Low-medicament-input organic wastewater advanced treatment method and device

Abstract

The application discloses a kind of low reagent input's organic wastewater advanced treatment method and device.The method includes the following steps: anaerobic biological iron sulfur reduction reaction process: elemental sulfur, ferric iron, iron sulfur reduction sludge, organic carbon-containing and electrically negative group organic pollutant wastewater is mixed sufficiently, anaerobic biological elemental sulfur reduction and iron reduction reaction are carried out, in situ directional generation polysulfide and ferrous sulfide;Nucleophilic substitution reaction process: electrically negative group organic pollutant and polysulfide carry out nucleophilic substitution reaction, and remove electronegativity group to generate reduced state organic product;Oxidation reaction process: ferrous sulfide and dissolved oxygen reaction produce hydroxyl radical, and oxidize degradation reduced state organic product, produce elemental sulfur and ferric iron;Sludge sedimentation process: sediment flows back to anaerobic biological iron sulfur reduction reaction zone, and clarified water is discharged.The application realizes the advanced degradation and detoxification of refractory organic pollution, with the advantages of low reagent input, low cost, no secondary pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method and device for deep treatment of organic wastewater with low chemical input. Background Art

[0002] Wastewater from industrial production and residential use contains a variety of organic pollutants, including organic carbon and recalcitrant organic pollutants with negatively charged groups. Compared to readily biodegradable organic carbon, recalcitrant organic pollutants with negatively charged groups, such as halogenated organic pollutants, azobenzene dyes, and organophosphates, are often carcinogenic, teratogenic, and mutagenic, as well as persistent and highly bioaccumulative, posing a serious threat to aquatic ecological safety. Therefore, the efficient removal of recalcitrant organic pollutants from wastewater is crucial for ensuring the safety of the aquatic ecosystem.

[0003] The presence of electronegative groups in recalcitrant organic pollutants makes them significantly bioinhibitory, resulting in extremely low removal efficiency of conventional wastewater biological treatment processes. Currently, the main treatment methods for removing recalcitrant organic pollutants from wastewater include advanced oxidation processes and chemical reduction methods.

[0004] Advanced oxidation processes (ADPs) generate highly oxidizing free radicals, which can oxidize and degrade recalcitrant organic pollutants in wastewater. However, existing ADP systems require large quantities of chemical oxidants and activators, resulting in high reagent inputs and processing costs. Furthermore, the unstable nature of chemical oxidants and their stringent requirements for transportation and storage further limit the application of existing ADP technologies.

[0005] Chemical reduction method uses reducing agents to reduce the toxicity and microbial inhibition of refractory organic pollutants and improve biodegradability. However, the commonly used reducing agents (Fe 0 、Fe 2+ ) have low reduction efficiency for difficult-to-degrade organic pollutants and are unable to completely mineralize and degrade them, easily leading to secondary pollution. Furthermore, chemical reducing agents consume large amounts of material and are expensive. Summary of the Invention

[0006] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a method for deep treatment of organic wastewater with low reagent input, which utilizes the polysulfide generated during the anaerobic biological iron-sulfur reduction reaction to undergo a nucleophilic substitution reaction, so that the organic pollutants with electronegative groups remove the electronegative groups and become reduced organic products; the ferrous sulfide generated during the anaerobic biological iron-sulfur reduction reaction is reacted with dissolved oxygen to produce hydroxyl radicals, which oxidize and degrade the reduced organic products, and under specific reaction conditions, achieve efficient deep degradation of difficult-to-degrade organic pollution with electronegative groups. At the same time, the precipitate generated at the end of the reaction contains recyclable elemental sulfur and ferric iron. By accurately controlling the redox conditions, the iron-sulfur mass ratio and pH, the recovery rate of elemental sulfur and ferric iron can be close to 100%, and there is no need to input chemical oxidants, activators and reducing agents, which greatly reduces the amount of reagent input, avoids the safety risks brought by dangerous reagents during transportation and storage, and reduces secondary pollution.

[0007] Another object of the present invention is to provide a device for realizing the above-mentioned method for deep treatment of organic wastewater with low chemical input.

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

[0009] The present invention provides a method for deep treatment of organic wastewater with low chemical input, comprising the following steps:

[0010] (1) Anaerobic biological iron-sulfur reduction reaction process: In the anaerobic biological iron-sulfur reduction reaction zone, elemental sulfur, trivalent iron, iron-sulfur reduction sludge, and wastewater containing organic carbon and organic pollutants with electronegative groups are fully mixed. Anaerobic biological elemental sulfur reduction and iron reduction reactions are carried out under the conditions of dissolved oxygen concentration less than 0.1 mg / L, pH 8.0-9.0, and iron-sulfur mass ratio of 0.5:1-4:1, to produce polysulfide and ferrous sulfide in situ.

