A kind of pretreatment method of wastewater containing benzene

Abstract

The invention discloses a pretreatment method for benzene-containing wastewater, comprising: step 1): using a horizontal flow sedimentation tank to carry out oil separation treatment on the benzene-containing wastewater, during the process of the sewage passing through the sedimentation tank, the solid suspended matter therein is gradually deposited to the mud bucket at the bottom of the sedimentation tank, and then enters the next process through overflow; step 2): the sewage treated by horizontal flow sedimentation is transported to a targeted adsorption device, the resin in the targeted adsorption device adsorbs the benzene series in the sewage, and then the benzene series is recycled by regeneration and desorption; step 3): the sewage obtained after the treatment in step 2) is transported to a coupled oxidation device, the treatment process of the coupled oxidation device is to carry out continuous oxidation treatment on the sewage by using a combined oxidation treatment process of pulse electrocoagulation oxidation + Fenton oxidation, the target pollutant benzene series is subjected to ring-opening and chain-breaking, and then the reagent oxidation is carried out; the invention enables the sewage to meet the requirements of entering biochemical treatment after the above pretreatment steps.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a pretreatment method for benzene-containing wastewater. Background Art

[0002] o-Chlorotoluene, also known as 2-chlorotoluene, is an organic compound with the chemical formula C7H7Cl. It is a colorless transparent liquid that can be dissolved in a variety of organic solvents such as benzene, toluene, alcohol, ether, ketone, butyl acetate, 1,2-dichloroethane, chloroform, etc. It is mainly used as an intermediate for dyes, medicines, organic synthesis, and a solvent for rubber and synthetic resins. p-Chlorotoluene, also known as 4-chlorotoluene, is an organic compound with the chemical formula C7H7Cl. It is mainly used as an intermediate for dyes, medicines, and organic synthesis, and can also be used as a solvent. In summary, o-chlorotoluene and p-chlorotoluene are both important intermediates for medicines and dyes and have a wide range of uses.

[0003] The above benzene-containing wastewater is difficult to treat because of its high concentration of benzene series and stable benzene ring. The simple oxidation process consumes a large amount of reagents, while biochemical treatment cannot meet the biochemical treatment water inlet requirements, and the treatment effect is poor. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a pretreatment method for benzene-containing wastewater, which can solve the problems raised in the background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a pretreatment method for benzene-containing wastewater, which comprises the following steps:

[0006] Step 1): using a horizontal flow sedimentation tank to separate the benzene-containing wastewater from oil. When the wastewater passes through the sedimentation tank, the solid suspended matter therein gradually settles to the mud bucket at the bottom of the sedimentation tank, and then enters the next process through overflow;

[0007] Step 2): The sewage after the advection sedimentation treatment is transported to the targeted adsorption device, and the benzene series in the sewage is adsorbed by the resin in the targeted adsorption device, and then the benzene series are recycled by regeneration and desorption, and the benzene series pollutants in the sewage are significantly reduced;

[0008] Step 3): The wastewater obtained after the treatment in step 2) is transported to a coupled oxidation device, wherein the treatment process of the coupled oxidation device is to continuously oxidize the wastewater using a combined oxidation treatment process of pulse electrocoagulation oxidation + Fenton oxidation, to perform ring-opening and chain-breaking on the target pollutant benzene, and then to perform chemical oxidation to reduce the content of benzene.

[0009] Preferably, the process indicators of the benzene-containing wastewater before treatment in step 1) are: temperature 40-50°C, COD content 3500-3750 mg / L, pH 6-7, benzene content ≤3250 mg / L, ammonia nitrogen ≤50 ppm, and suspended matter content ≤500 mg / L.

[0010] Preferably, 3-4 baffles 4 are arranged in the horizontal flow sedimentation tank. After the sewage hits the baffles 4 in the water flow direction and forms collision, the suspended matter therein is deposited into the mud bucket of the sedimentation tank under the action of gravity.

