A treatment method for high-salt mustard wastewater to meet discharge standards and recover feed-grade salt

Abstract

The invention provides a treatment method for high-salt mustard tuber wastewater, which meets discharge standards and recovers feed-grade salt, and relates to the technical field of wastewater treatment. The method comprises the following steps: S1: centrally storing the high-salt mustard tuber wastewater in a water collection tank for water quality homogenization treatment, and then introducing the wastewater into an anaerobic ammoniation reaction tank to convert organic nitrogen in the wastewater into ammonia nitrogen, and then introducing the wastewater into an STD salt-tolerant and high-efficiency denitrification tank to remove ammonia nitrogen and total nitrogen in the wastewater; S2: the effluent flows into a pH adjustment tank 1 by gravity, and the pH is adjusted to 5-7, and then the wastewater is pumped into a first-level FCD three-dimensional electrode catalytic oxidation reactor to treat macromolecular organic matter and COD organic matter; the invention has strong resistance to shock loads and stable operation, abandons traditional biochemical treatment processes, realizes efficient degradation of pollutants through physical and chemical synergistic technology, is not affected by fluctuations in wastewater salinity and pollutant load, and ensures long-term stable operation; and attaches equal importance to salt resource utilization and pollution prevention and control, and innovatively couples electrolytic oxidation and evaporation crystallization technology to realize efficient separation and purification of NaCl.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a treatment method for achieving discharge standards for high-salt mustard tuber wastewater and recovering feed-grade salt. Background Art

[0002] Conventional biochemical treatment processes are extremely sensitive to salinity. When the salinity of wastewater exceeds 1%, microbial activity is inhibited, resulting in a decrease in system treatment efficiency and unstable operation, making it difficult for the effluent quality to meet discharge standards. More seriously, the salt content in the treated wastewater is still high, and if discharged directly, it will cause multiple environmental hazards. Although membrane separation technology can achieve good solid-liquid separation effects, membrane elements are easily contaminated and the flux decays rapidly in high-salt environments. At the same time, the resulting concentrated water still needs further treatment, which also places higher demands on the salt tolerance of the membrane material. Although the Fenton oxidation process has a certain ability to degrade organic matter, its treatment efficiency is limited and requires precise control of the reagent addition ratio, which requires a high level of professional expertise from the operator. In addition, the process also produces a large amount of sludge, which increases the difficulty and cost of subsequent sludge treatment and disposal. These factors have restricted the application effect of conventional processes in the treatment of high-salt mustard mustard wastewater. Therefore, the present invention proposes a treatment method for high-salt mustard mustard wastewater to meet discharge standards and recover feed-grade salt to solve the problems existing in the prior art. Summary of the Invention

[0003] In response to the above problems, the present invention proposes a treatment method for achieving the discharge standard of high-salt mustard tuber wastewater and the recovery of feed-grade salt. This integrated treatment method for achieving the discharge standard of high-salt mustard tuber wastewater and the recovery of feed-grade salt adopts more efficient and stable technical means to ensure that the effluent water quality meets the standards while minimizing the negative impact on the environment and ecology.

[0004] To achieve the purpose of the present invention, the present invention is implemented by the following technical solution: a treatment method for high-salt mustard tuber wastewater to meet discharge standards and recover feed-grade salt, comprising the following steps:

[0005] S1: The high-salt mustard tuber wastewater is centrally stored in a water collection tank for water volume regulation and water quality homogenization treatment, and then passed into the anaerobic ammoniation reaction tank to convert the organic nitrogen in the wastewater into ammonia nitrogen and degrade some COD organic matter at the same time;

[0006] S2: The effluent flows into the STD salt-tolerant and high-efficiency denitrification tank by gravity, removing ammonia nitrogen and total nitrogen from the wastewater without the need for an external carbon source;

[0007] S3: The wastewater enters the pH adjustment tank 1, where the pH is adjusted to 5-7, and then is pumped into the first-stage FCD three-dimensional electrode catalytic oxidation reactor to treat macromolecular organic matter and COD organic matter;

[0008] S4: The wastewater enters the neutralization coagulation flocculation sedimentation tank 1, where the pH value is adjusted to 8.0-10.0. At the same time, aeration converts divalent iron ions into trivalent iron ions, removes volatile substances, and undergoes flocculation treatment. Then, solid-liquid separation is performed, and the supernatant enters the intermediate water tank 1 for unified collection;

[0009] S5: The collected water goes to the first sand filter to remove tiny suspended solids, and then enters the first-stage SAO3 ozone catalytic oxidation reactor to decompose and remove organic matter and remove color;

[0010] S6: The effluent is sent to the second pH adjustment tank, the second FCD three-dimensional electrode catalytic oxidation reactor, the second neutralization coagulation flocculation sedimentation tank, the second intermediate water tank, the second sand filter, and the second SAO3 ozone catalytic oxidation reactor, and the above treatment steps are repeated;

[0011] S7: The effluent from the three intermediate water tanks is collected and sent to the MVR evaporation system for evaporation to obtain crystalline white salt products. The condensate enters the clear water tank for collection and discharge in compliance with standards.

