Degradation-resistant wastewater treatment system

Abstract

The invention provides a degradation-resistant wastewater treatment system, which comprises: a chemical oxidation system, which comprises an acid adjusting tank, an electro-Fenton reaction tank, an alkali adding neutralization tank and a solid-liquid separation tank which are sequentially connected along a water flow direction; and the biochemical system comprises a denitration selection tank, an anaerobic tank, an anoxic tank, at least one aerobic tank and an eMBR membrane tank which are sequentially connected along the water flow direction. Compared with the prior art, the non-degradable wastewater treatment system has the advantages that the denitration selection tank is additionally arranged at the front end of the anaerobic tank, nitrite nitrogen returned by sludge is removed by using a raw water carbon source, the influence on the growth of phosphorus-accumulating bacteria is reduced, the phosphorus removal effect is improved, an anaerobic ammonia oxidation generation environment is created, and the denitrification effect of the system is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and more specifically, relates to a difficult-to-degrade wastewater treatment system. Background Art

[0002] Refractory wastewater generally refers to industrial wastewater generated during the production process of an enterprise that contains organic matter that is difficult to biodegrade. It has the characteristics of relatively high COD, low B / C ratio, high concentration of nitrogen and phosphorus pollutants, and difficulty in removing pollutants. The treatment process for refractory wastewater generally adopts the method of chemical oxidation + biochemical treatment. The principle is to first use chemical oxidation to oxidize the refractory organic matter into CO2 or small molecular organic matter that is easily biodegradable, and then remove pollutants such as carbon, nitrogen, and phosphorus in the wastewater through biochemical treatment methods.

[0003] At present, the most widely used chemical oxidation method is the Fenton oxidation method, which is based on the principle that hydrogen peroxide undergoes an oxidation reaction under the catalysis of ferrous ions to oxidize organic matter in water. However, the traditional Fenton oxidation method has the disadvantages of low reagent utilization rate (H2O2 utilization rate is about 40%-60%), large reagent usage, long process, high sludge production and high operating costs.

[0004] The biochemical treatment method in the treatment process of difficult-to-degrade wastewater is generally the AAO+MBR process. The MBR process has the advantages of less residual sludge, better operating effect, and stronger impact resistance. However, in order to ensure a better denitrification effect, the existing AAO technology needs to add more carbon sources to the system to ensure the progress of denitrification. The added carbon source is generally converted into a C / N ratio of 4:1-7:1, or even more. The MBR membrane must continue to be aerated in large quantities during operation, resulting in a high level of dissolved oxygen in the nitrification liquid return, destroying the anoxic environment of the anoxic tank and affecting the progress of denitrification; the return sludge contains nitrate nitrogen and high dissolved oxygen, which can affect the dominant growth of polyphosphate bacteria in the anaerobic tank, thereby affecting the phosphorus removal effect of the system, resulting in poor denitrification and phosphorus removal effects and high drug consumption costs. In addition, MBR membrane pollution will cause MBR membrane fouling and clogging, and cleaning is more frequent, resulting in a decrease in membrane flux. Frequent backwashing will also increase the consumption of chemicals and energy. Summary of the invention

[0005] The object of the present invention is to overcome at least one defect in the prior art and provide a difficult-to-degrade wastewater treatment system to improve the phosphorus removal and nitrogen removal effects.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides a difficult-to-degrade wastewater treatment system, which comprises:

[0007] A chemical oxidation system, comprising an acid conditioning tank, an electro-Fenton reaction tank, an alkali neutralization tank, and a solid-liquid separation tank, which are sequentially connected along the water flow direction; and

[0008] The biochemical system comprises a denitrification selection tank, an anaerobic tank, an anoxic tank, at least one aerobic tank, and an eMBR membrane tank which are sequentially connected along the water flow direction.

[0009] According to one embodiment of the non-degradable wastewater treatment system of the present invention, electrodes and a power supply are provided in the electro-Fenton reaction cell, and the electrodes include a graphite cathode and an iron anode.

[0010] According to one embodiment of the non-degradable wastewater treatment system of the present invention, an aeration pipe is provided at the bottom of the electro-Fenton reaction tank.

[0011] According to an embodiment of the non-degradable wastewater treatment system of the present invention, a stirrer is provided in the denitrification selection tank, the anaerobic tank, and the anoxic tank.

[0012] According to one embodiment of the non-degradable wastewater treatment system of the present invention, aeration pipes are arranged at the bottom of the at least one aerobic tank and the eMBR membrane tank.

