Device and method for harmless treatment and resource utilization of domestic sewage

Abstract

The invention provides a domestic sewage harmless treatment and resource utilization device and method, and belongs to the technical field of domestic sewage treatment. The device comprises a multi-lattice septic tank, the multi-lattice septic tank comprises a plurality of lattice chambers which are connected in sequence, the multi-lattice septic tank is suitable for carrying out precipitation and anaerobic fermentation on domestic sewage containing pathogenic microorganisms to obtain first treated sewage, and the ratio of chemical oxygen demand to total nitrogen of the first treated sewage is 1.5-3.0; the harmless chamber is connected with the multi-grid septic tank, an aeration device and a first biological filler are arranged in the harmless chamber, a biological membrane containing ammonia oxidizing bacteria is hung on the first biological filler, and the harmless chamber is suitable for carrying out nitrosation treatment on the first treated sewage from the multi-grid septic tank under the aeration condition to obtain second treated sewage containing 0.1-1.8 mg / L of free nitrous acid; wherein in the innocent treatment chamber, free nitrous acid is used for removing or killing pathogenic microorganisms, so that the innocent treatment is completed.

Description

Technical Field

[0001] This invention relates to the field of domestic sewage treatment, and in particular to an apparatus and method for the harmless treatment and resource utilization of domestic sewage. Background Technology

[0002] In rural areas, there is a tradition of using composted excrement from dry toilets as fertilizer for farmland; this model is known as the "farm-to-field recycling model." With socio-economic development, flush toilets have partially replaced traditional dry toilets, becoming the mainstream model for rural toilet renovation. The "flushing toilet + three-compartment septic tank" model accounts for a significant proportion. While this model improves the toilet environment for farmers, it also generates a large amount of wastewater. Returning this wastewater to farmland for resource utilization is a reasonable choice. However, before resource utilization, the wastewater must first be rendered harmless. It is well known that in addition to nutrients such as nitrogen and phosphorus, excrement may also contain pathogens. Direct resource utilization without harmless treatment poses safety risks. According to GB 7959-2012 "Hygienic Requirements for Harmless Treatment of Excrement," excrement needs to undergo composting and fermentation treatment for no less than 30 days to meet the harmless treatment standard. The currently promoted "flushing toilet + three-compartment septic tank" toilet renovation model cannot meet the requirement of harmlessness if the treated wastewater from the three-compartment septic tank is directly reused in farmland. This is because the wastewater stays in the three-compartment septic tank for about 15 days, which is far less than the minimum of 30 days stipulated in the "Sanitary Requirements for Harmless Treatment of Feces" and even less than the minimum of 60 days stipulated in the "Technical Specification for Construction of Rural Three-Compartment Household Toilets" GB / T 38836-2020.

[0003] To address the aforementioned issues, two conventional approaches exist: reducing toilet wastewater production and increasing the effective volume of the three-compartment septic tank. To meet the requirements of the "Technical Specification for Construction of Rural Three-Compartment Household Toilets" GB / T 38836-2020, following the first approach, the volume of toilet wastewater generated per use should not exceed 1.7 liters. However, based on the currently widely promoted "flush toilet + three-compartment septic tank" toilet renovation model, there is no feasible improvement technology to achieve such a low volume of toilet wastewater. Following the second approach, the effective volume of the three-compartment septic tank needs to be increased to approximately 6.5 cubic meters. Considering that each household already has a 1.5 cubic meter septic tank, installing another 4.8 cubic meter septic tank is unlikely to be feasible. This illustrates one of the challenges in promoting the resource utilization of toilet wastewater: how to achieve harmless treatment based on the current toilet renovation model. Summary of the Invention

[0004] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides an apparatus and method for the harmless treatment and resource utilization of domestic sewage.

[0005] According to one embodiment of the present invention, an apparatus for harmless treatment and resource utilization of domestic sewage is provided, comprising: a multi-compartment septic tank, including multiple compartments connected in sequence, suitable for sedimentation and anaerobic fermentation of domestic sewage containing pathogenic microorganisms to obtain first treated sewage, wherein the ratio of chemical oxygen demand (COD) to total nitrogen (TN) of the first treated sewage is 1.5 to 3.0; a harmless treatment chamber connected to the multi-compartment septic tank, wherein the harmless treatment chamber is equipped with an aeration device and a first biological packing material, the first biological packing material being coated with a biofilm containing ammonia-oxidizing bacteria (AOB), suitable for nitrification treatment of the first treated sewage from the multi-compartment septic tank under aeration conditions to obtain second treated sewage containing 0.1 to 1.8 mg / L of free nitrite (FNA); wherein, in the harmless treatment chamber, FNA is used to remove or kill pathogenic microorganisms in order to complete the harmless treatment.

