Method and device for water treatment using new floc of high-iron ferrate

Abstract

This invention provides a method and apparatus for water treatment using newly formed ferrate flocs in a cascade manner. The method includes the following steps: ① Passing the water to be treated into a flocculation reactor for flocculation treatment, then passing the flocculated water into an oxidation reactor, adding ferrate to the oxidation reactor for water treatment, and collecting the nascent flocs generated during the water treatment process in the oxidation reactor; the nascent flocs contain nascent Fe(III) as the reduction end product of ferrate; ② Returning a portion of the nascent flocs to the flocculation reactor, and returning the remaining nascent flocs to the oxidation reactor; ③ Discharging the water treated by the oxidation reactor, and collecting the iron sludge generated in the flocculation reactor for solid waste treatment. This invention can reduce or avoid the use of external activators, while simultaneously reducing the amount of iron sludge and lowering the cost of Fe(VI) water treatment technology.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and relates to a method and apparatus for water treatment using ferrate-based newly formed flocs in a cascade manner. Background Technology

[0002] Ferrate (FeO4) 2- Fe(VI), hereinafter referred to as Fe(VI), has redox potentials of +0.72V and +2.20V under alkaline and acidic conditions, respectively, and can oxidize and remove trace toxic pollutants in water, showing broad application prospects in the field of water treatment. However, existing technologies for applying Fe(VI) to water treatment face problems such as low organic matter mineralization rate and insufficient removal rate of biological toxicity. Furthermore, during the water treatment process using Fe(VI), the intermediate products tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)) (i.e., active iron) typically have reaction rate constants with pollutants that are 2 to 5 orders of magnitude higher than those of Fe(VI). Therefore, Fe(VI) activation technology can generate more highly active intermediate-valence tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)), thereby enhancing pollutant removal. For example, activating Fe(VI) with activators such as sodium thiosulfate, sodium sulfite, and hydrogen peroxide (H₂O₂) can increase the yield of tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)) and enhance the removal efficiency of pollutants. However, activating Fe(VI) with external activators not only increases the cost of reagents, leading to increased water treatment costs, but also raises concerns about the residual amounts of sodium sulfite, H₂O₂, and other reagents in the effluent. These factors limit the application of the method of activating Fe(VI) with external reagents in engineering practice.

[0003] The reduction end product of Fe(VI) during water treatment is Fe(III) (hereinafter referred to as nascent Fe(III)). Nascent Fe(III) is a complex of nano-sized amorphous Fe(III) and crystalline Fe(III). If nascent Fe(III) is not effectively utilized, it will eventually enter the iron sludge produced during Fe(VI) water treatment, resulting in a large output of iron sludge. This iron sludge requires harmless treatment before discharge, increasing the overall water treatment cost and workload. This invention aims to solve the aforementioned problems in current Fe(VI) water treatment technology. On the one hand, it reduces the dependence on external activators during Fe(VI) activation, effectively reducing or even avoiding the use of activators and saving activator costs. On the other hand, it reduces the output of iron sludge and lowers the cost of harmless treatment, better aligning with the principle of "subtraction" in wastewater treatment. Summary of the Invention

[0004] To address the problems of high reagent costs, reagent residues in effluent, and large amounts of iron sludge production in existing water treatment methods based on activating Fe(VI) with activators, this invention provides a method and apparatus for water treatment using newly formed ferrate flocs in a tiered manner. This reduces or eliminates the use of external activators, while simultaneously reducing the amount of iron sludge and lowering the cost of Fe(VI) water treatment technology.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for water treatment using ferrate-formed flocs in a cascade manner, the method comprising the following steps:

[0007] ① The water to be treated is fed into a flocculation reactor for flocculation treatment. The flocculated water is then fed into an oxidation reactor. Ferrate is added to the oxidation reactor for water treatment. The nascent flocs generated during the water treatment process in the oxidation reactor are collected. The nascent flocs contain nascent Fe(III), the reduction end product of ferrate.

[0008] ② A portion of the nascent flocs collected in step ① are returned to the flocculation reactor to perform flocculation treatment on the water body to be treated; the remaining nascent flocs collected in step ① are returned to the oxidation reactor to construct a ferrate / nascent floc synergistic oxidation system in the oxidation reactor, activating the ferrate to generate active intermediate valence states of tetravalent iron Fe(IV) and pentavalent iron Fe(V) to degrade pollutants in the water body;

[0009] ③ Discharge the water treated by the oxidation reactor and collect the iron sludge produced in the flocculation reactor for solid waste treatment.

[0010] In the above-mentioned method for water treatment using ferrate-based newly formed flocs, the volume ratio of the newly formed flocs returned to the flocculation reactor to the newly formed flocs returned to the oxidation reactor is (1-2):(1-2).

[0011] In the above-mentioned method for water treatment using ferrate-formed flocs in a cascade manner, the pH value of the water in the oxidation reactor is controlled to be 7–9. A mixture of sodium hydroxide and sodium bicarbonate is typically used to adjust the pH value of the water in the oxidation reactor.

