A sewage up-flow multi-filter-layer filter device, a sewage treatment system and method thereof, and a backwashing method

Abstract

The application discloses a sewage up-flow type multi-filter-layer filter device, a sewage treatment system and method and a backwashing method, and belongs to the technical field of environment rainwater treatment. The filter device comprises, from bottom to top, a sewage area, a filter area and a clean water area in sequence. The filter area comprises a first filter layer and a second filter layer. The first filter layer is arranged below the second filter layer. The first filter layer is filled with a first filter medium, and the second filter layer is filled with a second filter medium. The particle size of the first filter medium is larger than that of the second filter medium. The non-uniformity coefficient d60 / d10 of the second filter medium is 1.3-3.0, and the equivalent diameter d10 is 0.2mm-1mm. The filter device is provided with a water inlet and a water outlet on the sewage area. The filter device is provided with a clean water outlet and an air inlet on the clean water area. The application can remove suspended particulate matters and dissolved pollutants in water, and effectively improve the backwashing efficiency of the device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental rainwater treatment, and more particularly relates to a sewage upflow type multi-filtering layer filtering device, a sewage treatment system and method thereof, and a backwashing method. BACKGROUND

[0002] The accelerated urbanization process increases the proportion of impervious urban pavement, and the decrease in infiltration not only leads to higher flood peak flow, but also causes heavier runoff pollution load and other problems. At present, the urban runoff pollution situation is becoming increasingly serious, and the urban water environment is deteriorating. The study on the pollution situation of runoff rainwater has become the focus of scholars. Urban runoff pollution mainly comes from the exhaust gas emitted by motor vehicle fuel use, pesticide and chemical fertilizer residues, and pollutants in household garbage, etc. These pollutants are collected together under the action of rainwater scouring and atmospheric deposition, forming urban runoff.

[0003] At present, the treatment methods of runoff rainwater mainly include physical method, chemical method and ecological treatment method. The physical method is to remove the particulate matter in runoff rainwater by methods such as sedimentation, filtration and physical separation. Coagulation is the main chemical treatment method, but due to the great change of runoff rainwater quality and quantity, the conventional coagulation method includes slow flocculation and sedimentation stage, which generally takes about 15 minutes, and the reaction time is relatively long, the cost is high, the efficiency is low, and the removal of dissolved phosphorus and other dissolved substances mainly depends on the charge neutralization mechanism, while the charge neutralization mainly occurs in the early stage of flocculation (the first minute). Studies have shown that micro-flocculation and conventional coagulation including coagulation / sedimentation can achieve the same effect in terms of pollutant removal effect and operating cost. Micro-flocculation using polyaluminum chloride (PAC) flocculant is a more efficient wastewater treatment process, but at present, micro-flocculation is rarely applied to urban road runoff treatment. Urban runoff contains a large amount of suspended solids, dissolved organic matter and heavy metal substances, and the composition is complex and diverse, and the concentration range is large. Simple physical and chemical methods cannot efficiently remove dissolved organic matter and metal salts in water; ecological treatment method can comprehensively remove various pollutants in runoff rainwater. At present, rainwater wetlands, grassed swales and other rainwater ecological treatment technologies have been widely used in urban runoff rainwater treatment due to their low impact on the environment and high sustainability. However, since their goal is to reduce urban runoff peak, they cannot intercept pollutants in the catchment area, causing secondary pollution, and the occupied area is relatively large, so a treatment method is needed to solve the above problems.

[0004] According to the search, Chinese invention patent CN1319879C discloses a treatment method for electrolytic aluminum plant wastewater, which specifically discloses that the coagulation process includes two steps of flocculation and precipitation by adding reagent, alum is used as the added reagent, the time of the charged group combined with the reagent is relatively long, the precipitation and particulate matter in the water start to settle after flocculating into larger groups, the reaction time is longer, and the operation cost is increased.

[0005] For example, Chinese invention patent CN109879458B discloses a placed rainwater runoff filtration and purification system and purification body, which uses multiple filter layers to filter runoff rainwater to remove pollutants in the water. Although it has a certain purification effect on runoff water, it is difficult to efficiently remove fine particulate matter, dissolved organic matter and heavy metals in the water by using a simple filtration process, and the conventional up-flow and down-flow water flow direction is easy to cause blockage of the device, increasing the difficulty of backwashing.

