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

Abstract

The invention discloses denitrifying sludge particles and a sewage treatment process based on the denitrifying sludge particles, and belongs to the technical field of sewage treatment. The denitrification sludge particles are prepared from the following raw materials in parts by mass: 8 to 10 parts of polyvinyl alcohol, 10 to 15 parts of denitrification activated sludge, 0.3 to 0.5 part of organic carbon source, 2 to 4 parts of iron-manganese composite oxide modified diatomite, 0.3 to 0.6 part of sodium bicarbonate, 15 to 20 parts of cross-linking agent and 95 to 105 parts of water. The denitrifying activated sludge takes polyvinyl alcohol-boric acid as a carrier to load the denitrifying activated sludge, so that a stable microenvironment can be provided for denitrifying bacteria, and the loss of microorganisms is reduced; the adsorption and decomposition effects of the iron-manganese composite oxide modified diatomite on dissolved oxygen cooperate with a physical oxygen barrier structure to provide a low-oxygen or oxygen-free environment for denitrifying bacteria, promote the growth of the denitrifying bacteria, and improve the dissolved oxygen impact resistance of 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 particularly relates to a denitrifying sludge granule and a sewage treatment process based on the denitrifying sludge granule. Background Art

[0002] Against the backdrop of the continuous growth of the world's population and the accelerating urbanization process, establishing good sanitation facilities is an important step in urban and rural construction. Among them, the treatment of domestic sewage, which is closely related to us, is particularly important. Domestic sewage contains a large amount of organic and inorganic compounds, and improper treatment will cause serious impacts on the environment. Moreover, due to the decentralized discharge of rural domestic sewage, it further increases the difficulty of treating domestic sewage.

[0003] Currently, the treatment of domestic sewage mostly adopts traditional biological treatment processes. However, the effluent quality after sewage treatment using this treatment method is prone to the situation that the indicators do not meet the discharge standards. The A / O process adds an anoxic biological treatment process before the conventional aerobic sludge treatment system. The two work together to effectively achieve the denitrification and phosphorus removal of domestic sewage. And compared with the traditional biological treatment process, it can make full use of the organic matter in the raw sewage as a carbon source for denitrification, thus eliminating the need to add additional carbon sources.

[0004] When the A / O treatment process is used in rural sewage treatment, it can reduce the treatment cost and improve the treatment effect. However, the dissolved oxygen in rural domestic sewage is generally 2 - 4 mg / L. For the denitrification process, that is, the anoxic biological treatment process, too high a dissolved oxygen concentration will inhibit the denitrification process. Because under the condition of relatively high dissolved oxygen, microbial flocs remain in the aerobic state, and 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, denitrifying bacteria sludge will gradually become inactivated, the denitrification process is affected, and nitrogen cannot be removed through denitrification anymore, resulting in obstacles in the sewage treatment process. Summary of the Invention

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

[0006] The purpose of the present invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a denitrifying sludge granule, comprising the following raw materials in parts by mass: Polyvinyl alcohol 8 - 10 parts; Denitrifying activated sludge 10 - 15 parts; Organic carbon source 0.3 - 0.5 part; Iron-manganese composite oxide modified diatomite 2 - 4 parts; Sodium bicarbonate: 0.3 - 0.6 parts; Crosslinking agent: 15 - 20 parts; Water: 95 - 105 parts.

[0007] Preferably, the organic carbon source includes one or a combination of more of calcium carbonate, glucose, starch, and sodium acetate.

[0008] Preferably, the crosslinking agent is a saturated boric acid solution containing 2 - 2.5 wt% calcium chloride by mass.

[0009] The dissolved oxygen concentration in rural domestic sewage is high, which 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 loses. By adopting the above technical solution, the present invention uses polyvinyl alcohol - boric acid as the carrier material. The polyvinyl alcohol - boric acid carrier has high mechanical strength, is resistant to microbial decomposition, and is non-toxic to microorganisms. It is an excellent carrier material for denitrifying activated sludge, which can provide a stable microenvironment for denitrifying bacteria in the denitrifying activated sludge, enabling them to effectively carry out the denitrification reaction. And the denitrifying activated sludge can be effectively reduced in the loss of microorganisms by being fixed on the polyvinyl alcohol - boric acid carrier, improving the stability and shock resistance ability in the sewage treatment process.

