Pickling Wastewater Treatment System

Abstract

The present application provides an acid pickling wastewater treatment system, comprising: a wastewater precipitation unit having a receiving port for receiving acid pickling wastewater and an outflow port for the clarified liquid to flow out; a clarified liquid denitrification unit including a mixing tank, a water distributor, a circulation pump and a denitrification chamber; the mixing tank is provided with an inflow port, a filtration port and an output port; the inflow port is communicated with the outflow port of the wastewater precipitation unit to allow the clarified liquid to flow into the mixing tank for mixing to obtain a mixed liquid; inside the denitrification chamber, a fluidized zone, a separation zone and a reflux zone are provided from bottom to top; the fluidized zone is filled with fillers attached with microbial membranes to allow the mixed liquid to carry out a denitrification reaction for nitrogen removal to obtain a denitrified liquid; the bottom of the fluidized zone is communicated with the output port via the water distributor and the circulation pump; the separation zone allows the fillers to be separated and settled from the denitrified liquid to the fluidized zone; the reflux zone is provided with a drain port for discharging the denitrified liquid outwards, and the reflux zone is communicated with the filtration port. The present application effectively improves the treatment efficiency and effect of acid pickling wastewater treatment.

Description

Technical Field

[0001] This application relates to the technical field of pickling wastewater treatment systems, and in particular to a pickling wastewater treatment system. Background Art

[0002] During the production of stainless steel, a mixed acid of nitric acid and hydrofluoric acid is required for pickling. The strongly oxidizing nitric acid can oxidize metals and metal oxides to form a dense oxide film on the surface of the stainless steel to passivate the stainless steel. A small amount of pickling solution still adheres to the surface of the passivated stainless steel and must be rinsed with water. The rinsing water discharged therefrom is pickling wastewater. A large number of harmful elements such as metal ions, fluoride ions, and nitrate nitrogen exist in the pickling wastewater and need to be treated before being discharged.

[0003] Currently, the method of adding alkali for neutralization and precipitation is often used to treat metal ions and fluoride ions in wastewater, but this process does not treat nitrate nitrogen in the wastewater, resulting in the problem of excessive total nitrogen discharge. Summary of the Invention

[0004] The purpose of this application is to provide a pickling wastewater treatment system, which can effectively improve the anti-shock load capacity during denitrification and nitrogen removal, effectively avoid the loss of denitrifying bacteria during the treatment process, effectively improve the denitrification treatment effect, and further effectively improve the efficiency and effect of the overall purification treatment of pickling wastewater.

[0005] To solve the above technical problems, this application adopts the following technical solutions: a wastewater precipitation unit for precipitating and removing metal ions and fluoride ions in pickling wastewater to obtain a clarified liquid, which has a receiving port for receiving pickling wastewater and an outlet for the clarified liquid to flow out; a clarified liquid denitrification unit, which includes a mixing tank, a water distributor, a circulation pump, and a denitrification chamber; the mixing tank is provided with an inlet, a filtering port, and an outlet; the inlet is communicated with the outlet to allow the clarified liquid to flow into the mixing tank for mixing to obtain a mixed liquid; inside the denitrification chamber, a fluidization zone, a separation zone, and a reflux zone are provided from bottom to top; the fluidization zone is filled with fillers attached with microbial membranes for the mixed liquid to carry out denitrification reaction with the microbial membranes to obtain a denitrified liquid; the bottom of the fluidization zone is communicated with the outlet through the water distributor and the circulation pump; the separation zone is for separating the fillers from the denitrified liquid and settling them to the fluidization zone; the reflux zone is provided with a drain port for discharging the denitrified liquid outward, and the reflux zone is communicated with the filtering port to convey the denitrified liquid into the mixing tank.

[0006] Optionally, the wastewater sedimentation unit includes a primary mixing and sedimentation unit and a secondary mixing and sedimentation unit that are connected in sequence. The primary mixing and sedimentation unit is used to precipitate and remove metal ions and fluoride ions in the pickling wastewater through a primary flocculant to obtain primary wastewater. The secondary mixing and sedimentation unit is used to precipitate and remove metal ions and fluoride ions in the primary wastewater through a secondary flocculant to obtain a clarified liquid. The receiving port is arranged in the primary mixing and sedimentation unit, and the outflow port is arranged in the secondary mixing and sedimentation unit.

[0007] Optionally, the primary mixing and sedimentation unit includes a first mixing reaction tank and a first sedimentation tank. The secondary mixing and sedimentation unit includes a second mixing reaction tank and a second sedimentation tank. The first mixing reaction tank, the first sedimentation tank, the second mixing reaction tank, and the second sedimentation tank are connected in sequence. The first mixing reaction tank is used for the primary flocculant to react with the pickling wastewater to obtain a primary reaction liquid. The first sedimentation tank is used to precipitate and remove metal ions and fluoride ions in the primary reaction liquid to obtain primary wastewater. The second mixing reaction tank is used for the secondary flocculant to react with the primary wastewater to obtain a secondary reaction liquid. The second sedimentation tank is used to precipitate and remove metal ions and fluoride ions in the secondary reaction liquid to obtain a clarified liquid. The receiving port is arranged in the first mixing reaction tank, and the outflow port is arranged in the second sedimentation tank.

[0008] Optionally, the pickling wastewater treatment system further includes a primary flocculant addition unit and a secondary flocculant addition unit. The primary flocculant addition unit is connected to the first mixing reaction tank, and the secondary flocculant addition unit is connected to the second mixing reaction tank.

[0009] Optionally, the primary flocculant addition unit includes a calcium hydroxide dosing subunit, a sodium hydroxide dosing subunit, a sulfuric acid dosing subunit, and a polyacrylamide dosing subunit. The secondary flocculant addition unit includes a sulfuric acid dosing subunit, a polyacrylamide dosing subunit, and a polyaluminum chloride dosing subunit. The first mixing reaction tank includes a reaction tank, a neutralization tank, and a first flocculation tank that are connected in sequence. The reaction tank is connected to the calcium hydroxide dosing subunit. The neutralization tank is connected to the sodium hydroxide dosing subunit and the sulfuric acid dosing subunit. The first flocculation tank is connected to the polyacrylamide dosing subunit. The receiving port is arranged in the reaction tank. The first flocculation tank is connected to the first sedimentation tank. The second mixing reaction tank includes an adjustment tank, a second flocculation tank, and a third flocculation tank that are connected in sequence. The adjustment tank is connected to the sulfuric acid dosing subunit. The second flocculation tank is connected to the polyacrylamide dosing subunit. The third flocculation tank is connected to the polyaluminum chloride dosing subunit. The adjustment tank is connected to the first sedimentation tank, and the third flocculation tank is connected to the second sedimentation tank.

