Device for enhancing stability of aerobic granular sludge under action of macromolecular organic matters

Abstract

The invention discloses a device for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matters, and belongs to the technical field of biological treatment of sewage / wastewater. In order to solve the problems that granular sludge is long in forming time, easy to disintegrate, poor in stability and the like under the action of macromolecular organic matters, the invention provides a device for coupling iron electrolysis with an aerobic granular sludge reactor. According to the device, an iron electrolysis device is arranged in an aerobic granular sludge reactor, and the iron electrolysis device comprises an iron wire, a spiral titanium wire and a 1.5 V direct-current power supply. The iron wire and the spiral titanium wire are respectively arranged at the center and the inner wall of the aerobic granular sludge reactor and are respectively connected with the positive electrode and the negative electrode of a 1.5 V direct-current power supply, and the iron wire needs to be regularly polished. The hydrolysis process of macromolecular organic matters is promoted through the cooperation of the electric field and iron ions released by the anode, so that the biodegradability of the organic matters is improved, the storage process of polymers in microbial cells is facilitated, the sludge granulation time is shortened, and meanwhile, the stability of the granular sludge is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage / wastewater biological treatment, and relates to a device and method for strengthening the stability of aerobic granular sludge under the action of macromolecular organic matter. Background Art

[0002] Aerobic granular sludge (AGS) technology is a new type of sewage biological treatment technology that has emerged in recent years and is considered to be one of the most promising sewage biological treatment technologies. Different from traditional sewage biological treatment processes, AGS has a dense structure and an anaerobic / anoxic / aerobic microenvironment inside, which can achieve simultaneous removal of carbon, nitrogen and phosphorus, and does not require secondary sedimentation tanks and return facilities. The process flow is simplified, which can greatly save floor space, reduce operating energy consumption, and reduce carbon emissions.

[0003] At present, most of the research on AGS technology uses simple organic matter (such as sodium acetate, glucose, etc.) as the carbon source for influent. However, actual domestic sewage is mainly composed of macromolecular organic matter such as carbohydrates, proteins and lipids. These macromolecular organic matter needs to be hydrolyzed into small molecular substances before they can be used by microorganisms. The hydrolysis process is slow, which greatly affects the sludge granulation process and particle stability, and seriously hinders the actual promotion and application of AGS technology. Therefore, it is urgent to develop a method to enhance the stability of aerobic granular sludge under the action of macromolecular organic matter.

[0004] Studies have shown that iron electrolysis is beneficial to the formation and stability of AGS. On the one hand, the iron ions released from the anode can enhance the structural strength of the particles and contribute to the stability of AGS. At the same time, the electric field will stimulate the metabolism of microorganisms, increase the secretion of extracellular polymers (EPS), and promote the aggregation of microorganisms to form particles. However, previous studies mainly used simple organic matter as the influent substrate, and there are few reports on the use of iron electrolysis to enhance the stability of AGS under the action of macromolecular organic matter.

[0005] Patent publication number CN 109319924 A discloses a device and method for strengthening the aerobic sludge granulation process. The device and method promote the formation of AGS under the action of sodium acetate by using active iron as the anode and inert titanium as the cathode, and applying an external voltage of 0.8-1.5V. However, this device and method uses sodium acetate as the carbon source for the influent; and the reactor operation time is short, which is not enough to fully explain the effect of the device and method on the stability of AGS. Summary of the invention

[0006] The present invention aims to provide a device and method for using iron electrolysis to enhance the stability of aerobic granular sludge under the action of macromolecular organic matter, so as to solve the problems of long formation time and poor stability of aerobic granular sludge under the action of macromolecular organic matter, and realize the long-term and stable operation of the AGS system in actual sewage treatment.

