CN116854277A - Denitrification and dephosphorization system and method - Google Patents

Abstract

The application relates to a nitrogen and phosphorus removal system and a method, wherein the nitrogen and phosphorus removal system comprises a water inlet, a multi-stage AO system, a first sedimentation tank and a water outlet which are connected in sequence; the multi-stage AO system comprises an anaerobic tank, two or more anoxic tanks and two or more aerobic tanks, wherein the anaerobic tank is connected with the water inlet; the system also comprises a fermentation tank, wherein an inlet of the fermentation tank is connected with an outlet of the first sedimentation tank, and an outlet of the fermentation tank is connected with the anaerobic tank. The fermentation tank carries out anaerobic fermentation on the sludge precipitated in the multi-stage AO system, and a large amount of organic matters in the sludge are converted into small molecular carbon sources or biogas so as to maximize the sludge resource. The fermentation vat provides a system of internal carbon sources, which greatly reduces the cost of applying exogenous carbon. The internal carbon source provided in the fermentation tank is returned to the anaerobic tank, so that the utilization rate of endogenous carbon can be increased to the greatest extent, the utilization rate of sludge is further improved, and the denitrification efficiency of the system is greatly improved.

Description

A nitrogen and phosphorus removal system and method

Technical field

The invention relates to the field of sewage treatment, and in particular to a nitrogen and phosphorus removal system and method.

Background technique

In recent years, with the development of industrial production and the improvement of people's living standards, the total amount of industrial sewage and urban domestic sewage has increased at an alarming rate. This sewage has or is polluting the rivers, rivers and lakes on which human beings depend for survival. , constituting one of the reasons that threatens the human living environment. As water pollution continues to intensify, the sewage treatment and regeneration industry has received unprecedented attention. The sewage treatment industry has great development potential.

The AO process is also called anaerobic and aerobic processes. In the anaerobic section, anaerobic bacteria hydrolyze and acidify starch and carbohydrate soluble organic matter in domestic sewage, degrading large molecular organic matter into small molecular organic matter, thus improving subsequent aerobic treatment capabilities. The AO process is widely used to treat various types of sewage. This technology is an efficient sewage treatment technology that combines biofilm and traditional sludge methods.

There is a patent related to sewage treatment equipment in the existing AO process. This patent integrates the anoxic zone and the aerobic zone into a treatment unit, arranges the aeration pipes in the treatment unit regionally, and controls it through solenoid valves. The oxygen supply intervals run alternately at different times. Although this patent has a mixed liquid reflux device, the single-stage AO process wastewater reaction is not complete, which will lead to a significant decrease in denitrification efficiency during operation and later stages. There is a lack of carbon source in another sewage treatment device using the AO process, which will make the treatment efficiency of the device unable to meet expectations, and if an external carbon source is added, the cost will increase significantly.

Sewage treatment plants using biological phosphorus removal technology generally have the problem of insufficient carbon sources in the incoming water, and adding additional carbon sources will greatly increase the cost of sewage treatment. Therefore, it is urgent to find an effective sewage treatment method to solve the increasingly serious sewage treatment problem; and to reduce external carbon sources, thereby reducing the cost of sewage treatment.

Contents of the invention

The purpose of the present invention is to provide a denitrification and phosphorus removal system that solves the problem of excessively high sewage treatment costs caused by external carbon sources proposed in the above-mentioned background technology. It can also promote the treatment efficiency of the multi-stage AO process and effectively improve the quality of life. The water quality of sewage has the advantages of simple process, low treatment cost and convenient operation.

In order to achieve the above objects, the present invention provides the following technical solutions:

One aspect of the present invention proposes a denitrification and phosphorus removal system, including a water inlet, a multi-stage AO system, a first sedimentation tank and a water outlet connected in sequence; the multi-stage AO system includes an anaerobic tank connected to the water inlet, two One or more anoxic tanks and two or more aerobic tanks; the system also includes a fermentation tank, the inlet of the fermentation tank is connected to the outlet of the first sedimentation tank, and the outlet of the fermentation tank is connected to the anaerobic tank.

