Zero discharge process for high-concentration high-salinity organic wastewater

Abstract

The invention discloses a high-concentration high-salt organic wastewater zero discharge process, which comprises the following steps: enabling wastewater to pass through a grating adjusting tank, entering a coagulative precipitation tank for precipitation, enabling supernate to enter a heterogeneous catalytic oxidation system, performing hydrolytic acidification, and performing biological denitrification treatment in an AAO tank to obtain a denitrified solution; the denitrified solution is degraded and filtered by a solid waste-based ceramic flat sheet membrane and sequentially subjected to RO, first-stage DTRO and second-stage DTRO for three-stage concentration, produced water enters a recycling tank, obtained membrane concentrated liquid enters an MVR evaporation system, generated condensate water enters the recycling tank, and evaporated mud salt and mother liquor enter a drying system for dehydration; the sludge settled in the coagulative precipitation tank, the sludge subjected to hydrolytic acidification and the sludge obtained in the solid waste-based ceramic flat sheet membrane tank are mechanically dehydrated and then enter a drying system. According to the invention, zero discharge of wastewater can be realized, and the problems of high cost and incomplete degradation of high-concentration and high-salt organic wastewater degradation, large overall investment of a wastewater zero discharge process, high energy consumption and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and specifically relates to a zero-discharge process for high-concentration and high-salt organic wastewater. Background Art

[0002] The discharge of industrial wastewater is one of the main factors causing environmental pollution. Among them, about one-tenth of industrial wastewater is high-concentration and high-salt organic wastewater, and these high-concentration and high-salt organic wastewaters are difficult to be effectively treated. High-salt and high-concentration organic wastewater has complex components and poor biodegradability, with great treatment difficulty and high cost. The salts generated by evaporation and crystallization after the wastewater is not effectively treated often contain a large amount of organic matter. This part of waste salt usually has no good disposal channels, which may cause great environmental and safety hazards, and is also the main reason restricting the sustainable development bottleneck of industrial enterprises.

[0003] At present, the commonly used treatment processes for high-concentration and high-salt organic wastewater are combinations of technologies such as pretreatment, microbial degradation, membrane concentration, evaporation and crystallization, etc. However, there are many problems in each part of the treatment process. For example, the pretreatment system has a large amount of sludge production and unstable system operation; the biochemical system has high costs for degrading organic pollutants and incomplete degradation; the membrane system has a large investment, low water production rate, and the membrane is easy to be blocked and has a short service life; the evaporation system has high technical energy consumption and operation and maintenance costs, and low equipment efficiency.

[0004] In view of this, it is necessary to design a zero-discharge process for high-concentration and high-salt organic wastewater to solve the above problems. Summary of the Invention

[0005] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a zero-discharge process for high-concentration and high-salt organic wastewater. The present invention adopts a pretreatment technology combining multi-stage oxidation and biodegradation, a solid waste-based ceramic membrane technology, and a low-energy consumption MVR evaporation technology, aiming to solve the problems of high degradation cost and incomplete degradation of high-concentration and high-salt organic wastewater, and high overall investment and high energy consumption of the wastewater zero-discharge process. The COD removal rate for high-salt and high-concentration organic wastewater reaches more than 90%.

[0006] To achieve the above technical purpose, the present invention provides a zero-discharge process for high-concentration and high-salt organic wastewater. The method is to pass the wastewater through a grille regulating tank, enter a coagulation sedimentation tank for sedimentation, and the supernatant after sedimentation enters a heterogeneous catalytic oxidation system, then undergoes hydrolysis acidification and biological nitrogen removal treatment in an AAO tank to obtain a solution after nitrogen removal; the solution after nitrogen removal is further subjected to degradation and filtration by a solid waste-based ceramic flat membrane, and is concentrated in three stages by RO, first-stage DTRO, and second-stage DTRO in sequence. The produced water enters a reuse tank, the condensed water generated by the MVR evaporation system into which the obtained membrane concentrate enters also enters the reuse tank, and the evaporated sludge salts and mother liquor enter a drying system for dehydration; the sludge obtained after sedimentation in the coagulation sedimentation tank, the sludge after hydrolysis acidification, and the sludge obtained in the solid waste-based ceramic flat membrane tank also enter the drying system after mechanical dehydration.

[0007] In the technical solution of the present invention, a pretreatment technology coupling multi-stage oxidation and biodegradation is mainly adopted, combined with a solid waste-based ceramic membrane and low-energy-consuming MVR evaporation to deeply remove COD organic matter, ammonia nitrogen, etc. in the wastewater step by step. Specifically, the present invention first removes floating substances and suspended substances in the wastewater through a grille regulating tank to prevent blockage and entanglement of the water pump unit, and at the same time adjusts the water quality and water volume to ensure the normal operation of the subsequent sewage treatment system; then the wastewater is lifted from the grille regulating tank to a coagulation sedimentation tank, and under the action of a coagulant and a flocculant, most of the large-particle suspended substances and petroleum substances in the wastewater are removed, and the sedimented sludge enters the sludge storage tank, and the supernatant flows into the heterogeneous catalytic oxidation system; through the heterogeneous catalytic oxidation system, the refractory organic matter is oxidized and decomposed under the action of a heterogeneous catalyst to be converted into easily degradable small-molecule organic matter, improving the biodegradability of the wastewater. Then the wastewater passes through a hydrolysis acidification tank, which improves the BOD / COD ratio of the wastewater within a short residence time. At the same time, by the action of fermentative bacteria, the insoluble organic matter is hydrolyzed into soluble organic matter, and the macromolecular substances are decomposed into small-molecule substances, making the sewage more suitable for subsequent aerobic treatment and reducing the pollutant load; then it enters the AAO tank to carry out biological denitrification by using the different functions of the anoxic zone and the aerobic zone, and at the same time remove pollutants such as BOD5, COD Cr and total phosphorus. The denitrified solution enters the solid waste-based ceramic flat membrane tank, and under the action of activated sludge with a higher concentration, further removes pollutants such as COD and ammonia nitrogen in the wastewater. At the same time, the separation function of the membrane is used for filtration to remove most of the SS. The effluent from the membrane tank enters the RO membrane system, the mixed liquid is refluxed to the aerobic tank, the sludge is refluxed to the hydrolysis acidification tank, and the excess sludge is discharged into the sludge storage tank. After multi-stage concentration, finally a small amount of the second-stage DTRO membrane concentrate enters the MVR evaporation system for evaporation and crystallization, and the condensed water is recycled. And the sludge in the process can be hygienically landfilled after dehydration, realizing zero discharge of high-salt organic wastewater.

