Method for detecting quality of carbon source

Abstract

The application discloses a kind of detection methods of carbon source quality, by constructing aerobic aeration device and in which join activated sludge and sewage used in sewage plant, determine aeration length by adding carbon source, then determine effluent TOC under the aeration length determined, by comparing the effluent TOC of carbon source group and blank group, again in combination with carbon source routine detection index, including pH, COD or TOC, ammonia nitrogen, total phosphorus, total nitrogen, total salt content, can quickly and accurately judge the quality of carbon source added.Compared with the conventional detection method of carbon source, the detection method of the application can determine the quality of carbon source within 7~8h, ensure that the carbon source meets the requirement of improving the easily degradable COD concentration in sewage, and will not adversely affect the effluent quality.At the same time, the carbon source delivered on the same day can complete quality detection and unloading, speed up the detection speed, shorten the transportation cycle of carbon source, and has the advantages of accurate judgment result, simple operation and easy popularization, and has good application prospect.

Description

A method for detecting the quality of a carbon source Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for detecting the quality of carbon sources. Background Technology

[0002] Currently, my country has built and operates more than 4,000 wastewater treatment plants. However, with the continuous improvement of effluent discharge standards, the control of total nitrogen in effluent is becoming increasingly stringent, and the compliance limit is constantly decreasing. To ensure that the total nitrogen in effluent meets the standards, carbon sources have become an indispensable and commonly used agent in wastewater treatment plants, used in the denitrification process to remove total nitrogen.

[0003] The most commonly used single carbon sources in wastewater treatment plants are glucose and sodium acetate. There are also many commonly used composite carbon sources. For example, Chinese patent CN107162324A discloses the application of sodium acetate as an external carbon source in wastewater treatment plants. During transportation, sodium acetate is added as a carbon source for microorganisms, replacing methanol, thus solving its flammability and explosiveness issues and reducing wastewater treatment costs. Chinese patent CN112239274A discloses a composite carbon source and its preparation technology for enhanced nitrogen removal in wastewater treatment, comprising 30%-40% carbohydrates, 5%-10% methanol, 3%-5% sodium acetate, and 0.5%-1.0% trace elements. The carbohydrates are a mixture of two or more of glucose, sucrose, maltose, and fructose; the trace elements are a mixture of two or more of iron, boron, selenium, zinc, and molybdenum. This provides sufficient energy for uniform denitrification. Combined with the use of methanol, it is easily metabolized by denitrifying bacteria, increasing the denitrification rate. Simultaneously, sodium acetate can also adjust the pH of wastewater, improving the total nitrogen removal efficiency.

[0004] Whether it is a single carbon source or a composite carbon source, most of them use the COD of the carbon source meeting the value agreed in the purchase contract as the acceptance standard. However, in the process of using carbon sources, the concentration of carbon sources added is extremely low compared with the amount of wastewater to be treated. This can easily reduce the defects of low-quality carbon sources. Therefore, driven by profit, suppliers use high-concentration wastewater or mix in a large amount of miscellaneous salts to pass off inferior carbon sources as superior ones. This adulteration affects the physiological process of denitrifying bacteria in wastewater treatment, reduces denitrification efficiency, and thus causes the total nitrogen in the effluent to fail to meet the standards, resulting in the wastewater treatment plant effluent exceeding the standards.

[0005] Therefore, timely testing of the quality of each batch of carbon sources delivered to the wastewater treatment plant is particularly important. Chinese patent CN111596021B discloses a method, equipment, device, and readable storage medium for evaluating the quality of carbon sources in water bodies. By obtaining the COD and BOD5 of a first water body and the intracellular energy substance content of microorganisms in a second water body, the quality of the carbon source in the water body to be tested can be determined. This effectively solves the problem of poor specificity in existing wastewater biological degradation assessments, enabling accurate evaluation of the role of wastewater carbon sources in biological nitrogen and phosphorus removal processes. However, existing technologies have a long testing time for carbon source quality, making it impossible to test and obtain results on the day the carbon source arrives, and thus unable to promptly evaluate the carbon source quality and decide whether to retain the delivered carbon source. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for detecting the quality of carbon sources. By constructing an aerobic aeration device in the laboratory and using activated sludge and wastewater from the wastewater treatment plant itself to test the quality of purchased carbon sources, the detection time for carbon source quality can be significantly shortened.