[0006] According to another embodiment of the present invention, a method for treating domestic sewage using the apparatus for harmless treatment and resource utilization of domestic sewage as described above is provided, comprising the following steps: using a multi-compartment septic tank to perform sedimentation and anaerobic fermentation on domestic sewage containing pathogenic microorganisms to obtain first treated sewage, wherein the ratio of COD to TN in the first treated sewage is 1.5 to 3.0; using a harmless treatment chamber under aeration conditions to perform nitrification treatment on the first treated sewage from the multi-compartment septic tank to obtain second treated sewage containing 0.1 to 1.8 mg / L of free nitrite; and removing or killing pathogenic microorganisms in the second treated sewage based on FNA to complete the harmless treatment.

[0007] As can be seen from the above technical solutions, the apparatus and method for harmless treatment and resource utilization of domestic sewage of the present invention have at least one or a part of the following beneficial effects:

[0008] According to the embodiments of the present invention, a device for the harmless treatment and resource utilization of domestic sewage can be set up after a multi-compartment septic tank. By controlling the ratio of COD to TN of the sewage entering the harmless treatment chamber, a biofilm of suitable thickness can be formed under aeration conditions, constructing a biofilm system that can contact the dissolved oxygen gradient to ensure the dominant growth of AOB bacteria. Furthermore, based on the synergistic and sustained inhibition of nitrite-oxidizing bacteria (NOB) by high concentrations of FNA and low concentrations of contactable dissolved oxygen, the stability of the nitrification reaction is ensured, so that the FNA concentration is maintained at a relatively high level. This ensures that pathogenic microorganisms are effectively removed or killed using DNA within the harmless treatment chamber. In this way, it is not necessary to extend the composting and fermentation treatment to 30 days, nor is it necessary to equip a harmless treatment chamber with a large volume, thus ensuring the stability of the harmless treatment effect. Attached Figure Description

[0009] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0010] Figure 1 This is a schematic diagram of the structure of a device for harmless treatment and resource utilization of domestic sewage according to an embodiment of the present invention;

[0011] Figure 2 This is a schematic diagram of the structure of an apparatus for the harmless treatment and resource utilization of domestic sewage according to another embodiment of the present invention;

[0012] Figure 3 This is a flowchart illustrating the method for harmless treatment and resource utilization of domestic sewage according to an embodiment of the present invention.

[0013] In the above figures, the meanings of the reference numerals are as follows:

[0014] 10. Multi-compartment septic tank;

[0015] 11. Grid room;

[0016] 20. Disposal room;

[0017] 21. Aeration device;

[0018] 211. Aeration pipe;

[0019] 212. Aeration disc;

[0020] 22. First biological packing material;

[0021] 30. Soil treatment unit;

[0022] 31. Water distributor;

[0023] 32. Soil layer;

[0024] 40. Anaerobic ammonia oxidation unit;

[0025] 41. Buffer room;

[0026] 411. Pipeline access;

[0027] 412. Sedimentation and sludge storage hopper;

[0028] 42. Anaerobic ammonia oxidation chamber;

[0029] 421. Second biological packing material;

[0030] 422. Discharge tube. Detailed Implementation

[0031] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0033] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0034] Early research suggested that free radical septic tanks (FNAs) posed a threat to microorganisms within wastewater treatment systems and reduced treatment performance. However, further research revealed that utilizing the bactericidal activity of certain concentrations of FNAs could optimize integrated wastewater management, addressing issues such as corrosion and odor. Nevertheless, few studies reported its application in the eradication of pathogens in wastewater treatment. In realizing this invention, it was discovered that by equipping the third chamber of a widely constructed three-chamber septic tank with an aeration device, or by adding an aeration chamber after the third chamber as a harmless treatment chamber, aerobic treatment of the effluent from the three-chamber septic tank can be performed under aeration conditions. This generates FNAs, which are then maintained at a relatively stable concentration within a suitable range. FNAs can then be used to disinfect pathogens in domestic sewage, achieving harmless treatment of domestic wastewater. This eliminates the need for extended fermentation treatment exceeding 30 days and the requirement for a large-volume harmless treatment chamber, demonstrating significant potential for widespread application.

[0035] Specifically, according to one embodiment of the present invention, an apparatus for the harmless treatment and resource utilization of domestic sewage is provided. Figure 1 This is a schematic diagram of the structure of a device for the harmless treatment and resource utilization of domestic sewage according to an embodiment of the present invention. Figure 1As shown, the apparatus of the present invention may include a multi-compartment septic tank 10 and a harmless treatment chamber 20. The multi-compartment septic tank 10 includes multiple compartments 11 connected in sequence, suitable for sedimentation and anaerobic fermentation of domestic sewage containing pathogenic microorganisms to obtain first treated sewage, wherein the COD to TN ratio of the first treated sewage is 1.5~3.0. The harmless treatment chamber 20 is connected to the multi-compartment septic tank 10 and is equipped with an aeration device 21 and a first biological packing material 22. The first biological packing material 22 is covered with a biofilm containing AOB, suitable for nitrification treatment of the first treated sewage from the multi-compartment septic tank 10 under aeration conditions to obtain second treated sewage containing 0.1~1.8 mg / L of FNA. In the harmless treatment chamber 20, FNA is used to remove or kill pathogenic microorganisms to complete the harmless treatment.

