Concentration system and concentration method for high-salinity and high-hardness wastewater

Abstract

The invention relates to the technical field of wastewater treatment, and discloses a high-salinity and high-hardness wastewater concentration system and method.The concentration system comprises a calcium removal reaction tank used for removing calcium in high-salinity and high-hardness wastewater to obtain first wastewater containing calcium salt precipitates; the softening membrane device is connected with the calcium removal reaction tank and is used for filtering the first wastewater to obtain second wastewater; the first reverse osmosis device is connected with the softening membrane device and is used for carrying out first reverse osmosis treatment on the second wastewater to obtain first reverse osmosis concentrated water and first reverse osmosis produced water; the limit reverse osmosis device is connected with the first reverse osmosis device and is used for carrying out limit reverse osmosis treatment on the first reverse osmosis concentrated water to obtain limit reverse osmosis concentrated water and limit reverse osmosis fresh water; and the second reverse osmosis device is connected with the limit reverse osmosis device and is used for carrying out second reverse osmosis treatment on the limit reverse osmosis fresh water to obtain second reverse osmosis concentrated water and second reverse osmosis produced water. The high-salinity and high-hardness wastewater concentration system is simple in structure and relatively good in concentration effect.

Description

Technical Field

[0001] The present application relates to the field of wastewater treatment technology, and in particular, to a concentration system and a concentration method for high-salt and high-hardness wastewater. Background Art

[0002] Wastewater generated in industrial production such as electricity, metallurgy, chemical industry, printing and dyeing, and papermaking has the characteristics of high salt content and high hardness. Direct discharge of wastewater will seriously pollute water resources and endanger the natural environment and human living environment. In response to the hazards of industrial wastewater, the "zero emission" treatment process has become the most effective method. The main membrane method for traditional wastewater treatment is reverse osmosis. However, when using reverse osmosis for wastewater treatment, the wastewater needs to be pretreated, and the pretreatment involves a long process and many facilities. At the same time, the concentration and reduction effect of the wastewater is average, resulting in high operating costs. Therefore, one of the current challenges is to develop a wastewater concentration system and concentration method that is efficient, simple in process, and can reduce costs.

[0003] Application Contents

[0004] The present application aims to solve, at least to a certain extent, one of the technical problems in the related art. To this end, one purpose of the present application is to provide a high-salt and high-hardness wastewater concentration system and concentration method, which can be used to treat wastewater with a simple process, less equipment, or better concentration effect.

[0005] In a first aspect of the present application, a concentrating system for high-salt and high-hardness wastewater is proposed, comprising: a decalcification reaction tank for removing calcium from the high-salt and high-hardness wastewater to obtain a first wastewater containing calcium salt precipitates; a softening membrane device connected to the decalcification reaction tank, for filtering the first wastewater to obtain a second wastewater; a first reverse osmosis device connected to the softening membrane device, for performing a first reverse osmosis treatment on the second wastewater to obtain a first reverse osmosis concentrated water and a first reverse osmosis product water; an extreme reverse osmosis device connected to the first reverse osmosis device, for performing an extreme reverse osmosis treatment on the first reverse osmosis concentrated water to obtain extreme reverse osmosis concentrated water and extreme reverse osmosis fresh water; a second reverse osmosis device connected to the extreme reverse osmosis device, for performing a second reverse osmosis treatment on the extreme reverse osmosis fresh water to obtain a second reverse osmosis concentrated water and a second reverse osmosis product water.

[0006] The concentration system removes calcium salts from wastewater through a decalcification reaction tank and a softening membrane device. The resulting second wastewater meets the reverse osmosis requirements and can be directly transported to a reverse osmosis device and a limiting reverse osmosis device for concentration treatment. The salt content of the resulting limiting reverse osmosis concentrated water can reach 18% to 20%, greatly improving the efficiency of wastewater concentration. The fresh water after reverse osmosis treatment can be reused in industrial production. Therefore, the concentration system has a simple process and a good concentration effect.

[0007] In addition, the high-salt and high-hardness wastewater concentration system according to the above embodiment of the present application may also have the following additional technical features:

[0008] In some embodiments of the present application, the softening membrane device includes a softening membrane, and the softening membrane satisfies at least one of the following conditions:

[0009] The pore size of the softening membrane is 10nm to 20nm;

[0010] The material of the softening film includes polytetrafluoroethylene.

[0011] The above-mentioned softening membrane pore size range is conducive to improving the filtration efficiency of the softening membrane, and can remove impurities such as calcium salt precipitation, suspended solids, colloids, etc., without causing clogging of the softening membrane device; and polytetrafluoroethylene has stable chemical properties and is not easily corroded by salt in the wastewater during filtration, thereby ensuring the long-lasting filtration performance of the softening membrane and extending the service life of the softening membrane.

[0012] In some embodiments of the present application, the extreme reverse osmosis device includes an extreme reverse osmosis membrane, and the extreme reverse osmosis membrane satisfies at least one of the following conditions:

[0013] The membrane flux of the limit reverse osmosis membrane is 10L·m - 2 h -1 ~20L·m - 2 h -1 ;

[0014] The rejection rate of the limit reverse osmosis membrane is 60% to 65%;

[0015] The material of the limit reverse osmosis membrane includes modified polyamide.

