A sewage recycling treatment system for chlor-alkali chemical industry

Abstract

The utility model provides a kind of for chlor-alkali chemical industry's sewage reuse treatment system, covers domestic sewage treatment, industrial wastewater pretreatment, common advanced treatment and effluent unit, also includes sludge treatment unit. Domestic sewage treatment unit is treated by A / O biochemical treatment pool, integrated biochemical MBR membrane biological reaction pool etc.;Industrial wastewater pretreatment unit is equipped with wastewater collection tank, and after being combined with domestic sewage, it is treated by multiple steps such as neutralization, coagulation etc. Common advanced treatment unit is purified by multiple medium filter, ultrafiltration device etc. Effluent unit is divided into freshwater pool and concentrated water pool, freshwater is reused, and concentrated water is used for salt making or external discharge. System structure is unique, effectively reduces membrane pollution, and stable in operation;Component connection realizes energy and resource cascade utilization, and energy efficiency is high;Overall layout provides intensive concentrated water solution, and environmental benefit is good, realizes the chlor-alkali chemical enterprise sewage zero discharge target.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and more specifically to a wastewater reuse treatment system for chlor-alkali chemical industry. Background Technology

[0002] The combined ultrafiltration (UF) and reverse osmosis (RO) process is a mature technology in the field of industrial wastewater reuse and treatment, and it has been widely used in industries such as chlor-alkali chemicals. This process effectively removes suspended solids, colloids, organic matter, and dissolved salts from water through physical sieving and osmotic pressure difference, thus realizing the resource recovery of wastewater.

[0003] However, existing technologies still have significant shortcomings in the specific application scenario of chlor-alkali chemical industry. First, chlor-alkali wastewater has a complex composition and fluctuates greatly in quality, containing large amounts of recalcitrant organic matter, heavy metals, and high salinity, posing a severe challenge to membrane systems. Traditional pretreatment processes (such as conventional coagulation and sedimentation) are insufficient to completely remove colloids and specific organic matter, leading to the easy deposition of residual pollutants on the surfaces of ultrafiltration and RO membranes, causing serious membrane fouling problems, manifested as a rapid decline in membrane flux, increased cleaning frequency, and shortened lifespan. Second, to overcome fouling and osmotic pressure, RO units need to maintain high operating pressures, resulting in high overall system energy consumption. Finally, the high-salt concentrate generated by the RO process is difficult and costly to treat, and direct discharge poses environmental risks. Therefore, developing an optimized integrated system that can specifically address the challenges of membrane fouling, high energy consumption, and concentrate treatment is crucial for promoting the in-depth application of ultrafiltration-RO technology in the chlor-alkali chemical industry. Utility Model Content

[0004] To overcome the above-mentioned technical defects, this application provides a wastewater reuse treatment system for chlor-alkali chemical industry, including a domestic sewage treatment unit, an industrial wastewater pretreatment unit, a common advanced treatment unit, and an effluent unit.

[0005] The domestic sewage treatment unit includes a domestic sewage inlet, an A / O biochemical treatment tank, a collection tank, and an integrated biochemical MBR membrane bioreactor connected in sequence.

[0006] The industrial wastewater pretreatment unit includes an industrial wastewater inlet and a wastewater collection tank; wherein, the effluent from the integrated biochemical MBR membrane bioreactor is connected to the wastewater collection tank via pipelines and pumps, so that domestic sewage and industrial wastewater are combined in the wastewater collection tank; the effluent from the wastewater collection tank is connected sequentially via pipelines to a neutralization reaction tank, a coagulation and flocculation tank, a deep oxidation tank, and an inclined plate sedimentation tank; the supernatant outlet of the inclined plate sedimentation tank is connected to an intermediate water tank via pipelines;

[0007] The common deep treatment unit includes a multi-media filter, an activated carbon filter, a security filter, an ultrafiltration device, and an RO reverse osmosis device; the effluent from the intermediate water tank is connected in sequence to the multi-media filter, activated carbon filter, security filter, ultrafiltration device, ultrafiltration water tank, and RO reverse osmosis device via a pump.

