CN111018103A

CN111018103A - Method for directionally regulating and controlling stable operation of aerobic granular sludge

Info

Publication number: CN111018103A
Application number: CN202010043674.5A
Authority: CN
Inventors: 宋志伟; 张晴; 邓文婧; 潘宇
Original assignee: Heilongjiang University of Science and Technology
Current assignee: Heilongjiang University of Science and Technology
Priority date: 2020-01-15
Filing date: 2020-01-15
Publication date: 2020-04-17

Abstract

The invention relates to the field of stable operation of sludge, in particular to the field of a method for directionally regulating and controlling the stable operation of aerobic granular sludge. According to the method, exogenous AHLs signal molecules are periodically added into the aerobic granular sludge reactor, and the microorganisms are directly regulated and controlled by the signal molecules, so that the microorganisms are stimulated to secrete EPS, the aggregation of the microorganisms in the aerobic granular sludge is promoted, and the stability of the aerobic granular sludge is improved. The invention can regulate and control the stability of the aerobic granular sludge and solves the problem of poor stability of the aerobic granular sludge in the operation process. The addition of exogenous signal molecules enables the EPS secretion content of microorganisms to be increased rapidly, the repulsion between sludge and sludge is reduced, the coagulation performance is improved, and then the microorganisms are gathered more easily, and granular sludge with a compact structure is formed.

Description

Method for directionally regulating and controlling stable operation of aerobic granular sludge

Technical Field

The invention relates to the field of stable operation of sludge, in particular to the field of a method for directionally regulating and controlling the stable operation of aerobic granular sludge.

Background

Aerobic Granular Sludge (AGS) is a microbial mass formed by self-aggregation of microorganisms under aerobic conditions, the formation of the aerobic granular sludge is a complex process including physical, chemical and biological actions, and the aerobic granular sludge has the advantages of good sedimentation performance, high volume load resistance, high organic matter removal rate and the like, and is widely concerned in the field of sewage treatment.

The aerobic granular sludge has the problem of poor stability in the actual operation process, the key substance for maintaining the stable operation of the aerobic granular sludge is Extracellular Polymeric Substances (EPS), the EPS is a Polymeric compound which is secreted and generated to surround the cell wall in the microbial metabolism process, the surface hydrophobicity of the microorganism can be changed, the aggregation of the microorganism is promoted, the aerobic granular sludge mainly comprises Protein (PN) and Polysaccharide (PS), and the PN plays a main role in the aggregation and growth of the aerobic granular sludge. The operation condition of the aerobic granular sludge has great influence on the EPS secretion, when the culture condition fluctuates slightly, the EPS secretion is reduced, the surface hydrophobicity of the sludge is reduced, the electrostatic repulsion among microbial cells is increased, the agglomeration performance is reduced, the microbes are changed from aggregation to loosening, the aerobic granular sludge is loosened, the settling performance and the degradation performance are reduced, and the stability is lost. The application and popularization of the aerobic granular sludge in practical engineering are restricted.

At present, reports on methods for improving the stability of aerobic granular sludge change operation process parameters, such as: changing the water conservancy shearing force: the stability of the aerobic granular sludge is influenced by a key, but the optimal application range of the shearing force in different reactors can be changed correspondingly. Changing the organic load: aerobic granular sludge is cultured in the range of 2.5-19.5 kg/(m3 d), but the stability of the granular sludge shows different degrees under different organic load conditions. Changing the inoculated sludge: the richer the population structure in the inoculated sludge, the better the stability of the granular sludge is relatively. The three methods lack universality, and specific and accurate values of hydraulic shearing force and organic load and the type of inoculated sludge cannot be determined when the operating conditions are changed.

Disclosure of Invention

Aiming at the problems, the invention provides a method for directionally regulating and controlling the stable operation of aerobic granular sludge.

According to the method, exogenous AHLs signal molecules are periodically added into the aerobic granular sludge reactor, and the microorganisms are directly regulated and controlled by the signal molecules, so that the microorganisms are stimulated to secrete EPS, the aggregation of the microorganisms in the aerobic granular sludge is promoted, and the stability of the aerobic granular sludge is improved.

