Method for treating sewage by using multi-layer composite filler biological filter

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a method for treating sewage by using a multi-layer composite filler biological filter. The method comprises the following steps: inoculating activated sludge, and domesticating and culturing; adding a filler into the domesticated and cultured activated sludge, adding synthetic wastewater for microbial biofilm formation, and changing water every day until the removal rates of ammoniacal nitrogen, nitrate nitrogen and chemical oxygen demand of effluent are stable to obtain a biofilm formation filler; and paving the biofilm formation filler in a filler area of a multi-layer composite filler biological filter, and carrying out sewage treatment. Compared with natural biofilm culturing, the method has the advantages that biofilm culturing can be completed within 10-14 days, the biofilm culturing starting period of the multi-layer composite filler biofilter is greatly shortened, meanwhile, the stability and the pollutant removal efficiency are greatly improved, the problems of long microbial biofilm culturing time, poor adhesion, low biomass and poor stability are solved, and the biofilm culturing method is suitable for large-scale popularization and application. And rapid biofilm formation starting and high pollution removal rate of the multi-layer composite filler biofilter system are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a method for treating sewage by using a multi-layer composite packing biological filter tank. Background Art

[0002] With the enhancement of environmental protection awareness, the demand for water resource protection and sewage treatment technology is increasing continuously. Although traditional sewage treatment methods, such as the activated sludge method and the oxidation pond method, are effective to a certain extent, they have limitations in terms of treatment efficiency, operation complexity and environmental adaptability. Therefore, it is particularly important to research and develop new and efficient sewage treatment technologies.

[0003] The multi-layer composite packing biological filter tank is an emerging sewage treatment technology, and has attracted more and more attention due to its advantages such as good biodegradation ability, low energy consumption and small floor area. However, there is currently a lack of a method for treating sewage by using a multi-layer composite packing biological filter tank to achieve rapid biofilm formation of microorganisms and improve the efficiency of sewage treatment. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for treating sewage by using a multi-layer composite packing biological filter tank. The method for treating sewage according to the present invention has a fast biofilm formation speed of microorganisms and a high sewage treatment efficiency.

[0005] The present invention provides a method for treating sewage by using a multi-layer composite packing biological filter tank, comprising the following steps:

[0006] Inoculating activated sludge in a biofilm formation reactor for domestication and cultivation to obtain domesticated and cultivated activated sludge;

[0007] Adding packing to the domesticated and cultivated activated sludge, adding first synthetic wastewater for microbial biofilm formation, and changing water once a day until the removal rates of ammonia nitrogen, nitrate nitrogen and chemical oxygen demand in the effluent are stable to obtain biofilm-forming packing; the packing includes fine packing and coarse packing, the particle size of the fine packing is 4-8 mm, and the particle size of the coarse packing is 8-10 cm; the mass ratio of C, N, and P in the first synthetic wastewater is 95-105:4-6:0.9-1.1, the COD is 400-800 mg / L, the dissolved oxygen concentration is 1.5-3.5 mg / L, the pH value is 6.8-7.6, and the temperature is 15-25 °C;

[0008] Laying the biofilm-forming packing in the packing area of the multi-layer composite packing biological filter tank for sewage treatment.

[0009] Preferably, the activated sludge is aerobic activated sludge, and the activated sludge is taken from the secondary sedimentation tank of a sewage treatment plant.

[0010] Preferably, the suspended solid concentration of the activated sludge during inoculation is 3000 - 5000 mg / L.

[0011] Preferably, before the domestication and cultivation, it also includes: aerating the activated sludge in air; the dissolved oxygen concentration during the air aeration is 1.5 - 3.5 mg / L, and the time is 2 - 4 days.

[0012] Preferably, the mass ratio of C, N, and P in the first synthetic wastewater is 100:5:1, the COD is 400 - 500 mg / L, the dissolved oxygen concentration is 2.5 mg / L, the pH value is 7.2, and the temperature is 20°C.

[0013] Preferably, the first synthetic wastewater also contains trace elements, and the substances providing the trace elements include MgSO4, CaCl2, FeCl3·6H2O, MnCl2·4H2O, CuSO4·5H2O, H3BO3, KI, Na2MoO4·5H2O, CoCl2·6H2O, ZnSO4·7H2O, and EDTA;

[0014] The concentrations of MgSO4, CaCl2, FeCl3·6H2O, MnCl2·4H2O, CuSO4·5H2O, H3BO3, KI, Na2MoO4·5H2O, CoCl2·6H2O, ZnSO4·7H2O, and EDTA in the first synthetic wastewater are 50 - 70, 4 - 7, 1 - 3, 0.1 - 0.15, 0.01 - 0.05, 0.1 - 0.3, 0.15 - 0.2, 0.05 - 0.08, 0.1 - 0.2, 0.1 - 0.15, and 8 - 12 mg / L respectively.

[0015] Preferably, the domestication and cultivation are as follows: adding the second synthetic wastewater to the biofilm reactor, changing the water once a day, and the duration is 10 - 14 days.

[0016] Preferably, the packing area includes a fine packing layer, a coarse packing layer, a fine packing layer, a coarse packing layer, a fine packing layer, and a fine packing layer paved in layers from top to bottom, and the thickness of each packing layer is 20 cm.

[0017] Preferably, the coarse packing includes polyurethane sponge, modified basalt fiber, PVC combined packing balls, or corncob; the fine packing includes zeolite and / or iron-carbon microelectrolysis packing.

