A circulating cooling water biochemical regulation method and concentration limit determination method based on high concentration ratio operation

Abstract

The application is a circulating cooling water biochemical regulation method and concentration limit determination method based on high concentration ratio operation. By adding microbial bacteria liquid in the circulating cooling water, the synergistic effect of functional bacteria in the microbial bacteria liquid is used to carry out biochemical regulation on the circulating cooling water, so as to inhibit system scaling, corrosion and biological slime breeding, and then improve the system concentration ratio. By preparing different types of microbial bacteria liquid, the functional bacteria suitable for high concentration ratio operation and the best adding concentration are screened out. The scale, corrosion and slime prevention effects of the microbial functional bacteria are analyzed, and the key factors restricting the improvement of the concentration ratio of the circulating cooling water system and the concentration ratio limit value that can be reached are put forward.

Description

Technical Field

[0001] This invention relates to the field of circulating cooling water treatment technology, specifically to a biochemical method for treating circulating cooling water with a high concentration ratio and a concentration limit determination technique. Background Technology

[0002] Since my country proposed the "dual carbon" target, the whole society has been steadily transforming towards a green and low-carbon society. Industry, as the core source of carbon emissions, has become a key breakthrough point for emission reduction due to its high energy consumption and high emission characteristics. Carbon emissions from industrial production are closely linked to industrial water consumption. Among them, circulating cooling water systems are major water users in industry, accounting for more than 70% of total industrial water consumption. Therefore, researching methods for deep water-saving in circulating cooling water, especially achieving water savings by increasing the concentration ratio, is of significant practical importance for achieving industrial carbon emission reduction goals.

[0003] In the field of circulating cooling water treatment technology, traditional methods are mainly divided into chemical treatment methods and physical treatment methods, but both have obvious limitations in achieving high concentration ratios and balancing environmental protection and economy.

[0004] Chemical treatment is currently the most widely used technology. Its core principle is to add water quality stabilizers to circulating water, which is simple to operate and has good short-term treatment effects. However, this method has significant drawbacks: First, the use of chemical agents can pollute the environment, and some agents may even exacerbate the risk of scaling and corrosion in the system. For example, Zhang et al. reported that the use of phosphorus-based agents can generate calcium phosphate precipitates in circulating cooling water, leading to a decrease in heat exchanger efficiency. In addition, most chemical agents are non-biodegradable, and their large-scale use can cause parameters such as chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total phosphorus (TP), and turbidity in the concentrated effluent of circulating cooling water to exceed wastewater discharge standards. Second, the procurement and maintenance costs of chemical agents are high, which can impose a continuous economic burden on power plants and other industrial enterprises. More importantly, the concentration ratio of circulating cooling water after chemical treatment is generally low, making it difficult to meet the needs of deep water conservation, which has become the core bottleneck for its widespread application.

[0005] Physical treatment methods use technologies such as sound, light, electricity, and magnetism to alter the movement of ions and molecules in hard water, thereby achieving scale inhibition. Compared to chemical methods, it has significant advantages: it integrates descaling, corrosion inhibition, and sterilization, is convenient to use, causes no environmental pollution, and is relatively inexpensive, offering a broad commercial market and environmental benefits. However, physical methods also have drawbacks: high initial equipment investment costs, poor economic efficiency, and limited practicality for large-volume industrial circulating cooling water systems. For example, Xu et al. found that the quality of circulating cooling water significantly affects the scale inhibition effect of magnetic field treatment. When the circulating cooling water solution does not contain Mg... 2+ When the solution contains Mg, the average scale inhibition rate is 32.91%; 2+And Mg 2+ / Ca 2+ When the molar ratio is 1:1.2, its average scale inhibition rate is 27.89%; when Mg 2+ / Ca 2+ There is no scale inhibition effect when the molar ratio is 1:1.5. Moreover, the concentration ratio that can be achieved by physical methods is usually less than 5 times, which is far from meeting the high concentration ratio requirements for deep water conservation and is difficult to support long-term industrial water conservation goals.

[0006] Due to the limitations of chemical and physical methods in achieving high concentration ratios, environmental friendliness, and economic efficiency, researchers have begun to actively explore more efficient and sustainable treatment technologies, leading to the emergence of biochemical regulation methods. This method utilizes advanced biotechnology and production processes to prepare highly efficient bioactive bacterial agents, significantly shortening microbial cultivation time and increasing microbial concentration. It alleviates scaling and corrosion problems in circulating cooling water systems through the metabolism of the microorganisms themselves, and regulates the pH value of the circulating cooling water by utilizing the acid produced by the microorganisms. Compared to directly adding chemical agents, this method is gentler and effectively avoids drastic pH fluctuations in circulating water caused by chemical agents, thereby preventing equipment corrosion. The use of biochemical regulation can effectively improve water quality and reduce ammonia nitrogen and chemical oxygen demand in circulating cooling water. More importantly, biochemical regulation not only avoids secondary pollution but also achieves a concentration ratio far exceeding that of traditional methods—usually more than 10 times, resulting in significant water conservation. At the same time, although the treated wastewater has a high concentration of pollutants, it can be recycled as water for desulfurization systems, making it particularly suitable for water-scarce regions. This perfectly meets the dual needs of industrial water conservation and environmental protection under the "dual carbon" goal, providing a new technological direction for deep water conservation in circulating cooling water.

