High nitrate wastewater treatment processes and applications

Abstract

This invention belongs to the field of wastewater treatment technology, specifically relating to a process and application for treating high-nitrate wastewater. The high-nitrate wastewater treatment process includes the following steps: treating the high-nitrate wastewater with homogenization and denitrification steps to obtain treated wastewater; the water source in the homogenization step is reclaimed water; the reclaimed water includes the treated wastewater. The high-nitrate wastewater treatment process provided by this invention uses reclaimed water as a water source to homogenize the high-nitrate wastewater, achieving full utilization of water resources, thereby reducing treatment costs. The process is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a process and application for treating high nitrate wastewater. Background Technology

[0002] Wastewater generated in the catalyst material production field contains high concentrations of nitrates and carbonates, as well as small amounts of biodegradable organic matter and heavy metals, making it difficult to treat. Direct discharge would cause serious environmental pollution. Therefore, high-nitrate wastewater needs to be treated before discharge to meet discharge standards and reduce environmental pollution.

[0003] The high-nitrate wastewater generated during catalyst production has a daily production volume of approximately 200 m³. 3 The wastewater contains 10,000 mg / L to 20,000 mg / L of sodium nitrate, 500 mg / L to 1,000 mg / L of sodium carbonate, a small amount of dust (approximately 200 mg / L), and a pH of around 7. Currently, the main processes for treating this high-nitrate wastewater are as follows:

[0004] (1) Pretreatment removes catalyst dust, nitric acid is added to remove carbonate ions, and then crude sodium nitrate is obtained by MVR or multi-effect evaporation, which is then refined to obtain sodium nitrate product with higher purity. This process has at least two technical problems: First, cost: the water volume is large and the evaporation and crystallization require a large amount of steam, which is too expensive; second, sodium nitrate is an easily explosive chemical and has certain dangers.

[0005] (2) Common treatment scheme for high nitrate wastewater: denitrification. Pretreatment removes catalyst dust (heavy metals), followed by the addition of a large amount of carbon source (more than 4 times the amount of nitrate nitrogen) to induce denitrification under anaerobic conditions. However, because denitrifying bacteria cannot survive and perform denitrification under the high salinity of high nitrate wastewater, a large amount of fresh water (more than 2 times the amount of wastewater) needs to be continuously used for homogenization, which increases costs and causes serious waste of water resources.

[0006] (3) After pretreatment, the wastewater passes through a nanofiltration device and a reverse osmosis device before entering a bipolar membrane. The freshwater is recovered, and the concentrated water is electrodialyzed to produce acid and alkali solutions, which are then recovered. However, this treatment method requires a large investment in equipment and has high operating costs. The acid and alkali solutions produced are of low concentration and large quantity, making them difficult to recover, store, and utilize, which will inevitably increase the pressure on wastewater treatment. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a high-nitrate wastewater treatment process and application to resolve at least one aspect of the problems and defects mentioned above.

[0008] This invention is achieved through the following technical solution:

[0009] The first aspect of this invention provides a process for treating high-nitrate wastewater, comprising the following steps:

[0010] The high-nitrate wastewater is treated by homogenization and denitrification steps to obtain the treated wastewater.

[0011] The water source in the homogenization process is reclaimed water, and the total nitrogen content of the reclaimed water is below 15 mg / L.

[0012] The reclaimed water includes the treated wastewater.

[0013] The high-nitrate wastewater treatment process provided by this invention uses reclaimed water as a source to homogenize the wastewater. This not only reduces the impact of salt on denitrifying bacteria, satisfying their biological activity, but also fully utilizes water resources, thereby reducing treatment costs. The process is simple and easy to implement. Furthermore, the reclaimed water uses the treated wastewater as a source, forming a closed-loop water treatment system, further reducing treatment costs and improving water resource utilization.

[0014] In some possible implementations, the amount of the treated wastewater used as a water source is 100% to 500%.

[0015] In some possible implementations, during the homogenization step, the concentration of nitrate in the homogenized wastewater is 300 mg / L to 800 mg / L.

[0016] In some possible implementations, during the homogenization step, the mass fraction of salt in the homogenized wastewater is below 0.8%.

