Method and device for comprehensive treatment of cold rolling wastewater

Abstract

The application provides a comprehensive treatment method and device for cold rolling wastewater. The treatment method comprises the following steps: adding first oil-containing wastewater into a demulsifier for first air flotation to obtain first floating oil and air flotation wastewater. The first floating oil is mixed with second oil-containing wastewater, and then second air flotation is performed under the action of the demulsifier. Then, first pH adjustment, biochemical treatment and operation are sequentially performed to obtain first post-treatment water. The air flotation wastewater and acid-base wastewater are mixed, and then neutralization treatment is performed. Then, a flocculating agent is added for clarification. Then, second pH adjustment is performed, and oil removal and filtration are performed to obtain second post-treatment water. The oil and water in the first oil-containing wastewater are relatively easy to separate. In the comprehensive treatment method for the cold rolling wastewater, the treatment capacity of the acid-base wastewater is reasonably distributed according to the performance difference of the oil-containing wastewater, and the treatment capacity of the acid-base wastewater is increased, so that the treatment capacity of the total amount of the cold rolling wastewater is increased without expanding the capacity of the cold rolling wastewater station.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and more particularly to a comprehensive treatment method and apparatus for cold rolling wastewater. Background Technology

[0002] Wastewater generated from cold rolling includes oily wastewater, acid and alkali wastewater, and heavy metal wastewater. The oily wastewater and acid and alkali wastewater are treated separately and then collected in the discharge pool before entering the centralized sewage treatment plant for final water reuse.

[0003] The treatment process for oily wastewater typically involves removing floating oil through air flotation, adjusting the pH, and then performing biological treatment before being discharged into an effluent pond. However, this method of treating oily wastewater often fails to meet standards for COD and ammonia nitrogen levels. Extending the specific treatment time (such as extending the biological treatment time) does not significantly improve the effectiveness or fails to meet the requirements for the volume of oily wastewater to be treated. Summary of the Invention

[0004] The main objective of this invention is to provide a comprehensive treatment method and apparatus for cold rolling wastewater, in order to solve the technical problem that conventional methods often fail to meet the standards for COD and ammonia nitrogen in oily wastewater.

[0005] To achieve the above objectives, the present invention provides a comprehensive treatment method for cold rolling wastewater, comprising the following steps:

[0006] The oily wastewater undergoes a second air flotation process with the aid of a demulsifier, followed by a first pH adjustment and a biological treatment process to obtain the first post-treated water.

[0007] The first post-treated water is mixed with hypochlorite for chlorination treatment, wherein the amount of hypochlorite added is 80-120 grams per cubic meter of the first post-treated water.

[0008] After mixing the chlorinated first-treatment water and acid / alkali wastewater, neutralization is performed, followed by the addition of flocculant for clarification. Then, the water undergoes a second pH adjustment and oil removal filtration to obtain the second-treatment water. The acid / alkali wastewater includes at least one of the following: dilute alkali wastewater from galvanizing lines, acidic wastewater from pickling acid regeneration, and wastewater from a clean water circulation station.

[0009] According to embodiments of this application, the flocculant includes at least one of polyferric sulfate, polyacrylamide, and silica monomer.

[0010] According to an embodiment of this application, the flocculant includes polyacrylamide, polyferric sulfate, and silicate monomer, wherein the amounts of polyacrylamide, polyferric sulfate, and silicate monomer added are 1.5-2.5 mg / L, 25-35 mg / L, and 0.8-1.2 mg / L, respectively.

[0011] According to an embodiment of this application, the oil removal and filtration operation further includes the addition of clinoptilolite.

[0012] According to the embodiments of this application, the step of subjecting oily wastewater to a second air flotation under the action of a demulsifier, followed by a first pH adjustment and a biochemical treatment operation to obtain the first post-treated water includes:

[0013] The first oily wastewater is added to a demulsifier for first air flotation to obtain first floating oil and air-flotated wastewater. The first oily wastewater is at least one of the following: concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening processes.

[0014] The first oil float is mixed with the second oily wastewater, and then subjected to a second air flotation under the action of a demulsifier. Following this, the mixture undergoes a first pH adjustment and a biochemical treatment process to obtain the first post-treated water. The second oily wastewater is at least one of the following: oily wastewater from rolling mill emulsion, oily wastewater from leveling fluid, and oily wastewater from grinding fluid.

[0015] The step of mixing the first post-treatment water after chlorination and the acid and alkaline wastewater also includes mixing the flotation wastewater.

[0016] According to an embodiment of this application, the first oily wastewater includes at least concentrated alkaline wastewater from galvanizing lines.

[0017] According to an embodiment of this application, the second air flotation includes a first-stage air flotation and a second-stage air flotation performed sequentially.

[0018] According to an embodiment of this application, the neutralization treatment includes a primary neutralization treatment and a secondary neutralization treatment, and aeration is performed during the neutralization treatment process.

[0019] This application also provides a comprehensive treatment device for cold rolling wastewater, including an oily wastewater treatment system and an acid and alkali wastewater treatment system.

[0020] The oily wastewater treatment system comprises, in sequence, an oily wastewater equalization tank, a second air flotation mechanism, a first pH adjustment tank, a biological contact oxidation tank, and a pit. Hypochlorite is added to the pit at a rate of 80-120 grams per cubic meter of the first post-treated water. The oily wastewater undergoes a second air flotation process with the aid of a demulsifier in the second air flotation mechanism, a first pH adjustment in the first pH adjustment tank, a biological contact oxidation tank for biochemical treatment, and finally chlorination treatment with hypochlorite to obtain chlorinated first post-treated water.

[0021] The acid-base wastewater treatment system includes an acid-base wastewater equalization tank, a neutralization tank, an acid-base sedimentation tank, a second pH equalization tank, and an oil removal filter connected in sequence. The acid-base wastewater equalization tank is connected to the pit.

[0022] An acid-base wastewater equalization tank is used to receive and mix the chlorinated first-stage post-treatment water and the acid-base wastewater to obtain mixed acid-base wastewater. This mixed acid-base wastewater is then sequentially treated by a neutralization tank for neutralization, a flocculant-added clarification tank for acid-base sedimentation, a second pH adjustment tank for second pH adjustment, and an oil removal filter for oil removal to obtain second-stage post-treatment water. The acid-base wastewater includes at least one of the following: dilute alkali wastewater from galvanizing lines, acidic wastewater from pickling acid regeneration, and wastewater from a clean water circulation station.

