Denitrification sludge particles and wastewater treatment process based on denitrification sludge particles

Abstract

The present invention discloses denitrifying sludge particles and a sewage treatment process based on the denitrifying sludge particles, which belongs to the field of sewage treatment technology. The denitrifying sludge particles include the following raw materials in parts by weight: 8 to 10 parts of polyvinyl alcohol, 10 to 15 parts of denitrifying activated sludge, 0.3 to 0.5 parts of an organic carbon source, 2 to 4 parts of diatomaceous earth modified with iron-manganese composite oxide, 0.3 to 0.6 parts of sodium bicarbonate, 15 to 20 parts of a cross-linking agent, and 95 to 105 parts of water. The denitrifying activated sludge uses polyvinyl alcohol-boric acid as a carrier to load the denitrifying activated sludge, which can provide a stable microenvironment for denitrifying bacteria and reduce the loss of microorganisms; the adsorption and decomposition of dissolved oxygen by the iron-manganese composite oxide modified diatomaceous earth in coordination with the physical oxygen barrier structure can provide a low oxygen or anaerobic environment for denitrifying bacteria, promote the growth of denitrifying bacteria, and improve the dissolved oxygen shock resistance of the denitrifying sludge particles under long-term high dissolved oxygen conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to a denitrification sludge particle and a sewage treatment process based on the denitrification sludge particle. Background Art

[0002] Against the backdrop of continued global population growth and accelerated urbanization, establishing good sanitation facilities is a crucial step in urban development. The treatment of domestic sewage, which is so closely linked to our daily lives, is particularly crucial. Domestic sewage contains a large number of organic and inorganic compounds, and improper treatment can have serious environmental impacts. Furthermore, the decentralized discharge of domestic sewage in villages and towns further complicates its treatment.

[0003] Currently, most domestic sewage is treated using traditional biological treatment processes. However, the effluent quality from this treatment method often fails to meet discharge standards. The A / O process adds an anoxic biological treatment process to the conventional aerobic sludge treatment system. The two processes work together to effectively remove nitrogen and phosphorus from domestic sewage. Compared to traditional biological treatment processes, it can fully utilize organic matter in the raw sewage as a carbon source for denitrification, eliminating the need to add additional carbon sources.

[0004] The use of A / O treatment technology in village and town sewage treatment can reduce treatment costs and improve treatment effects. However, the dissolved oxygen content of village and town domestic sewage is generally 2-4 mg / L. For the denitrification process, that is, the anoxic biological treatment process, excessively high dissolved oxygen concentration will inhibit the denitrification process. Because under conditions of high dissolved oxygen, microbial flocs remain in an aerobic state, the presence of molecular dissolved oxygen will inhibit the synthesis and activity of nitrate reductase, and under the impact of long-term high dissolved oxygen, the denitrifying bacterial sludge will gradually inactivate, the denitrification process will be affected, and denitrification can no longer be performed, and the sewage treatment process will be hindered. Summary of the Invention

[0005] The purpose of the present invention is to provide denitrification sludge particles and a sewage treatment process based on the denitrification sludge particles, so as to solve the problems of poor resistance to dissolved oxygen shock and poor long-term stability of denitrification sludge.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a denitrification sludge granule comprising the following raw materials in parts by weight:

[0008] 8-10 parts of polyvinyl alcohol;

[0009] 10-15 parts of denitrification activated sludge;

[0010] 0.3-0.5 parts of organic carbon source;

[0011] 2-4 parts of iron-manganese composite oxide modified diatomaceous earth;

[0012] 0.3-0.6 parts of sodium bicarbonate;

[0013] 15-20 parts of cross-linking agent;

[0014] 95-105 parts of water.

[0015] Preferably, the organic carbon source comprises a combination of one or more of calcium carbonate, glucose, starch and sodium acetate.

[0016] Preferably, the cross-linking agent is a saturated boric acid solution containing 2 to 2.5 wt % calcium chloride.

[0017] The high dissolved oxygen concentration in domestic sewage in villages and towns has seriously exceeded the tolerance range of denitrifying bacteria, inhibiting the denitrification process. Under long-term high dissolved oxygen conditions, the activity of denitrifying activated sludge gradually decreases. By adopting the above technical solution, the present invention uses polyvinyl alcohol-boric acid as a carrier material. The polyvinyl alcohol-boric acid carrier has high mechanical strength, resists microbial decomposition, and is non-toxic to microorganisms. It is a high-quality carrier material for denitrifying activated sludge, and can provide a stable microenvironment for the denitrifying bacteria in the denitrifying activated sludge, enabling them to effectively carry out denitrification reactions. In addition, by fixing the denitrifying activated sludge on the polyvinyl alcohol-boric acid carrier, the loss of microorganisms can be effectively reduced, thereby improving the stability and shock load resistance of the sewage treatment process.