[0017] In some possible implementations, the sodium nitrate content in the high nitrate wastewater is 10,000 mg / L to 20,000 mg / L.

[0018] In some possible implementations, the denitrification step is carried out on a composite carrier, which is a composite material comprising single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramics, wherein the single-walled carbon nanotubes are loaded on the MOF-5, and the MOF-5 is loaded on the alumina honeycomb ceramics.

[0019] In some possible implementations, the step of loading the denitrifying bacteria onto the composite carrier includes:

[0020] The coating slurry is applied to alumina honeycomb ceramics;

[0021] The coating slurry includes MOF-5 loaded with single-walled carbon nanotubes and a silane coupling agent, wherein denitrifying bacteria are loaded on the surface of the single-walled carbon nanotubes.

[0022] In some possible implementations, the high nitrate wastewater treatment process further includes the steps of: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis;

[0023] The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps to obtain the treated wastewater.

[0024] The second aspect of this invention provides a high-nitrate wastewater treatment process provided by this invention, and its application in the field of wastewater treatment processes. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a high-nitrate wastewater treatment process in an embodiment of the present invention.

[0027] The purpose, features, and advantages of this accompanying drawing will be further explained in conjunction with the embodiments and with reference to the accompanying drawing. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described and illustrated below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0029] Obviously, the following description is merely some examples or embodiments of the present invention. Those skilled in the art can apply the present invention to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, modifications to design, manufacturing, or production based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient disclosure of the present invention.

[0030] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand the invention and is not intended to limit the subject matter of the claims.

[0031] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0032] The first aspect of this invention provides a process for treating high-nitrate wastewater, comprising the following steps:

[0033] S1. The high-nitrate wastewater is treated by homogenization and denitrification steps to obtain the treated wastewater;

[0034] The water source in the homogenization process is reclaimed water, and the total nitrogen content of the reclaimed water is below 15 mg / L.

[0035] Reclaimed water includes treated wastewater.

[0036] The high-nitrate wastewater treatment process provided in this invention uses reclaimed water as a source to homogenize the wastewater. This not only reduces the impact of salt on denitrifying bacteria, satisfying their biological activity, but also fully utilizes water resources, thereby reducing treatment costs. The process is simple and easy to implement. Furthermore, the reclaimed water uses the treated wastewater as a source, forming a closed-loop water treatment system, further reducing treatment costs and improving water resource utilization.

[0037] In this embodiment, the total nitrogen content of the reclaimed water is below 15 mg / L, which meets the Class 1A water discharge standard of GB18918 "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants". It should be noted that the source of the reclaimed water can be wastewater treated by the high-nitrate wastewater treatment process of this embodiment, or it can be obtained from the treatment of other industrial or municipal wastewater, as long as it meets the following requirements: total nitrogen content below 15 mg / L, meeting the Class 1A water discharge standard of GB18918 "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants".

[0038] In some embodiments, in step S1 above, the sodium nitrate content in the high-nitrate wastewater is 10,000 mg / L to 20,000 mg / L. In exemplary cases, it can be a typical but non-limiting content such as 10,000 mg / L, 15,000 mg / L, or 20,000 mg / L, or any range between two such contents. In this case, the treated wastewater can effectively dilute the high-nitrate wastewater, resulting in a nitrate concentration of 300 mg / L to 800 mg / L in the diluted wastewater. It should be noted that the sources of high-nitrate wastewater are well known in the art. The method of this embodiment is applicable to the treatment of all high-nitrate wastewater; however, as an example, the source of high-nitrate wastewater can be generated from catalyst production.

[0039] In some embodiments, in step S1 above, the high nitrate wastewater treatment process further includes the steps of: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis.

[0040] The high-nitrate wastewater undergoes a series of treatment steps, including high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis, to obtain the treated wastewater. In this process, the treated wastewater meets the Class 1A water discharge standard of GB18918 "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants," thus allowing it to be used as a water source for homogenizing the high-nitrate wastewater and achieving full utilization of water resources.

