Method for treating biomass-containing nitrogen-containing wastewater and fly ash together and preparing inorganic salt

Abstract

The present application belongs to the field of wastewater treatment, and particularly relates to a method for co-treatment of biomass-containing nitrogen-containing wastewater and fly ash and preparation of inorganic salt. The treatment method comprises nitration, membrane bioreactor (MBR), nanofiltration (NF) and reverse osmosis (RO) of the biomass-containing nitrogen-containing wastewater, mixing of the RO concentrated water with water washing liquid of fly ash treatment, concentration, adjustment of the proportion of inorganic salt, and entering of an evaporation system for preparation of inorganic salt, so as to realize co-treatment of the biomass-containing nitrogen-containing wastewater and fly ash, and harmless and resourceful treatment of pollutants. The present application also provides a treatment system for the method.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a method for the co-treatment of biomass-based nitrogen-containing wastewater and fly ash and the preparation of inorganic salts. Background Technology

[0002] Landfill leachate and kitchen wastewater are examples of biomass-based nitrogenous wastewater, containing high concentrations of organic matter, heavy metals, ammonia nitrogen, and pathogenic microorganisms. They are characterized by complex composition, high toxicity, and significant treatment challenges. Current mainstream technologies include biological treatment, membrane separation (such as reverse osmosis), and advanced oxidation processes. However, a single process is insufficient to completely remove pollutants and often leaves concentrated residues requiring secondary treatment. Traditional treatment technologies typically involve nitrification and denitrification, converting ammonia nitrogen into nitrates, which are then reduced back to nitrogen gas and released into the atmosphere by consuming a carbon source. Since the carbon-to-nitrogen ratio in some nitrogenous wastewaters is often unbalanced, additional carbon sources are frequently required, and this process also results in carbon dioxide emissions. Furthermore, these traditional methods suffer from large land requirements, high civil engineering investment, and high operating costs, and fail to achieve resource utilization of the high-value-added nitrates.

[0003] Fly ash is a hazardous waste (HW18 category) generated from the incineration of municipal solid waste. It is enriched with heavy metals such as dioxins, mercury, and lead, and has significant leaching toxicity. Improper disposal can easily cause soil and groundwater pollution. The mainstream methods are chelation solidification landfill or co-processing in cement kilns. However, the former requires land and carries the risk of leakage, while the latter is limited by the production capacity and high cost of cement kilns.

[0004] Literature reports that the co-treatment of leachate and fly ash can simultaneously solve the problems of two types of pollutants. For example, CN113503543A discloses an online treatment system and process for the co-treatment of waste fly ash and waste leachate, including a fly ash conveying system, a plasma melting furnace system, a slag discharge and collection system, a waste leachate conveying system, a secondary combustion chamber and combustion system, a waste heat boiler system, a quench tower, and a waste incineration plant flue gas purification system. CN111807576A discloses a method for treating municipal solid waste leachate using fly ash from municipal solid waste incineration. The method involves adding hydrochloric acid aqueous solution to the leachate; weighing water and municipal solid waste incineration fly ash separately, mixing and centrifuging to separate the solids and liquids, obtaining a municipal solid waste incineration fly ash washing liquid and a fly ash solid slurry; subjecting the municipal solid waste incineration fly ash washing liquid to electrostatic treatment, capturing the gas generated in the electrostatic anode chamber and directly introducing it into the acidified municipal solid waste leachate, while simultaneously aerating the leachate; scraping and filtering the municipal solid waste leachate to obtain oily nitrogen trichloride and denitrified leachate; weighing an iron-aluminum agent and fly ash solid slurry, vacuum drying to obtain fly ash purification powder; weighing the denitrified leachate and fly ash purification powder, mixing and stirring to separate the solids and liquids, obtaining a municipal solid waste leachate purification liquid and a gelled fly ash solid slurry. However, the above treatment method is relatively complex and lacks sufficient resource recovery and utilization. Summary of the Invention

[0005] Based on the above-mentioned technical problems, the present invention provides a method for the co-treatment of biomass nitrogen-containing wastewater and fly ash and the preparation of inorganic salts. The method includes nitrification, membrane bioreactor (MBR), nanofiltration (NF) and reverse osmosis (RO) of biomass nitrogen-containing wastewater, mixing the obtained RO concentrate with the washing liquid from fly ash treatment, concentrating, adjusting the inorganic salt ratio, and entering the evaporation system to prepare inorganic salts, thereby achieving the co-treatment of biomass nitrogen-containing wastewater and fly ash and realizing the harmless treatment of pollutants.

