High-nitrate wastewater treatment process and application

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a high-nitrate wastewater treatment process and application. The high-nitrate wastewater treatment process comprises the following steps: carrying out homogenization treatment and denitrification treatment on high-nitrate wastewater to obtain treated wastewater; a water source in the homogenizing treatment step is reclaimed water; the reclaimed water comprises the treated wastewater. According to the high-nitrate wastewater treatment process provided by the invention, the high-nitrate wastewater is homogenized by taking the reclaimed water as a water source, so that the aim of fully utilizing the water resource is fulfilled, the treatment cost is reduced, and the process is simple and easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a high-nitrate wastewater treatment process and application. Background Art

[0002] The wastewater generated in the catalyst material production field contains very high concentrations of nitrates and carbonates, a small amount of biodegradable organic matter and heavy metals and other pollutants, which are difficult to treat. If discharged directly, it will cause serious pollution to the environment. Therefore, it is necessary to treat the high nitrate wastewater before discharge so that it meets the discharge standards before discharge to reduce environmental pollution.

[0003] The high nitrate wastewater produced during the production of the catalyst is about 200m3 of wastewater per day. 3 / d, the content of sodium nitrate in the wastewater is 10000mg / L~20000mg / L, the content of sodium carbonate is 500mg / L~1000mg / L, a small amount of dust is about 200mg / L, and the pH is about 7. At present, the main processes for treating this high nitrate wastewater are as follows:

[0004] (1) Pre-treatment to remove catalyst dust, add nitric acid to remove carbonate, then obtain crude sodium nitrate through MVR or multi-effect evaporation, and then refine to obtain a sodium nitrate product with higher purity. This treatment process has at least two technical problems: one is cost: a large amount of water is required, and evaporation and crystallization require a large amount of steam, which is too costly; the other is that sodium nitrate is an explosive chemical and has certain risks.

[0005] (2) General treatment scheme for high-nitrate wastewater: denitrification. Pretreatment removes catalyst dust (heavy metals), and denitrification is carried out under anoxic conditions by adding a large amount of carbon source (more than 4 times the amount of nitrate nitrogen). Because denitrifying bacteria cannot survive and exert denitrification effects under the high salinity of high-nitrate wastewater, a large amount of fresh water (more than 2 times the amount of wastewater) must be continuously used for homogenization treatment, which invisibly increases costs and causes serious waste of water resources.

[0006] (3) After the wastewater is pre-treated, it passes through a nanofiltration device and a reverse osmosis device and then enters a bipolar membrane. Fresh water is recovered and concentrated water is electrodialyzed to produce acid and alkali solutions for recovery. However, this treatment method requires large equipment investment and high operating costs. The acid and alkali solutions produced are low in concentration and large in volume, making them difficult to recover, store and utilize, which invisibly increases the pressure on wastewater treatment. Summary of the invention

[0007] To solve the above problems, the present invention proposes a high nitrate wastewater treatment process and application to solve at least one aspect of the above problems and defects.

[0008] The present invention is achieved through the following technical solutions:

[0009] The first aspect of the present invention provides a high nitrate wastewater treatment process, comprising the following steps:

[0010] treating the high-nitrate wastewater by steps including homogenization and denitrification to obtain treated wastewater;

[0011] The water source in the homogenization step is recycled water, and the total nitrogen content of the recycled water is less than 15 mg / L;

[0012] The reclaimed water includes the treated wastewater.

[0013] The high nitrate wastewater treatment process provided by the present invention uses recycled water as a water source and homogenizes the high nitrate wastewater, which can not only reduce the impact of salt on denitrifying bacteria and meet their biological activity, but also achieve the purpose of making full use of water resources, thereby reducing the treatment cost, and the process is simple and easy to implement. Furthermore, the recycled water uses the treated wastewater as a water source to form a closed circulating water treatment system, further reducing the treatment cost and improving the utilization rate of water resources.

[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, in the homogenization step, the concentration of nitrate in the wastewater after homogenization is 300 mg / L to 800 mg / L.

[0016] In some possible implementations, in the homogenization step, the mass fraction of salt in the wastewater after homogenization is less than 0.8%.

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

[0018] In some possible implementations, in the denitrification step, the carrier of the denitrifying bacteria is a composite carrier, which is a composite material comprising 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.

