Enterobacter cloacae with flocculation activity, microbial flocculant and application thereof

Abstract

The present application provides a kind of enterobacter cloacae with flocculation activity, microbial flocculant and its application, it is related to microbial and sewage sludge treatment technical field.The enterobacter cloacae with flocculation activity (Enterobacter cloacae) strain KY163 is preserved in Guangdong Provincial Microbial Culture Collection Center, and the preservation number is GDMCC No.62893.Nine microbial strains with flocculation activity are preliminarily screened from 211 strains;After rescreening using activated sludge collected from a sewage treatment plant, a microbial strain KY163 with excellent flocculation effect on activated sludge is obtained, and the strain can effectively improve the dewatering performance of activated sludge.The present application provides a new high-efficiency strain for the application direction of microbial flocculation, and has good application prospect for sludge biochemical treatment.

Description

Technical Field

[0001] This invention relates to the field of microbial and sewage sludge treatment technology, and in particular to a flocculating Enterobacter cloacae, a microbial flocculant, and their applications. Background Technology

[0002] With industrial and urban development, wastewater discharge is constantly increasing. Currently, the activated sludge process is one of the most widely used methods for urban wastewater treatment (Wang-zhen et al., 1993). The activated sludge process involves the continuous reproduction and accumulation of biological organisms in wastewater, producing a large amount of byproduct – activated sludge. Currently, there is a serious problem of prioritizing water over sludge in wastewater sludge treatment and management, leading to a large accumulation of sludge. Sludge production and disposal has become a global challenge (Yu GH et al., 2008).

[0003] Activated sludge has a complex composition, including microorganisms, organic and inorganic particles, colloids, and a large amount of water (Niu Xiaorong, 2007), with a water content as high as 95%–99% (Yu Xiao, 2019). The "GB18918-2002 Standard for Pollutant Discharge from Municipal Wastewater Treatment Plants" requires an effluent sludge moisture content of ≤80%, while the "GB4284-2018 Standard for Pollutant Control of Agricultural Sludge" requires an agricultural sludge moisture content of ≤60%. Most wastewater treatment plants still maintain a high moisture content (above 80%) after gravity settling and mechanical compression (Chen Ning et al., 2019), far exceeding the discharge standards. Most of the water in the sludge originates from microbial cells and is difficult to remove by physical methods. Furthermore, the high moisture content leads to transportation difficulties and higher treatment costs. Therefore, it is essential to improve sludge dewatering performance to increase dewatering efficiency, reduce sludge volume, and facilitate subsequent sludge treatment.

[0004] Chemical flocculation sedimentation technology mainly uses the positive charge of the hydrolysis products of chemical conditioners to neutralize the negative charge on the surface of activated sludge, thereby making the sludge colloid lose stability and thus improving the dewatering performance of sludge. Due to its advantages such as simple equipment, convenient operation, high treatment efficiency and wide range of applications, it has become the most commonly used process. Currently, the various flocculants commonly used in wastewater treatment include iron salts (FeCl3 or Fe2(SO4)3)[6], aluminum salts (Al2(SO4)3) (P Aragonés-Beltrán et al., 2009), quicklime, magnesium carbonate, aluminum trichloride and polymers (polyaluminum chloride (PAC), polyaluminum sulfate chloride and polyferric sulfate, polyacrylamide (PAM)) etc. (Weydts D et al., 2015). However, numerous studies have found that the use of chemical flocculants in wastewater treatment may have negative impacts, including: accelerating the corrosion rate of metal facilities (Patrick N et al., 2004); some chemical conditioners containing metal ions can produce non-degradable heavy metals during sludge incineration, causing environmental pollution (Zhang, K. et al., 2005); and residual chemical flocculants released into the environment after sludge treatment may enter the food chain (Kluczka, J. et al., 2017; Mortula, M. et al., 2009), impacting human health, including central nervous system failure, dementia, Alzheimer's disease, and severe tremors (Barakwan, RA et al., 2019). Furthermore, polyacrylamide monomers have strong neurotoxicity and carcinogenic and mutagenic effects. Therefore, developing novel flocculants with good flocculation effects, high efficiency, safety, and no secondary pollution is of great significance.

