Background
A large amount of nutrient salts such as nitrogen and phosphorus enter the water body, which can lead to rapid growth and propagation of aquatic animals and plants, cause eutrophication of lakes, estuaries and coasts and influence the survival of aquatic organisms. The research generally considers that the total nitrogen boundary concentration of the eutrophication of the water body is 0.2mg/L, and the total phosphorus boundary concentration is 0.02mg/L. With the continuous influence of human activities, the circulating process of nitrogen and phosphorus in a ecological system is greatly changed, so that the concentration of nitrogen and phosphorus in most of the areas far exceeds the threshold value, and the ecological environment state gazette shows that among 107 important lakes (reservoirs) for monitoring the nutrition state, the lakes (reservoirs) in the nutrition-poor state account for 9.3%, the lakes (reservoirs) in the nutrition-poor state account for 62.6%, the light nutrition-rich state accounts for 22.4% and the medium nutrition-rich state accounts for 5.6%, so that the nitrogen and phosphorus emission standard of water discharged by urban sewage treatment plants is more strict.
The biological denitrification of the outdoor drainage design specification (GB 50014-2006) requires that the carbon nitrogen ratio BOD5/TKN is more than 4, and the BOD5/TKN ratio of about 70% of urban sewage treatment plants is less than 4. In order to achieve higher TN removal rate when treating sewage with low carbon nitrogen ratio, the traditional sewage treatment process needs to consider an additional carbon source (such as methanol, ethanol, acetic acid, glucose and the like) or to add industrial wastewater rich in biodegradable organic matters into town sewage to improve the carbon nitrogen ratio, thereby increasing the running cost of a sewage treatment plant, and being more unfavorable in the large-scale denitrification and dephosphorization treatment process of the town sewage.
The anaerobic zone on the traditional multistage AO technology is usually damaged by the backflow sludge and dissolved oxygen in the effluent of the aerobic zone, and the phosphorus release effect of phosphorus accumulating bacteria is affected. The effluent and the return sludge in the aerobic zone directly enter the anaerobic zone and are mixed with raw water, and the dissolved oxygen in the anaerobic zone also consumes valuable carbon sources in the raw water, so that the total nitrogen removal rate is low. In the process form, the sewage of the traditional multistage AO process is discharged after being subjected to alternate anaerobic and aerobic processes, and no suitable living environment is provided for phosphorus accumulating bacteria in the process, so that the biological phosphorus removal effect of the process is poor.
Moreover, in the traditional scheme, the mode that sewage enters the reactor is two-stage water inlet, and the reactor process adopts an A1 (anoxic) A2 (anaerobic) O1 (aerobic) A2 (anoxic) O2 (aerobic) process. The main process is that the first section (50%) of raw water and the return sludge enter A1 (anoxic) for denitrification. A1 The (anoxic) section effluent then enters the A2 section (anaerobic), denitrifying phosphorus accumulating bacteria stores an internal carbon source, partial carbon source A2 section (anaerobic) effluent is provided for subsequent anoxic denitrification, the O1 section (aerobic) is subjected to nitrification, and meanwhile, the O1 section (aerobic) nitrifying liquid flows back to the A1 section (anoxic). The second section (50%) of raw water and the (aerobic) nitrifying liquid of the O2 section enter the A2 (anoxic) section for denitrification. A2 The effluent from the anoxic section enters the O2 section (aerobic) for nitration reaction. Such a solution has the following drawbacks:
The raw water and the nitrifying liquid/return sludge containing nitrate nitrogen enter an anoxic section at the same time, such as a second section (50%) of the raw water and the (aerobic) nitrifying liquid of the O2 section enter an A2 (anoxic) section for denitrification. Nitrate nitrogen in the nitrified liquid/return sludge can consume a carbon source in raw water to finish denitrification, so that the storage of microorganisms on the internal carbon source is reduced;
Only 1 sludge is refluxed, and the biological driving force for converting the external carbon source into the internal carbon source is insufficient;
2-stage water inflow, inorganic denitrification is not considered, and the total nitrogen removal rate is low;
Short anoxic time is unfavorable for endogenous denitrification, and long aerobic time is unfavorable for energy conservation and consumption reduction.
