Pure water membrane cleaning and wastewater recycling system and process

Abstract

The invention relates to the technical field of water treatment, in particular to a pure water membrane cleaning and wastewater recycling system and process. The system comprises a raw water tank, a membrane element, a booster pump, a clean water tank, a cleaning pump, a wastewater return pipe, a wastewater discharge pipe, a wastewater online conductivity meter and a PLC control system. During normal water production, part of wastewater can flow back to the raw water tank to be recycled; and in a cleaning mode, the system stops producing water, pure water in the water purification tank is used for flushing the membrane element, all flushing wastewater returns to the raw water tank through the wastewater return pipe, the water quality is monitored in real time through the online conductivity meter, and the PLC control system automatically judges and stops cleaning according to the conductivity value. The system realizes full recovery of cleaning wastewater and intelligent cleaning control, and has the advantages of water saving, emission reduction, efficient cleaning, membrane service life prolonging, automatic operation and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, and particularly relates to a pure water cleaning membrane and a wastewater recovery system and process. BACKGROUND

[0002] Membrane separation technology, such as reverse osmosis (RO) and nanofiltration (NF), has been widely used in the field of water treatment for producing pure water, softening water, and wastewater treatment. However, membrane elements will be gradually intercepted by pollutants during use, leading to a decrease in membrane flux and a deterioration in the quality of the effluent. In order to restore the performance of the membrane, the membrane needs to be cleaned. Traditional membrane cleaning methods have problems such as low efficiency, high water consumption, and large wastewater discharge, which not only increase the operating cost but also may cause pollution to the environment. At the same time, wastewater recovery and utilization is an important way to improve water resource utilization, but how to effectively recover the wastewater generated during cleaning and combine it with the normal water production process to achieve energy saving and cost reduction is a key problem that needs to be solved in current technology. SUMMARY

[0003] The present application aims to solve the problems of low membrane cleaning efficiency, high water consumption, large wastewater discharge, and insufficient wastewater recovery and utilization in the prior art, and provides a pure water cleaning membrane and a wastewater recovery system and process. The system can effectively clean the membrane element and realize the recovery and utilization of cleaning wastewater and wastewater in the water production process, thereby improving water resource utilization, reducing operating cost, and prolonging the service life of the membrane element.

[0004] The technical solution adopted by the present application is: a pure water cleaning membrane and a wastewater recovery system, comprising: A raw water tank for storing raw water to be treated.

[0005] A membrane element, which is the core membrane separation unit, has a water inlet, a pure water outlet, and a wastewater outlet, and is connected to the raw water tank through a water inlet pipeline.

[0006] A booster pump provides driving force to send raw water into the membrane element. The water inlet end of the booster pump is connected to the water outlet of the raw water tank through a pipeline, and the water outlet end is connected to the water inlet of the membrane element.

[0007] A clean water tank for storing pure water produced by the membrane element.

[0008] A cleaning pump for pumping pure water in the clean water tank into the membrane element for flushing in the cleaning mode. The water inlet of the cleaning pump is connected to the water outlet of the clean water tank through a pipeline, and the water outlet is connected to the membrane element through a clean water flushing pipe.

[0009] A clean water flushing pipe connecting the cleaning pump and the membrane element for conveying pure water for membrane flushing. A one-way valve is provided on the pipeline to prevent backflow of flushing water.

[0010] Waste water discharge pipe: used for discharging partially treated waste water. The pipe is connected to the waste water outlet of the membrane element through a first branch pipe, and is provided with a waste water regulating valve II for controlling the discharge flow.

[0011] Waste water recovery pipe: used for recovering part of the waste water to the raw water tank. The pipe is connected to the waste water outlet of the membrane element through a second branch pipe and is connected back to the raw water tank. The pipe is provided with a waste water flushing solenoid valve for controlling the on-off of the waste water backflow.

[0012] Waste water online conductivity meter: arranged on the pipe downstream of the waste water outlet, for real-time detection of the water quality of the waste water, such as conductivity, to judge the cleaning effect (water quality in the membrane shell).

[0013] PLC control system: signal connection with the cleaning pump, waste water flushing solenoid valve and waste water online conductivity meter.

