A wastewater purification and denitrification process including artificial wetland treatment

Abstract

The present application relates to the field of ecological restoration technology, and specifically discloses a sewage purification and denitrification process including artificial wetland treatment. The process comprises the following steps: (1) introducing sewage into a sedimentation tank, and obtaining sediment and ammonia nitrogen residual water after static sedimentation; (2) adding nitrifying bacteria, denitrifying bacteria and Bacillus to the ammonia nitrogen residual water in a contact oxidation tank, completing biofilm formation on the filler, and achieving simultaneous nitrification and denitrification by controlling the aeration volume, and simultaneously removing ammonia nitrogen and part of the total nitrogen to obtain nitrate nitrogen residual water; (3) introducing the nitrate nitrogen residual water into a sulfur autotrophic denitrification subsurface wetland, collecting the effluent, and obtaining denitrified residual water; (4) introducing the denitrified residual water into an enhanced phosphorus removal horizontal subsurface artificial wetland, and discharging the effluent after purification. The present application overcomes the limitation of the organic matter concentration in sewage on the denitrification reaction, and helps to fully improve the effluent quality.

Description

Technical Field

[0001] The present application relates to the field of ecological restoration technology, and more specifically, to a sewage purification and denitrification process including artificial wetland treatment. Background Art

[0002] Denitrification refers to the biochemical process in which denitrifying bacteria reduce nitrogen from nitrates to nitrogen gas (N2) through a series of intermediate products. Denitrification is widely used in wastewater treatment to treat wastewater containing nitrate nitrogen. In actual water purification processes, it can be used in conjunction with nitrifying bacteria to reduce ammonia nitrogen concentrations.

[0003] In the related art, the mechanism of denitrification reaction involving denitrifying bacteria can be summarized as the following steps:

[0004] (1) NO3 - +2H + +2e - →NO2 - +H2O - ;

[0005] (2) NO2 - +2H + +e - →NO+H2O;

[0006] (3) 2NO + 2H + +2e - →N2O+H2O;

[0007] (4)N2O+2H + +2e - →N2+H2O;

[0008] (5)5C+2H2O+4NO3 - →2N2+4OH - +5CO2;

[0009] Among them, steps (1) to (4) can only be carried out by electron donors providing electrons. In the actual reaction process, the electron donors are mainly various biodegradable organic substances in wastewater.

[0010] Regarding the above-mentioned related technologies, the inventors believe that according to the mechanism of denitrification reaction, denitrifying bacteria need to consume organic matter to generate electrons when performing denitrification treatment. When there is insufficient organic matter in the sewage that can be directly utilized by denitrifying bacteria, the denitrification reaction will be difficult to proceed fully, resulting in a portion of nitrate nitrogen that does not participate in the reaction remaining in the effluent, affecting the effluent quality. Summary of the Invention

[0011] In related technologies, when there is insufficient organic matter in the wastewater that can be directly utilized by denitrifying bacteria, the denitrification reaction will be difficult to fully proceed, resulting in a portion of nitrate nitrogen remaining in the effluent that does not participate in the reaction, affecting the effluent quality. To improve this deficiency, the present application provides a wastewater purification and denitrification process that includes artificial wetland treatment.

[0012] The present application provides a wastewater purification and denitrification process including artificial wetland treatment, which adopts the following technical solutions:

[0013] A wastewater purification and denitrification process including artificial wetland treatment comprises the following steps:

[0014] (1) The sewage is introduced into a sedimentation tank, and after static sedimentation, sediment and ammonia nitrogen residual water are obtained;

[0015] (2) Adding nitrifying bacteria, denitrifying bacteria and Bacillus into the ammonia nitrogen residual water in the contact oxidation tank to form biofilm on the filler, and achieving simultaneous nitrification and denitrification by controlling the aeration volume, thereby simultaneously removing ammonia nitrogen and part of the total nitrogen to obtain nitrate nitrogen residual water;

