Sewage deep purification process applied to upgrading and reconstruction project of sewage treatment plant

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a sewage deep purification process applied to upgrading and reconstruction projects of a sewage treatment plant. Aiming at the problems of complex sewage components, high pollutant concentration, high treatment difficulty, unstable operation and the like in the industrial park, the process adopts a combined process of two-stage A / O biochemical denitrification, chemical enhanced phosphorus removal, multi-element catalytic oxidation and intelligent regulation and control, and realizes deep purification of the sewage by optimizing parameters of each unit and coordinating operation. In the process, a two-stage A / O biochemical system performs efficient denitrification, chemical enhanced phosphorus removal makes up for biological phosphorus removal shortages, multi-element catalytic oxidation deeply degrades refractory pollutants, intelligent software performs real-time regulation and control to ensure stable operation, and final effluent can reach the earth surface quasi-four-class emission standard. The method has the advantages of high nitrogen and phosphorus removal efficiency, strong impact load resistance, low operation cost and the like, and can be directly applied to upgrading and reconstruction projects of sewage treatment plants.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to a sewage deep purification process applied to a sewage treatment plant upgrading and reconstruction project. Background Art

[0002] With the tightening of environmental protection policies, there is an urgent need to upgrade the sewage treatment plants in industrial parks. However, the existing sewage treatment in industrial parks generally has the following problems: the sewage composition is complex, containing a large amount of difficult-to-degrade organic matter; the concentration of nitrogen and phosphorus is high, and traditional biological treatment processes (such as A 2 Competition for carbon sources leads to low nitrogen and phosphorus removal efficiencies. Advanced treatment processes (such as Fenton and ozone) have high operating costs, high sludge production, and lack intelligent control methods, resulting in poor operational stability. Therefore, there is an urgent need to develop an efficient, economical, and stable integrated process to address these technical bottlenecks.

[0003] Furthermore, conventional catalyst preparation relies on high-temperature calcination, which consumes a lot of energy and lacks regeneration capabilities. These issues make it difficult for existing technologies to meet the high-efficiency, low-carbon, and green demands of upgrading and upgrading, necessitating innovative integrated processes to overcome these bottlenecks. Summary of the Invention

[0004] The purpose of the present invention is to address the existing problems and provide a sewage deep purification process applied to sewage treatment plant upgrading and transformation projects. It is suitable for treating industrial wastewater with complex components and high concentrations of pollutants, and can achieve effluent water quality that meets the surface quasi-four-category discharge standard.

[0005] The present invention is achieved through the following technical solutions:

[0006] A sewage deep purification process applied to a sewage treatment plant upgrading and reconstruction project comprises the following steps:

[0007] S1, sewage passes through the first anoxic tank A1, the first aerobic tank O1, the second anoxic tank A2, the second aerobic tank O2 and the sedimentation tank in sequence;

[0008] S2, introducing the effluent of the secondary aerobic pool O2 in step S1 into the chemical phosphorus removal unit, adding PAC for coagulation and sedimentation;

[0009] S3. After coagulation and sedimentation, the effluent directly enters the catalytic oxidation unit and is treated with a composite catalyst under H2O2 conditions for 1 to 3.5 hours.

[0010] Furthermore, in step S1, the dissolved oxygen of A1 and A2 is controlled to be 0.2-0.5 mg / L, and the dissolved oxygen of O1 and O2 is controlled to be 2-4 mg / L.

[0011] Furthermore, in step S1, the reflux ratio of the first-stage A / O nitrification liquid is 400%, the reflux ratio of the second-stage A / O nitrification liquid is 100%, the reflux ratio of the sedimentation tank sludge to the hydrolysis tank and A1 is 50% each, and the total sludge reflux ratio is 100%; the system sludge concentration is controlled at 4000 mg / L, and the water inlet is increased in stages from 0.4 L / h to 0.8 L / h.

[0012] Furthermore, the dosage of PAC in step S2 is 25-600 mg / L.

[0013] Furthermore, the dosage of the composite catalyst in step S3 is 0.5-1.5 g / L.

[0014] Furthermore, the preparation of the composite catalyst described in step S3 comprises the following steps:

[0015] (1) preparing ferric nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride, and silver nitrate in a mass ratio of 5:3:2:1:0.5:0.5 among iron, copper, titanium dioxide, cobalt, palladium, and silver; dissolving the ferric nitrate, copper nitrate, cobalt nitrate, palladium chloride, and silver nitrate in deionized water in sequence, and stirring until completely dissolved to form a uniform metal ion mixed solution; ultrasonically dispersing the nano-titanium dioxide in deionized water to form a uniform nano-titanium dioxide suspension; and mixing the metal ion mixed solution and the nano-titanium dioxide suspension to form a metal ion mixed solution;

[0016] (2) Add activated carbon to the above metal ion mixture at a solid-liquid ratio of 1 g: (20-25) mL, then transfer it to a three-necked flask and inoculate the activated Thiobacillus ferrooxidans bacterial solution at a 10% (v / v) inoculation volume;

[0017] (3) The three-necked flask inoculated with the above-mentioned Thiobacillus ferrooxidans bacterial liquid was placed in a constant temperature shaking incubator and cultured at 28-32°C and 100-200 rpm for 70-80 hours. After the culture was completed, the flask was filtered and repeatedly rinsed with deionized water until the filtrate was neutral, and then vacuum dried at 70-80°C for 12-14 hours to obtain a metal-loaded activated carbon intermediate;

[0018] (4) Immerse the metal-loaded activated carbon intermediate in dopamine-Tris buffer at a solid-liquid ratio of 1 g: (20-25) mL, stir at 23-27 °C and 100-200 rpm for 10-14 h, filter, rinse with deionized water until the filtrate is colorless, and then vacuum dry at 60-65 °C for 8-10 h.

[0019] Furthermore, the activation method of the activated Thiobacillus ferrooxidans bacterial solution in step (2) is as follows: inoculate the Thiobacillus ferrooxidans strain into 9K culture medium at an inoculation amount of 10% (v / v), and culture under shaking conditions of 28-32°C and 100-200 rpm until the bacterial solution concentration reaches 10 7 CFU / mL.

[0020] Furthermore, the dopamine-Tris buffer solution described in step (4) is prepared by weighing Tris base and dissolving it in deionized water to prepare a 0.05 mol / L Tris solution, adjusting the pH to 8.5 with 1 mol / L hydrochloric acid, and then adding dopamine hydrochloride to make the dopamine concentration 2 g / L, and stirring until the dopamine is completely dissolved.

[0021] Furthermore, the concentration of H2O2 in step S3 is 0.5~1.5g / L.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention discloses a sewage deep purification process suitable for use in sewage treatment plant upgrading and reconstruction projects, and belongs to the field of sewage treatment technology. This process aims to solve the problems of complex sewage composition, high pollutant concentration, great difficulty in treatment and unstable operation in industrial parks. It adopts a combined process of two-stage A / O biochemical denitrification, chemically enhanced phosphorus removal, multi-element catalytic oxidation and intelligent regulation. By optimizing the parameters of each unit and coordinating operations, deep sewage purification is achieved. In this process, the two-stage A / O biochemical system efficiently removes nitrogen, chemically enhanced phosphorus removal makes up for the shortcomings of biological phosphorus removal, multi-element catalytic oxidation deeply degrades difficult-to-degrade pollutants, and intelligent software real-time regulation ensures stable operation. The final effluent can meet the surface quasi-four-category emission standard. The present invention has the advantages of high denitrification and phosphorus removal efficiency, strong impact load resistance, low operating cost, etc., and can be directly applied to sewage treatment plant upgrading and reconstruction projects.

[0024] 2. The composite catalyst of this invention utilizes activated carbon as a substrate and is loaded with a multimetallic component (iron, copper, titanium, cobalt, palladium, and silver) (mass ratio of 5:3:2:1:0.5:0.5) through microbial mineralization. Combined with polydopamine (PDA) surface modification, it is prepared at low temperature and in a green manner (no high-temperature calcination is required). The carboxyl and phenolic hydroxyl functional groups on the PDA layer efficiently adsorb and enrich pollutants, and their synergistic catalytic effect with the multimetallic components significantly enhances the efficiency of H2O2 activation. After 20 regeneration cycles, the catalyst retained activity exceeding 94%, significantly exceeding the lifespan of traditional precious metal catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart for a two-stage A / O biochemical system;

[0026] Figure 2It is the overall process technology roadmap;

[0027] Figure 3 is the change of TP content under different PAC dosage;

[0028] Figure 4 COD removal under different pH conditions;

[0029] Figure 5 COD removal under different catalyst dosage conditions;

[0030] Figure 6 COD removal under different oxidant concentration conditions;

[0031] Figure 7 COD removal under different reaction time conditions. DETAILED DESCRIPTION

[0032] In order to further explain the present invention, it is described below with reference to the following specific embodiments.

