Method for removing total phosphorus and COD in phosphating liquid wastewater

Abstract

The present application belongs to the technical field of water treatment, and particularly relates to a method for removing total phosphorus and COD in phosphating liquid wastewater, comprising the following steps: the phosphating liquid wastewater first enters a two-stage dosing sedimentation tank, and then enters a two-stage deep sedimentation tank; after passing through the two-stage deep sedimentation tank, the phosphating liquid wastewater enters a filter adsorption tower, the filter adsorption tower is internally provided with modified kaolin filter material, and the modified kaolin filter material accounts for 80-90% of the volume of the entire filter adsorption tower; after passing through the filter adsorption tower, the phosphating liquid wastewater is discharged up to the standard. According to the water quality and quantity of the phosphating liquid wastewater, the method develops an economic and efficient resource treatment process, takes recycling, energy saving and emission reduction as the main task, reduces environmental pollution, and actively responds to increasingly stringent environmental protection regulations. After being treated by the method, the water quality of the phosphating liquid wastewater is as follows: pH is 6.5-8.6, total phosphorus is 0.1-0.3 mg / L, and COD is 33-45 mg / L, so that the phosphating liquid wastewater can be directly discharged up to the standard.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water treatment, and particularly relates to a method for removing total phosphorus and COD in phosphating liquid wastewater. BACKGROUND

[0002] Steel phosphating is mainly used for corrosion protection and paint primer. Steel phosphating liquid is a major source of pollution wastewater in metal surface treatment liquid. The total phosphorus concentration in the phosphating liquid is higher than 10000 mg / L, and the COD is higher than 500 mg / L, which belongs to special difficult-to-treat wastewater.

[0003] The present application is aimed at phosphating liquid wastewater. The existing technology is to mix phosphating liquid wastewater with other wastewater for treatment. However, so far, there is no process for deep treatment of phosphating liquid wastewater. The national standard stipulates that the total phosphorus is lower than 0.5 mg / L and the COD is lower than 50 mg / L when the wastewater is discharged. The purpose of the present application is to develop an economic and efficient resource treatment process according to the water quality and quantity of phosphating liquid wastewater, to take recycling, energy saving and emission reduction as the main task, to reduce environmental pollution, and to actively respond to increasingly stringent environmental protection regulations. SUMMARY

[0004] In view of the above, the present application provides a method for removing total phosphorus and COD in phosphating liquid wastewater. The method develops an economic and efficient resource treatment process according to the water quality and quantity of phosphating liquid wastewater, takes recycling, energy saving and emission reduction as the main task, reduces environmental pollution, and actively responds to increasingly stringent environmental protection regulations.

[0005] The technical scheme of the present application is as follows:

[0006] A method for removing total phosphorus and COD in phosphating liquid wastewater, the water quality characteristics of the phosphating liquid wastewater: pH is 1.4-2.1, total phosphorus is 14920-15980 mg / L, and COD is 860-990 mg / L, comprising the following steps:

[0007] (1) The phosphating liquid wastewater enters a two-stage dosing sedimentation tank, which comprises a first-stage dosing stirring tank, a first-stage inclined plate sedimentation tank, a second-stage dosing stirring tank and a second-stage inclined plate sedimentation tank; 19.1-25.5 g / L of calcium hydroxide is added in the first-stage dosing stirring tank, and the phosphating liquid wastewater stays in the first-stage inclined plate sedimentation tank for 18-23 min; the phosphating liquid then enters the second-stage dosing stirring tank, 11.5-15.7 g / L of calcium hydroxide is added in the second-stage dosing stirring tank, and stays in the second-stage inclined plate sedimentation tank for 25-40 min;

[0008] (2) After two-stage dosing sedimentation tank, the phosphating solution enters two-stage depth sedimentation tank; two-stage depth sedimentation tank includes a pH adjustment tank, a hydrogen peroxide dosing stirring tank, a reaction sedimentation tank, a modified reagent stirring tank and a second reaction sedimentation tank; 3-5% hydrochloric acid is added in the pH adjustment tank to control the pH value of the phosphating solution wastewater between 7.2-8.7, 6-8ml / L of 30% hydrogen peroxide solution is added in the hydrogen peroxide dosing stirring tank, the phosphating solution stays in the reaction sedimentation tank for 8-12min; the phosphating solution then enters the modified reagent stirring tank, 456-845ml of modified reagent per liter of wastewater is added in the modified reagent stirring tank, and the phosphating solution stays in the second reaction sedimentation tank for 18-27min;

[0009] (3) After two-stage depth sedimentation tank, the phosphating solution wastewater enters a filter adsorption tower, the filter adsorption tower is filled with modified kaolin filter material, the modified kaolin filter material accounts for 80-90% of the volume of the filter adsorption tower; after the filter adsorption tower, the phosphating solution wastewater is discharged up to standard.