[0016] The aforementioned extreme reverse osmosis membrane flux range effectively intercepts various salts in wastewater, maintaining a stable desalination rate and contributing to improved wastewater concentration efficiency. Polyamide, with its stable chemical properties and high mechanical strength, ensures a stable membrane structure in wastewaters with varying pH levels. The appropriate membrane flux and suitable membrane material largely determine the membrane's retention rate, thereby influencing the concentration performance of the extreme reverse osmosis device.

[0017] In some embodiments of the present application, the high-salt, high-hardness wastewater concentrating system further includes a first intermediate water tank, disposed between the decalcification reaction tank and the softening membrane device, connected thereto, for receiving the first wastewater and delivering it to the softening membrane device. This helps maintain the stability of the water inflow to the softening membrane device and ensures uniform mixing of the first wastewater before delivery to the softening membrane device, further improving the stability of the water inflow to the softening membrane device.

[0018] In some embodiments of the present application, the high-salt, high-hardness wastewater concentration system further includes a second intermediate water tank disposed between the softening membrane device and the first reverse osmosis device, connected to the softening membrane device and the first reverse osmosis device, configured to receive the second wastewater and deliver the second wastewater to the first reverse osmosis device. This helps maintain the stability of the water inflow to the first reverse osmosis device.

[0019] In some embodiments of the present application, the high-salt, high-hardness wastewater concentrating system further includes a third intermediate water tank disposed between the first reverse osmosis device and the extreme reverse osmosis device, connected to the first reverse osmosis device and the extreme reverse osmosis device, configured to receive the first reverse osmosis concentrate and deliver the first reverse osmosis concentrate to the extreme reverse osmosis device. This helps maintain the stability of the water inflow to the extreme reverse osmosis device.

[0020] In some embodiments of the present application, the high-salt, high-hardness wastewater concentrating system further includes a connecting pipeline connected between the second reverse osmosis device and the third intermediate water tank, for transporting the second reverse osmosis concentrate to the third intermediate water tank. This allows the second reverse osmosis concentrate to be mixed with the first reverse osmosis concentrate, further improving the wastewater concentration effect.

[0021] In some embodiments of the present application, the operating pressure of the extreme reverse osmosis device is less than or equal to 7.5 MPa to 8.5 MPa, thereby helping to reduce the operating cost of the wastewater concentration device and improving the safety of system operation.

[0022] In some embodiments of the present application, the high-salt and high-hardness wastewater concentration system satisfies at least one of the following conditions:

[0023] The salt content in the first wastewater is 10mg / ml to 50mg / ml;

[0024] The calcium salt content in the second wastewater is less than 50 mg / L;

[0025] The salt content of the first reverse osmosis concentrated water is 60mg / ml to 80mg / ml;

[0026] The salt content of the first reverse osmosis produced water is less than 1 mg / ml;

[0027] The salt content of the extreme reverse osmosis concentrated water is 180mg / ml to 200mg / ml;

[0028] The salt content of the extreme reverse osmosis fresh water is 20mg / ml to 50mg / ml;

[0029] The salt content of the second reverse osmosis concentrated water is 50mg / ml to 70mg / ml;

[0030] The salt content of the second reverse osmosis produced water is less than 1 mg / ml.

[0031] This helps each processing link in the concentration system to operate efficiently and stably, further improving the wastewater concentration effect.

[0032] In a second aspect of the present application, a method for concentrating high-salt, high-hardness wastewater is proposed, comprising: precipitating calcium in the high-salt, high-hardness wastewater to obtain a first wastewater containing calcium salt precipitation; filtering the first wastewater using a softening membrane to obtain filter residue and a second wastewater; subjecting the second wastewater to a first reverse osmosis treatment to obtain a first reverse osmosis concentrate and a first reverse osmosis product water; subjecting the first reverse osmosis concentrate to an extreme reverse osmosis treatment to obtain an extreme reverse osmosis concentrate and extreme reverse osmosis fresh water; and subjecting the extreme reverse osmosis fresh water to a second reverse osmosis concentrate to obtain a second reverse osmosis concentrate and a second reverse osmosis product water. This concentration method helps to increase the salt content of the extreme reverse osmosis concentrate after the wastewater concentration treatment, and can make the extreme reverse osmosis concentrate have a higher salt content, thereby reducing the operating cost of wastewater treatment.

[0033] In some embodiments of the present application, the concentration method further includes: mixing the second reverse osmosis concentrated water with the first reverse osmosis concentrated water, and subjecting the obtained mixed concentrated water to the extreme reverse osmosis treatment, thereby further improving the wastewater concentration effect.

[0034] In some embodiments of the present application, the method for concentrating high-salt and high-calcium wastewater is implemented by the aforementioned high-salt and high-calcium wastewater concentration system. Therefore, the concentration method has all the characteristics and advantages of the aforementioned concentration system, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural diagram of a high-salt and high-hardness wastewater concentration system according to an embodiment of the present application.

[0036] Figure 2 It is a structural diagram of a high-salt and high-hardness wastewater concentration system according to an embodiment of the present application.

[0037] Figure 3 It is a flow chart of a method for concentrating high-salt and high-hardness wastewater according to an embodiment of the present application.

[0038] Figure 4 It is a flow chart of a method for concentrating high-salt and high-hardness wastewater according to an embodiment of the present application.

[0039] Reference numerals:

[0040] 1: Decalcification reaction tank 2: First intermediate water tank 3: Softening membrane device 4: Second intermediate water tank 5: First reverse osmosis device 6: Limit reverse osmosis device 7: Third intermediate water tank 8: Second reverse osmosis membrane device 9: Connecting pipeline DETAILED DESCRIPTION

[0041] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and intended to be used to explain the present application, but should not be understood as limiting the present application.

