A two-stage coagulation-based nanofiltration pretreatment device and method for printing and dyeing wastewater

Abstract

The present application relates to wastewater treatment technical field, specifically to a kind of based on two-stage coagulation's printing and dyeing wastewater nanofiltration pretreatment device and method, including coagulation treatment kettle, the bottom of the coagulation treatment kettle is provided with waste liquid output valve, further including: lifting filter disc, is embeddedly slidably arranged in the inside of the coagulation treatment kettle, the middle of the lifting filter disc is provided with annular filter screen.The printing and dyeing wastewater of nanofiltration is coagulated pretreatment by coagulation treatment kettle, central traction rod pulls lifting filter disc in the bottom of coagulation treatment kettle and slides up, and coagulation precipitate in it is filtered and intercepted, and coagulation precipitate is separated from printing and dyeing wastewater by lifting filter disc, after lifting filter disc is lifted to the top of coagulation treatment kettle, coagulation precipitate is filtered and intercepted, and flows to the periphery and is collected by annular collecting disc, the coagulation precipitate of printing and dyeing wastewater is separated quickly, so as to facilitate the continuous coagulation treatment of printing and dyeing wastewater, and the overall processing efficiency is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to a two-stage coagulation-based nanofiltration pretreatment device and method for printing and dyeing wastewater. BACKGROUND

[0002] As one of the largest industries in the world, the textile dyeing and finishing industry produces wastewater during the processes of pretreatment, dyeing, finishing, sizing, multiple washing and rinsing cycles. High COD, high color and high salinity are the main characteristics of printing and dyeing wastewater. Many dyes and auxiliaries have the characteristics of toxicity, carcinogenicity and non-biodegradability, and can easily cause sensory discomfort, environmental hazards and other problems. Therefore, it is extremely critical to treat printing and dyeing wastewater before discharge. At present, adsorption, advanced oxidation and membrane separation are used for the deep treatment of printing and dyeing wastewater. Membrane technology has the advantages of green and efficient process, simple process and high water quality.

[0003] Among various membrane technologies, ultrafiltration / microfiltration (UF / MF) has a high removal rate of suspended solids, macromolecular organic matter and other impurities in printing and dyeing wastewater. Nanofiltration (NF) is considered to have a good removal rate of color and high-valent salt in printing and dyeing wastewater. Reverse osmosis has a good desalination rate.

[0004] However, membrane fouling is the main bottleneck limiting the application of membrane technology in the treatment of printing and dyeing wastewater. Organic pollution is particularly serious, mainly because colloids and organic matter accumulate on the membrane surface, causing rapid decay of membrane flux and irreversible pollution. SUMMARY

[0005] Therefore, the present application aims to provide a two-stage coagulation-based nanofiltration pretreatment device and method for printing and dyeing wastewater to solve the problem of serious organic pollution during the current nanofiltration treatment of printing and dyeing wastewater, and the accumulation of colloids and organic matter on the membrane surface, causing rapid decay of membrane flux and irreversible pollution.

[0006] To achieve the above purpose, the present application provides a two-stage coagulation-based nanofiltration pretreatment device for printing and dyeing wastewater, which comprises a coagulation treatment kettle, a waste liquid output valve is arranged at the bottom of the coagulation treatment kettle, and the coagulation treatment kettle further comprises:

[0007] A lifting filter disc is embedded and slidably arranged on the inner side of the coagulation treatment kettle. An annular filter screen is arranged in the middle of the lifting filter disc. A central traction block is rotatably connected at the center of the lifting filter disc. An embedded connecting block is arranged at the top of the central traction block. A connecting conveying pipe is arranged inside the central traction block and the embedded connecting block. A plurality of cleaning injection holes are uniformly arranged on the outer wall of the central traction block. The connecting conveying pipe and the cleaning injection holes are in communication with each other.

[0008] The fixed filter frame is arranged above the top of the coagulation treatment kettle, a lifting guide sleeve is arranged at the center of the fixed filter frame, a fixed telescopic pipe is fixedly connected above the fixed filter frame, a booster delivery pump is connected at the top of the fixed telescopic pipe, a cleaning motor is fixedly connected below the fixed filter frame, and a drive gear is connected at the shaft end of the cleaning motor.

[0009] A center traction rod is inlaid and slidably arranged inside the lifting guide sleeve, a hollow delivery pipe is arranged inside the center traction rod, and the hollow delivery pipe and the fixed telescopic pipe are inlaid and slidably connected.

[0010] A inlaid connection sleeve is rotationally connected at the bottom of the center traction rod, the size of the inlaid connection sleeve and the inlaid connection block is matched with each other, a connection electromagnet is arranged around the bottom of the inlaid connection sleeve, a connection magnetic ring is connected around the top of the inlaid connection block, a rotating gear ring is arranged around the outside of the inlaid connection sleeve, and the rotating gear ring is in mesh with the drive gear when the rotating gear ring moves to the same height of the drive gear following the upward movement of the center traction rod.

[0011] An annular material collecting disc is arranged around the outside of the top of the coagulation treatment kettle, the inner side wall of the annular material collecting disc and the outer side wall of the coagulation treatment kettle are inlaid and slidably connected, and an inclined guide groove is arranged in the middle of the outside of the annular material collecting disc.

[0012] Further, a lifting rack is vertically arranged in the middle of the center traction rod, a traction gear is rotationally arranged in the middle of the lifting guide sleeve, a traction motor is connected at the shaft end of the traction gear, and the lifting rack and the traction gear are in mesh with each other.

[0013] Further, a rotary treatment frame is connected to the outside of the coagulation treatment kettle, a plurality of coagulation treatment kettles are uniformly and circumferentially arranged in the middle of the rotary treatment frame, a fixed rotary frame is arranged outside the rotary treatment frame, the rotary treatment frame is rotationally connected with the fixed rotary frame, the fixed filter frame is fixedly connected with the fixed rotary frame, and the rotary treatment frame drives all the coagulation treatment kettles to rotate synchronously and pass through the fixed filter frame below in turn.

[0014] Further, an adjusting gear ring is arranged around the outside of the annular material collecting disc, a lifting material collecting frame is arranged around the outside of the adjusting gear ring, a hydraulic telescopic rod is connected to the outside of the lifting material collecting frame, and the upper and lower ends of the hydraulic telescopic rod are respectively connected with the lifting material collecting frame and the fixed rotary frame.

