System and method for acid-base synergistic regulation of reverse osmosis concentrated water purification and solid waste utilization

Abstract

The application discloses an acid-alkali synergistically controlled reverse osmosis concentrated water purification and solid waste utilization system, which comprises a filtering device, and the output end of the filtering device is sequentially connected with a reverse osmosis device, a first pH adjusting tank, a first sedimentation and filtration tank, a second pH adjusting tank, a second sedimentation and filtration tank, a pH readjusting tank and a filter; further comprising a first filter press and a second filter press; the input end of the first filter press is communicated with the first sedimentation and filtration tank, and the output end is communicated with the input end of the first pH adjusting tank; the input end of the second filter press is communicated with the second sedimentation and filtration tank, and the output end is communicated with the input end of the second pH adjusting tank. The system has the advantages of simple structure, low medicament cost, step-by-step removal of silicon and hardness, waste treatment by waste, and efficient removal of silicon and hardness in reverse osmosis concentrated brine. An acid-alkali synergistically controlled reverse osmosis concentrated water purification and solid waste utilization method is further disclosed.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, specifically relating to an acid-base synergistic regulation system for reverse osmosis concentrate purification and solid waste utilization, and also to a method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization. Background Technology

[0002] As my country's primary energy source, coal generates a large amount of "three wastes" (fly ash, mine water / desulfurization wastewater, and flue gas / coal chemical waste gas) during its mining, processing, and power generation. Among these, the annual emissions of fly ash from power plants exceed 600 million tons, the annual emissions of mine water discharged from coal mines reach billions of cubic meters, and the CO2 emissions from power plant flue gas and coal chemical waste gas account for more than 40% of the total industrial emissions. The accumulation and discharge of these "three wastes" not only occupy a large amount of land resources but also cause ecological and environmental problems such as water pollution, air pollution, and soil salinization, thus hindering the green and low-carbon transformation and development of the coal industry.

[0003] Currently, the main technical process for zero-discharge treatment of mine water is "pretreatment + membrane concentration + secondary concentration + evaporation pretreatment + evaporation crystallization". During mine water operation, to prevent reverse osmosis and evaporator scaling, it is necessary to remove silicon and calcium / magnesium hardness ions from the mine water. Current methods for calcium / magnesium ion removal include scale inhibitor methods, chemical precipitation methods, and ion exchange methods. Silicon removal methods include precipitation removal, metal oxide adsorption removal, seed crystal precipitation removal, ion exchange removal, and electrocoagulation removal. Chemical precipitation methods require pH adjustment, consume large amounts of NaOH, CaO, and H2SO4, increasing water treatment costs, and introduce salt ions throughout the treatment process.

[0004] A patent application published on March 1, 2022, with publication number CN114105376A, discloses an electrochemical method for removing hardness from coal gasification ash water with high hardness and low carbonate alkalinity. This method utilizes carbon dioxide emitted from coal chemical processes to supplement inorganic carbon into the high-hardness, low-carbonate alkalinity coal gasification ash water. It employs an electrochemical hardening method primarily based on diaphragm electrolysis, supplemented by alkali supplementation, to improve the electrochemical hardening effect, reduce energy consumption, alleviate scaling problems in coal gasification systems, and achieve water conservation and emission reduction in coal gasification systems. However, this method suffers from complex operation procedures and unsatisfactory electrochemical performance under high-salt conditions.

[0005] A patent published on December 8, 2017, with publication number CN107445334A, discloses a reverse osmosis concentrate softening and desiliconization treatment process. This process includes a raw water collection tank, a first reaction tank, a second reaction tank, a concentration tank, a tubular membrane system, and a clear water tank, all connected sequentially by pipes. The effluent boasts high quality, low energy consumption, and high efficiency, with energy consumption per ton of water lower than conventional softening and desiliconization processes. However, in practice, this method involves large amounts of added acids and alkalis, increasing the salt ion content in subsequent treatment processes. In zero-discharge / near-zero-discharge processes, the removal of silicon and hardness from reverse osmosis concentrate faces challenges such as high reagent costs, large acid and alkali consumption, complex sludge composition making resource recovery difficult, and interference from multiple ion synergistic removal processes leading to fluctuations in effluent quality. Existing technologies using "waste-to-waste" methods simply replace acids and alkalis, resulting in poor reaction controllability, increased impurities, and significant sludge growth. This invention addresses the issue of "precise control and synergistic efficiency in the waste-to-waste process." Summary of the Invention

[0006] The first objective of this invention is to provide an acid-base synergistic regulation system for reverse osmosis concentrate purification and solid waste utilization. This system has a simple structure, low reagent cost, and removes silicon and hardness in stages, thus treating waste with waste and achieving efficient removal of silicon and hardness from reverse osmosis concentrated brine.

[0007] Another objective of this invention is to provide a method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization, which utilizes industrial alkaline solid waste and industrial acidic waste gas to achieve efficient removal of silicon and hardness from reverse osmosis concentrated brine.

[0008] The first technical solution adopted in this invention is an acid-base synergistic regulation reverse osmosis concentrate purification and solid waste utilization system, including a filtration device. The output end of the filtration device is connected in sequence to the reverse osmosis device, a primary pH adjustment tank, a primary sedimentation filtration tank, a secondary pH adjustment tank, a secondary sedimentation filtration tank, a pH adjustment tank, and a filter. It also includes a first filter press and a second filter press; the input end of the first filter press is connected to the primary sedimentation and filtration tank, and the output end is connected to the input end of the primary pH adjustment tank; the input end of the second filter press is connected to the secondary sedimentation and filtration tank, and the output end is connected to the input end of the secondary pH adjustment tank.

[0009] The invention is further characterized in that: It also includes a recycled water tank, which is connected to the reverse osmosis unit.

