A micro-oxygen denitrification wastewater treatment process

Abstract

The present invention belongs to the field of sewage treatment, and specifically relates to a micro-aerobic denitrification wastewater treatment process. Bacillus is introduced into a homogenizing tank, and a biological activation complex is added; the wastewater enters the homogenizing tank and is evenly mixed with the return sludge and the mixed liquid, and then enters a high-efficiency denitrification reactor; the dissolved oxygen in the micro-aerobic biochemical tank is gradually reduced from the water inlet to the water outlet, and the effluent of the high-efficiency denitrification reactor enters the micro-aerobic biochemical tank for further reaction; the nitrification liquid is refluxed to the high-efficiency denitrification reactor and the micro-aerobic biochemical tank, and the sludge after precipitation in the sedimentation tank is discharged to the sludge tank, and refluxed to the high-efficiency denitrification reactor and the micro-aerobic biochemical tank, and the wastewater that meets the standards is discharged. The process of the present invention can realize synchronous short-range nitrification and denitrification in the system, solves the problem of biological phase interference caused by the reflux of the nitrification liquid of the traditional activated sludge method, and at the same time greatly reduces the amount of additional carbon source required for denitrification compared with the traditional process.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, and in particular relates to a micro-oxygen denitrification wastewater treatment process. Background Art

[0002] Conventional biological denitrification processes for wastewater include A / O and A / A / O. In these processes, wastewater typically undergoes a series of cycles: anaerobic, anoxic, and aerobic. Sewage and return sludge first enter an anaerobic tank (DO < 0.2 mg / L) for thorough mixing. Anaerobic decomposition occurs over a period of 1-2 hours, removing some BOD and converting some nitrogenous compounds into nitrogen (denitrification). The wastewater then flows into an anoxic tank (DO <= 0.5 mg / L). Denitrifying bacteria in these tanks, using undecomposed carbon-containing organic matter in the wastewater as a carbon source, reduce nitrate ions (recirculated from the aerobic tank) to nitrogen, releasing nitrogen. The wastewater then flows into an aerobic tank (DO 2-4 mg / L), where NH3-N (ammonia nitrogen) in the water undergoes nitrification to produce nitrate ions. A reflux pump then returns the nitrified solution to the anoxic tank, completing denitrification.

[0003] In existing biological treatment processes, the dominant bacterial species in anaerobic tanks, anoxic tanks, and aerobic tanks are anaerobic bacteria, facultative anaerobic bacteria, and aerobic bacteria, respectively. The three dominant bacterial species have very different growth environments. In actual operation, bacterial strain acclimation and screening are achieved by controlling the growth environment of different bacterial species. However, process operation requires the nitrification liquid and aerobic sludge to be returned to the anoxic tank / anaerobic tank, that is, the aerobic bacteria are returned to the anoxic / anaerobic environment, which limits the normal growth of aerobic microorganisms. At the same time, the sewage from the anoxic tank flows into the aerobic tank, and the anoxic bacteria enter the aerobic environment, which also poses the same problem. Biological interference between aerobic and anaerobic bacteria exists throughout the biochemical system. Various conflicts between bacterial species in traditional A / A / O processes include conflicts in sludge age, carbon source competition, and residual interference from nitrate and dissolved oxygen (DO). Summary of the Invention

[0004] To address the issues of biological interference and high treatment costs caused by the recirculation of nitrification liquid in conventional activated sludge processes, the present invention provides a micro-aerobic denitrification wastewater treatment process that can treat both conventional municipal and industrial wastewater and, in particular, efficiently remove ammonia nitrogen from wastewater containing refractory organic matter. The technical solution is as follows:

[0005] A micro-aerobic denitrification wastewater treatment process comprises the following steps: introducing bacillus into a homogenizing tank and adding a bio-activated complex; the wastewater enters the homogenizing tank and is evenly mixed with the return sludge and a mixed liquid, and then enters a high-efficiency denitrification reactor; the dissolved oxygen in the micro-aerobic biochemical tank is gradually reduced from the water inlet to the water outlet, and the water outlet of the high-efficiency denitrification reactor enters the micro-aerobic biochemical tank for further reaction; the nitrification liquid is returned to the high-efficiency denitrification reactor and the micro-aerobic biochemical tank, and the sludge after sedimentation in the sedimentation tank is discharged to the sludge tank and returned to the high-efficiency denitrification reactor and the micro-aerobic biochemical tank, and the wastewater that meets the standards is discharged.

