A ship rust removal wastewater treatment method and device based on bioflocculation and ultra-micro dynamic precision filtration

Abstract

The application provides a ship rust removal wastewater treatment method and device based on bioflocculation and ultra-micro dynamic precision filtration, and belongs to the technical field of ship wastewater treatment. The wastewater treatment method comprises the following steps: (1) pretreatment: filtering ship rust removal wastewater, adjusting homogeneity and equal amount, and obtaining pretreated wastewater; (2) bioflocculation: adding a bioflocculant to the pretreated wastewater, realizing efficient flocculation through rapid mixing reaction, and obtaining flocculated wastewater; and (3) solid-liquid separation: feeding the flocculated wastewater into an ultra-micro dynamic precision filtration device, performing high-precision solid-liquid separation under pressure, and obtaining filtered clean water and filter cake. The dense flocs formed through bioflocculation are perfectly matched with the ultra-micro dynamic precision filtration device, the floc strength is high, the flocs can withstand high-pressure filtration without breaking and penetrating, and the water quality is excellent. In addition, the filter cake formed is loose and easy to desorb, and can be completely desorbed through back blowing, the filtration cycle is significantly prolonged, and the solid-liquid separation efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of ship wastewater treatment technology, specifically relating to a method and apparatus for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration. Background Technology

[0002] Removing old paint and rust is a necessary process in shipbuilding and repair. Currently, high-pressure jet rust removal technology is widely used to remove old paint and rust. This technology generates a large amount of wastewater containing iron oxide scale, rust residue, broken paint, colloidal suspended matter, and a small amount of oil and heavy metal ions. This ship rust removal wastewater has the following characteristics: (1) high concentration of suspended matter and wide distribution of solid particle size; (2) contains heavy metals, such as zinc, copper, and chromium, which are components from antifouling paint; (3) high COD and may contain a small amount of oil; (4) due to the intermittent nature of rust removal operations, the water quality and quantity fluctuate drastically and are highly corrosive. Therefore, the treatment of ship rust removal wastewater is of great significance.

[0003] Currently, traditional ship rust removal wastewater treatment technologies mostly employ inorganic flocculants (polyaluminum chloride, polyferric sulfate) or organic synthetic flocculants (polyacrylamide) in conjunction with sedimentation tanks, sand filters, plate and frame filter presses, etc. This process has the following obvious defects: (1) Chemical flocculant residues are prone to causing secondary pollution, which does not meet the requirements of green shipbuilding and repair; (2) The flocs are loose and have a high water content, resulting in a large sludge production and high disposal costs; (3) Traditional filtration equipment occupies a large area, is prone to clogging, and has a low degree of automation, making it unsuitable for the small spaces of docks and decks; (4) The treatment process is long and has poor resistance to shock loads, making it difficult to adapt to the intermittent discharge and large concentration fluctuations of rust removal wastewater.

[0004] In view of the above-mentioned shortcomings of traditional technologies for treating ship rust removal wastewater, this invention proposes a green, efficient, low-cost, compact, and stable method and device for treating ship rust removal wastewater by efficiently coupling bio-flocculation with ultra-micro dynamic filtration. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration, which aims to solve the technical problems of existing ship rust removal wastewater treatment technologies, such as chemical pollution, high treatment costs, large equipment footprint, and unstable treatment effects.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration, comprising the following steps: (1) Pretreatment: The rust removal wastewater from the ship is filtered and then homogenized and adjusted to obtain pretreated wastewater; (2) Bioflocculation: Add bioflocculating agent to the pretreated wastewater, and achieve efficient flocculation through rapid mixing reaction to obtain flocculated wastewater; (3) Solid-liquid separation: The flocculated wastewater is sent to an ultra-micro dynamic fine filtration device for high-precision solid-liquid separation under pressure to obtain filtered water and filter cake.

[0007] Preferably, in step (2), the bioflocculant is a quaternary ammonium cationic polysaccharide bioflocculant, and its dosage is 5-10 mg / L. The pH value of the wastewater during bioflocculation is 6.5-8.5.

[0008] Preferably, in step (2), the preparation method of the quaternary ammonium cationic polysaccharide bioflocculant includes the following steps: (A) Preparation of GTA-modified chitosan: Chitosan was dissolved in an aqueous acetic acid solution, the pH was adjusted, and then the temperature was raised. 2,3-epoxypropyltrimethylammonium chloride was added, and the grafting reaction was carried out by stirring while keeping warm. After the reaction was completed, GTA-modified chitosan was obtained by precipitation, separation, washing and drying. (B) Preparation of GTA-modified starch: Corn starch was dispersed in deionized water to obtain starch milk, and the pH was adjusted for alkali activation; then the temperature was raised, and 2,3-epoxypropyltrimethylammonium chloride was added, and the mixture was kept warm and stirred to carry out the etherification reaction; after the reaction was completed, the starch was neutralized, separated, washed and dried to obtain GTA-modified starch; (C) Compounding: GTA-modified chitosan and GTA-modified starch are mixed and stirred until homogeneous to obtain quaternary ammonium cationic polysaccharide bioflocculant.

