A chemical industrial park wastewater near-zero discharge treatment system
By combining ultrafiltration pretreatment with a combined membrane treatment process and evaporation crystallization to treat concentrated wastewater, the problems of low water production rate and high operating costs of wastewater treatment systems in chemical industrial parks have been solved, achieving near-zero discharge of wastewater from chemical industrial parks, and the effluent quality is superior to the standards for urban wastewater reuse.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ENVIRONMENTAL SCI RES & DESIGN INST OF ZHEJIANG PROVINCE
- Filing Date
- 2025-06-12
- Publication Date
- 2026-07-24
AI Technical Summary
Existing wastewater treatment systems in chemical industrial parks suffer from low water production rates, complex processes, high operational difficulty, and high costs.
The system employs ultrafiltration pretreatment and combined membrane treatment processes, including a pretreatment system and a combined membrane treatment system. It utilizes tubular ultrafiltration devices, ion exchange softeners, primary reverse osmosis devices, and concentrate reverse osmosis devices, combined with evaporation and crystallization to treat concentrate, achieving near-zero wastewater discharge.
The system's total water production rate has been increased to over 90%, the process flow has been simplified, the operation and management difficulty and cost have been reduced, and the effluent quality is better than the standards for urban wastewater reuse, achieving near-zero discharge of wastewater from the chemical industrial park.
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Abstract
Description
Technical Field
[0001] This application relates to the field of water treatment technology, and in particular to a near-zero discharge treatment system for wastewater from a chemical industrial park. Background Technology
[0002] Near-zero wastewater discharge, internationally defined as zero liquid discharge, refers to wastewater being treated through appropriate processes and then reused in the production process. Pollutants are concentrated and discharged in crystalline or other solid forms, with no further liquid pollutants released into the environment, thus achieving near-zero overall discharge. Applying the zero-discharge concept to industrial wastewater treatment can promote the development of industrial wastewater treatment technologies, reduce pollutant emissions, and improve water resource utilization. Currently, advanced wastewater treatment and reuse schemes in chemical industrial parks are complex, have high operating costs, and some schemes have low water resource recycling rates. To meet the new requirements of wastewater treatment in chemical industrial parks, improve water utilization, reduce the total amount of pollution discharged into the water environment, protect the ecological environment, and improve the regional investment environment, it is urgent to develop near-zero wastewater discharge processes for chemical industrial parks.
[0003] Chinese patent application CN112794500A, entitled "A Near-Zero Discharge Treatment System and Method for Concentrated Brine from Coking Wastewater," discloses a wastewater treatment system and method. The system comprises, in sequence, an equalization tank, a primary high-efficiency sedimentation tank, a secondary high-efficiency sedimentation tank, a primary multi-media filter, an ozone oxidation contact tank, a secondary multi-media filter, an ultrafiltration device, a weakly acidic cation exchange unit, a nanofiltration unit, a concentrated water nanofiltration unit, a reverse osmosis unit, and a concentrated water reverse osmosis unit. Wastewater passes through the nanofiltration unit, permeate enters the reverse osmosis unit, concentrated water enters the concentrated water nanofiltration unit, permeate from both the nanofiltration and concentrated water nanofiltration units enters the reverse osmosis unit, and concentrated water from the reverse osmosis unit enters the concentrated water reverse osmosis unit. The permeate from both units is combined and reused. Before nanofiltration, a molecular sieve modified with FeCl3 and SnCl4 is added to the effluent from the weakly acidic cation exchange unit. This system achieves a permeate production rate of 80% for treating concentrated brine from coking wastewater, with room for improvement.
[0004] Chinese patent application CN 107857438 B, entitled "A Zero-Discharge Process for Wastewater Treatment in Chemical Enterprises and Industrial Parks," discloses a wastewater treatment process. This process involves treating desalinated water and circulating water using a combination of softening sedimentation, sand filtration, ultrafiltration, and reverse osmosis. Wastewater from domestic and industrial processes undergoes physicochemical and biochemical treatment followed by a sand filtration, ultrafiltration, and reverse osmosis process. The concentrated wastewater from both treatments is then treated using a combination of catalytic oxidation, membrane treatment, and electrodialysis. The process is complex, difficult to operate, and expensive. Utility Model Content
[0005] This application provides a near-zero discharge treatment system for wastewater from chemical industrial parks, which at least solves the technical problems of low water production rate, complex process, difficult operation and high cost in the prior art.
