Sewage treatment plant group combined denitrification method based on carbon source recovery

Abstract

The invention relates to the field of sewage treatment plant denitrification, and discloses a sewage treatment plant group combined denitrification method based on carbon source recovery, and the method comprises the following steps: S1, organic matter capturing: capturing organic matters in sewage at the tail end of a sewage pretreatment process by adopting an organic matter capturing system; s2, recovering and extracting a high-value carbon source: performing high-value carbon source extraction and recovery on the captured organic matters by adopting a high-value carbon source extraction system; s3, carbon source calculation: calculating a carbon-nitrogen ratio required by sewage denitrification of each sewage treatment plant by adopting a carbon source calculation system, and determining a carbon source addition amount required by each sewage treatment plant; and S4, distribution: conveying the high-value carbon source recovered and extracted in the step S2 to a corresponding sewage treatment plant through a conveying tool according to the carbon source dosage required by each sewage treatment plant determined in the step S3 for denitrification. The method is suitable for combined denitrification of multiple urban sewage treatment plant groups or urban sewage treatment plants and industrial sewage treatment plants.

Description

Technical Field

[0001] This invention relates to the field of nitrogen removal technology in wastewater treatment plants, and specifically to a combined nitrogen removal method for a group of wastewater treatment plants based on carbon source recovery. Background Technology

[0002] With the increasing stringency of wastewater treatment plant discharge standards, total nitrogen removal has become a major challenge for these plants. Conventional denitrification technology converts nitrate and nitrite in water into nitrogen gas through the action of denitrifying bacteria. These bacteria consume organic matter as a carbon source during denitrification, typically requiring a carbon-to-nitrogen ratio of 3–5:1. To ensure thorough denitrification, wastewater treatment plants often need to supplement the denitrification process with carbon sources, commonly acetic acid, glucose, or waste molasses. This often leads to increased treatment costs and a rise in effluent COD (Chemical Oxygen Demand).

[0003] Meanwhile, wastewater treatment technologies guided by energy conservation and carbon reduction technologies such as carbon enrichment and energy recovery have become a research hotspot in the global water treatment industry, and COD removal is also shifting towards resource utilization. Conventional biological wastewater treatment processes generate a large amount of sludge, which requires further treatment to reduce environmental pollution. Although there are currently a series of technologies such as sludge drying and sludge fermentation that can reduce sludge environmental pollution, their utilization is limited and they require specialized disposal sites. Therefore, capturing wastewater carbon sources at the front end as denitrification carbon sources is a more suitable method. However, the carbon sources obtained by this method have complex compositions and contain certain amounts of nitrogen and phosphorus. Directly using them for denitrification will affect effluent indicators. At the same time, the mismatch between the demand for denitrification carbon sources and the captured carbon sources will cause new environmental problems.

[0004] Based on this, this technology proposes a high-value carbon source extraction technology based on wastewater treatment plants and a process for rationally allocating carbon sources to other wastewater treatment plants through calculation, in order to solve the above problems. Summary of the Invention

[0005] This invention provides a combined denitrification method for a group of wastewater treatment plants based on carbon source recovery. This method is suitable for urban wastewater or industrial wastewater with high organic content. By adding an organic matter capture process at the front end of the wastewater treatment denitrification process and treating the organic matter to recover high-value carbon sources, the high-value carbon sources are then distributed as denitrification carbon sources to wastewater treatment plants that need carbon sources for denitrification, which can help complete the removal of total nitrogen.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A combined nitrogen removal method for a wastewater treatment plant cluster based on carbon source recovery includes the following steps:

[0008] S1. Organic matter capture: An organic matter capture system is added at the end of the pretreatment process (bar screen, grit removal, oil removal, etc.) in wastewater treatment to capture organic matter in wastewater and obtain carbon-rich sludge.

[0009] S2. Recovery and extraction of high-value carbon sources: High-value carbon source extraction and recovery are performed on the carbon-rich sludge obtained in step S1 using a high-value carbon source extraction system.

[0010] S3. Carbon source calculation: The carbon source calculation system is used to calculate the carbon-nitrogen ratio required for denitrification of wastewater in each wastewater treatment plant. Based on the total nitrogen concentration of the influent and effluent of the denitrification process or the total nitrogen concentration of the influent and effluent of the biological process, the required carbon source dosage for each wastewater treatment plant is determined.