[0023] According to an embodiment of this application, the oily wastewater treatment system further includes a first air flotation mechanism, which is connected to the oily wastewater equalization tank. The first air flotation mechanism is used to add a demulsifier to the first oily wastewater for first air flotation, obtaining first floating oil and floated wastewater. The first floating oil is mixed with the second oily wastewater in the oily wastewater equalization tank. The first oily wastewater is at least one of the following: concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening processes. The second oily wastewater is at least one of the following: oily wastewater from rolling mill emulsions, oily wastewater from leveling solutions, and oily wastewater from grinding solutions.

[0024] The acid-base wastewater equalization tank receives the flotation wastewater and mixes it with the chlorinated first post-treatment water and the acid-base wastewater.

[0025] In the aforementioned comprehensive treatment method for cold rolling wastewater, the oily wastewater undergoes flotation, conditioning, and biochemical treatment, followed by chlorination. It is then mixed with acidic and alkaline wastewater and further treated using the acidic and alkaline wastewater treatment process, thereby reducing the COD and ammonia nitrogen levels of the oily wastewater. The acidic and alkaline wastewater treatment process is typically designed with a large processing capacity and a fast processing speed. Therefore, the addition of the first post-treatment water after chlorination will not exceed the maximum processing capacity of the acidic and alkaline wastewater, nor will it significantly prolong the treatment time. Under these conditions, the acidic and alkaline wastewater treatment process effectively reduces the COD and ammonia nitrogen levels of the first post-treatment water after chlorination. This comprehensive treatment method for cold rolling wastewater can effectively reduce the COD and ammonia nitrogen levels of oily wastewater without requiring a large amount of additional treatment equipment. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1This is a schematic diagram of a comprehensive treatment device for cold rolling wastewater based on related technologies;

[0028] Figure 2 This is a schematic diagram of a comprehensive treatment apparatus for cold rolling wastewater according to one embodiment of this application.

[0029] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0030] 100. Oily wastewater treatment system; 200. Acid and alkali wastewater treatment system;

[0031] 110. First air flotation unit; 120. Oily wastewater equalization tank; 130. First-stage air flotation unit; 140. First pH adjustment tank; 150. Heat exchanger; 160. Biological contact oxidation tank; 170. Sump;

[0032] 131. First-stage air flotation mechanism; 132. Second-stage air flotation mechanism;

[0033] 210. Acid-base wastewater equalization tank; 220. Neutralization tank; 230. Acid-base sedimentation tank; 240. Second pH adjustment tank; 250. Oil removal filter;

[0034] 221. Primary neutralization tank; 222. Secondary neutralization tank;

[0035] 300. Drainage pool; 400. Centralized sewage treatment pool. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0038] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0039] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0040] This application discloses a comprehensive treatment method for cold rolling wastewater, see [link to relevant documentation]. Figure 2 This includes the following steps:

[0041] S100: The oily wastewater undergoes a second air flotation under the action of a demulsifier, followed by a first pH adjustment and biological treatment operation to obtain the first post-treated water.

[0042] Oily wastewater typically includes one or more of the following: oily wastewater from rolling mill emulsions, oily wastewater from leveling solutions, oily wastewater from grinding solutions, concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening processes.

[0043] There are various methods of air flotation (e.g., vortex air flotation). After the second air flotation, the floating oil and the post-flotation wastewater undergo preliminary separation. The floating oil enters a waste oil collection tank, while the post-flotation wastewater is typically treated in a pH adjustment tank and a biological contact oxidation tank (e.g., a four-stage cascade biological contact oxidation tank) to reduce the oil and COD in the effluent. Cr Ammonia nitrogen is then used to obtain the first post-treated water.

[0044] COD may consist of oil in water, surfactants, rust inhibitors, and other organic substances. Cr The COD data is obtained by oxidizing water with potassium dichromate, hence the name COD. Cr .

[0045] Conventional oily wastewater treatment systems, even after biochemical treatment, still retain certain levels of COD and ammonia nitrogen, and direct discharge may still have some impact on the ecological environment. For example, the ammonia nitrogen in the water after contact with biological oxidation (i.e., the first post-treatment water) entering the station's sump still reaches 20-40 mg / L.

[0046] In this situation, one approach to related technologies is to add additional equipment for removing COD and ammonia nitrogen. This approach increases equipment costs, requires significant modification costs, and takes a considerable amount of time to debug the equipment.

[0047] S200: The first post-treated water is mixed with hypochlorite for chlorination treatment, wherein the amount of hypochlorite added is 80-120 grams of hypochlorite per cubic meter of the first post-treated water.

[0048] This application employs a method of first adding hypochlorite for chlorination treatment, then fully utilizing existing acid and alkaline wastewater treatment processes to remove the remaining ammonia nitrogen and COD. The hypochlorite dosage is 80-120 grams per cubic meter of wastewater, removing most of the ammonia nitrogen and a portion of the COD. Hypochlorite is added to the first post-treatment water for mixing; the hypochlorite oxidizes the COD and ammonia nitrogen in the first post-treatment water, a process referred to simply as chlorination for convenience. Hypochlorite can be sodium hypochlorite or calcium hypochlorite.

[0049] In some specific embodiments, the first post-treated water is discharged into a pit, and the required amount of hypochlorite is added to the first post-treated water in the pit.

[0050] S300: The first post-treatment water after chlorination and the acid / alkali wastewater are mixed, neutralized, clarified by adding flocculant, and then subjected to a second pH adjustment and oil removal filtration to obtain the second post-treatment water. The acid / alkali wastewater includes at least one of the following: dilute alkali wastewater from galvanizing lines, acidic wastewater from pickling acid regeneration, and wastewater from the clean water circulation station.

[0051] Neutralization, clarification with flocculants, followed by pH adjustment and oil removal filtration constitute the treatment process for acidic and alkaline wastewater. The treatment capacity of acidic and alkaline wastewater is typically designed to be large, and the treatment speed is also relatively fast. Therefore, the addition of the first post-treatment water after chlorination will not exceed the maximum treatment capacity range of the acidic and alkaline wastewater, nor will it significantly prolong the treatment time.