Disclosure of Invention
The invention aims to solve at least one technical problem in the background technology and provides a three-reflux multistage A/O device and method for strengthening endogenous synchronous denitrification and dephosphorization sludge.
In order to achieve the purpose, the invention provides a three-reflux multistage A/O device for strengthening endogenous synchronous denitrification and dephosphorization sludge, which comprises: the system comprises a water inlet tank, a multi-stage A/O reactor, a sludge precipitation reflux system and an aeration system;
The multistage a/O reactor comprises: the first anaerobic zone, the first anoxic zone, the first aerobic zone, the first short-time anoxic zone, the second anaerobic zone, the second anoxic zone, the second aerobic zone, the second short-time anoxic zone, the third anaerobic zone, the third aerobic zone and the third short-time anoxic zone are sequentially communicated;
The water inlet tank is respectively communicated with the first anaerobic zone, the second anaerobic zone and the third anaerobic zone through a first peristaltic pump, a second peristaltic pump and a third peristaltic pump;
the aeration system is arranged corresponding to the first aerobic zone, the second aerobic zone and the third aerobic zone respectively and continuously aerates the first aerobic zone, the second aerobic zone and the third aerobic zone;
The sludge sedimentation reflux system comprises a sedimentation tank, a first sludge reflux pump, a second sludge reflux pump and a third sludge reflux pump;
The effluent of the multistage A/O reactor is subjected to mud-water separation by the sedimentation tank, sediment sludge is respectively returned to the first anaerobic zone, the second anaerobic zone and the third anaerobic zone by the first sludge return pump, the second sludge return pump and the third sludge return pump, and the effluent after mud-water separation is discharged out of the device;
The multistage a/O reactor further comprises: a first nitrifying liquid reflux pump and a second nitrifying liquid reflux pump;
and the effluent water of the first aerobic zone and the second aerobic zone respectively flows back to the first anoxic zone and the second anoxic zone through a first nitrifying liquid reflux pump and a second nitrifying liquid reflux pump.
According to one aspect of the invention, the aeration system comprises: the device comprises a fan, a plurality of gas rotameters, a plurality of aeration discs and an aeration pipeline;
Each aeration disc is respectively arranged in the first aerobic zone, the second aerobic zone and the third aerobic zone;
the gas rotameter is arranged on the aeration pipeline between each aeration disc and the fan.
According to one aspect of the present invention, further comprising: a plurality of dissolved oxygen detectors;
Each dissolved oxygen detector is respectively arranged in the first aerobic zone, the second aerobic zone and the third aerobic zone.
According to one aspect of the invention, stirrers are arranged in the first anaerobic zone, the first anoxic zone, the first short-time anoxic zone, the second anaerobic zone, the second anoxic zone, the second short-time anoxic zone, the third anaerobic zone and the third short-time anoxic zone.
In order to achieve the above purpose, the invention also provides a synchronous denitrification and dephosphorization method using the reinforced endogenous synchronous denitrification and dephosphorization sludge three-reflux multi-stage A/O device, comprising the following steps:
The multistage a/O reactor was started up:
controlling the mass concentration of the dissolved oxygen in the first aerobic zone and the second aerobic zone to be in the range of 1.5-2.0mg/L, and controlling the mass concentration of the dissolved oxygen in the third aerobic zone to be in the range of 2.0-3.0 mg/L;
The first sludge reflux ratio of the precipitated sludge which is refluxed to the first anaerobic zone through a first sludge reflux pump is controlled to be 100%; during the starting period of the multistage A/O reactor, the first nitrifying liquid reflux pump and the second nitrifying liquid reflux pump are not started, and the second sludge reflux pump and the third sludge reflux pump are not started;
when the COD and total nitrogen removal rate of the multistage A/O reactor respectively reach more than 80 percent, the total phosphorus removal rate reaches more than 50 percent and is maintained for more than 10 days, the multistage A/O reactor is successfully started;
starting and running of a three-reflux multi-stage A/O device for strengthening endogenous synchronous denitrification and dephosphorization sludge:
controlling the reflux ratio of the first nitrifying liquid to the first anoxic zone to be 200-250% by the first nitrifying liquid reflux pump; controlling the reflux ratio of the second nitrifying liquid to the second anoxic zone to be 150-200% by controlling the reflux ratio of the second nitrifying liquid to the second anoxic zone by a second nitrifying liquid reflux pump; controlling the second sludge reflux ratio of the second sludge reflux pump to the second anaerobic zone to be 100-150%; controlling the third sludge reflux ratio of the third sludge reflux pump to the third anaerobic zone to be 100-150%; at the moment, the volume distribution ratio of an anaerobic zone consisting of a first anaerobic zone, a second anaerobic zone and a third anaerobic zone to an anoxic zone consisting of a first anoxic zone, a second anoxic zone and a short-time anoxic zone and an aerobic zone consisting of a first aerobic zone, a second aerobic zone and a third aerobic zone in the multistage A/O reactor is 3:7.2:4, and the sludge age is 8-12 days;
When the COD and total nitrogen removal rate of the multistage A/O reactor reach 88% or more respectively, and the total phosphorus removal rate reaches 95% or more and is maintained for 20 days or more, the three-reflux multistage A/O device of the endogenous synchronous denitrification and dephosphorization sludge is strengthened to be successfully started, and the operation parameters of the successful start stage are prolonged to continue operation in the operation stage;
the starting and the running of the three-reflux multistage A/O device for strengthening endogenous synchronous denitrification and dephosphorization sludge under the low-temperature condition are realized:
The raw water temperature is lower than 15 ℃ and is in a low-temperature condition, the hydraulic retention time is controlled to be 15-16 hours, the sludge age is controlled to be 12-13 days, the reflux ratio of the first nitrifying liquid is 250-300%, the reflux ratio of the second nitrifying liquid is 200-250%, the reflux ratio of the first sludge is 100-130%, the reflux ratio of the second sludge is 150-170%, the reflux ratio of the third sludge is 150-170%, the volume distribution ratio of an anaerobic zone, an anoxic zone and an aerobic zone in the multistage A/O reactor is 3:8:5, and meanwhile, suspension filler is added into the aerobic zone, and the filling ratio is 30%;
When the ammonia nitrogen removal rate of the enhanced endogenous synchronous denitrification and dephosphorization sludge three-reflux multi-stage A/O device reaches more than 99%, the total nitrogen removal rate reaches more than 90%, the total phosphorus removal rate reaches more than 95% and is maintained for more than 10 days, the reactor is successfully started under the low-temperature condition, and the operation stage continues to operate by using the operation parameters of the successful start stage.
According to the scheme of the invention, in the reinforced endogenous denitrification sludge three-reflux multistage A/O reactor, water inflow is divided into 3 sections of water inflow, microorganisms store organic matters in raw water as an internal carbon source in an anaerobic zone, microorganisms use the internal carbon source as an intracellular carbon source (such as PHA and Glycogen) as an electron donor in an anoxic zone, nitrate nitrogen is used as an electron acceptor, endogenous denitrification synchronous nitrogen and phosphorus removal is carried out by taking the internal carbon source as the electron donor, ammonia nitrogen is converted into nitrate nitrogen in an aerobic zone, and meanwhile, partial synchronous nitrification and denitrification can be realized due to lower dissolved oxygen control of a first aerobic zone and a second aerobic zone. Due to the arrangement of the anoxic section with longer hydraulic retention time, microorganisms are in a stage (starvation) of lack of a carbon source for a long time, so that biochemical reaction of the microorganisms in the anaerobic section for converting organic matters in raw water into an internal carbon source is enhanced, and in addition, 3-section sludge reflux is arranged, so that organic load of sludge is reduced, conversion of the organic matters into the internal carbon source is promoted, and endogenous denitrification synchronous deep denitrification and dephosphorization are facilitated.
According to the scheme of the invention, the concentration of dissolved oxygen is reduced by arranging the short-time anoxic zone behind the aerobic zone, so that the effluent of the aerobic zone is prevented from directly flowing back to the anoxic zone, and the ineffective waste of carbon sources can be reduced.
The enhanced endogenous denitrification nitrogen and phosphorus removal can utilize an internal carbon source to complete synchronous removal of nitrogen and phosphorus, thereby greatly saving carbon source consumption. Because the oxygen-deficient phosphorus absorption replaces the aerobic phosphorus absorption, the consumption of oxygen is reduced by 30 percent.
