A micro-aerobic aeration biochemical filter for wastewater treatment

Abstract

The present invention provides a micro-aerobic aeration biochemical filter for wastewater treatment, belonging to the field of environmental engineering. The biochemical filter includes a sludge hopper arranged at the bottom and a cylindrical filter body arranged above the sludge hopper. In the filter body, a water distributor, an aerator, an air distribution pipe, a filter plate, a supporting layer, a volcanic stone filter layer, a plastic filter layer, a filter media retaining net, a solid matter collection tank and a three-phase separator are arranged from bottom to top. The present invention arranges a three-phase separator and a solid matter collection tank above the filter layer, and uses volcanic stone and plastic fillers as filter media, optimizing the filter structure, and proposes a micro-aerobic aeration biochemical filter with a new type of combined filler. This micro-aerobic aeration biochemical filter has the function of a secondary sedimentation tank, achieving excellent backwashing effect, easy film hanging and quick start-up of the microbial film, fast reproduction speed, good heat preservation performance and high oxygen transfer efficiency, and has remarkable effects in energy conservation and consumption reduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a micro-aerobic aeration biochemical filter for wastewater treatment. Background Art

[0002] A micro-aerobic aeration biochemical filter is a device for treating sewage by biological methods. The main principle is that a biological film formed by microorganisms on the surface of the filter media is used to decompose various pollutants in water through its metabolic activities. This device combines biological treatment and filtration, and can effectively remove various pollutants in water. The key points determining the effect of this device and process lie in the selection of the filter media, and the backwashing process determines whether the filter can operate stably and efficiently.

[0003] A suitable filter media should be able to increase the contact efficiency between the biological film and the sewage, and should also be suitable for the growth of microorganisms, playing a role in promoting the formation of the biological film. Currently, commonly used traditional fillers such as quartz sand, zeolite, ceramsite, and other plastic products have defects such as insufficient strength, poor acid and alkali resistance, difficult regeneration, or poor adsorption capacity, although their costs are relatively low; although biological activated carbon has relatively excellent performance indicators, its price is expensive and its promotion is poor. Therefore, finding a filter media filler that can replace traditional filter media and is economically accessible has become a technical difficulty in the popularization and use of the filter. Volcanic stone is a vitreous lava with dense pores. The formation of its pores is due to the pressure change brought about by the temperature change of the magma before and after volcanic eruption, which causes the internal gas to quickly overflow and expand. Volcanic stone has many pores, a large specific surface area, high strength, heat insulation, acid and alkali resistance, corrosion resistance, no secondary pollution, and strong reusability. From the perspective of hydraulics, as a biological filter media, volcanic stone has no sharp shape and a large pore diameter, so the resistance to water is small, less filter media is required, and energy consumption is saved. Research shows that as a biological filter media, volcanic stone not only does not affect the activity of microorganisms, but its surface has a positive charge, which is beneficial to the growth of microorganisms, has strong hydrophilicity, and can provide a place for microorganisms to enrich and keep warm. It is an ideal filter media for the filter.

[0004] During the long-term operation of a micro-aerobic aerated biological filter, the physical adsorption of filter media on solid suspended substances in wastewater and the biological flocculation of biofilms often lead to the continuous filling of pores at the surface layer of filter media and at the junction of different layers of filter media in actual treatment. Moreover, microorganisms continuously metabolize on the surface of the filter media, the formed biofilms are continuously updated, and the shed biofilms continuously accumulate in the gaps between the same filter media, resulting in the decreasing size of the gaps, the decreasing water passing capacity and oxygen transfer efficiency, and the increasing head loss, leading to clogging. This inevitably results in frequent backwashing processes. Therefore, the backwashing of the micro-aerobic aerated biological filter is one of the key factors determining the stable and long-term operation of the filter. If the filter media is not thoroughly washed, agglomeration may occur, resulting in poor process operation and unsatisfactory effluent quality. If the lumps and large particulate matters washed out are not promptly discharged and remain in the filter, it will increase the backwashing frequency of the filter and reduce the treatment load of the entire filter, affecting both the efficiency and stability of the filter in treating wastewater and significantly increasing the energy consumption of the filter. The backwashing process uses the pressure of water and / or gas to flush open the clogged and compacted filter media, and uses the impact of water and / or gas to flush out the shed biofilms, lumps and small particulate matters, which are then discharged out of the filter along with the water flow. However, how to discharge these substances completely is the key to whether the structure of the biochemical filter including the backwashing system is reasonable.