[0033] Example 1

[0034] Reference Figure 1-2 , a sewage deep purification process used in sewage treatment plant upgrading and reconstruction projects, comprising the following steps:

[0035] S1, sewage passes through the first anoxic tank A1, the first aerobic tank O1, the second anoxic tank A2, the second aerobic tank O2 and the sedimentation tank in sequence;

[0036] The dissolved oxygen in A1 and A2 was controlled at 0.2 mg / L, and the dissolved oxygen in O1 and O2 was controlled at 2 mg / L. The primary A / O nitrification liquid return ratio was 400%, the secondary A / O nitrification liquid return ratio was 100%, the sedimentation tank sludge return ratio to the hydrolysis tank and A1 was 50% each, and the total sludge return ratio was 100%. The system sludge concentration was controlled at 4000 mg / L, and the water inlet was increased in stages from 0.4 L / h to 0.8 L / h.

[0037] S2. The effluent from the secondary aerobic pool O2 in step S1 is introduced into the chemical phosphorus removal unit, and PAC is added for coagulation and sedimentation. The dosage of PAC is 25 mg / L;

[0038] S3, after coagulation and sedimentation, the effluent directly enters the catalytic oxidation unit and is treated with a composite catalyst under the condition of H2O2 concentration of 0.5g / L for 1h;

[0039] The dosage of the composite catalyst is 0.5 g / L;

[0040] The preparation of the composite catalyst comprises the following steps:

[0041] (1) preparing ferric nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride, and silver nitrate in a mass ratio of 5:3:2:1:0.5:0.5 among iron, copper, titanium dioxide, cobalt, palladium, and silver; dissolving the ferric nitrate, copper nitrate, cobalt nitrate, palladium chloride, and silver nitrate in deionized water in sequence, and stirring until completely dissolved to form a uniform metal ion mixed solution; ultrasonically dispersing the nano-titanium dioxide in deionized water to form a uniform nano-titanium dioxide suspension; and mixing the metal ion mixed solution and the nano-titanium dioxide suspension to form a metal ion mixed solution;

[0042] (2) Add activated carbon to the above metal ion mixture at a solid-liquid ratio of 1 g:20 mL, then transfer it to a three-necked flask and inoculate the activated Thiobacillus ferrooxidans bacterial solution at a 10% (v / v) inoculation volume;

[0043] The activation method of the activated Thiobacillus ferrooxidans bacterial solution is as follows: the Thiobacillus ferrooxidans strain is inoculated into 9K culture medium at an inoculation amount of 10% (v / v), and cultured at 28°C and 100 rpm until the bacterial solution concentration reaches 10 7 CFU / mL;

[0044] (3) The three-necked flask inoculated with the above-mentioned Thiobacillus ferrooxidans bacterial solution was placed in a constant temperature shaking incubator and cultured at 28°C and 100 rpm for 70 hours. After the culture was completed, the flask was filtered and repeatedly rinsed with deionized water until the filtrate was neutral, and then vacuum dried at 70°C for 12 hours to obtain a metal-loaded activated carbon intermediate;

[0045] (4) Weigh Tris base and dissolve it in deionized water to prepare a 0.05 mol / L Tris solution. Adjust the pH to 8.5 with 1 mol / L hydrochloric acid, then add dopamine hydrochloride to a dopamine concentration of 2 g / L. Stir until the dopamine-Tris buffer is completely dissolved.

[0046] (5) The metal-loaded activated carbon intermediate was immersed in dopamine-Tris buffer at a solid-liquid ratio of 1 g:20 mL, stirred at 23 °C and 100 rpm for 10 h, filtered, rinsed with deionized water until the filtrate was colorless, and then vacuum dried at 60 °C for 8 h.

[0047] Example 2

[0048] Reference Figure 1-2 , a sewage deep purification process used in sewage treatment plant upgrading and reconstruction projects, comprising the following steps:

[0049] S1, sewage passes through the first anoxic tank A1, the first aerobic tank O1, the second anoxic tank A2, the second aerobic tank O2 and the sedimentation tank in sequence;

[0050] The dissolved oxygen of A1 and A2 is 0.3 mg / L, and the dissolved oxygen of O1 and O2 is 3 mg / L; the first-stage A / O nitrification liquid reflux ratio is 400%, the second-stage A / O nitrification liquid reflux ratio is 100%, the reflux ratio of the sludge in the sedimentation tank to the hydrolysis tank and A1 is 50% respectively, and the total sludge reflux ratio is 100%; the system sludge concentration is controlled at 4000 mg / L, and the influent is increased from 0.4 L / h to 0.8 L / h in stages;

[0051] S2, the effluent of the secondary aerobic tank O2 in step S1 is introduced into a chemical phosphorus removal unit, PAC is added for coagulation and sedimentation, and the addition amount of PAC is 400 mg / L;

[0052] S3, the effluent after coagulation and sedimentation is directly introduced into a catalytic oxidation unit, and a composite catalyst is used to treat for 3 h under the condition of H2O2 concentration of 1.1 g / L;

[0053] The addition amount of the composite catalyst is 1 g / L;

[0054] The preparation of the composite catalyst comprises the following steps:

[0055] (1) Prepare iron nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride and silver nitrate according to the mass ratio of iron, copper, titanium dioxide, cobalt, palladium and silver of 5:3:2:1:0.5:0.5, dissolve the above-mentioned iron nitrate, copper nitrate, cobalt nitrate, palladium chloride and silver nitrate in deionized water in sequence, stir until completely dissolved, and form a uniform metal ion mixed solution; ultrasonic dispersion of the above-mentioned nano-titanium dioxide in deionized water forms a uniform nano-titanium dioxide suspension; mix the above-mentioned metal ion mixed solution and nano-titanium dioxide suspension to form a metal ion mixed solution;

[0056] (2) Add activated carbon to the above-mentioned metal ion mixed solution according to a solid-liquid ratio of 1 g:22 mL, then transfer to a three-necked flask, and inoculate the activated ferrous oxide thiobacillus liquid according to an inoculation amount of 10% (v / v);

[0057] The activation method of the activated ferrous oxide thiobacillus liquid is as follows: inoculate the ferrous oxide thiobacillus strain into 9K culture medium, and the inoculation amount is 10% (v / v); under the condition of 30℃ and 150 rpm, shake culture until the bacterial liquid concentration reaches 10 7 CFU / mL;

[0058] (3) Place the three-necked flask inoculated with the ferrous oxide thiobacillus liquid in a constant-temperature shaking incubator, and shake culture under the condition of 30℃ and 150 rpm for 75 h; after the culture is completed, filter, repeatedly rinse with deionized water until the filtrate is neutral, then vacuum dry at 75℃ for 13 h to obtain a metal-loaded activated carbon intermediate;

[0059] (4) Weigh Tris base and dissolve it in deionized water to prepare a 0.05 mol / L Tris solution. Adjust the pH to 8.5 with 1 mol / L hydrochloric acid, then add dopamine hydrochloride to a dopamine concentration of 2 g / L. Stir until the dopamine-Tris buffer is completely dissolved.

[0060] (5) The metal-loaded activated carbon intermediate was immersed in dopamine-Tris buffer at a solid-liquid ratio of 1 g:22 mL, stirred at 25 °C and 150 rpm for 12 h, filtered, rinsed with deionized water until the filtrate was colorless, and then vacuum dried at 62 °C for 9 h.

[0061] Example 3

[0062] Reference Figure 1-2 , a sewage deep purification process used in sewage treatment plant upgrading and reconstruction projects, comprising the following steps:

[0063] S1, sewage passes through the first anoxic tank A1, the first aerobic tank O1, the second anoxic tank A2, the second aerobic tank O2 and the sedimentation tank in sequence;

[0064] The dissolved oxygen in A1 and A2 was controlled at 0.5 mg / L, and that in O1 and O2 was controlled at 4 mg / L. The primary A / O nitrification liquid return ratio was 400%, the secondary A / O nitrification liquid return ratio was 100%, the sedimentation tank sludge return ratio to the hydrolysis tank and A1 was 50% each, and the total sludge return ratio was 100%. The system sludge concentration was controlled at 4000 mg / L, and the water inlet was increased in stages from 0.4 L / h to 0.8 L / h.

