Primary rainwater treatment device for sponge city in arid and semi-arid areas

Abstract

The invention relates to the technical field of rainwater treatment in arid and semi-arid regions, in particular to a primary rainwater treatment device for a sponge city in arid and semi-arid regions, and solves the problems that an existing device is insufficient in saline-alkali regulation adaptation and unstable in microbial activity. The device comprises a pretreatment unit, a regulation unit, a depth stabilization unit and a water storage and recharge unit which are sequentially connected in series, the regulation and control unit is a core, a phase change heat preservation layer and a breathable moisture preservation film are arranged in a shell, a slow-release regulation and control bin is concentrically arranged in the shell, a customized slow-release agent is arranged in a slow-release cavity, a rotatable microorganism treatment unit is eccentrically arranged in the cavity, and coordination of saline-alkali regulation and microorganism activation is achieved. The depth stabilizing unit is provided with a composite filter layer to optimize water quality, and the water storage and recharge unit meets soil requirements. The device can maintain the microbial activity in the drought period, the effluent quality is stable, the soil salinity and alkalinity can be reduced, nutrients are activated, the structure is practical and easy to maintain, and the requirements of sponge city construction in arid and semi-arid regions are met.

Description

Technical Field

[0001] This invention relates to the field of rainwater treatment technology in arid and semi-arid regions, and specifically to a primary rainwater treatment device for sponge cities in arid and semi-arid regions. Background Technology

[0002] Arid and semi-arid regions are characterized by dry climates with little rainfall and high evaporation rates, leading to widespread soil salinization. Rainwater, as a scarce water resource, is crucial for the construction of sponge cities. Existing primary rainwater treatment devices primarily focus on particulate matter filtration and organic matter degradation; however, their suitability for controlling salinization in these regions is insufficient.

[0003] Existing salinity control technologies often employ a one-time addition of desulfurizing agents, which can easily lead to excessively high local calcium ion concentrations and disrupt the aquatic microenvironment. In microbial treatment units, it is difficult to simultaneously consider the adsorption performance of the carrier and the suitability for microbial habitat, and the carrier is prone to water loss during droughts, resulting in a sharp drop in microbial activity and making continuous and stable treatment impossible. Furthermore, traditional devices do not consider the linkage between rainwater treatment and soil nutrient activation; when treated rainwater is re-irrigated into the soil, nutrients are rapidly lost, the improvement effect is limited, and it is difficult to form an effective closed-loop system.

[0004] Therefore, developing a primary rainwater treatment device that adapts to the characteristics of arid and semi-arid regions and takes into account the linkage between salinity regulation, microbial stabilization treatment and soil improvement has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of this, the present invention provides a primary rainwater treatment device for sponge cities in arid and semi-arid regions, aiming to solve the problems of insufficient adaptation to salinity regulation and unstable microbial activity in existing devices in arid and semi-arid regions. To achieve the above objectives, the present invention adopts the following technical solution: A primary rainwater treatment device for sponge cities in arid and semi-arid regions includes a pretreatment unit and a water storage and reinjection unit. The pretreatment unit is connected to an inlet pipe, and the water storage and reinjection unit is connected to an outlet pipe. A control unit is connected in series between the pretreatment unit and the water storage and reinjection unit. The control unit is used for the coordinated operation of salinity regulation and microbial activation. The control unit includes an outer shell, inside which a slow-release control chamber is concentrically installed. The side wall of the slow-release control chamber is provided with a slow-release cavity. The shell wall of the slow-release cavity is uniformly provided with a plurality of first flow holes. The slow-release cavity is filled with a slow-release agent. The slow-release control chamber is equipped with a rotatable microbial treatment unit, which includes a cylindrical microbial carrier bed. The microbial carrier bed has a microbial cavity inside, and the shell wall of the microbial cavity is uniformly opened with a number of second flow holes. The microbial cavity contains a microbial carrier assembly, which is loaded with drought-resistant and salt-tolerant microbial flora. During the rotation of the microbial treatment unit, it forms dynamic contact with rainwater, avoiding adsorption saturation on the carrier surface, and at the same time ensuring uniform contact between the slow-release agent and the microorganisms, preventing excessively high local salt concentrations from inhibiting microbial activity. The bottom of the control unit's outer shell is equipped with a sludge collection section below the microbial carrier bed, which is used to collect the precipitates and microbial metabolites generated during the reaction and discharge them periodically.

