Papermaking reclaimed water reuse concentrated water resource treatment system

Abstract

The utility model discloses a papermaking reclaimed water reuse concentrated water resource treatment system which comprises a fresh water reuse treatment system and an acid and alkali production reuse treatment system, papermaking reclaimed water reuse concentrated water is treated by the fresh water reuse treatment system to recover fresh water or is discharged after reaching the standard, and then is treated by the acid and alkali production reuse treatment system to recover acid and alkali; the purpose of high effluent recycling rate is achieved, the emission can be reduced, the operation cost can be reduced, and the purpose of resource utilization can be achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of concentrated water treatment in the papermaking industry, in particular to a concentrated water resource treatment system for reuse of papermaking reclaimed water. Background Art

[0002] The papermaking process generates a large amount of wastewater, often characterized by high COD and hardness and relatively poor biodegradability. In the past, as national standards for papermaking wastewater discharge tightened, companies primarily relied on pretreatment and advanced treatment to meet more stringent discharge requirements and achieve partial water reuse. Pretreatment typically involves sedimentation, filtration, and biochemical treatment, primarily removing COD, hardness, and SS. Advanced treatment, on the other hand, often employs technologies such as advanced oxidation and membrane separation to further remove organic matter and suspended solids, ultimately ensuring that the effluent meets discharge standards or requires reuse. In areas with scarce water resources, to minimize emissions and achieve comprehensive water resource utilization, companies must establish water reuse systems after pretreatment and advanced treatment to further treat the wastewater, further reducing COD, hardness, and other indicators, thereby increasing water reuse rates. In the current climate of sustainable development, the papermaking industry, a heavily polluting industry, is required to comprehensively research and develop zero-discharge processes for papermaking wastewater to minimize environmental pollution. The current goal of zero-discharge papermaking wastewater processes is to concentrate and recycle wastewater for reuse, striving to achieve zero wastewater discharge. This requires treating the brine generated during the reclaimed water reuse process. However, this brine undergoes a multi-stage concentration process that continuously increases in salt, resulting in high COD and hardness. Proper final treatment poses a major challenge to the industry's zero-discharge wastewater process. The current primary solution for this salt-rich brine is a combined process of pretreatment, multi-stage membrane concentration, and evaporation and crystallization. This process concentrates and crystallizes the salts and solid impurities in the brine into a solid form, which is then sent to a landfill at a waste treatment plant or recycled as a chemical raw material for resource utilization. However, the core evaporation and crystallization process suffers from large land occupation, high operating costs, and inconsistent product salt quality. This large footprint makes it unsuitable for papermaking companies to utilize existing land for transformation and upgrading. High operating costs create significant operational pressure, while inconsistent product quality prevents resource utilization and directly reduces the economic benefits of the entire system.

[0003] How to use feasible and reasonable process technology to achieve a high water reuse rate, reduce emissions, lower operating costs and achieve the goal of resource utilization is an urgent problem that the papermaking industry needs to solve. Utility Model Content

[0004] In view of this, the purpose of the present invention is to provide a papermaking concentrated water resource treatment system that can achieve a high water reuse rate, reduce emissions, lower operating costs and achieve resource utilization.

[0005] The utility model relates to a papermaking recycled water recovery and concentrated water resource treatment system, comprising a fresh water recovery and treatment system and an acid and alkali production recovery and treatment system. The recycled water is firstly treated by the fresh water recovery and treatment system to recover fresh water or meet the discharge standards, and then treated by the acid and alkali production recovery and treatment system to recover acid and alkali.

[0006] Furthermore, the fresh water reuse treatment system includes a concentrated water regulating tank, a primary coagulation and sedimentation hardness removal system, a multi-media filter, a primary ozone oxidation system, an activated carbon biological filter, an ultrafiltration system and a reverse osmosis system that are connected in sequence. The concentrated water regulating tank is used to regulate and buffer the water quantity and water quality of the concentrated water. The primary coagulation and sedimentation hardness removal system is connected to the concentrated water regulating tank pipeline for coagulation and sedimentation and chemical hardness removal of the incoming water from the concentrated water regulating tank. The multi-media filter is connected to the primary coagulation and sedimentation hardness removal system pipeline for filtering the primary coagulation and sedimentation hardness removal effluent. The primary ozone oxidation system is connected to the multi-media filter pipeline for ozone oxidation treatment of the effluent from the multi-media filter. The activated carbon biological filter is connected to the primary ozone oxidation system pipeline for biological activated carbon filtration reaction treatment of the effluent from the primary ozone oxidation. The ultrafiltration system is connected to the activated carbon biological filter pipeline for ultrafiltration treatment of the effluent from the activated carbon biological filter. The reverse osmosis system is used to reverse osmosis treatment of the effluent from the ultrafiltration system to produce fresh water and high-salt concentrated water.

[0007] Further, the reverse osmosis system includes a primary reverse osmosis system and a concentrated water reverse osmosis system, the primary reverse osmosis system is connected to the ultrafiltration system pipeline for reverse osmosis treatment of the effluent of the ultrafiltration system, the primary reverse osmosis produces fresh water and concentrated water, the concentrated water reverse osmosis system is connected to the primary reverse osmosis system pipeline for reverse osmosis treatment of the concentrated water of the primary reverse osmosis system, the concentrated water reverse osmosis produces fresh water and highly concentrated brine;

[0008] Furthermore, the filter media of the multi-media filter is quartz sand and anthracite; the ultrafiltration membrane of the ultrafiltration system is at least one of a tubular ultrafiltration membrane, a plate and frame ultrafiltration membrane, a spiral ultrafiltration membrane, and a hollow fiber ultrafiltration membrane; the osmotic membrane of the primary reverse osmosis system and the concentrated water reverse osmosis system is an anti-pollution membrane, selected from at least one of a disc tube reverse osmosis membrane, a fiber reverse osmosis membrane, a spiral reverse osmosis membrane, and a plate and frame reverse osmosis membrane;

