A sulfur autotrophic multi-stage soil infiltration system and application

Abstract

The application 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 multistage soil infiltration reactor, an intermittent micro-aeration module, a uniform water distribution module and a water collection layer. The sulfur autotrophic multistage soil infiltration reactor is sequentially provided with a nitrification unit, a denitrification unit and a phosphorus removal unit from top to bottom. The nitrification unit comprises an infiltration layer, and the infiltration layer comprises filler I. The infiltration layer of the denitrification unit comprises mixed filler II, soil mixed blocks comprise mixed filler IV, the infiltration layer of the phosphorus removal unit comprises mixed filler III, and soil mixed blocks comprise mixed filler V. The sulfur autotrophic multistage soil infiltration system has excellent COD cr and nitrogen and phosphorus removal performance, good impact resistance and anti-blocking performance, high economic benefit, small land occupation, solves the problem of insufficient nitrification, strengthens the sulfur autotrophic denitrification process, and promotes the further treatment and application popularization of decentralized sewage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, and particularly relates to a sulfur autotrophic multistage soil infiltration system and application. BACKGROUND

[0002] Wastewater in remote areas is often directly discharged into the surrounding environment without treatment or substandard treatment due to scattered distribution, small scale and lack of perfect wastewater treatment infrastructure, which has an adverse impact on public health and ecosystems; decentralized wastewater treatment is an important part of achieving water pollution control goals. Existing decentralized wastewater treatment technologies mainly include biofilm technology, stabilization ponds, purification tanks, constructed wetlands and integrated equipment, but there are key technical problems such as insufficient nitrogen and phosphorus removal efficiency, large land occupation, easy clogging, large sludge production, high energy consumption and high requirements for professional technicians.

[0003] The multistage soil infiltration system (MSL system) as an environmentally friendly, low-cost and high-efficiency emerging decentralized wastewater treatment scheme was first proposed by Japanese environmental engineer Akira Yamamoto in 1989, which mainly relies on the nitration of the infiltration layer, the heterotrophic denitrification of the soil mixed block and the absorption and sedimentation removal of phosphorus. However, the system with traditional structure often shows insufficient nitration of the infiltration layer, and the heterotrophic denitrification process is greatly affected by the carbon source, and the sludge production is large, which leads to frequent problems such as intensified clogging and even filler leakage, insufficient nitrogen removal efficiency and the like. Compared with the heterotrophic denitrification technology, the elemental sulfur autotrophic denitrification takes S0 as the electron donor, and has the advantages of no need to add additional organic carbon source, weak influence of C / N, low sludge production rate and reduced secondary pollution risk, which is more in line with the requirements of 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 by constructing a soil infiltration layer with varying density and thickness, and extends the hydraulic retention time of sewage in the system. However, this system relies on the self-purification capacity of the soil, and the pollutant removal efficiency cannot be guaranteed. It also has a high risk of clogging and is difficult to maintain. Chinese patent CN114230103B discloses a rural decentralized domestic sewage treatment device based on a multi-stage soil infiltration system. It has advantages such as low construction cost, low operation and maintenance cost, and small footprint. However, the perforated plates used in this device easily affect the water flow pattern, and surface tension often leads to uncontrollable seepage holes. Chinese patent CN113461265A discloses a tiered soil infiltration system for treating rural domestic sewage. This invention provides a highly efficient and 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, neglects the nitrification process under aerobic conditions, potentially leading to insufficient ammonia nitrogen conversion or removal. Furthermore, the soil infiltration layer, by burying rice straw to enhance denitrification efficiency, increases the risk of clogging and secondary pollution. In addition, Professor Huang Guohe's team and Professor Wu Weizhong's team have conducted extensive research in my country on multi-stage soil infiltration systems for treating decentralized sewage. However, these studies primarily focus on traditional heterotrophic soil infiltration systems, involving multi-stage series connection, different packing media and ratios, operating parameters, solid carbon sources, analytical methods, or pollutants. Due to the unimproved system structure and the inherent limitations of heterotrophic denitrification, these systems generally exhibit poor nitrogen and phosphorus pollutant removal efficiency and inadequate anti-clogging performance.