[0013] According to an embodiment of the non-degradable wastewater treatment system of the present invention, the at least one aerobic tank comprises four aerobic tanks connected in sequence, and the number of aeration pipes arranged at the bottom of the four aerobic tanks decreases in sequence along the water flow direction.

[0014] According to one embodiment of the difficult-to-degrade wastewater treatment system of the present invention, a biological filter is provided in the aerobic tank adjacent to the anoxic tank, and a nitrification liquid reflux pump is provided in the aerobic tank adjacent to the eMBR membrane tank to return the nitrification liquid to the anoxic tank and the denitrification selection tank.

[0015] According to an embodiment of the non-degradable wastewater treatment system of the present invention, a solenoid valve is provided on the air inlet pipe of the at least one aerobic tank, and the dissolved oxygen in the aerobic tank is regulated by adjusting the solenoid valve.

[0016] According to an embodiment of the non-degradable wastewater treatment system of the present invention, the eMBR membrane pool is provided with an MBR membrane, an electrode and a power supply, wherein the electrode is made of activated carbon fiber.

[0017] According to one embodiment of the non-degradable wastewater treatment system of the present invention, a sludge return pump is provided in the eMBR membrane tank to return the activated sludge to the denitrification selection tank.

[0018] Compared with the prior art, the non-degradable wastewater treatment system of the present invention has the following beneficial technical effects:

[0019] 1. Improve the effect of nitrogen removal and phosphorus removal: The biochemical system adopts the improved activated sludge method, and the water enters the system in stages, so as to reasonably distribute the carbon source, reduce the competition for carbon source between nitrogen removal and phosphorus removal in the system, and reduce the consumption of reagents caused by adding external carbon source; add a denitrification selection tank unit at the front end of the anaerobic tank, and use the raw water carbon source to remove the nitrite nitrogen in the sludge return, reduce the impact on the growth of polyphosphate bacteria, improve the phosphorus removal effect, and create an environment for anaerobic ammonia oxidation to enhance the nitrogen removal effect of the system; the aerobic tank adopts the decreasing aeration technology, and the dissolved oxygen at the end is low, so the return of nitrification liquid has less impact on the anoxic environment in the anoxic tank, which can better maintain the anoxic environment required for denitrification, thereby improving the nitrogen removal effect.

[0020] 2. Save the cost of medicine consumption: Chemical oxidation adopts the electro-Fenton technology in the electro-oxidation technology. By applying electric current, H2O2 is generated at the cathode. At the same time, an iron electrode is introduced as the anode to generate ferrous ions online, thereby increasing the utilization rate of H2O2 (the utilization rate is 60% to 80%) and the output of ·OH, and reducing the dosage of the Fenton reaction reagents. The biochemical system adopts the technology of short-range nitrification and denitrification, so that the ammonia nitrogen in the sewage is only oxidized to nitrite nitrogen, and then the nitrite nitrogen is directly reduced to nitrogen gas, which reduces the consumption of organic matter in the denitrification process, thereby reducing the cost of reagents.

[0021] 3. High sludge concentration and strong impact resistance: The biochemical system adopts MBR technology, which can increase the sludge concentration of the system. At the same time, a biological filter is set at the front end of the aerobic tank to promote the attachment and growth of suspended microorganisms, thereby realizing the complementary advantages of the activated sludge method and the biofilm method.

[0022] 4. Significantly reduce the pollution of MBR membrane, high sludge activity, and ensure stable effluent: The MBR system adopts the electric-controlled membrane bioreactor technology (eMBR) in the electro-oxidation technology. By applying electrodes on both sides of the MBR membrane, the morphology and structure of the filter cake layer are electrochemically controlled to degrade the fouling substances, while rejecting the sludge particles and reducing the pollution of the MBR membrane. In addition, the appropriate current can stimulate the activity of organisms, and the electrolytic reaction between the electrodes can further remove pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following is a detailed description of the non-degradable wastewater treatment system and its technical effects in conjunction with the accompanying drawings and specific embodiments, wherein:

[0024] Figure 1 It is a structural schematic diagram of the difficult-to-degrade wastewater treatment system of the present invention.

[0025] Reference numerals:

[0026] Chemical oxidation system--10, acid adjustment tank--100, electro-Fenton reaction tank--102, alkali neutralization tank--104, solid-liquid separation tank--106;

[0027] Biochemical system--20, denitrification selection tank--200, anaerobic tank--202, anoxic tank--204, aerobic tank--206, eMBR membrane tank--208. DETAILED DESCRIPTION

[0028] In order to make the invention purpose, technical solution and technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described in this specification are only for explaining the present invention, not for limiting the present invention.

