Sulfur autotrophic multistage soil infiltration system and application

Abstract

The invention belongs to the technical field of sewage treatment, and provides a sulfur autotrophic multistage soil infiltration system and application. The system comprises a sulfur autotrophic multi-stage soil infiltration reactor, an intermittent micro-aeration module, a uniform water distribution module and a water collection layer, a nitrification unit, a denitrification unit and a phosphorus removal unit are sequentially distributed on the sulfur autotrophic multi-stage soil infiltration reactor from top to bottom; the nitration unit comprises a percolation layer, and the percolation layer comprises filler I; the percolation layer of the denitrification unit comprises a mixed filler II, the soil mixing block comprises a mixed filler IV, the percolation layer of the phosphorus removal unit comprises a mixed filler III, and the soil mixing block comprises a mixed filler V. The sulfur autotrophic multistage soil infiltration system has excellent CODcr and nitrogen and phosphorus removal performance, good impact resistance and anti-blocking performance, high economic benefit and small occupied area, solves the problem of insufficient nitrification, strengthens the sulfur autotrophic denitrification process, and promotes further treatment, application and popularization of decentralized sewage.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a sulfur autotrophic multi-stage soil infiltration system and application thereof. Background Art

[0002] Sewage in remote areas is often dispersed, small in scale, and lacks a sound sewage treatment infrastructure. A large amount of untreated or substandard wastewater is still directly discharged into the surrounding environment, which has an adverse impact on public health and the ecosystem. Decentralized sewage treatment is an important part of achieving water pollution control goals. Existing decentralized sewage treatment technologies mainly include biofilm technology, stabilization ponds, purification tanks, artificial wetlands, and integrated equipment, but they generally have key technical problems such as insufficient nitrogen and phosphorus removal efficiency, large land area, easy clogging, large sludge production, high energy consumption, and high requirements for professional and technical personnel.

[0003] The multi-stage soil infiltration system (MSL system) was first proposed by Japanese environmental engineer Akira Yamamoto in 1989 as an environmentally friendly, low-cost, and highly efficient decentralized sewage treatment solution. It mainly relies on its infiltration layer for nitrification, soil mixing blocks for heterotrophic denitrification, and phosphorus absorption and precipitation removal. However, the traditional structure system often shows insufficient nitrification in the infiltration layer, and the heterotrophic denitrification process is greatly affected by the carbon source, and the sludge production is large, resulting in increased blockage and even leakage of fillers, and problems such as insufficient denitrification efficiency frequently occur. Compared with heterotrophic denitrification technology, elemental sulfur autotrophic denitrification uses S0 as an electron donor. It has the advantages of no need to add an additional organic carbon source, weak influence of C / N, low sludge yield, and reduced secondary pollution risk, which is more in line with the requirements of high cost-effectiveness and sustainable development.

[0004] Chinese patent CN113087149A discloses a non-powered self-flowing underground soil infiltration system. This invention optimizes the zoning of the redox environment and prolongs the hydraulic retention time of sewage in the system by constructing a soil infiltration layer with variable density and thickness. However, this system relies on the self-purification ability of the soil, and the pollutant removal efficiency cannot be guaranteed. In addition, the risk of clogging is relatively high and it is not easy to maintain. Chinese patent CN114230103B discloses a rural decentralized domestic sewage treatment device based on a multi-stage soil infiltration system, which has the advantages of low construction cost, low operation and maintenance cost, and small footprint. However, the perforated plate used in this device easily affects the flow state of water, and the surface tension often causes the seepage holes to be uncontrollable. Chinese patent CN113461265A discloses a cascade soil infiltration system for treating rural domestic sewage. The invention provides an efficient, economical system suitable for treating rural domestic sewage in mountainous and semi-mountainous areas. However, the system composed of a plant layer, a soil infiltration layer and an impermeable layer underestimates the nitrification process under aerobic conditions, which may lead to insufficient ammonia nitrogen conversion or removal rate, and the soil infiltration layer improves the denitrification efficiency by burying rice straw, increasing the risks of blockage and secondary pollution. In addition, the team of Professor Huang Guohe and the team of Professor Wu Weizhong have carried out a large number of studies on the treatment of decentralized sewage by multi-stage soil infiltration systems in my country, but they are all studies on traditional heterotrophic soil infiltration systems with multiple stages in series, different filler media and ratios, operating parameters, solid carbon sources, analytical methods or pollutants. Due to the unimproved system structure and the limitations of the denitrification conditions of heterotrophic denitrification itself, there are generally poor nitrogen and phosphorus pollutant removal effects and poor anti-blocking performance.

