Biofilm formation starting method of biofilm system based on sulfur-based nano ceramic carrier
By preparing sulfur-based nanoceramic carriers and screening functional bacterial genera, a multifunctional biofilm system was constructed, which solved the problems of slow start-up and high energy consumption of biofilm systems, and achieved low-energy and high-efficiency wastewater treatment.
Patent Information
- Application Number
- CN202511707956.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-20
- Publication Date
- 2026-03-20
AI Technical Summary
Existing biofilm systems are difficult to start up quickly in wastewater treatment, and have high energy and chemical consumption, which affects the efficiency and stability of wastewater treatment.
Using a sulfur-based nanoceramic carrier, nano-alumina particles were prepared by precipitation and combined with laser cladding to load low-valence sulfur elements. Functional bacterial genera were screened and a heterotrophic bacteria preferential spray biofilm formation strategy was adopted to construct a multifunctional biofilm structure. Rapid start-up was achieved by optimizing process parameters.
It significantly shortens the system startup cycle, reduces energy and chemical consumption, constructs an efficient and multifunctional biofilm structure, adapts to different water quality scenarios, reduces operation and maintenance difficulty, is suitable for multi-level coupling design, and is adapted to special application scenarios.
Smart Images
Figure CN121698482A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater biological treatment technology, specifically to a biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier. Background Technology
[0002] In recent years, with the continuous increase in population size and the continuous improvement of urbanization level, a large amount of domestic and industrial wastewater has been generated. If it is discharged directly without treatment, it will inevitably cause great damage to natural water bodies and drinking water. Wastewater treatment methods usually include physical, chemical and biological methods. However, physical and chemical methods are not as economical and efficient as biological methods due to their high energy consumption and secondary pollution. However, the biological treatment process of wastewater is often accompanied by a large amount of energy consumption, especially aeration energy consumption, which can account for more than 50% of the total energy consumption of wastewater treatment. Therefore, how to break the situation of "using energy to treat pollution" and seek low-energy, low-chemical-consumption and high-efficiency wastewater treatment technologies is one of the effective means to help my country quickly achieve the "3060" dual carbon target. Biofilm systems enable the large-scale enrichment of microorganisms on material surfaces, effectively immobilizing dominant functional bacteria and leveraging their degradation capabilities. Compared to traditional activated sludge processes, biofilm systems have irreplaceable advantages. The key to achieving high efficiency and stability of biofilm systems lies in how to enable specific functional bacteria to rapidly attach to the material surface. Therefore, there is an urgent need for a low-energy, low-drug, and high-efficiency biofilm treatment technology to enable the rapid start-up of the biofilm system. Summary of the Invention
[0003] The purpose of this invention is to provide a biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier, in order to solve the problems mentioned in the background art, such as the difficulty in quickly starting up biofilm systems in wastewater treatment and the high energy and chemical consumption of existing treatment technologies.
[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for initiating biofilm formation in a biofilm system based on a sulfur-based nanoceramic carrier, the method comprising the following steps: S1. Modification of nano-ceramic carrier: Nano-ceramics are prepared by precipitation method. Aluminum chloride solution is mixed with precipitant and surfactant in a ratio of 20:1:2 and precipitated at 40~50℃ to form nano-alumina particles. After calcination at 400~500℃, ultrasonic pulverization and plate pressing, nano-ceramic carrier is obtained. Then, low-valence sulfur elements are loaded onto the surface of the carrier by laser cladding to serve as a metabolic substrate for sulfur-autotrophic denitrifying bacteria, thus obtaining a sulfur-based nano-ceramic carrier. S2. Screening of functional bacteria: Take fine yellowish-brown / dark brown forest soil from the top 0-20cm layer with a VSS / TSS ratio of 0.3-0.4, dilute it with water at a ratio of 2-4:1, and sonicate it at 300-600W for 30-60 minutes. After filtration, dilute it to a suspended solids concentration of 10000 mg / L. Use a medium containing sodium acetate / glucose to screen for heterotrophic bacteria, a medium containing ammonium chloride to screen for autotrophic nitrifying bacteria, and a medium containing potassium nitrate and a reducing sulfur source