Biological resourceful treatment method and system for brine discharge wastewater of retired lithium battery

Abstract

The invention relates to a biological resourceful treatment method and system for decommissioned lithium battery brine discharge wastewater, and the method comprises the following steps: (1) dividing the pretreated decommissioned lithium battery brine discharge wastewater into a first part of wastewater and a second part of wastewater, inoculating the first part of wastewater with a pre-domesticated salt-tolerant functional flora, hydrolyzing and fermenting organic components to generate fermentation liquor containing short-chain carboxylic acid; and (2) mixing the fermentation liquor with a second part of wastewater, and carrying out carbon chain extension reaction to generate treatment liquor containing medium-chain carboxylic acid and long-chain alcohol products. According to the method, the special pollutant composition and the high-salt characteristic of the discharge wastewater are utilized, the methanogenesis process is inhibited without using expensive chemical agents or treating inoculums at a high temperature and the like, electron donors such as ethanol or lactic acid and the like do not need to be additionally added, the agent or energy consumption cost in the process is greatly reduced while the organic pollutants in the wastewater are subjected to high-value conversion, and the method is suitable for industrial production. The method has the remarkable advantages of simple operation, green process, low cost and the like.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment and resource recycling technology, and in particular to a method and system for the biological resource utilization treatment of wastewater from the saline discharge of retired lithium batteries. Background Technology

[0002] In recent years, industries such as new energy vehicles and energy storage have developed rapidly. Waste lithium-ion batteries still retain some charge; direct decomposition and crushing can instantly generate a large current, potentially leading to spontaneous combustion or explosion. Saltwater discharge, which involves immersing the battery in NaCl or Na2SO4 solution, causes a short circuit between the positive and negative electrodes, releasing the residual charge. Simultaneously, the solution absorbs the heat generated during discharge, significantly reducing the risk of explosion. This is a prerequisite for safe production in storage, transportation, dismantling, and recycling, and has become the most commonly used discharge method in the industry. However, the discharge process is accompanied by varying degrees of electrolyte leakage and pollution, generating large amounts of discharge wastewater. This wastewater is characterized by uneven discharge, complex composition, high salinity, and heavy metal content, posing a significant environmental threat and requiring efficient treatment and disposal. Organic pollutants mainly originate from carbonate organic solutes and specific functional additives (such as flame retardants and organic film-forming additives) in the electrolyte.

[0003] As a new type of industrial wastewater, discharge wastewater lacks mature technological references. Currently, the industry typically uses conventional activated sludge or contact oxidation methods for harmless treatment. High influent salinity and frequent fluctuations frequently impact the sludge microbial community, leading to poor system stability and susceptibility to collapse. Therefore, there is an urgent need to develop efficient and stable discharge wastewater treatment technologies. CN109467261A discloses a method for treating wastewater from spent lithium-ion battery electrolytes, recovering lithium salt resources through adsorption, biodegrading organic matter, and finally recovering water resources through reverse osmosis. CN114804497A discloses a zero-emission treatment device and process for wastewater and exhaust gas generated during lithium-ion battery discharge, primarily focusing on the synergistic harmless treatment of HF present in wastewater and exhaust gas during the discharge process. CN218403896U provides a discharge wastewater recycling treatment device and a spent lithium-ion battery treatment system, which discharges spent batteries and performs sedimentation, defluorination, and electrochemical reactions on the fluid, reducing the content of harmful substances in the waste liquid while recycling it. The summary found that existing technologies mainly target the resource recovery and harmless disposal of inorganic components such as lithium ions or fluorides in wastewater. For organic components, namely the organic solutes in the electrolyte dissolved during discharge, there are no specific treatment and recovery methods.

