Method for discharging high-salinity wastewater up to standard of chlorine ion

Abstract

This invention provides a method for achieving chloride ion discharge standards in high-salinity wastewater, relating to the field of industrial wastewater treatment technology. The method includes steps of separate flow based on chloride ion concentration, pretreatment, EDR desalination, and resource recovery. First, high-salinity concentrated water with a chloride ion concentration of 5000-50000 mg / L is collected separately from low-salinity wastewater. The high-salinity concentrated water undergoes pretreatment via MF microfiltration and UF ultrafiltration before entering the EDR system. Desalination is achieved through a combination of electric field-driven and membrane separation, ensuring chloride ion levels meet standards. The EDR brine is then purified to recover sodium chloride, and the treated effluent can be reused. This invention reduces the treatment load through separate flow based on chloride ion concentration. The energy consumption of the EDR process is only 50%-70% of that of the traditional RO process, delaying membrane fouling, achieving chloride ion discharge standards, and recovering salts and water resources. This reduces investment and operating costs and solves a common problem in the industry.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a method for achieving chloride ion discharge standards for high-salinity wastewater. Background Technology

[0002] With the continuous acceleration of industrialization, the production scale of industries such as chemicals, printing and dyeing, pharmaceuticals, and petrochemicals has been expanding, leading to a year-on-year increase in the generation of high-salinity wastewater. This has become a prominent environmental problem restricting the green development of these industries. High-salinity wastewater is rich in high concentrations of chloride ions, sulfates, and other soluble salts. If discharged directly without adequate treatment, it will cause increased water salinity, soil salinization, groundwater pollution, and disrupt the balance of aquatic ecosystems, while also posing a serious threat to the safety of industrial and agricultural water use. To strictly control water and soil salt pollution, environmental protection departments have established strict limits for chloride ion emissions, placing unprecedented pressure on enterprises to meet environmental compliance requirements.

[0003] Currently, the mainstream treatment process for high-salinity industrial wastewater mostly adopts a combined route of A2O+EGSB+BAF+RO+MVR, achieving desalination and solid-liquid separation through biochemical degradation of organic matter, membrane separation desalination, and mechanical steam recompression evaporation crystallization. While this process can meet basic desalination requirements, it has significant technical and economic shortcomings: First, the equipment investment is large, with core devices such as reverse osmosis and evaporation crystallization being expensive and requiring a large system footprint; second, energy consumption and operating costs are high, with MVR evaporation and high-pressure reverse osmosis consuming huge amounts of electricity and steam, resulting in a treatment cost of around 100 yuan per ton of water, placing a heavy economic burden on enterprises; third, membrane fouling is a prominent problem, with organic matter, hardness ions, and salts in the wastewater easily causing membrane element fouling and scaling, leading to frequent membrane module replacements and continuously increasing maintenance difficulty and costs; fourth, resource utilization is low, with mixed salt crystallization products mostly disposed of as hazardous waste, failing to achieve efficient recovery and utilization of salt and water resources.

[0004] Current processes generally employ a mixed collection and centralized treatment model, failing to separate high-salinity wastewater from low-salinity / non-salinity wastewater at the source. This results in uneven load distribution in the treatment system, poor process adaptability, and further exacerbates energy consumption and cost pressures. The industry urgently needs a new high-salinity wastewater treatment technology that requires lower investment, consumes less energy, operates stably, and enables resource recovery, to solve the common industry problems of high costs, difficulty in meeting standards, and insufficient resource utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a method for achieving standard discharge of chloride ions in high-salinity wastewater. Through a synergistic process of pretreatment by different water quality and flow, deep desalination by EDR, and salt resource recovery, the method achieves stable standard discharge of chloride ions in high-salinity heparin sodium wastewater and resource utilization of sodium chloride, effectively reducing treatment energy consumption and operating costs.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a method for achieving chloride ion discharge standards for high-salinity wastewater, comprising the following steps: S1. Separate treatment based on quality and salinity: The raw water in the workshop is used as the starting water source. It is separated and treated according to the difference in salinity. The raw water is divided into two categories: high salinity and low salinity. They are transported to the corresponding pretreatment units through independent pipelines to achieve the separation of high and low salinity sources and enter the subsequent differentiated treatment process. S2, S2, Pretreatment: The high-salt concentrate obtained from the separation in S1 is first treated by the A2 / O+EGSB+BAF combined process, and then successively treated by MF microfiltration and UF ultrafiltration to remove suspended particulate matter, colloids and macromolecular organic matter, and control the effluent turbidity and fouling index SDI to meet the feed water requirements of the subsequent electrodialysis reverse osmosis EDR system. S3, EDR desalination: The high-salt concentrated water treated in S2 above is introduced into the electrodialysis reverse osmosis EDR system. Through the synergistic effect of ion migration and reverse osmosis membrane separation driven by the electric field, chloride ions and other salt substances in the water are removed, so that the chloride ion concentration of the effluent meets the discharge standards. S4. Resource recovery: The concentrated brine produced by the electrodialysis reverse osmosis (EDR) system in S3 is recovered and treated with sodium chloride to realize the resource utilization of salts and reduce the amount of concentrated water discharged.