[0011] Preferably, the targeted adsorption device is filled with a macroporous adsorption resin that can have a significant adsorption effect on benzene series substances, and a sand filter device is also provided at the front end of the targeted adsorption device.

[0012] Preferably, in step 3), the coupled oxidation device treatment process specifically comprises the following steps:

[0013] Step 3.1): Pulse electrocoagulation oxidation: After the sewage is treated in step 2), it is transported to the pulse electrocoagulation device. By applying a certain voltage and current to the electrocoagulation electrode, the sewage is electrolytically oxidized, and the macromolecular organic matter is finally converted into small molecular organic matter, which reduces the difficulty of oxidation;

[0014] Step 3.2): The wastewater treated in the above step flows to the reaction tank by gravity, and hydrogen peroxide and ferrous sulfate are added to react, and the COD in the wastewater is further degraded through the Fenton reaction, thereby reducing the load of the subsequent biochemical treatment steps.

[0015] Preferably, the horizontal flow sedimentation tank comprises a tank body, wherein a liquid inlet and a liquid outlet are respectively provided at the upstream and downstream of the tank body, and a plurality of flippable baffles are evenly spaced between the liquid inlet and the liquid outlet.

[0016] Preferably, a fixed shaft is passed through the center of the baffle, the bottom of the fixed shaft is fixed to the bottom of the pool body, rope rods are provided on both sides of the top of the baffle, and a fixed rope rod is provided on the top of the pool body corresponding to the baffle. Both rope rods are connected to the fixed rope rod through a long connecting rope, and one of the rope rods close to the fixed rope rod is also connected to the fixed rope rod through an anchor cable.

[0017] Preferably, when the impurities are fully adhered to the liquid-facing side of the baffle, the anchor cable is untied, and the long connecting rope is pulled so that the rope rod drives the baffle to rotate 180° around the fixed axis, and the rope rod close to the fixed rope rod is reconnected to the fixed rope rod through the anchor cable.

[0018] Beneficial effects of the present invention:

[0019] The present invention uses targeted adsorption to carry out targeted adsorption on sewage, so that the content of benzene series substances that need to be treated is significantly reduced, and the residual liquid after desorption can be reused for production; secondly, through the pulse electrocoagulation oxidation process in the coupled oxidation, the benzene series substances can be ring-opened and chain-broken, and then re-oxidized through Fenton oxidation, which can not only improve the Fenton oxidation efficiency, but also further convert the benzene series organic molecules into organic substances with two or three carbon atoms, greatly improving the efficiency of subsequent biochemical treatment;

[0020] The present invention rotates the baffle plate so that after the position change, the clean side faces upstream and the side full of impurities faces downstream. In this way, the baffle effect and sedimentation efficiency of the baffle plate can be quickly restored, and after a period of time, the impurities adhered to the surface of the side full of impurities will leave with the water flow, thereby achieving a self-cleaning effect. Therefore, the above steps can be performed once every period of time without the need for manual cleaning of the baffle plate, which greatly reduces the labor intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the advection sedimentation tank involved in the present invention;

[0022] Figure 2 for Figure 1 Schematic diagram of the top view structure. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] A method for pretreating benzene-containing wastewater comprises the following steps:

[0025] Step 1): Use a horizontal flow sedimentation tank to separate the benzene-containing wastewater from oil. When the wastewater passes through the sedimentation tank, the solid suspended matter in the wastewater gradually settles to the mud bucket at the bottom of the sedimentation tank, and then enters the next process through overflow; the horizontal flow sedimentation tank is used for sedimentation treatment to reduce the suspended matter in the water quality from 500 mg / L to below 100 mg / L.

[0026] Step 2): The sewage after the horizontal flow sedimentation treatment is transported to the targeted adsorption device, and the benzene series in the sewage is adsorbed by the resin in the targeted adsorption device, and then the benzene series are recycled by regeneration and desorption, and the benzene series pollutants in the sewage are significantly reduced; through this step, the benzene series content in the water quality can be reduced from 3250 mg / L to below 325 mg / L, and the inlet pH is controlled at about 6-7.