to screen for sulfur autotrophic denitrifying bacteria. All mediums are supplemented with low concentrations of nitrogen, phosphorus, and trace / macro elements. Soil and culture medium were mixed and enriched in three beakers under corresponding conditions. The bacterial suspension was transferred at a ratio of 5-15% until the removal rate and OD600 met the standards to obtain functional bacteria. S3, Functional bacterial genus inoculation and film attachment: First, inoculate 10 5 ~10 7 Mix 1000 mg / L of heterotrophic bacterial suspension with 1 mL of glucose, spray the carrier and open the ventilation window. After the COD removal rate is >80%, switch to continuous flow until a visible film forms on the carrier. Then 10 7 ~10 9 / mL of sulfur-autotrophic denitrifying bacteria is mixed with influent containing 50mg / L nitrate nitrogen and 150mgS / L reducing sulfur source, and sprayed in a closed system until the nitrate nitrogen removal rate is >50%; then 10 7 ~10 9 Mix 50 mg / L of autotrophic nitrifying bacteria with 50 mg / L of ammonia nitrogen in the influent, open the ventilation window until ammonia nitrogen < 5.0 mg / L and total nitrogen < 10.0 mg / L, and finally repeat the initial biofilm formation of heterotrophic bacteria. During the biofilm formation stage, maintain a pH of 7.0–8.0 and a temperature of 20.0–30.0℃. S4. Biofilm acclimatization: Using actual wastewater as influent, the flow is interrupted initially, and then switched to continuous flow when COD removal rate > 80%, ammonia nitrogen removal rate > 90%, and total nitrogen removal rate > 70%. S5. Process parameter optimization: Set C / N ratios of 2.5:1, 5:1, 10:1, and 20:1 (HRT 12.0h) to optimize influent load, and set HRTs of 2.0h, 6.0h, 12.0h, and 24.0h to optimize treatment efficiency; When COD removal rate is >80% and total nitrogen removal rate is >70%, the C / N ratio should be controlled at 5:1 to 20:1; when COD removal rate is >80% and ammonia nitrogen removal rate is >50%, the HRT should be controlled at 6.0 to 12.0 h; when only COD removal rate is >80%, the HRT should be controlled at 2.0 h. The biofilm system is a multi-stage coupled structure, with each stage containing a water collection and circulation device, a water distribution and spraying device, and a sedimentation device. The sulfur-based nano-ceramic carrier is folded and suspended vertically.
[0005] Preferably, in S1, the aluminum chloride solution concentration is 0.2~0.4M, the precipitant is sodium hydroxide / sodium carbonate with a concentration of 0.5~1.0M, the surfactant is polyethylene glycol 600 / 1500 with a concentration of 5~15g / L, the precipitation temperature is preferably 45℃, and the calcination temperature is preferably 450℃.
[0006] Preferably, the laser cladding material in S1 is iron sulfide, and the ratio of iron sulfide to nano-ceramic spraying is 5-10%. Laser spraying speed 1~10mm / s, input power 1~2kW, spot diameter 4~8mm, overlap rate 20~60%.
[0007] Preferably, in S2, the concentration of sodium acetate / glucose in the heterotrophic bacteria screening medium is 500-1000 mg / L, the concentration of ammonia nitrogen in the autotrophic nitrifying bacteria medium is 50-100 mg / L, the concentration of nitrate nitrogen in the sulfur autotrophic denitrifying bacteria medium is 50-100 mg / L, the concentration of reducing sulfur source is 100-300 mgS / L, and the sulfur-nitrogen ratio is 2-3. Low concentrations of nitrogen and phosphorus are ammonium chloride (ammonia nitrogen 10-20 mg / L) and potassium dihydrogen phosphate (phosphorus 2-4 mg / L).
[0008] Preferably, the culture conditions for heterotrophic bacteria and autotrophic nitrifying bacteria in S2 are DO 2.0–3.0 mg / L, pH 7.0–8.0, and temperature 20.0–30.0℃; The culture conditions for sulfur-autotrophic denitrifying bacteria were: DO 0.2–0.5 mg / L, pH 6.5–8.0, and temperature 20.0–30.0℃. The optimal enrichment and transfer ratio for the three rounds is 10%. The first round has a removal rate of >50% and transfer occurs, the second round has a removal rate of >80% and transfer occurs, and the third round ends when OD600 >0.1.
[0009] Preferably, the sulfur-based nano-ceramic carrier has a single-unit width of 1.0–1.5 m and a length of 1.8–2.2 m after being folded in half; Each system has 50 to 100 carriers, with a left-right spacing of 3.0 to 7.0 cm and a top-bottom stacking spacing of 3.0 to 7.0 cm between each carrier.
[0010] Preferably, the water spraying device is positioned 30-70cm above the carrier, with 1-3 devices configured per square meter; The water collection and circulation device is connected to the water distribution and spraying device to control the HRT, and the sedimentation device is located at the end of the system to collect aged biofilm.
[0011] Preferably, the concentration of the heterotrophic bacterial suspension for initial biofilm formation in step S3 is 10. 6 / mL, with glucose being the preferred organic matter; The optimal concentration of sulfur-autotrophic denitrifying bacteria suspension is 10. 8 / mL, the preferred concentration of autotrophic nitrifying bacteria suspension is 10. 8 / mL.
