A method for advanced treatment of biochemical effluent from coal chemical industry and its application

Abstract

The present application discloses a method for advanced treatment of biochemical effluent from coal chemical industry and its application, belonging to the technical field of sewage treatment. This advanced treatment method aims at the problem that the ammonia nitrogen in the common biochemical effluent from coal chemical industry can meet the standard stably, but the total nitrogen and COD cannot meet the standard stably. It adopts the combination of ultraviolet irradiation, oxidant and catalyst for advanced oxidation, and selects and sets specific oxidation methods and conditions according to different ammonia nitrogen and total nitrogen indexes of the influent water, so as to ensure the maximum removal efficiency of total nitrogen and COD on the basis of reducing energy consumption. Further applying this advanced treatment method to coal chemical wastewater can achieve zero discharge of coal chemical wastewater. After the biochemical effluent is deeply treated by the method of the present application, the treated wastewater is recycled to the coal chemical production process, creating economic benefits for the enterprise and realizing zero discharge of wastewater.

Description

Technical Field

[0001] The present application belongs to the technical field of coal chemical wastewater treatment, and specifically relates to a method for deep treatment of coal chemical biochemical effluent and its application. Background Art

[0002] The raw material used in coal chemical production is coal. Due to the particularity of the production process, the wastewater generated by this industry has the characteristics of large discharge volume, high pollutant concentration, high hardness, high turbidity, etc. At present, the physical and chemical + biochemical combined process is generally used for coal chemical wastewater treatment. After biochemical process treatment, the ammonia nitrogen in the biochemical effluent can often meet the emission requirements, but the COD and total nitrogen removal efficiency is not high. Part of the total nitrogen in the biochemical effluent is nitrate that has not been completely denitrified, and part of it is organic nitrogen that cannot be oxidized, which leads to excessive total nitrogen in the effluent.

[0003] In the relevant technology, for example, the Chinese invention patent with publication number CN105439311A records a method for deep treatment of biochemical effluent wastewater from coal chemical industry, which mainly utilizes two-stage ozone oxidation + activated carbon adsorption. The two-stage ozone catalytic oxidation in this method can achieve deep oxidation and decomposition of difficult-to-degrade organic matter, improve the effluent treatment effect, and at the same time combine with the activated carbon adsorption to ensure that the effluent water quality is stable and meets the emission and reuse standards. The device has strong impact load resistance and can be used for deep treatment of difficult-to-degrade wastewater. However, the activated carbon produced in this method is either used as hazardous waste or requires a matching activated carbon regeneration device, which invisibly increases the investment and operating costs of the enterprise. Another example is the Chinese invention patent with publication number CN108911410A, which records a coal chemical wastewater deep treatment system and a treatment method thereof. The deep treatment system includes a fluidized bed, a coagulation reaction tank and a sedimentation tank connected in sequence, as well as a COD degradation agent dosing device and a PAM dosing device. The COD degradation agent dosing device is connected to the fluidized bed, the PAM dosing device is connected to the coagulation reaction tank, and the sludge outlet of the sedimentation tank is connected to the fluidized bed. The invention uses a COD degradation agent to decompose the COD of the coal chemical wastewater, and removes suspended matter and COD in the wastewater by coagulation and sedimentation, so as to achieve the purpose of deep treatment of coal chemical wastewater and meet the relevant national emission standards. However, there are still problems such as secondary pollution caused by the addition of agents. Another example is the Chinese invention patent with publication number CN105645506A, which records a photo-Fenton catalytic oxidation coal chemical wastewater deep treatment system and a method for treating coal chemical wastewater. The system uses sunlight to react with TiO 2 Under the catalytic action of the above, not only can some organic matter be directly decomposed, but the iron hydroxy complex as a catalyst has good light absorption performance and absorbs photolysis, producing more OH with a fast reaction speed. Sunlight can also enhance the Fe 3+ The reduction of Fe 2+The concentration is conducive to the catalytic decomposition of ·OH, thereby improving the removal effect of pollutants. Through this process, the removal rate of COD and ammonia nitrogen is over 90%, and the chromaticity is also greatly removed; however, this method uses sunlight as the light source, which has low utilization rate, and the addition of divalent iron ions by photo-Fenton will cause secondary pollution.

[0004] The above-mentioned existing technologies still focus on the problem that the COD of coal chemical biochemical effluent does not meet the relevant national emission standards, or how to remove ammonia nitrogen, and ignore the problem of excessive total nitrogen in biochemical wastewater. The treatment of coal chemical biochemical effluent still has problems such as low denitrification efficiency, difficulty in completely removing organic matter, and immature zero-emission technical routes. Therefore, on the basis of reducing the COD of coal chemical biochemical effluent, how to further improve the removal efficiency of total nitrogen in coal chemical wastewater, especially nitrate nitrogen and organic nitrogen, and try not to produce secondary pollution has become a difficult problem that needs to be solved urgently for zero discharge of coal chemical wastewater.

