Composite filler for sulfur autotrophic denitrification biofilter and its preparation and application
By immobilizing ferrous sulfide and elemental sulfur nanoparticles within triethylamine polystyrene microspheres, the problems of slow NR-SOB proliferation and low nitrogen and phosphorus removal efficiency in traditional packing materials in sulfur autotrophic denitrification biological filters have been solved, achieving rapid start-up and efficient simultaneous nitrogen and phosphorus removal.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YANGZHOU UNIV
- Filing Date
- 2024-04-08
- Publication Date
- 2026-06-19
AI Technical Summary
Traditional biological filter media suffer from problems such as slow NR-SOB proliferation, long biofilm formation time, difficulty in start-up, low nitrogen and phosphorus removal efficiency, and poor operational stability during sulfur autotrophic denitrification. Furthermore, existing media cannot achieve simultaneous removal of nitrogen and phosphorus.
A process route of Fe3+ precursor introduction-in-situ precipitation decomposition was adopted to immobilize ferrous sulfide (nFeS) and elemental sulfur (SO) nanoparticles in triethylamine polystyrene microspheres. The composite filler nFeS/S0@TPM was prepared through electrostatic attraction and ion exchange to provide a stable low-valence reduced sulfur environment, promote the immobilization and attachment of NR-SOB, and achieve deep adsorption of phosphorus using Fe(OH)3.
It accelerated the start-up speed of the biological filter, improved the nitrogen and phosphorus removal performance, enhanced the mechanical strength and operational stability of the packing material, and achieved simultaneous removal of nitrogen and phosphorus, meeting the surface water environmental quality standards.
Smart Images
Figure CN118108346B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a composite packing material for a sulfur autotrophic denitrification biological filter, and also to a method for preparing the above-mentioned composite packing material and its application. Background Technology
[0002] The efficient removal of nitrogen and phosphorus from wastewater is an urgent need to alleviate eutrophication and meet increasingly stringent wastewater discharge standards. Biological methods are the mainstream wastewater treatment process. Traditional biological nitrogen removal technologies require two stages: aerobic nitrification and anoxic denitrification. The aerobic nitrification stage converts organic nitrogen and ammonia nitrogen in wastewater into nitrate nitrogen (NO3). - Biological phosphorus removal (BPR) reduces most of the biodegradable organic matter in wastewater, resulting in a lack of carbon source for heterotrophic denitrifying bacteria during the denitrification stage, thus significantly reducing nitrogen removal performance. Adding carbon source during denitrification would substantially increase wastewater treatment operating costs and pose a risk of COD exceeding standards. On the other hand, biological phosphorus removal technology generally works well for high-concentration phosphorus wastewater but cannot achieve deep phosphorus removal, especially for low-concentration phosphorus wastewater. Furthermore, biological phosphorus removal generates large amounts of residual sludge, which can easily cause secondary pollution and increase sludge treatment costs.
[0003] Sulfur autotrophic denitrification is a process in which denitrifying bacteria (NR-SOB) utilize inorganic carbon (such as CO3) under anoxic or anaerobic conditions to desulfurize sulfur. 2- HCO3 - Using sulfur and its compounds in a low-valence reduced state (such as S) as a carbon source 0 S 2- S2O3 2- Nitrate nitrogen (NO3) acts as an electron donor. - -N) and nitrite nitrogen (NO2) - The process of denitrification using sulfur (-N) as an electron acceptor. The price of sulfur and its compounds is far lower than that of conventional autotrophic denitrification carbon sources (such as methanol and sodium acetate), making them suitable as electron donors for denitrification, which can significantly reduce the system's operating costs. Simultaneously, sulfur autotrophic denitrification processes also offer advantages such as high nitrogen removal efficiency and low sludge production, making them particularly suitable for treating NO3- in wastewater. - Removal of -N.
[0004] Among numerous biological wastewater treatment processes, biofilters have attracted widespread attention due to their advantages such as simple operation, low operating costs, and stable effluent quality. The key to the normal operation of a sulfur-autotrophic denitrification biofilter is the formation of a biofilm rich in denitrifying sulfur-reducing bacteria (NR-SOB) on the filter media surface. In practical applications, NR-SOB suffers from slow proliferation, long biofilm formation time on the filter media, and difficulty in starting the filter. Traditional biofilter media (such as ceramsite, polyurethane sponge, and polypropylene hollow spheres) only serve as biological carriers, requiring the addition of low-valence reduced sulfur to provide electrons for NR-SOB, increasing system operating costs and management difficulty, and failing to achieve simultaneous removal of nitrogen and phosphorus from wastewater. Elemental sulfur (S) 0 While pyrite and other materials can provide stable low-valent reduced sulfur for NR-SOB, their direct use as fillers in sulfur autotrophic denitrification filters results in a small specific surface area, smooth surface, and strong hydrophobicity, which are not conducive to the adhesion and proliferation of NR-SOB, leading to long start-up times and unstable operation of the filter.
