Micro-aerobic denitrification wastewater treatment process

Abstract

The invention belongs to the field of sewage treatment, and particularly relates to a micro-aerobic denitrification wastewater treatment process. Bacillus is introduced into the homogenizing tank, and a biological activation compound is added; after the wastewater enters the homogenizing tank and is uniformly mixed with returned sludge and a mixed solution, the wastewater enters the efficient denitrification reactor; the dissolved oxygen in the micro-aerobic biochemical pool is gradually reduced from inlet water to outlet water, and the outlet water of the efficient denitrification reactor enters the micro-aerobic biochemical pool for further reaction; the nitrification liquid flows back to the efficient denitrification reactor and the micro-aerobic biochemical pool, sludge settled by the settling pool is respectively discharged to the sludge pool and flows back to the efficient denitrification reactor and the micro-aerobic biochemical pool, and wastewater reaching the standard is discharged. According to the process, synchronous short-cut nitrification and denitrification in the system can be realized, the problem of biological phase interference caused by nitrification liquid backflow in a traditional activated sludge method is solved, and meanwhile, compared with a traditional process, the amount of additionally added carbon sources required by denitrification is greatly reduced.

Description

Technical Field

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

[0002] Conventional biological denitrification processes for sewage mainly include: A / O, A / A / O, etc. In conventional processes, sewage generally undergoes several processes of anaerobic-anoxic-aerobic. Sewage and return sludge first enter the anaerobic tank (DO<0.2mg / L) for complete mixing. After a certain period of anaerobic decomposition (1~2h), part of the BOD is removed, and some nitrogen-containing compounds are converted into N2 (denitrification) and released. Then the sewage flows into the anoxic tank (DO<=0.5mg / L). The denitrifying bacteria in the tank use the undecomposed carbon-containing organic matter in the sewage as a carbon source, and reduce the nitrate ions that flow back through the internal circulation in the aerobic tank to N2 and release it. Next, the sewage flows into the aerobic tank (DO, 2-4mg / L), and the NH3-N (ammonia nitrogen) in the water undergoes nitrification reaction to generate nitrate ions, and then the nitrified liquid is returned to the anoxic tank through a reflux pump to achieve denitrification.

[0003] In the existing biological treatment process, the dominant bacteria in the anaerobic tank, anoxic tank and aerobic tank are anaerobic bacteria, facultative anaerobic bacteria and aerobic bacteria respectively. The growth environment of the three dominant bacteria is very different. In actual operation, the strain domestication and screening are achieved by controlling the growth environment of different strains. However, the 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 in the anoxic tank flows into the aerobic tank, and the anoxic bacteria enter the aerobic environment, which also has the same problem. There is biological interference between aerobic and anaerobic bacteria in the entire biochemical system. In the traditional A / A / O process, various contradictions and conflicts between bacterial species include sludge age contradictions, carbon source competition, nitrate and dissolved oxygen (DO) residual interference, etc. Summary of the invention

[0004] In order to solve the problems of biological interference and high treatment cost caused by the reflux of nitrification liquid in the traditional activated sludge method in the prior art, the present invention mainly provides a micro-oxygen denitrification wastewater treatment process that can not only treat conventional municipal and industrial sewage, but also effectively remove ammonia nitrogen from wastewater containing difficult-to-degrade organic matter. The technical scheme is as follows: 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 inlet to the outlet, and the outlet 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 respectively 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.

[0005] 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.

[0006] Furthermore, 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.

[0007] Furthermore, a promoter is added to the high-efficiency denitrification reactor; the preparation of the promoter and the bioactivation complex comprises 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 ferrous salt with biotin to form a biotin-ferrous complex; and mixing the biotin-ferrous complex and the remaining components with a chitosan solution to obtain a bioactivation complex.