The multi-stage AO system is the main reaction area for sewage treatment in this plan, in which the sewage can fully complete the anaerobic-anoxic-aerobic reaction. The sewage treatment process is: first, a large amount of sewage enters the anaerobic tank, where a large number of microorganisms such as phosphorus-accumulating bacteria (PAOs) with the ability to accumulate phosphorus release phosphorus, and then the sewage undergoes ammoniation and denitrification reactions; then , the sewage treated in the anaerobic tank flows into the anoxic tank, where the carbon source in the sewage is used for denitrification, and the nitrite and nitrate in the sewage are reduced to nitrogen for denitrification; subsequently, The sewage treated in the anoxic tank flows into the aerobic tank, where the nitrification reaction occurs. At the same time, the microorganisms in the sludge absorb phosphorus from the sewage and enrich the phosphorus in the microorganisms. A large amount of phosphorus is stored in the sludge. . After the sewage passes through the multi-stage AO reaction tank, on the basis of ensuring that the phosphate-accumulating bacteria fully release phosphorus, the carbon source in the incoming water can be prioritized for denitrification, and nitrification and denitrification reactions can be continuously carried out, thereby effectively reducing nitrogen and phosphorus in the water. contaminants.

The fermentation tank carries out anaerobic fermentation of the sludge precipitated in the multi-stage AO system, and uses a large amount of organic matter in the sludge to convert into small molecule carbon sources or biogas to maximize the resource utilization of the sludge. The fermentation tank provides an internal carbon source for the system, which greatly reduces the cost of applying exogenous carbon. The connection between the fermentation tank and the anaerobic tank can return the internal carbon source provided in the fermentation tank to the multi-stage AO system, which can maximize the utilization of endogenous carbon and promote the treatment efficiency of the multi-stage AO system. Moreover, this solution also has the advantages of simple process, low processing cost and easy operation.

Further, the system also includes a coagulation tank, which is installed between the fermentation tank and the anaerobic tank. The coagulation tank coagulates and precipitates the mud-water mixture in the fermentation tank, causing the particles in the mud water to gather together and form larger colloids; the coagulation tank speeds up the coagulation and precipitation of the mud-water mixture and improves the efficiency of mud-water separation in sewage treatment. .

Furthermore, activated carbon is added to the coagulation tank. By adding activated carbon to the coagulation tank, the particles that are difficult to settle in the sewage can aggregate with each other to form colloids, and then combine with impurities in the water to form larger flocs. Relying on the strong adsorption force of the flocs, it can not only absorb suspended solids, but also Adsorbs some bacteria and dissolved substances; the addition of activated carbon increases the settling capacity of the coagulation tank.

Further, the system also includes a second sedimentation tank, which is installed between the coagulation tank and the anaerobic tank. The second sedimentation tank can effectively separate mud and water, and the treated water will be discharged directly after reaching the standard; the sewage that does not meet the standard is discharged back to the anaerobic tank to continue reaction, and the separated phosphorus-rich remaining sludge can be recycled and reused. Improve the utilization rate of excess sludge and achieve reduction of excess sludge.

Further, there are a plurality of spaced inclined plates at the lower part of the first sedimentation tank and/or the second sedimentation tank. The first sedimentation tank and the second sedimentation tank can effectively separate mud and water, thereby improving the treatment efficiency of the multi-stage AO process and conducive to improving the water quality of domestic sewage.

Further, the outlet of the second sedimentation tank is connected to the inlet of the fermentation tank through a reflux pump. After the sludge is returned to the fermentation tank for reaction, it can effectively reduce the production cost of external carbon sources and make up for the lack of competition in carbon sources for nitrogen and phosphorus removal.

Further, the outlet of the second sedimentation tank is connected to the inlet of the coagulation tank through a return pump. The remaining sludge settled in the second sedimentation tank flows back to the coagulation tank for further sedimentation, which reduces the content of remaining sludge and improves the efficiency of sludge settling.

Further, the outlet of the first sedimentation tank is connected to the inlet of the anaerobic tank through a return pump. The return of sludge to the anaerobic tank can increase the sludge concentration at the front end of the process, improve the utilization rate of remaining sludge, and reduce the production of remaining sludge.

Further, the multi-stage AO system includes an anaerobic pool, a first anoxic pool, a first aerobic pool, a second anoxic pool and a second aerobic pool connected in sequence. The sewage from the first aerobic pool enters the second anoxic pool and the second aerobic pool to complete the second nitrification, denitrification, denitrification, and phosphorus removal reactions, and performs the second treatment of the water body, which can effectively reduce the concentration of water in the water. nitrogen and phosphorus pollutants, and this construction is cost-effective, efficient and economical.