[0005] In summary, sulfur autotrophic denitrification biological filters using traditional packing materials have drawbacks such as slow NR-SOB proliferation, long biofilm formation time, difficult start-up, low nitrogen and phosphorus removal efficiency, and poor operational stability. Summary of the Invention
[0006] Purpose of the invention: The purpose of this invention is to provide a biological filter packing material that can provide stable low-valent reduced sulfur for NR-SOB, promote NR-SOB immobilization and biofilm formation, and simultaneously achieve deep removal of nitrogen and phosphorus from wastewater; another purpose of this invention is to provide a method for preparing the above-mentioned packing material and its application.
[0007] Technical solution: The preparation method of the composite filler of the present invention includes the following steps:
[0008] (1) Triethylamine-modified polystyrene microspheres (triethylamine-modified polystyrene microspheres TPM) were thoroughly rinsed with a 5-10% NaOH solution, followed by rinsing with a 5-10% NaCl solution and deionized water until the effluent was neutral. The microspheres were then dried for later use. NaOH washing removed organic matter remaining in the pores after the preparation of the triethylamine-modified polystyrene microspheres. NaCl solution was used to convert exchangeable ions on the surface of the microspheres from OH-. - to Cl - ;
[0009] (2) Dissolve FeCl3 in a mixture containing HCl and NaCl to obtain a mixed solution; slowly add the triethylamine polystyrene microspheres cleaned and dried in step (1) to the mixed solution, and stir continuously at 15-25℃ for 12 hours to obtain a pre-loaded FeCl3 solution. 3+Triethylamine polystyrene microspheres; FeCl3 in a mixed solution of HCl and NaCl reacts to form [FeCl4]. - Complexed anions can enter the channels of triethylamine polystyrene microspheres through electrostatic attraction and ion exchange, thus preloading the microspheres with Fe. 3+ ;
[0010] (3) Preloaded with Fe 3+ The triethylamine polystyrene microspheres were filtered out and added to a mixture containing NaOH and Na₂S, and the reaction was carried out with continuous stirring at 15–25 °C for 12 h; in a strong alkaline solution, Fe 3+ With S 2- The reaction produces Fe₂S₃, not ferric hydroxide precipitate; the reaction equation is: 2Fe 3+ +3S 2- →Fe2S3;
[0011] (4) Filter out the reaction product obtained in step (3), wash it with a NaCl solution with a mass concentration of 5-10% until the effluent is neutral, add the washed solid product to deionized water with a pH of 7-8 and a temperature of 25-35℃, and stir continuously for 12 hours; in a neutral aqueous solution above 20℃, Fe2S3 will decompose into ferrous sulfide and sulfur, and the reaction equation is: Fe2S3→2FeS+S;
[0012] (5) Filter out the reaction product obtained in step (4), place it in a vacuum drying oven and dry it at 40-60℃ for 24 hours to obtain the composite filler nFeS / S 0 @TPM.
[0013] In step (1), the triethylamine polystyrene microspheres have a particle size of 0.6–1.2 mm, a wet density of 1.04–1.08 g / mL, a triethylamine group content of 1.8–2.2 mmol / g, a pore size distribution of 1–80 nm, and a pore volume of 0.05–0.1 cm³. 3 / g.
[0014] In step (2), the mixed solution contains 5-10% HCl, 5-10% NaCl, and 10-20% FeCl3 by mass. FeCl3 in this concentration range of HCl and NaCl can generate [FeCl4]. - Complexing anions; at the same time, the concentration of FeCl3 can ensure the Fe supported on the triethylamine polystyrene microspheres. 3+ While ensuring sufficient quantity, it avoids overloading the microspheres and clogging their pores, thus affecting the mass transfer process.
[0015] In step (2), the amount of triethylamine polystyrene microspheres added is 100-200 g / L of mixed solution.