[0006] Chinese utility model patent CN209619116U discloses a wetland circulation system capable of fully utilizing surface runoff, which uses artificial wetlands to treat runoff rainwater and recycle it. Although it reduces the pollution load to a certain extent and achieves the purpose of water resource recycling, it does not collect and treat pollutants, which may cause accumulation of heavy metals or other dissolved pollutants in the system.

[0007] As can be seen, the existing water treatment systems or methods for rainwater runoff and other wastewater have some indispensable shortcomings, especially the filtration efficiency and backwashing efficiency of the filtration device in the water treatment system are difficult to achieve. Therefore, there is an urgent need to design a device or method that can effectively improve the removal rate of pollutants and the backwashing efficiency of rainwater runoff and other wastewater. SUMMARY

[0008] 1. Problems to be solved

[0009] To solve the problems of low removal rate of particulate matter and soluble substances in wastewater and high difficulty of backwashing in the existing water treatment devices or methods, the present application provides a sewage up-flow type multi-filter layer filtration device, a sewage treatment system and a method thereof, and a backwashing method. By reasonably setting the filter layer and other structures in the filtration device, the problems of low removal rate of particulate matter and soluble substances in wastewater and high difficulty of backwashing in the existing water treatment devices or methods are effectively solved.

[0010] 2. Technical solutions

[0011] To solve the above problems, the technical solutions adopted by the present application are as follows:

[0012] The sewage up-flow multi-filter-layer filter device comprises a sewage area, a filter area and a purified water area from bottom to top, the filter area comprises a first filter layer and a second filter layer, the first filter layer is arranged below the second filter layer, the first filter layer is filled with a first filter medium, the second filter layer is filled with a second filter medium, the particle size of the first filter medium is larger than that of the second filter medium, the non-uniformity coefficient d60 / d10 of the second filter medium is 1.3-3.0, and the equivalent diameter d10 is 0.2mm-1mm, the filter device is provided with a water inlet and a water outlet, the filter device is further provided with an air inlet unit and a flushing unit, the purified water area is provided with a purified water outlet and an air inlet, the air inlet unit is connected with the air inlet, and the flushing unit is connected with the purified water outlet and used for flushing the filter device through the purified water outlet.

[0013] Preferably, the first filter medium and the second filter medium can be activated carbon, the particle size of the first filter medium is 5mm-14mm, and the particle size of the second filter medium is 0.3mm-1.4mm, the porosity of the filter medium is greater than 60%, the density is less than 0.6g / cm 3 -0.9g / cm 3 , the specific surface area is 5m 2 / g-10m 2 / g, the adsorption performance is excellent, the service life of the filter device is significantly prolonged, the filter material is made of waste glass, is simple and easy to obtain, and is low in cost.

[0014] Preferably, the height of the first filter layer is L1, the height of the second filter layer is L2, and the ratio of L1 to L2 is (1-11):1, the height of the first filter layer should not be greater than that of the second filter layer, and the first filter layer is too high, which can cause the device to be easily blocked and greatly reduce the service life.

[0015] Preferably, L1 is 200mm-600mm, and L2 is 50mm-300mm.

[0016] The sewage treatment system of the present application comprises a micro-flocculation tank and a filtering device, wherein the filtering device is a sewage up-flow multi-filtering layer filtering device as described in the present application, the micro-flocculation tank uses polyaluminum chloride to treat sewage, the outlet of the micro-flocculation tank is connected with the inlet of the filtering device through a pipeline, a second water pump is arranged on the pipeline, and the second water pump is used to pump water from the micro-flocculation tank into the filtering device. Since the conventional coagulation / flocculation includes a slow flocculation and sedimentation stage, the filtering efficiency is low and the cost is high. Compared with the conventional coagulation process with a treatment time of about 15 min, the micro-flocculation reaction time of the present application is about 3 min, which is shorter. In addition, due to the characteristics of the road runoff, a large amount of pollutants need to be treated in a short time, so the micro-flocculation is more suitable for treating road runoff.

[0017] Preferably, a feeding device and a sewage tank are included, the feeding device is connected with the micro-flocculation tank, the feeding device is used to add polyaluminum chloride into the micro-flocculation tank, and the sewage tank is connected with the micro-flocculation tank through a pipeline, a first water pump is arranged on the pipeline, and the first water pump is used to pump water from the sewage tank into the micro-flocculation tank.

[0018] Preferably, the flushing unit comprises a clean water tank, the clean water tank is connected with the clean water inlet through a first clean water pipe and a second clean water pipe respectively, a third water pump is arranged on the first clean water pipe, the third water pump is used to pump clean water in the clean water tank into the filtering device through the clean water inlet, and a drain valve is arranged on the second clean water pipe.