[0004] In recent years, the use of anaerobic microorganisms to convert organic waste and wastewater into medium-chain fatty acids has attracted attention. CN107363076A discloses a method for the resource utilization of organic waste, which involves inoculating lactic acid bacteria to ferment residual sludge, kitchen waste, and livestock waste into lactic acid, which is then converted into medium-chain fatty acids through a carbon chain elongation reaction and recovered. CN110734934B discloses a method for pretreatment to promote the anaerobic fermentation of residual sludge to produce medium-chain fatty acids, which uses free nitrite to promote the dissolution of organic matter in the biomass components of sludge, and then converts it into medium-chain fatty acids through the metabolic reaction of inoculated and domesticated microbial communities containing Clostridium, Oscillibacter, Dechloromonas, or Ruminococcaceae. Patent CN 115094095B discloses a method for promoting the anaerobic fermentation of residual sludge to produce medium-chain fatty acids and recover phosphorus, which uses ferrate pretreatment of biological sludge to promote dissolution, and then uses inoculated and domesticated sludge for bioconversion to obtain fermentation products rich in medium-chain fatty acids and sappansite. The summary reveals that existing patents primarily target easily biodegradable components such as municipal sludge, kitchen waste, food industry waste, and agricultural waste, and the inoculated microorganisms are mostly microbial communities that metabolize polysaccharides and proteins. However, the organic components in discharge wastewater mainly consist of carbonates and nitrile electrolyte organic solvents. These organic components have completely different characteristics from biomass and require entirely different degrading microbial communities. Furthermore, anaerobic targeted acid production targeting discharge wastewater or electrolyte organic solvents has not been reported. Meanwhile, CN110734934B and CN115094095B both require the addition of components such as ethanol, lactic acid, methanol, or hydrogen as electron donors to drive microbial synthesis of medium-chain fatty acids, while patent CN107363076A requires inoculation with lactic acid bacteria to produce lactic acid in situ as an electron donor. However, these operations undoubtedly increase operating costs and limit the large-scale application of the technology. Furthermore, for open-culture mixed microbial fermentation systems, both CN110734934B and CN115094095B require the addition of 2-bromoacetylsulfonic acid (15-30 g / L) or sodium 2-bromoacetylsulfonate (5-10 g / L) as methanogen inhibitors to prevent substrate competition and reduce medium-chain fatty acid production. Both 2-bromoacetylsulfonic acid and sodium 2-bromoacetylsulfonate are expensive chemicals, and this operation will undoubtedly further increase processing costs. Although patent CN 110643645 B proposes that high-temperature heat treatment can suppress the methanogenesis process, avoiding the need for chemical inhibitors, it is clear that the heat treatment process still requires additional energy consumption.

[0005] Existing technologies have drawbacks, such as the inability to recover organic components from discharge wastewater, and the need to add expensive methanogen inhibitors and electron donors for the recovery of organic components through microbial fermentation. Therefore, how to achieve efficient and green resource recovery of organic matter from discharge wastewater has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention focuses on waste lithium battery discharge wastewater characterized by high salinity, high organic load, high volatility, and complex composition. Based on its unique pollutant composition and the domesticated specialized anaerobic bacteria, a green and efficient bio-fermentation method is used to convert organic components into high-value-added, easily separable medium-chain carboxylic acids.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for the biological resource utilization treatment of wastewater from the brine discharge of retired lithium batteries, the method comprising the following steps:

[0009] (1) The pretreated wastewater from the decommissioned lithium battery salt discharge is divided into a first part of wastewater and a second part of wastewater. The first part of wastewater is inoculated with pre-acclimated salt-tolerant functional bacteria and subjected to organic component hydrolysis and fermentation to generate a fermentation broth containing short-chain carboxylic acids.

[0010] (2) The fermentation liquid is mixed with the second part of wastewater to carry out a carbon chain extension reaction to generate a treatment liquid containing medium-chain carboxylic acids and long-chain alcohols.

[0011] This invention utilizes a bio-fermentation method combined with the unique pollutant composition and high salt content of discharge wastewater to improve the conversion rate and selectivity of organic matter in discharge wastewater into medium-chain carboxylic acids and long-chain alcohols, achieving high-value conversion of organic matter in discharge wastewater without the addition of electron donors and methane inhibitors.

[0012] The short-chain carboxylic acids of the present invention are carboxylic acids with 2-5 carbon atoms, the medium-chain carboxylic acids are carboxylic acids with 6-10 carbon atoms, and the long-chain alcohols are alcohols with more than 4 carbon atoms.

[0013] As a preferred technical solution of the present invention, the pretreatment includes adjusting the salinity of the decommissioned lithium battery salt discharge wastewater to 25-30 g / L, for example, it can be 25 g / L, 26 g / L, 27 g / L, 28 g / L, 29 g / L or 30 g / L, etc.