[0008] As a preferred scheme, the pH range of the high-concentration high-salt organic wastewater is 6-9, the COD is greater than 1500, the BOD5 is greater than 300, the SS (suspended substances) is greater than 400, and the TDS is greater than 5000.

[0009] As a preferred scheme, an emergency accident tank is also provided in front of the grille regulating tank to balance the water quality and water volume of the wastewater. The water volume and water quality of industrial production wastewater generally fluctuate greatly. In order to ensure the stability of the subsequent process, an emergency accident tank is set up to balance the water quality and water volume of the wastewater. In case of emergency, open the valve, the wastewater flows into the emergency accident tank, and a medicament is added for water quality adjustment, and then it is discharged into the regulating tank after the water quality adjustment is completed.

[0010] As a preferred scheme, a submersible mixer, a dosing device and a mechanical grille are arranged in the grille regulating tank to adjust the water quality and prevent sludge deposition.

[0011] As a preferred solution, the coagulation sedimentation tank is sequentially divided into a coagulation zone, a flocculation zone and a sedimentation zone. A coagulation mixer and an automatic coagulant dosing device are arranged in the coagulation zone, a flocculation mixer and a flocculant automatic dosing device are arranged in the flocculation zone, and a sludge hopper, a sludge thickener and inclined tube fillers are arranged in the sedimentation zone.

[0012] As a preferred solution, the treatment time in the coagulation zone is 1.0 - 3.0 min; the treatment time in the flocculation zone is 10 - 20 min; the surface load of the sedimentation zone is 2.0 - 4.5 m 3 / (m 2 ·h).

[0013] As a preferred solution, the heterogeneous catalytic oxidation system is divided into an acid adjustment zone, an oxidation reaction zone, a neutralization zone and a solid-liquid separation zone; air stirring and automatic acid dosing are arranged in the acid adjustment zone, the pH of the acid adjustment zone is 5.0 - 6.0, the heterogeneous catalyst based on solid waste is loaded in the oxidation reaction zone, air stirring is arranged, and the treatment time in the oxidation reaction zone is 2 - 8 h. Air stirring and automatic alkali liquor dosing are arranged in the neutralization zone; the solid-liquid separation zone is completed by the sedimentation method, and dosing for assisting sedimentation can be set according to the water quality. The heterogeneous catalyst based on solid waste adopted in the present invention includes an electrolytic manganese slag-based catalyst, a metal oxide-based catalyst and a supported catalyst.

[0014] As a preferred solution, the hydrolysis acidification is of the upflow type, and the wastewater residence time is 8 - 12 h. A pulse water distributor is arranged to ensure uniform mixing of the influent, and a sludge discharge pump is arranged at the bottom of the tank for regular sludge discharge.

[0015] As a preferred solution, the dissolved oxygen in the anoxic zone of the AAO tank is controlled at 0.2 - 0.4 mg / L, and the dissolved oxygen in the aerobic zone is controlled at 2 - 4 mg / L; halophilic bacteria are added to the aerobic zone of the AAO tank, and then they are subjected to long-term domestication and cultivation in a culture medium containing the target salt concentration, and then added to the biochemical system.

[0016] As a preferred solution, the halophilic bacteria include but are not limited to halophilic nitrifying bacteria, halophilic denitrifying vibrio and halophilic actinomycetes obtained through domestication.

[0017] As a preferred solution, the halophilic bacteria need to be domesticated in a culture medium containing the target salt concentration. The domestication process is divided into two parts and six stages. The first part is that in the first stage, the influent COD concentration ranges from 500 mg / L to 1600 mg / L, and a nutrient solution containing BOD S , N and P is added, the biological phase is observed, and the domestication time is 7 - 9 days. The second part is the second to sixth stages, and salt is gradually added starting from this stage, Cl -The concentration is increased from 1500 mg / L to the final 15000 mg / L, with each stage lasting for 7 to 9 days until the COD removal rate stabilizes above 80%, indicating the completion of acclimation.

[0018] As a preferred solution, the solid waste-based ceramic flat membrane degradation and filtration is connected to the anoxic zone in the AAO tank by a mixed liquor return device, and the mixed liquor return ratio is controlled at 100% - 400%; the solid waste-based ceramic flat membrane degradation and filtration and the hydrolysis acidification tank are equipped with a sludge return device, and the sludge return ratio is controlled at 50% - 100%. The solid waste-based ceramic flat membrane used in the present invention has the advantages of low cost, strong anti-fouling performance, long service life, etc. A membrane module is arranged in the membrane tank and fixed by a membrane rack, and an aeration device is installed at the bottom of the membrane rack. At the same time, a mixed liquor return pump and a sludge return pump are provided.