[0036] According to an embodiment of the present invention, there is no obvious limitation on the number of compartments in the multi-compartment septic tank 10, as long as the first treated wastewater after treatment by the multi-compartment septic tank 10 can meet the condition of COD / TN being between 1.5 and 3.2. Thus, the thickness of the biofilm in the harmless treatment chamber 20 can be adjusted within a suitable range based on the appropriate COD / TN, and the FNA concentration can be maintained at a high level.

[0037] In some examples, the multi-compartment septic tank 10 can be a two-compartment or three-compartment septic tank, which is a common type of wastewater treatment facility that has already been constructed. For example... Figure 1 As shown, when the multi-compartment septic tank 10 is a two-compartment septic tank, the harmless treatment chamber 20 can be integrated with the multi-compartment septic tank 10 to form a three-compartment septic tank. That is, the last compartment of the three-compartment septic tank can be used as the harmless treatment chamber 20, reducing the renovation cost. Of course, it is not limited to this. The harmless treatment chamber 20 can also be added after the existing two-compartment septic tank. The harmless treatment chamber 20 can be connected to the two-compartment septic tank through pipes.

[0038] In some other examples, when the multi-compartment septic tank 10 is a three-compartment septic tank, the harmless treatment chamber 20 can be connected to the multi-compartment septic tank 10 through a pipe (not shown in the figure). In this case, the harmless treatment chamber 20 can be added after the last compartment of the three-compartment septic tank. The volume and structure of the harmless treatment chamber 20 can be flexibly adjusted according to the needs, and it has strong feasibility.

[0039] According to embodiments of the present invention, research has shown that pathogens such as Escherichia coli and Salmonella can be killed after exposure to FNA within a certain concentration range for a certain period of time. However, maintaining a stable high level of FNA concentration in a wastewater treatment system remains a challenge. In realizing the concept of this invention, it was found that influent conditions and biofilm thickness are both related to maintaining and stabilizing the concentration of free nitrite. Therefore, in the first treated wastewater obtained from the multi-compartment septic tank 10, the COD / TN ratio can be, for example, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, etc. At this time, the thickness of the biofilm in the harmless treatment chamber 20 can be controlled by the aforementioned appropriate ratio range, thereby ensuring the stable operation of the nitrification reaction. The proportion of ammonia nitrogen converted to nitrite nitrogen is approximately 50%~70%, the nitrite nitrogen concentration is stable, and thus the FNA concentration is maintained at a high level. If the COD / TN ratio is too low, for example, less than 1.5, the biofilm thickness is likely to be too small. In this initial stage, the proportion of ammonia nitrogen converted to nitrite nitrogen remains relatively high (approximately 50%–70%), but the nitrification reaction is prone to instability, weakening the inhibitory effect on NOB. The conversion of nitrite nitrogen to nitrate nitrogen becomes more prominent, and the FNA concentration is more likely to decrease (less than 0.01 mg / L), leading to a poorer harmlessness effect. If the COD / TN ratio is too high, for example, greater than 3.0, the biofilm thickness is likely to be too large, leading to rapid growth of heterotrophic microorganisms. These microorganisms cover the biofilm with AOB or NOB, directly reducing the proportion of ammonia nitrogen converted to nitrite nitrogen (approximately 10%–30%). The concentrations of nitrite nitrogen and FNA (less than 0.001 mg / L) are both low, resulting in a poorer harmlessness effect.

[0040] According to some specific embodiments of the present invention, for domestic sewage, such as toilet wastewater, the TN concentration is relatively stable before and after treatment by the multi-compartment septic tank 10. Therefore, the COD concentration of the effluent from the multi-compartment septic tank 10 can be changed by adjusting the COD removal effect or hydraulic retention time in the multi-compartment septic tank, thereby adjusting the COD / TN within the above-mentioned range. For example, as the hydraulic retention time increases, the COD / TN will decrease, and vice versa.

[0041] According to a more specific embodiment of the present invention, in the first treated wastewater, the COD can be 300~1600 mg / L, for example, it can be 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 700 mg / L, 800 mg / L, 1000 mg / L, 1200 mg / L, 1400 mg / L, 1600 mg / L, etc., and can be further selected as 300~800 mg / L. The ammonia nitrogen concentration can be 200–600 mg / L, for example, 200 mg / L, 220 mg / L, 240 mg / L, 260 mg / L, 280 mg / L, 300 mg / L, 320 mg / L, 350 mg / L, 380 mg / L, 400 mg / L, 450 mg / L, 500 mg / L, 550 mg / L, 600 mg / L, etc., and can be further selected as 200–300 mg / L. This is more conducive to controlling the biofilm thickness within a suitable range and ensuring the dominant growth of AOB on the biofilm, thereby maintaining the generated FNA concentration at a relatively stable high level.