[0009] Furthermore, the acid and alkali production recycling treatment system includes a secondary ozone oxidation system, a secondary coagulation and sedimentation hardness removal system, a sand filtration system, a resin softening system, an activated carbon filter, an electrodialysis system, a chelate resin system and a bipolar membrane electrodialysis system which are connected in sequence. The secondary ozone oxidation system is connected to the concentrated water reverse osmosis system pipeline for ozone oxidation treatment of the highly concentrated brine of the concentrated water reverse osmosis system, the secondary coagulation and sedimentation hardness removal system is connected to the secondary ozone oxidation system pipeline for precipitation and chemical hardness removal of the secondary ozone oxidation effluent, the sand filtration system is connected to the secondary coagulation and sedimentation hardness removal system pipeline for filtering the secondary coagulation and sedimentation hardness removal effluent, and the resin The fat softening system is connected to the sand filter pipeline for softening the sand filter effluent, the activated carbon filter is connected to the resin softening system pipeline for filtering and adsorbing the resin softened effluent, the electrodialysis system is connected to the activated carbon filter pipeline for performing electrodialysis concentration treatment on the effluent of the activated carbon filter, and fresh water and concentrated water are produced through electrodialysis concentration, the chelating resin system is connected to the electrodialysis system pipeline for performing chelating resin softening treatment on the concentrated water of the electrodialysis, and the bipolar membrane electrodialysis system is connected to the chelating resin system pipeline for performing bipolar membrane electrodialysis treatment on the effluent of the chelating resin, and acid, alkali and dilute brine are produced through bipolar membrane electrodialysis;

[0010] Furthermore, the secondary ozone oxidation system includes an ozone catalytic oxidation tank, an ozone tail gas destruction device, and an ozone aeration device; and / or, the secondary ozone oxidation and the primary ozone oxidation share an ozone generator; the resin softening system and the chelating resin system both use sodium ion exchangers, and / or, the resin softening system and the chelating resin system are connected to a regeneration water pump;

[0011] Furthermore, the electrodialysis system is connected to a first-stage reverse osmosis system pipeline, and the fresh water produced after treatment by the electrodialysis system is mixed with the first-stage reverse osmosis concentrated water;

[0012] Furthermore, the electrodialysis system includes a membrane stack, a matching water tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system, and an electrical instrument automation system; the bipolar membrane electrodialysis system includes a membrane stack, a matching water tank and storage tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system, and an electrical instrument automation system;

[0013] Furthermore, the bipolar membrane electrodialysis system is connected to the electrodialysis system pipeline for returning the dilute brine produced by the bipolar membrane electrodialysis system to the front end of the electrodialysis system for circulation treatment;

[0014] Furthermore, the multi-media filter, activated carbon biofilter, activated carbon filter, and sand filtration system are all connected to a backwash water pump for backwashing the filter tank and filter.

[0015] The beneficial effects of the present invention are as follows: the papermaking recycled water reuse and concentrated water resource treatment system of the present invention adopts a combination of an ozone oxidation system and an activated carbon biological filtration system to stably and efficiently remove most of the COD in the wastewater, and the effluent COD is ≤30mg / L, which meets the quality requirements of the recycled water; the coagulation and sedimentation hardness removal system and the resin softening system are adopted to efficiently remove the hardness in the wastewater, creating good conditions for the fresh water reuse and the final resource utilization of concentrated water; the use of a first-stage reverse osmosis, concentrated water reverse osmosis and electrodialysis system can obtain an ultra-high recycled water rate, and the fresh water reuse rate of the whole system can exceed 90%, while achieving the concentration and reduction of salt; the electrodialysis system is adopted to efficiently concentrate the salty water, and at the same time cooperates with the bipolar membrane system to produce acid and alkali, and the salt is converted into acid and alkali for reuse, realizing a high degree of resource utilization of concentrated water and greatly reducing the discharge of salt. At the same time, compared with evaporation crystallization, the bipolar membrane electrodialysis system occupies less space and has lower operating costs, which is suitable for the transformation and upgrading of existing factories. When the acid and alkali can be reused in the factory, the resource utilization advantage of the bipolar membrane electrodialysis system is obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0017] Figure 1 It is a structural diagram of the present utility model. DETAILED DESCRIPTION

[0018] The papermaking wastewater recycling and treatment system of this embodiment includes a freshwater recycling and treatment system and an acid and alkali production recycling and treatment system. The papermaking wastewater is first treated in the freshwater recycling and treatment system to recover freshwater or meet discharge standards, and then treated in the acid and alkali production recycling and treatment system to recover acid and alkali. The wood pulping process mainly produces black (red) liquor and midstream wastewater. Black (red) liquor is mainly pulping wastewater, and midstream wastewater includes pulp washing, screening, and bleaching wastewater. Of these, pulping wastewater is the most polluting, with high COD, high chroma, and high suspended solids content, accounting for 90% of the pollution in the entire papermaking industry.