[0015] Further, the annular aggregate tray is rotationally connected with the lifting aggregate frame through the adjusting tooth ring, the middle of the lifting aggregate frame is provided with an adjusting gear, the adjusting gear is meshed with the adjusting tooth ring, the shaft end of the adjusting gear is connected with an adjusting motor, the center of the fixed rotary frame is symmetrically provided with a first aggregate tank and a second recovery tank, and the inclined guide groove is arranged towards the center of the fixed rotary frame.

[0016] Further, the outer side of the fixed rotary frame is also connected with a lifting stirring frame, the outer side of the lifting stirring frame is connected with a lifting sliding sleeve, the inner side of the lifting sliding sleeve is nested with a vertical guide rod, the lifting stirring frame is slidingly connected with the vertical guide rod through the lifting sliding sleeve, the vertical guide rod is fixedly connected with the fixed rotary frame, the outer side of the lifting sliding sleeve is connected with a hydraulic lifting rod, and the upper and lower ends of the hydraulic lifting rod are respectively connected with the lifting sliding sleeve and the fixed rotary frame.

[0017] Further, the center of the lifting stirring frame is rotationally connected with a center stirring rod, the center of the center stirring rod is provided with a center conveying pipe, a plurality of conveying openings are arranged in the middle of the center stirring rod, the conveying openings are in communication with the center conveying pipe, the upper side of the fixed rotary frame is fixedly connected with a fixed conveying pipe, the fixed conveying pipe is slidingly connected with the center conveying pipe in a nested mode, the upper side of the fixed conveying pipe is connected with a metering conveying pump, and the outer side of the center stirring rod is also connected with a PH monitor.

[0018] Further, a plurality of embedded recovery tanks are uniformly arranged on the outer wall of the center stirring rod, a folding rotating shaft is arranged at the top end of the embedded recovery tank, a folding stirring rod is connected with the outer side of the folding rotating shaft, the folding stirring rod is rotationally connected with the center stirring rod through the folding rotating shaft, and the folding stirring rod and the embedded recovery tank are in cooperation with each other in size.

[0019] Further, the outer end of the folding stirring rod is connected with an elastic air bag, the middle of the elastic air bag is connected with a flexible air conveying pipe, and the outer end of the flexible air conveying pipe is connected with an air inflation pump.

[0020] A nanofiltration pretreatment method for printing and dyeing wastewater based on two-stage coagulation, comprising the following steps:

[0021] L1 pre-adjusting pH value: after the printing and dyeing wastewater is added into the coagulation treatment kettle, H2SO4 is added to adjust the pH of the printing and dyeing wastewater to 2.5;

[0022] L2 primary flocculation: after adding flocculants to the printing and dyeing wastewater, the wastewater is fully stirred and mixed to carry out flocculation reaction, wherein the flocculant is preferably polyaluminum chloride, and the polyaluminum chloride addition amount and the printing and dyeing wastewater volume ratio is 100 mg / L;

[0023] L3 primary coagulation: after adding coagulants to the printing and dyeing wastewater after the primary flocculation, the wastewater is stirred and mixed to carry out coagulation reaction, after 10 minutes of reaction, standing and settling, and then the lifting filter disc is pulled up by the central pulling rod to carry out filtration, the coagulation sediment and the printing and dyeing wastewater are separated, wherein the coagulant is preferably polyacrylamide, and the polyacrylamide addition amount and the printing and dyeing wastewater volume ratio is 1.5 mg / L;

[0024] L4 back to call pH value: after the printing and dyeing wastewater after the primary coagulation filtration, NaOH is added to call the pH of the printing and dyeing raw water to 6-8;

[0025] L6 secondary flocculation: after adding flocculants to the printing and dyeing wastewater after the pH value is called, the wastewater is fully stirred and mixed to carry out the second flocculation reaction, wherein the flocculant is preferably polyaluminum chloride, and the polyaluminum chloride addition amount and the printing and dyeing wastewater volume ratio is 50 mg / L;

[0026] L7 secondary coagulation: after adding coagulants to the printing and dyeing wastewater after the secondary flocculation, the wastewater is stirred and mixed to carry out coagulation reaction, after the reaction is completed, standing and settling, and then the lifting filter disc is pulled up by the central pulling rod to carry out filtration, the coagulation sediment and the printing and dyeing wastewater are separated, and the obtained printing and dyeing wastewater clear liquid enters the next processing process unit, wherein the coagulant is preferably polyacrylamide, and the polyacrylamide addition amount and the printing and dyeing wastewater volume ratio is 0.5 mg / L.

[0027] The beneficial effects of the present application: from the above, it can be seen that the printing and dyeing wastewater nanofiltration pretreatment device based on two-stage coagulation provided by the present application carries out coagulation pretreatment on the printing and dyeing wastewater subjected to nanofiltration through the coagulation treatment kettle, the printing and dyeing wastewater is subjected to flocculation and coagulation treatment in the coagulation treatment kettle by adding flocculants and coagulants, so that the organic impurities in the printing and dyeing wastewater are coagulated and settled, and then the central pulling rod can pull the lifting filter disc at the bottom of the coagulation treatment kettle to slide upward to filter the coagulation sediment, so that the coagulation sediment is filtered and intercepted on the lifting filter disc and separated from the printing and dyeing wastewater, and after the lifting filter disc is lifted to the top of the coagulation treatment kettle, the filtered and intercepted coagulation sediment flows naturally to the surrounding and is collected through the annular material collecting disc, and at the same time, the booster pump can deliver the booster water flow to the cleaning spray hole to spray out, so as to clean the surface of the lifting filter disc and wash away the coagulation sediment on the surface, thereby facilitating the rapid separation and treatment of the coagulation sediment of the printing and dyeing wastewater, and then the lifting filter disc can be lowered to the bottom of the coagulation treatment kettle again to continue the flocculation and coagulation treatment, so as to facilitate the continuous coagulation pretreatment of the printing and dyeing wastewater, and the overall treatment efficiency is higher;

[0028] The printing and dyeing wastewater nanofiltration pretreatment method based on two-stage coagulation enhances the removal of organic matters in the printing and dyeing wastewater through the mutual cooperation of two-stage coagulation operations, so that the accumulation of colloids and organic matters on the membrane surface during the subsequent nanofiltration treatment of the wastewater can be avoided, the rapid decay of the membrane flux and the occurrence of irreversible pollution can be avoided, compared with the current printing and dyeing wastewater pretreatment process, the treatment process is simpler, the cost is lower, the overall treatment efficiency is higher, and it is conducive to the large-scale use of printing and dyeing wastewater treatment and reuse. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present application or prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only a part of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 It is a local structure schematic diagram of the filtering state of the embodiment of the present application.

[0031] Figure 2 It is a front structure schematic diagram of the embodiment of the present application.