[0016] (3) introducing the nitrate nitrogen residual water into a sulfur autotrophic denitrification subsurface flow wetland, collecting the effluent of the sulfur autotrophic denitrification subsurface flow wetland, and obtaining denitrified residual water; the sulfur autotrophic denitrification subsurface flow wetland comprises an alternating section A and a section B, the section A is filled with a sulfur autotrophic filler and sulfur autotrophic bacteria, the components of the sulfur autotrophic filler include elemental sulfur and calcium carbonate, the section B is filled with a planting matrix, and wetland plants are planted in the planting matrix;

[0017] (4) The denitrification residual water is introduced into the enhanced phosphorus removal horizontal subsurface flow artificial wetland, and the effluent is discharged after being purified by the enhanced phosphorus removal horizontal subsurface flow artificial wetland.

[0018] By adopting the above technical solution, the present application first subjected the sewage to a static sedimentation treatment to obtain ammonia nitrogen residual water, and then added nitrifying bacteria, denitrifying bacteria and Bacillus to the ammonia nitrogen residual water. Nitrifying bacteria can convert the ammonia nitrogen in the ammonia nitrogen residual water into nitrate nitrogen, while denitrifying bacteria can convert nitrate nitrogen into nitrogen gas. Bacillus can degrade organic matter, reduce the molecular weight of the organic matter, and make the organic matter more easily utilized. When the organic matter in the sewage that can be directly utilized by denitrifying bacteria is insufficient to support the denitrification reaction, the degradation effect of Bacillus can increase the utilization rate of the organic matter by denitrifying bacteria, promote the denitrification reaction, help to obtain nitrate nitrogen residual water with a lower nitrate nitrogen concentration, and reduce the nitrate nitrogen treatment pressure in subsequent steps. In the sulfur autotrophic denitrifying subsurface flow wetland, sulfur autotrophic bacteria can utilize the sulfur element in section A to grow and reproduce, and convert most of the remaining nitrate nitrogen in the nitrate nitrogen residual water into nitrogen gas without the need for additional carbon source consumption. Calcium carbonate can consume the hydrogen ions produced by sulfur autotrophic bacteria, which helps to maintain the stability of the wetland pH value. The alternating arrangement of sections A and B reduces the loss of elemental sulfur, while also enhancing aesthetics and providing flexibility in construction layout, helping to maintain the long-term operation of the sulfur autotrophic denitrifying subsurface flow wetland. Water-purifying microorganisms can attach to the surface of the wetland fill, and combined with the absorption activity of wetland plant roots, they help absorb residual pollutants, achieving deep purification.

[0019] After continuous treatment in the immobilized high-efficiency microbial contact oxidation pond and the sulfur autotrophic denitrification subsurface wetland, the ammonia nitrogen content in the obtained denitrification residual water is significantly reduced compared to the imported sewage, and the nitrate nitrogen concentration is also maintained at a relatively low level. The effluent can be discharged after subsequent phosphorus removal treatment. The sewage purification and denitrification process of the present application increases the utilization rate of organic matter by denitrifying bacteria when organic matter is insufficient, and achieves secondary removal of nitrate nitrogen through the combination of sulfur autotrophic bacteria and sulfur autotrophic fillers, overcoming the limitations of the organic matter concentration in the sewage on the denitrification reaction, which helps to fully improve the effluent quality.

[0020] Preferably, the planting matrix of section B comprises alkaline volcanic rock.

[0021] By adopting the above technical solution, alkaline volcanic rock can not only be used as filter material, but also can consume hydrogen ions produced by sulfur autotrophic bacteria, which helps to reduce the impact of hydrogen ions on the roots of wetland plants and helps to maintain a normal growth environment for wetland plants.

[0022] Preferably, in step (2) of the denitrification process, a denitrification aid is added to the ammonia nitrogen residual water in the immobilized high-efficiency microbial contact oxidation tank. The components of the denitrification aid include an auxiliary carbon source, iron-loaded activated carbon and sponge iron. The iron-loaded activated carbon is activated carbon particles with ferrous sulfate loaded on the surface.

