Recycling method of wastewater containing benzene series pollutants

Abstract

The invention discloses a recycling method of wastewater containing benzene series pollutants, and belongs to the technical field of wastewater recycling treatment. The recycling method comprises the following steps: firstly, carrying out Fenton reaction on wastewater containing benzene series pollutants, a ferrous catalyst and an oxidizing agent to obtain a catalytic oxidation solution, adjusting the pH value of the catalytic oxidation solution to 6.5-7.0, adding a coagulant and a coagulant aid, and carrying out coagulating sedimentation treatment to obtain pretreated effluent; the pretreated effluent enters a biochemical unit for biochemical treatment, and biochemical effluent is obtained; the biochemical effluent is treated by a multi-medium filter, enters the ultrafiltration system for ultrafiltration after meeting the water inlet requirement of the ultrafiltration system, then is filtered by a security filter and enters a reverse osmosis device, the effluent and concentrated water are separated, the obtained water is used as a water resource, and the obtained concentrated water is returned to the homogenizing tank. The method is low in energy consumption, high in efficiency and clear in unit division of labor, has the advantages of simple process, low operation cost, low sludge yield, wide application range and the like, and can remarkably improve the biodegradability of the wastewater and reduce the toxicity of the wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage reuse treatment, and specifically relates to a method for reusing wastewater containing benzene-based pollutants. Background Art

[0002] Benzene derivatives are harmful to the human body and the ecological environment, and can affect the blood, nerves, reproductive system, etc. of animals. For example, benzene is an important basic raw material for petrochemicals, which is highly toxic and volatile, and can cause leukemia, nervous system diseases, etc. Another example is styrene, an important monomer for synthetic resins, ion exchange resins, and synthetic rubber, but it is highly toxic. Long-term contact with humans can cause eye or respiratory diseases, and there is a risk of cancer.

[0003] Synthetic rubber wastewater contains a large amount of unrecovered monomers such as styrene, benzaldehyde and acetophenone, as well as additives such as sodium dodecylbenzene sulfonate and rosin soap, which lead to complex composition of wastewater, high concentration of pollutants and difficulty in biodegradation. Direct discharge of wastewater containing benzene pollutants into sewage treatment plants will affect the stable operation of the biochemical system, resulting in excessive COD and TN in the effluent. Characteristic pollutants such as benzene may further polymerize in subsequent treatment, limiting the application of membrane technology in the field of wastewater reuse. Inorganic salt scale, natural organic matter, colloids and microorganisms in sewage will contaminate the reverse osmosis membrane system, destroy the membrane structure, greatly shorten the service life of the membrane, and increase the operating cost of the water treatment process. Therefore, wastewater containing benzene pollutants has become one of the most difficult wastewaters to treat in the current petrochemical industry.

[0004] In the existing technology, the treatment methods for wastewater containing benzene pollutants mainly include coagulation sedimentation, coagulation flotation, electrochemical method, biological method, etc., while most enterprises simply treat such wastewater by sedimentation and then mix it with other wastewater for biochemical treatment, which easily causes impact on the biochemical system, resulting in unstable operation of the biochemical treatment system, poor treatment effect, and widespread excessive COD and total phosphorus in drainage. A petrochemical company used a combination of physical and chemical + biochemical + flocculation filtration + activated carbon process to treat rubber wastewater containing benzene pollutants. The results showed that not only the concentrations of major organic pollutants such as COD and phosphorus exceeded the first-level discharge standard of the "Comprehensive Wastewater Discharge Standard" (GB 8978-1996), but also the treatment cost was high.

