Wastewater treatment method

Abstract

The invention discloses a wastewater treatment method which comprises the following steps: collecting wastewater to be treated; sequentially carrying out primary deslagging, COD (Chemical Oxygen Demand) removal treatment and secondary deslagging on the wastewater to be treated; carrying out multi-stage desalination concentration on the wastewater to be treated; the desalted and concentrated produced water is recycled, and the desalted and concentrated concentrated water is subjected to precipitation and crystallization and flows back before primary deslagging. According to the wastewater treatment method, the lithium iron phosphate high-concentration wastewater can be subjected to multi-stage treatment, suspended solids and impurities in the to-be-treated wastewater can be effectively removed, the to-be-treated wastewater can be subjected to multi-stage desalination and concentration, the component proportion of lithium ions in the concentrated water can be effectively increased, the water resource recycling rate can be increased, and the wastewater can be recycled. And the residual concentrated water after precipitation and crystallization can flow back before primary slag removal, so that zero discharge treatment of wastewater can be realized, and the requirements of related environmental protection laws and regulations and standards are met.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a wastewater treatment method. Background Art

[0002] Lithium iron phosphate is an important cathode material and is widely used in lithium-ion batteries. Lithium-ion batteries are high-performance, high-energy-density batteries that are widely used in mobile phones, laptops, electric vehicles and other fields.

[0003] It should be noted that when producing and processing lithium iron phosphate materials, attention should be paid to environmental protection and safety, especially in terms of wastewater treatment and waste disposal, relevant environmental protection laws and standards should be strictly observed. The lithium iron phosphate wastewater on the market now has the characteristics of large water volume and large fluctuations in water quality. The existing technology has a low treatment capacity for COD (Chemical Oxygen Demand) in wastewater. The concentration ratio is too low during zero-discharge treatment, resulting in a large amount of concentrated water. The proportion of lithium ions in the wastewater is low, and the water resource rate of the treated wastewater is too low. There is room for improvement. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a wastewater treatment method, which can effectively remove suspended matter and impurities in the wastewater to be treated, and can perform multi-stage desalination and concentration on the wastewater to be treated, effectively increase the proportion of lithium ions in the concentrated water, and can increase the water resource reuse rate, and can achieve zero discharge treatment of wastewater, meeting the requirements of relevant environmental protection laws and regulations and standards.

[0005] The wastewater treatment method according to the present invention comprises: collecting wastewater to be treated; sequentially performing primary slag removal, COD removal treatment and secondary slag removal on the wastewater to be treated; performing multi-stage desalination and concentration on the wastewater to be treated; recovering the produced water after desalination and concentration, and performing precipitation and crystallization on the concentrated water after desalination and concentration and refluxing it before the primary slag removal.

[0006] According to the wastewater treatment method of the present invention, high-concentration lithium iron phosphate wastewater can be treated in multiple stages to effectively remove suspended matter and impurities in the wastewater to be treated, and the wastewater to be treated can be desalted and concentrated in multiple stages to effectively increase the proportion of lithium ions in the concentrated water, and the water resource reuse rate can be increased. In addition, the concentrated water remaining after precipitation and crystallization can be returned to the first-level slag removal, thereby achieving zero-discharge treatment of wastewater and meeting the requirements of relevant environmental protection laws and standards.

[0007] According to the wastewater treatment method of the present invention, the primary slag removal includes: coagulation and sedimentation of the wastewater to be treated; and flotation slag removal of the wastewater to be treated.

[0008] According to the wastewater treatment method of the present invention, the coagulation and sedimentation of the wastewater to be treated includes: adding Ca(OH)2 to the wastewater to be treated and adjusting the pH to 11-13; then adding PAC of a first set concentration; then adding PAM of a second set concentration, and then performing flocculation and sedimentation; and adjusting the pH to 7-8.

[0009] According to the wastewater treatment method of the present invention, the flotation and slag removal of the wastewater to be treated includes: detecting the total phosphorus index of the wastewater to be treated; when the total phosphorus index is within a first set index, internally aerating the wastewater to be treated to scrape off suspended matter and residue; when the total phosphorus index is higher than the first set index, adding a second set concentration of PAM and a first set concentration of PAC to the wastewater to be treated for flocculation and sedimentation, and scraping off suspended matter and residue.

[0010] According to the wastewater treatment method of the present invention, the COD removal treatment includes: passing the wastewater to be treated into an XE catalytic device to degrade COD through the XE catalytic device; then passing the wastewater to be treated into a catalytic oxidation device to degrade COD through catalytic reactants; and controlling the pH of the wastewater to be treated within 7 to 8; passing the wastewater to be treated into an anaerobic tank, an anaerobic tank and an aerobic tank in sequence to control DO respectively.

[0011] According to the wastewater treatment method of the present invention, the secondary slag removal includes: performing MBR membrane filtration treatment on the wastewater to be treated; performing multi-media filtration on the wastewater to be treated; and performing ceramic membrane filtration treatment on the wastewater to be treated.