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

[0020] coating the coating slurry on the alumina honeycomb ceramic;

[0021] The coating slurry comprises MOF-5 loaded with single-walled carbon nanotubes and a silane coupling agent, wherein the 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 comprises the steps of: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, precipitation, sand filtration, security filtration, ultrafiltration and reverse osmosis;

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

[0024] A second aspect of the present invention provides a high nitrate wastewater treatment process provided by the present invention, and its application in the field of wastewater treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0026] Figure 1 The figure is a schematic diagram of a process for treating high nitrate wastewater in an embodiment of the present invention.

[0027] The purpose, features and advantages of this figure will be further described in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described and illustrated in conjunction with the embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0029] Obviously, the following descriptions are only some examples or embodiments of the present invention, and for those of ordinary skill in the art, the present invention can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in such a development process may be complex and lengthy, for those of ordinary skill in the art related to the contents disclosed in the present invention, some changes in design, manufacturing or production based on the technical contents disclosed in the present invention are just conventional technical means, and should not be understood as the contents disclosed in the present invention being insufficient.

[0030] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present invention and is not intended to limit the subject matter described in the claims.

[0031] If not otherwise specified, all embodiments and optional embodiments of the present invention may be combined with each other to form a new technical solution, and all technical features and optional technical features of the present invention may be combined with each other to form a new technical solution.

[0032] A first aspect of an embodiment of the present invention provides a high nitrate wastewater treatment process, comprising the following steps:

[0033] S1. treating the high nitrate wastewater by homogenization and denitrification to obtain treated wastewater;

[0034] The water source in the homogenization step is recycled water, and the total nitrogen content of the recycled water is less than 15 mg / L;

[0035] Recycled water includes treated wastewater.

[0036] The high-nitrate wastewater treatment process provided by the embodiment of the present invention uses recycled water as a water source and performs homogenization treatment on the high-nitrate wastewater, which can not only reduce the impact of salt on denitrifying bacteria and meet their biological activity; but also achieve the purpose of making full use of water resources, thereby reducing the treatment cost, and the process is simple and easy to implement. Furthermore, the recycled water uses the treated wastewater as a water source to form a closed circulating water treatment system, further reducing the treatment cost and improving the utilization rate of water resources.

[0037] In the embodiment, the total nitrogen content of the reclaimed water is less than 15 mg / L, which is the water discharge standard of Class 1A in the standard GB18918 "Pollutant Discharge Standard for Urban Sewage Treatment Plants". It should be noted that the source of the reclaimed water, in addition to the wastewater obtained by the high nitrate wastewater treatment process of the embodiment of the present invention, can also be obtained from other external industrial or urban sewage treatment, as long as it meets the following requirements: the total nitrogen content is less than 15 mg / L, which is the water discharge standard of Class 1A in the standard GB18918 "Pollutant Discharge Standard for Urban Sewage Treatment Plants", it can be used as the source of the reclaimed water in the embodiment of the present invention.

[0038] In some embodiments, in the above step S1, the content of sodium nitrate in the high nitrate wastewater is 10000mg / L to 20000mg / L. In the exemplary embodiment, it can be a typical but non-limiting content such as 10000mg / L, 15000mg / L, 20000mg / L, or a range between any two contents. In this case, the high nitrate wastewater can be effectively diluted by using the treated wastewater so that the nitrate concentration in the diluted wastewater is 300mg / L to 800mg / L. It should be noted that the source of high nitrate wastewater is well known in the art, and the method of the embodiment of the present invention is applicable to the treatment of all high nitrate wastewaters, but as an example, the source of high nitrate wastewater can be produced by catalyst production.

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

[0040] The high nitrate wastewater is processed through high nitrate wastewater collection, activated carbon filtration, homogenization, denitrification, aerobic treatment, precipitation, sand filtration, security filtration, ultrafiltration and reverse osmosis steps to obtain the treated wastewater. In this case, the treated wastewater can meet the water discharge standard of Class 1A in GB18918 "Pollutant Discharge Standard for Urban Sewage Treatment Plants", so that the treated wastewater can be used as a water source to homogenize the high nitrate wastewater, thereby achieving the purpose of making full use of water resources.

[0041] In some embodiments, the high nitrate wastewater collection step includes: after the high nitrate wastewater is subjected to cement separation, the water is subjected to the filtering step, and the mud is subjected to sludge drying. It should be noted that the hydraulic retention time in the mud removal step needs to be set according to the actual process and the actual situation of the high nitrate wastewater, and is not particularly limited in the embodiments of the present invention. However, as an example, the hydraulic retention time (HRT) can be more than 24 hours, generally 24 hours to 48 hours. And sludge drying is a conventional operation in the art, and is not particularly limited in the embodiments of the present invention.