[0006] Furthermore, the dissolved oxygen concentration in the process is 0.1~1.0 mg / L; the sludge concentration is 5000~40000 mg / L; and the operating ambient temperature is 40~0°C.

[0007] Furthermore, the bioactivation complex comprises the following components in parts by mass: 3-5 parts of aspartic acid, 12-16 parts of glycine, 0.3-0.6 parts of disodium hydrogen phosphate, 0.2-0.5 parts of 6-benzyladenine, 0.8-1.6 parts of biotin-ferrous complex and 20-30 parts of chitosan.

[0008] Furthermore, a promoter is added to the high-efficiency denitrification reactor; the preparation of the promoter and the bioactivation complex includes the following steps: reacting ferrous salt and oxalic acid in a chitosan solution to obtain ferrous oxalate and a chitosan solution; reducing the ferrous oxalate to obtain zero-valent iron, and loading the zero-valent iron on a carrier to obtain a promoter; combining the ferrous salt with biotin to form a biotin-ferrous complex; and mixing the biotin-ferrous complex and the remaining components with the chitosan solution to obtain a bioactivation complex.

[0009] Further, the following steps are included:

[0010] a. Dissolve oxalic acid in water, add chitosan and dissolve thoroughly, then dropwise add ferrous sulfate solution. Mix thoroughly at 30-40°C, and let stand for 2-4 hours to separate the chitosan solution and precipitate. Wash the precipitate thoroughly and dry it to obtain ferrous oxalate.

[0011] b. Calcining ferrous oxalate and glucose, mixing with bentonite, adding water to expand the mixture, and then granulating the granules; aging the granules for 1-2 days and then calcining them at 400-500°C to obtain the accelerator;

[0012] c. Disperse biotin in hot water to obtain a biotin solution. Add ferrous sulfate and ascorbic acid to the biotin solution and dissolve thoroughly. Then, react at 30-50°C for 0.5-1 hour. After standing for 20-60 minutes, cool to 5-20°C, add 3 volumes of ethanol, separate and collect the precipitate, and freeze-dry to obtain a biotin-ferrous complex.

[0013] d. The biotin-ferrous complex and the remaining components are mixed with the chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and broken to obtain a bioactivated complex.

[0014] Furthermore, in step a, the mass ratio of oxalic acid to ferrous sulfate is 1:1.3-1.65; the mass ratio of oxalic acid to chitosan is 1:8-10.

[0015] Furthermore, in step b, calcining the ferrous oxalate and glucose is to calcine the ferrous oxalate and glucose at 700-800° C. for 0.5-1.5 h under a nitrogen atmosphere.

[0016] Furthermore, in step b, the mass ratio of ferrous oxalate to glucose is 1:2-5; the mass ratio of ferrous oxalate to bentonite is 1:3-5; and the mass ratio of bentonite to water is 1:4-6.

[0017] Furthermore, the mass ratio of ferrous sulfate to ascorbic acid in step c is 1:0.5-0.8; the mass ratio of ferrous sulfate to biotin in step d is 1:1.6-2.

[0018] An application of the above-mentioned micro-aerobic denitrification wastewater treatment process in treating wastewater containing or not containing refractory organic matter.

