Percolation purification system and method for backwash water of underground deep well drinking water treatment equipment

Abstract

The present application relates to a filtration purification system and method for backwash drainage of underground deep well drinking water treatment equipment, and belongs to the field of water treatment equipment. The system comprises a backwash drainage collection pipeline and a water infiltration well. The water infiltration well is filled with coarse particle filter layer, medium particle adsorption layer, modified quartz sand fine adsorption layer and gravel supporting cushion layer from top to bottom, forming a gradient adsorption structure with particle size from large to small. The backwash drainage is collected and then flows into the water infiltration well by itself, is purified by the adsorption layers in sequence, and is then returned to groundwater through the permeation structure. The fine adsorption layer can use a carbon sand composite structure mixed by modified quartz sand and activated carbon at a ratio of 1:1 to cooperatively remove organic pollutants. The present application also discloses a preparation method of modified quartz sand. The present application realizes purification of backwash drainage, with a suspended solid removal rate of more than 96% and a COD removal rate of more than 87%, and is suitable for decentralized water treatment facilities in remote areas.

Description

Technical Field

[0001] This invention relates to the field of water treatment equipment technology, specifically to a percolation purification system and method for backwash drainage of underground deep well drinking water treatment equipment. Background Technology

[0002] Integrated water treatment equipment offers advantages such as simple construction, short construction period, and small footprint, making it widely used in small-scale, decentralized water supply projects. In some scattered villages, deep well water with slight contamination, such as suspended solids (SS), iron, manganese, arsenic, and fluoride, requires treatment to meet drinking water standards. Simultaneously, some remote areas suffer from power shortages or unstable power supply, limiting the application of traditional water treatment equipment that relies on continuous mains power.

[0003] Therefore, in developing drinking water treatment equipment suitable for these deep underground wells, common filtration units such as activated carbon filters, non-membrane filters, resin tanks, and ultrafiltration equipment generally require backwashing after long-term operation to restore the filtration performance of the filter media. Backwash drainage is one of the main sources of wastewater in water treatment systems, accounting for approximately 5% to 10% of the water treated by the filters. Its characteristics include high suspended solids (50-500 mg / L) and the presence of small amounts of filter media debris and chemical residues.

[0004] The existing backwash drainage treatment methods mainly include the following:

[0005] (1) Direct discharge: Directly discharging backwash wastewater into municipal sewage pipe networks or natural water bodies not only wastes water resources, but also increases the pressure of environmental protection treatment, and may even pollute the receiving water bodies.

[0006] (2) Backwashing back to the raw water treatment system: The backwash wastewater is returned to the inlet of the water treatment system for reprocessing. However, the high concentration of suspended solids and microorganisms in the backwash wastewater will impact the raw water treatment system, reduce treatment efficiency, and accelerate filter media fouling.

[0007] (3) Reuse after sedimentation: The wastewater is reused after sedimentation in a sedimentation tank, as disclosed in Chinese Patent CN204848523U, which sets up a backwash drainage thickening tank and overflows the supernatant after sedimentation to the raw water inlet pipe for treatment. However, this method still requires additional sedimentation tank facilities, and the settled sludge still needs further treatment.

[0008] (4) For other uses: Chinese patent CN201922412369.4 discloses a system for recycling backwash water from equipment, which reuses backwash water through a filter box and an activated carbon filter layer. However, this system requires additional filtration devices and energy consumption.

[0009] The aforementioned existing technologies have the following common problems in the treatment of backwash wastewater from decentralized water treatment equipment in rural and remote areas: ① The equipment is complex and energy-intensive, making it unsuitable for maintenance in remote areas; ② It fails to achieve comprehensive purification of multiple pollutants (suspended solids, heavy metals, and organic matter) in the backwash wastewater; ③ It fails to effectively replenish groundwater with the purified water to achieve water resource recycling; ④ It lacks an integrated treatment solution for backwash wastewater from multiple sources (activated carbon filter backwash water, non-membrane filter backwash water, and resin tank backwash water).