[0032] Figure 3 It is a top view structure schematic diagram of the embodiment of the present application.

[0033] Figure 4 It is a structure schematic diagram of the fixed rotating frame of the embodiment of the present application.

[0034] Figure 5 It is a structure schematic diagram of the rotating treatment frame of the embodiment of the present application.

[0035] Figure 6 It is a structure schematic diagram of the coagulation treatment kettle of the embodiment of the present application.

[0036] Figure 7 It is a structure schematic diagram of the lifting filter disc of the embodiment of the present application.

[0037] Figure 8 It is a structure schematic diagram of the fixed filter frame of the embodiment of the present application.

[0038] Figure 9 It is a structure schematic diagram of the center traction rod of the embodiment of the present application.

[0039] Figure 10 It is a structure schematic diagram of the annular material collecting disc of the embodiment of the present application.

[0040] Figure 11 It is a structure schematic diagram of the lifting stirring frame of the embodiment of the present application.

[0041] Figure 12 Structure diagram of the central stirring rod of the embodiment of the present application;

[0042] Figure 13 Structure diagram of the folding stirring rod of the embodiment of the present application;

[0043] Figure 14 Structure diagram of the folding stirring rod of the embodiment of the present application in the unfolded state.

[0044] Marked as:

[0045] 1, fixed rotary frame; 101, first material collecting groove; 102, second collecting groove; 103, rotary processing frame; 104, rotary tooth ring; 105, rotary gear; 106, rotary motor; 2, coagulation treatment kettle; 201, waste liquid output valve; 202, waste liquid output groove; 3, lifting stirring frame; 301, fixed conveying pipe; 302, metering conveying pump; 303, lifting sliding sleeve; 304, vertical guide rod; 305, hydraulic lifting rod; 306, stirring tooth ring; 307, stirring gear; 308, stirring motor; 4, central stirring rod; 401, PH monitor; 402, central conveying pipe; 403, conveying opening; 404, embedded collecting groove; 405, folding rotating shaft; 406, folding stirring rod; 407, elastic air bag; 408, flexible air conveying pipe; 409, inflation air pump; 5, lifting filter disc; 501, annular filter screen; 502, limiting baffle; 503, central traction block; 504, embedded connecting block; 505, connecting magnetic ring; 506, connecting conveying pipe; 507, cleaning jet hole; 6, fixed filter frame; 601, lifting guide sleeve; 602, traction gear; 603, traction motor; 604, limiting rotation block; 7, central traction rod; 701, lifting rack; 702, hollow conveying pipe; 703, fixed telescopic pipe; 704, booster conveying pump; 8, embedded connecting sleeve; 801, connecting electromagnet; 802, rotating tooth ring; 803, driving gear; 804, cleaning motor; 9, lifting material collecting frame; 901, hydraulic telescopic rod; 902, adjusting gear; 903, adjusting motor; 904, annular material collecting disc; 905, flushing and discharging pipe; 906, flushing nozzle; 907, inclined guide groove; 908, adjusting tooth ring. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with specific embodiments.

[0047] It should be noted that the technical terms or scientific terms used in the present application should be understood as the general meaning understood by those skilled in the art to which the present application belongs, unless otherwise defined. The "first", "second" and similar words used in the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Include" or "contain" and similar words mean that the elements or objects before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connected" or "connected" and similar words are not limited to physical or mechanical connection, but can include electrical connection, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to represent the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0048] As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 , a kind of based on two-stage coagulation printing and dyeing wastewater nanofiltration pretreatment device, including coagulation treatment kettle 2, coagulation treatment kettle 2 Bottom is provided with waste liquid output valve 201, still including:

[0049] Lifting filter disc 5, is embedded in the inside of coagulation treatment kettle 2 Slidingly, annular filter screen 501 is arranged in the middle of lifting filter disc 5, center traction block 503 is rotatably connected and arranged at the center of lifting filter disc 5, embedded connection block 504 is arranged at the top of center traction block 503, connection conveying pipe 506 is arranged in the inside of center traction block 503 and embedded connection block 504, a plurality of cleaning spray holes 507 are uniformly arranged on the outer wall of center traction block 503, and connection conveying pipe 506 and cleaning spray hole 507 are interconnected;

[0050] Fixed filter frame 6 is arranged above the top of coagulation treatment kettle 2, lifting guide sleeve 601 is arranged at the center of fixed filter frame 6, fixed telescopic pipe 703 is fixedly connected and arranged above fixed filter frame 6, booster delivery pump 704 is connected and arranged at the top of fixed telescopic pipe 703, cleaning motor 804 is fixedly connected and arranged below fixed filter frame 6, drive gear 803 is connected and arranged at the shaft end of cleaning motor 804;

[0051] Center traction rod 7 is embedded and slidably arranged in the inside of lifting guide sleeve 601, hollow conveying pipe 702 is arranged in the inside of center traction rod 7, hollow conveying pipe 702 and fixed telescopic pipe 703 are slidably connected and nested with each other;

[0052] The chimeric connecting sleeve 8 is rotatably connected to the bottom of the central traction rod 7. The size of the chimeric connecting sleeve 8 and the chimeric connecting block 504 are matched with each other. The bottom of the chimeric connecting sleeve 8 is surrounded by the connecting electromagnet 801. The top of the chimeric connecting block 504 is surrounded by the connecting magnetic ring 505. The outer side of the chimeric connecting sleeve 8 is surrounded by the rotating tooth ring 802. When the rotating tooth ring 802 moves up along with the central traction rod 7 to the same height as the driving gear 803, the rotating tooth ring 802 is engaged with the driving gear 803.

[0053] The annular material collecting disc 904 is surrounded by the top outer side of the coagulation treatment kettle 2. The inner side wall of the annular material collecting disc 904 is slidably connected with the outer side wall of the coagulation treatment kettle 2. The outer side of the annular material collecting disc 904 is provided with an inclined guide groove 907.

