Sewage treatment system and method

Abstract

The invention relates to a sewage treatment system and method.The method comprises the steps that sewage to be treated, a catalyst and an oxidizing agent are mixed in a premixer and then enter a catalytic oxidation reactor to be subjected to a catalytic oxidation reaction, and first treated sewage is obtained; mixing the first treated sewage with alkali liquor in a rear mixer, and then feeding the mixture into a solid-liquid separator for solid-liquid separation to obtain second treated sewage and first waste residue slurry; the second treated sewage is discharged from a drainage line, the first waste residue slurry is divided into two parts, the first part of the first waste residue slurry is discharged from a residue discharge line, the second part of the first waste residue slurry is mixed with acid liquor and then fed into an electro-catalytic reactor for electro-catalytic reaction, a first material is obtained, and the first material is returned to the premixer. According to the sewage treatment system and method, the dosage of the catalyst can be reduced, the sludge yield is reduced, the COD concentration of treated sewage is low, and the sewage treatment effect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a sewage treatment system and method. Background Art

[0002] Refractory industrial wastewater refers to industrial wastewater containing organic matter that is difficult to be biodegraded, including polycyclic aromatic hydrocarbons, organophosphorus pesticides, surfactants, organic dyes, etc. The common characteristics of these substances are high toxicity, complex composition, and difficulty in being degraded by microorganisms. At present, low-concentration wastewater or fresh water is often used for treatment after dilution, or pretreatment + advanced oxidation treatment is used before mixing with low-concentration wastewater for treatment. The current processes have the problems of long treatment process, easy impact on sewage treatment system, and inability to achieve stable discharge standards.

[0003] In industrial wastewater treatment plants, wastewater that has undergone biochemical treatment still contains low-concentration non-biodegradable organic matter, resulting in wastewater that does not meet the requirements of discharge standards. At present, the original process flow is mostly based on the addition of advanced oxidation + biochemical deep treatment to further reduce the content of organic matter. Among them, advanced oxidation units mostly use ozone catalytic oxidation, Fenton and other treatment technologies. The mechanism of Fenton oxidation is to combine catalysts with oxidants to produce highly active free radicals (such as OH) in the reaction; then through the addition, substitution, electron transfer, bond breaking, etc. between free radicals and organic compounds, the macromolecular refractory organic matter in the water body is oxidized and degraded into small molecules that are easy to biodegrade, and even directly degraded into CO2 and H2O, which is close to complete mineralization. Fenton oxidation technology has been widely studied because of its simple operation and fast reaction. However, in practical applications, traditional Fenton oxidation has the problems of large catalyst dosage and large amount of waste residue. In particular, the waste residue produced by Fenton oxidation is usually disposed of as hazardous waste, resulting in high treatment costs for Fenton oxidation treatment, all of which affect the wider application of Fenton oxidation technology in industry.

[0004] CN114180686A discloses a novel Fenton reactor, which proposes a reactor integrating electrocatalysis and Fenton reaction, adding an electric field inside the Fenton reaction system to improve the utilization rate of hydrogen peroxide, reduce the dosage of ferrous iron, and reduce the sludge production. However, the COD concentration of sewage produced by this method is still high.

[0005] Therefore, it is necessary to develop effective methods to reduce the COD concentration of sewage. Summary of the invention

[0006] The purpose of the present invention is to provide a sewage treatment system and method to solve the problem that the COD concentration of sewage treated by the existing Fenton oxidation technology is still high.

[0007] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a sewage treatment system, comprising a pre-mixer, a catalytic oxidation reactor, a post-mixer, a solid-liquid separator and an electrocatalytic reactor connected in sequence; the first inlet of the pre-mixer is connected to a water inlet line, and the water inlet line is connected to a catalyst line and an oxidant line; the pipeline between the catalytic oxidation reactor and the post-mixer is connected to an alkali addition line; the fourth outlet of the solid-liquid separator is connected to a drainage line, and the fifth outlet of the solid-liquid separator is connected to a slag discharge line; the fifth inlet of the electrocatalytic reactor is connected to an acid addition line; the sixth outlet of the electrocatalytic reactor is connected to the water inlet line; the electrocatalytic reactor is a spiral with a central tube, the spiral wall is the anode of the electrocatalytic reactor, and the central tube is the cathode of the electrocatalytic reactor.