[0007] Therefore, developing a biochemical regulation method and a concentration limit determination method for circulating cooling water suitable for high concentration ratio operation can significantly increase the concentration ratio of circulating water, greatly reduce the amount of fresh water used in industry, directly reduce water resource consumption, further reduce carbon emissions throughout the production process, provide an effective technical path for deep water conservation in industry, and meet the needs of enterprises for green and low-carbon transformation; at the same time, it can also promote research on exploring the key factors restricting the increase of the concentration ratio of circulating cooling water systems and the achievable concentration ratio limit. Summary of the Invention

[0008] Based on the characteristic that high concentration ratio can effectively achieve deep water saving in the system, this invention provides a biochemical regulation method for circulating cooling water based on high concentration ratio operation and a method for determining the concentration limit. This method can utilize the synergistic effect of multiple functional bacteria in microbial agents to biochemically regulate circulating cooling water, thereby solving problems such as scaling and corrosion caused by high concentration ratio in power plant circulating cooling water.

[0009] This invention provides a method for biochemical regulation of circulating cooling water based on high concentration ratio operation and a method for determining concentration limit, specifically including the following steps: Step S1. Preparation of microbial inoculum: Before use, the microbial inoculum powder, microbial nutrient and 0.9% sodium chloride solution should be mixed and heated in a water bath at 36°C for 24 hours to prepare the microbial inoculum.

[0010] Step S2. Addition of microbial solution: Detect and record the water quality parameters, biological slime quantity parameters, test tube parameters, electrochemical electrode parameters, and corrosion characteristics of the test piece in the raw water and system; then add the prepared microbial solution to the circulating cooling water system by shock dosing.

[0011] Step S3. System water replenishment: Monitor the water level of the circulating cooling water system in real time. When the water level reaches the minimum value of the circulating water level, replenish the circulating cooling water system with circulating cooling water.

[0012] Step S4. Add microbial nutrients: During the operation of the circulating cooling water system, add microbial nutrients to the circulating water 2 to 3 times a day. The amount of microbial nutrients added each time is 8% of the amount of microbial liquid added, so as to provide nutrients for the growth of microorganisms.

[0013] Step S5. Monitoring of microbial culture content: During the circulation of cooling water, the relative abundance of the microbial community is determined by microbial 16S amplicon sequencing to detect the dominant microbial community in the circulating cooling water. When the relative abundance of functional bacteria in the dominant microbial community of the circulating cooling water is less than 30%, microbial culture is added again.

[0014] Step S6. Anti-corrosion, anti-scaling and anti-sludge effect test: During the circulation process of the circulating cooling water, the water quality parameters, biological slime quantity parameters, test tube parameters, electrochemical electrode parameters and test piece corrosion characteristics are detected to monitor water quality indicators, concentration ratio, heat transfer resistance, corrosion rate and biological slime quantity, thereby achieving the test of anti-corrosion, anti-scaling and anti-sludge effect.

[0015] Step S7. Concentration Ratio Limit Detection: Based on the tested water quality parameters and test tube parameters, calculate the pH value and Δ in the circulating cooling water. N Value and Δ r ds The value is used to determine whether the circulating cooling water system has reached the concentration ratio limit.

[0016] The biological agent dry powder mentioned in step S1 is a dry powder made of 40-45% nitrifying bacteria, 15-20% Bacillus subtilis, 15-20% Bacillus cereus, 15-20% Pseudomonas, and 5-10% photosynthetic bacteria.

[0017] The microbial inoculum described in step S1 relies on nitrifying bacteria to oxidize NH3-N into HNO2 and HNO3 through nitrification, thereby lowering the pH value of the circulating cooling water. Simultaneously, under quantitative microbial nutrient conditions, the functional microorganisms can control the solution pH value within a slightly alkaline range of 7.84-8.12 without causing a continuous decrease in pH, effectively preventing equipment corrosion caused by drastic fluctuations in the circulating water pH value.

[0018] The dosage of the microbial inoculum in step S2 is 0.01-0.05% of the circulating cooling water volume.

[0019] The dosage of the microbial nutrient agent mentioned in step S4 is 8% of the microbial culture solution.

[0020] In step S5, the microbial 16S amplicon sequencing method uses the HiSeq platform to sequence the V3-V4 hypervariable regions of the 16S rRNA of the sample microorganisms, obtaining raw Clean Data sequencing data and filtering out low-quality reads. FLASH software is used for sequence assembly, utilizing overlap relationships to assemble paired reads obtained from paired-end sequencing into a single sequence, yielding tags for the hypervariable regions. The Usearch clustering method is used to cluster the tags according to 97% sequence similarity, generating OUT clusters. Then, OUT species are annotated using the Greengene database to obtain community composition information (relative abundance map) for each sample, ultimately determining the dominant bacterial population.

