Biological filter for sewage treatment and use method thereof

Abstract

The invention relates to the technical field of sewage treatment equipment, and particularly discloses a biological filter for sewage treatment and a use method thereof. The filter tank comprises a first filter tank and a second filter tank, the first filter tank comprises a first biological filler layer, and a first working liquid level line is arranged above the first biological filler layer; a second biological filler layer, an electrochemical filler layer and a third biological filler layer are sequentially arranged in the second filter tank from top to bottom, a second working liquid level line is arranged above the electrochemical filler layer, and the volume ratio of the second biological filler layer to the electrochemical filler layer to the third biological filler layer is (2-3): 1: (0.5-2); the liquid supply system comprises a working water path and a backflow water path. According to the invention, through the design of the structure of the biological filter, including optimal combination and volume ratio control of each filler layer, a microenvironment beneficial to growth and enrichment of anaerobic ammonium oxidation bacteria and development of anaerobic ammonium oxidation reaction is successfully constructed.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment equipment technology, specifically to a biological wastewater treatment device and its usage method. Background Technology

[0002] With the continuous improvement of urbanization, the discharge of urban domestic sewage continues to increase, among which nitrogen pollution has become one of the important factors affecting water environmental quality and ecological security. At present, the field of urban sewage treatment still mainly relies on the traditional nitrification-denitrification process. This type of process usually depends on a large amount of aeration and the addition of additional organic carbon sources, thus it has the disadvantages of high operating energy consumption and cost.

[0003] In recent years, anaerobic ammonia oxidation (AAO) technology has been considered an important development direction for energy conservation and emission reduction in wastewater treatment due to its advantages such as no need for external organic carbon sources, low oxygen demand, and low sludge production. This technology mainly relies on anaerobic ammonia oxidizing bacteria to eliminate nitrogen pollution in wastewater. However, due to objective conditions such as low ammonia nitrogen concentration in urban domestic wastewater, large fluctuations in influent water quality, and the difficulty in completely removing dissolved oxygen from the system, actual wastewater treatment processes suffer from slow growth rates and weak environmental adaptability of anaerobic ammonia oxidizing bacteria. This makes it difficult for anaerobic ammonia oxidizing bacteria to achieve rapid enrichment and long-term stable existence in practical urban wastewater treatment, thus severely restricting the widespread application of anaerobic ammonia oxidation technology in mainstream wastewater treatment systems.

[0004] Therefore, there is an urgent need for a wastewater treatment system or device that can achieve the enrichment and long-term stable existence of anaerobic ammonia oxidizing bacteria during the wastewater treatment process, so as to make anaerobic ammonia oxidation technology applicable to actual wastewater treatment. Summary of the Invention

[0005] One of the objectives of this invention is to provide a biological filter for wastewater treatment, which can achieve the enrichment of anaerobic ammonia oxidizing bacteria, and thus treat nitrogen pollution in wastewater by relying on anaerobic ammonia oxidation technology.

[0006] The second objective of this invention is to provide a method for using the aforementioned biofilter that ensures the enrichment of anaerobic ammonia-oxidizing bacteria.

[0007] This invention is achieved through the following technical solution:

[0008] A biological filter for wastewater treatment includes: a first filter filled with a first biological packing layer, wherein a first working liquid level line is located above the first biological packing layer; a second filter having a second biological packing layer, an electrochemical packing layer, and a third biological packing layer arranged sequentially from top to bottom, wherein a second working liquid level line is located above the electrochemical packing layer and the distance between the second working liquid level line and the top of the electrochemical packing layer is 2-10 cm, and the volume ratio of the second biological packing layer, the electrochemical packing layer, and the third biological packing layer is (2-3):1:(0.5-2); and a liquid supply system including a working water path and a return water path, wherein the working water path sequentially connects the first biological packing layer, the second biological packing layer, the electrochemical packing layer, and the third biological packing layer, and one end of the return water path is connected to the first filter and the other end is connected to the return outlet in the second filter, wherein the return outlet is located at the top of the electrochemical packing layer.