[0012] Preferably, in the domestication stage of S4, the biofilm forms a dissolved oxygen gradient, with the bottom layer being an anoxic / anaerobic zone and the surface layer being an aerobic zone, mainly composed of sulfur autotrophic denitrifying bacteria, autotrophic nitrifying bacteria, and heterotrophic bacteria.
[0013] Compared with the prior art, the beneficial effects of the present invention are: the biofilm initiation method of the biofilm system based on sulfur-based nanoceramic carrier: 1. Functional bacterial genera were screened from the topsoil (0-20cm, VSS / TSS 0.3-0.4) of vegetated forests. Highly active heterotrophic bacteria, autotrophic nitrifying bacteria, and sulfur autotrophic denitrifying bacteria were obtained through a process of "soil dilution-ultrasonic extraction-filtration and three-round beaker enrichment". A strategy of "prioritizing heterotrophic bacteria spraying for biofilm formation" was adopted. The extracellular polymers secreted by heterotrophic bacteria provided a stable attachment base for subsequent autotrophic bacteria, which significantly accelerated the colonization rate of autotrophic bacteria on the surface of sulfur-based nano-ceramic carriers and greatly shortened the system start-up cycle. At the same time, by spraying different functional bacterial genera in stages, the biofilm formed a clear functional stratification - the surface layer is an aerobic zone, which can efficiently realize the aerobic oxidation of organic pollutants and ammonia nitrogen nitrification, and the bottom layer is an anaerobic / anoxic zone, which relies on sulfur autotrophic denitrifying bacteria to complete nitrate nitrogen reduction. Finally, a multifunctional integrated biofilm structure of "decarbonization-nitrification-denitrification" was constructed without the need to build additional multi-stage treatment units. 2. Low energy and low chemical consumption operation helps achieve the "dual carbon" target. The sulfur-based nano-ceramic carrier uses the process of "preparing nano-alumina particles by precipitation - ultrasonic crushing - plate pressing into membrane" and combines the surface laser cladding with low-valence sulfur elements. This ensures that the carrier has a large biological attachment area and provides a continuous metabolic substrate for sulfur autotrophic denitrifying bacteria. There is no need to add denitrifying carbon source again. At the same time, the dissolved oxygen gradient of "aerobic surface - anoxic / anaerobic bottom layer" naturally formed by the biofilm can meet the dissolved oxygen requirements of different functional bacteria species, without the need for additional aeration equipment. In addition, the iron element in the carrier can effectively promote the electron transfer efficiency between microorganisms, further improving the removal efficiency of COD, ammonia nitrogen and total nitrogen. There is no additional energy and chemical consumption during the overall operation, which greatly reduces the energy consumption and chemical cost of sewage treatment. 3. Strong adaptability to water quality fluctuations, adaptable to multiple treatment scenarios. The system has a wide range of water quality adaptability through process parameter optimization: In terms of C / N ratio, when COD removal rate > 80% and total nitrogen removal rate > 70% are required, it can stably adapt to the C / N ratio range of 5:1 to 20:1 without adjusting carbon source addition due to fluctuations in the influent carbon-nitrogen ratio. In terms of hydraulic retention time (HRT), it can be flexibly set according to the effluent standard. If only COD removal rate > 80% is required, HRT can be shortened to 2.0h. If COD removal rate > 80% and ammonia nitrogen removal rate > 50% are required, HRT can be set to 6.0~12.0h. At the same time, the acclimatization stage uses the "intermittent flow-continuous flow" transition method to further improve the system's tolerance to fluctuations in actual wastewater quality, and can adapt to different water quality scenarios such as domestic sewage and low-concentration industrial wastewater. 4. The system boasts a high degree of modularity, convenient operation and maintenance, and adaptability to specific application scenarios. The biofilm system employs a "multi-level coupling" design, with each level equipped with an independent water collection and circulation device, a water distribution spraying device, and a sedimentation device. Furthermore, the sulfur-based nano-ceramic carrier utilizes a "folded vertical suspension" structure, allowing for flexible adjustment of the carrier quantity and system levels based on treatment scale. This results in high space utilization, a small footprint, and easy equipment integration. In addition, the system eliminates the need for aeration equipment and secondary carbon source addition devices. Maintenance only requires monitoring water temperature, pH, and influent and effluent water quality, simplifying management and making it particularly suitable for scenarios with inconvenient transportation and limited maintenance capabilities, such as rural and remote areas. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the treatment effect of the biofilm system based on sulfur-based nanoceramic carrier in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram illustrating the treatment effect of the biofilm system based on sulfur-based nanoceramic carrier in the comparative example of this invention. Detailed Implementation
[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0016] Please see Figures 1-2 The present invention provides a technical solution: a method for initiating biofilm formation in a biofilm system based on a sulfur-based nanoceramic carrier.