[0054] In the embodiment, the device coagulates and pretreats the printing and dyeing wastewater for nanofiltration through the coagulation treatment kettle 2. The printing and dyeing wastewater is treated by adding flocculants and coagulants in the coagulation treatment kettle 2 to flocculate and coagulate the organic impurities in the printing and dyeing wastewater, and the central traction rod 7 can slide up and down along the lifting guide sleeve 601. When filtration is needed, the central traction rod 7 drives the embedded connection sleeve 8 to move downward, so that the embedded connection sleeve 8 and the embedded connection block 504 on the lifting filter disc 5 are embedded and connected with each other, and are connected and fixed by the connection electromagnet 801 and the connection magnetic ring 505. Then the central traction rod 7 can drive the lifting filter disc 5 at the bottom of the coagulation treatment kettle 2 to move upward synchronously to lift, so as to filter and intercept the coagulation sediment generated in the coagulation treatment kettle 2 from the printing and dyeing wastewater, and separate the coagulation sediment from the printing and dyeing wastewater. When the lifting filter disc 5 is lifted to the top of the coagulation treatment kettle 2, the coagulation sediment filtered and intercepted on the lifting filter disc 5 naturally flows to the surrounding, and the top outside of the coagulation treatment kettle 2 is embedded and arranged in a ring shape to form a ring-shaped collecting disc 904, so that the coagulation sediment naturally falls into the ring-shaped collecting disc 904 for collection, thereby facilitating the rapid separation and treatment of the coagulation sediment of the printing and dyeing wastewater. Then the lifting filter disc 5 can be lowered to the bottom of the coagulation treatment kettle 2 and separated from the central traction rod 7, and then the central traction rod 7 is reset on the upper side to continue the flocculation and coagulation treatment, thereby facilitating the continuous coagulation pretreatment of the printing and dyeing wastewater, and improving the overall treatment efficiency. Meanwhile, the hollow conveying pipe 702 and the connecting conveying pipe 506 are arranged in the central traction rod 7 and the central traction block 503 respectively, the booster conveying pump 704 can convey the pressurized water flow, and the pressurized water flow is conveyed to the cleaning jet hole 507 through the hollow conveying pipe 702 and the connecting conveying pipe 506, and is sprayed out to clean the surface of the lifting filter disc 5 and flush away the coagulation sediment on the surface. Meanwhile, before the embedded connection sleeve 8 and the embedded connection block 504 are embedded and connected with each other, the embedded connection block 504 can be flushed by the high-pressure water flow to avoid the coagulation sediment on the surface affecting the subsequent connection. In addition, the outside of the embedded connection sleeve 8 is arranged in a rotating gear ring 802, and when the rotating gear ring 802 is lifted to the same height as the driving gear 803 by following the central traction rod 7, the rotating gear ring 802 is engaged with the driving gear 803, so that the cleaning motor 804 can drive the rotating gear ring 802 to rotate through the driving gear 803, and then drive the central traction block 503 to rotate, so that the water flow can fully clean the surface of the lifting filter disc 5 and flush away the coagulation sediment on the surface, thereby further improving the efficiency of separating the coagulation sediment, reducing the residue, and avoiding affecting the filtering efficiency of the lifting filter disc 5 and the treatment effect of the printing and dyeing wastewater. Meanwhile, the bottom of the fixed filter frame 6 and the upper surface edge of the lifting filter disc 5 are respectively provided with the limited rotation block 604 and the limiting baffle 502. The lifting filter disc 5 can be limited by the limited rotation block 604 and the limiting baffle 502 to avoid synchronous rotation with the central traction block 503.

[0055] As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 shown, preferably, the device is through the center traction rod 7 traction coagulation treatment kettle 2 bottom lifting filter disc 5 upward synchronous movement to lift, to filter coagulation treatment kettle 2 in printing and dyeing wastewater coagulation sediment generated, and the center traction rod 7 is vertically arranged in the middle of the lifting rack 701, the middle of the lifting guide sleeve 601 is arranged with traction gear 602, the shaft end of traction gear 602 is connected with traction motor 603, lifting rack 701 and traction gear 602 are engaged with each other, so that the traction motor 603 drives the center traction rod 7 up and down through the lifting rack 701 and the traction gear 602 to filter work, while the outer side of the coagulation treatment kettle 2 is connected with the rotary treatment frame 103, the rotary treatment frame 103 is uniformly surrounded by a plurality of coagulation treatment kettles 2 in the middle of the circumference, the outer side of the rotary treatment frame 103 is provided with a fixed rotary frame 1, the rotary treatment frame 103 is rotatably connected with the fixed rotary frame 1, the fixed filter frame 6 is fixedly connected with the fixed rotary frame 1, and the rotary treatment frame 103 is connected with the rotary gear ring 104 outside the rotary treatment frame 103, the rotary gear ring 104 is engaged with the rotary gear 105 in the middle, and the shaft end of the rotary gear 105 is connected with the rotary motor 106, the rotary motor 106 is fixedly connected with the fixed rotary frame 1, so that the rotary motor 106 can drive the rotary treatment frame 103 to rotate through the rotary gear 105 and the rotary gear ring 104, and then make the rotary treatment frame 103 drive all coagulation treatment kettles 2 to rotate synchronously and pass through the fixed filter frame 6 below in turn, so that the device can simultaneously treat the wastewater in multiple coagulation treatment kettles 2 continuously, so that the coagulation treatment kettle 2 can be placed after adding flocculating agent and coagulant, and then rotated to the fixed filter frame 6 below, and then filtered, so that the multiple coagulation treatment kettles 2 can be rotated by the fixed rotary frame 1, and then the wastewater in the multiple coagulation treatment kettles 2 can be coagulated and filtered in turn and continuously, so as to facilitate continuous coagulation pretreatment of a large amount of printing and dyeing wastewater, and the overall treatment efficiency is higher.

[0056] As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10As shown, preferably, the device collects the coagulation sediment filtered out by the lifting filter disc 5 through the annular collecting disc 904, and the outer side of the annular collecting disc 904 is provided with an adjusting tooth ring 908, the outer side of the adjusting tooth ring 908 is provided with a lifting collecting frame 9, the outer side of the lifting collecting frame 9 is connected with a hydraulic telescopic rod 901, and the upper and lower ends of the hydraulic telescopic rod 901 are respectively connected with the lifting collecting frame 9 and the fixed rotary frame 1, so that when the fixed rotary frame 1 drives the plurality of coagulation treatment kettles 2 to rotate, the hydraulic telescopic rod 901 can drive the annular collecting disc 904 to move upward and separate from the coagulation treatment kettle 2, avoiding blocking the coagulation treatment kettle 2, and when the coagulation treatment kettle 2 moves to the position directly below the fixed filter frame 6 for filtering work, the telescopic rod drives the annular collecting disc 904 to move downward and nest to the top outer side of the coagulation treatment kettle 2 for subsequent coagulation sediment guiding and collecting. Meanwhile, the annular collecting disc 904 is rotationally connected with the lifting collecting frame 9 through the adjusting tooth ring 908, the middle of the lifting collecting frame 9 is provided with an adjusting gear 902, the adjusting gear 902 is meshed with the adjusting tooth ring 908, the shaft end of the adjusting gear 902 is connected with an adjusting motor 903, the center of the fixed rotary frame 1 is symmetrically provided with a first collecting groove 101 and a second recycling groove 102, and the inclined guide groove 907 is arranged towards the center of the fixed rotary frame 1, so that the adjusting motor 903 can drive the annular collecting disc 904 to rotate through the adjusting gear 902 and the adjusting tooth ring 908, and then adjust the orientation angle of the inclined guide groove 907 arranged thereon, so that the inclined guide groove 907 is directed towards the first collecting groove 101 or the second recycling groove 102, which is convenient for adjusting according to different coagulation sediments generated by wastewater, avoiding mixing different sediments, facilitating separation, collection and treatment of the sediments, and being more flexible and convenient to use. In addition, the inner side of the annular collecting disc 904 is provided with a flushing and discharging pipe 905, a plurality of flushing nozzles 906 are arranged around the middle of the flushing and discharging pipe 905, and the flushing and discharging pipe 905 is connected with a booster delivery pump 704, so that water flow can be sprayed into the annular collecting disc 904 through the flushing nozzles 906 to flush out the filtered and separated sediments, avoiding residue and improving cleaning effect.