[0005] In addition, the applicant found that the efficiency of advanced oxidation of coal chemical wastewater with different water qualities, different types of organic matter and different concentrations varies greatly even under the same conditions. However, it is impractical and difficult to apply in engineering to establish advanced oxidation conditions suitable for different water qualities and different types of organic matter to improve the efficiency of advanced oxidation of organic matter in such wastewater. Summary of the invention

[0006] 1. Problem to be solved

[0007] This application aims to solve the problem that the ammonia nitrogen in the biochemical effluent in the treatment of coal chemical wastewater can stably meet the standards, but the total nitrogen and COD cannot stably meet the standards. It provides a method for deep treatment of biochemical effluent in coal chemical industry and its application. The deep treatment method uses a combination of ultraviolet irradiation, oxidant and catalyst to carry out advanced oxidation. On the other hand, in order to solve the problem of which oxidation conditions to use for treatment, a method for selecting and setting specific oxidation methods and conditions according to different influent ammonia nitrogen and total nitrogen indicators is provided, and the removal efficiency of total nitrogen and COD in wastewater is effectively improved through the combination of oxidation means. Further applying the deep treatment method to coal chemical wastewater can achieve zero discharge of coal chemical wastewater. After the biochemical effluent in the treatment of coal chemical wastewater is deeply treated by the method of this application, the treated wastewater is reused in the coal chemical production process, which reduces the treatment cost for the enterprise and achieves zero discharge of wastewater.

[0008] 2. Technical solution

[0009] In order to solve the above problems, the technical solutions adopted in this application are as follows:

[0010] The present application provides a method for advanced treatment of biochemical effluent from coal chemical industry. The advanced treatment method selectively adopts one or a combination of advanced oxidation methods such as ultraviolet irradiation, addition of oxidant, and addition of catalyst according to different ammonia nitrogen and total nitrogen indexes of the influent, and specifically includes the following steps:

[0011] S1: Measure the ammonia nitrogen and total nitrogen of the biochemical effluent from coal chemical industry;

[0012] S2: Select the advanced oxidation method and conditions according to the following conditions,

[0013] (i) When the C 氨氮 / C 总氮 value is between 0.5 and 1, advanced oxidation is carried out by ultraviolet irradiation and addition of oxidant at room temperature;

[0014] (ii) When the C 氨氮 / C 总氮 value is between 0.3 and 0.5, advanced oxidation is carried out by ultraviolet irradiation, addition of oxidant, and addition of catalyst under heating conditions. The catalyst is a catalyst with photocatalytic oxidation activity;

[0015] (iii) When the C 氨氮 / C 总氮 value is between 0 and 0.3, advanced oxidation is carried out in a segmented manner by ultraviolet irradiation, addition of oxidant, and addition of catalyst under heating conditions. The segmented advanced oxidation includes a front-stage advanced oxidation and a rear-stage advanced oxidation. The wastewater first enters the front-stage advanced oxidation section for reaction, and the changes in the ammonia nitrogen and total nitrogen contents are dynamically monitored during the reaction process. When the C 氨氮 / C 总氮 value rises from the initial 0 - 0.3 to 0.6 - 0.8, it immediately transfers to the rear-stage advanced oxidation section. The catalyst in the front-stage advanced oxidation is a catalyst with photocatalytic oxidation activity, and the catalyst in the rear-stage advanced oxidation is a catalyst with photocatalytic reduction activity.

[0016] Further, the ammonia nitrogen content in the above influent is between 0 and 20 mg / L.

[0017] Further, the catalyst with photocatalytic oxidation activity includes: titanium dioxide modified by metals such as iron and platinum.

[0018] Further, the catalyst with photocatalytic reduction activity includes: titanium dioxide modified by silver metal.

[0019] Further, the catalyst with photocatalytic oxidation activity is an iron-modified titanium dioxide catalyst. After being excited by ultraviolet light irradiation, electron-hole pairs are generated on the surface, enabling effective separation of carriers, thereby improving the photocatalytic oxidation activity, enhancing the removal rate of organic matter in the wastewater, and converting organic nitrogen in the wastewater into ammonia nitrogen and nitrate nitrogen.

[0020] Furthermore, the above-mentioned catalyst with photocatalytic reduction activity is a silver-modified titanium dioxide catalyst. The silver-modified titanium dioxide catalyst prepared by the photocatalytic reduction method has silver successfully doped into the titanium dioxide crystal phase and may still exist in the form of elemental silver. It has strong reducibility and can well achieve the goal of reducing nitrate nitrogen, enhancing the removal effect of nitrate nitrogen in wastewater.

[0021] Furthermore, the catalyst in the previous stage of advanced oxidation in the above-mentioned (iii) is an iron-modified titanium dioxide catalyst. After being excited by ultraviolet light irradiation, electron-hole pairs will be generated on the surface, enabling the effective separation of carriers, thereby improving the photocatalytic oxidation activity, enhancing the removal rate of organic matter in wastewater, and converting organic nitrogen in wastewater into ammonia nitrogen and nitrate nitrogen. The catalyst in the latter stage of advanced oxidation is a silver-modified titanium dioxide catalyst. The silver-modified titanium dioxide catalyst prepared by the photocatalytic reduction method has silver successfully doped into the titanium dioxide crystal phase and may still exist in the form of elemental silver. It has strong reducibility and can well achieve the goal of reducing nitrate nitrogen, enhancing the removal effect of nitrate nitrogen in wastewater.

[0022] Furthermore, the dosage of the above-mentioned catalyst is 0.1 - 0.3% of the mass of the sewage.