[0010] Iron - manganese composite oxide - modified diatomite is also added to the polyvinyl alcohol - boric acid carrier. On the one hand, the addition of diatomite can fill the large voids on the surface of the polyvinyl alcohol - boric acid carrier to form a physical barrier to effectively block the penetration of external dissolved oxygen, and can also enhance the mechanical strength of the polyvinyl alcohol - boric acid and reduce the swelling and deformation phenomenon of the formed denitrifying sludge particles; on the other hand, the microporous structure of diatomite can provide more attachment sites for denitrifying bacteria, which is beneficial to the proliferation of denitrifying bacteria, maintaining the denitrification activity under anoxic conditions, and can also promote substrate diffusion, improving the sewage treatment effect of the denitrifying sludge particles.

[0011] At the same time, the diatomite is also modified by iron - manganese composite oxide treatment, which can significantly increase the specific surface area of the diatomite, providing more adsorption sites for denitrifying activated sludge, greatly reducing the loss of microorganisms in the sewage treatment process, and improving the long - term stability of the obtained denitrifying sludge particles. At the same time, the iron - manganese composite oxide covers the surface of the diatomite, and can utilize the redox reaction of iron ions and manganese ions to decompose the invaded dissolved oxygen, creating a good anoxic environment for denitrifying activated sludge, significantly reducing the impact of dissolved oxygen on denitrifying activated sludge, and at the same time being able to adsorb free radicals or metabolic inhibitors generated under the impact of dissolved oxygen, protecting the activity of denitrifying activated sludge.

[0012] The adsorption and decomposition of iron-manganese composite oxides on dissolved oxygen, combined with the physical oxygen barrier of diatomite, can provide a low-oxygen or anoxic environment for denitrifying bacteria inside the denitrifying sludge granules, promote the growth of denitrifying bacteria and denitrification, and improve the ability of denitrifying sludge granules to withstand dissolved oxygen shock under long-term high dissolved oxygen conditions.

[0013] In the preparation process of the polyvinyl alcohol-boric acid carrier of the present invention, sodium bicarbonate is also added. On the one hand, sodium bicarbonate can act as a pH buffer to regulate the pH value inside the denitrifying sludge granules and avoid the inhibition of microbial activity by extreme pH values. On the other hand, sodium bicarbonate can also be used as a pore-forming agent. During the preparation of the denitrifying sludge granules, sodium bicarbonate decomposes and releases carbon dioxide gas, forming micron-sized pores inside the denitrifying sludge granules, increasing the adsorption sites inside the polyvinyl alcohol-boric acid carrier and reducing the mass transfer resistance of the denitrifying sludge granules, thereby enhancing the sewage treatment efficiency.

[0014] Preferably, the raw materials of the iron-manganese composite oxide modified diatomite include diatomite, iron hydrate and manganese hydrate with a mass ratio of 1: (1.5 - 2): (0.5 - 1).

[0015] Preferably, the iron hydrate includes one or a combination of ferric nitrate nonahydrate, ferric sulfate nonahydrate and ferric chloride hexahydrate; the manganese hydrate includes one or a combination of manganese acetate tetrahydrate, manganese chloride tetrahydrate and manganese sulfate monohydrate.

[0016] Preferably, the iron-manganese composite oxide modified diatomite is prepared by the following method: The diatomite is dried and then added to the mixed aqueous solution of iron hydrate and manganese hydrate, impregnated at room temperature for 12 - 15 h, then sodium hydroxide solution is added dropwise, stirred and reacted for 2 - 4 h, heat-treated at 100 - 110 °C, and finally washed and dried to obtain the iron-manganese composite oxide modified diatomite.

[0017] Preferably, the addition amount of sodium hydroxide is 0.8 - 1 wt% of the diatomite.

[0018] By adopting the above technical scheme, the diatomite is impregnated with the mixed aqueous solution of iron hydrate and manganese hydrate, and the metal ions in the solution can be attached to the surface of the diatomite by electrostatic action or surface hydroxyl attraction and complexation, and then under the action of sodium hydroxide, amorphous iron-manganese composite oxide is formed, successfully realizing the modification of the diatomite.