[0019] The sewage treatment method of the present application is based on the sewage treatment system as described in the present application, sewage is first introduced into the micro-flocculation tank, polyaluminum chloride solution is used to perform micro-flocculation treatment on the sewage, and then the sewage treated by micro-flocculation is injected into the filtering device at a flow rate of 10 m / h to 25 m / h for filtration.

[0020] Preferably, the specific steps of the micro-flocculation treatment are as follows: first, the sewage in the sewage tank is stirred at a rotation speed of 300 r / min to 500 r / min; then, the sewage with a volume of V1 in the sewage tank is introduced into the micro-flocculation tank, polyaluminum chloride solution with a concentration of 50 mg / L to 100 mg / L and a volume of V2 is added into the micro-flocculation tank at the same time, V1:V2=(0.8-1.2):1; finally, the liquid in the micro-flocculation tank is stirred at a rotation speed of 100 r / min to 200 r / min for 1 min to 2 min, and then is left to stand for 1 min to 2 min.

[0021] The backwashing method of the application is based on the sewage treatment system of the application; the filter device of the sewage area is provided with a pressure detection device; when the pressure detection device detects that the water pressure P1 in the sewage area is greater than or equal to 35 kPa, the filter device is rotated and the height of the clean water area is lower than that of the sewage area, compressed air is injected into the clean water area from the air inlet at a speed of 40 m / h to 50 m / h, and the injection time is 3 min to 5 min; the filter device is rotated again to make the height of the clean water area higher than that of the sewage area, and clean water is injected into the clean water area from the clean water outlet at a speed of 10 m / h to 15 m / h, and the injection time is 8 min to 12 min.

[0022] 3. Beneficial effects

[0023] Compared with the prior art, the beneficial effects of the application are:

[0024] (1) The sewage upflow type multi-filter layer filter device of the application comprises a sewage area, a filter area and a clean water area from bottom to top, the filter area comprises a first filter layer and a second filter layer, the first filter layer is arranged below the second filter layer; the first filter layer is filled with a first filter medium, the second filter layer is filled with a second filter medium, the particle size of the first filter medium is larger than that of the second filter medium; the non-uniformity coefficient d60 / d10 of the second filter medium is 1.3 to 3.0, and the equivalent diameter d10 is 0.2 mm to 1 mm; the filter device of the sewage area is provided with a water inlet and a water outlet; it also comprises an air inlet unit and a flushing unit; the filter device of the clean water area is provided with a clean water outlet and an air inlet; the air inlet unit is connected with the air inlet; the flushing unit is connected with the clean water outlet, and the flushing unit is used for flushing the filter device through the clean water outlet; through the above arrangement, when the filter device performs water treatment, the multi-filter medium system of the application can remove suspended particles and dissolved pollutants in water at the same time, and the bottom water inlet method adopted by the application can effectively avoid the blockage caused by flocculation, the backwashing efficiency is higher, and the reuse of filter material and the recovery and treatment of pollutants are facilitated; when the filter device performs backwashing, air can be injected into the filter device through the air inlet of the clean water area, the gas passes through the second filter medium and the first filter medium in sequence, the pollutants are loosened and detached through the bubbles generated by the high-pressure gas, and then clean water can be injected through the clean water outlet of the clean water area to remove the pollutants in the filter area; therefore, the filter device of the application can effectively improve the backwashing efficiency while removing suspended particles and dissolved pollutants in water, thereby increasing the recycling rate of the filter device.

[0025] (2) The sewage treatment system of the present application comprises a micro flocculation tank and a filtering device, wherein the filtering device is the sewage upflow multi-filtering layer filtering device of the present application, the micro flocculation tank uses polyaluminum chloride to treat sewage, the outlet of the micro flocculation tank is connected with the inlet of the filtering device through a pipeline, a second water pump is arranged on the pipeline, and the second water pump is used to pump water in the micro flocculation tank into the filtering device; through the above arrangement, the micro flocculation treatment improves the removal effect of particulate matter, soluble phosphorus, metals and organic matter in water, and the multi-medium filtration can effectively remove suspended particulate matter in water; compared with single rainwater runoff physical treatment and chemical treatment, the combination of micro flocculation and multi-medium filtration avoids the problem of single removal effect and can remove suspended particulate matter and soluble pollutants in water at the same time.

