Circulating water treatment system and method driven by solar energy

Abstract

The application relates to the technical field of water treatment, in particular to a circulating water treatment system and method based on solar driving, which comprises a solar energy supply unit for obtaining and storing electric energy; a data acquisition unit for obtaining photovoltaic power of the solar energy supply unit in real time; a water treatment unit, the water treatment unit comprising at least two groups of membrane assemblies, each of the membrane assemblies having a gas flow path and a water body flow path; and a control unit for controlling the water treatment unit to switch between a first treatment state and a second treatment state according to a comparison result of the photovoltaic power and a preset threshold value. The application realizes adaptive matching of a water treatment unit operation mode and solar energy supply adequacy by presetting the first treatment state and the second treatment state in the water treatment unit and driving the switching between the two states by the control unit according to the comparison result of the photovoltaic power and the preset threshold value.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a solar-powered circulating water treatment system and a solar-powered circulating water treatment method. Background Technology

[0002] A membrane aerated biofilm reactor (MABR) is a highly efficient technology for water remediation. Its core component is a hollow fiber membrane bundle, on which microorganisms attach to form a biofilm. Compressed air is introduced into the inner cavity of the membrane fibers, and oxygen diffuses from the inside of the fibers through the membrane wall to the outside, supplying oxygen to the biofilm; pollutants in the water diffuse from the outside to the surface of the membrane fibers and are degraded by the biofilm.

[0003] In a purely solar-driven, unattended MABR water remediation system, photovoltaic power supply is significantly affected by day-night cycles, weather conditions such as sunshine and rain, resulting in significant fluctuations and intermittency. When sunlight is insufficient, photovoltaic power drops sharply, and the system is easily forced to operate at reduced power or shut down intermittently, directly causing a significant reduction in water treatment efficiency and denitrification effect. Existing technologies mainly rely on passive compensation methods such as increasing battery energy storage capacity and shortening downtime intervals to cope with power supply fluctuations, but there are obvious shortcomings: First, expanding energy storage equipment will significantly increase equipment investment, land area, and subsequent maintenance costs; second, the overall uniform power reduction operation mode cannot match the differentiated energy consumption and process requirements of different stages of nitrification and denitrification in water treatment, and cannot balance treatment effect and energy-saving operation under low power supply conditions. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a solar-driven circulating water treatment system and method, as detailed below: On one hand, the present invention provides a solar-driven circulating water treatment system, comprising: Solar power units are used to acquire and store electrical energy; A data acquisition unit is used to acquire the photovoltaic power of the solar power supply unit in real time; A water treatment unit, the water treatment unit comprising at least two sets of membrane modules, each of the membrane modules having a gas flow path and a water flow path; The control unit is used to control the water treatment unit to switch between a first treatment state and a second treatment state based on the comparison result of the photovoltaic power and a preset threshold. When the photovoltaic power is higher than or equal to the preset threshold, the water treatment unit enters the first processing state, and the gas flow paths of all the membrane modules are connected, and the water flow paths of each membrane module are connected in parallel. When the photovoltaic power is lower than the preset threshold, the water treatment unit enters the second processing state, and the gas flow paths of each membrane module are alternately partially opened and partially closed according to a preset time sequence, while the water flow paths are connected in series.

[0005] As a further technical solution of the present invention, the water treatment unit further includes a submersible blower, the gas flow path of each membrane module is connected to the output end of the submersible blower through an air supply branch pipe, the gas flow paths of each membrane module are connected in parallel to the submersible blower, and each air supply branch pipe is provided with an air supply valve. In the first processing state, all the gas supply valves are open; In the second processing state, each of the gas supply valves is opened and closed alternately according to the preset timing sequence.