[0008] Optionally, a fifth inlet is provided at the lower part of the reactor wall of the electrocatalytic reactor, and a sixth outlet is provided at the upper part, the fifth inlet is connected to the lower part of the outermost circle of the spiral, and the sixth outlet is connected to the upper part of the innermost circle of the spiral.

[0009] Optionally, the first outlet of the pre-mixer is connected to the second inlet of the catalytic oxidation reactor, the second outlet of the catalytic oxidation reactor is connected to the third inlet of the post-mixer, the third outlet of the post-mixer is connected to the fourth inlet of the solid-liquid separator, and the fifth outlet of the solid-liquid reactor is connected to the fifth inlet of the electrocatalytic reactor.

[0010] Optionally, a first pH online probe is provided in the catalytic oxidation reactor, and the pH value is controlled by adjusting the amount of acid added by the regulating valve on the acid addition line; a second pH online probe is provided in the solid-liquid separator, and the pH value is controlled by adjusting the amount of alkali added by the regulating valve on the alkali addition line.

[0011] The second aspect of the present invention provides a sewage treatment method, which adopts the system provided by the first aspect of the present invention, and comprises the following steps:

[0012] S1, mixing the sewage to be treated, the catalyst and the oxidant evenly in a pre-mixer and then entering the catalytic oxidation reactor for catalytic oxidation reaction to obtain first treated sewage;

[0013] S2, mixing the first treated sewage with the alkali solution, continuing to mix in a post-mixer, and then entering a solid-liquid separator for solid-liquid separation to obtain a second treated sewage and a first waste residue slurry; and discharging the second treated sewage from a drainage line;

[0014] S3. Divide the first waste slurry into two streams, wherein the first waste slurry is discharged from the slag discharge line, and the second waste slurry is mixed with acid solution and sent to the electrocatalytic reactor for electrocatalytic reaction to obtain the first material, and the first material is returned to the pre-mixer; wherein the mixed material in the electrocatalytic reactor flows along the lower part of the outermost circle of the spiral body of the electrocatalytic reactor to the upper part of the innermost circle, and rises in a spiral from low to high.

[0015] Optionally, the pH value of the mixture in the catalytic oxidation reactor is <6, preferably 3-5; the pH value of the mixture in the solid-liquid separator is >6, preferably 7-9; the distribution ratio of the second first waste slurry to the first first waste slurry is 0.2-20:1, preferably 0.5-5:1.

[0016] Optionally, the COD concentration of the sewage to be treated is 50-1000 mg / L; the oxidant is one of hydrogen peroxide, sodium hypochlorite and sodium persulfate, preferably hydrogen peroxide, and the dosage of the oxidant is 0.1-10 times the COD concentration, preferably 0.5-4 times; the catalyst is ferrous sulfate or ferrous chloride, preferably ferrous sulfate, and the dosage of the catalyst is preferably 1-4 times the dosage of the oxidant.

[0017] Optionally, the residence time of the sewage to be treated in the catalytic oxidation reactor is 5-1200 min, preferably 30-300 min; the residence time of the first treated sewage in the solid-liquid separator is 20-1200 min, preferably 30-600 min; the residence time of the second first waste slurry in the electrocatalytic reactor is 2-600 min, preferably 20-240 min.

[0018] Optionally, the current density between the cathode and the anode in the electrocatalytic reactor is 0.1 to 1000 A / m 2 , preferably 1 to 500 A / m 2 ; The cathode is one of a ruthenium-iridium electrode, a SnO2 / Ti electrode, a PtO2 / Ti electrode, a graphite electrode, an activated carbon fiber electrode or a Pt electrode, preferably a SnO2 / Ti electrode; the anode is a metal electrode, preferably a stainless steel electrode.

