Fly ash-based ceramsite filter material for biological aerated filter as well as preparation method and application of fly ash-based ceramsite filter material

Abstract

The invention relates to the technical field of sewage treatment, in particular to a preparation method and application of a fly ash-based ceramsite filter material for a biological aerated filter, fly ash, red mud, coal gangue and a pore-forming agent are added, mixed, granulated, sintered for about 20 minutes at 1050-1120 DEG C and cooled to prepare ceramsite. The filter material is high in void ratio, large in specific surface area, resistant to acid and alkali, suitable for a biological aerated filter, beneficial to rapid biofilm formation and improvement of wastewater purification efficiency, especially capable of effectively removing chloride ions in desulfurization wastewater, capable of being recycled and capable of promoting solid waste recycling. Compared with a traditional clay filter material, the filter material has the advantages that the operation cost is reduced, the environmental protection benefit is improved, and the filter material is widely applicable to biochemical treatment and advanced treatment of domestic sewage and industrial wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a fly ash-based ceramsite filter material for an aerated biological filter tank and a preparation method and application thereof. Background Art

[0002] Among sewage treatment technologies, the biofilm method stands out for its high efficiency, among which the biological aerated filter (BAF) is particularly prominent. The BAF system removes pollutants through biological oxidation and physical interception of the biofilm on the filter material, and backwashes regularly to maintain its treatment efficiency. It can effectively remove suspended solids, organic matter, nitrogen, phosphorus and carbon, and is widely used in various sewage treatments due to its small footprint, simple process and low cost.

[0003] The filter material is the core of BAF, and its surface structure and physical and chemical properties directly affect the formation of biofilm and the efficiency of the system. Traditional filter materials such as shale, kaolin and clay ceramsite have the advantages of large specific surface area, rough surface, good porosity, strong adsorption capacity, strong biological adhesion, and good biofilm effect, which are conducive to the attachment and growth of microorganisms on the surface of ceramsite, but they are non-renewable resources, with high mining costs and harmful to the environment. Fly ash and red mud are solid wastes from coal-fired power plants and bauxite refining. Their components are rich in Al2O3, SiO2, Fe2O3, etc. In particular, the high alkali content in red mud limits its direct application, but it can adjust the composition, enhance bonding and reduce the sintering temperature when preparing ceramsite filter materials. Therefore, the use of fly ash and red mud to prepare BAF ceramsite filter materials not only reduces the cost of sewage treatment, but also realizes the resource utilization and harmless treatment of industrial solid waste, promotes the circular economy model of "waste treatment with waste", and shows significant comprehensive benefits in the fields of economy, society and environmental protection.

[0004] Therefore, there is an urgent need to develop a ceramsite filter material that can not only recycle a variety of solid wastes, but also be used in aerated biological filters. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, the present invention provides a fly ash-based ceramsite filter material for aerated biological filter tanks and its preparation method and application, aiming to overcome the adverse effects of cultivated land destruction caused by traditional clay-fired ceramsite filter material, and utilize the main mineral components of industrial solid wastes such as fly ash, red mud, and coal gangue, which are similar to clay, to mix and granulate these solid wastes and then roast them to prepare fly ash-based ceramsite filter material for aerated biological filter tanks, so as to realize resource utilization of filter material. And the filter material is applied to sewage treatment in different industries to achieve the purpose of treating waste with waste, thereby protecting the environment, saving resources, and improving the sewage treatment effect.

[0006] Specifically, the present invention provides a fly ash-based ceramsite filter material for an aerated biological filter, which is prepared from the following components by weight percentage:

[0007] Fly ash 60%~80%, red mud 5%~25%, coal gangue 3%~10%, pore-forming agent 5%~20%.

[0008] In some specific embodiments of the present invention, the catalyst is prepared from the following components by weight: 65% high-alumina fly ash, 15% red mud, 5% coal gangue, and 15% sludge.

[0009] In some specific embodiments of the present invention, the invention is prepared from the following components by weight percentage: 68% high-alumina fly ash, 16% red mud, 8% coal gangue, and 8% rice husk.

