Metal surface treatment wastewater inorganic salt separation and recycling process and wastewater treatment system

Abstract

The invention discloses a metal surface treatment wastewater inorganic salt separation and recycling process and a wastewater treatment system, by integrating multi-element treatment technologies such as a grating, an adjusting tank, a neutralizing tank, electric flocculation, biological contact oxidation, resin exchange, nanofiltration, reverse osmosis and ozone oxidation, the grating can intercept large-particle impurities, the adjusting tank can balance water quality and water quantity, and the neutralizing tank can intercept large-particle impurities. And then operations such as neutralization, electric flocculation and precipitation are carried out in sequence, so that a good treatment environment is provided for separation of metal ions. Then, heavy metals are removed through a first resin water treater, organic matters are degraded through biological contact oxidation, deep filtration is carried out through an HMF unit, the wastewater is mixed with low-concentration wastewater, separation of salt and water is achieved through nanofiltration and reverse osmosis, wastewater treatment can be achieved, most of sodium and magnesium ions and the like in the wastewater can be extracted, and resource recycling of the wastewater is achieved; all links of the process are closely coordinated, and the problems that the traditional process flow is lengthy, low in efficiency and long and incomplete in separation time are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and more specifically, to a process for separating and recycling inorganic salts from metal surface treatment wastewater, and also to a wastewater treatment system. Background Art

[0002] In the metal surface treatment industry, processes such as electroplating and anodic oxidation generate a large amount of wastewater. These wastewaters usually contain various metal ions, among which the contents of sodium and magnesium ions are relatively high. If not effectively treated and directly discharged, these wastewaters will not only cause serious environmental pollution but also waste valuable resources therein.

[0003] Currently, there are many problems in the traditional wastewater treatment methods for separating sodium and magnesium ions, such as low separation efficiency of sodium and magnesium ions, resulting in waste of related raw materials such as sodium and magnesium ions, causing high costs and great discharge pressure.

[0004] Therefore, a new solution is needed to solve this problem. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a process for separating and recycling inorganic salts from metal surface treatment wastewater and a wastewater treatment system.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A process for separating and recycling inorganic salts from metal surface treatment wastewater includes the following steps:

[0008] Step 1, perform grid filtration on the high-concentration wastewater to remove solid waste residues in the wastewater;

[0009] Step 2, the high-concentration wastewater after grid filtration flows into an adjustment tank to adjust and balance the water volume and water quality of the wastewater;

[0010] Step 3, the high-concentration wastewater flowing out of the adjustment tank enters a neutralization tank to adjust the pH value of the wastewater;

[0011] Step 4, the high-concentration wastewater flowing out of the neutralization tank enters an electrocoagulation unit to form flocs in the wastewater;

[0012] Step 5, the high-concentration wastewater flowing out of the electrocoagulation unit enters a sedimentation tank for solid-liquid separation;

[0013] Step 6, the supernatant of the sedimentation tank enters a first resin water treatment device. The first resin water treatment device is filled with a first exchange resin, and heavy metal ions are removed through the first exchange resin; after the first exchange resin in the first resin water treatment device is treated, it is eluted with HCl, and the eluted waste liquid is subjected to heavy metal recovery treatment;

[0014] Step 7: The high-concentration wastewater treated by the first resin water treatment unit enters the biological contact oxidation tank. In the biological contact oxidation tank, biological fillers are filled, and the organic matter in the wastewater is degraded under the action of microorganisms.

[0015] Step 8: The high-concentration wastewater flowing out of the biological contact oxidation tank enters the HMF unit. The high-intensity submerged membrane filtration unit uses PVDF hollow fiber membranes for filtration.

[0016] Step 9: The low-concentration metal wastewater directly enters the HMF unit and converges with the high-concentration wastewater for mixing; the mixed wastewater is subjected to membrane filtration treatment in the HMF unit.

[0017] Step 10: The mixed wastewater treated by the HMF unit enters the NF unit, and the mixed wastewater is separated by nanofiltration membranes.

[0018] Step 11: The produced water obtained after the treatment by the NF unit enters the NF unit product water tank, and the wastewater in the NF unit product water tank enters the first RO unit for reverse osmosis separation treatment.

[0019] Step 12: The produced water obtained after the treatment by the first RO unit enters the first RO unit product water tank, and the water in the first RO unit product water tank can be recycled.

[0020] Step 13: The concentrated water obtained after the treatment by the first RO unit, when the sodium chloride concentration in the concentrated water is lower than the preset value, the concentrated water will repeat Step 12; when the sodium chloride concentration in the concentrated water is not lower than the preset value, the concentrated water enters the first RO unit concentrated water tank and can be recycled as sodium chloride solution.

[0021] Step 14: The concentrated water obtained after the treatment by the NF unit enters the NF unit concentrated water tank.

[0022] Step 15: The wastewater flowing out of the NF unit concentrated water tank enters the ozone oxidation tank. Ozone is used to oxidize and decompose the residual organic matter and reducing substances in the wastewater.

[0023] Step 16: The wastewater treated by the ozone oxidation tank enters the second resin water treatment unit. The second resin water treatment unit is filled with the second exchange resin, and ion exchange treatment is carried out through the second exchange resin.

[0024] Step 17: The produced water obtained after the treatment by the second resin water treatment unit enters the NF unit product water tank and converges with the produced water obtained in Step 11.

[0025] Step 18: The second exchange resin in the second resin water treatment unit is eluted with HCl, and the eluate contains the adsorbed ions; the produced water after elution enters the second RO unit, and the produced water obtained after the treatment by the second RO unit enters the second RO unit product water tank, and the water in the second RO unit product water tank can be recycled.

[0026] Step XIX: The concentrated water is obtained after being treated by RO unit II. When the magnesium chloride concentration in the concentrated water is lower than the preset value, the concentrated water will be recycled to Step XVIII; when the magnesium chloride concentration in the concentrated water is not lower than the preset value, the concentrated water will enter the concentrated water tank of RO unit II and can be reused as magnesium chloride solution.

