Method for degrading naphthenic acid by electrocatalytic anaerobic microorganisms
By employing an electrocatalytic anaerobic microbial degradation method, key bacterial groups were domesticated and enriched, and voltage was applied to a bioelectrochemical system. This solved the problems of low treatment efficiency and secondary pollution in naphthenic acid wastewater, achieving highly efficient removal of naphthenic acid and COD.
Patent Information
- Application Number
- CN202610452549.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-08
- Publication Date
- 2026-05-19
AI Technical Summary
Existing technologies are insufficient for efficiently treating naphthenic acid-containing wastewater generated during petroleum refining and oil extraction, leading to environmental pollution and equipment corrosion. Conventional methods are inefficient, costly, and prone to secondary pollution.
An electrocatalytic anaerobic microbial degradation method was adopted. By domesticating and enriching key core bacterial groups such as Halobacteriota, Chloroflexota, and Bacteroidota, voltage was applied to the bioelectrochemical system, and Ta2O5, IrO2, Ti mesh electrode plates and stainless steel mesh electrode plates were used to achieve efficient degradation of naphthenic acids.
Within 24 hours, the removal rate of naphthenic acid exceeded 90%, and within 48 hours, the COD removal rate increased by over 100%. The constructed microbial community demonstrated stable COD removal performance and significantly improved degradation efficiency.
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Figure CN122059527A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to wastewater treatment methods, and more particularly to a method for electrocatalytic anaerobic microbial degradation of naphthenic acids. Background Technology
[0002] Naphthenic acids are naturally occurring acidic organic components in petroleum, primarily formed from crude oil through microbial degradation or oxidation reactions during long-term geological evolution. They are cyclic hydrocarbon compounds with carboxyl groups (general formula C10). n H 2n +ZO2). During crude oil refining, naphthenic acids are generated and enter the wastewater system through processes such as electro-desalting and distillation. More importantly, during the oil extraction stage, especially in oilfields using water-displacement technology, produced wastewater is the main pathway for naphthenic acids to enter the aquatic environment. As oilfields enter the later stages of development, the water content of the produced fluid can reach 80%-90%. This fluid contains a large amount of naphthenic acids eluted from crude oil, with concentrations reaching 110 mg / L, forming complex and difficult-to-treat naphthenic acid-containing wastewater. The treatment of this type of wastewater has become a major challenge in the field of wastewater treatment.
[0003] Naphthenic acids (NAAs) exhibit significant acute toxicity and endocrine disruption effects on aquatic organisms such as fish and algae, with toxicity increasing with the number of cyclic structures. If NAA-containing wastewater is discharged into the environment without proper treatment, it will cause long-term, cumulative damage to aquatic ecosystems. Simultaneously, in high-temperature oil refining units, NAAs severely corrode carbon steel pipes and equipment, leading to shortened equipment lifespan, increased downtime for maintenance, and even safety accidents, resulting in significant economic losses and operational risks for oil refining companies. NAAs are structurally stable, complex in composition, hydrophobic, and bioinhibitory; their sodium salts are readily soluble in water and possess surface activity, which can cause wastewater emulsification or foaming. NAAs pose multiple hazards to the ecological environment, industrial production, and human health, making their efficient treatment particularly urgent.
[0004] However, naphthenic acid wastewater is difficult to biodegrade. Conventional physical, chemical, and biological treatment methods suffer from low efficiency, high cost, and the potential for secondary pollution. Traditional biological treatment methods, in particular, are often ineffective due to their recalcitrant nature and microbial toxicity. Current technologies for treating wastewater with high naphthenic acid content generally employ pretreatment techniques such as extraction, adsorption, and flocculation. Extraction is costly and prone to emulsification, making it unsuitable for treating large volumes of low-concentration naphthenic acid wastewater. Existing technologies involve adding soluble calcium salts (such as calcium nitrate and calcium chloride) and activated carbon to adsorb naphthenic acid from the wastewater. However, this method requires a large amount of soluble calcium salts, resulting in high costs. The activated carbon adsorbent has a short regeneration cycle and lifespan, and also generates waste activated carbon, causing secondary pollution.
[0005] CN109456912A discloses a Bacillus strain capable of degrading naphthenic acids, and CN102442748A discloses a method for the advanced treatment of naphthenic acid wastewater, both of which can effectively degrade naphthenic acids. However, some existing technologies heavily rely on chemical additives, such as flocculants, Fenton's reagent, acids, and alkalis, which may produce sludge or secondary pollution, and are energy-intensive and costly; some existing technologies rely on only a single bacterial species, which can only inefficiently remove some naphthenic acid pollutants. Summary of the Invention
[0006] Purpose of the invention: The purpose of this invention is to provide a method for the efficient removal of naphthenic acids and the rapid optimization of microbial community composition through electrocatalytic anaerobic microbial degradation of naphthenic acids.