[0027] Step 3): The wastewater obtained after the treatment in step 2) is transported to a coupled oxidation device, wherein the coupled oxidation device treatment process is to continuously oxidize the wastewater using a combined oxidation treatment process of pulse electrocoagulation oxidation + Fenton oxidation, to perform ring-opening and chain-breaking on the target pollutant benzene series, and then to perform chemical oxidation to reduce the content of benzene series. This step can reduce the content of benzene series from 325 mg / L to about 32.5 mg / L.

[0028] Preferably, the process indicators of the benzene-containing wastewater before treatment in step 1) are: temperature 40-50°C, COD content 3500-3750 mg / L, pH 6-7, benzene content ≤3250 mg / L, ammonia nitrogen ≤50 ppm, and suspended matter content ≤500 mg / L.

[0029] Preferably, 3-4 baffles 4 are arranged in the horizontal flow sedimentation tank, and after the sewage hits the baffles 4 in the water flow direction, the suspended matter therein is deposited into the mud bucket of the sedimentation tank under the action of gravity. In this embodiment, the suspended matter in the sewage can reduce its flow rate through the collision process when passing through the baffles 4, and continuously settle to the mud bucket at the bottom of the sedimentation tank under the action of gravity, thereby improving the sedimentation efficiency.

[0030] Preferably, the targeted adsorption device is filled with a macroporous adsorption resin that can have a significant adsorption effect on benzene series, and a sand filter device is also provided at the front end of the targeted adsorption device. The function of the sand filter device is to further reduce the content of suspended matter in the wastewater, reduce the fouling of the adsorption device in the later stage, and reduce the adsorption resin clogging caused by suspended fouling in the adsorption device. The benzene substances in the wastewater are selectively and directionally adsorbed by high-efficiency adsorbents, and the concentrated organic matter obtained after chromatography and analysis can be separated and purified to achieve the recycling of organic matter in the wastewater. The adsorbent after adsorption saturation is regenerated by a forced regeneration process to achieve recycling.

[0031] Preferably, in step 3), the coupled oxidation device treatment process specifically comprises the following steps:

[0032] Step 3.1): Pulse electrocoagulation oxidation: After being treated in step 2, the sewage is transported to a pulse electrocoagulation device, where a certain voltage and current are applied to the electrocoagulation plates to electrolytically oxidize the sewage, and macromolecular organic matter is eventually converted into small molecular organic matter, thereby reducing the difficulty of oxidation. Specifically, the wastewater completes oxidation and reduction reactions in the pulse electrocoagulation reactor, and the benzene series in the sewage is further oxidized from 325 mg / L to below 292.5 mg / L.

[0033] The electrocoagulation oxidation optimization process is adopted, that is, during the electrocoagulation oxidation process, oxidation derivatives will be produced and attached to the electrocoagulation electrode plate. In this process, a scraper is used to continuously scrape the derivatives produced by oxidation from above the sewage to the scum bucket. The oxidative degradation mechanism of chlorobenzene by pulse electrocoagulation + Fenton process is mainly based on the oxidative degradation of strong oxidizing free radical ·OH. The reaction mechanism is as follows: the primary products of oxidative degradation of chlorobenzene and dichlorobenzene by ·OH are phenol and HCl, and the intermediate product is unstable chlorobenzene hydrate dichlorobenzene, which can be obtained through the following two pathways: one is that O.DCB is attacked by ·OH. Since Cl is an ortho-para positioning group, ·OH easily attacks the carbon atom on its ortho-para position, firstly quickly generating 2,3-dichlorophenol and 3,4-dichlorophenol, and then the chlorine atoms on the benzene ring are successively nucleophilically replaced / eliminated by OH to generate l,2,3.trihydroxybenzene and l,2,4.trihydroxybenzene; the other is that one chlorine atom on O is nucleophilically replaced / eliminated by OH to generate 2.chlorophenol, and then the other chlorine atom is subsequently replaced / eliminated to generate o-dihydroxybenzene. Since there is ·OH on the adjacent carbon, the compound is extremely unstable and easily undergoes isomerization, and dehydrates to generate carbonyl compounds. The 1,2,3-trihydroxybenzene, 1,2,4-trihydroxybenzene, o-dihydroxybenzene, and carbonyl compounds generated above are easily oxidized and undergo ring opening to generate low molecular weight organic matter. These small molecular weight organic matter are gradually and completely mineralized into CO2 and H2O as the degradation reaction proceeds.