[0005] The development and research of microbial flocculants is one of the directions of scientific and technological development. Microbial flocculants are high-molecular polymers secreted by microorganisms during fermentation, mainly composed of polysaccharides, proteins, DNA, cellulose, polyamino acids, and other components. Compared with organic synthetics or inorganic polymers, microbial flocculants have the characteristics of wide range, high activity, safety, and no environmental pollution, and can be widely used in aquaculture and wastewater treatment. Microorganisms that can produce flocculants in nature are widely distributed in soil and water, and are diverse, including bacteria, fungi, actinomycetes, yeasts, and algae (Chen Bo, 2020). Compared with traditional chemical flocculants, bioflocculants have great potential in removing pollutants from wastewater (heavy metals (Zhu Xuan, 2022), algae (Gong Liangyu et al., 2009), and decolorization of dyeing and printing wastewater (Gong Liangyu et al., 2006), COD of aquaculture wastewater (Song Yongqing et al., 2016), ammonia nitrogen (Zhang Shasha et al., 2021), and graphene oxide (Huo Mingyuan, 2015)). Therefore, it is necessary to screen and study more high-performance microorganisms that can produce flocculants.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a *Enterobacter cloacae* strain with flocculation activity, a microbial flocculant, and its applications. This invention provides a new, highly efficient strain for microbial flocculation applications, showing promising potential for the biochemical treatment of sludge.

[0008] The technical solution provided by this invention is as follows:

[0009] In one aspect, the present invention provides an Enterobacter cloacae strain KY163 with flocculation activity, which was deposited at the Guangdong Provincial Center for Microbial Culture Collection on October 14, 2022, with accession number GDMCC No. 62893.

[0010] This invention initially screened 9 microbial strains with flocculation activity from 211 strains; then, after rescreening with activated sludge collected from a wastewater treatment plant, a microbial strain KY163 with excellent flocculation effect on activated sludge was obtained. This strain can effectively improve the dewatering performance of activated sludge.

[0011] In another aspect, the present invention provides the application of the aforementioned Enterobacter cloacae strain KY163 in the preparation of microbial flocculants.

[0012] The Enterobacter cloacae strain KY163 of this invention can produce flocculants and is a bioflocculant, therefore it can be used to prepare microbial flocculants.

[0013] In another aspect, the present invention provides a microbial flocculant prepared by fermentation of the aforementioned Enterobacter cloacae strain KY163.

[0014] In one embodiment, the microbial flocculant further includes a carrier, excipients, or coagulant aid.

[0015] In one embodiment, the microbial flocculant further includes one or more of the following commonly used in the preparation of bioflocculants: solvents, cosolvents, emulsifiers, fillers, stabilizers, flow aids, preservatives, suspending agents, coating materials, pH adjusters, surfactants, thickeners, absorbents, etc.

[0016] In one embodiment, the microbial flocculant is the fermentation product of the Enterobacter cloacae strain, such as fermentation supernatant or fermentation broth.

[0017] In one embodiment, while using the strain of the present invention or the microbial flocculant prepared therefrom, a coagulant aid may also be used, such as adding a coagulant aid (including but not limited to calcium chloride) first, and then adding the bioflocculant for treatment. When using the strain of the present invention or the microbial flocculant prepared therefrom, other known chemical reagents that can improve coagulation and flocculation effects may also be used in conjunction.

[0018] In another aspect, the present invention provides a method for producing a microbial flocculant, the method comprising preparing a fermentation broth with flocculating activity from the aforementioned Enterobacter cloacae strain KY163;

[0019] Preferably, the method includes inoculating the Enterobacter cloacae into a liquid seed culture medium to obtain a seed liquid; and inoculating the seed liquid into a fermentation medium for fermentation to obtain a fermentation broth with flocculation activity.