[0006] As a further technical solution of the present invention, the water treatment unit further includes a circulating water pump. The inlet of each membrane module water flow path is connected to the outlet of the circulating water pump through a parallel water supply branch pipe, and a parallel water supply valve is provided on the parallel water supply branch pipe. The outlet of each membrane module water flow path is connected to the return port of the circulating water pump through a parallel return water branch pipe, and a parallel return water valve is provided on the parallel return water branch pipe. The outlet and inlet of two adjacent membrane module water flow paths are connected through a series branch pipe, and a series valve is provided on the series branch pipe. In the first processing state, both the parallel water supply valve and the parallel water return valve are open, and both series valves are closed; In the second processing state, both the parallel water supply valve and the parallel water return valve are closed, and both series valves are open. Water flows from the membrane module with the gas flow path open to the membrane module with the gas flow path closed, using the nitrate produced by the former as the substrate for the denitrification reaction of the latter.

[0007] As a further technical solution of the present invention, the preset threshold is any value between 15% and 25% of the rated power of the solar power unit.

[0008] As a further technical solution of the present invention, in the second processing state, the preset timing of the alternation of the gas flow path is any value between 0.5h and 4h.

[0009] As a further technical solution of the present invention, the inlet of the membrane module at the beginning of the water flow path is connected to the outlet of the circulating water pump, and the outlet of the membrane module at the end of the water flow path is connected to the return outlet of the circulating water pump.

[0010] As a further technical solution of the present invention, the control unit is further configured to: control the water treatment unit to switch from the first processing state to the second processing state only after the photovoltaic power drops from above or equal to the preset threshold to below the preset threshold and the below state is maintained for a first preset duration; and control the water treatment unit to switch from the second processing state back to the first processing state only after the photovoltaic power rises from below the preset threshold to above or equal to the preset threshold and the rise state is maintained for a second preset duration.

[0011] As a further technical solution of the present invention, both the first preset duration and the second preset duration are selected between 30 seconds and 10 minutes.

[0012] On the other hand, the present invention also provides a solar-driven circulating water treatment method, comprising the following steps: Real-time acquisition of photovoltaic power from solar power units; The photovoltaic power is compared with a preset threshold. When the photovoltaic power is higher than or equal to the preset threshold, the water treatment unit is controlled to enter the first processing state, so that the gas flow path of all membrane modules is connected and the water flow path of each membrane module is connected in parallel. When the photovoltaic power is lower than the preset threshold, the water treatment unit is controlled to enter the second processing state, so that the gas flow path of each membrane module is alternately partially opened and partially closed, and the water flow path is connected in series with each other according to a preset time sequence.

[0013] As a further technical solution of the present invention, in the second processing state, water flows from the membrane module with the gas flow path open to the membrane module with the gas flow path closed, and the nitrate produced by the former is used as the substrate for the denitrification reaction of the latter.

[0014] The beneficial effects of this invention are as follows: This invention presets a first and second treatment state in the water treatment unit and uses a control unit to drive the switching between the two states based on the comparison result of photovoltaic power and preset threshold. When there is sufficient light irradiance, the water treatment unit is in the first treatment state, all gas flow paths of the membrane modules are fully open, the water flow paths are connected in parallel, and all membrane treatment modules are in a state of simultaneous nitrification and denitrification. When there is insufficient light irradiance, the water treatment unit is in the second treatment state, the gas flow paths of each membrane module are alternately partially opened and partially closed according to a preset time sequence, and the water flow paths are connected in series. Thus, the water treatment unit's operating mode is adaptively matched with the sufficiency of solar energy supply. At the same time, in the second treatment state, the water flows from the membrane modules with open gas flow paths to the membrane modules with closed gas flow paths, and the nitrates generated in the open part are directionally transported to the closed part as denitrification substrate. This solves the problem of limited denitrification rate caused by the traditional MABR relying on the "passive spatial stratification" inside a single membrane module for simultaneous nitrification and denitrification.

[0015] In this invention, by using a preset timing sequence to alternately open and close the gas flow paths of each membrane module in the second processing state, and by rotating the opening and closing of the gas flow paths periodically, the equal rotation between operation and rest of each membrane module is achieved, avoiding the problem of irreversible decline in biofilm activity caused by some membrane modules being in a rest state for a long time in the alternating operation scheme.

