Chromium-containing wastewater treatment device and method

Abstract

The invention discloses a chromium-containing wastewater treatment device and method, and belongs to the technical field of passivation wastewater treatment.The chromium-containing wastewater treatment device comprises a raw water tank for storing chromium-containing wastewater, an outer side pipeline of the raw water tank communicates with an acid dosing tank through a first acid dosing pump, and a discharge outlet is formed in the bottom of the raw water tank and communicates with a raw water lifting unit; and the other side of the raw water lifting unit is communicated with a pipeline outside the reduction reaction unit. The system has the beneficial effects that the pH value of the wastewater in the raw water tank and the reduction reaction unit is regulated to 1.8-2.3, and the concentration of hydrogen ions (H < + >) is higher under the lower pH value (1.8-2.3), so that the reduction reaction of hexavalent chromium (Cr < 6 + >) can be accelerated. According to the chemical reaction of the reduction reaction, when the pH value is 1.8-2.3, the higher H < + > concentration can provide more reaction active sites, so that the reaction rate is accelerated.

Description

Technical Field

[0001] The present application relates to the technical field related to the treatment of chromium-containing wastewater, and in particular to a device and method for treating chromium-containing wastewater. Background Art

[0002] Currently, the electroplating industry uses chromate as the primary component of the plating solution for chrome plating to improve the hardness, wear resistance, and corrosion resistance of metal surfaces. The chrome plating process generates large amounts of plating tank overflow rinse water and chromic acid spray tower replacement water. These wastewaters contain high concentrations of hexavalent chromium. Discharge of this chromium-containing wastewater without treatment can increase chromium concentrations in water bodies. Hexavalent chromium is a strong oxidizing agent, severely harming aquatic organisms, inhibiting their growth and reproduction, and even causing death, disrupting the balance of aquatic ecosystems. Once it seeps into the soil, it increases chromium levels. Chromium is not easily decomposed by microorganisms in soil and accumulates over time, altering soil chemistry, affecting soil fertility and structure, and ultimately affecting plant growth. Once absorbed by plants, chromium is transferred and concentrated through the food chain, ultimately endangering human health. It also seeps into the ground, contaminating groundwater. Due to the poor mobility of groundwater, once it is contaminated, it is extremely difficult to repair and will pose a threat to the drinking water safety of surrounding areas. Therefore, before the discharge of chromium-containing wastewater, it is necessary to use a wastewater treatment device to treat the wastewater. In the current market, when treating wastewater, chemical reduction precipitation is generally used. In an acidic environment (pH 2-3), a reducing agent (such as ferrous sulfate, sodium sulfite, etc.) is added to the wastewater to reduce hexavalent chromium (Cr 6 ⁺) is reduced to trivalent chromium (Cr³⁺), and then the pH value of the wastewater is adjusted to 8-9 by adding alkaline substances (such as lime or sodium hydroxide) to cause the trivalent chromium to form chromium hydroxide precipitate (Cr(OH)3), as disclosed in the treatment method for chromium-containing wastewater with application number 201110302526.1.

[0003] However, in the aforementioned treatment methods, the Cr6+ reduction rate depends on factors such as reaction time, wastewater pH, and reducing agent dosage. In actual operation, the composition of wastewater can be more complex than theoretical models. For example, other impurity ions or organic matter may be present in the wastewater, and the actual stirring effect and reactor design can affect the Cr6+ reduction rate. Results show that low wastewater pH favors Cr6+ reduction, while a pH greater than 3 slows the reaction rate. Considering that excessively low pH results in increased acid consumption, increased treatment costs, and increased corrosion protection for equipment and pipelines, controlling the pH between 2 and 3 is not necessarily the optimal option in actual production.

[0004] Secondly, when the above-mentioned methods are used to treat wastewater in the existing market, the wastewater can only be treated once. Even if RO membrane or electrodialysis technology is used to treat the wastewater again, the wastewater is only treated once. Although RO membrane and electrodialysis device can effectively remove pollutants in wastewater, the effluent after one treatment may still contain a certain amount of impurities and cannot be directly reused in the production process. If recirculation treatment is not possible, the effluent can only be discharged directly, resulting in a waste of water resources, such as the recycling method disclosed in the application number 202020774566.0, a hexavalent chromium wastewater recycling and reuse system. Summary of the Invention

[0005] One of the purposes of this application is to solve the problem that chromium-containing wastewater in the current market cannot be treated optimally and to provide a treatment device and method for chromium-containing wastewater.

[0006] In order to achieve the above objectives, the technical solution adopted in the present application is: a device and method for treating chromium-containing wastewater, comprising a raw water tank for storing chromium-containing wastewater, the outer pipe of the raw water tank is connected to the acid dosing box through a No. 1 acid dosing pump, and a discharge port is provided at the bottom of the raw water tank to be connected to a raw water lifting unit, the other side of the raw water lifting unit is connected to a pipe outside the reduction reaction unit, the outer pipe of the reduction reaction unit is connected to the reducing agent dosing box through a reducing agent dosing pump, and a pipe is further provided on the outer side of the reduction reaction unit to be connected to the No. 2 acid dosing pump, the No. 1 acid dosing pump and the No. 2 acid dosing pump are respectively provided on both sides of the acid dosing box, the outer side of the reduction reaction unit is provided with a pipe to be connected to the precipitation reaction unit, a flocculation sedimentation box is provided on the outer side of the precipitation reaction unit, and the outer pipe of the flocculation sedimentation box is connected to the flocculant dosing box through the flocculant dosing pump, and the outer pipe of the flocculation sedimentation box is connected to the flocculant dosing box. The sludge lifting unit is connected to the filter press, and a pipe is provided on the outside of the filter press to connect it to the clean water tank. A pipe is also provided on the outside of the clean water tank to connect it to the top of the flocculation sedimentation tank. An RO lifting pump is provided on the outside of the clean water tank to connect it to the quartz sand filter. An activated carbon filter, a precision filter and an RO membrane assembly are also provided on the outside of the quartz sand filter. The quartz sand filter, the activated carbon filter, the precision filter and the RO membrane assembly are all interconnected through pipes. Two pipes are provided on the outside of the RO membrane assembly to connect them to the RO production water tank and the RO concentrated water tank respectively. A pipe is provided on the outside of the RO concentrated water tank to connect it to the electrodialysis water tank, and a pipe is provided on the outside of the electrodialysis water tank to connect it to the electrodialysis membrane stack. Three pipes are provided on the outside of the electrodialysis membrane stack, and they are respectively connected to the waste water tank, the polar water return pipe and the electrodialysis water tank. The filter press is provided with two groups of parallel settings, one for use and one for backup.