[0012] According to the wastewater treatment method of the present invention, the multi-stage desalination and concentration of the wastewater to be treated comprises: sequentially passing the wastewater to be treated into a primary RO membrane, a secondary RO membrane, and a tertiary RO membrane for concentration.

[0013] According to the wastewater treatment method of the present invention, the wastewater to be treated enters the primary RO membrane, the secondary RO membrane, and the tertiary RO membrane in sequence for concentration; the concentrated water treated by the primary RO membrane enters the secondary RO membrane; the concentrated water treated by the secondary RO membrane is crystallized, and the produced water treated by the secondary RO membrane enters the tertiary RO membrane; the concentrated water treated by the tertiary RO membrane is returned to the primary RO membrane, and the produced water treated by the tertiary RO membrane and the produced water treated by the primary RO membrane are recovered.

[0014] According to the wastewater treatment method of the present invention, the precipitation and crystallization of the concentrated water after desalination and concentration includes: adding a set proportion of carbonate to the concentrated water after desalination and concentration to perform precipitation and crystallization.

[0015] According to the wastewater treatment method of the present invention, the reflux before the primary slag removal includes: after the concentrated water after desalination and concentration is crystallized, if the conductivity of the concentrated water after desalination and concentration is greater than or equal to the set conductivity, low-temperature evaporation is performed; wherein, during the low-temperature evaporation process, vacuum is drawn to a set air pressure value, and the temperature is lower than the set temperature value.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 is a flow chart of a wastewater treatment method according to the present invention;

[0019] Figure 2 is a flow chart of primary deslagging of the wastewater treatment method according to the present invention;

[0020] Figure 3 is a flow chart of the coagulation and sedimentation of the wastewater treatment method according to the present invention;

[0021] Figure 4 is a flow chart of air flotation slag removal of the wastewater treatment method according to the present invention;

[0022] Figure 5 is a flow chart of a COD removal process of a wastewater treatment method according to the present invention;

[0023] Figure 6 is a flow chart of secondary deslagging of the wastewater treatment method according to the present invention;

[0024] Figure 7 Detailed description of the invention The invention is a flow chart of multi-stage desalination and concentration of wastewater according to the invention. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] Reference below Figure 1-Figure 7 The wastewater treatment method according to the present invention can perform multi-stage treatment on high-concentration lithium iron phosphate wastewater, effectively remove suspended matter and impurities in the wastewater to be treated, and perform multi-stage desalination and concentration on the wastewater to be treated, effectively increase the proportion of lithium ions in the concentrated water, and increase the water resource reuse rate. In addition, the concentrated water remaining after precipitation and crystallization can be returned to the first-level slag removal, thereby achieving zero-discharge treatment of wastewater and meeting the requirements of relevant environmental protection laws and standards.

[0029] like Figure 1 As shown, the wastewater treatment method according to the present invention comprises:

[0030] S10: Collect wastewater to be treated.

[0031] Specifically, the present application can be used to treat wastewater to make it comply with relevant environmental laws and standards. Before treating the wastewater, the wastewater can be collected first, and then the wastewater can be accumulated to a certain amount before being treated together, which can reduce energy consumption.

[0032] It should be noted that a wastewater collection pool can be set up to accommodate the wastewater to be treated and the wastewater to be treated can be collected, and the wastewater to be treated can be high-concentration lithium iron phosphate wastewater, that is, the wastewater treatment method of the present application can be used to treat high-concentration lithium iron phosphate wastewater.

[0033] S20: The wastewater to be treated is subjected to primary slag removal, COD removal treatment and secondary slag removal in sequence.

[0034] Specifically, after the wastewater to be treated is collected, it can be homogenized and weighed by aeration and stirring in the wastewater collection pool, and after staying for more than 24 hours, the wastewater to be treated is subjected to primary slag removal, COD removal treatment and secondary slag removal. The primary slag removal can remove some suspended matter and residue in the wastewater to be treated, the COD removal treatment can remove COD in the wastewater to be treated, and the secondary slag removal can further remove some suspended matter and impurities in the wastewater to be treated. The wastewater to be treated is subjected to primary slag removal, COD removal treatment and secondary slag removal in sequence. The collected wastewater to be treated can be subjected to primary slag removal first, and the wastewater to be treated after the primary slag removal can be subjected to COD removal treatment, and the wastewater to be treated after the COD removal treatment can be subjected to secondary slag removal. These three steps can be performed on all wastewater to be treated in sequence, which can improve the treatment effect and reliability, and the suspended matter and impurities in the wastewater to be treated can be effectively removed by performing the primary slag removal and the secondary slag removal in sequence.

[0035] Among them, it should be noted that the first-level slag removal module, the COD treatment module and the second-level slag removal module can be set to respectively perform the first-level slag removal, COD removal treatment and second-level slag removal on the wastewater to be treated, and the wastewater collection tank, the first-level slag removal module, the COD treatment module and the second-level slag removal module can be connected in sequence, so that the wastewater to be treated can flow from the wastewater collection tank through the first-level slag removal module, the COD treatment module and the second-level slag removal module in sequence to effectively remove suspended matter, residue and COD in the wastewater to be treated.

