Process for treating carbon fiber wastewater by enhanced electro-Fenton combined membrane bioreactor

Abstract

The invention discloses a process for treating carbon fiber wastewater by an enhanced electro-Fenton combined membrane bioreactor. The process comprises the steps of pretreatment, electro-Fenton enhancement, hydrolytic acidification and membrane bioreactor treatment, mass transfer and oxidation effects are enhanced by coupling micro-nano bubbles in electro-Fenton reaction, hydrogen peroxide is supplemented and added for reaction, and then wastewater enters a hydrolytic acidification pool and is treated by a membrane bioreactor and then discharged after reaching the standard. According to the method, the dimethyl sulfoxide and decomposition products in the wastewater are oxidized through the enhanced electro-Fenton system, the removal rate of the dimethyl sulfoxide can reach 99% or above, then biochemical treatment is carried out through hydrolytic acidification, COD and ammonia nitrogen of the wastewater are further reduced, finally, organic matter and nutrient substances are removed at high speed and high efficiency through MBR, and the treatment effect is good. The concentration of dimethyl sulfoxide is reduced to be below 10 mg / L, the concentration of COD is reduced to be below 100 mg / L, and the concentration of ammonia nitrogen is reduced to be below 10 mg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial wastewater treatment and relates to a process for treating carbon fiber wastewater by using an enhanced electro-Fenton combined membrane bioreactor. Background Art

[0002] As the global demand for high-performance materials grows, carbon fiber, as a lightweight, high-strength advanced composite material, has been widely used in aerospace, automobile, sports equipment and other fields. Carbon fiber wastewater mainly comes from the carbon fiber production process. For example, polyacrylonitrile (PAN)-based carbon fiber requires a large amount of organic solvents and acid-base chemicals during the preparation process. In the carbon fiber spinning process, dimethyl sulfoxide (DMSO) is an important solvent used to dissolve polymers and adjust the viscosity of the spinning solution. Dimethyl sulfoxide pollutants have the characteristics of strong stability, high toxicity, and strong solubility, which increases the difficulty of treatment.

[0003] The existing treatment methods for carbon fiber wastewater containing DMSO mainly include traditional Fenton method and biochemical method. The traditional Fenton method has a large dosage of reagents, limited treatment effect, and high civil engineering area; while in the pure biochemical method, DMSO is highly toxic to bacteria, limiting the effect of bacteria in degrading pollutants, and a certain amount of sulfur-containing volatiles will be produced during the degradation of DMSO under anaerobic conditions, causing secondary pollution; the degradation of DMSO under aerobic conditions has problems such as long degradation time and low removal rate. Summary of the invention

[0004] The purpose of the present invention is to provide a process for treating carbon fiber wastewater by an enhanced electro-Fenton combined membrane bioreactor, which can efficiently and reasonably treat carbon fiber wastewater containing dimethyl sulfoxide so that it meets discharge standards.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] The process of treating carbon fiber wastewater by enhanced electro-Fenton combined with membrane bioreactor includes pretreatment, enhanced electro-Fenton, hydrolysis acidification, and membrane bioreactor treatment. The specific steps are as follows:

[0007] (1) The carbon fiber wastewater containing DMSO is passed through a sand filter device for pretreatment;

[0008] (2) The pretreated wastewater is adjusted to pH 3-4 and then passed into an electro-Fenton device, wherein the electro-Fenton device is connected to a micro-nano bubble generator, and the micro-nano bubbles generated by the micro-nano bubble generator enhance the mass transfer and oxidation effect of the wastewater, and hydrogen peroxide is added to perform enhanced electro-Fenton treatment, followed by alkali adjustment for flocculation and precipitation;

[0009] (3) The wastewater after enhanced electro-Fenton treatment is passed into a hydrolysis acidification tank for treatment;

[0010] (4) The effluent from the hydrolysis and acidification tank is introduced into the membrane bioreactor, and the sludge load in the reactor is controlled to be 0.5-2.0 kg / (kg·d). An air pump is used for aeration, mixing and oxygenation, and the dissolved oxygen content is controlled to be 2-5 mg / L. The wastewater treated by the membrane bioreactor is directly discharged.

[0011] Furthermore, in step (1), the concentration of dimethyl sulfoxide in the DMSO-containing carbon fiber wastewater is 100 to 1000 mg / L.