[0005] For styrene-butadiene rubber wastewater, the commonly used treatment methods in the prior art mainly include: physical separation method, chemical oxidation method and membrane method. It is reported in the literature that Chen Xinyu et al. used hydrolysis acidification-biological contact oxidation method to treat rubber wastewater containing benzene pollutants. The experimental results show that when the influent COD is 650 mg / L, the average removal rates of the hydrolysis acidification tank and the biological contact oxidation method are 23.2% and 83.7% respectively. However, this method has the problems of easy clogging of the filler in the pool and poor treatment effect on wastewater with poor biodegradability. Patent CN116693077A provides a method for treating and reusing styrene-butadiene rubber wastewater, which adopts flotation + hydrolysis acidification + denitrification + MBBR + ozone oxidation + BAF + ultrafiltration + reverse osmosis treatment process to construct a crosslinking unit, but the use of initiators and crosslinkers increases the cost of reagents, 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 pre-membrane pretreatment unit to reduce wastewater COD, TOC and conductivity, while effectively reducing membrane pollution to 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 operating costs.

[0006] On the other hand, from the development trend of domestic water treatment, the current water-saving measures can no longer solve the contradiction between the increase of industrial production and domestic water use and the shortage of water resources, and wastewater reuse has become an inevitable trend in the development of water treatment. Although the above methods have achieved certain treatment effects on rubber wastewater, they are all conventional standard treatment methods, and have not achieved the analysis of benzene series in rubber wastewater, nor have they been deeply treated and reused. Due to the complex components and poor biodegradability of rubber wastewater, the treatment effect is unstable or the cost is high. In terms of practical technology, the deep treatment and reuse of rubber wastewater containing benzene characteristic pollutants after secondary biochemical treatment is basically blank. The methods disclosed in the prior art still have many restrictive factors such as unsatisfactory treatment efficiency, high treatment costs, secondary pollution, and unstable treatment effects, making it difficult to achieve industrial application.

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

[0008] 1. Wastewater containing benzene pollutants has complex components, high toxicity, is difficult to biodegrade, and has the characteristics of high salt content, high chroma, and high COD. In particular, the COD and pH fluctuation range of styrene-containing styrene-butadiene rubber wastewater is large, and the content of ammonia nitrogen and phosphorus is high. Direct discharge into the sewage treatment plant will affect the stable operation of the biochemical system.

[0009] 2. The residual benzene monomers such as styrene, benzaldehyde and acetophenone in the wastewater containing benzene pollutants and additives such as sodium dodecylbenzene sulfonate and rosin soap may further polymerize in the subsequent treatment, which can easily contaminate the reverse osmosis membrane system, destroy the membrane structure, shorten the membrane life, and increase the operating cost of the water treatment process.

[0010] 3. There is basically no deep treatment and reuse of rubber wastewater containing benzene pollutants in industry, and it is difficult to discharge concentrated water in compliance with discharge standards.

[0011] 4. The pH range of the traditional Fenton oxidation reaction is narrow, the amount of acid and alkali used to adjust the pH is large, the utilization rate of hydrogen peroxide is low, and the sludge output is large. Summary of the invention

[0012] In view of this, the present invention provides a method for recycling wastewater containing benzene pollutants to solve the above-mentioned technical problems. The method has low energy consumption, high efficiency, clear division of labor among each unit, simple process, low operating cost, low sludge output, wide application range, etc. It can significantly improve the biodegradability of wastewater and reduce the toxicity of wastewater.

[0013] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are as follows.

[0014] The method for recycling wastewater containing benzene series pollutants of the present invention comprises the following steps:

[0015] (1) After the wastewater containing benzene pollutants and the concentrated water obtained in step (3) are uniformly mixed in a homogenizing tank, an acid is added to adjust the pH to below 5.0, and acid demulsification is performed. The demulsified liquid obtained enters a catalytic oxidation tank and is fully mixed with a ferrous catalyst, and then undergoes a Fenton reaction with an oxidant. The catalytic oxidation liquid obtained enters a coagulation sedimentation tank, and one or both of the domestic sewage and the circulating water wastewater treated with alkali precipitation are added to the coagulation sedimentation tank, and the pH is adjusted to 6.5-7.0. A coagulant and a coagulant aid are added to perform coagulation sedimentation treatment to obtain pretreated effluent;

[0016] (2) the pre-treated effluent enters the biochemical unit for biochemical treatment to obtain biochemical effluent;

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

[0018] Preferably, in step (1), the wastewater containing benzene series substances is 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 concentrated water is not greater than 3.3:1.