[0006] A method for co-treating biomass-based nitrogenous wastewater and fly ash and preparing inorganic salts includes the following steps: (1) Pretreatment of biomass-based nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification; (3) The nitrified wastewater is subjected to MBR and nanofiltration to obtain nanofiltration concentrate and nanofiltration permeate. The nanofiltration concentrate is treated by two-stage material membranes. The concentrate from the first-stage material membrane is an organic concentrate. The permeate enters the second-stage material membrane system. The concentrate from the second-stage material membrane is treated by the hardness removal system and then enters the nitrification reaction tank to replenish the alkalinity of the system. The permeate from the second-stage material membrane and the permeate from nanofiltration are then treated by reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate. (4) The fly ash from the waste incineration plant enters the fly ash washing system. After the fly ash washing liquid removes heavy metals, it is mixed with the RO concentrate from step (3) to obtain a mixed liquid. (5) After the mixed liquid enters the hardening, defluorination and desiliconization system, it enters the filtration system. The effluent from the filtration system enters the NF system. The NF system permeate enters the oxidation system to remove organic matter and obtain the treated mixed liquid. The concentrated water from the NF system is returned to the washing liquid defluorination, hardening and desiliconization system to replenish sulfate. (6) Decarbonize and pH the treatment mixture, and then, according to the inorganic salt components and resource utilization requirements in the treatment mixture, use any of the methods in ai in the evaporation system for treatment; a: The inorganic components are mainly sodium chloride and sodium nitrate. The resource-based product requires sodium chloride and potassium nitrate. Potassium chloride is added to adjust the reaction, and after adjustment, the proportions of each ion satisfy [n(K]]. + )+ n(Cl - )]: [n(Na + )+ n(NO3 - )]=0.8-1.2; then, the mixture is evaporated and concentrated, evaporated and crystallized to obtain the second crystal (sodium chloride product salt), cooled and crystallized to obtain the third crystal (agricultural grade potassium nitrate), and the optional third crystal is refined to obtain the fourth crystal (industrial grade potassium nitrate); the remaining mother liquor of the third crystal and / or the fourth crystal is evaporated and dried to obtain mixed salt, or returned to the heavy metal removal step in step (4); b: The inorganic components are mainly sodium chloride and sodium nitrate, and the resource-based products are required to be sodium chloride and sodium nitrate; the process involves evaporation and concentration, evaporation and crystallization to obtain the second crystal (sodium chloride product salt), cooling and crystallization to obtain the third crystal (industrial grade sodium nitrate), and optional purification of the third crystal to obtain the fourth crystal (molten salt grade sodium nitrate); the remaining mother liquor from the third and / or fourth crystals is evaporated and dried to obtain impurities, or recycled to the washing liquid de-gravity system; c: The inorganic components are mainly sodium chloride and potassium chloride. The resource-based product requires sodium chloride and potassium nitrate. Sodium nitrate is added to adjust the reaction, and after adjustment, the proportions of each ion satisfy [n(K + )+ n(Cl - )]: [n(Na + )+ n(NO3 - )]=0.8-1.2; then, the mixture is evaporated and concentrated, evaporated and crystallized to obtain the second crystal (sodium chloride product salt), cooled and crystallized to obtain the third crystal (agricultural grade potassium nitrate), and the optional third crystal is refined to obtain the fourth crystal (industrial grade potassium nitrate); the remaining mother liquor of the third crystal and / or the fourth crystal is evaporated and dried to obtain mixed salt, or returned to the heavy metal removal step in step (4); d: The inorganic components are mainly sodium chloride and potassium chloride, and the resource-based products are required to be sodium chloride and potassium chloride. The product is then subjected to evaporation and concentration, evaporation and crystallization to obtain the second crystal (sodium chloride product salt), and cooling and crystallization to obtain the third crystal (industrial grade potassium chloride). The remaining mother liquor of the third crystal is evaporated and dried to obtain mixed salt, or returned to the heavy metal removal step in step (4).

[0007] e: The inorganic components are mainly sodium nitrate and potassium nitrate. The resource-based products are required to be sodium nitrate and potassium nitrate. The product is then subjected to evaporation and concentration, evaporation and crystallization to obtain the second crystal (sodium nitrate product salt), and freeze crystallization to obtain the third crystal (industrial grade potassium nitrate). The remaining mother liquor of the third crystal is evaporated and dried to obtain mixed salt or partially returned to the heavy metal removal step (4) for further processing.

[0008] f: The inorganic components are mainly sodium chloride, potassium chloride, and sodium nitrate. The resource-based products are required to be sodium chloride, potassium chloride, and sodium nitrate. First, the product is evaporated and concentrated, and then cooled and crystallized. Combined evaporation and crystallization are used to obtain the second crystal (sodium nitrate product salt), the mixed salt of sodium chloride and potassium chloride, and the remaining mother liquor of the mixed salt. The solution after the mixed salt is dissolved is processed by method c or method d to obtain the resource-based product salt of sodium chloride and potassium chloride. The remaining mother liquor is evaporated and dried to obtain the mixed salt or partially returned to the heavy metal removal step in step (4) for further processing.

[0009] g: The inorganic components are mainly sodium chloride, potassium chloride, and potassium nitrate. The resource-based products are required to be sodium chloride, potassium chloride, and potassium nitrate. First, the product is evaporated and concentrated, and then cooled and crystallized. Combined evaporation and crystallization are used to obtain the second crystal (potassium nitrate product salt), a mixed salt of sodium chloride and potassium chloride, and the remaining mother liquor of the mixed salt. The solution after the mixed salt is dissolved is processed by method c or method d to obtain the resource-based product salt of sodium chloride and potassium chloride. The remaining mother liquor is evaporated and dried to obtain mixed salt or partially returned to the heavy metal removal step in step (4) for further processing.

[0010] h: The inorganic components are mainly sodium chloride, sodium nitrate and potassium nitrate. The resource-based products are required to be sodium chloride, sodium nitrate and potassium nitrate. First, the product is concentrated by evaporation, and then the product is obtained by evaporation crystallization combined with cooling crystallization (sodium chloride product salt). The mixed salt of sodium nitrate and potassium nitrate, the remaining mother liquor of the mixed salt, and the solution after the mixed salt is dissolved are processed by method e to obtain the resource-based product salt of sodium nitrate and potassium nitrate. The remaining mother liquor is evaporated and dried to obtain mixed salt or partially returned to the heavy metal removal step in step (4) for further processing.

[0011] i: The inorganic components are mainly potassium chloride, sodium nitrate and potassium nitrate. The resource-based products are required to be potassium chloride, sodium nitrate and potassium nitrate. First, the product is evaporated and concentrated, and then evaporated and crystallized and cooled to obtain the second crystal (potassium chloride product salt), the mixed salt of sodium nitrate and potassium nitrate, and the remaining mother liquor of the mixed salt. The solution after the mixed salt is dissolved is processed by method e to obtain the resource-based product salt of sodium nitrate and potassium nitrate. The remaining mother liquor is evaporated and dried to obtain mixed salt or partially returned to the heavy metal removal step in step (4) for further processing.

