A sewage treatment method and sewage treatment equipment suitable for low carbon-nitrogen ratio water quality

Abstract

The present application relates to the field of wastewater treatment, in particular to a sewage treatment method and equipment suitable for low carbon-nitrogen ratio water quality, the sewage treatment method comprising the following steps: after the sewage with low carbon-nitrogen ratio water quality is subjected to physical and chemical treatment, the water quality and quantity thereof is adjusted, and then the sewage is sequentially delivered to a denitrification primary tank and a denitrification secondary tank to remove nitrate nitrogen; the C / N / P weight ratio of the effluent of the denitrification secondary tank is (95-105):(4-6):1; after the pH value of the effluent of the denitrification secondary tank is adjusted, the effluent is delivered to a biochemical system for hydrolysis, denitrification and aeration treatment; the effluent of the biochemical system is delivered to a buffer tank for treatment, the effluent of the buffer tank is filtered by MBR membrane, and the water filtered by the MBR membrane is discharged after monitoring and reaching the standard. The present application sets two-stage denitrification tanks before the biochemical system, removes part of phosphorus while removing nitrogen, helps the biochemical system to adjust the carbon-nitrogen ratio of the influent water quality, reduces the carbon source load of the biochemical system, improves the treatment efficiency of the biochemical system, and has the advantages of high efficiency, low cost and simple maintenance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, in particular to a sewage treatment method and sewage treatment equipment suitable for low carbon-nitrogen ratio water quality. BACKGROUND

[0002] The most common problem in the treatment of PCB wastewater, electroplating wastewater and other industrial wastewater is that it is difficult to reduce total nitrogen. Total nitrogen is usually divided into ammonia nitrogen and nitrate nitrogen. The current treatment process is to first convert ammonia nitrogen into nitrate nitrogen in the aerobic tank of the biochemical system, and then convert nitrate nitrogen into nitrogen gas in the anoxic tank of the biochemical system. The current anoxic tank consumes carbon source when converting nitrate nitrogen into nitrogen gas, and often has a problem of insufficient carbon source. In order to make the total nitrogen of the effluent meet the standard, carbon source needs to be added regularly. Since the amount of carbon source needs to be adjusted according to the water quality of the biochemical influent, the water quality of the biochemical influent will fluctuate in the actual treatment process, which makes it difficult to accurately control the amount of carbon source. Insufficient addition of carbon source can lead to excessive total nitrogen, and excessive addition of carbon source can lead to excessive COD. In the case of high effluent requirements, it is difficult to control both total nitrogen and COD within the standard. Therefore, the addition of carbon source is a major factor affecting the stability of the effluent water quality.

[0003] With the development of science and technology, there appears industrial wastewater with high nitrogen content, i.e. low carbon-nitrogen ratio. The increase of nitrogen content increases the speed of carbon source consumption, not only greatly increasing the treatment cost of the sewage plant, which is difficult for enterprises to bear, but also increasing the frequency of adding carbon source to the anoxic tank, which brings greater challenges to the stability of the effluent water quality. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a sewage treatment method and sewage treatment equipment suitable for low carbon-nitrogen ratio water quality. Two-stage denitrification tanks are arranged before the biochemical system to remove part of the phosphorus while denitrifying, help the biochemical system to adjust the carbon-nitrogen ratio of the influent water quality, not only reduce the carbon source load of the biochemical system and improve the treatment efficiency of the biochemical system, but also reduce the control difficulty of the carbon source addition amount and improve the stability of the effluent water quality, which has the advantages of high efficiency, low cost and simple maintenance.

[0005] The technical scheme of the present application is realized by the following way:

[0006] A sewage treatment method suitable for low carbon-nitrogen ratio water quality, comprising the following steps:

[0007] After the sewage with low carbon-nitrogen ratio water quality is treated by physical and chemical treatment, its water quality and quantity are adjusted, and then it is sequentially delivered to a denitrification first-stage tank and a denitrification second-stage tank to remove nitrate nitrogen. The C / N / P weight ratio of the effluent of the denitrification second-stage tank is (95-105):(4-6):1. The denitrification first-stage tank and the denitrification second-stage tank are sulfur autotrophic denitrification tanks.

[0008] After adjusting the pH value of the effluent of the denitrification secondary tank, the effluent is transported to a biochemical system for hydrolysis, denitrification and aeration treatment;

[0009] The effluent of the biochemical system is transported to a buffer tank for treatment, the effluent of the buffer tank is filtered by an MBR membrane, and the water filtered by the MBR membrane is discharged after monitoring.