[0014] Control logic of the PLC control system: When the equipment needs to enter the cleaning mode, the PLC control system will perform the following operations: Stop the booster pump: at this time, the system no longer produces raw water.

[0015] Turn on the waste water flushing solenoid valve: allow the waste water generated by flushing to flow back.

[0016] Start the cleaning pump: pump the pure water stored in the clean water tank into the membrane element for flushing.

[0017] Flushing waste water backflow: the waste water generated during the flushing process flows back to the raw water tank through the waste water recovery pipe, realizing waste water recovery.

[0018] Intelligent cleaning control: the PLC control system intelligently controls the start-stop of the cleaning pump and the on-off of the waste water flushing solenoid valve according to the waste water conductivity signal detected by the waste water online conductivity meter in real time. When the waste water conductivity reaches the preset cleaning standard, the cleaning process is automatically stopped to avoid over-cleaning.

[0019] Further, the waste water recovery pipe is further provided with a waste water regulating valve I for adjusting the proportion of recovered waste water. In this way, the proportion of recovered waste water in the total waste water can be more flexibly controlled to adapt to different operating conditions.

[0020] Further, the waste water recovery pipe is provided with a waste water flow meter I, and the waste water discharge pipe is provided with a waste water flow meter II. The waste water flow meters are used to monitor the flow of discharged and backflow waste water, providing data support for process optimization.

[0021] Further, the membrane element is a reverse osmosis membrane element or a nanofiltration membrane element.

[0022] The application also includes a pure water cleaning membrane and waste water recovery process: Normal water production procedure: Close the cleaning pump and the check valve to avoid cleaning during water production. Open the partial waste water regulating valve I and the waste water regulating valve II to allow waste water discharge and backflow. Start the booster pump to pump raw water into the membrane element for filtration. The purified water is stored in the purified water tank. The waste water is discharged through the waste water discharge pipe and backflowed to the raw water tank through the waste water recovery pipe to realize waste water recovery.

[0023] Membrane cleaning mode: Close the booster pump to stop raw water production. Close the waste water regulating valve I to stop direct waste water discharge. Open the waste water flushing solenoid valve to allow waste water backflow. Start the cleaning pump to flush the membrane element with purified water in the purified water tank. The waste water generated by flushing is backflowed to the raw water tank through the waste water recovery pipe.

[0024] Cleaning control procedure: The conductivity of the flushing waste water is monitored in real time through the waste water online conductivity instrument. When the conductivity value reaches the preset cleaning condition, the PLC control system controls the cleaning pump to stop and closes the waste water flushing solenoid valve to end the cleaning process. The PLC control system controls the working time and pressure of the cleaning pump and the waste water flushing solenoid valve by monitoring the real-time value of the conductivity instrument on the waste water recovery pipe to realize automatic and intelligent cleaning control.

[0025] Further, in the membrane cleaning mode, the purified water pressure range of the cleaning pump booster is 0.4 MPa to 0.8 MPa. This pressure range can effectively flush the membrane while avoiding excessive damage to the membrane.

[0026] Compared with the prior art, the beneficial effects of the present application are: 1. By backflowing the waste water generated by cleaning to the raw water tank and combining with the normal water production process, the utilization efficiency of water resources is significantly improved, and the consumption of fresh water is reduced.

[0027] 2. The discharge amount of waste water is reduced, and the cost of sewage treatment is reduced. At the same time, the intelligent cleaning control avoids unnecessary cleaning and saves the consumption of purified water.

[0028] 3. Purified water is used for cleaning, which avoids the damage to the membrane caused by the use of chemical agents. The intelligent cleaning control ensures that the membrane is cleaned when it is polluted to a certain extent, avoiding the shortening of the service life of the membrane caused by excessive pollution.

[0029] 4. The PLC control system combined with the online conductivity instrument realizes the automation and intelligence of the cleaning process, reduces manual intervention, and improves the convenience and accuracy of operation. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and are intended to provide a further understanding of the application, and are made a part of the specification. The drawings are: Figure 1 The structure of the present application is shown schematically.

