Device and method for treating coking wastewater by weak ultrasonic enhanced anoxic-membrane bioreactor

Abstract

The invention relates to a device and a method for treating coking wastewater by a weak ultrasonic enhanced anoxic-membrane bioreactor, and belongs to the field of coking wastewater treatment. The device comprises an anoxic reaction tank and a membrane bioreactor which are connected in series, a membrane plate is arranged in the membrane bioreactor, aeration strips are arranged on the two sides of the bottom of the membrane plate, and an ultrasonic vibration plate is arranged on the water outlet side and connected with an ultrasonic generator; a reflux pipeline is arranged outside the anoxic reaction tank and the membrane bioreactor, a reflux pump is arranged on the reflux pipeline, and reflux liquid flows into the anoxic reaction tank from the membrane bioreactor through the reflux pump; a membrane plate of the membrane bioreactor is connected with a water outlet tank through a water outlet pump, and treated water is discharged into the water outlet tank. According to the method disclosed by the invention, after ultrasonic waves are applied to the anoxic-membrane bioreactor device, the treatment effect of the biochemical effluent of the coking wastewater is improved under the conditions of proper sound energy density, action time and interval time.

Description

Technical Field

[0001] The invention belongs to the field of coking wastewater treatment, and in particular relates to a device and method for treating coking wastewater by using a weak ultrasound-enhanced anoxic-membrane bioreactor. Background Art

[0002] Coking wastewater contains a relatively high number of toxic and hazardous substances, making degradation difficult, and the concentrations of these harmful components vary. If untreated or improperly treated, coking wastewater is discharged into natural waterways, its high concentrations of pollutants and pungent odor can harm water, soil, the atmosphere, and human health. Ultrasonic water treatment technology is an advanced oxidation, incineration, and supercritical oxidation process. It offers the advantages of ease of operation and the absence of secondary pollution. It can be used alone or coupled with other processes, and has significant potential for application in water treatment. The membrane bioreactor, a process that combines membrane separation with activated sludge, surpasses traditional methods in effluent quality and efficiency. Its primary application areas include the treatment of industrial wastewater, such as coking wastewater, food processing wastewater, pharmaceutical wastewater, and chemical wastewater. It effectively removes pollutants such as organic matter, suspended solids, and heavy metal ions from wastewater, achieving standard discharge and resource utilization. Adding an anoxic end for denitrification and providing mixed liquor reflux to the front end of the membrane bioreactor can enhance the system's pollutant removal efficiency.

[0003] As weak ultrasound-enhanced wastewater treatment becomes a research hotspot, ultrasonic technology can be applied to the new water treatment process of anoxic-membrane bioreactor to improve the system's pollutant removal efficiency, coordinate sludge reduction and alleviate membrane fouling. Summary of the Invention

[0004] To achieve the above-mentioned objectives, the present invention provides a device and method for treating coking wastewater using an anoxic-membrane bioreactor using weak ultrasound. The present invention applies appropriate ultrasonic irradiation to the anoxic-membrane bioreactor process, which can significantly improve the degradation efficiency of effluent pollutants and provide technical guidance and theoretical basis for practical applications. After ultrasound is applied to the anoxic-membrane bioreactor device, the treatment effect of the biochemical effluent of the coking wastewater is improved under appropriate sound energy density, action time, and ultrasound interval time. The system's mixed liquor reflux ratio and sludge load are optimized, further improving the treatment effect of the coking wastewater.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A device for treating coking wastewater by weak ultrasound-enhanced anoxic-membrane bioreactor, comprising an anoxic reaction tank and a membrane bioreactor, wherein the anoxic reaction tank is connected to a water inlet tank via a water inlet pump, and the coking wastewater flows into the anoxic reaction tank via a water inlet. The anoxic reaction tank and the membrane bioreactor are connected in series and have water holes at the bottom.

