Pretreatment method of organic wastewater

Abstract

The invention discloses a pretreatment method of organic wastewater, and relates to the technical field of sewage pretreatment. The pretreatment method comprises the following steps: adopting a Fenton-flocculation method, generating free radicals through a Fenton reaction to initiate a polymerization reaction of organic matters in the organic wastewater to generate an organic polymer, and removing the organic polymer through flocculent precipitation and aging; the organic matter is an organic polymer monomer which can be subjected to polymerization reaction under the initiation of free radicals. The Fenton-flocculation method provided by the invention is different from a free radical degradation principle of Fenton reaction treatment of wastewater in the prior art, a lot of free radicals are generated through Fenton reaction for polymerization reaction, small organic molecules are subjected to reverse polymerization to form a macromolecular polymer, the macromolecular polymer is removed through flocculent precipitation, and the wastewater treatment efficiency is improved. The purpose of reducing the COD value of the organic wastewater with high efficiency and low cost is achieved, and the method has the advantages of being easy to operate, free of complex equipment and technology and easy to implement and maintain.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage pretreatment, and specifically relates to a method for treating organic wastewater. Background Art

[0002] With the growth of population and the acceleration of industrialization, the amount of wastewater discharge has continued to increase, which has brought serious impacts on the environment and human health. Wastewater contains a large amount of harmful substances such as organic matter, chemicals and microorganisms. If it is discharged directly into the water body without treatment, it will cause water quality deterioration, damage the ecosystem, and even cause water pollution and disease transmission. Therefore, effective treatment and purification of sewage is an important measure to protect the environment and maintain ecological balance.

[0003] Fenton's reagent has a stable and effective removal function for difficult-to-biodegrade wastewater, toxic wastewater and bioinhibitory wastewater. If used alone, the treatment cost is often very high. If Fenton oxidation technology is used as a pretreatment or deep treatment method for difficult-to-degrade organic wastewater, and then combined with other treatment methods (such as biological methods, flocculation methods, etc.), it can reduce wastewater treatment costs and improve treatment efficiency.

[0004] The Fenton reaction is an inorganic chemical reaction in which hydrogen peroxide (H2O2) reacts with divalent iron ions Fe 2+ The mixed solution of Fenton can oxidize many known organic compounds such as carboxylic acids, alcohols, and esters into inorganic states. The reaction has the ability to remove refractory organic pollutants and is widely used in the treatment of printing and dyeing wastewater, oily wastewater, phenolic wastewater, coking wastewater, nitrobenzene-containing wastewater, diphenylamine wastewater, etc. In the Fenton reaction, hydrogen peroxide (H2O2) acts as an oxidant. Hydrogen peroxide is oxidized by iron ions (Fe 2+ ) is catalytically decomposed into hydroxyl radicals (•OH), and the reaction mechanism is: Fe 2+ + H2O2→Fe 3+ +OH -+OH•, the hydroxyl radicals produced in the reaction have strong oxidizing properties and can react with organic matter to oxidize it. This oxidation reaction is the key step in the production of free radicals in the Fenton reaction, which helps to degrade organic pollutants in organic wastewater. For example, the wastewater treatment process based on Fenton oxidation reaction disclosed in Chinese invention patent CN111018187A includes: the wastewater enters a pH adjustment tank, and acid is added to adjust the pH of the wastewater to acidic; oxidation reaction: enters Fenton reaction tank A, ferrous sulfate is added and mixed evenly, and then flows to Fenton reaction tank B by gravity, and hydrogen peroxide is added to carry out Fenton catalytic oxidation reaction; neutralization reaction: flows by gravity into the Fenton neutralization tank, alkali solution is added for neutralization reaction, and the pH is adjusted to neutrality so that the effluent pH of the wastewater meets the standard; degassing reaction: enters the Fenton degassing tank to remove bubbles in the wastewater; flocculation reaction: flows by gravity to the Fenton flocculation tank, and flocculants are added and stirred to fully carry out the flocculation reaction, so that the iron sludge in the wastewater flocculates; precipitation reaction: flows by gravity to the Fenton precipitation tank to precipitate the iron sludge therein. This patented technology uses the highly oxidizing free radical ·OH generated by the Fenton reaction to react with organic matter RH to generate organic free radical R·. R· is further oxidized to eventually cause carbon chain fission in the organic structure and generate carbon dioxide gas and water, thereby achieving the degradation of organic compounds in wastewater and reducing the COD value of wastewater. The Fenton reaction can non-selectively oxidize most organic matter. However, the process and supporting equipment required for wastewater treatment using the Fenton reaction in this patent are complex and require maintenance after use, resulting in high costs. This invention degrades organic matter through the Fenton reaction and then removes macromolecular organic matter through flocculation and precipitation.

