Equipment for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment

Abstract

A device for real-time monitoring of membrane surface contamination behavior in high-salinity wastewater treatment, which is composed of an ultrafiltration pretreatment system, a cross-flow nanofiltration parallel system, a real-time monitoring system for membrane surface contamination behavior, and a real-time data acquisition system; the cross-flow nanofiltration parallel system is composed of a first cross-flow nanofiltration subsystem, a second cross-flow nanofiltration subsystem, and a water supply system connected in parallel; the real-time monitoring system for membrane surface contamination behavior is composed of a first optical coherence tomography scanner, a second optical coherence tomography scanner, a first membrane flux real-time monitoring device, and a second membrane flux real-time monitoring device; the real-time data acquisition system is a computer with data acquisition and processing software installed. This device uses optical coherence tomography for the first time to monitor the membrane surface contamination layer in the process of coal chemical high-salinity wastewater treatment, and can accurately and real-time obtain information on membrane surface contamination, and can use two membranes of different materials and structures at the same time to provide data support for membrane screening.

Description

Technical Field

[0001] The invention belongs to the field of monitoring membrane surface pollution behavior during high-salt wastewater treatment, and relates to a device for real-time monitoring of membrane surface pollution behavior during high-salt wastewater treatment. Background Art

[0002] my country's energy structure has enabled the rapid development of the coal chemical industry, but the problem that comes with it is the generation of a large amount of high-salt wastewater, mainly sodium sulfate and sodium chloride. At the same time, the high-salt wastewater is accompanied by some difficult-to-degrade organic matter. If it is directly discharged, it will not only waste resources, but also cause serious environmental pollution. With the strengthening of environmental protection efforts and the deepening of the concept of sustainable development, the disposal requirements for high-salt wastewater are becoming more and more stringent.

[0003] The widespread application of membrane treatment technology in wastewater treatment provides a reliable technology for high-quality reuse of industrial wastewater, and plays an extremely important role in the treatment of salt-containing wastewater in coal chemical industry. Nanofiltration and reverse osmosis membrane treatment technologies, as deep treatment technologies, have broad application prospects in the field of water treatment and have been widely used in wastewater treatment. However, the decrease in water flux, increase in operating energy consumption, shortened membrane service life, poor economic benefits, and deterioration of effluent quality caused by membrane pollution problems have always been important factors restricting its development. Therefore, in the water treatment process, it is very necessary to accurately judge the changes in membrane performance over time in the nanofiltration and reverse osmosis processes and estimate the membrane recovery time.

[0004] The existing equipment (or device) for monitoring membrane surface fouling behavior in the process of high-salt wastewater treatment includes a nanofiltration system or a reverse osmosis system as a set. The monitoring system is usually composed of a pressure gauge and / or a conductivity detector. The membrane desalination performance and membrane surface fouling are mainly determined by data such as trans-membrane pressure difference and / or conductivity. Since trans-membrane pressure difference and conductivity are macro data and the feedback is relatively slow, the following problems exist: 1. It is impossible to obtain information on membrane surface fouling accurately and in real time, making it difficult to accurately determine the changes in membrane performance over time during the nanofiltration and reverse osmosis processes and to accurately estimate the membrane recovery time; 2. It is impossible to use two membranes of different materials and structures at the same time to make the monitoring results comparable and provide data support for membrane screening; 3. It is impossible to provide accurate and effective information for the screening and use of antiscalants and descaling agents in the membrane cleaning process through real-time membrane fouling. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a device for real-time monitoring of membrane surface fouling behavior in high-salt wastewater treatment, so as to accurately and real-time obtain information on membrane surface fouling conditions, and to simultaneously use two membranes of different materials and structures to provide data support for membrane screening, as well as to provide more accurate and effective information for the screening and use of scale inhibitors in the membrane fouling process and scale removers in the membrane cleaning process.

