Iron-manganese composite filler, preparation method and method for enhancing deep denitrification of low c / n sewage

Abstract

The present application relates to sewage advanced denitrification treatment technical field, the present application discloses a kind of iron manganese composite filler, preparation method and the method for strengthening low C / N sewage advanced denitrification.Iron powder, activated carbon powder, manganese oxide and binder are calcined under high-temperature anaerobic condition to form iron manganese composite filler.Wastewater is extracted from water storage tank by peristaltic pump, first from the artificial wetland lower water inlet filled with iron manganese composite filler, it is fully reacted in artificial wetland under the condition of 20-22 ℃, hydraulic retention time is 12-24 h, then from the artificial wetland upper water outlet, the treated water is discharged through water outlet pipe.The advantages of the present application include:strengthening autotrophic denitrification advanced denitrification, the method does not need aeration, low cost, simple operation, easy to manage, improve the advanced denitrification performance of artificial wetland to sewage, the removal rate of nitrate nitrogen can reach 96.34% on average, the removal rate of total nitrogen can reach 84.68% on average, the removal rate of COD can reach 76.80% on average.

Description

A method for preparing an iron-manganese composite packing material and for enhancing deep nitrogen removal from low C / N wastewater. Technical Field

[0001] This invention relates to the field of deep denitrification technology for wastewater, and more particularly to a technology for enhanced deep denitrification of low C / N wastewater. Background Technology

[0002] With NO3 - Nitrogen total nitrogen (TN), primarily composed of nitrogen (N-O), is a key indicator determining the water quality of receiving water bodies, and controlling total TN emissions is a major environmental protection technological requirement. Deep denitrification of wastewater is currently one of the hot and challenging research topics in the field of water treatment. Biological denitrification technology has significant advantages for the effective control and removal of nitrogenous pollutants in wastewater.

[0003] Biological heterotrophic denitrification can utilize organic carbon sources as electron donors to achieve NO3 reduction. - NO3- removal is effective, but for low C / N habitats (sewage treatment plant effluent, unconventional water source reservoirs, groundwater, etc.), NO3- removal is still limited. - The removal of NO3- (NO3-) heavily relies on the input of external carbon sources. On the one hand, carbon sources are expensive, increasing treatment costs; on the other hand, the use of large amounts of carbon sources does not meet low-carbon requirements. Furthermore, carbon sources pose risks of breakthrough and residue, leading to secondary pollution from organic matter. In contrast, bioautotrophic denitrification nitrogen removal technology utilizes inorganic electron donors to replace organic carbon sources, relying on the extracellular respiration of chemoautotrophic bacteria to reduce NO3-. - -N, and generates its own metabolic energy, has the potential to solve deep denitrification under low C / N ratio conditions. Based on the different types of inorganic electron donors, it is mainly divided into autotrophic denitrification technologies such as sulfur, hydrogen, iron, and manganese.

[0004] In recent years, with Mn 2+ The manganese autotrophic denitrification process, with its electron donor, has attracted considerable research attention. Under the action of manganese autotrophic denitrifying bacteria, Mn... 2+ Oxidation donates electrons, causing NO3 to... - -N reduction yields manganese oxides (MnO) x MnO produced from N2 and N2 x It is reduced to Mn by manganese-reducing bacteria. 2+This allows for the continuous denitrification process, enabling the manganese oxide-reduction cycle to be recycled. Therefore, microbially driven manganese redox cycles can achieve continuous denitrification without the risk of secondary pollution. Furthermore, the manganese matrix is ​​widely available and inexpensive, making manganese autotrophic denitrification a promising technology. However, the conversion of manganese oxides to manganese ions is slow. To accelerate the reduction process, two strategies can be employed: biological and chemical enhancement. Chemical enhancement, with its advantages of ease of control, rapid results, and fewer limiting factors, shows promising application potential. Among many reducing agents, ZVI (zero-valent iron) is inexpensive and readily available, and elemental iron can be added to enhance the reduction process. However, elemental iron is prone to passivation. Therefore, developing materials to mitigate passivation is being considered. This could effectively reduce carbon source costs, provide more electron donors, and improve denitrification efficiency, demonstrating significant development potential and application prospects. Summary of the Invention

