A physicochemical-biochemical treatment method for high-concentration organic wastewater

Abstract

The present invention relates to the technical field of organic wastewater treatment, and discloses a physicochemical-biochemical treatment method for high-concentration organic wastewater. The method comprises the following steps: physicochemical pretreatment → anaerobic fermentation → anaerobic-aerobic treatment → physicochemical post-treatment. During the anaerobic fermentation process, anaerobic granular sludge is used that contains a conductive network composed of modified activated carbon fibers and modified biochar, where the surfaces of the modified activated carbon fibers and modified biochar have opposite charges at a pH of 6-8. The present invention utilizes a specific combination and sequence of process stages, and utilizes the anaerobic granular sludge containing the conductive network composed of the modified activated carbon fibers and modified biochar during the anaerobic fermentation process, thereby achieving effective treatment of high-concentration organic wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of organic wastewater treatment, in particular to a physicochemical-biochemical treatment method for high-concentration organic wastewater. Background Art

[0002] High-concentration organic wastewater comes from industries such as pharmaceuticals, printing and dyeing, papermaking, food processing, and modern coal chemical industry. Its organic pollutant concentrations are high, with chemical oxygen demand (COD) exceeding 2000 mg / L. Direct discharge into water bodies can cause eutrophication, reduce the water's self-purification capacity, severely damage the organisms within it, and pose a threat to human health. Effectively treating high-concentration organic wastewater to meet discharge standards and prevent harm to the ecological environment and human health is a hot topic in the environmental protection field.

[0003] In the treatment of high-concentration organic wastewater, there are problems such as complex composition, high pollutant content, non-biodegradability and difficulty in treatment. Traditional treatment methods such as single biochemical method and physicochemical method are ineffective. The physicochemical-biochemical method couples physicochemical treatment and biochemical treatment, which can combine the advantages of the two methods. It is an important breakthrough direction for solving the problem of difficult treatment of high-concentration organic wastewater.

[0004] The treatment effect of the physicochemical-biochemical method depends on the selected process sections and combinations, the treatment effect of each process section, and the order between each process section. Patent CN202010378292.8 discloses a method for treating high-concentration organic wastewater by deep anaerobic-aerobic coupling, comprising the following steps: the organic wastewater enters the anaerobic reaction unit, is fully mixed with the anaerobic granular sludge pre-added to the anaerobic reaction unit, and an anaerobic reaction occurs; the anaerobic effluent after the anaerobic reaction enters the aerobic reaction unit, undergoes a synchronous nitrification and denitrification process, and removes nitrogen; part of the effluent from the aerobic reaction unit is returned to the anaerobic reaction unit, and the other part of the effluent enters the next treatment process or meets the discharge standards. This patent couples anaerobic biological treatment and aerobic biological treatment in a cycle, which can use anaerobic treatment to improve the subsequent aerobic biochemical efficiency, and use aerobic treatment to further treat the anaerobic effluent in an environmentally friendly manner. However, in conventional anaerobic biological treatment, the interspecies electron transfer efficiency is low, and thus the anaerobic treatment efficiency is low, which in turn affects the overall treatment effect. In addition, the use of anaerobic-aerobic coupling method alone to treat high-concentration organic wastewater has the problem of poor biodegradability of the wastewater, which affects the efficiency of anaerobic biological treatment, and incomplete removal of organic pollutants, which will also result in poor overall wastewater treatment effect. Summary of the Invention

[0005] To address the technical issue of the poor treatment effectiveness of existing anaerobic-aerobic coupled methods for high-concentration organic wastewater, the present invention provides a physicochemical-biochemical treatment method for high-concentration organic wastewater. This method utilizes a combined and sequential process sequence of physicochemical pretreatment, anaerobic fermentation, anaerobic-aerobic treatment, and physicochemical post-treatment. Furthermore, during the anaerobic fermentation process, anaerobic granular sludge containing a conductive network composed of modified activated carbon fibers and modified biochar is employed, resulting in improved treatment effectiveness for high-concentration organic wastewater.

[0006] The specific technical solutions of the present invention are:

[0007] A physicochemical-biochemical treatment method for high-concentration organic wastewater comprises the following steps:

[0008] S1: Physical and chemical pretreatment of high-concentration organic wastewater to initially remove suspended solids and total phosphorus;

[0009] S2: After adjusting the pH of the wastewater treated in step S1 to 6-8, the wastewater is passed into an anaerobic reactor and mixed with anaerobic granular sludge for anaerobic fermentation, followed by sludge-water separation to obtain a supernatant and sludge; the anaerobic granular sludge contains a conductive network composed of modified activated carbon fibers and modified biochar, and the surfaces of the modified activated carbon fibers and the modified biochar have opposite charges at a pH of 6-8;

[0010] S3: After adjusting the pH of the supernatant obtained in step S2 to 7-8, performing anaerobic-aerobic treatment, and then performing mud-water separation to obtain supernatant and sludge;

[0011] S4: performing physicochemical post-treatment on the supernatant obtained in step S3.

[0012] In the anaerobic granular sludge used in the present invention, under a pH environment suitable for anaerobic microorganisms (pH 6-8), the modified activated carbon fibers and modified biochar have opposite surface charges, allowing them to bind through electrostatic attraction, forming a conductive network within the resulting anaerobic granular sludge. During anaerobic fermentation of wastewater, anaerobic microorganisms adhere to the anaerobic granular sludge and the activated carbon fibers and biochar therein. This conductive network promotes interspecies electron transfer between the microorganisms, thereby improving the efficiency of anaerobic treatment and facilitating better treatment of high-concentration organic wastewater.

