A method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source.

Abstract

This invention discloses a method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine (TCM) wastewater as a carbon source, belonging to the field of wastewater treatment technology. This invention adds TCM wastewater as the sole external carbon source to high-nitrate nitrogen wastewater, followed by the addition of denitrifying sludge. Under anoxic or anaerobic conditions, denitrification occurs, achieving a total nitrogen removal rate of over 95%. Compared to traditional carbon sources (such as sodium acetate and ethanol), this invention offers advantages such as low or even negative cost, high nitrogen treatment load, high nitrogen removal efficiency, and more thorough denitrification. In this method, TCM wastewater not only serves as a highly efficient carbon source but also enhances the denitrification performance of microorganisms and the stability of the system. This invention achieves the synergistic treatment of TCM wastewater resource utilization and wastewater denitrification, resulting in significant environmental and economic benefits and meeting the requirements of green circular economy development.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source, applicable to the combined treatment of high-organic-concentration traditional Chinese medicine wastewater and high-nitrate-nitrogen industrial wastewater. Background Technology

[0002] Currently, in the treatment of nitrate nitrogen in urban sewage treatment plants and some industrial wastewater, the denitrification process is often limited due to insufficient carbon sources. In engineering, it is usually necessary to add organic carbon sources such as methanol, ethanol, and sodium acetate to ensure that denitrification proceeds smoothly and efficiently. However, existing chemical carbon sources generally have the following problems: (1) low nitrogen treatment load; (2) high price and high operating cost; (3) low carbon source utilization rate, which easily leads to increased COD in effluent and secondary pollution; (4) low denitrification performance.

[0003] Although there are reports on treatments using kitchen waste (CN104324930A), composite carbon sources (CN111039399A), composite fillers (CN103232117A), and low C / N ratio high N treatment (CN112520849A), these treatments have problems such as the need for pretreatment, complex formulations, high raw material consumption, or low nitrogen load, making it difficult to achieve the three elements of "high nitrogen load - high performance - low cost".

[0004] The extraction, concentration, and washing processes of traditional Chinese medicine (TCM) generate large amounts of carbon-containing organic wastewater, which can serve as a high-quality carbon source. Existing technologies primarily focus on "pretreatment-anaerobic digestion" or "active ingredient recovery" of TCM wastewater, with no reports of directly using untreated TCM wastewater for denitrification. Therefore, developing a "no-pretreatment, direct addition, waste-to-waste" carbon source technology for TCM wastewater could reduce wastewater treatment costs, significantly lower denitrification operating costs, and improve denitrification efficiency, thus possessing significant engineering and environmental value. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of low nitrogen treatment load, low denitrification performance, high cost of purchased carbon sources, and low utilization rate of existing carbon sources. It provides a method for treating high nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source, realizing the synergistic treatment of traditional Chinese medicine wastewater by "treating waste with waste" and efficient biological denitrification.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source involves adding traditional Chinese medicine wastewater as the sole external carbon source to the high-nitrate nitrogen wastewater to obtain mixed wastewater; adding denitrifying sludge to the mixed wastewater and carrying out a denitrification reaction under anoxic or anaerobic conditions.

[0008] Furthermore, the wastewater from traditional Chinese medicine production includes at least one of the following: extraction wastewater, washing wastewater, concentrated mother liquor, and fermentation wastewater.

[0009] Furthermore, the pH value of the traditional Chinese medicine wastewater is 3.0-6.0, and the COD concentration is 4-200g / L.

[0010] Furthermore, the concentration of high nitrate nitrogen in the mixed wastewater is 200-3000 mg / L.

[0011] Furthermore, the C / N mass ratio of the mixed wastewater is 3:1-15:1.

[0012] Furthermore, the denitrification reaction is carried out in a denitrification reactor, which is one or a combination of two of the following: a batch reactor, a UASB reactor, and a denitrification reactor.

[0013] Furthermore, the VSS content in the denitrification sludge is 30-60 g / L, and the concentration of the denitrification sludge in the mixed wastewater is 2-3 g / L.

[0014] Furthermore, the denitrification reaction is carried out at a temperature of 25-35℃, a pH of 5-11, and a reaction time of 60-120h.

