Nitrate wastewater treatment method

Abstract

The invention relates to a treatment method of nitrate wastewater. The composite carbon source obtained by resourceful treatment of the water-based cutting waste liquid is used for carrying out nitrate wastewater treatment. The resourceful treatment method comprises the following steps: (1) carrying out acid precipitation treatment on the water-based cutting waste liquid, and standing; (2) reacting the lower-layer treating fluid obtained by standing in the step (1) under the action of a Fenton reagent, standing and filtering; (3) mixing the filtrate obtained by filtering in the step (2) with a nitrogen source and a phosphorus source to obtain a mixed solution, and performing hydrolytic acidification treatment to obtain a composite carbon source; and (4) mixing the composite carbon source obtained in the step (3) with nitrate wastewater to obtain a second mixed solution, and then carrying out denitrification treatment. The harmful water-based cutting waste liquid with high toxicity, high CODCr (Chemical Oxygen Demand) and poor biodegradability is recycled into a composite carbon source, the COD (Chemical Oxygen Demand) removal efficiency is high, the composite carbon source can be used as a carbon source during denitrification treatment of nitrate wastewater while wastes are effectively treated, the environmental pollution is reduced, and the resource recycling is realized.

Description

[0001] This application relates to application number 2022116374610, filed on December 16, 2022, entitled "A method for resource recovery treatment of water-based cutting waste fluid, its products and applications". Technical Field

[0002] This invention belongs to the technical field of wastewater treatment, specifically relating to a method for treating nitrate wastewater. Background Technology

[0003] Cutting fluid is used in machining processes to lubricate, cool, and clean machining tools and parts, improving product quality and reducing machine wear. Cutting fluid is a lubricant composed of various additives, and is classified according to processing requirements into oil-based cutting fluids that emphasize lubrication and water-based cutting fluids that emphasize cooling. The properties of water-based cutting fluids vary depending on the formulation. They contain not only large amounts of mineral oil but also recalcitrant high-molecular-weight organic compounds. While chemically stable, water-based cutting fluid waste is difficult to separate from oil and water, has high toxicity, and high COD. Cr It has a high content, reaching over 10,000 mg / L, poor biodegradability, and is difficult to treat. It seriously damages the aquatic ecological environment, and long-term accumulation can easily cause diseases such as cancer, posing a serious threat to human life and safety.

[0004] Currently, methods for treating cutting fluid waste can be categorized into physical, chemical, and biological methods. Physical methods, such as adsorption, utilize the porous nature and large specific surface area of ​​adsorbents to physically and chemically adsorb oil and organic matter from the cutting fluid. However, the adsorption capacity is limited, and the cost of recovering the adsorbent is high, leading to secondary pollution. Chemical methods, such as electrochemical methods, apply an electric current to the cutting fluid waste to induce physicochemical reactions and achieve purification. However, this consumes excessive amounts of electricity, resulting in high costs and posing certain risks. Biological methods, such as activated sludge processes, utilize the metabolic decomposition of organic matter by microorganisms into inorganic salts. However, cutting fluid waste is highly toxic and has a high COD (Chemical Oxygen Demand). Cr High concentrations pose a serious threat to the survival of microorganisms and affect processing efficiency. Summary of the Invention

[0005] In view of the problems existing in the prior art, one object of the present invention is to provide a resource-based treatment method for water-based cutting waste fluid. This resource-based treatment method enables the successful harmless treatment of water-based cutting waste fluid, yielding a composite carbon source as a resource product, and reducing the COD in the composite carbon source, which can be further used in denitrification systems to co-treat nitrate wastewater.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for the resource recovery treatment of water-based cutting waste fluid includes the following steps:

[0008] (1) Allow the water-based cutting waste fluid to stand after acid precipitation treatment;

[0009] (2) Allow the lower layer of the treatment liquid obtained by (1) to stand to react under the action of Fenton's reagent, stand, and filter;

[0010] (3) Mix the filtrate obtained from (2) with nitrogen and phosphorus sources, and then perform hydrolysis and acidification treatment to obtain resource products.

[0011] In step (1)

[0012] Preferably, the acid precipitation treatment includes a step of controlling the acidity of the water-based cutting waste fluid by using one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and oxalic acid.

