A method for treating rural domestic sewage

Abstract

The application discloses a novel rural domestic sewage treatment method, wherein domestic sewage is collected and flows into a regulating tank, sewage in the regulating tank can overflow into an anoxic tank; sewage in the anoxic tank is lifted by a gas lifting pump to a tubular aerobic biological filter for reprocessing, and the main part of the sewage treated by the tubular aerobic biological filter flows to a sedimentation tank for mud-water separation, and the other part is backflowed and delivered to the anoxic tank; the sewage in the sedimentation tank is subjected to mud-water separation, the supernatant is discharged, and the sludge part is lifted by a gas pressure lifting pump to a sludge drying and filtering tank; the air required by the gas lifting pump is sourced from an air compressor and a high-pressure gas storage tank, and the range of the gas pressure in the high-pressure gas storage tank is determined according to the requirement of the gas lifting pump and the gas pressure requirement of an aeration system of the tubular aerobic biological filter.

Description

Technical Field

[0001] This invention relates to a method for treating rural domestic sewage, belonging to the field of sewage treatment technology. Background Technology

[0002] Existing wastewater treatment processes are primarily suitable for large-scale urban domestic sewage or industrial wastewater. For rural domestic sewage, which has a smaller discharge volume or is more dispersed, these processes suffer from drawbacks such as high equipment investment, high energy consumption, complex operation and maintenance, and poor sustainability. The main reason is that rural domestic sewage discharge is dispersed, with individual villages generating very little sewage; typically, a single village collects no more than 30 cubic meters of domestic sewage per day. 3 / d, using traditional secondary biological treatment methods for such small-scale sewage treatment has many defects or shortcomings. First, the equipment selection is unreasonable, leading to energy waste and excessive energy consumption; because the rated capacity of sewage pumps, aeration blowers, sludge pumps, and other equipment currently available on the market far exceeds the actual needs of domestic sewage treatment in a single village. For example, the flow rate of sewage pumps currently available on the market is only 3m³ / h. 3 The aeration blower's air volume is mostly above 30m³ / h. 3 The sludge pump has a discharge capacity of 10m³ / h or more. 3 / h or more, while the sewage pump flow rate required for most village domestic sewage treatment facilities does not exceed 1m. 3 / h, aeration rate not exceeding 15m³ 3 / h, sludge discharge volume not exceeding 2m 3 Furthermore, most rural domestic sewage treatment facilities currently employ valve regulation, backflow, or intermittent treatment to address insufficient sewage volume. However, these measures either result in significant energy waste (overkill) or severely impact treatment efficiency. Moreover, most rural domestic sewage treatment facilities utilize an excessive number of easily damaged equipment such as pumps, sludge pumps, and blowers, leading to frequent malfunctions. Due to the small scale of sewage treatment in individual villages, dedicated personnel cannot be assigned for full-time maintenance, resulting in most rural domestic sewage treatment facilities being frequently out of service or paralyzed. Additionally, the small scale of treatment in most rural areas prevents the allocation of full-time personnel for regular sludge removal. Furthermore, the small sludge volume makes large-scale sludge treatment facilities too cost-effective; therefore, most rural domestic sewage treatment facilities lack sludge removal mechanisms, resulting in poor effluent quality, particularly the inability to separate total phosphorus (TP) from the sewage.

[0003] Taking the traditional AO process for treating rural domestic sewage as an example, its effluent quality can theoretically meet the discharge requirements of rural domestic sewage, but the following defects exist during operation:

[0004] 1. A separate aeration blower is required to supply oxygen to the aeration system in the aerobic tank. In addition, many other steps require the use of wastewater (sludge) pumps, such as lift pumps to transfer wastewater from the equalization tank to subsequent units, sand removal pumps to discharge sludge from the grit chamber, return pumps to circulate sludge from the aerobic tank to the anoxic tank, and sludge pumps for sludge discharge and circulation from the sedimentation tank. Since the amount of domestic sewage treated in most villages is very small, the average treatment volume is generally no more than 1 cubic meter. 3 / h, the air demand for aeration does not exceed 15m³ / h. 3 / h, sludge discharge volume not exceeding 2m 3 / d, however, most sewage pumps currently available on the market have a flow rate of 3m³ / d. 3 The air supply capacity of most aeration blowers is 30m³ / h or more. 3 For sludge pumps with a discharge capacity of over 15m³ / h, the discharge rate is mostly above 15m³ / h. 3 For pumps with a capacity of over 1000 cubic meters per hour, it is impossible to find sewage pumps or other equipment that match their scale. Although using large-capacity sewage pumps can meet the requirements through technical treatment, there will be a waste of energy due to the "oversized pump pulling a small cart" phenomenon.