[0005] The purpose of this invention is to provide an iron-manganese composite packing material, a preparation method, and a method for enhancing deep denitrification of low C / N wastewater, in order to solve the technical problems in the existing technology, such as insufficient electron donors, slow conversion of manganese oxides to manganese ions, and low denitrification efficiency during autotrophic denitrification.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for preparing an iron-manganese composite filler includes the following steps: calcining iron powder, activated carbon powder, manganese oxide and binder under high temperature and oxygen-free conditions to prepare the iron-manganese composite filler.

[0008] Furthermore, the manganese oxide material is natural manganese ore with an MnO2 content ranging from 10-40% and a particle size of 5-10 mm.

[0009] Furthermore, the ratio of the iron powder to the manganese oxide by mass is 1-5:1-5.

[0010] Furthermore, the specific steps include:

[0011] (1) Grind the manganese oxide material into powder;

[0012] (2) Mix iron powder, activated carbon powder, manganese oxide and binder in a mass ratio of 16:4:16:1 to obtain a uniformly mixed iron-carbon-manganese mixture.

[0013] (3) The iron-carbon-manganese mixture was used to prepare iron-manganese spherical packing with a particle size of 5-8 mm;

[0014] (4) Calcine the above filler at 800℃ for 60 minutes, cool it down to room temperature and take it out to obtain the iron-manganese composite filler.

[0015] The present invention also provides an iron-manganese composite filler obtained by the preparation method described above.

[0016] The present invention also provides an artificial wetland using the aforementioned iron-manganese composite filler, comprising an outer shell and an inorganic filler filled within the outer shell. The inorganic filler consists of a pebble support layer, an iron-manganese composite filler layer, and a gravel layer from bottom to top. An inlet is provided at the bottom of the outer shell, and an outlet is provided at the top, with the water flow direction being bottom in and top out.

[0017] Furthermore, the pebble support layer has a pebble size of 10-20 mm; the iron-manganese composite filler layer is composed of iron-manganese composite filler and gravel mixed in a volume ratio of 1:1, the iron-manganese composite filler has a pebble size of 5-8 mm, and the gravel has a pebble size of 5-10 mm; the gravel in the gravel layer has a pebble size of 5-10 mm.

[0018] The present invention also provides a denitrification reaction system using the constructed wetland, comprising: a water storage tank, a peristaltic pump, a constructed wetland, and an outlet pipe. The peristaltic pump is connected to the outlet of the water storage tank and to the inlet of the constructed wetland. The water storage tank, the peristaltic pump, and the constructed wetland are connected by a flexible hose, and the outlet pipe is connected to the outlet of the constructed wetland.

[0019] Furthermore, the water storage tank has a volume of 20L, the outer shell of the artificial wetland is made of plexiglass, and it is equipped with a light-shielding layer. It is 45cm high and 15cm in diameter. The water inlet is located 3cm from the bottom and the water outlet is located 10cm from the top. The water flow direction is from bottom to top. The artificial wetland is equipped with 4 sampling ports along its length, with each sampling port spaced 15cm apart.

[0020] This invention also provides a method for enhanced deep denitrification of low C / N wastewater using the aforementioned system. The process includes: inoculating an artificial wetland with activated sludge from an urban wastewater treatment plant, followed by a three-stage biofilm formation initiation process: aeration cultivation, simulated small-flow wastewater influent, and acclimatization with actual wastewater treatment plant effluent. Wastewater is drawn from a storage tank using a peristaltic pump, first entering through the lower inlet of the artificial wetland, and fully reacting within the artificial wetland at 20-22°C for a hydraulic retention time of 12-24 hours. Then, the wastewater flows out through the upper outlet of the artificial wetland and is discharged from the treated water body via an outlet pipe.