[0012] In the above-mentioned method for water treatment using newly formed ferrate flocs in a cascade manner, the ferrate is K2FeO4 or / and Na2FeO4.

[0013] In the above-mentioned method for water treatment using ferrate-based newly formed flocs, stirring is applied during the water treatment process in the oxidation reactor, and the stirring speed is controlled at 200-500 r / min.

[0014] In the above-mentioned method for water treatment using ferrate-based newly formed flocs, stirring is applied during the water treatment process in the flocculation reactor, and the stirring speed is controlled at 200-500 r / min.

[0015] In the above-mentioned method for water treatment using ferrate-based newly formed flocs, the hydraulic retention time in the oxidation reactor is determined according to the water quality of the water to be treated. Typically, the hydraulic retention time in the oxidation reactor is controlled to be 1 to 3 hours.

[0016] In the above-mentioned method for water treatment using newly formed ferrate flocs in a cascade manner, the concentration of ferrate in the oxidation reactor is determined according to the water quality of the water to be treated during the water treatment process in the oxidation reactor. Under normal circumstances, the concentration of ferrate in the water of the oxidation reactor is controlled to be 10-40 mg / L.

[0017] In the above-mentioned method for water treatment using newly formed ferrate flocs in a cascade manner, depending on the actual water quality of the treated water, an activator can be added to the oxidation reactor to activate Fe(VI) to produce tetravalent iron Fe(IV) and pentavalent iron Fe(V). The added activator can be sodium thiosulfate, sodium sulfite, hydrogen peroxide, etc. Compared with existing technologies that add external activators when activating Fe(VI) to produce tetravalent iron Fe(IV) and pentavalent iron Fe(V) without reusing the newly formed flocs, the method of this invention can effectively reduce the amount of external activator added.

[0018] The present invention also provides an apparatus for implementing the above-described water treatment method, but the apparatus for implementing the above-described water treatment method is not limited to the apparatus with the following structure, and the apparatus with the following structure is only one of many apparatuses that can implement the above-described water treatment method.

[0019] A cascade water treatment device utilizing newly formed ferrate flocs includes a flocculation reactor and an oxidation reactor, and further includes a reflux pipe and a reflux pump.

[0020] The flocculation reactor includes a first inclined plate zone, a flocculation reaction zone, a second inclined plate zone, a first inlet, a first outlet, a first reflux outlet, and a sludge discharge pipe. The flocculation reaction zone is equipped with a first hollow sphere flocculation unit. The first inclined plate zone is located at the upper part of the flocculation reactor, and the second inclined plate zone is located at the lower part of the flocculation reactor. The flocculation reaction zone is located between the first inclined plate zone and the second inclined plate zone. The first inlet is located between the first hollow sphere flocculation unit and the second inclined plate zone. The first outlet is located above the first inclined plate zone. The first reflux outlet is connected to the first hollow sphere flocculation unit, and the sludge discharge pipe is connected to the second inclined plate zone.

[0021] The oxidation reactor includes a third inclined plate zone, an oxidation reaction zone, a fourth inclined plate zone, a second inlet, a second outlet, a second reflux outlet, a newly formed floc discharge pipe, and a dosing port. The oxidation reaction zone is equipped with a second hollow sphere flocculation unit. The third inclined plate zone is located at the upper part of the oxidation reactor, and the fourth inclined plate zone is located at the lower part of the oxidation reactor. The oxidation reaction zone is located between the third and fourth inclined plate zones. The second inlet, the second reflux outlet, and the dosing port are connected to the oxidation reaction zone above the second hollow sphere flocculation unit. The second outlet is located above the third inclined plate zone, and the newly formed floc discharge pipe is connected to the fourth inclined plate zone.

[0022] The new floc discharge pipe is connected to the first return port via the first return pipe, the first return pump, and the control valve. At the same time, the new floc discharge pipe is connected to the second return port via the second return pipe, the second return pump, and the control valve. The first outlet is connected to the second inlet via a pipe fitting.

[0023] In the above-mentioned technical solution of the device for water treatment using ferrate-derived flocs in a cascade manner, the first hollow sphere flocculation unit consists of a horizontally set area separated from the flocculation reaction zone by two porous plates connected to the inner wall of the flocculation reactor, and flocculation reaction spheres filled in the area; the second hollow sphere flocculation unit consists of a horizontally set area separated from the oxidation reaction zone by two porous plates connected to the inner wall of the oxidation reactor, and flocculation reaction spheres filled in the area.

[0024] Furthermore, in the above-mentioned technical solution of the device for water treatment using ferrate-derived nascent flocs, the flocculation reaction ball, also known as a flocculation ball or flocculation ball packing, is a commonly used packing in the field of water treatment for flocculation treatment. Typically, the flocculation reaction ball has a hollow structure and several pores on its surface.