[0018] The present invention also provides the application of the method for treating sewage using the multi-layer composite packing biological filter in improving the microbial structure and composition of the biofilm according to the above technical solution.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for treating sewage by using a multi-layer composite packing biological filter, comprising the following steps: inoculating activated sludge in a film-forming reactor for domestication and cultivation to obtain domesticated and cultivated activated sludge; adding packing to the domesticated and cultivated activated sludge, adding first synthetic wastewater for microbial film formation, changing water once a day until the removal rates of ammonia nitrogen, nitrate nitrogen and chemical oxygen demand in the effluent are stable to obtain film-forming packing; the packing comprises fine packing and coarse packing, the particle size of the fine packing is 4-8 mm, and the particle size of the coarse packing is 8-10 cm; the mass ratio of C, N, and P in the first synthetic wastewater is 95-105:4-6:0.9-1.1, the COD is 400-800 mg / L, the dissolved oxygen concentration is 1.5-3.5 mg / L, the pH value is 6.8-7.6, and the temperature is 15-25 °C; paving the film-forming packing into the packing area of the multi-layer composite packing biological filter for sewage treatment.

[0021] The present invention uses activated sludge, providing rich microbial resources, which can accelerate the formation of the film. The specific film-forming conditions of the present invention can reduce the competition of adverse microorganisms, promote the rapid growth of beneficial microorganisms, and significantly shorten the formation time of the biofilm. The present invention selectively cultivates specific microbial populations, enhances the attachment and growth environment of microorganisms, optimizes the microbial community composition, and improves the removal rate of pollutants in sewage. The method of the present invention can accelerate the rapid film formation of functional microorganisms, realize the rapid construction of the system, so as to realize the rapid startup of the sewage treatment system and the improvement of sewage treatment efficiency.

[0022] In addition to supplementing necessary trace elements, the core components of the synthetic wastewater of the present invention are carbon, nitrogen, and phosphorus target pollutants, without other interfering substances. After film formation, it has very good removal effects. Experimental results show that the special structure and microbial growth mode of the multi-layer composite packing biological filter have aerobic, anaerobic, and anoxic spaces at the same time, and the growth of microorganisms on different layers of packing forms a gradient, making the whole system have strong shock load resistance.

[0023] Compared with the traditional natural film formation with actual wastewater, the present invention can realize the normal operation of sewage treatment in a shorter time, improve the treatment efficiency, and realize the rapid startup of the sewage treatment system. The present invention provides an effective solution for sewage treatment. The method for treating sewage by using a multi-layer composite packing biological filter of the present invention has important technical significance and broad application prospects.

[0024] The method of the present invention also has the following advantages:

[0025] (1) Strong adaptability: It can use a variety of packing materials, and can maintain stable treatment effects under different water quality conditions after startup, with wide adaptability.

[0026] (2) Maintenance Simplification: The characteristic of rapid biofilm formation reduces the need for frequent cleaning and maintenance. It enables modular assembly of the packing materials, and the packing materials themselves can be reused, reducing operating costs and enhancing the stability and reliability of the system.

[0027] (3) Environmentally Friendly: No toxic chemical agents are used during the treatment process, reducing the negative impact on the environment and meeting the requirements of green environmental protection.

[0028] (4) Enhancement of Economic Benefits: By improving treatment efficiency and reducing operating costs, the economic benefits of sewage treatment are enhanced, providing feasibility for the popularization of rural and small-scale sewage treatment facilities. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 It is a schematic cross-sectional view of the multi-layer composite filter media biological filter used in the embodiment or the comparative example;

[0031] Figure 2 It is a schematic three-dimensional structure view of the multi-layer composite filter media biological filter used in the embodiment or the comparative example;

[0032] Figure 3 It is a schematic structure view of the biofilm formation reactor used in the embodiment;

[0033] The reference numerals are: 1, filter media area; 2, ventilation area; 3, inlet pipe; 4, exhaust pipe; 5, rain protection cap; 6, non-powered wind cap; 7, water guiding groove; 8, water distribution holes; 9, fine filter media; 10, coarse filter media; 11, ventilation holes; 12, water inlet; 13, water outlet. Detailed Embodiments

[0034] The present invention provides a method for treating sewage using a multi-layer composite packing biological filter, including the following steps:

[0035] Inoculate the activated sludge in the biofilm formation reactor for domestication and cultivation to obtain the domesticated and cultivated activated sludge;

[0036] Add fillers to the domesticated and cultivated activated sludge, and introduce the first synthetic wastewater for microbial film formation. Change the water once a day until the removal rates of ammonia nitrogen, nitrate nitrogen, and chemical oxygen demand in the effluent are stable to obtain the film-forming fillers. The fillers include fine fillers and coarse fillers. The particle size of the fine fillers is 4-8 mm, and the particle size of the coarse fillers is 8-10 cm. In the first synthetic wastewater, the mass ratio of C, N, and P is 95-105:4-6:0.9-1.1, the COD is 400-800 mg / L, the dissolved oxygen concentration is 1.5-3.5 mg / L, the pH value is 6.8-7.6, and the temperature is 15-25 °C.

[0037] Lay the film-forming fillers in the filler area of the multi-layer composite filler biological filter for sewage treatment.

[0038] In the present invention, unless otherwise specified, the materials and equipment used are commercially available products in the art.

[0039] The present invention inoculates activated sludge in a film-forming reactor for domestication and cultivation to obtain domesticated and cultivated activated sludge.

[0040] In the present invention, the activated sludge is preferably aerobic activated sludge, and the activated sludge is preferably taken from the secondary sedimentation tank of a sewage treatment plant.

[0041] In the present invention, the suspended solid concentration of the activated sludge during inoculation is preferably 3000-5000 mg / L.

[0042] In the present invention, before domestication and cultivation, it is preferably further included: aerating the activated sludge in the air. The dissolved oxygen concentration during the air aeration is preferably 1.5-3.5 mg / L, and the time is 2-4 days, specifically 3 days. The function of the air aeration is to consume the nutrients in the sludge and make the microorganisms in a starving state.

[0043] In the present invention, the film-forming reactor is preferably an aerobic bioreactor.