[0016] In step (3), the mass concentration of NaOH in the mixture is 5-10%, and the mass concentration of Na2S is 10-20%; Fe is pre-loaded. 3+ The dosage of triethylamine polystyrene microspheres is 100-200 g / L of the mixture.
[0017] The composite filler prepared by the above method uses triethylamine polystyrene microspheres as a carrier, and ferrous sulfide (nFeS) nanoparticles and elemental sulfur (S) are immobilized within the cross-linked network of the triethylamine polystyrene microspheres. 0 Nanoparticles.
[0018] The composite filler has a particle size of 0.6–1.2 mm and a specific surface area of 25–50 m². 2 / g; In the composite filler, the content of nFeS is 10-15% (mass concentration, calculated as Fe), S 0 The content is 3-5% (mass concentration).
[0019] The above-mentioned composite packing material is used in a sulfur autotrophic denitrification wastewater treatment system. In this system, the wastewater treatment reactor used is an upflow biological filter.
[0020] The composite packing material accounts for 40-60% of the effective height of the reactor; the support layer is made of gravel or pebbles with a diameter of 20-40 mm, accounting for 15-20% of the effective height of the reactor; the influent flow rate is controlled to allow the empty bed contact time (EBCT) to be 30-120 min, the water temperature is controlled to be 30±3℃, and the pH is controlled to be 7.5±0.5.
[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:
[0022] (1) The method of the present invention uses Fe 3+ A precursor introduction-in-situ precipitation decomposition process was used to prepare triethylamine polystyrene microspheres (TPM) with ferrous sulfide (nFeS) and elemental sulfur (S) immobilized within the cross-linked network of the microspheres. 0 Composite materials of nanoparticles.
[0023] (2) The triethylamine groups modified on the polystyrene microspheres of the composite packing material of the present invention can enhance the hydrophilicity of the carrier material and generate electrostatic attraction with negatively charged microorganisms, so that denitrifying bacteria (NR-SOB) can attach to the surface of the composite packing material more stably and quickly, which is conducive to the proliferation of slow-growing NR-SOB and accelerates the start-up speed of the biological filter.
[0024] (3) The composite filler of the present invention contains ferrous sulfide (nFeS) and elemental sulfur (S). 0 Nanoparticles provide a suitable growing environment and stable low-valent reduced sulfur for NR-SOB growth, while the triethylamine groups on the carrier surface can selectively remove NO3- from the water. - -N accumulates on the surface of the composite filler through electrostatic interactions, which is beneficial for improving the NO3- retrieval efficiency of NR-SOB. - -N degradation efficiency.
[0025] (4) The Fe(OH)3 generated after the reaction of the supported ferrous sulfide (nFeS) nanoparticles can achieve deep adsorption and removal of phosphorus in wastewater through hydroxyl ligand exchange and coordination complexation, thereby effectively improving the simultaneous nitrogen and phosphorus removal performance of the sulfur autotrophic denitrification biological filter; thus, in the carrier and nFeS / S 0 Under the synergistic effect of these components, the composite packing material can effectively improve the start-up speed and nitrogen and phosphorus removal performance of the sulfur autotrophic denitrification biological filter.
[0026] (5) The composite filler of the present invention combines ferrous sulfide (nFeS) and elemental sulfur (S) 0 The nanoparticles are immobilized within the cross-linked nanopores of the TPM carrier, thus preventing nFeS and S from being released. 0 The problem of easy loss when nanoparticles are directly applied to water treatment systems can be addressed by improving the operational stability of sulfur autotrophic denitrification biological filters.
[0027] (6) The composite filler of the present invention has high mechanical strength and strong stability, and the breakage rate of the composite filler after long-term use is <3%. Attached Figure Description
[0028] Figure 1 The composite filler nFeS / S prepared in Example 2 of this invention 0 @TPM's exterior image;
[0029] Figure 2 The composite filler nFeS / S prepared in Example 2 of this invention 0 @TPM cross-sectional SEM-EDS plot;
[0030] Figure 3 The composite filler nFeS / S prepared in Example 2 of this invention 0 @TPM's TEM diagram;
[0031] Figure 4 This is a schematic diagram of an upflow biological filter (reactor). Detailed Implementation
[0032] Example 1
[0033] The method for preparing the composite filler of the present invention includes the following steps:
[0034] (1) The polystyrene microspheres (TPM) with a triethylamine content of 1.8 mmol / g were thoroughly rinsed with 5 wt% NaOH solution to remove residual substances in the microsphere channels. Then, they were rinsed with 5% NaCl solution and deionized water in sequence until the effluent was neutral. The microspheres were then dried and set aside for use.