[0019] By adopting the above scheme, the method of the present invention has the following advantages:

[0020] The process system of the present invention controls dissolved oxygen at 0.1-1.0 mg / L, far lower than the 2-4 mg / L required by conventional activated sludge biochemical processes. By removing ammonia nitrogen through short-range nitrification, aeration volume is reduced by approximately 40%, lowering operating electricity costs.

[0021] The denitrification mechanism of the process system of the present invention is short-range denitrification denitrification, which converts NO2-N into N2 to remove TN through short-range denitrification. Compared with the denitrification denitrification of traditional processes, there is no NO3-N conversion to NO2-N reaction section, and the carbon source supply is reduced by about 25%, reducing the operating agent cost. This can save a large amount of carbon source and effectively solve the problem of insufficient carbon source for denitrification denitrification.

[0022] The nitritation capacity of the Bacillus bacteria employed in the process system of the present invention is minimally affected by ambient temperature, and can stably convert ammonia nitrogen into NO₂-N even in low-temperature environments. In contrast, the nitrifying bacteria in traditional activated sludge processes typically experience reduced nitrification efficiency at ambient temperatures below 15°C, and virtually cease at temperatures below 5°C. Therefore, the process of the present invention can ensure stable removal of ammonia nitrogen even in cold winters, ensuring that the effluent meets standards.

[0023] The present invention can utilize the large amount of biologically active enzymes secreted during the proliferation of the bacteria, and has a strong decomposition ability for difficult-to-degrade organic matter such as cellulose and protein, which is impossible to achieve with traditional activated sludge processes, especially for industrial wastewater containing difficult-to-degrade organic matter.

[0024] The biochemical reaction tank of this invention utilizes a microaerobic mode, dividing the tank into several compartments with independently controlled aeration for each compartment, allowing for flexible adjustment of dissolved oxygen levels in the wastewater. Dissolved oxygen levels within the tank initially increase and then decrease, reaching as low as 0.1 mg / L at the outlet, creating an anoxic state. Dissolved oxygen levels throughout the reaction tank are significantly lower than those in conventional biochemical systems (2-4 mg / L in aerobic tanks). The bacteria within the system permanently maintain an anoxic state, enabling simultaneous nitrification, denitrification, and organic matter removal. There is no interference with dissolved oxygen levels in either internal or external recirculation, and no interference between aerobic and anaerobic bacteria.

[0025] The bioactivation complex of this invention can quickly promote bacterial growth, turning it into a dominant strain, and achieve sludge concentrations (reaching over 40,000 mg / L) that are over 10 times higher than those achieved with traditional processes (3,000-4,000 mg / L). The rich biomass enables rapid denitrification and simultaneous removal of organic matter. Furthermore, due to the combination of biotin and ferrous ions, and the encapsulation of various components by chitosan, the release of ingredients is smooth, the effect is long-lasting, and the effects are well-maintained. Frequent dosing is unnecessary, storage is convenient, and deterioration is not easily prevented.

[0026] The ferrous iron and zero-valent iron of the present invention can both serve as electron donors, providing raw materials for the rapid growth of Bacillus in the early bacterial proliferation process, and promoting each other with Bacillus to achieve denitrification of sewage in the efficient denitrification stage.

[0027] The ferrous oxalate of the present invention is micronized under the action of chitosan, resulting in a larger surface area and more uniform particles. The carbon and iron contained in the accelerator form micro-electrolysis, which can effectively promote microbial metabolism and denitrification, and promote the decomposition of difficult-to-degrade organic matter. In addition, the solidified accelerator facilitates the fixation of iron and the colonization of bacteria, facilitating the recovery and stable reproduction of bacteria.