[0010] Another technical solution adopted in this invention is a method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization, which employs the above-mentioned system, specifically as follows: Step 1: Treat industrial wastewater with reverse osmosis to obtain reverse osmosis concentrate; Step 2: Remove silica from the obtained reverse osmosis concentrate; Step 3: Remove calcium and magnesium from the desiliconized water obtained in Step 2, and remove the silicon that was not removed in the previous process. Step 4: Send the permeate obtained in Step 3 to adjust the pH value; Step 5: The sludge generated in Step 2 and Step 3 is concentrated by pressure filtration.

[0011] The invention is further characterized in that: Step 1 is as follows: After the industrial wastewater is filtered to remove suspended solids and impurities, the permeate is sent to the reverse osmosis unit. After the permeate is separated by the reverse osmosis membrane, it is sent to the reuse water tank for reuse. The reverse osmosis concentrate enters the primary pH adjustment tank. In step 1, the recovery rate of the filtration device is 90-100%. The filtration device is one or a combination of organic ultrafiltration membrane, inorganic ultrafiltration membrane, microfiltration membrane, multi-media filter, and tubular membrane. The filtration method is internal pressure or external pressure, and the operating pressure is 0.1MPa-1MPa. In step 1, the recovery rate of the reverse osmosis membrane is 50-90%, the operating pressure is 0-5 MPa, the Langerile saturation index of calcium carbonate on the concentrate side of the reverse osmosis membrane is 2.0-7.0, and a scale inhibitor is added during the reverse osmosis membrane concentration process. The scale inhibitor is a phosphorus-free scale inhibitor or a polymer scale inhibitor. The concentration of the scale inhibitor in the industrial wastewater in the filtration device is 1 mg / L-20 mg / L.

[0012] Step 2 is as follows: After the reverse osmosis concentrate passes through the primary pH adjustment tank, the pH is raised by alkaline solid waste leaching and then enters the primary sedimentation and filtration tank. The aluminum salt ions dissolved in the primary sedimentation and filtration tank are desiliconized. The sludge produced by desiliconization is sent to the first filter press, and the permeate is sent to the secondary pH adjustment tank. In step 2, the primary pH adjustment tank is filled with industrial aluminum-based alkaline solid waste. The pH value of the effluent from the primary pH adjustment tank is 8 to 12, the retention time of the concentrate is 0.5 h to 5 h, and the filling height of the alkaline solid waste is 10 to 90% of the tank depth.

[0013] Step 3 specifically involves: sending the desiliconized wastewater into a secondary pH adjustment tank, where the pH value is increased by alkaline solid waste leachate before it enters a secondary sedimentation and filtration tank. Sodium carbonate is added in the secondary sedimentation and filtration tank for calcium and OH removal. - The calcium and magnesium ions react to form magnesium hydroxide precipitate. The sludge produced from calcium and magnesium removal is sent to the second filter press, and the permeate is sent to the pH adjustment tank. At the same time, the silicon that was not removed at the front end is further removed by the generated magnesium hydroxide. In step 3, the secondary pH adjustment tank is filled with alkaline solid waste, which is one or more of steel slag, carbide slag, fly ash and phosphogypsum in any mass ratio combination. The pH value of the effluent from the secondary pH adjustment tank is 10-14, the retention time of the concentrate is 0.5-5 hours, and the filling height of the alkaline solid waste is 10-90% of the tank depth. In step 3, sodium carbonate is added to the secondary sedimentation filter tank at a mass ratio of carbonate to calcium ions of 1 to 5:1, and the reaction sedimentation time of the concentrated water is 0.5 to 5 hours.

[0014] Step 4 specifically involves: sending the permeate from the secondary sedimentation and filtration tank into the pH adjustment tank; aerating the pH adjustment tank and introducing industrial acidic wastewater to adjust the pH of the wastewater to the neutral range, and then sending it into the filter to remove suspended solids from the wastewater; In step 4, the pH value of the effluent from the pH adjustment tank is 7-9, and the industrial acidic waste gas introduced is coal chemical off-gas, industrial carbon dioxide waste gas, flue gas before desulfurization, flue gas after desulfurization, hydrogen chloride, SO2 or SO3.

[0015] Step 5 specifically involves: the first filter press filtration and concentration of the sludge produced by the primary sedimentation and filtration tank, the dewatered sludge being transported off-site for treatment, and the filtrate being returned to the corresponding primary pH adjustment tank for repeated treatment. The second filter press concentrates the sludge produced by the secondary sedimentation and filtration tank, and the sludge produced by dewatering is transported off-site for treatment. The filtrate is returned to the corresponding secondary pH adjustment tank in the previous stage for repeated treatment.

[0016] In step 5, the sludge produced by the first and second filter presses has a moisture content of 30-70%.

[0017] The beneficial effects of this invention are: (1) The system of the present invention achieves integrated removal of silicon and hardness in reverse osmosis concentrate through two-stage pH adjustment and two-stage precipitation filtration. First, the pH value is adjusted to a suitable condition for silicon precipitation through the first-stage pH adjustment tank. After silicon precipitation, the pH value is further increased through the second-stage pH adjustment tank to remove magnesium hardness. Then, silicon is further removed through magnesium hydroxide. This achieves step-by-step pH adjustment, saves reagents, and has a reasonable process, achieving efficient and simultaneous removal of silicon and hardness.

[0018] (2) In the method of the present invention, the pH value is adjusted by alkaline solid waste through two-stage pH adjustment. On the one hand, it saves the cost of purchased reagents, and on the other hand, it can remove the alkalinity of alkaline solid waste to lay the foundation for the next application. The pH value is adjusted by industrial acidic waste gas in the pH adjustment tank, which can reduce the discharge of industrial acidic waste gas. It achieves two goals at once, realizes the advantages of treating waste with waste and recycling waste, and meets the requirements of green and low-carbon production.