[0042] This application is based on the following findings and knowledge of the applicant:

[0043] As mentioned above, the high-salt and high-hardness wastewater concentration system in the related art includes a pretreatment device and a reverse osmosis device. The pretreatment device includes: a decalcification reaction tank, a sedimentation tank, a multi-media filter, an ultrafiltration device, etc. It can be seen that the pretreatment process is long, occupies a large area, and the device cost is high. It also requires a combination of multiple filter devices for filtration to make the wastewater meet the reverse osmosis requirements; and even at a higher working pressure, the reverse osmosis device has a low salt content in the concentrated water after concentration treatment (such as 10% to 12%), and the wastewater reduction effect is poor, which leads to a large scale and high cost of subsequent evaporation treatment. After further exploration, the applicant found that in the pretreatment stage, the particle size of the calcium salt precipitate obtained by decalcification and some suspended solid impurities, colloidal impurities, etc. contained in the wastewater is relatively large, basically above 0.02 microns. In order to remove these impurities through filtering with less equipment, on the one hand, the pore size of the filter membrane needs to be relatively small to improve the impurity filtration efficiency. Therefore, it is possible to consider setting the pore size of the filter membrane to ≤0.02 microns; on the other hand, considering that the filter membrane filters impurities for a long time, it is easy to cause the filter membrane to become clogged. Therefore, it is possible to consider modifying the filter membrane to make it anti-fouling and hydrophilic, thereby reducing the risk of fouling and clogging. In addition, when the pretreated water is concentrated, considering that the reverse osmosis membrane inlet pressure is proportional to the difference in salt content between the concentrated and produced water, a larger inlet pressure is required when reverse osmosis is performed on high-salt wastewater. Therefore, when the wastewater is reverse osmosis treated, the inlet pressure can be reduced by reducing the salt retention rate, that is, increasing the salt content of the produced water and reducing the difference in salt content between the concentrated and produced water. This requires improving the conventional reverse osmosis membrane to obtain a new reverse osmosis membrane that can reduce the inlet pressure. The new reverse osmosis membrane can be used in combination with the traditional reverse osmosis membrane to reduce the inlet pressure and improve the concentration effect of the wastewater. Based on the above considerations, the applicant has developed a new wastewater concentration system with a simple process, a low working pressure of the reverse osmosis device, and the ability to achieve efficient concentration of high-salt and high-hardness wastewater.

[0044] In the first aspect of the present application, a high-salt and high-hardness wastewater concentration system is proposed, referring to Figure 1, including: a decalcification reaction tank 1, used to remove calcium from high-salt and high-hardness wastewater to obtain first wastewater containing calcium salt precipitation; a softening membrane device 3, connected to the decalcification reaction tank 1, used to filter the first wastewater to obtain second wastewater; a first reverse osmosis device 5, connected to the softening membrane device 3, used to perform a first reverse osmosis treatment on the second wastewater to obtain first reverse osmosis concentrated water and first reverse osmosis product water; a limit reverse osmosis device 6, connected to the first reverse osmosis device 5, used to perform a limit reverse osmosis treatment on the first reverse osmosis concentrated water to obtain limit reverse osmosis concentrated water and limit reverse osmosis fresh water; a second reverse osmosis device 8, connected to the limit reverse osmosis device 6, used to perform a second reverse osmosis treatment on the limit reverse osmosis fresh water to obtain second reverse osmosis concentrated water and second reverse osmosis product water.

[0045] In some embodiments of the present application, the high-salt and high-hardness wastewater is wastewater with a salt content of 1wt% to 5wt% and a hardness of 2g / L to 5g / L. Specifically, the salt content of the high-salt and high-hardness wastewater can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, etc. In some embodiments, the main salts in the high-salt and high-hardness wastewater include Na2SO4, NaCl, CaSO4, MgCl2, etc. The hardness of the high-salt and high-hardness wastewater can be specifically 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, 4.5g / L, 5g / L, etc. In some embodiments, the hardness of the high-salt and high-hardness wastewater can be divided according to the concentration of calcium carbonate, that is, the hardness of the wastewater of 2g / L to 5g / L means that the concentration of calcium carbonate in the wastewater is 2g / L to 5g / L.

[0046] In some embodiments of the present application, the decalcification reaction tank is used to remove calcium from high-salt, high-hardness wastewater. Specific chemical reagents can be added to the decalcification reaction tank to convert soluble calcium salts in the wastewater into calcium salt precipitates, thereby removing calcium from the wastewater. In some embodiments, the chemical reagents that can be used include Na2CO3, NaOH combined with CO2, etc., and the resulting calcium salt precipitate can be CaCO3. This results in better decalcification effects and lower costs.

[0047] In some embodiments, the amount of the chemical reagent added can be calculated based on the calcium salt concentration in the wastewater, and the chemical reagent is added at a molar ratio of calcium salt to chemical reagent of 1:1.2. Specifically, the molar ratio can be 1:1, 1:1.1, 1:1.2, etc., and the reaction is carried out at room temperature for 60 minutes. This allows for more complete calcium removal, and the sodium ions in the chemical reagent can be removed in subsequent treatment.

[0048] In some embodiments of the present application, a softening membrane device can remove impurities such as calcium salt precipitation, suspended solids, and colloids from the first wastewater, producing a filter residue and a second wastewater. The filter residue can be regularly discharged, and the second wastewater can directly meet the requirements of subsequent reverse osmosis treatment. Specifically, the softening membrane has a pore size of 0.02 microns, which can filter and remove the aforementioned impurities, resulting in a sewage clogging index (SDI) of less than 3 for the filtered wastewater, meeting pretreatment requirements.