[0005] The present invention makes further technical improvements on the existing technology and proposes a pretreatment process for organic wastewater. A large number of free radicals are generated through the Fenton reaction to induce the polymerization of small organic molecules into large molecules, and then the large molecular organic matter is removed through flocculation and precipitation. No gas is generated during the reaction process, which can greatly simplify the steps of the production process and the required supporting equipment, thereby reducing the cost of production and maintenance. Summary of the invention

[0006] To achieve the above-mentioned purpose, the present invention provides a method for pretreating organic wastewater, which uses free radicals to initiate reverse polymerization of small organic molecules in the organic wastewater to generate organic polymers, and then removes large molecular organic polymers through flocculation and precipitation, thereby achieving high-efficiency and low-cost removal of organic matter in the organic wastewater.

[0007] As one of the purposes of the present invention, the present invention provides a method for pretreating organic wastewater, including adopting the Fenton-flocculation method, generating free radicals through the Fenton reaction to initiate a polymerization reaction of organic matter in the organic wastewater to generate organic polymers, and the organic polymers can be removed after flocculation precipitation and aging, thereby achieving the purpose of reducing the COD value of the organic wastewater.

[0008] Preferably, the organic matter includes an organic polymer monomer capable of undergoing a polymerization reaction under the initiation of free radicals.

[0009] Preferably, the organic matter in the organic wastewater of the present invention includes but is not limited to at least one of amide compounds, olefin nitrile compounds, vinyl compounds, propenyl compounds, oligomers, etc., or a combination of multiple thereof. The above organic matter can undergo polymerization reaction under the initiation of free radicals. For example, ethylene can undergo polymerization reaction to form polyethylene, vinylbenzene can undergo polymerization reaction to form polystyrene, propylene can undergo polymerization reaction to form polypropylene, vinyl chloride can undergo polymerization reaction to form polyvinyl chloride, etc.

[0010] In some specific embodiments, the Fenton reaction includes adding ferrous salt solution and hydrogen peroxide to untreated organic wastewater to carry out a Fenton reaction to generate free radicals and ferric hydroxide colloid.

[0011] As a preferred embodiment, the pretreatment method comprises the following specific steps: S1, introducing ferrous salt solution and hydrogen peroxide into the organic wastewater simultaneously to carry out Fenton reaction to generate free radicals; S2. After the Fenton reaction is completed, the pH of the organic wastewater is adjusted to alkaline; S3, introducing a flocculant aid aqueous solution into the alkaline organic wastewater in S2 for flocculation, precipitation and aging, thereby removing organic matter from the organic wastewater.

[0012] As a preferred implementation, in S1, the pH of the organic wastewater is 3-5.

[0013] Preferably, in S2, the pH of the organic wastewater is adjusted to 8-12; more preferably, to 9.5.

[0014] Preferably, the volume ratio of organic wastewater, ferrous salt solution and hydrogen peroxide is 1:0.02-0.10:0.02-0.14; the volumes of ferrous salt solution and hydrogen peroxide depend on the flow rate of the solution.

[0015] Preferably, the ferrous salt includes but is not limited to any one of ferrous sulfate, ferrous chloride, ferrous nitrate and the like.

[0016] Preferably, the concentration of the ferrous salt solution is 5-20 wt %, and the flow rate of the ferrous salt solution is 5-35 L / h.

[0017] Preferably, the mass fraction of hydrogen peroxide in hydrogen peroxide is 7.5-30%, and the flow rate of hydrogen peroxide is 5-26 L / h.