[0005] Patent CN201220061252.1 relates to an aerated biological filter based on Hainan volcanic rock filler, including a circular tower-shaped aerated biological filter. The aerated biological filter includes a backwashing water inlet, a backwashing air inlet, a water inlet, a filter media support plate, a cobblestone support layer, an air inlet aeration pipe, a filler outlet, a volcanic rock filler layer, a sedimentation area, a filler inlet, an inclined plate sedimentation area, a clear water area, an outlet trough, an outlet, and a backwashing overflow port. This utility model can effectively achieve the deep treatment of low-concentration domestic wastewater by utilizing the excellent properties of Hainan volcanic rock filter media, has good effects in removing suspended substances, COD and ammonia nitrogen, and has the characteristics of strong anti-load capacity, high treatment efficiency and low cost.

[0006] Patent CN202320238568 provides an ozone volcanic rock aerated biological filter, including a pool body with an inlet pipeline at the lower end and an outlet pipeline at the upper end, an ozone generation system connected to the inlet pipeline, a backwashing aeration system at the lower end of the pool body, and a filter layer with attached biofilms at the upper end of the pool body. It also includes a filter plate below the filter layer, and a number of filter heads with a downward water spraying function are installed on the filter plate. The filter plate and the lower space form a water distribution chamber, and a backwashing air inlet pipeline and a backwashing water inlet pipeline are connected in the water distribution chamber. The backwashing water outlet pipeline is located at the upper part of the pool body, and the filter layer is a volcanic rock filter media layer. This application simultaneously conducts biological treatment, ozone oxidation and volcanic rock adsorption treatment on sewage in one device, improves the biodegradability of sewage, improves the ozone utilization rate, and reduces the organic matter content in sewage.

[0007] However, the backwashing system in the above biological filter and the matching setting of the backwashing system with the biological filter layer structure are not energy-efficient enough. There is a need in the art for a new micro-aerobic aeration biochemical filter for wastewater treatment, enabling the micro-aerobic aeration biochemical filter to operate stably in the long term with low energy consumption. Summary of the Invention

[0008] Therefore, the present invention provides a micro-aerobic aeration biochemical filter for wastewater treatment. The biochemical filter is used for treating tunnel construction wastewater. The biochemical filter includes a sludge hopper (3) provided at the bottom and a cylindrical filter body provided above the sludge hopper (3). In the filter body, a water distributor (16), an aerator (15), an air distribution pipe, a filter plate (19), a supporting layer (14), a volcanic stone filter layer (13), a plastic filter layer (12), a filter media retaining net (21), a solid matter collection tank (10), and a three-phase separator (8) are arranged from bottom to top. The top of the three-phase separator (8) extends above the highest liquid level in the biochemical filter and is used for discharging the separated gas outside the biochemical filter. The outer wall (17) of the solid matter collection tank (10) is the inner wall of the filter body or the outer wall and the inner wall of the filter body are overlapped. The inner wall (18) of the solid matter collection tank (10) is in the shape of a frustum of a cone with a shorter diameter at the top and a longer diameter at the bottom. A tank bottom plate is arranged between the outer wall (17) and the inner wall (18). A sludge discharge port and a sludge discharge pipe are arranged above the tank bottom plate and on the side wall of the filter body. The solid-liquid separation section of the three-phase separator (8) is in the lower position and is in the shape of a cone. A water flow channel for purified water and dirty water to pass through is formed between the bottom edge of the three-phase separator (8) and the inner wall of the filter body. A sewage discharge pipe (20) for discharging the dirty water generated during the backwashing process and an overflow tank (7) for discharging the purified water generated during the wastewater treatment process are sequentially arranged from bottom to top above the bottom edge of the three-phase separator (8) and on the side wall of the filter body. The water distributor (16) is connected to a water inlet pump (4) arranged outside the filter body. The aerator (15) is connected to an aeration machine (5) arranged outside the filter body. The air distribution pipe is connected to a backwashing blower (22) arranged outside the filter body. A drain pipe (1) and a sludge discharge pump (23) arranged on the drain pipe (1) are provided at the bottom of the sludge hopper (3), as well as a backwashing water pipe and a backwashing water pump (2) connected to the drain pipe (1).

