Sludge reduction treatment method of fenton composite iron replacing ferrous sulfate

Abstract

The application relates to the technical field of sewage treatment, and discloses a sludge reduction treatment method of Fenton composite iron replacing ferrous sulfate, which comprises the following steps: S1, municipal or industrial sewage is taken, impurities are removed through filtration, and homogeneous sewage is obtained; S2, the homogeneous sewage is pumped into an adjusting tank to adjust temperature and pH; S3, Fenton composite iron loaded products are added, and hydrogen peroxide solution is slowly added after stirring; S4, lime milk is used to adjust pH, and the slurry is transferred into a plate-frame filter press to obtain filtrate and filter residue; and S5, the filtrate and the filter residue are subjected to subsequent treatment. The process solves the problems of low reagent utilization rate, unstable treatment effect, serious resource waste and the like in a traditional Fenton treatment process, has good industrial adaptability and operability, and provides a new scheme of high efficiency, environmental protection and economy for sewage sludge treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron. Background Technology

[0002] With the rapid development of the wastewater treatment industry, the amount of residual sludge generated during wastewater treatment has also increased significantly. Residual sludge has a complex composition, containing large amounts of organic matter, pathogens, heavy metals, and other pollutants. Improper disposal can easily cause secondary pollution. Currently, sludge reduction technologies mainly include biological methods, chemical oxidation methods, and physical methods. Among these, the Fenton oxidation method is widely used for sludge reduction due to its strong oxidation capacity and fast reaction rate.

[0003] Traditional Fenton oxidation processes typically use ferrous sulfate as the iron source, which, in conjunction with hydrogen peroxide, generates hydroxyl radicals. These radicals oxidize and decompose extracellular polymers and intracellular organic matter in the sludge, thus reducing sludge volume. However, traditional processes have several drawbacks: ferrous sulfate, as an iron source, has low catalytic activity, requiring large amounts of reagents to achieve the desired oxidation effect, leading to high reagent costs; residual ferrous ions after the reaction can easily cause iron pollution in water bodies; and the improvement in sludge dewatering performance is limited, resulting in a still high sludge moisture content and the sludge volume reduction effect not meeting expectations. Therefore, developing a Fenton iron source with high catalytic activity, mild reaction conditions, and low secondary sludge yield, along with a corresponding sludge reduction treatment method, has become crucial to overcoming the bottlenecks of traditional processes. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a sludge reduction treatment method that uses Fenton composite iron to replace ferrous sulfate.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron includes the following steps:

[0009] S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 0.5~1 mm to obtain homogeneous wastewater;

[0010] S2. Pump the homogenized wastewater into the equalization tank to adjust the temperature and pH.

[0011] S3. Add Fenton complex iron-supported product, stir and then slowly add hydrogen peroxide solution;

[0012] S4. After the reaction is complete, lime milk is added to the system to adjust the pH, and the mixture is then transferred to a plate and frame filter press to obtain filtrate and filter residue.

[0013] S5. The filtrate and filter residue are then processed.

[0014] Furthermore, in step S2, the temperature is adjusted to 25~30℃, and the pH is adjusted to 2.5~3.5 using 10~15% dilute hydrochloric acid.

[0015] Furthermore, the preparation method of the Fenton composite iron-supported product in step S3 includes the following steps:

[0016] A1. Soak 10-20 parts of polycaprolactone fiber in 100-200 parts of anhydrous ethanol and ultrasonically clean it with a power of 200-300W for 10-15 minutes. Place it in a vacuum drying oven at 40-50℃ for 2-3 hours and then transfer it to a low-temperature cryogenic pulverizer. Set the pulverizing temperature to -40 to -30℃ and the pulverizing speed to 3000-4000 r / min. After pulverizing, pass it through a 100-200 mesh sieve and place it in a low-temperature plasma treatment instrument. Use oxygen as the discharge gas, control the vacuum degree to 10-20 Pa, the discharge power to 100-150 W, and the treatment time to 8-12 minutes to obtain activated polycaprolactone fiber powder.

[0017] A2. Add 100 parts of acetone to a three-necked flask, and while stirring, add 5-8 parts of maleic anhydride and 0.3-0.5 parts of benzoyl peroxide. Heat to 50-60℃ and stir for 10-20 min. Add 8-16 parts of activated polycaprolactone fiber powder and stir for 1-2 h. Cool to 30-40℃ and add 0.5-1 parts of hexamethylenediamine. Stir for 0.5-1 h. Filter, wash with acetone 1-2 times, and vacuum dry at 40-50℃ for 2-4 h to obtain modified polycaprolactone fiber powder.

[0018] A3. Add 4-8 parts of Fenton composite iron to 50-80 parts of deionized water and stir evenly to form a suspension. Add 5-12 parts of modified polycaprolactone fiber powder to the suspension and shake at 25-30℃ and 150-200 r / min for 8-12 h. After shaking, centrifuge at 5000-6000 r / min for 10-15 min, wash with deionized water 2-3 times, and vacuum dry at 40-50℃ for 4-6 h to obtain the Fenton composite iron loaded product.

