Method for co-processing biomass nitrogenous wastewater and fly ash and preparing inorganic salt

Abstract

The invention belongs to the field of wastewater treatment, and particularly relates to a method for co-treating biomass nitrogen-containing wastewater and fly ash and preparing inorganic salt. The treatment method comprises the following steps: carrying out nitrification, membrane bioreactor (MBR), nanofiltration (NF) and reverse osmosis (RO) on the biomass nitrogen-containing wastewater, mixing the obtained RO concentrated water with a water washing liquid for fly ash treatment, concentrating, adjusting the proportion of inorganic salt, entering an evaporation system to prepare the inorganic salt, and the like, so as to realize the cooperative treatment of the biomass nitrogen-containing wastewater and the fly ash. And harmless and resourceful treatment of pollutants is realized. The invention also provides a processing system for the method.

Description

Technical Field

[0001] The present invention belongs to the field of wastewater treatment, and in particular relates to a method for co-treating biomass nitrogen-containing wastewater and fly ash and preparing inorganic salts. Background Art

[0002] Landfill leachate, restaurant biogas, and other biomass-derived nitrogenous wastewaters contain 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, single processes are incapable of completely removing pollutants and often produce residual concentrates, requiring secondary treatment. Traditional treatment technologies typically involve two steps: nitrification and denitrification, converting ammonia nitrogen into nitrates. Nitrates are then reduced to nitrogen gas through the consumption of a carbon source and released into the atmosphere. Because the carbon-nitrogen ratio in some nitrogenous wastewaters is often unbalanced, additional carbon sources are often required, and this process also results in carbon dioxide emissions into the atmosphere. Furthermore, these traditional methods require large land use, require high civil engineering investment, and are expensive to operate. Furthermore, they fail to fully utilize high-value-added nitrates as a resource.

[0003] Fly ash is a hazardous waste (HW18) generated after the incineration of municipal solid waste. It is rich in heavy metals such as dioxins, mercury, and lead, and exhibits significant leaching toxicity. Improper disposal can easily cause soil and groundwater contamination. The mainstream methods for its disposal are chelation solidification landfill or co-disposal in cement kilns. However, the former requires land and carries the risk of leakage, while the latter is limited by cement kiln capacity and high costs.

[0004] Literature reports suggest that the coordinated disposal of leachate and fly ash can simultaneously address both types of pollutants. For example, CN113503543A discloses an online disposal system and process for fly ash and leachate. The system includes a fly ash conveying system, a plasma melting furnace system, a slag collection and discharge system, a leachate conveying system, a secondary combustion chamber and combustion system, a waste heat boiler system, a quenching tower, and a waste incineration plant flue gas purification system. CN111807576A discloses a method for treating domestic waste leachate using fly ash from domestic waste incineration. The method includes adding aqueous hydrochloric acid to the domestic waste leachate; weighing water and domestic waste incineration fly ash separately, mixing and stirring, and centrifuging for solid-liquid separation to obtain a domestic waste incineration fly ash water wash and a fly ash solid slurry; subjecting the domestic waste incineration fly ash water wash to electrokinetic treatment, capturing gas generated in the electrokinetic anode chamber and directly introducing it into the acidified domestic waste leachate, while simultaneously aerating the domestic waste leachate; scraping the domestic waste leachate to obtain oily nitrogen trichloride and denitrified leachate; weighing an iron-aluminum agent and the fly ash solid slurry, and vacuum drying to obtain fly ash purification powder; and weighing the denitrified leachate and fly ash purification powder, mixing and stirring, and performing solid-liquid separation to obtain a domestic waste leachate purification solution and a gelled fly ash solid slurry. However, the above treatment method is relatively complex and does not adequately recycle resources. Summary of the Invention