[0012] Further, in step (1), the biomass-based nitrogen-containing wastewater is at least one of landfill leachate, kitchen wastewater, bio-fermentation, aquaculture wastewater, or livestock wastewater.

[0013] Furthermore, in step (1), one or more of the following methods are used for pretreatment: filtration, oil removal, and air flotation.

[0014] Furthermore, in step (1), anaerobic treatment can also be used to recover methane and reduce the load on the nitration reaction system.

[0015] Further, in step (1), the biomass-based nitrogen-containing wastewater has a COD of 3000-80000 mg / L, an ammonia nitrogen of 800-5000 mg / L, and a TDS of 20000-40000 mg / L.

[0016] Furthermore, in step (1), after pretreatment, the COD of the biomass nitrogen-containing wastewater is reduced to 8000mg / L-12000mg / L.

[0017] Further, in step (2), oxygenation is carried out to make the dissolved oxygen concentration in the wastewater 2-6 mg / L, the nitrification reaction time 72-168 hours, the pH 6-8, and the temperature 25-35℃; more preferably, the dissolved oxygen concentration in the wastewater is 2-4 mg / L, the reaction time is 96-144 hours, the pH is 7-8, and the temperature is 30-35℃.

[0018] Furthermore, the nitrate nitrogen concentration in the nitrified wastewater is 500-2000 mg / L, and the COD is 300-500 mg / L.

[0019] Furthermore, in step (3), the TDS in the reverse osmosis concentrate is 60,000-100,000 mg / L, the chloride ion concentration is 18,000-30,000 mg / L, and the nitrate concentration is 15,000-40,000 mg / L; the reverse osmosis permeate can be reused or discharged in compliance with standards.

[0020] Further, in step (3), the nanofiltration permeate is treated by reverse osmosis, and the nanofiltration concentrate is treated by a secondary material membrane treatment system (as shown in CN103626314A). The organic concentrate produced by the primary material membrane can be returned to the incinerator, treated by sedimentation, or enter the miscellaneous salt drying system. The permeate enters the secondary material membrane system. The secondary material membrane concentrate is treated by the hardening system, and the supernatant and dehydrated clear liquid are returned to the nitrification reaction tank. The secondary material membrane permeate enters the RO system.

[0021] Furthermore, in step (4), the fly ash from the waste incineration plant can undergo low-temperature detoxification treatment before entering the fly ash washing system to reduce the dioxin content; or after passing through the fly ash washing system, it can pass through the waste incinerator to reduce the dioxin content. Furthermore, in step (4), the fly ash washing solution is obtained by rinsing the fly ash (which can be done by single-stage or multi-stage washing); Furthermore, in step (4), the TDS in the fly ash washing solution is 120,000-250,000 mg / L, the chloride ion concentration is 40,000-80,000 mg / L, the sodium ion concentration is 15,000-40,000 mg / L, and the potassium ion concentration is 8,000-20,000 mg / L.

[0022] Furthermore, in step (5), the filtration system adopts a combination of sand filtration and ultrafiltration, or a TUF membrane system; Furthermore, in step (5), the NF system can be either primary or secondary, and the concentrated water from the NF system is returned to the washing solution to replenish sulfate ions in the hardening, fluoride removal, and silicon removal system; Further, in step (5), the TDS in the treated mixture is 130,000-280,000 mg / L, the sodium ion concentration is 30,000-70,000 mg / L, the potassium ion concentration is 10,000-40,000 mg / L, the chloride ion concentration is 60,000-140,000 mg / L, and the nitrate concentration is 10,000-30,000 mg / L.

[0023] Furthermore, in step (6), the typical water quality entering the evaporation system can be: TDS of 60,000-80,000 mg / L, chloride ion concentration of 15,000-20,000 mg / L, sulfate concentration of 10,000-15,000 mg / L, and nitrate concentration of 13,000-16,000 mg / L.

[0024] Furthermore, in step (6), the temperature at which the second crystal (sodium chloride product salt) is obtained by evaporation crystallization is 80-120°C and the pressure is 70-200 kPa (A).

[0025] Furthermore, in step (6), the temperature at which the third crystal (agricultural grade potassium nitrate) is obtained by cooling and crystallization is 20-40°C, and the pressure is atmospheric pressure.

[0026] Furthermore, in step (6), the temperature at which the third crystal (industrial grade sodium nitrate) is obtained by cooling and crystallization is 20-40°C, and the pressure is atmospheric pressure; Furthermore, in step (6), the temperature at which the third crystal (industrial grade potassium chloride) is obtained by cooling crystallization is 50-70°C and the pressure is 10-30 kPa.

[0027] Furthermore, in step (6), the method further includes refining the second crystal, and the refined product obtained meets at least the first-grade industrial dry salt standard specified in GB / T5462-2015, with sodium chloride content of 98.5 wt% or higher.

[0028] Furthermore, in step (6), the method further includes refining the third crystal to obtain a refined product, wherein the refined product contains sodium nitrate or potassium nitrate at a concentration of 99.0 wt% or higher; more preferably, the refined crystal is produced using concentrated permeate water generated in the front-end process (e.g., reverse osmosis permeate water from step 3).

[0029] Furthermore, in step (6), the condensate generated by the evaporation system is used for fly ash washing or reused if it meets the reuse standards.