[0015] In summary, the present invention has the following beneficial effects:

[0016] (1) Resource utilization: The untreated Chinese medicine wastewater is directly used as a carbon source for denitrification, realizing "waste treatment with waste". There is no need to purchase commercial carbon sources, which significantly reduces operating costs and opens up new ways for the high-value resource utilization of Chinese medicine wastewater.

[0017] (2) High nitrogen load: Under high nitrogen load, the traditional Chinese medicine wastewater can still maintain a stable and efficient denitrification process as a carbon source for denitrification, thereby achieving effective removal of total nitrogen from high nitrogen wastewater of 200-3000 mg / L.

[0018] (3) High efficiency in nitrogen removal: Traditional Chinese medicine wastewater contains polysaccharides, proteins, organic acids, alcohols, humic acid and other easily degradable organic matter. The nitrate nitrogen removal rate can reach more than 95%, which can optimize the microbial community structure, reduce the accumulation of nitrite nitrogen, and improve the denitrification rate and stability of the system.

[0019] (4) Environmentally friendly: There is no risk of secondary pollution, which is in line with the concept of green and circular sustainable development. Attached Figure Description

[0020] Figure 1 This is a comparison chart of the test results of effluent nitrate nitrogen concentration and nitrate nitrogen accumulation in the wastewater denitrification treatment experiments of Example 1, Comparative Example 1, and Comparative Example 2;

[0021] Figure 2 This is a comparison chart of the test results of effluent nitrate nitrogen concentration and nitrate nitrogen accumulation in the wastewater denitrification treatment experiments of Example 2, Comparative Example 3, and Comparative Example 4;

[0022] Figure 3 This is a comparison chart of the test results of effluent nitrate nitrogen concentration and nitrate nitrogen accumulation in the wastewater denitrification treatment experiments of Example 3, Comparative Example 5, and Comparative Example 6;

[0023] Figure 4 This is a comparison chart of the test results of effluent nitrate nitrogen concentration and nitrate nitrogen accumulation in the wastewater denitrification treatment experiments of Example 4, Comparative Example 7, and Comparative Example 8;

[0024] Figure 5 This is a comparison chart of the abundance test results of key denitrification functional genes (nirK, nirS, narK) in Example 4 and Comparative Examples 7 and 8. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention uses traditional Chinese medicine wastewater with a pH of 3.0-6.0 and a COD concentration of 4-200 g / L as the sole external carbon source (the traditional Chinese medicine wastewater is at least one of the extraction wastewater, washing wastewater, concentrated mother liquor, and fermentation wastewater generated in the production of traditional Chinese medicine, and the traditional Chinese medicine wastewater has not undergone physical, chemical, or biological pretreatment), added to high nitrate nitrogen wastewater to produce mixed wastewater with a final high nitrate nitrogen concentration of 200-3000 mg / L and a C / N mass ratio of 3:1-15:1; then, denitrifying sludge with a VSS content of 30-60 g / L is added to the mixed wastewater, and the concentration of denitrifying sludge in the mixed wastewater is controlled at 2-3 g / L. The denitrification reaction is carried out for 60-120 h at 25-35℃, pH of 5-11, and under anoxic or anaerobic conditions. The denitrification reaction is carried out in a denitrification reactor (such as one or a combination of two of the following: a batch reactor SBR, a UASB reactor). Nitrogen removal is achieved by using soluble organic matter in wastewater to reduce nitrate nitrogen to nitrogen gas.

[0027] Test method:

[0028] Nitrate nitrogen concentration was determined using ultraviolet spectrophotometry: 50 μL of the reacted sample was placed in a 25 mL colorimetric tube, diluted to the mark with water, and 1 mL of 1 mol / L hydrochloric acid solution and 0.1 mL of 0.8% aminosulfonic acid solution were added. After mixing, the mixture was allowed to stand for 15 min, and the nitrate nitrogen reading was obtained at a wavelength of 220 nm within 2 h. Any interference caused by dissolved organic matter was determined using a wavelength of 275 nm. For both samples and standards, twice the absorbance reading at 275 nm was subtracted from the 220 nm reading to obtain the absorbance caused by nitrate nitrogen.

[0029] The concentration of nitrite nitrogen was determined by colorimetry: 100 μL of the reacted sample was placed in a 25 mL colorimetric tube, diluted with water to the mark, 1 mL of nitrite nitrogen colorimetric reagent was added, mixed well and allowed to stand for 15 min. The nitrite nitrogen reading was obtained within 2 h using a wavelength of 540 nm.