[0049] In some embodiments of the present application, the salt content in the first wastewater is 10mg / ml to 50mg / ml, specifically, it can be 10mg / ml, 15mg / ml, 20mg / ml, 25mg / ml, 30mg / ml, 35mg / ml, 40mg / ml, 45mg / ml, 50mg / ml, etc. The salt content within the said range is high-salt wastewater, and high-salt wastewater has high requirements for equipment. Traditional wastewater concentration systems are not suitable for the concentration of high-salt wastewater. The high-salt and high-hardness wastewater concentration system can not only treat high-salt and high-calcium wastewater, but also give full play to the wastewater concentration function, so that the wastewater concentration effect is greatly improved.

[0050] In some embodiments of the present application, the softening membrane device includes a softening membrane having a pore size of 10 nm to 20 nm, specifically, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, etc. Within the above range, the filtration efficiency of the softening membrane is improved, and impurities such as calcium salt precipitates such as CaCO3 and CaSO4, suspended solids, and colloids can be trapped. If the pore size of the softening membrane is too small, the softening membrane device may be clogged, and if the pore size of the softening membrane is too large, the filtration efficiency may be reduced.

[0051] In some embodiments of the present application, the surface of the softening membrane has a hydrophilic anti-pollution layer, which can reduce the adsorption or deposition of pollutants in the wastewater on the surface of the softening membrane, prevent the surface of the softening membrane from being blocked and scaled, and keep the pore structure of the softening membrane unobstructed; at the same time, the softening membrane has an internal and external staggered pore size. On the surface of the softening membrane, the pore size is set to 0.02 microns, which can filter a large amount of impurities. The pore size inside the softening membrane is relatively large, so that the wastewater can pass through the softening membrane more smoothly, thereby improving the efficiency and flux of wastewater treatment.

[0052] In some embodiments of the present application, the material of the softening membrane includes polytetrafluoroethylene. Polytetrafluoroethylene, as a hydrophobic material, can effectively prevent water molecules from gathering on the surface of the softening membrane, avoiding clogging of the softening membrane pores due to water adsorption; at the same time, it has strong chemical stability and is not easily corroded by inorganic salts and organic salts in the wastewater during filtration, thereby ensuring the long-lasting filtration performance of the softening membrane and extending the service life of the softening membrane.

[0053] Specifically, the suspended solids in the first wastewater may include slag particles, grease particles, microbial aggregates, metal oxide particles, etc., and the colloids in the first wastewater may include hydroxide colloids, synthetic polymer colloids, colloidal silica, etc.

[0054] In some embodiments of the present application, the calcium salt content in the second wastewater is less than 50 mg / L, specifically, it can be 10 mg / ml, 20 mg / ml, 30 mg / ml, 40 mg / ml, 45 mg / ml, etc. The calcium salt content in the second wastewater within the above range indicates that the decalcification effect is good, which is conducive to the stable operation of subsequent concentration treatment.

[0055] In some embodiments of the present application, the SDI of the second wastewater is less than 1, specifically, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. Thus, the obtained second wastewater can effectively reduce the deposition of particulate pollutants in subsequent treatment steps, and further improve the wastewater concentration efficiency.

[0056] In some embodiments of the present application, the second wastewater obtained after the softening membrane filtration can be further subjected to reverse osmosis treatment to concentrate the wastewater. In order to obtain a better concentration effect, a first reverse osmosis device, an extreme reverse osmosis device and a second reverse osmosis device can be used to sequentially perform the first reverse osmosis treatment, the extreme reverse osmosis treatment and the second reverse osmosis treatment. Specifically, the first reverse osmosis treatment preliminarily concentrates the second wastewater, and the salt content of the first reverse osmosis concentrated water obtained meets the requirements of the extreme reverse osmosis treatment. Then, the extreme reverse osmosis treatment can be further concentrated to obtain extreme reverse osmosis concentrated water with an extremely high salt content (such as 18% to 20%). This can greatly improve the concentration effect, and the wastewater reduction effect is significantly improved. The subsequent evaporation treatment of the extreme reverse osmosis concentrated water is small in scale and low in cost, while the salt content of the extreme reverse osmosis fresh water is still relatively high. It can be further subjected to a second reverse osmosis treatment, and the second reverse osmosis product water obtained can be directly reused in industrial production, and the second reverse osmosis concentrated water obtained

[0057] In some embodiments of the present application, the first reverse osmosis device can concentrate the second wastewater to obtain first reverse osmosis concentrated water with a higher salt content and first reverse osmosis produced water with a lower salt content.

[0058] Herein, the first reverse osmosis produced water refers to water having a total dissolved solids concentration of less than 1000 mg / L. The first reverse osmosis produced water having the above-mentioned salt content can be directly reused in industrial production.

[0059] In some embodiments of the present application, the first reverse osmosis device includes a first reverse osmosis membrane, and the membrane flux of the first reverse osmosis membrane is 15 L·m - 2 h -1 ~20L·m- 2 h -1 , specifically, it can be 15L·m - 2 h -1 、16L·m - 2 h -1 、17L·m - 2 h -1 、18L·m - 2 h -1 、19L·m - 2 h -1 、20L·m - 2 h -1 The above membrane flux range can perform preliminary reverse osmosis treatment on the second wastewater, and at the same time make the salt content in the first reverse osmosis concentrated water meet the requirements of the limit reverse osmosis device. If the membrane flux is too large, the salt content in the first reverse osmosis concentrated water will be low, which will not reach the salt concentration required by the limit reverse osmosis device. If the membrane flux is too small, it will easily cause blockage of the first reverse osmosis membrane.