[0010] Further, the phosphating solution stays in the first dosing stirring tank for 5-7min and the stirring speed is 85-105rpm in step (1).

[0011] Further, the phosphating solution stays in the second dosing stirring tank for 6-8min and the stirring speed is 75-95rpm in step (1).

[0012] Further, the pH adjustment tank, the hydrogen peroxide dosing stirring tank and the modified reagent stirring tank in step (2) are equipped with automatic dosing systems.

[0013] Further, the phosphating solution stays in the pH adjustment tank for 5-7min in step (2).

[0014] Further, the phosphating solution stays in the first dosing stirring tank for 2-3min and the stirring speed is 45-65rpm in step (2).

[0015] Further, the phosphating solution stays in the modified reagent stirring tank for 3-5min and the stirring speed is 75-95rpm in step (2).

[0016] Further, the modified reagent in step (2) is prepared by the following steps: 1) selecting zeolite with a particle size of 1.0-1.5mm; 2) mixing the zeolite, calcium hypochlorite and potassium permanganate according to the mass ratio of (6-9):(3-5):1 to form a mixture; 3) preparing a 9-15% aluminum chloride solution, adding 15-23g of the mixture per liter of the aluminum chloride solution, and ultrasonicating for 10-15min to form the modified reagent.

[0017] Further, the residence time of the phosphating liquid wastewater in the filter adsorption tower in step (3) is 19-35 min, and the backwashing time is 1020-1230 h.

[0018] Further, the kaolin modified filter material is prepared by the following steps: 1) selecting kaolin with a particle size of 0.3-0.5 mm and a specific surface area of 16.1-18.7 m 2 / g; selecting Fe3O4 and activated carbon particles with a particle size of 0.1-0.3 mm; mixing the kaolin, Fe3O4 and activated carbon particles according to a mass ratio of (6-12):(3-5):1 to form a mixed solid; 2) preparing a ferric chloride solution with a mass ratio of 7-8%; soaking the mixed solid in the ferric chloride solution according to a solid-liquid ratio (mass ratio) of 1:(3-5); oscillating at a temperature of 55-65 DEG C for 3-7 h, filtering, and drying the mixed solid at 105 DEG C and naturally cooling; 3) placing the mixed solid in a muffle furnace, heating to 790-820 DEG C at a rate of 3-4 DEG C / min, maintaining the temperature for 60-75 min, and naturally cooling to form the kaolin modified filter material with a specific surface area of 34.1-42.9 m 2 / g. Detailed description of the invention:

[0020] The present application is a deep treatment technical solution for phosphating liquid wastewater, and the specific process is as follows:

[0021] The water quality characteristics of the phosphating liquid wastewater are as follows: pH is 1.4-2.1, total phosphorus is 14920-15980 mg / L, and COD is 860-990 mg / L.

[0022] A treatment system for removing total phosphorus and COD in phosphating liquid wastewater, comprising a water inlet pump, a two-stage dosing sedimentation tank, a primary water inlet pump, a two-stage deep sedimentation tank, a modified reagent, a secondary water inlet pump, a filter adsorption tower, a kaolin modified filter material, and a water outlet pump.

[0023] The phosphating liquid wastewater enters the two-stage dosing sedimentation tank through the water inlet pump. The two-stage dosing sedimentation tank comprises a first-stage dosing stirring tank, a first-stage inclined plate sedimentation tank, a second-stage dosing stirring tank and a second-stage inclined plate sedimentation tank. The first-stage and second-stage dosing stirring tanks are provided with an automatic dosing system. In the first-stage dosing stirring tank, 19.1-25.5 g / L of calcium hydroxide is added. The residence time of the phosphating liquid in the first-stage dosing stirring tank is 5-7 min, and the stirring speed is 85-105 rpm. The residence time in the first-stage inclined plate sedimentation tank is 18-23 min. The phosphating liquid then enters the second-stage dosing stirring tank, in which 11.5-15.7 g / L of calcium hydroxide is added. The residence time of the phosphating liquid in the second-stage dosing stirring tank is 6-8 min, and the stirring speed is 75-95 rpm. The residence time in the second-stage inclined plate sedimentation tank is 25-40 min. After the reaction of the two additions of calcium hydroxide, the precipitated solid waste is mainly Ca5(HPO4)3OH and Ca3(PO4)2. After the two-stage dosing sedimentation tank, the water quality of the phosphating liquid wastewater is pH 12.5-13.5, total phosphorus 15.3-22.6 mg / L and COD 760-845 mg / L.