[0028] The preparation method of the invention is simple, raw materials can be fully utilized, and the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the micro-aerobic denitrification wastewater treatment process of the present invention;

[0030] Figure 2 This is a comparison chart of the denitrification effects of the fermentation tanks of various embodiments;

[0031] Figure 3 This is a graph showing changes in total nitrogen concentrations in the inlet and outlet water of Example 1. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0033] Example 1: (1) 2 g of oxalic acid was dissolved in water, 20 g of chitosan was added and fully dissolved, and then a solution containing 3 g of ferrous sulfate was dropped into the solution, and the mixture was fully mixed at 30-40° C., and then allowed to stand for 2-4 h, and the chitosan solution containing ferrous sulfate and the precipitate were separated. The precipitate was fully washed and dried to obtain ferrous oxalate;

[0034] (2) 2 g of ferrous oxalate and 5 g of glucose were calcined at 750 °C for 1 h under a nitrogen atmosphere, mixed with 4 g of bentonite, and expanded with 20 mL of water before granulation. The resulting granules were aged for 1 day and then calcined at 450 °C to obtain a promoter.

[0035] (3) Disperse 1.5 g of biotin in hot water to obtain a biotin solution. Add 0.75 g of ferrous sulfate and 0.5 g of ascorbic acid to the biotin solution and fully dissolve it. Then react at 40 °C for 0.5 to 1 h. After standing for 40 min, cool to 8 °C and add 3 times the volume of ethanol. Separate and collect the precipitate, and freeze-dry to obtain a biotin-ferrous complex.

[0036] (4) Aspartic acid 4 g, glycine 13 g, sodium hydrogen phosphate 0.4 g, 6-benzyladenine 0.4 g, biotin-ferrous complex 1.2 g were mixed with chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and crushed to obtain a bioactivated complex.

[0037] Example 2: The difference from Example 1 is that:

[0038] (1) Dissolve 2g of oxalic acid in water, add 30g of chitosan and fully dissolve it, then drop a solution containing 3g of ferrous sulfate into it, mix thoroughly at 30-40℃, and then let it stand for 2-4h to separate the chitosan solution containing ferrous sulfate and the precipitate. Wash the precipitate thoroughly and dry it to obtain ferrous oxalate.

[0039] Example 3: The difference from Example 1 is that:

[0040] (2) 2 g of ferrous oxalate and 2 g of glucose were calcined at 750 °C for 1 h under a nitrogen atmosphere, mixed with 4 g of bentonite, expanded with 20 mL of water, and granulated; the obtained granules were aged for 1 day and then calcined at 450 °C to obtain a promoter.

[0041] Example 4: The difference from Example 1 is that:

[0042] (3) Disperse 1.2g of biotin in hot water to obtain a biotin solution. Add 0.75g of ferrous sulfate and 0.5g of ascorbic acid to the biotin solution and fully dissolve it. Then react at 40℃ for 0.5~1h. After standing for 40min, cool to 8℃ and add 3 times the volume of ethanol. Separate and collect the precipitate. After freeze-drying, obtain a biotin-ferrous complex.

[0043] Example 5: The difference from Example 1 is that:

[0044] (3) Disperse 1.5 g of biotin in hot water to obtain a biotin solution. Add 0.75 g of ferrous sulfate and 0.5 g of ascorbic acid to the biotin solution and fully dissolve it. Then react at 40 °C for 0.5 to 1 h. After standing for 40 min, cool to 20 °C and add 3 times the volume of ethanol. Separate and collect the precipitate, and freeze-dry it to obtain a biotin-ferrous complex.

[0045] Example 6: The difference from Example 1 is that:

[0046] (4) 5 g of aspartic acid, 16 g of glycine, 0.6 g of disodium hydrogen phosphate, 0.5 g of 6-benzyladenine, and 1.6 g of biotin-ferrous complex were mixed with chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and crushed to obtain a bioactivated complex.

[0047] Example 7: The difference from Example 1 is that:

[0048] (4) Aspartic acid 4 g, glycine 13 g, sodium hydrogen phosphate 0.4 g, 6-benzyladenine 0.4 g, biotin-ferrous complex 0.8 g were mixed with chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and crushed to obtain a bioactivated complex.