[0041] In some embodiments, the high-nitrate wastewater collection step includes: after cement separation, the water undergoes the filtration step, and the sludge undergoes sludge drying. It should be noted that the hydraulic retention time (HRT) in the sludge removal step needs to be set according to the actual process and the specific conditions of the high-nitrate wastewater. In this embodiment of the invention, no particular limitation is made; however, as an example, the HRT can be 24 hours or more, generally 24 to 48 hours. Sludge drying is a conventional operation in the art and is not particularly limited in this embodiment of the invention.

[0042] In some embodiments, during the activated carbon filtration step, activated carbon adsorbs non-sedimentary dust (containing heavy metals) and suspended solids (SS) in the wastewater, thereby further purifying the wastewater. It should be noted that the activated carbon used is an existing material and can be selected according to actual needs. However, as examples, common sources of activated carbon include wood-based activated carbon, fruit shell activated carbon, and coal-based activated carbon.

[0043] In some embodiments, in step S1 above, the hydraulic retention time in the homogenization step is 4h to 6h. In exemplary cases, it can be a typical but non-limiting hydraulic retention time such as 4h, 4.5h, 5h, 5.5h, or 6h, or any range between two hydraulic retention times. In this case, the high-nitrate wastewater can be sufficiently diluted and homogenized.

[0044] In some embodiments, in step S1 above, the concentration of nitrate in the homogenized wastewater is 300 mg / L to 800 mg / L. In exemplary cases, it can be a typical but non-limiting concentration such as 300 mg / L, 500 mg / L, 700 mg / L, or 800 mg / L, or any range between two concentrations. In some embodiments, in step S1 above, the mass fraction of salt in the homogenized wastewater is below 0.8%. In this case, the high nitrate wastewater at this nitrate and salt concentration can both maintain the biological activity of denitrifying bacteria and improve the nitrate conversion rate (too low a nitrate concentration would reduce the conversion rate).

[0045] The salt content in the homogenized wastewater mainly refers to the sum of nitrates and carbonates.

[0046] In some embodiments, in step S1 above, the denitrification step uses a composite carrier as the carrier for the denitrifying bacteria. This composite carrier is a composite material comprising single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramics. The single-walled carbon nanotubes are loaded onto the MOF-5, and the MOF-5 is loaded onto the alumina honeycomb ceramics. In this case, the composite carrier has a very large specific surface area, and both MOF-5 and alumina honeycomb ceramics themselves have good mechanical strength. This gives the composite carrier loaded with denitrifying bacteria high structural stability, making it less prone to deformation or breakage due to environmental changes (such as temperature, pH, etc.). It is suitable for denitrifying high-nitrate wastewater under various conditions. It should be noted that denitrifying bacteria are commonly used bacteria in the art and are not specifically limited in the embodiments of this invention.

[0047] MOF-5 is a metal-organic framework material with Zn as the coordinating metal and its molecular formula is C. 24 H4O 13 Zn4 has a molecular weight of 761.84076 g / mol.

[0048] Alumina honeycomb ceramics are ceramic materials with a honeycomb structure, prepared from alumina as the main raw material through specific molding processes (such as extrusion molding). The large specific surface area of ​​alumina honeycomb ceramics also gives it good mechanical strength and thermal stability.

[0049] In some embodiments, the step of loading denitrifying bacteria onto a composite carrier includes:

[0050] The coating slurry is applied to alumina honeycomb ceramic and then dried.

[0051] The coating slurry includes a mixture of MOF-5 loaded with single-walled carbon nanotubes and a silane coupling agent, wherein denitrifying bacteria are loaded on the surface of the single-walled carbon nanotubes.

[0052] In the above steps of loading denitrifying bacteria onto the composite carrier, the denitrifying bacteria are first loaded onto the surface of single-walled carbon nanotubes, and then loaded onto MOF-5, which has a larger specific surface area. This provides the denitrifying bacteria with a larger conversion site, improving conversion efficiency. Coating MOF-5 onto the alumina honeycomb ceramic increases the volume of the composite carrier, facilitating subsequent precipitation removal. Silane coupling agents, acting as dispersing solvents and binders, enable the uniform coating of MOF-5 onto the alumina honeycomb ceramic.

[0053] In some specific embodiments, the coating method is immersion coating. It should be noted that the number of immersions is adjusted according to the actual situation; when the MOF-5 content is high, the number of immersions is higher, and vice versa. The immersion time for each immersion can also be adjusted according to the actual situation. Each immersion is allowed to air dry naturally before the next immersion. However, as an example, the immersion time for each immersion can be 1 to 10 minutes.