[0013] Preferably, the acid precipitation treatment is carried out when the pH of the water-based cutting waste fluid is controlled to be 1.0 to 6.0; more preferably 1.0 to 3.0; and even more preferably 1.5 to 2.5.

[0014] According to a specific and preferred embodiment, the settling is carried out in a separatory funnel, which facilitates the collection of the lower layer of liquid and subsequent processing.

[0015] Furthermore, the settling time is more than 6 hours, and can be 6 hours, 10 hours, 14 hours, 18 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, 48 ​​hours, or 72 hours. The settling time can also be extended according to the stratification situation.

[0016] Furthermore, the mixture after acid precipitation can be left to stand overnight.

[0017] In step (2)

[0018] Preferably, the specific operation of step (2) is as follows: after controlling the pH of the lower layer of the treatment liquid obtained by standing (1) to 2.5 to 4.0, add Fenton's reagent and stir to react, then control the pH of the system to 4.0 to 8.0, and filter after standing to precipitate.

[0019] Preferably, the Fenton reagent comprises hydrogen peroxide and Fe... 2+ Iron salts.

[0020] Furthermore, the Fe-containing 2+ The iron salt is one or more of ferrous sulfate heptahydrate (FeSO4·7H2O), ferrous sulfate (FeSO4), and ferrous chloride (FeCl2).

[0021] According to some embodiments, the volume of hydrogen peroxide added accounts for 0.5 to 3% of the volume of water-based cutting waste liquid in (1); preferably 0.5 to 2%; more preferably 0.5 to 1%.

[0022] Preferably, the H2O2 content in the hydrogen peroxide is 20-30 wt%; more preferably, it is 25-30 wt%.

[0023] According to some embodiments, the Fe in the iron salt 2+ The molar ratio of H2O2 in hydrogen peroxide to H2O2 is 1:(4-16).

[0024] Furthermore, the Fe in the iron salt 2+ The molar ratio of H2O2 in hydrogen peroxide to H2O2 is 1:(4-12), for example 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12.

[0025] Furthermore, the Fe in the iron salt 2+ The molar ratio of H2O2 in the hydrogen peroxide to H2O2 is 1:(4-8).

[0026] Preferably, the substance used to control the pH of the lower layer of the treatment liquid obtained by (1) standing and the system is an inorganic alkaline salt, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, sodium acetate, etc.

[0027] Preferably, the reaction is carried out under stirring to promote the full progress of the Fenton reaction and improve reaction efficiency.

[0028] According to some embodiments, the reaction is carried out by stirring on a magnetic stirrer.

[0029] Preferably, the stirring speed is 200-350 rpm and the reaction time is 30-90 min.

[0030] Furthermore, the stirring speed is 200-300 rpm, and the reaction time is 30-80 min.

[0031] Furthermore, after adding Fenton's reagent, the pH of the system needs to be controlled at 6.0–8.0; more preferably 6.0–7.5.

[0032] In step (3)

[0033] Preferably, the COD in the filtrate obtained by filtration in step (2) is... Cr The mass ratio of feed to nitrogen source and phosphorus source is (100-600):(4-6):1.

[0034] Furthermore, the COD in the filtrate obtained from filtration in (2)Cr The mass ratio of the feed to the nitrogen and phosphorus sources is (150–550):(4–5):1, for example, 150:4:1, 200:4:1, 250:4:1, 300:4:1, 350:4:1, 400:4:1, 450:4:1, 500:4:1, 550:4:1, 150:4.5:1, 200:4.5:1, 250:4.5. :1, 300:4.5:1, 350:4.5:1, 400:4.5:1, 450:4.5:1, 500:4.5:1, 550:4.5:1, 150:5:1, 200:5:1, 250:5:1, 300:5:1, 350:5:1, 400:5:1, 450:5:1, 500:5:1, 550:5:1.

[0035] Furthermore, the COD in the filtrate obtained from filtration in (2) Cr The mass ratio of feed to nitrogen source and phosphorus source is (200-500):(4.5-5):1.

[0036] It should be noted that the COD in the filtrate obtained by filtration in (2) of this invention is... Cr The mass of the carbon source in the filtrate is equivalent to that in the filtrate, therefore the COD in the filtrate obtained by filtration can be determined based on (2). Cr Nitrogen and phosphorus sources are added according to a certain feeding ratio.

