Process and equipment for simultaneously oxidizing and coagulating water

Abstract

The invention provides a simultaneous oxidation and coagulation water treatment process and equipment, and belongs to the technical field of water treatment. According to the water treatment process, two water treatment methods of potassium ferrate oxidation and aluminum-iron covalent bond composite coagulant coagulation are integrated in one unit, the purpose of efficiently treating the organic arsenic wastewater is achieved through a synchronous oxidation and coagulation reaction, and floc generated by precipitation is refluxed and reused; and through synergistic adsorption, complexation and enhanced coagulation, organic matter degradation intermediates and inorganic arsenic are removed, and resource utilization and reduction of floc solid waste are achieved. Compared with a traditional pre-oxidation coagulation process, the synchronous oxidation coagulation reaction process constructed by the method disclosed by the invention has an obvious effect of removing pollutants by synergism and mutual promotion. Meanwhile, floc sludge flows back, the concentration of a flocculation medium can be increased, organic matter degradation intermediates and inorganic arsenic are removed through synergistic adsorption, complexation and enhanced coagulation, and waste reduction and efficiency improvement are achieved. The oxidation and coagulation integrated equipment provided by the invention is simple to operate, efficient, low in consumption, safe, green and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a simultaneous oxidation and coagulation water treatment process and integrated equipment. Background Art

[0002] In recent years, typical emerging pollutants (EOCs) such as organic arsenic have been continuously detected in water bodies. Organic arsenic has higher mobility than inorganic arsenic and can be converted into more toxic inorganic arsenic in the environment, causing great harm to water ecology and human health. Organic arsenic is widely used in agricultural production and aquaculture. This type of organic arsenic includes p-aminophenylarsonic acid, roxarsone, carbazine and nitrophenylarsonic acid. Livestock and poultry feed contains a high amount of arsanilic acid organic arsenic, which is difficult to be absorbed and converted after being ingested by poultry animals. More than 90% of them will be excreted from the body in the original structure with feces and urine. And tens of thousands of tons of organic arsenic waste are dumped in ponds or composted every year around the world, increasing the total arsenic content in soil and water in the environment, posing serious risks to the ecological environment and human health. In traditional water treatment processes, conventional coagulation technology has limited treatment capacity for organic arsenic and is difficult to meet people's requirements for water quality safety. Therefore, it is urgent to develop green and efficient enhanced removal technology for organic arsenic.

[0003] Patent 202310298635.3 discloses an activated carbon material modified with an iron-aluminum covalent bond coagulant that can simultaneously and efficiently remove organic arsenic by oxidation and adsorption, and a preparation method thereof. The degradation and removal of organic arsenic are achieved through Fenton-like oxidation and carbon adsorption produced by aluminum-iron modified activated carbon. However, there are still a series of problems such as limited adsorption capacity of activated carbon, high cost, difficulty in desorption of inorganic arsenic, and difficulty in handling regenerated liquid. Patent 202310487691.1 discloses a coagulation-membrane separation-Fenton reagent oxidation integrated water treatment experimental control device, discloses equipment for integrated oxidation and coagulation water treatment, and constructs a process of first coagulation, then Fenton oxidation, and finally ultrafiltration membrane separation for organic pollutants. If the above process equipment is used to treat organic arsenic wastewater, the organic arsenic cannot be removed by coagulation in the first unit, and then enters the second unit Fenton oxidation, which can only degrade the organic arsenic through hydroxyl radicals. The degradation efficiency of organic arsenic is difficult to achieve high efficiency, and most importantly, a large amount of highly toxic trivalent and pentavalent inorganic arsenic will be generated. Finally, these soluble inorganic arsenic enters the third reaction unit ultrafiltration membrane separation. The ultrafiltration membrane can intercept pollutants with a size of several microns to tens of microns, but inorganic arsenic is a small molecule soluble substance below the nanometer level and is almost not intercepted by the ultrafiltration membrane. Therefore, it is difficult to achieve efficient degradation of organic arsenic in the treatment of organic arsenic wastewater by the above coagulation, Fenton-like oxidation, and ultrafiltration membrane separation process equipment, and it will cause the generation of highly toxic inorganic arsenic, and it is impossible to simultaneously achieve the goals of organic arsenic degradation and inorganic arsenic removal.