[0011] The iron-sulfur reducing sludge contains elemental sulfur-reducing bacteria and iron-reducing bacteria;

[0012] (2) Nucleophilic substitution reaction process: The effluent from the anaerobic biological iron-sulfur reduction reaction zone is passed into the nucleophilic substitution reaction zone. Under the conditions of pH 8.0-9.0 and dissolved oxygen concentration less than 0.1 mg / L, polysulfides and organic pollutants with electronegative groups undergo nucleophilic substitution reaction. The organic pollutants with electronegative groups remove the electronegative groups to generate reduced organic products.

[0013] (3) Oxidation reaction process: The effluent from the nucleophilic substitution reaction zone is passed into the oxidation reaction zone. Under the conditions of dissolved oxygen content of 2.0-8.0 mg / L and pH of 6.0-9.0, ferrous sulfide reacts with dissolved oxygen to generate hydroxyl radicals in situ, which oxidize and degrade reduced organic products and produce elemental sulfur and trivalent iron precipitation;

[0014] (4) Sludge sedimentation process: The effluent from the oxidation reaction zone is passed into the sludge sedimentation zone for sedimentation separation and recovery of the precipitate; the precipitate is returned to the anaerobic biological iron-sulfur reduction reaction zone to achieve the recycling of elemental sulfur and trivalent iron; the clarified water is discharged through the outlet pipe; the recovery rate of the elemental sulfur is 78% to 96%; the recovery rate of the trivalent iron is 88% to 98%.

[0015] Preferably, the iron-sulfur mass ratio in step (1) is 0.5:1 to 2:1.

[0016] Preferably, the iron-sulfur mass ratio in step (1) is 0.5:1 to 1:1.

[0017] Preferably, the pH of the oxidation reaction process in step (3) is 6.0-7.0.

[0018] Preferably, the organic pollutant with negative electron groups is at least one of halogenated organic matter, azobenzene dye and organic phosphate.

[0019] Preferably, the hydraulic retention time of the anaerobic biological iron-sulfur reduction reaction process is 4 to 12 hours; the hydraulic retention time of the nucleophilic substitution reaction process is 2 to 9 hours; and the hydraulic retention time of the oxidation reaction process is 2 to 10 hours.

[0020] Preferably, the hydraulic retention time of the anaerobic biological iron-sulfur reduction reaction process is 6 to 8 hours; the hydraulic retention time of the nucleophilic substitution reaction process is 4 to 9 hours; and the hydraulic retention time of the oxidation reaction process is 6 to 9 hours.

[0021] Preferably, the anaerobic biological iron-sulfur reduction reaction process, the nucleophilic substitution reaction process, and the oxidation reaction process are all carried out at room temperature.

[0022] Preferably, the precipitate in step (4) contains elemental sulfur, trivalent iron and iron-sulfur reduced sludge.

[0023] Preferably, the oxygen supply method in the oxidation reaction process adopts at least one of microporous aeration, mechanical aeration and jet aeration.

[0024] Preferably, in step (1), the elemental sulfur is at least one of bio-sulfur, sublimed sulfur, and sulfur formed by oxidation of ferrous sulfide; further preferably, the elemental sulfur is at least one of bio-sulfur and sulfur formed by oxidation of ferrous sulfide; most preferably, the elemental sulfur is low-cost sulfur formed by oxidation of ferrous sulfide.

[0025] Preferably, in step (1), the trivalent iron is one or more of amorphous ferric hydroxide, ferrihydrite, lepidocrocite, and hematite; most preferably, the trivalent iron is amorphous ferric hydroxide.

[0026] Preferably, in step (1), the organic carbon is derived from at least one of domestic sewage and food processing wastewater.

[0027] Preferably, elemental sulfur-reducing bacteria can be obtained by acclimating and enriching any inoculum sludge using elemental sulfur as an electron acceptor, or by recovering the precipitate after the oxidation reaction. Iron-reducing bacteria can be obtained by acclimating and enriching sludge, soil, or sediment using iron oxides.

[0028] The present invention also provides a device for realizing the low-agent-input deep treatment method of organic wastewater, wherein the space inside the device is divided into an anaerobic biological iron-sulfur reduction reaction zone, a nucleophilic substitution reaction zone, an oxidation reaction zone, and a sludge sedimentation zone by a partition; the anaerobic biological iron-sulfur reduction reaction zone and the nucleophilic substitution reaction zone are both provided with stirring paddles; a reflux pipe is provided at the bottom of the sludge sedimentation zone, and the precipitate is refluxed to the anaerobic biological iron-sulfur reduction reaction zone through the reflux pipe.