[0042] According to an embodiment of the present invention, the thickness of the biofilm suspended on the first biological packing material 22 within the harmless treatment chamber 20 is 0.1~0.3 mm, for example, it can be 0.1 mm, 0.12 mm, 0.15 mm, 0.18 mm, 0.2 mm, 0.22 mm, 0.25 mm, 0.28 mm, 0.3 mm, etc. By controlling the biofilm thickness within the above range, a biofilm system driven by the concentration gradient of substrates such as contactable dissolved oxygen, ammonia nitrogen, and FNA can be constructed, that is, a layered structure in which AOB and NOB bacterial communities are distributed sequentially from the surface layer to the inner layer of the biofilm. This is more conducive to the dominant growth of AOB on the surface layer and the effective inhibition of NOB in the inner layer, thereby stabilizing the FNA concentration at 0.1~1.8 mg / L and ensuring the stability of the harmless treatment effect.

[0043] According to embodiments of the present invention, the FNA concentration within the harmless treatment chamber 20 can be, for example, 0.1 mg / L, 0.2 mg / L, 0.4 mg / L, 0.6 mg / L, 0.8 mg / L, 1.0 mg / L, 1.2 mg / L, 1.4 mg / L, 1.6 mg / L, 1.8 mg / L, etc. In practical applications, the FNA concentration is usually not fixed, but fluctuates within the aforementioned range depending on whether water enters the harmless treatment chamber. Based on this, the device provided by the present invention is suitable for treating domestic sewage, including toilet wastewater, which contains a large number of pathogenic microorganisms, such as fecal coliforms, Salmonella, and Ascaris eggs. The high concentration of FNA within the harmless treatment chamber 20 allows for the efficient elimination of these pathogenic microorganisms.

[0044] According to embodiments of the present invention, the hydraulic retention time of the harmless treatment chamber 20 is 16 hours to 2.7 days, for example, it can be 16 hours, 24 hours, 2.2 days, 2.5 days, 2.7 days, etc.; the hydraulic retention time of the multi-compartment septic tank 10 is less than or equal to 20 days, and can be further selected as 5 to 20 days, for example, 5 days, 6 days, 8 days, 10 days, 12 days, 14 days, 16 days, 18 days, 20 days, etc. It is understood that "hydraulic retention time" refers to the average retention time of domestic sewage in the harmless treatment chamber 20 or the multi-compartment septic tank 10, calculated as the ratio of the effective volume of the harmless treatment chamber 20 or the multi-compartment septic tank 10 to the influent flow rate. Here, "effective volume" refers to the actual usable space volume of the container, such as the harmless treatment chamber 20 or the multi-compartment septic tank 10. The hydraulic retention time of the harmless treatment chamber 20 affects the harmless treatment effect, and also affects the thickness and structure of the biofilm in the harmless treatment chamber by affecting COD / TN. By controlling the hydraulic retention time of the harmless treatment chamber 20 within the above range, the harmless treatment effect and stability can be further balanced.

[0045] According to an embodiment of the present invention, the volume ratio of the multi-compartment septic tank 10 to the harmless treatment chamber 20 can be (1~10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc. This ensures an effective retention time to guarantee the harmless treatment effect, while eliminating the need for a large-volume harmless treatment chamber 20, improving feasibility and reducing the construction or modification costs of the device.

[0046] According to an embodiment of the present invention, the first biological packing material 22 in the decontamination chamber 20 may be, for example, a spherical biological packing material. The material of the first biological packing material 22 may be polypropylene or the like, and is not particularly limited. This is beneficial for the biofilm growth of AOB and NOB.

[0047] According to an embodiment of the present invention, the aeration device 21 may include an aeration pipe 211 and an aeration disc 212 connected together. Air or oxygen is supplied to the aeration disc 212 through the aeration pipe 211. The aeration disc 212 may be located at the bottom of the harmless treatment chamber 20 to achieve uniform aeration. For example, the dissolved oxygen (DO) concentration in the harmless treatment chamber 20 may be 2~8 mg / L, such as 2 mg / L, 3 mg / L, 4 mg / L, 5 mg / L, 6 mg / L, 7 mg / L, 8 mg / L, etc., which can be used to regulate the reaction balance and optimize the microbial structure in conjunction with wastewater conditions.