[0019] Through the above technical scheme, the present invention mixes the sewage to be treated with the catalyst and the oxidant in a pre-mixer and then enters the catalytic oxidation reactor for catalytic oxidation reaction, so that the catalyst and the oxidant are combined, and highly active free radicals (such as OH) are generated in the reaction to degrade organic matter in the sewage. At the same time, the electrocatalytic reactor is added to accelerate the utilization rate of the oxidant, reduce the dosage of the catalyst, and reduce the sludge production. The COD concentration of the treated sewage is low, the treatment effect is good, and the treatment cost is low. It is suitable for treating difficult-to-degrade sewage.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 is a schematic diagram of a sewage treatment system of the present invention;

[0023] Figure 2 is a structural diagram of the electrocatalytic reactor of the present invention;

[0024] Figure 3 1 is a top view of the electrocatalytic reactor of the present invention.

[0025] Description of Reference Numerals

[0026] 1-pre-mixer, 2-catalytic oxidation reactor, 3-post-mixer, 4-solid-liquid separator, 5-electrocatalytic reactor;

[0027] S1-first inlet, S2-first outlet, S3-second inlet, S4-second outlet, S5-third inlet, S6-third outlet, S7-fourth inlet, S8-fourth outlet, S9-fifth outlet, S10-fifth inlet, S11-sixth outlet;

[0028] G1-water inlet line, G2-catalyst line, G3-oxidant line, G4-alkali addition line, G5-drainage line, G6-slag discharge line, G7-acid addition line. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0030] In the present invention, unless otherwise stated, the words "first", "second", "third", etc. are used only to distinguish different components and do not have actual meanings such as the order of front and back connection. In the present invention, the directional words used, such as "upper" and "lower", refer to the upper and lower parts of the device in normal use, and "inside" and "outside" refer to the outline of the device.

[0031] A first aspect of the present invention provides a sewage treatment system, such as Figure 1As shown, it includes a pre-mixer 1, a catalytic oxidation reactor 2, a post-mixer 3, a solid-liquid separator 4 and an electrocatalytic reactor 5 connected in sequence; the first inlet S1 of the pre-mixer 1 is connected to a water inlet line G1, and the water inlet line G1 is connected to a catalyst line G2 and an oxidant line G3; the first outlet S2 of the pre-mixer 1 is connected to the second inlet S3 of the catalytic oxidation reactor 2, the second outlet S4 of the catalytic oxidation reactor 2 is connected to the third inlet S5 of the post-mixer 3, and the catalytic oxidation reactor 2 is connected to the post-mixer 3. The pipeline between the reactor 3 is connected with an alkali adding line G4; the third outlet S6 of the post-mixer 3 is connected with the fourth inlet S7 of the solid-liquid separator 4, the fourth outlet S8 of the solid-liquid separator 4 is connected with a drainage line G5, and the fifth outlet S9 of the solid-liquid separator 4 is connected with a slag discharge line G6; the fifth outlet S9 of the solid-liquid reactor 4 is connected with the fifth inlet S10 of the electrocatalytic reactor 5, the fifth inlet S10 is connected with an acid adding line G7, and the sixth outlet S11 of the electrocatalytic reactor 5 is connected to the water inlet line G1; Figure 2 As shown, the electrocatalytic reactor 5 is a spiral body with a central tube, the spiral body wall is the anode of the electrocatalytic reactor 5, and the central tube is the cathode of the electrocatalytic reactor 5.

[0032] The sewage treatment system of the present invention, by providing a catalytic oxidation reactor and an electrocatalytic reactor, can reduce the amount of catalyst added, generate less waste residue, and produce less sludge. The COD concentration of the treated sewage is low, the treatment effect is good, and the treatment cost is low. The system is suitable for treating difficult-to-degrade sewage.