[0011] S4. Delivery: Based on the amount of carbon source required by each wastewater treatment plant as determined in step S3, the high-value carbon source recovered and extracted in step S2 is transported to the corresponding wastewater treatment plant by means of transport such as tank trucks for denitrification.

[0012] Preferably, the organic matter capture system involves adding an appropriate amount of flocculant to a flocculation sedimentation tank, allowing the flocculant to react with the organic matter in the wastewater through flocculation and sedimentation to obtain carbon-rich sludge (organic matter capture material); the hydraulic retention time of the flocculation sedimentation tank is 15–30 min.

[0013] Preferably, the flocculant is one or more of polyaluminum chloride, polyferric chloride, ferric chloride, ferric sulfate, and aluminum chloride.

[0014] Preferably, the amount of flocculant added is 15-25 ppm of flocculant per 100 mg / L COD in the wastewater.

[0015] Preferably, when the organic matter capture system captures organic matter, 5-10 ppm of polyacrylamide (PAM) is added to the flocculation sedimentation tank to increase the carbon source capture effect.

[0016] It should be noted that polyacrylamide (PAM) can accelerate the sedimentation rate of flocs, and the sludge obtained after flocculation is polycarbonate sludge.

[0017] Preferably, the high-value carbon source extraction system converts the carbon-rich sludge obtained in step S1 into a small molecule acid mixture (liquid) by adding a compound enzyme preparation into a temperature-controlled reaction vessel and carrying out an enzymatic hydrolysis reaction, thereby obtaining a high-value carbon source. The small molecule acid mixture includes, but is not limited to, acetic acid, propionic acid, and butyric acid.

[0018] Preferably, the compound enzyme preparation includes, but is not limited to, one or more of hydrolases, proteases, and laccases.

[0019] Preferably, the dosage of the compound enzyme preparation is 6–8 x 10⁻⁶. 8 u / m3 .

[0020] Preferably, the temperature of the enzymatic hydrolysis reaction is 35-45°C, the composite enzyme preparation needs to be fixed on a carrier, the carrier is silica gel or activated carbon, and the amount of carrier added is 1 / 4-1 / 2 of the volume of the reaction vessel.

[0021] Preferably, when the total nitrogen concentrations of the influent and effluent from the denitrification process are known, the formula for calculating the carbon source dosage is:

[0022] C = (1 - 1.5)·N·Q,

[0023] N = N 进水 -N 出水 ,

[0024] Where C represents the dosage of high-value carbon source; N represents the total nitrogen to be removed from the wastewater. 进水 The total nitrogen content (N) in the influent of the denitrification process. 出水 The design effluent total nitrogen content for the denitrification process is expressed in mg / L; Q represents the daily water volume in m³ / d.

[0025] When the total nitrogen concentrations of the influent and effluent of the biological treatment process are known, the formula for calculating the carbon source dosage is:

[0026] C = (1.5 - 2) × (TN / BOD5) × Q

[0027] TN = TN 进水 -TN 出水

[0028] BOD5 = BOD 5进水 -BOD 5出水

[0029] Among them, TN 进水 TN is the total nitrogen concentration in the influent of the biological process. 出水 The design values ​​for total nitrogen concentration in the effluent from the biological process are given, all in mg / L; BOD... 5进水 The influent BOD5 concentration, BOD 5出水 Q represents the BOD5 concentration in the effluent from the biological system, in mg / L; Q represents the daily water volume, in m³ / d.

[0030] In summary, the present invention has the following beneficial effects:

[0031] 1. This invention addresses urban sewage or industrial wastewater with high organic content by adding an organic matter capture process to the front end of conventional sewage treatment processes. The organic matter is then treated to recover a high-value carbon source, which is then distributed as a denitrification carbon source to sewage treatment plants that require carbon sources for denitrification to assist in the removal of total nitrogen. This method is applicable to multiple urban sewage treatment plant clusters or joint denitrification of urban sewage treatment plants and industrial wastewater treatment plants.