[0007] To achieve the above object, the technical solution of the present invention is as follows: A device for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter, the device comprises a reactor body, an iron electrolysis unit, a water inlet unit, an aeration unit and a water outlet unit, wherein: The reactor body is an acrylic cylinder with an inner diameter of 85 mm, an effective height of 800 mm, and an effective volume of 4.5 L; The iron electrolysis unit includes an iron wire (3 mm in diameter and 800 mm in length) located in the center of the reactor body and a spiral titanium wire (3 mm in diameter and 100 mm in pitch) placed on the inner wall of the reactor; the iron wire and the spiral titanium wire are respectively connected to the positive and negative electrodes of a 1.5 V DC power supply; The water inlet unit includes a water inlet bucket and a peristaltic pump, and the water outlet of the peristaltic pump is connected to the water inlet located at the bottom of the reactor; The aeration unit comprises an aeration sand head, an aeration pump, and a rotor flowmeter. The aeration sand head is placed at the bottom of the reactor and is connected to the rotor flowmeter and the aeration pump in sequence. The water outlet unit comprises a water outlet bucket and a solenoid valve for controlling water outlet; the solenoid valve is installed in the middle of the reactor and connected to the water outlet.

[0008] The reactor operates in an intermittent mode with an operation cycle of 4 hours, including a water inlet phase of 120 minutes, an aeration phase of 85-110 minutes, a sedimentation phase of 5-30 minutes, and a water outlet phase of 5 minutes.

[0009] The volume exchange rate of the reactor is 50%; the hydraulic retention time is 8 hours; the pH of the inlet water is 7.5; and the aeration volume in the aeration stage is controlled by a rotor flowmeter to be 2.5 L / min.

[0010] The water outlet unit is controlled by a solenoid valve installed at 400mm.

[0011] Polish the wire regularly.

[0012] The present invention also protects a method for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter. The method uses the device, and the steps of the method are: inoculating activated sludge into a reactor, using artificial water with macromolecular organic matter as a carbon source as influent, and starting and operating the reactor.

[0013] The activated sludge was taken from the secondary sedimentation tank of Tianjin Beicang Sewage Treatment Plant, and the inoculation concentration was 3.7 g / L.

[0014] The inlet water formula is: sodium acetate 307 mg / L, protein 123 mg / L, starch 176 mg / L, ammonia nitrogen 60 mg / L, total phosphorus 10 mg / L, magnesium chloride 78.3 mg / L, calcium chloride 55.5 mg / L, sodium bicarbonate 500 mg / L, 1 mL trace element solution.

[0015] 1L trace element solution contains: 30gEDTA,1.5gFeCl3·6H2O,0.05gMnSO4·H2O,0.05g(NH4)6MoO 24 ·4H2O, 0.05gAlCl3, 0.03gKI, 0.03gCuCl2, 0.03gCoCl2·6H2O, 0.03gH3BO3 and 0.03gNiCl2.

[0016] A method for enhancing the stability of AGS using the above device comprises the following steps: (1) The activated sludge was inoculated in the reactor. The inoculated sludge was taken from the secondary sedimentation tank of Tianjin Beicang Wastewater Treatment Plant. The inoculated sludge concentration was 3.7 g / L. (2) Prepare the influent with macromolecular organic matter as carbon source, which is composed of 307 mg / L sodium acetate, 123 mg / L protein, 176 mg / L starch, 60 mg / L ammonia nitrogen, 10 mg / L total phosphorus, 78.3 mg / L magnesium chloride, 55.5 mg / L calcium chloride, 500 mg / L sodium bicarbonate and 1 mL trace element. 1L trace element solution contains 30 g EDTA, 1.5 g FeCl3·6H2O, 0.05 g MnSO4·H2O, 0.05 g (NH4)6MoO 24 ·4H2O, 0.05gAlCl3, 0.03gKI, 0.03gCuCl2, 0.03gCoCl2·6H2O, 0.03gH3BO3 and 0.03gNiCl2. And adjust the inlet water pH to 7.5.

[0017] (3) Start the reactor, which operates in intermittent mode with a cycle of 4 hours, including 120 minutes of water inlet, 85-110 minutes of aeration, 5-30 minutes of sedimentation and 5 minutes of water outlet. The hydraulic retention time is 8 hours and the volume exchange rate is 50%. Polish the wire regularly to prevent electrode passivation.

[0018] Compared with the prior art, the advantages of the present invention are: 1. The aerobic granular sludge cultivated in the present invention has a stable structure, can maintain high biomass, excellent sedimentation performance, high COD removal rate during long-term operation, and has moderate particle size, clear outline and smooth surface.