[0018] It should be noted that the flow rate of hydrogen peroxide and ferrous salt solution refers to the flow rate of hydrogen peroxide and ferrous salt solution introduced into the Fenton reaction tank.

[0019] Preferably, the flocculant aid includes but is not limited to any one of polyacrylamide, activated silicic acid, sodium alginate and the like.

[0020] Preferably, the concentration of the flocculant aid aqueous solution is 0.01-0.1 wt %, and the flow rate is 5-15 L / h.

[0021] Preferably, the reaction time of flocculation precipitation is 5 to 10 minutes.

[0022] Preferably, the alkaline substance for adjusting pH can be any one of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonia water and the like.

[0023] Taking acrylonitrile wastewater as an example, the wastewater contains a large amount of acrylonitrile monomer compounds. The present invention uses free radicals generated by Fenton chemical reaction to initiate the reverse polymerization reaction of acrylonitrile monomers, and then precipitates the polymer under the action of a flocculant to remove organic matter from the wastewater, thereby purifying the water quality.

[0024] Specifically, the reaction principles include: First, ferrous ions and hydrogen peroxide are added to the wastewater to carry out the Fenton chemical reaction, and its mechanism of action is as follows: ; Reaction formula (1)-(3), Fe 2+ Catalyze the decomposition of H2O2 to produce hydroxyl radicals (·OH) and superoxide radicals (·O2 - ), superoxide radical (·HO2) and other free radicals with extremely strong oxidizing ability, reaction equations (4)-(5), during the reaction process, iron water complexes and iron hydroxide colloids with flocculation and adsorption functions will be generated, which can adsorb some organic matter and impurity particles to form suspended matter, thereby achieving efficient mineralization of organic matter.

[0025] Based on the above principle, when treating organic wastewater, the pH is 3~5. When pH < 3, the Fenton reaction effect is relatively poor compared to pH ≥ 3, because the complex [Fe(H2O)] 2+ , the generation of OH radicals is reduced; H2O2 with a pH below 3 is relatively stable, and H2O2 is more likely to form oxygen ions through solvated protons. Oxygen ions make hydrogen peroxide electrophilic, thereby improving the stability of hydrogen peroxide and may greatly reduce the reactivity with ferrous ions, as follows: H2O2 +H + →H3O2 + .

[0026] Therefore, the Fenton reaction at pH < 3 produces fewer types of free radicals than at pH 3-5, thereby reducing the effect of subsequent free radical-initiated polymerization reactions.

[0027] Furthermore, the acrylonitrile polymerization reaction belongs to a chain polymerization reaction, in which free radicals initiate acrylonitrile monomers to form monomer free radicals, and the reaction mechanism includes: ; Monomer free radicals and monomers continue to add to form polymer active chains. The reaction mechanism is:

[0028] Finally, the polymer active chain undergoes double radical termination (coupling or disproportionation termination), the activity disappears, and a polymer is formed. The reaction mechanism includes: ;

[0029] When the organic wastewater is adjusted back to alkaline, the Fenton reaction produces iron ions that generate iron water complexes and iron hydroxide colloids in an alkaline environment, and at the same time, a large number of free radicals are generated again. Under the initiation of free radicals, the polymer monomers undergo a reverse polymerization reaction and precipitate with iron hydroxide to form suspended matter. Finally, flocculation and precipitation occur under the action of flocculants, making the suspended matter in the wastewater more purified, and the organic matter is removed from the wastewater after aging.

[0030] Based on the above reaction principle, the present invention also provides a device for pretreatment of organic wastewater, which is composed of a Fenton reaction tank and a flocculation tank; after the organic wastewater undergoes Fenton reaction in the Fenton reaction tank, it is transferred to the flocculation tank for flocculation and precipitation, thereby completing the pretreatment of the organic wastewater. The device is simple and compatible with existing equipment in the prior art, and does not require further modification, which can greatly save costs.

[0031] Compared with the prior art, the present invention has the following beneficial effects: 1. The Fenton-flocculation method for pretreating organic wastewater provided by the present invention is different from the free radical degradation principle of the Fenton reaction in the prior art for treating wastewater. The present invention uses a free radical polymerization method to generate a large number of free radicals by the Fenton reaction to induce the polymerization of small organic molecules into large molecules, and then removes the large molecular organic matter in the wastewater by flocculation precipitation, thereby achieving high-efficiency and low-cost removal of organic matter in organic wastewater.