[0010] Therefore, there is an urgent need in this field for a water treatment equipment backwash drainage purification system that is simple in structure, eco-friendly, and suitable for remote areas. Summary of the Invention

[0011] This invention addresses the shortcomings of existing technologies by providing a percolation purification system and method for backwash drainage from underground deep well drinking water treatment equipment. The technical solution is as follows:

[0012] The first aspect is the infiltration and purification system for the backwash drainage of underground deep well drinking water treatment equipment, including:

[0013] Backwash drain collection pipe, used to receive and collect backwash drain from at least two filter units;

[0014] The seepage well is located underground and is connected to the end of the backwash drainage collection pipe;

[0015] The interior of the seepage well is filled with an adsorbent material, which, from top to bottom, comprises:

[0016] The coarse particle filter layer is made of one or more of the following materials: gravel, ceramsite, anthracite, pebbles, magnetite filter media, garnet filter media, and ceramic sand filter media.

[0017] The medium-particle adsorption layer is made of one or more materials selected from zeolite, volcanic rock, maifanite, bentonite, activated alumina balls, and sponge iron.

[0018] Fine-particle adsorption layer, the material of which is selected from modified quartz sand, or a mixture of modified quartz sand and activated carbon;

[0019] The supporting layer is made of one or more of the following materials: gravel, ceramsite, anthracite, pebbles, magnetite filter media, garnet filter media, and ceramic sand filter media.

[0020] The bottom and / or sidewalls of the seepage well are provided with a seepage structure for infiltrating water purified by the adsorption material into the surrounding soil or groundwater layer.

[0021] Furthermore, the filtration unit includes at least two of the following: an activated carbon filter, a non-membrane filter, and a resin tank.

[0022] Furthermore, the thickness of the supporting pad layer is 10-20cm, and the thickness of the coarse particle filter layer is 30-50cm.

[0023] Furthermore, the permeable structure is a permeable concrete layer or a perforated pipe disposed on the sidewall of the seepage well.

[0024] Furthermore, the bottom of the seepage well is provided with a replaceable adsorption material cage, and the adsorption material is contained within the adsorption material cage.

[0025] Secondly, the infiltration purification method for backwash drainage from underground deep well drinking water treatment equipment includes the following steps:

[0026] Step a: Drain the backwash water from the filter unit into the backwash water collection pipe;

[0027] Step b: Allow the backwashed water after the confluence to flow into the top of the seepage well by gravity or pumping.

[0028] Step c: Allow the backwash drainage to flow from top to bottom through the coarse particle filter layer, medium particle adsorption layer, fine particle adsorption layer and support pad layer in the seepage well.

[0029] Step d: Allow the purified water to seep into the surrounding soil or groundwater layer through the permeable structure.

[0030] Furthermore, it also includes step e: when the adsorbent material is saturated, the entire adsorbent material is removed for regeneration or replacement.

[0031] Furthermore, the preparation method of the modified quartz sand includes the following steps:

[0032] Step 1: Acid wash the quartz sand with trifluoromethanesulfonic acid solution, then wash with water and dry to obtain activated quartz sand;

[0033] Step 2: Knead the cattail stalks and then crush them into cattail fluff;

[0034] Step 3: After uniformly mixing activated quartz sand, sawdust, cattail fluff and metal salt powder, add it to an ultrasonic disperser and disperse it by wet vibration. Then add sodium hydroxide solution and allow in-situ precipitation reaction to occur under ultrasonic dispersion environment. Filter to obtain the precipitate product. The metal salt powder is a mixture of soluble iron salt and soluble aluminum salt.

[0035] Step 4: The precipitated product is calcined at 500~510℃ under an inert atmosphere, crushed, washed with water and dried to obtain modified quartz sand.

[0036] Furthermore, the mass ratio of each raw material used in step 3 is as follows:

[0037] Activated silica sand: sawdust: cattail fluff: metal salt powder = 1:(0.28~0.33):(0.18~0.22):(0.18~0.25).

[0038] Furthermore, in step 3, the moisture content of the wet material during wet dispersion is controlled at 55%~60%.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. This invention achieves the step-by-step synergistic removal of suspended solids, heavy metal ions, fluorine, arsenic and organic matter in backwash drainage by arranging multi-layer adsorption materials in the seepage well from top to bottom according to the gradient of particle size from large to small and adsorption precision from coarse to fine. The removal rate of suspended solids is over 96%, the removal rate of heavy metals is over 92%, and the removal rate of COD is over 87%.