[0019] As a preferred solution, the effluent from the solid waste-based ceramic flat membrane tank enters the intermediate water raw water tank, is decontaminated by a precision filter before entering the RO membrane, and then the RO membrane is used for salt separation. The produced water is discharged into the reclaimed water tank, and the concentrated water is sent to the first-stage DTRO for concentration, and the concentrated water from the first-stage DTRO is sent to the second-stage DTRO for further concentration. The main purpose of using three-stage concentration in the present invention is to minimize the generation amount of membrane concentrate as much as possible, reduce the investment and operating costs of the evaporation system. The latter two-stage membrane concentration uses DTRO mainly because it has the advantages of high pollutant removal efficiency, strong anti-fouling performance, and low maintenance cost in treating high-concentration and high-salt organic wastewater.

[0020] As a preferred solution, the RO, the first-stage DTRO, and the second-stage DTRO are all equipped with scale inhibitors, bactericides, and cleaning chemical dosing devices.

[0021] As a preferred solution, the operating pressure of the RO is 10 - 25 bar, the operating pressure of the first-stage DTRO is 60 - 90 bar, and the operating pressure of the second-stage DTRO is 90 - 120 bar.

[0022] As a preferred solution, the MVR evaporation adopts a forced circulation process, and a hardness removal device is arranged at the front end; the sludge dewatering system includes a sludge storage tank, a sludge thickening tank, a sludge conditioning tank, and sludge dewatering equipment, and high-pressure plate frames are used for sludge dewatering.

[0023] As a preferred solution, after the sludge enters the drying system and is dewatered, the supernatant is returned to the grille regulating tank, and the dewatered sludge, the mud salt and the mother liquor generated by the MVR are dried in the sludge drying system and then hygienically landfilled.

[0024] As a preferred solution, the water content of the sludge after mechanical dewatering of the sludge after sedimentation in the coagulation sedimentation tank, the sludge after hydrolysis acidification, and the sludge obtained from the solid waste-based ceramic flat membrane tank is less than or equal to 70%.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] 1) The present invention adopts a pretreatment technology combining multi-stage oxidation and biodegradation, combines a solid waste-based ceramic membrane and low-energy MVR evaporation to deeply remove COD organic matter and ammonia nitrogen in wastewater step by step, and the COD removal rate of high-salt and high-concentration organic wastewater reaches more than 90%.

[0027] 2) The present invention adopts a solid waste-based heterogeneous catalytic oxidation pretreatment technology to effectively reduce investment and improve oxidation effect; adopts a solid waste-based ceramic flat membrane technology, which has the advantages of low material cost, large membrane flux, strong anti-fouling and blocking performance, long service life, etc., can effectively reduce investment and operation and maintenance costs, and adopts a low-energy MVR evaporation technology to effectively reduce the energy consumption of evaporation crystallization.

[0028] 3) The present invention can fully degrade high-concentration and high-salt organic wastewater, realize zero discharge of wastewater, with low overall investment, low energy consumption and stable system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the process flow chart of the present invention.

[0030] Figure 2 is the process diagram of the MVR evaporation system in the present invention.

[0031] Figure 3 is the comparison chart of the heterogeneous catalytic inlet water and the solid waste-based ceramic flat membrane outlet water effects of high-concentration and high-salt wastewater in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The technical solution of the present invention will be further described below in conjunction with specific embodiments of the present invention. It should be noted that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; these embodiments are only for better understanding of the present invention, rather than limiting the scope protected by the present invention.

[0033] Unless otherwise specified, various reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0034] The water quality parameters of the high-concentration and high-salt organic wastewater treated in the embodiments of the present invention are as shown in Table 1 below.

[0035] Table 1 Water quality parameters of high-concentration and high-salt organic wastewater (unit: mg / L)

[0036] Pollution factor pH COD <![CDATA[BOD5]]> SS TDS Concentration 6～9 1500～2000 300～500 400～500 5000～6000

[0037] Example 1

[0038] This embodiment is a zero-discharge process for high-concentration and high-salt organic wastewater, which successively includes grid regulation, emergency accident regulation, coagulation sedimentation filtration, heterogeneous catalytic oxidation degradation, hydrolysis acidification degradation, microbial degradation, solid waste-based ceramic flat membrane degradation and filtration, RO concentration and DTRO concentration, MVR evaporation crystallization, sludge dewatering, and sludge drying. The process flow chart of the embodiment of the present invention is as shown in Figure 1 and the specific operation steps are as follows:

[0039] Step 1: Grid regulation.

[0040] The high-concentration and high-salt organic wastewater enters the grid regulation tank, and large-particle pollutants and floating substances are filtered out under the action of the mechanical grid, and then flow into the regulation tank for homogenization and equalization regulation. The submersible mixer is used to prevent the deposition and anaerobic fermentation of wastewater sludge.

[0041] Step 2: Coagulation sedimentation.

[0042] The wastewater is lifted to the coagulation sedimentation tank by a sewage pump. First, it passes through the coagulation zone, and a coagulant is added, and a coagulation reaction is carried out under the action of a coagulation mixer, with a reaction time of 2 min; then it enters the flocculation zone, and a flocculant is added, and a flocculation reaction is carried out under the action of a flocculation mixer, with a reaction time of 10 min; finally, it enters the sedimentation zone, and the surface load is 2.0 - 4.5 m 3 / (m 2 ·h). The wastewater undergoes mud-water separation under the action of a sludge concentrator and inclined tube packing. The supernatant is discharged into the heterogeneous catalytic oxidation system, and the sludge sinks into the sludge hopper and is regularly discharged into the sludge storage tank through a sludge pump.