[0012] Further improvements are as follows: in S1, the high-salt mustard wastewater flows into the collection tank by gravity and is then lifted to the anaerobic ammoniation reaction tank. The reaction time is 8-12 hours. A low-speed stirring device is set in the anaerobic ammoniation reaction tank to maintain the dissolved oxygen content of the wastewater at 0.05-0.1 mg / L. A three-phase separator is set at the top of the anaerobic ammoniation reaction tank to separate gas, sludge and water.

[0013] Further improvements are: in S2, the reaction time in the STD salt-tolerant and efficient denitrification tank is 12-48h, an aeration system is set in the STD salt-tolerant and efficient denitrification tank, and an alkali solution dosing pipeline is arranged to adjust the pH value in the water so that the water quality pH value is adjusted to the range of 8.0-11.0.

[0014] Further improvements are as follows: in the S3, a sulfuric acid dosing device and a pH online monitoring system are set in the pH adjustment tank to track and adjust the pH value in the water, the wastewater and the reagent are stirred and mixed by a stirrer, and the pH is controlled to be maintained in the range of 5.0-7.0, and the wastewater is pumped into a first-level FCD three-dimensional electrode catalytic oxidation reactor. The reaction time is 1-3h, wherein 3-5 groups of electrode plates are arranged in the first-level FCD three-dimensional electrode catalytic oxidation reactor, and the electrode plate spacing is controlled in the range of 20-30cm. FCD particle electrode materials are evenly filled between the electrode plates to form a composite catalytic system. The water inlet, aeration, and backwashing pipeline systems are arranged at the bottom of the reactor to evenly distribute the wastewater. The contact efficiency between the pollutants and the electrodes is improved by aeration and stirring. A high-frequency pulsed DC power supply is equipped, and the electrode plates-particle electrodes are electrically connected to form a complete three-dimensional electrode catalytic oxidation system. At the same time, a two-pole alternating operation mode is adopted to degrade pollutants.

[0015] Further improvements are as follows: in the S4, during the treatment in the neutralization coagulation flocculation sedimentation tank 1, the pH value in the water is tracked and adjusted in the neutralization tank through the alkali dosing device and the pH online monitoring system to control it to be maintained within the range of 8.0-10.0, and an aeration pipe is arranged in the neutralization tank to promote the dissolution of alkali solution in the wastewater and convert the divalent iron ions in the wastewater into trivalent iron ions, while removing volatile substances in the wastewater; PAC solution is added to the coagulation tank, and PAM solution is added to the flocculation tank, and agitators are respectively set in the coagulation and flocculation tanks to control the full contact between the reagents and the pollutants, so that the polluted suspended matter undergoes flocculation and then enters the sedimentation tank. Inclined tube fillers are arranged in the sedimentation tank to promote the precipitation of the suspended matter and solid-liquid separation. After the water quality is clarified, the supernatant flows into the intermediate water tank 1 by gravity.

[0016] A further improvement is that in the S5, the sand filter is filled with 0.5-1.2 mm quartz sand, and a backwash device is provided for flushing suspended matter retained on the filter material. In the first-stage SAO3 ozone catalytic oxidation reactor, the reaction time is 2-6 h, the reactor is filled with SAO3-II ozone catalyst, and a water inlet, microporous titanium plate gas distribution, and backwash pipeline system are arranged at the bottom of the reactor to control the uniform distribution of gas and liquid. The deactivation of the ozone catalyst caused by the accumulation of pollutants is prevented by backwashing and stirring. An ozone generation system is provided, and the produced ozone gas enters the reactor through the microporous titanium plate gas distribution system. Under the catalytic oxidation action of ozone and the catalyst, strongly oxidizing hydroxyl radicals (·OH) are generated, which react with pollutants to decompose and remove organic matter such as COD, and break down colored functional groups, thereby removing chroma.

[0017] Further improvements are as follows: in the above S7, after temporary storage in the intermediate water tank three, the wastewater is transported to the MVR evaporation system by the lifting pump for deep treatment, and the evaporation concentration realizes salt crystallization and separation. The high-purity crystalline salt produced by the system is dried and packaged and then used as a feed-grade additive resource. The condensate generated during the evaporation process is collected in the clear water tank and then discharged in compliance with the standards.

[0018] Further improvements are as follows: the sludge produced by the anaerobic ammoniation reaction tank and the neutralization coagulation flocculation sedimentation tanks 1 and 2 is discharged into the sludge pool through a pipe, and then filtered through a filter press. The generated sewage is collected in a collection tank, and the generated dry sludge is stored at a fixed point and piled up for landfill.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention has strong resistance to shock loads and stable operation. It abandons traditional biochemical treatment processes and achieves efficient pollutant degradation through physical and chemical synergy technology. It is not affected by fluctuations in wastewater salinity and pollutant load, ensuring long-term stable operation. It also attaches equal importance to salt resource utilization and pollution prevention and control, and innovatively couples electrolytic oxidation with evaporation crystallization technology to achieve efficient separation and purification of NaCl, eliminating the ecological risks of high-salt wastewater to soil / groundwater and creating additional economic benefits.