[0049] Process Example: Bacillus spores are introduced into a homogenization tank, along with a bioactivation complex. Wastewater enters the homogenization tank via a lift pump, where it is mixed evenly with the return sludge and mixed liquor, then flows by gravity into a high-efficiency denitrification reactor, which utilizes a membrane bioreactor. The free ammonia concentration in the reactor is controlled to no more than 30.0 mg / L, and the influent pH and temperature are controlled to manage the organic load. The effluent from the reactor enters a microaerobic biochemical tank for further reaction. The tank is divided into several compartments, each with independent aeration control to flexibly adjust the dissolved oxygen content in the wastewater. The dissolved oxygen level in the tank is high at the beginning and low at the end, reaching as low as 0.1 mg / L at the outlet, creating an anoxic state. In the microaerobic biochemical tank, all ammonia nitrogen in the wastewater is converted to NO₂-N, which is then partially denitrified through denitrification. The remaining nitrogen is then returned to the high-efficiency denitrification reactor via nitrification liquid for further denitrification. The internal reflux ratio is controlled between 200% and 400%, and the external reflux ratio is controlled between 100% and 200%. Wastewater that meets the standards is discharged.

[0050] Example sample test:

[0051] The promoters and bioactivation complexes of Examples 1 to 7 were respectively placed in a culture bottle at a ratio of 100 mg / L. The culture bottle was injected with simulated wastewater containing ammonium chloride, disodium hydrogen phosphate, sodium acetate, 20 mg / L calcium chloride, and 40 mg / L magnesium sulfate. The simulated wastewater was set to a carbon-nitrogen ratio of 2, NH4 + -N concentration was 60 mg / L, COD concentration was 600 mg / L, and total phosphorus was 6 mg / L; Bacillus was inoculated at 10% inoculum, cultured at 10℃, and NH4 + -N and COD removal rates. The results are as follows Figure 2 shown.

[0052] Depend on Figure 2It can be seen that using the promoters and bioactivation complexes of each embodiment, under the premise of low carbon input, the ammonia nitrogen removal rate of each embodiment and comparative example can reach more than 93%, and the COD removal rate can also reach more than 73%, indicating that the process of the present invention has a lower degree of dependence on the carbon source. Among them, the ammonia nitrogen and COD removal effects of Example 2 with a higher chitosan content and Example 7 with a lower amount of biotin-ferrous complex are not as good as those of Example 1. It is possible that the higher amount of chitosan affects the uniform release of the raw materials in the initial complex, which has a certain impact on the decomposition of ammonia nitrogen, while the reduction of biotin-ferrous complex affects the reproduction of the early bacterial population. The denitrification effect of Example 5 is comparable to that of Example 1, but the output of biotin-ferrous complex decreases during the preparation process, indicating that the low temperature here is conducive to the precipitation of the product. The denitrification effect of Examples 3 and 6 is slightly reduced, which may be because the lower amount of glucose is not conducive to the generation of zero-valent iron, and the lower amount of chitosan is not conducive to the packaging of the raw materials in the bioactivation complex, affecting the durability of the activation.

[0053] according to Figure 1 The process was carried out in November using the accelerator and bioactivation complex of Example 1 and sewage from a sewage treatment plant in Nanjing. The total nitrogen in the inlet and outlet water was measured to evaluate the nitrogen removal effect. The results are as follows. Figure 3 shown.

[0054] Depend on Figure 3 It can be seen that the treatment process of the present invention, combined with the promoter and the biological activation complex, can significantly improve the sewage treatment efficiency, and the average daily effluent total nitrogen concentration can be reduced by more than 50% compared with the influent total nitrogen concentration.

