CN113480004B

CN113480004B - Method for deeply denitrifying urban sewage after carbon and phosphorus capture and realizing phosphorus recovery through PDA (personal digital Assistant)

Info

Publication number: CN113480004B
Application number: CN202110800567.7A
Authority: CN
Inventors: 彭永臻; 尚涛涛; 宫小斐; 宫庆腾
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2021-07-15
Filing date: 2021-07-15
Publication date: 2023-04-07
Anticipated expiration: 2041-07-15
Also published as: CN113480004A

Abstract

A device and a method for deeply denitrifying urban sewage after carbon and phosphorus capture and realizing phosphorus recovery through PDA belong to the field of sewage sludge biological treatment. The domestic sewage enters a carbon capture reactor which is in anaerobic/aerobic operation, organic matters in the sewage are captured and phosphorus is absorbed, the rest sludge at the bottom is discharged after standing and enters a sludge fermentation tank, and a medicament is added to recover the phosphorus released in the fermentation. And the effluent of the carbon capture reactor enters a nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor, ammonia nitrogen in the water is partially oxidized into nitrate nitrogen in an aerobic section, the fermented supernatant subjected to centrifugation and phosphorus removal enters the nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor in an anoxic section, and the short-range denitrifying bacteria reduce the nitrate nitrogen into nitrite nitrogen by using organic matters in the fermented supernatant, and the nitrite nitrogen and the ammonia nitrogen perform anaerobic ammonia oxidation reaction. The invention utilizes the carbon capture reactor to enrich organic matters, provides a carbon source which is easy to be utilized by microorganisms through the hydrolytic acidification of sludge, and realizes the deep denitrification and phosphorus recovery of the municipal sewage.

Description

Method for deeply denitrifying urban sewage after carbon and phosphorus capture and realizing phosphorus recovery through PDA (personal digital Assistant)

Technical Field

The invention designs a method for anaerobic ammonia oxidation by coupling carbon capture reactor-sludge fermentation-nitrification/short-cut denitrification, belonging to the technical field of sewage and sludge treatment. The method is suitable for deep denitrification and phosphorus recovery of the low C/N ratio urban domestic sewage, does not need external carbon source input, and can realize resource recovery and sludge reduction.

Background

Along with the increase of the living standard of people in China, the yield of urban domestic sewage is also increased year by year, if the sewage is not treated to reach the standard and then is discharged, the nitrogen and phosphorus content in natural water is easily increased, so that the eutrophication of the water is caused, and therefore, the discharge standard of urban sewage treatment plants is gradually improved in China in recent years. Discharge standard of pollutants from municipal wastewater treatment plantThe emission standard of the first level A in the soup (GB 18918-2002) stipulates: COD of the effluent is less than or equal to 50mg/L, NH ₄ ⁺ N is less than or equal to 5mg/L, TN is less than or equal to 15mg/L, and TP is less than or equal to 0.5mg/L. However, different from the water quality of domestic town sewage, domestic town sewage has the characteristic of low organic matter content, which causes a serious problem for sewage treatment plants, namely, in order to meet the treatment standard, an external carbon source needs to be added into domestic sewage with low C/N ratio, which not only increases the cost of sewage treatment, but also causes the problem of excess sludge, and in order to treat the excess sludge, additional treatment process and cost are needed, and the traditional domestic sewage denitrification process cannot meet the economic, energy-saving and green concept.

The denitrification in the traditional water treatment process is generated according to the classical nitrogen circulation theory, namely organic nitrogen in water is firstly converted into ammonia nitrogen through ammoniation, then converted into nitrate nitrogen through nitrification, and then generated nitrogen through denitrification is discharged into the atmosphere. The discovery of the anaerobic ammonium oxidation bacteria updates the cognition of people on the traditional nitrogen circulation and also brings a new process and idea for the denitrification treatment of the sewage. The anaerobic ammonia oxidation is a process for realizing denitrification by the anaerobic ammonia oxidation bacteria by reacting ammonia nitrogen and nitrite nitrogen in a ratio of 1.32, and a carbon source is not required to be added in the reaction process of the anaerobic ammonia oxidation bacteria, and aeration is not required, so that the carbon source and the energy are saved, and the anaerobic ammonia oxidation has a wide application prospect in the treatment of urban domestic sewage. However, the anammox has certain limitations in practical application, firstly, the anammox bacteria are slow in proliferation and very sensitive to the external environment, so that the anammox sludge is mainly put into practical use in the form of granular sludge or filler in the actual domestic sewage treatment, and secondly, stable nitrite nitrogen sources are needed for the anammox, so that the anammox is usually coupled with short-cut nitrification or short-cut denitrification for denitrification, and in addition, the anammox reaction can generate a small amount of nitrate nitrogen, and the deep denitrification can be better realized by combining with other processes.