[0005] Therefore, developing new integrated devices and methods with high hydraulic load, low cost, strong environmental adaptability, fully automatic non-powered operation, simple maintenance, long service life, and high sewage purification efficiency is of great significance for the effective treatment of decentralized sewage. Summary of the Invention

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

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a sulfur autotrophic multi-stage soil infiltration system, which includes 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 arranged 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 > the height of the denitrification unit > the height of the phosphorus removal unit;

[0010] The nitrification unit comprises an infiltration layer, and the infiltration layer comprises the filler I;

[0011] The denitrification unit and the phosphorus removal unit each comprise an infiltration layer and soil mixed blocks;

[0012] The infiltration layer 11 of the denitrification unit comprises the mixed filler II, the soil mixed blocks 12 and 13 of the denitrification unit comprise the mixed filler IV, the infiltration layer 15 of the phosphorus removal unit comprises the mixed filler III, and the soil mixed blocks 16 and 17 of the phosphorus removal unit comprise the 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 mixed blocks are in the form of spheres and / or bricks, the soil mixed blocks are arranged in horizontal equidistant layers, and the sulfur autotrophic denitrifying bacteria and denitrifying phosphorus accumulating bacteria grow inside the soil mixed blocks.

[0015] Preferably, the uniform water distribution module comprises a water inlet 6, an adjustable three-way water valve 7 connected with a hose, a square tube 20 and a fixed rope 21, and water is supplied through the pump pressure of a low-position water storage tank or the water head pressure of a high-position 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 green zeolite, the mixed filler II comprises green zeolite and sulfur autotrophic synthetic material, the mass ratio of the green zeolite and the sulfur autotrophic synthetic material is 4-6:4-6, the mixed filler III comprises green zeolite and phosphorus removal synthetic material, the mass ratio of the green zeolite and the phosphorus removal synthetic material is 5-7:3-5, and the particle size of the green zeolite in the filler I, the mixed filler II and the mixed filler III is 2-4 mm.

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

[0019] Preferably, the water collecting layer comprises pebbles, the particle size of the pebbles is 2-4 cm, and the pebbles are filled flat by covering gravel on the top surface of the pebbles, and the particle size of the gravel is 4-6 mm.

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

[0021] The beneficial effects of the application include the following aspects:

[0022] 1) The sulfur autotrophic multi-stage soil infiltration system (SAD-MSL system) of the application adopts a brand-new structure combined with fusion innovation, wherein one of the brand-new structures is a three-stage 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 nitrification unit > denitrification unit > phosphorus removal unit; the other is a spherical soil mixed block; the fusion innovation is the combination of sulfur autotrophic denitrification process and MSL system.

[0023] 2) The sulfur autotrophic multi-stage soil infiltration system of the application has excellent COD cr and nitrogen and phosphorus removal performance; the application adopts a simple stacked design, which is convenient for filling; the nitrification unit is separated and enlarged to ensure that ammonia nitrogen is fully converted before entering the denitrification unit, and the heterotrophic nitrification-aerobic denitrification effect in the nitrification unit is remarkable, and the removal of COD cr is promoted by intermittent micro-aeration; the sulfur autotrophic synthetic material is added to the soil mixed block in the denitrification unit, which does not consume organic carbon source, prolongs the service 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 realizes effective and stable removal of total nitrogen; the phosphorus removal unit is arranged in the lower layer to ensure sufficient microbial nutrients in the whole process, the phosphorus removal synthetic material is mixed in the infiltration layer, the phosphorus adsorption is improved, the soil mixed phosphorus removal synthetic material is used in the soil mixed block, and the absorption and utilization of microorganisms are enhanced. By controlling the combination and proportion of each part of the filler, excellent COD cr and nitrogen and phosphorus removal performance are maintained.

[0024] 3) The sulfur autotrophic multi-stage soil infiltration system of the application has good impact resistance and anti-blocking performance. In the nitrification unit of the application, green zeolite is filled, and no soil mixed block is arranged, so that the buffering performance is improved to withstand higher hydraulic load; the spherical soil mixed block is used in the denitrification unit and the phosphorus removal unit to improve the anti-blocking performance and reduce the risk of filler leakage.

