CN111732190A

CN111732190A - Rapid culture method of denitrified granular sludge

Info

Publication number: CN111732190A
Application number: CN202010447695.3A
Authority: CN
Inventors: 王磊; 何晔
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-05-25
Filing date: 2020-05-25
Publication date: 2020-10-02

Abstract

The invention discloses a rapid culture method of denitrified granular sludge, which comprises the following steps of putting dewatered sludge granules into a sequencing batch reactor, wherein the sequencing batch reactor is used for carrying out a plurality of culture periods, and each culture period comprises: the method comprises the steps of water feeding, oxygen deficiency, aerobic step, standing precipitation and water drainage, wherein the pH is not adjusted within the first 48-480 hours of the operation of the sequencing batch reactor, and the dehydrated sludge particles in the sequencing batch reactor are subjected to micro-expansion. The invention provides a foundation for the rapid culture of the denitrified granular sludge and the rapid formation of the denitrified performance, and the dehydrated granules have better denitrified and organic pollutant removing effects immediately after being added into the SBR reactor which operates according to the parameters contained in the invention.

Description

Rapid culture method of denitrified granular sludge

Technical Field

The invention relates to the technical field of biological wastewater treatment, in particular to a rapid culture method of denitrified granular sludge.

Background

With the acceleration of production and life and urbanization processes, nitrogen pollution in water bodies is increasingly serious, the eutrophication degree of the water bodies is aggravated, the traditional biological denitrification process is established on the basis of flocculent sludge, and has the problems of long process flow, large occupied area, high capital cost, low treatment efficiency, low impact load resistance and the like, the development and research of the high-efficiency and low-consumption wastewater denitrification technology becomes an irreparable task in the field of water pollution control, and researchers pay more and more attention.

Compared with the common traditional activated sludge, the aerobic granular sludge has the characteristics of high specific gravity and biological compactness, so that the aerobic granular sludge has a rapid sedimentation speed, is beneficial to sludge-water separation, reduces or omits a secondary sedimentation tank of the sludge, simplifies the process flow, and reduces the occupied area and the investment cost of a sewage treatment system. Moreover, the higher sludge concentration and the higher volume load of the aerobic granular sludge can bear the impact caused by water quality fluctuation and high organic load, and the good effluent quality is ensured. In addition, based on a gradient dissolved oxygen environment formed by an aerobic granular sludge compact structure and a larger grain size, an external aerobic-internal anoxic layered structure enables functional microorganisms to be colonized in a partitioning manner, and synchronous nitrification and denitrification in the same reactor are realized. Researches show that Ammonia Oxidizing Bacteria (AOB) and Nitrite Oxidizing Bacteria (NOB) can coexist with heterotrophic bacteria in aerobic granular sludge, wherein ammonia oxidizing bacteria Nitrosomonasp are mainly distributed at the position of 70-100 mu m of the outer layer of the granules, nitrite oxidizing bacteria Nitrosobactrsp and Nitrospirasp are arranged at the inner layer of the granules, nitration reaction mainly occurs in the surface layer of the granules within 300 mu m, and facultative bacteria Rhodocyclaceae and Paraccuscasis and anaerobic bacteria Bacteroides are mainly used at the position of 800-900 mu m away from the surface. Based on the advantages of the aerobic granular sludge, the aerobic granular sludge technology is combined with the latest biological denitrification process, and a feasible path for finding a simple, efficient and energy-saving carbon and nitrogen removal process is found.