[0008] Further, the following steps are included: a. Dissolve oxalic acid in water, add chitosan to fully dissolve, then drop ferrous sulfate solution, mix thoroughly at 30-40°C, then let stand for 2-4 hours, separate the chitosan solution and precipitate, wash the precipitate thoroughly and dry it to obtain ferrous oxalate; b. After calcining ferrous oxalate and glucose, mix them with bentonite, add water to expand them and then granulate them; after aging the obtained granules for 1 to 2 days, calcine them at 400 to 500°C to obtain a promoter; c. Disperse biotin in hot water to obtain a biotin solution, add ferrous sulfate and ascorbic acid to the biotin solution, fully dissolve, and then react at 30-50°C for 0.5-1h, let stand for 20-60min, cool to 5-20°C, add 3 times the volume of ethanol, separate and collect the precipitate, and freeze-dry to obtain a biotin-ferrous complex; d. The biotin-ferrous complex and other 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.

[0009] 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.

[0010] Furthermore, 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.

[0011] 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.

[0012] 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.

[0013] An application of the above-mentioned micro-oxygen denitrification wastewater treatment process in treating wastewater containing or not containing difficult-to-degrade organic matter.

[0014] By adopting the above scheme, the method of the present invention has the following advantages: The dissolved oxygen in the process system of the present invention is controlled at 0.1-1.0 mg / L, which is much lower than the 2-4 mg / L required by the conventional activated sludge biochemical process. The ammonia nitrogen is removed by short-range nitrification, and the aeration volume is reduced by about 40%, thereby reducing the operating electricity cost.

[0015] The denitrification mechanism of the process system of the present invention is short-range denitrification, which converts NO2-N into N2 to remove TN. Compared with the denitrification denitrification of the traditional process, 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 lot of carbon source and effectively solve the problem of insufficient carbon source for denitrification denitrification.

[0016] The nitrification ability of the Bacillus used in the process system of the present invention is minimally affected by the ambient temperature, and can still stably convert ammonia nitrogen into NO2-N in a low temperature environment. However, the nitrifying bacteria in the traditional activated sludge process usually have a reduced nitrification reaction efficiency when the ambient temperature is below 15°C, and the nitrification reaction is basically stopped when the ambient temperature is below 5°C. Therefore, the process of the present invention can still ensure the stable removal of ammonia nitrogen in the cold winter and ensure that the effluent meets the standards.

[0017] The present invention can utilize the biologically active enzymes secreted in large quantities 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 the traditional activated sludge process, especially for industrial wastewater containing difficult-to-degrade organic matter.

[0018] The biochemical reaction pool of the present invention adopts a micro-oxygen mode, and the pool body is divided into several grids. Each grid controls aeration independently, and the dissolved oxygen in the sewage is flexibly adjusted. The dissolved oxygen in the pool is high at the beginning and low at the end. The dissolved oxygen at the outlet can be as low as 0.1 mg / L, and the system is in anoxic state. The dissolved oxygen in the entire reaction pool is much lower than that in conventional biochemical systems (the dissolved oxygen in an aerobic pool is 2-4 mg / L). The bacteria in the system live in anoxic state for a long time, and nitrification, denitrification and removal of organic matter can be carried out simultaneously in the system. Whether it is internal reflux or external reflux, there will be no dissolved oxygen interference problem, and there will be no biological interference problem between aerobic bacteria and anaerobic bacteria.

[0019] The biological activation complex of the present invention can promote the rapid growth of bacteria to become dominant bacteria in a short time. The sludge concentration (up to 40000 mg / L) is more than 10 times that of the traditional process (3000-4000 mg / L). The rich biological phase enables it to quickly achieve denitrification reaction and remove organic matter at the same time. And because biotin and ferrous ions are combined, each component is wrapped by chitosan, the components are released steadily, the effect is long, the effect can be well maintained, and frequent addition is not required. It is easy to store and not easy to deteriorate.