[0032] 2. The Fenton-flocculation method adopted in the technical solution of the present invention is suitable for organic wastewater containing amide compounds, olefin nitrile compounds, vinyl compounds, acryl compounds and / or oligomers; it can effectively remove organic matter and pollutants in water and improve water quality.

[0033] 3. The Fenton-flocculation method provided by the present invention is characterized by high efficiency, rapidity and easy operation. In particular, the organic wastewater only needs to be transferred once during the operation, and no gas is generated during the reaction. The operation process and the required supporting equipment can be greatly simplified. Only a Fenton reaction tank and a flocculation tank are required to complete all the pretreatment steps, which shortens the treatment time and reduces the production and maintenance costs. It has the advantages of easy implementation and maintenance and is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a comparison chart of COD values ​​of wastewater before and after reaction treatment in Example 1 of the present invention and Comparative Examples 1-2. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be described in detail below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. In order to describe concisely, it is impossible for this specification to describe in detail all the features of the actual implementation method. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be noted that, unless otherwise defined, the technical terms or scientific terms used in this specification should be known to those in the technical field described in this application.

[0036] The organic wastewater pretreatment process provided by the present invention comprises the following steps: extracting organic wastewater without any treatment into a Fenton reaction tank, adding ferrous salt and hydrogen peroxide to carry out Fenton reaction; transferring the wastewater after the reaction into a flocculation tank, adjusting the pH to alkaline; then adding a flocculant to carry out flocculation precipitation, and the supernatant after aging is the treated organic wastewater, which can continue to be subjected to subsequent deep treatment.

[0037] Preferably, the organic wastewater is organic wastewater containing amide compounds, olefin nitrile compounds, and oligomers; and the pH of the organic wastewater is 3-5, preferably pH 4.

[0038] In some specific embodiments, the added ferrous salt includes but is not limited to any one or more of ferrous sulfate, ferrous chloride, ferrous nitrate, etc., and preferably the ferrous salt is ferrous sulfate; more preferably, the concentration of the ferrous salt solution is 10% and the flow rate is 23L / h.

[0039] In some specific embodiments, the mass fraction of hydrogen peroxide in hydrogen peroxide is 7.5-30%, and the flow rate is 5-26 L / h, preferably 7.5% and 19 L / h.

[0040] In some specific embodiments, the concentration of the added ferrous salt solution is 5-20 wt %, and the flow rate is 5-35 L / h.

[0041] The flow rate is adjusted according to the required volumes of ferrous salt and hydrogen peroxide, and the two have a corresponding relationship.

[0042] In some specific embodiments of the present invention, the volume ratio of organic wastewater, ferrous salt solution and hydrogen peroxide is 1:0.02~0.10:0.02~0.14.

[0043] In some specific embodiments, the alkaline substance added is sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonia water, etc., and sodium hydroxide is preferably used as the alkaline substance; the wastewater after the Fenton reaction is adjusted to alkaline, with a pH of 8-12; preferably, the pH is 9.5.

[0044] In some specific embodiments, the flocculant includes but is not limited to any one of polyacrylamide, activated silicic acid, sodium alginate, etc.; preferably, the flocculant is polyacrylamide.

[0045] In some specific embodiments, the concentration of the flocculant aid is 0.01-0.1 wt %, and the flow rate is 5-15 L / h; preferably, the concentration is 0.05 wt %, and the flow rate is 11 L / h.

[0046] In some specific embodiments, the flocculation reaction time is 5-10 minutes.

[0047] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0048] Unless otherwise specified, the solution concentrations in the following examples are all by mass fraction.

[0049] The technical solution of the present invention is described in detail below through specific embodiments.

[0050] Example 1 This embodiment provides a pretreatment process for organic wastewater, and the device used only requires a Fenton reaction tank and a flocculation tank, and the existing equipment in the prior art can be selected without replacement. During operation, the organic wastewater is added to the Fenton reaction tank, and then a ferrous salt solution and a hydrogen peroxide solution are introduced, mixed evenly, and a Fenton reaction is performed; then the wastewater after the reaction is pumped into the flocculation tank, and after adjusting the pH, a flocculant is added, and the wastewater can be subjected to subsequent treatment steps after precipitation and aging.