[0019] Furthermore, the preparation method of Fenton composite iron in step A3 includes the following steps:

[0020] Maintain a slight positive pressure of nitrogen (0.01-0.02 MPa) in the reactor, add 80-100 parts of deionized water, start stirring at 600-800 r / min and 25-30℃, slowly add 5-8 parts of ferrous chloride, stir for 10-15 min, then add 3-5 parts of ferrous tartrate and 1-2 parts of ferrous citrate, stir for 10-15 min, add 0.5-0.8 parts of disodium ethylenediaminetetraacetate, stir for 10-15 min, adjust the pH to 3.0-3.5, raise the temperature to 35-40℃, treat for 1-2 h, filter, and freeze-dry under vacuum to obtain Fenton composite iron.

[0021] Further, in step S3, Fenton composite iron-loaded product is added at 0.15~0.25% of the wastewater mass, and hydrogen peroxide solution with a mass fraction of 25~30% is added at a molar ratio of hydrogen peroxide to ferrous ions of 2~4:1.

[0022] Further, in step S4, after adjusting the pH to 6.5-7.5 by adding 8-10% lime milk, 0.1-0.2% cationic polyacrylamide is added, and the mixture is stirred at 80-100 r / min for 5-8 min before being transferred to a plate and frame filter press.

[0023] Furthermore, in step S4, the feed pressure of the plate and frame filter press is 0.3~0.5 MPa, the pressing pressure is 0.6~0.8 MPa, the rinsing pressure is 0.4~0.6 MPa, and the pore size is 5~10 μm.

[0024] Further, after the filter residue in step S5 is dehydrated, it is separated by a 100-200 mesh vibrating screen. The residue on the screen is taken and sent to a desorption reaction vessel. 3-5 times the volume of 5-10% dilute hydrochloric acid is added, and the mixture is stirred at 30-35℃ and 150-200 r / min for 20-30 min. The mixture is then filtered and separated. The separated product is washed 2-3 times with deionized water until the pH of the washing liquid is ≥5.0. The product is then transferred to a dryer and vacuum dried at 40-50℃ for 2-3 h. 8-12% of the volume of the filtrate is added to a 3-5% sodium bisulfite solution, and the mixture is stirred for 15-20 min.

[0025] (iii) Beneficial technical effects

[0026] This invention replaces ferrous sulfate with Fenton composite iron-loaded products. Leveraging the complexing and adsorption effects of modified polycaprolactone fiber powder, it enhances ferrous utilization and hydroxyl radical generation efficiency, strengthens the destruction of extracellular polymers in sludge, and improves the degradation of organic pollutants, achieving superior sludge reduction and wastewater purification. Fenton composite iron is composed of ferrous chloride, ferrous tartrate, and ferrous citrate, with disodium EDTA for complexation stabilization. Combined with the loading modification of modified polycaprolactone fiber powder, it further improves the reaction stability and long-term effectiveness of ferrous ions, avoiding the drawbacks of insufficient reaction and high risk of secondary pollution associated with traditional Fenton reagents. The addition of cationic polyacrylamide in the process promotes the aggregation of sludge flocs into a dense structure, significantly optimizing the dewatering effect of plate and frame filter presses and reducing the burden on subsequent sludge treatment. Meanwhile, through recycling steps such as vibrating screen separation, dilute hydrochloric acid desorption, and sodium bisulfite reduction, the efficient recycling and reuse of polycaprolactone fiber loading material and ferrous ions are achieved. This not only reduces the consumption of reagents and the amount of solid waste generated, but also lowers the process operating costs, taking into account both environmental benefits and economic efficiency.

[0027] The process of this invention not only solves the problems of low reagent utilization, unstable treatment effect and serious waste of resources in the traditional Fenton treatment process, but also has good industrial adaptability and operability, providing a new, efficient, environmentally friendly and economical solution for sewage and sludge treatment. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all components of the Fenton composite iron-supported product formulation of this invention are commercially available.

[0030] Ferrous chloride purity ≥96%, ferrous tartrate purity ≥96%, ferrous citrate purity ≥98%;

[0031] Polycaprolactone fiber was purchased from Zhejiang Hisun Biomaterials Co., Ltd.

[0032] Cationic polyacrylamide was purchased from Henan Boyuan New Materials Co., Ltd.

[0033] All parts used in this invention are parts by weight;

[0034] Example 1

[0035] A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron includes the following steps:

[0036] S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 0.5 mm to obtain homogeneous wastewater;

[0037] S2. Pump the homogenized wastewater into the equalization tank, adjust the temperature and pH, and mix at 150 r / min for 10 min.

[0038] S3. Add Fenton composite iron-supported product, stir and slowly add hydrogen peroxide solution. After the addition is complete, heat to 30°C and stir to react for 1 h.