[0033] According to the present invention, optionally, a fifth inlet S10 is provided at the lower portion of the reactor wall of the electrocatalytic reactor 5, and a sixth outlet S11 is provided at the upper portion, wherein the fifth inlet S10 is connected to the lower portion of the outermost circle of the spiral, and the sixth outlet S11 is connected to the upper portion of the innermost circle of the spiral.

[0034] According to the present invention, optionally, a first pH online probe is provided in the catalytic oxidation reactor 2, and the pH value is controlled by adjusting the amount of acid added by the regulating valve on the acid addition line G7; a second pH online probe is provided in the solid-liquid separator 4, and the pH value is controlled by adjusting the amount of alkali added by the regulating valve on the alkali addition line G4.

[0035] The second aspect of the present invention provides a sewage treatment method, which adopts the system provided by the first aspect of the present invention, and comprises the following steps:

[0036] S1, the sewage to be treated, the catalyst and the oxidant are mixed evenly in the pre-mixer 1 and then enter the catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain the first treated sewage;

[0037] S2, mixing the first treated sewage with the alkali solution, continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; discharging the second treated sewage from the drainage line G5;

[0038] S3. Divide the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, and the second stream of the first waste slurry is mixed with the acid solution and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and return the first material to the pre-mixer 1; wherein the flow direction of the mixed material in the electrocatalytic reactor 5 is along the lower part of the outermost circle of the spiral body of the electrocatalytic reactor 5 to the upper part of the innermost circle, and spirally rises from low to high.

[0039] The electrode plate in the electrocatalytic reactor 5 of the present invention is a spiral electrode plate, which has a better mass transfer effect. The mixed material can have a longer time and larger area transmission contact with the anode membrane during the spiral rising process, and the catalytic reduction effect is better.

[0040] The present invention mixes the sewage to be treated with a catalyst and an oxidant in a pre-mixer and then enters a catalytic oxidation reactor for catalytic oxidation reaction, so that the catalyst and the oxidant are combined, and highly active free radicals (such as OH) are generated in the reaction to degrade organic matter in the sewage. At the same time, an electrocatalytic reactor is added to accelerate the utilization rate of the oxidant, reduce the dosage of the catalyst, and reduce the sludge output. The COD concentration of the treated sewage is low, the treatment effect is good, and the treatment cost is low. The present invention is suitable for treating difficult-to-degrade sewage.

[0041] According to the present invention, optionally, the COD concentration of the sewage to be treated is 50-1000 mg / L; the oxidant is one of hydrogen peroxide, sodium hypochlorite and sodium persulfate, preferably hydrogen peroxide, and the dosage of the oxidant is 0.1-10 times the COD concentration, preferably 0.5-4 times; the catalyst is ferrous sulfate or ferrous chloride, preferably ferrous sulfate, and the dosage of the catalyst is preferably 1-4 times the dosage of the oxidant.

[0042] According to the present invention, optionally, the pH value of the mixture in the catalytic oxidation reactor 2 is <6, preferably 3-5; the pH value of the mixture in the solid-liquid separator 4 is >6, preferably 7-9; the distribution ratio of the second first waste slurry to the first first waste slurry is 0.2-20:1, preferably 0.5-5:1; the distribution ratio of the first first waste slurry to the second first waste slurry is within the above range, and the iron-based waste slag can be electro-reduced to produce divalent iron for continued catalytic oxidation reaction, thereby reducing waste slag emissions and reducing the amount of catalyst used.

[0043] The first waste residue slurry in the present invention contains ferric hydroxide. The first waste residue can undergo an acidic reduction reaction in an electrocatalytic reactor under acidic conditions, that is, trivalent iron is converted into divalent iron, and then returned for catalytic oxidation reaction; the amount of catalyst used can be reduced, and the sludge output can be reduced.

