Process for treating acidified oil wastewater

Abstract

The application belongs to the technical field of grease chemistry, and discloses a kind of acidified oil wastewater treatment process, which comprises the steps of pretreatment, conditioning, anaerobic treatment, anoxic treatment, aerobic treatment and oxidation treatment, wherein the hydrolysis acidification tank in the conditioning step is added with an iron-containing additive (iron filings powder and steel slag particles are compounded) made from steel scrap, a micro-electrolysis reaction occurs in a weak acidic environment, promotes the decomposition of long-chain fatty acids into volatile fatty acids, and at the same time, the steel slag releases alkalinity to stabilize pH, effectively reduces the toxicity of sulfate, improves the biodegradability of wastewater, significantly improves the efficiency of subsequent biological treatment, and the effluent COD, total phosphorus and other indicators all meet the first-level standard of the "Integrated Wastewater Discharge Standard", and realizes the resource utilization of solid waste, with low cost and no secondary pollution. The application has the advantages and effects of stabilizing and improving the hydrolysis acidification efficiency, ensuring the effluent quality, ensuring the long-term stable operation of the subsequent biological treatment system, realizing the efficient purification of acidified oil wastewater and meeting the discharge standard.

Description

Technical Field

[0001] This invention belongs to the field of oleochemical technology, and specifically relates to a process for treating acidified oil wastewater. Background Technology

[0002] Vegetable acidified oil is an oil-based chemical raw material produced by using byproducts such as soap residue, waste oil, and oil residue generated during the refining of vegetable oils (such as soybeans, corn, rapeseed, and palm oil) as raw materials. It is processed through steps such as alkali saponification, filtration and separation, acidification treatment, and water washing and separation. The wastewater generated during its production process is called acidified oil wastewater, which is characterized by high chemical oxygen demand (COD), high nitrogen and phosphorus, high sulfate, high conductivity, and low pH. It is difficult to treat and may cause serious environmental pollution, ecological damage, and harm to residents' health if untreated vegetable acidified oil wastewater is directly discharged into natural water bodies.

[0003] Currently, there is relatively little research on the treatment of plant acidified oil wastewater. The current research on the treatment of plant acidified oil wastewater mainly includes physicochemical methods, biochemical methods, and advanced oxidation methods. Biological methods (such as anaerobic-aerobic combined processes) have become the main treatment method due to their advantages such as low operating costs and no secondary pollution. However, long-chain fatty acids and oils in acidified oil wastewater have an inhibitory effect on microorganisms, especially at high concentrations, which can easily lead to the inactivation of bacteria in anaerobic reactors, sludge floating or rancidity, and unstable treatment efficiency.

[0004] In practical engineering applications, hydrolysis acidification is a key step in improving the biodegradability of wastewater. Its treatment effect directly determines the operational stability of subsequent anaerobic, anoxic, and aerobic processes. However, existing technologies for hydrolysis acidification of acidified oily wastewater still have significant shortcomings: the hydrolysis acidification process is easily affected by fluctuations in wastewater quality and the accumulation of organic acids, resulting in incomplete decomposition of long-chain fatty acids, low yield of volatile fatty acids, and unstable composition. This leads to limited improvement in the biodegradability of the effluent and large fluctuations in water quality. When this unstable effluent enters the subsequent anaerobic treatment, it can easily cause inhibition of methanogenic bacteria activity, a decrease in gas production, or even reactor acidification failure, thereby affecting the purification efficiency and effluent compliance stability of the entire biological treatment system. Summary of the Invention

[0005] The purpose of this invention is to provide an acidified oil wastewater treatment process that can stably improve hydrolysis and acidification efficiency, ensure effluent quality, thereby guarantee the long-term stable operation of the subsequent biological treatment system, and achieve efficient purification and compliant discharge of acidified oil wastewater.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: an acidified oil wastewater treatment process, comprising the following steps:

[0007] S1. Pretreatment: The acidified oil wastewater to be treated is pumped into the air flotation machine and the oil separator in sequence. Then, lime is added to adjust the pH to 7-8. The wastewater with adjusted pH flows into the coagulation reaction tank by gravity and coagulant is added to react for a period of time. Then, it flows into the flocculation reaction tank with flocculant added to react for a period of time. Then, it is introduced into the sedimentation tank and centrifuged to obtain the pretreated wastewater.