[0039] S4. After the reaction is complete, add lime milk to the system to adjust the pH, stir at 80 r / min for 10 min, and transfer to a plate and frame filter press to obtain filtrate and filter residue.

[0040] S5. The filtrate and filter residue are then processed.

[0041] In step S2, the temperature is adjusted to 25°C, and the pH is adjusted to 2.5 using 10% hydrochloric acid.

[0042] The preparation method of the Fenton composite iron-supported product in step S3 includes the following steps:

[0043] A1. Soak 10 parts of polycaprolactone fiber in 100 parts of anhydrous ethanol and ultrasonically clean it at 200 W for 10 min. Place it in a vacuum drying oven at 40℃ for 2 h and then transfer it to a low-temperature cryogenic pulverizer. Set the pulverizing temperature to -40℃ and the pulverizing speed to 3000 r / min. After pulverizing, pass it through a 100-mesh sieve and place it in a low-temperature plasma treatment instrument. Use oxygen as the discharge gas and control the vacuum degree to 10 Pa, the discharge power to 100 W, and the treatment time to 8 min to obtain activated polycaprolactone fiber powder.

[0044] A2. Add 100 parts of acetone to a three-necked flask, add 5 parts of maleic anhydride and 0.3 parts of benzoyl peroxide while stirring, heat to 50°C, stir for 10 min, add 8 parts of activated polycaprolactone fiber powder, stir for 1 h, cool to 30°C, add 0.5 parts of hexamethylenediamine, stir for 0.5 h, filter, wash once with acetone, and vacuum dry at 40°C for 2 h to obtain modified polycaprolactone fiber powder.

[0045] A3. Add 4 parts of Fenton composite iron to 50 parts of deionized water and stir evenly to form a suspension; add 5 parts of modified polycaprolactone fiber powder to the suspension, shake at 25℃ and 150 r / min for 8 h, after shaking, centrifuge at 5000 r / min for 10 min, wash twice with deionized water, and vacuum dry at 40℃ for 4 h to obtain the Fenton composite iron loaded product.

[0046] The preparation method of Fenton composite iron in step A3 includes the following steps:

[0047] The reactor was kept under a slight positive pressure of nitrogen (0.01 MPa). 80 parts of deionized water were added, and the stirring was started at 600 r / min and 25℃. 5 parts of ferrous chloride were slowly added and stirred for 10 min. Then, 3 parts of ferrous tartrate and 1 part of ferrous citrate were added and stirred for 10 min. 0.5 parts of disodium ethylenediaminetetraacetate were added and stirred for 10 min. The pH was adjusted to 3.0, the temperature was raised to 35℃, and the mixture was treated for 1 h. After filtration, the mixture was freeze-dried under vacuum to obtain Fenton composite iron.

[0048] In step S3, Fenton composite iron-loaded product is added at 0.15% of the wastewater mass, and hydrogen peroxide solution with a mass fraction of 25% is added at a molar ratio of hydrogen peroxide to ferrous ions of 2:1.

[0049] In step S4, after adjusting the pH to 6.5 with 8% lime milk by mass, add 0.1% cationic polyacrylamide by mass, stir at 80 r / min for 5 min, and then transfer to a plate and frame filter press.

[0050] In step S4, the plate and frame filter press has a feed pressure of 0.3 MPa, a pressing pressure of 0.6 MPa, a rinsing pressure of 0.4 MPa, and a pore size of 5 μm.

[0051] After dehydration of the filter residue in step S5, it is separated by a 100-mesh vibrating screen. The residue on the screen is collected and sent to a desorption reaction vessel. Three times the volume of 5% dilute hydrochloric acid is added, and the mixture is stirred at 30°C and 150 r / min for 20 min. The mixture is then filtered and separated. The separated product is washed twice with deionized water until the pH of the washing solution is ≥5.0. The product is then transferred to a dryer and vacuum dried at 40°C for 2 h. 8% of the filtrate volume of 3% sodium bisulfite solution is added to the filtrate, and the mixture is stirred for 15 min.

[0052] Example 2

[0053] A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron includes the following steps:

[0054] S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 0.5 mm to obtain homogeneous wastewater;

[0055] S2. Pump the homogenized wastewater into the equalization tank, adjust the temperature and pH, and mix at 180 r / min for 12 min.

[0056] S3. Add Fenton composite iron-supported product, stir and slowly add hydrogen peroxide solution. After the addition is complete, raise the temperature to 32°C and stir to react for 1.5 h.

[0057] S4. After the reaction is complete, add lime milk to the system to adjust the pH, stir at 90 r / min for 12 min, and transfer to a plate and frame filter press to obtain filtrate and filter residue.

[0058] S5. The filtrate and filter residue are then processed.

[0059] In step S2, the temperature is adjusted to 28°C, and the pH is adjusted to 3 using 12% hydrochloric acid.