[0004] The traditional coagulation process can only have a good coagulation removal effect on pentavalent inorganic arsenic, so it is necessary to first degrade the organic arsenic into inorganic arsenic by oxidation, and then remove it by coagulation. For the water treatment process technology of oxidation and coagulation, a series of pre-oxidation-coagulation processes have been developed and applied to various types of water treatment, and have achieved certain positive effects. Patent CN116553789A discloses an ozone-aluminum salt and iron salt pre-oxidation coagulation process, which first pre-oxidizes the sewage for 15 minutes, then adjusts the pH value of the wastewater to 9-10, and finally adds polyaluminum or polyferric salt for coagulation, which can effectively remove COD in the sewage. It can be seen from this that the pre-oxidation coagulation process can have a good oxidation and degradation effect on organic matter in water, but it still needs to adjust the pH value of the wastewater to alkalinity, and it requires a two-step method to complete. More importantly, ozone requires proprietary production equipment to be prepared on-site. Ozone pre-oxidation coagulation is a heterogeneous reaction process, and the mass transfer effect of ozone will also affect the oxidation effect. Patent CN1 14772795A discloses a sewage treatment process integrating catalytic oxidation coagulation and sedimentation, which uses chlorine dioxide for pre-oxidation for 2 to 4 hours, then adds aluminum salt and iron salt coagulants, and adjusts the pH value to the range of 6.5 to 7.5. It can effectively remove COD in sewage, but still requires secondary addition of oxidant and coagulant and adjustment of pH to near neutrality. It cannot achieve the goal of efficient oxidation and coagulation to remove pollutants in a wider pH range, and the oxidation of organic matter by chlorine dioxide may produce disinfection by-products. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a simultaneous oxidation and coagulation water treatment process and integrated equipment, so that the process can give full play to the effectiveness of the oxidation and coagulation unit methods in a homogeneous reaction system, achieve mutual promotion and synergy of simultaneous oxidation and coagulation, and simultaneously and efficiently degrade organic arsenic and remove inorganic arsenic.

[0006] The present invention is achieved through the following technical solutions.

[0007] The present invention provides a simultaneous oxidation coagulation water treatment process, which specifically comprises the following steps:

[0008] (1) fully dissolving the oxidant by magnetic stirring to prepare an oxidant solution;

[0009] (2) fully dissolving the coagulant by magnetic stirring to prepare a coagulant solution;

[0010] (3) In the oxidation coagulation reactor, the pH of the organic wastewater is adjusted to be in the range of 5 to 9, and the oxidant and coagulant are added to the wastewater at the same time, firstly stirred rapidly for 3 to 5 minutes, then stirred slowly for 30 to 40 minutes, and then discharged into the subsequent precipitation reactor;

[0011] (4) The residence time in the sedimentation reactor is maintained for 15-20 minutes, and the solid and liquid are separated to obtain the supernatant water. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at a ratio of 4%-5% of the treated water mass, and is added simultaneously with the oxidant and coagulant.

[0012] Furthermore, in step (1), the oxidant is potassium ferrate.

[0013] Furthermore, in step (2), the coagulant is an aluminum-iron covalent bond composite coagulant, which is prepared by ferric chloride, aluminum chloride and a silane coupling agent through alkaline hydrolysis condensation, and the composite coagulant contains Si-O-Fe and Si-O-Al chemical bonds; the molar ratio of ferric chloride to aluminum chloride is 8:2; and the molar ratio of Si / (Al+Fe) in the silane coupling agent is 0.6.

[0014] Furthermore, in step (3), the oxidation coagulation reactor is a mechanical stirring tank, the fast stirring speed is 200-300 rpm, and the slow stirring speed is 30-50 rpm.

[0015] Furthermore, in step (3), the organic wastewater is organic arsenic wastewater containing roxarsone, arsanilic acid or pentavalent arsenic.

[0016] Furthermore, in step (3), the oxidant and coagulant are added simultaneously through two independent dosing systems to ensure that the oxidant and coagulant are added at the same time.

[0017] Furthermore, in step (4), the precipitation reactor is an upward flow inclined plate sedimentation tank, and the surface load is controlled at 5.0 to 9.0 m 3 / (m 2 h).

[0018] Furthermore, in step (4), the upward flow inclined plate sedimentation tank includes two inclined plate areas: a same-wave plate area and an abnormal-wave plate area, and the water flows first through the abnormal-wave plate area and then enters the same-wave plate area.

[0019] The present invention also provides equipment for realizing the above-mentioned simultaneous oxidation and coagulation water treatment process, which equipment consists of an oxidant dosing device, a coagulant dosing device, a metering pump, an oxidant dosing pipe, a coagulant dosing pipe, a fast agitator motor, a fast agitator, a guide wall, an overflow weir, a uniform corrugated plate, a heterogeneous corrugated plate, a scraper motor, a scraper, a check valve, a return sludge pump, a butterfly valve, a return sludge pipe, a flow controller, a residual sludge pump and a residual sludge discharge pipe. The oxidant dosing device is connected to the first metering pump, and the oxidant dosing device is installed before the first metering pump, and then connected to the water inlet pipe of the equipment through the oxidant dosing pipe; the coagulant dosing device is connected to the second metering pump, and the coagulant dosing device is installed before the second metering pump, and then connected to the water inlet pipe of the equipment through the coagulant dosing pipe; after the water flows into the equipment, it flows through the first reaction zone and the oxidizing coagulation reaction tank at the same time, and then flows through the second reaction zone for inclined plate sedimentation separation; the fast agitator motor is connected to the fast agitator; in the sedimentation zone, the same corrugated plate is connected to the different corrugated plate, and the same corrugated plate is installed on the different corrugated plate, and the water flows first through the different The scraper motor is connected to the scraper to scrape the bottom sludge in the sludge area; the overflow weir at the top of the sedimentation tank is connected to the terminal outlet channel to discharge the clarified water; on the sludge discharge pipe, the check valve, the return sludge pump, the butterfly valve, the return sludge pipe, and the flow controller are connected together, and the return flocculent sludge passes through the return sludge pipe, passes through the flow controller, the butterfly valve, the return sludge pump, the check valve in turn, and is then connected to the water inlet pipe of the integrated equipment, so that the return flocculent sludge enters the reaction equipment; the residual sludge pump is connected to the residual sludge discharge pipe, and the remaining waste flocculent sludge is discharged out of the equipment through the residual sludge pump and the residual sludge discharge pipe.

