Treatment method for up-to-standard discharge of high-salt preserved szechuan pickle wastewater and feed-grade salt recovery

Abstract

The invention provides a treatment method for up-to-standard discharge of high-salt preserved szechuan pickle wastewater and feed-grade salt recovery, and relates to the technical field of wastewater treatment.The treatment method comprises the following steps that S1, the high-salt preserved szechuan pickle wastewater is intensively stored in a water collecting tank to be subjected to water quality homogenization treatment and then introduced into an anaerobic ammonification reaction tank, organic nitrogen in the wastewater is converted into ammonia nitrogen, and the ammonia nitrogen is recycled; the wastewater enters an STD salt-resistant efficient denitrification tank, and ammonia nitrogen and total nitrogen in the wastewater are removed; s2, effluent automatically flows into a pH adjusting tank 1, the pH is adjusted to 5-7, then the effluent is pumped into a first-stage FCD three-dimensional electrode catalytic oxidation reactor, and macromolecular organic matter and COD organic matter are treated; the method is high in impact load resistance and stable in operation, a traditional biochemical treatment process is abandoned, efficient degradation of pollutants is achieved through a physicochemical synergistic technology, the method is not affected by wastewater salinity and pollutant load fluctuation, and long-term stable operation is guaranteed; salt recycling and pollution prevention and control are both emphasized, electrolytic oxidation and evaporative crystallization technologies are innovatively coupled, and efficient separation and purification of NaCl are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly relates to a treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt. Background Art

[0002] Traditional biochemical treatment processes are extremely sensitive to salinity. When the salinity of the wastewater exceeds 1%, the microbial activity will be inhibited, resulting in a decline in the treatment efficiency of the system and unstable operation, and it is difficult for the effluent quality to meet the discharge standards. More seriously, the salt content in the treated wastewater is still relatively high. If directly discharged, it will cause multiple harms to the environment. Although the membrane separation technology can achieve good solid-liquid separation effects, the membrane elements are easily contaminated and the flux decays rapidly in a high-salt environment. At the same time, the produced concentrated water still needs to be further treated, which also poses higher requirements for the salt tolerance of the membrane materials. Although the Fenton oxidation process has a certain ability to degrade organic matter, its treatment efficiency is limited, and it requires precise control of the dosing ratio of the chemicals, which requires a high professional level of the operators. In addition, this process will also generate a large amount of sludge-containing substances, increasing 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 pickled mustard wastewater. Therefore, the present invention proposes a treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt to solve the problems existing in the prior art. Summary of the Invention

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

[0004] To achieve the object of the present invention, the present invention is realized through the following technical solutions: A treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt, comprising the following steps: S1: Concentrate and store the high-salt pickled mustard wastewater in a collecting tank for water volume adjustment and water quality homogenization treatment, and then introduce it into an anaerobic ammonification reaction tank to convert the organic nitrogen in the wastewater into ammonia nitrogen, and at the same time degrade a part of the COD organic matter; S2: The effluent flows by gravity into a STD salt-tolerant high-efficiency denitrification tank, without adding external carbon sources, to remove ammonia nitrogen and total nitrogen in the wastewater; S3: The wastewater enters pH adjustment tank 1 to adjust the pH to 5-7, and then is pumped into a 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 and flocculation sedimentation tank 1, where the pH value is adjusted to 8.0 - 10.0. Meanwhile, aeration is carried out to convert ferrous ions into ferric ions, remove volatile substances, and perform flocculation treatment. Then, solid-liquid separation is carried out, and the supernatant enters the intermediate water tank 1 for unified collection. S5: The collected water goes to the sand filter 1 to remove tiny suspended solids, and then enters the first-stage SAO3 ozone catalytic oxidation reactor to decompose and remove organic substances and remove color. S6: The effluent goes to the pH adjustment tank 2, the second-stage FCD three-dimensional electrode catalytic oxidation reactor, the neutralization coagulation and flocculation sedimentation tank 2, the intermediate water tank 2, the sand filter 2, and the second-stage SAO3 ozone catalytic oxidation reactor, repeating the above treatment steps. S7: The effluent is uniformly collected in the intermediate water tank 3 and sent to the MVR evaporation system to evaporate and obtain crystalline white salt products, and the condensate enters the clean water tank for collection and up-to-standard discharge.

[0005] The further improvement lies in that: in S1, the high-salt pickled mustard wastewater flows into the collecting tank by gravity and is then lifted to the anaerobic ammonification reaction tank. The reaction time is 8 - 12 h. A low-speed stirring device is arranged in the anaerobic ammonification reaction tank to maintain the dissolved oxygen of the wastewater at 0.05 - 0.1 mg / L. A three-phase separator is arranged at the top of the anaerobic ammonification reaction tank to separate gas, sludge, and water.