[0009] In this invention, the arrangement of the first working liquid level line and the first biological packing layer in the first filter bed first forms a pre-anaerobic zone, thereby effectively alleviating the load on the subsequent treatment units and providing the basic conditions for the stable operation of the multi-stage biological filter bed in this invention.

[0010] The wastewater to be treated is then transported to the second filter tank via the working waterway. In the second filter tank, through the second working liquid level line and the position and volume control of each packing layer, it is ensured that the wastewater flowing through the second biological packing layer can fully contact the air to obtain sufficient dissolved oxygen. This constitutes the aerobic zone for wastewater treatment within the second biological packing layer. In this zone, the microorganisms abundant in the second biological packing layer can convert most of the ammonia nitrogen in the wastewater into nitrate through nitrification under aerobic conditions, thus removing nitrogen pollution from the wastewater. Simultaneously, some ammonia nitrogen is retained for subsequent growth and enrichment of anaerobic ammonia-oxidizing bacteria. Secondly, the arrangement of the second working liquid level line and the electrochemical packing layer ensures that a small amount of oxygen and some ammonia nitrogen remain in the wastewater placed in the electrochemical packing layer. A micro-aerobic reaction zone is formed within the electrochemical packing layer. Wastewater placed in this zone participates in the electrochemical reactions of the packing layer, achieving effective conversion of nitrogen forms and consumption of dissolved oxygen. In this way, while ammonia nitrogen is consumed and nitrogen pollution is removed, an anaerobic environment necessary for the growth of anaerobic ammonia oxidizing bacteria is gradually created within the electrochemical packing layer. Furthermore, the reactions within the electrochemical packing layer lead to the formation of substances such as nitrite, thus providing the necessary substrates for the anaerobic ammonia oxidation reaction. This ensures the full growth, enrichment, and participation of anaerobic ammonia oxidizing bacteria in the treatment of nitrogen pollution in wastewater. Ultimately, anaerobic ammonia oxidizing bacteria can remain and accumulate in the electrochemical packing layer and the third biological packing layer, thereby deeply participating in the treatment of nitrogen pollution in wastewater in the biological filter, contributing more than 15% to the total nitrogen removal.

[0011] As a further improvement of the present invention, the electrochemical filler layer contains iron-carbon material, wherein the mass ratio of iron, carbon and catalyst in the iron-carbon material is (6~18):1:1.

[0012] As a further improvement of the present invention, the catalyst contains at least Mn, Ni, Si and S, and the mass ratio of the four is 1:1:1:(0.5~1).

[0013] As a further improvement of the present invention, the particle size of the iron-carbon material is 3~10mm.

[0014] When iron-carbon materials are selected as electrochemical fillers, they can participate in multiple reactions simultaneously and cooperate with the aforementioned second biological filler layer, thereby ensuring the occurrence of anaerobic ammonia oxidation reaction and providing a suitable environment for the growth and enrichment of anaerobic ammonia oxidizing bacteria.

[0015] Specifically, in this invention, the iron-carbon material selected by the inventors, in combination with other packing layers, can provide the necessary environment for the anaerobic ammonium oxidation reaction. This iron-carbon material can undergo in-situ micro-electrolysis in an aquatic environment. Therefore, without the need for external energy or organic carbon sources, by controlling its dosage, nitrates produced in the aforementioned nitrification process in wastewater can be reduced to nitrites. Simultaneously, through the coordinated control of the volume and dosage of the second biological packing layer, a portion of ammonia nitrogen remains in the wastewater entering the electrochemical packing layer. Thus, the nitrites and ammonia nitrogen in the wastewater within the electrochemical packing layer together provide the necessary substrate for the anaerobic ammonium oxidation reaction, providing the necessary conditions for the reaction to proceed and enabling anaerobic ammonium oxidizing bacteria to participate in wastewater treatment.