[0020] Furthermore, the folding plate spacing at the trough of the different wave folding plate is 0.4m, the folding plate spacing at the crest is 0.8m, and the folding plate angle is 120°; the two folding plates of the same wave folding plate are arranged in parallel, the folding plate spacing is maintained at 0.4m, and the folding plate angle is 120°.

[0021] The specific degradation mechanism of organic arsenic in the present invention is described as follows: under the promotion of aluminum-iron covalent bond composite coagulant, strong oxidizing substances such as tetravalent iron and pentavalent iron generated by self-decomposition after potassium ferrate hydrolysis attack the As-C bond connected to the arsenate ion and the benzene ring on the organic arsenic through the oxygen transfer process, and aniline, p-aminophenol and trivalent arsenic are formed after breaking. The trivalent arsenic is rapidly oxidized to pentavalent arsenic by hexavalent iron and intermediate valent iron, and p-aminophenol is also instantly oxidized to p-nitrophenol. When hexavalent iron and intermediate valent iron oxidize p-aminophenol, p-aminophenoxy free radicals are formed through single and double electron transfer processes. On the one hand, these free radicals can further react with hexavalent iron and intermediate valent iron, promote the self-decomposition of hexavalent iron to the intermediate valent iron, and form oxidation products such as p-benzoquinone. On the other hand, p-aminophenoxy free radicals will combine through the free radical-free radical self-coupling process to form 4,4′-(hydrazine-1,2-diyl)bisphenol in the system, and these bisphenol substances can be further oxidized by hexavalent iron to form organic intermediates. Finally, the dominant aluminum-iron complex form produced by the hydrolysis of covalent aluminum-iron, the divalent and trivalent iron oxides produced by the self-decomposition of potassium ferrate, and the reflowing floc sludge synergistically and efficiently adsorb, complex, and coagulate to remove pentavalent inorganic arsenic and organic intermediates.

[0022] Compared with the prior art, the present invention has the following technical advantages:

[0023] 1. The present invention has the advantage of mutual promotion and synergy of the simultaneous oxidation coagulation process: on the one hand, the hydrolysis of the metal aluminum salt and the iron salt in the coagulant changes the pH microenvironment on the surface of potassium ferrate in water, accelerates the activation of potassium ferrate and its self-decomposition rate, produces more highly active intermediate valence iron and active oxygen free radicals, and improves the degradation efficiency of organic arsenic to inorganic arsenic; on the other hand, the self-decomposition of potassium ferrate in turn promotes the hydrolysis of the metal aluminum salt and the iron salt in the coagulant, produces richer and higher valence advantageous hydrolysis hydroxyl complex products, and simultaneously enhances the adsorption, complexation, coagulation and other solidification effects on inorganic arsenic in water.

[0024] 2. The potassium ferrate used in the present invention is a highly efficient and multifunctional new type of non-chlorine green disinfectant and oxidant. It does not produce halogenated disinfection by-products, has strong oxidative activity, and has a redox potential much higher than commonly used potassium permanganate and potassium dichromate. It can produce abundant intermediate valence iron in water treatment, including tetravalent iron and pentavalent iron with high oxidative activity, and trivalent iron, divalent iron and their oxides with coagulation, adsorption and complexing capabilities, which can enhance the degradation of organic matter in organic arsenic, the removal of intermediate products, and the solidification of inorganic arsenic.

[0025] 3. Compared with conventional coagulants formed by hydrogen bonds and intermolecular forces, the aluminum-iron covalent bond composite coagulant used in the present invention utilizes the hydrolysis of silane coupling agent to generate Si-OH bonds, which react with the inorganic metal component -OX to undergo dehydration condensation reaction to form Si-OX covalent bond coagulant, which has the advantages of strong stability, high floc density, low effluent residue, and good coagulation effect. In addition, the silane coupling agent combines the advantages of aluminum and iron metal salts into one, and produces more advantageous aluminum-iron hydrolysis complex forms in water treatment, which can better adapt to water quality changes such as pH and pollutant concentration, and strengthen the removal of coagulation and complex organic intermediates and inorganic arsenic.