[0044] In the present invention, the domestication and cultivation preferably include: adding the second synthetic wastewater to the film-forming reactor, changing the water once a day, and the duration is 10-14 days. The concentration of the second synthetic wastewater added during the domestication and cultivation process preferably increases from low to high, so that the microorganisms can adapt slowly. The increasing amplitudes are 20%, 50%, 80%, and 100% in sequence, and finally it is consistent with the concentration of the first synthetic wastewater. Each increasing concentration preferably lasts for 3 days. During the increasing process, continuously detect the removal rates of COD, nitrogen, and phosphorus. After the removal rates are stable, increase to the next concentration gradient.

[0045] In the present invention, the second synthetic wastewater is preferably the same as the first synthetic wastewater.

[0046] In the present invention, a filler is added to the domesticated and cultured activated sludge, and the first synthetic wastewater is added for microbial film formation. The water is changed once a day until the removal rates of ammonia nitrogen, nitrate nitrogen, and chemical oxygen demand in the effluent are stable, obtaining a film-forming filler. The filler includes a fine filler and a coarse filler. The particle size of the fine filler is 4 - 8 mm, and the particle size of the coarse filler is 8 - 10 cm.

[0047] In the present invention, the mass ratio of C, N, and P in the first synthetic wastewater is preferably 100:5:1, the COD is preferably 400 - 500 mg / L, the dissolved oxygen concentration is preferably 2.5 mg / L, the pH value is preferably 7.2, and the temperature is preferably 20 °C.

[0048] In the present invention, the first synthetic wastewater also contains trace elements. The substances providing the trace elements preferably include MgSO4, CaCl2, FeCL3·6H2O, MnCl2·4H2O, CuSO4·5H2O, H3BO3, KI, Na2MoO4·5H2O, CoCl2·6H2O, ZnSO4·7H2O, and EDTA. The concentrations of MgSO4, CaCl2, FeCL3·6H2O, MnCl2·4H2O, CuSO4·5H2O, H3BO3, KI, Na2MoO4·5H2O, CoCl2·6H2O, ZnSO4·7H2O, and EDTA in the first synthetic wastewater are respectively preferably 50 - 70, 4 - 7, 1 - 3, 0.1 - 0.15, 0.01 - 0.05, 0.1 - 0.3, 0.15 - 0.20, 0.05 - 0.08, 0.1 - 0.2, 0.1 - 0.15, and 8 - 12 mg / L, and more preferably 60, 5, 1.5, 0.12, 0.03, 0.15, 0.18, 0.06, 0.15, 0.12, and 10 mg / L.

[0049] In the present invention, the time for film formation is preferably 10 - 14 days.

[0050] After obtaining the film-forming filler, in the present invention, the film-forming filler is paved in the filler area of the multi-layer composite filler biological filter for sewage treatment.

[0051] In the present invention, the fine filler preferably includes zeolite and / or iron-carbon microelectrolysis filler, and the fine filler is preferably used in a mesh bag with a pore diameter of 2.5 mm. The volume ratio of zeolite to iron-carbon microelectrolysis material is preferably 3:2. The filler composition described in the present invention can optimize the attachment and growth environment of microorganisms, thereby accelerating the formation of biofilm and improving the sewage treatment efficiency.

[0052] In the present invention, the coarse filler preferably includes polyurethane sponge, modified basalt fiber, PVC combined filler ball, or corncob, and the structure of the coarse filler is a hollow structure.

[0053] In the present invention, the multi-layer composite packing biological filter is preferably the multi-layer composite packing biological filter driven by height difference in the Chinese patent with the authorization announcement number of CN 220642763U. The multi-layer composite packing biological filter includes a packing area and a ventilation area, and the main body includes a biological filter tank body with upward inlet and downward outlet, an air inlet pipe and an air outlet pipe with ventilation holes, and a power-free wind cap.

[0054] In the present invention, the packing area preferably includes zeolite layers, polyurethane layers, zeolite layers, polyurethane layers, zeolite layers and zeolite layers paved in layers from top to bottom, and the thickness of each packing layer is preferably 20 cm.

[0055] The present invention selects coarse packing and fine packing, combines packings with different particle sizes, can ensure good specific surface area and microbial adhesion performance, can optimize water flow velocity and distribution, enhance mass transfer efficiency, and promote the growth of microorganisms. The present invention designs the packing in layers, places packings with different characteristics at different layers, and can realize the step-by-step treatment of water flow when passing through different packings.

[0056] The present invention also provides the application of the method for treating sewage by using the multi-layer composite packing biological filter described in the above technical solution in improving the microbial structure and composition of the biofilm.

[0057] In the present invention, the microorganisms preferably include bacteria and / or fungi.

[0058] In order to further illustrate the present invention, the method for treating wastewater by using the multi-layer composite packing biological filter provided by the present invention will be described in detail below with reference to the drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0059] In the examples or comparative examples of the present invention, total nitrogen (TN) was determined by the alkaline potassium persulfate digestion ultraviolet spectrophotometry (HJ636-2012). Nitrate nitrogen (NO3 - -N) was determined by ultraviolet spectrophotometry; ammonium nitrogen (NH4 + -N) was determined by salicylic acid spectrophotometry (HJ536-2009). Total phosphorus (TP) was determined by flow injection-molybdate ammonium spectrophotometry (HJ671-2013). Chemical oxygen demand (COD) was determined by a 5B-3C(V8) COD rapid detector (Lanzhou Lianhua Environmental Protection Technology Co., Ltd.).