[0016] In this invention, a working condition switching delay confirmation mechanism is added. The operating state is switched only when the photovoltaic power deviates from the preset threshold for a certain period of time. This effectively filters out instantaneous interferences such as cloud cover and short-term solar radiation fluctuations, avoids frequent changes in system operating conditions, achieves a smooth transition between the two processing states, and improves the operational stability in unattended scenarios. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the framework of the solar-driven circulating water treatment system of the present invention.

[0018] Figure 2 This is a schematic diagram of the water treatment unit of the present invention.

[0019] Figure 3 This is a schematic diagram of the cooperation structure between the membrane module and the submersible fan in the first treatment state of the present invention.

[0020] Figure 4 This is a schematic diagram of the cooperation structure between the membrane module and the submersible fan in the second treatment state of the present invention.

[0021] Figure 5 This is a schematic diagram of the cooperation structure between the membrane module and the circulating water pump of the present invention in the first treatment state.

[0022] Figure 6This is a schematic diagram of the cooperation structure between the membrane module and the circulating water pump in the second treatment state of the present invention.

[0023] Figure label: 100. Membrane module; 110. Air supply branch pipe; 111. Air supply valve; 120. Parallel water supply branch pipe; 121. Parallel water supply valve; 130. Parallel return water branch pipe; 131. Parallel return water valve; 140. Series branch pipe; 141. Series valve; 200. Submersible blower; 300. Circulating water pump. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0025] The present invention provides Figure 1 A framework diagram of a solar-driven circulating water treatment system is shown. Figure 1 The solar-powered circulating water treatment system includes: Solar power units are used to acquire and store electrical energy; A data acquisition unit is used to acquire the photovoltaic power of the solar power supply unit in real time; Water treatment unit; The control unit is used to control the water treatment unit to switch between a first treatment state and a second treatment state based on a comparison result between the photovoltaic power and a preset threshold. When the photovoltaic power is higher than or equal to the preset threshold, the water treatment unit enters the first treatment state and the water treatment unit operates at full load. When the photovoltaic power is lower than the preset threshold, the water treatment unit enters the second processing state, in which the water treatment unit operates partly and stops partly in a time-sharing alternating manner.

[0026] In this system, the control unit, data acquisition unit, and water treatment unit all rely on the power supply of the solar power unit to operate. The solar power unit, data acquisition unit, control unit, and water treatment unit are connected to each other wirelessly or via wired means.

[0027] In light of the aforementioned precondition that solar-driven photothermal irradiance conditions will fluctuate uncontrollably with the alternation of day and night and weather changes, two operating states are preset in the water treatment unit: Under the premise of sufficient solar irradiance and photovoltaic power higher than or equal to a preset threshold, the system enters the first processing state, and the water treatment unit operates in full-load mode to maximize the use of the current abundant energy to complete the processing task. Under the preconditions of insufficient solar radiation and photovoltaic power below the preset threshold, the system automatically switches to the second processing state. The water treatment unit operates in a time-sharing and alternating manner, and stops in a time-sharing and functional zoning manner. Under the condition of limited energy, the limited energy supply is prioritized to ensure the normal operation of the operating part, while the stopped part completes the complementary processing function.

[0028] In this invention, the preset threshold is any value between 15% and 25% of the rated power of the solar power unit; for example, the preset threshold is set to 20% of the rated power of the solar power unit. When the photovoltaic power acquired by the data acquisition unit in real time is greater than or equal to 20%, the control unit controls the water treatment unit to enter the first processing state. When the photovoltaic power acquired by the data acquisition unit in real time is less than 20%, the control unit controls the water treatment unit to enter the second processing state, thereby achieving switching.