[0010] In some specific embodiments of the present invention, the catalyst is prepared from the following components by weight: 68% high-alumina fly ash, 17% red mud, 10% coal gangue, and 8% limestone.

[0011] In some specific embodiments of the present invention, the composition is prepared from the following components by weight percentage:

[0012] Fly ash 60%~70%, red mud 10%~15%, coal gangue 3%~10%, pore-forming agent 10%~15%.

[0013] In some specific embodiments of the present invention, the chemical composition of the red mud is as follows: 15-25% Al2O3, 18-25% SiO2, 20-30% Fe2O3, the loss on ignition of the red mud is 10-20%, and the plasticity index is 5-7.

[0014] In some specific embodiments of the present invention, the fly ash is high-aluminum fly ash, and the chemical composition of the high-aluminum fly ash is as follows: 40% to 50% Al2O3, the total percentage of Al2O3, SiO2 and Fe2O3 is between 85% and 95%, the loss on ignition of the high-aluminum fly ash is ≤2%; the particle size of the high-aluminum fly ash is 45μm and the residue on sieve is ≤50%.

[0015] In some specific embodiments of the present invention, the pore former is at least one of limestone, rice bran and sludge.

[0016] In some specific embodiments of the present invention, the pore former is one of limestone, rice bran and sludge.

[0017] In some specific embodiments of the present invention, the sludge is pharmaceutical sludge, and the loss on ignition is 40% to 50%.

[0018] The present invention also provides a method for preparing fly ash-based ceramsite filter material for an aerated biological filter, comprising the following preparation steps:

[0019] S1. Raw material pretreatment: drying and grinding red mud to obtain red mud powder; crushing and grinding coal gangue to obtain coal gangue powder, the red mud powder and coal gangue powder after grinding have a particle size range of 150 to 200 meshes; when sludge or limestone is selected as a pore-forming agent, it is necessary to dry and grind it to obtain a pore-forming agent powder, and its particle size range is also 150 to 200 meshes; when the pore-forming agent is rice bran, there is no need to perform a grinding step, and the rice bran can be used directly;

[0020] S2. Raw material ratio: weigh the raw materials according to the following weight percentages: 60% to 80% fly ash, 5% to 25% red mud, 3% to 10% coal gangue, 5% to 20% pore-forming agent, and then put the weighed raw materials into a mixer and stir evenly;

[0021] S3. Water spray granulation: The mixed raw materials are transported to a disc granulator and water spray granulated to prepare ceramsite filter raw balls;

[0022] S4. Sintering and granulation: The filter material raw material balls are sintered in a single barrel rotary kiln to obtain fly ash based ceramsite filter material for aerated biological filter.

[0023] In some specific embodiments of the present invention, the raw materials in S2 are weighed according to the following weight percentages: fly ash 60% to 70%, red mud 10% to 15%, coal gangue 3% to 10%, and pore former 10% to 15%.

[0024] In some specific embodiments of the present invention, the sintering temperature range in the single-barrel rotary kiln in S4 is 1050-1120° C., and the sintering time is 15-30 min.

[0025] In some specific embodiments of the present invention, the chemical composition of the red mud is as follows: 15% to 25% Al2O3, 18% to 25% SiO2, 20% to 30% Fe2O3, the loss on ignition of the red mud is 10 to 20%, and the plasticity index is 5 to 7; the fly ash is high-aluminum fly ash, and the chemical composition of high-aluminum fly ash is as follows: 40% to 50% Al2O3, the total percentage of Al2O3, SiO2 and Fe2O3 is between 85% and 95%, and the loss on ignition of the high-aluminum fly ash is ≤2%; the particle size of the high-aluminum fly ash is 45μm and the sieve residue is ≤50%; the pore-forming agent is at least one of limestone, rice bran and sludge.

[0026] The present invention also provides the use of any of the above-mentioned fly ash-based ceramsite filter materials for aerated biological filters or the ceramsite filter materials prepared by the above-mentioned method for preparing fly ash-based ceramsite filter materials for aerated biological filters in aerated biological filters for treating sewage.

