Treatment method for grinding fluid wastewater of grinding machine

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses a treatment method for grinding fluid wastewater of a grinder, which comprises the following steps: pretreatment and demulsification, multi-stage chemical purification, biochemical deep treatment, deep purification and recycling, and sludge treatment. A specific supported heterogeneous catalyst is adopted in the multi-stage chemical purification step, nano zero-valent iron and copper oxide composite active components constructed on the surface of the catalyst can enhance the generation efficiency and stability of free radicals in the advanced oxidation process, and a composite coagulant with an optimized ratio in the coagulating sedimentation step is cooperated, so that the purification efficiency of the high-grade oxidation process is improved. An efficient continuous removal system for heavy metal ions and refractory organic pollutants is formed; meanwhile, in the pretreatment step, the demulsifier is composed of specific components, through the synergistic effect of all the components, rapid demulsification of the emulsified oil phase in the grinding fluid wastewater is achieved, favorable conditions are created for subsequent deep treatment, and therefore the purification efficiency and operation stability of the technology are overall improved.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically a method for treating grinding fluid wastewater from grinding mills. Background Technology

[0002] Grinding fluid is a liquid used for processing and polishing surfaces, composed of aviation gasoline, kerosene, transformer oil, various vegetable oils, animal oils, and hydrocarbons, along with several additives. Grinding fluid wastewater from grinding machines is a common and difficult-to-treat wastewater in industrial processing. Its composition is complex, containing pollutants such as metal particles, abrasives, lubricating oil, and surfactants. Direct discharge of such wastewater can cause serious harm to the environment.

[0003] Currently, in the treatment of grinding fluid wastewater from grinding mills, the wastewater contains oils, suspended solids, various heavy metal ions, and recalcitrant organic pollutants, resulting in complex and fluctuating composition. Existing conventional single and simple combination treatment methods cannot dynamically adjust the process parameters and reagent dosage of each treatment unit according to the real-time changes in the influent water quality. This leads to incomplete demulsification, excessive consumption of chemical reagents, or insufficient reaction, resulting in increased load on subsequent treatment and higher operating costs.

[0004] Therefore, a method for treating grinding fluid wastewater from grinding machines is proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for treating grinding fluid wastewater from grinding mills, which solves the problems mentioned in the background art, such as incomplete demulsification, excessive consumption of chemical reagents, or insufficient reaction, which lead to increased load on subsequent treatment and higher operating costs.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for treating grinding fluid wastewater from a grinding mill, comprising the following steps:

[0007] Step 1: Pretreatment and demulsification. The grinding slurry wastewater is introduced into the equalization tank for water quality and quantity balance and pH adjustment. Then, a demulsifier is added to carry out the demulsification reaction. The floating oil phase and some suspended solids are then removed by the air flotation separation equipment to obtain the air flotation effluent.

[0008] Step 2: Multi-stage chemical purification. The air flotation effluent is sent to a multi-stage reaction system. First, a coagulation and sedimentation reaction is carried out to obtain a coagulated supernatant. Then, the coagulated supernatant is subjected to an advanced oxidation reaction to remove heavy metal ions and recalcitrant organic matter.

[0009] Step 3: Deep biochemical treatment. The effluent after the multi-stage chemical purification is introduced into the biochemical treatment system, passing through the hydrolysis acidification section and the aerobic biological treatment section in sequence to further degrade the residual organic pollutants and obtain biochemical effluent.

[0010] Step 4: Deep purification and reuse. The biochemical effluent is subjected to deep purification through a membrane separation system and / or activated carbon adsorption device to obtain product water.

[0011] Step 5: Sludge treatment. The sludge generated in the previous steps is concentrated, dewatered, and heat-treated, and the solid products after heat treatment are recovered.

[0012] In step one, the demulsifier is made from the following raw materials in parts by weight: 30-50 parts of polyaluminum chloride, 5-15 parts of cationic polyacrylamide, 10-20 parts of modified diatomaceous earth, and 2-5 parts of coagulation activator.

[0013] Preferably, the pretreatment and demulsification in step one includes the following steps: pumping the grinding slurry wastewater into an equalization tank, homogenizing the water quality through stirring and aeration, and controlling the pH value of the wastewater within the range of 6.5-7.5 using an acid-base adjuster. Then, the wastewater is sent to a demulsification reactor, the demulsifier is added, and the reaction is carried out for 15-30 minutes at a stirring speed of 150-300 r / min. After the reaction is completed, the mixture is introduced into a dissolved air flotation machine, the dissolved air pressure is set to 0.3-0.5 MPa, the hydraulic retention time is 20-40 minutes, and the separated scum is discharged into a sludge thickening tank.

[0014] Preferably, the coagulant activator is prepared by the following method: ferrous sulfate powder is calcined at 450-550℃ for 2-4 hours under inert gas protection to obtain active iron oxide powder; the active iron oxide powder is mixed with citric acid aqueous solution at a mass ratio of 1:5, stirred and activated at 60-80℃ for 1-2 hours, and then spray-dried to obtain nano-sized composite activated particles, which are the coagulant activator.

[0015] Preferably, the coagulation and sedimentation reaction in step two includes the following steps: pumping the air flotation effluent into a coagulation reaction tank, adding a composite coagulant, wherein the composite coagulant is a mixture of polyferric sulfate and anionic polyacrylamide in a mass ratio of 15-25:1, controlling the stirring gradient, first stirring rapidly at 200-400 r / min for 2-5 minutes, then stirring slowly at 50-100 r / min for 10-20 minutes, and then entering an inclined plate sedimentation tank for sedimentation and separation, with a sedimentation time of 1.5-2.5 hours, and the resulting supernatant is the coagulation supernatant.

