CN106115920B

CN106115920B - The method and apparatus for realizing municipal sewage part short distance nitration and Anammox using fermented sludge

Info

Publication number: CN106115920B
Application number: CN201610799348.0A
Authority: CN
Inventors: 彭永臻; 刘瑾瑾; 袁悦; 王淑莹
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2016-08-31
Filing date: 2016-08-31
Publication date: 2019-03-22
Anticipated expiration: 2036-08-31
Also published as: CN106115920A

Abstract

The method and apparatus for realizing municipal sewage part short distance nitration and Anammox using fermented sludge, belong to municipal sewage treatment and sludge biochemical treatment field.The removal and the effect of part short-cut nitrification and denitrification that organic matter and phosphorus are carried out in the first SBR of reactor, during which by DO and pH real-time control, and pass through the removal of spoil disposal realization phosphorus.The first SBR of reactor water outlet enters the 2nd SBR of reactor and carries out Anammox reaction, to achieve the purpose that advanced nitrogen dephosphorization.The present invention is by the way that by excess sludge and sanitary sewage mixed processing, the problem of realizing short distance nitration cannot be stablized by being able to solve sanitary sewage because ammonia nitrogen concentration is low, can also be saved carbon source, be improved denitrogenation dephosphorizing efficiency, while realize that sludge reduction is handled.

Description

The side of municipal sewage part short distance nitration and Anammox is realized using fermented sludge Method and device

Technical field

The present invention relates to the method for realizing municipal sewage part short distance nitration and Anammox using fermented sludge and The optimal control of device belongs to municipal sewage treatment and sludge biochemical treatment field.This technique is suitable for the low city C/N, C/P The reinforcing advanced nitrogen dephosphorization of sanitary sewage.

Background technique

In biological denitrification process, denitrifying bacterium needs organic matter as electron donor reduction-oxidation state as heterotroph Nitrogen；In Biological Phosphorus Removal Process, polyP bacteria absorbs short chain fatty acids VFA synthesis PHA storage in the cell in anaerobism section, aerobic Section decomposed P HA is as energy needed for excessive suction phosphorus.So organic carbon source is extremely important for biological carbon and phosphorous removal.However, The problem of China's most cities sewage generally existing carbon source wretched insufficiency, its own carbon source is unable to satisfy wanting for denitrogenation dephosphorizing Ask so that water outlet be difficult to it is up to standard.By adding methanol, although the outer carbon source such as sodium acetate can achieve good outlet effect, but It is that cost is too high, but also will increase excess sludge production.Nearly 1/3 organic matter is converted to sludge inside sewage, remaining dirty The processing disposition of mud is also a great problem, so carbon source in sewage is insufficient and excess sludge processing cost is too high asks to solve Topic, can be by exploitation excess sludge internal carbon source come enhanced sewage treatment plant biological carbon and phosphorous removal.Excess sludge anaerobic fermentation energy Generating a large amount of short chain fatty acids can be used as high-quality carbon source during biological carbon and phosphorous removal, Lai Tigao sewage denitrification and dephosphorization effect Fruit, while realizing the minimizing processing of sludge.Selection utilization can be separated for fermentation liquid and sludge by developing excess sludge internal carbon source Fermentation liquid can also directly utilize its sludge fermentation mixture.The problems such as in view of operating cost, only utilizes sludge fermentation supernatant Liquid cost is too high, can choose and utilizes excess sludge fermenting mixture.

The method and apparatus for realizing municipal sewage part short distance nitration and Anammox using fermented sludge, with remaining dirty Mud and municipal sewage are research object, short by the anaerobic phosphorus release of the first SBR of sequencing batch reactor, aerobic phosphorus absorption and part first Journey nitrification, denitrification dephosphorization effect carry out the removal of organic matter and nitrogen phosphorus, and the water outlet of the first SBR of sequencing batch reactor is using sequence Advanced nitrogen is realized in the Anammox processing of the 2nd SBR of batch reactor, improves the denitrification percent of system.Certainly using sewage plant The sludge of body discharge saves the expense of additional carbon as carbon source while improving denitrogenation dephosphorizing efficiency；It is sent out using sludge The process of sludge and separation of fermentative broth, save the cost is omitted in ferment mixture, while realizing sludge reduction processing.