[0060] The preparation method of the Fenton composite iron-supported product in step S3 includes the following steps:

[0061] A1. Soak 15 parts of polycaprolactone fiber in 150 parts of anhydrous ethanol and ultrasonically clean it at 250 W for 10 min. Place it in a vacuum drying oven at 45℃ for 2.5 h and then transfer it to a low-temperature cryogenic pulverizer. Set the pulverizing temperature to -35℃ and the pulverizing speed to 3500 r / min. After pulverizing, pass it through a 150-mesh sieve and place it in a low-temperature plasma treatment instrument. Use oxygen as the discharge gas and control the vacuum degree to 15 Pa, the discharge power to 120 W, and the treatment time to 10 min to obtain activated polycaprolactone fiber powder.

[0062] A2. Add 100 parts of acetone to a three-necked flask, add 6 parts of maleic anhydride and 0.4 parts of benzoyl peroxide while stirring, heat to 55°C, stir for 15 min, add 12 parts of activated polycaprolactone fiber powder, stir for 1.5 h, cool to 35°C, add 0.8 parts of hexamethylenediamine, stir for 0.6 h, filter, wash once with acetone, and vacuum dry at 45°C for 3 h to obtain modified polycaprolactone fiber powder;

[0063] A3. Add 6 parts of Fenton composite iron to 60 parts of deionized water and stir evenly to form a suspension; add 8 parts of modified polycaprolactone fiber powder to the suspension, shake at 28℃ and 180 r / min for 10 h, after shaking, centrifuge at 5500 r / min for 10 min, wash twice with deionized water, and vacuum dry at 45℃ for 5 h to obtain the Fenton composite iron loaded product.

[0064] The preparation method of Fenton composite iron in step A3 includes the following steps:

[0065] The reactor was kept under a slight positive pressure of nitrogen (0.01 MPa). 90 parts of deionized water were added, and the stirring was started at 700 r / min and 28℃. 6 parts of ferrous chloride were slowly added and stirred for 10 min. 4 parts of ferrous tartrate and 1.5 parts of ferrous citrate were added sequentially and stirred for 12 min. 0.7 parts of disodium ethylenediaminetetraacetate were added and stirred for 15 min. The pH was adjusted to 3.2, the temperature was raised to 38℃, and the mixture was treated for 1.5 h. After filtration, the mixture was freeze-dried under vacuum to obtain Fenton composite iron.

[0066] In step S3, Fenton composite iron-loaded product is added at 0.2% of the wastewater mass, and hydrogen peroxide solution with a mass fraction of 28% is added at a molar ratio of hydrogen peroxide to ferrous ions of 3:1.

[0067] In step S4, after adjusting the pH to 7 with 9% lime milk by mass, add 0.15% cationic polyacrylamide by mass, stir at 90 r / min for 6 min, and then transfer to a plate and frame filter press.

[0068] In step S4, the plate and frame filter press has a feed pressure of 0.4 MPa, a pressing pressure of 0.7 MPa, a rinsing pressure of 0.5 MPa, and a pore size of 8 μm.

[0069] After dehydration of the filter residue in step S5, it is separated by a 150-mesh vibrating screen. The residue on the screen is collected and sent to a desorption reaction vessel. Four times the volume of 6% dilute hydrochloric acid is added, and the mixture is stirred at 32°C and 180 r / min for 25 min. The mixture is then filtered and separated. The separated product is washed three times with deionized water until the pH of the washing solution is ≥5.0. The product is then transferred to a dryer and vacuum dried at 45°C for 2.5 h. 10% of the filtrate volume of 4% sodium bisulfite solution is added to the filtrate, and the mixture is stirred for 20 min.

[0070] Example 3

[0071] A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron includes the following steps:

[0072] S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 1 mm to obtain homogeneous wastewater.

[0073] S2. Pump the homogenized wastewater into the equalization tank, adjust the temperature and pH, and mix at 200 r / min for 15 min.

[0074] S3. Add Fenton composite iron-supported product, stir and slowly add hydrogen peroxide solution. After the addition is complete, heat to 35°C and stir to react for 2 h.

[0075] S4. After the reaction is complete, add lime milk to the system to adjust the pH, stir at 100 r / min for 15 min, and transfer to a plate and frame filter press to obtain filtrate and filter residue.

[0076] S5. The filtrate and filter residue are then processed.

[0077] In step S2, the temperature is adjusted to 30°C, and the pH is adjusted to 3.5 using 15% hydrochloric acid.

[0078] The preparation method of the Fenton composite iron-supported product in step S3 includes the following steps:

[0079] A1. Soak 20 parts of polycaprolactone fiber in 200 parts of anhydrous ethanol and ultrasonically clean it at 300 W for 15 min. Place it in a vacuum drying oven at 50℃ for 3 h and then transfer it to a low-temperature cryogenic pulverizer. Set the pulverizing temperature to -30℃ and the pulverizing speed to 4000 r / min. After pulverizing, pass it through a 200-mesh sieve and place it in a low-temperature plasma treatment instrument. Use oxygen as the discharge gas and control the vacuum degree to 20 Pa, the discharge power to 150 W, and the treatment time to 12 min to obtain activated polycaprolactone fiber powder.