The three sludge reflux areas are arranged to reduce the organic load of sludge in the anoxic area, and the anoxic area with longer hydraulic retention time is arranged to enable microorganisms to be in a starvation state (endogenous respiration period), so that the conversion and storage of internal carbon sources by the microorganisms in the anaerobic section are enhanced, and the sludge yield is reduced.
By arranging two nitrifying liquid reflux, the synchronous denitrification and dephosphorization is completed by strengthening the denitrification of microorganisms in an anoxic zone by using intracellular carbon sources (such as PHA and Glycogen) as electron donors.
Under the low temperature condition (the water temperature is lower than 15 ℃), the organic load of the sludge is reduced by increasing the reflux ratio of the sludge, the total nitrogen removal rate is improved by increasing the reflux ratio of the nitrified liquid, the hydraulic retention time is prolonged, and the sludge age is prolonged to resist the influence of the low temperature on the biochemical reaction process of microorganisms.
Because the mass concentration of the dissolved oxygen in the first aerobic zone and the second aerobic zone is controlled to be 1.5-2.0mg/L, the concentration of the dissolved oxygen is lower, the aeration energy consumption is saved, and the partial synchronous nitrification and denitrification can be realized.
Detailed Description
The present disclosure will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are merely to enable those of ordinary skill in the art to better understand and thus practice the teachings of the present invention and do not imply any limitation on the scope of the invention.
As used herein, the term "comprising" and variants thereof are to be interpreted as meaning "including but not limited to" open-ended terms. The term "based on" is to be interpreted as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment.
FIG. 1 schematically shows a block diagram of the structural arrangement of a three-reflux multistage A/O device for enhancing endogenous synchronous nitrogen and phosphorus removal sludge according to an embodiment of the invention. As shown in fig. 1, in the present embodiment, the enhanced endogenous synchronous denitrification and dephosphorization sludge three-reflux multistage a/O device includes: a water inlet tank 1, a multi-stage A/O reactor 2, a sludge precipitation reflux system 3 and an aeration system 4;
The multistage a/O reactor 2 comprises: the first anaerobic zone 5, the first anoxic zone 6, the first aerobic zone 7, the first short-time anoxic zone 8, the second anaerobic zone 9, the second anoxic zone 10, the second aerobic zone 11, the second short-time anoxic zone 12, the third anaerobic zone 13, the third aerobic zone 14 and the third short-time anoxic zone 15 are sequentially communicated;
The water inlet tank 1 is respectively communicated with the first anaerobic zone 5, the second anaerobic zone 9 and the third anaerobic zone 13 through a first peristaltic pump 16, a second peristaltic pump 17 and a third peristaltic pump 18;
the aeration system 4 is arranged corresponding to the first aerobic zone 7, the second aerobic zone 11 and the third aerobic zone 14 respectively, and continuously aerates the first aerobic zone 7, the second aerobic zone 11 and the third aerobic zone 14;
the sludge sedimentation reflux system 3 comprises a sedimentation tank 19, a first sludge reflux pump 20, a second sludge reflux pump 21 and a third sludge reflux pump 22;
The effluent of the multistage A/O reactor 2 is subjected to mud-water separation through a sedimentation tank 19, and sediment sludge is respectively returned to the first anaerobic zone 5, the second anaerobic zone 9 and the third anaerobic zone 13 through a first sludge return pump 20, a second sludge return pump 21 and a third sludge return pump 22, and the effluent after mud-water separation is discharged out of the device;
the multistage a/O reactor 2 further comprises: a first nitrifying liquid reflux pump 23 and a second nitrifying liquid reflux pump 24;
The effluent water of the first aerobic zone 7 and the second aerobic zone 11 respectively flows back to the first anoxic zone 6 and the second anoxic zone 10 through a first nitrifying liquid reflux pump 23 and a second nitrifying liquid reflux pump 24.
Further, as shown in fig. 1, in the present embodiment, the aeration system 4 includes: a fan 25, a plurality of gas rotameters 26, a plurality of aeration trays 27 and an aeration pipeline 28;
Each aeration disc 27 is respectively arranged in the first aerobic zone 7, the second aerobic zone 11 and the third aerobic zone 14;
An air rotameter 26 is arranged on an aeration pipeline 28 between each aeration disc 27 and the fan 25.