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

[0006] A method for co-processing biomass nitrogen-containing wastewater and fly ash and preparing inorganic salts comprises the following steps: (1) Pretreatment of biomass nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification reaction; (3) The wastewater after nitrification is subjected to MBR and nanofiltration to obtain nanofiltration concentrated water and nanofiltration product water. The nanofiltration concentrated water is treated by two-stage material membrane. The first-stage material membrane concentrated water is an organic concentrate, and the product water enters the second-stage material membrane system. The second-stage material membrane concentrated water is treated by the hardness removal system and then enters the nitrification reaction tank to supplement the system alkalinity. The second-stage material membrane product water and the nanofiltration product water are then subjected to reverse osmosis treatment to obtain reverse osmosis product water and reverse osmosis concentrated water; (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 concentrated water from step (3) to obtain a mixed liquid; (5) The mixed liquid enters the hardness, fluorine and silicon removal system and then enters the filtration system. The effluent of the filtration system enters the NF system. The water produced by the NF system enters the oxidation system to remove organic matter to obtain a treated mixed liquid. The concentrated water of the NF system is returned to the water washing liquid defluorine, hardness and silicon removal system to replenish sulfate; (6) Decarbonize and adjust the pH of the treated mixed liquid, and then use any of the methods in the evaporation system to treat it according to the inorganic salt components in the treated mixed liquid and the requirements of the resource-based products; a: The inorganic components are mainly sodium chloride and sodium nitrate. The resource products are required to be sodium chloride and potassium nitrate. Potassium chloride is added to adjust the reaction. After adjustment, the ratio of each ion meets [n(K + )+ n(Cl - )]: [n(Na + )+ n(NO 3- )]=0.8-1.2; then, evaporation concentration and evaporation crystallization are carried out in sequence to obtain a second crystal (sodium chloride product salt), cooling crystallization is carried out to obtain a third crystal (agricultural grade potassium nitrate), and the third crystal is optionally refined to obtain a 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 miscellaneous salts, or refluxed to the heavy metal removal step of step (4); b: The inorganic components are mainly sodium chloride and sodium nitrate, and the resource products are required to be sodium chloride and sodium nitrate; evaporation concentration and evaporation crystallization are carried out in sequence to obtain a second crystal (sodium chloride product salt), cooling crystallization is carried out to obtain a third crystal (industrial grade sodium nitrate), and the third crystal is optionally refined to obtain a fourth crystal (molten salt grade sodium nitrate); the remaining mother liquor of the third crystal and / or fourth crystal is evaporated and dried to obtain miscellaneous salts, or is refluxed to the water wash liquid weight removal system; c: The inorganic components are mainly sodium chloride and potassium chloride. The resource products are required to be sodium chloride and potassium nitrate. Sodium nitrate is added to adjust the reaction. After adjustment, the ratio of each ion meets [n(K + )+ n(Cl - )]: [n(Na + )+ n(NO 3- )]=0.8-1.2; then, evaporation concentration and evaporation crystallization are carried out in sequence to obtain a second crystal (sodium chloride product salt), cooling crystallization is carried out to obtain a third crystal (agricultural grade potassium nitrate), and the third crystal is optionally refined to obtain a 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 miscellaneous salts, or refluxed to the heavy metal removal step of step (4); d: The inorganic components are mainly sodium chloride and potassium chloride, and the resource products are required to be sodium chloride and potassium chloride; evaporation concentration and evaporation crystallization are carried out in sequence to obtain the second crystal (sodium chloride product salt), cooling crystallization is carried out to obtain the third crystal (industrial grade potassium chloride), and the remaining mother liquor of the third crystal is evaporated and dried to obtain miscellaneous salts, or refluxed to the heavy metal removal step of step (4).

[0007] e: The inorganic components are mainly sodium nitrate and potassium nitrate, and the resource products are required to be sodium nitrate and potassium nitrate; evaporation concentration and evaporation crystallization are carried out in sequence to obtain the second crystal (sodium nitrate product salt), and freeze crystallization is used to obtain the third crystal (industrial grade potassium nitrate). The remaining mother liquor of the third crystal is evaporated and dried to obtain miscellaneous salts or partially refluxed to the heavy metal removal step of step (4) for further treatment.

[0008] f: The inorganic components are mainly sodium chloride, potassium chloride and sodium nitrate, and the resource products are required to be sodium chloride, potassium chloride and sodium nitrate; first, evaporation and concentration are carried out, and then cooling crystallization and evaporation crystallization are combined 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 dissolved solution after the mixed salt is dissolved is treated by method c or method d to obtain the resource product salt of sodium chloride and potassium chloride. The remaining mother liquor is evaporated and dried to obtain miscellaneous salts or partially refluxed to the heavy metal removal step of step (4) for further treatment.

[0009] g: The inorganic components are mainly sodium chloride, potassium chloride and potassium nitrate, and the resource products are required to be sodium chloride, potassium chloride and potassium nitrate; first, evaporation and concentration are carried out, and then cooling crystallization and evaporation crystallization are combined to obtain the second crystal (potassium nitrate product salt), the mixed salt of sodium chloride and potassium chloride, and the remaining mother liquor of the mixed salt. The dissolved solution after the mixed salt is dissolved is treated by method c or method d to obtain the resource product salt of sodium chloride and potassium chloride. The remaining mother liquor is evaporated and dried to obtain miscellaneous salts or partially refluxed to the heavy metal removal step of step (4) for further treatment.

[0010] h: The inorganic components are mainly sodium chloride, sodium nitrate and potassium nitrate, and the resource products are required to be sodium chloride, sodium nitrate and potassium nitrate; first, evaporation and concentration are carried out, and then evaporation crystallization is combined with cooling crystallization to obtain the second crystal (sodium chloride product salt), the mixed salt of sodium nitrate and potassium nitrate, and the remaining mother liquor of the mixed salt. The dissolved solution after the mixed salt is dissolved is treated by method e to obtain the resource product salt of sodium nitrate and potassium nitrate. The remaining mother liquor is evaporated and dried to obtain miscellaneous salts or partially refluxed to the heavy metal removal step of step (4) for further treatment.

[0011] i: The inorganic components are mainly potassium chloride, sodium nitrate and potassium nitrate, and the resource products are required to be potassium chloride, sodium nitrate and potassium nitrate; first, evaporation and concentration are carried out, and then evaporation crystallization is combined with cooling crystallization to obtain a second crystal (potassium chloride product salt), a mixed salt of sodium nitrate and potassium nitrate, and the remaining mother liquor of the mixed salt. The dissolved solution after the mixed salt is dissolved is treated by method e to obtain resource product salts of sodium nitrate and potassium nitrate. The remaining mother liquor is evaporated and dried to obtain miscellaneous salts or partially refluxed to the heavy metal removal step of step (4) for further treatment.