[0005] Therefore, it is of great significance to develop new integrated devices and methods with high hydraulic load, low cost, strong environmental adaptability, fully automatic and power-free operation, simple maintenance, long service life, not easy to clog and high sewage purification efficiency for the effective treatment of decentralized sewage. Summary of the invention

[0006] The purpose of the present invention is to provide a sulfur autotrophic multi-stage soil infiltration system and application in order to overcome the deficiencies of the prior art, so as to solve the problems of low processing efficiency, insufficient nitrification capacity, strong dependence on external carbon sources, clogging risk and long-term operation instability of the current traditional MSL system in practical applications.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a sulfur autotrophic multi-stage soil infiltration system, which comprises a sulfur autotrophic multi-stage soil infiltration reactor 1, an intermittent micro-aeration module 2, a uniform water distribution module 5, and a water collection layer 18;

[0009] The sulfur autotrophic multi-stage soil infiltration reactor is sequentially distributed with a nitrification unit 8, a denitrification unit 10 and a phosphorus removal unit 14 from top to bottom, wherein the height of the nitrification unit is greater than the height of the denitrification unit and greater than the height of the phosphorus removal unit;

[0010] The nitrification unit comprises a percolation layer, and the percolation layer comprises filler I;

[0011] The denitrification unit and the phosphorus removal unit both comprise a percolation layer and a soil mixing block;

[0012] The infiltration layer 11 of the denitrification unit contains mixed filler II, and the soil mixed blocks 12 and 13 of the denitrification unit contain mixed filler IV; the infiltration layer 15 of the phosphorus removal unit contains mixed filler III, and the soil mixed blocks 16 and 17 of the phosphorus removal unit contain mixed filler V.

[0013] Preferably, the mixed filler II of the denitrification unit and the mixed filler III of the phosphorus removal unit fill the gaps between the soil mixed blocks and are attached with nitrifying bacteria.

[0014] Preferably, the soil mixing block is in the shape of a sphere and / or a brick, and is arranged in equal intervals in horizontal layers, and sulfur autotrophic denitrifying bacteria and denitrifying phosphate-accumulating bacteria grow inside the soil mixing block.

[0015] Preferably, the uniform water distribution module comprises a water inlet 6, an adjustable three-way water valve 7 connected in series with a hose, a square tube 20, and a fixing rope 21; water is introduced through the pump pressure of a low-level water storage tank or the water head pressure of a high-level water storage tank.

[0016] Preferably, the intermittent micro-aeration module is located in the middle and lower part of the nitrification unit, and the intermittent micro-aeration module comprises an aeration pump 3, a relay 4 and a lower opening aeration pipeline 9.

[0017] Preferably, the filler I is chlorite, the mixed filler II contains chlorite and sulfur autotrophic synthetic material, and the mass ratio of chlorite to sulfur autotrophic synthetic material is 4-6:4-6; the mixed filler III contains chlorite and phosphorus removal synthetic material, and the mass ratio of chlorite to phosphorus removal synthetic material is 5-7:3-5; in filler I, mixed filler II and mixed filler III, the particle size of chlorite is 2-4 mm.

[0018] Preferably, the mixed filler IV comprises soil and sulfur autotrophic synthetic material, and the mass ratio of soil to sulfur autotrophic synthetic material is 4-6:4-6; the mixed filler V comprises soil and phosphorus removal synthetic material, and the mass ratio of soil to phosphorus removal synthetic material is 5-7:3-5.

[0019] Preferably, the water collection layer comprises pebbles, the particle size of the pebbles is 2-4 cm, and the pebbles are covered with gravel to fill them, and the particle size of the gravel is 4-6 mm.

[0020] The invention also provides application of the sulfur autotrophic multi-stage soil infiltration system in treating decentralized sewage.

[0021] The beneficial effects of the present invention include the following:

[0022] 1) The sulfur autotrophic multi-stage soil infiltration system (SAD-MSL system) of the present invention adopts a brand-new structure combined with fusion innovation. The first brand-new structure is a three-level stacked unit structure of "nitrification-denitrification-phosphorus removal" distributed from top to bottom in the sulfur autotrophic multi-stage soil infiltration reactor, and the volume distribution follows the nitrification unit>denitrification unit>phosphorus removal unit; the second is a spherical soil mixing block; the fusion innovation is the combination of the sulfur autotrophic denitrification process and the MSL system.