[0029] Please refer to Figure 1 As shown, the non-degradable wastewater treatment system of the present invention comprises:

[0030] The chemical oxidation system 10 includes: an acid adjustment tank 100, an electro-Fenton reaction tank 102, an alkali neutralization tank 104, and a solid-liquid separation tank 106; and

[0031] The biochemical system 20 includes, in order along the water flow direction: a denitrification selection tank 200, an anaerobic tank 202, an anoxic tank 204, at least one aerobic tank 206 and an eMBR membrane tank 208.

[0032] According to a preferred embodiment of the present invention, the chemical oxidation system 10 is an electro-Fenton reaction system, which includes an acid adjustment tank 100, an electro-Fenton reaction tank 102, an alkali neutralization tank 104, and a solid-liquid separation tank 106. The electro-Fenton reaction tank 106 is provided with electrodes and a power supply, wherein the cathode is a graphite electrode, the anode is an iron electrode, and an aeration pipe is provided at the bottom of the electro-Fenton reaction tank 106.

[0033] According to a preferred embodiment of the present invention, a stirrer is provided in the denitrification selection tank 200, the anaerobic tank 202, and the anoxic tank 204. At least one aerobic tank includes four aerobic tanks 206 connected in sequence (aerobic tank 1, aerobic tank 2, aerobic tank 3, and aerobic tank 4 shown in the figure). Aeration pipes are arranged at the bottom of the four aerobic tanks 206 and the eMBR membrane tank 208, and the number of aeration pipes arranged at the bottom of the four aerobic tanks 206 decreases in sequence along the water flow direction. Solenoid valves are respectively provided on the air inlet pipes of the aerobic tanks 206, and the dissolved oxygen in the aerobic tank is adjusted by adjusting the solenoid valves. The membrane flux of the eMBR tank 208 is 20-30L / m 2 h, the current density is set to 0-0.2 mA / cm 2 .

[0034] According to a preferred embodiment of the present invention, a biological filter is provided in the aerobic tank 206 (aerobic tank 1) adjacent to the anoxic tank 204, and microorganisms can attach to the biological filter and grow to form a layer of biofilm, thereby increasing the microbial biomass and sludge concentration of the system. A nitrification liquid return pump is provided in the aerobic tank 206 (aerobic tank 4) adjacent to the eMBR membrane tank 208 to return the nitrification liquid to the anoxic tank 204.

[0035] According to a preferred embodiment of the present invention, the eMBR membrane pool 208 is provided with an MBR membrane, an electrode and a power supply, wherein the electrode material is activated carbon fiber. In addition, a sludge return pump is provided in the eMBR membrane pool 208 to return the activated sludge to the denitrification selection pool 200.

[0036] The following combination Figure 1 , the treatment method of the difficult-to-degrade wastewater treatment system of the present invention is described in detail:

[0037] The refractory wastewater enters the acid adjustment tank 100 to adjust the pH value to 2-3;

[0038] The wastewater after pH adjustment then enters the electro-Fenton reaction tank 102, and the power is turned on. In the electro-Fenton reaction tank 102, H2O2 is produced at the cathode and ferrous ions are produced at the anode through electrolysis reaction, so that the Fenton reaction occurs in the electro-Fenton reaction tank 102, and a small amount of ferrous ions and hydrogen peroxide are added to assist. After the electro-Fenton oxidation reaction of the refractory wastewater, the refractory organic matter therein is decomposed into CO2 or small molecular biodegradable organic matter; wherein, the hydraulic retention time of the electro-Fenton reaction tank 102 is 1h, and the current density is 10mA / cm 2 -30 mA / cm 2 .

[0039] The wastewater flowing out of the electro-Fenton reaction tank 102 then enters the alkali neutralization tank 104, and after the pH is adjusted to neutral, enters the solid-liquid separation tank 106 for solid-liquid separation, and the clarified liquid after separation enters the subsequent biochemical system 20.

[0040] After the electro-Fenton reaction pretreatment, the wastewater is divided into two sections, one of which enters the denitrification selection tank 200, and the other enters the anaerobic tank 202. In the denitrification selection tank 200, microorganisms use the carbon source in the influent to perform short-range denitrification to remove nitrite nitrogen in the return sludge and the return nitrification liquid, reducing the impact on the subsequent polyphosphate bacteria, and then the wastewater flows into the anaerobic tank 202. In the anaerobic tank 202, the polyphosphate bacteria use the carbon source in the raw water to complete the phosphorus release reaction and form a dominant growth strain. When the phosphorus content in the influent is low, the return nitrite nitrogen can react with the ammonia nitrogen in the influent to undergo anaerobic ammonia oxidation to further remove total nitrogen.