[0035] (2) FeCl3 was fully dissolved in a mixture containing 5 wt% HCl and 5 wt% NaCl to obtain a mixed solution; the mass concentration of FeCl3 in the mixed solution was controlled to be 10%; the triethylamine polystyrene microspheres cleaned and dried in step (1) were slowly added to the above mixed solution, and the amount of triethylamine polystyrene microspheres added was controlled to be 100 g / L solution, and the reaction was continuously stirred at 15℃ for 12 h; a pre-loaded FeCl3 solution was obtained. 3+ Triethylamine polystyrene microspheres;
[0036] (3) The above preloaded with Fe 3+ The triethylamine polystyrene microspheres were filtered out and slowly added to a mixture containing 5 wt% NaOH and 10 wt% Na2S. The mixture was stirred continuously at 15 °C for 12 h. The microspheres were pre-loaded with Fe. 3+ The dosage of triethylamine polystyrene microspheres was 100 g / L solution;
[0037] (4) Filter out the reaction product obtained in step (3), rinse it with a 5% NaCl solution until the effluent is neutral, and then add the washed solid product to deionized water with pH 7-8 and temperature 25°C and stir continuously for 12 hours.
[0038] (5) The reaction product obtained in step (4) is filtered out and dried in a vacuum drying oven at 40°C for 24 hours to prepare the composite filler nFeS / S 0 @TPM, in which the content of nFeS is 10% (mass concentration, calculated as Fe), S 0 The content is 3% (mass concentration).
[0039] The composite filler nFeS / S prepared in Example 1 0 @TPM is used to fill filter columns with a diameter of 150mm and an effective height of 1000mm. The composite packing material is nFeS / S. 0 The TPM fill height is 600mm; the support layer uses gravel with a diameter of 20mm and a fill height of 150mm.
[0040] The inoculum sludge for the biological filter was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant, with a suspended solids (MLSS) concentration of 7000 mg / L. The filter operates in an upflow configuration, with an influent total nitrogen (TN) concentration of 15 mg / L and nitrate nitrogen (NO3) concentration of... - The concentrations of nitrogen (N) were 14 mg / L, total phosphorus (TP) 1 mg / L, and chemical oxygen demand (COD) <50 mg / L. The influent flow rate was controlled, the empty bed contact time (EBCT) was 30 min, the water temperature was controlled at 30 ± 3℃, and the pH was controlled at 7.5 ± 0.5.
[0041] After 7 days of acclimatization and biofilm formation, the total nitrogen (TN) concentration in the effluent was <1.5 mg / L and the total phosphorus (TP) concentration was <0.2 mg / L, which is better than the Class IV water quality standard in the "Surface Water Environmental Quality Standard" (GB3838-2002). The damage rate of the composite packing material nFeS / S0@TPM after 60 days of continuous operation was <3%.
[0042] Example 2
[0043] The method for preparing the composite filler of the present invention includes the following steps:
[0044] (1) The polystyrene microspheres (TPM) with a triethylamine content of 2 mmol / g were thoroughly rinsed with 7.5 wt% NaOH solution to remove residual substances in the microsphere channels, and then rinsed with 7.5% NaCl solution and deionized water in sequence until the effluent was neutral. The microspheres were then dried for later use.
[0045] (2) FeCl3 was fully dissolved in a mixture containing 7.5 wt% HCl and 7.5 wt% NaCl to obtain a mixed solution; the mass concentration of FeCl3 in the mixed solution was controlled to be 15%; the triethylamine polystyrene microspheres cleaned and dried in step (1) were slowly added to the above mixed solution, and the amount of triethylamine polystyrene microspheres added was controlled to be 150 g / L solution, and the reaction was continuously stirred at 20℃ for 12 h; a pre-loaded FeCl3 solution was obtained. 3+ Triethylamine polystyrene microspheres;
[0046] (3) The above preloaded with Fe 3+ The triethylamine polystyrene microspheres were filtered out and slowly added to a mixture containing 7.5 wt% NaOH and 15 wt% Na₂S, and the mixture was stirred continuously at 20 °C for 12 h; Fe was pre-loaded... 3+ The dosage of triethylamine polystyrene microspheres was 150 g / L solution;
[0047] (4) Filter out the reaction product obtained in step (3), rinse it with a NaCl solution with a mass concentration of 7.5% until the effluent is neutral, and then add the washed solid product to deionized water with a pH of 7-8 and a temperature of 30°C and stir continuously for 12 hours.