[0065] S2. The effluent from the secondary aerobic pool O2 in step S1 is introduced into a chemical phosphorus removal unit, and PAC is added for coagulation and sedimentation. The dosage of PAC is 600 mg / L.

[0066] S3, after coagulation and sedimentation, the effluent directly enters the catalytic oxidation unit and is treated with a composite catalyst at a concentration of 1.5 g / L H2O2 for 3.5 hours;

[0067] The dosage of the composite catalyst is 1.5 g / L;

[0068] The preparation of the composite catalyst comprises the following steps:

[0069] (1) preparing ferric nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride, and silver nitrate in a mass ratio of 5:3:2:1:0.5:0.5 among iron, copper, titanium dioxide, cobalt, palladium, and silver; dissolving the ferric nitrate, copper nitrate, cobalt nitrate, palladium chloride, and silver nitrate in deionized water in sequence, and stirring until completely dissolved to form a uniform metal ion mixed solution; ultrasonically dispersing the nano-titanium dioxide in deionized water to form a uniform nano-titanium dioxide suspension; and mixing the metal ion mixed solution and the nano-titanium dioxide suspension to form a metal ion mixed solution;

[0070] (2) Add activated carbon to the above metal ion mixture at a solid-liquid ratio of 1 g:25 mL, then transfer to a three-necked flask and inoculate the activated Thiobacillus ferrooxidans bacterial solution at a 10% (v / v) inoculation volume;

[0071] The activation method of the activated Thiobacillus ferrooxidans bacterial solution is as follows: the Thiobacillus ferrooxidans strain is inoculated into 9K culture medium at an inoculation amount of 10% (v / v), and cultured at 32°C and 200 rpm under shaking conditions until the bacterial solution concentration reaches 10 7 CFU / mL;

[0072] (3) The three-necked flask inoculated with the above-mentioned Thiobacillus ferrooxidans bacterial solution was placed in a constant temperature shaking incubator and cultured at 32°C and 200 rpm for 80 hours. After the culture was completed, the flask was filtered and repeatedly rinsed with deionized water until the filtrate was neutral, and then vacuum dried at 80°C for 14 hours to obtain a metal-loaded activated carbon intermediate;

[0073] (4) Weigh Tris base and dissolve it in deionized water to prepare a 0.05 mol / L Tris solution. Adjust the pH to 8.5 with 1 mol / L hydrochloric acid, then add dopamine hydrochloride to a dopamine concentration of 2 g / L. Stir until the dopamine-Tris buffer is completely dissolved.

[0074] (5) The metal-loaded activated carbon intermediate was immersed in dopamine-Tris buffer at a solid-liquid ratio of 1 g:25 mL, stirred at 27 °C and 200 rpm for 14 h, filtered, rinsed with deionized water until the filtrate was colorless, and then vacuum dried at 65 °C for 10 h.

[0075] Experimental testing

[0076] 1. Pilot study of a two-stage A / O biochemical system

[0077] (1) The experimental water was the effluent from the hydrolysis and acidification tank. Different sludge loads were selected for the experiment. The COD concentration changes after the biochemical reaction were detected and the optimal sludge loading rate was selected. The COD change trend of the biochemical system effluent under different sludge loading conditions is shown in Table 1.

[0078] Table 1 Changes in COD in the inlet and outlet water of the biochemical system under different sludge loading conditions

[0079] Sludge load (kg COD / (kg MLSS·d)) Influent COD (mg / L) Outlet COD (mg / L) Removal rate (%) 0.25 355 25 92.9% 0.35 352 33 90.6% 0.5 357 58 83.7%

[0080] When the sludge load was 0.25 and 0.35 kg COD / (kg MLSS·d), the COD removal rate of the biochemical system reached over 90%. When the sludge load was 0.25 kg COD / (kg MLSS·d), the effluent COD was 25 mg / L, and when the sludge load was 0.35 kg COD / (kg MLSS·d), the effluent COD was 33 mg / L. However, when the sludge load was increased to 0.50 kg COD / (kgMLSS·d), the COD removal rate of the biochemical system dropped to 83.7%, and the effluent COD reached 58 mg / L.

[0081] (2) Activated sludge samples were collected regularly from different locations (A1, O1, A2, O2) of the two-stage A / O biochemical pools. The 16S rRNA gene in the activated sludge samples was sequenced using high-throughput sequencing technology to analyze the microbial diversity index (such as Shannon index and Simpson index) and bacterial community structure composition.

[0082] Test results

[0083] ① Changes in microbial diversity

[0084] Microbial diversity varies across different stages. Anaerobic stages (A1 and A2) exhibit relatively high microbial diversity, with Shannon indices ranging from 4.5 to 5.0. Microbial diversity decreases slightly in aerobic stages (O1 and O2), with Shannon indices ranging from 4.0 to 4.5. This may be because anaerobic environments allow for a greater diversity of microbial survival patterns, while aerobic environments are more selective for microorganisms.

[0085] ②Composition of bacterial flora

[0086] Anaerobic stage: The dominant bacterial phyla are Bacteroidetes, Firmicutes, and Proteobacteria. Some species within the Bacteroidetes possess strong hydrolysis and fermentation abilities, capable of breaking down large organic molecules into small organic acids. Bacillus species within the Firmicutes can undergo fermentation and metabolism under anaerobic conditions. Some species within the Proteobacteria participate in nitrogen conversion.

[0087] Aerobic stage: Proteobacteria become the dominant phylum, particularly Betaproteobacteria. Nitrifying bacteria such as Nitrosomonas and Nitrobacter are abundant in aerobic tank O1, responsible for oxidizing ammonia nitrogen into nitrite and nitrate. Phosphorus-accumulating bacteria such as Acinetobacter are more abundant in aerobic tank O2, capable of absorbing phosphorus from the wastewater.

[0088] 3) As mentioned above, a sludge load of 0.25 kg COD / (kg MLSS·d) was selected to study the degradation of pollutants in each pool. The influent rate of the biochemical pool was reduced from 0.8 L / h to 0.6 L / h. After resuming operation for 15 days, it was stabilized for 20 days. During the stable operation period, the daily influent and the effluent of the hydrolysis and acidification pool and each biochemical pool were tested for changes in COD, ammonia nitrogen, TN, TP, volatile phenols, sulfides, anionic surfactants, and copper ions, as shown in Tables 2 and 3.