Summary of the invention

In view of the deficiencies of the prior art, the present invention proposes that a kind of utilization fermented sludge realizes municipal sewage part short distance nitration With the method and apparatus of Anammox, excess sludge mixture is pumped into handle low C/N, C/P sanitary sewage batch-type it is anti- It answers in the first SBR of device, polyP bacteria largely releases phosphorus using the abundant carbon source progress in sludge fermentation mixture and sanitary sewage, and stores up A large amount of PHA are deposited, next aeration carries out part short distance nitration and polyP bacteria inhales the reaction of phosphorus, and removal part ammonia nitrogen is converted For nitrite nitrogen and nitrate nitrogen, anoxia stirring in short-term is entered back into, carries out denitrifying phosphorus uptake, it is by nitrate nitrogen and residual on last stage Remaining phosphorus ligands；The 2nd SBR that the first SBR water outlet is pumped into inoculation anaerobic ammonium oxidation sludge is subjected to Anammox reaction again, Ammonia nitrogen and nitrite nitrogen are removed, to achieve the purpose that advanced nitrogen dephosphorization.

The present invention is achieved through the following technical solutions:

(1) starting of excess sludge fermentor: excess sludge fermentor (2) is semi batch reacor, sludge retention time SRT controlled pH 9~10 at 6~20 days；Excess sludge fermenting mixture to fermenting mixture is discharged daily according to SRT to store Simultaneously isometric fresh excess sludge is added to excess sludge fermentor (2) in tank (9)；

(2) batch-type reaction the starting of the first SBR of sequencing batch reactor: is injected using short distance nitration sludge as seed sludge The first SBR (13) of device, while the city domestic sewage to add sodium acetate injects sanitary sewage water tank (8) as raw water, makes into water C/N ratio maintains 5~6, squeezes into the first SBR (13) of sequencing batch reactor by third peristaltic pump, that is, intake pump (10), transports daily In 2~3 periods of row, than maintaining 50~80%, each period includes water inlet for draining, and anaerobism stirs, aeration, and anoxia stirring is sunk It forms sediment, drains, leave unused, run reactor under the above conditions, when aerobic last nitrite accumulation rate is greater than 95%, water outlet TP exists When 1mg/L or less, the Start-up and Adjustment of the first SBR (13) of sequencing batch reactor is completed；

(3) starting of the 2nd SBR of sequencing batch reactor: using anaerobic ammonium oxidation granular sludge or floc sludge as inoculation Sludge injects the 2nd SBR (20) of sequencing batch reactor, meanwhile, with NH₄ ⁺- N and NO₂ ^—The mass concentration ratio of N is 1:1~1.3 Water distribution is water inlet injection intermediate water tank (17), squeezes into the 2nd SBR (20) of sequencing batch reactor, water inlet while anaerobism by peristaltic pump Stirring, as water outlet NH₄ ⁺- N concentration < 1mg/L or NO₂ ^-When-N concentration < 1mg/L, the starting of the 2nd SBR of sequencing batch reactor is completed Debugging；

(4) after sequencing batch reactor the first SBR and the 2nd SBR is respectively completed starting, by the two series operation: batch-type is anti- Device the first SBR (13) each cycle is answered successively to undergo water inlet and sludge fermentation mixture, anaerobism stirring, aeration, anoxia stirring, precipitating Drain 5 processes；Sequencing batch reactor the 2nd SBR (20) each cycle successively undergoes water inlet (i.e. the water outlet of the first SBR), anoxic to stir It mixes, 3 processes of sedimentation and drawing.

The first SBR of sequencing batch reactor:

I water inlet, fermenting mixture set inflow as the 1/2~4/5 of reactor effective volume, are into fermenting mixture amount The 1/50~1/10 of volume of intaking both is controlled by time switch, and after system starting, the sewage in sewage water tank (8) is logical It crosses intake pump (10) and enters the first SBR (13) of sequencing batch reactor, the fermentation during water inlet, in excess sludge fermentor (2) Mixture enters the first SBR (13) by the second peristaltic pump (11)；The index of substance is as follows in fermenting mixture: SCOD 3380 ± 420mg/L, SCFAs are 1221 ± 40mg COD/L, NH₄ ⁺- N is 198 ± 20mg/L, PO₄ ^3-- P is 95 ± 10mg/L；