[0021] 2. The present invention achieves deep and coordinated removal of pollutants and integrates efficient multi-stage treatment processes to deeply remove pollutants such as salt, COD, ammonia nitrogen, total nitrogen, and total phosphorus, ensuring that the wastewater treatment effect is stable and meets the standards. After a series of process pretreatments, the pollutant indicators of the concentrated mother liquor produced by evaporation are far lower than the raw water quality. It can be returned to the collection tank and mixed with the raw liquid for treatment, forming a closed-loop benign circulation system for the mother liquor, ensuring the complete degradation of pollutants and avoiding secondary pollution caused by the discharge of high-salt wastewater.

[0022] 3. The present invention saves space and has strong adaptability. It abandons the traditional biochemical treatment process and adopts a process flow with pretreatment combined with advanced oxidation treatment and evaporation as the main line, which greatly reduces the occupied area, reduces construction costs, reduces sludge production, and greatly reduces the difficulty and cost of subsequent disposal. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples. The examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Example 1:

[0025] according to Figure 1 As shown, this embodiment proposes a method for treating high-salt mustard tuber wastewater to meet discharge standards and recover feed-grade salt, comprising the following steps:

[0026] High-salt mustard wastewater is uniformly collected in a collection pool, where water volume regulation and water quality homogenization are achieved through centralized storage.

[0027] The wastewater in the collection tank is lifted by the water inlet pump and enters the anaerobic ammoniation reaction tank, where the organic nitrogen is converted into ammonia nitrogen by anaerobic ammonium oxidizing bacteria, while a part of the COD organic matter is degraded at the same time;

[0028] The effluent enters the STD salt-tolerant and efficient denitrification tank, which uses salt-tolerant special denitrification bacteria to directly convert ammonia nitrogen into nitrogen gas (N2) in a high-salt environment without adding nutrients, removing ammonia nitrogen and total nitrogen at the same time;

[0029] The effluent treated in the STD salt-tolerant and high-efficiency denitrification tank flows by gravity into the pH adjustment tank 1, into which sulfuric acid solution is added to adjust the pH of the wastewater to within the range of 5-7.

[0030] The wastewater after pH adjustment is pumped into the first-stage FCD three-dimensional electrode catalytic oxidation reactor by a water pump to perform ring-opening and chain-breaking on the macromolecular organic matter in the wastewater and degrade the COD organic matter at the same time;

[0031] The wastewater after electrolytic treatment enters the neutralization coagulation flocculation sedimentation tank 1. Alkali solution is added to the neutralization tank to adjust the pH value of the wastewater to 8.0-10.0. At the same time, divalent iron ions are converted into trivalent iron ions through aeration, and volatile substances in the wastewater are removed. Coagulant is added to the coagulation tank, and flocculant is added to the flocculation tank to cause flocculation of suspended matter. The wastewater then enters the sedimentation tank to allow the flocculated suspended matter to settle and achieve solid-liquid separation.

[0032] The supernatant after precipitation enters the middle water tank 1 and is collected uniformly by the middle water tank 1;

[0033] The wastewater in the intermediate water tank 1 is lifted by the lifting pump to the sand filter 1, and the sand filter 1 removes the tiny suspended solids in the water;

[0034] The effluent after sand filtration enters the first-stage SAO3 ozone catalytic oxidation reactor, which uses the strong oxidizing properties of ozone and catalyst to decompose and remove organic matter such as COD, and also breaks down colored functional groups to remove color;

[0035] The ozone effluent flows into the pH adjustment tank 2 by gravity, and sulfuric acid solution is added to the pH adjustment tank 2. The pH of the wastewater is adjusted to the range of 5-7 by stirring with a mixer.

[0036] The wastewater after pH adjustment is pumped into the secondary FCD three-dimensional electrode catalytic oxidation reactor by a water pump, and the macromolecular organic matter in the wastewater is again subjected to ring-opening and chain-breaking, thereby degrading the COD organic matter.

[0037] The wastewater after secondary electrolysis treatment enters the second neutralization coagulation flocculation sedimentation tank. Alkali solution is added to the neutralization tank to adjust the pH value of the wastewater to 8.0-10.0. At the same time, divalent iron ions are converted into trivalent iron ions through aeration, and volatile substances in the wastewater are removed. Coagulant is added to the coagulation tank, and flocculant is added to the flocculation tank to cause flocculation of suspended matter. The wastewater then enters the sedimentation tank to allow the flocculated suspended matter to settle and achieve solid-liquid separation.

[0038] The supernatant after precipitation enters the middle water tank 2 and is collected uniformly by the middle water tank 2;

[0039] The wastewater in the intermediate water tank 2 is lifted by the lifting pump to the sand filter 2, which removes the tiny suspended solids in the water;

[0040] The effluent from the sand filter enters the secondary SAO3 ozone catalytic oxidation reactor, where the strong oxidizing properties of ozone and the catalyst are used to decompose and remove organic matter such as COD, as well as to break down colored functional groups and remove color.

[0041] The ozone-generating water flows by gravity into the intermediate water pool for unified collection. The wastewater is then lifted by a lifting pump and sent to the MVR evaporation system, where the water is evaporated. The resulting crystalline white salt product can be used as a feed additive, realizing resource utilization. The condensate produced is collected in the clear water pool and then discharged in compliance with standards.

[0042] The high-salt wastewater generated by mustard tuber production is treated using a process based on "pretreatment + advanced oxidation + MVR evaporation". Before entering the MVR evaporation system, the wastewater needs to undergo a series of pretreatment measures to remove COD, ammonia nitrogen, total nitrogen, heavy metals, solids, suspended matter, etc.

