Isopropanol high-salt wastewater biodegradation method based on gradient domestication salt-tolerant flora

Abstract

The invention discloses an isopropanol high-salt wastewater biodegradation method based on gradient domestication salt-tolerant flora, which specifically comprises the following steps: selecting salt-tolerant activated sludge as an inoculation source, inoculating the salt-tolerant activated sludge into a sequencing batch reactor (SBR), setting domestication initial salinity and influent chemical oxygen demand (COD) load by taking isopropanol-containing high-salt wastewater as influent, and performing gradient domestication on the high-salt wastewater by using the domestication initial salinity and the influent chemical oxygen demand (COD) load; the influent salinity and the organic load are cooperatively regulated and controlled according to a preset gradient, and are gradually increased to a target threshold value, so that the microbial community gradually adapts to a high-salinity environment, and the stable biodegradation capability on isopropanol is established. According to the biodegradation method disclosed by the invention, stable construction of the salt-tolerant degrading flora is realized through a controlled gradient domestication process, and the biodegradation method has the characteristics of high operation stability, good process controllability and strong replicability.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a method for the biodegradation of high-salt isopropanol wastewater based on gradient domestication of salt-tolerant bacterial communities. Background Technology

[0002] With the rapid development of the semiconductor, photovoltaic cell, and some fine chemical industries, the use of isopropanol (IPA) as a cleaning or solvent in production processes is constantly increasing, leading to a rising trend in the discharge of IPA-containing wastewater. This type of wastewater is typically accompanied by high concentrations of dissolved salts (in terms of total dissolved solids (TDS) and Cl-). - (represented by) and contains a certain concentration of organic pollutants, characterized by high salinity, complex composition, and biodegradability significantly affected by salinity.

[0003] Among existing wastewater treatment technologies, biological treatment is widely used due to its relatively low operating cost and wide applicability. However, under high-salt conditions, salt stress can easily cause osmotic pressure imbalance in microbial cells, inhibit the activity of metabolism-related enzymes, and lead to fluctuations in the microbial community structure. This, in turn, causes traditional activated sludge systems to experience problems such as difficulty in starting up, decreased organic matter degradation rate, loose sludge floc structure, and weakened settling performance. These adverse effects further weaken the system's ability to continuously remove organic pollutants, such as isopropanol (IPA), and its overall operational stability.

[0004] For the biological treatment of high-salinity organic wastewater, existing technologies typically involve inoculating and acclimatizing salt-tolerant sludge, and then adjusting operating parameters such as dissolved oxygen (DO), sludge retention time (SRT), hydraulic retention time (HRT), and nutrient ratio to improve the system's salt tolerance. However, these strategies still have certain limitations in practical applications: (1) Microorganisms have a long salt tolerance acclimatization period and are quite sensitive to fluctuations in influent salinity; (2) Under high-salt conditions, the degradation efficiency of biodegradable organic matter, represented by alcohols, is limited; (3) Existing process optimizations mostly use total dissolved solids (TDS) as a single indicator of salinity, and rarely consider Cl. - Including salinity composition characteristic parameters such as TDS in key control variables leads to insufficient controllability and reproducibility of process regulation.

[0005] Therefore, there is an urgent need to develop a biological treatment method suitable for high-salt isopropanol wastewater, which can enable the microbial community to achieve stable adaptation and efficient degradation in a high-salt environment, and maintain good treatment effect and operational stability even when the salinity level and salt composition change. Summary of the Invention

[0006] The purpose of this invention is to provide a method for the biodegradation of high-salt isopropanol wastewater based on gradient domestication of salt-tolerant bacterial communities, which has the characteristics of high operational stability, good process controllability, and strong reproducibility.