[0019] In this embodiment, the fresh water reuse treatment system includes a concentrated water regulating tank, a primary coagulation and sedimentation hardness removal system, a multi-media filter, a primary ozone oxidation system, an activated carbon biological filter, an ultrafiltration system and a reverse osmosis system connected in sequence. The concentrated water regulating tank is used to regulate and buffer the water quantity and water quality of concentrated water. The primary coagulation and sedimentation hardness removal system is connected to the concentrated water regulating tank pipeline for coagulation and sedimentation and chemical hardness removal of the incoming water from the concentrated water regulating tank. The multi-media filter is connected to the primary coagulation and sedimentation hardness removal system pipeline for filtering the primary coagulation and sedimentation hardness removal effluent. The primary ozone oxidation system is connected to the multi-media filter. The pipeline connection is used to ozone-oxidize the effluent from the multi-media filter. The activated carbon biofilter is connected to the primary ozone oxidation system through a pipeline for biological activated carbon filtration reaction treatment of the effluent from the primary ozone oxidation. The ultrafiltration system is connected to the activated carbon biofilter through a pipeline for ultrafiltration treatment of the effluent from the activated carbon biofilter. The reverse osmosis system is used to reverse osmosis-treat the effluent from the ultrafiltration system to produce fresh water and high-salt concentrated water. The regulating tank primarily functions to regulate water volume, balance water quality, and perform pretreatment. The concentrated water regulating tank of the present invention is used to regulate and buffer the concentrated water volume and quality. The coagulation and sedimentation hardness removal system generally refers to equipment that uses a coagulation and sedimentation hardness removal process and is currently available. A multi-media filter utilizes two or more filter media to force turbid water through a layer of granular or non-granular material at a certain pressure, effectively removing suspended impurities and clarifying the water. Common filter media include quartz sand, anthracite, and manganese sand. It is primarily used for water treatment, turbidity removal, water softening, and pre-treatment of purified water, achieving effluent turbidity levels below 3°C. A multi-media filter (filter bed) utilizes two or more media as filter layers. In industrial circulating water treatment systems, it is used to remove impurities and adsorb oil from wastewater, ensuring that water quality meets recycling requirements. Filtration primarily removes suspended or colloidal impurities from water, particularly small particles and bacteria that cannot be removed by precipitation techniques. It also has some effectiveness in removing BOD5 and COD. An ozone oxidation system primarily consists of an ozone generation system, an ozone source system, a cooling water system, an ozone dosing system, an exhaust gas destruction system, and system control. This is currently available technology. Ultrafiltration is a membrane separation method that utilizes the microporous structure of a semipermeable membrane, using a constant external pressure (0.1-0.5 MPa) as the driving force, to achieve the selective separation and recovery of substances. In wastewater treatment, it is primarily used to separate and recover macromolecules and colloids with molecular weights greater than 500 and diameters of 0.005-10 μm, such as enzymes, proteins, viruses, and other low- to medium-concentration dissolved and colloidal contaminants. An ultrafiltration system refers to existing equipment and devices that utilize ultrafiltration technology. Reverse osmosis, also known as reverse osmosis, is a membrane separation process that uses a pressure differential as the driving force to separate a solvent from a solution. Pressure is applied to the liquid on one side of the membrane. When the pressure exceeds its osmotic pressure, the solvent permeates in the opposite direction of its natural osmotic flow.Thus, the permeate is obtained on the low-pressure side of the membrane; the concentrated solution is obtained on the high-pressure side. Compared with other traditional separation projects, the reverse osmosis separation process has its unique advantages: (1) Pressure is the main driving force of the reverse osmosis separation process, and there is no phase change with energy-intensive exchange, so the energy consumption is low; (2) Reverse osmosis does not require a large amount of precipitants and adsorbents, and the operating cost is low; (3) The design and operation of the reverse osmosis separation project are simple, and the construction period is short; (4) Reverse osmosis purification efficiency is high and environmentally friendly. Therefore, reverse osmosis technology has been widely used in domestic and industrial water treatment, such as seawater and brackish water desalination, medical and industrial water production, pure water and ultrapure water preparation, industrial wastewater treatment, food processing concentration, gas separation, etc. Reverse osmosis system refers to existing equipment and devices that use reverse osmosis technology.

[0020] In this embodiment, the reverse osmosis system includes a primary reverse osmosis system and a concentrate reverse osmosis system. The primary reverse osmosis system is connected to an ultrafiltration system pipeline for reverse osmosis treatment of the effluent from the ultrafiltration system, producing fresh water and concentrate. The concentrate reverse osmosis system is connected to the primary reverse osmosis system pipeline for reverse osmosis treatment of the concentrate from the primary reverse osmosis system, producing fresh water and highly concentrated brine. During reverse osmosis, the osmotic membrane is selected from at least one of a disc-tube reverse osmosis membrane, a fiber reverse osmosis membrane, a spiral reverse osmosis membrane, and a plate-and-frame reverse osmosis membrane. During primary reverse osmosis, the operating pressure is 0.5 to 2 MPa, preferably 1.2 MPa. During concentrate reverse osmosis, the operating pressure is 0.5 to 2 MPa, preferably 1.5 MPa.