[0018] Diatomaceous earth modified with iron-manganese composite oxide is also added to the polyvinyl alcohol-boric acid carrier. The addition of diatomaceous earth can fill the large gaps on the surface of the polyvinyl alcohol-boric acid carrier to form a physical barrier, effectively blocking the penetration of external dissolved oxygen. It can also enhance the mechanical strength of polyvinyl alcohol-boric acid and reduce the swelling and deformation of the formed denitrification sludge particles. On the other hand, the microporous structure of diatomaceous earth can provide more attachment sites for denitrifying bacteria, which is beneficial to the proliferation of denitrifying bacteria and the maintenance of denitrification activity under anoxic conditions. It can also promote substrate diffusion and improve the treatment effect of denitrifying sludge particles on sewage.

[0019] At the same time, the diatomaceous earth is modified with iron-manganese composite oxides, which significantly increases its specific surface area, providing more adsorption sites for denitrifying activated sludge, greatly reducing the loss of microorganisms during the sewage treatment process, and improving the long-term stability of the resulting denitrifying sludge particles. The iron-manganese composite oxides coat the diatomaceous earth surface, utilizing the redox reaction of iron and manganese ions to decompose invading dissolved oxygen, creating a favorable anoxic environment for the denitrifying activated sludge and significantly reducing the impact of dissolved oxygen on the denitrifying activated sludge. They also adsorb free radicals or metabolic inhibitors generated by the dissolved oxygen impact, protecting the activity of the denitrifying activated sludge.

[0020] The adsorption and decomposition of dissolved oxygen by iron-manganese composite oxides, combined with the physical oxygen barrier of diatomaceous earth, can provide a low-oxygen or anaerobic environment for the denitrifying bacteria inside the denitrifying sludge particles, promote the growth of denitrifying bacteria and denitrification, and improve the ability of denitrifying sludge particles to withstand dissolved oxygen shock under long-term high dissolved oxygen conditions.

[0021] The present invention also adds sodium bicarbonate during the preparation of the polyvinyl alcohol-boric acid carrier. Sodium bicarbonate acts as a pH buffer, regulating the pH inside the denitrifying sludge particles and preventing extreme pH values from inhibiting microbial activity. Furthermore, sodium bicarbonate also acts as a porogen. During the preparation of the denitrifying sludge particles, sodium bicarbonate decomposes to release carbon dioxide gas, forming micron-sized pores within the denitrifying sludge particles. This increases the adsorption sites within the polyvinyl alcohol-boric acid carrier and reduces the mass transfer resistance of the denitrifying sludge particles, thereby enhancing wastewater treatment efficiency.

[0022] Preferably, the raw materials for the iron-manganese composite oxide modified diatomaceous earth include diatomaceous earth, iron salt hydrate and manganese salt hydrate in a mass ratio of 1: (1.5-2): (0.5-1).

[0023] Preferably, the iron salt hydrate includes a combination of one or more of ferric nitrate nonahydrate, ferric sulfate nonahydrate and ferric chloride hexahydrate; and the manganese salt hydrate includes a combination of one or more of manganese acetate tetrahydrate, manganese chloride tetrahydrate and manganese sulfate monohydrate.

[0024] Preferably, the iron-manganese composite oxide modified diatomaceous earth is prepared according to the following method:

[0025] After drying, the diatomaceous earth is added to a mixed aqueous solution of iron salt hydrate and manganese salt hydrate, immersed at room temperature for 12 to 15 hours, then a sodium hydroxide solution is added dropwise, stirred and reacted for 2 to 4 hours, heat-treated at 100 to 110° C., and finally washed and dried to obtain the iron-manganese composite oxide modified diatomaceous earth.

[0026] Preferably, the amount of sodium hydroxide added is 0.8 to 1 wt % of the diatomaceous earth.

[0027] By adopting the above technical solution, diatomaceous earth is impregnated with a mixed aqueous solution of iron salt hydrate and manganese salt hydrate. The metal ions in the solution can be attached to the surface of the diatomaceous earth through electrostatic action or surface hydroxyl attraction and complexation. Then, under the action of hydrogen hydroxide, amorphous iron-manganese composite oxides are formed, successfully achieving the modification of the diatomaceous earth.