[0027] In some specific embodiments of the present invention, the application includes the following application steps: placing the ceramsite filter material in each layer of the tower body of the packed absorption tower, and the amount of the ceramsite filter material fills 70% to 85% of the volume of the aerated biological filter tank; injecting sewage into the water tank at the bottom of the tower, and adding activated sludge; after the sewage is continuously aerated for 24 hours, the sewage is pumped into the filter column for treatment, the circulating water flow rate is set to 200L / h, and the system runs continuously for 10 to 20 days.

[0028] In some specific embodiments of the present invention, the sewage is sewage containing chloride ions.

[0029] In some specific embodiments of the present invention, ceramsite filter material is placed in each layer of the three-layer tower body of the packed absorption tower, and the amount of the ceramsite filter material fills 70% to 85% of the volume of the aerated biological filter tank; domestic sewage or industrial wastewater is injected into the water tank, activated sludge is added to the water tank, and the sewage is continuously aerated. After the sewage is continuously aerated for 24 hours, the sewage is pumped into the filter column for treatment, the circulating water flow rate is set to 200L / h-300L / h, and it is continuously operated for 10 to 20 days.

[0030] In some specific embodiments of the present invention, ceramsite filter material is placed in each layer of the three-layer tower body of the packed absorption tower, and the amount of the ceramsite filter material fills 70% to 85% of the volume of the aerated biological filter tank; domestic sewage or industrial wastewater is injected into the water tank, activated sludge is added to the water tank, and the sewage is continuously aerated. After the sewage is continuously aerated for 24 hours, the sewage is pumped into the filter column for treatment, the circulating water flow rate is set to 200L / h, and it is continuously operated for 10 to 20 days.

[0031] In some specific embodiments of the present invention, the ceramsite filter material is used in an amount that fills 75% of the volume of the aerated biological filter.

[0032] Compared with the prior art, the present invention has the following significant advantages and effects:

[0033] 1. Efficient pollutant removal: The fly ash-based ceramsite filter material of the present invention can effectively remove suspended solids, chemical oxygen demand (COD), ammonia nitrogen (NH4 + -N) and chloride ions (Cl-), especially the removal effect of chloride ions is particularly significant, which provides a new idea for the comprehensive utilization of industrial solid waste and improves the overall effect of wastewater treatment.

[0034] 2. Excellent regeneration performance: After backwashing, the filter material can completely restore its original filtering performance, ensuring the continuous and efficient operation of the system.

[0035] 3. Biocompatibility and economy: Compared with the traditional aerated biological filter media, the fly ash-based ceramsite filter media of the present invention has better biocompatibility, supports the good growth of microbial communities, and greatly reduces the operating costs due to its reusability.

[0036] 4. Environmentally friendly production process: The present invention adopts industrial solid wastes such as sludge and rice bran as pore-forming agents to replace traditional chemicals. The prepared filter material has a uniform pore structure, high porosity and specific surface area, and enhances corrosion resistance, wear resistance and erosion resistance, thereby improving the wastewater purification efficiency.

[0037] 5. Optimized firing technology: The fly ash ceramsite filter material fired in a single-drum rotary kiln simplifies the production process, and the temperature gradient distribution is more reasonable, which is conducive to improving product quality. The longer firing zone temperature ensures sufficient firing reaction and improves the performance of the filter material.

[0038] 6. Efficient utilization of resources: The present invention breaks through the tradition in the selection of raw materials and uses a variety of industrial solid wastes such as fly ash, red mud, and coal gangue. The utilization rate of solid waste exceeds 90%, realizing the high added value transformation and utilization of industrial solid waste, with obvious economic and environmental benefits.

[0039] 7. Cost control: The introduction of red mud as an iron source not only effectively reduces the sintering temperature and energy consumption, but also exhibits a certain degree of adhesion due to its high sodium oxide content, which helps to reduce the use of binders, thereby further reducing production costs.