[0043] High-salt mustard tuber wastewater flows primarily by gravity into a collection tank and then into an anaerobic ammoniation reactor. The reaction time is 8-12 hours. A low-speed agitator is installed in the reactor to prevent sludge sedimentation, improve contact between the bacterial flora and the wastewater, and maintain a dissolved oxygen level of 0.05-0.1 mg / L. A three-phase separator is installed at the top of the reactor to separate gas, sludge, and water. The effluent from the anaerobic ammoniation reactor flows by gravity into a high-efficiency, salt-tolerant denitrification tank. The reaction time is 12-48 hours. An aeration system is installed in the tank to provide dissolved oxygen for the denitrifying bacteria. Alkali dosing lines are also installed to adjust the pH of the water to a range of 8-11. This treatment unit removes ammonia nitrogen and total nitrogen from wastewater through anaerobic ammonia-oxidizing bacteria and special high-efficiency denitrifying bacteria in a high-salt environment. Compared with traditional denitrification processes, this process can still maintain an efficient denitrification rate of 80-90% under salinity ≤15g / L, without the need for external carbon sources and with low sludge production. The anaerobic ammoniation reaction tank and STD salt-tolerant high-efficiency denitrification tank are used as the first-stage treatment units after the water collection tank, forming a synergistic relationship with subsequent physicochemical processes (electrocatalysis, ozone) to reduce the nitrogen load for subsequent physicochemical processes.

[0044] The effluent from the STD salt-tolerant and high-efficiency denitrification tank flows by gravity into the pH adjustment tank 1. A sulfuric acid dosing device and a pH online monitoring system are set to track and adjust the pH value in the water. The wastewater and the reagent are stirred and mixed by a mixer to control the pH value to be maintained within the range of 5.0-7.0, creating favorable conditions for the first-level FCD three-dimensional electrode catalytic oxidation reaction.

[0045] After pH adjustment, the wastewater is pumped into a first-stage FCD three-dimensional electrode catalytic oxidation reactor using an inlet pump. The reaction lasts 1-3 hours. Three to five sets of electrodes are arranged within the reactor, with spacing between the plates kept within a range of 20-30 cm. FCD particle electrode material is evenly packed between the plates, forming a composite catalytic system. A water inlet, aeration, and backwash piping system is located at the bottom of the reactor to ensure uniform wastewater distribution. Aeration and agitation enhance pollutant-electrode contact and prevent electrode deactivation due to pollutant accumulation. The system is equipped with a high-frequency pulsed DC power supply. The plates and particle electrodes are electrically connected to form a complete three-dimensional electrode catalytic oxidation system. The alternating polarity operation effectively mitigates electrode passivation, extends electrode life, and improves mass transfer efficiency, enhancing pollutant degradation. In a weakly acidic environment, the anode surface and the FCD particle electrode material synergistically generate highly active hydroxyl radicals (·OH), which enhance the ring-opening and chain-scission of large organic molecules, reducing the pollutant load in the wastewater. At the same time, acidic conditions can reduce competitive oxidation reactions of chloride ions (Cl⁻) in high-salinity wastewater, preventing the formation of chlorinated organic compounds. Furthermore, they can promote the redox cycle of Fe²⁺ / Fe³⁺ in the particle electrode material, further enhancing the catalytic degradation effect and creating better water quality conditions for subsequent ozone oxidation.

[0046] After electrolytic treatment, wastewater flows by gravity into the neutralization, coagulation, and flocculation sedimentation tank 1. Within the neutralization tank, an alkali dosing device and an online pH monitoring system track and adjust the pH value, maintaining it within the range of 8.0-10.0. Aeration pipes are installed within the neutralization tank to promote the dissolution of alkali in the wastewater and convert any ferrous ions into ferric ions, facilitating subsequent dosing and precipitation, while also removing volatile substances. PAC solution is added to the coagulation tank, and PAM solution is added to the flocculation tank. Agitators are installed in each tank to ensure sufficient contact between the chemicals and pollutants, causing flocculation of suspended solids. The wastewater then enters the sedimentation tank, where inclined tube packing is installed to facilitate more efficient and rapid sedimentation of suspended solids, enabling solid-liquid separation. Once the water is clarified, the supernatant flows by gravity into the intermediate tank 1.

[0047] Wastewater from Intermediate Tank 1 is pumped by the inlet pump to Sand Filter 1, which primarily removes fine suspended solids from the water. This is essential for ensuring maximum pollutant reduction before the wastewater enters the SAO3 ozone catalytic oxidation reactor. The sand filter is filled with 0.5-1.2mm quartz sand and equipped with a backwash device to flush out suspended solids trapped on the filter media.

[0048] Water passing through the sand filter enters the primary SAO3 ozone catalytic oxidation reactor, where the reaction time is 2-6 hours. The reactor is filled with an SAO3-II ozone catalyst. The reactor's bottom is equipped with a water inlet, microporous titanium plate gas distribution, and backwash piping system to ensure even gas-liquid distribution. Backwashing and agitation prevent ozone catalyst deactivation caused by pollutant accumulation. The system is equipped with an ozone generation system. The generated ozone gas enters the reactor through the microporous titanium plate gas distribution system. The ozone and catalyst catalyze oxidation to produce highly oxidizing hydroxyl radicals (·OH), which react with pollutants to decompose and remove organic matter such as COD, and degrade colored functional groups, thereby removing color.