[0028] After loading the modified diatomite with iron-manganese composite oxides, finer nanopores are formed on its surface, further enhancing the ability of the polyvinyl alcohol-boric acid carrier to block the diffusion of external dissolved oxygen into the interior, thereby better protecting the anoxic microenvironment of denitrifying bacteria. Furthermore, the properties of the iron-manganese composite oxides on the surface of the modified diatomite can help improve the diatomite's ability to absorb dissolved oxygen. They can also react and decompose dissolved oxygen that has invaded the interior of denitrifying sludge particles, maintaining the denitrification process in the denitrifying activated sludge and reducing the impact of dissolved oxygen on the denitrification process.

[0029] Preferably, the denitrification activated sludge is obtained by domesticating the residual sludge from the secondary sedimentation tank of a village sewage treatment plant as raw material.

[0030] Preferably, the denitrification activated sludge is obtained by domestication according to the following method:

[0031] The residual sludge from the secondary sedimentation tank of a village sewage treatment plant is mixed with the denitrification sludge culture medium in a volume ratio of 1: (1.5-2), and is acclimated and cultured under anoxic conditions. During the culture process, the dissolved oxygen concentration is controlled at 0.5-1 mg / L, the pH value is 7.0-7.5, and the temperature is 30-32°C. Denitrification activated sludge is obtained by culturing for 10-14 days.

[0032] More preferably, the denitrification sludge culture medium is a mixture of potassium nitrate, glucose, disodium hydrogen phosphate and trace elements in a mass ratio of (0.8-1.2): (3-5): (1-2): (0.1-0.2); the trace element mixture includes a combination of two or more of magnesium sulfate heptahydrate, calcium chloride dihydrate and copper sulfate pentahydrate.

[0033] By adopting the above technical solution, residual sludge from sewage treatment is used as raw material, activated sludge enriched with denitrifying bacteria is domesticated and screened, and the domesticated denitrifying activated sludge is loaded on a polyvinyl alcohol-boric acid carrier. Through physical barrier and the adsorption and decomposition of external dissolved oxygen by diatomaceous earth modified with iron-manganese composite oxide, a good anoxic environment is provided for the denitrification process of the denitrifying activated sludge, and the pore structure of the diatomaceous earth and the carrier will not affect the mass transfer of the substrate and will not affect the denitrification reaction.

[0034] Preferably, the raw material of the denitrification sludge particles further includes 1 to 3 parts by weight of ethylene-vinyl alcohol copolymer.

[0035] By adopting the above technical solution, during the process of treating sewage, the denitrifying sludge particles obtained by cross-linking and solidifying the denitrifying activated sludge loaded on the polyvinyl alcohol-boric acid carrier will produce a large amount of gas, such as methane and carbon dioxide, in the denitrification reaction. During the process of these gases escaping from the interior of the denitrifying sludge particles, due to the modification effect of the iron-manganese composite oxide modified diatomaceous earth, a relatively dense oxygen barrier structure is formed on the outside of the polyvinyl alcohol-boric acid carrier, making it difficult for these gases to escape quickly and effectively in the first time. This will cause the denitrifying sludge particles to float and swell with gas, and even burst. The swollen and floating particles will squeeze each other, reducing the surface area between the denitrifying sludge particles and domestic sewage, which greatly affects the effect of wastewater treatment.

[0036] Therefore, ethylene-vinyl alcohol copolymer is also added in the preparation process of denitrification sludge particles. The hydrophobic ethylene segment and the hydrophilic vinyl alcohol segment in the ethylene-vinyl alcohol copolymer can form an amphiphilic structure. The hydrophobic segment is enriched on the outside of the denitrification sludge particles, and the hydrophilic segment is enriched inside the denitrification sludge particles. This gradient structure can, on the one hand, block the penetration of dissolved oxygen, and on the other hand, provide a directional diffusion channel for the gas generated inside, ensuring the permeability of the internal macropores and avoiding gas retention.

[0037] Moreover, the addition of ethylene-vinyl alcohol copolymer can also produce a cross-linking reaction with the polyvinyl alcohol-boric acid carrier, which can enhance the mechanical strength of the denitrification sludge particles, reduce the risk of denitrification sludge particles rupture due to internal gas pressure, and indirectly improve the denitrification sludge particles' ability to resist dissolved oxygen shock.

[0038] Preferably, the denitrification sludge particles are prepared according to the following method:

[0039] Dissolving polyvinyl alcohol in water, adding an organic carbon source, iron-manganese composite oxide modified diatomaceous earth, sodium bicarbonate and ethylene-vinyl alcohol copolymer in sequence, and stirring evenly to obtain a pre-embedding agent;

[0040] The pre-embedding agent is mixed with the denitrification activated sludge, a cross-linking agent is added dropwise, and the mixture is stirred and cross-linked to form spherical particles. The cross-linking and curing is continued at 3 to 4° C. for 30 to 40 minutes, and finally the denitrification sludge particles are obtained by washing.