[0023] Furthermore, the above-mentioned ultraviolet irradiation intensity is 20 - 150 mw / cm 2 , and the wavelength of the ultraviolet irradiation is 254 nm.

[0024] Furthermore, the above-mentioned oxidant is one or more of hydrogen peroxide, sodium hypochlorite solution, and sodium persulfate solution. Further, the oxidant is one or more of 28 wt% hydrogen peroxide, 8 wt% sodium hypochlorite solution, and 1 mol / L sodium persulfate solution.

[0025] Furthermore, the above-mentioned oxidant is added in a one-time manner, and the dosage of the oxidant is 0.1 - 0.3% of the mass of the sewage.

[0026] Furthermore, in the above-mentioned (ii) and (iii), the heating condition is to heat to 30 - 60 °C. Under this temperature condition, the rate and efficiency of the advanced oxidation reaction can be taken into account. When the reaction temperature > 60 °C, the economic value is not high in practical applications. When the reaction temperature < 30 °C, it is found in practical applications that although the effect of the treated wastewater is better than that at room temperature, the treated wastewater is difficult to meet the reuse requirements.

[0027] Furthermore, the reaction pH value of the above-mentioned advanced treatment is between 6 and 9, and the pH does not need to be adjusted during the reaction process.

[0028] The present application also provides an application of the above-mentioned method for advanced treatment of biochemical effluent from coal chemical industry in the treatment of biochemical effluent from coal chemical industry.

[0029] Further, the above application is a treatment method for zero discharge of biochemical effluent from coal chemical industry, and the method comprises the following steps:

[0030] (1) Advanced treatment of biochemical effluent: The method for advanced treatment of biochemical effluent from coal chemical industry described in any one of the above is used to conduct advanced treatment on the biochemical wastewater, and the COD and ammonia nitrogen in the treated wastewater are respectively controlled within 30 mg / L and 5 mg / L.

[0031] (2) Reuse of reclaimed water: The double-membrane method of ultrafiltration + reverse osmosis is used to further treat the wastewater that has undergone advanced treatment in step (1), and the membrane permeate after treatment is reused, and the membrane concentrate (brine) enters the subsequent crystallization and salt separation treatment; on the one hand, ultrafiltration can remove some organic matters in the wastewater and reduce the chromaticity, and can also intercept some colloids, bacteria and other impurities, prolonging the service life of the subsequent reverse osmosis membrane; while the reverse osmosis membrane can remove most of the salts in the water, and also has a very high removal effect on hardness, COD, etc., thus ensuring the quality of the reclaimed water.

[0032] (3) Crystallization and salt separation: The membrane concentrate (reverse osmosis concentrate) is subjected to salt separation by nanofiltration. The nanofiltration permeate mainly contains monovalent salts such as sodium chloride and sodium nitrate, and the nanofiltration concentrate contains salts such as sodium chloride, sodium nitrate and sodium sulfate. The nanofiltration permeate and concentrate are respectively highly concentrated by high-pressure reverse osmosis, and the concentrated solutions are respectively subjected to thermal separation crystallization, the salts are disposed of resourcefully, and the condensate is reused.

[0033] The present application also provides a treatment system for zero discharge of biochemical effluent from coal chemical industry. The system comprises a sequentially connected advanced treatment unit, a reclaimed water reuse unit and a brine crystallization and salt separation unit. The advanced treatment unit includes an advanced oxidation treatment method that can simultaneously achieve the combination of the above-mentioned ultraviolet irradiation, addition of oxidant and addition of catalyst.

[0034] 3. Beneficial effects

[0035] Compared with the prior art, the beneficial effects of the present application are as follows:

[0036] (1) A method for advanced treatment of biochemical effluent from coal chemical industry provided by this application is proposed by the applicant based on a large number of actual industrial advanced oxidation treatments of coal chemical industry. By exploring the degradation law of organic matter, different advanced oxidation conditions are controlled according to different influent indexes, so that the advanced oxidation process can be carried out efficiently. According to different influent ammonia nitrogen and total nitrogen indexes, one or more combinations of ultraviolet irradiation, adding oxidants, and adding catalysts are selectively used for the advanced oxidation method. When the influent total nitrogen concentration is low, the synergistic effect of oxidants and ultraviolet is mainly used. When the influent total nitrogen concentration is high, the synergistic effect of the combination of ultraviolet irradiation, oxidants, and catalysts is used for segmented oxidation, and different types of catalysts can be used according to needs. When it is necessary to enhance the removal rate of organic matter in wastewater and convert organic nitrogen into ammonia nitrogen and nitrate nitrogen, a titanium dioxide catalyst modified by iron can be used. When it is necessary to remove nitrate nitrogen in wastewater, a silver-modified titanium dioxide catalyst can be used. On the one hand, the catalyst can effectively improve the removal efficiency of organic matter COD in wastewater, and on the other hand, it can also improve the removal efficiency of ammonia nitrogen in wastewater.

[0037] (2) A method for advanced treatment of biochemical effluent from coal chemical industry provided by this application uses the detection indexes of biochemical effluent as the standard to measure the difficulty of advanced oxidation. For different monitoring indexes in different ranges, different advanced oxidation conditions are adopted, which can effectively improve the advanced oxidation efficiency of organic matter in wastewater, and solve the problem that it is difficult to select the advanced oxidation method, resulting in waste of resources and high treatment costs.