[0040] In summary, the present invention not only provides a new type of aerated biological filter material, but also its unique preparation method and application process enable the filter material to demonstrate significant technical advantages in the actual wastewater treatment process, which is of great significance to promoting the advancement of industrial wastewater and domestic sewage treatment technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a diagram showing the effect of pollutant removal in domestic sewage after the operation of the fly ash-based ceramsite filter material in Example 4;

[0043] Figure 2 This is a graph showing the effect of removing chloride ions from desulfurization wastewater during the start-up and operation of the fly ash-based ceramsite filter film in Example 5;

[0044] Figure 3 This is a diagram showing the effect of pollutant removal in desulfurization wastewater after the operation of the fly ash-based ceramsite filter material in Example 5;

[0045] Figure 4 This is a diagram showing the effect of fly ash-based ceramsite filter material in Example 5 treating desulfurization wastewater without film formation;

[0046] Figure 5 is a surface SEM image of the fly ash-based ceramsite filter material prepared in Example 1;

[0047] Figure 6 is a surface SEM image of the fly ash-based ceramsite filter material prepared in Example 1;

[0048] Figure 7 is a cross-sectional SEM image of the fly ash-based ceramsite filter material prepared in Example 1;

[0049] Figure 8 is a cross-sectional SEM image of the fly ash-based ceramsite filter material prepared in Example 1;

[0050] Fig. 9 It is the XRD diagram of the fly ash-based ceramsite filter material prepared in Example 1. DETAILED DESCRIPTION

[0051] In conjunction with specific embodiments, the present invention will be further described. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the application.

[0052] Example 1: Preparation of fly ash-based ceramsite filter material (pore-forming agent is sludge) for aerated biological filter

[0053] Prepare raw materials of red mud, sewage sludge, coal gangue and high-aluminum fly ash, the chemical composition of the red mud is as follows: 15-25% Al2O3, 18-25% SiO2, 20-30% Fe2O3, the loss on ignition of the red mud is 10-20%, and the plasticity index is 5-7; the chemical composition of the high-aluminum fly ash is as follows: 40%-50% Al2O3, the total percentage of Al2O3, SiO2 and Fe2O3 is between 85% and 95%, and the loss on ignition of the high-aluminum fly ash is ≤2%; the particle size of the high-aluminum fly ash is 45μm and the sieve residue is ≤50%;

[0054] S1. Raw material grinding: The red mud and sludge were dried and ground to obtain red mud powder and sludge powder, and the gangue was crushed and ground to obtain gangue powder. The red mud powder, sludge powder and gangue powder after grinding had a particle size of 150-200 mesh;

[0055] S2. Raw material ratio: weigh the raw materials according to the following weight percentages: 65% high-alumina fly ash, 15% red mud, 5% coal gangue, 15% sludge, and then put the weighed raw materials into a mixer and stir evenly;

[0056] S3. Water spray granulation: The mixed raw materials are transported to the disc granulator and water spray granulated to prepare ceramsite filter raw balls of about 10 mm;

[0057] S4. Sintering and granulation: The filter material raw material balls are sintered in a single barrel rotary kiln at a sintering temperature of 1100° C. for 20 min to obtain fly ash-based ceramsite filter material for aerated biological filter.

[0058] The fly ash-based ceramsite filter material prepared above for aerated biological filter was tested, and the bulk density of the fly ash-based ceramsite filter material was determined to be 856.5 kg / m 3 , the porosity is 48.96% and the specific surface area is 1.1cm 2 / g, the sum of the crushing rate and the wear rate is 0.88%, the mud content is 0.70%, and the hydrochloric acid solubility is 0.1%.

[0059] Example 2: Preparation of fly ash-based ceramsite filter material (pore-forming agent is rice bran) for aerated biological filter

[0060] Prepare raw materials of red mud, rice bran (particle size ≤ 1.5 mm), coal gangue and high-aluminum fly ash, the chemical composition of the red mud is as follows: 15-25% Al2O3, 18-25% SiO2, 20-30% Fe2O3, the loss on ignition of the red mud is 10-20%, and the plasticity index is 5-7; the chemical composition of the high-aluminum fly ash is as follows: 40%-50% Al2O3, the total percentage of Al2O3, SiO2 and Fe2O3 is between 85% and 95%, and the loss on ignition of the high-aluminum fly ash is ≤ 2%; the particle size of the high-aluminum fly ash is 45 μm and the sieve residue is ≤ 50%;