[0048] (5) The reaction product obtained in step (4) is filtered out and dried in a vacuum drying oven at 50°C for 24 hours to prepare the composite filler nFeS / S 0 @TPM, in which the content of nFeS is 12.5% (mass concentration, based on Fe), S 0 The content is 4% (mass concentration).
[0049] pass Figure 2 It can be seen that the composite filler nFeS / S 0 The TPM profile shows a uniform distribution of Fe and S elements, indicating that FeS and S are present in the TPM profile. 0 It has been successfully loaded into the TPM carrier channels. Figure 3 It can be seen that FeS and S 0 It is fixed in the TPM carrier pores in the form of nanoparticles or nanoclusters with a particle size of 20-40 nm.
[0050] The composite filler nFeS / S prepared in Example 2 0 @TPM is used to fill filter columns with a diameter of 150mm and an effective height of 1000mm. The composite packing material is nFeS / S. 0 The TPM fill height is 500mm. The support layer uses 30mm diameter gravel with a fill height of 180mm.
[0051] The inoculum sludge for the biological filter was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant, with a suspended solids (MLSS) concentration of 8000 mg / L. The filter operates in an upflow configuration, with an influent total nitrogen (TN) concentration of 23 mg / L and nitrate nitrogen (NO3) concentration of... - The concentrations of nitrogen (N) were 21 mg / L, total phosphorus (TP) 1.5 mg / L, and chemical oxygen demand (COD) <50 mg / L. The influent flow rate was controlled, the empty bed contact time (EBCT) was 60 min, the water temperature was controlled at 30 ± 3℃, and the pH was controlled at 7.5 ± 0.5.
[0052] After 6 days of acclimatization and biofilm formation, the total nitrogen (TN) concentration in the effluent was <1.5 mg / L and the total phosphorus (TP) concentration was <0.2 mg / L, which is better than the Class IV water quality standard in the "Surface Water Environmental Quality Standard" (GB3838-2002). The composite packing material nFeS / S was continuously operated for 60 days. 0 @TPM's breakage rate is <3%.
[0053] Example 3
[0054] The method for preparing the composite filler of the present invention includes the following steps:
[0055] (1) The polystyrene microspheres (TPM) with a triethylamine content of 2.2 mmol / g were thoroughly rinsed with 10 wt% NaOH solution to remove residual substances in the microsphere channels. Then, they were rinsed with 10% NaCl solution and deionized water until the effluent was neutral. The microspheres were then dried and set aside for use.
[0056] (2) FeCl3 was fully dissolved in a mixture containing 10 wt% HCl and 10 wt% NaCl to obtain a mixed solution; the mass concentration of FeCl3 in the mixed solution was controlled to be 20%; the triethylamine polystyrene microspheres cleaned and dried in step (1) were slowly added to the above mixed solution, and the amount of triethylamine polystyrene microspheres added was controlled to be 200 g / L solution, and the reaction was continuously stirred at 25°C for 12 h; a pre-loaded FeCl3 solution was obtained. 3+ Triethylamine polystyrene microspheres;
[0057] (3) The above preloaded with Fe 3+ The triethylamine polystyrene microspheres were filtered out and slowly added to a mixture containing 10 wt% NaOH and 20 wt% Na₂S. The mixture was stirred continuously at 25 °C for 12 h. The mixture was pre-loaded with Fe. 3+ The dosage of triethylamine polystyrene microspheres was 200 g / L solution;
[0058] (4) Filter out the reaction product obtained in step (3), rinse it with a 10% NaCl solution until the effluent is neutral, and then add the washed solid product to deionized water with pH 7-8 and temperature 35℃ and stir continuously for 12 hours.
[0059] (5) The reaction product obtained in step (4) is filtered out and dried in a vacuum drying oven at 60°C for 24 hours to prepare the composite filler nFeS / S 0 @TPM, in which the content of nFeS is 15% (mass concentration, calculated as Fe), S 0 The content is 5% (mass concentration).
[0060] The composite filler nFeS / S prepared in Example 3 was used... 0 @TPM is used to fill filter columns with a diameter of 150mm and an effective height of 1000mm. The composite packing material is nFeS / S. 0 The TPM fill height is 400mm. The support layer uses 40mm diameter pebbles with a fill height of 200mm.