[0013] Furthermore, the present invention first performs a physicochemical pretreatment to preliminarily remove suspended solids and total phosphorus, which can improve the biodegradability of high-concentration organic wastewater; then performs anaerobic fermentation, which can greatly reduce the COD of the wastewater; then performs anaerobic-aerobic treatment (A / O process), using facultative anaerobic microorganisms to convert large molecules and difficult-to-degrade organic matter in the wastewater into small molecules and easily degradable organic matter, and then uses aerobic microorganisms to further remove COD and ammonia nitrogen in the wastewater; after the above-mentioned biochemical treatment, the wastewater is further removed through physicochemical post-treatment, which can further remove pollutants (such as suspended solids and total phosphorus) in the wastewater. The above process stage combination and sequence can achieve a better treatment effect for high-concentration organic wastewater, effectively removing COD, nitrogen, phosphorus, and suspended solids.

[0014] Preferably, the surface of the modified activated carbon fiber has a positive charge, and the surface of the modified biochar has a negative charge; the modified activated carbon fiber is loaded with nano-zero-valent iron.

[0015] Nano-zero-valent iron can directly act as an electron donor or react with water to produce hydrogen as an electron donor, promoting the degradation of pollutants in wastewater by anaerobic microorganisms. The present invention loads nano-zero-valent iron in modified activated carbon fibers, which form a conductive network with modified biochar and exist in anaerobic granular sludge. The electrons provided by the nano-zero-valent iron can be transferred along the conductive network to the anaerobic microorganisms attached to the activated carbon fibers and biochar. At the same time, the hydrogen generated by the nano-zero-valent iron can be transferred along the pores in the anaerobic sludge particles to the anaerobic microorganisms attached to the anaerobic sludge particles. In this way, the nano-zero-valent iron in the modified activated carbon fibers cooperates with the conductive network in the anaerobic granular sludge, which can fully utilize the role of the nano-zero-valent iron in providing electrons and improve the anaerobic treatment efficiency to a greater extent.

[0016] In addition, the surface of nano zero-valent iron carries a positive charge. If it is loaded in modified biochar, it will affect the bonding between the modified biochar and the modified activated carbon fiber, thereby affecting the formation of the conductive network. Therefore, the present invention loads nano zero-valent iron in modified activated carbon fiber.

[0017] Preferably, the method for preparing the anaerobic granular sludge comprises the following steps:

[0018] (1) (2-aminoethyl)trimethylammonium chloride is grafted onto the surface of activated carbon fibers through a condensation reaction between carboxyl groups and amino groups to obtain modified activated carbon fibers;

[0019] (2) subjecting the biochar to acid oxidation treatment to obtain modified biochar;

[0020] (3) The modified biochar and modified activated carbon fiber are dispersed in water, the pH is adjusted to 6-8, and a conductive dispersion is prepared. The conductive dispersion is then added to an anaerobic reactor together with flocculent sludge. After mixing, anaerobic granular sludge is cultured to form anaerobic granular sludge.

[0021] Activated carbon fiber is an activated carbon fiber with a relatively large porous structure and a relatively large specific surface area, which is conducive to the attachment of microorganisms. At the same time, the surface of the activated carbon fiber also carries relatively more oxygen-containing groups (such as hydroxyl, carboxyl, and carbonyl). In step (1), the carboxyl groups on the surface of the activated carbon fiber react with the amino groups in (2-aminoethyl) trimethylammonium chloride to graft the quaternary ammonium groups onto the activated carbon fiber, so that it carries a positive charge; in step (2), the surface of the biochar can be made negatively charged in an environment of pH 6-8 by acid oxidation treatment; in step (3), the modified biochar and the modified activated carbon fiber are made into a conductive dispersion liquid, and the two can be combined by electrostatic attraction to form a conductive network in advance. Then, during the cultivation process of anaerobic granular sludge, the flocculent sludge and the conductive network form a self-aggregate through biological coagulation (such as the adhesion of bacteria), i.e., anaerobic granular sludge.

[0022] Preferably, the specific process of step (1) includes the following steps: adding activated carbon fiber to a solution containing (2-aminoethyl)trimethylammonium chloride, reacting at a temperature of 70-80°C for 2.5-3.5h, separating the product, and obtaining modified activated carbon fiber.

[0023] Preferably, in step (1), the concentration of the solution containing (2-aminoethyl)trimethylammonium chloride is 8-16wt%; the mass volume ratio of the activated carbon fiber to the solution containing (2-aminoethyl)trimethylammonium chloride is 1g:90-100mL.

[0024] Preferably, the specific process of step (2) includes the following steps: adding biochar to a 20-25 wt% nitric acid solution, stirring for 8-12 hours, separating the product, and obtaining modified biochar.

[0025] Preferably, in step (2), the mass volume ratio of the biochar to the nitric acid solution is 1 g:150-250 mL.

[0026] Preferably, in step (3), the mass ratio of the flocculent sludge, modified activated carbon fiber and modified biochar is 1:0.2-0.4:0.05-0.1.

[0027] Preferably, in step (3), the specific process of culturing the anaerobic granular sludge comprises the following steps: introducing organic wastewater with a COD of 1500-2000 mg / L and a pH of 6-8 into an anaerobic reactor, controlling the stirring speed to 70-80 r / min, and the hydraulic retention time to 20-24 h, until the COD of the anaerobic reactor effluent is stable, increasing the influent COD to 3000-4000 mg / L, controlling the influent pH to 6-8, the stirring speed to 100-110 r / min, and the hydraulic retention time to 10-12 h, until the COD of the anaerobic reactor effluent is stable.

