Method for testing performance of denitrification carbon source

Abstract

The invention discloses a denitrification carbon source performance testing method, and particularly relates to the technical field of sewage treatment.The method comprises the steps that firstly, a mixed solution needed for biological denitrification nitrogen removal carbon source performance detection is taken; taking a proper amount of the mixed solution and testing the sludge concentration; measuring the mixed solution, pouring the mixed solution into a reaction beaker, fully mixing, measuring the DO value of the mixed solution by using a DO instrument, and when the dissolved oxygen of the mixed solution measured by using the DO instrument is lower than 0.5 mg / L, considering that the requirement of the anoxic denitrification nitrogen removal carbon source test on the anoxic condition is met; adding a carbon source and stirring the mixed solution until the mixed solution is fully mixed with the carbon source; starting timing and sampling at regular time until the TN or nitrate concentration in the sample tends to be constant; carrying out solid-liquid separation by adopting filter paper after sampling each time, discarding initial filtrate to obtain a water sample, and carrying out cold storage; determining CODCr and TN of the water samples at different reaction times; and calculating indexes such as biological denitrification / denitrification rate, sludge carbon source consumption rate, TN removal rate and the like.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a method for testing the performance of a denitrification carbon source. Background Art

[0002] my country's requirements for ecological civilization construction and environmental quality are constantly increasing, and emission standards are also increasing accordingly, especially the requirements for total nitrogen. For sewage treatment plants with low C / N ratios, adding organic carbon sources has become an inevitable choice for the stable TN of sewage treatment plant effluent without changing the existing process.

[0003] At present, the common organic substances used as carbon sources for denitrification in sewage treatment plants include: organic acids (formic acid, acetic acid / sodium acetate, propionic acid, lactic acid, citric acid, glycine, sodium succinate, sodium succinate, etc.); alcohols (methanol, ethanol, propanol, propylene glycol, allyl alcohol, etc.); sugars (starch, glucose, sucrose, fructose, etc.); esters (ethyl acetate, isobutyl acetate); in addition, there are composite carbon sources, biological fermentation carbon sources and slow-release carbon sources. Different carbon sources have different denitrification rates, denitrification effects, denitrification carbon source unit consumption, sludge production rate, unit price, and effects on sludge performance. Therefore, according to the denitrification treatment requirements and treatment process characteristics of sewage treatment plants, how to scientifically, reasonably, simply and quickly select a suitable carbon source with high cost performance is of great significance for sewage treatment plants to ensure TN treatment effects, reduce carbon source costs, and ensure the performance of activated sludge. There is an urgent need for a method for evaluating and screening the performance of external carbon sources for denitrification and denitrification treatment of sewage, so as to achieve scientific and reasonable selection of cost-effective carbon sources suitable for the denitrification treatment requirements and process characteristics of sewage treatment plants. Summary of the invention

[0004] To this end, the present invention provides a denitrification carbon source performance testing method to solve the problems raised in the background technology.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a method for testing the performance of a denitrification carbon source, comprising the following steps: Step 1. Take the mixed liquor required for the biological denitrification carbon source performance test: take the mixed liquor at the end of the aerobic stage in the oxidation ditch process; take the mixed liquor at the end of the aerobic reaction and before precipitation in the sequencing batch activated sludge process; the mixed liquor taken at the above time and space has good stability, the nitrogen-containing substances in it are mainly nitrate nitrogen, and the soluble COD in the mixed liquor is Cr The value is low and stable, and is basically not affected by the influent and external carbon source addition, and has little interference with the performance detection of biological denitrification carbon source; Step 2. Take an appropriate amount of the mixed solution from step 1 above to test the sludge concentration, including suspended solids concentration SS, total nitrogen TN or nitrate nitrogen and chemical oxygen demand COD CrWhen the nitrate nitrogen content in the mixed solution is 8 ~ 10 mg / L, a carbon source can be directly added for detection. When it is lower than this value, nitrate is added to increase the nitrate nitrogen content in the mixed solution by 10 ~ 20 mg / L.