[0041] Then the sewage enters the anoxic tank 204, where a short-range denitrification reaction occurs, reducing the nitrite nitrogen in the reflux nitrification liquid to nitrogen gas, thereby removing it from the system. At the same time, according to the concentration change of the influent carbon source, an appropriate amount of carbon source is added to the anoxic tank 204 to maintain the short-range denitrification. Agitators are provided in the denitrification selection tank 200, the anaerobic tank 202, and the anoxic tank 204 to fully mix the muddy water.

[0042] Then the wastewater enters the aerobic pool 206, which is divided into aerobic pool 1, aerobic pool 2, aerobic pool 3, and aerobic pool 4 according to the direction of water flow. By controlling the opening size of the air inlet valve of each aerobic pool 206 and the number of aeration pipes arranged at the bottom of the pool, the dissolved oxygen concentration in aerobic pool 1, aerobic pool 2, aerobic pool 3, and aerobic pool 4 is gradually reduced, so that the aerobic pool 206 mainly undergoes a short-range nitrification reaction, and ammonia nitrogen is only oxidized to nitrite nitrogen. Among them, a biological filter is provided in the aerobic pool 1, and microorganisms can attach to the biological filter and grow fixedly to form a biofilm, thereby increasing the microbial phase and microbial concentration in the system and enhancing the system's resistance to shock load. A nitrification liquid reflux pump is provided in the aerobic pool 4 to reflux the nitrification liquid to the denitrification selection pool 200 and the anoxic pool 204 for a short-range denitrification reaction.

[0043] The wastewater then enters the eMBR membrane pool 208, where the mixed liquid is separated into solid and liquid by the interception effect of the MBR membrane, and the clean water is extracted from the MBR membrane. At the same time, an electric field is applied to both ends of the MBR membrane pool to change the structure and chemical properties of the mud cake through the action of the electric field, thereby reducing the pollution of the MBR membrane. The electric field can stimulate the activity of microorganisms and increase the removal rate of carbon, nitrogen and phosphorus in the system. A sludge return pump is provided in the eMBR membrane pool 208 to return the sludge to the denitrification selection pool 200 at the front end.

[0044] It should be noted that in the above treatment method, the influent of the biochemical system 20 enters the denitrification selection tank 200 and the anaerobic tank 202 respectively, and the proportion of the influent to the total influent is 10%-30% and 90%-70% respectively, and the dissolved oxygen concentration of each aerobic tank 206 gradually decreases, among which, the dissolved oxygen in aerobic tank 1> the dissolved oxygen in aerobic tank 2> the dissolved oxygen in aerobic tank 3> the dissolved oxygen in aerobic tank 4, the dissolved oxygen concentration of aerobic tank 1 is 2mg / L-3mg / L, the dissolved oxygen concentration of aerobic tank 2 is 1.5mg / L-2mg / L, the dissolved oxygen concentration of aerobic tank 3 is 1mg / L-1.5mg / L, and the dissolved oxygen concentration of aerobic tank 4 is 0.5mg / L-1mg / L.

[0045] The aerobic pool 4 is provided with a nitrification liquid return pump, and the total nitrification liquid return ratio is 200%-300%. The nitrification liquid is returned to the denitrification selection pool 200 and the anoxic pool 204 respectively, wherein the return amount to the denitrification selection pool 200 accounts for 0%-15% of the total nitrification liquid return amount, and the return amount to the anoxic pool 204 accounts for 100%-85% of the total nitrification liquid return amount. The sludge concentration in the system is 4000mg / L, and the volume ratio of the total aeration gas volume per unit time to the sewage volume entering the system per unit time (i.e., the gas-water ratio) is 3-4:1. The TN removal rate of the biochemical system can reach 77%.

[0046] Combined with the above detailed description of the embodiments of the present invention, it can be seen that, compared with the prior art, the non-degradable wastewater treatment system of the present invention has the following beneficial technical effects:

[0047] 1. Improve the effect of nitrogen removal and phosphorus removal: The biochemical system 20 adopts the improved activated sludge method, and the water enters the system in stages, so as to reasonably distribute the carbon source, reduce the competition for carbon source between nitrogen removal and phosphorus removal in the system, and reduce the consumption of reagents caused by adding external carbon sources; a denitrification selection tank 200 is added at the front end of the anaerobic tank 202, and the raw water carbon source is used to remove the nitrite nitrogen in the sludge return flow, reduce the impact on the growth of polyphosphate bacteria, improve the phosphorus removal effect, and create an environment for anaerobic ammonia oxidation to enhance the nitrogen removal effect of the system; the aerobic tank 206 adopts the decreasing aeration technology, and the dissolved oxygen at the end is relatively low, so the return of the nitrified liquid has less impact on the anoxic environment in the anoxic tank 204, which can better maintain the anoxic environment required for denitrification, thereby improving the nitrogen removal effect.