[0021] Optionally, the fresh water recovery rate of the first-stage reverse osmosis membrane is 60-75% (v / v), and the fresh water is reused in production. That is, the volume of the effluent passing through the reverse osmosis membrane accounts for 60-75% of the volume of the reverse osmosis inlet water; the fresh water recovery rate of the concentrated water reverse osmosis membrane is 40-60% (v / v), and the fresh water is reused in production. That is, the volume of the effluent passing through the reverse osmosis membrane accounts for 40-60% of the volume of the reverse osmosis inlet water; the membrane flux of the first-stage reverse osmosis membrane is 16-20LMH, and the membrane flux of the concentrated water reverse osmosis membrane is 13-15LMH, where LMH is L / m 2*h; Optionally, the primary coagulation and sedimentation removal and the secondary coagulation and sedimentation removal use a high-efficiency sedimentation tank; the multi-media filter material uses quartz sand + anthracite; the primary ozone oxidation system includes an ozone generator, an ozone catalytic oxidation tank, an ozone tail gas destruction device, and an ozone aeration device, all of which are existing technologies; the water tank of the primary ozone oxidation system adopts water sealing, and an exhaust gas treatment device is provided at the exhaust end, which can be specifically an exhaust gas collection and destruction device; between the primary coagulation and sedimentation removal and the multi-media filter, the Intermediate water tanks are installed between the primary ozone oxidation and the activated carbon biofilter, and between the activated carbon biofilter and the ultrafiltration system, for storing water. Once the water volume reaches a certain level, it enters the subsequent process. The multi-media filtration, activated carbon biofilter, activated carbon filter, and sand filtration are all connected to backwash pumps for regular or irregular backwashing of the filter and filter to prevent clogging. The ultrafiltration membrane of the ultrafiltration system is selected from at least one of tubular ultrafiltration membranes, plate-and-frame ultrafiltration membranes, roll-type ultrafiltration membranes, and hollow fiber ultrafiltration membranes. The brine from the ultrafiltration system is connected to a brine conditioning tank via a pipeline, allowing the brine to return to the brine conditioning step for reprocessing. The osmotic membranes used in the primary reverse osmosis system and the brine reverse osmosis are selected from at least one of disc-tube reverse osmosis membranes, fiber-type reverse osmosis membranes, roll-type reverse osmosis membranes, and plate-and-frame reverse osmosis membranes, and are anti-fouling membranes. The reverse osmosis system includes a roll-type composite polyamide membrane, and the fresh water outlet of the reverse osmosis system is connected to the water inlet tank of the water-demanding production equipment. The concentrate outlet of the primary reverse osmosis system is connected to the primary reverse osmosis concentrate tank, and the water inlet pump suction pipe of the concentrate reverse osmosis system is connected to the primary reverse osmosis concentrate tank, so that the concentrate reverse osmosis can absorb water from the primary reverse osmosis concentrate tank. The COD of the concentrate is ≤100mg / L, the total hardness is ≤1500mg / L, and the TDS is 5000-6500mg / L. The concentrate is the concentrate produced after the papermaking wastewater is treated by the reclaimed water reuse system. During the primary coagulation and sedimentation reaction to remove hardness, the coagulant is selected from one of polyaluminum chloride (PAC) and polyferric sulfate (PFS), and the flocculant is PAM (polyacrylamide). During the primary coagulation and sedimentation reaction to remove hardness, the coagulant dosage is 30mg / L, the flocculant dosage is 2mg / L, the lime dosage is 1800mg / L, and the soda ash dosage is 1600mg / L. During the primary coagulation and sedimentation reaction, the coagulation reaction time is 2 to 5 minutes, preferably 3 minutes; the flocculation reaction time is 10 to 20 minutes, preferably 15 minutes; the hardness removal reaction time is 20 to 40 minutes, preferably 30 minutes; after the flocculation reaction, the sedimentation time is 30 to 60 minutes, preferably 30 minutes. When the multi-media filter is working, the filtration rate is 10 to 15 m / h, preferably 10 m / h, and the turbidity of the effluent is controlled to be ≤10 NTU. During the primary ozone oxidation, fillers, catalysts and aerators are set in the reaction tank, the tank is water-sealed, and an exhaust gas absorption device is set at the end.During primary ozone oxidation, the mass ratio of ozone and COD is (3-4):1, preferably 3:1. During primary ozone oxidation, the reaction time is 1-2 hours, preferably 2 hours. In the activated carbon biofilter, the height of the activated carbon filler is 1.5-2 meters, and the filtration rate is 3-5 m / h. When the activated carbon biofilter is working, the COD of the filtered effluent is ≤30 mg / L, and the turbidity of the effluent is 1-5 NTU. During ultrafiltration, the ultrafiltration membrane is selected from at least one of a tubular ultrafiltration membrane, a plate and frame ultrafiltration membrane, a roll ultrafiltration membrane, and a hollow fiber ultrafiltration membrane. During ultrafiltration, the operating pressure is 0.2-0.4 MPa, preferably 0.2-0.3 MPa; the clean water recovery rate is not less than 90% (v / v).

[0022] In this embodiment, the acid and alkali production reuse treatment system includes a secondary ozone oxidation system, a secondary coagulation and sedimentation hardness removal system, a sand filtration system, a resin softening system, an activated carbon filter, an electrodialysis system, a cacodylation resin system and a bipolar membrane electrodialysis system that are connected in sequence. The secondary ozone oxidation system is connected to the concentrated water reverse osmosis system pipeline for ozone oxidation treatment of the highly concentrated brine of the concentrated water reverse osmosis system, the secondary coagulation and sedimentation hardness removal system is connected to the secondary ozone oxidation system pipeline for precipitation and chemical de-hardening of the secondary ozone oxidation effluent, the sand filtration system is connected to the secondary coagulation and sedimentation hardness removal system pipeline for filtering the secondary coagulation and sedimentation hardness removal effluent, and the resin softening system is connected to the sand filtration pipeline for The sand filter effluent is softened, the activated carbon filter is connected to the resin softening system pipeline for filtering and adsorbing the resin softened effluent, the electrodialysis system is connected to the activated carbon filter pipeline for electrodialysis concentration of the activated carbon filter effluent, and fresh water and concentrated water are produced through electrodialysis concentration, the chelating resin system is connected to the electrodialysis system pipeline for chelating the concentrated water of the electrodialysis with resin, the bipolar membrane electrodialysis system is connected to the chelating resin system pipeline for bipolar membrane electrodialysis of the effluent of the chelating resin, and acid, alkali and dilute brine are produced through bipolar membrane electrodialysis; the secondary ozone oxidation system includes an ozone catalytic oxidation tank, an ozone tail gas destruction device, and an ozone aeration device. Optionally, the secondary ozone oxidation and the primary ozone oxidation share an ozone generating device; the resin softening and resin chelating equipment adopts a sodium ion exchanger; the resin softening and resin chelating equipment is connected to a backwash water pump and a regeneration water pump; the electrodialysis system adopts a complete set of equipment, including a membrane stack, a matching water tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system, and an electrical instrument automation system, all of which are prior art; the bipolar membrane electrodialysis system adopts a complete set of equipment, including a membrane stack, a matching water tank and storage tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system, and an electrical instrument automation system, all of which are prior art.