[0025] 4) The sulfur autotrophic multi-stage soil infiltration system of the application has high economic benefits. Sulfur autotrophic denitrification is used to replace heterotrophic denitrification, which does not require additional organic carbon source, saves cost, reduces greenhouse gas emissions, and reduces sludge production and secondary pollution; the microbial community can maintain performance under different environmental conditions, has good adaptability and stability, and sulfur autotrophic denitrification can achieve higher nitrate removal rate under shorter hydraulic retention time, so it can provide higher treatment efficiency under the same treatment capacity. The system of the application has low energy consumption and basically does not need maintenance, and has low requirements for the professional and technical skills of the operation and maintenance personnel.

[0026] 5) The sulfur autotrophic multi-stage soil infiltration system of the present application has a small footprint. The present application scientifically plans the purification process of sewage through a stacked partition design, and the integrated box device can be selected to be buried underground or placed on the ground according to local terrain and climate conditions.

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

[0028] Fig. 1 Figure 1 is a schematic diagram of the device structure of the multi-stage soil infiltration system with added brick-shaped soil mixed blocks of Example 1;

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

[0030] Fig. 3 Figure 3 is a schematic diagram of the structure of the uniform water distribution module of the present application;

[0031] Figs. 1-3 In the figure, 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 hole aeration pipeline, 10 is a denitrification unit, 11 is a denitrification unit infiltration layer, 12 is a denitrification unit spherical soil mixed block, 13 is a denitrification unit brick-shaped soil mixed block, 14 is a phosphorus removal unit, 15 is a phosphorus removal unit infiltration layer, 16 is a phosphorus removal unit spherical soil mixed block, 17 is a phosphorus removal unit brick-shaped soil mixed block, 18 is a water collection layer, 19 is a water outlet, 20 is a square tube, and 21 is a fixed rope.

[0032] Fig. 4 Figure 5 shows the removal rates of COD cr by the sulfur autotrophic multi-stage soil infiltration systems of Examples 1-4 and Comparative Examples 1-4 under different hydraulic loading rates;

[0033] Fig. 5 Figure 6 shows the removal rates of TP by the sulfur autotrophic multi-stage soil infiltration systems of Examples 1-4 and Comparative Examples 1-4 under different hydraulic loading rates;

[0034] Fig. 6 Figure 7 shows the removal rates of NH4 + -N by the sulfur autotrophic multi-stage soil infiltration systems of Examples 1-4 and Comparative Examples 1-4 under different hydraulic loading rates;

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

[0036] 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 collecting layer 18.

[0037] The sulfur autotrophic multi-stage soil infiltration reactor comprises, from top to bottom, a nitrification unit 8, a denitrification unit 10, and a phosphorus removal unit 14, wherein the height of the nitrification unit > the height of the denitrification unit > the height of the phosphorus removal unit.

[0038] The nitrification unit comprises a filtration layer, and the filtration layer comprises filler I.

[0039] The denitrification unit and the phosphorus removal unit each comprise a filtration layer and soil mixed blocks.

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

[0041] In the present application, the sulfur autotrophic multi-stage soil infiltration reactor comprises a three-stage stacked unit structure of “nitrification-denitrification-phosphorus removal” from top to bottom, and the volume of the nitrification unit, the denitrification unit, and the phosphorus removal unit is adjusted according to the composition and concentration of specific pollutants.

[0042] In the present application, 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 application, the microorganisms of the sulfur autotrophic multi-stage soil infiltration reactor are derived from soil and added exogenous sludge, and the nitrification unit comprises nitrifying bacteria.

[0044] In the present application, the soil mixed blocks are preferably in the form of spheres and / or bricks, and the soil mixed blocks are arranged in horizontal equidistant layers, and the inside grows sulfur autotrophic denitrifying bacteria and denitrifying phosphorus accumulating bacteria.

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

[0046] In the present application, the filtration layer and the soil mixed blocks in the denitrification unit and the phosphorus removal unit are overlapped and filled in a regular distribution.

[0047] In the application, the uniform water distribution module preferably comprises a water inlet 6, an adjustable three-way water valve 7 connected with a hose, a square tube 20 and a fixed rope 21; and preferably, water is supplied by a pump in a low-position water storage tank or by water head pressure in a high-position water storage tank.

[0048] In the application, one end of the three-way water valve is connected with a water inlet pipe, and the other end is provided with a plug; the three-way water valve is adjusted according to the water quantity to maintain the uniformity of water inlet.