[0007] To achieve the above objectives, the present invention provides a method for detecting the quality of a carbon source, comprising the following steps:

[0008] (1) Detect the pH, COD or TOC, ammonia nitrogen, total phosphorus, total nitrogen, and total salt content of the carbon source;

[0009] (2) Construct an aerobic aeration device and add activated sludge and wastewater;

[0010] (3) Determination of aeration time: Divide the aerobic aeration device constructed in step (1) into two groups, one group is given a carbon source and the other group is not given a carbon source. Aerate at the same time until the difference between COD or TOC between the two groups is ≤10%, and record the aeration time.

[0011] (4) Detection of carbon source quality: Divide the aerobic aeration device constructed in step (1) into two groups, one group is given carbon source and the other group is not given carbon source. Aerate simultaneously for the aeration time determined in step (2). Record the COD or TOC of the effluent of the two groups after aeration is completed.

[0012] When the COD or TOC value of the effluent from the carbon source addition group is less than or equal to 1.1 times the COD or TOC value of the effluent from the group without carbon source addition, the carbon source is considered qualified.

[0013] When the COD or TOC value of the effluent from the carbon source addition group is greater than 1.1 times that of the effluent from the group without carbon source addition, the carbon source is considered unqualified.

[0014] Preferably, the aerobic aeration device described in step (2) maintains the dissolved oxygen content of the solution at 2-4 mg / L during the reaction.

[0015] Preferably, the aerobic aeration device in step (2) includes an aeration pump and an aeration tank. The aeration pump is connected to the aeration head via an aeration hose, and the aeration head is placed inside the aeration tank.

[0016] More preferably, the aeration hose includes a first aeration hose and a second aeration hose, and the aeration head includes a first aeration head and a second aeration head.

[0017] Preferably, the method for obtaining activated sludge in step (2) is to take the sludge-water mixture from the end of the aerobic tank of the sewage treatment plant, let it stand, pour off the supernatant, retain the sludge and wash it with sewage, repeat the standing-washing process 2-3 times to obtain activated sludge.

[0018] Preferably, the wastewater in step (2) is wastewater near the carbon source addition point at the front end of the anoxic pool of the wastewater treatment plant, with a COD of 100mg / L to 200mg / L or a TOC of 40mg / L to 80mg / L.

[0019] Preferably, the wastewater treatment plant is any one of a municipal wastewater treatment plant, an industrial wastewater treatment plant, or a wastewater treatment plant that treats both municipal wastewater and industrial wastewater.

[0020] Preferably, the amount of carbon source added in the carbon source group mentioned in steps (3) and (4) is to increase the raw COD or TOC value of the wastewater by 45%-55%.

[0021] The beneficial effects of this invention are as follows: An aerobic aeration device is constructed using activated sludge and wastewater already used in the wastewater treatment plant, resulting in a simple and easy-to-operate structure. Purchased carbon sources are added to this aerobic aeration device. By determining the aeration duration and then using that duration to test the effluent TOC or COD value, combined with conventional carbon source testing indicators including pH, COD or TOC, ammonia nitrogen, total phosphorus, total nitrogen, and total salt content, the quality of the carbon source can be quickly determined. When the effluent COD or TOC value of the carbon source-added group is ≤ 1.1 times that of the group without carbon source addition, the carbon source is considered qualified; when the effluent COD or TOC value of the carbon source-added group is > 1.1 times that of the group without carbon source addition, the carbon source is considered unqualified. This invention's carbon source quality testing method only requires determining the aeration duration once for carbon sources purchased from different companies, thus shortening the testing time to within 7-8 hours, ensuring same-day delivery and unloading of the carbon source.