[0025] In the above-mentioned technical solution of the device for water treatment using ferrate-derived nascent flocs, the volume filling rate of the flocculation reaction balls in the first hollow sphere flocculation unit is 30% to 50%, and the volume filling rate of the flocculation reaction balls in the second hollow sphere flocculation unit is 30% to 50%.

[0026] In the above-mentioned technical solution of the device for water treatment using ferrate-derived nascent flocs, a first stirring device is provided in the flocculation reaction zone above the first hollow sphere flocculation unit of the flocculation reactor. The first stirring device is mainly used to generate a swirling effect through stirring, thereby promoting the interaction between the water and the flocculation reactor in the first hollow sphere flocculation unit. A second stirring device is provided in the oxidation reaction zone above the second hollow sphere flocculation unit of the oxidation reactor. The second stirring device is mainly used to promote the interaction between the water and persulfate and the nascent flocs through stirring.

[0027] In the above-mentioned technical solution of the device for water treatment using ferrate-derived flocs, the first inclined plate zone in the flocculation reactor is composed of several inclined plates, which is mainly used to settle the flocs in the water and prevent the flocs in the water from entering the first outlet above the first inclined plate zone; the second inclined plate zone in the flocculation reactor is composed of several inclined plates, which is mainly used to promote the settling of flocs and solid particle impurities in the water. After the flocs and solid particles (collectively referred to as iron sludge) in the water settle to the second inclined plate zone, they can be discharged periodically or irregularly through the sludge discharge pipe.

[0028] In the above-mentioned technical solution of the device for water treatment using ferrate-derived nascent flocs, the third inclined plate zone in the oxidation reactor is composed of several inclined plates, which are mainly used to settle flocs in the water and prevent flocs in the water from entering the second outlet above the third inclined plate zone; the fourth inclined plate zone in the oxidation reactor is composed of several inclined plates, which are mainly used to promote the settling of nascent flocs generated in the oxidation reactor.

[0029] In the above-mentioned technical solution of the device for water treatment using ferrate-derived nascent flocs in a cascade manner, a guide plate is provided in the region between the first hollow sphere flocculation unit and the first inclined plate region of the flocculation reactor, mainly used to guide the water entering the flocculation reactor from the first inlet more smoothly into the first hollow sphere flocculation unit; a guide plate is provided in the region between the third inclined plate region and the second hollow sphere flocculation unit of the oxidation reactor, mainly used to guide the nascent flocs more smoothly into the second hollow sphere flocculation unit.

[0030] In the above-mentioned technical solution of the device for water treatment using newly formed flocs of ferrate in stages, the first outlet is connected to the second inlet via a pipe fitting. When the position of the first outlet is higher than the position of the second inlet, the first outlet can be directly connected to the second inlet via a pipe fitting, or the first outlet can be connected to the second inlet via a pipe fitting and a conveying pump. When the position of the first outlet is lower than or equal to the position of the second inlet, the first outlet is connected to the second inlet via a pipe fitting and a conveying pump.

[0031] The water treatment method using the aforementioned cascade water treatment device that utilizes newly formed ferrate flocs is as follows:

[0032] ① The water to be treated is fed into the flocculation reactor through the first inlet for flocculation treatment. The flocculated water is then fed into the oxidation reactor through the first outlet and the second inlet. Ferrate or ferrate and activator are added to the oxidation reactor through the dosing port for water treatment. The nascent flocs generated during the water treatment process in the oxidation reactor are collected. The nascent flocs contain nascent Fe(III), the reduction end product of ferrate.

[0033] ② A portion of the nascent flocs collected in step ① are returned to the flocculation reactor via the newly formed floc discharge pipe, the first return pipe, the first return pump, and the control valve. The nascent flocs are then used to flocculate the water to be treated. The remaining nascent flocs collected in step ① are returned to the oxidation reactor via the newly formed floc discharge pipe, the second return pipe, the second return pump, and the control valve. In the oxidation reactor, a ferrate / nascent floc synergistic oxidation system is constructed. The ferrate is activated to generate active intermediate valence states of tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)) to degrade pollutants in the water.

[0034] ③ The water treated by the oxidation reactor is discharged through the second outlet, and the iron sludge produced in the flocculation reactor is collected and discharged through the sludge discharge pipe for solid waste treatment.

[0035] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0036] 1. This invention provides a method for water treatment using newly formed ferrate flocs in a tiered manner. The main technology and concept lie in collecting the nascent flocs generated during the ferrate water treatment process. A portion is returned to the flocculation process for further flocculation, while the other portion is returned to the ferrate oxidation and degradation process to activate the ferrate and generate highly active tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)) to degrade pollutants in the water. Because the nascent flocs contain nascent Fe(III), the reduction end product of ferrate, on the one hand, nascent Fe(III) has the characteristics of small particle size and large specific surface area, which can effectively remove pollutants from the water through flocculation; on the other hand, nascent Fe(III) can activate ferrate to generate active intermediate-valence tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)), forming a ferrate / nascent floc synergistic oxidation system, which is beneficial to improving the degradation capacity of pollutants in the water. The method of this invention can effectively reduce the amount of external activator added, or even avoid the use of external activator. This not only helps to reduce the cost of activator, but also reduces the activator residue in the effluent, allowing the new ecological flocs to be reused. It also helps to reduce the production of iron sludge and lower the cost of harmless treatment of iron sludge.