[0012] Furthermore, in step (2), the current of the electro-Fenton device is adjusted to 200A, the average diameter of the micro-nano bubbles is 100nm, the dosage of hydrogen peroxide is 0.5-1‰ of the total volume of the wastewater, and the hydraulic retention time is 1-2 hours.

[0013] Furthermore, in step (3), the hydraulic retention time is 8 to 12 hours.

[0014] Furthermore, in step (4), the water temperature in the membrane bioreactor is controlled at 25-35° C., and the hydraulic retention time is 8-12 hours.

[0015] The invention adopts a novel treatment process of "enhanced electro-Fenton + hydrolysis acidification + membrane bioreactor (MBR)". Under the process, dimethyl sulfoxide wastewater passes through an enhanced electro-Fenton system, and hydrogen peroxide and free radical OH are used to oxidize high molecular organic matter in the wastewater under the action of the electro-Fenton reaction. Micro-nano bubbles play an enhanced mass transfer effect and enhance the oxidation effect in the enhanced electro-Fenton system. In addition, during the rupture process of the micro-nano bubbles, due to the drastic change of the disappearance of the gas-liquid interface, the high-concentration ions gathered on the interface will release chemical energy, which can stimulate the generation of a large number of hydroxyl free radicals and reduce the dosage of the system. The dimethyl sulfoxide wastewater is oxidized by the enhanced electro-Fenton system. The dimethyl sulfoxide and decomposition products in the wastewater are then biochemically treated by hydrolysis acidification to further reduce the COD and ammonia nitrogen of the wastewater. Finally, the organic matter and nutrients are removed at a high speed and high efficiency through the MBR.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) Hydrogen peroxide and free radical OH are produced during the electrolytic reduction process of the electro-Fenton system. At the same time, new Fe is continuously produced, and the catalytic effect on hydrogen peroxide will not be weakened. Therefore, the amount of hydrogen peroxide added during the treatment process is reduced to the greatest extent, thereby reducing operating costs. In addition, by coupling micro-nano bubbles, mass transfer in the Fenton system can be enhanced, oxidation has no dead zone, and the effluent is more stable. At the same time, the introduction of micro-nano bubbles can stimulate the generation of a large number of free radicals, further reducing the amount of hydrogen peroxide added.

[0018] (2) According to the process of the present invention, 1000 mg / L DMSO wastewater is oxidized by an enhanced electro-Fenton system to remove DMSO and its decomposition products, and the removal rate of DMSO can reach more than 99%. Then, biochemical treatment is performed by hydrolysis and acidification to further reduce the COD and ammonia nitrogen in the wastewater. Finally, organic matter and nutrients are removed at a high speed and high efficiency through MBR, and DMSO is reduced to less than 10 mg / L, COD is reduced to less than 100 mg / L, and ammonia nitrogen is reduced to less than 10 mg / L, so that the wastewater can be stably discharged and meet the discharge standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0021] The following examples and comparative examples use the same batch of DMSO-containing carbon fiber wastewater, and the concentration of dimethyl sulfoxide in the original wastewater is 1000 mg / L.

[0022] Comparative Example 1

[0023] The carbon fiber wastewater containing DMSO was passed into a sand filtration device for pretreatment, and then the pH was adjusted to 7 and entered the membrane bioreactor for treatment for 12 hours. The sludge load in the reactor was controlled at 1.5 kg / (kg·d), the water temperature was 25°C, and an air pump was used for aeration, mixing and oxygenation to control the dissolved oxygen content to 4 mg / L. The dimethyl sulfoxide concentration in the effluent was 868 mg / L, the COD was 371 mg / L, and the ammonia nitrogen was 26 mg / L.

[0024] Comparative Example 2

[0025] The carbon fiber wastewater containing DMSO from the same batch as that in Comparative Example 1 was passed into a sand filter for pretreatment, and then entered a traditional Fenton tank. The dosage of hydrogen peroxide was 2‰, the pH value of the Fenton inlet water was controlled at 3, the hydraulic retention time was 6 hours, the alkali was adjusted for flocculation and precipitation, and then the wastewater entered the hydrolysis acidification tank and stayed for 12 hours. After that, the wastewater entered the membrane bioreactor for treatment for 12 hours, and the sludge load in the reactor was controlled at 1.5 kg / (kg·d), the water temperature was 25°C, and an air pump was used for aeration, mixing and oxygenation to control the dissolved oxygen content to 4 mg / L. The wastewater after treatment in the membrane bioreactor had a dimethyl sulfoxide concentration of 349 mg / L, a COD of 190 mg / L, and ammonia nitrogen of 17 mg / L.