[0026] 4. The equipment of the present invention integrates oxidation and coagulation, and only requires two reaction units of oxidation coagulation and precipitation, while the three reaction units of oxidation, coagulation and precipitation required by the traditional pre-oxidation-coagulation process saves equipment volume and cost, and shortens the reaction time. It realizes efficient removal of pollutants through short-process oxidation, coagulation and adsorption, and has the advantages of simple operation, high efficiency and low consumption of reagents, safety, greenness and environmental protection, economy and availability, and is suitable for market promotion and application.

[0027] 5. In the sedimentation area of ​​the integrated equipment of the present invention, the sewage after oxidation and flocculation first flows through the different corrugated plate area and then flows through the same corrugated plate area, while the traditional sedimentation area only has the same corrugated plate area. In comparison, the different corrugated plate area in the sedimentation area of ​​the present invention can accelerate the collision and coagulation of flocs, increase the volume of flocs, promote the sedimentation of sludge, and can save sedimentation time while improving the efficiency of mud-water separation.

[0028] 6. The flocs formed in the process of the present invention have more active groups and active sites on the surface compared to the flocs formed in the traditional pre-oxidation coagulation process. By recirculating a certain proportion of the floc sludge, the organic intermediates such as hydrocarbons, hydrocarbons and oxygen produced by the degradation of organic arsenic and inorganic arsenic can be removed through the floc surface groups, metal coordination and morphological structure for adsorption, complexation and enhanced coagulation, thereby reducing the organic matter and total arsenic content in the effluent and realizing the resource utilization of the floc sludge waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the infrared spectrum of the aluminum-iron covalent bond composite coagulant used in the present invention.

[0030] Figure 2 This is the self-decomposition rate diagram of potassium ferrate in the simultaneous oxidation coagulation process and the single oxidation process under pH = 6 conditions.

[0031] Figure 3 This is the aluminum and iron form distribution diagram of simultaneous oxidation coagulation process and separate coagulation process under pH = 5, 6, and 7 conditions.

[0032] Figure 4Performance diagram of treating organic arsenic wastewater under pH 5, 6, 7 and 9 by single oxidation process, single coagulation process and simultaneous oxidation and coagulation process.

[0033] Figure 5 This is the performance diagram of simultaneous oxidation coagulation process and pre-oxidation coagulation process for treating organic arsenic wastewater.

[0034] Figure 6 This is a diagram of the equipment for realizing the simultaneous oxidation and coagulation integrated process of the present invention.

[0035] Figure 7 Schematic diagram of water flow direction in the sedimentation zone of the second reaction tank.

[0036] Figure 8 Schematic diagram of the same corrugated plate in the sedimentation area of ​​the second reaction tank.

[0037] Fig. 9 Schematic diagram of the folded plate in the sedimentation area of ​​the second reaction tank.

[0038] The numbers and letters in the figure represent:

[0039] 1. Oxidant dosing device; 2. Coagulant dosing device; 3. Metering pump; 3-1. The first metering pump; 3-2. The second metering pump; 4. Oxidant dosing pipe; 5. Coagulant dosing pipe; 6. Rapid agitator motor; 7. Rapid agitator; 8. Diversion wall; 9. Overflow weir; 10. Same corrugated plate; 11. Different corrugated plate; 12. Scraper motor; 13. Scraper; 14. Check valve; 15. Return sludge pump; 16. Butterfly valve; 17. Return sludge pipe; 18. Flow controller; 19. Residual sludge pump; 20. Residual sludge discharge pipe; 21. Outlet channel; A. First reaction tank; B. Second reaction tank; C. Sedimentation area; D. Sludge area. DETAILED DESCRIPTION

[0040] In order to further illustrate the present invention, the simultaneous oxidation coagulation process provided by the present invention is described in detail below in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0043] (2) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0044] (3) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 5, potassium ferrate and CSAF (Al:Fe=8:2) described in (1) and (2) were added to the wastewater at the same time, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0045] (4) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume, and is added simultaneously with the oxidant and coagulant.

[0046] Example 2

[0047] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0048] (2) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0049] (3) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 6, potassium ferrate and CSAF (Al:Fe=8:2) described in (1) and (2) were added to the wastewater at the same time, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0050] (4) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 4% of the treated water volume, and is added simultaneously with the oxidant and coagulant.

[0051] Example 3

[0052] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0053] (2) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0054] (3) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 7, and the potassium ferrate and CSAF (Al:Fe=8:2) coagulants described in (1) and (2) were added to the wastewater at the same time, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0055] (4) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume, and is added simultaneously with the oxidant and coagulant.

[0056] Example 4

[0057] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0058] (2) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0059] (3) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 9, and the potassium ferrate and CSAF (Al:Fe=8:2) coagulants described in (1) and (2) were added to the wastewater at the same time, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0060] (4) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 4% of the treated water volume, and is added simultaneously with the oxidant and coagulant.