[0060] Figure 1 and Figure 2 is the multi-layer composite packing power-free biological filter used in the examples or comparative examples, where Figure 1 is a schematic sectional view, Figure 2It is a schematic diagram of a three-dimensional structure. This multi-layer composite filler non-powered biological filter mainly includes a filler area 1 and a ventilation area 2. The main body includes a biological filter tank body with an upper-in and lower-out structure, an air inlet pipe 3 and an air outlet pipe 4 with ventilation holes, a rain cap 5, and a non-powered air cap 6. Specifically, a water guide groove 7 is fixed inside the biological filter filler area 1, and water distribution holes 8 are evenly arranged on the side wall of the water guide groove 7. The air inlet pipe 3 and the air outlet pipe 4 are respectively inserted into the bottom of the ventilation areas 2 on the left and right sides. The horizontal height of the air inlet pipe 3 is lower than the horizontal height of the air outlet pipe 4, so that the air pressure at the air inlet of the air inlet pipe 3 is higher than the air pressure at the air outlet of the air outlet pipe 4, realizing the autonomous flow of air. The setting of the rain cap 5 can prevent rainwater from entering the biological filter, and the setting of the non-powered air cap 6 can increase the suction rate of air through the wind force, accelerate the air flow, and realize non-powered ventilation. The fine filler 9 and the coarse filler 10 are laid in a staggered manner from top to bottom in the filler area 1, ensuring that the uppermost layer and the lowermost layer of the filler in the filler area 1 are both fine fillers 9. The number of layers of the fine filler 9 and the coarse filler 10 is determined according to the volume of the filler area 1. The size of the fine filler 9 is much smaller than the size of the coarse filler 10. The fine filler is filled in a mesh bag to achieve layered laying, preventing the fine filler from entering the coarse filler layer, the ventilation holes of the air inlet pipe and the air outlet pipe, and causing air flow blockage. Ventilation holes 11 are distributed at the positions of the air inlet pipe 3 and the air outlet pipe 4 corresponding to the coarse filler layer 10. The size of the ventilation holes 11 is smaller than the sizes of the fine filler 9 and the coarse filler 10, avoiding the filler from entering the ventilation holes 11 and causing blockage, which hinders the air flow. Through the staggered paving method, the fine filler 9 and the coarse filler 10 realize the filtration of the incoming sewage. The ventilation holes 11 of the air inlet pipe 3 and the air outlet pipe 4 are arranged corresponding to the coarse filler layer 10. The coarse filler 10 with larger gaps can ensure the normal flow of air and increase the oxygen content of the sewage. It realizes the efficient treatment of sewage integrating aerobic, anoxic, and anaerobic conditions, and at the same time, it does not require an aeration device, is easy to install and maintain, and saves costs and energy.

[0061] The multi-layer composite filler biological filter constructs an aerobic environment by using the height difference drive oxygen supply method. By setting the height of the air outlet pipe lower than that of the air inlet pipe, the air pressure at the air inlet is higher than the air pressure at the air outlet, and air automatically enters the air inlet and is discharged from the air outlet, realizing non-powered ventilation. The exhaust device in the laboratory is designed according to the ventilation volume of the non-powered air cap, and a power fan is used instead of the non-powered air cap. The size of the filler area is 30×30×120 cm (length×width×height), with each 20 cm as a layer, and a total of 6 layers are divided. The zeolite (4 - 8 mm) and polyurethane filler (diameter 10 cm) are washed with distilled water and dried, and then laid in layers.

[0062] Unless otherwise specified, in the multi-layer composite packing biological filter of the examples or comparative examples, the packing from top to bottom is as follows: the first layer (0 - 20 cm) is a zeolite packing layer, the second layer (20 - 40 cm) is a polyurethane packing layer, the third layer (40 - 60 cm) is a zeolite packing layer, the fourth layer (60 - 80 cm) is a polyurethane packing layer, the fifth layer (80 - 100 cm) is a zeolite packing layer, and the sixth layer (100 - 120 cm) is a zeolite packing layer.

[0063] Unless otherwise specified, the ventilation volume of the examples or comparative examples is 100 m 3 / h.

[0064] Comparative Example 1

[0065] A certain rural domestic sewage was used to carry out film formation cultivation by feeding water from the upper part of the multi-layer composite packing biological filter. The water feeding method was continuous water feeding, and the hydraulic load was 0.6 m 3 / m 2 / d. The physical and chemical indexes of the influent and effluent of the sewage were detected every 3 days. After 23 days, the effluent was basically stable. After the effluent indexes were stable for 7 days, it was regarded as the completion of film formation, and the film formation was completed in 30 days. The effluent indexes and pollutant removal rates after stable operation are shown in Table 1.

[0066] Table 1 Physical and chemical indexes of the effluent and pollutant removal rates under natural film formation conditions

[0067] Index Effluent Removal rate COD 102 mg / L 59.4％ TN 30.1 mg / L 68.2％ TP 2.2 mg / L 25.4％ <![CDATA[NO3 - -N]]> 0.3 mg / L 90.1％ <![CDATA[NH4 + -N]]> 25.1 mg / L 67.5％

[0068] After stable operation, the removal efficiencies of COD, TN, TP, NO3 - -N and NH4 + -N were 59.4%, 68.2%, 25.4%, 90.1% and 67.5% respectively.

[0069] In the following examples or comparative examples, the trace elements added to the synthetic wastewater used were MgSO4, CaCl2, FeCL3·6H2O, MnCl2·4H2O, CuSO4·5H2O, H3BO3, KI, Na2MoO4·5H2O, CoCl2·6H2O, ZnSO4·7H2O and EDTA, and the concentrations were 60, 5, 1.5, 0.12, 0.03, 0.15, 0.18, 0.06, 0.15, 0.12 and 10 mg / L respectively.