[0030] This invention also provides a treatment system for the co-treatment of biomass nitrogen-containing wastewater and fly ash, and the preparation of inorganic salts, such as... Figure 1 As shown, it includes a process system 1 (mainly for treating nitrogen-containing wastewater), a process system 2 (mainly for treating fly ash), and a process system 3 (mainly for preparing inorganic salts through an evaporation system).

[0031] The process system includes a conditioning pretreatment system, an optional anaerobic system, a nitrification reactor, a membrane bioreactor (MBR system), a nanofiltration system (NF system), and a reverse osmosis system (RO system) connected in sequence. The conditioning pretreatment system includes filtration, oil removal, and air flotation, which are used to remove oil, remove organic pollutants and / or degrade macromolecular organic matter. The optional anaerobic system mainly performs anaerobic treatment. Some biomass nitrogen-containing wastewater (landfill leachate, kitchen wastewater) may not need to undergo anaerobic treatment. The anaerobic sludge produced can be dewatered by sludge treatment equipment and transported off-site. The dewatered sludge from the sludge treatment equipment can be returned to the conditioning pretreatment system. The biomass nitrogen-containing wastewater after pretreatment or anaerobic treatment enters the nitrification reaction tank, which is an oxygenated nitrification reaction system, where nitrifying bacteria convert nitrogen-containing substances into nitrates. The permeate from the membrane bioreactor enters the nanofiltration system, and the sludge produced can be returned to the nitrification tank or sent to the sludge treatment equipment. The nanofiltration permeate from the nanofiltration system enters the reverse osmosis system. The nanofiltration concentrate passes through a secondary material membrane treatment system (as shown in CN103626314A). The organic concentrate produced by the primary material membrane can be returned to the incinerator, treated by sedimentation, or enter the miscellaneous salt drying system. The permeate enters the secondary material membrane system. The secondary material membrane concentrate is treated by the hardening system, and the supernatant and dehydrated clear liquid are returned to the nitrification reaction tank. The permeate from the secondary material membrane enters the reverse osmosis system. The concentrate from the reverse osmosis system enters the second process system, where it is mixed with the fly ash washing liquid used to remove heavy metals and treated synergistically. The permeate from the reverse osmosis system is discharged in compliance with standards or reused. The second process system includes an optional low-temperature detoxification system, fly ash washing system, washing liquid degravation system, washing liquid hardening, defluorination and desilting system, filtration system, second nanofiltration system and oxidation system; Fly ash from incineration plants can be treated in an optional low-temperature detoxification system to reduce the content of toxic substances such as dioxins (fly ash entering high-temperature melting, plasma, or other systems may not require low-temperature detoxification). The fly ash washing system can use recycled process water or evaporation condensate to obtain fly ash washing liquid, which then enters the washing liquid degravimetric system. The washing liquid de-gravity system is used to remove heavy metals such as lead (Pb), cadmium (Cd), and chromium (Cr). It is then mixed with the concentrated water from the reverse osmosis system in process one for co-treatment and enters the washing liquid hardening, fluoride removal, and silicon removal system. The sludge settled in the washing liquid de-gravity system can be treated by sludge treatment equipment, and the dewatered clear liquid can be returned to the washing liquid de-gravity system. After dewatering, the sludge is transported off-site. The washing liquid enters the filtration system after being treated by the hardening, fluoride, and silicon removal system. The precipitated sludge can be treated by the sludge treatment equipment, and the dewatered clear liquid can be returned to the washing liquid hardening, fluoride, and silicon removal system. The dewatered sludge is then transported off-site. The filtration system employs a combination of sand filtration and ultrafiltration, or a TUF membrane system; The nanofiltration system can be a single-stage or two-stage system. The permeate from the nanofiltration system enters the oxidation system, and the concentrate from the nanofiltration system is returned to the hardness removal, fluoride removal, and silicon removal system. The oxidation system removes organic matter from the concentrate in the nanofiltration system, resulting in a mixed solution that enters the third process treatment system. The third process system includes a decarbonization and pH adjustment system, an optional reaction adjustment system, an evaporation and concentration system, a sodium chloride evaporation and crystallization system, a potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride crystallization system), an optional potassium nitrate refining system (which can be replaced by a sodium nitrate refining system), an evaporation mother liquor tank and miscellaneous salt drying equipment, and a reflux device. The reaction regulation system is used to add potassium chloride or sodium nitrate to adjust the ion level. Whether a reaction regulation system is needed depends on the inorganic salt composition of the concentrate and the requirements of the resource-based products. The sodium chloride evaporation crystallization system can obtain sodium chloride product salt (second crystal), and the mother liquor after evaporation enters the potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride crystallization system). The potassium nitrate crystallization system can obtain agricultural-grade potassium nitrate. It is determined whether it needs to enter an optional potassium nitrate refining system as needed. The mother liquor from the potassium nitrate crystallization system and the optional potassium nitrate refining system enters the evaporation mother liquor tank. The dried salt obtained by the aforementioned salt drying equipment is then transported off-site for disposal. The condensate from the evaporation and concentration system, sodium chloride evaporation and crystallization system, potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride crystallization system), and potassium nitrate refining system (which can be replaced by a sodium nitrate refining system) meets the reuse standards and can be reused.

[0032] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. By nitrifying, membrane bioreactor (MBR), nanofiltration (NF) and reverse osmosis (RO) the biomass-based nitrogen-containing wastewater, and then mixing the RO concentrate with the washing liquid from fly ash treatment, the co-treatment of biomass-based nitrogen-containing wastewater and fly ash can be achieved.

[0033] 2. By washing and removing heavy metals from fly ash from waste incineration plants, harmful substances can be significantly reduced and resource utilization improved.