[0023] 2) The sulfur autotrophic multi-stage soil infiltration system of the present invention has excellent COD cr The present invention adopts a simple stacking design for easy filling. The nitrification unit is independent and expanded to ensure that ammonia nitrogen enters the denitrification unit after being fully converted. The heterotrophic nitrification-aerobic denitrification effect in the nitrification unit is significant, and intermittent micro-aeration is used to promote COD cr The removal of total nitrogen; sulfur autotrophic synthetic materials are added to the soil mixing block of the denitrification unit, which does not consume organic carbon sources, prolongs the efficient operation life of the system, changes the dominant flora of soil microorganisms, significantly promotes soil denitrification, is not affected by the C / N of sewage, and achieves effective and stable removal of total nitrogen; the phosphorus removal unit is set in the lower layer to ensure sufficient microbial nutrients throughout the process, and phosphorus removal synthetic materials are mixed in the infiltration layer to improve phosphorus adsorption. Soil mixed phosphorus removal synthetic materials are used in the soil mixing block to enhance microbial absorption and utilization. By controlling the combination and proportion of each part of the filler, excellent COD is maintained. cr and nitrogen and phosphorus removal performance.

[0024] 3) The sulfur autotrophic multi-stage soil infiltration system of the present invention has good impact resistance and anti-blocking performance. The nitrification unit of the present invention is filled with chlorite, and no soil mixing block is provided, so as to improve the buffering performance and be able to withstand higher hydraulic loads; the denitrification unit and the phosphorus removal unit use spherical soil mixing blocks to improve the anti-blocking performance and reduce the risk of leakage of the filler.

[0025] 4) The sulfur autotrophic multi-stage soil infiltration system of the present invention has high economic benefits. Sulfur autotrophic denitrification replaces abnormal denitrification, and no external organic carbon source is required, which saves costs, reduces greenhouse gas emissions, and reduces sludge production and secondary pollution; its microbial community can maintain performance under different environmental conditions, has good adaptability and stability, and sulfur autotrophic denitrification can achieve a higher nitrate removal rate at a shorter hydraulic retention time, so it can provide a higher treatment efficiency at the same treatment capacity. The system of the present invention has low operating energy consumption, basically does not require maintenance, and has low professional and technical requirements for operation and maintenance personnel.

[0026] 5) The sulfur autotrophic multi-stage soil infiltration system of the present invention occupies a small area. The present invention scientifically plans the sewage purification process through stacking and partitioning design, and the integrated box device can be buried underground or placed on the ground according to local terrain and climate.

[0027] 6) The present invention provides a decentralized sewage treatment system with high hydraulic load, low operation and maintenance cost, low clogging and high pollutant removal efficiency, which solves the problem of insufficient nitrification, strengthens the sulfur autotrophic denitrification process, and promotes the further treatment and popularization of decentralized sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of a multi-stage soil infiltration system device with brick-shaped soil mixing blocks added in Example 1;

[0029] Figure 2 This is a schematic diagram of the structure of a multi-stage soil infiltration system device with spherical soil mixing blocks added in Example 2;

[0030] Figure 3 It is a structural schematic diagram of the uniform water distribution module of the present invention;

[0031] Figures 1 to 3 Among them, 1 is a sulfur autotrophic multi-stage soil infiltration reactor, 2 is an intermittent micro-aeration module, 3 is an aeration pump, 4 is a relay, 5 is a uniform water distribution module, 6 is a water inlet, 7 is an adjustable three-way water valve, 8 is a nitrification unit, 9 is a lower opening aeration pipeline, 10 is a denitrification unit, 11 is a denitrification unit infiltration layer, 12 is a spherical soil mixing block of the denitrification unit, 13 is a brick-shaped soil mixing block of the denitrification unit, 14 is a phosphorus removal unit, 15 is a phosphorus removal unit infiltration layer, 16 is a spherical soil mixing block of the phosphorus removal unit, 17 is a brick-shaped soil mixing block of the phosphorus removal unit, 18 is a water collection layer, 19 is a water outlet, 20 is a square tube, and 21 is a fixed rope;

[0032] Figure 4 The sulfur autotrophic multi-stage soil infiltration system of Examples 1 to 4 and Comparative Examples 1 to 4 is subjected to different hydraulic loading rates to determine COD cr Removal rate of

[0033] Figure 5 is the removal rate of TP by the sulfur autotrophic multi-stage soil infiltration system of Examples 1 to 4 and Comparative Examples 1 to 4 at different hydraulic loading rates;

[0034] Figure 6 The sulfur autotrophic multi-stage soil infiltration system of Examples 1 to 4 and Comparative Examples 1 to 4 is subjected to NH4 + -N removal rate;

[0035] Figure 7The removal rates of TN by the sulfur autotrophic multi-stage soil infiltration systems of Examples 1 to 4 and Comparative Examples 1 to 4 at different hydraulic loading rates. DETAILED DESCRIPTION

[0036] The present invention provides a sulfur autotrophic multi-stage soil infiltration system, which comprises a sulfur autotrophic multi-stage soil infiltration reactor 1, an intermittent micro-aeration module 2, a uniform water distribution module 5, and a water collection layer 18;