[0007] The technical solution adopted in this invention is: The biodegradation method for high-salt isopropanol wastewater based on gradient domestication of salt-tolerant bacterial communities is as follows: Salt-tolerant activated sludge was selected as the inoculum source and inoculated into a sequencing batch reactor (SBR). Wastewater containing isopropanol was used as the influent. The initial salinity and influent COD load were set in the SBR, and the influent salinity and organic load were gradually increased according to a preset gradient until the COD or salinity threshold was reached, so that the sludge could form a stable degradation capacity for isopropanol.

[0008] The invention is further characterized by: Salt-tolerant activated sludge is activated sludge derived from leachate treatment systems in waste incineration plants or from biological treatment systems that treat saline wastewater over a long period of time.

[0009] Salinity was characterized by total dissolved solids (TDS). The initial salinity was 10,000-12,000 mg / L, and the salinity increase for each level was 500-5,000 mg / L, with a target increase of 35,000 mg / L. In the organic loading gradient, the influent COD load increases by 500~1000 mg / L at each stage, gradually increasing to 3000 mg / L.

[0010] During the acclimation process, the COD of the effluent is monitored in real time. Once the preset stability criteria are met under the current salinity and load gradient, the system enters the next salinity / organic load gradient. The specific stability criteria are: the COD removal rate fluctuation does not exceed ±5% for at least 3 consecutive operating cycles, and the effluent COD concentration fluctuation does not exceed ±10%.

[0011] During SBR operation, Cl - Concentration and Cl - mass ratio of Cl to total dissolved solids - / TDS is used as a control index for salinity composition. By adjusting the salinity composition of the influent, Cl - The / TDS ratio remained at Cl - The system maintains a TDS level of <0.5 to mitigate salt inhibition and improve operational stability. Simultaneously, dissolved oxygen, pH, hydraulic retention time, and sludge age are controlled to maintain a suitable reaction environment for biodegradation.

[0012] The adaptive adjustment strategy for aeration time in the SBR system is as follows: the aeration time during the aerobic reaction phase is set to 4–8 hours, and when Cl… -When the concentration increases to 15000 mg / L or the effluent indicators deviate from the stability criteria, the aeration time should be adjusted to 6-8 hours to mitigate the salt inhibition effect.

[0013] The method of the present invention also includes a salinity threshold identification step: under the condition of constant influent organic load, gradually increasing Cl - Concentration and TDS concentration, when Cl - When the concentration increases to 15,000~20,000 mg / L and the TDS increases to 30,000~35,000 mg / L, and the COD removal rate of the system effluent decreases to below the preset threshold, the current salinity is determined to be the salinity tolerance threshold.

[0014] The method of the present invention also includes: collecting sludge samples at different salinity stages during the domestication process for 16S rRNA gene sequencing analysis, which is used to monitor changes in microbial community structure and assist in process regulation.

[0015] The beneficial effects of this invention are: (1) The method of the present invention selects salt-tolerant activated sludge as the inoculum source and adopts a gradient acclimatization strategy of salinity and organic load in the sequencing batch reactor to gradually increase the total dissolved solids (TDS) and chemical oxygen demand (COD) load of the influent, effectively alleviate the impact of high salt and organic load mutation on the microbial system, promote the gradual enrichment of salt-tolerant degrading functional bacteria, and improve the system stability. (2) The method of the present invention removes chloride ions (Cl... - ) concentration and Cl - The / TDS ratio, as a key control index of salt composition, clarifies the limiting effect of chloride ratio on the degradation efficiency of organic matter, realizes the precise characterization and regulation of salt inhibition effect, and overcomes the problem of insufficient process controllability and reproducibility caused by the traditional method of using TDS as a single salinity index. (3) The method of the present invention constructs a linkage response control mechanism between salinity and aeration time. By dynamically adjusting the aeration process, it effectively compensates for the inhibition of microbial activity under high salinity conditions, and improves the system's continuous treatment capacity and operational stability for isopropanol high salinity wastewater under conditions of salinity and salt composition fluctuation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the operation process of the biological treatment system of the present invention; Figure 2 This is a curve showing the change of COD concentration in the effluent of the SBR system during the acclimatization period as a function of the operating cycle in Example 1 of this invention; Figure 3 This is the COD degradation efficiency change curve under the three-stage salinity gradient and organic load conditions during the stable period in Example 2 of the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] This invention relates to a method for the biodegradation of high-salt isopropanol wastewater based on gradient acclimation of salt-tolerant bacterial communities, such as... Figure 1 As shown, please follow these steps: Step 1, vaccination: Salt-tolerant activated sludge was selected as the inoculum source and inoculated into a sequencing batch reactor (SBR). The operating cycle of the SBR includes influent, reaction (stirring / aeration), sedimentation, effluent discharge, and idle phases.