[0034] 3. Before entering the evaporation system, by adjusting the ion ratio of inorganic salts in the concentrate, two kinds of inorganic salts can be obtained in the evaporation system through simple evaporation crystallization and cooling crystallization, and different resource-based products can be obtained as needed.

[0035] 4. The produced water, condensate, and mother liquor generated during the preparation process can be recycled, improving economic efficiency.

[0036] 5. This technical solution has strong water quality adaptability, requires no additional carbon source, and can efficiently treat biomass nitrogen-containing wastewater and fly ash together and prepare inorganic salts. 6. This method is not only economical and efficient, but also helps to reduce carbon emissions, achieve the harmless treatment of pollutants, and utilize the high-value-added product nitrates.

[0037] 7. This technology has significant advantages in terms of civil engineering investment, land area and operating costs, while taking into account both environmental and economic benefits. Attached Figure Description

[0038] Figure 1 This invention relates to a treatment system and process for the co-treatment of biomass-based nitrogen-containing wastewater and fly ash, and the preparation of inorganic salts. Detailed Implementation

[0039] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Examples of the embodiments are shown in the accompanying drawings. It should be understood that the specific embodiments described in the following embodiments of the invention are merely illustrative examples of specific implementations of the invention and are intended to explain the invention, but do not constitute a limitation thereof.

[0040] The endpoints of the ranges and any values ​​disclosed herein are not limited to the exact ranges or values, which should be understood to include those close to them.

[0041] Example 1 A treatment system for the co-treatment of biomass-based nitrogenous wastewater and fly ash, and the preparation of inorganic salts, such as... Figure 1 As shown, it includes a process system 1 (mainly for treating nitrogen-containing wastewater), a process system 2 (mainly for treating fly ash), and a process system 3 (mainly for preparing inorganic salts through an evaporation system).

[0042] The process system includes a conditioning pretreatment system, an optional anaerobic system, a nitrification reactor, a membrane bioreactor (MBR system), a nanofiltration system (NF system), and a reverse osmosis system (RO system) connected in sequence. The conditioning pretreatment system includes filtration, oil removal, and air flotation, which are used to remove oil, remove organic pollutants and / or degrade macromolecular organic matter. The optional anaerobic system mainly performs anaerobic treatment. Some biomass nitrogen-containing wastewater (landfill leachate, kitchen wastewater) may not need to undergo anaerobic treatment. The anaerobic sludge produced can be dewatered by sludge treatment equipment and transported off-site. The dewatered sludge from the sludge treatment equipment can be returned to the conditioning pretreatment system. The biomass nitrogen-containing wastewater after pretreatment or anaerobic treatment enters the nitrification reaction tank, which is an oxygenated nitrification reaction system, where nitrifying bacteria convert nitrogen-containing substances into nitrates. The permeate from the membrane bioreactor enters the nanofiltration system, and the sludge produced can be returned to the nitrification tank. The nanofiltration permeate from the nanofiltration system enters the reverse osmosis system. The nanofiltration concentrate passes through a secondary material membrane treatment system (as shown in CN103626314A). The organic concentrate produced by the primary material membrane can be returned to the incinerator, treated by sedimentation, or enter the miscellaneous salt drying system. The permeate enters the secondary material membrane system. The secondary material membrane concentrate is treated by the hardening system, and the supernatant and dehydrated clear liquid are returned to the nitrification reaction tank. The permeate from the secondary material membrane enters the reverse osmosis system. The concentrate from the reverse osmosis system enters the second process system, where it is mixed with the fly ash washing liquid used to remove heavy metals and treated synergistically. The permeate from the reverse osmosis system is discharged in compliance with standards or reused. The second process system includes an optional low-temperature detoxification system, fly ash washing system, washing liquid degravation system, washing liquid hardening, defluorination and desilting system, filtration system, second nanofiltration system and oxidation system; Fly ash from incineration plants can be treated in an optional low-temperature detoxification system to reduce the content of toxic substances such as dioxins (fly ash entering high-temperature melting, plasma, or other systems may not require low-temperature detoxification). The fly ash washing system can use recycled process water or evaporation condensate to obtain fly ash washing liquid, which then enters the washing liquid degravimetric system. The washing liquid de-gravity system is used to remove heavy metals such as lead (Pb), cadmium (Cd), and chromium (Cr). It is then mixed with the concentrated water from the reverse osmosis system in process one for co-treatment and enters the washing liquid hardening, fluoride removal, and silicon removal system. The sludge settled in the washing liquid de-gravity system can be treated by sludge treatment equipment, and the dewatered clear liquid can be returned to the washing liquid de-gravity system. After dewatering, the sludge is transported off-site. After being processed by the washing liquid hardening, defluorination and desiliconization system, it enters the filtration system. The precipitated sludge can be treated by the sludge treatment equipment. The dewatered clear liquid can be returned to the washing liquid hardening, defluorination and desiliconization system. The dewatered sludge is then transported off-site. The filtration system employs a combination of sand filtration and ultrafiltration, or a TUF membrane system; The nanofiltration system can be a single-stage or two-stage system. The permeate from the nanofiltration system enters the oxidation system, and the concentrate from the nanofiltration system is returned to the hardness removal, fluoride removal, and silicon removal system. The oxidation system removes organic matter from the concentrate in the nanofiltration system, resulting in a mixed solution that enters the third process treatment system. The third process system includes a decarbonization and pH adjustment system, an optional reaction adjustment system, an evaporation and concentration system, a sodium chloride evaporation and crystallization system, a potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride crystallization system), an optional potassium nitrate refining system (which can be replaced by a sodium nitrate refining system), an evaporation mother liquor tank and miscellaneous salt drying equipment, and a reflux device. The reaction regulation system is used to add potassium chloride or sodium nitrate to adjust the ion level. Whether a reaction regulation system is needed depends on the inorganic salt composition of the concentrate and the requirements of the resource-based products. The sodium chloride evaporation crystallization system can obtain sodium chloride product salt (second crystal), and the mother liquor after evaporation enters the potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride crystallization system). The potassium nitrate crystallization system can obtain agricultural-grade potassium nitrate. It is determined whether it needs to enter an optional potassium nitrate refining system as needed. The mother liquor from the potassium nitrate crystallization system and the optional potassium nitrate refining system enters the evaporation mother liquor tank. The dried salt obtained by the aforementioned salt drying equipment is then transported off-site for disposal. The condensate from the evaporation and concentration system, sodium chloride evaporation and crystallization system, potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride crystallization system), and potassium nitrate refining system (which can be replaced by a sodium nitrate refining system) meets the reuse standards and can be reused.