[0019] (3) In the process of removing silicon and hardness from reverse osmosis concentrate, the method of the present invention does not require the purchase of acids and alkalis. It uses industrial alkaline solid waste and industrial acidic waste gas as raw materials, realizing the recycling of waste materials. While reducing the consumption of reagents in the wastewater treatment process, it also reduces the emission of solid waste and harmful gases from enterprises, and achieves efficient removal of silicon and hardness from concentrated brine.

[0020] (4) The method of the present invention adjusts the pH value stepwise, which is not a simple two-stage alkali adjustment, but a "gradient destabilization": the first-stage alkali adjustment to a specific range (pH value of 8 to 12) preferentially achieves the removal of silicon, and the second-stage alkali adjustment to a higher range (pH value of 10 to 14) promotes the efficient precipitation of hardness ions. Moreover, the timing of the addition of alkaline solid waste in the second stage synergistically forms with the residual reagent in the first-stage effluent. This reduces the amount of alkali used to adjust the pH value, and the silicon that is not removed in the first-stage sedimentation filter can be further removed in the second-stage sedimentation filter through the formation of Mg(OH)2. On the one hand, magnesium ions in the wastewater can be used as a reagent, and on the other hand, the removal effect of silicon can be improved.

[0021] (5) The industrial acidic waste gas used in the method of the present invention is a mixed waste gas. The multi-acidic components such as CO2 / HCl / SO2 in the waste gas are used to rebuild the buffer system in the pH adjustment tank, so as to avoid pH overshoot and local corrosion caused by strong acid adjustment. The filtrate is returned to the front end of the over-adjustment tank, which can dilute and control the ion concentration and reuse the residual reagents. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the system of the present invention; In the diagram, 1. Filtration device, 2. Reverse osmosis device, 3. Primary pH adjustment tank, 4. Primary sedimentation and filtration tank, 5. Secondary pH adjustment tank, 6. Secondary sedimentation and filtration tank, 7. pH adjustment tank, 8. Filter, 9. Reclaimed water tank, 10. First filter press, 11. Second filter press. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0024] This invention provides an acid-base synergistic regulation system for reverse osmosis concentrate purification and solid waste utilization, such as... Figure 1 As shown, the system includes a filtration device 1, the output of which is sequentially connected to a reverse osmosis device 2, a primary pH adjustment tank 3, a primary sedimentation filter tank 4, a secondary pH adjustment tank 5, a secondary sedimentation filter tank 6, a pH adjustment tank 7, and a filter 8; it also includes a first filter press 10 and a second filter press 11; the input end of the first filter press 10 is connected to the primary sedimentation filter tank 4, and the output end of the first filter press 10 is connected to the input end of the primary pH adjustment tank 3; the input end of the second filter press 11 is connected to the secondary sedimentation filter tank 6, and the output end of the second filter press 11 is connected to the input end of the secondary pH adjustment tank 5.

[0025] It also includes a recycled water tank 9, which is connected to the reverse osmosis unit 2.

[0026] The inlet of the recycled water tank 9 is connected to the outlet of the reverse osmosis unit 2 and is used to store reverse osmosis permeate. The inlets of the first filter press 10 and the second filter press 11 are respectively connected to the sludge discharge outlets of the primary sedimentation filter tank 4 and the secondary sedimentation filter tank 6 for dewatering the sludge discharged from the filter tanks. The dewatered sludge is transported off-site for disposal, and the filtrate is returned to the corresponding pH adjustment tank in the previous stage for repeated treatment.

[0027] The system includes: a filter device 1 for preliminary filtration of wastewater, with industrial wastewater as its input; a reverse osmosis device for removing dissolved salts, colloids, microorganisms, organic matter, and other impurities from the water; a primary pH adjustment tank 3 for adjusting the pH of the water to a suitable value to remove silicon from the wastewater; a primary sedimentation filter tank 4 for the precipitation process of aluminum salt ions in alkaline solid waste to remove silicon; a secondary pH adjustment tank 5 for further increasing the pH of the wastewater to a suitable value to precipitate magnesium ions and further remove calcium ions from the wastewater; a secondary sedimentation filter tank 6 for the precipitation process of hardening agents reacting with calcium and magnesium; a pH adjustment tank 7 for adjusting the pH of the wastewater for subsequent treatment; and a first filter press 10 and a second filter press 11 for dewatering the silicon-removing sludge and hardening-removing sludge.

[0028] In addition, the outputs of the first filter press 10 and the second filter press 11 are also connected to the inputs of the primary pH adjustment tank 3 and the secondary pH adjustment tank 4 to circulate the filtrate. The output of the reverse osmosis unit 2 is also connected to the recycled water tank 9, which is used to store the permeate from the reverse osmosis membrane for reuse.

[0029] The primary pH adjustment tank 3 is filled with industrial aluminum-based alkaline solid waste, specifically from red mud from alumina plants and alkaline corrosion slag from aluminum profile plants. The effluent pH of the primary pH adjustment tank 3 is 8–12, the concentrate retention time is 0.5–5 hours, and the alkaline solid waste filling height is 10–90% of the tank depth. The secondary pH adjustment tank 5 is filled with alkaline solid waste, including steel slag, carbide slag, fly ash, and phosphogypsum. The effluent pH of the secondary pH adjustment tank 5 is 10–14, the concentrate retention time is 0.5–5 hours, and the alkaline solid waste filling height is 10–90% of the tank depth. The pH adjustment tank 7 has an effluent pH of 7–9. The introduced industrial acidic waste gas includes coal chemical off-gas, industrial carbon dioxide waste gas, pre-desulfurization flue gas, post-desulfurization flue gas, hydrogen chloride, SO2, SO3, etc. The waste gas enters through jetting, bottom aeration devices, pressurized dissolution, and nanobubble technologies.

