Complex surface water treatment system and water treatment and backwash water recovery process

Abstract

This invention discloses a complex surface water treatment system and a water treatment and backwash water recycling process. Through a collaborative design of a multi-stage water treatment process ("multi-media → ultrafiltration → dual-stage reverse osmosis → EDI") and PLC intelligent linkage control, this invention achieves both stable water quality assurance and the dual benefits of water conservation, high efficiency, cost reduction, and emission reduction. The PLC monitors the water quality and pressure differential parameters of each treatment stage in real time, and combined with automatic backwashing and chemical cleaning mechanisms, effectively avoids water quality fluctuations caused by filter / reverse osmosis membrane clogging, stably producing high-purity water suitable for precision water use scenarios, and ensuring the long-term operational stability of the system. Simultaneously, PLC linkage enables graded reuse of water sources. Backwashing prioritizes the use of reverse osmosis concentrate and ultrafiltration permeate to replace fresh raw water, secondary reverse osmosis concentrate is returned to the front end for reuse, and redundant water is used for low-quality water use stages, increasing the system's water utilization rate to over 80%, reducing fresh water consumption by 30%, and significantly reducing water waste.

Description

Technical Field

[0001] This invention belongs to the field of high-purity water preparation technology, specifically relating to a complex surface water treatment system and a water treatment and backwash water recovery process. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Glass fiber production has extremely stringent requirements for the quality of process water (such as resistivity, silicon content, and particle count), requiring it to meet high-purity water standards. Traditional water treatment systems mostly use tap water with stable water quality as raw water, employing a simple process of "sand filtration → activated carbon filtration → single-stage reverse osmosis". The backwash water and concentrate produced by the system are mostly discharged directly, resulting in low water resource utilization.

[0004] As resource constraints intensify, more and more factories are using complex surface water sources such as rivers and lakes as their water sources. Natural lake water quality fluctuates wildly, with conductivity ranging from 500 to 2000 µS / cm and turbidity exceeding 100 NTU after heavy rains. Directly applying traditional tap water treatment processes presents serious challenges: First, complex water quality easily clogs ultrafiltration membranes, leading to increased backwashing frequency and generating large amounts of backwash and chemical cleaning wastewater, resulting in high operating loads and costs. Second, in traditional water treatment systems, reverse osmosis concentrate and filter backwash water are directly discharged, causing the overall system recovery rate to often fall below 70%, resulting in significant water waste. Furthermore, insufficient pretreatment can affect the quality of reverse osmosis feed water (exceeding SDI standards, etc.), increasing the risk of membrane fouling, threatening product water stability, and ultimately affecting the quality of glass fiber products.

[0005] Therefore, there is an urgent need to develop a new water treatment solution for the complex characteristics of surface water. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a complex surface water treatment system and a water treatment and backwash water recovery process. It is particularly suitable for the preparation of high-purity water for glass fiber production. This process constructs a closed-loop system of graded recovery and reuse by separately collecting ultrafiltration backwash water and reverse osmosis concentrate, and then using a concentrate reverse osmosis unit for graded recovery and reuse. This maximizes the utilization of water resources and significantly reduces wastewater discharge.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a complex surface water treatment system, including a raw water pretreatment unit, a reverse osmosis (RO) treatment unit, an advanced treatment unit, and a recycling unit; The raw water pretreatment unit includes a multi-media filter connected in series to intercept large particulate impurities. The outlet of the multi-media filter is connected to an ultrafiltration device to intercept colloids and microorganisms.

[0008] The reverse osmosis treatment unit includes a primary reverse osmosis unit and a secondary reverse osmosis unit, which are used for stepwise desalination. The concentrate from the secondary reverse osmosis unit is returned to the primary reverse osmosis unit through a pipeline and a concentrate tank for secondary desalination, producing primary pure water. The concentrate from the secondary reverse osmosis is returned to the primary water tank and used as primary pure water for production.

[0009] The permeate water parameters for the first-stage reverse osmosis are: conductivity <100μs / cm, and the permeate water parameters for the second-stage reverse osmosis are: conductivity <10μs / cm, for use in EDI equipment.