[0009] In a specific embodiment, a drain pipe (9) and a drain valve for discharging clear water are arranged at the bottom of the overflow tank (7). Preferably, the biochemical filter is used for treating tunnel construction wastewater in alpine and plateau regions.

[0010] In a specific embodiment, the sludge discharge pipe includes a first sludge discharge pipe (6) and a second sludge discharge pipe (11) arranged symmetrically.

[0011] In a specific embodiment, a thermal insulation layer is provided on the outer wall of the filter tank body. The heating wire (24) is wrapped by thermal insulation cotton (25) to form the thermal insulation layer. Preferably, a tin foil for decoration and wrapping is provided on the outside of the thermal insulation layer.

[0012] In a specific embodiment, the bottom height of the three-phase separator (8) is higher than the top height of the solid collection tank (10), and the top of the three-phase separator (8) is a circular pipe for exhaust.

[0013] In a specific embodiment, the supporting layer (14) is a cobblestone layer, and the particle diameter therein is 2 - 3 cm, and the density is 2.3 - 2.6 g / cm 3 。

[0014] In a specific embodiment, the height of the volcanic stone filter layer (13) is 0.6 - 1.2 m, the particle diameter therein is 3 - 5 cm, and the density is 1.5 - 1.8 g / cm 3 , and the porosity is 60% - 80%.

[0015] In a specific embodiment, the height of the plastic filter layer (12) is 0.4 - 0.8 m, the diameter of the spherical plastic particles therein is 2 - 3 cm, and the density is 1.1 - 1.3 g / cm 3 , and the porosity is 50% - 70%.

[0016] In a specific embodiment, the filter media retaining net (21) is arranged 20 - 40 cm above the plastic filter layer (12).

[0017] In a specific embodiment, the filter media retaining net (21) is a stainless steel triangular mesh retaining net.

[0018] Generally speaking, in view of the deficiencies of incomplete discharge of particulate matter, high backwashing energy consumption, and low microbial activity at low temperatures during the backwashing process of the micro-aerobic aeration biochemical filter tank, the present invention provides a micro-aerobic aeration biochemical filter tank with a novel combined filler by arranging a three-phase separator and a solid collection tank above the filter layer, and using volcanic stone and plastic fillers as filter media to optimize the filter tank structure. The micro-aerobic aeration biochemical filter tank has the function of a secondary sedimentation tank, achieving excellent backwashing effect, easy film hanging and quick startup of the microbial film, fast reproduction speed, good heat preservation performance, and high oxygen transfer efficiency, and has remarkable effects in energy conservation and consumption reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the micro-aerobic aeration biochemical filter tank for wastewater treatment provided by the present invention.

[0020] Wherein: 1 - drain pipe; 2 - backwash water pump; 3 - sludge hopper; 4 - influent pump; 5 - aerator; 6 - first sludge discharge pipe; 7 - overflow trough; 8 - three-phase separator; 9 - drain pipe; 10 - solid collection tank; 11 - second sludge discharge pipe; 12 - plastic filter layer; 13 - volcanic stone filter layer; 14 - supporting layer; 15 - aerator; 16 - water distributor; 17 - outer wall of the trough; 18 - inner wall of the trough; 19 - filter plate; 20 - sewage discharge pipe; 21 - filter media retaining net; 22 - backwash air blower; 23 - sludge discharge pump; 24 - heating wire; 25 - heat preservation cotton. Detailed implementation manners

[0021] The following combines the attached Figure 1 drawings and application examples to further illustrate the present invention.