[0024] The phosphating liquid enters the two-stage deep sedimentation tank through the primary water inlet pump. The two-stage deep sedimentation tank comprises a first-stage pH adjustment tank, a first-stage hydrogen peroxide dosing stirring tank, a first-stage reaction sedimentation tank, a second-stage modified reagent stirring tank and a second-stage reaction sedimentation tank. The first-stage pH adjustment tank, the first-stage hydrogen peroxide dosing stirring tank and the second-stage modified reagent stirring tank are provided with an automatic dosing system. In the first-stage pH adjustment tank, 3-5% of hydrochloric acid is added to control the pH value of the phosphating liquid wastewater to be 7.2-8.7. The residence time of the phosphating liquid in the first-stage pH adjustment tank is 5-7 min. In the first-stage hydrogen peroxide dosing stirring tank, 6-8 ml / L of a 30% hydrogen peroxide solution is added. The residence time in the first-stage dosing stirring tank is 2-3 min, and the stirring speed is 45-65 rpm. The residence time in the first-stage reaction sedimentation tank is 8-12 min. The phosphating liquid then enters the second-stage modified reagent stirring tank, in which 456-845 mL of modified reagent is added per liter of wastewater. The residence time of the phosphating liquid in the second-stage modified reagent stirring tank is 3-5 min, and the stirring speed is 75-95 rpm. The residence time in the second-stage reaction sedimentation tank is 18-27 min. After the two-stage deep sedimentation tank, the water quality of the phosphating liquid wastewater is pH 6.4-8.8, total phosphorus 0.9-1.5 mg / L and COD 89-105 mg / L.

[0025] The modified reagent of the application is prepared according to the water quality characteristics of phosphating liquid wastewater. The preparation method is as follows: 1) selecting zeolite with a particle size of 1.0-1.5 mm; 2) mixing the zeolite, calcium hypochlorite and potassium permanganate according to a mass ratio of (6-9):(3-5):1 to form a mixture; and 3) preparing an aluminum chloride solution with a mass fraction of 9-15%, adding 15-23 g of the mixture per liter of the aluminum chloride solution, and ultrasonic treating for 10-15 min to form the modified reagent.

[0026] The phosphating liquid wastewater enters a filter adsorption tower through a secondary water inlet pump, and the kaolin modified filter material accounts for 80-90% of the volume of the filter adsorption tower. The residence time of the phosphating liquid wastewater in the filter adsorption tower is 19-35 min, and the backwashing time is 1020-1230 h.

[0027] The kaolin modified filter material of the application is prepared according to the characteristics of the phosphating liquid wastewater. 1) selecting kaolin with a particle size of 0.3-0.5 mm and a specific surface area of 16.1-18.7 m 2 / g; selecting ferroferric oxide and activated carbon particles with a particle size of 0.1-0.3 mm; mixing the kaolin, ferroferric oxide and activated carbon particles according to a mass ratio of (6-12):(3-5):1 to form a mixed solid; 2) preparing an iron chloride solution with a mass fraction of 7-8%, and soaking the mixed solid in the iron chloride solution according to a solid-liquid ratio (mass ratio) of 1:(3-5); oscillating at a temperature of 55-65 ℃ for 3-7 h, filtering, and drying the mixed solid at 105 ℃ and naturally cooling; and 3) placing the mixed solid in a muffle furnace, heating at a rate of 3-4 ℃ / min to 790-820 ℃, maintaining the temperature for 60-75 min, and naturally cooling to form the kaolin modified filter material with a specific surface area of 34.1-42.9 m 2 / g, which improves the adsorption capacity for total phosphorus and COD.

[0028] After passing through the filter adsorption tower, the water quality of the phosphating liquid wastewater is as follows: pH is 6.5-8.6, total phosphorus is 0.1-0.3 mg / L, and COD is 33-45 mg / L. Subsequently, the phosphating liquid wastewater is discharged by a water outlet pump.