[0041] Preferably, the technical effect of the present application can be achieved without adding ethylene-vinyl alcohol copolymer during the preparation process.

[0042] In a second aspect, the present invention provides a sewage treatment process based on denitrification sludge particles, which sewage treatment process includes microbial sewage treatment and artificial wetland treatment;

[0043] The process steps of microbial sewage treatment include: passing the domestic sewage of villages and towns through anoxic tanks, aerobic tanks and sedimentation tanks for the first purification, and finally the supernatant obtained from the sedimentation tank flows into the artificial wetland treatment tank;

[0044] The anoxic tank is provided with the denitrifying sludge particles obtained above; the aerobic tank is provided with nitrifying bacteria sludge; aeration devices are provided at the bottom of the anoxic tank and the aerobic tank; part of the sludge in the sedimentation tank is returned to the anoxic tank through a sludge pump, and the other part is composted.

[0045] Preferably, the volume filling rate of the denitrification sludge in the anoxic tank is 10-15%.

[0046] Preferably, the process steps of artificial wetland treatment include: the supernatant obtained from the sedimentation tank flows into the artificial wetland treatment tank, submerging the soil layer in the artificial wetland treatment tank for a second purification, the purified effluent meeting the standards is discharged, and the effluent that does not meet the standards is returned to the anoxic tank;

[0047] The soil layer is planted with landscape aquatic plants.

[0048] By adopting the above-mentioned technical solution and applying denitrifying sludge granules to the sewage treatment process, even in rural and town sewage with high dissolved oxygen content, the denitrifying sludge granules can effectively utilize the organic carbon source in the sewage to carry out denitrification reactions. The denitrifying sludge granules reduce the COD (chemical oxygen demand) concentration in the anoxic tank sewage, thereby improving the COD degradation capacity of the sewage treatment process of the present invention. The alkalinity generated by the denitrification process in the anoxic tank can internally supplement the alkalinity consumed by the nitrification process in the aerobic tank, compensating for the alkalinity consumed during nitrification, thereby improving the sludge settling performance and effectively controlling sludge bulking.

[0049] At the same time, the sewage treatment process of the present invention also adds artificial wetland treatment after microbial treatment. On the one hand, the nitrifying bacteria sludge flowing out with the supernatant in the sedimentation tank can continue to undergo nitrification in the artificial wetland treatment tank, and perform a second purification of ammonia nitrogen degradation; on the other hand, landscape aquatic plants are also planted on the soil layer of the artificial wetland treatment tank. The landscape aquatic plants also have a certain water quality purification function on water, which can assist the second purification process, improve the quality of discharged water, and greatly improve the COD removal rate of domestic sewage.

[0050] Beneficial effects of the present invention:

[0051] 1. The present invention provides a denitrifying sludge granule, which uses polyvinyl alcohol-boric acid as a carrier and is loaded with denitrifying activated sludge, thereby providing a stable microenvironment for denitrifying bacteria and reducing the loss of microorganisms. In addition, diatomaceous earth modified with iron-manganese composite oxide is added during the preparation of the denitrifying sludge granule. The adsorption and decomposition effect of the iron-manganese composite oxide on dissolved oxygen, combined with the physical oxygen barrier of the diatomaceous earth, can provide a low-oxygen or anaerobic environment for the denitrifying bacteria inside the denitrifying sludge granule, promote the growth of denitrifying bacteria and denitrification, and improve the dissolved oxygen shock resistance of the denitrifying sludge granule under long-term high dissolved oxygen conditions.

[0052] 2. The present invention provides a wastewater treatment process based on denitrification sludge particles, which includes microbial wastewater treatment and constructed wetland treatment. The use of the above-described denitrification sludge particles, which are resistant to dissolved oxygen shock, in the microbial wastewater treatment process can improve the COD degradation capacity in domestic wastewater treatment. Furthermore, the process incorporates constructed wetland treatment and the planting of landscape aquatic plants with water purification capabilities to assist in secondary purification, thereby improving effluent quality. DETAILED DESCRIPTION

[0053] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] Preparation Example

[0055] Preparation Example 1: An iron-manganese composite oxide modified diatomaceous earth was prepared according to the following method:

[0056] Take 100g of diatomaceous earth (diatomaceous earth diameter is 0.2-0.8mm) and dry it in an oven at 100°C for 8 hours; add 180g of ferric nitrate nonahydrate and 70g of manganese sulfate monohydrate to 500mL of water and stir to dissolve to obtain a mixed aqueous solution of ferric nitrate nonahydrate and manganese sulfate monohydrate;

[0057] The dried diatomaceous earth was added to a mixed aqueous solution of ferric nitrate nonahydrate and manganese sulfate monohydrate, immersed at room temperature for 14 hours, and then 10 mL of a 10% sodium hydroxide solution was added dropwise. The mixture was stirred for 3 hours and heat-treated at 100°C. Finally, it was washed and dried to obtain iron-manganese composite oxide modified diatomaceous earth.

