JP2000140509A - Novel flocculant and sludge treatment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a novel flocculant safe to animals and plants and not bringing about environmental pollution without using an acrylamide polymer generating an aluminum salt or a carcinogenic substance being a cause substance of Alzheimer's desease as a flocculant in the sludge treatment of urban sewage/ factory waste water, and a sludge treatment method using the same. SOLUTION: Safety and environment purifying properties are ensured by selecting a substance produced by an organism as a flucculant added at a time of sludge treatment. That is, a flocculant to be used is constituted of a microbiologically produced flocculant and chitin/chitosan obtained from a shell of a crab or a lobster. Especially, a flocculation active substance based on glycoprotein produced by Gram-positive bacteria containing Rhodococcus erythropolis or a flocculation active substance based on acidic polysaccharide produced by a strain of the genus Aureobasidium is used as the microbiologically produced flocculant. Further, as the chitin/chitosan, a chitin/ chitosan obtained by deacetylating 80% or more of chitin is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coagulant for coagulating and sedimenting sludge generated from municipal sewage, agricultural settlement drainage, livestock drainage, factory drainage, etc., civil engineering / building sludge, etc. More particularly, the present invention relates to a coagulant produced by microorganisms. The present invention relates to a flocculant which uses chitin and chitosan obtained from a biomass resource as a flocculant and which is safe for animals and plants and has high flocculation and sedimentation efficiency without causing environmental pollution, and a sludge treatment method using the flocculant.

[0002]

2. Description of the Related Art In general, an activated sludge method is generally used as a method for treating various kinds of wastewater containing organic matter. This activated sludge method is a highly efficient wastewater treatment method,
It is the most widely used because of the economical characteristics of high quality treated water.

[0003] Excess sludge and civil engineering / building sludge after treatment by this activated sludge method must be coagulated, settled, filtered and dewatered. In this case, a flocculant described later is added to the suspended sludge to stir the coagulation. This is separated by filtration by a conventional method to separate clear treated water and a hydrated sludge cake.
Clear treated water is discharged after sterilization, but it is customary to return the hydrous sludge cake to the natural environment by landfilling.

[0004] For example, a series of processes of sewage treatment will be described. First, sand and the like are removed from inflowing sewage by sedimentation, and suspended substances are first settled and separated in a sedimentation basin. Oxidative decomposition of organic matter by biofilm treatment method,
Finally, the suspended solids remaining in the final sedimentation basin are removed by settling and the clear water is discharged as final treated water. In order to reduce the volume and weight of the separated hydrous sludge, a flocculant is used. The hydrated sludge cake whose water content is reduced as much as possible is landfilled.

In this coagulation treatment step, a large amount of an inorganic coagulant or a synthetic polymer coagulant has been used. Inorganic coagulants include aluminum salts such as sulfuric acid bands and polyaluminum chloride, and water-soluble polysulfates such as iron salts such as ferric chloride, ferric sulfate, and ferric polysulfate (commonly referred to as polyiron). Valent metal salts are often used. Synthetic polymer-based flocculants include cationic synthetic polymers such as polydimethylaminoethyl acrylate, anionic synthetic polymers such as polyacrylamide, hydrolysates thereof, and polyacrylic acid, and other nonionic synthetic polymers. It has been used favorably.

[0006] The sludge separated by these flocculants is
Reclaimed land is used as land for construction and agricultural land. However, when used as agricultural land, serious safety problems and environmental pollution problems arise. First, the inorganic coagulant not only increases the weight of the hydrated sludge cake because it is a polyvalent metal salt, but also introduces polyvalent metal ions into the soil to modify it into soil that is unsuitable for plant growth. Would.
Among them, aluminum ion is also said to be a causative substance of Alzheimer's disease, and has a risk of accumulating in humans through agricultural products. Second, in the case of a synthetic polymer flocculant,
Due to its poor biodegradability, it accumulates in soil and inhibits plant growth. In particular, since acrylamide, which is a monomer of polyacrylamide, has carcinogenicity and neurotoxicity, there is great concern that acrylamide monomer remains.

[0007]

In order to overcome the drawbacks of such a chemical flocculant, a microbial flocculant produced by utilizing recent biotechnology has been developed. For example, Japanese Patent Application Laid-Open No. 8-256787 discloses Rhodococus erythropolis.
olis) KR-S-1 strain (FERM BP-4913) is described. During this growth process, the microorganism-producing coagulant is excreted and produced in the extracellular medium. According to the Chemical Society of Japan, No. 5, 1992, the microbial coagulant produced by Rhodococcus is NOC-1.
And biochemical analysis revealed that it was a glycoprotein.

[0008] These publications and reports contain NOC-
No. 1 is a highly safe substance excellent in biodegradability and described as a flocculant having no risk of secondary pollution. In addition, it is reported that it has a strong flocculating effect on a wide range of suspended sludge ranging from inorganic sludge to organic sludge. Thus, the present inventor has applied this NOC-1 to actual coagulation sedimentation of agricultural settlement drainage, and has found that NOC-1 alone shows almost no coagulation activity. And this NOC
It was found that -1 exhibited an aggregating effect only when an inorganic aggregating agent such as calcium (Ca2 +, Mg2 +, Fe2 +, Al3 +, etc. was used as a polyvalent ion) which should not be used was used at the same time. In addition, it was found that NOC-1 alone can exert the coagulation effect only on inorganic sludge such as kaolin, and the coagulation effect by itself is small for a wide range of organic sludge.