[0052] For example, the chlorinated first-treatment water and acid / alkali wastewater are mixed in an acid / alkali wastewater equalization tank. In some embodiments, aeration is also performed in the acid / alkali wastewater equalization tank, which oxidizes ferrous iron to ferric iron and degrades some COD and ammonia nitrogen.

[0053] The neutralization process involves adding slaked lime powder to neutralize the acid in the acidic or alkaline wastewater. The neutralized wastewater becomes weakly alkaline, facilitating subsequent clarification. In some embodiments, slaked lime powder is added to a solution prepared in water to neutralize the acid in the wastewater.

[0054] In some embodiments, a two-stage neutralization process is performed, exemplarily in a primary neutralization tank and a secondary neutralization tank. The primary neutralization tank is for coarse pH adjustment, and the secondary neutralization tank is for fine pH adjustment, so that after aeration, ferric iron, along with oil, silicon, organic matter, and other metal ions, precipitates in the ferric hydroxide flocs entering the acid-base precipitation tank. To accelerate the mixing and reaction of the quicklime solution with the acid-base wastewater, in some embodiments, aeration is performed during the neutralization process.

[0055] After neutralization, flocculant is added for clarification. Due to the introduction of the first post-treatment water after chlorination, the amount of flocculant added should be appropriately increased to remove the additional substances brought in by the first post-treatment water after chlorination. Subsequently, a second pH adjustment is performed to adjust the wastewater, which was originally weakly alkaline after neutralization, to neutral or near-neutral.

[0056] The oil removal and filtration process may be the same as or different from the conventional processes for treating acidic and alkaline wastewater in related technologies.

[0057] Adding flocculants for clarification accelerates the clarification process, increasing the treatment capacity of acid and alkaline wastewater and making it suitable for handling wastewater volumes following the initial post-treatment water after chlorination. The main rate-limiting step in an acid and alkaline wastewater treatment system is the flocculant clarification step; therefore, increasing the treatment rate of this step will significantly improve the system's overall treatment capacity.

[0058] In contrast, the main rate-limiting step in oily wastewater treatment systems is the treatment rate of the biological contact oxidation tank, which is difficult to increase. Due to the low efficiency of the biological treatment process in removing COD and ammonia nitrogen, oily wastewater requires a long residence time during biological treatment, and the longer the residence time, the better the effect. Therefore, to achieve good treatment results, the residence time often needs to exceed 8 hours or even longer.

[0059] In this embodiment, a flocculant is added for clarification, accelerating the clarification process and shortening the sedimentation time (2-4 hours). This solves the problem of balancing treatment capacity and reduces the load on the oily wastewater treatment system. Therefore, the inventors chose to improve the treatment capacity of the acid and alkali wastewater treatment system, thereby enhancing the overall treatment capacity of the cold rolling wastewater station and adapting to the increased demand for cold rolling wastewater treatment.

[0060] In general, the above-mentioned comprehensive treatment method for cold rolling wastewater involves treating the first post-treatment water with hypochlorite, then mixing it with the acid and alkali wastewater, and continuing the treatment process in the acid and alkali wastewater treatment system.

[0061] For example, the biochemical effluent from the wastewater treatment plant is introduced into the plant's underground pit and then into an acid-base wastewater equalization tank. This embodiment extends the oily wastewater treatment process, aiming to reduce the COD and ammonia nitrogen levels in the wastewater through subsequent aeration, flocculation sedimentation, and oil removal filtration of the acid-base wastewater.

[0062] In the aforementioned comprehensive treatment method for cold rolling wastewater, the oily wastewater undergoes flotation, conditioning, and biochemical treatment, followed by chlorination. It is then mixed with acidic and alkaline wastewater and further treated using the acidic and alkaline wastewater treatment process, thereby reducing the COD and ammonia nitrogen levels of the oily wastewater. The acidic and alkaline wastewater treatment process is typically designed with a large processing capacity and a fast processing speed. Therefore, the addition of the first post-treatment water after chlorination will not exceed the maximum processing capacity of the acidic and alkaline wastewater, nor will it significantly prolong the treatment time. Under these conditions, the acidic and alkaline wastewater treatment process effectively reduces the COD and ammonia nitrogen levels of the first post-treatment water after chlorination. This comprehensive treatment method for cold rolling wastewater can effectively reduce the COD and ammonia nitrogen levels of oily wastewater without requiring a large amount of additional treatment equipment.

[0063] In some embodiments, the flocculant includes at least one of polyferric sulfate, polyacrylamide, and silicate monomer.

[0064] (1) Polyferric sulfate (PFS)

[0065] Polymerized flocculation (PFS) is an intermediate product in the hydrolysis of Fe2(SO4)3, which is gradually converted into Fe(OH)3. It polymerizes into an inorganic polymer through a hydroxyl-bridged reaction. PFS has two performance indicators: basicity and degree of polymerization. Basicity B = [OH] / 3 [Fe], representing the equivalent ratio of hydroxyl groups to iron in the compound. Generally, higher basicity indicates a greater number of low-charge, high-polymerization polynuclear complexes, resulting in better flocculation and bonding properties. Conversely, lower basicity leads to a predominance of high-charge, low-polymerization inorganic polymers, which compress the electric double layer and neutralize charges, thus achieving better colloidal destabilization. The basicity range of PFS is typically around 9%–16%. Using PFS alone cannot achieve optimal coagulation and flocculation results.

[0066] (2) Polyacrylamide (PAM)

[0067] PAM is a high molecular weight coagulant that disperses into a large number of linear chain polymers after dissolving in water. These large chain molecules can act as adhesives and bridges, while the charged groups on the molecules can compress the electric double layer and neutralize charges. Currently, anionic PAM is used, but the colloidal particles in wastewater are generally negatively charged. In such wastewater, anionic coagulants can only perform flocculation. PAM has a relatively narrow application range; excessive dosage can lead to colloidal protection, which increases the stability of the colloids and worsens the coagulation effect.