[0030] Metagenomic sequencing technology was used to test denitrification sludge to obtain raw sequencing data. Fastp was used to perform quality control on the raw data to remove low-quality sequences, adapter sequences, and sequences containing N, thereby improving data quality. Gene prediction was performed directly on the sequencing reads, and the predicted genes were compared with the KEGG functional database to obtain functional gene information. The abundance results of key denitrification functional genes (nirK, nirS, narK) in the examples and comparative examples were obtained.

[0031] Example 1: Denitrification treatment of traditional Chinese medicine wastewater with 1000 mg / L nitrate nitrogen simulated wastewater (C / N ratio of 10).

[0032] (1) Use Chinese medicine wastewater as carbon source (denoted as CMW) and determine its COD concentration.

[0033] The COD concentration test method is as follows: Take the traditional Chinese medicine wastewater and dilute it 100 times with water (according to the COD test range of the multi-parameter water quality analyzer, dilute the traditional Chinese medicine wastewater to a suitable range). Take 2.5 mL of the diluted wastewater and place it in a reaction tube. Add 0.7 mL of special consumable D reagent and 4.8 mL of special consumable E reagent (the special consumable D reagent and special consumable E reagent are COD wastewater detection reagent LH-DE-500 purchased from Beijing Lianhua Yongxing Technology Development Co., Ltd.) to the reaction tube and mix well. Place the reaction tube into the digestion port of the multi-parameter water quality analyzer and digest at 165℃ for 10 min. At the same time, turn on the colorimetric system to preheat. After digestion, place the sample in the sample cell and air cool for 5 min. Add 2.5 mL of ultrapure water and mix well. Place it in the cooling water tank and cool for 5 min. After water cooling, pour the solution into a cuvette for colorimetric testing (use the COD high-range cuvette colorimetric mode and select curve M01-1). The COD concentration of the diluted wastewater was 738.6 mg / L, therefore the COD concentration of the original Chinese medicine wastewater was 73860 mg / L.

[0034] (2) Based on the COD concentration of the traditional Chinese medicine wastewater, prepare a CMW-potassium nitrate solution (pH=7.0) with a nitrate nitrogen concentration of 1000 mg / L and a C / N ratio of 10. Add 0.4 L of the CMW-potassium nitrate solution to the SBR reactor, add 25 mL of denitrifying sludge with a VSS content of 40 g / L, and purge with high-purity nitrogen for 30 min to remove oxygen from the solution. React in a constant temperature air bath shaker at 30℃ and 180 rpm for 84 h. Take samples at 0, 12, 24, 36, 48, 60, 72, and 84 h, and immediately filter through a 0.45 μm filter membrane to determine NO3. - -N, NO2 - -N concentration.

[0035] The results show (see) Figure 1 Under conditions of an initial nitrate nitrogen concentration of 1000 mg / L and a C / N ratio of 10, denitrification treatment was carried out using traditional Chinese medicine wastewater as the sole carbon source. After 84 hours of reaction, the effluent nitrate nitrogen concentration decreased to 10 mg / L, achieving a removal rate of 99%; the nitrite nitrogen accumulation was less than 0.5 mg / L, with almost no secondary pollution. The SBR system entered a stable denitrification stage after 48 hours, demonstrating good denitrification rate and stability.

[0036] Comparative Example 1

[0037] The SBR reaction was performed according to Example 1, but sodium acetate was used as the carbon source for denitrification, denoted as carbon source SA.

[0038] Comparative Example 2

[0039] The SBR reaction was performed according to Example 1, but ethanol was used as the carbon source for denitration, denoted as carbon source ALC.

[0040] Example 2: Denitrification treatment of traditional Chinese medicine wastewater with 1000 mg / L nitrate nitrogen simulated wastewater (C / N ratio of 5)

[0041] Using the traditional Chinese medicine wastewater from Example 1 as the carbon source, a CMW-potassium nitrate solution (pH=7.0) with a nitrate nitrogen concentration of 1000 mg / L and a C / N ratio of 5 was prepared. 0.4 L of the CMW-potassium nitrate solution was added to an SBR reactor, along with 25 mL of denitrifying sludge with a VSS content of 40 g / L. High-purity nitrogen was bubbled through the reactor for 30 min to remove oxygen. The reactor was then subjected to constant temperature air bath shaking at 30°C and 180 rpm for 84 h. Samples were taken at 0, 12, 24, 36, 48, 60, 72, and 84 h, and immediately filtered through a 0.45 μm filter membrane to determine NO3. - -N, NO2 - -N concentration.