Enter anaerobism agitation phases after the stirring water inlet of II anaerobism, sets mixing time as 3~3.5h, polyP bacteria utilizes Abundant carbon source progress in fermenting mixture and sanitary sewage largely releases phosphorus, and stores a large amount of PHA；；

III aeration opens air compressor machine (16), oxygen is provided to the first SBR (13) of sequencing batch reactor, by the ammonia in water inlet Nitrogen is converted into oxidation state nitrogen；It maintains dissolved oxygen DO in 0.5~1.5mg/L by real-time control apparatus, and monitors pH, setting aeration Time (inflection point that ammonia valley point rises after referring to that pH value is fallen before), NH before 1~2h and ammonia valley point occur₄ ⁺- N is under low oxygen conditions Short distance nitration effect occurs, while aeration time control preceding achievable NH is occurred into ammonia valley point₄ ⁺The part short distance nitration of-N gathers Phosphorus bacterium suction part PO₄ ^3--P；

IV anoxia stirring sets 0.5~1h of mixing time, the NO generated when anoxic can guarantee aeration in short-term₃ ^—N passes through Denitrification removal, while by remaining PO₄ ^3-- P is acted on by denitrification dephosphorization and being removed；；

VI sedimentation and drawing sets 1~2h of sedimentation time, drains, is discharged into intermediate water tank (17) after mud-water separation, drains ratio It is 50%~80%.

The 2nd SBR of sequencing batch reactor:

I water inlet is intake from intermediate water tank (17), is set inflow as the 1/2~3/4 of reactor effective volume, is passed through time control Switch control；

II anoxia stirring sets 2~3h of mixing time, by the NH in the first SBR water outlet₄ ⁺- N and NO₂ ^-- N passes through anaerobism ammonia Oxidation removal；

IV sedimentation and drawing sets 1~2h of sedimentation time, drains after mud-water separation, and draining is than being 50%~75%.

In conclusion the present invention provides a kind of utilization excess sludge fermenting mixture reinforcing city domestic sewage advanced nitrogen The control method and device of dephosphorization pass through sequencing batch reactor first using excess sludge and municipal sewage as research object first Anaerobic phosphorus release, aerobic phosphorus absorption and the part short distance nitration of SBR, denitrification dephosphorization effect carry out the removal of organic matter and nitrogen phosphorus, sequence The water outlet of the first SBR of batch reactor realizes advanced nitrogen using the Anammox processing of the 2nd SBR of sequencing batch reactor, Improve the denitrification percent of system.Using the sludge of sewage plant itself discharge as carbon source, while improving denitrogenation dephosphorizing efficiency Save the expense of additional carbon；It is omitted the process of sludge and separation of fermentative broth using sludge fermentation mixture, save the cost, Sludge reduction processing is realized simultaneously.

Detailed description of the invention:

Fig. 1 is the structural schematic diagram of apparatus of the present invention

In figure: 1 --- the first peristaltic pump；2 --- excess sludge fermentor；3 --- the first blender；4 --- temperature control Device processed；5 --- the first pH controller；6 --- process controller；7 --- computer；8 --- sewage water tank；9 --- fermentation is mixed Close object holding vessel；10 --- third peristaltic pump；11 --- the second peristaltic pump；12 --- the first dissolved oxygen controller；13 --- sequence The first SBR of batch reactor；14 --- the 2nd pH controller；15 --- the second blender；16 --- air compressor machine；17 --- it is intermediate Water tank；18 --- the 4th peristaltic pump；19 --- the second dissolved oxygen controller；20 --- the 2nd SBR of sequencing batch reactor；21—— 3rd pH controller；22 --- third blender；

Fig. 2 is the method for operation of sequencing batch reactor SBR.

Specific embodiment

The application patent is further illustrated in conjunction with attached drawing and example: as shown in Figure 1, the present invention includes excess sludge fermentation Tank, sludge fermentation mixture holding vessel, sewage water tank, intermediate water tank, the first SBR of sequencing batch reactor, sequencing batch reactor Two SBR.The effective volume of six devices is 5L, 3L, 30L, 30L, 12L, 9L respectively, and wherein excess sludge fermentor, sludge are sent out Ferment mixture holding vessel and sequencing batch reactor SBR are made of organic glass；Intermediate water tank, sewage water tank are by organic plastics system At.