[0010] The sewage treatment method suitable for low carbon-nitrogen ratio water quality provided by the application sets two-stage denitrification tanks before the biochemical system, removes part of the phosphorus while removing nitrogen, helps the biochemical system to adjust the carbon-nitrogen ratio of the influent water quality, not only reduces the carbon source load of the biochemical system, improves the treatment efficiency of the biochemical system, but also reduces the control difficulty of the carbon source addition amount, improves the stability of the effluent water quality, and has the advantages of high efficiency, low cost and simple maintenance.

[0011] Further, the pH value of the effluent of the denitrification secondary tank is adjusted to 8-9. Adjusting the pH value of the effluent of the denitrification secondary tank before entering the biochemical system to 8-9 is conducive to ensuring the high treatment efficiency of the biochemical system.

[0012] Further, the following steps are further included: detecting the pH value of the effluent of the denitrification primary tank, if the pH value of the effluent of the denitrification primary tank is ≤7, adding sodium carbonate or sodium bicarbonate to the denitrification primary tank, and stopping adding when the pH value of the effluent of the denitrification primary tank is 8-9. Ensuring that the pH of the water before entering the denitrification secondary tank is >7 is conducive to ensuring the overall nitrogen removal effect.

[0013] Further, two denitrification primary tanks are included, and the two denitrification primary tanks are arranged in parallel. Arranging two denitrification primary tanks is conducive to improving the treatment load and prolonging the maintenance period of the denitrification primary tank.

[0014] Further, the denitrification primary tank and the denitrification secondary tank use a sulfur autotrophic denitrification tank.

[0015] Further, the following steps are further included: transporting the nitrification liquid of the buffer tank to the biochemical system for denitrification and aeration treatment. Treating the nitrification liquid of the buffer tank reduces the generation of sewage.

[0016] Further, the following steps are further included: transporting the sludge of the buffer tank and the sludge filtered by the MBR membrane to the biochemical system for denitrification and aeration treatment. Re-treating the sludge generated in the treatment process is conducive to reducing the generation of sludge.

[0017] Further, the method further comprises the following steps: if the water filtered by the MBR membrane does not meet the monitoring standards, the water is transported to the denitrification secondary pool for treatment; if the nitrogen content in the low carbon-nitrogen ratio sewage is high, the total nitrogen after the system treatment is still over the standard, the sewage is transported to the denitrification secondary pool for re-treatment, so as to ensure that the total nitrogen meets the standard.

[0018] The application further provides a sewage treatment device suitable for the sewage treatment method for low carbon-nitrogen ratio water quality.

[0019] Further, the biochemical system comprises an anaerobic pool, an anoxic pool and an aerobic pool arranged in sequence, the anaerobic pool is used for hydrolysis treatment, the anoxic pool is used for denitrification treatment, and the aerobic pool is used for aeration treatment; the sludge output end of the buffer pool is communicated with the anoxic pool through a pipeline, and the nitrated liquid output end of the buffer pool is communicated with the anoxic pool through a pipeline; the sludge output end of the MBR membrane pool is communicated with the anoxic pool through a pipeline.

[0020] In order to better understand and implement, the application will be described in detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The process flow diagram of the sewage treatment method for low carbon-nitrogen ratio water quality is described in an embodiment of the application. DETAILED DESCRIPTION

[0022] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0023] The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the description of the application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It also will be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0024] The following description refers to the accompanying drawings. In the following description, same numbers represent similar features that have a similar function and / or structure. The following embodiments described below are merely exemplary embodiments in accordance with the present application. Rather, they are only examples of apparatus and methods in accordance with some aspects of the present application as detailed in the appended claims. In the description of the application, it should be understood that the terms "first", "second", "third", etc., merely identify similar objects, and are not necessarily intended to indicate a specific sequential or chronological order, or a relative importance of such objects. The specific meanings of the above terms in the present application can be understood according to the specific circumstances by those of ordinary skill in the art.

[0025] Furthermore, in the description of the application, "a plurality of" means two or more, unless otherwise specified. "And / or", which describes the association relationship of associated objects, means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0026] It should be understood that the embodiments of the present application are not limited to the precise structures described and shown in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the embodiments of the present application is only limited by the appended claims.