[0029] The application has the following beneficial technical effects:

[0030] The application provides a method for removing total phosphorus and COD in phosphating liquid wastewater. The method is an economic and efficient resource treatment process developed according to the water quality and quantity of the phosphating liquid wastewater, and mainly aims at recycling, energy saving and emission reduction, and reducing environmental pollution to actively respond to increasingly stringent environmental protection regulations.

[0031] The water quality of the phosphating liquid wastewater treated by the method of the application is as follows: pH is 6.5-8.6, total phosphorus is 0.1-0.3 mg / L, and COD is 33-45 mg / L, which can be directly discharged. Attached Figure Description

[0032] Figure 1 A treatment system for removing total phosphorus and COD from phosphating wastewater;

[0033] The system includes: inlet pump-1, two-stage dosing sedimentation tank-2, primary inlet pump-3, two-stage deep sedimentation tank-4, modified agent-5, secondary inlet pump-6, filter adsorption tower-7, kaolin modified filter media-8, and outlet pump-9. Detailed Implementation

[0034] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0035] Example 1:

[0036] The water quality characteristics of the phosphating wastewater are: pH 2.1, total phosphorus 15980 mg / L, and COD 945 mg / L.

[0037] A treatment system for removing total phosphorus and COD from phosphating wastewater includes an influent pump, a two-stage dosing sedimentation tank, a primary influent pump, a two-stage deep sedimentation tank, a modified reagent, a secondary influent pump, a filter adsorption tower, kaolin modified filter media, and an effluent pump.

[0038] The phosphating wastewater is pumped into a two-stage chemical dosing sedimentation tank, which includes a first-stage stirring tank, a first-stage inclined plate sedimentation tank, a second-stage stirring tank, and a second-stage inclined plate sedimentation tank. Both the first and second stages are equipped with automatic dosing systems. In the first-stage stirring tank, 25.5 g / L of calcium hydroxide is added. The residence time of the phosphating solution in the first-stage stirring tank is 7 minutes, with a stirring speed of 105 rpm. The residence time in the first-stage inclined plate sedimentation tank is 23 minutes. The phosphating solution then enters the second-stage stirring tank, where 15.7 g / L of calcium hydroxide is added. The residence time of the phosphating solution in the second-stage stirring tank is 6–8 minutes, with a stirring speed of 95 rpm. The residence time in the second-stage inclined plate sedimentation tank is 40 minutes. After the two calcium hydroxide additions and reactions, the precipitated solid waste mainly consists of Ca5(HPO4)3OH and Ca3(PO4)2. After passing through a two-stage dosing and sedimentation tank, the phosphating wastewater had a pH of 13.5, a total phosphorus content of 21.1 mg / L, and a COD of 810 mg / L.

[0039] The phosphating liquid enters the two-stage deep sedimentation tank through a primary water inlet pump. The two-stage deep sedimentation tank comprises a first-stage pH adjusting tank, a first-stage hydrogen peroxide dosing and stirring tank, a first-stage reaction and sedimentation tank, a second-stage modified reagent stirring tank and a second-stage reaction and sedimentation tank, and the first-stage pH adjusting tank, the first-stage hydrogen peroxide dosing and stirring tank and the second-stage modified reagent stirring tank are provided with an automatic dosing system. 5% hydrochloric acid is added to the first-stage pH adjusting tank to control the pH value of the phosphating liquid wastewater to be 8.1, and the residence time of the phosphating liquid in the first-stage pH adjusting tank is 7 min. 8 ml / L of 30% hydrogen peroxide solution is added to the first-stage hydrogen peroxide dosing and stirring tank, the residence time of the first-stage dosing and stirring tank is 3 min, the stirring speed is 65 r / min, and the residence time of the first-stage reaction and sedimentation tank is 12 min. The phosphating liquid then enters the second-stage modified reagent stirring tank, and the second-stage modified reagent stirring tank is added with 845 mL of modified reagent per liter of wastewater, the residence time of the phosphating liquid in the second-stage modified reagent stirring tank is 5 min, the stirring speed is 95 r / min, and the residence time of the second-stage reaction and sedimentation tank is 27 min. After passing through the two-stage deep sedimentation tank, the water quality of the phosphating liquid wastewater is that the pH value is 8.2, the total phosphorus is 1.3 mg / L, and the COD is 101 mg / L.