[0010] Optionally, the pickling wastewater treatment system further includes a denitrification feed water tank and a denitrification feed water pump for adjusting the pH value of the clarified liquid and adding nutrient elements required by microorganisms; the inlet of the denitrification feed water tank is communicated with the outlet of the wastewater sedimentation unit, the outlet of the denitrification feed water tank is communicated with the inlet of the denitrification feed water pump, and the outlet of the denitrification feed water pump is communicated with the inlet of the denitrification unit.

[0011] Optionally, the wastewater sedimentation unit further has a discharge port for discharging precipitates of metal ions and fluoride ions obtained by sedimenting pickling wastewater; the pickling wastewater treatment system further includes a precipitate dewatering unit for compressing and dewatering the precipitates of metal ions and fluoride ions to obtain filtrate; the precipitate dewatering unit includes a sediment inlet and a supernatant reflux port; the sediment inlet is communicated with the discharge port, and the reflux port is communicated with the receiving port.

[0012] Optionally, the precipitate dewatering unit includes a sludge tank and a filter press; the sediment inlet and the reflux port are arranged on the sludge tank; the sludge tank is connected to the filter press.

[0013] Optionally, the water distributor is arranged at the bottom of the fluidization zone, and the outlet of the water distributor is arranged upward; the mixing tank is arranged in the reflux zone, and the filter port is opened on the tank wall of the mixing tank, so that the filter port is communicated with the reflux zone; the circulation pump is arranged outside the denitrification chamber; the output port is communicated with the inlet of the circulation pump through a first conveying pipeline, and the outlet of the circulation pump is communicated with the inlet of the water distributor through a second conveying pipeline.

[0014] Optionally, the first conveying pipeline is composed of alternately arranged first pipelines and second pipelines, and the diameter of the second pipeline is larger than that of the first pipeline.

[0015] Optionally, the cross-sectional area of the separation zone is larger than that of the fluidization zone.

[0016] Optionally, the mixing tank is divided into a sump and a mixing pool by a vertically arranged partition plate; a communication hole is opened on the partition plate; the inlet is opened at the upper end of the mixing pool, the output port is opened at the lower end of the mixing pool; the filter port is opened on the side wall of the sump facing the reflux zone.

[0017] Optionally, an overflow weir is arranged in the reflux zone, the height of the overflow weir is higher than that of the filter port, and a groove with an upward opening is formed between the overflow weir and the shell of the denitrification chamber; the drain port is opened on the shell of the denitrification chamber located in the groove.

[0018] Optionally, a water distribution plate is further arranged in the denitrification chamber to isolate the fluidized zone from the area below the water distribution plate; the water distributor is arranged on the water distribution plate, the outlet of the water distributor is located above the water distribution plate, and the inlet of the water distributor is located below the water distribution plate.

[0019] Optionally, the pickling wastewater treatment system further includes a grid channel for intercepting suspended solids in the pickling wastewater and a regulating tank for regulating the water quality and quantity of the pickling wastewater; the grid channel is arranged before the inlet of the regulating tank, the outlet of the regulating tank is communicated with the receiving port, and the reflux port is communicated with the inlet of the regulating tank through the receiving port.

[0020] As can be seen from the above technical solutions, the present application has at least the following advantages and positive effects: In the pickling wastewater treatment system of the present application, first, metal ions and fluoride ions in the pickling wastewater are removed by precipitation in the wastewater precipitation unit to obtain a clarified liquid. Then, for the clarified liquid, denitrification treatment is carried out in the clarified liquid denitrification unit to obtain a denitrified liquid for discharge.

[0021] The clarified liquid denitrification unit includes a mixing tank, a water distributor, a circulation pump and a denitrification chamber; the mixing tank is provided with a fluid inlet, a filtration port and an output port; the clarified liquid can flow into the mixing tank through the fluid inlet to be mixed to obtain a mixed liquid, and the clarified liquid is diluted. At the same time, a fluidized zone, a separation zone and a reflux zone are established from bottom to top in the denitrification chamber; the fluidized zone is filled with fillers attached with microbial membranes for the mixed liquid to carry out denitrification reaction with the microbial membranes to obtain a denitrified liquid; the bottom of the fluidized zone is communicated with the output port through the water distributor and the circulation pump; the separation zone is for the fillers to be separated and settled from the denitrified liquid to the fluidized zone. The bottom of the fluidized zone is communicated with the output port through the water distributor and the circulation pump, and the reflux zone is also connected with the filtration port of the mixing tank to convey the denitrified liquid into the mixing tank to form a reflux circulation loop; secondly, the reflux zone is provided with a drain port to form a drainage path parallel to the reflux loop.

[0022] Driven by the circulation pump, the mixed liquid in the mixing tank can be distributed into the fluidized zone from the bottom by the water distributor, driving the fillers attached with microbial membranes to move in a fluidized state from bottom to top. In the fluidized zone, denitrification of the mixed liquid is carried out by the microbial membranes to obtain a denitrified liquid. The fillers are separated and settled from the denitrified liquid in the separation zone and fall into the fluidized zone. The denitrified liquid enters the reflux zone. In the reflux zone, part of the denitrified liquid enters the mixing tank through the filtration port for reflux mixing, and part of the denitrified liquid is discharged through the drain port.

[0023] In this way, when the clarified liquid is denitrified, the reflux circulation loop is parallel to the drainage passage. The reflux loop forms an internal circulation loop. In the fluidized zone, the denitrification of the clarified liquid can be carried out through the packing with attached microbial film. When the packing moves from top to bottom, it will be filtered. The whole treatment process has a strong impact load resistance ability, and the structural design can effectively prevent the loss of bacterial species, resulting in more thorough denitrification, effectively improving the denitrification treatment efficiency and effect, and thus effectively improving the treatment efficiency and effect of pickling wastewater as a whole. Description of the Drawings

[0024] Figure 1 It is a process flow chart of an embodiment of the pickling wastewater treatment system of the present application.

[0025] Figure 2 It is a structural schematic diagram of an embodiment of the clarified liquid denitrification unit of the present application.