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

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

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

[0023] Preferably, in step (1), acid is added to adjust the pH to 3.0-5.0.

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

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

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

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

[0028] Preferably, in step (1), the coagulant aid is polyacrylamide (PAM) and the dosage is 1 to 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 to 60° C., and the Fenton reaction time is 20 to 40 min.

[0031] Preferably, in step (2), the biochemical unit comprises a hydrolysis and acidification tank, an AO biochemical section anoxic tank, an O tank and a sedimentation tank, the pretreated effluent first enters the hydrolysis and acidification tank for acid hydrolysis, the obtained sewage enters the AO biochemical section anoxic tank for denitrification, the effluent after denitrification enters the O tank for aeration, a part of the nitrified effluent after treatment in the O tank is refluxed 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 upper clear water 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 anoxic tank of the AO biochemical section is 1 to 4 hours; the hydraulic retention time of the O tank is 2 to 10 hours; the hydraulic retention time of the sedimentation tank is 2 to 10 hours;

[0033] More preferably, the dissolved oxygen concentration of the hydrolysis acidification tank is 0.2-0.3 mg / L; the dissolved oxygen concentration of the anoxic tank of the AO biochemical stage is 0.1-0.3 mg / L; the dissolved oxygen concentration of 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 nitrification effluent is 3-5, and the reflux ratio of the sedimentation tank sludge is 0.3-0.5.

[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 with the multi-media filter is less than 5 NTU.

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

[0038] Preferably, in step (3), the ultrafiltration system uses full-volume filtration with an operating flux of 40 to 120 L / m 2 ·h, the operation cycle is 30 to 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 device is 10 to 45°C, and the operating flux is 12 to 30 L / m 2 ·h.

[0041] The principle of the present invention is as follows: in the method for recycling wastewater containing benzene pollutants of the present invention, 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 most of the organic matter in the wastewater. Coagulation and precipitation use polyaluminium chloride as a coagulant and polyacrylamide as a coagulant aid. After coagulation and precipitation treatment, suspended matter (SS), styrene, oils, etc. in the water are condensed into large micelles along with dissolved colloidal substances and removed together with the precipitation, wherein the removal rate of SS and styrene is above 92%, achieving the purpose of reducing biochemical load, strengthening microbial denitrification, and reducing environmental pollution. The pre-treated effluent first enters the hydrolysis acidification tank as biochemical influent, and the macromolecular difficult-to-degrade substances in the sewage are hydrolyzed into small molecular substances that are easily biodegradable, thereby greatly improving the biodegradability of the sewage. The biochemical effluent passes through a multi-media filter to remove turbidity and reduce the silt density index. After meeting the water inlet requirements of the ultrafiltration system, it enters the ultrafiltration system to intercept tiny particles, reduce suspended matter, bacteria, etc., and further remove turbidity, color and part of COD in the water. After that, it passes through a security filter to intercept fine gravel and large suspended matter that may be lost in the front-end water treatment unit, and then enters the reverse osmosis device for reuse. The produced water is used as process water, etc., and the concentrated water returns to the front-end pretreatment section.

[0042] In addition, domestic sewage and circulating water wastewater contain relatively high calcium and total hardness. In order to achieve reuse, the method of the present invention first performs alkali precipitation treatment on them and then passes them into a coagulation sedimentation tank. Since the effluent after precipitation has a relatively high pH, ​​the pH of the catalytic oxidation liquid can be adjusted to 6.5-7.0, thereby saving the use of caustic soda and meeting the pH requirements of biochemical water inlet.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The method for recycling wastewater containing benzene pollutants of the present invention has the advantages of simple process, low energy consumption, high efficiency, strong operability and low investment cost. It can not only effectively degrade benzene, toluene, styrene and other benzene pollutants in wastewater, but also effectively degrade other organic substances such as butadiene and dinitrile diamine formaldehyde condensate (CA) in wastewater with few by-products, significantly improve the biodegradability of such wastewater and reduce the toxicity of wastewater. According to the test, the removal rate of SS, styrene and the like in wastewater containing benzene pollutants is above 92%. After catalytic oxidation, the styrene content of a certain wastewater is reduced from 210 mg / L to below 1 mg / L, and the COD is reduced from 1100 mg / L to 230 mg / L, and the biochemical load is significantly reduced. The sewage treatment plant that originally required two-stage biochemical treatment can meet the water inlet requirements of the recycling system with only the first stage. Furthermore, after biochemical treatment and ultrafiltration reverse osmosis treatment and other processes, the COD of the produced water is reduced to below 0.5 mg / L, and the conductivity is less than 200 μS / cm, so that it can be recycled.