[0016] Building upon the above, the introduction of iron-carbon materials can also provide an environment conducive to the growth and accumulation of anaerobic ammonia oxidizing bacteria. Specifically, the carbon dioxide produced during denitrification of the iron-carbon materials can serve as an inorganic carbon source for these bacteria. During micro-electrolysis, the iron-carbon materials effectively consume the small amount of dissolved oxygen remaining in the wastewater, creating a strictly anaerobic environment that meets the oxygen-sensitive requirements of anaerobic ammonia oxidizing bacteria. Furthermore, the porous structure of the iron-carbon materials provides a high specific surface area, offering stable attachment points for the bacteria. The quinone and phenolic hydroxyl groups on the carbon material surface act as electron shuttles, accelerating interspecies electron transfer and enhancing the activity of anaerobic ammonia oxidizing bacteria. Iron is an essential trace element for the metabolism of anaerobic ammonia oxidizing bacteria, participating in electron transport chains and cytochrome synthesis, and the iron-carbon materials provide a stable source of iron. Therefore, the introduction of iron-carbon materials can provide the necessary growth and accumulation environment for anaerobic ammonia oxidizing bacteria at a relatively low operating cost.

[0017] In summary, by introducing iron-carbon materials as electrochemical fillers and controlling their dosage, the inventors simultaneously provided a growth and enrichment environment for anaerobic ammonia oxidizing bacteria, as well as the necessary conditions for non-anaerobic ammonia oxidation reactions, thereby enabling anaerobic ammonia oxidation treatment technology to effectively participate in the treatment of nitrogen pollution in wastewater.

[0018] As a further improvement of the present invention, the working water path includes a water distribution device for introducing wastewater to be treated into the second filter tank. The water distribution device can disperse the wastewater into small-diameter water droplets, thereby achieving sufficient contact with air during their fall and thus obtaining sufficient dissolved oxygen.

[0019] As a further improvement of the present invention, the first biological packing layer, the second biological packing layer and the third biological packing layer all contain biological packing material, which is selected from at least one of volcanic rock, ceramsite, coal slag and pebbles.

[0020] As a further improvement of the present invention, the particle size of the biological filler is 3~5mm.

[0021] As a further improvement of the present invention, a buffer layer is provided at the bottom of both the first and second filter tanks. The arrangement of this layer can provide buffer space for the flow of sewage to avoid problems such as short-circuiting during operation.

[0022] Secondly, the present invention provides a method for using a filter bed for any of the above-mentioned biological filters for wastewater treatment, wherein the flow rate of wastewater to be treated from the first filter bed to the second filter bed in the working water circuit and the return flow rate in the return water circuit are both 2 to 5 times the influent flow rate.

[0023] In this invention, the growth, accumulation, and effective participation of anaerobic ammonia-oxidizing bacteria in wastewater treatment are influenced by the synergistic effects of multiple reactions within the second biological packing layer and the electrochemical packing layer. Controlling the occurrence of these reactions (such as nitrification) and the partial retention of ammonia nitrogen are therefore crucial. The inventors primarily controlled the input flow rate of wastewater into the second filter bed by regulating the hydraulic conditions, such as the flow rate, thereby influencing the contact between the wastewater and air as it entered the second filter bed. This ultimately controlled the oxygen content of the wastewater in the aerobic zone of the second filter bed. This control ensured that the second biological packing layer produced the required nitrates and retained the required ammonia nitrogen, that the electrochemical packing layer produced nitrites, and that the remaining dissolved oxygen was completely consumed. Specifically, under the aforementioned hydraulic conditions, the dissolved oxygen concentration between the second biological packing layer and the electrochemical packing layer was ensured to be less than 0.5 mg / L, the ammonia nitrogen concentration to be maintained at 2~5 mg / L, and the nitrate concentration to be maintained at 4~10 mg / L in the second filter bed; the oxidation-reduction potential between the electrochemical packing layer and the third biological packing layer was maintained at -250~-350 mV, and the dissolved oxygen concentration to be less than 0.1 mg / L. This ensured the normal occurrence of the aforementioned reaction processes and the normal operation of the entire filter bed system.

[0024] As a further improvement of the present invention, the total hydraulic retention time in the biological filter for wastewater treatment is 8 to 16 hours.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) In this invention, through the design of the structure of the biofilter, including the optimized combination and volume ratio control of each packing layer, a microenvironment conducive to the growth, enrichment and anaerobic ammonia oxidation reaction of anaerobic ammonia oxidizing bacteria was successfully constructed.