[0026] Explanation of the reference numerals in the drawings is as follows:

[0027] 100, pickling wastewater treatment system;

[0028] 1, grille channel;

[0029] 2, regulating tank; 21, regulating tank inlet; 22, regulating tank outlet;

[0030] 3, wastewater precipitation unit; 31, receiving port; 32, outflow port; 33, discharge port; 34, primary mixing and precipitation unit; 341, first mixing reaction tank; 3411, reaction tank; 3412, neutralization tank; 3413, first flocculation tank; 342, first sedimentation tank; 35, secondary mixing and precipitation unit; 351, second mixing reaction tank; 3511, pre-adjustment tank; 3512, second flocculation tank; 3513, third flocculation tank; 352, second sedimentation tank;

[0031] 4, primary flocculant addition unit;

[0032] 5, secondary flocculant addition unit;

[0033] 6, precipitate dewatering unit; 61, sediment inlet; 62, reflux port; 63, sludge tank; 64, filter press;

[0034] 7, denitrification water supply tank;

[0035] 8, denitrification water supply pump;

[0036] 9. Clarified liquid denitrification unit; 91. Mixing tank; 911. Inlet; 912. Filtration port; 913. Outlet; 914. First conveying pipeline; 9141. First pipeline; 9142. Second pipeline; 915. Partition board; 916. Sump; 917. Mixing pool; 92. Water distributor; 921. Water distributor outlet; 923. Water distributor inlet; 93. Circulation pump; 931. Second conveying pipeline; 94. Denitrification chamber; 941. Fluidization zone; 942. Separation zone; 943. Return zone; 95. Drain outlet; 96. Overflow weir; 97. Collection pipe; 98. Water distribution plate;

[0037] 10. Effluent tank. Detailed implementation manners

[0038] Typical implementation manners reflecting the features and advantages of the present application will be described in detail in the following description. It should be understood that the present application can have various variations in different implementation manners, all of which do not depart from the scope of the present application, and the descriptions and illustrations therein are essentially for illustrative purposes rather than for limiting the present application.

[0039] Refer to Figure 1 , according to an embodiment of the present application, the pickling wastewater treatment system 100 includes: grille channel 1, regulating tank 2, wastewater precipitation unit 3, primary flocculant addition unit 4, secondary flocculant addition unit 5, precipitate dewatering unit 6, denitrification feed water tank 7, denitrification feed water pump 8, clarified liquid denitrification unit 9 and effluent tank 10.

[0040] The grille channel 1 is arranged such that when pickling wastewater passes through the grille channel 1, suspended solids in the wastewater are intercepted to prevent debris from clogging pumps and valves and affecting the operation of the system. The grille in the grille channel 1 can be a flat or curved grille, etc.

[0041] The regulating tank 2 is arranged to regulate the water quality and water volume of the pickling wastewater entering the regulating tank 2; a regulating tank inlet 21 and a regulating tank outlet 22 are provided on the regulating tank 2. The grille channel 1 is arranged before the regulating tank inlet 21, and the pickling wastewater passes through the grille channel 1 and enters the regulating tank 2 after intercepting the suspended solids in the pickling wastewater. In this example, the average hydraulic retention time in the regulating tank 2 is about 12 h.

[0042] The wastewater precipitation unit 3 is used to precipitate and remove metal ions and fluoride ions in the pickling wastewater to obtain clarified liquid; the wastewater precipitation unit 3 has a receiving port 31 for receiving pickling wastewater, an outflow port 32 for the clarified liquid to flow out, and a discharge port 33 for discharging the metal ions and fluoride ion precipitates obtained by precipitating the pickling wastewater.

[0043] The receiving port 31 of the wastewater sedimentation unit 3 is connected to the outlet 22 of the regulating tank. Thus, the pickling wastewater after adjusting the water quality and quantity can enter the wastewater sedimentation unit 3 from the receiving port 31, where the metal ions and fluoride ions in the pickling wastewater are removed by sedimentation to obtain a clarified liquid, and then the clarified liquid flows out from the outflow port 32. Among them, the outlet 22 of the regulating tank is connected to the receiving port 31 of the wastewater sedimentation unit 3 through a lift pump (not shown in the figure), and thus the pickling wastewater in the regulating tank 2 can be lifted to the wastewater sedimentation unit 3 by the lift pump.

[0044] The wastewater sedimentation unit 3 specifically includes a first-stage mixing and sedimentation unit 34 and a second-stage mixing and sedimentation unit 35 that are connected in sequence. The first-stage mixing and sedimentation unit 34 is used to remove metal ions and fluoride ions in the pickling wastewater by sedimentation with a first-stage flocculant to obtain first-stage wastewater, and the second-stage mixing and sedimentation unit 35 is used to remove metal ions and fluoride ions in the first-stage wastewater by sedimentation with a second-stage flocculant to obtain a clarified liquid. Furthermore, the receiving port 31 is arranged on the first-stage mixing and sedimentation unit 34, the outflow port 32 is arranged on the second-stage mixing and sedimentation unit 35, and discharge ports 33 are arranged in both the first-stage mixing and sedimentation unit 34 and the second-stage mixing and sedimentation unit 35. By arranging the first-stage mixing and sedimentation unit 34 and the second-stage mixing and sedimentation unit 35, multiple sedimentation removals can be carried out, making the removal of metal ions and fluoride ions in the pickling wastewater more thorough. It can be understood that according to requirements, the wastewater sedimentation unit 3 may include more than two stages of mixing and sedimentation units.

[0045] Furthermore, the pickling wastewater treatment system 100 further includes a first-stage flocculant addition unit 4 and a second-stage flocculant addition unit 5. The first-stage flocculant addition unit 4 is used to add a first-stage flocculant, and the second-stage flocculant addition unit 5 is used to add a second-stage flocculant.

[0046] Specifically, the first-stage flocculant addition unit 4 includes a calcium hydroxide dosing subunit, a sodium hydroxide dosing subunit, a sulfuric acid dosing subunit, and a polyacrylamide dosing subunit. The second-stage flocculant addition unit 5 includes a sulfuric acid dosing subunit, a polyacrylamide dosing subunit, and a polyaluminum chloride dosing subunit. Each dosing subunit includes a medicine tank and a dosing pump, and can automatically add the corresponding medicine.

[0047] The first-stage flocculant addition unit 4 is connected to the first-stage mixing and sedimentation unit 34 and can add the first-stage flocculant to the first-stage mixing and sedimentation unit 34. The second-stage flocculant addition unit 5 is connected to the second-stage mixing and sedimentation unit 35 and can add the second-stage flocculant to the second-stage mixing and sedimentation unit 35.

[0048] In the embodiment of this example, the primary mixing and sedimentation unit 34 includes a first mixing reaction tank 341 and a first sedimentation tank 342; the secondary mixing and sedimentation unit 35 includes a second mixing reaction tank 351 and a second sedimentation tank 352. The first mixing reaction tank 341 is communicated with the primary flocculant adding unit 4, and the primary flocculant adding unit 4 is used to add the primary flocculant to the first mixing reaction tank 341; in the first mixing reaction tank 341, the primary flocculant and the pickling wastewater are mixed and reacted to obtain a primary reaction solution, and the first sedimentation tank 342 is used to precipitate and remove metal ions and fluoride ions in the primary reaction solution to obtain primary wastewater. The second mixing reaction tank 351 is communicated with the secondary flocculant adding unit 5, and the secondary flocculant adding unit 5 is used to add the secondary flocculant to the second mixing reaction tank 351. In the second mixing reaction tank 351, the secondary flocculant and the primary wastewater are mixed and reacted to obtain a secondary reaction solution, and the second sedimentation tank 352 is used to precipitate and remove metal ions and fluoride ions in the secondary reaction solution to obtain a clarified solution.