[0029] In this invention, the solar power supply unit includes a photovoltaic module and a storage battery; wherein, the photovoltaic module is used to convert solar energy into electrical energy, and the storage battery is used to store electrical energy, both of which are existing technologies; when the photovoltaic power is high, part of the electrical energy converted by the photovoltaic module is directly delivered to the water treatment unit, and the other part is stored through the storage battery; when the photovoltaic power is low, all the electrical energy converted by the photovoltaic module is delivered to the water treatment unit, and the insufficient part is supplemented by the electrical energy stored in the storage battery.

[0030] In this invention, the data acquisition unit includes a voltage sampling module, a current sampling module, and a power calculation submodule; the voltage sampling module is connected in parallel to acquire the real-time output voltage of the photovoltaic module, and the current sampling module is connected in series to the main output circuit of the photovoltaic module to acquire the real-time output current; the power calculation submodule calculates the real-time photovoltaic power based on the acquired voltage and current, and sends the photovoltaic power signal to the control unit in real time.

[0031] The present invention provides Figure 2 A structural diagram of the water treatment unit is shown; Figure 2 The water treatment unit includes: At least two membrane modules 100, each of the membrane modules 100 having a gas flow path and a water flow path; Submersible blower 200, the submersible blower 200 is connected to the gas flow path of each membrane module 100, and is used to independently supply gas to each membrane module 100; A circulating water pump 300 is connected to the water flow path of each membrane module 100 and is used to drive the water to be treated to circulate through each membrane module 100.

[0032] The present invention provides Figure 3 and Figure 4 A structural diagram showing the assembly of membrane module 100 and submersible fan 200 is provided; wherein, Figure 3 The diagram shows the structure of the membrane module 100 and the submersible blower 200 in the first treatment state. Figure 4 The diagram shows the structure of the membrane module 100 and the submersible blower 200 in the second treatment state; Figure 3 and Figure 4 In this process, the gas flow path of each membrane module 100 is connected to the output end of the submersible blower 200 through the gas supply branch pipe 110, and the gas flow paths of each membrane module 100 are connected in parallel to the submersible blower 200. Each gas supply branch pipe 110 is equipped with a gas supply valve 111. In the first processing state, all the air supply valves 111 are open, and the submersible blower 200 simultaneously supplies air to all membrane modules 100; In the second processing state, each of the gas supply valves 111 is opened and closed alternately. At the same time, some of the gas supply valves 111 are open and others are closed, and they are switched alternately according to a preset time sequence.

[0033] In the second processing state, the preset timing is 0.5h-4h.

[0034] The following explanation uses three membrane modules 100 as an example. The three membrane modules 100 are referred to as membrane module 100a, membrane module 100b, and membrane module 100c, respectively. Each membrane module 100a, membrane module 100b, and membrane module 100c has a corresponding air supply branch pipe 110, and each air supply branch pipe 110 has an air supply valve 111. The gas flow paths of membrane modules 100a, membrane module 100b, and membrane module 100c are connected in parallel to the submersible blower 200 through their corresponding air supply branch pipes 110, with a preset timing of 1 hour.

[0035] like Figure 3 As shown, in the first processing state, the air supply valves 111 corresponding to membrane modules 100a, 100b, and 100c are all kept open, and the submersible blower 200 simultaneously supplies compressed air to membrane modules 100a, 100b, and 100c. like Figure 4As shown, in the second processing state, the air supply valves 111 corresponding to membrane modules 100a, 100b, and 100c are alternately opened and closed at intervals; during a certain period, the air supply valves 111 corresponding to membrane modules 100a and 100c are open, and the air supply valve 111 corresponding to membrane module 100b is closed. At this time, the submersible blower 200 only supplies air to membrane modules 100a and 100c; after 1 hour, the air supply valves 111 corresponding to membrane modules 100a, 100b, and 100c are closed. The gas flow path state corresponding to 0c is switched; in another time period with at least one of them, the gas supply valve 111 corresponding to membrane module 100a and membrane module 100c is closed, and the gas supply valve 111 corresponding to membrane module 100b is opened. At this time, the submersible blower 200 only supplies gas to membrane module 100b; and it is certain that at the same time, the gas flow path of at least one membrane module 100 is connected to the submersible blower 200, and the gas flow path of at least another membrane module 100 is not connected to the submersible blower 200.

