A method for preparing a biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons.

Abstract

This invention discloses a method for preparing a biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs). The method comprises: Step 1, preparation of soybean fermentation liquid: weigh soybeans, soak them in ultrapure water at a solid-liquid ratio of 1:20-1:50 for 12-48 hours, and after pulping, add ultrapure water to a final volume of 500 mL to obtain a soybean milk substrate; inoculate the soybean milk substrate with 10 mL of indigenous microbial culture solution for PAH-contaminated groundwater, and carry out closed fermentation under constant temperature and shaking conditions; Step 2, multifunctional... Preparation of the compound sustained-release agent: Weigh 35-60 parts of FeSO4·7H2O, 1-5 parts of rhamnolipin, 5-10 parts of humic acid, 1-5 parts of methionine, 5-10 parts of peanut peptide, 1-10 parts of soybean lecithin, 3-10 parts of yeast extract, and 40-60 parts of the soybean milk fermentation liquid obtained in the first step according to the following parts by weight; Beneficial effects: Significantly enhances the degradation efficiency of organic pollutants such as polycyclic aromatic hydrocarbons, providing a reliable material basis and theoretical support for the engineering application of groundwater bioremediation technology.

Description

Technical Field

[0001] This invention relates to a method for preparing a biomass-based slow-release agent, and more particularly to a method for preparing a biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons. Background Technology

[0002] Currently, microbial remediation, as a green and economical method for treating petroleum pollution, has received widespread research and attention. The biodegradation efficiency of petroleum hydrocarbons is influenced by various factors, including their physicochemical properties (such as bioavailability, hydrophobicity, and solubility), environmental conditions (such as temperature, pH, salinity, and the content of nutrients like nitrogen and phosphorus), and the environmental medium. These factors affect degradation capacity by altering microbial activity and community structure. Petroleum hydrocarbons entering groundwater environments easily lead to problems such as nutrient imbalance (high C / N ratio, low N / P), low temperature, hypoxia, and nutrient deficiency, inhibiting microbial proliferation and reducing degradation efficiency. By adding biostimulants such as nutrients, energy substances, and electron acceptors to groundwater, the metabolic activity of indigenous microorganisms can be enhanced, accelerating petroleum hydrocarbon degradation and shortening the remediation cycle. This method, based on in-situ remediation using indigenous functional microorganisms, conforms to the natural succession laws of micro-ecosystems and avoids the risks of ecological invasion or water quality deterioration that may result from the introduction of exogenous microorganisms.

[0003] Currently, research on biostimulants largely focuses on single nutrient components, with insufficient systematic research on compound stimulants. In practical applications, single-component stimulants have limited remediation effects, while multi-component compound bionutrients demonstrate higher efficiency and better applicability due to their synergistic effects. The biostimulant industry is currently developing towards diversification, greenness, and high efficiency, emphasizing the concept of "reduced application and increased efficiency" to promote the sustainable development of remediation technologies. The focus of global groundwater remediation has gradually shifted to groundwater ecological health, with core objectives including optimizing microecological structure, restoring environmental balance, and improving nutrient utilization efficiency. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing a biomass-based slow-release agent for remediating polycyclic aromatic hydrocarbon-contaminated groundwater, thereby optimizing the microecological structure, restoring environmental balance, and improving nutrient utilization efficiency during the groundwater remediation process.

[0005] The present invention provides a method for preparing a biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs). The method includes the following steps:

[0006] Step 1: Preparation of Soybean Milk Fermentation Liquid:

[0007] Weigh soybeans and soak them in ultrapure water at a solid-liquid ratio of 1:20-1:50 for 12-48 hours. After pulping, add ultrapure water to a final volume of 500 mL to obtain a soybean milk substrate. Inoculate the soybean milk substrate with 10 mL of polycyclic aromatic hydrocarbon-contaminated groundwater indigenous microbial culture solution and carry out closed fermentation under constant temperature and shaking conditions. The closed fermentation temperature is 10-20℃, the time is 7-15 days, and the shaking speed is 500-2000 rpm.