[0037] 2. Experiments have demonstrated that, compared to methods that do not reuse nascent flocs, or methods that reuse all nascent flocs separately in the flocculation process, or methods that reuse all nascent flocs separately in the ferrate oxidation and degradation water treatment process, the present invention, which returns a portion of the nascent flocs to the flocculation process and another portion to the ferrate oxidation and degradation water treatment process, can significantly improve the removal capacity of pollutants in water.

[0038] 3. This invention also experimentally confirms that, for water quality parameters (COD) Cr For water bodies with the same concentration (96 mg / L, ammonia nitrogen concentration 0.56±0.06 mg / L, total phosphorus concentration 0.51±0.1 mg / L, pH=7.10±0.01), the method described in this invention, with the addition of an activator and the reuse of nascent flocs, can reduce the amount of activator added by approximately 40% compared to existing technologies that add an activator without reusing nascent flocs.

[0039] 4. The present invention also provides a device for water treatment by cascading utilization of newly formed ferrate flocs. This device organically combines a flocculation reactor and an oxidation reactor, and can be used to realize the cascading utilization of newly formed ferrate flocs for water treatment using the method of the present invention. The device has a simple structure and is conducive to widespread application. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the flocculation reactor.

[0041] Figure 2 This is a schematic diagram of the oxidation reactor.

[0042] Figure 3 This is a schematic diagram of a device for water treatment using ferrate-based newly formed flocs in a cascade manner.

[0043] Figures 1-3 In the diagram, 1—flocculation reactor, 1-1—first inclined plate zone, 1-2—flocculation reaction zone, 1-3—second inclined plate zone, 1-4—first inlet, 1-5—first outlet, 1-6—first reflux port, 1-7—sludge discharge pipe, 1-8—first hollow sphere flocculation unit, 2—oxidation reactor, 2-1—third inclined plate zone, 2-2—oxidation reaction zone, 2-3—fourth inclined plate zone, 2-4—second inlet, 2-5—second outlet, 2-6—second reflux port, 2-7—newly formed floc discharge pipe, 2-8—second hollow sphere flocculation unit, 2-9—dosing port, 3-1—first reflux pipe, 3-2—second reflux pipe, 4-1—first reflux pump, 4-2—second reflux pump, 5-1—first stirring device, 5-2—second stirring device, 6—guide plate, 7—control valve, 8—transfer pump. Detailed Implementation

[0044] The following examples further illustrate the method and apparatus for water treatment using ferrate-derived newly formed flocs provided by the present invention. It should be noted that the following examples are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0045] Example 1

[0046] In this embodiment, a structure for a cascade water treatment device utilizing newly formed ferrate flocs is provided, and its structural schematic diagram is shown below. Figure 3 As shown.

[0047] The device for water treatment using ferrate-based newly formed flocs according to the present invention includes a flocculation reactor 1 and an oxidation reactor 2, and also includes a reflux pipe and a reflux pump.

[0048] The structure of the flocculation reactor 1 is as follows: Figure 1 As shown, the flocculation reactor consists of a cylindrical body and a conical shell with an open bottom. One end of the cylindrical body is connected to the bottom of the conical shell as a single unit. The flocculation reactor includes a first inclined plate zone 1-1, a flocculation reaction zone 1-2, a second inclined plate zone 1-3, a first inlet 1-4, a first outlet 1-5, a first return outlet 1-6, and a sludge discharge pipe 1-7. A control valve 7 is installed on the sludge discharge pipe. A first hollow spherical flocculation unit 1-8 is installed in the flocculation reaction zone 1-2. The first inclined plate zone... Unit 1-1 is located at the upper part of the flocculation reactor, and the second inclined plate area 1-3 is located at the lower part of the flocculation reactor. The flocculation reaction zone 1-2 is located between the first inclined plate area 1-1 and the second inclined plate area 1-3. The first inlet 1-4 is located between the first hollow sphere flocculation unit 1-8 and the second inclined plate area 1-3. The first outlet is located above the first inclined plate area 1-1. The first return port 1-6 is connected to the first hollow sphere flocculation unit 1-8. The sludge discharge pipe 1-7 is connected to the lower part of the second inclined plate area 1-3. The first hollow sphere flocculation unit 1-8 consists of a horizontally arranged area separated from the flocculation reaction zone 1-2 by two horizontally arranged perforated plates connected to the inner wall of the flocculation reactor, and flocculation reaction balls filled in this area. The volume filling rate of the flocculation reaction balls in the first hollow sphere flocculation unit is 40%. The flocculation reaction balls have a hollow structure and several pores on their surface. In this embodiment, ABS flocculation reaction balls can be used. A first stirring device 5-1 is installed in the flocculation reaction zone 1-2 above the first hollow sphere flocculation unit 1-8 of the flocculation reactor 1. The first stirring device is mainly used to generate a swirling effect through stirring, promoting the interaction between the water and the flocculation reactor in the first hollow sphere flocculation unit. The first inclined plate zone consists of several inclined plates, mainly used to settle flocculent matter in the water and prevent flocculent matter in the water from entering the first outlet above the first inclined plate zone. The second inclined plate zone consists of several inclined plates, mainly used to promote the settling of flocculent matter and solid particulate impurities in the water. After the flocculent matter and solid particles (collectively referred to as iron sludge) in the water settle to the second inclined plate zone, they can be discharged periodically or irregularly through the sludge discharge pipe. A guide plate is installed in the area between the first hollow sphere flocculation unit and the first inclined plate zone, mainly used to guide the water entering the flocculation reactor from the first inlet more smoothly into the first hollow sphere flocculation unit.