[0028] Preferably, before step (1), nano-zero-valent iron is loaded on the activated carbon fiber, and the specific process includes the following steps: after the activated carbon fiber is immersed in an iron salt or ferrous salt solution, a sodium borohydride solution is added dropwise thereto under the protection of an inert gas and the action of ultrasound to reduce trivalent or divalent iron to zero-valent iron, and separate the product.

[0029] Preferably, the content of the ferric salt or ferrous salt in the ferric salt or ferrous salt solution is 1.5-6.0 wt%.

[0030] Preferably, the concentration of the sodium borohydride solution is 0.5-2.5 wt %; the mass ratio of the ferric salt or ferrous salt to sodium borohydride is 1:0.5-1.5.

[0031] Preferably, in step S2, the anaerobic reactor is an EGSB reactor.

[0032] Preferably, the specific process of step S3 includes the following steps:

[0033] S3.1: After adjusting the pH of the supernatant obtained in step S2 to 7-8, the supernatant is subjected to a primary anaerobic-aerobic treatment, followed by mud-water separation to obtain a supernatant and sludge;

[0034] S3.2: The supernatant obtained in step S3.2 is subjected to secondary anaerobic-aerobic treatment and membrane retention by a mud-membrane mixing method, and then mud-water separation is performed to obtain supernatant and sludge.

[0035] The use of two-stage anaerobic-aerobic treatment can remove the remaining organic pollutants in the wastewater after anaerobic fermentation to a greater extent. In addition, the mud-membrane hybrid method used in the secondary anaerobic-aerobic treatment can use the membrane to intercept sludge and free microorganisms in the wastewater, reducing the loss of sludge and microorganisms in the anaerobic-aerobic treatment system. At the same time, the membrane interception can also remove other solid matter and large molecular organic matter in the wastewater.

[0036] Preferably, in steps S3.1 and S3.2, during the primary anaerobic-aerobic treatment and the secondary anaerobic-aerobic treatment, a carbon source is added to the anaerobic section, and aeration is performed in the aerobic section to control the dissolved oxygen content to 2-4 mg / L.

[0037] Preferably, the specific process of step S1 includes the following steps: adjusting the pH of the high-concentration organic wastewater to 3-11, performing a coagulation reaction, and then performing mud-water separation to obtain a supernatant and sludge.

[0038] Preferably, the specific process of step S4 includes the following steps:

[0039] S4.1: The supernatant obtained in step S3 is subjected to coagulation reaction, and then mud-water separation is performed to obtain supernatant and sludge;

[0040] S4.2: Perform flotation treatment on the supernatant obtained in step S4.1.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] (1) The present invention adopts a specific process section combination and sequence to achieve better treatment effect of high-concentration organic wastewater, effectively removing COD, nitrogen, phosphorus and suspended solids therein;

[0043] (2) The present invention uses anaerobic granular sludge containing a conductive network composed of modified activated carbon fibers and modified biochar during the anaerobic fermentation process, which can promote interspecies electron transfer of anaerobic microorganisms, improve the anaerobic treatment efficiency, and thus improve the treatment effect of high-concentration organic wastewater;

[0044] (3) The present invention loads nano-zero-valent iron in modified activated carbon fibers, which can cooperate with the conductive network in anaerobic granular sludge, so that the role of nano-zero-valent iron in providing electrons is fully utilized without affecting the formation of the conductive network. Therefore, the anaerobic treatment efficiency can be improved to a greater extent, thereby improving the treatment effect of high-concentration organic wastewater. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the embodiments.

[0046] Overall embodiment

[0047] A physicochemical-biochemical treatment method for high-concentration organic wastewater, characterized by comprising the following steps:

[0048] S1: Physical and chemical pretreatment of high-concentration organic wastewater to initially remove suspended solids and total phosphorus;

[0049] S2: After adjusting the pH of the wastewater treated in step S1 to 6-8, the wastewater is passed into an anaerobic reactor and mixed with anaerobic granular sludge for anaerobic fermentation, followed by sludge-water separation to obtain a supernatant and sludge; the anaerobic granular sludge contains a conductive network composed of modified activated carbon fibers and modified biochar, and the surfaces of the modified activated carbon fibers and the modified biochar have opposite charges at a pH of 6-8;

[0050] S3: After adjusting the pH of the supernatant obtained in step S2 to 7-8, performing anaerobic-aerobic treatment, and then performing mud-water separation to obtain supernatant and sludge;

[0051] S4: performing physicochemical post-treatment on the supernatant obtained in step S3.

[0052] As a specific implementation, the specific process of step S1 includes the following steps: adjusting the pH of high-concentration organic wastewater to 3-11, performing coagulation reaction, and then performing mud-water separation to obtain supernatant and sludge.

[0053] As a specific implementation, in step S2, the anaerobic reactor is an EGSB reactor.

[0054] As a specific embodiment, in step S2, the method for preparing anaerobic granular sludge includes the following steps:

[0055] (1) Nano-zero-valent iron was loaded into activated carbon fibers to obtain nZVI-ACF composite materials;

[0056] (2) (2-aminoethyl)trimethylammonium chloride was grafted onto the surface of nZVI-ACF composite material through condensation reaction between carboxyl group and amino group to obtain modified activated carbon fiber;

[0057] (3) subjecting the biochar to acid oxidation treatment to obtain modified biochar;

[0058] (4) The modified biochar and modified activated carbon fiber are dispersed in water, the pH is adjusted to 6-8, and a conductive dispersion is prepared. The conductive dispersion is then added to an anaerobic reactor together with flocculent sludge. After mixing, anaerobic granular sludge is cultured to form anaerobic granular sludge.