[0068] (3) Silicate monomers

[0069] The condensation polymerization of silica monomers in solution is a result of hydroxyl and oxygen bridging. The inorganic polymers formed by condensation polymerization have tetrahedral anions that can develop into filamentous, branched chain, or spherical particles. It only acts as a flocculator for negatively charged colloidal particles in water. Therefore, it is often used as a coagulant aid in combination with aluminum and iron salts. Even at very low dosages, it can significantly enhance the flocculation process, reduce the amount of coagulant needed, and improve coagulation performance under low temperature and low alkalinity conditions.

[0070] The main rate-limiting step in an acid and alkali wastewater treatment system is the clarification step by adding flocculants. Therefore, if the treatment rate of this step is increased, the treatment capacity of the acid and alkali wastewater treatment system will be greatly improved.

[0071] The inventors conducted a series of experiments, using combinations of different types and amounts of flocculants in the clarification step to clarify neutralized acidic and alkaline wastewater, and then tested the COD in the clarified liquid. Cr Oil content, calculate COD Cr The removal rates and oil removal rates are shown in Tables 1 and 2.

[0072] Table 1. Dosage and type of flocculant added (mg / L)

[0073]

[0074] Table 2 COD and petroleum hydrocarbon removal rates

[0075]

[0076] Among them, COD Cr Removal rate = (1 - COD in the supernatant) Cr COD of neutralized acidic and alkaline wastewater Cr ) 100%, oil removal rate = (1 - oil content in the clarified liquid / oil content in the neutralized acidic / alkaline wastewater) 100%.

[0077] It is evident that using any of the aforementioned flocculants can improve flocculation efficiency, thereby enhancing the treatment capacity of acid and alkaline wastewater treatment systems without requiring expansion.

[0078] Taking into account the properties of the wastewater, treatment effect, and cost, a mixture of PAM, PFS, and activated silica can be selected for addition. Therefore, in some embodiments, the flocculant includes polyacrylamide, polyferric sulfate, and silica monomers, with the addition amounts of polyacrylamide, polyferric sulfate, and silica monomers being 1.5-2.5 mg / L, 25-35 mg / L, and 0.8-1.2 mg / L, respectively. Under these conditions, the flocculation effect is better, and the treatment capacity of the acid-alkali wastewater treatment system is further improved. Specifically, the order of addition of PAM, PFS, and activated silica is not limited; however, adding a mixture of the three to the neutralized acid-alkali wastewater can fully achieve the expected treatment effect.

[0079] In some embodiments, see Figure 2 The oil removal and filtration operation also includes the addition of clinoptilolite.

[0080] Oil removal filtration can be achieved using a walnut shell filter, as its large surface area is effective for oil filtration. Taking a walnut shell filter as an example, clinoptilolite can be added. Zeolite is an aluminosilicate, and clinoptilolite is primarily used for removing ammonia nitrogen. Clinoptilolite has a sieving effect on ions in wastewater, as well as exchange adsorption effects, and is effective against NH4+. + It exhibits strong selectivity and can be used in exchange adsorption processes to remove ammonia nitrogen from water. It serves as the final step in removing ammonia nitrogen from cold rolling wastewater before it enters a centralized wastewater treatment plant.

[0081] In some embodiments, the step of subjecting oily wastewater to a second air flotation under the action of a demulsifier, followed by a first pH adjustment and a biological treatment operation to obtain first post-treated water includes:

[0082] The first oily wastewater is added to a demulsifier for first air flotation to obtain first floating oil and air-flotated wastewater. The first oily wastewater is at least one of the following: concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening processes.

[0083] The first oil float is mixed with the second oily wastewater, and then subjected to a second air flotation under the action of a demulsifier. Following this, the mixture undergoes a first pH adjustment and a biochemical treatment process to obtain the first post-treated water. The second oily wastewater is at least one of the following: oily wastewater from rolling mill emulsion, oily wastewater from leveling fluid, and oily wastewater from grinding fluid.

[0084] The step of mixing the first post-treatment water after chlorination and the acid and alkaline wastewater also includes mixing the flotation wastewater.

[0085] In addition to the high ammonia nitrogen and COD values ​​in the first post-treatment water, the inventors discovered another problem. With the continuous increase in cold rolling mills, the amount of wastewater generated is also increasing. The treatment capacity of the oily wastewater treatment system cannot meet the demand, and expanding the cold rolling wastewater station to increase treatment capacity is costly and requires a lot of time.

[0086] Therefore, the inventors conducted targeted research and design. Wastewater generated during cold rolling is classified into oily wastewater and acid / alkali wastewater based on its properties. Oily wastewater typically includes oily wastewater from rolling mill emulsions, oily wastewater from leveling solutions, oily wastewater from grinding solutions, concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and coiling machines, and wastewater from finishing and straightening processes.

[0087] In related technologies, see Figure 1 The above six types of oily wastewater are treated uniformly in the oily wastewater treatment system. For example, they are separately collected in an equalization tank, mixed, and then subjected to air flotation (e.g., vortex air flotation). After air flotation, the floating oil and the wastewater are initially separated. The floating oil enters the waste oil collection tank, while the wastewater after air flotation is usually treated through a pH adjustment tank, a heat exchanger, and a biological contact oxidation tank (e.g., a four-stage cascade biological contact oxidation tank) to complete the treatment.

[0088] The applicant discovered through extensive research that the three types of oily wastewater—rolling mill emulsion oily wastewater, leveling fluid oily wastewater, and grinding fluid oily wastewater—remain partially miscible with water and oil even after demulsification. Furthermore, these three types of oily wastewater contain high levels of water-soluble surfactants and rust inhibitors, resulting in high levels of COD and ammonia nitrogen.

[0089] The sources of ammonia nitrogen in cold rolling wastewater include: 1. Acid regeneration wastewater containing NH4. + 1. Because ammonia is added to adjust the pH in the acid regeneration desilication process, acidic wastewater containing ammonia nitrogen is produced; 2. The rust inhibitor in oily wastewater contains organic matter containing amino groups, such as leveling fluid wastewater, emulsion wastewater, and grinding fluid wastewater.

[0090] In the case of demulsification, the concentrated alkaline wastewater from galvanizing lines, the oily wastewater from uncoiling and winding machines, and the wastewater from finishing and straightening machines are basically completely separated from the oil. Moreover, the content of surfactants and rust inhibitors in these three types of wastewater is relatively low and they are relatively easy to remove. For example, they can be removed by subsequent aeration in acid and alkali wastewater equalization tanks, flocculant addition, and the action of walnut shell filters.