[0021] In step S6, when the conductivity and Ca of the circulating cooling water are... 2+ Cl - The total alkalinity continues to rise, and the rate of increase in fouling thermal resistance is less than 10%. -6 (m 2 When the temperature (°C / W) / d is considered to be ℃ / W / d, it can be considered that microbial agents can effectively improve the scale prevention effect; when the electrode parameters in the circulating cooling water are... R p When the value is higher and the total iron ions in the circulating cooling water are lower, it can be considered that the microbial agent can effectively improve the anti-corrosion effect; when the amount of biological slime in the circulating cooling water does not continue to rise, it can be considered that the microbial agent can effectively improve the anti-sliming effect.

[0022] In step S6, the electrode parameters R p It was obtained by conducting linear polarization tests.

[0023] Linear polarization (LPR) involves scanning a narrow range of linear DC potential (±10mV) relative to the active polarization point (OCP) to control the polarization potential within the micro-polarization region of the OCP. The polarization potential and polarization current of the working electrode are measured at regular intervals; the slope at zero point yields the linear polarization resistance. R p The calculation formula is as follows:

[0024] In the formula: R p —Linear polarization resistance, kΩ·cm 2 ; E —Polarization potential, mV; i —Polarization current, μA / cm 2 .

[0025] The corrosion current density can be calculated from the resistance value, and then the instantaneous corrosion rate of the metal can be calculated. The calculation formula is as follows:

[0026]

[0027] In the formula: i corr —Corrosion current density, μA / cm 2 ; β a —Anode Tafel slope, mV; β c —Cathode Tafel slope, mV; v —Instantaneous corrosion rate, mm / a; M —Molar mass of the metal, g / mol; n —Number of electrons transferred; F —Faraday constant, 96500 C / mol; R p —Linear polarization resistance, kΩ·cm 2 ; ρ —Density of metallic materials, g / cm³ 3 .

[0028] It can be seen that, R p A higher value indicates a lower corrosion rate and a better corrosion protection effect.

[0029] In step S6, the amount of biological slime is calculated, and the amount of slime is expressed as... V It indicates that the unit is milliliters per cubic meter (mL / m³) 3 ), calculate according to the following formula:

[0030] In the formula: V 1 — The volume of clay in the graduated cylinder, expressed in milliliters (mL); V 2—The volume of circulating cooling water passing through during the interval for measuring biological slime quantity, expressed in cubic meters (m³). 3 ).

[0031] The concentration ratio limit mentioned in step S7 is determined by the following condition: Δ N Values ​​exceeding 0.2, pH values ​​exceeding 8.2, and Δ r ds Values ​​exceeding 10 -6 (m 2 ·℃ / W) / d. Due to the continuous concentration of circulating cooling water, the total hardness and Cl... - As the concentration increases, the concentration ratios of the two become equal. When scaling occurs in the system, the Cl in the water... - It will not deposit, while Ca 2+ When scale ions deposit, the increase in the concentration ratio of total hardness decreases, and the difference in concentration ratio Δ between the two factors becomes smaller. N The value gradually increases. Related studies show that when Δ N When ≤0.2, the system is in a metastable state where scaling does not occur. N A value exceeding 0.2 can be used as a criterion for judging whether the system has a tendency to scale. Δ N The value is calculated as follows:

[0032] In the formula: Δ N —Cl - The difference between the concentration ratio of the active ingredient and the concentration ratio of the total hardness; N Cl- , N YD —Cl - Concentration ratio of total hardness; Cl - i 、 YD i Cl in circulating cooling water - Total hardness; Cl - 0、 YD0—Cl in circulating cooling water makeup water - Total hardness.

[0033] When scale forms in a circulating cooling water system, some deposits increase heat transfer resistance. This thermal resistance caused by deposits is commonly referred to as fouling thermal resistance. r ds The fouling thermal resistance is obtained by subtracting the cleaning tube thermal resistance from the instantaneous heat transfer thermal resistance, expressed in m. 2 The instantaneous thermal resistance and fouling resistance, expressed in °C / W, are calculated using the following formula:

[0034] In the formula: d —Inner diameter of the test tube, in meters; L —Effective heat exchange length of the test tube, in meters; C p —Specific heat capacity of water, J / (kg·℃); G w —Flow rate of circulating cooling water entering the test tube, L / h; t s —Constant temperature water bath, °C; t w1 —Inlet circulating cooling water temperature of the test tube, °C; t w2 —Temperature of circulating cooling water at the outlet of the test tube, °C.

[0035]

[0036] In the formula: r i —Instantaneous thermal resistance of the test tube, m 2 ·℃ / W; r 0 — Thermal resistance of the cleaning tube, m 2 ·℃ / W.