[0019] 2. The present invention enhances the biodegradability of macromolecular organic matter through iron-electric synergy, which can effectively promote the synthesis of intracellular polymers (poly-β-hydroxybutyric acid, PHB) by microorganisms, thereby enhancing the stability of aerobic granular sludge in long-term operation.

[0020] 3. The present invention improves the activity of microbial hydrolases through iron-electric synergy, enhances the secretion of redox active substances (cytochrome C and humic acid), promotes the redox cycle between Fe (II) / Fe (III), and thus effectively improves the electron transfer rate in the system, which is beneficial to the hydrolysis of macromolecular organic matter and its conversion into intracellular polymers.

[0021] 4. The aerobic granular sludge cultured in the present invention is enriched with functional bacteria such as Lactococcus, Tetrasphaera, and Trichococcus, and also inhibits the reproduction of filamentous bacteria (Herpetosiphon), which is conducive to the structural stability of the granular sludge.

[0022] 5. The device and method of the present invention have simple structure, are easy to operate and have low operating cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a schematic structural diagram of an aerobic granular sludge stability device under the action of macromolecular organic matter enhanced by iron electrolysis: wherein 1 is a reactor body, 2 is an iron wire, 3 is a spiral titanium wire, 4 is a DC power supply, 5 is a water inlet bucket, 6 is a peristaltic pump, 7 is a water inlet, 8 is an electromagnetic valve, 9 is an aeration sand head, 10 is a rotor flowmeter, 11 is an aeration pump, and 12 is a water outlet bucket.

[0024] Figure 2 is a granular sludge morphology diagram: wherein a, b, c, d are granular sludge morphology diagrams of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 1 when the operation is 120 days. bd, fh, jl, np are granular sludge morphology diagrams of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 1 when the operation is 200 days.

[0025] Figure 3 The changes in MLVSS concentration (a), granular sludge particle size (b), SVI5 value (c), and COD removal efficiency (d) of Examples 1, 2, and 3 compared with Example 1 are shown. DETAILED DESCRIPTION

[0026] The present invention provides a device and method for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter. In order to more clearly understand the characteristics and advantages of the present invention, the scheme of the present invention is further described below in conjunction with the accompanying drawings. More specific details are elaborated in the following description to facilitate a full understanding of the present invention.

[0027] Example 1 This embodiment provides a device and method for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter.

[0028] The device of this embodiment is as follows: like Figure 1 As shown, the main body of the device used in this embodiment is a cylindrical reactor 1 with an inner diameter of 100 mm and an effective height of 800 mm. An iron wire 2 with a diameter of 3 mm and a height of 800 mm is installed in the center of the reactor, and a spiral titanium wire 3 with a diameter of 3 mm and a pitch of 100 mm is installed on the inner wall of the reactor. The iron wire 2 and the spiral titanium wire 3 are respectively connected to the positive and negative electrodes of a 1.5 V DC power supply 4. The water enters from the water inlet bucket 5 through the peristaltic pump 6 at the water inlet 7 at the bottom of the reactor. The water outlet is controlled by a solenoid valve 8 installed at 400 mm. The aeration sand head 9 is located at the bottom of the reactor and is connected to a rotor flowmeter 10 and an aeration pump 11 in sequence.

[0029] The method steps of this embodiment are as follows: The activated sludge is inoculated into the reaction device, and the artificial water with macromolecular organic matter as the carbon source is used as the inlet water. The reactor is started and operated in an intermittent mode. Sludge and effluent samples are taken regularly to observe the physical and chemical properties of the sludge and the effluent COD concentration.

[0030] The inoculated sludge was taken from the secondary sedimentation tank sludge of Tianjin Beicang Sewage Treatment Plant, and the reactor inoculated sludge concentration was 3.7 g / L.

[0031] The influent composition is: sodium acetate 307 mg / L, protein 123 mg / L, starch 176 mg / L, ammonia nitrogen 60 mg / L, total phosphorus 10 mg / L, magnesium chloride 78.3 mg / L, calcium chloride 55.5 mg / L, sodium bicarbonate 500 mg / L, 1 mL trace element solution. 1 L of trace element solution contains 30 g EDTA, 1.5 g FeCl3·6H2O, 0.05 g MnSO4·H2O, 0.05 g (NH4)6MoO 24 ·4H2O, 0.05gAlCl3, 0.03gKI, 0.03gCuCl2, 0.03gCoCl2·6H2O, 0.03gH3BO3 and 0.03gNiCl2.