[0030] This invention also provides a method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization, employing the above-mentioned system, such as... Figure 1As shown, wastewater passes through filtration device 1 and reverse osmosis device 2 sequentially to obtain reverse osmosis concentrated brine. The reverse osmosis concentrated brine first enters the primary pH adjustment tank 3, which is lined with alkaline solid waste. The alkaline solid waste raises the pH value of the concentrated brine. Then it enters the primary sedimentation filter tank 4, where aluminum salt ions released by the alkaline solid waste remove silicon. Next, it enters the secondary pH adjustment tank 5, which is also lined with alkaline solid waste. The alkaline solid waste raises the pH value of the concentrated brine again. Then it enters the secondary sedimentation filter tank 6, where sodium carbonate is added to remove calcium ions from the water and precipitate magnesium ions from the wastewater. At the same time, silicon not removed in the upstream process is further removed by magnesium hydroxide. Then it enters the pH adjustment tank 7, where the pH value of the wastewater is adjusted using industrial acidic waste gas. The effluent from the pH adjustment tank 7 enters the filter 8, where suspended solids are removed before subsequent treatment.

[0031] The method of this invention is implemented according to the following steps: Step 1: Treat industrial wastewater with reverse osmosis to obtain reverse osmosis concentrate; Step 1 is as follows: After the industrial wastewater passes through the filtration device 1 to remove suspended solids and impurities, the permeate is sent to the reverse osmosis device 2. After the permeate is separated by the reverse osmosis membrane, it is sent to the reuse water tank 9 for reuse. The reverse osmosis concentrate enters the primary pH adjustment tank 3. In step 1, the recovery rate of filter device 1 is 90-100%. Filter device 1 is one or a combination of organic ultrafiltration membrane, inorganic ultrafiltration membrane, microfiltration membrane, multi-media filter, and tubular membrane. The filtration method is internal pressure or external pressure, and the operating pressure is 0.1MPa-1MPa. In step 1, the recovery rate of the reverse osmosis membrane is 50-90%, the operating pressure is 0-5 MPa, the Langerile saturation index of calcium carbonate on the concentrate side of the reverse osmosis membrane is 2.0-7.0, and a scale inhibitor is added during the reverse osmosis membrane concentration process. The scale inhibitor is a phosphorus-free scale inhibitor or a polymer scale inhibitor. The concentration of the scale inhibitor in the industrial wastewater in the filtration device is 1 mg / L-20 mg / L.

[0032] Step 2: Remove silica from the obtained reverse osmosis concentrate; Step 2 is as follows: After the reverse osmosis concentrate passes through the primary pH adjustment tank 3, the pH is raised by alkaline solid waste leachate before entering the primary sedimentation and filtration tank 4. In the primary sedimentation and filtration tank 4, aluminum salt ions leached from industrial aluminum-based alkaline solid waste are used for silicon removal. This active ingredient has a dual effect of charge neutralization and entrapment on dissolved silicon and colloidal silicon under a specific pH window, and its silicon removal activity is significantly higher than that of conventional aluminum salts. The sludge produced by silicon removal is sent to the first filter press 10, and the permeate is sent to the secondary pH adjustment tank 5. In step 2, the primary pH adjustment tank 3 is filled with industrial aluminum-based alkaline solid waste. The specific sources of the alkaline solid waste are red mud from alumina plants and alkaline corrosion slag from aluminum profile plants. The pH value of the effluent from the primary pH adjustment tank 3 is 8 to 12, the retention time of the concentrate is 0.5 h to 5 h, and the filling height of the alkaline solid waste is 10 to 90% of the tank depth.

[0033] The alkaline solid waste is a "slow-release composite alkali source + coagulation aid matrix", from which the leached active Al(OH)4 - The components participate in the subsequent precipitation reaction; when the effluent from the primary sedimentation and filtration tank enters the secondary pH adjustment tank, the residual suspended micronuclei provide seed crystals for the secondary hardening removal, accelerating the crystallization and sedimentation of calcium carbonate / magnesium hydroxide. The reaction principle for silicon removal within the reaction apparatus is as follows: AlO2 - + 2H₂O → Al(OH)₃ + OH⁻ - [Al(OH)3] n + (H2SiO3) n → (AlO) n (SiO) n / 2 OH 2n Step 3: Remove calcium and magnesium from the desiliconized water obtained in Step 2, and remove the silicon that was not removed in the previous process. Step 3 specifically involves: sending the desiliconized wastewater into the secondary pH adjustment tank 5, where the pH value is increased by alkaline solid waste leachate before it enters the secondary sedimentation and filtration tank 6. Sodium carbonate is added to the secondary sedimentation and filtration tank 6 to remove calcium and OH. - The calcium and magnesium ions react to form magnesium hydroxide precipitate. The sludge produced from calcium and magnesium removal is sent to the second filter press 11, and the permeate is sent to the pH adjustment tank 7. At the same time, the silicon that was not removed at the front end is further removed by the generated magnesium hydroxide. The pH value of the reverse osmosis concentrate is adjusted to alkaline by dissolving alkaline substances such as CaO and MgO from the alkaline solid waste. Then it enters the secondary sedimentation and filtration tank 6 to remove CO3 from the hardening agent (sodium carbonate). 2- It reacts with calcium ions in concentrated water to form calcium carbonate, OH- - It reacts with magnesium ions to form magnesium hydroxide. The reaction principle is as follows: Ca(OH)2→Ca 2+ +2OH - OH - +Mg 2+ →Mg(OH)2↓ Ca 2+ +CO3 2- →CaCO3↓ The reaction principle of magnesium hydroxide in removing silicon is as follows: Mg(HCO3)2+ 2H4SiO4→ MgSi3O6(OH)2+ 6H2O + 2CO2 In step 3, the secondary pH adjustment tank is filled with alkaline solid waste, which is one or more of steel slag, carbide slag, fly ash and phosphogypsum in any mass ratio combination. The pH value of the effluent from the secondary pH adjustment tank is 10-14, the retention time of the concentrate is 0.5-5 hours, and the filling height of the alkaline solid waste is 10-90% of the tank depth. In step 3, sodium carbonate is added to the secondary sedimentation filter tank 6 at a mass ratio of carbonate to calcium ions of 1 to 5:1, and the reaction sedimentation time of the concentrated water is 0.5 h to 5 h.