[0091] The first type of oily wastewater includes at least one of the following: concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening processes.

[0092] In this situation, the inventors classified and treated the oily wastewater. The first oily wastewater underwent a first air flotation process to obtain first floating oil and air flotation wastewater. Only the first floating oil was transferred to the oily wastewater treatment system for further treatment, reducing the treatment load on the oily wastewater treatment system. The air flotation wastewater was transferred to the acid and alkali wastewater treatment system for further treatment, making full use of the design margin of the treatment system.

[0093] In some embodiments, the demulsifier includes nitric acid, PAC, and PAM.

[0094] In some specific embodiments, the demulsification step involves first adding nitric acid with a concentration of 40%-45% to the first oily wastewater, at a concentration of 1-3‰ of the wastewater's volume. The specific amount is adjusted between 0.1% and 0.3% depending on the oil content of the wastewater. Then, PAC and PAM are added. The concentration of PAC added to the first oily wastewater is 30-50 g / m³, and the concentration of PAM added is 1-3 g / m³. PAC is polyaluminum chloride, and PAM is polyacrylamide (e.g., cationic polyacrylamide).

[0095] In some other specific embodiments, nitric acid, PAC, and PAM are simultaneously added to the first oily wastewater to demulsify it.

[0096] The following describes the oil-water separation of concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening machines, using vortex-type air flotation as an example.

[0097] The concentrated alkaline wastewater from galvanizing lines is generated from cleaning residual emulsion on the surface of steel strips using alkaline cleaning agents. It is highly alkaline but contains oil, surfactants, and iron-containing powdery sludge. However, after removing the upper layer of floating oil through vortex-induced air flotation demulsification and oil flocculation, the lower layer of iron-containing powdery sludge, due to its higher density, settles or remains suspended in the liquid. The middle layer of liquid is the air flotation wastewater.

[0098] Oily wastewater from unwinding and coiling machines is caused by the leakage of lubricating oil and hydraulic oil into the wastewater. In this type of wastewater, the oil and water are originally separated into layers due to the density difference. After the upper layer of floating oil is removed by vortex air flotation demulsification and oil flocculation, the clear water is the air flotation wastewater.

[0099] When the wastewater from the optical straightening process is left to settle, it separates into three layers: an oily layer, a clear water layer, and a zinc powder layer. After removing the upper layer of floating oil through vortex-induced flotation demulsification and oil flocculation, the lower layer of iron and zinc powder sludge, due to its higher density, settles or remains suspended in the liquid. The middle layer of liquid is the flotation wastewater.

[0100] Correspondingly, some changes have been made to the treatment process of oily wastewater. The first oil flotation is mixed with the second oily wastewater, and then subjected to a second air flotation under the action of a demulsifier. Following this, the wastewater undergoes a first pH adjustment and a biological treatment process to obtain the first post-treated water. The second oily wastewater includes at least one of the following: oily wastewater from rolling mill emulsion, oily wastewater from leveling fluid, and oily wastewater from grinding fluid.

[0101] See Figure 2 In this step, the first floating oil is mixed with the second oily wastewater, such as in an oily wastewater equalization tank. The type and ratio of demulsifier can be referenced in the aforementioned demulsifier section and will not be repeated here. Overall, the addition of PAC and cationic PAM causes oil ions to accumulate and grow, floating on the liquid surface. The floating oil from the rolling mill emulsion, leveling fluid, and grinding fluid enters the waste oil collection tank. The wastewater, excluding the upper layer, then undergoes a first pH adjustment and biological treatment operation to obtain the first post-treated water.

[0102] In some embodiments, heat exchange is also included between the first pH adjustment and the biochemical treatment operation. The microorganisms in the biological contact oxidation tank have an optimal survival temperature at which their reactivity is highest. For example, the optimal survival temperature for the microorganisms in the biological contact oxidation tank is in the range of 30-36°C. Therefore, adjusting the temperature of the wastewater after the first pH adjustment to the optimal survival temperature for the microorganisms before performing the biochemical treatment operation allows the microorganisms to more efficiently degrade COD.

[0103] There are also some variations in acid and alkali wastewater treatment systems. For example, flotation wastewater, acid and alkali wastewater, and the first post-treatment water after chlorination are mixed, such as in an acid and alkali wastewater equalization tank.

[0104] Overall, the above-mentioned comprehensive treatment methods for cold rolling wastewater separate oily wastewater from rolling mill emulsion, oily wastewater from leveling solution, oily wastewater from grinding solution, concentrated alkaline wastewater from galvanizing line, oily wastewater from uncoiling and coiling machine, and wastewater from finishing and straightening, based on the different characteristics of the wastewater.

[0105] Faced with the problem of a large wastewater treatment load, the load on the oily wastewater treatment system was reduced by rationally allocating the wastewater's destination without reducing the total wastewater treatment load.

[0106] In the aforementioned comprehensive treatment method for cold rolling wastewater, the oil and water in the first oily wastewater are relatively easy to separate. Therefore, the first oily wastewater undergoes a first-stage air flotation process. The flotation wastewater is then mixed with acidic and alkaline wastewater and treated according to the treatment method for acidic and alkaline wastewater, thus reducing the treatment load on the oily wastewater. During the treatment process according to the acidic and alkaline wastewater treatment method, flocculants are added for clarification, accelerating the clarification speed and increasing the treatment capacity for acidic and alkaline wastewater, which can be adapted to the wastewater treatment volume after the addition of flotation wastewater. In the aforementioned comprehensive treatment method for cold rolling wastewater, based on the performance differences in the oily wastewater, air flotation is used to rationally allocate the treatment volume of oily wastewater and acidic and alkaline wastewater, and the treatment capacity for acidic and alkaline wastewater is increased. This increases the total treatment capacity for cold rolling wastewater without expanding the cold rolling wastewater treatment plant.

[0107] In some embodiments, see Figure 2 The first oily wastewater includes at least concentrated alkaline wastewater from the galvanizing line.