[0049] Among them, the first mixing reaction tank 341, the first sedimentation tank 342, the second mixing reaction tank 351 and the second sedimentation tank 352 are connected in sequence; the receiving port 31 is arranged to enter the first mixing reaction tank 341, and the outflow port 32 is arranged in the second sedimentation tank 352. The pickling wastewater in the regulating tank 2 enters the first mixing reaction tank 341 from the receiving port 31, and then reacts and precipitates in sequence in the second sedimentation tank 352 to obtain the final clarified solution, which flows out from the outflow port 32. Secondly, discharge ports 33 are respectively arranged on the first sedimentation tank 342 and the second sedimentation tank 352, and the precipitates in the first sedimentation tank 342 and the second sedimentation tank 352 can be discharged respectively.

[0050] In the embodiment of this example, the first mixing reaction tank 341 includes a reaction tank 3411, a neutralization tank 3412 and a first flocculation tank 3413 connected in sequence; the reaction tank 3411 is connected with the calcium hydroxide dosing subunit, the neutralization tank 3422 is connected with the sodium hydroxide dosing subunit and the sulfuric acid dosing subunit, and the first flocculation tank 3413 is connected with the polyacrylamide dosing subunit; furthermore, by controlling different subunits, the agents can be accurately added to the reaction tank 3411, the neutralization tank 3412 and the first flocculation tank 3413 respectively. Stirrers are respectively arranged in the reaction tank 3411, the neutralization tank 3412 and the first flocculation tank 3413, so that the pickling wastewater and the agents can be fully mixed and reacted.

[0051] At this time, the receiving port 31 is arranged in the reaction tank 3411. The pickling wastewater in the regulating tank 2 is first sent into the reaction tank 3411 from the receiving port 31, and then flows into the neutralization tank 3412 and the first flocculation tank 3413 in sequence; at the same time, the first flocculation tank 3413 is communicated with the first sedimentation tank 342, and the primary reaction solution after reaction in the first flocculation tank 3413 can be sent into the first sedimentation tank 342.

[0052] The second mixing reaction tank 351 includes a pre-adjustment tank 3511, a second flocculation tank 3512, and a third flocculation tank 3513 that are connected in sequence; the pre-adjustment tank 3511 is connected to the sulfuric acid dosing subunit, the second flocculation tank 3512 is connected to the polyacrylamide dosing subunit, and the third flocculation tank 3513 is connected to the polyaluminum chloride dosing subunit; thus, different subunits can be controlled to accurately add chemicals to the pre-adjustment tank 3511, the second flocculation tank 3512, and the third flocculation tank 3513 respectively. A stirrer is provided in each of the pre-adjustment tank 3511, the second flocculation tank 3512, and the third flocculation tank 3513, so that the pickling wastewater and the chemicals can be fully mixed and reacted.

[0053] At this time, the pre-adjustment tank 3511 is connected to the first sedimentation tank 342, and the primary wastewater obtained by sedimentation removal in the first sedimentation tank 342 can be received into the pre-adjustment tank 3511. The third flocculation tank 3513 is connected to the second sedimentation tank 352, and the secondary reaction liquid mixed and reacted in the third flocculation tank 3513 can be transported to the second sedimentation tank 352 for sedimentation filtration.

[0054] The pickling wastewater treatment system 100 further includes a sediment dehydration unit 6 for compressing and dehydrating the metal ion and fluoride ion precipitates to obtain a sludge cake and filtrate; the sediment dehydration unit 6 includes a sediment inlet 61 and a supernatant reflux port 62; the sediment inlet 61 is connected to the discharge port 33, and the sediment can be received into the sediment dehydration unit 6; the reflux port 62 is connected to the receiving port 31, and the supernatant obtained after sedimentation of the sediment can be refluxed to the wastewater sedimentation unit 3. Specifically, the reflux port 62 is connected to the receiving port 31 through the regulating tank inlet 21, that is, the supernatant is first refluxed to the regulating tank 2 and then enters the wastewater sedimentation unit 3.

[0055] The sediment dehydration unit 6 includes a sludge tank 63 and a filter press 64; the sediment inlet 61 and the reflux port 62 are provided on the sludge tank 63; the sludge tank 63 is connected to the filter press 64. The sediment enters the sludge tank 63 for sedimentation to obtain a supernatant and a sediment. At the same time, the sediment is filtered by the filter press 64 to obtain a sludge cake and filtrate after solid-liquid separation. In this example, the filter press is a high-pressure plate-frame filter press.

[0056] Furthermore, the precipitates in the first sedimentation tank 342 and the second sedimentation tank 352 are discharged to the sludge tank 63 through the sludge discharge pipe. The reflux port 62 on the sludge tank 63 is refluxed to the regulating tank 2 through a pipeline. The sediment is subjected to solid-liquid separation through the high-pressure plate-frame filter press 64 and its automatic control system to obtain a sludge cake and filtrate, and the sludge cake is automatically input into a special container.

[0057] The pickling wastewater treatment system 100 further includes a denitrification feed water tank 7 and a denitrification feed water pump 8 for adjusting the pH value of the clarified liquid and adding nutrient elements required by microorganisms; the inlet of the denitrification feed water tank 7 is communicated with the outlet 32, so as to receive the clarified liquid obtained by removing metal ions and fluoride ions from the pickling wastewater by precipitation into the denitrification feed water tank 7, and adjust the pH value of the clarified liquid and add nutrient elements required by microorganisms.

[0058] The outlet of the denitrification feed water tank 7 is communicated with the inlet of the denitrification feed water pump 8, and the outlet of the denitrification feed water pump 8 is communicated with the inlet 91 of the clarified liquid denitrification unit 9 in the next process node. Further, the clarified liquid after adjusting the pH value and adding nutrient elements required by microorganisms can be sent into the clarified liquid denitrification unit 9 through the denitrification feed water pump 8 for denitrification.

[0059] The clarified liquid denitrification unit 9 is used for carrying out denitrification treatment on the clarified liquid to obtain a denitrified liquid for discharge. The clarified liquid denitrification unit 9 includes a mixing tank 91, a water distributor 92, a circulation pump 93 and a denitrification chamber 94. The mixing tank 91 is used for mixing the received clarified liquid with the denitrified liquid obtained by denitrification in the denitrification chamber 94 to obtain a mixed liquid, and the clarified liquid can be diluted to a certain extent by the denitrified liquid. The circulation pump 93 is used to provide the power for the flow of the mixed liquid. The water distributor 92 is used to distribute the mixed liquid into the denitrification chamber 94. The denitrification chamber 94 is used for carrying out a denitrification reaction between the filler with a surface-attached microbial film and the mixed liquid, carrying out denitrification on the mixed liquid to obtain a denitrified liquid (i.e., the wastewater that can be discharged), and sending part of the denitrified liquid into the mixing tank 91 and discharging part of the denitrified liquid. Among them, the filler is set to have a high specific surface area and a high specific gravity.

