CN111484199A

CN111484199A - Intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process

Info

Publication number: CN111484199A
Application number: CN202010322875.9A
Authority: CN
Inventors: 张唯; 段昌群; 李世玉; 程立忠; 王海玉; 罗春梅
Original assignee: Yunnan University YNU
Current assignee: Yunnan University YNU
Priority date: 2020-04-22
Filing date: 2020-04-22
Publication date: 2020-08-04
Anticipated expiration: 2040-04-22
Also published as: CN111484199B

Abstract

The invention discloses a process for ultra-deep removal of nitrogen and phosphorus by intermittent double-sludge denitrification AN (AO) n full-nitrification, which comprises the following steps: according to the denitrification nitrogen and phosphorus removal principle, denitrifying bacteria and nitrifying bacteria are separately cultured in a denitrification tank and a nitrification tank, nitrification and denitrification reaction end point control is realized by monitoring pH, ORP and DO on line, residual ammonia nitrogen carried by sludge in the denitrification tank is removed through multiple nitrification and denitrification to realize complete removal of nitrogen, the anaerobic phosphorus release, the denitrification phosphorus absorption and the aerobic phosphorus absorption are utilized, and the phosphorus concentration monitoring and flocculation-assisted enhanced phosphorus removal are realized through the orthophosphate radical concentration monitoring and the flocculation-assisted enhanced phosphorus removal, so that the ultra-deep and stable phosphorus removal is realized, and the problems of poor nitrogen and phosphorus purification effect and unstable effluent quality existing in the traditional double-sludge denitrification process are solved.

Description

Intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process

Technical Field

The invention relates to the technical field of sewage treatment, in particular to a process for ultra-deep removal of nitrogen and phosphorus by intermittent double-sludge denitrification AN (AO) n full-nitrification.

Background

At present, the discharge standard of pollutants for municipal wastewater treatment plants GB18918-2002 and the environmental quality standard of surface water GB3838-2002 implemented in China are seriously disjointed, and the domestic application of the sewage treatment process is relatively wide: the AB method, the oxidation ditch method, the A/O process, the A/A/O process, the SBR method and the like lack deep nitrogen and phosphorus removal links, are only equivalent to surface water inferior V types after purification, cause damage to the ecology, landscape and water body functions of the surface water, and simultaneously cause potential threat to the quality of the underground water. With the rapid development of economic society, the requirements of people on water environment quality are higher and higher, the discharge standard of sewage treatment in China will gradually meet the standard of surface water quality, and the upgrading and reconstruction of sewage plants and the deep and ultra-deep treatment of sewage become the focus of attention. The existing sewage deep and ultra-deep treatment process is difficult to be popularized on a large scale in a short period due to high manufacturing cost and operation and maintenance cost. Therefore, the research on how to upgrade and modify the prior art, reduce the treatment cost, develop a new process and a new technology which are suitable for the national conditions of China and directly reach the water quality standards of II or III types of surface water by biochemical treatment of sewage is one of the fundamental ways to solve the problem of water environment pollution of China.

In recent years, although automatic control technology has been rapidly developed and widely used, the on-line control technology of sewage treatment process is still in the primary research stage due to the multi-parameter, multi-environment variable and dynamic water quality and water quantity change, and particularly, the control technology for simultaneously realizing ultra-deep nitrogen and phosphorus removal is rarely reported. Therefore, in the sewage treatment process, a computer is used for carrying out accurate end point and process control, so that the denitrification and the dephosphorization are in the best working condition, and the method has important significance for the deep and ultra-deep treatment of sewage treatment.

The double sludge denitrification process is a sewage treatment process which perfectly combines nitrogen and phosphorus removal and simultaneously realizes the triple purposes of CODcr, nitrogen and phosphorus removal, the process separates nitrifying microorganisms and denitrifying microorganisms to be cultured in independent and proper environments, fully utilizes an organic carbon source in sewage, enriches DPAOs by anaerobic/anoxic alternate operation, synthesizes an internal carbon source PHA by VFAs in raw water under anaerobic conditions, takes nitrate as an electron acceptor to oxidize and decompose the PHA in vivo under anoxic conditions, and completes an excessive phosphorus absorption reaction, thereby solving the problem of insufficient organic carbon source in the nitrogen and phosphorus removal process of the traditional sewage treatment process, having the characteristics of high efficiency, low energy consumption, low sludge production and the like, being concerned at present and being a novel biological nitrogen and phosphorus removal technology with great prospect. The double-sludge denitrification nitrogen and phosphorus removal mainly represents processes of A2N and Dephanox.

However, the existing intermittent flow double-sludge denitrification nitrogen and phosphorus removal process has the following three disadvantages: firstly, due to a large amount of ammonia nitrogen carried by sludge, the concentration of the ammonia nitrogen and nitrate radical in effluent is higher; secondly, the removal of nitrogen and phosphorus is based on biochemical reaction, and once the proportion of nitrate nitrogen or organic carbon source is disordered, the whole reaction can not be normally carried out, the deterioration can occur, so that the stability of the process is poor; thirdly, the nitrogen and phosphorus removal efficiency is low, and ultra-deep nitrogen and phosphorus removal cannot be realized.

Disclosure of Invention

The invention aims to provide a process for ultra-deep nitrogen and phosphorus removal by intermittent double-sludge denitrification AN (AO) n total nitrification, which solves the problems of ultra-deep nitrogen and phosphorus removal and unstable effluent quality.

In order to solve the technical problems, the invention adopts the following technical scheme:

an intermittent double-sludge denitrification AN (AO) n full-Nitrification ultra-deep nitrogen and phosphorus removal process, AN (AO) n is Anaerobic, Nitrification and multiple Anoxic and aerobic, Anaerobic and Anoxic and aerobic, and the process comprises a device part; the device part comprises: a sewage storage tank, a denitrification tank, a nitrification tank, an intermediate tank and a flocculation sedimentation tank;

the sewage storage tank is connected with a first pipeline, a water pump is arranged on the first pipeline, the sewage storage tank is connected with the denitrification tank through the first pipeline, a decanter is arranged in the denitrification tank, a water outlet of the decanter is connected with a second pipeline and a third pipeline, the decanter is connected with the nitrification tank through the second pipeline, and a supernatant transfer pump and an electromagnetic valve are arranged on the second pipeline;

the decanter is connected with the flocculation sedimentation tank through a third pipeline;

the nitrifying tank is connected with a fourth pipeline, the nitrifying tank is connected with the intermediate tank through the fourth pipeline, a nitrifying liquid transfer pump is arranged on the fourth pipeline, the intermediate tank is connected with a fifth pipeline, a nitrifying liquid reflux pump is arranged on the fifth pipeline, and the intermediate tank is connected with the denitrification tank through the fifth pipeline.

Further, the method comprises the following steps of; aeration heads are arranged at the bottoms of the denitrification tank and the nitrification tank, the aeration heads are connected with an air inlet pipe, a gas flowmeter is arranged on the air inlet pipe, the air inlet pipe is connected with an aeration pump, and the aeration pump is connected with a frequency converter;

the top of the denitrification tank is provided with a cover which is in a semi-sealed state, and the top of the denitrification tank is provided with an exhaust hole;

the bottoms of the denitrification tank and the nitrification tank are respectively provided with a first sludge discharge pipe, and a sludge discharge pump is arranged on the first sludge discharge pipe;

the bottom of the nitrification tank is connected with a second sludge discharge pipe, the nitrification tank is connected with the denitrification tank through the second sludge discharge pipe, and a first sludge discharge valve is arranged on the second sludge discharge pipe.

Further, the method comprises the following steps of; the upper part of the flocculation sedimentation tank is cylindrical, the lower part of the flocculation sedimentation tank is a funnel-shaped cone with an angle of 45-70 degrees, a third sludge discharge pipe is arranged at the bottom of the flocculation sedimentation tank, and a second sludge discharge valve is arranged on the third sludge discharge pipe;

the flocculation sedimentation tank is connected with a dephosphorization flocculant pipe and a PAM flocculant pipe, the dephosphorization flocculant pipe is provided with a dephosphorization flocculant pump, the PAM flocculant pipe is provided with a PAM flocculant pipe pump, the flocculation sedimentation tank is connected with a dephosphorization flocculant barrel through the dephosphorization flocculant pipe, the flocculation sedimentation tank is connected with the PAM flocculant barrel through the PAM flocculant pipe, the side wall of the flocculation sedimentation tank is provided with a drain pipe, and the drain pipe is provided with a drain valve;

the flocculation sedimentation tank is connected with an online phosphate tester, and the online phosphate tester is connected with an industrial computer.