[0012] Furthermore, in step (1), the biomass nitrogen-containing wastewater is at least one of landfill leachate, restaurant biogas, biological fermentation, aquaculture wastewater, or livestock wastewater.

[0013] Furthermore, in step (1), pretreatment is performed by one or more methods including filtration, oil removal, and flotation.

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

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

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

[0017] Furthermore, in step (2), oxygen is introduced so that the dissolved oxygen concentration in the wastewater is 2-6 mg / L, the nitrification reaction time is 72-168 hours, the pH is 6-8, and the temperature is 25-35°C; 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°C.

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

[0019] Furthermore, in step (3), the TDS of the reverse osmosis concentrated water 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 produced water can be reused or discharged in compliance with the standards.

[0020] Furthermore, in step (3), the nanofiltration water is subjected to reverse osmosis treatment, and the nanofiltration concentrated water passes through a secondary material membrane treatment system (as shown in CN103626314A). The organic concentrated liquid produced by the primary material membrane can be returned to the incinerator, precipitated or enter the salt drying system, and the produced water enters the secondary material membrane system. After the secondary material membrane concentrated water is treated by the hardness removal system, the supernatant and the dehydrated clear liquid are returned to the nitrification reaction tank, and the secondary material membrane produced water enters the RO system.

[0021] Furthermore, in step (4), the fly ash from the waste incineration plant may be subjected to a 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 may be passed through the waste incinerator to reduce the dioxin content; Furthermore, in step (4), the fly ash washing liquid is obtained by rinsing the fly ash (single-stage or multi-stage washing may be used); Furthermore, in step (4), the TDS of 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.

[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 a primary or secondary system, and the concentrated water of the NF system is returned to the water washing liquid de-hardness, de-fluorination and de-siliconization system to supplement sulfate; Furthermore, in step (5), the TDS of the treated mixed solution 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 may 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 of evaporation crystallization to obtain the second crystal (sodium chloride product salt) is 80-120° C. and the pressure is 70-200 KPa (A).

[0025] Furthermore, in step (6), the temperature of the cooling crystallization to obtain the third crystal (agricultural grade potassium nitrate) is 20-40° C. and the pressure is normal pressure.

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

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

[0028] Furthermore, in step (6), the method further comprises refining the third crystal to obtain a refined product, wherein the sodium nitrate or potassium nitrate in the refined product is above 99.0 wt %. More preferably, the refined crystallization uses concentrated water produced in the front-end process (e.g., reverse osmosis water produced in step 3).

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

[0030] The present invention also provides a treatment system for the coordinated treatment of biomass nitrogen-containing wastewater and fly ash and the preparation of inorganic salts, such as Figure 1 As shown, it includes process one treatment system (mainly for nitrogen-containing wastewater treatment), process two treatment system (mainly for fly ash treatment), and process three treatment system (mainly for the evaporation system to prepare inorganic salts).