[0008] Step 2: Preparation of the multifunctional composite sustained-release agent:

[0009] Weigh out 35-60 parts of FeSO4·7H2O, 1-5 parts of rhamnolipin, 5-10 parts of humic acid, 1-5 parts of methionine, 5-10 parts of peanut peptide, 1-10 parts of soybean lecithin, 3-10 parts of yeast extract, and 40-60 parts of the soybean milk fermentation liquid obtained in the first step according to the weight ratio; mix the above components and stir evenly using a homogenizer with a stirring speed greater than 4000 rpm to obtain a multifunctional compound sustained-release agent.

[0010] The prepared biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs) is used to remediate organically contaminated groundwater, especially PAH-contaminated groundwater.

[0011] The beneficial effects of this invention are:

[0012] This invention provides a method for preparing a biomass-based slow-release agent for remediating polycyclic aromatic hydrocarbon (PAH) contaminated groundwater, resulting in a multifunctional composite slow-release agent suitable for the remediation of organically contaminated groundwater. This agent significantly alleviates the inhibitory effect of high concentrations of PAHs on microorganisms by supplementing various nutrients and activating the microbial detoxification enzyme system. On day 10, the indigenous biomass in the agent-treated group reached 13.739±0.668 mg / L, a 7.40-fold increase compared to the control group (1.856±0.075 mg / L); the phenanthrene removal rate increased to 91.25±3.26%, significantly higher than the control group (68.81±2.50%). In long-term, periodic batch experiments (10 cycles, totaling over 50 days), the agent demonstrated excellent sustained stability: the indigenous biomass remained at a high level (e.g., 8.166±0.265 mg / L in cycle X), compared to only 0.903±0.165 mg / L in the control group during the same period; the phenanthrene removal rate still reached 53.63±3.82% in cycle X, significantly higher than the control group (33.88±4.80%), effectively delaying the decline in microbial degradation activity. This agent can achieve continuous and stable release of nutrients, avoiding ecological adaptation problems caused by rapid migration and instantaneous overdose, significantly enhancing the degradation efficiency of organic pollutants such as polycyclic aromatic hydrocarbons, and providing a reliable material basis and theoretical support for the engineering application of groundwater bioremediation technology. Detailed Implementation

[0013] The present invention provides a method for preparing a biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs). The method includes the following steps:

[0014] Step 1: Preparation of Soybean Milk Fermentation Liquid:

[0015] Weigh soybeans and soak them in ultrapure water at a solid-liquid ratio of 1:20-1:50 for 12-48 hours. After pulping, add ultrapure water to a final volume of 500 mL to obtain a soybean milk substrate. Inoculate the soybean milk substrate with 10 mL of polycyclic aromatic hydrocarbon-contaminated groundwater indigenous microbial culture solution and carry out closed fermentation under constant temperature and shaking conditions. The closed fermentation temperature is 10-20℃, the time is 7-15 days, and the shaking speed is 500-2000 rpm.

[0016] Step 2: Preparation of the multifunctional composite sustained-release agent:

[0017] Weigh out 35-60 parts of FeSO4·7H2O, 1-5 parts of rhamnolipin, 5-10 parts of humic acid, 1-5 parts of methionine, 5-10 parts of peanut peptide, 1-10 parts of soybean lecithin, 3-10 parts of yeast extract, and 40-60 parts of the soybean milk fermentation liquid obtained in the first step according to the weight ratio; mix the above components and stir evenly using a homogenizer with a stirring speed greater than 4000 rpm to obtain a multifunctional compound sustained-release agent.

[0018] The specific implementation method is as follows:

[0019] Example 1

[0020] The nutrient composition ratio (mass ratio: %) of the multifunctional compound sustained-release agent is as follows: FeSO4·7H2O (37.593%), peanut peptide (4.092%), rhamnose lipolipin (1.762%), soybean lecithin (0.821%), humic acid (8.882%), yeast extract (4.092%), methionine (1.762%), and soybean milk fermentation liquid (40.996%).