[0059] As a specific embodiment, the specific process of step (1) includes the following steps: after the activated carbon fiber is immersed in a 1.5-6.0wt% iron salt or ferrous salt solution according to a mass volume ratio of 1g:15-25mL, 0.5-2.5wt% sodium borohydride solution is added dropwise thereto under the protection of inert gas and ultrasonic action, the mass ratio of iron salt or ferrous salt to sodium borohydride is controlled to be 1:0.5-1.5, trivalent or divalent iron is reduced to zero-valent iron, and the product is separated.

[0060] As a specific embodiment, the specific process of step (2) includes the following steps: adding the nZVI-ACF composite material to a solution containing 8-16wt% (2-aminoethyl)trimethylammonium chloride according to a mass volume ratio of 1g:90-100mL, reacting at a temperature of 70-80°C for 2.5-3.5h, separating the product, and obtaining modified activated carbon fiber.

[0061] As a specific embodiment, the specific process of step (3) includes the following steps: adding biochar to 20-25wt% nitric acid solution according to a mass volume ratio of 1g:150-250mL, stirring for 8-12h, separating the product, and obtaining modified biochar.

[0062] As a specific implementation, in step (4), the mass ratio of the flocculent sludge, modified activated carbon fiber and modified biochar is 1:0.2-0.4:0.05-0.1.

[0063] As a specific embodiment, in step (4), the specific process of anaerobic granular sludge cultivation includes the following steps: organic wastewater with a COD of 1500-2000 mg / L and a pH of 6-8 is introduced into the anaerobic reactor, the stirring speed is controlled to 70-80 r / min, the hydraulic retention time (HRT) is 20-24 h, and after the COD of the anaerobic reactor effluent is stable, the influent COD is increased to 3000-4000 mg / L, the influent pH is controlled to 6-8, the stirring speed is controlled to 100-110 r / min, and the hydraulic retention time is 10-12 h, until the COD of the anaerobic reactor effluent is stable.

[0064] As a specific implementation, the specific process of step S3 includes the following steps:

[0065] S3.1: After adjusting the pH of the supernatant obtained in step S2 to 7-8, the supernatant is subjected to a primary anaerobic-aerobic treatment, a carbon source is added to the anaerobic section, aeration is performed in the aerobic section, and the dissolved oxygen content is controlled at 2-4 mg / L. Then, mud and water are separated to obtain a supernatant and sludge;

[0066] S3.2: The supernatant obtained in step S3.2 is subjected to secondary anaerobic-aerobic treatment using a mud-membrane mixing method. A carbon source is added to the anaerobic section, aeration is performed in the aerobic section, and the dissolved oxygen content is controlled to 2-4 mg / L. Membrane retention is performed, and then mud-water separation is performed to obtain supernatant and sludge.

[0067] As a specific implementation, the specific process of step S4 includes the following steps:

[0068] S4.1: The supernatant obtained in step S3 is subjected to coagulation reaction, and then mud-water separation is performed to obtain supernatant and sludge;

[0069] S4.2: Perform flotation treatment on the supernatant obtained in step S4.1.

[0070] Example 1

[0071] The physicochemical-biochemical method was used to treat high-concentration organic wastewater (COD 8160 mg / L) from a pharmaceutical factory. The steps are as follows:

[0072] S1: Preparation of anaerobic granular sludge:

[0073] S1.1: Activated carbon fiber was added to a 5.0 wt% ferric chloride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) at a mass volume ratio of 1 g:20 mL, stirred for 2 h, and then nitrogen was introduced to replace the air in the reaction vessel and the solution. Under ultrasonic action, a 1.5 wt% sodium borohydride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) was added dropwise at a rate of 2.5 mL / min. The masses of ferric chloride and sodium borohydride were controlled to be the same. After the addition was completed, the mixture was maintained for 30 min, and vacuum filtration was performed. The separated solid matter was washed with anhydrous ethanol and vacuum dried to obtain an nZVI-ACF composite material.

[0074] S1.2: Dissolve (2-aminoethyl)trimethylammonium chloride hydrochloride in water to prepare a 10 wt% (2-aminoethyl)trimethylammonium chloride solution; add the nZVI-ACF composite material to the (2-aminoethyl)trimethylammonium chloride solution at a mass volume ratio of 1 g:100 mL, introduce nitrogen to replace the air in the reaction vessel and the solution, stir at 75°C for 3 h, vacuum filter, wash the separated solid matter with water, and vacuum dry to obtain modified activated carbon fiber.

[0075] S1.3: Add the biochar to a 25 wt % nitric acid solution, stir at room temperature for 10 h, filter, wash the separated solid matter with water until neutral, and vacuum dry to obtain modified biochar.

[0076] S1.4: Add modified activated carbon fiber and modified biochar to water in a mass volume ratio of 1g:0.2g:5mL, adjust the pH to 7.2, and stir for 5 minutes to prepare a conductive dispersion; add flocculent sludge and conductive dispersion to the EGSB reactor, the amount of flocculent sludge added is 3 / 5 of the effective volume of the EGSB reactor, the mass ratio of flocculent sludge to modified activated carbon fiber is 1:0.3, and stir well.