[0061] Example 5 (Equipment Operation Process)

[0062] The operation process and flow of the simultaneous oxidation and coagulation integrated equipment described in this embodiment are as follows: the oxidant is added through the device 1, the dosage is measured by the first metering pump 3-1, and the oxidant does not enter the water inlet pipe of the integrated equipment through the oxidant dosing pipe 4; at the same time, the coagulant is added through the device 2, the dosage is measured by the second metering pump 3-2, and the coagulant does not enter the water inlet pipe of the integrated equipment through the coagulant dosing pipe 5; the two reagents enter the first unit oxidation coagulation reaction water treatment unit through the water inlet pipe at the same time, and the device rapid stirring motor 6 is turned on to drive the rapid stirrer 7 to stir and mix the wastewater and the reagent to form mixed treated water; the mixed treated water enters the sedimentation area of ​​the second reaction unit through the guide wall 8, and the water flows through the inclined plate sedimentation tank through the upward flow, first flows through the different folding plate 11, and then flows through the same folding plate Plate 10, the clarified water flows into the outlet channel through the overflow weir 9, the sludge precipitated on the inclined plate falls to the bottom sludge area of ​​the sedimentation tank, the scraper plate motor 12 is turned on, the sludge is collected by the scraper plate 13 and discharged from the bottom sludge discharge pipe; the discharged sludge is returned according to a certain proportion of floc sludge, the flow rate is controlled by the flow controller 18, flows through the return sludge pipe 17, the butterfly valve 16 and the check valve 14 are turned on, and the return floc sludge is added to the water inlet pipe of the integrated equipment through the return sludge pump 15, and then enters the oxidation coagulation reaction zone of the first unit, and together with the added oxidant and flocculant, it undergoes contact flocculation and adsorption reaction with the wastewater to be treated, and the above-mentioned water treatment reaction process is repeated; the excess waste floc sludge is discharged through the residual sludge pump 19 through the residual sludge discharge pipe 20.

[0063] Comparative Example 1 (Oxidation)

[0064] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40% potassium ferrate solution;

[0065] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 5, and the potassium ferrate described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0066] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the oxidant.

[0067] Comparative Example 2 (Oxidation)

[0068] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40% potassium ferrate solution;

[0069] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 6, and the potassium ferrate described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0070] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the oxidant.

[0071] Comparative Example 3 (Oxidation)

[0072] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0073] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 7, and the potassium ferrate described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0074] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the oxidant.

[0075] Comparative Example 4 (Oxidation)

[0076] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0077] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 9, and the potassium ferrate described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0078] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the oxidant.

[0079] Comparative Example 5 (coagulation)

[0080] (1) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0081] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 5, and the CSAF (Al:Fe=8:2) described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0082] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the coagulant.

[0083] Comparative Example 6 (coagulation)

[0084] (1) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0085] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 6, and the CSAF (Al:Fe=8:2) described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0086] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the coagulant.

[0087] Comparative Example 7 (coagulation)

[0088] (1) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0089] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 7, and the CSAF (Al:Fe=8:2) described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0090] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the coagulant.

[0091] Comparative Example 8 (Pre-oxidation Coagulation)

[0092] (1) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0093] (2) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol was prepared, the pH of the roxarsone wastewater was adjusted to 9, and the CSAF (Al:Fe=8:2) described in (1) was added to the wastewater, first stirred rapidly for 3 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0094] (3) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the coagulant.

[0095] Comparative Example 9 (Pre-oxidation Coagulation)

[0096] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0097] (2) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0098] (3) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol is prepared, the pH of the roxarsone wastewater is adjusted to 5, the potassium ferrate described in (1) and (2) is added to the wastewater, firstly stirred rapidly for 5 minutes, then a certain amount of CSAF (Al:Fe=8:2) is added to the wastewater, stirred rapidly for 2 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0099] (4) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the coagulant.

[0100] Comparative Example 10 (Pre-oxidation Coagulation)

[0101] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0102] (2) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0103] (3) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol is prepared, the pH of the roxarsone wastewater is adjusted to 6, the potassium ferrate described in (1) and (2) is added to the wastewater, firstly stirred rapidly for 5 minutes, then a certain amount of CSAF (Al:Fe=8:2) is added to the wastewater, stirred rapidly for 2 minutes, then stirred slowly for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0104] (4) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 4% of the treated water volume and is added simultaneously with the coagulant.

