A method for treating aromatic nitro compound wastewater

Abstract

This invention discloses a method for treating aromatic nitro compound wastewater, belonging to the field of wastewater treatment technology. The method includes the following steps: S1. Dividing the water body to be treated into a first part and a second part; S2. Performing iron-carbon micro-electrolysis treatment on the first part to obtain effluent from the iron-carbon micro-electrolysis treatment; S3. Performing Fenton oxidation treatment on the effluent from the iron-carbon micro-electrolysis treatment and the second part to obtain effluent from the Fenton oxidation treatment; S4. Further performing biological treatment on the effluent from the Fenton oxidation treatment. In step S1, the volume ratio of the first part to the second part is (2-4):1, so that the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent from the Fenton oxidation treatment is 1:(1-2). This method is used for the degradation of aromatic nitro compounds in aromatic nitro compound wastewater and to improve the removal efficiency of total nitrogen in wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a method for treating wastewater containing aromatic nitro compounds. Background Technology

[0002] Aromatic nitro compound wastewater is a common type of industrial wastewater, generated during the manufacture of pesticides, herbicides, explosives, dyes, and plasticizers. Most aromatic nitro compounds are highly toxic, mutagenic, and carcinogenic, such as nitrobenzene, nitrotoluene, and nitrophenol. Direct discharge of this wastewater into the environment can cause serious public health and environmental problems. Common wastewater treatment methods include biological processes and advanced oxidation processes. Biological processes can treat low concentrations of aromatic nitro compound wastewater, but high concentrations can inhibit microbial growth. Advanced oxidation processes can effectively degrade aromatic nitro compounds, but they struggle to selectively convert the nitrogen in the nitro groups into nitrogen gas, often resulting in high-concentration nitrogen-containing wastewater. Subsequent nitrification-denitrification denitrification processes are costly.

[0003] Chinese patent CN111892237A discloses a method and system for treating wastewater with high salinity and high concentration of nitro compounds. This method combines advanced oxidation and biological processes. First, the wastewater, including p-nitrobenzoic acid wastewater and TNT production wastewater, is pretreated. This pretreatment includes acidification and micro-electrolysis of the p-nitrobenzoic acid wastewater, followed by mixing it with the TNT production wastewater in a predetermined ratio and coagulation and sedimentation. Next, biochemical treatment is performed, using highly efficient microorganisms immobilized on a carrier to treat the pretreated wastewater, thereby reducing the concentration of nitro compounds and COD. However, this method does not address the impact of nitro compounds in the TNT wastewater on microorganisms or the removal of total nitrogen from the wastewater.

[0004] Therefore, it is necessary to develop an economical and efficient method to treat aromatic nitro compound wastewater, which can effectively degrade aromatic nitro compounds to avoid their impact on microorganisms in biochemical treatment, while achieving the goal of nitrogen removal, i.e., total nitrogen removal. Summary of the Invention

[0005] 1. The technical problem that the invention aims to solve

[0006] To address the problems of poor degradation of aromatic nitro compounds and poor removal of total nitrogen in aromatic nitro compound wastewater in existing technologies, a method for treating aromatic nitro compound wastewater is provided.

[0007] 2. Technical Solution

[0008] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0009] A method for treating aromatic nitro compound wastewater according to the present invention includes the following steps:

[0010] S1. Divide the water body to be treated into a first part and a second part;

[0011] S2. The first part of the water body is subjected to iron-carbon micro-electrolysis treatment to obtain the effluent treated by iron-carbon micro-electrolysis.

[0012] S3. The effluent from the iron-carbon micro-electrolysis treatment and the second part of the water body are subjected to Fenton oxidation treatment to obtain Fenton oxidation treated effluent;

[0013] S4. The effluent from the Fenton oxidation treatment undergoes biological treatment;

[0014] In step S1, the volume ratio of the first part of water to the second part of water is (2-4):1, specifically (2.95-3.05):1, (2.9-3.1):1, (2.7-3.3):1, (2.5-3.5):1, (2.3-3.7):1, and (2.1-3.9):1.

[0015] It is important to note that the process of dividing the water body into two parts, namely step S1, is crucial. The first part of the water body undergoes iron-carbon micro-electrolysis and Fenton oxidation, while the second part undergoes Fenton oxidation. The resulting effluent is then subjected to biological treatment. The aromatic nitro compounds in the first part of the water body are converted into aromatic amino compounds after iron-carbon micro-electrolysis. After Fenton oxidation, these aromatic amino compounds are completely mineralized or oxidized to produce ammonia nitrogen and small molecule acids. Similarly, the aromatic nitro compounds in the second part of the water body are completely mineralized or oxidized to produce nitrite nitrogen and small molecule acids after Fenton oxidation.