[0007] The membrane bioreactor has a membrane plate on the water inlet side through a slot, aeration strips on both sides of the bottom of the membrane plate, and an ultrasonic vibration plate on the water outlet side, which is connected to an ultrasonic generator;

[0008] A reflux pipe is provided outside the anoxic reaction tank and the membrane bioreactor, and a reflux pump is provided on the reflux pipe to flow the reflux liquid from the membrane bioreactor into the anoxic reaction tank through the reflux pump;

[0009] The membrane plates of the membrane bioreactor are connected to the outlet tank through an outlet pump, and the treated water is discharged into the outlet tank.

[0010] Furthermore, a magnetic stirrer is provided in the anoxic reaction tank.

[0011] Furthermore, a submersible pump is provided near the membrane plate for stirring.

[0012] Furthermore, a pressure gauge is provided between the membrane plate of the membrane bioreactor and the outlet pump. The reading on the pressure gauge indicates the degree of membrane contamination, and the outlet pump adjusts the water output.

[0013] A method for treating coking wastewater by using a weak ultrasound-enhanced anoxic membrane bioreactor comprises the following steps:

[0014] 1) Coking wastewater enters the anoxic reaction tank through the water inlet pipe and water pump, and then enters the membrane bioreactor through the water hole;

[0015] 2) Maintain the coking sludge concentration in the anoxic reaction tank and membrane bioreactor at 3000-3500 mg / L, and the hydraulic retention time of the system at 24-48 hours;

[0016] 3) Start the aeration strip to flush the membrane plate;

[0017] 4) Start the reflux pump, control the mixed liquid reflux ratio to 200%, and return the mixed liquid in the membrane bioreactor to the anoxic reaction tank;

[0018] 5) Turn on the ultrasonic generator, maintain the acoustic energy density at 4.07-10.19 W / L, and ultrasonicate for 5-10 minutes.

[0019] 6) Turn off the ultrasonic generator, wait 48 hours, then turn it on again, maintaining the acoustic energy density at 4.07–10.19 W / L and the ultrasonic exposure time at 5–10 minutes, and repeat this cycle.

[0020] 7) Turn on the pressure gauge and water outlet pump to ensure that the diaphragm continuously discharges water.

[0021] Furthermore, in the step 2), the anoxic reaction tank and the membrane bioreactor contain a mixture of coking sludge and coking wastewater containing various nitrifying and denitrifying bacteria among Thauera, Thiobacillus, Pseudomonas, and Limnobacter.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention provides a weak ultrasound-enhanced anoxic membrane bioreactor device, which can provide a reference for engineering applications. This device can improve the degradation rate of organic matter in the biochemical effluent of coking wastewater. This invention regularly applies weak ultrasound to improve sludge properties and promote sludge reduction, with a reduction of 9.99% under optimal parameters. Ultrasound can also reduce membrane fouling by 18.40%. Ultrasound causes some damage to cell membranes, promotes microbial metabolism, increases sludge enzyme activity, promotes microbial community succession, and accelerates the degradation of pollutants in coking wastewater.

[0024] 2. It has been verified that the device of the present invention has improved removal rates of COD, ammonia nitrogen and total nitrogen in wastewater compared with the device without ultrasound application, and typical difficult-to-degrade organic matter such as phenols are almost completely degraded, confirming that the weak ultrasonic coupling device has a good deep treatment effect on difficult-to-degrade organic matter in wastewater.

[0025] 3. The device of the present invention can be used in the field of deep treatment of coking wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of the device of the present invention.

[0027] In the figure, 1. water inlet tank, 2. water inlet pump, 3. magnetic stirrer, 4. pressure gauge, 5. water outlet pump, 6. water outlet tank, 7. ultrasonic vibration plate, 8. ultrasonic generator, 9. reflux pump, 10. aeration strip, 11. slot, 12. anoxic reaction tank, 13. membrane plate, 14. membrane bioreactor, 15. water hole, 16. reflux liquid outlet, 17. reflux liquid inlet, 18. water inlet. DETAILED DESCRIPTION

[0028] The technical solutions and effects of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] In order to improve the degradation rate of pollutants in coking wastewater, the present invention provides a device and method for treating coking wastewater by using a weak ultrasound-enhanced anoxic-membrane bioreactor. The device and method combine weak ultrasound with anoxic-membrane bioreactor, and improve the degradation efficiency of pollutants in coking wastewater by regulating the ultrasonic sound energy density, ultrasonic time, and ultrasonic interval time.