[0023] By adopting the above technical solution, the present application introduces iron-loaded activated carbon and sponge iron into the ammonia nitrogen residual water in the immobilized high-efficiency microbial contact oxidation pond. The iron-loaded activated carbon releases ferrous sulfate in the ammonia nitrogen residual water, while the sponge iron can inhibit the oxidation of ferrous ions. Ferrous ions can promote the progress of denitrification, thereby improving the effect of denitrification treatment, facilitating the full removal of nitrate nitrogen in the ammonia nitrogen residual water, and reducing the denitrification pressure of sulfur autotrophic bacteria, which is conducive to the long-term operation of the sulfur autotrophic denitrification subsurface wetland.

[0024] Preferably, the iron-loaded activated carbon is prepared according to the following method:

[0025] (1) mixing ferrous sulfate and water to obtain a ferrous sulfate solution for subsequent use;

[0026] (2) The activated carbon is immersed in a ferrous sulfate solution for 100-140 minutes, and then the activated carbon is recovered by filtration and vacuum dried to obtain iron-loaded activated carbon.

[0027] By adopting the above technical solution, the present application soaks activated carbon in a ferrous sulfate solution. The porous structure of the activated carbon is able to adsorb the ferrous sulfate, and the surface of the activated carbon also carries the ferrous sulfate solution. After vacuum drying, the ferrous sulfate in the ferrous sulfate solution carried on the surface of the activated carbon is loaded onto the surface of the activated carbon, thereby obtaining iron-loaded activated carbon.

[0028] Preferably, in step (2) of preparing the iron-loaded activated carbon, the weight ratio of the activated carbon to the ferrous sulfate solution is 1:(60-120).

[0029] By adopting the above technical solution, the weight ratio of activated carbon to ferrous sulfate solution is optimized. Within this weight ratio range, after the activated carbon is adsorbed, the change in the concentration of ferrous sulfate is relatively small, which helps to fully increase the total amount of ferrous sulfate carried on the surface of the activated carbon.

[0030] Preferably, the concentration of the ferrous sulfate solution is 0.050-0.075 mol / L.

[0031] By adopting the above technical solution, the concentration of the ferrous sulfate solution is optimized, which helps to fully improve the effect of the iron-loaded activated carbon in releasing ferrous sulfate while saving ferrous sulfate.

[0032] Preferably, the amount of the iron-loaded activated carbon is 125-155% of the weight of the sponge iron.

[0033] By adopting the above technical scheme, the dosage of iron-loaded activated carbon is optimized, which helps to fully improve the removal effect of nitrate nitrogen while saving iron-loaded activated carbon, reduces the denitrification pressure of sulfur autotrophic bacteria, and is beneficial to the long-term operation of sulfur autotrophic denitrifying subsurface flow wetlands.

[0034] Preferably, the auxiliary carbon source comprises enzymatically hydrolyzed corncob powder, which is obtained by enzymatically hydrolyzing corncob powder with cellulase.

[0035] By adopting the above technical solution, compared with corn cob powder, the molecular weight of corn cob powder polysaccharides is reduced because the corn cob powder has undergone enzymatic hydrolysis, making the auxiliary carbon source easier to be utilized by denitrifying bacteria, which helps to improve the denitrification effect of denitrifying bacteria.

[0036] Preferably, the enzymatically hydrolyzed corncob powder is prepared according to the following method:

[0037] The corn cob powder and cellulase are mixed and stirred to obtain a mixture, and then the mixture is mixed with an acidic buffer solution at 50-60° C. and stored at this temperature for 20-24 hours. The mixture is then dried and ground to obtain enzymatically hydrolyzed corn cob powder.

[0038] By adopting the above technical solution, the present application optimizes the preparation process of enzymatically hydrolyzed corncob powder, which helps to improve the effect of enzymatic hydrolysis of corncob powder.

[0039] Preferably, the cellulase content in the mixture is 800-1000 U / g.

[0040] By adopting the above technical solution, the present application optimizes the cellulase content in the mixture, which helps to improve the effect of enzymatic hydrolysis of corn cob powder while saving cellulase.