[0016] Based on the above treatment method, the amino and nitro groups in aromatic amino compounds and aromatic nitro compounds can be removed from the benzene ring, preventing toxic inhibition of microorganisms in the biochemical treatment. It can also effectively ensure that different types and degrees of oxidation products exist in the influent of the biochemical treatment, and the volume ratio of the first part of the water body and the second part of the water body is (2-4):1, so that the mass ratio of ammonia nitrogen to nitrite nitrogen in the Fenton oxidation treatment effluent is 1:(1-2), which is the optimal substrate condition for subsequent biochemical treatment and is conducive to nitrogen removal.

[0017] Further, step S3 involves mixing the effluent from the iron-carbon micro-electrolysis treatment with the second part of the water body and performing Fenton oxidation treatment to obtain Fenton oxidation treated effluent.

[0018] Because Fe is generated during iron-carbon micro-electrolysis. 2+ and Fe 3+ Therefore, at this time, the Fenton oxidation treatment does not require the addition of Fe. 2+ .

[0019] Furthermore, in step S3, the Fenton oxidation treatment includes adding H2O2, wherein the ratio of the amount of H2O2 added to the COD content is greater than or equal to 0.1 and less than 1.

[0020] Furthermore, the hydraulic residence time of the Fenton oxidation treatment satisfies the following condition: 0.2h ≤ hydraulic residence time (also known as HRT) < 2h.

[0021] It should also be noted that, unlike the recommended standards in the industry standard Technical Specification for Fenton Oxidation Wastewater Treatment Engineering (HJ 1095-2020), this application requires that the hydrogen peroxide concentration and hydraulic retention time in the Fenton oxidation process be controlled below the industry standard recommended standards in order to ultimately ensure that the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent from the Fenton oxidation treatment is 1:(1~2).

[0022] On the other hand, after repeated research, the inventors found that in step S3, the ratio of H2O2 dosage to COD content in the Fenton oxidation treatment, as well as the setting of HRT, are essentially related to the nature of other electron groups on the benzene ring of the aromatic nitro compound being treated. Specifically, there are three situations: First, for wastewater mainly composed of aromatic nitro compounds (such as p-nitrophenol, p-nitroaniline, etc.) with a nitro group and other strong electron-donating groups on the benzene ring, the ratio of H2O2 dosage to COD content is 0.1 to 0.4, with the optimal ratio being 0.2, and the hydraulic retention time is 0.2 to 1 h, with the optimal hydraulic retention time being 0.5 h.

[0023] Secondly, for wastewater mainly composed of aromatic nitro compounds (such as p-nitrotoluene, p-nitrobenzoic acid, etc.) containing a nitro group on the benzene ring and other weak electron-donating or weak electron-withdrawing groups, as well as aromatic nitro compounds (nitrobenzene) without other groups, the ratio of H2O2 dosage to COD content is 0.2 to 0.6, with the optimal ratio being 0.4. The hydraulic retention time is 0.5 to 1.5 h, with the optimal hydraulic retention time being 1 h.

[0024] Thirdly, for wastewater mainly composed of aromatic nitro compounds (such as p-1-chloro-3-nitrobenzene) with one nitro group and other strong electron-withdrawing groups on the benzene ring, as well as aromatic nitro compounds with two or more nitro groups (such as 1,4-dinitrobenzene), the ratio of H2O2 dosage to COD content is 0.4 to 0.8, with the optimal ratio being 0.6. The hydraulic retention time is 1h ≤ hydraulic retention time < 2h, with the optimal hydraulic retention time being 1.5h.

[0025] Furthermore, step S1 also includes pH adjustment.

[0026] The pH adjustment process involves adjusting the pH of the water to be treated to <7.

[0027] Preferably, the pH value of the water to be treated is adjusted to 2 to 6, and more preferably, the pH value of the water to be treated is adjusted to 3 to 4.

[0028] Adjusting the pH value to ensure that the pH value of the first part of the water before the iron-carbon micro-electrolysis treatment is below 7, and to ensure that the pH value of the second part of the water before the Fenton oxidation treatment is also below 7, can improve the effectiveness of the iron-carbon micro-electrolysis treatment and the Fenton oxidation treatment.

[0029] Furthermore, the pH adjustment process uses an acid solution to adjust the pH value.

[0030] The acid solution is sulfuric acid.

[0031] Furthermore, in step S2, aeration is performed simultaneously with the iron-carbon micro-electrolysis treatment.

[0032] The aeration treatment adopts an intermittent aeration method, with an interval of 2 to 4 minutes between the first and last aerations;

[0033] Each aeration session lasts 4–8 minutes, with an aeration rate of 1–3 L / min.

[0034] Further, in step S2, the iron concentration in the iron-carbon micro-electrolysis treatment is 0.4-5 g / L, and the mass ratio of iron to carbon is (4-10):1;

[0035] The HRT of the iron-carbon micro-electrolysis treatment is 0.5 to 2 hours.

[0036] It should be noted that in the iron-carbon micro-electrolysis treatment, the iron concentration of 0.4-5 g / L means that 0.4-5 g of iron is added per liter of the first part of the water.