[0006] Step 3. Measure 1.0-1.5 L of the mixed solution in step 1 above and pour it into a reaction beaker. The sludge concentration is greater than 4000 mg / L. Place it on a magnetic stirrer or a six-way stirrer and stir it at a speed of 50-65 r / min to ensure that the sludge mixed solution is fully mixed and the mud-water interface is lower than the water surface. After adjusting the speed, the DO value of the mixed solution can be measured with a DO meter. When the dissolved oxygen of the mixed solution measured by the DO meter is lower than 0.5 mg / L, it is considered to meet the anoxic conditions required for the anoxic denitrification carbon source test; Step 4. Add a certain amount of carbon source, the amount of addition is based on COD Cr / ΔTN=4~7 is used for calculation and addition. After the carbon source is added, the mixed liquid is stirred until it is fully mixed with the carbon source. The rapid stirring speed is not less than 100 r / min, and the mixing time is about 5s; Step 5. Start timing after adding the carbon source, starting from 0 o'clock, and sample every 30 to 60 minutes (sampling interval is shortened when the sludge concentration is high) until the TN or nitrate concentration in the sample tends to be constant; Sampling requires rapid sampling, and the sampling volume must meet the sample volume required for index analysis, but should not be too large to affect the anoxic reaction. The sampling volume is less than 1 / 20 of the initial reaction mixture volume. When the initial reaction mixture volume is 1 L, the sampling volume is 50 mL; immediately after each sampling, use 0.45 um filter paper for solid-liquid separation, discard the initial filtrate to obtain the water sample (make sure the filter vessel is clean and dry before filtering), and store the water sample in a refrigerator at 4°C; Determine the COD of the above water samples at different reaction times as soon as possible Cr and TN, and nitrate nitrogen and ammonia nitrogen can be tested if necessary; Step 6. Calculate the biological denitrification / denitrification rate, sludge carbon source consumption rate, TN removal rate, and denitrification carbon source consumption index as shown in equations (1), (2), (3), and (4); Y N = (N1-N2) / (SS*Δt) (1); Y C = (C1-C2) / (SS*Δt) (2); θ=(N1-N2) / N1*100%(3); ΔCOD / ΔTN=(C1-C2) / (N1-N2)(4); Where: Y N : Denitrification / denitrification rate (mg TN / g SS.h); Y C : Sludge carbon source consumption rate (mg COD Cr / g SS.h); N1, N2: TN or NO3 corresponding to the start and end of denitrification reaction - -N concentration (mg / L); SS sludge concentration (g / L); C1, C2: COD corresponding to the start and end of denitrification reaction Cr Concentration (mg / L); Δt: denitrification time (h); θ: removal rate; ΔCOD / ΔTN: Carbon source consumption for denitrification, that is, the carbon source required to remove unit TN.

[0007] Preferably, in step 3, if there is no DO meter, the mixed solution is allowed to stand for 15 minutes before use, so that the dissolved oxygen in the mixed solution is less than 0.5 mg / L.

[0008] Preferably, in step 3, if the sludge concentration of the obtained sludge mixed liquor is lower than 3000 mg / L, the sludge mixed liquor is allowed to settle for 5 to 10 minutes, and part of the supernatant is removed to make the sludge concentration greater than 4000 mg / L.

[0009] Preferably, in step 5, if the sludge concentration is greater than 6000 mg / L, or the sludge is relatively dispersed, or the sludge performance is poor resulting in slow filtration or the filtration time exceeds 5 min, centrifugation is performed first and then filtration, at 4°C, at a speed of 5000-6000 r / min, and centrifugation is performed for 5 min.

[0010] Preferably, in step 5, if the water sample index determination time exceeds 24 h, 98% concentrated sulfuric acid is added dropwise to acidify the water sample until the pH of the water sample is ≤2.

[0011] The present invention has the following advantages: 1. Compared with the prior art, the method designed by this invention does not require complete isolation from the air, and the experimental process is simple and easy to operate, which is convenient for sewage plant technicians to quickly get started.

[0012] 2. The experimental equipment and materials involved in the method designed by the invention are easy to obtain and prepare (generally available in sewage treatment plant laboratories), and it is easy to achieve the purpose of evaluating and screening the performance of suitable carbon sources.

[0013] 3. The experimental results obtained by the method designed by this invention are consistent with the results of the actual sewage treatment production line.