Further, the method comprises the following steps of; submersible stirrers are arranged in the denitrification tank, the nitrification tank and the flocculation sedimentation tank;

the dephosphorization flocculating agent barrel and the PAM flocculating agent barrel are both provided with flocculating agent stirrers.

Further, the method comprises the following steps of; the denitrification tank and the nitrification tank are respectively provided with a DO online tester, a water level probe and a pH online tester;

the denitrification tank is provided with an ORP (oxidation-reduction potential) measuring instrument;

the water pump, the pump nitrification liquid transfer pump, the supernatant transfer pump, the electromagnetic valve, the nitrification liquid reflux pump, the aeration pump, the second sludge discharge valve, the drain valve, the water level probe, the first sludge discharge valve, the submersible stirrer and the flocculant stirrer are connected and controlled with P L C;

the decanter, the sludge discharge pump, the ORP measuring instrument, the phosphorus removal flocculant pump, the PAM flocculant pipe pump, the DO online measuring instrument, the pH online measuring instrument, the online phosphate radical measuring instrument and the frequency converter are connected with the industrial personal computer through communication lines;

the P L C is connected with an industrial personal computer through a communication line, and the whole system is controlled by the industrial personal computer to operate;

the sludge discharge pump, the dephosphorization flocculant pump and the PAM flocculant pipe pump are quantitative pumps.

Further, the method comprises the following steps of; the process comprises a control method part, wherein the control method comprises the following steps:

a biochemical treatment control flow: the whole device runs periodically, firstly, sewage in a sewage storage tank enters a denitrification tank, the sewage is subjected to anaerobic stirring and then is kept stand and settled, supernatant liquid enters a nitrification tank through a decanter, nitrified liquid in an intermediate tank enters a denitrification tank, the supernatant liquid is subjected to aerobic aeration nitrification reaction in the nitrification tank, when the nitrification reaction reaches the end point, aeration and stirring are stopped, the supernatant liquid is kept stand and settled, then the nitrified liquid in the nitrification tank enters the intermediate tank for storage, after the nitrified liquid enters the denitrification tank, the denitrification tank is subjected to first anoxic denitrification reaction and simultaneously denitrification phosphorus absorption, when the denitrification reaches the end point, the denitrification tank is switched to an aerobic aeration nitrification section, the nitrogen is converted into nitrogen through repeated aerobic nitrification reaction and anoxic denitrification ammonia nitrogen for complete removal, the phosphorus is removed through aerobic phosphorus absorption and denitrification phosphorus absorption, the denitrification tank is finally subjected to aerobic nitrogen blow-off, the denitrification tank after the standing and settling drains water into a flocculation settling tank through the decanter, after the drainage is finished, quantitative sludge discharge is started, and the next cycle is started after the cycle operation of the denitrification tank is finished;

b, strengthening a phosphorus removal control process: after the wastewater enters a denitrification tank of a flocculation sedimentation tank, measuring by an online soluble phosphorus measuring instrument, when the concentration of soluble phosphate radicals meets the requirement, only removing suspended sludge debris to improve the purification efficiency of total phosphorus, stirring for 10-20min by using a PAM (polyacrylamide) dephosphorization flocculating agent by using an industrial personal computer, stopping stirring, standing for sedimentation for 10-30min, and then draining and discharging sludge; when the concentration of the soluble phosphorus is more than a set value, one of alum, polymeric ferric sulfate or ferric trichloride dephosphorization flocculant is selected, after the dephosphorization flocculant is added, the mixture is stirred for 10-20min, the stirring is stopped, the mixture is kept still and settled for 5min, the concentration of the soluble phosphate radical is measured by sampling, when the concentration of the soluble phosphate radical is less than the set concentration, the mixture is kept still for 10-30min, then the sedimentation is carried out, sludge discharge and drainage are carried out, when the concentration of the soluble phosphate radical is more than the set concentration, the dephosphorization flocculant is added again, the flocculation and the standing measurement are carried out again until the concentration of the phosphate radical meets the set requirement, the mixture is kept still and settled for 10-30 min.

Further, the method comprises the following steps of; the water outlet of the decanter is arranged at 1/5-1/2 of the effective depth of the denitrification tank, the drainage height of the decanter is 1/4-1/2 of the effective height of the denitrification tank when the purification of the denitrification tank is finished, and the discharge height of the supernatant of the decanter is 1/5-1/3 when the anaerobic section of the denitrification tank is finished;

the drainage height of the nitrification tank is 1/4-1/3 of the effective height of the nitrification tank.

Further, the method comprises the following steps of; the sludge in the denitrification tank stays for 10-30 days, and the sludge stays for 20-40 days in the nitrification tank;

the nitrification tank regularly supplies the content of nitrifying bacteria in the denitrification tank to the sludge discharged from the denitrification tank.

Further, the method comprises the following steps of; the longest time of the first anoxic denitrification reaction of the denitrification tank is not more than 4h, and the time of each anoxic denitrification reaction for multiple times is not more than 2 h;

the aerobic section of the denitrification tank is set to be timed and added with nitrification end point judgment control: the operating time of the aerobic section is 5-60min each time, the aerobic section is converted into an anoxic denitrification section when reaching the set time, the aeration is stopped to be switched into the anoxic denitrification section when reaching the set aerobic aeration nitrification time and not reaching the nitrification end point, the aerobic aeration is stopped when reaching the nitrification end point, the denitrification tank enters the last anoxic denitrification section, and nitrogen pollutants are completely converted into nitrogen to be removed; the denitrification section of the denitrification tank is set to be controlled by judging and adding a denitrification end point: before the aerobic nitrification reaches the end point, each time the anoxic denitrification reaction reaches the denitrification end point within the set time, starting aeration and switching to the aerobic section, and when the anoxic denitrification reaction does not reach the denitrification end point within the set time, directly entering the last aerobic nitrogen stripping section; when the last anoxic denitrification is finished, the denitrification tank enters a timing aerobic nitrogen stripping section for 10-30 min;

the nitration end point control method comprises the following steps: the industrial personal computer monitors and judges that the pH has a valley point through the pH on-line measuring instrument, the first derivative of the pH is changed from a negative value to a positive value, and meanwhile, the DO on-line measuring instrument monitors that the DO has an obvious jump;

the denitrification end point is judged as follows: the pH on-line measuring instrument monitors that the pH has a peak point, the first derivative of the pH is changed from positive rotation to continuous zero or less, or the ORP measuring instrument in the anoxic section monitors that the second derivative of the ORP is continuously negative;

the time length and the aeration intensity of the tail-end nitrogen stripping section are based on completely stripping nitrogen in the sludge mixed liquor, when the concentration of soluble orthophosphate measured for the first time in the flocculation sedimentation tank exceeds the standard, the time length and the aeration intensity of each aerobic nitrification section are adjusted, the control range of the tail-end nitrogen stripping ORP is adjusted, and the aeration amount and the aeration time of nitrogen stripping are changed to control the phosphorus purification efficiency of the next period; ORP control range at the end of terminal nitrogen stripping: 50-200 mv.

Further, the method comprises the following steps of; the stirring time of the anaerobic section of the denitrification tank is 1-2.5h, the standing and settling time of the anaerobic section of the denitrification tank is 30-60min after the completion, and the standing and settling time is 30-60min after nitrogen stripping.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention provides a process for ultra-deep denitrification and ultra-deep removal of nitrogen and phosphorus by intermittent double-sludge denitrification AN (AO) N, aiming at solving the problems that the prior denitrification nitrogen and phosphorus removal processes such as A2N and Dephanox and the like cannot realize ultra-deep nitrogen and phosphorus removal and the quality of effluent is unstable, wherein the process adds N aerobic sections behind an anoxic section of the traditional intermittent double-sludge A2N process based on the end point control technology of nitrification reaction and denitrification reaction according to the principle of double-sludge denitrification and phosphorus removal, gradually exceeds the residual ammonia nitrogen of sludge through aerobic nitrification and gradually reduces the nitrate nitrogen and nitrite nitrogen converted in each aerobic section into N through denitrification and final reduction by the increased N-1 anoxic sections₂And (2) removing gas, wherein the phosphorus is synchronously absorbed in an ultra-deep manner in the denitrification process by a denitrification phosphorus absorption principle and an aerobic phosphorus absorption principle, a chemical phosphorus removal unit is added to monitor the phosphorus concentration of the effluent of the denitrification tank, and a phosphorus removal flocculating agent is added to remove suspended sludge debris in the effluent, so that the treatment effect of the total phosphorus is further improved, and meanwhile, when the system is unstable and the concentration of the influent phosphorus is higher, the phosphorus is assisted by adding a chemical phosphorus removal agent to remove phosphorus, so that the phosphorus concentration of the effluent is controlled at a lower level.