[0060] The mixing tank 91 is provided with an inlet 911, a filtering port 912 and an outlet 913; the inlet 911 is communicated with the outlet 32 in the wastewater precipitation unit 3 for the clarified liquid to flow into the mixing tank 91 and mix with the denitrified liquid entering from the filtering port 912 to obtain a mixed liquid; specifically, the inlet 911 is communicated with the outlet 32 through the denitrification feed water tank 7 and the denitrification feed water pump 8.

[0061] Inside the denitrification chamber 94, a fluidization zone 941, a separation zone 942 and a reflux zone 943 are established from bottom to top. The fluidization zone 941 is filled with a filler attached with a microbial film for the mixed liquid to carry out a denitrification reaction with the microbial film to obtain a denitrified liquid. The separation zone 942 is for the filler to be separated and settled from the denitrified liquid to the fluidization zone. The reflux zone 943 is used for the discharge of the denitrified liquid and the reflux of the denitrified liquid into the mixing tank 91 for reflux mixing.

[0062] The bottom of the fluidized zone 941 is connected to the outlet 913 on the mixing tank 91 through a water distributor 92 and a circulation pump 93, and the reflux zone 943 is also connected to the filtration port 912 of the mixing tank 91 to convey the denitrified liquid into the mixing tank 91. Furthermore, driven by the circulation pump 93, the mixed liquid in the mixing tank 91 is distributed from the bottom into the fluidized zone by the water distributor 92, driving the packing with attached microbial membranes to move in a fluidized state from bottom to top. In the fluidized zone 941, the mixed liquid undergoes denitrification and nitrogen removal through the microbial membrane to obtain the denitrified liquid, which is separated and settled from the denitrified liquid through the packing in the separation zone and enters the reflux zone. In the reflux zone, part of the denitrified liquid enters the mixing tank through the filtration port for reflux mixing, forming a reflux circulation loop.

[0063] Secondly, a drain port 95 is provided in the reflux zone 943. Thus, the mixed liquid in the mixing tank 91 is distributed from the bottom into the fluidized zone by the water distributor 92, driving the packing with attached microbial membranes to move from bottom to top. In the fluidized zone, the mixed liquid undergoes denitrification and nitrogen removal through the microbial membrane (the mixed liquid undergoes a denitrification reaction with the microbial membrane) to obtain the denitrified liquid, which enters the reflux zone 943 after being settled and filtered by the packing in the separation zone 942. Additionally, part of the denitrified liquid is discharged through the drain port 95, forming a discharge path.

[0064] In this way, when treating the clarified liquid for nitrogen removal, a form in which a reflux circulation loop and a drainage path are parallel is formed. The reflux loop forms an internal circulation loop. In the fluidized zone, the clarified liquid can undergo denitrification and nitrogen removal through the packing with attached microbial membranes. The packing will be filtered when moving from top to bottom. The entire treatment process has a strong anti-shock load capacity, and the structural design can effectively prevent the loss of bacteria species, achieving more thorough nitrogen removal, effectively improving the nitrogen removal treatment efficiency and effect, and thus effectively enhancing the treatment efficiency and effect of pickling wastewater as a whole.

[0065] In the embodiment of this example, refer to Figure 2 As shown, the water distributor 92 is arranged at the bottom of the fluidized zone 941 in the denitrification chamber 94, and the water distributor outlet 921 is arranged upward, such that the mixed liquid is directly distributed upward from the water distributor outlet 921; the mixing tank 91 is arranged in the reflux zone 943, and the filtration port 912 on the mixing tank 91 is opened on the tank wall of the mixing tank 91, such that the filtration port 912 is connected to the reflux zone 943; the circulation pump 93 is arranged outside the denitrification chamber 94; the outlet 913 on the mixing tank 91 is connected to the inlet of the circulation pump 93 through a first conveying pipeline 914, and the outlet of the circulation pump 93 is connected to the water distributor inlet 922 through a second conveying pipeline 931.

[0066] It can be understood that in other examples, the water distributor 92 is arranged outside the denitrification chamber 94, but the water distributor outlet 921 extends into the bottom of the fluidized zone 941; the mixing tank 91 is arranged outside the denitrification chamber 94, but its filtration port 912 is connected to the reflux zone 943 through a pipeline.

[0067] Specifically, the cavity of the mixing tank 91 is divided into a water collecting pool 916 and a mixing pool 917 by a vertically arranged partition plate 915; a communication hole is formed in the partition plate 915 to connect the water collecting pool 916 and the mixing pool 917; at the same time, the inflow port 911 of the mixing tank 91 is opened on the upper end surface of the mixing pool (which is also the upper end surface of the denitrification chamber 94), and the output port 913 of the mixing tank 91 is opened on the lower end surface of the mixing pool 917; the filtering port 912 of the mixing tank 91 is opened on the side wall of the water collecting pool 916 facing the reflux area 943. Thus, the denitrified liquid in the reflux area 943 can enter the water collecting pool 916 through the filtering port 912, and then enter the mixing pool 917 through the communication hole formed in the partition plate 915, and be mixed with the clarified liquid flowing in from the inflow port 911 in the mixing pool 917. Among them, the shape of the partition plate 915 can be set according to the actual situation, for example, a straight plate or an annular plate, etc.

[0068] Furthermore, the filtering port 912 is connected to the mixing pool 917 through a water collecting pipe 97. Filtering holes are formed in the side wall of the water collecting pipe 97, and the aperture of the filtering holes is smaller than the diameter of the packing, so as to further filter the packing and prevent the packing from entering the mixing tank.

[0069] Furthermore, the water collecting pipe 97 is horizontally arranged in the reflux area, so that when the water flows upward, the denitrified liquid can be widely collected into the water collecting pool through the filtering holes on the side wall, ensuring the collection effect.

[0070] In the embodiment of this example, the cavity of the mixing tank 91 is in the shape of a cylinder with its axis vertically established; the cavity of the mixing tank 91 is divided into a mixing pool 917 located at the central position of the cavity of the mixing tank 91 and a water collecting pool 916 surrounding the mixing pool 917 by a vertically arranged annular partition plate 915; a communication hole is formed in the partition plate 915 to connect the water collecting pool 916 and the mixing pool 917, and the water in the water collecting pool 916 can overflow into the middle mixing pool 917; at the same time, the filtering port 912 is opened on the shell of the mixing tank 91, that is, the filtering port 912 is opened on the side wall where the water collecting pool 916 contacts the reflux area 943, and there are multiple filtering ports 912, which are arranged in an array around the mixing tank 91. Each filtering port 912 is connected to a water collecting pipe 97, and the water collecting pipe 97 is horizontally arranged.