[0009] Preferably, in step (A), 10% NaOH solution is added to adjust the pH to 6.5-7.5; the molar ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride is 1:2-1:4; during the reaction, 2,3-epoxypropyltrimethylammonium chloride is added in 2-3 batches in the form of an aqueous solution; the grafting reaction temperature is 70-75℃, and the time is 6-8h. In step (B), the solid-liquid ratio of corn starch to deionized water is 1 g / 7-9 mL; NaOH solution is added to adjust the pH to 10.5-11.5 for alkaline activation; the mass ratio of corn starch to 2,3-epoxypropyltrimethylammonium chloride is 1:0.5-1:1, and 2,3-epoxypropyltrimethylammonium chloride is added in 2-3 batches in the form of aqueous solution during the reaction; the etherification reaction temperature is 55-65℃, and the time is 3-5 h. In step (C), GTA-modified chitosan and GTA-modified starch are prepared into GTA-modified chitosan mother liquor and GTA-modified starch mother liquor with a mass fraction of 0.5% respectively, and the two are mixed at a mass ratio of 1:4-1:6.

[0010] Preferably, in step (3), the ultra-micro dynamic fine filtration equipment is a scraper-type self-cleaning filter with a stainless steel filter screen, a filter screen pore size of 1-5μm, a pressure of 0.4-0.6MPa during ultra-micro dynamic fine filtration, and a filtration cycle of 4-8h.

[0011] Preferably, in step (3), the SS of the filtered water is ≤30mg / L, the SS removal rate is >99%, the oil content is ≤5mg / L, the oil removal rate is >90%, and the filter cake moisture content is as low as 60%-65%.

[0012] The present invention also provides a bio-flocculation coupled ultra-micro dynamic filtration ship rust removal wastewater treatment device, which adopts any of the above treatment methods and includes a pretreatment unit, a bio-flocculation unit and a solid-liquid separation unit connected in sequence by pipelines; The pretreatment unit is equipped with a first booster pump, a filter, and a recycled water tank connected in sequence. The bioflocculation unit is equipped with a second lift pump and a pipeline mixer connected in sequence. The inlet end of the second lift pump is connected to the outlet end of the recycled water tank. A dosing tank is provided outside the pipeline mixer, and a dosing pump is connected to the dosing tank. The outlet end of the dosing pump is connected to the pipeline mixer. The solid-liquid separation unit is equipped with an ultra-micro dynamic fine filtration device. The ultra-micro dynamic fine filtration device is equipped with a tank. The tank is equipped with a feed inlet, a liquid outlet, and a slag discharge outlet. The feed inlet is connected to the outlet end of the pipeline mixer, the liquid outlet is connected to the clear water tank, and the slag discharge outlet is connected to the filter residue collection box.

[0013] Preferably, the recycled water tank is equipped with an air vent valve and a first level gauge; the dosing tank is equipped with a second level gauge.

[0014] Preferably, the tank body is provided with a precision filter assembly, which is composed of a stainless steel filter screen; The tank body is also provided with a central shaft, a rotating scraper is provided on the central shaft, and a drive motor is provided on the tank body, with the output shaft of the drive motor connected to the central shaft; The tank is also equipped with a compressed air backflush pipeline, which is used to periodically remove the filter cake layer on the surface of the precision filter assembly by backflushing with compressed air at the end of the filtration cycle. The tank is also equipped with a differential pressure gauge, and the top of the tank is equipped with an exhaust port.

[0015] Preferably, it also includes an automatic control unit, which is a PLC control cabinet, and the automatic control unit is electrically connected to the pretreatment unit, the bioflocculation unit, and the solid-liquid separation unit.

[0016] This invention provides a method and apparatus for treating ship rust removal wastewater using bio-flocculation coupled with ultra-micro dynamic filtration. Compared with the prior art, the advantages of this invention are: (1) This invention provides a method for preparing a bio-flocculant - a high-substitution-degree quaternary ammonium cationic polysaccharide bio-flocculant. The quaternary ammonium cationic polysaccharide bio-flocculant is non-toxic and harmless, can be completely biodegraded, and has no risk of secondary pollution. Moreover, the high-substitution-degree cationic characteristics of the quaternary ammonium cationic polysaccharide bio-flocculant endow it with extremely strong charge neutralization and adsorption bridging capabilities, which can efficiently capture oil and fine particles. At the same time, it has excellent salt resistance and heavy metal complexation capabilities, making it particularly suitable for the treatment of ship rust removal wastewater with high salt content and high rust content. The dosage is small and the effect is significant.

[0017] (2) This invention provides a method and apparatus for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration. The dense flocs formed by bio-flocculation are perfectly matched with the ultra-micro dynamic filtration equipment. The flocs have high strength and can withstand high-pressure filtration of 0.4-0.6MPa without breaking or penetrating, ensuring excellent effluent quality (suspended solids concentration SS≤30mg / L, SS removal rate>99%). In addition, the filter cake formed is loose and easy to desorb. The backflushing pressure only needs to be 0.4-0.5MPa to completely desorb the cake, which significantly extends the filtration cycle and improves the solid-liquid separation efficiency. Moreover, the sludge discharge has a low water content (60%-65%), reducing the volume and weight of sludge and significantly reducing the cost of cleaning and disposal.

[0018] (3) The bio-flocculation coupled ultra-micro dynamic filtration ship rust removal wastewater treatment device of the present invention is fully enclosed, occupies a small area, is easy to move, and operates fully automatically without manual supervision. It is perfectly suited for small spaces such as docks, decks, and mobile ship repair platforms. At the same time, the enclosed operation effectively prevents wastewater volatilization and aerosol diffusion, and improves the operating environment.