[0022] This invention can quickly determine whether the quality of carbon sources meets the requirements of wastewater treatment plants, has high detection accuracy, and also has the advantages of simple detection methods that are easy to promote. Attached Figure Description

[0023] Figure 1 shows the aerobic aeration device constructed in Example 1. In the figure, 1 is the first aeration head, 2 is the second aeration head, 3 is the aeration tank, 4 is the second aeration hose, 5 is the aeration pump, and 6 is the first aeration hose. Detailed Implementation

[0024] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0025] The wastewater and aerobic sludge samples used in the following examples were taken from the Nanjing Jiangbei New Area Chemical Park Centralized Industrial Wastewater Treatment Plant (hereinafter referred to as "Nanjing Sembcorp Wastewater Treatment Plant") operated by Nanjing Sembcorp Water Co., Ltd.

[0026] The carbon source was purchased from Hangzhou Kaiyuan Environmental Protection Technology Co., Ltd., and the batch number was Hzky20210608. Its COD value was approximately 200,000 mg / L, the BOD5 test result was approximately 170,000 mg / L, the B / C ratio was 0.85, and the carbon source had excellent biodegradability. The pH was 7.17, the ammonia nitrogen content was 10.53 mg / L, the total phosphorus content was 1.89 mg / L, the total nitrogen content was 12.51 mg / L, and the total salt content was 8200 mg / L. It was selected as a qualified carbon source.

[0027] The recalcitrant chemical wastewater was taken from the concentrated wastewater discharged from the production workshop of a chemical enterprise in Nanjing Chemical Industrial Park. Its COD value was about 200,000 mg / L and the B / C ratio was 0.05, indicating that the easily degradable COD value was about 10,000 mg / L.

[0028] A qualified carbon source was mixed with recalcitrant wastewater at a volume ratio of 1:1 to form a non-qualified carbon source. Its COD value was approximately 200,000 mg / L. The easily degradable COD value was 1*0.5 + 20*0.5 = 105,000 mg / L, and the recalcitrant COD value was approximately 95,000 mg / L. The pH was 6.03, the ammonia nitrogen content was 316 mg / L, the total phosphorus content was 25 mg / L, the total nitrogen content was 429 mg / L, and the total salt content was 15,000 mg / L.

[0029] Example 1: Construction of an aerobic aeration device

[0030] An aerobic aeration device as shown in Figure 1 is constructed, comprising connecting a first aeration hose (6) and a second aeration hose (4) to an aeration pump (5), the first aeration hose (6) being connected to a first aeration head (1), and the second aeration hose (4) being connected to a second aeration head (2). The first aeration head (1) and the second aeration head (2) are respectively placed in an aeration tank (3). In use, the aeration pump (5) is powered on, and gas is delivered to the first aeration head (1) and the second aeration head (2) through the first aeration hose (6) and the second aeration hose (4) respectively, and released through the first aeration head (1) and the second aeration head (2) to aerate the bottom of the aeration tank (3).

[0031] Example 2: Determining carbon source quality by detecting TOC

[0032] Test the pH, COD or TOC, ammonia nitrogen, total phosphorus, total nitrogen, and total salt content of the purchased qualified carbon source. Based on these parameters, conduct TOC testing on the effluent to determine the accuracy of the testing method. The specific steps include:

[0033] (1) Take a 10L wastewater sample near the carbon source addition point at the front end of the anoxic tank of Nanjing Sembcorp wastewater treatment plant;

[0034] (2) At the same time, take 1L of mud-water mixture at the end of the aerobic tank where aeration is intense. After standing for 10 minutes, pour out most of the supernatant and keep the sludge. Inject the wastewater sample obtained in step (1) into the sludge until the liquid level reaches the 1L mark. After standing for another 10 minutes, pour out the supernatant and keep the sludge. The sludge that is kept is the activated sludge used in the experiment, and its SV30 is about 30% to 40%.

[0035] (3) Take the activated sludge obtained in step (2) and add it to the aerobic aeration device constructed in Example 1, and add the sewage sample obtained in step (1) until the liquid level reaches the 1L mark.