A great deal of research shows that in an SBR system mainly based on aerobic granular sludge, when an anoxic mode (A/O) is added before an aerobic mode, the denitrification rate can be increased to 60 percent, and when the dissolved oxygen concentration in an aerobic stage is further controlled to be at a lower level (less than 2mg/L), the denitrification rate can be further increased to 80 percent. The denitrification efficiency of the system is improved by adopting an alternative anoxic/aerobic strategy (A/O/A/O), and the SBR denitrification rate reaches over 70 percent. The water inlet mode mainly comprises one-time water inlet and step water inlet. The problem of insufficient carbon source in the later operation stage of the SBR reactor is solved by the step-by-step water inlet mode, and the denitrification efficiency is high. However, this mode of water entry is often combined with certain modes of operation to enhance denitrification. Chen and the like adopt an alternative anoxic/aerobic strategy and combine with sectional water inlet, so that the denitrification efficiency is improved to more than 93 percent. Therefore, the proper multi-parameter combination operation mode is selected to be more beneficial to improving the denitrification performance.

The research mostly changes the operation mode on the basis of aerobic granular sludge, thereby improving the denitrification performance of the system. However, under the same operation mode, at least 40 days are needed for starting the enhanced denitrification aerobic granular sludge system by using the flocculated sludge as the inoculant. Obviously, the rapid acquisition or cultivation of a large amount of aerobic granular sludge is the key to rapidly start the enhanced denitrification aerobic granular sludge system. However, the slow cultivation speed makes it difficult to obtain AGS as a scarce resource in a large amount, and it becomes a bottleneck restricting its application in large-scale projects.

Disclosure of Invention

The invention aims to provide a rapid culture method of denitrified granular sludge aiming at wastewater with high ammonia nitrogen and low carbon-nitrogen ratio. The rapid culture method of the denitrified granular sludge can rapidly and effectively improve the concentration of the aerobic granular sludge, and solves the problems of low culture speed of the denitrified granular sludge and serious sludge loss in the initial starting stage and low denitrification efficiency of the existing process method.

The technical scheme adopted by the invention for solving the problems is as follows:

a rapid culture method of denitrified granular sludge is characterized in that: the method comprises the following steps:

step S1, preparing denitrified granular sludge inoculated sludge, sequentially dehydrating, extruding and cutting activated sludge to obtain dehydrated sludge granules,

step S2, the dewatered sludge particles are put into a Sequencing Batch Reactor (SBR) that performs a plurality of culture cycles, each culture cycle including:

(1) s2.1, a water inlet step, namely pumping the wastewater with the low carbon-nitrogen ratio into a sequencing batch reactor;

(2) s2.2, an anoxic step, namely carrying out anoxic stirring in the sequencing batch reactor;

(3) s2.3, an aerobic step, wherein aeration is carried out through an aeration device to fully mix and react mud and water;

(4) s2.4, standing and precipitating to realize sludge-water separation;

(5) step S2.5, a water drainage step,

in step S2, the pH value is not adjusted (the pH value is controlled to be 6.9-7.3) in the first 48-480 hours of the operation of the sequencing batch reactor, the dehydrated sludge particles in the sequencing batch reactor are subjected to micro-expansion, so that the SVI5 and the SVI30 in the sequencing batch reactor reach 50-60 mL/g, and then the pH value of inlet water is adjusted to be 7.5-8.5.

Further, in step S2, it is preferable that each culture period is 6 to 12 hours.

Further, preferably, in step S2.4, the shorter standing and precipitating time is maintained in each culture period, and the time for precipitating the particles with the particle size of 0.1-0.2 mm to the water outlet is selected.

The Sequencing Batch Reactor (SBR) is in a long column shape, the settling time refers to the time from the stop of the reactor, the particles in the sequencing batch reactor settle for a certain time, and then a drainage valve is opened for drainage. At the moment, the sludge with poor settling property is discharged, and the sludge with good settling property is remained in the reactor, namely, the time for settling particles of 0.1-0.2 mm to a water outlet is selected.

Further, preferably, the ratio of the time of the anoxic step in the step S2.2 to the time of the aerobic step in the step S2.3 is 1:1 to 1: 3.