[0080] A2. Add 100 parts of acetone to a three-necked flask, add 8 parts of maleic anhydride and 0.5 parts of benzoyl peroxide while stirring, heat to 60°C, stir for 20 min, add 16 parts of activated polycaprolactone fiber powder, stir for 2 h, cool to 40°C, add 1 part of hexamethylenediamine, stir for 1 h, filter, wash twice with acetone, and vacuum dry at 50°C for 4 h to obtain modified polycaprolactone fiber powder.

[0081] A3. Add 8 parts of Fenton composite iron to 80 parts of deionized water and stir evenly to form a suspension; add 12 parts of modified polycaprolactone fiber powder to the suspension, shake at 30℃ and 200 r / min for 12 h, after shaking, centrifuge at 6000 r / min for 15 min, wash 3 times with deionized water, and vacuum dry at 50℃ for 6 h to obtain the Fenton composite iron loaded product.

[0082] The preparation method of Fenton composite iron in step A3 includes the following steps:

[0083] The reactor was kept under a slight positive pressure of nitrogen (0.02 MPa). 100 parts of deionized water were added, and the stirring was started at 800 r / min and 30℃. 8 parts of ferrous chloride were slowly added and stirred for 15 min. 5 parts of ferrous tartrate and 2 parts of ferrous citrate were added in sequence and stirred for 15 min. 0.8 parts of disodium ethylenediaminetetraacetate were added and stirred for 15 min. The pH was adjusted to 3.5, the temperature was raised to 40℃, and the mixture was treated for 2 h. After filtration, the mixture was freeze-dried under vacuum to obtain Fenton composite iron.

[0084] In step S3, Fenton composite iron-loaded product is added at 0.25% of the wastewater mass, and hydrogen peroxide solution with a mass fraction of 30% is added at a molar ratio of hydrogen peroxide to ferrous ions of 4:1.

[0085] In step S4, after adjusting the pH to 7.5 with 10% lime milk by mass, add 0.2% cationic polyacrylamide by mass, stir at 100 r / min for 8 min, and then transfer to a plate and frame filter press.

[0086] In step S4, the plate and frame filter press has a feed pressure of 0.5 MPa, a pressing pressure of 0.8 MPa, a rinsing pressure of 0.6 MPa, and a pore size of 10 μm.

[0087] After dehydration of the filter residue in step S5, it is separated by a 200-mesh vibrating screen. The residue on the screen is collected and sent to a desorption reaction vessel. Five times the volume of 10% dilute hydrochloric acid is added, and the mixture is stirred at 35°C and 200 r / min for 30 min. The mixture is then filtered and separated. The separated product is washed three times with deionized water until the pH of the washing solution is ≥5.0. The product is then transferred to a dryer and vacuum dried at 50°C for 3 h. A 12% (by volume) 4% sodium bisulfite solution is added to the filtrate, and the mixture is stirred for 20 min.

[0088] Comparative Example 1

[0089] A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron includes the following steps:

[0090] S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 0.5 mm to obtain homogeneous wastewater;

[0091] S2. Pump the homogenized wastewater into the equalization tank, adjust the temperature and pH, and mix at 150 r / min for 10 min.

[0092] S3. Add ferrous sulfate, stir, and then slowly add hydrogen peroxide solution. After the addition is complete, raise the temperature to 30°C and stir to react for 1 hour.

[0093] S4. After the reaction is complete, add lime milk to the system to adjust the pH, stir at 80 r / min for 10 min, and transfer to a plate and frame filter press to obtain filtrate and filter residue.

[0094] S5. The filtrate and filter residue are then processed.

[0095] In step S2, the temperature is adjusted to 25°C, and the pH is adjusted to 2.5 using 10% hydrochloric acid.

[0096] In step S3, ferrous sulfate is added at 0.15% of the wastewater mass, and a 25% hydrogen peroxide solution is added at a molar ratio of hydrogen peroxide to ferrous ions of 2:1.

[0097] In step S4, after adjusting the pH to 6.5 with 8% lime milk by mass, add 0.1% cationic polyacrylamide by mass, stir at 80 r / min for 5 min, and then transfer to a plate and frame filter press.

[0098] In step S4, the plate and frame filter press has a feed pressure of 0.3 MPa, a pressing pressure of 0.6 MPa, a rinsing pressure of 0.4 MPa, and a pore size of 5 μm.