[0032] 2. This invention overcomes the resource mismatch caused by the recycling and utilization of carbon sources within existing sewage treatment plants; by constructing a combined carbon removal and denitrification system for sewage / wastewater treatment plants, the amount of carbon source input can be reduced; and it solves the problems of high cost of adding methanol and acetic acid carbon sources during denitrification, and increased COD value of effluent caused by adding glucose, waste molasses and other carbon sources, thus helping to reduce carbon emissions. Attached Figure Description

[0033] Figure 1 This is a flowchart of a combined denitrification method for a group of wastewater treatment plants based on carbon source recovery. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be described in further detail below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0036] This invention provides a method for combined nitrogen removal in a wastewater treatment plant cluster based on carbon source recovery. This method is applicable to multiple urban wastewater treatment plant clusters or combined nitrogen removal in urban wastewater treatment plants and industrial wastewater treatment plants, and specifically includes the following steps:

[0037] S1, Organic Matter Capture

[0038] For urban sewage or industrial wastewater with high organic content, an organic matter capture system is added at the end of the pretreatment process (bar screen, grit removal, oil removal, etc.) in wastewater treatment to capture organic matter in the sewage. The main body of the organic matter capture system is a flocculation sedimentation tank with a hydraulic retention time of 15-30 minutes. By adding an appropriate amount of flocculant to the flocculation sedimentation tank, the flocculant reacts with the organic matter in the sewage. Alternatively, 5-10 ppm of polyacrylamide (PAM) can be selectively added to the flocculation sedimentation tank to accelerate the sedimentation rate. The sludge obtained after flocculation sedimentation is carbon-rich sludge (organic matter capture material).

[0039] The flocculant is one or more of polyaluminum chloride, polyferric chloride, ferric chloride, ferric sulfate, and aluminum chloride. The flocculant dosage is 15-25 ppm per 100 mg / L COD.

[0040] S2. Recover and extract high-value carbon sources

[0041] A high-value carbon source extraction system is used to extract and recover high-value carbon sources from the organic matter (carbon-rich sludge) captured in step S1; that is, 6-8 x 10⁶ carbon atoms are added to a temperature-controlled reactor at 35-45°C. 8 u / m 3 The compound enzyme preparation carries out an enzymatic hydrolysis reaction to convert the organic matter (carbon-rich sludge) captured in step S1 into a mixture of small molecule acids (liquid) such as acetic acid, propionic acid, and butyric acid, thereby obtaining a high-value carbon source.

[0042] The compound enzyme preparation mainly includes one or more of hydrolases, proteases and laccases, which are fixed on a carrier (silica gel or activated carbon). The amount of carrier added is 1 / 4 to 1 / 2 of the volume of the reaction vessel.

[0043] S3. Carbon source calculation: The high-value carbon source recovered and extracted in step S2 is calculated using a carbon source calculation system. By detecting the composition and components of the high-value carbon source, the carbon and nitrogen ratio required for denitrification of wastewater in each wastewater treatment plant is calculated. Based on the total nitrogen concentration of the influent and effluent of the denitrification process or the total nitrogen concentration of the influent and effluent of the biological process, the required amount of carbon source to be added for each wastewater treatment plant is determined.

[0044] When the total nitrogen concentrations of the influent and effluent in the denitrification process are known, the formula for calculating the carbon source dosage is:

[0045] C = (1 - 1.5)·N·Q,

[0046] N = N 进水 -N 出水 ,

[0047] Where C represents the dosage of high-value carbon source; N represents the total nitrogen to be removed from the wastewater. 进水 The total nitrogen content (N) in the influent of the denitrification process.出水 The design effluent total nitrogen content for the denitrification process is expressed in mg / L; Q represents the daily water volume in m³ / d.

[0048] When the total nitrogen concentrations of the influent and effluent of the biological treatment process are known, the formula for calculating the carbon source dosage is:

[0049] C = (1.5 - 2) × (TN / BOD5) × Q

[0050] TN = TN 进水 -TN 出水

[0051] BOD5 = BOD 5进水 -BOD 5出水

[0052] Among them, TN 进水 TN is the total nitrogen concentration in the influent of the biological process. 出水 The total nitrogen concentration in the effluent from the biochemical process is designed, and the units are all mg / L; BOD 5进水 The influent BOD5 concentration, BOD 5出水 Q represents the BOD5 concentration in the effluent from the biological system, in mg / L; Q represents the daily water volume, in m³ / d.