Further, the outlet of the first aerobic pool is connected to the inlet of the first anoxic pool through a backflow pump, and the outlet of the second aerobic pool is connected to the inlet of the first anoxic pool and/or the second anoxic pool through a backflow pump. . The mixed liquid in the first section flows back from the end of the first aerobic tank to the head end of the first anoxic tank, and the mixed liquid in the second section flows back from the end of the second aerobic tank to the first anoxic tank and/or the second anoxic tank. The head end of the oxygen pool; the sewage in the second aerobic pool can choose to flow back to the first anoxic pool or the second anoxic pool as the concentration of the test sample changes, or to flow into the first anoxic pool 2 and the second anoxic pool at the same time. In the pool 4; when the return flow of sewage is large, the sewage flows into the first anoxic pool 2 and the second anoxic pool 4 at the same time, which helps to improve the efficiency of sewage treatment and reduces the number of wastewater in the first anoxic pool 2 and the second anoxic pool 4. 2. The workload in the anoxic pool 4; such a multi-stage reflux device can save the time of denitrification reflux and help improve the effect of denitrification and phosphorus removal, thereby achieving complete denitrification.

The second aspect of the present invention proposes a method for denitrification and phosphorus removal, which sequentially passes the sewage through the water inlet, the multi-stage AO system and the first sedimentation tank, and outputs it through the water outlet, and the sedimentation sludge generated in the first sedimentation tank is Send it to the fermentation tank; and transfer the small molecule carbon source and biogas converted from the settled sludge in the fermentation tank to the anaerobic tank in the multi-stage AO system. In this method, the fermentation tank can produce small molecule carbon sources, thereby reducing the cost of adding external carbon sources, which is economical and environmentally friendly; moreover, this solution effectively reduces the volume of remaining sludge and achieves maximum wastewater treatment. harmless treatment.

The invention has the following beneficial effects:

The fermentation tank carries out anaerobic fermentation of the sludge precipitated in the multi-stage AO system, and uses a large amount of organic matter in the sludge to convert into small molecule carbon sources or biogas to maximize the resource utilization of the sludge. The fermentation tank provides an internal carbon source for the system, which greatly reduces the cost of applying exogenous carbon. In addition, a multiple return flow system is set up, which can not only improve the reprocessing of sewage, but also improve the reuse rate of sludge. Returning the internal carbon source provided in the fermentation tank to the anaerobic tank can maximize the utilization of endogenous carbon, thereby further improving the utilization of sludge and greatly improving the denitrification efficiency of the system. The multiple backflow system can not only improve the reprocessing of sewage, but also improve the reuse rate of sludge. By treating domestic sewage, the damage caused by domestic sewage to the surrounding ecological environment can be effectively reduced, which has good social, economic and environmental benefits.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of a nitrogen and phosphorus removal system of the present invention;

Figure 2 is a diagram showing the changes in ammonia nitrogen concentration in the anaerobic pool and the aerobic pool with operating time during the operation of a nitrogen and phosphorus removal system;

Figure 3 is a graph showing the changes in nitrate nitrogen concentration in the anaerobic pool and the aerobic pool with operating time during the operation of a nitrogen and phosphorus removal system;

Figure 4 is a graph showing the changes in nitrite nitrogen concentration in the anaerobic pool and the aerobic pool with operating time during the operation of a nitrogen and phosphorus removal system;

Figure 5 is a diagram showing the changes in phosphate concentration in the anaerobic pool and the aerobic pool with operating time during the operation of a nitrogen and phosphorus removal system;

Figure 6 is a graph showing the changes in COD concentration in the anaerobic pool and the aerobic pool with operating time during the operation of a nitrogen and phosphorus removal system.

The reference numbers are:

1. Anaerobic tank; 2. First anoxic tank; 3. First aerobic tank; 4. Second anoxic tank; 5. Second aerobic tank; 6. First sedimentation tank; 7. Fermentation tank; 8. Coagulation tank; 9. Second sedimentation tank; 101. Sewage return device; 102 first sludge return device; 103 second sludge return device.

Detailed ways

Excessive presence of nitrogen and phosphorus will lead to eutrophication of water bodies and loss of diversity. Therefore, limiting nitrogen and phosphorus emissions is of great significance to control eutrophication of water bodies. Most existing AO process devices can only process small amounts of sewage; moreover, an external carbon source is required to improve system efficiency during operation. Although it can effectively remove nitrogen and phosphorus, as the operation time increases, the operation cost also increases. It shows a linear growth, so the conventional AO process requires an external carbon source, resulting in high costs.

In order to solve the above problems, this application provides a nitrogen and phosphorus removal system and method, which uses a side-flow fermentation system to provide carbon sources in the system, greatly reducing operating costs, and at the same time, it can also promote the processing efficiency of the multi-stage AO process, effectively It improves the water quality of domestic sewage and has the advantages of simple process, low treatment cost and convenient operation.

The technical solution of this patent will be described in further detail below in conjunction with specific embodiments. It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanation of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meanings commonly understood by one of ordinary skill in the art to which this application belongs.