[0023] In this embodiment, the electrodialysis system is connected to the primary reverse osmosis system via piping, and the freshwater produced after treatment by the electrodialysis system is mixed with the primary reverse osmosis concentrate. The electrodialysis system includes a membrane stack, a supporting water tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system, and an electrical instrumentation automation system. The bipolar membrane electrodialysis system also includes a membrane stack, a supporting water tank and storage tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system, and an electrical instrumentation automation system. The bipolar membrane electrodialysis system is connected to the electrodialysis system via piping to return the dilute brine produced by the bipolar membrane electrodialysis system to the front end of the electrodialysis system for circulation. The multi-media filter, activated carbon biofilter, activated carbon filter, and sand filtration system are all connected to a backwash pump for backwashing the filter tank and filter. During secondary ozone oxidation, filler, catalyst, and aerator are placed in the oxidation tank, the tank body is water-sealed, and an exhaust gas absorption device is installed at the end. All of the above are prior art. During the secondary ozone oxidation, the mass ratio of ozone and COD is (3-4):1, preferably 3:1; optionally, during the secondary coagulation and sedimentation reaction for removing hardness, the coagulant is selected from one of polyaluminum chloride (PAC) and polyferric sulfate (PFS), and the flocculant is PAM (polyacrylamide). During the secondary coagulation and sedimentation reaction for removing hardness, the coagulant dosage is 30 mg / L, the flocculant dosage is 2 mg / L, the lime dosage is 250 mg / L, and the soda ash dosage is 200 mg / L. During the secondary coagulation and sedimentation reaction for removing hardness, the coagulation reaction time is 2-5 min, preferably 3 min; the flocculation reaction time is 10-20 min, preferably 15 min; the hardness removal reaction time is 20-40 min, preferably 30 min; after the flocculation reaction, the sedimentation is 30-60 min, preferably 30 min. During sand filtration, the filtration rate is 8-10 m / h, preferably 8 m / h. When the resin is softened, the filtration rate is 20-25 m / h, preferably 20 m / h; the working exchange capacity is 800-900 mol / m 3 Resin. In resin softening, the resin filling height is 1.6 to 2 meters. In activated carbon filter, the activated carbon filling height is 1.5 to 2 meters.

[0024] The filtration rate is 3-5m / h, and the COD of the filtered water is controlled to be ≤20mg / L. When the chelate resin is working, the filtration rate is 20-25m / h, preferably 20m / h; the working exchange capacity is 800-900mol / m 3 Resin, with a resin filling height of 1.6 to 2 meters. The TDS of electrodialysis fresh water is 10,000 to 20,000 mg / L, preferably 15,000 mg / L. The TDS of electrodialysis concentrated water is 100,000 to 180,000 mg / L, preferably 150,000 mg / L. The concentration of acid and base produced by bipolar membrane electrodialysis is controlled at 4 to 8%, and the concentration of dilute brine produced by bipolar membrane electrodialysis is controlled at 2 to 4%.

[0025] The specific steps for using the above system to treat concentrated water from papermaking industry are:

[0026] 1) Brine regulation: The brine from the reclaimed water treatment enters the regulating tank for water quantity and water quality adjustment and buffering. The effluent from the regulating tank is lifted by the lifting pump and enters the high-efficiency sedimentation tank.

[0027] 2) Primary Coagulation and Sedimentation Hardness Removal: After water quality and quantity adjustments, the concentrated water enters a high-efficiency sedimentation tank for coagulation and sedimentation hardness removal. Four reagents are added: a coagulant, flocculant, lime, and soda ash. The coagulant is selected from polyaluminum chloride (PAC) and polyferric sulfate (PFS), and the flocculant is polyacrylamide (PAM). After precipitation, the resulting sludge with a moisture content of 95% to 98% is discharged to a supporting sludge dewatering system. This step primarily removes most of the SS and hardness in the wastewater, controlling the effluent hardness to ≤150 mg / L.

[0028] 3) Multi-media filter: The multi-media filter uses quartz sand and anthracite as filter media, with a filtration rate of 10-15 m / h, which can be adjusted according to the turbidity of the effluent. This step mainly filters out suspended matter with a particle size of 0.01-1 mm. This step mainly removes suspended matter remaining from the previous stage to ensure the treatment effect of the subsequent ozone unit.

[0029] 4) Primary Ozone Oxidation: The primary ozone oxidation tank is equipped with fillers and catalysts, an aerator at the bottom, and an ozone exhaust destruction device at the end. Anti-corrosion measures are implemented and the tank is tightly sealed. Depending on the influent COD, the ozone dosage is 300-450 mg / L, and the effective reaction time is 1-2 hours. In the reactor, recalcitrant organic matter undergoes ring opening, and large organic molecules are oxidized to small molecules, reducing COD.

[0030] 5) Activated Carbon Biofilter: After primary ozone oxidation, wastewater enters the activated carbon biofilter for treatment. Serving as both an adsorption and biofilter, the activated carbon biofilter adsorbs and biooxidizes the small-molecule organic matter produced by ozone oxidation, while simultaneously reducing the suspended solids content in the wastewater, removing COD and SS, and ensuring stable operation of the filtration unit. During operation, the activated carbon biofilter ensures that the effluent COD is ≤30mg / L and the effluent turbidity is 1-5NTU, facilitating reuse and meeting the inlet requirements of the ultrafiltration system.

[0031] 6) Ultrafiltration System: The operating pressure of ultrafiltration is 0.2-0.4 MPa. The clear water from the ultrafiltration system accounts for approximately 80%-95% (v / v) of the ultrafiltration inlet water. This clear water enters the reverse osmosis system for further treatment. The ultrafiltration concentrate and backwash wastewater (accounting for approximately 5-20% of the volume of the ultrafiltration inlet water) are returned to the concentrate regulating tank for further treatment. This step primarily serves as a filtration step, removing suspended solids with a particle size of 1-100 μm to ensure the treatment efficiency of the reverse osmosis membrane.

[0032] 7) Primary Reverse Osmosis System: The operating pressure of the primary reverse osmosis system is 0.5-2 MPa. Freshwater effluent from the primary reverse osmosis system accounts for approximately 60-75% (v / v) of the RO inlet water and is reused in production. The effluent concentrate (approximately 25-40% of the RO inlet water by volume) enters the concentrate reverse osmosis system for further treatment. The primary function of reverse osmosis is to remove inorganic salts from the wastewater and reduce its conductivity, ultimately meeting the water quality requirements for reused water. Key indicators for the final reused water are salt and COD, which must be removed before reuse. A reverse osmosis membrane separates salt from the wastewater, which then enters the concentrate.

[0033] 8) Brine Reverse Osmosis System: The operating pressure of the first-stage reverse osmosis system is 0.5-2 MPa. Freshwater effluent from the brine reverse osmosis system accounts for approximately 40-60% (v / v) of the reverse osmosis inlet water and is reused for production or discharged to meet standards. The highly concentrated brine effluent (accounting for approximately 40-60% of the reverse osmosis inlet water by volume) enters the subsequent system. The primary function of the brine reverse osmosis system is to reduce the amount of brine, increase the water reuse rate, and concentrate the salt to meet the feed requirements of the electrodialysis system.