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

[0050] The intermittent micro-aeration module is arranged in the middle and lower part of the nitrification unit in the "nitrification-denitrification-phosphorus removal" three-stage stacked unit structure, the aeration pipeline is buried in the nitrification unit filler and the air hole faces downward, the air pipe is connected with the aeration pump and the buried aeration pipeline respectively, and the intermittent aeration time is controlled by the relay in cooperation with the water inlet period.

[0051] In the application, the nitrification unit is a single medium infiltration layer, the denitrification unit and the phosphorus removal unit are infiltration layers and soil mixed blocks which are distributed in an interlaced manner, in addition, the abundance and activity of functional microorganisms are improved and the start-up period is shortened by inoculating exogenous activated sludge in the nitrification unit and the soil mixed block respectively.

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

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

[0054] In the application, the brick-shaped soil mixed block of the denitrification unit and the phosphorus removal unit is sewn into a cuboid-shaped shell by a cloth bag to cover the mixed fillers IV and V; the spherical soil mixed block is filled with mixed fillers by a cloth bag to prevent leakage, and is shaped into a regular sphere by a suspension ball, and the manufacturing process of the spherical soil mixed block is more simple.

[0055] In the application, the nitration unit accounts for a large proportion of the system, and the green zeolite is fully filled and inoculated with a small amount of sludge in layers to ensure ammonia nitrogen adsorption and continuous use of nitrifying bacteria; the green zeolite has a higher total pore volume and BET specific surface area, and a wide mesopore distribution; in the denitrification unit, the sulfur autotrophic synthetic material provides a sulfur electron donor, an inorganic carbon source, trace elements and a microbial life activity site, and can release alkalinity to maintain suitable pH value and stability throughout the process.

[0056] In the application, the water collecting layer preferably comprises cobblestones, the particle size of the cobblestones is preferably 2-4 cm, and the cobblestones are preferably covered with gravel to fill them flat, and the particle size of the gravel is preferably 4-6 mm.

[0057] In the application, the sulfur autotrophic multistage soil infiltration reactor is provided with two symmetric water outlets 19 at the bottom of the nitration unit, the denitrification unit and the water collecting layer.

[0058] The application further provides application of the sulfur autotrophic multistage soil infiltration system in treatment of decentralized sewage.

[0059] In the operation process of the sulfur autotrophic multistage soil infiltration system, the wastewater falls into the sulfur autotrophic multistage soil infiltration reactor through the uniform water distribution module, is subjected to intermittent micro-aeration when flowing through the nitration unit, then sequentially passes through the denitrification unit and the phosphorus removal unit, and is discharged after entering the water collecting layer. The water outlets are symmetrically distributed at the bottom of the nitration unit, the denitrification unit and the water collecting layer, and the homogeneous flow state of the water in the seepage field is maintained as much as possible.

[0060] The technical solutions provided by the application will be described in detail below in combination with the embodiments, but they should not be understood as limiting the protection scope of the application.

[0061] In the embodiments, the particle size of the green zeolite is 2-4 mm, the particle size of the soil is ≤2 mm, the particle size of the cobblestones is 2-4 mm, the particle size of the gravel is 4-6 mm, and the particle size of the sulfur autotrophic synthetic material and the phosphorus removal synthetic material is 3-5 mm.

[0062] The exogenous sludge is taken from the end of the aerobic tank of a sewage treatment plant, and the 30 min settling ratio (SV30) is 23%. The supernatant is discarded, and 180 mL of sludge is inoculated in the soil or the green zeolite in the nitration section of the soil mixed block. In the soil mixed block, 12 mL is inoculated in each of the 10 cm diameter spheres and large bricks, and 6 mL is inoculated in each of the 8 cm diameter spheres and small bricks, and the soil is mixed. In the nitration section, 36 mL is inoculated every 7 cm of green zeolite until the filling is completed, and a total of 5 times.