[0020] The ferrous iron and zero-valent iron of the present invention can both serve as electron donors, provide raw materials for the rapid growth of Bacillus in the early bacterial proliferation process, and promote each other with Bacillus to achieve denitrification of sewage in the efficient denitrification stage. The ferrous oxalate of the present invention is micronized under the action of chitosan, with a larger surface area and more uniform particles. The carbon and iron contained in the promoter form micro-electrolysis, which can effectively promote the metabolism and denitrification of microorganisms and is conducive to the decomposition of difficult-to-degrade organic matter. In addition, the solidified promoter is conducive to the fixation of iron and the colonization of bacteria, which is convenient for the recovery and stable reproduction of bacteria.

[0021] 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

[0022] Figure 1 This is a schematic diagram of the micro-oxygen denitrification wastewater treatment process of the present invention; Figure 2 This is a comparison diagram of the denitrification effect of the fermentation tanks of various embodiments; Figure 3 This is a graph showing changes in total nitrogen concentrations in the inlet and outlet water of Example 1. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] 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 hours, and the chitosan solution containing ferrous sulfate and the precipitate were separated, and the precipitate was fully washed and dried to obtain ferrous oxalate; (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, 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; (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, fully dissolve, and 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. (4) 4 g of aspartic acid, 13 g of glycine, 0.4 g of disodium hydrogen phosphate, 0.4 g of 6-benzyladenine, and 1.2 g of biotin-ferrous complex were mixed with the chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and crushed to obtain a bioactivated complex.

[0025] Embodiment 2: The difference from Embodiment 1 is that: (1) Dissolve 2 g of oxalic acid in water, add 30 g of chitosan to fully dissolve, then drop a solution containing 3 g of ferrous sulfate into it, mix thoroughly at 30-40 °C, and then let it stand for 2-4 hours to separate the chitosan solution containing ferrous sulfate and the precipitate. Wash the precipitate thoroughly and dry it to obtain ferrous oxalate.

[0026] Embodiment 3: The difference from Embodiment 1 is that: (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.

[0027] Embodiment 4: The difference from Embodiment 1 is that: (3) Disperse 1.2 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 0.5-1 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. Embodiment 5: The difference from Embodiment 1 is that: (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 them. 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 to obtain a biotin-ferrous complex.

[0028] Embodiment 6: The difference from Embodiment 1 is that: (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 the chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and crushed to obtain a bioactivated complex.

[0029] Embodiment 7: The difference from Embodiment 1 is that: (4) 4 g of aspartic acid, 13 g of glycine, 0.4 g of disodium hydrogen phosphate, 0.4 g of 6-benzyladenine, and 0.8 g of biotin-ferrous complex were mixed with the chitosan solution, fully dispersed, formed into a film along the flow, and then sheared and crushed to obtain a bioactivated complex.

[0030] Process example: Bacillus is introduced into the homogenization tank, and a biological activation complex is added; the sewage enters the homogenization tank through a lifting pump, is mixed evenly with the return sludge and the mixed liquid, and then flows into the high-efficiency denitrification reactor by gravity. The high-efficiency denitrification reactor adopts a membrane bioreactor. The free ammonia concentration in the high-efficiency denitrification reactor is controlled to be no higher than 30.0 mg / L, the pH and temperature of the inlet water are controlled, and the organic load is controlled. The effluent of the high-efficiency denitrification reactor enters the micro-aerobic biochemical tank for further reaction. The tank body of the micro-aerobic biochemical reaction tank is divided into several grids, and each grid controls aeration separately to flexibly adjust the dissolved oxygen in the sewage. The dissolved oxygen in the tank is high at the beginning and low at the end, and the dissolved oxygen at the outlet can be as low as 0.1 mg / l, and the system is in anoxic state. The ammonia nitrogen in the sewage can be completely converted into NO2-N in the micro-aerobic biochemical reaction tank, and then part of it completes the denitrification reaction through denitrification, and the remaining part is returned to the high-efficiency denitrification reactor through the nitrification liquid for denitrification reaction. 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.