[0036] (4) The aerobic aeration device constructed in step (3) was divided into two groups. One group was not added to the carbon source as a blank group, and the background TOC value of the wastewater in it was measured to be 64.14 mg / L. The other group was added to the carbon source as an experimental group. Aeration was carried out at the same time, and the TOC value was measured at the same time after 4 hours of aeration. Then, the TOC value was measured again every 1 hour until the difference in TOC between the two groups of effluent did not exceed 10%. The aeration time was recorded (Table 1).

[0037] Table 1. TOC values ​​of the experimental group and the control group under the same aeration time.

[0038] Experimental group, control group: Raw water TOC (mg / L) 95.56 64.14; After 4 hours of aeration, TOC (mg / L) 25.16 21.34; After 5 hours of aeration, TOC (mg / L) 22.87 20.07; After 6 hours of aeration, TOC (mg / L) 19.84 19.46; After 7 hours of aeration, TOC (mg / L) 18.94 18.63; After 8 hours of aeration, TOC (mg / L) 18.56 18.05 surface

[0039] (5) Based on the data in Table 1, the aeration time is determined to be 6 hours;

[0040] (6) Two sets of aerobic aeration devices were constructed again. One set was used as a control group without carbon source, and the other set was used as an experimental group with 0.4 mL of carbon source. Both groups were aerated for 6 hours, and the TOC value of the effluent was measured. The results are shown in Table 2.

[0041] Table 2 TOC values ​​of the experimental group and the control group after 6 hours of aeration.

[0042] Experimental group vs. control group: Raw water TOC (mg / L): 92.47 vs. 60.12; After 6 hours of aeration: TOC (mg / L): 19.05 vs. 18.29 surface

[0043] The results showed that after 6 hours of aeration, the TOC values ​​of the effluent from the experimental group and the control group differed by about 4%. That is, the TOC value of the effluent from the carbon source-added group was less than 1.1 times that of the effluent from the group without carbon source added. Therefore, the quality of the added carbon source was deemed to be qualified, which is consistent with the carbon source quality test results, indicating that the test method is accurate in detecting the carbon source quality.

[0044] Example 3

[0045] The pH, COD or TOC, ammonia nitrogen, total phosphorus, total nitrogen, and total salt content of the unqualified carbon source were tested. Based on the condition that the carbon source met the standards, an experiment was conducted to test the TOC of the effluent to determine the accuracy of the testing method. The specific methods and steps were the same as in Example 2, except that the aeration time was set to 6 hours. Two sets of aerobic aeration devices were constructed again, with an experimental group and a control group respectively. The TOC value of the effluent was measured, and the results are shown in Table 3.

[0046] Table 3 TOC values ​​of the experimental group and the control group after 6 hours of aeration.

[0047] Experimental group vs. control group: Raw water TOC (mg / L): 92.47 vs. 60.12; After 6 hours of aeration: TOC (mg / L): 35.58 vs. 17.69 surface

[0048] The results showed that after 6 hours of aeration, the difference in TOC values ​​between the experimental group and the control group was as high as 50%. The TOC value of the effluent from the carbon source-added group was 1.1 times higher than that of the group without carbon source added. Therefore, it was determined that the added carbon source was of unqualified quality. This was consistent with the test results of the prepared carbon source, indicating that the test method can accurately detect unqualified carbon sources.

[0049] Comparative Example 1

[0050] According to the "Determination of Chemical Oxygen Demand in Water - Potassium Dichromate Method" published by HJ 828-2017, the COD values ​​of purchased qualified carbon sources and prepared unqualified carbon sources were tested separately. The results showed that the COD value of both qualified and unqualified carbon sources was about 200,000 mg / L, indicating that the COD value detected by this method is the sum of easily degradable COD and difficult-to-degrade COD. Therefore, this method cannot determine whether the quality of the carbon source is qualified.