[0017] The low concentrations of nitrogen and phosphorus, as well as trace / macro elements, added to the culture medium in the examples are shown in Table 1 below.
[0018] Table 1. Major and Trace Elements element Concentration (g / L) Addition ratio (wastewater volume: dosage) CaCl2 30 1000:1 MgSO4 25 1000:1 FeSO4 20 1000:1 H3BO3 0.05 10000:1 ZnCl2 0.05 10000:1 CuCl2 0.05 10000:1 MnSO4 0.05 10000:1 (NH4)6Mo7O24 0.05 10000:1 AlCl3 0.05 10000:1 CoCl2 0.05 10000:1 NiCl2 0.05 10000:1 The soil used in this example was collected from forest land in Qingdao City, Shandong Province. The surface layer is rich in vegetation all year round, the soil texture is fine and there is no obvious sandy texture. The initial VSS / TSS of the soil is 0.3 to 0.4. The results of soil microbial community diversity analysis are shown in Table 2.
[0019] Table 2. Microbial community diversity analysis sample cutoff OTUs ACE Chao Shannon Simpson Coverage soil 0.03 1534 1490.6075 1489 5.232516 0.006759 0.993425 Example 1: A rapid start-up method for a biofilm system based on a sulfur-based nanoceramic carrier, including nanoceramic carrier modification, screening of functional bacterial genera, inoculation and biofilm formation of functional bacterial genera, biofilm acclimatization, and process parameter optimization steps.
[0020] (1) Preparation of sulfur-based nano-ceramic carrier materials: Sulfur-based nano-ceramic carrier modification refers to the addition of low-valence sulfur elements during the preparation of nano-ceramics to prepare sulfur-based nano-ceramic carrier materials, which are then used as biofilm carrier materials to achieve an efficient integrated biological decarbonization and sulfur autotrophic denitrification biofilm system.
[0021] The preparation of preferred sulfur-based nanoceramic carrier materials mainly includes the preparation of nanoceramic materials and surface modification with low-valence sulfur elements.
[0022] The preferred method for preparing nano-ceramics is as follows: According to the present invention, the preferred preparation method is precipitation, in which an aluminum chloride solution of a certain concentration is mixed evenly with a precipitant and a surfactant, and precipitated under a certain temperature condition to form nano-alumina particles with a smaller particle size, which are then calcined, crushed and pressed to form a nano-ceramic carrier material.
[0023] The carrier's performance indicators are as follows: 1. Physical structure and mechanical properties (1) Specific surface area: controlled at 150~300m2 / g. This range provides sufficient active sites for microbial attachment, which helps biofilm to form quickly and remain stable.
[0024] (2) Porosity: Controlled at 40%~60% Suitable pore structure promotes microbial colonization and nutrient diffusion, while maintaining good hydraulic conductivity.
[0025] (3) Wear resistance: Controlled at ≥95%. High wear resistance ensures that the carrier is not easily pulverized during long-term water flow and mutual collision, effectively extending its service life.
[0026] (4) Mechanical strength (compressive strength): controlled at ≥1MPa. Sufficient compressive strength ensures the structural stability of the carrier in the vertical suspension and multi-stage coupling system and resists the stress caused by water scouring and biofilm growth.
[0027] 2. Chemical composition and surface properties (1) Surface roughness (Ra): controlled at 0.5~2.0μm. The micro-rough surface provides attachment anchors for microorganisms, enhances the adhesion ability of the bacterial community, and prevents the biofilm from peeling off due to hydraulic shear.
[0028] (2) Sulfur loading: controlled at 5%~15% (by mass of S element). This loading provides a continuous substrate source for the sulfur autotrophic denitrification process and ensures the long-term denitrification capacity of the system.
[0029] (3) Sulfur release rate: Controlled at 0.5~2.0 mgS / (L·d). Stable sulfur supply helps maintain the metabolic stability of denitrifying bacteria and avoids system fluctuations or secondary pollution caused by excessively rapid release of sulfur.
[0030] According to the present invention, the preferred concentration of aluminum chloride solution is 0.2~0.4M, preferably 0.3M; the preferred precipitant is sodium hydroxide or sodium carbonate, preferably sodium carbonate, with a concentration of 0.5~1.0M, preferably 0.8M; the preferred surfactant is polyethylene glycol 600 or polyethylene glycol 1500, preferably polyethylene glycol 1500, with a concentration of 5~15g / L, preferably 10g / L; the preferred ratio of aluminum chloride: precipitant: surfactant is 20:1:2; the preferred precipitation temperature is 40~50℃, preferably 45℃.