[0058] Preparation Example 2, an iron-manganese composite oxide modified diatomaceous earth, is different from Preparation Example 1 only in that the amount of ferric nitrate nonahydrate added is 150 g; the amount of manganese sulfate monohydrate added is 100 g.

[0059] Preparation Example 3, an iron-manganese composite oxide modified diatomaceous earth, is different from Preparation Example 1 only in that the amount of ferric nitrate nonahydrate added is 200 g; the amount of manganese sulfate monohydrate added is 50 g.

[0060] Preparation Example 4: An iron oxide-modified diatomaceous earth was prepared according to the following method:

[0061] Take 100 g of diatomaceous earth (diatomaceous earth diameter is 0.2-0.8 mm) and dry it in an oven at 100°C for 8 hours; add 250 g of ferric nitrate nonahydrate to 500 mL of water and stir to dissolve to obtain an aqueous solution of ferric nitrate nonahydrate;

[0062] The dried diatomaceous earth was added to an aqueous solution of ferric nitrate nonahydrate and immersed at room temperature for 14 hours. Then, 10 mL of a 10% sodium hydroxide solution was added dropwise, stirred for 3 hours, heat-treated at 100°C, and finally washed and dried to obtain iron oxide-modified diatomaceous earth.

[0063] Preparation Example 5: A manganese composite oxide-modified diatomaceous earth was prepared according to the following method:

[0064] Take 100 g of diatomaceous earth (diatomaceous earth diameter is 0.2-0.8 mm) and dry it in an oven at 100°C for 8 hours; add 250 g of manganese sulfate monohydrate to 500 mL of water and stir to dissolve to obtain a manganese sulfate monohydrate aqueous solution;

[0065] The dried diatomaceous earth was added to a monohydrated manganese sulfate aqueous solution and immersed at room temperature for 14 hours. Then, 10 mL of a 10% sodium hydroxide solution was added dropwise, stirred for 3 hours, and heat-treated at 100°C. Finally, the manganese oxide-modified diatomaceous earth was washed and dried.

[0066] Example 1 Denitrification Sludge Granules

[0067] Example 1-1, a denitrification sludge granule, prepared according to the following method:

[0068] Acclimation of denitrification activated sludge:

[0069] The residual sludge from the secondary sedimentation tank of a village sewage treatment plant was mixed with a denitrification sludge culture medium (a mixture of potassium nitrate, glucose, disodium hydrogen phosphate and trace elements in a mass ratio of 1:4:1.5:0.15, wherein the trace element mixture was a mixture of magnesium sulfate heptahydrate, dihydrate, calcium chloride and copper sulfate pentahydrate in a mass ratio of 1:1:1) in a volume ratio of 1:2, and cultured under anoxic conditions. During the culture process, the dissolved oxygen concentration was controlled at 0.5 mg / L, the pH value was 7.0, and the temperature was 30°C. Denitrification activated sludge was obtained after 12 days of culture.

[0070] Dissolve 10 g of polyvinyl alcohol (molecular weight 1750 ± 50) in 100 g of water, add 0.4 g of glucose, 3 g of diatomaceous earth modified with the iron-manganese composite oxide prepared in Preparation Example 1, and 0.5 g of sodium bicarbonate in sequence, and stir evenly to obtain a pre-embedding agent;

[0071] The pre-embedding agent was mixed with 12 g of the denitrification activated sludge obtained above, and 18 g of a saturated boric acid solution containing 2 wt% calcium chloride was added dropwise. The mixture was stirred and cross-linked to form spherical particles. The cross-linking and curing was continued at 4°C for 30 min, and the denitrification sludge particles were finally obtained by washing.

[0072] Examples 1-2 and 1-3 are denitrification sludge granules, which differ from Example 1-1 only in that the raw material ratio of the denitrification sludge granules is adjusted, as shown in Table 1:

[0073] Table 1 Raw material ratio table of Example 1-1 to Example 1-3

[0074]

[0075] Wherein, both Examples 1-2 and 1-3 use the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1.

[0076] Example 1-4 is a denitrification sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is replaced by an equal amount of the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 2.

[0077] Example 1-5 is a denitrification sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is replaced by an equal amount of the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 3.