[0006] The device for real-time monitoring of membrane surface contamination behavior in high-salt wastewater treatment of the present invention is composed of an ultrafiltration pretreatment system, a cross-flow nanofiltration parallel system, a real-time monitoring system for membrane surface contamination behavior and a real-time data acquisition system; the cross-flow nanofiltration parallel system is composed of a first cross-flow nanofiltration subsystem, a second cross-flow nanofiltration subsystem and a water delivery system for delivering pretreated wastewater to the two cross-flow nanofiltration subsystems connected in parallel, the first cross-flow nanofiltration subsystem contains a first cross-flow nanofiltration device, and the second cross-flow nanofiltration subsystem contains a second cross-flow nanofiltration device; the real-time monitoring system for membrane surface contamination behavior is composed of a first optical coherence tomography scanner, a second optical coherence tomography scanner, a first membrane flux real-time monitoring device and a second membrane flux real-time monitoring device; the real-time data acquisition system is a computer installed with data acquisition and processing software;

[0007] The ultrafiltration pretreatment system is connected to the water delivery system in the cross-flow nanofiltration parallel system through pipes to deliver the pretreated wastewater to the water delivery system; the observation head of the first optical coherence tomography scanner is combined with the first observation window set in the first cross-flow nanofiltration device, and the observation head of the second optical coherence tomography scanner is combined with the second observation window set in the second cross-flow nanofiltration device; the first membrane flux real-time monitoring device is connected to the water production outlet of the first cross-flow nanofiltration device through pipes, and the second membrane flux real-time monitoring device is connected to the water production outlet of the second cross-flow nanofiltration device through pipes; the computer is respectively connected to the first optical coherence tomography scanner, the second optical coherence tomography scanner, the first membrane flux real-time monitoring device, and the second membrane flux real-time monitoring device through data lines to receive information on the surface contamination status of the nanofiltration membranes in the first cross-flow nanofiltration device and the second cross-flow nanofiltration device from them and process and save it.

[0008] In the above-mentioned equipment for monitoring membrane surface contamination behavior in high-salt wastewater treatment, the water delivery subsystem in the cross-flow nanofiltration parallel system is composed of a second water delivery pump, a heat exchanger, a jacketed water bath water storage tank, a third water delivery pump, a high-pressure pump and a flow control valve. The second water delivery pump, the water storage tank of the jacketed water bath water storage tank, the third water delivery pump, and the high-pressure pump are connected in sequence through pipe fittings, the heat exchanger is connected to the jacket of the jacketed water bath water storage tank through pipe fittings, the liquid inlet of the flow control valve is connected to the liquid outlet of the high-pressure pump through pipe fittings, and the liquid outlet of the flow control valve is connected to the water storage tank of the jacketed water bath water storage tank through pipe fittings; the first cross-flow nanofiltration subsystem is composed of a first pressure gauge, a first liquid inlet valve, a first cross-flow nanofiltration device, a second pressure gauge, a first back pressure regulator, and a first flow meter connected in sequence through pipe fittings, and the second cross-flow nanofiltration subsystem is composed of a third pressure gauge, a second liquid inlet valve, a second cross-flow nanofiltration device, a fourth pressure gauge, a second back pressure regulator, and a second flow meter connected in sequence through pipe fittings.

[0009] In the above-mentioned equipment for real-time monitoring of membrane surface contamination behavior in high-salt wastewater treatment, the ultrafiltration pretreatment system is composed of a regulating tank, a first water delivery pump, a filter, an ultrafiltration device, and a produced water storage tank connected in sequence through pipes, a first drain valve is provided at the lower part of the regulating tank, and a second drain valve is provided at the lower part of the produced water storage tank; the produced water storage tank is connected to the liquid inlet of the second water delivery pump in the water delivery system through pipes.

[0010] In the above-mentioned device for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment, the concentrated water output by the first cross-flow nanofiltration device and the second cross-flow nanofiltration device can be collected separately or sent to the regulating tank in the ultrafiltration pretreatment system. In view of simplifying the equipment structure, it is preferably sent to the regulating tank in the ultrafiltration pretreatment system. When the selected technical solution is to send the concentrated water output by the first cross-flow nanofiltration device and the second cross-flow nanofiltration device to the regulating tank in the ultrafiltration pretreatment system, the concentrated water outlet of the first cross-flow nanofiltration device in the first cross-flow nanofiltration subsystem and the concentrated water outlet of the second cross-flow nanofiltration device in the second cross-flow nanofiltration subsystem are respectively connected to the regulating tank in the ultrafiltration pretreatment system through pipes.

