An electronic industry early stage rainwater treatment system and method

Abstract

The application is a kind of electronic industry initial rainwater treatment system and method, comprising: collected initial rainwater is filtered by two stages to remove larger suspended solids and fine particles in water; pumped into the biological retention tank I chamber, flows through the adsorption filler layer to remove most of the heavy metal ions, fluoride ions and cyanate ions in water; the treated initial rainwater enters the biological retention tank II chamber by gravity, the rainwater stays in the biological retention tank II chamber to remove residual COD, fluoride ions, and the microorganisms in the chamber further remove COD and phosphate. The application has the advantages that: the adsorption filler layer can efficiently adsorb and remove heavy metals, fluorides and cyanides in rainwater, reducing the toxic effect on functional microorganisms in the biological retention tank; at the same time, the inverted electrolysis reinforced biological retention tank with upper cathode and lower anode can simultaneously reinforce the removal of COD and fluoride ions and other pollutants, so that the final effluent can meet the direct discharge standard requirements in the "Electronic Industry Water Pollutant Discharge Standard".

Description

TECHNICAL FIELD

[0001] The present application relates to an electronic industry early rainwater treatment system and method, belonging to the technical field of wastewater treatment. BACKGROUND

[0002] Electronic industry includes six categories of electronic product manufacturing industries, namely, electronic special materials, electronic components, printed circuit boards, semiconductor devices, display devices and optoelectronic devices, and electronic terminal products.

[0003] In the production process of electronic industry, the main pollutants include cyanide, sulfide, fluoride, various heavy metals such as copper, zinc, lead, cadmium, chromium, arsenic, nickel, and oil pollutants, ammonia nitrogen, and phosphate, etc. These substances mainly come from raw materials, various products, and waste.

[0004] During transportation, production, and storage, volatile substances will volatilize into the atmosphere, be adsorbed by particulate matter, and fall to the ground through atmospheric deposition. After being washed by rainwater, these harmful substances will enter the early rainwater and form water pollutants. In addition, the residues generated during transportation and stacking will also enter the early rainwater and form water pollutants under the washing of rainwater.

[0005] In December 2020, the Ministry of Ecological Environment released the “Electronic Industry Water Pollutant Discharge Standard” (GB39731-2020), which requires new enterprises to implement it from July 2021, and existing enterprises to implement it from January 2024. Enterprises with accumulated materials (raw materials, fuels, waste residues, etc. stacked in the open air, and garbage storage sites), and dust pollution must include early rainwater in wastewater discharge, and the corresponding main pollutants in water pollution equivalent calculation.

[0006] The composition of early rainwater in electronic enterprises is complex (including SS, COD, ammonia nitrogen, phosphate, heavy metals, cyanide, fluoride, etc.), the concentration is low, and the discharge standard is high.

[0007] In the prior art, early rainwater treatment devices mainly focus on urban road and roof early rainwater treatment.

[0008] CN217103489U discloses a biological retention tank, which includes a submerged layer, a planting layer, a composite filler layer, a gravel drainage layer, and an anaerobic layer. The retention tank adds fly ash to the composite filler layer to improve the pH of red soil, thereby enhancing the adsorption of red soil to phosphorus pollution and improving the water conductivity of red soil. In addition, an anaerobic zone is formed at the bottom of the retention tank, and iron-carbon balls are added to the anaerobic layer to improve the hydrolysis of pollutants, efficiently remove nitrogen and COD, and improve the pollution purification effect. However, the retention tank is only used to remove COD, phosphate, and nitrogen elements, and cannot remove toxic and harmful substances such as heavy metals, cyanide, and fluoride in early rainwater in electronic factories.

[0009] CN115340184A discloses an anti-clogging bioretention tank system and its working method. The bioretention tank mainly relies on pulsed plant filter bed and packing layer to remove organic matter and nitrogen and phosphorus pollutants in water. However, this method still cannot remove pollutants such as heavy metals, cyanide, and fluoride from initial rainwater.

[0010] CN115095007A discloses a rainwater runoff purification system for mountainous riverside roads. This system primarily removes petroleum hydrocarbons, suspended solids, organic matter, and nutrients from initial rainwater through an interception system, oil separation and sedimentation, filtration and adsorption, and plant purification. While the system mainly utilizes the filtration effect of expanded clay particles and plant roots to remove suspended solids and nutrients, it struggles to remove toxic and harmful substances such as heavy metals, cyanides, and fluorides.