[0008] S2, Conditioning: The pretreated wastewater is sent to the hydrolysis acidification tank. Iron-containing additives are added to the hydrolysis acidification tank, and sodium bicarbonate is added intermittently to keep the pH between 5 and 6.5. The effluent enters the heating tank and is heated to 30-35℃.

[0009] S3. Anaerobic treatment: The effluent from the heating tank is sent to the anaerobic treatment tank, and 3%-7% of the wastewater mass of anaerobic microorganisms are added. Anaerobic treatment is carried out for 14-18 hours. The dissolved oxygen content in the anaerobic treatment tank is controlled to be below 0.2 mg / L. After treatment, the mixture is allowed to stand and settle for 1-2 hours.

[0010] S4. Anoxic treatment: The effluent from the anaerobic tank is sent to the anoxic treatment tank. 3%-7% of the wastewater mass is added with anoxic treatment microorganisms. The dissolved oxygen content in the anoxic treatment tank is controlled at 0.2-0.5 mg / L. The anoxic treatment lasts for 8-14 hours. After treatment, the mixture is allowed to stand and settle for 1-2 hours.

[0011] S5. Aerobic treatment: The effluent from the anoxic tank is sent to the aerobic treatment tank. 1%-3% of the wastewater mass of aerobic treatment microorganisms are added to control the dissolved oxygen content in the aerobic treatment tank to be greater than 2mg / L. The aerobic treatment time is 8-24h. The effluent from the aerobic tank is then sent to the secondary sedimentation tank for further treatment.

[0012] S6. Oxidation treatment: The supernatant from the secondary sedimentation tank is sent to the oxidation reaction tank for ozone oxidation for 1-3 hours, and then enters the final sedimentation tank for further treatment to obtain treated water that meets the discharge standards.

[0013] A further provision of the present invention is as follows: In step S2, the iron-containing additive includes the following steps: crushing steel waste into fragments with a particle size of 2-5 cm, soaking the fragments in a 2 mol / L NaOH solution for 2-3 h, rinsing with deionized water until neutral, and then grinding in a planetary ball mill to obtain iron filings powder with a particle size between 1 and 3 mm; separately taking steel slag, grinding it in a grinder for 5-8 min, sieving to obtain steel slag particles with a particle size of 5-20 mm, and mixing the steel slag particles and iron filings powder in a certain proportion to obtain the iron-containing additive.

[0014] A further provision of the present invention is that the mass ratio of the steel slag particles to the iron filings is 1-2:1.

[0015] A further provision of the present invention is that the dosage of the iron-containing additive is 20-30 g / L.

[0016] A further setting of the present invention is as follows: in step S1, the coagulant is polyaluminum chloride, the dosage is 300 mg / L, the flocculant is polyacrylamide, the dosage is 5 mg / L, and the treatment time is 0.5-1 h.

[0017] A further feature of the present invention is that, in step S2, the hydraulic retention time in the hydrolysis acidification tank is 6-12 hours.

[0018] A further setting of the present invention is that: in step S3, the anaerobic treatment microorganism is anaerobic activated sludge, and its dosage is 5%-6% of the wastewater mass.

[0019] A further setting of the present invention is that in step S6, the ozone dosage for ozone oxidation is 50-200 mg / L.

[0020] The beneficial effects of this invention are:

[0021] 1. In this invention, an iron-containing additive is added to the hydrolysis acidification tank in the conditioning step (S2). The iron powder contains elemental iron and iron oxide (Fe2O3, Fe3O4). Under a weakly acidic environment of pH 5-6.5, the elemental iron undergoes a micro-electrolysis reaction to produce Fe. 2+ And active hydrogen atoms [H]; at the same time, Fe(III) / Fe(II) redox pairs exist on the surface of iron oxide, which can participate in electron transfer; active hydrogen atoms can attack the carbon-carbon double bonds and ester bonds of long-chain fatty acids, promote the chain scission and decomposition of large organic molecules into small volatile fatty acids (VFA), and increase the hydrolysis acidification rate and VFA yield; while Fe 2+ As a trace element essential for microbial growth, it activates the key enzyme system of hydrolytic acidifying bacteria, further enhancing biodegradation and providing high-quality substrates for subsequent anaerobic, anoxic, and aerobic treatments.