[0042] In some embodiments, in the activated carbon filtration step, the activated carbon adsorbs dust (including heavy metals) and SS (suspended solids) that cannot be settled in the wastewater, thereby achieving the purpose of further purifying the wastewater. It should be noted that the types of activated carbon are existing materials and can be selected according to actual needs, but as an example, common sources of activated carbon are wood activated carbon, fruit shell activated carbon, and coal-based activated carbon.

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

[0044] In some embodiments, in the above step S1, the concentration of nitrate in the wastewater after homogenization is 300 mg / L to 800 mg / L. In the exemplary embodiment, it can be 300 mg / L, 500 mg / L, 700 mg / L, 800 mg / L, etc., which are typical but non-limiting concentrations, or a range between any two concentrations. In some embodiments, in the above step S1, the mass fraction of salt in the wastewater after homogenization is less than 0.8%. In this case, the high nitrate wastewater under the nitrate concentration and salt concentration can not only maintain the biological activity of denitrifying bacteria, but also increase the conversion rate of nitrate (too low nitrate concentration will reduce the conversion rate).

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

[0046] In some embodiments, in the above step S1, in the denitrification step, the carrier of the denitrifying bacteria is a composite carrier, and the composite carrier is a composite material comprising 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. 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, so that the composite carrier loaded with denitrifying bacteria also has a high structural stability, and is not easily deformed or broken due to environmental changes (such as temperature, pH value, etc.), and is suitable for denitrification of high nitrate wastewater under various conditions. It should be noted that denitrifying bacteria are commonly used fungi in the art, and no special limitation is required in the embodiments of the present invention.

[0047] MOF-5 is a metal organic framework material with Zn as the coordination metal. Its molecular formula is C 24 H 4 O 13 Zn 4, the molecular weight is 761.84076g / mol.

[0048] Alumina honeycomb ceramics are made of alumina as the main raw material and are made into a ceramic material with a honeycomb structure through a specific molding process (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 on the composite carrier comprises:

[0050] The coating slurry is coated on the 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 the denitrifying bacteria are loaded on the surface of the single-walled carbon nanotubes.

[0052] In the above step of loading the denitrifying bacteria on the composite carrier, the denitrifying bacteria are first loaded on the surface of the single-walled carbon nanotubes, and then loaded on the MOF-5 with a larger specific surface area, so that the denitrifying bacteria have a larger conversion site and improve the conversion efficiency; and coating the MOF-5 on the aluminum honeycomb ceramic can increase the volume of the composite carrier for subsequent precipitation and removal. The silane coupling agent, as a dispersing solvent and adhesive, can evenly coat the MOF-5 on the alumina honeycomb ceramic.

[0053] In some specific embodiments, the coating method is dipping coating. It should be noted that the number of dipping times is adjusted according to the actual situation. When the content of MOF-5 is high, the number of dipping times is high, and vice versa. The time of each dipping can also be adjusted according to the actual situation. Each dipping is naturally dried before the next dipping. However, as an example, the time of each dipping can be 1 min to 10 min.

[0054] In some embodiments, the viscosity of the coating slurry is 300 mPa·s to 500 mPa·s. In exemplary embodiments, the viscosity may be 300 mPa·s, 400 mPa·s, 500 mPa·s, or any other typical but non-limiting viscosity or a range between any two viscosities. In this case, the viscosity may improve the dip coating effect.

[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 the exemplary embodiment, it can be a typical but non-restrictive mass ratio such as 0.2:9:1, 0.3:12:1, 0.1:7:1, or a range between any two mass ratios. In this case, the single-walled carbon nanotubes can be well loaded on MOF-5, and MOF-5 can also be well loaded on alumina honeycomb ceramics, thereby improving the overall mechanical strength of the composite carrier, thereby improving 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 also be adjusted according to the actual preparation conditions, and the mass ratio range of the embodiment of the present invention is only used as an example range.

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

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

[0058] In some specific embodiments, in the step of loading the denitrifying bacteria on the composite carrier, the drying temperature is 20°C to 25°C and the drying time is 5h to 12h. In this case, free water is removed while maintaining the activity of the denitrifying bacteria. It should be noted that the drying method is a conventional technology in the art and is not particularly limited in the embodiments of the present invention, but as an example, the drying method can be air drying, air drying, oven drying, etc.