[0007] Technical solution: The method for electrocatalytic anaerobic microbial degradation of naphthenic acids according to the present invention includes the following steps: (1) An acclimatization and enrichment experiment was conducted using anaerobic granular sludge to obtain acclimatized sludge. (2) The acclimation of sludge is characterized by obtaining key core microbial communities, which include Halobacteriota, Chloroflexota and Bacteroidota phyla; (3) Naphthenic acid degradation was carried out using domesticated sludge under electric conditions.
[0008] In step (3), the power application is achieved by applying a voltage of 1-3V; the degradation of cycloalkanoic acid is carried out in a bioelectrochemical system, with the anode using a mesh electrode plate including Ta2O5, IrO2, and Ti, and the cathode using a stainless steel mesh electrode plate; the cycloalkanoic acid is cyclohexanecarboxylic acid; and the concentration of cyclohexanecarboxylic acid is 80-200 mg / L.
[0009] The anaerobic granular sludge mentioned in step (1) is taken from an IC reactor for industrial wastewater treatment; the acclimated sludge contains a complex microbial community, with key core bacteria including Halobacteriota, Methanobacteriota, Chloroflexota, Bacteroidota, and Nitrospirota; the acclimation and enrichment experiment water is simulated wastewater, which includes naphthenic acid with a COD concentration of 1500-2500 mg / L.
[0010] In step (3), the nitrogen source for the cycloalkanoic acid degradation experiment is 2-15 mg / L NO3. - -N and 2-15 mg / L NH3 - -N, more preferably 5-10 mg / L NO3 - -N and 5-10 mg / L NH3 --N, more preferably 5 mg / L NO3 - -N and 5 mg / L NH3 - -N.
[0011] Invention Principle: This method first optimizes and screens microbial communities through electrocatalysis to construct a complex functional microbial community with highly efficient degradation effects on naphthenic acid target pollutants. Building upon this, electrocatalysis technology is further coupled to enhance inter- and intra-species electron transfer efficiency, effectively overcoming the rate-limiting barriers to recalcitrant pollutants. This achieves simultaneous high-efficiency degradation of target pollutants and high-efficiency removal of chemical oxygen demand (COD), realizing the dual benefits of economic efficiency and environmental friendliness.
[0012] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The method accelerates the optimization of the composition of the microbial community through electrocatalysis technology and promotes the enrichment of functional microorganisms; (2) The method forms a complex microbial community that has the effect of degrading naphthenic acid pollutants through electrocatalysis technology. Under electrocatalytic conditions, naphthenic acid is rapidly degraded, so that the naphthenic acid removal rate exceeds 90% within 24 hours and the COD removal rate is increased by more than 100% within 48 hours; (3) The microbial community constructed by the method has a relatively stable effect on COD removal. Attached Figure Description
[0013] Figure 1 This is a comparative example of COD removal from naphthenic acid wastewater treated by a conventional anaerobic reactor. Figure 2 The COD change curve for Comparative Example 1 during the 11th period; Figure 3 The COD removal performance of the mixed electromicrobial catalytic method inoculated with acclimatized sludge in the fourth cycle of Example 1, Comparative Example 2, and Comparative Example 5 is shown. Figure 4 The results show the removal of CHCA by mixed electromicrobial catalysis in the fourth cycle of acclimatization sludge in Example 1, Comparative Example 2, and Comparative Example 5. Figure 5 This describes the COD removal performance of the hybrid electromicrobial catalysis during the fifth cycle of acclimatization sludge inoculation in Example 1. Figure 6 The treatment effect of the hybrid electromicrobial reactor for the acclimatization sludge inoculation in the 5th cycle of Example 2; Figure 7 The treatment effect of the H-type electromicrobial reactor for acclimatizing sludge in the fifth cycle in Comparative Example 3 was shown. Figure 8 To compare the treatment effect of the H-type electrocatalytic reactor in Example 3; Figure 9To compare the COD treatment effects of the hybrid electrocatalytic reactors in Examples 2 and 4; Figure 10 A comparison chart of COD removal rates under various reaction conditions over 48 hours; Figure 11 Principal coordinate analysis diagram of archaea PCoA; Figure 12 The relative abundance of dominant archaeal species in each group; Figure 13 The relative abundance of dominant bacterial species in each group. Detailed Implementation
[0014] The technical solution of the present invention will be further described below with reference to the embodiments.
