Energy-saving and environment-friendly treatment method for sewage generated by spinning electrostatic deoiling device

Abstract

The invention relates to the technical field of sewage treatment, and discloses an energy-saving and environment-friendly treatment method for sewage generated by a spinning electrostatic deoiling device. The method comprises the following steps: performing oil separation pretreatment on the oily agent wastewater, and treating in a pH adjusting tank in two stages: in the first stage, adjusting the pH value to 9-10, and adding polyaluminum chloride while quickly stirring; and in the second stage, the pH is further adjusted to 11-12, polyacrylamide is added with slow stirring, and finally, standing, precipitation and separation are performed. According to the method, the pollutant removal efficiency is remarkably improved and the COD (Chemical Oxygen Demand) removal rate is high by accurately regulating and controlling the pH value, adding the flocculating agent in batches and controlling the stirring speed. Meanwhile, compared with a traditional process, consumption of a large amount of acid and alkali is avoided, generation of hazardous waste such as sludge is reduced, the dosage of a flocculating agent and the treatment cost are reduced, and the efficient, economical and environment-friendly sewage treatment target is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to an energy-saving and environmentally friendly treatment method for sewage generated by a spinning electrostatic deoiling device. Background Art

[0002] During the spinning process, the operation of the electrostatic degreasing equipment generates a large amount of wastewater containing oily agents. Testing and analysis have shown that over 90% of this wastewater is cooling water used for cleaning, and it also contains complex pollutants such as emulsified oil and surfactants. If this wastewater is discharged without effective treatment, it will not only corrode the pipe network but also cause serious damage to the receiving water ecosystem, leading to problems such as microbial inhibition and eutrophication.

[0003] Within the industry, there are significant differences in processing technology among companies of different sizes: A large-scale sewage treatment plant that relies on supporting facilities adopts a combination of "pretreatment, biological treatment and deep treatment" processes, such as anaerobic-aerobic (A / O) biological denitrification and carbon removal processes, membrane bioreactors (MBRs), etc. Although it can achieve stable emission standards, the initial equipment investment is large, and the operating energy consumption cost accounts for about 35% of the treatment cost, which is too costly.

[0004] In addition, there is another commonly used process: the "pretreatment tank, pH adjustment tank, Fenton reaction tank and filter press" process is often used. Its technical details and defects are as follows: Technical principle and parameters: Fenton reaction is carried out through H2O2 and Fe 2+ Strong oxidizing hydroxyl free radicals are produced to degrade organic matter, but the pH needs to be adjusted to a strong acidic condition of 2-4. After the reaction, the pH needs to be adjusted back to 8-9 for flocculation and precipitation, and the consumption of acid and alkali reagents is large.

[0005] Actual treatment results: Chemical oxygen demand (COD) is a key indicator of the amount of organic pollutants in water. Due to fluctuations in reaction conditions, COD removal rates are unstable (averaging only 60-70%), making it difficult to meet stringent emission standards. This also produces a large amount of sludge, which is considered a hazardous waste. Summary of the Invention

[0006] To solve the above problems, the present invention provides an energy-saving and environmentally friendly treatment method for wastewater generated by a spinning electrostatic deoiling device. By optimizing pH parameters, adding different flocculants in batches, and controlling process parameters such as stirring speed, the removal efficiency of pollutants in wastewater is improved, the amount of flocculants used is reduced, thereby reducing treatment costs, and at the same time reducing the amount of hazardous waste generated, thereby achieving efficient, economical and environmentally friendly treatment of spinning oil-containing wastewater.