[0049] The structure of the oxidation reactor 2 is as follows: Figure 2 As shown, the oxidation reactor consists of a cylindrical body and a conical shell with an open bottom. One end of the cylindrical body is connected to the bottom of the conical shell as a single unit. The oxidation reactor includes a third inclined plate zone 2-1, an oxidation reaction zone 2-2, a fourth inclined plate zone 2-3, a second inlet 2-4, a second outlet 2-5, a second reflux port 2-6, a new floc discharge pipe 2-7, and a dosing port 2-9. The oxidation reaction zone 2-2 is equipped with a second hollow sphere flocculation unit 2-8. The third inclined plate zone 2-1... -1 is located at the upper part of the oxidation reactor, the fourth inclined plate area 2-3 is located at the lower part of the oxidation reactor, the oxidation reaction zone 2-2 is located between the third inclined plate area 2-1 and the fourth inclined plate area 2-3, the second inlet 2-4, the second reflux port 2-6 and the dosing port 2-9 are connected to the oxidation reaction zone 2-2 above the second hollow ball flocculation unit 2-8, the second outlet 2-5 is located above the third inclined plate area 2-1, and the new floc discharge pipe 2-7 is connected to the lower part of the fourth inclined plate area 2-3. The second hollow ball flocculation unit 2-8 consists of a horizontally set area separated from the oxidation reaction zone 2-2 by two horizontally set porous plates connected to the inner wall of the oxidation reactor, and flocculation reaction balls filled in this area; the volume filling rate of the flocculation reaction balls in the second hollow ball flocculation unit is 40%; the flocculation reaction balls have a hollow structure and several pores on their surface, and in this embodiment, ABS flocculation reaction balls can be used. A second stirring device 5-2 is installed in the oxidation reaction zone 2-2 above the second hollow sphere flocculation unit 2-8 of the oxidation reactor 2. This second stirring device is mainly used to promote the interaction between the water, persulfate, and nascent flocs through stirring. The third inclined plate zone consists of several inclined plates, mainly used to settle flocs in the water and prevent them from entering the second outlet above the third inclined plate zone. The fourth inclined plate zone also consists of several inclined plates, mainly used to promote the settling of nascent flocs generated in the oxidation reactor. A guide plate is installed in the area between the third inclined plate zone and the second hollow sphere flocculation unit, mainly to guide the nascent flocs more smoothly into the second hollow sphere flocculation unit.

[0050] The new floc discharge pipe 2-7 is connected to the first return port 1-6 via the first return pipe 3-1, the first return pump 4-1, and the control valve 7. At the same time, the new floc discharge pipe 2-7 is connected to the second return port 2-6 via the second return pipe 3-2, the second return pump 4-2, and the control valve 7. The first outlet 1-5 is connected to the second inlet 2-4 via pipe fittings and the delivery pump 8.

[0051] Example 2

[0052] In this embodiment, a method for water treatment using ferrate-formed flocs in a cascade manner is provided, comprising the following steps:

[0053] Step 1: The water to be treated is fed into a flocculation reactor for flocculation treatment. The flocculated water is then fed into an oxidation reactor. Ferrate or ferrate and activator are added to the oxidation reactor for water treatment. The nascent flocs generated during the water treatment process in the oxidation reactor are collected. The nascent flocs contain nascent Fe(III), the reduction end product of ferrate.

[0054] Step 2: A portion of the nascent flocs collected in Step 1 are returned to the flocculation reactor for flocculation treatment of the water body to be treated; the remaining nascent flocs collected in Step 1 are returned to the oxidation reactor to construct a ferrate / nascent floc synergistic oxidation system, which activates the ferrate to generate active intermediate valence states of tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)) to degrade pollutants in the water body;

[0055] Step 3: Discharge the water treated by the oxidation reactor and collect the iron sludge produced in the flocculation reactor for solid waste treatment.