[0060] In some embodiments of the present application, the material of the first reverse osmosis membrane includes polyamide. Polyamide has stable chemical properties and can ensure the stability of the membrane structure in wastewater with different pH values (pH = 3 to 12). At the same time, polyamide has high mechanical strength and can withstand the high-pressure environment during the operation of the wastewater concentration system.

[0061] In some embodiments of the present application, the rejection rate of the first reverse osmosis membrane is above 95%, thereby helping to improve the concentration effect of the first reverse osmosis.

[0062] In some embodiments of the present application, the salt content of the first reverse osmosis concentrated water is 60 mg / ml to 80 mg / ml, specifically, it can be 60 mg / ml, 65 mg / ml, 70 mg / ml, 75 mg / ml, 80 mg / ml, etc. The salt content of the first reverse osmosis concentrated water within the above range helps to improve the wastewater concentration effect. If the salt content of the first reverse osmosis concentrated water is too low, it cannot meet the salt intake requirement of the ultimate reverse osmosis device. If the salt content of the first reverse osmosis concentrated water is too high, the process requirements for the first reverse osmosis membrane will also be higher.

[0063] In some embodiments of the present application, the salt content of the first reverse osmosis produced water is less than 1 mg / ml, specifically, it can be 0.1 mg / ml, 0.2 mg / ml, 0.3 mg / ml, 0.4 mg / ml, 0.5 mg / ml, 0.6 mg / ml, 0.7 mg / ml, 0.8 mg / ml, 0.9 mg / ml, 1 mg / ml, etc. Water with a salt content within this range can be directly reused in industrial production, thereby effectively recycling wastewater, helping to reduce wastewater discharge and being green and environmentally friendly.

[0064] In some embodiments of the present application, the extreme reverse osmosis device can further concentrate the first reverse osmosis concentrated water to obtain extreme reverse osmosis concentrated water with a higher salt content and extreme reverse osmosis fresh water with a relatively low salt content.

[0065] In some embodiments of the present application, the limit reverse osmosis device includes a limit reverse osmosis membrane, and the membrane flux of the limit reverse osmosis membrane is 10 L·m - 2 h -1 ~20L·m - 2 h -1 Specifically, it can be 10L·m - 2 h -1 、11L·m - 2 h -1 、12L·m - 2 h -1 、13L·m - 2 h -1 、14L·m - 2 h -1 、15L·m - 2 h -1 、16L·m - 2 h -1 、17L·m - 2 h -1 、18L·m - 2 h -1 、19L·m - 2 h -1 、20L·m - 2 h -1 The membrane flux range of the aforementioned extreme reverse osmosis membrane enables a rejection rate of 60% to 65% for the extreme reverse osmosis device, effectively intercepting various salts in the wastewater while maintaining a relatively low salinity difference across the membrane. This allows the device to operate stably at a low operating pressure and achieve excellent concentration results. Excessive membrane flux of the extreme reverse osmosis membrane reduces the reverse osmosis effect, while too low a flux results in a high rejection rate, a large salinity difference across the membrane, and the required operating pressure is excessive.

[0066] Specifically, the operating pressure of the extreme reverse osmosis device depends on the salt difference on both sides of the extreme reverse osmosis membrane. The larger the difference, the greater the required operating pressure. The retention rate of the extreme reverse osmosis membrane is 60% to 65%. While ensuring the reverse osmosis effect of wastewater, the salt difference on both sides of the membrane can be made appropriate, so that the operating pressure required by the extreme reverse osmosis membrane device is relatively low.

[0067] In some embodiments of the present application, the operating pressure of the extreme reverse osmosis device is 7.5 MPa to 8.5 MPa, specifically, 7.5 MPa, 7.6 MPa, 7.7 MPa, 7.8 MPa, 7.9 MPa, 8.0 MPa, 8.1 MPa, 8.2 MPa, 8.3 MPa, 8.4 MPa, 8.5 MPa, etc. This helps reduce the operating cost of the wastewater concentration device and improves the safety of system operation.

[0068] In some embodiments of the present application, the material of the limiting reverse osmosis membrane includes modified polyamide. Polyamide has stable chemical properties and can ensure the stability of the membrane structure in wastewater with different pH values (pH = 3-12). Polyamide also has high mechanical strength and can withstand the high pressure environment during operation of the wastewater concentration system.

[0069] In some embodiments of the present application, the salt content of the extreme reverse osmosis concentrated water is 180mg / ml to 200mg / ml, specifically, it can be 180mg / ml, 183mg / ml, 185mg / ml, 187mg / ml, 190mg / ml, 193mg / ml, 195mg / ml, 197mg / ml, 200mg / ml, etc. The extreme reverse osmosis concentrated water can be directly collected within the above range for subsequent treatment of concentrated wastewater, which helps to reduce the scale of evaporation, thereby reducing project investment and operating costs. If the salt content of the extreme reverse osmosis concentrated water is too high, the process requirements for the extreme reverse osmosis membrane will be high, and the required operating pressure will be too high. If the salt content of the extreme reverse osmosis concentrated water is too low, the scale of subsequent treatment of concentrated wastewater will be large and the cost will be high.