[0049] The first-stage ozone effluent flows by gravity into the second pH adjustment tank. A sulfuric acid dosing device and a pH online monitoring system are set to track and adjust the pH value in the water. The wastewater and the reagent are stirred and mixed by a mixer to control the pH value to be maintained within the range of 5.0-7.0, creating favorable conditions for the second-stage FCD three-dimensional electrode catalytic oxidation reaction.

[0050] After pH adjustment, the wastewater is pumped into a two-stage FCD three-dimensional electrode catalytic oxidation reactor using an inlet pump. The reaction lasts 1-3 hours. Three to five sets of electrodes are arranged within the reactor, with spacing between the plates kept within a range of 20-30 cm. FCD particle electrode material is evenly packed between the plates, forming a composite catalytic system. A water inlet, aeration, and backwash piping system is located at the bottom of the reactor to ensure uniform wastewater distribution. Aeration and agitation enhance pollutant-electrode contact and prevent electrode deactivation caused by pollutant accumulation. The system is equipped with a high-frequency pulsed DC power supply. The plates and particle electrodes are electrically connected to form a complete three-dimensional electrode catalytic oxidation system. The alternating polarity operation effectively mitigates electrode passivation, extends electrode life, improves mass transfer efficiency, and enhances pollutant degradation. In a weakly acidic environment, the anode surface and the FCD particle electrode material synergistically generate highly active hydroxyl radicals (·OH), which enhance the ring-opening and chain-scission of large organic molecules, reducing the pollutant load in the wastewater. At the same time, acidic conditions reduce competitive oxidation reactions of chloride ions (Cl⁻) in high-salinity wastewater, preventing the formation of chlorinated organic matter. Furthermore, they promote the redox cycle of Fe²⁺ / Fe³⁺ in the particle electrode material, further enhancing the catalytic degradation effect. This two-stage three-dimensional electrode catalytic oxidation treatment unit specifically targets stubborn organic matter remaining after primary treatment, achieving a 40-50% improvement in COD removal efficiency compared to a single-stage system. This cascaded "primary degradation - secondary mineralization" treatment design achieves the gradual degradation and thorough mineralization of difficult-to-degrade organic matter, creating more ideal water quality conditions for the subsequent ozone oxidation unit.

[0051] After electrolytic treatment, wastewater flows by gravity into the second neutralization, coagulation, and flocculation sedimentation tank. Within the neutralization tank, an alkali dosing device and an online pH monitoring system track and adjust the pH value, maintaining it within the range of 8.0-10.0. Aeration pipes are installed within the neutralization tank to promote the dissolution of alkali in the wastewater and convert any ferrous ions into ferric ions, facilitating subsequent dosing and precipitation, while also removing volatile substances. PAC solution is added to the coagulation tank, and PAM solution is added to the flocculation tank. Agitators are installed in each tank to ensure sufficient contact between the chemicals and the pollutants, causing flocculation of suspended solids. The wastewater then enters the sedimentation tank, where inclined tube packing is installed to facilitate more efficient and rapid sedimentation of suspended solids, enabling solid-liquid separation. Once the water is clarified, the supernatant flows by gravity into the second intermediate tank.

[0052] Wastewater from Intermediate Tank 2 is pumped by the inlet pump to Sand Filter 2, which removes small suspended solids from the water, ensuring maximum pollutant reduction before entering the SAO3 ozone catalytic oxidation reactor. The sand filter is filled with 0.5-1.2mm quartz sand and equipped with a backwash device to flush suspended solids trapped on the filter media.

[0053] Water passing through the sand filter enters the secondary SAO3 ozone catalytic oxidation reactor, where the reaction time is 2-6 hours. The reactor is filled with an SAO3-II ozone catalyst. The bottom of the reactor is equipped with a water inlet, microporous titanium plate gas distribution, and backwash piping system to ensure uniform gas-liquid distribution. Backwashing and agitation prevent ozone catalyst deactivation caused by pollutant accumulation. The system is equipped with an ozone generation system. The generated ozone gas enters the reactor through the microporous titanium plate gas distribution system. Under the catalytic oxidation action of ozone and the catalyst, highly oxidizing hydroxyl radicals (·OH) are generated. These react with pollutants, further decomposing and removing residual COD and other organic matter, and breaking down colored functional groups, thereby deeply removing color.

[0054] After secondary ozone catalytic oxidation treatment, the effluent flows by gravity into the intermediate water tank for temporary storage. A lift pump then transports the wastewater to the MVR evaporation system for further treatment. Evaporation and concentration achieve salt crystallization and separation. The high-purity crystalline salt produced by the system is dried and packaged for reuse as a feed-grade additive. The condensate produced during the evaporation process is collected in a clear water tank and then discharged in compliance with discharge standards.

[0055] The sludge produced by the anaerobic ammoniation tank and the neutralization coagulation flocculation sedimentation tank is discharged into the sludge pool through pipes, and then filtered through a filter press. The generated sewage is collected in a collection tank, and the generated dry sludge is stored at a designated location and can be transported to relevant landfills for stacking and landfilling, which further ensures zero pollution emissions.