[0054] In some embodiments, the viscosity of the coating slurry is 300 mPa·s to 500 mPa·s. In exemplary cases, it can be a typical but non-limiting viscosity such as 300 mPa·s, 400 mPa·s, or 500 mPa·s, or any range between two viscosities. In this case, the immersion coating effect can be improved at this viscosity.

[0055] In some specific embodiments, the mass ratio of single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramics is (0.1–0.3):(7–15):1. In exemplary cases, typical but non-limiting mass ratios such as 0.2:9:1, 0.3:12:1, and 0.1:7:1, or any range between two mass ratios, are possible. In this case, single-walled carbon nanotubes can be well loaded onto MOF-5, and MOF-5 can also be well loaded onto alumina honeycomb ceramics, improving the overall mechanical strength of the composite carrier and thus enhancing the structural stability of the denitrifying bacteria-loaded composite carrier. It should be noted that the mass ratio of single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramics can be adjusted according to the actual preparation conditions; the mass ratio range in the embodiments of this invention is only an example range.

[0056] In some specific embodiments, the specific surface area of ​​MOF-5 is 1000 m². 2 / g~2000m 2 / g, in the example, can be 1000m 2 / g、1575m 2 / g、2000m 2 The specific surface area is typically, but not limitingly, such as / g or any range between two specific surface areas. In this case, MOF-5 can promote the denitrification reaction of denitrifying bacteria and increase the conversion rate of nitrate. It should be noted that the specific surface area of ​​MOF-5 can be adjusted according to actual conditions and is not limited to the specific surface area shown in the embodiments of the present invention; furthermore, the specific surface area of ​​single-walled carbon nanotubes and the pore size of alumina honeycomb ceramics can be selected according to actual conditions, as long as the single-walled carbon nanotubes are loaded on the surface of MOF-5 and the MOF-5 is loaded in the pore size of alumina honeycomb ceramics, the requirements can be met.

[0057] In the embodiments, the type of silane coupling agent can be selected according to actual needs, but as an example, commonly used silane coupling agents such as KH-550 and KH-560 can be selected.

[0058] In some specific embodiments, during the step of loading denitrifying bacteria onto the composite carrier, the drying temperature is 20℃~25℃, and the drying time is 5h~12h. In this case, free moisture is removed while maintaining the activity of the denitrifying bacteria. It should be noted that the drying method is a conventional technique in the art and is not particularly limited in the embodiments of the present invention. However, as examples, the drying method can be air drying, sun drying, oven drying, etc.

[0059] In some embodiments, in step S1 above, the carbon source in the denitrification step is acetic acid. In this case, using acetic acid as a carbon source both reduces the alkalinity of the wastewater and provides a carbon source for the denitrification process.

[0060] In some specific embodiments, the amount of acetic acid used (in BOD equivalent) was 4.75 times the total nitrogen concentration in the wastewater, and the actual dosage was 5 times, which was slightly excessive.

[0061] In some embodiments, in step S1 above, the amount of treated wastewater used as a water source is 100% to 500%. In exemplary cases, it can be a typical but non-limiting amount such as 100%, 200%, 300%, 400%, 500%, or any range between two amounts. In this case, when the first batch of high-nitrate wastewater is homogenized for the first time, no treated wastewater is generated. It needs to be diluted with external reclaimed water, clean water, or tap water (the amount used is the same as or similar to the daily wastewater discharge). After the treated wastewater is generated, it is stored. When new high-nitrate wastewater is treated subsequently, the treated wastewater can be used for dilution.

[0062] The amount of treated wastewater used as a water source is the same as or similar to the daily wastewater discharge. For example, if the daily wastewater discharge is 10t, then the amount of treated wastewater used as a water source is 100% to 500% of the daily wastewater discharge of 10t.