[0032] The operation cycle of the reaction device is 4 hours, and the operation parameters are: water inlet stage 120 minutes, aeration stage 85-110 minutes, precipitation stage 5-30 minutes, water outlet stage 5 minutes, reactor volume exchange rate 50%, hydraulic retention time 8 hours, water inlet pH 7.5, air flow rate in the aeration stage is controlled by rotor flowmeter to 2.5L / min. The iron wire is polished regularly to prevent electrode passivation.

[0033] The sampling position is arranged in the middle of the reactor.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that the reaction device is a traditional AGS reactor, and the iron electrolysis device including iron wire, spiral titanium wire and 1.5V DC power supply is not provided.

[0035] The device of this comparative example is as follows: The main body of the reaction device is a cylindrical reactor with an inner diameter of 100mm and an effective height of 800mm. The water enters the water inlet at the bottom of the reactor from the water inlet bucket through a peristaltic pump. The water outlet is controlled by a solenoid valve installed at 400mm. The aeration sand head is located at the bottom of the reactor and is connected to the rotor flowmeter and the aeration pump in sequence.

[0036] The method steps of this comparative example are as follows: The activated sludge is inoculated into the reaction device, and the artificial water with macromolecular organic matter as the carbon source is used as the inlet water. The reactor is started and operated in an intermittent mode. Sludge and effluent samples are taken regularly to observe the physical and chemical properties of the sludge and the effluent COD concentration.

[0037] The inoculated sludge was taken from the secondary sedimentation tank sludge of Tianjin Beicang Sewage Treatment Plant, and the reactor inoculated sludge concentration was 3.7 g / L.

[0038] The influent composition is: sodium acetate 307 mg / L, protein 123 mg / L, starch 176 mg / L, ammonia nitrogen 60 mg / L, total phosphorus 10 mg / L, magnesium chloride 78.3 mg / L, calcium chloride 55.5 mg / L, sodium bicarbonate 500 mg / L, 1 mL trace element solution. 1 L of trace element solution contains 30 g EDTA, 1.5 g FeCl3·6H2O, 0.05 g MnSO4·H2O, 0.05 g (NH4)6MoO 24 ·4H2O, 0.05gAlCl3, 0.03gKI, 0.03gCuCl2, 0.03gCoCl2·6H2O, 0.03gH3BO3 and 0.03gNiCl2.

[0039] The operation cycle of the reaction device is 4 hours, and the operation parameters are: water inlet stage 120 minutes, aeration stage 85-110 minutes, sedimentation stage 5-30 minutes, water outlet stage 5 minutes, reactor volume exchange rate is 50%, hydraulic retention time is 8 hours, water inlet pH is 7.5, and the air flow rate in the aeration stage is controlled by a rotor flowmeter to be 2.5L / min.

[0040] The sampling position is arranged in the middle of the reactor.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that iridium-plated titanium wire is used in the reaction device instead of the iron wire in Example 1.

[0042] The device of this comparative example is as follows: like Figure 1 As shown, the main body of the device used in this comparative example is a cylindrical reactor with an inner diameter of 100 mm and an effective height of 800 mm. An iridium-plated titanium wire with a diameter of 3 mm and a height of 800 mm is installed in the center of the reactor, and a spiral titanium wire with a diameter of 3 mm and a pitch of 100 mm is installed on the inner wall of the reactor. The iridium-plated titanium wire and the titanium wire are respectively connected to the positive and negative electrodes of a 1.5 V DC power supply. The inlet water enters from the water inlet bucket through the peristaltic pump at the water inlet at the bottom of the reactor, and the outlet water is controlled by a solenoid valve installed at 400 mm. The aeration sand head is located at the bottom of the reactor and is connected to the rotor flowmeter and the aeration pump in sequence.