[0070] Acclimation and cultivation of activated sludge: Activated sludge was inoculated into the biofilm reactor. The activated sludge used was the secondary sedimentation tank sludge of a certain urban sewage treatment plant, and the suspended solid concentration of the inoculated activated sludge was 3000 mg / L. Then, synthetic wastewater (30% sludge volume + 70% wastewater volume) was added. The concentration of the synthetic wastewater increased gradually from low to high to allow the microorganisms to adapt slowly, with increasing amplitudes of 20%, 50%, 80%, and 100%. Each of the first three concentrations was maintained for 3 days. The mass ratio of C:N:P in the synthetic wastewater was 100:5:1. The final influent COD was controlled at 400 mg / L, the dissolved oxygen concentration was 2.5 mg / L, the pH value was 7.2, and the temperature was 20 °C. The water was changed once a day, and the acclimation and cultivation lasted for 14 days.

[0071] Example 1

[0072] Compared with Comparative Example 1, the difference is that: First, the packing (including fine packing and coarse packing) was pre-coated with biofilm using the Figure 3 shown biofilm reactor.

[0073] The packing was added to the acclimated and cultivated activated sludge, and the synthetic wastewater (the same as the final synthetic wastewater during acclimation and cultivation) was changed daily to coat the packing with microorganisms. When the removal effects of ammonia nitrogen, nitrate nitrogen, and chemical oxygen demand in the biofilm reactor reached stability, it was proved that the biofilm coating was completed. The biofilm coating time in this example was 10 days. Finally, the packed packing with completed biofilm coating was packaged and installed in a multi-layer composite packing biological filter for sewage treatment, and it could operate stably on the first day.

[0074] The synthetic wastewater was used to test its treatment effect. The mass ratio of C:N:P in the synthetic wastewater = 100:10:1, and the influent COD was controlled at 500 mg / L. The influent mode was continuous influent, and the hydraulic load was 0.6 m 3 / m 2 / d. The physical and chemical indexes of the influent and effluent of the sewage were detected every 3 days. The effluent indexes were regarded as stable operation after 7 days of stability. The effluent indexes and pollutant removal rates after stable operation are shown in Table 2.

[0075] Table 2 Physical and chemical indexes of the effluent and pollutant removal rates under the condition of rapid biofilm coating of sludge

[0076] Index Effluent Removal rate COD 95 mg / L 81％ TN 6.9 mg / L 86％ TP 3.1 mg / L 38％ <![CDATA[NO3 - -N]]> 0.01 mg / L 98.1％ <![CDATA[NH4 + -N]]> 5 mg / L 90％

[0077] After stable operation, the removal rates of COD, TN, TP, NO3 - -N, and NH4 + -N were 81%, 86%, 38%, 98.1%, and 90% respectively. Compared with Comparative Example 1, for COD, TN, TP, NO3 - -N, and NH4 +The -N removal rates increased by 21.6%, 17.8%, 12.6%, 8.0% and 22.5% respectively.

[0078] Example 2

[0079] The difference from Example 1 is that: the effect of a certain rural domestic sewage in Comparative Example 1 was tested, and the pollutant removal rate was comparable to that of Example 1.

[0080] Example 3

[0081] The difference from Example 1 is that: the effect was tested by changing the influent conditions. The C:N:P of the synthetic wastewater was 100:10:1, 100:20:1 and 100:40:1 respectively, and the hydraulic load was 0.4, 0.6 and 0.8 m 3 / m 2 / d, and the influent modes were continuous influent and intermittent influent respectively. Each condition was run for 14 d, and the effluent was considered to be in stable operation after 7 d of stability.

[0082] Under different influent conditions, the removal rates of COD, TN, TP, NO3 - -N and NH4 + -N were maintained at 81±0.5%, 86±0.7%, 38±0.4%, 98.1±0.3% and 90±0.8%. It can be seen that the fluctuation of the influent basically has no effect on the effect of the multi-layer composite packing biological filter, which proves that the method of the present invention has high stability in sewage treatment effect and strong impact resistance.

[0083] Comparative Example 2

[0084] The difference from Comparative Example 1 is that: 100% of the zeolite volume was replaced with iron-carbon microelectrolysis packing.

[0085] The film hanging time was similar to that of Comparative Example 1, about 30 days. The effluent indexes and pollutant removal rates after stable operation are shown in Table 3.

[0086] Table 3 Physicochemical indexes and pollutant removal rates of the effluent with 100% iron-carbon microelectrolysis packing added under natural film hanging conditions

[0087] Index Effluent Removal rate COD 60 mg / L 88％ TN 6.1 mg / L 89％ TP 0.99 mg / L 80.2％ <![CDATA[NO3 - -N]]> 0.008 mg / L 99.2％ <![CDATA[NH4 + -N]]> 2 mg / L 96％

[0088] After stable operation, the removal rates of COD, TN, TP, NO3 - -N and NH4 + -N were 88%, 89%, 80.2%, 99.1% and 96% respectively. Compared with Comparative Example 1, for COD, TN, TP, NO3 - -N and NH4 +The -N removal rates increased by 28.6%, 20.8%, 54.8%, 9.1% and 28.5% respectively. The iron-carbon microelectrolysis filler significantly increased the amount of microbial biofilm attachment, promoted the growth of microorganisms such as ammonia-assimilating bacteria, and improved the pollutant removal rate.

[0089] Comparative Example 3

[0090] The difference from Comparative Example 2 is only that ventilation is not carried out.

[0091] After stable operation, the removal rates of COD, TN, TP, NO3 - -N and NH4 + -N were 69.3%, 78.3%, 64.8%, 98.4% and 80.3% respectively.

[0092] It can be seen from Comparative Examples 2 and 3 that under ventilation conditions, the pollutant removal rate can be improved. Compared with Comparative Example 2, the microbial biofilm attachment cycle in Comparative Example 3 is not much different, but there are significant differences in the amount of microbial biofilm attachment and microbial activity. The amount of biofilm attachment is larger under the condition of induced draft oxygen supply (ventilation), the microbial diversity is richer, the activity is higher, and the removal effect is better.