Example 1:

In view of the shortcomings of external carbon sources in the existing AO process, the purpose of the present invention is to develop a process technology that can provide internal carbon sources and effectively denitrify and remove phosphorus in sewage, thereby reducing the concentration of sewage pollutants, and thereby effectively Reduce costs while improving the quality of domestic sewage. This embodiment provides a nitrogen and phosphorus removal system.

Please refer to Figure 1, which is a schematic diagram of a nitrogen and phosphorus removal system. The first part of the nitrogen and phosphorus removal system is a multi-stage AO system, including an anaerobic pool 1, a first anoxic pool 2, a first aerobic pool 3, a second anoxic pool 4 and a second aerobic pool 5 arranged in series. . The main purpose of the multi-stage AO system is to set up a multi-stage AO process so that the sewage can fully complete the anaerobic-anoxic-aerobic reaction. A large amount of sewage enters the anaerobic tank 1. A large number of microorganisms such as phosphorus-accumulating bacteria release phosphorus in the anaerobic tank 1, and then ammonia and denitrification occur in the sewage; the initially treated sewage flows into the first anoxic tank 2, In the first anoxic tank 2, the sewage uses carbon sources to perform denitrification, reducing nitrite and nitrate to nitrogen for denitrification; then, the treated sewage flows into the first aerobic tank 3, where nitrification is performed reaction, at the same time, the microorganisms in the sludge absorb phosphorus from the sewage, thereby producing phosphorus-rich sludge; then, the sewage enters the second anoxic tank 4 and the second aerobic tank 5 for further nitrification, denitrification, denitrification and removal. Phosphorus reaction achieves efficient nitrogen and phosphorus removal; and this system has high treatment efficiency and can be applied to large-discharge sewage treatment. After the sewage passes through the multi-stage AO reaction tank, on the basis of ensuring that the phosphorus-accumulating bacteria can fully release phosphorus, the carbon source in the incoming water can be used for denitrification, and the nitrification and denitrification reactions can be continuously carried out, thereby effectively reducing the phosphorus content in the water. Nitrogen and phosphorus pollutants. The connection between the fermentation tank and the anaerobic tank can return the internal carbon source provided in the fermentation tank to the multi-stage AO system, which can maximize the utilization of endogenous carbon and promote the treatment efficiency of the multi-stage AO system.

The second part of the nitrogen and phosphorus removal system is the side-flow fermentation system, which includes a first sedimentation tank 6, a fermentation tank 7, a coagulation tank 8 and a second sedimentation tank 9. The inlet of the first sedimentation tank 6 is connected to the outlet of the second aerobic tank 5, and the outlet of the first sedimentation tank 6 is connected to the inlet of the fermentation tank 7; the inlet of the coagulation tank 8 is connected to the outlet of the fermentation tank 7, The outlet of the coagulation tank 8 is connected with the inlet of the second settling tank 9 . The side-flow fermentation system is the core system of this technology; its main purpose is to anaerobically ferment the sludge precipitated by the multi-stage AO system, and use the large amount of organic matter in the sludge to convert into small molecule carbon sources or biogas to maximize the sludge Resource utilization provides sufficient carbon source for system reactions, thereby reducing process costs. The first sedimentation tank 6 performs large-scale mud and water separation. The water after reaching the standard is discharged from the outlet of the first sedimentation tank 6, and part of the remaining sludge is also discharged from the outlet of the first sedimentation tank 6. Part of the remaining sludge is transported to the side stream. Other parts of the fermentation system are further utilized; the first inclined plate sedimentation tank 6 improves the treatment efficiency of the multi-stage AO process, thereby effectively improving the water quality of domestic sewage, and has the advantages of simple process, low treatment cost and easy operation. The fermentation tank 7 will perform anaerobic fermentation on the sludge obtained from the sewage treated by the multi-stage AO system, thereby converting a large amount of organic matter in the sludge into a small molecule carbon source or biogas, thereby producing an endogenous carbon source, which will Sludge resource disposal. Returning the internal carbon source provided in the fermentation tank to the anaerobic tank can maximize the utilization of endogenous carbon, thereby further improving the utilization of sludge and greatly improving the denitrification efficiency of the system. The coagulation tank 8 is installed behind the fermentation tank 7 to coagulate and precipitate the mud-water mixture in the fermentation tank 7 so that the particles in the mud water gather together and form larger colloids. The coagulation tank 8 speeds up the coagulation and sedimentation of the mud-water mixture and improves the efficiency of mud-water separation in sewage treatment. The second sedimentation tank 9 can effectively separate mud and water, and the treated water will be discharged directly after reaching the standard; the sewage that does not meet the standard is discharged back to the anaerobic tank 1 to continue reaction, and the separated phosphorus-rich remaining sludge can be recycled and reused. , thereby improving the utilization rate of excess sludge and achieving reduction of excess sludge.