[0014] Preferably, the salinity adjustment uses NaCl or Na2SO4 as the salinity regulator.

[0015] Preferably, the volume ratio of the first part of wastewater to the second part of wastewater is 1:1.5 to 1:2.5, for example, it can be 1:1.5, 1:1.7, 1:2, 1:2.2 or 1:2.5, etc.

[0016] As a preferred technical solution of the present invention, the pre-domesticated salt-tolerant functional bacteria in step (1) are domesticated using the following method:

[0017] Wastewater containing carbonate and / or nitrile organic matter was used as the substrate, with an initial salinity of 10 g / L. After inoculation with the initial bacterial population, acclimatization was carried out for 5-7 days, for example, 5 days, 5.5 days, 6 days, 6.5 days, or 7 days. The salinity gradient increase in each acclimatization cycle was 5-10 g / L, for example, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, or 10 g / L. When the salinity reached 30 g / L and the acid production efficiency of the bacterial population stabilized, the acclimatization was completed, and a pre-acclimatized salt-tolerant functional bacterial population was obtained.

[0018] Preferably, the initial microbial community is an anaerobic mixed microbial community, such as anaerobic water treatment sludge, anaerobic digestion sludge, or anaerobic fermentation sludge.

[0019] Preferably, the acid production efficiency is stable with an acid production rate fluctuation of ≤5% and maintained for more than 24 hours.

[0020] Preferably, the salt-tolerant functional bacterial community includes dominant species of Clostridium, Desmodium, and Halophilic Sporangia, and the relative abundance of the dominant species is ≥65%, for example, 65%, 70%, 75%, 80%, 85%, or 90%.

[0021] Preferably, the dominant species of Clostridium include Clostridium sartagoforme, Clostridium cochlearium, or Clostridium kluyverii.

[0022] Preferably, the dominant species of the Sedimentibacter genus include Sedimentibacter acidaminivorans, Sedimentibacter hongkongensis, or Sedimentibacter saalensis.

[0023] Preferably, the dominant species of the genus *Haloimpatiens* include *Haloimpatiens sporogenes*, *Haloimpatiens massiliensis*, or *Haloimpatiens myeolchijeotgali*.

[0024] Preferably, the abundance of methanogenic bacteria in the salt-tolerant functional bacterial community is <2%, for example, it can be 0.1%, 0.5%, 0.8%, 1%, 1.5% or 1.8%, etc.

[0025] This invention obtains salt-tolerant functional bacteria through pre-acclimatization, enabling these bacteria to selectively transform organic components in high-salt discharge wastewater and inhibit methanogenic bacteria.

[0026] As a preferred technical solution of the present invention, the pH of the hydrolysis and fermentation of the organic components in step (1) is 5.5-6.5, for example, it can be 5.5, 5.6, 5.7, 5.8, 5.9, 6.0 or 6.5, etc.

[0027] By controlling the pH during the hydrolysis-fermentation process within the aforementioned range, this invention can further inhibit the activity of methanogens and improve the selectivity of short-chain carboxylic acids during the hydrolysis-fermentation stage.

[0028] The pH adjuster used in this invention includes hydrochloric acid, sodium hydroxide, or sodium bicarbonate. The amount added can be selected and optimized according to the pH of the reaction system, and no further limitation is made here.

[0029] Preferably, the temperature for the hydrolysis and fermentation of the organic components is 35-40°C, for example, 35°C, 36°C, 37°C, 38°C, 39°C, or 40°C.

[0030] Preferably, the hydraulic retention time for the hydrolysis and fermentation of the organic components is 48-72 hours, for example, 48 hours, 54 hours, 60 hours, 66 hours or 72 hours.

[0031] Preferably, the cumulative concentration of short-chain carboxylic acids in the fermentation broth is 8-12 g COD / L, for example, it can be 8.0 g COD / L, 9.0 g COD / L, 10.0 g COD / L, 11.0 g COD / L or 12.0 g COD / L, etc.

[0032] As a preferred technical solution of the present invention, the pH of the carbon chain elongation reaction in step (2) is 7.0-7.5, for example, it can be 7.0, 7.1, 7.2, 7.3 or 7.5, etc.

[0033] Preferably, the temperature of the carbon chain elongation reaction is 30-35°C, for example, 30°C, 31°C, 32°C, 34°C or 35°C.