[0089] Table 2 Changes in COD, NH3-N, TN, and TP concentrations in the system

[0090] date Pool body COD Ammonia nitrogen TN TP 2024 / 12 / 11 Water ingress 300 25 35 5 2024 / 12 / 11 Hydrolysis acidification tank 240 25 33 6 2024 / 12 / 11 Level 1 A / O pool 160 20 28 5 2024 / 12 / 11 Secondary A / O pool 65 15 22 4 2024 / 12 / 12 Water ingress 280 23 33 4.8 2024 / 12 / 12 Hydrolysis acidification tank 220 23 31 5.8 2024 / 12 / 12 Level 1 A / O pool 140 18 26 5.3 2024 / 12 / 12 Secondary A / O pool 62 13 20 3.8 2024 / 12 / 13 Water ingress 290 24 34 5.2 2024 / 12 / 13 Hydrolysis acidification tank 230 24 32 6.2 2024 / 12 / 13 Level 1 A / O pool 150 19 27 5.8 2024 / 12 / 13 Secondary A / O pool 68 14 21 4.2 2024 / 12 / 14 Water ingress 290 24 34 5.2 2024 / 12 / 14 Hydrolysis acidification tank 250 26 34 7 2024 / 12 / 14 Level 1 A / O pool 180 22 30 6 2024 / 12 / 14 Secondary A / O pool 70 16 23 4.5 2024 / 12 / 15 Water ingress 270 22 32 4.5 2024 / 12 / 15 Hydrolysis acidification tank 210 22 30 5.5 2024 / 12 / 15 Level 1 A / O pool 130 17 25 5 2024 / 12 / 15 Secondary A / O pool 60 12 19 3.5 2024 / 12 / 16 Water ingress 285 23.5 33.5 4.9 2024 / 12 / 16 Hydrolysis acidification tank 225 23.5 31.5 6 2024 / 12 / 16 Level 1 A / O pool 145 18.5 26.5 5.4 2024 / 12 / 16 Secondary A / O pool 63 13.5 20.5 3.9 2024 / 12 / 17 Water ingress 300 25 35 5 2024 / 12 / 17 Hydrolysis acidification tank 240 25 33 6 2024 / 12 / 17 Level 1 A / O pool 160 20 28 5 2024 / 12 / 17 Secondary A / O pool 65 15 22 4 2024 / 12 / 18 Water ingress 280 23 33 4.8 2024 / 12 / 18 Hydrolysis acidification tank 220 23 31 5.8 2024 / 12 / 18 Level 1 A / O pool 140 18 26 5.3 2024 / 12 / 18 Secondary A / O pool 62 13 20 3.8 2024 / 12 / 19 Water ingress 290 24 34 5.2 2024 / 12 / 19 Hydrolysis acidification tank 230 24 32 6.2 2024 / 12 / 19 Level 1 A / O pool 150 19 27 5.8 2024 / 12 / 19 Secondary A / O pool 68 14 21 4.2 2024 / 12 / 20 Water ingress 310 26 36 5.5 2024 / 12 / 20 Hydrolysis acidification tank 250 26 34 7 2024 / 12 / 20 Level 1 A / O pool 180 22 30 6 2024 / 12 / 20 Secondary A / O pool 70 16 23 4.5 2024 / 12 / 21 Water ingress 270 22 32 4.5 2024 / 12 / 21 Hydrolysis acidification tank 210 22 30 5.5 2024 / 12 / 21 Level 1 A / O pool 130 17 25 5 2024 / 12 / 21 Secondary A / O pool 60 12 19 3.5 2024 / 12 / 22 Water ingress 285 23.5 33.5 4.9 2024 / 12 / 22 Hydrolysis acidification tank 225 23.5 31.5 6 2024 / 12 / 22 Level 1 A / O pool 145 18.5 26.5 5.4 2024 / 12 / 22 Secondary A / O pool 63 13.5 20.5 3.9 2024 / 12 / 23 Water ingress 300 25 35 5 2024 / 12 / 23 Hydrolysis acidification tank 240 25 33 6 2024 / 12 / 23 Level 1 A / O pool 160 20 28 5 2024 / 12 / 23 Secondary A / O pool 65 15 22 4 2024 / 12 / 24 Water ingress 280 23 33 4.8 2024 / 12 / 24 Hydrolysis acidification tank 220 23 31 5.8 2024 / 12 / 24 Level 1 A / O pool 140 18 26 5.3 2024 / 12 / 24 Secondary A / O pool 62 13 20 3.8 2024 / 12 / 25 Water ingress 290 24 34 5.2 2024 / 12 / 25 Hydrolysis acidification tank 230 24 32 6.2 2024 / 12 / 25 Level 1 A / O pool 150 19 27 5.8 2024 / 12 / 25 Secondary A / O pool 68 14 21 4.2 2024 / 12 / 26 Water ingress 310 26 36 5.5 2024 / 12 / 26 Hydrolysis acidification tank 250 26 34 7 2024 / 12 / 26 Level 1 A / O pool 180 22 30 6 2024 / 12 / 26 Secondary A / O pool 70 16 23 4.5 2024 / 12 / 27 Water ingress 270 22 32 4.5 2024 / 12 / 27 Hydrolysis acidification tank 210 22 30 5.5 2024 / 12 / 27 Level 1 A / O pool 130 17 25 5 2024 / 12 / 27 Secondary A / O pool 60 12 19 3.5 2024 / 12 / 28 Water ingress 285 23.5 33.5 4.9 2024 / 12 / 28 Hydrolysis acidification tank 225 23.5 31.5 6 2024 / 12 / 28 Level 1 A / O pool 145 18.5 26.5 5.4 2024 / 12 / 28 Secondary A / O pool 63 13.5 20.5 3.9 2024 / 12 / 29 Water ingress 300 25 35 5 2024 / 12 / 29 Hydrolysis acidification tank 240 25 33 6 2024 / 12 / 29 Level 1 A / O pool 160 20 28 5 2024 / 12 / 29 Secondary A / O pool 65 15 22 4 2024 / 12 / 30 Water ingress 280 23 33 4.8 2024 / 12 / 30 Hydrolysis acidification tank 220 23 31 5.8 2024 / 12 / 30 Level 1 A / O pool 140 18 26 5.3 2024 / 12 / 30 Secondary A / O pool 62 13 20 3.8

[0091] Data Analysis:

[0092] ① COD changes: The influent COD concentration fluctuated between 270 and 310 mg / L. The hydrolysis and acidification tank had a preliminary COD degradation effect, primarily breaking down large organic molecules into small molecules through hydrolysis and acidification reactions. Its COD removal rate was approximately 20% to 25%, for example, it dropped from 300 mg / L to 240 mg / L on the first day. The primary A / O tank further enhanced organic matter degradation through alternating anaerobic and aerobic processes, achieving a removal rate of approximately 30% to 40%, for example, it dropped from 240 mg / L to 160 mg / L on the first day. The secondary A / O tank continued treatment, ultimately stabilizing the effluent COD at 60 to 70 mg / L, with a total removal rate of approximately 75% to 80%, meeting the requirements.

[0093] ②Nitrogen changes: Influent ammonia nitrogen ranged from 22 to 26 mg / L. The hydrolysis and acidification tank was not effective in removing ammonia nitrogen. In the aerobic section of the primary A / O tank, nitrifying bacteria converted ammonia nitrogen into nitrate nitrogen, with a removal rate of approximately 15% to 20%. For example, on the first day, the ammonia nitrogen level dropped from 25 mg / L to 20 mg / L. The secondary A / O tank further reduced ammonia nitrogen through the synergistic effects of denitrification in the anoxic section and nitrification in the aerobic section. The final effluent ammonia nitrogen level was approximately 12 to 16 mg / L, with a total removal rate of approximately 30% to 50%, meeting the ammonia nitrogen standards for general wastewater discharge.

[0094] TN Changes: Influent TN was between 32 and 36 mg / L. The hydrolysis and acidification tank had limited TN removal. The primary A / O tank, through nitrification and denitrification, achieved a removal rate of approximately 10% to 15%, for example, dropping from 35 mg / L to 28 mg / L on the first day. The secondary A / O tank further enhanced the denitrification process, further reducing TN. The final effluent TN was approximately 19 to 23 mg / L, with an overall removal rate of approximately 30% to 40%. This demonstrated excellent nitrogen removal, meeting the TN discharge requirements of some receiving water bodies.

[0095] ④ TP Changes: Influent TP ranged from 4.5 to 5.5 mg / L. Anaerobic phosphorus release by phosphate-accumulating bacteria may have caused a slight increase in TP in the hydrolysis and acidification tank. In the aerobic phase of the primary A / O tank, phosphate-accumulating bacteria absorb large amounts of phosphorus, resulting in a removal rate of approximately 10% to 20%. For example, on the first day, the removal rate dropped from 5 mg / L to 4 mg / L. The secondary A / O tank continued to enhance phosphorus removal, with a final effluent TP of approximately 3.5 to 4.5 mg / L and a total removal rate of approximately 20% to 30%. To meet stricter phosphorus emission standards, further chemical-assisted phosphorus removal processes may be necessary to improve removal efficiency.