[0037] The sulfur autotrophic multi-stage soil infiltration reactor is sequentially distributed with a nitrification unit 8, a denitrification unit 10 and a phosphorus removal unit 14 from top to bottom, wherein the height of the nitrification unit is greater than the height of the denitrification unit and greater than the height of the phosphorus removal unit;

[0038] The nitrification unit comprises a percolation layer, and the percolation layer comprises filler I;

[0039] The denitrification unit and the phosphorus removal unit both comprise a percolation layer and a soil mixing block;

[0040] The infiltration layer 11 of the denitrification unit contains mixed filler II, and the soil mixed blocks 12 and 13 of the denitrification unit contain mixed filler IV; the infiltration layer 15 of the phosphorus removal unit contains mixed filler III, and the soil mixed blocks 16 and 17 of the phosphorus removal unit contain mixed filler V.

[0041] In the present invention, the sulfur autotrophic multi-stage soil infiltration reactor is a three-stage stacked unit structure of "nitrification-denitrification-phosphorus removal" from top to bottom; the volumes of the nitrification unit, the denitrification unit and the phosphorus removal unit are appropriately adjusted according to the composition and concentration of specific pollutants.

[0042] In the present invention, the mixed filler II of the denitrification unit and the mixed filler III of the phosphorus removal unit fill the gaps between the soil mixed blocks and are attached with nitrifying bacteria.

[0043] In the present invention, the microorganisms of the sulfur autotrophic multi-stage soil infiltration reactor are derived from the soil and the added exogenous sludge, and the nitrification unit contains nitrifying bacteria.

[0044] In the present invention, the soil mixing block is preferably in the shape of a sphere and / or a brick, and the soil mixing block is arranged in equal intervals in horizontal layers, and sulfur autotrophic denitrifying bacteria and denitrifying phosphate-accumulating bacteria grow inside.

[0045] In the present invention, in the denitrification unit and the phosphorus removal unit, the total number of layers of the spherical soil mixing blocks is preferably ≥4 layers, more preferably 5 to 7 layers; the total number of layers of the brick-shaped soil mixing blocks is preferably ≥5 layers, more preferably 6 to 8 layers.

[0046] In the present invention, the infiltration layers and soil mixed blocks in the denitrification unit and the phosphorus removal unit are overlapped and filled in a regular distribution.

[0047] In the present invention, the uniform water distribution module preferably comprises a water inlet 6, an adjustable three-way water valve 7 connected in series with a hose, a square tube 20, and a fixing rope 21; water is preferably introduced through the pump pressure of a low-level water tank or the water head pressure of a high-level water tank.

[0048] In the present invention, one end of the three-way water valve is connected to the water inlet pipe, and the other end is installed with a plug. The three-way water valve is adjusted according to the water volume to maintain the uniformity of water inlet.

[0049] In the present invention, the intermittent micro-aeration module is preferably located in the middle and lower part of the nitrification unit, and the intermittent micro-aeration module preferably comprises an aeration pump 3, a relay 4 and a lower opening aeration pipeline 9, and the aeration pump is connected to the air pipe.

[0050] The intermittent micro-aeration module is set in the middle and lower part of the nitrification unit in the three-level stacked unit structure of "nitrification-denitrification-phosphorus removal". The aeration pipeline is buried in the nitrification unit filler with the air holes facing downward. The air pipes are respectively connected to the aeration pump and the buried aeration pipeline. The intermittent aeration time is controlled by a relay in coordination with the water inlet period.

[0051] In the present invention, the nitrification unit is a single medium percolation layer, the denitrification unit and the phosphorus removal unit are distributed in an overlapping manner with the percolation layer and the soil mixing block. In addition, by inoculating exogenous activated sludge into the nitrification unit and the soil mixing block respectively, the abundance and activity of functional microorganisms are improved and the startup period is shortened.

[0052] In the present invention, the filler I is preferably chlorite, the mixed filler II preferably comprises chlorite and sulfur autotrophic synthetic material, the mass ratio of chlorite and sulfur autotrophic synthetic material is preferably 4-6:4-6, and more preferably 5:5; the mixed filler III preferably comprises chlorite and phosphorus removal synthetic material, the mass ratio of chlorite and phosphorus removal synthetic material is preferably 5-7:3-5, and more preferably 6:4; in filler I, mixed filler II and mixed filler III, the particle size of chlorite is preferably 2-4 mm.

[0053] In the present invention, the mixed filler IV preferably comprises soil and sulfur autotrophic synthetic material, and the mass ratio of the soil and the sulfur autotrophic synthetic material is preferably 4-6:4-6, and more preferably 5:5; the mixed filler V preferably comprises soil and phosphorus removal synthetic material, and the mass ratio of the soil and the phosphorus removal synthetic material is preferably 5-7:3-5, and more preferably 6:4.