[0036] S30: multi-stage desalination and concentration of the wastewater to be treated.

[0037] Specifically, after treating the suspended solids, residues and COD in the wastewater to be treated, the wastewater to be treated can be subjected to multi-stage desalination and concentration. Desalination and concentration are used to increase the proportion of recoverable resources in the concentrated water and the water resource reuse rate. Multi-stage desalination and concentration can be performed on the wastewater to be treated for multiple desalination and concentration in sequence, which can increase the concentration multiples to further increase the proportion of recoverable resources in the concentrated water and the water resource reuse rate.

[0038] Among them, it should be noted that the multi-stage desalination and concentration can be at least one stage of desalination and concentration, that is, it can be one-stage desalination and concentration, two-stage desalination and concentration or three-stage desalination and concentration, etc., which can be flexibly selected according to specific circumstances, and a multi-stage membrane composite concentrating device can be set up to carry out multi-stage desalination and concentration and produce water for the treated wastewater, and the secondary slag removal module can be connected to the multi-stage membrane composite concentrating device, so that the wastewater to be treated after being treated by the secondary slag removal module can enter the multi-stage membrane composite concentrating device for multi-stage desalination and concentration.

[0039] S40: recovering the produced water after desalination and concentration, and performing precipitation and crystallization on the concentrated water after desalination and concentration and refluxing it before the first stage of slag removal.

[0040] Specifically, after multi-stage desalination and concentration of the wastewater to be treated, the produced water that meets the production water standards can be recycled, and the concentrated water after desalination and concentration can be precipitated and crystallized to extract recyclable resources in the concentrated water, thereby improving the reuse rate of resources and creating more profits for the enterprise. The remaining concentrated water after precipitation and crystallization is returned to the first-level slag removal so that the remaining concentrated water can enter the system again and undergo a new round of treatment together with the new wastewater to be treated.

[0041] Among them, it should be noted that the produced water that meets the production water standards can be recycled by setting up a reuse water tank, the produced water can be used again in workshop production, and a crystallization sedimentation tank can be set up to recycle the recyclable resources in the wastewater to be treated, and the multi-stage membrane composite concentrating device can be connected to the reuse water tank and the crystallization sedimentation tank respectively, so that the produced water after multi-stage desalination and concentration can enter the reuse water tank for recycling, and the concentrated water after multi-stage desalination and concentration can enter the crystallization sedimentation tank to recycle the recyclable resources, and the crystallization sedimentation tank can be connected to the first-level slag removal module, so that the concentrated water remaining after precipitation and crystallization can enter the system again, and undergo a new round of treatment together with the new wastewater to be treated, so as to achieve zero discharge treatment of wastewater.

[0042] Furthermore, the present application can be used to treat high-concentration lithium iron phosphate wastewater, that is, the lithium ions in the concentrated water after desalination and concentration can be recovered, the proportion of lithium ions in the concentrated water can be increased, and the reuse rate of water resources can be increased.

[0043] According to the wastewater treatment method of the present invention, high-concentration lithium iron phosphate wastewater can be treated in multiple stages to effectively remove suspended matter and impurities in the wastewater to be treated, and the wastewater to be treated can be desalted and concentrated in multiple stages to effectively increase the proportion of lithium ions in the concentrated water, and the water resource reuse rate can be increased. In addition, the concentrated water remaining after precipitation and crystallization can be returned to the first-level slag removal, thereby achieving zero-discharge treatment of wastewater and meeting the requirements of relevant environmental protection laws and standards.

[0044] like Figure 2 As shown, according to the wastewater treatment method of the present invention, the first-level deslagging comprises:

[0045] S21: Coagulation and sedimentation of the wastewater to be treated.

[0046] Specifically, after the wastewater to be treated is collected in the wastewater collection tank, the wastewater to be treated can enter the primary slag removal module from the wastewater collection tank, and the primary slag removal is performed in the primary slag removal module, and some suspended matter and residue in the wastewater to be treated are preliminarily treated. The primary slag removal includes coagulation and sedimentation of the wastewater to be treated. A pretreatment sedimentation tank can be set up, and the pretreatment sedimentation tank and the wastewater collection tank are connected, so that the wastewater to be treated in the wastewater collection tank can be pumped from the wastewater collection tank into the pretreatment sedimentation tank through a centrifugal pump, and the suspended matter, phosphorus and some precipitable substances contained in the wastewater to be treated are precipitated in the pretreatment sedimentation tank.

[0047] Among them, polyferric chloride can be put into the pretreatment sedimentation tank to precipitate phosphate, that is, to precipitate phosphorus in the wastewater to be treated, and the suspended matter contained in the wastewater to be treated can be removed by stirring and sedimentation.

[0048] S22: The wastewater to be treated is subjected to air flotation to remove slag.

[0049] Specifically, the first-level slag removal also includes flotation slag removal of the wastewater to be treated. An air flotation slag removal tank can be set up, and the pretreatment sedimentation tank and the air flotation slag removal tank are connected, so that the wastewater to be treated after being treated in the pretreatment sedimentation tank can enter the air flotation slag removal tank from the pretreatment sedimentation tank, and the suspended matter and other residues remaining in the wastewater to be treated are removed through the air flotation slag removal tank.