[0016] Preferably, the advanced oxidation reaction in step two adopts a Fenton-like oxidation method, including the following steps: introducing the coagulated supernatant into the advanced oxidation reaction tower, adjusting the pH to 3-4, and sequentially adding ferrous sulfate and hydrogen peroxide as catalyst and oxidant, wherein the dosage of ferrous sulfate is 200-500 mg / L, the dosage of hydrogen peroxide is 500-1500 mg / L, the reaction temperature is 30-50℃, and the reaction time is 40-80 minutes; after the reaction is completed, adjusting the pH to 7-8, so that the iron ions form ferric hydroxide flocs and are separated.

[0017] Preferably, the advanced oxidation reaction tower is filled with a supported heterogeneous catalyst. The catalyst uses porous ceramic as a support, and a composite active component of nano-zero-valent iron and copper oxide is loaded onto the surface of the support by an impregnation-calcination method. The impregnation-calcination method includes: impregnating the porous ceramic support in a mixed solution containing soluble iron salt and soluble copper salt; after impregnation, drying at 60-120°C for 2-6 hours; and then calcining in a reducing atmosphere at 400-600°C for 2-4 hours to form the composite active component on the surface of the support; the catalyst filling volume accounts for 15%-30% of the effective volume of the reaction tower.

[0018] Preferably, the operating conditions of the hydrolysis and acidification section in step three are: hydraulic retention time of 8-12 hours, pH value maintained at 5.5-6.5, and temperature controlled at 35-38℃; the aerobic biological treatment section adopts a membrane bioreactor, and the operating conditions are: hydraulic retention time of 10-14 hours, dissolved oxygen concentration maintained at 2-4 mg / L, and sludge concentration maintained at 8000-12000 mg / L.

[0019] Preferably, in the influent of the hydrolysis acidification section, a microbial growth promoter is added at a rate of 50-100 grams per cubic meter of wastewater. The microbial growth promoter is prepared by mixing yeast extract powder, trace element solution and vitamin B complex in a mass ratio of 8-12:4-6:0.8-1.2. The trace element solution contains iron, molybdenum, cobalt and nickel.

[0020] Preferably, the membrane separation system in step four employs an ultrafiltration-reverse osmosis dual-membrane method, specifically including the following operations: First, the biochemical effluent is subjected to ultrafiltration treatment. The ultrafiltration treatment uses a membrane with a pore size of 0.01-0.1 μm and an operating pressure of 0.1-0.3 MPa to remove suspended solids, colloids, and macromolecular organic matter. Subsequently, the ultrafiltration permeate is subjected to reverse osmosis treatment. The reverse osmosis treatment uses a polyamide composite membrane and an operating pressure of 1.0-1.5 MPa to further remove dissolved salts, small molecule organic matter, and heavy metal ions, ultimately obtaining the product water. The activated carbon adsorption device uses a granular activated carbon filter bed, with an empty bed contact time of 15-30 minutes.

[0021] Preferably, the sludge treatment in step five specifically includes:

[0022] The sludge generated in the aforementioned steps is collected and subjected to gravity thickening for 12-24 hours to obtain concentrated sludge with a moisture content of 95%-97%. The concentrated sludge is then sent to a dewatering device for mechanical dewatering, and the moisture content of the dewatered sludge cake is no higher than 80%. Subsequently, the dewatered sludge cake is transported to a pyrolysis furnace for low-temperature pyrolysis treatment at a temperature of 350-450℃ and a residence time of 30-60 minutes. The solid products generated after pyrolysis are sorted to recover the metal oxide components, and the residual carbonaceous components are either recycled or safely landfilled.

[0023] Compared with the prior art, the present invention provides a method for treating grinding fluid wastewater from a grinding mill, which has the following beneficial effects:

[0024] 1. In this invention, the specific supported heterogeneous catalyst used in the multi-stage chemical purification steps has a nano-zero-valent iron and copper oxide composite active component built on its surface, which can enhance the generation efficiency and stability of free radicals in the advanced oxidation process. It works synergistically with the optimized composite coagulant in the coagulation and sedimentation step to form a highly efficient and continuous removal system for heavy metal ions and recalcitrant organic pollutants. At the same time, the demulsifier composed of specific components in the pretreatment step achieves rapid demulsification of the emulsified oil phase in the grinding slurry wastewater through the synergistic effect of the components, creating favorable conditions for subsequent deep treatment, thereby improving the overall purification efficiency and operational stability of the process.

[0025] 2. In this invention, the biochemical deep treatment step activates and maintains the metabolic activity of the functional microbial community by adding a specific ratio of microbial growth promoter in the hydrolysis and acidification stage, enabling it to efficiently degrade residual organic pollutants after the previous chemical purification. At the same time, the process conditions of the hydrolysis and acidification and aerobic biological treatment stages are synergistically optimized to form an efficient biological metabolic chain, which is closely connected with the pre-chemical purification and post-membrane separation system to jointly construct a multi-level, complementary pollutant degradation and separation barrier, enhance the system's ability to cope with water quality fluctuations, and ensure the long-term stable compliance of the final effluent water quality.

