Method for electrochemically treating semi-coke wastewater based on BDD electrode and application of method

Abstract

The invention discloses a method for electrochemically treating semi-coke wastewater based on a BDD electrode and application of the method, and the method comprises the following steps: S1, introducing the semi-coke wastewater into an oil removal section for oil removal to obtain semi-coke wastewater after crude separation; s2, introducing the semi-coke wastewater subjected to crude separation into an ammonia distillation dephenolization section, and sequentially carrying out deamination treatment and dephenolization treatment to obtain pretreated semi-coke wastewater; s3, the pretreated semi-coke wastewater is introduced into a BDD electrode anode chamber of an electrochemical oxidation section for electrolytic treatment, and electro-catalyzed semi-coke wastewater, acid liquor and alkali liquor are obtained; s4, alkalifying the semi-coke wastewater subjected to electro-catalysis by using alkali liquor, introducing the alkalified semi-coke wastewater into a biochemical section, and carrying out biochemical treatment to obtain wastewater meeting the discharge standard; the acid liquor and the alkali liquor in the step S3 are collected and used for acidification and alkalization treatment in the step S2 and the step S4. According to the method provided by the invention, the organic load of a biochemical system is reduced through electrochemical oxidation, and the BOD (Biochemical Oxygen Demand) in the wastewater is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and specifically relates to a method for electrochemically treating blue carbon wastewater based on a BDD electrode and an application thereof. Background Art

[0002] The composition of coal chemical semi-coke wastewater is complex, containing a large number of difficult-to-degrade and highly toxic pollutants. It is a typical industrial wastewater with high pollutant content and high difficulty in toxicity treatment. The green industrialization upgrade of the semi-coke industry will shift from decentralized distribution to centralized distribution in industrial parks. The centralized treatment of semi-coke wastewater will expand the scale of treatment. If the original treatment method cannot stably meet the standards, it needs to be treated with reverse osmosis membrane concentration, and the concentrated liquid is more difficult to treat, resulting in a sharp increase in treatment costs.

[0003] In the large-volume sewage treatment process, the biochemical method has the advantages of low investment and operation costs, good treatment effect, and strong sustainability. However, when treating wastewater containing high concentrations of organic matter, certain toxicity, and unstable water quality characteristics, it is difficult to stably treat and meet the standards. It is necessary to use advanced oxidation processes to strengthen the biochemical method so that its effluent can stably meet the standards.

[0004] Electrochemical oxidation is a relatively mild oxidation method, and most of the time, no additional reagents are required. Boron-doped diamond (BDD) electrodes have extremely high oxygen evolution potential and extremely wide electrochemical window, which can mineralize most organic matter in organic wastewater into carbon dioxide and water, and have excellent effects in treating organic wastewater that is difficult to biodegrade. However, due to the large amount of wastewater generated, high concentration of organic pollutants, and high total amount of organic matter treated, blue carbon wastewater requires a long electrolysis time, which makes the total power consumption of BDD electrodes when treating blue carbon wastewater higher. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for electrochemically treating blue carbon wastewater based on BDD electrodes. The method uses BDD electrodes for electrochemical treatment, which reduces the organic load of the biochemical system on the one hand, and recycles the acid and alkali generated by electrolysis to adjust the pH on the other hand, thereby reducing the salt content in the wastewater and improving its biodegradability.

[0006] The present invention also proposes the application of the above method.

[0007] According to a first aspect of the present invention, a method for electrochemically treating blue carbon wastewater based on a BDD electrode is proposed, the method comprising the following steps:

[0008] S1: introducing the semi-coke wastewater into the oil removal section for oil removal to obtain semi-coke wastewater after rough separation;

[0009] S2: introducing the semi-coke wastewater after the rough separation into the steam ammonia dephenolization section, and sequentially performing deamination treatment and dephenolization treatment to obtain pre-treated semi-coke wastewater; before the deamination treatment, alkalizing the semi-coke wastewater after the rough separation with alkali solution; before the dephenolization treatment, acidifying the semi-coke wastewater after the deamination treatment with acid solution;

[0010] S3: introducing the pretreated blue carbon wastewater into the BDD electrode anode chamber of the electrochemical oxidation section for electrolysis treatment to obtain electrocatalyzed blue carbon wastewater, acid solution and alkali solution;

[0011] S4: using alkaline solution to alkalize the electrocatalyzed blue carbon wastewater and introduce it into the biochemical section to obtain wastewater that meets the discharge standards after biochemical treatment;

[0012] The acid solution and the alkali solution in step S3 are collected and used in the acidification and alkalization treatments in steps S2 and S4.

[0013] In some embodiments of the present invention, the oil removal method in step S1 includes any one of gravity sedimentation oil separation, centrifugal separation oil removal, coagulation oil removal, acid precipitation oil removal, membrane separation oil removal and adsorption oil removal.

[0014] The main function of the oil removal section is to remove oil and suspended matter from the lignite wastewater. The oil removal treatment can prevent equipment damage and pipeline blockage; the oil removal treatment can also avoid interference with subsequent treatment processes. For example, in the biochemical section, oil substances will cover the surface of microorganisms, blocking the transfer of oxygen and nutrients, thereby inhibiting the activity of microorganisms.