[0019] (4) The bio-flocculation coupled ultra-micro dynamic filtration method and device for treating ship rust removal wastewater of the present invention has the advantages of low reagent dosage, stable treatment effect, low equipment energy consumption, long filter material life, low sludge production and low disposal cost, and low overall treatment cost compared with traditional methods. It has the dual advantages of being environmentally friendly and economically feasible. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1A schematic diagram of a bio-flocculation coupled ultra-micro dynamic filtration device for treating ship rust removal wastewater is provided in one embodiment of this application; Figure 2 for Figure 1 The diagram shows the structure of the pretreatment unit in the bio-flocculation coupled ultra-micro dynamic filtration ship rust removal wastewater treatment device. Figure 3 for Figure 1 The diagram shows the structure of the bioflocculation unit in the bioflocculation coupled ultra-micro dynamic filtration system for treating ship rust removal wastewater. Figure 4 for Figure 1 The diagram shows the structure of the solid-liquid separation unit in the bio-flocculation coupled ultra-micro dynamic filtration ship rust removal wastewater treatment device. Figure 5 This is a flowchart of a method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration, provided as an embodiment of this application.

[0022] Explanation of symbols in the diagram: 1. Pretreatment unit; 101. First booster pump; 102. Filter; 103. Recycled water tank; 104. Air vent valve; 105. First level gauge; 2. Bioflocculation unit; 201. Second booster pump; 202. Pipeline mixer; 203. Dosing tank; 204. Dosing pump; 205. Second level gauge; 3. Solid-liquid separation unit; 301. Ultrafine dynamic filtration equipment; 30101. Tank; 30102. Feed inlet; 30103. Liquid outlet; 30104. Slag discharge outlet; 30105. Precision filter assembly; 30106. Central shaft; 30107. Rotary scraper; 30108. Drive motor; 30109. Compressed air backflush pipeline; 30110. Differential pressure gauge; 30111. Exhaust port; 302. Clear water tank; 303. Filter residue collection box. Detailed Implementation

[0023] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0024] It should be noted that when a component is referred to as being "fixed" or "set" to another component, it can be directly or indirectly attached to that other component. When a component is referred to as being "connected" to another component, it can be directly or indirectly connected to that other component.

[0025] It should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and should not be construed as indicating or implying that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Unless otherwise specified, the raw materials, apparatus, and equipment used in this invention are all conventional commercially available products; and the methods used are all conventional methods unless otherwise specified.

[0027] (I) Ship Rust Removal Wastewater Treatment Device with Bioflocculation Coupled with Ultra-Micro Dynamic Filtration Please see Figure 1 This is a schematic diagram of a bio-flocculation coupled ultra-micro dynamic filtration device for treating ship rust removal wastewater according to an embodiment of this application. For ease of explanation, only the parts relevant to this embodiment are shown, and the details are as follows: In one embodiment, please refer to Figures 2-4 A bio-flocculation coupled ultra-micro dynamic filtration device for treating ship rust removal wastewater includes a pretreatment unit 1, a bio-flocculation unit 2, and a solid-liquid separation unit 3 connected in sequence by pipelines; the pretreatment unit 1 is equipped with a first lift pump 101, a filter 102, and a recovery water tank 103 connected in sequence. The bioflocculation unit 2 is equipped with a second lift pump 201 and a pipeline mixer 202 connected in sequence. The inlet end of the second lift pump 201 is connected to the outlet end of the recovery water tank 103. A dosing tank 203 is provided outside the pipeline mixer 202. A dosing pump 204 is connected to the dosing tank 203. The outlet end of the dosing pump 204 is connected to the pipeline mixer 202. The solid-liquid separation unit 3 is equipped with an ultra-micro dynamic fine filtration device 301. The ultra-micro dynamic fine filtration device 301 is equipped with a tank 30101. The tank 30101 is equipped with a feed inlet 30102, a liquid outlet 30103 and a slag discharge outlet 30104. The feed inlet 30102 is connected to the outlet end of the pipeline mixer 202, the liquid outlet 30103 is connected to the clear water tank 302, and the slag discharge outlet 30104 is connected to the filter residue collection box 303.

[0028] During use, the ship's rust removal wastewater enters the filter 102 through the first lift pump 101 for filtration to remove large particles of paint residue and debris. After that, it enters the recovery water tank 103 for homogenization and quantity adjustment to ensure the stability of the subsequent treatment load and obtain pre-treated wastewater. The pretreated wastewater enters the pipeline mixer 202 via the second booster pump 201. At the same time, the bio-flocculator in the dosing tank 203 is added to the pipeline mixer 202 via the dosing pump 204. Through the rapid mixing reaction in the pipeline mixer 202, the suspended solids, colloids and oils in the wastewater form dense and high-strength flocs, achieving efficient mixing and efficient flocculation, and obtaining flocculated wastewater. The flocculated wastewater is fed into the ultra-micro dynamic fine filtration equipment 301 through the feed inlet 30102. Under pressure, high-precision solid-liquid separation is carried out to obtain filtered clean water and filter cake. The filtered clean water is discharged into the clean water tank 302 through the liquid outlet 30103. After the filtration cycle is completed, the filter cake layer on the surface of the filter screen is periodically removed by backflushing with compressed air to achieve automatic detachment of the filter cake. The low moisture content filter cake is discharged through the slag discharge port 30104 and then discharged into the filter slag collection box 303.