[0054] In the present invention, the brick-shaped soil mixing blocks of the denitrification unit and the phosphorus removal unit are sewn into a rectangular shell by cloth bags to cover the mixed fillers IV and V; the spherical soil mixing blocks are filled with mixed fillers by cloth bags to prevent leakage, and are shaped into regular spheres by suspended balls, so that the production process of the spherical soil mixing blocks is simpler.

[0055] In the present invention, the nitrification unit accounts for a large proportion of the system, is fully filled with chlorite and inoculated with a small amount of sludge in layers, so as to ensure the adsorption of ammonia nitrogen and the continuous utilization of nitrifying bacteria; the chlorite has a higher total pore volume and BET specific surface area, and the mesopores are widely distributed; in the denitrification unit, sulfur autotrophic synthetic materials are used to provide sulfur electron donors, inorganic carbon sources, trace elements and microbial life activity sites, and can release alkalinity to maintain a suitable pH value and stability in the whole process.

[0056] In the present invention, the water collection layer preferably comprises pebbles, the particle size of the pebbles is preferably 2-4 cm, the pebbles are preferably covered with gravel to fill them, and the particle size of the gravel is preferably 4-6 mm.

[0057] In the present invention, the sulfur autotrophic multi-stage soil infiltration reactor is provided with bilaterally symmetrical water outlets 19 at the nitrification unit, the denitrification unit and the bottom of the water collection layer.

[0058] The invention also provides application of the sulfur autotrophic multi-stage soil infiltration system in treating decentralized sewage.

[0059] In the present invention, during the operation of the sulfur autotrophic multi-stage soil infiltration system, sewage falls into the sulfur autotrophic multi-stage soil infiltration reactor through the uniform water distribution module, undergoes intermittent micro-aeration when flowing through the nitrification unit, and then passes through the denitrification unit and the phosphorus removal unit in sequence, and then enters the water collection layer and discharges. The water outlets are symmetrically distributed at the bottom of the nitrification unit, the denitrification unit and the water collection layer, respectively, to keep the homogeneous flow state of water in the seepage field as much as possible.

[0060] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0061] In the embodiment, the particle size of chlorite is 2-4 mm, the particle size of soil is ≤2 mm, the particle size of pebbles is 2-4 mm, the particle size of gravel is 4-6 mm, and the particle sizes of sulfur autotrophic synthetic material and phosphorus removal synthetic material are both 3-5 mm.

[0062] The exogenous sludge was taken from the end of the aerobic pool of the sewage treatment plant, with a 30-minute sedimentation ratio (SV30) of 23%. The supernatant was discarded, and 180 mL of sludge was inoculated into the soil or nitrification section chlorite in the soil mixing block. In the soil mixing block, 12 mL of each sphere and large brick with a diameter of 10 cm, and 6 mL of each sphere and small brick with a diameter of 8 cm, were inoculated and mixed with the soil. In the nitrification section, 36 mL was inoculated for each 7 cm of chlorite until it was filled, a total of 5 times.

[0063] In the present invention, the sulfur autotrophic synthetic material and the phosphorus removal synthetic material are the same as the preparation process of the patent application number CN202411654303.5, the invention name: a combined filler for artificial wetland denitrification and phosphorus removal, and an artificial wetland denitrification and phosphorus removal device and materials used in the application thereof. The sulfur autotrophic synthetic material is a nearly spherical solid with a particle size of 3 to 5 mm and a density of 1.1 to 2.2 g / cm 3 , which is hot-pressed from elemental sulfur, calcium carbonate and minerals, wherein the mass ratio of elemental sulfur to calcium carbonate is 2:1. The main components of sulfur autotrophic synthetic materials include S, O, Ca, Mg, C and Al, in addition to trace elements such as Fe, Ba, Na, P, Ti, Cr and Mn. Sulfur autotrophic synthetic materials can provide elemental sulfur electron donors, and at the same time provide alkalinity and inorganic carbon sources. The phosphorus removal synthetic material uses dolomite clay and montmorillonite clay powder as raw materials, and adds water, soluble starch and aluminum sulfate to form granulated molds. The mass ratio of dolomite clay, montmorillonite clay, soluble starch and aluminum sulfate is 1:1:1:1.