[0037] Preferably, the nitrogen source is selected from one or more of ammonium chloride, urea, ammonium sulfate, ammonium nitrate, and ammonium carbonate; more preferably, it is one or two of ammonium chloride and ammonium sulfate.

[0038] Preferably, the phosphorus source is selected from one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, ammonium monohydrogen phosphate, and potassium phosphate; more preferably, it is selected from one or more of potassium dihydrogen phosphate and sodium dihydrogen phosphate.

[0039] Preferably, the pH of the mixture is controlled to be 6-8 before hydrolysis and acidification treatment; more preferably 7-8; and even more preferably 7-7.5.

[0040] Furthermore, after controlling the pH of the mixture to be 6-8, it is necessary to add an alkaline salt with a buffering effect to provide alkalinity and maintain the mixture within a certain pH range during the later hydrolysis and acidification process.

[0041] Furthermore, examples of alkaline salts with buffering properties include sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, sodium dihydrogen phosphate, sodium hydrogen phosphate, and sodium acetate.

[0042] According to some embodiments, the mass concentration of the additive in the system is 0.5 to 1.5 g / L; preferably 0.8 to 1.2 g / L.

[0043] Preferably, the mixture is subjected to hydrolysis and acidification treatment after the salt concentration (TDS) is controlled to be below 15 g / L.

[0044] Furthermore, the salt concentration TDS of the mixture is controlled to be below 14 g / L, for example, 13.5 g / L, 13 g / L, 12.5 g / L, 12 g / L, 11.5 g / L, 11 g / L, 10.5 g / L, 10 g / L, etc.

[0045] Preferably, the hydrolysis acidification treatment is carried out in an anaerobic hydrolysis acidification system, wherein the anaerobic hydrolysis acidification system uses anaerobic granular sludge.

[0046] Furthermore, in the anaerobic hydrolysis acidification system, the reactor stirring speed is 25 rpm to 120 rpm, the hydraulic residence time (HRT) is 18 h to 4 d, and the reaction temperature is 25 to 55 °C.

[0047] Furthermore, in the anaerobic hydrolysis acidification system, the reactor stirring speed is 25 rpm to 105 rpm (e.g., 25 rpm, 35 rpm, 45 rpm, 55 rpm, 65 rpm, 75 rpm, 85 rpm, 95 rpm, 105 rpm), the hydraulic retention time (HRT) is 1 day to 3.5 days (e.g., 1 day, 1.5 days, 2 days, 2.5 days, 3 days, 3.5 days), and the reaction temperature is 25 to 40℃ (25℃, 30℃, 35℃, 40℃).

[0048] Furthermore, in the anaerobic hydrolysis acidification system, the reactor stirring speed is 29 rpm to 100 rpm, the hydraulic residence time (HRT) is 1.5 days to 3 days, and the reaction temperature is 25 to 35°C.

[0049] The second objective of this invention is to provide a composite carbon source obtained by the resource recovery treatment method for the water-based cutting waste fluid described above.

[0050] The third objective of this invention is to provide a method for treating nitrate wastewater, wherein the above-mentioned composite carbon source is mixed with nitrate wastewater to obtain a second mixture, and denitrification is performed using a denitrification system.

[0051] Preferably, the COD in the second mixture is controlled. Cr NO3 - After the content is ≥3%, it enters the denitrification system; more preferably, the COD in the second mixture is higher. Cr NO3 - Content ≥4; more preferably, COD in the second mixture Cr NO3 - Content ≥5. According to a specific and preferred embodiment, the COD in the second mixture is controlled.Cr NO3 - The content is ≤10, and further preferred to be ≤8.

[0052] Preferably, the second mixture is introduced into the denitrification system after the pH is adjusted to 4.5-8; more preferably, the pH of the second mixture is 5.5-8; and even more preferably, the pH of the second mixture is 6.5-7.5.

[0053] Preferably, the second mixture is introduced into the denitrification system when the salt content is adjusted to 2.0-6.0%; more preferably, the salt content of the second mixture is 2.5-5.5%; and even more preferably, the salt content of the second mixture is 3.0-5.0%.