2. The process is suitable for treating domestic sewage with CODcr of 150 mg/L-1000 mg/L and carbon-nitrogen ratio of 6-14, and the indexes of total nitrogen, total phosphorus and CODcr of effluent can basically reach the standards of more than three types of surface water.

Drawings

FIG. 1 is a schematic view of the structure of the present invention.

In the drawing, a sewage storage tank (1), a denitrification tank (2), a nitrification tank (3), an intermediate tank (4), a flocculation sedimentation tank (5), a first pipeline (6), a water pump (7), a second pipeline (8), a decanter (9), a third pipeline (10), a nitrified liquid transfer pump (11), a supernatant transfer pump (12), an electromagnetic valve (13), a fourth pipeline (14), a fifth pipeline (15), a nitrified liquid reflux pump (16), an air inlet pipe (17), a gas flow meter (18), an aeration pump (19), an aeration head (20), a first sludge discharge pipe (21), a sludge discharge pump (22), a third sludge discharge pipe (23), a second sludge discharge valve (24), a frequency converter (25), an ORP determinator (26), a PAM flocculant pipe (27), a dephosphorization pump (28), a PAM flocculant pipe pump (29), a flocculant barrel (30), a PAM barrel (31), a drain pipe (32), a flocculant stirrer (33), a submersible flocculant stirrer (34), a DO water level determinator (35), a DO probe (36), a DO), a pH control line stirrer (36), a P) and a phosphate discharge valve (40), a computer-based sludge discharge meter (40).

Detailed Description

Fig. 1 is a schematic diagram illustrating an embodiment of the present invention, and the following detailed description is provided to explain the present invention. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1:

an intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process comprises a device part; the device part comprises: a sewage storage tank 1, a denitrification tank 2, a nitrification tank 3, an intermediate tank 4 and a flocculation sedimentation tank 5;

the sewage storage tank 1 is connected with a first pipeline 6, a water pump 7 is arranged on the first pipeline 6, the sewage storage tank 1 is connected with a denitrification tank 2 through the first pipeline 6, a decanter 9 is arranged in the denitrification tank 2, a water outlet of the decanter 9 is connected with a second pipeline 8 and a third pipeline 10, the decanter 9 is connected with a nitrification tank 3 through the second pipeline 8, and a supernatant transfer pump 12 and an electromagnetic valve 13 are arranged on the second pipeline 8;

the decanter 9 is connected with the flocculation sedimentation tank 5 through a third pipeline 10;

the nitrification tank 3 is connected with a fourth pipeline 14, the nitrification tank 3 is connected with the intermediate tank 4 through the fourth pipeline 14, a nitrified liquid transfer pump 11 is arranged on the fourth pipeline 14, the intermediate tank 4 is connected with a fifth pipeline 15, a nitrified liquid reflux pump 16 is arranged on the fifth pipeline 15, and the intermediate tank 4 is connected with the denitrification tank 2 through the fifth pipeline 15; sewage is added into the denitrification tank from the sewage storage tank 1 through the water pump 72, anaerobic stirring is carried out in the denitrification tank 2, the activated sludge microorganisms absorb and adsorb organic substances to synthesize an internal carbon source PHA, release phosphorus and settle, the liquid rich in ammonia nitrogen enters the nitrification tank 3 to carry out aerobic nitrification reaction, when the nitrification reaches the end point, the nitrification liquid is transferred to the intermediate tank 4 through the nitrification liquid transfer pump 11, the nitrification liquid stored in the intermediate tank 4 returns to the denitrification tank 2 after the supernatant liquid in the denitrification tank 2 is transferred, and is mixed with the settled sludge in the denitrification tank 2 to carry out the first anoxic denitrification reaction, and nitrate nitrogen and nitrite nitrogen are reduced to N₂Releasing and simultaneously performing denitrification phosphorus absorption, converting ammonia nitrogen remained in the settled sludge into nitrate nitrogen and nitrite nitrogen through subsequent multiple aerobic nitrification, and converting the multiple anoxic denitrification into nitrogen to be thoroughly removed; and (3) blowing off the denitrification tank 2 by aerobic nitrogen, stopping stirring, standing and settling, draining water from the denitrification tank 2 after settling, draining water from the decanter 9 for the first few minutes to the nitrification tank 3 for cleaning the decanter 9, draining water from the flocculation and settling tank 5 by the decanter 9, discharging quantitative sludge after the drainage of the denitrification tank 2 is finished, and starting the next cycle of operation or leaving unused for water inlet in the next cycle after the sludge discharge is finished.

Example 2:

on the basis of the embodiment 1, aeration heads 20 are arranged at the bottoms of the denitrification tank 2 and the nitrification tank 3, the aeration heads 20 are communicated with an air inlet pipe 17, a gas flowmeter 18 is arranged on the air inlet pipe 17, the air inlet pipe 17 is connected with an aeration pump 19, and the aeration pump 19 is connected with a frequency converter 25;

the top of the denitrification tank 2 is provided with a cover which is in a semi-sealed state, and the top of the denitrification tank 2 is provided with an exhaust hole;

the bottoms of the denitrification tank 2 and the nitrification tank 3 are respectively provided with a first sludge discharge pipe 21, and a sludge discharge pump 22 is arranged on the first sludge discharge pipe 21;

the bottom of the nitrification tank 3 is connected with a second sludge discharge pipe 43, the nitrification tank 3 is connected with the denitrification tank 2 through the second sludge discharge pipe 43, and a first sludge discharge valve 40 is arranged on the second sludge discharge pipe 43; the air inlet pipe 17 is used for introducing air into the air inlet pipe 17 under the action of the aeration pump 19, and aeration is finally carried out through the aeration head 20, so that the denitrification tank 2 and the nitrification tank 3 can conveniently react, the top of the denitrification tank 2 is provided with a cover and is in a semi-sealed shape, and meanwhile, the denitrification tank 2 can be communicated with the atmosphere through an exhaust hole formed in the top; the first sludge discharge pipe 21 can discharge sludge in the denitrification tank 2 and the nitrification tank 3 according to requirements.

Example 3:

on the basis of the embodiment 1-2, the upper part of the flocculation sedimentation tank 5 is set to be cylindrical, the lower part of the flocculation sedimentation tank is set to be a funnel-shaped cone with an angle of 45-70 degrees, the bottom of the flocculation sedimentation tank 5 is provided with a third sludge discharge pipe 23, and the third sludge discharge pipe 23 is provided with a second sludge discharge valve 24;

the flocculation sedimentation tank 5 is connected with a dephosphorization flocculant pipe 39 and a PAM flocculant pipe 27, a dephosphorization flocculant pump 28 is arranged on the dephosphorization flocculant pipe 39, a PAM flocculant pipe pump 29 is arranged on the PAM flocculant pipe 27, the flocculation sedimentation tank 5 is connected with a dephosphorization flocculant barrel 30 through the dephosphorization flocculant pipe 39, the flocculation sedimentation tank 5 is connected with the PAM flocculant barrel 31 through the PAM flocculant pipe 27, a drain pipe 32 is arranged on the side wall of the flocculation sedimentation tank 5, and a drain valve 33 is arranged on the drain pipe 32;

the flocculation sedimentation tank 5 is connected with an online phosphate tester 41, and the online phosphate tester 41 is connected with the industrial personal computer 38; carrying out sludge discharge and water discharge according to requirements; in order to increase the activity and concentration of nitrifying bacteria in the denitrification tank 2, the sludge in the nitrification tank 3 can be discharged into the denitrification tank 2 periodically after the nitrification tank 3 drains water.

Example 4:

on the basis of the embodiments 1-3, submersible stirrers 34 are arranged in the denitrification tank 2, the nitrification tank 3 and the flocculation sedimentation tank 5;

the dephosphorization flocculant bucket 30 and the PAM flocculant bucket 31 are both provided with flocculant stirrers 42; has the function of stirring.