[0053] S4. Delivery: Based on the amount of carbon source required by each wastewater treatment plant as determined in step S3, the high-value carbon source recovered and extracted in step S2 is transported to the corresponding wastewater treatment plant by means of transport such as tank trucks for denitrification.

[0054] Example 1:

[0055] A company owns five wastewater treatment plants in a certain city. The largest wastewater treatment plant (Plant A) has a daily treatment capacity of 650,000 tons / day. There are also two other wastewater treatment plants (Plant B and Plant C) with a daily treatment capacity of 150,000 tons / day and 100,000 tons / day respectively, and two wastewater treatment plants (Plants D and E) with a daily treatment capacity of 50,000 tons / day respectively.

[0056] The specific parameters of Plant A are as follows: The influent COD of the wastewater treatment plant is approximately 400 mg / L, BOD is approximately 180 mg / L, and ammonia nitrogen is 45 mg / L. A carbon source recovery and high-value carbon source conversion system is set up after the grit chamber, including one flocculation tank with a retention time of 10 minutes and four mixers. Polyferric chloride is added to the system at a dosage of 80 ppm. A sedimentation tank with a retention time of 20 minutes is also included. The flocculated wastewater enters the sedimentation tank, and the resulting carbon-rich sludge is piped into an enzyme hydrolysis tank. The temperature of the enzyme hydrolysis tank is controlled at 40℃, and silica gel soil is selected as the carrier with a loading of 6.5 x 10 mm. 8 u / m 3 A 1:1 mixture of hydrolytic enzymes and proteases was prepared, with silica gel added at 1 / 2 of the reactor volume. After hydrolysis, a high-load carbon source was obtained.

[0057] The influent and effluent quality of plants B, C, D, and E are basically the same as that of plant A. The effluent needs to meet the Class A standard. Based on the calculation C = (1.5-2) × (TN / BOD5) × Q, the four wastewater treatment plants require high-load carbon sources of 3.6 tons, 2.4 tons, 1.2 tons, and 1.2 tons respectively. The carbon sources are transported by tanker trucks and put into the denitrification process section of the wastewater treatment plants. This will not only ensure that the effluent of the plants meets the standards, but also reduce the purchase of glucose carbon sources by the plants.

[0058] Example 2:

[0059] A brewery in a certain city produces 3,000 tons of wastewater daily, with an influent COD of 3,000 mg / L and ammonia nitrogen of 95 mg / L. A carbon source recovery and high-value carbon source conversion system is installed after the bar screen in the brewery's wastewater treatment plant. Specific parameters are as follows: One flocculation tank with a retention time of 10 minutes, equipped with one mixer; ferric sulfate added at 500 ppm; PAM added at 10 mg / L; and one sedimentation tank with a retention time of 30 minutes. After flocculation, the wastewater enters the sedimentation tank, and the resulting carbon-rich sludge is piped to an enzyme hydrolysis tank. The enzyme hydrolysis tank temperature is controlled at 40℃, and activated carbon is used as the carrier, with a loading of 8 x 10... 8 u / m 3 A mixed enzyme preparation of hydrolase, protease, and laccase in a 2:1:2 ratio, with activated carbon added at half the reactor volume, yields a high-load carbon source after hydrolysis. A nearby municipal wastewater treatment plant with a capacity of 50,000 tons / day has an effluent nitrate nitrogen level of 25 mg / L from its biological treatment tanks, and aims to reduce the effluent nitrate nitrogen level to below 15 mg / L. Calculations using the formula C = (1-1.5)·N·Q indicate that 0.5 tons of carbon source are required. The carbon source will be transported by tanker truck and added to the denitrification process of the wastewater treatment plant. This will ensure stable effluent compliance with standards while reducing the plant's reliance on sodium acetate as a carbon source.

[0060] In summary, this invention overcomes the resource mismatch caused by the recycling and utilization of carbon sources within existing wastewater treatment plants; by constructing a combined carbon removal and denitrification system for wastewater / sewage treatment plant groups, the amount of carbon source input can be reduced; and it solves the problems of high cost of adding methanol and acetic acid carbon sources during denitrification, and increased COD value of effluent caused by adding glucose, waste molasses, and other carbon sources, thus helping to reduce carbon emissions.