[0027] Please refer to Figure 1 As an embodiment of the present application, the present embodiment provides a sewage treatment method suitable for low carbon-nitrogen ratio water quality, comprising the following steps:

[0028] After the sewage with low carbon-nitrogen ratio water quality is subjected to physical and chemical treatment, its water quality and quantity are adjusted, and then it is sequentially delivered to a denitrification primary tank and a denitrification secondary tank to remove nitrate nitrogen; the C / N / P weight ratio of the effluent of the denitrification secondary tank is (95-105):(4-6):1; the denitrification primary tank and the denitrification secondary tank are sulfur autotrophic denitrification tanks;

[0029] After adjusting the pH value of the effluent of the denitrification secondary tank, it is delivered to a biochemical system for hydrolysis, denitrification and aeration treatment;

[0030] The effluent of the biochemical system is transported to a buffer pool for treatment, the effluent of the buffer pool is filtered by an MBR membrane, and the water filtered by the MBR membrane is discharged after monitoring.

[0031] Further, the pH value of the effluent of the denitrification secondary pool is adjusted to 8-9.

[0032] Further, the following steps are further included: detecting the pH value of the effluent of the denitrification primary pool, if the pH value of the effluent of the denitrification primary pool is ≤7, adding sodium carbonate or sodium bicarbonate to the denitrification primary pool, and stopping adding when the pH value of the effluent of the denitrification primary pool is 8-9.

[0033] Further, two denitrification primary pools are included, and the two denitrification primary pools are arranged in parallel.

[0034] Further, the denitrification primary pool and the denitrification secondary pool adopt a sulfur autotrophic denitrification pool.

[0035] Further, the following steps are further included: transporting the nitrification liquid of the buffer pool to the biochemical system for denitrification and aeration treatment.

[0036] Further, the following steps are further included: transporting the sludge of the buffer pool and the sludge filtered by the MBR membrane to the biochemical system for denitrification and aeration treatment.

[0037] Further, the following steps are further included: if the water filtered by the MBR membrane does not meet the monitoring standards, transporting to the denitrification secondary pool for treatment. If the nitrogen content in the low carbon-nitrogen ratio water quality sewage is very high, resulting in that the total nitrogen is still over standard after system treatment, the sewage is input into the denitrification secondary pool for re-treatment to ensure that the total nitrogen meets the standards.

[0038] The application also provides a sewage treatment device suitable for the sewage treatment method of any one of the above, which comprises a biochemical intermediate water pool, a denitrification primary pool, a denitrification secondary pool, a pH adjusting pool, a biochemical system, a buffer pool, an MBR membrane pool and a discharge monitoring pool arranged in sequence, the biochemical intermediate water pool contains the low carbon-nitrogen ratio water quality sewage after physical and chemical treatment and adjusts the water quality and quantity thereof; the pH adjusting pool is used for adjusting the pH value of the effluent of the denitrification secondary pool to 8-9; the MBR membrane pool is provided with an MBR membrane for filtering the effluent of the buffer pool; the sludge output end of the buffer pool is communicated with the part of the biochemical system for denitrification treatment through a pipeline, the nitrification liquid output end of the buffer pool is communicated with the part of the biochemical system for denitrification treatment through a pipeline; the sludge output end of the MBR membrane pool is communicated with the part of the biochemical system for denitrification treatment through a pipeline; and the filtrate output end of the MBR membrane pool is also communicated with the denitrification secondary pool through a pipeline.

[0039] Further, the biochemical system comprises an anaerobic tank, an anoxic tank and an aerobic tank arranged in sequence, the anaerobic tank is used for hydrolysis treatment, the anoxic tank is used for denitrification treatment, and the aerobic tank is used for aeration treatment; the sludge output end of the buffer tank is communicated with the anoxic tank through a pipeline, and the nitrification liquid output end of the buffer tank is communicated with the anoxic tank through a pipeline; and the sludge output end of the MBR membrane tank is communicated with the anoxic tank through a pipeline.

[0040] The physical property index and the test method thereof in the embodiment of the application are as follows:

[0041] COD is detected by the dichromate reflux method (HJ 828-2017);

[0042] TN is detected by the alkaline potassium persulfate digestion ultraviolet spectrophotometry method (HJ 636-2012);

[0043] TP is detected by the ammonium molybdate spectrophotometry method (GB 11893-1989).