[0063] In the embodiments, the specific treatment processes for the aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps after denitrification are all conventional technical solutions in the art and are not particularly limited in the embodiments of the present invention. Specifically, the aerobic treatment step involves excessive aeration to remove COD generated from unconsumed carbon sources in the wastewater after denitrification and to balance the alkalinity of the wastewater (removing excess carbon dioxide); the sedimentation step can perform sludge-water separation, and in a specific embodiment, a vertical flow sedimentation tank (surface loading 0.8 m / s to 1.0 m / s) can be used for sedimentation followed by sludge-water separation; the conditions for the sand filtration, security filtration, ultrafiltration, and reverse osmosis steps are not particularly limited in the embodiments of the present invention.

[0064] The following description, in conjunction with specific embodiments, provides further details.

[0065] Example 1

[0066] Example 1 provides a process for treating high nitrate wastewater, the steps of which are as follows:

[0067] (1) The sodium nitrate content in the selected high nitrate wastewater is 15000 mg / L.

[0068] (2) Figure 1 As shown, the high nitrate wastewater is treated through the following steps: high nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis, to obtain the treated wastewater.

[0069] In the denitrification step, the carbon source is acetic acid, and the amount of acetic acid used (in BOD equivalent) is 5 times the total nitrogen concentration in the wastewater.

[0070] The water source in the homogenization process is the treated wastewater, and the amount of treated wastewater used is 200%.

[0071] The nitrate concentration in the wastewater after homogenization was 500 mg / L.

[0072] Example 2

[0073] Example 2 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0074] In step (2), the amount of treated wastewater is 100%, and the nitrate concentration in the wastewater after homogenization is 800 mg / L.

[0075] Example 3

[0076] Example 3 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0077] In step (2), the amount of treated wastewater is 300%, and the nitrate concentration in the wastewater after homogenization is 700 mg / L.

[0078] Example 4

[0079] Example 4 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0080] In step (2), the amount of treated wastewater is 400%, and the nitrate concentration in the wastewater after homogenization is 500 mg / L.

[0081] Example 5

[0082] Example 5 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0083] In step (2), the denitrification process uses a composite carrier for the denitrifying bacteria. This composite carrier consists of single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramic in a mass ratio of 0.2:9:1; the specific surface area of ​​MOF-5 is 1575 m². 2 / g.

[0084] The steps for loading denitrifying bacteria onto the composite carrier are as follows:

[0085] ① At a constant temperature of 20℃, single-walled carbon nanotubes were ultrasonically dispersed in ethanol, and then denitrifying bacteria were added and dispersed before drying to obtain single-walled carbon nanotubes loaded with denitrifying bacteria.

[0086] ② At a constant temperature of 20℃, MOF-5 was dispersed in acetone, and then single-walled carbon nanotubes loaded with denitrifying bacteria were added, dispersed, and dried.

[0087] ③ Mix MOF-5 obtained in step ② with KH-560 (silane coupling agent) to form a coating slurry with a viscosity of 400 mPa·s.

[0088] ④ The coating slurry is applied to the alumina honeycomb ceramic and impregnated three times, each time for 2 minutes. Each time, the ceramic is allowed to air dry naturally before the next impregnation.

[0089] ⑤ After the impregnation coating is completed, dry at 20℃ for 10 hours.

[0090] Example 6

[0091] Example 6 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0092] In step (2), the denitrification process uses a composite carrier for the denitrifying bacteria. This composite carrier consists of single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramic in a mass ratio of 0.3:12:1; wherein the specific surface area of ​​MOF-5 is 2000 m². 2 / g.

[0093] The steps for loading denitrifying bacteria onto the composite carrier are as follows:

[0094] ① At a constant temperature of 20℃, single-walled carbon nanotubes were ultrasonically dispersed in ethanol, and then denitrifying bacteria were added and dispersed before drying to obtain single-walled carbon nanotubes loaded with denitrifying bacteria.

[0095] ② At a constant temperature of 20℃, MOF-5 was dispersed in acetone, and then single-walled carbon nanotubes loaded with denitrifying bacteria were added, dispersed, and dried.

[0096] ③ Mix MOF-5 obtained in step ② with KH-560 (silane coupling agent) to form a coating slurry with a viscosity of 500 mPa·s.

[0097] ④ The coating slurry is applied to the alumina honeycomb ceramic and impregnated three times, each time for 5 minutes. Each time, the surface is allowed to air dry before the next impregnation.