[0061] S1. Raw material grinding: The red mud and sludge were dried and ground to obtain red mud powder and sludge powder, and the gangue was crushed and ground to obtain gangue powder. The red mud powder, sludge powder and gangue powder after grinding had a particle size of 150-200 mesh;

[0062] S2. Raw material ratio: weigh the raw materials according to the following weight percentages: 68% high-alumina fly ash, 16% red mud, 8% coal gangue, 8% rice bran, and then put the weighed raw materials into a mixer and stir evenly;

[0063] S3. Water spray granulation: The mixed raw materials are transported to the disc granulator and water spray granulated to prepare ceramsite filter raw balls of about 10 mm;

[0064] S4. Sintering and granulation: The filter material raw material balls are sintered in a single barrel rotary kiln at a sintering temperature of 1050°C for 20 minutes to obtain fly ash-based ceramsite filter material for aerated biological filter.

[0065] The fly ash-based ceramsite filter material prepared above for aerated biological filter was tested, and the bulk density of the fly ash-based ceramsite filter material was determined to be 810.5 kg / m 3 , the porosity is 46.78% and the specific surface area is 0.93cm 2 / g, the sum of the crushing rate and the wear rate is 0.72%, the mud content is 0.25%, and the hydrochloric acid solubility is 0.08%.

[0066] Example 3: Preparation of fly ash-based ceramsite filter material (pore-forming agent is limestone) for aerated biological filter

[0067] Prepare raw materials red mud, limestone, coal gangue and high-alumina fly ash. The chemical composition of the red mud is as follows:

[0068] 15-25% Al2O3, 18-25% SiO2, 20-30% Fe2O3, the loss on ignition of the above-mentioned red mud is 10-20%, and the plasticity index is 5-7; the chemical composition of the above-mentioned high-aluminum fly ash is as follows: 40%-50% Al2O3, the total percentage of Al2O3, SiO2 and Fe2O3 is between 85% and 95%, so the loss on ignition of the above-mentioned high-aluminum fly ash is ≤2%; the particle size of the above-mentioned high-aluminum fly ash is 45μm sieve residue ≤50%; the loss on ignition of the above-mentioned limestone is 42.35%, calcium oxide is 44.62%, and the 45μm sieve residue is ≤45.2%.

[0069] S1. Raw material grinding: The red mud and sludge were dried and ground to obtain red mud powder and sludge powder, and the gangue was crushed and ground to obtain gangue powder. The red mud powder, sludge powder and gangue powder after grinding had a particle size of 150-200 mesh;

[0070] S2. Raw material ratio: weigh the raw materials according to the following weight percentages: 68% high-alumina fly ash, 17% red mud, 10% coal gangue, 8% limestone, and then put the weighed raw materials into a mixer and stir evenly;

[0071] S3. Water spray granulation: The mixed raw materials are transported to the disc granulator and water spray granulated to prepare ceramsite filter raw balls of about 10 mm;

[0072] S4. Sintering and granulation: The filter material raw material balls are sintered in a single barrel rotary kiln at a sintering temperature of 1120° C. for 20 min to obtain fly ash-based ceramsite filter material for aerated biological filter.

[0073] The fly ash-based ceramsite filter material prepared above for aerated biological filter was tested, and the bulk density of the fly ash-based ceramsite filter material was determined to be 905 kg / m 3 , the porosity is 51.4% and the specific surface area is 1.03cm 2 / g, the sum of the crushing rate and the wear rate is 1.25%, the mud content is 0.48%, and the hydrochloric acid solubility is 0.15%.

[0074] Example 4: Application of the ceramsite filter material prepared in Example 1 in sewage treatment by aerated biological filter

[0075] The domestic sewage of a certain factory was taken as the treatment object, with initial suspended solids of 18.5 mg / L, COD of 129 mg / L, chloride ions of 409 mg / L, and ammonia nitrogen of 61.3 mg / L. The aerated biological filter reactor was filled with fly ash-based ceramsite filter material (prepared in Example 1) accounting for 75% of the volume in three layers. Commercially available water treatment activated sludge was placed in a water tank, and after the sewage was filled, continuous aeration was performed in the sewage. After the sewage was continuously aerated for 24 hours, the sewage was pumped into the filter column for treatment. The circulating water flow rate was set to 200 L / h, the gas-water ratio was 3:1, and it was continuously operated for 15 days.