[0044] Example 1

[0045] Please refer to Figure 1 The embodiment provides a sewage treatment method suitable for low carbon-nitrogen ratio water quality, which is used for treating the sewage with low carbon-nitrogen ratio water quality of an electronic circuit industrial park, and is operated for 24 hours per day, and the water treatment capacity is 15 t / h; after the system is operated stably, the operation data are continuously detected for about 3 months; the water quality of the sewage with low carbon-nitrogen ratio is continuously detected, and the detection result shows that the COD of the sewage with low carbon-nitrogen ratio is between 300 mg / L and 500 mg / L, the TN is between 150 mg / L and 200 mg / L, and the TP is between 6 mg / L and 15 mg / L; the sewage treatment method suitable for low carbon-nitrogen ratio water quality comprises the following steps:

[0046] After the sewage is subjected to physical and chemical treatment, the sewage is transported to a biochemical intermediate tank; after the water quantity and the concentration are adjusted in the biochemical intermediate tank, the sewage is transported to a denitrification primary tank for treatment; the denitrification primary tank is used for removing nitrate nitrogen; the denitrification primary tank in the embodiment is a sulfur autotrophic denitrification tank; two denitrification primary tanks are arranged in parallel in the embodiment; the effluent of the biochemical intermediate tank is transported to the two denitrification primary tanks for treatment; and the effluent of the two denitrification primary tanks is transported to the same denitrification secondary tank.

[0047] The effluent pH value of the denitrification primary tank is detected, and if the effluent pH value of the denitrification primary tank is less than or equal to 7, sodium bicarbonate solution is added to the denitrification primary tank, and when the effluent pH value of the denitrification primary tank is 8-9, the addition of sodium bicarbonate solution is stopped, and the denitrification secondary tank is used for removing residual nitrate nitrogen, and the denitrification secondary tank in the embodiment is a sulfur autotrophic denitrification tank; after passing through the denitrification primary tank and the denitrification secondary tank, the total nitrogen in the water is mainly composed of ammonia nitrogen, and the total nitrogen concentration is greatly reduced as a whole, and since the denitrification primary tank and the denitrification secondary tank contain phosphorus accumulating organisms, and the substances dissolved from the filter material can also react with part of the phosphorus-containing substances, part of the phosphorus in the water can also be removed; the water quality of the effluent of the denitrification secondary tank in the embodiment is continuously detected, and the detection results show that the COD is between 290 mg / L and 450 mg / L, the TN is between 60 mg / L and 90 mg / L, the TP is between 5 mg / L and 8 mg / L, the weight ratio of C / N / P is close to 100:5:1, the carbon source load of the biochemical system is greatly reduced, and the treatment efficiency is improved.

[0048] The effluent of the denitrification secondary tank is transported to the pH adjusting tank, and the pH in the pH adjusting tank is adjusted to 8-9 to ensure that the microorganisms in the subsequent ecological system can better play their roles;

[0049] The effluent of the pH adjusting tank is transported to the biochemical system, and the ecological system in the embodiment includes an anaerobic tank, an anoxic tank and an aerobic tank arranged in sequence, that is, the effluent of the pH adjusting tank is transported to the anaerobic tank, the anoxic tank and the aerobic tank in sequence for treatment, wherein the anaerobic tank mainly plays a hydrolysis role and is used for hydrolyzing macromolecules in wastewater into small molecules; the anoxic tank in the embodiment is a heterotrophic denitrification tank and mainly plays a denitrification role to remove nitrate nitrogen, and part of the phosphorus is used by the microorganisms themselves through metabolic action; the aerobic tank is composed of an aeration system and aerobic microorganisms (including aerobic microorganisms that convert ammonia nitrogen into nitrate nitrogen or nitrite nitrogen and phosphorus accumulating organisms), and plays a role in removing ammonia nitrogen and phosphorus in wastewater;

[0050] The effluent of the aerobic tank is transported to the buffer tank, and the buffer tank is provided with a sludge discharge system and mainly plays a buffering and sedimentation separation role to preliminarily separate sludge and water, part of the supernatant will continuously return to the anoxic tank in the form of nitrated liquid through a pipeline, and the other part of the supernatant will enter the MBR tank through a pipeline, and the sludge will continuously return to the anoxic tank through a pipeline; the setting of the buffer tank can reduce the sludge and suspended solids in the supernatant entering the MBR tank, thereby reducing the membrane blockage of the MBR tank and reducing the cleaning frequency of the MBR tank;

[0051] The effluent of the buffer pool is transported to the MBR membrane pool, the sludge filtered by the MBR membrane pool is continuously backflowed to the anoxic pool through a pipeline for treatment, and the effluent of the MBR membrane pool is discharged to the discharge monitoring pool. When the SV30 concentration of the sludge of the embodiment is too high (greater than 35%), sludge is discharged.

[0052] After the sewage is treated by the sewage treatment method suitable for low carbon-nitrogen ratio water quality of the embodiment, the effluent water quality meets the urban sewage discharge level A standard, in which the COD is between 20 mg / L and 25 mg / L, the TN is between 4 mg / L and 10 mg / L, and the TP is between 0.1 mg / L and 0.2 mg / L.