[0044] According to the present invention, optionally, the alkali solution is one of sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution, and the acid solution is one of concentrated sulfuric acid solution, concentrated hydrochloric acid solution, nitric acid solution and phosphoric acid solution.

[0045] According to the present invention, optionally, the residence time of the sewage to be treated in the catalytic oxidation reactor 2 is 5-1200 min, preferably 30-300 min; the residence time of the first treated sewage in the solid-liquid separator 4 is 20-1200 min, preferably 30-600 min; the residence time of the second first waste slurry in the electrocatalytic reactor 5 is 2-600 min, preferably 20-240 min.

[0046] According to the present invention, optionally, the current density between the cathode and the anode in the electrocatalytic reactor 5 is 0.1 to 1000 A / m 2 , preferably 1 to 500 A / m 2 ; The cathode is one of a ruthenium-iridium electrode, a SnO2 / Ti electrode, a PtO2 / Ti electrode, a graphite electrode, an activated carbon fiber electrode or a Pt electrode, preferably a SnO2 / Ti electrode; the anode is a metal electrode, preferably a stainless steel electrode.

[0047] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0048] The present invention takes the secondary biochemical effluent (wastewater to be treated) of a petrochemical enterprise's biochemical treatment system as the experimental object, and the basic water quality indicators are shown in Table 1:

[0049] Table 1 Secondary biochemical effluent from a petrochemical wastewater treatment plant

[0050]

[0051] Example 1

[0052] The sewage treatment method of this embodiment comprises the following steps:

[0053] S1, the sewage to be treated, ferrous sulfate (using concentration of 200 mg / L), and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in a pre-mixer 1 and then sent to a catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain a first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0054] S2, mixing the first treated sewage with sodium hydroxide, continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 32.5 mg / L;

[0055] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and returning the first material to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 2:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0056] Example 2

[0057] The sewage treatment method of this embodiment is different from that of Embodiment 1 in that: in the electrocatalytic reactor 5, the cathode is an activated carbon fiber electrode and the anode is a stainless steel electrode; specifically, the following steps are included:

[0058] S1, the sewage to be treated, ferrous sulfate (using concentration of 200 mg / L), and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in a pre-mixer 1 and then sent to a catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain a first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0059] S2, mixing the first treated sewage with sodium hydroxide, continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 34.0 mg / L;

[0060] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and returning the first material to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 2:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is an activated carbon fiber electrode and the anode is a stainless steel electrode.

[0061] Example 3

[0062] The sewage treatment method of this embodiment is different from that of Embodiment 1 in that the ratio of the first first waste slurry to the second first waste slurry is 3:1; the method specifically comprises the following steps:

[0063] S1, the sewage to be treated, ferrous sulfate (using concentration of 200 mg / L), and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in a pre-mixer 1 and then sent to a catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain a first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0064] S2, mixing the first treated sewage with sodium hydroxide, continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 29.8 mg / L;

[0065] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and returning the first material to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 3:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0066] Example 4

[0067] The sewage treatment method of this embodiment is different from that of Embodiment 1 in that the concentration of ferrous sulfate used is 400 mg / L; and specifically comprises the following steps:

[0068] S1, the sewage to be treated, ferrous sulfate (using concentration of 400 mg / L) and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in the pre-mixer 1 and then sent to the catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain the first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0069] S2, mixing the first treated sewage with sodium hydroxide, continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 27.0 mg / L;

[0070] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and returning the first material to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 2:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0071] Example 5

[0072] The sewage treatment method of this embodiment is different from that of Embodiment 1 in that the ratio of the first first waste slurry to the second first waste slurry is 10:1; the method specifically comprises the following steps:

[0073] S1, the sewage to be treated, ferrous sulfate (using concentration of 200 mg / L), and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in a pre-mixer 1 and then sent to a catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain a first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0074] S2, mixing the first treated sewage with sodium hydroxide, continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 48.5 mg / L;