[0020] Preferably, the fermentation broth is concentrated and precipitated to obtain a precipitate product; more preferably, the precipitate product is freeze-dried to obtain a solid microbial flocculant.

[0021] This invention provides a method for directly obtaining low-cost flocculants without complex operations. The microbial culture conditions are relatively simple; after inoculation, fermentation is all that is needed to obtain the bioflocculant.

[0022] In one embodiment, the microbial flocculant is an extracellular polymeric substance obtained by fermentation, extraction, separation, and purification of the Enterobacter cloacae strain.

[0023] In another aspect, the present invention provides the use of the Enterobacter cloacae strain KY163 or the microbial flocculant in the precipitation of solid suspensions, decolorization of pigments and / or removal of heavy metal ions.

[0024] The Enterobacter cloacae strain KY163 or the microbial flocculant of the present invention can be used to remove suspended solids in water.

[0025] In one embodiment, the system to be flocculated is a kaolin suspension. The strain of the present invention achieved a flocculation rate of 70.93% in a 10 g / L kaolin suspension. The Enterobacter cloacae strain KY163 or the microbial flocculant of the present invention can also be used for the removal of heavy metals and decolorization of pigments in municipal and industrial sludge.

[0026] In another aspect, the present invention provides the application of the Enterobacter cloacae strain KY163 or the microbial flocculant in wastewater or sludge treatment.

[0027] In one implementation, the application includes water quality improvement of polluted water bodies. For example, in the treatment of urban water supply and sewage (including industrial wastewater), the bacteria are brought into full contact with suspended solids and returned sludge in the wastewater to form flocculent particles. This invention can achieve highly efficient flocculation and sedimentation, reduce suspended particulate matter in water bodies, and reduce water turbidity, which has important research significance for sewage treatment and remediation.

[0028] In one implementation, the application includes sludge dewatering and / or sludge reduction.

[0029] Currently, there are no reports in the art regarding the application of *Enterobacter cloacae* alone in sludge flocculation and dewatering. Experiments in this invention show that different *Enterobacter cloacae* strains exhibit varying flocculation abilities in activated sludge. *Enterobacter cloacae* KY163 demonstrates a strong flocculation capacity. Subsequent measurements of sludge specific resistance and moisture content revealed that the fermentation broth of strain KY163 effectively improves the flocculation and dewatering performance of activated sludge. The *Enterobacter cloacae* strain KY163 or the microbial flocculant described in this invention can be used to achieve sludge reduction, dewatering, and harmless treatment.

[0030] Sludge has a complex composition, and microorganisms have low utilization efficiency in it. Experiments have shown that the strain KY163 described in this invention can improve sludge dewatering efficiency. After adding 5% KY163 fermentation broth, the sludge specific resistance decreased from 3.24 × 10⁻⁶ to 3.24 × 10⁻⁶ compared to the blank control. 9 s 2 / g decreased to 2.71×10 9 s 2 / g; moisture content decreased from 84.62% to 78.22%.

[0031] In this invention, the sludge includes, for example, but not limited to, oxidized pond sludge and sediments from livestock farm wastewater and waste, thickening tank sludge, anaerobic fermentation sludge, and high-temperature anaerobic digester sludge. The bacterial agent or microbial flocculant of this invention can be added to aeration tanks, sludge thickening tanks, or secondary sedimentation tanks containing activated sludge.

[0032] In another aspect, the present invention also provides a method for improving the dewatering performance of sludge, wherein the method comprises adding the *Enterobacter cloacae* strain KY163 or the microbial flocculant to the sludge to be dewatered and mixing them evenly. The present invention can significantly improve the flocculation and dewatering performance of activated sludge.

[0033] Preservation Information: Enterobacter cloacae strain KY163 was deposited on October 14, 2022, at the Guangdong Provincial Center for Microbial Culture Collection (GDMCC) with accession number GDMCC No. 62893. The address is: 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, Guangdong Academy of Sciences, 510070, China. The strain was confirmed as viable by the collection center on October 14, 2022.