[0034] 9) Secondary Ozone Oxidation: The secondary ozone oxidation tank is equipped with packing, catalysts, and an aerator, with an ozone tail gas destruction device at the end. The tank is protected against corrosion and tightly sealed. Depending on the influent COD, the ozone dosage is 300-450 mg / L, with an effective reaction time of 1-2 hours. After reverse osmosis concentration, the COD of the concentrated water increases. This step primarily aims to reduce the COD to meet the influent requirements of the subsequent electrodialysis and bipolar membrane electrodialysis systems.

[0035] 10) Secondary coagulation and sedimentation to remove hardness: After reverse osmosis concentration, the hardness of the concentrated water increases, necessitating secondary coagulation and sedimentation to remove hardness. This process involves the addition of four agents: a coagulant, a flocculant, lime, and soda ash. The coagulant is selected from polyaluminum chloride (PAC) and polyferric sulfate (PFS), and the flocculant is polyacrylamide (PAM). After precipitation, the sludge with a moisture content of 95% to 98% is discharged to a supporting sludge system for dehydration. This step primarily removes hardness, controlling the effluent hardness to ≤200 mg / L, in preparation for the subsequent electrodialysis system.

[0036] 11) Sand Filtration: The sand filter has a filtration rate of 8-10 m / h, which can be adjusted according to the turbidity of the effluent. This step mainly removes the suspended solids left by the coagulation and sedimentation, ensuring the treatment effect of the subsequent system.

[0037] 12) Resin softening system: When the resin is softened, the filtration rate is 20-25 m / h, and the working exchange capacity is selected to be 800-900 mol / m 3 The resin filling height is 1.6 to 2 meters. The main purpose of this step is to further remove the hardness and control the effluent hardness to ≤1mg / L to meet the requirements of the subsequent electrodialysis system.

[0038] 13) Activated Carbon Filter: After the resin softens, the concentrated water enters the activated carbon filter for treatment. The activated carbon filter has a filtration rate of 3-5 m / h and a packing height of 1.5-2 meters. The main purpose of this step is to further remove COD and control the COD of the filtered water to ≤20 mg / L, meeting the requirements of the subsequent electrodialysis system.

[0039] 14) Electrodialysis System: The electrodialysis system further concentrates the saline water, achieving a TDS of 10,000-20,000 mg / L for the fresh electrodialysis water and 100,000-180,000 mg / L for the concentrate, preparing it for entry into the bipolar membrane system. The fresh electrodialysis water returns to the concentrate RO front end and is mixed with the primary RO concentrate for further concentration and reduction.

[0040] 15) Chelate resin system: The filtration rate of the chelate resin is 20-25 m / h, and the working exchange capacity is 800-900 mol / m 3 The resin filling height is 1.6 to 2 meters. The hardness of the concentrated water increases after electrodialysis. The main purpose of this step is to further remove the hardness and control the effluent hardness to ≤1mg / L, meeting the water inlet requirements of the bipolar membrane electrodialysis system.

[0041] 16) Bipolar Membrane Electrodialysis System: The electrodialysis system concentrates the TDS to 100,000-180,000 mg / L before entering the bipolar membrane electrodialysis system. Under the action of a DC electric field, the bipolar membrane dissociates water, producing hydrogen ions and hydroxide ions on either side of the membrane. Leveraging this characteristic, salt in the aqueous solution can be converted into its corresponding acid and base without introducing new components. Sodium chloride is used to produce acids and bases using a bipolar membrane. Under the action of a DC electric field, the salt is converted into hydrochloric acid and sodium hydroxide, achieving the ultimate resource utilization of salt. The concentration of acid and base produced by the bipolar membrane is controlled at 4-8% and can be adjusted according to usage. The concentration of the dilute brine produced by bipolar membrane electrodialysis is controlled at 2-4%, and the dilute brine returns to the electrodialysis front end for recycling.