[0037] Furthermore, the iron is one or both of iron filings and iron shavings;

[0038] The carbon is one or both of activated carbon and charcoal.

[0039] Furthermore, step S4 also includes a coagulation treatment, which is carried out before the biochemical treatment and is used to settle ferrous ions and ferric ions.

[0040] Furthermore, the coagulation treatment specifically involves adjusting the pH value of the effluent from the Fenton oxidation treatment.

[0041] Furthermore, the pH value was adjusted to 7–9 using an alkaline reagent.

[0042] Furthermore, the alkaline reagent is one, two, or more of calcium hydroxide, calcium oxide, and sodium carbonate.

[0043] The coagulation treatment removes some of the ferrous and ferric ions from the effluent of the Fenton oxidation treatment, which settle to form Fenton iron sludge. The remaining ferrous and ferric ions are then introduced into the biological treatment to enhance the anaerobic ammonia oxidation process. Furthermore, because the amount of iron in the iron-carbon microelectrolysis treatment and the amount of H2O2 added during the Fenton oxidation treatment are relatively small, the amount of Fenton iron sludge generated during the coagulation treatment is also reduced.

[0044] Furthermore, in step S4, the biochemical treatment includes anaerobic ammonia oxidation treatment and denitrification treatment;

[0045] The anaerobic ammonia oxidation treatment uses anaerobic ammonia oxidation sludge.

[0046] The denitrification process uses denitrified sludge.

[0047] It should be noted that anaerobic ammonia oxidation can only degrade ammonia nitrogen and nitrite nitrogen, and will produce a small amount of nitrate nitrogen. Furthermore, the first and second portions of water treated by iron-carbon micro-electrolysis will inevitably produce some nitrate nitrogen during Fenton oxidation. Denitrification can utilize the small-molecule acids produced during Fenton oxidation as a carbon source to remove this nitrate nitrogen, without requiring additional carbon source or aeration, thus achieving deep nitrogen removal. Moreover, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent from Fenton oxidation is 1:(1-2), which serves as optimal substrate conditions and can effectively improve the removal of nitrogen by biological treatment.

[0048] The anaerobic ammonia oxidation and denitrification processes can be carried out in any of the following ways:

[0049] Method 1: The anaerobic ammonia oxidation treatment is carried out in reactor 1, and the effluent from the anaerobic ammonia oxidation treatment is subjected to denitrification treatment in reactor 2.

[0050] Furthermore, the anaerobic ammonia oxidation sludge is anaerobic ammonia oxidation granular sludge;

[0051] The denitrifying sludge is a denitrifying flocculent sludge;

[0052] The concentration ratio of the anaerobic ammonia oxidation granular sludge to the denitrification flocculent sludge is (1-3):1.

[0053] Furthermore, the concentration of the anaerobic ammonia oxidation granular sludge is 4000–6000 mg MLSS / L, and the concentration of the denitrification flocculent sludge is 2000–4000 mg MLSS / L.

[0054] Furthermore, the biochemical treatment is carried out continuously for 2 to 3 weeks, followed by sludge removal.

[0055] It should be noted that the sludge discharge treatment refers to discharging the denitrified flocculent sludge after the reaction from reactor two.

[0056] Furthermore, in the anaerobic ammonia oxidation treatment, the dissolved oxygen concentration ranges from 0.1 to 0.5 mg / L, and the hydraulic retention time is from 2 to 6 hours.

[0057] In the denitrification process, the dissolved oxygen concentration ranges from 0.1 to 0.5 mg / L, and the hydraulic retention time is from 2 to 6 hours.

[0058] Method 2: The anaerobic ammonia oxidation treatment and denitrification treatment are carried out in the same reactor.

[0059] Furthermore, the anaerobic ammonia oxidation sludge is anaerobic ammonia oxidation granular sludge;

[0060] The denitrifying sludge is a denitrifying flocculent sludge;

[0061] The concentration ratio of the anaerobic ammonia oxidation granular sludge to the denitrification flocculent sludge is (1-3):1.

[0062] Furthermore, the concentration of the anaerobic ammonia oxidation granular sludge is 4000–6000 mg MLSS / L, and the concentration of the denitrification flocculent sludge is 2000–4000 mg MLSS / L.

[0063] Furthermore, the biochemical treatment is carried out continuously for 2 to 3 weeks, followed by sludge removal.

[0064] It should be noted that the sludge discharge treatment refers to discharging the denitrified flocculent sludge after the reaction from the reactor.

[0065] Furthermore, in the anaerobic ammonia oxidation treatment, the dissolved oxygen concentration ranges from 0.1 to 0.5 mg / L, and the hydraulic retention time is from 2 to 6 hours.

[0066] In the denitrification process, the dissolved oxygen concentration ranges from 0.1 to 0.5 mg / L, and the hydraulic retention time is from 2 to 6 hours.

[0067] Preferably, the dissolved oxygen concentration is 0.2 mg / L.

