Sulfur autotrophic denitrification sewage deep denitrification deep-bed filter tank and sewage deep denitrification filtering method

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a sulfur autotrophic denitrification sewage deep denitrification deep bed filter tank and a sewage deep denitrification filtering method. A filter material is loaded in the sulfur autotrophic denitrification sewage deep nitrogen removal deep bed filter tank, the filter material comprises a ceramsite layer and a sulfur autotrophic denitrification biological carrier layer, and the ceramsite layer is located below the sulfur autotrophic denitrification biological carrier layer; the sulfur autotrophic denitrification biological carrier is prepared by mixing elemental sulfur with oyster shells, quick lime and modified hydrotalcite. According to the deep bed filter disclosed by the invention, the sulfur autotrophic denitrification biological carrier and the ceramsite form a graded filter material, so that the problem that short flow is formed due to the fact that particles become smaller after the carrier is consumed in pure sulfur autotrophic denitrification is well solved, and meanwhile, an external carbon source is not needed in a sewage treatment process; the TN of the effluent filtered by the filtering method can reach the IV-class water standard of surface water.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a sewage deep-bed filter for deep denitrification by sulfur autotrophic denitrification and a sewage deep denitrification filtration method. Background Art

[0002] At present, my country's efforts to control water pollution are constantly increasing, and the effluent standards of urban sewage treatment plants are constantly improving, from the original national standard Class B to national standard Class A, and then to the current quasi-Class IV local standards in various places. As water pollution prevention and control becomes more in-depth, the emission standards of urban sewage treatment plants will be further improved, which means that the emission standards for TN of urban sewage treatment plants will be more stringent.

[0003] Currently, municipal wastewater treatment plants primarily rely on AO biological treatment and heterotrophic denitrification biofilters for biological denitrification to remove nitrogen. However, the heterotrophic denitrification process requires an organic carbon source as an electron donor for nitrogen reduction, but the BOD5 / TN ratio in municipal wastewater is generally low. To meet TN emission requirements, an external carbon source is required for biological denitrification. This is particularly true in the heterotrophic denitrification biofilter stage, where denitrification relies primarily on an external carbon source. This use of carbon sources significantly increases wastewater treatment costs. Furthermore, the addition concentration of the external carbon source cannot be completely accurate, leading to frequent COD emissions exceeding standards.

[0004] Sulfur autotrophic denitrification is a process in which some microorganisms utilize inorganic carbon sources (such as CO3 2- and HCO3 - etc.), with reduced sulfur (H2S, S 2- 、S2O3 2- Sulfur autotrophic denitrification uses sulfur as an electron donor to complete the autotrophic denitrification process. Compared to traditional heterotrophic denitrification, it offers advantages such as requiring no organic carbon addition and lower sludge production, making it a hot topic of industry research and attention in recent years. However, sulfur autotrophic denitrification has drawbacks such as slow startup and recovery times and poor adaptability to low-temperature conditions.

[0005] Furthermore, sulfur autotrophic denitrification primarily uses solid material carriers as electron donors. These carriers are consumable and require periodic replenishment to maintain the system's denitrification capacity. Over time, the carrier's morphology and structure change, leading to uneven particle size distribution and the appearance of numerous fine particles. This can increase filter media resistance, uneven flow rate distribution, and even cause localized short-flow or blockages, requiring periodic system downtime for cleaning or replacement, significantly increasing operating and maintenance costs. Smaller particles can also flow out of the system during backwashing or operation, impacting effluent quality. Summary of the Invention

[0006] Based on the above technical background, the main object of the present invention is to provide a deep bed filter for advanced nitrogen removal from sewage by sulfur autotrophic denitrification and a method for advanced nitrogen removal from sewage by filtration, so as to overcome the deficiencies in the prior art.

[0007] To achieve the foregoing invention object, the technical solutions adopted by the present invention include: In the first aspect of the present invention, there is provided a deep bed filter for advanced nitrogen removal from sewage by sulfur autotrophic denitrification. The deep bed filter for advanced nitrogen removal from sewage by sulfur autotrophic denitrification includes a pool body, and a filter material layer is loaded in the pool body. The filter material layer includes a ceramsite layer and a sulfur autotrophic denitrification biological carrier layer, and the ceramsite layer is laid below the sulfur autotrophic denitrification biological carrier layer; The sulfur autotrophic denitrification biological carrier layer is composed of sulfur autotrophic denitrification biological carriers with a particle size of 2 - 4 mm; The sulfur autotrophic denitrification biological carrier is prepared by mixing elemental sulfur with oyster shells, quicklime, and modified hydrotalcite.