[0043] The method steps of this comparative example are as follows: The activated sludge is inoculated into the reaction device, and the artificial water with macromolecular organic matter as the carbon source is used as the inlet water. The reactor is started and operated in an intermittent mode. Sludge and effluent samples are taken regularly to observe the physical and chemical properties of the sludge and the effluent COD concentration.

[0044] The inoculated sludge was taken from the secondary sedimentation tank sludge of Tianjin Beicang Sewage Treatment Plant, and the reactor inoculated sludge concentration was 3.7 g / L.

[0045] The influent composition is: sodium acetate 307 mg / L, protein 123 mg / L, starch 176 mg / L, ammonia nitrogen 60 mg / L, total phosphorus 10 mg / L, magnesium chloride 78.3 mg / L, calcium chloride 55.5 mg / L, sodium bicarbonate 500 mg / L, 1 mL trace element solution. 1 L of trace element solution contains 30 g EDTA, 1.5 g FeCl3·6H2O, 0.05 g MnSO4·H2O, 0.05 g (NH4)6MoO 24 ·4H2O, 0.05gAlCl3, 0.03gKI, 0.03gCuCl2, 0.03gCoCl2·6H2O, 0.03gH3BO3 and 0.03gNiCl2.

[0046] The operation cycle of the reaction device is 4 hours, and the operation parameters are: water inlet stage 120 minutes, aeration stage 85-110 minutes, sedimentation stage 5-30 minutes, water outlet stage 5 minutes, reactor volume exchange rate is 50%, hydraulic retention time is 8 hours, water inlet pH is 7.5, and the air flow rate in the aeration stage is controlled by a rotor flowmeter to be 2.5L / min.

[0047] The sampling position is arranged in the middle of the reactor.

[0048] Comparative Example 3 The difference between this comparative example and Example 1 is that the reaction device is not equipped with iron wire, titanium wire and 1.5V DC power supply, but additional Fe 2+ .Fe2+ The amount of addition is determined by calculation based on the current value in Example 1 and Faraday's law of electrolysis.

[0049] The device of this comparative example is as follows: The main body of the reaction device is a cylindrical reactor with an inner diameter of 100mm and an effective height of 800mm. The water enters through the water inlet at the bottom of the reactor through a peristaltic pump, and the water outlet is controlled by a solenoid valve installed at 400mm. The aeration sand head is located at the bottom of the reactor and is connected to the rotor flowmeter and the aeration pump in sequence.

[0050] The method steps of this comparative example are as follows: The activated sludge was inoculated into the reaction device, and artificial water with macromolecular organic matter as carbon source was used as influent, and Fe 2+ , start and operate the reactor in intermittent mode. Take sludge and effluent samples regularly to observe the physical and chemical properties of the sludge and the effluent COD concentration.

[0051] The inoculated sludge was taken from the secondary sedimentation tank sludge of Tianjin Beicang Sewage Treatment Plant, and the reactor inoculated sludge concentration was 3.7 g / L.

[0052] The influent composition is: sodium acetate 307 mg / L, protein 123 mg / L, starch 176 mg / L, ammonia nitrogen 60 mg / L, total phosphorus 10 mg / L, magnesium chloride 78.3 mg / L, calcium chloride 55.5 mg / L, sodium bicarbonate 500 mg / L, 1 mL trace element solution. 1 L of trace element solution contains 30 g EDTA, 1.5 g FeCl3·6H2O, 0.05 g MnSO4·H2O, 0.05 g (NH4)6MoO 24 ·4H2O, 0.05gAlCl3, 0.03gKI, 0.03gCuCl2, 0.03gCoCl2·6H2O, 0.03gH3BO3 and 0.03gNiCl2.

[0053] The operation cycle of the reaction device is 4 hours, and the operation parameters are: water inlet stage 120 minutes, aeration stage 85-110 minutes, sedimentation stage 5-30 minutes, water outlet stage 5 minutes, reactor volume exchange rate is 50%, hydraulic retention time is 8 hours, water inlet pH is 7.5, and the air flow rate in the aeration stage is controlled by a rotor flowmeter to be 2.5L / min.

[0054] The sampling position is arranged in the middle of the reactor.