[0008] The effluent unit includes a freshwater tank and a concentrated water tank; the freshwater outlet of the RO reverse osmosis unit is connected to the freshwater tank through a pipeline, and the concentrated water outlet is connected to the concentrated water tank through a pipeline; the freshwater tank is connected to the industrial water tank in the production area through a reuse pipeline, and the concentrated water tank is connected to the salting process or an external wastewater treatment plant through a diversion pipeline.

[0009] It also includes a sludge treatment unit, which is connected to the sludge discharge outlet of the A / O biological treatment tank, the integrated biological MBR membrane bioreactor, the inclined plate sedimentation tank, and the ultrafiltration device via sludge pipes.

[0010] As a preferred embodiment of this application, the A / O biological treatment tank includes an equalization tank, an anoxic tank, and an aerobic tank; the equalization tank is equipped with an influent distributor, the anoxic tank is equipped with a mixed liquor return pipe connected to the aerobic tank, and is also equipped with a micro-aeration device; the aerobic tank is equipped with a sludge return pipe connected to the anoxic tank, and is also equipped with an aeration disc and a dissolved oxygen monitor.

[0011] As a preferred embodiment of this application, the integrated biochemical MBR membrane bioreactor includes a membrane module and a suction pump; the membrane module is a hollow fiber membrane or a flat sheet membrane, and the suction pump is connected to the permeate side of the membrane module through a pipeline.

[0012] As a preferred embodiment of this application, the neutralization reaction tank is equipped with a pH adjustment device, including an acid adder and an alkali adder; the acid adder is connected to a hydrochloric acid storage tank via a metering pump, and the alkali adder is connected to a sodium hydroxide storage tank via a metering pump; the neutralization reaction tank is equipped with a stirrer and an online pH monitor.

[0013] As a preferred embodiment of this application, the coagulation and flocculation tank is equipped with a coagulant dosing device and a flocculant dosing device; the coagulant dosing device is connected to a polyaluminum chloride storage tank via a pipeline, and the flocculant dosing device is connected to a polyacrylamide storage tank via a pipeline; the coagulation and flocculation tank is equipped with a compressed air stirring system and a reaction time controller.

[0014] As a preferred embodiment of this application, the deep oxidation tank is equipped with an oxidant dosing device connected to a hydrogen peroxide storage tank via a metering pump; the deep oxidation tank is equipped with an aeration disc and a compressed air supply system to provide a stirring and oxidation reaction environment.

[0015] As a preferred embodiment of this application, the inclined plate sedimentation tank is equipped with an inlet distributor, an inclined plate assembly, an outlet weir, and a sludge collection device; the sludge collection device is a sludge scraper, and the bottom is equipped with a sludge collection pit and a sludge discharge valve; the outlet weir is connected to an intermediate water tank through a pipeline.

[0016] As a preferred embodiment of this application, the multi-media filter is filled with multiple layers of filter media consisting of quartz sand and anthracite, and has a gravel support layer and a backwashing system at the bottom; the security filter is a disc filter or a bag filter, installed on the pipeline between the multi-media filter and the ultrafiltration device; both the multi-media filter and the security filter are equipped with backwash water return pipelines connected to the neutralization reaction tank.

[0017] As a preferred embodiment of this application, both the ultrafiltration device and the RO reverse osmosis device are equipped with a membrane cleaning system; the membrane cleaning system of the ultrafiltration device includes a NaOH dosing device and a backwashing pipeline, and the cleaning wastewater is discharged to the salt treatment process; the membrane cleaning system of the RO reverse osmosis device includes a scale inhibitor dosing device, a residual chlorine reducing agent dosing device and a special membrane cleaning agent dosing device.

[0018] As a preferred embodiment of this application, the sludge treatment unit includes a sludge pump and a plate and frame filter press; the sludge pump is connected to each sludge discharge point through pipelines to transport the sludge to the sludge tank for dewatering by the plate and frame filter press.