[0043] Step 3: Heterogeneous catalytic oxidation.

[0044] A solid waste-based heterogeneous catalyst (electrolytic manganese slag-based catalyst) is adopted, and the dosage is 30 g / L. The refractory organic matter in the wastewater is oxidized and decomposed in the system, converted into easily degradable small-molecule organic matter, improving the biodegradability of the wastewater and reducing the load of subsequent processes. The system is divided into an acid adjustment zone, an oxidation reaction zone, a neutralization zone, and a solid-liquid separation zone. In the acid adjustment zone, air stirring and automatic acid addition are set to control the pH to 5.0; the oxidation reaction zone is filled with a solid waste-based heterogeneous catalyst, air stirring and automatic hydrogen peroxide addition are set, and the hydraulic retention time is 8 h. The organic matter in the wastewater undergoes a catalytic oxidation reaction under the action of the catalyst and the oxidant, decomposing the macromolecular organic matter into easily degradable small-molecule organic matter; in the neutralization zone, air stirring and automatic alkali addition are set to adjust the pH to neutral; the solid-liquid separation zone uses the precipitation method to complete mud-water separation.

[0045] Step 4: Hydrolysis acidification.

[0046] Under anaerobic conditions, anaerobic bacteria are used to hydrolyze the organic matter in the wastewater into soluble organic matter, break down macromolecular substances into small molecular substances, and further improve the biodegradability. The hydrolysis acidification tank adopts an upflow type, with a hydraulic retention time of 12 h. A pulse water distributor is set to ensure uniform mixing of the influent. A sludge discharge pump is set at the bottom of the tank to discharge sludge regularly.

[0047] Step 5: AAO.

[0048] Utilize the different functions of the anoxic zone and the aerobic zone for biological denitrification, while removing pollutants such as BOD5, COD Cr and total phosphorus. An OPR is installed in the anoxic zone to control the dissolved oxygen at 0.2 mg / L for denitrification reaction to reduce nitrate nitrogen to N2; micro-pore aerators and dissolved oxygen meters are installed in the aerobic tank to control the dissolved oxygen at 2 mg / L for nitrification reaction under the action of microbial inoculants to convert ammonia nitrogen into nitrate nitrogen and consume organic matter at the same time. The microbial inoculant added in the aerobic zone is halophilic bacteria. The halophilic bacteria used in this embodiment are domesticated from halophilic nitrifying bacteria, halophilic denitrifying vibrio, and halophilic actinomycetes in a medium with a target salt concentration according to the dosing mass ratio of 3:1:1. The domestication process is divided into two parts and six stages. The first part is the first stage where the influent COD concentration ranges from 500 mg / L to 1600 mg / L, and a nutrient solution with BOD S :N:P = 100:5:1 is added, and the biological phase is observed with a domestication time of 7 days. The second part is the second to sixth stages, where salt is gradually added starting from a Cl - concentration of 1500 mg / L to the final 15000 mg / L, with each stage lasting 7 - 9 days until the COD removal rate is stable above 80% to complete the domestication.

[0049] Step 6: Degradation and filtration by solid waste-based ceramic flat membrane.

[0050] Utilize the degradation and filtration effects of the membrane pool microorganisms to remove COD, ammonia nitrogen, and SS. Membrane modules are set in the membrane pool and fixed by membrane racks. Aeration devices are installed at the bottom of the membrane racks, and a mixed liquor return pump and a sludge return pump are installed at the same time. The mixed liquor is returned to the anoxic zone of the AAO tank with the reflux ratio controlled between 200%, and the sludge is returned to the hydrolysis acidification tank with the reflux ratio controlled between 50%. The solid waste-based ceramic flat membrane has the characteristics of large membrane flux, strong anti-fouling performance, and long service life because its main raw material for preparation is fly ash, and it is suitable for the treatment of high-concentration and high-salt organic wastewater.

[0051] Step 7: Membrane concentration.

[0052] Three - stage concentration is carried out using RO, first - stage DTRO, and second - stage DTRO. The produced water enters the recycled water tank, and the concentrated liquid of the second - stage DTRO membrane enters the MVR evaporation system. The operating pressure of RO is 10 bar, the operating pressure of the first - stage DTRO is 60 bar, and the operating pressure of the second - stage DTRO is 120 bar. Scale inhibitors, bactericides, and cleaning chemical dosing devices are set in the membrane system, and cleaning is carried out regularly.

[0053] After treatment by the reverse osmosis membrane, the salts and organic matters in the wastewater are basically separated into the concentrated water. In this embodiment, membrane concentration adopts three - stage concentration. The main purpose is to minimize the generation amount of the membrane concentrated liquid as much as possible, and reduce the investment and operating costs of the evaporation system.

[0054] In this embodiment, the latter two - stage membrane concentration adopts DTRO, mainly because it has advantages such as high pollutant removal efficiency, strong anti - fouling performance, and low maintenance cost in treating high - concentration, high - salinity organic wastewater.

[0055] Step 8: Evaporation and crystallization.

[0056] The MVR evaporator is used to evaporate the concentrated water of the second - stage DTRO. The condensed water is recycled, and the evaporated sludge salts and mother liquor enter the drying system. As Figure 2 shown, the MVR evaporation adopts a forced - circulation process, and a hardness removal device is set at the front end.

[0057] In this embodiment, the adopted MVR evaporation technology reduces the steam consumption and system energy consumption by recovering and utilizing the latent heat of the secondary steam. Therefore, the application of this technology can effectively reduce the operating cost of the zero - discharge process.

[0058] Step 9: Sludge dewatering and drying.