Example 5:

on the basis of the embodiments 1 to 4, the denitrification tank 2 and the nitrification tank 3 are both provided with a DO online measuring instrument 35, a water level probe 36 and a pH online measuring instrument 37;

the denitrification tank 2 is provided with an ORP measuring instrument 26;

the water pump 7, the pump nitrifying liquid transfer pump 11, the supernatant transfer pump 12, the electromagnetic valve 13, the nitrifying liquid reflux pump 16, the aeration pump 19, the second sludge discharge valve 24, the water discharge valve 33, the water level probe 36, the first sludge discharge valve 40, the submersible stirrer 34 and the flocculant stirrer 42 are connected with and controlled by P L C44;

the decanter 9, the sludge discharge pump 22, the ORP measuring instrument 26, the phosphorus removal flocculant pump 28, the PAM flocculant pipe pump 29, the DO online measuring instrument 35, the pH online measuring instrument 37, the online phosphate radical measuring instrument 41 and the frequency converter 25 are connected with the industrial personal computer 38 through communication lines;

the P L C is connected with the industrial personal computer 38 through a communication line, and the whole system is controlled by the industrial personal computer 38 to operate;

the sludge discharge pump 22, the dephosphorization flocculant pump 28 and the PAM flocculant pipe pump 29 are quantitative pumps, when the denitrification tank 2 is in aerobic nitrogen stripping, the industrial control computer 38 judges whether denitrification reaches a denitrification end point or whether the denitrification reaches a set aerobic time by reading the pH and DO data of the DO online determinator 35 and the pH online determinator 37, namely the industrial control computer 38 controls an aerobic section by controlling the start and stop of the decanter 9 when the denitrification tank 2 reaches the end point, when the denitrification tank 2 reaches the nitrification end point, the pH has a valley point, the first-order derivative of the pH is changed into a positive value, the DO is suddenly increased, and the industrial control computer 38 stops the operation of the aeration pump through P L C when the DO reaches the nitrification end point;

the denitrification end point control system of the denitrification tank 3 consists of an ORP (oxidation-reduction potential) measuring instrument 26 arranged in sludge mixed liquid in the denitrification tank 3, and an industrial control computer 38 connected with a corresponding control system program, wherein when a peak point appears in pH, a positive value of a first-order derivative of the pH is changed into a negative value, the first-order derivative of the ORP is the negative value, and a denitrification end point is marked when a second-order derivative of the pH is continuously less than zero, at the moment, the industrial control computer switches the state of the denitrification tank 3 from an anoxic state to an aerobic state, and starts an aeration pump 19 to start aeration;

the nitrification end point control system of the nitrification tank 3 is composed of an aeration head 20 arranged at the bottom of the nitrification tank 3, an aeration pump 19 connected with the power output end of a decanter 9, the decanter 9 connected with an industrial personal computer 38 through a communication line, and a DO online determinator 35 arranged in the nitrification tank 3, wherein the industrial personal computer 38 judges whether the nitrification end point is reached through read pH and DO data, when the nitrification end point is reached, a valley point appears in pH, a negative value appears in a first derivative of pH, the pH value becomes a positive value, the DO suddenly rises, the two appear at the same time, and the industrial personal computer 38 stops the operation of the aeration pump through P L C;

the aerobic nitrogen blowing of the denitrification tank 2 has the function of controlling the ORP potential value before water outlet besides the nitrogen blowing function, the ORP value before water outlet of the denitrification tank is controlled by the industrial control computer 38 through controlling the aeration time and the aeration intensity to be higher than the set value, the aerobic absorption of phosphorus is enhanced through the enhanced aeration at the tail end, the purification efficiency of phosphorus is improved, the ORP control range is 80-220mv, the ORP control range at the tail end is preferably not influenced by denitrification at an anoxic section, and the carbon source in the activated sludge is excessively consumed due to the too high ORP range at the tail end, so that the denitrification time of the next period is prolonged or denitrification cannot be finished; if the ORP control range is too low and the organic carbon source is too much, the denitrification phosphorus absorption effect and the aerobic phosphorus absorption effect are not facilitated, and the phosphorus concentration of the effluent is higher;

when the denitrification tank 2 is in the aerobic nitrification stage, the frequency of the decanter 9 is controlled to control the aeration amount of the aeration pump 19, so that the dissolved oxygen concentration of the denitrification tank 2 is not higher than 3 mg/L, and when the aerobic nitrogen is blown off, the dissolved oxygen concentration is not limited.

Example 6:

on the basis of the embodiments 1-5, the process comprises a control method part, and the control method comprises the following steps:

a biochemical treatment control flow: the whole device runs periodically, firstly, sewage in a sewage storage tank 1 enters a denitrification tank 2, the sewage is subjected to anaerobic stirring and then is kept stand for sedimentation, supernatant liquid enters a nitrification tank 3 through a decanter, nitrification in an intermediate tank 4 enters a denitrification tank 2, the supernatant liquid is subjected to aerobic aeration nitrification reaction in the nitrification tank 3, when the nitrification reaction reaches the end point, aeration and stirring are stopped, the supernatant liquid is kept stand for sedimentation, then nitrification liquid in the nitrification tank 3 enters the intermediate tank 4 for storage, after the nitrification liquid enters the denitrification tank 2, the denitrification tank 2 is subjected to first anoxic denitrification reaction and simultaneously denitrification phosphorus absorption, when the denitrification reaches the end point, the denitrification section is switched to an aerobic aeration nitrification section, ammonia nitrogen is converted into nitrogen through repeated aerobic nitrification reaction and anoxic denitrification reaction for multiple times to be thoroughly removed, phosphorus is removed through aerobic phosphorus absorption and denitrification phosphorus absorption, and the denitrification tank is finally subjected to aerobic nitrogen stripping, draining water from the denitrification tank 2 to the flocculation sedimentation tank 5 through a decanter 9 after standing sedimentation, starting quantitative sludge drainage after the drainage is finished, and starting the next cycle after the denitrification tank 2 runs for the next cycle;

b, strengthening a phosphorus removal control process: after entering the denitrification tank 2 of the flocculation sedimentation tank 5, the discharged water is measured by an online soluble phosphorus measuring instrument 41, when the concentration of soluble phosphate radicals meets the requirement, only suspended sludge fragments are required to be removed to improve the purification efficiency of total phosphorus, the industrial personal computer 38 uses a PAM dephosphorization flocculating agent, the stirring is stopped for 10min, the stirring is stopped, the standing sedimentation is carried out for 10min, and then the water and the sludge are discharged; when the concentration of the soluble phosphorus is greater than a set value, one of alum, polymeric ferric sulfate or ferric trichloride dephosphorization flocculant is selected, the mixture is stirred for 10min after the dephosphorization flocculant is added, the stirring is stopped, the mixture is kept still and settled for 5min, the concentration of soluble phosphate radical is measured by sampling, when the concentration of the soluble phosphate radical is less than the set concentration, the mixture is kept still for 10min and then settled for sludge discharge and drainage, when the concentration of the soluble phosphate radical is greater than the set concentration, the dephosphorization flocculant is added again, the flocculation and the standing measurement are carried out again until the concentration of the phosphate radical meets the set requirement, the mixture is kept still and settled for 10min and then drained and sludge is finally drained, and; realizes the on-line measurement of the soluble phosphate radical.

Example 7:

on the basis of the examples 1-6, the process comprises a control method part, and the control method comprises the following steps:

a biochemical treatment control flow: the whole device runs periodically, firstly, sewage in a sewage storage tank 1 enters a denitrification tank 2, the sewage is subjected to anaerobic stirring and then is kept stand for sedimentation, supernatant liquid enters a nitrification tank 3 through a decanter, nitrified liquid in an intermediate tank 4 enters a denitrification tank 2, the supernatant liquid is subjected to aerobic aeration nitrification reaction in the nitrification tank 3, when the nitrification reaction reaches the end point, aeration and stirring are stopped, the supernatant liquid is kept stand for sedimentation, then the nitrified liquid in the nitrification tank 3 enters the intermediate tank 4 for storage, after the nitrified liquid enters the denitrification tank 2, the denitrification tank 2 is subjected to first anoxic denitrification reaction and simultaneously denitrification phosphorus absorption, when the denitrification reaches the end point, the denitrification section is switched to an aerobic aeration nitrification section, ammonia nitrogen is converted into nitrogen through repeated aerobic nitrification reaction and anoxic denitrification reaction to be thoroughly removed, phosphorus is removed through aerobic phosphorus absorption and denitrification phosphorus absorption, and the denitrification tank is finally subjected to aerobic nitrogen stripping, draining water from the denitrification tank 2 to the flocculation sedimentation tank 5 through a decanter 9 after standing sedimentation, starting quantitative sludge drainage after the drainage is finished, and starting the next cycle after the denitrification tank 2 runs for the next cycle;

b, strengthening a phosphorus removal control process: after entering the denitrification tank 2 of the flocculation sedimentation tank 5, the discharged water is measured by an online soluble phosphorus measuring instrument 41, when the concentration of soluble phosphate radicals meets the requirement, only suspended sludge debris is required to be removed to improve the purification efficiency of total phosphorus, the industrial personal computer 38 uses a PAM dephosphorization flocculating agent, the stirring is stopped for 20min, the stirring is stopped, the standing sedimentation is carried out for 30min, and then the water is discharged and the sludge is discharged; when the concentration of the soluble phosphorus is greater than a set value, one of alum, polymeric ferric sulfate or ferric trichloride dephosphorization flocculant is selected, the mixture is stirred for 20min after the dephosphorization flocculant is added, the stirring is stopped, the mixture is kept still and settled for 5min, the concentration of soluble phosphate radical is measured by sampling, when the concentration of the soluble phosphate radical is less than the set concentration, the mixture is kept still for 30min and then settled for sludge discharge and drainage, when the concentration of the soluble phosphate radical is greater than the set concentration, the dephosphorization flocculant is added again, the flocculation and the standing measurement are carried out again until the concentration of the phosphate radical meets the set requirement, the mixture is kept still and settled for 30min and then drained and sludge is finally drained, and; realizes the on-line measurement of the soluble phosphate radical.

