A method and apparatus for soil infiltration wastewater treatment based on MABR / EHBR biofilm

Abstract

This invention proposes a soil infiltration wastewater treatment method and apparatus based on MABR / EHBR biofilm, belonging to the field of wastewater treatment technology. The apparatus, from top to bottom, includes a natural cultivated layer, a water distribution layer, a soil infiltration layer, and a water collection layer. The soil infiltration layer, from top to bottom, includes a permeable layer and a soil permeation layer body. The permeable layer comprises uniformly laid gravel, with an EHBR membrane laid within the gravel. The soil permeation layer body comprises loam and biochar, with the MABR membrane laid in the middle of the soil infiltration layer. This invention can significantly improve the removal of ammonia nitrogen, COD, total phosphorus, and lead from wastewater, achieving effluent that meets the Class IV surface water standard.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a soil infiltration wastewater treatment method and apparatus based on MABR / EHBR biofilm. Background Technology

[0002] Soil infiltration is a wastewater treatment technology based on the principle of natural purification. It is a small-scale wastewater treatment system widely used in decentralized rural domestic wastewater treatment. It features wastewater resource recovery, low system investment, and low operating energy consumption.

[0003] Soil infiltration typically uses soil buried deep underground. Deep soil layers lack carbon sources, therefore, it's necessary to improve the soil substrate by mixing biochar into the soil. This improves soil structure and increases the removal efficiency of phosphorus, ammonia nitrogen, nitrate nitrogen, and heavy metals. Simultaneously, it adds a carbon source that can be released slowly and continuously, providing energy for microorganisms to convert nitrogen.

[0004] Currently, the application of soil infiltration technology has not been widely and deeply studied, and there is no unified research and evaluation on its removal of heavy metals. In practical applications, problems such as unstable denitrification and dephosphorization efficiency, insufficient oxygen supply, and easy clogging of pores in the soil layer exist, which have an impact on the surrounding ecological environment.

[0005] In addition, traditional physical, chemical, and biological methods have certain limitations in treating phosphorus, ammonia nitrogen, and heavy metals, requiring a multi-faceted approach to research.

[0006] To address the bottlenecks in soil infiltration methods, such as clogging, nitrogen removal, and phosphorus removal, this invention combines the characteristics of MABR / EHBR biofilms by arranging the two membranes vertically in the middle of the soil medium. This increases the aerobic environment in the system while creating an anaerobic environment in the structure, thus promoting nitrification and denitrification processes.

[0007] MABR / EHBR membrane technology is a wastewater treatment technology that combines gas membrane technology with biofilm technology. It uses an oxygen-permeable membrane as a carrier for microorganisms, with a biofilm on its surface that non-bubbly transports oxygen. Oxygen and pollutants diffuse into the biofilm from both sides and are gradually consumed. It is a low-energy, high-efficiency biofilm water treatment method. The hollow structure of the MABR membrane provides oxygen that diffuses from the inside out, while pollutants diffuse from the water into the biofilm. This counter-current movement creates a concentration gradient, optimizing biological metabolic efficiency, enhancing endogenous microbial metabolism, reducing sludge production, and minimizing clogging. The bubbling and aeration of the EHBR membrane ensures an effective supply of oxygen and carbon sources, improving denitrification efficiency and enhancing the ecological environment. Summary of the Invention

[0008] In view of this, the present invention proposes a method and apparatus for soil infiltration wastewater treatment based on MABR / EHBR biofilm.

[0009] In a first aspect, the present invention provides a soil infiltration wastewater treatment device based on MABR / EHBR biofilm, which includes, from top to bottom, a natural cultivation layer, a water distribution layer, a soil infiltration layer and a water collection layer; The soil infiltration layer, from top to bottom, includes a permeable layer and a soil infiltration layer body; the permeable layer includes uniformly laid gravel, and the EHBR membrane is laid in the gravel; the soil infiltration layer body includes loam and biochar, and the MABR membrane is laid in the middle of the soil infiltration layer.

[0010] Based on the above technical solutions, the soil and biochar can be laid in multiple alternating layers or mixed together.