[0027] The present invention is further configured that in Step II, the regulating tank is connected to the grille through a pipeline, and the wastewater flows out from the grille into the regulating tank by gravity or a pumping system; a stirring device is provided inside the regulating tank to stir evenly.

[0028] The present invention is further configured that in Step III, a pH monitoring and acid-base addition system is provided in the neutralization tank, which can detect the pH value in the neutralization tank and add acid-base regulators to the neutralization tank according to the pH value.

[0029] The present invention is further configured that in Step VI, the resin water treatment unit I is connected to the sedimentation tank through a pipeline, and a flow control device is installed on the pipeline, which can detect the flow rate from the sedimentation tank into the resin water treatment unit I.

[0030] The present invention is further configured that in Step VI, the exchange resin in the resin water treatment unit I is a heavy metal ion adsorption resin, and a heavy metal-containing solution is obtained by elution for reusing heavy metal inorganic salts.

[0031] The present invention is further configured that in Step VII, the resin water treatment unit I is connected to the biological contact oxidation tank through a pipeline, and an aeration system is provided in the biological contact oxidation tank, which can aerate the biological contact oxidation tank.

[0032] The present invention is further configured that in Step IX, the low-concentration metal wastewater directly enters the HMF unit through a pipeline and converges and mixes with the high-concentration wastewater in the HMF unit.

[0033] The present invention is further configured that the exchange resin in the resin water treatment unit II is a magnesium ion adsorption resin, and a magnesium chloride-containing solution is obtained by elution for subsequent reuse of magnesium chloride salt.

[0034] The present invention is further configured that in Step XIII and Step XIX, concentration detection sensors are installed at the concentrated water outlet ends of RO unit I and RO unit II, which can detect the concentration in the concentrated water; and two branches are formed at the concentrated water outlet end, and the on-off conditions of the two branches are controlled by valves.

[0035] The present invention also provides a wastewater treatment system, including an electrocoagulation unit, and the electrocoagulation unit includes a cathode tube, an anode core rod and a buffer bin. The cathode tube is erected in the vertical direction and is divided into several pipe segments distributed from top to bottom. Adjacent pipe segments are respectively connected through the buffer bin. A pipe cavity is provided in the pipe segment, and a buffer inner cavity is provided in the buffer bin. The pipe cavity and the buffer inner cavity are interconnected to form an upper and lower connected wastewater channel;

[0036] The anode mandrel is coaxially inserted into the lumen of the tube and passes through the buffer lumen;

[0037] The upper end of the anode mandrel is installed on the upper lifting part to achieve lifting limit, and the lower end of the anode mandrel is in a hanging state;

[0038] A support assembly is installed in the buffer lumen, and the support assembly is used for horizontally limiting the anode mandrel.

[0039] The present invention is further configured such that the support assembly includes a support cylinder, a first support block, and a second support block. The support cylinder is fixedly installed on the lower side wall of the inner cavity of the buffer lumen; the support cylinder is provided with a gap part penetrating through the inner and outer circumferences;

[0040] The present invention is further configured such that both the first support block and the second support block are in an annular structure. The first support block is installed on the inner circumference of the support cylinder, and the second support block is installed on the outer circumference of the anode mandrel. At least a part of the second support block extends into the inner circumference of the first support block and realizes circumferential pressing limit.

[0041] The present invention is further configured such that the inner circumferential surface of the first support block and the outer circumferential surface of the second support block are in a mutually adapted inverted conical structure, and the inner circumferential surface of the first support block and the outer circumferential surface of the second support block are partially sleeved with each other and press against each other;

[0042] The present invention is further configured such that the outer circumference of the first support block is slidably adapted to the upper and lower parts of the support cylinder, and a support spring is installed on the lower side of the first support block. The support spring is used to apply an upward force to the first support block;

[0043] The present invention is further configured such that a limiting retaining ring is fixedly connected to the upper section of the inner circumference of the support cylinder, and the limiting retaining ring is used to block and limit the first support block.

[0044] The present invention is further configured such that the lower end of the anode mandrel passes through the lower sleeve part, which is used for horizontally limiting the anode mandrel and can realize relative up and down movement; the upper lifting part can be adjusted up and down.

[0045] The present invention is further configured such that connection ports are provided on both the upper and lower sides of the buffer bin, and the connection ports on the upper and lower sides are opposite to each other up and down; a cylindrical filter residue net is provided at the upper end of the support cylinder. The filter residue net is in an annular cylindrical structure. The lower end of the filter residue net is connected to the upper end of the support cylinder, and the upper end of the filter residue net is connected to the outer circumference of the upper connection port.

[0046] The present invention is further configured such that the inner diameter of the buffer lumen is larger than the inner diameter of the tube lumen. The buffer lumen is used for buffering the flocculation residue in the wastewater; two slag discharge pipes are connected to the outer circumference of the buffer bin, and the two slag discharge pipes are respectively used for the inflow and outflow of the wastewater with flocculation residue.

[0047] The present invention is further configured such that two slag discharge ports are respectively provided on the left and right sides of the buffer bin, the two slag discharge ports are respectively connected to two slag discharge pipes, and the lower sides of the slag discharge ports are flush with the lower side of the buffer cavity; the gap part on the outer periphery of the support cylinder corresponds to the height of the slag discharge port.

[0048] The present invention is further configured such that the electrocoagulation unit further includes a circulation pump, a filter, a circulation main path, and a circulation pipeline; the circulation pump and the filter are both installed on the circulation pipeline, the filter is located on the water inlet side of the circulation pump, and the two slag discharge pipes on the outer periphery of the buffer bin are respectively connected to both ends of the circulation pipeline.