[0022] 2. The steel slag particles (5-20mm in diameter) in this invention contain alkaline oxides such as CaO and MgO, as well as iron oxides such as Fe2O3 and Fe3O4. Their porous structure can adsorb suspended oil and some dissolved organic matter in wastewater, reducing biological toxicity. The alkaline oxides slowly release OH⁻ in an acidic environment, automatically neutralizing the organic acids produced during hydrolysis and acidification. Together with the intermittently added sodium bicarbonate, they stabilize the pH at 5-6.5, preventing a sharp drop in pH that inhibits bacterial activity. The steel slag particles act as a rigid skeleton, uniformly dispersing iron filings on their surface and in their pores, preventing iron filings from agglomerating, hardening, and becoming passivated, thus extending the effective service life of the iron-containing additives.

[0023] 3. The iron filings and steel slag particles of this invention have a synergistic effect. On the one hand, numerous micro-galvanic cells are formed between the elemental iron (anode) in the iron filings, the iron oxide (cathode) in the iron filings, and the iron oxides (cathode) in the steel slag, constituting multiple electrode pairs, which accelerates the release of electrons from elemental iron and increases the micro-electrolysis reaction rate. On the other hand, Fe(III) on the surface of iron oxide can be reduced to Fe(II), and Fe(II) can be partially oxidized back to Fe(III) in the presence of oxygen (the hydrolysis acidification tank is a micro-oxygen environment), forming a Fe(II) / Fe(III) cycle, continuously generating active oxygen species, which assists in the decomposition of recalcitrant organic matter. Secondly, the micro-electrolysis of elemental iron consumes H2O. + (Promoting pH rise), the steel slag slowly releases alkalinity, and both work together to maintain the pH of the hydrolysis acidification tank within the optimal range, which can reduce the amount of sodium bicarbonate added; finally, Fe 2+ With S in wastewater 2- The formation of FeS precipitate, combined with the adsorption effect of steel slag, further captures tiny sulfide particles, effectively reducing the toxicity of sulfate to subsequent anaerobic methanogens and preventing acidification failure of the anaerobic reactor due to sulfide accumulation; Fe 2+ It is oxidized to Fe in the subsequent aerobic stage. 3+ It reacts with phosphates in wastewater to form Fe3(PO4)2 and FePO4 precipitates, which have a synergistic effect on phosphorus removal. The final effluent can stably meet the Class I standard of the Integrated Wastewater Discharge Standard (GB8978-1996).

[0024] 4. The iron-containing additive of this invention directly uses steel waste (scrap iron and scrap steel slag) as raw materials, which are widely available and inexpensive. At the same time, it realizes the resource utilization of industrial solid waste. Compared with commercially available iron-carbon fillers, the preparation cost of the additive is reduced. Due to the buffering effect of steel slag and the high efficiency of micro-galvanic cells, the amount of sodium bicarbonate added is reduced, and the hydraulic retention time of hydrolysis acidification is shortened to 6-12 hours, significantly reducing the energy consumption and reagent cost per ton of water treated. In addition, the iron-containing additive can be recycled as iron-containing sludge after use, without secondary pollution. Detailed Implementation

[0025] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] This embodiment provides a process for treating acidified oily wastewater, the specific steps of which are as follows:

[0028] S1. Pretreatment: Wastewater discharged from a plant acidified oil production workshop is pumped sequentially into an air flotation machine and an oil separator to remove floating oil. Lime is added to adjust the pH to 7.5. The pH-adjusted wastewater is then flowed into a coagulation reaction tank and coagulant polyaluminum chloride (PAC, dosage 300 mg / L) is added and reacted for 0.5 h. After that, it flows into a flocculation reaction tank with flocculant polyacrylamide (PAM, dosage 5 mg / L) added and reacted for 0.5 h. Then it is introduced into a sedimentation tank and centrifuged to obtain pretreated wastewater.

[0029] S2. Conditioning: The pretreated wastewater is sent to the hydrolysis acidification tank with a hydraulic retention time of 6 hours. An iron-containing additive is added to the tank at a dosage of 20 g / L. The iron-containing additive is prepared by crushing steel waste into 2-5 cm pieces, soaking them in a 2 mol / L NaOH solution for 2-3 hours, rinsing them with deionized water until neutral, and grinding them with a planetary ball mill to obtain 1-3 mm iron filings. Separately, steel slag is ground for 5 minutes and sieved to obtain 5-20 mm steel slag particles. The two are mixed evenly at a mass ratio of 1:1 (steel slag: iron filings). Sodium bicarbonate is added intermittently during the hydrolysis acidification process to keep the pH at 5.5-6.0. The effluent is then heated to 30-35°C in a heating tank.