[0057] As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 11 , Figure 12 , Figure 13 and Figure 14As shown, preferably, the outer side of the fixed rotary frame 1 of the device is also connected to be provided with a lifting stirring frame 3, the outer side of the lifting stirring frame 3 is connected to be provided with a lifting sliding sleeve 303, the inner side of the lifting sliding sleeve 303 is nested to be provided with a vertical guide rod 304, the lifting stirring frame 3 is slidingly connected with the vertical guide rod 304 through the lifting sliding sleeve 303, the vertical guide rod 304 is fixedly connected with the fixed rotary frame 1, the outer side of the lifting sliding sleeve 303 is connected to be provided with a hydraulic lifting rod 305, the upper and lower ends of the hydraulic lifting rod 305 are respectively connected with the lifting sliding sleeve 303 and the fixed rotary frame 1, the rotary treatment frame 103 drives all the coagulation treatment kettles 2 to rotate synchronously and pass through the position right below the lifting stirring frame 3 in turn, so that when the coagulation treatment kettle 2 moves to the position right below the lifting stirring frame 3, the hydraulic lifting rod 305 can drive the lifting stirring frame 3 to move up and down to stir the printing and dyeing wastewater in the coagulation treatment kettle 2, which facilitates the mixing of the required additives and wastewater.

[0058] As shown in Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 11 , Figure 12 , Figure 13 and Figure 14 , preferably, the center of the lifting stirring frame 3 of the device is rotatably connected to be provided with a central stirring rod 4, so that when the lifting stirring frame 3 descends, the central stirring rod 4 is driven to descend synchronously and insert into the coagulation treatment kettle 2, and the top outer side of the central stirring rod 4 is surrounded to be provided with a stirring tooth ring 306, the outer side of the stirring tooth ring 306 is engaged to be provided with a stirring gear 307, and the shaft end of the stirring gear 307 is connected to be provided with a stirring motor 308, so that the stirring motor 308 can drive the central stirring rod 4 to rotate to stir the printing and dyeing wastewater in the coagulation treatment kettle 2 through the stirring gear 307 and the stirring tooth ring 306, which improves the mixing uniformity and treatment efficiency, and the center of the central stirring rod 4 is provided with a central conveying pipe 402, a plurality of conveying openings 403 are arranged in the central stirring rod 4, the conveying openings 403 are in communication with the central conveying pipe 402, a fixed conveying pipe 301 is fixedly connected above the fixed rotary frame 1, the fixed conveying pipe 301 is slidingly connected with the central conveying pipe 402, a metering conveying pump 302 is connected above the fixed conveying pipe 301, so that the metering conveying pump 302 can quantitatively convey the printing and dyeing wastewater, flocculants, acid and alkali liquids required for adjusting the pH value of the printing and dyeing wastewater, etc., which facilitates quantitative conveying treatment and automatic feeding according to the best treatment ratio, and the outer side of the central stirring rod 4 is also connected to be provided with a pH monitor 401, which facilitates real-time monitoring of the pH value of the printing and dyeing wastewater, and is more flexible and convenient to use.

[0059] As shown in Figure 1 ,Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 11 、 Figure 12 、 Figure 13 and Figure 14 As shown in the figure, preferably, the device drives the rotation of the central stirring rod 4 in the dyeing wastewater treatment kettle 2 by the stirring motor 308 to stir the dyeing wastewater, and the outer wall of the central stirring rod 4 is uniformly surrounded by a plurality of embedded recovery grooves 404, the top end of the embedded recovery groove 404 is provided with a folding pivot 405, the outer side of the folding pivot 405 is connected and provided with a folding stirring rod 406, the folding stirring rod 406 is rotationally connected with the central stirring rod 4 through the folding pivot 405, and the size of the folding stirring rod 406 and the embedded recovery groove 404 is matched with each other, so that when the central stirring rod 4 rotates, the folding stirring rod 406 is subjected to centrifugal force and naturally turns up to a near-horizontal state to improve the stirring effect, and when the central stirring rod 4 stops rotating, the folding stirring rod 406 is subjected to gravity and naturally rotates downward to be embedded in the embedded recovery groove 404 for storage, so as to avoid further disturbance to the dyeing wastewater when the central stirring rod 4 rises out, facilitate the flocculation and coagulation of the dyeing wastewater, and avoid pollution of the stirring structure by intercepting and carrying the precipitate generated by flocculation and coagulation above the folding stirring rod 406.

[0060] As shown in the figure, Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 11 、 Figure 12 、 Figure 13 and Figure 14 Preferably, the outer end of the folding stirring rod 406 of the device is connected and provided with an elastic air bag 407, the middle of the elastic air bag 407 is connected and provided with a flexible gas conveying pipe 408, and the outer end of the flexible gas conveying pipe 408 is connected and provided with an inflation air pump 409. When stirring, the inflation air pump 409 and the flexible gas conveying pipe 408 can inflate the elastic air bag 407 to make it swell, and then the folding stirring rod 406 is turned up by buoyancy, and after stirring is completed, the inflation air pump 409 and the flexible gas conveying pipe 408 can extract the gas in the elastic air bag 407 to make it shrink and lose buoyancy, and the folding stirring rod 406 is subjected to gravity and naturally rotates downward to be embedded in the embedded recovery groove 404 for storage, so as to realize the natural unfolding and storage of the folding stirring rod 406, ensure a larger stirring range when slowly rotating and stirring, and avoid affecting the flocculation and coagulation effect of the dyeing wastewater by excessive and rapid stirring.