[0034] Step 4: Send the permeate obtained in Step 3 to adjust the pH value; Step 4 specifically involves: the permeate from the secondary sedimentation and filtration tank 6 is sent to the pH adjustment tank 7; industrial acidic wastewater is introduced into the pH adjustment tank 7 to adjust the pH of the wastewater to the neutral range (pH value 7-9), and then it is sent to the filter 8 to remove suspended solids in the wastewater, and finally sent to the subsequent treatment device. In step 4, the effluent pH value of pH adjustment tank 7 is 7-9. The industrial acidic waste gas introduced includes coal chemical off-gas, industrial carbon dioxide waste gas, flue gas before desulfurization, flue gas after desulfurization, hydrogen chloride, SO2, or SO3. The waste gas enters pH adjustment tank 7 through technologies such as jetting, bottom aeration devices, pressurized dissolution, and nanobubbles. The gas-liquid contact structure of pH adjustment tank 7 includes spray towers and bubble towers. The inlet pressure / flow rate of the acidic waste gas is monitored and linked to the pH value online.

[0035] Step 5: The sludge generated in Step 2 and Step 3 is concentrated by pressure filtration.

[0036] Step 5 specifically involves: the first filter press 10 presses and concentrates the sludge produced by the primary sedimentation and filtration tank 4, and the sludge produced by dewatering is transported off-site for treatment, while the filtrate is returned to the corresponding primary pH adjustment tank 3 for repeated treatment. The second filter press 11 filters and concentrates the sludge produced by the secondary sedimentation and filtration tank 6. The sludge produced by dewatering is transported off-site for treatment, and the filtrate is returned to the corresponding secondary pH adjustment tank 5 in the front section for repeated treatment. Alkaline solid waste that has been released from alkaline substances is recycled and reused.

[0037] In step 5, the sludge produced by the first filter press 10 and the second filter press 11 has a water content of 30-70%.

[0038] Example 1 This embodiment specifically includes the following steps: Step 1: Mine water discharged from a coal mine in Yulin was selected as the water source to be treated. The suspended solids were 37 mg / L, the influent TDS was 3287 mg / L, the hardness was 368 mg / L, and the silica was 36.9 mg / L. After the mine water was filtered by filter device 1, the permeate was sent to reverse osmosis device 2. After separation by reverse osmosis membrane, the permeate was sent to reuse water tank 9, and the concentrate entered the subsequent primary pH adjustment tank 3. The recovery rate of filter device 1 was 90%. Filter device 1 is an organic ultrafiltration membrane, the filtration method is internal pressure, and the operating pressure is 0.2 MPa.

[0039] The reverse osmosis membrane has a recovery rate of 50%, an operating pressure of 1 MPa, and a Langerier saturation index of calcium carbonate on the concentrate side of the reverse osmosis membrane of 2.0. A phosphorus-free antiscalant is added during the reverse osmosis membrane concentration process. The concentration of the antiscalant in the industrial wastewater in the filtration unit is 1 mg / L.

[0040] Step 2: After the reverse osmosis concentrate passes through the primary pH adjustment tank 3, the pH value is raised to 8 by the red mud leaching material from the alumina plant, and then enters the primary sedimentation and filtration tank 4. In the sedimentation and filtration tank, aluminum salt ions are dissolved to remove silicon. The sludge produced by silicon removal is sent to the first filter press 10, and the permeate is sent to the secondary pH adjustment tank 5. The primary pH adjustment tank 3 is filled with fly ash, the concentrate retention time is 0.5h, and the alkaline solid waste filling height is 30% of the tank depth.

[0041] Step 3: After the desiliconized water is sent to the secondary pH adjustment tank 5, the pH value is raised to 10 by the alkaline solid waste calcium carbide slag leachate. The concentrated water retention time is 0.5h and it enters the secondary sedimentation and filtration tank 6. In the sedimentation and filtration tank, carbonate / calcium ions with a mass ratio of 1:1 are added to remove calcium. The concentrated water reaction sedimentation time is 0.5h and the alkaline solid waste filling height is 30% of the tank depth.

[0042] Step 4: The permeate from the secondary sedimentation and filtration tank 6 is sent to the pH adjustment tank 7. In the pH adjustment tank 7, industrial carbon dioxide-containing waste gas is introduced through the bottom aeration device to adjust the pH value of the wastewater to 7.0. Then, it is sent to the filter 8 to remove suspended solids in the wastewater, and finally sent to the subsequent treatment device.

[0043] Step 5: The first filter press 10 presses and concentrates the sludge produced by the primary sedimentation filter tank 4, and the second filter press 11 presses and concentrates the sludge produced by the secondary sedimentation filter tank 6. The sludge produced by dewatering is transported off-site for treatment, and the filtrate is returned to the first-stage pH adjustment tank 3 and the second-stage pH adjustment tank 5 for repeated treatment. The alkaline solid waste after the release of alkaline substances is recycled and reused. The sludge produced by filter pressing has a water content of 30%.

[0044] The test results showed that the hardness of the reverse osmosis concentrate was 715 mg / L and the silica was 72 mg / L. After silica removal and hardness removal, the hardness was reduced to 135 mg / L and the silica was reduced to 19 mg / L. The hardness removal rate reached 81.1% and the silica removal rate reached 73.6%.