[0019] The wastewater treatment system provided by this utility model has the advantage of effectively solving the problems in the prior art through its unique system structure and component layout:

[0020] 1. The system design effectively reduces membrane fouling and ensures more stable operation: This utility model features a multi-stage, differentiated pretreatment unit layout. For complex industrial wastewater, the system specifically integrates an enhanced pretreatment chain including a neutralization reaction tank, a coagulation and flocculation tank, a deep oxidation tank, and an inclined plate sedimentation tank. This structure efficiently removes suspended solids, colloids, and recalcitrant organic matter from wastewater through the synergistic effect of physical and chemical methods, reducing the treatment load on subsequent membrane systems from the source. In particular, the series connection of the coagulation and flocculation tank and the deep oxidation tank provides a dedicated container for adding agents such as PAC and H2O2 and achieving efficient reactions, ensuring the pretreatment effect and significantly reducing the fouling rate of ultrafiltration and RO membranes, extending the cleaning cycle and service life of membrane elements.

[0021] 2. Component Connection Enables Tiered Energy and Resource Utilization for Higher Energy Efficiency: This utility model's system achieves graded and segmented water resource reuse through innovative pipe and pump connection methods. The system combines the high-quality effluent from the integrated MBR membrane bioreactor with industrial wastewater for treatment. The MBR permeate itself has extremely low turbidity, reducing the burden on subsequent advanced treatment units. More importantly, the system features a separate desalination tank and a concentrate tank at the end, connected to the production reuse point and the salinization process via pipelines. This structural design allows the desalination water produced by RO to be directly reused, while the high-salinity concentrate is utilized as a resource. This not only improves the overall water resource recovery rate but also avoids the high energy consumption of concentrate treatment, reducing operating costs at the system level.

[0022] 3. The overall layout provides an intensive concentrated wastewater solution with good environmental benefits: This utility model's system directly connects the RO concentrated wastewater tank to the brine treatment process through an output pipeline, providing a stable and reliable outlet for the harmless and resource-based treatment of concentrated brine. This built-in structural design transforms concentrated wastewater treatment from traditional end-of-pipe treatment to internal recycling within the production process, reducing the amount of wastewater discharged and the risk of environmental pollution at the source of the system. The layout is compact and environmentally friendly. Attached Figure Description

[0023] Figure 1 This utility model presents an overall schematic diagram of a wastewater reuse treatment system for chlor-alkali chemical industry;

[0024] In the diagram: 1. A / O biological treatment tank; 101. Equalization tank; 102. Anoxic tank; 103. Aerobic tank; 2. Collection tank; 3. Integrated biochemical MBR membrane bioreactor; 4. Neutralization reaction tank; 401. Acid dosing device; 402. Alkali dosing device; 403. Hydrochloric acid storage tank; 404. Sodium hydroxide storage tank; 5. Coagulation and flocculation tank; 501. Coagulant dosing device; 502. Flocculant dosing device; 503. Polyaluminum chloride storage tank. 504. Polyacrylamide storage tank; 6. Multi-media filter; 7. Security filter; 8. Ultrafiltration device; 9. Ultrafiltration water tank; 10. RO reverse osmosis device; 11. Freshwater tank; 12. Concentrated water tank; 13. Deep oxidation tank; 131. Oxidant dosing device; 132. Hydrogen peroxide storage tank; 14. Inclined plate sedimentation tank; 15. Intermediate water tank; 16. Sludge tank; 17. Plate and frame filter press; 18. Wastewater collection tank; 19. Activated carbon filter. Detailed Implementation

[0025] To facilitate understanding of this utility model, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of this utility model are shown in the drawings. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this utility model.

[0026] Unless otherwise defined, 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. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] When describing positional relationships, unless otherwise specified, when an element is referred to as being "on" another element, it may be directly on the other element or there may be intermediate elements. It is also understood that when an element is referred to as being "between" two elements, it may be the only one between the two elements, or there may be one or more intermediate elements.

[0028] When using the terms “including,” “having,” and “comprising” as described herein, another component may be added unless explicitly qualifying terms such as “only,” “consisting of,” etc. are used. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0029] It should also be understood that, in interpreting an element, although not explicitly described, the element is interpreted as including a range of error, which should be within the acceptable deviation range of a particular value as determined by a person skilled in the art. For example, "approximately," "about," or "substantially" can mean within one or more standard deviations, without limitation herein.