[0030] The structure diagram of the device is as follows Figure 1 The following describes in detail the device and method for treating coking wastewater using a weak ultrasound-enhanced anoxic membrane bioreactor according to a specific embodiment of the present invention.

[0031] Example 1

[0032] like Figure 1 As shown, the device for treating coking wastewater by using weak ultrasound-enhanced anoxic-membrane bioreactor comprises an anoxic reaction tank 12 and a membrane bioreactor 14. The anoxic reaction tank 12 is connected to the water inlet tank 1 via a water inlet pump 2. The coking wastewater flows into the anoxic reaction tank 12 via a water inlet 18. The anoxic reaction tank 12 and the membrane bioreactor 14 are connected in series and are provided with a water hole 15 at the bottom.

[0033] The anoxic reaction tank 12 is provided with a magnetic stirrer 3;

[0034] The membrane bioreactor 14 has a membrane plate 13 on the water inlet side through a slot 11, aeration strips 10 are provided on both sides of the bottom of the membrane plate 13, and a submersible pump is provided near the membrane plate 13 for stirring; an ultrasonic vibration plate 7 is provided on the water outlet side, connected to an ultrasonic generator 8;

[0035] The anoxic reaction tank 12 and the membrane bioreactor 14 are externally provided with a reflux pipe, and a reflux pump 9 is provided on the reflux pipe. Specifically, a reflux liquid inlet 17 is provided on the water inlet side of the anoxic reaction tank 12, and a reflux liquid outlet 16 is provided on the water outlet side of the membrane bioreactor 14. The reflux liquid flows from the membrane bioreactor 14 into the anoxic reaction tank 12 through the reflux pump 9.

[0036] The membrane plates 13 of the membrane bioreactor 14 are connected to the water outlet tank 6 via the water outlet pump 5 , and the treated water is discharged into the water outlet tank 6 .

[0037] In this embodiment, a pressure gauge 4 is provided between the membrane plate 13 of the membrane bioreactor 14 and the outlet pump 5. The reading on the pressure gauge 4 indicates the degree of membrane fouling, and the outlet pump 5 adjusts the water output.

[0038] In this embodiment, the top of the anoxic reaction pool 12 is a sealed structure to maintain an anoxic environment inside.

[0039] As a specific embodiment, the anoxic reaction tank 12 and the membrane bioreactor 14 are integrated and made of organic glass material as a whole, with an effective volume of 7.2 L, a total height of 40 cm, a total width of 60 cm, a width of 15 cm for the anoxic reaction tank, a width of 45 cm for the membrane bioreactor, a membrane plate size of 25 cm × 10 cm, a reflux liquid outlet and a water hole for the anoxic reaction tank to flow into the membrane bioreactor 10 cm away from the bottom of the tank, a water inlet and a reflux liquid inlet 5 cm away from the top, and an outer diameter of 1 cm.

[0040] Example 2

[0041] This embodiment provides a method for treating coking wastewater by using a weak ultrasound-enhanced anoxic membrane bioreactor based on the apparatus of Example 1, comprising the following steps:

[0042] 1) Coking wastewater enters the anoxic reaction tank through the water inlet pipe and water pump, and then enters the membrane bioreactor through the water hole;

[0043] 2) Maintain the coking sludge concentration in the anoxic reaction tank and membrane bioreactor at 3000-3500 mg / L, and the hydraulic retention time of the system at 24-48 hours;

[0044] 3) Start the aeration strip to flush the membrane plate;

[0045] 4) Start the reflux pump, control the mixed liquid reflux ratio to 200%, and return the mixed liquid in the membrane bioreactor to the anoxic reaction tank;

[0046] 5) Turn on the ultrasonic generator, maintain the acoustic energy density at 4.07-10.19 W / L, and ultrasonicate for 5-10 minutes.