[0005] 2. The sewage pumps and blowers used in the treatment process are a large number of easily damaged equipment with a high failure rate. They require regular inspection, maintenance or replacement and full-time operation and maintenance by professional personnel. However, the amount of rural domestic sewage to be treated in general villages is too small. If professional personnel are arranged for full-time operation and maintenance, the labor cost is too high. Therefore, most rural domestic sewage treatment facilities are operated and maintained by local villagers on a part-time basis. However, this operation and maintenance method cannot guarantee the normal operation of sewage treatment facilities, which is the main reason why "most rural domestic sewage treatment facilities are not operating normally or even paralyzed".

[0006] 3. Direct aeration using aeration blowers to aerate the aeration discs (rods or tubes) in the aerobic tank has several drawbacks. First, oxygen utilization is very low. Under normal pressure, oxygen has limited solubility in wastewater, and most of the oxygen escapes from the biological treatment tank into the atmosphere before being absorbed by the wastewater. Second, the aerobic tank requires a large number of aeration discs (rods or tubes) and air delivery pipes, resulting in high construction costs and susceptibility to malfunctions. On the other hand, the aeration volume and pressure depend on the performance parameters of the aeration blower, which are not adjustable. However, the air pressure and volume required by the wastewater treatment plant during operation often do not match the air pressure and volume provided by the aeration blower. Therefore, most wastewater treatment technologies (including traditional AO) currently use blowers that are over-configured, leading to significant waste of air volume and energy, and also affecting the biological treatment effect of wastewater.

[0007] 4. The more types of pumps and other equipment are needed, the higher the energy consumption. Water pumps are easily damaged equipment, and the higher the failure rate, which further exacerbates the instability of the sewage treatment plant operation.

[0008] 5. Traditional processes use sludge pumps to discharge sludge, resulting in sludge with excessively high moisture content. Furthermore, the remaining sludge requires pretreatment with chemical agents followed by dewatering using a plate and frame filter press. While this method is effective, it is complex, requires dedicated personnel, and is costly. It is suitable for medium to large-scale wastewater treatment plants. For wastewater treatment volumes less than 30 cubic meters... 3 Small-scale sewage treatment plants are too costly and unsuitable.

[0009] In view of this, how to solve the problems of large equipment investment, high energy consumption and poor treatment effect of existing rural domestic sewage treatment technologies is a topic that needs to be studied and solved by those skilled in the art. Summary of the Invention

[0010] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a rural domestic sewage treatment process that solves the problems of high energy consumption, high equipment failure rate and high maintenance cost of the existing technology.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A method for treating rural domestic sewage is characterized in that domestic sewage is collected and flows into an equalization tank, the elevation of which is higher than that of an anoxic tank, and the sewage in the equalization tank can overflow into the anoxic tank; an air lift pump is installed in the anoxic tank to lift the sewage to a tubular aerobic biological filter for further treatment; after treatment by the tubular aerobic biological filter, part of the sewage flows by gravity to a sedimentation tank for sludge-water separation, and the other part is returned to the anoxic tank; after sludge-water separation, the supernatant in the sedimentation tank is discharged, and the sludge at the bottom is lifted by an air lift pump to the anoxic tank and a sludge drying and filtration tank;

[0013] The air required for both the airlift pump and the air pressure boosting pump comes from an air compressor and a high-pressure air storage tank. Based on the requirements of the airlift pump and the air pressure requirements of the tubular aerobic biological treatment tank aeration system, the range of air pressure in the high-pressure air storage tank (i.e., the upper limit P) is determined. 上 and lower limit P 下 The pressure value of the high-pressure gas storage tank is transmitted to the first controller via a data signal; when the pressure inside the high-pressure gas storage tank is lower than P... 下 At that time, the first controller sends a command to the air compressor to start compressing air into the high-pressure air tank. When the air pressure in the high-pressure air tank is higher than P... 上 At that time, the first controller sends a command to the air compressor to stop pressing air into the high-pressure air tank.