[0031] Process 1 treatment system, including a conditioning pretreatment system, an optional anaerobic system, a nitrification reaction tank, a membrane biological reactor system (MBR system), a nanofiltration system (NF system), and a reverse osmosis system (RO system) connected in sequence; The conditioning and pretreatment system includes filtration, oil removal, flotation, etc., 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-based nitrogen-containing wastewater (landfill leachate, restaurant biogas) may not undergo anaerobic treatment. The anaerobic sludge produced can be dehydrated by the sludge treatment equipment and then transported out. The dehydrated clear liquid from the sludge treatment equipment can be returned to the conditioning pretreatment system. The biomass nitrogen-containing wastewater treated by the pretreatment system or the anaerobic system is regulated to enter the nitrification reaction tank, which is an aerobic nitrification reaction system, where nitrifying bacteria convert nitrogen-containing substances into nitrates; The water produced by the membrane biological reaction system enters the nanofiltration system, and the generated sludge can be returned to the nitrification reaction tank or enter the sludge treatment equipment; The nanofiltration water produced by the nanofiltration system enters the reverse osmosis system, and the nanofiltration concentrated water passes through the secondary material membrane treatment system (as shown in CN103626314A). The organic concentrated liquid produced by the primary material membrane can be returned to the incinerator, precipitated or entered into the salt drying system, and the produced water enters the secondary material membrane system. The secondary material membrane concentrated water is treated by the hardness removal system, and the supernatant and dehydrated clear liquid are returned to the nitrification reaction tank. The secondary material membrane produced water enters the reverse osmosis system; The concentrated water from the reverse osmosis system enters the second process system, is mixed with the fly ash water washing liquid for removing heavy metals, and is synergistically treated. The reverse osmosis produced water meets the standards for discharge or reuse. Process II system, including optional low-temperature detoxification system, fly ash washing system, wash liquid weight removal system, wash liquid hardness, fluorine and silicon removal system, filtration system, second nanofiltration system and oxidation system; Fly ash from incineration plants enters an optional low-temperature detoxification system to reduce the content of toxic substances such as dioxins (fly ash entering high-temperature melting, plasma, etc. systems does not require low-temperature detoxification treatment); The fly ash washing system can use recycled process water or evaporated condensed water to obtain fly ash washing liquid which enters the washing liquid weight removal system; The water wash liquid de-weighting system is used to remove heavy metals such as lead (Pb), cadmium (Cd), and chromium (Cr). The water wash liquid is then mixed with the concentrated water from the reverse osmosis system in process one for collaborative treatment and then enters the water wash liquid de-hardness, de-fluorination, and de-siliconization system. The precipitated sludge from the water wash liquid de-weighting system can be treated by sludge treatment equipment, and the dehydrated clear liquid can be returned to the water wash liquid de-weighting system. The dehydrated sludge is then transported out. The water washing liquid is processed by the hardness, fluorine and silicon removal system and then enters the filtration system. The precipitated sludge can be processed by the sludge treatment equipment. The dehydrated clear liquid can be returned to the water washing liquid hardness, fluorine and silicon removal system. The sludge is transported out after dehydration. The filtration system uses a combination of sand filtration and ultrafiltration, or a TUF membrane system; The nanofiltration system can be a single-stage or a two-stage system. The water produced by the nanofiltration system flows into the oxidation system, and the concentrated water of the nanofiltration system flows back to the hardness, fluorine and silicon removal system. The oxidation system removes organic matter from the concentrated water of the nanofiltration system to obtain a mixed liquid, which enters the process three treatment system; Process three treatment system, including sequentially connected decarbonization and pH adjustment system, optional reaction adjustment system, evaporation concentration system, sodium chloride evaporation crystallization system, potassium nitrate crystallization system (replaceable with sodium nitrate crystallization system or potassium chloride crystallization system), optional potassium nitrate refining system (replaceable with sodium nitrate refining system), evaporation mother liquor tank and miscellaneous salt drying equipment, and reflux equipment; The reaction regulating system is used to add potassium chloride or sodium nitrate to adjust the ion level. The need for a reaction regulating system is determined based on the inorganic salt components in the concentrate and the requirements of the resource product. 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, and whether it needs to enter the optional potassium nitrate refining system is determined according to needs. The mother liquor of the potassium nitrate crystallization system and the optional potassium nitrate refining system enters the evaporation mother liquor tank; The miscellaneous salt drying equipment is used to dry the miscellaneous salt and then transport it for disposal; The condensate from the evaporation and concentration system, the sodium chloride evaporation and crystallization system, the potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride purification system), and the potassium nitrate refining system (which can be replaced by a sodium nitrate refining system) can be reused if it meets the reuse standards.

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

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

[0035] 4. The produced water, condensate, mother liquor, etc. in the preparation process can be recycled to improve economic benefits.

[0036] 5. This technical solution has strong adaptability to water quality and does not require additional carbon sources. It can efficiently treat biomass nitrogen-containing wastewater and fly ash and prepare inorganic salts; 6. This method is not only economical and efficient, but also helps reduce carbon emissions, achieve harmless treatment of pollutants and resource utilization of high value-added products such as nitrates.

[0037] 7. This technology has significant advantages in terms of civil engineering investment, floor space and operating costs, while taking into account both environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention provides a treatment system and process for the coordinated treatment of biomass nitrogen-containing wastewater and fly ash and the preparation of inorganic salts. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention is 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 present invention are only exemplary descriptions of the specific embodiments of the present invention, intended to be used for explaining the present invention, and do not constitute a limitation of the present invention.

[0040] The endpoints of ranges and any values ​​disclosed herein are not limited to the exact range or value, and these ranges or values ​​should be understood to include approximations to these ranges.

[0041] Example 1 A treatment system for the coordinated treatment of biomass nitrogen-containing wastewater and fly ash and the preparation of inorganic salts, such as Figure 1 As shown, it includes process one treatment system (mainly for nitrogen-containing wastewater treatment), process two treatment system (mainly for fly ash treatment), and process three treatment system (mainly for the evaporation system to prepare inorganic salts).

