A method for reusing wastewater containing benzene series pollutants

Abstract

The application discloses a method for recycling wastewater containing benzene series pollutants, and belongs to the technical field of wastewater recycling treatment. The method comprises the following steps: firstly, the wastewater containing benzene series pollutants is subjected to Fenton reaction with ferrous catalyst and oxidant; secondly, the catalytic oxidation liquid obtained in the first step is adjusted to pH 6.5-7.0, and then a coagulant and a coagulant aid are added to the catalytic oxidation liquid to perform coagulation and sedimentation treatment, so as to obtain pretreated effluent; thirdly, the pretreated effluent is subjected to biochemical treatment in a biochemical unit to obtain biochemical effluent; fourthly, the biochemical effluent is subjected to multi-medium filter treatment, and then is subjected to ultrafiltration in an ultrafiltration system after meeting the water inlet requirement of the ultrafiltration system; fifthly, the biochemical effluent is subjected to security filter treatment after the ultrafiltration, and then is subjected to reverse osmosis treatment, so as to separate water and concentrated water, and the water is used as water resources, and the concentrated water is returned to a homogenizing tank. The method has the advantages of low energy consumption, high efficiency, clear division of labor of each unit, simple process, low operation cost, small sludge yield, wide application range and the like, can significantly improve the biodegradability of wastewater, and reduce the toxicity of the wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater reuse and treatment technology, specifically relating to a method for reusing wastewater containing benzene-based pollutants. Background Technology

[0002] Benzene compounds are harmful to humans and the environment, and can affect the blood, nervous system, and reproductive system of animals. For example, benzene is an important basic raw material in the petrochemical industry, characterized by high toxicity and volatility, and can cause leukemia and nervous system diseases. Styrene, on the other hand, is an important monomer in synthetic resins, ion exchange resins, and synthetic rubber, but it is highly toxic; prolonged exposure can cause eye or respiratory diseases and carries a carcinogenic risk.

[0003] Synthetic rubber wastewater contains large amounts of incompletely recovered monomers such as styrene, benzaldehyde, and acetophenone, as well as additives like sodium dodecylbenzenesulfonate and rosin soap, resulting in complex wastewater composition, high pollutant concentrations, and difficulty in biodegradation. Direct discharge of benzene-containing wastewater into wastewater treatment plants can disrupt the stable operation of biological treatment systems, leading to excessive levels of COD and TN in the effluent. Furthermore, characteristic pollutants like benzene may further polymerize during subsequent treatment, limiting the application of membrane technology in wastewater reuse. In addition, inorganic scale, natural organic matter, colloids, and microorganisms in the wastewater can contaminate reverse osmosis membrane systems, damaging membrane structures, significantly shortening membrane lifespan, and increasing the operating costs of water treatment processes. Therefore, benzene-containing wastewater has become one of the most difficult wastewaters to treat in the petrochemical industry.

[0004] In existing technologies, the main treatment methods for wastewater containing benzene-related pollutants include coagulation sedimentation, coagulation flotation, electrochemical methods, and biological methods. However, most enterprises simply treat this type of wastewater through sedimentation and then mix it with other wastewater for biological treatment. This can easily cause shocks to the biological treatment system, leading to instability in its operation, poor treatment results, and widespread exceedances of COD and total phosphorus in the effluent. A petrochemical company used a combined process of physicochemical + biological + flocculation filtration + activated carbon to treat rubber wastewater containing benzene-related pollutants. The results showed that not only did the concentrations of major organic pollutants such as COD and phosphorus exceed the Class I discharge standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996), but the treatment costs were also high.

[0005] For styrene-butadiene rubber (SBR) wastewater, commonly used treatment methods in existing technologies mainly include physical separation, chemical oxidation, and membrane methods. Literature reports that Chen Xinyu et al. used a hydrolysis acidification-biological contact oxidation method to treat rubber wastewater containing benzene-based pollutants. Experimental results showed that when the influent COD was 650 mg / L, the average removal rates of the hydrolysis acidification tank and the biological contact oxidation method were 23.2% and 83.7%, respectively. However, this method suffers from problems such as easy clogging of the packing material in the tank and insignificant treatment effect on wastewater with poor biodegradability. Patent CN116693077A provides a method for the reuse of treated SBR wastewater containing styrene, employing a process of air flotation + hydrolysis acidification + denitrification + MBBR + ozone oxidation + BAF + ultrafiltration + reverse osmosis to construct a crosslinking unit. However, the use of initiators and crosslinking agents increases reagent costs, and the ozone oxidation process increases energy consumption. Patent CN103058424A uses a combination of a multi-media filter and a fixed-bed three-dimensional electrode electrolysis device as a pretreatment unit before the membrane to reduce COD, TOC and conductivity of wastewater. At the same time, it can effectively reduce membrane fouling and achieve long-term stability and water conservation and emission reduction. However, the electrolysis device has a large investment and high energy consumption, and the short cleaning cycle of the multi-media filter will also increase the operating cost.