[0006] This application provides a near-zero discharge treatment system for wastewater from a chemical industrial park, comprising a pretreatment system and a combined membrane treatment system. The pretreatment system includes, in sequence, an equalization tank, a high-efficiency sedimentation tank, a sedimentation product water tank, a tubular ultrafiltration unit, an ion exchange softener, and a softened product water tank. A sludge dewatering system is installed after the high-efficiency sedimentation tank. The combined membrane treatment system includes, in sequence, a primary reverse osmosis unit, a reverse osmosis concentrate tank, a concentrate-reverse osmosis unit, a high-salinity water tank, and a reclaimed water tank.
[0007] Compared with existing technologies, the near-zero discharge treatment system for chemical industrial park wastewater in this application has the following advantages:
[0008] This application addresses the characteristics of wastewater from chemical industrial parks, such as complex water quality, high salinity, and difficulty in biodegradation. It adopts an ultrafiltration pretreatment and combined membrane treatment process, and the reverse osmosis concentrate is treated by evaporation and crystallization. Return water pipes are set in the tubular ultrafiltration device, ion exchange softener, and concentrate reverse osmosis device, so that the total water production rate of the system is ≥90%. The process flow is simple, the operation and management are easy, and the effluent is better than the standards for urban wastewater reuse, which can achieve near-zero discharge of wastewater from chemical industrial parks.
[0009] According to wastewater quality classification, for moderately polluted chemical wastewater with a COD (Chemical Oxygen Demand) content of 500-1000 mg / L, the treatment fee is generally 10-18 yuan per ton; when the COD content exceeds 3000 mg / L, it is considered high-concentration polluted wastewater, and the treatment fee often exceeds 20 yuan per ton. In one embodiment of the technical solution of this application, the influent COD content is 700-1500 mg / L, and the operating cost is about 9-10 yuan per ton of water (excluding evaporation and solid waste disposal costs). The technical solution of this application also has certain advantages in terms of operating costs.
[0010] In one embodiment, the near-zero discharge treatment system for wastewater in the chemical industrial park is also equipped with a sludge dewatering system. The high-efficiency sedimentation tank is connected to the sludge dewatering system via a channel. The sludge dewatering system is connected to the equalization tank via a return water pipe, so that the wastewater generated by the sludge dewatering system can enter the equalization tank.
[0011] In one embodiment, the tubular ultrafiltration device is connected to the equalization tank via a return water pipe, allowing the wastewater from the tubular ultrafiltration device to enter the equalization tank.
[0012] In one embodiment, the ion exchange softener is connected to the equalization tank via a return water pipe, allowing the wastewater from the ion exchange softener to enter the equalization tank.
[0013] In one embodiment, the recycled water tank is connected to the ion exchange softener via a pipe, so that the recycled water tank provides cleaning water to the ion exchange softener.
[0014] In one embodiment, the concentrate reverse osmosis unit is connected to the softening product water tank via a return water pipe, allowing the product water from the concentrate reverse osmosis unit to enter the softening product water tank for further freshwater recovery. This improves the water production rate and ensures the quality of the effluent.
[0015] In one embodiment, the high-salinity water tank is connected to the evaporation device.
[0016] In one embodiment, the recycled water tank is equipped with a regenerated return water pipe, allowing the regenerated water from the recycled water tank to be transferred through the regenerated return water pipe. The water in the regenerated return water pipe can be used, depending on different standards, as makeup water for indirect cooling open-loop circulating cooling water systems, boiler feed water, process water, product water, direct-flow cooling water, washing water, toilet flushing, vehicle washing, urban greening, road cleaning, fire protection, and construction.
[0017] In one possible implementation, the equalization tank is arranged adjacent to the tubular ultrafiltration unit and the ion exchange softener, while the softened permeate tank is arranged adjacent to the primary reverse osmosis unit and the concentrate reverse osmosis unit. This layout reduces the length of the return water pipe, increases the return water efficiency, and reduces return water energy consumption, resulting in lower overall operating costs.
[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent from the following description. Attached Figure Description
[0019] The above and other objects, features and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings.
[0020] Figure 1 This invention discloses a structural diagram of a near-zero discharge treatment system for wastewater in a chemical industrial park.
[0021] Figure 2 The processing flow and water balance diagram of an embodiment of this utility model are shown. Detailed Implementation
[0022] To make the objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0023] like Figure 1 As shown, a near-zero discharge wastewater treatment system for a chemical industrial park includes a pretreatment system and a combined membrane treatment system. The pretreatment system comprises, in sequence, an equalization tank, a high-efficiency sedimentation tank, a sedimentation permeate tank, a tubular ultrafiltration unit, an ion exchange softener, and a softened permeate tank. A sludge dewatering system is installed after the high-efficiency sedimentation tank. The sludge dewatering system, the tubular ultrafiltration unit, and the ion exchange softener are all connected to the equalization tank via return water pipes. The combined membrane treatment system comprises, in sequence, a primary reverse osmosis unit, a reverse osmosis concentrate tank, a concentrate reverse osmosis unit, a high-salinity water tank, and a reclaimed water tank. The concentrate reverse osmosis unit is connected to the softened permeate tank via a return water pipe. The reclaimed water tank is equipped with a regeneration return water pipe. The reclaimed water tank is connected to the primary reverse osmosis unit, allowing the reverse osmosis permeate from the primary reverse osmosis unit to enter the reclaimed water tank. The arrows in the figure indicate the direction of permeate or product transfer.