The technical scheme of the invention is as follows:

(1) the hydraulic retention time in the running process of the reactor is 6 h, the temperature is controlled to be 30 +/-1 ℃, the surface gas flow rate is 2.4 m/s, and the aeration rate is 0.32 m³And h, inoculating flocculent sludge into the reactor, conveying the wastewater to be treated into the reactor from a water inlet tank through a water inlet pump, carrying out primary culture on aerobic granular sludge, and detecting the concentrations of C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL in the sludge in the running process.

(2) Preparing an exogenous signal molecule AHLs mother solution, wherein the purity of the exogenous signal molecule AHLs is more than 95%, the species of the exogenous signal molecule AHLs can be one or more of C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL, and the exogenous signal molecule AHLs are added when the concentration of one or more signal molecules in the aerobic granular sludge is reduced by 20%.

Description of the drawings:

in the step (1), the reactor is a self-made SBAR reactor and is composed of double layers of organic glass (the volume of a cylinder is 5.0L, the external pipe diameter is about 8 cm, the height is about 120 cm, the internal pipe diameter is about 6 cm, and the height is about 90 cm); the reactor operates according to the sequence of water injection, aeration, sedimentation and drainage, and during the operation period, the water injection time is 5-8 min, the aeration time is 329-; the inoculated sludge is flocculent activated sludge in a secondary sedimentation tank of a beer wastewater treatment plant, and the final concentration of the inoculated sludge is 7000-9000 mg/L; the wastewater to be treated is artificially synthesized wastewater, glucose is used as a carbon source, and 1 mL/L of trace elements is added.

In the step (2), the species of the exogenous signal molecule to be added is determined according to the following conditions:

detecting the concentration change of signal molecules of C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL in the running process of the reactor, and adding corresponding kinds of signal molecules when the concentration of one or more signal molecules is reduced by 20%.

In the step (2), the adding mode of the exogenous signal molecules AHLs is that the exogenous signal molecules AHLs enter a reactor along with water inflow, the exogenous signal molecules AHLs are dissolved in Tris-HCl buffer solution, and then the prepared mixed solution is added into a water inflow tank, wherein the pH value of the Tris-HCl buffer solution is 7.0.

Technical description:

key point 1: the type of signal molecule added.

The phenomenon of weakening information communication among substances is often accompanied in the destabilization process of the aerobic granular sludge. The aerobic granular sludge with poor stability has loose structure, rough surface and poor sedimentation performance, and the main reasons are that the EPS content secreted by microorganisms is reduced, the extracellular polysaccharide and protein content are reduced, and the intercellular cohesion is reduced, so that the aerobic granular sludge can not adhere to each other to grow to form granules.

Through research, when the EPS content is changed, the content of one or more signal molecules in AHLs signal molecules C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL secreted by certain microorganisms is changed in a certain correlation manner, and because the relation between the signal molecules and various physicochemical properties of aerobic granular sludge is unknown, whether one or more signal molecules in the AHLs signal molecules C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL can regulate and guide the EPS secretion of the microorganisms to become difficult points and key points can be determined, on the basis, only one or more signal molecules related to the EPS secretion are selected as the signal molecules which can be added, however, in practice, since aerobic granular sludge is a very complex system of microbial communities, the population structure of aerobic granular sludge cultured with different inoculated sludge is also very different, for example, studies have shown that certain signal molecules exist in aerobic granular sludge systems cultured by taking activated sludge of wastewater treatment plants in farms as inoculated sludge, the same signal molecules are not detected in an aerobic granular sludge system formed by inoculating activated sludge in a secondary sedimentation tank of a certain urban domestic sewage treatment plant, therefore, in order to select a signal molecule which is applicable to all aerobic granular sludge systems, the patent only takes the activated sludge of the secondary sedimentation tank of the beer wastewater treatment plant as the aerobic granular sludge system cultured by inoculating sludge as an example, finding out one or more signal molecules secreted by the flora in the system provides a way for developing a new method for regulating and controlling aerobic granular sludge.