[0041] 2. The present invention adopts a carbon-sand composite structure in the fine adsorption layer, which is a 1:1 mixture of modified quartz sand and activated carbon. It combines the broad-spectrum physical adsorption of activated carbon with the selective chemical adsorption and catalytic function of modified quartz sand. The removal rate of organic pollutants such as pesticides such as dichlorvos, dimethoate and atrazine, as well as petroleum hydrocarbons such as chloroform, is significantly better than that of single filter media and layered stacked combinations.

[0042] 3. This invention utilizes gravity flow to achieve zero-energy operation. After purification, the water replenishes groundwater through a permeable structure, eliminating the need for external discharge. It is particularly suitable for backwashing and drainage treatment of decentralized water treatment equipment in remote rural areas. Detailed Implementation

[0043] The present invention will be described in detail below with reference to specific embodiments. These embodiments are merely some, not all, implementations of the present invention. All other implementations obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] In some embodiments, the underground deep well drinking water treatment equipment includes a deep water well, a deep water pump, an ozone oxidation tank, an activated carbon filter, a non-membrane filter, a resin tank, an ultrafiltration device, a constant pressure water supply pump, an ozone generator, a hypochlorous acid generator, photovoltaic panels, energy storage equipment, and integrated power control equipment. The photovoltaic panels are used to generate electricity and can work in conjunction with the mains power supply to ensure power availability. After being pumped up by the deep water pump, the groundwater first enters the ozone oxidation tank, where it mixes with ozone supplied by the ozone generator to complete sterilization, disinfection, and oxidation of ions such as iron, manganese, and arsenic. Subsequently, it flows sequentially through an activated carbon filter to adsorb residual chlorine and organic matter, a non-membrane filter to remove fine particles and colloids, a resin tank to remove calcium, magnesium, and specific ions, and finally, through the fine separation of the hollow fiber membrane in the ultrafiltration device, it enters the underground water storage tank. The constant pressure water supply pump draws water from the underground water storage tank and delivers it to the user end through a constant pressure water supply pipeline. Before the purified water enters the underground water storage tank, the hypochlorous acid generating equipment adds hypochlorous acid into the ultrafiltration water production pipeline through the hypochlorous acid dosing pipeline to ensure continuous antibacterial effect at the end of the pipeline network.

[0046] The activated carbon filter, non-membrane filter, and resin tank in the aforementioned underground deep well drinking water treatment equipment are each equipped with backwash drainage pipes.

[0047] In some embodiments, the backwash drainage infiltration purification system includes: a first branch pipe connected to the backwash drainage outlet of the activated carbon filter, a second branch pipe connected to the backwash drainage outlet of the non-membrane filter, a third branch pipe connected to the backwash drainage outlet of the resin tank, and a main conduit that gathers the first, second, and third branch pipes. The end of the main conduit is connected to a seepage well.

[0048] Backwash wastewater is purified through adsorption, filtration and biodegradation during the infiltration process, achieving environmentally friendly discharge.

[0049] The seepage well is located underground near the underground equipment room, with a depth of 4m and a diameter of 2m. The interior of the seepage well is filled from top to bottom as follows:

[0050] Upper layer: coarse gravel layer; particle size 10~30mm; thickness 0.5m; its function is to intercept large suspended particles and filter media debris.

[0051] Middle layer: zeolite layer; particle size 2~5mm; thickness 0.5m; its function is to adsorb heavy metal ions (iron, manganese, arsenic) and ammonia nitrogen;

[0052] Lower layer: Modified quartz sand layer; particle size 0.5~2mm; thickness 0.4m; its function is to finely adsorb fluorine, arsenic, residual chlorine and trace organic matter;

[0053] Bottom layer: bottom gravel cushion layer; particle size is 10~20mm; thickness is 0.1m; its function is to prevent silt from rising from the bottom of the well and to collect water evenly.

[0054] The sidewall of the seepage well is equipped with a permeable concrete layer (10cm thick, 25% porosity).

[0055] During operation, the backwash drainage from the activated carbon filter, non-membrane filter, and resin tank is collected through branch pipes to the main main pipe, where it flows by gravity into the top of the seepage well. The backwash drainage flows from top to bottom through a coarse gravel layer, a zeolite layer, a modified quartz sand layer, and a bottom gravel cushion layer. The purified water seeps into the surrounding soil through the permeable concrete layer on the sidewalls, replenishing the groundwater.