[0006] On the other hand, considering the development trend of water treatment in China, current water-saving measures can no longer resolve the contradiction between the increasing water consumption in industrial production and domestic use and the scarcity of water resources. Wastewater reuse has become an inevitable trend in water treatment development. While the aforementioned methods have achieved certain treatment effects on rubber wastewater, they are all conventional methods for meeting standards and have not achieved analysis of benzene compounds in the wastewater, nor have they addressed deep treatment or reuse. Due to the complex composition and poor biodegradability of rubber wastewater, treatment effects are unstable or costs are high. In terms of practical technology, there is essentially a gap in the deep treatment and reuse of rubber wastewater containing benzene-related characteristic pollutants after secondary biological treatment. Existing methods also suffer from numerous constraints such as insufficient treatment efficiency, high treatment costs, secondary pollution, and unstable treatment effects, making industrial application difficult.

[0007] In summary, the following technical problems exist in the current reuse of wastewater containing benzene series pollutants:

[0008] 1. Wastewater containing benzene-based pollutants has a complex composition, high toxicity, and is difficult to biodegrade. It is also characterized by high salt content, high color, and high COD. In particular, styrene-containing styrene-butadiene rubber wastewater has a large range of COD and pH fluctuations, and high levels of ammonia nitrogen and phosphorus. Direct discharge into sewage treatment plants will affect the stable operation of the biological treatment system.

[0009] 2. Benzene monomers such as styrene, benzaldehyde, and acetophenone remaining in wastewater containing benzene pollutants, along with additives such as sodium dodecylbenzenesulfonate and rosin soap, may further polymerize during subsequent treatment. This can easily contaminate the reverse osmosis membrane system, damage the membrane structure, shorten the membrane life, and increase the operating costs of the water treatment process.

[0010] 3. There is basically no field in the deep treatment and reuse of rubber wastewater containing benzene series pollutants in industry, and concentrated wastewater is difficult to meet discharge standards.

[0011] 4. Traditional Fenton oxidation reactions have a narrow pH range, require large amounts of acid and alkali to adjust the pH, have low hydrogen peroxide utilization, and produce a large amount of sludge. Summary of the Invention

[0012] In view of this, in order to solve the above-mentioned technical problems, the present invention provides a method for reusing wastewater containing benzene-based pollutants. This method has low energy consumption, high efficiency, clear division of labor among units, and has the advantages of simple process, low operating cost, low sludge production, and wide applicability. It can significantly improve the biodegradability of wastewater and reduce its toxicity.

[0013] The technical solution adopted by the present invention to achieve the above objectives is as follows.

[0014] The method for reusing wastewater containing benzene-based pollutants according to the present invention includes the following steps:

[0015] (1) After the wastewater containing benzene pollutants and the concentrated water obtained in step (3) are mixed evenly in a homogenizing tank, acid is added to adjust the pH to below 5.0 for acidification and demulsification. The demulsified liquid is then introduced into a catalytic oxidation tank and fully mixed with ferrous catalyst. After the catalytic oxidation liquid is reacted with oxidant, it is introduced into a coagulation sedimentation tank. One or two of the domestic sewage and circulating water discharge after alkaline precipitation are added to the coagulation sedimentation tank to adjust the pH to 6.5-7.0. Coagulant and coagulant aid are added for coagulation sedimentation treatment to obtain pretreated effluent.

[0016] (2) The pretreated effluent enters the biological treatment unit for biological treatment to obtain biological effluent;

[0017] (3) The biochemical effluent is first treated by a multi-media filter to meet the inlet water requirements of the ultrafiltration system, and then enters the ultrafiltration system for ultrafiltration. After being filtered by a security filter, it enters the reverse osmosis unit to separate the effluent and the concentrate. The water obtained is used as a water resource, and the concentrate is returned to the homogenization tank.

[0018] Preferably, in step (1), the benzene-containing wastewater is a chemical wastewater containing one or more of benzene, toluene, ethylbenzene, and styrene.

[0019] Preferably, in step (1), the volume ratio of the wastewater containing benzene pollutants to the concentrated water is not greater than 3.3:1.

[0020] Preferably, in step (1), the homogenizing tank is a storage tank, trough, or pool equipped with a stirring device.

[0021] Preferably, in step (1), the acid, oxidant, coagulant and coagulant aid are all added through a drug delivery system.

[0022] Preferably, in step (1), the acid is sulfuric acid.

[0023] Preferably, in step (1), the addition of acid adjusts the pH to 3.0 to 5.0.

[0024] Preferably, in step (1), the ferrous catalyst is magnetite.

[0025] Preferably, in step (1), the oxidant is hydrogen peroxide with a concentration of 10wt% to 30wt% and an oxidant dosage of 500mg / L to 1100mg / L;

[0026] The ferrous catalyst is magnetite, and the mass ratio of 30 wt% hydrogen peroxide to FeSO4·7H2O in the magnetite is 0.5 to 1.5:1.