[0029] For details, please refer to Figure 4 The tank 30101 is equipped with a precision filter assembly 30105, which is composed of a stainless steel filter screen. The precision filter assembly 30105 intercepts suspended solids, flocs and other impurities in the wastewater through the stainless steel filter screen, achieving high-precision solid-liquid separation.

[0030] The tank body 30101 also has a central shaft 30106, on which a rotating scraper 30107 is mounted. A drive motor 30108 is mounted on the tank body 30101, and the output shaft of the drive motor 30108 is connected to the central shaft 30106. During wastewater filtration, the rotating scraper 30107 maintains a gap with the stainless steel filter screen to avoid damage. During backflushing and slag discharge, the drive motor 30108 drives the rotating scraper 30107 to rotate via the central shaft 30106, scraping off the filter cake layer on the surface of the precision filter screen assembly 30105, assisting in the removal of the filter cake.

[0031] The tank 30101 is also equipped with a compressed air backflush line 30109, which is used to periodically remove the filter cake layer on the surface of the precision filter assembly 30105 by backflushing with compressed air at the end of the filtration cycle.

[0032] In one embodiment, please refer to Figure 2 The first lift pump 101 is a pneumatic diaphragm pump used to transport rust removal wastewater from the ship to the filter 102. Other types of pumps can also be used for the first lift pump 101.

[0033] In one embodiment, please refer to Figure 2 Filter 102 is a funnel-type filter used to filter rust removal wastewater from ships, removing large particles of paint residue and debris. Filter 102 can also be made of other types of filters.

[0034] In one embodiment, please refer to Figure 2 The recycled water tank 103 is equipped with an air vent valve 104. The air vent valve 104 is used to release air from the recycled water tank 103, prevent air blockage, and stabilize the pressure.

[0035] In one embodiment, please refer to Figure 2 The recovery water tank 103 is also equipped with a first level gauge 105. The first level gauge 105 is used to monitor the level of the recovery water tank 103 and control the start and stop of the first booster pump 101 and indicate the operating status according to the level.

[0036] In one embodiment, please refer to Figure 3 The second lift pump 201 is a pneumatic diaphragm pump used to transport the pretreated wastewater to the pipeline mixer 202. Other types of pumps can also be used for the second lift pump 201.

[0037] In one embodiment, please refer to Figure 3 A second level gauge 205 is installed on the dosing tank 203. The second level gauge 205 is used to monitor the liquid level in the dosing tank 203.

[0038] In one embodiment, please refer to Figure 4 The tank body 30101 is also equipped with a differential pressure gauge 30110. The differential pressure gauge 30110 is used to monitor the pressure difference before and after filtration by the precision filter assembly 30105 in order to determine the degree of blockage and trigger backflushing to unload the slag.

[0039] In one embodiment, please refer to Figure 4 The top of the tank 30101 is provided with an exhaust port 30111. The exhaust port 30111 is used to discharge the air inside the tank 30101 to prevent air blockage.

[0040] In one embodiment, please refer to Figure 4 The 301 ultra-micro dynamic fine filtration device is a scraper-type self-cleaning filter with a stainless steel filter screen and a pore size of 1-5μm. The 301 ultra-micro dynamic fine filtration device can be purchased commercially or manufactured in-house. If purchasing, it can be customized from specific manufacturers such as Shenyang Wuheng Filtration Equipment Co., Ltd.

[0041] In one embodiment, please refer to Figures 2-4 It also includes an automatic control unit, which is a PLC control cabinet. The automatic control unit is electrically connected to the pretreatment unit 1, the bioflocculation unit 2, and the solid-liquid separation unit 3. During the wastewater treatment process, the automatic control unit automatically adjusts the dosage of bioflocculator according to the actual water quality and quantity, and automatically controls the operation of the ultra-micro dynamic fine filtration equipment 301. When the pressure of the ultra-micro dynamic fine filtration equipment 301 reaches the set limit, the automatic control unit controls the ultra-micro dynamic fine filtration equipment 301 to stop and perform backflushing and sludge discharge.

[0042] (II) Treatment method for ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration Please see Figure 5 The flowchart below shows a method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration, according to an embodiment of this application. For ease of explanation, only the parts relevant to this embodiment are shown, and the details are as follows: In one embodiment, a method for treating ship rust removal wastewater using bioflocculation coupled with ultra-micro dynamic filtration employs the aforementioned bioflocculation coupled with ultra-micro dynamic filtration device for treating ship rust removal wastewater. The treatment method includes the following steps: (1) Pretreatment: The ship rust removal wastewater enters the filter 102 through the first lift pump 101 for filtration to remove large particles of paint residue and debris. After that, it enters the recovery water tank 103 for homogenization and flow regulation to ensure the stability of the subsequent treatment load and obtain the pretreated wastewater.

[0043] (2) Bioflocculation: The pretreated wastewater enters the pipeline mixer 202 via the second booster pump 201. At the same time, the bioflocculant in the dosing tank 203 is added to the pipeline mixer 202 via the dosing pump 204. Through the rapid mixing reaction in the pipeline mixer 202, the suspended solids, colloids, and oils in the wastewater form dense, high-strength flocs, achieving efficient mixing and efficient flocculation, and obtaining flocculated wastewater. The bioflocculant is a quaternary ammonium cationic polysaccharide bioflocculant, with a dosage of 5-10 mg / L. The pH value of the wastewater during bioflocculation is 6.5-8.5.