[0010] The advanced treatment unit includes an EDI (electrodeionization) unit. Secondary reverse osmosis permeate enters the EDI unit to remove residual ions, producing high-purity water that enters the pure water tank. EDI wastewater flows through pipelines into an external drainage pool, where it undergoes simple treatment before being discharged in compliance with standards. The EDI unit's permeate water specifications are: conductivity <0.2μs / cm.

[0011] The recovery unit includes a backwash recovery tank and a high-density water tank. The backwash water from the ultrafiltration device and the multi-media filter is returned to the backwash recovery tank, treated in the high-density water tank, and then reused in the raw water pretreatment unit. The high-density clarifier is a high-efficiency water treatment structure that integrates mixing, flocculation, sedimentation, and concentration functions. Its core functions are to maintain stable water quality, ensure equipment operating efficiency, and reduce energy consumption and maintenance costs.

[0012] The system also includes water tanks, comprising an ultrafiltration water tank connected to the outlet of the ultrafiltration unit, an ultrafiltration backwash water tank connected to the ultrafiltration product water tank, a primary water tank located between the primary and secondary reverse osmosis units, a secondary water tank located between the secondary reverse osmosis unit and the EDI unit, a pure water tank connected to the outlet of the EDI unit, and a concentrate tank connected to the primary and secondary reverse osmosis units. A primary reverse osmosis pump is installed between the ultrafiltration water tank and the primary reverse osmosis unit, and a secondary reverse osmosis pump is installed between the primary water tank and the secondary reverse osmosis unit.

[0013] The system also includes sensors, including a flow sensor and a turbidity sensor installed between the high-density clarifier and the multi-media filter, between the multi-media filter and the ultrafiltration unit, and between the ultrafiltration unit and the ultrafiltration water tank; a flow sensor installed on the tap water supply pipe connected to the ultrafiltration water tank; a conductivity sensor installed between the ultrafiltration water tank and the first-stage reverse osmosis pump; a flow sensor installed between the first-stage reverse osmosis pump and the first-stage reverse osmosis unit; a conductivity sensor and a flow sensor installed between the first-stage water tank and the second-stage reverse osmosis pump; a conductivity sensor connected to the second-stage water tank; a flow sensor, a pH sensor, and a conductivity sensor installed between the second-stage water tank and the EDI water supply pump; and differential pressure sensors installed at both ends of the ultrafiltration unit, the first-stage reverse osmosis unit, and the second-stage reverse osmosis unit.

[0014] A dosing line with a chemical pump is installed between the high-density clarifier and the multi-media filter for adding flocculants, coagulants, NaClO, and other chemicals; a dosing line with a chemical pump is installed between the multi-media filter and the ultrafiltration unit for adding acids, alkalis, NaClO, reducing agents, and other chemicals; a dosing line with a chemical pump is installed between the primary reverse osmosis pump and the primary reverse osmosis filter for adding reducing agents and scale inhibitors; and a dosing line is installed between the secondary reverse osmosis pump and the primary water tank for adding alkalis.

[0015] It also includes a PLC controller. The flow sensor, conductivity sensor, turbidity sensor, differential pressure sensor, water pump, and chemical pump are respectively connected to the PLC controller for signal transmission. The flow sensor, conductivity sensor, turbidity sensor, and differential pressure sensor, as sensor modules, send water quality signals to the PLC controller. The water pump and chemical pump, as actuator modules, operate under the control of the PLC controller. The actuator modules also include an alarm device.

[0016] Secondly, the present invention provides a water treatment and backwash water recycling process, comprising the following stages: Pretreatment stage: Raw water first passes through a multi-media filter to remove larger particulate impurities. It then enters an ultrafiltration unit for precision filtration, effectively removing bacteria, colloids, and large organic molecules. The resulting ultrafiltration permeate is stored in the ultrafiltration permeate tank. This stage ensures the safety of the feed water to the subsequent precision membrane elements.

[0017] During this process, the system continuously monitors the pressure difference and running time.

[0018] When the pressure difference between the filter inlet and outlet water is greater than 0.15 MPa, or when the set backwash timer has elapsed, the system will automatically start the backwash process.