[0059] In some embodiments, in the above step S1, in the denitrification step, the carbon source is acetic acid. In this case, using acetic acid as a carbon source not only reduces the alkalinity of the wastewater, but also provides a carbon source for the denitrification process.

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

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

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

[0063] In the embodiment, the specific treatment processes of aerobic treatment, precipitation, sand filtration, security filtration, ultrafiltration and reverse osmosis steps after the denitrification step are all conventional technical solutions in the field and are not particularly limited in the embodiments of the present invention. Among them, excessive aeration in the aerobic treatment step removes COD produced by unconsumed carbon sources in the wastewater after denitrification and balances the alkalinity of the wastewater (removes excess carbon dioxide); the precipitation step can be used for mud and water separation, and in a specific embodiment, a vertical flow sedimentation tank (surface load 0.8m / s~1.0m / s) can be used for mud and water separation after precipitation; the conditions of sand filtration, security filtration, ultrafiltration and reverse osmosis steps are not particularly limited in the embodiments of the present invention.

[0064] The following is further described in conjunction with specific embodiments.

[0065] Example 1

[0066] Example 1 provides a high nitrate wastewater treatment process, the steps are as follows:

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

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

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

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

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

[0072] Example 2

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

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

[0075] Example 3

[0076] Example 3 provides a high nitrate wastewater treatment process, the steps 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 treatment is 700 mg / L.

[0078] Example 4

[0079] Example 4 provides a high nitrate wastewater treatment process, the steps 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 treatment is 500 mg / L.

[0081] Example 5

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

[0083] In the denitrification step of step (2), the carrier of the denitrifying bacteria is a composite carrier, wherein the composite carrier is single-walled carbon nanotubes, MOF-5 and alumina honeycomb ceramics, with a mass ratio of 0.2:9:1; the specific surface area of ​​MOF-5 is 1575m 2 / g.

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

[0085] ① At a constant temperature of 20° C., single-walled carbon nanotubes are ultrasonically dispersed in ethanol, and denitrifying bacteria are added, dispersed, and then dried to obtain single-walled carbon nanotubes loaded with denitrifying bacteria.

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

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

[0088] ④ The coating slurry is impregnated on the alumina honeycomb ceramic for three times, each impregnation time is 2 minutes, and each impregnation is naturally dried before the next impregnation.

[0089] ⑤ After the dip coating is completed, dry at 20°C for 10 hours.

[0090] Example 6

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

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

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

[0094] ① At a constant temperature of 20° C., single-walled carbon nanotubes are ultrasonically dispersed in ethanol, and denitrifying bacteria are added, dispersed, and then dried to obtain single-walled carbon nanotubes loaded with denitrifying bacteria.

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

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

[0097] ④ The coating slurry is impregnated on the alumina honeycomb ceramic for three times, each impregnation time is 5 minutes, and each impregnation is naturally dried before the next impregnation.

[0098] ⑤ After the dip coating is completed, dry at 25°C for 8 hours.

[0099] Example 7

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

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

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

[0103] ① At a constant temperature of 20° C., single-walled carbon nanotubes are ultrasonically dispersed in ethanol, and denitrifying bacteria are added, dispersed, and then dried to obtain single-walled carbon nanotubes loaded with denitrifying bacteria.

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

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

[0106] ④ The coating slurry is impregnated on the alumina honeycomb ceramic for three times, each impregnation time is 10 minutes, and each impregnation is naturally dried before the next impregnation.

[0107] ⑤ After the dip coating is completed, dry at 25°C for 8 hours.

[0108] Comparative Example 1

[0109] Comparative Example 1 provides a high nitrate wastewater treatment process, the steps are basically the same as those in Example 1, except that the treatment process also includes the step of: a homogenization step using clean water or tap water as a water source, and the amount used is the same as that in Example 1.

[0110] Comparative Example 2

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

[0112] In the denitrification step of step (2), the carrier of the denitrifying bacteria is a composite carrier of single-walled carbon nanotubes and alumina honeycomb ceramics, 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 are basically the same as those in Example 1, except that:

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

[0116] Comparative Example 4

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

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

[0119] In order to verify the progressiveness of a high nitrate wastewater treatment process provided by an embodiment of the present invention, the high nitrate wastewater treatment process provided by the embodiment and the comparative example was used to detect the nitrate (N) concentration in the wastewater obtained by the denitrification step according to standard HJ / T 346 "Determination of Nitrate Nitrogen in Water Quality by Ultraviolet Spectrophotometry (Trial)", and the results are shown in Table 1 below.