[0034] Beneficial effects:

[0035] This invention is the first to discover that Enterobacter cloacae strain KY163 not only has high flocculation activity, but can also be used alone to effectively improve the flocculation and dewatering performance of activated sludge, providing more ways for microbial treatment of sewage sludge;

[0036] The strain of this invention has strong flocculation ability, which can promote the formation of granular sludge in activated sludge systems, improve the dewatering of sludge, realize rapid and efficient dewatering and volume reduction of industrial sludge, effectively improve the potential for subsequent resource utilization of sludge, reduce the cost of sludge treatment, and has good economic and social benefits.

[0037] The Enterobacter cloacae strain of the present invention or the microbial flocculant prepared therefrom is low in cost, stable in performance, simple in preparation steps, pollution-free, safe, can be mass-produced, and has good application prospects. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 The flocculation of different strains in 10 g / L kaolin suspension provided in the embodiments of the present invention;

[0040] Figure 2 The flocculation of different treatment groups in sludge according to embodiments of the present invention (OD) 600 ;

[0041] Figure 3 The flocculation situation in activated sludge within 1 minute for different treatment groups provided in the embodiments of the present invention;

[0042] Figure 4Flocculation in sludge of different treatment groups (CK, 0.002% PAM, 50% (v / v) KY58 and 50% (v / v) KY163) provided for embodiments of the present invention. 600 ;

[0043] Figure 5 The flocculation of different treatment groups (CK, 0.002% PAM, 50% KY58 and 50% KY163) in activated sludge within 12S according to embodiments of the present invention;

[0044] Figure 6 This is a schematic diagram of the sludge resistivity measuring device used in this invention. Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1. Screening and identification of microbial flocculant-producing bacteria

[0047] 1.1 Preliminary screening of kaolin suspension

[0048] 1.1.1 Experimental Materials

[0049] Microbial strains: Microbial strain bank of Kang Shengyuan (Zhaoqing) Biotechnology Co., Ltd.

[0050] Source of activated sludge: Second sedimentation tank of the Second Wastewater Treatment Plant in Zhaoqing High-tech Zone.

[0051] Culture medium:

[0052] R2A liquid culture medium: 0.5g peptone, 0.5g yeast, 0.5g tryptone, 0.5g soluble starch, 0.5g glucose, 0.3g K2HPO4, 0.3g sodium pyruvate, 0.05g MgSO4·7H2O, 1000mL distilled water, autoclaved at 121℃ for 30min.

[0053] R2A solid culture medium: 0.5g peptone, 0.5g yeast, 0.5g tryptone, 0.5g soluble starch, 0.5g glucose, 0.3g K2HPO4, 0.3g sodium pyruvate, 0.05g MgSO4·7H2O, 1000mL distilled water, 15g agar powder, autoclaved at 121℃ for 30min.

[0054] 1.1.2 Experimental Procedure

[0055] (1) The strains in the microbial strain library were cultured on R2A solid medium.

[0056] (2) Use an inoculation loop to scrape single colonies on R2A solid culture medium into sterile water to prepare bacterial solution.

[0057] (3) Inoculate the bacterial culture into 50 mL of R2A liquid culture medium to make the bacterial concentration in the liquid culture medium OD. 600 =0.05, cultured on a shaker at 30℃ and 200r / min for 72 hours.

[0058] (4) Prepare a 10 g / L kaolin suspension, stir it at 150 r / min for 2 min, and let it stand for 5 to 10 min.

[0059] (5) Fermentation broth of different bacteria was added, and the blank control group was given the same volume of sterile water as the experimental group. Three parallel treatments were set up for each treatment.

[0060] (6) After thoroughly mixing the different treatment groups, let them stand for 1 hour, and then use an ultraviolet-visible spectrophotometer to measure the OD. 550 The absorbance of the supernatant was measured, and the flocculation efficiency was quantified by the change in absorbance. The formula for calculating the flocculation rate is:

[0061]

[0062] A0 represents the blank control group; the supernatant after treatment was measured at OD... 550 The absorbance value; A i The supernatant of the experimental group after treatment was measured at OD 550 The absorbance value.