[0075] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and returning the first material to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 10:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0076] Comparative Example 1

[0077] The sewage treatment method of this comparative example is different from that of Example 1 in that the electrode plates in the electrocatalytic reactor 5 are different; specifically, the following steps are included:

[0078] S1, the sewage to be treated, ferrous sulfate (using concentration of 200 mg / L), and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in a pre-mixer 1 and then sent to a catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain a first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0079] S2, mixing the first treated sewage with sodium hydroxide and continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 46.5 mg / L;

[0080] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and the first material is returned to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 2:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the electrode plates (spiral electrode plates) in the electrocatalytic reactor 5 of this embodiment are different from those in Example 1. The electrode plates in this embodiment are ordinary rectangular plates, and the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0081] Comparative Example 2

[0082] The sewage treatment method of this comparative example is different from that of Example 1 in that the first waste slurry does not enter the electrocatalytic reactor 5 for electrocatalytic reaction; specifically, the following steps are included:

[0083] S1, the sewage to be treated, ferrous sulfate (using concentration of 200 mg / L), and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in a pre-mixer 1 and then sent to a catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain a first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0084] S2. After mixing the first treated sewage with sodium hydroxide, continue mixing in the post-mixer 3 and then enter the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste slurry; discharge the second treated sewage from the drainage line G5, and discharge the first waste slurry from the slag discharge line G6; the amount of sodium hydroxide makes the pH of the first treated sewage 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 56.0 mg / L.

[0085] Comparative Example 3

[0086] The sewage treatment method of this comparative example is different from that of Example 1 in that: the first waste slurry does not enter the electrocatalytic reactor 5 for electrocatalytic reaction, and the concentration of ferrous sulfate used is 400 mg / L, and the concentration of hydrogen peroxide used is 200 mg / L; specifically, the following steps are included:

[0087] S1, the sewage to be treated, ferrous sulfate (using concentration of 400 mg / L) and hydrogen peroxide (using concentration of 200 mg / L) are mixed uniformly in the pre-mixer 1 and then sent to the catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain the first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 min;

[0088] S2. After mixing the first treated sewage with sodium hydroxide, continue mixing in the post-mixer 3 and then enter the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste slurry; discharge the second treated sewage from the drainage line G5, and discharge the first waste slurry from the slag discharge line G6; the amount of sodium hydroxide makes the pH of the first treated sewage 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 41.0 mg / L.

[0089] Comparative Example 4

[0090] The sewage treatment method of this comparative example is different from that of Example 1 in that ferrous sulfate and hydrogen peroxide are not added; the method specifically comprises the following steps:

[0091] S1, mixing the sewage to be treated evenly in the pre-mixer 1 to obtain a mixed material;

[0092] S2, mixing the mixed material with sodium hydroxide and continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain a second treated sewage and a first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 60.0 mg / L;

[0093] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and returning the first material to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 2:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0094] Comparative Example 5

[0095] The sewage treatment method of this comparative example is different from that of Example 1 in that no ferrous sulfate is added; the method specifically comprises the following steps:

[0096] S1, the sewage to be treated and hydrogen peroxide (using concentration of 100 mg / L) are mixed uniformly in the pre-mixer 1 and then sent to the catalytic oxidation reactor 2 for catalytic oxidation reaction to obtain the first treated sewage; the residence time in the catalytic oxidation reactor 2 is 60 minutes;

[0097] S2, mixing the first treated sewage with sodium hydroxide and continuing to mix in the post-mixer 3, and then entering the solid-liquid separator 4 for solid-liquid separation to obtain the second treated sewage and the first waste residue slurry; the second treated sewage is discharged from the drainage line G5; the amount of sodium hydroxide is such that the pH of the first treated sewage is 7, and the residence time of the first treated sewage in the solid-liquid separator 4 is 60 minutes; the COD of the second treated sewage is 45.0 mg / L;