[0022] A novel combined packing micro-aerobic aeration biochemical filter with efficient backwashing. The filter is composed of an influent system, a main body of the micro-aerobic aeration biochemical filter, an aeration system, a backwashing system, a filter layer area, a three-phase separator, and a solid collection tank. Among them, the filter device includes a sludge hopper, a supporting layer, a volcanic stone filter layer, a plastic filter layer, an upper clear water area, a solid collection tank, a three-phase separator, and an overflow trough from bottom to top. The water distributor and the aerator are connected to the bottom of the micro-aerobic aeration biochemical filter device, and a sludge discharge pipe and a sludge discharge valve are arranged at the solid collection tank. In the present invention, the filter operates in an up-flow influent mode. Sewage enters the filter through the water distributor, and under the action of aeration, uniform mixing of the water quality is achieved. Solid suspended substances, ammonia nitrogen, COD and other substances in the sewage are purified through the physical adsorption, biological flocculation and filtration of the filter layer. Finally, the clear water flows out through the overflow trough and is discharged through the drain pipe 9. This filter has high adsorption efficiency, small resistance, fast flow rate, short film hanging time, and fully exerts the combined effects of the filtration effect of the micro-aerobic aeration biochemical low-carbon filter and biological adsorption.

[0023] In the present invention, sludge bacteria need to be introduced only at the beginning of establishing the biochemical filter tank, and subsequently, only the excess sludge needs to be discharged from the sludge discharge pipe above the filter layer and the emptying pipe at the bottom of the filter tank. The three-phase separator is, for example, an inverted funnel shape, and the air generated by aeration or the air from the backwash fan 22 during backwashing is discharged through the pipe at the top of the three-phase separator. During filtration, the valve on the sewage discharge pipe 20 is closed, and the clear water below the three-phase separator enters the overflow tank 7 upward through the water flow channel and is then discharged outside the biochemical filter tank through the drain pipe 9; during the backwashing process, the valve on the sewage discharge pipe 20 is opened, and the sludge below the three-phase separator falls into the solid collection tank 10 and is then discharged outside the biochemical filter tank through the first sludge discharge pipe 6 and the second sludge discharge pipe 11, while the dirty water is discharged outside the biochemical filter tank from the sewage discharge pipe 20. In the present invention, during the backwashing process, the sludge and the dirty water are separated by solid-liquid separation and then discharged from the biochemical filter tank, so that the dirty water after backwashing can be prevented from not being discharged outside the biochemical filter tank in time and smoothly. In the present invention, the three-phase separator is fixed on the side wall of the filter tank body by, for example, a rib structure.

[0024] The filter layer of the micro-aerobic aeration biochemical filter tank includes a plastic filter layer and a volcanic stone filter layer. The plastic filter layer is on the top and the volcanic stone filter layer is on the bottom. Among them, the thickness of the plastic filter layer is 400 mm - 800 mm, the thickness of the volcanic stone layer is 600 - 1200 mm, and the total thickness of the bed layer is 1000 - 2000 mm. The bottom layer is a filter media support layer paved with cobblestones.

[0025] The diameter of the spherical plastic particles in the plastic filter layer ranges from 20 to 30 mm, and the density is slightly greater than the density of water, with the density ranging from 1.1 to 1.3 g / cm 3 , and the porosity is 50% - 70%; the particle diameter of the volcanic stone filter layer ranges from 30 to 50 mm, and the density ranges from 1.5 to 1.8 g / cm 3 , and the porosity is 60% - 80%; the support layer in the filter tank is cobblestones, and the particle size ranges from 20 to 30 mm, and the density ranges from 2.3 to 2.6 g / cm 3 .

[0026] The installation height of the filter media retaining net 21 is 200 - 400 mm above the plastic filter layer 12. Its material is stainless steel SS304, and its feature is a triangular mesh structure, which can effectively block the spherical plastic fillers and prevent the plastic fillers from accumulating at the retaining net, affecting the water flow. While effectively intercepting the plastic particles, the filter media retaining net 21 also fully ensures the smooth water flow of the sewage in the filter layer. The stainless steel material is durable and not easily deformed.