[0051] The specific steps include: This embodiment is described by taking the mixed organic wastewater generated in the production process of acrylic fiber in the wet spinning process as an example.

[0052] The mixed organic wastewater contains acrylonitrile and oligomers, dimethylacetamide, dimethylformamide, ammonium persulfate, etc. The specific organic components and contents are shown in Table 1.

[0053] Table 1 Main components and organic matter content indexes of organic wastewater in Example 1 ; The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate solution and hydrogen peroxide are added to carry out Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and alkaline substances are added to adjust the pH to alkaline. Then, an aqueous solution of a flocculant is added and flowed into the flocculation tank for flocculation and precipitation. The supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0054] Among them, the pH value of untreated organic wastewater is 4; the concentration of the added ferrous sulfate solution is 10wt%, and the flow rate is 23L / h; the hydrogen peroxide solution has a mass fraction of 7.5% of hydrogen peroxide and a flow rate of 19L / h; the volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.10:0.08.

[0055] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0056] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05 wt % and the flow rate is 11 L / h; the flocculation reaction time is 5-10 minutes.

[0057] The COD removal effect before and after the reaction is determined by Figure 1 As shown in the figure, adding ferrous sulfate and hydrogen peroxide at the same time for subsequent flocculation can achieve a higher COD removal effect. Its mechanism of action is as follows: ; Reaction formula (1)-(3), Fe 2+ Catalyze the decomposition of H2O2 to produce hydroxyl radicals with extremely strong oxidizing ability, which in turn efficiently mineralizes organic matter and reduces COD. Reaction equations (4)-(5) will generate iron water complexes and iron hydroxide colloids with flocculation and adsorption functions during the reaction process, which can remove some organic matter and impurity particles in the water.

[0058] The principles of PET flocculation and decomposition are as follows: ;

[0059] The principle of polystyrene polymerization and decomposition is as follows: ;

[0060] Example 2 This embodiment provides a pretreatment process for organic wastewater, and the specific steps include: extracting untreated organic wastewater into a Fenton reaction tank, adding ferrous chloride and hydrogen peroxide to carry out Fenton reaction, and the reaction time is 1.5 hours. Use a submersible pump to pump the reacted wastewater into a flocculation tank, adjust the pH to alkaline; then add a flocculant aid aqueous solution and pass it into the flocculation tank for flocculation precipitation, and the supernatant after aging for 6 minutes can be subjected to subsequent deep treatment.

[0061] The pH of the organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% of the hydrogen peroxide solution, and the flow rate is 19 L / h; the concentration of the ferrous chloride solution is 10%, and the flow rate is 23 L / h; the volume ratio of the organic wastewater, the ferrous chloride solution and the hydrogen peroxide solution is 1:0.10:0.08.

[0062] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0063] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt% and the flow rate is 11L / h; the flocculation reaction time is 5-10 minutes.

[0064] The COD removal effects before and after the reaction are shown in Table 1.

[0065] Example 3 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous nitrate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant aqueous solution is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0066] The pH of the organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% of the hydrogen peroxide solution, and the flow rate is 19L / h. The concentration of the added ferrous nitrate is 10%, and the flow rate is 23L / h; the volume ratio of the added organic wastewater, ferrous nitrate solution and hydrogen peroxide is 1:0.10:0.08.

[0067] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0068] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt% and the flow rate is 11L / h; the flocculation reaction time is 5-10 minutes.

[0069] The COD removal effects before and after the reaction are shown in Table 2.

[0070] Example 4 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0071] The pH of organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% of hydrogen peroxide solution, and the flow rate is 19L / h; the concentration of ferrous sulfate is 10%, and the flow rate is 23L / h; the volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.10:0.08.

[0072] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0073] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt% and the flow rate is 11L / h; the flocculation reaction time is 5-10 minutes.

[0074] The COD removal effects before and after the reaction are shown in Table 2.