[0056] Effluent water quality (third-party testing):

[0057] The removal rates were as follows: suspended solids 96.3%; iron 93.1%; manganese 92.0%; fluorine 85.5%; arsenic 88.3%; COD 87.0%; and after 15 months of continuous operation, no blockages or sludge contamination were observed.

[0058] Example 2

[0059] This embodiment is basically the same as Embodiment 1, except that:

[0060] The bottom of the seepage well is equipped with a replaceable stainless steel absorbent material cage (2m in diameter).

[0061] The adsorbent material inside the stainless steel adsorbent cage is filled from top to bottom:

[0062] Upper layer: Ceramsite layer; particle size 10~20mm; thickness 0.5m; its function is to intercept large suspended particles and filter media debris.

[0063] Middle layer: volcanic rock layer; particle size 3~6mm; thickness 0.5m; the volcanic rock layer, as a medium particle adsorption layer, has multiple functions, including physical interception, chemical adsorption of heavy metals and ammonia nitrogen, and degradation of organic matter by microbial carriers, achieving synergistic purification while protecting the fine adsorption material in the lower layer.

[0064] Bottom layer: Mixed fine adsorption layer (modified quartz sand and activated carbon mixed in a 1:1 mass ratio); thickness is 0.7m; particle size of modified quartz sand is 0.5~2mm; particle size of activated carbon is 0.5~2mm; the two filter media in the carbon sand composite fine adsorption layer are fully mixed to form a carbon sand interwoven composite structure, which combines the strong adsorption performance of activated carbon and the chemical adsorption and physical filtration functions of modified quartz sand;

[0065] Bottom layer: bottom gravel cushion layer; particle size is 10~20mm; thickness is 0.1m; its function is to prevent silt from rising from the bottom of the well and to collect water evenly.

[0066] After 28 months of operation, the stainless steel adsorption material cage and its internal adsorption material will be lifted out as a whole and replaced with a new stainless steel adsorption material cage and its internal adsorption material. The original stainless steel adsorption material cage and its internal adsorption material will be sent to the factory for regeneration.

[0067] Effluent water quality: suspended solids removal rate 97.0%, fluoride removal rate 90.6%, arsenic removal rate 92.2%, COD removal rate 90.7%.

[0068] Example 3

[0069] The modification methods for the modified quartz sand in Examples 1 and 2 include the following steps:

[0070] 1. Pickle 2 kg of quartz sand using a 1% trifluoromethanesulfonic acid solution. After pickling, wash with water to remove surface impurities and activate the surface of the quartz sand. Dry the quartz sand to obtain activated quartz sand.

[0071] 2. Knead the dark-colored cattail stalks and then crush them into cattail fluff with a particle size of less than 1mm;

[0072] Cattails can be selected from plants such as cattails, calamus, and sweet flag;

[0073] 3. Mix 1 kg of activated quartz sand, 0.3 kg of sawdust with a particle size less than 2 mm, 0.2 kg of cattail fluff, and metal salt powder (0.12 kg of ferric chloride and 0.08 kg of aluminum nitrate) evenly. Then, add the mixture to an ultrasonic disperser (ultrasonic frequency of 20 kHz) and use a wet method (moisture content of the wet material controlled at 55-60%) for vibration dispersion. The mechanical force is used to break down the surface structure of the quartz sand and promote the uniform dispersion and adhesion of the metal salt. Then, pour 0.6 kg of 11% sodium hydroxide solution into the ultrasonic disperser. Under the ultrasonic dispersion environment, an in-situ precipitation reaction occurs, causing the metal hydroxide to nucleate and grow on the surface and pores of the quartz sand, cattail fluff, and sawdust. Filter to obtain the precipitate product.

[0074] 4. The precipitated product is calcined at 500~510℃ for 3 hours in an inert atmosphere (such as nitrogen) to dehydrate the hydroxide and transform it into a stable crystalline metal oxide. At the same time, the carbonized sawdust and cattail fluff form a porous carbon skeleton. The agglomerated quartz sand is broken up and the particle size is controlled to be 0.5~2mm.

[0075] 5. Rinse repeatedly with tap water to remove unreacted free ions and loose particles, and finally dry to obtain modified quartz sand.

[0076] In this embodiment, the sawdust is produced by mechanical crushing, and its shape is irregular, mostly in the form of small wood blocks, short and thick fiber bundles or irregular fragments; the particles are loosely physically stacked.