[0059] High - pressure plate - and - frame is used for sludge dewatering, mainly for mechanically dewatering the sludge in the coagulation sedimentation tank, hydrolysis acidification tank, and solid - waste - based ceramic flat - membrane tank, reducing the water content to below 70%. Then it enters the drying system for drying. The MVR mother liquor and sludge salts are also dried, reducing the water content to below 40%, and then they are respectively landfilled hygienically.

[0060] Continuous influent and effluent tests are carried out using this embodiment. The comparison of the influent and effluent effects of each step is shown in Tables 2 - 4. The results show that through the discharge process of this embodiment, the COD removal rate of the organic wastewater reaches over 90%, and the quality of the obtained effluent is significantly improved compared with the influent.

[0061] Table 2 Heterogeneous catalytic oxidation COD removal effect test

[0062] Serial number Influent of heterogeneous catalytic system (mg / L) Effluent of heterogeneous catalytic system (mg / L) Removal rate 1 1651 906 45.12％ 2 1664 893 46.33％ 3 1578 826 47.66％ 4 1456 721 50.48％ 5 1508 877 41.84％ 6 1610 917 43.04％ 7 1618 798 50.68％ 8 1480 687 53.58％ 9 1634 691 57.71％ 10 1569 605 61.44％ 11 1532 723 52.81％ 12 1651 879 46.76％ 13 1678 853 49.17％ 14 1562 789 49.49％ 15 1580 765 51.58％ 16 1467 823 43.90％ 17 1615 859 46.81％ 18 1388 650 53.17％ 19 1617 675 58.26％ 20 1530 781 48.95％

[0063] Table 3 COD and SS removal effects of solid - waste - based ceramic flat - membrane

[0064]

[0065]

[0066] Table 4 Test results of TDS concentration of the second-stage DTRO membrane concentrate

[0067]

[0068]

[0069] Example 2

[0070] This example is a zero-discharge process for high-concentration and high-salt organic wastewater, which successively includes grid regulation, emergency accident regulation, coagulation sedimentation filtration, heterogeneous catalytic oxidation degradation, hydrolysis acidification degradation, microbial degradation, solid waste-based ceramic flat membrane degradation and filtration, RO concentration and DTRO concentration, MVR evaporation crystallization, sludge dewatering, and sludge drying. The process flow chart of the embodiment of the present invention is as Figure 1 shown, and the specific operation steps are as follows:

[0071] Step 1: Grid regulation.

[0072] The high-concentration and high-salt organic wastewater enters the grid regulation tank, and large-particle pollutants and floating substances are filtered out under the action of the mechanical grid, and then flow into the regulation tank for homogenization and equalization regulation. The submersible mixer is used to prevent the wastewater sludge from depositing and anaerobic fermentation.

[0073] Step 2: Coagulation sedimentation.

[0074] The wastewater is lifted to the coagulation sedimentation tank by a sewage pump. First, it passes through the coagulation zone, and a coagulant is added, and a coagulation reaction is carried out under the action of a coagulation mixer, and the reaction time is 3 min; then it enters the flocculation zone, and a flocculant is added, and a flocculation reaction is carried out under the action of a flocculation mixer, and the reaction time is 20 min; finally, it enters the sedimentation zone, and the surface load is 2.0 - 4.5 m 3 / (m 2 ·h). The wastewater is separated from mud and water under the action of a sludge concentrator and inclined tube fillers. The supernatant is discharged into the heterogeneous catalytic oxidation system, and the sludge sinks into the sludge hopper and is regularly discharged into the sludge storage tank by a sludge pump.

[0075] Step 3: Heterogeneous catalytic oxidation.

[0076] Using a solid waste-based heterogeneous catalyst (electrolytic manganese slag-based catalyst) with a dosage of 40 g / L, the refractory organic matter in the wastewater is oxidized and decomposed in the system, converted into easily degradable small-molecule organic matter, improving the biodegradability of the wastewater and reducing the load of subsequent processes. The system is divided into an acid adjustment area, an oxidation reaction area, a neutralization area, and a solid-liquid separation area. In the acid adjustment area, air agitation and automatic acid dosing are set to control the pH to 6.0; the oxidation reaction area is filled with a solid waste-based heterogeneous catalyst, air agitation and automatic hydrogen peroxide dosing are set, and the hydraulic retention time is 2 h. The organic matter in the wastewater undergoes a catalytic oxidation reaction under the action of the catalyst and the oxidant, decomposing the macromolecular organic matter into easily degradable small-molecule organic matter; in the neutralization area, air agitation and automatic alkali dosing are set to adjust the pH to neutral; the solid-liquid separation area uses the precipitation method to complete the separation of mud and water, and chemical dosing for assisting sedimentation is set according to the water quality situation.

[0077] Step 4: Hydrolysis acidification.

[0078] Under anaerobic conditions, anaerobic bacteria are used to hydrolyze the organic matter in the wastewater into soluble organic matter, and macromolecular substances are decomposed into small-molecule substances, further improving the biodegradability. The hydrolysis acidification tank is of the upflow type, with a hydraulic retention time of 8 h, a pulse distributor is set to ensure uniform mixing of the influent, and a sludge discharge pump is set at the bottom of the tank for regular sludge discharge.

[0079] Step 5: AAO.

[0080] Utilize the different functions of the anoxic zone and the aerobic zone for biological denitrification, while removing pollutants such as BOD5, COD Cr and total phosphorus. An OPR is installed in the anoxic zone to control the dissolved oxygen at 0.4 mg / L for denitrification reaction to reduce nitrate nitrogen to N2; micro-pore aerators and dissolved oxygen meters are installed in the aerobic tank to control the dissolved oxygen at 4 mg / L, and nitrification reaction is carried out under the action of microbial inoculants to convert ammonia nitrogen into nitrate nitrogen while consuming organic matter. The microbial inoculant added in the aerobic zone is a halophilic bacterium, and the strain type and domestication steps are the same as those in Example 1.