Preferably, the carbon-nitrogen ratio of the low carbon-nitrogen ratio wastewater in the aerobic step of step S2.3 is 3 to 10, the MLSS (mixed liquor suspended solids concentration) of the low carbon-nitrogen ratio wastewater is 3 to 7g/L, the DO concentration (Dissolved Oxygen) of the low carbon-nitrogen ratio wastewater is 2.5 to 4mg/L, and the volume exchange rate (volumetric exchange rate) of the low carbon-nitrogen ratio wastewater is 50 to 60%.

Further, in the aerobic step of step S2.3, the ratio of the feed water ammonia nitrogen concentration to the MLSS (mixed liquor suspended solids concentration) concentration in the sequencing batch reactor is preferably 1:60 to 1: 80.

Further preferably, in the aerobic step of step S2.3, trace elements are added to the sequencing batch reactor.

Further, in step S1, preferably, the activated sludge is aerobic activated sludge, and the activated sludge is screened by a 100-mesh screen to remove large particles therein, wherein MLVSS (mixed liquor volatile suspended solids concentration)/MLSS (mixed liquor suspended solids concentration) of the activated sludge is 0.5-0.75, so as to ensure the number of microorganisms in the dewatered activated sludge.

Further, in step S1, preferably, in step S1, the water content of the dewatered activated sludge is reduced to 65% to 75%, and the dewatering method is belt dewatering, plate and frame filter pressing or centrifugal dewatering, and then drying treatment is performed at a temperature of 35 ℃ to 42 ℃.

Further, in step S1, it is preferable that the dehydrated sludge is cut into a short cylindrical shape having a particle diameter of 0.5mm to 0.8mm and a cylindrical length of 1mm to 4mm in step S1.

Compared with the prior art, the invention has the following advantages and effects:

(1) the invention leads filamentous fungi to be moderately propagated by controlling PH in the initial reaction stage, forms a buffer layer on the surface of dehydrated sludge particles, not only can reduce the breakage of the particles in the initial stage, but also provides excellent conditions for the attachment of microorganisms and the change of the whole particle structure. Provides a foundation for the rapid culture of the denitrified granular sludge and the rapid formation of the denitrogenation performance, and has better denitrogenation and organic pollutant removal effects immediately after the dehydrated granules are added into the SBR reactor which operates according to the parameters contained in the invention.

(2) According to the initial ammonia nitrogen concentration, sludge with the corresponding sludge concentration and the appropriate aeration amount are added, so that the high-efficiency denitrification can be quickly realized.

(3) The system for denitrifying granular sludge can realize granulation immediately, granules in the reactor have better sedimentation performance in the whole operation process, and the reduction of the sludge concentration at the initial starting stage can be ignored.

(4) Combining the dewatered sludge granules with the micro-bulking technique of filamentous bacteria at the initial start-up of the reactor reduces the sludge concentration loss due to reduced initial granule breakup and attrition.

(5) Aiming at the problem that filamentous fungi are difficult to control, the swelling of the filamentous fungi is successfully controlled within a reasonable range by utilizing PH, DO and SVI.

Drawings

FIG. 1 is a block diagram showing the steps of a rapid culture method of denitrified granular sludge according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the steps of the culture cycle of a rapid culture method for denitrified granular sludge according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail below by way of examples with reference to the accompanying drawings, which are illustrative of the present invention and are not to be construed as limiting the present invention.

The aerobic granular sludge culture device adopts a Sequencing Batch Reactor (SBR), inoculated sludge is active sludge from an aerobic biochemical section of a certain sewage treatment plant, and denitrification granular sludge is cultured by taking simulated wastewater with low carbon-nitrogen ratio as inlet water.

The parameters of the sequencing batch reactor (hereinafter referred to as "SBR reactor") used in this example were as follows: SBR reactor adopts the organic glass material, and diameter 80mm, height 500mm, effective volume 2L, SBR reactor bottom sets up aeration equipment, and the air gets into the reactor through the aeration machine.

The water quality characteristics of the simulated wastewater in this example are as follows: the pH value is 6.8-7.0, the ammonia nitrogen is 60mg/L, and the COD concentration is 360 mg/L.