[0019] After being modified, diatomite can form finer nano-pores on its surface after being loaded with iron-manganese composite oxides, 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. At the same time, the properties of the iron-manganese composite oxides on the surface of the modified diatomite can help improve the ability of diatomite to adsorb dissolved oxygen, and can also decompose the dissolved oxygen invading into the interior of denitrifying sludge particles through reactions, maintaining the denitrification process of denitrifying activated sludge and reducing the impact of dissolved oxygen on the denitrification process.

[0020] Preferably, the denitrifying activated sludge is domesticated from the excess sludge in the secondary sedimentation tank of a rural sewage treatment plant.

[0021] Preferably, the denitrifying activated sludge is domesticated according to the following method: Mix the excess sludge in the secondary sedimentation tank of a rural sewage treatment plant with a denitrifying sludge medium in a volume ratio of 1:(1.5 - 2), and carry out domestication and cultivation under anoxic conditions. During the cultivation process, control the dissolved oxygen concentration at 0.5 - 1 mg / L, the pH value at 7.0 - 7.5, and the temperature at 30 - 32 °C. After culturing for 10 - 14 days, the denitrifying activated sludge is obtained.

[0022] More preferably, the denitrifying sludge medium is a mixture of potassium nitrate, glucose, disodium hydrogen phosphate, and trace elements with a mass ratio of (0.8 - 1.2):(3 - 5):(1 - 2):(0.1 - 0.2); the trace element mixture includes two or more combinations of magnesium sulfate heptahydrate, calcium chloride dihydrate, and copper sulfate pentahydrate.

[0023] By adopting the above technical solutions, using the excess sludge from sewage treatment as raw materials, domesticating and screening the activated sludge enriched with denitrifying bacteria, and loading the domesticated denitrifying activated sludge on a polyvinyl alcohol-boric acid carrier, through the physical barrier and the adsorption and decomposition of external dissolved oxygen by iron-manganese composite oxide modified diatomite, a good anoxic environment is provided for the denitrification process of denitrifying activated sludge, and the pore structures of diatomite and the carrier do not affect the mass transfer of substrates and do not affect the denitrification reaction.

[0024] Preferably, the raw materials of the denitrifying sludge particles further include 1 - 3 parts by mass of ethylene-vinyl alcohol copolymer.

[0025] By adopting the above technical solution, during the process of treating sewage with denitrifying sludge particles obtained by cross-linking and solidifying denitrifying activated sludge supported on a polyvinyl alcohol-boric acid carrier, a large amount of gases such as methane and carbon dioxide will be generated by denitrifying bacteria inside during the denitrification reaction. During the process of these gases escaping from the inside of the denitrifying sludge particles, due to the modification of iron-manganese composite oxide-modified diatomite, a relatively dense oxygen-blocking structure is formed outside the polyvinyl alcohol-boric acid carrier. These gases are difficult to escape quickly and effectively in the first place, which 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, and greatly affecting the effect of treating wastewater.

[0026] Therefore, ethylene-vinyl alcohol copolymer is also added during the preparation of the denitrifying sludge particles. The hydrophobic ethylene segments and hydrophilic vinyl alcohol segments in the ethylene-vinyl alcohol copolymer can form an amphiphilic structure. The hydrophobic segments are enriched outside the denitrifying sludge particles, and the hydrophilic segments are enriched inside the denitrifying 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 gases generated inside to ensure the connectivity of the internal macropores and avoid gas retention.

[0027] Moreover, the addition of ethylene-vinyl alcohol copolymer can also undergo a cross-linking reaction with the polyvinyl alcohol-boric acid carrier, which can enhance the mechanical strength of the denitrifying sludge particles, reduce the risk of rupture of the denitrifying sludge particles caused by internal gas pressure, and indirectly improve the ability of the denitrifying sludge particles to withstand dissolved oxygen shock.

