Sulfur autotrophic denitrification biological filter, sewage treatment system and treatment method thereof
Technical Field
The invention relates to a sewage treatment system, in particular to a sulfur autotrophic denitrification biological filter, a sewage treatment system and a treatment method thereof.
Background
Nitrogen is one of the indispensable elements for animal and plant growth, but also one of the key indicators for determining water quality. Excessive discharge thereof can cause a series of environmental problems and even harm human health. Biological denitrification is an economical and efficient means and is therefore widely used in sewage treatment plants worldwide. The traditional heterotrophic denitrification method is to reduce nitrate into N by using organic matters as electron acceptors through heterotrophic bacteria2. However, at present, a considerable part of sewage treatment plants in China have low C/N of inlet water, and the denitrification process is often limited by insufficient carbon sources, so that the sewage discharge reaching the standard is difficult. The problem that the effluent of a sewage treatment plant does not reach the standard is the common problem at present; the water amount of the sludge digestive liquid only accounts for 0.5-2% of the water inlet amount of the sewage treatment plant, but the nitrogen content accounts for 10-25% of the nitrogen load of the inlet water, so that the reduction of the nitrogen content in the sludge digestive liquid is of great significance for reducing the nitrogen load of the inlet water.
In recent years, researchers at home and abroad develop a great deal of research on how to solve the problem that sewage treatment does not reach the standard due to low carbon-nitrogen ratio of inlet water of a sewage treatment plant. At present, the main solutions to the problem of low carbon-nitrogen ratio are to develop new technology, improve process flow and the like. For example, a nitrification filter and a denitrification filter are added after the secondary effluent; an oxidation process; a membrane separation method; the methods such as the artificial wetland and the like can effectively remove nitrogen in secondary effluent of a sewage treatment plant, but all have obvious defects. The denitrification filter, the artificial wetland and the like can greatly increase the occupied area of a sewage treatment plant, and increase the operation cost and the infrastructure cost; the oxidation method needs to add chemical agents into the wastewater, although the initial investment is low, the operation cost is high, and secondary pollution can be caused after treatment; the membrane separation method has the problems of membrane pollution, high requirements of partial membrane separation technology on the quality of wastewater and the like.
Disclosure of Invention
The invention aims to provide a sulfur autotrophic denitrification biological filter to solve the problem of poor sewage denitrification effect.
The invention also aims to provide a sewage treatment system based on the sulfur autotrophic denitrification biological filter to solve the problem of high nitrogen load of inlet water of a sewage treatment plant.
The invention also aims to provide a sewage treatment method based on the sulfur autotrophic denitrification biological filter so as to realize the standard discharge of a sewage treatment plant.
One of the objects of the invention is achieved by: a sulfur autotrophic denitrification biological filter comprises a tank body and a filter filler filled in the tank body; the filter filler comprises volcanic rock particles with the particle size of 11-23 mm, limestone particles with the particle size of 15-21 mm, pyrite particles with the particle size of 7-11 mm and zeolite particles with the particle size of 8-17 mm, and the volume ratio of the four filler particles is 1: 3.
Preferably, the lower part of the side wall of the tank body is connected with a water inlet pipe, the upper part of the side wall of the tank body is connected with a water outlet pipe, and the filling amount of the filtering filler is controlled to be lower than the setting height of the water outlet pipe on the top surface of the filler, so that the water outlet is prevented from being blocked, the loss of the filler in the tank body is avoided, and the water outlet is smooth.
Preferably, the water inlet pipe is inserted into the tank body, so that the inlet water is gradually filtered from the bottom of the whole tank body upwards, and a better filtering effect is achieved.
The second purpose of the invention is realized by the following steps: a sewage treatment system comprises a primary sedimentation tank, a biological treatment section, a secondary sedimentation tank, a sludge concentration tank, an anaerobic digestion tank and a nitrification tank, and is characterized by also comprising a sulfur autotrophic denitrification biological filter, wherein the water outlet end of the nitrification tank is connected with the water inlet pipe of the sulfur autotrophic denitrification biological filter, and the water outlet pipe of the sulfur autotrophic denitrification biological filter is connected to the water inlet pipe of the system;
comprises a tank body and a filter filler filled in the tank body; the filter filler comprises volcanic rock particles with the particle size of 11-23 mm, limestone particles with the particle size of 15-21 mm, pyrite particles with the particle size of 7-11 mm and zeolite particles with the particle size of 8-17 mm, and the volume ratio of the four filler particles is 1: 3.