[0078] Example 1-6, a denitrification sludge granule, was prepared according to the following method:

[0079] Dissolve 10 g of polyvinyl alcohol (molecular weight: 1750 ± 50) in 100 g of water, and add 0.4 g of glucose, 3 g of diatomaceous earth modified with the iron-manganese composite oxide prepared in Preparation Example 1, 0.5 g of sodium bicarbonate, and 2 g of ethylene-vinyl alcohol copolymer (ethylene content: 38.0 mol%) in sequence, and stir evenly to obtain a pre-embedding agent.

[0080] The pre-embedding agent was mixed with 12 g of the denitrification activated sludge prepared according to Example 1-1, and 18 g of a saturated boric acid solution containing 2 wt% calcium chloride was added dropwise. The mixture was stirred and cross-linked to form spherical particles. The cross-linking and curing was continued at 4°C for 30 min, and the denitrification sludge particles were finally washed.

[0081] Example 1-7 is a denitrification sludge granule, which is different from Example 1-6 only in that the added amount of ethylene-vinyl alcohol copolymer is 0.5 g.

[0082] Example 1-8 is a denitrification sludge granule, which is different from Example 1-6 only in that the added amount of ethylene-vinyl alcohol copolymer is 4 g.

[0083] Comparative Example 1 Denitrification Sludge Granules

[0084] Comparative Example 1-1 is a denitrification sludge granule, which is different from Example 1-1 only in that the amount of the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is 1 g.

[0085] Comparative Example 1-2 is a denitrification sludge granule, which is different from Example 1-1 only in that the amount of the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is 1 g.

[0086] Comparative Example 1-3 is a denitrification sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is replaced by an equal amount of the iron oxide modified diatomaceous earth prepared in Preparation Example 4.

[0087] Comparative Example 1-4 is a denitrification sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is replaced by an equal amount of manganese oxide modified diatomaceous earth prepared in Preparation Example 5.

[0088] Comparative Example 1-5 is a denitrification sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is replaced by an equal amount of unmodified diatomaceous earth.

[0089] Comparative Example 1-6 is a denitrification sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomaceous earth prepared in Preparation Example 1 is not added.

[0090] Comparative Example 1-7 is a denitrification sludge granule, which is different from Example 1-1 only in that no sodium bicarbonate is added.

[0091] Example 2 Sewage treatment process based on denitrification sludge

[0092] Example 2-1, a treatment process based on denitrification sludge, comprising the following process steps:

[0093] Microbial sewage treatment: Domestic sewage from villages and towns was extracted by a water pump and passed through an anoxic tank, an aerobic tank, and a sedimentation tank in sequence for the first purification. The anoxic tank was equipped with the denitrifying sludge particles prepared in Example 1-1, and the volume filling rate of the denitrifying sludge particles prepared in Example 1-1 was 12%. The aerobic tank was equipped with nitrifying bacteria sludge. Aeration devices were installed at the bottom of the anoxic tank and the aerobic tank. After sedimentation in the sedimentation tank, the obtained supernatant flowed into the artificial wetland treatment tank. Part of the obtained sludge was returned to the anoxic tank through the sludge pump, and the other part was composted.

[0094] Artificial wetland treatment: The supernatant obtained by sedimentation in the sedimentation tank flows into the artificial wetland treatment pool, submerging the soil layer in the artificial wetland treatment pool for a second purification. Landscape aquatic plants with water purification function are planted in the soil layer. After purification, the effluent meets the standards and is discharged. The effluent that does not meet the standards is returned to the anoxic pool.

[0095] Example 2-2 is a treatment process based on denitrification sludge, which differs from Example 2-1 only in that the denitrification sludge particles prepared in Example 1-1 are replaced with an equal amount of denitrification sludge particles prepared in Example 1-6.

[0096] Comparative Example 2 Sewage treatment process based on denitrification sludge

[0097] Comparative Example 2-1 is a treatment process based on denitrification sludge, which differs from Example 2-1 only in that the denitrification sludge particles prepared in Example 1-1 are replaced by an equal amount of denitrification sludge particles prepared in Comparative Example 1-5.

[0098] Comparative Example 2-2 is a treatment process based on denitrification sludge, which differs from Example 2-1 only in that the denitrification sludge particles prepared in Example 1-1 are replaced by an equal amount of denitrification sludge particles prepared in Comparative Example 1-6.

[0099] Comparative Example 2-3 is a treatment process based on denitrification sludge, which differs from Example 2-1 only in that the denitrification sludge particles prepared in Example 1-1 are replaced by an equal amount of denitrification sludge particles prepared in Comparative Example 1-7.

[0100] Comparative Example 2-4 is a treatment process based on denitrification sludge, which differs from Example 2-1 only in that the denitrification sludge particles prepared in Example 1-1 are replaced with an equal amount of denitrification activated sludge.