[0027] (2) Under preferred conditions, the introduction and use of iron-carbon materials in the electrochemical packing layer effectively utilizes its in-situ micro-electrolysis reaction, etc., providing key substrates for anaerobic ammonia oxidation reaction. It also consumes dissolved oxygen, provides inorganic carbon source, trace element iron and stable attachment sites through the reaction, significantly improving the activity and abundance of anaerobic ammonia oxidizing bacteria.

[0028] (3) In the method of use, by controlling the flow rate of the working water circuit and the return water circuit in the liquid supply system, as well as adjusting the total hydraulic residence time, the process parameters of each reaction zone (such as dissolved oxygen, ammonia nitrogen, nitrate concentration, redox potential, etc.) are kept within a suitable range, ensuring the coordinated and efficient operation of nitrification, denitrification and anaerobic ammonia oxidation.

[0029] (4) Overall, by controlling the structure and usage of the filter, the biological filter can achieve deep removal of nitrogen pollution in wastewater without the need to add additional organic carbon sources and reduce aeration energy consumption. The total nitrogen removal rate is effectively improved, and the contribution rate of anaerobic ammonia oxidizing bacteria to total nitrogen removal can reach more than 15%. This provides a practical solution for the promotion and application of anaerobic ammonia oxidation technology in mainstream wastewater treatment systems. Attached Figure Description

[0030] The accompanying drawings are provided below to illustrate the preferred embodiments of the invention and to aid in understanding the objectives and advantages of the invention, wherein:

[0031] Figure 1 This is a schematic diagram of a biological filter for wastewater treatment.

[0032] Figure 2 This is a summary diagram of the abundance of major microorganisms at various points in a biological filter for wastewater treatment and in the inoculated sludge.

[0033] Figure 3 This is a summary chart of wastewater indicators at various monitoring points in a biological filter used for wastewater treatment. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0036] Example 1:

[0037] This embodiment provides a biological filter for wastewater treatment, comprising a first filter 1 and a second filter 2. For example, in this embodiment, the effective height of the first filter 1 is 120cm, the diameter is 15cm, and the effective volume is 17.7L; the dimensions of the second filter 2 are the same as those of the first filter 1.

[0038] In this embodiment, the biological filler used is volcanic rock with a particle size of about 3-5 mm; the electrochemical filler used is iron-carbon, which contains iron, carbon and catalyst. In this embodiment, the mass ratio of the three components in the iron-carbon material is controlled within the range of (10-12):1:1. The catalyst contains four elements: Mn, Ni, Si and S, with a mass ratio of 1:1:1:1. The particle size of the iron-carbon is about 4-5 mm.

[0039] like Figure 1 As shown, the first filter bed 1 is completely filled with volcanic rock to form a first biological packing layer 101 with a height of 100cm. The first working liquid level line L1 in the first filter bed 1 is 5cm higher than the top of the first biological packing layer 101, so as to ensure that when the liquid level reaches the first working liquid level line L1, all the volcanic rock in the first filter bed 1 is placed in the sewage, thereby forming the required anaerobic environment.

[0040] like Figure 1 As shown, the second filter 2 is filled from top to bottom with volcanic rock as the second biological packing layer 201, iron-carbon as the electrochemical packing layer 202, and volcanic rock as the third biological packing layer 203. The total height of all packing materials in the second filter 2 is 100cm. The electrochemical packing layer 202 is arranged in the height range of 40-60cm in the second filter 2, and the second working liquid level line L2 in the second filter 2 is set at its height of 62cm. Therefore, in this embodiment, the volume ratio of the second biological packing layer 201, the electrochemical packing layer 202, and the third biological packing layer 203 in the second filter 2 is 2:1:2.

