fourth flocculation zone 402 is 5min. The total residence time of the A / O biofilm denitrification device 300 is 12 hours, and the residence times of the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm 303, and the second aerobic biofilm zone 304 are 4 hours, 4 hours, 3 hours, and 1 hour, respectively. The residence time of the ozone oxidation tank 501 is 1 hour, and the residence time of the biological contact oxidation device is 3 hours. The fluoride concentration of the effluent of the first-stage defluoridation device 100 is 45 mg / L, the fluoride concentration of the effluent of the second-stage defluoridation device 200 is 10 mg / L and the pH is 6.5, the fluoride concentration of the effluent of the third-stage defluoridation device 400 is 1.8 mg / L and the pH is 6.9, and the fluoride concentration of the effluent of the fourth-stage defluoridation device 500 is 0.7 mg / L and the pH is 6.4.

[0056] Water quality indicators Fluoride mg / L CODmg / L Ammonia nitrogen mg / L TNmg / L pH Influent water quality 288 118 10 21 6-9 Outlet water quality 0.7 35 0.7 9 6.4

[0057] Example 7

[0058] Photovoltaic wastewater with COD80mg / L, ammonia nitrogen5mg / L, TN10mg / L, fluoride202mg / L is treated by the present device. The residence time of the first coagulation zone 101 is 15min, the residence time of the second coagulation zone 102 is 10min, and the residence time of the first flocculation zone 103 is 5min; the residence time of the second coagulation zone 201 is 20min, and the residence time of the second flocculation zone 202 is 5min; the residence time of the third first coagulation zone 401 is 15min, the residence time of the third second coagulation zone 402 is 10min, and the residence time of the third flocculation zone 403 is 5min; the residence time of the fourth coagulation zone 601 is 20min, and the residence time of the fourth flocculation zone 602 is 5min. The total residence time of the A / O biofilm denitrification device 300 is 12 hours, and the residence times of the first anoxic biofilm zone 301, the first aerobic biofilm zone 302, the second anoxic biofilm 303, and the second aerobic biofilm zone 304 are 4 hours, 4 hours, 3 hours, and 1 hour, respectively. The residence time of the ozone oxidation tank 501 is 1 hour, and the residence time of the biological contact oxidation device is 3 hours. The fluoride concentration of the effluent of the first-stage defluoridation device 100 is 38 mg / L, the fluoride concentration of the effluent of the second-stage defluoridation device 200 is 8 mg / L and the pH is 7.6, the fluoride concentration of the effluent of the third-stage defluoridation device 400 is 1.5 mg / L and the pH is 6.2, and the fluoride concentration of the effluent of the fourth-stage defluoridation device 600 is 0.5 mg / L and the pH is 6.8.

[0059] Water quality indicators Fluoride mg / L CODmg / L Ammonia nitrogen mg / L TNmg / L pH Influent water quality 202 80 5 10 6-9 Outlet water quality 0.5 32 0.7 6 6.8

Claims

1. A photovoltaic wastewater deep treatment device, characterized in that: The invention comprises a first-stage defluorination device (100), a second-stage defluorination device (200), an A / O biofilm denitrification device (300), a third-stage defluorination device (400), an ozone oxidation-biological contact oxidation coupling device (500) and a fourth-stage defluorination device (600) which are connected in sequence, and a defluorination agent dosing system and an acid-base intelligent device; wherein a sludge external return device is provided between the first-stage defluorination device (100) and the second-stage defluorination device (200) and between the third-stage defluorination device (400) and the fourth-stage defluorination device (600), and the defluorination agent dosing system and the acid-base intelligent device are provided in the first defluorination device (100) and the second defluorination device (200), and both are intelligently controlled by a control system.

2. The photovoltaic wastewater deep treatment device according to claim 1 is characterized in that: The first-stage defluorination device (100) comprises a first-stage first coagulation zone (101), a second-stage second coagulation zone (102), a first-stage flocculation zone (103), a first-stage sedimentation zone (104), and a sludge internal return device arranged between the first-stage sedimentation zone (104) and the first-stage first coagulation zone (101); the second-stage defluorination device (200) comprises a second-stage coagulation zone (201), a second-stage flocculation zone (202), a second-stage sedimentation zone (203), and a sludge external return device arranged between the second-stage sedimentation zone (203) and the first-stage first coagulation zone (101); the third-stage defluorination device (400) comprises a third-stage first coagulation zone (401), a third-stage second coagulation zone (402), a second-stage sedimentation zone (403), and a sludge external return device arranged between the second-stage sedimentation zone (203) and the first-stage first coagulation zone (101); 02), a third-level flocculation zone (403), a third-level sedimentation zone (404), and a sludge internal reflow device arranged between the third-level sedimentation zone (404) and the third-level first coagulation zone (401); the fourth-level defluorination device (600) includes a fourth-level coagulation zone (601), a fourth-level flocculation zone (602), a fourth-level sedimentation zone (603), and a sludge external reflow device arranged between the fourth-level sedimentation zone (404) and the third-level first coagulation zone (401); wherein the first-level sedimentation zone (104), the second-level sedimentation zone (203), the third-level sedimentation zone (404), and the fourth-level sedimentation zone (603) are all provided with a sump for diverting the wastewater supernatant and a sludge hopper for discharging the sludge.