[0040] The modified reagent of the present application is prepared according to the water quality characteristics of the phosphating liquid wastewater. The preparation method is as follows: 1) zeolite with a particle size of 1.5 mm is selected; 2) the zeolite, calcium hypochlorite and potassium permanganate are mixed in a mass ratio of 9:5:1 to form a mixture; and 3) an aluminum chloride solution with a mass fraction of 15% is prepared, 23 g of the mixture is added per liter of the aluminum chloride solution, and ultrasonic treatment is performed for 15 min to form the modified reagent.

[0041] The phosphating liquid wastewater enters the filtration and adsorption tower through a secondary water inlet pump, and the modified kaolin filter material accounts for 90% of the volume of the entire filtration and adsorption tower. The residence time of the phosphating liquid wastewater in the filtration and adsorption tower is 35 min, and the backwashing time is 1230 h.

[0042] The modified kaolin filter material of the present application is prepared according to the characteristics of the phosphating liquid wastewater. 1) kaolin with a particle size of 0.3 mm and a specific surface area of 18.7 m 2 / g is selected. Ferric oxide and activated carbon particles with a particle size of 0.3 mm are selected. The kaolin, ferric oxide and activated carbon particles are mixed in a mass ratio of 12:5:1 to form a mixed solid. 2) an iron chloride solution with a mass fraction of 7-8% is prepared, and the mixed solid is soaked in the iron chloride solution at a solid-liquid ratio (mass ratio) of 1:5. The mixture is shaken at 65°C for 7 h, filtered, and the mixed solid is dried at 105°C and naturally cooled. 3) the mixed solid is placed in a muffle furnace, heated to 820°C at a rate of 4°C / min, kept at a constant temperature for 75 min, and naturally cooled to form the modified kaolin filter material, which has a specific surface area of 41.1 m 2 / g, and the adsorption capacity for total phosphorus and COD is improved.

[0043] After the filtration adsorption tower, the water quality of phosphating liquid wastewater is pH 8.3, total phosphorus 0.3 mg / L, and COD 33-45 mg / L. Subsequently, the phosphating liquid wastewater is discharged by the effluent pump.

[0044] Example 2

[0045] The water quality characteristics of the phosphating liquid wastewater are pH 1.4, total phosphorus 15090 mg / L, and COD 860 mg / L.

[0046] A treatment system for removing total phosphorus and COD in phosphating liquid wastewater includes a water inlet pump, a two-stage dosing sedimentation tank, a primary water inlet pump, a two-stage deep sedimentation tank, a modified reagent, a secondary water inlet pump, a filtration adsorption tower, kaolin modified filter material, and an effluent pump.

[0047] The phosphating liquid wastewater enters the two-stage dosing sedimentation tank through the water inlet pump, and the two-stage dosing sedimentation tank includes a first-stage dosing stirring tank, a first-stage inclined plate sedimentation tank, a second-stage dosing stirring tank, and a second-stage inclined plate sedimentation tank. The first-stage and second-stage dosing stirring tanks are provided with an automatic dosing system. In the first-stage dosing stirring tank, 20.6 g / L of calcium hydroxide is added, the residence time of the phosphating liquid in the first-stage dosing stirring tank is 5 min, the stirring speed is 85 rpm, and the residence time in the first-stage inclined plate sedimentation tank is 18 min. The phosphating liquid then enters the second-stage dosing stirring tank, 12.8 g / L of calcium hydroxide is added in the second-stage dosing stirring tank, the residence time of the phosphating liquid in the second-stage dosing stirring tank is 6 min, the stirring speed is 75 rpm, and the residence time in the second-stage inclined plate sedimentation tank is 25 min. After the reaction of the two additions of calcium hydroxide, the main precipitated solid waste is Ca5(HPO4)3OH and Ca3(PO4)2. After the two-stage dosing sedimentation tank, the water quality of the phosphating liquid wastewater is pH 12.6, total phosphorus 15.8 mg / L, and COD 790 mg / L.