[0015] Example 1
[0016] The method for electrocatalytic anaerobic microbial degradation of naphthenic acids according to the present invention includes the following steps: (1) Anaerobic granular sludge was used for acclimation and enrichment experiments. The sludge was taken from an IC reactor used in industrial wastewater treatment. Simulated wastewater was used in the experiments, and glucose (C6H4O) was employed. 12 Using O6 and cyclohexanecarboxylic acid (CHCA) as carbon sources, the wastewater also contains essential trace elements such as ammonium chloride (NH4Cl), sodium dihydrogen phosphate (NaH2PO4), and calcium chloride dihydrate (CaCl2·H2O). Washed anaerobic granular sludge was added to sterilized serum bottles, along with naphthenic acid-simulated wastewater (containing glucose as a carbon source) with a COD concentration of approximately 2000 mg / L, and 1 mL of trace element stock solution. The bottles were then sealed and placed in a 37°C incubator for anaerobic enrichment and acclimatization, resulting in sludge containing a complex microbial community, termed acclimatized sludge (defined as Group A).
[0017] (2) In the bioelectrochemical system, naphthenic acid degradation experiments were conducted using acclimated sludge under a 1V voltage. Cyclohexanecarboxylic acid (CHCA) at 100 mg / L was used as the sole carbon source. The anode material was a 30×30×1 mm Ta₂O₅+IrO₂+Ti mesh electrode plate, and the cathode was a 30×30×1 mm stainless steel mesh electrode plate. The water composition was as follows: carbon source was 100 mg / L CHCA, equivalent to 225 mg / L COD; nitrogen source was 5 mg / L NO₃⁻. - -N and 5 mg / L NH3 - -N; 1000 mg / L NaHCO3, 6.2 mg / L KH2PO4, 3.7 mg / L CaCl2·2H2O, 6.2 mg / L MgSO4·7H2O, pH=8.13. (The sludge formed after electromicrobial catalysis is defined as Group B, and the product obtained is defined as 1V-BES).
[0018] Example 2
[0019] The similarities to Example 1 will not be repeated here. The difference is that the voltage in step (2) is 3V in a hybrid electromicrobial reactor. (The obtained product is defined as 3V-BES).
[0020] Comparative Example 1 The similarities to Example 1 will not be repeated here. The difference is that in step (2), the voltage is 0 (without the electrode plates), that is, a traditional anaerobic bioreactor system with low concentration naphthenic acid (target wastewater) as influent is used for long-term operation. (The obtained product is defined as R250-BS).
[0021] Comparative Example 2 The similarities to Example 1 will not be repeated here. The difference is that the anaerobic granular sludge from step (1) was used to conduct a naphthenic acid degradation experiment under 1V power supply and without acclimated sludge. (The obtained product is defined as 1V-ES).
[0022] Comparative Example 3 The similarities to Example 1 will not be repeated here. The difference is that in step (2), the voltage is 3V and an H-type electrobioreactor with an ion-exchange membrane is used. (The product obtained is defined as 3V-H-BES).
[0023] Comparative Example 4 The similarities with Comparative Example 2 will not be repeated here. The difference is that the voltage in step (2) is 3V and no acclimatized sludge is used. (The product obtained is defined as 3V-ES).
[0024] Comparative Example 5 The similarities to Example 1 will not be repeated here, except that the voltage is 0 in step (2). (The obtained product is defined as BS).
[0025] COD and naphthenic acid removal rates were tested in each experiment.
[0026] Figure 1 , Figure 2 This serves as Comparative Example 1, demonstrating the long-term effectiveness of a traditional anaerobic sludge reactor in treating target naphthenic acid wastewater. The naphthenic acid wastewater contained 100 mg / L cyclohexanecarboxylic acid, 5 mg / L nitrate nitrogen, and 5 mg / L ammonium nitrogen, and operated continuously for approximately 131 days. A 12-day cycle was implemented with intermittent influent, and water was replaced at the end of each cycle while maintaining a COD removal rate above 80%. Figure 2 It is evident that the COD removal rate of the conventional anaerobic reactor without electrocatalysis (Comparative Example 1) was only 33.33% in the 11th cultivation cycle (day 131), with a single cycle of 48 hours. In Comparative Example 1, the long-term cultured sludge (without external electrocatalysis) was defined as Group C.
[0027] Figure 3 , 4 Example 1 shows that, under 1V power supply, a mixed electrocatalytic reactor containing acclimated sludge (4th cycle) treated naphthenic acid wastewater, achieving a naphthenic acid removal rate of over 90% in 24 hours, which is more than twice the naphthenic acid removal rate of the unpowered control group BS. Figure 4 The COD removal rate after 48 hours was more than 2.5 times that of the group without electricity. Figure 3 At 1V, the mixed reactor containing acclimated sludge (5th cycle) (Example 1) achieved a COD removal rate of 82.37% within 48 hours. Figure 5 ).