[0070] In some embodiments of the present application, the salt content of the extreme reverse osmosis fresh water is 20 mg / ml to 50 mg / ml, specifically, it can be 20 mg / ml, 25 mg / ml, 30 mg / ml, 35 mg / ml, 40 mg / ml, 45 mg / ml, 50 mg / ml, etc., which helps to further improve the concentration effect of wastewater and realize efficient operation of the entire wastewater concentration system. If the salt content of the extreme reverse osmosis fresh water is too high, the concentration effect of the extreme reverse osmosis device will be deteriorated. If the salt content of the extreme reverse osmosis fresh water is too low, the operating pressure of the extreme reverse osmosis device will be too high.

[0071] In some embodiments of the present application, the second reverse osmosis device can further concentrate the limited reverse osmosis fresh water to obtain second reverse osmosis concentrated water with a higher salt content and second reverse osmosis produced water with a lower salt content.

[0072] Herein, the second reverse osmosis product water refers to water with a total dissolved solids concentration of less than 1000 mg / L. The second reverse osmosis product water with the above-mentioned salt content can meet the requirements of direct recycling, such as direct use as industrial water.

[0073] In some embodiments of the present application, the second reverse osmosis device includes a second reverse osmosis membrane, and the membrane flux of the second reverse osmosis membrane is 15 L·m - 2 h -1 ~20L·m - 2 h -1 , specifically, it can be 15L·m - 2 h -1 、16L·m - 2 h -1 、17L·m - 2 h -1 、18L·m - 2 h -1 、19L·m - 2 h -1 、20L·m - 2 h -1 The above membrane flux range can further increase the salt content in the limit reverse osmosis fresh water, which is helpful to improve the concentration effect. If the membrane flux of the second reverse osmosis membrane is too large, it will lead to poor osmosis effect, and if the membrane flux is too small, it will easily cause the blockage of the second reverse osmosis membrane.

[0074] In some embodiments of the present application, the material of the second reverse osmosis membrane includes polyamide. Polyamide has stable chemical properties and can ensure the stability of the membrane structure in wastewater with different pH values (pH = 3 to 12). At the same time, polyamide has high mechanical strength and can withstand the high-pressure environment during the operation of the wastewater concentration system.

[0075] In some embodiments of the present application, the rejection rate of the second reverse osmosis membrane is above 95%, thereby helping to improve the concentration effect of the second reverse osmosis.

[0076] In some embodiments of the present application, the salt content of the second reverse osmosis concentrated water is 50 mg / ml to 70 mg / ml, specifically, it can be 50 mg / ml, 55 mg / ml, 60 mg / ml, 65 mg / ml, 70 mg / ml, etc. The salt content of the second reverse osmosis concentrated water within the above range can meet the salt intake requirements of the extreme reverse osmosis device, which helps to further improve the concentration effect.

[0077] In some embodiments of the present application, the salt content of the second reverse osmosis produced water is less than 1 mg / ml, specifically, it can be 0.1 mg / ml, 0.2 mg / ml, 0.3 mg / ml, 0.4 mg / ml, 0.5 mg / ml, 0.6 mg / ml, 0.7 mg / ml, 0.8 mg / ml, 0.9 mg / ml, 1 mg / ml, etc. Water with a salt content within this range can be directly reused in industrial production, thereby effectively recycling wastewater, helping to reduce wastewater discharge and being green and environmentally friendly.

[0078] In some embodiments of the present application, reference is made to Figure 2 The high-salt and high-hardness wastewater concentration system also includes: a first intermediate water tank 2, which is arranged between the decalcification reaction tank 1 and the softening membrane device 3, connected to the decalcification reaction tank 1 and the softening membrane device 3, and is used to receive the first wastewater and transport the first wastewater to the softening membrane device 3. Due to different water qualities and different working conditions, the production volume of the first wastewater may be uneven. The first intermediate water tank can store a certain amount of the first wastewater. When the production volume of the first wastewater is greater than the processing capacity of the subsequent treatment device, it plays a role in storage and regulation to avoid overflow of the first wastewater, thereby helping to maintain the stability of the water inlet of the softening membrane device. In addition, the first wastewater contains a large amount of impurities such as precipitation and suspended solids. The first intermediate water tank can perform preliminary precipitation and interception of precipitation, suspended solids, etc. in the wastewater, thereby improving the efficiency of subsequent filtration.

[0079] In some embodiments of the present application, reference is made to Figure 2 The high-salt, high-hardness wastewater concentration system also includes a second intermediate water tank 4, located between and connected to the softening membrane device 3 and the first reverse osmosis device 5, for receiving the second wastewater and delivering it to the first reverse osmosis device. This helps maintain the stability of the water inflow to the first reverse osmosis device. Furthermore, the mixing effect of the second intermediate water tank allows the second wastewater, filtered by the softening membrane device, to be evenly mixed, resulting in relatively stable water quality entering the first reverse osmosis device, thereby improving treatment efficiency and stability.

[0080] In some embodiments of the present application, reference is made to Figure 2 The high-salinity, high-hardness wastewater concentrating system also includes a third intermediate water tank 7, located between the first reverse osmosis unit 5 and the extreme reverse osmosis unit 6. The third intermediate water tank 7 is connected to both units and receives the first reverse osmosis concentrate and delivers it to the extreme reverse osmosis unit. This helps maintain the stability of the water inflow to the extreme reverse osmosis unit and improves the quality of the first reverse osmosis concentrate, further enhancing the treatment efficiency of the extreme reverse osmosis unit.