[0026] 3. In this invention, the sludge treatment step uniformly performs low-temperature pyrolysis resource recovery treatment on the sludge generated in each stage. This process not only reduces the volume and renders the sludge harmless, but also recovers the enriched metal oxide components through the sorting of the pyrolysis products. At the same time, the residual carbonaceous components have the potential to be used as adsorbent materials and fuels, transforming waste into reusable resources. This achieves an organic combination of waste disposal and resource recovery, thereby improving the sustainability and environmental and economic benefits of the entire wastewater treatment method. Detailed Implementation

[0027] 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.

[0028] Example 1: A method for treating grinding fluid wastewater from a grinding mill, comprising the following steps:

[0029] Step 1: Pretreatment and demulsification. The grinding slurry wastewater is introduced into the equalization tank for water quality and quantity balance and pH adjustment. Then, a demulsifier is added to carry out the demulsification reaction. The floating oil phase and some suspended solids are then removed by the air flotation separation equipment to obtain the air flotation effluent.

[0030] Step 2: Multi-stage chemical purification. The air flotation effluent is sent to a multi-stage reaction system. First, a coagulation and sedimentation reaction is carried out to obtain a coagulated supernatant. Then, the coagulated supernatant is subjected to an advanced oxidation reaction to remove heavy metal ions and recalcitrant organic matter.

[0031] Step 3: Deep biological treatment. The effluent after multi-stage chemical purification is introduced into the biological treatment system, passing through the hydrolysis acidification section and the aerobic biological treatment section in sequence to further degrade the residual organic pollutants and obtain biological effluent.

[0032] Step 4: Deep purification and reuse. The biochemical effluent is subjected to deep purification through a membrane separation system and / or activated carbon adsorption device to obtain product water.

[0033] Step 5: Sludge treatment. The sludge generated in the previous steps is concentrated, dewatered, and heat-treated, and the solid products after heat treatment are recovered.

[0034] In step one, the demulsifier is made from the following raw materials in parts by weight: 30 parts polyaluminum chloride, 5 parts cationic polyacrylamide, 10 parts modified diatomaceous earth, and 2 parts coagulation activator.

[0035] The pretreatment and demulsification in step one includes the following steps: the grinding slurry wastewater is pumped into the equalization tank, and the water quality is homogenized by stirring and aeration. The pH value of the wastewater is controlled at 6.5 using an acid-base adjuster. Then, the wastewater is sent to the demulsification reactor, a demulsifier is added, and the reaction is carried out for 15 minutes at a stirring speed of 150 r / min. After the reaction is completed, the mixture is introduced into the dissolved air flotation machine, the dissolved air pressure is set to 0.3 MPa, the hydraulic retention time is 20 minutes, and the separated scum is discharged into the sludge thickening tank.

[0036] The coagulant activator is prepared by the following method: ferrous sulfate powder is calcined at 450°C for 2 hours under inert gas protection to obtain activated iron oxide powder; the activated iron oxide powder is mixed with citric acid aqueous solution at a mass ratio of 1:5, stirred and activated at 60°C for 1 hour, and then spray-dried to obtain nano-sized composite activated particles, which are the coagulant activator.

[0037] Step 2, the coagulation and sedimentation reaction, includes the following steps: the air flotation effluent is pumped into the coagulation reaction tank, a composite coagulant is added, which is a mixture of polyferric sulfate and anionic polyacrylamide in a mass ratio of 15:1. The stirring gradient is controlled, first at 200 r / min for 2 minutes, then at 50 r / min for 10 minutes, and then into an inclined plate sedimentation tank for sedimentation and separation. The sedimentation time is 1.5 hours, and the resulting supernatant is the coagulation supernatant.

[0038] The advanced oxidation reaction in step two adopts a Fenton-like oxidation method, which includes the following steps: the coagulated supernatant is introduced into the advanced oxidation reaction tower, the pH is adjusted to 3, and ferrous sulfate and hydrogen peroxide are added sequentially as catalyst and oxidant, respectively, wherein the dosage of ferrous sulfate is 200 mg / L and the dosage of hydrogen peroxide is 500 mg / L, the reaction temperature is 30℃, and the reaction time is 40 minutes; after the reaction is completed, the pH is adjusted back to 7, so that the iron ions form ferric hydroxide flocs and are separated.

[0039] The advanced oxidation reaction tower is filled with a supported heterogeneous catalyst. The catalyst uses porous ceramic as a support, and a composite active component of nano-zero valent iron and copper oxide is loaded on the surface of the support through an impregnation-calcination method. The impregnation-calcination method includes: impregnating the porous ceramic support in a mixed solution containing soluble iron salt and soluble copper salt; after impregnation, drying at 60°C for 2 hours; and then calcining at 400°C for 2 hours in a reducing atmosphere to form a composite active component on the surface of the support; the catalyst filling volume accounts for 15% of the effective volume of the reaction tower.

[0040] The operating conditions for the hydrolysis and acidification section in step three are: hydraulic retention time of 8 hours, pH value maintained at 5.5, and temperature controlled at 35℃; the aerobic biological treatment section uses a membrane bioreactor, and the operating conditions are: hydraulic retention time of 10 hours, dissolved oxygen concentration maintained at 2 mg / L, and sludge concentration maintained at 8000 mg / L.

[0041] In the influent of the hydrolysis and acidification section, a microbial growth promoter is added at a rate of 50 grams per cubic meter of wastewater. The microbial growth promoter is made by mixing yeast extract powder, trace element solution and vitamin B complex in a mass ratio of 8:4:0.8. The trace element solution contains iron, molybdenum, cobalt and nickel.