[0048] According to embodiments of the present invention, for example... Figure 1As shown, the device of the present invention may further include a soil treatment unit 30, which includes a soil layer 32 and a water distributor 31. The soil layer 32 is supplemented with ferric chloride-modified biochar, and the mass ratio of the ferric chloride-modified biochar to the soil is less than or equal to 2%, further preferably 0.5% to 2%, suitable for adsorbing and purifying the second-treated wastewater; the water distributor 31 is buried in the soil layer 32 and connected to the harmless treatment chamber 20, suitable for evenly distributing the second-treated wastewater in the soil layer 32.

[0049] In some examples, the mixing mass ratio of ferric chloride-modified biochar and soil can be 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, etc. Ferric chloride-modified biochar enhances the adsorption of nitrogen and phosphorus. By controlling it within the aforementioned ranges, effective phosphorus and nitrogen fixation is ensured. Combined with the low nitrate nitrogen concentration in the harmless treatment chamber 20 and the effective adsorption of nitrogen by the soil layer 32, nitrate nitrogen infiltration into groundwater can be effectively prevented. This solves the problem of weak nitrate nitrogen adsorption and retention capacity in general soil systems, leading to serious groundwater pollution.

[0050] Thus, through the aforementioned land reclamation and reuse method, domestic sewage, such as toilet wastewater, is treated harmlessly and then utilized on-site as a resource, enhancing the nitrogen and phosphorus fixation effects of the soil system. In the second-treatment wastewater, after harmless treatment, nitrogen and phosphorus are adsorbed by soil layer 32 and purified by microorganisms. Soil layer 32 adsorbs most of the phosphorus, and modified biochar adsorbs most of the nitrogen. The adsorbed nitrogen and phosphorus will be released when soil layer 32 lacks or needs nutrients, for example, for crop growth.

[0051] In some examples, ferric chloride-modified biochar can be prepared by impregnation. Furthermore, in this invention, the preparation method of ferric chloride-modified biochar may include steps 1 to 3.

[0052] In step 1, the process involves impregnation, sonication, and evaporation. Specifically, biochar can be impregnated in a ferric chloride solution, followed by sonication and evaporation to obtain modified biochar, ensuring that ferric chloride is fully adsorbed or loaded onto the biochar. For example, 677.6 g of FeCl3·6H2O is weighed and dissolved in 28 L of deionized water (the solid can be added in portions to avoid clumping and excessive local concentration due to exothermic reactions). 2.8 kg of biochar is impregnated in 28 L of ferric chloride solution, sonicated at 25°C for 30 min, and the mixture is transferred to a beaker and evaporated in a water bath (until no significant free water remains).

[0053] Step 2: Tube furnace heat treatment. Specifically, the modified biochar obtained after evaporation can be heat-treated in a tube furnace to obtain calcined modified biochar. For example, the modified biochar obtained in Step 1 can be loaded into a quartz boat and pushed into the isothermal zone of the tube furnace. Vacuum is drawn, followed by high-purity nitrogen: this vacuuming / nitrogen purging is repeated 2-3 times to fully replace the air. Heating is performed under nitrogen protection: the temperature is increased to 300°C at a rate of 10°C / min and held for 60 min. After natural cooling to room temperature, the sample is removed.

[0054] Step 3: Washing, Drying, and Preservation. Specifically, the calcined modified biochar can be washed, dried, and preserved sequentially. For example, the calcined sample can be rinsed three times with deionized water and then dried in a 45°C oven for 24 hours to obtain ferric chloride modified biochar.

[0055] According to some specific embodiments of the present invention, the water distributor 31 can be buried within 40 cm below the soil layer 32, so that the second treated wastewater can be evenly distributed within the soil layer 32 under gravity. For example, the water distributor 31 can be a water distribution pipe with a diameter of DN40 and a water distribution hole diameter of 8 mm.

[0056] According to some embodiments of the present invention, for some environmentally sensitive areas or situations where there are no conditions or needs for resource utilization, an anaerobic ammonia oxidation unit 40 can be used to replace the aforementioned soil treatment unit. After treatment by the anaerobic ammonia oxidation unit 40, the wastewater can achieve the standard discharge.

[0057] Figure 2 This is a schematic diagram of a device for the harmless treatment and resource utilization of domestic sewage according to another embodiment of the present invention, wherein the multi-compartment septic tank 10 is omitted. Figure 2 As shown, the apparatus of the present invention may further include an anaerobic ammonia oxidation unit 40, which includes a buffer chamber 41 and an anaerobic ammonia oxidation chamber 42. The buffer chamber 41 is connected to the harmless treatment chamber 20 and is used to reduce dissolved oxygen in the second treated wastewater from the harmless treatment chamber 20 to obtain third treated wastewater. The anaerobic ammonia oxidation chamber 42 is connected to the buffer chamber 41 and is inoculated with anaerobic ammonia oxidation sludge. It is used to perform anaerobic ammonia oxidation treatment on the third treated wastewater from the buffer chamber 41, so that the effluent from the anaerobic ammonia oxidation chamber 42 meets environmental discharge standards. It is understood that the environmental discharge standards are determined based on the actual discharge area and discharge water area, and may be standards such as the "Urban Wastewater Treatment Plant Pollutant Discharge Standard" or the "Integrated Wastewater Discharge Standard." For example, environmental discharge standards may include: COD not exceeding 100 mg / L, ammonia nitrogen not exceeding 15 mg / L, and TN not exceeding 20 mg / L.