Example 8:

on the basis of examples 1-7, the process includes a control method section, said control method including:

b, strengthening a phosphorus removal control process: after entering the denitrification tank 2 of the flocculation sedimentation tank 5, the discharged water is measured by an online soluble phosphorus measuring instrument 41, when the concentration of soluble phosphate radicals meets the requirement, only suspended sludge debris is required to be removed to improve the purification efficiency of total phosphorus, the industrial personal computer 38 uses a PAM dephosphorization flocculating agent, the stirring is stopped for 15min, the stirring is stopped, the standing sedimentation is carried out for 20min, and then the water is discharged and the sludge is discharged; when the concentration of the soluble phosphorus is greater than a set value, one of alum, polymeric ferric sulfate or ferric trichloride dephosphorization flocculant is selected, the mixture is stirred for 15min after the dephosphorization flocculant is added, the stirring is stopped, the mixture is kept still and settled for 5min, the concentration of soluble phosphate radical is measured by sampling, when the concentration of the soluble phosphate radical is less than the set concentration, the mixture is kept still for 20min and then settled for sludge discharge and drainage, when the concentration of the soluble phosphate radical is greater than the set concentration, the dephosphorization flocculant is added again, the flocculation and the standing measurement are carried out again until the concentration of the phosphate radical meets the set requirement, the mixture is kept still and settled for 20min and then drained and finally drained, and the drainage; realizes the on-line measurement of the soluble phosphate radical.

Example 9:

on the basis of the embodiments 1 to 8, the water outlet of the decanter 9 is arranged at 1/5 of the effective depth of the denitrification tank 2, when the purification of the denitrification tank 2 is finished, the drainage height of the decanter 9 is 1/4 of the effective height of the denitrification tank 2, and when the anaerobic section of the denitrification tank 2 is finished, the supernatant discharge height of the decanter 9 is 1/5;

the drainage height of the nitrification tank 3 is 1/4 of the effective height of the nitrification tank 3; is convenient for the normal work of the decanter 9, the denitrification tank 2 and the nitrification tank 3.

Example 10:

on the basis of the embodiments 1 to 9, the water outlet of the decanter 9 is arranged at 1/2 of the effective depth of the denitrification tank 2, when the purification of the denitrification tank 2 is finished, the drainage height of the decanter 9 is 1/2 of the effective height of the denitrification tank 2, and when the anaerobic section of the denitrification tank 2 is finished, the supernatant liquid drainage height of the decanter 9 is 1/3;

the drainage height of the nitrification tank 3 is 1/3 of the effective height of the nitrification tank 3; is convenient for the normal work of the decanter 9, the denitrification tank 2 and the nitrification tank 3.

Example 11:

on the basis of the embodiments 1 to 10, the water outlet of the decanter 9 is arranged at 3/10 of the effective depth of the denitrification tank 2, when the purification of the denitrification tank 2 is finished, the drainage height of the decanter 9 is 3/8 of the effective height of the denitrification tank 2, and when the anaerobic section of the denitrification tank 2 is finished, the supernatant discharge height of the decanter 9 is 4/15;

the drainage height of the nitrification tank 3 is 3/12 of the effective height of the nitrification tank 3; is convenient for the normal work of the decanter 9, the denitrification tank 2 and the nitrification tank 3.

Example 12:

on the basis of the examples 1 to 11, the sludge in the denitrification tank 2 stays for 10 days, and the sludge in the nitrification tank 3 stays for 20 days;

the nitrification tank 3 periodically discharges sludge to the denitrification tank 2 to supplement the content of nitrifying bacteria in the denitrification tank 2; is convenient for the concentration of the sludge in the denitrification tank 2 and the nitrification tank 3 and is beneficial to the reaction.

Example 13:

on the basis of the examples 1 to 12, the sludge in the denitrification tank 2 stays for 30 days, and the sludge in the nitrification tank 3 stays for 40 days;

Example 14:

on the basis of the examples 1 to 13, the sludge in the denitrification tank 2 stays for 20 days, and the sludge in the nitrification tank 3 stays for 30 days;

Example 15:

on the basis of the embodiments 1 to 14, the longest time of the first anoxic denitrification reaction in the denitrification tank 2 is not more than 4h, and the time of each anoxic denitrification reaction for multiple times is not more than 2 h;

the aerobic section of the denitrification tank 2 is set to be timed and added with nitrification end point judgment control: the running time of each aerobic section is 60min, the aerobic section is converted into an anoxic denitrification section when reaching the set time, the aeration is stopped and the anaerobic denitrification section is switched when reaching the set aerobic aeration nitrification time and not reaching the nitrification end point, the aerobic aeration is stopped when reaching the nitrification end point, the denitrification tank 2 enters the last anoxic denitrification section, and nitrogen pollutants are completely converted into nitrogen to be removed; the denitrification section of the denitrification tank 2 is set to be controlled by judging and adding a denitrification end point: before the aerobic nitrification reaches the end point, each time the anoxic denitrification reaction reaches the denitrification end point within the set time, starting aeration and switching to the aerobic section, and when the anoxic denitrification reaction does not reach the denitrification end point within the set time, directly entering the last aerobic nitrogen stripping section; when the last anoxic denitrification is finished, the denitrification tank 2 enters a timing aerobic nitrogen stripping section for 30 min;

when the anoxic denitrification section of the denitrification tank 2 cannot reach the denitrification end point within the set time, the time of each aerobic aeration can be shortened or the aeration intensity can be reduced;

the nitration end point control method comprises the following steps: the industrial personal computer 38 monitors and judges that the pH has a valley point through the pH on-line measuring instrument 37, the first derivative of the pH is changed from a negative value to a positive value, and meanwhile, the DO on-line measuring instrument 35 monitors that the DO has an obvious jump;

the denitrification end point is judged as follows: the pH on-line measuring instrument 37 monitors the pH to have a peak point, the first derivative of the pH is changed from positive rotation to continuous zero or less, or the ORP measuring instrument 26 in the anoxic section monitors that the second derivative of the ORP is continuously negative;

the time length and the aeration intensity of the tail-end nitrogen stripping section are based on completely stripping nitrogen in the sludge mixed liquor, when the concentration of soluble orthophosphate measured for the first time in the flocculation sedimentation tank exceeds the standard, the time length and the aeration intensity of each aerobic nitrification section are adjusted, the control range of the tail-end nitrogen stripping ORP is adjusted, and the aeration amount and the aeration time of nitrogen stripping are changed to control the phosphorus purification efficiency of the next period; ORP control range at the end of terminal nitrogen stripping: 50 mv; and the judgment and control of each end point in the denitrification tank 2 and the digestion tank 3 are facilitated.

Example 16:

on the basis of the embodiments 1 to 15, the longest time of the first anoxic denitrification reaction in the denitrification tank 2 is not more than 4h, and the time of each anoxic denitrification reaction for multiple times is not more than 2 h;

the time length and the aeration intensity of the tail-end nitrogen stripping section are based on completely stripping nitrogen in sludge mixed liquor, when the concentration of soluble orthophosphate measured for the first time in the flocculation sedimentation tank exceeds the standard, the time length and the aeration intensity of the aerobic nitrification section at each time are adjusted, the tail-end nitrogen stripping ORP control range is adjusted, the aeration quantity and the aeration time of nitrogen stripping are changed to control the purification efficiency of phosphorus in the next period, and the ORP control range at the tail-end nitrogen stripping terminal point is controlled: 200 mv; and the judgment and control of each end point in the denitrification tank 2 and the digestion tank 3 are facilitated.