[0021] An indoor microcosm simulation experiment was conducted, with a gradient exposure system established: a certain volume of groundwater (initial phenanthrene concentration gradient: 50, 100, 250, 500, and 1000 μg / L) was placed in a 500 mL amber glass bottle, and different volume ratios of a multifunctional composite slow-release agent (V / V, 0.0%, 0.1%, 0.5%, 1.0%, 2.0%, 5.0%, and 10.0%) were added to form 500 mL of phenanthrene-contaminated groundwater. A sterilization group (multifunctional composite slow-release agent + phenanthrene) and a blank group (microbial community + phenanthrene) were set up as controls. All treatments were performed in triplicate, incubated at 10℃ and 100 rpm in the dark, and samples were taken at time points 3, 5, 7, and 10 days to determine microbial biomass and phenanthrene content.

[0022] The multifunctional composite slow-release agent exhibits a significant positive stimulating effect on both bacterial growth and phenanthrene degradation. This effect is concentration-dependent and time-cumulative, and is significantly modulated by the initial phenanthrene concentration, demonstrating excellent long-term durability. In short-term concentration gradient experiments, the slow-release agent provided by this invention showed significant bioaugmentation effects in remediating groundwater contaminated with different concentration gradients of phenanthrene. Experimental results showed that under low-concentration pollution conditions (phenanthrene 50 μg / L, initial indigenous microbial biomass 0.03 mg / L), the addition of 10.0% slow-release agent enabled the bacterial biomass to reach 12.597±0.354 mg / L on day 10, an increase of nearly 9.36 times compared to the control group (1.346±0.045 mg / L). The improvement in phenanthrene removal efficiency was even more time-advantageous, reaching 68.34±4.73% on day 3, an increase of 16.8% compared to the control group (58.50±1.90%), and reaching 95.29±0.64% on day 10. Under medium-to-high concentration pollution conditions (250–1000 μg / L), the slow-release agent of this invention exhibits more prominent enhanced efficacy and possesses a unique "relief-activation" dual mechanism of action. In environments with high concentrations of phenanthrene (1000 μg / L) and low initial microbial biomass (0.03 mg / L), the bacterial biomass of the 10.0% multifunctional composite slow-release agent treatment group increased to 13.739±0.668 mg / L on day 10, a 7.40-fold increase compared to the control group (1.856±0.075 mg / L); the phenanthrene removal rate increased to 91.25±3.26%, significantly higher than the control group (68.81±2.50%). Especially under high pollution load conditions (500–1000 μg / L), the addition of the multifunctional composite slow-release agent significantly alleviated the inhibitory effect of high concentrations of phenanthrene on microorganisms through nutrient supplementation and activation of detoxification enzyme systems. Both microbial biomass and degradation rate continuously improved with increasing stimulant ratio, indicating its excellent environmental adaptability and bioactivation potential. This differentiated effect suggests that the multifunctional composite slow-release agent focuses on "accelerating degradation" at low phenanthrene concentrations and "improving efficiency and mitigating toxicity" at medium to high concentrations, thus covering the remediation needs of phenanthrene pollution at multiple concentration gradients, and is particularly suitable for the bio-enhanced remediation of medium to high-level polluted groundwater.

[0023] Example 2

[0024] The nutrient composition ratio (mass ratio: %) of the multifunctional compound sustained-release agent is as follows: FeSO4·7H2O (37.593%), peanut peptide (4.092%), rhamnose lipolipin (1.762%), soybean lecithin (0.821%), humic acid (8.882%), yeast extract (4.092%), methionine (1.762%), and soybean milk fermentation liquid (40.996%).

[0025] 950 mL of groundwater (initially 250 μg / L phenanthrene) was placed in a 1000 mL amber glass bottle, and 2% (v / v) of a multifunctional compound sustained-release agent was added. A sterile group (multifunctional compound sustained-release agent + phenanthrene) and a blank group (microbial community + phenanthrene) were set up as controls. All treatments were performed in triplicate and incubated at 10℃, 100 rpm in the dark for 5 days. The dynamic changes in microbial biomass and phenanthrene concentration were then measured. Subsequently, phenanthrene (without adding other components) was added back to the culture medium to a final concentration of 250 μg / L, and the next experimental cycle was initiated. A total of 10 cycles were performed, sequentially labeled I–X.