[0019] The preferred inoculum source is activated sludge from the leachate treatment system of a waste incineration plant or a biological treatment system that has been treating saline wastewater for a long time. This type of sludge is in a high ammonia nitrogen and high salt environment for a long time, and has strong tolerance potential and rich microbial diversity. If necessary, the inoculum source can be pre-cultured with low salt or target salinity to reduce the salinity shock during the start-up phase.

[0020] Step 2, Salinity and Organic Load Gradient Acclimation: Wastewater containing isopropanol (IPA) was used as influent. The initial salinity and influent chemical oxygen demand (COD) load were set in the SBR, and the influent salinity and organic load were gradually increased according to the preset gradient until the COD or salinity threshold was reached. This allowed the microorganisms to gradually adapt to the coupled changes of salt stress and substrate load, and form a stable degradation capacity for isopropanol.

[0021] Salinity is characterized by total dissolved solids (TDS). The initial salinity is 10,000-12,000 mg / L, and the salinity increase for each level is 500-5,000 mg / L, with a target increase of 35,000 mg / L.

[0022] In the organic loading ladder, the influent COD load increases by 500~1000 mg / L at each stage, gradually increasing to 3000 mg / L.

[0023] During the acclimation process, the system monitors the effluent COD or isopropanol concentration in real time. Once the preset stability criteria are met under the current salinity and load gradient, the system moves to the next salinity / organic load gradient. The specific stability criteria are: COD removal rate fluctuation not exceeding ±5% and effluent COD concentration fluctuation not exceeding ±10% for at least 3 consecutive operating cycles.

[0024] During SBR operation, based on Cl - / TDS and effluent indicators are linked to adjust the salinity gradient and aeration time, specifically as follows: During each operating cycle, obtain the total dissolved solids (TDS) and chloride ion concentration (Cl) in the influent and / or reactor. -It can monitor chemical oxygen demand (COD) and sludge concentration (MLSS) or sludge settling performance to assess system stability and assist in adjusting salinity gradients or aeration time.

[0025] Chloride ions (Cl) - Concentration and mass ratio of chloride ions to total dissolved solids (Cl) - / TDS) is used as a salt composition control index. By adjusting the influent salt composition, Cl - The / TDS ratio remained at Cl - To mitigate salt inhibition and improve operational stability, the TDS is kept within the range of <0.5. Simultaneously, key SBR operating parameters, including but not limited to dissolved oxygen (DO), pH, hydraulic retention time (HRT), and sludge age (SRT), are controlled to maintain a suitable reaction environment for biodegradation.

[0026] The adaptive adjustment strategy for system aeration time is as follows: the aeration time during the aerobic reaction phase of the SBR is set to 4–8 hours, and adjusted according to Cl... - The aeration time is adaptively adjusted based on changes in concentration and indicators: when Cl is detected... - When the concentration increases to 15000 mg / L or the effluent indicators deviate from the stability criteria, the aeration time should be adjusted to 6-8 hours to mitigate the salt inhibition effect and maintain the system's treatment stability.