[0029] The basic principles of the present invention are:

[0030] During the anaerobic biological iron-sulfur reduction reaction, elemental sulfur-reducing bacteria (S 0 RB) and iron-reducing bacteria (IRB) use biodegradable organic carbon (e.g., acetic acid CH3COOH) in organic wastewater as electron donors to reduce elemental sulfur to hydrogen sulfide and ferric iron to divalent iron products. The reaction equations are shown in (1)-(3). On the other hand, ferric iron oxides can also be chemically reduced by hydrogen sulfide, and the two are combined to form ferrous sulfide (FeS) and elemental sulfur (S 0 ), the reaction equation is shown in (4). Under weak alkaline conditions of pH 8.0~9.0, elemental sulfur and hydrogen sulfide further combine to form polysulfide (S n 2- ), the reaction equation is shown in (5). Since the iron-sulfur mass ratio, redox conditions and pH will significantly affect S n 2- and FeS production, these factors need to be precisely regulated to ensure S n 2- and the directional and efficient production of FeS.

[0031] (1)

[0032] (2)

[0033] (3)

[0034] (4)

[0035] (5)

[0036] In the nucleophilic substitution reaction, S n 2- It can undergo nucleophilic substitution reaction with the electronegative group-resistant organic matter (RX) in organic wastewater, remove the electronegative group (X), and convert it into reduced organic product, thereby improving its biodegradability and reducing toxicity. The reaction equation is shown in (6). Due to the presence of acidic conditions and dissolved oxygen, S n 2- Decomposition, therefore, the nucleophilic substitution reaction process requires specific dissolved oxygen content and pH conditions to enhance the reductive degradation of refractory organic matter.

[0037] (6)

[0038] During the oxidation reaction, ferrous sulfide reacts with dissolved oxygen to produce trivalent iron oxides and hydroxyl radicals. The reaction equation is shown in (7). These hydroxyl radicals can further deeply oxidize and degrade organic products. At the same time, hydrogen sulfide is oxidized by oxygen to elemental sulfur. The reaction equation is shown in (8). The trivalent iron oxides and elemental sulfur generated by the reaction are transported to the anaerobic biological iron-sulfur reduction reaction zone through the sludge return pipeline for recycling. Maintaining aerobic conditions and specific pH conditions in the oxidation reaction zone can promote the generation of hydroxyl radicals and the selective oxidation of hydrogen sulfide to elemental sulfur, as well as the formation of iron hydroxide precipitation, ensuring efficient degradation of reduced organic products while maximizing the recovery and utilization efficiency of iron and sulfur substances and reducing reagent input and treatment costs.

[0039] (7)

[0040] (8)

[0041] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0042] (1) The low-medicament-input organic wastewater advanced treatment method of the present application utilizes the nucleophilic substitution reaction of polysulfides generated in the process of anaerobic biological iron-sulfur reduction reaction to remove the electronegative groups of organic pollutants to form reduced organic products; the reaction of ferrous sulfide generated in the process of anaerobic biological iron-sulfur reduction reaction with dissolved oxygen produces hydroxyl radicals to oxidatively degrade the reduced organic products, and under specific reaction conditions, the high-efficiency advanced degradation of refractory organic pollutants with electronegative groups is realized. At the same time, the precipitate generated at the end of the reaction contains elemental sulfur and ferric iron which can be recycled, and by accurately controlling the redox conditions, the mass ratio of iron to sulfur and pH, the recovery rate of elemental sulfur and ferric iron can be close to 100%, and in the preferred scheme, no additional elemental sulfur and ferric iron need to be input in the subsequent reaction, and no chemical oxidants, activators and reducing agents need to be input, which greatly reduces the amount of medicament input and production cost; also avoids the safety risks brought by dangerous medicaments in the process of transportation and storage, and reduces secondary pollution.

[0043] (2) The low-medicament-input organic wastewater advanced treatment method of the present application can cooperatively remove organic carbon and electronegative group-containing organic pollutants in wastewater, simplify the wastewater treatment process, and is suitable for the advanced treatment of wastewater in the chemical, dyeing and pesticide production industries.

[0044] (3) The low-medicament-input organic wastewater advanced treatment device of the present application, the anaerobic biological iron-sulfur reduction reaction zone, the chemical reduction zone, the oxidation reaction zone and the sludge sedimentation zone are arranged in an integrated wastewater treatment device, which can reduce the land occupation of wastewater treatment facilities and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a schematic diagram of the low-medicament-input organic wastewater advanced treatment device of the embodiment of the present application;

[0046] Figure 2 is a diagram showing the changes of iron-sulfur substance concentration before and after the anaerobic biological iron-sulfur reduction reaction in the embodiment of the present application;

[0047] Figure 3 is a diagram showing the production of sulfides in the process of anaerobic biological iron-sulfur reduction reaction under different pH conditions in the embodiment of the present application;