[0101] Performance testing

[0102] 1. Simulation test:

[0103] Using village and town domestic sewage as the test wastewater, the initial COD concentration of the test wastewater was measured to be 220 mg / L and the dissolved oxygen concentration was 3.5 mg / L. The denitrification sludge particles obtained in Example 1 and Comparative Example 1 were respectively added to the test wastewater at a volume filling rate of 12%. The batch water inlet was controlled to be 0.5 L, aerated for 6 hours, and allowed to stand for 15 minutes before the supernatant was discharged. The COD concentration of the supernatant was measured, and the COD removal rate was calculated:

[0104] .

[0105] 2. Practical application test:

[0106] The COD concentrations of the influent and the final effluent of Example 2 and Comparative Example 2 were tested respectively to compare the COD removal efficiencies.

[0107] The above test results are shown in Table 2 and Table 3 respectively:

[0108] Table 2 Simulation test results

[0109]

[0110] Table 3 Practical application test results

[0111]

[0112] According to Table 2 and Table 3, in combination with Example 1-1, Example 1-6, Example 2-1 and Example 2-2, it can be seen that the COD removal rate of Example 1-6 is increased compared with that of Example 1-1. The reason is that the only difference between Example 1-6 and Example 1-1 is that ethylene-vinyl alcohol copolymer is added to the iron-manganese composite oxide modified diatomaceous earth, which can further improve the mechanical strength and stability of the denitrification sludge particles, enhance the ability of the denitrification sludge particles to block dissolved oxygen penetration, and promote the rapid escape of internal gas, which is beneficial to the treatment efficiency of the denitrification sludge particles for sewage. Similarly, Example 2-2 uses the denitrification sludge particles prepared by Example 1-6, and the sewage treatment capacity is also improved.

[0113] Combining Example 1-1, Comparative Example 1-1, Comparative Example 1-2, Comparative Example 1-6, and Comparative Example 2-2, it can be seen that the COD removal rates of Comparative Examples 1-1, Comparative Example 1-2, and Comparative Example 1-6 are lower than those of Example 1-1, and the sewage treatment effect of Comparative Example 2-2 is also lower than that of Example 2-1. The reason is that in Comparative Example 1-1, the amount of diatomaceous earth modified with iron-manganese composite oxide is reduced, and the physical barrier effect of the denitrification sludge particles on dissolved oxygen and the adsorption and decomposition efficiency of dissolved oxygen are reduced. Dissolved oxygen penetrates into the denitrification sludge particles, inhibiting the denitrification process of the denitrification activated sludge, and the sewage treatment effect is reduced. In Comparative Example 1-6, no iron-manganese composite oxide modified diatomaceous earth is added. Under the impact of long-term high dissolved oxygen concentration, the performance of the sludge particles is more significantly reduced. From the comparison of Comparative Example 2-2 and Example 2-1, it can also be seen that not adding iron-manganese composite oxide modified diatomaceous earth will lead to a decline in sewage treatment effect. In Comparative Example 1-2, the amount of diatomaceous earth modified with iron-manganese composite oxide was increased. The addition of excessive diatomaceous earth modified with iron-manganese composite oxide would clog the surface pores of the polyvinyl alcohol-boric acid carrier. Although it could block the intrusion of dissolved oxygen, it also affected the mass transfer efficiency of the substrate, and the internal gas was difficult to escape, resulting in a decrease in the performance of the sludge particles.

[0114] Combining Example 1-1, Comparative Example 1-5, and Comparative Example 2-1, it can be seen that the COD removal rate of Comparative Example 1-5 is lower than that of Example 1-1, and the sewage treatment effect of Comparative Example 2-1 is also lower than that of Example 2-1. This is because the diatomaceous earth added to the denitrifying sludge particles in Comparative Example 1-5 has not been modified. Although the addition of diatomaceous earth forms a certain physical barrier structure, the unmodified diatomaceous earth has a weak adsorption capacity for dissolved oxygen. Dissolved oxygen can still penetrate into the sludge particles through the pores, affecting the activity of denitrifying bacteria. In particular, under the impact of long-term high dissolved oxygen concentrations, the denitrification process of the denitrifying sludge particles will be inhibited.

[0115] Combining Example 1-1, Comparative Example 1-3 and Comparative Example 1-4, it can be seen that the COD removal rates of Comparative Examples 1-3 and Comparative Example 1-4 are lower than those of Example 1-1. The reason is that Comparative Examples 1-3 and Comparative Example 1-4 use diatomaceous earth modified with a single metal oxide, and the decomposition reaction activity of the single metal oxide with dissolved oxygen is limited, and the structural stability is also reduced, thereby affecting the denitrification process of the denitrifying sludge particles.