[0028] Preferably, the denitrifying sludge particles are prepared by the following method: Dissolve polyvinyl alcohol in water, and sequentially add an organic carbon source, iron-manganese composite oxide-modified diatomite, sodium bicarbonate, and ethylene-vinyl alcohol copolymer, and stir evenly to obtain a pre-embedding agent; Mix the pre-embedding agent with denitrifying activated sludge, dropwise add a cross-linking agent, stir and cross-link to form spherical particles, continue cross-linking and solidifying at 3 - 4 °C for 30 - 40 min, and finally obtain denitrifying sludge particles after washing.

[0029] Preferably, the technical effect of the present application can also be achieved without adding ethylene-vinyl alcohol copolymer during the preparation process.

[0030] In a second aspect, the present invention provides a sewage treatment process based on denitrifying sludge particles. This sewage treatment process includes microbial sewage treatment and constructed wetland treatment; The process steps of microbial sewage treatment include: sequentially passing rural domestic sewage through an anoxic tank, an aerobic tank, and a sedimentation tank for the first purification, and finally flowing the supernatant obtained in the sedimentation tank into a constructed wetland treatment tank; The denitrifying sludge particles obtained above are provided in the anoxic tank; nitrifying bacteria sludge is provided in the aerobic tank; aeration devices are provided at the bottoms of the anoxic tank and the aerobic tank; part of the sludge in the sedimentation tank is refluxed to the anoxic tank through a sludge pump, and the other part is composted.

[0031] Preferably, the volume filling rate of the denitrifying sludge in the anoxic tank is 10-15%.

[0032] Preferably, the technological steps of the constructed wetland treatment include: the supernatant obtained from the sedimentation tank flows into the constructed wetland treatment tank, submerging the soil layer in the constructed wetland treatment tank for secondary purification, and the effluent that meets the standard is discharged after purification, and the effluent that does not meet the standard is refluxed to the anoxic tank; The soil layer is planted with landscape aquatic plants.

[0033] By adopting the above technical solution, the denitrifying sludge particles are applied to the sewage treatment process. In the face of rural domestic sewage with high dissolved oxygen, the denitrifying sludge particles can also effectively utilize the organic carbon source in the sewage for denitrification reaction. The COD (chemical oxygen demand) concentration in the sewage of the anoxic tank decreases under the action of the denitrifying sludge particles, which can improve the ability to degrade COD in the sewage treatment process of the present invention. The alkalinity generated by the denitrification process in the anoxic tank can play an internal supplementary role in compensating for the consumption of alkalinity in the nitrification process in the aerobic tank, making up for the consumption of alkalinity in the nitrification process, which is beneficial to the sedimentation performance of the sludge and effectively controlling the sludge bulking.

[0034] At the same time, the sewage treatment process of the present invention is also provided with a constructed wetland treatment after the microbial treatment. On the one hand, the nitrifying bacteria sludge flowing out together with the supernatant in the sedimentation tank can continue to carry out nitrification in the constructed wetland treatment tank for secondary purification of ammonia nitrogen degradation; on the other hand, landscape aquatic plants are also planted on the soil layer of the constructed wetland treatment tank, and the landscape aquatic plants also have a certain water purification function for water, which can assist the secondary purification process and improve the quality of the discharged water, greatly improving the COD removal rate of domestic sewage.

[0035] The beneficial effects of the present invention: 1. The present invention provides a kind of denitrifying sludge particles, using polyvinyl alcohol - boric acid as a carrier, loaded with denitrifying activated sludge, which can provide a stable microenvironment for denitrifying bacteria and reduce the loss of microorganisms; and iron - manganese composite oxide modified diatomite is also added in the preparation process of the denitrifying sludge particles. The adsorption and decomposition of dissolved oxygen by the iron - manganese composite oxide cooperate with the physical oxygen - blocking barrier of diatomite, which can provide a low - oxygen or anoxic environment for the denitrifying bacteria inside the denitrifying sludge particles, promote the growth of denitrifying bacteria and denitrification, and improve the dissolved - oxygen shock resistance ability of the denitrifying sludge particles under long - term high - dissolved - oxygen conditions.