[0048] Figure 4 is a concentration comparison diagram of S n 2- in the embodiment of the present application after the anaerobic biological iron-sulfur reduction reaction under different pH conditions;

[0049] Figure 5 is a diagram showing the concentration changes of sulfides in the process of anaerobic biological iron-sulfur reduction reaction under different iron-sulfur mass ratios in the embodiment of the present application;

[0050] Figure 6 is the S in the anaerobic biological iron-sulfur reduction reaction under different iron-sulfur mass ratios in the embodiment of the present invention. n 2- Concentration change diagram of ;

[0051] Figure 7 Graph showing changes in FeS concentration during anaerobic biological iron-sulfur reduction reaction under different iron-sulfur mass ratios in an embodiment of the present invention;

[0052] Figure 8 S under different pH conditions in the embodiments of the present invention n 2- Removal effect of atrazine by reduction degradation (C / C0 in the figure is the ratio of undegraded atrazine to initial atrazine concentration in the solution);

[0053] Figure 9 In the embodiment of the present invention, S n 2- Figure 3 shows the removal effect of atrazine under reduced degradation conditions (C / C0 in the figure is the ratio of the undegraded atrazine to the initial atrazine concentration in the solution);

[0054] Figure 10 3. This is a diagram showing the effect of FeS oxidation to remove atrazine under aerobic conditions in an embodiment of the present invention (in the figure, C / C0 is the ratio of the undegraded atrazine concentration in the solution to the initial atrazine concentration);

[0055] Figure 11 This is a graph showing the cumulative amount of ·OH generated by oxidation of FeS under different pH conditions in an embodiment of the present invention;

[0056] Figure 12 This is a graph showing the cumulative results of ·OH generated by oxidation of FeS at different concentrations in an embodiment of the present invention;

[0057] Figure 13 This is a graph showing the change in concentration of iron and sulfur substances before and after the oxidation reaction in an embodiment of the present invention;

[0058] Figure 14 Graph showing the effect of pH on the recovery rate of low-elemental sulfur and ferric iron and the cumulative amount of ·OH during the oxidation reaction in an embodiment of the present invention;

[0059] Figure 15 Graph showing the effect of the iron-sulfur mass ratio on the recovery of elemental sulfur and ferric iron in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0061] Example

[0062] Figure 1 The figure shows an embodiment of a low-agent-input organic wastewater deep treatment device according to the present invention, comprising an inlet pipe 1, an anaerobic biological iron-sulfur reduction reaction zone 2, a nucleophilic substitution reaction zone 3, an oxidation reaction zone 4, a sludge sedimentation zone 5, an outlet pipe 6, a sludge return pipe 7, a first connecting pipe 8, a second connecting pipe 9, and a third connecting pipe 10. The anaerobic biological iron-sulfur reduction reaction zone 2, the nucleophilic substitution reaction zone 3, the oxidation reaction zone 4, and the sludge sedimentation zone 5 are all arranged within a space within the device and separated by baffles. The first connecting pipe 8 is provided between the anaerobic biological iron-sulfur reduction reaction zone 2 and the nucleophilic substitution reaction zone 3; the second connecting pipe 9 is provided between the nucleophilic substitution reaction zone 3 and the oxidation reaction zone 4; and the third connecting pipe 10 is provided between the oxidation reaction zone 4 and the sludge sedimentation zone 5. The water inlet pipe 1 is located at the bottom of the anaerobic biological iron-sulfur reduction reaction zone 2; the first connecting pipe 8 is located above the anaerobic biological iron-sulfur reduction reaction zone 2 and the nucleophilic substitution reaction zone 3; the second connecting pipe 9 is located below the nucleophilic substitution reaction zone 3 and the oxidation reaction zone 4; the third connecting pipe 10 is located above the oxidation reaction zone 4 and the sludge sedimentation zone 5; and the water outlet pipe 6 is located above the sludge sedimentation zone 5. The sludge return pipe 7 is located at the bottom of the sludge sedimentation zone 5. Clarified water is discharged through the water outlet pipe 6, and the sediment is returned to the anaerobic biological iron-sulfur reduction reaction zone through the sludge return pipe 7.

[0063] A stirring paddle is provided in the anaerobic biological iron-sulfur reduction reaction zone 2 and the nucleophilic substitution reaction zone 3; the stirring paddle is used for stirring to ensure homogenization in the anaerobic biological iron-sulfur reduction reaction zone 2 and the nucleophilic substitution reaction zone 3; an aeration device 11 is provided in the oxidation reaction zone 4, and the aeration device 11 can be one or more of microporous aeration, mechanical aeration, and jet aeration; the aeration device 11 is used to supply oxygen.