[0076] Finally, the average suspended solids in the water supernatant was 1.43 mg / L, with an average removal rate of 92.27%, the average COD was 13.5 mg / L, with an average removal rate of 89.53%, the average chloride ion was 112.0 mg / L, with an average removal rate of 72.62%, and the average ammonia nitrogen was 22.0 mg / L, with an average removal rate of 64.11%. The pollutant removal effect diagram is as shown in the attached figure. Figure 1 shown.

[0077] Example 5: Comparative test of sewage treatment effect of ceramsite filter material in aerated biological filter with and without biofilm formation

[0078] Implementation Plan 1: Wastewater Treatment under Biofilm Conditions

[0079] The desulfurization wastewater of a power plant was taken as the treatment object, with initial suspended solids of 37.47 mg / L, COD of 379 mg / L, chloride ions of 14387 mg / L, ammonia nitrogen of 279 mg / L, and total phosphorus of 56 mg / L. The aerated biological filter reactor was filled with fly ash-based ceramsite filter material (prepared in Example 1) accounting for 75% of the volume in three layers, and commercially available water treatment activated sludge was placed in the water tank. After the sewage was filled, continuous aeration was performed in the sewage. After the sewage was continuously aerated for 24 hours, the sewage was pumped into the filter column for treatment, the circulating water flow rate was set to 200 L / h, the gas-water ratio was 3:1, and it was continuously operated for 15 days.

[0080] Finally, the average suspended solids in the supernatant was 2.53 mg / L, with a removal rate of 93.25%, the average COD was 67 mg / L, with a removal rate of 82.32%, the average total phosphorus was 45 mg / L, with a removal rate of 19.64%, the average ammonia nitrogen was 132 mg / L, with a removal rate of 52.69%, and the average chloride ion was 12185 mg / L, with an average removal rate of 15.31%. The chloride ion removal effect diagram in the desulfurization wastewater during the start-up and operation of the biofilm is shown in the attached figure. Figure 2 As shown; the effect diagram of pollutant removal in desulfurization wastewater is shown in the attached Figure 3 shown.

[0081] Implementation Plan 2: Wastewater Treatment without Biofilm Formation

[0082] The desulfurization wastewater of a power plant was taken as the treatment object, with initial suspended solids of 37.47 mg / L, COD of 379 mg / L, chloride ions of 14387 mg / L, ammonia nitrogen of 279 mg / L, and total phosphorus of 56 mg / L. The aerated biological filter reactor was filled with fly ash-based ceramsite filter material (prepared in Example 1) accounting for 75% of the volume in three layers, and after being filled with sewage, continuous aeration was performed in the sewage. After the sewage was continuously aerated for 24 hours, the sewage was pumped into the filter column for treatment, the circulating water flow rate was set to 200 L / h, the gas-water ratio was 3:1, and it was continuously operated for 15 days.

[0083] The final removal rate of suspended solids in the effluent was 97.35%, COD removal rate was 37.14%, total phosphorus removal rate was 3.65%, ammonia nitrogen removal rate was 16.67%, and chloride ion removal rate was basically zero. The effect diagram of desulfurization wastewater treatment without biofilm is shown in the attached figure. Figure 4 shown.

[0084] Comparative tests of implementation plans 1 and 2 show that under biofilm conditions, fly ash-based ceramsite filter media can effectively remove suspended solids, COD, ammonia nitrogen and chloride ions in wastewater through the synergistic effect of physical adsorption and biodegradation. In the absence of biofilm, the removal effect of the filter media on chloride ions is almost zero, which shows the importance of microbial biofilm for chloride ion removal. In addition, the removal effect of the filter media after biofilm formation on other pollutants is also significantly better than that of the non-biofilm state.