Example 17:

on the basis of the embodiments 1 to 16, the longest time of the first anoxic denitrification reaction in the denitrification tank 2 is not more than 4h, and the time of each anoxic denitrification reaction for multiple times is not more than 2 h;

the aerobic section of the denitrification tank 2 is set to be timed and added with nitrification end point judgment control: the time length of each operation of the aerobic section is 30min, the aerobic section is converted into an anoxic denitrification section when reaching the set time, the aeration is stopped to be switched into the anoxic denitrification section when reaching the set aerobic aeration nitrification time and not reaching the nitrification end point, the aerobic aeration is stopped when reaching the nitrification end point, the denitrification tank 2 enters the last anoxic denitrification section, and nitrogen pollutants are completely converted into nitrogen to be removed; the denitrification section of the denitrification tank 2 is set to be controlled by judging and adding a denitrification end point: before the aerobic nitrification reaches the end point, each time the anoxic denitrification reaction reaches the denitrification end point within the set time, starting aeration and switching to the aerobic section, and when the anoxic denitrification reaction does not reach the denitrification end point within the set time, directly entering the last aerobic nitrogen stripping section; when the last anoxic denitrification is finished, the denitrification tank 2 enters a timed aerobic nitrogen stripping section for 20 min;

the time length and the aeration intensity of the tail-end nitrogen stripping section are based on completely stripping nitrogen in the sludge mixed liquor, when the concentration of soluble orthophosphate measured for the first time in the flocculation sedimentation tank exceeds the standard, the time length and the aeration intensity of each aerobic nitrification section are adjusted, the control range of the tail-end nitrogen stripping ORP is adjusted, and the aeration amount and the aeration time of nitrogen stripping are changed to control the phosphorus purification efficiency of the next period; ORP control range at the end of terminal nitrogen stripping: 125 mv; and the judgment and control of each end point in the denitrification tank 2 and the digestion tank 3 are facilitated.

Example 18:

on the basis of the embodiments 1 to 17, the stirring time of the anaerobic section of the denitrification tank 2 is 1h, the standing and settling time of the anaerobic section of the denitrification tank 2 is 30min, and the standing and settling time of the anaerobic section after nitrogen stripping is 30 min; facilitating the denitrification tank 2 and the denitrification nitrogen stripping reaction.

Example 19:

on the basis of the examples 1 to 18, the stirring time of the anaerobic section of the denitrification tank 2 is 2.5 hours, the standing and settling time of the anaerobic section of the denitrification tank 2 is 60 minutes, and the standing and settling time after nitrogen stripping is 60 minutes; facilitating the denitrification tank 2 and the denitrification nitrogen stripping reaction.

Example 20:

on the basis of the embodiments 1 to 19, the stirring time of the anaerobic section of the denitrification tank 2 is 2 hours, the standing and settling time of the anaerobic section of the denitrification tank 2 is 45 minutes, and the standing and settling time after nitrogen stripping is 45 minutes; facilitating the denitrification tank 2 and the denitrification nitrogen stripping reaction.

And (3) testing:

the sludge concentration of the denitrification tank 2 is controlled to be 2500-2800 mg/L, the sludge concentration of the nitrification tank 3 is controlled to be 1900-2200 mg/L, the sludge retention time of the denitrification tank 2 is 20 days, and the sludge retention time of the nitrification tank 3 is 30 days.

The control range of orthophosphate in the effluent of the flocculation sedimentation tank 5 is 0.05 mg/L.

The water outlet of the decanter 9 of the denitrification tank 2 is arranged at 1/5 of the effective depth of the denitrification tank 2, the water discharge height is 1/2 of the effective height, the supernatant discharge height is 1/5, and the water discharge height of the nitrification tank 2 is 1/4 of the effective height of the nitrification tank 2.

Firstly, a water pump 7 conveys sewage from a sewage storage tank 1 to a denitrification tank 2, an industrial control computer 38 controls the height of inlet water through a water level probe 36, the denitrification tank 2 starts anaerobic stirring to release phosphorus and absorb organic carbon sources, the stirring and standing sedimentation is stopped for 30min after two hours of anaerobic stirring, supernatant is transferred to a nitrification tank 3 through a supernatant transfer pump 12 and a corresponding electromagnetic valve by slowly descending a decanter 9, the transferred volume is 4/5 of the effective volume of the denitrification tank 2, the nitrification tank 3 starts aerobic aeration and nitrification, a submersible stirrer 34 starts stirring, the aeration amount is constant, the industrial control computer 38 starts to continuously monitor the change of the pH value of the nitrification tank 3, when the valley point of the pH value occurs, namely the negative change of the first derivative of the pH value to a positive value, and the DO aeration value rises, the nitrification reaches the end point, the submersible stirring is stopped, the standing sedimentation is 30min, nitrifying liquid is transferred to the intermediate tank 4 through a nitrifying liquid transfer pump 16; then the nitrification tank 3 begins to discharge sludge, and the sludge is discharged to the denitrification tank 2 once every seven days through the first sludge discharge pipe 21 so as to increase the concentration of nitrifying bacteria in the denitrification tank 2; after the supernatant liquid is transferred to the nitrification tank 3 by the denitrification tank 2, the nitrification liquid return pump returns the nitrification liquid in the upper period of the middle tank to the denitrification tank 2, then starting first anoxic denitrification by anoxic stirring, wherein the longest time of the first anoxic denitrification is 3h, when the pH value is marked by a peak point, the pH first derivative is changed from a positive value to be continuously less than or equal to zero, or when the second derivative of ORP continuously shows negative value, the denitrification is finished, the first aerobic nitrification is started, the industrial control computer 38 controls the denitrification aeration pump 19 through the decanter 9 to work at constant frequency to provide stable aeration quantity, simultaneously keeping the stirring function of the submersible stirrer 34, wherein the aeration time is 30min each time, then the aeration pump 19 is closed, the anaerobic denitrification stirring is switched, each time the anaerobic denitrification is denitrification end point control and the longest anaerobic denitrification time control, the aerobic nitrification is timed aerobic nitrification control and nitrification end point control; controlling a nitrification end point during aerobic nitrification aeration, immediately stopping aeration when the nitrification end point is reached, performing last anoxic denitrification, entering a last aerobic nitrogen stripping process for 20min when the denitrification end point is reached, then starting standing and settling for 30min, draining water through a decanter 9, starting sludge discharge after the drainage is finished, and then entering a water inlet stage of the next period; the discharged water of the denitrification tank 2 in the first few minutes is discharged to the nitrification tank 3 through a supernatant transfer pump 12 for cleaning the residual high-concentration ammonia nitrogen and soluble phosphorus on the pipeline, and then the water is discharged to the flocculation sedimentation tank 5.

After the drainage of the denitrification tank 2 is finished, the concentration of soluble phosphorus in the solution of the flocculation and sedimentation tank is detected by an online soluble phosphorus determinator, and since the detected concentrations are all less than 0.05 mg/L, a phosphorus and phosphorus removal flocculating agent is not required to be added, the industrial control computer 38 controls the flocculating agent stirrer 42, PAM flocculating agent is added to the flocculation and sedimentation tank 5 through a metering pump, the concentration of the PAM flocculating agent is 0.1%, the adding amount is 1L/m 3, then the submersible stirrer 34 of the flocculation and sedimentation tank 5 is started, the stirring is stopped for 10min, the stirring is stopped, the standing sedimentation is carried out for 30min, then a sludge discharge pump of the flocculation and sedimentation tank 5 is started, sludge is discharged outwards, and then the purified water of the whole system is discharged.

When the pH, ORP and DO electrodes in the denitrification tank 2 and the nitrification tank 3 and the like run for a long time, a large amount of sludge and biological membranes are attached to the electrodes, so that the monitoring precision of the electrodes is reduced, the accuracy is deteriorated, and the control of the system is influenced; therefore, the water level probe 36 is provided with a cleaning nozzle for regular washing, and is connected by a pipeline, and the water outlet is arranged about 1-5cm below the electrode. The nitrification tank 3 and the denitrification tank 2 are washed for a short time after water is drained.

When the pH, ORP and DO electrodes in the denitrification tank 2 and the nitrification tank 3 and the like run for a long time, a large amount of sludge and biological membranes are attached to the electrodes, so that the monitoring precision of the electrodes is reduced, the accuracy is deteriorated, and the control of the system is influenced, therefore, the electrodes are required to be washed regularly. The denitrification end point control method of the anoxic denitrification section of the denitrification tank 2 is to take an average sample every 5minEach sample is an average value of 30 points, the average samples are collected once every 2 seconds, adjacent average samples are subtracted to obtain dpH/5min, the dpH/5min is approximate to a first derivative of pH, adjacent ORP values are subtracted to obtain dORP/d5min, and the adjacent ORP values are subtracted again to obtain d²ORP/d²(5min), the second derivative of the approximate ORP; when dpH is changed from positive to continuous twice or more and is less than or equal to zero, the dpH is used as a denitrification end point, or when the second derivative of ORP in the anoxic section is continuously negative twice or more and is used as a denitrification end point, when the two indexes are simultaneously shown, the two characteristics can be used as the denitrification end point for judgment only by simultaneously showing once; the longest time of the first anoxic denitrification is set to be 3h, and the longest anoxic time from the second anoxic section to the nth anoxic section is set to be 1.5 h.