[0098] S3, dividing the first waste slurry into two streams, wherein the first stream of the first waste slurry is discharged from the slag discharge line G6, wherein the second stream of the first waste slurry is mixed with sulfuric acid and sent to the electrocatalytic reactor 5 for electrocatalytic reaction to obtain the first material, and returning the first material to the pre-mixer 1; wherein the amount of sulfuric acid added makes the pH of the first waste slurry be 4, the ratio of the second stream of the first waste slurry to the first stream of the first waste slurry is 2:1, and the residence time of the second stream of the first waste slurry in the electrocatalytic reactor 5 is 60min; the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0099] Comparative Example 6

[0100] The difference between the sewage treatment method of this comparative example and that of Example 1 is that the materials in the pre-mixer 1 are evenly mixed and then directly sent to the electrocatalytic reactor 5 for electrocatalytic reaction; specifically, the following steps are included:

[0101] S1. The sewage to be treated is mixed evenly with ferrous sulfate (using concentration of 200 mg / L) and hydrogen peroxide (using concentration of 100 mg / L) in a pre-mixer 1, and then mixed with sulfuric acid and sent to an electrocatalytic reactor 5 for electrocatalytic reaction to obtain a second material, and the second material is sent to a solid-liquid separator 4 for solid-liquid separation to obtain a third treated sewage and a second waste slurry; the third treated sewage is discharged from a drainage line G5, and the second waste slurry is discharged from a slag discharge line G6; the COD of the third treated sewage is 53.9 mg / L; wherein, the amount of sulfuric acid added is such that the pH of the mixed material in the electrocatalytic reactor 5 is 4, and the current density between the cathode and the anode in the electrocatalytic reactor 5 is 200 A / m 2 ; The cathode is SnO2 / Ti electrode and the anode is stainless steel electrode.

[0102] Table 2

[0103]

[0104] As can be seen from Table 2, the present invention performs a catalytic oxidation reaction by mixing the sewage to be treated with ferrous sulfate and hydrogen peroxide, so that the ferrous sulfate is combined with the hydrogen peroxide to generate highly active free radicals (such as OH) in the reaction, degrading organic matter in the sewage, and simultaneously performing an electrocatalytic reaction to convert the trivalent iron in the first waste slurry into divalent iron, which is then returned for the catalytic oxidation reaction, thereby accelerating the utilization rate of hydrogen peroxide, reducing the dosage of ferrous sulfate, and reducing the sludge output; at the same time, under the condition of controlling the same sludge discharge amount and catalyst consumption, the COD concentration of the treated sewage can be reduced further, and the treatment effect is better.

[0105] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0106] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0107] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A sewage treatment system, characterized in that: It comprises a pre-mixer (1), a catalytic oxidation reactor (2), a post-mixer (3), a solid-liquid separator (4) and an electrocatalytic reactor (5) which are connected in sequence; The first inlet (S1) of the pre-mixer (1) is connected to a water inlet line (G1), and the water inlet line (G1) is connected to a catalyst line (G2) and an oxidant line (G3); The pipeline between the catalytic oxidation reactor (2) and the post-mixer (3) is connected to an alkali adding line (G4); the fourth outlet (S8) of the solid-liquid separator (4) is connected to a drainage line (G5), and the fifth outlet (S9) of the solid-liquid separator (4) is connected to a slag discharge line (G6); The fifth inlet (S10) of the electrocatalytic reactor (5) is connected to an acid addition line (G7); the sixth outlet (S11) of the electrocatalytic reactor (5) is connected to the water inlet line (G1); The electrocatalytic reactor (5) is a spiral body with a central tube, the spiral body wall is the anode of the electrocatalytic reactor (5), and the central tube is the cathode of the electrocatalytic reactor (5).