[0006] Preferably, the slow-release agent includes slow-release particles, which are composite particles of calcium oxide and gypsum. The surface of the slow-release particles is coated with a slow-release film to control the calcium ion release rate to 0.5~1.2 mg / (L·h). The released calcium ions react with bicarbonate and chloride ions in rainwater to precipitate, thereby reducing the salinity and alkalinity of rainwater. At the same time, the gypsum particles can replenish the sulfur element required by the soil.

[0007] Preferably, the mass ratio of calcium oxide to gypsum in the slow-release particles is (2~2.5):1, and the particle size is 5-8 mm.

[0008] The sustained-release membrane is a composite membrane made of polyvinyl alcohol and sodium alginate in a mass ratio of (3~3.5):1, with a membrane thickness of 0.1~0.3 mm.

[0009] Preferably, the microbial carrier component is a modified straw charcoal carrier, which is carbonized at 400-500℃ for 2-3 hours and then activated with 10-15% sodium hydroxide solution, with a specific surface area ≥300m² / g and a porosity of 60-70%.

[0010] The drought- and salt-tolerant microbial community loaded on the carrier surface consists of a mixture of Bacillus subtilis and Pseudomonas aeruginosa at a volume ratio of 1:(1.8~2.5), with a community concentration ≥10. 8 CFU / g.

[0011] Preferably, the inner shell of the microbial carrier bed is provided with an installation channel, the installation channel is fitted onto the installation shaft, the installation shaft is eccentrically installed in the slow-release control chamber through the installation plate frame, the input end of the installation shaft is connected to the output end of the drive device, the installation channel is provided with a limiting groove to restrict relative rotation, and the installation shaft is provided with a matching limiting block.

[0012] Preferably, the pretreatment unit is provided with a first filter screen, with the inlet of the pretreatment unit located above the first filter screen and the outlet located below the first filter screen.

[0013] A second filter screen is provided above the slow-release control chamber. The inlet of the control unit is located below the second filter screen, and the outlet is located above the second filter screen.

[0014] Preferably, the inner wall of the control unit is provided with a phase change insulation layer, which is made of a composite phase change material of paraffin and expanded graphite, with a phase change temperature of 25~30℃ and a latent heat of at least 180J / g.

[0015] The inner side of the phase change insulation layer is provided with a breathable and moisturizing membrane, which is used to absorb and store environmental heat during the dry period to maintain the temperature stability inside the cavity, while releasing a small amount of moisture to maintain the humidity required by microorganisms inside the cavity and prevent them from becoming inactive due to water loss.

[0016] Preferably, a deep stabilization unit is connected in series between the control unit and the water storage and reinjection unit; The depth stabilization unit is equipped with a composite filter layer. The inlet of the depth stabilization unit is located below the composite filter layer, and the outlet is located above the composite filter layer.

[0017] Preferably, the deep stabilization unit is provided with multiple composite filter layers arranged from bottom to top in the vertical direction. The composite filter layer is composed of zeolite and bentonite in a mass ratio of (2~4):1, which is used to further adsorb residual heavy metal ions and unreacted calcium ions in rainwater, while adjusting the pH value of rainwater to 6.5~7.5, improving the stability of the effluent, and providing suitable water quality for subsequent soil recharge.

[0018] Preferably, a multi-stage connecting pipe is provided between the deep stabilization unit and the water storage and reinjection unit, and the multi-stage connecting pipe includes multiple water inlet ends distributed between two adjacent composite filter layers.