[0034] Preferably, the reaction time for the carbon chain elongation reaction is 96-120 hours, for example, 96 hours, 102 hours, 108 hours, 114 hours or 120 hours.

[0035] Preferably, the yield of medium-chain carboxylic acid in the carbon chain elongation reaction is 0.45-0.52 g COD / g COD, for example, it can be 0.45 g COD / g COD, 0.47 g COD / g COD, 0.49 g COD / g COD, 0.50 g COD / g COD, or 0.52 g COD / g COD, etc.

[0036] Preferably, the partial pressure of hydrogen in the carbon chain elongation reaction is 100-200 Pa, for example, it can be 100 Pa, 125 Pa, 150 Pa, 175 Pa or 200 Pa.

[0037] This invention regulates the electron transfer pathway of microorganisms by controlling the partial pressure of hydrogen, thereby enhancing the competitive advantage of carbon chain elongation bacteria over substrates and promoting microbial fermentation reactions toward obtaining high-value medium-chain carboxylic acids.

[0038] As a preferred technical solution of the present invention, the COD conversion rate of the decommissioned lithium battery brine discharge wastewater treated by the method is >90%, for example, it can be 91%, 92%, 93%, 95% or 99%, etc.

[0039] Preferably, the system of the method can tolerate salinity fluctuations within a range of ±15%.

[0040] Preferably, the organic loading of the system in the method is 8-10 kg COD / (m³·d), for example, it can be 8.0 kg COD / (m³•d), 8.5 kg COD / (m³•d), 9.0 kg COD / (m³•d), 9.5 kg COD / (m³•d) or 10.0 kg / (m³•d), etc.

[0041] In a second aspect, the present invention provides a processing system for the method described in the first aspect, the processing system comprising a salinity adjustment unit, a hydrolysis fermenter, and a carbon chain extension reactor, wherein the salinity adjustment unit is connected to the inlet of the hydrolysis fermenter and the carbon chain extension reactor, and the outlet of the hydrolysis fermenter is connected to the inlet of the carbon chain extension reactor.

[0042] As a preferred embodiment of the present invention, the salinity adjustment unit includes a salinity sensor and an automatic dosing device.

[0043] As a preferred technical solution of the present invention, the hydrolysis fermenter includes a corrosion-resistant stirrer and an online pH control module.

[0044] Preferably, the carbon chain extension reactor includes an airtight headspace gas recovery device.

[0045] As a preferred embodiment of the present invention, the volume ratio of the hydrolysis fermenter to the carbon chain extension reactor is 1:2;

[0046] Preferably, the carbon chain extension reactor is filled with a carbon fiber carrier;

[0047] Preferably, the specific surface area of ​​the carbon fiber carrier is 500-800 m². 2 / m 3 For example, it could be 500 m 2 / m 3 600m 2 / m 3 650 m 2 / m 3 700 m 2 / m 3 or 800 m 2 / m 3 wait.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) The method provided by the present invention can treat saline discharge wastewater with high salinity, high organic load, high volatility and complex composition. The pre-acclimated salt-tolerant functional bacteria can make full use of the high salt characteristics of the wastewater to carry out the resource transformation of organic components in the wastewater, and at the same time, there is no need to add exogenous electron donors and methanogenic inhibitors.

[0050] (2) The method provided by the present invention converts the products into high-value-added medium-chain carboxylic acids and long-chain alcohols. The method is green, consumes no external reagents, is simple to operate, and has good economic benefits. Detailed Implementation

[0051] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0052] Example 1

[0053] This embodiment provides a method for the biological resource utilization treatment of brine discharge wastewater from retired lithium batteries, the method comprising the following steps:

[0054] (1) Adjust the salinity of the wastewater from the decommissioned lithium battery salt discharge to 25 g / L, take 1 / 3 of the volume to inoculate pre-acclimated salt-tolerant functional bacteria, carry out organic component hydrolysis fermentation at pH 5.5 and temperature 35℃, with a hydraulic retention time of 72 hours, to generate fermentation broth containing short-chain carboxylic acids, with a cumulative concentration of 12 g COD / L.