[0007] Preferably, the reduction reaction unit includes a reduction reaction box A and a reduction reaction box B, which are arranged in sequence from left to right and are connected by a pipeline. The outer side of the reduction reaction box A is connected to the raw water lifting unit box, and its top is connected to the reducing agent dosing pump, wherein the raw water lifting unit includes two raw water lifting pumps, and the two raw water lifting pumps are connected in parallel, one for use and one for backup.

[0008] Preferably, the precipitation reaction unit includes a precipitation reaction box A and a precipitation reaction box B, which are arranged in sequence from left to right and are connected by a pipeline. The precipitation reaction box A is connected to the reduction reaction box B, and its outside is connected to the alkali dosing pump. The outside of the precipitation reaction box B is connected to the flocculation sedimentation tank. The sludge lifting unit connected to the outside of the flocculation sedimentation tank includes two pneumatic diaphragm pumps, and the two pneumatic diaphragm pumps are connected in parallel, one for use and one for backup.

[0009] Preferably, the electrodialysis water tank includes a pole water tank, a concentrate water tank and a fresh water tank, and the tops of both the pole water tank and the concentrate water tank are connected to the middle of a fixed pipe, one side of the fixed pipe is connected to the RO concentrate water tank, and the other side is connected to the fresh water tank. The outside of the pole water tank is connected to the electrodialysis membrane stack through a pole water pump, the outside of the concentrate water tank is connected to the electrodialysis membrane stack through a concentrate water pump, and the outside of the fresh water tank is connected to the electrodialysis membrane stack through a fresh water pump. A pipe is also provided on the outside of the fresh water tank to connect to the clean water tank.

[0010] Preferably, the electrodialysis membrane stack includes a second precision filter and an electrodialyzer. There are three groups of second precision filters, which are respectively penetrated by the other side of the pole water pump, the concentrate water pump and the fresh water pump. The outside of the three second precision filters is provided with pipes connected to the electrodialyzer. The outside of the electrodialyzer is provided with three pipes, which are respectively connected to the waste water tank, the pole water return pipe and the fresh water tank. A branch pipe is also provided in the middle of the pipe connected to the waste water tank to communicate with the concentrate water tank. The pole water tank, the concentrate water tank and the fresh water tank are all provided with solenoid valves.

[0011] Preferably, the raw water tank, reduction reaction tank A and precipitation reaction tank A are each provided with a stirring assembly for stirring. The stirring assembly includes a drive motor and a stirring blade. The drive motor is used to control the driving of the stirring blade to perform rotational stirring. Each pump body and solenoid valve in the processing device are controlled by a PLC.