[0056] More specifically, this embodiment uses the device described in Embodiment 1 for water treatment. The water quality parameters of the water to be treated are as follows: COD Cr The concentration was 64 mg / L, ammonia nitrogen concentration was 0.53 ± 0.06 mg / L, total phosphorus concentration was 0.48 ± 0.1 mg / L, pH = 7.10 ± 0.01, and the water treatment steps were as follows:

[0057] ① The water to be treated is fed into the flocculation reactor through the first inlet for flocculation treatment. During the flocculation process, the water is stirred at a speed of 200 r / min by the first stirring device. The flocculated water is then fed into the oxidation reactor through the first outlet and the second inlet. K2FeO4 prepared by wet oxidation is added to the oxidation reactor through the dosing port for water treatment. During the water treatment process, the water is stirred at a speed of 200 r / min by the second stirring device. The nascent flocs generated during the water treatment process in the oxidation reactor are collected. The nascent flocs contain nascent Fe(III), the reduction end product of ferrate.

[0058] In this step, the concentration of K2FeO4 in the water of the oxidation reactor is controlled at 10 mg / L, and the hydraulic retention time in the oxidation reactor is controlled at 1.5 h.

[0059] ② A portion of the nascent flocs collected in step ① are returned to the flocculation reactor via the nascent floc discharge pipe, the first return pipe, the first return pump, and the control valve. The nascent flocs are used to flocculate the water to be treated. The flocculation process can effectively flocculate and precipitate large hydrophobic organic molecules. The remaining nascent flocs collected in step ① are returned to the oxidation reactor via the nascent floc discharge pipe, the second return pipe, the second return pump, and the control valve. In the oxidation reactor, a ferrate / nascent floc synergistic oxidation system is constructed. The ferrate is activated to generate active intermediate valence states of tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)) to degrade pollutants in the water. This process is beneficial for the deep degradation of pollutants in the water and reduces the biotoxicity of the water.

[0060] In this step, the volume ratio of nascent flocs returned to the flocculation reactor to that returned to the oxidation reactor is controlled at 1:1. In actual operation, the volume ratio is controlled by controlling the flow rate ratio of the first return pump to the second return pump at 1:1.

[0061] ③ The water treated by the oxidation reactor is discharged through the second outlet, and the iron sludge produced in the flocculation reactor is collected and discharged through the sludge discharge pipe for solid waste treatment.

[0062] Water quality was measured using water from the second outlet. The results showed that the method described in this embodiment effectively reduced COD levels. Cr The removal rates of acute toxicity of luminescent bacteria and total phosphorus were 67.2%, 68%, and 83.9%, respectively.

[0063] Comparative Example 1

[0064] In this comparative example, K2FeO4 was used alone for water treatment. The water quality parameters of the water to be treated were the same as those used in Example 2. The operation was as follows:

[0065] The water to be treated is introduced into the oxidation reactor through the second inlet. K2FeO4, prepared by wet oxidation, is added to the oxidation reactor through the dosing port for water treatment. During the water treatment process, the reactor is stirred at a speed of 200 r / min using a second stirring device. The concentration of K2FeO4 in the water in the oxidation reactor is controlled at 10 mg / L, and the hydraulic retention time in the oxidation reactor is controlled at 1.5 h.

[0066] Water quality was measured from the effluent at the second outlet. The results showed that the method used in this comparative study had an effect on COD. Cr The removal rates of acute toxicity of luminescent bacteria and total phosphorus were 23.6%, 20%, and 55.8%, respectively.

[0067] Comparative Example 2

[0068] The operation of this comparative example is basically the same as that of Example 2, except that all the new ecological flocs collected in step ① are returned to the flocculation reactor through the new floc discharge pipe, the first return pipe, the first return pump and the control valve.

[0069] Water quality was measured from the effluent at the second outlet. The results showed that the method used in this comparative study had an effect on COD. Cr The removal rates of acute toxicity of luminescent bacteria and total phosphorus were 31.3%, 24%, and 63.5%, respectively.

[0070] Comparative Example 3

[0071] The operation of this comparative example is basically the same as that of Example 2, except that all the new ecological flocs collected in step ① are returned to the oxidation reactor through the new floc discharge pipe, the second return pipe, the second return pump and the control valve.

[0072] Water quality was measured from the effluent at the second outlet. The results showed that the method used in this comparative study had an effect on COD. Cr The removal rates of acute toxicity of luminescent bacteria and total phosphorus were 39.4%, 60%, and 67.3%, respectively.

[0073] As can be seen from Example 2 and Comparative Examples 1-3, the method of the present invention, by returning a portion of the nascent flocs collected in step ① to the flocculation reactor and another portion to the oxidation reactor, can not only enhance the pollutant removal capacity of the flocculation process, but also effectively enhance the pollutant removal capacity of the oxidation process, ultimately improving the pollutant removal effect.