[0063] 1.1.3 Results

[0064] The flocculation rates of different strains in 10 g / L kaolin suspension are shown in Table 1. The flocculation conditions are as follows: Figure 1 As shown.

[0065] A total of 211 strains were screened from the microbial strain library, from which 9 strains exhibiting flocculation activity in 10 g / L kaolin suspension were obtained. Among them, 8 strains had flocculation activity of over 35% as a bioflocculator, and 3 strains had activity of over 50%. Five strains formed large flocs with high settling velocities when flocculating kaolin suspension.

[0066] Table 1. Flocculation rate of different strains in 10 g / L kaolin suspension

[0067]

[0068] 1.2 Strain Identification

[0069] 1.2.1 Preparation of DNA template

[0070] Microbial strains exhibiting flocculation ability in the initial screening of kaolin were identified. Purified single colonies were picked and placed at the bottom of EP tubes, and 200 μL of 5% (w / v) BT-chelex 100 (prepared with distilled water and sterilized at 121℃ for 30 min) was added. The tubes were boiled in a water bath for 15 min, then rapidly frozen at -20℃ or -80℃, thawed at room temperature, centrifuged at 6000 rpm for 3 min, and 2 μL of the supernatant was used as a template. The 16S gene was amplified according to the 16S amplification system.

[0071]

[0072] PCR amplification procedure:

[0073] Step 1: 94℃, 5 minutes;

[0074] Step 2: 94℃, 1 min; 55℃, 1 min; 72℃; 1.5 min; 35 cycles;

[0075] Step 3: 72℃, 10min; 4 cycles.

[0076] 1.2.2 16S rDNA sequencing results

[0077] 16S rDNA homology sequence analysis of the microbial flocculant-producing strains revealed that they mainly belonged to five genera: *Enterobacter cloacae*, *Bacillus subtilis*, *Bacillus cereus*, *Arthrobacter oryzae* strain, and *Arthrobacter* sp. Strains with a flocculation rate of over 40% were selected for secondary screening in activated sludge.

[0078] 1.3 Secondary screening of activated sludge

[0079] 1.3.1 Experimental Procedure

[0080] Four bacterial strains (KY139, KY154, KY157, and KY163) with a flocculation rate of over 40% were re-screened in activated sludge. OD values ​​of the supernatant from different treatment groups were measured at five time points: 1 min, 2 min, 3 min, 4 min, and 5 min. 600 .

[0081] 1.3.2 Results

[0082] OD was measured at different time points in the supernatant of different treatment groups.600 The absorbance values ​​are as follows: Figure 2 and Figure 3 As shown.

[0083] Figure 2 and Figure 3 It is evident that different strains exhibited varying degrees of flocculation in the sludge; compared to the other three strains, KY163 produced a clearer sludge supernatant. Within 5 minutes, compared to the control (CK), KY163 showed a significantly higher OD value. 600 It dropped to 0.171.

[0084] 16S rDNA homology sequence analysis was performed, comparing 1416 bases (sequence 1) of strain KY163 with GenBank and 16S rDNA databases. The results showed that this strain had a high homology of 99.65% with *Enterobacter cloacae*. The strain was identified as *Enterobacter cloacae*. Among the nine microbial flocculant-producing strains screened from kaolin suspension, KY58 also belongs to *Enterobacter cloacae*. Therefore, further experiments were conducted on strains KY58 and KY163. Since polyacrylamide (PAM) is used as a sludge flocculant in actual sludge treatment plants, 0.002% PAM was used as a positive control in the following experiments.

[0085] Sequence 1 (SEQ ID No.1):

[0086]

[0087] Example 2. Flocculation of two types of Enterobacter cloacae in activated sludge

[0088] 2.1 Experimental Methods

[0089] The flocculation of Enterobacter cloacae KY58 and KY163 in activated sludge was measured. OD values ​​of supernatant from different treatment groups were measured at five time points: 1 min, 2 min, 3 min, 4 min, and 5 min. 600 .