[0042] Example 1

[0043] Use Figure 1In the treatment system shown, the concentrated water produced by the water reuse system of papermaking wastewater is lifted into the concentrated water regulating tank, and the water quality and water quantity are balanced in the regulating tank (the hydraulic retention time of the regulating tank is 2h, and the designed effluent is COD: 100mg / L, hardness: 1500mg / L, TDS: 6500mg / L). The effluent is lifted into the high-efficiency sedimentation tank I for primary coagulation and sedimentation to remove hardness. 30mg / L of polyaluminum chloride, 2mg / L of polyacrylamide, 1800mg / L of lime, and 1600mg / L of soda ash are added to the high-efficiency sedimentation tank. The hydraulic retention time of the flocculation reaction is 10min. After the flocculation reaction, the water enters the inclined tube sedimentation area. The surface load of the inclined tube sedimentation area is 4m 3 / m 2·h, mud and water are separated in the sedimentation tank, and the clean water enters the multi-media filter to remove fine suspended matter. The filtration rate of the multi-media filter is 10m / h. The filtered water uses the residual pressure to enter the ozone oxidation tank for primary ozone oxidation. The filter backwash water is discharged into the backwash water collection tank. The primary ozone oxidation is installed in the reaction tank with filler, catalyst and aerator. The mass ratio of ozone to COD is 3:1. The ozone dosage is 300-450mg / L based on the COD of the influent. The hydraulic retention time of the ozone reaction tank is 2h. The tank is completely sealed with water, and the end of the tank body is equipped with an exhaust gas collection and destruction device. The wastewater after ozone oxidation is lifted and enters the activated carbon biofilter, where COD and SS are further removed. The activated carbon biofilter operates at a filtration rate of 4 m / h, with the activated carbon packing height set at 2 meters. The filter is equipped with a backwash pump, backwash blower, and aeration blower, and the backwash effluent is discharged into a backwash effluent collection tank. The filtered clean water enters an intermediate tank, where it is pumped by a lift pump to the ultrafiltration system. The ultrafiltration utilizes hollow ultrafiltration membrane elements, operating at a flux of less than 40 LMH, an inlet pressure of 0.3 MPa, and an ultrafiltration recovery rate of 90% (v / v). The ultrafiltration effluent enters an ultrafiltration production tank before being pumped to a primary reverse osmosis system. The primary reverse osmosis system utilizes a spiral composite polyamide membrane and anti-fouling membranes in a two-stage configuration, achieving an overall recovery rate of 75% (v / v). The reverse osmosis membrane has a flux of 17 LMH and an operating pressure of 1.2 MPa. The treated clean water is reused for workshop production, while the concentrate enters the primary reverse osmosis concentrate tank before being pumped to the concentrate reverse osmosis system. The brine reverse osmosis system utilizes a rolled composite polyamide membrane and an anti-fouling membrane, achieving an overall recovery rate of 50% (v / v). The reverse osmosis membrane has a membrane flux of 13LMH and an operating pressure of 1.5 MPa. Fresh water treated by brine reverse osmosis is reused in the workshop or discharged to standard. The brine, utilizing residual pressure, enters the ozone oxidation tank for secondary ozone oxidation. For secondary ozone oxidation, packing, catalysts, and aerators are installed in the reaction tank. The ozone and COD dosage ratio is 3:1, and the ozone dosage is 300-450 mg / L depending on the influent COD. The ozone oxidation tank has a hydraulic retention time of 2 hours. The tank is water-sealed and equipped with an exhaust gas collection and destruction device. After secondary ozone oxidation, the wastewater flows by gravity into the high-efficiency sedimentation tank II for secondary coagulation and sedimentation to remove hardness. Add 30mg / L of polyaluminium chloride, 2mg / L of polyacrylamide, 250mg / L of lime and 200mg / L of soda ash into the high-efficiency sedimentation tank. The hydraulic retention time of flocculation reaction is 10min. After flocculation reaction, it enters the inclined tube sedimentation area of ​​the high-efficiency sedimentation tank. The surface load of the inclined tube sedimentation is 4m 3 / m 2·h, mud and water are separated in the sedimentation tank. The clear water enters the intermediate water tank I, where it is lifted and then enters the sand filter. The sand filter uses a filter type with a filtration rate of 8m / h to remove fine suspended matter remaining after sedimentation. The sand filter is equipped with a backwash pump and backwash fan. After sand filtration, the clear water enters the resin softener using the residual pressure. The resin softening filtration rate is 20m / h, and the working exchange capacity is selected to be 800mol / m 3 The resin is filled at a height of 1.6 meters to further remove the hardness of the concentrated water. The resin softening is equipped with a regeneration system. After the resin is softened, the residual pressure is used to enter the activated carbon filter to further remove COD. The activated carbon filter has a filtration rate of 4m / h and a filling height of 2 meters. A backwash water pump is installed. The backwash drainage enters the backwash drainage tank. The filtered water enters the intermediate water tank II and enters the electrodialysis system after being lifted. The electrodialysis system uses a complete set of equipment, with 2 sets of membrane stacks, supporting water tanks, water pumps, safety filters, heat exchangers, cleaning devices, dosing devices, piping systems, and electrical instrument automation systems. The TDS of the electrodialysis fresh water is controlled at about 15,000 mg / L. The fresh water returns to the first-stage reverse osmosis concentrated water tank. The TDS of the electrodialysis concentrated water is controlled at about 140,000 mg / L. The concentrated water enters the intermediate water tank III and enters the bipolar membrane electrodialysis system after being lifted to the chelate resin for softening. The chelate resin filtration rate is 20m / h, and the working exchange capacity is selected to be 800mol / m 3 The resin, packed to a height of 1.6 meters, further removes hardness from the brine. The resin is equipped with a regeneration system, and the effluent enters Intermediate Tank IV. From Intermediate Tank IV, the brine is pumped to the bipolar membrane electrodialysis system. The system is a complete set of equipment, equipped with two membrane stacks, supporting water tanks, acid and alkali storage tanks, pumps, safety filters, heat exchangers, cleaning equipment, dosing equipment, piping, and electrical instrumentation automation systems. The concentration of acid and alkali produced by the bipolar membrane is controlled at 4%-8%, while the concentration of the dilute brine is controlled at 2-4%. The dilute brine returns to the electrodialysis intermediate tank II for recirculation. The acid and alkali are stored in tanks and pumped from there to the Fenton system within the plant for utilization.