[0014] Furthermore, the tubular aerobic biological filter is modified from a PVC pipe or corrugated pipe with an inner diameter of 60-100cm. Both ends of the pipe are sealed, and both ends are equipped with inlet, outlet and vent valve. The pipe is filled with biological suspended packing material with a diameter of about 3cm. The oxygen required for the aerobic biochemical reaction in the tubular aerobic biological filter comes from the oxygen lifted by the air lift pump, and the amount of air can be controlled by the air volume regulating valve.

[0015] Furthermore, a level gauge and a second controller are installed in the anoxic tank. When the sewage in the anoxic tank accumulates to a certain height, the second controller will send a command to the first solenoid valve to open the valve. The air in the high-pressure air tank drives the air lift pump to lift the sewage in the anoxic tank to the tubular aerobic biological filter. At the same time, the air discharged by the air lift pump is also transported to the tubular aerobic biological filter to provide the oxygen needed for the aerobic biochemical reaction of the microorganisms in the tubular aerobic biological filter. The required air flow rate can be adjusted by the air volume regulating valve.

[0016] Furthermore, the sludge return in the sedimentation tank is accomplished by a third controller, a second solenoid valve, and a pneumatic lift pump. The third controller opens or closes the second solenoid valve according to the set time to ensure that the pneumatic lift pump lifts the sludge according to the set time. Part of the lifted sludge is discharged to the sludge drying and filtration tank, the generated filtrate is discharged to the equalization tank, and the other part of the sludge is returned to the anoxic tank.

[0017] Furthermore, the sludge drying and filtration tank is a prefabricated square frame structure placed directly above the equalization tank. The bottom plate of the sludge drying and filtration tank is perforated with a pore diameter of approximately 0.5 cm and a pore spacing of approximately 1 cm. Polypropylene filter cloth (or other filter cloth with good corrosion resistance, acid and alkali resistance, wear resistance, stability, high temperature resistance, and air permeability) is laid on top of the bottom plate. The pore diameter of the filter cloth is approximately 10 micrometers.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] First, this invention creatively proposes an energy-saving air supply method, employing an air compressor, high-pressure air storage tank, and controller to provide the air source. The controller maintains the air pressure within the high-pressure air storage tank within a certain range, eliminating the need for continuous operation of the air compressor. Air is only forced in when the pressure falls below the set lower limit, and automatically stops when the pressure exceeds the set upper limit. Compared to the traditional method of continuously supplying air with aeration blowers, this invention's air supply system eliminates the need for continuous operation, avoiding air waste and saving energy. Furthermore, by eliminating the use of easily damaged equipment such as blowers and sludge pumps, the failure rate of wastewater treatment facilities is significantly reduced, operational stability is significantly improved, and maintenance is greatly simplified. This significantly alleviates the problems of difficult maintenance and frequent malfunctions in rural domestic wastewater treatment facilities, while also reducing construction costs.

[0020] Secondly, by designing control strategies and utilizing equipment such as controllers, solenoid valves, air lift pumps, and air pressure boosting pumps, the energy waste phenomenon of "overkill" in the conventional sewage treatment process for rural domestic sewage is avoided.

[0021] Third, the pipeline aerobic biological filter designed in this invention can significantly improve the solubility of oxygen in wastewater and prolong the residence time of oxygen in wastewater, thereby significantly improving the oxygen utilization rate and significantly reducing the air demand, thus greatly reducing operating costs. Furthermore, the invention rationally utilizes the aeration method of the airlift pump, that is, while completing the wastewater lifting process, aeration and oxygen supply to the pipeline aerobic biological filter are simultaneously completed, eliminating the need for additional aeration equipment such as aeration blowers, aeration discs, and air supply pipes, significantly reducing the failure rate, operating energy consumption, and construction costs.

[0022] Fourth, the pneumatic lift pump for sludge removal designed in this invention flexibly utilizes air lift technology, enabling a single aeration blower and corresponding lifter to complete all operations in the wastewater treatment process, including wastewater lifting, sludge circulation, and sludge removal. This eliminates the need for separate wastewater lift pumps, sludge pumps, and return pumps, significantly reducing the number of easily damaged pumps used in the wastewater treatment process. Furthermore, compared to conventional air lift pumps, the pneumatic lift pump used in this design has a higher sludge removal efficiency and can achieve small-scale sludge removal compared to sludge pumps available on the market.

[0023] Fifth, this invention designs a sludge drying and filtration pond to address the characteristics of rural domestic sewage generation and discharge, thus solving the problems of sludge discharge and disposal and improving sewage treatment efficiency, especially significantly improving the TP treatment effect. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of rural domestic sewage treatment according to the present invention;

[0025] Figure 2 This is a schematic diagram of the airlift pump structure in the equalization tank and aerobic tank of the present invention;

[0026] Figure 3 This is a schematic diagram of the sedimentation tank air lift pump structure in this invention.