[0090] 2.2 Results

[0091] OD was measured at different time points in the supernatant of different treatment groups. 600 The absorbance values ​​are as follows: Figure 4 and Figure 5 As shown.

[0092] Both KY163 and KY58 belong to the genus *Enterobacter cloacae*, and exhibit different flocculation behaviors in activated sludge, as shown in the figure. Compared with the blank control, the supernatant of KY58 was more turbid and showed no obvious flocculation, while the supernatant of KY163 was clearer, with more obvious sludge settling and larger sludge particles. At 10 minutes, compared with the blank control, the OD600 of KY163 decreased to 0.101, indicating that KY163 has a strong flocculation ability for activated sludge.

[0093] Example 3. Determination of specific resistance and moisture content of KY163 fermentation broth sludge

[0094] 3.1 Specific resistance measurement of sludge

[0095] Specific resistance of sludge is a comprehensive indicator of sludge filtration characteristics, referring to the resistance per unit dry weight of filter cake per unit filtration area. The higher the specific resistance of sludge, the worse its dewatering performance, and vice versa.

[0096] 3.1.1 Experimental Setup

[0097] One vacuum pump (pressure), one 250mL measuring cylinder, one set of vacuum tubing, one Buchner funnel, one suction filter cartridge, one vacuum gauge, one set of experimental stand, connecting pipes, power switch, etc. Sludge specific resistivity measuring device, such as... Figure 6 As shown.

[0098] 3.1.2 Experimental Procedure

[0099] (1) Determine the moisture content and solids concentration of the sludge: Measure 100 mL of sludge, place it in a petri dish, weigh it and record the data C1, then place it in an oven to dry to constant weight, cool it and weigh it, record the data C2, and calculate the solids concentration C. i .

[0100]

[0101] C0 = 1 - C i (Equation 3);

[0102] C0: Moisture content of sludge;

[0103] C i Solids concentration of sludge;

[0104] C1: Weight of the original sludge;

[0105] C2: Weight of sludge dried to constant weight.

[0106] (2) Take a dry petri dish and medium-speed filter paper, weigh them with an analytical balance to get M0, place the weighed filter paper at the bottom of the Buchner funnel, and moisten it with water so that the filter paper is close to the periphery of the Buchner funnel.

[0107] (3) Prepare PAM at 0.2% of the sludge solids concentration. Add the same volume of the corresponding reagent to adjust the sludge for different treatment types.

[0108] (4) Add the adjusted sludge into the Buchner funnel, turn on the vacuum pump and keep the pressure constant at 0.03 MPa, start the stopwatch and record the initial filtrate volume V0 in the measuring cylinder when the vacuum pump is turned on.

[0109] (5) Record the volume of filtrate in the measuring cylinder at the corresponding time point every 10 seconds. Use the volume of filtrate V as the abscissa and t / V as the ordinate to obtain the slope b of the straight line.

[0110] (6) Continue filtering until cracks appear on the surface of the filter cake. Turn off the vacuum pump, remove the filter cake, place it in a petri dish, weigh it, and record the data M1. Dry it in an oven at 105℃ until constant weight, weigh it again, and record the data M2. Calculate the moisture content of the filter cake (according to CJ / T 221-2005 Method for Testing Sludge in Urban Wastewater Treatment Plants) to obtain the solids concentration C of the filter cake. f Find the amount of solids ω per unit volume of filtrate.

[0111]

[0112] ω: The mass of solids retained on the filter medium per unit volume of filtrate, in g / mL;

[0113] C i The amount of dry sludge in 100g of sludge;

[0114] C f : The amount of dry sludge in 100g of filter cake.