[0027] The method of this invention also includes salinity threshold identification: under constant influent organic load conditions, gradually increasing Cl... - The concentration and TDS concentration were monitored, and changes in the system's COD removal rate were tracked. When the COD removal rate dropped below a preset threshold, the current salinity was determined as the salinity tolerance threshold. The specific criteria for determining the salinity tolerance threshold range are as follows: when Cl... - When the concentration increases to 15,000-20,000 mg / L and the TDS increases to 30,000-35,000 mg / L, the COD removal rate of the system effluent decreases to below 50%.

[0028] The method of the present invention also includes community monitoring: sludge samples at different salinity stages are collected for 16S rRNA gene sequencing analysis to monitor changes in microbial community structure and assist in process regulation.

[0029] Example 1: This embodiment provides a method for the start-up and first-stage acclimatization of a salt-tolerant sludge system: (1) Inoculation sludge: Activated sludge taken from the biochemical pool of the leachate treatment system of a waste incineration plant was used as inoculation sludge.

[0030] (2) Reactor: SBR is used for operation, and the COD, TDS and Cl of the influent and effluent are monitored. -Indicators such as...

[0031] (3) Influent conditions: Influent COD is 600 mg / L, TDS is 12000 mg / L, Cl... - It is 3000 mg / L.

[0032] (4) Execution results: such as Figure 2 As shown, after 14 consecutive cycles of operation, the COD removal rate gradually increased from 18.3% in the first cycle to 86.5%, and the effluent COD decreased from 600 mg / L to approximately 81 mg / L.

[0033] The above results indicate that, after targeted acclimatization by SBR, sludge from this specific source can gradually adapt to salinity conditions and develop a stable COD removal capacity.

[0034] Example 2: Based on Example 1, a three-stage stable operation verification under salinity-load gradient was conducted: (1) Stage 1 (medium salt / medium load): Influent COD = 1500 mg / L, TDS = 18000 mg / L, Cl - =3000mg / L; the average COD removal rate after the system stabilized was 72.0%.

[0035] (2) Stage 2 (Increased load): Influent COD = 2500 mg / L, TDS = 20000 mg / L, Cl - =4000mg / L; the average COD removal rate after the system stabilized was 82.5%.

[0036] (3) Stage 3 (high salt / high load, low Cl) - / TDS): Influent COD = 3000 mg / L, TDS = 25000 mg / L, Cl - =5000 mg / L, control Cl - / TDS mass ratio ≤0.2; after the system stabilizes, the average COD removal rate is 71.8%.

[0037] Changes in COD degradation efficiency under three-stage salinity gradient and organic load conditions are as follows: Figure 3 As shown, the gradient-acclimated microbial community can maintain good treatment capacity within a certain high-salt range, and its stability can be improved by controlling the salt composition.

[0038] Example 3: Based on Example 2, high salt inhibition and threshold evaluation were performed: With the influent COD kept constant at 3000 mg / L, the Cl- concentration was gradually increased. - Compare with TDS and observe performance changes.

[0039] (1) When Cl - When the concentration of COD is 5000 mg / L (TDS = 25000 mg / L), extending the aeration time from 4 h to 8 h increases the average COD removal rate from 71.8% to 83.8%.

[0040] (2) When Cl - When the concentration of COD is ≥15000mg / L (TDS≥30000mg / L), the average COD removal rate decreases to 48.37%~50.05%.

[0041] (3) Further, when Cl - When the COD removal ratio was <0.5 and TDS ≤25000 mg / L, the average COD removal rate remained between 71.89% and 83.78%; when Cl - When TDS ≥ 0.5, the COD removal rate drops to below 50.05%.

[0042] The above results indicate that Cl - Concentration and Cl - The / TDS ratio is correlated with system processing efficiency, and controlling Cl... - Keeping TDS in a low range and limiting TDS to a certain level helps alleviate salt inhibition and maintain stable operation.