[0055] The salt-tolerant functional bacteria were domesticated using the following method:

[0056] Wastewater containing carbonate organic matter was used as the substrate, with an initial salinity of 10 g / L. Anaerobic wastewater treatment sludge was inoculated and then acclimated for 7 days, with a salinity increase of 5 g / L per acclimation period. Acclimation was completed when the salinity reached 30 g / L and the acid production efficiency of the bacterial community stabilized, resulting in a pre-acclimated salt-tolerant functional bacterial community. This salt-tolerant functional community included dominant species of *Clostridium*, *Seminobacter*, and *Halophyte*, with a relative abundance of 80% for these dominant species.

[0057] (2) The fermentation liquid is mixed with the remaining decommissioned lithium battery brine discharge wastewater and subjected to a carbon chain elongation reaction for 96 hours at pH 7.0 and temperature 30°C. During the reaction, the hydrogen partial pressure is maintained at 100 Pa to generate a treatment liquid containing medium-chain carboxylic acids and long-chain alcohols.

[0058] Example 2

[0059] This embodiment provides a method for the biological resource utilization treatment of brine discharge wastewater from retired lithium batteries, the method comprising the following steps:

[0060] (1) Adjust the salinity of the wastewater from the decommissioned lithium battery salt discharge to 27.5 g / L, take 1 / 3 of the volume and inoculate it with pre-acclimated salt-tolerant functional bacteria. The organic components are hydrolyzed and fermented at pH 6.0 and temperature 37.5℃. The hydraulic retention time is 60 hours, and a fermentation broth containing short-chain carboxylic acids is generated. The cumulative concentration of short-chain carboxylic acids is 10 g COD / L.

[0061] The salt-tolerant functional bacteria were domesticated using the following method:

[0062] Wastewater containing carbonate organic matter was used as the substrate, with an initial salinity of 10 g / L. Anaerobic wastewater treatment sludge was inoculated and then acclimated for 6 days, with a salinity gradient increase of 7.5 g / L per acclimation period. When the salinity reached 30 g / L and the acid production efficiency of the bacterial community stabilized, acclimation was completed, resulting in a pre-acclimated salt-tolerant functional bacterial community. This salt-tolerant functional community included dominant species of *Clostridium*, *Seminobacter*, and *Halophyte*, with a relative abundance of 75%.

[0063] (2) The fermentation liquid is mixed with the remaining decommissioned lithium battery brine discharge wastewater and subjected to a carbon chain elongation reaction for 108 hours at a pH of 7.25 and a temperature of 32.5°C. During the reaction, the hydrogen partial pressure is maintained at 150 Pa to generate a treatment liquid containing medium-chain carboxylic acids and long-chain alcohols.

[0064] Example 3

[0065] This embodiment provides a method for the biological resource utilization treatment of brine discharge wastewater from retired lithium batteries, the method comprising the following steps:

[0066] (1) Adjust the salinity of the wastewater from the decommissioned lithium battery salt discharge to 30 g / L, take 1 / 3 of the volume to inoculate pre-acclimated salt-tolerant functional bacteria, carry out organic component hydrolysis fermentation under the conditions of pH 6.5 and temperature 40℃, the hydraulic retention time is 48 hours, and a fermentation broth containing short-chain carboxylic acids is generated, with a cumulative concentration of 8 g COD / L.

[0067] The salt-tolerant functional bacteria were domesticated using the following method:

[0068] Wastewater containing carbonate organic matter was used as the substrate, with an initial salinity of 10 g / L. Anaerobic wastewater treatment sludge was inoculated and then acclimated for 5 days, with a salinity increase of 10 g / L per acclimation period. When the salinity reached 30 g / L and the acid production efficiency of the bacterial community stabilized, acclimation was complete, resulting in a pre-acclimated salt-tolerant functional bacterial community. This salt-tolerant functional community included dominant species of *Clostridium*, *Seminobacter*, and *Halophyte*, with a relative abundance of 77%.

[0069] (2) The fermentation liquid is mixed with the remaining decommissioned lithium battery brine discharge wastewater and subjected to a carbon chain elongation reaction for 120 hours at a pH of 7.5 and a temperature of 35°C. During the reaction, the hydrogen partial pressure is maintained at 200 Pa to generate a treatment liquid containing medium-chain carboxylic acids and long-chain alcohols.