[0047] 6) Turn off the ultrasonic generator, and after 48 hours, turn it on again, maintaining the acoustic energy density at 4.07-10.19 W / L, and the ultrasonic action time at 5-10 minutes, and repeat this cycle. The ultrasonic frequency can be selected at 40 kHz.

[0048] 7) Turn on the pressure gauge and water outlet pump to ensure that the diaphragm continuously discharges water.

[0049] In this embodiment, in step 2), the anoxic reaction tank and the membrane bioreactor contain a mixture of coking sludge and coking wastewater containing various nitrifying and denitrifying bacteria of the species Thauera, Thiobacillus, Pseudomonas, and Limnobacter.

[0050] Example 3

[0051] This embodiment puts into practical use a device and method for treating coking wastewater using a weak ultrasound-enhanced anoxic-membrane bioreactor according to the embodiments 1 and 2.

[0052] The coking wastewater and coking sludge used in this example were from a coking plant in Pingdingshan City, Henan Province. The phenol concentration in the influent was 183.60 mg / L, the COD concentration was 821.95 mg / L, the ammonia nitrogen concentration was 39.24 mg / L, and the total nitrogen concentration was 59.77 mg / L.

[0053] The coking sludge concentration in the anoxic reaction tank and membrane bioreactor was set at 3596 mg / L. The dominant bacterial genera were Thiobacillus, Pseudomonas, Limnobacter, and Thauera, with relative abundances of 3.45%, 0.14%, 1.70%, and 3.82%, respectively. The hydraulic retention time of the system was 24 hours; the mixed liquor reflux ratio was 200%.

[0054] A parallel experiment was conducted to compare the conditions of not turning on ultrasound and setting the optimal ultrasound sound energy density, ultrasound time and interval time. Ultrasound was applied 10 times and run for 20 days. The specific indicators are shown in Table 1.

[0055] Test 1: Without ultrasound, after 2 days of purification, the effluent phenol concentration was 2.73 mg / L, COD concentration was 203.44 mg / L, ammonia nitrogen concentration was 23.68 mg / L, and total nitrogen concentration was 42.64 mg / L. The system ran continuously for 20 days.

[0056] Experiment 2: Without ultrasound, after 20 days of purification, the effluent phenol concentration was 1.69 mg / L, COD concentration was 166.25 mg / L, ammonia nitrogen concentration was 18.11 mg / L, and total nitrogen concentration was 34.11 mg / L.

[0057] Test 3: Ultrasound was turned on, the sound energy density was 10.19 W / L, the ultrasonic time was 10 minutes, the interval time was 48 hours, and it was repeated once; after 2 days of purification, the effluent phenol concentration was 2.53 mg / L, COD concentration was 192.48 mg / L, ammonia nitrogen concentration was 22.91 mg / L, and total nitrogen concentration was 40.69 mg / L, and it ran continuously for a total of 20 days.

[0058] Test 4: Ultrasound was turned on, the sound energy density was 10.19 W / L, the ultrasonic time was 10 minutes, the interval was 48 hours, and repeated 9 times; that is, after 20 days of purification, the effluent phenol concentration was 1.31 mg / L, COD concentration was 125.64 mg / L, ammonia nitrogen concentration was 15.64 mg / L, and total nitrogen concentration was 31.45 mg / L.

[0059] Table 1 Degradation rate of pollutants under different conditions

[0060]

[0061] In the present invention, the ultrasonic effect of the ultrasonic vibration plate does not act directly on the membrane plate, but acts downward on the mud-water mixture. The results show that the transmembrane pressure difference of the non-ultrasonicated group is 43.10 kPa, and the transmembrane pressure difference of the ultrasonicated group is 36.40 kPa. Ultrasound can still reduce the degree of membrane fouling by 18.40%; the sludge amount is reduced by 9.99% after ultrasound; the sludge enzyme activity is improved, the dehydrogenase activity increases from 410.40 μg / d / g to 493.70 μg / d / g, an increase of 28.95%, the nitrate reductase (NR) activity increases from 17.24 μmol / d / g to 22.90 μmol / d / g, and the nitrite reductase (NiR) activity increases from 49.92 μmol / d / g to 51.11 μmol / d / g.