[0098] ⑤ After the impregnation coating is completed, dry at 25℃ for 8 hours.

[0099] Example 7

[0100] Example 7 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0101] In step (2), the denitrification process uses a composite carrier for the denitrifying bacteria. This composite carrier consists of single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramic in a mass ratio of 0.1:7:1; wherein the specific surface area of ​​MOF-5 is 1000 m². 2 / g.

[0102] The steps for loading denitrifying bacteria onto the composite carrier are as follows:

[0103] ① At a constant temperature of 20℃, single-walled carbon nanotubes were ultrasonically dispersed in ethanol, and then denitrifying bacteria were added and dispersed before drying to obtain single-walled carbon nanotubes loaded with denitrifying bacteria.

[0104] ② At a constant temperature of 20℃, MOF-5 was dispersed in acetone, and then single-walled carbon nanotubes loaded with denitrifying bacteria were added, dispersed, and dried.

[0105] ③ Mix MOF-5 obtained in step ② with KH-560 (silane coupling agent) to form a coating slurry with a viscosity of 300 mPa·s.

[0106] ④ The coating slurry is applied to the alumina honeycomb ceramic and impregnated three times, each time for 10 minutes. Each time, the surface is allowed to air dry before the next impregnation.

[0107] ⑤ After the impregnation coating is completed, dry at 25℃ for 8 hours.

[0108] Comparative Example 1

[0109] Comparative Example 1 provides a high-nitrate wastewater treatment process, with steps that are basically the same as those in Example 1, except that the treatment process further includes a homogenization step using clean water or tap water as the water source, with the same amount as in Example 1.

[0110] Comparative Example 2

[0111] Comparative Example 2 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0112] In step (2), the denitrification process uses a composite carrier of single-walled carbon nanotubes and alumina honeycomb ceramics as the carrier for denitrifying bacteria, with a mass ratio of 0.1:1.

[0113] Comparative Example 3

[0114] Comparative Example 3 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0115] In step (2), the denitrification process uses a composite carrier of MOF-5 and alumina honeycomb ceramics as the carrier for denitrifying bacteria, with a mass ratio of 7:1.

[0116] Comparative Example 4

[0117] Comparative Example 4 provides a high-nitrate wastewater treatment process, the steps of which are basically the same as those in Example 1, except that:

[0118] In step (2), the denitrification process uses a composite carrier of single-walled carbon nanotubes and MOF-5 as the carrier for denitrifying bacteria, with a mass ratio of 0.1:7.

[0119] To verify the advancement of the high nitrate wastewater treatment process provided in this embodiment of the invention, the high nitrate wastewater treatment processes provided in the embodiments and comparative examples were tested according to the standard HJ / T 346 "Determination of Nitrate Nitrogen in Water - Ultraviolet Spectrophotometry (Trial)" to detect the nitrate (N) concentration in the wastewater obtained after the denitrification step. The results are shown in Table 1 below.

[0120] Table 1

[0121]

[0122] From the data in Table 1 above, at least the following conclusions can be drawn:

[0123] (1) The high-nitrate wastewater treatment process provided in this embodiment of the invention uses the treated wastewater as a water source to homogenize the high-nitrate wastewater. This not only reduces the impact of salt on denitrifying bacteria and satisfies their biological activity, but also achieves the goal of fully utilizing water resources, thereby reducing treatment costs. The process is simple and easy to implement. In addition, using the treated wastewater as a water source for reclaimed water allows the treatment process to form a closed-loop water treatment system, further reducing treatment costs and improving water resource utilization.