[0045] Example 2 This embodiment specifically includes the following steps: Step 1: Mine water discharged from a coal mine in Yulin was selected as the water source to be treated. The suspended solids were 41 mg / L, the influent TDS was 4126 mg / L, the hardness was 416 mg / L, and the silica was 35.6 mg / L. After the mine water was filtered by filter device 1, the permeate was sent to reverse osmosis device 2. After separation by reverse osmosis membrane, the permeate was sent to reuse water tank 9, and the concentrate entered the subsequent first-stage pH adjustment tank 3. The recovery rate of filter device 1 was 92%. Filter device 1 is a tubular ultrafiltration membrane, the filtration method is external pressure, and the operating pressure is 1 MPa.

[0046] The reverse osmosis membrane has a recovery rate of 75%, an operating pressure of 1.6 MPa, and a Langerier saturation index of calcium carbonate on the concentrate side of the reverse osmosis membrane of 3.5. A polymeric antiscalant is added during the reverse osmosis membrane concentration process. The concentration of the antiscalant in the industrial wastewater in the filtration unit is 20 mg / L.

[0047] Step 2: After passing through the primary pH adjustment tank 3, the reverse osmosis concentrate is raised to pH 12 by the alkaline etching residue from the aluminum profile factory. It then enters the primary sedimentation and filtration tank 4. The aluminum salt ions dissolved in the sedimentation and filtration tank are desiliconized. The sludge produced by the desiliconization is sent to the first filter press 10, and the permeate is sent to the secondary pH adjustment tank 5. The primary pH adjustment tank 3 is filled with alkaline etching residue from the aluminum profile factory. The concentrate retention time is 5 hours, and the alkaline solid waste filling height is 90% of the tank depth.

[0048] Step 3: After the desiliconized water is sent to the secondary pH adjustment tank 5, the pH value is raised to 14 by the alkaline solid waste calcium carbide slag leachate. The concentrated water retention time is 1 hour, and it enters the secondary sedimentation and filtration tank 6. In the sedimentation and filtration tank, carbonate / calcium ions with a mass ratio of 5:1 are added for calcium removal. The concentrated water reaction sedimentation time is 5 hours, and the alkaline solid waste filling height is 90% of the tank depth.

[0049] Step 4: The permeate from the secondary sedimentation and filtration tank 6 is sent to the pH adjustment tank 7. In the pH adjustment tank 7, industrial carbon dioxide-containing waste gas is introduced through the bottom aeration device to adjust the pH value of the wastewater to 9.0. Then, it is sent to the filter 8 to remove suspended solids in the wastewater, and finally sent to the subsequent treatment device.

[0050] Step 5: The first filter press 10 presses and concentrates the sludge produced by the primary sedimentation filter tank 4, and the second filter press 11 presses and concentrates the sludge produced by the secondary sedimentation filter tank 6. The sludge produced by dewatering is transported off-site for treatment, and the filtrate is returned to the first-stage pH adjustment tank 3 and the second-stage pH adjustment tank 5 for repeated treatment. The alkaline solid waste after the release of alkaline substances is recycled and reused. The sludge produced by filter pressing has a water content of 70%.

[0051] The test results showed that the hardness of the reverse osmosis concentrate was 1620 mg / L and the silica was 138 mg / L. After silica removal and hardness removal, the hardness was reduced to 156 mg / L and the silica was reduced to 22 mg / L. The hardness removal rate reached 90.4% and the silica removal rate reached 84.1%.

[0052] Example 3 This embodiment specifically includes the following steps: Step 1: Mine water discharged from a coal mine in Yulin was selected as the water source to be treated. The suspended solids were 36 mg / L, the influent TDS was 5218 mg / L, the hardness was 436 mg / L, and the silica was 41 mg / L. After the mine water was filtered by filter device 1, the permeate was sent to reverse osmosis device 2. After separation by reverse osmosis membrane, the permeate was sent to reuse water tank 9, and the concentrate entered the subsequent first-stage pH adjustment tank 3. The recovery rate of filter device 1 was 95%. Filter device 1 is a tubular microfiltration membrane, the filtration method is external pressure, and the operating pressure is 0.6 MPa.

[0053] The reverse osmosis membrane has a recovery rate of 80%, an operating pressure of 2.2 MPa, and a Langerier saturation index of calcium carbonate on the concentrate side of the reverse osmosis membrane of 5.0. A polymeric antiscalant is added during the reverse osmosis membrane concentration process. The concentration of the antiscalant in the industrial wastewater in the filtration unit is 15 mg / L.

[0054] Step 2: After the reverse osmosis concentrate passes through the primary pH adjustment tank 3, the pH value is raised to 11 by alkaline solid waste leaching and then enters the primary sedimentation and filtration tank 4. In the sedimentation and filtration tank, aluminum salt ions are dissolved for silicon removal. The sludge produced by silicon removal is sent to the filter press, and the permeate is sent to the secondary pH adjustment tank 5. The primary pH adjustment tank 3 is filled with red mud from the alumina plant. The concentrate retention time is 3 hours, and the alkaline solid waste filling height is 70% of the tank depth.

[0055] Step 3: After the desiliconized water is sent to the secondary pH adjustment tank 5, the pH value is raised to 13 by the alkaline solid waste calcium carbide slag leachate. The concentrated water retention time is 5 hours, and it enters the secondary sedimentation and filtration tank 6. In the sedimentation and filtration tank, carbonate / calcium ions with a mass ratio of 3:1 are added to remove calcium. The concentrated water reaction sedimentation time is 3 hours, and the alkaline solid waste filling height is 70% of the tank depth.