[0007] As an improvement, the ordinary low-salt wastewater in S1 includes cooling water, softened water, and equipment cleaning water, which undergoes simple pretreatment through a bar screen and equalization tank before sand filtration, eliminating the need for it to enter the electrodialysis reverse osmosis (EDR) desalination system.

[0008] As an improvement, the MF microfiltration in S2 is used to intercept suspended particulate matter and colloids in the wastewater, and the UF ultrafiltration is used to deeply remove macromolecular organic matter and colloidal silica, so that the turbidity and pollution index SDI of the treated high-salt concentrated water meet the feed water requirements of the electrodialysis reverse osmosis EDR system.

[0009] As an improvement, the operating energy consumption of the electrodialysis reverse osmosis (EDR) system in S3 is 50%-70% of that of the traditional reverse osmosis (RO) process, and its desalination efficiency is precisely controlled by adjusting the electric field voltage and current density to achieve precise control of the chloride ion rejection rate.

[0010] As an improvement, the separation of water into different components in S1 reduces the amount of high-salt wastewater entering the electrodialysis reverse osmosis (EDR) desalination system by 30%-60%, thereby reducing energy consumption, reagent consumption, and equipment operating costs in subsequent desalination processes.

[0011] As an improvement, the MF microfiltration and UF ultrafiltration treatments in S2 reduce the turbidity and organic matter content of high-salt concentrate, thus delaying the fouling and clogging of membrane modules in the electrodialysis reverse osmosis (EDR) system and extending the membrane cleaning cycle and service life.

[0012] As an improvement, the treated and neutralized effluent from the electrodialysis reverse osmosis (EDR) system in S3 can be reused for production or directly discharged, and the sodium chloride recovered in S4 can be reused as an industrial raw material, forming a closed-loop treatment of compliant discharge, resource recovery, and cost control.

[0013] As an improvement, the low-salinity water is treated using a combined process of mechanical bar screen → equalization tank → air flotation machine → hydrolysis acidification tank → sand filtration neutralization reaction tank → neutralization reaction tank.

[0014] As an improvement, the concentrated brine in S4 is purified by ozone disinfection and MF microfiltration technology to obtain high-purity sodium chloride.

[0015] As an improvement, the treated effluent that meets the standards can be reused for cooling tower makeup water, boiler feedwater, or process water, realizing the secondary utilization of water resources.

[0016] The beneficial effects of this invention are as follows: by adopting a separate flow system, high-salt concentrated water and low-salt wastewater are collected and treated independently, which significantly reduces the amount of high-salt wastewater entering the EDR desalination system, greatly reduces the load on subsequent systems, and reduces equipment investment and operating energy consumption. Through MF microfiltration + UF ultrafiltration, suspended solids, colloids and macromolecular organic matter are effectively removed, reducing effluent turbidity and SDI value, significantly delaying EDR membrane module fouling, scaling and clogging, extending membrane life and reducing operation and maintenance costs; The system employs a combined EDR (electrodialysis and reverse osmosis) desalination process, achieving efficient chloride ion removal under the dual effects of electric field drive and membrane separation. The effluent chloride ion levels can stably meet discharge standards. Furthermore, the operating energy consumption is only 50%-70% of that of the traditional RO process, resulting in a significant reduction in the cost per ton of water treated and outstanding economic efficiency. To achieve closed-loop utilization of salt resources, the high-concentration brine generated by EDR can be purified and crystallized to recover high-purity industrial-grade sodium chloride, which can be reused in the production process, avoiding the generation of hazardous waste mixed with salt, improving resource utilization, and the qualified clean water can be reused for cooling tower replenishment, equipment cleaning, process water and other scenarios, improving water resource reuse rate, reducing fresh water consumption, and achieving both environmental and economic benefits. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for achieving chloride ion discharge standards for high-salt wastewater according to the present invention. Detailed Implementation

[0018] The invention will be more readily understood by referring to the following detailed description of preferred embodiments and included examples. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail.