[0048] The phosphating liquid enters the two-stage deep sedimentation tank through a primary water inlet pump. The two-stage deep sedimentation tank comprises a first-stage pH adjusting tank, a first-stage hydrogen peroxide dosing and stirring tank, a first-stage reaction and precipitation tank, a second-stage modified reagent stirring tank and a second-stage reaction and precipitation tank, and the first-stage pH adjusting tank, the first-stage hydrogen peroxide dosing and stirring tank and the second-stage modified reagent stirring tank are provided with an automatic dosing system. 3% hydrochloric acid is added to the first-stage pH adjusting tank to control the pH value of the phosphating liquid wastewater to 7.5, and the residence time of the phosphating liquid in the first-stage pH adjusting tank is 5 min. 6ml / L of a 30% hydrogen peroxide solution is added to the first-stage hydrogen peroxide dosing and stirring tank, the residence time of the first-stage dosing and stirring tank is 2 min, the stirring speed is 45r / min, and the residence time of the first-stage reaction and precipitation tank is 8 min. The phosphating liquid then enters the second-stage modified reagent stirring tank, and the second-stage modified reagent stirring tank is added with 558ml of modified reagent per liter of wastewater, the residence time of the phosphating liquid in the second-stage modified reagent stirring tank is 3 min, the stirring speed is 75r / min, and the residence time of the second-stage reaction and precipitation tank is 18 min. After passing through the two-stage deep sedimentation tank, the water quality of the phosphating liquid wastewater is that the pH value is 7.6, the total phosphorus is 1.1mg / L, and the COD is 93mg / L.

[0049] The modified reagent of the present application is prepared according to the water quality characteristics of the phosphating liquid wastewater. The preparation method is as follows: 1) zeolite with a particle size of 1.0mm is selected; 2) the zeolite, calcium hypochlorite and potassium permanganate are mixed in a mass ratio of 7:3:1 to form a mixture; and 3) an aluminum chloride solution with a mass fraction of 10% is prepared, 17g of the mixture is added per liter of the aluminum chloride solution, and ultrasonic treatment is performed for 11min to form the modified reagent.

[0050] The phosphating liquid wastewater enters the filtration and adsorption tower through a secondary water inlet pump, and the kaolin modified filter material accounts for 85% of the volume of the entire filtration and adsorption tower. The residence time of the phosphating liquid wastewater in the filtration and adsorption tower is 21min, and the backwashing time is 1020h.

[0051] The kaolin modified filter material of the present application is prepared according to the characteristics of the phosphating liquid wastewater. 1) kaolin with a particle size of 0.5mm and a specific surface area of 16.9m 2 / g is selected, and 0.1mm particle size ferric oxide and activated carbon particles are selected. The kaolin, ferric oxide and activated carbon particles are mixed in a mass ratio of 7:4:1 to form a mixed solid. 2) an iron chloride solution with a mass fraction of 7% is prepared, and the mixed solid is soaked in the iron chloride solution at a solid-liquid ratio (mass ratio) of 1:3. The mixture is shaken at a temperature of 55℃ for 4h, filtered, and the mixed solid is dried at 105℃ and naturally cooled. 3) the mixed solid is placed in a muffle furnace, heated to 790℃ at a rate of 4℃ / min, kept at a constant temperature for 65min, and naturally cooled to form the kaolin modified filter material, and the specific surface area of the kaolin modified filter material is 36.3m 2 / g, and the adsorption capacity for total phosphorus and COD is improved.

[0052] After filtering and adsorbing tower, the water quality of phosphating liquid wastewater is that pH is 7.7, total phosphorus is 0.1 mg / L, and COD is 35 mg / L.

[0053] In summary, the application first proposes a deep treatment method of desulfurization wastewater, and therefore belongs to a green and environmental protection production process system.

[0054] Of course, those skilled in the art should recognize that the above-mentioned embodiments are only used to illustrate the application, and are not used as a limitation to the application, and as long as the above-mentioned embodiments are changed and deformed within the scope of the spirit of the application, they will fall within the scope of the claims of the application.

Claims

1. A method for removing total phosphorus and COD from phosphating wastewater, wherein the phosphating wastewater has the following water quality characteristics: pH 1.4~2.1, total phosphorus 14920~15980 mg / L, and COD 860~990 mg / L, characterized in that... Includes the following steps: In step (1), the phosphating wastewater enters a two-stage dosing sedimentation tank, which includes a first-stage dosing stirring tank, a first-stage inclined plate sedimentation tank, a second-stage dosing stirring tank, and a second-stage inclined plate sedimentation tank. 19.1~25.5 g / L of calcium hydroxide is added to the first-stage dosing stirring tank, and the phosphating wastewater remains in the first-stage inclined plate sedimentation tank for 18~23 min. The phosphating solution then enters the second-stage dosing stirring tank, where 11.5~15.7 g / L of calcium hydroxide is added, and the phosphating wastewater remains in the second-stage inclined plate sedimentation tank for 25~40 min. Step (2) After passing through the two-stage dosing sedimentation tank, the phosphating solution enters the two-stage deep sedimentation tank. The two-stage deep sedimentation tank includes a pH adjustment tank, a hydrogen peroxide dosing and stirring tank, a reaction sedimentation tank, a second-stage modified agent stirring tank, and a second-stage reaction sedimentation tank. 3-5% hydrochloric acid is added to the pH adjustment tank to control the pH value of the phosphating solution wastewater between 7.2 and 8.