[0056] After a series of pretreatments at the front end, the concentrated mother liquor produced by evaporation is far lower than the high-salt mustard wastewater raw liquid, and can be directly returned to the collection tank for mixed treatment, forming a virtuous cycle.

[0057] The entire pretreatment process adopts anaerobic ammoniation + STD salt-tolerant and efficient denitrification + FCD three-dimensional electrocatalysis + coagulation and sedimentation + physical filtration + SAO3 ozone catalytic oxidation and other measures to degrade COD, ammonia nitrogen, total nitrogen, heavy metals, SS and other pollution indicators in the water and clarify the water quality, so that it can fully meet the water inlet requirements of the subsequent MVR evaporation system and achieve the dual goals of wastewater discharge meeting standards and resource recovery.

[0058] The treatment efficiency and effluent of each unit under the action of the present invention on high-salt mustard tuber wastewater of different water qualities are summarized in the following table:

[0059] Table 1

[0060] ;

[0061] Table 2

[0062] ;

[0063] Table 3

[0064] ;

[0065] It can be seen from the above data table that high-salt mustard tuber wastewater with different concentrations, after being treated by the method of the present invention, not only meets the relevant requirements of the comprehensive sewage discharge standard, but also meets the relevant provisions of the farmland irrigation water quality standard.

[0066] The technical indicators of the salt product after being refined by the method of the present invention are shown in the following table:

[0067] Table 4

[0068] ;

[0069] It can be seen from the data in the above table that the refined salt obtained from the high-salt mustard wastewater treated by the method of the present invention has a purity and impurity content that meet the standard requirements and has resource recycling value. Example 2:

[0070] according to Figure 1 As shown, this embodiment proposes a treatment method for high-salt mustard tuber wastewater to meet discharge standards and recover feed-grade salt. The method targets high-salt mustard tuber wastewater (COD 10480 mg / L, ammonia nitrogen 570 mg / L, chloride ion 112000 mg / L), and includes the following steps:

[0071] The high-salt mustard wastewater is transported to a collection pool through a pipeline, where the water volume is balanced and the water quality is mixed and homogenized.

[0072] The wastewater in the collection tank is pumped into the anaerobic ammoniation reaction tank through a lifting pump. The reaction time is 10 hours, and the dissolved oxygen in the wastewater is maintained at 0.05-0.1 mg / L. The organic nitrogen is converted into ammonia nitrogen by using anaerobic ammonium oxidizing bacteria, and a part of the COD organic matter is degraded at the same time.

[0073] The effluent enters the STD salt-tolerant high-efficiency denitrification tank with a reaction time of 24 hours. The pH value of the wastewater is controlled at 10 by adding alkali solution. The salt-tolerant special denitrification bacteria are used to directly convert ammonia nitrogen into nitrogen gas (N2) in a high-salt environment without adding nutrients, thereby removing ammonia nitrogen and total nitrogen at the same time.

[0074] The effluent after high-efficiency denitrification treatment flows by gravity into pH adjustment tank 1, and the pH of the wastewater is adjusted to 6 by adding sulfuric acid solution and stirring.

[0075] The wastewater after pH adjustment is transported by the water inlet pump to the first-stage FCD three-dimensional electrode catalytic oxidation reactor. Four sets of plates are arranged in the reactor. The distance between the plates is controlled at 20 cm. A high-frequency pulsed DC power supply is connected to the plates. Electrochemical oxidation occurs under the support of the particle electrodes. The reaction time is 1 hour, and the macromolecular organic matter is opened and chain broken, while COD pollutants are degraded.

[0076] After electrolytic treatment, wastewater flows into the neutralization, coagulation, and flocculation sedimentation tank. In the neutralization tank, the pH value is controlled at 9 through an online pH monitoring system and the addition of NaOH solution. Simultaneously, aeration and oxidation convert divalent iron into trivalent iron, and volatile organic compounds are blown off. PAC solution and PAM solution are added to the coagulation and flocculation tanks, respectively, to promote the flocculation of suspended solids, ultimately achieving mud-water separation in the sedimentation zone.

[0077] After sedimentation, the supernatant overflows into the intermediate water tank 1 and is temporarily stored as primary treated effluent.

[0078] The wastewater in the intermediate water tank 1 is pressurized by the lifting pump and enters the sand filter 1, where the remaining fine suspended particles are intercepted by the quartz sand filter layer.

[0079] The sand filtered water enters the first-stage SAO3 ozone catalytic oxidation reactor. The reaction time is 3 hours. Under the synergistic effect of ozone and catalyst, strong oxidizing hydroxyl radicals (·OH) are generated, which further oxidize and decompose the COD in the wastewater and destroy the chromogenic groups to remove the color.

[0080] The wastewater after ozone oxidation flows into the pH adjustment tank 2 by gravity, and sulfuric acid solution is added again to adjust the pH value of the wastewater to 6 through stirring.