[0058] This setup utilizes the buffer chamber 41 to consume dissolved oxygen from the second-treated wastewater, thereby providing an anaerobic environment for the anaerobic ammonia oxidation reaction in the anaerobic ammonia oxidation chamber 42. The third-treated wastewater from the buffer chamber 41 is then treated through the anaerobic ammonia oxidation reaction. Unreacted ammonia nitrogen reacts with the generated nitrite nitrogen to produce nitrogen gas. The COD and nitrogen content in the effluent can meet environmental emission standards, making it suitable for use in areas with sensitive water sources or where there are no conditions or needs for resource utilization.

[0059] According to an embodiment of the present invention, the bottom of the buffer chamber 41 is funnel-shaped, suitable for storing sludge settled in the second treated wastewater, preventing the sludge from accumulating and entering the anaerobic ammonia oxidation chamber 42. For example, the bottom of the buffer chamber 41 is provided with a funnel-shaped sedimentation sludge storage hopper 412 for settling the activated sludge in the second treated wastewater transported through the pipeline passage 411.

[0060] At this point, the second treated wastewater can enter from the bottom of the buffer chamber 41 as the lower plugging liquid. After sufficient sedimentation and reduction of dissolved oxygen in the buffer chamber 41, the third treated wastewater is obtained. Subsequently, the third treated wastewater can exit from the top of the buffer chamber 41 as the upper plugging liquid.

[0061] According to an embodiment of the present invention, a second biological packing material 421 is provided inside the anaerobic ammonia oxidation chamber 42, and the second biological packing material 421 is loaded with anaerobic ammonia oxidation sludge. Thus, the content of ammonia nitrogen and nitrite nitrogen in the effluent after treatment by the anaerobic ammonia oxidation chamber 42 is significantly reduced. The wastewater treated by the anaerobic ammonia oxidation chamber 42 can be discharged through the effluent pipe 422.

[0062] For example, the second biological packing material 421 can be a polyurethane sponge packing material, which can grow anaerobic ammonia oxidation sludge within the interlayer of different polyurethane sponge packing materials, thus facilitating the fixation and growth of anaerobic ammonia oxidation sludge.

[0063] According to another aspect of the present invention, a method for treating domestic sewage using the apparatus for harmless treatment and resource utilization of domestic sewage as described above is also provided. Figure 3 This is a flowchart illustrating the method for harmless treatment and resource utilization of domestic sewage according to an embodiment of the present invention. Figure 3 As shown, the method of the present invention may include the following steps S1 to S3.

[0064] In step S1, the domestic sewage containing pathogenic microorganisms is subjected to sedimentation and anaerobic fermentation in the multi-compartment septic tank 10 to obtain the first treated sewage, wherein the ratio of COD to TN of the first treated sewage is 1.5 to 3.0; the specific sedimentation and anaerobic fermentation equipment and conditions have been described above and will not be repeated here.

[0065] In step S2, the first treated wastewater from the multi-compartment septic tank 10 is subjected to nitrification treatment in the harmless treatment chamber 20 under aeration conditions to obtain the second treated wastewater containing 0.1~1.8 mg / L of FNA; the specific nitrification treatment device and conditions have been described above and will not be repeated here.

[0066] In step S3, pathogenic microorganisms in the second treated wastewater are removed or killed based on FNA in order to complete the harmless treatment; the specific harmless treatment device and conditions have been described above and will not be repeated here.

[0067] According to an embodiment of the present invention, based on the above method, after fermenting domestic sewage using a multi-compartment septic tank 10, the present invention can perform nitrification treatment on the effluent of the multi-compartment septic tank 10 under aeration conditions to obtain FNA at a high concentration. FNA can be used to disinfect pathogens in domestic sewage, which has a good harmless effect. Moreover, the treatment time is short, the process is simple and easy to implement, and it has a broad application prospect.

[0068] According to an embodiment of the present invention, the volume ratio of the first treated wastewater entering the harmless treatment chamber 20 to the effective volume of the harmless treatment chamber 20 is 1 / 16 to 1 / 4, for example, it can be 1 / 16, 1 / 14, 1 / 12, 1 / 10, 1 / 8, 1 / 6, 1 / 4, etc.