[0064] A method for deep treatment of organic wastewater with low chemical input using a deep treatment device for organic wastewater with low chemical input according to one embodiment of the present invention comprises the following steps:

[0065] (1) Anaerobic biological iron-sulfur reduction reaction process: In the anaerobic biological iron-sulfur reduction reaction zone, elemental sulfur, trivalent iron, iron-sulfur reduction sludge, and wastewater containing organic carbon and organic pollutants with electronegative groups are fully mixed. Anaerobic biological sulfur reduction and iron reduction reactions are carried out under the conditions of dissolved oxygen concentration less than 0.1 mg / L, pH 8.0-9.0, and iron-sulfur mass ratio of 0.5:1-4:1, to produce polysulfide and ferrous sulfide in situ.

[0066] The iron-sulfur reducing sludge contains elemental sulfur-reducing bacteria and iron-reducing bacteria;

[0067] (2) Nucleophilic substitution reaction process: The effluent from the anaerobic biological iron-sulfur reduction reaction zone is passed into the nucleophilic substitution reaction zone, and the reaction is carried out under the conditions of pH 8.0-9.0 and dissolved oxygen concentration less than 0.1 mg / L: polysulfide undergoes nucleophilic substitution reaction with organic pollutants with electronegative groups, and the organic pollutants with electronegative groups remove the electronegative groups to generate reduced organic products;

[0068] (3) Oxidation reaction process: The effluent from the nucleophilic substitution reaction zone is passed into the oxidation reaction zone and the reaction is carried out under the conditions of dissolved oxygen content of 2.0-8.0 mg / L and pH of 6.0-9.0: ferrous sulfide reacts with dissolved oxygen to generate hydroxyl radicals in situ, which oxidize and degrade reduced organic products and produce elemental sulfur and trivalent iron precipitation;

[0069] (4) Sludge sedimentation process: The effluent from the oxidation reaction zone is passed into the sludge sedimentation zone for sedimentation and separation, and the precipitate is recovered; the precipitate is returned to the anaerobic biological iron-sulfur reduction reaction zone to achieve the recycling of elemental sulfur and trivalent iron; the clarified water is discharged through the effluent pipe.

[0070] In some embodiments of the present invention, the iron-sulfur mass ratio in step (1) is 0.5:1 to 2:1.

[0071] In some embodiments of the present invention, the pH of the oxidation reaction process in step (3) is 6.0-7.0.

[0072] In some embodiments of the present invention, the iron-sulfur mass ratio in step (1) is 0.5:1~1:1; the recovery rate of elemental sulfur in step (4) is 77.4%~95.3%; and the recovery rate of trivalent iron in step (4) is 89.4%~97.4%.

[0073] In some embodiments of the present invention, the organic pollutant with negatively charged groups is at least one of a halogenated organic compound, an azobenzene dye, and an organic phosphate.

[0074] In some embodiments of the present invention, the hydraulic retention time of the anaerobic biological iron-sulfur reduction reaction process is 4 to 12 hours; the hydraulic retention time of the nucleophilic substitution reaction process is 2 to 9 hours; and the hydraulic retention time of the oxidation reaction process is 2 to 10 hours. More preferably, the hydraulic retention time of the anaerobic biological iron-sulfur reduction reaction process is 6 to 8 hours; the hydraulic retention time of the nucleophilic substitution reaction process is 4 to 9 hours; and the hydraulic retention time of the oxidation reaction process is 6 to 9 hours.

[0075] In some embodiments of the present invention, the anaerobic biological iron-sulfur reduction reaction process, the nucleophilic substitution reaction process, and the oxidation reaction process are all carried out at room temperature.

[0076] In some embodiments of the present invention, iron-sulfur reduction sludge is prepared by an acclimation and enrichment method, and the specific process is as follows:

[0077] The strain of elemental sulfur-reducing bacteria can be taken from the anaerobic tank of any sewage treatment plant. After the sludge is retrieved, it is allowed to stand for 1 hour. After the mud and water are separated, the supernatant is poured out; the sludge is poured into a closed container and an excess of sublimated sulfur powder is added; it is domesticated using simulated domestic sewage; the simulated domestic sewage contains 500 mg-C / L organic carbon and 500 mg / L alkalinity; it is stirred using a blender at a stirring speed of 300 rpm; the simulated domestic sewage is replaced every 5 days and cultured at room temperature for 3 months; samples are regularly taken to test indicators such as sulfide concentration and sludge performance to judge the sludge domestication status; after 3 months of domestication, the average sulfide concentration and sludge settling performance are significantly improved, indicating that the elemental sulfur-reducing sludge is successfully cultured.

[0078] The strain of iron-reducing bacteria comes from the sludge in the anaerobic tank of the sewage treatment plant. 1000 mg / L of ferric hydroxide and simulated biological sewage are regularly added to the sludge, and it is continuously stirred under anaerobic conditions for domestication. The simulated domestic sewage is replaced every 5 days, and samples are regularly taken to measure the concentration of divalent iron to determine the enrichment of iron-reducing bacteria. After 3 months of domestication, sludge rich in iron-reducing bacteria can be obtained.