[0093] Example 4

[0094] The difference from Example 1 is that 100% of the zeolite volume is replaced by the iron-carbon microelectrolysis filler. The effluent indexes and pollutant removal rates after stable operation are shown in Table 4.

[0095] Table 4 Physicochemical indexes and pollutant removal rates of the effluent with 100% iron-carbon microelectrolysis filler added under the condition of rapid sludge biofilm attachment

[0096] Index Effluent Removal rate COD 34 mg / L 93.3％ TN 1.5 mg / L 97％ TP 0.54 mg / L 92.7％ <![CDATA[NO3 - -N]]> 0.002 mg / L 99.8％ <![CDATA[NH4 + -N]]> 0.5 mg / L 98.5％

[0097] It can be seen that under the condition of rapid sludge biofilm attachment with 100% iron-carbon microelectrolysis filler added, the quality of the effluent can reach the first-class standard for comprehensive discharge of domestic sewage.

[0098] It can be seen that Comparative Example 1 uses the natural biofilm attachment method, with a slow biofilm attachment speed and a low pollutant removal rate after stable operation; while the method of the present invention can achieve rapid biofilm attachment and a high pollutant removal rate after stable operation.

[0099] Regulation of microbial community composition by iron-carbon microelectrolysis fillers with different volume ratios: The significant differences in the top 10 phyla of the biofilms in the CFBF system of iron-carbon microelectrolysis fillers with 100%, 40%, and 0% (percentage of zeolite volume) were tested for inter-group differences. It was found that Firmicutes, Campilobacterota, Synergistota, and Desulfobacterota were enriched in the 100% IC-ME group, Verrucomicrobiota and WPS-2 were enriched in the 40% IC-ME group, and Bacteroidota, Chloroflexi, Patescibacteria, and Bdellovibrionota were enriched in the 0% IC-ME group.

[0100] Growth of the system biofilm:

[0101] 1. Analysis results of the biofilms on the surfaces of different packing layers (from top to bottom) in Example 1 (first biofilm formation): The thicknesses of the biofilms on the zeolite surfaces at 5, 10, 50, and 90 cm were 113.54, 83.66, 71.71, and 65.73 μm respectively, and the activity of the biofilm increased with the increase in depth.

[0102] The top five dominant phyla in terms of biofilm abundance at a depth of 5 cm were Pseudomonadota (57.44%), Bacteroidota (14.19%), Actinomycetota (9.09%), Bacillota (8.02%), and Bdellovibrionota (1.41%); after treatment with PMA (propylene glycol methyl ether acetate), Pseudomonadota and Actinomycetota increased by 2.00% and 2.52% respectively, while Bacteroidota, Bacillota, and Bdellovibrionota decreased by 1.41%, 3.83%, and 0.25% respectively.

[0103] The top five dominant phyla in terms of biofilm abundance at a depth of 10 cm were Pseudomonadota (60.66%), Bacteroidota (16.79%), Actinomycetota (8.91%), Basidiomycota (3.20%), and Acidobacteriota (2.39%); after PMA treatment, Pseudomonadota and Acidobacteriota increased by 1.39% and 0.36% respectively, while Bacteroidota, Actinomycetota, and Basidiomycota decreased by 0.23%, 0.41%, and 0.95% respectively;

[0104] The top five dominant phyla in terms of biofilm abundance at a depth of 30 cm were Pseudomonadota (40.25%), Bacteroidota (29.43%), Actinomycetota (10.25%), Bdellovibrionota (3.73%), and Verrucomicrobiota (2.09%); after PMA treatment, Pseudomonadota and Actinomycetota increased by 1.39% and 2.03% respectively, while Bacteroidota, Bdellovibrionota, and Verrucomicrobiota decreased by 2.61%, 0.14%, and 0.36% respectively;

[0105] The top five dominant phyla in terms of biofilm abundance at a depth of 50 cm were Pseudomonadota (56.27%), Bacteroidota (21.22%), Actinomycetota (4.36%), Bacillota (3.94%), and Bdellovibrionota (3.59%); after PMA treatment, Pseudomonadota and Bacteroidota increased by 3.97% and 0.04% respectively, while Actinomycetota, Bacillota, and Bdellovibrionota decreased by 0.02%, 0.15%, and 1.73% respectively;

[0106] The top five dominant phyla in terms of biofilm abundance at a depth of 70 cm were Pseudomonadota (49.18%), Bacteroidota (24.16%), Actinomycetota (12.36%), Bdellovibrionota (2.60%), and Basidiomycota (2.19%); after PMA treatment, Bacteroidota and Actinomycetota increased by 3.30% and 4.16% respectively, while Pseudomonadota, Bdellovibrionota, and Basidiomycota decreased by 5.88%, 0.02%, and 0.68% respectively;

[0107] The top five dominant phyla in terms of biofilm abundance at a depth of 90 cm were Pseudomonadota (52.59%), Bacteroidota (21.00%), Actinomycetota (11.15%), Bdellovibrionota (2.43%), and Basidiomycota (2.43%); after PMA treatment, Bacteroidota, Actinomycetota, Bdellovibrionota, and Basidiomycota increased by 0.05%, 2.26%, 0.27%, and 0.62% respectively, while Pseudomonadota decreased by 2.43%;

[0108] The top five dominant phyla in terms of biofilm abundance at a depth of 110 cm were Pseudomonadota (58.57%), Bacteroidota (13.72%), Bacillota (10.43%), Bdellovibrionota (6.17%), and Actinomycetota (3.62%); after PMA treatment, Pseudomonadota and Actinomycetota increased by 6.33% and 1.32% respectively, while Bacteroidota, Bacillota, and Bdellovibrionota decreased by 1.58%, 5.47%, and 0.80% respectively.