[0042] The membrane separation system in step four employs an ultrafiltration-reverse osmosis dual-membrane method, specifically including the following operations: First, the biochemical effluent is subjected to ultrafiltration treatment using a membrane with a pore size of 0.01 μm and an operating pressure of 0.1 MPa to remove suspended solids, colloids, and large molecular organic matter. Subsequently, the ultrafiltration permeate is subjected to reverse osmosis treatment using a polyamide composite membrane at an operating pressure of 1.0 MPa to further remove dissolved salts, small molecular organic matter, and heavy metal ions, ultimately obtaining permeate. The activated carbon adsorption device uses a granular activated carbon filter bed with an empty bed contact time of 15 minutes.

[0043] Step five, sludge treatment, specifically includes:

[0044] The sludge generated in the aforementioned steps is collected and subjected to gravity thickening for 12 hours to obtain concentrated sludge with a water content of 95%. The concentrated sludge is then sent to a dewatering device for mechanical dewatering. The water content of the dewatered sludge cake is no more than 80%. Subsequently, the dewatered sludge cake is transported to a pyrolysis furnace for low-temperature pyrolysis treatment at a temperature of 350°C and a residence time of 30 minutes. The solid products generated after pyrolysis are sorted to recover the metal oxide components, and the residual carbonaceous components are either recycled or safely landfilled.

[0045] Example 2: A method for treating grinding fluid wastewater from a grinding mill, comprising the following steps:

[0046] Step 1: Pretreatment and demulsification. The grinding slurry wastewater is introduced into the equalization tank for water quality and quantity balance and pH adjustment. Then, a demulsifier is added to carry out the demulsification reaction. The floating oil phase and some suspended solids are then removed by the air flotation separation equipment to obtain the air flotation effluent.

[0047] Step 2: Multi-stage chemical purification. The air flotation effluent is sent to a multi-stage reaction system. First, a coagulation and sedimentation reaction is carried out to obtain a coagulated supernatant. Then, the coagulated supernatant is subjected to an advanced oxidation reaction to remove heavy metal ions and recalcitrant organic matter.

[0048] Step 3: Deep biological treatment. The effluent after multi-stage chemical purification is introduced into the biological treatment system, passing through the hydrolysis acidification section and the aerobic biological treatment section in sequence to further degrade the residual organic pollutants and obtain biological effluent.

[0049] Step 4: Deep purification and reuse. The biochemical effluent is subjected to deep purification through a membrane separation system and / or activated carbon adsorption device to obtain product water.

[0050] Step 5: Sludge treatment. The sludge generated in the previous steps is concentrated, dewatered, and heat-treated, and the solid products after heat treatment are recovered.

[0051] In step one, the demulsifier is made from the following raw materials in parts by weight: 40 parts polyaluminum chloride, 10 parts cationic polyacrylamide, 15 parts modified diatomaceous earth, and 3 parts coagulant activator.

[0052] The pretreatment and demulsification in step one includes the following steps: the grinding slurry wastewater is pumped into the equalization tank, and the water quality is homogenized by stirring and aeration. The pH value of the wastewater is controlled at 7 using an acid-base adjuster. Then, the wastewater is sent to the demulsification reactor, a demulsifier is added, and the reaction is carried out for 20 minutes at a stirring speed of 220 r / min. After the reaction is completed, the mixture is introduced into the dissolved air flotation machine, the dissolved air pressure is set to 0.4 MPa, the hydraulic retention time is 30 minutes, and the separated scum is discharged into the sludge thickening tank.

[0053] The coagulant activator is prepared by the following method: ferrous sulfate powder is calcined at 500°C for 3 hours under inert gas protection to obtain activated iron oxide powder; the activated iron oxide powder is mixed with citric acid aqueous solution at a mass ratio of 1:5, stirred and activated at 70°C for 1.5 hours, and then spray-dried to obtain nano-sized composite activated particles, which are the coagulant activator.

[0054] Step 2, the coagulation and sedimentation reaction, includes the following steps: the air flotation effluent is pumped into the coagulation reaction tank, a composite coagulant is added, which is a mixture of polyferric sulfate and anionic polyacrylamide in a mass ratio of 20:1. The stirring gradient is controlled, first at 300 r / min for 3 minutes, then at 70 r / min for 15 minutes, and then into an inclined plate sedimentation tank for sedimentation and separation. The sedimentation time is 2 hours, and the resulting supernatant is the coagulation supernatant.

[0055] The advanced oxidation reaction in step two adopts a Fenton-like oxidation method, including the following steps: the coagulated supernatant is introduced into the advanced oxidation reaction tower, the pH is adjusted to 3.5, and ferrous sulfate and hydrogen peroxide are added sequentially as catalyst and oxidant, respectively, wherein the dosage of ferrous sulfate is 350 mg / L and the dosage of hydrogen peroxide is 1000 mg / L, the reaction temperature is 40℃, and the reaction time is 60 minutes; after the reaction is completed, the pH is adjusted back to 7.5, so that the iron ions form ferric hydroxide flocs and are separated.