Although the short-cut nitrification can save oxygen supply and carbon source and provide nitrite nitrogen for anaerobic ammonia oxidation, the maintenance and the starting of the short-cut nitrification in an actual water plant are not easy to realize on a large scale, and once the short-cut nitrification is damaged, the nitrate nitrogen in a reactor is increased, so that the total nitrogen of effluent can not reach the first-level A discharge standard. Compared with the short-cut nitrification, the short-cut denitrification is easier to maintain, and can remove a small amount of nitrate nitrogen generated by anaerobic ammonia oxidation reaction, so that the deep denitrification of the domestic sewage is easier to realize by using the short-cut denitrification coupled with the anaerobic ammonia oxidation in the actual operation. The domestic sewage can be subjected to full-course nitration reaction to oxidize ammonia nitrogen in water into nitrate nitrogen, and then subjected to short-range denitrification coupling anaerobic ammoxidation, and the short-range denitrification reduces the nitrate nitrogen into nitrite nitrogen, so that a stable nitrite nitrogen source can be provided for the anaerobic ammoxidation.

At present, a large amount of excess sludge generated by nitrogen and phosphorus removal of municipal domestic sewage needs to be properly treated, and sludge fermentation is one of promising methods. The sludge fermentation can produce volatile fatty acid which mainly comprises acetic acid, propionic acid, n/isobutyric acid and n/isovaleric acid, and the volatile fatty acid is easier to be absorbed and utilized by microorganisms compared with other organic matters, so that the residual sludge fermentation can supplement a carbon source for the denitrification process. The carbon capture reactor has the characteristics of high water inflow load and low sludge age, can quickly adsorb most organic matters in water through flocculation, is suitable for sludge fermentation to provide a carbon source for the reactor, and can absorb phosphorus in sewage by the anaerobic/aerobic carbon capture reactor which alternately operates, release the absorbed phosphorus in the hydrolytic acidification process of sludge fermentation, and can recycle the phosphorus by adding a coagulant, thereby realizing resource recycling.

The method combines the carbon capture and sludge fermentation processes, can provide a carbon source which is easily absorbed and utilized by microorganisms for a post-positioned nitrification-shortcut denitrification coupling anaerobic ammonia oxidation process, does not need an external carbon source, and realizes deep nitrogen and phosphorus removal of domestic sewage, resource recycling and sludge reduction.

Disclosure of Invention

The invention aims to provide a device and a method for treating municipal sewage based on a carbon capture, sludge fermentation, nitrification/short-cut denitrification coupling anaerobic ammonia oxidation process, aiming at the problems of deep nitrogen and phosphorus removal and sludge reduction of the municipal sewage with low carbon-nitrogen ratio. Firstly, domestic sewage enters a carbon capture reactor through a water inlet pump, a stirring device is opened simultaneously for anaerobic stirring, anaerobic phosphorus release is carried out while water is fed, aeration is carried out in an aerobic stage, microorganisms adsorb organic matters in the water and simultaneously absorb phosphorus in the water, part of sludge discharged from the bottom enters a sludge storage tank for fermentation in a sludge fermentation tank, part of fermentation liquor discharged from the sludge fermentation tank in each period is added with isometric fresh sludge, the fermentation liquor is centrifuged and then enters a second intermediate water tank, a medicament (lime or coagulant) is added for recovering phosphorus, the effluent of the carbon capture reactor enters a first intermediate water tank and then enters a nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor, certain ammonia nitrogen in the water is oxidized into nitrate nitrogen in the aerobic stage, the fermentation supernatant in the second intermediate water tank in the anoxic stage enters the reactor for anoxic stirring, the fermentation supernatant provides a carbon source for short-range denitrification, and can also supplement a part of ammonia nitrogen, the nitrate nitrogen is reduced into nitrite nitrogen by short-range denitrification and is removed by anaerobic ammonia oxidation as a substrate reaction with the ammonia nitrogen, and further deep phosphorus removal of the municipal domestic sewage is realized.

The purpose of the invention is realized by the following technical scheme:

the device and the method for treating the municipal sewage based on the processes of carbon capture, sludge fermentation, nitrification/short-cut denitrification coupling anaerobic ammonia oxidation are applied to the device, and the device is provided with a raw water tank, a carbon capture reactor, a sludge storage tank, a first intermediate water tank, a sludge fermentation tank, a nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor and a second intermediate water tank; the raw water tank is connected with the carbon capture reactor through a first water inlet pump; the carbon capture reactor is provided with a stirring device, an aeration head, a gas flowmeter and an aeration pump, is connected with the first intermediate water tank through an electromagnetic drain valve, and is connected with the sludge storage tank through a sludge discharge pump; the sludge storage tank is connected with the sludge fermentation tank through a sludge inlet pump, the sludge fermentation tank is provided with a stirring device, and the second intermediate water tank is provided with a dosing pump; the first intermediate water tank is connected in parallel with the second intermediate water tank through a second water inlet pump and a third water inlet pump into the nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor, the nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor is provided with a stirring device, a polypropylene hollow ring suspended filler, an electromagnetic drain valve, an aeration head and a gas flowmeter, and the effluent of the reactor is discharged out of the system through the electromagnetic drain valve.