[0079] Iron-sulfur reducing sludge can be obtained by mixing sludge rich in elemental sulfur-reducing bacteria and iron-reducing bacteria in equal proportions.

[0080] In order to illustrate the necessity of accurately controlling the pH conditions and the iron-sulfur mass ratio in the low-agent-input organic wastewater deep treatment method of the present invention, this example tests the effects of different pH conditions and different iron-sulfur mass ratios on the degradation effect of organic pollutants and the effects on the recovery rates of trivalent iron and elemental sulfur in each reaction process. The results are as follows: Figures 2-15 In the following tests, the dissolved oxygen concentration during the anaerobic biological iron-sulfur reduction reaction and the nucleophilic substitution reaction was less than 0.1 mg / L; the dissolved oxygen content during the oxidation reaction was 7.0 mg / L; and the input trivalent iron was amorphous ferric hydroxide.

[0081] Figure 2 The figure shows the change of iron and sulfur concentration before and after anaerobic biological iron and sulfur reduction reaction (reaction conditions: pH = 9, iron and sulfur mass ratio Fe(Ⅲ): S 0 =1:1,[S 0 ]=1 g / L, organic carbon=500mg / L). After anaerobic biological iron-sulfur reduction reaction, S 0 and Fe(Ⅲ) concentrations decreased significantly, while dissolved sulfide (S 2-) and polysulfide, and a large amount of ferrous sulfide (FeS) and adsorbed Fe(II) were also produced. The results showed that the anaerobic biological iron-sulfur reduction reaction could produce reduced iron-sulfur active components such as polysulfide and ferrous sulfide.

[0082] Figure 3 Figure for the production of sulfide under different pH conditions in the process of anaerobic biological iron-sulfur reduction reaction (reaction conditions: [S 0 ]=4 g / L, [Fe(III)]=0 g / L, organic carbon=500 mg / L, [NaHCO3]=1.68 g / L); Figure 4 Figure for the concentration of S n 2- under different pH conditions after anaerobic biological iron-sulfur reduction reaction (reaction conditions: [S 0 ]=4 g / L, [Fe(III)]=0 g / L, organic carbon=500 mg / L, [NaHCO3]=1.68 g / L). Without the addition of ferric iron, elemental sulfur-reducing bacteria used organic matter as an electron donor to reduce elemental sulfur to hydrogen sulfide, and elemental sulfur and hydrogen sulfide further combined into S n 2- The solution pH significantly affected the production rate of S 2- and S n 2- When the pH increased from 6.0 to 9.0, the production of S 2- and S n 2- The results showed that the anaerobic biological iron-sulfur reduction reaction zone needed to maintain weak alkaline conditions with a pH of 8.0-9.0 to promote the production of S 2- and S n 2-

[0083] Figure 5 Figure for the concentration change of sulfide in the process of anaerobic biological iron-sulfur reduction reaction under different iron-sulfur mass ratios (pH=9, [S 0 ]=4 g / L, organic carbon=500 mg / L, [NaHCO3]=1.68 g / L). Figure 6 Figure for the concentration change of S n 2- in the process of anaerobic biological iron-sulfur reduction reaction under different iron-sulfur mass ratios (pH=9, [S 0 ]=4 g / L, organic carbon=500 mg / L, [NaHCO3]=1.68 g / L). Figure 7 Figure for the concentration change of FeS in the process of anaerobic biological iron-sulfur reduction reaction under different iron-sulfur mass ratios (pH=9, [S 0 ​]=4g / L, organic carbon=500 mg / L, [NaHCO3]=1.68g / L). When ferric iron and elemental sulfur are added at the same time, ferric iron will chemically oxidize and precipitate sulfide S produced by elemental sulfur-reducing bacteria. 2- Convert to S 0 and FeS; it will also stimulate the biological iron reduction process to produce divalent iron, thereby precipitating S 2- , generating FeS. When the iron-sulfur mass ratio increases from 0.5:1 to 4:1, S 2- The formation of S will be inhibited. When the iron-sulfur mass ratio is 1:1~2:1, S n 2- The amount of FeS produced is large; in addition, when the iron-sulfur mass ratio is 0.5:1~1:1, the amount of FeS produced is large. These indicate that in order to simultaneously and efficiently produce the S required for the degradation of organic pollutants with negatively charged groups that are difficult to degrade, n 2- and FeS, preferably the iron-sulfur mass ratio is controlled at around 1:1.