[0036] 2. The present invention provides a sewage treatment process based on denitrifying sludge particles, which includes microbial sewage treatment and constructed wetland treatment. By introducing the obtained denitrifying sludge particles with the ability to withstand dissolved oxygen shock in the microbial sewage treatment, the ability to degrade COD in domestic sewage treatment can be improved. And a constructed wetland treatment is added, and landscape aquatic plants with water purification functions are planted to help with secondary purification and improve the effluent quality. Detailed implementation mode

[0037] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0038] Preparation example

[0039] Preparation example 1, an iron-manganese composite oxide modified diatomite, is prepared according to the following method: Take 100 g of diatomite (diatomite diameter is 0.2 - 0.8 mm), and dry it in an oven at 100 °C for 8 h; add 180 g of ferric nitrate nonahydrate and 70 g of manganese sulfate monohydrate to 500 mL of water and stir to dissolve to obtain a mixed aqueous solution of ferric nitrate nonahydrate and manganese sulfate monohydrate; Add the dried diatomite to the mixed aqueous solution of ferric nitrate nonahydrate and manganese sulfate monohydrate, impregnate it at room temperature for 14 h, then dropwise add 10 mL of a sodium hydroxide solution with a mass fraction of 10%, stir and react for 3 h, perform heat treatment at 100 °C, and finally wash and dry to obtain the iron-manganese composite oxide modified diatomite.

[0040] Preparation example 2, an iron-manganese composite oxide modified diatomite, is different from preparation example 1 only in that the addition amount of ferric nitrate nonahydrate is 150 g; the addition amount of manganese sulfate monohydrate is 100 g.

[0041] Preparation example 3, an iron-manganese composite oxide modified diatomite, is different from preparation example 1 only in that the addition amount of ferric nitrate nonahydrate is 200 g; the addition amount of manganese sulfate monohydrate is 50 g.

[0042] Preparation example 4, an iron oxide modified diatomite, is prepared according to the following method: Take 100 g of diatomite (diatomite diameter is 0.2 - 0.8 mm), and dry it in an oven at 100 °C for 8 h; add 250 g of ferric nitrate nonahydrate to 500 mL of water and stir to dissolve to obtain a ferric nitrate nonahydrate aqueous solution; The diatomite after drying treatment was added to an aqueous solution of iron(III) nitrate nonahydrate, impregnated at room temperature for 14 h, then 10 mL of a 10% sodium hydroxide solution was added dropwise, and the mixture was stirred and reacted for 3 h. Heat treatment was carried out at 100 °C, and finally, the iron oxide-modified diatomite was obtained by washing and drying.

[0043] Preparation Example 5, a manganese composite oxide-modified diatomite, was prepared by the following method: 100 g of diatomite (diatomite diameter: 0.2 - 0.8 mm) was taken and dried in an oven at 100 °C for 8 h; 250 g of manganese(II) sulfate monohydrate was added to 500 mL of water and stirred to dissolve to obtain an aqueous solution of manganese(II) sulfate monohydrate; The diatomite after drying treatment was added to the aqueous solution of manganese(II) sulfate monohydrate, impregnated at room temperature for 14 h, then 10 mL of a 10% sodium hydroxide solution was added dropwise, and the mixture was stirred and reacted for 3 h. Heat treatment was carried out at 100 °C, and finally, the manganese oxide-modified diatomite was obtained by washing and drying.

[0044] Example 1 Denitrifying sludge granules

[0045] Example 1-1, a kind of denitrifying sludge granules, was prepared by the following method: Acclimation of denitrifying activated sludge: The excess sludge from the secondary sedimentation tank of a rural sewage treatment plant was mixed with a denitrifying sludge medium (a mixture of potassium nitrate, glucose, disodium hydrogen phosphate, and trace elements in a mass ratio of 1:4:1.5:0.15, where the trace element mixture is a mixture of magnesium sulfate heptahydrate, calcium chloride dihydrate, and copper sulfate pentahydrate in a mass ratio of 1:1:1) in a volume ratio of 1:2, and acclimation culture was carried out under anoxic conditions. During the culture process, the dissolved oxygen concentration was controlled at 0.5 mg / L, the pH value was 7.0, the temperature was 30 °C, and the denitrifying activated sludge was obtained after culturing for 12 d.