[0027] In the diagram, 1 - air compressor, 2 - high-pressure air storage tank, 3 - sludge drying and filtration tank, 4 - equalization tank, 5 - anoxic tank, 6 - sedimentation tank, 7 - air lift pump, 8 - level gauge, 9 - air pressure lift pump, 10 - tubular aerobic biological filter, 11 - first controller, 12 - second controller, 13 - third controller, 14 - air volume regulating valve, 15 - first solenoid valve, 16 - second solenoid valve, 17 - gas release port, 18 - safety valve, 19 - partition screen, 20 - aeration and sludge removal pipe, 21 - check valve, 22 - nano aeration ring, 23 - air collection hood, 24 - air inlet pipe, 25 - sewage lift pipe, 26 - sewage conveying pipe, 27 - sludge inlet pipe, 28 - pressure relief valve rotary switch, 29 - float plate, 30 - pressure relief and exhaust pipe. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments.

[0029] All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended, meaning that they include but are not limited to.

[0030] This invention addresses the characteristics of small-volume and highly biodegradable rural domestic sewage discharge by developing and designing a rural domestic sewage treatment technology. This technology is suitable for rural domestic sewage treatment scales of less than 30m³. 3 The case of / d.

[0031] like Figure 1 As shown, this invention provides a method for treating rural domestic sewage, comprising: collecting domestic sewage and flowing it into an equalization tank, the equalization tank being at a higher elevation than the anoxic tank, and the sewage in the equalization tank flowing by gravity into the anoxic tank for treatment; the anoxic tank is equipped with an air lift pump, which lifts the sewage to a tubular aerobic biological filter for further treatment; after treatment by the tubular aerobic biological filter, part of the sewage flows by gravity to a sedimentation tank for sludge-water separation, and the other part is returned to the anoxic tank; after sludge-water separation, the supernatant in the sedimentation tank is discharged, and the bottom sludge is lifted by an air pressure lift pump to a sludge drying filter tank and the anoxic tank. Figure 1In the diagram, 1 is an air compressor, 2 is a high-pressure air storage tank, 3 is a sludge drying and filtration tank, 4 is an equalization tank, 5 is an anoxic tank, 6 is a sewage sedimentation tank, 7 is an air lift pump, 8 is a level gauge, 9 is an air pressure lift pump, 10 is a tubular aerobic biological filter, 11 is the first controller, 12 is the second controller, 13 is the third controller, 14 is an air volume regulating valve, 15 is the first solenoid valve, 16 is the second solenoid valve, 17 is a gas release port, 18 is a safety valve, 19 is a screen, 20 is an aeration and sludge removal pipe, and 21 is a check valve.

[0032] This invention employs an air source control method, utilizing an air compressor, a high-pressure air storage tank, and a controller to provide the air supply. Both the air lift pump and the air pressure boosting pump are driven by high-pressure air from the high-pressure air storage tank. The controller maintains the air pressure within the high-pressure air storage tank within a specific range. The air compressor does not need to operate continuously; it only compresses air when the pressure falls below the set lower limit and automatically stops operating when the pressure exceeds the set upper limit. Compared to traditional continuous aeration methods using blowers, this invention eliminates the need for continuous air compressor operation, protecting the equipment, avoiding air waste, and saving energy. All air required by the air lift pump comes from the air compressor and the high-pressure air storage tank. The high-pressure air storage tank is equipped with a pressure detector, a safety valve, and a controller. The air pressure range (i.e., the upper limit P) within the high-pressure storage tank is determined based on the air lift pump's required wastewater lifting height and the air pressure requirements of the aerobic biological treatment tank aeration system. 上 and lower limit P 下 The pressure value of the high-pressure gas storage tank is transmitted to the first controller via a data signal; when the pressure inside the high-pressure gas storage tank is lower than P... 下 At that time, the first controller sends a command to the air compressor to start compressing air into the high-pressure air tank. When the air pressure in the high-pressure air tank is higher than P... 上 At that time, the first controller sends a command to the air compressor to stop pressing air into the high-pressure air tank.