[0014] 4. The method of the invention has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A graph showing the hourly changes in nitrate nitrogen in the denitrification process provided by the present invention; Figure 2 The total nitrogen hourly variation diagram of the denitrification process provided by the present invention; Figure 3 The hourly variation diagram of TN of effluent from denitrification with different carbon sources provided by the present invention; Figure 4 This is a graph showing the hourly changes in nitrate nitrogen in the effluent from denitrification with different carbon sources added provided by the present invention. DETAILED DESCRIPTION

[0016] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Table 1 shows the sewage quality received by some urban sewage treatment plants in my country. As can be seen from the table, the northernmost of these sewage treatment plants is located in D City in Northeast my country, while the southernmost is located in K City in Y Province in the southwest of my country. From the perspective of water quality indicators, the highest BOD5 / TN is 3.03, and the lowest is only 1.42, both of which are typical low C / N ratio domestic sewage. According to traditional denitrification theory, denitrification removes 1 mg of NO3 - -N, the amount of carbon source required is converted into BOD5, which is 2.86 mg. However, since the growth of microorganisms also requires carbon sources, efficient denitrification can only be achieved when the actual B / N ratio is above 4.0. In addition, biological phosphorus removal also requires a carbon source, so the carbon source required for simultaneous denitrification and phosphorus removal will be higher, and my country's urban sewage plants generally face the problem of shortage of carbon sources in sewage for denitrification and phosphorus removal.

[0018] Table 1 Water quality indicators of some urban sewage treatment plants in my country

[0019] Example 1: The activated sludge used in the test was taken from the mixed liquid at the end of the aerobic tank. After testing, the background value of nitrate nitrogen was 6.12 mg / L, COD Cr 8mg / L, sludge concentration MLSS 5847mg / L, adding carbon source at a certain carbon source concentration, stirring the reaction quickly, and then sampling and analyzing the mixed solution at different reaction times. Cr The equivalent test results are shown in Table 2, and the comparative test results are shown in Table 3. Figure 1 and Figure 2 shown.

[0020] Table 2 Comparison of test results of carbon sources

[0021] Table 3 Carbon source denitrification performance test results

[0022] It can be seen from Table 3 that under the same carbon source COD Cr At the added concentration, after 3 h of denitrification, the denitrification rate of 1#LL carbon source 1 was 0.6 mg TN / g SS.h, the denitrification rate of 2#LL carbon source 2 was 0.86 mg TN / g SS.h, the denitrification rate of 3#LL carbon source 3 was 0.85 mg TN / g SS.h, and the denitrification rate of 4#plant carbon source was 0.50 mg TN / g SS.h; The total nitrogen removal efficiency of 1#LL carbon source 1 was 67.74%, that of 2#LL carbon source 2 was 93.23%, that of 3#LL carbon source 3 was 94.29%, and that of 4#plant carbon source was 57.38%.

[0023] That is, the denitrification effects (denitrification rate and total nitrogen removal rate) of the three LL biological carbon sources are better than the carbon sources currently used in the plant, among which LL carbon source 2 has the best denitrification effect, with a denitrification rate of 72% higher than that of the carbon sources in the plant, and a total nitrogen removal rate of about 62.48% higher than that of the carbon sources in the plant. From the perspective of denitrification rate, LL carbon source 2>LL carbon source 3>LL carbon source 1>the carbon sources currently used in the plant. It can be seen that although it was used for the first time, the LL biological carbon source can be absorbed and utilized by the activated sludge denitrifying bacteria in the plant, and it shows a high denitrification rate and denitrification effect, indicating that the LL composite biological carbon source has good denitrification efficiency and adaptability.

[0024] Comparison of unit consumption of biological denitrification with different carbon sources Under the experimental conditions, the reaction lasted for 3 hours, and the calculation results of the denitrification and nitrogen removal unit consumption of the four carbon sources are shown in Table 4 below.

[0025] Table 4 Calculation results of carbon source denitrification unit consumption

[0026] It can be seen from Table 4 that the unit consumption of denitrification of LL carbon source 3 is lower than that of the carbon source in the plant.

[0027] Example 2: This experiment aims to investigate the denitrification performance of different types of LL carbon sources and on-site carbon sources at the same carbon source COD addition concentration. The denitrification activated sludge system used in this experiment was taken from the mixed sludge at the end of the biochemical reaction section of the second plant. After adding about 46 mg / L of nitrate nitrogen (potassium nitrate solution), the indicators of the mixed solution were tested, as shown in Table 5. The types of carbon sources and COD used in this experiment CrThe measured results are shown in Table 6. Carbon source addition tests were carried out according to the dosage in Table 7 to compare the denitrification and denitrification effects of different carbon sources. The test and analysis results are shown in Tables 8, 9, 10 and Figure 3 shown.

[0028] Table 5 Denitrification mixed solution test results

[0029] Note:* The nitrate nitrogen data are the test results of LL laboratory according to the national standard method.