[0031] According to the present invention, the preferred calcination temperature is 400~500℃, more preferably 450℃; the preferred pulverization method is ultrasonic pulverization; and the preferred pressing method is plate pressing into a film.
[0032] According to the present invention, the preferred surface modification of nano-ceramic materials involves loading low-valence sulfur elements onto the material surface by laser cladding, so that it can serve as a metabolic substrate for sulfur autotrophic denitrification functional bacteria.
[0033] According to the present invention, the preferred laser cladding material is sulfur in a low valence state, preferably iron sulfide, and its cladding ratio is 5~10% (iron sulfide: nano-ceramics), preferably 8%.
[0034] According to the present invention, the preferred laser spraying speed is 1~10mm / s, preferably 5mm / s; the input power is 1~2kW, preferably 1.5kW; the preferred spot diameter is 4~8mm, and the overlap rate is 20~60%.
[0035] (2) After the soil is retrieved, it is first diluted with water at a ratio of soil:water = 2 to 4:1. After dilution, it is further subjected to ultrasonic treatment to remove inorganic particles and attached microorganisms on plant roots and stems, thereby increasing the organic matter content of the pretreated soil. The preferred ultrasonic frequency is 300 to 600 W and the ultrasonic time is 30 to 60 min. After ultrasonic treatment, the soil suspension is filtered to remove larger inorganic particles and plant roots and stems.
[0036] The selection of preferred functional bacterial genera is carried out according to the following method: The filtered soil suspension was diluted to ensure that the initial mixed liquid suspended solids concentration was 10000 mg / L. Culture media with different substrates and trace amounts of exogenous co-metabolites were prepared to screen different functional bacterial genera. Sodium acetate or glucose was preferred as the sole carbon source for screening heterotrophic functional bacterial genera, ammonium chloride was preferred as the nitrogen source for screening autotrophic nitrifying bacteria, and potassium nitrate and reducing sulfur sources were preferred as nitrogen and sulfur sources for screening sulfur autotrophic denitrifying functional bacterial genera.
[0037] The preferred screening medium for heterotrophic bacteria has a sodium acetate or glucose concentration of 500-1000 mg / L; the screening medium for autotrophic nitrifying bacteria has an ammonia nitrogen concentration of 50-100 mg / L; the screening medium for sulfur-autotrophic denitrifying bacteria has a nitrate nitrogen concentration of 50-100 mg / L and a reducing sulfur source concentration of 100-300 mgS / L, with a preferred sulfur to nitrogen ratio of 2-3.
[0038] Preferred trace exogenous co-metabolites include low concentrations of nitrogen and phosphorus, trace elements, and macro elements. The low concentrations of nitrogen and phosphorus are ammonium chloride and potassium dihydrogen phosphate, with a preferred ammonia nitrogen concentration of 10-20 mg / L and a preferred phosphorus concentration of 2-4 mg / L; the trace and macro elements are shown in Table 1.
[0039] According to the present invention, the preferred culture conditions for heterotrophic bacteria and autotrophic nitrifying bacteria are a pH of 7.0–8.0, a temperature of 20.0–30.0°C, and a dissolved oxygen concentration of 2.0–3.0 mg / L; the culture conditions for sulfur-autotrophic denitrifying bacteria are a pH of 6.5–8.0, a temperature of 20.0–30.0°C, and a dissolved oxygen concentration of 0.2–0.5 mg / L.
[0040] According to the present invention, the pretreated soil is mixed evenly with the culture medium and then screened and enriched. Three rounds of beaker experiments are conducted, with the removal rates of COD, ammonia nitrogen, and nitrate nitrogen as the research objects. The changes in the removal rates are continuously observed. When the removal rate is greater than 50%, a certain proportion of the soil bacterial suspension is transferred to a new culture medium, and the first round of beaker experiments ends. When the removal rate is greater than 80%, a certain proportion of the bacterial suspension is transferred to a new culture medium again, and the second round of beaker experiments ends. The above operation is repeated for the third round of beaker experiments. When the OD600 absorbance value measured at a wavelength of 600 nm is greater than 0.1, the third round of beaker experiments ends. The preferred transfer ratio is 5-15%, preferably 10%.