[0031] Example sample test: The promoters and bioactivation complexes of Examples 1 to 7 were respectively placed in a culture bottle at a ratio of 100 mg / L, and simulated wastewater containing ammonium chloride, disodium hydrogen phosphate, sodium acetate, 20 mg / L calcium chloride, and 40 mg / L magnesium sulfate was injected into the culture bottle. The simulated wastewater was set to have 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% inoculation rate and cultured at 10℃ to detect NH4 + -N and COD removal rates. The results are as follows Figure 2 shown.

[0032] Depend on Figure 2 It can be seen that, using the promoter and bioactivation complex 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 carbon source. Among them, the ammonia nitrogen and COD removal effects of embodiment 2 with more chitosan content and embodiment 7 with less biotin-ferrous complex are not as good as those of embodiment 1. It is possible that more chitosan affects the uniform release of raw materials in the initial complex, which has a certain effect on the decomposition of ammonia nitrogen, and the reduction of biotin-ferrous complex affects the reproduction of the early bacterial community. The denitrification effect of embodiment 5 is comparable to that of embodiment 1, but during the preparation process, the output of biotin-ferrous complex is reduced, indicating that the low temperature here is conducive to the precipitation of the product. The denitrification effect of embodiment 3 and embodiment 6 is slightly reduced, which may be that less glucose is not conducive to the generation of zero-valent iron, and less chitosan is not conducive to the encapsulation of raw materials in the bioactivation complex, affecting the persistence of activation.

[0033] 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 according to the process example. 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.

[0034] 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.

[0035] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A micro-oxygen denitrification wastewater treatment process, characterized in that: The method comprises the following steps: introducing bacillus into a homogenizing tank and adding a biological activation complex; the wastewater enters the homogenizing tank and is mixed evenly 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 inlet to the outlet, and the 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 precipitation in the sedimentation tank is respectively 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.

2. The micro-oxygen 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; the operating ambient temperature is 40~0℃.

3. The micro-oxygen denitrification wastewater treatment process according to claim 1, characterized in that: 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.

4. The micro-oxygen denitrification wastewater treatment process according to claim 1, characterized in that: A promoter is added to a high-efficiency denitrification reactor; the preparation of the promoter and the biological activation complex comprises the following steps: Ferrous salt and oxalic acid are reacted in a chitosan solution to obtain ferrous oxalate and a chitosan solution; ferrous oxalate is reduced to obtain zero-valent iron, and the zero-valent iron is loaded on a carrier to obtain a promoter; ferrous salt is combined with biotin to form a biotin-ferrous complex; the biotin-ferrous complex and other components are mixed with a chitosan solution to obtain a bioactivated complex.

5. The micro-oxygen denitrification wastewater treatment process according to claim 1, characterized in that: The following steps are involved: a. Dissolve oxalic acid in water, add chitosan to fully dissolve, then drop ferrous sulfate solution, mix thoroughly at 30-40°C, then let stand for 2-4 hours, separate the chitosan solution and precipitate, wash the precipitate thoroughly and dry it to obtain ferrous oxalate; b. After calcining ferrous oxalate and glucose, mix with bentonite, add water to expand and granulate; age the obtained granules for 1-2 days and then calcine at 400-500°C to obtain a promoter; c. Disperse biotin in hot water to obtain a biotin solution, add ferrous sulfate and ascorbic acid to the biotin solution, fully dissolve, and then react at 30-50°C for 0.5-1h, let stand for 20-60min, cool to 5-20°C, add 3 times the volume of ethanol, separate and collect the precipitate, and freeze-dry to obtain a biotin-ferrous complex; d. The biotin-ferrous complex and other 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.

6. The micro-oxygen denitrification wastewater treatment process according to claim 5, characterized in that: 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.

7. The micro-oxygen denitrification wastewater treatment process according to claim 5, 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.

8. The micro-oxygen denitrification wastewater treatment process according to claim 5, 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.

9. The micro-oxygen denitrification wastewater treatment process according to claim 5, 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.

10. Use of the micro-oxygen denitrification wastewater treatment process according to any one of claims 1 to 9 in treating wastewater containing or not containing refractory organic matter.

Images