[0120] Table 1

[0121]

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

[0123] (1) The high nitrate wastewater treatment process provided by the embodiment of the present invention uses the treated wastewater as the water source, and homogenizes the high nitrate wastewater, which can not only reduce the impact of salt on denitrifying bacteria and meet their biological activity, but also achieve the purpose of making full use of water resources, thereby reducing the treatment cost, and the process is simple and easy to implement. In addition, the recycled water uses the treated wastewater as the water source, which can form a closed circulating water treatment system for the treatment process, further reducing the treatment cost and improving the utilization rate of water resources.

[0124] (2) It can be seen from the concentration of nitrate in the wastewater after denitrification in Example 1, Examples 5 to 7 and Comparative Examples 2 to 4 that the use of a composite material comprising single-walled carbon nanotubes, MOF-5 and alumina honeycomb ceramics as a composite carrier of denitrifying bacteria can promote denitrification (the concentration of nitrate after denitrification in Examples 5 to 7 is significantly reduced); in Comparative Example 2, due to the large size difference between the single-walled carbon nanotubes and the alumina honeycomb ceramics, the single-walled carbon nanotubes cannot be well loaded on the alumina honeycomb ceramics, and the effect of the large specific surface area of ​​the composite carrier cannot be exerted; similarly, in Comparative Example 3, the volume of the denitrifying bacteria is quite different from the pore size of MOF-5; and in Comparative Example 4, the composite carrier of the single-walled carbon nanotubes and MOF-5 has a low mechanical strength, resulting in poor structural stability and easy deformation due to environmental changes (such as temperature, pH value, etc.). It can be seen that the high nitrate wastewater treatment process provided by the embodiment of the present invention adopts a composite material comprising single-walled carbon nanotubes, MOF-5 and alumina honeycomb ceramics as a composite carrier of denitrifying bacteria. The composite carrier has a very large specific surface area, and MOF-5 and alumina honeycomb ceramics themselves have good mechanical strength, so that the composite carrier loaded with denitrifying bacteria also has high structural stability, and is not easily deformed or broken 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-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present invention are all included in the technical scope of the present invention. In addition, without departing from the scope of the main purpose of the present invention, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. A high nitrate wastewater treatment process, characterized in that: The steps include: treating the high-nitrate wastewater by steps including homogenization and denitrification to obtain treated wastewater; The water source in the homogenization step is recycled water, and the total nitrogen content of the recycled water is less than 15 mg / L; The reclaimed water includes the treated wastewater.

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 less than 0.8%.

5. The high nitrate wastewater treatment process according to claim 4, characterized in that: The content of sodium nitrate in the high nitrate wastewater is 10000 mg / L to 20000 mg / L.

6. The high nitrate wastewater treatment process according to claim 5, characterized in that: In the denitrification step, the carrier of the denitrifying bacteria is a composite carrier, which is a composite material comprising 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.

7. The high nitrate wastewater treatment process according to claim 6, characterized in that: The step of loading the denitrifying bacteria on the composite carrier comprises: The coating slurry is coated on the alumina honeycomb ceramic and then dried; The coating slurry comprises MOF-5 loaded with single-walled carbon nanotubes and a silane coupling agent, wherein the denitrifying bacteria are loaded on the surface of the single-walled carbon nanotubes.

8. The high nitrate wastewater treatment process according to claim 7, characterized in that: The viscosity of the coating slurry is 300mPa·s to 500mPa·s; And / or, the mass ratio of the single-walled carbon nanotube, the MOF-5 and the alumina honeycomb ceramic is (1-2):(1-2):

1.

9. The high nitrate wastewater treatment process according to any one of claims 1 to 8, characterized in that: The high nitrate wastewater treatment process also includes the steps of: high nitrate wastewater collection, activated carbon filtration, aerobic treatment, precipitation, sand filtration, security filtration, ultrafiltration and reverse osmosis; The high-nitrate wastewater is treated through high-nitrate wastewater collection, activated carbon filtration, homogenization treatment, denitrification, aerobic treatment, precipitation, sand filtration, security filtration, ultrafiltration and reverse osmosis steps to obtain the treated wastewater.

10. Use of the high nitrate wastewater treatment process according to any one of claims 1 to 9 in the field of wastewater treatment processes.

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