[0007] To achieve the above object, the present invention provides the following technical solutions: An energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic degreasing device, comprising the following specific steps: S1. Wastewater pretreatment: The spinning oil-containing wastewater is discharged into the mixing tank and the pretreatment tank, and then the oil separator is used for preliminary oil filtration to separate most of the floating oil; S2. pH adjustment and flocculation: The wastewater after oil separation treatment is transported to the pH adjustment tank. In the first stage, an alkaline regulator is added to the wastewater to adjust the pH value of the wastewater to 9-10, and the wastewater is stirred evenly to cause preliminary coagulation of some oil agents and pollutants in the wastewater. After the pH adjustment in the first stage is completed, stir rapidly at a stirring speed of 150-200 r / min, and add flocculant polyaluminum chloride at the same time. The stirring time is 10-15 minutes to allow the flocculant to disperse quickly and fully contact with the pollutants; The second stage: After an interval of 30-60 minutes, continue to add alkaline regulator to further adjust the pH value of the wastewater to 11-12, stir evenly, and promote the destabilization of colloidal particles in the wastewater; After the pH adjustment in the second stage is completed, reduce the stirring speed to 50-80r / min, add flocculant polyacrylamide, and stir for 20-30 minutes to promote the growth and aggregation of flocs; S3. Sedimentation and separation: After the gradient stirring flocculation is completed, the sedimentation is allowed to stand for 12-18 hours to allow the flocs to fully settle. The supernatant is then pumped into the oil acidification tank for subsequent treatment. The sludge at the bottom is transported to the sludge collection tank by a pneumatic diaphragm pump and then collected by filter pressing using a screw press. The small amount of concentrated oil separated is collected in an isolation tank.

[0008] As an inorganic flocculant, polyaluminium chloride (PAC) can generate high-valent polynuclear complex ions through hydrolysis, compressing the double layer of colloidal particles and destabilizing and agglomerating them. It is suitable for use at higher pH (9-12). Adding PAC flocculants in batches can quickly neutralize the charge during the initial destabilization of the wastewater (pH 9-10), forming fine floc nuclei.

[0009] As an organic polymer flocculant, polyacrylamide connects small floc cores into larger flocs through the bridging effect of long-chain molecules. Adding polyacrylamide after initial coagulation of polyaluminium chloride and adjusting the pH to 6-8 prevents damage to the polyacrylamide molecular chains caused by high pH. Slow stirring promotes bridging, forming dense flocs.

[0010] If two reagents are added at one time, polyaluminum chloride may not be fully hydrolyzed due to the high local concentration, and polyacrylamide may be neutralized by metal ions due to premature contact with polyaluminum chloride, reducing the bridging efficiency; adding them in batches can ensure that polyaluminum chloride is destabilized first, and then polyacrylamide is efficiently bridged, reducing the amount of reagents used.

[0011] In addition, rapid stirring after adding polyaluminium chloride can accelerate the diffusion of the agent in the wastewater, allowing the polynuclear complex ions produced by its hydrolysis to quickly come into contact with destabilised colloidal particles (such as oils and suspended solids), forming fine flocs. If stirring is too slow, polyaluminium chloride may aggregate locally, resulting in uneven coagulation.

[0012] Slow stirring after adding polyacrylamide prevents high shear forces from disrupting the already formed floc structure. It also provides ample time for long-chain molecules to collide with and bridge small flocs, promoting floc growth. The gentle water flow created by slow stirring allows the flocs to gradually aggregate through adsorption and bridging, forming large, easily precipitated flocs.

[0013] As an energy-saving and environmentally friendly treatment method for wastewater generated by a spinning electrostatic degreasing device, Preferably, the wastewater comes from cooling water and cleaning water of an electrostatic oil removal device, wherein the water content is greater than 90%.

[0014] Preferably, the alkaline regulator in step S2 is sodium hydroxide.

[0015] Preferably, the acidic regulator in step S3 is sulfuric acid.

[0016] Preferably, the amount of polyaluminium chloride added is such that the concentration of polyaluminium chloride in the wastewater reaches 80-100 mg / L.

[0017] Preferably, the amount of polyacrylamide added is such that the concentration of polyacrylamide in the wastewater reaches 4-6 mg / L.

[0018] Preferably, in the third stage of pH adjustment, an acidic regulator is added to adjust the pH value of the wastewater to 6-8.