[0068] The preferred method, biochemical treatment, can reduce the number of equipment and the floor space required for facilities, thereby lowering costs.

[0069] When using the above-mentioned method two for biochemical treatment, the reactor can be one of an upflow anaerobic sludge blanket (UASB), an internal circulation anaerobic reactor (IC), or a sequencing batch reactor (SBR).

[0070] Furthermore, the anaerobic ammonia oxidation granular sludge and denitrification flocculation sludge have been operating stably in the integrated anaerobic SBR reactor for more than 180 days.

[0071] In the integrated anaerobic SBR reactor, the inoculum amount of anaerobic ammonia oxidation granular sludge is higher than that of denitrification flocculent sludge.

[0072] Furthermore, the inoculum amount of the anaerobic ammonia oxidation granular sludge is 150% to 300% of the inoculum amount of the denitrification flocculent sludge.

[0073] Furthermore, the concentration of aromatic nitro compounds in the water to be treated is 1000–10000 mg / L.

[0074] 3. Beneficial effects

[0075] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0076] (1) The present invention provides a method for treating wastewater containing aromatic nitro compounds. In this method, the water body to be treated is divided into a first part and a second part. The aromatic nitro compounds in the first part are reduced to aromatic amino compounds by iron-carbon micro-electrolysis. Then, the aromatic amino compounds and the aromatic nitro compounds in the second part are completely mineralized or oxidized by Fenton oxidation to generate small-molecule acids, ammonia nitrogen, nitrite nitrogen and a small amount of nitrate nitrogen. This achieves the removal of amino and nitro groups from the benzene ring in both parts of the water body, thereby degrading the aromatic nitro compounds and preventing them from causing toxic inhibition to microorganisms in the biochemical treatment. This is conducive to the stable and efficient removal of aromatic nitro compounds. The mass ratio of the generated ammonia nitrogen to nitrite nitrogen is 1:(1~2), which provides the optimal substrate conditions for subsequent biochemical treatment, so as to facilitate the removal of total nitrogen.

[0077] (2) The method for treating aromatic nitro compound wastewater provided by the present invention includes anaerobic ammonia oxidation treatment and denitrification treatment in the biochemical treatment. In the anaerobic ammonia oxidation treatment, anaerobic ammonia oxidizing bacteria use ammonia nitrogen and nitrite nitrogen as substrates for autotrophic denitrification. In the denitrification treatment, denitrifying bacteria use easily biodegradable small molecule acids and nitrite nitrogen as substrates for heterotrophic denitrification. Based on the ammonia nitrogen and nitrite nitrogen produced by Fenton oxidation treatment with a mass ratio of 1:(1~2), the advanced oxidation method and the biological method are combined to achieve the purpose of nitrogen removal. Moreover, compared with the traditional nitrification and denitrification denitrification process, there is no need to add carbon source and aeration during biochemical treatment, which reduces the cost of denitrification.

[0078] (3) The method for treating aromatic nitro compound wastewater provided by the present invention carries out anaerobic ammonia oxidation and denitrification in the same reactor, which reduces the number of equipment and structures and lowers the cost; using flocculent sludge for short-cut nitrification, i.e. denitrification, and granular sludge for anaerobic ammonia oxidation, the denitrifying bacteria with faster growth cycle are more easily discharged from the reactor, while the anaerobic ammonia oxidizing bacteria with slower growth cycle are retained in the reactor, thus overcoming the contradiction of inconsistent growth cycles between anaerobic ammonia oxidizing bacteria and denitrifying bacteria. Attached Figure Description

[0079] Figure 1 This is a schematic flowchart of the treatment method for the target water body in Embodiment 1 of the present invention. Detailed Implementation

[0080] This disclosure can be more readily understood by referring to the following description in conjunction with examples, all of which form part of this disclosure. It should be understood that this disclosure is not limited to the specific products, methods, conditions, or parameters described and / or shown herein. Furthermore, the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting, unless otherwise stated.

[0081] It should also be understood that, for clarity, certain features of this disclosure may be described herein in the context of individual embodiments, but may also be provided in combination with each other in individual embodiments. That is, unless obviously incompatible or specifically excluded, each individual embodiment is considered to be combinable with any other embodiment, and such combination is considered to represent another different embodiment. Conversely, for brevity, various features of this disclosure described in the context of individual embodiments may also be provided individually or in any sub-combination. Finally, while a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure may also be considered an independent embodiment in itself.

[0082] Unless otherwise stated, it should be understood that each individual element in the list and each combination of individual elements in the list will be interpreted as a different embodiment. For example, a list of embodiments denoted as "A, B, or C" should be interpreted as including embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C".

[0083] In this disclosure, the singular forms of the articles “a,” “one,” and “the” also include the corresponding plural references, and references to a particular value include at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “substance” is a reference to at least one of such substance and its equivalents.