[0077] S1.5: Dilute the high-concentration organic wastewater to a COD of 2000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 75 r / min and the HRT to 24 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater.

[0078] S1.6: Dilute the high-concentration organic wastewater to a COD of 4000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 105 r / min and the HRT to 12 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater and complete the cultivation of anaerobic granular sludge.

[0079] S2: After adjusting the pH of high-concentration organic wastewater to 8.0±1.0, PAM and PAC were added for coagulation reaction, and then mud-water separation was performed to obtain supernatant and sludge.

[0080] S3: After adjusting the pH of the supernatant obtained in step S2 to 7.0±1.0, steam heating it to 35±2.0°C, which meets the conditions for mesophilic anaerobic fermentation, and introducing it into the EGSB reactor to mix with anaerobic granular sludge for anaerobic mesophilic fermentation with an HRT of 48h. Then, mud and water separation is performed to obtain supernatant and sludge.

[0081] S4: After adjusting the pH of the supernatant obtained in step S3 to 7.5±0.5, a primary anaerobic-aerobic treatment is performed, a carbon source is added to the anaerobic section with an HRT of 33h, aeration is performed in the aerobic section and the dissolved oxygen content is controlled to 3±1mg / L with an HRT of 54h, and then mud and water separation is performed to obtain supernatant and sludge.

[0082] S5: The supernatant obtained in step S4 is subjected to secondary anaerobic-aerobic treatment by using a mud-membrane mixing method. A carbon source is added to the anaerobic section with an HRT of 12 h. Aeration is performed in the aerobic section and the dissolved oxygen content is controlled to 3±1 mg / L with an HRT of 14 h. Membrane retention is performed, and then mud-water separation is performed to obtain supernatant and sludge.

[0083] S6: adding PAM and PAC to the supernatant obtained in step S5 to perform a coagulation reaction, and then performing mud-water separation to obtain a supernatant and sludge;

[0084] S7: Perform flotation treatment on the supernatant obtained in step S6.

[0085] The process continues to operate according to steps S2-S7, and the COD of the effluent after flotation treatment is continuously monitored during the operation. The effluent COD is measured to be ≤110 mg / L within 0-15 days after stable operation.

[0086] Example 2

[0087] The high-concentration organic wastewater from a pharmaceutical factory (the same batch as in Example 1) was treated using a physicochemical-biochemical method, and the steps are as follows:

[0088] S1: Preparation of anaerobic granular sludge:

[0089] S1.1: Activated carbon fiber was added to a 6.0 wt% ferric chloride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) at a mass volume ratio of 1 g:25 mL, stirred for 1.5 h, and then nitrogen was introduced to replace the air in the reaction vessel and the solution. Under ultrasonic action, a 2.5 wt% sodium borohydride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) was added dropwise at a rate of 2.5 mL / min. The mass ratio of ferric chloride to sodium borohydride was controlled to be 1:0.5. After the addition was completed, it was maintained for 30 min, and vacuum filtration was performed. The separated solid matter was washed with anhydrous ethanol and vacuum dried to obtain an nZVI-ACF composite material.

[0090] S1.2: Dissolve (2-aminoethyl)trimethylammonium chloride hydrochloride in water to prepare a 16 wt% (2-aminoethyl)trimethylammonium chloride solution; add the nZVI-ACF composite material to the (2-aminoethyl)trimethylammonium chloride solution at a mass volume ratio of 1 g:90 mL, introduce nitrogen to replace the air in the reaction vessel and the solution, stir at 80°C for 2.5 h, vacuum filter, wash the separated solid matter with water, and vacuum dry to obtain modified activated carbon fiber.

[0091] S1.3: Add the biochar to a 20 wt % nitric acid solution, stir at room temperature for 12 h, filter, wash the separated solid matter with water until neutral, and vacuum dry to obtain modified biochar.

[0092] S1.4: Add modified activated carbon fiber and modified biochar to water in a mass volume ratio of 1g:0.5g:7.5mL, adjust the pH to 7.9, and stir for 3 minutes to prepare a conductive dispersion; add flocculent sludge and conductive dispersion to the EGSB reactor, the amount of flocculent sludge added is 3 / 5 of the effective volume of the EGSB reactor, the mass ratio of flocculent sludge to modified activated carbon fiber is 1:0.2, and stir well.

[0093] S1.5: Dilute the high-concentration organic wastewater to a COD of 2000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 80 r / min and the HRT to 20 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater.

[0094] S1.6: Dilute the high-concentration organic wastewater to a COD of 4000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 110 r / min and the HRT to 10 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater and complete the cultivation of anaerobic granular sludge.

[0095] S2: After adjusting the pH of high-concentration organic wastewater to 5.0±1.0, PAM and PAC are added for coagulation reaction, and then mud-water separation is performed to obtain supernatant and sludge.

[0096] S3: After adjusting the pH of the supernatant obtained in step S2 to 7.0±1.0, steam heating it to 35±2.0°C, which meets the conditions for mesophilic anaerobic fermentation, and introducing it into the EGSB reactor to mix with anaerobic granular sludge for anaerobic mesophilic fermentation with an HRT of 48h. Then, mud and water separation is performed to obtain supernatant and sludge.

[0097] S4: After adjusting the pH of the supernatant obtained in step S3 to 7.5±0.5, a primary anaerobic-aerobic treatment is performed, a carbon source is added to the anaerobic section with an HRT of 33h, aeration is performed in the aerobic section and the dissolved oxygen content is controlled to 3±1mg / L with an HRT of 54h, and then mud and water separation is performed to obtain supernatant and sludge.