[0019] Core desalination stage: Ultrafiltration permeate is pumped into the primary reverse osmosis system by a high-pressure pump. The reverse osmosis membrane removes most dissolved salts and organic matter, producing primary pure water which enters the primary pure water tank. To achieve even higher water quality, the primary pure water undergoes secondary reverse osmosis treatment for further desalination, producing high-quality secondary pure water which is stored in the secondary pure water tank. This secondary pure water is then transported to the EDI (Electronic Dioxide) equipment to prepare ultrapure water for further production and use.

[0020] Water quality classification and storage: The system ultimately produces two types of production water: high-quality ultrapure water and first-grade pure water, which are stored separately to achieve differentiated water supply and optimize costs and resources.

[0021] The method also includes the selection of the backwash water source: After the backwash process is started, the system first checks the level of the primary reverse osmosis concentrate tank and selects the backwash water source based on the level: High liquid level (liquid level ≥ 80%): Select the first-stage reverse osmosis concentrate as the backwash water source. Purpose: to give priority to the use of concentrate and save raw water.

[0022] Medium liquid level (30%≤liquid level<80%): The system enters a waiting state for the liquid level to rise, suspends subsequent operations, and continues until the liquid level reaches the high liquid level standard.

[0023] Low liquid level (liquid level <30%): Switch the water source to raw water for emergency replenishment as the backwash water source. Purpose: To ensure that backwashing can proceed normally and prevent filter media clogging due to insufficient concentrate.

[0024] The method also includes a recycling process to achieve resource recycling.

[0025] The core recycling design of this system is mainly reflected in two aspects, which greatly improve water utilization and reduce wastewater discharge: Concentrate reuse: The high-salinity concentrate produced by the first-stage reverse osmosis is not discharged directly, but is desalinated a second time through the concentrate reverse osmosis membrane and then used as water for auxiliary equipment. This significantly reduces the overall sewage discharge and raw water consumption of the system.

[0026] Backwash water recovery: Ultrafiltration units and multi-media filters require backwashing to restore performance, and the resulting backwash water is collected in a dedicated recovery tank. This wastewater can be recycled and is typically returned to the raw water unit at the front end of the system for reprocessing, achieving internal circulation of cleaning wastewater and avoiding waste.

[0027] The method also includes performing a backwashing process: Triggering conditions: The backwashing process is initiated when the system detects that the transmembrane pressure difference is too high or the set time interval has been reached.

[0028] Water source detection: The system first checks the liquid level in the ultrafiltration permeate tank. If the liquid level is ≥50%, backwashing is performed; otherwise, the system performs delayed backwashing and triggers an alarm, waiting for the liquid level to rise or reminding the operator to check.

[0029] Unlike conventional purely physical rinsing, this process includes a decision point at this stage, which selects different cleaning modes based on the degree of membrane fouling or process settings: Path 1: Enhanced Chemical Backwashing: After entering this path, the system will add chemicals (such as acid, alkali or sodium hypochlorite) to perform enhanced chemical backwashing on the membrane in conjunction with backwash water, so as to more effectively remove organic matter or biological contaminants.

[0030] Pathway 2: Conventional physical cleaning: No chemicals are added, only ultrafiltration permeate is used for hydraulic rinsing.

[0031] Once the water source is selected, perform the following cleaning steps in sequence to ensure the filter media remains clean: Air washing: Perform air scrubbing for 3 minutes. The air bubbles cause the filter media to rub against each other, loosening and peeling off the surface deposits.

[0032] Water wash: Then perform a 5-minute backwash with water to carry the detached dirt out of the filter.

[0033] In the method, the stopping condition is determined by the turbidity of the effluent: the turbidity of the effluent is continuously monitored during the backwashing process.

[0034] When the effluent turbidity is ≤ X NTU (X is the set acceptable threshold), it is determined that the backwashing is complete and the backwashing is stopped.

[0035] The method also includes wastewater discharge: all wastewater generated during the entire air washing and water washing process is discharged into the backwash water tank for subsequent treatment or reuse.

[0036] Thirdly, the present invention provides the application of the aforementioned water treatment and backwash water recycling process in the preparation of water for glass fiber production.