The side-flow fermentation system performs anaerobic hydrolysis and fermentation of partially returned activated sludge, and provides the produced dissolved chemical oxygen demand (SCOD) and volatile fatty acids (VFAs) to the phosphorus release process of the phosphorus-accumulating bacteria in the mainstream anaerobic zone. . In the side-flow fermentation system, the phosphorus-accumulating bacteria Tetrasphaera and Accumulibacter have a symbiotic synergistic promotion effect. Tetrasphaera hydrolyzes slowly degradable organic matter in the sewage through hydrolysis and fermentation in the deep anaerobic environment of the fermentation tank, producing VFAs and releasing phosphoric acid. Salts, VFAs produced during hydrolysis are absorbed and stored by Accumulibacter and release phosphorus at the same time.

The side-flow fermentation system can achieve enhanced biological phosphorus removal from low C/N ratio sewage, greatly reducing the dosage of external carbon sources and chemical phosphorus removal agents. And the acid production process is completed, that is, VFAs are produced, and methane and CO ₂ are also produced. The substances in the sludge are used to provide carbon sources for the system, allowing efficient utilization of sludge and reducing the cost of external carbon sources in the multi-stage AO process. cost.

The third part of the nitrogen and phosphorus removal system is the return system, which mainly includes a sewage return system and two sludge return systems. Its main purpose is to improve the mud water reuse rate of the system to achieve resource recycling. The sewage return system 101 connects the outlet of the first aerobic pool 3 with the inlet of the first anoxic pool 2, and the first mixed liquid flows back from the end of the first aerobic pool 3 to the head end of the first anoxic pool 2 , which helps to improve the effect of nitrogen and phosphorus removal; the outlet of the second aerobic pool 5 is connected to the inlet of the first anoxic pool 2 and the second anoxic pool 4, and the second mixed liquid is supplied from the second aerobic pool 5 returns to the first end of the first anoxic pool 2 and/or the second anoxic pool 4; the sewage in the second aerobic pool 5 chooses to flow back to the first anoxic pool 2 or the second anoxic pool 5 as the concentration of the test sample changes. The second anoxic pool 4, or flows into the first anoxic pool 2 and the second anoxic pool 4 at the same time; when the return flow of sewage is large, the sewage flows into the first anoxic pool 2 and the second anoxic pool 4 at the same time. It helps to improve the efficiency of sewage treatment and reduces the workload in the first anoxic tank 2 and the second anoxic tank 4; such a multi-stage reflux device can save the time of denitrification reflux and help improve the denitrification reflux. Nitrogen and phosphorus removal, thereby achieving complete nitrogen removal. The return water can dilute, dilute, adjust the concentration and pH of the liquid in the first anoxic pool 2 and the second anoxic pool 4, and increase the gas production rate. The first sludge return device 102 connects the outlet of the second sedimentation tank 9 with the inlet of the fermentation tank 7. After the sludge is returned to the fermentation tank 7 for reaction, it can effectively reduce the production cost of external carbon sources and slow down the denitrification and phosphorus removal. Lack of competition for carbon sources. The second sludge return device 103 connects the outlet of the second sedimentation tank 9 and the inlet of the coagulation tank 8 . The remaining sludge settled in the second sedimentation tank 9 flows back to the coagulation tank 8 for further sedimentation, which reduces the content of the remaining sludge and improves the efficiency of sludge settlement; the outlet of the first sedimentation tank 6 is connected to the anaerobic tank 1 is connected to the entrance. Returning the sludge to the anaerobic tank 1 can increase the sludge concentration at the front end of the process, improve the utilization rate of the remaining sludge, and reduce the output of the remaining sludge.

The fermentation tank carries out anaerobic fermentation of the sludge precipitated in the multi-stage AO system, and uses a large amount of organic matter in the sludge to convert into small molecule carbon sources or biogas to maximize the resource utilization of the sludge. The fermentation tank provides an internal carbon source for the system, which greatly reduces the cost of applying exogenous carbon. Returning the internal carbon source provided in the fermentation tank to the anaerobic tank allows the internal carbon source provided in the fermentation tank to flow back into the multi-stage AO system, which can maximize the utilization rate of endogenous carbon and further improve the pollution efficiency. The utilization rate of mud can greatly improve the denitrification efficiency of the system. Moreover, this solution also has the advantages of simple process, low processing cost and easy operation.

Example 2:

In this embodiment, a nitrogen and phosphorus removal system is optimized to further improve the system's phosphorus removal efficiency.