[0070] Example 4

[0071] This embodiment provides a method for the biological resource utilization of wastewater from the saline discharge of retired lithium batteries. Except for the fact that the acclimatization of the bacterial community does not use gradient salinity increase, but directly uses wastewater with a salinity of 30 g / L for acclimatization, the rest of the method is the same as in Example 1.

[0072] Example 5

[0073] This embodiment provides a method for the biological resource utilization treatment of wastewater from the discharge of decommissioned lithium batteries using brine. Except for the gradient of salinity increase for the acclimatization of the bacterial community being 15 g / L, the method is the same as that in Example 1.

[0074] Example 6

[0075] This embodiment provides a method for the biological resource utilization treatment of wastewater from the discharge of decommissioned lithium batteries using brine. Except for the gradient of salinity increase for the acclimatization of the bacterial community being 3 g / L, the method is the same as that in Example 1.

[0076] Example 7

[0077] This embodiment provides a method for the biological resource utilization of wastewater from the discharge of decommissioned lithium batteries using brine. The method is the same as that in Embodiment 1, except that the pH of the hydrolysis fermentation is 5.

[0078] Example 8

[0079] This embodiment provides a method for the biological resource utilization treatment of wastewater from the discharge of decommissioned lithium batteries using brine. Except for the pH of 7 during hydrolysis and fermentation, the method is the same as that in Embodiment 1.

[0080] Comparative Example 1

[0081] This comparative example provides a method for the biological resource utilization of wastewater from the saline discharge of retired lithium batteries. The method is the same as that in Example 1, except that the pre-acclimatization of salt-tolerant bacteria is not carried out and the anaerobic water treatment sludge is directly inoculated.

[0082] Comparative Example 2

[0083] This comparative example provides a method for the biological resource utilization of wastewater from decommissioned lithium batteries undergoing brine discharge. The method does not involve stepwise reactions. The wastewater from decommissioned lithium batteries is adjusted to a salinity of 25 g / L, inoculated with pre-acclimated salt-tolerant functional bacteria, and reacted for 7 days at a pH of 6.0 and a temperature of 37.5℃ to obtain the treated solution.

[0084] Test methods

[0085] After centrifugation to separate the solid and liquid components of the treated solutions obtained in Examples 1-6 and Comparative Examples 1-2, the contents of medium-chain carboxylic acids and long-chain alcohols in the treated solutions were determined by gas chromatography equipped with a flame ionization detector, and the yields were further calculated. The test results are shown in Table 1.

[0086]

[0087] In the formula: Yield m The yield of biotransformation product m; COD dw Measured CODcr concentration of lithium battery brine discharge wastewater; ThCOD m The theoretical COD value of product m in the treatment solution is obtained by conversion from the measured product concentration.

[0088] Test Results

[0089] Table 1

[0090]

[0091] The test results show that:

[0092] (1) As can be seen from Examples 1 to 3, the present invention can realize the high-value conversion of organic matter in lithium battery salt discharge wastewater by pre-domesticated salt-tolerant bacteria. No methanogen inhibitors and electron donors need to be added during the bio-fermentation process. The process is economical, green and has a high yield of high-value organic matter.

[0093] (2) As can be seen from Examples 1 and 4-8, by further optimizing the process of gradient domestication of salt-tolerant bacteria, the present invention can screen and retain dominant bacteria in the domestication stage, optimize the pH of hydrolysis and fermentation, inhibit the activity of methanogens in the reaction stage, and achieve a higher yield of high-value organic matter.

[0094] (3) As can be seen from Example 1 and Comparative Examples 1-2, the present invention can improve the yield of medium-chain carboxylic acids and long-chain alcohols by pre-domestication and stepwise bio-fermentation. However, when pre-domestication is not carried out, the salt tolerance of the bacterial community is low and the abundance of the dominant bacterial community is low. When stepwise reaction is not carried out, the bacterial community for chain elongation reaction cannot react under optimal conditions, resulting in a significant decrease in the yield of medium-chain carboxylic acids and long-chain alcohols.

[0095] In summary, by utilizing the unique pollutant composition and high salt content of discharge wastewater, the process of inhibiting methanogenesis can be achieved without the need for expensive chemical agents or high-temperature treatment of inoculum, or by the addition of electron donors such as ethanol or lactic acid. This significantly reduces the chemical or energy costs of the process while achieving high-value conversion of organic pollutants in wastewater.