[0061] The inoculum sludge for the biological filter was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant, with a suspended solids (MLSS) concentration of 9000 mg / L. The filter operates in an upflow configuration, with an influent total nitrogen (TN) concentration of 30 mg / L and nitrate nitrogen (NO3) concentration of... - The concentrations of nitrogen (N) were 27 mg / L, total phosphorus (TP) 2 mg / L, and chemical oxygen demand (COD) <50 mg / L. The influent flow rate was controlled, the empty bed contact time (EBCT) was 120 min, the water temperature was controlled at 30 ± 3℃, and the pH was controlled at 7.5 ± 0.5.
[0062] After 5 days of acclimatization and biofilm formation, the total nitrogen (TN) concentration in the effluent was <1.5 mg / L and the total phosphorus (TP) concentration was <0.2 mg / L, which is better than the Class IV water quality standard in the "Surface Water Environmental Quality Standard" (GB3838-2002). The composite packing material nFeS / S was continuously operated for 60 days. 0 @TPM's breakage rate is <3%.
[0063] Comparative Example 1
[0064] The preparation method of the composite filler in Comparative Example 1 and Example 2 is basically the same, except that Na2S was not added in step (3), and the composite filler HFO@TPM was prepared.
[0065] The composite packing material HFO@TPM prepared in Comparative Example 1 was filled into a filter column with a diameter of 150 mm and an effective height of 1000 mm. The filling height of the composite packing material HFO@TPM was 500 mm. The support layer consisted of gravel with a diameter of 30 mm and a filling height of 180 mm.
[0066] The inoculum sludge for the biological filter was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant, with a suspended solids (MLSS) concentration of 8000 mg / L. The filter operates in an upflow configuration, with an influent total nitrogen (TN) concentration of 23 mg / L and nitrate nitrogen (NO3) concentration of... - The concentrations of nitrogen (N) were 21 mg / L, total phosphorus (TP) 1.5 mg / L, and chemical oxygen demand (COD) <50 mg / L. The influent flow rate was controlled, the empty bed contact time (EBCT) was 60 min, the water temperature was controlled at 30 ± 3℃, and the pH was controlled at 7.5 ± 0.5.
[0067] After 10 days of acclimatization and biofilm formation, the total nitrogen (TN) concentration in the effluent was greater than 10 mg / L, and the total phosphorus (TP) concentration was less than 0.2 mg / L.
[0068] Because Na2S was not added in step (3), nFeS and S could not be generated in the prepared composite filler. 0Instead of nanoparticles, hydrated iron oxide (HFO) particles were formed. During the acclimation and biofilm formation process, the lack of low-valence reduced sulfur to provide electrons prevented the cultivation of a biofilm containing denitrifying bacteria (NR-SOB), and only traditional heterotrophic denitrifying bacteria could be used for nitrogen removal. The influent lacked the carbon source (COD < 50 mg / L) required for the metabolism of heterotrophic denitrifying bacteria, resulting in a significant decrease in nitrogen removal performance.
[0069] Comparative Example 2
[0070] The preparation method of the composite filler in Comparative Example 2 is basically the same as that in Example 2, except that NaOH was not added in step (3), and the composite filler S was prepared. 0 @TPM.
[0071] The composite filler S prepared in Comparative Example 2 0 @TPM is used to fill filter columns with a diameter of 150mm and an effective height of 1000mm. Composite packing S 0 The TPM fill height is 500mm. The support layer uses 30mm diameter gravel with a fill height of 180mm.
[0072] The inoculum sludge for the biological filter was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant, with a suspended solids (MLSS) concentration of 8000 mg / L. The filter operates in an upflow configuration, with an influent total nitrogen (TN) concentration of 23 mg / L and nitrate nitrogen (NO3) concentration of... - The concentrations of nitrogen (N) were 21 mg / L, total phosphorus (TP) 1.5 mg / L, and chemical oxygen demand (COD) <50 mg / L. The influent flow rate was controlled, the empty bed contact time (EBCT) was 60 min, the water temperature was controlled at 30 ± 3℃, and the pH was controlled at 7.5 ± 0.5.
[0073] After 15 days of acclimatization and biofilm formation, the total nitrogen (TN) concentration in the effluent was 2-4 mg / L, and the total phosphorus (TP) concentration was >1 mg / L.