[0043] Example 4: While performing Example 3, microbial community analysis (16S rRNA sequencing) was conducted at different salinity levels: 16S rRNA sequencing analysis was performed on sludge samples from different stages of the SBR using a high-throughput sequencing platform. A1: TDS = 22320 mg / L, Cl - =9517mg / L, COD=3137mg / L; B1: TDS = 25000 mg / L, Cl - =5000mg / L, COD=3000mg / L; C1: TDS = 35000 mg / L, Cl - =20000mg / L, COD=3000mg / L.

[0044] Analysis shows that: in Cl - In the ≤5000 mg / L range, Thaurea (a type of bacteria) is one of the dominant functional bacterial groups; in Cl - At a concentration of 20000 mg / L, the community structure changes and corresponds to a decrease in the system's COD removal rate; when Cl... -At concentrations >15000 mg / L, the abundance of Thaurera decreased from 31.04% to 21.31%, which is consistent with high Cl levels. - The trend of decreasing system degradation efficiency under the same conditions is consistent.

[0045] Example 5: This embodiment describes a method for the biodegradation of high-salt isopropanol wastewater based on the gradient acclimation of salt-tolerant bacterial communities. Specifically: Salt-tolerant activated sludge was selected as the inoculum source and inoculated into a sequencing batch reactor (SBR). Wastewater containing isopropanol was used as the influent. The initial salinity and influent COD load were set in the SBR, and the influent salinity and organic load were gradually increased according to a preset gradient until the COD or salinity threshold was reached, so that the sludge could form a stable degradation capacity for isopropanol.

[0046] Salt-tolerant activated sludge is activated sludge derived from leachate treatment systems in waste incineration plants or from biological treatment systems that treat saline wastewater over a long period of time.

[0047] Salinity was characterized by total dissolved solids (TDS). The initial salinity was 10,000-12,000 mg / L, and the salinity increase for each level was 500-5,000 mg / L, with a target increase of 35,000 mg / L. In the organic loading gradient, the influent COD load increases by 500~1000 mg / L at each stage, gradually increasing to 3000 mg / L.

[0048] Example 6: This embodiment describes a method for the biodegradation of high-salt isopropanol wastewater based on the gradient acclimation of salt-tolerant bacterial communities. Specifically: Salt-tolerant activated sludge was selected as the inoculum source and inoculated into a sequencing batch reactor (SBR). Wastewater containing isopropanol was used as the influent. The initial salinity and influent COD load were set in the SBR, and the influent salinity and organic load were gradually increased according to a preset gradient until the COD or salinity threshold was reached, so that the sludge could form a stable degradation capacity for isopropanol.

[0049] Salt-tolerant activated sludge is activated sludge derived from leachate treatment systems in waste incineration plants or from biological treatment systems that treat saline wastewater over a long period of time.

[0050] Salinity was characterized by total dissolved solids (TDS). The initial salinity was 10,000-12,000 mg / L, and the salinity increase for each level was 500-5,000 mg / L, with a target increase of 35,000 mg / L. In the organic loading gradient, the influent COD load increases by 500~1000 mg / L at each stage, gradually increasing to 3000 mg / L.

[0051] During the acclimation process, the COD of the effluent is monitored in real time. Once the preset stability criteria are met under the current salinity and load gradient, the system enters the next salinity / organic load gradient. The specific stability criteria are: the COD removal rate fluctuation does not exceed ±5% for at least 3 consecutive operating cycles, and the effluent COD concentration fluctuation does not exceed ±10%.

[0052] During SBR operation, Cl - Concentration and Cl - mass ratio of Cl to total dissolved solids - / TDS is used as a control index for salinity composition. By adjusting the salinity composition of the influent, Cl - The / TDS ratio remained at Cl - The system maintains a TDS level of <0.5 to mitigate salt inhibition and improve operational stability. Simultaneously, dissolved oxygen, pH, hydraulic retention time, and sludge age are controlled to maintain a suitable reaction environment for biodegradation.

[0053] The adaptive adjustment strategy for aeration time in the SBR system is as follows: the aeration time during the aerobic reaction phase is set to 4–8 hours, and when Cl… - When the concentration increases to 15000 mg / L or the effluent indicators deviate from the stability criteria, the aeration time should be adjusted to 6-8 hours to mitigate the salt inhibition effect.