[0041] The biological filter's supply system 3 also includes a working water path 301 and a return water path 302. For example... Figure 1 As shown, the working water passage 301 is sequentially connected to the first biological packing layer 101, the second biological packing layer 201, the electrochemical packing layer 202, and the third biological packing layer 203; the return water passage 302 is connected at one end to the top of the first filter tank 1 to input return liquid into the first filter tank 1, and at the other end to the return outlet in the second filter tank 2. The return outlet is located at the top of the electrochemical packing layer 202 and is 1 cm above the top to ensure that the return liquid can be received.

[0042] Preferably, such as Figure 1 As shown, empty layers are evenly distributed at the bottom of the first filter tank 1 and the second filter tank 2, and the height of the empty layers is 20cm. This height is not included in the effective height of the filter tank.

[0043] Preferably, such as Figure 1 As shown, a water distribution device 301-1 is arranged in the working water channel 301, and a water distribution drip filter device is set on the top of the second filter tank 2 to disperse the sewage when sewage is input into the second filter tank 2, so that it forms fine water droplets and can fully contact the air during the falling process to obtain the required dissolved oxygen.

[0044] Preferably, such as Figure 1 As shown, infusion pumps are installed in both the working water circuit 301 and the return water circuit 302 to control the flow rate in the two water circuits respectively.

[0045] Example 2:

[0046] This embodiment provides a method for using the biological filter for wastewater treatment as described in Example 1. During use, the wastewater is taken from actual domestic wastewater after the fine screen at a municipal wastewater treatment plant. The wastewater contains parameters such as COD and NH4+. + The initial concentrations of -N, TN, and TP were 181.6±31 mg / L, 32.6±8.1 mg / L, 39.2±3.6 mg / L, and 6.3±2.4 mg / L, respectively, and the pH was 7.0~8.0. The inoculum sludge used in this embodiment was taken from the concentrated sludge of the wastewater treatment plant. Testing showed that no anaerobic ammonia-oxidizing bacteria were detected in the inoculum sludge.

[0047] During use, the influent flow rate in the first filter is controlled to be Q; in the working water circuit, the transport flow rate of sewage from the first filter to the second filter is 2Q; the return flow rate from the second filter to the first filter is 2Q; and the effluent flow rate of the second filter is Q.

[0048] The total hydraulic retention time of the wastewater in the entire filter tank is controlled to be 12 hours.

[0049] Performance testing:

[0050] In this embodiment, during operation, the ammonia nitrogen concentration in the wastewater between the second biological packing layer and the electrochemical packing layer (i.e., the end of the aerobic zone) was detected to be 2~5 mg / L, the dissolved oxygen concentration was less than 0.5 mg / L, the oxidation-reduction potential was -320~-350 mV, and the pH was about 6.5~6.9, which met the growth requirements of anaerobic ammonia oxidizing bacteria.

[0051] like Figure 2 As shown, this study illustrates the abundance distribution of major microorganisms in the second biological packing layer, electrochemical packing layer, and third biological packing layer of the second filter, as well as in the inoculated sludge. In the second biological packing layer, the abundance of nitrifying bacteria *Nitrospira* reached 16.12%, providing sufficient microbial support for the effective oxidation of ammonia nitrogen. In the electrochemical packing layer, the abundance of anaerobic ammonia oxidizing bacteria *Candidatus brocadia* reached 5.15%, a relatively high level in actual urban wastewater treatment systems. In the third biological packing layer, the abundance of anaerobic ammonia oxidizing bacteria *Candidatus brocadia* also reached a relatively high level of 3.05%. Therefore, the results indicate that anaerobic ammonia oxidizing bacteria were enriched in the electrochemical and third biological packing layers, enabling the effective implementation of the anaerobic ammonia oxidation denitrification pathway in mainstream urban wastewater treatment processes with low ammonia nitrogen and large flow volumes.

