Preparation method of algal-bacterial symbiotic aerobic granular sludge

Abstract

The application provides a preparation method of algal-bacterial symbiotic aerobic granular sludge, and comprises the following steps: S1, preparing dewatered sludge as a base material, culturing chlorella and scenedesmus respectively to obtain chlorella algae liquid and scenedesmus algae liquid as the base material; S2, adding the chlorella algae liquid and the scenedesmus algae liquid into the dewatered sludge, and stirring to obtain a mixture; S3, preparing the mixture into granular sludge, and obtaining microalgae-dewatered sludge particles after drying and demolding; and S4, inoculating the microalgae-dewatered sludge particles into a photic sequencing batch reactor, and performing cyclic operation according to the sequence of water feeding, anaerobic stirring, aeration, sedimentation, water draining and idling to obtain the algal-bacterial symbiotic aerobic granular sludge. The application solves the problems of long start-up period, high energy consumption and easy loss of biomass of the algal-bacterial symbiotic aerobic granular sludge, and provides a preparation method which is simple in preparation, low in cost, and has the advantages of large particle size, stable granular structure, good sedimentation and the like of the cultured granular sludge.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a preparation method of algal-bacterial symbiotic aerobic granular sludge. BACKGROUND

[0002] The aerobic granular sludge is a biological aggregate formed by self-agglomeration, and the algal-bacterial granular sludge, as a derivative product thereof, is considered as a new technology for urban sewage treatment that is environmentally sustainable and economically feasible, and has attracted extensive research in recent years. Previous studies have shown that the algal-bacterial granular sludge is a promising alternative to traditional bacteria-based aerobic granular sludge, and has a more compact structure, higher biomass yield, better settling ability and excellent nutrient removal capacity. In such a symbiotic system, algae provide oxygen to bacteria to oxidize organic matter through photosynthesis, while bacteria produce carbon dioxide for algae to perform photosynthesis. Benefiting from the synergy between algae and bacteria, the energy consumption related to external aeration in the algal-bacterial granular sludge system can be greatly reduced, which is conducive to environmental sustainability. However, it takes one to three months to achieve complete granulation of the algal-bacterial granular sludge, which limits the large-scale application of this technology.

[0003] The aerobic granular sludge is a biological aggregate formed by self-agglomeration, and the self-agglomeration process is also a limiting step for the formation of the biological aggregate. The dewatered sludge is a product obtained by forced dewatering of activated sludge, and although it is not formed by self-agglomeration, it is also a biological aggregate. It has been found that by inoculating dewatered sludge granules to start the aerobic granular sludge, it is found that the aerobic granular sludge system can skip the cultivation period and directly obtain the aerobic granular sludge, and the obtained aerobic granular sludge maintains a relatively complete spherical structure, has good stability and excellent pollutant treatment effect in long-term operation.

[0004] At present, attempts to cultivate algal-bacterial granular sludge mainly focus on exposing activated sludge to natural or artificial sunlight conditions to induce algal self-growth, or culturing activated sludge flocs into aerobic granular sludge, then inoculating microalgae, and forming algal-bacterial granular sludge after light culture for a period of time. However, no matter which way of forming algal-bacterial granular sludge, it takes a long reaction time to obtain complete granulation of the algal-bacterial granular sludge. Therefore, how to quickly cultivate engineered algal-bacterial symbiotic aerobic granular sludge has become a problem of concern in the industry. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of algal-bacterial symbiotic aerobic granular sludge, so as to solve the problems of long sludge start-up period, high energy consumption and easy loss of biomass in the conventional preparation method.

[0006] To solve the above problems, the present application provides a preparation method of algal-bacterial symbiotic aerobic granular sludge, comprising the following steps:

[0007] S1: preparing dewatered sludge as a base material, culturing chlorella and scenedesmus respectively to obtain chlorella liquid and scenedesmus liquid as a base material;

[0008] S2: adding the chlorella liquid and the scenedesmus liquid to the dewatered sludge to obtain a mixture by stirring;

[0009] S3: placing the mixture into a mold to make granular sludge, and obtaining microalgae-dewatered sludge particles after drying and demolding the granular sludge;

[0010] S4: inoculating the microalgae-dewatered sludge particles into a photic sequencing batch reactor, and sequentially circulating according to the order of water feeding, anaerobic stirring, aeration, sedimentation, water draining and idling to obtain algal-bacterial symbiotic aerobic granular sludge.

[0011] As a preferred scheme, in the step S1, the dewatered sludge is sludge discharged from a sewage plant.

[0012] As a preferred scheme, the water content of the dewatered sludge is 65-85%.