[0044] (3) Solid-liquid separation: The flocculated wastewater is fed into the ultra-micro dynamic fine filtration equipment 301 through the feed inlet 30102. Under pressure, high-precision solid-liquid separation is performed to obtain filtered clean water and filter cake. The filtered clean water is discharged into the clean water tank 302 through the liquid outlet 30103. After the filtration cycle is completed, compressed air is introduced through the compressed air backflushing pipeline 30109. The compressed air backflushing periodically removes the filter cake layer on the surface of the filter screen assembly 30105, realizing automatic filter cake detachment. The low moisture content filter cake is discharged through the slag discharge port 30104 and then discharged into the filter slag collection box 303. The ultra-micro dynamic fine filtration equipment 301 is a scraper-type self-cleaning filter with a stainless steel filter screen with a pore size of 1-5μm. The pressure during ultra-micro dynamic fine filtration is 0.4-0.6MPa, and the filtration cycle is 4-8h.

[0045] During the wastewater treatment process, the automatic control unit automatically adjusts the dosage of biological flocculant according to the actual water quality and quantity, and automatically controls the operation of the ultra-micro dynamic fine filtration equipment 301. When the pressure of the ultra-micro dynamic fine filtration equipment 301 reaches the set limit, the automatic control unit controls the ultra-micro dynamic fine filtration equipment 301 to stop and perform backflushing and sludge discharge.

[0046] In one embodiment, the preparation method of the quaternary ammonium cationic polysaccharide bioflocculant includes the following steps: (A) Preparation of GTA-modified chitosan: Dissolve chitosan in a 2% acetic acid aqueous solution and stir at room temperature for 2-3 hours until completely transparent and free of particles. Then, slowly add 10% NaOH solution to adjust the pH to 6.5-7.5. Subsequently, heat the solution in a water bath to 70-75℃ and maintain the temperature. Add 2,3-epoxypropyltrimethylammonium chloride (GTA) in 2-3 batches, with GTA added in aqueous solution every 2 hours, while continuously stirring. After all the GTA has been added, keep the solution warm and stir for 6-8 hours to carry out the grafting reaction. The molar ratio of chitosan to GTA is 1:2-1:4.

[0047] After the reaction was completed, the reaction solution was cooled to room temperature, and then slowly poured into 2 times the volume of cold ethanol. The mixture was stirred to precipitate a white flocculent precipitate. The precipitate was filtered and washed three times with 100 mL of anhydrous ethanol each time to remove unreacted GTA and salt. Then it was washed once with acetone for rapid dehydration. Finally, it was vacuum dried at 40-50℃ for 6-8 hours, pulverized, and passed through an 80-mesh sieve to obtain GTA-modified chitosan, which was then sealed and stored in a cool place.

[0048] (B) Preparation of GTA-modified starch: Add corn starch to deionized water and stir at room temperature for 20-40 minutes to form a uniformly suspended starch slurry; the solid-liquid ratio of corn starch to deionized water is 1 g / 7-9 mL; then slowly add NaOH solution and stir continuously for 20-40 minutes to adjust the pH to 10.5-11.5 for alkali activation; then heat the water bath to 55-65℃ and maintain the temperature, adding 2,3-epoxypropyltrimethylammonium chloride (GTA) in 2-3 batches, with GTA added in aqueous solution every 2 hours and stirring continuously; after all GTA has been added, keep the temperature and stir for 3-5 hours to carry out the etherification reaction; the mass ratio of corn starch to GTA is 1:0.5-1:1.

[0049] After the reaction is complete, cool to room temperature and neutralize the pH to 6.0-7.0 with 10% dilute hydrochloric acid; then filter, wash the filter cake 2-3 times with anhydrous ethanol to remove residual salts and unreacted GTA; finally, dry at low temperature and vacuum at 40-50℃ for 6-8 hours, pulverize, pass through an 80-mesh sieve to obtain GTA-modified starch, and store in a sealed container.

[0050] (C) Compound preparation: GTA-modified chitosan and GTA-modified starch were prepared into GTA-modified chitosan mother liquor and GTA-modified starch mother liquor with a mass fraction of 0.5% respectively. Then, the GTA-modified chitosan mother liquor and GTA-modified starch mother liquor were mixed at a mass ratio of 1:4-1:6 and stirred until homogeneous to obtain quaternary ammonium cationic polysaccharide bioflocculant.

[0051] (III) Treatment effect of bio-flocculation coupled with ultra-micro dynamic filtration for ship rust removal wastewater Example 1 (A) Preparation of GTA-modified chitosan: Prepare a 2% acetic acid aqueous solution by dissolving 2g of glacial acetic acid in 490mL of deionized water. Then, dissolve 10g of chitosan (DD≥85%) in the 2% acetic acid aqueous solution and stir at room temperature for 3h until completely transparent and free of particles. Next, slowly add 10% NaOH solution to adjust the pH to 6.5-7.5. Then, heat the solution in a water bath to 75℃ and maintain the temperature. Add 30g of GTA in two batches, in the form of a 70% aqueous solution, every 2h while continuously stirring. After all the GTA has been added, keep the temperature constant for 8h to carry out the grafting reaction.

[0052] After the reaction was completed, the reaction solution was cooled to room temperature, and then slowly poured into 2 times the volume of cold ethanol. Stirring was performed to precipitate a white flocculent precipitate. The precipitate was filtered and washed three times with 100 mL of anhydrous ethanol each time to remove unreacted GTA and salt. Then it was washed once with acetone for rapid dehydration. Finally, it was vacuum dried at 40-50℃ for 8 hours, pulverized, and passed through an 80-mesh sieve to obtain GTA-modified chitosan with a degree of substitution DS≈0.4. It was then sealed and stored in a cool place.