[0011] In the above-mentioned equipment for real-time monitoring of membrane surface fouling behavior in high-salt wastewater treatment, the first membrane flux real-time monitoring device and the second membrane flux real-time monitoring device in the real-time monitoring membrane surface fouling behavior system are both composed of an electronic balance and a water container placed on the electronic balance, and the electronic balance is connected to the computer via a data cable.

[0012] The device for real-time monitoring of membrane surface fouling behavior in high-salt wastewater treatment of the present invention is used and operated as follows:

[0013] 1. The high-salt wastewater from coal chemical industry is transported to the regulating tank in the ultrafiltration pretreatment system. After being regulated in the regulating tank, it enters the filter and ultrafiltration device in sequence through the first water delivery pump and the pipeline. The ultrafiltration product water treated by the ultrafiltration device enters the product water storage tank through the pipeline (it can be regulated again);

[0014] 2. The second water delivery pump in the water delivery system of the cross-flow nanofiltration parallel system injects the wastewater pre-treated by ultrafiltration in the production water storage tank into the water storage tank of the jacketed water bath water storage tank, and the feed water temperature is circulated through the heat exchanger to control the feed water temperature. The wastewater in the water storage tank of the jacketed water bath water storage tank is sequentially input into the first cross-flow nanofiltration device and the second cross-flow nanofiltration device in the first cross-flow nanofiltration subsystem and the second cross-flow nanofiltration subsystem through the pipeline for treatment (or membrane pollution experiment). During the treatment (or experiment), the flow control valve in the water delivery system controls the liquid inlet amount, and the flowmeter in the first cross-flow nanofiltration subsystem and the second cross-flow nanofiltration subsystem displays the real-time flow rate. The pressure is jointly adjusted and controlled by the water supply pressure and the back pressure regulator and the liquid inlet valve in the first cross-flow nanofiltration subsystem and the second cross-flow nanofiltration subsystem, and the pressure gauge in the first cross-flow nanofiltration subsystem and the second cross-flow nanofiltration subsystem displays the real-time pressure.

[0015] 3. During the wastewater treatment (or experiment) process of the first cross-flow nanofiltration device and the second cross-flow nanofiltration device, the first optical coherence tomography scanner and the second optical coherence tomography scanner in the real-time monitoring system for the fouling behavior of the membrane surface perform real-time in-situ scanning of the dynamic growth process of the fouling layer on the surface of the nanofiltration membrane, and obtain vertical 2D images with certain pixels in the x and z directions from the first cross-flow nanofiltration device and the second cross-flow nanofiltration device at fixed time intervals, and convert the obtained images into electrical signals and transmit them to the computer through the data line; the first membrane flux real-time monitoring device and the second membrane flux real-time monitoring device in the real-time monitoring system for the fouling behavior of the membrane surface collect the membrane water quality of the first cross-flow nanofiltration device and the second cross-flow nanofiltration device in real time and feed them back to the computer through the data line;

[0016] 4. The computer constituting the real-time data acquisition system processes the received information to obtain data on the thickness of the membrane fouling layer and the membrane flux over time.

[0017] 5. During the wastewater treatment (or experiment) process of the first cross-flow nanofiltration device and the second cross-flow nanofiltration device, the output concentrated water is transported to the regulating tank in the ultrafiltration pretreatment system through a pipeline for treatment or collected in a container, and the nanofiltration produced water is collected by the first membrane flux real-time monitoring device and the second membrane flux real-time monitoring device for analysis and detection.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) Since the device described in the present invention is composed of an optical coherence tomography scanner and a membrane flux real-time monitoring device to construct a real-time monitoring system for membrane surface fouling behavior, optical coherence tomography is used for the first time to monitor the membrane surface fouling layer during the treatment of high-salt wastewater in coal chemical industry, thus realizing the real-time in-situ monitoring of the dynamic growth process of the membrane surface fouling layer for the first time, and obtaining data on the thickness of the membrane fouling layer changing with the treatment time. Combined with the data on the membrane flux changing with the treatment time obtained by the membrane flux real-time monitoring device, it is possible to accurately judge the changes in membrane performance over time during the nanofiltration process and accurately estimate the membrane recovery time, as well as screen out the most effective antiscalant and descaling agent, thereby providing a guarantee for the effective treatment of wastewater.