[0045] (2) The method for recycling wastewater containing benzene pollutants of the present invention adopts polyaluminium chloride as a coagulant, which saves catalytic oxidation process reagents, achieves the same flocculation and precipitation effect, and greatly reduces the reagent cost.

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

[0047] (4) The method for recycling wastewater containing benzene-based pollutants of the present invention returns concentrated water to the homogenization tank for use, thus solving the problem of concentrated water reaching the discharge standard.

[0048] (5) The method for recycling wastewater containing benzene pollutants of the present invention has a relatively high concentration of hardness and calcium in domestic sewage and circulating water. The pH of biochemical influent and ultrafiltration influent generally needs to be controlled at 6.5-7.0. The present invention performs pre-precipitation 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 recycling wastewater containing benzene pollutants of the present invention can be reused as surface water source replenishment water, farmland and public facility water, landscape water, circulating water replenishment and process water replenishment after deep treatment, thereby reducing the water consumption per ton of oil in 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 polyols, styrene, etc., and has good application prospects and environmental benefits.

[0051] (8) The method for recycling wastewater containing benzene pollutants of the present invention adopts catalytic oxidation pretreatment + biochemical treatment + ultrafiltration and reverse osmosis treatment process to realize the recycling of wastewater containing benzene pollutants. The system operates for a long period of time, provides valuable industrial application cases and reliable process technology for the recycling of wastewater containing benzene pollutants, and implements the requirements of water saving and emission reduction. It complies with the national policies on water saving, pollution control, and water resource utilization, effectively utilizes water resources, not only exerts the economic benefits of the process equipment, but also has important significance for improving the local water environment, protecting groundwater resources, increasing the total amount of available water resources, alleviating the current situation of water shortage in new projects, and comprehensive pollution control. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are only some specific implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0053] Figure 1 The present invention is a process flow chart of the method for recycling wastewater containing benzene pollutants. DETAILED DESCRIPTION

[0054] In order 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, rather than limiting the claims of the present invention.

[0055] like Figure 1 As shown, the method for recycling wastewater containing benzene series pollutants of the present invention comprises the following steps:

[0056] (1) Pretreatment;

[0057] (1-1) After the wastewater containing benzene pollutants and the concentrated water obtained in step (3) are uniformly mixed in a homogenizing tank, an acid is added to adjust the pH to below 5.0, and acidification and demulsification are performed to obtain a demulsified liquid;

[0058] (1-2) the demulsified liquid enters the catalytic oxidation tank and is fully mixed with the ferrous catalyst, and then undergoes a Fenton reaction with the oxidant to obtain a catalytic oxidation liquid;

[0059] (1-3) The catalytic oxidation liquid enters the coagulation sedimentation tank, and one or both of the domestic sewage and the circulating water wastewater after the alkali precipitation treatment are added to the coagulation sedimentation tank, the pH is adjusted to 6.5-7.0, a coagulant and a coagulant aid are added, and a coagulation sedimentation treatment is performed to obtain pretreated effluent;

[0060] (2) the pre-treated effluent enters the biochemical unit for biochemical treatment to obtain biochemical effluent;

[0061] (3) The biochemical effluent is first treated by a multi-media filter. After meeting the water inlet requirements of the ultrafiltration system, it enters the ultrafiltration system for ultrafiltration, and then is filtered by a security filter before entering a reverse osmosis device to separate the effluent and the concentrated water. The obtained water is used as a water resource, such as process water, and the concentrated water is returned to the homogenization tank.