[0084] Figure 8 S in the nucleophilic substitution reaction under different pH conditions n 2- Removal effect of atrazine by reduction degradation (reaction conditions: atrazine = 1 mg / L, [S n 2- ]=30mM); Figure 9 The concentrations of S in the nucleophilic substitution reaction are different. n 2- Figure 2 shows the effect of atrazine removal by reduction degradation (reaction conditions: pH = 9, atrazine = 1 mg / L). Under anaerobic conditions, when the pH is 6-7, S n 2- The effect of reducing and removing atrazine was not significant; when pH was 8, S n 2- More than 50% of atrazine can be reduced and degraded within 6 hours; when the pH is 9, S n 2- More than 80% of atrazine can be reduced and degraded within 4 hours. n 2- It has strong nucleophilic substitution ability under the condition of pH 8-9, and can effectively reduce and degrade atrazine. The optimal pH of the reaction process is 9. When the pH is 9, as S n 2- As the concentration increases, the degradation efficiency of atrazine increases.

[0085] Figure 10 This is the effect of FeS oxidation to remove atrazine under aerobic conditions (reaction conditions: pH = 6, [FeS] = 3.0 g / L);Figure 11 This is a graph showing the cumulative amount of strongly oxidizing hydroxyl radicals ·OH generated by FeS oxidation under different pH conditions (reaction conditions: [FeS] = 3.0 g / L, [sodium benzoate] = 10 mM); Figure 12 Figure 2 shows the accumulation of strongly oxidizing hydroxyl radicals (OH) generated by the oxidation of FeS at different concentrations (reaction conditions: pH = 6, [sodium benzoate] = 10 mM). Under aerobic conditions, FeS transfers stored electrons to dissolved oxygen, generating strongly oxidizing hydroxyl radicals (OH). The results indicate that the generated strongly oxidizing hydroxyl radicals (OH) can effectively oxidize and degrade atrazine. As a key component in the oxidative degradation of atrazine and its reductive degradation products, the generation of strongly oxidizing hydroxyl radicals (OH) is affected by solution pH and FeS concentration. The accumulation of strongly oxidizing hydroxyl radicals (OH) is highest at pH = 6.0, and increasing FeS concentration also significantly increases the accumulation of strongly oxidizing hydroxyl radicals (OH).

[0086] Figure 13 The graph shows the change in the concentration of iron and sulfur substances before and after the oxidation reaction (reaction conditions: [FeS] = 3.0 g / L, pH = 6). After the oxidation reaction, the concentrations of Fe(Ⅱ) and S-FeS decreased significantly. At the same time, S 0 The concentrations of Fe(Ⅱ) and S-FeS were oxidized to Fe(Ⅲ) and S 0 The results show that FeS mainly produces Fe(Ⅲ) and S after oxidation. 0 After recovery, it can be recycled in the anaerobic biological iron-sulfur reduction process.

[0087] Figure 14 The effect of pH on the recovery rate of elemental sulfur and trivalent iron and the accumulation of strong oxidizing hydroxyl radicals OH in the oxidation reaction zone (reaction conditions: Fe(Ⅲ): S 0 =1:1,[S 0] = 4 g / L). The Fe recovery rate fluctuates significantly with pH. At a pH of 5, ferric hydroxide precipitation is difficult to form, resulting in the lowest Fe recovery rate of approximately 19%. The Fe recovery rate increases with increasing pH, reaching 99.97% at a pH of 9. The S recovery rate is not significantly affected by pH, slowly increasing with increasing pH and stabilizing at 70%-85%. The accumulation of strongly oxidizing hydroxyl radicals (OH) produced by FeS oxidation decreases with increasing pH over 9 hours. At a pH of 5, the accumulation of strongly oxidizing hydroxyl radicals (OH) reaches as high as 103.23 μM, while at a pH of 9, it drops to a low of 13.7 μM. Taking into account the recycling rate of iron and sulfur species and the degradation efficiency of organic pollutants with electronegative groups, a pH of 6 in the oxidation reaction zone ensures efficient pollutant degradation while maximizing the recycling of iron and sulfur species, reducing the input of reagents for organic wastewater treatment and, consequently, lowering treatment costs.

[0088] Figure 15 The figure shows the effect of the iron-sulfur mass ratio on the recovery rate of elemental sulfur and trivalent iron (pH of the oxidation reaction zone = 6). Sulfide, polysulfide and Fe(Ⅱ) are oxidized to elemental sulfur and Fe(Ⅲ) respectively after oxidation reaction. The recovery rates of elemental sulfur and trivalent iron are measured after sludge sedimentation and reflux. When the iron-sulfur mass ratio is 0.5:1~4:1, the recovery rate of elemental sulfur is between 78% and 96%, and the recovery rate of trivalent iron is between 88% and 98%. The above results show that by controlling the reaction conditions, the present invention can stably and efficiently recover elemental sulfur and Fe(Ⅲ), recycle them in the anaerobic biological iron-sulfur reaction process, and produce S required for deep degradation of difficult-to-degrade organic pollutants. n 2- and FeS, which can significantly reduce the input of chemicals and costs for deep treatment of organic wastewater.