Therefore, when the exogenous signal molecule species is selected and added, the species of which the signal molecule secretion is increased and then reduced in the aerobic granular sludge culture process needs to be selected, and the signal molecule is selected because the signal molecule only appears in the stabilization phase of the aerobic granular sludge or the secretion is obviously increased in the stabilization phase, which indicates that the signal molecule plays a main regulation and control role on microorganisms, so that the EPS secretion of the microorganisms in the aerobic granular sludge is increased, the stability of the aerobic granular sludge is further maintained, and the regulation and control role on the microorganisms in the aerobic granular sludge is ensured.

Key point 2: the adding time and adding amount of the signal molecules.

The function of adding the signal molecules is to enable the aerobic granular sludge to play a regulating and controlling role when the structure of the aerobic granular sludge is loose and the sedimentation performance is poor, the effect of each signal molecule on quorum sensing is known to play a role when the secretion of the signal molecule reaches a threshold value, and when the aerobic granular sludge stably runs, the intercellular substance effect of the aerobic granular sludge is also in a dynamic balance state, namely the quantity of certain signal molecules secreted by cells is the quantity capable of stimulating microorganisms to secrete EPS (expandable polystyrene), so that the effect of the added signal molecules on the system is not obvious and resources are wasted, but the aerobic granular sludge is unstable and irregular when the aerobic granular sludge is unstable, so that the aerobic granular sludge system cannot be added until the specific day, and the stable state can be recovered by the number of continuous adding days.

If the adding time can not be selected only according to the running time, judgment according to the running state of the system can be considered, so that the adding can be considered when the concentration of one or more of AHLs signal molecules C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL begins to be reduced or is reduced by 20%. In this case, the stability of the aerobic granular sludge is lowered, but the influence on the performance of the granular sludge itself is not at the most deteriorated stage, so that the addition of the aerobic granular sludge can return the aerobic granular sludge to a stable state in the shortest time without greatly affecting the performance of the aerobic granular sludge.

The amount of signal molecules added is selected to ensure that the threshold range within which each signal molecule has its specific threshold range of action, and is therefore within a threshold range. It can be known from theory that the aerobic granular sludge system can be recovered to a stable state by determining the adding amount of a certain concentration within a threshold range, but in practical application, if the lowest threshold value is selected, the effect is likely to be slow, the adding time is prolonged, and if the highest threshold value is selected, the defect that the expected effect is achieved but the size is small can occur, so that the proper adding amount and adding time are selected according to the practical conditions of sludge concentration, dominant species and quantity and the like in the system.

The invention has the following beneficial effects:

(1) the method adopts a mode of adding signal molecules AHLs from an external source, and when the aerobic granular sludge is unstable, the aerobic granular sludge with reduced degradation performance, settling performance or agglomeration performance is reformed into stable aerobic granular sludge, wherein in the aspect of degradation performance, compared with the aerobic granular sludge without signal molecules (namely a blank group), the COD removal rate of the aerobic granular sludge after continuous signal molecule addition for 10 days is over 90 percent, the COD removal rate is improved by about 20 percent, the COD removal rate is higher by about 40 percent compared with the blank group, the TP removal rate is over 95 percent, the TP removal rate is improved by about 30 percent, and the COD removal rate is higher by about 45 percent compared with the non-addition rate; in the aspect of agglomeration performance, the EPS content reaches 140 mg/g, the secretion is increased by about 30 mg/g, and compared with the EPS which is not added, the EPS content is increased by about 50 mg/g; in the aspect of sedimentation performance, the SVI value is reduced from about 50 to below 30, and is reduced by more than 40 compared with the blank group, which shows that the aerobic granular sludge has compact structure and high particle density. The degradation performance, the sedimentation performance and the coagulation performance of the aerobic granular sludge after the signal molecules are added are all rapidly improved and reach the state of the aerobic granular sludge in a stable period, so that the stability of the aerobic granular sludge can be regulated and controlled, and the problem of poor stability in the operation process of the aerobic granular sludge is solved.