[0081] The wastewater after pH adjustment is pumped by the water inlet pump to the secondary FCD three-dimensional electrode catalytic oxidation reactor. Four sets of plates are arranged in the reactor. The distance between the plates is controlled at 20 cm. A high-frequency pulsed DC power supply is connected to the plates. Electrochemical oxidation occurs under the support of the particle electrodes. The reaction time is 1 hour, which enhances the electrochemical degradation effect of organic pollutants.

[0082] The secondary electrolysis effluent enters the second neutralization, coagulation, and flocculation sedimentation tank. In the neutralization tank, the pH value of the wastewater is controlled at 9 through an online pH monitoring system and the addition of NaOH solution. Aeration and oxidation convert divalent iron into trivalent iron, and volatile organic compounds are blown off. In the coagulation and flocculation tanks, solid-liquid separation is achieved through secondary addition of PAC and PAM for flocculation and precipitation.

[0083] The supernatant from sedimentation tank 2 is collected in intermediate water tank 2 for temporary storage.

[0084] The wastewater from the intermediate water tank 2 is pressurized by the lifting pump and enters the sand filter 2, where the remaining fine suspended particles are intercepted by the quartz sand filter layer.

[0085] The sand filtered water enters the secondary SAO3 ozone catalytic oxidation reactor. The reaction time is 3 hours. Under the synergistic effect of ozone and catalyst, hydroxyl radicals (·OH) are generated, which oxidize and decompose the COD in the wastewater again and destroy the chromogenic groups to remove the color.

[0086] After the secondary ozone catalytic oxidation treatment, the effluent flows by gravity into the intermediate water tank for temporary storage. A lift pump then transports the wastewater to the MVR evaporation system for evaporation and concentration, achieving salt crystallization and separation. The salt is recycled as a feed additive, and the concentrated mother liquor is returned to the collection tank for recycling. The condensate is collected in the clear water tank and then discharged in compliance with standards.

[0087] The removal rate effect table of this embodiment using the method of the present invention is as follows:

[0088] Table 5

[0089] ;

[0090] The technical indicators of the salt product after being refined by the method of the present invention in this embodiment are as follows:

[0091] Table 6

[0092] .

[0093] This invention offers strong resistance to shock loads and stable operation, abandoning traditional biochemical treatment processes. It achieves efficient pollutant degradation through physicochemical synergy, unaffected by fluctuations in wastewater salinity and pollutant loads, ensuring long-term stable operation. It also prioritizes both salt resource utilization and pollution prevention and control, innovatively coupling electrolytic oxidation with evaporative crystallization technology to achieve efficient separation and purification of NaCl, eliminating the ecological risks of high-salinity wastewater to soil and groundwater while creating additional economic benefits. Simultaneously, pollutants are deeply and synergistically removed, integrating a highly efficient multi-stage treatment process to deeply remove pollutants such as salt, COD, ammonia nitrogen, total nitrogen, and total phosphorus, ensuring stable and standard wastewater treatment results. In addition, after a series of process pretreatments, the pollutant index of the concentrated mother liquor produced by evaporation is far lower than that of the raw water quality, and can be returned to the collection tank for mixing with the raw liquor for treatment, forming a closed-loop benign circulation system for the mother liquor, ensuring the complete degradation of pollutants and avoiding secondary pollution caused by the discharge of high-salt wastewater; finally, the present invention saves space and has strong adaptability. It abandons the traditional biochemical treatment process and adopts a process flow with pretreatment combined with advanced oxidation treatment and evaporation as the main line, which greatly reduces the occupied area, reduces construction costs, reduces sludge production, and greatly reduces the difficulty and cost of subsequent disposal.

[0094] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating high-salt mustard tuber wastewater to meet discharge standards and recover feed-grade salt, characterized in that: The following steps are involved: S1: The high-salt mustard tuber wastewater is centrally stored in a water collection tank for water volume regulation and water quality homogenization treatment, and then passed into the anaerobic ammoniation reaction tank to convert the organic nitrogen in the wastewater into ammonia nitrogen and degrade some COD organic matter at the same time; S2: The effluent flows into the STD salt-tolerant and high-efficiency denitrification tank by gravity, removing ammonia nitrogen and total nitrogen from the wastewater without the need for an external carbon source; S3: The wastewater enters the pH adjustment tank 1, where the pH is adjusted to 5-7, and then is pumped into the first-stage FCD three-dimensional electrode catalytic oxidation reactor to treat macromolecular organic matter and COD organic matter; S4: The wastewater enters the neutralization coagulation flocculation sedimentation tank 1, where the pH value is adjusted to 8.0-10.

0. At the same time, aeration converts divalent iron ions into trivalent iron ions, removes volatile substances, and undergoes flocculation treatment. Then, solid-liquid separation is performed, and the supernatant enters the intermediate water tank 1 for unified collection; S5: The collected water goes to the first sand filter to remove tiny suspended solids, and then enters the first-stage SAO3 ozone catalytic oxidation reactor to decompose and remove organic matter and remove color; S6: The effluent is sent to the second pH adjustment tank, the second FCD three-dimensional electrode catalytic oxidation reactor, the second neutralization coagulation flocculation sedimentation tank, the second intermediate water tank, the second sand filter, and the second SAO3 ozone catalytic oxidation reactor, and the above treatment steps are repeated; S7: The effluent from the three intermediate water tanks is collected and sent to the MVR evaporation system for evaporation to obtain crystallized white salt products. The condensate is collected in the clear water tank and discharged in compliance with the standards. In the S3, a sulfuric acid dosing device and a pH online monitoring system are set in the pH adjustment tank to track and adjust the pH value in the water. The wastewater and the reagent are stirred and mixed by a stirrer to control the pH to be maintained in the range of 5.0-7.