[0026] (3) The sewage treatment method of the present application is based on the sewage treatment system of the present application; first, sewage is introduced into the micro flocculation tank, and polyaluminum chloride solution is used to perform micro flocculation treatment on the sewage, and then the sewage treated by micro flocculation is injected into the filtering device at a flow rate of 10 m / h to 25 m / h for filtration; through the above method, the reaction time of flocculation treatment can be effectively shortened, the treatment time of about 15 min of the conventional flocculation process is shortened to about 3 min, and the water treatment efficiency is improved.

[0027] (4) The backwashing method of the present application is based on the sewage treatment system of the present application; a pressure detection device is arranged on the filtering device in the sewage area; when the pressure detection device detects that the water pressure P1 in the sewage area is greater than or equal to 35 kPa, the filtering device is rotated and the height of the clean water area is lower than that of the sewage area, compressed air is injected into the clean water area from the air inlet at a speed of 40 m / h to 50 m / h, and the injection time is 3 min to 5 min; then the filtering device is rotated again to make the height of the clean water area higher than that of the sewage area, and clean water is injected into the clean water area from the clean water outlet at a speed of 10 m / h to 15 m / h, and the injection time is 8 min to 12 min; through the above backwashing method, when the height of the clean water area is lower than that of the sewage area, the gas bubbles generated by the high-pressure gas entering the filtering medium can continuously rise to one end of the sewage area by buoyancy, and under the scouring and friction of the gas bubbles, the insoluble particulate matter falls off rapidly; when the height of the clean water area is higher than that of the sewage area, the water from the clean water outlet can further elute the pollutants, thereby effectively improving the backwashing efficiency of the filtering device. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a schematic diagram of the sewage treatment system of the present application;

[0029] Figure 2 It is a schematic diagram of the sewage upflow multi-filtering layer filtering device of the present application.

[0030] In the figure:

[0031] 100, filtering device; 110, clean water area; 111, clean water valve; 112, air inlet valve; 113, air inlet; 114, clean water outlet; 115, air pump; 120, second filtering layer; 130, metal mesh; 140, first filtering layer; 150, sewage area; 151, water inlet valve; 152, pressure detection device; 153, water inlet; 160, collector; 161, water outlet; 162, water outlet valve;

[0032] 200, sewage pool; 210, first stirring motor; 220, first stirring paddle; 230, first water pump;

[0033] 300, micro-flocculation pool; 310, second stirring motor; 320, second stirring paddle; 330, feeding device; 340, first valve; 350, second water pump;

[0034] 400, clean water pool; 410, first clean water pipe; 411, third water pump; 420, second clean water pipe; 421, drain valve. DETAILED DESCRIPTION

[0035] The following more detailed description of the embodiments of the application is not intended to limit the scope of the claimed application, but merely to provide an example of how the application can be put into practice, and to further describe the features and characteristics of the application, which are considered to be of particular interest to the person skilled in the art. It is understood that various modifications and variations can be made to the details of the application without departing from the scope of the application as defined by the appended claims. The detailed description and the accompanying drawings are therefore to be taken as illustrative only, and not limiting in nature. If there is any conflict between what is described in the detailed description and what is depicted in the drawings, then the detailed description is deemed to be controlling. Furthermore, the background section is intended to provide a context for the present technology, and is not intended to be used to limit the application or the scope of the application.

[0036] The structure, proportion, size, etc. shown in the drawings of the specification are only used to cooperate with the content disclosed in the specification, to be understood and read by those skilled in the art, and are not used to limit the conditions that can be implemented by the present application, so they do not have technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and the like used in the specification are only for the purpose of clear understanding of the description, and are not used to limit the scope of implementation, and the change or adjustment of the relative relationship is also considered as the scope of implementation of the present application without substantial change of the technical content; unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by those skilled in the art in the technical field of the present application; the terms used in the specification of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0037] The present application is further described below in conjunction with specific embodiments.