[0085] Example 6: Application of the ceramsite filter material prepared in Example 2 in sewage treatment by aerated biological filter

[0086] The desulfurization wastewater of a power plant was taken as the treatment object, with initial suspended solids of 37.47 mg / L, COD of 379 mg / L, chloride ions of 14387 mg / L, ammonia nitrogen of 279 mg / L, and total phosphorus of 56 mg / L. The aerated biological filter reactor was filled with fly ash-based ceramsite filter material (prepared in Example 2) accounting for 75% of the volume in three layers, and commercially available water treatment activated sludge was placed in the water tank. After the sewage was filled, continuous aeration was performed in the sewage. After the sewage was continuously aerated for 24 hours, the sewage was pumped into the filter column for treatment, the circulating water flow rate was set to 200 L / h, the gas-water ratio was 3:1, and it was continuously operated for 15 days.

[0087] The final determination showed that the average suspended solids in the water supernatant was 3.85 mg / L, with a removal rate of 89.73%, the average COD was 85 mg / L, with a removal rate of 77.57%, the average total phosphorus was 40.5 mg / L, with a removal rate of 27.68%, the average ammonia nitrogen was 137 mg / L, with a removal rate of 50.9%, and the average chloride ion was 11079 mg / L, with an average removal rate of 23%.

[0088] Example 6: Application of the ceramsite filter material prepared in Example 3 in sewage treatment by aerated biological filter

[0089] The desulfurization wastewater of a power plant was taken as the treatment object, with an initial suspended solid of 45.8 mg / L, COD of 426 mg / L, chloride ion of 13849 mg / L, ammonia nitrogen of 316 mg / L, and total phosphorus of 48.5 mg / L. The aerated biological filter reactor was filled with fly ash-based ceramsite filter material (prepared in Example 3) accounting for 75% of the volume in three layers, and commercially available water treatment activated sludge was placed in the water tank. After the sewage was filled, continuous aeration was performed in the sewage. After the sewage was continuously aerated for 24 hours, the sewage was pumped into the filter column for treatment, the circulating water flow was set to 200 L / h, the gas-water ratio was 3:1, and it was continuously operated for 15 days.

[0090] The final determination showed that the average suspended solids in the water supernatant was 4.58 mg / L, with a removal rate of 90%, the average COD was 78 mg / L, with a removal rate of 81.9%, the average total phosphorus was 22.5 mg / L, with a removal rate of 53.61%, the average ammonia nitrogen was 152 mg / L, with a removal rate of 51.9%, and the average chloride ion was 10287.5 mg / L, with an average removal rate of 25.72%.

[0091] Example 7: SEM and XRD characterization of the ceramsite filter material prepared in Example 1

[0092] In order to further explore the reaction mechanism of fly ash-based ceramsite filter material in treating wastewater, scanning electron microscopy (SEM), X-ray diffractometer (XRD) and energy dispersive spectrometer were used to comprehensively characterize the fly ash-based ceramsite filter material. The results are as follows: Figures 5 to 9 shown.

[0093] Through SEM observation, it is found that the surface of fly ash-based ceramsite is rough and undulating. There are a large number of holes distributed widely on its inner and outer surfaces, which is very conducive to the attachment, fixation and biofilm formation of microorganisms. At the same time, the number of surface pores of fly ash-based ceramsite filter materials is small, while the internal pores are extremely developed. The distribution of pores between the skeletons makes the internal structure of ceramsite relatively loose, which has the advantages of light bulk density and low water absorption rate.

[0094] XRD analysis results show that the crystal structure of fly ash ceramsite is mainly composed of oxides and silicates, among which the main crystal phases are quartz and mullite.

[0095] In summary, the fly ash-based ceramsite filter material for aerated biological filter prepared by the present invention can fully meet the strict requirements of aerated biological filter for filter material in terms of microstructure. This makes the aerated biological filter more advantageous in the biofilm formation stage, can achieve rapid start-up, and shows extremely broad application prospects in the field of wastewater treatment.

[0096] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fly ash-based ceramsite filter material for an aerated biological filter, characterized in that: The composition is prepared from the following components by weight percentage: Fly ash 60%~80%, red mud 5%~25%, coal gangue 3%~10%, pore-forming agent 5%~20%.