[0116] Combining Example 1-1, Comparative Example 1-7, and Comparative Example 2-3, it can be seen that the COD removal rate of Comparative Example 1-7 is lower than that of Example 1-1, and the sewage treatment efficiency of Comparative Example 2-3 is lower than that of Example 2-1. This is because no sodium bicarbonate was added during the preparation of the iron-manganese composite oxide-modified diatomaceous earth in Comparative Example 1-7. This reduced the internal pore structure of the denitrifying sludge particles formed, reduced the adsorption sites for the denitrifying activated sludge, and increased the mass transfer resistance, thereby affecting the denitrification process of the denitrifying sludge particles.

[0117] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0118] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A denitrification sludge granule, characterized in that: The denitrification sludge granules include the following raw materials in parts by mass: 8-10 parts of polyvinyl alcohol; 10-15 parts of denitrification activated sludge; 0.3-0.5 parts of organic carbon source; 2-4 parts of iron-manganese composite oxide modified diatomaceous earth; 0.3-0.6 parts of sodium bicarbonate; 15-20 parts of cross-linking agent; 95-105 parts water; The raw materials of the denitrification sludge particles also include 1 to 3 parts by weight of ethylene-vinyl alcohol copolymer.

2. The denitrification sludge granules according to claim 1, characterized in that The raw materials of the iron-manganese composite oxide modified diatomaceous earth include diatomaceous earth, iron salt hydrate and manganese salt hydrate in a mass ratio of 1: (1.5-2): (0.5-1).

3. The denitrification sludge granules according to claim 2, characterized in that: The iron salt hydrate includes a combination of one or more of ferric nitrate nonahydrate, ferric sulfate nonahydrate and ferric chloride hexahydrate; the manganese salt hydrate includes a combination of one or more of manganese acetate tetrahydrate, manganese chloride tetrahydrate and manganese sulfate monohydrate.

4. The denitrification sludge granules according to claim 2, characterized in that: The iron-manganese composite oxide modified diatomaceous earth is prepared according to the following method: After drying, the diatomaceous earth is added to a mixed aqueous solution of iron salt hydrate and manganese salt hydrate, immersed at room temperature for 12 to 15 hours, then a sodium hydroxide solution is added dropwise, stirred and reacted for 2 to 4 hours, heat-treated at 100 to 110° C., and finally washed and dried to obtain the iron-manganese composite oxide modified diatomaceous earth.

5. The denitrification sludge granules according to claim 1, characterized in that: The denitrification activated sludge is obtained by domesticating the residual sludge from the secondary sedimentation tank of a village sewage plant as raw material.

6. The denitrification sludge granules according to claim 1, characterized in that: The denitrification sludge particles are prepared according to the following method: Dissolving polyvinyl alcohol in water, adding an organic carbon source, iron-manganese composite oxide modified diatomaceous earth, sodium bicarbonate and ethylene-vinyl alcohol copolymer in sequence, and stirring evenly to obtain a pre-embedding agent; The pre-embedding agent is mixed with the denitrification activated sludge, a cross-linking agent is added dropwise, and the mixture is stirred and cross-linked to form spherical particles. The cross-linking and curing is continued at 3 to 4° C. for 30 to 40 minutes, and finally the denitrification sludge particles are obtained by washing.

7. A sewage treatment process based on denitrification sludge particles, characterized in that: The sewage treatment process includes microbial sewage treatment and artificial wetland treatment; The process steps of the microbial sewage treatment include: passing the village and town domestic sewage through an anoxic tank, an aerobic tank and a sedimentation tank in sequence for the first purification, and finally flowing the supernatant obtained in the sedimentation tank into the artificial wetland treatment tank; The anoxic tank is provided with denitrifying sludge particles according to any one of claims 1 to 6; the aerobic tank is provided with nitrifying bacteria sludge; aeration devices are provided at the bottom of the anoxic tank and the aerobic tank; part of the sludge in the sedimentation tank is returned to the anoxic tank through a sludge pump, and the other part is composted.

8. The sewage treatment process based on denitrification sludge particles according to claim 7, characterized in that: The volume filling rate of the denitrification sludge in the anoxic tank is 10-15%.

9. The sewage treatment process based on denitrification sludge particles according to claim 7, characterized in that: The process steps of the artificial wetland treatment include: the supernatant obtained from the sedimentation tank flows into the artificial wetland treatment tank, submerging the soil layer in the artificial wetland treatment tank for a second purification, and the purified effluent meets the standards for discharge, and the effluent that does not meet the standards is returned to the anoxic tank; The soil layer is planted with landscape aquatic plants.

Images