[0038] Example 1

[0039] As Figure 1 And Figure 2As shown, the embodiment provides a sewage up-flow multi-filter layer filter device which is made of cylindrical high-strength acrylic material, the total height is 95 cm, the bottom height, i.e. the sewage area 150 height is 20 cm, the top height, i.e. the purified water area 110 height is 15 cm, the inner diameter is 10 cm, and the filter material total height in the column is 60 cm. Inside the filter device, from bottom to top, it includes the sewage area 150, the filter area and the purified water area 110 in sequence, the filter area includes the first filter layer 140 and the second filter layer 120, the first filter layer 140 is arranged below the second filter layer 120, and the two ends of the first filter layer 140 and the second filter layer 120 are fixed by the metal mesh 130, so the two filter layers are also separated by the metal mesh 130; the first filter layer 140 is filled with the first filter medium, and the second filter layer 120 is filled with the second filter medium, the particle size of the first filter medium is greater than that of the second filter medium; the non-uniformity coefficient d60 / d10 of the second filter medium is 2.14, and the equivalent diameter d10 is between 0.2 mm and 1 mm; the filter device of the sewage area 150 is provided with the water inlet 153 and the water outlet 161; and it further includes an air inlet unit and a flushing unit; the filter device of the purified water area 110 is provided with the purified water outlet 114 and the air inlet 113; the air inlet unit in the embodiment includes the air inlet pump 115, the air inlet pump 115 is connected with the air inlet 113; the flushing unit is connected with the purified water outlet 114, and the flushing unit is used for flushing the filter device by water through the purified water outlet 114.

[0040] In the embodiment, the first filter medium and the second filter medium are both glass lightweight stones; the first filter medium is stone-shaped glass lightweight stone filler, the particle size range is 5 mm-14 mm, and the second filter medium is sand-shaped glass lightweight stone filler, the particle size range is 0.3 mm-1.4 mm; the height of the first filter layer 140 is L1, and the height of the second filter layer 120 is L2; L1:L2=2:1; L1=400 mm, and L2=200 mm; in addition, the glass lightweight stone porosity in the embodiment is greater than 60%, the density is less than 0.8 g / cm 3 , and the specific surface area is 8.5 m 2 / g.

[0041] The embodiment further provides a sewage treatment system which includes a micro-flocculation tank 300 and a filter device 100, the filter device 100 is the sewage up-flow multi-filter layer filter device in the embodiment, the micro-flocculation tank 300 uses polyaluminum chloride to treat sewage; the water outlet end of the micro-flocculation tank 300 is connected with the water inlet 153 of the filter device 100 through a pipeline, the pipeline is provided with a second water pump 350, and the second water pump 350 is used for pumping the water in the micro-flocculation tank 300 into the filter device 100.

[0042] In addition, the sewage treatment system of the embodiment further comprises a feeding device 330, a sewage pool 200 and a clean water pool 400; the feeding device 330 is connected with the micro-flocculation pool 300, and the feeding device 330 is used for feeding polyaluminum chloride into the micro-flocculation pool 300; the sewage pool 200 is connected with the micro-flocculation pool 300 through a pipeline, and a first water pump 230 is arranged on the pipeline; the first water pump 230 is used for pumping water in the sewage pool 200 into the micro-flocculation pool 300; the clean water pool 400 is connected with the clean water outlet 114 through a first clean water pipe 410 and a second clean water pipe 420 respectively; the first clean water pipe 410 is provided with a third water pump 411; the third water pump 411 is used for pumping clean water in the clean water pool 400 into the filtering device 100 through the clean water outlet 114; and the second clean water pipe 420 is provided with a drain valve 421.

[0043] The embodiment further provides a sewage treatment method based on the sewage treatment system; sewage is first pumped into the micro-flocculation pool 300, and polyaluminum chloride solution is used for micro-flocculation treatment of the sewage; then the sewage treated by micro-flocculation is injected into the filtering device 100 at a flow rate of 20 m / h for filtration; and the specific steps of the micro-flocculation treatment are as follows: first, the first stirring motor 210 is started to drive the first stirring paddle 220 to stir the sewage in the sewage pool 200 at a rotating speed of 500 r / min; then the sewage with a volume of V1 in the sewage pool 200 is pumped into the micro-flocculation pool 300 by the first water pump 230, and polyaluminum chloride solution with a concentration of 50 mg / L and a volume of V2 is added into the micro-flocculation pool 300 by the feeding device 330, and V1:V2 = 1:1; finally, the second stirring motor 310 is started to drive the second stirring paddle 320 to stir the liquid in the micro-flocculation pool 300 at a rotating speed of 150 r / min for 1 min, and then the liquid is left to stand for 2 min.

[0044] Therefore, the sewage treatment method is used for treating urban runoff, and the water quality of inlet and outlet is recorded in Table 1. The specific operation steps are as follows: first, runoff with a suspended solid (SS) concentration of 2500 mg / L, a dissolved phosphorus (phosphate) concentration of 1 mg / L and a heavy metal cadmium ion concentration of 0.04 mg / L is pumped into the sewage pool 200; after the above micro-flocculation treatment, the first valve 340, the second water pump 350 and the water inlet valve 151 are opened; then the sewage treated by micro-flocculation is pumped into the filtering device 100 through the water inlet 153; at this time, the air inlet valve 112 and the water outlet valve 162 are closed, the clean water valve 111 is opened, the sewage is filtered by the filtering device 100, at this time, the third water pump 411 and the drain valve 421 are closed, and the clean water is discharged from the clean water outlet 114 and flows into the clean water pool 400; when the clean water pool 400 is full of clean water, the drain valve 421 is opened for normal drainage.