[0062] In the above technical solution, in step (1-1), the Fenton reaction is the reaction of H2O2 with Fe 2+ The ·OH free radical generated under catalysis has an oxidation capacity second only to fluorine, as high as 2.8V, which can oxidize most organic matter in water. 2+ As a catalyst, it can be oxidized to Fe 3+ , Fe 3+ It can also catalyze the decomposition of H2O2 to produce ·OH free radicals. The principle of ·OH free radicals in removing organic matter is to remove hydrogen from single bonds and add to open double bonds. Acidic conditions are conducive to Fe 2+ Stable existence to prevent it from being oxidized to Fe3+ Or form precipitation; and the acidic environment is conducive to the decomposition of H2O2, accelerating the generation of OH free radicals. At the same time, at a certain pH, Fe(OH)3 colloids may appear, playing a certain flocculation role. The Fenton reaction has the characteristics of good treatment effect, mild reaction conditions, easy availability of chemical reagents, no complex equipment, low energy consumption, environmental friendliness, and low dosage of reagents.

[0063] In the above technical solution, since the concentrated water yield is 25% to 30%, in step (1-1), the volume ratio of the wastewater containing benzene pollutants to the concentrated water is preferably not greater than 3.3:1.

[0064] In the above technical scheme, in step (1-1), the preferred pH is 3.0 to 5.0, because a high pH will inhibit the generation of hydroxyl radicals in the solution, and the activity of the catalyst ferrous ions will decrease or even disappear; when the pH is too low, the reducibility of the trivalent iron ions is greatly reduced, which is not conducive to the reaction.

[0065] In the above technical scheme, in step (1-2), in order to prevent scaling, the pH of the biochemical influent and the further ultrafiltration influent is generally controlled at 6.5-7.0, usually 6.8; the domestic sewage and circulating water wastewater containing high calcium and total hardness are first subjected to alkali precipitation treatment (the pH before alkali precipitation is 8.2), so that the effluent after precipitation still has a high pH, ​​and is passed into a coagulation sedimentation tank to adjust the pH to 6.5-7.0, thereby saving the use of sodium hydroxide and meeting the pH requirements of the biochemical influent.

[0066] In the above technical scheme, in step (1-3), the coagulation and sedimentation treatment causes the suspended solids (SS), styrene, oils, etc. in the catalytic oxidation liquid to condense into large flocs along with the dissolved colloidal substances, and are removed together with the precipitate, wherein the removal rate of SS and styrene is above 92%, thereby achieving the purpose of reducing the biochemical load, strengthening the microbial denitrification, and reducing environmental pollution.

[0067] In the above technical scheme, in step (1), preferably: the wastewater containing benzene series is chemical wastewater containing one or more of benzene, toluene, ethylbenzene and styrene. The homogenizing tank is a storage tank, a tank or a pool with a stirring device. The alkali is sodium hydroxide and sodium carbonate. The acid, the oxidant, the coagulant and the coagulant aid are all added through the dosing system. The acid is sulfuric acid. The oxidant is hydrogen peroxide with a concentration of 10wt%-30wt%, and the oxidant dosage is 500mg / L-1100mg / L. The coagulant is polyaluminium 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°C, and the Fenton reaction time is 20-40min. The ferrous catalyst is magnetite, and the amount used needs to be converted into pure substances for calculation. Based on 30wt% hydrogen peroxide, the mass ratio of 30wt% hydrogen peroxide to FeSO4·7H2O in the magnetite is 0.5-1.5:1.

[0068] In the above technical solution, the function of step (2) is to hydrolyze the macromolecular difficult-to-degrade substances in the pretreated water into small molecular substances that are easily biodegradable, thereby greatly improving the biodegradability of the sewage.