[0050] Among them, in the flotation deslagging tank, the suspended matter and residue in the wastewater to be treated can be exposed to the top of the flotation deslagging tank by internal aeration, and then the suspended matter and residue can be scraped out by scrapers and other tools.

[0051] Also, it should be noted that the phosphorus content in the wastewater to be treated collected in the wastewater collection tank can reach more than 1000ppm, and the phosphorus content after treatment in the pretreatment sedimentation tank and the flotation slag removal tank can be reduced to less than 100ppm, and more than 99% of the impurities and sediments in the wastewater to be treated can be removed, and the high-concentration wastewater to be treated after being treated by the entire wastewater treatment method can be diluted by at least 26.7 times after entering the pretreatment sedimentation tank, which greatly reduces the impact on the new wastewater to be treated entering the pretreatment sedimentation tank from the wastewater collection tank, and due to the intermittent source of the wastewater to be treated, the dilution multiple fully meets the requirements of secondary treatment.

[0052] like Figure 3 As shown, according to the wastewater treatment method of the present invention, the coagulation and sedimentation of the wastewater to be treated includes:

[0053] S211: Add Ca(OH)2 to the wastewater to be treated and adjust the pH to 11-13.

[0054] Specifically, the pretreatment sedimentation tank and the wastewater collection tank are connected so that the wastewater to be treated in the wastewater collection tank can enter the pretreatment sedimentation tank from the wastewater collection tank, and coagulation and sedimentation are performed in the pretreatment sedimentation tank. Ca(OH)2 can be added to the pretreatment sedimentation tank, that is, Ca(OH)2 can be added to the wastewater to be treated in the pretreatment sedimentation tank to adjust the pH value of the wastewater to be treated, and the pH value of the wastewater to be treated is adjusted to within 11-13 to control the pH value within an optimal range, promote the formation of precipitation and remove it from the wastewater to be treated, and adjust the pH value of the wastewater to be treated by adding alkaline substances to break the viscosity of the wastewater to be treated, thereby reducing the possibility of components in the equipment being blocked and damaged due to excessive viscosity of the wastewater to be treated, and the total phosphorus in the wastewater to be treated can be combined with Ca(OH)2 to form calcium phosphate precipitation to be removed from the wastewater to be treated.

[0055] S212: Add PAC at the first set concentration.

[0056] Secondly, PAC (Polymerized Aluminum Chloride) with a first set concentration can be added to the pretreatment sedimentation tank, that is, PAC with a first set concentration can be added to the wastewater to be treated whose pH value has been adjusted to 11-13. PAC, as a commonly used coagulant, can combine with the total phosphorus in the wastewater to be treated to form aluminum phosphate to remove it from the wastewater to be treated, wherein the first set concentration can be 5%.

[0057] S213: PAM of a second set concentration is added, followed by flocculation and precipitation.

[0058] Then, PAM (Polyacrylamide) with a second set concentration can be added to the pretreatment sedimentation tank, that is, PAM with a second set concentration can be added to the wastewater to be treated after the addition of PAC. PAM can be used as a flocculant to flocculate and precipitate the wastewater to be treated to remove some suspended matter and impurities in the wastewater to be treated. The second set concentration can be 0.2%.

[0059] S214: Adjust the pH to between 7 and 8.

[0060] Finally, the pH value of the wastewater to be treated after flocculation and sedimentation can be adjusted again to a pH value of 7 to 8 to improve the effect of subsequent treatment of the wastewater to be treated.

[0061] like Figure 4 As shown, according to the wastewater treatment method of the present invention, flotation slag removal of the wastewater to be treated includes:

[0062] S221: Detect the total phosphorus index of the wastewater to be treated.

[0063] Specifically, the flotation slag removal tank is connected to the pretreatment sedimentation tank, and the wastewater to be treated after being treated in the pretreatment sedimentation tank can enter the flotation slag removal tank for flotation slag removal, and the pretreatment sedimentation tank can remove suspended matter, total phosphorus and impurities in the wastewater to be treated. The flotation slag removal tank is equipped with an online monitoring device for total phosphorus to detect the total phosphorus index in the wastewater to be treated in real time, that is, the removal effect of the pretreatment sedimentation tank on the total phosphorus in the wastewater to be treated can be detected. When the total phosphorus index in the wastewater to be treated meets the requirements, the flotation slag removal can continue to be carried out on the wastewater to be treated. When the total phosphorus index in the wastewater to be treated does not meet the requirements, the total phosphorus can be removed again, and then the flotation slag removal can be carried out again.

[0064] S222: When the total phosphorus index is within the first set index, the wastewater to be treated is internally aerated to scrape off suspended matter and residues.