[0045] The embodiment also provides a backwashing method based on the sewage treatment system described in the embodiment. The filter device of the sewage area 150 is provided with a pressure detection device 152, which is a pressure gauge in the embodiment. When the pressure detection device 152 detects that the water pressure P1 in the sewage area 150 is greater than or equal to 35 kPa, the filter device 100 is rotated and the height of the clean water area 110 is lower than that of the sewage area 150. For the convenience of operation, the filter device 100 is directly vertically flipped by 180 degrees in the embodiment, and after being turned upside down, compressed air is injected into the clean water area 110 at a speed of 50 m / h from the air inlet 113, and the injection time is 3 min. The filter device 100 is rotated again to make the height of the clean water area 110 higher than that of the sewage area 150. For the convenience of operation, the filter device is vertically flipped by 180 degrees again in the embodiment, that is, the placement state in the filtering process is restored. At this time, the third water pump 411 is started, and the clean water in the clean water tank 400 is injected into the clean water area 110 at a speed of 12.5 m / h from the clean water outlet 114, and the injection time is 10 min. The washing water after washing is collected by the collector 160, and then the water outlet valve 162 is opened and discharged from the water outlet 161. Finally, the concentration of phosphate in the backwashing sewage discharged from the water outlet 161 is measured, and the backwashing efficiency is calculated according to the concentration of phosphate. The backwashing efficiency is obtained by the ratio of the recovery amount of phosphate to the injection amount. First, 20 L of sewage is injected for filtration, and then 20 L of clean water is used for backwashing. The concentration of phosphate in the backwashing sewage is measured, and the ratio of the concentration of phosphate in the backwashing sewage to the concentration of phosphate in the sewage is the backwashing efficiency. The backwashing efficiency data of the embodiment can be seen in Table 1.

[0046] Table 1, comparison of water quality before and after water of each embodiment and comparative example

[0047]

[0048]

[0049] Embodiment 2

[0050] The embodiment provides a sewage up-flowing multi-filtering layer filter device, a sewage treatment system and a method and a backwashing method thereof. The specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically the same as those of Embodiment 1. The main difference lies in that the parameters of the first filtering medium and the second filtering medium in the filter device of the embodiment are different, the L1: L2 = 5: 1, the L1 = 500 mm, and the L2 = 100 mm. The final water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0051] Embodiment 3

[0052] The embodiment provides a sewage up-flow type multi-filter-layer filter device, a sewage treatment system and a method and a backwashing method thereof. The specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically same as those of the embodiment 1. The main difference is that the parameters of the first filter medium and the second filter medium in the filter device of the embodiment are different, the L1:L2=1:1, the L1=300 mm, and the L2=300 mm. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0053] Embodiment 4

[0054] The embodiment provides a sewage up-flow type multi-filter-layer filter device, a sewage treatment system and a method and a backwashing method thereof. The specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically same as those of the embodiment 1. The main difference is that the parameters of the first filter medium and the second filter medium in the filter device of the embodiment are different, the L1:L2=1:1, the L1=300 mm, and the L2=300 mm. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0055] Embodiment 5

[0056] The embodiment provides a sewage up-flow type multi-filter-layer filter device, a sewage treatment system and a method and a backwashing method thereof. The specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically same as those of the embodiment 1. The main difference is that the parameters of the first filter medium and the second filter medium in the filter device of the embodiment are different, the L1:L2=2:1, the L1=200 mm, and the L2=100 mm. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0057] Embodiment 6

[0058] The embodiment provides a sewage up-flow type multi-filter-layer filter device, a sewage treatment system and a method and a backwashing method thereof. The specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically same as those of the embodiment 1. The main difference is that the parameters of the first filter medium and the second filter medium in the filter device of the embodiment are different, the L1:L2=2:1, the L1=600 mm, and the L2=300 mm. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0059] From the comparison of Examples 1, 2, 3 and 4, it is concluded that the filtration device 100 has good effect of removing suspended particulate matters and relatively optimal filtration speed when the ratio of stone-like and sand-like glass beads is 2. From Examples 1, 5 and 6, it is concluded that the height of the filler has little effect on the removal efficiency of suspended matters, and the height that is too high will make the reaction time longer and increase the difficulty of backwashing, so the total height of the filler is selected as 600 mm, and the water treatment efficiency and backwashing efficiency are relatively optimal when L1 = 400 mm and L2 = 200 mm.