[0015] In some embodiments of the present invention, the deamination treatment method in step S2 includes any one of distillation deamination, air stripping deamination, chemical precipitation deamination and gas membrane deamination.

[0016] In some embodiments of the present invention, the dephenolization treatment in step S2 includes any one of physical adsorption dephenolization, membrane separation dephenolization, chemical precipitation dephenolization and solvent extraction dephenolization.

[0017] In some embodiments of the present invention, the pH value of the blue carbon wastewater after the alkalization treatment in step S2 is 9-10.

[0018] In some embodiments of the present invention, the pH value of the blue carbon wastewater after the acidification treatment in step S2 is 2-4.

[0019] The deammoniation treatment can avoid the interference of high concentration of ammonia nitrogen on subsequent treatment processes. For example, the activity of microorganisms in the biochemical stage will be inhibited by ammonia nitrogen.

[0020] The dephenolization treatment can reduce the chemical oxygen demand (COD) of the blue carbon wastewater and improve the biodegradability of the blue carbon wastewater.

[0021] In some embodiments of the present invention, the pH value of the acid solution obtained in step S3 is less than 2.

[0022] In some embodiments of the present invention, the pH value of the alkaline solution obtained in step S3 is greater than 12.

[0023] The BDD electrode anode chamber in step S3 is an anode chamber in an electrochemical device with BDD as the anode and separated by a proton membrane. After being energized, it can directly degrade part of the organic pollutants in the semi-coke wastewater into CO2 and H2O, and the other part is oxidized into small molecular organic matter that is easily biodegradable.

[0024] In some embodiments of the present invention, the biochemical treatment method in step S4 includes any one of an activated sludge process, an aerated biological filter process and a membrane bioreactor process.

[0025] In some embodiments of the present invention, the pH value of the blue carbon wastewater after the alkalization treatment in step S4 is 7-8.

[0026] The biochemical treatment can remove organic pollutants in the lignite wastewater and significantly reduce the chemical oxygen demand and biochemical oxygen demand of the wastewater; compared with some physical and chemical treatment methods, biochemical treatment has cost advantages in large-scale treatment of lignite wastewater, and does not need to consume a large amount of chemicals and energy like some chemical oxidation processes, further saving treatment costs.

[0027] According to the second aspect of the present invention, a method according to the first aspect of the present invention is provided for treating organic wastewater which is difficult to biodegrade.

[0028] The present invention has at least the following beneficial effects:

[0029] The method for treating blue carbon wastewater provided by the present invention reduces the organic load of the biochemical system through BDD electrochemical oxidation, increases the BOD in the wastewater, and makes the operation of the biochemical system more stable; the method also uses a BDD proton membrane to separate the acid solution in the anode chamber and the alkali solution in the cathode chamber in the electrochemical device and further uses it to adjust the pH value in different treatment stages, thereby reducing the salt content in the wastewater and improving the biodegradability of the wastewater; the present invention does not need to add strong acids and alkalis, reduces the difficulty of operating and managing the wastewater treatment system, and reduces the cost of operating and managing the wastewater treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0031] Figure 1 This is a schematic flow chart of the method for electrochemically treating blue carbon wastewater based on BDD electrodes in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a method for electrochemically treating blue carbon wastewater based on BDD electrodes, and uses this method to treat blue carbon wastewater from a blue carbon production enterprise in Shenmu City. The initial water quality of the blue carbon wastewater includes: COD is 36730 mg / L, NH4 + The concentration is 4221 mg / L, the total nitrogen content (TN) is 4625 mg / L, the total dissolved solids (TDS) is 11100 mg / L, and the pH value is 9; the flow diagram of this method is as follows Figure 1 As shown, the specific steps include:

[0035] 1) Oil removal section: After the semi-coal wastewater is collected at the sewage treatment station, it first enters the oil removal section. After 2 days of gravity sedimentation and oil separation treatment, the semi-coal wastewater after rough separation is obtained, and its COD is reduced to 31940 mg / L and pH is 8;

[0036] 2) Ammonia evaporation and dephenolization stage: The semi-carbon wastewater obtained in step 1) is alkalized (alkaline solution is added to adjust the pH value to about 9.5) and then deaminated by a deammonification tower. At this time, the COD of the semi-carbon wastewater is reduced to 27130 mg / L, and the NH4 + The concentration dropped to 264 mg / L; the deaminated wastewater was then acidified (acid was added to adjust the pH value to about 3), and extracted and dephenolized through an extraction tower (the extractant was methyl isobutyl ketone) and a distillation tower to obtain pretreated semi-coke wastewater, whose COD dropped to 4386 mg / L and NH4 + The concentration dropped to 115 mg / L.