[0034] Step 3.2): The sewage treated in the above step flows to the reaction tank, and hydrogen peroxide and ferrous sulfate are added to react, and the COD in the sewage is further degraded through the Fenton reaction, reducing the load of the subsequent biochemical treatment steps. Specifically, the final effluent benzene series is reduced to below 32.5 mg / L.

[0035] In addition, the benzene content and removal rate of different benzene contents after the targeted adsorption device are shown in Table 1 below, and the benzene content and removal rate of different benzene contents after coupled oxidation are shown in Table 2 below.

[0036] Table 1: BTEX content and removal rate of different BTEX contents after targeted adsorption device

[0037]

[0038] Table 2: BTEX content and removal rate after coupled oxidation at different BTEX contents

[0039]

[0040] Preferably, the horizontal flow sedimentation tank comprises a tank body 1, wherein a liquid inlet 2 and a liquid outlet 3 are respectively provided upstream and downstream of the tank body 1, and a plurality of flippable baffles 4 are evenly spaced between the liquid inlet 2 and the liquid outlet 3.

[0041] Preferably, a fixed shaft 5 is passed through the center of the baffle 4, and the bottom of the fixed shaft 5 is fixed to the bottom of the pool body 1. Rope-tying rods 6 are provided on both sides of the top of the baffle 4. A rope-fixing rod 7 is provided on the top of the pool body 1 corresponding to the baffle 4. Both rope-tying rods 6 are connected to the rope-fixing rod 7 through a long connecting rope, and one of the rope-tying rods 6 close to the rope-fixing rod 7 is also connected to the rope-fixing rod 7 through an anchor cable.

[0042] Preferably, when impurities are fully adhered to the liquid-facing side of the baffle 4, the anchor cable is untied, and the long connecting rope is pulled so that the rope tie rod 6 drives the baffle 4 to rotate 180° around the fixed axis 5, and the rope tie rod 6 close to the rope fixing rod 7 is reconnected to the rope fixing rod 7 through the anchor cable.

[0043] Because in the actual production and treatment process, after the baffle 4 contacts the suspended matter in the sewage for a long time, the side of the baffle 4 facing the liquid (i.e. the side close to the upstream) is more likely to adhere to impurities, while the other side of the baffle 4 is not easy to adhere to impurities, because the side (i.e. the side close to the downstream) is where the water flows away, and there is a similar effect of negative pressure. Therefore, when the impurities on the side facing the liquid of the baffle 4 are fully adhered, the impurities are agglomerated, which will cause the water flow in the vicinity of the baffle 4 to be unsmooth, and it is easy to cause blockage and water flow turbulence, affecting the baffle effect and sedimentation efficiency; therefore, by rotating the baffle 4, after the position is changed, the clean side faces upstream, and the side full of impurities faces downstream, so that the baffle effect and sedimentation efficiency of the baffle can be quickly restored, and after a period of time, the impurities adhered to the surface of the side full of impurities will leave with the departure of the water flow, playing a self-cleaning role; therefore, the above steps can be operated once every period of time, without the need to manually clean the baffle, which greatly reduces the labor intensity. In addition, this method of pulling the rope to rotate the baffle 4 is simple, convenient and efficient.