[0011] CN115095007A discloses an in-situ rainwater leaching remediation system for contaminated soil. In this system, the leaching wastewater mainly removes organic pollutants through a microbial introduction tank, and then electrolyzes heavy metals through an electric separation tank to obtain purified rainwater leaching liquid. However, this system lacks the ability to remove major pollutants such as fluoride ions and thiocyanate ions from the initial rainwater of electronics factories.

[0012] CN214936329U discloses a rainwater bioretention tank in which an electric current is passed through microbial-encapsulated balls, allowing electrons in the current to act on the nitrification and denitrification processes of the microorganisms, thereby enhancing these processes. However, this bioretention tank does not employ a closed-loop design, resulting in weaker electron transfer and transmission. Furthermore, the upper anode and lower cathode structure of the retention tank also limits its effectiveness in removing heavy metals, fluoride ions, and thiocyanate ions from the initial water in the electronics factory.

[0013] In summary, there is a need to develop a new technology that can be applied to the initial rainwater pollution control of electronics enterprises, capable of removing both conventional pollutants and toxic and harmful substances, including heavy metals, fluoride ions, and thiocyanate. Summary of the Invention

[0014] The present invention proposes a system and method for treating initial rainwater in the electronics industry, which aims to overcome the above-mentioned shortcomings of the existing technology and achieve effective treatment of initial rainwater in the electronics industry.

[0015] The technical solution of the present application: an electronic industry initial rainwater treatment system, which comprises a biological retention tank I chamber and a biological retention tank II chamber arranged adjacently from top to bottom, the biological retention tank I chamber comprises a first sandy soil layer, a gravel layer and an adsorption filler layer arranged in sequence from top to bottom, plants are planted in the first sandy soil layer, the roots of the plants extend through the gravel layer to the upper part of the adsorption filler layer in sequence, the biological retention tank II chamber comprises a second sandy soil layer, an initial rainwater inlet is arranged at the top of one side of the adsorption filler layer, the adsorption filler layer is communicated with the top of the corresponding side of the second sandy soil layer through a water delivery pipe, and a water outlet pipe is arranged downward at the bottom of the other side of the second sandy soil layer.

[0016] Preferably, a cathode is arranged in the upper part of the adsorption filler layer, a first insulating layer is arranged at the bottom of the adsorption filler layer, an anode is arranged in the lower part of the second sandy soil layer, a second insulating layer is arranged at the bottom of the second sandy soil layer, and the cathode and the anode are connected through a wire with a resistor. The electrolytic strengthening biological retention tank can strengthen the removal of COD and fluorine ions and other pollutants.

[0017] Preferably, the plants are cattails and / or reeds.

[0018] Preferably, the height-diameter ratio of the first sandy soil layer is 0.2:1-0.4:1.

[0019] Preferably, the particle size of the gravel layer is 20-40 mm, and the height-diameter ratio is 0.1:1-0.2:1.

[0020] Preferably, the adsorption filler layer is composed of activated carbon composite material loaded with calcium carbonate and barium carbonate, the volume ratio is 9:1-7:3, and the height-diameter ratio of the adsorption bed layer is 0.2:1-0.4:1.

[0021] Preferably, the preparation method of the activated carbon composite material loaded with calcium carbonate and barium carbonate comprises the following steps:

[0022] 1) After the granular activated carbon is washed with water, it is dried at 120 DEG C for standby use;

[0023] 2) The dried activated carbon particles are weighed and added to a mixed solution of 1 mol / L calcium chloride and barium chloride, stirred at room temperature for 2 h, and the volume ratio of the activated carbon to the solution is 1:2;

[0024] 3) Under stirring conditions, an equal volume of 1 mol / L sodium carbonate solution is added dropwise to the mixed solution within 2 h, and after the dropwise addition is completed, it is reacted for another 0.5 h to obtain the composite material, and the filtered composite material is washed with water until no chlorine ions are present;

[0025] 4) The washed composite material is dried at 120 DEG C to obtain the activated carbon composite material loaded with calcium carbonate and barium carbonate.

[0026] Preferably, the second sandy soil layer has a height-diameter ratio of 1:1-2:1.

[0027] Preferably, the cathode and the anode are made of graphite felt, and the power supply voltage is 4-6V.