[0019] Example: Treatment of high-salinity wastewater from heparin sodium production plants The high-salt wastewater generated during the company's production process mainly originates from the purification and washing stages of heparin sodium, with chloride ion concentrations ranging from 8000 to 45000 mg / L. Simultaneously, a large amount of low-salt wastewater (chloride ion concentration < 1000 mg / L) is generated, including cooling water and equipment cleaning water. The method described in this application is used for treatment, comprising the following steps: S1. Separate Collection and Flow of Wastewater: Independent collection networks for high-salinity and low-salinity wastewater are established. Diversion valves and concentration detection devices are installed at the wastewater discharge outlets in the production workshop to monitor and classify the wastewater in real time. High-salinity concentrated wastewater with chloride ion concentrations of 8000-45000 mg / L is transported to the pretreatment unit through a dedicated pipeline network, while low-salinity wastewater such as cooling water and equipment cleaning water is transported to a simplified pretreatment unit through another pipeline network. After diversion, the amount of high-salinity wastewater entering the EDR desalination system is reduced compared to the traditional mixed treatment mode, significantly reducing the load on subsequent treatment processes.

[0020] S2. Pretreatment: The high-salt concentrate collected in S1 is first treated by a combined A2 / O+EGSB+BAF process, and then sent to an MF microfiltration device. A microfiltration membrane with a pore size of 0.1μm is selected, and the operating pressure is controlled at 0.15-0.25MPa and the flow rate at 10-15m³ / h. 3 The system filters suspended particulate matter, colloids, and other impurities from wastewater at a rate of [per hour]. The microfiltration effluent then enters an ultrafiltration (UF) unit, using an ultrafiltration membrane with a molecular weight cutoff of 10,000 Da and operating at a pressure controlled at 0.2-0.3 MPa, to deeply remove large molecular organic matter, colloidal silica, and other pollutants from the water. After pretreatment, the turbidity of the high-salt concentrate is ≤0.5 NTU, and the SDI (Specialized Difference in Degradation) index is ≤3, fully meeting the feed water requirements of the EDR system and effectively delaying the fouling and clogging of subsequent membrane modules.

[0021] S3, EDR Desalination: The high-salt concentrate after S2 pretreatment is fed into the EDR desalination system, and the system electric field voltage is adjusted to 20-30V and the current density to 15-25A / m. 2Driven by an electric field, chloride and sodium ions migrate in a directional manner, combined with the separation effect of the reverse osmosis membrane, efficiently removing chloride ions and other salts from water. During operation, the effluent chloride ion concentration is monitored in real time, and the voltage and current density are dynamically adjusted based on the monitoring results to ensure that the effluent chloride ion concentration is stably controlled below 500 mg / L (meeting the Class I discharge standard of the Integrated Wastewater Discharge Standard GB8978-1996). The EDR system's energy consumption is measured to be 1.8-2.2 kWh / m³. 3 It is only comparable to traditional RO processes (4.0-4.5kWh / m³). 3 It accounts for about 55% of the energy consumption, showing a significant advantage.

[0022] S4. Resource Recovery: The concentrated brine (chloride ion concentration ≥80000mg / L) generated by the EDR system in S3 is sent to the purification unit. First, it is disinfected using an ozone disinfection device with an ozone dosage of 5-8mg / L and a disinfection time of 15-20 minutes to remove residual organic matter and microorganisms. After disinfection, it is sent to an FM filtration device using a 0.05μm pore size filter membrane to remove minute impurities, obtaining a high-purity sodium chloride solution. After evaporation, concentration, crystallization, and drying, industrial-grade sodium chloride with a purity ≥98.5% is obtained, which can be recycled as a raw material for enterprise production, realizing the resource utilization of salts. Simultaneously, the treated and neutralized effluent from the EDR system (chloride ion concentration <500mg / L), after simple disinfection, is reused for cooling tower makeup and equipment cleaning in the plant area, increasing the water resource reuse rate and significantly reducing the consumption of fresh water.