[0012] A method for treating chromium-containing wastewater, the method comprising the following steps: S1: Chromium-containing wastewater from the outside enters the raw water tank through a pipe for storage. The wastewater entering the raw water tank is monitored by a pH sensor inside the raw water tank for pH value. When the pH value is higher than the set value, the PLC controller receives a signal from the pH sensor and controls the No. 1 acid dosing pump according to the preset pH value range to add sulfuric acid inside the acid dosing tank into the raw water tank. When the wastewater level in the raw water tank reaches a specified height, the liquid level sensor detects the interior of the raw water tank and monitors the water level. When the set value is reached, the PLC controller receives a signal and simultaneously starts a raw water lifting pump in the raw water lifting unit, a flocculant dosing pump, a starter diaphragm pump in the sludge lifting unit, and a drive motor on the stirring assembly. S2: The raw water lift pump will pump the wastewater after pH adjustment inside the raw water tank through the pipeline into the reduction reaction tank A and the reduction reaction tank B respectively. The pH value of the wastewater is first monitored by the internal pH sensor inside the reduction reaction tank A. When the pH value is higher than the set value, the PLC controller receives the signal from the pH sensor and controls the No. 2 acid dosing pump according to the preset pH value range to add sulfuric acid inside the acid dosing tank to the inside of the reduction reaction tank A until the pH value inside the reduction reaction tank A is lower than the set value. At this time, the PLC controller receives the signal from the pH sensor and starts the reducing agent dosing pump, so that the reducing agent inside the reducing agent dosing tank reaches the inside of the reduction reaction tank A for stirring and reduction. After that, it reaches the inside of the reduction reaction tank B again through the pipeline for another reduction reaction, so that the wastewater reduces Cr6+ to Cr3+ inside the reduction reaction tanks A and B. The chemical reaction is: ; S3: The water source after reduction in the reduction reaction box B will reach the interior of the precipitation reaction box A. At this time, the pH sensor inside the precipitation reaction box A performs pH value detection. When the pH value is lower than the set value, the PLC controller receives the signal from the pH sensor and controls the alkali dosing pump to start according to the preset pH value range, adding the alkali inside the alkali dosing tank to the interior of the precipitation reaction box A for stirring reaction. After that, it reaches the interior of the precipitation reaction box B for continued precipitation reaction. Therefore, in the interiors of the precipitation reaction boxes A and B, Cr3+ is generated into insoluble Cr(0H)3 and removed. The chemical reaction is Cr(OH)3 precipitation reaction: ; S4: After the sedimentation reaction, the water source will reach the inside of the flocculation sedimentation tank. Since the flocculant dosing pump in S1 is already in the started state, at this time, the flocculant dosing pump adds the flocculant in the flocculant dosing tank to the inside of the flocculation sedimentation tank for flocculation; S5: The flocculated sewage sediment is sucked into the filter press by the diaphragm pump started in S1 for filtration, forming a chromium-containing filter cake and then discharged. The unfiltered water source will enter the clean water tank again through the pipeline; S6: The supernatant of the sewage after flocculation will reach the inside of the clean water tank through the upper pipe. After the liquid level sensor detects the liquid level inside the clean water tank, when the liquid level reaches the set value, at the same time, the liquid level sensors inside the RO production water tank and RO concentrate water tank detect that the water levels inside the RO production water tank and RO concentrate water tank are lower than the set value, the PLC controller, after receiving the signals generated by the clean water tank, RO production water tank and RO concentrate water tank, controls the automatic valve heads on the quartz sand filter, the automatic valve heads on the activated carbon filter and the automatic valve heads on the first precision filter to start, and simultaneously starts the solenoid valves on the RO production water tank and RO concentrate water tank to open. After that, it delays 10 seconds to control the RO lifting pump to start, and sucks the clean water tank into the inside of the quartz sand filter, activated carbon filter and first precision filter for filtration. After the RO lifting pump starts, it delays 60 seconds to control the RO high-pressure pump to start, and sucks water into the inside of the RO membrane assembly for wastewater separation and water production. S7: During the water production process, the fresh water produced will enter the RO water production tank through the solenoid valve on the RO water production tank. When the liquid level reaches the set value, the external recycling water pump is started to pump the fresh water away for use, and the concentrated water produced will pass through the solenoid valve on the RO concentrated water tank and enter the RO concentrated water tank for storage; S8: When the RO produced water tank level is high or the RO concentrated water tank level is high or the clean water tank level is low, the solenoid valve on the RO concentrated water tank is controlled to open, and then the RO high-pressure pump is turned off after a delay of 60 seconds, and the RO boost pump is turned off after a delay of 60 seconds, and the automatic valve head on the quartz sand filter, the automatic valve head on the activated carbon filter, the automatic valve head on the first precision filter, and the solenoid valves on the RO produced water tank and the RO concentrated water tank are closed after a delay of 10 seconds; S9: The concentrated water entering the RO concentrated water tank reaches the middle liquid level setting value, and the concentrated water tank and the concentrated water tank are closed; When the liquid levels of the pole water tank, concentrate water tank and fresh water tank are at low levels, the solenoid valves on the pole water tank, concentrate water tank and fresh water tank are controlled to open, and the water supply pump is started after a delay of 10 seconds. Conversely, when the water source reaches the inside of the pole water tank, concentrate water tank and fresh water tank, and the PLC receiver receives that the liquid levels of the pole water tank, concentrate water tank and fresh water tank have reached the middle liquid level, the pole water pump, concentrate water pump and fresh water pump are turned on at the same time, and a delay of 20 seconds is used to start the three rectifiers, so that the second precision filter and electrodialyzer perform electrodialysis. When any liquid level of the pole water tank, concentrate water tank and fresh water tank does not reach the middle liquid level, the three rectifiers are controlled to close together, and a delay of 20 seconds is used to turn off the pole water pump, concentrate water pump and fresh water pump. S10: The polar water after electrodialysis in the electrodialyzer is returned to the polar water tank for further treatment. The generated concentrated water is tested for conductivity. The conductivity is ≤ 100μS / cm, at this time the PLC controller controls the concentrated water return valve to open and the concentrated water discharge valve to close, so that the concentrated water enters the wastewater tank for storage. According to the liquid level detection, when the high liquid level is reached, the wastewater delivery pump is started to discharge the concentrated water for concentration, evaporation and discharge. After the conductivity of the generated concentrated water is detected, the conductivity is greater than 100μS / cm. At this time, the PLC controller controls the concentrated water return valve to close and the concentrated water discharge valve to open, so that the concentrated water flows back to the concentrated water tank for further treatment. The conductivity of the generated fresh water is greater than 100μS / cm. At this time, the PLC controller controls the fresh water return valve to open and the fresh water discharge valve to close, so that the fresh water enters the fresh water tank for further treatment. The conductivity of the generated fresh water is ≤100μS / cm. At this time, the PLC controller controls the fresh water return valve to close and the fresh water discharge valve to open, so that the fresh water reaches the inside of the clean water tank and executes the commands inside the clean water tank. This cycle is repeated to complete the wastewater treatment work.

[0013] Preferably, the setting value of the pH value in the raw water tank in S1 and the reduction reaction tank A in S2 is 1.8~2.3, the reaction time is 30 minutes, the setting value of the pH value in the precipitation reaction tank A in S3 is 8~8.5, the reaction time is 20~30 minutes, S1~S5 are the dosing treatment process sections, and S6~S10 are the membrane treatment process sections.

[0014] Preferably, the reducing agent in the reducing agent dosing box in S2 is sodium sulfite (Na2SO3).

[0015] Preferably, the alkali in the alkali dosing box in S3 is NaOH, and the flocculants in S4 are PAC (polyaluminium chloride) and PAM (polyacrylamide).

[0016] Compared with the prior art, the present invention has the following advantages: (1) The pH value of the wastewater in the raw water tank and the reduction reaction unit is adjusted to between 1.8 and 2.3, and the reaction time is 0.5 h. Since the concentration of hydrogen ions (H⁺) is higher at a lower pH value (1.8-2.3), this will accelerate the reduction of hexavalent chromium (Cr 6 According to the chemical reaction of the reduction reaction, when the pH value is 1.8-2.3, a higher H⁺ concentration can provide more reactive sites, thereby accelerating the reaction rate. Sodium sulfite is more stable at a pH value of 1.8-2.3. The effects of wastewater pH and reaction time on the Cr6+ reduction effect are shown in Figure 6 .

[0017] (2) In this application, when the membrane treatment process section controls the water quality discharge, the polar water can be returned for further treatment, while the concentrated water and fresh water are tested by the conductivity standard to effectively determine the dissolved solid content therein). Only when the conductivity meets the standard is it allowed to be discharged, thereby ensuring that the effluent water quality meets the standard and avoiding pollution to the environment. Unqualified water is returned to the system for further treatment, which can maximize the recovery and reuse of water resources. This not only reduces the demand for fresh water resources, but also reduces the water resource costs of the enterprise. Through recycling treatment, more water can be purified to qualified standards, thereby reducing the amount of wastewater finally discharged and further reducing the impact on the environment. This treatment method is in line with the concept of sustainable development and achieves the coordinated development of economic, social and environmental benefits by minimizing resource waste and environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a working diagram of the device of the present invention.