[0027] Preferably, a heating wire insulation layer is provided around the filter tank. The heating wire is wound around the device and then wrapped with heat insulation cotton. When the sewage temperature is lower than 10°C, the heating wire is turned on for heating; when the sewage water temperature is higher than 15°C, the heating of the sewage is turned off.

[0028] The specific principle of improving backwashing efficiency and reducing energy consumption in the present invention is as follows: During the long-term operation of the filter tank, when large particulate matters are intercepted by the filter layer, the shed biofilm blocks the gaps between the filter media, causing the water passing through the filter tank to gradually decrease and even resulting in a clogging phenomenon, making it impossible for sewage and oxygen to pass through the filter layer smoothly. At this time, close the water inlet, stop the sewage from entering, open the drain valve on the bottom drain pipe, and first drain all the water in the filter tank; when the sewage in the filter tank is drained completely, close the drain valve, turn on the backwashing water pump, introduce backwashing water, and increase the air distribution volume of the backwashing blower. Since the density of the selected filter media (plastic filter media and volcanic stone filter media) is slightly greater than that of water, the filter media shows a slightly lifted phenomenon in the filter tank under the action of the co-flow of air and water, and then maintain this air distribution volume for backwashing. Compared with the traditional process method, the present invention can greatly reduce the energy consumed during air distribution, achieving the purpose of energy conservation. When the liquid level rises to the bottom of the three-phase separator, open the drain valve provided at the solid matter collection tank and located on the first sludge discharge pipe 6 and the second sludge discharge pipe 11. Utilizing the three-phase separation principle of gas, solid, and liquid in the three-phase separator, the gas is discharged from above through the gas guide pipe provided at the upper end, the liquid slowly rises through the surrounding liquid passing channels and is discharged from the sewage discharge pipe, and the solid substances or sludge settle in the solid matter collection tank under the guiding action of the conical baffle of the three-phase separator and are then discharged out of the filter tank through the drain valve. When the air distribution stops, some larger lumps intercepted at the bottom of the filter layer and the biofilm and particulate matters shed in the gaps between the filter media settle freely in the sludge collection hopper 3 at the bottom. Open the drain valve on the drain pipe 1 to drain the sludge completely, achieving the purpose of emptying the sludge, preventing accumulation, and improving the backwashing efficiency.

[0029] In the micro-aerobic aeration biological filter of the present invention, compared with the traditional micro-aerobic aeration biological filter, the selected filter media is a combination of plastic filter media and volcanic stone filter media. The densities of both are slightly greater than that of water, and there is a density difference between them. Without a large backwashing air distribution volume, when the two filter media are slightly lifted under the action of the air flow, the lifted heights of the two filter media are different, and the biofilm and large particulate matters shed between different filter media and between the same filter media can be washed out. Moreover, due to characteristics such as specific surface area, surface smoothness, and porosity of the two filter media, there are obvious differences in the microbial population structures formed in the two filter layers, enhancing the sewage purification ability and shock load resistance ability of the biofilm.

[0030] In the present invention, a water distributor and an aerator are arranged between the filter layer and the sludge sump, and a filter plate is used to separate the filter layer above and the water distributor and aerator below. The diameter of the filter plate is the same as the inner diameter of the filter tank. The diameter of the perforations provided in the filter plate is, for example, 5 mm, and they are evenly distributed. The gap between holes is, for example, 2.5 mm, which can prevent the filter media from passing through the filter plate and entering the sludge sump, and at the same time, it will not reduce the oxygen transfer efficiency and water flow velocity. The water distributor 16 can be annularly arranged on the pipe wall of the filter tank, and water outlets are provided at regular intervals. The aerator 15 can be composed of two concentric annular pipes, and a number of aeration holes are evenly provided on the annular pipes. A microporous aeration disc can also be provided on the aeration holes. The water distributor is arranged below the aerator, for example, 20 cm below it, so that the influent water can be evenly mixed under the action of aeration.

[0031] The bottom of the present invention is a sludge sump 3, which is used to collect the intercepted lumps and settled sludge during normal influent water filtration and backwashing stages, and discharge these sundries out of the filter tank through the drain pipe at the bottom.