[0081] Step 6: Degradation and filtration by solid waste-based ceramic flat membrane.

[0082] Utilize the degradation and filtration effects of the microorganisms in the membrane tank to remove COD, ammonia nitrogen, and SS. Membrane modules are set in the membrane tank, fixed by membrane racks, an aeration device is installed at the bottom of the membrane rack, and a mixed liquor return pump and a sludge return pump are installed at the same time. The mixed liquor is returned to the anoxic zone of the AAO tank, and the reflux ratio is controlled at 400%, and the sludge is returned to the hydrolysis acidification tank, and the reflux ratio is controlled at 50%. Since the main raw material for the preparation of the solid waste-based ceramic flat membrane is fly ash, it has the characteristics of large membrane flux, strong anti-fouling performance, and long service life, and is suitable for the treatment of high-concentration and high-salt organic wastewater.

[0083] Step 7: Membrane concentration.

[0084] Three - stage concentration is carried out using RO, first - stage DTRO, and second - stage DTRO. The produced water enters the recycled water tank, and the concentrated liquid of the second - stage DTRO enters the MVR evaporation system. The operating pressure of RO is 25 bar, the operating pressure of the first - stage DTRO is 90 bar, and the operating pressure of the second - stage DTRO is 90 bar. Scale inhibitors, bactericides, and cleaning chemical dosing devices are set in the membrane system, and cleaning is carried out regularly.

[0085] After being treated by the reverse osmosis membrane, the salts and organic matters in the wastewater are basically separated into the concentrated water. In this embodiment, the membrane concentration adopts three - stage concentration. The main purpose is to minimize the generation amount of the membrane concentrated liquid as much as possible and reduce the investment and operating costs of the evaporation system.

[0086] In the last two - stage membrane concentration of this embodiment, DTRO is adopted mainly because it has advantages such as high pollutant removal efficiency, strong anti - fouling performance, and low maintenance cost in treating high - concentration and high - salinity organic wastewater.

[0087] Step 8: Evaporation and crystallization.

[0088] The concentrated water of the second - stage DTRO is evaporated using an MVR evaporator. The condensed water is recycled, and the evaporated sludge salts and mother liquor enter the drying system. As Figure 2 shown, the MVR evaporation adopts a forced - circulation process, and a hardness removal device is set at the front end.

[0089] In this embodiment, the adopted MVR evaporation technology reduces the steam consumption and system energy consumption by recovering and utilizing the latent heat of the secondary steam. Therefore, the application of this technology can effectively reduce the operating cost of the zero - discharge process.

[0090] Step 9: Sludge dewatering and drying.

[0091] High - pressure plate - and - frame is used for sludge dewatering. Mainly, the sludge from the coagulation sedimentation tank, hydrolysis acidification tank, and solid - waste - based ceramic flat - membrane tank is mechanically dewatered, and the water content is reduced to below 70%. Then it enters the drying system for drying. The mother liquor and sludge salts of MVR are also dried, and the water content is reduced to below 40%. Then they are respectively landfilled hygienically.

[0092] Table 5 COD removal effect of the solid - waste - based ceramic flat - membrane

[0093]

[0094]

[0095] Table 6 Test results of the TDS concentration of the concentrated liquid of the second - stage DTRO membrane

[0096]

[0097]

[0098] Example 3

[0099] This example is a zero - discharge process for high - concentration and high - salinity organic wastewater, which successively includes grille regulation, emergency accident regulation, coagulation sedimentation filtration, heterogeneous catalytic oxidation degradation, hydrolysis acidification degradation, microbial degradation, solid - waste - based ceramic flat - membrane degradation and filtration, RO concentration and DTRO concentration, MVR evaporation crystallization, sludge dewatering, and sludge drying. The process flow chart of the embodiment of the present invention is as shown in Figure 1 shown, and the specific operation steps are as follows:

[0100] Step 1: Grille regulation.

[0101] The high - concentration and high - salinity organic wastewater enters the grille regulation tank, and large - particle pollutants and floating substances are filtered out under the action of the mechanical grille, and then flow into the regulation tank for homogenization and equalization regulation. A submersible mixer is used to prevent the deposition and anaerobic fermentation of wastewater sludge.

[0102] Step 2: Coagulation sedimentation.

[0103] The wastewater is lifted to the coagulation sedimentation tank by a sewage pump. First, it passes through the coagulation zone, where a coagulant is added and a coagulation reaction is carried out under the action of a coagulation mixer for 1 min. Then it enters the flocculation zone, where a flocculant is added and a flocculation reaction is carried out under the action of a flocculation mixer for 15 min. Finally, it enters the sedimentation zone with a surface load of 2.5 - 3 m 3 / (m 2 ·h). The wastewater is separated into mud and water under the action of a sludge concentrator and inclined - tube packing. The supernatant is discharged into the heterogeneous catalytic oxidation system, and the sludge sinks into the sludge hopper and is regularly discharged into the sludge storage tank by a sludge pump.

[0104] Step 3: Heterogeneous catalytic oxidation.