[0038] (3) A method for advanced treatment of biochemical effluent from coal chemical industry provided by this application uses the combination process of ultraviolet + oxidant + catalyst for the treatment of coal chemical wastewater, and compares the removal effects with Fenton, ozone, oxidant + ozone, and ultraviolet + oxidant processes. The advanced oxidation efficiency of this application is significantly improved. Description of the Drawings

[0039] Figure 1 It is the process flow chart of the scheme of Example 1. Detailed Embodiments

[0040] The following further describes this application in combination with specific embodiments.

[0041] It should be noted that terms such as "upper", "lower", "left", "right", "middle" cited in this specification are only for the convenience of narration and are not used to limit the scope that can be implemented. The change or adjustment of their relative relationship, without substantial change in technical content, should also be regarded as the scope that this application can implement.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0044] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement, or value. One of ordinary skill in the art can readily determine the degree of flexibility for a specific variable.

[0045] As used herein, the term "at least one of..." is intended to be synonymous with "one or more of...". For example, "at least one of A, B, and C" specifically includes only A, only B, only C, and their respective combinations.

[0046] Concentrations, amounts, and other numerical data may be presented herein in a range format. It should be understood that such range formats are used merely for convenience and brevity and should be interpreted flexibly to include not only the explicitly recited values as the limits of the range, but also all individual values or sub-ranges subsumed within the stated range as if each value and sub-range were explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted to include not only the explicitly recited limits of 1 to about 4.5, but also the individual numbers (such as 2, 3, 4) and sub-ranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that recite only one numerical value, such as "less than about 4.5," which should be interpreted to include all of the above values and ranges. In addition, this interpretation should apply regardless of the breadth of the range or feature described.

[0047] Example 1

[0048] This example provides a method for advanced treatment of biochemical effluent from coal chemical industry, specifically including:

[0049] S1: Determine the ammonia nitrogen, total nitrogen, and COD contents of the biochemical effluent from coal chemical industry;

[0050] S2: Select the advanced oxidation method and conditions according to the following conditions,

[0051] (i) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0.5 and 1, advanced oxidation is carried out by ultraviolet irradiation and adding an oxidant at room temperature;

[0052] (ii) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0.3 and 0.5, advanced oxidation is carried out by means of ultraviolet irradiation, adding an oxidant, and adding a catalyst under heating conditions. The catalyst is a catalyst with photocatalytic oxidation activity;

[0053] (iii) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0 and 0.3, staged advanced oxidation is carried out by means of ultraviolet irradiation, adding an oxidant, and adding a catalyst under heating conditions. The staged advanced oxidation includes the first-stage advanced oxidation and the second-stage advanced oxidation. The wastewater first enters the first-stage advanced oxidation section for reaction, and the changes in the ammonia nitrogen and total nitrogen contents are dynamically monitored during the reaction. When the C 氨氮 / C 总氮 value increases from the initial 0 - 0.3 to 0.6 - 0.8, it immediately transfers to the second-stage advanced oxidation section. The catalyst in the first-stage advanced oxidation is a catalyst with photocatalytic oxidation activity, and the catalyst in the second-stage advanced oxidation is a catalyst with photocatalytic reduction activity.

[0054] The sample is the biochemical effluent from the biochemical unit of a coal chemical enterprise. After testing, COD = 92.5 mg / L, ammonia nitrogen = 10.8 mg / L, total nitrogen = 19.2 mg / L, and C 氨氮 / C 总氮 = 0.5625. Therefore, (i) is adopted, that is, advanced oxidation is carried out by means of ultraviolet irradiation and adding an oxidant at normal temperature. Specifically:

[0055] The advanced oxidation unit is ultraviolet irradiation with a wavelength of 254 nm and an oxidant. The ultraviolet light intensity is controlled at 20 mw / cm 2 , the dosage of the oxidant (hydrogen peroxide) is controlled at 0.2% (mass ratio), and the advanced oxidation reaction time is 15 min. After treatment, COD is reduced to 27.1 mg / L, ammonia nitrogen is reduced to 4.4 mg / L, and total nitrogen is reduced to 9.8 mg / L (meeting the requirements of the subsequent advanced treatment unit for reclaimed water reuse production process, COD ≤ 30 mg / L, ammonia nitrogen ≤ 5 mg / L). The effluent after advanced oxidation enters the subsequent reclaimed water reuse treatment unit for resource utilization, achieving zero discharge of coal chemical wastewater.

[0056] Comparative Example 1A

[0057] For comparison, other treatment conditions were the same as those in Example 1, and the same wastewater was treated. The difference was that the Fenton process was used to replace the advanced oxidation step in Example 1 for treatment. The specific steps and conditions were as follows: Hydrochloric acid was added to the wastewater to adjust the pH of the effluent to 3. The dosage of hydrogen peroxide was 0.2% (mass ratio) and the dosage of ferrous sulfate was 100 mg / L. Stirring was carried out by means of bottom aeration. During the whole reaction process, the pH of the wastewater was controlled at about 3 by adding HCl or liquid caustic soda. The reaction time was 90 min. After the reaction ended, liquid caustic soda was added to adjust the pH of the wastewater to about 9. After aeration for 30 min, the supernatant was taken for testing after standing still.