[0074] Because NaOH was not added in step (3), nFeS nanoparticles could not be generated in the prepared composite filler, and elemental sulfur (S) was generated only through redox reactions. 0 The reaction equation for the nanoparticles is:
[0075] 2Fe 3+ +S 2- →2Fe 2+ +S
[0076] During the biofilm formation process, although a biofilm containing a certain amount of denitrifying bacteria (NR-SOB) can be cultivated, the low solubility of sulfur in water limits mass transfer capacity, thus affecting the reaction rate. This results in low efficiency of NR-SOB bacterial proliferation and deep denitrification, leading to an increased biofilm formation start-up time and decreased denitrification efficiency in the biofilter. Simultaneously, because the composite packing material lacks nFeS particles, Fe(OH)3 cannot be generated during the denitrification reaction, resulting in a significant decrease in the biofilter's TP removal performance.
[0077] Comparative Example 3
[0078] Comparative Example 3 replaced the composite packing material prepared in Example 2 in the biofilter with a packing material loaded with elemental sulfur (S) with a diameter of 3-6 mm. 0 ) ceramsite filler.
[0079] Loaded with elemental sulfur (S) 0 The ceramsite packing material is filled into a filter column with a diameter of 150 mm and an effective height of 1000 mm, with a filling height of 500 mm. The support layer consists of gravel with a diameter of 30 mm and a filling height of 180 mm.
[0080] The inoculum sludge for the biological filter was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant, with a suspended solids (MLSS) concentration of 8000 mg / L. The filter operates in an upflow configuration, with an influent total nitrogen (TN) concentration of 23 mg / L and nitrate nitrogen (NO3) concentration of... - The concentrations of nitrogen (N) were 21 mg / L, total phosphorus (TP) 1.5 mg / L, and chemical oxygen demand (COD) <50 mg / L. The influent flow rate was controlled, the empty bed contact time (EBCT) was 60 min, the water temperature was controlled at 30 ± 3℃, and the pH was controlled at 7.5 ± 0.5.
[0081] After 30 days of acclimatization and biofilm formation, the total nitrogen (TN) concentration in the effluent was 4–6 mg / L, and the total phosphorus (TP) concentration was >1 mg / L.
[0082] Due to the presence of elemental sulfur (S) 0 The surface of the ceramsite packing material lacks amine groups, making it unable to generate electrostatic attraction with negatively charged microorganisms. Consequently, denitrifying and desulfurizing bacteria (NR-SOB) cannot stably attach to the packing surface, hindering the proliferation of the slow-growing NR-SOB and significantly increasing the biofilm formation start-up time of the biological filter. Furthermore, the lack of triethylamine groups on the ceramsite surface prevents it from selectively removing NO3- from the water. - -N accumulates on the filler surface through electrostatic interactions, making NR-SOB more resistant to NO3-. - The degradation efficiency of -N decreases, thereby reducing the denitrification performance of the biofilter.
[0083] Comparative Example 4
[0084] In Comparative Example 4, the composite packing material prepared in Example 2 was replaced with pyrite packing material with a diameter of 3-6 mm in the biofilter.
[0085] Pyrite filler was used to fill filter columns with a diameter of 150 mm and an effective height of 1000 mm, with a filling height of 500 mm. The support layer consisted of gravel with a diameter of 30 mm and a filling height of 180 mm.
[0086] The inoculum sludge for the biological filter was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant, with a suspended solids (MLSS) concentration of 8000 mg / L. The filter operates in an upflow configuration, with an influent total nitrogen (TN) concentration of 23 mg / L and nitrate nitrogen (NO3) concentration of... - The concentrations of nitrogen (N) were 21 mg / L, total phosphorus (TP) 1.5 mg / L, and chemical oxygen demand (COD) <50 mg / L. The influent flow rate was controlled, the empty bed contact time (EBCT) was 60 min, the water temperature was controlled at 30 ± 3℃, and the pH was controlled at 7.5 ± 0.5.
[0087] After 30 days of acclimatization and biofilm formation, the total nitrogen (TN) concentration in the effluent was 3-5 mg / L, and the total phosphorus (TP) concentration was <0.5 mg / L.
[0088] Because pyrite packing material has a large particle size, small specific surface area, and lacks polar groups on its surface, it is highly hydrophobic and cannot generate electrostatic attraction with negatively charged microorganisms. Therefore, denitrifying and desulfurizing bacteria (NR-SOB) cannot stably attach to the pyrite surface, hindering the proliferation of the slow-growing NR-SOB and significantly increasing the biofilm formation start-up time of the biological filter. Furthermore, pyrite packing material lacks triethylamine groups, making it unable to selectively remove NO3- from the water. - -N accumulates on the filler surface through electrostatic interactions, making NR-SOB more resistant to NO3-. - The degradation efficiency of -N decreases, thereby reducing the denitrification performance of the biofilter.