[0098] S5: The supernatant obtained in step S4 is subjected to secondary anaerobic-aerobic treatment by using a mud-membrane mixing method. A carbon source is added to the anaerobic section with an HRT of 12 h. Aeration is performed in the aerobic section and the dissolved oxygen content is controlled to 3±1 mg / L with an HRT of 14 h. Membrane retention is performed, and then mud-water separation is performed to obtain supernatant and sludge.

[0099] S6: adding PAM and PAC to the supernatant obtained in step S5 to perform a coagulation reaction, and then performing mud-water separation to obtain a supernatant and sludge;

[0100] S7: Perform flotation treatment on the supernatant obtained in step S6.

[0101] The process continues in accordance with steps S2-S7, during which the COD of the effluent after flotation treatment is continuously monitored. The effluent COD is measured to be ≤122 mg / L within 0-15 days after stable operation.

[0102] Example 3

[0103] The high-concentration organic wastewater from a pharmaceutical factory (the same batch as in Example 1) was treated using a physicochemical-biochemical method, and the steps are as follows:

[0104] S1: Preparation of anaerobic granular sludge:

[0105] S1.1: Activated carbon fiber was added to a 1.5 wt% ferric chloride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) at a mass volume ratio of 1 g:15 mL, stirred for 2 h, and then nitrogen was introduced to replace the air in the reaction vessel and the solution. Under ultrasonic action, 0.5 wt% sodium borohydride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) was added dropwise at a rate of 2.5 mL / min. The mass ratio of ferric chloride to sodium borohydride was controlled to be 1:1.5. After the addition was completed, it was maintained for 20 min, and vacuum filtration was performed. The separated solid matter was washed with anhydrous ethanol and vacuum dried to obtain nZVI-ACF composite material.

[0106] S1.2: Dissolve (2-aminoethyl)trimethylammonium chloride hydrochloride in water to prepare an 8 wt% (2-aminoethyl)trimethylammonium chloride solution; add the nZVI-ACF composite material to the (2-aminoethyl)trimethylammonium chloride solution at a mass volume ratio of 1 g:100 mL, introduce nitrogen to replace the air in the reaction vessel and the solution, stir at 70°C for 3.5 h, vacuum filter, wash the separated solid matter with water, and vacuum dry to obtain modified activated carbon fiber.

[0107] S1.3: Add the biochar to a 25 wt % nitric acid solution, stir at room temperature for 8 h, filter, wash the separated solid matter with water until neutral, and vacuum dry to obtain modified biochar.

[0108] S1.4: Add modified activated carbon fiber and modified biochar to water in a mass volume ratio of 1g:1.25g:3.75mL, adjust the pH to 6.0, and stir for 10 minutes to prepare a conductive dispersion; add flocculent sludge and conductive dispersion to the EGSB reactor, the amount of flocculent sludge added is 3 / 5 of the effective volume of the EGSB reactor, the mass ratio of flocculent sludge to modified activated carbon fiber is 1:0.4, and stir well.

[0109] S1.5: Dilute the high-concentration organic wastewater to a COD of 2000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 70 r / min and the HRT to 22 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater.

[0110] S1.6: Dilute the high-concentration organic wastewater to a COD of 4000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 100 r / min and the HRT to 10 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater and complete the cultivation of anaerobic granular sludge.

[0111] S2: After adjusting the pH of high-concentration organic wastewater to 9.0±1.0, PAM and PAC were added for coagulation reaction, and then mud-water separation was performed to obtain supernatant and sludge.

[0112] S3: After adjusting the pH of the supernatant obtained in step S2 to 7.0±1.0, steam heating it to 35±2.0°C, which meets the conditions for mesophilic anaerobic fermentation, and introducing it into the EGSB reactor to mix with anaerobic granular sludge for anaerobic mesophilic fermentation with an HRT of 48h. Then, mud and water separation is performed to obtain supernatant and sludge.

[0113] S4: After adjusting the pH of the supernatant obtained in step S3 to 7.5±0.5, a primary anaerobic-aerobic treatment is performed, a carbon source is added to the anaerobic section with an HRT of 33h, aeration is performed in the aerobic section and the dissolved oxygen content is controlled to 3±1mg / L with an HRT of 54h, and then mud and water separation is performed to obtain supernatant and sludge.

[0114] S5: The supernatant obtained in step S4 is subjected to secondary anaerobic-aerobic treatment by using a mud-membrane mixing method. A carbon source is added to the anaerobic section with an HRT of 12 h. Aeration is performed in the aerobic section and the dissolved oxygen content is controlled to 3±1 mg / L with an HRT of 14 h. Membrane retention is performed, and then mud-water separation is performed to obtain supernatant and sludge.

[0115] S6: adding PAM and PAC to the supernatant obtained in step S5 to perform a coagulation reaction, and then performing mud-water separation to obtain a supernatant and sludge;

[0116] S7: Perform flotation treatment on the supernatant obtained in step S6.

[0117] The process continues in accordance with steps S2-S7, during which the COD of the effluent after flotation treatment is continuously monitored. The effluent COD is measured to be ≤114 mg / L within 0-15 days after stable operation.