[0033] Both the equalization tank and the anoxic tank are equipped with biological packing materials. The main function of the equalization tank is to homogenize the water quality and quantity, and it also has the function of anaerobic biochemical treatment. Its effluent flows by gravity into the anoxic tank. At the same time, part of the effluent from the subsequent aerobic biological filter is also returned to the anoxic tank. The two are mixed in the anoxic tank and a denitrification reaction occurs.

[0034] The anoxic tank is equipped with a level gauge and a second controller. When the wastewater level in the anoxic tank exceeds a certain height, the second controller sends a command to the first solenoid valve to open it. Air from the high-pressure air tank drives an airlift pump to lift the wastewater from the anoxic tank to the subsequent pipeline aerobic biological filter. Simultaneously, the air discharged from the airlift pump is also delivered to the pipeline aerobic biological filter. The oxygen required for the aerobic biochemical reactions of the microorganisms in the pipeline aerobic biological filter comes from the air used by the airlift pump to lift the wastewater. The required air flow rate can be adjusted by an air volume regulating valve. Wastewater in the regulating tank automatically overflows into the anoxic tank. The wastewater level range (i.e., upper limit H) in the anoxic tank is set according to the daily wastewater inflow and daily wastewater treatment volume. 上 and lower limit H 下 A level gauge is installed in the anoxic tank. The level gauge sends the sewage level data in the equalization tank to the second controller. When the level in the equalization tank is higher than H... 上 At this time, the second controller sends a command to the first solenoid valve, which opens or closes periodically according to the time set by the controller. The high-pressure air storage tank begins to supply air to the airlift pump, lifting the sewage in the anoxic tank to the pipeline aerobic biological filter. When the liquid level in the regulating tank is lower than H... 下 At this time, the second controller sends a command to the first solenoid valve to close the valve, the high-pressure air storage tank stops supplying air to the airlift pump, and the airlift pump stops lifting sewage. The high-pressure air storage tank supplies air to the airlift pump, which mixes with the sewage in the pump chamber to form a gas-water mixture with a density lower than the sewage. Under the pressure of the external sewage, this gas-water mixture is lifted and transported to the tubular aerobic biological filter. The oxygen contained in the gas-water mixture provides oxygen for the aerobic microorganisms to degrade the organic matter in the sewage. The amount of air can be controlled by the air volume regulating valve. Therefore, the airlift pump of this invention not only completes the lifting and transportation of sewage but also aerates the tubular aerobic biological filter, eliminating the need for a separate aeration system for the tubular aerobic biological filter.

[0035] The sludge return in the sedimentation tank is accomplished by a third controller, a second solenoid valve, and a pneumatic lift pump. The third controller opens or closes the second solenoid valve according to a set time, ensuring that the pneumatic lift pump lifts the sludge according to the set time. Part of the lifted sludge is returned to the anoxic tank, and the other part is discharged to the sludge drying and filtration tank. The resulting filtrate is discharged to the equalization tank. In addition, to facilitate better sludge discharge from the sedimentation tank, the sedimentation tank must be equipped with a radial flow or vertical flow sedimentation tank with a single sludge hopper. The pneumatic lift pump is located outside the sedimentation tank and is connected to the sludge hopper of the sedimentation tank via a sludge discharge pipe.

[0036] Further, see Figure 1In the tubular aerobic biological filter, the aeration system, through an air compressor, high-pressure air tank, and air lift pump, simultaneously lifts and transports wastewater, while also supplying air to the tubular aerobic biological filter, providing oxygen for the growth and reproduction of aerobic microorganisms, thus completing aeration. Traditional domestic wastewater treatment technologies require separate wastewater lift pumps for lifting wastewater, and separate aeration fans, air pipelines, and aeration discs (rockers) for the aeration system within the aerobic tank, resulting in numerous equipment requirements and high energy consumption. This invention, however, only requires an air compressor, high-pressure air tank, and air lift pump, simultaneously lifting wastewater and supplying aeration to the tubular aerobic biological filter, simplifying equipment and reducing construction costs and energy consumption. Employing air lift aeration technology, only one air compressor, high-pressure air tank, and matching air lift device are needed to lift wastewater from the anoxic tank to the tubular aerobic biological filter, while simultaneously supplying oxygen to the filter.