[0006] The further improvement lies in that: in S2, the reaction time in the STD salt-tolerant high-efficiency denitrification tank is 12 - 48 h. An aeration system is arranged in the STD salt-tolerant high-efficiency denitrification tank, and at the same time, an alkali solution dosing pipeline is arranged to adjust the pH value of the water, so that the pH value of the water quality is adjusted to the range of 8.0 - 11.0.

[0007] The further improvement lies in that: in S3, a sulfuric acid dosing device and a pH on-line monitoring system are arranged in the pH adjustment tank 1 to track and adjust the pH value of the water. The wastewater and the reagent are stirred and mixed by a stirrer to control its pH to be maintained within the range of 5.0 - 7.0. The wastewater is pumped into the first-stage FCD three-dimensional electrode catalytic oxidation reactor, and the reaction time is 1 - 3 h. Among them, 3 - 5 groups of electrode plates are arranged in the first-stage FCD three-dimensional electrode catalytic oxidation reactor, and the electrode plate spacing is controlled within the range of 20 - 30 cm. FCD particle electrode materials are uniformly filled between the electrode plates to form a composite catalytic system. An inlet water, aeration, and backwashing pipeline system is arranged at the bottom of the reactor to make the wastewater evenly distributed. The contact efficiency between pollutants and the electrode is improved by aeration stirring. A high-frequency pulsed DC power supply is equipped, and the electrode plate - particle electrode forms a complete three-dimensional electrode catalytic oxidation system through electrical connection. At the same time, an operation mode of alternating two poles is adopted to degrade pollutants.

[0008] Further improvements are as follows: in the S4, when the neutralization coagulation flocculation sedimentation tank 1 is used for treatment, 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, PAM solution is added to the flocculation tank, and agitators are respectively arranged 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, and an inclined tube filler is arranged in the sedimentation tank to promote the precipitation of the suspended matter and the solid-liquid separation. After the water quality is clarified, the supernatant flows into the intermediate water tank 1 by gravity.

[0009] The further improvement is that: in the S5, the sand filter 1 is filled with 0.5-1.2 mm quartz sand, and a backwash device is provided to wash the suspended matter intercepted on the filter material, and in the first-stage SAO3 ozone catalytic oxidation reactor, the reaction time is 2-6 hours, the reactor is filled with SAO3-Ⅱ ozone catalyst, and the bottom of the reactor is arranged with water inlet, microporous titanium plate gas distribution, and backwashing pipeline system to control the uniform distribution of gas and liquid, and prevent the deactivation of the ozone catalyst caused by the accumulation of pollutants 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, and generates strong oxidizing hydroxyl radicals (·OH) under the catalytic oxidation action of ozone and catalyst, which react with pollutants to decompose and remove COD organic matter, and crack colored functional groups, thereby removing chromaticity.

[0010] Further improvement is that in S7, after temporary storage in the intermediate water tank 3, the wastewater is transported to the MVR evaporation system by the lifting pump for deep treatment, and the evaporation concentration realizes the crystallization and separation of salt. The high-purity crystalline salt produced by the system is dried and packaged and then utilized 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.

[0011] Further improvements are: 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 pipeline, 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.

[0012] The beneficial effects of the present invention are: 1. The present invention has a strong resistance to impact load and stable operation. It abandons the traditional biochemical treatment process and realizes the efficient degradation of pollutants through the physical-chemical synergistic technology. It is not affected by the salinity of the wastewater and the fluctuation of pollutant load, ensuring long-term stable operation. Moreover, it emphasizes both the resource utilization of salts and pollution prevention and control. By innovatively coupling electrolytic oxidation and evaporation crystallization technologies, it realizes the efficient separation and purification of NaCl, eliminating the ecological risk of high-salt wastewater to soil / groundwater and creating additional economic benefits.

[0013] 2. The present invention deeply removes pollutants synergistically and integrates an efficient multi-stage treatment process. It deeply removes pollutants such as salts, COD, ammonia nitrogen, total nitrogen, and total phosphorus to ensure that the wastewater treatment effect meets the standards stably. After a series of process pre-treatments, the pollutant indicators of the concentrated mother liquor generated by evaporation are much lower than those of the raw water quality. It can be refluxed to the collecting tank for mixing and treatment with the original solution, forming a closed-loop benign cycle system for the mother liquor to ensure the complete degradation of pollutants and avoid secondary pollution caused by the discharge of high-salt wastewater.