[0042] Process 1 treatment system, including a conditioning pretreatment system, an optional anaerobic system, a nitrification reaction tank, a membrane biological reactor system (MBR system), a nanofiltration system (NF system), and a reverse osmosis system (RO system) connected in sequence; The conditioning and pretreatment system includes filtration, oil removal, flotation, etc., 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-based nitrogen-containing wastewater (landfill leachate, restaurant biogas) may not undergo anaerobic treatment. The anaerobic sludge produced can be dehydrated by the sludge treatment equipment and then transported out. The dehydrated clear liquid from the sludge treatment equipment can be returned to the conditioning pretreatment system. The biomass nitrogen-containing wastewater treated by the pretreatment system or the anaerobic system is regulated to enter the nitrification reaction tank, which is an aerobic nitrification reaction system, where nitrifying bacteria convert nitrogen-containing substances into nitrates; The produced water of the membrane biological reaction system enters the nanofiltration system, and the produced sludge can be returned to the nitrification reaction tank; The nanofiltration water produced by the nanofiltration system enters the reverse osmosis system, and the nanofiltration concentrated water passes through the secondary material membrane treatment system (as shown in CN103626314A). The organic concentrated liquid produced by the primary material membrane can be returned to the incinerator, precipitated or entered into the salt drying system, and the produced water enters the secondary material membrane system. The secondary material membrane concentrated water is treated by the hardness removal system, and the supernatant and dehydrated clear liquid are returned to the nitrification reaction tank. The secondary material membrane produced water enters the reverse osmosis system; The concentrated water from the reverse osmosis system enters the second process system, is mixed with the fly ash water washing liquid for removing heavy metals, and is synergistically treated. The reverse osmosis produced water meets the standards for discharge or reuse. Process II system, including optional low-temperature detoxification system, fly ash washing system, wash liquid weight removal system, wash liquid hardness, fluorine and silicon removal system, filtration system, second nanofiltration system and oxidation system; Fly ash from incineration plants enters an optional low-temperature detoxification system to reduce the content of toxic substances such as dioxins (fly ash entering high-temperature melting, plasma, etc. systems does not require low-temperature detoxification treatment); The fly ash washing system can use recycled process water or evaporated condensed water to obtain fly ash washing liquid which enters the washing liquid weight removal system; The water wash liquid de-weighting system is used to remove heavy metals such as lead (Pb), cadmium (Cd), and chromium (Cr). The water wash liquid is then mixed with the concentrated water from the reverse osmosis system in process one for collaborative treatment and then enters the water wash liquid de-hardness, de-fluorination, and de-siliconization system. The precipitated sludge from the water wash liquid de-weighting system can be treated by sludge treatment equipment, and the dehydrated clear liquid can be returned to the water wash liquid de-weighting system. The dehydrated sludge is then transported out. The water washing liquid enters the filtration system after being processed by the hardness, fluorine and silicon removal system, and the precipitated sludge can be processed by the sludge treatment equipment, and the dehydrated clear liquid can be returned to the water washing liquid hardness, fluorine and silicon removal system, and the sludge is transported out after dehydration; The filtration system uses a combination of sand filtration and ultrafiltration, or a TUF membrane system; The nanofiltration system can be a single-stage or a two-stage system. The water produced by the nanofiltration system flows into the oxidation system, and the concentrated water of the nanofiltration system flows back to the hardness, fluorine and silicon removal system. The oxidation system removes organic matter from the concentrated water of the nanofiltration system to obtain a mixed liquid, which enters the process three treatment system; Process three treatment system, including sequentially connected decarbonization and pH adjustment system, optional reaction adjustment system, evaporation concentration system, sodium chloride evaporation crystallization system, potassium nitrate crystallization system (replaceable with sodium nitrate crystallization system or potassium chloride crystallization system), optional potassium nitrate refining system (replaceable with sodium nitrate refining system), evaporation mother liquor tank and miscellaneous salt drying equipment, and reflux equipment; The reaction regulating system is used to add potassium chloride or sodium nitrate to adjust the ion level. The need for a reaction regulating system is determined based on the inorganic salt components in the concentrate and the requirements of the resource product. 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, and whether it needs to enter the optional potassium nitrate refining system is determined according to needs. The mother liquor of the potassium nitrate crystallization system and the optional potassium nitrate refining system enters the evaporation mother liquor tank; The miscellaneous salt drying equipment is used to dry the miscellaneous salt and then transport it for disposal; The condensate from the evaporation and concentration system, the sodium chloride evaporation and crystallization system, the potassium nitrate crystallization system (which can be replaced by a sodium nitrate crystallization system or a potassium chloride purification system), and the potassium nitrate refining system (which can be replaced by a sodium nitrate refining system) can be reused if it meets the reuse standards.

[0043] like Figure 1 As shown, the treatment system in process three varies slightly depending on the inorganic salt components in the concentrate and the requirements for resource-based products, and four treatment methods can be used. Taking method 1 as an example, the inorganic salt components are mainly sodium chloride and sodium nitrate. In the reaction regulation system, potassium chloride is added to adjust the ion ratio. Then, through evaporation concentration, sodium chloride evaporation crystallization, potassium nitrate crystallization system and optional potassium nitrate refining system, evaporation mother liquor tank and miscellaneous salt drying equipment, and reflux equipment, sodium chloride product salt, agricultural-grade potassium nitrate, industrial-grade potassium nitrate, and dried miscellaneous salts are obtained respectively.

[0044] Example 2 Following the process of Example 1, this example uses leachate from a waste incineration plant (COD approximately 80,000 mg / L, ammonia nitrogen approximately 3,000 mg / L, and TDS approximately 35,000 mg / L). After anaerobic pretreatment, the majority of organic matter is removed, reducing the effluent COD to approximately 15,000 mg / L. After treatment in the nitrification reaction tank, the ammonia nitrogen concentration of the nitrified liquid is approximately 10 mg / L, with an ammonia nitrogen conversion rate exceeding 95%. The nitrified liquid is separated by the MBR membrane to produce MBR product water and primary sludge. The ultrafiltration product water is nanofiltered 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, producing a first nanofiltration concentrate and first nanofiltration product water. The first nanofiltration product water is then subjected to reverse osmosis at an operating pressure of 2.8-3.2 MPa to produce reverse osmosis concentrate and reverse osmosis product water. Among them, the TDS of reverse osmosis concentrated water is about 60,000 mg / L, the chloride ion concentration is about 25,000 mg / L, and the nitrate concentration is about 22,000 mg / L.