[0055] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A micro-aerobic denitrification wastewater treatment process, characterized in that: The following steps are included: Bacillus is introduced into the homogenization tank and a bio-activated complex is added; an accelerator is added to the high-efficiency denitrification reactor; the wastewater enters the homogenization tank and is evenly mixed with the return sludge and mixed liquid before entering the high-efficiency denitrification reactor; the dissolved oxygen in the micro-aerobic biochemical tank is gradually reduced from the inlet to the outlet, and the outlet water of the high-efficiency denitrification reactor enters the micro-aerobic biochemical tank for further reaction; the nitrified liquid is returned to the high-efficiency denitrification reactor and the micro-aerobic biochemical tank, and the sludge after sedimentation in the sedimentation tank is discharged into the sludge tank and returned to the high-efficiency denitrification reactor and the micro-aerobic biochemical tank respectively, and the wastewater that meets the standards is discharged; The bioactivation complex comprises the following components by weight: 3-5 parts of aspartic acid, 12-16 parts of glycine, 0.3-0.6 parts of disodium hydrogen phosphate, 0.2-0.5 parts of 6-benzyladenine, 0.8-1.6 parts of biotin-ferrous complex, and 20-30 parts of chitosan; The preparation of the accelerator and bioactivation complex comprises the following steps: a. Dissolve oxalic acid in water, add chitosan and dissolve thoroughly, then dropwise add ferrous sulfate solution. Mix and allow to stand, then separate to obtain the chitosan solution and precipitate. Wash the precipitate thoroughly and dry to obtain ferrous oxalate. b. Calcinate ferrous oxalate and glucose, mix with bentonite, add water to expand, and form granules; age the resulting granules, and then calcine to obtain the accelerator; c. Disperse biotin in hot water to obtain a biotin solution. Add ferrous sulfate and ascorbic acid to the biotin solution and allow to fully dissolve. Allow to react and allow to stand. After cooling, add ethanol. Separate and collect the precipitate. Freeze-dry to obtain a biotin-ferrous complex. d. The biotin-ferrous complex and the remaining components are mixed with the chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and broken to obtain a bioactivated complex.

2. The micro-aerobic denitrification wastewater treatment process according to claim 1, characterized in that: The dissolved oxygen concentration in the process is 0.1~1.0mg / L; the sludge concentration is 5000~40000mg / L; and the operating ambient temperature is 0~40℃.

3. The micro-aerobic denitrification wastewater treatment process according to claim 1, characterized in that: The mixing and standing in step a is to fully mix at 30-40°C and then stand for 2-4 hours; the aging and calcination in step b is to age the obtained particles for 1-2 days and then calcine at 400-500°C; the standing after reaction in step c is to react at 30-50°C for 0.5-1 hour and stand for 20-60 minutes; the cooling in step c is to drop to 5-20°C; and the ethanol added in step c is 3 times the volume of the system.

4. The micro-aerobic denitrification wastewater treatment process according to claim 1, characterized in that: The mass ratio of oxalic acid to ferrous sulfate in step a is 1:1.3-1.65; the mass ratio of oxalic acid to chitosan is 1:8-10.

5. The micro-aerobic denitrification wastewater treatment process according to claim 1, characterized in that: The calcining of ferrous oxalate and glucose in step b is to calcine ferrous oxalate and glucose at 700-800° C. for 0.5-1.5 h under a nitrogen atmosphere.

6. The micro-aerobic denitrification wastewater treatment process according to claim 1, characterized in that: In step b, the mass ratio of ferrous oxalate to glucose is 1:2-5; the mass ratio of ferrous oxalate to bentonite is 1:3-5; and the mass ratio of bentonite to water is 1:4-6.

7. The micro-aerobic denitrification wastewater treatment process according to claim 1, characterized in that: The mass ratio of ferrous sulfate to ascorbic acid in step c is 1:0.5-0.8; the mass ratio of ferrous sulfate to biotin in step d is 1:1.6-2.

8. Use of the micro-aerobic denitrification wastewater treatment process according to any one of claims 1 to 7 in treating wastewater containing or not containing refractory organic matter.

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