A side-flow phosphorus removal tank is set up between the anaerobic tank 1 and the first anoxic tank 2, and iron salts and aluminum salts are added to the phosphorus removal tank, thereby effectively improving the phosphorus removal efficiency of the system. By adding metal salts to the sewage in the phosphorus removal tank, the metal salts and the soluble phosphates present in the sewage form insoluble granular phosphate precipitates, thereby achieving sewage phosphorus removal. Iron is a transition metal with very diverse chemical properties. Therefore, in addition to chemical precipitation and chemical complexation in the iron salt-assisted biological phosphorus removal process system, it can also be dissolved in water through ion exchange and the precipitation of iron phosphate salt itself. Phosphorus undergoes adsorption to remove phosphate. The principle of phosphorus removal by aluminum salt is that when aluminum salt is dispersed in water, on the one hand, Al ions react with phosphate, on the other hand, Al ions are first hydrolyzed to form mononuclear complexes Al(OH) ²⁺ and AlO ^2- , etc. Mononuclear complexes are further condensed through collision to form a series of multinuclear complexes. These aluminum multinuclear complexes often have high positive charges and specific surface areas, and can quickly absorb negatively charged impurities in water and neutralize them. Colloidal charge compresses the electric double layer and reduces the colloidal potential, which promotes the rapid destabilization, agglomeration and precipitation of colloids and suspended solids, showing good phosphorus removal effect. Aluminum salts and iron salts as side-stream phosphorus removal agents can increase the phosphorus release of the system, thereby maximizing the recovery and utilization of phosphorus resources and reducing the time cost of sewage treatment.

In a further embodiment, activated carbon is added to the coagulation tank 8 so that particles that are difficult to settle in the sewage can aggregate with each other to form colloids, and then combine with impurities in the water to form larger flocs, relying on the strong adsorption of the flocs. It can not only absorb suspended solids, but also absorb some bacteria and dissolved substances; the addition of activated carbon increases the settling capacity of the coagulation tank 8.

Example 3:

In this embodiment, various experiments are used to verify the various advantages of the nitrogen and phosphorus removal method provided by this solution in the sewage treatment process.

Total nitrogen, referred to as TN, refers to the total amount of various forms of nitrogen (ammonia nitrogen, nitrate nitrogen, nitrite nitrogen and various organic nitrogen) in the water body. It reflects the degree of pollution and eutrophication of the water body. one of the important indicators.

Ammonia nitrogen refers to nitrogen that exists in the form of free ammonia and ammonium ions in water. The source of ammonia nitrogen in water is mainly produced by the decomposition of nitrogen-containing organic matter in domestic sewage by microorganisms. Some industrial wastewater also contains ammonia nitrogen. Ammonia nitrogen is an essential element for plant growth. When there is too much ammonia nitrogen, it will stimulate the reproduction of algae and other plankton, leading to eutrophication of water bodies. Eutrophic water bodies will reduce the amount of dissolved oxygen in the water, thus affecting the respiration and survival of aquatic organisms. Secondly, ammonia nitrogen can directly poison aquatic organisms, such as fish, crabs, etc. When the ammonia nitrogen content is too high, it will cause the death of fish and crabs, seriously affecting the ecological balance of the water body.

Please refer to Figure 2, which is a graph showing changes in ammonia nitrogen concentration with operating time in the anaerobic pool 1 and the aerobic pool 5 during the operation of the present invention. The abscissa is time, the ordinate is ammonia nitrogen concentration, and the line segment containing squares indicates anaerobic The changing trend of ammonia nitrogen concentration in Pool 1. The circular line segment shows the changing trend of ammonia nitrogen concentration in the second aerobic pool 5. Figure 2 shows that after the operation of the denitrification and phosphorus removal system, the ammonia nitrogen concentration in the second aerobic pool 5 It started to decrease from a low level, and the ammonia nitrogen concentration in the second aerobic tank 5 approached 0 after the sixth day; the ammonia nitrogen concentration in the anaerobic tank 1 started to decrease from a high level, and the downward trend was relatively stable during the operation. The above results show that the anaerobic pool and aerobic pool in this system can continuously reduce the ammonia nitrogen concentration in sewage and have a good denitrification effect.

Nitrate in water is the most stable nitrogen compound among various forms of nitrogen-containing compounds under aerobic conditions. It is usually used to represent the decomposition products of the final stage of inorganicization of nitrogen-containing organic matter. When the water sample contains only nitrate and no other organic or inorganic nitrogen compounds, the organic nitrogen compounds are considered to be completely decomposed. If the water contains a large amount of nitrate and other nitrogen-containing compounds, it means that pollutants have entered the water system and the "self-purification" effect of the water is still in progress.