A method for treating urban sewage based on carbon capture, sludge fermentation, nitrification/short-cut denitrification coupling anaerobic ammonia oxidation technology is characterized by comprising the following steps:

(1) Starting a carbon capture reactor and a sludge fermentation tank: the reactor is an SBR reactor, the water discharge ratio is 40%, the excess sludge discharged by a secondary sedimentation tank of a municipal sewage treatment plant is inoculated, the sludge concentration of the carbon capture reactor is maintained within the range of 5000-6000mg/L, the operation is carried out for 4-6 cycles every day, and the excess sludge is discharged into a sludge storage tank at the sedimentation stage; pumping raw water into a carbon capture reactor through a first water inlet pump, starting a stirring device, enabling the reactor to enter an anaerobic stirring stage, carrying out anaerobic phosphorus release reaction, and maintaining for 10-20min; in the aerobic stage, starting an aeration pump, adjusting a gas flowmeter to maintain the dissolved oxygen at 3-4mg/L, carrying out aerobic phosphorus absorption, and enabling organic matters in the sewage to be adsorbed on the surface of microorganisms, wherein the aerobic stage lasts for 30-40min; then the carbon capture reactor is kept stand for sedimentation, and after sludge and water are separated, the residual sludge is pumped into a sludge storage tank through a sludge pump; discharging the supernatant into a first intermediate water tank; the reactor is operated under the conditions, and when the COD removal rate of the system is more than 70 percent, the concentration of phosphate in effluent is less than 0.5mg/L and the system is continuously maintained for more than 15 days, the carbon capture reactor is successfully started; inoculating sludge into a sludge fermentation tank, wherein the sludge is the residual sludge of the carbon capture reactor, the sludge age of the fermentation tank is 7-10d, discharging a fermentation sludge-water mixture every day according to the sludge age, and adding fresh sludge with the same volume;

(2) Starting a nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor: the nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor is an SBR reactor, the water discharge ratio is 50%, floc sludge is inoculated into excess sludge discharged from a sedimentation tank of a municipal sewage treatment plant and short-cut denitrification sludge in the starting process, the sludge concentration is maintained to be 3000-4000mg/L, and anaerobic ammonia oxidation fillers are inoculated, the filling ratio is 20-30%, and the operation is carried out for 2 periods every day; firstly domesticating nitrobacteria, inoculating residual sludge discharged from a sedimentation tank of an urban sewage treatment plant, artificially distributing water for water inflow, starting the ammonia nitrogen concentration to be 60mg/L, gradually increasing the ammonia nitrogen concentration to 120mg/L in a gradient of 15mg/L, adjusting a gas flowmeter to maintain the dissolved oxygen at 2-3mg/L, aerating for 3-4h, controlling the mass concentration ratio of ammonia nitrogen to nitrate nitrogen to be 1.4-1.6, ending the aerobic stage, operating the reactor under the conditions, and starting the nitrification reactor when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen is continuously maintained for more than 15 days. Inoculating floc sludge with short-range denitrification activity into a reactor, controlling the concentration of the inoculated floc sludge to be 3000-4000mg/L, inoculating anaerobic ammonium oxidation filler, controlling the filling ratio to be 20-30%, adopting water distribution containing ammonia nitrogen for water inflow, controlling the initial ammonia nitrogen concentration to be 60mg/L, gradually increasing the concentration to 120mg/L by a gradient of 15mg/L, adding sodium acetate into an anoxic section to ensure that the SCOD concentration in the reactor is 120-250mg/L, firstly carrying out nitrification in an aerobic section of the reactor, carrying out full-range nitrification, ending the aerobic section when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen is 1.4-1.6, then adding sodium acetate, carrying out anoxic stirring for 4-6h, carrying out short-range denitrification and anaerobic ammonium oxidation in the reactor, and indicating that the successful nitrification/short-range denitrification and anaerobic ammonium oxidation coupling process is realized when the total nitrogen removal rate of the system reaches more than 90% and is continuously maintained for more than 15 days; and replacing sodium acetate with the supernatant of the fermentation product as a carbon source for short-cut denitrification to continuously maintain the concentration of SCOD at 120-250mg/L, and indicating that the start of the nitrification/short-cut denitrification coupled anaerobic ammonia oxidation reactor is finished when the total nitrogen removal rate of the system is higher than 90% and is continuously maintained for more than 15 days.