[0019] The present invention includes at least the following beneficial technical effects: This invention achieves synergistic effects between salinity regulation and microbial activation, significantly improving the precision and stability of rainwater treatment. Specifically, the invention constructs a synergistic system of slow release and dynamic degradation through the concentric design of a slow-release regulation chamber and a rotating microbial treatment unit: the slow-release agent uses calcium oxide and gypsum composite particles and a customized slow-release membrane to control the calcium ion release rate, effectively reacting with bicarbonate and chloride ions in rainwater to reduce salinity while avoiding excessively high local calcium ion concentrations that could disrupt the aquatic microenvironment; simultaneously, the eccentric rotation of the microbial carrier bed creates dynamic contact, preventing carrier saturation, improving organic matter degradation efficiency, and promoting uniform diffusion of slow-release ions, thus avoiding the problem of inhibited microbial activity. Compared to existing technologies where salinity regulation and microbial treatment are disconnected, easily leading to local environmental imbalances, this device achieves deep integration of the two functions, resulting in more stable treatment effects.

[0020] This invention addresses the problems of carrier dehydration, sharp decline in microbial activity, and large diurnal temperature variations during drought periods. The device incorporates a phase-change insulation layer and a breathable, moisturizing membrane on the outer shell of the control unit. The phase-change insulation layer maintains a stable internal temperature of 25-30°C, while the breathable, moisturizing membrane adsorbs and releases trace amounts of moisture, providing a suitable temperature and humidity environment for salt-tolerant microbial communities and preventing microbial inactivation during drought. Simultaneously, the modified straw charcoal carrier possesses a high specific surface area and porosity, which, combined with drought- and salt-tolerant composite microbial communities, further enhances the resilience of the microbial system. Compared to traditional devices that are prone to failure and interruption during droughts, this device can operate continuously in harsh environments without frequent maintenance, making it suitable for the long-term rainwater treatment needs of sponge cities in arid and semi-arid regions.

[0021] This invention constructs a closed-loop system for rainwater treatment and soil improvement, enhancing the value of rainwater resource utilization. Specifically, this device breaks through the limitations of traditional rainwater treatment methods that only focus on water purification, achieving a linkage between treatment effects and soil nutrient activation. Specifically, the gypsum particles in the slow-release agent replenish the sulfur element needed by the soil, and the deep stabilization unit adjusts the pH of the effluent to 6.5-7.5 through a composite filter layer of zeolite and bentonite, adapting to soil recharge requirements. When the treated rainwater is recharged, it not only avoids exacerbating soil salinization but also activates soil nutrients through the slow-release components and stabilized water quality, reducing nutrient loss. This closed-loop design upgrades rainwater from being discharged after purification to being used to improve soil after purification, maximizing the ecological value of scarce rainwater resources in arid and semi-arid regions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0023] Figure 2 This is a schematic diagram of the internal structure of the control unit.

[0024] Figure 3 This is a schematic diagram of the internal structure of the control warehouse.

[0025] Figure 4 for Figure 3 A magnified structural diagram of point A in the middle.

[0026] Figure 5 This is a schematic diagram of the internal structure of a microbial carrier bed.

[0027] The reference numerals in the attached figures are as follows: 100, pretreatment unit; 110, inlet pipe; 120, first filter screen; 200, control unit; 210, second filter screen; 220, control chamber; 221, mounting shaft; 222, mounting tray; 223, slow-release chamber; 2231, first flow hole; 2232, slow-release agent; 22321, slow-release granules; 22322, slow-release membrane; 230, microbial treatment unit; 231, microbial chamber; 2311, second flow hole; 2312, microbial carrier assembly; 232, mounting channel; 2321, limiting groove; 240, phase change insulation layer; 300, depth stabilization unit; 310, composite filter layer; 320, multi-stage connecting pipe; 400, water storage and reinjection unit; 410, outlet pipe; 500, sludge collection section. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0029] Figures 1 to 5 A primary rainwater treatment device for sponge cities in arid and semi-arid regions is presented. It is suitable for arid and semi-arid areas with annual precipitation of 200-400 mm and soil salinity of 0.3-0.8%. The device enables primary purification, salinity regulation, microbial activation, and stable reinjection of collected rainwater, forming a closed-loop system of collection, treatment, regulation, and reinjection. Each unit in the device is connected by corresponding pipes and flanges, and the top is equipped with a detachable end cap for easy disassembly, maintenance, and component replacement. It is suitable for sponge city green spaces, roadside green belts, and can also be placed vertically next to small rainwater collection ponds.