[0060] Example 7

[0061] The present example provides a sewage upflow multi-filter layer filtration device, a sewage treatment system and a method thereof and a backwashing method. The specific structure of the filtration device and the sewage treatment system, the sewage treatment method and the backwashing method are basically the same as those of Example 1, and the main difference is that the filtration device of the present example comprises three layers of filter layers from bottom to top: 15 mm to 25 mm particle size of glass beads, 5 mm to 14 mm particle size of glass beads, and 0.3 mm to 1.4 mm particle size of glass beads, and the filler height is 300 mm, 200 mm and 100 mm respectively. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0062] Example 8

[0063] The present example provides a sewage upflow multi-filter layer filtration device, a sewage treatment system and a method thereof and a backwashing method. The specific structure of the filtration device and the sewage treatment system, the sewage treatment method and the backwashing method are basically the same as those of Example 1, and the main difference is that the second filter medium of the present example has a non-uniformity coefficient d60 / d10 = 1.85, and the equivalent diameter d10 is in the range of 0.2 mm to 1 mm. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0064] Comparative Example 1

[0065] The present comparative example provides a sewage upflow multi-filter layer filtration device, a sewage treatment system and a method thereof and a backwashing method. The specific structure of the filtration device and the sewage treatment system, the sewage treatment method and the backwashing method are basically the same as those of Example 1, and the main difference is that the present comparative example only uses 600 mm high stone-like glass beads as the filler, and the particle size of the glass beads is in the range of 5 mm to 14 mm. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0066] It can be seen from the comparison of Example 1 and Example 7 with Comparative Example 1 that, compared with a single filter layer, the multiple filter layers, and the different sizes of filter materials in the multiple filter layers, the urban runoff removal effect of different particle size pollutants is better, and the selection of two sizes of filter materials can achieve better backwashing efficiency and water treatment efficiency; and under the action of the filter device 100 of the present application, the backwashing efficiency is higher.

[0067] Comparative Example 2

[0068] The present comparative example provides a sewage upflow type multi-filter layer filter device, a sewage treatment system and a method thereof, and a backwashing method, and the specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically the same as those of Example 1, the main difference is that the micro-flocculation treatment of the present comparative example uses 50 mg / L of alum solution, reacts for 20 minutes, and precipitates for 10 minutes. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0069] Comparative Example 3

[0070] The present comparative example provides a sewage upflow type multi-filter layer filter device, a sewage treatment system and a method thereof, and a backwashing method, and the specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically the same as those of Example 1, the main difference is that the micro-flocculation treatment of the present comparative example uses 50 mg / L of FeCl3·6H2O solution, reacts for 20 minutes, and precipitates for 10 minutes. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0071] Comparative Example 4

[0072] The present comparative example provides a sewage upflow type multi-filter layer filter device, a sewage treatment system and a method thereof, and a backwashing method, and the specific structure of the filter device and the sewage treatment system, the sewage treatment method and the backwashing method are basically the same as those of Example 1, the main difference is that the micro-flocculation treatment of the present comparative example uses 50 mg / L of FeCl3·6H2O solution, reacts for 20 minutes, and precipitates for 10 minutes. The final effluent water quality parameters and backwashing efficiency parameters are shown in Table 1.

[0073] By comparing Example 1 and Comparative Examples 2-4, the results show that the rapid micro-flocculation of the present application has little difference in removal effect compared with the conventional coagulation process of adding alum and iron-based flocculants, and can also quickly remove dissolved pollutants in rainwater runoff, but saves time and reduces cost.

[0074] More specifically, although illustrative embodiments of the application have been described herein, the present application should be understood to include any and all embodiments falling within the scope of the application as defined by the appended claims, and their equivalents. The limitations in the claims are to be construed as limiting only to the precise language used in the claims. Accordingly, the breadth and scope of the present application should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Any and all limitations which can be present in any one of the foregoing aspects should be seen as applicable to each and every aspect of the present application. Thus, the breadth and scope of the present application should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. If there is a conflict between usages of terms in the specification and usages of terms in the patentable claim or claims, the definitions that are in the claim or claims shall govern. "Range" or "ranging" as used herein in connection with a quantity, a concentration, a temperature, a time, or any other value or parameter of any kind, means a range of values, preferably a range of values of any kind, including any and all sub-ranges thereof, each range of values of any kind encompassing any other or all sub-ranges thereof. For example, a range of "1 to 50", when combined with a range of "2 to 20" can form a range of "1 to 20", "1 to 50", "2 to 50", "2 to 20", "1 to 10", "1 to 20", "2 to 10", or "10 to 50". In each instance the data can be presented in a tabular format. For example, a range of "1 to 50" can be presented as follows: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50.