The aerobic nitrification section of the denitrification tank is controlled by adding nitrification end point judgment for 30min, aerobic aeration is carried out for fixing aeration quantity, DO is smaller than the range of 3 mg/L, if no nitrification end point mark appears in 30min, aerobic nitrification is carried out at least once, the nitrification end point is judged, when a valley point appears in pH, a first derivative of pH, namely an adjacent pH difference value, is changed from a negative value to a positive value, in order to avoid error judgment, rapid jump of DO is also taken as auxiliary judgment of the nitrification end point, an industrial control computer 38 takes an average sample every 5 minutes through an online pH and DO monitor, namely, data is read every two seconds, the average value of 30 points is taken, the average samples of the two adjacent points of pH are subtracted to obtain an approximate first derivative for judging the end point, sudden and large amplitude rise of the difference value of the adjacent DO is taken as the auxiliary judgment basis, in order to avoid error judgment, the nitrification end point takes the jump of the DO as a necessary condition, and the change of the pH first derivative to the positive value to the nitrification end point is taken as the negative value.

When the nitrification end point is reached, an average of about 3-4 times of aerobic nitrification sections and 4-5 times of anoxic denitrification sections are carried out, and the total nitrogen brought by the water inflow is completely converted into nitrogen to be removed.

The time of the aerobic nitrogen stripping section of the denitrification tank 2 is 15min, and the ORP control range is 120-150 mv.

And when the denitrification reaction in the denitrification tank 2 is finished, the concentration of soluble phosphorus in the mixed solution is about 0.03-0.05 mg/L and is less than the set 0.05 mg/L. therefore, when denitrification drainage enters the flocculation sedimentation tank 5, PAM is added to flocculate and sediment a small amount of sludge chips suspended in water in the drainage according to the result measured by an on-line soluble phosphorus measuring instrument without adding a phosphorus removal flocculating agent, the stirring is stopped for 10min, the flocculation sedimentation tank 5 is kept stand for 30min to start sludge discharge for 5min, and then drainage is started.

The adopted sewage is campus biological sewage, the CODcr of the campus biological sewage is 330-760 mg/L, the total nitrogen is 45-70 mg/L, the carbon-nitrogen ratio is 8-14, the total phosphorus is 6.2-15.0 mg/L, the denitrification efficiency is basically between 98-99.5%, the dephosphorization efficiency is basically between 98.5-99.0%, the purification efficiency of the CODcr is 94-97%, the effluent concentration of TN is only 0-0.5 mg/L, the effluent concentration of the total phosphorus is only 0.01-0.05 mg/L and is less than 15 m/L, obviously, the TN of the effluent reaches the water quality above class II of surface water, the TP reaches the water quality above class III of surface water lakes and reservoirs, the CODcr reaches the water quality above class I of surface water, and the aim of ultra-deep purification of the domestic sewage is successfully achieved.

Comparison table for super-deep purification efficiency of domestic sewage by different processes

As can be seen from the above table, the method of the invention has good denitrification efficiency and dephosphorization efficiency, and the effect is superior to other prior art. The concentration of nitrogen, phosphorus and COD in the effluent reaches the water quality of more than II and III types of surface water, so that the sewage reaches higher recycling value after being treated, and meanwhile, the concentration of nitrogen and phosphorus in the discharged water belongs to the range of poor nutrient concentration, so that the propagation of microorganisms such as algae, bacteria and the like in the water body is avoided, and the method has higher practical value and application prospect particularly for water resource protection areas and eutrophication key control areas.

Abbreviations and remarks:

AB method: the AB process is divided into two stages of aeration treatment processes A and B, each stage is provided with an aeration process and a sludge-water separation process which are isolated and independent from each other, the return of the activated sludge is also isolated from each other, the activated sludge generated by the section A sedimentation tank returns to the section A aeration tank, and the activated sludge separated from the section B sedimentation tank returns to the section B aeration tank.

An A/O process: called anaerobic-aerobic process, and is mainly used for water treatment.

A/A/O process: also called A2/O process, is the first letter of Anaerobic-Anaerobic-Oxic in English, called Anaerobic-Anoxic-aerobic for short. In a practical sense, the process is an anaerobic-anoxic-aerobic method, and the biological nitrogen and phosphorus removal process is short for.

SBR method: the activated sludge sewage treatment method, referred to as SBR, consists of five basic processes of water inlet, aeration, precipitation, drainage and standby in the same reactor according to time sequence.

CODcr: is prepared from potassium dichromate (K)₂Cr₂O₇) The chemical oxygen consumption, i.e. the dichromate index, was measured as the oxidant. Chemical oxygen demand was measured in a strongly acidic solution using potassium dichromate as an oxidizing agent.

DPAOs: denitrifying phosphorus accumulating bacteria.

VFAs: and (3) alkaline anaerobic acidogenesis of organic sludge.

PHA: a polyhydroxyfatty acid.

pH value: is an expression method for showing the pH value of a certain solution or substance.

DO: the molecular oxygen in air dissolved in water is called dissolved oxygen

ORP: oxidation-reduction potential.

PAM flocculating agent: PAM flocculant chemical name polyacrylamide.

Although the invention has been described herein with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More specifically, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, other uses will also be apparent to those skilled in the art.

Claims

1. An intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process is characterized in that: the process includes a device portion; the device part comprises: a sewage storage tank (1), a denitrification tank (2), a nitrification tank (3), an intermediate tank (4) and a flocculation sedimentation tank (5);

the sewage storage tank (1) is connected with a first pipeline (6), a water pump (7) is arranged on the first pipeline (6), the sewage storage tank (1) is connected with the denitrification tank (2) through the first pipeline (6), a decanter (9) is arranged in the denitrification tank (2), a water outlet of the decanter (9) is connected with a second pipeline (8) and a third pipeline (10), the decanter (9) is connected with the nitrification tank (3) through the second pipeline (8), and a supernatant transfer pump (12) and an electromagnetic valve (13) are arranged on the second pipeline (8);

the decanter (9) is connected with the flocculation sedimentation tank (5) through a third pipeline (10);

the nitrification tank (3) is connected with a fourth pipeline (14), the nitrification tank (3) is connected with the intermediate tank (4) through the fourth pipeline (14), the nitrification liquid transfer pump (11) is arranged on the fourth pipeline (14), the intermediate tank (4) is connected with a fifth pipeline (15), the nitrification liquid reflux pump (16) is arranged on the fifth pipeline (15), and the intermediate tank (4) is connected with the denitrification tank (2) through the fifth pipeline (15).

2. The intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process according to claim 1, characterized in that; aeration heads (20) are arranged at the bottoms of the denitrification tank (2) and the nitrification tank (3), the aeration heads (20) are communicated with an air inlet pipe (17), a gas flowmeter (18) is arranged on the air inlet pipe (17), the air inlet pipe (17) is connected with an aeration pump (19), and the aeration pump (19) is connected with a frequency converter (25);

the top of the denitrification tank (2) is provided with a cover which is in a semi-sealed state, and the top of the denitrification tank (2) is provided with an exhaust hole;

the bottoms of the denitrification tank (2) and the nitrification tank (3) are respectively provided with a first sludge discharge pipe (21), and a sludge discharge pump (22) is arranged on the first sludge discharge pipe (21);

the bottom of the nitrification tank (3) is connected with a second sludge discharge pipe (43), the nitrification tank (3) is connected with the denitrification tank (2) through the second sludge discharge pipe (43), and a first sludge discharge valve (40) is arranged on the second sludge discharge pipe (43).