[0008] Preferably, the mass ratio of the elemental sulfur, oyster shells, quicklime, and modified hydrotalcite is 1:(1 - 1.5):(3 - 5):0.1.

[0009] More preferably, the mass ratio of the elemental sulfur, oyster shells, quicklime, and modified hydrotalcite is 1:1.2:4:0.1.

[0010] Preferably, the oyster shells are obtained by the following method: soaking the oyster shells in an organic solution for 48 - 72 h; The organic solution is selected from aqueous solutions of organic acids such as acetic acid and citric acid or the hydrolyzed supernatant of sewage plant sludge, and the total organic concentration is 500 - 1000 mg / L.

[0011] Preferably, the modified hydrotalcite is modified by the following method: mixing distearate and absolute ethanol in a mass ratio of 1:(5 - 15) to obtain a modifier; then mixing hydrotalcite and the modifier in a mass ratio of 1:(10 - 20), and then heating to 80 - 90 °C for modification for 1 - 3 h to obtain the modified hydrotalcite.

[0012] Preferably, the ceramsite layer is composed of ceramsites with a particle size of 4 - 8 mm, and the filling depth of the ceramsite layer is 1 - 3 m; The filling depth of the sulfur autotrophic denitrification biological carrier layer is 1 - 4 m.

[0013] More preferably, the filling depth of the ceramsite layer is 1.5 - 2 m; The filling depth of the sulfur autotrophic denitrification biological carrier layer is 2 - 2.5 m.

[0014] The second aspect of the present invention lies in providing a method for deep denitrification filtration of sewage. This filtration method uses the deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification described in the first aspect of the present invention. The filtration method includes: The secondary biologically treated and coagulation-sedimentation treated municipal sewage is introduced into the deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification for denitrification filtration. The hydraulic retention time of the sewage in the deep bed filter is 30 - 60 min.

[0015] The beneficial effects of the present invention are as follows: (1) In the deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification described in the present invention, filter media is loaded. The filter media includes a ceramsite layer and a sulfur autotrophic denitrification biological carrier layer. The sulfur autotrophic denitrification biological carrier (SND biological carrier) is prepared by mixing elemental sulfur with oyster shells, quicklime, and modified hydrotalcite. By using the SND biological carrier and ceramsite in graded form as filter media, Thiobacillus denitrificans can be enriched on the surface of ceramsite with a larger specific surface area. The reasonable grading makes the filtration effect of the deep bed filter better, solves the problem of increased head loss of the filter caused by the consumption of the SND biological carrier, and makes the suspended solid (SS) content in the effluent lower, solving the problems of weak enrichment ability of microorganisms and high SS in the effluent in the traditional sulfur autotrophic denitrification process.

[0016] (2) By adding oyster shell components to the SND carrier of the filter media in the present invention, the problem of the decrease in the pH of water caused by hydrogen ions generated in the traditional sulfur autotrophic denitrification process is solved; at the same time, the added modified hydrotalcite can adsorb sulfate ions generated in the sulfur autotrophic denitrification process, so that the sulfate ion concentration in the treated effluent can meet the effluent water quality requirements.

[0017] (3) In the denitrification filtration method described in the present invention, the secondary biologically treated and coagulation-sedimentation treated municipal sewage is introduced into the deep bed filter described in the present invention for treatment, and deep denitrification is achieved through sulfur autotrophic denitrification, so that the TN in the effluent can reach the surface water class IV standard. Specific embodiments

[0018] The present invention will be described in detail below, and the features and advantages of the present invention will become clearer and more definite with these descriptions.

[0019] The first aspect of the present invention lies in providing a deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification. The deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification includes a pool body, and a filter media layer is loaded in the pool body. The filter media layer includes a ceramsite layer and a sulfur autotrophic denitrification biological carrier layer, and the ceramsite layer is laid below the sulfur autotrophic denitrification biological carrier layer.

[0020] The ceramsite layer is composed of ceramsite with a particle size of 4 - 8 mm, and the filling depth of the ceramsite layer is 1 - 3 m, preferably 1.5 - 2 m.

[0021] The sulfur autotrophic denitrification biological carrier layer is composed of sulfur autotrophic denitrification biological carriers (SND biological carriers) with a particle size of 2-4 mm. The filling depth of the sulfur autotrophic denitrification biological carrier layer is 1-4 m, and preferably the filling depth is 2-2.5 m.