[0032] The biochemical filter tank of the present invention can also be applicable to treating urban domestic sewage, rural domestic sewage, etc.

[0033] The method for efficient backwashing and energy consumption reduction using this device includes the following steps:

[0034] 1) When the phenomenon of blockage occurs during the upward water flow in the micro-aerobic aeration biochemical low-carbon filter tank, close the influent water pump 4 to stop the influent water. Open the drain pipe 1 at the bottom to drain the original sewage in the filter tank.

[0035] 2) When the sewage in the filter tank is drained completely, close the drain pipe 1, open the backwashing water pump 2 to introduce backwashing water, and open the backwashing air blower 22. When the filter media shows a slightly lifted phenomenon, due to the inconsistent densities of the two filter media, the lifted heights are also inconsistent, and some large particles and the shed biofilms are washed out.

[0036] 3) When the liquid level rises to the bottom of the three-phase separator 8, open the sludge discharge valves on the sludge discharge pipes 6 and 11. Utilize the gas, solid, and liquid three-phase separation principle of the three-phase separator 8. The gas is discharged from above through the gas guide pipe provided at the upper end, the liquid slowly rises from the peripheral space and is discharged from the sewage discharge pipe 20, and the solid substances or sludge, through the guiding action of the conical baffle of the three-phase separator 8, settle in the solid substance collection tank 10 and are then discharged out of the filter tank through the sludge discharge valve.

[0037] During the stage of stopping aeration in backwashing, some larger lumps intercepted at the bottom of the filter layer and the biofilms and particles shed in the filter media gaps settle freely in the sludge sump 3 at the bottom by sedimentation. Open the sludge discharge pump 23 and the drain valve on the drain pipe 1 to discharge them completely.

[0038] A heat tracing wire insulation layer is provided on the side wall of the device. The heat tracing wire is wound and then wrapped with heat insulating cotton. When the sewage water temperature is lower than 10°C, the heat tracing wire is turned on for heating. When the sewage water temperature is higher than 15°C, the heat tracing wire heating is turned off.

[0039] In the present invention, ① the upper and lower layer filter media have different particle sizes and densities, which can better intercept pollutants such as suspended solids, impurities and bacteria in water, and improve the filtration effect; ② the plastic filter media particles are finer, which can better filter fine particles in water; the lower layer of volcanic rock layer filter media particles are coarser, which can better intercept large particles. This combination can extend the service life of the filter media, reduce the replacement times and maintenance costs; ③ due to the different particle sizes and densities of the plastic particles and volcanic rock particles in the upper and lower layer filter media, a certain gap is formed between the layers, making the water flow more smoothly when passing through and not easily blocked, thereby improving the water flow through efficiency; the design of the double-layer different filter media can also reduce the backwashing time and water consumption, and reduce energy consumption and costs.

[0040] In the biochemical filter tank, in the presence of oxygen, the organic matter in the wastewater is adsorbed, oxidized and reduced by the microorganisms in the microbial film adhering to the packing, and the complex macromolecular organic matter is oxidized and decomposed into simple inorganic substances, so as to achieve the purpose of purifying the wastewater. The biochemical filter tank will also nitrify the ammonia nitrogen in the wastewater, converting NH 3 -N into NO 3 -N or NO 2 -N, so as to finally achieve the removal of ammonia nitrogen.

[0041] During the operation of the biochemical filter tank, the aeration volume supplied by the aerator (5) and the dissolved oxygen concentration in the biochemical filter tank should be regulated, the hydraulic load, backwashing cycle and the amount of biological film in the filter tank should be adjusted, and the transparency of the supernatant in the filter tank, the color, state, smell, etc. of the biological film on the surface of the filter media should be observed in time. When the water temperature of the biochemical filter tank is relatively low, heat tracing wire heating should be adopted, and / or methods such as appropriately extending the aeration time and reducing the hydraulic load should be taken to ensure the treatment effect. If the nutrients in the influent water are lacking and affect the self-metabolism of the microorganisms in the biological film, nutrient agents can be added to the tank according to the situation of the biological film, for example, adding nutrient sources in the ratio of BOD 5 :N:P = 100:5:1. The N source is urea, and the P source is sodium phosphate or disodium hydrogen phosphate. When the growth of the microbial film in the biochemical filter tank is too fast, resulting in too thick a biological film or too much suspended matter intercepted by the filter layer, affecting the normal treated water quality, the filter tank needs to be backwashed.