[0065] That is to say, when the total phosphorus index is within the first set index, that is, the total phosphorus index in the wastewater to be treated meets the requirements, the wastewater to be treated can be subjected to subsequent flotation deslagging, and the wastewater to be treated can be internally aerated so that the suspended matter and residue in the wastewater to be treated can be exposed to the top of the flotation deslagging tank, and then the suspended matter and residue can be scraped out for removal by scrapers and other tools, wherein the first set index can be 5ppm.

[0066] Among them, a small air compressor can be set up to perform aeration and slag removal, so that the scraped residue can enter the slag removal bucket, and the wastewater to be treated can continue to proceed with subsequent treatment steps.

[0067] S223: When the total phosphorus index is higher than the first set index, PAM of the second set concentration and PAC of the first set concentration are added to the wastewater to be treated for flocculation and sedimentation, and the suspended matter and residue are scraped off.

[0068] That is to say, when the total phosphorus index is higher than the first set index, the total phosphorus in the wastewater to be treated can be removed again. That is, the total phosphorus index in the wastewater to be treated does not meet the requirements, and the second set concentration of PAM and the first set concentration of PAC can be added to the wastewater to be treated again, so that the total phosphorus in the wastewater to be treated can be combined with PAC and flocculated and precipitated, and then the suspended matter and residue can be scraped out by scrapers and other tools for removal.

[0069] like Figure 5 As shown, according to the wastewater treatment method of the present invention, COD removal treatment includes:

[0070] S231: The wastewater to be treated is passed into the XE catalytic device to degrade COD.

[0071] Specifically, COD in the wastewater to be treated can be removed by catalytic oxidation. An XE catalytic device can be set up, and the XE catalytic device is connected to the primary slag removal module, so that the wastewater to be treated after being treated by the primary slag removal module can enter the XE catalytic device, and the COD in the wastewater to be treated is degraded in the XE catalytic device. The COD can be oxidized by generating free radical hydroxyl groups by electrifying the positive and negative titanium plates of the XE catalytic structure, and the COD can be separated into carbon dioxide and water, etc.

[0072] Among them, when the positive and negative titanium plates of the XE catalytic structure are energized, the current can be adjusted to 3A, the voltage to 36V, the pH of the inlet water to 7, and the ionization time to 2H.

[0073] S232: The wastewater to be treated is then passed into a catalytic oxidation device to degrade COD through the catalytic reactants;

[0074] Specifically, the COD in the wastewater to be treated can be further removed by bacterial growth and consumption. A catalytic oxidation device can be set up, and the catalytic oxidation device can be connected to the XE catalytic device, so that the wastewater to be treated after being treated by the XE treatment device can enter the catalytic oxidation device, and the COD can be further oxidized in the catalytic oxidation device. The COD can be subjected to a composite secondary oxidation by adding ferrous iron, sulfuric acid and hydrogen peroxide in the catalytic oxidation device, and all the COD in the wastewater to be treated can be oxidized and separated into carbon dioxide, water and degradable COD, so as to enhance the ability and effect of oxidizing COD.

[0075] Among them, when the COD is oxidized by using a catalytic oxidation device, the pH can be adjusted to 2 by adding sulfuric acid, and then ferrous iron and hydrogen peroxide are added to perform a composite secondary oxidation on the COD.

[0076] Also, it should be noted that the COD content in the wastewater to be treated collected in the wastewater collection pool can reach more than 1000ppm. After the XE catalytic device and the catalytic oxidation device, the difficult-to-degrade COD in the wastewater to be treated can be removed by 50%, and the easily degradable COD can be removed by more than 30%, so that the COD content in the wastewater to be treated can reach less than 200ppm before entering the biochemical treatment structure, and then enter the biochemical treatment structure, and more than 90% of the COD is consumed by the growth of biological bacteria, that is, the COD content in the wastewater to be treated after treatment by the COD treatment module can be stably controlled below 20ppm.

[0077] S233: Control the pH of the wastewater to be treated within a range of 7 to 8.

[0078] Specifically, after the wastewater to be treated is chemically catalytically degraded, the wastewater to be treated can enter the biochemical treatment structure, and the COD in the wastewater to be treated can be removed by the growth and consumption of biological bacteria. Before the wastewater to be treated enters the biochemical treatment structure, the pH value of the wastewater to be treated can be adjusted first. The pH of the wastewater to be treated can be controlled within the range of 7 to 8, that is, the pH value can be adjusted to the range most suitable for the growth of microorganisms to promote the growth and activity of microorganisms. Among them, the pH of the wastewater to be treated before entering the biochemical treatment structure is optimally between 7 and 8.

[0079] S234: The wastewater to be treated is sequentially introduced into the anaerobic tank, the facultative aerobic tank and the aerobic tank to control DO respectively.

[0080] Specifically, after the pH value is adjusted, the COD in the wastewater to be treated can be treated through the biochemical treatment structure, and DO (Dissolved Oxygen) can be controlled. An anaerobic tank, an anaerobic tank and an aerobic tank can be set up, and the anaerobic tank, the anaerobic tank and the aerobic tank are connected in sequence, so that the wastewater to be treated can be passed into the anaerobic tank, the anaerobic tank and the aerobic tank in sequence, and the DO can be controlled respectively.