[0013] As a preferred scheme, in the step S1, the culture conditions of the chlorella and the scenedesmus are as follows: culturing in a BG11 culture medium to the logarithmic growth phase.

[0014] In the present application, by controlling the chlorella and the scenedesmus to be cultured in a BG11 culture medium to the logarithmic growth phase, the cell metabolic activity reaches the strongest, and the cells are in a vigorous growth state. The time interval for each cell division is the shortest, and the number of cells doubles in unit time, so the growth rate constant (average generation number per unit time) reaches the maximum.

[0015] Secondly, the cells in the logarithmic growth phase are in balanced growth, and various components in the cells are most uniform, and the morphology and physiological characteristics are relatively consistent. In addition, the enzyme system in this period is active, and the metabolism is vigorous, which is beneficial to rapid proliferation and growth.

[0016] Therefore, by culturing to the logarithmic growth phase in advance, the culture process of the algal-bacterial symbiotic aerobic granular sludge obtained by the present application is further shortened, and the decontamination effect is also improved.

[0017] As a preferred scheme, in the step S2, the volume ratio of the chlorella liquid and the scenedesmus liquid to the dewatered sludge is (0-2):(0-2):6, and the total volume of the chlorella liquid and the scenedesmus liquid is 1 / 3 of the dewatered sludge.

[0018] In the present application, only one of the Chlorella algae liquid and the Scenedesmus algae liquid can be added to achieve the technical purpose of the present application, and the two can be added simultaneously to achieve a synergistic effect and further improve the pollutant removal efficiency of the cultivated algal-bacterial symbiotic granular sludge.

[0019] As a preferred scheme, in the step S2, the stirring time is 10-20 min.

[0020] As a preferred scheme, in the step S3, the mold is a multi-well plate mold, the pore size of the multi-well plate mold is 1 mm, the thickness is 0.6 mm, and the granular sludge is a cylindrical granular sludge.

[0021] As a preferred scheme, in the step S3, the drying and demolding conditions are: drying temperature 25-35℃, drying time 20-40 min, and the moisture content of the granular sludge is 60-75% after drying.

[0022] As a preferred scheme, in the step S4, the light intensity during the operation of the sequencing batch reactor is 4000-6000 Lux, and the drainage ratio is 45-55%.

[0023] In the control of light conditions, too low light is not conducive to algal photosynthesis, and too high light will inhibit the activity of nitrifying bacteria, therefore, the light intensity is controlled to 4000-6000 Lux in the present application, which is more conducive to algal photosynthesis, thereby improving the technical effect of the present application. In the control of the drainage ratio, the size of the SBR process discharge ratio determines the initial organic matter concentration of the SBR process reaction. The smaller the discharge ratio, the lower the initial organic matter concentration, and vice versa. According to the law of microbial degradation of organic matter, when the organic matter concentration is high, the organic matter degradation rate is large, and the aeration time can be reduced, therefore, the drainage ratio is preferably controlled to 45-55%.

[0024] As a preferred scheme, in the step S4, the water inlet time is 2-4 min, the anaerobic stirring time is 100-140 min, the aeration time is 180-220 min, the settling time is 3-7 min, the drainage time is 1-3 min, and the idle time is 20-40 min.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) The present application directly prepares microalgae-dehydrated sludge particles, skips the long-period cultivation process of granular sludge, directly starts the algal-bacterial symbiotic aerobic granular sludge system, realizes the rapid granulation of algal-bacterial symbiotic sludge, and solves the problems of long reaction time and high energy consumption in complete granulation by conventional methods.

[0027] (2) The granular sludge prepared by the method has the advantages of simple preparation process, low cost, wide source of raw materials (dehydrated sludge, chlorella and scenedesmus), direct investment in the sewage treatment system, low biomass loss in the initial operation, good sludge-water separation performance, and good pollutant removal effect. The method for preparing the algal-bacterial symbiotic aerobic granular sludge has the advantages of simplicity, low cost, and large particle size, stable granular structure, and good settling performance of the cultured granules, and is easy to engineer and culture. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a morphological diagram of algal-bacterial symbiotic granular sludge under a stereomicroscope;

[0029] Figure 2 It is red light emitted by algal-bacterial symbiotic granular sludge (obtained by the method) under a fluorescence microscope;

[0030] Figure 3 It is a morphological diagram of a single algal-bacterial symbiotic granular sludge (obtained by the method) under a stereomicroscope;