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

[0070] In the above technical solution, the function of step (3) is as follows: the biochemical effluent is filtered through a multi-media filter to remove turbidity and reduce the silt density index; the ultrafiltration system intercepts tiny particles, reduces suspended matter, bacteria, etc., and further removes turbidity, color and part of COD in the water; the security filter is used to intercept fine gravel and large suspended matter that may be lost from the front-end water treatment unit, protect the safe operation of the reverse osmosis device, and prevent the reverse osmosis membrane element 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 0.0001μm and greater than or equal to 0.0001μm in the effluent of the security filter.

[0071] In the above technical solution, in step (3), the turbidity of the biochemical effluent after being treated by the multi-media filter is less than 5 NTU. The filter material of the multi-media filter includes two or more of quartz sand, anthracite, activated carbon, magnetite, and garnet. The ultrafiltration system adopts full-volume filtration, and the operating flux is 40 to 120 L / m 2 ·h, the operation cycle is 30 to 60 minutes. The security filter filters solid particles with a diameter greater than 5μm. The operating temperature of the reverse osmosis device is 10 to 45°C, and the operating flux is 12 to 30L / m 2 ·h.

[0072] The present invention provides a device capable of implementing the above-mentioned recovery method, but is not limited thereto, including:

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

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

[0075] A coagulation sedimentation tank located downstream of the catalytic oxidation tank and connected to the catalytic oxidation tank through a pipeline, wherein the coagulation sedimentation tank is provided with a domestic sewage and circulating water sewage inlet;

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

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

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

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

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

[0081] The reverse osmosis device is connected to the homogenization tank through a pipeline, and a water outlet is provided on the reverse osmosis device;

[0082] It can also include a dosing system connected to the homogenization tank, the catalytic oxidation tank and the coagulation sedimentation tank through pipelines respectively.

[0083] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings.

[0084] In the following examples, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, devices, instruments, equipment, etc. used in the following examples can be obtained from commercial sources.

[0085] Example 1

[0086] A styrene butadiene rubber wastewater (flow rate 200m 3 / h, COD950mg / L, TN140mg / L, styrene50mg / L, dinitrile diamine formaldehyde condensation30mg / L, suspended matter350mg / L, conductivity6000μS / cm).

[0087] The method for recycling wastewater containing benzene pollutants is as follows:

[0088] (1) After 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) are mixed uniformly in a homogenizing tank, an acid is added to adjust the pH to 3.0-5.0, and acidification and demulsification are performed to obtain a demulsified liquid; the demulsified liquid enters a catalytic oxidation tank and is mixed with 0.15 kg / m 3 After fully mixing with 0.7kg / m 3 The hydrogen peroxide (30 wt%) was subjected to Fenton reaction at 40-60°C for 30 min to obtain a catalytic oxidation liquid; the catalytic oxidation liquid was fed into a coagulation sedimentation tank, and the domestic sewage and circulating water wastewater treated with alkali precipitation were added to the coagulation sedimentation tank to adjust the pH to neutral, and 0.15 kg / m 3 Coagulant PAC and 0.002kg / m 3 The coagulant aid PAM is used for coagulation and sedimentation treatment to obtain pretreated effluent;

[0089] (2) The pre-treated effluent enters the biochemical unit for biochemical treatment to obtain biochemical effluent, and the turbidity of the biochemical effluent is less than 5 NTU;

[0090] (3) The biochemical effluent is first treated by a multi-media filter. After meeting the water inlet requirements of the ultrafiltration system, it enters the ultrafiltration system for ultrafiltration, and then is filtered by a security filter before entering a reverse osmosis device to separate the effluent and concentrated water. The obtained water is used as process water, and the concentrated water is returned to the homogenization tank. Among them, the ultrafiltration system adopts full-volume filtration, with an operating flux of 40 to 120 L / m 2 ·h, the operation cycle is 30-60min; the operating temperature of the reverse osmosis device is 10-45℃, and the operating flux is 12-30L / m 2 ·h.