[0019] Figure 2 It is a schematic diagram of the dosing treatment process section of the present invention.

[0020] Figure 3 It is a schematic diagram of the membrane treatment process section of the present invention.

[0021] Figure 4 It is a processing process diagram of the present invention.

[0022] Figure 5 This is a control flow chart of the dosing treatment process section of the present invention.

[0023] Figure 6 This is a schematic diagram of the effect of pH value and reaction time on Cr6+ reduction in the present invention.

[0024] Figure 7 It is a schematic diagram of the membrane treatment process section of the present invention.

[0025] Figure 8 This is a parameter diagram of the reduction treatment process section of the present invention.

[0026] Figure 9 This is a parameter diagram of the precipitation treatment process section of the present invention.

[0027] Figure 10 This is a parameter diagram of the reverse osmosis process section of the present invention.

[0028] In the figure: 1. Raw water tank; 2. Acid dosing box; 3. Reduction reaction unit; 31. Reduction reaction box A; 32. Reduction reaction box B; 4. Reductant dosing box; 5. Precipitation reaction unit; 51. Precipitation reaction box A; 52. Precipitation reaction box B; 6. Alkali dosing box; 7. Flocculant dosing box; 8. Flocculation sedimentation tank; 9. Filter press; 10. Clean water tank; 11. Quartz sand filter; 12. Activated carbon filter; 13. First precision filter; 14. RO membrane assembly; 15. RO produced water tank; 16. RO concentrated water tank; 17. Electrodialysis water tank; 171. Electrode water tank; 172. Concentrated water tank; 173. Fresh water tank; 18. Electrodialysis membrane stack; 181. Second precision filter; 182. Electrodialyzer; 19. Wastewater tank; 20. Stirring assembly. DETAILED DESCRIPTION

[0029] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0030] In the description of this application, it should be noted that for directional words, such as the terms "center", "horizontal", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and so on, indicating the orientation and position relationship are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of this application.

[0031] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0032] One of the preferred embodiments of this application is as follows: Figures 1 to 10As shown, a device and method for treating chromium-containing wastewater includes a raw water tank 1 for storing chromium-containing wastewater, wherein the outer pipe of the raw water tank 1 is connected to the acid dosing box 2 through a No. 1 acid dosing pump, and a discharge port is provided at the bottom of the raw water tank 1 to communicate with a raw water lifting unit, and the other side of the raw water lifting unit is connected to the outer pipe of the reduction reaction unit 3, and the outer pipe of the reduction reaction unit 3 is connected to the reducing agent dosing box 4 through a reducing agent dosing pump, and the outer side of the reduction reaction unit 3 is also connected. A pipeline is provided to communicate with the No. 2 acid dosing pump, and the No. 1 acid dosing pump and the No. 2 acid dosing pump are respectively provided on both sides of the acid dosing box 2. A pipeline is provided on the outside of the reduction reaction unit 3 to communicate with the precipitation reaction unit 5. A flocculation sedimentation box 8 is provided on the outside of the precipitation reaction unit 5, and the outer pipeline of the flocculation sedimentation box 8 is connected to the flocculant dosing box 7 through the flocculant dosing pump. The outer pipeline of the flocculation sedimentation box 8 is connected to the filter press 9 through the sludge lifting unit, and the filter press 9 is connected to the filter press 9. The outside of the clean water tank 10 is provided with a pipe connected to the clean water tank 10, and the outside of the clean water tank 10 is also provided with a pipe connected to the top of the flocculation sedimentation tank 8. The outside of the clean water tank 10 is provided with an RO lifting pump connected to the quartz sand filter 11. The outside of the quartz sand filter 11 is also provided with an activated carbon filter 12, a precision filter 13 and an RO membrane assembly 14. The quartz sand filter 11, the activated carbon filter 12, the precision filter 13 and the RO membrane assembly 14 are all connected to each other through pipes. Two pipes are provided on the outside of the RO membrane assembly 14, which are respectively connected to the RO water production tank 15 and the RO concentrated water tank 16. A pipe is provided on the outside of the RO concentrated water tank 16 to connect with the electrodialysis water tank 17, and a pipe is provided on the outside of the electrodialysis water tank 17 to connect with the electrodialysis membrane stack 18. Three pipes are provided on the outside of the electrodialysis membrane stack 18, and are respectively connected to the waste water tank 19, the polar water return pipe and the electrodialysis water tank 17. The filter press 9 is provided with two groups connected in parallel, one for use and one for backup.

[0033] [The reduction reaction unit 3 includes a reduction reaction box A31 and a reduction reaction box B32, which are arranged in sequence from left to right and are connected by a pipeline. The outer side of the reduction reaction box A31 is connected to the raw water lifting unit box, and its top is connected to the reducing agent dosing pump, wherein the raw water lifting unit includes two raw water lifting pumps, and the two raw water lifting pumps are connected in parallel, one for use and one for backup.

[0034] The precipitation reaction unit 5 includes a precipitation reaction box A51 and a precipitation reaction box B52, which are arranged in sequence from left to right and are connected by a pipeline. The precipitation reaction box A51 is connected to the reduction reaction box B32, and its outside is connected to the alkali dosing pump. The outside of the precipitation reaction box B52 is connected to the flocculation sedimentation box 8. The sludge lifting unit connected to the outside of the flocculation sedimentation box 8 includes two pneumatic diaphragm pumps, and the two pneumatic diaphragm pumps are connected in parallel, one for use and one for backup.