[0053] (B) Preparation of GTA-modified starch: Add 20g of corn starch to 160mL of deionized water and stir at room temperature for 30min to form a uniformly suspended starch milk. Then slowly add 30% NaOH solution and stir continuously for 30min to adjust the pH to 10.5-11.5 for alkali activation. Then heat the water bath to 65℃ and keep it at a constant temperature. Add 15g of GTA in two batches, with the GTA added in the form of 70% aqueous solution, every 2h, while stirring continuously. After all the GTA has been added, keep the temperature and stir for 4h to carry out the etherification reaction.

[0054] After the reaction was completed, the mixture was cooled to room temperature and the pH was neutralized to 6.0-7.0 with 10% dilute hydrochloric acid. Then, it was filtered and the filter cake was washed three times with anhydrous ethanol to remove residual salts and unreacted GTA. Finally, it was dried under low temperature vacuum at 40-50℃ for 8 hours, pulverized, and passed through an 80-mesh sieve to obtain GTA-modified starch with a degree of substitution DS≈0.3. The starch was then sealed and stored.

[0055] (C) Compound preparation: 2.5g of GTA-modified starch was added to 500mL of room temperature deionized water and stirred for 30min until completely dissolved without clumping, yielding a 0.5% GTA-modified starch mother liquor. 2.5g of GTA-modified chitosan was added to 500mL of room temperature deionized water and stirred for 40min until completely dissolved without clumping, yielding a 0.5% GTA-modified chitosan mother liquor. Then, 83mL of the GTA-modified chitosan mother liquor was mixed with 417mL of the GTA-modified starch mother liquor and stirred until homogeneous, yielding a quaternary ammonium cationic polysaccharide bioflocculant, named J-CPB bioflocculant.

[0056] Example 2 The wastewater from the high-pressure water rust removal process on a ship in Shanghai has the following characteristics: SS = 2600 mg / L, oil content = 40 mg / L, and pH = 7.3.

[0057] The above wastewater is treated using the following steps: (1) Pretreatment: The above wastewater enters the filter 102 through the first booster pump 101 for filtration to remove large particles of paint residue and debris. Then it enters the recovery water tank 103 for homogenization and quantity adjustment to ensure the stability of the subsequent treatment load and obtain the pretreated wastewater.

[0058] (2) Bioflocculation: The pretreated wastewater enters the pipeline mixer 202 through the second lift pump 201. At the same time, the J-CPB bioflocculator (in Example 1) in the dosing tank 203 is added to the pipeline mixer 202 through the dosing pump 204 at a dosage of 6 mg / L. Through the rapid mixing reaction of the pipeline mixer 202, the suspended solids, colloids and oils in the wastewater form dense and high-strength flocs, achieving efficient mixing and efficient flocculation, and obtaining flocculated wastewater.

[0059] (3) Solid-liquid separation: The flocculated wastewater is fed into the ultra-micro dynamic fine filtration equipment 301 through the feed port 30102. High-precision solid-liquid separation is carried out under the pressure of 0.4MPa. The filtration cycle is 8h, and filtered water and filter cake are obtained. The filtered water is discharged into the clear water tank 302 through the liquid outlet 30103. After the filtration cycle is completed, compressed air is introduced through the compressed air backflush pipeline 30109. The compressed air backflush periodically removes the filter cake layer on the surface of the filter screen assembly 30105, so that the filter cake can be automatically detached. The low moisture content filter cake is discharged through the slag discharge port 30104 and then discharged into the filter slag collection box 303.

[0060] The filtered water and filter cake were tested, and the results are shown in Table 1.

[0061] Example 3 Wastewater from sandblasting and rust removal on a ship in Guangdong Province has the following characteristics: SS = 3800 mg / L, oil content = 32 mg / L, and pH = 7.4.

[0062] The above wastewater is treated using the following steps: (1) Pretreatment: The above wastewater enters the filter 102 through the first booster pump 101 for filtration to remove large particles of paint residue and debris. Then it enters the recovery water tank 103 for homogenization and quantity adjustment to ensure the stability of the subsequent treatment load and obtain the pretreated wastewater.

[0063] (2) Bioflocculation: The pretreated wastewater enters the pipeline mixer 202 through the second lift pump 201. At the same time, the J-CPB bioflocculator (in Example 1) in the dosing tank 203 is added to the pipeline mixer 202 through the dosing pump 204 at a dosage of 10 mg / L. Through the rapid mixing reaction of the pipeline mixer 202, the suspended solids, colloids and oils in the wastewater form dense and high-strength flocs, achieving efficient mixing and efficient flocculation, and obtaining flocculated wastewater.

[0064] (3) Solid-liquid separation: The flocculated wastewater is fed into the ultra-micro dynamic fine filtration equipment 301 through the feed port 30102. High-precision solid-liquid separation is carried out under the pressure of 0.45MPa. The filtration cycle is 6h, and filtered water and filter cake are obtained. The filtered water is discharged into the clear water tank 302 through the liquid outlet 30103. After the filtration cycle is completed, compressed air is introduced through the compressed air backflush pipeline 30109. The compressed air backflush periodically removes the filter cake layer on the surface of the filter screen assembly 30105, so that the filter cake can be automatically detached. The low moisture content filter cake is discharged through the slag discharge port 30104 and then discharged into the filter slag collection box 303.