[0109] It can be seen that the composition and relative abundance of the dominant phyla in the biofilms at different depths of the CFBF system changed before and after PMA treatment. Notably, the trends of the composition and relative abundance of the dominant phyla in the biofilms at different depths were different after PMA treatment. Taking Pseudomonadota as an example, PMA treatment decreased the relative abundance of Pseudomonadota at depths of 5, 10, 30, 50, and 110 cm, while the opposite trend was observed at depths of 70 and 90 cm. Meanwhile, the relative abundance of Pseudomonadota changed the most at a depth of 10 cm.

[0110] Overall, the main dominant phyla in the upper biofilms of the CFBF system included Pseudomonadota, Bacteroidota, Actinomycetota, Bacillota, and Bdellovibrionota. However, in the lower biofilms, Basidiomycota replaced Bacillota as the dominant phylum. Pseudomonadota was the phylum with the highest relative abundance in the biofilms of this system and showed significant dominance in the biofilms at depths of 5 cm, 10 cm, 50 cm, and 110 cm. Bacillota was also a dominant bacterial group in the biofilms at depths of 5 cm, 10 cm, and 50 cm, while the relative abundance of Bacteroidota was low at 5 cm and 10 cm. Notably, the relative abundance of Actinomycetota was the lowest in the biofilm at a depth of 10 cm, while the relative abundance of Bdellovibrionota reached its peak at this depth. These results indicate that the structure of the dominant bacterial groups (at the phylum level) in the biofilms at different depths in the CFBF system has obvious spatial heterogeneity.

[0111] PMA treatment can mask the inactive microorganisms in the biofilm of the CFBF system. Among them, the dominant genera in the biofilm of the CFBF system are Pseudomonas, Janthinobacterium, Tolumonas, Raoultella, Pedobacter, Flavobacterium, Microbacterium, Acidovorax, unclassified_f__Rhodanobacteraceae, and Sphaerotilus. Among them, after the biofilm of the CFBF system at different depths was treated with PMA, the relative abundance of Pseudomonas increased the most (5.47%) at a depth of 10 cm and decreased the most (1.88%) at a depth of 10 cm. The composition and relative abundance changes of the genus-level microorganisms in the biofilm of the CFBF system at depths of 5 and 10 cm were consistent before and after PMA treatment. After the biofilm of the CFBF system at different depths was treated with PMA, the relative abundances of Tolumonas, Lactococcus, Pseudomonas, and Raoultella changed significantly.

[0112] Overall, the main dominant genera in the upper biofilm of the CFBF system include Pseudomonas, Lactococcus, Raoultella, Tolumonas, and Janthinobacterium, while the relative abundance of Sphaerotilus is the lowest. Pseudomonas is the genus with the highest relative abundance in the biofilm of this system and occupies a significant advantage in the biofilms at depths of 5, 10, 50, and 110 cm. Pseudomonas belongs to Pseudomonadota at the phylum level. With the increase in depth, the relative abundance of Sphaerotilus gradually increases. Fluviicola, Dechloromonas, Paenarthrobacter, and Variovorax showed the highest relative abundances at depths of 30, 50, 70, and 90 cm, respectively. It is worth noting that the polyphosphate-accumulating bacterium Rhodanobacteraceae is enriched in the bottom biofilm, while the relative abundance of Lactococcus is the lowest. In summary, the biofilms at different depths in the CFBF system show a complex microbial community structure and dynamic changes. In particular, the abundance differences of Pseudomonas and Rhodanobacteraceae in the biofilm reflect their important roles in sewage treatment.

[0113] 2. Addition of iron-carbon microelectrolysis (IC-ME) materials (0% IC-ME for Comparative Example 1 and 100% IC-ME for Comparative Example 2)

[0114] The addition amount of IC-ME increased the growth rate of MLVSS (Mixed Liquor Volatile Suspended Solids Concentration) (100% IC-ME > 40% IC-ME > 0% IC-ME), especially during the mature stage of biofilm growth and colonization, and there were significant differences in the growth rate of biofilms. During the stable stage of biofilm growth and colonization, the MLVSS of the biofilm in the CFBF system with 100% IC-ME addition was 1331 mg / L, the MLVSS of the biofilm in the CFBF system with 40% IC-ME addition was 1121 mg / L, and the MLVSS of the biofilm in the CFBF system with 0% IC-ME addition was 975 mg / L.

[0115] During the mature stage of biofilm colonization, the thicknesses of the biofilms in the CFBF systems with 100%, 40%, and 0% IC-ME addition were 89, 74, and 47 μm respectively. During the stable stage of biofilm colonization, the thicknesses of the biofilms in the CFBF systems with 100%, 40%, and 0% IC-ME addition were 134, 115, and 86 μm respectively.

[0116] The Ace indices of the microorganisms in the biofilms of the CFBF systems with 100%, 40%, and 0% IC-ME addition were 973.81, 1129.90, and 1117.60 respectively. When the addition amount of IC-ME was 100%, the Shannon index and Simpson index were 4.32 and 0.05 respectively. When the addition amount of IC-ME was 40%, the Shannon index and Simpson index were 4.69 and 0.03 respectively. When the addition amount of IC-ME was 0%, the Shannon index and Simpson index were 4.65 and 0.03 respectively.