[0021] The main technical principles of this invention are as follows:

[0022] Under the action of manganese autotrophic denitrifying bacteria, Mn 2+ The oxidation process donates electrons, causing NO3 in wastewater to... - -N reduction produces manganese oxide and N2, respectively. The manganese oxide produced is then reduced to Mn by manganese-reducing bacteria. 2+ This allows for continuous denitrification, which can be recycled. Microbially driven manganese redox cycles enable sustained denitrification performance.

[0023] However, manganese oxides are converted to Mn 2+ The conversion is relatively slow. To accelerate the reduction of manganese oxides and promote the conversion of Mn... 2+ The dissolution of manganese promotes the autotrophic denitrification process, and the addition of elemental iron can enhance the reduction process. The iron-carbon packing material can mitigate the passivation of elemental iron, and the zero-valent iron in the iron-carbon packing material can enhance the reduction process of manganese oxides in natural manganese ore, promoting the reduction of Mn. 2+ The dissolution of manganese oxides in the iron-manganese composite packing promotes the autotrophic denitrification process. Simultaneously, the presence of manganese oxides in the iron-manganese composite packing also promotes the dissolution of iron ions in the iron-carbon packing, providing more electron donors, promoting the reduction of manganese oxides and ensuring complete denitrification, while reducing the byproduct NO2. - The generation of -N effectively avoids the reduction of NO3. - When -N is present, iron-carbon fillers are prone to insufficient electron donors, and incomplete reaction processes lead to NO2. - The problem of -N accumulation.

[0024] Based on the characteristics of the changes in the valence state of iron and manganese under the action of microorganisms, the degradation of organic matter, and the transformation of nitrogen, and the principle of nitrogen removal and pollution control by iron, carbon, and manganese oxides, iron, carbon, and manganese oxides are combined and used as the main functional matrix to construct an iron-manganese composite system for enhancing nitrogen removal.

[0025] As can be seen from the above, the present invention has the following advantages:

[0026] This invention utilizes the combination of iron, carbon, and manganese ore to generate more electron donors, thereby enhancing the redox activity of microorganisms. Based on the interaction characteristics between the valence state changes of iron and manganese elements under the action of microorganisms, the degradation of organic matter, and the transformation of nitrogen elements, as well as the principle of denitrification and pollution removal by iron, carbon, and manganese oxides, it reduces the use of carbon sources, effectively removes organic matter and nitrate nitrogen from wastewater, and achieves the goal of enhanced deep carbon reduction and extreme denitrification of low C / N wastewater, thus realizing the simultaneous "carbon reduction and denitrification" efficiency of urban wastewater treatment plant effluent. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 is a schematic diagram of the structure of the autotrophic denitrification reaction system in Example 1, which promotes the generation of inorganic electron donors from iron-carbon-manganese ore to enhance the denitrification reaction.

[0029] Figure 2 is a schematic diagram of the constructed wetland structure filled with different fillers in Example 2;

[0030] Figure 3 is a statistical chart showing the changes in COD influent and effluent concentrations in the denitrification system of an artificial wetland using different fillers in Example 2.

[0031] Figure 4 is a statistical chart showing the changes in TN influent and effluent concentrations in the denitrification system of the constructed wetland with different fillers in Example 2.

[0032] Figure 5 shows the NO3 removal system of an artificial wetland filled with different fillers in Example 2. - Statistical chart of changes in -N influent and effluent concentrations;

[0033] Figure 6 shows the NO2 removal system of an artificial wetland filled with different fillers in Example 2. - -N effluent concentration statistics chart; Detailed Implementation

[0034] The following detailed description, in conjunction with embodiments, illustrates the construction and application methods of the bioreaction system based on iron-carbon and manganese ore provided by the present invention.