[0051] Comparative Example 2

[0052] According to the "Dilution and Inoculation Method for Determination of Five-Day Biochemical Oxygen Demand (BOD5) in Water" published in HJ 505-2009, BOD5 was tested on both the purchased qualified carbon source and the prepared unqualified carbon source. The results showed that the BOD5 of the qualified carbon source was approximately 170,000 mg / L, with a B / C ratio of 0.85, consistent with the initial test data. The BOD5 of the unqualified carbon source was approximately 50,000 mg / L, which was lower than expected. This was due to the inhibitory effect of recalcitrant COD, making it difficult for microorganisms to utilize the large amount of recalcitrant COD in the unqualified carbon source, and the toxicity of recalcitrant COD to microorganisms. However, the BOD5 detection method takes 5 days to obtain results. It also suffers from incomplete consumption of organic matter by microorganisms, meaning that not all recalcitrant COD in wastewater can be detected, and only most readily biodegradable COD can be detected. Furthermore, the upper limit of BOD5 detection is 6000 mg / L. When testing water samples with concentrations higher than this, the water samples need to be diluted. However, the more diluted the sample, the lower the accuracy of the BOD5 detection, resulting in inaccurate test results.

Claims

1. A method for detecting the quality of a carbon source, characterized in that: Includes the following steps: (1) Detect the pH, COD or TOC, ammonia nitrogen, total phosphorus, total nitrogen, and total salt content of the carbon source; (2) Construct an aerobic aeration device and add activated sludge and wastewater; (3) Determine the aeration time: Divide the aerobic aeration device constructed in step (2) into two groups, add carbon source to one group and do not add carbon source to the other group, and aerate at the same time until the difference between COD or TOC of the two groups is ≤10%, and record the aeration time; (4) Detect the carbon source quality: Divide the aerobic aeration device constructed in step (2) into two groups. Two groups were formed, one with carbon source added and the other without. Both groups were aerated simultaneously for the aeration time determined in step (3). After aeration, the COD or TOC of the effluent from both groups was recorded. When the COD or TOC value of the effluent from the carbon source-added group was less than or equal to 1.1 times the COD or TOC value of the effluent from the group without carbon source added, the carbon source was considered qualified. When the COD or TOC value of the effluent from the carbon source-added group was greater than or equal to 1.1 times the COD or TOC value of the effluent from the group without carbon source added, the carbon source was considered unqualified.

2. The method for detecting the quality of a carbon source according to claim 1, characterized in that: The aerobic aeration device described in step (2) maintains the dissolved oxygen content of the solution at 2~4 mg / L during the reaction.

3. A method for detecting the quality of a carbon source according to claim 1 or 2, characterized in that: The aerobic aeration device described in step (2) includes an aeration pump (5) and an aeration tank (3). The aeration pump (5) is connected to the aeration head through an aeration hose, and the aeration head is placed inside the aeration tank (3).

4. The method for detecting the quality of a carbon source according to claim 3, characterized in that: The aeration hose includes a first aeration hose (6) and a second aeration hose (4), and the aeration head includes a first aeration head (1) and a second aeration head (2).

5. The method for detecting the quality of a carbon source according to claim 1, characterized in that: The method for obtaining activated sludge in step (2) is to take the sludge-water mixture from the end of the aerobic tank of the sewage treatment plant, let it stand, pour off the supernatant, retain the sludge and wash it with sewage, repeat the standing-washing process 2-3 times to obtain activated sludge.

6. A method for detecting the quality of a carbon source according to claim 1 or 5, characterized in that: The wastewater mentioned in step (2) is the wastewater near the carbon source addition point at the front end of the anoxic pool of the wastewater treatment plant, with a COD of 100mg / L~200mg / L or a TOC of 40mg / L~80mg / L.

7. The method for detecting the quality of a carbon source according to claim 5, characterized in that: The wastewater treatment plant mentioned is any one of a municipal wastewater treatment plant, an industrial wastewater treatment plant, or a wastewater treatment plant that treats a mixture of municipal wastewater and industrial wastewater.

8. The method for detecting the quality of a carbon source according to claim 1, characterized in that: In steps (3) and (4), the amount of carbon source added is to increase the COD or TOC value of the raw wastewater by 45%-55%.

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