[0020] (2) Since two sets of cross-flow nanofiltration subsystems are arranged in the cross-flow nanofiltration parallel system of the equipment described in the present invention, the cross-flow nanofiltration devices in the two sets of cross-flow nanofiltration subsystems can use nanofiltration membranes of different materials and structures during wastewater treatment. The data on the thickness of the membrane fouling layer changing with the treatment time and the data on the membrane flux changing with the treatment time can provide data support for membrane screening.

[0021] (3) Since the equipment described in the present invention is equipped with an ultrafiltration pretreatment system, it can be used to monitor the fouling behavior of the membrane surface during the actual treatment of high-salinity wastewater, and can also use actual coal chemical high-salinity wastewater as influent for membrane fouling experiments in scientific research, making the research results more in line with actual wastewater treatment conditions.

[0022] (4) The device of the present invention is easy to operate and can be used not only for monitoring the surface fouling behavior of high-salinity wastewater treatment membranes, but also for monitoring the surface fouling behavior of other wastewater treatment membranes, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the device for real-time monitoring of membrane surface contamination behavior in high-salt wastewater treatment according to the present invention. In the figure, 1 is a regulating tank, 2 is a first vent valve, 3 is a first water pump, 4 is a filter, 5 is an ultrafiltration device, 6 is a produced water storage tank, 7 is a second vent valve, 8 is a second water pump, 9 is a heat exchanger, 10 is a jacketed water bath storage tank, 11 is a third water pump, 12 is a high-pressure pump, 13 is a flow control valve, 14 is a first pressure gauge, 15 is a first liquid inlet valve, 16 is a first cross-flow nanofiltration device, 17 is The first observation window, 18—the first optical coherence tomography scanner, 19—the second pressure gauge, 20—the first back pressure regulator, 21—the first flow meter, 22—the first membrane flux real-time monitoring device, 23—the third pressure gauge, 24—the second liquid inlet valve, 25—the second cross-flow nanofiltration device, 26—the second observation window, 27—the second optical coherence tomography scanner, 28—the fourth pressure gauge, 29—the second back pressure regulator, 30—the second flow meter, 31—the second membrane flux real-time monitoring device, 32—the computer.

[0024] Figure 2 This is a normalized graph showing the change in membrane flux versus treatment time during the high-salt wastewater treatment process.

[0025] Figure 3 This is a graph showing the change in the thickness of the fouling layer on the membrane surface during the treatment of high-salt wastewater with treatment time. DETAILED DESCRIPTION

[0026] The device for real-time monitoring of membrane surface fouling behavior in high-salt wastewater treatment and its use are further described below through examples and in conjunction with the accompanying drawings.

[0027] Example 1

[0028] In this embodiment, the equipment for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment is as follows: Figure 1 As shown, it consists of an ultrafiltration pretreatment system, a cross-flow nanofiltration parallel system, a real-time monitoring system for membrane surface fouling behavior, and a real-time data acquisition system.

[0029] The ultrafiltration pretreatment system is composed of a regulating tank 1, a first water pump 3, a filter 4, an ultrafiltration device 5, and a produced water storage tank 6 which are connected in sequence through pipes. A first drain valve 2 is provided at the lower part of the regulating tank 1 for draining the high-salt wastewater in the regulating tank. A second drain valve 7 is provided at the lower part of the produced water storage tank 6 for draining the pretreated high-salt wastewater in the produced water storage tank.