[0027] Preferably, in step (1), the coagulant is polyaluminum chloride (PAC), and the dosage is 100-200 mg / L.

[0028] Preferably, in step (1), the coagulant is polyacrylamide (PAM), and the dosage is 1-20 mg / L.

[0029] Preferably, in step (1), the alkali is sodium hydroxide and sodium carbonate.

[0030] Preferably, in step (1), the Fenton reaction temperature is 40-60°C and the Fenton reaction time is 20-40 min.

[0031] Preferably, in step (2), the biochemical unit includes a hydrolysis acidification tank, an AO biochemical section anoxic tank, an O tank, and a sedimentation tank. The pretreated effluent first enters the hydrolysis acidification tank for acidification and hydrolysis. The resulting wastewater enters the AO biochemical section anoxic tank for denitrification. The denitrified effluent enters the O tank for aeration. Part of the nitrified effluent treated in the O tank is returned to the AO biochemical section anoxic tank as nitrification liquid, and the remaining part enters the sedimentation tank. The sludge at the bottom of the sedimentation tank is returned to the AO biochemical section anoxic tank, and the clear water at the top is the biochemical effluent.

[0032] More preferably, the hydraulic retention time of the hydrolysis acidification tank is 1 to 1.5 hours; the hydraulic retention time of the AO biochemical section anoxic tank is 1 to 4 hours; the hydraulic retention time of the O tank is 2 to 10 hours; and the hydraulic retention time of the sedimentation tank is 2 to 10 hours.

[0033] More preferably, the dissolved oxygen concentration in the hydrolysis acidification tank is 0.2–0.3 mg / L; the dissolved oxygen concentration in the anoxic tank of the AO biological treatment section is 0.1–0.3 mg / L; the dissolved oxygen concentration in the O tank is 4–6 mg / L; the pH of the sedimentation tank is 6.0–9.0, and the sludge age is 15–18 days.

[0034] More preferably, the reflux ratio of the nitrified effluent is 3 to 5, and the reflux ratio of the sedimentation tank sludge is 0.3 to 0.5.

[0035] Preferably, in step (2), the turbidity of the biochemical effluent is less than 10 NTU, the COD value is 25-60 mg / L, the TOC value is 10-30 mg / L, and the conductivity is less than 4700 μS / cm.

[0036] Preferably, in step (3), the turbidity of the biochemical effluent after treatment by the multi-media filter is less than 5 NTU.

[0037] Preferably, in step (3), the filter media of the multi-media filter includes two or more of the following: quartz sand, anthracite, activated carbon, magnetite, and garnet.

[0038] Preferably, in step (3), the ultrafiltration system employs full-volume filtration with an operating flux of 40–120 L / m³. 2 The cycle time is 30-60 minutes.

[0039] Preferably, in step (3), the security filter filters solid particles with a diameter greater than 5 μm.

[0040] Preferably, in step (3), the operating temperature of the reverse osmosis unit is 10–45°C, and the operating flux is 12–30 L / m³. 2 ·h.

[0041] The principle of this invention is as follows: In the method for reusing wastewater containing benzene series pollutants, magnetite is used as a ferrous catalyst in the catalytic oxidation tank to promote the decomposition of hydrogen peroxide to generate ·OH free radicals with extremely high oxidation potential, which are used to remove the vast majority of organic matter in the wastewater. Coagulation and sedimentation use polyaluminum chloride as a coagulant and polyacrylamide as a coagulant aid. After coagulation and sedimentation treatment, suspended solids (SS), styrene, oils, etc., in the water coagulate into large flocs along with dissolved colloidal substances and are removed along with the sediment. The removal rate of SS and styrene is over 92%, achieving the purpose of reducing biochemical load, enhancing microbial denitrification, and mitigating environmental pollution. The pretreated effluent, as the biochemical influent, first enters the hydrolysis acidification tank, where large, recalcitrant molecules in the wastewater are hydrolyzed into easily biodegradable small molecules, greatly improving the biodegradability of the wastewater. The biochemical effluent passes through a multi-media filter to remove turbidity and reduce the sludge density index. After meeting the influent requirements of the ultrafiltration system, it enters the ultrafiltration system to intercept tiny particles, reduce suspended solids and bacteria, and further remove turbidity, color and some COD from the water. Then, after passing through a security filter to intercept fine sand and large suspended solids that may be lost from the upstream water treatment unit, it enters the reverse osmosis unit for reuse. The product water is used as process water, and the concentrate is returned to the upstream pretreatment section.