[0118] Example 4

[0119] The high-concentration organic wastewater from a pharmaceutical factory (the same batch as in Example 1) was treated using a physicochemical-biochemical method, and the steps are as follows:

[0120] S1: Preparation of anaerobic granular sludge:

[0121] S1.1: Dissolve (2-aminoethyl)trimethylammonium chloride hydrochloride in water to prepare a 10 wt% (2-aminoethyl)trimethylammonium chloride solution; add activated carbon fiber to the (2-aminoethyl)trimethylammonium chloride solution at a mass volume ratio of 1 g:100 mL, introduce nitrogen to replace the air in the reaction vessel and the solution, stir at 75°C for 3 h, vacuum filter, wash the separated solid matter with water, and vacuum dry to obtain modified activated carbon fiber.

[0122] S1.2: Add the biochar to a 25 wt% nitric acid solution, stir at room temperature for 10 h, filter, wash the separated solid matter with water until neutral, and vacuum dry to obtain modified biochar.

[0123] S1.3: Add modified activated carbon fiber and modified biochar to water in a mass volume ratio of 1g:0.2g:5mL, adjust the pH to 7.2, and stir for 5 minutes to prepare a conductive dispersion; add flocculent sludge, conductive dispersion and nano-zero-valent iron to the EGSB reactor, the amount of flocculent sludge added is 3 / 5 of the effective volume of the EGSB reactor, the mass ratio of flocculent sludge, modified activated carbon fiber and nano-zero-valent iron is 1:0.27:0.03, and stir evenly.

[0124] S1.4: Dilute the high-concentration organic wastewater to a COD of 2000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 75 r / min and the HRT to 24 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater.

[0125] S1.5: Dilute the high-concentration organic wastewater to a COD of 4000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 105 r / min and the HRT to 12 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater and complete the cultivation of anaerobic granular sludge.

[0126] S2-S7: Same as steps S2-S7 in Example 1.

[0127] The process continues to operate according to steps S2-S7, and the COD of the effluent after flotation treatment is continuously monitored during the operation. The effluent COD is measured to be ≤293 mg / L within 0-15 days after stable operation.

[0128] Results: Example 1 demonstrated superior COD removal efficiency in high-concentration organic wastewater compared to Example 4, demonstrating that loading nano-zero-valent iron onto modified activated carbon fibers and then adding them to anaerobic granular sludge improves anaerobic biological treatment efficiency, compared to dispersing nano-zero-valent iron and modified activated carbon fibers into anaerobic granular sludge. This is because when nano-zero-valent iron is loaded onto modified activated carbon fibers, the modified activated carbon fibers and modified biochar form a conductive network that exists within the anaerobic granular sludge. Electrons provided by the nano-zero-valent iron can be transferred along this conductive network to anaerobic microorganisms attached to the activated carbon fibers and biochar. Simultaneously, hydrogen generated by the nano-zero-valent iron can be transferred along the pores within the anaerobic sludge particles to anaerobic microorganisms attached to the anaerobic sludge particles. This fully utilizes the electron-donating function of the nano-zero-valent iron, significantly improving anaerobic treatment efficiency.

[0129] Comparative Example 1

[0130] The high-concentration organic wastewater from a pharmaceutical factory (the same batch as in Example 1) was treated using a physicochemical-biochemical method, and the steps are as follows:

[0131] S1: Preparation of anaerobic granular sludge:

[0132] S1.1: Add flocculent sludge to the EGSB reactor, dilute the high-concentration organic wastewater to a COD of 2000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 75 r / min and the HRT to 24 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater.

[0133] S1.2: Dilute the high-concentration organic wastewater to a COD of 4000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 105 r / min and the HRT to 12 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater and complete the cultivation of anaerobic granular sludge.

[0134] S2-S7: Same as steps S2-S7 in Example 1.

[0135] The process continues to operate according to steps S2-S7, and the COD of the effluent after flotation treatment is continuously monitored during the operation. The effluent COD is measured to be ≤563 mg / L within 0-15 days after stable operation.

[0136] Comparative Example 2

[0137] The high-concentration organic wastewater from a pharmaceutical factory (the same batch as in Example 1) was treated using a physicochemical-biochemical method, and the steps are as follows:

[0138] S1: Preparation of anaerobic granular sludge:

[0139] S1.1: Activated carbon fiber was added to a 5.0 wt% ferric chloride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) at a mass volume ratio of 1 g:20 mL, stirred for 2 h, and then nitrogen was introduced to replace the air in the reaction vessel and the solution. Under ultrasonic action, a 1.5 wt% sodium borohydride solution (the solvent was an ethanol aqueous solution with a concentration of 30 vol%) was added dropwise at a rate of 2.5 mL / min. The masses of ferric chloride and sodium borohydride were controlled to be the same. After the addition was completed, the mixture was maintained for 30 min, and vacuum filtration was performed. The separated solid matter was washed with anhydrous ethanol and vacuum dried to obtain an nZVI-ACF composite material.

[0140] S1.2: Add nZVI-ACF composite material and biochar to water in a mass volume ratio of 1g:0.2g:5mL, adjust the pH to 7.2, and stir for 5 minutes to prepare a conductive dispersion; add flocculent sludge and conductive dispersion to the EGSB reactor, the amount of flocculent sludge added is 3 / 5 of the effective volume of the EGSB reactor, the mass ratio of flocculent sludge to nZVI-ACF composite material is 1:0.3, and stir evenly.

[0141] S1.5: Dilute the high-concentration organic wastewater to a COD of 2000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 75 r / min and the HRT to 24 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater.