[0063] In the present application, the sulfur autotrophic synthetic material and the phosphorus removal synthetic material have the same preparation process as the material in patent application number CN202411654303.5, invention name: a combined filler for denitrification and phosphorus removal in a constructed wetland, a denitrification and phosphorus removal device for a constructed wetland, and application thereof. The sulfur autotrophic synthetic material is a nearly spherical solid with a particle size of 3-5 mm and a density of 1.1-2.2 g / cm 3 , which is formed by hot pressing of elemental sulfur, calcium carbonate, and minerals, wherein the mass ratio of elemental sulfur to calcium carbonate is 2:1. The main components of the sulfur autotrophic synthetic material include S, O, Ca, Mg, C, and Al, in addition to trace elements such as Fe, Ba, Na, P, Ti, Cr, and Mn. The sulfur autotrophic synthetic material can provide an elemental sulfur electron donor, as well as alkalinity and inorganic carbon sources. The phosphorus removal synthetic material uses dolomite clay and montmorillonite clay powder as raw materials, with the addition of water, soluble starch, and aluminum sulfate for granulation and molding. 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 organic glass with a size of 50 cm x 10 cm x 90 cm. The water inlet is lifted to one end of the uniform water distribution module by a peristaltic pump. The sulfur autotrophic multi-stage soil infiltration reactor has a three-stage stacked unit structure from top to bottom, with "nitrification-denitrification-phosphorus removal". The nitrification unit contains nitrifying bacteria and heterotrophic nitrification-aerobic denitrifying bacteria. The denitrification unit and the phosphorus removal unit each contain an infiltration layer and a soil mixing block. The infiltration layer is a mixed filler layer that fills the gaps between the soil mixing blocks and has nitrifying bacteria attached to it. The soil mixing blocks are arranged horizontally and equally spaced, with sulfur autotrophic denitrifying bacteria and denitrifying phosphorus accumulating bacteria growing inside. The infiltration layer and the soil mixing block in the denitrification unit and the phosphorus removal unit are overlapped and regularly distributed. The uniform water distribution module includes a water inlet, an adjustable three-way water valve connected in series with a hose, a square tube, and a fixed rope. One end of the three-way water valve is connected to the water inlet pipe, and the other end is fitted with a plug. The intermittent micro-aeration module is located in the middle and lower part of the nitrification unit. The intermittent micro-aeration module includes an aeration pump, a relay, and a lower hole aeration pipeline. The aeration pipeline is buried in the nitrification unit filler with the air holes facing downward, and the air pipe is 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 green zeolite; the height of the denitrification unit is 25 cm, and the brick-shaped soil mixture block is filled with soil and sulfur autotrophic synthetic material at a mass ratio of 1:1, and the mixed filler of the infiltration layer is green zeolite and sulfur autotrophic synthetic material at a mass ratio of 1:1; the height of the phosphorus removal unit is 10 cm, and the brick-shaped soil mixture block is filled with soil and phosphorus removal synthetic material at a mass ratio of 3:2, and the infiltration layer is filled with green zeolite and phosphorus removal synthetic material at a mass ratio of 7:3; the size of the brick-shaped soil mixture block is 14 cm x 10 cm x 4 cm (13) and 5 cm x 10 cm x 4 cm (4), and the horizontal spacing is 4 cm and the vertical spacing is 3 cm; the filling mass of the brick-shaped soil mixture block remains consistent.

[0067] The height of the water collection layer is 10 cm, filled with pebbles, and covered with gravel to fill in; 4 water outlet taps are symmetrically arranged at the bottom of the nitrification unit, the denitrification unit and the water collection layer.

[0068] The steps of the sulfur autotrophic multi-stage soil infiltration system for treating decentralized sewage are as follows: the water quality indicators of the influent are: COD Cr = 375.7-511.5 mg / L, TP = 5.0-6.1 mg / L, NH4 + -N = 42.1-53.6 mg / L, NO 3- -N = 5.9-9.0 mg / L, organic nitrogen = 18.7-23.3 mg / L, TN = 71.3-81.3 mg / L. The simulated decentralized sewage in the water storage tank enters the uniform water distribution module through the peristaltic pump, and then uniformly drips above the sulfur autotrophic multi-stage soil infiltration reactor, and the influent is intermittently aerated at the same time. The decentralized sewage passes through the nitrification unit, the denitrification unit and the phosphorus removal unit in turn, and is collected in the water collection layer and flows out naturally through the symmetrically arranged outlets at the bottom. The nitrification unit is inoculated with 180 mL of exogenous sludge, and the wastewater flows through the nitrification unit while the intermittent aeration time is controlled by the relay in cooperation with the influent period, and then passes through the denitrification unit and the phosphorus removal unit in turn, and the effluent enters the water collection layer; during system operation, the symmetrically arranged outlets at the bottom of the water collection layer are opened, and the outlets at the bottom of the nitrification unit and the denitrification unit are opened and closed as needed. Among them, in order to simulate the discharge period and volatility of decentralized sewage, the influent is 12 hours per day, and the influent period is 6-8, 9-11, 12-14, 15-17, 18-20 and 21-23. The test period is 90 days, and the initial hydraulic loading rate is 180 L / m 2 ·d, which is adjusted to 360 L / m 2 ·d and 1440 L / m 2 ·d every 30 days.