In the sulfur autotrophic denitrification biological filter, nitrate is used as an electron acceptor, and sulfide (such as H)2S,S2O3 2-And S) is oxidized to SO by autotrophic denitrifying bacteria4 2-While the nitrate is reduced to N2The reaction equation is shown as the following formula:
1.06 NO- 3+1.11S+0.3CO2+0.785H2O → 0.06C5H7O2N+0.5N2+1.11SO4 2-+1.16H+ (1)
in addition, the pH value is reduced and the alkalinity is continuously consumed in the sewage treatment process, so limestone is added into the biological filter tank system to maintain the pH value in the sewage treatment process; meanwhile, a part of inorganic carbon source is provided for the sulfur autotrophic denitrification, and the reaction equation is shown as the following formula:
CaCO3 + H+ → Ca2+ + HCO3 - (2)
the sewage treatment system disclosed by the invention is based on the traditional sewage treatment plant, and the digestive juice in the sludge digestion stage is subjected to nitrification and sulfur autotrophic denitrification for denitrification and then flows back to the inlet water of the sewage treatment system, so that the proportion of the inlet water to a nitrogen source is reduced, the carbon-nitrogen ratio is improved, and the denitrification efficiency in the biological treatment stage is further improved; simultaneously treating sludge digestive juice which has high ammonia nitrogen and low carbon nitrogen ratio and contains a large amount of pathogenic microorganisms.
The third purpose of the invention is realized by the following steps: a sewage treatment method based on a sulfur autotrophic denitrification biological filter comprises the following steps:
a. constructing the sewage treatment system, and performing microbial acclimation and biofilm formation treatment on a sulfur autotrophic denitrification biological filter in the sewage treatment system;
b. the sewage enters a primary sedimentation tank of a sewage treatment system through a grid for primary sedimentation separation;
c. the effluent of the primary sedimentation tank enters a biological treatment section for biological treatment;
d. the effluent of the biological treatment section enters a secondary sedimentation tank for secondary sedimentation separation;
e. one part of sludge in the secondary sedimentation tank flows back to the anoxic tank of the biological treatment section, the other part of sludge enters the sludge concentration tank and is concentrated by gravity, and the sludge reflux ratio is 25-100%;
f. the sludge in the sludge concentration tank enters an anaerobic digestion tank for medium-temperature fermentation;
h. the digestive fluid in the anaerobic digestion tank automatically flows into the nitrification tank through gravity, and the ammonia nitrogen component in the sludge digestive fluid is oxidized into nitrate nitrogen;
i. the effluent of the nitrification tank enters the sulfur autotrophic denitrification biological filter from the bottom, nitrate is removed through sulfur autotrophic denitrification bacteria attached to zeolite and volcanic rock, and the treated water flows out from the top of the sulfur autotrophic denitrification biological filter;
j. the effluent of the sulfur autotrophic denitrification biological filter flows back to a water inlet pipeline of the sewage treatment system.
The microorganism domestication and biofilm formation treatment mode in the step a is that activated sludge of a sewage treatment plant is used as inoculated sludge, nutrient solution with a carbon-nitrogen ratio of 400: 5 is introduced at room temperature environment, the sulfur autotrophic denitrification biological filter is domesticated and biofilm formation is carried out, after the concentration of effluent nitrate nitrogen is stable, the carbon source proportion is reduced, and after the effluent nitrate nitrogen is stabilized again, the carbon source proportion is continuously reduced; the above steps are circulated until all carbon sources are eliminated; completing film formation when the concentration of the nitrate and the nitrogen in the effluent is stable and reaches the standard; during the period, the effluent of the sewage treatment system flows back completely until the film formation is finished.
The treatment time of microbial acclimation and biofilm formation treatment of the sulfur autotrophic denitrification biological filter is 35-50 d, and the water power stays for 18h after biofilm formation is completed.
On the basis of the treatment process of the traditional sewage treatment plant, the invention adds a sulfur autotrophic denitrification biological filter behind the sludge anaerobic digestion tank in the sludge treatment stage through process improvement, can further reduce nitrogen load under the condition of ensuring the supply of influent carbon source, and has important environmental and ecological significance for the treatment of domestic sewage in China.