[0037] 3) Electrochemical oxidation section: The pretreated semi-carbon wastewater obtained in step 2) is introduced into the oxidation section of the BDD anode chamber. If the conductivity of the solution is lower than 3ms / cm, sodium sulfate needs to be added to improve the conductivity. The amount of sodium sulfate added is 3g / L (1-5g / L). The semi-carbon wastewater after electrocatalysis is obtained through BDD electrochemical oxidation treatment, and its COD is reduced to 2545mg / L, and the B / C ratio is increased from 0.21 of the extraction dephenolization effluent to 0.36;

[0038] In the electrochemical oxidation stage, part of the organic pollutants in the semi-carbon wastewater are directly degraded into CO2 and H2O in the anode chamber of the electrochemical device with BDD as anode and proton membrane as separator, and the other part is oxidized into small molecular organic matter that is easily biodegradable. In this stage of electrolysis, the anode chamber produces H + Acid solution is formed, and OH is produced in the cathode chamber - Forming alkaline solution, the pH value of the acid solution is less than 2, and the pH value of the alkaline solution is greater than 12, and the acid solution and alkaline solution collected here are used for acidification and alkalization in step 2) and step 4);

[0039] 4) Biochemical stage: Use alkali solution to adjust the pH value of the electrocatalyzed blue carbon wastewater obtained in step 3) to neutral (pH 7-8 is acceptable). After biochemical treatment, wastewater that meets the discharge standards is obtained, and its COD is reduced to 118 mg / L, and NH4 + The concentration dropped to 1mg / L, and TN dropped to 43mg / L, meeting the local discharge standards to the wastewater network (discharge standards are COD < 150mg / L, NH4 + <30mg / L, TN <50mg / L, pH 7~8).

[0040] Comparative Example 1

[0041] This comparative example provides a conventional treatment method for blue carbon wastewater, which specifically includes four steps of oil removal, distillation tower ammonia evaporation, extraction dephenolization pretreatment and biochemical degradation, which correspond to step 1), step 2) and step 4) in Example 1; dilute sulfuric acid and liquid alkali are used in the acidification and alkalization processes of this comparative example, respectively, and the blue carbon wastewater treated is the same as that in Example 1;

[0042] In this comparative example, the COD of the semi-carbon wastewater was reduced to 3362 mg / L and the NH4 + The concentration dropped to 93mg / L, and TN dropped to 323mg / L; the wastewater was then discharged into the sewage network after biochemical degradation treatment, COD dropped to 289mg / L, NH4 + The concentration dropped to 1 mg / L and TN dropped to 90 mg / L. The COD of the final treated wastewater was still higher than the local requirements for discharge into the sewage network, so additional sewage care fees were required.

[0043] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for electrochemically treating blue carbon wastewater based on BDD electrodes, characterized in that: The method comprises the following steps: S1: introducing the semi-coke wastewater into the oil removal section for oil removal to obtain semi-coke wastewater after rough separation; S2: introducing the semi-coke wastewater after the rough separation into the steam ammonia dephenolization section, and sequentially performing deamination treatment and dephenolization treatment to obtain pre-treated semi-coke wastewater; before the deamination treatment, alkalizing the semi-coke wastewater after the rough separation with alkali solution; before the dephenolization treatment, acidifying the semi-coke wastewater after the deamination treatment with acid solution; S3: introducing the pretreated blue carbon wastewater into the BDD electrode anode chamber of the electrochemical oxidation section for electrolysis treatment to obtain electrocatalyzed blue carbon wastewater, acid solution and alkali solution; S4: using alkaline solution to alkalize the electrocatalyzed blue carbon wastewater and introduce it into the biochemical section to obtain wastewater that meets the discharge standards after biochemical treatment; The acid solution and alkali solution in step S3 are collected and used in the acidification and alkalization treatments in steps S2 and S4.

2. The method according to claim 1, characterized in that The oil removal method in step S1 includes any one of gravity sedimentation oil separation, centrifugal separation oil removal, coagulation oil removal, acid precipitation oil removal, membrane separation oil removal and adsorption oil removal.

3. The method according to claim 1, characterized in that The deamination treatment method in step S2 includes any one of distillation deamination, air stripping deamination, chemical precipitation deamination and gas membrane deamination.

4. The method according to claim 1, characterized in that The dephenolization treatment method in step S2 includes any one of physical adsorption dephenolization, membrane separation dephenolization, chemical precipitation dephenolization and solvent extraction dephenolization.

5. The method according to claim 1, characterized in that The pH value of the blue carbon wastewater after the alkalization treatment in step S2 is 9-10.

6. The method according to claim 1, characterized in that The pH value of the blue carbon wastewater after the acidification treatment in step S2 is 2-4.

7. The method according to claim 1, characterized in that The pH value of the acid solution obtained in step S3 is less than 2; And / or, the pH value of the alkali solution obtained in step S3 is greater than 12.

8. The method according to claim 1, characterized in that The biochemical treatment method in step S4 includes any one of an activated sludge process, an aerated biological filter process and a membrane bioreactor process.

9. The method according to claim 1, characterized in that: The pH value of the blue carbon wastewater after the alkalization treatment in step S4 is 7-8.

10. Use of the method according to any one of claims 1 to 9 in the treatment of poorly biodegradable organic wastewater.

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