[0036] The present invention provides Figure 5 and Figure 6 A structural diagram showing the assembly of membrane module 100 and circulating water pump 300 is provided; wherein, Figure 5 The diagram shows the structure of the membrane module 100 and the circulating water pump 300 in the first treatment state. Figure 6 The diagram shows the structure of the membrane module 100 and the circulating water pump 300 in the second treatment state. Figure 5 and Figure 6 In this configuration, the inlet of each membrane module 100 water flow path is connected to the outlet of the circulating water pump 300 via a parallel water supply branch pipe 120, and a parallel water supply valve 121 is installed on the parallel water supply branch pipe 120; the outlet of each membrane module 100 water flow path is connected to the return water port of the circulating water pump 300 via a parallel return water branch pipe 130, and a parallel return water valve 131 is installed on the parallel return water branch pipe 130; the outlet and inlet of two adjacent membrane module 100 water flow paths are connected via a series branch pipe 140, and a series valve 141 is installed on the series branch pipe 140; In the first processing state, all the parallel water supply valves 121 and parallel return water valves 131 are open, all the series valves 141 are closed, and the water flow path of each membrane module 100 is connected in parallel with the circulating water pump 300. In the second processing state, all the parallel water supply valves 121 and parallel water return valves 131 are closed, all the series valves 141 are open, and the water flow path of each membrane module 100 is connected in series with the circulating water pump 300.

[0037] The following description uses three membrane modules 100 as an example, referred to as membrane module 100a, membrane module 100b, and membrane module 100c. Each membrane module 100a, membrane module 100b, and membrane module 100c has a corresponding parallel water supply branch pipe 120 and a parallel water return branch pipe 130. Each parallel water supply branch pipe 120 is equipped with a parallel water supply valve 121, and each parallel water return branch pipe 130 is equipped with a parallel water return valve 131. The outlet of membrane module 100a and the inlet of membrane module 100b, and the outlet of membrane module 100b and the inlet of membrane module 100c are connected by series branch pipes 140. Each series branch pipe 140 is equipped with a series valve 141.

[0038] like Figure 5 As shown, in the first processing state, the parallel water supply valves 121 and parallel return water valves 131 corresponding to membrane modules 100a, 100b, and 100c are all kept open, and all the series valves 141 are closed; the circulating water pump 300 drives the water to be treated to enter membrane modules 100a, 100b, and 100c simultaneously through each parallel water supply branch pipe 120, and after flowing through each membrane module, it converges back to the circulating water pump 300 through each parallel return water branch pipe 130. The water flow path of each membrane module is simultaneously connected to the circulating water pump 300 in parallel.

[0039] like Figure 6 As shown, in the second processing state, the parallel water supply valve 121 and parallel water return valve 131 corresponding to membrane modules 100a, 100b, and 100c are all closed, and all the series valves 141 are open; the circulating water pump 300 drives the water to be treated to flow sequentially through membrane module 100a, series branch pipe 140, membrane module 100b, series branch pipe 140, and membrane module 100c before returning to the circulating water pump 300. The water flow path of each membrane module is connected to the circulating water pump 300 in series.

[0040] It needs to be emphasized that, Figure 5 and Figure 6 In the process, each membrane module has a parallel water supply branch pipe 120 and a parallel water return branch pipe 130. However, in the actual pipeline, there is no need to install a parallel water supply valve 121 on the parallel water supply branch pipe 120 of the first membrane module 100; nor is there a need to install a parallel water return valve 131 on the parallel water return branch pipe 130 of the last membrane module 100, because both are in the open state in the first treatment state and the second treatment state, and no extra control is required.