[0056] The advanced oxidation reaction tower is filled with a supported heterogeneous catalyst. The catalyst uses porous ceramic as a support, and a composite active component of nano-zero valent iron and copper oxide is loaded on the surface of the support through an impregnation-calcination method. The impregnation-calcination method includes: impregnating the porous ceramic support in a mixed solution containing soluble iron salt and soluble copper salt; after impregnation, drying at 100°C for 4 hours; and then calcining at 500°C for 3 hours in a reducing atmosphere to form a composite active component on the surface of the support; the catalyst filling volume accounts for 25% of the effective volume of the reaction tower.

[0057] The operating conditions for the hydrolysis and acidification section in step three are: hydraulic retention time of 10 hours, pH value maintained at 6, and temperature controlled at 36℃; the aerobic biological treatment section uses a membrane bioreactor, and the operating conditions are: hydraulic retention time of 12 hours, dissolved oxygen concentration maintained at 3 mg / L, and sludge concentration maintained at 10000 mg / L.

[0058] In the influent of the hydrolysis and acidification section, a microbial growth promoter is added at a rate of 70 grams per cubic meter of wastewater. The microbial growth promoter is made by mixing yeast extract powder, trace element solution and vitamin B complex in a mass ratio of 10:5:1. The trace element solution contains iron, molybdenum, cobalt and nickel.

[0059] The membrane separation system in step four employs an ultrafiltration-reverse osmosis dual-membrane method, specifically including the following operations: First, the biochemical effluent is subjected to ultrafiltration treatment using a membrane with a pore size of 0.05 μm and an operating pressure of 0.2 MPa to remove suspended solids, colloids, and large molecular organic matter. Subsequently, the ultrafiltration permeate is subjected to reverse osmosis treatment using a polyamide composite membrane at an operating pressure of 1.2 MPa to further remove dissolved salts, small molecular organic matter, and heavy metal ions, ultimately obtaining permeate. The activated carbon adsorption device uses a granular activated carbon filter bed with an empty bed contact time of 20 minutes.

[0060] Step five, sludge treatment, specifically includes:

[0061] The sludge generated in the aforementioned steps is collected and subjected to gravity thickening for 18 hours to obtain concentrated sludge with a water content of 96%. The concentrated sludge is then sent to a dewatering device for mechanical dewatering. The water content of the dewatered sludge cake is no more than 80%. Subsequently, the dewatered sludge cake is transported to a pyrolysis furnace for low-temperature pyrolysis treatment at a temperature of 400°C and a residence time of 45 minutes. The solid products generated after pyrolysis are sorted to recover the metal oxide components, and the residual carbonaceous components are either recycled or safely landfilled.

[0062] Example 3: A method for treating grinding fluid wastewater from a grinding mill, comprising the following steps:

[0063] Step 1: Pretreatment and demulsification. The grinding slurry wastewater is introduced into the equalization tank for water quality and quantity balance and pH adjustment. Then, a demulsifier is added to carry out the demulsification reaction. The floating oil phase and some suspended solids are then removed by the air flotation separation equipment to obtain the air flotation effluent.

[0064] Step 2: Multi-stage chemical purification. The air flotation effluent is sent to a multi-stage reaction system. First, a coagulation and sedimentation reaction is carried out to obtain a coagulated supernatant. Then, the coagulated supernatant is subjected to an advanced oxidation reaction to remove heavy metal ions and recalcitrant organic matter.

[0065] Step 3: Deep biological treatment. The effluent after multi-stage chemical purification is introduced into the biological treatment system, passing through the hydrolysis acidification section and the aerobic biological treatment section in sequence to further degrade the residual organic pollutants and obtain biological effluent.

[0066] Step 4: Deep purification and reuse. The biochemical effluent is subjected to deep purification through a membrane separation system and / or activated carbon adsorption device to obtain product water.

[0067] Step 5: Sludge treatment. The sludge generated in the previous steps is concentrated, dewatered, and heat-treated, and the solid products after heat treatment are recovered.

[0068] In step one, the demulsifier is made from the following raw materials in parts by weight: 50 parts polyaluminum chloride, 15 parts cationic polyacrylamide, 20 parts modified diatomaceous earth, and 5 parts coagulant activator.

[0069] The pretreatment and demulsification in step one includes the following steps: the grinding slurry wastewater is pumped into the equalization tank, and the water quality is homogenized by stirring and aeration. The pH value of the wastewater is controlled at 7.5 using an acid-base adjuster. Then, the wastewater is sent to the demulsification reactor, a demulsifier is added, and the reaction is carried out for 30 minutes at a stirring speed of 300 r / min. After the reaction is completed, the mixture is introduced into the dissolved air flotation machine, the dissolved air pressure is set to 0.5 MPa, the hydraulic retention time is 40 minutes, and the separated scum is discharged into the sludge thickening tank.

[0070] The coagulant activator is prepared by the following method: ferrous sulfate powder is calcined at 550°C for 4 hours under inert gas protection to obtain activated iron oxide powder; the activated iron oxide powder is mixed with citric acid aqueous solution at a mass ratio of 1:5, stirred and activated at 80°C for 2 hours, and then spray-dried to obtain nano-sized composite activated particles, which are the coagulant activator.

[0071] Step 2, the coagulation and sedimentation reaction, includes the following steps: the effluent from the air flotation is pumped into the coagulation reaction tank, a composite coagulant is added, which is a mixture of polyferric sulfate and anionic polyacrylamide in a mass ratio of 25:1. The stirring gradient is controlled, first at 400 r / min for 5 minutes, then at 100 r / min for 20 minutes, and then into an inclined plate sedimentation tank for sedimentation and separation. The sedimentation time is 2.5 hours, and the resulting supernatant is the coagulation supernatant.