[0031] Figure 4 It is a schematic diagram of the implementation process of the method. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] The present application provides a method for preparing algal-bacterial symbiotic aerobic granular sludge, as shown in Figure 4 The working principle diagram of the present application is as follows: Figure 4 The working principle diagram of the present application is as follows:

[0034] The present application comprises the following steps:

[0035] S1: Prepare dehydrated sludge as a base material, and obtain chlorella and scenedesmus algal liquid as base materials after culturing chlorella and scenedesmus respectively;

[0036] S2: Add the chlorella algal liquid and the scenedesmus algal liquid to the dehydrated sludge, and stir to obtain a mixture;

[0037] S3: Put the mixture into a mold to make granular sludge, and obtain microalgae-dehydrated sludge particles after drying and demolding the granular sludge;

[0038] S4: inoculating the microalgae-dewatered sludge particles into a sequencing batch photoreactor, and sequentially circulating in the order of influent, anaerobic stirring, aeration, sedimentation, effluent and idling to obtain algal-bacterial symbiotic aerobic granular sludge.

[0039] Preferably, in the step S1, the dewatered sludge is sludge discharged from a sewage plant.

[0040] Preferably, the dewatered sludge has a water content of 65-85%.

[0041] Preferably, in the step S1, the Chlorella and Scenedesmus are cultured in a BG11 medium to the logarithmic growth phase.

[0042] Preferably, in the step S2, the volume ratio of the Chlorella and Scenedesmus algal liquid to the dewatered sludge is (0-2):(0-2):6, and the total volume of the Chlorella and Scenedesmus algal liquid is 1 / 3 of the dewatered sludge.

[0043] Preferably, in the step S2, the stirring time is 10-20 min.

[0044] Preferably, in the step S3, the mold is a multi-well plate mold, the well diameter of the multi-well plate mold is 1 mm, and the thickness is 0.6 mm, and the granular sludge is cylindrical granular sludge.

[0045] Preferably, in the step S3, the drying and demolding conditions are: drying temperature 25-35℃, drying time 20-40 min, and the water content of the granular sludge is 60-75% after drying.

[0046] Preferably, in the step S4, the light intensity during the operation of the sequencing batch photoreactor is 4000-6000 Lux, and the effluent ratio is 45-55%.

[0047] Preferably, in the step S4, the influent time is 2-4 min, the anaerobic stirring time is 100-140 min, the aeration time is 180-220 min, the sedimentation time is 3-7 min, the effluent time is 1-3 min, and the idling time is 20-40 min.

[0048] The following describes the present application in combination with the above data range: Example 1

[0049] The present example 1 provides a preparation method of algal-bacterial symbiotic aerobic granular sludge, comprising the following steps:

[0050] S1: Prepare the sludge discharged by the sewage plant with a water content of 80% as a base material, and culture Chlorella vulgaris and Scenedesmus in BG11 medium to the logarithmic growth phase to obtain Chlorella vulgaris algae liquid and Scenedesmus algae liquid as base materials;

[0051] S2: Add the Chlorella vulgaris algae liquid and the Scenedesmus algae liquid to the dewatered sludge, and obtain a mixture after stirring for 10-20 min; in step S2, the volume ratio of the Chlorella vulgaris algae liquid, the Scenedesmus algae liquid and the dewatered sludge is 1:1:6;

[0052] S3: Place the mixture into a multi-well plate mold to prepare granular sludge, the multi-well plate mold has a well diameter of 1 mm and a thickness of 0.6 mm, to obtain cylindrical granular sludge, and the granular sludge is dried and demolded to obtain microalgae-dewatered sludge granules; the drying conditions are: a drying temperature of 30°C, a drying time of 30 min, and the granular sludge is dried to a water content of 60-75%;

[0053] S4: Inoculate the microalgae-dewatered sludge granules into a photo sequencing batch reactor, the light intensity during the operation of the photo sequencing batch reactor is 5000 Lux, and the drainage ratio is 45-55%; sequentially circulate according to the order of water inflow, anaerobic stirring, aeration, sedimentation, drainage and idling to obtain algal-bacterial symbiotic aerobic granular sludge; the water inflow time is 3 min, the anaerobic stirring time is 120 min, the aeration time is 200 min, the sedimentation time is 5 min, the drainage time is 2 min, and the idling time is 30 min. Example 2

[0054] The present embodiment 2 provides a preparation method of algal-bacterial symbiotic aerobic granular sludge, comprising the following steps:

[0055] S1: Prepare the sludge discharged by the sewage plant with a water content of 65% as a base material, and culture Chlorella vulgaris and Scenedesmus in BG11 medium to the logarithmic growth phase to obtain Chlorella vulgaris algae liquid and Scenedesmus algae liquid as base materials;