[0031] In the figure: 1 - raw water inlet electric valve; 2 - raw water tank; 3 - ball valve I; 4 - raw water pump; 5 - precision filter; 6 - water inlet electric valve; 7 - booster pump; 8 - pressure gauge I; 9 - remote pressure gauge II; 10 - cleaning pump; 11 - check valve; 12 - pressure gauge I; 13 - remote pressure gauge II; 14 - waste water online conductivity meter; 15 - waste water regulating valve I; 16 - waste water regulating valve II; 17 - waste water flushing electromagnetic valve; 18 - water inlet pipeline; 19 - waste water flowmeter I; 20 - waste water flowmeter II; 21 - membrane element; 22 - clean water flowmeter; 23 - clean water online conductivity meter; 24 - clean water tank; 25 - ball valve II; 26 - water tank liquid level meter I; 27 - water tank liquid level meter II; 28 - PLC control system; 29 - waste water recovery pipe; 30 - waste water discharge pipe; 31 - clean water pipe; 32 - clean water flushing pipe; 33 - raw water inlet pipe; 34 - check valve. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present application will be described hereinafter with reference to the drawings, and it is to be understood that the preferred embodiments described herein are illustrative of the application and are not intended to limit the application. The following description of the preferred embodiments is provided so that others skilled in the art can make and use the application.

[0033] As shown in the figure, the present application provides a pure water cleaning membrane and waste water recovery system, which comprises a raw water tank 2 for storing raw water to be treated. The raw water tank 2 is connected to the water inlet end of a booster pump 7 through a water inlet pipeline 18, and the water outlet end of the booster pump 7 is connected to the water inlet of a membrane element 21 through a pipeline. The membrane element 21 is provided with a pure water outlet and a waste water outlet. The pure water outlet of the membrane element 21 is connected to the water inlet of a clean water tank 24 through a clean water pipe 31, for storing the prepared pure water.

[0034] The water inlet of a cleaning pump 10 is connected to the water outlet of the clean water tank 24 through a pipeline, and its water outlet is connected to the membrane element 21 through a clean water flushing pipe 32. A check valve 11 is provided on the clean water flushing pipe 32 to prevent reverse water flow in the flushing interface of the membrane element 21 during normal water preparation.

[0035] A waste water discharge pipe 30 is connected to the waste water outlet of the membrane element 21 through a first branch pipe, and a waste water regulating valve II 16 is provided thereon for controlling the flow of discharged waste water. A waste water recovery pipe 29 is connected to the waste water outlet of the membrane element 21 through a second branch pipe and is connected back to the raw water tank 2, and a waste water flushing electromagnetic valve 17 is provided thereon for controlling the on-off of waste water backflow.

[0036] The wastewater online conductivity meter 14 is installed on the pipeline downstream of the wastewater outlet of the membrane element 21 to detect the conductivity of the wastewater in real time.

[0037] The PLC control system 28 is the core control unit of this system. It is connected to the cleaning pump 10, the wastewater flushing solenoid valve 17 and the wastewater online conductivity meter 14 to realize the automatic control of the system.

[0038] System workflow: Normal water production mode: The PLC control system 28 keeps the cleaning pump 10 in the off state, and the one-way valve 11 is also closed or inactive. Wastewater regulating valves I and II are opened to appropriate degrees to adjust the wastewater discharge and return ratio. The booster pump 7 is started, and the raw water is pressurized and sent to the membrane element 21. The membrane element 21 filters the raw water, producing pure water and wastewater. The pure water enters the purified water tank 24 for storage through the purified water pipe 31. Part of the wastewater is discharged through the wastewater discharge pipe 30, and the other part is returned to the raw water tank 2 through the wastewater recovery pipe 29.

[0039] Membrane cleaning mode: When the PLC control system 28 detects that the operating time of the membrane element 21 has reached the preset value, or when the user manually starts the cleaning mode: the PLC control system 28 controls the booster pump 7 to stop running, stopping the raw water production. The PLC control system 28 closes the wastewater regulating valve I 15, stopping the direct discharge of wastewater. The PLC control system 28 opens the wastewater flushing solenoid valve 17, preparing for wastewater return. The PLC control system 28 starts the cleaning pump 10, pumping the pure water stored in the clean water tank 24 into the membrane element 21 for flushing. The wastewater generated during the flushing process flows back to the raw water tank 2 through the wastewater recovery pipe 29.