[0142] S1.6: Dilute the high-concentration organic wastewater to a COD of 4000 mg / L, adjust the pH to 7.0±1.0, and pass it into the EGSB reactor. Control the stirring speed in the reactor to 105 r / min and the HRT to 12 h. Monitor the effluent COD. When the COD stabilizes, stop passing the wastewater and complete the cultivation of anaerobic granular sludge.

[0143] The process continues in accordance with steps S2-S7, during which the COD of the effluent after flotation treatment is continuously monitored. The effluent COD is measured to be ≤317 mg / L within 0-15 days after stable operation.

[0144] Result analysis: The removal effect of COD in high-concentration organic wastewater in Comparative Example 2 is better than that in Comparative Example 1, but lower than that in Example 1. This shows that compared with activated carbon fiber and biochar, the use of modified activated carbon fiber and modified biochar added to anaerobic sludge can improve the efficiency of anaerobic biological treatment to a greater extent. The reason is that the modified activated carbon fiber and modified biochar can utilize the opposite charges on their surfaces to combine through electrostatic attraction and exist in the form of a conductive network in the anaerobic granular sludge. During the anaerobic fermentation of wastewater, anaerobic microorganisms attach to the anaerobic granular sludge and the activated carbon fiber and biochar therein. The conductive network can promote interspecies electron transfer of microorganisms, thereby improving the efficiency of anaerobic treatment.

[0145] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0146] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A physicochemical-biochemical treatment method for high-concentration organic wastewater, characterized in that: The following steps are involved: S1: Physical and chemical pretreatment of high-concentration organic wastewater to initially remove suspended solids and total phosphorus; S2: After adjusting the pH of the wastewater treated in step S1 to 6-8, the wastewater is passed into an anaerobic reactor and mixed with anaerobic granular sludge for anaerobic fermentation, followed by sludge-water separation to obtain a supernatant and sludge; the anaerobic granular sludge contains a conductive network composed of modified activated carbon fibers and modified biochar, the surfaces of the modified activated carbon fibers and the modified biochar having positive and negative charges at a pH of 6-8, respectively, and the modified activated carbon fibers are loaded with nano-zero-valent iron; S3: After adjusting the pH of the supernatant obtained in step S2 to 7-8, performing anaerobic-aerobic treatment, and then performing mud-water separation to obtain supernatant and sludge; S4: performing physicochemical post-treatment on the supernatant obtained in step S3.

2. The physicochemical-biochemical treatment method according to claim 1, characterized in that: The preparation method of the anaerobic granular sludge comprises the following steps: (1) (2-aminoethyl)trimethylammonium chloride is grafted onto the surface of activated carbon fiber through a condensation reaction between carboxyl and amino groups to obtain modified activated carbon fiber; (2) Acid oxidation treatment of biochar to obtain modified biochar; (3) The modified biochar and modified activated carbon fiber are dispersed in water, the pH is adjusted to 6-8, and a conductive dispersion is prepared. The dispersion is then added to an anaerobic reactor together with flocculent sludge. After mixing, anaerobic granular sludge is cultured to form anaerobic granular sludge.

3. The physicochemical-biochemical treatment method according to claim 2, characterized in that: In step (3), the mass ratio of the flocculent sludge, modified activated carbon fiber and modified biochar is 1:0.2-0.4:0.05-0.

1.

4. The physicochemical-biochemical treatment method according to claim 2, characterized in that: In step (3), the specific process of culturing the anaerobic granular sludge includes the following steps: introducing organic wastewater with a COD of 1500-2000 mg / L and a pH of 6-8 into the anaerobic reactor, controlling the stirring speed to 70-80 r / min, and the hydraulic retention time to 20-24 h, until the COD of the anaerobic reactor effluent is stable, increasing the influent COD to 3000-4000 mg / L, controlling the influent pH to 6-8, the stirring speed to 100-110 r / min, and the hydraulic retention time to 10-12 h, until the COD of the anaerobic reactor effluent is stable.

5. The physicochemical-biochemical treatment method according to claim 2, characterized in that: Prior to step (1), nano-zero-valent iron is loaded on the activated carbon fiber. The specific process includes the following steps: after the activated carbon fiber is immersed in an iron salt or ferrous salt solution, a sodium borohydride solution is added dropwise thereto under the protection of an inert gas and the action of ultrasound to reduce trivalent or divalent iron to zero-valent iron, and the product is separated.

6. The physicochemical-biochemical treatment method according to claim 1, characterized in that: In step S2, the anaerobic reactor is an EGSB reactor.

7. The physicochemical-biochemical treatment method according to claim 1, characterized in that: The specific process of step S3 includes the following steps: S3.1: After adjusting the pH of the supernatant obtained in step S2 to 7-8, the supernatant is subjected to a primary anaerobic-aerobic treatment, followed by mud-water separation to obtain a supernatant and sludge; S3.2: The supernatant obtained in step S3.1 is subjected to secondary anaerobic-aerobic treatment and membrane retention by a mud-membrane mixing method, and then mud-water separation is performed to obtain supernatant and sludge.

8. The physicochemical-biochemical treatment method according to claim 1, wherein: The specific process of step S1 includes the following steps: adjusting the pH of the high-concentration organic wastewater to 3-11, performing a coagulation reaction, and then performing mud-water separation to obtain a supernatant and sludge.

9. The physicochemical-biochemical treatment method according to claim 1, characterized in that: The specific process of step S4 includes the following steps: S4.1: The supernatant obtained in step S3 is subjected to coagulation reaction, and then mud-water separation is performed to obtain supernatant and sludge; S4.2: Perform flotation treatment on the supernatant obtained in step S4.1.