[0023] In addition, the low-salt wastewater collected in S1 is sent to the equalization tank to adjust the water quality and quantity after large particulate impurities are removed by the screen. After sand filtration and neutralization treatment, the effluent meets the Class I discharge standard of the Integrated Wastewater Discharge Standard GB8978-1996 and can be directly discharged or used for auxiliary reuse.

[0024] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for achieving chloride ion discharge standards for high-salinity wastewater, characterized in that, Includes the following steps: S1. Separate treatment based on quality and salinity: The raw water in the workshop is used as the starting water source. It is separated and treated according to the difference in salinity. The raw water is divided into two categories: high salinity and low salinity. They are transported to the corresponding pretreatment units through independent pipelines to achieve the separation of high and low salinity sources and enter the subsequent differentiated treatment process. S2. Pretreatment: The high-salt concentrate obtained from S1 is first treated by the A2 / O+EGSB+BAF combined process, and then successively treated by MF microfiltration and UF ultrafiltration to remove suspended particulate matter, colloids and macromolecular organic matter, and control the effluent turbidity and pollution index SDI to meet the feed water requirements of the subsequent electrodialysis reverse osmosis EDR system. S3, EDR desalination: The high-salt concentrated water treated in S2 above is introduced into the electrodialysis reverse osmosis EDR system. Through the synergistic effect of ion migration and reverse osmosis membrane separation driven by the electric field, chloride ions and other salt substances in the water are removed, so that the chloride ion concentration of the effluent meets the discharge standards. S4. Resource recovery: The concentrated brine produced by the electrodialysis reverse osmosis (EDR) system in S3 is recovered and treated with sodium chloride to realize the resource utilization of salts and reduce the amount of concentrated water discharged.

2. The method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The ordinary low-salt wastewater mentioned in S1 includes cooling water, softened water, and equipment cleaning water. After simple pretreatment by a bar screen and equalization tank, it undergoes sand filtration and does not need to enter the electrodialysis reverse osmosis (EDR) desalination system.

3. The method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The MF microfiltration in S2 is used to intercept suspended particulate matter and colloids in wastewater, while the UF ultrafiltration is used to deeply remove macromolecular organic matter and colloidal silica, so that the turbidity and pollution index SDI of the treated high-salt concentrated water meet the feed water requirements of the electrodialysis reverse osmosis EDR system.

4. The method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The operating energy consumption of the electrodialysis reverse osmosis (EDR) system in S3 is 50%-70% of that of the traditional reverse osmosis (RO) process. Its desalination efficiency is precisely controlled by adjusting the electric field voltage and current density to achieve precise control of the chloride ion rejection rate.

5. The method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The separation of wastewater into different components in S1 reduces the amount of high-salt wastewater entering the electrodialysis reverse osmosis (EDR) desalination system by 30%-60%, thereby reducing energy consumption, reagent consumption, and equipment operating costs in subsequent desalination processes.

6. The method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The MF microfiltration and UF ultrafiltration treatments in S2 reduce the turbidity and organic matter content of high-salt concentrated water, thus delaying the fouling and clogging of membrane modules in the electrodialysis reverse osmosis (EDR) system and extending the membrane cleaning cycle and service life.

7. The method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The treated and neutralized effluent from the electrodialysis reverse osmosis (EDR) system in S3 can be reused in production or directly discharged. The sodium chloride recovered in S4 can be reused as an industrial raw material, forming a closed-loop treatment of compliant discharge, resource recovery, and cost control.

8. The method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The low-salinity water is treated using a combined process: mechanical bar screen → equalization tank → air flotation machine → hydrolysis acidification tank → sand filtration neutralization reaction tank → neutralization reaction tank.

9. A method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The concentrated brine in S4 is purified using ozone disinfection and MF microfiltration technology to obtain high-purity sodium chloride.

10. A method for achieving chloride ion discharge standards for high-salinity wastewater according to claim 1, characterized in that, The treated effluent that meets the standards can be reused for cooling tower makeup water, boiler feed water, or process water, realizing the secondary utilization of water resources.

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