[0108] The inventors also discovered that the cost of treating cold rolling wastewater accounts for a large portion of the overall cost. In particular, acidic wastewater constitutes a significant portion of the treatment cost, while oily wastewater is alkaline. Therefore, in conventional treatment processes, large amounts of alkaline substances such as lime are often added to acidic wastewater to neutralize the acidity, while oily wastewater, being alkaline, requires the addition of acidic substances such as nitric acid to neutralize the alkali.

[0109] Therefore, the inventors fully utilized the alkalinity of oily wastewater to reduce wastewater treatment costs. The middle layer of the concentrated alkaline wastewater from galvanizing lines contains alkali and a small amount of iron powder. The alkali and the small amount of iron powder can neutralize the acidic wastewater, reducing the amount of quicklime that needs to be added.

[0110] In oily wastewater, since the alkali and iron powder carried by the concentrated alkaline wastewater that originally entered the oily wastewater no longer enter the mixing process, the acid consumed in this part does not need to be added, such as reducing the amount of nitric acid that needs to be added.

[0111] Therefore, in the above embodiments, wastewater resources are effectively utilized to treat waste, while reducing the dosage of acidic and alkaline substances and lowering the cost of wastewater treatment.

[0112] In some embodiments, see Figure 2 The second air flotation includes a first-stage air flotation and a second-stage air flotation performed sequentially.

[0113] Since oil-containing wastewater from rolling mill emulsions, leveling fluids, and grinding fluids is difficult to separate from water after demulsification, the existing two-stage vortex air flotation system is used for demulsification and oil flocculation. In addition, the load on the oil-containing wastewater treatment system is reduced. Therefore, the oil-containing wastewater from rolling mill emulsions, leveling fluids, and grinding fluids can be treated slowly and efficiently through two-stage vortex air flotation and biochemical treatment to achieve good treatment results.

[0114] This application also provides a comprehensive treatment device for cold rolling wastewater, including an oily wastewater treatment system 100 and an acid and alkali wastewater treatment system 200.

[0115] The oily wastewater treatment system 100 includes an oily wastewater equalization tank 120, a second air flotation mechanism, a first pH adjustment tank 140, a biological contact oxidation tank 160, and a pit 170 connected in sequence. Hypochlorite is added to the pit 170 at a rate of 80-120 grams per cubic meter of the first post-treated water. The oily wastewater undergoes a second air flotation process with the aid of a demulsifier in the second air flotation mechanism, a first pH adjustment in the first pH adjustment tank 140, a biochemical treatment process in the biological contact oxidation tank 160, and chlorination treatment with hypochlorite to obtain chlorinated first post-treated water.

[0116] The acid-base wastewater treatment system 200 includes an acid-base wastewater equalization tank 210, a neutralization tank 220, an acid-base sedimentation tank 230, a second pH equalization tank 240, and an oil removal filter 250 connected in sequence. The acid-base wastewater equalization tank 210 is connected to the pit 170.

[0117] Acid-base wastewater equalization tank 210 is used to receive and mix the chlorinated first post-treated water and the acid-base wastewater to obtain mixed acid-base wastewater. The mixed acid-base wastewater is then sequentially neutralized in a neutralization tank 220, clarified by adding flocculant in an acid-base sedimentation tank 230, adjusted to a second pH in a second pH adjustment tank 240, and filtered for oil removal in an oil removal filter 250 to obtain second post-treated water. The acid-base wastewater includes at least one of the following: dilute alkali wastewater from a galvanizing line, acidic wastewater from pickling acid regeneration, and wastewater from a clean water circulation station.

[0118] The comprehensive treatment device for cold rolling wastewater corresponds to the comprehensive treatment method for cold rolling wastewater described above, and is used to implement the aforementioned treatment method. When selecting the treatment method of different embodiments, the comprehensive treatment device for cold rolling wastewater can be appropriately adjusted. The comprehensive treatment device for cold rolling wastewater corresponds to the comprehensive treatment method for cold rolling wastewater and has the corresponding beneficial effects, which will not be elaborated further.

[0119] According to an embodiment of this application, the oily wastewater treatment system 100 further includes a first air flotation mechanism 110, which is connected to the oily wastewater equalization tank 120. The first air flotation mechanism 110 is used to add a demulsifier to the first oily wastewater for first air flotation to obtain first floating oil and air-flotated wastewater. The first floating oil and the second oily wastewater are mixed in the oily wastewater equalization tank 120. The first oily wastewater is at least one of the following: concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening processes. The second oily wastewater is at least one of the following: oily wastewater from rolling mill emulsions, oily wastewater from leveling solutions, and oily wastewater from grinding solutions.

[0120] The acid-base wastewater equalization tank 210 receives the flotation wastewater and mixes it with the first post-treatment water after chlorination and the acid-base wastewater.

[0121] This type of integrated treatment device for cold rolling wastewater addresses the problem of high wastewater treatment load. Without reducing the total wastewater treatment load, it alleviates the load on the oily wastewater treatment system 100 by rationally allocating the wastewater's destination.

[0122] The integrated treatment device for cold rolling wastewater rationally allocates the treatment volume of oily wastewater and acid / alkali wastewater by using air flotation to address the performance differences in oily wastewater, and increases the treatment capacity of acid / alkali wastewater. Thus, without expanding the cold rolling wastewater treatment station, the device increases the total treatment capacity of cold rolling wastewater.

[0123] To better illustrate the technical solution of this application, a more detailed embodiment will be used to describe the technical solution of this application.

[0124] Example 1

[0125] This application also provides a comprehensive treatment device for cold rolling wastewater, see [link to relevant documentation]. Figure 2 This includes oily wastewater treatment systems and acid / alkali wastewater treatment systems.

[0126] The oily wastewater treatment system includes a first air flotation unit 110, an oily wastewater regulating tank 120, a first-stage air flotation unit 131, a second-stage air flotation unit 132, a first pH regulating tank 140, a biological contact oxidation tank 160, and a pit 170 connected in sequence.

[0127] The acid and alkali wastewater treatment system includes an acid and alkali wastewater equalization tank 210, a primary neutralization tank 221, a secondary neutralization tank 222, an acid and alkali sedimentation tank 230, a second pH adjustment tank 240, and an oil removal filter 250, which are connected in sequence.

[0128] The first air flotation unit 110 adds a demulsifier to the first oily wastewater to perform a first air flotation, obtaining first floating oil and air-flotated wastewater. The first oily wastewater includes at least one of the following: concentrated alkaline wastewater from galvanizing lines, oily wastewater from uncoiling and winding machines, and wastewater from finishing and straightening processes.