[0019] Also provided is an energy-saving and environmentally friendly treatment system for the wastewater generated by the spinning electrostatic deoiling device of the treatment method, comprising a mixing tank and a pretreatment tank, an oil separator, a pH adjustment tank, a sludge collection tank and a screw stacker connected in sequence; a stirring device and a reagent dosing device are provided in the pH adjustment tank; the stirring device can achieve switching of the stirring speed from 0 to 300 r / min.

[0020] The beneficial effects of the present invention are: (1) Efficient pollutant removal: By adjusting the pH value in stages and combining flocculants with different characteristics, combined with stirring speed adjustment, efficient pollutant removal is achieved. After adjusting the pH to 9-10, rapid stirring at a speed of 150-200 r / min and adding polyaluminum chloride can accelerate the diffusion of the agent, so that the multi-nuclear complex ions produced by its hydrolysis quickly contact with the destabilized colloidal particles to form fine flocs; after further adjusting the pH to 11-12, the stirring speed is reduced to 50-80 r / min, and polyacrylamide is added. Slow stirring can avoid high shear forces from destroying the formed floc structure, while providing sufficient time for long-chain molecules to collide with and bridge the fine flocs, promoting floc growth. Compared with traditional processes, the COD removal rate is significantly improved.

[0021] (2) Energy saving and environmental protection: This process avoids the large amount of acid and alkali reagent consumption caused by the traditional Fenton reaction process, which requires adjusting the pH to a strong acid (2-4) and then back to an alkaline pH (pH 8-9). In addition, it reduces the amount of hazardous waste such as sludge, lowers the cost of hazardous waste treatment and environmental risks, and achieves the goal of energy saving and environmental protection.

[0022] (3) Reduce treatment costs: Adding flocculants in batches avoids mutual interference between reagents, improves the efficiency of reagent use, reduces the amount of polyaluminum chloride and polyacrylamide, reduces the overall treatment cost, and has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a photo of a wastewater treatment pH adjustment tank; Figure 2 This is a photo of the sample placement after adding the flocculant polyaluminium chloride in Example 1; Figure 3 This is a photo of the sample placement after adding the flocculant polyacrylamide in Example 1; Figure 4 1 to 3 and the COD value curves after purification of Comparative Examples 1 and 2; Figure 5 1 to 3, Comparative Example 3 and Comparative Example 4 are the COD value curves after purification; Figure 6 1 to 3, Comparative Example 5 and Comparative Example 6 are the COD value curves after purification; Figure 7 It is a schematic diagram of an energy-saving and environmentally friendly treatment system for wastewater generated by a spinning electrostatic deoiling device. DETAILED DESCRIPTION

[0024] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the following embodiments. The following is merely an example and illustration of the concept of the present invention. Those skilled in the art may make various modifications, additions, or substitute similar methods for the specific embodiments described. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0025] Example 1 An energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device comprises the following steps: S1. Wastewater pretreatment: Take 1 ton of spinning oil-containing wastewater, discharge it into the mixing tank and pretreatment tank, and perform preliminary oil filtration in the oil separator to separate most of the floating oil; S2, pH adjustment and flocculation: The wastewater after oil separation treatment is transported to the pH adjustment tank, The first stage: add NaOH regulator to the wastewater to adjust the pH value of the wastewater to 9 and stir evenly; after the pH adjustment of the first stage is completed, stir rapidly at a stirring speed of 150r / min, and add flocculant polyaluminum chloride (concentration reaches 80mg / L) at the same time and stir for 10 minutes; Second stage: After an interval of 30 minutes, continue to add NaOH regulator to further adjust the pH value of the wastewater to 11 and stir evenly; after the pH adjustment in the second stage is completed, reduce the stirring speed to 50r / min, add flocculant polyacrylamide (concentration reaches 4mg / L), and stir for 20 minutes; S3, Sedimentation and Separation: After flocculation is complete, the mixture is allowed to settle for 12 hours. The supernatant is then pumped into an oil acidification tank for subsequent treatment with sulfuric acid to adjust the pH value of the wastewater back to 6. The sludge at the bottom is pumped to a sludge collection tank via a pneumatic diaphragm pump and then filtered and collected by a screw press. The small amount of concentrated oil separated is collected in an isolation tank and outsourced for processing. Also provided is an energy-saving and environmentally friendly treatment system for the wastewater generated by the spinning electrostatic deoiling device of the above-mentioned treatment method, comprising a mixing tank and a pretreatment tank, an oil separator, a pH adjustment tank, a sludge collection tank and a screw stacking machine connected in sequence; a stirring device is provided in the pH adjustment tank; the stirring device can achieve switching of the stirring speed from 0 to 300 r / min.