[0041] According to the present invention, the inoculation steps for the preferred functional bacterial genera are as follows: The inoculation of functional bacteria includes the initial biofilm formation and colonization. Initial biofilm formation refers to the preferential spraying of heterotrophic functional bacteria onto the surface of the nano-ceramic substrate, forming a biofilm structure dominated by heterotrophic bacteria on the carrier surface to accelerate the subsequent growth of autotrophic bacteria. The selected and enriched heterotrophic bacterial suspension is mixed evenly with a certain concentration of organic matter. The preferred bacterial suspension concentration is 10⁵–10⁷ / mL, preferably 10⁶ / mL. The organic matter is sodium acetate or glucose, preferably glucose, with a preferred concentration of 1000 mg / L. During the initial biofilm formation stage, the ventilation windows are kept open to maintain good ventilation within the system. Spraying is stopped when the COD removal rate in the water collection and circulation device exceeds 80%, and the influent is replaced with fresh water. Simultaneously, the intermittent flow is changed to continuous flow until a thin, visible film is formed on the carrier surface, marking the end of the initial biofilm formation.
[0042] According to the present invention, the preferred colonization of functional bacteria refers to the colonization of sulfur autotrophic denitrifying bacteria and autotrophic nitrifying bacteria after the initial biofilm formation on the carrier. Sulfur autotrophic denitrifying bacteria colonization is prioritized. Potassium nitrate and a reducing sulfur source are preferably used as the influent substrate, which is then uniformly mixed with the sulfur autotrophic denitrifying bacteria. The preferred nitrate nitrogen concentration is 50 mg / L, the reducing sulfur source concentration is 150 mg / L, and the preferred concentration of the denitrifying functional bacteria is 10⁷–10⁹ / mL, preferably 10⁸ / mL. During the colonization stage of the sulfur autotrophic denitrifying bacteria, the ventilation windows are kept closed to maintain a closed system environment. When the nitrate nitrogen removal rate in the water collection and circulation device exceeds 50%, spraying is stopped, and the influent is replaced with a mixture of autotrophic nitrifying bacteria and ammonium chloride, while simultaneously colonizing the functional bacteria of the autotrophic nitrifying bacteria. The preferred concentration of nitrifying bacteria is 10⁷–10⁹ / mL, preferably 10⁸ / mL, and the preferred ammonia nitrogen concentration is 50 mg / L. During the colonization stage of autotrophic nitrifying bacteria, the ventilation windows are kept open to maintain a good ventilation environment inside the system. Once the ammonia nitrogen concentration in the water collection and circulation device is lower than 5.0 mg / L and the total nitrogen concentration is lower than 10.0 mg / L, the spraying is finished. The influent is then replaced with a heterotrophic functional bacteria mixture, and the above-mentioned preliminary biofilm formation operation is repeated.
[0043] According to the present invention, a certain proportion of trace and macro elements are added to the mixed solution during the biofilm formation stage as shown in Table 1, and the pH of the bacterial solution is maintained at 7.0-8.0 and the temperature at 20.0-30.0℃.
[0044] (3) Biofilm acclimatization: According to the present invention, after the biofilm is attached, a biofilm structure mainly composed of sulfur autotrophic denitrifying bacteria, autotrophic nitrifying bacteria and heterotrophic bacteria is formed on the surface of the carrier. The biofilm has an obvious dissolved oxygen gradient. The bottom layer of the biofilm is an anaerobic or hypoxic zone and the surface layer is an aerobic zone. The biofilm acclimatization work is carried out in this stage. The influent in the acclimatization stage is the actual treated wastewater. In the early stage of acclimatization, the system is set to intermittent flow. When the COD removal rate of the wastewater in the water collection and circulation device is greater than 80%, the ammonia nitrogen removal rate is greater than 90%, and the total nitrogen removal rate is greater than 70%, the intermittent flow is changed to continuous flow.
[0045] (4) According to the present invention, the preferred process parameter optimization mainly includes influent load optimization and hydraulic retention time optimization. To adapt to different application scenarios, influent load optimization mainly includes setting different C / N ratios, namely 2.5:1, 5:1, 10:1 and 20:1, with a hydraulic retention time of 12.0 h for all biofilm systems, focusing on COD and total nitrogen removal rates. Hydraulic retention time optimization mainly involves setting different hydraulic retention times according to different treatment standards, namely 2.0 h, 6.0 h, 12.0 h and 24.0 h, with COD and ammonia nitrogen removal rates as the research objects. When the COD removal rate is required to be greater than 80% and the total nitrogen removal rate is required to be greater than 70%, the adaptable C / N ratio range is 5:1 to 20:1. When the COD removal rate is required to be greater than 80% and the ammonia nitrogen removal rate is required to be greater than 50%, the hydraulic retention time is preferably 6.0 to 12.0 hours. When the COD removal rate is required to be greater than 80% and the ammonia nitrogen removal rate is not limited, the hydraulic retention time is preferably 2.0 hours.