[0045] Part of the sludge produced by ultrafiltration is returned to the nitrification reaction tank, and the rest is dehydrated and transported for external treatment.

[0046] After low-temperature detoxification (400°C), the fly ash's dioxin content is below 50 ng-TEQ / kg, meeting the HJ1134-2020 standard. After multi-stage countercurrent rinsing, the rinse liquid enters a de-weighting system, where sodium sulfide, PFS, or a heavy metal precipitator is used to precipitate heavy metal ions. No lead or cadmium was detected in the wash liquid after de-weighting. Reverse osmosis concentrate is mixed with the heavy metal-depleted fly ash wash water in a ratio of 1:0.5-1:5. The mixture is then passed through a hardness removal system to remove calcium and magnesium ions. After hardness removal, no calcium or magnesium ions are detected in the mixed liquid.

[0047] After hardness removal, the mixed solution is subjected to sand filtration + ultrafiltration, nanofiltration and oxidation treatment. In this step, the nanofiltration concentrated water is returned to the hardness removal system, and the nanofiltration product water enters the oxidation system. After oxidation treatment, the mixed solution enters the reaction regulation system, and potassium salt or nitrate regulator is added to the system to adjust the ion ratio of the mixed solution so that the amount of potassium ions, chloride ions, sodium ions and nitrate ions in the mixed solution meets n(K + )+ n(Cl - ): n(Na + )+ n(NO3 - ) is approximately 0.8.

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

[0049] The sodium chloride purity of the first crystallized product is >95%, and the second crystallized product meets the requirements for first-grade potassium nitrate for agricultural use as specified in GB / T 20784-2018. Over 98% by weight of the salts in the landfill leachate and fly ash are recovered. Condensate water is recycled for leachate pretreatment and fly ash rinsing, reducing fresh water consumption. Potassium nitrate undergoes secondary recrystallization, and the product meets the GB / T 1918-2021 Class I standard.

[0050] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and do not constitute a limitation of the present invention. Within the technical concept of the present invention, the technical solutions of the present invention may be subjected to various simple modifications, including combining the various technical features in any other appropriate manner. These simple modifications and combinations should also be considered as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for co-processing biomass nitrogen-containing wastewater and fly ash and preparing inorganic salts, characterized in that: The steps include: (1) Pretreatment of biomass nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification reaction; (3) The wastewater after nitrification is subjected to MBR and nanofiltration to obtain nanofiltration concentrated water and nanofiltration product water. The nanofiltration concentrated water is treated by two-stage material membrane. The first-stage material membrane concentrated water is an organic concentrate, and the product water enters the second-stage material membrane system. The second-stage material membrane concentrated water is treated by the hardness removal system and then enters the nitrification reaction tank to supplement the system alkalinity. The second-stage material membrane product water and the nanofiltration product water are then subjected to reverse osmosis treatment to obtain reverse osmosis product water and reverse osmosis concentrated water; (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 concentrated water from step (3) to obtain a mixed liquid; (5) The mixed liquid enters the hardness, fluorine and silicon removal system and then enters the filtration system. The filtration system uses a combination of sand filtration and ultrafiltration or a tubular microfiltration membrane. The effluent of the filtration system enters the NF system. The water produced by the NF system enters the oxidation system to remove organic matter and obtain a treated mixed liquid. The NF concentrated water is returned to the water washing liquid defluorine, hardness and silicon removal system to replenish sulfate; (6) Decarbonize and adjust the pH of the treated mixed liquor. The inorganic components in the treated mixed liquor are mainly sodium chloride and sodium nitrate. The resource products are required to be sodium chloride and potassium nitrate. Potassium chloride is added to adjust the reaction. After adjustment, the ratio of each ion meets [n(K + )+ n(Cl - )]: [n(Na + )+ n(NO 3- )]=0.8-1.2; then, evaporation concentration, evaporation crystallization to obtain a second crystal, cooling crystallization to obtain a third crystal, and optional purification of the third crystal to obtain a fourth crystal; the remaining mother liquor of the third crystal and / or the fourth crystal is evaporated and dried to obtain impurity salts, or refluxed to the heavy metal removal step of step (4).