[0124] (2) The concentration of nitrate in the denitrified wastewater of Examples 1, 5-7 and Comparative Examples 2-4 shows that using a composite material containing single-walled carbon nanotubes, MOF-5 and alumina honeycomb ceramics as a composite carrier for denitrifying bacteria can promote denitrification (the concentration of nitrate after denitrification in Examples 5-7 is significantly reduced). In Comparative Example 2, due to the large size difference between single-walled carbon nanotubes and alumina honeycomb ceramics, the single-walled carbon nanotubes cannot be well loaded on the alumina honeycomb ceramics, and the large specific surface area of ​​the composite carrier cannot be utilized. Similarly, in Comparative Example 3, the volume of denitrifying bacteria and the pore size of MOF-5 are significantly different. In Comparative Example 4, the composite carrier of single-walled carbon nanotubes and MOF-5 has low mechanical strength, resulting in poor structural stability and easy deformation due to environmental changes (such as temperature, pH value, etc.). Therefore, the high nitrate wastewater treatment process provided in this embodiment of the invention uses a composite material containing single-walled carbon nanotubes, MOF-5, and alumina honeycomb ceramics as a composite carrier for denitrifying bacteria. The composite carrier has a very large specific surface area, and both MOF-5 and alumina honeycomb ceramics have good mechanical strength, which makes the composite carrier loaded with denitrifying bacteria also have high structural stability. It is not easy to deform or break due to environmental changes (such as temperature, pH value, etc.), and is suitable for denitrification of high nitrate wastewater under various conditions.

[0125] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A process for treating high-nitrate wastewater, characterized in that, Includes the following steps: The high-nitrate wastewater is treated by homogenization and denitrification steps to obtain the treated wastewater. The water source in the homogenization process is reclaimed water, and the total nitrogen content of the reclaimed water is below 15 mg / L. The reclaimed water includes the treated wastewater; The sodium nitrate content in the high nitrate wastewater is 10000 mg / L to 20000 mg / L; In the denitrification step, the carrier for the denitrifying bacteria is a composite carrier, which is a composite material containing single-walled carbon nanotubes, MOF-5 and alumina honeycomb ceramics; the single-walled carbon nanotubes are loaded on the MOF-5, and the MOF-5 is loaded on the alumina honeycomb ceramics.

2. The high-nitrate wastewater treatment process according to claim 1, characterized in that, The amount of the treated wastewater used as a water source is 100% to 500%.

3. The high-nitrate wastewater treatment process according to claim 1 or 2, characterized in that, In the homogenization step, the concentration of nitrate in the wastewater after homogenization is 300 mg / L to 800 mg / L.

4. The high-nitrate wastewater treatment process according to claim 3, characterized in that, In the homogenization step, the mass fraction of salt in the wastewater after homogenization is below 0.8%.

5. The high-nitrate wastewater treatment process according to claim 1, characterized in that, The step of loading the denitrifying bacteria onto the composite carrier includes: The coating slurry is applied to alumina honeycomb ceramic and then dried. The coating slurry includes MOF-5 loaded with single-walled carbon nanotubes and a silane coupling agent, wherein denitrifying bacteria are loaded on the surface of the single-walled carbon nanotubes.

6. The high-nitrate wastewater treatment process according to claim 5, characterized in that, The viscosity of the coating slurry is 300 mPa·s to 500 mPa·s; And / or, the mass ratio of the single-walled carbon nanotubes, the MOF-5 and the alumina honeycomb ceramic is (0.1~0.3):(7~15):

1.

7. The high-nitrate wastewater treatment process according to claim 1, characterized in that, The high nitrate wastewater treatment process also includes the following steps: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis; The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps to obtain the treated wastewater.

8. The high-nitrate wastewater treatment process according to claim 2, characterized in that, The high nitrate wastewater treatment process also includes the following steps: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis; The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps to obtain the treated wastewater.

9. The high-nitrate wastewater treatment process according to claim 3, characterized in that, The high nitrate wastewater treatment process also includes the following steps: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis; The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps to obtain the treated wastewater.

10. The high-nitrate wastewater treatment process according to claim 4, characterized in that, The high nitrate wastewater treatment process also includes the following steps: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis; The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps to obtain the treated wastewater.

11. The high-nitrate wastewater treatment process according to claim 5, characterized in that, The high nitrate wastewater treatment process also includes the following steps: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis; The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps to obtain the treated wastewater.

12. The high-nitrate wastewater treatment process according to claim 6, characterized in that, The high nitrate wastewater treatment process also includes the following steps: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis; The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, sedimentation, sand filtration, security filtration, ultrafiltration, and reverse osmosis steps to obtain the treated wastewater.

13. The application of a high nitrate wastewater treatment process as described in any one of claims 1 to 12 in the field of wastewater treatment processes.

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