[0014] 3. The present invention saves land and has strong adaptability. It abandons the traditional biochemical treatment process and adopts a process flow mainly based on pretreatment combined with advanced oxidation treatment and evaporation, greatly reducing the floor area, lowering the construction cost, having less sludge production, and significantly reducing the difficulty and cost of subsequent disposal. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] To deepen the understanding of the present invention, the following will further elaborate on the present invention in combination with embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation to the protection scope of the present invention.

[0017] Embodiment 1: According to Figure 1 shown, this embodiment proposes a treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt, including the following steps: The high-salt pickled mustard wastewater is uniformly converged into the collecting tank, and water volume adjustment and water quality homogenization treatment are realized through centralized storage.

[0018] The wastewater in the collecting tank is lifted into the anaerobic ammonia oxidation reaction tank by a feed pump. By using anaerobic ammonia-oxidizing bacteria, organic nitrogen is converted into ammonia nitrogen, and at the same time, a part of COD organic matter is degraded; The effluent enters the STD salt-tolerant high-efficiency denitrification tank. Using salt-tolerant special denitrifying bacteria, ammonia nitrogen is directly converted into nitrogen gas (N2) in a high-salt environment without adding nutrients, removing ammonia nitrogen and total nitrogen at the same time; The effluent after being treated by the STD salt-tolerant high-efficiency denitrification tank flows into pH adjustment tank 1 by gravity. Sulfuric acid solution is added to pH adjustment tank 1 to adjust the pH of the wastewater to the range of 5-7.

[0019] Use a water pump to pump the wastewater after pH adjustment into the first-stage FCD three-dimensional electrode catalytic oxidation reactor to break the rings and chains of macromolecular organic substances in the wastewater, and at the same time degrade the COD organic substances; The wastewater after electrolytic treatment enters the neutralization coagulation flocculation sedimentation tank 1. Add alkali solution to the neutralization tank to adjust the pH value of the wastewater to 8.0 - 10.0. At the same time, convert divalent iron ions into trivalent iron ions through aeration, and remove the volatile substances in the wastewater; Add coagulant in the coagulation tank and flocculant in the flocculation tank to make the suspended substances flocculate, and then enter the sedimentation tank to precipitate the flocculated suspended substances and achieve solid-liquid separation; The supernatant after precipitation enters the intermediate water tank 1 and is uniformly collected by the intermediate water tank 1; The wastewater in the intermediate water tank 1 is lifted to the sand filter 1 by a lift pump, and the sand filter 1 removes the tiny suspended substances in the water; The water outlet after sand filtration enters the first-stage SAO3 ozone catalytic oxidation reactor. Use the strong oxidizing property of ozone and catalyst to decompose and remove the COD organic substances, and crack the colored functional groups to remove the chromaticity; The ozone effluent flows into the pH adjustment tank 2 by gravity. Add sulfuric acid solution to the pH adjustment tank 2 and stir with a stirrer to adjust the pH of the wastewater within the range of 5 - 7.

[0020] Use a water pump to pump the wastewater after pH adjustment into the second-stage FCD three-dimensional electrode catalytic oxidation reactor to break the rings and chains of macromolecular organic substances in the wastewater again and degrade the COD organic substances; The wastewater after secondary electrolytic treatment enters the neutralization coagulation flocculation sedimentation tank 2. Add alkali solution to the neutralization tank to adjust the pH value of the wastewater to 8.0 - 10.0. At the same time, convert divalent iron ions into trivalent iron ions through aeration, and remove the volatile substances in the wastewater; Add coagulant in the coagulation tank and flocculant in the flocculation tank to make the suspended substances flocculate, and then enter the sedimentation tank to precipitate the flocculated suspended substances and achieve solid-liquid separation; The supernatant after precipitation enters the intermediate water tank 2 and is uniformly collected by the intermediate water tank 2; The wastewater in the intermediate water tank 2 is lifted to the sand filter 2 by a lift pump, and the sand filter 2 removes the tiny suspended substances in the water; The water outlet after sand filtration enters the second-stage SAO3 ozone catalytic oxidation reactor. Use the strong oxidizing property of ozone and catalyst to decompose and remove the COD and other organic substances again, and crack the colored functional groups to remove the chromaticity; The water with ozone flows into the intermediate pool 3 by gravity for unified collection, and then the wastewater is lifted into the MVR evaporation system by a lift pump. The MVR evaporation system evaporates the water, and the final crystalline white salt product can be used as a feed additive to achieve resource utilization. The produced condensate is collected in the clean water pool and then discharged up to standard. The process with the main line of "pretreatment + advanced oxidation + MVR evaporation" is adopted to treat the high-salt wastewater generated in the production of pickled mustard tuber. A series of pretreatment measures are required before the wastewater enters the MVR evaporation system to remove COD, ammonia nitrogen, total nitrogen, heavy metals, solids, suspended solids, etc. in the water.