[0037]

[0038] In the formula: Δ r ds — Rate of increase in thermal resistance due to fouling, (m 2 ·℃ / W) / d; h —Measurement interval, d.

[0039] When Δ NWhen the value increases and exceeds 0.2, the fouling thermal resistance also shows an upward trend. When the rate of increase in fouling thermal resistance Δ r ds Value greater than 10 -6 (m 2 When the temperature reaches ℃ / W / d, the system already shows a tendency to scale.

[0040] After adding microbial inoculants to circulating cooling water, the pH value initially decreases due to the acid-producing ability of the microorganisms. However, as the circulating cooling water continues to evaporate and concentrate, the pH value will rise. When the pH value of the circulating cooling water is below 8.2, the carbonate compounds in the water are mainly in the form of HCO3-. - It exists in a certain form, CO3 2- The content of different forms is low, at which point CO3 2- With Ca 2+ The ion product is insufficient to reach the solubility product required for CaCO3 precipitation, and the system does not show a tendency for carbonate scaling. However, when the pH exceeds 8.2, the acidic substances produced by the functional microorganisms are no longer sufficient to adjust the continuously concentrated pH of the circulating cooling water to HCO3. - Within the range of the maximum proportion, carbonate compounds in water gradually change from HCO3- - Formation changes to CO3 2- Form, CO3 2- As the concentration continues to increase, CO3 2- With Ca 2+ When the ion product gradually exceeds its solubility product, scaling will occur in the system.

[0041] Further research indicates that scaling is the limiting factor for the concentration limit of biochemical treatment of circulating cooling water; therefore, the concentration limit is exceeded when the pH value exceeds 8.2 and Δ... N Values ​​exceeding 0.2 and Δ r ds Values ​​exceeding 10 -6 (m 2 The concentration ratio (℃ / W) / d can be considered as the criterion for determining whether a circulating cooling water system has reached its concentration ratio limit.

[0042] Compared with existing technologies, the beneficial effects of this invention are: by adding microbial bacterial solution to the circulating cooling water, power plant equipment can operate in circulating cooling water with a high concentration ratio. The biochemical regulation method used to treat the circulating cooling water can be applied to power plant circulating cooling water systems with high concentration ratios, typically more than 10 times, resulting in significant water-saving effects. Simultaneously, the regulatory capacity of the microorganisms significantly improves the anti-corrosion, anti-scaling, and anti-sludge performance of the circulating cooling water system. Attached Figure Description

[0043] Figure 1 A flowchart of a circulating cooling water biochemical regulation method based on high concentration ratio operation; Figure 2 This is a graph showing the change in thermal resistance due to fouling. Figure 3 For circulating cooling water, (a) pH value and (b) concentration ratio and Δ N Change diagram; Figure 4 This is a graph showing the effect of solution pH on the speciation of carbonate compounds. Detailed Implementation

[0044] The technical solutions of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. However, these embodiments do not limit the present invention. The following non-limiting embodiments can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0045] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0046] In this embodiment, nitrifying bacteria, Bacillus subtilis, Bacillus cereus, Pseudomonas, and photosynthetic bacteria are all conventional strains in the field and can be obtained commercially.

[0047] Examples 1, 2, and 3 were tested on the apparatus described in "GB / T 34550.4-2017 Performance Evaluation Methods for Seawater Cooling Water Treatment Agents Part 4: Dynamic Simulation Test".

[0048] Example 1

[0049] This embodiment evaluates the anti-scaling, anti-corrosion, and anti-sliding effects of a microbial agent composed of different proportions of functional bacteria at the same initial concentration ratio, and includes the following steps: (1) Experimental preparation: Take water from the circulating cooling water system as the initial water, fill the water tank with the test water, and divide the circulating cooling water into three groups. Detect and record the water quality parameters, biological slime quantity parameters, test tube parameters, and electrochemical electrode parameters in the original water.

[0050] (2) Add microbial inoculum: Add 0.03% of the prepared microbial inoculum to each of the three groups of circulating cooling water.

[0051] The first group of microbial inoculum solutions mentioned above is mainly composed of dry powder made from nitrifying bacteria, Bacillus subtilis, Bacillus cereus, Pseudomonas, photosynthetic bacteria, etc. After being mixed with microbial nutrients and a 0.9% sodium chloride solution, the microbial inoculum solution is added in an impact-type dosing method.

[0052] The second group of microbial solutions mentioned above is mainly composed of dry powder made from scale-dissolving bacteria, quenching bacteria, Bacillus subtilis, photosynthetic bacteria, etc. After being mixed with microbial nutrients and a 0.9% sodium chloride solution, the microbial solution is added in an impact-type dosing method.

[0053] The aforementioned third group of microbial inoculum is mainly composed of dry powder made from nitrifying bacteria, Bacillus subtilis, Thiobacillus denitrification, photosynthetic bacteria, etc. After being mixed with microbial nutrients and a 0.9% sodium chloride solution, it is added in an impact-type dosing method.