[0061] In use, first connect the pipelines of the device, then rotate the motor 106 to drive the rotating treatment frame 103 to rotate through the rotating gear 105 and the rotating gear ring 104, and then the rotating treatment frame 103 drives all the coagulation treatment kettles 2 to rotate synchronously and pass through the lifting stirring frame 3 one by one, when the coagulation treatment kettle 2 moves to the position directly below the lifting stirring frame 3, the hydraulic lifting rod 305 drives the lifting stirring frame 3 to move downward, and then drives the central stirring rod 4 to descend synchronously and insert into the coagulation treatment kettle 2, then the printing and dyeing wastewater is quantitatively delivered into the coagulation treatment kettle 2 through the metering delivery pump 302, the central delivery pipe 402 and the delivery opening 403, and then the flocculating agent, the acid and alkali liquid required for adjusting the pH value of the printing and dyeing wastewater, etc. are delivered, so as to coagulate and pretreat the printing and dyeing wastewater, at the same time, the flexible air pipe 408 can be inflated to make the elastic air bag 407 expand through the inflation air pump 409, and then the folding stirring rod 406 is turned up through the buoyancy, then the stirring motor 308 drives the central stirring rod 4 and all the folding stirring rods 406 to rotate, so as to mix and stir the printing and dyeing wastewater, after the stirring is completed, the elastic air bag 407 is retracted to lose the buoyancy through the inflation air pump 409 and the flexible air pipe 408, the folding stirring rod 406 is naturally rotated downward and embedded into the embedded recovery groove 404 for storage under the action of gravity, then the hydraulic lifting rod 305 drives the central stirring rod 4 to rise and reset through the lifting stirring frame 3, the rotating treatment frame 103 drives the coagulation treatment kettle 2 to continue to rotate, and another coagulation treatment kettle 2 is moved to the position directly below the lifting stirring frame 3, so as to carry out the feeding and stirring work, and after the printing and dyeing wastewater in the coagulation treatment kettle 2 is reacted and precipitated for a certain time, the coagulation treatment kettle 2 is moved to the position directly below the fixed filter frame 6 through the rotating treatment frame 103, then the ring-shaped material collecting disc 904 is moved downward and nested to the top outside of the coagulation treatment kettle 2 through the compression and extension rod, the central traction rod 7 is driven downward through the traction motor 603, the lifting rack 701 and the traction gear 602, so as to make the embedded connection sleeve 8 and the embedded connection block 504 on the lifting filter disc 5 embedded and connected with each other, and then the embedded connection sleeve 8 and the embedded connection block 504 are fixedly connected through the connection electromagnet 801 and the connection magnetic ring 505, then the lifting filter disc 5 at the bottom of the coagulation treatment kettle 2 is synchronously moved upward and lifted through the central traction rod 7, so as to filter the coagulation precipitate generated in the printing and dyeing wastewater in the coagulation treatment kettle 2, and the coagulation precipitate is filtered and intercepted on the lifting filter disc 5 and separated from the printing and dyeing wastewater, after the lifting filter disc 5 is lifted to the top of the coagulation treatment kettle 2, the coagulation precipitate filtered and intercepted on the lifting filter disc 5 naturally flows to the surrounding and falls into the ring-shaped material collecting disc 904 for collection, at the same time, the pressurized water flow is delivered through the pressurized delivery pump 704, and then the pressurized water flow is delivered to the cleaning jet hole 507 through the hollow delivery pipe 702 and the connection delivery pipe 506, so as to clean the surface of the lifting filter disc 5 and flush away the coagulation precipitate on the surface, so as to quickly separate and treat the coagulation precipitate of the printing and dyeing wastewater, then the lifting filter disc 5 is lowered to the bottom of the coagulation treatment kettle 2 and separated from the central traction rod 7, then the central traction rod 7 is reset on the upper side,At the same time, the hydraulic telescopic rod 901 drives the annular aggregate disc 904 to move upward as a whole to separate from the coagulation treatment kettle 2, then the rotary treatment frame 103 drives the coagulation treatment kettle 2 to continue to rotate, and another coagulation treatment kettle 2 is moved to be located directly below the lifting stirring frame 3, through rotation circulation, the waste water in the plurality of coagulation treatment kettles 2 can be sequentially and continuously circulated for coagulation and filtration, and the printing and dyeing waste water treated for multiple times is discharged to the waste liquid output tank 202 through the waste liquid output valve 201, and then is transported to the next processing process unit.

[0062] The printing and dyeing waste water nanofiltration pretreatment device based on two-stage coagulation provided by the application can coagulate and pretreat the printing and dyeing waste water for nanofiltration through the coagulation treatment kettle 2, the printing and dyeing waste water is subjected to flocculation and coagulation treatment in the coagulation treatment kettle 2 by adding flocculants and coagulants, so that the organic impurities in the printing and dyeing waste water are coagulated and settled, then the central traction rod 7 can pull the lifting filter disc 5 at the bottom of the coagulation treatment kettle 2 to slide upward to filter the coagulation and settlement, the coagulation and settlement is filtered and intercepted on the lifting filter disc 5 to be separated from the printing and dyeing waste water, after the lifting filter disc 5 is lifted to the top of the coagulation treatment kettle 2, the filtered and intercepted coagulation and settlement flows naturally to the surrounding and is collected through the annular aggregate disc 904, at the same time, the booster delivery pump 704 can deliver the booster water flow to the cleaning spray hole 507 to spray out, so as to clean the surface of the lifting filter disc 5 and wash away the coagulation and settlement on the surface, thereby facilitating the rapid separation and treatment of the coagulation and settlement of the printing and dyeing waste water, then the lifting filter disc 5 can be lowered to the bottom of the coagulation treatment kettle 2 again to continue the flocculation and coagulation treatment, so as to continuously coagulate and pretreat the printing and dyeing waste water, and the overall treatment efficiency is higher.