[0056] S2: Add the Chlorella vulgaris algae liquid and the Scenedesmus algae liquid to the dewatered sludge, and obtain a mixture after stirring for 10 min; in step S2, the volume ratio of the Chlorella vulgaris algae liquid, the Scenedesmus algae liquid and the dewatered sludge is 2:0:6;

[0057] S3: the mixture is put into a porous plate mold to make granular sludge, the pore size of the porous plate mold is 1 mm, the thickness is 0.6 mm, a cylindrical granular sludge is obtained, and the granular sludge is dried and demolded to obtain microalgae-dehydrated sludge particles; the drying conditions are: drying temperature 25℃, drying time 20min, and the moisture content of the granular sludge is about 60-75% after drying;

[0058] S4: the microalgae-dehydrated sludge particles are inoculated into a photic sequencing batch reactor, the light intensity during the operation of the photic sequencing batch reactor is 4000Lux, the drainage ratio is 45%, and the operation is sequentially circulated according to the order of water inlet, anaerobic stirring, aeration, sedimentation, drainage and idling, to obtain algal-bacterial symbiotic aerobic granular sludge; the water inlet time is 2min, the anaerobic stirring time is 100min, the aeration time is 180min, the sedimentation time is 3min, the drainage time is 1min, and the idling time is 20min. Example 3

[0059] The present embodiment 3 provides a preparation method of algal-bacterial symbiotic aerobic granular sludge, comprising the following steps:

[0060] S1: preparing sludge with a moisture content of 85% discharged from a sewage plant as a base material, culturing chlorella and scenedesmus in BG11 medium to the logarithmic growth phase to obtain chlorella and scenedesmus algal liquid as a base material;

[0061] S2: adding the chlorella and scenedesmus algal liquid to the dehydrated sludge, stirring for 20min to obtain a mixture; in step S2, the volume ratio of the chlorella and scenedesmus algal liquid to the dehydrated sludge is 0:2:6;

[0062] S3: the mixture is put into a porous plate mold to make granular sludge, the pore size of the porous plate mold is 1 mm, the thickness is 0.6 mm, a cylindrical granular sludge is obtained, and the granular sludge is dried and demolded to obtain microalgae-dehydrated sludge particles; the drying conditions are: drying temperature 35℃, drying time 40min, and the moisture content of the granular sludge is about 60-75% after drying;

[0063] S4: inoculate the microalgae-dewatered sludge particles into a light sequencing batch reactor, the light intensity during operation of the light sequencing batch reactor is 6000 Lux, the drainage ratio is 55%, and the light sequencing batch reactor is sequentially and circularly operated according to the order of water feeding, anaerobic stirring, aeration, sedimentation, drainage and idling, to obtain algal-bacterial symbiotic aerobic granular sludge; the water feeding time is 4 min, the anaerobic stirring time is 140 min, the aeration time is 220 min, the sedimentation time is 7 min, the drainage time is 3 min, and the idling time is 40 min. Example 4

[0064] Example 4 uses the material ratio and reaction conditions in the preparation method of Example 1, combined with actual reaction data and the amount of specific reaction materials, to further develop and explain Example 1 and subsequent specific experimental tests, so as to better explain the present application:

[0065] S1: take 150 ml of dewatered sludge with a water content of about 80% from a municipal wastewater treatment plant;

[0066] Chlorella vulgaris and Scenedesmus were respectively cultured in BG11 medium to the logarithmic growth phase to obtain Chlorella vulgaris and Scenedesmus algal liquid.

[0067] S2: add 25 ml of Chlorella vulgaris and Scenedesmus algal liquid to 150 ml of dewatered sludge, and stir for 10 min to mix thoroughly.

[0068] S3: extrude the above mixture through a porous plate mold with a pore size of 1 mm and a thickness of 0.6 mm to obtain cylindrical sludge with a diameter of 1 mm and a height of 0.6 mm; place the above porous plate mold in a 30°C oven for about 30 min, cool to room temperature, and demold to obtain microalgae-dewatered sludge particles with a water content of about 70%.

[0069] S4: inoculate the above microalgae-dewatered sludge particles into a light sequencing batch reactor, the operation conditions of the light sequencing batch reactor are as follows: sequentially and circularly operated according to the order of water feeding, anaerobic stirring, aeration, sedimentation, drainage and idling; the water feeding time is 3 min, the anaerobic stirring time is 120 min, the aeration time is 200 min, the sedimentation time is 5 min, the drainage time is 2 min, and the idling time is 30 min; during operation, the aeration intensity is 2 L / min, the light intensity is 5000 Lux, and the drainage ratio is 45-55%.