[0011] Based on the above technical solution, the biochar is further composed of biochar A, biochar B and coconut shell activated carbon. Biochar A is obtained by calcining cotton stalks, and biochar B is obtained by calcining lobster shells. The mass ratio of biochar A, biochar B and coconut shell activated carbon is (1~3):1:(1~3).

[0012] Wastewater is evenly distributed to the soil infiltration layer through the distribution pipes and diffused through capillary action. The oxygen content of the soil infiltration layer gradually decreases from top to bottom, forming a transition from an aerobic area to an anaerobic area. The soil infiltration layer consists of an EHBR membrane, gravel, loam, biochar, and MABR membrane from top to bottom.

[0013] EHBR membranes are membranes that can efficiently and rapidly oxygenate water and serve as robust carriers for microorganisms. They are widely used for the ecological restoration of open water bodies such as rivers, lakes, reservoirs, and ponds. MABR membranes are bubble-free, aerated biofilms where aerobic organisms grow near the membrane fiber surface, while anoxic or anaerobic organisms grow on the outer layer. This biological gradient enables simultaneous nitrification and denitrification, and is often used for low-carbon / nitrogen water sources. They can be directly integrated into existing wastewater biological treatment ponds.

[0014] Wastewater flows through a distribution layer to a soil infiltration layer, which includes both EHBR and MABR membranes. The EHBR membrane, positioned on top of the soil infiltration layer, utilizes its powerful mixing and aeration capabilities to rapidly remove most organic pollutants from the wastewater. The MABR membrane, located in the middle of the soil infiltration layer, leverages its highly efficient simultaneous nitrification and denitrification capabilities to deeply remove residual ammonia nitrogen and total nitrogen from the upstream stage. Since the upstream EHBR has already consumed most of the dissolved oxygen and carbon source, the downstream MABR membrane operates in a low-carbon / dissolved oxygen environment, which is more conducive to the MABR's micro-aeration technology achieving nitrification and denitrification in the anoxic zone, resulting in higher nitrogen removal efficiency.

[0015] Biochar added to the soil infiltration layer contains abundant plant fibers and pores, providing energy and electrons for the biological reactions in the lower soil layers and promoting microbial exchange. The porous structure inside the biochar increases the porosity of the filter layer, fixing nitrate and nitrite ions at adsorption sites through ion exchange. Heavy metal ions also complex with the surface groups of the biochar through complexation, introducing more active sites and groups into the soil to improve the removal of pollutants and provide a better environment and space for microorganisms to transform pollutants.

[0016] The introduction of MABR membranes, EHBR membranes, and biochar increases the efficiency of soil microorganisms in wastewater conversion, increases oxygen utilization, reduces sludge production, increases porosity to reduce the risk of clogging, improves the denitrification function of soil infiltration, and extends the service life of the system.

[0017] This invention is based on the characteristics of EHBR / MABR membrane technology, combined with the principle and purification target of soil infiltration. It utilizes EHBR / MABR membranes to remove pollutants such as COD, ammonia nitrogen, and TN, while soil and biochar mainly absorb elements such as nitrogen, phosphorus, and heavy metals. The complementary advantages achieve balanced water quality compliance and improvement.

[0018] Based on the above technical solutions, further, the particle size of the gravel is 20~35mm, the particle size of the loam is 0.002mm~2mm, and the particle size of the biochar is 0.90mm~1.20mm.

[0019] Based on the above technical solution, the water distribution layer further includes, from top to bottom, a first filter cloth, a first quartz sand, and an inlet water distribution pipe.

[0020] Based on the above technical solution, the particle size of the first quartz sand is further specified as 1~2mm.

[0021] Based on the above technical solutions, the thickness of the water distribution layer is further 40~50mm.

[0022] Based on the above technical solutions, the natural cultivation layer further includes, from top to bottom, plants and natural cultivation soil.

[0023] Based on the above technical solutions, the thickness of the natural cultivated soil is further 30-50cm.