[0043] like Figure 1 As shown, the processing system for Process 3 differs slightly depending on the inorganic salt components and resource utilization requirements in the concentrate, and can be processed in four ways. Taking Method 1 as an example, the inorganic salt components are mainly sodium chloride and sodium nitrate. In the reaction regulation system, potassium chloride salt is added to adjust the ion ratio. Then, the solution is sequentially passed through evaporation and concentration, sodium chloride evaporation and crystallization, potassium nitrate crystallization system and optional potassium nitrate refining system, evaporation mother liquor tank and miscellaneous salt drying equipment, and reflux equipment to obtain sodium chloride product salt, agricultural grade potassium nitrate, industrial grade potassium nitrate and dried miscellaneous salt, respectively.

[0044] Example 2 Following the process in Example 1, this example uses leachate from a waste incineration plant (COD approximately 80,000 mg / L, ammonia nitrogen approximately 3,000 mg / L, TDS approximately 35,000 mg / L). After anaerobic pretreatment, most of the organic matter is removed, and the effluent COD is reduced to approximately 15,000 mg / L. After treatment in a nitrification reactor, the ammonia nitrogen concentration in the nitrified liquid is approximately 10 mg / L, and the ammonia nitrogen conversion rate reaches over 95%. The nitrified liquid is separated through an MBR membrane to obtain MBR permeate and first sludge. The ultrafiltration permeate is subjected to nanofiltration using a first-stage nanofiltration membrane with a molecular weight cutoff of 200-1000 Da and an operating pressure of 0.8-1.2 MPa to obtain first nanofiltration concentrate and first nanofiltration permeate. The first nanofiltration permeate is then subjected to reverse osmosis with an operating pressure of 2.8-3.2 MPa to obtain reverse osmosis concentrate and reverse osmosis permeate. The TDS of the reverse osmosis concentrate is approximately 60,000 mg / L, the chloride ion concentration is approximately 25,000 mg / L, and the nitrate concentration is approximately 22,000 mg / L.

[0045] Part of the sludge produced by ultrafiltration is returned to the nitrification reactor, and the rest is dewatered and transported for treatment.

[0046] After low-temperature detoxification (400℃), the dioxin content of fly ash was below 50 ng-TEQ / kg, meeting the HJ1134-2020 standard. After multi-stage countercurrent rinsing, the rinsing solution entered the heavy metal removal system, where sodium sulfide, PFS, or a heavy metal precipitant was used to precipitate heavy metal ions. No lead or cadmium was detected in the washing solution after heavy metal removal. The reverse osmosis concentrate and the fly ash washing solution after heavy metal removal were mixed at a ratio of 1:0.5-1:5 and then passed through a hardening system to remove calcium and magnesium ions from the mixture. After hardening, no calcium or magnesium ions were detected in the mixture.

[0047] After hardening, the mixture undergoes sand filtration + ultrafiltration, nanofiltration, and oxidation. In this step, the nanofiltration concentrate is returned to the hardening system, while the nanofiltration permeate enters the oxidation system. After oxidation, the mixture enters the reaction conditioning system, where potassium or nitrate regulators are added to adjust the ion ratio of the mixture, ensuring that the amounts of potassium, chloride, sodium, and nitrate ions in the mixture satisfy n(K) = ... + )+ n(Cl - ): n(Na + )+ n(NO3 - It is approximately 0.8.

[0048] After the above treatment, the mixture enters the evaporation system and undergoes a first evaporation at 105°C. Evaporation is stopped when the TDS of the mixture exceeds 300,000 mg / L, yielding a concentrated evaporation solution. The concentrated solution is then transferred to a sodium chloride evaporation crystallization system for a second evaporation at 50°C, yielding a first crystalline product containing sodium chloride and a mother liquor. The mother liquor is transferred to a potassium nitrate evaporation crystallization system and cooled at 20°C, yielding a second crystalline product containing potassium nitrate and a cooling mother liquor. The condensate from these systems is reused for fly ash washing.

[0049] The sodium chloride crystals in the first crystal have a purity >95%, and the second crystal meets the requirements for Grade I agricultural potassium nitrate as specified in GB / T20784-2018. More than 98 wt% of the salts in the landfill leachate and fly ash are recovered. The condensate is recycled for leachate pretreatment and fly ash washing, reducing fresh water consumption. The potassium nitrate undergoes secondary recrystallization, and the product meets the Class I standard of GB / T 1918-2021.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and do not constitute a limitation on the content of the present invention. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed in the present invention and all fall within the protection scope of the present invention.