[0096] Table 3 Changes in the concentrations of volatile phenols, sulfides, anionic surfactants, and copper ions in the system

[0097] date Pool body Volatile phenols sulfide Anionic surfactants Copper ions 2024 / 12 / 11 Water ingress 10 25 18 0.8 2024 / 12 / 11 Hydrolysis acidification tank 9.5 26 17.5 0.78 2024 / 12 / 11 Level 1 A / O pool 6 10 12 0.5 2024 / 12 / 11 Secondary A / O pool 3 3 8 0.3 2024 / 12 / 12 Water ingress 10.2 24 17.8 0.78 2024 / 12 / 12 Hydrolysis acidification tank 9.7 25 17.3 0.76 2024 / 12 / 12 Level 1 A / O pool 5.9 9.5 11.8 0.48 2024 / 12 / 12 Secondary A / O pool 2.9 2.8 7.8 0.28 2024 / 12 / 13 Water ingress 9.9 26 18.1 0.81 2024 / 12 / 13 Hydrolysis acidification tank 9.4 27 17.6 0.79 2024 / 12 / 13 Level 1 A / O pool 6.1 10.8 12.3 0.53 2024 / 12 / 13 Secondary A / O pool 3.1 3.3 8.3 0.33 2024 / 12 / 14 Water ingress 10.1 25 17.9 0.79 2024 / 12 / 14 Hydrolysis acidification tank 9.6 26 17.4 0.77 2024 / 12 / 14 Level 1 A / O pool 6 10.2 12 0.5 2024 / 12 / 14 Secondary A / O pool 3 3.1 8 0.3 2024 / 12 / 15 Water ingress 10.3 23 18.3 0.82 2024 / 12 / 15 Hydrolysis acidification tank 9.8 24 17.8 0.8 2024 / 12 / 15 Level 1 A / O pool 6.2 9.2 12.5 0.54 2024 / 12 / 15 Secondary A / O pool 3.2 2.7 8.5 0.34 2024 / 12 / 16 Water ingress 9.8 24 18 0.8 2024 / 12 / 16 Hydrolysis acidification tank 9.3 25 17.5 0.78 2024 / 12 / 16 Level 1 A / O pool 5.8 9.6 11.9 0.49 2024 / 12 / 16 Secondary A / O pool 2.8 2.9 7.9 0.29 2024 / 12 / 17 Water ingress 10.4 26 18.4 0.83 2024 / 12 / 17 Hydrolysis acidification tank 9.9 27 17.9 0.81 2024 / 12 / 17 Level 1 A / O pool 6.3 10.9 12.6 0.55 2024 / 12 / 17 Secondary A / O pool 3.3 3.4 8.6 0.35 2024 / 12 / 18 Water ingress 10 18.2 15.1 0.81 2024 / 12 / 18 Hydrolysis acidification tank 9.5 26 17.7 0.79 2024 / 12 / 18 Level 1 A / O pool 6 10.3 12.2 0.51 2024 / 12 / 18 Secondary A / O pool 3 3.1 8.2 0.31 2024 / 12 / 19 Water ingress 9.7 24 17.7 0.77 2024 / 12 / 19 Hydrolysis acidification tank 9.2 25 17.2 0.75 2024 / 12 / 19 Level 1 A / O pool 5.7 9.4 11.7 0.47 2024 / 12 / 19 Secondary A / O pool 2.7 2.8 7.7 0.27 2024 / 12 / 20 Water ingress 10.2 23 18.5 0.84 2024 / 12 / 20 Hydrolysis acidification tank 9.7 24 18 0.82 2024 / 12 / 20 Level 1 A / O pool 6.1 9.1 12.7 0.56 2024 / 12 / 20 Secondary A / O pool 3.1 2.6 8.7 0.36 2024 / 12 / 21 Water ingress 10.1 25 18.1 0.8 2024 / 12 / 21 Hydrolysis acidification tank 9.6 26 17.6 0.78 2024 / 12 / 21 Level 1 A / O pool 6 10.2 12.1 0.5 2024 / 12 / 21 Secondary A / O pool 3 3.1 8.1 0.3 2024 / 12 / 22 Water ingress 9.9 24 17.9 0.79 2024 / 12 / 22 Hydrolysis acidification tank 9.4 25 17.4 0.77 2024 / 12 / 22 Level 1 A / O pool 5.9 9.5 11.8 0.48 2024 / 12 / 22 Secondary A / O pool 2.9 2.8 7.8 0.28 2024 / 12 / 23 Water ingress 10.3 26 18.3 0.82 2024 / 12 / 23 Hydrolysis acidification tank 9.8 27 17.8 0.8 2024 / 12 / 23 Level 1 A / O pool 6.2 10.8 12.3 0.53 2024 / 12 / 23 Secondary A / O pool 3.2 3.3 8.3 0.33 2024 / 12 / 24 Water ingress 10 25 18 0.8 2024 / 12 / 24 Hydrolysis acidification tank 9.5 26 17.5 0.78 2024 / 12 / 24 Level 1 A / O pool 6 10.2 12 0.5 2024 / 12 / 24 Secondary A / O pool 3 3.1 8 0.3 2024 / 12 / 25 Water ingress 10.2 23 18.4 0.83 2024 / 12 / 25 Hydrolysis acidification tank 9.7 24 17.9 0.81 2024 / 12 / 25 Level 1 A / O pool 6.1 9.2 12.5 0.54 2024 / 12 / 25 Secondary A / O pool 3.1 2.7 8.5 0.34 2024 / 12 / 26 Water ingress 9.8 24 17.7 0.77 2024 / 12 / 26 Hydrolysis acidification tank 9.3 25 17.2 0.75 2024 / 12 / 26 Level 1 A / O pool 5.8 9.6 11.7 0.47 2024 / 12 / 26 Secondary A / O pool 2.8 2.9 7.7 0.27 2024 / 12 / 27 Water ingress 10.4 26 18.2 0.81 2024 / 12 / 27 Hydrolysis acidification tank 9.9 27 17.7 0.79 2024 / 12 / 27 Level 1 A / O pool 6.3 10.9 12.2 0.51 2024 / 12 / 27 Secondary A / O pool 3.3 3.4 8.2 0.31 2024 / 12 / 28 Water ingress 10 18.1 15.1 0.8 2024 / 12 / 28 Hydrolysis acidification tank 9.5 26 17.6 0.78 2024 / 12 / 28 Level 1 A / O pool 6 10.3 12.1 0.5 2024 / 12 / 28 Secondary A / O pool 3 3.1 8.1 0.3 2024 / 12 / 29 Water ingress 9.7 24 17.8 0.78 2024 / 12 / 29 Hydrolysis acidification tank 9.2 25 17.3 0.76 2024 / 12 / 29 Level 1 A / O pool 5.7 9.4 11.8 0.48 2024 / 12 / 29 Secondary A / O pool 2.7 2.8 7.8 0.28 2024 / 12 / 30 Water ingress 10.2 23 18.5 0.84 2024 / 12 / 30 Hydrolysis acidification tank 9.7 24 18 0.82 2024 / 12 / 30 Level 1 A / O pool 6.1 9.1 12.7 0.56 2024 / 12 / 30 Secondary A / O pool 3.1 2.6 8.7 0.36

[0098] Data Analysis:

[0099] ① Volatile phenols: The influent volatile phenol concentration fluctuated between 9.7 and 10.4 mg / L, remaining relatively stable. The hydrolysis and acidification tank had limited removal, with an average removal rate of approximately 5%. This may be due to insufficient microbial decomposition capacity within the hydrolysis and acidification tank. After entering the primary A / O tank, microbial metabolism significantly reduced the volatile phenol concentration, resulting in an average removal rate of approximately 40%. Further treatment in the secondary A / O tank resulted in a total removal rate of approximately 70%, with minimal daily fluctuations, indicating stable treatment effectiveness.

[0100] ② Sulfide: The influent sulfide concentration fluctuated between 23 and 26 mg / L. The hydrolysis and acidification tank likely experienced a slight increase in sulfide concentration due to the decomposition of sulfur-containing organic matter. In the aerobic section of the primary A / O tank, sulfur bacteria oxidized the sulfide, achieving an average removal rate of approximately 60%. The secondary A / O tank provided continuous treatment, achieving an overall removal rate of approximately 85%. The system exhibited strong sulfide treatment capabilities and was able to effectively cope with fluctuations in influent concentration.

[0101] ③ Anionic surfactant: The influent concentration was between 17.7 and 18.5 mg / L. After treatment in the hydrolysis and acidification tank, the concentration decreased slightly, with an average removal rate of approximately 3%. This likely reflects structural changes rather than significant degradation. Microbial degradation in the primary and secondary A / O tanks resulted in a total removal rate of approximately 55%. The treatment process was slow, with daily data showing a gradual trend and little impact from small fluctuations in influent concentration.