[0054] The microbial nutrients in the above three groups are all composed of glucose, ammonium sulfate, and disodium hydrogen phosphate in a ratio of 1:1:1.

[0055] Among them, the bacteria with anti-scaling effect are nitrifying bacteria and scale-dissolving bacteria; the bacteria with anti-corrosion effect are Bacillus cereus, Pseudomonas, and Thiobacillus denitrification; and the bacteria with anti-sludge effect are photosynthetic bacteria and Bacillus subtilis.

[0056] Water replenishment control: During the operation of the circulating cooling water system, when the water level of each group of circulating cooling water reaches the minimum value, replenish the circulating cooling water system to the maximum scale line.

[0057] Adding microbial nutrients: During the operation of the circulating cooling water system, add microbial nutrients to the circulating water 2 to 3 times a day. The amount of microbial nutrients added each time is 8% of the amount of microbial liquid added.

[0058] Dominant microbial community detection: The relative abundance of microbial communities can be determined by microbial 16S amplicon sequencing to detect the dominant microbial community in the circulating cooling water. When the content of functional bacteria in the dominant microbial community of the circulating cooling water is less than 30%, microbial solution is added again.

[0059] (5) Operation monitoring: After the circulating water system is in operation, water samples are collected every 2 days to measure water quality parameters (conductivity, Ca). 2+ Cl - (Total alkalinity, total hardness, total iron ion concentration, suspended solids, turbidity); collect tube wall slime every 10 days using a biological slime sampler and measure the slime amount; calculate and record the fouling thermal resistance every 5 days by measuring test tube parameters; measure the linear polarization resistance every 3 days using the linear polarization method. R p value.

[0060] (6) Analysis of Microbial Sludge Growth Tendency: Functional bacteria such as Bacillus subtilis can produce bioflocculants, which can flocculate and settle suspended particulate matter, reducing suspended solids and turbidity in circulating cooling water and preventing the formation of biosludge by mixing suspended particulate matter with mucus. However, in all groups of experiments, no biosludge growth tendency was observed in the system. Therefore, the amount of microbial slime is not a limiting factor for increasing the system's concentration ratio when using biochemical methods to treat circulating cooling water.

[0061] (7) Corrosion Tendency Analysis: After adding microbial inoculants to the circulating cooling water, functional bacteria such as Bacillus cereus and Pseudomonas aeruginosa will form a biofilm on the stainless steel surface. The dense biofilm can protect the stainless steel from corrosive substances. However, with the increase of the concentration ratio, the circulating cooling water Cl - The concentration increased linearly over time, while Cl... - Increased concentration inhibits the activity of the formed biofilm, thus gradually weakening this protective effect. R p The value will show a trend of first increasing and then decreasing. Furthermore, as time progresses and Cl... - With increasing concentration, biofilm activity gradually decreases, and the protective effect of the biofilm on stainless steel gradually weakens. R p The values ​​showed a downward trend. However, under the conditions of this experiment, the stainless steel electrodes in each group... R p The value did not show a significant downward trend (exponential decline). Therefore, metal corrosion is not a factor limiting the improvement of the system concentration ratio when using biochemical methods to treat circulating cooling water.

[0062] (8) Scaling tendency analysis: such as Figure 2 As shown, the change in fouling thermal resistance was small in the early stage of the experiment, and the rate of increase in fouling thermal resistance Δ r ds Less than 10 -6 (m 2 ·℃ / W) / d. Therefore, biofilm formation does not cause an increase in fouling thermal resistance, and no scaling tendency was observed in the circulating cooling water system during this period. However, the fouling thermal resistance value showed a significant upward trend in the later stage. This is because scaling tendency appeared in the circulating cooling water system, and scaling occurred inside the test tube, thus continuously increasing the fouling thermal resistance. The rate of increase in fouling thermal resistance Δ after 20 days of the experiment. r ds Greater than 10 -6 (m 2 The temperature (℃ / W) / d shows a trend of being fast at first and then slow.

[0063] (9) Judgment of concentration ratio limit: such as Figure 3As shown, the circulating cooling water system exhibits a tendency to scale during operation, but no tendency to corrode or grow biological slime. Therefore, scaling can be considered the limiting factor for increasing the concentration ratio of the circulating cooling water system. Therefore, when the pH value exceeds 8.2, Δ... N Values ​​exceeding 0.2 and Δ r ds Values ​​exceeding 10 -6 (m 2 When the concentration ratio of the circulating cooling water system reaches the limit of the concentration ratio (℃ / W / d), the test ends.

[0064] (10) Screening of microbial strains: According to the experimental data, the maximum concentration ratio of the first group of circulating cooling water is 22 times; the maximum concentration ratio of the second group of circulating cooling water is 16 times; and the maximum concentration ratio of the third group of circulating cooling water is 14 times. The microbial agent with the higher system concentration ratio was selected comprehensively—a biological agent composed of nitrifying bacteria, Bacillus cereus, Pseudomonas, Bacillus subtilis, and photosynthetic bacteria.