[0105] A solid - waste - based heterogeneous catalyst (electrolytic manganese slag - based catalyst) is used, with a dosage of 30 g / L. The refractory organic matter in the wastewater is oxidized and decomposed in the system, converted into easily degradable small - molecule organic matter, improving the biodegradability of the wastewater and reducing the load of subsequent processes. The system is divided into an acid - adjustment zone, an oxidation reaction zone, a neutralization zone, and a solid - liquid separation zone. In the acid - adjustment zone, air stirring and automatic acid dosing are set to control the pH to 5.5. The oxidation reaction zone is filled with a solid - waste - based heterogeneous catalyst, and air stirring and automatic hydrogen peroxide dosing are set, with a hydraulic retention time of 5 h. The organic matter in the wastewater undergoes a catalytic oxidation reaction under the action of the catalyst and the oxidant, decomposing macromolecular organic matter into easily degradable small - molecule organic matter. The neutralization zone is provided with air stirring and automatic alkali dosing to adjust the pH to neutral. The solid - liquid separation zone uses the precipitation method to complete the separation of mud and water, and chemical dosing for assisting sedimentation can be set according to the water quality.

[0106] Step 4: Hydrolysis acidification.

[0107] Under anaerobic conditions, anaerobic bacteria are used to hydrolyze the organic matter in the wastewater into soluble organic matter, break down macromolecular substances into small molecular substances, and further improve the biodegradability. The hydrolysis acidification tank adopts an up-flow type, with a hydraulic retention time of 10 h. A pulse water distributor is set to ensure uniform mixing of the influent. A sludge discharge pump is set at the bottom of the tank to discharge sludge regularly.

[0108] Step 5: AAO.

[0109] Utilize the different functions of the anoxic zone and the aerobic zone to carry out biological denitrification, and simultaneously remove pollutants such as BOD5, COD Cr and total phosphorus. An OPR is installed in the anoxic zone to control the dissolved oxygen at 0.3 mg / L for denitrification reaction to reduce nitrate nitrogen to N2; a microporous aerator and a dissolved oxygen meter are installed in the aerobic tank to control the dissolved oxygen at 3 mg / L. Under the action of microbial inoculants, nitrification reaction is carried out to convert ammonia nitrogen into nitrate nitrogen and consume organic matter at the same time. The microbial inoculant added in the aerobic zone is halophilic bacteria, and the strain type and domestication process are the same as those in Example 1.

[0110] Step 6: Degradation and filtration by solid waste-based ceramic flat membrane.

[0111] Utilize the degradation and filtration effects of the microorganisms in the membrane tank to remove COD, ammonia nitrogen and SS. Membrane modules are set in the membrane tank and fixed by membrane racks. An aeration device is installed at the bottom of the membrane rack, and a mixed liquor return pump and a sludge return pump are installed at the same time. The mixed liquor is returned to the anoxic zone of the AAO tank, and the reflux ratio is controlled at 300%; the sludge is returned to the hydrolysis acidification tank, and the reflux ratio is controlled at 75%. Since the main raw material for the preparation of the solid waste-based ceramic flat membrane is fly ash, it has the characteristics of large membrane flux, strong anti-fouling and blocking performance, long service life, etc., and is suitable for the treatment of high-concentration and high-salt organic wastewater.

[0112] Step 7: Membrane concentration.

[0113] Perform three-stage concentration using RO, first-stage DTRO, and second-stage DTRO. The produced water enters the reused water tank, and the second-stage DTRO membrane concentrate enters the MVR evaporation system. The operating pressure of RO is 20 bar, the operating pressure of the first-stage DTRO is 80 bar, and the operating pressure of the second-stage DTRO is 100 bar. Scale inhibitors, bactericides, and cleaning chemical dosing devices are set in the membrane system, and cleaning is carried out regularly.

[0114] After treatment by the reverse osmosis membrane, the salts and organic matter in the wastewater are basically separated into the concentrated water. In this embodiment, three-stage concentration is adopted for membrane concentration, and the main purpose is to minimize the generation amount of the membrane concentrate as much as possible and reduce the investment and operating costs of the evaporation system.

[0115] In this embodiment, the latter two-stage membrane concentration adopts DTRO, mainly because it has the advantages of high pollutant removal efficiency, strong anti-fouling and blocking performance, and low maintenance cost in the treatment of high-concentration and high-salt organic wastewater.

[0116] Step 8: Evaporative crystallization.

[0117] Use an MVR evaporator to evaporate the concentrated water from the second-stage DTRO. The condensed water is recycled, and the evaporated sludge salts and mother liquor enter the drying system. As Figure 2 shown, the MVR evaporation adopts a forced circulation process, and a hardening removal device is set at the front end.

[0118] In this embodiment, the MVR evaporation technology adopted reduces the steam consumption and system energy consumption by recovering and utilizing the latent heat of the secondary steam. Therefore, the application of this technology can effectively reduce the operation cost of the zero-discharge process.

[0119] Step 9: Sludge dewatering and drying.

[0120] Use a high-pressure plate and frame for sludge dewatering. Mainly mechanically dewater the sludge from the coagulation sedimentation tank, hydrolysis acidification tank, and solid waste-based ceramic flat membrane tank until the water content is reduced to below 70%, and then enter the drying system for drying. The MVR mother liquor and sludge salts are also dried until the water content is reduced to below 40%, and then they are respectively sent to sanitary landfills.

[0121] Table 7 COD removal effect of the solid waste-based ceramic flat membrane

[0122]

[0123]

[0124] Table 8 Test results of the TDS concentration of the second-stage DTRO membrane concentrate

[0125] Serial number RO influent TDS (mg / L) TDS of concentrated water from the second-stage DTRO (mg / L) 1 5231 65387 2 5672 65196 3 5831 70253 4 5220 69650 5 5076 55780 6 4835 71102 7 5456 70857 8 5268 71190 9 6230 75978 10 5455 64940 11 5239 54010 12 5876 63869 13 5912 74836 14 5210 72365 15 6235 67044 16 5754 70170 17 5433 63918 18 5632 63280 19 5310 55313 20 5532 74756

[0126] Comparative Example 1

[0127] Compared with Example 1, the difference in this comparative example is only that the heterogeneous catalytic oxidation in Step 3 is cancelled, and the other conditions and steps are the same. The COD of the ceramic flat membrane effluent is as shown in Table 9 below.