[0022] The sulfur autotrophic denitrification biological carrier is prepared by mixing elemental sulfur with oyster shells, quicklime, and modified hydrotalcite.

[0023] Preferably, the mass ratio of the elemental sulfur, oyster shells, quicklime, and modified hydrotalcite is 1:(1-1.5):(3-5):0.1.

[0024] More preferably, the mass ratio of the elemental sulfur, oyster shells, quicklime, and modified hydrotalcite is 1:1.2:4:0.1.

[0025] In the present invention, the oyster shells are obtained by the following method: soaking the oyster shells in an organic solution for 48-72 h.

[0026] The organic solution is selected from aqueous solutions of organic acids such as acetic acid and citric acid or the hydrolyzed supernatant of sewage plant sludge, and the total organic matter concentration is 500-1000 mg / L.

[0027] Preferably, the oyster shells are obtained by the following method: soaking the oyster shells in the hydrolyzed supernatant of sewage plant sludge or an aqueous solution of citric acid for 60 h.

[0028] After being soaked in the organic solution, the surface activity of the oyster shells can be improved, the dissolution rates of organic matter and calcium carbonate can be increased, and the alkaline substances dissolved in the sewage treatment reaction can neutralize the hydrogen ions generated in the sulfur autotrophic denitrification process, enabling Thiobacillus denitrificans to grow in an environment with a pH of 7-7.5, which is beneficial to improving the sewage treatment effect and treatment efficiency.

[0029] The modified hydrotalcite is obtained by the following method: Mixing distearate and absolute ethanol in a mass ratio of 1:(5-15) to obtain a modifier; then mixing hydrotalcite and the modifier in a mass ratio of 1:(10-20), and subsequently heating to 80-90 °C for modification for 1-3 h to obtain the modified hydrotalcite.

[0030] Preferably, the modified hydrotalcite is obtained by the following method: mixing distearate and absolute ethanol in a mass ratio of 1:10 to obtain a modifier; then mixing hydrotalcite and the modifier in a mass ratio of 1:16, and subsequently heating to 85 °C for modification for 2 h to obtain the modified hydrotalcite.

[0031] The modified hydrotalcite obtained by the above method can adsorb sulfate ions generated in the sulfur autotrophic denitrification process, ensuring that the sulfate ions in the effluent are maintained within a certain range, so that the sulfate concentration in the treated effluent can meet the requirements of the effluent.

[0032] The second aspect of the present invention lies in providing a method for deep denitrification filtration of sewage. This filtration method uses the deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification described in the first aspect of the present invention. The filtration method includes: The municipal sewage after secondary biological treatment and coagulation sedimentation treatment is introduced into the deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification for denitrification filtration. The hydraulic retention time of the sewage in the deep bed filter is 30 - 60 min, preferably 45 min. Example

[0033] The present invention is further illustrated by the following specific examples. These examples are only for illustrating the present invention and are not used to limit the scope of the present invention.

[0034] The raw materials (except oyster shells and modified hydrotalcite) used in the examples of the present invention were all purchased.

[0035] The oyster shells were obtained by the following method: The oyster shells were soaked in an aqueous citric acid solution (the concentration of citric acid was 700 mg / L) for 60 h.

[0036] The modified hydrotalcite was obtained by the following method: Dioctyl phthalate and absolute ethanol were mixed in a mass ratio of 1:10 to obtain a modifier; then the hydrotalcite and the modifier were mixed in a mass ratio of 1:16, and then the temperature was raised to 85°C for modification for 2 h to obtain the modified hydrotalcite. Example