[0040] Cleaning control: An online conductivity meter 14 monitors the conductivity of the wastewater in the wastewater recovery pipe 29 in real time. The PLC control system 28 determines the cleaning effect based on the real-time signal from the conductivity meter. When the conductivity value drops to a preset cleaning standard, the PLC control system 28 automatically stops the cleaning pump 10 and closes the wastewater flushing solenoid valve 17, ending the cleaning process. During the cleaning process, the PLC control system 28 can also control the flushing pressure and flow rate as needed by controlling the speed or start / stop frequency of the cleaning pump 10 and adjusting the opening degree of the wastewater flushing solenoid valve 17 to achieve the best cleaning effect.

[0041] The wastewater recovery pipe 29 is also equipped with a wastewater regulating valve II 16, which is used to adjust the proportion of recovered wastewater to the total wastewater volume. By adjusting the opening of the wastewater regulating valve II 16, the user can flexibly control the amount of recovered wastewater according to the actual situation.

[0042] Wastewater flow meter I19 is installed on the wastewater recovery pipe 29, and wastewater flow meter II20 is installed on the wastewater discharge pipe 30. These are used to accurately measure the flow rate of discharged and returned wastewater, providing important data for system operation and data analysis.

[0043] The membrane element 21 can be a reverse osmosis membrane element or a nanofiltration membrane element. This system is suitable for treating raw water of various qualities and producing pure water or ultrapure water of different grades.

[0044] The pure water cleaning membrane and wastewater recovery process of the present invention specifically include the following steps: Normal water production procedure: Ensure that the cleaning pump 10 is off and the one-way valve 11 is inactive. Set the wastewater regulating valve I 15 and wastewater regulating valve II 16 to appropriate openings. For example, during the initial water production, the wastewater recirculation ratio is higher to improve system stability; when the pure water tank 24 reaches the set value, the wastewater discharge ratio can be appropriately increased. Start the booster pump 7 to drive the raw water through the membrane element 21 for filtration. The produced pure water enters the clean water tank 24. Part of the generated wastewater is discharged through the wastewater discharge pipe 30, and the other part is returned to the raw water tank 2 through the wastewater recovery pipe 29.

[0045] Membrane cleaning mode: After the system has been running for a period of time, the membrane fouling level increases, affecting the water production efficiency. The PLC control system 28 issues a cleaning command. The booster pump 7 is shut down, stopping raw water production. The wastewater regulating valve I 15 is closed. The wastewater flushing solenoid valve 17 is opened. The cleaning pump 10 is started, pumping pure water from the clean water tank 24 into the membrane element 21 for flushing. The wastewater generated during flushing flows back to the raw water tank 2 through the wastewater recovery pipe 29.

[0046] Cleaning control steps: The PLC control system 28 monitors the readings of the online conductivity meter 14 for wastewater in real time. When the conductivity value is lower than a preset threshold, for example, indicating that membrane fouling has been significantly removed, the PLC control system 28 automatically performs the following operations: stops the cleaning pump 10 and closes the wastewater flushing solenoid valve 17.

[0047] Throughout the cleaning process, the PLC control system 28 will intelligently control the working time and pressure of the cleaning pump 10, as well as the on / off state of the wastewater flushing solenoid valve 17, based on the real-time data from the conductivity meter 14, in order to achieve the best cleaning effect and save energy.

[0048] In membrane cleaning mode, the pure water pressure boosted by the cleaning pump 10 is set between 0.4 MPa and 0.8 MPa. This pressure range can effectively flush out contaminants on the membrane surface while avoiding excessive pressure that could cause mechanical damage to the membrane element 21, thus ensuring the long-term stable operation of the membrane element.

[0049] Example 1:

[0050] The water purification equipment in this embodiment is suitable for reverse osmosis (RO) membrane systems. The membrane element 21 is a 4040 type RO membrane, the purified water tank 24 has a volume of 500L, and the raw water tank 2 has a volume of 500L.