[0037] The aforementioned pipeline aerobic biological filter can be modified from commercially available PVC pipes or corrugated pipes with an inner diameter of 60-100cm. Both ends of the pipe are sealed, and both ends are equipped with inlets, outlets, and vent valves. The pipe is filled with biological suspended packing material with a diameter of approximately 3cm. This pipeline aerobic biological filter no longer uses aeration discs (sticks) or other aeration methods. Instead, it utilizes the air dissolved in when the wastewater is lifted by an air lift pump to provide an aerobic environment for the growth of aerobic microorganisms. The air volume can be adjusted by using an air volume regulating valve and by changing the inner diameter of the air lift pump's lifting pipe to ultimately adjust the air-to-water ratio within the filter. Because the pipeline is completely sealed and under high pressure, the solubility of air pumped into the pipeline by the airlift pump is significantly increased in the wastewater. Air must migrate to the vent at the other end of the pipeline to be released from the wastewater, a longer migration distance. This migration is also hindered, segmented, and shredded by the packing material, and the residence time in the water is greatly extended, which is more conducive to the absorption and utilization of microorganisms in the wastewater. This significantly improves the utilization rate of oxygen by microorganisms, reduces aeration waste and aeration volume, and lowers energy consumption. To prevent clogging of the pipeline aerobic biological filter, inlets, outlets, and vents are installed at both ends of the pipeline. The wastewater inlet is periodically changed to alternate the flow direction of the wastewater within the pipeline. This serves to backwash the biological packing material inside the pipeline, preventing clogging. To better remove accumulated sludge from the pipeline, nano-aeration pipes are installed and fixed at the bottom of the pipeline. These pipes are periodically aerated to loosen the sludge deposited at the bottom of the pipeline, ensuring that the wastewater can flush out all the accumulated sludge, thereby improving the sludge removal effect. To ensure uniform distribution of the packing material within the pipeline, fixed mesh screens are installed at regular intervals at both ends of the pipeline to prevent the packing material from being impacted and accumulated at one end by sewage. To prevent pipeline rupture due to excessive pressure, a pressure relief safety valve is installed in the pipeline. If the pressure inside the pipeline exceeds the set limit, the safety valve will automatically open to release a portion of the steam-water mixture.

[0038] Furthermore, the sludge drying and filtration tank in this invention is designed for the characteristics of small domestic sewage treatment volume and small sludge discharge. It is a prefabricated, square-frame structure placed directly above the equalization tank. The sludge drying and filtration tank uses materials with different load-bearing capacities depending on the scale of sewage treatment. The bottom plate of the sludge drying and filtration tank is completely perforated with pores approximately 0.5 cm in diameter and spaced approximately 1 cm apart. Polypropylene filter cloth (or other filter cloth with good corrosion resistance, acid and alkali resistance, wear resistance, stability, high temperature resistance, and air permeability) is laid on top of the bottom plate. The pore size of the filter cloth is approximately 10 micrometers. Sludge in the sedimentation tank is preferentially lifted and returned to the anoxic tank by a pneumatic lift pump. Unreturned sludge is transported to the sludge drying and filtration tank. Most of the water in the sludge permeates through the filter cloth under gravity and flows into the equalization tank. The sludge matrix retained in the drying and filtration tank further evaporates and dehydrates under natural weathering. The sludge drying and filtration tank should be at least 20cm high (enough to store sludge from the sedimentation tank for at least one month). Its size should be designed based on the equalization tank size, ensuring it sits directly above the equalization tank and that all seeping wastewater flows into it. A rainproof canopy should be installed directly above the sludge drying and filtration tank, with sufficient distance between the canopy and the tank for both ventilation and rain protection. As sludge accumulates in the tank, it needs to be manually cleaned periodically (approximately once a month), and the filter cloth and bottom plate should be rinsed to prevent clogging. The dried sludge produced can be used for soil improvement in nearby farmland or other suitable purposes.

[0039] See Figure 2 The airlift pump located in the anoxic tank not only lifts the wastewater but also supplies oxygen to the tubular aerobic biological filter. In the diagram, 22 is the nano-aeration ring, 23 is the air collection hood, 24 is the air inlet pipe, 25 is the wastewater lift pipe, and 26 is the wastewater delivery pipe.