[0105] Comparative Example 11 (Pre-oxidation Coagulation)

[0106] (1) fully dissolving potassium ferrate having a mass fraction of 198.04 g / mol by magnetic stirring to prepare a 40 μM potassium ferrate solution;

[0107] (2) CSAF (Al:Fe=8:2) was fully dissolved by magnetic stirring to prepare a 20 mg / L coagulant solution;

[0108] (3) In an oxidation coagulation reactor, 20 μM roxarsone wastewater with a mass fraction of 263.04 g / mol is prepared, the pH of the roxarsone wastewater is adjusted to 7, the potassium ferrate described in (1) and (2) is added to the wastewater, and the wastewater is first rapidly stirred for 5 minutes, and then a certain amount of CSAF (Al:Fe=8:2) is added to the wastewater, and the wastewater is rapidly stirred for 2 minutes, and then slowly stirred for 30 minutes, and then discharged into a subsequent precipitation reactor;

[0109] (4) The residence time in the sedimentation reactor is maintained for 20 minutes, and the solid and liquid are separated to obtain the supernatant effluent. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at 5% of the treated water volume and is added simultaneously with the coagulant.

[0110] Comparative Example 12 (coagulation-Fenton-like-ultrafiltration)

[0111] (1) Prepare 20 mg / L polyferric sulfate coagulant and 40 μM Fenton-like reagent solution;

[0112] (2) preparing 20 μμM roxarsone wastewater with a mass fraction of 263.04 g / mol, adjusting the pH of the roxarsone wastewater to 5, first adding the coagulant described in (1) to the wastewater, stirring rapidly for 2 minutes, and then stirring slowly for 30 minutes;

[0113] (3) Add the Fenton oxidation reagent described in (1), stir rapidly for 5 minutes, and then enter an ultrafiltration reaction device with a pore size of 0.01 μm, and then obtain purified water.

[0114] The following is further described in conjunction with the accompanying drawings:

[0115] Figure 1 This is the red spectrum of the coagulant CSAF (Al:Fe=8:2) described in the present invention. Figure 1 It can be seen that there are mainly 579cm -1 The peaks at and correspond to Si-O-Al and Si-O-Fe groups, respectively, confirming the existence of Si-O-Fe and Si-O-Al chemical bonds in the coagulant.

[0116] Figure 2 This is the self-decomposition rate diagram of potassium ferrate in the simultaneous oxidation coagulation process and the single oxidation process under pH = 6. Figure 2 It can be seen that the comparison of the potassium ferrate self-decomposition rate constants during the water treatment process of the simultaneous oxidation coagulation process in Example 2 and the single oxidation process in Comparative Example 2 indicates that the addition of the coagulant can significantly accelerate the self-decomposition of potassium ferrate, produce more highly active intermediate valence iron and active oxygen free radicals, and improve the degradation efficiency of organic arsenic to inorganic arsenic.

[0117] Figure 3 The distribution diagram of aluminum and iron forms in the simultaneous oxidation coagulation process and the single coagulation process under the conditions of pH = 5, 6, and 7. Figure 3 The Al / Fe-Ferron experiments under the various systems shown in the figure show that after adding potassium ferrate, the simultaneous oxidation coagulation process is compared with the single coagulation process water treatment process (Al+Fe) c The ratio showed different degrees of reduction under the conditions of pH = 5, 6, and 7, indicating that the addition of potassium ferrate slowed down the polymerization process of the coagulant's own hydrolysis, and instead produced richer and higher-valent advantageous hydrolysis hydroxyl complex products, which simultaneously enhanced the adsorption, complexation, coagulation and other solidification effects on inorganic arsenic in water, and could better play the complexation effect of metal ions and enhance the removal effect of pollutants.

[0118] Figure 4 The performance diagram of treating organic arsenic wastewater under the conditions of pH 5=, 6, 7 and 9 is shown in the figure below: Figure 4 It can be seen that the performance of treating organic arsenic wastewater by the single oxidation process (Comparative Examples 1-4), the single coagulation process (Comparative Examples 5-8) and the simultaneous oxidation and coagulation process of Examples 1-4 under the conditions of pH = 5, 6, 7 and 9 in the comparative examples was better than that of the single oxidation process / single coagulation process, indicating that there is a synergistic effect between potassium ferrate and the coagulant in the process of removing organic arsenic.

[0119] Figure 5 This is the performance diagram of treating organic arsenic wastewater by simultaneous oxidation coagulation process and pre-oxidation coagulation process. Figure 5 As shown, by comparing the performance of the simultaneous oxidation coagulation process for treating organic arsenic wastewater under pH=5-7 in implementation cases 1-3 with the performance of the pre-oxidation coagulation process for treating organic arsenic wastewater under pH=5-7 in comparative examples 9-11, it is found that the simultaneous oxidation coagulation process for treating organic arsenic wastewater under pH=5-7 is better than the pre-oxidation coagulation process. Specifically, at pH=5, the removal rate of organic arsenic by the simultaneous oxidation coagulation process increased by 19.28% (from 70.73% to 90.01%) compared with the pre-oxidation coagulation process, increased by 14.42% (from 64.33% to 78.75%) at pH=6, and increased by 10.59% (from 31.59% to 42.18%) at pH=7. Overall, the simultaneous oxidation coagulation process has a higher effect in removing organic arsenic, indicating that the two synergistically enhance the removal of pollutants.