[0030] The cross-flow nanofiltration parallel system is composed of a first cross-flow nanofiltration subsystem and a second cross-flow nanofiltration subsystem connected in parallel, and a water delivery subsystem for delivering pretreated high-salinity wastewater to the two cross-flow nanofiltration subsystems; the water delivery subsystem is composed of a second water delivery pump 8, a heat exchanger 9, a jacketed water bath water storage tank 10, a third water delivery pump 11, a high-pressure pump 12 and a flow control valve 13. The second water delivery pump 8, the water storage tank of the jacketed water bath water storage tank 10, the third water delivery pump 11 and the high-pressure pump 12 are sequentially connected through pipe fittings, the heat exchanger 9 is connected to the jacket of the jacketed water bath water storage tank 10 through pipe fittings, and the inlet of the flow control valve 13 is connected to the outlet of the jacketed water bath water storage tank 10. The liquid port is connected to the liquid outlet of the high-pressure pump 12 through a pipe fitting, and the liquid outlet of the flow control valve 13 is connected to the water tank of the jacketed water bath water storage tank 10 through a pipe fitting; the first cross-flow nanofiltration subsystem is composed of a first pressure gauge 14, a first liquid inlet valve 15, a first cross-flow nanofiltration device 16, a second pressure gauge 19, a first back pressure regulator 20, and a first flow meter 21 connected in sequence through pipe fittings; the second cross-flow nanofiltration subsystem is composed of a third pressure gauge 23, a second liquid inlet valve 24, a second cross-flow nanofiltration device 25, a fourth pressure gauge 28, a second back pressure regulator 29, and a second flow meter 30 connected in sequence through pipe fittings.

[0031] The system for real-time monitoring of membrane surface contamination behavior is composed of a first optical coherence tomography scanner 18, a second optical coherence tomography scanner 27, a first membrane flux real-time monitoring device 22 and a second membrane flux real-time monitoring device 31; the first membrane flux real-time monitoring device 22 and the second membrane flux real-time monitoring device 31 are both composed of an electronic balance and a water container placed on the electronic balance.

[0032] The real-time data acquisition system is a computer 32 installed with data acquisition and processing software, which includes OHAUS data acquisition software and ImageJ image processing software. The OHAUS data acquisition software is provided by the American OHAUS, a manufacturer of membrane flux real-time monitoring device, and the ImageJ image processing software is open source free software.

[0033] The above systems are combined through relevant components or devices in the system to form equipment for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment. The specific combination is as follows:

[0034] The produced water storage tank 6 in the ultrafiltration pretreatment system is connected to the liquid inlet of the second water delivery pump 8 of the water delivery system in the cross-flow nanofiltration parallel system through a pipe; the concentrated water outlet of the first cross-flow nanofiltration device 16 of the first cross-flow nanofiltration subsystem and the concentrated water outlet of the second cross-flow nanofiltration device 25 of the second cross-flow nanofiltration subsystem in the cross-flow nanofiltration parallel system are respectively connected to the regulating tank 1 in the ultrafiltration pretreatment system through pipes; the observation head of the first optical coherence tomography scanner 18 in the real-time monitoring system of membrane surface contamination behavior is combined with the first observation window 17 set in the first cross-flow nanofiltration device 16, and the second optical The observation head of the coherence tomography scanner 27 is combined with the second observation window 26 set in the second cross-flow nanofiltration device 25; the first membrane flux real-time monitoring device 22 in the real-time monitoring system of membrane surface contamination behavior is connected to the water production outlet of the first cross-flow nanofiltration device 16 through a pipe, and the second membrane flux real-time monitoring device 31 is connected to the water production outlet of the second cross-flow nanofiltration device 25 through a pipe; the computer 32 is respectively connected to the first optical coherence tomography scanner 18, the second optical coherence tomography scanner 27, the first membrane flux real-time monitoring device 22, and the second membrane flux real-time monitoring device 31 through data cables.