Further, as shown in fig. 1, in this embodiment, the enhanced endogenous synchronous denitrification and dephosphorization sludge three-reflux multistage a/O device further includes: a plurality of dissolved oxygen detectors 29;
the dissolved oxygen detectors 29 are respectively disposed in the first aerobic zone 7, the second aerobic zone 11 and the third aerobic zone 14.
Further, as shown in fig. 1, in the present embodiment, agitators 30 are provided in each of the first anaerobic zone 5, the first anoxic zone 6, the first short-time anoxic zone 8, the second anaerobic zone 9, the second anoxic zone 10, the second short-time anoxic zone 12, the third anaerobic zone 13 and the third short-time anoxic zone 15.
According to the scheme, the strengthening of the endogenous denitrification process is beneficial to solving the problem of lack of external carbon sources in raw water, simultaneously TN removal rate can be improved, denitrifying phosphorus removal bacteria (DPAOs) and denitrifying polysaccharide bacteria (DGAOs) can absorb organic matters in raw water in an anaerobic zone to store internal carbon sources, and by controlling the reflux ratio of nitrifying liquid, microorganisms are strengthened to utilize intracellular carbon sources (such as PHA and Glycogen) as electron donors for denitrification in an anoxic zone to complete synchronous denitrification and dephosphorization. The endogenous denitrification synchronous denitrification dephosphorization technology can save the consumption of COD (chemical oxygen demand) by 50 percent, and the consumption of oxygen is reduced by about 30 percent because the anoxic phosphorus absorption replaces the aerobic phosphorus absorption, thereby greatly reducing the aeration energy consumption, reducing the sludge yield by about 50 percent and reducing the release amount of carbon dioxide by about 20 percent.
The different process forms can strengthen the endogenous denitrification process through working condition adjustment, wherein one domestication mode is rich/hunger operation, namely, a condition (rich) with sufficient carbon source is provided for microorganisms under anaerobic conditions, and the microorganisms are in a carbon source deficiency stage (hunger) through setting an anoxic zone with longer hydraulic retention time, and the two modes are operated alternately. Another way of acclimation is to intensify the endogenous denitrification process by reducing the organic load of the sludge in the anoxic zone.
In the prior art, the effluent of the aerobic zone directly enters the anoxic zone, and the dissolved oxygen in the effluent of the aerobic zone can cause ineffective waste of carbon sources.
Further, according to the scheme of the invention, in the reinforced endogenous denitrification sludge three-reflux multistage A/O reactor, water inflow is divided into 3 sections of water inflow, microorganisms store organic matters in raw water as an internal carbon source in an anaerobic zone, microorganisms use the internal carbon source as an intracellular carbon source (such as PHA and Glycogen) as an electron donor in an anoxic zone, and nitrate nitrogen is used as an electron acceptor to perform denitrification to complete synchronous denitrification and dephosphorization, ammonia nitrogen is converted into nitrate nitrogen in an aerobic zone, and meanwhile, partial synchronous nitrification and denitrification can be realized due to the fact that the first aerobic zone and the second aerobic zone control lower dissolved oxygen. Due to the arrangement of the anoxic section with longer hydraulic retention time, microorganisms are in a stage (starvation) of lack of a carbon source for a long time, so that biochemical reaction of the microorganisms in the anaerobic section for converting organic matters in raw water into an internal carbon source is enhanced, and in addition, 3-section sludge reflux is arranged, so that organic load of sludge is reduced, conversion of the organic matters into the internal carbon source is promoted, and endogenous denitrification synchronous deep denitrification and dephosphorization are facilitated.