[0030] The device includes a pretreatment unit 100, a control unit 200, a deep stabilization unit 300, and a water storage and reinjection unit 400 connected in series. The top of the pretreatment unit 100 is connected to the inlet pipe 110, and the bottom of the water storage and reinjection unit 400 is connected to the outlet pipe 410. Both the inlet pipe 110 and the outlet pipe 410 are equipped with flow control valves, which can adjust the water flow rate according to the rainwater runoff and treatment requirements, and control the overall hydraulic retention time to 2.5-3.5 hours to ensure a balance between treatment effect and treatment efficiency.

[0031] The core function of the pretreatment unit 100 is to remove large particulate impurities from rainwater, such as fallen leaves, sand, and dust, preventing clogging of the flow holes, carriers, and filter layers in subsequent units and ensuring stable operation of the device. Multiple layers of first filter screens 120 can be installed inside the pretreatment unit 100. The edges of the filter screens are fixed to the inner wall of the pretreatment unit 100 with bolts, facilitating periodic disassembly and cleaning. The inlet of the pretreatment unit 100 is located above the first filter screens 120, employing a funnel-shaped structure to expand the water inlet coverage and reduce impurity splashing caused by water flow impact. The outlet is located below the first filter screens 120, with the outlet position 30cm lower than the inlet. Rainwater settles naturally due to gravity, while large particulate impurities are intercepted by the first filter screens 120 under gravity and accumulate above the filter screens. These can be cleaned periodically through the inspection port at the top of the pretreatment unit 100. After treatment by the pretreatment unit 100, the rainwater lays the water quality foundation for the precise treatment by the subsequent control unit 200.

[0032] Among them, the control unit 200 is the core functional unit of the device, which mainly realizes the synergistic treatment of salt and alkali control and microbial activation. At the same time, through the phase change heat preservation and moisture retention design, it ensures the stability of microbial activity during the drought period.

[0033] The control unit 200 includes an outer shell, and a phase change insulation layer 240 is attached to the inner wall of the outer shell. The outer side of the phase change insulation layer 240 is tightly attached to the inner wall of the outer shell, and the inner side is covered with a breathable and moisturizing film, forming a dual protective structure of heat preservation and moisture retention.

[0034] The control unit 200 has a concentrically mounted slow-release control chamber 220 inside its outer shell. The slow-release control chamber 220 has a cylindrical structure with a double-layered sidewall, forming an annular slow-release cavity 223. The shell wall of the slow-release cavity 223 has several uniformly distributed first flow holes 2231, each with a diameter of 2-4 mm and a spacing of 3-5 cm. This ensures sufficient contact between rainwater and the slow-release agent 2232 while preventing leakage of the slow-release agent 2232 particles. The slow-release cavity 223 contains the slow-release agent 2232, which is a composite particle of calcium oxide and gypsum.

[0035] The composite process of the composite particles is strictly controlled to achieve precise slow release of calcium ions: First, calcium oxide and gypsum are mixed in a mass ratio of 2:1 to 2.5:1, and 15% of deionized water is added. The mixture is stirred into a uniform paste and then extruded into granules with a particle size of 6-7 mm using a granulator. The granules are then dried in a constant temperature drying oven at 100°C or higher to remove moisture until the moisture content is less than 5%. Subsequently, a slow-release membrane 22322 coating solution is prepared by mixing polyvinyl alcohol and sodium alginate in a mass ratio of 3:1 to 3.5:1, adding 85°C deionized water, and stirring until completely dissolved to form a 5% mass fraction coating solution. The dried composite particles are immersed in the coating solution for 12 minutes, and then dried in a ventilated environment at around 35°C for more than 3 hours to form a composite slow-release membrane 22322 with a thickness of 0.1-0.3 mm. This membrane can control the calcium ion release rate of 0.8-1.0 mg / (L·h) through its own pore structure. The core function of slow-release agent 2232 is to slowly release calcium ions, which react chemically with bicarbonate and chloride ions in rainwater to form calcium carbonate and calcium chloride precipitates, thereby reducing the salinity and alkalinity of rainwater. At the same time, gypsum particles can replenish the sulfur element needed by the soil, laying the foundation for the activation of soil nutrients in subsequent recharge. The precise slow-release rate can avoid excessive local calcium ion concentration, protecting the microenvironment of the water body and the activity of microorganisms.