[0071] Furthermore, the cross-section of the separation zone 942 is larger than that of the fluidization zone 941. When the denitrification liquid drives the packing into the separation zone 942, due to the expansion of the cross-section (diameter) of the separation zone 942, the upward flow velocity of the liquid will decrease. Under the action of gravity, the carried packing will settle back to the fluidization zone to continue participating in the denitrification reaction. In the implementation mode of this example, the contour of the separation zone 942 is trumpet-shaped and opens upward, so that there is a transition section in the housing part of the denitrification chamber in the separation zone 942 that smoothly extends to the fluidization zone 941. Starting from the fluidization zone, the cross-section of the separation zone 942 gradually expands from bottom to top. Furthermore, when the packing settles, it will smoothly fall along the transition section to the fluidization zone 941 when it touches the housing. In this example, the transition section is straight. It can be understood that in other examples, the transition section can also have a certain curvature.

[0072] Furthermore, an overflow weir 96 is arranged in the reflux zone 943. The height of the overflow weir 96 is higher than that of the filtering port 912. A groove opening upward is formed between the overflow weir 96 and the housing of the denitrification chamber 94; the drain port 95 is arranged on the housing of the denitrification chamber 94 located in the groove. Furthermore, the denitrification liquid first enters the mixing tank 91 through the filtering port 912 and then rises to the overflow weir 96, overflows the overflow weir 96 and enters the groove and flows out through the drain port 95, ensuring that the denitrification liquid can be refluxed and discharged at the same time.

[0073] Furthermore, the conveying pipeline 914 connecting the output port 913 and the inlet of the circulation pump 93 is composed of alternately arranged first pipelines 9141 and second pipelines 9142, and the pipe diameter of the second pipeline 9142 is larger than that of the first pipeline 9141, so that the second pipeline 9142 forms a mixer for the mixed liquid when the mixed liquid flows through. That is, due to the different diameters of the first pipeline 9141 and the second pipeline 9142, when the mixed liquid preliminarily mixed in the mixing tank 91 flows into the second pipeline 9142 through the pipeline, due to the expansion of the flow channel, the mixed liquid flows under the reverse pressure gradient and generates vortices, promoting the deep mixing of the mixed liquid. In the implementation mode of this example, the number of the second pipelines 9142 is 3. It can be understood that the number of the second pipelines 9142 can be set according to requirements, such as 1 or 5, etc.

[0074] Furthermore, a water distribution plate 98 is also arranged in the denitrification chamber 94, so that the fluidization zone 941 is isolated from the area below the water distribution plate 98; at the same time, the water distributor 92 is arranged above the water distribution plate 98, and the water distributor outlet 921 is located above the water distribution plate 98, and the water distributor inlet 922 is located below the water distribution plate. Furthermore, the second conveying pipeline connecting the circulation pump and the water distributor inlet 922 is located in the area below the water distribution plate 98, which can avoid being corroded by the liquid in the fluidization zone.

[0075] Further, the pickling wastewater treatment system 100 further includes an effluent tank 10. The effluent tank 10 is communicated with the drain port 95, can receive the denitrification liquid, and then is transported to the discharge point for discharge through the effluent pump communicated to the effluent tank 10.

[0076] Continue to refer to Figure 1 and Figure 2 As shown, the process flow of an embodiment of the pickling wastewater treatment system according to the present application is as follows:

[0077] (1) The pickling wastewater passes through the grid channel 1 to intercept the suspended solids in the pickling wastewater, avoiding blockage of pumps and valves by sundries and affecting the operation of the system.

[0078] (2) The pickling wastewater filtered by the grid channel 1 enters the regulating tank 2 through the regulating tank inlet 21, and the water quality and water volume are regulated in the regulating tank 2. Among them, the average hydraulic retention time of the regulating tank 2 is about 12 h.

[0079] (3) Then, the pickling wastewater is lifted by a lift pump and enters the reaction tank 3411 in the first mixing reaction tank 341. At the same time, the automatic control system for dosing of the calcium hydroxide dosing sub-unit is started. According to the fluoride ion concentration in the pickling wastewater measured by the fluoride ion automatic detector and the system settings, the dosing pump automatically adjusts the dosing target amount of calcium hydroxide (Ca(OH) 2 ) to the reaction tank 3411, so that sufficient calcium ions react completely with the fluoride ions in the wastewater to form calcium fluoride (CaF 2 ) precipitates, and precipitates in the first sedimentation tank 342.

[0080] Since the fluoride ions and pH value in the pickling wastewater have certain fluctuations, and the precipitation of calcium fluoride (CaF 2 ) has certain condition requirements for the pH value, in this embodiment, an automatic detection and adjustment system for the pH value of the pickling wastewater in the neutralization tank 3412 is set after the automatic dosing of the calcium hydroxide dosing sub-unit:

[0081] When the pH value of the pickling wastewater entering the neutralization tank 3412 is lower than the set value after sufficient calcium hydroxide is dosed, mixed and reacted, the automatic control system of the sodium hydroxide dosing sub-unit is started. The dosing pump automatically adjusts the dosing amount of sodium hydroxide added to the neutralization tank 3412 according to the pH value in the neutralization tank 3412 and the target value set by the control system, so that the pH value of the pickling wastewater in the neutralization tank 3412 reaches the set value;

[0082] When the pH value of the pickling wastewater in the neutralization tank 3412 is higher than the set value after sufficient calcium hydroxide is added, mixed, and reacted, the dosing automatic control system of the sulfuric acid dosing sub-unit is activated. The dosing pump automatically adjusts the sulfuric acid dosing amount added to the neutralization tank 3412 according to the pH value in the neutralization tank 3412 and the target value set by the control system, so that the pH value of the pickling wastewater in the neutralization tank 3412 reaches the set value.

[0083] After the pH value of the pickling wastewater in the neutralization tank 3412 reaches the set value, it enters the first flocculation tank 3413. According to the need, the dosing control system of the polyacrylamide dosing sub-unit is started to add the flocculant polyacrylamide. After sufficient mixing and stirring, the primary reaction liquid is obtained, and the primary reaction liquid flows into the first sedimentation tank 342 by gravity. In the first sedimentation tank 342, the precipitates of metal ions such as CaF 2 , Cr(OH) 3 , Ni(OH) 2 , Mn(OH) 2 etc. precipitate in the sedimentation area to achieve sediment-water separation and obtain the primary wastewater. The precipitate enters the mud hopper in the first sedimentation tank 342 and is regularly discharged into the sludge tank 63. The supernatant of the primary wastewater flows into the second mixing reaction tank 351 by gravity.