(3) And (3) controlling a strategy in an operation stage: after the carbon capture reactor and the nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor are respectively started, all devices are connected in series for operation, and the carbon capture reactor is connected with the first intermediate water tank; the carbon capture reactor operates for 4-6 periods every day, each period comprises water inlet, anaerobic stirring, aeration, precipitation, water discharge and idle stages, the water discharge ratio of the reactor is set to be 40%, the sludge concentration is maintained at 5000-6000mg/L, the sludge age is controlled at 3-5d, domestic sewage enters the carbon capture reactor through a water inlet pump, a stirring device is started at the same time, an anaerobic stirring stage is carried out for 10-20min, then an aeration pump is started, a gas flowmeter is adjusted to maintain dissolved oxygen at 3-4mg/L, aeration is carried out for 30-40min, then the sludge enters the precipitation stage, after sludge-water separation, residual sludge at the bottom is pumped into a sludge storage tank through a sludge pump, sludge in the sludge storage tank is pumped into a sludge fermentation tank through a sludge inlet pump, and water discharged from the carbon capture reactor is discharged into a first intermediate water tank through an electromagnetic water discharge valve; controlling the sludge age of the sludge fermentation tank to be 7-10d, controlling the pH to be 9-10, supplementing equivalent fresh residual sludge after discharging the fermentation mixture, centrifuging the fermentation mixture discharged from the fermentation tank, pumping the fermentation supernatant into a second intermediate water tank, starting a medicine feeding pump, feeding a medicine (lime or coagulant) to separate phosphorus in the fermentation liquor, and discharging and recovering the phosphorus; the nitrification/short-range denitrification coupling anaerobic ammonium oxidation reactor maintains the sludge concentration to be 3000-4000mg/L, the reactor runs for 2 periods every day, each period comprises water inlet, aeration, stirring, sedimentation, water discharge and idle stages, the water inlet is carbon capture reactor outlet water (aerobic section inlet) and fermentation supernatant liquid (anoxic section inlet), the dissolved oxygen of the reactor is controlled to be 2-3mg/L in the aeration stage, aeration is carried out for 3-4h, then anoxic stirring is carried out, the anoxic stirring time is 4-6h, the outlet water is discharged through a water discharge valve, and the water discharge ratio is 50%.

The method for treating the municipal sewage based on the carbon capture, sludge fermentation, nitrification and short-cut denitrification coupling anaerobic ammonia oxidation process has the following advantages:

1. stably maintain the deep denitrification. The nitrification reactor provides sufficient nitrate nitrogen for the short-cut denitrification coupling anaerobic ammonia oxidation reactor, the short-cut denitrification bacteria reduce the nitrate nitrogen into nitrite nitrogen by using organic acid generated by sludge fermentation, a substrate is provided for the anaerobic ammonia oxidation bacteria, and the problem that the nitrite nitrogen is difficult to stably obtain in the short-cut nitrification process can be effectively solved. Meanwhile, nitrate nitrogen generated in the anaerobic ammonia oxidation process can be removed in situ to meet the requirement of deep denitrification.

2. Effectively remove and recover the phosphorus. The anaerobic and aerobic operation of the system in the carbon capture stage is beneficial to the excessive absorption of phosphorus in sewage by microorganisms, phosphorus stored in the body can be released into fermentation mixed liquid again in the fermentation process of sludge due to microbial cell lysis, and the phosphorus released by the microorganisms in the fermentation process can be recovered by adding a chemical flocculant into the supernatant after centrifugal treatment.

3. Sludge reduction and resource utilization. Fermentation supernatant is added into the short-cut denitrification coupling anaerobic ammonia oxidation reactor, volatile fatty acid generated by sludge fermentation can be utilized by short-cut denitrifying bacteria, and in addition, ammonia nitrogen generated by sludge fermentation can also be directly utilized by anaerobic ammonia oxidation bacteria as a substrate. The excess sludge generated by the system can be added into a sludge fermentation tank for resource recovery, and even exogenous excess sludge can be added, so that sludge reduction treatment and effective resource utilization are realized, and the sludge treatment cost of a sewage plant is reduced.

Drawings

FIG. 1 is a schematic diagram of a municipal sewage treatment device based on a carbon capture, sludge fermentation, nitrification/short-cut denitrification coupling anaerobic ammonia oxidation process

Detailed Description

The present invention will be described in further detail with reference to fig. 1 and the following detailed description.