[0074] Example 3

[0075] In this embodiment, the method provided by the present invention is used for water treatment. The water quality parameters of the water body to be treated are as follows: COD Cr The concentrations were 96 mg / L, ammonia nitrogen 0.56 ± 0.06 mg / L, total phosphorus 0.51 ± 0.1 mg / L, and pH 7.10 ± 0.01. The operation of this embodiment is basically the same as that of Embodiment 2, except that in step ①, the concentration of K2FeO4 in the water of the oxidation reactor is controlled at 30 mg / L, and the hydraulic retention time in the oxidation reactor is controlled at 2 hours; simultaneously, in step ②, activator H2O2 is added to the nascent flocs returned to the oxidation reactor, so that the concentration of activator H2O2 in the water of the oxidation reactor is 1.6 mg / L.

[0076] Water quality was measured using water from the second outlet. The results showed that the method described in this embodiment effectively reduced COD levels. Cr The removal rates of acute toxicity of luminescent bacteria and total phosphorus were 76.4%, 71%, and 96.6%, respectively.

[0077] Comparative Example 4

[0078] In this comparative example, K2FeO4 was activated with H2O2 for water treatment. The water quality parameters of the water to be treated were the same as those used in Example 3. The operation was as follows:

[0079] The water to be treated is introduced into the oxidation reactor through the second inlet. K2FeO4, prepared by wet oxidation, is added to the oxidation reactor through the dosing port for water treatment. During the water treatment process, the reactor is stirred at a speed of 200 r / min using a second stirring device. The concentration of K2FeO4 in the water in the oxidation reactor is controlled at 30 mg / L, and the hydraulic retention time in the oxidation reactor is controlled at 2 h.

[0080] By adjusting the amount of activator H2O2 added, the effluent quality of the second outlet was made comparable to that of Example 3. It was found that the effluent quality of the second outlet could only reach a level close to that of Example 3 when the concentration of activator H2O2 in the water of the oxidation reactor was 2.2 mg / L.

[0081] As can be seen from Example 3 and Comparative Example 4, when the treatment effect on water bodies of the same quality is comparable, the method of the present invention, which returns the newly generated flocs in step ① to the flocculation reactor and the oxidation reactor, can effectively reduce the amount of external activator added. For example, for the activator H2O2 in Example 3 and Comparative Example 4, the amount of activator added can be reduced by about 40%. This not only helps to reduce the cost of activator, but also reduces the activator residue in the effluent. Reusing the newly generated flocs also helps to reduce the production of iron sludge and reduce the cost and workload of harmless treatment of iron sludge.

[0082] Example 4

[0083] In this embodiment, the method provided by the present invention is used for water treatment. The water quality parameters of the water to be treated are as follows: COD concentration 102 mg / L, ammonia nitrogen concentration 0.59 ± 0.06 mg / L, total phosphorus concentration 0.65 ± 0.1 mg / L, pH = 7.10 ± 0.01. The operation of this embodiment is basically the same as that of Embodiment 2, except that: in step ①, the concentration of K2FeO4 in the water of the oxidation reactor is controlled to be 25 mg / L, the hydraulic retention time in the oxidation reactor is controlled to be 1.5 h, and the first stirring device is used to apply stirring at a speed of 300 r / min during the flocculation process, and the second stirring device is used to apply stirring at a speed of 300 r / min during the water treatment process; in step ②, the volume ratio of the nascent flocs returned to the flocculation reactor to the nascent flocs returned to the oxidation reactor is controlled to be 2:1. In actual operation, the volume ratio is controlled by controlling the flow rate ratio of the first return pump to the second return pump to be 2:1.

[0084] Water quality was measured at the second outlet. The results showed that the method in this embodiment achieved removal rates of 66.4%, 60.1%, and 95.6% for COD, acute toxicity of luminescent bacteria, and total phosphorus, respectively.

[0085] Example 5

[0086] The operation of this embodiment is basically the same as that of embodiment 4, except that in step ②, the volume ratio of the nascent flocs returned to the flocculation reactor to the nascent flocs returned to the oxidation reactor is controlled to be 1:2. In actual operation, the volume ratio is controlled by controlling the flow ratio of the first return pump to the second return pump to be 1:2.

[0087] Water quality was measured at the second outlet. The results showed that the method in this embodiment achieved removal rates of 75.5% for COD, 80.2% for acute toxicity of luminescent bacteria, and 99.4% for total phosphorus.