Figure 3 is a diagram showing changes in nitrate nitrogen concentration with operating time in the anaerobic pool 1 and the second aerobic pool 5 during the operation of the present invention. The abscissa is time, the ordinate is nitrate nitrogen concentration, and the line segments containing squares are displayed. The changing trend of nitrate nitrogen concentration in anaerobic tank 1. The circular line segment shows the changing trend of nitrate nitrogen concentration in the second aerobic tank 5. Figure 3 shows that after the operation of the nitrogen and phosphorus removal system, the second best The nitrate nitrogen concentration in the oxygen tank 5 is maintained at a low level; the nitrate nitrogen concentration in the anaerobic tank 1 starts to decrease from a high level and gradually decreases during operation. The above results show that the anaerobic pool and aerobic pool in this system can continuously reduce the concentration of nitrate nitrogen in sewage, and the denitrification effect is relatively stable.

Nitrite is an intermediate product of the nitrogen cycle. Nitrite nitrogen is unstable and can be oxidized to nitrate nitrogen or reduced to ammonia nitrogen. Therefore, while measuring their content and understanding the nitrate and ammonia content in the water, the degree of pollution of the water system by nitrogen-containing compounds and the self-purification status can be judged.

Figure 4 is a diagram showing changes in nitrite nitrogen concentration with operating time in the anaerobic pool 1 and the aerobic pool 5 during the operation of the present invention. The abscissa is time, the ordinate is nitrite nitrogen concentration, and the line segments containing squares are displayed. The changing trend of nitrite nitrogen concentration in anaerobic tank 1. The circular line segment shows the changing trend of nitrite nitrogen concentration in the second aerobic tank 5. Figure 4 shows that after the operation of the denitrification and phosphorus removal system, the The nitrite nitrogen concentration in the second aerobic pool 5 began to decrease from a low level, and after the fourth day, the ammonia nitrogen concentration in the second aerobic pool 5 approached 0; the ammonia nitrogen concentration in the anaerobic pool 1 started from a high level On the eighth day, the concentration of nitrite nitrogen in anaerobic pool 1 reached the lowest level, and then began to rise slowly. The above results show that this system can continuously reduce the concentration of nitrite nitrogen in the aerobic pool and the denitrification effect is stable.

Phosphorus in wastewater comes partly from chemical fertilizers and agricultural waste. At the same time, the extensive use of phosphorus-containing detergents in daily life has also significantly increased the phosphorus content in domestic sewage. In addition, wastewater discharged from chemical, papermaking, rubber, dye and textile printing and dyeing, pesticide, coking, petrochemical, fermentation, pharmaceutical and medical, and food industries often contains organophosphorus compounds. Phosphorus in sewage can cause harm to humans and marine life. Excessive phosphorus can cause great harm to water bodies and cause eutrophication of water bodies.

Figure 5 is a diagram showing changes in phosphate concentration in anaerobic pool 1 and aerobic pool 5 with operating time during the operation of the present invention. The abscissa is time, the ordinate is phosphate concentration, and the line segment containing squares shows anaerobic pool 1. The changing trend of the phosphate concentration in the second aerobic pool 5. The circular line segment shows the changing trend of the phosphate concentration in the second aerobic pool 5. Figure 5 shows that after the denitrification and phosphorus removal system is operated, the phosphoric acid in the second aerobic pool 5 The salt concentration began to decrease from a high level, and the phosphate concentration in the second aerobic pool 5 remained at a low level after the fourth day; the phosphate concentration in the anaerobic pool 1 began to decrease from a high level, and after the fourth day The phosphate concentration in anaerobic tank 1 then decreased steadily. The above results show that this system can continuously reduce the concentration of phosphate in the anaerobic and aerobic tanks, and the phosphorus removal effect is stable.

Chemical oxygen demand, also known as Chemical Oxygen Demand (COD), uses chemical oxidants to oxidize and decompose oxidizable substances in water (such as organic matter, nitrites, ferrous salts, sulfides, etc.), and then determines the residual Calculate the oxygen consumption based on the amount of oxidant. Reducing substances in water include various organic substances, nitrites, sulfides, ferrous salts, etc. The main ones are organic substances. Therefore, chemical oxygen demand (COD) is often used as an indicator to measure the content of organic matter in water. The unit of COD is ppm or mg/L. The smaller the value, the lighter the degree of water pollution.