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

[0070] Table 1. Pollutant concentrations and removal rates in influent and effluent under different hydraulic loading rates in Example 1

[0071]

[0072]

[0073] Table 1 shows the average removal rate. As can be seen from Table 1, COD... Cr The average removal rate consistently remained above 91.4%, unaffected by hydraulic load; the average removal rate of TP was 180 L / m³. 2 ·d and 360L / m 2 The hydraulic loading rate is above 90.3% at d, and increases to 1440 L / m. 2 At ·d, the average removal rate of TP decreased to 51.8%; NH4 + The average removal rate of -N remained stable at 94.4%–100.0% at 180 L / m³. 2 ·d and 360L / m 2 • Complete removal was achieved at a hydraulic loading rate of 1440 L / m. 2 ·d time NH4 + The average removal rate of -N remained at 94.4%; the average removal rate of TN was 88.7-97.7%, which decreased with increasing hydraulic loading rate.

[0074] Example 2 (MSL6)

[0075] The brick-shaped soil mixing blocks of Example 1 were replaced with spherical soil mixing blocks, which were suspended spheres with diameters of 10cm (10 blocks) and 8cm (10 blocks). The filling material of the spherical soil mixing blocks was kept consistent, and other conditions were the same as in Example 1.

[0076] Table 2 shows the concentrations and removal rates of pollutants in the influent and effluent of the sulfur autotrophic multi-stage soil infiltration system of Example 2 under different hydraulic loading rates.

[0077] Table 2. Pollutant concentrations and removal rates in influent and effluent under different hydraulic loading rates in Example 2.

[0078]

[0079]

[0080] Table 2 shows the average removal rate. As can be seen from Table 2, COD... CrThe average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. 2 The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. 2 The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. 2 The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. + The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. + The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. 2 The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. 2 The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased. 2 The average removal rate of TN was 86.2-87.7%, and was basically the same under the three hydraulic loading rates, which had high and stable removal efficiency for TN and was less affected by hydraulic load. From Table 1 and Table 2, under the hydraulic loading rates of 180 L / m2·d and 360 L / m2·d, the pollutants had high removal efficiency, and when the hydraulic loading rate was increased to 1440 L / m2·d, the removal rate of the pollutants fluctuated, and the removal effect was weakened as the hydraulic loading rate increased.

[0081] Example 3 (MSL7)

[0082] The inoculated sludge of the nitrification unit in Example 1 was replaced with soil mixed block inoculated 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 with soil mixed block inoculated sludge, and other conditions were the same as in Example 2.

[0085] Comparative Example 1 (MSL1)

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

[0087] Comparative Example 2 (MSL2)

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

[0089] Comparative Example 3 (MSL3)

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

[0091] Comparative Example 4 (MSL4)

[0092] The nitrification unit inoculation sludge in Example 2 was replaced with soil mixed block inoculation sludge, intermittent aeration was replaced with natural reoxygenation, and other conditions were the same as in Example 2.

[0093] The effects of different hydraulic loading rates on COD in the sulfur autotrophic multi-stage soil infiltration systems of Examples 1-4 and Comparative Examples 1-4 cr Removal rate of , TP removal rate, NH4 + The removal rates of -N and TN are respectively as follows: Figs. 4-7 As shown in the figure, brick-shaped soil mixes are more effective at removing TP, while spherical soil mixes are less effective at removing NH4. + -N and TN removal are more stable and efficient; sludge inoculation in nitrification units is superior to inoculation in soil mixed blocks, compensating for the low microbial abundance in nitrification units; intermittent aeration can significantly promote COD removal. cr NH4 + Removal of -N and TN.