(2) According to the invention, the stability of aerobic granular sludge is regulated and controlled by adding exogenous signal molecules AHLs, the content of EPS secreted by microorganisms is rapidly increased by adding the exogenous signal molecules, the hydrophobicity of the sludge is increased, the repulsion between the sludge is reduced, the coagulation performance is improved, and the microorganisms are more easily aggregated to form granular sludge with a compact structure.

(3) In the invention, after the exogenous signal molecules are added, the main contributor of the increase of the EPS content is protein, namely, when the EPS content is increased, the polysaccharide content has no obvious change, the increase trend of the protein content is the same as the increase trend of the EPS, which shows that the protein in the EPS has promotion effect on the hydrophobicity of the sludge and the aggregation of microorganisms in aerobic granular sludge.

Drawings

FIG. 1 is a graph showing the change in COD removal rate with the addition of different concentrations of signal molecule C10-HSL.

FIG. 2 is a graph showing the change in TP removal rate with the addition of different concentrations of signal molecule C10-HSL.

FIG. 3 is a graph of the change in EPS values with the addition of different concentrations of signal molecule C10-HSL.

FIG. 4 is a graph showing the change in the amount of SVI secretion when different concentrations of signal molecule C10-HSL were added.

Detailed Description

In order to further understand the contents of the present invention, the following description will be made with reference to the examples.

Example 1

A method for directionally regulating and controlling stable operation of aerobic granular sludge comprises the following specific steps:

(1) sludge inoculation: flocculent activated sludge taken from a certain beer wastewater treatment plant of Harbin is taken as inoculated sludge, the content of signal molecules in the inoculated sludge is detected, the inoculated sludge is added into a reactor, and the initial sludge concentration is 8000 g/L.

(2) Preparing artificial synthetic wastewater: the COD concentration in the wastewater is about 1500 mg/L, the ammonia nitrogen is about 70 mg/L, the total phosphorus is about 9 mg/L, the composition of the wastewater is 470 mg/L glucose, 150 mg/L ammonium chloride, 30 mg/L calcium chloride, 10 mg/L magnesium sulfate heptahydrate, 15 mg/L ferrous sulfate heptahydrate, 25 mg/L dipotassium hydrogen phosphate, 10.5 mg/L potassium dihydrogen phosphate, 33mg/L peptone, 22.5 mg/L beef extract and 1 mL/L trace elements, wherein the trace elements are: 150 mg/L boric acid, 120 mg/L zinc sulfate heptahydrate, 120 mg/L manganese chloride heptahydrate, 30 mg/L copper sulfate pentahydrate, 65 mg/L sodium molybdate, 50mg/L nickel chloride, 150 mg/L cobalt chloride hexahydrate and 30 mg/L potassium iodide.

(3) Injecting inlet water into a reactor by a water inlet pump, controlling the temperature of the reactor to be 30 +/-1 ℃, controlling the hydraulic retention time to be 6 hours, operating the reactor in a water injection-aeration-sedimentation-drainage sequence, wherein each cycle is a period, the time of operating the period is 6 hours, the water inflow time is 5min, the aeration time is 340 min, the sedimentation time is 10min and the drainage time is 5min in the period, and controlling the reflux ratio to be 0.5 by adopting a continuous flow water inflow mode to carry out primary culture on aerobic sludge; after 30 d operation culture, the degradation performance of the aerobic granular sludge is nearly stable, namely the COD removal rate is gradually improved and stabilized to be more than 90%, and the TP removal rate is gradually improved and stabilized to be 95%; the agglomeration performance of the polymer is also gradually improved and stabilized, and the EPS content is gradually improved to 141.42 mg/g and the change tends to be stable; sedimentation performance SVI values are below 30. The aerobic granular sludge reaches the mature and stable period.

(4) Detecting the content of signal molecules in the aerobic granular sludge in the mature and stable period; and (3) continuing culturing, and adding a signal molecule C10-HSL when the degradation performance, the sedimentation performance and the coagulation performance of the aerobic granular sludge all have a descending trend (namely the COD removal rate in the degradation performance of the sludge is reduced from more than 90% to about 65% in a stable period, the TP removal rate is reduced from more than 95% to less than 60% in the best case, the EPS content in the coagulation performance is reduced from about 140 mg/g to less than 100 mg/g, the SVI value is also improved to more than 50, and the phenomena show that the stability of the aerobic granular sludge is reduced).