[0041] In summary, this application has the following beneficial effects:

[0042] 1. The sewage purification and denitrification process of the present application increases the utilization rate of organic matter by denitrifying bacteria when organic matter is insufficient, and realizes secondary removal of nitrate nitrogen through the combination of sulfur autotrophic bacteria and sulfur autotrophic fillers, overcoming the limitation of organic matter concentration in sewage on denitrification reaction, which helps to fully improve the effluent quality.

[0043] 2. This application introduces iron-loaded activated carbon and sponge iron into the ammonia nitrogen wastewater in an immobilized high-efficiency microbial contact oxidation pond. The iron-loaded activated carbon releases ferrous sulfate in the ammonia nitrogen wastewater, while the sponge iron inhibits the oxidation of ferrous ions. Ferrous ions promote denitrification, thereby improving the denitrification process, facilitating the full removal of nitrate nitrogen from the ammonia nitrogen wastewater, reducing the denitrification pressure on sulfur autotrophic bacteria, and facilitating the long-term operation of the sulfur autotrophic denitrification subsurface wetland.

[0044] 3. The present application reduces the molecular weight of corn cob powder polysaccharides by enzymatic hydrolysis, thereby making the auxiliary carbon source more easily utilized by denitrifying bacteria, which helps to improve the denitrification effect of denitrifying bacteria. DETAILED DESCRIPTION

[0045] The present application is further described in detail below with reference to the Examples, Preparation Examples and Comparative Examples. The raw materials involved in the present application can all be obtained commercially.

[0046] Preparation example of iron-loaded activated carbon

[0047] The following is an explanation using Preparation Example 1.

[0048] Preparation Example 1

[0049] In this preparation example, iron-loaded activated carbon was prepared according to the following method:

[0050] (1) Mixing ferrous sulfate and water to obtain a ferrous sulfate solution with a concentration of 0.025 mol / L, and setting aside;

[0051] (2) The activated carbon is immersed in a ferrous sulfate solution and soaked for 60 minutes. During the soaking, nitrogen is introduced into the ferrous sulfate solution for bubbling and deoxygenation. After the soaking is completed, the activated carbon is filtered and recovered and vacuum-dried until constant weight is obtained to obtain iron-loaded activated carbon. In this step, the activated carbon is powdered activated carbon with an average particle size of 40 μm, and the weight ratio of the activated carbon to the ferrous sulfate solution is 1:40.

[0052] As shown in Table 1, the difference between Preparation Examples 1-5 is that the activated carbon is immersed in the ferrous sulfate solution for different times.

[0053] Table 1

[0054] sample Soaking time / min Preparation Example 1 60 Preparation Example 2 80 Preparation Example 3 100 Preparation Example 4 120 Preparation Example 5 140

[0055] Preparation Examples 6-9

[0056] As shown in Table 2, the difference between Preparation Examples 6-9 and Preparation Example 5 is that the weight ratio of activated carbon to ferrous sulfate solution is different.

[0057] Table 2

[0058] sample Activated carbon: ferrous sulfate Preparation Example 5 1:40 Preparation Example 6 1:60 Preparation Example 7 1:80 Preparation Example 8 1:100 Preparation Example 9 1:120

[0059] As shown in Table 3, the difference between Preparation Examples 10-13 and Preparation Example 9 is that the concentration of the ferrous sulfate solution is different.

[0060] Table 3 Concentration of ferrous sulfate solution

[0061] sample Concentration of ferrous sulfate solution / (mol / L) Preparation Example 9 0.025 Preparation Example 10 0.050 Preparation Example 11 0.063 Preparation Example 12 0.075 Preparation Example 13 0.100

[0062] Preparation example of enzymatically hydrolyzed corncob powder

[0063] The following is an explanation using Preparation Example 14 as an example.