The device includes that excess sludge is pumped into excess sludge fermentor (2) by the first pump peristaltic pump (1), excess sludge hair First blender (3), temperature control equipment (4), the first pH controller (5) are installed in fermentation tank (2)；Excess sludge fermentor (2) It is connect with fermenting mixture holding vessel (9), fermenting mixture holding vessel (9) passes through the second peristaltic pump (11) and sequencing batch reactor First SBR (13) connection；Sanitary sewage water tank (8) passes through third peristaltic pump, that is, intake pump (10) and sequencing batch reactor first SBR (13) connection.Second blender (15), the first dissolved oxygen controller (12) are installed in the first SBR (13) of sequencing batch reactor With the 2nd pH controller (14)；Aeration head in the first SBR (13) of sequencing batch reactor is connect with air compressor machine (16), and batch-type is anti- The first SBR (13) of device is answered to connect with intermediate water tank (17)；Intermediate water tank (17) is reacted by the 4th peristaltic pump (18) with batch-type The 2nd SBR (20) connection of device.Installation third blender (22), the control of the second dissolved oxygen in the 2nd SBR (20) of sequencing batch reactor Device (19) and the 3rd pH controller (21).In addition, the process controller (6) that setting is connected with computer (7), to control first Peristaltic pump (1), the second peristaltic pump (11), third peristaltic pump (10), the 4th peristaltic pump (18), the first blender (3), the second stirring Device (15), third blender (22), temperature controller (4), the first pH controller (5), the 2nd pH controller (14), the 3rd pH control Device (21) processed, the first dissolved oxygen controller (12), the second dissolved oxygen controller (19), air compressor machine (16).

City domestic sewage used in specific example is derived from the septic tank of Beijing dependents' district, wherein COD COD is in 180~200mg/L, NH₄ ⁺The concentration of-N is in 60~70mg/L, PO₄ ^3-The concentration of-P is in 5.0~7.5mg/L, and C/N is 2 ~4, C/P < 40, itself carbon source are unable to satisfy the purpose of advanced nitrogen dephosphorization.

Specific implementation process is as follows:

Excess sludge fermentor is semi batch reacor, and sludge concentration MLSS is in 7500~8000mg/L, sludge retention Between SRT at 6 days, control pH 10 ± 0.2, temperature is at 30 ± 2 DEG C.Discharge the fermentation mixing of 833mL excess sludge daily according to SRT The fresh excess sludge of 833mL is added to excess sludge fermentor to fermenting mixture holding vessel in object (FM).Sludge fermentation is mixed The main indicator closed in object is as follows: SCOD is 3380 ± 420mg/L, and SCFAs is 1221 ± 40mg COD/L, NH₄ ⁺- N be 198 ± 20mg/L, PO₄ ^3-- P is 95 ± 10mg/L.

The starting of the first SBR of sequencing batch reactor: sequencing batch reactor is injected using short distance nitration sludge as seed sludge First SBR, while the city domestic sewage to add sodium acetate injects sanitary sewage water tank as raw water, makes to maintain into water C/N ratio 6, the first SBR of sequencing batch reactor is squeezed by intake pump, runs 2 periods daily, draining ratio maintains 70%, Mei Gezhou Phase includes water inlet, and anaerobism stirring is aerated, anoxia stirring, precipitates, drain, leaves unused, run reactor under the above conditions, be a good Oxygen end nitrite accumulation rate is greater than 95%, is discharged TP in 1mg/L or less, completes the starting of the first SBR of sequencing batch reactor Debugging；

The starting of the 2nd SBR of sequencing batch reactor: dirty using anaerobic ammonium oxidation granular sludge or floc sludge as inoculation Mud injects the 2nd SBR of sequencing batch reactor, meanwhile, with NH₄ ⁺- N and NO₂ ^-The water distribution that the mass concentration ratio of-N is 1:1.3 be into Water injects intermediate water tank, squeezes into the 2nd SBR of sequencing batch reactor, water inlet anaerobism stirring simultaneously, as water outlet NH by peristaltic pump₄ ⁺-N Concentration < 1mg/L or NO₂ ^-When-N concentration < 1mg/L, the Start-up and Adjustment of the 2nd SBR of sequencing batch reactor is completed；

After sequencing batch reactor the first SBR and the 2nd SBR is respectively completed starting, by the two series operation.Batch-type reaction The first SBR each cycle of device successively undergoes water inlet and sludge fermentation mixture, anaerobism stirring, aeration, anoxia stirring, sedimentation and drawing 5 A process；The 2nd SBR each cycle of sequencing batch reactor successively undergoes water inlet (i.e. the water outlet of the first SBR), stirring, sedimentation and drawing 3 A process, such as Fig. 2.