2. The fly ash-based ceramsite filter material for aerated biological filter according to claim 1, characterized in that: The chemical composition of the red mud is as follows: 15% to 25% Al2O3, 18% to 25% SiO2, 20% to 30% Fe2O3, the loss on ignition of the red mud is 10% to 20%, and the plasticity index is 5 to 7.

3. The fly ash-based ceramsite filter material for aerated biological filter according to claim 1, characterized in that: The fly ash is high-aluminum fly ash, and the chemical composition of the high-aluminum fly ash is as follows: 40% to 50% Al2O3, the total percentage of Al2O3, SiO2 and Fe2O3 is between 85% and 95%, the loss on ignition of the high-aluminum fly ash is ≤2%; the particle size of the high-aluminum fly ash is 45μm and the sieve residue is ≤50%.

4. The fly ash-based ceramsite filter material for aerated biological filter according to any one of claims 1 to 3, characterized in that: The pore-forming agent is at least one of limestone, rice bran and sludge.

5. A method for preparing fly ash-based ceramsite filter material for aerated biological filter, characterized in that: The method comprises the following preparation steps: S1. Raw material pretreatment: drying and grinding red mud to obtain red mud powder; crushing and grinding coal gangue to obtain coal gangue powder, the red mud powder and coal gangue powder after grinding have a particle size range of 150 to 200 meshes; when sludge or limestone is selected as a pore-forming agent, it is necessary to dry and grind it to obtain a pore-forming agent powder, and its particle size range is also 150 to 200 meshes; when the pore-forming agent is rice bran, there is no need to perform a grinding step, and the rice bran can be used directly; S2. Raw material ratio: weigh the raw materials according to the following weight percentages: 60% to 80% fly ash, 5% to 25% red mud, 3% to 10% coal gangue, 5% to 20% pore-forming agent, and then put the weighed raw materials into a mixer and stir evenly; S3. Water spray granulation: The mixed raw materials are transported to a disc granulator and water spray granulated to prepare ceramsite filter raw balls; S4. Sintering and granulation: The filter material raw material balls are sintered in a single barrel rotary kiln to obtain fly ash based ceramsite filter material for aerated biological filter.

6. The method for preparing fly ash-based ceramsite filter material for aerated biological filter according to claim 4, characterized in that: The sintering temperature range in the single barrel rotary kiln in S4 is 1050-1120° C., and the sintering time is 15-30 minutes.

7. The method for preparing fly ash-based ceramsite filter material for aerated biological filter according to claim 4, characterized in that: The chemical composition of the red mud is as follows: 15% to 25% Al2O3, 18% to 25% SiO2, 20% to 30% Fe2O3, the loss on ignition of the red mud is 10% to 20%, and the plasticity index is 5 to 7; the fly ash is high-aluminum fly ash, and the chemical composition of the high-aluminum fly ash is as follows: 40% to 50% Al2O3, the total percentage of Al2O3, SiO2 and Fe2O3 is between 85% and 95%, and the loss on ignition of the high-aluminum fly ash is ≤2%; the particle size of the high-aluminum fly ash is 45μm and the sieve residue is ≤50%; the pore-forming agent is at least one of limestone, rice bran and sludge.

8. Use of the fly ash-based ceramsite filter material for aerated biological filters as claimed in any one of claims 1 to 4 or the ceramsite filter material prepared by the method for preparing the fly ash-based ceramsite filter material for aerated biological filters as claimed in any one of claims 5 to 7 in treating sewage in aerated biological filters.

9. The use according to claim 8, characterized in that The sewage is sewage containing chloride ions.

10. The use according to any one of claims 8 to 9, characterized in that: The application comprises the following application steps: placing the ceramsite filter material in each layer of the tower body of the packed absorption tower, and the amount of the ceramsite filter material fills 70% to 85% of the volume of the aerated biological filter tank; injecting sewage into the water tank at the bottom of the tower, and adding activated sludge; after the sewage is continuously aerated for 24 hours, the sewage is pumped into the filter column for treatment, the circulating water flow is set to 200L / h-300L / h, and the system runs continuously for 10 to 20 days.

Images