[0042] In addition, domestic sewage and circulating water discharge contain high levels of calcium and total hardness. To achieve reuse, the method of this invention first treats them with alkali precipitation, and then passes them into a coagulation sedimentation tank. Because the effluent after sedimentation has a high pH, ​​the pH of the catalytic oxidation liquid can be adjusted to 6.5-7.0, while saving the use of caustic soda and meeting the pH requirements of the biological influent.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] (1) The method for reusing wastewater containing benzene series pollutants of the present invention is simple, energy-efficient, highly operable, and low in investment cost. It can not only effectively degrade benzene, toluene, styrene and other benzene series pollutants in wastewater, but also effectively degrade other organic matter in wastewater such as butadiene and dinitrile diamine formaldehyde condensate (CA) with few by-products. It can significantly improve the biodegradability of such wastewater and reduce its toxicity. According to the test, the removal rate of SS, styrene and other pollutants in wastewater containing benzene series pollutants is over 92%. After catalytic oxidation, the styrene in a certain wastewater decreased from 210 mg / L to below 1 mg / L, and the COD decreased from 1100 mg / L to 230 mg / L. The biochemical load was significantly reduced. The sewage treatment plant that originally required two-stage biochemical treatment can meet the influent requirements of the reuse system with only the first stage. Then, through biochemical treatment and ultrafiltration reverse osmosis treatment, the COD of the produced water is reduced to below 0.5 mg / L and the conductivity is less than 200 μS / cm, realizing reuse.

[0045] (2) The method for reusing wastewater containing benzene-based pollutants of the present invention uses polyaluminum chloride as a coagulant, which saves the reagents in the catalytic oxidation process, achieves the same flocculation and sedimentation effect, and significantly reduces the cost of reagents.

[0046] (3) The method for reusing benzene-containing pollutant wastewater of the present invention uses magnetite as ferrous catalyst, which can be recycled and has the advantages of wide pH range, low acid consumption, high hydrogen peroxide utilization rate and low sludge production.

[0047] (4) The method for reusing wastewater containing benzene-based pollutants of the present invention returns the concentrated water to the homogenizing tank for use, thus solving the problem of the concentrated water meeting the standards for discharge.

[0048] (5) In the method for reusing wastewater containing benzene series pollutants of the present invention, domestic sewage and circulating water effluent have high concentrations of hardness and calcium, and the pH of the biochemical influent and ultrafiltration influent generally needs to be controlled at 6.5 to 7.0. The present invention pre-precipitates at high pH, ​​optimizes the order and amount of acid and alkali addition, and avoids secondary addition of acid and alkali.

[0049] (6) The method for reusing wastewater containing benzene pollutants of the present invention can be reused after deep treatment as supplementary water for surface water sources, water for farmland and public facilities, water for landscape, water for replenishing circulating water and process water, etc., reducing the water consumption per ton of oil for enterprises and alleviating the "water shortage".

[0050] (7) The method for recycling wastewater containing benzene-based pollutants of the present invention has a wide range of applications, namely wastewater containing benzene-based pollutants such as toluene, ethylbenzene, and styrene, such as wastewater generated by synthetic rubber, polymer polyol, and styrene plants, and has good application prospects and environmental benefits.

[0051] (8) The method for reusing benzene-containing wastewater of the present invention adopts a process of catalytic oxidation pretreatment + biochemical treatment + ultrafiltration and reverse osmosis to achieve the reuse of benzene-containing wastewater. The system operates for a long period of time, providing a valuable industrial application case and reliable process technology for the reuse of benzene-containing wastewater, and implementing the requirements of water conservation and emission reduction. It conforms to the national policies of water conservation, pollution control and water resource utilization, effectively utilizes water resources, not only maximizes the economic benefits of the process equipment, but also plays an important role in improving the local water environment, protecting groundwater resources, increasing the total amount of usable water resources, alleviating the current situation of water shortage in new projects, and comprehensively controlling pollution. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are only some specific embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a process flow diagram of the method for reusing wastewater containing benzene-based pollutants according to the present invention. Detailed Implementation

[0054] To further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0055] like Figure 1 As shown, the method for reusing wastewater containing benzene-based pollutants according to the present invention includes the following steps:

[0056] (1) Pretreatment;

[0057] (1-1) After mixing the wastewater containing benzene pollutants with the concentrated water obtained in step (3) in a homogenizing tank, acid is added to adjust the pH to below 5.0 for acidification and demulsification to obtain the demulsified liquid.

[0058] (1-2) After the demulsifier is fully mixed with the ferrous catalyst in the catalytic oxidation tank, it undergoes a Fenton reaction with the oxidant to obtain the catalytic oxidation liquid;

[0059] (1-3) The catalytic oxidation liquid enters the coagulation sedimentation tank, and one or two of the domestic sewage and circulating water discharge after alkaline precipitation are added to the coagulation sedimentation tank to adjust the pH to 6.5-7.0. Coagulant and coagulant aid are added to carry out coagulation sedimentation treatment to obtain pretreated effluent.