7. 6-8 ml / L of 30% hydrogen peroxide solution is added to the hydrogen peroxide dosing and stirring tank. The phosphating solution stays in the first-stage reaction sedimentation tank for 8-12 minutes. The phosphating solution then enters the second-stage modified agent stirring tank, where 456-845 mL of modified agent per liter of wastewater is added. The phosphating solution stays in the second-stage reaction sedimentation tank for 18-27 minutes. The modified agent is prepared by the following steps: 1) screening zeolite with a particle size of 1.0~1.5 mm; 2) mixing zeolite, calcium hypochlorite and potassium permanganate in a mass ratio of (6~9):(3~5):1 to form a mixture; 3) preparing an aluminum chloride solution with a mass fraction of 9~15%, adding 15~23 g of the mixture to each liter of aluminum chloride solution, and sonicating for 10~15 min to form the modified agent; Step (3) After passing through the two-stage deep sedimentation tank, the phosphating wastewater enters the filtration and adsorption tower. The filtration and adsorption tower is equipped with kaolin-modified filter media, which accounts for 80-90% of the total volume of the filtration and adsorption tower. After passing through the filtration and adsorption tower, the phosphating wastewater meets the discharge standards. The modified kaolin filter media is prepared by the following steps: 1) Selecting kaolin with a particle size of 0.3~0.5 mm and a specific surface area of ​​16.1~18.7 m². 2 / g; Select 0.1~0.3 mm particle size of ferric oxide and activated carbon particles; Mix kaolin, ferric oxide and activated carbon particles at a mass ratio of (6~12): (3~5):1 to form a mixed solid; 2) Prepare a 7~8% ferric chloride solution, and soak the mixed solid in the ferric chloride solution at a solid-liquid mass ratio of 1: (3~5); Shake at 55~65℃ for 3~7 h, filter, dry the mixed solid at 105 ℃, and cool naturally; 3) Put the mixed solid into a muffle furnace, heat it to 790~820℃ at 3~4℃ / min, hold it at 60~75 min, and cool naturally to form kaolin-modified filter material with a specific surface area of ​​34.1~42.9 m². 2 / g.

2. The method for removing total phosphorus and COD from phosphating wastewater according to claim 1, characterized in that, In step (1), the residence time of the phosphating solution in the first-stage dosing and stirring tank is 5-7 minutes, and the stirring speed is 85-105 rpm.

3. The method for removing total phosphorus and COD from phosphating wastewater according to claim 1, characterized in that, In step (1), the residence time of the phosphating solution in the two-stage dosing and stirring tank is 6-8 min, and the stirring speed is 75-95 rpm.

4. The method for removing total phosphorus and COD from phosphating wastewater according to claim 1, characterized in that, In step (2), an automatic dosing system is provided in the first pH adjustment tank, the first hydrogen peroxide dosing and mixing tank, and the second modified agent mixing tank.

5. The method for removing total phosphorus and COD from phosphating wastewater according to claim 1, characterized in that, In step (2), the phosphating solution stays in a pH adjustment tank for 5 to 7 minutes.

6. The method for removing total phosphorus and COD from phosphating wastewater according to claim 1, characterized in that, In step (2), the residence time in a dosing and mixing tank is 2-3 minutes, and the mixing speed is 45-65 revolutions / min.

7. The method for removing total phosphorus and COD from phosphating wastewater according to claim 1, characterized in that, In step (2), the residence time of the phosphating solution in the two-stage modified agent mixing tank is 3-5 min, and the stirring speed is 75-95 rpm.

8. The method for removing total phosphorus and COD from phosphating wastewater according to claim 1, characterized in that, In step (3), the residence time of the phosphating wastewater in the filtration and adsorption tower is 19~35 min, and the backwashing time is 1020~1230 h.

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