A device for deeply denitrifying urban sewage after carbon and phosphorus capture and realizing phosphorus recovery through PDA is characterized by comprising a raw water tank (1), a carbon capture reactor (2), a sludge storage tank (3), a first intermediate water tank (4), a sludge fermentation tank (5), a nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor (6) and a second intermediate water tank (7); the raw water tank (1) is connected with the carbon capture reactor (2) through a first water inlet pump (1.1), the effective volume of the carbon capture reactor is 10L and is set to be in anaerobic and aerobic alternative operation, the reactor is provided with a stirring device (2.1), an aeration head (2.3), a gas flowmeter (2.4) and an aeration pump (2.5), the reactor is connected with a first intermediate water tank (4) through an electromagnetic drain valve (2.2) and is connected with a sludge storage tank (3) through a sludge discharge pump (2.6), after the reaction is finished and the sludge and the water are separated, the residual sludge at the bottom of the carbon capture reactor is pumped into the sludge storage tank through the sludge discharge pump, and the supernatant of the carbon capture reactor flows into the first intermediate water tank (4) through the electromagnetic drain valve; the sludge storage tank is connected with a sludge fermentation tank (5) through a sludge inlet pump (3.1), sludge in the sludge storage tank is pumped into the sludge fermentation tank through the sludge inlet pump (3.1), the effective volume of the sludge fermentation tank is 10L, the sludge age is controlled to be 7-10d, the pH is controlled to be 9-10, the sludge fermentation tank is provided with a stirring device (5.1), the fermentation tank discharges a certain volume of fermentation sludge-water mixture every day and supplements equal volume of fresh residual sludge, the discharged fermentation sludge-water mixture discharges fermentation supernatant into a second intermediate water tank (7) after centrifugation and chemical phosphorus removal treatment, and the second intermediate water tank is provided with a medicine adding pump (7.2); the nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor (6) is connected in parallel to the nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor (6) through a third water inlet pump (7.1) through a second water inlet pump (4.1) and a second middle water tank (7), the effective volume of the nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor is 10L, the reactor is provided with a stirring device (6.1), a polypropylene hollow ring suspension filler (6.2), an electromagnetic drain valve (6.3), an aeration head (6.4) and a gas flowmeter (6.5), the polypropylene hollow ring suspension filler is provided with enriched anaerobic ammonia oxidizing bacteria, and effluent of the reactor passes through the electromagnetic drain valve discharge system.

The test water in this embodiment is actual urban sewage, and the specific water quality is as follows: pH of 6-8, COD of 200-300mg/L, NH ₄ ⁺ -N is 60-80mg/L, NO ₂ ^- -N≤0.5mg/L，NO ₃ ^- -N≤0.5mg/L，PO ₄ ^3- -P is 4-8mg/L. The specific operation process is as follows:

the original water tank and the sludge storage tank are respectively filled with urban sewage and fresh excess sludge.