[0064] Preparation Example 14

[0065] In this preparation example, enzymatic hydrolysis corncob powder was prepared according to the following method:

[0066] Corncob powder and cellulase were mixed and stirred to obtain a mixture having an average cellulase content of 700 U / g (this content was per gram of the mixture). The mixture was then mixed with a pH 5.0 buffer solution at 50°C and stored at this temperature for 20 hours. The mixture was then dried and ground to obtain enzymatically hydrolyzed corncob powder. The buffer solution was an acetic acid-sodium acetate buffer solution, and the amount of the buffer solution was 35% by weight of the mixture.

[0067] Preparation Example 15

[0068] The difference between this preparation example and preparation example 14 is that the heat preservation storage temperature is 55° C. and the time is 22 h.

[0069] Preparation Example 16

[0070] The difference between this preparation example and preparation example 14 is that the heat preservation storage temperature is 60° C. and the time is 24 h.

[0071] Preparation Examples 17-20

[0072] As shown in Table 4, the difference between Preparation Examples 17-20 and Preparation Example 16 is that the cellulase content in the mixture is different.

[0073] Table 4 Cellulase content

[0074] sample Cellulase / (U / g) Preparation Example 16 700 Preparation Example 17 800 Preparation Example 18 900 Preparation Example 19 1000 Preparation Example 20 1100

[0075] Example

[0076] Examples 1-5

[0077] The following description will be given using Example 1 as an example.

[0078] Example 1

[0079] This embodiment provides a wastewater purification and denitrification process including artificial wetland treatment, comprising the following steps:

[0080] (1) Wastewater with an ammonia nitrogen concentration of 10 mg / L and no nitrate nitrogen detected was introduced into a sedimentation tank, and after static precipitation, a precipitate and ammonia nitrogen residual water were obtained; in this step, the static precipitation time was 2 hours; the ammonia nitrogen in the wastewater was converted into nitrate ions according to the principle of invariance of nitrogen atoms, and the calculated carbon-nitrogen ratio (ratio of the mass concentration of COD to nitrate ions) was 0.8;

[0081] (2) The ammonia nitrogen residual water is introduced into an immobilized high-efficiency microbial contact oxidation tank equipped with a membrane filter material, and nitrifying bacteria, denitrifying bacteria and Bacillus are added to the ammonia nitrogen residual water in the immobilized high-efficiency microbial contact oxidation tank, and nitrate nitrogen residual water is obtained after membrane formation and aeration treatment; the membrane filter material has a density of 20kg / m 3 , a polyurethane sponge with a pore size of 45PPI and an open porosity of 99%; nitrifying bacteria, denitrifying bacteria and Bacillus are added in the form of bacterial powder, and the Bacillus is Bacillus subtilis; 1 t of nitrifying bacteria, denitrifying bacteria and Bacillus powder are added for every 10,000 cubic meters of sewage, and the number of viable bacteria of each bacterial powder is 10 12 CFU / g;

[0082] (3) The nitrate nitrogen residual water is introduced into the sulfur autotrophic denitrification subsurface wetland, and the effluent of the sulfur autotrophic denitrification subsurface wetland is collected to obtain the denitrified residual water; the sulfur autotrophic denitrification subsurface wetland includes alternating sections A and B (three sections each, arranged in an ABABAB manner), section A is filled with sulfur autotrophic filler, and sulfur autotrophic bacteria are added; the components of the sulfur autotrophic filler include sulfur and calcium carbonate, and the sulfur and calcium carbonate are mixed in a weight ratio of 1:3; the sulfur autotrophic bacteria are added in the form of bacterial powder, and the addition amount is 1 t of bacterial powder per 1000 cubic meters of sewage, and the number of viable bacteria in the bacterial powder is 10 8 CFU / g; Section B is filled with a planting matrix, which is volcanic rock and planted with wetland plants;

[0083] (4) The denitrification residual water is introduced into the enhanced phosphorus removal horizontal subsurface flow artificial wetland, and the effluent is discharged after being purified by the enhanced phosphorus removal horizontal subsurface flow artificial wetland.