[0030] S3. Anaerobic treatment: The effluent from the heating tank is sent to the anaerobic treatment tank, and 3%-7% of the wastewater mass of anaerobic activated sludge is added. Anaerobic treatment is carried out for 14-18 hours, and the dissolved oxygen is <0.2mg / L. The tank is then allowed to stand for 1-2 hours for sedimentation.

[0031] S4. Anoxic treatment: Send the effluent from the anaerobic tank into the anoxic treatment tank, add 3%-7% of the wastewater mass of anoxic treatment microorganisms (mainly denitrifying bacteria), dissolved oxygen 0.2-0.5 mg / L, anoxic treatment for 8-14 hours, and let it stand for 1-2 hours to settle.

[0032] S5. Aerobic treatment: Send the effluent from the anoxic tank into the aerobic treatment tank, add 1%-3% of aerobic treatment microorganisms (activated sludge) by the wastewater mass, dissolved oxygen >2mg / L, aerobic treatment for 8-24 hours, and the effluent enters the secondary sedimentation tank for sedimentation.

[0033] S6. Oxidation treatment: The supernatant from the secondary sedimentation tank is sent to the oxidation reaction tank for ozone oxidation. The ozone dosage is 50 mg / L, the oxidation time is 1-3 hours, and then it enters the final sedimentation tank for sedimentation.

[0034] Example 2

[0035] This embodiment provides a process for treating acidified oily wastewater, the specific steps of which are as follows:

[0036] S1. Pretreatment: Wastewater discharged from a plant acidified oil production workshop is pumped into an air flotation machine and an oil separator to remove floating oil. Lime is added to adjust the pH to 7.5. The pH-adjusted wastewater is then flowed into a coagulation reaction tank and coagulant polyaluminum chloride (PAC, dosage 300 mg / L) is added and reacted for 1 hour. After that, it flows into a flocculation reaction tank with flocculant polyacrylamide (PAM, dosage 5 mg / L) added and reacted for 1 hour. Then it is introduced into a sedimentation tank and centrifuged to obtain pretreated wastewater.

[0037] S2, Conditioning: The pretreated wastewater is sent to the hydrolysis acidification tank with a hydraulic retention time of 9 hours. An iron-containing additive is added to the tank at a dosage of 25 g / L. The iron-containing additive is prepared by crushing steel waste into 2-5 cm pieces, soaking them in a 2 mol / L NaOH solution for 2-3 hours, rinsing them with deionized water until neutral, and grinding them with a planetary ball mill to obtain 1-3 mm iron filings. Separately, steel slag is ground for 5 minutes and sieved to obtain 5-20 mm steel slag particles. The two are mixed evenly at a mass ratio of 1.5:1 (steel slag: iron filings). Sodium bicarbonate is added intermittently during the hydrolysis acidification process to keep the pH at 5.5-6.0. The effluent is then heated to 30-35°C in a heating tank.

[0038] S3. Anaerobic treatment: The effluent from the heating tank is sent to the anaerobic treatment tank, and 3%-7% of the wastewater mass of anaerobic activated sludge is added. Anaerobic treatment is carried out for 14-18 hours, and the dissolved oxygen is <0.2mg / L. The tank is then allowed to stand for 1-2 hours for sedimentation.

[0039] S4. Anoxic treatment: Send the effluent from the anaerobic tank into the anoxic treatment tank, add 3%-7% of the wastewater mass of anoxic treatment microorganisms (mainly denitrifying bacteria), dissolved oxygen 0.2-0.5 mg / L, anoxic treatment for 8-14 hours, and let it stand for 1-2 hours to settle.

[0040] S5. Aerobic treatment: Send the effluent from the anoxic tank into the aerobic treatment tank, add 1%-3% of aerobic treatment microorganisms (activated sludge) by the wastewater mass, dissolved oxygen >2mg / L, aerobic treatment for 8-24 hours, and the effluent enters the secondary sedimentation tank for sedimentation.

[0041] S6. Oxidation treatment: The supernatant from the secondary sedimentation tank is sent to the oxidation reaction tank for ozone oxidation. The ozone dosage is 130 mg / L, the oxidation time is 1-3 hours, and then it enters the final sedimentation tank for sedimentation.

[0042] Example 3

[0043] This embodiment provides a process for treating acidified oily wastewater, the specific steps of which are as follows:

[0044] S1. Pretreatment: Wastewater discharged from a plant acidified oil production workshop is pumped sequentially into an air flotation machine and an oil separator to remove floating oil. Lime is added to adjust the pH to 7.5. The pH-adjusted wastewater is then flowed into a coagulation reaction tank and coagulant polyaluminum chloride (PAC, dosage 300 mg / L) is added and reacted for 0.75 h. After that, it flows into a flocculation reaction tank with flocculant polyacrylamide (PAM, dosage 5 mg / L) added and reacted for 0.75 h. Then it is introduced into a sedimentation tank and centrifuged to obtain pretreated wastewater.