[0064] Example 1 (MSL5)

[0065] The sulfur autotrophic multi-stage soil infiltration system is made of plexiglass and has a size of 50cm×10cm×90cm. The influent is lifted to one end of the uniform water distribution module by a peristaltic pump; the sulfur autotrophic multi-stage soil infiltration reactor is a three-level stacked unit structure of "nitrification-denitrification-phosphorus removal" from top to bottom; the nitrification unit contains nitrifying bacteria and heterotrophic nitrification-aerobic denitrification bacteria; the denitrification unit and the phosphorus removal unit both contain a percolation layer and a soil mixing block. The percolation layer is a mixed filler layer. The mixed filler fills the gaps between the soil mixing blocks and is attached with nitrifying bacteria; the soil mixing blocks are arranged in equal intervals in layers horizontally, and sulfur autotrophic denitrifying bacteria and denitrifying bacteria grow inside. Polyphosphate bacteria; the percolation layer and soil mixed block in the denitrification unit and the phosphorus removal unit are overlapped and filled in a regular distribution; the uniform water distribution module includes a water inlet, an adjustable three-way water valve connected in series with a hose, a square pipe, and a fixed rope; one end of the three-way water valve is connected to the water inlet pipe, and the other end is installed with a plug; the intermittent micro-aeration module is located in the middle and lower part of the nitrification unit, and the intermittent micro-aeration module includes an aeration pump, a relay, and a lower opening aeration pipeline; the aeration pipeline is buried in the nitrification unit filler with the air hole facing downward, and the air pipe is respectively connected to the aeration pump and the buried aeration pipeline;

[0066] The height of the nitrification unit is 35 cm, and the infiltration layer is filled with chlorite; the height of the denitrification unit is 25 cm, and the brick-shaped soil mixed block is filled with soil and sulfur autotrophic synthetic materials in a mass ratio of 1:1, and the mixed filler of the infiltration layer is chlorite and sulfur autotrophic synthetic materials in a mass ratio of 1:1; the height of the phosphorus removal unit is 10 cm, and the brick-shaped soil mixed block is filled with soil and phosphorus removal synthetic materials in a mass ratio of 3:2, and the infiltration layer is filled with chlorite and phosphorus removal synthetic materials in a mass ratio of 7:3; the sizes of the brick-shaped soil mixed blocks are 14cm×10cm×4cm (13 pieces) and 5cm×10cm×4cm (4 pieces), with a horizontal spacing of 4cm and a vertical spacing of 3cm; the filling quality of the brick-shaped soil mixed blocks remains consistent.

[0067] The height of the water collection layer is 10 cm, filled with pebbles and covered with gravel; four tap outlets are symmetrically set at the nitrification unit, denitrification unit and both ends of the bottom of the water collection layer.

[0068] The steps of treating decentralized sewage by sulfur autotrophic multi-stage soil infiltration system are as follows: The influent water quality index is: COD Cr =375.7~511.5mg / L, TP=5.0~6.1mg / L, NH4 + -N=42.1~53.6mg / L,NO 3- -N=5.9~9.0mg / L, organic nitrogen=18.7~23.3mg / L, TN=71.3~81.3mg / L. The simulated decentralized sewage in the water storage tank enters the uniform water distribution module through the peristaltic pump, and then drips evenly above the sulfur autotrophic multi-stage soil infiltration reactor. The intermittent micro-aeration module works while the water enters. The decentralized sewage passes through the nitrification unit, denitrification unit and phosphorus removal unit in turn, gathers in the water collection layer, and flows out naturally from the symmetrical outlets at both ends of the bottom. 180mL of exogenous sludge is inoculated in layers in the nitrification unit. When the sewage flows through the nitrification unit, the intermittent aeration time is controlled by the relay in conjunction with the water inlet period, and then passes through the denitrification unit and the phosphorus removal unit in turn, and enters the water collection layer and then discharges; when the system is running, the symmetrical outlets at the bottom of the water collection layer are all opened, and the outlets at the bottom of the nitrification unit and the denitrification unit are opened and closed as appropriate. In order to simulate the discharge period and volatility of decentralized sewage, water was introduced for 12 hours every day, and the water inlet periods were: 6-8, 9-11, 12-14, 15-17, 18-20, and 21-23. The test period was 90 days, and the initial hydraulic loading rate was 180L / m 2 ·d, adjusted to 360L / m every 30 days 2 d and 1440L / m 2 ·d.

[0069] The pollutant concentrations and removal rates of the inlet and outlet water of the sulfur autotrophic multi-stage soil infiltration system of Example 1 at different hydraulic loading rates are shown in Table 1.

[0070] Table 1 Inlet and outlet water pollutant concentrations and removal rates at different hydraulic loading rates in Example 1

[0071]

[0072]

[0073] Table 1 shows the average removal rate. It can be seen from Table 1 that COD Cr The average removal rate of TP is always maintained at above 91.4%, which is not affected by hydraulic load; the average removal rate of TP is 180L / m 2 d and 360L / m 2 · The hydraulic loading rate of d is above 90.3%, and the hydraulic loading rate increases to 1440L / m 2 ·d, the average TP removal rate dropped to 51.8%; NH4 + The average removal rate of -N remained stable at 94.4-100.0%. 2 d and 360L / m 2 The removal was basically complete at a hydraulic loading rate of 1440 L / m 2 ·d hour NH4 + The average removal rate of -N was still 94.4%; the average removal rate of TN was 88.7-97.7%, which decreased with the increase of hydraulic loading rate.