[0065] The filtered water and filter cake were tested, and the results are shown in Table 1.

[0066] Comparative Example 1 The difference between this comparative example and Example 3 is that step (2) is omitted, and bioflocculation treatment is not performed. The wastewater is directly sent to the ultra-micro dynamic fine filtration device 301 for high-precision solid-liquid separation. The other steps are the same, and filtered water and filter cake are obtained. The filtered water and filter cake are tested, and the results are shown in Table 1.

[0067] Comparative Example 2 The difference between this comparative example and Example 3 is that step (3) is omitted, and ultra-micro dynamic filtration is not performed. Instead, the wastewater is subjected to bio-flocculation and then separated into solid and liquid components by filtration. The other steps are the same, resulting in filtered water and filter residue. The filtered water and filter residue were tested, and the results are shown in Table 1.

[0068] Please refer to Table 1 for the test results of filtered water and filter cake / residue in Examples 2-3 and Comparative Examples 1-2.

[0069] Table 1. Detection results of filtered water and filter cake / residue in Examples 2-3 and Comparative Examples 1-2

[0070] As can be seen from Table 1: Comparing Examples 2-3 and Comparative Examples 1-2, it can be seen that the SS removal rate and oil removal rate of Examples 2-3 are significantly higher than those of Comparative Examples 1-2, and the filter cake moisture content of Examples 2-3 is significantly lower than that of Comparative Examples 1-2. Furthermore, Examples 2-3 operates continuously without clogging, demonstrating superior performance compared to Comparative Examples 1-2. This indicates that the ship rust removal wastewater treatment method and apparatus of the present invention, through the efficient coupling of bioflocculation and ultra-micro dynamic filtration, exhibits excellent wastewater purification effects.

[0071] The present invention provides a bio-flocculation coupled ultra-micro dynamic filtration method for treating ship rust removal wastewater, wherein the filtered water has SS ≤ 30 mg / L, SS removal rate > 99%, oil ≤ 5 mg / L, oil removal rate > 90%, and filter cake moisture content as low as 60%-65%.

[0072] In summary, this invention provides a method and apparatus for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration, which, compared with the prior art: (1) This invention provides a method for preparing a bio-flocculant - a high-substitution-degree quaternary ammonium cationic polysaccharide bio-flocculant. The quaternary ammonium cationic polysaccharide bio-flocculant is non-toxic and harmless, can be completely biodegraded, and has no risk of secondary pollution. Moreover, the high-substitution-degree cationic characteristics of the quaternary ammonium cationic polysaccharide bio-flocculant endow it with extremely strong charge neutralization and adsorption bridging capabilities, which can efficiently capture oil and fine particles. At the same time, it has excellent salt resistance and heavy metal complexation capabilities, making it particularly suitable for the treatment of ship rust removal wastewater with high salt content and high rust content. The dosage is small and the effect is significant.

[0073] (2) This invention provides a method and apparatus for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration. The dense flocs formed by bio-flocculation are perfectly matched with the ultra-micro dynamic filtration equipment. The flocs have high strength and can withstand high-pressure filtration of 0.4-0.6MPa without breaking or penetrating, ensuring excellent effluent quality (suspended solids concentration SS≤30mg / L, SS removal rate>99%). In addition, the filter cake formed is loose and easy to desorb. The backflushing pressure only needs to be 0.4-0.5MPa to completely desorb the cake, which significantly extends the filtration cycle and improves the solid-liquid separation efficiency. Moreover, the sludge discharge has a low water content (60%-65%), reducing the volume and weight of sludge and significantly reducing the cost of cleaning and disposal.

[0074] (3) The bio-flocculation coupled ultra-micro dynamic filtration ship rust removal wastewater treatment device of the present invention is fully enclosed, occupies a small area, is easy to move, and operates fully automatically without manual supervision. It is perfectly suited for small spaces such as docks, decks, and mobile ship repair platforms. At the same time, the enclosed operation effectively prevents wastewater volatilization and aerosol diffusion, and improves the operating environment.

[0075] (4) The bio-flocculation coupled ultra-micro dynamic filtration method and device for treating ship rust removal wastewater of the present invention has the advantages of low reagent dosage, stable treatment effect, low equipment energy consumption, long filter material life, low sludge production and low disposal cost, and low overall treatment cost compared with traditional methods. It has the dual advantages of being environmentally friendly and economically feasible.

[0076] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration, characterized in that, Includes the following steps: (1) Pretreatment: The rust removal wastewater from the ship is filtered and then homogenized and adjusted to obtain pretreated wastewater; (2) Bioflocculation: Add bioflocculating agent to the pretreated wastewater, and achieve efficient flocculation through rapid mixing reaction to obtain flocculated wastewater; (3) Solid-liquid separation: The flocculated wastewater is sent to an ultra-micro dynamic fine filtration device for high-precision solid-liquid separation under pressure to obtain filtered water and filter cake.

2. The method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration according to claim 1, characterized in that, In step (2), the bioflocculant is a quaternary ammonium cationic polysaccharide bioflocculant, and its dosage is 5-10 mg / L. The pH value of the wastewater during bioflocculation is 6.5-8.

5.