[0021] The high-salt pickled mustard tuber wastewater mainly flows into the collection pool by gravity and is then lifted to the anaerobic ammoniaization reaction pool. The reaction time is 8 - 12h. A low-speed stirring device is set in the anaerobic ammoniaization reaction pool to prevent sludge sedimentation, improve the contact efficiency between the bacterial community and the wastewater, and maintain the dissolved oxygen in the wastewater at 0.05 - 0.1mg / L. A three-phase separator is set at the top of the anaerobic ammoniaization reaction pool to separate gas, sludge and water. The effluent of the anaerobic ammoniaization reaction pool flows into the STD salt-tolerant high-efficiency denitrification pool by gravity. The reaction time is 12 - 48h. An aeration system is set in the STD salt-tolerant high-efficiency denitrification pool to provide dissolved oxygen for the denitrifying bacteria. At the same time, an alkali solution dosing pipeline is arranged to adjust the pH value of the water and adjust the pH value of the water quality to the range of 8 - 11. This treatment unit removes ammonia nitrogen and total nitrogen in the wastewater through anaerobic ammonia oxidation bacteria and special high-efficiency denitrifying bacteria in a high-salt environment. Compared with the traditional denitrification process, this process can still maintain a high denitrification rate of 80 - 90% under the condition of salinity ≤ 15g / L, and no external carbon source is required, and the sludge yield is low. The anaerobic ammoniaization reaction pool and the STD salt-tolerant high-efficiency denitrification pool are used as the primary treatment units after the collection pool, and form synergy with the subsequent physical and chemical processes (electrocatalysis, ozone) to reduce the nitrogen load for the subsequent physical and chemical processes.

[0022] The effluent of the STD salt-tolerant high-efficiency denitrification pool flows into the pH adjustment pool 1 by gravity. A sulfuric acid dosing device and a pH on-line monitoring system are set to track and adjust the pH value of the water. The wastewater and the reagent are stirred and mixed by a stirrer to control its pH to be maintained within the range of 5.0 - 7.0, creating favorable conditions for the first-stage FCD three-dimensional electrode catalytic oxidation reaction.

[0023] After the pH of the wastewater is adjusted, it is pumped into the first-stage FCD three-dimensional electrode catalytic oxidation reactor by an inlet water pump. The reaction time is 1-3 h. 3-5 groups of electrode plates are arranged in the first-stage FCD three-dimensional electrode catalytic oxidation reactor, and the distance between the electrode plates is controlled within the range of 20-30 cm. The FCD particle electrode material is evenly filled between the electrode plates to form a composite catalytic system. The inlet water, aeration, and backwashing pipeline systems are arranged at the bottom of the reactor to evenly distribute the wastewater, improve the contact efficiency between the pollutants and the electrodes through aeration and stirring, and prevent the inactivation of the electrodes caused by the accumulation of pollutants. The system is equipped with a high-frequency pulsed DC power supply. Through electrical connection, the electrode plate - particle electrode forms a complete three-dimensional electrode catalytic oxidation system. At the same time, an alternating two-pole operation mode is adopted, which can effectively alleviate electrode passivation, extend the electrode life, improve the mass transfer efficiency, and enhance the pollutant degradation effect. In a weak acid environment, hydroxyl radicals (·OH) with high oxidation activity are more easily generated on the anode surface in cooperation with the FCD particle electrode material, enhancing the ring-opening and chain-breaking of macromolecular organic matter and reducing the pollutant load in the wastewater. At the same time, the acidic condition can reduce the competitive oxidation reaction of chloride ions (Cl⁻) in the high-salt wastewater and avoid the generation of chlorinated organic compounds. In addition, it can promote the redox cycle of Fe²⁺ / Fe³⁺ in the particle electrode material, further strengthening the catalytic degradation effect and creating better water quality conditions for subsequent ozone oxidation.