[0077] Cattail fluff is generally composed of long, thin filaments or needles that are several millimeters or even longer in length, with a diameter typically only tens of micrometers. These filaments often have extremely small longitudinal stripes or micro-spiks on their surface, which form a highly fluffy three-dimensional network structure.

[0078] Characterization test of adsorption and degradation of trace organic pollutants (pesticides, petroleum hydrocarbons):

[0079] Select 5 acrylic filter columns of the same specifications and lay a gravel pad at the bottom;

[0080] Five types of filter media were tested: mixed fine adsorption layer, ordinary activated carbon filter media, quartz sand filter media, modified quartz sand filter media, and layered composite filter media (modified quartz sand filter media and ordinary activated carbon filter media were layered and stacked in a 1:1 mass ratio); the thickness of all filter media was 15cm.

[0081] Trace pollutants were added to tap water to simulate the concentration of the following substances: dichlorvos 20 μg / L, dimethoate 20 μg / L, DDT 10 μg / L, atrazine 30 μg / L, and chloroform 50 μg / L; low concentrations of COD and SS were added simultaneously to simulate the infiltration water from farmland.

[0082] Simulated water was continuously flowed for 7 days to construct an aerobic / anaerobic microbial membrane in the filter layer; after acclimatization, the simulated water in the column was drained. The hydraulic retention time was standardized, and simulated water was pumped in, with all five filter columns operating synchronously; influent and effluent samples were collected from each group of filter columns. The concentrations of five pollutants in the water samples were measured, and the removal rate of each single component was calculated using the following formula:

[0083] Removal rate = (Influent concentration − Effluent concentration) / Influent concentration × 100%;

[0084] The removal rate data for each group were compiled, and the results are shown in Table 1:

[0085] Table 1

[0086]

[0087] As shown in Table 1, the mixed fine adsorption layer made of modified quartz sand and activated carbon in a 1:1 ratio has the best overall removal effect on the five target pollutants, with all indicators higher than the other four types of filter media; the layered combined filter media has the second best overall performance; ordinary activated carbon alone has only a moderate removal effect on hydrophobic and difficult-to-degrade pollutants; and pure ordinary quartz sand has the worst purification capacity.

[0088] For pesticides like dichlorvos and dimethoate, the advantage likely lies in the fact that the mixed fine adsorption layer is not simply a physical stack of sand and charcoal. Its core advantage is that the biofilm formed within the filter layer contains both aerobic nitrifying bacteria on the sand surface and anaerobic denitrifying bacteria on the charcoal surface, complementing each other in a vertical gradient. Furthermore, the Fe / Al oxides attached to the modified quartz sand surface within the mixed fine adsorption layer may act as catalysts, especially in the biofilm system formed within the filter layer. These Fe / Al oxides are more effective at catalyzing and degrading pesticides like dichlorvos and dimethoate, as well as petroleum hydrocarbons. This results in better adsorption and degradation of groundwater locally contaminated with organic pesticides and petroleum hydrocarbons.

[0089] In addition, compared to dichlorvos insecticide, although it is also a widely used agricultural pesticide, easily detected in runoff / seepage wells, and a trace hydrophobic organic pesticide (DDT insecticide), it relies solely on physical adsorption and cannot be catalyzed / degraded by microorganisms. Ordinary activated carbon has basic adsorption capacity but limited adsorption performance; modified quartz sand has limited improvement in the removal of this type of substance because it does not construct a biofilm with a suitable spatial structure, and the improvement in catalytic effect is limited.

[0090] Pure quartz sand relies solely on weak physical retention, lacks adsorption sites and catalytic oxidation capabilities, resulting in extremely low removal rates for all trace organic pollutants in Table 1.

[0091] Dichlorvos, dimethoate, atrazine, and chloroform are pollutants that can be removed through multiple pathways. In the stratified system, modified quartz sand provides multiple benefits, including catalysis, charge neutralization, biodegradation, and pre-retention. Combined with improved activated carbon utilization, this completely offsets or even surpasses the losses caused by halving the activated carbon dosage, resulting in a better overall effect. However, DDT mainly relies on physical adsorption by activated carbon, and modified quartz sand is very ineffective against it. Therefore, if the quality of activated carbon decreases, the overall removal efficiency will decline to some extent.