[0054] According to some preferred embodiments, the second mixture further includes a supplementary carbon source, wherein the replacement rate of the composite carbon source is 50-90%; preferably 50-85%; and more preferably 50-80%.

[0055] The substitution rate of the composite carbon source in this invention refers to the COD content of the composite carbon source. Cr For the entire COD in the second mixture Cr The contribution value. For example, a 50% substitution rate for the composite carbon source indicates that the COD in the second mixture... Cr 50% of it comes from composite carbon sources, and the remaining 50% comes from COD in supplementary carbon sources. Cr To supplement.

[0056] Furthermore, the supplementary carbon source is a carbon-containing organic compound, such as acetic acid, formic acid, methanol, ethanol, sodium acetate, glucose, etc.

[0057] Preferably, the denitrification system is an ascending anaerobic reactor with internal circulation.

[0058] Furthermore, the denitrification system uses anoxic sludge from the municipal wastewater biochemical treatment stage.

[0059] Furthermore, in the denitrification system, the hydraulic retention time (HRT) is 14–24 h, the internal circulation ratio is 100–300%, and the reaction temperature is 20–40 °C.

[0060] Furthermore, in the denitrification system, the hydraulic retention time (HRT) is 18–23 h, the internal circulation ratio is 150–250%, and the reaction temperature is 25–40 °C.

[0061] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0062] (1) In this invention, the water-based cutting waste fluid is acidified, and the lower layer of the treated fluid obtained by settling is subjected to Fenton oxidation reaction. Finally, it is subjected to hydrolysis and acidification reaction with nitrogen and phosphorus sources, resulting in a highly toxic and COD-free solution. Cr Highly hazardous water-based cutting fluids with poor biodegradability can be recycled into a composite carbon source. While effectively treating the waste, it can also be used as a carbon source for denitrification treatment of nitrates, saving or even completely replacing the addition of carbon sources, reducing the treatment cost of cutting fluids, and also saving the carbon source cost required for the biological denitrification treatment of nitrate waste fluids.

[0063] (2) The resource-based treatment method in this invention has no secondary pollution, is low-cost, environmentally friendly, and has high removal efficiency. It reduces environmental pollution while realizing resource reuse, successfully implementing the new concept of "treating waste with waste and turning waste into treasure". Attached Figure Description

[0064] Figure 1 A flowchart illustrating the resource-based treatment method for water-based cutting fluids and the co-treatment of nitrate wastewater. Detailed Implementation

[0065] All features disclosed in this invention, or steps in all methods or processes disclosed, may be combined in any way, except for mutually exclusive features or steps.

[0066] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0067] With rapid urbanization and increasing industrial production, large amounts of wastewater containing nitrates are generated, seriously threatening the ecological environment and human health. The most economical and environmentally friendly treatment method for nitrate wastewater is biological denitrification, which converts nitrates into nitrogen gas without secondary pollution. However, this method often requires an external carbon source, increasing treatment costs, and different carbon sources have significantly different treatment effects.

[0068] This invention effectively reduces the COD and toxicity of water-based cutting wastewater through acid precipitation, Fenton oxidation, and hydrolysis-acidification, achieving its harmless treatment. Furthermore, the resulting resource product is a composite carbon source, which can be used to save on or even replace the addition of carbon sources in denitrification systems. First, acid precipitation of the water-based cutting wastewater facilitates the separation of oily substances from the aqueous phase. Then, the lower layer of the treated liquid undergoes oxidation in the presence of Fenton's reagent, causing the numerous free radicals with oxidizing properties present in the reagent to rapidly decompose the organic matter in the treated liquid. Finally, the filtrate obtained after decomposition and filtration is mixed with nitrogen and phosphorus sources and subjected to hydrolysis-acidification, further converting the large-molecule organic matter into small-molecule carbon-containing substances, while simultaneously forming an element-rich composite carbon source. This facilitates its use in denitrification systems for the synergistic treatment of nitrate wastewater.

[0069] Furthermore, in this invention, acid precipitation treatment is performed when the pH of the water-based cutting waste fluid is controlled at 1.0 to 3.0, which can achieve demulsification of the water-based cutting waste fluid, improve the COD removal rate in the system, and facilitate oil-water separation in the cutting waste fluid after settling. This results in unusable oil in the upper layer and a large amount of large-molecule organic matter in the lower layer of the treated liquid. The upper layer of the treated liquid will not be transferred to the lower layer of the treated liquid, making it convenient for centralized collection and treatment.