[0037] The core objective of this invention is to overcome the shortcomings of traditional water treatment processes, such as low recovery rates and large wastewater volumes, when dealing with complex surface water, and to provide a highly efficient and intensive water resource utilization solution. By constructing a closed-loop system of graded recovery and differentiated reuse, the conversion efficiency from raw water to high-purity water is significantly improved, resulting in a substantial increase in the overall water recovery rate of the system. This invention particularly emphasizes the deep treatment and recycling of by-product water streams such as backwash water and concentrated water, thereby minimizing the amount of wastewater discharged while ensuring the high-purity water quality required for glass fiber production, achieving a synergistic goal of water conservation, energy saving, and environmental emission reduction.

[0038] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: 1. This invention provides a complex water treatment system and method with multi-media filtration, ultrafiltration, and two-stage reverse osmosis combined with EDI treatment as the core, avoiding the use of traditional acid and alkali regeneration, and is environmentally friendly.

[0039] This invention ensures the stability and high purity of the final product water through multi-stage filtration and desalination units. It integrates backwashing and reverse osmosis chemical cleaning; the primary reverse osmosis concentrate is collected for backwashing the front-end filter, achieving graded water utilization and saving water. The system can automatically maintain its operation based on pressure differential, flux, time, and other conditions, ensuring long-term stable operation.

[0040] This invention provides a novel water treatment process for complex surface water characteristics, which, while ensuring the quality of high-purity water, achieves efficient recycling of backwash water and concentrate, comprehensively improves the system recovery rate, and achieves the goals of water conservation, energy saving, and stable operation.

[0041] 2. This invention achieves stable water quality and dual benefits of water conservation, high efficiency, cost reduction, and emission reduction through a multi-stage water treatment process involving multiple media, ultrafiltration, dual-stage reverse osmosis, and EDI, coupled with PLC intelligent linkage control. The PLC monitors water quality and pressure differential parameters in each treatment stage in real time, and combined with automatic backwashing and chemical cleaning mechanisms, effectively avoids water quality fluctuations caused by filter / reverse osmosis membrane clogging, stably producing high-purity water suitable for precision water use scenarios and ensuring long-term system stability. Simultaneously, PLC linkage enables graded reuse of water sources. Backwashing prioritizes the use of reverse osmosis concentrate and ultrafiltration permeate to replace fresh raw water, while secondary reverse osmosis concentrate is returned to the front end for reuse. Redundant water is used for low-quality water use stages, increasing the system's water utilization rate to over 80% and reducing fresh water consumption by 30%, significantly reducing water waste. Furthermore, water recycling not only directly reduces fresh water procurement costs but also reduces wastewater discharge by over 25%, significantly reducing environmental treatment load and achieving a synergistic balance between economic and environmental benefits. Attached Figure Description

[0042] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0043] Figure 1 This is a structural diagram of the complex surface water treatment system provided by the present invention; Figure 2 This is a flowchart of the backwashing control process for a multi-media filter provided by the present invention; Figure 3 This is a backwashing control flowchart of the ultrafiltration device provided by the present invention; Figure 4 The overall process flow diagram provided for this invention.

[0044] Among them, 1-multi-media filter, 2-ultrafiltration device, 3-first-stage reverse osmosis device, 4-second-stage reverse osmosis device, 5-EDI device, 6-backwash recovery tank, 7-high-density water tank, 8-ultrafiltration water tank; 301 - Primary water tank, 401 - Secondary water tank, 402 - Concentrate tank, 501 - Pure water tank, 801 - Ultrafiltration backwash tank. Detailed Implementation

[0045] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0046] The present invention will be further described below with reference to the embodiments.

[0047] Example 1 A complex surface water treatment system, such as Figure 1 As shown, it includes a raw water pretreatment unit, a reverse osmosis (RO) treatment unit, a deep treatment unit, and a recycling unit.

[0048] The raw water pretreatment unit includes a multi-media filter 1 connected in series to intercept large particulate impurities, and an ultrafiltration device 2 connected to the outlet of the multi-media filter to intercept colloids and microorganisms.

[0049] The reverse osmosis treatment unit includes a primary reverse osmosis unit 3 and a secondary reverse osmosis unit 4 for stepwise desalination. The concentrate from the secondary reverse osmosis unit 4 is returned to the primary reverse osmosis unit 3 (secondary desalination) through a pipeline via a concentrate tank 8, and the produced water is primary pure water. The secondary reverse osmosis concentrate is returned to the primary water tank 301 and used as primary pure water for production.