[0049] In summary, the present invention has the following beneficial effects:

[0050] By integrating multiple treatment technologies such as a grille, an adjustment tank, a neutralization tank, electrocoagulation, biological contact oxidation, resin exchange, nanofiltration, reverse osmosis, and ozone oxidation, the grille can intercept large particulate impurities, the adjustment tank can balance the water quality and quantity, and then neutralization, electrocoagulation, precipitation, etc. are carried out in sequence to provide a good treatment environment for the separation of metal ions. Then, heavy metals are removed by a resin water treatment device I, organic matter is degraded by biological contact oxidation, the HMF unit performs deep filtration, and after mixing with low-concentration wastewater, salt and water are separated by nanofiltration and reverse osmosis, which can achieve wastewater treatment, can extract most of the sodium and magnesium ions in the wastewater, realize the resource reuse of the wastewater, and moreover, all links of the process cooperate closely to solve the problems of long traditional process flow, low efficiency, long separation time and incomplete separation.

[0051] By detecting the concentration at the concentrated water outlets of the RO unit I and the RO unit II, the flow direction of the concentrated water can be switched according to the height of the concentration, the low-concentration wastewater can be recycled, the aggregation of sodium and magnesium ions can be realized to form a high-concentration solution, and then the reuse of the high-concentration sodium and magnesium ion solution can be realized, which can reduce resource waste and lower the raw material procurement cost; moreover, by recycling the solution, emissions can also be reduced, and the risk of secondary pollution can be reduced, which is lower in cost and less polluting compared with the traditional treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a three-dimensional view of a wastewater treatment system in Embodiment 2;

[0053] Figure 2 It is a cross-sectional view of a wastewater treatment system in Embodiment 2;

[0054] Figure 3 It is an enlarged cross-sectional view of a wastewater treatment system in Embodiment 2;

[0055] Figure 4Schematic diagram of the force structure of the anode mandrel in Embodiment 2;

[0056] Figure 5 Schematic diagram of the structure of the support assembly and the anode mandrel in Embodiment 2;

[0057] Figure 6 is Figure 4 partial enlarged view in;

[0058] Figure 7 Schematic diagram of the structure of the circulation pipeline in Embodiment 2;

[0059] Figure 8 Flow chart in Embodiment 1.

[0060] Reference numerals: Cathode tube 1; Tube section 100; Tube cavity 101; Anode mandrel 2; Upper end 201; Upper lifting part 2011; Lower end 202; Lower sleeve part 2021; Buffer bin 3; Buffer inner cavity 301; Connection port 302; Slag discharge port 303; Slag discharge pipe 4; Support assembly 5; Support cylinder 51; Gap part 511; Limit retaining ring 512; First support block 52; Inner peripheral surface 521; Second support block 53; Outer peripheral surface 531; Support spring 54; Filter residue net 6; Circulation pump 7; Circulation pipeline 71; Filter 8. Detailed implementation manners

[0061] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0062] Embodiment 1

[0063] This embodiment discloses a process for separating and recycling inorganic salts from metal surface treatment wastewater. Referring to Figure 8 as shown, it can treat metal surface treatment wastewater. The wastewater is divided into high-concentration wastewater and low-concentration wastewater. The height of the concentration can be distinguished according to specific treatment requirements, and a preset value for the distinction can be preset. Through this treatment process, heavy metal pollution in the wastewater can be separated and treated separately; high-concentration sodium chloride and magnesium chloride are easily separated and recycled as corresponding solutions; in addition, pure water with a relatively high purity can also be separated and recycled as process water. It can separate different metal ion pollutions in the wastewater and achieve the circular recycling of resources.

[0064] The process for separating and recycling inorganic salts from metal surface treatment wastewater includes the following steps:

[0065] Step 1: Conduct grid filtration on the high-concentration wastewater to remove solid waste residues in the wastewater. The high-concentration metal surface treatment wastewater first enters the grid. The grid plays a role in physical filtration. Its fence or screen structure can intercept larger suspended solids and impurities in the wastewater, such as metal debris and large solid waste residues, which can avoid causing blockages and equipment wear and ensure the normal operation of the entire treatment system.

[0066] Step 2: The high-concentration metal surface treatment wastewater after grid filtration flows into the regulation tank. In the regulation tank, the water volume and water quality of the wastewater can be adjusted and balanced to reach a relatively stable state within a certain period of time. During the metal surface treatment process, the generated wastewater may fluctuate in terms of flow rate and water quality composition. The regulation tank can play a buffering role, preventing subsequent treatment units from being impacted by large fluctuations in water quality and water volume, and ensuring the stability and continuity of the subsequent treatment process.

[0067] In Step 2, the regulation tank is connected to the grid by a pipeline, and the wastewater flows out of the grid into the regulation tank by gravity or a pumping system; a stirring device is installed inside the regulation tank to stir evenly.

[0068] Step 3: The wastewater flowing out of the regulation tank enters the neutralization tank to adjust the pH value of the wastewater. Since the pH values of the wastewater generated during different metal surface treatment processes may be different, and subsequent treatment steps such as electrocoagulation have certain requirements for the pH value of the wastewater, it is necessary to adjust the pH value of the wastewater to an appropriate range. In the neutralization tank, a pH monitoring and acid-base addition system is set up. By adding acid-base regulators and according to the data fed back by the on-line pH monitoring device, the acid-base addition amount is accurately controlled to reach the required pH value range, creating good chemical conditions for subsequent treatment.

[0069] Step 4: The neutralized high-concentration metal surface treatment wastewater enters the electrocoagulation unit. This unit utilizes an electrochemical reaction to generate metal hydroxide colloids with flocculation ability through electrodes (usually iron or aluminum electrodes). When a direct current electric field is applied, redox reactions occur at the electrodes, and the generated metal ions hydrolyze to form colloids. These colloids can adsorb colloids, suspended particles, some heavy metal ions, and some organic substances in the wastewater, causing them to coagulate into larger flocs, preparing for subsequent precipitation separation.

[0070] Step 5: The wastewater after electrocoagulation enters the sedimentation tank, where solid-liquid separation is achieved. In the sedimentation tank, using the principle of gravity sedimentation, the larger flocs formed by flocculation settle to the bottom of the tank. The sedimented sludge contains a large amount of impurities and can be collected by equipment such as a sludge scraper for subsequent sludge treatment or resource recovery and utilization, while the supernatant after precipitation can enter the next treatment stage.