[0084] Example 2

[0085] The difference between this embodiment and Example 1 is that, in step (2) of the denitrification process, a denitrification aid is further added to the ammonia nitrogen waste water in the immobilized high-efficiency microbial contact oxidation tank. The denitrification aid is composed of a mixture of an auxiliary carbon source, iron-loaded activated carbon and sponge iron. The auxiliary carbon source is corn cob powder. The amount of the auxiliary carbon source is converted according to the nitrate nitrogen content in the nitrate nitrogen waste water in Example 1. The ratio of the organic matter (COD) supplemented by the auxiliary carbon source to the nitrate nitrogen content (calculated as nitrate ions) in the nitrate nitrogen waste water in Example 1 is 3.7; the amount of sponge iron is 1 / 5 of the weight of corn cob powder, and the amount of iron-loaded activated carbon is 115% of the weight of sponge iron. The iron-loaded activated carbon is prepared according to the method of Preparation Example 1.

[0086] As shown in Table 5, the main difference between Examples 2-14 is that the iron-loaded activated carbon was prepared with reference to different preparation examples.

[0087] Table 5 Preparation example of iron-loaded activated carbon

[0088]

[0089]

[0090] Examples 15-18

[0091] As shown in Table 6, the difference between Examples 15-18 and Example 14 is that the percentage of the amount of iron-loaded activated carbon to the weight of the sponge iron (hereinafter referred to as the iron-loaded activated carbon percentage) is different.

[0092] Table 6 Proportion of iron-loaded activated carbon

[0093] sample Example 14 Example 15 Example 16 Example 17 Example 18 Iron-loaded activated carbon proportion / % 115 125 135 145 155

[0094] Example 19

[0095] The difference between this example and Example 18 is that the auxiliary carbon source is the enzymatically hydrolyzed corn cob powder of Preparation Example 14.

[0096] Examples 20-25

[0097] As shown in Table 7, the difference between Examples 20-25 and Example 19 is that the preparation examples of enzymatically hydrolyzed corncob powder are different.

[0098] Table 7 Preparation example of enzymatic hydrolysis corncob powder

[0099] sample Preparation Example Example 19 Preparation Example 14 Example 20 Preparation Example 15 Example 21 Preparation Example 16 Example 22 Preparation Example 17 Example 23 Preparation Example 18 Example 24 Preparation Example 19 Example 25 Preparation Example 20

[0100] Comparative Example

[0101] Comparative Example 1

[0102] The difference between this comparative example and Example 1 is that no elemental sulfur is added to Section A of the sulfur autotrophic denitrifying subsurface flow wetland.

[0103] Comparative Example 2

[0104] The difference between this comparative example and Example 1 is that no Bacillus was added to the immobilized high-efficiency microbial contact oxidation tank.

[0105] Performance testing methods

[0106] Referring to the method described in GB 7480-1987 Water quality - Determination of nitrate nitrogen - Phenol disulfonic acid spectrophotometric method, the nitrate nitrogen concentration of nitrate nitrogen residual water and denitrification residual water was tested. The nitrate nitrogen concentration of nitrate nitrogen residual water C1 and the nitrate nitrogen concentration of denitrification residual water C2 are shown in Table 8.

[0107] Table 8 Nitrate nitrogen concentration

[0108] sample <![CDATA[C1 / (mg / L)]]> <![CDATA[C2(mg / L)]]> sample <![CDATA[C1 / (mg / L)]]> <![CDATA[C2(mg / L)]]> Example 1 5.2 0.3 Example 15 3.4 0.2 Example 2 4.7 0.3 Example 16 3.2 0.3 Example 3 4.6 0.2 Example 17 3.1 0.3 Example 4 4.4 0.3 Example 18 3.0 0.2 Example 5 4.3 0.2 Example 19 2.8 0.2 Example 6 4.2 0.2 Example 20 2.8 0.2 Example 7 4.1 0.3 Example 21 2.7 0.3 Example 8 4.0 0.2 Example 22 2.5 0.2 Example 9 4.0 0.3 Example 23 2.3 0.3 Example 10 3.9 0.2 Example 24 2.2 0.2 Example 11 3.7 0.3 Example 25 2.1 0.3 Example 12 3.6 0.2 Comparative Example 1 5.3 5.2 Example 13 3.5 0.2 Comparative Example 2 5.9 0.2 Example 14 3.5 0.3 / / /

[0109] Combining Example 1 and Comparative Example 1 and Table 8, it can be seen that the C2 measured in Example 1 is lower than that in Comparative Example 1, indicating that in the sulfur autotrophic denitrification subsurface flow wetland, the sulfur autotrophic bacteria utilized elemental sulfur and denitrified the nitrate nitrogen in the nitrate nitrogen residual water, thereby obtaining denitrified residual water with a lower nitrate nitrogen concentration.