[0024] The wastewater after electrolytic treatment flows into the neutralization coagulation and flocculation sedimentation tank 1 by gravity. In the neutralization tank, the pH value of the water is tracked and adjusted through an alkali dosing device and a pH on-line monitoring system, and it is controlled to be within the range of 8.0-10.0. Aeration pipelines are arranged in the neutralization tank to promote the dissolution of the alkali solution in the wastewater and convert the divalent iron ions in the wastewater into trivalent iron ions, making it more conducive to subsequent dosing and precipitation, and at the same time removing the volatile substances in the wastewater. PAC solution is added to the coagulation tank, and PAM solution is added to the flocculation tank. Mixers are respectively set in the coagulation and flocculation tanks to ensure full contact between the medicaments and the pollutants, causing the polluted suspended substances to flocculate, and then entering the sedimentation tank. Inclined tube fillers are arranged in the sedimentation tank to promote the more effective and rapid precipitation of the suspended substances and achieve solid-liquid separation. After the water quality is clarified, the supernatant flows into the intermediate water tank 1 by gravity.

[0025] The wastewater in the intermediate water tank 1 is lifted to the sand filter 1 by an inlet water pump. It is mainly used to remove the tiny suspended substances in the water and is an essential link to ensure the maximum reduction of pollutants before the wastewater enters the SAO3 ozone catalytic oxidation reactor. The sand filter is filled with quartz sand of 0.5-1.2 mm, and a backwashing device is set to wash the suspended substances intercepted on the filter material.

[0026] The water passing through the sand filter enters the first-stage SAO3 ozone catalytic oxidation reactor. The reaction time is 2 - 6 hours. The reactor is filled with SAO3-II ozone catalyst. At the bottom of the reactor, there are inlet water, microporous titanium plate gas distribution, and backwashing pipeline systems to ensure uniform gas-liquid distribution. Backwashing and stirring are carried out to prevent the inactivation of the ozone catalyst 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 of ozone and the catalyst, strongly oxidizing hydroxyl radicals (·OH) are generated, which react with pollutants to decompose and remove organic matters such as COD, and crack colored functional groups, thereby removing color.

[0027] The effluent from the first-stage ozone flows by gravity into the pH adjustment tank 2. A sulfuric acid dosing device and a pH on-line monitoring system are set up to track and adjust the pH value of the water. The wastewater and the reagent are stirred and mixed by a stirrer to control its pH within the range of 5.0 - 7.0, creating favorable conditions for the second-stage FCD three-dimensional electrode catalytic oxidation reaction.

[0028] The wastewater after pH adjustment is pumped into the second-stage FCD three-dimensional electrode catalytic oxidation reactor by a feed pump. The reaction time is 1 - 3 hours. In the second-stage FCD three-dimensional electrode catalytic oxidation reactor, 3 - 5 groups of electrode plates are arranged, and the electrode plate spacing is controlled within the range of 20 - 30 cm. FCD particle electrode materials are evenly filled between the electrode plates to form a composite catalytic system. At the bottom of the reactor, there are inlet water, aeration, and backwashing pipeline systems to evenly distribute the wastewater. Through aeration and stirring, the contact efficiency between pollutants and the electrodes is improved, and the inactivation of the electrodes caused by pollutant accumulation is prevented. The system is equipped with a high-frequency pulsed DC power supply. Through electrical connection, the electrode plate - particle electrode forms a complete three-dimensional electrode catalytic oxidation system. At the same time, an alternating two-pole operation mode is adopted, which can effectively relieve electrode passivation, extend the electrode life, improve the mass transfer efficiency, and enhance the pollutant degradation effect. In a weak acid environment, it is easier to generate highly oxidizing hydroxyl radicals (·OH) under the synergistic action of the anode surface and the FCD particle electrode material, enhancing the ring-opening and chain-breaking of macromolecular organic matters and reducing the pollutant load in the wastewater. At the same time, the acidic condition can reduce the competitive oxidation reaction of chloride ions (Cl⁻) in the high-salt wastewater and avoid the generation of chlorinated organic compounds. In addition, it can promote the redox cycle of Fe²⁺ / Fe³⁺ in the particle electrode material and further strengthen the catalytic degradation effect. This second-stage three-dimensional electrode catalytic oxidation treatment unit is specifically designed for the stubborn organic matters remaining after the first-stage treatment, and the COD removal efficiency is 40 - 50% higher than that of the single-stage system. Through the cascade treatment mode design of "first-stage cracking - second-stage mineralization", the step-by-step cracking and complete mineralization of refractory organic matters are realized, and more ideal water quality conditions are created for the subsequent ozone oxidation unit.