[0028] Figure 6 In Example 2, under a 3V power supply, the mixed reactor containing acclimated sludge (Example 2) achieved a COD removal rate of 45.19% within 48 hours. This indicates that under optimized conditions of 1V electrocatalysis, acclimated sludge can rapidly degrade naphthenic acids and significantly improve the degradation efficiency of both naphthenic acids and COD.
[0029] Figure 7 , 8 For Comparative Example 3, based on 48 hours, the H-type electrocatalytic reactor (without sludge) under 3V conditions showed low removal rates of naphthenic acid and COD, at 41.7% and 9.71%, respectively. Under 3V conditions, although the H-type electrocatalytic bioreactor achieved a naphthenic acid removal rate exceeding 90%, its COD removal rate was low, at only 5.19%. Therefore, the hybrid electrocatalytic bioreactor of this patent performs better than the H-type electroreactor.
[0030] Figure 9 For Comparative Examples 2 and 4, under the condition of 1V voltage (mixed electrocatalytic reactor) and no acclimated sludge (Comparative Example 2), naphthenic acid and COD showed almost no degradation; under the condition of 3V voltage and no acclimated sludge (Comparative Example 4), naphthenic acid showed slight degradation.
[0031] Further biosequencing was performed on the aforementioned acclimatized sludge (Group A), low-concentration COD acclimatized sludge (Group C), and 1V mixed-type electrified sludge (Group B). Figure 10 The figure shows the PCoA principal coordinate analysis of 16S rRNA archaea sequencing. In the figure, B-ES0 is taken from the acclimated sludge (cycle 5) in Example 1, and B-BES1 is taken from the acclimated sludge after being charged with 1V for 48 hours in a mixed electromicrobial reactor. It can be seen that the microbial community structure of group B deviates significantly from group A after a short period of charging and shows a trend of converging with the characteristic species of group C. It can be seen that charging induces convergent evolution of biological community function, causing the community function of the acclimated sludge to converge with the microbial community after about 110 days of acclimation and enrichment in a low-concentration COD reactor. This indicates that charging greatly promotes the enrichment of relevant functional microorganisms.
[0032] Under 1V conditions, the abundance of the archaea Halobacteriota and Methanobacteriota phyla increased after the domesticated sludge was electrified, while the abundance of Thermoplasmatota and Thermoproteota phyla decreased. Under the same conditions, the abundance of the bacteria Chloroflexota (also known as Chloroflexi) increased by 1.33%, demonstrating its adaptability to harsh environments, ability to degrade toxic organic matter, and denitrification capabilities. The abundance of the bacteria Bacteroidota phylum increased by 2.15%, exhibiting the ability to metabolize oils and polysaccharides under extreme conditions. Figure 11 , Figure 12 ).
Claims
1. A method for electrocatalytic anaerobic microbial degradation of naphthenic acids, characterized in that, Includes the following steps: (1) An acclimatization and enrichment experiment was conducted using anaerobic granular sludge to obtain acclimatized sludge. (2) The acclimation of sludge is characterized by obtaining key core microbial communities, which include Halobacteriota, Chloroflexota and Bacteroidota phyla; (3) Naphthenic acid degradation was carried out using domesticated sludge under electric conditions.
2. The method according to claim 1, characterized in that, The power-on condition in step (3) is to apply a voltage of 1-3V.
3. The method according to claim 1, characterized in that, The degradation of naphthenic acid in step (3) is carried out in a bioelectrochemical system. The anode is a Ti mesh electrode plate with a coating of Ta2O5 and IrO2, and the cathode is a stainless steel mesh electrode plate.
4. The method according to claim 1, characterized in that, The cycloalkanoic acid mentioned in step (3) is cyclohexanecarboxylic acid.
5. The method according to claim 4, characterized in that, The concentration of the cyclohexanecarboxylic acid is 80-200 mg / L.
6. The method according to claim 1, characterized in that, The anaerobic granular sludge mentioned in step (1) is taken from the anaerobic reactor for industrial wastewater treatment.
7. The method according to claim 1, characterized in that, The acclimatized sludge described in step (1) contains a complex microbial community, with key core bacteria including Halobacteriota, Methanobacteriota, Chloroflexota, Bacteroidota, and Nitrospirota.
8. The method according to claim 1, characterized in that, The water used in the acclimatization and enrichment experiment in step (1) is simulated wastewater, which includes naphthenic acid and glucose with a COD concentration of 1500-2500 mg / L.
9. The method according to claim 1, characterized in that, The nitrogen source in the cycloalkanoic acid degradation described in step (3) is 2-15 mg / L NO3. - -N and 2-15 mg / L NH3 - -N.
10. The method according to claim 1, characterized in that, The nitrogen source in the cycloalkanoic acid degradation described in step (3) is 5-10 mg / L NO3. - -N and 5-10 mg / L NH3 - -N.