[0070] The influent substrate is: 770.0 mg / L NaAc, 113.1 mg / L NH4Cl, 30.3 mg / L K2HPO4, 50.0 mg / L MgSO4·7H2O, 20.0 mg / L CaCl2, 40.0 mg / L Fe2SO4, 40.0 mg / L NaHCO3.

[0071] In Example 4, as shown in FIG. 5, most of the microalgae-dewatered sludge particles still maintain a relatively complete particle structure within 7 days of cultivation, and as shown in FIG. 6, the microalgae-dewatered sludge particles emit red light under the fluorescence intensity of 488 nm fluorescence microscope, indicating that the microalgae are attached to the granular sludge. Therefore, it can be considered that the algal-bacterial symbiotic granular sludge can be directly obtained by pre-preparing microalgae-dewatered sludge particles. Figure 1 Figure 2 As shown in FIG. 7, the algal-bacterial symbiotic granular sludge (obtained by using the method) is a morphological diagram of a single algal-bacterial symbiotic granular sludge under a stereomicroscope. Moreover, the algal-bacterial symbiotic granular sludge cultivated by the preparation method of the present application has good pollutant removal efficiency, which is reflected in the removal rate of TOC of 81.77% and the removal rate of TN of 71.04% measured in the effluent on the 7th day. Figure 3

[0072] The above examples also further prove that the problems of long sludge start-up period, high energy consumption, and easy loss of biomass in the conventional preparation method are solved by the present application, and a preparation method of algal-bacterial symbiotic aerobic granular sludge is provided, which has the advantages of low cost, simplicity, low energy consumption, and short time, and the prepared granules have the advantages of large particle size, stable particle structure, and good settling property, solving the problems existing in the prior art.

[0073] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited to this. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present application.​​

Claims

1. A method for preparing an algal-bacterial symbiotic aerobic granular sludge, characterized by: The method comprises the following steps: S1: preparing dewatered sludge as a base material, culturing chlorella and scenedesmus respectively to obtain chlorella liquid and scenedesmus liquid as the base material; S2: adding the chlorella liquid and the scenedesmus liquid to the dewatered sludge, and stirring to obtain a mixture; S3: placing the mixture into a mold to form granular sludge, and drying and demolding the granular sludge to obtain microalgae-dewatered sludge particles; S4: inoculating the microalgae-dewatered sludge particles into a photic sequencing batch reactor, and sequentially circulating in the order of water feeding, anaerobic stirring, aeration, sedimentation, water draining and idling to obtain algal-bacterial symbiotic aerobic granular sludge; In the step S1, the chlorella and the scenedesmus are cultured in a BG11 culture medium to the logarithmic growth phase; In the step S2, the volume ratio of the chlorella liquid to the scenedesmus liquid to the dewatered sludge is (0-2):(0-2):6, wherein the ratio of the chlorella liquid to the scenedesmus liquid is not 0, and the total volume of the chlorella liquid and the scenedesmus liquid is 1 / 3 of the volume of the dewatered sludge; In the step S3, the drying temperature is 25-35℃, and the drying time is 20-40min.

2. The method of claim 1, wherein the method is characterized by: In the step S1, the dewatered sludge is sludge discharged from a sewage plant.

3. The method of claim 2, wherein the method is characterized by: The water content of the dewatered sludge is 65-85%.

4. The method of claim 1, wherein the method is characterized by: In the step S2, the stirring time is 10-20min.

5. The method of claim 1, wherein the method is characterized by: In the step S3, the mold is a multi-well plate mold, the pore diameter of the multi-well plate mold is 1mm, the thickness is 0.6mm, and the granular sludge is cylindrical granular sludge. 6.The method of claim 1, wherein the method comprises: culturing the microalgae and the bacteria in the culture medium to form the algal-bacterial symbiotic aerobic granular sludge. In the step S3, the drying and demolding conditions are that the water content of the granular sludge is 60-75%.

7. The method of claim 1, wherein the method is characterized by: In the step S4, the light intensity during the operation of the photic sequencing batch reactor is 4000-6000Lux, and the water draining ratio is 45-55%. 8.The method of claim 1, wherein the method comprises: culturing the microalgae and the bacteria in the culture medium to form the algal-bacterial symbiotic aerobic granular sludge. In the step S4, the water feeding time is 2-4min, the anaerobic stirring time is 100-140min, the aeration time is 180-220min, the sedimentation time is 3-7min, the water draining time is 1-3min, and the idling time is 20-40min.

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