Claims

1. A method for biodegradation of high-salt isopropanol wastewater based on gradient acclimation of salt-tolerant bacterial communities, characterized in that, Specifically: Salt-tolerant activated sludge was selected as the inoculum source and inoculated into a sequencing batch reactor (SBR). Wastewater containing isopropanol was used as the influent. The initial salinity and influent COD load were set in the SBR, and the influent salinity and organic load were gradually increased according to a preset gradient until the COD or salinity threshold was reached, so that the sludge could form a stable degradation capacity for isopropanol.

2. The method for biodegradation of high-salt isopropanol wastewater based on gradient acclimatization of salt-tolerant bacteria according to claim 1, characterized in that, The salt-tolerant activated sludge is activated sludge derived from leachate treatment systems of waste incineration plants or biological treatment systems that treat saline wastewater over a long period of time.

3. The method for biodegradation of high-salt isopropanol wastewater based on gradient acclimation of salt-tolerant bacterial communities according to claim 1, characterized in that, The salinity is characterized by total dissolved solids (TDS). The initial salinity is 10,000-12,000 mg / L, and the salinity increase for each level is 500-5,000 mg / L, with a target increase of 35,000 mg / L. In the organic loading gradient, the influent COD load increases by 500~1000 mg / L at each stage, gradually increasing to 3000 mg / L.

4. The method for biodegradation of high-salt isopropanol wastewater based on gradient acclimatization of salt-tolerant bacteria according to claim 1, characterized in that, During the acclimation process, the COD of the effluent is monitored in real time. Once the preset stability criteria are met under the current salinity and load gradient, the system enters the next salinity / organic load gradient. The specific stability criteria are: the COD removal rate fluctuation does not exceed ±5% for at least 3 consecutive operating cycles, and the effluent COD concentration fluctuation does not exceed ±10%.

5. The method for biodegradation of high-salt isopropanol wastewater based on gradient acclimation of salt-tolerant bacterial communities according to claim 1, characterized in that, During SBR operation, Cl - Concentration and Cl - mass ratio of Cl to total dissolved solids - / TDS is used as a control index for salinity composition. By adjusting the salinity composition of the influent, Cl - The / TDS ratio remained at Cl - The system maintains a TDS level of <0.5 to mitigate salt inhibition and improve operational stability. Simultaneously, dissolved oxygen, pH, hydraulic retention time, and sludge age are controlled to maintain a suitable reaction environment for biodegradation.

6. The method for biodegradation of high-salt isopropanol wastewater based on gradient acclimation of salt-tolerant bacterial communities according to claim 1, characterized in that, The adaptive adjustment strategy for aeration time in the SBR system is as follows: the aeration time during the aerobic reaction phase is set to 4–8 hours, and when Cl… - When the concentration increases to 15000 mg / L or the effluent indicators deviate from the stability criteria, the aeration time should be adjusted to 6-8 hours to mitigate the salt inhibition effect.

7. The method for biodegradation of high-salt isopropanol wastewater based on gradient acclimation of salt-tolerant bacterial communities according to claim 1, characterized in that, The method further includes a salinity threshold identification step: under constant influent organic load conditions, gradually increasing the Cl... - Concentration and TDS concentration, when Cl - When the concentration increases to 15,000~20,000 mg / L and the TDS increases to 30,000~35,000 mg / L, and the COD removal rate of the system effluent decreases to below the preset threshold, the current salinity is determined to be the salinity tolerance threshold.

8. The method for biodegradation of high-salt isopropanol wastewater based on gradient acclimation of salt-tolerant bacterial communities according to claim 1, characterized in that, The method also includes: collecting sludge samples at different salinity stages during the acclimation process for 16S rRNA gene sequencing analysis, which is used to monitor changes in microbial community structure and assist in process regulation.

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