[0026] Comparative Example 3

[0027] The carbon fiber wastewater containing DMSO from the same batch as that in Comparative Example 1 was passed into a sand filter device for pretreatment, and then entered the electro-Fenton device, and hydrogen peroxide was added. The dosage of hydrogen peroxide was 1‰, the pH value of the electro-Fenton inlet water was controlled at 3, the current was 200A, the hydraulic retention time was 2 hours, the alkali was adjusted for flocculation and precipitation, and then the wastewater entered the hydrolysis acidification tank and stayed for 12 hours. After that, the wastewater entered the membrane bioreactor for treatment for 12 hours, and the sludge load in the reactor was controlled at 1.5kg / (kg·d), the water temperature was 25°C, and an air pump was used for aeration, mixing and oxygenation to control the dissolved oxygen content to 4mg / L. The wastewater after treatment in the membrane bioreactor had a dimethyl sulfoxide concentration of 139mg / L, a COD of 103mg / L, and an ammonia nitrogen of 12mg / L.

[0028] Example 1

[0029] The carbon fiber wastewater containing DMSO from the same batch as that in Comparative Example 1 was passed into a sand filter for pretreatment, and then entered an electro-Fenton device, which was connected to a micro-nano bubble generator. The micro-nano bubbles generated by the micro-nano bubble generator enhanced the mass transfer and oxidation effect of the wastewater. The average diameter of the micro-nano bubbles was 100 nm, and hydrogen peroxide was added. The dosage of hydrogen peroxide was 1‰. The pH value of the electro-Fenton inlet water was controlled at 3, the current was 200A, the hydraulic retention time was 2 hours, the alkali was adjusted for flocculation and precipitation, and then the wastewater entered the hydrolysis acidification tank and stayed for 12 hours. After that, the wastewater entered the membrane bioreactor for treatment for 12 hours, and the sludge load in the reactor was controlled at 1.5 kg / (kg·d), the water temperature was 25°C, and an air pump was used for aeration, mixing and oxygenation to control the dissolved oxygen content to 4 mg / L. The wastewater treated by the membrane bioreactor had a dimethyl sulfoxide concentration of 9 mg / L, a COD of 78 mg / L, and ammonia nitrogen of 6 mg / L.

Claims

1. A process for treating carbon fiber wastewater by strengthening electro-Fenton combined with membrane bioreactor, characterized in that: The specific steps are as follows: (1) Carbon fiber wastewater containing DMSO is passed through a sand filter for pretreatment; (2) The pretreated wastewater is adjusted to pH 3-4 and then passed into an electro-Fenton device, wherein the electro-Fenton device is connected to a micro-nano bubble generator, and the micro-nano bubbles generated by the micro-nano bubble generator enhance the mass transfer and oxidation effect of the wastewater, and hydrogen peroxide is added to perform enhanced electro-Fenton treatment, followed by alkaline flocculation and precipitation; (3) The wastewater after enhanced electro-Fenton treatment is passed into a hydrolysis acidification tank for treatment; (4) The effluent from the hydrolysis and acidification tank is introduced into the membrane bioreactor, and the sludge load in the reactor is controlled at 0.5~2.0kg / (kg·d). An air pump is used for aeration and mixing to control the dissolved oxygen content at 2~5mg / L. The wastewater treated by the membrane bioreactor is directly discharged.

2. The process according to claim 1, characterized in that In step (1), the concentration of dimethyl sulfoxide in the carbon fiber wastewater containing DMSO is 100-1000 mg / L.

3. The process according to claim 1, characterized in that In step (2), the current of the electro-Fenton device is adjusted to 200A, the average diameter of the micro-nano bubbles is 100nm, the dosage of hydrogen peroxide is 0.5-1‰ of the total volume of the wastewater, and the hydraulic retention time is 1-2 hours.

4. The process according to claim 1, characterized in that In step (3), the hydraulic retention time is 8 to 12 hours.

5. The process according to claim 1, characterized in that In step (4), the water temperature in the membrane bioreactor is controlled at 25-35°C, and the hydraulic retention time is 8-12 hours.

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