[0037] Taking the domestic sewage treatment in Taibus Banner, Xilingol League, Inner Mongolia as an example, the domestic sewage after secondary biological treatment and coagulation sedimentation treatment was introduced into the deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification for denitrification filtration. The influent volume of the sewage treatment plant was 9000 - 11000 m 3 / d, and the hydraulic retention time of the sewage in the deep bed filter was 45 min. The average concentration of chemical oxygen demand (COD) in the domestic sewage after biochemical treatment and coagulation sedimentation was 33.05 mg / L, the average concentration of biochemical oxygen demand (BOD5) was 4.85 mg / L, the average concentration of total nitrogen (TN) was 21.5 mg / L, the average concentration of suspended solids (SS) was 19.5 mg / L, and the average pH value was 7.25. The total filtration area of the deep bed filter for deep denitrification of sewage by sulfur autotrophic denitrification was 72 m 2(Divided into two grids, each with an area size of 6m * 6m), the deep bed filter is filled with filter media. The filter media includes a ceramsite layer and a sulfur autotrophic denitrification biological carrier layer. The ceramsite layer is located below the sulfur autotrophic denitrification biological carrier layer. The total filling height of the filter media is 4.2m. Among them, the ceramsite layer is composed of ceramsite filter media with an average particle size of 4 - 6mm, and the height of the ceramsite layer is 1.8m. The sulfur autotrophic denitrification biological carrier layer is composed of SND biological carriers with an average particle size of 2 - 4mm, and the height of the sulfur autotrophic denitrification biological carrier layer is 2.4m. The SND biological carrier is obtained by mixing elemental sulfur, oyster shells, quicklime, and modified hydrotalcite in a mass ratio of 1:1.2:4:0.1.

[0038] After the sewage is treated by this deep bed filter, the water quality of the effluent is detected. Among them, COD is determined by the national standard GB11914 - 89 chemical oxygen demand, BOD5 is tested by the standard dilution method, SS is determined by the GB11901 - 89 gravimetric method, TN is determined by the alkaline potassium persulfate digestion ultraviolet spectrophotometry, and pH is determined by the GB / T6920 - 1986 glass electrode method. The water quality of the effluent from January 7th to January 26th is monitored, and the test results are shown in Table 1.

[0039] Table 1

[0040] As can be seen from Table 1, after being treated by this deep bed filter, the average concentration of COD in the effluent is 22.17mg / L, the average concentration of BOD5 is 5mg / L, the average concentration of TN is 4.66mg / L, the average concentration of SS is 6.19mg / L, and the average value of pH is 7.29.

[0041] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A deep bed filter for advanced nitrogen removal from sewage by sulfur autotrophic denitrification, characterized in that, The deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification includes a tank body, in which a filter material layer is loaded. The filter material layer includes a ceramsite layer and a sulfur autotrophic denitrification biological carrier layer, and the ceramsite layer is laid below the sulfur autotrophic denitrification biological carrier layer; The sulfur autotrophic denitrification biological carrier layer is composed of sulfur autotrophic denitrification biological carriers with a particle size of 2 - 4 mm; The sulfur autotrophic denitrification biological carrier is prepared by mixing elemental sulfur with oyster shells, quicklime, and modified hydrotalcite.

2. The deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification according to claim 1, characterized in that, The mass ratio of the elemental sulfur, oyster shells, quicklime, and modified hydrotalcite is 1:(1 - 1.5):(3 - 5):0.

1.

3. The deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification according to claim 2, characterized in that, The mass ratio of the elemental sulfur, oyster shells, quicklime, and modified hydrotalcite is 1:1.2:4:0.

1.

4. The deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification according to claim 2, characterized in that, The oyster shells are obtained by the following method: soaking the oyster shells in an organic solution for 48 - 72 h; The organic solution is selected from aqueous solutions of organic acids such as acetic acid and citric acid or the hydrolyzed supernatant of sewage plant sludge, and the total organic concentration is 500 - 1000 mg / L.

5. The deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification according to claim 2, characterized in that, The modified hydrotalcite is obtained by the following method: mixing distearate and absolute ethanol according to a mass ratio of 1:(5 - 15) to obtain a modifier; then mixing hydrotalcite and the modifier according to a mass ratio of 1:(10 - 20), and then heating to 80 - 90 °C for modification for 1 - 3 h to obtain it.

6. The deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification according to claim 1, characterized in that, The ceramsite layer is composed of ceramsite with a particle size of 4 - 8 mm, and the filling depth of the ceramsite layer is 1 - 3 m; The filling depth of the sulfur autotrophic denitrification biological carrier layer is 1 - 4 m.

7. The deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification according to claim 6, characterized in that, The filling depth of the ceramsite layer is 1.5 - 2 m; The filling depth of the sulfur autotrophic denitrification biological carrier layer is 2 - 2.5 m.

8. A method for deep denitrification filtration of sewage, characterized in that, This filtration method uses the deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification according to any one of claims 1 to 7 for filtration. The filtration method includes: Passing the urban sewage after secondary biological treatment and coagulation sedimentation treatment into the deep bed filter for advanced nitrogen removal of sewage by sulfur autotrophic denitrification for nitrogen removal filtration, and the hydraulic retention time of the sewage in the deep bed filter is 30 - 60 min.

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