Figure 6 is a graph showing changes in COD concentration in anaerobic pool 1 and aerobic pool 5 with operating time during the operation of the present invention. The abscissa is time, the ordinate is COD concentration, and the line segment containing squares shows the COD in anaerobic pool 1. The changing trend of the concentration. The circular line segment shows the changing trend of the COD concentration in the second aerobic pool 5; Figure 6 shows that after the denitrification and phosphorus removal system is operated, the COD concentration in the second aerobic pool 5 changes from low to low. The level began to decrease, and after the eighth day, the COD concentration in the second aerobic tank 5 remained at a low level; the COD concentration in the anaerobic tank 1 was relatively stable. The above results show that this system can continuously reduce the COD concentration in the aerobic pool and the effect of reducing the organic content in the sewage is stable.

It can be seen from the above experiments that the nitrogen and phosphorus removal system manufactured by this solution effectively reduces the concentration of ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen in the sewage, thereby reducing the total nitrogen content in the sewage; and this system stably reduces the concentration of sewage. The phosphate concentration and COD concentration in the water indicate that the system can stably carry out nitrogen and phosphorus removal and remove organic matter in sewage.

In summary, this application starts from the sewage treatment system, considers the feasibility of adding a flow measurement fermentation system to the multi-stage AO system, and designs a nitrogen and phosphorus removal system and method. The nitrogen and phosphorus removal system also includes a fermentation tank, the inlet of the fermentation tank is connected to the outlet of the first sedimentation tank, and the outlet of the fermentation tank is connected to the anaerobic tank. The fermentation tank carries out anaerobic fermentation of the sludge precipitated in the multi-stage AO system, and uses a large amount of organic matter in the sludge to convert into small molecule carbon sources or biogas to maximize the resource utilization of the sludge. The fermentation tank provides an internal carbon source for the system, which greatly reduces the cost of applying external carbon and helps to improve the nitrogen and phosphorus removal efficiency of the system and achieve efficient purification of water quality. Returning the internal carbon source provided in the fermentation tank to the anaerobic tank can maximize the utilization of endogenous carbon, thereby further improving the utilization of sludge and greatly improving the denitrification efficiency of the system. The multi-stage AO process makes up for the shortcomings of incomplete nitrogen and phosphorus removal in the single-stage AO process, and the multiple reflux system can not only improve the reprocessing of sewage, but also improve the reuse rate of sludge. The nitrogen and phosphorus removal system treats domestic sewage, which can effectively reduce the damage of domestic sewage to the surrounding ecological environment and has good social, economic and environmental benefits.

Although the embodiments of the present patent have been described, those of ordinary skill in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the patent. The scope of this patent is defined by the appended claims and their equivalents.

The above descriptions are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be practiced in other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims (10)

1. A denitrification and dephosphorization system comprises a water inlet, a multi-stage AO system, a first sedimentation tank and a water outlet which are connected in sequence; the multi-stage AO system comprises an anaerobic tank, two or more anoxic tanks and two or more aerobic tanks which are connected with the water inlet; the system is characterized by further comprising a fermentation tank, wherein an inlet of the fermentation tank is connected with an outlet of the first sedimentation tank, and an outlet of the fermentation tank is connected with the anaerobic tank.

2. The system of claim 1, further comprising a coagulation tank mounted between the fermentation tank and the anaerobic tank.

3. The system of claim 2, further comprising a second sedimentation tank mounted between the coagulation tank and the anaerobic tank.

4. The system of claim 1, wherein the lower portion of the first sedimentation tank and/or the second sedimentation tank has a plurality of spaced inclined plates.

5. A system according to claim 2 or 3, characterized in that the outlet of the second sedimentation tank is connected to the inlet of the fermentation tank by means of a return pump.

6. The system of claim 5, wherein the outlet of the second sedimentation tank is connected to the inlet of the coagulation tank by a reflux pump.

7. The system of claim 1, wherein the outlet of the first sedimentation tank is connected to the inlet of the anaerobic tank by a reflux pump.

8. The system of claim 1 wherein the multi-stage AO system comprises the anaerobic tank, a first anoxic tank, a first aerobic tank, a second anoxic tank, and a second aerobic tank connected in sequence.

9. The system of claim 8, wherein the outlet of the first aerobic tank is connected to the inlet of the first anoxic tank by a return pump and the outlet of the second aerobic tank is connected to the inlet of the first anoxic tank and/or the second anoxic tank by a return pump.

10. A denitrification and dephosphorization method sequentially passes sewage through a water inlet, a multi-stage AO system and a first sedimentation tank and outputs the sewage through a water outlet, is characterized in that,

sending the precipitated sludge generated in the first precipitation tank to a fermentation tank;

and transferring the small molecule carbon source converted from the precipitated sludge in the fermentation tank and biogas to an anaerobic tank in the multi-stage AO system.