[0024] Wastewater from the chemical industrial park enters a high-efficiency sedimentation tank after passing through an equalization tank. Chemicals are added in the high-efficiency sedimentation tank to soften the wastewater before it reaches the sedimentation product water tank. Then, it enters a tubular ultrafiltration unit for further solid-liquid separation. The product water from the tubular ultrafiltration unit enters an ion exchange softener to further remove hardness before entering a softened product water tank. The product water from the tubular ultrafiltration unit is pumped to a first-stage reverse osmosis unit for desalination. After desalination, the freshwater enters a reclaimed water tank, and the concentrated water enters a reverse osmosis concentrated water tank. The concentrated water is then further processed by a reverse osmosis unit to generate freshwater, which returns to the softened product water tank. The concentrated water from the reverse osmosis unit enters a high-salinity water tank and is treated by evaporation and crystallization using an evaporator.
[0025] The tubular ultrafiltration membrane unit employed features high operating flux and high fouling resistance, along with simple installation and maintenance, and low energy consumption and replacement costs. The tubular ultrafiltration unit is primarily used to remove suspended solids and bacteria, ensuring the integrity of membrane modules in subsequent processes. The tubular ultrafiltration unit has a designed membrane flux of 65 LMH, a maximum designed pressure of 6 bar, and a recovery rate of 93%.
[0026] The tubular ultrafiltration unit produces water that is further softened by an ion exchange softener to remove hardness from the raw water, ensuring that no calcium sulfate or calcium fluoride precipitates are formed after the raw water is concentrated by the first-stage reverse osmosis unit and the concentrate reverse osmosis unit.
[0027] The first-stage reverse osmosis unit is designed with a flux of 15 LMH, a maximum design pressure of 28 bar, and a recovery rate of 75%.
[0028] The concentrate reverse osmosis unit employs DTRO (disc tube reverse osmosis) technology. The distance between the two guide plates of the membrane module is 3 mm. The surface of the guide plates has protrusions arranged in a specific pattern. When the treated liquid flows through the filter membrane surface under pressure and collides with the protrusions, it forms turbulence, increasing the permeate rate and self-cleaning function, thereby avoiding membrane clogging and concentration polarization. The concentrate reverse osmosis unit is designed with a flux of 10 LMH, a maximum design pressure of 120 bar, and a recovery rate of 70%.
[0029] The near-zero discharge treatment system for wastewater from the chemical industrial park applied for utilizes a tubular ultrafiltration device, an ion exchange softener, a primary reverse osmosis device, and a concentrate reverse osmosis device. The process is simple, easy to operate and manage, and the total water production rate of the system is ≥90%. The effluent quality is good and superior to the standards for urban wastewater reuse.
[0030] The concentrated water from the reverse osmosis unit is not discharged externally. Instead, it is treated by evaporation and crystallization, and all the treated water is reused, achieving near-zero wastewater discharge from the chemical industrial park.
[0031] like Figure 2 As shown, in this embodiment, the amount of raw water entering the equalization tank is designed to be 500 m³. 3 / d, the flow rate from the equalization tank to the high-efficiency sedimentation tank is 588m³ / d. 3 / d, including: 500m³ of raw water 3 / d, 40m³ of wastewater returned from the tubular ultrafiltration unit to the equalization tank 3 / d, 40m³ of wastewater returned from the ion exchange softener to the equalization tank 3 / d. Approximately 8m³ of wastewater enters the equalization tank from the sludge dewatering system. 3 / d; High-efficiency sedimentation tank is nearly 8m 3 The flow rate of / d is carried into the sludge dewatering system and then returned to the equalization tank, with the remaining 580m³ flow rate. 3 The water flow rate is / d, which sequentially enters the sedimentation tank and the tubular ultrafiltration unit; the tubular ultrafiltration unit has a water production rate of 93% and an ultrafiltration permeate of 540m³. 3 After further hardness removal in the ion exchange softener, the water enters the softened product water tank; the flow rate from the softened product water tank to the first-stage reverse osmosis unit is 654 m³ / d. 3 / d, including: 540m³ of water produced by the ion exchange softener. 3 / d, 114m³ of permeate water returned from the concentrate reverse osmosis unit to the softening permeate tank. 3 / d, the first-stage reverse osmosis unit has a water production rate of 75%, producing 490m³ of water. 3 / d Enters the recycled water tank, 164m³ of primary reverse osmosis concentrate. 3 / d enters the reverse osmosis concentrate tank; the concentrate reverse osmosis unit has a product rate of 70%, producing 114m³ of water. 3 / d Return to softened permeate tank, concentrate 50m 3 / d enters the high salinity tank; 40m of the recycled water tank 3 / d of water enters the ion exchange softener for cleaning, and the remaining 450m³ 3 / d of produced water is reused through a reclaimed water return pipe, meaning the raw water flow rate is 500m³ / day. 3 The outflow rate is 450m³ / d. 3 / d, water production rate 90%.