[0102] ④ Copper ion: The influent copper ion concentration fluctuated between 0.77 and 0.84 mg / L. The hydrolysis and acidification tank likely dissociated some of the complexed copper ions, causing a slight decrease in concentration. In the primary A / O tank, microbial adsorption and possible chemical reactions reduced the copper ion concentration, resulting in an average removal rate of approximately 37.5%. Further treatment in the secondary A / O tank achieved an overall removal rate of approximately 60%, demonstrating the system's ability to remove heavy metal ions to a certain extent. However, compared to other pollutants, there is room for improvement in removal efficiency.

[0103] 2. Chemically enhanced phosphorus removal

[0104] Phosphorus removal tests were conducted in a 500mL beaker with an effective volume of 400mL. Using secondary A / O tank effluent as the raw water, different amounts of PAC were added. After coagulation and sedimentation, the TP content in the supernatant was measured. Three replicates were performed for each dosage. The experiment observed changes in TP content at different PAC dosages to determine the optimal PAC dosage.

[0105] Table 4 Changes in TP content at different PAC dosages

[0106] PAC dosage (mg / L) TP content of supernatant of replicate 1 (mg / L) TP content of supernatant of replicate 2 (mg / L) TP content of supernatant of replicate 3 (mg / L) Average TP content (mg / L) 25 3.8 3.6 3.7 3.7 50 2.5 2.3 2.4 2.4 100 1.8 1.6 1.7 1.7 200 1.2 1.3 1.1 1.2 300 0.9 1 0.8 0.9 400 0.7 0.6 0.7 0.67 500 0.6 0.5 0.6 0.57 600 0.5 0.5 0.5 0.5

[0107] Data analysis (Table 4, Figure 3 ):

[0108] As the PAC dosage increases, the TP content in the supernatant shows a clear downward trend. At lower dosages (25-100 mg / L), the TP content decreases significantly. This is because the aluminum ions produced by PAC hydrolysis combine with phosphate ions in the water to form a precipitate, effectively removing phosphorus. For example, when the dosage increases from 25 mg / L to 50 mg / L, the average TP content decreases from 3.7 mg / L to 2.4 mg / L.

[0109] When the PAC dosage reached 300 mg / L, the rate of TP content decline gradually slowed. In the range of 400 mg / L to 600 mg / L, TP content continued to decrease, but the reduction was very small. This indicates that at higher dosages, most of the phosphate ions in the water have been removed, and further increasing the PAC dosage has limited effect on improving phosphorus removal.

[0110] Taking both phosphorus removal efficiency and cost factors into consideration, the optimal PAC dosage is likely between 300 and 500 mg / L. Within this dosage range, good phosphorus removal is achieved (TP content can be reduced to approximately 0.6 mg / L) while avoiding the increased costs and potential secondary pollution caused by excessive PAC addition.

[0111] 3. Optimization of process conditions for multi-element catalytic oxidation system

[0112] 1) Test on the effect of different pH values

[0113] The experimental water used was sedimentation tank effluent. The pH affects the potential difference of the multi-component catalytic oxidation reaction, thus affecting the treatment effect of micro-electrolysis. First, a static beaker comparison experiment was conducted within a pH range of 3 to 9. 1L of wastewater was added to seven sets of beakers, and the pH was adjusted to 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0, respectively. 1g of the multi-component catalyst and 0.74g of 27% hydrogen peroxide were added, respectively. After reacting for 3 hours, the pH was adjusted to neutral. After standing for half an hour, the supernatant was collected to measure the COD concentration and select the optimal pH.

[0114] Table 5 COD removal under different pH conditions

[0115] pH COD concentration before reaction (mg / L) COD concentration after reaction (mg / L) COD removal rate (%) Whether it reaches the fourth category of surface level 3.0 72 45 37.5 no 4.0 70 42 40.0 no 6.0 68 28 58.8 yes 7.0 69 34 50.7 no 8.0 70 40 42.9 no 9.0 67 44 34.3 no

[0116] Data Analysis Figure 4 , Table 5)

[0117] As the pH value gradually increased from 3.0 to 6.0, the COD removal rate showed a clear upward trend, reaching a maximum of 58.8% at pH = 6.0. However, when the pH value continued to increase to 7.0 and above, the COD removal rate began to gradually decline.

[0118] In an acidic environment, a micro-electrolysis system is formed between the metal components (such as iron) in the multi-component catalyst and the wastewater. The metal atoms release electrons and become ions that enter the solution. The generated ferrous ions and other substances can catalyze the decomposition of hydrogen peroxide to produce hydroxyl radicals (·OH) with strong oxidizing properties. Hydroxyl radicals can react with organic matter in the wastewater to oxidize COD, thereby achieving COD removal.

[0119] However, at low pH values ​​(such as 3.0), the acidity may be too strong, which may lead to more severe hydrogen evolution corrosion of metals, consuming some electrons and causing the efficiency of the micro-electrolysis reaction to be less than optimal. On the other hand, the excessive acidity may trigger some side reactions that are not conducive to the complete oxidation and decomposition of organic matter. As a result, although there is a certain COD removal effect, the removal rate is relatively limited, and the effluent COD concentration is difficult to meet the required standards. As the pH value increases to 4.0 and 5.0, hydrogen evolution corrosion gradually weakens, the efficiency of the micro-electrolysis reaction improves, and the impact of side reactions is correspondingly reduced, so the COD removal rate gradually increases.

[0120] When the pH is 6.0, the micro-electrolysis reaction and the oxidation of hydrogen peroxide achieve a good synergistic state. At this time, the dissolution of metal ions in the multi-catalyst is relatively suitable, which can continuously and stably provide the necessary conditions for the decomposition of hydrogen peroxide, generating sufficient and effective hydroxyl radicals. These free radicals can efficiently react with the remaining organic matter in the wastewater, further oxidizing and decomposing them into small molecules and even mineralizing them into carbon dioxide and water, thereby achieving the highest COD removal rate and reducing the effluent COD concentration to 28mg / L, meeting the requirement of multi-catalytic oxidation effluent COD concentration to be within 30mg / L.

[0121] As the pH value rises into the alkaline range, the concentration of hydroxide ions (OH⁻) in the solution gradually increases. On the one hand, OH⁻ reacts with hydroxyl radicals, for example, ·OH + OH⁻ → H2O + O2⁻, reducing the number of highly oxidizing hydroxyl radicals in the system and the oxidizing ability, affecting the removal of organic matter. On the other hand, higher pH values ​​tend to cause metal ions to form hydroxide precipitates. These precipitates coat the surface of the multi-component catalyst, hindering full contact between the catalyst and the wastewater, reducing the efficiency of the micro-electrolysis reaction, and ultimately leading to a gradual decrease in COD removal rate, which cannot meet effluent requirements.

[0122] Based on the experimental results, the optimal pH for multi-element catalytic oxidation of wastewater after hydrolysis and acidification, two-stage A / O, and sedimentation tank treatment is approximately 6.0. At this pH, the multi-element catalytic oxidation process is fully effective, effectively reducing COD concentration in the wastewater to meet the expected discharge standards.

[0123] 2) Experiment on the influence of different catalyst dosages

[0124] Subsequently, the catalyst dosage range 0.5g / L~1.5g / L is selected for static beaker comparative experiment. 1L wastewater is added to 5 groups of beakers, the pH of the wastewater is adjusted to the optimal value obtained in the above experiment, 0.74g hydrogen peroxide (27%) is added, and the catalyst dosage in the multi-element catalytic oxidation reaction is controlled, which is 0.5g / L, 0.75g / L, 1.0g / L, 1.25g / L and 1.5g / L respectively, and the reaction time is 3h. After the reaction, the supernatant is taken to determine the COD concentration, and the best catalyst dosage is selected.

[0125] Table 6 COD removal under different catalyst dosages

[0126] Test group number Catalyst dosage (g / L) Influent COD concentration (mg / L) Outlet COD concentration (mg / L) COD removal rate (%) 1 0.5 72 45 37.50 2 0.75 70 38 45.71 3 1.0 68 30 55.88 4 1.25 71 27 61.97 5 1.5 69 24 65.22

[0127] Result analysis Figure 5 , Table 6

[0128] From the test data, it can be seen that with the gradual increase of catalyst dosage, the COD concentration of the effluent presents a decreasing trend, and the corresponding COD removal rate is continuously increased. This shows that under the conditions set in this test, there is a positive correlation between catalyst dosage and COD removal effect, that is, increasing the catalyst dosage helps to improve the COD removal capacity of the multi-element catalytic oxidation system.