[0120] Figure 6 This is a diagram of the equipment for realizing the integrated process of simultaneous oxidation and coagulation of the present invention. The connection relationship between the various components of the equipment is as follows: the oxidant dosing device 1 is connected to the first metering pump 3-1, and then connected to the water inlet pipe of the equipment through the oxidant dosing pipe 4; the coagulant dosing device 2 is connected to the second metering pump 3-2, and then connected to the water inlet pipe of the equipment through the coagulant dosing pipe 5; after the water flows into the equipment, it flows through the first reaction tank A for simultaneous oxidation and coagulation reaction tank, and then flows through the second reaction tank B for inclined plate sedimentation separation; the fast agitator motor 6 is connected to the fast agitator 7; in the sedimentation area C, the same corrugated plate 10 is connected to the different corrugated plate 11, and the same corrugated plate 10 is installed on the different corrugated plate 11, and the water flows through the different corrugated plate 11 first, and then flows through the same corrugated plate 10; the scraper motor 12 is connected to the scraper 13 to scrape the bottom sludge in the sludge area D; the overflow weir 9 at the upper part of the sedimentation tank is connected to the terminal outlet channel 21 to discharge the clarified water; on the sludge discharge pipe, the check valve 14, the return sludge pump 15, the butterfly valve 16, the return sludge pipe 17, and the flow controller 18 are connected together, and the return flocculent sludge passes through the return sludge pipe 17, passes through the flow controller 18, the butterfly valve 16, the return sludge pump 15, the check valve 14 in sequence, and is then connected to the water inlet pipe of the integrated equipment, so that the return flocculent sludge enters the reaction equipment; the residual sludge pump 19 is connected to the residual sludge discharge pipe 20, and the remaining waste flocculent sludge passes through the residual sludge pump 19 and is discharged out of the equipment through the residual sludge discharge pipe 20.

[0121] Figure 7 Figure 1 is a schematic diagram of the water flow direction in the sedimentation zone of the second reaction tank. Figure 7It can be seen that after entering the second reaction tank 23 from the first reaction tank 22, the water flow first enters the sedimentation area from under the fold plate, flows upward, first flows through the 11 different fold plates, then flows through the 10 same fold plates, and finally flows upward to the weir and enters the 9 outlet weir, and merges into the 21 outlet channel at the end, and is discharged from the sedimentation tank.

[0122] Figure 8 This is a schematic diagram of the same corrugated plate in the sedimentation area of ​​the second reaction tank. Figure 8 It can be seen that the two folded plates of the same corrugated plate are arranged in parallel, the distance between the folded plates is maintained at 0.4m, and the folded plate angle is 120°.

[0123] Fig. 9 This is a schematic diagram of the folded plate in the sedimentation area of ​​the second reaction tank. Figure 8 It can be seen that for the special wave folded plate, the spacing between the folded plates at the trough is 0.4m, the spacing between the folded plates at the peak is 0.8m, and the folded plate angle is 120°.

[0124] Table 1 is a comparison of ROX removal rate and arsenic residue of three different processes at pH = 5

[0125]

[0126] It can be seen from Table 1 that, compared with the pre-oxidation coagulation process of Comparative Example 9 and the coagulation-Fenton-like-ultrafiltration process of Comparative Example 12, the simultaneous oxidation coagulation process of Example 1 treats organic arsenic wastewater, and has the highest removal rate of organic arsenic ROX (90.01%), the lowest content of trivalent arsenic (0.07 μM) and pentavalent arsenic (0.12 μM); the coagulation-Fenton-like-ultrafiltration process has the lowest removal rate of organic arsenic ROX (58.08%), and the highest content of trivalent arsenic (4.82 μM) and pentavalent arsenic (10.21 μM). The above results show that the simultaneous oxidation coagulation process is more capable of degrading organic arsenic more efficiently than the pre-oxidation coagulation process and the coagulation-Fenton-like oxidation-ultrafiltration membrane process, and can simultaneously and efficiently remove highly toxic trivalent arsenic and pentavalent arsenic.

Claims

1. A simultaneous oxidation coagulation water treatment process, characterized in that The steps include: (1) fully dissolving the oxidant by magnetic stirring to prepare an oxidant solution; (2) fully dissolving the coagulant by magnetic stirring to prepare a coagulant solution; (3) In the oxidation coagulation reactor, the pH of the organic wastewater is adjusted to be in the range of 5 to 9, and the oxidant and coagulant are added to the wastewater at the same time, firstly stirred rapidly for 3 to 5 minutes, then stirred slowly for 30 to 40 minutes, and then discharged into the subsequent precipitation reactor; (4) The residence time in the sedimentation reactor is maintained for 15-20 minutes, and the solid and liquid are separated to obtain the supernatant water. The precipitated flocculent sludge is returned to the aforementioned oxidation coagulation reactor at a ratio of 4%-5% of the treated water mass, and is added simultaneously with the oxidant and coagulant.