[0089] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for deep treatment of organic wastewater with low chemical input, characterized in that: The following steps are involved: (1) Anaerobic biological iron-sulfur reduction reaction process: In the anaerobic biological iron-sulfur reduction reaction zone, elemental sulfur, trivalent iron, iron-sulfur reduction sludge, and wastewater containing organic carbon and organic pollutants with electronegative groups are fully mixed. Anaerobic biological elemental sulfur reduction and iron reduction reactions are carried out under the conditions of dissolved oxygen concentration less than 0.1 mg / L, pH 8.0-9.0, and iron-sulfur mass ratio of 0.5:1-4:1, to produce polysulfide and ferrous sulfide in situ. The iron-sulfur reducing sludge contains elemental sulfur-reducing bacteria and iron-reducing bacteria; (2) Nucleophilic substitution reaction process: The effluent from the anaerobic biological iron-sulfur reduction reaction zone is passed into the nucleophilic substitution reaction zone. Under the conditions of pH 8.0-9.0 and dissolved oxygen concentration less than 0.1 mg / L, polysulfides and organic pollutants with electronegative groups undergo nucleophilic substitution reaction. The organic pollutants with electronegative groups remove the electronegative groups to generate reduced organic products. (3) Oxidation reaction process: The effluent from the nucleophilic substitution reaction zone is passed into the oxidation reaction zone. Under the conditions of dissolved oxygen content of 2.0-8.0 mg / L and pH of 6.0-9.0, ferrous sulfide reacts with dissolved oxygen to generate hydroxyl radicals in situ, which oxidize and degrade reduced organic products and produce elemental sulfur and trivalent iron precipitation; (4) Sludge sedimentation process: The effluent from the oxidation reaction zone is passed into the sludge sedimentation zone for sedimentation and separation, and the sediment is recovered; the sediment is returned to the anaerobic biological iron-sulfur reduction reaction zone to achieve the recycling of elemental sulfur and trivalent iron; the clarified water is discharged through the outlet pipe; The recovery rate of the elemental sulfur is 78% to 96%; the recovery rate of the trivalent iron is 88% to 98%.

2. The method for deep treatment of organic wastewater with low chemical input according to claim 1, characterized in that: The iron-sulfur mass ratio in step (1) is 0.5:1~2:

1.

3. The method for deep treatment of organic wastewater with low chemical input according to claim 1, characterized in that: The iron-sulfur mass ratio in step (1) is 0.5:1~1:

1.

4. The method for deep treatment of organic wastewater with low chemical input according to claim 3, characterized in that: The pH of the oxidation reaction process in step (3) is 6.0-7.

0.

5. The method for deep treatment of organic wastewater with low chemical input according to claim 1, characterized in that: The organic pollutant with electronegative groups is at least one of halogenated organic matter, azobenzene dye and organic phosphate.

6. The method for deep treatment of organic wastewater with low chemical input according to claim 1, characterized in that: The hydraulic retention time of the anaerobic biological iron-sulfur reduction reaction process is 4 to 12 hours; the hydraulic retention time of the nucleophilic substitution reaction process is 2 to 9 hours; and the hydraulic retention time of the oxidation reaction process is 2 to 10 hours.

7. The method for deep treatment of organic wastewater with low chemical input according to claim 1, characterized in that: The hydraulic retention time of the anaerobic biological iron-sulfur reduction reaction process is 6 to 8 hours; the hydraulic retention time of the nucleophilic substitution reaction process is 4 to 9 hours; and the hydraulic retention time of the oxidation reaction process is 6 to 9 hours.

8. The method for deep treatment of organic wastewater with low chemical input according to claim 1, characterized in that: The anaerobic biological iron-sulfur reduction reaction process, the nucleophilic substitution reaction process and the oxidation reaction process are all carried out at room temperature.

9. The method for deep treatment of organic wastewater with low chemical input according to claim 1, characterized in that: The precipitate in step (4) contains elemental sulfur, trivalent iron and iron-sulfur reduction sludge.

10. A device for implementing the method for deep treatment of organic wastewater with low chemical input according to any one of claims 1 to 9, characterized in that: The space inside the device is divided into an anaerobic biological iron-sulfur reduction reaction zone, a nucleophilic substitution reaction zone, an oxidation reaction zone and a sludge sedimentation zone by a partition; the anaerobic biological iron-sulfur reduction reaction zone and the nucleophilic substitution reaction zone are both provided with stirring paddles; a reflux pipe is provided at the bottom of the sludge sedimentation zone, and the precipitate flows back to the anaerobic biological iron-sulfur reduction reaction zone through the reflux pipe.

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