[0044] In summary, the utility model provides a new combined process for the resource utilization of concentrated water in papermaking reclaimed water system, which effectively combines coagulation and sedimentation for hardness removal, multi-media filtration, ozone oxidation, activated carbon biological filter, membrane system, resin softening, sand filtration, electrodialysis, and bipolar membrane electrodialysis; utilizes primary coagulation and sedimentation for hardness removal to remove most of the hardness and suspended matter in wastewater; utilizes ozone oxidation to open the ring of refractory organic matter and oxidize large molecular organic matter into small molecular organic matter; utilizes activated carbon biological filter to remove small molecular organic matter after ozone oxidation, and further The process further reduces the COD content of wastewater; ultrafiltration removes fine suspended matter and turbidity, reducing the burden on reverse osmosis; in the membrane system, reverse osmosis membranes are used to reduce salinity to meet the quality requirements for recycled water, while simultaneously reducing and concentrating the brine; secondary coagulation and sedimentation, combined with resin softening, further remove the majority of the hardness in the brine; activated carbon filters further remove COD; electrodialysis further concentrates the brine, and bipolar membranes convert the resulting brine into acid and alkali, achieving resource utilization and reducing the environmental impact of salt discharge. Compared to traditional processes, the recovery rate of clean recycled water is higher, with the entire process system achieving a water yield exceeding 90%, with only a small amount of concentrated liquid entering the bipolar membrane electrodialysis system.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model and are not limiting. Although the utility model is described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A papermaking water reuse and concentrated water resource treatment system, characterized by: It includes a fresh water reuse treatment system and an acid and alkali production reuse treatment system. The concentrated water from papermaking is first treated by the fresh water reuse treatment system to recover fresh water or meet the discharge standards, and then treated by the acid and alkali production reuse treatment system to recover acid and alkali. The fresh water reuse treatment system includes a concentrated water regulating tank, a primary coagulation sedimentation and hardness removal system, a multi-media filter, a primary ozone oxidation system, an activated carbon biofilter, an ultrafiltration system and a reverse osmosis system which are connected in sequence. The concentrated water regulating tank is used to regulate and buffer the water volume and water quality of the concentrated water. The primary coagulation sedimentation and hardness removal system is connected to the concentrated water regulating tank pipeline for coagulation, sedimentation and chemical hardness removal of the incoming water from the concentrated water regulating tank. The medium filter is connected to the pipeline of the primary coagulation and sedimentation hardness removal system for filtering the primary coagulation and sedimentation hardness removal effluent, the primary ozone oxidation system is connected to the pipeline of the multi-media filter for ozone oxidation treatment of the effluent of the multi-media filter, the activated carbon biological filter is connected to the pipeline of the primary ozone oxidation system for biological activated carbon filtration reaction treatment of the effluent of the primary ozone oxidation, the ultrafiltration system is connected to the pipeline of the activated carbon biological filter for ultrafiltration treatment of the effluent of the activated carbon biological filter, the reverse osmosis system is used to reverse osmosis treatment of the effluent of the ultrafiltration system to produce fresh water and high-salt concentrated water, the acid and alkali production is reused for treatment The system includes a secondary ozone oxidation system, a secondary coagulation and sedimentation hardness removal system, a sand filtration system, a resin softening system, an activated carbon filter, an electrodialysis system, a cacodylation resin system and a bipolar membrane electrodialysis system which are connected in sequence. The secondary ozone oxidation system is connected to the concentrated water reverse osmosis system pipeline for ozone oxidation treatment of the highly concentrated brine of the concentrated water reverse osmosis system. The secondary coagulation and sedimentation hardness removal system is connected to the secondary ozone oxidation system pipeline for precipitation and chemical hardness removal of the secondary ozone oxidation effluent. The sand filtration system is connected to the secondary coagulation and sedimentation hardness removal system pipeline for filtering the secondary coagulation and sedimentation hardness removal effluent. The resin softening system is connected to the sand filtration system pipeline. The pipeline connection is used to soften the water outlet of the sand filter pipeline, the activated carbon filter is connected to the resin softening system pipeline for filtering and adsorption treatment of the resin softened water outlet, the electrodialysis system is connected to the activated carbon filter pipeline for electrodialysis concentration treatment of the activated carbon filter outlet, and fresh water and concentrated water are produced through electrodialysis concentration, the chelating resin system is connected to the electrodialysis system pipeline for chelating resin softening treatment of the electrodialysis concentrated water, the bipolar membrane electrodialysis system is connected to the chelating resin system pipeline for bipolar membrane electrodialysis treatment of the chelating resin outlet, and acid, alkali and dilute brine are produced through bipolar membrane electrodialysis.

2. The papermaking wastewater recycling and concentrated water resource treatment system according to claim 1 is characterized by: The reverse osmosis system includes a primary reverse osmosis system and a concentrated water reverse osmosis system. The primary reverse osmosis system is connected to the ultrafiltration system pipeline for performing reverse osmosis treatment on the effluent of the ultrafiltration system. The primary reverse osmosis produces fresh water and concentrated water. The concentrated water reverse osmosis system is connected to the primary reverse osmosis system pipeline for performing reverse osmosis treatment on the concentrated water of the primary reverse osmosis system. The concentrated water reverse osmosis produces fresh water and highly concentrated brine.

3. The papermaking wastewater recycling and concentrated water resource treatment system according to claim 2 is characterized by: The ultrafiltration membrane of the ultrafiltration system is at least one of a tubular ultrafiltration membrane, a plate and frame ultrafiltration membrane, a roll ultrafiltration membrane, and a hollow fiber ultrafiltration membrane; the osmotic membrane of the primary reverse osmosis system and the concentrated water reverse osmosis system is an anti-pollution membrane, selected from at least one of a disc tube reverse osmosis membrane, a fiber reverse osmosis membrane, a roll reverse osmosis membrane, and a plate and frame reverse osmosis membrane.

4. The papermaking wastewater recycling and concentrated water resource treatment system according to claim 3 is characterized by: The secondary ozone oxidation system includes an ozone catalytic oxidation tank, an ozone tail gas destruction device, and an ozone aeration device; and / or, the secondary ozone oxidation and the primary ozone oxidation share an ozone generating device; the resin softening system and the chelating resin system both use sodium ion exchangers, and / or, the equipment of the resin softening system and the chelating resin system are connected to a regeneration water pump.

5. The papermaking wastewater recycling and concentrated water resource treatment system according to claim 4 is characterized in that: The electrodialysis system is connected to the first-stage reverse osmosis system pipeline, and the fresh water produced after being treated by the electrodialysis system is mixed with the first-stage reverse osmosis concentrated water.

6. The papermaking wastewater recycling and concentrated water resource treatment system according to claim 1 is characterized by: The electrodialysis system includes a membrane stack, a matching water tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system and an electrical instrument automation system; the bipolar membrane electrodialysis system includes a membrane stack, a matching water tank and storage tank, a water pump, a safety filter, a heat exchanger, a cleaning device, a dosing device, a piping system and an electrical instrument automation system.

7. The papermaking wastewater recycling and concentrated water resource treatment system according to claim 1 is characterized by: The bipolar membrane electrodialysis system is connected to the electrodialysis system pipeline to return the dilute brine generated by the bipolar membrane electrodialysis system to the front end of the electrodialysis system for circulation treatment.

8. The papermaking wastewater recycling and concentrated water resource treatment system according to claim 1 is characterized by: The multi-media filter, activated carbon biological filter, activated carbon filter and sand filter system are all connected to a backwash water pump for backwashing the filter tank and the filter.

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