Referring to fig. 1, the rapid culture method of the denitrification granular sludge is carried out according to the following steps:

step S1, preparing denitrified granular sludge inoculated sludge, wherein the inoculated sludge is flocculent sludge from an aerobic tank, large granules are filtered by a 100-mesh screen, and then the flocculent sludge is mechanically dehydrated to 80 percent, then the flocculent sludge is extruded and cut into cylindrical dehydrated sludge granules with the diameter of 0.5mm and the height of 0.5mm, and then the dewatered sludge granules are dried at the temperature of 40 ℃ until the water content is 70 percent.

Step S2, inoculating the dewatered sludge granules into the SBR reactor, performing a plurality of culture cycles in the SBR reactor:

referring to fig. 2, each culture cycle comprises the following steps:

step s2.1, water is fed for 1 minute, step s2.1, simulated wastewater (wastewater with low carbon-nitrogen ratio) is pumped into the reactor, and the volume exchange rate is 50%;

step s2.2, stirring for 30 minutes in the absence of oxygen,

step s2.3, carrying out aerobic aeration for 80 minutes, and carrying out aeration through an aeration device paved at the bottom of the SBR reactor to ensure that mud and water are fully mixed and react, wherein the aeration rate is 2L/min, and the aeration time is 240 min;

s2.4, standing and precipitating for 5min after the aeration is stopped to realize mud-water separation;

and S2.5, draining water from a water outlet of the reactor for 10 min.

Repeating the steps in sequence, wherein DO at the initial aeration stage is 3.0-4.0 mg/L; the three culture periods form a large culture period, and the large culture period is controlled to be about 6 hours.

In the aerobic granular sludge culture process, the sludge concentration in the SBR reactor is controlled at 5g/L, and SVI (sludge volume index), Chemical Oxygen Demand (COD) and nitrogen indexes of inlet and outlet water are monitored every day. And (4) carrying out microscopic observation and detection on SVI5 (sludge volume index) and SVI30 (sludge volume index), and adjusting the pH value of the sequencing batch reactor to be 7.5-8 when MLSS (suspended solid concentration) is more than 70 ml/g.

And step s2.3, adding a certain amount of trace elements into the SBR reactor, wherein the trace elements comprise 30mg/L of magnesium sulfate, 20mg/L of ferric chloride, 20mg/L of copper sulfate, 3mg/L of zinc sulfate, 0.3mg/L of cobalt chloride, 0.4mg/L of manganese chloride and 80ug/L of aluminum chloride.

The SVI30 of the sludge in the SBR reactor is increased from 30mL/g to 70mL/g 3 days before operation, the PH is increased to 7.5-8, the SVI30 is gradually decreased from 70mL/g and stabilized at 40mL/g to 50mL/g, the particle sludge accounts for more than 80% in the whole operation process, the MLSS reduction amount of the SBR reactor in the first three days is less than 10%, then the MLSS (suspended solid concentration) is basically maintained at about 6000mg/L, the ammonia nitrogen removal rate is basically 100%, and the total nitrogen and COD removal rate are both more than 90% in the whole operation process.

The method for culturing aerobic granular sludge by using dehydrated sludge granules is a feasible idea, and at present, a great deal of research exists for culturing denitrification granular sludge by using part of aerobic granular sludge as an inoculum, so that the method for culturing denitrification granular sludge by using dehydrated sludge granules instead of aerobic granular sludge as the inoculum is worth trying.

According to the conclusion that the dehydrated sludge particles are broken in a large amount at the initial stage of inoculation, MLSS is rapidly reduced and the like, and filamentous fungi play a skeleton role in the granular sludge and the like. The method takes the specially treated dehydrated sludge as the inoculum, and the sludge is not easy to break, has high density and high settling speed, so that the sludge is not easy to lose under the condition of shorter settling time, the concentration of the sludge is not reduced, and the concentration of the sludge is quickly and effectively improved. In addition, lower dissolved oxygen content, lower hydraulic shear, also reduces particle breakage, and thus reduces sludge loss. The above is beneficial to quickly starting the denitrification granular sludge system. The rapid culture method of the denitrified granular sludge can rapidly and effectively improve the concentration of the aerobic granular sludge, and solves the problems of low culture speed of the denitrified granular sludge and large sludge loss in the culture process in the prior art.