The sewage treatment method of the invention utilizes the sulfur autotrophic denitrification technology to convert nitrogen in sludge digestive juice into N2And (4) removing, thereby reducing the water inlet nitrogen load of a sewage treatment plant: in the sulfur autotrophic denitrification biological filter, nitrate is used as an electron acceptor, and sulfide (such as H)2S,S2O3 2-And S) is oxidized to SO by autotrophic denitrifying bacteria4 2-While the nitrate is reduced to N2(ii) a In addition, the process can cause the reduction of Ph and the consumption of alkalinity, so limestone is added into the biological filter tank system to maintain the pH, and a part of inorganic carbon source is provided for the sulfur autotrophic denitrification; furthermore volcanic rocks and zeolites are commonly used as packing materials, which can provide more space for microorganisms on the surface and induce facultative anaerobic zones relative to modified biosuspension fillers.
Experiments prove that the average removal rate of the sulfur autotrophic denitrification biological filter on the total nitrogen reaches 82 percent when the hydraulic retention time is 18 hours. At 20X 104 m3The contribution of the sulfur autotrophic denitrification biofilter to the C/N improvement of the sewage treatment plant is calculated by taking the municipal sewage plant of/d as an example. The flow of the sludge digestive juice is calculated by 1 percent of the total water volume of the municipal sewage plant, namely the water volume of the sludge digestive juice is 2000m3D, NH of sludge digestion liquid4 +-the nitrogen load of the sludge digest is 2000Kg/d =2T/d when the N concentration is 1000mg/L and the total nitrogen TN of the raw water of the municipal sewage plant is 50 mg/L; the raw water nitrogen load of the urban sewage plant is 50g/m3×20×104m3D =10000 Kg/d = 10T/d. The sludge digest accounted for 16.7% of the nitrogen load of the municipal sewage plant, which was 20% of the nitrogen load of the raw water. The sulfur autotrophic denitrification biological filter can remove 82% of total nitrogen in sludge digestive juice, only consumes about 10% of carbon source, and obviously improves the C/N ratio of inlet water.
Drawings
FIG. 1 is a flow chart of the sewage treatment process of the present invention.
FIG. 2 is a schematic structural diagram of the sulfur autotrophic denitrification biological filter.
Detailed Description
Example 1:
as shown in figure 2, the sulfur autotrophic denitrification biological filter comprises a tank body 1 and a filter filler 2 filled in the tank body; the filter filler 2 comprises volcanic rock particles with the particle size of 11-23 mm, limestone particles with the particle size of 15-21 mm, pyrite particles with the particle size of 7-11 mm and zeolite particles with the particle size of 8-17 mm, and the volume ratio of the four filler particles is 1: 3. The lower part of the side wall of the tank body 1 is connected with a water inlet pipe 3, and the water inlet pipe is inserted into the tank body. The upper part of the side wall of the tank body 1 is connected with a water outlet pipe 4, and the filling amount of the filter filler 2 in the tank body 1 is controlled to be lower than the setting height of the water outlet pipe 4 on the top surface of the filler.
Example 2:
as shown in figure 1, the sewage treatment system comprises a primary sedimentation tank, a biological treatment section, a secondary sedimentation tank, a sludge concentration tank, an anaerobic digestion tank, a nitrification tank and a sulfur autotrophic denitrification biological filter, wherein the water outlet end of the nitrification tank is connected with the water inlet pipe of the sulfur autotrophic denitrification biological filter, and the water outlet pipe of the sulfur autotrophic denitrification biological filter is connected to the water inlet pipe of the system. The biological treatment section in the sewage treatment system comprises an anaerobic tank, an anoxic tank and an aerobic tank.
As shown in FIG. 2, the sulfur autotrophic denitrification biological filter in the sewage treatment system of the present invention comprises a tank body 1 and a filter filler 2 filled in the tank body; the filter filler 2 comprises volcanic rock particles with the particle size of 11-23 mm, limestone particles with the particle size of 15-21 mm, pyrite particles with the particle size of 7-11 mm and zeolite particles with the particle size of 8-17 mm, and the volume ratio of the four filler particles is 1: 3. The lower part of the side wall of a tank body 1 of the sulfur autotrophic denitrification biological filter is connected with a water inlet pipe 3, and the water inlet pipe is inserted into the tank body. The upper part of the side wall of the tank body 1 is connected with a water outlet pipe 4, and the filling amount of the filter filler 2 in the tank body 1 is controlled to be lower than the setting height of the water outlet pipe 4 on the top surface of the filler.