Before the system was run continuously, the carbon capture reactor and sludge fermentor were first started: the carbon capture reactor has the functions of absorbing organic matters in sewage and removing phosphorus, the reactor is an SBR reactor with the effective volume of 6L, the water discharge ratio is 40%, excess sludge discharged by a secondary sedimentation tank of an urban sewage treatment plant is inoculated, the sludge concentration of the reactor is maintained within the range of 5000-6000mg/L, 4-6 periods of operation are carried out every day, actual urban sewage is used as raw water for starting, the raw water is pumped into the carbon capture reactor (2) through a first water inlet pump (1.1), and then a stirring device (2.1) is started, so that the reactor enters an anaerobic stirring stage to carry out anaerobic phosphorus release reaction, and the anaerobic phosphorus release reaction is maintained for 10-20min; in the aerobic stage, starting an aeration pump (2.5), adjusting a gas flowmeter (2.4) to maintain the dissolved oxygen at 3-4mg/L, carrying out aerobic phosphorus absorption, and enabling organic matters in the sewage to be adsorbed on the surface of microorganisms, wherein the aerobic stage lasts for 30-40min; then the carbon capture reactor is kept still for sedimentation, and after mud and water are separated, the residual sludge is pumped into a sludge storage tank (3) through a sludge pump (2.6); the supernatant is discharged into a first intermediate water tank (4); the reactor is operated under the conditions, and when the COD removal rate of the system is more than 70 percent, the concentration of phosphate in effluent is less than 0.5mg/L and the system is continuously maintained for more than 15 days, the carbon capture reactor is started to be finished; the sludge fermentation tank (5) is used for providing an organic carbon source which is easily utilized by microorganisms for a subsequent short-cut denitrification process, the sludge is inoculated into the sludge fermentation tank and is the residual sludge of the carbon capture reactor, the effective volume of the fermentation tank is 10L, the sludge age is 7-10d, a fermentation sludge-water mixture is discharged every day according to the sludge age, and the same volume of fresh sludge is added. Subsequently, starting a nitrification/short-cut denitrification coupled anaerobic ammonia oxidation reactor: the nitrification/short-cut denitrification coupling anaerobic ammonium oxidation reactor (6) is an SBR reactor with the effective volume of 10L, the water discharge ratio is 50 percent, floc sludge is inoculated into excess sludge discharged from a sedimentation tank of a municipal sewage treatment plant and short-cut denitrification sludge in the starting process, the sludge concentration is maintained to be 3000-4000mg/L, and anaerobic ammonium oxidation fillers are inoculated, the filling ratio is 20-30 percent, and the reactor is operated for 2 periods every day. Firstly domesticating nitrobacteria, inoculating residual sludge discharged from a sedimentation tank of an urban sewage treatment plant, artificially distributing water for water inflow, starting ammonia nitrogen concentration to be 60mg/L, gradually increasing the ammonia nitrogen concentration to be 120mg/L in a gradient of 15mg/L, adjusting a gas flow meter (6.5) to keep dissolved oxygen at 2-3mg/L, aerating for 3-4h, carrying out full-process nitrification, controlling the mass concentration ratio of ammonia nitrogen to nitrate nitrogen to be 1.4-1.6, ending an aerobic stage, operating a reactor under the above conditions, and ending the start of the nitrification reactor when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen is continuously maintained for more than 15 days. Inoculating floc sludge with short-range denitrification activity into a reactor, controlling the concentration of the inoculated floc sludge to be 3000-4000mg/L, inoculating anaerobic ammonium oxidation filler, controlling the filling ratio to be 20-30%, adopting water distribution containing ammonia nitrogen for water inflow, controlling the initial ammonia nitrogen concentration to be 60mg/L, gradually increasing the concentration to 120mg/L by a gradient of 15mg/L, adding sodium acetate into an anoxic section as a carbon source for short-range denitrification to enable the concentration of SCOD (dissolved oxygen) in the reactor to be 120-250mg/L, firstly carrying out nitrification in an aerobic section by adjusting a gas flow meter, keeping dissolved oxygen at 2-3mg/L, aerating for 3-4h, carrying out whole-range nitrification, finishing an aerobic section when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen is 1.4-1.6, then adding sodium acetate, carrying out anoxic stirring for 4-6h, carrying out short-range denitrification and anaerobic ammonium oxidation in the reactor, and realizing the anaerobic denitrification and anaerobic ammonium oxidation processes when the total nitrogen removal rate of the system reaches more than 90% and is continuously maintained for more than 15 days; and replacing sodium acetate with the supernatant of the fermentation product as a carbon source for short-range denitrification to continuously maintain the concentration of SCOD at 120-250mg/L, wherein when the total nitrogen removal rate of the system is higher than 90% and the system is continuously maintained for more than 15 days, the start of the anaerobic ammonia oxidation reactor coupled with the fermentation-short-range denitrification of the excess sludge is finished.

After the carbon capture reactor and the nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor are respectively started, all devices are connected in series to operate, and the carbon capture reactor (2) is connected with the first intermediate water tank (4); the carbon capture reactor operates for 4-6 periods every day, each period comprises water inlet, anaerobic stirring, aeration, sedimentation, water discharge and idle stages, the water discharge ratio of the reactor is set to be 40%, the sludge concentration is maintained at 5000-6000mg/L, the sludge age is controlled at 3-5d, domestic sewage enters the carbon capture reactor through a water inlet pump, simultaneously a stirring device (2.1) is started to perform an anaerobic stirring stage for 10-20min, an anaerobic phosphorus release reaction is performed, then an aeration pump (2.5) is started, a gas flowmeter (2.4) is adjusted to maintain dissolved oxygen at 3-4mg/L, aeration is performed for 30-40min, aerobic phosphorus absorption is performed, organic matters in the sewage are adsorbed on the surface of microorganisms and then enter the sedimentation stage, sludge and water are separated, residual sludge at the bottom is pumped into a sludge storage tank (3) through a sludge discharge pump (2.6), sludge in the sludge storage tank is pumped into a sludge fermentation tank (5) through a sludge inlet pump (3.1), and water outlet of the carbon capture reactor is discharged into a first intermediate water discharge valve (4.2); the effective volume of a sludge fermentation tank is 10L, the sludge age is controlled to be 7-10d, the pH is controlled to be 9-10, hydrolysis acidification reaction of excess sludge is carried out, a large amount of volatile fatty acid, partial ammonia nitrogen and phosphate are generated, the sludge fermentation tank supplements equivalent fresh excess sludge after discharging a fermentation sludge-water mixture, the fermentation mixture of the fermentation tank is discharged, the mixture is centrifuged (the rotating speed is 4000r/min and is 10 min), the fermentation supernatant is injected into a second intermediate water tank (7) after centrifugation, a dosing pump (7.2) is started, and a medicament (lime or coagulant) is added to separate phosphorus in the fermentation liquor and is discharged and recovered; the nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor (6) maintains the sludge concentration to be 3000-4000mg/L, runs for 2 cycles every day, and comprises the stages of water inlet, aeration, stirring, sedimentation, water drainage and idle, wherein the water inlet is the outlet water of the carbon capture reactor (connected with the first intermediate water tank through the second water inlet pump) and the fermentation supernatant (connected with the second intermediate water tank through the third water inlet pump), the dissolved oxygen of the reactor is controlled to be 2-3mg/L in the aeration stage, the aeration is carried out for 3-4h, the ammonia nitrogen part of the carbon capture inlet water is nitrified into nitrate nitrogen, then anoxic stirring is carried out, the fermentation supernatant enters the reactor, the anoxic stirring time is 4-6h, the nitrate nitrogen is nitrified into nitrite nitrogen, the nitrite nitrogen and the ammonia nitrogen are subjected to anaerobic ammonia oxidation reaction, the outlet water of the reactor is discharged through an electromagnetic drain valve (6.3), and the water discharge ratio is 50%.