[0062] Under weak ultrasound, the sludge structure loosens, and the clustered flocs accelerate pollutant degradation (Test 4 outperforms Test 2). The dominant bacterial genera in the system under weak ultrasound are Thauera, Thiobacillus, Pseudomonas, and Limnobacter, with relative abundances of 9.85%, 8.47%, 6.46%, and 3.02%, respectively. Compared to the non-ultrasounded group, the relative abundances of these genera were 6.84%, 5.45%, 3.32%, and 2.69%, respectively. The relative abundance of the dominant genera increased after weak ultrasound. In this invention, weak ultrasound simultaneously promotes the proliferation and metabolism of the dominant bacterial genera, which have the ability to coordinate the system's denitrification process. This invention can effectively improve pollutant degradation efficiency (Test 4 outperforms Test 2).

[0063] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A device for treating coking wastewater by using a weak ultrasound-enhanced anoxic membrane bioreactor, characterized in that: The device comprises an anoxic reaction tank and a membrane bioreactor. The anoxic reaction tank is connected to a water inlet tank via a water inlet pump. Coking wastewater flows into the anoxic reaction tank via a water inlet. The anoxic reaction tank and the membrane bioreactor are connected in series and have water holes at the bottom. The membrane bioreactor has a membrane plate on the water inlet side through a slot, aeration strips on both sides of the bottom of the membrane plate, and an ultrasonic vibration plate on the water outlet side, which is connected to an ultrasonic generator; A reflux pipe is provided outside the anoxic reaction tank and the membrane bioreactor, and a reflux pump is provided on the reflux pipe to flow the reflux liquid from the membrane bioreactor into the anoxic reaction tank through the reflux pump; The membrane plates of the membrane bioreactor are connected to the outlet tank through an outlet pump, and the treated water is discharged into the outlet tank.

2. The device for treating coking wastewater by weak ultrasound-enhanced anoxic-membrane bioreactor according to claim 1 is characterized in that: A magnetic stirrer is provided in the anoxic reaction tank.

3. The device for treating coking wastewater by weak ultrasound-enhanced anoxic-membrane bioreactor according to claim 1 is characterized in that: A submersible pump is provided near the membrane plate for stirring.

4. The device for treating coking wastewater by weak ultrasound-enhanced anoxic-membrane bioreactor according to claim 1, characterized in that: A pressure gauge is provided between the membrane plate of the membrane bioreactor and the outlet pump. The reading on the pressure gauge indicates the degree of membrane contamination, and the outlet pump adjusts the water output.

5. A method for treating coking wastewater by using a weak ultrasound-enhanced anoxic membrane bioreactor, characterized in that: The method comprises the following steps: 1) Coking wastewater enters the anoxic reaction tank through the water inlet pipe and water inlet pump, and then enters the membrane bioreactor through the water hole; 2) Maintain the coking sludge concentration in the anoxic reaction tank and membrane bioreactor at 3000-3500 mg / L, and the hydraulic retention time of the system at 24-48 hours; 3) Start the aeration strip to flush the membrane plate; 4) Start the reflux pump, control the mixed liquid reflux ratio to 200%, and return the mixed liquid in the membrane bioreactor to the anoxic reaction tank; 5) Turn on the ultrasonic generator, maintain the acoustic energy density at 4.07-10.19 W / L, and ultrasonicate for 5-10 minutes. 6) Turn off the ultrasonic generator, wait 48 hours, then turn it on again, maintaining the acoustic energy density at 4.07–10.19 W / L and the ultrasonic exposure time at 5–10 minutes, and repeat this cycle. 7) Turn on the pressure gauge and water outlet pump to ensure that the diaphragm continuously discharges water.

6. The method for treating coking wastewater by using weak ultrasound-enhanced anoxic membrane bioreactor according to claim 5, characterized in that: In the step 2), the anoxic reaction tank and the membrane bioreactor contain Thauera 、 Thiobacillus 、 Pseudomonas 、 Limnobacter A mixture of coking sludge and coking wastewater containing a variety of nitrifying and denitrifying bacteria.

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