[0028] An electronic industry initial rainwater treatment method using the electronic industry initial rainwater treatment system, comprising the following steps:

[0029] Step S1: The collected initial rainwater is filtered through screens with pore diameters of 1mm and 0.5mm respectively to remove large suspended solids and fine particles in the water;

[0030] Step S2: The initial rainwater filtered in step S1 is pumped into the biological retention tank I chamber and flows through the adsorption filler layer from one side to the other side at a rate of 2-5BV / h, V being the volume of the adsorption filler layer, to remove most of the heavy metal ions, fluoride ions and cyanate ions in the water;

[0031] Step S3: The initial rainwater treated in S2 is introduced into the biological retention tank II chamber by gravity, and the rainwater stays in the biological retention tank II chamber for 5-10h to remove residual COD and fluoride ions, and the microorganisms in the chamber further remove COD and phosphate.

[0032] The electronic industry initial rainwater treatment system of the present application has the advantages of reasonable system structure and method design, the adsorption filler layer can efficiently adsorb and remove heavy metals, fluorides and cyanides in the rainwater, and reduce the toxic effect on the functional microorganisms in the biological retention tank; meanwhile, the inverted electrolysis of the upper cathode and the lower anode strengthens the biological retention tank, the electrodes can simultaneously strengthen the removal of COD and fluoride ions and other pollutants, and the final effluent can meet the direct discharge standard requirements in the "Electronic Industry Water Pollutant Discharge Standard" GB39731-2020. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a cross-sectional structure schematic view of the electronic industry initial rainwater treatment system of the present application.

[0034] Figure 2 is a top view of Figure 1

[0035] Figure 3 is a schematic view of the electrode arrangement in Figure 1

[0036] In the figure, 1 is a plant, 2 is a first sandy soil layer, 3 is a gravel layer, 4 is an adsorption filler layer, 5 is a cathode, 6 is a first insulating layer, 7 is a second sandy soil layer, 8 is an anode, and 9 is a second insulating layer. DETAILED DESCRIPTION

[0037] ​​The application will be further described in detail below in connection with the embodiments and specific implementation manners.

[0038] An electronic industry initial rainwater treatment method, comprising the following steps:

[0039] The collected initial rainwater is first filtered through two stages to remove large suspended solids and fine particles such as silt in the water.

[0040] Then the initial rainwater enters the biological retention tank I chamber, and the heavy metal ions, fluoride ions and cyanate ions in the rainwater are removed by adsorption after the initial rainwater flows through the adsorption filler layer at a certain rate from left to right; in addition, the active oxygen species produced by the cathode can also degrade COD in the water, and stimulate the physiological metabolism of plant root systems to strengthen the removal of heavy metal ions, phosphates and nitrates in the rhizosphere microenvironment.

[0041] After the treated rainwater flows into the biological retention tank II chamber, oxygen is produced by the anode in the chamber during the residence period, which changes the redox environment in the lower area of the biological retention tank II chamber, realizes the oxidative degradation of residual COD in the area, and directly electro-oxidizes residual fluoride ions, so that the two pollutants are deeply purified. At the same time, the anode and the cathode are connected by a wire with a resistor to form an electric closed circuit state, which promotes electron transfer and strengthens the electrode purification function of the I and II chambers. In addition, the microorganisms in the chamber can further remove COD and phosphates in the rainwater to achieve the purpose of deep purification.

[0042] As shown in Figures 1-3 An electronic industry initial rainwater treatment system, which comprises a biological retention tank I chamber and a biological retention tank II chamber arranged adjacently from top to bottom, the biological retention tank I chamber comprises a first sandy soil layer 2, a gravel layer 3, an adsorption filler layer 4 and a first insulation layer 6 arranged in sequence from top to bottom, plants 1 are planted in the first sandy soil layer 2, the roots of the plants 1 extend through the gravel layer 3 to the upper part of the adsorption filler layer 4 in sequence from the first sandy soil layer 2, a cathode 5 is arranged in the upper part of the adsorption filler layer 4, the biological retention tank II chamber comprises a second sandy soil layer 7 and a second insulation layer 9 arranged from top to bottom, an anode 8 is arranged in the lower part of the second sandy soil layer 7, the cathode 5 and the anode 8 are connected by a wire with a resistor, a rainwater inlet is arranged at the top of one side of the adsorption filler layer 4, a water conveying pipe is arranged between the top of the other side of the adsorption filler layer 4 corresponding to the second sandy soil layer 7 and the bottom of the other side of the second sandy soil layer 7, and a water outlet pipe is arranged downward through the second insulation layer 9 at the bottom of the other side of the second sandy soil layer 7.

[0043] The plants 1 can be selected from Typha and / or reed.

[0044] The first sandy soil layer 2 can be selected from ordinary sandy soil, and the height-diameter ratio is 0.2:1-0.4:1.