[0035] Example 1

[0036] As shown in Figure 1, this embodiment provides an iron-manganese composite packing system for promoting donor electron generation and enhancing autotrophic denitrification reaction, which includes: a water storage tank 1, a peristaltic pump 2, an artificial wetland 3, and an outlet pipe. The peristaltic pump 2 is connected to the outlet of the water storage tank 1 and to the inlet of the artificial wetland 3. The water storage tank 1, the peristaltic pump 2, and the artificial wetland 3 are connected by a flexible hose, and the outlet pipe is connected to the outlet of the artificial wetland 3.

[0037] The water storage tank 1 has a volume of 20L, and the sewage in the tank can be selected from, but is not limited to, wastewater from sewage treatment plants, polluted water bodies in rivers and lakes, and polluted groundwater.

[0038] The outer shell of the constructed wetland 3 is made of plexiglass, 45cm high and 15cm in inner diameter. Its inlet is located 3cm from the bottom and its outlet is located 10cm from the top, with water flowing from bottom to top. Four sampling ports are arranged along the perimeter of the constructed wetland 3, spaced 15cm apart. The outer shell of the constructed wetland 3 is filled with inorganic filler, which, from bottom to top, consists of:

[0039] The pebble support layer is 5cm thick, and the pebble size is 10-20mm.

[0040] The iron-manganese composite filler layer is 15cm thick and is composed of iron-manganese composite filler and gravel mixed in a 1:1 volume ratio. The iron-manganese composite filler is made by mixing iron powder, activated carbon powder, manganese oxide powder and binder in a mass ratio of 16:4:16:1 to form spherical fillers with a particle size of 5-8mm. These fillers are then calcined at 800℃ under oxygen-free conditions for 60 minutes and cooled to room temperature. The gravel has a particle size of 5-10mm.

[0041] The gravel layer is 15cm thick, with gravel particles ranging from 5 to 10mm in diameter.

[0042] Gravel and pebbles can promote the dissolution of inorganic electron donors, provide sufficient attachment and growth carriers for microorganisms, and accelerate the denitrification rate of the reaction system.

[0043] Constructed Wetland 3 is wrapped in black kraft paper to prevent light from degrading the target pollutants. Constructed Wetland 3 is operated indoors at 20-22℃.

[0044] The above-mentioned iron-manganese composite packing material is used to enhance the autotrophic denitrification reaction system by promoting the generation of donor electrons, and the process is as follows:

[0045] After the constructed wetland is inoculated with activated sludge from an urban wastewater treatment plant, the biofilm formation is initiated through a three-stage process: aeration cultivation, simulated small-flow wastewater influent, and acclimatization with actual wastewater treatment plant effluent. Wastewater is drawn from the storage tank 1 through the peristaltic pump 2 and then enters the constructed wetland 3 through the inlet at the bottom. The wastewater fully reacts within the constructed wetland 3, with a hydraulic retention time of 1 day, and then flows out from the outlet at the top of the constructed wetland 3, discharging the treated water through the effluent pipe.

[0046] Example 2

[0047] As shown in Figure 2, four artificial wetlands were constructed in the laboratory, numbered A, B, C, and D respectively. The construction of each artificial wetland is as follows:

[0048] A. Constructed Wetland: Constructed according to Example 1;

[0049] Constructed Wetland B: Unlike Constructed Wetland A, Constructed Wetland B uses a manganese ore / gravel layer instead of an iron-manganese composite filler layer. The manganese ore / gravel layer is made by mixing natural manganese ore and gravel in a 1:1 volume ratio. The rest is the same as Constructed Wetland A.

[0050] Constructed Wetland C: Unlike constructed wetland A, constructed wetland C uses an iron-carbon / gravel layer instead of an iron-manganese composite filler layer. The iron-carbon / gravel layer is made by mixing iron-carbon filler and gravel in a volume ratio of 1:1. The iron-carbon filler is made by calcining iron powder, activated carbon powder and binder in a mass ratio of 16:4:1 under oxygen-free conditions at 800℃. The rest is the same as constructed wetland A.

[0051] Constructed Wetland D: As a control, the difference between constructed wetland A and constructed wetland D is that constructed wetland D uses a gravel layer instead of an iron-manganese composite filler layer. The rest is the same as constructed wetland A.