The test result shows that: after the system runs stably, the COD of the effluent is 40-50mg/L, NH ₄ ⁺ N is 1-5mg/L, TN is 10-15mg/L, PO ₄ ^3- The P is 0.5-2mg/L, and the sludge is reduced by 20-25%. The system successfully realizes low-consumption high-efficiency deep denitrification and sludge reduction of urban sewage.

Claims

1. A method for deeply denitrifying urban sewage after carbon and phosphorus capture and realizing phosphorus recovery by PDA (personal digital assistant) comprises the steps that a device used in the method is provided with a raw water tank (1), a carbon capture reactor (2), a sludge storage tank (3), a first intermediate water tank (4), a sludge fermentation tank (5), a nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor (6) and a second intermediate water tank (7); the raw water tank (1) is connected with the carbon capture reactor (2) through a first water inlet pump (1.1); the carbon capture reactor is provided with a stirring device (2.1), an aeration head (2.3), a gas flowmeter (2.4) and an aeration pump (2.5), is connected with the first intermediate water tank (4) through an electromagnetic drain valve (2.2), and is connected with the sludge storage tank (3) through a sludge discharge pump (2.6); the sludge storage tank (3) is connected with a sludge fermentation tank (5) through a sludge inlet pump (3.1), and the sludge fermentation tank is provided with a stirring device (5.1); the second intermediate water tank is provided with a dosing pump (7.2), the first intermediate water tank (4) is connected in parallel with the second intermediate water tank (7) through a second water inlet pump (4.1) and a third water inlet pump (7.1) to a nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor (6), the nitrification/short-range denitrification coupling anaerobic ammonia oxidation reactor is provided with a stirring device (6.1), a polypropylene hollow ring suspension filler (6.2), an electromagnetic drain valve (6.3), an aeration head (6.4) and a gas flowmeter (6.5), and effluent of the reactor is discharged out of the system through the electromagnetic drain valve;

the method is characterized by comprising the following steps:

(1) Starting a carbon capture reactor and a sludge fermentation tank: the reactor is an SBR reactor, the water discharge ratio is 40%, the excess sludge discharged by a secondary sedimentation tank of an urban sewage treatment plant is inoculated, the sludge concentration of the carbon capture reactor (2) is maintained within the range of 5000-6000mg/L, the operation is carried out for 4-6 cycles every day, and the excess sludge is discharged into a sludge storage tank (3) in the sedimentation stage; pumping raw water into a carbon capture reactor (2) through a first water inlet pump (1.1), starting a stirring device (2.1), and enabling the reactor to enter an anaerobic stirring stage for anaerobic phosphorus release reaction for 10-20min; in an aerobic stage, starting an aeration pump (2.5), adjusting a gas flowmeter (2.4) to maintain dissolved oxygen at 3-4mg/L, carrying out aerobic phosphorus absorption, and enabling organic matters in the sewage to be adsorbed on the surface of the microorganism, wherein the aerobic stage lasts for 30-40min; then the carbon capture reactor is kept still for sedimentation, and after mud and water are separated, the residual sludge is pumped into a sludge storage tank (3) through a sludge pump (2.6); the supernatant is discharged into a first intermediate water tank (4); the reactor is operated under the conditions, and when the COD removal rate of the system is more than 70 percent, the concentration of phosphate in effluent is less than 0.5mg/L and the system is continuously maintained for more than 15 days, the carbon capture reactor is started to be finished; sludge is inoculated into the sludge fermentation tank (5) to be residual sludge of the carbon capture reactor, the sludge age of the fermentation tank is 7-10d, a fermentation sludge-water mixture is discharged every day according to the sludge age, and fresh sludge with the same volume is added;