[0051] Equipment assembly: The raw water tank 2, booster pump 7, RO membrane element 21, purified water tank 24, and cleaning pump 10 are connected sequentially via pipelines. A branch pipe is installed at the wastewater outlet of the RO membrane element 21, connecting to wastewater discharge pipe 30 and wastewater recovery pipe 29 respectively. Wastewater recovery pipe 29 is connected to the raw water tank 2. A purified water flushing pipe 32 is installed between the purified water tank 24 and the RO membrane element 21, and cleaning pump 10 and check valve 11 are installed on the purified water flushing pipe 32. Wastewater regulating valve I 15 is installed on the wastewater discharge pipe 30, and wastewater regulating valve II 16 and wastewater flushing solenoid valve 17 are installed on the wastewater recovery pipe 29. An online wastewater conductivity meter 14 is installed on the wastewater recovery pipe 29. The PLC control system 28 is connected to cleaning pump 10, wastewater flushing solenoid valve 17, and online wastewater conductivity meter 14.

[0052] Cleaning and wastewater recirculation operations: Normal water production: Close the cleaning pump 10 and check valve 11, and open the wastewater regulating valve I 15 and wastewater regulating valve II 16. Start the booster pump 7. The tap water in the raw water tank 2 is pressurized to 0.8 MPa by the booster pump 7 and then enters the RO membrane element 21. During the water production process, the pure water production rate is 65%, and the pure water enters the purified water tank 24. Part of the wastewater is discharged through the wastewater discharge pipe 30, for example, 20%, and the other part is returned to the raw water tank 2 through the wastewater recovery pipe 29, for example, 15%, to mix with the raw water.

[0053] Membrane Cleaning: After the RO membrane element 21 has been running for a period of time, the amount of suspended solids, colloids, and inorganic salts trapped inside the membrane increases, triggering the membrane cleaning mode: the PLC control system 28 stops the booster pump 7, closes the wastewater regulating valve I 15, opens the wastewater flushing solenoid valve 17, and starts the cleaning pump 10. Pure water from the clean water tank 24 is pumped into the RO membrane element 21 at a pressure of 0.4 MPa through the clean water flushing pipe 32 to flush the membrane surface. The flushing time is determined by the PLC control system 28 stopping the cleaning pump 10 and closing the wastewater flushing solenoid valve 17 when the online conductivity meter 14 value drops to the preset minimum point. The flushed wastewater flows back to the raw water tank 2 through the wastewater recovery pipe 29 and mixes with the raw water.

[0054] Water production restoration: After cleaning, the PLC control system 28 executes the water production restoration procedure, shutting down the cleaning pump 10 and the wastewater flushing solenoid valve 17, and restarting the booster pump 7 and the wastewater regulating valve I 15. At this time, the membrane flux of the RO membrane element 21 is restored to more than 98% of its initial state.

[0055] Example 2:

[0056] The water purification equipment in this embodiment is applicable to nanofiltration (NF) water purification equipment. The membrane element 21 is an 8040 type NF membrane, the purified water tank 24 has a volume of 2m³, and the raw water tank 2 has a volume of 2m³.

[0057] Membrane cleaning mode: In membrane cleaning mode, the cleaning pump 10 pressurizes the pure water in the purified water tank 24 to a pressure of 0.4MPa to 0.8MPa, preferably 0.6MPa, and flushes the NF membrane element 21 through the purified water flushing pipe 32. The cleaning time is 15 minutes, or the PLC control system 28 automatically stops when the conductivity value reaches a preset condition based on the real-time detection signal from the wastewater online conductivity meter 14. The cleaning wastewater flows back to the raw water tank 2 through the wastewater recovery pipe 29, mixes with the raw water, and re-enters the water production process. After cleaning, the operating pressure of the NF membrane element 21 drops from the initial 1.2MPa to 1.0MPa, the membrane flux recovers to 99% of the initial state, and the recycling rate of the cleaning wastewater reaches 100%.