[0026] Example 2 An energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device comprises the following steps: S1. Wastewater pretreatment: Take 1 ton of spinning oil-containing wastewater, discharge it into the mixing tank and pretreatment tank, and perform preliminary oil filtration in the oil separator to separate most of the floating oil; S2, pH adjustment and flocculation: The wastewater after oil separation treatment is transported to the pH adjustment tank, Stage 1: Add NaOH regulator to the wastewater to adjust the pH value of the wastewater to 9.5 and stir evenly; after the pH adjustment in the first stage is completed, stir rapidly at a stirring speed of 170r / min, and add flocculant polyaluminum chloride (concentration reaches 90mg / L) at the same time and stir for 12 minutes; Second stage: After an interval of 40 minutes, continue to add NaOH regulator to further adjust the pH value of the wastewater to 11.4 and stir evenly; after the pH adjustment in the second stage is completed, reduce the stirring speed to 60r / min, add flocculant polyacrylamide (concentration reaches 5mg / L), and stir for 25 minutes; S3. Sedimentation and separation: After flocculation is completed, the mixture is allowed to settle for 16 hours. The supernatant is pumped into the oil acidification tank for subsequent treatment with sulfuric acid to adjust the pH value of the wastewater to 7.2. The sludge at the bottom is transported to the sludge collection tank by a pneumatic diaphragm pump and then collected by filter pressing using a screw press. The small amount of concentrated oil separated is collected in an isolation tank.

[0027] Example 3 An energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device comprises the following steps: S1. Wastewater pretreatment: Take 1 ton of spinning oil-containing wastewater, discharge it into the mixing tank and pretreatment tank, and perform preliminary oil filtration in the oil separator to separate most of the floating oil; S2, pH adjustment and flocculation: The wastewater after oil separation treatment is transported to the pH adjustment tank, The first stage: add NaOH regulator to the wastewater, adjust the pH value of the wastewater to 10, and stir evenly; after the pH adjustment of the first stage is completed, stir rapidly at a stirring speed of 200r / min, and add flocculant polyaluminum chloride (concentration reaches 100mg / L) at the same time, and stir for 15 minutes; Second stage: After an interval of 60 minutes, continue to add NaOH regulator to further adjust the pH value of the wastewater to 12 and stir evenly; after the pH adjustment in the second stage is completed, reduce the stirring speed to 80r / min, add flocculant polyacrylamide (concentration reaches 6mg / L), and stir for 30 minutes; S3. Sedimentation and separation: After flocculation is completed, the mixture is allowed to settle for 18 hours. The supernatant is pumped into the oil acidification tank for subsequent treatment with sulfuric acid to adjust the pH value of the wastewater to 8. The sludge at the bottom is transported to the sludge collection tank by a pneumatic diaphragm pump and then collected by filter pressing using a screw press. The small amount of concentrated oil separated is collected in an isolation tank.

[0028] Comparative Example 1 The difference from Example 1 is that no flocculant polyacrylamide is added in the second stage of step S2.

[0029] Comparative Example 2 The difference from Example 1 is that in the first stage of step S2, no flocculant polyaluminium chloride is added.

[0030] Comparative Example 3 In the first stage of step S2 in Example 1, flocculants polyacrylamide and polyaluminum chloride are directly added, and no flocculant is added in the second stage. Other processes are the same.