[0063] A printing and dyeing waste water nanofiltration pretreatment method based on two-stage coagulation, comprising the following steps:

[0064] L1 pre-adjusting pH value: after the printing and dyeing waste water is added into the coagulation treatment kettle 2, H2SO4 is added to adjust the pH of the printing and dyeing waste water to 2.5;

[0065] L2 primary flocculation: after the flocculants are added into the printing and dyeing waste water, the printing and dyeing waste water is fully stirred and mixed to perform flocculation reaction, wherein the flocculants are preferably polyaluminum chloride, and the polyaluminum chloride is added in a volume ratio of 100 mg / L to the printing and dyeing waste water;

[0066] L3 primary coagulation: after the coagulants are added into the printing and dyeing waste water subjected to the primary flocculation, the printing and dyeing waste water is stirred and mixed to perform coagulation reaction, after 10 minutes of reaction, the printing and dyeing waste water is placed and settled, then the lifting filter disc 5 is pulled upward by the central traction rod 7 to perform filtration, so as to separate the coagulation and settlement from the printing and dyeing waste water, wherein the coagulants are preferably polyacrylamide, and the polyacrylamide is added in a volume ratio of 1.5 mg / L to the printing and dyeing waste water;

[0067] L4 pH value callback: NaOH is added to the printing and dyeing wastewater after primary coagulation filtration to callback the pH value of the printing and dyeing raw water to 6-8;

[0068] L6 secondary flocculation: after the pH value of the printing and dyeing wastewater is adjusted, a flocculant is added to the wastewater and fully stirred to carry out a second flocculation reaction, wherein the flocculant is preferably polyaluminum chloride, and the polyaluminum chloride is added in an amount of 50 mg / L based on the volume of the printing and dyeing wastewater;

[0069] L7 secondary coagulation: a coagulant is added to the printing and dyeing wastewater after secondary flocculation and stirred to carry out a coagulation reaction. After the reaction is completed, the wastewater is allowed to stand and settle, and then the coagulation sediment is separated from the printing and dyeing wastewater by lifting the filter disc 5 upward through the central traction rod 7. The separated printing and dyeing wastewater is then subjected to the next treatment process unit. The coagulant is preferably polyacrylamide, and the polyacrylamide is added in an amount of 0.5 mg / L based on the volume of the printing and dyeing wastewater.

[0070] The polyaluminum chloride (PACl, 98%), polyacrylamide (PAM, anionic, molecular weight 5 million), sulfuric acid (H2SO4, AR, 95%-98%), and sodium hydroxide (NaOH, AR, 95%) are prepared into stock solutions of 5000 mg / L and 200 mg / L, respectively, before use.

[0071] Under acidic conditions, the zeta potential decreases and the steady state is broken. The addition of coagulants such as polyaluminum chloride and polyacrylamide accelerates the settling of humic acid, polysaccharides, and proteins in the printing and dyeing wastewater, and some dyes and impurities are also removed simultaneously. However, this process also causes the dissolution and release of metal salts in the coagulant. Then, by adjusting the pH value to neutral, metal hydroxide colloids are generated. The addition of coagulants such as polyaluminum chloride and polyacrylamide accelerates the settling of these suspended solids, and also removes a small amount of residual organic matter. The two-stage coagulation operation is mutually synergistic, enhancing the removal of organic matter in the printing and dyeing wastewater. This can avoid the accumulation of colloids and organic matter on the membrane surface during subsequent nanofiltration treatment, causing rapid decay of membrane flux and irreversible pollution. Compared with current printing and dyeing wastewater pretreatment processes, the treatment process is simpler, the cost is lower, and the overall treatment efficiency is higher, which is conducive to the large-scale use of printing and dyeing wastewater treatment and reuse.

[0072] Those skilled in the art should understand that the above discussion of any embodiment is only exemplary, and is not intended to suggest that the present application is limited to these examples; under the idea of the present application, the above embodiments or technical features among different embodiments can also be combined, and the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above, which are not provided in details for the sake of brevity. Any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A two-stage coagulation-based nanofiltration pretreatment device for printing and dyeing wastewater, comprising a coagulation treatment kettle (2), wherein a waste liquid output valve (201) is arranged at the bottom of the coagulation treatment kettle (2), characterized in that, Also include: Lifting filter disc (5), chimeric sliding is arranged in the inside of the coagulation treatment kettle (2), the middle of the lifting filter disc (5) is provided with annular filter screen (501), the center of the lifting filter disc (5) is rotatably connected with center traction block (503), the top of the center traction block (503) is provided with chimeric connecting block (504), the inside of the center traction block (503) and chimeric connecting block (504) is provided with connecting conveying pipe (506), the outer wall of the center traction block (503) is uniformly provided with multiple cleaning injection holes (507), the connecting conveying pipe (506) and the cleaning injection hole (507) are communicated with each other; Fixed filter frame (6) is arranged above the top of the coagulation treatment kettle (2), the center of the fixed filter frame (6) is provided with lifting guide sleeve (601), the top of the fixed filter frame (6) is fixedly connected with fixed telescopic pipe (703), the top of the fixed telescopic pipe (703) is connected with booster delivery pump (704), the lower side of the fixed filter frame (6) is fixedly connected with cleaning motor (804), the shaft end of the cleaning motor (804) is connected with driving gear (803); Center traction rod (7) is arranged in the inside of the lifting guide sleeve (601), the inside of the center traction rod (7) is provided with hollow conveying pipe (702), the hollow conveying pipe (702) and the fixed telescopic pipe (703) are nested and slidably connected with each other; Chimeric connecting sleeve (8) is rotatably connected to the bottom of the center traction rod (7), the size of the chimeric connecting sleeve (8) and the chimeric connecting block (504) is matched with each other, the bottom of the chimeric connecting sleeve (8) is surrounded by connecting electromagnet (801), the top of the chimeric connecting block (504) is surrounded by connecting magnetic ring (505), the outside of the chimeric connecting sleeve (8) is surrounded by rotating gear ring (802), when the rotating gear ring (802) moves up to the same height of the driving gear (803) following the center traction rod (7), the rotating gear ring (802) is engaged with the driving gear (803); Annular aggregate disc (904) is surrounded by the outside of the top of the coagulation treatment kettle (2), the inner side wall of the annular aggregate disc (904) and the outer side wall of the coagulation treatment kettle (2) are slidably connected with each other, the middle of the outside of the annular aggregate disc (904) is provided with inclined guide groove (907); The outside of the coagulation treatment kettle (2) is connected with rotary treatment frame (103), a plurality of coagulation treatment kettles (2) are uniformly surrounded by the middle of the rotary treatment frame (103) in a circular manner, the outside of the rotary treatment frame (103) is provided with fixed rotary frame (1), the rotary treatment frame (103) is rotatably connected with the fixed rotary frame (1), the fixed filter frame (6) is fixedly connected with the fixed rotary frame (1), the rotary treatment frame (103) drives all coagulation treatment kettles (2) to rotate synchronously and pass through the fixed filter frame (6) below in turn.