[0030] As attached Figure 1 As shown, this application provides a wastewater reuse treatment system for chlor-alkali chemical industry, including a domestic sewage treatment unit, an industrial wastewater pretreatment unit, a combined deep treatment unit, and an effluent unit;

[0031] The domestic sewage treatment unit includes a domestic sewage inlet, an A / O biochemical treatment tank 1, a collection tank 2, and an integrated biochemical MBR membrane bioreactor 3 connected in sequence.

[0032] The industrial wastewater pretreatment unit includes an industrial wastewater inlet and a wastewater collection tank 18. The effluent from the integrated biochemical MBR membrane bioreactor 3 is connected to the wastewater collection tank 18 via pipes and pumps, allowing domestic sewage and industrial wastewater to be combined within the wastewater collection tank 18. The effluent from the wastewater collection tank 18 is sequentially connected via pipes to a neutralization reaction tank 4, a coagulation and flocculation tank 5, a deep oxidation tank 13, and an inclined plate sedimentation tank 14. The supernatant outlet of the inclined plate sedimentation tank 14 is connected via a pipe to an intermediate water tank 15.

[0033] The common deep treatment unit includes a multi-media filter 6, an activated carbon filter 19, a security filter 7, an ultrafiltration device 8, and an RO reverse osmosis device 10; the effluent from the intermediate water tank 15 is connected in sequence to the multi-media filter 6, the activated carbon filter 19, the security filter 7, the ultrafiltration device 8, the ultrafiltration water tank 9, and the RO reverse osmosis device 10 via a pump.

[0034] The effluent unit includes a freshwater tank 11 and a concentrated water tank 12; the freshwater outlet of the RO reverse osmosis unit 10 is connected to the freshwater tank 11 through a pipeline, and the concentrated water outlet is connected to the concentrated water tank 12 through a pipeline; the freshwater tank 11 is connected to the industrial water tank in the production area through a reuse pipeline, and the concentrated water tank 12 is connected to the salting process or an external sewage treatment plant through a diversion pipeline.

[0035] It also includes a sludge treatment unit, which is connected to the sludge discharge outlet of the A / O biological treatment tank 1, the integrated biological MBR membrane bioreactor 3, the inclined plate sedimentation tank 14, and the ultrafiltration device 8 via sludge pipes.

[0036] In one embodiment of this application, the A / O biological treatment tank is the core of the domestic sewage treatment unit, specifically designed for the efficient degradation of organic pollutants and nutrients such as nitrogen and phosphorus in domestic sewage. Further technical details are as follows:

[0037] The equalization tank 101 is not only used to regulate the water volume, but more importantly, it achieves water quality homogenization through the inlet distributor, buffering water quality fluctuations (such as changes in grease and detergent concentration) from different sources of sewage such as office buildings, canteens, and bathhouses, so as to provide stable inlet water conditions for subsequent biological treatment.

[0038] The function of anoxic tank 102 is to achieve denitrification. Dissolved oxygen is precisely controlled below 0.5 mg / L using a micro-aeration device, creating a facultative anaerobic environment. The mixed liquor recirculated from aerobic tank 103 (rich in nitrates) and the organic carbon source in the influent are utilized by denitrifying bacteria here, converting nitrate nitrogen (NO3) into nitrogen. - ) and nitrite nitrogen (NO2) - The sludge is reduced to nitrogen (N2) and discharged, while some BOD is removed. The sludge returned here also maintains a high concentration of activated sludge.

[0039] Aerobic tank 103 is the main site for nitrification and carbonization reactions. Sufficient oxygen is provided through aeration discs, and nitrifying bacteria convert ammonia nitrogen (NH4+) into nitrogen. + Phosphorus is converted into nitrate nitrogen, while heterotrophic bacteria degrade large amounts of organic matter (BOD / COD). An online dissolved oxygen monitor is installed in the tank, linked to the aeration system, to ensure dissolved oxygen is maintained within the optimal range of 2-4 mg / L, preventing incomplete nitrification due to insufficient dissolved oxygen or energy waste due to excessively high dissolved oxygen levels. Polyphosphate-accumulating bacteria absorb excess phosphorus here, and phosphorus removal is achieved through the discharge of excess sludge.