[0081] In some embodiments of the present application, the high-salt, high-hardness wastewater concentrating system further includes a connecting pipe 9 connected between the second reverse osmosis device 8 and the third intermediate water tank 7, for conveying the second reverse osmosis concentrate to the third intermediate water tank. This allows the second reverse osmosis concentrate to be mixed with the first reverse osmosis concentrate, further improving the wastewater concentration effect.

[0082] In the second aspect of the present application, a method for concentrating high-salt and high-hardness wastewater is proposed, referring to Figure 3 , the method comprises the following steps:

[0083] S10: precipitating calcium in the high-salt and high-hardness wastewater to obtain first wastewater containing calcium salt precipitate.

[0084] In this step, specific chemical agents are added to the high-salt and high-hardness wastewater to cause a chemical reaction, thereby converting the soluble calcium salt in the wastewater into calcium salt precipitate.

[0085] S20: Filtering the first wastewater using a softening membrane to obtain filter residue and second wastewater.

[0086] In this step, the first wastewater containing calcium salt precipitation obtained above is filtered using a softening membrane to obtain filter residue and second wastewater. The filter residue is centrally processed so that it does not participate in subsequent steps.

[0087] S30: performing a first reverse osmosis treatment on the second wastewater to obtain a first reverse osmosis concentrated water and a first reverse osmosis product water.

[0088] In this step, the wastewater is subjected to a first reverse osmosis treatment to concentrate the salt in the wastewater on the concentrated water side, thereby preliminarily concentrating the second wastewater, and the first reverse osmosis product water is directly reused for industrial production.

[0089] S40: subjecting the first reverse osmosis concentrated water to extreme reverse osmosis treatment to obtain extreme reverse osmosis concentrated water and extreme reverse osmosis fresh water.

[0090] In this step, the first reverse osmosis concentrated water is pressurized by a pump to a limit reverse osmosis device for limit reverse osmosis treatment to further concentrate the first reverse osmosis concentrated water.

[0091] S50: performing a second reverse osmosis treatment on the extreme reverse osmosis fresh water to obtain a second reverse osmosis concentrated water and a second reverse osmosis product water.

[0092] In this step, the extreme reverse osmosis fresh water is pressurized by a pump to the second reverse osmosis device for a second reverse osmosis treatment, and the extreme reverse osmosis fresh water is further concentrated to obtain second reverse osmosis concentrated water and second reverse osmosis produced water, which is directly reused for industrial production.

[0093] In some embodiments of the present application, reference is made to Figure 4 , the concentration method further comprises:

[0094] S60: mixing the second reverse osmosis concentrated water with the first reverse osmosis concentrated water, and subjecting the obtained mixed concentrated water to the extreme reverse osmosis treatment.

[0095] In this step, the second reverse osmosis concentrate and the first reverse osmosis concentrate are mixed evenly, and the mixed concentrate is pumped to the extreme reverse osmosis device for extreme reverse osmosis treatment, thereby further improving the wastewater concentration effect.

[0096] The concentrated water obtained according to the method for concentrating high-salt and high-hardness wastewater of the present application can be subsequently treated by membrane distillation and evaporation crystallization.

[0097] By treating high-salt and high-hardness wastewater through the high-salt and high-calcium wastewater concentration method of the present application, the salt content of the final concentrated water can reach 18% to 20%, which largely solves the problem of requiring complex concentration processes and high costs to achieve the purpose of efficient concentration.

[0098] It can be understood that the method for concentrating high-salt and high-hard wastewater of the present application can be implemented by the high-salt and high-hard wastewater concentration system described above. The specific operations, types of substances, performance parameters, etc. involved in each step involved in the method for concentrating high-salt and high-hard wastewater can be consistent with the description in the high-salt and high-hard wastewater concentration system mentioned above, and will not be repeated here.

[0099] The present application is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present application in any way. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in the product instructions shall be followed.

[0100] Example 1

[0101] The high-salt and high-hardness wastewater concentration system and method of the present application are used to concentrate metal smelting wastewater, specifically as follows:

[0102] Provided wastewater: wastewater generated by copper smelting enterprises, the salt content of the wastewater is 2wt%, the calcium concentration is 800mg / L, and the hardness is 2g / L.

[0103] Decalcification: The above wastewater is discharged into the decalcification reaction tank of the wastewater concentration system of the present application, and an appropriate amount of NaOH is added to the decalcification reaction tank and stirring is started, maintaining the pH = 9, while CO2 gas is introduced into the wastewater and reacted at room temperature for 60 minutes.

[0104] Softened membrane filtration: The pore size of the softened membrane is 0.02 microns and the material is modified polytetrafluoroethylene.

[0105] The second wastewater has a salt content of 1.5 wt%, a calcium salt content of 30 mg / L, and an SDI of 3.

[0106] First reverse osmosis treatment: The membrane flux of the first reverse osmosis membrane is 18L·m - 2 h -1 The first reverse osmosis treatment process has a working pressure of 7 MPa, and the salt content of the first reverse osmosis concentrated water is 6 wt%, and the salt content of the first reverse osmosis produced water is less than 1000 mg / mL.

[0107] Extreme reverse osmosis treatment: The membrane flux of the extreme reverse osmosis membrane is 20L·m - 2 h -1 The material is modified polyamide. The maximum reverse osmosis working pressure is 7 MPa and the maximum reverse osmosis fresh water salt content is 2 wt%.