First SBR:

I water inlet, 1/2 that fermenting mixture inflow is reactor effective volume, i.e. 6L.It is water inlet into fermenting mixture amount The 3/50 of volume is both controlled by time switch, and after system starting, the sewage in raw water water tank enters sequence by intake pump The first SBR of batch reactor, during water inlet, the fermenting mixture in fermenting mixture holding vessel enters first by peristaltic pump SBR.；

Enter anaerobism agitation phases after the stirring water inlet of II anaerobism, sets mixing time as 3h, polyP bacteria utilizes fermentation Abundant carbon source progress in mixture and sanitary sewage largely releases phosphorus, and stores a large amount of PHA；

III aeration maintains dissolved oxygen DO in 0.5~1.5mg/L by real-time control apparatus, and monitors pH, when setting is aerated Between in 2h (ammonia valley point occur before), NH₄ ⁺Short distance nitration effect occurs under low oxygen conditions for-N, while aeration time being controlled in ammonia Valley point achievable NH before occurring₄ ⁺The part short distance nitration of-N, polyP bacteria suction part PO₄ ^3--P；

IV anoxia stirring sets mixing time 1h, the NO generated when anoxic can guarantee aeration in short-term₃ ^-- N passes through anti-nitre Change removal, while by remaining PO₄ ^3-- P is acted on by denitrification dephosphorization and being removed；

V sedimentation and drawing sets sedimentation time 2h, drains after mud-water separation, is discharged into intermediate water tank, draining is than being 70%.

2nd SBR:

I is intake from intermediate water tank water intake, is set inflow as the 1/2 of reactor effective volume, i.e. 4.5L, is opened by time control Close control；

II anoxia stirring sets mixing time 3h, by the NH in the first SBR water outlet₄ ⁺- N and NO₂ ^-- N passes through Anammox Effect removal；

IV sedimentation and drawing sets sedimentation time 2h, drains after mud-water separation, and draining is than being 60%.

The results showed that COD concentration is 30~43mg/L, NH in water outlet after stable₄ ⁺- N concentration be 0.2~ 2.5mg/L, TN removal rate are 80~85%；PO₄ ^3-- P concentration is 0.1~0.7mg/L, and removal rate is 90%~97%.

Claims

1. A method for realizing partial short-range nitrification and anammox ammonium oxidation of urban sewage by utilizing fermented sludge, using the following system: the first pump peristaltic pump (1) is connected to the excess sludge fermentation tank (2), and the excess sludge fermentation tank (2) A first stirrer (3), a temperature control device (4) and a first pH controller (5) are installed inside; the excess sludge fermentation tank (2) is connected with the fermentation mixture storage tank (9), and the fermentation mixture storage tank (9) ) is connected with the first SBR (13) of the sequencing batch reactor by the second peristaltic pump (11); the domestic sewage water tank (8) is connected to the first SBR ( 13) Connection; a second agitator (15), a first dissolved oxygen controller (12) and a second pH controller (14) are installed in the first SBR (13) of the sequencing batch reactor; The aeration head in the first SBR (13) is connected to the air compressor (16), and the first SBR (13) of the sequencing batch reactor is connected to the intermediate water tank (17); the intermediate water tank (17) passes through the fourth peristaltic pump (18) ) is connected with the second SBR (20) of the sequencing batch reactor; the third agitator (22), the second dissolved oxygen controller (19) and the third pH control are installed in the second SBR (20) of the sequencing batch reactor device (21); in addition, a process controller (6) connected to the computer (7) is provided to control the first peristaltic pump (1), the second peristaltic pump (11), the third peristaltic pump (10), the Four peristaltic pumps (18), a first stirrer (3), a second stirrer (15), a third stirrer (22), a temperature controller (4), a first pH controller (5), a second pH a controller (14), a third pH controller (21), a first dissolved oxygen controller (12), a second dissolved oxygen controller (19) and an air compressor (16);

It is characterized in that, comprises the following steps:

(1) Start-up of the excess sludge fermentation tank: the excess sludge fermentation tank (2) is a semi-continuous reactor, the sludge residence time SRT is 6-20 days, and the pH is controlled at 9-10; the excess sludge is discharged every day according to the SRT Fermentation mixture to fermentation mixture storage tank (9) and adding equal volume of fresh excess sludge to excess sludge fermentation tank (2);

(2) Start-up of the first SBR of the sequencing batch reactor: The short-range nitrification sludge is used as the inoculated sludge to inject into the first SBR (13) of the sequencing batch reactor, and the urban domestic sewage added with sodium acetate is used as the raw water to inject into the domestic life. The sewage water tank (8) keeps the C/N ratio of the influent water at 5-6, and is pumped into the first SBR (13) of the sequencing batch reactor through the third peristaltic pump, namely the influent pump (10), and runs 2-3 times a day cycle, the drainage ratio is maintained at 50-80%, and each cycle includes water intake, anaerobic stirring, aeration, anoxic stirring, precipitation, drainage, and idle. When the accumulation rate is greater than 95% and the effluent TP is below 1 mg/L, the start-up and debugging of the first SBR (13) of the sequencing batch reactor is completed;

(3) Start-up of the second SBR of the sequencing batch reactor: the ANAMMOX granular sludge or flocculent sludge is injected into the second SBR (20) of the sequencing batch reactor as the seed sludge, and at the same time, the NH ₄ ⁺ -N and NO ₂ ^- -N with a mass concentration ratio of 1:1 to 1.3 is the influent water, which is injected into the intermediate water tank (17), and is pumped into the second SBR (20) of the sequencing batch reactor through a peristaltic pump. Anaerobic stirring, when the effluent NH ₄ ⁺ -N concentration is less than 1 mg/L, or the NO ₂ ^- -N concentration is less than 1 mg/L, the start-up and commissioning of the second SBR of the sequencing batch reactor is completed;

(4) After the first SBR and the second SBR of the sequencing batch reactor are respectively started up, the two are operated in series: the first SBR (13) of the sequencing batch reactor undergoes in turn the influent and sludge fermentation mixture, There are 5 processes of oxygen stirring, aeration, anoxic stirring, and sedimentation drainage; the second SBR (20) of the sequencing batch reactor undergoes 3 processes of water inflow, anoxic stirring, and sedimentation drainage in sequence in each cycle;

Sequencing Batch Reactor First SBR:

The water inlet and fermentation mixture are set to be 1/2 to 4/5 of the effective volume of the reactor, and the amount of the fermentation mixture to be 1/50 to 1/10 of the influent volume. Both are controlled by a time-controlled switch. After the system is started, the sewage in the sewage water tank (8) enters the first SBR (13) of the sequencing batch reactor through the inlet pump (10), and during the water inlet process, the fermentation mixture in the excess sludge fermentation tank (2) passes through the first SBR (13). Two peristaltic pumps (11) enter the first SBR (13); the indicators of the substances in the fermentation mixture are as follows: SCOD is 3380 ± 420 mg/L, SCFAs is 1221 ± 40 mgCOD/L, NH ₄ ⁺ -N is 198 ± 20 mg/L, PO ₄ ^3- -P is 95±10mg/L;

II Enter the anaerobic stirring stage after anaerobic stirring is completed, and set the stirring time to 3-3.5h;

III Aeration turns on the air compressor (16), provides oxygen to the first SBR (13) of the sequencing batch reactor, and converts the ammonia nitrogen in the influent into oxidized nitrogen; maintains the dissolved oxygen DO between 0.5 and 1.5 through the real-time control device mg/L, and monitor the pH, set the aeration time to 1-2h and before the ammonia valley point appears;

IV Hypoxia stirring set stirring time 1 ~ 1.5h;

VI sedimentation drainage set sedimentation time 1 ~ 2h, after the separation of mud and water, drainage is discharged into the intermediate water tank (17), the drainage ratio is 50% ~ 80%;

Sequencing Batch Reactor Second SBR:

I inlet water is supplied from the intermediate water tank (17), and the water inlet amount is set to be 1/2 to 3/4 of the effective volume of the reactor, which is controlled by a time-controlled switch;

II Hypoxia stirring set stirring time 2～3h;

IV Precipitation and drainage Set the settling time for 1 to 2 hours. After the mud and water are separated, the drainage is performed, and the drainage ratio is 50% to 75%.