[0072] The advanced oxidation reaction in step two adopts a Fenton-like oxidation method, which includes the following steps: the coagulated supernatant is introduced into the advanced oxidation reaction tower, the pH is adjusted to 4, and ferrous sulfate and hydrogen peroxide are added sequentially as catalyst and oxidant, respectively, wherein the dosage of ferrous sulfate is 500 mg / L and the dosage of hydrogen peroxide is 1500 mg / L, the reaction temperature is 50℃, and the reaction time is 80 minutes; after the reaction is completed, the pH is adjusted back to 8, so that the iron ions form ferric hydroxide flocs and are separated.

[0073] The advanced oxidation reaction tower is filled with a supported heterogeneous catalyst. The catalyst uses porous ceramic as a support, and a composite active component of nano-zero valent iron and copper oxide is loaded on the surface of the support through an impregnation-calcination method. The impregnation-calcination method includes: impregnating the porous ceramic support in a mixed solution containing soluble iron salt and soluble copper salt; after impregnation, drying at 120°C for 6 hours; and then calcining at 600°C for 4 hours in a reducing atmosphere to form a composite active component on the surface of the support; the catalyst filling volume accounts for 30% of the effective volume of the reaction tower.

[0074] The operating conditions for the hydrolysis and acidification section in step three are: hydraulic retention time of 12 hours, pH value maintained at 6.5, and temperature controlled at 38℃; the aerobic biological treatment section uses a membrane bioreactor, and the operating conditions are: hydraulic retention time of 14 hours, dissolved oxygen concentration maintained at 4 mg / L, and sludge concentration maintained at 12000 mg / L.

[0075] In the influent of the hydrolysis and acidification section, a microbial growth promoter is added at a rate of 100 grams per cubic meter of wastewater. The microbial growth promoter is made by mixing yeast extract powder, trace element solution and vitamin B complex in a mass ratio of 12:6:1.2. The trace element solution contains iron, molybdenum, cobalt and nickel.

[0076] The membrane separation system in step four employs an ultrafiltration-reverse osmosis dual-membrane method, specifically including the following operations: First, the biochemical effluent is subjected to ultrafiltration treatment using a membrane with a pore size of 0.1 μm and an operating pressure of 0.3 MPa to remove suspended solids, colloids, and large molecular organic matter. Subsequently, the ultrafiltration permeate is subjected to reverse osmosis treatment using a polyamide composite membrane at an operating pressure of 1.5 MPa to further remove dissolved salts, small molecular organic matter, and heavy metal ions, ultimately obtaining permeate. The activated carbon adsorption device uses a granular activated carbon filter bed with an empty bed contact time of 30 minutes.

[0077] Step five, sludge treatment, specifically includes:

[0078] The sludge generated in the aforementioned steps is collected and subjected to gravity thickening for 24 hours to obtain concentrated sludge with a water content of 97%. The concentrated sludge is then sent to a dewatering device for mechanical dewatering, and the water content of the dewatered sludge cake is no more than 80%. Subsequently, the dewatered sludge cake is transported to a pyrolysis furnace for low-temperature pyrolysis treatment at a temperature of 450°C and a residence time of 60 minutes. The solid products generated after pyrolysis are sorted to recover the metal oxide components, and the residual carbonaceous components are either recycled or safely landfilled.

[0079] Comparative Example 1: The difference between this comparative example and Example 1 is that no coagulation activator was added when preparing the demulsifier in this comparative example.

[0080] Comparative Example 2 differs from Example 1 in that a supported heterogeneous catalyst was not used in the advanced oxidation reaction.

[0081] Comparative Example 3 differs from Example 1 in that: no microbial growth promoter was added to the hydrolysis and acidification section during the deep biochemical treatment step in this comparative example.

[0082] Comparative Example 4 differs from Example 1 in that it does not include the low-temperature pyrolysis treatment in the sludge treatment step.

[0083] The performance of the grinding fluid wastewater treatment methods implemented in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and test methods are as follows:

[0084] The chemical oxygen demand (COD) removal rate was tested in a laboratory simulation or on an actual treatment line. Samples were taken at the inlet of the treatment system, after the advanced oxidation reaction, at the effluent of the biological treatment, and at the outlet of the final product water. The COD value of the water samples was determined by the potassium dichromate method according to the standard method, and the COD removal rate of each unit and the whole was calculated.

[0085] For the heavy metal ion removal rate test, samples were taken at the inlet of the treatment system and the final product water outlet. After the water samples were pretreated by digestion, the total chromium concentration was determined by inductively coupled plasma atomic emission spectrometry or atomic absorption spectrometry, and the removal rate was calculated.

[0086] The sludge reduction rate and resource recovery effect test recorded and weighed the amount of original sludge generated during one complete cycle of the method. After being processed by the concentration, dewatering and pyrolysis steps described in the method, the mass of the final solid residue was weighed and calculated, and the sludge reduction rate was calculated. X-ray diffraction and component analysis were performed on the solid products after pyrolysis to identify and qualitatively evaluate the types and enrichment of metal oxides.

[0087] The total suspended solids (TSS) removal rate test involves taking samples at the inlet and outlet of the treatment system, shaking them thoroughly, filtering a certain volume of water sample using a constant-weight filter membrane, drying the filter membrane and the retained material at a specific temperature to constant weight, calculating the concentration of total suspended solids in the water sample based on the mass difference of the filter membrane before and after filtration and the volume of the water sample, and calculating the removal rate of this index by the system.