The lower initial dissolved oxygen concentration reduces the hydraulic shear and thus the breakage rate of the granules, since the less initial breakage, the faster the granulation speed. Due to the low dissolved oxygen concentration, filamentous fungi on the surface of the particles are moderately propagated, a buffer layer is formed on the surface of the particles, and the particle breakage is reduced. Meanwhile, the specific surface area of the granules is increased, the granules are more favorable for the attachment of various microorganisms, particularly aerobic nitrification and nitrosobacteria with a longer generation period, and meanwhile, the filamentous bacteria forming a loose structure can also improve the diffusion depth of nutrients and dissolved oxygen, so that the denitrification performance of the granules is further improved. The invention leads filamentous fungi to be moderately propagated by controlling PH in the initial reaction stage, forms a buffer layer on the surface of dehydrated sludge particles, not only can reduce the breakage of the particles in the initial stage, but also provides excellent conditions for the attachment of microorganisms and the change of the whole particle structure. Provides a foundation for the rapid culture of the denitrified granular sludge and the rapid formation of the denitrification performance.

Because the dewatered sludge particles used in the invention are flocculent activated sludge in the aerobic tank, the activated sludge has good pollutant removal capacity, and the influence of the dewatering condition on the activity of the sludge is small, the particles are added into the reactor and combined with a denitrification operation mode, so that the better denitrification and pollutant removal effects are achieved immediately. In addition, because the flocculent sludge is dehydrated into the granular sludge, the specific surface area of the sludge is greatly reduced, the number of ammonia oxidizing bacteria and nitrifying bacteria is reduced to a certain extent, and the generation period of the bacteria is longer, so that the concentration of specific sludge and the amount of treated ammonia nitrogen are constant under the condition of a certain grain diameter. The invention has better denitrification and organic pollutant removal effects immediately after the dehydrated particles are added into the SBR reactor operated by the parameters contained in the invention. According to the initial ammonia nitrogen concentration, sludge with the corresponding sludge concentration and the appropriate aeration amount are added, so that the high-efficiency denitrification can be quickly realized.

Because the dehydrated particles are pretreated (with low water content and cylindrical), the hydraulic shear force is reduced due to low dissolved oxygen, the filamentous fungi on the surface layer play a role in buffering when colliding, and the factors can reduce the breakage of the particles. Meanwhile, the low breaking rate means that the particle size of the particles is larger, so that the precipitation speed is high and the sedimentation performance is good. The reasons are favorable for the stable and rapid increase of the sludge concentration of the SBR system. Currently, the standard in the literature for granulation is that granulation is achieved when the mass percentage of particles with a particle size greater than 0.2mm is more than 90% of the total mass. Therefore, a low crushing rate is advantageous to increase the granulation speed. The system for denitrifying granular sludge can realize granulation immediately, granules in the reactor have better sedimentation performance in the whole operation process, and the reduction of the sludge concentration at the initial starting stage can be ignored.

The low dissolved oxygen and acidic conditions are favorable for the mass propagation of the filamentous fungi, but the related documents report that the filamentous fungi can be inhibited by high pH, and the invention hopes that the filamentous fungi on the surface of the aerobic granules are moderately expanded in the early operation stage of the reactor, so the dissolved oxygen is selected from the range above. The aerobic granular sludge has the advantages that the sedimentation performance is expressed by SVI (sludge sedimentation index), the expansion is allowed, but the sedimentation performance is in a certain range, so the SVI is used as an indication index, and when the SVI exceeds the standard, the pH value is properly increased (7.5-8.2) to control filamentous bacteria, so that the SVI is always kept in a reasonable range. In this case, the filamentous fungi are aggregates of the skeleton to which a large number of microorganisms are attached, and fall off from the particle surface to form new small particles. The invention combines the dehydrated sludge particles with the micro-expansion technology of the filamentous bacteria at the initial startup of the reactor, thereby reducing the sludge concentration loss caused by the reduction of the crushing and abrasion of the particles at the initial stage. Aiming at the problem that filamentous fungi are difficult to control, the swelling of the filamentous fungi is successfully controlled within a reasonable range by utilizing PH, DO and SVI.