[0092] Comparative Example 1

[0093] The only difference between this example and Example 3 is that this example uses a 1% sulfuric acid solution instead of a trifluoromethanesulfonic acid solution; all other aspects are the same. In this example, the mixed fine adsorption layer achieved a 95.8% removal rate of dichlorvos insecticide in the initial stage (0 backwashes); after 100 backwashes, the removal rate of dichlorvos insecticide was 62.7%.

[0094] In Example 3, the mixed fine adsorption layer achieved a removal rate of 87.0% for dichlorvos insecticide after 100 backwashes.

[0095] Analysis reveals that trifluoromethanesulfonic acid, a superacid, has a better activation effect on quartz sand than sulfuric acid, which is beneficial to the bonding of porous carbon skeletons. Therefore, under long-term erosion, the porous carbon skeletons on the surface of modified quartz sand may fall off in large areas, resulting in a significant decrease in adsorption sites, especially catalytic oxidation capacity, and also disrupting the structure of biofilms.

[0096] Comparative Example 2

[0097] The only difference between this example and Example 3 is that sawdust is used instead of cattail fluff in this example. In other words, the porous carbon skeleton on the surface of the modified quartz sand in this example comes from sawdust carbonization. All other aspects are the same.

[0098] In this example, the mixed fine adsorption layer achieved a removal rate of 95.4% for dichlorvos insecticide in the initial stage (0 backwashes); after 5 backwashes, the removal rate of dichlorvos insecticide was 41.3%.

[0099] Based on the structural characteristics of sawdust and cattail fluff, the reasons can be analyzed as follows: using only sawdust makes it difficult to construct a stable porous carbon skeleton on the surface of quartz sand, and it is also not conducive to the adhesion of metal oxides on it; sawdust is short and coarse debris, which forms isolated particles after carbonization, lacking fiber entanglement and reinforcement, and quickly falls off under the backwash water force; therefore, after only 5 backwash impacts, the ability to degrade organic matter significantly decreased, indicating that the constructed catalytic oxidation-biodegradation system was seriously disturbed.

[0100] Comparative Example 3

[0101] The only difference between this example and Example 3 is that cattail fluff is used instead of sawdust in this example. In other words, the porous carbon skeleton on the surface of the modified quartz sand in this example comes from the carbonization of cattail fluff. Everything else is the same.

[0102] In this example, the mixed fine adsorption layer achieved a removal rate of 92.6% for dichlorvos insecticide in the initial stage (0 backwashes); after 25 backwashes, the removal rate of dichlorvos insecticide was 37.6%.

[0103] Based on the structural characteristics of sawdust and cattail fluff, the reason can be analyzed as follows: if cattail fluff is used entirely, it is impossible to build a stable porous carbon skeleton on the surface of quartz sand. Sawdust, as the main load medium, and cattail fluff, as the fiber structure wrapped around it, will have a very stable structure; while the porous carbon skeleton built solely by cattail fluff has relatively poor stability.

[0104] Comparative Example 4

[0105] The only difference between this example and Example 3 is that sawdust and cattail fluff are not used in this example. That is, 1 kg of activated quartz sand is mixed evenly with metal salt powder (0.12 kg of ferric chloride and 0.08 kg of aluminum nitrate), and then added to an ultrasonic disperser for wet dispersion (the moisture content of the wet material is controlled at 55-60%). Mechanical force is used to break the surface structure of the quartz sand and promote the uniform dispersion and adhesion of the metal salt. Then, 0.6 kg of 11% sodium hydroxide solution is poured into the ultrasonic disperser, and an in-situ precipitation reaction occurs under ultrasonic dispersion, causing the metal hydroxide to nucleate and grow on the surface of the quartz sand. After filtration, the precipitate is obtained. The precipitate is calcined at 500-510°C for 3 hours in an inert atmosphere (such as nitrogen) to dehydrate the hydroxide and transform it into a stable crystalline state of metal oxide. The agglomerated quartz sand is broken up, and the particle size is controlled at 0.5-2 mm. The unreacted free ions and loose particles are repeatedly washed with tap water to remove them. Finally, the modified quartz sand is obtained by drying.

[0106] In this example, the mixed fine adsorption layer achieved a removal rate of 77.9% for dichlorvos insecticide in the initial stage (0 backwashes); this indicates that if a porous carbon framework is not used as the attachment medium for metal oxides, and the relevant sites are simply loaded directly onto the quartz sand surface, the removal rate is significantly reduced.