[0050] The permeate water parameters for the first-stage reverse osmosis are: conductivity <100μs / cm, and the permeate water parameters for the second-stage reverse osmosis are: conductivity <10μs / cm, for use in EDI equipment.

[0051] The advanced treatment unit includes an EDI device 5. Secondary reverse osmosis permeate enters the EDI device 5 to remove residual ions. The permeate is high-purity water and enters the pure water tank 501. EDI wastewater is piped into an external drainage pool and discharged after simple treatment to meet standards.

[0052] EDI unit water production parameters: conductivity < 0.2 μs / cm.

[0053] The recovery unit includes a backwash recovery tank 6, a high-density water tank 7, and the backwash water from the ultrafiltration device 2 and the multi-media filter 1 is returned to the backwash recovery tank 6, treated by the high-density water tank 7, and reused in the raw water pretreatment unit. The high-density clarifier (Densadeg) is a high-efficiency water treatment structure that integrates mixing, flocculation, sedimentation and concentration functions. Its core treatment function is to maintain stable water quality, ensure equipment operating efficiency, and reduce energy consumption and maintenance costs.

[0054] The concentrated reverse osmosis produces first-stage pure water which is supplied externally as auxiliary water for external equipment.

[0055] High-density water tank 7 water production indicators: Turbidity: 0-2 NTU.

[0056] It also includes water tanks, which include an ultrafiltration water tank 8 connected to the outlet of the ultrafiltration unit, an ultrafiltration backwash water tank 801 connected to the ultrafiltration product water tank 7, a primary water tank 301 connecting the outlet of the primary reverse osmosis unit to the secondary reverse osmosis unit, a secondary water tank 401 connecting the outlet of the secondary reverse osmosis unit to the EDI unit, a pure water tank 501 connected to the outlet of the EDI unit, and a concentrate tank 402 connected to the primary and secondary reverse osmosis units. A primary reverse osmosis pump is installed between the ultrafiltration water tank 8 and the primary reverse osmosis unit, and a secondary reverse osmosis pump is installed between the primary water tank 301 and the secondary reverse osmosis unit.

[0057] The system includes a flow sensor and a turbidity sensor installed between the high-density clarifier 7 and the multi-media filter 1; a flow sensor and a turbidity sensor installed between the multi-media filter 1 and the ultrafiltration unit 2; a flow sensor and a turbidity sensor installed between the ultrafiltration unit 2 and the ultrafiltration water tank 8; a flow sensor installed on the tap water supply pipe connected to the ultrafiltration water tank 7; a conductivity sensor installed between the ultrafiltration water tank 8 and the first-stage reverse osmosis pump; a flow sensor installed between the first-stage reverse osmosis pump and the first-stage reverse osmosis unit 3; a conductivity sensor and a flow sensor installed between the first-stage water tank 301 and the second-stage reverse osmosis pump; a conductivity sensor connected to the second-stage water tank 401; a flow sensor, a pH sensor, and a conductivity sensor installed between the second-stage water tank 401 and the EDI water supply pump; and differential pressure sensors installed at both ends of the ultrafiltration unit 2, the first-stage reverse osmosis unit 3, and the second-stage reverse osmosis unit 4.

[0058] A dosing line with a chemical pump is installed between the high-density clarifier and the multi-media filter for adding flocculants, coagulants, NaClO, and other chemicals; a dosing line with a chemical pump is installed between the multi-media filter and the ultrafiltration unit for adding acids, alkalis, NaClO, reducing agents, and other chemicals; a dosing line with a chemical pump is installed between the primary reverse osmosis pump and the primary reverse osmosis filter for adding reducing agents and scale inhibitors; and a dosing line is installed between the secondary reverse osmosis pump and the primary water tank for adding alkalis.

[0059] It also includes a PLC controller. The flow sensor, conductivity sensor, turbidity sensor, differential pressure sensor, water pump, and chemical pump are respectively connected to the PLC controller for signal transmission. The flow sensor, conductivity sensor, turbidity sensor, and differential pressure sensor, as sensor modules, send water quality signals to the PLC controller. The water pump and chemical pump, as actuator modules, operate under the control of the PLC controller. The actuator modules also include an alarm device.