The above description of the present invention is intended to be illustrative. Various modifications, additions and substitutions for the specific embodiments described may be made by those skilled in the art without departing from the scope of the invention as defined in the accompanying claims.

Claims

1. A rapid culture method of denitrified granular sludge is characterized in that: the method comprises the following steps:

step S2, placing the dewatered sludge particles into a sequencing batch reactor, the sequencing batch reactor performing a plurality of culturing cycles, each culturing cycle comprising:

(4) s2.4, standing and precipitating to realize sludge-water separation;

(5) step S2.5, a water drainage step,

in step S2, the pH is not adjusted in the first 48-480 hours of the operation of the sequencing batch reactor, the dehydrated sludge particles in the sequencing batch reactor are subjected to micro-expansion, so that SVI5 and SVI30 in the sequencing batch reactor reach 50-60 mL/g, and then the pH of the inlet water is adjusted to be 7.5-8.5.

2. The rapid culture method of denitrified granular sludge according to claim 1, wherein: step S2, each culture period is 6 to 12 hours.

3. The rapid culture method of denitrified granular sludge according to claim 1, wherein: s2.4, maintaining a short standing and precipitating time in each culture period, and selecting a time for precipitating the particles of 0.1-0.2 mm to a water outlet.

4. The rapid culture method of denitrified granular sludge according to claim 1, wherein: the time ratio of the anoxic step in the step S2.2 to the aerobic step in the step S2.3 is 1: 1-1: 3.

5. The rapid culture method of denitrified granular sludge according to claim 1, wherein: in the aerobic step of the step S2.3, the carbon-nitrogen ratio of the wastewater with the low carbon-nitrogen ratio is 3-10, the MLSS of the wastewater with the low carbon-nitrogen ratio is 3-7 g/L, the DO concentration of the wastewater with the low carbon-nitrogen ratio is 2.5-4 mg/L, and the volume exchange rate of the inflow water of the wastewater with the low carbon-nitrogen ratio is 50-60%.

6. The rapid culture method of denitrified granular sludge according to claim 1, wherein: in the aerobic step of the step S2.3, the ratio of the concentration of the ammonia nitrogen in the inlet water to the concentration of MLSS in the sequencing batch reactor is 1: 60-1: 80.

7. The rapid culture method of denitrified granular sludge according to claim 1, wherein: and in the aerobic step of the step S2.3, adding trace elements into the sequencing batch reactor.

8. The rapid culture method of denitrified granular sludge according to claim 1, wherein: in step S1, the activated sludge is aerobic activated sludge, and the activated sludge is screened by a 100-mesh screen to remove large particles therein, wherein MLVSS/MLSS of the activated sludge is 0.5-0.75, so as to ensure the number of microorganisms in the dehydrated activated sludge.

9. The rapid culture method of denitrified granular sludge according to claim 1, wherein: in the step S1 and the step S1, the water content of the dehydrated activated sludge is reduced to 65-75%, and the dehydration method adopts belt type dehydration, plate and frame filter pressing or centrifugal dehydration, and then drying treatment is carried out at the temperature of 35-42 ℃.

10. The rapid culture method of denitrified granular sludge according to claim 1, wherein: in step S1, in step S1, the dehydrated sludge particles are cut into short cylinders with the diameter of 0.5 mm-0.8 mm and the length of 1 mm-4 mm.