[0046] The processing effect is as follows Figure 1 As shown, the biofilm system achieved stable treatment performance around day 10, with COD, ammonia nitrogen, and total nitrogen removal rates reaching 92.2%, 98.6%, and 86.2%, respectively. Using the method of this invention, rapid start-up and stable and efficient operation of a biofilm system based on a sulfur-based nanoceramic carrier can be achieved.
[0047] Example 2: This experiment was conducted using the same method as Example 1, but with the addition of a two-stage biofilm system during stable operation. This shortened the hydraulic retention time of each stage of the biofilm system, allowing for further investigation of its treatment capacity and optimization of the device configuration. The results showed that the removal rates of COD, ammonia nitrogen, and total nitrogen in the effluent from the two-stage sulfur-based nano-ceramic carrier biofilm system reached 90.2%, 96.4%, and 88.2%, respectively.
[0048] Example 3: This experiment was conducted according to Example 1, except that the hydraulic retention time of the biofilm system was shortened to 2.0 h. The results showed that under high hydraulic load conditions, the biofilm system could still maintain the stability of the biofilm structure and retain a high concentration of influent ammonia nitrogen, which is of great significance for the treatment of effluent for municipal greening water use. The COD removal rate was 90.% and the ammonia nitrogen removal rate was 10.2%, which met the experimental expectations.
[0049] Comparative example: As shown in Experiment 1, the difference is: The biofilm attachment method was changed to in-situ aeration start-up, that is, the biofilm carrier was immersed in a mixed solution containing different functional bacteria genera for aeration. In the continuous flow stage, the water inlet method was changed from spraying to peristaltic pumping into the biofilm system, and aeration was set to provide an appropriate dissolved oxygen concentration (3-4 mg / L).
[0050] Experimental results: Using this method for biofilm initiation, a clear biofilm structure can be observed on the carrier surface in about 20 days. However, the biofilm thickness is less than that in Experiment 1 during the same period, and the biofilm initiated by this method does not have a clear hypoxic zone, resulting in poor colonization of denitrifying bacteria. Figure 2 As shown, the biofilm system started by this method has a relatively long start-up period. The COD and ammonia nitrogen removal rates are comparable to those of Experimental Example 1 (90.4% and 97.6%, respectively), but the total nitrogen removal rate of the comparative example (52%) is much lower than that of the experimental example (86.2%).
[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for initiating biofilm formation in a biofilm system based on a sulfur-based nanoceramic carrier, characterized in that: The method includes the following steps: S1. Modification of nano-ceramic carrier: Nano-ceramics are prepared by precipitation method. Aluminum chloride solution is mixed with precipitant and surfactant in a ratio of 20:1:2 and precipitated at 40~50℃ to form nano-alumina particles. After calcination at 400~500℃, ultrasonic pulverization and plate pressing, nano-ceramic carrier is obtained. Then, low-valence sulfur elements are loaded onto the surface of the carrier by laser cladding to serve as a metabolic substrate for sulfur-autotrophic denitrifying bacteria, thus obtaining a sulfur-based nano-ceramic carrier. S2. Screening of functional bacteria: Take fine yellowish-brown / dark brown forest soil from the top 0-20cm layer with a VSS / TSS ratio of 0.3-0.4, dilute it with water at a ratio of 2-4:1, and sonicate it at 300-600W for 30-60 minutes. After filtration, dilute it to a suspended solids concentration of 10000 mg / L. Use a medium containing sodium acetate / glucose to screen for heterotrophic bacteria, a medium containing ammonium chloride to screen for autotrophic nitrifying bacteria, and a medium containing potassium nitrate and a reducing sulfur source to screen for sulfur autotrophic denitrifying bacteria. All mediums are supplemented with low concentrations of nitrogen, phosphorus, and trace / macro elements. Soil and culture medium were mixed and enriched in three beakers under corresponding conditions. The bacterial suspension was transferred at a ratio of 5-15% until the removal rate and OD600 met the standards to obtain functional bacteria. S3, Functional bacterial genus inoculation and film attachment: First, inoculate 10 5 ~10 7 Mix 1000 mg / L of heterotrophic bacterial suspension with 1 mL of glucose, spray the carrier and open the ventilation window. After the COD removal rate is >80%, switch to continuous flow until a visible film forms on the carrier. Then 10 7 ~10 9 / mL of sulfur-autotrophic denitrifying bacteria is mixed with influent containing 50mg / L nitrate