[0117] Pseudomonadota, Actinobacteriota, Firmicutes, Bacteroidota, Campilobacterota, Chdoroflexi, Patescibacteria, Verrucomicrobiota, Synergistota, and Desulfobacterota are the top 10 phyla with the highest relative abundances. Pseudomonadota has the highest relative abundance, which is 58%, 61%, and 60% when the addition amounts of IC-ME are 100%, 40%, and 0%, respectively. Pseudomonadota contains a variety of known pathogenic bacteria (such as Escherichia coli and Salmonella) and is involved in different stages of the N cycle (such as nitrification, denitrification, nitrogen fixation, and ammonia assimilation, etc.). Actinobacteriota is involved in the decomposition of organic matter and the formation of humus, and its relative abundance decreases with the increase in the addition amount of IC-ME (the relative abundances are 10%, 12%, and 14%, respectively). Firmicutes (Bacillota) mainly includes the classes Bacilli and Clostridia and plays various important roles in the ecosystem (such as the degradation of organic matter and the fermentation process, etc.). The relative abundance of Firmicutes increases with the increase in the addition amount of IC-ME, and the relative abundance of 100% IC-ME is 11% higher than that of 0% IC-ME. The relative abundance of Bacteroidota decreases with the increase in the addition amount of IC-ME (8%, 11%, and 13%), and it has various functions in the ecosystem, including participating in food digestion and nutrient absorption in the intestine, the decomposition of organic matter in soil and water bodies, and the degradation of complex polysaccharides (such as cellulose and starch). The relative abundance of Campilobacterota is the highest (3%) when the addition amount of IC-ME is 100%. It is involved in microaerophilic metabolism, sulfur metabolism, and the N cycle process. The relative abundance of Chdoroflexi decreases with the increase in the addition amount of IC-ME (0%, 1%, and 2%). It can be seen that different addition amounts of IC-ME change the composition and relative abundances of the dominant phyla in the CFBF system.

[0118] 3. Influence of ventilation (Comparative Examples 2 and 3)

[0119] The top 10 genera in the ventilation group, sorted by relative abundance, are Acidovorax, Brevundimonas, Flavobacterium, Rheinheimera, Trichococcus, Acinetobacter, Leucobacter, Pseudomonas, Simplicispira, and Planomicrobium. The top 10 genera in the non-ventilation group, sorted by relative abundance, are Trichococcus, unclassified_f__Rhodobacteraceae, Acidovorax, Acinetobacter, Rheinheimera, Pseudomonas, Brevundimonas, Flavobacterium, Leucobacter, and norank_f__JG30-KF-CM45. This shows that ventilation changes the composition and relative abundance of the dominant genera of biofilm microorganisms.

[0120] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments according to the embodiments of the present invention without creative work, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for treating sewage by using a multi-layer composite filler biological filter, characterized in that, It includes the following steps: Inoculate activated sludge in a biofilm reactor for domestication and cultivation to obtain domesticated and cultivated activated sludge; Add packing materials to the domesticated and cultivated activated sludge, add the first synthetic wastewater for microbial biofilm formation, change the water once a day until the removal rates of ammonia nitrogen, nitrate nitrogen and chemical oxygen demand in the effluent are stable, and obtain biofilm-packed materials; the packing materials include fine packing materials and coarse packing materials, the particle size of the fine packing materials is 4 - 8 mm, and the particle size of the coarse packing materials is 8 - 10 cm; in the first synthetic wastewater, the mass ratio of C, N, and P is 95 - 105:4 - 6:0.9 - 1.1, the COD is 400 - 800 mg / L, the dissolved oxygen concentration is 1.5 - 3.5 mg / L, the pH value is 6.8 - 7.6, and the temperature is 15 - 25 °C; Lay the biofilm-packed materials in the packing area of a multi-layer composite packing biological filter for sewage treatment.

2. The method for treating sewage according to claim 1, wherein The activated sludge is aerobic activated sludge, and the activated sludge is taken from the secondary sedimentation tank of a sewage treatment plant.

3. The method for treating sewage according to claim 1, wherein The suspended solid concentration of the activated sludge during inoculation is 3000 - 5000 mg / L.

4. The method for treating sewage according to claim 1, 2 or 3, characterized in that, Before the domestication and cultivation, it also includes: aerating the activated sludge; the dissolved oxygen concentration during the aeration is 1.5 - 3.5 mg / L, and the time is 2 - 4 days.

5. The method for treating sewage according to claim 1, wherein In the first synthetic wastewater, the mass ratio of C, N, and P is 100:5:1, the COD is 400 - 500 mg / L, the dissolved oxygen concentration is 2.5 mg / L, the pH value is 7.2, and the temperature is 20 °C.

6. The method for treating sewage according to claim 5, characterized in that, The first synthetic wastewater also contains trace elements, and the substances providing the trace elements include MgSO4, CaCl2, FeCl3·6H2O, MnCl2·4H2O, CuSO4·5H2O, H3BO3, KI, Na2MoO4·5H2O, CoCl2·6H2O, ZnSO4·7H2O and EDTA; The concentrations of MgSO4, CaCl2, FeCl3·6H2O, MnCl2·4H2O, CuSO4·5H2O, H3BO3, KI, Na2MoO4·5H2O, CoCl2·6H2O, ZnSO4·7H2O and EDTA in the first synthetic wastewater are 50 - 70, 4 - 7, 1 - 3, 0.1 - 0.15, 0.01 - 0.05, 0.1 - 0.3, 0.15 - 0.2, 0.05 - 0.08, 0.1 - 0.2, 0.1 - 0.15 and 8 - 12 mg / L respectively.

7. The method for treating sewage according to claim 1, characterized in that, The domestication and cultivation are: adding the second synthetic wastewater to the biofilm reactor, changing the water once a day, and the duration is 10 - 14 days.

8. The method for treating sewage according to claim 1, wherein, The packing area includes a fine packing layer, a coarse packing layer, a fine packing layer, a coarse packing layer, a fine packing layer and a fine packing layer paved in layers from top to bottom in sequence, and the thickness of each packing layer is 20 cm.

9. The method for treating sewage according to claim 1, characterized in that, The coarse packing materials include polyurethane sponge, modified basalt fiber, PVC combined packing balls or corncobs; the fine packing materials include zeolite and / or iron-carbon microelectrolysis packing materials.

10. Application of the method for treating sewage using a multi-layer composite packing biological filter according to any one of claims 1 - 9 in improving the microbial structure and composition of biofilms.

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