[0081] Among them, the anaerobic tank can treat some nitrogen-containing compounds in the wastewater to be treated by culturing denitrifying bacteria, converting them into nitrogen gas for release, and the denitrifying bacteria can absorb the total phosphorus adsorbed by the phosphorus-rich bacteria in the aerobic tank that returns to the anaerobic tank. The facultative aerobic tank can denitrify the nitrate ions in the wastewater to be treated that returns from the aerobic tank and convert them into nitrogen gas for release. The aerobic tank can nitrify NH3-N (ammonia nitrogen) in the wastewater to be treated to generate nitrate ions. At the same time, bacteria reproduce and absorb COD and can oxidize and decompose COD to provide energy to phosphorus-absorbing microorganisms. Microorganisms can absorb phosphorus from the wastewater to be treated, and the phosphorus enters the cell tissue and is enriched in the microorganisms. After sedimentation and separation, it is discharged in the form of phosphorus-rich sludge.

[0082] Also, it should be noted that the oxidized wastewater to be treated first enters the anaerobic tank, where the DO can be controlled below 0.2ppm and below -250mvORP, to denitrify nitrate nitrogen and release rich phosphorus, and then flows by gravity into the facultative aerobic tank, where the DO is controlled at 0.2ppm~0.5ppm and below -100mvORP, to carry out secondary denitrification to treat total nitrogen, and finally flows by gravity into the aerobic tank, where the DO is controlled at above 0.5ppm and between +300mv and +500mvORP, to carry out nitrification of ammonia nitrogen, and consume organic matter, nitrogen and phosphorus through the growth of microorganisms, the reflux ratio of the external return to the anaerobic tank is controlled at 50%-100%, the reflux ratio of the internal return to the facultative aerobic tank is controlled at more than 200%, and the overall temperature is best controlled at 15~30°.

[0083] like Figure 6As shown, according to the wastewater treatment method of the present invention, the secondary deslagging comprises:

[0084] S241: The wastewater to be treated is treated by MBR membrane filtration.

[0085] Specifically, the untreated wastewater treated by the COD treatment module can enter the secondary slag removal module, and secondary slag removal is performed in the secondary slag removal module to further remove suspended matter and impurities in the untreated wastewater. The secondary slag removal includes MBR membrane filtration treatment of the untreated wastewater. A deep treatment tank can be set up, and the deep treatment tank is connected with the COD treatment module so that the untreated wastewater treated by the COD treatment module can enter the deep treatment tank. An MBR membrane can be set up in the deep treatment tank. The MBR membrane can be used for sludge precipitation and clarified effluent. The sludge interception and secondary microbial consumption can be performed through the sludge hanging capacity of the MBR membrane to remove organic matter, ammonia nitrogen, phosphorus and sludge. Among them, the membrane flux is 10L / m2·h, and a PTFE hollow fiber membrane is used. The pressure backwash pressure is controlled to be 0.15MPa. The untreated wastewater is filtered through the MBR membrane, the sludge is intercepted, and the pollution and SS (Suspended Solids) in the wastewater are removed, so that the clarified untreated wastewater can enter the subsequent treatment steps.

[0086] S242: Perform multi-media filtration on the wastewater to be treated.

[0087] Specifically, the secondary slag removal also includes multi-media filtration of the wastewater to be treated. A multi-media filter can be set up and connected to the deep treatment tank so that the wastewater to be treated after being treated in the deep treatment tank can enter the multi-media filter, and some suspended matter and impurities in the wastewater to be treated are processed by the multi-media filter.

[0088] S243: The wastewater to be treated is treated by ceramic membrane filtration.

[0089] In addition, the secondary slag removal also includes ceramic membrane filtration treatment of the wastewater to be treated. A ceramic membrane device can be set up, and the ceramic membrane device is connected to a multi-media filter, so that the wastewater to be treated after being treated by the multi-media filter can enter the ceramic membrane device, and the tiny suspended matter and impurities in the wastewater to be treated are further treated by the ceramic membrane device. Impurities larger than 0.1μm in the wastewater can be filtered, and the main body pressure is controlled at more than 0.6MPa to ensure that the wastewater entering the subsequent treatment steps has good water quality.

[0090] Thus, the wastewater to be treated can flow through the MBR membrane pool, the multi-media filter and the ceramic membrane device in sequence in the secondary slag removal module to remove sludge, suspended matter and impurities in the wastewater to be treated.

[0091] Also, it should be noted that the COD content in the wastewater to be treated can be controlled at an extremely low level through the COD treatment module to ensure that there is no pollution to the MBR membrane, and the wastewater to be treated after being treated by the COD treatment module flows through the MBR membrane pool, and a very small part of the COD in the wastewater to be treated can be removed by the activated sludge and residual biological bacteria in the MBR membrane pool, and then further treated by a multi-media filter and a ceramic membrane device to ensure that the water quality before entering the next treatment step is clear and meets the requirements.