[0096] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for the biological resource utilization treatment of wastewater from the brine discharge of retired lithium batteries, characterized in that, The method includes the following steps: (1) The pretreated wastewater from the decommissioned lithium battery salt discharge is divided into a first part of wastewater and a second part of wastewater. The first part of wastewater is inoculated with pre-acclimated salt-tolerant functional bacteria and subjected to organic component hydrolysis and fermentation to generate a fermentation broth containing short-chain carboxylic acids. (2) The fermentation liquid is mixed with the second part of wastewater to carry out a carbon chain extension reaction to generate a treatment liquid containing medium-chain carboxylic acids and long-chain alcohols.

2. The method according to claim 1, characterized in that, The pretreatment includes adjusting the salinity of the decommissioned lithium battery brine discharge wastewater to 25-30 g / L; Preferably, the salinity adjustment uses NaCl or Na2SO4 as the salinity regulator; Preferably, the volume ratio of the first part of wastewater to the second part of wastewater is 1:1.5 to 1:2.

5.

3. The method according to claim 1 or 2, characterized in that, The pre-acclimatized salt-tolerant functional bacteria in step (1) are acclimatized using the following method: Wastewater containing carbonate and / or nitrile organic matter was used as the substrate, with an initial salinity of 10 g / L. After inoculation with the initial bacterial population, acclimatization was carried out for 5-7 days, with a salinity gradient increase of 5-10 g / L in each acclimatization cycle. When the salinity reached 30 g / L and the acid production efficiency of the bacterial population was stable, the acclimatization was completed, and a pre-acclimatized salt-tolerant functional bacterial population was obtained. Preferably, the initial microbial community is an anaerobic mixed microbial community; Preferably, the salt-tolerant functional bacterial community includes dominant species of Clostridium, Sedibacter, and Halophilic cysts, with the relative abundance of the dominant species being ≥65%. Preferably, the abundance of methanogenic bacteria in the salt-tolerant functional bacterial community is <2%.

4. The method according to any one of claims 1-3, characterized in that, The pH of the organic component hydrolysis fermentation in step (1) is 5.5-6.5; Preferably, the temperature for the hydrolysis and fermentation of the organic components is 35-40°C; Preferably, the hydraulic retention time for the hydrolysis and fermentation of the organic components is 48-72 hours; Preferably, the cumulative concentration of short-chain carboxylic acids in the fermentation broth is 8-12 g COD / L.

5. The method according to any one of claims 1-4, characterized in that, The pH of the carbon chain elongation reaction in step (2) is 7.0-7.5; Preferably, the temperature of the carbon chain elongation reaction is 30-35°C; Preferably, the reaction time for the carbon chain elongation reaction is 96-120 hours; Preferably, the yield of medium-chain carboxylic acids in the carbon chain elongation reaction is 0.45-0.52 g COD / g COD; Preferably, the partial pressure of hydrogen in the carbon chain elongation reaction is 100-200 Pa.

6. The method according to any one of claims 1-5, characterized in that, The COD conversion rate of the decommissioned lithium battery brine discharge wastewater treated by the method is >90%; Preferably, the system of the method can tolerate salinity fluctuations within a range of ±15%; Preferably, the organic loading of the system in the method is 8-10 kg COD / (m³·d).

7. A processing system for the method according to any one of claims 1-6, characterized in that, The processing system includes a salinity adjustment unit, a hydrolysis fermenter, and a carbon chain extension reactor. The salinity adjustment unit is connected to the inlet of the hydrolysis fermenter and the carbon chain extension reactor, and the outlet of the hydrolysis fermenter is connected to the inlet of the carbon chain extension reactor.

8. The processing system according to claim 7, characterized in that, The salinity adjustment unit includes a salinity sensor and an automatic dosing device.

9. The processing system according to claim 7, characterized in that, The hydrolysis fermenter includes a corrosion-resistant stirrer and an online pH control module; Preferably, the carbon chain extension reactor includes an airtight headspace gas recovery device.

10. The processing system according to any one of claims 7-9, characterized in that, The volume ratio of the hydrolysis fermenter to the carbon chain extension reactor is 1:2; Preferably, the carbon chain extension reactor is filled with a carbon fiber carrier; Preferably, the specific surface area of ​​the carbon fiber carrier is 500-800 m². 2 / m 3 .

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