[0036] The phase change insulation layer 240 uses a composite phase change material of paraffin wax and expanded graphite. The composite process is as follows: industrial-grade paraffin wax is heated to 70℃ and melted into a liquid state. Expanded graphite is added at a mass ratio of 6:1 to 7:1 and stirred to make the expanded graphite evenly dispersed in the liquid paraffin wax. Then, polyethylene wax accounting for 3% of the total mass is added as a binder and stirring is continued. Then, it is poured into the preset groove on the inner wall of the control unit 200 and naturally cooled to room temperature to form. After forming, the phase change insulation layer 240 has a thickness of 20mm, a phase change temperature of 27-29℃, and a latent heat of about 185J / g. In arid areas with large diurnal temperature differences, it can absorb and store ambient heat during the day and release heat at night to maintain the temperature inside the cavity at 25-30℃, which can avoid the impact of temperature fluctuations on microbial activity.

[0037] The breathable and moisturizing membrane is a composite membrane made of polyvinyl alcohol and sodium carboxymethyl cellulose, with a thickness of 0.08 mm. The composite process is as follows: polyvinyl alcohol and sodium carboxymethyl cellulose are mixed at a mass ratio of 4:1, deionized water is added and heated to 85°C to dissolve, and the mixture is stirred until a uniform colloid is formed. This colloid is then coated on the inner side of the phase change insulation layer 240 and dried in a 40°C constant temperature drying oven for 3 hours to form the membrane. This membrane has the characteristics of being breathable but not water-permeable. During dry periods, it can absorb trace amounts of water vapor released by the phase change insulation layer 240, maintaining the relative humidity inside the cavity at 60-70%, providing a suitable humidity environment for microorganisms, and preventing the carrier from losing water and causing microbial inactivation.

[0038] The slow-release control chamber 220 is equipped with a rotatable microbial treatment unit 230, whose core function is to degrade organic matter (such as a small amount of oil and humus) in rainwater through salt- and drought-resistant microbial communities. At the same time, it works synergistically with the slow-release agent 2232 to further optimize water quality.

[0039] The microbial treatment unit 230 includes a cylindrical microbial carrier bed with a plurality of second flow holes 2311 evenly distributed on its sidewalls. The diameter of the second flow holes 2311 is 2.5-3 mm, and the spacing between the holes is 1-4 cm, which facilitates rainwater penetration and full contact with the microorganisms. The microbial carrier bed is provided with a microbial cavity 231, which contains a microbial carrier component 2312. This component is a modified straw charcoal carrier, and the surface of the carrier is loaded with drought-resistant and salt-alkali-resistant microbial flora. The flora consists of Bacillus subtilis and Pseudomonas aeruginosa mixed in a volume ratio of 1:1.8 to 1:2.5.

[0040] The loading process employed the impregnation and adsorption method: both bacterial strains were cultured separately in LB medium at 37°C with constant temperature and shaking for at least 18 hours to prepare a bacterial suspension with a concentration of 1.5 × 10⁻⁶. 9 A single bacterial culture of CFU / mL was mixed in a specific ratio to obtain a composite bacterial culture. The modified straw charcoal carrier was then immersed in the composite bacterial culture and subjected to constant temperature shaking at 30℃ for approximately 5 hours, maintaining a shaking rate of 150 r / min to ensure the bacteria were fully adsorbed onto the carrier pores and surface. After removal, the carrier was allowed to air dry naturally. The final bacterial concentration on the carrier was 1.2 × 10⁻⁶. 8 CFU / g. This bacterial community can remain active in saline-alkali environments (pH 7.5-9.0) and under arid and low-humidity conditions. Bacillus subtilis can degrade organic matter and secrete extracellular polysaccharides, enhancing the adsorption performance of the carrier surface, while Pseudomonas can promote the conversion of salt ions. The two work synergistically to improve the water purification effect.