[0035] The electrodialysis water tank 17 includes an electrode water tank 171, a concentrate water tank 172 and a fresh water tank 173, and the tops of the electrode water tank 171 and the concentrate water tank 172 are both connected to the middle of a fixed pipe, one side of the fixed pipe is connected to the RO concentrate water tank 16, and the other side is connected to the fresh water tank 173. The outer side of the electrode water tank 171 is connected to the electrodialysis membrane stack 18 through a electrode water pump, the outer side of the concentrate water tank 172 is connected to the electrodialysis membrane stack 18 through a concentrate water pump, and the outer side of the fresh water tank 173 is connected to the electrodialysis membrane stack 18 through a fresh water pump. A pipe is also provided on the outer side of the fresh water tank 173 to connect to the clean water tank 10.

[0036] The electrodialysis membrane stack 18 includes a second precision filter 181 and an electrodialyzer 182. The second precision filter 181 is provided with three groups, and is respectively penetrated by the other side of the polar water pump, the concentrated water pump and the fresh water pump. The outside of the three second precision filters 181 is provided with pipes connected to the electrodialyzer 182. The outside of the electrodialyzer 182 is provided with three pipes, which are respectively connected to the waste water tank 19, the polar water return pipe and the fresh water tank 173. A branch pipe is also provided in the middle of the pipe connected to the waste water tank 19 to communicate with the concentrated water tank 172. The polar water tank 171, the concentrated water tank 172 and the fresh water tank 173 are all provided with solenoid valves.

[0037] The raw water tank 1, the reduction reaction tank A31 and the precipitation reaction tank A51 are each provided with a stirring assembly 20 for stirring. The stirring assembly 20 includes a drive motor and a stirring blade. The drive motor is used to control the driving of the stirring blade to perform rotational stirring. Each pump body and solenoid valve in the processing device are controlled by a PLC.

[0038] Another technical solution provided by this application is a wastewater treatment method, which is specifically implemented by using a wastewater treatment device. The specific steps are as follows: S1: The chromium-containing wastewater from the outside enters the raw water tank 1 through a pipe for storage. The wastewater entering the raw water tank 1 is monitored by a pH sensor inside the raw water tank 1 for its pH value. When the pH value is higher than the set value, the PLC controller receives a signal from the pH sensor and controls the No. 1 acid dosing pump according to the preset pH=1.8 to add sulfuric acid inside the acid dosing tank 2 into the raw water tank 1. When the wastewater level in the raw water tank 1 reaches a specified height, the liquid level sensor detects the interior of the raw water tank 1 and monitors the water level. When the high set value is reached, the PLC controller receives a signal and simultaneously starts a raw water lifting pump in the raw water lifting unit, a flocculant dosing pump, a starter diaphragm pump in the sludge lifting unit, and a drive motor on the stirring assembly 20; S2: The raw water lifting pump will pump the wastewater after pH adjustment in the raw water tank 1 through the pipeline into the reduction reaction tank A31 and the reduction reaction tank B32 respectively. The pH value of the wastewater is first monitored by the internal pH sensor in the reduction reaction tank A31. When the pH value is higher than 1.8, the PLC controller receives the signal from the pH sensor and controls the second acid dosing pump according to the preset pH value range to add sulfuric acid in the acid dosing tank 2 to the reduction reaction tank A31 until the pH value in the reduction reaction tank A31 is lower than the set value of 1.8. The reaction time is controlled to 30 minutes. Then, at this time, the PLC controller receives the signal from the pH sensor and the signal from the timer, and starts the reducing agent dosing pump, so that the sodium sulfite Na2SO3 in the reducing agent dosing tank 4 reaches the interior of the reduction reaction tank A31 for stirring and reduction. After that, it reaches the interior of the reduction reaction tank B32 through the pipeline again and enters and exits the reduction reaction again, so that the wastewater reduces Cr6+ to Cr3+ in the reduction reaction tanks A31 and B32. The chemical reaction is: ; S3: The water source after reduction in the reduction reaction box B32 will reach the interior of the precipitation reaction box A51. At this time, the pH sensor inside the precipitation reaction box A51 performs pH value detection. When the pH value is lower than the set value of 8, the PLC controller receives the signal from the pH sensor and controls the alkali dosing pump to start according to the preset pH value range, and adds the sodium hydroxide NaOH inside the alkali dosing box 6 to the interior of the precipitation reaction box A51 for stirring reaction. After that, it reaches the interior of the precipitation reaction box B52 for continued precipitation reaction. Therefore, in the interior of the precipitation reaction box A51 and the precipitation reaction box B52, the reaction time is controlled to 30min, so that Cr3+ generates insoluble Cr(0H)3 and is removed. The chemical reaction is Cr(OH)3 precipitation reaction: ; S4: After the precipitation reaction, the water source reaches the inside of the flocculation sedimentation tank 8. Since the flocculant dosing pump in S1 is already in the started state, at this time, the flocculant dosing pump adds PAC (polyaluminum chloride) and PAM (polyacrylamide) in the flocculant dosing tank 7 to the inside of the flocculation sedimentation tank (8) for flocculation. S5: The flocculated wastewater sediment is sucked into the filter press 9 by the diaphragm pump activated in S1 for filtration, forming a chromium-containing filter cake and then discharged. The unfiltered water source will enter the clean water tank 10 again through the pipeline; S6: The supernatant of the flocculated sewage will reach the inside of the clean water tank 10 through the upper pipe. After the liquid level sensor detects the liquid level inside the clean water tank 10, when the liquid level reaches the set value, at the same time, the liquid level sensors inside the RO water tank 15 and the RO concentrated water tank 16 detect that the water levels inside the RO water tank 15 and the RO concentrated water tank 16 are lower than the set value, the PLC controller, after receiving the signals generated by the clean water tank 10, the RO water tank 15 and the RO concentrated water tank 16, controls the automatic valve head and the active valve on the quartz sand filter 11. The automatic valve heads on the carbon filter 12 and the first precision filter 13 are activated, and the solenoid valves on the RO produced water tank 15 and the RO concentrated water tank 16 are opened at the same time. After that, the RO boost pump is controlled to start after a delay of 10 seconds, sucking the clean water from the tank 10 into the interior of the quartz sand filter 11, the activated carbon filter 12, and the first precision filter 13 for filtration. After the RO boost pump starts working, the RO high-pressure pump is controlled to start after a delay of 60 seconds, sucking water into the interior of the RO membrane assembly 14 for wastewater separation and water production. S7: During the water production process, the produced fresh water will enter the RO water production tank 15 through the solenoid valve on the RO water production tank 15. When the liquid level reaches the set value, the external recycling water pump is started to pump the fresh water away for use, and the produced concentrated water will pass through the solenoid valve on the RO concentrated water tank 16 and enter the RO concentrated water tank 16 for storage; S8: When the liquid level in the RO produced water tank 15 is high, the liquid level in the RO concentrated water tank 16 is high, or the liquid level in the clean water tank 10 is low, the solenoid valve on the RO concentrated water tank 16 is controlled to open, and then the RO high-pressure pump is turned off after a delay of 60 seconds, the RO boost pump is turned off after a delay of 60 seconds, and the automatic valve head on the quartz sand filter 11, the automatic valve head on the activated carbon filter 12, the automatic valve head on the first precision filter 13, and the solenoid valves on the RO produced water tank 15 and the RO concentrated water tank 16 are closed after a delay of 10 seconds; S9: When the concentrated water entering the RO concentrated water tank 16 reaches the middle liquid level setting value, and the liquid levels of the three water tanks 171, 172 and 173 are at low levels, the electromagnetic valves on the three water tanks 171, 172 and 173 are controlled to open, and the water supply pump is started after a delay of 10 seconds. On the contrary, when the water source reaches the inner parts of the concentrated water tank 171, 172 and 173, the PLC receiver receives the electromagnetic valves on the three water tanks 171, 172 and 173 at the same time. After the liquid levels of the cathode water tank 172 and the fresh water tank 173 have reached the middle liquid level, the cathode water pump, the concentrate water pump and the fresh water pump are turned on at the same time, with a delay of 20 seconds, and the three rectifiers are started to make the second precision filter 181 and the electrodialyzer 182 perform electrodialysis. When any of the liquid levels of the cathode water tank 171, the concentrate water tank 172 and the fresh water tank 173 has not reached the middle liquid level, the three rectifiers are controlled to be turned off together, with a delay of 20 seconds, and the cathode water pump, the concentrate water pump and the fresh water pump are turned off. S10: The polar water produced after electrodialysis in the electrodialyzer 182 (model DSC280*600-50) is returned to the polar water tank 171 for further treatment. The concentrated water produced is tested for conductivity and the conductivity is ≤ 100μS / cm, at this time the PLC controller controls the concentrated water return valve to open and the concentrated water discharge valve to close, so that the concentrated water enters the waste water tank 19 for storage. According to the liquid level detection, when the high liquid level is reached, the waste water delivery pump is started to discharge for concentration, evaporation and discharge. After the conductivity of the generated concentrated water is detected, the conductivity is greater than 100μS / cm. At this time, the PLC controller controls the concentrated water return valve to close and the concentrated water discharge valve to open, so that the concentrated water flows back to the concentrated water tank 172 for further treatment. The generated fresh water conductivity is greater than 100μS / cm. At this time, the PLC controller controls the fresh water return valve to open and the fresh water discharge valve to close, so that the fresh water enters the fresh water tank 173 for further treatment. The generated fresh water conductivity is ≤100μS / cm. At this time, the PLC controller controls the fresh water return valve to close and the fresh water discharge valve to open, so that the fresh water reaches the inside of the clean water tank 10, executes the command inside the clean water tank 10, and repeats this process to complete the wastewater treatment work. The parameters of the reduction treatment process section are as follows Figure 8 , the parameters of the precipitation treatment process are as follows Figure 9 , the reverse osmosis process parameters are as follows Figure 10 .