[0056] Step 4: The permeate from the secondary sedimentation and filtration tank 6 is sent to the pH adjustment tank 7. In the pH adjustment tank 7, industrial carbon dioxide-containing waste gas is introduced through the bottom aeration device to adjust the pH value of the wastewater to 8.6. Then, it is sent to the filter 8 to remove suspended solids in the wastewater, and finally sent to the subsequent treatment device.

[0057] Step 5: The first filter press 10 presses and concentrates the sludge produced by the primary sedimentation filter tank 4, and the second filter press 11 presses and concentrates the sludge produced by the secondary sedimentation filter tank 6. The sludge produced by dewatering is transported off-site for treatment, and the filtrate is returned to the first-stage pH adjustment tank 3 and the second-stage pH adjustment tank 5 for repeated treatment. The alkaline solid waste after the release of alkaline substances is recycled and reused. The sludge produced by filter pressing has a water content of 50%.

[0058] The test results showed that the hardness of the reverse osmosis concentrate was 2100 mg / L and the silica was 138 mg / L. After silica removal and hardness removal, the hardness was reduced to 138 mg / L and the silica was reduced to 25 mg / L. The hardness removal rate reached 93.4% and the silica removal rate reached 81.9%.

[0059] Example 4 A reverse osmosis concentrate purification and solid waste utilization system with acid-base synergistic regulation includes a filtration device 1. The output end of the filtration device 1 is sequentially connected to a reverse osmosis device 2, a primary pH adjustment tank 3, a primary sedimentation filter tank 4, a secondary pH adjustment tank 5, a secondary sedimentation filter tank 6, a pH adjustment tank 7, and a filter 8. It also includes a first filter press 10 and a second filter press 11. The input end of the first filter press 10 is connected to the primary sedimentation filter tank 4, and the output end of the first filter press 10 is connected to the input end of the primary pH adjustment tank 3. The input end of the second filter press 11 is connected to the secondary sedimentation filter tank 6, and the output end of the second filter press 11 is connected to the input end of the secondary pH adjustment tank 5.

[0060] It also includes a recycled water tank 9, which is connected to the reverse osmosis unit 2.

[0061] The inlet of the recycled water tank 9 is connected to the outlet of the reverse osmosis unit 2 to store reverse osmosis permeate. The inlets of the first filter press 10 and the second filter press 11 are respectively connected to the sludge discharge outlets of the primary sedimentation filter tank 4 and the secondary sedimentation filter tank 5 for dewatering the sludge discharged from the filter tanks. The dewatered sludge is transported off-site for disposal, and the filtrate is returned to the front section to enter the filter unit 1 for repeated treatment.

[0062] Example 5 Based on Example 4, alkaline solid waste is filled into the primary pH adjustment tank 3 and the secondary pH adjustment tank 4 to adjust the pH value of the water to a suitable value in the future.

[0063] Example 6 The acid-base synergistic regulation method for reverse osmosis concentrate purification and solid waste utilization, using the system of Example 5, involves the reverse osmosis concentrated brine first entering a primary pH adjustment tank, where alkaline solid waste is laid to raise the pH of the concentrated brine. It then enters a primary sedimentation and filtration tank 4, where sodium aluminate is added to remove silicon. Next, it enters a secondary pH adjustment tank 5, where alkaline solid waste is laid to further raise the pH of the concentrated brine. It then enters a secondary sedimentation and filtration tank 6, where sodium carbonate is added to remove calcium ions and precipitate magnesium ions. Finally, it enters a pH adjustment tank 7, where industrial acidic waste gas is used to adjust the pH of the wastewater. The effluent from pH adjustment tank 7 enters a filter 8, where suspended solids are removed before further treatment.

[0064] Comparative Example 1 Comparative Example 1 is the same as Example 1 in other aspects, except that it is a one-step alkali adjustment and simultaneous silicon and hardness removal, with only one pH adjustment tank and one sedimentation and filtration tank. The reverse osmosis concentrate is adjusted to pH 13 through alkaline solid waste, and then sodium aluminate and sodium carbonate are added to the sedimentation and filtration tank respectively.

[0065] The test results showed that the hardness of the reverse osmosis concentrate was 715 mg / L and the silica was 72 mg / L. After silica removal and hardness removal, the hardness was reduced to 150 mg / L and the silica was reduced to 39 mg / L. The hardness removal rate reached 79.0% and the silica removal rate reached 45.8%.

[0066] Comparative Example 2 Comparative Example 2 is the same as Example 2 in all other aspects, except that NaOH is used to adjust the reverse osmosis wastewater in the primary pH adjustment tank and the secondary pH adjustment tank, and sodium aluminate and sodium carbonate are added to the primary sedimentation and filtration tank and the secondary sedimentation and filtration tank, respectively.

[0067] The overall cost of adding chemicals increased by 62%.

[0068] Therefore, the method of this invention achieves efficient, stepwise removal of silicon and hardness from reverse osmosis concentrate through two-stage pH adjustment and two-stage sedimentation filtration. The pH adjustment in the two-stage pH stage utilizes alkaline solid waste to regulate the pH, saving on the cost of purchased reagents and removing alkalinity from the solid waste, laying the foundation for subsequent applications. The pH adjustment tank uses acidic industrial waste gas to adjust the pH, reducing the emission of such gas. This achieves two goals at once, realizing the advantages of treating waste with waste and recycling waste, meeting the requirements of green and low-carbon production, and possessing significant ecological and economic value.

Claims

1. An acid-base synergistic regulation system for reverse osmosis concentrate purification and solid waste utilization, characterized in that, The filter includes a filter device (1), and the output end of the filter device (1) is connected in sequence to a reverse osmosis device (2), a primary pH adjustment tank (3), a primary sedimentation filter tank (4), a secondary pH adjustment tank (5), a secondary sedimentation filter tank (6), a pH adjustment tank (7), and a filter (8). It also includes a first filter press (10) and a second filter press (11); the input end of the first filter press (10) is connected to the primary sedimentation filter tank (4), and the output end is connected to the input end of the primary pH adjustment tank (3); the input end of the second filter press (11) is connected to the secondary sedimentation filter tank (6), and the output end is connected to the input end of the secondary pH adjustment tank (5).