[0046] 10 g of polyvinyl alcohol (molecular weight: 1750 ± 50) was dissolved in 100 g of water, and 0.4 g of glucose, 3 g of the iron-manganese composite oxide-modified diatomite prepared in Preparation Example 1, and 0.5 g of sodium bicarbonate were added in sequence. After stirring evenly, a pre-embedding agent was obtained; The pre-embedding agent was mixed with 12 g of the above-obtained denitrifying activated sludge, and 18 g of a saturated boric acid solution containing 2 wt% calcium chloride was added dropwise. The mixture was stirred and crosslinked to form spherical particles, and crosslinking and curing were continued at 4 °C for 30 min. Finally, the denitrifying sludge granules were obtained by washing.

[0047] Examples 1-2 and 1-3, a kind of denitrifying sludge granules, are different from Example 1-1 only in that the raw material ratio of the denitrifying sludge granules was adjusted, as shown in Table 1 specifically: Table 1 Raw material ratio table of Examples 1-1 to 1-3

[0048] Among them, both Example 1-2 and Example 1-3 use the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1.

[0049] Example 1-4, a denitrifying sludge granule, is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomite prepared in Preparation Example 2 is used to replace the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 in an equal amount.

[0050] Example 1-5, a denitrifying sludge granule, is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomite prepared in Preparation Example 3 is used to replace the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 in an equal amount.

[0051] Example 1-6, a denitrifying sludge granule, is prepared by the following method: Dissolve 10 g of polyvinyl alcohol (molecular weight 1750 ± 50) in 100 g of water, and sequentially add 0.4 g of glucose, 3 g of the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1, 0.5 g of sodium bicarbonate, and 2 g of ethylene-vinyl alcohol copolymer (ethylene content 38.0 mol%). After stirring evenly, a pre-embedding agent is obtained; Mix the pre-embedding agent with 12 g of the denitrifying activated sludge prepared according to Example 1-1, dropwise add 18 g of a saturated boric acid solution containing 2 wt% calcium chloride, stir and crosslink to form spherical particles, continue crosslinking and curing at 4°C for 30 min, and finally obtain denitrifying sludge granules after washing.

[0052] Example 1-7, a denitrifying sludge granule, is different from Example 1-6 only in that the addition amount of the ethylene-vinyl alcohol copolymer is 0.5 g.

[0053] Example 1-8, a denitrifying sludge granule, is different from Example 1-6 only in that the addition amount of the ethylene-vinyl alcohol copolymer is 4 g.

[0054] Comparative Example 1 Denitrifying sludge granule

[0055] Comparative Example 1-1, a denitrifying sludge granule, is different from Example 1-1 only in that the addition amount of the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 is 1 g.

[0056] Comparative Example 1-2, a denitrifying sludge granule, is different from Example 1-1 only in that the addition amount of the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 is 1 g.

[0057] Comparative Example 1-3, a denitrifying sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 is replaced with the iron oxide modified diatomite prepared in Preparation Example 4 in equal amount.

[0058] Comparative Example 1-4, a denitrifying sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 is replaced with the manganese oxide modified diatomite prepared in Preparation Example 5 in equal amount.

[0059] Comparative Example 1-5, a denitrifying sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 is replaced with the unmodified diatomite in equal amount.

[0060] Comparative Example 1-6, a denitrifying sludge granule, which is different from Example 1-1 only in that the iron-manganese composite oxide modified diatomite prepared in Preparation Example 1 is not added.

[0061] Comparative Example 1-7, a denitrifying sludge granule, which is different from Example 1-1 only in that sodium bicarbonate is not added.