[0060] The PLC automatic control system uses program logic to automatically start, stop, and regulate the water pumps, valves, and dosing devices throughout the entire treatment process. It also has the function of automatically alarming, interlocking shutdown, or switching operating modes when abnormal pressure, flow, or water quality parameters are detected.

[0061] The PLC automatic control system controls the backwashing of the multi-media filter by: automatically triggering the backwashing program based on the first time period set by the first timer and the differential pressure data monitored by the inlet and outlet differential pressure sensors; and intelligently selecting the effluent from the secondary reverse osmosis concentrate or backwash water recovery tank as the backwash water source based on the liquid level of the concentrate tank of the secondary reverse osmosis unit monitored by the liquid level gauge.

[0062] Example 2 Taking the inflow of lake water as an example, such as Figures 2-4 As shown, the water treatment and backwash water recycling process includes the following stages: Pretreatment stage: Raw water first passes through a multi-media filter to remove larger particulate impurities. It then enters an ultrafiltration unit for precision filtration, effectively removing bacteria, colloids, and large organic molecules. The resulting "ultrafiltration permeate" is stored in the ultrafiltration permeate tank. This stage ensures the safety of the feed water to the subsequent precision membrane elements.

[0063] During this process, the system continuously monitors the pressure difference and running time.

[0064] When the pressure difference between the filter inlet and outlet water is greater than 0.15 MPa, or when the set backwash timer has elapsed, the system will automatically start the backwash process.

[0065] Core desalination stage: Ultrafiltration permeate is pumped into the primary reverse osmosis system by a high-pressure pump. The reverse osmosis membrane removes most of the dissolved salts and organic matter, producing "primary pure water" which enters the primary pure water tank. To achieve even higher water quality, the primary pure water undergoes secondary reverse osmosis treatment for further desalination, producing high-quality "secondary pure water" which is stored in the secondary pure water tank. The secondary pure water is then transported to the EDI equipment to prepare ultrapure water for further production and use.

[0066] Water quality classification and storage: The system ultimately produces two types of production water: high-quality ultrapure water and first-grade pure water, which are stored separately to achieve differentiated water supply and optimize costs and resources.

[0067] After the backwash process is started, the system first checks the level of the primary reverse osmosis concentrate tank and selects the backwash water source based on the level: High liquid level (liquid level ≥ 80%): Select the first-stage reverse osmosis concentrate as the backwash water source. Purpose: to give priority to the use of concentrate and save raw water.

[0068] Medium liquid level (30% ≤ liquid level < 80%): The system enters a waiting state for the liquid level to rise, suspends subsequent operations, and continues until the liquid level reaches the high liquid level standard.

[0069] Low liquid level (liquid level <30%): Switch the water source to raw water for emergency replenishment as the backwash water source. Purpose: To ensure that backwashing can proceed normally and prevent filter media clogging due to insufficient concentrate.

[0070] Recycling process (resource recycling) The core recycling design of this system is mainly reflected in two aspects, which greatly improve water utilization and reduce wastewater discharge: Concentrate reuse: The high-salt "concentrate" produced by the first-stage reverse osmosis is not directly discharged. Instead, it is desalinated by the reverse osmosis membrane and used as auxiliary equipment water (i.e., the "concentrate reuse" path shown in the figure). This significantly reduces the overall sewage discharge and raw water consumption of the system.

[0071] Backwash water recovery: Ultrafiltration units and multi-media filters require backwashing to restore performance, and the resulting "backwash wastewater" is collected in a dedicated recovery tank. This wastewater can be recycled and is usually returned to the raw water unit at the front end of the system for reprocessing, achieving internal circulation of cleaning wastewater and avoiding waste.

[0072] Perform the backwashing procedure: Triggering conditions: The backwashing process is initiated when the system detects flux conditions (such as excessive transmembrane pressure differential) or when the set time interval is reached.

[0073] Water source detection: The system first checks the liquid level in the ultrafiltration permeate tank.

[0074] Backwashing allowed: If the liquid level is ≥ 50%, proceed to the next cleaning decision.