[0084] (4) An automatic pH monitoring system is set at the outlet of the first sedimentation tank 342. According to the measured pH value and the target value set by the system, the sulfuric acid dosing amount added to the second mixing reaction tank 351 by the sulfuric acid dosing sub-unit is automatically adjusted, so that the pH value of the primary wastewater transported from the first sedimentation tank 342 to the second mixing reaction tank 351 reaches the set value.

[0085] Similarly, according to the water quality requirements, the polyacrylamide dosing sub-unit and the polyaluminum chloride dosing sub-unit are controlled to add polyacrylamide and polyaluminum chloride to the second mixing reaction tank 351 to promote the coagulation and sedimentation of the flocs and particulate matters such as residual CaF 2 , Cr(OH) 3 , Ni(OH) 2 , Mn(OH) 2 etc. in the primary wastewater. After sufficient mixing and stirring, the secondary reaction liquid is obtained, and the secondary reaction liquid flows into the second sedimentation tank 352 by gravity. The flocs in the secondary reaction liquid precipitate here to achieve secondary sediment-water separation and obtain the clarified liquid. The precipitate enters the mud hopper and is regularly discharged into the sludge tank 63. The supernatant of the clarified liquid is pumped into the denitrification water supply tank 7.

[0086] (5)Set up a denitrification feed water tank 7 to automatically monitor the pH value of the clarified liquid. According to the measured pH value of the clarified liquid and the target value set by the system, automatically adjust the dosage of sulfuric acid added to the denitrification feed water tank 7 to make the pH value of the clarified liquid in the denitrification feed water tank 7 reach the set value. And add carbon source, nitrogen and phosphorus nutrients as needed to provide the nutrients required by denitrifying bacteria (microbial film on the surface of the packing). After stirring and mixing evenly, it is lifted by a denitrification feed water pump 8 and enters the clarified liquid denitrification unit 9 for denitrification reaction.

[0087] (6)Set up a clarified liquid denitrification unit 9, equipped with a circulation pump 93 for internal circulation reflux to improve the load of the clarified liquid denitrification unit 9; the clarified liquid added with carbon source, nitrogen and phosphorus nutrients flows into the mixing tank 917 from the inlet 911, and after mixing with the denitrified liquid overflowing from the communication hole on the partition plate 915 in the collecting tank 916, it flows into the mixer formed by the second pipeline 9142 through the first pipeline 9141 at the bottom of the mixing tank 917. Since the diameter of the mixer formed by the second pipeline 9142 is different from that of the first pipeline 9141, when the mixed liquid flows from the first pipeline 9141 into the second pipeline 9142, the flow channel expands, and the mixed liquid flows under the reverse pressure gradient to generate vortices, promoting further mixing of the liquid. After the mixed liquid is evenly mixed through multiple sections of the second pipeline 9142, it is pumped into the second conveying pipeline 931 by a circulation pump and flows into the interior of the denitrification chamber through the outlet of a water distributor 921 connected to the second conveying pipeline 931. By controlling the water flow velocity, the packing in the fluidized zone 941 is in a fluidized state of motion, and the mixed liquid flows through the fluidized zone 941 and reacts fully with the microbial film attached to the surface of the packing. After the reaction, the denitrified liquid enters the separation zone 942. Since the cross-sectional area of the separation zone 942 expands, the upward flow velocity of the wastewater will decrease. Under the action of gravity, the carried packing will fall back to the fluidized zone 941 to continue to participate in the reaction, and then the denitrified liquid enters the reflux zone 943. Part of the denitrified liquid is collected into the collecting tank 916 through a collecting pipe 97. At this time, the packing that has not settled will be isolated outside the collecting pipe 97. The denitrified liquid in the collecting tank 916 overflows into the mixing tank 917 through the communication hole on the partition plate 915 and is mixed with the clarified liquid for further cyclic reaction. The remaining part of the denitrified liquid flows through the overflow weir 96 and is discharged from the drain port 95, flowing by gravity into the outlet tank 10 and is transported to the discharge point for discharge through an outlet water pump.

[0088] Among them, the precipitates in the first sedimentation tank 342 and the second sedimentation tank 352 are discharged to the sludge tank 63 from the sediment inlet 61 through a sludge discharge pipe. The filtrate obtained by pressure filtration in the sludge tank 63 flows back to the regulating tank 2 through a pipeline via the regulating tank inlet 21.

[0089] This embodiment can completely remove metal ions and fluoride ions in the pickling wastewater, and at the same time effectively carry out denitrification treatment on nitrate nitrogen (NO 3 -N) in the pickling wastewater, with high denitrification efficiency, strong shock resistance, high volume load and small floor area.

[0090] Meanwhile, through optimized structural design, the denitrification unit of the clarified liquid can effectively prevent the loss of packing, ensure the treatment efficiency and long-term stable operation of the system, and maintain the denitrification efficiency of the system. Meanwhile, the fluid is evenly mixed during movement, eliminating the need for traditional mechanical stirring and saving energy consumption.

[0091] It can be understood that the parameters in the above process flow are only illustrative and can be adjusted according to actual situations, and the present application does not make any limitations in this regard.

[0092] In addition, the above drawings are only schematic illustrations of the processes included in the exemplary embodiments of the present application, rather than for limiting purposes. Those skilled in the art will readily conceive of other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of the present application and include known common knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and embodiments are only regarded as exemplary, and the true scope and spirit of the present application are pointed out by the claims.

Claims

1. An acid pickling wastewater treatment system, characterized in that, it comprises: A wastewater precipitation unit for precipitating and removing metal ions and fluoride ions in the acid pickling wastewater to obtain a clarified liquid, which has a receiving port for receiving the acid pickling wastewater and an outflow port for the clarified liquid to flow out; A clarified liquid denitrification unit, which includes a mixing tank, a water distributor, a circulation pump and a denitrification chamber; an inlet, a filter port and an outlet are provided on the mixing tank; the inlet is communicated with the outflow port of the wastewater precipitation unit for the clarified liquid to flow into the mixing tank for mixing to obtain a mixed liquid; inside the denitrification chamber, a fluidized zone, a separation zone and a reflux zone are provided from bottom to top; the fluidized zone is filled with fillers attached with microbial membranes for the mixed liquid to carry out denitrification reaction with the microbial membranes to obtain a denitrified liquid; the bottom of the fluidized zone is communicated with the outlet through the water distributor and the circulation pump; the separation zone is for the fillers to separate and settle from the denitrified liquid to the fluidized zone; the reflux zone is provided with a drain port for discharging the denitrified liquid outwards, and the reflux zone is communicated with the filter port to transport the denitrified liquid into the mixing tank; wherein, the mixing tank is arranged in the reflux zone, and the cavity of the mixing tank is in the shape of a vertically established cylinder; the cavity of the mixing tank is divided into a mixing pool located at the central position of the cavity of the mixing tank and a collecting pool surrounding the mixing pool by a vertically arranged annular partition plate, and communication holes are provided on the partition plate to connect the collecting pool with the mixing pool; the inlet is opened on the upper end surface of the mixing pool, the outlet is opened on the lower end surface of the mixing pool, and the filter port is opened on the side wall of the collecting pool facing the reflux zone, so that the filter port is communicated with the reflux zone, and the filter port is multiple, and the multiple filter ports are arranged in an array around the mixing tank.