[0042] The backwashing process of the biochemical filter tank usually adopts three steps: "air washing → air-water combined backwashing → water rinsing".

[0043] 1) Air washing

[0044] Close the influent pump 4 → Close the aerator 5 → Close the aeration valve → Open the drain pipe 1 and the sludge pump 23 to drain all the sewage → Close the drain pipe 1 and the sludge pump 23 → Open the sewage discharge pipe 20 → Open the air inlet valve on the backwashing fan 22 → Start the backwashing fan 22 → Conduct air washing. Under the action of air shear and friction between the filter media, the impurities on the surface of the filter media and the aged biological film fall off; the main purpose of air washing is to loosen the filter media layer and make the filter media layer expand. The air washing intensity is generally 12 - 20 L / (m 2 ·s). The backwashing time is generally 7 minutes.

[0045] 2) Air-water combined backwashing

[0046] While conducting air washing, open the water valve on the backwashing pump 2 → Start the backwashing pump 2 → Conduct air-water combined backwashing. The backwashing water enters the filter tank to further wash the filter media. The main purpose of air-water combined backwashing is to wash out the suspended solids and aged microbial film intercepted on the filter media.

[0047] When the biological filter tank adopts air-water combined backwashing, the air and water intensities of backwashing should be appropriate. The air washing intensity is generally 12 - 20 L / (m 2 ·s). The air velocity of backwashing is generally 70 - 100 m 3 / h, and the water washing intensity of backwashing is generally 6.0 - 10 L / (m 2 ·s). The washing time is generally controlled within 7 - 22 minutes, and the backwashing time can also be adjusted according to specific conditions.

[0048] 3) Water rinsing

[0049] Stop the backwashing fan 22 → Close the air inlet valve on the backwashing fan → Stop air washing and conduct separate water rinsing to flush the impurities in the water into the solid matter collection tank 10, the sewage discharge pipe 20 or the sludge hopper 3. The main purpose of water rinsing is to wash out the suspended solids and aged microbial film on the surface of the filter media from the biological filter tank. The time is generally 6 - 10 minutes.

[0050] Generally speaking, the present invention relates to a micro-aerobic aeration biochemical filter for wastewater treatment, its wastewater treatment method and backwashing method. The densities of the two selected filter materials (plastic filter material and volcanic stone filter material) are slightly greater than that of water. Under the action of co-current flow of air and water, the filter materials show a slightly lifted phenomenon in the filter tank, thus greatly reducing the energy consumption during air distribution and achieving the purpose of energy conservation. When aeration and air distribution are stopped, some larger lumps intercepted at the bottom of the filter layer and the biofilm and particulate matter shed in the gaps between the filter materials settle freely in the sludge hopper through sedimentation. Open the sludge discharge valve on the drain pipe 1 and the sludge pump 23 to discharge them completely, achieving the purpose of emptying the sludge, preventing accumulation and improving the backwashing efficiency. The porous structures of the two filter materials can provide a place for the enrichment and insulation of microorganisms, and the heating of the heating wire on the outer wall of the filter tank can provide sufficient heat for wastewater treatment to ensure the treatment activity of microorganisms.

[0051] That is to say, the biochemical filter provided by the present invention integrates packing interception and biological adsorption, and has the characteristics of a large biofilm surface area, good microorganism attachment effect, high activity, high adsorption efficiency, small resistance, fast flow rate and short film hanging time. It gives full play to the combined effect of the filtration effect and biological adsorption of the micro-aerobic aeration biochemical filter, and at the same time makes up for the deficiencies of the existing biochemical filter, such as incomplete backwashing, poor sewage discharge, high energy consumption and low microorganism activity at low temperature.