[0040] See Figure 3 The pneumatic lift pump, located outside the sedimentation tank, is used to preferentially lift and return the sludge from the sedimentation tank to the anoxic tank. The sludge that cannot be returned is discharged into the sludge drying and filtration tank. The pneumatic lift pump 9 includes a sealed shell (cavity) body, on which are provided an air inlet pipe 24, a pressure relief and exhaust pipe 30, a sewage lift pipe 25, and a sludge inlet pipe 27. The air inlet pipe 24 is equipped with a second solenoid valve 16 and is controlled by a third controller 13; one end of the pressure relief pipe 30 is connected to the inner cavity of the sealed housing through a pressure relief valve. The pressure relief valve drives the pressure relief rotary switch 28 to rotate through the raising and lowering of the float 29, so as to realize the connection or closure of the pressure relief pipe with the inner cavity of the sealed housing. The rotary switch is connected to the float 29 through a connecting rod. The float 29 rises and falls with the rise and fall of the water level in the sealed housing, thereby driving the pressure relief valve to rotate back and forth, ultimately realizing the opening or closing of the pressure relief valve; one end of the sewage lifting pipe is located at the bottom of the sealed housing (cavity), and the other end is connected to the anoxic tank and the sludge drying tank. Figure 1 Its working principle is as follows: After the second solenoid valve on the air inlet pipe is opened, the high-pressure gas in the high-pressure storage tank enters the sealed shell (cavity) of the air pressure boosting pump 9, increasing the air pressure inside the sealed shell (cavity). Under the pressure inside the sealed cavity, the check valve in the sludge discharge pipe closes and prevents the sludge inside the sealed shell (cavity) from flowing back to the sedimentation tank. The sewage inside the sealed shell (cavity) is driven by the high-pressure gas and is lifted and transported to the anoxic tank and sludge drying tank through the booster pipe. At the same time, the liquid level inside the sealed shell (cavity) begins to drop, and the float (density approximately 0.50 kg / L, volume and gravity must meet the rotation requirements of the pressure relief valve) drops with the liquid level under the action of gravity, driving the pressure relief valve to rotate. When the water level inside the sealed shell (cavity) drops to the set lower limit, the float drops to its lowest position, rotating the pressure relief valve to the open position. At this time, the inner cavity of the sealed shell (cavity) is connected to the outside atmosphere through the exhaust pipe, and at the same time, the second controller sends a closing command to the second The solenoid valve and high-pressure air tank stop supplying air to the sealed shell (cavity). At this time, the gas in the cavity is discharged into the atmosphere through the pressure relief pipe until the air pressure in the sealed shell (cavity) equals the atmospheric pressure. When the pressure on the other side of the sludge discharge pipe check valve is higher than the air pressure in the sealed shell (cavity), the mud-water mixture in the sludge discharge pipe pushes open the check valve and enters the sealed shell (cavity). The mud-water level in the sealed shell (cavity) begins to rise, and the float plate begins to rise under the action of buoyancy, driving the pressure relief valve to rotate. When the liquid level in the sealed shell cavity rises to the highest position, the pressure relief valve is finally rotated to the closed position, isolating the sealed shell (cavity) from the outside atmosphere. After the set time is reached, the third controller opens the second solenoid valve for air intake again, lifting the sludge again. This cycle repeats, completing the discharge of sludge from the sedimentation tank. The lifting rate, height, and amount of sludge can be controlled by the air intake and the air pressure in the high-pressure air tank. The lifting time and frequency can be set by the controller, thereby realizing the timed and quantitative lifting of sludge to the anoxic tank and the sludge drying and filtration tank. A portion of the sludge discharged by the air pressure booster pump is returned to the anoxic tank, while the remainder is treated through a drying and filtration tank. Compared to traditional sludge discharge pumps, the sludge discharge system designed in this invention discharges sludge with lower moisture content and a smaller discharge volume, reducing the burden and cost of subsequent sludge disposal. Compared to traditional mechanical sludge dewatering methods such as plate and frame dewatering machines, the sludge disposal method designed in this invention is a natural drying and filtration process, requiring no manpower or dewatering machinery. It features simple operation, no energy consumption, low labor requirements, and low construction costs.