(2) Starting a nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor: the nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor (6) is an SBR reactor, the water discharge ratio is 50%, floc sludge is inoculated into residual sludge discharged from a sedimentation tank of a municipal sewage treatment plant and short-cut denitrification sludge in the starting process, the sludge concentration is maintained to be 3000-4000mg/L, and anaerobic ammonia oxidation fillers are inoculated, the filling ratio is 20-30%, and the operation is carried out for 2 periods every day; firstly domesticating nitrobacteria, inoculating residual sludge discharged from a sedimentation tank of an urban sewage treatment plant, artificially distributing water for inflow, starting ammonia nitrogen concentration to be 60mg/L, gradually increasing the ammonia nitrogen concentration to be 120mg/L by a gradient of 15mg/L, adjusting a gas flowmeter (6.5) to maintain dissolved oxygen at 2-3mg/L, aerating for 3-4h, controlling the mass concentration ratio of ammonia nitrogen to nitrate nitrogen to be 1.4-1.6, ending an aerobic stage, operating a reactor under the above conditions, and ending the start of a nitrification reactor when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen is continuously maintained for more than 15 days; inoculating floc sludge with short-range denitrification activity into a reactor, controlling the concentration of the inoculated floc sludge to be 3000-4000mg/L, inoculating anaerobic ammonium oxidation filler, controlling the filling ratio to be 20-30%, adopting water distribution containing ammonia nitrogen for water inflow, controlling the initial ammonia nitrogen concentration to be 60mg/L, gradually increasing the concentration to 120mg/L by a gradient of 15mg/L, adding sodium acetate into an anoxic section to ensure that the SCOD concentration in the reactor is 120-250mg/L, firstly carrying out nitrification in an aerobic section of the reactor, carrying out full-range nitrification, ending the aerobic section when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen is 1.4-1.6, then adding sodium acetate, carrying out anoxic stirring for 4-6h, carrying out short-range denitrification and anaerobic ammonium oxidation in the reactor, and indicating that the successful nitrification/short-range denitrification and anaerobic ammonium oxidation coupling process is realized when the total nitrogen removal rate of the system reaches more than 90% and is continuously maintained for more than 15 days; replacing sodium acetate with the supernatant of the fermentation product as a carbon source for short-range denitrification to continuously maintain the concentration of SCOD at 120-250mg/L, and indicating that the start of the nitrification/short-range denitrification coupled anaerobic ammonia oxidation reactor is finished when the total nitrogen removal rate of the system is higher than 90% and is continuously maintained for more than 15 days;

(3) And (3) controlling a strategy in an operation stage: after the carbon capture reactor and the nitrification/short-cut denitrification coupling anaerobic ammonia oxidation reactor are respectively started, all devices are connected in series for operation, and the carbon capture reactor (2) is connected with the first intermediate water tank (4); the carbon capture reactor operates for 4-6 periods every day, each period comprises water inlet, anaerobic stirring, aeration, precipitation, water discharge and idle stages, the water discharge ratio of the reactor is set to be 40%, the sludge concentration is maintained at 5000-6000mg/L, the sludge age is controlled at 3-5d, domestic sewage enters the carbon capture reactor through a water inlet pump, a stirring device (2.1) is started at the same time to perform an anaerobic stirring stage of 10-20min, then an aeration pump (2.5) is started, a gas flowmeter (2.4) is adjusted to maintain dissolved oxygen at 3-4mg/L, aeration is performed for 30-40min, then the carbon capture reactor enters the precipitation stage, after mud and water are separated, bottom residual sludge is pumped into a sludge storage tank (3) through a sludge discharge pump (2.6), sludge in the sludge storage tank is pumped into a sludge fermentation tank (5) through a sludge inlet pump (3.1), and effluent of the carbon capture reactor is discharged into a first intermediate water tank (4) through an electromagnetic drain valve (2.2); supplementing the same amount of fresh residual sludge after the fermentation mixture is discharged from the sludge fermentation tank, centrifuging the fermentation mixture of the fermentation tank, pumping the fermentation supernatant into a second intermediate water tank (7), starting a medicine feeding pump (7.2), feeding a medicine to separate phosphorus in the fermentation liquor, and discharging and recovering the phosphorus; the nitrification/short-range denitrification coupling anaerobic ammonium oxidation reactor (6) maintains the sludge concentration to be 3000-4000mg/L, runs for 2 cycles every day, and each cycle comprises the stages of water inlet, aeration, stirring, sedimentation, water drainage and idling, wherein the water inlet is the effluent of the carbon capture reactor and fermentation supernatant, the effluent of the carbon capture reactor enters the nitrification/short-range denitrification coupling anaerobic ammonium oxidation reactor when the reactor is started, the dissolved oxygen of the reactor is controlled to be 2-3mg/L in the aeration stage, the aeration is carried out for 3-4h, then anoxic stirring is carried out, the fermentation supernatant enters the reactor when the reactor is subjected to anoxic stirring, the anoxic stirring time is 4-6h, the effluent is discharged through a drain valve, and the water discharge ratio is 50%.