Claims

1. A method for water treatment using ferrate-formed flocs in a cascade manner, characterized in that, This method uses a water treatment device with the following structure for water treatment, which includes a flocculation reactor (1), an oxidation reactor (2), a reflux pipe, and a reflux pump. The flocculation reactor (1) includes a first inclined plate zone (1-1), a flocculation reaction zone (1-2), a second inclined plate zone (1-3), a first inlet (1-4), a first outlet (1-5), a first return outlet (1-6), and a sludge discharge pipe (1-7). A first hollow spherical flocculation unit (1-8) is provided in the flocculation reaction zone (1-2). The first inclined plate zone (1-1) is located at the upper part of the flocculation reactor, and the second inclined plate zone (1-3) is located at the lower part of the flocculation reaction zone. The lower part of the reactor is a flocculation reaction zone (1-2) between the first inclined plate area (1-1) and the second inclined plate area (1-3). The first inlet (1-4) is located between the first hollow ball flocculation unit (1-8) and the second inclined plate area (1-3). The first outlet is located above the first inclined plate area (1-1). The first return port (1-6) is connected to the first hollow ball flocculation unit (1-8). The sludge discharge pipe (1-7) is connected to the second inclined plate area (1-3). The oxidation reactor (2) includes a third inclined plate zone (2-1), an oxidation reaction zone (2-2), a fourth inclined plate zone (2-3), a second inlet (2-4), a second outlet (2-5), a second reflux outlet (2-6), a new floc discharge pipe (2-7), and a dosing port (2-9). The oxidation reaction zone (2-2) is equipped with a second hollow sphere flocculation unit (2-8). The third inclined plate zone (2-1) is located at the top of the oxidation reactor, and the fourth inclined plate zone (2-3)... Located at the bottom of the oxidation reactor, the oxidation reaction zone (2-2) is between the third inclined plate zone (2-1) and the fourth inclined plate zone (2-3). The second inlet (2-4), the second reflux port (2-6), and the dosing port (2-9) are connected to the oxidation reaction zone (2-2) above the second hollow sphere flocculation unit (2-8). The second outlet (2-5) is located above the third inclined plate zone (2-1). The newly formed floc discharge pipe (2-7) is connected to the fourth inclined plate zone (2-3). The new floc discharge pipe (2-7) is connected to the first return port (1-6) via the first return pipe (3-1), the first return pump (4-1), and the control valve. At the same time, the new floc discharge pipe (2-7) is connected to the second return port (2-6) via the second return pipe (3-2), the second return pump (4-2), and the control valve. The first outlet (1-5) is connected to the second inlet (2-4) via a pipe fitting. The method includes the following steps: ① The water to be treated is fed into a flocculation reactor for flocculation treatment. The flocculated water is then fed into an oxidation reactor. Ferrate is added to the oxidation reactor for water treatment. The nascent flocs generated during the water treatment process in the oxidation reactor are collected. The nascent flocs contain nascent Fe(III), the reduction end product of ferrate. ② A portion of the nascent flocs collected in step ① are returned to the flocculation reactor for flocculation treatment of the water body to be treated; the remaining nascent flocs collected in step ① are returned to the oxidation reactor to construct a ferrate / nascent floc synergistic oxidation system, activating the ferrate to generate active intermediate valence states of tetravalent iron Fe(IV) and pentavalent iron Fe(V) to degrade pollutants in the water body; the volume ratio of nascent flocs returned to the flocculation reactor to that returned to the oxidation reactor is (1~2):(1~2); ③ Discharge the water treated by the oxidation reactor and collect the iron sludge produced in the flocculation reactor for solid waste treatment.

2. The method for water treatment using ferrate-formed flocs in a cascade manner according to claim 1, characterized in that, The pH of the water in the oxidation reactor is controlled to be 7-9.

3. The method for water treatment using ferrate-formed flocs in a cascade manner according to claim 1, characterized in that, During water treatment in the oxidation reactor, stirring is applied, and the stirring speed is controlled at 200~500 r / min.

4. The method for water treatment using ferrate-formed flocs in a cascade manner according to any one of claims 1 to 3, characterized in that, The hydraulic retention time in the oxidation reactor is controlled to be 1-3 h.

5. The method for water treatment using ferrate-formed flocs in a cascade manner according to any one of claims 1 to 3, characterized in that, An activator is added to the oxidation reactor to activate ferrates to produce tetravalent iron (Fe(IV)) and pentavalent iron (Fe(V)).

6. The method for water treatment using ferrate-formed flocs in a cascade manner according to any one of claims 1 to 3, characterized in that, The concentration of ferrate in the water of the oxidation reactor is controlled at 10~40 mg / L.

7. The method for water treatment using ferrate-formed flocs in a cascade manner according to claim 1, characterized in that, The first hollow sphere flocculation unit (1-8) consists of a horizontally set area separated from the flocculation reaction zone (1-2) by two porous plates connected to the inner wall of the flocculation reactor, and flocculation reaction spheres filled in the area; the second hollow sphere flocculation unit (2-8) consists of a horizontally set area separated from the oxidation reaction zone (2-2) by two porous plates connected to the inner wall of the oxidation reactor, and flocculation reaction spheres filled in the area.

8. The method for water treatment using ferrate-formed flocs in a cascade manner according to claim 1, characterized in that, A first stirring device (5-1) is provided in the flocculation reaction zone (1-2) above the first hollow sphere flocculation unit (1-8) of the flocculation reactor (1), and a second stirring device (5-2) is provided in the oxidation reaction zone (2-2) above the second hollow sphere flocculation unit (2-8) of the oxidation reactor (2).

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