[0099] After dehydration of the filter residue in step S5, it is separated by a 100-mesh vibrating screen. The residue on the screen is collected and sent to a desorption reaction vessel. Three times the volume of 5% dilute hydrochloric acid is added, and the mixture is stirred at 30°C and 150 r / min for 20 min. The mixture is then filtered and separated. The separated product is washed twice with deionized water until the pH of the washing solution is ≥5.0. The product is then transferred to a dryer and vacuum dried at 40°C for 2 h. 8% of the filtrate volume of 3% sodium bisulfite solution is added to the filtrate, and the mixture is stirred for 15 min.

[0100] Comparative Example 2

[0101] A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron includes the following steps:

[0102] S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 0.5 mm to obtain homogeneous wastewater;

[0103] S2. Pump the homogenized wastewater into the equalization tank, adjust the temperature and pH, and mix at 150 r / min for 10 min.

[0104] S3. Add Fenton composite iron, stir and then slowly add hydrogen peroxide solution. After the addition is complete, heat to 30°C and stir to react for 1 h.

[0105] S4. After the reaction is complete, add lime milk to the system to adjust the pH, stir at 80 r / min for 10 min, and transfer to a plate and frame filter press to obtain filtrate and filter residue.

[0106] S5. The filtrate and filter residue are then processed.

[0107] In step S2, the temperature is adjusted to 25°C, and the pH is adjusted to 2.5 using 10% hydrochloric acid.

[0108] The preparation method of Fenton composite iron in step S3 includes the following steps:

[0109] The reactor was kept under a slight positive pressure of nitrogen (0.01 MPa). 80 parts of deionized water were added, and the stirring was started at 600 r / min and 25℃. 5 parts of ferrous chloride were slowly added and stirred for 10 min. Then, 3 parts of ferrous tartrate and 1 part of ferrous citrate were added and stirred for 10 min. 0.5 parts of disodium ethylenediaminetetraacetate were added and stirred for 10 min. The pH was adjusted to 3.0, the temperature was raised to 35℃, and the mixture was treated for 1 h. After filtration, the mixture was freeze-dried under vacuum to obtain Fenton composite iron.

[0110] In step S3, Fenton composite iron is added at 0.15% of the wastewater mass, and a 25% hydrogen peroxide solution is added at a hydrogen peroxide to ferrous ion molar ratio of 2:1.

[0111] In step S4, after adjusting the pH to 6.5 with 8% lime milk by mass, add 0.1% cationic polyacrylamide by mass, stir at 80 r / min for 5 min, and then transfer to a plate and frame filter press.

[0112] In step S4, the plate and frame filter press has a feed pressure of 0.3 MPa, a pressing pressure of 0.6 MPa, a rinsing pressure of 0.4 MPa, and a pore size of 5 μm.

[0113] After dehydration of the filter residue in step S5, it is separated by a 100-mesh vibrating screen. The residue on the screen is collected and sent to a desorption reaction vessel. Three times the volume of 5% dilute hydrochloric acid is added, and the mixture is stirred at 30°C and 150 r / min for 20 min. The mixture is then filtered and separated. The separated product is washed twice with deionized water until the pH of the washing solution is ≥5.0. The product is then transferred to a dryer and vacuum dried at 40°C for 2 h. 8% of the filtrate volume of 3% sodium bisulfite solution is added to the filtrate, and the mixture is stirred for 15 min.

[0114] Comparative Example 3

[0115] A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron includes the following steps:

[0116] S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 0.5 mm to obtain homogeneous wastewater;

[0117] S2. Pump the homogenized wastewater into the equalization tank, adjust the temperature and pH, and mix at 150 r / min for 10 min.

[0118] S3. Add Fenton composite iron, stir and then slowly add hydrogen peroxide solution. After the addition is complete, heat to 30°C and stir to react for 1 h.

[0119] S4. After the reaction is complete, add lime milk to the system to adjust the pH, stir at 80 r / min for 10 min, and transfer to a plate and frame filter press to obtain filtrate and filter residue.

[0120] S5. The filtrate and filter residue are then processed.

[0121] In step S2, the temperature is adjusted to 25°C, and the pH is adjusted to 2.5 using 10% hydrochloric acid.

[0122] The preparation method of Fenton composite iron in step S3 includes the following steps:

[0123] The reactor was kept under a slight positive pressure of nitrogen (0.01 MPa). 80 parts of deionized water were added, and the stirring was started at 600 r / min and 25℃. 5 parts of ferrous chloride were slowly added and stirred for 10 min. Then, 3 parts of ferrous tartrate and 1 part of ferrous citrate were added and stirred for 10 min. 0.5 parts of disodium ethylenediaminetetraacetate were added and stirred for 10 min. The pH was adjusted to 3.0, the temperature was raised to 35℃, and the mixture was treated for 1 h. After filtration, the mixture was freeze-dried under vacuum to obtain Fenton composite iron.

[0124] In step S3, Fenton composite iron is added at 0.15% of the wastewater mass, and a 25% hydrogen peroxide solution is added at a hydrogen peroxide to ferrous ion molar ratio of 2:1.

[0125] In step S4, after adding 8% lime slurry to adjust the pH to 6.5, the mixture is then transferred to a plate and frame filter press.