[0024] Based on the above technical solution, the water collection layer further includes, from top to bottom, a second filter cloth, a second quartz sand, gravel, and an outlet water collection pipe.

[0025] Based on the above technical solution, the particle size of the second quartz sand is 1~2mm, and the particle size of the gravel is 30~40mm.

[0026] The natural topsoil can be used to grow vegetables or landscape plants.

[0027] The water distribution layer includes a first layer of quartz sand, an inlet water distribution pipe, and a first filter cloth. The pipe is embedded in the first layer of quartz sand, and a first filter cloth is laid on the first layer of quartz sand to form an isolation between the natural cultivated layer and the soil of the upper natural cultivated layer. Multiple water distribution pipes are evenly distributed in the water distribution layer, and small water outlet holes are evenly distributed along the pipe direction.

[0028] The soil infiltration layer comprises gravel, an EHBR membrane, loam, biochar, and a MABR membrane. The top layer, a permeable layer of gravel, prevents blockage of the inlet distribution pipe and blocks larger impurities from migrating downwards, ensuring that wastewater and air can evenly enter the lower soil layer under gravity. The EHBR membrane, embedded in the gravel, provides oxygen to the wastewater through bubble-bursting aeration, creating an aerobic zone in the upper layer. Simultaneously, the membrane fiber surface provides a growth medium for microorganisms. Below the gravel is the main soil infiltration layer, consisting of alternating or mixed media of loam and biochar. Loam is the most versatile arable soil, possessing excellent aeration, fertilizer retention, and ease of cultivation. Suspended solids are filtered through capillary action between soil particles. Additionally, MABR membranes are evenly distributed in the middle of the soil infiltration layer. The non-bubbling aeration of the MABR membrane helps to balance the transformation process of wastewater by microorganisms in the soil, while the membrane fiber surface provides a growth medium for microorganisms.

[0029] Biochar contains abundant plant fibers and pores, providing energy and electrons for biological reactions in the underlying soil and promoting microbial exchange. The porous structure inside biochar can increase the porosity of the filter layer and, combined with clay minerals in the loam, enhance the adsorption of nitrate and nitrite ions through ion exchange.

[0030] In addition, biochar can remove ammonia nitrogen, phosphorus, nitrate nitrogen, lead, arsenic and nickel, which helps to improve the activity of microorganisms and provide them with a better environment and space for the transformation of pollutants.

[0031] The water collection layer includes a second filter cloth, a second quartz sand, gravel, and an outlet water collection pipe. The second filter cloth and the second quartz sand form an isolation layer for the upper soil medium. The gravel helps the clean water purified through the soil infiltration layer to seep into the water collection layer under the action of gravity. The outlet water collection pipe is pre-buried at the bottom of the gravel, with water inlet holes evenly distributed along the pipe direction.

[0032] Secondly, the present invention also provides a wastewater treatment method using the soil infiltration wastewater treatment device based on the MABR / EHBR biofilm, comprising the following steps: pumping wastewater to the soil infiltration wastewater treatment device, the wastewater infiltrating into the water distribution layer, the soil infiltration layer and the water collection layer through the inlet water distribution pipe, and then discharging from the outlet water collection pipe.

[0033] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention retains the main soil elements in the soil infiltration process, and loam is relatively easy to obtain.

[0034] (2) The introduction of EHBR membrane, MABR membrane and coconut shell activated carbon increases the efficiency of soil microorganisms in wastewater conversion, increases oxygen utilization, reduces sludge production, reduces the risk of blockage, improves the denitrification function of soil infiltration, and extends the service life of the system.

[0035] (3) The combination of the foamed aeration technology of EHBR membrane and the non-foamed aeration technology of MABR membrane, distributed vertically, provides a rich oxygen-containing area for the system, providing a reasonable environment for aerobic and anaerobic biological reactions, improving aeration efficiency and reducing energy consumption. At the same time, the membrane fiber area can provide a growth carrier for microorganisms, promoting the decomposition, transformation and absorption of ammonia nitrogen and phosphorus in wastewater.