[0030] Table 6 COD of experimental carbon sources Cr Equivalence test results

[0031] Table 7 Carbon source addition conditions in the denitrification performance test of different carbon sources

[0032] Table 8 Total nitrogen test results of denitrification test effluent

[0033] Note: Total nitrogen data are the actual and instrumental measurement results of Hach, and the total nitrogen at 0 hours is based on the total nitrogen of the original solution.

[0034] Table 9 Denitrification test effluent COD cr Test Results

[0035] Note: COD at 0h is calculated by adding COD of the original solution to COD concentration of the actual added carbon source.

[0036] Table 10 Test results of nitrate nitrogen in denitrification test effluent

[0037] Note: Nitrate nitrogen data is the test result of LL laboratory according to the national standard method. Nitrate nitrogen at 0 hours is calculated based on the original solution nitrate nitrogen Table 11 Comparison of denitrification effects of different carbon sources

[0038] Note: (1) Due to Figure 3 The straight line segment of the denitrification curve is not obvious, so Y N1 and Y N2 The calculation is based on Figure 3 and Figure 4 The average value is calculated for the first 4 hours. (2) ΔCOD / ΔTN and total nitrogen removal rate are calculated based on the end of the reaction at 18 hours, where ΔCOD is calculated based on the COD concentration of the added carbon source. (3) Total nitrogen removal rate and nitrate nitrogen removal rate are calculated based on the end of the reaction at 18 hours.

[0039] This experiment obtained the mixed liquid at the end of the biochemical pool of the sewage plant, COD CrThe concentration is 392 mg / L. Through blank test control, from Table 8, Table 10, Figure 3 and Figure 4 It can be seen that as the reaction time increases, the total nitrogen concentration of the mixed liquid system remains basically unchanged, and the COD Cr The effect on denitrification is small, and it is basically COD that is not easily absorbed and utilized by microorganisms. Cr .

[0040] from Figure 3 Table 11 Denitrification rate Y N1 From the perspective of LL carbon source 2>LL carbon source 3>LL carbon source 1>glucose, the denitrification rate of LL carbon source 2 increased by 220% compared with glucose. N2 From the above, LL carbon source 2>LL carbon source 1≈LL carbon source 3>glucose, among which the denitrification rate of LL carbon source 1 composite carbon source increased by 60% compared with glucose, LL carbon source 2 increased by 125%, and LL carbon source 3 increased by 53%. Therefore, the denitrification rate and denitrification rate of the three LL carbon sources in this pilot test were higher than the glucose currently used in the sewage plant, among which LL carbon source 2 had the best denitrification performance.

[0041] Analysis of the denitrification carbon source consumption of the four carbon sources shows that LL carbon source 2 < LL carbon source 1 = LL carbon source 3 < glucose, among which the denitrification carbon source consumption of LL carbon source 1 and LL carbon source 3 composite carbon sources is 29.7% lower than that of glucose, and LL carbon source 2 is 77.14% lower than that of glucose. Therefore, the denitrification carbon source consumption of the three LL composite carbon sources in this pilot test is lower than that of the current glucose carbon source, which means that the use of LL carbon source to remove unit nitrate nitrogen (TN) is less than that of glucose carbon source, thereby saving the cost of carbon source use.

[0042] After 18 hours of reaction, the total nitrogen removal rates of denitrification effluent involving LL carbon source 1, LL carbon source 2, LL carbon source 3 and glucose were 41.01%, 56.12%, 41.01% and 31.65%, respectively, while the nitrate nitrogen removal rates were 55.52%, 71.20%, 51.57% and 37.36%, respectively. The three LL carbon sources performed better, among which LL carbon source 2 had the highest removal rate for denitrification reaction.

[0043] In summary, LL carbon source 2 showed better denitrification performance than glucose carbon source: higher denitrification rate, lower denitrification carbon source consumption and higher TN removal rate.

[0044] In summary, the experimental results obtained by the test method designed by the present invention are consistent with the results of the actual sewage treatment production line, so as to achieve scientific and reasonable selection of cost-effective carbon sources suitable for the denitrification treatment requirements and process characteristics of the sewage plant, thereby reducing costs (according to the above experimental data: denitrification rate, denitrification carbon source unit consumption and TN removal rate can be seen) Comparative example: Compared with a sewage treatment external carbon source screening device and its use method with publication number CN111398521A, the carbon source obtained by the method designed by the present invention meets the anoxic condition requirement of the anoxic denitrification denitrification carbon source test, making the experimental process simple and easy to operate, and convenient for sewage treatment plant technicians to quickly get started; and the experimental equipment and materials involved in the test method of this embodiment are easy to obtain and prepare (generally available in sewage treatment plant laboratories), and it is easy to achieve the purpose of evaluating and screening the performance of suitable carbon sources.