[0055] Results: Figure 2 As shown in the figure, the granular sludge formed in Example 1 has a smooth surface and a clear outline. In contrast, the granular sludge formed in Comparative Examples 1, 2, and 3 has a fluffy structure, indicating the presence of a "finger-like" structure. Figure 3As shown, Example 1 has a high sludge concentration, good sedimentation performance, high COD removal efficiency, and remains stable after 200 days of operation in the reactor. In contrast, Comparative Examples 1, 2, and 3 all experienced varying degrees of sludge loss, excessive particle size growth, deterioration of sedimentation performance, and reduced COD removal efficiency. These results show that Example 1 achieves long-term and stable operation of aerobic granular sludge under the action of macromolecular organic matter, which is of great significance for the application of aerobic granular sludge technology in the field of treating actual domestic sewage.

[0056] Finally, it should be noted that the above embodiments are only implementation schemes for illustrating the present invention and should not be regarded as limiting the present method. The protection scope of the present invention should be the technical scheme recorded in the claims, including the equivalent replacement schemes of the technical features in the technical scheme recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A device for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter, characterized in that: The device comprises a reactor body, an iron electrolysis unit, a water inlet unit, an aeration unit and a water outlet unit, wherein: The reactor body is an acrylic cylinder with an inner diameter of 85 mm, an effective height of 800 mm, and an effective volume of 4.5 L; The iron electrolysis unit includes an iron wire located in the center of the reactor body and a spiral titanium wire placed on the inner wall of the reactor; the iron wire and the spiral titanium wire are respectively connected to the positive electrode and the negative electrode of a 1.5V DC power supply; the diameter of the iron wire is 3mm and the length is 800mm; the diameter of the spiral titanium wire is 3mm and the pitch is 100mm; The water inlet unit includes a water inlet bucket and a peristaltic pump, and the water outlet of the peristaltic pump is connected to the water inlet located at the bottom of the reactor; The aeration unit comprises an aeration sand head, an aeration pump, and a rotor flowmeter. The aeration sand head is placed at the bottom of the reactor and is connected to the rotor flowmeter and the aeration pump in sequence. The water outlet unit comprises a water outlet bucket and a solenoid valve for controlling water outlet; the solenoid valve is installed in the middle of the reactor and connected to the water outlet.

2. The device for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter according to claim 1, characterized in that: The reactor operates in an intermittent mode with an operation cycle of 4 hours, including a water inlet phase of 120 minutes, an aeration phase of 85-110 minutes, a sedimentation phase of 5-30 minutes, and a water outlet phase of 5 minutes.

3. The device for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter according to claim 1, characterized in that: The volume exchange rate of the reactor is 50%; the hydraulic retention time is 8h; the inlet pH is 7.5; and the aeration volume during the aeration stage is controlled by a rotor flowmeter to be 2.5L / min.

4. The device for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter according to claim 1, characterized in that: Polish the wire regularly.

5. A method for enhancing the stability of aerobic granular sludge under the action of macromolecular organic matter, characterized in that: The method uses the device described in any one of claims 1 to 4, and the steps of the method are: inoculating activated sludge into a reactor, using artificial water with macromolecular organic matter as a carbon source as influent, and starting and operating the reactor.

6. The method according to claim 5, characterized in that The activated sludge was taken from the secondary sedimentation tank of Tianjin Beicang Sewage Treatment Plant, and the inoculation concentration was 3.7 g / L.

7. The method according to claim 5, characterized in that The inlet water formula is: sodium acetate 307 mg / L, protein 123 mg / L, starch 176 mg / L, ammonia nitrogen 60 mg / L, total phosphorus 10 mg / L, magnesium chloride 78.3 mg / L, calcium chloride 55.5 mg / L, sodium bicarbonate 500 mg / L, 1 mL trace element solution.

8. The method according to claim 7, characterized in that 1L trace element solution contains 30 g of EDTA, 1.5 g of FeCl3·6H2O, 0.05 g of MnSO4·H2O, 0.05 g of (NH4)6MoO 24 ·4H2O, 0.05 g of AlCl3, 0.03 g of KI, 0.03 g of CuCl2, 0.03 g of CoCl2·6H2O, 0.03 g of H3BO3 and 0.03 g of NiCl2.

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