2. A method for co-processing biomass nitrogen-containing wastewater and fly ash and preparing inorganic salts, characterized in that: The steps include: (1) Pretreatment of biomass nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification reaction; (3) The wastewater after nitrification is subjected to MBR and nanofiltration to obtain nanofiltration concentrated water and nanofiltration product water. The nanofiltration concentrated water is treated by two-stage material membrane. The first-stage material membrane concentrated water is an organic concentrate, and the product water enters the second-stage material membrane system. The second-stage material membrane concentrated water is treated by the hardness removal system and then enters the nitrification reaction tank to supplement the system alkalinity. The second-stage material membrane product water and the nanofiltration product water are then subjected to reverse osmosis treatment to obtain reverse osmosis product water and reverse osmosis concentrated water; (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 concentrated water from step (3) to obtain a mixed liquid; (5) The mixed liquid enters the hardness, fluorine and silicon removal system and then enters the filtration system. The filtration system uses a combination of sand filtration and ultrafiltration or a tubular microfiltration membrane. The effluent of the filtration system enters the NF system. The water produced by the NF system enters the oxidation system to remove organic matter and obtain a treated mixed liquid. The NF concentrated water is returned to the water washing liquid defluorine, hardness and silicon removal system to replenish sulfate; (6) The treated mixed liquor is decarbonized and the pH is adjusted. The inorganic components in the concentrated liquor are mainly sodium chloride and sodium nitrate, and the resource products are required to be sodium chloride and sodium nitrate; evaporation concentration and evaporation crystallization are carried out in sequence to obtain a second crystal, cooling crystallization is carried out to obtain a third crystal, and the third crystal is optionally refined to obtain a fourth crystal; the remaining mother liquor of the third crystal and / or the fourth crystal is evaporated and dried to obtain miscellaneous salts, or refluxed to the heavy metal removal step of step (4).

3. A method for synergistically treating biomass nitrogen-containing wastewater and fly ash and preparing inorganic salts, characterized in that: The steps include: (1) Pretreatment of biomass nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification reaction; (3) The wastewater after nitrification is subjected to MBR and nanofiltration to obtain nanofiltration concentrated water and nanofiltration product water. The nanofiltration concentrated water is treated by two-stage material membrane. The first-stage material membrane concentrated water is an organic concentrate, and the product water enters the second-stage material membrane system. The second-stage material membrane concentrated water is treated by the hardness removal system and then enters the nitrification reaction tank to supplement the system alkalinity. The second-stage material membrane product water and the nanofiltration product water are then subjected to reverse osmosis treatment to obtain reverse osmosis product water and reverse osmosis concentrated water; (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 concentrated water from step (3) to obtain a mixed liquid; (5) The mixed liquid enters the hardness, fluorine and silicon removal system and then enters the filtration system. The filtration system uses a combination of sand filtration and ultrafiltration or a tubular microfiltration membrane. The effluent of the filtration system enters the NF system. The water produced by the NF system enters the oxidation system to remove organic matter and obtain a treated mixed liquid. The NF concentrated water is returned to the water washing liquid defluorine, hardness and silicon removal system to replenish sulfate; (6) Decarbonize and adjust the pH of the treated mixed liquor. The inorganic components in the concentrated liquor are mainly sodium chloride and potassium chloride. The resource products are required to be sodium chloride and potassium nitrate. Sodium nitrate is added to adjust the reaction. After adjustment, the ratio of each ion meets [n(K + )+n(Cl - )]: [n(Na + )+ n(NO 3- )]=0.8-1.2; then, evaporation concentration, evaporation crystallization to obtain a second crystal, cooling crystallization to obtain a third crystal, and optional purification of the third crystal to obtain a fourth crystal; the remaining mother liquor of the third crystal and / or the fourth crystal is evaporated and dried to obtain impurity salts, or refluxed to the heavy metal removal step of step (4).

4. A method for co-processing biomass nitrogen-containing wastewater and fly ash and preparing inorganic salts, characterized in that: The steps include: (1) Pretreatment of biomass nitrogen-containing wastewater for oil removal, removal of organic pollutants and / or degradation of macromolecular organic matter; (2) The pretreated wastewater undergoes nitrification reaction; (3) The wastewater after nitrification is subjected to MBR, nanofiltration and reverse osmosis to obtain nanofiltration concentrated water and nanofiltration product water; (3) The wastewater after nitrification is subjected to MBR and nanofiltration to obtain nanofiltration concentrated water and nanofiltration product water. The nanofiltration concentrated water is treated by two-stage material membrane. The first-stage material membrane concentrated water is an organic concentrate, and the product water enters the second-stage material membrane system. The second-stage material membrane concentrated water is treated by the hardness removal system and then enters the nitrification reaction tank to supplement the system alkalinity. The second-stage material membrane product water and the nanofiltration product water are then subjected to reverse osmosis treatment to obtain reverse osmosis product water and reverse osmosis concentrated water; (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 concentrated water from step (3) to obtain a mixed liquid; (5) The mixed liquid enters the hardness, fluorine and silicon removal system and then enters the filtration system. The filtration system uses a combination of sand filtration and ultrafiltration or a tubular microfiltration membrane. The effluent of the filtration system enters the NF system. The water produced by the NF system enters the oxidation system to remove organic matter and obtain a treated mixed liquid. The NF concentrated water is returned to the water washing liquid defluorine, hardness and silicon removal system to replenish sulfate; (6) Decarbonizing and adjusting the pH of the treated mixed liquor. The inorganic components in the treated mixed liquor are mainly sodium chloride and potassium chloride, and the resource products are required to be sodium chloride and potassium chloride. Evaporation concentration and evaporation crystallization are carried out in sequence to obtain the second crystal, and cooling crystallization is carried out to obtain the third crystal. The remaining mother liquor of the third crystal is evaporated and dried to obtain miscellaneous salts, or refluxed to the heavy metal removal step of step (4).