[0045] The gravel layer 3 can have a particle size of 20-40 mm and a height-diameter ratio of 0.1:1-0.2:1.

[0046] The adsorption filler layer 4 can be composed of activated carbon composite material loaded with calcium carbonate and barium carbonate, with a composition volume ratio of 9:1-7:3, and a height-diameter ratio of the adsorption bed layer of 0.2:1-0.4:1.

[0047] As an embodiment, the preparation method of the activated carbon composite material loaded with calcium carbonate and barium carbonate includes the following steps:

[0048] 1) After the granular activated carbon is washed with water, it is dried at 120°C for standby use;

[0049] 2) A certain amount of dried activated carbon particles are weighed and added to a mixed solution of calcium chloride and barium chloride with a volume of 1 mol / L, stirred at room temperature for 2 h, wherein the volume ratio of activated carbon to solution is 1:2;

[0050] 3) Under stirring conditions, an equal volume of 1 mol / L sodium carbonate solution is added dropwise to the mixed solution within 2 h, and after the dropwise addition is completed, it is reacted for another 0.5 h to obtain the activated carbon composite material loaded with calcium carbonate and barium carbonate. The filtered composite material is washed with water until no chloride ions are present;

[0051] 4) The washed composite material is dried at 120°C to obtain the activated carbon composite material in the adsorption filler layer 4.

[0052] The second sandy soil layer 7 can have a height-diameter ratio of 1:1-2:1.

[0053] The cathode 5 and the anode 8 can be made of graphite felt, with a power supply voltage of 4-6V, and the power supply can be a storage battery and a solar power supply system.

[0054] According to the above structure, specifically, an electronic industry initial rainwater treatment method includes the following steps:

[0055] Step S1: The collected initial rainwater is filtered through filter screens with pore sizes of 1 mm and 0.5 mm, respectively, to remove larger suspended solids and fine particles such as silt in the water after two-stage filtration.

[0056] Step S2: The filtered initial rainwater in step S1 is pumped into the biological retention tank I chamber, and the initial rainwater flows through the adsorption filler layer 4 at a rate of 2-5 BV (volume of the adsorption filler layer 4) / h from one side to the other side (e.g. from left to right) of the adsorption filler layer 4. During the contact of the rainwater with the adsorption filler layer 4, the heavy metal ions, fluoride ions and cyanate ions in the water are removed by adsorption. In addition, the cathode 5 can also use the oxygen released by the plant 1 root system and the oxygen-rich surface water to produce reactive oxygen species to degrade COD, while stimulating the physiological metabolism of the plant 1 root system and strengthening the removal of heavy metal ions, phosphates and nitrates in the rhizosphere microenvironment. In addition, the plants 1 such as cattails and / or reeds can enrich heavy metals in the plants through root absorption and adsorption, and realize ion transfer of the adsorption filler layer 4 through plant harvesting. In addition, the plants 1 can also absorb nitrogen, phosphorus and COD in the water, thereby reducing the concentration of pollutants in the water and realizing the growth of the plants 1.

[0057] Step S3: The initial rainwater treated in S2 enters the biological retention tank II chamber by gravity. The rainwater stays in the biological retention tank II chamber for 5-10 h, during which the anode 8 produces oxygen, changes the redox environment in the lower layer area of the biological retention tank II chamber, realizes the oxidative degradation of residual COD in the area, and directly electro-oxidizes residual fluoride ions, thereby deeply purifying the two pollutants. At the same time, the anode 5 and the cathode 8 are connected by a wire with a resistor to form an electric closed circuit state, which promotes electron transfer and strengthens the electrode purification function of the I and II chambers. In addition, the microorganisms in the chamber can further remove COD and phosphates in the rainwater to achieve the purpose of deep purification. Embodiment

[0058] Step S1: The collected initial rainwater (COD 375 mg / L, ammonia nitrogen 55 mg / L, total phosphorus 3.5 mg / L, SS 485 mg / L, fluoride ions 25 mg / L, cyanate 1.3 mg / L, copper ions 3.5 mg / L) is filtered through two-stage filter screens of 1 mm and 0.5 mm to remove larger particles such as leaves, weeds, cement blocks, plastic bags, and small particles such as silt, dust, and large suspended solids.