Claims

1. A method for the co-treatment of biomass-based nitrogenous wastewater and fly ash, and the preparation of inorganic salts, characterized in that, Includes the following steps: (1) Pretreatment of biomass-based nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification; (3) The nitrified wastewater is subjected to MBR and nanofiltration to obtain nanofiltration concentrate and nanofiltration permeate. The nanofiltration concentrate is treated by two-stage material membranes. The concentrate from the first-stage material membrane is organic concentrate, which is returned to the incinerator, treated by sedimentation or entered into the miscellaneous salt drying system. The permeate enters the second-stage material membrane system. The concentrate from the second-stage material membrane is treated by the hardness removal system and then enters the nitrification reaction tank to replenish the system alkalinity. The permeate from the second-stage material membrane and the permeate from nanofiltration are then treated by reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate. (4) The fly ash from the waste incineration plant enters the fly ash washing system. After the fly ash washing liquid removes heavy metals, it is mixed with the reverse osmosis concentrate from step (3) to obtain a mixed liquid. (5) After the mixed liquid enters the hardening, defluorination and desiliconization system, it enters the filtration system. The filtration system adopts a combination of sand filtration and ultrafiltration or tubular microfiltration membrane. The effluent from the filtration system enters the NF system. The NF system permeate enters the oxidation system to remove organic matter and obtain the treated mixed liquid. The NF concentrate is returned to the washing liquid defluorination, hardening and desiliconization system to replenish sulfate. (6) The treated mixture is decarbonized and pH adjusted. The inorganic components in the treated mixture are mainly sodium chloride and sodium nitrate. The resource-based products are required to be sodium chloride and potassium nitrate. Potassium chloride is added for reaction adjustment. After adjustment, the ratio of each ion meets [n(K + )+ n(Cl - )]: [n(Na + )+ n(NO3 - )]=0.8-1.2; then, the following steps are performed: evaporation and concentration, evaporation and crystallization to obtain the second crystal product sodium chloride salt, cooling and crystallization to obtain the third crystal agricultural grade potassium nitrate, and the optional third crystal is refined to obtain the fourth crystal industrial grade potassium nitrate; the remaining mother liquor of the third crystal and / or the fourth crystal is evaporated and dried to obtain mixed salt, or returned to the heavy metal removal step in step (4); In step (4), the fly ash from the waste incineration plant undergoes low-temperature detoxification treatment before entering the fly ash washing system to reduce the dioxin content; or after passing through the fly ash washing system, it passes through the waste incinerator to reduce the dioxin content; in step (4), the TDS in the fly ash washing liquid is 120,000-250,000 mg / L, the chloride ion concentration is 40,000-80,000 mg / L, the sodium ion concentration is 15,000-40,000 mg / L, and the potassium ion concentration is 8,000-20,000 mg / L; In step (6), the temperature for evaporation crystallization to obtain the second crystal is 80-120℃ and the pressure is 70-200 kPa; the temperature for cooling crystallization to obtain the third crystal is 20-40℃ and the pressure is atmospheric pressure; the temperature for cooling crystallization to obtain the third crystal is 50-70℃ and the pressure is 10-30 kPa; step (6) also includes a step of refining the second crystal and the third crystal to obtain a refined product; In step (6), the condensate generated by the evaporation system is used for fly ash washing or reused if it meets the reuse standards.

2. A method for the co-treatment of biomass-based nitrogenous wastewater and fly ash, and the preparation of inorganic salts, characterized in that, Includes the following steps: (1) Pretreatment of biomass-based nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification; (3) The nitrified wastewater is subjected to MBR and nanofiltration to obtain nanofiltration concentrate and nanofiltration permeate. The nanofiltration concentrate is treated by two-stage material membranes. The concentrate from the first-stage material membrane is organic concentrate, which is returned to the incinerator, treated by sedimentation or entered into the miscellaneous salt drying system. The permeate enters the second-stage material membrane system. The concentrate from the second-stage material membrane is treated by the hardness removal system and then enters the nitrification reaction tank to replenish the system alkalinity. The permeate from the second-stage material membrane and the permeate from nanofiltration are then treated by reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate. (4) The fly ash from the waste incineration plant enters the fly ash washing system. After the fly ash washing liquid removes heavy metals, it is mixed with the reverse osmosis concentrate from step (3) to obtain a mixed liquid. (5) After the mixed liquid enters the hardening, defluorination and desiliconization system, it enters the filtration system. The filtration system adopts a combination of sand filtration and ultrafiltration or tubular microfiltration membrane. The effluent from the filtration system enters the NF system. The NF system permeate enters the oxidation system to remove organic matter and obtain the treated mixed liquid. The NF concentrate is returned to the washing liquid defluorination, hardening and desiliconization system to replenish sulfate. (6) The treated mixture is decarbonized and pH adjusted. The inorganic components in the concentrate are mainly sodium chloride and potassium chloride. The resource-based products are required to be sodium chloride and potassium nitrate. Sodium nitrate is added for reaction adjustment. After adjustment, the ratio of each ion meets [n(K + )+n(Cl - )]: [n(Na + )+ n(NO3 - )]=0.8-1.2; then, the following steps are performed: evaporation and concentration, evaporation and crystallization to obtain the second crystal product sodium chloride salt, cooling and crystallization to obtain the third crystal agricultural grade potassium nitrate, and the optional third crystal is refined to obtain the fourth crystal industrial grade potassium nitrate; the remaining mother liquor of the third crystal and / or the fourth crystal is evaporated and dried to obtain mixed salt, or returned to the heavy metal removal step in step (4); In step (4), the fly ash from the waste incineration plant undergoes low-temperature detoxification treatment before entering the fly ash washing system to reduce the dioxin content; or after passing through the fly ash washing system, it passes through the waste incinerator to reduce the dioxin content; in step (4), the TDS in the fly ash washing liquid is 120,000-250,000 mg / L, the chloride ion concentration is 40,000-80,000 mg / L, the sodium ion concentration is 15,000-40,000 mg / L, and the potassium ion concentration is 8,000-20,000 mg / L; In step (6), the temperature for evaporation crystallization to obtain the second crystal is 80-120℃ and the pressure is 70-200 kPa; the temperature for cooling crystallization to obtain the third crystal is 20-40℃ and the pressure is atmospheric pressure; the temperature for cooling crystallization to obtain the third crystal is 50-70℃ and the pressure is 10-30 kPa; step (6) also includes a step of refining the second crystal and the third crystal to obtain a refined product; In step (6), the condensate generated by the evaporation system is used for fly ash washing or reused if it meets the reuse standards.