2. The acid-base synergistic regulation reverse osmosis concentrate purification and solid waste utilization system according to claim 1, characterized in that, It also includes a recycled water tank (9), which is connected to the reverse osmosis unit (2).

3. A method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization, characterized in that, The system described in any one of claims 1-2 is specifically as follows: Step 1: Treat industrial wastewater with reverse osmosis to obtain reverse osmosis concentrate; Step 2: Remove silica from the obtained reverse osmosis concentrate; Step 3: Remove calcium and magnesium from the desiliconized water obtained in Step 2, and remove the silicon that was not removed in the previous process. Step 4: Send the permeate obtained in Step 3 to adjust the pH value; Step 5: The sludge generated in Step 2 and Step 3 is concentrated by pressure filtration.

4. The method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization according to claim 3, characterized in that, Step 1 is as follows: After the industrial wastewater is filtered by the filter device (1) to remove suspended solids and impurities, the permeate is sent to the reverse osmosis device (2). After the permeate is separated by the reverse osmosis membrane, it is sent to the reuse water tank (9) for reuse. The reverse osmosis concentrate enters the primary pH adjustment tank (3). In step 1, the recovery rate of the filter device (1) is 90-100%. The filter device (1) is one or a combination of organic ultrafiltration membrane, inorganic ultrafiltration membrane, microfiltration membrane, multi-media filter, and tubular membrane. The filtration method is internal pressure or external pressure, and the operating pressure is 0.1MPa-1MPa. In step 1, the recovery rate of the reverse osmosis membrane is 50-90%, the operating pressure is 0-5 MPa, the Langerier saturation index of calcium carbonate on the concentrate side of the reverse osmosis membrane is 2.0-7.0, and a scale inhibitor is added during the reverse osmosis membrane concentration process. The scale inhibitor is a phosphorus-free scale inhibitor or a polymer scale inhibitor. The concentration of the scale inhibitor in the industrial wastewater in the filter device (1) is 1 mg / L-20 mg / L.

5. The method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization according to claim 3, characterized in that, Step 2 is as follows: After the reverse osmosis concentrate passes through the primary pH adjustment tank (3), the pH is raised by alkaline solid waste leaching and then enters the primary sedimentation and filtration tank (4). The aluminum salt ions dissolved in the primary sedimentation and filtration tank (4) are desiliconized, and the sludge generated from the desiliconization is sent to the first filter press (10). The permeate is sent to the secondary pH adjustment tank (5). In step 2, the primary pH adjustment tank (3) is filled with industrial aluminum-based alkaline solid waste. The pH value of the effluent from the primary pH adjustment tank (3) is 8 to 12, the retention time of the concentrate is 0.5 h to 5 h, and the filling height of the alkaline solid waste is 10 to 90% of the tank depth.

6. The method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization according to claim 3, characterized in that, Step 3 specifically involves: sending the desiliconized wastewater into the secondary pH adjustment tank (5), raising the pH value through alkaline solid waste leachate, and then entering the secondary sedimentation and filtration tank (6). Sodium carbonate is added to the secondary sedimentation and filtration tank (6) for calcium removal. - The magnesium hydroxide precipitate is generated by reacting with magnesium ions. The sludge generated from calcium and magnesium removal is sent to the second filter press (11), and the permeate is sent to the pH adjustment tank (7). At the same time, the silicon that was not removed at the front end is further removed by the generated magnesium hydroxide. In step 3, the secondary pH adjustment tank is filled with alkaline solid waste, which is one or more of steel slag, carbide slag, fly ash and phosphogypsum in any mass ratio combination. The pH value of the effluent from the secondary pH adjustment tank is 10-14, the retention time of the concentrate is 0.5h-5h, and the filling height of the alkaline solid waste is 10-90% of the tank depth. In step 3, sodium carbonate is added to the secondary sedimentation filter tank (6) at a mass ratio of carbonate to calcium ions of 1 to 5:1, and the reaction sedimentation time of the concentrated water is 0.5 h to 5 h.

7. The method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization according to claim 3, characterized in that, Step 4 is as follows: the permeate from the secondary sedimentation and filtration tank (6) is sent to the pH adjustment tank (7); industrial acidic wastewater is introduced into the pH adjustment tank (7) to adjust the pH of the wastewater to the neutral range, and then sent to the filter (8) to remove suspended solids in the wastewater; In step 4, the pH value of the effluent from the pH adjustment tank is 7-9, and the industrial acidic waste gas introduced is coal chemical off-gas, industrial carbon dioxide waste gas, flue gas before desulfurization, flue gas after desulfurization, hydrogen chloride, SO2 or SO3.

8. The method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization according to claim 3, characterized in that, Step 5 is as follows: The first filter press (10) presses and concentrates the sludge produced by the primary sedimentation filter tank (4), and the sludge produced by dewatering is transported off-site for treatment. The filtrate is returned to the corresponding primary pH adjustment tank (3) in the front section for repeated treatment. The second filter press (11) filters and concentrates the sludge produced by the secondary sedimentation filter tank (6), and the sludge produced by dewatering is transported off-site for treatment. The filtrate is returned to the corresponding secondary pH adjustment tank (5) in the front section for repeated treatment.

9. The method for acid-base synergistic regulation of reverse osmosis concentrate purification and solid waste utilization according to claim 3, characterized in that, In step 5, the sludge produced by the first filter press (10) and the second filter press (11) has a water content of 30-70%.

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