[0045] S2. Conditioning: The pretreated wastewater is sent to a hydrolysis acidification tank with a hydraulic retention time of 12 hours. An iron-containing additive is added to the tank at a dosage of 30 g / L. The iron-containing additive is prepared by crushing steel waste into 2-5 cm pieces, soaking them in a 2 mol / L NaOH solution for 2-3 hours, rinsing them with deionized water until neutral, and grinding them with a planetary ball mill to obtain 1-3 mm iron filings. Separately, steel slag is ground for 5 minutes and sieved to obtain 5-20 mm steel slag particles. The two are mixed evenly at a mass ratio of 2:1 (steel slag: iron filings). Sodium bicarbonate is added intermittently during the hydrolysis acidification process to keep the pH at 5.5-6.0. The effluent is then heated to 30-35°C in a heating tank.

[0046] S3. Anaerobic treatment: The effluent from the heating tank is sent to the anaerobic treatment tank, and 3%-7% of the wastewater mass of anaerobic activated sludge is added. Anaerobic treatment is carried out for 14-18 hours, and the dissolved oxygen is <0.2mg / L. The tank is then allowed to stand for 1-2 hours for sedimentation.

[0047] S4. Anoxic treatment: Send the effluent from the anaerobic tank into the anoxic treatment tank, add 3%-7% of the wastewater mass of anoxic treatment microorganisms (mainly denitrifying bacteria), dissolved oxygen 0.2-0.5 mg / L, anoxic treatment for 8-14 hours, and let it stand for 1-2 hours to settle.

[0048] S5. Aerobic treatment: Send the effluent from the anoxic tank into the aerobic treatment tank, add 1%-3% of aerobic treatment microorganisms (activated sludge) by the wastewater mass, dissolved oxygen >2mg / L, aerobic treatment for 8-24 hours, and the effluent enters the secondary sedimentation tank for sedimentation.

[0049] S6. Oxidation treatment: The supernatant from the secondary sedimentation tank is sent to the oxidation reaction tank for ozone oxidation. The ozone dosage is 200 mg / L, the oxidation time is 1-3 hours, and then it enters the final sedimentation tank for sedimentation.

[0050] Comparative Example 1 (without iron-containing additives)

[0051] This comparative example is basically the same as Example 1, except that no iron-containing additive is added in step S2, and the pH is maintained at 5.5-6.0 by intermittently adding sodium bicarbonate.

[0052] Comparative Example 2 (The iron-containing additive does not contain steel slag particles)

[0053] This comparative example is basically the same as Example 1, except that only iron filings are used in the iron-containing additive, and no steel slag particles are added. That is, only iron filings are added in step S2 (addition amount 20g / L), and the rest are the same.

[0054] Comparative Example 3 (pH not controlled, no sodium bicarbonate added)

[0055] This comparative example is basically the same as Example 1, except that sodium bicarbonate is not added in step S2, and the pH is not controlled. It relies solely on the buffering effect of the iron-containing additive (prepared in the same way as in Example 1).

[0056] Wastewater from acidified oil processing at an oil factory was collected. Considering the dilution effect of recycled water in the actual process, the wastewater was diluted and used as raw water. The raw water quality indicators and the treated water quality indicators are shown in Table 1. The removal rates of COD, total phosphorus, and sulfate were calculated, and the results are shown in Table 2. The B / C value is the BOD5 / COD value measured in the effluent after step S2.

[0057] Table 1

[0058]

[0059] Table 2

[0060]

[0061] As shown in the table above, the effluent COD, TP, ammonia nitrogen, and pH values ​​of Examples 1-3 all stably meet the Class I standard requirements of the "Integrated Wastewater Discharge Standard" (GB8978-1996). Among them, the COD removal rate is higher than 99.88%, the total phosphorus removal rate is higher than 99.94%, and the sulfate removal rate is higher than 93%. The B / C value is increased to 0.46~0.51, indicating that the biodegradability of the hydrolyzed acidified effluent enhanced by the iron-containing additive is significantly improved, providing a high-quality substrate for the stable operation of the subsequent anaerobic-anoxic-aerobic process. The effluent indicators of Examples 1-3 are significantly better than those of the comparative examples, which fully verifies that the iron-containing additive described in this invention: iron scrap powder + steel slag particles compound has the comprehensive effects of enhancing micro-electrolysis, promoting the degradation of long-chain fatty acids, stabilizing pH, reducing sulfate toxicity, and synergistic phosphorus removal in the hydrolyzed acidification stage. It can effectively ensure the long-term stable operation of the entire biological treatment system and achieve efficient purification and compliant discharge of acidified oily wastewater.