[0041] The pneumatic lift pump of this invention is a stable structural device that does not require the consumption of electricity or oil. It can lift sewage under the action of high-pressure gas. Compared with traditional sewage pumps, sludge pumps, return pumps and other electrical equipment, it has the advantages of energy saving, less damage, and especially less clogging. Compared with conventional air lift pumps, it has the advantages of low air consumption, low energy consumption, higher lifting height, larger flow rate and faster speed.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for treating rural domestic sewage, characterized in that, Domestic sewage is collected and flows into the equalization tank, which is at a higher elevation than the anoxic tank. The sewage in the equalization tank can flow into the anoxic tank by gravity. The anoxic tank is equipped with an air lift pump, which lifts the sewage to a tubular aerobic biological filter for further treatment. After treatment by the tubular aerobic biological filter, part of the sewage flows by gravity to the sedimentation tank for sludge-water separation, and the other part is returned to the anoxic tank. After sludge-water separation, the supernatant in the sedimentation tank is discharged, and the sludge at the bottom is lifted by an air lift pump to the anoxic tank and the sludge drying and filtration tank. The air required for both the airlift pump and the air pressure boosting pump comes from an air compressor and a high-pressure air storage tank. Based on the requirements of the airlift pump and the air pressure requirements of the tubular aerobic biological filter aeration system, the upper limit P of the air pressure in the high-pressure air storage tank is determined. 上 and lower limit P 下 The pressure value of the high-pressure gas storage tank is transmitted to the first controller via a data signal; when the pressure inside the high-pressure gas storage tank is lower than P... 下 At that time, the first controller sends a command to the air compressor to start compressing air into the high-pressure air tank. When the air pressure in the high-pressure air tank is higher than P... 上 At that time, the first controller sends a command to the air compressor to stop pressing air into the high-pressure air tank; The tubular aerobic biological filter is made of PVC pipe or corrugated pipe with an inner diameter of 60-100cm. Both ends of the pipe are sealed, and both ends are equipped with inlet, outlet and vent valve. The pipe is filled with biological suspended packing material with a diameter of 3cm. The oxygen required for the aerobic biochemical reaction in the tubular aerobic biological filter comes from the oxygen lifted by the air lift pump. The amount of air can be controlled by the air volume regulating valve. The pipe is completely sealed. The air delivered into the pipe by the air lift pump migrates to the vent at the other end of the pipe before being released from the sewage. The pneumatic lift pump includes a sealed housing, on which are provided an air inlet pipe, a pressure relief and exhaust pipe, a sewage lift pipe, and a sludge inlet pipe. The air inlet pipe is equipped with a second solenoid valve and is controlled by a third controller. One end of the pressure relief and exhaust pipe is connected to the inner cavity of the sealed housing through a pressure relief valve. The pressure relief valve is driven by the raising and lowering of a float plate to rotate a pressure relief valve rotary switch, thereby opening or closing the pressure relief and exhaust pipe from the inner cavity of the sealed housing. The pressure relief valve rotary switch is connected to the float plate through a connecting rod. The float plate rises and falls with the water level in the sealed housing, thereby driving the pressure relief valve rotary switch to rotate back and forth, ultimately opening or closing the pressure relief valve. One end of the sewage lift pipe is located at the bottom of the sealed housing, and the other end is connected to an anoxic tank and a sludge drying and filtration tank.

2. The rural domestic sewage treatment method according to claim 1, characterized in that, The anoxic tank is equipped with a level gauge and a second controller. When the sewage in the anoxic tank accumulates to a certain height, the second controller sends a command to the first solenoid valve to open the valve. The air in the high-pressure air tank drives the air lift pump to lift the sewage in the anoxic tank to the tubular aerobic biological filter. At the same time, the air discharged by the air lift pump is also transported to the tubular aerobic biological filter to provide the oxygen needed for the aerobic biochemical reactions of the microorganisms in the tubular aerobic biological filter. The required air flow rate can be adjusted by the air volume regulating valve.

3. The rural domestic sewage treatment method according to claim 1, characterized in that, The sludge return in the sedimentation tank is accomplished by a third controller, a second solenoid valve, and a pneumatic lift pump. The third controller opens or closes the second solenoid valve according to the set time to ensure that the pneumatic lift pump lifts the sludge according to the set time. Part of the lifted sludge is returned to the anoxic tank, and the other part is discharged to the sludge drying and filtration tank. The resulting filtrate is discharged to the equalization tank.

4. The rural domestic sewage treatment method according to claim 1, characterized in that, The sludge drying and filtration tank is a prefabricated square frame structure placed directly above the equalization tank. The bottom plate of the sludge drying and filtration tank is perforated with a pore diameter of 0.5 cm and a pore spacing of 1 cm. Polypropylene filter cloth or other filter cloth with good corrosion resistance, acid and alkali resistance, wear resistance, stability, high temperature resistance and air permeability is laid on the bottom plate. The pore diameter of the filter cloth is 10 micrometers.

5. The rural domestic sewage treatment method according to claim 1, characterized in that, The high-pressure gas storage tank is equipped with a gas volume regulating valve and a check valve on its exhaust pipe.

6. The rural domestic sewage treatment method according to claim 2, characterized in that, The tubular aerobic biological filter is also equipped with a gas release port and a safety valve.

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