[0036] (4) The soil layer and biochar layer are arranged alternately to ensure an effective supply of oxygen and carbon source, increase porosity and improve denitrification efficiency; the water purification capacity of soil infiltration is enhanced by the removal of different heavy metals by biochar, and the raw materials of this biochar are different biological wastes, which reduces resource waste and improves the ecological environment. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the soil infiltration wastewater treatment device based on MABR / EHBR biofilm of the present invention. Figure 2 This is a schematic diagram of the wastewater treatment method of the present invention. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] In the following specific implementation, the MABR and EHBR membranes were purchased from Tianjin Haizhihuang Technology Co., Ltd.

[0041] In the following specific implementation, the thickness of the naturally cultivated soil is 30-50cm, and the thickness can be adjusted according to the depth of the plant roots; the number of water inlet pipes in the water distribution layer can be arranged in combination with the water inflow and cross-sectional area; the number of water outlet pipes in the water collection layer can be arranged in combination with the water outflow and cross-sectional area.

[0042] In the following specific embodiments, the particle size of the gravel is 20-35 mm, the particle size of the loam is 0.002 mm to 2 mm, the particle size of the biochar is 0.90 mm to 1.20 mm, the particle size of the second quartz sand (42) is 1-2 mm, and the particle size of the gravel (43) is 30-40 mm.

[0043] In the following specific implementation, volcanic rock, ceramsite, iron filings, limestone, and fly ash can be mixed into the soil to increase the soil porosity and carbon source, and enhance the adsorption and conversion of phosphorus.

[0044] In the following specific embodiments, when using the soil infiltration wastewater treatment device to treat wastewater, the wastewater can be pumped to the soil infiltration wastewater treatment device by a pump in an intermittent or continuous manner as needed.

[0045] Example 1 The soil infiltration wastewater treatment device based on MABR / EHBR biofilm provided in this embodiment is as follows: Figure 1 As shown, from top to bottom, it includes a natural cultivation layer 1, a water distribution layer 2, a soil infiltration layer 3, and a water collection layer 4.

[0046] The top layer is the natural cultivation layer 1, which contains plants 11 and natural cultivation soil 12.

[0047] The water distribution layer 2, from top to bottom, includes a first quartz sand layer 22, an inlet water distribution pipe 23, and a first filter cloth 21. The inlet water distribution pipe 23 is pre-embedded in the first quartz sand layer 22, and the first quartz sand layer 22 and the first filter cloth 21 laid on it form an isolation between the natural cultivated layer and the quartz sand layer 22, preventing soil loss from the upper natural cultivated layer 1. Three inlet water distribution pipes 23 are evenly distributed in the water distribution layer 2. Small water outlet holes are evenly distributed along the pipe direction on the inlet water distribution pipe 23.

[0048] The water inlet pipe 23 is DN32, and the first filter cloth 21 is polyester fiber eco-friendly non-woven fabric.

[0049] The soil infiltration layer 3 comprises gravel 31, EHBR membrane 34, loam 33, biochar 32, and MABR membrane 35. The soil infiltration layer 3 has a thickness of 320 mm, and the materials and thicknesses of each filter layer are as follows: gravel 60 mm, loam 60 mm, biochar 20 mm, loam 100 mm, biochar 20 mm, and loam 60 mm.

[0050] The top of the soil infiltration layer 3 is a permeable layer composed of gravel 31, which prevents the water inlet pipe from being blocked and also blocks larger impurities from migrating downwards, ensuring that sewage and air can enter the lower soil layer evenly under the action of gravity.

[0051] The EHBR membrane 34, pre-embedded in gravel, provides oxygen to the wastewater through bubble aeration, creating an aerobic zone in the upper layer while simultaneously providing a growth carrier for microorganisms on the membrane fiber surface. Three EHBR membranes 34 are evenly distributed below the inlet water distribution pipe 23, with each membrane having an area of ​​3.5 m². 2 .