[0092] According to the wastewater treatment method of the present invention, multi-stage desalination and concentration of the wastewater to be treated comprises:

[0093] The wastewater to be treated enters the primary RO membrane, the secondary RO membrane and the tertiary RO membrane in sequence for concentration.

[0094] Specifically, the wastewater to be treated after being treated by the secondary slag removal module can enter the multi-stage membrane composite concentrating device, which is used for multi-stage concentration and water production of the wastewater to be treated. When concentrating the wastewater to be treated, the wastewater to be treated can enter the primary RO membrane (CR100, pressure resistance above 3MPa), the secondary RO membrane (CR100, pressure resistance above 3MPa), and the tertiary RO membrane (CR100, pressure resistance above 3MPa) in sequence for concentration, that is, the multi-stage membrane composite concentrating device includes a primary RO membrane, a secondary RO membrane and a tertiary RO membrane, and the primary RO membrane, the secondary RO membrane and the tertiary RO membrane can all be used to concentrate the wastewater to be treated. The primary RO membrane, the secondary RO membrane and the tertiary RO membrane are connected in sequence, so that the wastewater to be treated can flow through the primary RO membrane, the secondary RO membrane and the tertiary RO membrane in sequence, so that the wastewater to be treated can be concentrated in multiple stages, the concentration multiple can be increased, and the proportion of lithium ions in the concentrated concentrated water and the water resource reuse rate can be increased.

[0095] like Figure 7 As shown, according to the wastewater treatment method of the present invention, the wastewater to be treated sequentially enters the primary RO membrane, the secondary RO membrane, and the tertiary RO membrane for concentration.

[0096] S31: The concentrated water treated by the primary RO membrane enters the secondary RO membrane.

[0097] Specifically, the untreated wastewater after being treated by the secondary slag removal module can first enter the primary RO membrane and be concentrated by the primary RO membrane, so that the primary concentrated water after being treated by the primary RO membrane can enter the secondary RO membrane for concentration, and the primary produced water after being treated by the primary RO membrane is recovered, and the TDS (Total Dissolved Solids) of the produced water is controlled below 200.

[0098] S32: The concentrated water treated by the secondary RO membrane is crystallized, and the produced water treated by the secondary RO membrane enters the tertiary RO membrane.

[0099] Specifically, the primary concentrated water after treatment by the primary RO membrane can enter the secondary RO membrane for concentration. The secondary RO membrane can be a high-pressure STRO membrane (MP8042, with a pressure resistance of more than 10MPa), so that the secondary high-pressure concentrated water after treatment by the secondary RO membrane can enter the crystallization sedimentation tank for crystallization to recover the lithium ions in the concentrated water, and the secondary high-pressure produced water after treatment by the secondary RO membrane can enter the tertiary RO membrane for concentration.

[0100] S33: The concentrated water after the tertiary RO membrane treatment is returned to the primary RO membrane, and the produced water after the tertiary RO membrane treatment and the produced water after the primary RO membrane treatment are recovered.

[0101] Specifically, the secondary high-pressure produced water after treatment by the secondary RO membrane can enter the tertiary RO membrane for concentration, so that the tertiary concentrated water after treatment by the tertiary RO membrane can be returned to the primary RO membrane, and the tertiary produced water after treatment by the tertiary RO membrane can be combined with the primary produced water to produce water, and the produced water can enter the reuse water tank for standby, ensuring that the TDS of the produced water is below 200, the COD is within 5, and the total phosphorus and ammonia nitrogen are within 0.5.

[0102] According to the wastewater treatment method of the present invention, the concentrated water after desalination and concentration is precipitated and crystallized, comprising:

[0103] A set proportion of carbonate is added to the concentrated water after desalination to perform precipitation and crystallization.

[0104] Specifically, the concentrated water after desalination and concentration is precipitated and crystallized, that is, the secondary high-pressure concentrated water after the secondary RO membrane treatment can enter the crystallization sedimentation tank for precipitation and crystallization, and the conductivity of the concentrated water can be controlled between 100,000 and 150,000 μs / cm. A carbonate with a set ratio is added to the crystallization sedimentation tank, that is, a carbonate with a set ratio is added to the secondary high-pressure concentrated water. By adding the carbonate, high-purity lithium carbonate can be crystallized to recover the lithium ions in the concentrated water, wherein the set ratio can be 30%, and the concentration of the crystallized lithium salt can reach 95% or above.

[0105] According to the wastewater treatment method of the present invention, the reflux before the primary slag removal comprises:

[0106] After the concentrated water after desalination and concentration is crystallized, low-temperature evaporation is performed if the conductivity of the concentrated water after desalination and concentration is greater than or equal to the set conductivity.