nitrogen and 150mgS / L reducing sulfur source, and sprayed in a closed system until the nitrate nitrogen removal rate is >50%; then 10 7 ~10 9 Mix 50 mg / L of autotrophic nitrifying bacteria with 50 mg / L of ammonia nitrogen in the influent, open the ventilation window until ammonia nitrogen < 5.0 mg / L and total nitrogen < 10.0 mg / L, and finally repeat the initial biofilm formation of heterotrophic bacteria. During the biofilm formation stage, maintain a pH of 7.0–8.0 and a temperature of 20.0–30.0℃. S4. Biofilm acclimatization: Using actual wastewater as influent, the flow is interrupted initially, and then switched to continuous flow when COD removal rate > 80%, ammonia nitrogen removal rate > 90%, and total nitrogen removal rate > 70%. S5. Process parameter optimization: Set C / N ratios of 2.5:1, 5:1, 10:1, and 20:1 (HRT 12.0h) to optimize influent load, and set HRTs of 2.0h, 6.0h, 12.0h, and 24.0h to optimize treatment efficiency; When COD removal rate is >80% and total nitrogen removal rate is >70%, the C / N ratio should be controlled at 5:1 to 20:1; when COD removal rate is >80% and ammonia nitrogen removal rate is >50%, the HRT should be controlled at 6.0 to 12.0 h; when only COD removal rate is >80%, the HRT should be controlled at 2.0 h. The biofilm system is a multi-stage coupled structure, with each stage containing a water collection and circulation device, a water distribution and spraying device, and a sedimentation device. The sulfur-based nano-ceramic carrier is folded and suspended vertically.
2. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: In S1, the aluminum chloride solution concentration is 0.2~0.4M, the precipitant is sodium hydroxide / sodium carbonate with a concentration of 0.5~1.0M, the surfactant is polyethylene glycol 600 / 1500 with a concentration of 5~15g / L, the precipitation temperature is preferably 45℃, and the calcination temperature is preferably 450℃.
3. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: The laser cladding material in S1 is iron sulfide, and the ratio of iron sulfide to nano-ceramic spraying is 5-10%. Laser spraying speed 1~10mm / s, input power 1~2kW, spot diameter 4~8mm, overlap rate 20~60%.
4. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: In the S2 culture medium for screening heterotrophic bacteria, the sodium acetate / glucose concentration is 500-1000 mg / L; the ammonia nitrogen concentration in the culture medium for autotrophic nitrifying bacteria is 50-100 mg / L; and the nitrate nitrogen concentration, reducing sulfur source concentration, and sulfur-nitrogen ratio are 2-3 in the culture medium for sulfur autotrophic denitrifying bacteria. Low concentrations of nitrogen and phosphorus are ammonium chloride (ammonia nitrogen 10-20 mg / L) and potassium dihydrogen phosphate (phosphorus 2-4 mg / L).
5. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: The culture conditions for heterotrophic and autotrophic nitrifying bacteria in S2 are: DO 2.0–3.0 mg / L, pH 7.0–8.0, and temperature 20.0–30.0℃. The culture conditions for sulfur-autotrophic denitrifying bacteria were: DO 0.2–0.5 mg / L, pH 6.5–8.0, and temperature 20.0–30.0℃. The optimal enrichment and transfer ratio for the three rounds is 10%. The first round has a removal rate of >50% and transfer occurs, the second round has a removal rate of >80% and transfer occurs, and the third round ends when OD600 >0.
1.
6. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: The sulfur-based nano-ceramic carrier, when folded in half, has a single unit width of 1.0–1.5 m and a length of 1.8–2.2 m; Each system has 50 to 100 carriers, with a left-right spacing of 3.0 to 7.0 cm and a top-bottom stacking spacing of 3.0 to 7.0 cm between each carrier.
7. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: The water spraying device is set 30-70cm above the carrier, with 1-3 devices per square meter; The water collection and circulation device is connected to the water distribution and spraying device to control the HRT, and the sedimentation device is located at the end of the system to collect aged biofilm.
8. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: The preferred concentration of the heterotrophic bacterial suspension for initial biofilm formation in S3 is 10. 6 / mL, with glucose being the preferred organic matter; The optimal concentration of sulfur-autotrophic denitrifying bacteria suspension is 10. 8 / mL, the preferred concentration of autotrophic nitrifying bacteria suspension is 10. 8 / mL.
9. The biofilm initiation method for a biofilm system based on a sulfur-based nanoceramic carrier according to claim 1, characterized in that: In the S4 acclimatization stage, the biofilm forms a dissolved oxygen gradient, with the bottom layer being an anaerobic / hypoxic zone and the surface layer being an aerobic zone, dominated by sulfur autotrophic denitrifying bacteria, autotrophic nitrifying bacteria, and heterotrophic bacteria.