[0041] The preparation process of the modified straw char carrier is as follows: Corn stalks are selected, impurities are removed, and under the protection of inert gas (nitrogen), they are placed in a tube furnace and carbonized at 450℃ for more than 2 hours. After carbonization, they are naturally cooled to room temperature. Then, they are immersed in a 12%~15% sodium hydroxide solution and soaked at room temperature for more than 3 hours to allow the straw char to fully contact the alkaline solution and activate its internal pore structure. After soaking, it is washed with deionized water until neutral and placed in a constant temperature drying oven at about 100℃~110℃ to dry to constant weight. The modified straw char carrier has a specific surface area of ​​320m² / g and a porosity of 65%, exhibiting excellent adsorption performance and microbial habitat capacity.

[0042] To achieve dynamic contact between the microbial treatment unit 230 and rainwater, the microbial carrier bed is connected to the drive device via an installation shaft 221. The specific installation structure is as follows: The inner shell of the microbial carrier bed is provided with a circular installation channel 232, and the inner wall of the installation channel 232 is provided with a limiting groove 2321 to restrict relative rotation; the installation shaft 221 is made of stainless steel, and a limiting block adapted to the limiting groove 2321 is provided on the shaft. The installation hole limiting sleeve is fitted on the installation shaft 221. Through the cooperation of the limiting groove 2321 and the limiting block, relative rotation between the carrier bed and the installation shaft 221 is prevented; the installation shaft 221 is eccentrically installed in the slow-release control chamber 220 via an installation tray 222, with an eccentricity of 8~12cm. The input end of the installation shaft 221 passes through the slow-release control chamber 220 and the outer shell of the control unit 200, and is connected to the output end of the drive device (a small geared motor can be selected) via a coupling. The drive device drives the mounting shaft 221 to rotate, which in turn drives the microbial carrier bed to rotate eccentrically. During the rotation, the microbial carrier component 2312 in the carrier bed moves circumferentially with the carrier bed and forms dynamic contact with rainwater. On the one hand, this can prevent the carrier surface from becoming saturated with adsorption and promptly update the contact interface between the carrier and the rainwater, thereby improving adsorption and degradation efficiency. On the other hand, it can drive the calcium ions released by the slow-release chamber 223 to diffuse evenly in the rainwater, preventing excessively high local salt concentrations from inhibiting microbial activity and achieving a synergistic effect of salt and alkali regulation and microbial activation.

[0043] The control unit 200 is equipped with a second filter 210 above the slow-release control chamber 220. Its function is to intercept the precipitate, microbial metabolites, and a small amount of detached carrier particles generated during the reaction. The inlet of the control unit 200 is located below the second filter 210, and the outlet is located above it. Water entering from below first undergoes synergistic treatment by the slow-release control chamber 220 and the microbial treatment unit 230, then passes through the second filter 210 to filter impurities, and finally flows out from the outlet above, forming a bottom-in, top-out water flow path. This extends the residence time of the water within the control unit 200, ensuring effective treatment. The bottom of the control unit 200, below the microbial carrier bed, has a sludge collection section 500. The sludge collection section 500 has a conical structure to facilitate sedimentation and accumulation. A drain valve is located at the bottom of the sludge collection section 500, which can be opened periodically to backwash or discharge the collected precipitate and microbial metabolites, preventing impurities from accumulating and affecting the operation of the device.