[0070] Further, after controlling the pH of the lower layer of the treatment solution obtained by (1) to be 2.5-4.0, Fenton's reagent was added and the reaction was stirred. The Fe in Fenton's reagent 2+ In an acidic environment, hydrogen peroxide catalyzes the production of ·OH radicals, which can degrade organic matter, thereby removing most organic compounds from the system. If the pH of the solution is too high, it can lead to Fe... 2+ Ferric hydroxide precipitate forms, resulting in loss of catalytic activity. If the pH of the solution is too low, the oxidized Fe will be lost. 3+ Cannot be successfully reduced to Fe 2+ .

[0071] Furthermore, by controlling the mass ratio of the filtrate, nitrogen source, and phosphorus source obtained in (2) to (200-500):5:1, a complex carbon source rich in elements can be obtained in the anaerobic hydrolysis acidification system, which can meet the common reproduction of multiple microorganisms. At the same time, it avoids the microbial domestication caused by a single carbon source, which in turn affects the decarbonization reaction in the denitrification process. Using it as a carbon source can promote the denitrification reaction.

[0072] The composite carbon source obtained in this invention has high treatment efficiency, good denitrification effect, and no nitrite accumulation effect when used for synergistic treatment of nitrate wastewater. It realizes the development of a new technology of "treating waste with waste and turning waste into treasure", reduces treatment costs, has strong practicality, and can be used as a treatment method for high-salt and high-concentration nitrate wastewater.

[0073] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0074] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the experimental materials used, unless otherwise specified, were purchased from conventional biochemical reagent manufacturers.

[0075] The experimental methods in the following examples use water-based cutting waste fluid generated after using 10% water-based cutting fluid TM-3.

[0076] Example 1

[0077] This embodiment provides an application of the resource-based product prepared by a method for the resource recovery of water-based cutting waste fluid in the treatment of nitrate wastewater. Water-based cutting waste fluid (waste fluid generated after using 10% water-based cutting fluid TM-3) and high-concentration nitrate wastewater from electroless nickel plating are used as research objects. Figure 1 As shown: Includes the following steps:

[0078] (1) Adjust the pH of the water-based cutting waste liquid to about 2.0 with sulfuric acid, perform acid precipitation treatment, let it stand overnight in a separatory funnel, and take the lower layer of treated liquid.

[0079] (2) Take the waste liquid after treatment in step (1), adjust the pH to about 3.0 with 1M sodium hydroxide, add Fenton's reagent, and the dosage of Fenton's reagent is 0.5% of the volume ratio of hydrogen peroxide (H2O2) to waste liquid, Fe 2+ The mixture was stirred with H2O2 at a molar ratio of 1:4 for 60 minutes on a magnetic stirrer (220 rpm), then the pH was adjusted to 6.0, and the mixture was allowed to settle and then filtered.

[0080] (3) The filtrate prepared in step (2) is mixed with ammonium chloride and dipotassium hydrogen phosphate at a C:N:P ratio of 200:5:1. The pH of the mixture is adjusted to 7.0 with 1M sodium hydroxide. Sodium bicarbonate is added to provide alkalinity at a content of 1g / L and the TDS of the salt is 13g / L. The mixture is then fed into an anaerobic hydrolysis acidification system (using anaerobic granular sludge) for hydrolysis acidification treatment to prepare a composite carbon source. The stirring reactor speed is 100rpm, the hydraulic retention time is 3d, and the reaction temperature is 30℃.

[0081] (4) The composite carbon source obtained from step (3) is mixed with nitrate waste liquid, and the COD of the mixture is... Cr NO3 - The pH is 7.0, the salinity is 3.0%, the composite carbon source replacement rate is 50%, and the remaining part is supplemented with acetic acid as a carbon source. It is put into the denitrification treatment system. The denitrification system uses anoxic sludge from the municipal wastewater biological treatment stage. The hydraulic retention time is 23h, the internal circulation ratio is 200%, and the temperature is 35℃ for denitrification treatment.