[0042] The results show (see) Figure 2 Under conditions of a C / N ratio of 5 and an initial nitrate nitrogen concentration of 1000 mg / L, the effluent nitrate nitrogen concentration was 12 mg / L after 84 hours of reaction, with a removal rate of 98%. Although the carbon source was relatively insufficient, the system maintained a high denitrification efficiency, but the reaction rate decreased slightly, indicating that the wastewater from traditional Chinese medicine still has good usability under low C / N ratio conditions.

[0043] Comparative Example 3

[0044] The SBR reaction was performed according to Example 2, but sodium acetate was used as the carbon source for denitrification (denoted as carbon source SA).

[0045] Comparative Example 4

[0046] The SBR reaction was performed according to Example 2, but ethanol was used as the carbon source for denitration (denoted as carbon source ALC).

[0047] Example 3: Denitrification treatment of traditional Chinese medicine wastewater with 2000 mg / L nitrate nitrogen simulated wastewater (C / N ratio of 10)

[0048] Using the traditional Chinese medicine wastewater from Example 1 as the carbon source, a CMW-potassium nitrate solution (pH=7.0) with a nitrate nitrogen concentration of 2000 mg / L and a C / N ratio of 10 was prepared. 0.4 L of the CMW-potassium nitrate solution was added to an SBR reactor, along with 25 mL of denitrifying sludge with a VSS content of 40 g / L. The reactor was subjected to constant temperature air bath shaking at 30°C and 180 rpm for 108 h. Samples were taken at 0, 12, 24, 36, 48, 60, 72, 84, 96, and 108 h, and immediately filtered through a 0.45 μm filter membrane to determine NO3. - -N, NO2 - -N concentration.

[0049] The results show (see) Figure 3 Under conditions where the initial nitrate nitrogen concentration was increased to 2000 mg / L and the C / N ratio was 10, the effluent nitrate nitrogen concentration was approximately 30 mg / L after 108 hours of reaction, achieving a removal rate of 97%. The SBR system maintained stable operation under high nitrogen load without significant inhibition, indicating that traditional Chinese medicine wastewater is suitable for deep denitrification treatment of high-concentration nitrate nitrogen wastewater.

[0050] Comparative Example 5

[0051] The SBR reaction was performed according to Example 3, but sodium acetate was used as the carbon source for denitrification (denoted as carbon source SA).

[0052] Comparative Example 6

[0053] The SBR reaction was performed according to Example 3, but ethanol was used as the carbon source for denitration (denoted as carbon source ALC).

[0054] Example 4: Denitrification treatment of traditional Chinese medicine wastewater with 2000 mg / L nitrate nitrogen simulated wastewater (C / N ratio of 5)

[0055] Using the traditional Chinese medicine wastewater from Example 1 as the carbon source CMW, a CMW-potassium nitrate solution (pH=7.0) with a nitrate nitrogen concentration of 2000 mg / L and a C / N ratio of 5 was prepared. 0.4 L of the CMW-potassium nitrate solution was added to an SBR reactor, along with 25 mL of denitrifying sludge with a VSS content of 40 g / L. High-purity nitrogen was bubbled through the reactor for 30 min to remove oxygen. The reactor was then subjected to constant temperature air bath shaking at 30°C and 180 rpm for 108 h. Samples were taken at 0, 12, 24, 36, 48, 60, 72, 84, 96, and 108 h, and immediately filtered through a 0.45 μm filter membrane to determine NO3. - -N, NO2 - -N concentration.

[0056] The results show (see) Figure 4 Under conditions of a C / N ratio of 5 and a reaction time of 108 h, the system's treatment effect on 2000 mg / L nitrate nitrogen wastewater was basically the same as in Example 3, with an effluent nitrate nitrogen concentration of 35 mg / L and a removal rate of 96.5%. This further verifies the stability and high efficiency of traditional Chinese medicine wastewater as a carbon source under high load conditions.

[0057] Comparative Example 7

[0058] The SBR reaction was performed according to Example 4, but sodium acetate was used as the carbon source for denitrification (denoted as carbon source SA).