[0084] Ordinal terms such as “first” and “second” may be used to describe various components or fluids, but these components and fluids are not limited by these terms. Therefore, without departing from the teachings of this disclosure, these terms are used only to distinguish one component / fluid from another.

[0085] When an item is described using the combined terms “...and / or ...", the description should be understood to include any one of the listed items and all combinations thereof.

[0086] Generally, the use of the term "about" indicates an approximation that can vary depending on the desired characteristics obtained from the disclosed subject matter and will be interpreted in a context-dependent manner based on function. Therefore, those skilled in the art will be able to interpret a degree of difference on a case-by-case basis. In some cases, the number of significant figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about." In other cases, a gradient within a range of values ​​can be used to determine the range of differences allowed by the term "about." Furthermore, all ranges in this disclosure are inclusive and composable, and references to values ​​within a range include every value within that range.

[0087] 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 invention pertains; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0088] Unless otherwise specified in the following examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0089] The total nitrogen in the embodiments and comparative examples of this invention is calculated as follows:

[0090] Total nitrogen = organic nitrogen + ammonia nitrogen + nitrite nitrogen + nitrate nitrogen;

[0091] In the formula, organic nitrogen includes organic nitrogen in p-nitrophenol and organic nitrogen in p-aminophenol.

[0092] The method for calculating the removal rate of p-nitrophenol is as follows:

[0093]

[0094] In the formula, the concentration of p-nitrophenol in the effluent is the concentration of p-nitrophenol in the effluent after biochemical treatment.

[0095] The present invention will be further illustrated below with reference to specific embodiments, but these embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. The essential features and significant effects of the present invention can be seen from the following embodiments. The described embodiments are some, but not all, embodiments of the present invention, and therefore do not limit the present invention in any way. Any non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are within the protection scope of the present invention.

[0096] Example 1

[0097] I. The target water quality treated in this embodiment is as follows:

[0098] Aromatic nitro compounds: p-nitrophenol;

[0099] The target water body has a p-nitrophenol concentration of 5000 mg / L and a COD content of 7700 mg / L.

[0100] II. The steps for treating the target water body in this embodiment (e.g.) Figure 1 (As shown) and the parameters are as follows:

[0101] S1. pH adjustment of the target water body: Use concentrated sulfuric acid with a mass fraction of 98% to adjust the pH of the target water body to be treated to a range of 3 to 4. Divide the target water body to be treated into a first part and a second part according to a volume ratio of 3:1.

[0102] S2. After the first part of the water is treated by iron-carbon micro-electrolysis, it enters the Fenton oxidation treatment.

[0103] In the iron-carbon micro-electrolysis treatment, the concentration of iron filings added is 2 g / L, and the mass ratio of iron filings to activated carbon is 6:1; the HRT of the iron-carbon micro-electrolysis treatment is 1 h; at the same time, the iron-carbon micro-electrolysis treatment needs to be carried out simultaneously, and the intermittent aeration method is adopted, aerating once every 3 min, each aeration lasting 6 min, and the aeration rate is controlled at 1-3 L / min.

[0104] S3. The second part of the water body and the first part of the water body that has undergone iron-carbon micro-electrolysis treatment are mixed and treated in the Fenton oxidation treatment step.

[0105] During Fenton oxidation treatment, the ratio of H2O2 dosage to COD content in the target water body was 0.2, and the hydraulic retention time was 0.5 h. H2O2 was added through a 30% (w / w) H2O2 solution.

[0106] During operation, the amounts of ammonia nitrogen and nitrite nitrogen in the effluent from the Fenton oxidation treatment were measured every 3 days. Based on the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent from the Fenton oxidation treatment was within the range of 1:(1.0 to 1.2).

[0107] S4. Add calcium hydroxide to the effluent from the Fenton oxidation treatment for coagulation treatment, and control the pH value of the coagulation treatment to 8.

[0108] The effluent from the Fenton oxidation treatment, after coagulation, is fed into an SBR reactor that integrates anaerobic ammonia oxidation and denitrification. Anaerobic ammonia oxidation and denitrification are then performed. During the anaerobic ammonia oxidation and denitrification process, the dissolved oxygen concentration is controlled at 0.2 mg / L, the water temperature is controlled at 30–35℃, and the hydraulic retention time is 4 hours. Sludge is removed once every three weeks of continuous operation.

[0109] The SBR reactor is filled with anaerobic ammonia oxidation granular sludge and denitrification flocculent sludge; the concentration of the anaerobic ammonia oxidation granular sludge is 5000 mg MLSS / L, and the concentration of the denitrification flocculent sludge is 2500 mg MLSS / L, ultimately ensuring that the concentration ratio of the anaerobic ammonia oxidation granular sludge to the denitrification flocculent sludge is 2:1.