[0035] The water delivery pump, filter, ultrafiltration device, heat exchanger, high-pressure pump, flow control valve, liquid inlet valve, vent valve, pressure gauge, flow meter, back pressure regulator, cross-flow nanofiltration device, optical coherence tomography scanner, membrane flux real-time monitoring device and computer involved in this embodiment are all purchased from the market. Among them, the specification of the filter 4 is 10 inches; the specification of the ultrafiltration device 5 is 5 inches; the model of the high-pressure pump 12 is Hydra-cell, and the pressure range is 0-6.9Mpa; the cross-flow nanofiltration device: the nanofiltration membrane pool CF042SS, the size is 220mm×110mm×60mm, the channel size is 130mm×50mm×2mm, the observation window size is 4.3cm×4.3cm, and the pressure range is 0-6.9MPa; the optical coherence tomography scanner: Lumedica, USA, model OQLabscope2.0; the membrane flux real-time monitoring device: OHAUS, USA, model STX6201ZH; the computer is a PC.

[0036] Example 2

[0037] This example uses the equipment described in Example 1 to conduct an experiment to monitor the fouling behavior of the membrane surface in real time during the treatment of high-salinity wastewater. The composition of the high-salinity wastewater is shown in Table 1.

[0038] Table 1 Composition of high-salinity wastewater

[0039] In the device used in this embodiment for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment, the nanofiltration membranes of the first cross-flow nanofiltration device 16 and the second cross-flow nanofiltration device 25 are both nanofiltration 270 (Dow), the feed temperature of the membrane fouling experiment is 25±1°C, the operating pressure is 2.0±0.02MPa, and the feed flow rate is 0.35L / min. The operation is as follows:

[0040] 1. Before the membrane fouling experiment, the nanofiltration membrane was compacted with deionized water at a pressure of 2.0±0.02MPa for 24h.

[0041] 2. Close the first vent valve 2 provided at the lower part of the regulating tank 1 and the second vent valve 7 provided at the lower part of the produced water storage tank 6 in the ultrafiltration pretreatment system, pour the high-salt wastewater from the coal chemical industry into the regulating tank 1, regulate it through the flocculant polyacrylamide and the biocide isothiophosphonium, remove the suspended particles, microorganisms, etc. in the wastewater, and then adjust the pH value of the wastewater to about 7.0 with sodium hydroxide or hydrochloric acid; then start the first water delivery pump 3, and the high-salt wastewater is pretreated through the filter 4 and the ultrafiltration device 5 in turn through the pipeline, and the ultrafiltration produced water is injected into the produced water storage tank 6 through the pipeline. The pretreatment section can intercept more than 90% of the colloidal particles, bacteria and macromolecular organic matter in the high-salt wastewater.

[0042] 3. Turn on the second water delivery pump 8 of the water delivery system in the cross-flow nanofiltration parallel system to inject the ultrafiltration produced water into the water storage tank of the jacketed water bath storage tank 10 through the pipeline, and control the temperature of the ultrafiltration produced water in the water storage tank at 25±1°C through the heat exchanger 9; turn on the third water delivery pump 11 and the high-pressure pump 12 in turn to deliver the ultrafiltration produced water at a temperature of 25±1°C to the first cross-flow nanofiltration device 16 in the first cross-flow nanofiltration subsystem and the second cross-flow nanofiltration device 25 in the second cross-flow nanofiltration subsystem through the pipeline to carry out the membrane fouling experiment During the experiment, the feed flow rate was controlled to be 0.35L / min by the flow control valve 13, and the real-time flow rate was displayed by the first flow meter 21 and the second flow meter 30. The feed pressure was controlled to be 2.0±0.02MPa by the water supply pressure, the first back pressure regulator 20, the second back pressure regulator 29 and the first liquid inlet valve 15 and the second liquid inlet valve 24. The real-time pressure was displayed by the first pressure gauge 14, the second pressure gauge 19, the third pressure gauge 23 and the fourth pressure gauge 28.