[0065] Nitrifying bacteria oxidize NH3-N into HNO2 and HNO3 through nitrification, causing a decrease in the pH of the circulating cooling water. Simultaneously, functional microorganisms, under controlled conditions of a specific amount of microbial nutrients, can maintain the solution pH within a slightly alkaline range of 7.84-8.12, preventing a sustained decrease in pH. Figure 4 As shown, H produced by functional microbial bacteria + The pH of the solution is controlled within a slightly alkaline range of 7.84-8.12 to reduce the CO3 content in the water. 2- Transformed into HCO3 - Reduce carbonate compounds to CO3 2- The proportion of the present form inhibits CO3. 2- With Ca 2+ It combines to form CaCO3 scale, thereby improving the scale prevention effect of circulating cooling water.

[0066] Bacillus cereus and Pseudomonas can secrete EPS. The functional groups such as carboxyl, hydroxyl, and sulfonic acid groups on EPS can attach to the active growth sites of CaCO3 crystals, causing CaCO3 crystal phase transformation, thereby inhibiting the growth of CaCO3 crystals and effectively improving the scale prevention effect of the circulating cooling water system.

[0067] EPS secreted by Bacillus cereus, Pseudomonas, and other bacteria gradually form a biofilm on the metal surface. The biofilm can isolate dissolved oxygen on the metal surface and inhibit the cathodic oxygen reduction reaction. At the same time, the biofilm can also act as a physical barrier layer, preventing corrosive substances in the circulating cooling water from contacting the metal, inhibiting the metal substrate from being damaged by corrosive substances in the water, and improving the corrosion resistance of the circulating cooling water system.

[0068] Bioflocs secreted by flocculating bacteria such as Bacillus subtilis contain functional groups such as amino, hydroxyl, and carboxyl groups. These functional groups can flocculate and settle suspended particles in circulating cooling water through adsorption bridging, charge neutralization, and entrapment, thereby reducing suspended solids and turbidity in the circulating cooling water and improving the anti-sludge effect of the circulating cooling water system.

[0069] Photosynthetic bacteria and other functional bacteria play a role in improving water quality. They can utilize organic matter and sulfides in the water as hydrogen donors, carbon sources, and nitrogen sources for photosynthesis, thereby achieving the goal of reducing COD and improving water quality. Photosynthetic bacteria can also increase the dissolved oxygen concentration in the water, playing a positive role in the growth and reproduction of other functional bacteria.

[0070] Therefore, the first group of microbial agents, composed of nitrifying bacteria, Bacillus subtilis, Bacillus cereus, Pseudomonas, and photosynthetic bacteria, has the best effect. Since scaling is the main factor restricting the increase of the concentration ratio of the circulating cooling water system, the scale prevention effect of the microbial agents should be improved. Therefore, the weight percentage of each bacterial species is as follows: nitrifying bacteria 40-45%, Bacillus subtilis 15-20%, Bacillus cereus 15-20%, Pseudomonas cereus 15-20%, and photosynthetic bacteria 5-10%.

[0071] Example 2

[0072] This embodiment evaluates the anti-scaling, anti-corrosion, and anti-sludge effects of the same microbial agent on circulating cooling water at different dosage concentrations, including the following steps: (1) Experimental preparation: Fill the water tank with circulating cooling water as the initial water, and then divide the circulating cooling water into three groups. Detect and record the water quality parameters, biological slime quantity parameters, test tube parameters, electrochemical electrode parameters and coating corrosion characteristics in the original water.

[0073] (2) Addition of microbial inoculum: Select a specific combination of bacteria, consisting of nitrifying bacteria, Bacillus subtilis, Bacillus cereus, Pseudomonas, photosynthetic bacteria, etc., in the following proportions: nitrifying bacteria 40-45%, Bacillus subtilis 15-20%, Bacillus cereus 15-20%, Pseudomonas cereus 15-20%, and photosynthetic bacteria 5-10%.

[0074] The first group was given 0.01% of the circulating cooling water volume of activated microbial solution; the second group was given 0.03% of the circulating cooling water volume of activated microbial solution; and the third group was given 0.05% of the circulating cooling water volume of activated microbial solution.

[0075] (3) Adding fresh water: When the circulating cooling water level reaches its lowest value during operation, add fresh water to the circulating cooling water system.

[0076] (4) Dominant microbial community detection: The dominant microbial community in the circulating cooling water was detected by measuring the relative abundance of the microbial community using microbial 16S amplicon sequencing. When the relative abundance of functional bacteria in the dominant microbial community in the circulating cooling water was less than 30%, the microbial solution was added again.

[0077] (5) Adding microbial nutrients: During the operation of the circulating cooling water system, add microbial nutrients to the circulating water 2 to 3 times a day. The amount of microbial nutrients added each time is 8% of the amount of microbial liquid added.