[0091] After testing, the COD in the pre-treated effluent was reduced to below 200 mg / L, styrene was reduced to below 0.5 mg / L, dinitrile diamine formaldehyde condensation was not detected, and suspended solids were below 10 mg / L; the COD of the biochemical effluent was below 30 mg / L, and TN was below 11 mg / L; the average water production rate of the reverse osmosis device was 75%, the conductivity of the produced water was 140-160 μS / cm, the COD of RO concentrated water was 60-80 mg / L, the conductivity was 12000 μS / cm-13000 μS / cm, the COD of RO produced water was below 5 mg / L, the total hardness (calculated as CaCO3) was less than 20 mg / L, the chloride ions and sulfate ions were both less than 50 mg / L, and the TDS was below 150 mg / L, meeting the reuse requirements for process water.

[0092] Example 2

[0093] Wastewater containing benzene pollutants (flow rate 200m 3 / h, COD1200mg / L, TN100mg / L, styrene210mg / L, suspended solids300mg / L, conductivity5700μS / cm).

[0094] The method for recycling wastewater containing benzene pollutants is as follows:

[0095] (1) After 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) are mixed uniformly in a homogenizing tank, an acid is added to adjust the pH to 3.0-5.0, and acidification and demulsification are performed to obtain a demulsified liquid; the demulsified liquid enters a catalytic oxidation tank and is mixed with 0.25 kg / m 3 After fully mixing with 0.8kg / m 3 The hydrogen peroxide (30 wt%) was subjected to Fenton reaction at 40-60°C for 30 min to obtain a catalytic oxidation liquid; the catalytic oxidation liquid was fed into a coagulation sedimentation tank, and the domestic sewage and circulating water wastewater treated with alkali precipitation were added to the coagulation sedimentation tank to adjust the pH to neutral, and 0.15 kg / m 3 Coagulant PAC and 0.002kg / m 3The coagulant aid PAM is used for coagulation and sedimentation treatment to obtain pretreated effluent;

[0096] (2) The pre-treated effluent enters the biochemical unit for biochemical treatment to obtain biochemical effluent, and the turbidity of the biochemical effluent is less than 5 NTU;

[0097] (3) The biochemical effluent is first treated by a multi-media filter. After meeting the water inlet requirements of the ultrafiltration system, it enters the ultrafiltration system for ultrafiltration, and then is filtered by a security filter before entering a reverse osmosis device to separate the effluent and concentrated water. The obtained water is used as process water, and the concentrated water is returned to the homogenization tank. Among them, the ultrafiltration system adopts full-volume filtration, with an operating flux of 40 to 120 L / m 2 ·h, the operation cycle is 30-60min; the operating temperature of the reverse osmosis device is 10-45℃, and the operating flux is 12-30L / m 2 ·h.

[0098] After testing, the COD in the pre-treated effluent was reduced to 230mg / L, styrene was reduced to below 1mg / L, and the suspended solids were 20mg / L; the COD of the biochemical effluent was 35mg / L, and the TN was 7mg / L; the average water production rate of the reverse osmosis device was 75%, the conductivity of the produced water was 140-180μS / cm, the COD of RO concentrated water was less than 160mg / L, the conductivity was 12000μS / cm-13000μS / cm, the COD of RO produced water was less than 10mg / L, the total hardness (calculated as CaCO3) was less than 20mg / L, the chloride ions and sulfate ions were both less than 50mg / L, and the TDS was less than 150mg / L, meeting the reuse requirements of process water.

[0099] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A method for recycling wastewater containing benzene-based pollutants, characterized in that: The following steps are involved: (1) After the wastewater containing benzene pollutants and the concentrated water obtained in step (3) are uniformly mixed in a homogenizing tank, an acid is added to adjust the pH to below 5.0, and acid demulsification is performed. The demulsified liquid obtained enters a catalytic oxidation tank and is fully mixed with a ferrous catalyst, and then undergoes a Fenton reaction with an oxidant. The catalytic oxidation liquid obtained enters a coagulation sedimentation tank, and one or both of the domestic sewage and the circulating water wastewater treated with alkali precipitation are added to the coagulation sedimentation tank, and the pH is adjusted to 6.5-7.