3. The intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process according to claim 1, characterized in that; the upper part of the flocculation sedimentation tank (5) is arranged to be cylindrical, the lower part of the flocculation sedimentation tank is arranged to be a funnel-shaped cone with an angle of 45-70 degrees, a third sludge discharge pipe (23) is arranged at the bottom of the flocculation sedimentation tank (5), and a second sludge discharge valve (24) is arranged on the third sludge discharge pipe (23);

the method comprises the following steps that a flocculation settling pond (5) is connected with a phosphorus removal flocculant pipe (39), a PAM flocculant pipe (27), a phosphorus removal flocculant pump (28) is arranged on the phosphorus removal flocculant pipe (39), the PAM flocculant pipe (27) is provided with a PAM flocculant pipe pump (29), the flocculation settling pond (5) is connected with a phosphorus removal flocculant barrel (30) through the phosphorus removal flocculant pipe (39), the flocculation settling pond (5) is connected with the PAM flocculant barrel (31) through the PAM flocculant pipe (27), a drain pipe (32) is arranged on the side wall of the flocculation settling pond (5), and a drain valve (33) is arranged on the drain pipe (32);

the flocculation sedimentation tank (5) is connected with an online phosphate tester (41), and the online phosphate tester (41) is connected with an industrial computer (38).

4. The intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process according to claim 1, characterized in that; submersible stirrers (34) are arranged in the denitrification tank (2), the nitrification tank (3) and the flocculation sedimentation tank (5);

the dephosphorization flocculating agent bucket (30) and the PAM flocculating agent bucket (31) are both provided with flocculating agent stirrers (42).

5. The intermittent double-sludge denitrification AN (AO) n full-nitrification ultra-deep nitrogen and phosphorus removal process according to claim 1, which is characterized in that; the denitrification tank (2) and the nitrification tank (3) are respectively provided with a DO online tester (35), a water level probe (36) and a pH online tester (37);

the denitrification tank (2) is provided with an ORP measuring instrument (26);

a water pump (7), a nitrified liquid transfer pump (11), a supernatant transfer pump (12), an electromagnetic valve (13), a nitrified liquid reflux pump (16), an aeration pump (19), a second sludge discharge valve (24), a drain valve (33), a water level probe (36), a first sludge discharge valve (40), a submersible stirrer (34) and a flocculant stirrer (42) are connected with and controlled by a P L C (44);

the decanter (9), the sludge discharge pump (22), an ORP measuring instrument (26), a dephosphorization flocculant pump (28), a PAM flocculant pipe pump (29), a DO online measuring instrument (35), a pH online measuring instrument (37), an online phosphate measuring instrument (41) and a frequency converter (25) are connected with an industrial personal computer (38) through communication lines;

the P L C is connected with the industrial personal computer (38) through a communication line, and the whole system is controlled by the industrial personal computer (38) to operate;

a sludge discharge pump (22), a dephosphorization flocculant pump (28) and a PAM flocculant pipe pump (29) are quantitative pumps.

6. The process for ultra-deep nitrogen and phosphorus removal by intermittent double-sludge denitrification AN (AO) n according to any one of claims 1 to 5, which is characterized in that; the process comprises a control method part, wherein the control method comprises the following steps:

a biochemical treatment control flow: the whole device runs periodically, firstly, sewage in a sewage storage tank (1) enters a denitrification tank (2), the sewage is subjected to anaerobic stirring and then is subjected to standing sedimentation, supernatant enters a nitrification tank (3) through a decanter, nitrified liquid in an intermediate tank (4) enters the denitrification tank (2), the supernatant is subjected to aerobic aeration nitrification reaction in the nitrification tank (3), when the nitrification reaction reaches the end point, aeration and stirring are stopped, the supernatant is subjected to standing sedimentation, then the nitrified liquid in the nitrification tank (3) enters the intermediate tank (4) for storage, after the nitrified liquid enters the denitrification tank (2), the denitrification tank (2) is subjected to first anoxic denitrification reaction and is subjected to denitrification phosphorus absorption, when the denitrification reaches the end point, the denitrification stage is switched to an aerobic aeration nitrification stage, ammonia nitrogen is converted into nitrogen through repeated aerobic nitrification reaction and anoxic denitrification reaction to be thoroughly removed, and phosphorus is removed through aerobic phosphorus absorption and denitrification, finally, the denitrification tank is blown off by aerobic nitrogen, the denitrification tank (2) is drained to the flocculation sedimentation tank (5) through a decanter (9) after standing sedimentation, quantitative sludge discharge is started after the drainage is finished, and the next cycle is started after the denitrification tank (2) runs periodically;

b, strengthening a phosphorus removal control process: after entering the drainage of the denitrification tank (2) of the flocculation sedimentation tank (5), measuring by an online soluble phosphorus measuring instrument (41), when the concentration of soluble phosphate radicals meets the requirement, only suspended sludge scraps need to be removed to improve the purification efficiency of total phosphorus, using a PAM dephosphorization flocculating agent by an industrial personal computer (38), stirring for 10-20min, stopping stirring, standing and settling for 10-30min, and then draining and discharging sludge; when the concentration of the soluble phosphorus is more than a set value, one of alum, polymeric ferric sulfate or ferric trichloride dephosphorization flocculant is selected, after the dephosphorization flocculant is added, the mixture is stirred for 10-20min, the stirring is stopped, the mixture is kept still and settled for 5min, the concentration of the soluble phosphate radical is measured by sampling, when the concentration of the soluble phosphate radical is less than the set concentration, the mixture is kept still for 10-30min, then the sedimentation is carried out, sludge discharge and drainage are carried out, when the concentration of the soluble phosphate radical is more than the set concentration, the dephosphorization flocculant is added again, the flocculation and the standing measurement are carried out again until the concentration of the phosphate radical meets the set requirement, the mixture is kept still and settled for 10-30 min.

7. The process for the ultra-deep removal of nitrogen and phosphorus by intermittent double-sludge denitrification AN (AO) n according to claim 6, which is characterized in that; the water outlet of the decanter (9) is arranged at 1/5-1/2 of the effective depth of the denitrification tank (2), when the purification of the denitrification tank (2) is finished, the drainage height of the decanter (9) is 1/4-1/2 of the effective height of the denitrification tank (2), and when the anaerobic section of the denitrification tank (2) is finished, the supernatant liquid discharge height of the decanter (9) is 1/5-1/3;

the drainage height of the nitrification tank (3) is 1/4-1/3 of the effective height of the nitrification tank (3).

8. The process for the ultra-deep removal of nitrogen and phosphorus by intermittent double-sludge denitrification AN (AO) n according to claim 6, which is characterized in that; the sludge in the denitrification tank (2) stays for 10-30 days, and the sludge in the nitrification tank (3) stays for 20-40 days;

the nitrification tank (3) periodically discharges sludge to the denitrification tank (2) to supplement the content of nitrifying bacteria in the denitrification tank (2).

9. The process for the ultra-deep removal of nitrogen and phosphorus by intermittent double-sludge denitrification AN (AO) n according to claim 6, which is characterized in that; the longest time of the first anoxic denitrification reaction of the denitrification tank (2) is not more than 4h, and the time of each anoxic denitrification reaction for multiple times is not more than 2 h;

the aerobic section of the denitrification tank (2) is set to be timed and added with nitrification end point judgment control: the running time of each aerobic section is 5-60min, the aerobic section is converted into an anoxic denitrification section when reaching the set time, the aeration is stopped to be switched into the anoxic denitrification section when reaching the set aerobic aeration nitrification time and not reaching the nitrification end point, the aerobic aeration is stopped when reaching the nitrification end point, the denitrification tank (2) enters the last anoxic denitrification section, and nitrogen pollutants are completely converted into nitrogen to be removed; the denitrification section of the denitrification tank (2) is set to be controlled by judging and adding a denitrification end point: before the aerobic nitrification reaches the end point, each time the anoxic denitrification reaction reaches the denitrification end point within the set time, starting aeration and switching to the aerobic section, and when the anoxic denitrification reaction does not reach the denitrification end point within the set time, directly entering the last aerobic nitrogen stripping section; when the last anoxic denitrification is finished, the denitrification tank (2) enters a timing aerobic nitrogen stripping section for 10-30 min;

the nitration end point control method comprises the following steps: the industrial control computer (38) monitors and judges that the pH has a valley point through the pH on-line measuring instrument (37), the first derivative of the pH is changed from a negative value to a positive value, and meanwhile the DO on-line measuring instrument (35) monitors that the DO has an obvious jump;

the denitrification end point is judged as follows: the pH on-line measuring instrument (37) monitors the pH to generate a peak point, the first derivative of the pH is changed from positive rotation to zero or less continuously, or the ORP measuring instrument (26) in an anoxic section monitors that the second derivative of the ORP is continuously negative;

10. The process for the ultra-deep removal of nitrogen and phosphorus by intermittent double-sludge denitrification AN (AO) n according to claim 6, which is characterized in that; the stirring time of the anaerobic section of the denitrification tank (2) is 1-2.5h, the standing and settling time of the anaerobic section of the denitrification tank (2) is 30-60min, and the standing and settling time after nitrogen stripping is 30-60 min.