[0069] Thus, the thickness of the biofilm within the harmless treatment chamber 20 can be controlled within the aforementioned appropriate ratio range, thereby ensuring the stable operation of the nitrification reaction. The proportion of ammonia nitrogen converted to nitrite nitrogen is approximately 50%~70%, the nitrite nitrogen concentration is stable, and consequently, the FNA concentration is maintained at a high level. If the volume ratio is too small, for example less than 1 / 16, the biofilm thickness is likely to be too small. In this state, the proportion of ammonia nitrogen converted to nitrite nitrogen is still relatively high in the initial stage (approximately 50%~70%), but the nitrification reaction is prone to instability, the inhibitory effect on NOB is weakened, the reaction of nitrite nitrogen to nitrate nitrogen becomes prominent, and the FNA concentration is more likely to decrease (less than 0.01 mg / L), thus leading to a poorer harmless treatment effect. If the volume ratio is too large, such as greater than 1 / 4, the biofilm thickness is likely to be too large, which will lead to the rapid growth of heterotrophic microorganisms. Covering the biofilm with AOB or NOB directly reduces the proportion of ammonia nitrogen converted to nitrite nitrogen (about 10%~30%). The concentrations of nitrite nitrogen and FNA (less than 0.001 mg / L) are both low, resulting in poor harmlessness.

[0070] The following example, using a farmer who has installed a flush toilet and a three-compartment septic tank, will further illustrate the apparatus and method for harmless treatment and resource utilization of domestic sewage of the present invention.

[0071] Application Example 1

[0072] With an effective volume of 1.5 m³ 3 Following the three-compartment septic tank is a harmless treatment chamber 20 with an effective volume of 150 L. The bottom of the harmless treatment chamber 20 is equipped with an aeration disc 212, which is connected to an aeration blower via an aeration pipe 211. The aeration blower has a power of 10 W and an aeration rate of 15 L / min. At the same time, spherical biological fillers with a diameter of 5 cm are filled into the harmless treatment chamber 20 as the first biological filler 22. The material is polypropylene, and the filling rate is 55%. After the harmless treatment chamber 20 is connected to the three-compartment septic tank, the toilet wastewater in the three-compartment septic tank enters the newly added harmless treatment chamber 20 through the outlet of the last compartment 11. The water quality entering the harmless treatment chamber 20 is approximately COD 800, ammonia nitrogen 300, total nitrogen 320, and total phosphorus 15, all in mg / L. The fecal coliform count does not meet the "Sanitary Requirements for Harmless Treatment of Feces". In addition, there are other hygienic indicators such as Salmonella and Ascaris eggs that do not meet the "Sanitary Requirements for Harmless Treatment of Feces". After being treated in the harmless treatment chamber 20, the water quality is approximately COD 100 (excluding nitrite), ammonia nitrogen 140, nitrite 160, and total phosphorus 12, all in mg / L. The fecal coliform count is less than or equal to 10^-4, and other hygienic indicators such as Salmonella mortality rate of 100% and Ascaris egg mortality rate of greater than or equal to 95%. The concentration of free nitrite in the harmless treatment chamber 20 is maintained at 0.1-1.5 mg / L, which is sufficient to achieve the harmless treatment of toilet wastewater. The dissolved oxygen concentration in the wastewater in the harmless treatment chamber 20 is 2-8 mg / L, and the biofilm thickness on the biological packing is 0.1-0.2 mm, which allows for a gradient change in the dissolved oxygen concentration accessible to microorganisms from the liquid phase to the sludge phase, with the lowest concentration reaching below 1 mg / L.

[0073] After being treated to render it harmless, the wastewater is evenly distributed over a 5 m wide area by gravity flow through distributor 31. 2 On the soil layer 32, the water distributor 31 uses a DN40 water distribution pipe with a water distribution hole diameter of 8 mm. FeCl3-modified biochar is added to the soil layer 32 within 40 cm below the water distribution pipe and to the surface above the water distribution pipe, with a mixing ratio of 1% between the FeCl3-modified biochar and the soil. Nitrogen and phosphorus in the toilet wastewater treated in the harmless treatment chamber 20 are adsorbed by the soil layer 32 and purified by microorganisms. The soil layer 32 adsorbs most of the phosphorus, and the modified biochar adsorbs most of the nitrogen. The adsorbed nitrogen and phosphorus will be released when the soil layer 32 lacks or needs nutrients, for example, for crop growth.