Further, in order to achieve the above purpose, the invention also provides a synchronous denitrification and dephosphorization method using the reinforced endogenous synchronous denitrification and dephosphorization sludge three-reflux multi-stage A/O device, comprising the following steps:
the multistage a/O reactor 2 is started up:
Inoculating surplus sludge of the town domestic sewage plant into the multi-stage A/O reactor 2, and keeping the overall sludge concentration of the reactor at about 4500-5000 mg/L; the inflow water adopts the effluent water of an aeration grit chamber of a municipal wastewater treatment plant, the COD mass concentration is 96-220mg/L, the ammonia nitrogen mass concentration is 45-55mg/L, and the total phosphorus mass concentration is 3.5-6.2mg/L; the water inlet distribution ratio is 50 percent to 35 percent to 15 percent, the hydraulic retention time is 12 to 14.2 hours, and the sludge age is controlled to 8 to 12 days;
Controlling the mass concentration of the dissolved oxygen in the first aerobic zone 7 and the second aerobic zone 11 to be in the range of 1.5-2.0mg/L, and controlling the mass concentration of the dissolved oxygen in the third aerobic zone 14 to be in the range of 2.0-3.0 mg/L;
The first sludge recirculation ratio of the precipitated sludge recirculated into the first anaerobic zone 5 via the first sludge recirculation pump 20 is controlled to be 100%; during the startup of the multistage A/O reactor, the first nitrifying liquid reflux pump 23 and the second nitrifying liquid reflux pump 24 are both closed, and the second sludge reflux pump 21 and the third sludge reflux pump 22 are closed;
when the COD and total nitrogen removal rate of the multistage A/O reactor (2) respectively reach more than 80 percent, the total phosphorus removal rate reaches more than 50 percent and is maintained for more than 10 days, the multistage A/O reactor is successfully started;
starting and running of a three-reflux multi-stage A/O device for strengthening endogenous synchronous denitrification and dephosphorization sludge:
After the multistage A/O reactor 2 is successfully started, the inoculated activated sludge has a certain COD, total nitrogen and total phosphorus removal capacity, then the sludge reflux and the nitrifying liquid reflux are increased, and the endogenous denitrification depth synchronous denitrification and dephosphorization capacity of the activated sludge is domesticated.
Controlling the reflux ratio of the first nitrifying liquid to be 200-250% after the reflux of the first nitrifying liquid to the first anoxic zone 6 by the first nitrifying liquid reflux pump 23; controlling the reflux ratio of the second nitrifying liquid to the second anoxic zone 10 by the second nitrifying liquid reflux pump 24 to be 150-200%; controlling the second sludge recirculation ratio of the second sludge recirculation pump 21 to be 100-150% for recirculating the second anaerobic zone 6; controlling the third sludge recirculation ratio of the third sludge recirculation pump 22 to be 100-150% for recirculating the third anaerobic zone 13; at this time, the volume distribution ratio between the anaerobic zone consisting of the first anaerobic zone 5, the second anaerobic zone 9 and the third anaerobic zone 13, the anoxic zone consisting of the first anoxic zone 6 and the second anoxic zone 10 and the aerobic zone consisting of the first aerobic zone 7, the second aerobic zone 11 and the third aerobic zone 14 in the multistage A/O reactor 2 is 3:7.2:4, and the sludge age is 8-12 days;
when the COD and total nitrogen removal rate of the multistage A/O reactor 2 reach 88% or more respectively, and the total phosphorus removal rate reaches 95% or more and is maintained for 20 days or more, the three-reflux multistage A/O device of the endogenous synchronous denitrification and dephosphorization sludge is strengthened to be successfully started, and the operation parameters of the successful start stage are prolonged to continue operation in the operation stage;
the starting and the running of the three-reflux multistage A/O device for strengthening endogenous synchronous denitrification and dephosphorization sludge under the low-temperature condition are realized:
The raw water temperature is lower than 15 ℃ and is in a low-temperature condition, the hydraulic retention time is controlled to be 15-16h, the sludge age is controlled to be 12-13 days, the reflux ratio of the first nitrifying liquid is 250-300%, the reflux ratio of the second nitrifying liquid is 200-250%, the reflux ratio of the first sludge is 100-130%, the reflux ratio of the second sludge is 150-170%, the reflux ratio of the third sludge is 150-170%, the volume distribution ratio of an anaerobic zone, an anoxic zone and an aerobic zone in the multistage A/O reactor 2 is 3:8:5, and meanwhile, suspension filler is added into the aerobic zone, and the filling ratio is 30%;
When the ammonia nitrogen removal rate of the enhanced endogenous synchronous denitrification and dephosphorization sludge three-reflux multi-stage A/O device reaches more than 99%, the total nitrogen removal rate reaches more than 90%, the total phosphorus removal rate reaches more than 95% and is maintained for more than 10 days, the reactor is successfully started under the low-temperature condition, and the operation stage continues to operate by using the operation parameters of the successful start stage.