[0129] One outlet pipe of the first air flotation unit 110 is connected to the oily wastewater equalization tank 120, and the first floating oil is transported to the oily wastewater equalization tank 120. The other outlet pipe of the first air flotation unit 110 is connected to the acid-base wastewater equalization tank 210, and the air flotation wastewater is transported to the acid-base wastewater equalization tank 210.

[0130] Oily wastewater equalization tank 120 receives and mixes the first floating oil and the second oily wastewater to obtain mixed oily wastewater.

[0131] The mixed oily wastewater is sequentially treated by a first-stage air flotation unit 131, a second-stage air flotation unit 132 under the action of a demulsifier for second air flotation, a first pH adjustment tank 140 for first pH adjustment, a heat exchanger 150 for temperature adjustment, and a biological contact oxidation tank 160 for biochemical treatment to obtain first post-treated water. The second oily wastewater includes at least one of the following: oily wastewater from rolling mill emulsion, oily wastewater from leveling fluid, and oily wastewater from grinding fluid.

[0132] The first post-treatment water is treated with hypochlorite in pit 170 and then enters acid-base wastewater equalization tank 210.

[0133] Acid-base wastewater equalization tank 210 receives and mixes the second oily wastewater, acid-base wastewater, and the treated first post-treatment water to obtain mixed acid-base wastewater. The mixed acid-base wastewater is then sequentially neutralized in a primary neutralization tank 221 and a secondary neutralization tank 222, clarified by adding flocculant in an acid-base sedimentation tank 230, adjusted to a second pH in a second pH adjustment tank 240, and filtered for oil removal in an oil removal filter 250 to obtain second post-treatment water. The acid-base wastewater includes at least one of the following: dilute alkali wastewater from a galvanizing line, acidic wastewater from pickling acid regeneration, and wastewater from a clean water circulation station.

[0134] The second post-treatment water can be stored in the discharge pool 300, and after being treated by the centralized sewage treatment station, it can be reused or discharged.

[0135] Example 2

[0136] The comprehensive treatment method for cold rolling wastewater was implemented using the comprehensive treatment device for cold rolling wastewater described in Example 1. The specific treatment process will not be repeated here. The COD value, ammonia nitrogen and oil content of the wastewater before and after treatment were measured in some parts.

[0137] The oily wastewater (COD 4000-8000 mg / L; ammonia nitrogen 60-100 mg / L; oil 50-500 mg / L) in the oily wastewater equalization tank, after being treated by two-stage cascade air flotation (i.e., by the first-stage air flotation unit 131 and the second-stage air flotation unit 132), has the following parameters: COD 1800-2000 mg / L; ammonia nitrogen 60-100 mg / L; oil 7-10 mg / L.

[0138] After air flotation and further treatment in a biological contact oxidation tank, the oily wastewater (i.e., the first post-treatment water) has the following parameters: COD 100-120 mg / L; ammonia nitrogen 20-40 mg / L; oil 3-5 mg / L. This oily wastewater does not meet the new national standard GB 13456-2012 "Emission Standard of Water Pollutants for Iron and Steel Industry" (COD ≤50 mg / L; ammonia nitrogen ≤5 mg / L; oil ≤3 mg / L).

[0139] Oily wastewater treated in the biological contact oxidation tank is treated with hypochlorite and then becomes the first post-treatment water after chlorination. The indicators of the first post-treatment water after chlorination are: COD 80-100 mg / L; ammonia nitrogen 10-20 mg / L; oil 3-5 mg / L.

[0140] The wastewater from finishing and straightening (oil 8-10 mg / L), the oily wastewater from unwinding and coiling machines (oil 10-200 mg / L), and the concentrated alkaline wastewater (COD 1500-2000 mg / L; oil 10-50 mg / L) is called flotation wastewater after the first-stage flotation (i.e., first flotation). The indicators of the flotation wastewater are: COD 400-600 mg / L; oil 8-20 mg / L.

[0141] The flotation wastewater, the first post-treatment water after chlorination, and the acid and alkaline wastewater (including dilute alkaline wastewater, with COD of 200-300 mg / L and oil of 8-10 mg / L) are mixed in the acid and alkaline wastewater equalization tank to obtain the effluent from the acid and alkaline wastewater equalization tank (COD of 100-200 mg / L, oil of 3-7 mg / L, and ammonia nitrogen of 5-10 mg / L). This effluent undergoes primary neutralization to pH 8-9 and secondary neutralization to pH 9.5-10.5. After passing through the acid and alkaline clarification tank, the effluent (COD of 40-60 mg / L, oil of 2-4 mg / L, and ammonia nitrogen of 5-8 mg / L) is filtered through walnut shells (filled with clinoptilolite) and the water quality in the discharge tank (COD of 30-50 mg / L, oil of 1-2 mg / L, and ammonia nitrogen of 1-4 mg / L) meets the discharge standards.

[0142] Comparative Example

[0143] by Figure 1The existing cold rolling wastewater treatment device shown is used to implement the cold rolling wastewater treatment method. The specific treatment process will not be described in detail. The COD value, ammonia nitrogen and oil content of the wastewater before and after treatment are detected by some of the components.

[0144] Oily wastewater in the oily wastewater equalization tank (including oily wastewater from rolling mill emulsion, leveling solution, grinding solution, concentrated alkaline wastewater from galvanizing line, oily wastewater from uncoiling and coiling machines, and finishing and straightening wastewater, with an overall COD of 2000-5000 mg / L, ammonia nitrogen of 50-80 mg / L, and oil of 50-500 mg / L) is treated with air emulsification. After treatment, the oily wastewater (COD of 1200-2500 mg / L, ammonia nitrogen of 50-80 mg / L, and oil of 10-20 mg / L) is treated with a four-stage cascade biological contact oxidation tank. After treatment, the oily wastewater (COD of 80-120 mg / L, ammonia nitrogen of 20-40 mg / L, and oil of 5-8 mg / L) is treated with air emulsification. According to the new national standard GB 13456-2012 "Water Pollutant Discharge Standard for Iron and Steel Industry" (COD ≤50mg / L; ammonia nitrogen ≤5mg / L; oil ≤3mg / L), it does not meet the standards.