[0074] Example 2 (MSL6)

[0075] The brick-shaped soil mixing blocks in Example 1 were replaced with spherical soil mixing blocks, the sizes of which were suspended ball shells with diameters of 10 cm (10 pieces) and 8 cm (10 pieces); the filling mass of the spherical soil mixing blocks remained consistent, and other conditions were the same as in Example 1.

[0076] The pollutant concentrations and removal rates of the inlet and outlet water of the sulfur autotrophic multi-stage soil infiltration system of Example 2 at different hydraulic loading rates are shown in Table 2.

[0077] Table 2 Inlet and outlet water pollutant concentrations and removal rates at different hydraulic loading rates in Example 2

[0078]

[0079]

[0080] Table 2 shows the average removal rate. It can be seen from Table 2 that COD CrThe average removal rate of TP was always maintained at 92.0-93.0%, which did not decrease with the increase of hydraulic loading rate, but increased slightly. The average removal rate of TP was 180L / m 2 d and 360L / m 2 The hydraulic loading rate of d was 74.0-76.7%. The increase of hydraulic load weakened the removal efficiency of TP. The hydraulic loading rate increased to 1440L / m 2 ·d, the average TP removal rate dropped to 56.2%; NH4 + The average removal rate of -N is kept stable at above 97.2%, and NH4 + -N removal is highly efficient and not affected by hydraulic load; the average removal rate of TN is 86.2-87.7%, which is basically the same under three hydraulic loading rates. It has high efficiency and stability in TN removal and is less disturbed by hydraulic load. As shown in Table 1 and Table 2, at 180L / m 2 d and 360L / m 2 The pollutants have a high removal efficiency at the hydraulic loading rate of d, and the hydraulic loading rate increases to 1440L / m 2 The pollutant removal rate fluctuated at d, and the overall removal effect weakened with the increase of hydraulic loading rate.

[0081] Example 3 (MSL7)

[0082] The nitrification unit inoculation sludge of Example 1 was replaced by soil mixed block inoculation sludge, and other conditions were the same as in Example 1.

[0083] Example 4 (MSL8)

[0084] The inoculated sludge of the nitrification unit in Example 2 was replaced by the inoculated sludge of the soil mixed block, and the other conditions were the same as in Example 2.

[0085] Comparative Example 1 (MSL1)

[0086] The intermittent aeration in Example 1 was replaced by natural reoxygenation, and other conditions were the same as in Example 1.

[0087] Comparative Example 2 (MSL2)

[0088] The intermittent aeration in Example 2 was replaced by natural reoxygenation, and other conditions were the same as in Example 2.

[0089] Comparative Example 3 (MSL3)

[0090] The inoculum sludge of the nitrification unit in Example 1 was replaced by soil mixed block inoculum sludge, and the intermittent aeration was replaced by natural reoxygenation. Other conditions were the same as in Example 1.

[0091] Comparative Example 4 (MSL4)

[0092] The inoculum sludge of the nitrification unit in Example 2 was replaced by soil mixed block inoculum sludge, and the intermittent aeration was replaced by natural reoxygenation. Other conditions were the same as in Example 2.

[0093] The sulfur autotrophic multi-stage soil infiltration system of Examples 1 to 4 and Comparative Examples 1 to 4 has a significant effect on COD under different hydraulic loading rates. cr Removal rate of TP, NH4 + The removal rates of -N and TN are as follows: Figures 4 to 7 As shown in the figure, brick-shaped soil mixing blocks are more effective in removing TP, while spherical soil mixing blocks are more effective in removing NH4 + -N and TN removal is more stable and efficient; sludge inoculated in nitrification unit is better than inoculated in soil mixed block, which makes up for the problem of low microbial abundance in nitrification unit; intermittent aeration can greatly promote COD cr NH4 + - Removal of N and TN.