[0053] The sewage treatment method suitable for low carbon-nitrogen ratio water quality of the embodiment has the advantages of high efficiency, low cost, simple maintenance, no sludge production in the denitrification process, simultaneous phosphorus removal, help to load adjustment of the biochemical system, and ensuring that the total nitrogen of the effluent can meet the standard. On the other hand, since the two-stage sulfur autotrophic denitrification is pre-positioned and is taken over by the biochemical system, the release of excess reducing substances from the filler under the condition of low total nitrogen concentration of the influent can be effectively prevented, which directly enters the discharge monitoring pool without being utilized, resulting in high COD detection value.

[0054] In other embodiments, if the ammonia nitrogen of the effluent of the denitrification secondary pool is very high, resulting in that the total nitrogen after treatment by the biochemical system still cannot meet the standard, the effluent of the MBR pool is not discharged to the discharge monitoring pool, but is pumped to the denitrification secondary pool by a backflow pump for re-treatment.

[0055] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, and the present application also intends to include these modifications and improvements.

Claims

1. A sewage treatment method suitable for low carbon-nitrogen ratio water quality, characterized by, The method comprises the following steps: The wastewater with low carbon-nitrogen ratio is treated by physical and chemical methods, and then the water quality and quantity are adjusted, and the wastewater is sequentially delivered to a denitrification first tank and a denitrification second tank to remove nitrate nitrogen; the C / N / P weight ratio of the effluent of the denitrification second tank is (95-105):(4-6):1; the denitrification first tank and the denitrification second tank are sulfur autotrophic denitrification tanks; After the pH value of the effluent of the denitrification second tank is adjusted, the effluent is delivered to a biochemical system for hydrolysis, denitrification and aeration treatment; The effluent of the biochemical system is delivered to a buffer tank for treatment, the effluent of the buffer tank is filtered by an MBR membrane, and the filtered water is discharged after monitoring. The sludge of the buffer tank and the sludge filtered by the MBR membrane are delivered to the biochemical system for denitrification and aeration treatment.

2. The method for sewage treatment suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized by, The pH value of the effluent of the denitrification second tank is adjusted to 8-9.

3. The method for treating sewage suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized by, The method further comprises the following steps: The pH value of the effluent of the denitrification first tank is detected, if the pH value of the effluent of the denitrification first tank is less than or equal to 7, sodium carbonate or sodium bicarbonate is added to the denitrification first tank, and the addition is stopped when the pH value of the effluent of the denitrification first tank is 8-9.

4. The method for treating sewage suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized by, Two denitrification first tanks are included, and the two denitrification first tanks are arranged in parallel.

5. The method for treating sewage suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized by, The method further comprises the following steps: The nitrification liquid of the buffer tank is delivered to the biochemical system for denitrification and aeration treatment.

6. The method for treating sewage suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized by, The method further comprises the following steps: If the filtered water does not meet the monitoring standards, the water is delivered to the denitrification second tank for treatment.

7. A wastewater treatment device suitable for the wastewater treatment method for low carbon-to-nitrogen ratio water as described in any one of claims 1 to 6, characterized in that, The method comprises a biochemical intermediate tank, a denitrification first tank, a denitrification second tank, a pH adjusting tank, a biochemical system, a buffer tank, an MBR membrane tank and a discharge monitoring tank arranged in sequence, the biochemical intermediate tank contains wastewater with low carbon-nitrogen ratio treated by physical and chemical methods, and adjusts the water quality and quantity; the pH adjusting tank is used for adjusting the pH value of the effluent of the denitrification second tank to 8-9; the MBR membrane tank is provided with an MBR membrane for filtering the effluent of the buffer tank; the sludge output end of the buffer tank is communicated with a part of the biochemical system for denitrification treatment through a pipeline, the nitrification liquid output end of the buffer tank is communicated with a part of the biochemical system for denitrification treatment through a pipeline; the sludge output end of the MBR membrane tank is communicated with a part of the biochemical system for denitrification treatment through a pipeline; and the filtrate output end of the MBR membrane tank is also communicated with the denitrification second tank through a pipeline.

8. The sewage treatment apparatus according to claim 7, characterized by The biochemical system comprises an anaerobic tank, an anoxic tank and an aerobic tank arranged in sequence, the anaerobic tank is used for hydrolysis treatment, the anoxic tank is used for denitrification treatment, and the aerobic tank is used for aeration treatment; the sludge output end of the buffer tank is communicated with the anoxic tank through a pipeline, the nitrification liquid output end of the buffer tank is communicated with the anoxic tank through a pipeline; and the sludge output end of the MBR membrane tank is communicated with the anoxic tank through a pipeline.

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