[0059] Step S2: After filtering in step S1, the initial rainwater enters the biological retention tank I chamber at a rate of 2BV / h. The tank is planted with cattails, and the sand layer 2 has a height-diameter ratio of 0.2:1. The gravel layer 3 has a particle size of 20mm and a height-diameter ratio of 0.1:1. The adsorption filler layer is composed of activated carbon composite material loaded with calcium carbonate and barium carbonate, and the adsorption bed has a height-diameter ratio of 0.2:1. After adsorption through the adsorption filler layer, absorption and adsorption by cattail roots, and oxidation by electrodes, the removal rates of fluoride ions, cyanate, heavy metals, refractory organic matter, COD, ammonia nitrogen, and phosphate in the initial rainwater are 85%, 87%, 92%, 87%, 40%, 55%, and 63%, respectively.

[0060] Step S3: The initial rainwater treated in S2 is introduced into the electrode-enhanced rainwater biological retention tank II chamber by gravity. The sand layer 7 in the chamber has a height-diameter ratio of 1:1, and the electrode voltage is 4V. The rainwater stays in the tank II chamber for 5h. Under the synergistic action of current and microorganisms in the tank, the remaining COD, ammonia nitrogen, and phosphate in the initial rainwater can be removed by 91%, 92%, and 94%, respectively. The effluent fully meets the direct discharge standard requirements in GB39731-2020 of the "Water Pollutant Discharge Standard for Electronic Industry". Embodiment

[0061] Step S1: The collected initial rainwater (COD 375mg / L, ammonia nitrogen 55mg / L, total phosphorus 3.5mg / L, SS 485mg / L, fluoride ions 25mg / L, cyanate 1.3mg / L, copper ions 3.5mg / L) is filtered through two-stage filter screens of 1mm and 0.5mm to remove larger particles such as leaves, weeds, cement blocks, plastic bags, and small particles such as silt, dust, and large suspended solids.

[0062] Step S2: After filtering in step S1, the initial rainwater enters the biological retention tank I chamber at a rate of 3BV / h. The tank is planted with reeds, and the sand layer 2 has a height-diameter ratio of 0.3:1. The gravel layer 3 has a particle size of 30mm and a height-diameter ratio of 0.15:1. The adsorption filler layer is composed of activated carbon composite material loaded with calcium carbonate and barium carbonate, and the adsorption bed has a height-diameter ratio of 0.3:1. After adsorption through the adsorption filler layer, absorption and adsorption by cattail roots, and oxidation by electrodes, the removal rates of fluoride ions, cyanate, heavy metals, refractory organic matter, COD, ammonia nitrogen, and phosphate in the initial rainwater are 95%, 98%, 97%, 92%, 53%, 65%, and 73%, respectively.

[0063] Step S3: The S2 treated initial rainwater is introduced into the electrode enhanced rainwater bioretention pool II chamber by gravity, the sand layer 7 has a height-diameter ratio of 1.5:1, and the electrode voltage is 5V. The rainwater stays in the bioretention pool II chamber for 8h, and under the synergistic effect of the current and microorganisms in the bioretention pool, 95% of the residual COD in the initial rainwater can be removed, 96% of the ammonia nitrogen can be removed, and 97% of the phosphate can be removed, and the effluent completely meets the direct discharge standard requirements in GB39731-2020 of the Water Pollutant Discharge Standard for Electronic Industry. Embodiment

[0064] Step S1: The collected initial rainwater (COD 375mg / L, ammonia nitrogen 55mg / L, total phosphorus 3.5mg / L, SS 485mg / L, fluoride ion 25mg / L, cyanate 1.3mg / L, and copper ion 3.5mg / L) is filtered through two-stage filter screens with a mesh size of 1mm and 0.5mm to remove larger particles such as leaves, weeds, cement blocks, plastic bags, and small particles such as silt, dust, and large suspended solids.

[0065] Step S2: The initial rainwater filtered in step S1 is introduced into the bioretention pool I chamber at a flow rate of 5BV / h, the bioretention pool I chamber is planted with cattails, the sand layer 2 has a height-diameter ratio of 0.4:1, the gravel layer 3 has a particle size of 40mm and a height-diameter ratio of 0.2:1, and the adsorption filler layer is composed of activated carbon composite material loaded with calcium carbonate and barium carbonate, and the adsorption bed layer has a height-diameter ratio of 0.4:1. After adsorption by the adsorption filler layer, absorption and adsorption by the cattail root system, and oxidation by the electrode, the removal rates of fluoride ion, cyanate, heavy metal, refractory organic matter, COD, ammonia nitrogen, and phosphate in the initial rainwater are 93%, 99%, 94%, 90%, 67%, 75%, and 82%, respectively.