[0029] The wastewater after electrolysis flows by gravity into the neutralization coagulation flocculation sedimentation tank 2. In the neutralization tank, the pH value in the water is tracked and adjusted through the alkali dosing device and the pH online monitoring system to control it to be kept 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, making it more conducive to the subsequent dosing precipitation and removing volatile substances in the wastewater. PAC solution is added to the coagulation tank, PAM solution is added to the flocculation tank, and agitators are respectively set in the coagulation and flocculation tanks to ensure full contact between the reagents and the pollutants, so that the polluted suspended matter can flocculate and then enter the sedimentation tank. The inclined tube filler is arranged in the sedimentation tank to promote the more effective and rapid precipitation of the suspended matter and achieve solid-liquid separation. After the water quality is clarified, the supernatant flows by gravity into the intermediate water tank 2.

[0030] The wastewater from the intermediate water tank 2 is lifted by the water inlet pump to the sand filter 2, which is mainly used to remove tiny suspended solids in the water to ensure that the wastewater is minimized to the greatest extent before entering the SAO3 ozone catalytic oxidation reactor. The sand filter is filled with 0.5-1.2mm quartz sand and is equipped with a backwash device to wash the suspended solids intercepted on the filter material.

[0031] The water that has passed through the sand filter enters the secondary SAO3 ozone catalytic oxidation reactor. The reaction time is 2-6h. The reactor is filled with SAO3-Ⅱ ozone catalyst. The bottom of the reactor is equipped with water inlet, microporous titanium plate gas distribution, and backwashing pipeline system to ensure uniform distribution of gas and liquid. Backwashing and stirring are used to prevent the deactivation of the ozone catalyst caused by the accumulation of pollutants. The system is equipped with an ozone generation system. The produced ozone gas enters the reactor through the microporous titanium plate gas distribution system. Under the catalytic oxidation of ozone and catalyst, strong oxidizing hydroxyl radicals (·OH) are generated, which react with pollutants, further completely decompose and remove residual COD and other organic matter, and crack the colored functional groups, thereby deeply removing chromaticity.

[0032] The effluent after the secondary ozone catalytic oxidation treatment flows by gravity into the intermediate water tank 3 for temporary storage, and then the lifting pump transports the wastewater to the MVR evaporation system for deep treatment, and evaporation and concentration realize salt crystallization separation. The high-purity crystalline salt produced by the system can be used as a feed-grade additive after drying and packaging; the condensate generated during the evaporation process is collected in the clear water tank and then discharged in compliance with the standards.

[0033] 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.

[0034] After a series of pre-treatments at the front end, the concentrated mother liquor generated by evaporation is much lower than the original high-salt pickled mustard wastewater, and can be directly recycled to the collection pool for mixed treatment, forming a virtuous cycle.

[0035] The entire pre-treatment process adopts measures such as anaerobic ammonification + STD salt-tolerant high-efficiency denitrification + FCD three-dimensional electrocatalysis + coagulation precipitation + physical filtration + SAO3 ozone catalytic oxidation to degrade pollution indicators such as COD, ammonia nitrogen, total nitrogen, heavy metals, and SS in water and clarify the water quality, so as to fully meet the inlet requirements of the subsequent MVR evaporation system, achieving the dual goals of up-to-standard discharge of wastewater and resource recovery.

[0036] The treatment efficiency of each unit and the summary of the effluent of the present invention for different water qualities of high-salt pickled mustard wastewater are shown in the following table: Table 1 ; Table 2 ; Table 3 ; It can be seen from the above data table that after the high-salt pickled mustard wastewater with different concentrations is treated by the method of the present invention, it not only meets the relevant requirements of the comprehensive wastewater discharge standard, but also meets the relevant regulations of the farmland irrigation water quality standard.

[0037] The technical indicators of the salt product refined by the method of the present invention are shown in the following table: Table 4 ; It can be seen from the data in the above table that the refined salt obtained from the high-salt pickled mustard wastewater treated by the method of the present invention meets the standard requirements in terms of purity and impurity content, and has the value of resource recovery and utilization.

[0038] Embodiment 2: According to Figure 1 shown, this embodiment proposes a treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt. Taking a certain pickled mustard processing high-salt wastewater (COD 10480 mg / L, ammonia nitrogen 570 mg / L, chloride ion 112000 mg / L) as the target, it includes the following steps: The high-salt pickled mustard wastewater is transported through pipelines to the collection pool for collection, where water volume balance adjustment and water quality mixing and homogenization are carried out.

[0039] The wastewater in the collection pool is sent to the anaerobic ammonification reaction tank by a lift pump. The reaction time is 10 h, and the dissolved oxygen of the wastewater is maintained at 0.05 - 0.1 mg / L. By using anaerobic ammonia-oxidizing bacteria, organic nitrogen is converted into ammonia nitrogen, and at the same time, a part of the COD organic matter is degraded.