[0060] (2) The pretreated effluent enters the biological treatment unit for biological treatment to obtain biological effluent;

[0061] (3) The biochemical effluent is first treated by a multi-media filter to meet the inlet water requirements of the ultrafiltration system, and then enters the ultrafiltration system for ultrafiltration. After being filtered by a security filter, it enters the reverse osmosis unit to separate the effluent and the concentrate. The water obtained is used as a water resource. If it is used as process water, the concentrate is returned to the homogenizing tank.

[0062] In the above technical solution, in step (1-1), the Fenton reaction is the reaction of H2O2 on Fe... 2+ The ·OH radicals generated under catalysis have an oxidizing power second only to fluorine, reaching 2.8V, and can oxidize most organic matter in water. Meanwhile, Fe... 2+ As a catalyst, it can ultimately be oxidized to Fe. 3+ Fe 3+ Similarly, H₂O₂ can catalytically decompose to produce ·OH radicals. The principle behind ·OH radicals removing organic matter is the removal of hydrogen from single bonds and the opening of double bonds through addition. Acidic conditions favor Fe. 2+ It exists stably, preventing it from being oxidized to Fe.3+ It may form a precipitate; and an acidic environment is conducive to the decomposition of H2O2, accelerating the generation of ·OH free radicals. At the same time, under certain pH conditions, Fe(OH)3 colloids may appear, playing a certain role in flocculation. The Fenton reaction has the characteristics of good treatment effect, mild reaction conditions, readily available chemical reagents, no complicated equipment, low energy consumption, environmental friendliness, and small amount of reagents used.

[0063] In the above technical solution, since the concentrate yield is 25% to 30%, in step (1-1), the volume ratio of wastewater containing benzene pollutants to concentrate is preferably no greater than 3.3:1.

[0064] In the above technical solution, in step (1-1), the pH is preferably 3.0 to 5.0, because high pH will inhibit the generation of hydroxyl radicals in the solution and reduce or even eliminate the activity of ferrous ions in the catalyst; when the pH is too low, the reducing power of ferric ions is greatly reduced, which is not conducive to the reaction.

[0065] In the above technical solution, in steps (1-2), to prevent scaling, the pH of the biochemical influent and the further ultrafiltration influent generally needs to be controlled at 6.5-7.0, usually 6.8; domestic sewage and circulating water discharge containing high calcium and total hardness are first treated with alkali precipitation (the pH is 8.2 before alkali precipitation), so the effluent after precipitation still has a high pH. It is then passed into the coagulation sedimentation tank to adjust the pH to 6.5-7.0, saving the use of sodium hydroxide, while meeting the pH requirements of the biochemical influent.

[0066] In the above technical solution, in steps (1-3), the coagulation and sedimentation treatment causes suspended solids (SS), styrene, oil, etc. in the catalytic oxidation liquid to coagulate into large flocs along with dissolved colloidal substances and be removed along with the sediment. The removal rate of SS and styrene is over 92%, thereby reducing the biochemical load, enhancing the microbial denitrification effect, and mitigating environmental pollution.

[0067] In the above technical solution, step (1) preferably includes: Benzene-containing wastewater is chemical wastewater containing one or more of benzene, toluene, ethylbenzene, and styrene. The homogenizing tank is a storage tank, trough, or pool equipped with a stirring device. The alkali is sodium hydroxide and sodium carbonate. The acid, oxidant, coagulant, and coagulant aid are all added through a dosing system. The acid is sulfuric acid. The oxidant is hydrogen peroxide, with a concentration of 10wt%-30wt%, and the dosage is 500mg / L-1100mg / L. The coagulant is polyaluminum chloride (PAC), with a dosage of 100-200mg / L. The coagulant aid is polyacrylamide (PAM), with a dosage of 1-20mg / L. The Fenton reaction temperature is 40-60℃, and the Fenton reaction time is 20-40min. The ferrous catalyst is magnetite, and the amount used needs to be converted into pure substance calculations. Based on 30wt% hydrogen peroxide, the mass ratio of 30wt% hydrogen peroxide to FeSO4·7H2O in magnetite is 0.5 to 1.5:1.

[0068] The function of step (2) in the above technical solution is to hydrolyze the large molecular recalcitrant substances in the pretreated effluent into small molecular substances that are easily biodegradable, thereby greatly improving the biodegradability of the wastewater.