[0061] The above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A combined denitrification method for a sewage treatment plant group based on carbon source recovery, characterized in that: The steps include: S1. Organic matter capture: An organic matter capture system is added at the end of the pretreatment process in sewage treatment to capture organic matter in sewage and obtain carbon-rich sludge; S2. Recovering and extracting high-value carbon sources: extracting and recovering high-value carbon sources from the carbon-rich sludge obtained in step S1 using a high-value carbon source extraction system; S3. Carbon source calculation: The carbon source calculation system is used to calculate the carbon-nitrogen ratio required for denitrification of sewage in each sewage treatment plant. The amount of carbon source required for each sewage treatment plant is determined based on the total nitrogen concentration of the inlet and outlet water of the denitrification process or the total nitrogen concentration of the inlet and outlet water of the biochemical process; S4. Distribution: According to the required carbon source dosage of each sewage treatment plant determined in step S3, the high-value carbon source recovered and extracted in step S2 is transported to the corresponding sewage treatment plant through a transport tool for denitrification.

2. A method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to claim 1, characterized in that: The organic matter capture system is to add a proper amount of flocculant into a flocculation sedimentation tank, so that the flocculant and organic matter in the sewage undergo flocculation reaction and precipitation to obtain carbon-rich sludge; the hydraulic retention time of the flocculation sedimentation tank is 15 to 30 minutes.

3. A method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to claim 2, characterized in that: The flocculant is one or more of polyaluminium chloride, polyferric chloride, ferric chloride, ferric sulfate and aluminium chloride.

4. A method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to claim 3, characterized in that: The amount of flocculant added is 15-25 ppm for every 100 mg / L COD in the sewage.

5. A method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to any one of claims 2 to 4, characterized in that: When the organic matter capturing system captures organic matter in sewage, 5-10 ppm polyacrylamide needs to be added to the flocculation sedimentation tank.

6. The method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to claim 1, characterized in that: The high-value carbon source extraction system is to add a composite enzyme preparation into a temperature-controllable reactor to perform an enzymatic hydrolysis reaction to convert the carbon-rich sludge obtained in step S1 into a small molecule acid mixture to obtain a high-value carbon source, wherein the small molecule acid mixture is not limited to acetic acid, propionic acid and butyric acid.

7. A method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to claim 6, characterized in that: The complex enzyme preparation includes but is not limited to one or more of hydrolases, proteases and laccases.

8. The method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to claim 6, characterized in that: The dosage of the composite enzyme preparation is 6 to 8 x 10 8 u / m 3 .

9. A combined denitrification method for a sewage treatment plant group based on carbon source recovery according to claim 7 or 8, characterized in that: The temperature of the enzymatic hydrolysis reaction is 35-45° C. The composite enzyme preparation needs to be fixed on a carrier, which is silica gel or activated carbon. The amount of the carrier added is 1 / 4-1 / 2 of the volume of the reactor.

10. The method for combined denitrification of a sewage treatment plant group based on carbon source recovery according to claim 1, characterized in that: When the total nitrogen concentration of the inlet and outlet water during the denitrification process is known, the calculation formula for the carbon source dosage is: C = (1-1.5)·N·Q, N=N 进水 -N 出水 , Among them, C is the amount of high-value carbon source added; N is the total nitrogen that needs to be removed from the sewage, N 进水 is the total nitrogen content of the influent in the denitrification process, N 出水 is the total nitrogen content of the designed effluent in the denitrification process, in mg / L; Q is the daily water volume, in m 3 / d; When the total nitrogen concentration of the inlet and outlet water of the biochemical process is known, the calculation formula for the carbon source dosage is: C=(1.5-2)×(TN / BOD5)×Q TN=TN 进水 -TN 出水 BEING5=BEING 5进水 - THAT 5出水 Among them, TN 进水 is the total nitrogen concentration of the influent in the biochemical process, TN 出水 The total nitrogen concentration of the designed effluent in the biochemical process, in mg / L; BOD 5进水 is the influent BOD5 concentration, BOD 5出水 is the BOD5 concentration of the biochemical system effluent, in mg / L; Q is the daily water volume, in m 3 / d.

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