[0041] Combination Figures 3-6 The following is a comprehensive description of the first and second treatment states in conjunction with the membrane module 100, the submersible fan 200, and the circulating water pump 300.

[0042] In the first processing state: In terms of air supply, the air supply valves 111 corresponding to each membrane module 100 are kept open, and the submersible blower 200 supplies air to all membrane modules 100 simultaneously. Regarding the water flow, the parallel water supply valve 121 and parallel water return valve 131 corresponding to each membrane module 100 are all open, and the series valve 141 is all closed; the circulating water pump 300 drives the water to be treated to enter all the membrane modules 100 simultaneously, and finally return to the circulating water pump 300.

[0043] In the second processing state: Regarding air supply, the air supply valves 111 corresponding to each membrane module 100 are opened and closed alternately. At the same time, some of the air supply valves 111 are open and others are closed, and they are switched alternately according to a preset time sequence. At the same time, the submersible fan 200 only supplies compressed air to the membrane module 100 with the air supply valve 111 open, and the membrane module 100 with the air supply valve 111 closed is in a stopped air supply state. Regarding the water flow, the parallel water supply valve 121 and parallel water return valve 131 corresponding to each membrane module 100 are closed, and each series valve 141 is open; the circulating water pump 300 drives the water to be treated to flow through each membrane module 100 in sequence, and the water flows from the membrane module 100 with the air supply valve 111 open to the membrane module 100 with the air supply valve 111 closed, using the nitrate produced by the former as the substrate for the denitrification reaction of the latter, and finally returning to the circulating water pump 300.

[0044] In this invention, the water treatment unit further includes a water inlet pipe and an overflow pipe. One end of the water inlet pipe is connected to an external water body, and the other end is connected to the return water pipe at the front end of the suction port of the circulating water pump. The overflow pipe is located on the outlet side of the water treatment unit and is used to passively overflow and discharge when the water level exceeds a preset height. In this invention, photovoltaic power is used as a switching control parameter, enabling the water treatment unit to adaptively select the optimal operating mode based on real-time energy sufficiency. When solar irradiance is sufficient, it operates in parallel at full load, maximizing the use of current energy to complete the treatment task. When solar irradiance is insufficient, it operates in series alternately in a time-sharing manner. Through time-sharing functional zoning, limited energy supply is prioritized to ensure the normal operation of the operating parts under energy-constrained conditions, while the idle parts complete complementary treatment functions.

[0045] Furthermore, to avoid the water treatment unit frequently switching processing states near a preset threshold due to short-term fluctuations in solar radiation (such as passing clouds), the control unit is also configured to: control the water treatment unit to switch from the first processing state to the second processing state only after the photovoltaic power drops from above or equal to the preset threshold to below the preset threshold and this below state is maintained for a first preset duration; and control the water treatment unit to switch from the second processing state back to the first processing state only after the photovoltaic power recovers from below the preset threshold to above or equal to the preset threshold and this recovery state is maintained for a second preset duration.

[0046] The first and second preset durations can be selected between 30 seconds and 10 minutes depending on the actual application scenario. For example, the first preset duration can be set to 2 minutes and the second preset duration to 5 minutes. If the preset duration is too short, it will not be able to effectively filter instantaneous fluctuations; if the preset duration is too long, it may cause system response delays and affect the processing effect. Therefore, by introducing a delayed confirmation mechanism for state switching, the interference of instantaneous light fluctuations on the system operation mode can be effectively filtered, ensuring a smooth and reliable transition of the water treatment unit between different processing states.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A solar-driven circulating water treatment system, characterized in that, include: Solar power units are used to acquire and store electrical energy; A data acquisition unit is used to acquire the photovoltaic power of the solar power supply unit in real time; A water treatment unit, the water treatment unit comprising at least two sets of membrane modules, each of the membrane modules having a gas flow path and a water flow path; The control unit is used to control the water treatment unit to switch between a first treatment state and a second treatment state based on the comparison result of the photovoltaic power and a preset threshold. When the photovoltaic power is higher than or equal to the preset threshold, the water treatment unit enters the first processing state, and the gas flow paths of all the membrane modules are connected, and the water flow paths of each membrane module are connected in parallel. When the photovoltaic power is lower than the preset threshold, the water treatment unit enters the second processing state, and the gas flow paths of each membrane module are alternately partially opened and partially closed according to a preset time sequence, while the water flow paths are connected in series.