[0031] Comparative Example 4 In the second stage of step S2 in Example 1, flocculants polyacrylamide and polyaluminum chloride are directly added, and no flocculant is added in the first stage. Other processes are the same.

[0032] Comparative Example 5 The difference from Example 1 is that the stirring speed in the first stage of step S2 is 50 r / min.

[0033] Comparative Example 6 The difference from Example 1 is that the stirring speed in the second stage in step S2 is 200 r / min.

[0034] Calculation of COD value: Potassium dichromate method (national standard method, GB 11914-89): Principle: Use potassium dichromate as an oxidant to oxidize organic matter in sewage under strong acid and heating conditions. Excess potassium dichromate is titrated with ammonium ferrous sulfate, and the COD value is calculated based on the consumed oxidant.

[0035] step: 1. Take 10 mL of test water sample, add potassium dichromate standard solution and silver sulfate catalyst, and heat under reflux for 2 hours.

[0036] 2. After cooling, titrate the remaining potassium dichromate with ammonium ferrous sulfate solution using ferrous sulfate as an indicator.

[0037] 3. Calculate the COD concentration (in mg / L) based on the titration data.

[0038] The following is an analysis and explanation with reference to the accompanying drawings.

[0039] Figure 1 This is a photo of a wastewater treatment pH adjustment tank.

[0040] Figure 2In Example 1, polyaluminium chloride was added as a flocculant, and then samples were taken and placed in the photo. It can be seen that after adding polyaluminium chloride as a flocculant and stirring for 15 minutes, the pollutants in the sewage were quickly precipitated after sampling.

[0041] Figure 3 This is a photo of adding flocculant polyacrylamide in Example 1 and then taking samples and placing them; it can be seen that after adding the flocculant polyacrylamide and stirring for 30 minutes, after sampling, the pollutants in the sewage quickly precipitated and the sewage became clear.

[0042] Figure 4 The COD value curves after purification of Examples 1 to 3 and Comparative Examples 1 and 2 are shown. It can be seen that the purification effect of adding only one flocculant is significantly poor.

[0043] Figure 5 The COD curves after purification for Examples 1-3, Comparative Examples 3, and Comparative Examples 4 are shown. Comparison shows that adding the flocculant in batches results in better purification. This is because polyaluminum chloride, as an inorganic flocculant, can generate high-valent polynuclear complex ions through hydrolysis, compressing the double layer of the colloidal particles, destabilizing and agglomerating them, making it suitable for use at higher pH levels (9-12). Adding the polyaluminum chloride flocculant in batches quickly neutralizes the charge during the initial destabilization of the wastewater (pH 9-10), forming fine floc cores.

[0044] As an organic polymer flocculant, polyacrylamide connects small floc cores into larger flocs through the bridging effect of long-chain molecules. Adding polyacrylamide after initial coagulation of polyaluminium chloride and adjusting the pH to 6-8 prevents damage to the polyacrylamide molecular chains caused by high pH. Slow stirring promotes bridging, forming dense flocs.

[0045] If two reagents are added at one time, polyaluminum chloride may not be fully hydrolyzed due to the high local concentration, and polyacrylamide may be neutralized by metal ions due to premature contact with polyaluminum chloride, reducing the bridging efficiency; adding them in batches can ensure that polyaluminum chloride is destabilized first, and then polyacrylamide is efficiently bridged, reducing the amount of reagents used.

[0046] Figure 6 The following are the COD curves after purification for Examples 1-3, Comparative Examples 5, and Comparative Examples 6. Comparison of the results shows that the stirring speeds set in Examples 1-3 provide better purification results. This is because rapid stirring after the addition of polyaluminum chloride accelerates the diffusion of the agent into the wastewater, allowing the polynuclear complex ions produced by its hydrolysis to quickly come into contact with destabilized colloidal particles (such as oil and suspended matter), forming fine flocs. If stirring is too slow, the polyaluminum chloride may aggregate locally, resulting in uneven coagulation; if stirring is too fast, the initial floc core formation is disrupted.