[0069] In the above technical solution, step (2) preferably includes a hydrolysis acidification tank, an AO biochemical section anoxic tank, an O tank and a sedimentation tank. The pretreated effluent first enters the hydrolysis acidification tank for acidification and hydrolysis. The resulting wastewater enters the AO biochemical section anoxic tank for denitrification. The denitrified effluent enters the O tank for aeration. Part of the nitrified effluent treated in the O tank is returned to the AO biochemical section anoxic tank as nitrification liquid, and the remaining part enters the sedimentation tank. The sludge at the bottom of the sedimentation tank is returned to the AO biochemical section anoxic tank, and the clear water at the top is the biochemical effluent. More preferably: the hydraulic retention time in the hydrolysis acidification tank is 1–1.5 h; the hydraulic retention time in the anoxic tank of the AO biological treatment section is 1–4 h; the hydraulic retention time in the O tank is 2–10 h; the hydraulic retention time in the sedimentation tank is 2–10 h; the dissolved oxygen concentration in the hydrolysis acidification tank is 0.2–0.3 mg / L; the dissolved oxygen concentration in the anoxic tank of the AO biological treatment section is 0.1–0.3 mg / L; the dissolved oxygen concentration in the O tank is 4–6 mg / L; the pH of the sedimentation tank is 6–9, and the sludge age is 15–18 days; the reflux ratio of the nitrification effluent is 3–5, and the sludge reflux ratio of the sedimentation tank is 0.3–0.5. The turbidity of the biological effluent is less than 10 NTU, the COD value is 25–60 mg / L, the TOC value is 10–30 mg / L, and the conductivity is less than 4700 μS / cm.

[0070] In the above technical solution, step (3) serves the following purposes: the biochemical effluent passes through a multi-media filter to remove turbidity and reduce the sludge density index; the ultrafiltration system intercepts tiny particles, reduces suspended solids and bacteria, and further removes turbidity, color, and some COD from the water; the security filter intercepts fine sand and large suspended solids that may be lost from the upstream water treatment unit, protecting the safe operation of the reverse osmosis device and preventing the reverse osmosis membrane elements from being blocked or scratched by large particles, thereby extending the service life of the reverse osmosis membrane. The reverse osmosis device separates substances with a diameter less than 0.0001 μm and greater than or equal to 0.0001 μm from the effluent of the security filter.

[0071] In the above technical solution, in step (3), the turbidity of the biochemical effluent treated by the multi-media filter is less than 5 NTU. The filter media of the multi-media filter includes two or more of the following: quartz sand, anthracite, activated carbon, magnetite, and garnet. The ultrafiltration system adopts full-volume filtration with an operating flux of 40–120 L / m³. 2 The operating cycle is 30–60 minutes. The security filter filters solid particles larger than 5 μm in diameter. The reverse osmosis unit operates at a temperature of 10–45℃ and a flow rate of 12–30 L / m³. 2 ·h.

[0072] This invention provides an apparatus capable of implementing the above-described recycling method, but is not limited thereto, comprising:

[0073] Homogenizing tank, wherein the homogenizing tank is provided with an inlet for wastewater containing benzene-based pollutants;

[0074] A catalytic oxidation tank located downstream of the homogenizing tank and connected to the homogenizing tank via a pipeline;

[0075] A coagulation sedimentation tank located downstream of the catalytic oxidation tank and connected to the catalytic oxidation tank via a pipeline is provided with inlets for domestic sewage and circulating water discharge.

[0076] A biochemical unit located downstream of the coagulation sedimentation tank and connected to the coagulation sedimentation tank via a pipeline;

[0077] A multi-media filter located downstream of the biological treatment unit water and connected to the biological treatment unit water via a pipeline;

[0078] An ultrafiltration system located downstream of a multi-media filter and connected to the multi-media filter via a pipeline;

[0079] A security filter located downstream of the ultrafiltration system and connected to the ultrafiltration system via a pipeline;

[0080] A reverse osmosis unit located downstream of the security filter and connected to the security filter via a pipeline;

[0081] The reverse osmosis device is connected to the homogenization tank via a pipe, and the reverse osmosis device is equipped with a water outlet;

[0082] It may also include a drug delivery system that is connected to a homogenizing tank, a catalytic oxidation tank, and a coagulation sedimentation tank via pipelines.

[0083] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings.

[0084] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0085] Example 1

[0086] Wastewater from a certain styrene-butadiene rubber plant (flow rate 200 m³) 3 / h, COD 950mg / L, TN 140mg / L, styrene 50mg / L, dinitrile diamine formaldehyde condensation 30mg / L, suspended solids 350mg / L, conductivity 6000μS / cm).

[0087] The reuse method for wastewater containing benzene series pollutants involves the following steps:

[0088] (1) After mixing the wastewater containing benzene pollutants and the concentrated water obtained in step (3) (the volume ratio of the wastewater containing benzene pollutants to the concentrated water is not greater than 3.3:1) evenly in a homogenizing tank, acid is added to adjust the pH to 3.0-5.0 for acidification and demulsification, and the resulting demulsified liquid is introduced into a catalytic oxidation tank and mixed with 0.15 kg / m³ of water. 3 After being thoroughly mixed with magnetite, it was then mixed with 0.7 kg / m³ of... 3 Hydrogen peroxide (30 wt%) was subjected to a Fenton reaction at 40–60 °C for 30 min to obtain a catalytic oxidation solution. This catalytic oxidation solution was then introduced into a coagulation sedimentation tank. Domestic sewage and circulating wastewater treated with alkali precipitation were also added to the coagulation sedimentation tank to adjust the pH to neutral. 0.15 kg / m³ of [amount of water / water] was then added. 3 The coagulant PAC and 0.002 kg / m³ 3 The coagulant PAM is used for coagulation and sedimentation treatment to obtain pretreated effluent;