[0039] The above describes the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and the specification merely illustrate the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. These changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A device for treating chromium-containing wastewater, characterized in that: The invention comprises a raw water tank (1) for storing chromium-containing wastewater, wherein the outer pipe of the raw water tank (1) is connected to the acid dosing box (2) through a first acid dosing pump, and a discharge port is provided at the bottom of the raw water tank (1) to be connected to a raw water lifting unit, and the other side of the raw water lifting unit is connected to the pipe outside the reduction reaction unit (3), and the outer pipe of the reduction reaction unit (3) is connected to the reducing agent dosing box (4) through a reducing agent dosing pump, and a pipe is further provided on the outer side of the reduction reaction unit (3) to be connected to the second acid dosing pump. The first acid dosing pump and the second acid dosing pump are respectively arranged on both sides of the acid dosing box (2); a pipeline is arranged on the outside of the reduction reaction unit (3) and is connected to the precipitation reaction unit (5); a flocculation sedimentation box (8) is arranged on the outside of the precipitation reaction unit (5); and the outer pipeline of the flocculation sedimentation box (8) is connected to the flocculant dosing box (7) through the flocculant dosing pump; the outer pipeline of the flocculation sedimentation box (8) is connected to the filter press (9) through the sludge lifting unit, and the outside of the filter press (9) is provided with a pipeline connected to the clean water tank (10). The clean water tank (10) is connected to each other, and a pipeline is provided on the outside of the clean water tank (10) to communicate with the top of the flocculation sedimentation tank (8). An RO lifting pump is provided on the outside of the clean water tank (10) to communicate with the quartz sand filter (11). An activated carbon filter (12), a precision filter (13) and an RO membrane assembly (14) are provided on the outside of the quartz sand filter (11). The quartz sand filter (11), the activated carbon filter (12), the precision filter (13) and the RO membrane assembly (14) are all connected to each other through pipelines. Two pipes are provided on the outside of the RO membrane assembly (14), which are respectively connected to the RO water production tank (15) and the RO concentrated water tank (16). A pipe is provided on the outside of the RO concentrated water tank (16) to connect with the electrodialysis water tank (17), and a pipe is provided on the outside of the electrodialysis water tank (17) to connect with the electrodialysis membrane stack (18). Three pipes are provided on the outside of the electrodialysis membrane stack (18), and are respectively connected to the wastewater tank (19), the polar water return pipe and the electrodialysis water tank (17). The filter press (9) is provided with two sets of parallel settings, one for use and one for backup.