2. The solar-driven circulating water treatment system according to claim 1, characterized in that, The water treatment unit also includes a submersible blower. The gas flow path of each membrane module is connected to the output end of the submersible blower through an air supply branch pipe. The gas flow paths of each membrane module are connected in parallel to the submersible blower. Each air supply branch pipe is equipped with an air supply valve. In the first processing state, all the gas supply valves are open; In the second processing state, each of the gas supply valves is opened and closed alternately according to the preset timing sequence.

3. The solar-driven circulating water treatment system according to claim 1, characterized in that, The water treatment unit also includes a circulating water pump. The inlet of each membrane module's water flow path is connected to the outlet of the circulating water pump via a parallel water supply branch pipe, and a parallel water supply valve is provided on the parallel water supply branch pipe. The outlet of each membrane module's water flow path is connected to the return outlet of the circulating water pump via a parallel return water branch pipe, and a parallel return water valve is provided on the parallel return water branch pipe. The outlets and inlets of two adjacent membrane module water flow paths are connected via a series branch pipe, and a series valve is provided on the series branch pipe. In the first processing state, both the parallel water supply valve and the parallel water return valve are open, and both series valves are closed; In the second processing state, both the parallel water supply valve and the parallel water return valve are closed, and both series valves are open. Water flows from the membrane module with the gas flow path open to the membrane module with the gas flow path closed, using the nitrate produced by the former as the substrate for the denitrification reaction of the latter.

4. The solar-driven circulating water treatment system according to claim 3, characterized in that, The preset threshold is any value between 15% and 25% of the rated power of the solar power unit.

5. The solar-driven circulating water treatment system according to claim 3, characterized in that, In the second processing state, the preset timing for the alternation of gas flow paths is any value between 0.5h and 4h.

6. The solar-driven circulating water treatment system according to claim 5, characterized in that, The inlet of the membrane module at the beginning of the water flow path is connected to the outlet of the circulating water pump, and the outlet of the membrane module at the end of the water flow path is connected to the return outlet of the circulating water pump.

7. The solar-driven circulating water treatment system according to claim 6, characterized in that, The control unit is further configured to: control the water treatment unit to switch from the first processing state to the second processing state only after the photovoltaic power drops from above or equal to the preset threshold to below the preset threshold and the below state is maintained for a first preset duration; and control the water treatment unit to switch from the second processing state back to the first processing state only after the photovoltaic power rises from below the preset threshold to above or equal to the preset threshold and the rise state is maintained for a second preset duration.

8. The solar-driven circulating water treatment system according to claim 6, characterized in that, Both the first preset duration and the second preset duration are selected between 30 seconds and 10 minutes.

9. A solar-driven circulating water treatment method, characterized in that, Includes the following steps: Real-time acquisition of photovoltaic power from solar power units; The photovoltaic power is compared with a preset threshold. When the photovoltaic power is higher than or equal to the preset threshold, the water treatment unit is controlled to enter the first processing state, so that the gas flow path of all membrane modules is connected and the water flow path of each membrane module is connected in parallel. When the photovoltaic power is lower than the preset threshold, the water treatment unit is controlled to enter the second processing state, so that the gas flow path of each membrane module is alternately partially opened and partially closed, and the water flow path is connected in series with each other according to a preset time sequence.

10. The solar-driven circulating water treatment method according to claim 9, characterized in that, In the second treatment state, water flows from the membrane module with the gas flow path open to the membrane module with the gas flow path closed, using the nitrate produced by the former as the substrate for the denitrification reaction of the latter.

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