[0089] (2) The pretreated effluent enters the biological treatment unit for biological treatment to obtain biological effluent with a turbidity of less than 5 NTU;

[0090] (3) The biochemical effluent is first treated by a multi-media filter to meet the influent requirements of the ultrafiltration system before entering the ultrafiltration system for ultrafiltration. After passing through a security filter, it enters the reverse osmosis unit to separate the effluent and concentrate. The resulting water is used as process water, while the concentrate is returned to the homogenization tank. The ultrafiltration system uses full-volume filtration with an operating flux of 40–120 L / m³. 2 The operating time is 30–60 min; the operating temperature of the reverse osmosis unit is 10–45℃, and the operating flux is 12–30 L / m³. 2 ·h.

[0091] Testing revealed that the COD in the pretreated effluent was reduced to below 200 mg / L, styrene to below 0.5 mg / L, dinitrile diamine formaldehyde condensation was not detected, and suspended solids were below 10 mg / L. The COD in the biochemical effluent was below 30 mg / L, and TN was below 11 mg / L. The average permeate rate of the reverse osmosis unit was 75%, with permeate conductivity ranging from 140 to 160 μS / cm. The COD of the RO concentrate was 60 to 80 mg / L, with conductivity ranging from 12000 μS / cm to 13000 μS / cm. The COD of the RO permeate was below 5 mg / L, the total hardness (calculated as CaCO3) was less than 20 mg / L, both chloride and sulfate ions were less than 50 mg / L, and TDS was below 150 mg / L, meeting the requirements for reuse of process water.

[0092] Example 2

[0093] A wastewater containing benzene series pollutants (flow rate 200m³) 3 / h, COD 1200mg / L, TN 100mg / L, styrene 210mg / L, suspended solids 300mg / L, conductivity 5700μS / cm).

[0094] The reuse method for wastewater containing benzene series pollutants involves the following steps:

[0095] (1) After mixing the wastewater containing benzene pollutants and the concentrated water obtained in step (3) (the volume ratio of the wastewater containing benzene pollutants to the concentrated water is not greater than 3.3:1) evenly in a homogenizing tank, acid is added to adjust the pH to 3.0-5.0 for acidification and demulsification to obtain the demulsified liquid; the demulsified liquid enters the catalytic oxidation tank and is mixed with 0.25 kg / m³ of water. 3 After being thoroughly mixed with magnetite, it was then combined with 0.8 kg / m³ of... 3 Hydrogen peroxide (30 wt%) was subjected to a Fenton reaction at 40–60 °C for 30 min to obtain a catalytic oxidation solution. This catalytic oxidation solution was then introduced into a coagulation sedimentation tank. Domestic sewage and circulating wastewater treated with alkali precipitation were also added to the coagulation sedimentation tank to adjust the pH to neutral. 0.15 kg / m³ of [amount of water / water] was then added. 3 The coagulant PAC and 0.002 kg / m³ 3The coagulant PAM is used for coagulation and sedimentation treatment to obtain pretreated effluent;

[0096] (2) The pretreated effluent enters the biological treatment unit for biological treatment to obtain biological effluent with a turbidity of less than 5 NTU;

[0097] (3) The biochemical effluent is first treated by a multi-media filter to meet the influent requirements of the ultrafiltration system before entering the ultrafiltration system for ultrafiltration. After passing through a security filter, it enters the reverse osmosis unit to separate the effluent and concentrate. The resulting water is used as process water, while the concentrate is returned to the homogenization tank. The ultrafiltration system uses full-volume filtration with an operating flux of 40–120 L / m³. 2 The operating time is 30–60 min; the operating temperature of the reverse osmosis unit is 10–45℃, and the operating flux is 12–30 L / m³. 2 ·h.

[0098] Testing revealed that the COD in the pretreated effluent was reduced to 230 mg / L, styrene to below 1 mg / L, and suspended solids to 20 mg / L; the COD in the biochemical effluent was 35 mg / L, and TN to 7 mg / L; the average permeate rate of the reverse osmosis unit was 75%, with permeate conductivity ranging from 140 to 180 μS / cm; the COD of the RO concentrate was less than 160 mg / L, with conductivity ranging from 12000 μS / cm to 13000 μS / cm; the COD of the RO permeate was less than 10 mg / L; the total hardness (calculated as CaCO3) was less than 20 mg / L; both chloride and sulfate ions were less than 50 mg / L; and the TDS was less than 150 mg / L, meeting the requirements for reuse of process water.