5. The method according to any one of claims 1 to 4, characterized in that In step (1), the biomass nitrogen-containing wastewater is at least one of landfill leachate, restaurant biogas, and biological fermentation wastewater; and is pretreated by one or more of filtration, oil removal, and flotation; Preferably, the biomass nitrogen-containing wastewater has a COD of 3000-80000 mg / L, ammonia nitrogen of 800-5000 mg / L, and a TDS of 20000-40000 mg / L; More preferably, after pretreatment, the COD of the biomass nitrogen-containing wastewater is reduced to 8000 mg / L-12000 mg / L.

6. The preparation method according to any one of claims 1 to 4, wherein In step (2), oxygen is introduced so that the dissolved oxygen concentration in the wastewater is 2-6 mg / L, the nitrification reaction time is 72-168 hours, the pH is 6-8, and the temperature is 25-35°C; 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°C; More preferably, the nitrate nitrogen concentration in the wastewater after nitrification is 500-2000 mg / L, and the COD is 300-500 mg / L.

7. The method according to any one of claims 1 to 4, characterized in that In step (4), the fly ash from the waste incineration plant is subjected to 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 is passed through the waste incinerator to reduce the dioxin content; Preferably, in step (4), the TDS of 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.

8. The method according to any one of claims 1 to 4, characterized in that In step (5), the TDS of the treated mixed solution 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.

9. The method according to any one of claims 1 to 4, wherein In step (6), the temperature of the second crystals obtained by evaporation crystallization is 80-120°C and the pressure is 70-200 KPa (A); the temperature of the third crystals obtained by cooling crystallization is 20-40°C and the pressure is normal pressure; the temperature of the third crystals obtained by cooling crystallization is 50-70°C and the pressure is 10-30 KPa; step (6) also includes the step of refining the second crystals and the third crystals to obtain a refined product.

10. A processing system for the method according to any one of claims 1 to 9, comprising: Process 1 processing system, process 2 processing system, process 3 processing system; Process 1 treatment system, including a conditioning pretreatment system, an optional anaerobic system, a nitrification reaction tank, a membrane bioreactor system (MBR system), a nanofiltration system (NF system), a two-stage material membrane system, and a reverse osmosis system (RO system) connected in sequence; The conditioning pretreatment system is used for removing oil, removing organic pollutants and / or degrading macromolecular organic matter; The biomass nitrogen-containing wastewater treated by the pretreatment system or the anaerobic system is regulated to enter the nitrification reaction tank, which is an aerobic nitrification reaction system, where nitrifying bacteria convert nitrogen-containing substances into nitrates; The produced water of the membrane biological reaction system enters the nanofiltration system, and the produced sludge flows back to the nitrification reaction tank or enters the sludge treatment equipment; The nanofiltration water produced by the nanofiltration system enters the reverse osmosis system, the nanofiltration concentrated water passes through the secondary material membrane treatment system, and the secondary material membrane produced water enters the reverse osmosis system; The concentrated water from the reverse osmosis system enters the process 2 system and is mixed with the fly ash water wash solution for removing heavy metals; Process 2 system, including optional low-temperature detoxification system, fly ash washing system, washed fly ash return to furnace incineration system, washing liquid weight removal system, washing liquid hardness, fluorine and silicon removal system, filtration system, second nanofiltration system and oxidation system; The fly ash from the incineration plant enters an optional low-temperature detoxification system for treatment or is washed and then sent back to the incineration system to reduce dioxin content; The fly ash washing system uses recycled process water or evaporated condensate, and the resulting fly ash washing liquid enters the washing liquid weight removal system; The water washing liquid deweighting system is used to remove heavy metals. The treated water washing liquid is mixed with the concentrated water of the reverse osmosis system in process one and enters the water washing liquid dehardness, defluorination and desiliconization system; The water washing liquid is treated by the hardness, fluorine and silicon removal system and then enters the filtration system, which adopts a combination of sand filtration and ultrafiltration, or a TUF membrane system; The nanofiltration system adopts one or two stages, the water produced by the nanofiltration system flows into the oxidation system, and the concentrated water of the nanofiltration system flows back to the hardness, fluorine and silicon removal system; The oxidation system removes organic matter from the concentrated water of the nanofiltration system to obtain a mixed liquid, which enters the process three treatment system; Process three treatment system, including sequentially connected decarbonization and pH adjustment system, optional reaction adjustment system, evaporation concentration system, sodium chloride evaporation crystallization system, nitrate or chloride crystallization system, optional nitrate or chloride refining system, evaporation mother liquor tank and miscellaneous salt drying equipment, and reflux equipment; 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 is evaporated and enters the nitrate or chloride crystallization system; The nitrate or chloride crystallization system can obtain nitrate or chloride, and the mother liquor remaining from the crystallization enters the mother liquor evaporation tank; The nitrate or chloride salt enters an optional nitrate or chloride salt refining system for refining; The mother liquor evaporated in the evaporation mother liquor tank enters the impurity salt drying equipment to be dried, and the impurity salt is transported out for disposal or refluxed to the water washing liquid weight removal system.

Images