3. The method as described in claim 1 or 2, characterized in that, In step (1), the biomass-based nitrogen-containing wastewater is at least one of landfill leachate, kitchen wastewater, and biological fermentation wastewater; it is pretreated by one or more methods such as filtration, oil removal, and flotation.

4. The method as described in claim 3, characterized in that, The biomass-based nitrogen-containing wastewater has a COD of 3000-80000 mg / L, an ammonia nitrogen of 800-5000 mg / L, and a TDS of 20000-40000 mg / L.

5. The method as described in claim 1 or 2, characterized in that, In step (2), oxygenation is introduced to make the dissolved oxygen concentration in the wastewater 2-6 mg / L, the nitrification reaction time 72-168 hours, the pH 6-8, and the temperature 25-35℃.

6. The method as described in claim 5, characterized in that, The dissolved oxygen concentration in the wastewater is 2-4 mg / L, the reaction time is 96-144 hours, the pH is 7-8, and the temperature is 30-35℃; the nitrate nitrogen concentration in the nitrified wastewater is 500-2000 mg / L, and the COD is 300-500 mg / L.

7. The method as described in claim 1 or 2, characterized in that, In step (5), the TDS concentration in the treated mixture is 130,000-280,000 mg / L, the sodium ion concentration is 30,000-70,000 mg / L, the potassium ion concentration is 10,000-40,000 mg / L, the chloride ion concentration is 60,000-140,000 mg / L, and the nitrate concentration is 10,000-30,000 mg / L.

8. A processing system for the method of any one of claims 1-7, comprising: Processing system 1, processing system 2, and processing system 3; The process system includes a conditioning pretreatment system, an optional anaerobic system, a nitrification reactor, a membrane bioreactor, a nanofiltration system, a two-stage material membrane system, and a reverse osmosis system, connected in sequence. The conditioning pretreatment system is used for oil removal, removal of organic contaminants and / or degradation of macromolecular organic matter; The biomass nitrogen-containing wastewater after pretreatment or anaerobic treatment enters the nitrification reaction tank, which is an oxygenated nitrification reaction system, where nitrifying bacteria convert nitrogen-containing substances into nitrates. The permeate from the membrane bioreactor enters the nanofiltration system, and the sludge produced is returned to the nitrification tank or enters the sludge treatment equipment. The nanofiltration permeate from the nanofiltration system enters the reverse osmosis system, the nanofiltration concentrate passes through a secondary material membrane treatment system, and the permeate from the secondary material membrane enters the reverse osmosis system. The concentrate from the reverse osmosis system enters the second process system and is mixed with the fly ash washing liquid used to remove heavy metals. The second process system includes an optional low-temperature detoxification system, a fly ash washing system, a fly ash washing and incineration system, a washing liquid degravation system, a washing liquid hardening, defluorination and desiliconization system, a filtration system, a second nanofiltration system and an oxidation system; The fly ash from the incineration plant is treated in an optional low-temperature detoxification system or washed with water before being returned to the incineration system to reduce dioxin content. The fly ash washing system uses recycled process water or evaporation condensate, and the resulting fly ash washing liquid enters the washing liquid degravation system. The washing solution heavy metal removal system is used to remove heavy metals. The treated washing solution is mixed with the concentrated water from the reverse osmosis system of process one and then enters the washing solution hardening, fluoride removal and silicon removal system. The washing liquid enters the filtration system after being treated by a hardening, defluorination and desilicon removal system. The filtration system adopts a combination of sand filtration and ultrafiltration, or a TUF membrane system. The nanofiltration system is either a single-stage or two-stage system. The permeate from the nanofiltration system enters the oxidation system, and the concentrate from the nanofiltration system is returned to the hardness removal, fluoride removal, and silicon removal system. The oxidation system removes organic matter from the concentrate in the nanofiltration system, resulting in a mixed solution that enters the third process treatment system. The third process system includes, in sequence, a decarbonization and pH adjustment system, a reaction adjustment system, an evaporation and concentration system, a sodium chloride evaporation and crystallization system, a nitrate or chloride crystallization system, an optional nitrate or chloride refining system, an evaporation mother liquor tank and miscellaneous salt drying equipment, and a reflux device; The reaction regulation system is used to add potassium chloride or sodium nitrate to adjust the ion level; The sodium chloride evaporation crystallization system obtains sodium chloride product salt, and the remaining mother liquor after evaporation enters the nitrate or chloride crystallization system. The nitrate or chloride crystallization system can obtain nitrates or chlorides, and the remaining mother liquor after crystallization is sent to the evaporation mother liquor tank. The nitrate or chloride is then purified in an optional nitrate or chloride refining system. The mother liquor after evaporation in the evaporation mother liquor tank enters the miscellaneous salt drying equipment to be dried, and the miscellaneous salt is transported off-site for disposal or returned to the water washing liquid deweighting system. The condensate of the evaporation concentration system, sodium chloride evaporation crystallization system, nitrate or chloride crystallization system, and nitrate or chloride refining system meets the reuse standard and is reused.

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