[0040] In one embodiment of this application, the integrated biochemical MBR membrane bioreactor 3 includes a membrane module, a suction pump, and a membrane cleaning interface. The membrane module uses a hollow fiber membrane or a flat sheet membrane, with a pore size typically below 0.1 micrometers, which can efficiently retain activated sludge, suspended solids, and most bacteria and viruses. This allows the sludge concentration (MLSS) in the reactor to be maintained at a high level of 8000-12000 mg / L, far exceeding that of the traditional activated sludge process, thereby greatly enhancing the biodegradation efficiency and reducing the reactor volume.

[0041] The suction pump is connected to the permeate side of the membrane module via piping. The suction pump operates intermittently (e.g., running for 13 minutes, then stopping for 2 minutes), and, combined with regular backwashing (using purified effluent) and maintenance chemical cleaning (e.g., weekly with a low-concentration NaClO solution), effectively mitigates membrane fouling and extends membrane lifespan. The membrane cleaning interface facilitates connection to a cleaning agent dosing system for restorative chemical cleaning.

[0042] The MBR process produces excellent effluent quality with nearly zero suspended solids (SS) and turbidity below 0.1 NTU, providing near-ideal feed conditions for the subsequent RO reverse osmosis system and fundamentally reducing the physical fouling load on ultrafiltration and RO membranes.

[0043] In one embodiment of this application, the neutralization reaction tank 4 is equipped with a pH adjustment device, the core of which is closed-loop automatic control. An online pH monitor detects the influent pH value in real time, and the signal is transmitted to the control system. The control system automatically adjusts the frequency of the metering pumps of the acid dosing device 401 (dosing 31% hydrochloric acid) or the alkali dosing device 402 (dosing 18% NaOH) to accurately add the reagents. This design can quickly respond to water quality fluctuations caused by drainage from the KOH production unit, ensuring that the effluent pH remains stable within the range of 6-9, meeting the optimal pH requirements for subsequent coagulation and biological treatment, and preventing acidic or alkaline wastewater from corroding concrete structures and equipment.

[0044] In one embodiment of this application, the coagulation and flocculation tank 5 is provided with a coagulant dosing device 501 and a flocculant dosing device 502; the coagulant dosing device 501 is connected to a polyaluminum chloride storage tank 503 via a pipeline, and the flocculant dosing device 502 is connected to a polyacrylamide storage tank 504 via a pipeline; the coagulation and flocculation tank 5 is provided with a compressed air stirring system and a reaction time controller.

[0045] The PAC added by coagulant dosing device 501 is an inorganic polymeric coagulant, whose main function is to destabilize negatively charged colloidal particles in the water through charge neutralization. The PAM added by flocculant dosing device 502 is an organic polymeric flocculant, which utilizes its long molecular chains to "adsorb and bridge" between the destabilized colloidal particles, forming larger and stronger flocs and accelerating the settling speed. The compressed air agitation is adjusted to a slow speed at this stage to avoid breaking the already formed flocs.

[0046] In one embodiment of this application, the deep oxidation tank 13 is equipped with an oxidant dosing device 131, which is connected to a hydrogen peroxide storage tank 132 via a metering pump. The deep oxidation tank 13 contains an aeration disc and a compressed air supply system to provide a stirring and oxidation reaction environment. The oxidant dosing device 131 adds hydrogen peroxide (H2O2) via the metering pump. Under the oxygen provided by the compressed air supply system and the stirring action, strong oxidizing substances such as hydroxyl radicals may be generated (especially under specific catalyst or pH conditions). This partially oxidizes and decomposes recalcitrant organic matter (such as chlorinated organics and characteristic pollutants) in the wastewater, improving the biodegradability of the wastewater and reducing the organic pollution load of the subsequent membrane treatment unit. The microbubbles generated by the aeration disc not only provide the oxygen required for the oxidation reaction but also act as a stirrer, ensuring thorough mixing of the hydrogen peroxide and wastewater, and guaranteeing efficient and uniform oxidation. This unit design effectively addresses the problem of complex organic composition and poor biodegradability in chlor-alkali chemical wastewater.