[0075] Example 5 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and alkaline substances are added to make the pH alkaline; then flocculants are added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0076] The pH value of the organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% to 30% and the flow rate is 10L / h; the concentration of ferrous sulfate is 10% and the flow rate is 20L / h; the volume ratio of the added organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.08:0.04.

[0077] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0078] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt%, and the flow rate is 11L / h; and the flocculation reaction time is 5-10 minutes.

[0079] The COD removal effects before and after the reaction are shown in Table 3. The amount of organic wastewater with ferrous sulfate and hydrogen peroxide is optimal.

[0080] Example 6 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0081] The pH of the organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% to 30% of hydrogen peroxide solution, the flow rate is 19L / h; the concentration of ferrous sulfate is 10%, the flow rate is 23L / h; the volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.09:0.07.

[0082] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0083] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt%, and the flow rate is 11L / h; and the flocculation reaction time is 5-10 minutes.

[0084] The COD removal effects before and after the reaction are shown in Table 4. The pH value is optimal, and the trivalent iron is almost completely converted into ferric hydroxide colloid, thereby enhancing the flocculation effect.

[0085] Example 7 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0086] The pH value of organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% and the flow rate is 7.5 L / h; the concentration of ferrous sulfate is 10% and the flow rate is 20 L / h; the volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.03:0.08.

[0087] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0088] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt%, and the flow rate is 11L / h; the flocculation reaction time is 5-10 minutes.

[0089] The COD removal effect before and after the reaction is shown in Table 3. The hydrogen peroxide content is insufficient and the COD removal effect is still poor.

[0090] Example 8 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0091] The pH of organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% of hydrogen peroxide solution, the flow rate is 19L / h. The concentration of ferrous sulfate added is 10%, and the flow rate is 23L / h.

[0092] The volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.09:0.07.

[0093] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 8.5.

[0094] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt%, and the flow rate is 11L / h; and the flocculation reaction time is 5-10 minutes.

[0095] The COD removal effect before and after the reaction is shown in Table 4. When the pH value is 8.5, the generated iron hydroxide colloid is less than that when the pH value is 9.5, and the flocculation effect is relatively poor.

[0096] Example 9-Example 11 The only difference between Example 9, Example 10 and Example 11 and Example 1 is the aging time, and the other steps are the same.

[0097] The aging times of Example 9 to Example 11 are 8 min, 10 min and 12 min, respectively.

[0098] The COD removal effect before and after the reaction is shown in Table 5. Obviously, the best aging time is 8 minutes, and then the COD removal effect gradually decreases.

[0099] Comparative Example 1 This embodiment provides a pretreatment process for organic wastewater, comprising the following steps: The untreated organic wastewater was pumped into the Fenton reaction tank, and only ferrous sulfate was added for reaction, and the reaction time was 1.5 hours.

[0100] Use a submersible pump to pump the reacted wastewater into the flocculation tank and adjust the pH to alkaline; then add flocculants into the flocculation tank for flocculation and precipitation. After aging for 6 minutes, the supernatant can be used for subsequent deep treatment.

[0101] The pH value of the organic wastewater without any treatment is 4; the concentration of ferrous sulfate is 10% and the flow rate is 23 L / h; the volume ratio of the organic wastewater to the ferrous salt solution is 1:0.10.

[0102] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0103] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt% and the flow rate is 11L / h; the flocculation reaction time is 5-10 minutes.

[0104] The COD removal effect before and after the reaction is Figure 1 As shown, the Fenton reaction tank only adds ferrous sulfate for subsequent flocculation, and the COD removal effect is very poor.

[0105] Comparative Example 2 Based on a pretreatment process of organic wastewater, the process comprises the following steps: The untreated organic wastewater is pumped into the Fenton reaction tank, and only hydrogen peroxide is added for reaction, and the reaction time is 1.5 hours. The wastewater after reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added and flows into the flocculation tank for flocculation and precipitation. The supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0106] The pH value of the organic wastewater without any treatment is 4; the mass fraction of hydrogen peroxide is 7.5% of the hydrogen peroxide solution, and the flow rate is 19 L / h; the volume ratio of the organic wastewater to the hydrogen peroxide solution is 1:0.08.