2. A simultaneous oxidation coagulation water treatment process as claimed in claim 1, characterized in that: In step (1), the oxidant is potassium ferrate.

3. A simultaneous oxidation coagulation water treatment process as claimed in claim 1, characterized in that: In step (2), the coagulant is an aluminum-iron covalent bond composite coagulant, which is prepared by ferric chloride, aluminum chloride and a silane coupling agent through alkaline hydrolysis condensation, and the composite coagulant contains Si-O-Fe and Si-O-Al chemical bonds; the molar ratio of ferric chloride to aluminum chloride is 8:2; and the molar ratio of Si / (Al+Fe) in the silane coupling agent is 0.

6.

4. A simultaneous oxidation coagulation water treatment process as claimed in claim 1, characterized in that: In step (3), the oxidation coagulation reactor is a mechanical stirring tank, the fast stirring speed is 200-300 rpm, and the slow stirring speed is 30-50 rpm.

5. A simultaneous oxidation coagulation water treatment process as claimed in claim 1, characterized in that: In step (3), the organic wastewater is organic arsenic wastewater containing roxarsone, arsanilic acid or pentavalent arsenic.

6. A simultaneous oxidation coagulation water treatment process as claimed in claim 1, characterized in that: In step (3), the oxidant and coagulant are added simultaneously through two independent dosing systems to ensure that the oxidant and coagulant are added at the same time.

7. A simultaneous oxidation coagulation water treatment process as claimed in claim 1, characterized in that: In step (4), the precipitation reactor is an upward flow inclined plate sedimentation tank, and the surface load is controlled at 5.0 to 9.0 m 3 / (m 2 h).

8. A simultaneous oxidation coagulation water treatment process as claimed in claim 7, characterized in that: In step (4), the upward flow inclined plate sedimentation tank includes two inclined plate areas: a same-bend plate area and an different-bend plate area, and the water flows first through the different-bend plate area and then enters the same-bend plate area.

9. A device for implementing the simultaneous oxidation coagulation water treatment process according to any one of claims 1 to 8, characterized in that: The equipment comprises an oxidant dosing device (1), a coagulant dosing device (2), a metering pump (3), an oxidant dosing pipe (4), a coagulant dosing pipe (5), a fast agitator motor (6), a fast agitator (7), a guide wall (8), an overflow weir (9), a uniform folding plate (10), a heterogeneous folding plate (11), a scraper motor (12), a scraper (13), a check valve (14), a return sludge pump (15), a butterfly valve (16), a return sludge pipe (17), a flow controller (18), a surplus sludge pump (19), a surplus sludge discharge pipe (20), an outlet channel (21), a first reaction tank (A), a second reaction tank (B), a sedimentation zone (C) and a sludge zone (D); The oxidant dosing device (1) is connected to the first metering pump (3-1), and the oxidant dosing device (1) is installed before the first metering pump (3-1), and then connected to the water inlet pipe of the equipment through the oxidant dosing pipe (4); the coagulant dosing device (2) is connected to the second metering pump (3-2), and the coagulant dosing device (2) is installed before the second metering pump (3-2), and then connected to the water inlet pipe of the equipment through the coagulant dosing pipe (5); after the water flows into the equipment, it flows through the first reaction zone (A) and the oxidation coagulation reaction tank at the same time, and then flows into the second ... The second reaction zone is used for inclined plate sedimentation separation; the rapid agitator motor (6) is connected to the rapid agitator (7); in the sedimentation zone (C), the same folding plate (10) is connected to the different folding plate (11), and the same folding plate (10) is installed on the different folding plate (11), and the water flows through the different folding plate (11) first, and then flows through the same folding plate (10); the scraper motor (12) is connected to the scraper (13), and the bottom sludge is scraped in the sludge zone (D); the overflow weir (9) at the upper part of the sedimentation tank is connected to the terminal outlet channel (21) to discharge the clarified water; On the sludge discharge pipe, a check valve (14), a return sludge pump (15), a butterfly valve (16), a return sludge pipe (17), and a flow controller (18) are connected together. The return flocculent sludge passes through the return sludge pipe (17), sequentially passes through the flow controller (18), the butterfly valve (16), the return sludge pump (15), and the check valve (14), and is then connected to the water inlet pipe of the integrated equipment, so that the return flocculent sludge enters the reaction equipment; the excess sludge pump (19) is connected to the excess sludge discharge pipe (20), and the excess waste flocculent sludge passes through the excess sludge pump (19) and is discharged outside the equipment through the excess sludge discharge pipe (20).

10. The device for realizing simultaneous oxidation coagulation water treatment process according to claim 9, characterized in that: The different-wave folding plate (11) has a folding plate spacing of 0.4m at the trough, a folding plate spacing of 0.8m at the peak, and a folding plate angle of 120°; the same-wave folding plate (10) has two folding plates arranged in parallel, a folding plate spacing of 0.4m, and a folding plate angle of 120°.

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