2. The device for treating chromium-containing wastewater according to claim 1, wherein: The reduction reaction unit (3) includes a reduction reaction box A (31) and a reduction reaction box B (32), wherein the reduction reaction box A (31) and the reduction reaction box B (32) are arranged in sequence from left to right and are connected to each other through a pipeline, wherein the outer side of the reduction reaction box A (31) is connected to the raw water lifting unit box, and the top end thereof is connected to the reducing agent dosing pump, wherein the raw water lifting unit includes two raw water lifting pumps, and the two raw water lifting pumps are connected in parallel, one for use and the other for standby.

3. The device for treating chromium-containing wastewater according to claim 1, wherein: The precipitation reaction unit (5) includes a precipitation reaction box A (51) and a precipitation reaction box B (52), which are arranged in sequence from left to right and are connected to each other through a pipeline. The precipitation reaction box A (51) is connected to the reduction reaction box B (32), and its outside is connected to the alkali dosing pump. The outside of the precipitation reaction box B (52) is connected to the flocculation sedimentation box (8), and the sludge lifting unit connected to the outside of the flocculation sedimentation box (8) includes two pneumatic diaphragm pumps, and the two pneumatic diaphragm pumps are connected in parallel, one for use and one for standby.

4. The device for treating chromium-containing wastewater according to claim 1, wherein: The electrodialysis water tank (17) includes an electrode water tank (171), a concentrated water tank (172) and a fresh water tank (173), and the tops of the electrode water tank (171) and the concentrated water tank (172) are both connected to the middle of a fixed pipe. One side of the fixed pipe is connected to the RO concentrated water tank (16), and the other side is connected to the fresh water tank (173). The outer side of the electrode water tank (171) is connected to the electrodialysis membrane stack (18) through the electrode water pump, the outer side of the concentrated water tank (172) is connected to the electrodialysis membrane stack (18) through the concentrated water pump, and the outer side of the fresh water tank (173) is connected to the electrodialysis membrane stack (18) through the fresh water pump. A pipe is also provided on the outer side of the fresh water tank (173) to connect to the clean water tank (10).

5. The device for treating chromium-containing wastewater according to claim 4, wherein: The electrodialysis membrane stack (18) includes a second precision filter (181) and an electrodialyzer (182). The second precision filter (181) is provided with three groups and is respectively penetrated with the other side of the polar water pump, the concentrated water pump and the fresh water pump. The three second precision filters (181) are provided with pipes outside to connect with the electrodialyzer (182). The electrodialyzer (182) is provided with three pipes outside to connect with the waste water tank (19), the polar water return pipe and the fresh water tank (173). A branch pipe is also provided in the middle of the pipe connected to the waste water tank (19) to connect with the concentrated water tank (172). The polar water tank (171), the concentrated water tank (172) and the fresh water tank (173) are all provided with solenoid valves.

6. The device for treating chromium-containing wastewater according to claim 5, wherein: The raw water tank (1), the reduction reaction tank A (31) and the precipitation reaction tank A (51) are each provided with a stirring assembly (20) for stirring. The stirring assembly (20) comprises a driving motor and a stirring blade. The driving motor is used to control the driving of the stirring blade to rotate and stir. Each pump body and solenoid valve in the processing device is controlled by a PLC.