According to the scheme, the short-time anoxic zone is arranged behind the aerobic zone to reduce the concentration of dissolved oxygen, so that the effluent of the aerobic zone is prevented from directly flowing back to the anoxic zone, and the ineffective waste of carbon sources can be reduced.
The enhanced endogenous denitrification nitrogen and phosphorus removal can utilize an internal carbon source to complete synchronous removal of nitrogen and phosphorus, thereby greatly saving carbon source consumption. Because the oxygen-deficient phosphorus absorption replaces the aerobic phosphorus absorption, the consumption of oxygen is reduced by 30 percent.
The organic load of sludge in the anoxic zone is reduced by arranging three sludge reflux and the anoxic zone with longer hydraulic retention time is arranged to enable microorganisms to be in a starvation state (endogenous respiration period), so that the storage of the microorganisms on an internal carbon source is enhanced and the sludge yield is reduced.
By arranging two nitrifying liquid reflux, the synchronous denitrification and dephosphorization is completed by strengthening the denitrification of microorganisms in an anoxic zone by using intracellular carbon sources (such as PHA and Glycogen) as electron donors.
Under the low temperature condition (the water temperature is lower than 15 ℃), the organic load of the sludge is reduced by increasing the reflux ratio of the sludge, the total nitrogen removal rate is improved by increasing the reflux ratio of the nitrified liquid, the hydraulic retention time is prolonged, and the sludge age is prolonged to resist the influence of the low temperature on microorganisms.
Because the mass concentration of the dissolved oxygen in the first aerobic zone and the second aerobic zone is controlled to be 1.5-2.0mg/L, the concentration of the dissolved oxygen is lower, and partial synchronous nitrification and denitrification can be realized while the power consumption is saved.
According to the scheme, in practice, a short-time anoxic section is arranged at the end of the process, so that the dissolved oxygen of the effluent is reduced, and the dissolved oxygen of the return sludge is reduced, so that the anaerobic environment of an anaerobic zone is not damaged.
According to the invention, an anaerobic section (2-nitrification liquid internal reflux is increased) with a longer hydraulic retention time is coupled by adopting a sectional water inlet (3-section water inlet) and a mode of arranging 3 sludge reflux (reducing sludge load in an anaerobic zone) is adopted to form a famine-plump working condition similar to an A-B method, so that microorganisms are enhanced to convert an external carbon source into an internal carbon source, and further endogenous denitrification is enhanced.
According to the invention, by setting two nitrifying liquid reflux and a higher nitrifying liquid internal reflux ratio, the synchronous denitrification and dephosphorization are completed by strengthening that microorganisms perform denitrification and dephosphorization in an anoxic zone by using intracellular carbon sources (such as PHA and Glycogen) as electron donors and using nitrate nitrogen as electron acceptors.
The hydraulic retention time of the anoxic section of the invention accounts for 50.70 percent of the total hydraulic retention time, the ratio of the aerobic section accounts for 28.17 percent, and the dissolved oxygen of the first two aerobic sections is set to be 1.5-2mg/L. Because the denitrification dephosphorization biochemical process is slower, the arrangement of a longer anoxic section is beneficial to the deep denitrification dephosphorization and the formation of the 'famine' working condition (the working condition is beneficial to the storage of internal carbon sources). When the carbon source is stored in the cell in the form of an internal carbon source, the lower dissolved oxygen (1.5-2 mg/L, the effect of avoiding aeration penetration) is set, so that the organic matters can be prevented from being utilized by other heterotrophic bacteria, and the dissolved oxygen is facilitated to be absorbed by nitrifying bacteria (autotrophic bacteria) more to complete the nitrification of ammonia nitrogen, therefore, the invention can set a shorter aerobic section, and realize energy conservation and consumption reduction.
Finally, it is noted that the above-mentioned preferred embodiments are only intended to illustrate rather than limit the invention, and that, although the invention has been described in detail by means of the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.