[0107] Specifically, after the concentrated water after desalination and concentration is precipitated and crystallized, a very small amount of concentrated water remaining after crystallization can be returned to the pretreatment sedimentation tank, mixed with new wastewater to be treated entering the pretreatment sedimentation tank from the wastewater collection tank to be diluted in the pretreatment sedimentation tank, and then a new round of treatment is carried out together with the new wastewater to be treated. If the conductivity of the concentrated water remaining after crystallization is greater than or equal to the set conductivity, that is, there are more salt substances in the concentrated water, low-temperature evaporation can be carried out to remove the salt substances in the concentrated water, and the evaporated low-concentration condensed water is sent to the pretreatment sedimentation tank, diluted with new wastewater to be treated entering the pretreatment sedimentation tank from the wastewater collection tank in the pretreatment sedimentation tank, and enters a new treatment process together with the new wastewater to be treated, so as to achieve zero discharge treatment of wastewater, and transport the evaporated impure salts for treatment. If the conductivity of the concentrated water remaining after crystallization is less than the set conductivity, the concentrated water can be returned to the pretreatment sedimentation tank for secondary treatment, wherein the set conductivity can be 150000μs / cm.

[0108] In the low-temperature evaporation process, the vacuum is drawn to a set pressure value, and the temperature is lower than the set temperature value.

[0109] Specifically, a low-temperature evaporator can be set up to evaporate the concentrated water at low temperature. During the low-temperature evaporation of the concentrated water, the vacuum can be drawn to a set air pressure value, and the evaporation temperature can be lowered to the set temperature value to start evaporation. The evaporated low-concentration condensed water is sent to a pretreatment sedimentation tank for secondary treatment, and the evaporated impurities are transported out for treatment. The set air pressure value can be -80 to -100 KPa, and the set temperature value can be 35°.

[0110] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0111] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A wastewater treatment method, characterized in that: include: Collecting wastewater for treatment; The wastewater to be treated is subjected to primary slag removal, COD removal treatment and secondary slag removal in sequence; Performing multi-stage desalination and concentration on the wastewater to be treated; The produced water after desalination and concentration is recovered, and the concentrated water after desalination and concentration is precipitated and crystallized and refluxed before the first-stage deslagging.

2. The wastewater treatment method according to claim 1, characterized in that: The primary slag removal comprises: Carrying out coagulation and sedimentation on the wastewater to be treated; The wastewater to be treated is subjected to air flotation to remove slag.

3. The wastewater treatment method according to claim 2, characterized in that: The coagulation and sedimentation of the wastewater to be treated comprises: Adding Ca(OH)2 to the wastewater to be treated and adjusting the pH to 11-13; Then adding PAC of the first set concentration; Then, PAM of the second set concentration is added, followed by flocculation and precipitation; Adjust the pH to between 7 and 8.

4. The wastewater treatment method according to claim 2, characterized in that: The flotation slag removal of the wastewater to be treated comprises: Detecting the total phosphorus index of the wastewater to be treated; When the total phosphorus index is within the first set index, the wastewater to be treated is internally aerated to scrape off suspended matter and residue; When the total phosphorus index is higher than the first set index, PAM of the second set concentration and PAC of the first set concentration are added to the wastewater to be treated for flocculation and sedimentation, and suspended matter and residue are scraped off.

5. The wastewater treatment method according to claim 1, characterized in that: The COD removal process comprises: Passing the wastewater to be treated into an XE catalytic device to degrade COD; Then the wastewater to be treated is passed into a catalytic oxidation device to degrade COD through the catalytic reactants; And, controlling the pH of the wastewater to be treated within a range of 7 to 8; The wastewater to be treated is sequentially introduced into an anaerobic tank, an anaerobic tank and an aerobic tank to control DO respectively.

6. The wastewater treatment method according to claim 1, characterized in that: The secondary slag removal comprises: Performing MBR membrane filtration treatment on the wastewater to be treated; Performing multi-media filtration on the wastewater to be treated; The wastewater to be treated is subjected to ceramic membrane filtration treatment.

7. The wastewater treatment method according to claim 1, characterized in that: The multi-stage desalination and concentration of the wastewater to be treated comprises: The wastewater to be treated enters the primary RO membrane, the secondary RO membrane and the tertiary RO membrane in sequence for concentration.

8. The wastewater treatment method according to claim 7, characterized in that: The wastewater to be treated is sequentially passed through a primary RO membrane, a secondary RO membrane, and a tertiary RO membrane for concentration; The concentrated water treated by the primary RO membrane enters the secondary RO membrane; The concentrated water treated by the secondary RO membrane is crystallized, and the produced water treated by the secondary RO membrane enters the tertiary RO membrane; The concentrated water after the treatment by the tertiary RO membrane is returned to the primary RO membrane, and the produced water after the treatment by the tertiary RO membrane and the produced water after the treatment by the primary RO membrane are recovered.

9. The wastewater treatment method according to claim 1, characterized in that: The precipitation and crystallization of the concentrated water after desalination and concentration comprises: A set proportion of carbonate is added to the concentrated water after desalination to perform precipitation and crystallization.

10. The wastewater treatment method according to claim 1, characterized in that: The reflux before the first-stage slag removal comprises: After the concentrated water after desalination and concentration is crystallized, if the conductivity of the concentrated water after desalination and concentration is greater than or equal to the set conductivity, low-temperature evaporation is performed; Wherein, during the low-temperature evaporation process, the vacuum is drawn to a set pressure value, and the temperature is lower than the set temperature value.

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