2. The two-stage coagulation based nanofiltration pretreatment device for dyeing wastewater according to claim 1, characterized in that, The middle vertical of the center traction rod (7) is provided with a lifting rack (701), the middle rotation of the lifting guide sleeve (601) is provided with a traction gear (602), the shaft end of the traction gear (602) is connected with a traction motor (603), and the lifting rack (701) and the traction gear (602) are meshed with each other.

3. The two-stage coagulation based nanofiltration pretreatment device for dyeing wastewater according to claim 1, characterized in that, The outer side of the annular aggregate disc (904) is provided with an adjusting tooth ring (908), the outer side of the adjusting tooth ring (908) is provided with a lifting aggregate frame (9), the outer side of the lifting aggregate frame (9) is connected with a hydraulic telescopic rod (901), and the upper and lower ends of the hydraulic telescopic rod (901) are connected with the lifting aggregate frame (9) and the fixed rotary frame (1) respectively.

4. The two-stage coagulation based nanofiltration pretreatment device for dyeing wastewater according to claim 3, characterized in that, The annular aggregate disc (904) is rotationally connected with the lifting aggregate frame (9) through the adjusting tooth ring (908), the middle of the lifting aggregate frame (9) is provided with an adjusting gear (902), the adjusting gear (902) is meshed with the adjusting tooth ring (908), the shaft end of the adjusting gear (902) is connected with an adjusting motor (903), the center of the fixed rotary frame (1) is symmetrically provided with a first aggregate groove (101) and a second recycling groove (102), and the inclined guide groove (907) is arranged towards the center of the fixed rotary frame (1).

5. The two-stage coagulation based nanofiltration pretreatment device for dyeing wastewater according to claim 4, characterized in that, The outer side of the fixed rotary frame (1) is also connected with a lifting stirring frame (3), the outer side of the lifting stirring frame (3) is connected with a lifting sliding sleeve (303), the inner side of the lifting sliding sleeve (303) is nested with a vertical guide rod (304), the lifting stirring frame (3) is slidingly connected with the vertical guide rod (304) through the lifting sliding sleeve (303), the vertical guide rod (304) is fixedly connected with the fixed rotary frame (1), the outer side of the lifting sliding sleeve (303) is connected with a hydraulic lifting rod (305), and the upper and lower ends of the hydraulic lifting rod (305) are connected with the lifting sliding sleeve (303) and the fixed rotary frame (1) respectively, and the rotary treatment frame (103) drives all the coagulation treatment kettles (2) to rotate synchronously and pass through the lifting stirring frame (3) below in turn.

6. The two-stage coagulation based nanofiltration pretreatment device for dyeing wastewater according to claim 5, characterized in that, The center of the lifting stirring frame (3) is rotationally connected with a center stirring rod (4), the center of the center stirring rod (4) is provided with a center conveying pipe (402), a plurality of conveying openings (403) are arranged in the middle of the center stirring rod (4), the conveying openings (403) and the center conveying pipe (402) are in communication, a fixed conveying pipe (301) is fixedly connected above the fixed rotary frame (1), the fixed conveying pipe (301) and the center conveying pipe (402) are slidingly connected in a nested manner, a metering conveying pump (302) is connected above the fixed conveying pipe (301), and the outer side of the center stirring rod (4) is also connected with a PH monitor (401).

7. The two-stage coagulation based nanofiltration pretreatment device for dyeing wastewater according to claim 6, characterized in that, The outer wall of the central stirring rod (4) is uniformly surrounded by a plurality of embedded recovery grooves (404), the top end of the embedded recovery groove (404) is provided with a folding pivot (405), the outer side of the folding pivot (405) is connected and provided with a folding stirring rod (406), the folding stirring rod (406) is rotationally connected with the central stirring rod (4) through the folding pivot (405), and the folding stirring rod (406) and the embedded recovery groove (404) are mutually matched in size.

8. The two-stage coagulation based nanofiltration pretreatment device for dyeing wastewater according to claim 7, characterized in that, The outer end of the folding stirring rod (406) is connected and provided with an elastic air bag (407), the middle of the elastic air bag (407) is connected and provided with a flexible gas conveying pipe (408), and the outer end of the flexible gas conveying pipe (408) is connected and provided with an inflation air pump (409).

9. A dyeing wastewater nanofiltration pretreatment method using the two-stage coagulation-based dyeing wastewater nanofiltration pretreatment apparatus according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: L1, pre-adjusting the pH value: after the printing and dyeing wastewater is added into the coagulation treatment kettle (2), H2SO4 is added to adjust the pH of the printing and dyeing wastewater to 2.5; L2, primary flocculation: after the flocculant is added into the printing and dyeing wastewater, the printing and dyeing wastewater is fully stirred and mixed to carry out the flocculation reaction, wherein the flocculant is polyaluminum chloride, the polyaluminum chloride is added in an amount of 100 mg / L based on the volume of the printing and dyeing wastewater; L3, primary coagulation: after the coagulant is added into the printing and dyeing wastewater after the primary flocculation, the printing and dyeing wastewater is stirred and mixed to carry out the coagulation reaction, after 10 minutes of reaction, the printing and dyeing wastewater is allowed to stand and settle, and then the lifting filter disc (5) is pulled up by the central pulling rod (7) to carry out the filtration, so that the coagulation sediment is separated from the printing and dyeing wastewater, wherein the coagulant is polyacrylamide, the polyacrylamide is added in an amount of 1.5 mg / L based on the volume of the printing and dyeing wastewater; L4, readjusting the pH value: NaOH is added into the printing and dyeing wastewater after the primary coagulation and filtration, so that the pH of the printing and dyeing raw water is readjusted to 6-8; L6, secondary flocculation: after the flocculant is added into the printing and dyeing wastewater after the readjustment of the pH value, the printing and dyeing wastewater is fully stirred and mixed to carry out the second flocculation reaction, wherein the flocculant is polyaluminum chloride, the polyaluminum chloride is added in an amount of 50 mg / L based on the volume of the printing and dyeing wastewater; L7, secondary coagulation: after the coagulant is added into the printing and dyeing wastewater after the secondary flocculation, the printing and dyeing wastewater is stirred and mixed to carry out the coagulation reaction, after the reaction is completed, the printing and dyeing wastewater is allowed to stand and settle, and then the lifting filter disc (5) is pulled up by the central pulling rod (7) to carry out the filtration, so that the coagulation sediment is separated from the printing and dyeing wastewater, and the obtained printing and dyeing wastewater clear liquid enters the next processing process unit, wherein the coagulant is polyacrylamide, the polyacrylamide is added in an amount of 0.5 mg / L based on the volume of the printing and dyeing wastewater.

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