[0094] Decentralized sewage enters the sulfur autotrophic multi-stage soil infiltration system of the present invention, first flows through the nitrification unit, and the COD cr Part of the pollutants such as nitrogen and phosphorus are intercepted and adsorbed by the filler, and the inoculated activated sludge grows and metabolizes under aeration conditions, consuming a large amount of COD cr The filler is used to absorb a large amount of ammonia nitrogen; organic matter is consumed by aerobic microorganisms through respiration or assimilated by heterotrophic microorganisms as nutrients, a part of the ammonia nitrogen is assimilated and utilized by aerobic microorganisms as a nitrogen source, and most of the ammonia nitrogen is fully nitrified. The chlorite continues to undergo a dynamic equilibrium adsorption and microbial desorption process, and there is a heterotrophic nitrification-aerobic denitrification process. It continues to flow through the denitrification unit, mainly converting the NO3 - -N is reduced to nitrogen gas by sulfur autotrophic denitrifying bacteria. The sulfur autotrophic synthetic material not only provides elemental sulfur electron donors, inorganic carbon sources and trace elements necessary for microbial growth, but also maintains the environmental pH value in the neutral range, promoting the sulfur autotrophic denitrification process. Finally, it flows through the phosphorus removal unit, where phosphorus, as an essential nutrient for microbial growth, is assimilated and absorbed by microorganisms in the previous unit or used for enzyme synthesis. The synergistic effect of phosphorus removal synthetic materials and soil further adsorbs and intercepts residual phosphorus for continuous use by microorganisms, while promoting the growth of polyphosphate bacteria to achieve efficient removal of phosphorus.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A sulfur autotrophic multi-stage soil infiltration system, characterized in that: The sulfur autotrophic multi-stage soil infiltration system comprises a sulfur autotrophic multi-stage soil infiltration reactor (1), an intermittent micro-aeration module (2), a uniform water distribution module (5), and a water collection layer (18); The sulfur autotrophic multi-stage soil infiltration reactor has a nitrification unit (8), a denitrification unit (10) and a phosphorus removal unit (14) distributed in sequence from top to bottom, wherein the height of the nitrification unit is greater than the height of the denitrification unit and greater than the height of the phosphorus removal unit; The nitrification unit comprises a percolation layer, and the percolation layer comprises filler I; The denitrification unit and the phosphorus removal unit both comprise a percolation layer and a soil mixing block; The infiltration layer (11) of the denitrification unit contains mixed filler II, and the soil mixing blocks (12, 13) of the denitrification unit contain mixed filler IV; the infiltration layer (15) of the phosphorus removal unit contains mixed filler III, and the soil mixing blocks (16, 17) of the phosphorus removal unit contain mixed filler V.

2. The sulfur autotrophic multi-stage soil infiltration system according to claim 1, characterized in that: The mixed filler II of the denitrification unit and the mixed filler III of the phosphorus removal unit fill the gaps between the soil mixed blocks and are attached with nitrifying bacteria.

3. The sulfur autotrophic multi-stage soil infiltration system according to claim 1 or 2, characterized in that: The soil mixing block is in the shape of a sphere and / or a brick. The soil mixing block is horizontally arranged in equal intervals and layers, and sulfur autotrophic denitrifying bacteria and denitrifying phosphorus-accumulating bacteria grow inside the soil mixing block.

4. The sulfur autotrophic multi-stage soil infiltration system according to claim 3, characterized in that: The uniform water distribution module comprises a water inlet (6), an adjustable three-way water valve (7) connected in series with a hose, a square pipe (20), and a fixing rope (21); water is introduced through the pump pressure of a low-position water storage tank or the water head pressure of a high-position water storage tank.

5. The sulfur autotrophic multi-stage soil infiltration system according to claim 3, characterized in that: The intermittent micro-aeration module is located in the middle and lower part of the nitrification unit, and comprises an aeration pump (3), a relay (4) and a lower opening aeration pipeline (9).

6. The sulfur autotrophic multi-stage soil infiltration system according to claim 4 or 5, characterized in that: The filler I is chlorite, the mixed filler II contains chlorite and sulfur autotrophic synthetic material, and the mass ratio of chlorite to sulfur autotrophic synthetic material is 4-6:4-6; the mixed filler III contains chlorite and phosphorus removal synthetic material, and the mass ratio of chlorite to phosphorus removal synthetic material is 5-7:3-5; in filler I, mixed filler II and mixed filler III, the particle size of chlorite is 2-4 mm.

7. The sulfur autotrophic multi-stage soil infiltration system according to claim 6, characterized in that: The mixed filler IV comprises soil and sulfur autotrophic synthetic material, and the mass ratio of the soil to the sulfur autotrophic synthetic material is 4-6:4-6; the mixed filler V comprises soil and phosphorus removal synthetic material, and the mass ratio of the soil to the phosphorus removal synthetic material is 5-7:3-5.

8. The sulfur autotrophic multi-stage soil infiltration system according to claim 7, characterized in that: The water collection layer comprises pebbles, the particle size of the pebbles is 2-4 cm, and the pebbles are covered with gravels to fill them, and the particle size of the gravels is 4-6 mm.

9. Use of the sulfur autotrophic multi-stage soil infiltration system according to any one of claims 1 to 8 in treating decentralized sewage.

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