[0052] After inoculating the four constructed wetlands with activated sludge from a municipal wastewater treatment plant, biofilm formation was initiated through a three-stage process: aeration cultivation, simulated low-flow wastewater influent, and acclimatization with actual wastewater treatment plant effluent. The four constructed wetlands then shared a 20L storage tank for wastewater treatment. The storage tank, peristaltic pumps, and constructed wetlands were connected by flexible hoses. Wastewater with average COD, TN, and TP concentrations of 60, 15, and 1.5 mg / L, respectively, was introduced into each constructed wetland using peristaltic pumps. The wastewater first entered through the bottom inlet of each constructed wetland, underwent sufficient reaction, and then flowed out through the top outlet, with a hydraulic retention time of one day. The apparatus was operated in a temperature-controlled laboratory, and the devices were wrapped in black kraft paper to prevent light-induced degradation of the target pollutants. The indoor temperature was 20-22℃, and the water temperature was 22-24℃.

[0053] Nitrate nitrogen removal and conversion: Nitrate nitrogen denitrification involves two steps. The first step converts nitrate nitrogen into nitrite nitrogen, and the second step converts nitrite into nitric oxide, nitrous oxide, and nitrogen gas. Therefore, the generation of the byproduct nitrite nitrogen mainly stems from the first step of nitrate nitrogen denitrification. Constructed wetlands B and D showed poor nitrate nitrogen removal efficiency, resulting in less nitrite nitrogen as a byproduct. Therefore, this study only compares the advantages of constructed wetlands A and C in reducing byproducts. Further verification of the advantages of composite packing material compared to single packing material was conducted. The results are shown in Figure 3-6. Under continuous operation conditions, compared to the control, constructed wetland A showed the best nitrogen removal efficiency, achieving maximum removal rates of 90.6% for COD and 84.4% for TN, and significantly lower removal rates for NO3. - The removal rate of -N can reach up to 98.5%, and compared with C constructed wetlands, it reduces the generation of by-product nitrite nitrogen, further verifying the denitrification advantages of iron-manganese composite packing.

[0054] Example 3

[0055] This embodiment tests the denitrification effect of the reaction system in Example 1 under different hydraulic retention times. After inoculating the constructed wetland with activated sludge from a municipal wastewater treatment plant, biofilm formation was initiated through a three-stage process: aeration cultivation, simulated low-flow wastewater influent, and acclimatization with actual wastewater treatment plant effluent. Wastewater with average COD, TN, and TP concentrations of 30, 15, and 1.5 mg / L, respectively, was introduced into the constructed wetland using a peristaltic pump. It first entered from the bottom of the constructed wetland, and after sufficient reaction, flowed out from the top effluent pipe. The hydraulic retention time was 24 hours for days 1-15, 18 hours for days 15-30, and 12 hours for days 30-45. The constructed wetland was operated in a temperature-controlled laboratory with an indoor temperature of 20-22°C and a water temperature of 22-24°C. The constructed wetland was wrapped in black kraft paper to prevent light from degrading the target pollutants.

[0056] The results showed that under continuous operation conditions, with a hydraulic retention time of 24 h, the average removal rates of COD and TN by the constructed wetland were 76.80% and 84.68%, respectively, and the removal rate of NO3 was [missing information]. - The average removal rate of nitrogen (N) was 96.34%; with a hydraulic retention time of 18 h, the average removal rates of COD and TN by the constructed wetland were 66.20% and 60.22%, respectively, and for NO3... - The average removal rate of -N was 88.30%; with a hydraulic retention time of 12 h, the average removal rates of COD and TN by the iron-carbon-manganese ore composite filler constructed wetland reactor were 49.40% and 21.99%, respectively, and the removal rate of NO3 was... - The average removal rate of -N was 75.93%.