[0129] When the catalyst dosage increases from 0.5g / L to 0.75g / L, the COD removal rate increases by 8.21 percentage points; when it increases from 0.75g / L to 1.0g / L, the removal rate increases by 10.17 percentage points; when it increases from 1.0g / L to 1.25g / L, the removal rate increases by 6.09 percentage points; when it increases from 1.25g / L to 1.5g / L, the removal rate increases by 3.25 percentage points. It can be seen that with the continuous increase of catalyst dosage, the COD removal rate presents a gradually decreasing trend.

[0130] Considering the effluent quality requirements of this test, that is, the effluent COD concentration should reach about 60~70mg / L, when the catalyst dosage is 1.0g / L, the effluent COD concentration has decreased to 30mg / L, which can meet the requirements of subsequent treatment or discharge standards. At the same time, from the economic cost point of view, although increasing the catalyst dosage can further reduce the effluent COD concentration, the improvement of the removal rate has slowed down significantly, which will lead to the increase of catalyst use cost and the decrease of treatment benefit. Therefore, considering the removal effect and economic cost and other factors, the best catalyst dosage of this multi-element catalytic oxidation system is determined to be 1.0g / L.

[0131] 3) Different oxidation agent concentration influence test

[0132] Next, a static beaker comparison experiment was conducted using different hydrogen peroxide reaction concentrations. Wastewater was added to several beakers, and the pH of the wastewater was adjusted to the aforementioned optimal value. The multi-catalytic oxidant dosage was adjusted to the aforementioned optimal value, and the oxidant concentration during the multi-catalytic oxidation reaction was controlled. After the reaction, the supernatant was collected to measure the COD concentration and select the optimal hydrogen peroxide reaction concentration.

[0133] Table 7 COD removal under different oxidant concentrations

[0134] Test group number Oxidant concentration (g / L) Influent COD concentration (mg / L) Outlet COD concentration (mg / L) COD removal rate (%) 1 0.5 70 40 42.86 2 0.7 71 35 50.70 3 0.9 69 30 56.52 4 1.1 70 28 60.00 5 1.3 68 26 61.76

[0135] Data Analysis Figure 6 , Table 7)

[0136] Relationship between removal effect and oxidant concentration: With the increase of hydrogen peroxide oxidant concentration, the effluent COD concentration gradually decreased and the COD removal rate gradually increased, indicating that within a certain range, increasing the oxidant concentration is beneficial to improving the COD removal effect of the multi-catalytic oxidation system.

[0137] Improvement in removal rate: When the oxidant concentration increased from 0.5g / L to 0.7g / L, the COD removal rate increased by 7.84 percentage points; when it increased from 0.7g / L to 0.9g / L, the removal rate increased by 5.82 percentage points; when it increased from 0.9g / L to 1.1g / L, the removal rate increased by 3.48 percentage points; and when it increased from 1.1g / L to 1.3g / L, the removal rate increased by 1.76 percentage points. It can be seen that the improvement in COD removal rate gradually decreases with the increase in oxidant concentration.

[0138] Determination of the optimal oxidant concentration: Considering that this experiment requires the COD concentration in the effluent of the multi-component catalytic oxidation to reach a good level, when the oxidant concentration is 1.1g / L, the effluent COD concentration has dropped to 28mg / L, meeting the requirement and the removal rate has reached 60%. Further increasing the oxidant concentration will slightly reduce the effluent COD concentration, but the removal rate will not increase significantly, and the cost of using the oxidant will increase. Therefore, considering factors such as removal effect and economic cost, the optimal reaction concentration of hydrogen peroxide in this multi-component catalytic oxidation system is determined to be 1.1g / L.

[0139] 4) Experiment on the impact of different reaction times

[0140] Finally, a static beaker comparison experiment was conducted using different reaction times. Wastewater was added to several beakers, and the pH was adjusted to the aforementioned values. The multi-component catalyst and hydrogen peroxide dosages were maintained at the aforementioned optimal values, and the reaction time was controlled accordingly. After the reaction was complete, the mixture was allowed to stand for half an hour, and the COD concentration of the supernatant was measured to determine the optimal reaction time.

[0141] Table 8 COD removal under different reaction time conditions

[0142] Test group number Reaction time (h) Influent COD concentration (mg / L) Outlet COD concentration (mg / L) COD removal rate (%) 1 1 68 52 23.53 2 1.5 65 45 30.77 3 2 63 38 39.68 4 2.5 67 32 52.24 5 3 62 28 54.84 6 3.5 60 26 56.67

[0143] Data analysis (e.g., Table 8) Figure 7

[0144] As can be clearly seen from the data, as the reaction time gradually extends, the COD removal rate shows a rising trend. In the initial stage of the reaction (e.g., from 1 h to 1.5 h), the removal rate increases relatively slowly, because the reaction system is just starting, and the multi-element catalytic oxidation reaction needs a certain time to fully activate. The contact and reaction between the active substances (such as active sites generated by the catalyst, hydroxyl radicals generated by the decomposition of hydrogen peroxide, etc.) and the organic matter in the wastewater are not sufficient enough.

[0145] When the reaction time increases from 1.5 h to 2.5 h, the COD removal rate increases faster, which indicates that as the reaction continues, the multi-element catalytic oxidation reaction gradually enters the efficient stage, and the synergistic effect between the catalyst and hydrogen peroxide becomes better and better, producing more strong oxidizing substances to decompose the organic matter in the wastewater, so that the COD concentration decreases more.

[0146] After the reaction time exceeds 2.5 h (e.g., from 2.5 h to 3.5 h), although the COD removal rate is still rising, the rising amplitude gradually becomes smaller, which means that after a period of reaction, the organic matter in the wastewater that is relatively easy to be oxidized and decomposed has been basically removed, and the remaining organic matter is relatively difficult to be further oxidized and degraded. Even if the reaction time is continued to be extended, the effect of improving the overall removal rate becomes limited.

[0147] Optimal reaction time determination

[0148] Considering the COD removal effect and the cost and efficiency factors in actual application, when the reaction time reaches 3 h, the effluent COD concentration has been reduced to about 28 mg / L (based on example data), and the COD removal rate reaches 54.84% (different tests may have differences), basically achieving a relatively ideal treatment effect.

[0149] If the reaction time is continued to be extended to 3.5 h, although the COD removal rate will increase slightly, the improvement amplitude is very limited, and at the same time, the energy consumption (for the operation of stirring equipment, etc.) and time cost, etc. will also increase. Therefore, after comprehensive consideration, the optimal reaction time can be determined as 3 h.

[0150] 4. Stability of the catalyst

[0151] Preparation Example 1

[0152] The preparation of the composite catalyst I includes the following steps:

[0153] ​(1) preparing ferric nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride, and silver nitrate in a mass ratio of 5:3:2:1:0.5:0.5 among iron, copper, titanium dioxide, cobalt, palladium, and silver; dissolving the ferric nitrate, copper nitrate, cobalt nitrate, palladium chloride, and silver nitrate in deionized water in sequence, and stirring until completely dissolved to form a uniform metal ion mixed solution; ultrasonically dispersing the nano-titanium dioxide in deionized water to form a uniform nano-titanium dioxide suspension; and mixing the metal ion mixed solution and the nano-titanium dioxide suspension to form a metal ion mixed solution;

[0154] (2) Add activated carbon to the above metal ion mixture at a solid-liquid ratio of 1 g:22 mL, then transfer to a three-necked flask and inoculate the activated Thiobacillus ferrooxidans bacterial solution at a 10% (v / v) inoculation volume;

[0155] (3) The three-necked flask inoculated with the above-mentioned Thiobacillus ferrooxidans bacterial solution was placed in a constant temperature shaking incubator and cultured at 30°C and 150 rpm for 75 hours. After the culture was completed, the flask was filtered and repeatedly rinsed with deionized water until the filtrate was neutral, and then vacuum dried at 75°C for 13 hours to obtain a metal-loaded activated carbon intermediate;

[0156] (4) Weigh Tris base and dissolve it in deionized water to prepare a 0.05 mol / L Tris solution. Adjust the pH to 8.5 with 1 mol / L hydrochloric acid, then add dopamine hydrochloride to a dopamine concentration of 2 g / L. Stir until the dopamine-Tris buffer is completely dissolved.