[0082] Water samples were taken from each stage for testing and analysis, and the results are shown in Table 1.

[0083] Among them, COD Cr The determination was carried out according to the national standard GB11914-89 "Determination of Chemical Oxygen Demand - Dichromate Method";

[0084] NO3-N(NO3 - The content of nitrate nitrogen was determined according to the national standard SL 84-1994 "Determination of nitrate nitrogen (ultraviolet spectrophotometry)".

[0085] Table 1. Water quality testing results at each stage in Example 1

[0086] <![CDATA[COD Cr (mg / L)]]> <![CDATA[NO3-N(mg / L)]]> pH TM-3 10% Water-Based Cutting Fluid 150000 -- 11 Acid precipitation water 25000 -- 2.0 Fenton emerges from water 23200 -- 6.0 Hydrolysis and acidification of influent 18000 -- 7.0 Hydrolysis and acidification effluent 17250 -- 6.2 Denitrification system inlet water 11000 1800 7.0 Denitrification system effluent 3960 5.48 9.3

[0087] The results in Table 1 show that the composite carbon source prepared from water-based cutting waste fluid after acid precipitation-Fenton-hydrolysis acidification effectively replaces the use of conventional carbon sources, and has a high nitrate removal rate of up to 99.7%.

[0088] Example 2

[0089] It is basically the same as Example 1, except that:

[0090] In step (2), the dosage of Fenton's reagent is 0.5% by volume for hydrogen peroxide (H2O2) and waste liquid, and Fe... 2+ The reaction mixture was stirred on a magnetic stirrer at a molar ratio of 1:8 with H2O2. After adjusting the pH to 7.5, the mixture was allowed to settle and then filtered.

[0091] Step (3) After mixing ammonium chloride and dipotassium hydrogen phosphate at a C:N:P ratio of 500:5:1, adjust the pH of the mixture to 7.5 and the TDS of the salt to 11 g / L. Then, add it to the anaerobic hydrolysis acidification system for hydrolysis acidification treatment to prepare a composite carbon source. The stirring reactor speed is 29 rpm and the hydraulic residence time is 2 days.

[0092] Step (4) COD of the mixture Cr NO3 - The pH value is 5, the salt content is 6.7, and the overall salt content is 5.0%, with a composite carbon source substitution rate of 80%.

[0093] Water samples were taken from each stage for testing and analysis, and the results are shown in Table 2.

[0094] Table 2. Water quality testing results at each stage in Example 2

[0095] <![CDATA[COD Cr (mg / L)]]> <![CDATA[NO3-N(mg / L)]]> pH TM-3 10% Water-Based Cutting Fluid 150000 -- 11 Acid precipitation water 24800 -- 2.0 Fenton emerges from water 23900 -- 7.2 Hydrolysis and acidification of influent 20000 -- 7.5 Hydrolysis and acidification effluent 19550 -- 6.0 Denitrification system inlet water 16000 3140 6.7 Denitrification system effluent 3960 7.04 9.5

[0096] Compared with Example 1, the amount of related reagents used in Example 2 was reduced, but the nitrate load and salinity of the denitrification system increased significantly, and the replacement rate of the composite carbon source was further improved. The nitrate nitrogen removal rate of the denitrification system effluent could still reach 99.7%, which further illustrates that this method can be used as a treatment method for high-salt and high-concentration nitrate wastewater.

[0097] Example 3

[0098] It is basically the same as Example 1, except that:

[0099] Step (2) The dosage of Fenton's reagent was as follows: hydrogen peroxide (H2O2) and waste liquid were added at a volume ratio of 2%, Fe 2+ The molar ratio of H2O2 to H2O2 is 1:2.

[0100] Water samples were taken at each stage for testing and analysis, and the results are shown in Table 3.

[0101] Table 3. Water quality testing results at each stage in Example 3

[0102] <![CDATA[COD Cr (mg / L)]]> <![CDATA[NO3-N(mg / L)]]> pH TM-3 10% Water-Based Cutting Waste Fluid 150000 -- 11 Acid precipitation water 24560 -- 2.0 Fenton emerges from water 22510 -- 6.5 Hydrolysis and acidification of influent 20920 -- 7.2 Hydrolysis and acidification effluent 20500 -- 7.6 Denitrification system inlet water 6000 1000 7.0 Denitrification system effluent 5200 890 7.8

[0103] Compared with Examples 1 and 2, Example 3 uses a higher amount of related reagents, but the removal rate of nitrate nitrogen is not high, only 11%, under the condition of reducing nitrate load. This indicates that the resource-based products prepared under this operating condition cannot be used as alternative carbon sources.