[0052] Below the gravel layer 3 is the main soil permeability layer 3, consisting of alternating layers of loam 33 and biochar 32. Loam 33 is the most versatile arable soil, possessing excellent aeration, fertilizer retention, and ease of cultivation. Suspended solids are filtered through capillary action between soil particles. The loam 33 is taken from ordinary vegetable gardens. Biochar 32 is a mixture of biochar A, biochar B, and coconut shell activated carbon. Biochar A is prepared by calcining cotton stalks at 600℃ for 2 hours, and biochar B is prepared by calcining crayfish shells at 600℃ for 2 hours. The mass ratio of biochar A, biochar B, and coconut shell activated carbon is 2:1:2, with biochar A weighing 8 kg, biochar B weighing 4 kg, and coconut shell activated carbon weighing 8 kg.

[0053] MABR membranes 35 are evenly distributed in the middle of the soil infiltration layer 3. The bubble-free aeration of the MABR membranes 35 can balance the transformation process of wastewater by microorganisms in the soil. At the same time, the surface of the membrane fibers provides a growth carrier for microorganisms. Three MABR membranes 35 are evenly distributed in the middle of the loam 33, and the area of ​​each membrane is 3.5m². 2 .

[0054] The water collection layer 4 consists of a second filter cloth 41, a second quartz sand 42, gravel 43, and an outlet water collection pipe 44. The second filter cloth 41 and the second quartz sand 42 form an isolation layer for the upper soil medium. The gravel 43 helps the purified water that has passed through the soil infiltration layer to seep into the outlet water collection pipe 44 under the action of gravity. Four outlet water collection pipes 44 are evenly embedded at the bottom of the gravel 43, with inlet holes evenly distributed along the pipe direction, and the water is discharged to other uses.

[0055] The second filter cloth 41 is a water-permeable but soil-impermeable eco-friendly non-woven fabric made of polypropylene or polyester fiber.

[0056] The water outlet collection pipe 44 is DN40.

[0057] Example 2 The difference between this embodiment and Embodiment 1 is that the mass ratio of biochar A, biochar B and coconut shell activated carbon is 3:1:1.

[0058] Comparative Example 1 The difference between this comparative example and Example 1 is that it does not contain a MABR membrane.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that it does not contain an EHBR membrane.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is that it does not contain MABR membrane and EHBR membrane.

[0061] Comparative Example 4 The difference between this comparative example and Example 1 is that it does not contain biochar.

[0062] Comparative Example 5 The difference between this comparative example and Example 1 is that the mass ratio of biochar A, biochar B and coconut shell activated carbon is 10:1:2.

[0063] Comparative Example 6 The difference between this comparative example and Example 1 is that the mass ratio of biochar A, biochar B and coconut shell activated carbon is 2:10:2.

[0064] Application examples This application example provides a wastewater treatment method using the soil infiltration wastewater treatment device based on MABR / EHBR biofilm in Examples 1-3 and Comparative Examples 1-6, including the following steps: Figure 2 As shown, wastewater is pumped intermittently to the soil infiltration wastewater treatment device. The wastewater infiltrates into the distribution layer, soil infiltration layer, and collection layer through the inlet distribution pipe, and then exits from the outlet collection pipe. The wastewater load is 1.2 cm / h, the aeration pressure is 20 kPa, and continuous aeration is used. After two weeks of commissioning and one month of continuous operation, COD, ammonia nitrogen, total phosphorus, and lead content were tested according to the spectrophotometric standards: COD HJ / T 399-2007, ammonia nitrogen HJ 535-2009, total phosphorus GB 11893-89, and lead GB / T 223.29-2008. The test results are shown in Table 1. The values ​​of each indicator measured in the influent and effluent are the average values ​​under stable operation.

[0065] Table 1. Water quality test results of the examples and comparative examples

[0066] A comparison of Examples 1 and 2 shows that the higher the content of biochar A and biochar B, the higher the final removal rate of phosphorus and lead.

[0067] As can be seen from the comparison between Example 1 and Comparative Example 1, when there is no MABR membrane, the lack of bubble-free explosion gas from the MABR membrane reduces the efficiency of the entire system for denitrification.