[0047] Slow stirring after adding polyacrylamide prevents high shear forces from disrupting the already formed floc structure. It also provides ample time for long-chain molecules to collide with and bridge small flocs, promoting floc growth. The gentle water flow created by slow stirring allows the flocs to gradually aggregate through adsorption and bridging, forming large, easily precipitated flocs.

[0048] Figure 7 This is a schematic diagram of the energy-saving and environmentally friendly treatment system for wastewater generated by the spinning electrostatic deoiling device. It includes a mixing tank and pretreatment tank, an oil separator, a pH adjustment tank, a sludge collection tank, and a spiral stacker, all connected in sequence. The pH adjustment tank is equipped with a stirring device.

[0049] In summary, the present invention provides an energy-saving and environmentally friendly treatment method for wastewater generated by a spinning electrostatic deoiling device. By optimizing pH parameters, adding different flocculants in batches, and controlling process parameters such as stirring speed, the removal efficiency of pollutants in wastewater is improved, the amount of flocculants used is reduced, and thus the treatment cost is reduced, thereby achieving efficient, economical and environmentally friendly treatment of spinning oil-containing wastewater.

Claims

1. An energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device, characterized in that: The following steps are involved: S1. Wastewater pretreatment: The spinning oil-containing wastewater is discharged into the mixing tank and the pretreatment tank, and then the oil separator is used for preliminary oil filtration to separate most of the floating oil; S2, pH adjustment and flocculation: The wastewater after oil separation treatment is transported to the pH adjustment tank, The first stage: add alkaline regulator to the wastewater, adjust the pH value of the wastewater to 9-10, and stir evenly; after the pH adjustment of the first stage is completed, stir rapidly at a stirring speed of 150-200r / min, and add flocculant polyaluminum chloride at the same time, stirring for 10-15 minutes; Second stage: After an interval of 30-60 minutes, continue to add alkaline regulator to further adjust the pH value of the wastewater to 11-12 and stir evenly; after the pH adjustment in the second stage is completed, reduce the stirring speed to 50-80r / min, add flocculant polyacrylamide, and stir for 20-30 minutes; S3. Sedimentation and separation: After flocculation is completed, let it settle for 12-18 hours, pump the supernatant liquid into the oil acidification tank acid regulator for subsequent treatment, and the bottom sludge is transported to the sludge collection tank by a pneumatic diaphragm pump, and then collected by filter pressing through a screw press; the small amount of concentrated oil separated is collected in the isolation tank.

2. The energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device according to claim 1, characterized in that: The wastewater comes from cooling water and cleaning water of an electrostatic oil removal device, wherein the water content is greater than 90%.

3. The energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device according to claim 1, characterized in that: The alkaline regulator in step S2 is sodium hydroxide.

4. The energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device according to claim 1, characterized in that: The acidic regulator in step S3 is sulfuric acid.

5. The energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device according to claim 1, characterized in that: The amount of polyaluminium chloride added is such that the concentration of polyaluminium chloride in the wastewater reaches 80-100 mg / L.

6. The energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device according to claim 1, characterized in that: The amount of polyacrylamide added is such that the concentration of polyacrylamide in the wastewater reaches 4-6 mg / L.

7. The energy-saving and environmentally friendly method for treating wastewater generated by a spinning electrostatic deoiling device according to claim 1, characterized in that: In the third stage of pH adjustment, an acidic regulator is added to adjust the pH value of the wastewater to 6-8.

8. An energy-saving and environmentally friendly treatment system for wastewater generated by a spinning electrostatic deoiling device for implementing the treatment method according to any one of claims 1 to 7, characterized in that: It includes a mixing tank and a pretreatment tank, an oil separator, a pH adjustment tank, a sludge collection tank and a screw stacker connected in sequence; the pH adjustment tank is equipped with a stirring device and a reagent dosing device; the stirring device can achieve a switching stirring speed of 0-300r / min.

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