[0088] The test data of the grinding fluid wastewater treatment methods implemented in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0089] Testing items COD removal rate (%) Total chromium removal rate (%) TSS removal rate (%) Sludge reduction rate (%) Example 1 94.5±1.2 99.2±0.3 98.8±0.5 75.3±2.1 Example 2 93.8±1.5 98.9±0.5 97.5±0.8 73.9±2.5 Example 3 95.1±1.0 99.5±0.2 99.0±0.4 76.8±1.8 Comparative Example 1 81.2±3.5 95.6±1.2 85.4±2.8 72.5±3.0 Comparative Example 2 87.5±2.0 92.3±2.1 96.0±1.5 74.1±2.8 Comparative Example 3 89.3±1.8 98.1±0.8 97.8±1.0 74.5±2.2 Comparative Example 4 94.0±1.3 99.0±0.4 98.5±0.6 35.2±5.0

[0090] By comparing and analyzing the data in the table, it can be seen that the grinding fluid wastewater treated by the complete process in Examples 1-3 exhibits excellent key performance indicators. This indicates that the specific supported heterogeneous catalyst used in the multi-stage chemical purification steps, with its surface-constructed nano-zero-valent iron and copper oxide composite active components, can enhance the generation efficiency and stability of free radicals during advanced oxidation processes. Together with the optimized composite coagulant in the coagulation and sedimentation steps, it forms a highly efficient and continuous removal system for heavy metal ions and recalcitrant organic pollutants. At the same time, the demulsifier composed of specific components in the pretreatment step, through the synergistic effect of various components, achieves rapid demulsification of the emulsified oil phase in the grinding fluid wastewater, creating favorable conditions for subsequent deep treatment, thereby improving the overall purification efficiency and operational stability of the process. The advanced biochemical treatment step activates and maintains the metabolic activity of functional microbial communities by adding a specific ratio of microbial growth promoters in the hydrolysis and acidification stage, enabling them to efficiently degrade residual organic pollutants after the initial chemical purification. Simultaneously, the process conditions of the hydrolysis and acidification and aerobic biological treatment stages are synergistically optimized to form a highly efficient biological metabolic chain. This chain, closely integrated with the pre-treatment chemical purification and post-treatment membrane separation system, constructs a multi-layered, complementary barrier for pollutant degradation and separation, enhancing the system's ability to cope with water quality fluctuations and ensuring the long-term stable compliance of the final effluent quality. The sludge treatment step involves the unified low-temperature pyrolysis and resource recovery of sludge generated from each stage. This process not only reduces sludge volume and renders it harmless but also recovers the enriched metal oxide components through the sorting of the pyrolysis products. Furthermore, the residual carbonaceous components possess the potential to serve as adsorbent materials and fuel, transforming waste into reusable resources. This achieves an organic combination of waste disposal and resource recovery, thereby improving the sustainability and environmental and economic benefits of the entire wastewater treatment method.

[0091] By comparing and analyzing the relevant data in the table, it can be seen that the treatment method of the present invention not only achieves efficient and stable removal of pollutants from wastewater, but also demonstrates outstanding performance in sludge reduction and resource recovery. This indicates that the treatment method for grinding fluid wastewater provided by the present invention has superior overall performance.

[0092] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0093] 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 treating grinding fluid wastewater from a grinding mill, characterized in that: Includes the following steps: Step 1: Pretreatment and demulsification. The grinding slurry wastewater is introduced into the equalization tank for water quality and quantity balance and pH adjustment. Then, a demulsifier is added to carry out the demulsification reaction. The floating oil phase and some suspended solids are then removed by the air flotation separation equipment to obtain the air flotation effluent. Step 2: Multi-stage chemical purification. The air flotation effluent is sent to a multi-stage reaction system. First, a coagulation and sedimentation reaction is carried out to obtain a coagulated supernatant. Then, the coagulated supernatant is subjected to an advanced oxidation reaction to remove heavy metal ions and recalcitrant organic matter. Step 3: Deep biochemical treatment. The effluent after the multi-stage chemical purification is introduced into the biochemical treatment system, passing through the hydrolysis acidification section and the aerobic biological treatment section in sequence to further degrade the residual organic pollutants and obtain biochemical effluent. Step 4: Deep purification and reuse. The biochemical effluent is subjected to deep purification through a membrane separation system and / or activated carbon adsorption device to obtain product water. Step 5: Sludge treatment. The sludge generated in the previous steps is concentrated, dewatered, and heat-treated, and the solid products after heat treatment are recovered. In step one, the demulsifier is made from the following raw materials in parts by weight: 30-50 parts of polyaluminum chloride, 5-15 parts of cationic polyacrylamide, 10-20 parts of modified diatomaceous earth, and 2-5 parts of coagulation activator.

2. The method for treating grinding fluid wastewater from a grinding mill according to claim 1, characterized in that: The pretreatment and demulsification in step one includes the following steps: the grinding slurry wastewater is pumped into an equalization tank, and the water quality is homogenized by stirring and aeration. The pH value of the wastewater is controlled within the range of 6.5-7.5 using an acid-base adjuster. Then, the wastewater is sent to a demulsification reactor, the demulsifier is added, and the reaction is carried out at a stirring speed of 150-300 r / min for 15-30 minutes. After the reaction is completed, the mixture is introduced into a dissolved air flotation machine, the dissolved air pressure is set to 0.3-0.5 MPa, the hydraulic retention time is 20-40 minutes, and the separated scum is discharged into a sludge thickening tank.