[0032] The actual treated water volume is 300-400 t / d, with a water production rate exceeding 90%. Influent COD is 700-1500 mg / L, ammonia nitrogen 20-100 mg / L, Cl- 100-400 mg / L, total phosphorus 30-50 mg / L, and conductivity 1000-3000 mg / L. Effluent COD is 10-15 mg / L, ammonia nitrogen 1-3 mg / L, Cl- 10-20 mg / L, total phosphorus ≤0.1 mg / L, and conductivity 10-50 mg / L. All effluent indicators are superior to those specified in "Water Quality Standards for Industrial Water Use in Urban Wastewater Reuse" (GB / T19923-2024), "Water Quality Standards for Green Space Irrigation Water Use in Urban Wastewater Reuse" (GB / T 25499-2010), and "Water Quality Standards for Urban Miscellaneous Water Use in Urban Wastewater Reuse" (GB / T 18920-2020). See Table 1 for a detailed comparison.
[0033] Table 1
[0034]
[0035] Compared to industrial wastewater treatment plants that discharge effluent according to the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002), this embodiment, assuming complete reuse of produced water, is based on a 500 m³... 3 Based on the water volume calculation, COD emissions can be reduced by 9.13 t / a, ammonia nitrogen emissions by 0.91 (1.46) t / a, and total phosphorus emissions by 0.09 t / a.
[0036] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A near-zero discharge treatment system for wastewater from a chemical industrial park, characterized in that: Includes pretreatment systems and combined membrane treatment systems; The pretreatment system includes: an equalization tank, a high-efficiency sedimentation tank, a sedimentation product water tank, a tubular ultrafiltration device, an ion exchange softener, and a softened product water tank connected in sequence; a sludge dewatering system is provided after the high-efficiency sedimentation tank; the combined membrane treatment system includes: a primary reverse osmosis device, a reverse osmosis concentrate tank, a concentrate reverse osmosis device, a high salinity tank, and a reclaimed water tank connected in sequence.
2. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The equalization tank is equipped with an inlet so that wastewater from the chemical industrial park can enter the equalization tank.
3. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The high-efficiency sedimentation tank is connected to the sludge dewatering system via a channel, and the sludge dewatering system is connected to the equalization tank via a return water pipe, so that the wastewater generated by the sludge dewatering system can enter the equalization tank.
4. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The tubular ultrafiltration device is connected to the equalization tank via a return water pipe, allowing the wastewater from the tubular ultrafiltration device to flow back to the equalization tank. The membrane of the tubular ultrafiltration device has a designed flux of 65 LMH, a designed maximum pressure of 6 bar, and a recovery rate of 93%.
5. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The ion exchange softener is connected to the equalization tank via a return water pipe, allowing the wastewater from the ion exchange softener to flow back to the equalization tank.
6. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The recycled water tank is connected to the ion exchange softener via a pipe, so that the recycled water tank provides cleaning water to the ion exchange softener.
7. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: A booster pump is installed between the softened water product tank and the first-stage reverse osmosis unit, so that the water in the softened water product tank can enter the reverse osmosis unit for desalination treatment. The first-stage reverse osmosis unit is designed with a flux of 15 LMH, a maximum design pressure of 28 bar, and a recovery rate of 75%.
8. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The concentrate reverse osmosis unit is connected to the softened product water tank via a return water pipe, allowing the product water from the concentrate reverse osmosis unit to enter the softened product water tank for further freshwater recovery. The concentrate reverse osmosis unit adopts disc tube reverse osmosis technology, and the membrane module of the concentrate reverse osmosis unit is a novel flat-plate structure membrane module. The concentrate reverse osmosis unit has a designed flux of 10 LMH, a designed maximum pressure of 120 bar, and a recovery rate of 70%.
9. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The high-salinity water tank is connected to the evaporation device.
10. The near-zero discharge treatment system for wastewater in chemical industrial parks according to claim 1, characterized in that: The recycled water tank is equipped with a regenerated water return pipe, which allows the recycled water in the recycled water tank to be transferred through the regenerated water return pipe.