[0062] Example 2 Sewage treatment process based on denitrifying sludge

[0063] Example 2-1, a treatment process based on denitrifying sludge, comprising the following process steps: Microbial sewage treatment: The rural domestic sewage is pumped by a water pump and purified for the first time through an anoxic tank, an aerobic tank and a sedimentation tank in sequence. Among them, the denitrifying sludge granules prepared in Example 1-1 are provided in the anoxic tank, and the volume filling rate of the denitrifying sludge granules prepared in Example 1-1 is 12%. Nitrifying bacteria sludge is provided in the aerobic tank. Aeration devices are provided at the bottoms of the anoxic tank and the aerobic tank. After sedimentation in the sedimentation tank, the supernatant obtained flows into the constructed wetland treatment tank, and a part of the sludge obtained is refluxed to the anoxic tank through a sludge pump, and the other part is composted. Constructed wetland treatment: The supernatant obtained by sedimentation in the sedimentation tank flows into the constructed wetland treatment tank and submerges the soil layer in the constructed wetland treatment tank for secondary purification. The soil layer is planted with landscape aquatic plants with water purification functions. After purification, the qualified effluent is discharged, and the unqualified effluent is refluxed to the anoxic tank.

[0064] Example 2-2, a treatment process based on denitrifying sludge, which is different from Example 2-1 only in that the denitrifying sludge granules prepared in Example 1-6 are used to replace the denitrifying sludge granules prepared in Example 1-1 in equal amount.

[0065] Comparative Example 2 Sewage treatment process based on denitrifying sludge

[0066] Comparative Example 2-1, a treatment process based on denitrifying sludge, is different from Example 2-1 only in that the denitrifying sludge particles prepared in Comparative Example 1-5 are used to replace the denitrifying sludge particles prepared in Example 1-1 in equal amounts.

[0067] Comparative Example 2-2, a treatment process based on denitrifying sludge, is different from Example 2-1 only in that the denitrifying sludge particles prepared in Comparative Example 1-6 are used to replace the denitrifying sludge particles prepared in Example 1-1 in equal amounts.

[0068] Comparative Example 2-3, a treatment process based on denitrifying sludge, is different from Example 2-1 only in that the denitrifying sludge particles prepared in Comparative Example 1-7 are used to replace the denitrifying sludge particles prepared in Example 1-1 in equal amounts.

[0069] Comparative Example 2-4, a treatment process based on denitrifying sludge, is different from Example 2-1 only in that the denitrifying activated sludge is used to replace the denitrifying sludge particles prepared in Example 1-1 in equal amounts.

[0070] Performance detection test

[0071] 1. Simulation test: Using rural 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 denitrifying sludge particles obtained in Example 1 and Comparative Example 1 were respectively put into the test wastewater at a volume filling rate of 12%, the batch influent volume was controlled to be 0.5 L, aerated for 6 h, the supernatant was discharged after standing for 15 min, the COD concentration of the supernatant was measured, and the COD removal rate was calculated: .

[0072] 2. Practical application test: The influent COD concentration and the COD concentration of the finally discharged water in Example 2 and Comparative Example 2 were respectively tested, and the COD removal efficiency was compared.

[0073] The above test results are shown in Table 2 and Table 3 respectively: Table 2 Test results of simulation test

[0074] Table 3 Test results of practical application test

[0075] According to Tables 2 and 3, in combination with Examples 1-1, 1-6, 2-1 and 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 diatomite, which can further improve the mechanical strength and stability of the denitrifying sludge particles, enhance the ability of the denitrifying sludge particles to block the penetration of dissolved oxygen, and at the same time promote the rapid escape of internal gas, which is beneficial to the sewage treatment efficiency of the denitrifying sludge particles. Similarly, Example 2-2 uses the denitrifying sludge particles prepared in Example 1-6, and the sewage treatment capacity is also improved.

[0076] In combination with Examples 1-1, Comparative Examples 1-1, 1-2, 1-6 and 2-2, it can be seen that the COD removal rates of Comparative Examples 1-1, 1-2 and 1-6 are decreased compared with that of Example 1-1, and the sewage treatment effect of Comparative Example 2-2 is also decreased compared with that of Example 2-1. The reason is that in Comparative Example 1-1, the addition amount of the iron-manganese composite oxide modified diatomite is reduced, so the physical barrier effect of the denitrifying sludge particles on dissolved oxygen and the adsorption and decomposition efficiency of dissolved oxygen are both decreased. The penetration of dissolved oxygen into the interior of the denitrifying sludge particles will inhibit the denitrification process of the denitrifying activated sludge, and the sewage treatment effect will be decreased. In Comparative Example 1-6, the iron-manganese composite oxide modified diatomite is not added, and under the impact of long-term high dissolved oxygen concentration, the performance of the sludge particles decreases more significantly. It can also be seen from the comparison between Comparative Example 2-2 and Example 2-1 that the sewage treatment effect will be decreased without adding the iron-manganese composite oxide modified diatomite. In Comparative Example 1-2, the addition amount of the iron-manganese composite oxide modified diatomite is increased. The addition of excessive iron-manganese composite oxide modified diatomite will block the pores on the surface of the polyvinyl alcohol-boric acid carrier. Although it can block the intrusion of dissolved oxygen, it also affects the mass transfer efficiency of the substrate, and it is difficult for the internal gas to escape, resulting in the decrease of the sludge particle performance.