[0052] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A micro-aerobic aeration biochemical filter for wastewater treatment, Characterized in that, The biochemical filter is used for treating tunnel construction wastewater. The biochemical filter includes a sludge hopper (3) arranged at the bottom and a cylindrical filter body arranged above the sludge hopper (3). In the filter body, a water distributor (16), an aerator (15), an air distribution pipe, a filter plate (19), a supporting layer (14), a volcanic rock filter layer (13), a plastic filter layer (12), a filter media retaining net (21), a solid matter collection tank (10), and a three-phase separator (8) are arranged from bottom to top. The top of the three-phase separator (8) extends above the highest position of the liquid level in the biochemical filter and is used for discharging the separated gas outside the biochemical filter. The outer wall (17) of the solid matter collection tank (10) is the inner wall of the filter body or the outer wall overlaps with the inner wall of the filter body. The inner wall (18) of the solid matter collection tank (10) is in the shape of a frustum of a cone with a shorter upper diameter and a longer lower diameter. A tank bottom plate is arranged between the outer wall (17) and the inner wall (18). A sludge discharge port and a sludge discharge pipe are arranged above the tank bottom plate and on the side wall of the filter body. The solid-liquid separation section of the three-phase separator (8) is in the lower position and is in the shape of a cone. A water flow channel for clean water and dirty water to pass through is formed between the bottom edge of the three-phase separator (8) and the inner wall of the filter body. A sewage discharge pipe (20) for discharging the dirty water generated during the backwashing process and an overflow tank (7) for discharging the clean water generated during the wastewater treatment process are arranged from bottom to top above the bottom edge of the three-phase separator (8) and on the side wall of the filter body. A drain pipe (9) and a drain valve for discharging clear water are arranged at the bottom of the overflow tank (7). The water distributor (16) is connected to a water inlet pump (4) arranged outside the filter body. The aerator (15) is connected to an aeration machine (5) arranged outside the filter body. The air distribution pipe is connected to a backwashing blower (22) arranged outside the filter body. A drain pipe (1) and a sludge discharge pump (23) arranged on the drain pipe (1) are arranged at the bottom of the sludge hopper (3), and a backwashing water pipe and a backwashing water pump (2) connected to the drain pipe (1). The height of the volcanic rock filter layer (13) is 0.6 - 1.2 m, the particle diameter is 3 - 5 cm, and the density is 1.5 - 1.8 g / cm 3 , and the porosity is 60% - 80%. The height of the plastic filter layer (12) is 0.4 - 0.8 m, the diameter of the spherical plastic particles is 2 - 3 cm, and the density is 1.1 - 1.3 g / cm 3 , and the porosity is 50% - 70%.

2. The micro-aerobic aeration biochemical filter according to claim 1, Characterized in that, The sludge discharge pipe includes a first sludge discharge pipe (6) and a second sludge discharge pipe (11) symmetrically arranged.

3. The micro-aerobic aeration biochemical filter according to claim 1, Characterized in that, A heat preservation layer is provided on the outer wall of the filter main body. The heat tracing wire (24) is wrapped by the heat preservation cotton (25) to form the heat preservation layer, and a tin foil for decoration and wrapping is provided on the outside of the heat preservation layer.

4. The micro-aerobic aeration biochemical filter according to claim 1, Characterized in that, The bottom height of the three-phase separator (8) is higher than the top edge height of the solid collection tank (10), and the top of the three-phase separator (8) is a circular pipe for exhaust.

5. The micro-aerobic aeration biochemical filter according to any one of claims 1 to 4, Characterized in that, The supporting layer (14) is a cobblestone layer, in which the particle diameter is 2 - 3 cm and the density is 2.3 - 2.6 g / cm 3 .

6. The micro-aerobic aeration biochemical filter according to any one of claims 1 to 4, Characterized in that, The filter media retaining net (21) is arranged 20-40 cm above the plastic filter layer (12).

7. The micro-aerobic aeration biochemical filter according to claim 6, Characterized in that, The filter media retaining net (21) is a stainless steel triangular mesh retaining net.

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