The sewage treatment method based on the sulfur autotrophic denitrification biological filter comprises the following steps:
1. constructing the sewage treatment system in the embodiment 2, and performing microbial acclimation and biofilm formation treatment on a sulfur autotrophic denitrification biological filter in the sewage treatment system;
2. the sewage enters a primary sedimentation tank of a sewage treatment system through a grid for primary sedimentation separation;
3. the effluent of the primary sedimentation tank enters a biological treatment section for biological treatment;
4. the effluent of the biological treatment section enters a secondary sedimentation tank for secondary sedimentation separation;
5. one part of sludge in the secondary sedimentation tank flows back to the anoxic tank of the biological treatment section, the other part of sludge enters the sludge concentration tank and is concentrated by gravity, and the sludge reflux ratio is 25-100%;
6. the sludge in the sludge concentration tank enters an anaerobic digestion tank for medium-temperature fermentation;
7. the digestive fluid in the anaerobic digestion tank automatically flows into the nitrification tank through gravity, and the ammonia nitrogen component in the sludge digestive fluid is oxidized into nitrate nitrogen;
8. the effluent of the nitrification tank enters the sulfur autotrophic denitrification biological filter from the bottom, nitrate is removed through sulfur autotrophic denitrification bacteria attached to zeolite and volcanic rock, and the treated water flows out from the top of the sulfur autotrophic denitrification biological filter;
9. the effluent of the sulfur autotrophic denitrification biological filter flows back to a water inlet pipeline of the sewage treatment system.
The microorganism domestication and biofilm formation treatment mode in the step 1 is that activated sludge of a sewage treatment plant is used as inoculated sludge, nutrient solution with the carbon-nitrogen ratio of 400: 5 is introduced at room temperature, the sulfur autotrophic denitrification biological filter is domesticated and biofilm formation is carried out, after the concentration of effluent nitrate nitrogen is stable, the carbon source proportion is reduced, and after the effluent nitrate nitrogen is stabilized again, the carbon source proportion is continuously reduced; the above steps are circulated until all carbon sources are eliminated; completing film formation when the concentration of the nitrate and the nitrogen in the effluent is stable and reaches the standard; during the period, the effluent of the sewage treatment system flows back completely until the film formation is finished. The treatment time of microbial acclimation and biofilm formation treatment of the sulfur autotrophic denitrification biological filter is 35-50 d, and the water power stays for 18h after biofilm formation is completed.
Application example 1 of the present invention: the municipal wastewater of the actual sewage treatment plant is treated by using the operation mode. The biofilm formation stage of 41 days is carried out before the sulfur autotrophic denitrification biological filter is formally operated. In order to verify the best efficiency of the sulfur autotrophic denitrification biological filter in winter, the formal operation of the sulfur autotrophic denitrification biological filter is divided into three stages, and each stage is operated for 40 days. Each stage is not temperature controlled, i.e. the water temperature changes following the local weather changes. The hydraulic retention time of the first stage is 6 hours, the hydraulic retention time of the second stage is 12 hours, and the hydraulic retention time of the third stage is 18 hours.
The influent water of the sulfur autotrophic denitrification biological filter is tail water of a municipal sewage treatment plant, and the influent water quality characteristics are shown in table 1.
Table 1: quality of inlet water
When the sewage treatment system operates stably, the operation result is as follows: first stage on TN and NO3The average removal efficiency of N is stable, 71.2% and 73.4%, respectively; second stage on TN and NO3The average removal of-N drops to 52.3% and 50.6%, respectively; third stage on TN and NO3The average removal of-N is optimal, 82.6% and 86.1%, respectively. NH of inlet and outlet water during operation4 +The concentration of N is stabilized to be about 0.7 mg/L; the average COD concentration of the inlet water is 24.6mg/L, and the average COD concentration of the outlet water is 21.3mg/L, which is slightly reduced. Therefore, the sewage treatment method can obviously reduce the nitrogen load in water, the removal rate reaches 80 percent, and the carbon source supply in water is not influenced.
Application example 2 of the present invention: the tail water of the simulated urban domestic sewage treatment plant is treated by running the device and the application example 1 of the invention under the same conditions, and the inlet water quality characteristics are shown in the table 2.
Table 2: quality of inlet water
When the sewage treatment system operates stably, the operation result is as follows: first stage on TN and NO3The average removal efficiency of N is stable, 80.2% and 83.3%, respectively; second stage on TN and NO3The average removal of-N decreased to 53.9% and 51.5%, respectively; third stage on TN and NO3The average removal rate of-N reaches the optimum score87.4% and 91.2% respectively. NH of inlet and outlet water during operation4 +The concentration of N is stabilized to be about 0.85 mg/L; the average COD concentration of the inlet water is 32mg/L, and the average COD concentration of the outlet water is 30.4mg/L, which is slightly reduced. The method can obviously reduce the nitrogen load in the water, the removal rate reaches 87%, and the carbon source supply in the water is not influenced.