[0071] Step 6: The supernatant of the sedimentation tank enters the first resin water treatment unit. The first resin water treatment unit is filled with the first exchange resin, and heavy metal ions are removed through the first exchange resin. The first exchange resin is selected to remove heavy metal ions while retaining sodium and magnesium ions. While achieving efficient removal of heavy metal pollution in the wastewater and avoiding affecting subsequent biological treatment, it can also be further prepared for heavy metal recovery. After being treated, the first exchange resin in the first resin water treatment unit is eluted with HCl, and the eluted waste liquid is subjected to heavy metal recovery treatment.

[0072] In Step 6, the first resin water treatment unit is connected to the sedimentation tank through a pipeline, and a flow control device is installed on the pipeline, which can detect the flow rate of the wastewater entering the first resin water treatment unit from the sedimentation tank to ensure that the wastewater enters the first resin water treatment unit at an appropriate flow rate. The first ion exchange resin inside the first resin water treatment unit has a certain adsorption capacity. When the adsorption reaches saturation, its exchange capacity can be restored through backwashing and regeneration operations. Generally, regeneration is carried out with acid-base solutions, and hydrochloric acid is used for elution. The eluate can be used for the recovery and utilization of heavy metals in it.

[0073] Step 7: The high-concentration wastewater treated by the first resin water treatment unit enters the biological contact oxidation tank. In the biological contact oxidation tank, biological fillers are filled, and the organic matter in the wastewater is degraded under the action of microorganisms. The microorganisms attach to the fillers to form a biological film. Through the metabolic activities of the microorganisms, the organic matter is decomposed into carbon dioxide, water, and harmless substances, reducing the content of organic pollutants in the wastewater.

[0074] In Step 7, the first resin water treatment unit is connected to the biological contact oxidation tank through a pipeline. An aeration system is set inside the biological contact oxidation tank, which can aerate the biological contact oxidation tank to provide sufficient oxygen for the microorganisms, enabling the microorganisms to carry out aerobic metabolism. The microorganisms degrade the organic matter under certain hydraulic retention time and suitable conditions such as temperature and pH.

[0075] Step 8: The high-concentration wastewater flowing out of the biological contact oxidation tank enters the HMF unit. The HMF unit is a high-intensity submerged membrane filtration unit that uses PVDF hollow fiber membrane filtration. The PVDF hollow fiber membrane filtration technology can further remove fine particles, colloids, some organic matter, and some ions in the wastewater, improving the treatment effect of the wastewater.

[0076] Step 9: The low-concentration metal wastewater directly enters the HMF unit and converges with the high-concentration wastewater; the mixed wastewater is subjected to membrane filtration treatment in the HMF unit to achieve the overall treatment and resource recovery goals.

[0077] In Step 9, the low-concentration wastewater directly enters the HMF unit through a separate pipeline and is mixed with the high-concentration wastewater in the HMF unit. The mixing process can be achieved through simple pipeline mixing or by installing a mixing device in the inlet section of the HMF unit to ensure uniform mixing of the wastewater, and then they jointly undergo the filtration treatment in the HMF unit.

[0078] Step 10: The mixed wastewater treated by the HMF unit enters the NF unit, and the mixed wastewater is separated by a nanofiltration membrane. The NF unit is the nanofiltration unit. The nanofiltration process is a membrane separation process between ultrafiltration and reverse osmosis. It can selectively retain divalent and multivalent ions and larger organic substances, allowing monovalent ions and small-molecule substances to pass through, thereby further separating and purifying the wastewater, improving the quality of the produced water, and also achieving the separation of monovalent and divalent inorganic salts, further separating and purifying the inorganic salts in the wastewater to prepare for subsequent recycling.

[0079] Step 11: The produced water obtained after the treatment by the NF unit enters the NF unit product water tank, and the wastewater in the NF unit product water tank enters RO Unit 1 for reverse osmosis separation treatment. RO Unit 1 operates using a reverse osmosis membrane under a relatively high pressure, allowing only water molecules to pass through the reverse osmosis membrane while salts and other impurities are retained, further improving the purity of the produced water, which can be used for reuse.

[0080] Step 12: The produced water obtained after the treatment by RO Unit 1 enters the RO Unit 1 product water tank, and the water in the RO Unit 1 product water tank can be reused; this part of the water meets relatively high water quality standards and can be directly reused in different links of the metal surface treatment process, such as as rinsing water, cooling circulating water, etc., to achieve the recycling of water resources, reduce the demand for fresh water, and lower production costs.

[0081] Step 13: The concentrated water obtained after the treatment by RO Unit 1, when the sodium chloride concentration in the concentrated water is lower than the preset value, the concentrated water will repeat Step 12; when the sodium chloride concentration in the concentrated water is not lower than the preset value, the concentrated water enters the RO Unit 1 concentrated water tank and can be reused as a sodium chloride solution.

[0082] In Step 13, concentration detection sensors are installed at the concentrated water outlet end of RO Unit 1 to detect the concentration in the concentrated water; and two branches are formed at the concentrated water outlet end, and the on-off conditions of the two branches are controlled by valves to further realize the flow direction of the concentrated water.

[0083] Step 14: The concentrated water obtained after the treatment by the NF unit enters the NF unit concentrated water tank. The nanofiltration concentrated water contains a relatively high concentration of divalent ions and some organic substances, and further treatment is required to recover the resources therein or achieve up-to-standard discharge.

[0084] Step 15: The wastewater flowing out of the concentrated water tank of the NF unit enters the ozone oxidation tank. The ozone oxidation tank utilizes the strong oxidizing property of ozone to oxidize and decompose the residual organic matter and reducing substances in the wastewater, improving the wastewater quality and creating better conditions for subsequent treatment.

[0085] Step 16: The wastewater treated by the ozone oxidation tank enters the second resin water treatment device. The second resin water treatment device is filled with the second exchange resin, and ion exchange treatment is carried out through the second exchange resin. The magnesium ions are relatively abundant in the wastewater, and the resin exchanges the magnesium ions through ion exchange, and at the same time further improves the water quality.