[0128] Table 9

[0129]

[0130] Comparative Example 2

[0131] Compared with Example 2, the difference is only that the solid waste-based ceramic flat membrane in the present invention is cancelled, and the other steps and conditions are the same. The COD of the effluent from its AAO system is as shown in Table 10 below.

[0132] Table 10

[0133] Serial number COD of influent of hydrolysis acidification (mg / L) COD of effluent of AAO system (mg / L) Removal rate 1 906 105 88.41％ 2 893 99 88.91％ 3 826 97 88.26％ 4 721 98 86.41％ 5 877 113 87.12％ 6 917 94 89.75％ 7 798 102 87.22％ 8 687 75 89.08％ 9 691 65 90.59％ 10 605 53 91.24％ 11 723 72 90.04％ 12 879 89 89.87％ 13 853 93 89.10％ 14 789 98 87.58％ 15 765 96 87.45％ 16 823 106 87.12％ 17 859 121 85.91％ 18 650 71 89.08％ 19 675 67 90.07％ 20 781 90 88.48％

[0134] Compared with Comparative Example 2, in Example 2, since the ceramic flat membrane is a biological membrane and the addition of the ceramic flat membrane results in a higher sludge concentration in the biochemical system than that in the AAO system, the COD removal efficiency in Example 2 is higher than that in Comparative Example 2.

[0135] In summary, the zero-discharge process for high-concentration and high-salt organic wastewater described in the present invention achieves zero discharge of wastewater. The process of the present invention solves the problems of high degradation cost and incomplete degradation of high-concentration and high-salt organic wastewater, as well as high overall investment and high energy consumption of the zero-discharge process for wastewater.

[0136] The above embodiments are only for better explaining the principle and practical application of the present invention, so that those skilled in the relevant technical fields can better understand and utilize the present invention. It does not limit the patent scope of the present invention. Any equivalent transformation made by using the content of the present invention falls within the patent protection scope of the present invention.

Claims

1. A zero-discharge process for high-concentration and high-salt organic wastewater, characterized by: The wastewater passes through a screen regulating tank and enters a coagulation sedimentation tank for sedimentation. The supernatant enters a heterogeneous catalytic oxidation system, and then undergoes hydrolysis and acidification before biological denitrification in an AAO tank to obtain a denitrified solution. The denitrified solution is subjected to solid waste-based ceramic flat membrane degradation filtration, and sequentially subjected to RO, primary DTRO, and secondary DTRO for three-stage concentration. The produced water enters a reuse tank, and the obtained membrane concentrated liquid enters an MVR evaporation system. The condensed water generated then enters the reuse tank, while the evaporated mud salt and mother liquor enter a drying system for dehydration. The sludge precipitated in the coagulation sedimentation tank, the sludge after hydrolysis and acidification, and the sludge obtained in the solid waste-based ceramic flat membrane tank enter the drying system after mechanical dehydration.

2. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 1, characterized in that: An emergency pool is also provided in front of the grid regulating pool to balance the quality and quantity of wastewater.

3. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 1, characterized in that: The coagulation sedimentation tank is divided into a coagulation zone, a flocculation zone and a sedimentation zone in sequence.

4. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 3, characterized in that: The treatment time of the coagulation zone is 1.0 to 3.0 minutes; the treatment time of the flocculation zone is 10 to 20 minutes; the surface load of the sedimentation zone is 2.0 to 4.5 m 3 / (m 2 h).

5. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 4, characterized in that: The heterogeneous catalytic oxidation system is divided into an acid adjustment zone, an oxidation reaction zone, a neutralization zone and a solid-liquid separation zone; the pH of the acid adjustment zone is 5.0-6.0, and the treatment time of the oxidation reaction zone is 2-8 hours.

6. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 1, characterized in that: The hydrolysis acidification adopts an upflow method, and the wastewater retention time is 8 to 12 hours.

7. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 1, characterized in that: The dissolved oxygen in the anoxic zone of the AAO pool is controlled to be 0.2-0.4 mg / L, and the dissolved oxygen in the aerobic zone is controlled to be 2-4 mg / L; halophilic bacteria are added to the aerobic zone of the AAO pool, and then acclimated and cultured for a long time in a culture medium containing a target salt concentration, and then added to the biochemical system.

8. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 7, characterized in that: The solid waste-based ceramic flat membrane degradation filtration and the anoxic zone in the AAO pool are connected with a mixed liquor reflux device, and the mixed liquor reflux ratio is controlled to be 100% to 400%; the solid waste-based ceramic flat membrane degradation filtration and hydrolysis acidification pool is provided with a sludge reflux device, and the sludge reflux ratio is controlled to be 50% to 100%.

9. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 1, characterized in that: The operating pressure of the RO is 10-25 bar, the operating pressure of the first-stage DTRO is 60-90 bar, and the operating pressure of the second-stage DTRO is 90-120 bar.

10. A zero-discharge process for high-concentration and high-salt organic wastewater according to claim 9, characterized in that: The moisture content of the sludge after precipitation in the coagulation sedimentation tank, the sludge after hydrolysis and acidification, and the sludge obtained from the solid waste-based ceramic flat membrane tank after mechanical dehydration is less than or equal to 70%.

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