[0047] In one embodiment of this application, the inclined plate sedimentation tank 14 is equipped with an inlet distributor, an inclined plate assembly, an outlet weir, and a sludge collection device. The sludge collection device employs a scraper and has a sludge collection pit and a sludge discharge valve at the bottom. The outlet weir is connected to an intermediate water tank 15 via a pipeline. The inlet distributor evenly distributes water flow across the entire tank cross-section, allowing it to pass smoothly through the inclined plate assembly. The inclined plates significantly increase the settling area and shorten the settling distance of particles, thereby significantly improving settling efficiency and reducing the footprint of the sedimentation tank. The scraper operates slowly, scraping the sludge settled at the bottom of the tank into the sludge collection pit, and the sludge is periodically discharged through the sludge discharge valve. The efficient sludge-water separation ensures the quality of the supernatant; the suspended solids (SS) and turbidity of the supernatant collected by the outlet weir are significantly reduced, laying a good foundation for entry into the intermediate water tank and subsequent deep filtration units.

[0048] In one embodiment of this application, the multi-media filter 6 is filled with multiple layers of filter media consisting of quartz sand and anthracite, and has a gravel support layer and a backwashing system at the bottom. The security filter 7 is a disc filter or a bag filter, installed on the pipeline between the multi-media filter 6 and the ultrafiltration device 8. Both the multi-media filter 6 and the security filter 7 are equipped with backwash water return pipes connected to the neutralization reaction tank 4. The quartz sand (fine particle size, used for fine filtration) and anthracite (coarse particle size, used to trap larger particles) filled in the multi-media filter form an ideal filtration layer from top to bottom, effectively removing trace suspended solids and colloids remaining in the effluent from the inclined plate sedimentation tank. The gravel support layer at the bottom prevents filter media loss. The periodically activated backwashing system (using water and air) removes impurities trapped in the filter layer, and the backwash water return pipe leads this wastewater back to the neutralization reaction tank or wastewater collection tank, avoiding direct discharge and load impact.

[0049] Security filters typically use filter cartridges (disc or bag type) with a filtration accuracy of 5–10 microns. They act as "bodyguards" for ultrafiltration units, ensuring that no particles that could damage or clog the pores of the ultrafiltration membrane enter subsequent units. They are the last physical barrier protecting expensive membrane elements.

[0050] In one embodiment of this application, the ultrafiltration device 8 and the RO reverse osmosis device 10 are further provided with a membrane cleaning system;

[0051] The membrane cleaning system of ultrafiltration unit 8 includes periodically performed chemical enhanced backwashing (CEB) and restorative cleaning (CIP). CEB typically involves adding a low concentration of NaOH or NaClO solution to remove organic fouling and biofilm. CIP is performed when membrane fouling is severe, using a specially formulated acid (such as citric acid to remove inorganic scale) and alkali (such as NaOH + NaClO to remove organic matter and biofouling) for cyclic cleaning. The cleaning wastewater contains high concentrations of pollutants and is transported to a salt treatment process for centralized treatment to prevent secondary pollution.

[0052] The membrane cleaning system of the ultrafiltration device 8 includes a NaOH dosing device and a backwashing pipeline, and the cleaning wastewater is discharged to the salt treatment process; the membrane cleaning system of the RO reverse osmosis device 10 includes a scale inhibitor dosing device, a residual chlorine reducing agent dosing device and a special membrane cleaning agent dosing device.

[0053] The membrane cleaning system of the RO reverse osmosis unit 10 is more complex. Its pretreatment includes an antiscalant dosing device (to prevent the formation of scale on the membrane surface from slightly soluble salts such as CaCO3 and CaSO4) and a residual chlorine reducing agent dosing device (usually sodium bisulfite, to protect the polyamide RO membrane from oxidative damage by residual chlorine). CIP cleaning uses specialized acidic and alkaline cleaning agents to clean specific fouling substances from the RO membrane. This system significantly extends the service life of the RO membrane and reduces replacement frequency and costs.

[0054] In one embodiment of this application, the sludge treatment unit includes a sludge pump and a plate and frame filter press; the sludge pump is connected to each sludge discharge point via pipelines to transport the sludge to the salt treatment process for filter press dewatering. The sludge pump collects the excess sludge from the A / O tank, MBR tank, inclined plate sedimentation tank, and ultrafiltration backwashing.