2. The system according to claim 1, wherein: The reactor wall of the electrocatalytic reactor (5) is provided with a fifth inlet (S10) at the lower part and a sixth outlet (S11) at the upper part; the fifth inlet (S10) is connected to the lower part of the outermost circle of the spiral, and the sixth outlet (S11) is connected to the upper part of the innermost circle of the spiral.

3. The system according to claim 1, wherein: The first outlet (S2) of the pre-mixer (1) is connected to the second inlet (S3) of the catalytic oxidation reactor (2), the second outlet (S4) of the catalytic oxidation reactor (2) is connected to the third inlet (S5) of the post-mixer (3), the third outlet (S6) of the post-mixer (3) is connected to the fourth inlet (S7) of the solid-liquid separator (4), and the fifth outlet (S9) of the solid-liquid reactor (4) is connected to the fifth inlet (S10) of the electrocatalytic reactor (5).

4. The system according to claim 1, wherein: The catalytic oxidation reactor (2) is provided with a first pH online probe, and the pH value is controlled by adjusting the amount of acid added through the regulating valve on the acid addition line (G7); The solid-liquid separator (4) is provided with a second pH online probe, and the pH value is controlled by adjusting the amount of alkali added through a regulating valve on the alkali adding line (G4).

5. A method for treating sewage, the method using the system according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, the sewage to be treated, the catalyst and the oxidant are uniformly mixed in a pre-mixer (1) and then enter into a catalytic oxidation reactor (2) for catalytic oxidation reaction to obtain first treated sewage; S2, mixing the first treated sewage with the alkali solution, continuing to mix in a post-mixer (3), and then entering a solid-liquid separator (4) for solid-liquid separation to obtain a second treated sewage and a first waste residue slurry; and discharging the second treated sewage from a drainage line (G5); S3. Divide the first waste slurry into two streams, wherein the first waste slurry is discharged from the slag discharge line (G6), and the second waste slurry is mixed with acid liquid and sent to the electrocatalytic reactor (5) for electrocatalytic reaction to obtain the first material, and the first material is returned to the pre-mixer (1); wherein the mixed material in the electrocatalytic reactor (5) flows from the lower part of the outermost circle of the spiral body of the electrocatalytic reactor (5) to the upper part of the innermost circle, and rises in a spiral from low to high.

6. The method according to claim 5, wherein: The pH value of the mixture in the catalytic oxidation reactor (2) is less than 6, preferably 3-5; The pH value of the mixture in the solid-liquid separator (4) is >6, preferably 7-9.

7. The method according to claim 5, wherein: The distribution ratio of the second first waste slurry to the first first waste slurry is 0.2-20:1, preferably 0.5-5:

1.

8. The method according to claim 5, wherein: The COD concentration of the sewage to be treated is 50-1000 mg / L; The oxidant is one of hydrogen peroxide, sodium hypochlorite and sodium persulfate, preferably hydrogen peroxide, and the dosage of the oxidant is 0.1 to 10 times the COD concentration, preferably 0.5 to 4 times; The catalyst is ferrous sulfate or ferrous chloride, preferably ferrous sulfate, and the dosage of the catalyst is preferably 1 to 4 times the dosage of the oxidant.

9. The method according to claim 5, wherein: The residence time of the sewage to be treated in the catalytic oxidation reactor (2) is 5-1200 min, preferably 30-300 min; The residence time of the first treated sewage in the solid-liquid separator (4) is 20-1200 min, preferably 30-600 min; The residence time of the second first waste slurry in the electrocatalytic reactor (5) is 2-600 min, preferably 20-240 min.

10. The method according to claim 5, wherein: The current density between the cathode and the anode in the electrocatalytic reactor (5) is 0.1 to 1000 A / m 2 , preferably 1 to 500 A / m 2 ; The cathode is one of a ruthenium-iridium electrode, a SnO2 / Ti electrode, a PtO2 / Ti electrode, a graphite electrode, an activated carbon fiber electrode or a Pt electrode, preferably a SnO2 / Ti electrode; the anode is a metal electrode, preferably a stainless steel electrode.

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