(5) Keeping the operation condition of the reactor unchanged, wherein every 6 hours, the exogenous signal molecule C10-HSL mother liquor enters the reactor along with inflow water, so that the final concentration of the exogenous signal molecule C10-HSL is 100 plus of 100Nm, and after 10 days of operation, compared with the aerobic granular sludge without adding the signal molecule, the degradation performance is obviously improved, as shown in figures 1 and 2, the COD removal rate of the added aerobic granular sludge is rapidly increased from less than 70 percent to about 90 percent, the COD removal rate is increased by nearly 20 percent, the COD removal rate of the aerobic granular sludge without adding the signal molecule is lower than 60 percent, the TP removal rate is stabilized from the initial 70 percent to the later stage to more than 95 percent, wherein the highest removal rate can reach 98.7 percent, and the TP removal rate of the aerobic granular sludge without adding is only about 60 percent; the COD and TP removal rates reach the degradation performance of aerobic granular sludge when the COD and TP removal rates are stable; the stability of the aerobic granular sludge in the aspect of the coagulation performance is enhanced, as shown in figure 3, the EPS secretion is increased to 141.42 mg/g from 101.25 mg/g when the EPS secretion is unstable, and the increase reaches 30 mg/g; the sedimentation performance is also improved, as shown in fig. 4, after the signal molecules are added, the SVI value of the aerobic granular sludge is reduced to below 30 from about 50 when the signal molecules are unstable, the sedimentation standard of the aerobic granular sludge is reached in a stable period, and the SVI value of the sludge without the added signal molecules is higher than 50 and is continuously increased to about 70. The change of the performance of the aerobic granular sludge after the signal molecules are added is comprehensively analyzed, which shows that the aerobic granular sludge reaches a stable state again.

The judgment of whether the aerobic granular sludge is stable is based on the following:

the higher the removal rate of effluent indexes COD and TP is, the better the degradation performance of the aerobic granular sludge is, and when the removal rate of the aerobic granular sludge and the removal rate of the effluent indexes TP is lower than 80%, the degradation performance is reduced, and the aerobic granular sludge is in an unstable running state; the higher the ESP secretion is, the better the aerobic granular sludge coagulation performance is, the more stable the granular structure is, the more obvious the EPS decrease or the secretion is less than 100 mg/g, the lower the aerobic granular sludge coagulation performance is, the granular structure becomes loose and has a tendency of disintegration, the lower the SVI value is, the better the aerobic granular sludge sedimentation performance is, usually the SVI value of the mature and stable aerobic granular sludge is 30 or less, when the SVI value is increased or exceeds 50, the aerobic granular sludge is almost disintegrated and is close to flocculent sludge.

Example 2

The method for directionally regulating and controlling the stable operation of the aerobic granular sludge is the same as the method in the embodiment 1, and the difference is that:

in step (4), the final concentration of exogenous signal molecule C10-HSL was 100 nM.

Keeping the operation condition of the reactor unchanged, wherein at intervals of 6 hours, the exogenous signal molecule C10-HSL mother liquor enters the reactor along with the inflow water so that the final concentration of the exogenous signal molecule C10-HSL is 100nM, and after 10 days of feeding operation, the EPS secreted by the aerobic granular sludge is increased from 104.5 mg/g to 112.57 mg/g in the aspect of coagulation performance; the increment is close to 10 mg/g, which shows that the structural stability is increased, the agglomeration performance is improved, and in the aspect of degradation performance, the COD removal rate is about 80 percent from the initial close to 65 percent to the final; the TP removal rate is close to 80% from about 70% when the TP is unstable to the later stage, the degradation performance of the aerobic granular sludge in the stable period can be achieved, in the sedimentation performance aspect, the SVI value is improved from about 50 to close to 30, which shows that the grain density of the aerobic granular sludge is increased in a short time, the sedimentation performance is improved, the three aspects of performances are integrated to obtain that the aerobic granular sludge can be stable again when the final concentration of the exogenous signal molecule C10-HSL is 100nM, but the total performance is ideal when the addition amount is not 500 nM.