[0107] Comparative Example 5

[0108] The only difference between this example and Example 3 is that this example does not use an ultrasonic disperser, but a mixer with a stirring rate of 300 r / min; all other aspects are the same.

[0109] In this example, the mixed fine adsorption layer achieved a removal rate of 51.6% for dichlorvos insecticide in the initial stage (0 backwashes). This demonstrates that in this wet reaction system of the present invention, ultrasonic dispersion provides a significantly better adhesion effect than stirring.

[0110] Furthermore, it should be understood that those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A percolation purification system for backwash drainage of underground deep well drinking water treatment equipment, characterized in that, include: Backwash drain collection pipe, used to receive and collect backwash drain from at least two filter units; The seepage well is located underground and is connected to the end of the backwash drainage collection pipe; The interior of the seepage well is filled with an adsorbent material, which, from top to bottom, comprises: The coarse particle filter layer is made of one or more of the following materials: gravel, ceramsite, anthracite, pebbles, magnetite filter media, garnet filter media, and ceramic sand filter media. The medium-particle adsorption layer is made of one or more materials selected from zeolite, volcanic rock, maifanite, bentonite, activated alumina balls, and sponge iron. Fine-particle adsorption layer, the material of which is selected from modified quartz sand, or a mixture of modified quartz sand and activated carbon; The supporting layer is made of one or more of the following materials: gravel, ceramsite, anthracite, pebbles, magnetite filter media, garnet filter media, and ceramic sand filter media. The bottom and / or sidewalls of the seepage well are provided with a seepage structure for infiltrating water purified by the adsorption material into the surrounding soil or groundwater layer.

2. The system according to claim 1, characterized in that, The filtration unit includes at least two of the following: activated carbon filter, non-membrane filter, and resin tank.

3. The system according to claim 1, characterized in that, The thickness of the supporting pad layer is 10~20cm, and the thickness of the coarse particle filter layer is 30~50cm.

4. The system according to claim 1, characterized in that, The permeable structure is a permeable concrete layer or a perforated pipe installed on the sidewall of the seepage well.

5. The system according to claim 1, characterized in that, The bottom of the seepage well is equipped with a replaceable adsorption material cage, and the adsorption material is contained in the adsorption material cage.

6. A method for purifying backwash drainage from underground deep well drinking water treatment equipment by means of the system described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step a: Drain the backwash water from the filter unit into the backwash water collection pipe; Step b: Allow the backwashed water after the confluence to flow into the top of the seepage well by gravity or pumping. Step c: Allow the backwash drainage to flow from top to bottom through the coarse particle filter layer, medium particle adsorption layer, fine particle adsorption layer and support pad layer in the seepage well. Step d: Allow the purified water to seep into the surrounding soil or groundwater layer through the permeable structure.

7. The method according to claim 6, characterized in that, It also includes step e: when the adsorbent material is saturated, the entire adsorbent material is removed for regeneration or replacement.

8. The system according to claim 1 or the method according to claim 6, characterized in that, The method for preparing the modified quartz sand includes the following steps: Step 1: Acid wash the quartz sand with trifluoromethanesulfonic acid solution, then wash with water and dry to obtain activated quartz sand; Step 2: Knead the cattail stalks and then crush them into cattail fluff; Step 3: After uniformly mixing activated quartz sand, sawdust, cattail fluff and metal salt powder, add it to an ultrasonic disperser and disperse it by wet vibration. Then add sodium hydroxide solution and allow in-situ precipitation reaction to occur under ultrasonic dispersion environment. Filter to obtain the precipitate product. The metal salt powder is a mixture of soluble iron salt and soluble aluminum salt. Step 4: The precipitated product is calcined at 500~510℃ under an inert atmosphere, crushed, washed with water and dried to obtain modified quartz sand.

9. The system or method according to claim 8, characterized in that, The mass ratio of each raw material used in step 3 is as follows: Activated silica sand: sawdust: cattail fluff: metal salt powder = 1:(0.28~0.33):(0.18~0.22):(0.18~0.25).

10. The system or method according to claim 8, characterized in that, In step 3, the moisture content of the wet material during wet dispersion is controlled at 55%~60%.

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