[0115] (7) Calculate the specific resistance of the sludge using the following formula:

[0116]

[0117] r: Specific resistance of sludge, s 2 / g;

[0118] P: Filtration pressure, g / cm³ 2 ;

[0119] A: Filter area, cm² 2 ;

[0120] b: The slope of the straight line shown by the filter equation t / V = bV + a, in s / cm 6 ;

[0121] μ: Filtrate viscosity, g / cm·s

[0122] ω: The mass of solids retained on the filter medium per unit volume of filtrate, in g / mL.

[0123] 3.1.3 Experimental Results

[0124] Table 2. Sludge dewatering performance of different treatment groups

[0125]

[0126] Adding fermentation broth from strain KY163 significantly improved the flocculation and dewatering performance of activated sludge, as shown in Table 2. Table 2 shows that after adding 5% KY163 fermentation broth, compared to the blank control, the sludge specific resistance decreased from 3.24 × 10⁻⁶. 9 s 2 / g decreased to 2.71×10 9 s 2 / g; moisture content decreased from 84.62% to 78.22%. Compared to the positive control, the specific resistance of the sludge with added 5% KY163 fermentation broth was 2.71 × 10⁻⁶. 9 s 2 / g was slightly higher than the positive control group (2.68×10). 9 s 2 / g, the moisture content was reduced by 6.23% compared to the positive control. In conclusion, the addition of fermentation broth from strain KY163 significantly improved the flocculation and dewatering performance of activated sludge compared to the blank control group.

[0127] Conclusion: This study used a high-concentration (10 g / L) kaolin suspension to screen 9 microbial strains from 211 strains in a microbial strain library, identifying 9 strains with preliminary potential for producing microbial flocculants. Further screening using activated sludge collected from a wastewater treatment plant yielded a strain with superior flocculation activity in activated sludge. Sequence analysis of the 16S rDNA of this strain confirmed KY163 as *Enterobacter cloacae*. Compared to the other 8 initially screened microbial strains from kaolin, KY163 exhibited stronger flocculation ability in activated sludge, with a higher OD value at 10 minutes. 600 Compared to the control (CK), the concentration decreased to 0.101. The study also found that KY163 can effectively improve the dewatering performance of activated sludge. Therefore, KY163 is a microbial strain that produces microbial flocculants and can effectively improve the flocculation and dewatering performance of activated sludge.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of Enterobacter cloacae with flocculating activity ( Enterobacter cloacae strain KY163, characterized in that, The strain was deposited at the China General Microbiological Culture Collection Center (GDMCC) on October 14, 2022, with accession number GDMCC No. 62893; The strain KY163 is used for sludge dewatering and / or sludge reduction.

2. A microbial flocculant, characterized in that, The microbial flocculant is composed of Enterobacter cloacae as described in claim 1 (… Enterobacter cloacae The microbial flocculant was prepared by fermentation with strain KY163; the microbial flocculant was used for sludge dewatering and / or sludge reduction.

3. The microbial flocculant according to claim 2, characterized in that, The microbial flocculant also includes a carrier or a coagulant aid.

4. A method for producing a microbial flocculant, characterized in that, The method includes utilizing Enterobacter cloacae as described in claim 1 (… Enterobacter cloacae Fermentation broth with flocculation activity was prepared using strain KY163; The method includes inoculating the Enterobacter cloacae into a liquid seed culture medium and culturing it to obtain a seed solution; The seed liquid was inoculated into a fermentation medium and cultured for fermentation to obtain a fermentation broth with flocculation activity; The fermentation broth was concentrated and precipitated to obtain a precipitate; the precipitate was freeze-dried to obtain a solid microbial flocculant.

5. The Enterobacter cloacae described in claim 1 ( Enterobacter cloacae The application of strain KY163 or the microbial flocculant according to claim 2 or 3 in wastewater or sludge treatment; The applications include sludge dewatering and / or sludge reduction.

6. A method for improving sludge dewatering performance, characterized in that, The method involves using the Enterobacter cloacae described in claim 1 (… Enterobacter cloacae The strain KY163 or the microbial flocculant described in claim 2 or 3 is added to the sludge to be dewatered and mixed evenly.

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