[0026] This embodiment validated the persistence of action of the sustained-release agent through a long-term, periodic batch experiment (10 cycles in total, with a total duration of over 50 days). The experiment used the continuous consumption of nutrients as the key environmental pressure to test the long-term effect of the stimulant. Under the conditions of a phenanthrene concentration of 250 μg / L and an initial indigenous microbial biomass of 0.03 mg / L: the results showed that the blank control group exhibited significant biomass decline and a decrease in phenanthrene removal rate as the culture cycle (cycles I to X) progressed. The microbial biomass decreased from 1.707±0.045 mg / L to 0.903±0.165 mg / L, and the phenanthrene removal rate decreased from 59.87±1.50% to 33.88±4.80%, fully reflecting the adverse effects of substrate limitation on microbial metabolism and enzyme synthesis. In comparison, the stimulating group of the slow-release agent of this invention maintained a high biomass and degradation efficiency throughout the entire cycle: at cycle X, the biomass of the stimulating group was 8.166±0.265 mg / L, which was 8.03 times higher than that of the control group at the same time; the phenanthrene removal rate remained at 53.63±3.82% at cycle X, while that of the control group was only 33.88±4.80% at the same time. The above results indicate that the slow-release agent of this invention significantly delayed the decline of the degradation activity of the microbial community by continuously providing nutritional support, demonstrating excellent long-term stability.

[0027] The combined short-term and long-term experimental results demonstrate that the multifunctional composite slow-release agent exhibits both "high efficiency" and "long-lasting" regulatory effects on phenanthrene-degrading microbial communities: in the short term, it can precisely activate bacterial community function according to phenanthrene concentration gradients, alleviating toxicity and improving degradation efficiency at medium to high concentrations; in the long term, it can withstand nutrient depletion pressure, maintaining stable bacterial growth and degradation activity. A deeper analysis of the long-term mechanism of action of the multifunctional composite slow-release agent reveals that its core advantage as a stable composite stimulant suitable for groundwater environments stems from the synergistic design of its components: on the one hand, components such as peanut peptides, soybean lecithin, yeast extract, fermented soybean milk, and humic acid enable the slow release of nutrients, avoiding short-term nutrient oversupply or rapid depletion, matching the need for slow nutrient replenishment in groundwater environments; on the other hand, components such as peanut peptides, soybean lecithin, yeast extract, and fermented soybean milk continuously generate small-molecule carbon sources, nitrogen sources, and growth factors (such as vitamins and signaling molecules) through natural fermentation, providing stable metabolic support for microorganisms. This synergistic mechanism of "slow release + natural fermentation" allows the biostimulatory effect of the multifunctional compound slow-release agent to last for more than 50 days, which is far superior to traditional single nutrient agents. This not only reduces the engineering costs of frequent stimulator additions, but also reduces the disturbance to the groundwater environment caused by multiple additions.

Claims

1. A method for preparing a biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons, characterized in that: The method includes the following steps: Step 1: Preparation of Soybean Milk Fermentation Liquid: Weigh soybeans and soak them in ultrapure water at a solid-liquid ratio of 1:20-1:50 for 12-48 hours. After pulping, add ultrapure water to a final volume of 500 mL to obtain a soybean milk substrate. Inoculate the soybean milk substrate with 10 mL of polycyclic aromatic hydrocarbon-contaminated groundwater indigenous microbial culture solution and carry out closed fermentation under constant temperature and shaking conditions. The closed fermentation temperature is 10-20℃, the time is 7-15 days, and the shaking speed is 500-2000 rpm. Step 2: Preparation of the multifunctional composite sustained-release agent: Weigh out 35-60 parts of FeSO4·7H2O, 1-5 parts of rhamnolipin, 5-10 parts of humic acid, 1-5 parts of methionine, 5-10 parts of peanut peptide, 1-10 parts of soybean lecithin, 3-10 parts of yeast extract, and 40-60 parts of the soybean milk fermentation liquid obtained in the first step according to the following parts by weight: mix them and stir evenly using a homogenizer with a stirring speed greater than 4000 rpm to obtain a multifunctional compound sustained-release agent.

2. A biomass-based slow-release agent for remediating groundwater contaminated with polycyclic aromatic hydrocarbons, characterized in that: It is prepared according to the preparation method according to claim 1.

3. The biomass-based slow-release agent for remediating polycyclic aromatic hydrocarbon-contaminated groundwater as described in claim 2, characterized in that: The organic pollution mentioned is polycyclic aromatic hydrocarbon pollution.