3. The method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration according to claim 2, characterized in that, In step (2), the preparation method of the quaternary ammonium cationic polysaccharide bioflocculant includes the following steps: (A) Preparation of GTA-modified chitosan: Chitosan was dissolved in an aqueous acetic acid solution, the pH was adjusted, and then the temperature was raised. 2,3-epoxypropyltrimethylammonium chloride was added, and the grafting reaction was carried out by stirring while keeping warm. After the reaction was completed, GTA-modified chitosan was obtained by precipitation, separation, washing and drying. (B) Preparation of GTA-modified starch: Corn starch was dispersed in deionized water to obtain starch milk, and the pH was adjusted for alkali activation; then the temperature was raised, and 2,3-epoxypropyltrimethylammonium chloride was added, and the mixture was kept warm and stirred to carry out the etherification reaction; after the reaction was completed, the starch was neutralized, separated, washed and dried to obtain GTA-modified starch; (C) Compounding: GTA-modified chitosan and GTA-modified starch are mixed and stirred until homogeneous to obtain quaternary ammonium cationic polysaccharide bioflocculant.

4. The method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration according to claim 3, characterized in that, In step (A), 10% NaOH solution is added to adjust the pH to 6.5-7.5; the molar ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride is 1:2-1:4, and 2,3-epoxypropyltrimethylammonium chloride is added in 2-3 batches in the form of aqueous solution during the reaction; the grafting reaction temperature is 70-75℃, and the time is 6-8h; In step (B), the solid-liquid ratio of corn starch to deionized water is 1 g / 7-9 mL; NaOH solution is added to adjust the pH to 10.5-11.5 for alkaline activation; the mass ratio of corn starch to 2,3-epoxypropyltrimethylammonium chloride is 1:0.5-1:1, and 2,3-epoxypropyltrimethylammonium chloride is added in 2-3 batches in the form of aqueous solution during the reaction; the etherification reaction temperature is 55-65℃, and the time is 3-5 h. In step (C), GTA-modified chitosan and GTA-modified starch are prepared into GTA-modified chitosan mother liquor and GTA-modified starch mother liquor with a mass fraction of 0.5% respectively, and the two are mixed at a mass ratio of 1:4-1:

6.

5. The method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration according to claim 1, characterized in that, In step (3), the ultra-micro dynamic fine filtration equipment is a scraper-type self-cleaning filter with a stainless steel filter screen and a pore size of 1-5μm. The pressure during ultra-micro dynamic fine filtration is 0.4-0.6MPa, and the filtration cycle is 4-8h.

6. The method for treating ship rust removal wastewater by bio-flocculation coupled with ultra-micro dynamic filtration according to claim 1, characterized in that, In step (3), the SS of the filtered water is ≤30mg / L, the SS removal rate is >99%, the oil is ≤5mg / L, the oil removal rate is >90%, and the filter cake moisture content is as low as 60%-65%.

7. A bio-flocculation coupled ultra-micro dynamic filtration device for treating ship rust removal wastewater, employing the treatment method as described in any one of claims 1-6, characterized in that, It includes a pretreatment unit (1), a bioflocculation unit (2), and a solid-liquid separation unit (3) that are connected in sequence by pipelines. The pretreatment unit (1) is equipped with a first booster pump (101), a filter (102) and a recycling tank (103) connected in sequence. The bioflocculation unit (2) is provided with a second lift pump (201) and a pipeline mixer (202) connected in sequence. The inlet end of the second lift pump (201) is connected to the outlet end of the recovery water tank (103). A dosing tank (203) is provided outside the pipeline mixer (202). A dosing pump (204) is connected to the dosing tank (203). The outlet end of the dosing pump (204) is connected to the pipeline mixer (202). The solid-liquid separation unit (3) is equipped with an ultra-micro dynamic fine filtration device (301). The ultra-micro dynamic fine filtration device (301) is equipped with a tank (30101). The tank (30101) is equipped with an inlet (30102), an outlet (30103) and a slag discharge port (30104). The inlet (30102) is connected to the outlet end of the pipeline mixer (202). The outlet (30103) is connected to the clear water tank (302). The slag discharge port (30104) is connected to the filter residue collection box (303).

8. The bio-flocculation coupled ultra-micro dynamic filtration device for treating ship rust removal wastewater according to claim 7, characterized in that, The recovery water tank (103) is equipped with an air vent valve (104) and a first level gauge (105); the dosing tank (203) is equipped with a second level gauge (205).

9. The bio-flocculation coupled ultra-micro dynamic filtration device for treating ship rust removal wastewater according to claim 7, characterized in that, The tank (30101) is equipped with a precision filter assembly (30105), which is composed of a stainless steel filter screen. The tank body (30101) is also provided with a central shaft (30106), a rotating scraper (30107) is provided on the central shaft (30106), and a drive motor (30108) is provided on the tank body (30101). The output shaft of the drive motor (30108) is connected to the central shaft (30106). The tank (30101) is also provided with a compressed air backflush pipeline (30109), which is used to periodically remove the filter cake layer on the surface of the precision filter assembly (30105) by backflushing with compressed air at the end of the filtration cycle. The tank (30101) is also equipped with a differential pressure gauge (30110), and the top of the tank (30101) is equipped with an exhaust port (30111).

10. The bio-flocculation coupled ultra-micro dynamic filtration device for treating ship rust removal wastewater according to claim 7, characterized in that, It also includes an automatic control unit, which is a PLC control cabinet, and the automatic control unit is electrically connected to the pretreatment unit (1), the bioflocculation unit (2), and the solid-liquid separation unit (3).

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