[0078] (6) Analysis of dominant microbial communities: In the first group of experiments, after 30 days of operation, the dominant microbial community was found to be less than 30%, and the addition cycle was 30 days. In the second group of experiments, after 50 days of operation, the dominant microbial community was found to be less than 30%, and the addition cycle was 50 days. In the third group of experiments, after 60 days of operation, the dominant microbial community was found to be less than 30%, and the addition cycle was 60 days.

[0079] (7) Screening of Dosage Concentration: Taking a year of 365 days, a circulating cooling water volume of 200L, and a microbial nutrient dosage of 3 times per day as an example. Based on the dosage frequency and dosage, the consumption of microbial liquid in the first group was calculated to be 0.2433L, and the dosage of microbial nutrient was 21.313L; the consumption of microbial liquid in the second group was 0.438L, and the dosage of microbial nutrient was 38.3688L; the consumption of microbial liquid in the third group was 0.6083L, and the dosage of microbial nutrient was 53.287L; the microbial liquid dosage concentration of the first group with the lowest total consumption of 0.01% of the circulating cooling water volume was selected.

[0080] Example 3

[0081] This embodiment evaluates the anti-scaling, anti-corrosion, and anti-sludge effects of adding microbial agents to circulating cooling water versus not adding microbial agents, and includes the following steps: (1) Experimental preparation: Fill the water tank with circulating cooling water as the initial water, then divide the circulating cooling water into two groups, and detect and record the water quality parameters, biological slime quantity parameters, test tube parameters, and electrochemical electrode parameters in the original water.

[0082] (2) Addition of microbial inoculum: Select the combination of bacteria determined in Implementation 1, which consists of nitrifying bacteria, Bacillus subtilis, Bacillus cereus, Pseudomonas, photosynthetic bacteria, etc., in the following proportions: nitrifying bacteria 40-45%, Bacillus subtilis 15-20%, Bacillus cereus 15-20%, Pseudomonas cereus 15-20%, and photosynthetic bacteria 5-10%.

[0083] The first group contains activated microbial solution added at 0.01% of the circulating cooling water volume; the second group contains circulating cooling water without added microbial solution.

[0084] (3) Adding fresh water: When the circulating cooling water level reaches its lowest value during operation, add fresh water to the circulating cooling water system.

[0085] (4) Dominant microbial community detection: The dominant microbial community in the circulating cooling water was detected by measuring the relative abundance of the microbial community using microbial 16S amplicon sequencing. When the relative abundance of functional bacteria in the dominant microbial community in the circulating cooling water was less than 30%, the microbial solution was added again.

[0086] (5) Adding microbial nutrients: During the operation of the circulating cooling water system, add microbial nutrients to the circulating water 2 to 3 times a day. The amount of microbial nutrients added each time is 8% of the amount of microbial liquid added.

[0087] (6) Operation monitoring: After the circulating water system is in operation, water samples are collected every 2 days to measure water quality parameters (conductivity, Ca). 2+ Cl - (Total alkalinity, total hardness, total iron ion concentration, suspended solids, turbidity); collect tube wall slime every 10 days using a biological slime sampler and measure the slime amount; calculate and record the fouling thermal resistance every 5 days by measuring test tube parameters; measure the linear polarization resistance every 3 days using the linear polarization method. R p value.

[0088] (7) Judgment of Concentration Ratio Limit: The circulating cooling water system exhibited a tendency to scale during operation, but no tendency towards corrosion or biological slime growth. Therefore, scaling can be considered the limiting factor for increasing the concentration ratio of the circulating cooling water system. Therefore, when the pH value exceeds 8.2, Δ... N Values ​​exceeding 0.2 and Δ r ds Values ​​exceeding 10 -6 (m 2 When the concentration ratio of the circulating cooling water system reaches the limit of ℃ / W / d, the test ends. After the test ends, the test data shows that the limit concentration ratio of the circulating cooling water after adding microbial liquid is 22 times, and the limit concentration ratio of the circulating cooling water without adding microbial liquid is 6 times.

[0089] (8) Calculation of scale prevention rate, corrosion prevention rate, and sludge prevention rate: The scale prevention rate is calculated as follows:

[0090] In the formula: η1—Scale prevention rate, % r ds0 —The rate of increase in fouling thermal resistance in the group without the addition of microbial inoculum (m 2 ·℃ / W) / d; r ds1 —The rate of increase in fouling thermal resistance of the microbial inoculum group (m 2 ·℃ / W) / d.

[0091] The corrosion resistance efficiency is calculated as follows:

[0092] In the formula: η 2—Corrosion resistance efficiency, % ν 0—Instantaneous corrosion rate of the group without microbial inoculum, mm / a; ν 1 — Instantaneous corrosion rate of the microbial inoculum group (mm / a).

[0093] The anti-sliding rate is calculated as follows:

[0094] In the formula: η 3—Anti-sliding rate, % V 0 — Amount of biological slime in the group without microbial inoculum addition, mL / m 3 ; V 1 — Amount of biological slime in the group with added microbial inoculum, mL / m 3 .