[0043] 4. During the membrane fouling experiment, the first membrane flux real-time monitoring device 22 and the second membrane flux real-time monitoring device 31 are used to collect the produced water of the first cross-flow nanofiltration device 16 and the second cross-flow nanofiltration device 25 and measure the quality change of the produced water; the computer 32 receives the quality change data of the produced water from the first cross-flow nanofiltration device 16 and the second cross-flow nanofiltration device 25 and calculates the quality change of the produced water through formula (1) (where J, V, A, and t are real-time membrane flux, real-time membrane flux permeate volume, membrane area, and operation time, respectively) The initial membrane flux J is calculated o Real-time membrane flux at different time points during the fouling process J c , and then from formula (2) (N f The real-time normalized membrane flux N at different time points was calculated. f , we can get the change of normalized membrane flux over experimental time, see Figure 2 Formula (1) and formula (2) are from the third page of the paper "Behaviours and mechanisms of nanofiltration membrane fouling by anionic polyacrylamide with different molecular weights in brackish wastewater desalination" (https: / / doi.org / 10.1016 / j.desal.2019.06.024) in the journal Desalination, which is included in Elsevier Publishing. Figure 2It can be seen that the membrane flux decreased rapidly during the period of 0-800 min. The reason may be that under high-pressure operation, the salt ion concentration on the membrane surface and its vicinity is much greater than its concentration in the main solution. When it reaches the solubility product of the corresponding precipitate or the saturation of the crystalline salt, it will form a precipitate or precipitate crystalline salt on the membrane surface and its vicinity, and migrate and adhere to the membrane surface with the osmotic driving force, gradually blocking the membrane pores and reducing the effective filtration area. With the increase of filtration time, the membrane pollution becomes more and more serious, causing the membrane flux to further decrease; during the period of 800-1400 min, the membrane flux decrease tends to be gentle. At this stage, the membrane surface is seriously polluted, and a dense filter cake layer of a certain thickness is formed on the membrane surface.

[0044] During the membrane fouling experiment, the first optical coherence tomography scanner 18 and the second optical coherence tomography scanner 27 are used to monitor the real-time growth of the fouling layer on the surface of the nanofiltration membrane in the first cross-flow nanofiltration device 16 and the second cross-flow nanofiltration device 25, respectively. The optical coherence tomography scanner observes the 0.1 cm×0.1 cm membrane area in real time through the observation window equipped on the cross-flow nanofiltration device, and obtains vertical 2D images from the device at intervals of 1 hour. The size of the image in the x and z directions is 1000 pixels×800 pixels respectively; the computer 32 receives the optical image signals from the first optical coherence tomography scanner 18 and the second optical coherence tomography scanner 27, and the thickness of the fouling layer in the obtained image is evaluated by the ImageJ image processing software. The obtained black and white image is adjusted using the Fire lookup table in ImageJ to distinguish the membrane surface (yellow) from the fouling layer (purple), and the thickness of the fouling layer is determined by converting the pixels in the image into a metric scale (a 1 mm glass slide is used as a reference for measuring the fouling thickness, and there are a total of 330 pixels in 1 mm, so 1 pixel is converted to 3 The thickness of the fouling layer on the membrane surface changes with time. Figure 3 As shown, from Figure 3 It can be seen that during the period of 0-800 min, the deposition rate of fouling on the membrane surface was fast, and during the period of 800-1400 min, the deposition rate of fouling on the membrane surface became slow. At this time, a relatively thick fouling layer had formed on the membrane surface, and under the action of cross-flow shear force, the fouling layer gradually became dense and stable. The growth of the fouling layer was consistent with the downward trend of the membrane flux, indicating that the optical coherence tomography scanner can effectively monitor the dynamic growth of membrane surface contamination over time.