Claims

1. A backwash method characterized by, A sewage treatment system is disclosed; The sewage treatment system comprises a micro-flocculation tank (300) and a filtering device (100), The filtering device (100) comprises, from bottom to top, a sewage area (150), a filtering area and a clean water area (110), the filtering area comprises a first filtering layer (140) and a second filtering layer (120), and the first filtering layer (140) is arranged below the second filtering layer (120); The first filtering layer (140) is filled with a first filtering medium, the second filtering layer (120) is filled with a second filtering medium, the particle size of the first filtering medium is larger than that of the second filtering medium, the non-uniformity coefficient d60 / d10 of the second filtering medium is 1.3-3.0, and the equivalent diameter d10 is 0.2-1 mm; the filtering device of the sewage area (150) is provided with a water inlet (153) and a water outlet (161); the height of the first filtering layer (140) is L1, the height of the second filtering layer (120) is L2, and L1:L2=(1-11):1; the filtering device of the clean water area (110) is provided with a clean water outlet (114) and an air inlet (113); the air inlet unit is connected with the air inlet (113); the flushing unit is connected with the clean water outlet (114), and the flushing unit is used for flushing the filtering device by injecting water into the clean water outlet (114); when the water inlet (153) is used for water injection, the height of the clean water area (110) is higher than that of the sewage area (150); when the air inlet (113) is used for air injection, the filtering device is vertically turned over by 180 degrees so that the height of the clean water area (110) is lower than that of the sewage area (150); when the clean water outlet (114) is used for water injection, the filtering device is vertically turned over by 180 degrees again so that the height of the clean water area (110) is higher than that of the sewage area (150); The micro-flocculation tank (300) is used for treating sewage by using polyaluminum chloride; the water outlet end of the micro-flocculation tank (300) is connected with the water inlet (153) of the filtering device (100) through a pipeline, and a second water pump (350) is arranged on the pipeline; the second water pump (350) is used for pumping water in the micro-flocculation tank (300) into the filtering device (100); A pressure detection device (152) is arranged on the filtering device of the sewage area (150); when the pressure detection device (152) detects that the water pressure P1 in the sewage area (150) is greater than or equal to 35 kPa, the filtering device (100) is rotated so that the height of the clean water area (110) is lower than that of the sewage area (150), compressed air is injected into the clean water area (110) from the air inlet (113) at a speed of 40-50 m / h, and the injection time is 3-5 min; the filtering device (100) is rotated again so that the height of the clean water area (110) is higher than that of the sewage area (150), and clean water is injected into the clean water area (110) from the clean water outlet (114) at a speed of 10-15 m / h, and the injection time is 8-12 min.

2. A backwash method as claimed in claim 1, characterized in that The sewage treatment system further comprises a feeding device (330) and a sewage pool (200); the feeding device (330) is connected with the micro-flocculation pool (300), and the feeding device (330) is used for feeding polyaluminum chloride into the micro-flocculation pool (300); the sewage pool (200) is connected with the micro-flocculation pool (300) through a pipeline, and a first water pump (230) is arranged on the pipeline; the first water pump (230) is used for pumping water in the sewage pool (200) into the micro-flocculation pool (300).

3. A backwash method according to claim 2, wherein, The flushing unit comprises a clean water pool (400), and the clean water pool (400) is connected with the clean water outlet (114) through a first clean water pipe (410) and a second clean water pipe (420) respectively; a third water pump (411) is arranged on the first clean water pipe (410), and the third water pump (411) is used for pumping clean water in the clean water pool (400) into the filtering device (100) through the clean water outlet (114); a drain valve (421) is arranged on the second clean water pipe (420).

4. A backwash method according to claim 3, wherein, The first filtering medium and the second filtering medium are both glass lightweight stones; the particle size of the first filtering medium is 5mm-14mm, and the particle size of the second filtering medium is 0.3mm-1.4mm.

5. A backwash method according to claim 4, wherein, The L1=200mm-600mm, and the L2=50mm-300mm.

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