[0110] The anaerobic ammonia oxidation granular sludge and denitrification flocculent sludge have been operating stably in the integrated anaerobic SBR reactor II for more than 180 days. The inoculum size of the anaerobic ammonia oxidation granular sludge in the integrated anaerobic SBR reactor II is 250% of the inoculum size of the denitrification flocculent sludge. The specific process conditions of the integrated anaerobic SBR reactor II are as follows: the influent contains 200 mg N / L ammonia nitrogen, 250 mg N / L nitrite nitrogen, and 50 mg N / L nitrate nitrogen, and the effluent total nitrogen is less than 3 mg N / L, with a removal rate of more than 99%.

[0111] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, Fenton oxidation treatment, and biological treatment were taken for analysis and testing. The treatment results are shown in Table 1.

[0112] Table 1. Wastewater quality before and after treatment in this embodiment.

[0113]

[0114]

[0115] In the simulated engineering case, this embodiment can treat wastewater with a p-nitrophenol concentration of 5000 mg / L to 6.9 mg / L, producing 2.2 mg / L of p-aminophenol, with a p-nitrophenol removal rate of over 99%; and treat total nitrogen from 503.6 mgN / L to 1.3 mgN / L, with a total nitrogen removal rate of over 99%. It demonstrates excellent p-nitrophenol degradation and nitrogen removal capabilities; the entire biochemical treatment process does not require the addition of carbon sources or aeration, greatly reducing denitrification costs.

[0116] Comparative Example 1-1-1

[0117] This comparative example is basically the same as Example 1, except that: the target water body to be treated is not diverted or subjected to iron-carbon micro-electrolysis treatment, but is directly subjected to Fenton oxidation treatment.

[0118] During operation, the amounts of ammonia nitrogen and nitrite nitrogen in the effluent from the Fenton oxidation treatment were measured every 3 days. According to the results of each test, the ammonia nitrogen in the effluent from the Fenton oxidation treatment was below the detection limit, and the nitrite nitrogen concentration was in the range of 400-450 mgN / L.

[0119] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, Fenton oxidation treatment, and biological treatment were taken for analysis and testing. The treatment results are shown in Table 2.

[0120] Table 2. Wastewater quality before and after treatment in this comparative example.

[0121]

[0122] In the simulated engineering case, the removal rate of p-nitrophenol was over 95%, but 152.9 mg / L of p-nitrophenol still remained; the total nitrogen removal rate was about 78%, and the remaining 113.0 mg N / L of total nitrogen was difficult to remove because the concentration of nitrite nitrogen produced after Fenton oxidation was too high. Therefore, directly performing Fenton oxidation treatment without iron-carbon micro-electrolysis treatment is not conducive to the removal of organic matter and total nitrogen.

[0123] Comparative Example 1-1-2

[0124] This comparative example is basically the same as Example 1, except that: the target water body to be treated is not diverted, but directly enters the Fenton oxidation treatment step after being treated by iron-carbon micro-electrolysis.

[0125] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(0.4 to 0.6).

[0126] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, Fenton oxidation treatment, and biological treatment were taken for analysis and testing. The treatment results are shown in Table 3.

[0127] Table 3. Wastewater quality before and after treatment in this comparative example.

[0128]

[0129] In the simulated engineering case, this solution can treat wastewater with a p-nitrophenol concentration of 5000 mg / L to 4.3 mg / L, producing 2.6 mg / L of p-aminophenol. The p-nitrophenol removal rate is over 99%, because p-nitrophenol is more easily removed by Fenton oxidation after iron-carbon micro-electrolysis. However, the total nitrogen removal rate is only about 67%, and the remaining 164.6 mg N / L of total nitrogen is difficult to remove because the Fenton oxidation treatment produces a large amount of ammonia nitrogen that cannot be removed. Therefore, this method is beneficial for the removal of organic matter but not for the removal of total nitrogen.

[0130] Comparative Example 1-2-1

[0131] This comparative example is basically the same as Example 1, except that in step S1, the target water body to be treated is divided into a first part of water body and a second part of water body according to a 1:1 volume ratio.

[0132] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(2.2 to 2.5).

[0133] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, Fenton oxidation treatment, and biological treatment were taken for analysis and testing. The treatment results are shown in Table 4.

[0134] Table 4. Wastewater quality before and after treatment in this comparative example.

[0135]

[0136] In the simulated engineering case, this solution can treat wastewater with a p-nitrophenol concentration of 5000 mg / L to 8.6 mg / L, producing 1.2 mg / L of p-aminophenol, with a p-nitrophenol removal rate of over 99%. The total nitrogen removal rate is around 89%, but the remaining 54.4 mg N / L of total nitrogen is difficult to remove because the concentration of nitrite nitrogen produced after Fenton oxidation is too high. Therefore, this method can effectively remove organic matter but is not conducive to the removal of total nitrogen.

[0137] Comparative Example 1-2-2

[0138] This comparative example is basically the same as Example 1, except that in step S1, the target water body to be treated is divided into a first part of water body and a second part of water body according to a volume ratio of 5:1.

[0139] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(0.6 to 0.8).