[0066] Step S3: The S2 treated initial rainwater is introduced into the electrode enhanced rainwater bioretention pool II chamber by gravity, the sand layer 7 has a height-diameter ratio of 2:1, and the electrode voltage is 6V. The rainwater stays in the bioretention pool II chamber for 10h, and under the synergistic effect of the current and microorganisms in the bioretention pool, 97% of the residual COD in the initial rainwater can be removed, 98% of the ammonia nitrogen can be removed, and 97% of the phosphate can be removed, and the effluent completely meets the direct discharge standard requirements in GB39731-2020 of the Water Pollutant Discharge Standard for Electronic Industry.

[0067] According to the results of Embodiments 1-3, it can be seen that the electronic industry initial rainwater treatment system and method can be used for initial rainwater treatment in an electronic enterprise factory area.

[0068] The above merely describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application.

Claims

1. An electronic industry initial rainwater treatment system, characterized by, The system comprises a bioretention tank I and a bioretention tank II arranged adjacently, the bioretention tank I comprises a first sand layer (2), a gravel layer (3) and an adsorption filler layer (4) arranged in sequence from top to bottom, the first sand layer (2) is planted with plants (1), the roots of the plants (1) extend from the first sand layer (2) to the adsorption filler layer (4) through the gravel layer (3) in sequence, the bioretention tank II comprises a second sand layer (7), a primary rainwater inlet is arranged at the top of one side of the adsorption filler layer (4), the adsorption filler layer (4) and the second sand layer (7) are communicated through a water delivery pipe between the top of the other side of the adsorption filler layer (4) and the top of the corresponding side of the second sand layer (7), and a water outlet pipe is arranged at the bottom of the other side of the second sand layer (7); The adsorption filler layer (4) is composed of the activated carbon composite material loaded with calcium carbonate and barium carbonate, and the volume ratio is 9:1-7:3, and the height-diameter ratio of the adsorption bed layer is 0.2:1-0.4:1; The preparation method of the activated carbon composite material loaded with calcium carbonate and barium carbonate comprises the following steps: 1) The granular activated carbon is cleaned with water and then dried at 120 DEG C for standby use; 2) The dried activated carbon particles are weighed and added into a mixed solution of 1 mol / L calcium chloride and barium chloride, and stirred for 2 hours at room temperature, and the volume ratio of the activated carbon to the solution is 1:2; 3) Under the stirring condition, an equal volume of 1 mol / L sodium carbonate solution is added dropwise into the mixed solution within 2 hours, and after the dropwise addition is completed, the reaction is continued for 0.5 hours, so that the composite material is obtained, and the filtered composite material is cleaned with water until no chlorine ions are present; 4) The cleaned composite material is dried at 120 DEG C, and the activated carbon composite material loaded with calcium carbonate and barium carbonate is obtained.

2. An electronic industry initial rainwater treatment system as claimed in claim 1, characterized in that, The plants (1) are cattails and / or reeds.

3. An electronic industry initial rainwater treatment system as claimed in claim 1, characterized in that, The height-diameter ratio of the first sand layer (2) is 0.2:1-0.4:

1.

4. An electronic industry initial rainwater treatment system as claimed in claim 1, characterized in that, The particle size of the gravel layer (3) is 20-40 mm, and the height-diameter ratio is 0.1:1-0.2:

1.

5. An electronic industry initial rainwater treatment system as claimed in claim 1, characterized in that, The height-diameter ratio of the second sand layer (7) is 1:1-2:

1.

6. An electronic industry initial rainwater treatment system as claimed in claim 1, characterized in that, The materials of the cathode (5) and the anode (8) are graphite felt, and the power voltage is 4-6 V.

7. An electronic industry initial rainwater treatment method, characterized by, The system comprises the following steps: Step S1: The collected primary rainwater is filtered through filter screens with hole diameters of 1 mm and 0.5 mm in sequence to remove larger suspended solids and fine particles in the water; Step S2: The primary rainwater filtered in step S1 is pumped into the bioretention tank I, and flows through the adsorption filler layer at a rate of 2-5 BV / h from one side to the other side of the adsorption filler layer, V being the volume of the adsorption filler layer, so that most of the heavy metal ions, fluoride ions and cyanate ions in the water are removed; Step S3: The S2 treated initial rainwater enters the bioretention tank II chamber by gravity, and the rainwater stays in the bioretention tank II chamber for 5-10 hours to remove residual COD, fluoride ions, and the microorganisms in the chamber further remove COD and phosphate.

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