[0086] Step 17: The product water obtained after being treated by the second resin water treatment device enters the NF unit product water tank, converges and mixes with the product water obtained in Step 11, and then they are subjected to subsequent reuse or further treatment together to improve the comprehensive utilization efficiency of water.

[0087] Step 18: The second exchange resin in the second resin water treatment device is eluted with HCl, and the eluate contains the adsorbed ions; the product water after elution enters the second RO unit, and the product water obtained after being treated by the second RO unit enters the second RO unit product water tank. The water in the second RO unit product water tank can be reused and can be used in occasions with higher water quality requirements, such as the final cleaning water in the metal surface treatment process or the water for preparing chemical agents, etc.

[0088] Step 19: The concentrated water obtained after being treated by the second RO unit, when the magnesium chloride concentration in the concentrated water is lower than the preset value, the concentrated water will be re - processed in Step 18; when the magnesium chloride concentration in the concentrated water is not lower than the preset value, the concentrated water enters the second RO unit concentrated water tank and can be reused as a magnesium chloride solution, realizing the reuse of resources.

[0089] In Step 19, concentration detection sensors are installed at the concentrated water outlet ends of the second RO unit, which can detect the concentration in the concentrated water; and two branches are formed at the concentrated water outlet ends, and the on - off conditions of the two branches are controlled by valves. According to the concentration detection results, the flow direction of the concentrated water is controlled by switching the valves.

[0090] By integrating multiple treatment technologies such as grids, regulating ponds, neutralization ponds, electrocoagulation, biological contact oxidation, resin exchange, nanofiltration, reverse osmosis, and ozone oxidation, the grid can intercept large particulate impurities, the regulating pond can balance the water quality and quantity, and then neutralization, electrocoagulation, precipitation and other operations are carried out in sequence to provide a good treatment environment for the separation of metal ions. Then, heavy metals are removed by a resin water treatment unit 1, organic matter is degraded by biological contact oxidation, the HMF unit conducts deep filtration, and after mixing with low-concentration wastewater, salt and water are separated through nanofiltration and reverse osmosis, enabling wastewater treatment, extracting most of the sodium, magnesium ions, etc. in the wastewater, realizing the resource reuse of wastewater. Moreover, all links of the process are closely coordinated to solve the problems of long traditional process flow, long separation time and incomplete separation.

[0091] By detecting the concentration at the concentrated water outlets of RO unit 1 and RO unit 2, the flow direction of the concentrated water can be switched according to the height of the concentration, the low-concentration wastewater can be recycled, the aggregation of sodium, magnesium ions, etc. can be achieved to form a high-concentration solution, and then the reuse of the high-concentration sodium and magnesium ion solutions can be realized, reducing resource waste and the procurement cost of raw materials; moreover, through the reuse of the solution, emissions can also be reduced, and the risk of secondary pollution can be reduced, with lower cost and less pollution compared to traditional treatment processes.

[0092] Embodiment 2

[0093] This embodiment discloses a wastewater treatment system that can treat wastewater by the process in the above embodiment, and for details, refer to Figures 1-7 for a detailed description.

[0094] Refer to Figure 1 、 Figure 2 As shown in

[0095] , the wastewater treatment system in this embodiment includes an electrocoagulation unit, and the electrocoagulation unit includes a cathode tube 1, an anode core rod 2, and a buffer bin 3. The cathode tube 1 is erected in the up-down direction and is divided into several pipe sections 100 distributed from top to bottom. Adjacent pipe sections 100 are respectively connected through the buffer bin 3. A pipe cavity 101 is arranged in the pipe section 100, and a buffer inner cavity 301 is arranged in the buffer bin 3.

[0096] The anode core rod 2 is coaxially inserted into the pipe cavity 101 and passes through the buffer inner cavity 301. The anode core rod 2 is inserted into the pipe cavity 101, forming an annular flow channel between the cathode tube 1 and the anode core rod 2 for conveying the wastewater to be treated. During the treatment process, the wastewater flows in the upward direction from bottom to top. The anode core rod 2 serves as the anode material for electrocoagulation, while the cathode tube 1 serves as the cathode material for electrocoagulation. During the electrocoagulation process, the anode core rod 2 undergoes wear. By adopting a tubular electrocoagulation structure, the cathode material can be used as the outer tube body for wastewater conveyance, and the core body of the anode can be inserted in the middle, which can improve the reaction efficiency between the wastewater and the cathode and anode materials and enhance the electrocoagulation efficiency.

[0097] The cross-sections of both the anode core rod 2 and the cathode tube 1 are circular structures and are coaxially installed, which can keep the distance between the outer periphery of the anode core rod 2 and the inner periphery of the cathode tube 1 basically the same. Furthermore, it can ensure that during the wear process of the anode core rod 2, the wear rates at various positions on the outer periphery are basically the same, and can maintain the anode core rod 2 in a roughly cylindrical structure, ensuring a relatively uniform and stable state during the reaction process.

[0098] Refer to Figure 3 、 Figure 4 As shown, the upper end 201 of the anode core rod 2 is installed on the upper lifting part 2011. The upper lifting part 2011 serves as a fixed point for support and can achieve lifting limit. The lower end 202 of the anode core rod 2 is in a hanging state. The anode core rod 2 forms an installation structure with upper-end lifting. Under the action of gravity, it can avoid the situation of the anode core rod 2 being bent, and can further avoid the bad situation of the direct contact between the anode core rod 2 and the cathode tube 1 caused by bending.

[0099] To maintain the installation stability of the anode core rod 2, a support assembly 5 can be installed in the buffer inner cavity 301. The support assembly 5 is used to limit the anode core rod 2 in the horizontal direction, thereby avoiding the situation of lateral bending displacement in the middle section of the anode core rod 2.

[0100] Refer to Figure 5 、 Figure 6 As shown, the support assembly 5 includes a support cylinder 51, a first support block 52, and a second support block 53. The support cylinder 51 is a tubular structure that penetrates up and down. The lower side is fixedly installed on the lower side wall of the inner cavity of the buffer inner cavity 301, and the support cylinder 51 is sleeved on the outer periphery of the anode core rod 2.