[0058] After testing, after the advanced oxidation treatment of the wastewater by the Fenton process in this comparative example, the COD was reduced to 58.5 mg / L, the ammonia nitrogen was reduced to 6.5 mg / L, and the total nitrogen was reduced to 14.1 mg / L.

[0059] Comparative Example 1B

[0060] For comparison, other treatment conditions were the same as those in Example 1, and the same wastewater was treated. The difference was that the ozone process was used to replace the advanced oxidation step in Example 1 for treatment. The specific steps and conditions were as follows: The pH of the wastewater was adjusted to 8. During the reaction process, the pH of the wastewater was controlled at about 8 by adding HCl or liquid caustic soda. The ozone production rate was controlled at 30 mg / min, and the reaction time was 30 min.

[0061] After testing, after the advanced oxidation treatment of the wastewater by the ozone oxidation process in this comparative example, the COD was reduced to 47.3 mg / L, the ammonia nitrogen was reduced to 5.6 mg / L, and the total nitrogen was reduced to 11.2 mg / L.

[0062] Comparative Example 1C

[0063] For comparison, other treatment conditions were the same as those in Example 1, and the same wastewater was treated. The difference was that the oxidant + ozone combined process was used to replace the advanced oxidation step in Example 1 for treatment. The specific steps and conditions were as follows: The pH of the wastewater was adjusted to 8. During the reaction process, the pH of the wastewater was controlled at about 8 by adding HCl or liquid caustic soda. The dosage of hydrogen peroxide was controlled at 0.2% (mass ratio), the ozone production rate was controlled at 30 mg / min, and the reaction time was 30 min;

[0064] After testing, after the advanced oxidation treatment of the wastewater by the oxidant + ozone combined process in this comparative example, the COD of the wastewater was reduced to 43.5 mg / L, the ammonia nitrogen was reduced to 5.2 mg / L, and the total nitrogen was reduced to 10.5 mg / L.

[0065] Example 2

[0066] This embodiment provides a method for advanced treatment of biochemical effluent from coal chemical industry, specifically including:

[0067] S1: Measure the ammonia nitrogen, total nitrogen and COD contents of the biochemical effluent from coal chemical industry;

[0068] S2: Select the advanced oxidation method and conditions according to the following conditions,

[0069] (i) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0.5 and 1, advanced oxidation is carried out by ultraviolet irradiation and adding oxidant at room temperature;

[0070] (ii) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0.3 and 0.5, advanced oxidation is carried out by ultraviolet irradiation, adding oxidant and adding catalyst under heating conditions. The catalyst is a catalyst with photocatalytic oxidation activity;

[0071] (iii) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0 and 0.3, advanced oxidation is carried out by ultraviolet irradiation, adding oxidant and adding catalyst in a segmented manner under heating conditions. The segmented advanced oxidation includes the front-stage advanced oxidation and the back-stage advanced oxidation. The wastewater first enters the front-stage advanced oxidation section for reaction, and the changes in ammonia nitrogen and total nitrogen contents are dynamically monitored during the reaction. When the C 氨氮 / C 总氮 value increases from the initial 0 - 0.3 to 0.6 - 0.8, it is immediately transferred to the back-stage advanced oxidation section. The catalyst in the front-stage advanced oxidation is a catalyst with photocatalytic oxidation activity, and the catalyst in the back-stage advanced oxidation is a catalyst with photocatalytic reduction activity.

[0072] The sample is the biochemical effluent taken from the biochemical effluent of the coal chemical biochemical unit of an enterprise. After testing, COD = 162.5 mg / L, ammonia nitrogen = 14.8 mg / L, total nitrogen = 43.2 mg / L, C 氨氮 / C 总氮 = 0.3426. Therefore, (ii) is adopted, that is, advanced oxidation is carried out by ultraviolet irradiation, adding oxidant and adding catalyst under heating conditions. The catalyst is a catalyst with photocatalytic oxidation activity, specifically:

[0073] Advanced oxidation unit treatment is carried out at 30 °C by ultraviolet irradiation, oxidant (hydrogen peroxide), and adding iron-modified titanium dioxide as the catalyst: The advanced oxidation unit is carried out simultaneously with ultraviolet irradiation at a wavelength of 254 nm and oxidant (hydrogen peroxide), and the ultraviolet light intensity is controlled at 30 mw / cm 2, the dosage of hydrogen peroxide was controlled at 0.3% (mass ratio), and the catalyst used was iron-modified titanium dioxide, aiming to enhance the removal rate of organic matter in the wastewater and convert the organic nitrogen in the wastewater into ammonia nitrogen and nitrate nitrogen; the reaction was carried out at 30 °C for 30 min. After the above treatment, the COD was reduced to 28.5 mg / L, the ammonia nitrogen was reduced to 3.2 mg / L, and the total nitrogen was reduced to 16.8 mg / L (meeting the requirements of the subsequent advanced treatment unit for reclaimed water production process, COD ≤ 30 mg / L, ammonia nitrogen ≤ 5 mg / L).