[0099] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for reusing wastewater containing benzene-based pollutants, characterized in that, Includes the following steps: (1) After the wastewater containing benzene pollutants and the concentrated water obtained in step (3) are mixed evenly in a homogenizing tank, acid is added to adjust the pH to below 5.0 for acidification and demulsification. The demulsified liquid is then introduced into a catalytic oxidation tank and fully mixed with ferrous catalyst. After the catalytic oxidation liquid is reacted with oxidant, it is introduced into a coagulation sedimentation tank. One or two of the domestic sewage and circulating water discharge after alkaline precipitation are added to the coagulation sedimentation tank to adjust the pH to 6.5~7.

0. Coagulant and coagulant aid are added for coagulation sedimentation treatment to obtain pretreated effluent. (2) The pretreated effluent enters the biochemical unit for biochemical treatment to obtain biochemical effluent; (3) The biochemical effluent is first treated by a multi-media filter to meet the inlet water requirements of the ultrafiltration system, and then enters the ultrafiltration system for ultrafiltration. After being filtered by a security filter, it enters the reverse osmosis unit to separate the effluent and the concentrate. The water obtained is used as a water resource, and the concentrate is returned to the homogenizing tank. In step (1), the ferrous catalyst is magnetite, and the mass ratio of 30 wt% hydrogen peroxide to FeSO4·7H2O in magnetite is 0.5~1.5:1; the Fenton reaction temperature is 40~60℃, and the Fenton reaction time is 20~40min. In step (2), the turbidity of the biochemical effluent is less than 10 NTU, the COD value is 25~60 mg / L, the TOC value is 10~30 mg / L, and the conductivity is less than 4700 μS / cm. In step (3), the ultrafiltration system uses full-volume filtration with an operating flux of 40~120 L / m³. 2 •h, the operating cycle is 30~60min; in step (3), the security filter filters solid particles with a diameter greater than 5μm; And / or, the reverse osmosis unit operates at a temperature of 10~45℃ and an operating flux of 12~30 L / m³. 2 ·h.

2. The method for reusing wastewater containing benzene series pollutants according to claim 1, characterized in that, In step (1), the wastewater containing benzene-based pollutants is chemical wastewater containing one or more of benzene, toluene, ethylbenzene, and styrene; And / or, the volume ratio of the benzene-containing wastewater to the concentrated water is not greater than 3.3:1; And / or, the addition of acid adjusts the pH to 3.0-5.0; And / or, the acid is sulfuric acid; And / or, the oxidant is hydrogen peroxide, with a concentration of 10wt%~30wt% and an oxidant dosage of 500mg / L~1100mg / L; And / or, the base is sodium hydroxide and sodium carbonate; And / or, the coagulant is polyaluminum chloride, and the dosage is 100~200 mg / L; And / or, the coagulant is polyacrylamide, and the dosage is 1~20 mg / L.

3. The method for reusing wastewater containing benzene series pollutants according to claim 1, characterized in that, In step (1), the homogenizing tank is a storage tank, trough, or pool equipped with a stirring device; And / or, the acid, oxidant, coagulant and coagulant aid are all added via a drug delivery system.

4. The method for reusing wastewater containing benzene-based pollutants according to claim 1, characterized in that, In step (2), the biochemical unit includes a hydrolysis acidification tank, an AO biochemical section anoxic tank, an O tank, and a sedimentation tank. The pretreated effluent first enters the hydrolysis acidification tank for acidification and hydrolysis. The resulting wastewater enters the AO biochemical section anoxic tank for denitrification. The denitrified effluent enters the O tank for aeration. Part of the nitrified effluent treated in the O tank is returned to the AO biochemical section anoxic tank as nitrification liquid, and the remaining part enters the sedimentation tank. The sludge at the bottom of the sedimentation tank is returned to the AO biochemical section anoxic tank, and the clear water at the top is the biochemical effluent.

5. The method for reusing wastewater containing benzene series pollutants according to claim 4, characterized in that, The hydraulic retention time of the hydrolysis acidification tank is 1~1.5h; the hydraulic retention time of the AO biochemical section anoxic tank is 1~4h; the hydraulic retention time of the O tank is 2~10h; and the hydraulic retention time of the sedimentation tank is 2~10h. The dissolved oxygen concentration in the hydrolysis acidification tank is 0.2~0.3 mg / L; the dissolved oxygen concentration in the anoxic tank of the AO biological section is 0.1~0.3 mg / L; the dissolved oxygen concentration in the O tank is 4~6 mg / L; the pH of the sedimentation tank is 6.0~9.0, and the sludge age is 15~18 days; The reflux ratio of the nitrified effluent is 3-5, and the reflux ratio of the sedimentation tank sludge is 0.3-0.

5.

6. The method for reusing wastewater containing benzene series pollutants according to claim 1, characterized in that, In step (3), the turbidity of the biochemical effluent after treatment by the multi-media filter is less than 5 NTU; And / or, the filter media of the multi-media filter includes two or more of the following: quartz sand, anthracite, activated carbon, magnetite, and garnet.

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