[0101] Specifically, the installation position of the support cylinder 51 is opposite to the position of the connection port 302 on the lower side of the buffer bin 3 and is installed on the upper side of the connection port 302. That is, the wastewater flowing upward from the connection port 302 will directly enter the support cylinder 51. A gap part 511 that penetrates the inner and outer peripheries is provided on the side wall of the support cylinder 51, and the wastewater can flow through the gap part 511.

[0102] Both the first support block 52 and the second support block 53 are in an annular structure. The first support block 52 is installed on the inner circumference of the support cylinder 51, and the second support block 53 is installed on the outer circumference of the anode mandrel 2. The second support block 53 is fixedly connected to the anode mandrel 2. At least a part of the second support block 53 extends into the inner circumference of the first support block 52 and realizes circumferential pressing and limiting.

[0103] The first support block 52 can be limited by the support cylinder 51. By the inner and outer surfaces of the first support block 52 and the second support block 53 pressing against each other, axial limiting can be achieved, ensuring the position stability of the anode mandrel 2 and avoiding lateral offset and bending.

[0104] Furthermore, the inner circumferential surface 521 of the first support block 52 and the outer circumferential surface 531 of the second support block 53 are in a mutually adapted inverted conical structure. The inner circumferential surface 521 of the first support block 52 and the outer circumferential surface 531 of the second support block 53 are partially sleeved with each other and press against each other. Through the mutual pressing of the two conical surfaces, automatic centering and positioning can be formed. Since the axes of the two conical surfaces are both coaxial with the axis of the cathode tube 1, it can be ensured that the anode mandrel 2 and the cathode tube 1 are coaxial after centering, maintaining the position stability of the anode mandrel 2.

[0105] Furthermore, the outer circumference of the first support block 52 is slidably and adaptively connected to the upper and lower parts of the support cylinder 51, that is, the first support block 52 can slide up and down in the support cylinder 51, and the sliding direction is the same as the axis direction of the cathode tube 1. A limiting retaining ring 512 is fixedly connected to the upper section of the inner circumference of the support cylinder 51. The limiting retaining ring 512 is used to block and limit the first support block 52, and can prevent the first support block 52 from slipping upward excessively and detaching.

[0106] A support spring 54 is installed on the lower side of the first support block 52. The lower end of the support spring 54 presses against the lower side wall of the buffer inner cavity 301, and the upper end presses against the lower side of the support block. The support spring 54 is used to apply an upward force to the first support block 52 to form an upward elastic support.

[0107] Refer to Figure 4 As shown, in the installed state of the anode mandrel 2, the upper end 201 of the anode mandrel 2 is hoisted by the upper hoisting part 2011 to form an upward acting force to counteract most of the gravity of the anode mandrel 2. A plurality of second support blocks 53 are fixed in the middle section of the anode mandrel 2, and cooperate with other components of the support assembly 5 to provide an upward supporting acting force, thereby counteracting part of the gravity of the anode mandrel 2; specifically, the second support block 53 is mainly affected by the upward elastic force of the support spring 54. The support spring 54 is in a semi-compressed state, that is, the support spring 54 is compressed and not completely compressed. The upward supporting action of the support spring 54 is mainly to maintain the conical surfaces of the first support block 52 and the second support block 53 pressing against each other, so as to maintain the up and down pressing and be in an automatic centering state, and undertake part of the upward supporting action on the anode mandrel 2.

[0108] Through the support component 5, an upward auxiliary support effect can be exerted on the middle section of the anode mandrel 2, which can share the self-weight stress of the anode mandrel 2 and avoid the situation that the hoisting stress of the anode mandrel 2 is too large and causes bending. Moreover, since the first support block 52 can flexibly move up and down, the distance between two adjacent support points of the anode mandrel 2 can also be adjusted, thereby avoiding the situation that a certain section of the anode mandrel 2 is stressed in two opposite directions and causes the anode mandrel 2 to be stressed and bent.

[0109] Refer to Figure 4 As shown, a lower sleeve part 2021 is provided at the lower end 202 of the anode mandrel 2. The lower sleeve part 2021 is not directly connected and fixed to the lower end 202 of the anode mandrel 2. The lower sleeve part 2021 is connected to other parts of the equipment to keep the position fixed, and a hole penetrating up and down is opened in the lower sleeve part 2021, which is adapted to the outer diameter of the anode mandrel 2. The anode mandrel 2 axially penetrates through the hole of the lower sleeve part 2021, and can limit the anode mandrel 2 in the horizontal direction.

[0110] The upper hoisting part 2011 can be adjusted up and down, and an adaptive relative up and down movement can also occur between the lower end 202 of the anode mandrel 2 and the lower sleeve part 2021. Through adjustment, the up and down height of the anode mandrel 2 can be adjusted, and then the height position of the second support block 53 outside the anode mandrel 2 can be synchronously adjusted. After the second support block 53 adjusts the height position, the compression degree of the support spring 54 between the first support block 52 and the second support block 53 will be changed, and then the support condition of the support spring 54 on the anode mandrel 2 can be adjusted.

[0111] Through detection, when the hoisting force received by the upper hoisting part 2011 is too small, the upper hoisting part 2011 can be appropriately adjusted downward, so that the anode mandrel 2 and each second support block 53 can be adjusted downward, so that the support spring 54 can be compressed by a larger amount, and a greater support force can be provided. As a result, the stress on each section of the anode mandrel 2 is more uniform, and the situation of uneven stress and bending will not occur, avoiding uneven electrocoagulation caused by bending.

[0112] During use, as the equipment is used, the outer periphery of the anode mandrel 2 will be gradually worn, the diameter of the anode mandrel 2 will become thinner, and its weight will also gradually decrease. At this time, the support force formed by the combination of each support spring 54 may be greater than the gravity of the anode mandrel 2, which may cause the anode mandrel 2 to be stressed in the up and down directions, resulting in the possibility of bending of the anode mandrel 2. Therefore, the position of the upper hoisting part 2011 can be adjusted to change the compression condition of the support spring 54, so that the support force of the support spring 54 can be adjusted appropriately, and the hoisting stress state of the anode mandrel 2 can be maintained, and then the vertical installation state can be maintained.