[0126] In step S4, the plate and frame filter press has a feed pressure of 0.3 MPa, a pressing pressure of 0.6 MPa, a rinsing pressure of 0.4 MPa, and a pore size of 5 μm.

[0127] After dehydration of the filter residue in step S5, it is separated by a 100-mesh vibrating screen. The residue on the screen is collected and sent to a desorption reaction vessel. Three times the volume of 5% dilute hydrochloric acid is added, and the mixture is stirred at 30°C and 150 r / min for 20 min. The mixture is then filtered and separated. The separated product is washed twice with deionized water until the pH of the washing solution is ≥5.0. The product is then transferred to a dryer and vacuum dried at 40°C for 2 h. 8% of the filtrate volume of 3% sodium bisulfite solution is added to the filtrate, and the mixture is stirred for 15 min.

[0128] Performance testing:

[0129] 1. Basic experimental conditions

[0130] The wastewater originates from the Wuxi Taihu New City Wastewater Treatment Plant;

[0131] Wastewater quality: COD 300±20 mg / L, TN 25±2 mg / L, TP 3±0.5 mg / L, SS 200±30 mg / L, pH 7.0±0.3;

[0132] 2. Test Items

[0133] Sludge dry weight reduction rate (%): Difference in sludge dry weight before and after reaction / Initial dry weight × 100%;

[0134] Filtrate COD (mg / L): The filtrate from the plate and frame filter press was tested according to standard HJ 828-2017.

[0135] Iron ion residue in filtrate (mg / L): Refer to HJ / T 345-2007 to test the filtrate of the plate and frame filter press;

[0136] Reagent recovery rate (%): After desorption filtration of the filter cake from the plate and frame filter press, the recovery rate of polycaprolactone fiber-loaded material and the reduction rate of ferrous ions are calculated as follows: Polycaprolactone fiber-loaded material recovery rate (%) = (recovered mass after sieving / total added mass) × 100%; Ferrous ion reduction rate (%) = (Fe after reduction) / Fe 2+ Fe in mass / desorption solution 3+ Quality × 100%.

[0137] Table 1. Results of sludge reduction and effluent water quality tests Group Sludge dry weight reduction rate (%) COD of filtrate (mg / L) Residual iron ions in the filtrate (mg / L) Example 1 56.8 32.6 0.16 Example 2 60.2 28.5 0.14 Example 3 62.5 25.8 0.12 Comparative Example 1 38.5 58.7 0.78 Comparative Example 2 47.3 43.2 0.45 Comparative Example 3 45.1 41.8 0.43

[0138] Table 2. Resource recycling efficiency test results Group Recovery rate of polycaprolactone fiber loading (%) Ferrous ion reduction rate (%) Example 1 65.3 91.5 Example 2 68.7 93.2 Example 3 71.2 94.8 Comparative Example 1 - 86.6 Comparative Example 2 - 89.3 Comparative Example 3 - 88.9

[0139] As shown in Table 1, the sludge dry weight reduction rate in Examples 1-3 remained between 56.8% and 62.5%, the filtrate COD was between 25.8 and 32.6 mg / L, and the residual iron ion content in the filtrate was between 0.12 and 0.16 mg / L. Comparative Example 1, using traditional ferrous sulfate, achieved a sludge dry weight reduction rate of 38.5%, a filtrate COD of 58.7 mg / L, and a residual iron ion content of 0.78 mg / L. Ferrous sulfate is easily oxidized and hydrolyzed, resulting in low ferrous utilization and hindering efficient reaction. Comparative Examples 2 and 3 showed sludge reduction rates of 47.3% and 45.1%, respectively, with CODs exceeding 40 mg / L, demonstrating the crucial role of Fenton composite iron loading modification and cationic polyacrylamide flocculation in improving treatment efficiency.

[0140] As shown in Table 2, the recovery rate of polycaprolactone fiber-supported materials in Examples 1-3 was 65.3-71.2%, and the ferrous ion reduction rate was 91.5-94.8%. The ferrous ion reduction rate of Comparative Examples 1-3 was 86.6-89.3%, indicating that the polycaprolactone fiber-supported materials can effectively enrich ferrous ions and achieve ferrous ion recovery.

[0141] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reducing sludge volume by replacing ferrous sulfate with Fenton composite iron, characterized in that, Includes the following steps: S1. Take municipal or industrial wastewater, remove coarse impurities with a particle size >5 mm by a bar screen, and then filter it through a hydraulic screen with a pore size of 0.5~1 mm to obtain homogeneous wastewater; S2. Pump the homogenized wastewater into the equalization tank to adjust the temperature and pH. S3. Add Fenton complex iron-supported product, stir and then slowly add hydrogen peroxide solution; S4. After the reaction is complete, lime milk is added to the system to adjust the pH, and then the mixture is transferred to a plate and frame filter press to obtain filtrate and filter residue. S5. The filtrate and filter residue are then processed.