[0074] Application Example 2

[0075] The main difference from Example 1 is that the wastewater treated in the harmless treatment chamber 20 is connected to the anaerobic ammonia oxidation unit 40. The anaerobic ammonia oxidation unit 40 includes a buffer chamber 41 and an anaerobic ammonia oxidation chamber 42. The buffer chamber 41 has an effective volume of 50 L and is connected to the harmless treatment chamber 20 at the bottom through a pipe passage 411. The substrate of the buffer chamber 41 is funnel-shaped and used for sludge storage. The anaerobic ammonia oxidation chamber 42 has an effective volume of 250 L and is connected to the upper part of the buffer chamber 41 through a water passage. The interior is filled with polyurethane sponge packing, and anaerobic ammonia oxidation sludge grows between the different sponge packing layers. After treatment by the anaerobic ammonia oxidation unit 40, the wastewater has the following properties: COD 30, ammonia nitrogen 5, and total nitrogen 15, all in mg / L.

[0076] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are 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 device for the harmless treatment and resource utilization of domestic sewage, comprising: A multi-compartment septic tank, comprising multiple compartments connected in sequence, is suitable for sedimentation and anaerobic fermentation of domestic sewage containing pathogenic microorganisms to obtain first-treated sewage, wherein the ratio of chemical oxygen demand to total nitrogen in the first-treated sewage is 1.5 to 3.

0. The harmless treatment chamber is connected to the multi-compartment septic tank. The harmless treatment chamber is equipped with an aeration device and a first biological packing material. The first biological packing material is covered with a biofilm containing ammonia-oxidizing bacteria. It is suitable for nitrifying the first treated wastewater from the multi-compartment septic tank under aeration conditions to obtain a second treated wastewater containing 0.1~1.8 mg / L of free nitrite. In the harmless treatment chamber, the free nitrite is used to remove or kill the pathogenic microorganisms in order to complete the harmless treatment.

2. The apparatus according to claim 1, wherein, The thickness of the biofilm is 0.1~0.3 mm.

3. The apparatus according to claim 1, wherein, The hydraulic retention time of the harmless treatment chamber is 16 hours to 2.7 days; the hydraulic retention time of the multi-compartment septic tank is less than or equal to 20 days, preferably 5 to 20 days.

4. The apparatus according to claim 1, further comprising a soil treatment unit, the soil treatment unit comprising: The soil layer contains ferric chloride-modified biochar, wherein the mass ratio of the ferric chloride-modified biochar to the soil is less than or equal to 2%, preferably 0.5% to 2%, which is suitable for adsorbing and purifying the second treated wastewater. A water distributor is buried in the soil layer and connected to the harmless treatment chamber. It is suitable for evenly spreading the second treated wastewater in the soil layer.

5. The apparatus according to claim 1, further comprising an anaerobic ammonium oxidation unit, the anaerobic ammonium oxidation unit comprising: A buffer chamber, connected to the harmless treatment chamber, is used to reduce the dissolved oxygen in the second treated wastewater from the harmless treatment chamber to obtain the third treated wastewater. An anaerobic ammonia oxidation chamber is connected to the buffer chamber. The anaerobic ammonia oxidation chamber is inoculated with anaerobic ammonia oxidation sludge and is suitable for anaerobic ammonia oxidation treatment of the third-stage wastewater from the buffer chamber, so that the effluent from the anaerobic ammonia oxidation chamber meets environmental discharge standards.

6. The apparatus according to claim 5, wherein: The bottom of the buffer chamber is funnel-shaped, which is suitable for storing sludge settled in the second treated wastewater; And / or, the anaerobic ammonia oxidation chamber is provided with a second biological packing material, the second biological packing material being loaded with the anaerobic ammonia oxidation sludge.

7. The apparatus according to claim 1, wherein, The multi-compartment septic tank is a three-compartment septic tank, and the multi-compartment septic tank and the harmless treatment chamber are connected by pipes; Alternatively, the multi-compartment septic tank and the harmless treatment chamber can form an integrated three-compartment septic tank.

8. The apparatus according to claim 1 or 7, wherein, The volume ratio of the multi-compartment septic tank to the harmless treatment chamber is (1~10):

1.

9. A method for treating domestic sewage using the apparatus for harmless treatment and resource utilization of domestic sewage as described in any one of claims 1 to 8, comprising the following steps: A multi-compartment septic tank is used to settle and anaerobic ferment domestic sewage containing pathogenic microorganisms to obtain first-treated sewage, wherein the ratio of chemical oxygen demand to total nitrogen in the first-treated sewage is 1.5 to 3.

0. The first treated wastewater from the multi-compartment septic tank was subjected to nitrification treatment in a harmless treatment chamber under aeration conditions to obtain a second treated wastewater containing 0.1~1.8 mg / L of free nitrite. The free nitrite is used to remove or kill pathogenic microorganisms in the second treated wastewater in order to complete the harmless treatment.

10. The method according to claim 9, wherein, The chemical oxygen demand (COD) of the first treated wastewater is 300-1600 mg / L, and the ammonia nitrogen concentration is 200-600 mg / L. And / or, the volume ratio of the first treated wastewater in the harmless treatment chamber to the effective volume of the harmless treatment chamber is 1 / 16 to 1 / 4.

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