[0113] Furthermore, referring to Figure 7 as shown in the figure, connection ports 302 are provided on both the upper and lower sides of the buffer bin 3, and the connection ports 302 on the upper and lower sides are opposite to each other vertically. Moreover, several pairs of connection ports 302 are provided, and several groups of cathode tubes 1 are installed on both the upper and lower sides of the buffer bin 3, and each group of cathode tubes 1 forms a parallel and side-by-side structure.

[0114] The inner diameter of the buffer inner cavity 301 is larger than the inner diameter of the tube cavity 101, and the buffer inner cavity 301 is used to buffer the flocculant residue in the wastewater. Through the buffer inner cavity 301 with a larger inner cavity size, multiple buffer spaces can be formed in the middle section of the cathode tube 1, so that during the flocculation process, the over-large flocs generated can be buffered in the buffer inner cavity 301, avoiding the problem of floc blockage in the cathode tube 1.

[0115] Since each support component 5 in the middle section of the anode core rod 2 is installed in the buffer inner cavity 301, the installation size is relatively large, and thus it is not easy to generate a blocking situation, which is beneficial to the flow of wastewater in the buffer inner cavity 301.

[0116] Moreover, two slag discharge pipes 4 are connected to the outer periphery of the buffer bin 3, and the two slag discharge pipes 4 are respectively used for the inlet and outlet of wastewater with flocculant residue. The gap part 511 on the outer periphery of the support cylinder 51 corresponds to the height of the slag discharge port 303. Two slag discharge ports 303 are respectively provided on the left and right sides of the buffer bin 3, and the two slag discharge ports 303 are respectively connected to the two slag discharge pipes 4, and the lower side of the slag discharge port 303 is flush with the lower side surface of the buffer inner cavity 301.

[0117] By introducing fresh water into the buffer bin 3 from the slag discharge port 303, the buffer bin 3 can be flushed, and the aggregates in the buffer inner cavity 301 can also be discharged, reducing the wastewater flow pressure in the cathode tube 1. Moreover, the gap part 511 on the outer periphery of the support cylinder 51 corresponds to the height of the slag discharge port 303, so that the water flow output from the slag discharge port 303 can wash the vicinity of the gap part 511, avoiding excessive aggregation of flocs near the gap part 511. During the flushing process, the anode core rod 2 can be adjusted up and down. During the adjustment process, the first support block 52, the second support block 53 and the support spring 54 can be in the support cylinder 51 and can also disturb the vicinity of the gap part 511, making the flocs flow more easily and pushing the aggregated system out, forming the discharge of flocs.

[0118] In addition, the electrocoagulation unit further includes a circulation pump 7, a filter 8, a circulation main path 72, and a circulation pipeline 71. The circulation pump 7 and the filter 8 are both installed on the circulation pipeline 71. The filter 8 is located on the water inlet side of the circulation pump 7. The two slag discharge pipes 4 on the outer periphery of the buffer bin 3 are respectively connected to both ends of the circulation pipeline 71. Through the circulation pumping of the circulation pump 7, the wastewater in the buffer inner cavity 301 will be discharged from one of the slag discharge pipes 4 and flow back from the other side, enabling the circulating flow of the wastewater. During the flowing process, the wastewater will circulate through the filter 8, which can separate and filter the flocs in the wastewater, and thus gradually remove the floc blockage therein. Specifically, the circulation pump 7 can operate regularly, thereby alleviating the floc blockage in the buffer inner cavity 301, especially near the support assembly 5.

[0119] Furthermore, a cylindrical filter residue net 6 is also installed at the upper end of the support cylinder 51. The filter residue net 6 has an annular cylindrical structure. The lower end of the filter residue net 6 is connected to the upper end of the support cylinder 51, and the upper end of the filter residue net 6 is connected to the outer periphery of the upper connection port 302. During the flowing process of the wastewater, it is input from the lower connection port 302 of the buffer bin 3, passes through the gap portion 511 of the support cylinder 51, enters the space outside the support cylinder 51, then enters the inner periphery of the filter residue net 6 through the filter residue net 6, and is discharged from the upper connection port 302 of the support cylinder 51 and enters the pipe section 100 of the upper cathode tube 1 to achieve the circulation of the wastewater. Most of the flocs in the wastewater can be blocked inside the support cylinder 51 and can be collected and processed along with the circulation of the circulation main path 72.

[0120] The filter residue net 6 is generally installed only in 1 - 2 buffer bins 3 near the lowermost end, mainly for treating the initially entering wastewater and separating the excessive large - particle impurities mixed therein.