[0140] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, the Fenton oxidation treatment, and the biochemical treatment were taken for analysis and testing. The treatment results are shown in Table 5.

[0141] Table 5. Wastewater quality before and after treatment in this comparative example.

[0142]

[0143] In the simulated engineering case, this solution can treat wastewater with a p-nitrophenol concentration of 5000 mg / L to 4.6 mg / L, producing 2.5 mg / L of p-aminophenol, with a p-nitrophenol removal rate of over 99% and a total nitrogen removal rate of over 90%. However, the remaining 42.4 mg N / L of total nitrogen is difficult to remove because a large amount of ammonia nitrogen is generated after Fenton oxidation treatment. Therefore, this method can effectively remove organic matter but is not conducive to the removal of total nitrogen.

[0144] Comparative Example 1-3-1

[0145] This comparative example is basically the same as Example 1, except that in step S3, the ratio of H2O2 dosage to target COD content in the water body during Fenton oxidation treatment is 0.05.

[0146] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(0.7 to 0.9).

[0147] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, the Fenton oxidation treatment, and the biochemical treatment were taken for analysis and testing. The treatment results are shown in Table 6.

[0148] Table 6. Water quality before and after wastewater treatment in this comparative example.

[0149]

[0150] In the simulated engineering case, this comparative example can treat wastewater with a p-nitrophenol concentration of 5000 mg / L to 1889.8 mg / L, but produces 1165.3 mg / L of p-aminophenol. This is because the hydrogen peroxide concentration is too low, and the Fenton oxidation treatment is almost ineffective. In addition, severe floating and death of sludge in the biological treatment section were observed. This is because the high concentrations of p-nitrophenol and p-aminophenol have a toxic effect on microorganisms, resulting in almost no removal of total nitrogen. Therefore, this method cannot remove organic matter and total nitrogen, and it will damage the biological system.

[0151] Comparative Example 1-3-2

[0152] This comparative example is basically the same as Example 1, except that in step S3, the ratio of H2O2 dosage to target COD content in the water body during Fenton oxidation treatment is 0.8.

[0153] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(0.4 to 0.7).

[0154] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, the Fenton oxidation treatment, and the biochemical treatment were taken for analysis and testing. The treatment results are shown in Table 7.

[0155] Table 7 Water quality before and after wastewater treatment in this comparative example.

[0156]

[0157] In the simulated engineering case, this comparative example can treat wastewater with a p-nitrophenol concentration of 5000 mg / L to 3.7 mg / L, producing 1.2 mg / L of p-aminophenol, with a p-nitrophenol removal rate of over 99%. The total nitrogen removal rate is around 78%, leaving 113.2 mg N / L of total nitrogen that is difficult to remove. This is because excessive hydrogen peroxide is added, and nitrite nitrogen is further oxidized to nitrate nitrogen during the Fenton process, resulting in insufficient nitrite nitrogen required for subsequent anaerobic ammonia oxidation, making ammonia nitrogen difficult to remove. Therefore, this method can effectively remove organic matter but is not conducive to the removal of total nitrogen.

[0158] Comparative Example 1-3-3

[0159] This comparative example is basically the same as Example 1, except that in step S3, the ratio of H2O2 dosage to COD content of the target water body during Fenton oxidation treatment is 1.

[0160] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(0.04 to 0.1).

[0161] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, the Fenton oxidation treatment, and the biochemical treatment were taken for analysis and testing. The treatment results are shown in Table 8.

[0162] Table 8. Water quality before and after wastewater treatment in the comparative examples.

[0163]

[0164] In the simulated engineering case, this comparative example can treat wastewater with a p-nitrophenol concentration of 5000 mg / L to 4.1 mg / L, producing 1.5 mg / L of p-aminophenol, with a p-nitrophenol removal rate of over 99%. However, the total nitrogen removal rate is only around 34%, leaving 332.2 mg N / L of total nitrogen that is difficult to remove. This is because excessive hydrogen peroxide was added, causing nitrite nitrogen to be almost completely oxidized to nitrate nitrogen during the Fenton process. This results in insufficient nitrite nitrogen required for subsequent anaerobic ammonia oxidation, making ammonia nitrogen difficult to remove. Furthermore, the high concentration of ammonia nitrogen also inhibits the removal of nitrate nitrogen by denitrifying bacteria. Therefore, this method can effectively remove organic matter but is not conducive to the removal of total nitrogen.

[0165] Example 2

[0166] The treatment was basically the same as in Example 1, except that the concentration of p-nitrophenol in the target water body was 1000 mg / L and the COD content was 1540 mg / L.

[0167] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(1 to 1.4).

[0168] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, the Fenton oxidation treatment, and the biochemical treatment were taken for analysis and testing. The treatment results are shown in Table 9.

[0169] Table 9. Water quality before and after wastewater treatment in this embodiment.