2. The acid pickling wastewater treatment system according to claim 1, characterized in that, the wastewater precipitation unit includes a primary mixing and precipitation unit and a secondary mixing and precipitation unit which are connected in sequence. The primary mixing and precipitation unit is used for precipitating and removing metal ions and fluoride ions in the acid pickling wastewater through a primary flocculant to obtain primary wastewater, and the secondary mixing and precipitation unit is used for precipitating and removing metal ions and fluoride ions in the primary wastewater through a secondary flocculant to obtain a clarified liquid; the receiving port is arranged on the primary mixing and precipitation unit, and the outflow port is arranged on the secondary mixing and precipitation unit.

3. The acid pickling wastewater treatment system according to claim 2, characterized in that, The primary mixing and sedimentation unit includes a first mixing reaction tank and a first sedimentation tank; the secondary mixing and sedimentation unit includes a second mixing reaction tank and a second sedimentation tank; the first mixing reaction tank, the first sedimentation tank, the second mixing reaction tank, and the second sedimentation tank are connected in sequence; the first mixing reaction tank is used for mixing and reacting a primary flocculating agent with pickling wastewater to obtain a primary reaction liquid, the first sedimentation tank is used for sedimenting and removing metal ions and fluoride ions in the primary reaction liquid to obtain primary wastewater, the second mixing reaction tank is used for mixing and reacting a secondary flocculating agent with the primary wastewater to obtain a secondary reaction liquid, and the second sedimentation tank is used for sedimenting and removing metal ions and fluoride ions in the secondary reaction liquid to obtain a clarified liquid; The receiving port is arranged in the first mixing reaction tank, and the outflow port is arranged in the second sedimentation tank.

4. The pickling wastewater treatment system according to claim 3, wherein, the pickling wastewater treatment system further includes a primary flocculating agent adding unit and a secondary flocculating agent adding unit; the primary flocculating agent adding unit is connected to the first mixing reaction tank, and the secondary flocculating agent adding unit is connected to the second mixing reaction tank.

5. The pickling wastewater treatment system according to claim 4, wherein, the primary flocculating agent adding unit includes a calcium hydroxide dosing subunit, a sodium hydroxide dosing subunit, a sulfuric acid dosing subunit, and a polyacrylamide dosing subunit; the secondary flocculating agent adding unit includes a sulfuric acid dosing subunit, a polyacrylamide dosing subunit, and a polyaluminum chloride dosing subunit; the first mixing reaction tank includes a reaction tank, a neutralization tank, and a first flocculation tank connected in sequence; the reaction tank is connected to the calcium hydroxide dosing subunit, the neutralization tank is connected to the sodium hydroxide dosing subunit and the sulfuric acid dosing subunit, and the first flocculation tank is connected to the polyacrylamide dosing subunit; the receiving port is arranged in the reaction tank; the first flocculation tank is connected to the first sedimentation tank; the second mixing reaction tank includes an adjustment tank, a second flocculation tank, and a third flocculation tank connected in sequence; the adjustment tank is connected to the sulfuric acid dosing subunit, the second flocculation tank is connected to the polyacrylamide dosing subunit, and the third flocculation tank is connected to the polyaluminum chloride dosing subunit; the adjustment tank is connected to the first sedimentation tank, and the third flocculation tank is connected to the second sedimentation tank.

6. The pickling wastewater treatment system according to claim 1, wherein, the pickling wastewater treatment system further includes a denitrification water supply tank and a denitrification water supply pump for adjusting the pH value of the clarified liquid and adding nutrient elements required by microorganisms; the inlet of the denitrification water supply tank is connected to the outflow port of the wastewater sedimentation unit, the outlet of the denitrification water supply tank is connected to the inlet of the denitrification water supply pump, and the outlet of the denitrification water supply pump is connected to the inlet of the denitrification unit.

7. The pickling wastewater treatment system according to any one of claims 1-6, wherein, the wastewater sedimentation unit further has a discharge port for discharging metal ion and fluoride ion precipitates obtained by sedimenting pickling wastewater; The pickling wastewater treatment system further includes a precipitate dewatering unit for compressing and dewatering metal ion and fluoride ion precipitates to obtain filtrate; the precipitate dewatering unit includes a sediment inlet for the precipitate and a supernatant reflux port; the sediment inlet is communicated with the discharge port, and the reflux port is communicated with the receiving port.

8. The pickling wastewater treatment system according to claim 7, wherein, the precipitate dewatering unit includes a sludge tank and a filter press; the sediment inlet and the reflux port are arranged on the sludge tank; the sludge tank is connected to the filter press.

9. The pickling wastewater treatment system according to claim 1, wherein, the water distributor is arranged at the bottom of the fluidization zone, and the outlet of the water distributor is arranged upward; the circulation pump is arranged outside the denitrification chamber; the output port is communicated with the inlet of the circulation pump through a first conveying pipeline, and the outlet of the circulation pump is communicated with the inlet of the water distributor through a second conveying pipeline.

10. The pickling wastewater treatment system according to claim 9, wherein, the first conveying pipeline is composed of alternately arranged first pipelines and second pipelines, and the diameter of the second pipeline is larger than that of the first pipeline.

11. The pickling wastewater treatment system according to claim 9, wherein, the cross-section of the separation zone is larger than that of the fluidization zone.

12. The pickling wastewater treatment system according to claim 9, wherein, an overflow weir is arranged in the reflux zone, the height of the overflow weir is higher than that of the filtering port, and a groove with an upward opening is formed between the overflow weir and the shell of the denitrification chamber; the drain port is opened on the shell of the denitrification chamber located in the groove.

13. The pickling wastewater treatment system according to claim 9, wherein, a water distribution plate is further arranged in the denitrification chamber to isolate the fluidization zone from the area below the water distribution plate; the water distributor is arranged on the water distribution plate, the outlet of the water distributor is above the water distribution plate, and the inlet of the water distributor is below the water distribution plate.

14. The pickling wastewater treatment system according to claim 8, wherein, the pickling wastewater treatment system further includes a grid channel for intercepting suspended solids in the pickling wastewater and a regulating tank for regulating the water quality and water volume of the pickling wastewater; the grid channel is arranged before the inlet of the regulating tank, the outlet of the regulating tank is communicated with the receiving port, and the reflux port is communicated with the inlet of the regulating tank and the receiving port through connection.

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