[0107] The alkaline substance added is sodium hydroxide.

[0108] The pH of the wastewater after the Fenton reaction was adjusted to 9.5.

[0109] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05wt% and the flow rate is 11L / h; the flocculation reaction time is 5-10 minutes.

[0110] COD removal effect before and after the reaction Figure 1 As shown, the Fenton reaction tank only adds hydrogen peroxide for subsequent flocculation, and the COD removal effect is very poor.

[0111] Comparative Example 3 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0112] The pH of organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5%~30% of hydrogen peroxide solution, and the flow rate is 19L / h. The concentration of ferrous sulfate is 10%, and the flow rate is 23L / h; the volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.07~0.12:0.05~0.09.

[0113] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 7.

[0114] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05 wt % and the flow rate is 11 L / h; the flocculation reaction time is 5-10 minutes.

[0115] The COD removal effects before and after the reaction are shown in Table 4. When the pH value is too low, less iron hydroxide colloid is generated, resulting in poor flocculation effect.

[0116] Comparative Example 4 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0117] The pH value of organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% of hydrogen peroxide solution, and the flow rate is 5 L / h; the concentration of ferrous sulfate solution is 10%, and the flow rate is 5 L / h; the volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.02:0.02.

[0118] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0119] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05 wt % and the flow rate is 11 L / h; the flocculation reaction time is 5-10 minutes.

[0120] The COD removal effects before and after the reaction are shown in Table 3. The content of hydrogen peroxide is excessive, and the excess hydrogen peroxide acts as a part of false COD.

[0121] Comparative Example 5 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0122] The pH of organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5%~30% of hydrogen peroxide solution, with a flow rate of 5L / h; the concentration of ferrous sulfate is 10%, with a flow rate of 10L / h; the volume ratio of organic wastewater, ferrous salt solution and hydrogen peroxide is 1:0.02:0.04.

[0123] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0124] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05 wt % and the flow rate is 11 L / h; the flocculation reaction time is 5-10 minutes.

[0125] The COD removal effect before and after the reaction is shown in Table 3. The hydrogen peroxide and ferrous sulfate reacted almost completely, but the amount of ferrous sulfate and hydrogen peroxide was too small, resulting in incomplete removal of part of the COD in the wastewater.

[0126] Comparative Example 6 The untreated organic wastewater is pumped into the Fenton reaction tank, and ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction for 1.5 hours. The wastewater after the reaction is pumped into the flocculation tank by a submersible pump, and the pH is adjusted to alkaline; then the flocculant is added to flow into the flocculation tank for flocculation and precipitation, and the supernatant after aging for 6 minutes can be used for subsequent deep treatment.

[0127] The pH of organic wastewater is 4; the mass fraction of hydrogen peroxide is 7.5% to 30% and the flow rate is 5L / h. The concentration of ferrous sulfate added is 10% and the flow rate is 20L / h; the volume ratio of organic wastewater, ferrous sulfate solution and hydrogen peroxide is 1:0.02:0.08.

[0128] The alkaline substance added to adjust the pH is sodium hydroxide; the pH is 9.5.

[0129] The flocculant is polyacrylamide; the concentration of the flocculant aqueous solution is 0.05 wt % and the flow rate is 11 L / h; the flocculation reaction time is 5-10 minutes.

[0130] The COD removal effects before and after the reaction are shown in Table 3. Due to the excess of ferrous sulfate and less hydrogen peroxide, it can be clearly observed that the color of the flocculation tank is green.

[0131] Comparative Example 7-Comparative Example 9 The difference between Comparative Examples 7 to 9 and Example 1 is only the aging time, and the other steps are the same.

[0132] The aging times of Comparative Examples 7 to 9 are 0 min, 2 min and 4 min, respectively.

[0133] 0min means that the supernatant after the reaction is directly taken without the aging step.

[0134] The COD removal effect before and after the reaction is shown in Table 5. Obviously, when the aging time is 5 minutes, the COD removal effect is not good.