[0077] In combination with Examples 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 decreased compared with that of Example 1-1, and the sewage treatment effect of Comparative Example 2-1 is also decreased compared with that of Example 2-1. The reason is that in Comparative Example 1-5, the diatomite added to the denitrifying sludge particles is not modified. Although the addition of diatomite forms a certain physical barrier structure, the unmodified diatomite has weak adsorption ability for dissolved oxygen, and dissolved oxygen can still penetrate into the interior of the sludge particles through the pores, affecting the activity of denitrifying bacteria. Especially under the impact of long-term high dissolved oxygen concentration, the denitrification process of the denitrifying sludge particles will be inhibited.

[0078] Combined with Example 1-1, Comparative Examples 1-3 and 1-4, it can be seen that the COD removal rates of Comparative Examples 1-3 and 1-4 are lower than that of Example 1-1. The reason is that in Comparative Examples 1-3 and 1-4, single metal oxide modified diatomite is used, and the decomposition reaction activity of the single metal oxide with dissolved oxygen is limited, and the structural stability also decreases, thus affecting the denitrification process of denitrifying sludge particles.

[0079] Combined with Example 1-1, Comparative Examples 1-7 and 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. The reason is that in the preparation of iron-manganese composite oxide modified diatomite in Comparative Example 1-7, sodium bicarbonate was not added, resulting in a reduction in the internal pore structure of the formed denitrifying sludge particles, a decrease in the adsorption sites of denitrifying activated sludge, and an increase in mass transfer resistance, thus affecting the denitrification process of denitrifying sludge particles.

[0080] It should be noted that in this article, relational terms such as first and second are only used 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 "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0081] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A denitrification sludge particle, characterized in that: The denitrification sludge particles 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 diatomaceous earth modified by iron-manganese composite oxide; 0.3-0.6 parts of sodium bicarbonate; 15-20 parts of cross-linking agent; 95-105 parts of water.

2. The denitrification sludge particles 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 particles 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 particles according to claim 2, characterized in that: The iron-manganese composite oxide modified diatomite is prepared according to the following method: After being dried, 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 for reaction 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 particles according to claim 1, characterized in that: The denitrification activated sludge is obtained by domesticating the residual sludge in the secondary sedimentation tank of a village sewage plant as raw material.

6. The denitrification sludge particles according to claim 1, characterized in that: The raw material of the denitrification sludge particles also includes 1 to 3 parts by weight of ethylene-vinyl alcohol copolymer.

7. The denitrification sludge particles according to claim 6, characterized in that: The denitrification sludge particles are prepared according to the following method: Dissolving polyvinyl alcohol in water, adding organic carbon source, iron-manganese composite oxide modified diatomaceous earth, sodium bicarbonate and ethylene-vinyl alcohol copolymer in sequence, stirring evenly to obtain a pre-embedding agent; The pre-embedded 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.

8. 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 domestic sewage of villages and towns through anoxic tanks, aerobic tanks and sedimentation tanks 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 7; the aerobic tank is provided with nitrifying bacteria sludge; an aeration device is 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.

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

10. The sewage treatment process based on denitrification sludge particles according to claim 8, 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, submerges the soil layer in the artificial wetland treatment tank for a second purification, and the purified effluent meets the standards and is discharged, and the effluent that does not meet the standards is returned to the anoxic tank; The soil layer is planted with landscape aquatic plants.

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