0. A coagulant and a coagulant aid are added to perform coagulation sedimentation treatment to obtain pretreated effluent; (2) the pre-treated effluent enters the biochemical unit for biochemical treatment to obtain biochemical effluent; (3) The biochemical effluent is first treated by a multi-media filter. After meeting the water inlet requirements of the ultrafiltration system, it enters the ultrafiltration system for ultrafiltration, and then is filtered by a security filter before entering a reverse osmosis device to separate the effluent and the concentrated water. The obtained water is used as a water resource, and the obtained concentrated water is returned to the homogenization tank.

2. The method for recycling wastewater containing benzene pollutants according to claim 1, characterized in that: In step (1), the wastewater containing benzene series is chemical wastewater containing one or more of benzene, toluene, ethylbenzene and styrene; and / or, the volume ratio of the wastewater containing benzene pollutants to concentrated water is not greater than 3.3:1; and / or, adding an acid to adjust the pH to 3.0-5.0; and / or, the acid is sulfuric acid; And / or, the oxidant is hydrogen peroxide, the concentration is 10wt% to 30wt%, and the dosage of the oxidant is 500mg / L to 1100mg / L; The ferrous catalyst is magnetite, and based on 30wt% hydrogen peroxide, the mass ratio of 30wt% hydrogen peroxide to FeSO4·7H2O in the magnetite is 0.5-1.5:1; And / or, the base is sodium hydroxide and sodium carbonate; And / or, the coagulant is polyaluminium chloride, and the dosage is 100-200 mg / L; And / or, the coagulant aid is polyacrylamide, and the dosage is 1-20 mg / L.

3. The method for recycling wastewater containing benzene pollutants according to claim 1, characterized in that: In step (1), the Fenton reaction temperature is 40 to 60° C., and the Fenton reaction time is 20 to 40 min.

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

5. The method for recycling wastewater containing benzene pollutants according to claim 1, characterized in that: In step (2), the biochemical unit includes a hydrolysis and acidification tank, an AO biochemical section anoxic tank, an O tank and a sedimentation tank. The pretreated effluent first enters the hydrolysis and acidification tank for acidification and hydrolysis, and the resulting sewage enters the AO biochemical section anoxic tank for denitrification. The effluent after denitrification enters the O tank for aeration. A portion of the nitrified effluent after treatment in the O tank is refluxed to the AO biochemical section anoxic tank as nitrification liquid, and the remaining portion enters the sedimentation tank. The sludge at the bottom of the sedimentation tank is returned to the AO biochemical section anoxic tank, and the upper clear water is the biochemical effluent.

6. The method for recycling wastewater containing benzene pollutants according to claim 5, characterized in that: The hydraulic retention time of the hydrolysis acidification tank is 1 to 1.5 hours; the hydraulic retention time of the anoxic tank of the AO biochemical section is 1 to 4 hours; the hydraulic retention time of the O tank is 2 to 10 hours; the hydraulic retention time of the sedimentation tank is 2 to 10 hours; The dissolved oxygen concentration of the hydrolysis acidification tank is 0.2-0.3 mg / L; the dissolved oxygen concentration of the AO biochemical section anoxic tank is 0.1-0.3 mg / L; the dissolved oxygen concentration of 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 nitrification effluent is 3-5, and the reflux ratio of the sedimentation tank sludge is 0.3-0.

5.

7. The method for recycling wastewater containing benzene pollutants according to claim 1, characterized in that: 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.

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

9. The method for recycling wastewater containing benzene pollutants according to claim 1, characterized in that: In step (3), the ultrafiltration system uses full-volume filtration with an operating flux of 40 to 120 L / m 2 ·h, the operation cycle is 30 to 60 minutes.

10. The method for recycling wastewater containing benzene-based pollutants according to claim 1, characterized in that: In step (3), the security filter filters solid particles with a diameter greater than 5 μm; And / or, the reverse osmosis device has an operating temperature of 10-45°C and an operating flux of 12-30 L / m 2 ·h.

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