[0074] The effluent after advanced oxidation entered the subsequent advanced treatment unit for reclaimed water for resource utilization, realizing zero discharge of coal chemical wastewater.

[0075] Comparative Example 2A

[0076] For comparison, other treatment conditions were the same as those in Example 2, treating the same wastewater. The difference was that the Fenton process was used instead of the advanced oxidation step in Example 2. The specific steps and conditions were as follows: hydrochloric acid was added to the wastewater to adjust the pH of the effluent to 3. The dosage of hydrogen peroxide was 0.3% (mass ratio) and the dosage of ferrous sulfate was 150 mg / L. Stirring was carried out by bottom aeration. During the whole reaction process, the pH of the wastewater needed to be controlled at about 3 by adding HCl or liquid caustic soda. The reaction time was 45 min. After the reaction, liquid caustic soda was added to adjust the pH of the wastewater to about 9, aeration was carried out for 45 min, and then the supernatant was taken for detection after standing.

[0077] After detection, after the wastewater was treated by the Fenton process in this comparative example for advanced oxidation, the COD was reduced to 108.5 mg / L, the ammonia nitrogen was reduced to 9.5 mg / L, and the total nitrogen was reduced to 33.6 mg / L.

[0078] Comparative Example 2B

[0079] For comparison, other treatment conditions were the same as those in Example 2, treating the same wastewater. The difference was that ozone oxidation was used instead of the advanced oxidation step in Example 2. The specific steps and conditions were as follows: the pH of the wastewater was adjusted to 8, and during the reaction process, the pH of the wastewater needed to be controlled at about 8 by adding HCl or liquid caustic soda. The ozone production rate was controlled at 30 mg / min, and the reaction time was 45 min.

[0080] After detection, after the wastewater was treated by the ozone oxidation process in this comparative example for advanced oxidation, the COD was reduced to 64.5 mg / L, the ammonia nitrogen was reduced to 8.5 mg / L, and the total nitrogen was reduced to 30.7 mg / L.

[0081] Comparative Example 2C

[0082] For comparison, other treatment conditions were the same as those in Example 2, and the same wastewater was treated. The difference was that the combined process of oxidant + ozone was used to replace the advanced oxidation step in Example 2 for treatment. The specific steps and conditions were as follows: The pH of the wastewater was adjusted to 8, and during the reaction process, the pH of the wastewater was controlled at about 8 throughout by adding HCl or liquid caustic soda. The dosage of hydrogen peroxide was controlled at 0.2% (mass ratio); the ozone production rate was controlled at 30 mg / min, and the reaction time was 45 min.

[0083] After detection, after treating the wastewater with the combined process of oxidant + ozone in this comparative example, the COD of the wastewater was reduced to 55.5 mg / L, the ammonia nitrogen was reduced to 6.5 mg / L, and the total nitrogen was reduced to 27.5 mg / L.

[0084] Comparative Example 2D

[0085] For comparison, other treatment conditions were the same as those in Example 2, and the same wastewater was treated. The difference was that no catalyst was added. Under the condition of 30 °C, the ultraviolet light intensity was 30 mw / cm 2 , and the dosage of hydrogen peroxide was controlled at 0.3% (mass ratio). After the reaction ended, after detection, the COD of the wastewater was reduced to 28.5 mg / L, the ammonia nitrogen was reduced to 8.1 mg / L, and the total nitrogen was reduced to 24.8 mg / L.

[0086] Example 3

[0087] This example provides a method for advanced treatment of biochemical effluent from coal chemical industry, which specifically includes:

[0088] S1: Measure the ammonia nitrogen, total nitrogen and COD contents of the biochemical effluent from coal chemical industry;

[0089] S2: Select the advanced oxidation method and conditions according to the following conditions,

[0090] (i) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0.5 and 1, advanced oxidation is carried out by ultraviolet irradiation and adding an oxidant at room temperature;

[0091] (ii) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮 value is between 0.3 and 0.5, advanced oxidation is carried out by ultraviolet irradiation, adding an oxidant and adding a catalyst under heating conditions, and the catalyst is a catalyst with photocatalytic oxidation activity;

[0092] (iii) When the ammonia nitrogen content is between 0 and 20 mg / L and the C 氨氮 / C 总氮When the value is between 0 and 0.3, under heating conditions, ultraviolet irradiation, addition of oxidant, and addition of catalyst are used for staged advanced oxidation. The staged advanced oxidation includes the first-stage advanced oxidation and the second-stage advanced oxidation. The wastewater first enters the first-stage advanced oxidation section for reaction, and the changes in ammonia nitrogen and total nitrogen contents are dynamically monitored during the reaction process. When C 氨氮 / C 总氮 rises from the initial 0 - 0.3 to 0.6 - 0.8, it immediately transfers to the second-stage advanced oxidation section. The catalyst in the first-stage advanced oxidation is a catalyst with photocatalytic oxidation activity, and the catalyst in the second-stage advanced oxidation is a catalyst with photocatalytic reduction activity.