[0040] The effluent enters the STD salt-tolerant and efficient denitrification tank. The reaction time is 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. The effluent after high-efficiency denitrification treatment flows by gravity into the pH adjustment tank 1, and the pH of the wastewater is adjusted to 6 by adding sulfuric acid solution and stirring.

[0041] 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. The macromolecular organic matter is opened and chain broken, and COD pollutants are degraded at the same time.

[0042] The wastewater after electrolysis treatment flows into the neutralization coagulation flocculation sedimentation tank 1. In the neutralization tank, the pH value of the wastewater is controlled to 9 through the pH online monitoring system and the addition of NaOH solution. At the same time, aeration oxidation converts divalent iron into trivalent iron, and volatile organic matter is blown off. PAC solution and PAM solution are added to the coagulation tank and flocculation tank respectively to promote the flocculation of suspended matter, and finally achieve mud and water separation in the sedimentation area.

[0043] After sedimentation, the supernatant overflows into the intermediate water tank 1 and is temporarily stored as primary treated effluent.

[0044] 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.

[0045] The sand filtered water enters the primary SAO3 ozone catalytic oxidation reactor for 3 hours. Under the synergistic effect of ozone and catalyst, strong oxidizing hydroxyl radicals (·OH) are generated to further oxidize and decompose the COD in the wastewater and destroy the chromogenic groups to remove the color.

[0046] 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.

[0047] 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.

[0048] The secondary electrolyzed effluent enters the neutralization, coagulation and flocculation sedimentation tank 2. In the neutralization tank, the pH value of the wastewater is controlled at 9 by the pH on-line monitoring system and the addition of NaOH solution. Aeration oxidation converts divalent iron into trivalent iron and strips off volatile organic compounds. In the coagulation tank and the flocculation tank, solid-liquid separation is achieved by secondary addition of PAC and PAM for flocculation and sedimentation.

[0049] The supernatant of the sedimentation tank 2 is collected and temporarily stored in the intermediate tank 2.

[0050] The wastewater in the intermediate tank 2 is pressurized by a lift pump and then enters the sand filter 2, where the residual fine suspended particles are intercepted by the quartz sand filter layer.

[0051] The sand filter effluent enters the secondary SAO3 ozone catalytic oxidation reactor. The reaction time is 3 h. Hydroxyl radicals (·OH) are generated under the synergistic action of ozone and the catalyst, oxidizing and decomposing the COD in the wastewater again and destroying the chromogenic groups to remove the color.

[0052] The effluent after secondary ozone catalytic oxidation treatment flows by gravity into the intermediate tank 3 for temporary storage. Then, the lift pump transports the wastewater to the MVR evaporation system for evaporation and concentration to achieve salt crystallization and separation. The salt is recycled as a feed additive. The concentrated mother liquor is refluxed to the collecting tank for circular treatment. The condensate is collected in the clean water tank and then discharged up to the standard.

[0053] The removal rate effect table of the treatment by the method of the present invention in this embodiment: Table 5 ; The technical index table of the salt product refined by the method of the present invention in this embodiment: Table 6 ; The present invention has strong resistance to impact load and stable operation. It abandons the traditional biochemical treatment process and realizes the efficient degradation of pollutants through the physical-chemical synergistic technology. It is not affected by the salinity of wastewater and the fluctuation of pollutant load, ensuring long-term stable operation. Moreover, it attaches equal importance to salt resource utilization and pollution prevention and control, innovatively couples electrolytic oxidation and evaporation crystallization technologies to achieve the efficient separation and purification of NaCl, which not only eliminates the ecological risk of high-salt wastewater to soil / groundwater but also creates additional economic benefits. At the same time, pollutants are deeply and synergistically removed. An efficient multi-stage treatment process is integrated to deeply remove pollutants such as salinity, COD, ammonia nitrogen, total nitrogen, and total phosphorus, ensuring that the wastewater treatment effect meets the standards stably. In addition, after a series of process pre-treatments, the pollutant indexes of the concentrated mother liquor generated by evaporation are much lower than those of the raw water quality. It can be refluxed to the collection tank and mixed with the original solution for treatment, forming a closed-loop and benign circulation system for the mother liquor to ensure the complete degradation of pollutants and avoid secondary pollution caused by the discharge of high-salt wastewater. Finally, the present invention saves land and has strong adaptability. It abandons the traditional biochemical treatment process and adopts a process flow mainly based on pretreatment combined with advanced oxidation treatment and evaporation, greatly reducing the floor area, lowering the construction cost, having less sludge production, and significantly reducing the difficulty and cost of subsequent disposal.