[0057] A comparison of the nitrogen removal efficiency of bioreactors using iron-manganese composite packing as a matrix at different hydraulic retention times reveals that the nitrogen removal efficiency of constructed wetlands using iron-manganese composite packing is significantly affected by the hydraulic retention time. The best nitrogen removal efficiency was observed with a hydraulic retention time of 24 hours. This phenomenon is primarily due to the fact that when the hydraulic retention time is too short, pollutants in the wastewater do not have sufficient time to be fully degraded or adsorbed by the system.

[0058] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing an iron-manganese composite filler, characterized in that, The specific steps include: calcining iron powder, activated carbon powder, manganese oxide and binder in a mass ratio of 16:4:16:1 under high temperature and oxygen-free conditions to produce iron-manganese composite filler.

2. The method for preparing an iron-manganese composite filler according to claim 1, characterized in that, The manganese oxide material is natural manganese ore with an MnO2 content ranging from 10% to 40% and a particle size of 5-10 mm.

3. The method for preparing an iron-manganese composite filler according to claim 1 or 2, characterized in that, The specific steps include: (1) grinding manganese oxide material into powder; (2) mixing iron powder, activated carbon powder, manganese oxide and binder in a mass ratio of 16:4:16:1 to obtain a uniformly mixed iron-carbon-manganese mixture; (3) preparing spherical fillers with a particle size of 5-8 mm from the obtained iron-carbon-manganese mixture; (4) calcining the above fillers at 800℃ for 60 min, cooling them to room temperature and then taking them out to obtain iron-manganese composite fillers.

4. An iron-manganese composite filler obtained by any one of the preparation methods described in claims 1-3.

5. An artificial wetland using the iron-manganese composite filler of claim 4, characterized in that, It includes an outer shell and inorganic filler filling the outer shell. The inorganic filler consists of a pebble support layer, an iron-manganese composite filler layer, and a gravel layer from bottom to top. The lower part of the outer shell is provided with a water inlet and the upper part is provided with a water outlet. The water flow direction is bottom inlet and top outlet.

6. An artificial wetland using iron-manganese composite filler according to claim 5, characterized in that, The cobblestone support layer has a cobblestone particle size of 10-20 mm; the iron-manganese composite filler layer is composed of iron-manganese composite filler and gravel mixed in a volume ratio of 1:1, with the iron-manganese composite filler having a particle size of 5-8 mm and the gravel having a particle size of 5-10 mm; the gravel in the gravel layer has a gravel particle size of 5-10 mm.

7. A denitrification nitrogen removal reaction system using an artificial wetland as described in claim 6, characterized in that, include: The system includes a water storage tank, a peristaltic pump, an artificial wetland, and an outlet pipe. The peristaltic pump is connected to the outlet of the water storage tank and the inlet of the artificial wetland. The water storage tank, the peristaltic pump, and the artificial wetland are connected by a flexible hose. The outlet pipe is connected to the outlet of the artificial wetland.

8. The denitrification nitrogen removal reaction system using the constructed wetland according to claim 7, characterized in that, The water storage tank has a volume of 20 L. The outer shell of the artificial wetland is made of plexiglass and has a light-shielding layer. It is 45 cm high and 15 cm in diameter. The water inlet is located 3 cm from the bottom and the water outlet is located 10 cm from the top. The water flow direction is from bottom to top. There are 4 sampling ports along the artificial wetland, with each sampling port spaced 15 cm apart.

9. A method for enhanced deep denitrification of low C / N wastewater using the system described in claim 7 or 8, characterized in that, The process includes: after inoculating the constructed wetland with activated sludge from the urban wastewater treatment plant, the biofilm formation is initiated in three stages: aeration cultivation, simulated small-flow wastewater influent, and acclimatization with actual wastewater treatment plant effluent. Wastewater is drawn from the storage tank through a peristaltic pump and first enters through the lower inlet of the constructed wetland. Under conditions of 20-22℃, it fully reacts in the constructed wetland with a hydraulic retention time of 12-24 hours, and then flows out through the upper outlet of the constructed wetland and is discharged from the treated water body through the effluent pipe.

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