[0108] Second reverse osmosis treatment: The membrane flux of the second reverse osmosis membrane is 18L·m - 2 h -1 The second reverse osmosis treatment process has a working pressure of 7 MPa, and the salt content of the second reverse osmosis concentrated water is 6 wt%, and the salt content of the second reverse osmosis produced water is less than 1000 mg / mL.

[0109] The salt content of the concentrated water finally collected after the high-salt and high-calcium wastewater is concentrated is 20wt%.

[0110] Related test methods:

[0111] Testing method for wastewater hardness: EDTA complexometric titration.

[0112] Test method for calcium concentration in wastewater: atomic absorption spectrometry.

[0113] Test method for salt concentration in wastewater: gravimetric method.

[0114] Wastewater SDI test method: Standard SDI test.

[0115] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0116] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", 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 application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0117] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A high-salt and high-hardness wastewater concentration system, characterized in that: include: A decalcification reaction tank is used to remove calcium from high-salt and high-hardness wastewater to obtain first wastewater containing calcium salt precipitation; a softening membrane device, connected to the decalcification reaction tank, for filtering the first wastewater to obtain second wastewater; a first reverse osmosis device, connected to the softening membrane device, for performing a first reverse osmosis treatment on the second wastewater to obtain a first reverse osmosis concentrated water and a first reverse osmosis product water; an extreme reverse osmosis device, connected to the first reverse osmosis device, for performing extreme reverse osmosis treatment on the first reverse osmosis concentrated water to obtain extreme reverse osmosis concentrated water and extreme reverse osmosis fresh water; The second reverse osmosis device is connected to the extreme reverse osmosis device and is used to perform a second reverse osmosis treatment on the extreme reverse osmosis fresh water to obtain a second reverse osmosis concentrated water and a second reverse osmosis product water.

2. The concentration system according to claim 1, characterized in that The softening membrane device includes a softening membrane, and the softening membrane satisfies at least one of the following conditions: The pore size of the softening membrane is 10nm to 20nm; The material of the softening film includes polytetrafluoroethylene.

3. The concentration system according to claim 1, characterized in that The extreme reverse osmosis device includes an extreme reverse osmosis membrane, and the extreme reverse osmosis membrane satisfies at least one of the following conditions: The membrane flux of the limit reverse osmosis membrane is 10L·m - 2 h -1 ~320L·m - 2 h -1 ; The rejection rate of the limit reverse osmosis membrane is 60% to 65%; The material of the limit reverse osmosis membrane includes modified polyamide.

4. The concentration system according to claim 1, characterized in that Also includes at least one of the following: a first intermediate water tank, disposed between the decalcification reaction tank and the softening membrane device, connected to the decalcification reaction tank and the softening membrane device, for receiving the first wastewater and delivering the first wastewater to the softening membrane device; a second intermediate water tank, disposed between the softening membrane device and the first reverse osmosis device, connected to the softening membrane device and the first reverse osmosis device, for receiving the second wastewater and delivering the second wastewater to the first reverse osmosis device; The third intermediate water tank is arranged between the first reverse osmosis device and the extreme reverse osmosis device, connected to the first reverse osmosis device and the extreme reverse osmosis device, and is used to receive the first reverse osmosis concentrated water and transport the first reverse osmosis concentrated water to the extreme reverse osmosis device.

5. The concentration system according to claim 4, characterized in that Also includes: A connecting pipeline is connected between the second reverse osmosis device and the third intermediate water tank, and is used to transport the second reverse osmosis concentrated water to the third intermediate water tank.

6. The concentration system according to claim 1, characterized in that The operating pressure of the extreme reverse osmosis device is less than or equal to 7.5 MPa to 8.5 MPa.

7. The concentration system according to claim 1, characterized in that Meet at least one of the following conditions: The salt content in the first wastewater is 10mg / ml to 50mg / ml; The calcium salt content in the second wastewater is less than 50 mg / L; The salt content of the first reverse osmosis concentrated water is 60mg / ml to 80mg / ml; The salt content of the first reverse osmosis produced water is less than 1 mg / ml; The salt content of the extreme reverse osmosis concentrated water is 180mg / ml to 200mg / ml; The salt content of the extreme reverse osmosis fresh water is 20mg / ml to 50mg / ml; The salt content of the second reverse osmosis concentrated water is 50mg / ml to 70mg / ml; The salt content of the second reverse osmosis produced water is less than 1 mg / ml.

8. A method for concentrating high-salt and high-hardness wastewater, characterized in that: include: precipitating calcium in the high-salt and high-hardness wastewater to obtain first wastewater containing calcium salt precipitation; filtering the first wastewater using a softening membrane to obtain filter residue and second wastewater; performing a first reverse osmosis treatment on the second wastewater to obtain a first reverse osmosis concentrated water and a first reverse osmosis produced water; The first reverse osmosis concentrated water is subjected to extreme reverse osmosis treatment to obtain extreme reverse osmosis concentrated water and extreme reverse osmosis fresh water; The extreme reverse osmosis fresh water is subjected to a second reverse osmosis treatment to obtain a second reverse osmosis concentrated water and a second reverse osmosis product water.

9. The concentration method according to claim 8, characterized in that Also includes: The second reverse osmosis concentrated water is mixed with the first reverse osmosis concentrated water, and the obtained mixed concentrated water is subjected to the extreme reverse osmosis treatment.

10. The concentration method according to claim 8, characterized in that The concentration is carried out by the concentration system according to any one of claims 1 to 7.

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