0. The wastewater is pumped into the first-level FCD three-dimensional electrode catalytic oxidation reactor for a reaction time of 1-3 hours. Among them, 3-5 groups of electrode plates are arranged in the first-level FCD three-dimensional electrode catalytic oxidation reactor, and the electrode plate spacing is controlled in the range of 20-30 cm. FCD particle electrode materials are evenly filled between the electrode plates to form a composite catalytic system. The water inlet, aeration, and backwashing pipeline systems are arranged at the bottom of the reactor to evenly distribute the wastewater. The contact efficiency between the pollutants and the electrodes is improved by aeration and stirring. A high-frequency pulsed DC power supply is equipped, and the electrode plates and particle electrodes are electrically connected to form a complete three-dimensional electrode catalytic oxidation system. At the same time, a two-pole alternating operation mode is adopted to degrade pollutants.

2. The method for treating high-salt mustard tuber wastewater to achieve standard discharge and recover feed-grade salt according to claim 1, characterized in that: In S1, the high-salt mustard wastewater flows into the collection tank by gravity and is then lifted to the anaerobic ammoniation reaction tank. The reaction time is 8-12 hours. A low-speed stirring device is set in the anaerobic ammoniation reaction tank to maintain the dissolved oxygen content of the wastewater at 0.05-0.1 mg / L. A three-phase separator is set at the top of the anaerobic ammoniation reaction tank to separate gas, sludge and water.

3. The method for treating high-salt mustard tuber wastewater to achieve standard discharge and recover feed-grade salt according to claim 1, characterized in that: In the S2, the reaction time in the STD salt-tolerant and efficient denitrification tank is 12-48 hours. An aeration system is set in the STD salt-tolerant and efficient denitrification tank, and an alkali solution dosing pipeline is arranged to adjust the pH value in the water so that the pH value of the water quality is adjusted to the range of 8.0-11.

0.

4. The method for treating high-salt mustard tuber wastewater to achieve standard discharge and recover feed-grade salt according to claim 1, characterized in that: In the S4, during the treatment in the neutralization coagulation flocculation sedimentation tank 1, the pH value of the water is tracked and adjusted by the alkali dosing device and the pH online monitoring system in the neutralization tank to control it to be maintained within the range of 8.0-10.

0. An aeration pipe is arranged in the neutralization tank to promote the dissolution of alkali solution in the wastewater and convert the divalent iron ions in the wastewater into trivalent iron ions, while removing volatile substances in the wastewater; PAC solution is added to the coagulation tank, PAM solution is added to the flocculation tank, and stirrers are respectively set in the coagulation and flocculation tanks to control the full contact between the reagents and the pollutants, so that the polluted suspended matter undergoes flocculation and then enters the sedimentation tank. The inclined tube filler is arranged in the sedimentation tank to promote the precipitation of the suspended matter and solid-liquid separation. After the water quality is clarified, the supernatant flows into the intermediate water tank 1 by gravity.

5. The method for treating high-salt mustard tuber wastewater to achieve standard discharge and recover feed-grade salt according to claim 1, characterized in that: In the S5, the sand filter is filled with 0.5-1.2 mm quartz sand, and a backwash device is provided for flushing the suspended matter intercepted on the filter material. The reaction time in the first-stage SAO3 ozone catalytic oxidation reactor is 2-6 h, and the reactor is filled with SAO3-II ozone catalyst. The bottom of the reactor is provided with a water inlet, a microporous titanium plate gas distribution, and a backwash pipeline system to control the uniform distribution of gas and liquid. The ozone catalyst is deactivated by backwashing and stirring to prevent the accumulation of pollutants. An ozone generation system is provided, and the produced ozone gas enters the reactor through the microporous titanium plate gas distribution system. Under the catalytic oxidation action of ozone and the catalyst, strong oxidizing hydroxyl radicals are generated, which react with the pollutants to decompose and remove COD organic matter, and break down the colored functional groups, thereby removing the chromaticity.

6. The method for treating high-salt mustard tuber wastewater to achieve standard discharge and recover feed-grade salt according to claim 1, characterized in that: In S7, after temporary storage in the intermediate water tank 3, the wastewater is transported by the lifting pump to the MVR evaporation system for deep treatment. Evaporation and concentration realize salt crystallization and separation. The high-purity crystalline salt produced by the system is dried and packaged and then used as a feed-grade additive. The condensate generated during the evaporation process is collected in the clear water tank and then discharged in compliance with the standards.

7. The method for treating high-salt mustard tuber wastewater to achieve standard discharge and recover feed-grade salt according to claim 1, characterized in that: The sludge produced by the anaerobic ammoniation reaction tank and the neutralization coagulation flocculation sedimentation tanks 1 and 2 is discharged into the sludge pool through pipes, and then filtered through a filter press. The generated sewage is collected in a collection tank, and the generated dry sludge is stored at a designated location and piled up for landfill.

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