[0093] The sample is the biochemical effluent from the biochemical unit of a coal chemical enterprise. After testing, COD = 222.5 mg / L, ammonia nitrogen = 16.8 mg / L, total nitrogen = 64.3 mg / L, and C 氨氮 / C 总氮 = 0.2612. Therefore, method (iii) is adopted, that is, under heating conditions, ultraviolet irradiation, addition of hydrogen peroxide, and addition of catalyst are used for staged advanced oxidation. The staged advanced oxidation includes the first-stage advanced oxidation and the second-stage advanced oxidation. The catalyst in the first-stage advanced oxidation is a catalyst with photocatalytic oxidation activity, and the catalyst in the second-stage advanced oxidation is a catalyst with photocatalytic reduction activity. Specifically:

[0094] Carry out advanced oxidation unit treatment: The advanced oxidation unit simultaneously performs ultraviolet irradiation with a wavelength of 254 nm, hydrogen peroxide, and catalyst. The ultraviolet light intensity is controlled at 40 mw / cm 2 throughout the process, the dosage of the oxidant is controlled at 0.3% (mass ratio) L, and staged oxidation is adopted. Catalysts are added in both the first-stage oxidation and the second-stage oxidation. In the first-stage oxidation reaction, the catalyst used is iron-modified titanium dioxide to enhance the removal rate of organic matter in the wastewater. When converting organic nitrogen into ammonia nitrogen and nitrate nitrogen, when C 氨氮 / C 总氮 rises from the initial 0.2612 to 0.65, it immediately transfers to the second-stage advanced oxidation section. In the second-stage reaction, the catalyst used is silver-modified titanium dioxide to enhance the removal effect of nitrate nitrogen in the wastewater; the dosage of the catalyst is 0.2% of the wastewater mass; the system temperature is controlled at 45°C throughout the process, and the advanced oxidation reaction time is 30 min. After the above treatment, COD is reduced to 26.5 mg / L, ammonia nitrogen is reduced to 3.2 mg / L, and total nitrogen is reduced to 15.3 mg / L (meeting the requirements of the subsequent advanced treatment unit for reclaimed water reuse production process, COD ≤ 30 mg / L, ammonia nitrogen ≤ 5 mg / L).

[0095] The effluent after advanced oxidation enters the subsequent reclaimed water reuse treatment unit for resource utilization, achieving zero discharge of coal chemical wastewater.

[0096] Comparative Example 3A

[0097] For comparison, other treatment conditions were the same as those in Example 3, treating the same wastewater. The difference was that: the ozone + hydrogen peroxide combined process was used to replace the advanced oxidation step in Example 3 for treatment. The specific steps and conditions were as follows: the pH of the wastewater was adjusted to 8, and the pH of the wastewater was controlled at about 8 throughout the reaction process by adding HCl or liquid caustic soda. The dosage of hydrogen peroxide was controlled at 0.3% (mass ratio), the ozone production rate was controlled at 30 mg / min, and the reaction time was 45 min;

[0098] After detection, after treating the wastewater with the ozone + oxidant combined process in this comparative example, the COD of the wastewater was reduced to 50.5 mg / L, the ammonia nitrogen was reduced to 11.5 mg / L, and the total nitrogen was reduced to 53.5 mg / L.

[0099] Comparative Example 3B

[0100] For comparison, other treatment conditions were the same as those in Example 3, treating the same wastewater. The difference was that: without adding a catalyst, ultraviolet + hydrogen peroxide was used to treat the wastewater. The same reaction time as in Example 3 was used, and the wastewater entered the post-stage oxidation after the pre-stage oxidation.

[0101] After the above treatment, the COD was reduced to 62.9 mg / L, the ammonia nitrogen was reduced to 12.8 mg / L, and the total nitrogen was reduced to 47.5 mg / L. The results showed that without adding a catalyst, it was difficult to meet the requirements for the treatment of this wastewater, mainly because the presence of the catalyst increased the removal effect of COD and ammonia nitrogen.

[0102] Comparative Example 3C

[0103] For comparison, other treatment conditions were the same as those in Example 3, treating the same wastewater. The difference was that: only iron-modified titanium dioxide catalyst was added throughout the process.

[0104] After the reaction ended, the COD was reduced to 28.5 mg / L, the ammonia nitrogen was reduced to 5.1 mg / L, and the total nitrogen was reduced to 31.3 mg / L. The results showed that only adding iron-modified titanium dioxide catalyst was difficult to meet the requirements for the treatment of this wastewater, mainly because when using only one kind of iron-modified titanium dioxide catalyst, as a photocatalytic oxidation active catalyst, it only increased the removal effect of COD and ammonia nitrogen. Without the help of a photocatalytic reduction active catalyst, it was impossible to remove COD, ammonia nitrogen, and total nitrogen in water to a higher degree.

[0105] Example 4

[0106] This application also provides a treatment system for zero discharge of biochemical effluent from coal chemical industry, as Figure 1 shown.