Claims

1. An acidized oil wastewater treatment process characterized by: Includes the following steps: S1. Pretreatment: The acidified oil wastewater to be treated is pumped into the air flotation machine and the oil separator in sequence. Then, lime is added to adjust the pH to 7-8. The wastewater with adjusted pH flows into the coagulation reaction tank by gravity and coagulant is added to react for a period of time. Then, it flows into the flocculation reaction tank with flocculant added to react for a period of time. Then, it is introduced into the sedimentation tank and centrifuged to obtain the pretreated wastewater. S2, Conditioning: The pretreated wastewater is sent to the hydrolysis acidification tank. Iron-containing additives are added to the hydrolysis acidification tank, and sodium bicarbonate is added intermittently to keep the pH between 5 and 6.

5. The effluent enters the heating tank and is heated to 30-35℃. S3. Anaerobic treatment: The effluent from the heating tank is sent to the anaerobic treatment tank, and 3%-7% of the wastewater mass of anaerobic microorganisms are added. Anaerobic treatment is carried out for 14-18 hours. The dissolved oxygen content in the anaerobic treatment tank is controlled to be below 0.2 mg / L. After treatment, the mixture is allowed to stand and settle for 1-2 hours. S4. Anoxic treatment: The effluent from the anaerobic tank is sent to the anoxic treatment tank. 3%-7% of the wastewater mass is added with anoxic treatment microorganisms. The dissolved oxygen content in the anoxic treatment tank is controlled at 0.2-0.5 mg / L. The anoxic treatment lasts for 8-14 hours. After treatment, the mixture is allowed to stand and settle for 1-2 hours. S5. Aerobic treatment: The effluent from the anoxic tank is sent to the aerobic treatment tank. 1%-3% of the wastewater mass of aerobic treatment microorganisms are added to control the dissolved oxygen content in the aerobic treatment tank to be greater than 2mg / L. The aerobic treatment time is 8-24h. The effluent from the aerobic tank is then sent to the secondary sedimentation tank for further treatment. S6. Oxidation treatment: The supernatant from the secondary sedimentation tank is sent to the oxidation reaction tank for ozone oxidation for 1-3 hours, and then enters the final sedimentation tank for further treatment to obtain treated water that meets the discharge standards.

2. The acidified oil wastewater treatment process according to claim 1, characterized in that: In step S2, the iron-containing additive includes the following steps: crushing steel waste into fragments with a particle size of 2-5 cm, soaking the fragments in a 2 mol / L NaOH solution for 2-3 hours, rinsing with deionized water until neutral, and then grinding in a planetary ball mill to obtain iron filings powder with a particle size between 1 and 3 mm. Separately, take steel slag, grind it in a grinder for 5-8 minutes, and sieve it to obtain steel slag particles with a particle size of 5-20 mm. Mix the steel slag particles and iron filings powder evenly in a certain proportion to obtain the iron-containing additive.

3. The acidified oil wastewater treatment process according to claim 2, characterized in that: The mass ratio of steel slag particles to iron filings is 1-2:

1.

4. The acidified oil wastewater treatment process according to claim 1, characterized in that: The dosage of the iron-containing additive is 20-30 g / L.

5. The acidified oil wastewater treatment process according to claim 1, characterized in that: In step S1, the coagulant is polyaluminum chloride, with a dosage of 300 mg / L, and the flocculant is polyacrylamide, with a dosage of 5 mg / L. The treatment time for both is 0.5-1 h.

6. The acidified oil wastewater treatment process according to claim 1, characterized in that: In step S2, the hydraulic retention time in the hydrolysis acidification tank is 6-12 hours.

7. The acidified oil wastewater treatment process according to claim 1, characterized in that: In step S3, the anaerobic treatment microorganism is anaerobic activated sludge, and its dosage is 5%-6% of the wastewater mass.

8. The acidified oil wastewater treatment process according to claim 1, characterized in that: In step S6, the ozone dosage for ozone oxidation is 50-200 mg / L.

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