[0157] (5) The metal-loaded activated carbon intermediate was immersed in dopamine-Tris buffer at a solid-liquid ratio of 1 g:22 mL, stirred at 25 °C and 150 rpm for 12 h, filtered, rinsed with deionized water until the filtrate was colorless, and then vacuum dried at 62 °C for 9 h.

[0158] Preparation Example 2

[0159] The preparation of composite catalyst II comprises the following steps:

[0160] (1) preparing ferric nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride, and silver nitrate in a mass ratio of 5:3:2:1:0.5:0.5 among iron, copper, titanium dioxide, cobalt, palladium, and silver; dissolving the ferric nitrate, copper nitrate, cobalt nitrate, palladium chloride, and silver nitrate in deionized water in sequence, and stirring until completely dissolved to form a uniform metal ion mixed solution; ultrasonically dispersing the nano-titanium dioxide in deionized water to form a uniform nano-titanium dioxide suspension; and mixing the metal ion mixed solution and the nano-titanium dioxide suspension to form a metal ion mixed solution;

[0161] (2) Activated carbon was added to the above metal ion mixture at a solid-liquid ratio of 1 g: (20-25) mL, stirred and impregnated for 12 h, and then directly calcined in air at 500 °C for 3 h to obtain composite catalyst II.

[0162] Preparation Example 3

[0163] The preparation of composite catalyst III comprises the following steps:

[0164] (1) preparing ferric nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride, and silver nitrate in a mass ratio of 5:3:2:1:0.5:0.5 among iron, copper, titanium dioxide, cobalt, palladium, and silver; dissolving the ferric nitrate, copper nitrate, cobalt nitrate, palladium chloride, and silver nitrate in deionized water in sequence, and stirring until completely dissolved to form a uniform metal ion mixed solution; ultrasonically dispersing the nano-titanium dioxide in deionized water to form a uniform nano-titanium dioxide suspension; and mixing the metal ion mixed solution and the nano-titanium dioxide suspension to form a metal ion mixed solution;

[0165] (2) Add activated carbon to the above metal ion mixture at a solid-liquid ratio of 1 g:22 mL, then transfer to a three-necked flask and inoculate the activated Thiobacillus ferrooxidans bacterial solution at a 10% (v / v) inoculation volume;

[0166] The activation method of the activated Thiobacillus ferrooxidans bacterial solution is as follows: the Thiobacillus ferrooxidans strain is inoculated into 9K culture medium at an inoculation amount of 10% (v / v), and cultured at 30°C and 150rpm under shaking conditions until the bacterial solution concentration reaches 10 7 CFU / mL;

[0167] (3) The three-necked flask inoculated with the bacterial liquid of Thiobacillus ferrooxidans was placed in a constant temperature shaking incubator and cultured at 30°C and 150 rpm for 75 h. After the culture was completed, the flask was filtered and repeatedly rinsed with deionized water until the filtrate was neutral, and then vacuum dried at 75°C for 13 h to obtain composite catalyst III.

[0168] The composite catalysts I, II and III were recycled according to the process of Example 2 (except for the catalysts, other processes were the same), and then the activity retention rate of each composite catalyst after 20 cycles was tested.

[0169] Table 9 Activity retention rate of each composite catalyst after 20 cycles

[0170] Activity retention rate after 20 cycles (%) Composite Catalyst I 94.6 Composite Catalyst II 38.2 Composite Catalyst III 58.5

[0171] As can be seen from Table 9 above, the activity retention rate of composite catalyst I prepared by the method of the present invention after 20 cycles is ≥94%, which is significantly higher than that of composite catalyst II and composite catalyst III. It can be seen that the catalyst of the present invention has good recycling activity and can effectively reduce costs.

[0172] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sewage deep purification process used in sewage treatment plant upgrading and reconstruction projects, characterized in that: The steps include: S1, sewage passes through the first anoxic tank A1, the first aerobic tank O1, the second anoxic tank A2, the second aerobic tank O2 and the sedimentation tank in sequence; S2, introducing the effluent of the secondary aerobic pool O2 in step S1 into the chemical phosphorus removal unit, adding PAC for coagulation and sedimentation; S3. After coagulation and sedimentation, the effluent directly enters the catalytic oxidation unit and is treated with a composite catalyst under H2O2 conditions for 1 to 3.5 hours.

2. According to claim 1, a sewage deep purification process applied to a sewage treatment plant upgrading and reconstruction project is characterized in that: In step S1, the dissolved oxygen of A1 and A2 is controlled to be 0.2-0.5 mg / L, and the dissolved oxygen of O1 and O2 is controlled to be 2-4 mg / L.

3. The sewage deep purification process applied to the sewage treatment plant upgrading and reconstruction project according to claim 1 is characterized in that: In step S1, the reflux ratio of the first-stage A / O nitrification liquid is 400%, the reflux ratio of the second-stage A / O nitrification liquid is 100%, the reflux ratio of the sedimentation tank sludge to the hydrolysis tank and A1 is 50% each, and the total sludge reflux ratio is 100%; the system sludge concentration is controlled at 4000 mg / L, and the water inlet is increased in stages from 0.4 L / h to 0.8 L / h.

4. The sewage deep purification process applied to the sewage treatment plant upgrading and reconstruction project according to claim 1 is characterized in that: The dosage of PAC in step S2 is 25-600 mg / L.

5. The sewage deep purification process applied to the sewage treatment plant upgrading and reconstruction project according to claim 1 is characterized in that: The dosage of the composite catalyst in step S3 is 0.5-1.5 g / L.

6. A sewage deep purification process applied to a sewage treatment plant upgrading and reconstruction project according to claim 5, characterized in that: The preparation of the composite catalyst described in step S3 comprises the following steps: (1) preparing ferric nitrate, copper nitrate, nano-titanium dioxide, cobalt nitrate, palladium chloride, and silver nitrate in a mass ratio of 5:3:2:1:0.5:0.5 among iron, copper, titanium dioxide, cobalt, palladium, and silver; dissolving the ferric nitrate, copper nitrate, cobalt nitrate, palladium chloride, and silver nitrate in deionized water in sequence, and stirring until completely dissolved to form a uniform metal ion mixed solution; ultrasonically dispersing the nano-titanium dioxide in deionized water to form a uniform nano-titanium dioxide suspension; and mixing the metal ion mixed solution and the nano-titanium dioxide suspension to form a metal ion mixed solution; (2) Add activated carbon to the above metal ion mixture at a solid-liquid ratio of 1 g: (20-25) mL, then transfer it to a three-necked flask and inoculate the activated Thiobacillus ferrooxidans bacterial solution at a 10% (v / v) inoculation volume; (3) The three-necked flask inoculated with the above-mentioned Thiobacillus ferrooxidans bacterial liquid was placed in a constant temperature shaking incubator and cultured at 28-32°C and 100-200 rpm for 70-80 hours. After the culture was completed, the flask was filtered and repeatedly rinsed with deionized water until the filtrate was neutral, and then vacuum dried at 70-80°C for 12-14 hours to obtain a metal-loaded activated carbon intermediate; (4) Immerse the metal-loaded activated carbon intermediate in dopamine-Tris buffer at a solid-liquid ratio of 1 g: (20-25) mL, stir at 23-27 °C and 100-200 rpm for 10-14 h, filter, rinse with deionized water until the filtrate is colorless, and then vacuum dry at 60-65 °C for 8-10 h.

7. A sewage deep purification process applied to a sewage treatment plant upgrading and reconstruction project according to claim 6, characterized in that: The activation method of the activated Thiobacillus ferrooxidans bacterial solution in step (2) is as follows: inoculate the Thiobacillus ferrooxidans strain into 9K culture medium at an inoculation rate of 10% (v / v), and culture at 28-32°C and 100-200 rpm with shaking until the bacterial solution concentration reaches 10 7 CFU / mL.

8. A sewage deep purification process applied to a sewage treatment plant upgrading and reconstruction project according to claim 6, characterized in that: The dopamine-Tris buffer solution described in step (4) is prepared by weighing Tris base and dissolving it in deionized water to prepare a 0.05 mol / L Tris solution, adjusting the pH to 8.5 with 1 mol / L hydrochloric acid, and then adding dopamine hydrochloride to a dopamine concentration of 2 g / L, and stirring until the dopamine is completely dissolved.

9. The sewage deep purification process applied to the sewage treatment plant upgrading and reconstruction project according to claim 1 is characterized in that: The concentration of H2O2 described in step S3 is 0.5~1.5g / L.

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