Claims

1. A device for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment, Features The equipment is composed of an ultrafiltration pretreatment system, a cross-flow nanofiltration parallel system, a real-time monitoring system for membrane surface fouling behavior, and a real-time data acquisition system; The cross-flow nanofiltration parallel system is composed of a first cross-flow nanofiltration subsystem, a second cross-flow nanofiltration subsystem and a water delivery subsystem for delivering pre-treated wastewater to the two cross-flow nanofiltration subsystems, wherein the first cross-flow nanofiltration subsystem comprises a first cross-flow nanofiltration device (16), and the second cross-flow nanofiltration subsystem comprises a second cross-flow nanofiltration device (25); The real-time monitoring system for membrane surface contamination behavior is composed of a first optical coherence tomography scanner (18), a second optical coherence tomography scanner (27), a first membrane flux real-time monitoring device (22) and a second membrane flux real-time monitoring device (31); The real-time data acquisition system is a computer (32) installed with data acquisition and processing software; The ultrafiltration pretreatment system is connected to the water delivery system in the cross-flow nanofiltration parallel system through a pipe so as to deliver the pretreated wastewater to the water delivery system; the observation head of the first optical coherence tomography scanner (18) is combined with the first observation window (17) provided in the first cross-flow nanofiltration device (16), and the observation head of the second optical coherence tomography scanner (27) is combined with the second observation window (26) provided in the second cross-flow nanofiltration device (25); the first membrane flux real-time monitoring device (22) is connected to the water output outlet of the first cross-flow nanofiltration device (16) through a pipe. The second membrane flux real-time monitoring device (31) is connected to the water production outlet of the second cross-flow nanofiltration device (25) through a pipe fitting; the computer (32) is respectively connected to the first optical coherence tomography scanner (18), the second optical coherence tomography scanner (27), the first membrane flux real-time monitoring device (22), and the second membrane flux real-time monitoring device (31) through a data line, so as to receive information on the surface contamination status of the nanofiltration membranes in the first cross-flow nanofiltration device (16) and the second cross-flow nanofiltration device (25) from them and process and save the information.

2. The device for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment according to claim 1, Features The water delivery system in the cross-flow nanofiltration parallel system is composed of a second water delivery pump (8), a heat exchanger (9), a jacketed water bath water storage tank (10), a third water delivery pump (11), a high-pressure pump (12) and a flow control valve (13); the second water delivery pump (8), the water storage tank of the jacketed water bath water storage tank (10), the third water delivery pump (11) and the high-pressure pump (12) are connected in sequence through pipe fittings; the heat exchanger (9) is connected to the jacket of the jacketed water bath water storage tank (10) through pipe fittings; the liquid inlet of the flow control valve (13) is connected to the liquid outlet of the high-pressure pump (12) through pipe fittings; and the liquid outlet of the flow control valve (13) is connected to the water storage tank of the jacketed water bath water storage tank (10) through pipe fittings; The first cross-flow nanofiltration subsystem is formed by connecting a first pressure gauge (14), a first liquid inlet valve (15), a first cross-flow nanofiltration device (16), a second pressure gauge (19), a first back pressure regulator (20), and a first flow meter (21) in sequence through pipe fittings, and the second cross-flow nanofiltration subsystem is formed by connecting a third pressure gauge (23), a second liquid inlet valve (24), a second cross-flow nanofiltration device (25), a fourth pressure gauge (28), a second back pressure regulator (29), and a second flow meter (30) in sequence through pipe fittings.

3. The device for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment according to claim 2, Features The ultrafiltration pretreatment system is composed of a regulating tank (1), a first water delivery pump (3), a filter (4), an ultrafiltration device (5), and a produced water storage tank (6) which are connected in sequence through pipe fittings; a first drain valve (2) is provided at the lower part of the regulating tank (1), and a second drain valve (7) is provided at the lower part of the produced water storage tank (6); the produced water storage tank (6) is connected to the liquid inlet of the second water delivery pump (8) in the water delivery system through pipe fittings.

4. The device for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment according to claim 3, Features The concentrate outlet of the first cross-flow nanofiltration device (16) in the first cross-flow nanofiltration subsystem and the concentrate outlet of the second cross-flow nanofiltration device (25) in the second cross-flow nanofiltration subsystem are respectively connected to the regulating tank (1) in the ultrafiltration pretreatment system through pipe fittings.

5. The device for real-time monitoring of membrane surface fouling behavior in high-salinity wastewater treatment according to any one of claims 1 to 4, Features The first membrane flux real-time monitoring device (22) and the second membrane flux real-time monitoring device (31) in the system for real-time monitoring of membrane surface fouling behavior are both composed of an electronic balance and a water container placed on the electronic balance, and the electronic balance is connected to the computer (32) via a data cable.

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