[0107] The system includes a advanced treatment unit, a reclaimed water reuse unit and a concentrated brine crystallization and salt separation unit connected in sequence. The advanced treatment unit can simultaneously achieve the combination of ultraviolet irradiation, addition of oxidant, and addition of catalyst for advanced oxidation, where:

[0108] (1) Advanced treatment of biochemical effluent: The biochemical wastewater is subjected to advanced treatment using any one of the above-mentioned advanced treatment methods for coal chemical biochemical effluent. After treatment, the COD and ammonia nitrogen in the wastewater are controlled within 30 mg / L and 5 mg / L respectively;

[0109] (2) Reclaimed water reuse: The wastewater after advanced treatment in step (1) is further treated by the dual-membrane method of ultrafiltration + reverse osmosis. The membrane permeate after treatment is reused, and the membrane concentrate (concentrated brine) enters the subsequent crystallization and salt separation treatment; Ultrafiltration can remove some organic matters in the wastewater and reduce the chromaticity, and can also intercept some colloids, bacteria and other impurities, prolonging the service life of the subsequent reverse osmosis membrane; The reverse osmosis membrane can remove most of the salts in the water, and also has a very high removal effect on hardness, COD, etc., thus ensuring the quality of the reclaimed water;

[0110] (3) Crystallization and salt separation: The membrane concentrate (reverse osmosis concentrate) is subjected to salt separation by nanofiltration. The nanofiltration permeate mainly contains monovalent salts such as sodium chloride and sodium nitrate, and the nanofiltration concentrate contains salts such as sodium chloride, sodium nitrate and sodium sulfate. The nanofiltration permeate and concentrate are respectively highly concentrated by high-pressure reverse osmosis, and the concentrated solutions are respectively subjected to thermal separation crystallization, the salts are disposed of resourcefully, and the condensate is reused.

[0111] The above-mentioned embodiments are only the preferred embodiments of the present invention, but the implementation manners of the present invention are not limited by the above-mentioned embodiments. For example, combinations of various forms of the solutions in Embodiments 1 to 4, and any other changes, modifications, substitutions, and combinations made without departing from the spirit and principle of the present invention shall be equivalent substitution methods and are all within the protection scope of the present invention.

Claims

1. A method for advanced treatment of biochemical effluent from coal chemical industry, characterized in that, the advanced treatment method selectively adopts one or a combination of advanced oxidation methods such as ultraviolet irradiation, addition of oxidant, and addition of catalyst according to different influent ammonia nitrogen and total nitrogen indexes, and specifically includes the following steps: S1: Measure the ammonia nitrogen and total nitrogen of the biochemical effluent from coal chemical industry; S2: Select the advanced oxidation method and conditions according to the following conditions, (i) When the C 氨氮 / C 总氮 value is between 0.5 and 1, advanced oxidation is carried out by ultraviolet irradiation and adding an oxidant at room temperature; (ii)When C 氨氮 / C 总氮 has a value between 0.3 and 0.5, advanced oxidation is carried out by means of ultraviolet irradiation, addition of an oxidant and addition of a catalyst under heating conditions, and the catalyst is a catalyst with photocatalytic oxidation activity; (iii) When C 氨氮 / C 总氮 is between 0 and 0.3, under heating conditions, ultraviolet irradiation, addition of oxidant and addition of catalyst are used for staged advanced oxidation. The staged advanced oxidation includes the first-stage advanced oxidation and the second-stage advanced oxidation. The wastewater first enters the first-stage advanced oxidation section for reaction, and the changes in the ammonia nitrogen and total nitrogen contents are dynamically monitored during the reaction. When C 氨氮 / C 总氮 increases from the initial 0 - 0.3 to 0.6 - 0.8, it immediately transfers to the second-stage advanced oxidation section. The catalyst in the first-stage advanced oxidation is a catalyst with photocatalytic oxidation activity, and the catalyst in the second-stage advanced oxidation is a catalyst with photocatalytic reduction activity; the catalyst with photocatalytic oxidation activity is one or more of titanium dioxide modified by iron and platinum; the catalyst with photocatalytic reduction activity is a silver-modified titanium dioxide catalyst; The ultraviolet irradiation intensity is 20~150 mw / cm 2 , and the wavelength of the ultraviolet irradiation is 254 nm; the oxidant is one or more of hydrogen peroxide, sodium hypochlorite solution, and sodium persulfate solution; in the above (ii) and (iii), the heating condition is to heat to 30-60 °C.

2. A method for advanced treatment of biochemical effluent from coal chemical industry according to claim 1, characterized in that, the dosage of the oxidant is 0.1-0.3% by mass ratio.

3. Application of the method for advanced treatment of biochemical effluent from coal chemical industry according to claim 1 or 2 in treating biochemical effluent from coal chemical industry.

4. A treatment method for zero discharge of biochemical effluent from coal chemical industry, characterized in that, the method includes the following steps: (1) Advanced treatment of biochemical effluent: Use the method for advanced treatment of biochemical effluent from coal chemical industry according to claim 1 or 2 to perform advanced treatment on the biochemical wastewater, and control the COD and ammonia nitrogen in the treated wastewater within 30 mg / L and 5 mg / L respectively; (2) Reuse of reclaimed water: Use the dual-membrane method of ultrafiltration + reverse osmosis to treat the wastewater after advanced treatment in step (1) again, and the membrane permeate after treatment is reused, and the membrane concentrate enters the subsequent crystallization and salt separation treatment; (3) Crystallization and salt separation: The membrane concentrate is separated by nanofiltration, and the nanofiltration permeate and concentrate are respectively highly concentrated by high-pressure reverse osmosis. The concentrated solutions are respectively subjected to thermal separation crystallization, the salts are disposed of resourcefully, and the condensate is reused.

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