[0110] Combining Example 1 and Comparative Example 2 with Table 8, it can be seen that the C1 measured in Example 1 is lower than that in Comparative Example 2, indicating that when the organic matter in the sewage that can be directly utilized by denitrifying bacteria is insufficient to support the denitrification reaction, the degradation effect of Bacillus can increase the utilization rate of the organic matter by the denitrifying bacteria, promote the denitrification reaction, and help to obtain nitrate nitrogen residual water with a lower nitrate nitrogen concentration, thereby reducing the nitrate nitrogen treatment pressure in subsequent steps.

[0111] In combination with Example 1, Examples 2-6 and Table 8, it can be seen that the relative removal rates of nitrate nitrogen measured in Examples 2-6 gradually increase, indicating that extending the immersion time of activated carbon in ferrous sulfate solution helps the activated carbon to fully adsorb ferrous sulfate, improves the effect of iron-loaded activated carbon in releasing ferrous sulfate, and is conducive to fully removing nitrate nitrogen in ammonia nitrogen residual water.

[0112] It can be seen from Examples 6-10 and Table 8 that the relative removal rates of nitrate nitrogen measured in Examples 7-10 are all greater than those in Example 6, indicating that when the concentration of the ferrous sulfate solution remains unchanged, increasing the dosage of the ferrous sulfate solution helps to reduce the change in the concentration of ferrous sulfate due to the adsorption of the activated carbon, and helps to fully increase the total amount of ferrous sulfate carried on the surface of the activated carbon.

[0113] In conjunction with embodiment 10-14 and in conjunction with table 8, it can be seen that the nitrate nitrogen relative removal rate that embodiment 11-14 records is all greater than embodiment 10, illustrates that the lifting of ferrous sulfate solution concentration is conducive to improving the effect of iron-carrying activated carbon releasing ferrous sulfate.The nitrate nitrogen relative removal rate that embodiment 13 and embodiment 14 record is close, illustrates that continuing to increase the concentration of ferrous sulfate is difficult to further increase the ferrous sulfate total amount of iron-carrying activated carbon surface load.Therefore, when the concentration of ferrous sulfate solution is 0.050-0.075mol / L, contribute to fully improve the effect of iron-carrying activated carbon releasing ferrous sulfate under the premise of saving ferrous sulfate.If cost factor is not considered, then the effect of embodiment 14 is optimal in embodiment 10-14.

[0114] From Examples 14-18 and Table 8, it can be seen that the relative removal rates of nitrate nitrogen measured in Examples 15-18 are all greater than those in Example 14, indicating that when the amount of iron-loaded activated carbon used is 125-155% of the weight of sponge iron, the iron-loaded activated carbon can relatively fully release ferrous sulfate, which helps to more fully remove nitrate nitrogen from ammonia nitrogen residual water within a limited time.

[0115] Combining Examples 18, 19-21 and Table 8, it can be seen that the relative removal rates of nitrate nitrogen measured in Examples 19-21 are all greater than those in Example 18, indicating that enzymatic hydrolysis helps the enzymatic hydrolysis of corn cob powder. Compared with corn cob powder, the molecular weight of polysaccharides is smaller, making the auxiliary carbon source more easily utilized by denitrifying bacteria, thereby improving the denitrification effect of denitrifying bacteria.