[0145] Dilute alkaline wastewater (COD 200-300 mg / L; oil 8-10 mg / L). Effluent from the acid-base wastewater equalization tank (COD 100-150 mg / L; oil 3-5 mg / L; ammonia nitrogen 5-10 mg / L) undergoes primary neutralization to pH 8-9, followed by secondary neutralization to pH 9.5-10.5. After passing through the acid-base clarification tank, the effluent (COD 30-50 mg / L; oil 1-3 mg / L; ammonia nitrogen 5-10 mg / L) is filtered through walnut shells before being discharged into the effluent tank. The effluent quality is: COD 30-40 mg / L; oil 1-2 mg / L; ammonia nitrogen 5-10 mg / L (ammonia nitrogen still exceeds the standard).

[0146] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A comprehensive treatment method of cold rolling wastewater, characterized by, The method comprises the following steps: The oily wastewater is subjected to second air flotation under the action of a demulsifier, and then subjected to first pH adjustment and biochemical treatment to obtain first post-treatment water; The first post-treatment water is mixed with hypochlorite for chlorination treatment, and the amount of the hypochlorite added is 80-120 g per cubic meter of the first post-treatment water; After the chlorinated first post-treatment water is mixed with acid-alkali wastewater, neutralization treatment is performed, a flocculant is added for clarification, second pH adjustment is performed, and oil removal filtration is performed to obtain second post-treatment water; the acid-alkali wastewater comprises at least one of galvanizing line dilute alkali wastewater, pickling acid regeneration acid-containing wastewater, and drainage from a clean water station; The step of subjecting the oily wastewater to second air flotation under the action of a demulsifier, and then subjecting to first pH adjustment and biochemical treatment to obtain first post-treatment water comprises: The first oily wastewater is added to a demulsifier for first air flotation to obtain first floating oil and air flotation wastewater; the first oily wastewater is at least one of galvanizing line concentrated alkali wastewater, uncoiling and winding machine oily wastewater, and finishing and straightening oily wastewater; The first floating oil is mixed with second oily wastewater, and then subjected to second air flotation under the action of a demulsifier, and then subjected to first pH adjustment and biochemical treatment to obtain first post-treatment water; the second oily wastewater is at least one of rolling mill emulsion oily wastewater, skin pass liquid oily wastewater, and grinding fluid oily wastewater; In the step of mixing the chlorinated first post-treatment water with acid-alkali wastewater, the air flotation wastewater is also mixed.

2. The integrated treatment method of cold rolling wastewater according to claim 1, characterized by, The flocculant comprises at least one of polyferric sulfate, polyacrylamide, and silicic acid monomer.

3. The integrated treatment method of cold rolling wastewater according to claim 2, characterized by, The flocculant comprises polyacrylamide, polyferric sulfate, and silicic acid monomer, and the amount of the polyacrylamide, the polyferric sulfate, and the silicic acid monomer added is 1.5-2.5 mg / L, 25-35 mg / L, and 0.8-1.2 mg / L, respectively.

4. The integrated treatment method of cold rolling wastewater according to claim 1, characterized by, In the oil removal filtration operation, clinoptilolite is also added.

5. The integrated treatment method of cold rolling wastewater according to claim 1, characterized by, The first oily wastewater at least comprises galvanizing line concentrated alkali wastewater.

6. The integrated treatment method of cold rolling wastewater according to claim 1, characterized by, The second air flotation comprises first-stage air flotation and second-stage air flotation performed in sequence.

7. The integrated treatment method of cold rolling wastewater according to claim 1, characterized by, The neutralization treatment comprises first-stage neutralization treatment and second-stage neutralization treatment, and aeration is performed during the neutralization treatment.

8. A comprehensive treatment device for cold rolling wastewater, characterized by comprising: The method comprises an oily wastewater treatment system and an acid-alkali wastewater treatment system; The oily wastewater treatment system comprises an oily wastewater conditioning tank, a second air flotation mechanism, a first pH adjustment tank, a biological contact oxidation tank, and a pit connected in sequence; the pit is provided with hypochlorite, and the amount of the hypochlorite added is 80-120 g per cubic meter of the first post-treatment water; the oily wastewater is subjected to second air flotation under the action of a demulsifier in the second air flotation mechanism, first pH adjustment in the first pH adjustment tank, biochemical treatment in the biological contact oxidation tank, and chlorination treatment with the hypochlorite to obtain chlorinated first post-treatment water; The acid-alkali wastewater treatment system comprises an acid-alkali wastewater conditioning tank, a neutralization tank, an acid-alkali precipitation tank, a second pH adjustment tank, and an oil removal filter connected in sequence, and the acid-alkali wastewater conditioning tank is connected with the pit. The acid-base wastewater conditioning tank is used for receiving and mixing the chlorinated first post-treatment water and the acid-base wastewater, to obtain mixed acid-base wastewater, and the mixed acid-base wastewater is sequentially subjected to neutralization treatment in a neutralization tank, clarification by adding a flocculating agent in an acid-base precipitation tank, second pH adjustment in a second pH adjustment tank, and oil removal filtration in an oil removal filter, to obtain second post-treatment water; wherein the acid-base wastewater comprises at least one of galvanizing line dilute alkali wastewater, pickling acid regeneration acid-containing wastewater, and drainage from a clean water station; The oil-containing wastewater treatment system further comprises a first air flotation mechanism in communication with the oil-containing wastewater conditioning tank, and the first air flotation mechanism is used for adding a first oil-containing wastewater to a demulsifying agent for first air flotation, to obtain first floating oil and air flotation wastewater; wherein the first floating oil is mixed with second oil-containing wastewater in the oil-containing wastewater conditioning tank; the first oil-containing wastewater is at least one of galvanizing line concentrated alkali wastewater, uncoiling and winding machine oil-containing wastewater, and finishing and straightening oil-containing wastewater; and the second oil-containing wastewater is at least one of rolling mill emulsion oil-containing wastewater, skin-pass liquid oil-containing wastewater, and grinding fluid oil-containing wastewater; The acid-base wastewater conditioning tank receives the air flotation wastewater and mixes it with the chlorinated first post-treatment water and the acid-base wastewater.

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