[0170]

[0171] In the simulated engineering case, this embodiment can treat wastewater with a p-nitrophenol concentration of 1000 mg / L to 5.2 mg / L, producing 1.9 mg / L of p-aminophenol, with a p-nitrophenol removal rate of over 99%; and treat total nitrogen from 100.7 mgN / L to 1.2 mgN / L, with a total nitrogen removal rate of over 98%. It demonstrates excellent p-nitrophenol degradation and nitrogen removal capabilities; the entire biochemical treatment process does not require the addition of carbon sources or aeration, greatly reducing denitrification costs.

[0172] Example 3

[0173] The treatment was basically the same as in Example 1, except that the concentration of p-nitrophenol in the target water body was 10,000 mg / L and the COD content was 15,400 mg / L.

[0174] During operation, the amount of ammonia nitrogen and nitrite nitrogen in the effluent of Fenton oxidation treatment is measured every 3 days. According to the results of each test, the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of Fenton oxidation treatment is in the range of 1:(1 to 1.4).

[0175] After 30 days of stable operation, samples of the effluent from the iron-carbon micro-electrolysis treatment, the Fenton oxidation treatment, and the biochemical treatment were taken for analysis and testing. The treatment results are shown in Table 10.

[0176] Table 10 Water quality before and after wastewater treatment in this embodiment.

[0177]

[0178] In the simulated engineering case, this embodiment can treat wastewater with a p-nitrophenol concentration of 10000 mg / L to 7.8 mg / L, producing 2.7 mg / L of p-aminophenol, with a p-nitrophenol removal rate of over 99%; it can also treat total nitrogen from 1007.2 mgN / L to 4.6 mgN / L, with a total nitrogen removal rate of over 99%. This demonstrates excellent p-nitrophenol degradation and nitrogen removal capabilities. The entire biochemical treatment process does not require the addition of a carbon source or aeration, greatly reducing denitrification costs.

Claims

1. A method for treating wastewater containing aromatic nitro compounds, characterized in that, Includes the following steps: S1. Divide the water body to be treated into a first part and a second part; S2. The first part of the water body is subjected to iron-carbon micro-electrolysis treatment to obtain the effluent treated by iron-carbon micro-electrolysis. S3. The effluent from the iron-carbon micro-electrolysis treatment and the second part of the water body are subjected to Fenton oxidation treatment to obtain Fenton oxidation treated effluent; S4. The effluent from the Fenton oxidation treatment undergoes biological treatment; In step S1, the volume ratio of the first part of water to the second part of water is (2~4):1; In step S3, the Fenton oxidation treatment includes adding H2O2, wherein the ratio of the amount of H2O2 added to the COD content is greater than or equal to 0.1 and less than 1; the hydraulic retention time of the Fenton oxidation treatment satisfies: 0.2h ≤ hydraulic retention time < 2h; and the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of the Fenton oxidation treatment is guaranteed to be 1:(1~2). In step S4, the biochemical treatment includes anaerobic ammonia oxidation treatment and denitrification treatment.

2. The method for treating aromatic nitro compound wastewater according to claim 1, characterized in that: Step S1 also includes pH adjustment. The pH adjustment process involves adjusting the pH of the water to be treated to <7.

3. The method for treating aromatic nitro compound wastewater according to claim 1 or 2, characterized in that: In step S2, aeration is performed simultaneously with the iron-carbon micro-electrolysis treatment. The aeration treatment adopts an intermittent aeration method, with an interval of 2-4 minutes between the first and last aerations, a duration of 4-8 minutes for each aeration, and an aeration rate of 1-3 L / min.

4. The method for treating aromatic nitro compound wastewater according to claim 3, characterized in that: In the iron-carbon micro-electrolysis treatment, the iron concentration is 0.4~5 g / L, and the mass ratio of iron to carbon is (4~10):1; The hydraulic retention time for the iron-carbon micro-electrolysis treatment is 0.5~2h.

5. The method for treating aromatic nitro compound wastewater according to claim 4, characterized in that: Step S4 also includes a coagulation treatment, which is performed before the biochemical treatment.

6. The method for treating aromatic nitro compound wastewater according to claim 5, characterized in that: The anaerobic ammonia oxidation treatment uses anaerobic ammonia oxidation sludge. The denitrification process uses denitrified sludge.

7. The method for treating aromatic nitro compound wastewater according to claim 6, characterized in that: The anaerobic ammonia oxidation sludge is anaerobic ammonia oxidation granular sludge. The denitrifying sludge is a denitrifying flocculent sludge; The concentration ratio of the anaerobic ammonia oxidation granular sludge to the denitrification flocculent sludge is (1~3):

1.

8. The method for treating aromatic nitro compound wastewater according to claim 7, characterized in that: In the anaerobic ammonia oxidation treatment, the dissolved oxygen concentration ranges from 0.1 to 0.5 mg / L, and the hydraulic retention time is 2 to 6 hours. In the denitrification process, the dissolved oxygen concentration ranges from 0.1 to 0.5 mg / L, and the hydraulic retention time is 2 to 6 hours.

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