[0094] Decentralized wastewater entering the sulfur autotrophic multi-stage soil infiltration system of this invention first flows through the nitrification unit, where the COD in the wastewater... cr Pollutants such as nitrogen and phosphorus are partially trapped and adsorbed by the packing material. The inoculated activated sludge grows and metabolizes under aeration conditions, consuming a large amount of COD. cr The packing material adsorbs a large amount of ammonia nitrogen; organic matter is consumed by aerobic microorganisms through respiration or assimilated by heterotrophic microorganisms as nutrients, a portion of the ammonia nitrogen is assimilated and utilized by aerobic microorganisms as a nitrogen source, and most of the ammonia nitrogen undergoes full nitrification. Green zeolite continuously undergoes a dynamic equilibrium adsorption and microbial desorption process, and a heterotrophic nitrification-aerobic denitrification process also occurs. Continuing to flow through the denitrification unit, the main process is to remove the NO3 produced by full nitrification. - -N is reduced to nitrogen gas by sulfur-autotrophic denitrifying bacteria. The sulfur-autotrophic synthetic material not only provides elemental sulfur as an electron donor, inorganic carbon source, and trace elements essential for microbial growth, but also maintains the environmental pH within 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 the microorganisms in the preceding unit or used for enzyme synthesis. The synergistic effect of the phosphorus removal synthetic material and the soil further adsorbs and retains residual phosphorus for continuous use by microorganisms, while also promoting the growth of polyphosphate-accumulating bacteria, achieving highly efficient phosphorus removal.

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within 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 includes 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 consists of a nitrification unit (8), a denitrification unit (10), and a phosphorus removal unit (14) arranged from top to bottom, wherein the height of the nitrification unit is greater than the height of the denitrification unit, which is greater than the height of the phosphorus removal unit. The nitration unit includes a percolation layer, and the percolation layer includes packing material I; Both the denitrification unit and the phosphorus removal unit include an infiltration 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. The soil mixture blocks are spherical and / or brick-shaped, and are arranged in horizontal, equidistant layers. Sulfate autotrophic denitrifying bacteria and denitrifying polyphosphate-accumulating bacteria grow inside them. The filler I is green zeolite; the mixed filler II comprises green zeolite and sulfur autotrophic synthetic material, with a mass ratio of green zeolite to sulfur autotrophic synthetic material of 4~6:4~6; the mixed filler III comprises green zeolite and phosphorus removal synthetic material, with a mass ratio of green zeolite to phosphorus removal synthetic material of 5~7:3~5; in filler I, mixed filler II, and mixed filler III, the particle size of green zeolite is 2~4mm; The mixed filler IV comprises soil and sulfur autotrophic synthetic material, with a mass ratio of soil to sulfur autotrophic synthetic material of 4~6:4~6; the mixed filler V comprises soil and phosphorus removal synthetic material, with a mass ratio of soil to phosphorus removal synthetic material of 5~7:3~5. The sulfur-autotrophic synthetic material is a nearly spherical solid with a particle size of 3-5 mm and a density of 1.1-2.2 g / cm³. 3 It is made by hot pressing of elemental sulfur, calcium carbonate and minerals, wherein the mass ratio of elemental sulfur to calcium carbonate is 2:1; The phosphorus removal synthetic material uses dolomite clay and montmorillonite clay powder as raw materials, and adds water, soluble starch and aluminum sulfate to granulate and cast; the mass ratio of dolomite clay, montmorillonite clay, soluble starch and aluminum sulfate is 1:1:1:

1.

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

3. The sulfur autotrophic multi-stage soil infiltration system according to claim 2, characterized in that, The uniform water distribution module includes 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 the low-level water storage tank or the water head pressure of the high-level water storage tank.

4. 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. The intermittent micro-aeration module includes an aeration pump (3), a relay (4), and a lower-opening aeration pipeline (9).

5. The sulfur autotrophic multi-stage soil infiltration system according to claim 4, characterized in that, The water collection layer contains pebbles with a particle size of 2-4 cm, and the pebbles are covered with gravel with a particle size of 4-6 mm to fill the gap.

6. The application of the sulfur autotrophic multi-stage soil infiltration system according to any one of claims 1 to 5 in the treatment of decentralized wastewater.

Images