[0055] Plate and frame filter presses dewater mixed sludge under high pressure, forming sludge cakes with low moisture content (typically below 60%). These sludge cakes are then sent to the salt treatment process as general solid waste. The proposal mentions that the sludge can be treated as general solid waste or recycled (such as potential use in building materials), reflecting the system's environmental friendliness and circular economy principles in solid waste disposal.

[0056] Working principle: This wastewater treatment system adopts the principle of "graded pretreatment, combined deep treatment, and resource reuse" to achieve efficient purification and near-zero discharge of complex wastewater from chemical industrial parks.

[0057] The system first separates domestic sewage and industrial wastewater for treatment. Domestic sewage undergoes preliminary denitrification and carbon removal in an A / O biological treatment tank, followed by deep biological treatment and ultrafiltration separation using an integrated MBR membrane bioreactor, producing clear, high-quality effluent rich in activated sludge. Industrial wastewater is collected in a wastewater collection tank.

[0058] After merging, the wastewater enters the main industrial wastewater treatment line. First, the pH is adjusted to neutral in a neutralization reaction tank to create an optimal environment for subsequent reactions. In the coagulation and flocculation tank and the deep oxidation tank, agents such as PAC, PAM, and H2O2 are added. Through charge neutralization, adsorption bridging, and oxidative decomposition, suspended solids, colloids, and recalcitrant organic matter are efficiently removed. This enhanced pretreatment unit is one of the core innovations of this process, aiming to minimize the fouling load on the subsequent membrane system. The treated sludge-water mixture undergoes efficient separation in an inclined plate sedimentation tank.

[0059] The supernatant enters the advanced treatment unit, where it undergoes fine filtration through a multi-media filter and a security filter to thoroughly remove fine particulate matter before finally entering the core of the membrane system. The ultrafiltration unit serves as pretreatment for RO, further ensuring the quality of the feed water, and its permeate enters the RO reverse osmosis unit. Under high pressure, the RO membrane completely separates water molecules from dissolved salts, organic matter, and other contaminants, producing high-quality freshwater for reuse in production. The concentrated wastewater, due to the high concentration of contaminants, is partially reused for desalination, with the excess discharged.

[0060] All sludge generated throughout the process is collected and dewatered, achieving solid waste reduction and proper disposal. The entire system effectively solves the problems of membrane fouling, high energy consumption, and concentrated saline wastewater treatment by optimizing pretreatment and enhancing the coupling of biochemical and membrane processes, ultimately achieving the dual recovery and utilization of water resources and salt.

[0061] The above embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them. Although the embodiments of this application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope defined by the claims of this application.

Claims

1. A wastewater reuse treatment system for chlor-alkali chemical industry, characterized in that, It includes a domestic sewage treatment unit, an industrial wastewater pretreatment unit, a combined advanced treatment unit, and an effluent unit; The domestic sewage treatment unit includes a domestic sewage inlet, an A / O biochemical treatment tank (1), a collection tank (2), and an integrated biochemical MBR membrane bioreactor (3) connected in sequence. The industrial wastewater pretreatment unit includes an industrial wastewater inlet and a wastewater collection tank (18); the effluent from the integrated biochemical MBR membrane bioreactor (3) is connected to the wastewater collection tank (18) via pipes and pumps, so that domestic sewage and industrial wastewater are combined in the wastewater collection tank (18); the effluent from the wastewater collection tank (18) is connected in sequence via pipes to the neutralization reaction tank (4), the coagulation and flocculation tank (5), the deep oxidation tank (13), and the inclined plate sedimentation tank (14); the supernatant outlet of the inclined plate sedimentation tank (14) is connected to the intermediate water tank (15) via pipes. The common deep treatment unit includes a multi-media filter (6), a security filter (7), an activated carbon filter (19), an ultrafiltration device (8), and an RO reverse osmosis device (10); the effluent from the intermediate water tank (15) is connected in sequence to the multi-media filter (6), the activated carbon filter (19), the security filter (7), the ultrafiltration device (8), the ultrafiltration water tank (9), and the RO reverse osmosis device (10) via a pump; The effluent unit includes a freshwater tank (11) and a concentrated water tank (12); the freshwater outlet of the RO reverse osmosis unit (10) is connected to the freshwater tank (11) through a pipeline, and the concentrated water outlet is connected to the concentrated water tank (12) through a pipeline; the freshwater tank (11) is connected to the industrial water tank in the production area through a reuse pipeline, and the concentrated water tank (12) is connected to the salting process or an external sewage treatment plant through a diversion pipeline; It also includes a sludge treatment unit, which is connected to the sludge discharge port of the A / O biological treatment tank (1), the integrated biological MBR membrane bioreactor (3), the inclined plate sedimentation tank (14), and the ultrafiltration device (8) via sludge pipes.