[0044] A deep stabilization unit 300 is connected in series between the regulation unit 200 and the water storage and recharge unit 400. Its core function is to further adsorb residual heavy metal ions (such as Pb²⁺, Cd²⁺, etc.) and unreacted calcium ions in the rainwater, while adjusting the pH value of the rainwater to a suitable range, improving the stability of the outflow, and providing suitable water quality for subsequent soil recharge.

[0045] The deep stabilization unit 300 has three composite filter layers 310 arranged from bottom to top in the vertical direction. Adjacent filter layers can be separated by stainless steel screens to prevent the filter media from mixing. The porosity of the filter layers decreases from top to bottom. For example, in this embodiment, the porosity of the upper layer is 45%, the middle layer is 35%, and the lower layer is 25%, which realizes step-by-step adsorption and purification and improves the purification accuracy.

[0046] The composite filter layer 310 is composed of zeolite and bentonite in a mass ratio of 2:1 to 4:1. The composite process involves mixing natural zeolite and bentonite in a specific ratio, adding 8% deionized water as a binder, stirring thoroughly, pressing the mixture into a mold to form a filter plate structure, and then drying it in a constant temperature drying oven at approximately 110℃ until the moisture content is ≤3%. The resulting filter plate exhibits good structural stability, is not easily broken, and retains sufficient pores for water flow. Zeolite possesses excellent ion exchange properties, capable of adsorbing heavy metal ions and residual calcium ions, while bentonite has strong adsorption and pH adjustment capabilities. The synergistic effect of these two materials further removes impurities from rainwater, adjusting the rainwater pH to 6.5-7.5, meeting the water quality requirements for soil recharge in arid and semi-arid regions.

[0047] The inlet of the deep stabilization unit 300 is located below the bottom composite filter layer 310, and the outlet is located above the top composite filter layer 310. A multi-stage connecting pipe 320 is provided between the deep stabilization unit 300 and the water storage and recharge unit 400. The multi-stage connecting pipe 320 includes three inlet ends, which are distributed between two adjacent composite filter layers 310. Each inlet end is equipped with a valve, which can adjust the water flow distribution ratio according to the adsorption load of each filter layer, avoid local adsorption saturation of the filter layer due to single water inlet, extend the service life of the filter layer, and ensure stable effluent water quality.

[0048] The core function of the water storage and recharge unit 400 is to store deeply treated rainwater, regulate the outflow rate to meet soil recharge needs, and further settle residual trace impurities in the rainwater. The bottom of the water storage and recharge unit 400 is connected to the outlet pipe 410, which is equipped with a flow sensor and an automatic control valve. The flow sensor can automatically adjust the recharge flow rate based on the signal from the soil moisture sensor.

[0049] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0050] The terms "upper," "lower," "outer," "inner," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish relative positional relationships and are not necessarily qualitative. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0051] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A primary rainwater treatment device for sponge cities in arid and semi-arid regions, comprising a pretreatment unit and a water storage and reinjection unit, wherein the pretreatment unit is connected to an inlet pipe and the water storage and reinjection unit is connected to an outlet pipe; characterized in that: A control unit is connected in series between the pretreatment unit and the water storage and reinjection unit. The control unit is used for the coordinated operation of salinity regulation and microbial activation. The control unit includes an outer shell, inside which a slow-release control chamber is concentrically installed. The side wall of the slow-release control chamber is provided with a slow-release cavity. The shell wall of the slow-release cavity is uniformly provided with a plurality of first flow holes. The slow-release cavity is filled with a slow-release agent. The slow-release control chamber is equipped with a rotatable microbial treatment unit, which includes a cylindrical microbial carrier bed. The microbial carrier bed has a microbial cavity inside, and the shell wall of the microbial cavity is uniformly opened with a number of second flow holes. The microbial cavity contains a microbial carrier assembly, which is loaded with drought-resistant and salt-tolerant microbial flora. During the rotation of the microbial treatment unit, it forms dynamic contact with rainwater, avoiding adsorption saturation on the carrier surface, and at the same time ensuring uniform contact between the slow-release agent and the microorganisms, preventing excessively high local salt concentrations from inhibiting microbial activity. The bottom of the control unit's outer shell is equipped with a sludge collection section below the microbial carrier bed, which is used to collect the precipitates and microbial metabolites generated during the reaction and discharge them periodically.