[0059] Comparative Example 8

[0060] The SBR reaction was performed according to Example 4, but ethanol was used as the carbon source for denitration (denoted as carbon source ALC).

[0061] In the above embodiments and comparative examples, those using CMW as the carbon source are denoted as the CMW group, those using SA as the carbon source are denoted as the SA group, and those using ALC as the carbon source are denoted as the ALC group.

[0062] The effluent quality of the SBR reactors in each embodiment and comparative example was measured, and the denitrification effect was analyzed and compared. Figure 1 It can be seen that in the treatment of simulated nitrate nitrogen wastewater with a nitrate nitrogen concentration of 1000 mg / L and a C / N ratio of 10, the nitrate reduction rate from high to low is CMW group, ALC group, and SA group. The nitrate nitrogen removal rate of both CMW group and ALC group is ≥98%. Figure 2 It can be seen that in the treatment of nitrate nitrogen simulated wastewater with a nitrate nitrogen concentration of 1000 mg / L and a C / N ratio of 5, the CMW group and the ALC group still maintained a high removal rate, while the SA group had a removal rate of 86% due to low carbon source utilization. The accumulation of nitrite nitrogen was in the order of SA > ALC > CMW, indicating that the denitrification performance of CMW reached or even exceeded that of commercial carbon sources.

[0063] Depend on Figure 3 It can be seen that under a high nitrogen load of 2000 mg / L, the CMW group with a C / N ratio of 5 had lower nitrate and nitrite nitrogen contents in the effluent than other groups, indicating better water quality. In contrast, excessive addition of commercial salt carbon source (at a high nitrogen load of 2000 mg / L and a C / N ratio of 10) led to increased system salinity, inhibited microbial activity, and decreased denitrification efficiency. Figure 4 Further gene abundance analysis showed that the abundance of key genes (nirS, nirK) for nitrite reductase and the membrane transport protein gene narK in the CMW group (Example 4) was simultaneously higher than that in the SA group (Comparative Example 7) and the ALC group (Comparative Example 8). The functional bacteria's ability to reduce nitrite and substrate transport efficiency were simultaneously enhanced, thus significantly improving the system's denitrification rate and operational stability. Specifically, as shown below... Figure 5 As shown.

[0064] In the above examples and comparative examples, the traditional Chinese medicine wastewater came from the wastewater generated by Zhejiang Kang Enbei Traditional Chinese Medicine Co., Ltd. in the production of compound houttuynia cordata mixture (wastewater generated in the extraction, concentration and washing sections, without physical, chemical or biological pretreatment); the denitrification sludge came from the anaerobic denitrification tank of Lishui Jiayuan Environmental Protection Engineering Co., Ltd.

[0065] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source, characterized in that, Traditional Chinese medicine wastewater was added as the sole external carbon source to high-nitrate nitrogen wastewater to obtain mixed wastewater, in which the traditional Chinese medicine wastewater was generated during the production of compound houttuynia cordata mixture; denitrifying sludge was added to the mixed wastewater to carry out denitrification reaction under anoxic or anaerobic conditions.

2. The method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source according to claim 1, characterized in that, Traditional Chinese medicine wastewater refers to at least one of the following generated during the production of traditional Chinese medicine: extraction wastewater, washing wastewater, concentrated mother liquor, and fermentation wastewater.

3. The method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source according to claim 1, characterized in that, The pH value of the Chinese herbal medicine wastewater is 3.0-6.0, and the COD concentration is 4-200g / L.

4. The method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source according to claim 1, characterized in that, The concentration of high nitrate nitrogen in the mixed wastewater is 200-3000 mg / L.

5. The method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source according to claim 1, characterized in that, The C / N mass ratio of the mixed wastewater is 3:1-15:

1.

6. The method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source according to claim 1, characterized in that, The denitrification reaction is carried out in a denitrification reactor, which is one or a combination of two of the following: a batch reactor, a UASB reactor, and a denitrification reactor.

7. The method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source according to claim 1, characterized in that, The VSS content in the denitrification sludge is 30-60 g / L, and the concentration of denitrification sludge in the mixed wastewater is 2-3 g / L.

8. The method for treating high-nitrate nitrogen wastewater using traditional Chinese medicine wastewater as a carbon source according to claim 1, characterized in that, The reaction temperature for denitrification is 25-35℃, the pH value is 5-11, and the reaction time is 60-120h.

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