[0044] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for pretreating benzene-containing wastewater, characterized in that: It includes the following steps: Step 1): Use a horizontal flow sedimentation tank to separate the benzene-containing wastewater from oil. When the wastewater passes through the sedimentation tank, the suspended solids in it gradually settle to the mud bucket at the bottom of the sedimentation tank, and then enter the next process through overflow; Step 2): The sewage after the advection sedimentation treatment is transported to the targeted adsorption device, and the benzene series in the sewage is adsorbed by the resin in the targeted adsorption device, and then the benzene series are recycled by regeneration and desorption, and the benzene series pollutants in the sewage are significantly reduced; Step 3): The wastewater obtained after the treatment in step 2) is transported to a coupled oxidation device, wherein the treatment process of the coupled oxidation device is to continuously oxidize the wastewater by using a combined oxidation treatment process of pulse electrocoagulation oxidation + Fenton oxidation, to perform ring-opening and chain-breaking on the target pollutant benzene series, and then to perform chemical oxidation to reduce the content of benzene series; The advection sedimentation tank comprises a tank body (1), wherein a liquid inlet (2) and a liquid outlet (3) are respectively provided upstream and downstream of the tank body (1), and a plurality of reversible baffles (4) are evenly spaced between the liquid inlet (2) and the liquid outlet (3); A fixed shaft (5) is passed through the center of the baffle (4), the bottom of the fixed shaft (5) is fixed to the bottom of the tank body (1), rope tie rods (6) are provided on both sides of the top of the baffle (4), and a rope fixing rod (7) is provided on the top of the tank body (1) corresponding to the baffle (4), both rope tie rods (6) are connected to the rope fixing rod (7) via a long connecting rope, and one of the rope tie rods (6) close to the rope fixing rod (7) is also connected to the rope fixing rod (7) via an anchor cable; When the impurities are fully adhered to the liquid-facing side of the baffle (4), the anchor cable is untied, and the long connecting rope is pulled so that the anchor rod (6) drives the baffle (4) to rotate 180 degrees around the fixed axis (5), and the anchor rod (6) close to the fixed rope rod (7) is reconnected to the fixed rope rod (7) through the anchor cable.

2. A method for pretreating benzene-containing wastewater according to claim 1, characterized in that: The process indicators of the benzene-containing wastewater before treatment in step 1) are: temperature 40-50°C, COD content 3500-3750 mg / L, pH 6-7, benzene content ≤3250 mg / L, ammonia nitrogen ≤50 ppm, and suspended matter content ≤500 mg / L.

3. A method for pretreating benzene-containing wastewater according to claim 1, characterized in that: The horizontal flow sedimentation tank is provided with 3-4 baffles (4). After the sewage hits the baffles (4) in the direction of the water flow and forms a collision, the suspended matter therein is deposited into the mud bucket of the sedimentation tank under the action of gravity.

4. A method for pretreating benzene-containing wastewater according to claim 1, characterized in that: The targeted adsorption device is filled with a macroporous adsorption resin that can have a significant adsorption effect on benzene series substances, and a sand filter device is also arranged at the front end of the targeted adsorption device.

5. A method for pretreating benzene-containing wastewater according to claim 1, characterized in that: In step 3), the coupled oxidation device treatment process specifically includes the following steps: Step 3.1): Pulse electrocoagulation oxidation: After the sewage is treated in step 2), it is transported to the pulse electrocoagulation device. By applying a certain voltage and current to the electrocoagulation electrode, the sewage is electrolytically oxidized, and the macromolecular organic matter is finally converted into small molecular organic matter, which reduces the difficulty of oxidation; Step 3.2): The wastewater treated in the above step flows to the reaction tank by gravity, and hydrogen peroxide and ferrous sulfate are added to react. The COD in the wastewater is further degraded through the Fenton reaction, reducing the load of subsequent biochemical treatment steps.

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