2. A wastewater reuse treatment system for chlor-alkali chemical industry as claimed in claim 1, wherein, The A / O biological treatment tank (1) includes an equalization tank (101), an anoxic tank (102), and an aerobic tank (103); the equalization tank (101) is equipped with an inlet distributor, the anoxic tank (102) is equipped with a mixed liquor return pipe connected to the aerobic tank (103), and is equipped with a micro-aeration device; the aerobic tank (103) is equipped with a sludge return pipe connected to the anoxic tank (102), and is equipped with an aeration disc and a dissolved oxygen monitor.

3. A wastewater reuse treatment system for chlor-alkali chemical industry as claimed in claim 1 wherein, The integrated biochemical MBR membrane bioreactor (3) includes a membrane module and a suction pump; the membrane module is a hollow fiber membrane or a flat sheet membrane, and the suction pump is connected to the product water side of the membrane module through a pipeline.

4. A wastewater reuse treatment system for chlor-alkali chemical industry as described in claim 1, characterized in that, The neutralization reaction tank (4) is equipped with a pH adjustment device, including an acid adder (401) and an alkali adder (402); the acid adder (401) is connected to the hydrochloric acid storage tank (403) via a metering pump, and the alkali adder (402) is connected to the sodium hydroxide storage tank (404) via a metering pump; the neutralization reaction tank (4) is equipped with a stirrer and an online pH monitor.

5. A wastewater reuse treatment system for chlor-alkali chemical industry as described in claim 1, characterized in that, The coagulation and flocculation tank (5) is equipped with a coagulant dosing device (501) and a flocculant dosing device (502); the coagulant dosing device (501) is connected to a polyaluminum chloride storage tank (503) through a pipeline, and the flocculant dosing device (502) is connected to a polyacrylamide storage tank (504) through a pipeline.

6. A wastewater reuse treatment system for chlor-alkali chemical industry as described in claim 1, characterized in that, The deep oxidation tank (13) is equipped with an oxidant dosing device (131), which is connected to a hydrogen peroxide storage tank (132) via a metering pump; the deep oxidation tank (13) is equipped with an aeration disc and a compressed air supply system to provide a stirring and oxidation reaction environment.

7. A wastewater reuse treatment system for chlor-alkali chemical industry as described in claim 1, characterized in that, The inclined plate sedimentation tank (14) is equipped with an inlet distributor, an inclined plate group, an outlet weir and a sludge collection device; the sludge collection device adopts a sludge scraper, and the bottom is equipped with a sludge collection pit and a sludge discharge valve; the outlet weir is connected to the intermediate water tank (15) through a pipeline.

8. A wastewater reuse treatment system for chlor-alkali chemical industry as claimed in claim 1 wherein, The multi-media filter (6) is filled with a multi-layer filter media of quartz sand and anthracite, and has a gravel support layer and a backwashing system at the bottom; the security filter (7) is a disc filter or a bag filter, installed on the pipeline between the multi-media filter (6) and the ultrafiltration device (8); both the multi-media filter (6) and the security filter (7) are equipped with backwash water return pipelines, which are connected to the neutralization reaction tank (4).

9. A wastewater reuse treatment system for chlor-alkali chemical industry as described in claim 1, characterized in that, The sludge treatment unit includes a sludge pump and a plate and frame filter press (17); the sludge pump is connected to each sludge discharge point through a pipeline to transport the sludge to the sludge tank (16) and the plate and frame filter press (17) dewaters it.

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