[0068] The comparison between Example 1 and Comparative Example 2 shows that when there is no EHBR membrane, the lack of EHBR results in bubble bursts, reduced oxygen content in the tank, reduced water distribution uniformity, and reduced decomposition rate of COD and ammonia nitrogen by microorganisms.

[0069] As can be seen from the comparison between Example 1 and Comparative Example 3, the removal rates of ammonia nitrogen and COD are significantly reduced when MABR membrane and EHBR membrane are not present.

[0070] As can be seen from the comparison between Example 1 and Comparative Example 4, when biochar is not present, the removal rates of phosphorus and lead are reduced, and the adsorption function of biochar is required to make the effluent meet the Class V water standard.

[0071] As can be seen from the comparison between Example 1 and Comparative Examples 5 and 6, both excessive and insufficient amounts of biochar A and biochar B will affect the removal rates of phosphorus and lead.

[0072] In summary, the soil infiltration wastewater treatment method and apparatus based on MABR / EHBR biofilm provided by this invention can significantly improve the removal of ammonia nitrogen, COD, total phosphorus and heavy metal lead from wastewater, and the effluent can meet the Class IV surface water standard (GB3838-2022).

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A soil infiltration sewage treatment device based on MABR / EHBR biofilm, characterized in that, From top to bottom, it includes the natural cultivation layer (1), the water distribution layer (2), the soil infiltration layer (3), and the water collection layer (4). The soil infiltration layer (3) consists of a permeable layer and a soil infiltration layer body from top to bottom; the permeable layer includes uniformly laid gravel (31), and an EHBR membrane (34) is laid in the gravel (31); the soil infiltration layer body includes loam (33) and biochar (32), and a MABR membrane (35) is laid in the middle of the soil infiltration layer. The biochar (32) is a mixture of biochar A, biochar B and coconut shell activated carbon. Biochar A is obtained by calcining cotton stalks, and biochar B is obtained by calcining lobster shells. The mass ratio of biochar A, biochar B and coconut shell activated carbon is (1~3):1:(1~3).

2. The soil infiltration wastewater treatment device based on MABR / EHBR biofilm as described in claim 1, characterized in that, The loam (33) and biochar (32) are laid alternately or mixed together.

3. The soil infiltration wastewater treatment device based on MABR / EHBR biofilm as described in claim 1, wherein the particle size of the gravel (31) is 20-35 mm, the particle size of the loam (33) is 0.002 mm to 2 mm, and the particle size of the biochar (32) is 0.90 mm to 1.20 mm.

4. A soil infiltration wastewater treatment device based on MABR / EHBR biofilm as described in claim 1, characterized in that, The water distribution layer (2) includes, from top to bottom, a first filter cloth (21), a first quartz sand (22), and an inlet water distribution pipe (23).

5. A soil infiltration wastewater treatment device based on MABR / EHBR biofilm as described in claim 4, characterized in that, The particle size of the first quartz sand (22) is 1~2 mm.

6. A soil infiltration wastewater treatment device based on MABR / EHBR biofilm as described in claim 1, characterized in that, The natural cultivated layer (1) consists of plants (11) and natural cultivated soil (12) from top to bottom.

7. A soil infiltration wastewater treatment device based on MABR / EHBR biofilm as described in claim 1, characterized in that, The water collection layer (4) includes, from top to bottom, a second filter cloth (41), a second quartz sand (42), gravel (43) and an outlet water collection pipe (44).

8. A soil infiltration wastewater treatment device based on MABR / EHBR biofilm as described in claim 7, characterized in that, The particle size of the second quartz sand (42) is 1~2 mm, and the particle size of the gravel (43) is 30~40 mm.

9. A wastewater treatment method using a soil infiltration wastewater treatment device based on a MABR / EHBR biofilm as described in any one of claims 1 to 8, characterized in that, The process includes the following steps: the sewage is pumped to the soil infiltration sewage treatment device, the sewage infiltrates into the water distribution layer (2), the soil infiltration layer (3) and the water collection layer (4) through the inlet water distribution pipe (23), and then exits from the outlet water collection pipe (44).

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