[0052] After 60 days of operation of the biological filter, wastewater samples were taken from the inlet of the biological filter, the effluent of the first filter (i.e., the end of the anaerobic zone), the area between the second biological packing layer and the electrochemical packing layer in the second filter (i.e., the end of the aerobic zone), and the effluent outlet, and the concentrations of various pollutants were tested. Figure 3 As shown, this illustrates the changes in pollutant concentrations at each monitoring point. The average concentrations of ammonia nitrogen and nitrate at the end of the anaerobic zone were 11 mg / L and 0.5 mg / L, respectively; at the end of the aerobic zone, the average concentrations were 3.0 mg / L and 6.8 mg / L, respectively; and at the effluent, the average concentrations were 0.8 mg / L and 4.2 mg / L, respectively. No significant accumulation of nitrite was detected at any monitoring point. The results indicate that during the wastewater flow from the end of the aerobic zone through the electrochemical packing layer to the effluent, ammonia nitrogen and nitrate exhibit simultaneous removal characteristics, while... Figure 2 The bacterial abundance test results show that anaerobic ammonia oxidizing bacteria participated in the anaerobic ammonia oxidation reaction and played a role in nitrogen removal. Calculations indicate that in this embodiment, the anaerobic ammonia oxidation pathway contributes approximately 15.8% to the total nitrogen removal of the system. Furthermore, after the reaction in the biofilter of this embodiment, the concentrations of COD, TN, and TP in the effluent were 23 mg / L, 6.2 mg / L, and 0.23 mg / L, respectively, all significantly better than the Class A limit requirements of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002). Therefore, the biofilter in this embodiment effectively participated in the wastewater treatment process.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biological filter for wastewater treatment, characterized in that, Includes: The first filter (1) is filled with a first biological packing layer (101), wherein the first working liquid level line (L1) is located above the first biological packing layer (101); The second filter (2) is provided with a second biological packing layer (201), an electrochemical packing layer (202) and a third biological packing layer (203) arranged from top to bottom. The second working liquid level line (L2) is set above the electrochemical packing layer (202) and the distance between it and the top of the electrochemical packing layer (202) is 2~10cm. The volume ratio of the second biological packing layer (201), the electrochemical packing layer (202) and the third biological packing layer (203) is (2~3):1:(0.5~2). The liquid supply system (3) includes a working water path (301) and a return water path (302), wherein the working water path (301) is connected in sequence to the first biological packing layer (101), the second biological packing layer (201), the electrochemical packing layer (202) and the third biological packing layer (203), one end of the return water path (302) is connected to the first filter (1) and the other end is connected to the return outlet in the second filter (2), and the return outlet is opened at the top of the electrochemical packing layer (202).

2. A biological filter for wastewater treatment according to claim 1, characterized in that, The electrochemical filler layer (202) contains iron-carbon material, wherein the mass ratio of iron, carbon and catalyst in the iron-carbon material is (6~18):1:

1.

3. A biological filter for wastewater treatment according to claim 2, characterized in that, The catalyst contains at least Mn, Ni, Si, and S, and the mass ratio of the four is 1:1:1:(0.5~1).

4. A biological filter for wastewater treatment according to claim 2, characterized in that, The particle size of the iron-carbon material is 3~10mm.

5. A biological filter for wastewater treatment according to claim 1, characterized in that, The working waterway (301) includes a water distribution device (301-1) for inputting wastewater to be treated into the second filter (2).

6. A biological filter for wastewater treatment according to claim 1, characterized in that, The first biological filler layer (101), the second biological filler layer (201) and the third biological filler layer (203) all contain biological fillers, which are selected from at least one of volcanic rock, ceramsite, coal slag and pebbles.

7. A biological filter for wastewater treatment according to claim 6, characterized in that, The particle size of the biological packing material is 3~5mm.

8. A biological filter for wastewater treatment according to claim 1, characterized in that, The bottom of the first filter (1) and the second filter (2) are evenly provided with a void layer (4).

9. A method of using a filter bed, for operating a biological filter bed for wastewater treatment as described in any one of claims 1 to 8, characterized in that, The flow rate of the wastewater to be treated from the first filter (1) to the second filter (2) in the control working water circuit (301) and the return flow rate in the return water circuit (302) are both 2 to 5 times the influent flow rate.

10. A method of using a filter bed according to claim 9, characterized in that, The total hydraulic retention time in biological filters used for wastewater treatment is 8 to 16 hours.

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