7. A method for treating chromium-containing wastewater, using the wastewater treatment device of claim 1, characterized in that: The method comprises the following steps: S1: The chromium-containing wastewater from the outside enters the raw water tank (1) through a pipe for storage. The wastewater entering the raw water tank (1) is monitored for pH value by a pH sensor inside the raw water tank (1). When the pH value is higher than the set value, the PLC controller receives a signal from the pH sensor and controls the No. 1 acid dosing pump according to a preset pH value range to add sulfuric acid inside the acid dosing tank (2) into the raw water tank (1). When the wastewater level in the raw water tank (1) reaches a specified height, the level sensor detects the inside of the raw water tank (1) and performs water level monitoring. When the set value is reached, the PLC controller receives a signal and simultaneously starts a raw water lifting pump, a flocculant dosing pump, a starter diaphragm pump in the sludge lifting unit, and a drive motor on the stirring assembly (20). S2: The PH-adjusted wastewater in the raw water tank (1) is pumped into the reduction reaction tank A (31) and the reduction reaction tank B (32) through the raw water lifting pump. The pH value of the wastewater is first monitored by the internal pH sensor in the reduction reaction tank A (31). When the pH value is higher than the set value, the PLC controller receives the signal from the pH sensor and controls the second acid dosing pump according to the preset pH value range to add sulfuric acid in the acid dosing tank (2) into the reduction reaction tank A (31) until the pH value in the reduction reaction tank A (31) is lower than the set value. At this time, the PLC controller receives the signal from the pH sensor and starts the reducing agent dosing pump, so that the reducing agent in the reducing agent dosing tank (4) reaches the reduction reaction tank A (31) for stirring and reduction. After that, the reducing agent reaches the reduction reaction tank B (32) again through the pipeline for reduction reaction, so that the wastewater reduces Cr6+ to Cr3+ in the reduction reaction tanks A (31) and B (32). The chemical reaction is: S3: The water source after being reduced by the reduction reaction box B (32) will reach the interior of the precipitation reaction box A (51). At this time, the pH sensor inside the precipitation reaction box A (51) detects the pH value. When the pH value is lower than the set value, the PLC controller receives the signal of the pH sensor and controls the alkali dosing pump to start according to the preset pH value range, and adds the alkali inside the alkali dosing box (6) to the interior of the precipitation reaction box A (51) for stirring reaction. After that, it reaches the interior of the precipitation reaction box B (52) for continued precipitation reaction. Therefore, in the interior of the precipitation reaction box A (51) and the precipitation reaction box B (52), Cr3+ is generated into insoluble Cr(0H)3 and removed. The chemical reaction is Cr(OH)3 precipitation reaction: Cr 3+ +3NaOH→Cr(OH)3↓+3Na + ; S4: After the precipitation reaction, the water source reaches the inside of the flocculation sedimentation tank (8). Since the flocculant dosing pump in S1 is already in the started state, at this time, the flocculant dosing pump adds the flocculant in the flocculant dosing tank (7) to the inside of the flocculation sedimentation tank (8) to perform flocculation. S5: The flocculated sewage sediment is sucked into the filter press (9) by the diaphragm pump activated in S1 for filtration, forming a chromium-containing filter cake and then discharged. The unfiltered water source will enter the clean water tank (10) again through the pipeline; S6: The supernatant of the flocculated sewage will reach the inside of the clean water tank (10) through the upper pipe. After the liquid level sensor detects the liquid level inside the clean water tank (10), when the liquid level reaches the set value, at the same time, the liquid level sensors inside the RO water tank (15) and the RO concentrated water tank (16) detect that the water levels inside the RO water tank (15) and the RO concentrated water tank (16) are lower than the set value, the PLC controller, after receiving the signals generated by the clean water tank (10), the RO water tank (15) and the RO concentrated water tank (16), controls the automatic valve head and the active valve on the quartz sand filter (11). The automatic valve heads on the activated carbon filter (12) and the first precision filter (13) are started, and the electromagnetic valves on the RO water production tank (15) and the RO concentrated water tank (16) are opened at the same time. After that, the RO lifting pump is controlled to work after a delay of 10 seconds, and the clean water tank (10) is sucked into the interior of the quartz sand filter (11), the activated carbon filter (12) and the first precision filter (13) for filtration. After the RO lifting pump works, the RO high-pressure pump is controlled to start after a delay of 60 seconds, and the water source is sucked into the interior of the RO membrane assembly (14) for wastewater separation and water production. S7: During the water production process, the produced fresh water will enter the RO water production tank (15) through the solenoid valve on the RO water production tank (15). When the liquid level reaches the set value, the external recycling water pump is started to pump the fresh water away for use, and the produced concentrated water will pass through the solenoid valve on the RO concentrated water tank (16) and enter the RO concentrated water tank (16) for storage; S8: When the liquid level of the RO produced water tank (15) is high or the liquid level of the RO concentrated water tank (16) is high or the liquid level of the clean water tank (10) is low, the solenoid valve on the RO concentrated water tank (16) is controlled to open, and then the RO high-pressure pump is turned off after a delay of 60 seconds, the RO boost pump is turned off after a delay of 60 seconds, and the automatic valve head on the quartz sand filter (11), the automatic valve head on the activated carbon filter (12), the automatic valve head on the first precision filter (13) and the solenoid valves on the RO produced water tank (15) and the RO concentrated water tank (16) are closed after a delay of 10 seconds; S9: When the concentrated water entering the RO concentrated water tank (16) reaches the middle liquid level setting value, and the liquid levels of the three water tanks (171), concentrated water tank (172) and fresh water tank (173) are at low liquid levels, the electromagnetic valves on the water tank (171), concentrated water tank (172) and fresh water tank (173) are controlled to open, and the water supply pump is started after a delay of 10 seconds. On the contrary, when the water source reaches the interior of the water tank (171), concentrated water tank (172) and fresh water tank (173), the PLC receiver receives the water supply from the water tank (171) at the same time. ), after the liquid levels of the concentrated water tank (172) and the fresh water tank (173) all reach the middle liquid level, the cathode water pump, the concentrated water pump and the fresh water pump are turned on at the same time, with a delay of 20 seconds, and the three rectifiers are started, so that the second precision filter (181) and the electrodialyzer (182) perform electrodialysis. When any liquid level of the cathode water tank (171), the concentrated water tank (172) and the fresh water tank (173) does not reach the middle liquid level, the three rectifiers are controlled to be turned off together, with a delay of 20 seconds, and the cathode water pump, the concentrated water pump and the fresh water pump are turned off; S10: The polar water produced after the electrodialysis of the electrodialyzer (182) is returned to the polar water tank (171) for further treatment. After the conductivity of the concentrated water is tested, the conductivity is ≤100μS / cm. At this time, the PLC controller controls the concentrated water return valve to open and the concentrated water discharge valve to close, so that the concentrated water enters the waste water tank (19) for storage. According to the liquid level detection, when the high liquid level is reached, the waste water delivery pump is started to discharge the concentrated water for concentration, evaporation and discharge. After the conductivity of the concentrated water is tested, the conductivity is>100μS / cm. At this time, the PLC controller controls the concentrated water return valve to open and the concentrated water discharge valve to close, so that the concentrated water enters the waste water tank (19) for storage. According to the liquid level detection, when the high liquid level is reached, the waste water delivery pump is started to discharge the concentrated water for concentration, evaporation and discharge. The concentrated water discharge valve is opened, and the concentrated water is returned to the concentrated water tank (172) for further treatment. The generated fresh water conductivity is greater than 100 μS / cm. At this time, the PLC controller controls the fresh water return valve to open and the fresh water discharge valve to close, so that the fresh water enters the fresh water tank (173) for further treatment. The generated fresh water conductivity is less than or equal to 100 μS / cm. At this time, the PLC controller controls the fresh water return valve to close and the fresh water discharge valve to open, so that the fresh water reaches the inside of the clean water tank (10) and executes the command inside the clean water tank (10). This cycle is repeated to complete the wastewater treatment work.

8. The method for treating chromium-containing wastewater according to claim 7, wherein: The pH value in the raw water tank (1) in S1 and the reduction reaction tank A (31) in S2 is set to 1.8-2.3, and the reaction time is 30 minutes. The pH value in the precipitation reaction tank A (51) in S3 is set to 8-8.5, and the reaction time is 20-30 minutes. S1-S5 are the dosing treatment process sections, and S6-S10 are the membrane treatment process sections.

9. The method for treating chromium-containing wastewater according to claim 7, wherein: The reducing agent in the reducing agent dosing box (4) in S2 is sodium sulfite (Na2SO3).

10. The method for treating chromium-containing wastewater according to claim 7, wherein: The alkali in the alkali dosing box (6) in S3 is NaOH, and the flocculants in S4 are PAC (polyaluminium chloride) and PAM (polyacrylamide).

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