3. The photovoltaic wastewater deep treatment device according to claim 1 is characterized in that: The defluorinating agent dosing system comprises a defluorinating agent dosing device, an online fluoride monitoring device arranged at the water outlet of the first defluorinating device (100), and an online fluoride monitoring device arranged at the water outlet of the second defluorinating device (200); the acid-base intelligent device comprises a liquid alkali dosing device, an online pH meter arranged in the first-level second coagulation zone (102), and an online pH meter arranged in the second-level coagulation zone (201); the defluorinating agent dosing system and the acid-base intelligent device are centrally controlled by a control system.

4. The photovoltaic wastewater deep treatment device according to claim 1 is characterized in that: The A / O biofilm device (300) is composed of a first anoxic biofilm zone (301), a first aerobic biofilm zone (302), a second anoxic biofilm zone (303), and a second aerobic biofilm zone (304) in sequence, and also includes a first nitrification liquid reflux device connected to the first aerobic biofilm zone (302) and the first anoxic biofilm zone (301), respectively, and a second nitrification liquid reflux device connected to the second aerobic biofilm zone (304) and the second anoxic biofilm zone (303), respectively.

5. The photovoltaic wastewater deep treatment device according to claim 4 is characterized in that: Agitators are provided in the first anoxic biofilm zone (301) and the second anoxic biofilm zone (303), and aerators are provided in the first aerobic biofilm zone (302) and the second aerobic biofilm zone (304).

6. The photovoltaic wastewater deep treatment device according to claim 1 is characterized in that: The ozone oxidation-biological contact oxidation coupling device (500) comprises an ozone oxidation tank (501), a degassing tank (502) for removing ozone, a biological contact oxidation tank (503), and a micro-nano gas dissolving device (504) for adding ozone, which are connected in sequence.

7. A method for treating photovoltaic wastewater using the device according to claims 1 to 6, characterized in that: The following steps are involved: S1: adding lime or calcium chloride and liquid alkali to the first coagulation zone (101) and the second coagulation zone (201); adding aluminum salt or mixed defluoridation agent and liquid alkali to the third first coagulation zone (401) and the fourth coagulation zone (601); and adding flocculants to the first flocculation zone (103), the second flocculation zone (202), the third flocculation zone (403) and the fourth flocculation zone (602); S2: The wastewater stays in the first coagulation zone (101) for no less than 15 minutes, in the second coagulation zone (102) for no less than 10 minutes, and in the first flocculation zone (103) for no less than 5 minutes; the wastewater stays in the second first coagulation zone (201) for no less than 20 minutes, and in the second flocculation zone (202) for no less than 5 minutes; the wastewater stays in the third first coagulation zone (401) for no less than 15 minutes, in the third second coagulation zone (402) for no less than 10 minutes, and in the third flocculation zone (403) for no less than 5 minutes; the wastewater stays in the fourth first coagulation zone (601) for no less than 20 minutes, and in the fourth flocculation zone (602) for no less than 5 minutes; S3: The ratio of the residence time of the wastewater in the first anoxic biofilm zone (301), the first aerobic biofilm zone (302), the second anoxic biofilm zone (303), and the second aerobic biofilm zone (304) is 4:4:3:1, and the total residence time of the wastewater in the A / O biofilm denitrification device 300 is 10-15 hours; S4: The wastewater stays in the ozone oxidation tank (501) for 0.5-3 hours, and in the biological contact oxidation tank (503) for 2-5 hours.

8. A photovoltaic wastewater deep treatment method according to claim 7, characterized in that: The step S3 maintains the dissolved oxygen concentration of the first anoxic biofilm area (301) and the second anoxic biofilm area (303) at 0.2-0.5 mg / L.

9. A photovoltaic wastewater deep treatment method according to claim 7, characterized in that: In step S3, the dissolved oxygen in the first aerobic biofilm zone (302) and the second aerobic biofilm zone (304) is 2-4 mg / L.

10. A photovoltaic wastewater deep treatment method according to claim 7, characterized in that: In the step S3, part of the nitrification liquid in the first aerobic biofilm zone (302) flows back to the first anoxic biofilm zone (301), and part of the nitrification liquid in the second aerobic biofilm zone (304) flows back to the second anoxic biofilm zone (303).

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