2. The sludge reduction treatment method using Fenton composite iron to replace ferrous sulfate according to claim 1, characterized in that, In step S2, the temperature is adjusted to 25~30℃, and the pH is adjusted to 2.5~3.5 with 10~15% dilute hydrochloric acid.

3. The sludge reduction treatment method according to claim 1, using Fenton composite iron to replace ferrous sulfate, is characterized in that... The preparation method of the Fenton composite iron-supported product in step S3 includes the following steps: A1. Soak 10-20 parts of polycaprolactone fiber in 100-200 parts of anhydrous ethanol and ultrasonically clean it at a power of 200-300 W for 10-15 min. Place it in a vacuum drying oven at 40-50℃ for 2-3 h and then transfer it to a low-temperature cryogenic pulverizer. Set the pulverizing temperature to -40 to -30℃ and the pulverizing speed to 3000-4000 r / min. After pulverizing, pass it through a 100-200 mesh sieve and place it in a low-temperature plasma treatment instrument. Use oxygen as the discharge gas, control the vacuum degree to 10-20 Pa, the discharge power to 100-150 W, and the treatment time to 8-12 min to obtain activated polycaprolactone fiber powder. A2. Add 100 parts of acetone to a three-necked flask, add 5-8 parts of maleic anhydride and 0.3-0.5 parts of benzoyl peroxide while stirring, heat to 50-60℃, stir for 10-20 min, add 8-16 parts of activated polycaprolactone fiber powder, stir for 1-2 h, cool to 30-40℃, add 0.5-1 parts of hexamethylenediamine, stir for 0.5-1 h, filter, wash with acetone 1-2 times, vacuum dry at 40-50℃ for 2-4 h to obtain modified polycaprolactone fiber powder; A3. Add 4-8 parts of Fenton composite iron to 50-80 parts of deionized water and stir evenly to form a suspension. Add 5-12 parts of modified polycaprolactone fiber powder to the suspension and shake at 25-30℃ and 150-200 r / min for 8-12 h. After shaking, centrifuge at 5000-6000 r / min for 10-15 min, wash with deionized water 2-3 times, and vacuum dry at 40-50℃ for 4-6 h to obtain the Fenton composite iron loaded product.

4. The sludge reduction treatment method using Fenton composite iron to replace ferrous sulfate according to claim 3, characterized in that, The preparation method of Fenton composite iron in step A3 includes the following steps: Maintain a slight positive pressure of nitrogen (0.01-0.02 MPa) in the reactor, add 80-100 parts of deionized water, start stirring at 600-800 r / min and 25-30℃, slowly add 5-8 parts of ferrous chloride, stir for 10-15 min, then add 3-5 parts of ferrous tartrate and 1-2 parts of ferrous citrate, stir for 10-15 min, add 0.5-0.8 parts of disodium ethylenediaminetetraacetate, stir for 10-15 min, adjust the pH to 3.0-3.5, raise the temperature to 35-40℃, treat for 1-2 h, filter, and freeze-dry under vacuum to obtain Fenton composite iron.

5. The sludge reduction treatment method using Fenton composite iron to replace ferrous sulfate according to claim 1, characterized in that, In step S3, Fenton composite iron-loaded product is added at 0.15~0.25% of the wastewater mass, and hydrogen peroxide solution with a mass fraction of 25~30% is added at a molar ratio of hydrogen peroxide to ferrous ions of 2~4:

1.

6. The sludge reduction treatment method according to claim 1, using Fenton composite iron to replace ferrous sulfate, is characterized in that, In step S4, after adjusting the pH to 6.5-7.5 by adding 8-10% lime milk, add 0.1-0.2% cationic polyacrylamide, stir at 80-100 r / min for 5-8 min, and then transfer to a plate and frame filter press.

7. The sludge reduction treatment method according to claim 1, using Fenton composite iron to replace ferrous sulfate, is characterized in that... In step S4, the feed pressure of the plate and frame filter press is 0.3~0.5 MPa, the pressing pressure is 0.6~0.8 MPa, the rinsing pressure is 0.4~0.6 MPa, and the pore size is 5~10 μm.

8. The sludge reduction treatment method according to claim 1, using Fenton composite iron to replace ferrous sulfate, is characterized in that, After the filter residue in step S5 is dehydrated, it is separated by a 100-200 mesh vibrating screen. The residue on the screen is taken and sent to a desorption reaction tank. 3-5 times the volume of 5-10% dilute hydrochloric acid is added. The mixture is stirred at 30-35℃ and 150-200 r / min for 20-30 min, and then filtered and separated. Wash the separated product with deionized water 2-3 times until the pH of the washing solution is ≥5.

0. Transfer it to a dryer and vacuum dry at 40-50℃ for 2-3 h. Add 8-12% of the filtrate volume of a 3-5% sodium bisulfite solution and stir for 15-20 min.