Example 3

in step (4), the final concentration of exogenous signal molecule C10-HSL was 1000 nM.

Keeping the running condition of the reactor unchanged, and feeding the exogenous signal molecule C10-HSL mother liquor into the reactor along with water every 6 hours to ensure that the final concentration of the exogenous signal molecule C10-HSL is 1000nM, and running for 10 days to improve the condensation performance. The EPS secreted by the aerobic granular sludge is increased from 96.43 mg/g to 134.43 mg/g, and the increase is close to 40 mg/g; the microorganisms in the aerobic granular sludge are tightly gathered, and compared with the examples 1 and 2, the EPS increment is the highest, the adding concentration has influence on promoting the microorganisms to secrete EPS, the higher the adding amount is, the higher the EPS secretion amount is, the better the aerobic granular sludge agglomeration performance is, and in the degradation performance, the COD removal rate is improved from the initial 66.4% to more than 85%; the TP removal rate can reach more than 90% from about the first 72% to the last, the treatment effect of the aerobic granular sludge in the stabilization period is achieved, in the aspect of sedimentation performance, the SVI value is reduced to less than 30 from more than 50, and the SVI value can reach 25 in the optimal case, which shows that the sedimentation performance is rapidly recovered after the addition, and the synthesis shows that the aerobic granular sludge can be recovered and stabilized again when the final concentration of the exogenous signal molecules C10-HSL is 1000nM, and the aerobic granular sludge has good performance which is close to the performance of the aerobic granular sludge when the final concentration of the exogenous signal molecules C10-HSL is 500 nM, and the effect of stabilizing the aerobic granular sludge is achieved.

Tests show that after the operation of example 2 for 10 days, the effect is relatively insignificant compared with examples 1 and 3 due to the fact that the concentration of the added exogenous signal molecule C10-HSL is low, and the unstable aerobic granular sludge can be recovered and stabilized, while the effect of examples 1 and 3 is similar, the adding amount of the exogenous signal molecule C10-HSL of example 3 is 2 times of that of example 1, so that the higher the adding amount is, the better the adding amount is, and the better the proper concentration value is, and the optimal effect is achieved.

Claims

1. A method for directionally regulating and controlling the stable operation of aerobic granular sludge, which is characterized in that,

step 1: sludge inoculation: taking flocculent activated sludge as inoculated sludge, detecting signal molecules C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL in the inoculated sludge, and adding the inoculated sludge into a reactor;

step 2: injecting inlet water into a reactor by a water inlet pump, controlling the temperature of the reactor to be 30 +/-1 ℃, controlling the hydraulic retention time to be 6 hours, operating the reactor in a water injection-aeration-sedimentation-drainage sequence, wherein each cycle is a period, the time of operating the period is 6 hours, the water inflow time is 5 minutes, the aeration time is 340 minutes, the sedimentation time is 10 minutes and the drainage time is 5 minutes in the period, and controlling the reflux ratio to be 0.5 by adopting a continuous flow water inflow mode; after 30 d of operation culture, the aerobic granular sludge reaches the mature and stable period;

and step 3: detecting the content of signal molecules C4-HSL, C6-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C12-HSL and 3-oxo-C14-HSL in aerobic granular sludge in a maturation stabilization period; when the concentration of the signal molecules begins to decrease by 20 percent, adding the signal molecules;

and 4, step 4: keeping the operation condition of the reactor unchanged, wherein the exogenous signal molecule mother liquor enters the reactor along with the inflow water at the interval of 6 hours, so that the final concentration of the exogenous signal molecule is 100-1000nM, the operation is carried out for 10 days, and the aerobic granular sludge reaches the stable state again.

2. The method of claim 1, wherein the final concentration of the exogenous signal molecule in step 4 is 100 nM.

3. The method for directionally regulating and controlling the stable operation of the aerobic granular sludge according to claim 1, wherein the final concentration of the exogenous signal molecules in the step 5 is 1000 nM.