[0095] (9) Results analysis: According to calculations, the scale prevention rate of the circulating cooling water increased by 60.87%, the corrosion prevention rate increased by 62.80%, and the sludge prevention rate increased by 25.89% after the addition of microbial solution. The addition of microbial solution achieved a synergistic improvement in the scale prevention, corrosion prevention, and sludge prevention performance of the circulating cooling water system, providing reliable support for the green treatment of industrial circulating cooling water.

Claims

1. A method for biochemical regulation of circulating cooling water based on high concentration ratio operation and a method for determining concentration limit, characterized in that, Specifically, the following steps are included: Step S1. Preparation of microbial inoculum: Before adding the microbial agent to the circulating cooling water, it is necessary to add microbial nutrients and a 0.9% sodium chloride solution to prepare the microbial inoculum; Step S2. Addition of microbial inoculum: Add microbial inoculum to the circulating cooling water using an impact dosing method; Step S3. System water replenishment: When the circulating cooling water level reaches its lowest value, replenish the circulating cooling water system with new water; Step S4. Add microbial nutrients: During the operation of the circulating cooling water system, add microbial nutrients to the circulating cooling water at regular intervals; Step S5. Monitoring of microbial inoculum content: During the circulation of the circulating cooling water, the relative abundance of the microbial community can be determined by microbial 16S amplicon sequencing to detect the dominant microbial community in the circulating cooling water. When the content of functional bacteria in the dominant microbial community in the circulating cooling water is less than 30%, microbial inoculum is added again. Step S6. Anti-corrosion, anti-scaling and anti-sludge effect test: After the circulating cooling water system has been running for a period of time, the water quality parameters, biological slime quantity parameters, test tube parameters and electrochemical electrode parameters in the circulating cooling water are tested to determine the water quality index, concentration ratio, biological slime quantity, heat transfer resistance and corrosion rate, thereby judging the anti-corrosion, anti-scaling and anti-sludge effect. Step S7. Concentration Ratio Limit Detection: Detect the pH value and Δ in the circulating cooling water. N Value and Δ r ds The value is used to determine whether the circulating cooling water system has reached the concentration ratio limit.

2. The method for biochemical regulation of circulating cooling water based on high concentration ratio operation and the method for determining concentration limit according to claim 1, characterized in that: The microbial agent described in step S1 is mainly a dry powder made from strains of nitrifying bacteria, Bacillus subtilis, Bacillus cereus, Pseudomonas, and photosynthetic bacteria. The weight percentages of each component are as follows: nitrifying bacteria 40-45%, Bacillus subtilis 15-20%, Bacillus cereus 15-20%, Pseudomonas cereus 15-20%, and photosynthetic bacteria 5-10%. The microbial nutrient is composed of glucose, ammonium sulfate, and disodium hydrogen phosphate in a ratio of 1:1:

1. The treatment temperature is 36°C.

3. The method for biochemical regulation of circulating cooling water based on high concentration ratio operation and the method for determining concentration limit according to claim 1, characterized in that: In step S1, the microbial inoculum relies on nitrifying bacteria to control the pH value of the solution within a weakly alkaline range of 7.84-8.12 through nitrification.

4. The method for biochemical regulation of circulating cooling water based on high concentration ratio operation and the method for determining concentration limit according to claim 1, characterized in that: The dosage of the microbial solution in step S2 is 0.01-0.05% of the circulating cooling water.

5. The method for biochemical regulation of circulating cooling water based on high concentration ratio operation and the method for determining concentration limit according to claim 1, characterized in that: The dosage of the microbial nutrient agent in step S4 is 8% of the microbial liquid.

6. The method for biochemical regulation of circulating cooling water based on high concentration ratio operation and the method for determining concentration limit according to claim 1, characterized in that: In step S5, the method of microbial 16S amplicon sequencing is to sequence the 16S amplicon of the sample microorganisms to obtain the community composition information of each sample, and finally obtain the information of the dominant bacterial group.

7. The method for biochemical regulation of circulating cooling water based on high concentration ratio operation and the method for determining concentration limit according to claim 1, characterized in that: In step S6, the scale-preventing effect of the microbial agent is determined by measuring the rate of increase in the thermal resistance of the fouling; the scale-preventing effect is assessed by measuring the detection electrode. R p The value is used to determine the anti-corrosion effect of microbial agents; the anti-slitting effect of microbial agents is determined by detecting changes in the amount of biological slime in circulating cooling water.

8. The method for biochemical regulation of circulating cooling water based on high concentration ratio operation and the method for determining concentration limit according to claim 1, characterized in that: The determination condition for the concentration ratio limit of the circulating cooling water system in step S7 is Δ N Values ​​exceeding 0.2, pH values ​​exceeding 8.2, and Δ r ds Values ​​exceeding 10 -6 (m 2 ·℃ / W) / d.

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