Claims

1. A pure water cleaning membrane and wastewater recycling system, characterized in that, include: Raw water tank (2) is used to store raw water; The membrane element (21) has an inlet, a pure water outlet and a wastewater outlet, and is connected to the raw water tank (2) through an inlet pipe (18); A booster pump (7) is installed on the inlet pipe (18), with its inlet end connected to the outlet of the raw water tank (2) and its outlet end connected to the inlet of the membrane element (21). The water tank (24) has its inlet connected to the pure water outlet of the membrane element (21) via a water purification pipe (31); The cleaning pump (10) has its inlet connected to the outlet of the water tank (24) via a pipe, and its outlet connected to the membrane element (21) via a water rinsing pipe (32). The water rinsing pipe (32) is equipped with a one-way valve (11). Wastewater discharge pipe (30) is connected to the wastewater outlet of the membrane element (21) through the first branch pipe, and is equipped with a wastewater regulating valve II (16) for controlling the discharge flow rate. Wastewater recovery pipe (29) is connected to the wastewater outlet of the membrane element (21) through a second branch pipe and is connected back to the raw water tank (2), which is equipped with a wastewater flushing solenoid valve (17). An online conductivity meter (14) for wastewater is installed on the pipeline downstream of the wastewater outlet of the membrane element (21) for detecting wastewater quality. The PLC control system (28) is connected to the cleaning pump (10), the wastewater flushing solenoid valve (17) and the wastewater online conductivity meter (14) respectively. The PLC control system (28) is configured to: when the equipment enters the cleaning mode, control the booster pump (7) to stop, control the wastewater flushing solenoid valve (17) to open, and start the cleaning pump (10) to pump the pure water in the clean water tank (24) into the membrane element (21) for flushing. The wastewater generated by flushing flows back to the raw water tank (2) through the wastewater recovery pipe (29). The PLC control system (28) also controls the start and stop of the cleaning pump (10) and the opening and closing of the wastewater flushing solenoid valve (17) according to the real-time detection signal of the wastewater online conductivity meter (14).

2. The pure water cleaning membrane and wastewater recovery system according to claim 1, characterized in that: The wastewater recovery pipe (29) is also equipped with a wastewater regulating valve I (15) for adjusting the proportion of recovered wastewater.

3. The pure water cleaning membrane and wastewater recovery system according to claim 1, characterized in that: Wastewater flow meter I (19) is installed on the wastewater recovery pipe (29), and wastewater flow meter II (20) is installed on the wastewater discharge pipe (30).

4. The pure water cleaning membrane and wastewater recovery system according to claim 1, characterized in that: The membrane element (21) is a reverse osmosis membrane element or a nanofiltration membrane element.

5. A pure water cleaning membrane and wastewater recycling process, characterized in that, Includes the following steps: Normal water production steps: Close the cleaning pump (10) and check valve (11), open the wastewater regulating valve I (15) and wastewater regulating valve II (16), start the booster pump (7), so that the raw water passes through the booster pump (7) and is filtered by the membrane element (21). The pure water is stored in the clean water tank (24). Part of the wastewater is discharged through the wastewater discharge pipe (30), and the other part is returned to the raw water tank (2) through the wastewater recovery pipe (29). Membrane cleaning mode: Close the booster pump (7) and wastewater regulating valve I (15), open the wastewater flushing solenoid valve (17) and start the cleaning pump (10), use the pure water in the clean water tank (24) to flush the membrane element (21), and the flushing wastewater flows back to the raw water tank (2) through the wastewater recovery pipe (29). Cleaning control steps: The conductivity of the flushing wastewater is monitored in real time by an online conductivity meter (14), and the cleaning pump (10) is stopped and the wastewater flushing solenoid valve (17) is closed when the conductivity value reaches the preset condition. The PLC control system (28) monitors the real-time value of the conductivity meter (14) on the wastewater recovery pipe (29) and controls the working time and pressure of the cleaning pump (10) and the wastewater flushing solenoid valve (17).

6. The pure water cleaning membrane and wastewater recovery process according to claim 5, characterized in that: In membrane cleaning mode, the pure water pressure boosted by the cleaning pump (10) ranges from 0.4 MPa to 0.8 MPa.

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