[0116] Combining Examples 21-25 with Table 8, it can be seen that the relative nitrate-nitrogen removal rates measured in Examples 22-25 are all greater than that in Example 21, while the relative nitrate-nitrogen removal rate measured in Example 25 is close to that in Example 24. This indicates that when the cellulase content in the mixture is 800-1000 U / g, it helps improve the enzymatic hydrolysis of corncob powder while saving cellulase. If cost is not a consideration, the solution of Example 25 is more effective in improving the removal of nitrate-nitrogen.

[0117] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A wastewater purification and denitrification process comprising artificial wetland treatment, characterized in that: The steps include: (1) The sewage is introduced into a sedimentation tank, and after static sedimentation, sediment and ammonia nitrogen residual water are obtained; (2) Adding nitrifying bacteria, denitrifying bacteria and Bacillus to the ammonia nitrogen wastewater in the contact oxidation tank, completing biofilm formation on the filler, and achieving simultaneous nitrification and denitrification by controlling the aeration volume, and simultaneously removing ammonia nitrogen and part of the total nitrogen to obtain nitrate nitrogen wastewater; in this step, a denitrification aid is also added to the ammonia nitrogen wastewater in the immobilized high-efficiency microbial contact oxidation tank, and the components of the denitrification aid include an auxiliary carbon source, iron-loaded activated carbon and sponge iron, and the iron-loaded activated carbon is activated carbon particles with ferrous sulfate loaded on the surface; (3) introducing the nitrate nitrogen residual water into a sulfur autotrophic denitrification subsurface flow wetland, collecting the effluent of the sulfur autotrophic denitrification subsurface flow wetland, and obtaining denitrified residual water; the sulfur autotrophic denitrification subsurface flow wetland comprises an alternating section A and a section B, the section A is filled with a sulfur autotrophic filler and sulfur autotrophic bacteria, the components of the sulfur autotrophic filler include elemental sulfur and calcium carbonate, the section B is filled with a planting matrix, and wetland plants are planted in the planting matrix; (4) The denitrification residual water is introduced into the enhanced phosphorus removal horizontal subsurface flow artificial wetland, and the effluent is discharged after being purified by the enhanced phosphorus removal horizontal subsurface flow artificial wetland; The iron-loaded activated carbon is prepared according to the following method: (1) Mix ferrous sulfate and water to obtain a ferrous sulfate solution for later use; (2) Soak the activated carbon in ferrous sulfate solution for 100-140 minutes, then filter and recover the activated carbon and vacuum dry it to obtain iron-loaded activated carbon.

2. The wastewater purification and denitrification process comprising artificial wetland treatment according to claim 1, characterized in that: The planting matrix of section B includes alkaline volcanic rock.

3. The wastewater purification and denitrification process comprising artificial wetland treatment according to claim 2, characterized in that: In step (2) of preparing the iron-loaded activated carbon, the weight ratio of the activated carbon to the ferrous sulfate solution is 1:(60-120).

4. The sewage purification and denitrification process comprising artificial wetland treatment according to claim 2, characterized in that: The concentration of the ferrous sulfate solution is 0.050-0.075 mol / L.

5. The wastewater purification and denitrification process comprising artificial wetland treatment according to claim 2, characterized in that: The amount of the iron-loaded activated carbon is 125-155% of the weight of the sponge iron.

6. The wastewater purification and denitrification process comprising artificial wetland treatment according to claim 1, characterized in that: The auxiliary carbon source comprises enzymatically hydrolyzed corncob powder, which is obtained by enzymatically hydrolyzing corncob powder with cellulase.

7. The wastewater purification and denitrification process comprising artificial wetland treatment according to claim 6, characterized in that: The enzymatic hydrolysis corncob powder is prepared according to the following method: The corn cob powder and cellulase are mixed and stirred to obtain a mixture, and then the mixture is mixed with an acidic buffer solution at 50-60° C. and stored at this temperature for 20-24 hours. The mixture is then dried and ground to obtain enzymatically hydrolyzed corn cob powder.

8. The wastewater purification and denitrification process comprising artificial wetland treatment according to claim 7, characterized in that: The cellulase content in the mixture is 800-1000 U / g.

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