[0054] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt, characterized in that, It includes the following steps: S1: Concentrate and store the high-salt pickled mustard wastewater in a collection pool for water volume adjustment and water quality homogenization treatment, and then introduce it into an anaerobic ammonification reaction tank to convert the organic nitrogen in the wastewater into ammonia nitrogen and degrade a part of the COD organic matter at the same time; S2: The effluent flows into a STD salt-tolerant high-efficiency denitrification tank by gravity, without adding external carbon source, to remove ammonia nitrogen and total nitrogen in the wastewater; S3: The wastewater enters pH adjustment tank 1 to adjust the pH to 5-7, and then is pumped into a first-stage FCD three-dimensional electrode catalytic oxidation reactor to treat macromolecular organic matter and COD organic matter; S4: The wastewater enters neutralization coagulation and flocculation sedimentation tank 1 to adjust the pH value to 8.0-10.

0. At the same time, aerate to convert divalent iron ions into trivalent iron ions, remove volatile substances, and carry out flocculation treatment. Then, separate the solid and liquid, and the supernatant enters intermediate tank 1 for unified collection; S5: The collected water goes to sand filter 1 to remove tiny suspended solids, and then enters a first-stage SAO3 ozone catalytic oxidation reactor to decompose and remove organic matter and remove color; S6: The effluent goes to pH adjustment tank 2, a second-stage FCD three-dimensional electrode catalytic oxidation reactor, neutralization coagulation and flocculation sedimentation tank 2, intermediate tank 2, sand filter 2, and a second-stage SAO3 ozone catalytic oxidation reactor to repeat the above treatment steps; S7: Intermediate tank 3 uniformly collects the effluent and sends it to an MVR evaporation system to evaporate and obtain crystalline white salt products, and the condensate enters the clear water tank for collection and up-to-standard discharge.

2. The treatment method for achieving up-to-standard discharge of high-salt pickled mustard wastewater and recovering feed-grade salt according to claim 1, wherein: In S1, the high-salt pickled mustard wastewater flows into the collection pool by gravity and is then lifted to the anaerobic ammonification reaction tank. The reaction time is 8-12h. A low-speed stirring device is arranged in the anaerobic ammonification reaction tank to maintain the dissolved oxygen of the wastewater at 0.05-0.1mg / L. A three-phase separator is arranged at the top of the anaerobic ammonification reaction tank to separate gas, sludge and water.

3. A treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt according to claim 1, characterized in that: In S2, the reaction time in the STD salt-tolerant high-efficiency denitrification tank is 12-48h. An aeration system is arranged in the STD salt-tolerant high-efficiency denitrification tank, and at the same time, an alkali liquor dosing pipeline is arranged to adjust the pH value of the water, so that the pH value of the water quality is adjusted to the range of 8.0-11.

0.

4. A treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt according to claim 1, characterized in that: In S3, a sulfuric acid dosing device and a pH on-line monitoring system are arranged in pH adjustment tank 1 to track and adjust the pH value of the water. The wastewater and the reagent are stirred and mixed by a stirrer to control its pH to be kept within the range of 5.0-7.

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

5. A treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of 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 in 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, 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 the volatile substances in the wastewater; PAC solution is added to the coagulation tank, PAM solution is added to the flocculation tank, and agitators are respectively arranged 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, and an inclined tube filler is arranged in the sedimentation tank to promote the precipitation of the suspended matter and the solid-liquid separation. After the water quality is clarified, the supernatant flows into the intermediate water tank 1 by gravity.

6. A treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt according to claim 1, characterized in that: In the S5, the sand filter 1 is filled with quartz sand of 0.5-1.2 mm, and a backwash device is provided to wash the suspended matter intercepted on the filter material. In the first-stage SAO3 ozone catalytic oxidation reactor, the reaction time is 2-6 hours, and the reactor is filled with SAO3-Ⅱ ozone catalyst. The bottom of the reactor is provided with water inlet, microporous titanium plate gas distribution, and 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 (·OH) are generated, which react with the pollutants to decompose and remove COD organic matter, and break the colored functional groups, thereby removing the chromaticity.

7. A treatment method for the up-to-standard discharge of high-salt pickled mustard wastewater and the recovery of feed-grade salt according to claim 1, characterized in that: In S7, after being temporarily stored in the intermediate water tank 3, the wastewater is transported to the MVR evaporation system by the lifting pump for deep treatment, and the evaporation concentration realizes the crystallization and separation of salt. 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.

8. A treatment method for the up-to-standard discharge of high-salt pickle wastewater and the recovery of 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 a pipeline, and then filtered through a filter press. The generated sewage is collected in a water collection tank, and the generated dry sludge is stored at a fixed point and piled up for landfill.

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