[0048] 2. Save the cost of medicine consumption: Chemical oxidation adopts the electro-Fenton technology in the electro-oxidation technology. By applying electric current, H2O2 is generated at the cathode. At the same time, an iron electrode is introduced as the anode to generate ferrous ions online, thereby increasing the utilization rate of H2O2 (the utilization rate is 60% to 80%) and the output of ·OH, and reducing the dosage of the Fenton reaction reagents. The biochemical system 20 adopts the technology of short-range nitrification and denitrification, so that the ammonia nitrogen in the sewage is only oxidized to nitrite nitrogen, and then the nitrite nitrogen is directly reduced to nitrogen gas, which reduces the consumption of organic matter in the denitrification process, thereby reducing the cost of reagents.

[0049] 3. High sludge concentration and strong impact resistance: The biochemical system 20 adopts the MBR process, which can increase the sludge concentration of the system. At the same time, a biological filter is set at the front end of the aerobic tank 206 to promote the attachment and growth of suspended microorganisms, thereby realizing the complementary advantages of the activated sludge method and the biofilm method.

[0050] 4. Significantly reduce the pollution of MBR membrane, high sludge activity, and ensure stable effluent: The MBR system adopts the electric-controlled membrane bioreactor technology (eMBR) in the electro-oxidation technology. By applying electrodes on both sides of the MBR membrane, the morphology and structure of the filter cake layer are electrochemically controlled to degrade the fouling substances, while rejecting the sludge particles and reducing the pollution of the MBR membrane. In addition, the appropriate current can stimulate the activity of organisms, and the electrolytic reaction between the electrodes can further remove pollutants.

[0051] According to the above principles, the present invention can also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A system for treating refractory wastewater, characterized in that: include: A chemical oxidation system, which includes an acid adjustment tank, an electro-Fenton reaction tank, an alkali neutralization tank, and a solid-liquid separation tank which are sequentially connected along the water flow direction; as well as The biochemical system comprises a denitrification selection tank, an anaerobic tank, an anoxic tank, at least one aerobic tank, and an eMBR membrane tank which are sequentially connected along the water flow direction.

2. The non-degradable wastewater treatment system according to claim 1, characterized in that: The electro-Fenton reaction cell is provided with electrodes and a power supply, wherein the electrodes include a graphite cathode and an iron anode.

3. The non-degradable wastewater treatment system according to claim 1, characterized in that: An aeration pipe is arranged at the bottom of the electro-Fenton reaction tank.

4. The non-degradable wastewater treatment system according to claim 1, characterized in that: Agitators are arranged in the denitrification selection tank, the anaerobic tank and the anoxic tank.

5. The non-degradable wastewater treatment system according to claim 1, characterized in that: Aeration pipes are arranged at the bottom of the at least one aerobic tank and the eMBR membrane tank.

6. The non-degradable wastewater treatment system according to claim 1, characterized in that: The at least one aerobic tank comprises four aerobic tanks connected in sequence, and the number of aeration pipes arranged at the bottom of the four aerobic tanks decreases in sequence along the water flow direction.

7. The non-degradable wastewater treatment system according to claim 6, characterized in that: A biological filter is arranged in the aerobic pool adjacent to the anoxic pool, and a nitrification liquid reflux pump is arranged in the aerobic pool adjacent to the eMBR membrane pool to reflux the nitrification liquid to the anoxic pool and the denitrification selection pool.

8. The non-degradable wastewater treatment system according to claim 1, characterized in that: An electromagnetic valve is provided on the air inlet pipe of the at least one aerobic pool, and the dissolved oxygen in the aerobic pool is regulated by adjusting the electromagnetic valve.

9. The non-degradable wastewater treatment system according to claim 1, characterized in that: The eMBR membrane pool is provided with an MBR membrane, electrodes and a power supply, wherein the electrodes are made of activated carbon fibers.

10. The non-degradable wastewater treatment system according to claim 1, characterized in that: The eMBR membrane tank is provided with a sludge return pump to return the activated sludge to the denitrification selection tank.

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