Claims

1. A method for treating nitrate wastewater, characterized in that: The treatment of nitrate wastewater using a composite carbon source obtained from the resource recovery of water-based cutting waste fluid includes the following steps: (1) Allow the water-based cutting waste fluid to stand after acid precipitation treatment; (2) Allow the lower layer of the treatment liquid obtained by (1) to stand to react under the action of Fenton's reagent, stand, and filter; (3) The filtrate obtained from (2) is mixed with a nitrogen source and a phosphorus source in a ratio of (100-600):(4-6):1 for the amount of CODCr in the filtrate to the amount of nitrogen source and phosphorus source. After controlling the salt content TDS of the mixture to be lower than 15 g / L and the pH to be 6-8, it is subjected to hydrolysis acidification treatment in an anaerobic hydrolysis acidification system to obtain a composite carbon source. The anaerobic hydrolysis acidification system uses anaerobic granular sludge, the reactor stirring speed is 25 rpm to 120 rpm, the hydraulic retention time (HRT) is 18 h to 4 d, and the reaction temperature is 25-55 °C. (4) The composite carbon source obtained in (3) is mixed with nitrate wastewater to obtain a second mixture, which is then subjected to denitrification treatment using a denitrification system. The second mixture also includes an additional carbon source to control the COD in the second mixture. Cr NO3 - After the content is ≥3, the pH is 4.5-8, and the salt content is 2.0-6.0%, it enters the denitrification system.

2. The method for treating nitrate wastewater according to claim 1, characterized in that: In step (4), the substitution rate of the composite carbon source is 50-85%.

3. The method for treating nitrate wastewater according to claim 1, characterized in that: The denitrification system is an upward-flowing anaerobic reactor with internal circulation; The denitrification system uses anoxic sludge from the municipal wastewater biochemical treatment stage, with a hydraulic retention time of 14–24 h, an internal circulation ratio of 100–300%, and a reaction temperature of 20–40 °C.

4. The method for treating nitrate wastewater according to claim 1, characterized in that: In step (3), the nitrogen source is selected from one or more of ammonium chloride, urea, ammonium sulfate, ammonium nitrate, and ammonium carbonate; The phosphorus source is selected from one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and potassium phosphate.

5. The method for treating nitrate wastewater according to claim 1, characterized in that: In step (2), the Fenton reagent includes hydrogen peroxide and a solution containing Fe. 2+ The iron salts, wherein the volume of hydrogen peroxide added accounts for 0.5 to 3% of the volume of water-based cutting waste liquid in (1); Fe in the iron salt 2+ The molar ratio of H2O2 in hydrogen peroxide to H2O2 in hydrogen peroxide is 1:(4~16); The hydrogen peroxide contains 20-30 wt% H2O2; The containing Fe 2+ The iron salt is selected from one or more of ferrous sulfate heptahydrate, ferrous sulfate, and ferrous chloride.

6. The method for treating nitrate wastewater according to claim 1, characterized in that: The specific operation of step (2) is as follows: control the pH of the lower layer of the treatment liquid obtained by standing (1) to 2.5 to 4.0, add Fenton's reagent and stir to react, then control the pH of the system to 4.0 to 8.0, let it stand to precipitate and then filter.

7. The method for treating nitrate wastewater according to claim 1 or 6, characterized in that: In step (2), the reaction is carried out under stirring, and the stirring speed is 200-350 rpm; And / or, the reaction time is 30 min to 90 min.

8. The method for treating nitrate wastewater according to claim 1, characterized in that: In step (1), the acid precipitation treatment includes a step of controlling the water-based cutting waste fluid to be acidic by using one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and oxalic acid. And / or, control the pH of the water-based cutting waste fluid to be 1.0 to 6.0 during acid precipitation treatment; And / or, the settling time is 6 hours or more.

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