[0045] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for testing the performance of a denitrification carbon source, characterized in that: The following steps are involved: Step 1. Take the mixed liquor required for the biological denitrification carbon source performance test: take the mixed liquor at the end of the aerobic stage in the oxidation ditch process; take the mixed liquor at the end of the aerobic reaction and before precipitation in the sequencing batch activated sludge process; Step 2. Take an appropriate amount of the mixed solution from step 1 above to test the sludge concentration, including suspended solids concentration SS, total nitrogen TN or nitrate nitrogen and chemical oxygen demand COD Cr ; When the nitrate nitrogen content in the mixed solution is 8 ~ 10 mg / L, directly add carbon source for detection. When it is lower than this value, add nitrate to increase the nitrate nitrogen content in the mixed solution by 10 ~ 20 mg / L; Step 3. Measure 1.0-1.5 L of the mixed solution in step 1 above and pour it into a reaction beaker. The sludge concentration is greater than 4000 mg / L. Place it on a magnetic stirrer or a six-way stirrer and stir it at a speed of 50-65 r / min to ensure that the sludge mixed solution is fully mixed and the mud-water interface is lower than the water surface. After adjusting the speed, the DO value of the mixed solution can be measured with a DO meter. When the dissolved oxygen of the mixed solution measured by the DO meter is lower than 0.5 mg / L, it is considered to meet the anoxic conditions required for the anoxic denitrification carbon source test; Step 4. Add a certain amount of carbon source, the amount of addition is based on COD Cr / ΔTN=4~7 for calculation and addition. After adding the carbon source, stir the mixed liquid until it is fully mixed with the carbon source. The rapid stirring speed is not less than 100 r / min, and the time is about 5s. Step 5. After adding the carbon source, start timing from 0 o'clock, and take samples every 30 to 60 minutes until the TN or nitrate concentration in the sample tends to be constant; Sampling should be done quickly, with the sampling volume being less than 1 / 20 of the initial reaction mixture volume; after each sampling, use 0.45 um filter paper to separate the solid and liquid immediately, discard the initial filtrate to obtain the water sample, and store the water sample in a refrigerator at 4°C; Determine the COD of the above water samples at different reaction times within 24 hours after sampling Cr and TN; Step 6. Calculate the biological denitrification / denitrification rate, sludge carbon source consumption rate, TN removal rate, and denitrification carbon source consumption index as shown in equations (1), (2), (3), and (4); Y N =(N1-N2) / (SS*Δt)(1); Y C =(C1-C2) / (SS*Δt)(2); θ=(N1-N2) / N1*100%(3); ΔCOD / ΔTN=(C1-C2) / (N1-N2)(4); Where: Y N : Denitrification / denitrification rate (mg TN / g SS.h); Y C : Sludge carbon source consumption rate (mg COD Cr / g SS.h); N1, N2: TN or NO3 corresponding to the start and end of denitrification reaction - -N concentration (mg / L); SS sludge concentration (g / L); C1, C2: COD corresponding to the start and end of denitrification reaction Cr Concentration (mg / L); Δt: denitrification time (h); θ: removal rate; ΔCOD / ΔTN: Carbon source consumption for denitrification, that is, the carbon source required to remove unit TN.

2. The denitrification carbon source performance testing method according to claim 1, characterized in that: In step 3, if there is no DO meter, let the mixed solution stand for 15 minutes before use, so that the dissolved oxygen in the mixed solution is less than 0.5 mg / L.

3. The denitrification carbon source performance testing method according to claim 1, characterized in that: In step 3, if the sludge concentration of the obtained sludge mixed liquor is lower than 3000 mg / L, the sludge mixed liquor is allowed to settle for 5 to 10 minutes, and part of the supernatant is removed to make the sludge concentration greater than 4000 mg / L.

4. The denitrification carbon source performance testing method according to claim 1, characterized in that: In step 5, if the sludge concentration is greater than 6000 mg / L, or the sludge is relatively dispersed, or the sludge performance is poor resulting in slow filtration or the filtration time exceeds 5 minutes, centrifuge first and then filter at 4°C, at a speed of 5000-6000 r / min, for 5 minutes.

5. The denitrification carbon source performance testing method according to claim 1, characterized in that: In step 5, if the water sample index determination time exceeds 24 h, add 98% concentrated sulfuric acid to acidify the water sample until the pH of the water sample is ≤2.

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