2. The primary rainwater treatment device as described in claim 1, characterized in that: The slow-release agent includes slow-release particles, which are composite particles of calcium oxide and gypsum. The surface of the slow-release particles is coated with a slow-release film to control the calcium ion release rate at 0.5~1.2 mg / (L·h). The released calcium ions react with bicarbonate and chloride ions in rainwater to precipitate, thereby reducing the salinity and alkalinity of rainwater. At the same time, the gypsum particles can replenish the sulfur element required by the soil.

3. The primary rainwater treatment device as described in claim 2, characterized in that: The slow-release granules have a calcium oxide to gypsum mass ratio of (2~2.5):1 and a particle size of 5-8 mm; The sustained-release membrane is a composite membrane made of polyvinyl alcohol and sodium alginate in a mass ratio of (3~3.5):1, with a membrane thickness of 0.1~0.3 mm.

4. The primary rainwater treatment device as described in claim 3, characterized in that: The microbial carrier component is a modified straw charcoal carrier, which is carbonized at 400-500℃ for 2-3 hours and then activated with 10-15% sodium hydroxide solution, with a specific surface area ≥300m² / g and a porosity of 60-70%. The drought- and salt-tolerant microbial community loaded on the carrier surface consists of a mixture of Bacillus subtilis and Pseudomonas aeruginosa at a volume ratio of 1:(1.8~2.5), with a community concentration ≥10. 8 CFU / g.

5. The primary rainwater treatment device as described in claim 1, characterized in that: The inner shell of the microbial carrier bed is provided with an installation channel. The installation channel is fitted onto the installation shaft. The installation shaft is eccentrically installed in the slow-release control chamber through the installation plate frame. The input end of the installation shaft is connected to the output end of the drive device. The installation channel is provided with a limiting groove to restrict relative rotation. The installation shaft is provided with a matching limiting block.

6. The primary rainwater treatment device as described in claim 1, characterized in that: The pretreatment unit is equipped with a first filter screen, with the inlet of the pretreatment unit located above the first filter screen and the outlet located below the first filter screen. A second filter screen is provided above the slow-release control chamber. The inlet of the control unit is located below the second filter screen, and the outlet is located above the second filter screen.

7. The primary rainwater treatment device as described in claim 1, characterized in that: The inner wall of the outer shell of the control unit is provided with a phase change insulation layer. The phase change insulation layer is made of a composite phase change material of paraffin and expanded graphite, with a phase change temperature of 25~30℃ and a latent heat of at least 180J / g. The inner side of the phase change insulation layer is provided with a breathable and moisturizing membrane, which is used to absorb and store environmental heat during the dry period to maintain the temperature stability inside the cavity, while releasing a small amount of moisture to maintain the humidity required by microorganisms inside the cavity and prevent them from becoming inactive due to water loss.

8. The primary rainwater treatment device as described in any one of claims 1 to 7, characterized in that: A deep stabilization unit is connected in series between the control unit and the water storage and reinjection unit. The depth stabilization unit is equipped with a composite filter layer. The inlet of the depth stabilization unit is located below the composite filter layer, and the outlet is located above the composite filter layer.

9. The primary rainwater treatment device as described in claim 1, characterized in that: The deep stabilization unit is provided with multiple composite filter layers arranged from bottom to top in the vertical direction. The composite filter layer is composed of zeolite and bentonite in a mass ratio of (2~4):

1. It is used to further adsorb residual heavy metal ions and unreacted calcium ions in rainwater, while adjusting the pH value of rainwater to 6.5~7.5, improving the stability of the effluent, and providing suitable water quality for subsequent soil recharge.

10. The primary rainwater treatment device as described in claim 9, characterized in that: A multi-stage connecting pipe is provided between the deep stabilization unit and the water storage and reinjection unit. The multi-stage connecting pipe includes multiple water inlet ends distributed between two adjacent composite filter layers.

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