[0135] In combination with Example 1, Example 9-Example 11 and Comparative Example 7-Example 9, the aging step has a significant effect on the removal of COD. After aging for 4 minutes, the COD removal rate is only 15%, while it can reach 27% after aging for 6 minutes. Therefore, using the method of the technical solution of the present invention, the aging time is best for 6 to 12 minutes, preferably 6 to 10 minutes, and more preferably 8 minutes.

[0136] Comparative Example 10 The only difference between this comparative example and Example 1 is that the pH of the organic wastewater is adjusted to 2.

[0137] The COD removal rate of Comparative Example 10 was 20%, which was significantly lower than the effect of removing organic matter at a pH of 4 in Example 1.

[0138] Table 2 Comparison of COD removal effects before and after the reaction of Example 2-Example 4

[0139] Table 3 Comparison of COD removal effects before and after the reaction of Example 5, Example 7 and Comparative Example 5-Comparative Example 7

[0140] Table 4 Comparison of COD removal effects before and after the reaction of Example 8-Example 9 and Comparative Example 3

[0141] Table 5 Comparison of aging time on COD removal effect

[0142] The above are only preferred embodiments of the present invention, which do not limit the protection scope of the present invention. For those skilled in the art, the present invention may have various modifications and changes. Within the spirit and principle of the present invention, changes, modifications, replacements, integrations and parameter changes to these embodiments by conventional substitutions or capable of achieving the same functions without departing from the principles and spirit of the present invention all fall within the protection scope of the present invention.

Claims

1. A method for pretreating organic wastewater, characterized in that: The method comprises adopting the Fenton-flocculation method, in which free radicals are generated by the Fenton reaction to initiate polymerization reaction of organic matter in the organic wastewater to generate organic polymers, and the organic polymers can be removed after flocculation precipitation and aging.

2. The method for pretreating organic wastewater according to claim 1, characterized in that: The organic matter is one or more of amide compounds, olefin nitrile compounds, vinyl compounds, propenyl compounds and oligomers.

3. The method for pretreating organic wastewater according to claim 1, characterized in that: The specific steps include: S1, introducing ferrous salt solution and hydrogen peroxide into the organic wastewater simultaneously to carry out Fenton reaction to generate free radicals; S2. After the Fenton reaction is completed, the pH of the organic wastewater is adjusted to alkaline; S3. The organic matter in the organic wastewater can be removed by introducing an aqueous solution of a flocculant into the alkaline organic wastewater for flocculation, precipitation and aging.

4. The method for pretreating organic wastewater according to claim 3, characterized in that: In S1, the pH of the organic wastewater is 3-5; And / or, in S2, the pH of the organic wastewater is adjusted to 8-12.

5. The method for pretreating organic wastewater according to claim 3, characterized in that: The volume ratio of the organic wastewater, the ferrous salt solution and the hydrogen peroxide is 1:0.02-0.10:0.02-0.

14.

6. The method for pretreating organic wastewater according to claim 3, characterized in that: Ferrous salts include any one or a combination of ferrous sulfate, ferrous chloride, and ferrous nitrate; The concentration of the ferrous salt solution is 5-20wt%, and the flow rate of the ferrous salt solution is 5-35L / h.

7. The method for pretreating organic wastewater according to claim 3, characterized in that: The mass fraction of hydrogen peroxide in hydrogen peroxide is 7.5-30%, and the flow rate of hydrogen peroxide is 5-26 L / h.

8. The method for pretreating organic wastewater according to claim 1, characterized in that: The flocculant is any one of polyacrylamide, activated silicic acid and sodium alginate; The concentration of the flocculant aid aqueous solution is 0.01-0.1 wt %, and the flow rate is 5-15 L / h; And / or, the flocculation sedimentation time is 5 to 10 minutes.

9. The method for pretreating organic wastewater according to any one of claims 1 to 8, characterized in that: The aging time is 6 to 12 minutes; and / or, the aging time is 6 to 10 minutes; and / or, the aging time is 8 minutes.

10. A device for pretreatment of organic wastewater, comprising a Fenton reaction tank and a flocculation tank; after the organic wastewater undergoes Fenton reaction in the Fenton reaction tank, it is transferred to the flocculation tank for flocculation and sedimentation, thereby completing the pretreatment of the organic wastewater.

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