[0089] The composite filler of this invention uses triethylamine (-N(C2H5)3)-based polystyrene microspheres with a rich cross-linked network structure as a carrier, and is applied via Fe... 3+ The precursor introduction-in-situ precipitation decomposition process route combines ferrous sulfide (nFeS) nanoparticles and elemental sulfur (S) 0 Nanoparticles were immobilized within the nanopores of polystyrene microspheres to prepare the composite filler nFeS / S. 0@TPM. This composite packing material has the dual functions of a biofilm carrier for denitrifying bacteria (NR-SOB) and an electron donor, which is conducive to the attachment and proliferation of NR-SOB and can effectively improve the start-up speed and denitrification performance of the sulfur autotrophic denitrification biological filter; at the same time, the denitrification reaction product Fe(OH)3 can also efficiently adsorb phosphate in wastewater, enabling the biological filter to achieve simultaneous removal of nitrogen and phosphorus from wastewater.
Claims
1. A composite packing material for a sulfur autotrophic denitrification biological filter, characterized in that, Includes the following steps: (1) Rinse the triethylamine polystyrene microspheres thoroughly with a 5-10% NaOH solution, then rinse them with a 5-10% NaCl solution and deionized water until the effluent is neutral, and dry them for later use. (2) dissolving FeCl3 in a mixed solution containing HCl and NaCl to obtain a mixed solution; slowly adding the triethylamine-based polystyrene microspheres cleaned and dried in step (1) into the mixed solution, and continuously stirring and reacting at 15-25°C; and obtaining the triethylamine-based polystyrene microspheres pre-loaded with Fe 3+ after the reaction; (3) Preload Fe 3+ The triethylamine polystyrene microspheres were filtered out and added to a mixture containing NaOH and Na2S, and the mixture was stirred continuously at 15~25℃. (4) Filter out the reaction product obtained in step (3), rinse it with a NaCl solution with a mass concentration of 5~10% until the effluent is neutral, add the washed solid product to deionized water with a pH of 7~8 and a temperature of 25~35℃, and continue to stir the reaction. (5) Filter out the reaction product obtained in step (4), place it in a vacuum drying oven and dry it at 40~60℃ to obtain the composite filler nFeS / S 0 @TPM; In the composite packing, the mass concentration of nFeS, calculated as Fe, is 10~15%, and S 0 The mass concentration is 3-5%.
2. The composite packing material for a sulfur autotrophic denitrification biological filter according to claim 1, characterized in that: In step (2), the mass concentration of HCl in the mixed solution is 5-10%, the mass concentration of NaCl is 5-10%, and the mass concentration of FeCl3 is 10-20%.
3. The composite packing material for a sulfur autotrophic denitrification biological filter according to claim 1, characterized in that: In step (2), the dosage of triethylamine polystyrene microspheres is 100~200 g / L of mixed solution.
4. The composite packing material for a sulfur autotrophic denitrification biological filter according to claim 1, characterized in that: In step (3), the mass concentration of NaOH in the mixture is 5-10%, and the mass concentration of Na2S is 10-20%.
5. The composite packing material for a sulfur autotrophic denitrification biological filter according to claim 1, characterized in that: In step (3), the preload contains Fe 3+ The dosage of triethylamine polystyrene microspheres is 100~200 g / L of the mixture.
6. The composite filler according to any one of claims 1 to 5, characterized in that: The composite filler uses triethylamine polystyrene microspheres as a carrier, and ferrous sulfide nanoparticles and elemental sulfur nanoparticles are fixed within the cross-linked network of the triethylamine polystyrene microspheres.
7. The composite filler according to claim 6, characterized in that: The composite filler has a particle size of 0.6~1.2mm and a specific surface area of 25~50m². 2 / g.
8. The application of the composite packing material according to claim 6 in a sulfur autotrophic denitrification wastewater treatment system, characterized in that: The wastewater treatment reactor used in the system is an upflow biological filter, with composite packing material filling the biological filter.
9. The application of the composite packing material according to claim 8 in a sulfur autotrophic denitrification wastewater treatment system, characterized in that: The composite packing material is filled to a height of 40-60% of the effective height of the reactor.