[0075] Backwashing not allowed (liquid level <50%): The system executes "delayed backwashing + alarm trigger", waiting for the liquid level to rise or reminding the operator to check.

[0076] Unlike conventional purely physical rinsing, this process includes a decision point at this stage, which selects different cleaning modes based on the degree of membrane fouling or process settings: Path 1: Chemically Enhanced Backwashing Once in this path, the system will add chemicals (such as acid, alkali or sodium hypochlorite) to chemically enhance backwashing of the membrane in conjunction with backwash water, so as to more effectively remove organic matter or biological contaminants.

[0077] Path 2: Conventional physical cleaning No chemicals are added; only ultrafiltration permeate is used for hydraulic flushing.

[0078] Once the water source is selected, perform the following cleaning steps in sequence to ensure the filter media remains clean: Air washing: Perform air scrubbing for 3 minutes. The air bubbles cause the filter media to rub against each other, loosening and peeling off the surface deposits.

[0079] Water wash: Then perform a 5-minute backwash with water to carry the detached dirt out of the filter.

[0080] Stopping conditions and drainage Effluent turbidity assessment: Continuously monitor effluent turbidity during backwashing.

[0081] When the effluent turbidity is ≤ X NTU (X is the set acceptable threshold), it is determined that the backwashing is complete and the backwashing is stopped.

[0082] Wastewater discharge: All wastewater generated during the entire air washing and water washing process is discharged into the backwash water tank for further treatment or reuse.

[0083] In the pretreatment stage, flow sensors ensure stable processing loads for each unit, pressure sensors monitor the inlet and outlet pressure differences of the multi-media filter and ultrafiltration to determine clogging status, and turbidity sensors directly evaluate the purification effect of these two filtration stages. In the core desalination stage, conductivity sensors are deployed in the ultrafiltration tank, the inlet and outlet of the secondary reverse osmosis system, and the secondary pure water tank to monitor and evaluate the desalination efficiency of the reverse osmosis membrane and subsequent purification processes in real time. At the system's power source and final product water point, pressure sensors also ensure the safe operation of the high-pressure pump, while a combination of flow, pH, and conductivity sensors installed at the outlet of the secondary pure water tank provides final control over key product water indicators, ensuring that the effluent flow rate, pH, and purity all meet requirements.

[0084] Flocculants are added at the raw water inlet to coagulate fine suspended solids and colloids into larger particles for removal in subsequent pretreatment. Scale inhibitors are added before the multi-media filter to prevent scale-forming ions such as calcium and magnesium from forming on the surface of the subsequent reverse osmosis membrane. A reducing agent is added before the security filter to remove residual chlorine and protect the oxidant-sensitive reverse osmosis membrane from oxidative degradation. A bactericide is added before the reverse osmosis membrane to inhibit microbial growth and prevent biofouling. Finally, a pH adjuster is added before the effluent to adjust the pH of the product water to the required range.

[0085] The PLC automatic control system controls the backwashing of the ultrafiltration device by: automatically triggering a physical backwashing procedure based on a second time period set by a second timer or based on flux data monitored by a membrane flux sensor; and automatically triggering a chemically enhanced backwashing procedure by adding sodium hypochlorite based on a third time period set by a third timer.

[0086] This invention introduces the backwash water that meets the standards from the multi-media filtration unit and the ultrafiltration unit into the backwash water recycling tank, and after pretreatment, it is returned to the front end of the raw water pretreatment unit for recycling and reuse.

[0087] The water test results after treatment in Example 2 are as follows:

[0088] As can be seen from the above results, this invention, through the coordinated design of a multi-stage water treatment process ("multi-media filtration → ultrafiltration → dual-stage reverse osmosis → EDI") and PLC intelligent linkage control, not only achieves stable water quality assurance but also achieves the dual benefits of water conservation, high efficiency, cost reduction, and emission reduction. The PLC monitors the water quality and pressure difference parameters of each treatment section in real time. Combined with the automatic backwashing and chemical cleaning mechanism, it effectively avoids water quality fluctuations caused by filter / reverse osmosis membrane clogging, stably produces high-purity water, and ensures the long-term operational stability of the system. The system achieves graded reuse of water sources through PLC linkage. Backwashing prioritizes the use of reverse osmosis concentrate and ultrafiltration permeate to replace fresh raw water. Secondary reverse osmosis concentrate is returned to the front end for reuse, which increases the system water utilization rate to over 80%, reduces fresh water consumption by 30%, and significantly reduces water waste. Water recycling not only reduces the cost of fresh water procurement, but also reduces the amount of wastewater discharged by more than 25%, significantly reducing the environmental protection treatment load and achieving a synergistic balance between economic and environmental benefits.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A complex surface water treatment system, characterized in that, include: Raw water pretreatment unit; Reverse osmosis treatment unit; Deep processing unit; as well as Recycling unit; The raw water pretreatment unit includes a multi-media filter and an ultrafiltration device connected in series; the reverse osmosis treatment unit includes a primary reverse osmosis device and a secondary reverse osmosis device; the advanced treatment unit includes an EDI device; and the recovery unit includes a backwash recovery tank and a high-density water tank.

2. The system according to claim 1, characterized in that, It also includes water tanks, which include an ultrafiltration water tank connected to the outlet of the ultrafiltration device, an ultrafiltration backwash water tank connected to the ultrafiltration product water tank, a primary water tank located between the primary reverse osmosis device and the secondary reverse osmosis device, a secondary water tank located between the secondary reverse osmosis device and the EDI device, a pure water tank connected to the outlet of the EDI device, and a concentrate tank connected to the primary reverse osmosis device and the secondary reverse osmosis device.

3. The system according to claim 1, characterized in that, It also includes dosing pipelines installed between each treatment unit for adding one or more of the following: flocculant, coagulant aid, NaClO, acid, alkali, reducing agent, and scale inhibitor.

4. The system according to claim 1, characterized in that, It also includes flow sensors, turbidity sensors, conductivity sensors, pH sensors, and differential pressure sensors located between each processing unit.

5. The system according to claim 4, characterized in that, It also includes a PLC controller, and the flow sensor, turbidity sensor, conductivity sensor, pH sensor and differential pressure sensor are respectively connected to the PLC controller for signal transmission with the execution module.

6. A water treatment and backwash water recovery process based on the system described in any one of claims 1 to 5, characterized in that, include: Pretreatment stage: The raw water first passes through a multi-media filter, and then enters an ultrafiltration device for precision filtration. The produced ultrafiltration water is stored in the ultrafiltration water tank. Core desalination stage: Ultrafiltration permeate is pumped into the first-stage reverse osmosis system by a high-pressure pump, where the reverse osmosis membrane removes most of the dissolved salts and organic matter, producing first-stage pure water that enters the first-stage pure water tank; Furthermore, the primary pure water undergoes secondary reverse osmosis treatment for further deep desalination, producing high-quality secondary pure water which is stored in a secondary pure water tank. The secondary pure water is then transported to an EDI device to prepare high-purity water for further production and use. Water quality classification and storage stage: The system ultimately produces two types of production water: high-quality ultrapure water and first-grade pure water, which are stored separately.

7. The water treatment and backwash water recovery process according to claim 6, characterized in that, It also includes the selection and recycling process of backwash water sources; The backwash water source is selected based on the liquid level of the primary reverse osmosis concentrate tank: concentrate is used when the liquid level is ≥80%, and raw water is used for emergency replenishment when the liquid level is <30%. The recycling process includes freshwater reuse: the high-salinity concentrate produced by the first-stage reverse osmosis is desalinated a second time by the concentrate reverse osmosis membrane and then used as water for auxiliary equipment; And backwash water recycling: Ultrafiltration units and multi-media filters require backwashing to restore performance, and the resulting backwash water is collected in a dedicated recycling tank.

8. The water treatment and backwash water recovery process according to claim 6, characterized in that, The ultrafiltration backwashing process includes a backwashing step, which is initiated when the system detects that the transmembrane pressure difference is too high or the set time interval has been reached.

9. The water treatment and backwash water recovery process according to claim 8, characterized in that, The backwashing includes air washing and water washing, and the stopping condition is determined by the turbidity of the effluent.

10. The application of the water treatment and backwash water recycling process according to claim 6 in the production of water for glass fiber production.

Images