3. The method for treating grinding fluid wastewater from a grinding mill according to claim 1, characterized in that: The coagulant activator is prepared by the following method: ferrous sulfate powder is calcined at 450-550℃ for 2-4 hours under inert gas protection to obtain active iron oxide powder; the active iron oxide powder is mixed with citric acid aqueous solution at a mass ratio of 1:5, stirred and activated at 60-80℃ for 1-2 hours, and then spray-dried to obtain nano-sized composite activated particles, which are the coagulant activator.

4. The method for treating grinding fluid wastewater from a grinding mill according to claim 1, characterized in that: The coagulation and sedimentation reaction in step two includes the following steps: pumping the air flotation effluent into the coagulation reaction tank, adding a composite coagulant, which is a mixture of polyferric sulfate and anionic polyacrylamide in a mass ratio of 15-25:1, controlling the stirring gradient, first stirring rapidly at 200-400 r / min for 2-5 minutes, then stirring slowly at 50-100 r / min for 10-20 minutes, and then entering an inclined plate sedimentation tank for sedimentation and separation, with a sedimentation time of 1.5-2.5 hours, and the resulting supernatant is the coagulation supernatant.

5. A method for treating grinding fluid wastewater from a grinding mill according to claim 4, characterized in that: The advanced oxidation reaction in step two adopts a Fenton-like oxidation method, including the following steps: the coagulated supernatant is introduced into the advanced oxidation reaction tower, the pH is adjusted to 3-4, and ferrous sulfate and hydrogen peroxide are added sequentially as catalyst and oxidant, wherein the dosage of ferrous sulfate is 200-500 mg / L, the dosage of hydrogen peroxide is 500-1500 mg / L, the reaction temperature is 30-50℃, and the reaction time is 40-80 minutes; after the reaction is completed, the pH is adjusted back to 7-8, so that the iron ions form ferric hydroxide flocs and are separated.

6. A method for treating grinding fluid wastewater from a grinding mill according to claim 5, characterized in that: The advanced oxidation reaction tower is filled with a supported heterogeneous catalyst. The catalyst uses porous ceramic as a support, and a composite active component of nano-zero-valent iron and copper oxide is loaded onto the surface of the support through an impregnation-calcination method. The impregnation-calcination method includes: impregnating the porous ceramic support in a mixed solution containing soluble iron salt and soluble copper salt; after impregnation, drying at 60-120°C for 2-6 hours; and then calcining in a reducing atmosphere at 400-600°C for 2-4 hours to form the composite active component on the surface of the support. The catalyst filling volume accounts for 15%-30% of the effective volume of the reaction tower.

7. A method for treating grinding fluid wastewater from a grinding mill according to claim 1, characterized in that: The operating conditions for the hydrolysis and acidification section in step three are: hydraulic retention time of 8-12 hours, pH value maintained at 5.5-6.5, and temperature controlled at 35-38℃; the aerobic biological treatment section adopts a membrane bioreactor, and the operating conditions are: hydraulic retention time of 10-14 hours, dissolved oxygen concentration maintained at 2-4 mg / L, and sludge concentration maintained at 8000-12000 mg / L.

8. A method for treating grinding fluid wastewater from a grinding mill according to claim 7, characterized in that: In the influent of the hydrolysis acidification section, a microbial growth promoter is added at a rate of 50-100 grams per cubic meter of wastewater. The microbial growth promoter is prepared by mixing yeast extract powder, trace element solution and vitamin B complex in a mass ratio of 8-12:4-6:0.8-1.

2. The trace element solution contains iron, molybdenum, cobalt and nickel.

9. A method for treating grinding fluid wastewater from a grinding mill according to claim 1, characterized in that: The membrane separation system in step four employs an ultrafiltration-reverse osmosis dual-membrane method, specifically including the following operations: First, the biochemical effluent is subjected to ultrafiltration treatment. The ultrafiltration treatment uses a membrane with a pore size of 0.01-0.1 μm and an operating pressure of 0.1-0.3 MPa to remove suspended solids, colloids, and macromolecular organic matter. Subsequently, the ultrafiltration permeate is subjected to reverse osmosis treatment. The reverse osmosis treatment uses a polyamide composite membrane and an operating pressure of 1.0-1.5 MPa to further remove dissolved salts, small molecule organic matter, and heavy metal ions, ultimately obtaining the product water. The activated carbon adsorption device uses a granular activated carbon filter bed, with an empty bed contact time of 15-30 minutes.

10. A method for treating grinding fluid wastewater from a grinding mill according to claim 1, characterized in that: The sludge treatment in step five specifically includes: The sludge generated in the aforementioned steps is collected and subjected to gravity thickening for 12-24 hours to obtain concentrated sludge with a moisture content of 95%-97%. The concentrated sludge is then sent to a dewatering device for mechanical dewatering, and the moisture content of the dewatered sludge cake is no higher than 80%. Subsequently, the dewatered sludge cake is transported to a pyrolysis furnace for low-temperature pyrolysis treatment at a temperature of 350-450℃ and a residence time of 30-60 minutes. The solid products generated after pyrolysis are sorted to recover the metal oxide components, and the residual carbonaceous components are either recycled or safely landfilled.