[0121] The above - mentioned are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above - mentioned embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A process for separating and reusing inorganic salts from metal surface treatment wastewater, characterized in that: The steps include: Step 1, removing solid waste residues from high-concentration wastewater; Step 2: high-concentration wastewater flows into the regulating tank for regulation; Step 3: The high-concentration wastewater flowing out of the regulating tank enters the neutralization tank to adjust the pH value of the wastewater; Step 4: the high-concentration wastewater flowing out of the neutralization tank enters the electrocoagulation unit for flocculation; Step 5, the high-concentration wastewater flowing out of the electro-flocculation unit enters the sedimentation tank; Step 6: The supernatant from the sedimentation tank enters the resin water treatment unit to remove heavy metal ions; Step 7, the high-concentration wastewater treated by the resin water treatment device 1 enters the biological contact oxidation tank for microbial degradation; Step 8, the high-concentration wastewater flowing out of the biological contact oxidation tank enters the HMF unit; Step nine, low-concentration metal wastewater directly enters the HMF unit and mixes with high-concentration wastewater; the mixed wastewater is subjected to membrane filtration treatment in the HMF unit; Step 10, the mixed wastewater after being treated by the HMF unit enters the NF unit for nanofiltration membrane separation; Step 11, the produced water obtained after the NF unit treatment enters the NF unit water production pool, and the wastewater in the NF unit water production pool enters the RO unit 1 for reverse osmosis separation treatment; Step 12, the produced water obtained after being treated by RO unit 1 enters the RO unit 1 water production pool; Step 13, concentrated water is obtained by treatment in RO unit 1. When the sodium chloride concentration in the concentrated water is lower than the preset value, the concentrated water will be processed again in step 12; when the sodium chloride concentration in the concentrated water is not lower than the preset value, the concentrated water enters the concentrated water tank of RO unit 1; Step 14, the concentrated water obtained after the NF unit treatment enters the NF unit concentrated water tank; Step 15, the wastewater flowing out of the NF unit concentrated water tank enters the ozone oxidation tank; Step 16, the wastewater after being treated in the ozone oxidation tank enters the resin water treatment unit 2 for ion exchange treatment; Step 17, the produced water obtained by the resin water treatment device 2 enters the NF unit water production pool and is mixed with the produced water obtained in step 11; Step 18, the exchange resin 2 in the resin water treatment device 2 is eluted with HCl, and the produced water after the elution enters the RO unit 2, and the produced water obtained after the treatment of the RO unit 2 enters the RO unit 2 water production pool; In step 19, concentrated water is obtained after being processed by RO unit 2. When the magnesium chloride concentration in the concentrated water is lower than the preset value, the concentrated water will be processed again by step 18; when the magnesium chloride concentration in the concentrated water is not lower than the preset value, the concentrated water enters the concentrated water tank of RO unit 2.

2. The process for separating and reusing inorganic salts from metal surface treatment wastewater according to claim 1, characterized in that: In step 2, the wastewater flows out of the screen into the regulating tank by gravity or a pumping system; a stirring device is provided inside the regulating tank to stir the wastewater evenly.

3. The process for separating and reusing inorganic salts from metal surface treatment wastewater according to claim 1, characterized in that: In step three, a pH monitoring and acid-base addition system is set in the neutralization tank, which can detect the pH value in the neutralization tank and add acid-base regulators into the neutralization tank according to the pH value.

4. The process for separating and reusing inorganic salts from metal surface treatment wastewater according to claim 1, characterized in that: In step six, the resin water treatment device 1 is connected to the sedimentation tank through a pipeline, and a flow control device is installed on the pipeline.

5. The process for separating and reusing inorganic salts from metal surface treatment wastewater according to claim 1, characterized in that: In step seven, the resin water treatment unit 1 is connected to the biological contact oxidation tank via a pipeline, and an aeration system is provided in the biological contact oxidation tank.

6. The process for separation and reuse of inorganic salts from metal surface treatment wastewater according to claim 1, characterized in that: In step nine, low-concentration metal wastewater directly enters the HMF unit through a pipeline, where it is mixed with high-concentration wastewater; In step 13 and step 19, concentration detection sensors are installed at the concentrate outlets of RO unit 1 and RO unit 2 to detect the concentration in the concentrate; and two branches are formed at the concentrate outlets, and the on-off status of the two branches is controlled by valves.

7. The process for separating and reusing inorganic salts from metal surface treatment wastewater according to claim 1, characterized in that: In step 6, the exchange resin in the resin water treatment device 1 is a heavy metal ion adsorption resin, and the heavy metal-containing solution is obtained by elution for recycling the heavy metal inorganic salt; In step 18, the exchange resin in the resin water treatment device 2 is a magnesium ion adsorption resin, and the magnesium chloride-containing solution obtained by elution is subsequently used for recycling magnesium chloride salt.

8. A wastewater treatment system, characterized in that: Treating wastewater using the process described in any one of claims 1 to 7; The wastewater treatment system comprises an electro-flocculation unit, wherein the electro-flocculation unit comprises a cathode tube (1), an anode core rod (2) and a buffer bin (3). The cathode tube (1) is vertically arranged in the up-down direction and is divided into a plurality of tube sections (100) distributed from top to bottom. Adjacent tube sections (100) are respectively connected via a buffer bin (3). A tube cavity (101) is provided in the tube section (100), and a buffer inner cavity (301) is provided in the buffer bin (3). The tube cavity (101) and the buffer inner cavity (301) are interconnected to form a wastewater channel that is interconnected from top to bottom. The anode core rod (2) is coaxially arranged in the tube cavity (101) and passes through the buffer inner cavity (301); The upper end (201) of the anode core rod (2) is mounted on the upper hanging portion (2011) to achieve hanging limit, and the lower end (202) of the anode core rod (2) is in a hanging state; A support assembly (5) is installed in the buffer inner cavity (301), and the support assembly (5) is used to limit the horizontal position of the anode core rod (2).

9. The wastewater treatment system according to claim 8, characterized in that: The support assembly (5) comprises a support tube (51), a support block 1 (52) and a support block 2 (53); the support tube (51) is fixedly mounted on the lower side wall of the buffer inner cavity (301); the support tube (51) is provided with a gap portion (511) penetrating the inner and outer circumferences; The support block 1 (52) and the support block 2 (53) are both annular structures. The support block 1 (52) is installed on the inner circumference of the support tube (51), and the support block 2 (53) is installed on the outer circumference of the anode core rod (2). At least part of the support block 2 (53) extends into the inner circumference of the support block 1 (52) to achieve circumferential pressure limiting.

10. The wastewater treatment system according to claim 9, characterized in that: The inner circumferential surface (521) of the support block 1 (52) and the outer circumferential surface (531) of the support block 2 (53) are in an inverted cone structure that fits with each other. The inner circumferential surface (521) of the support block 1 (52) and the outer circumferential surface (531) of the support block 2 (53) are partially fitted on each other and pressed against each other. The outer periphery of the support block 1 (52) is adapted to slide up and down with the support tube (51), and a support spring (54) is installed on the lower side of the support block 1 (52), and the support spring (54) is used to apply an upward force to the support block 1 (52); The upper section of the inner circumference of the support tube (51) is fixedly connected to a limit stop ring (512), and the limit stop ring (512) is used to block the support block 1 (52).

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