On the other hand, Japanese Patent Application Laid-Open No. Hei 8-81501 discloses that
An acidic polysaccharide produced by a strain belonging to the genus Aureobasidium (FERM P-14228) has been reported. This acidic polysaccharide has aggregating activity,
Since it is described as a non-toxic wastewater treatment agent, it can be understood that it is a kind of microbial coagulant. In addition, this acidic polysaccharide is commercially available under the trade name Amy as described below, and is a rare example that has been put to practical use while practically no microorganism-producing coagulant has been found.

[0010] The present inventors applied the above-mentioned coagulation and sedimentation of agricultural settlement drainage to confirm the coagulation effect of Amy and found that Amy alone did not have coagulation activity. In addition, it was also found that this Amy exhibited the coagulation effect only when an inorganic coagulant such as polyiron was used simultaneously.
Therefore, this acidic polysaccharide also has the same properties as the glycoprotein of Rhodococcus erythropolis.

Japanese Patent Application Laid-Open No. 59-160509 discloses that chitin / chitosan functions as a flocculant for dewatering sludge. Its deacetylation rate is 67
It is described that the coagulation effect is remarkably improved when the content is ~ 75 mol%. However, according to a test conducted by the present inventors, it has been found that the aggregation performance of chitin / chitosan alone is small and cannot be put to practical use.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages, and a novel flocculant according to the present invention is characterized in that a microorganism-producing flocculant is used in combination with chitin / chitosan. Have. In addition, an agglutinating active substance mainly composed of a glycoprotein produced by Gram-positive bacteria including Rhodococcus erythropolis as the microorganism-producing flocculant or an agglutinating activity mainly composed of an acidic polysaccharide produced by a strain of Aureobasidium. A coagulant using chitin / chitosan obtained by deacetylating chitin to 80% or more as the chitin / chitosan using the substance is proposed.

Further, the present invention proposes a flocculant wherein the combined weight ratio of the microorganism-produced flocculant and chitin / chitosan is 1: 9 to 5: 5. The present invention proposes a sludge treatment method in which each of the above-mentioned coagulants is added to the water to be treated to cause coagulation and sedimentation of the sludge, or is added to hydrous sludge to dewater the sludge.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that, although the conventional microorganism-producing coagulant has a small effect of coagulating organic sludge by itself, when an inorganic coagulant that generates polyvalent metal cations is added, an organic coagulant is used. We focused on the fact that it exerts a strong coagulation action on sludge. That is, it was considered that the microorganism-produced flocculant had a property of exhibiting a strong flocculating performance by a synergistic effect with other cationic flocculants. Accordingly, the present inventors have conducted intensive studies to find another safe flocculant having the same action and effect as the inorganic flocculant, and as a result, have found chitin / chitosan having a cationic functional group.

[0015] Even when this chitin / chitosan is added simultaneously with the microorganism-producing coagulant to the water to be treated, or when it is added sequentially, a strong coagulation effect is exerted on sludge. Sequential addition means that after adding the microorganism-producing coagulant,
Both the case where chitosan is added and the case where chitin / chitosan is added first and the microorganism-producing coagulant is added later are included.

Chitin is a major component of shells and cell walls of crustaceans such as crabs and shrimps and insects, and forms a complex with calcium and proteins. As a biomass resource that is bio-generated on earth, it accounts for the second amount after cellulose. A substance obtained by removing calcium and protein from the chitin is called chitin, and a substance obtained by deacetylating the chitin is called chitosan. Both chitin and chitosan are natural polymers. However, it is difficult to deacetylate chitin by 100%, and even with a substance called chitosan, chitin and chitosan are complexed at a predetermined ratio. In the present invention, such a composite substance is called chitin / chitosan.

In the scientific name, chitin is β- (1 → 4) -2-
Acetamide-2-deoxy-β-D-glucose, and chitosan is β- (1 → 4) -2-amino-2-deoxy-β-D-glucose. Chitin / chitosan has a molecular structure in which these two types coexist.

As the chitin / chitosan used in the present invention, Koyo Chitosan, a trade name of a powder sold by Koyo Chemical Co., Ltd., is used. Since chitin / chitosan is a substance produced from natural biomass resources, its safety for humans and animals is extremely high. In addition, it is reported that, of course, it has not only mutagenicity against microorganisms but also strong antimutagenicity.

As described above, Japanese Patent Application Laid-Open No. 59-16050
No. 9 describes that chitin / chitosan functions as a flocculant for sludge dewatering. However, tests by the present inventors have revealed that the cohesion performance is small when used alone. Chitin with such small coagulation performance
The reason why strong coagulation performance is exhibited when chitosan is used in combination with a microorganism-producing coagulant of a similar character, is as follows.
Empirical elucidation has not progressed yet. However, the present inventors now believe that chitin / chitosan has a cationic functional group, and that this cationic functional group may exert the same aggregation promoting effect on microbial aggregating agents as polyvalent metal cations. ing. In any case, the synergistic effect of the chitin / chitosan and the microbial coagulant discovered by the present inventors has led to the completion of a safe and powerful coagulant.

In addition, it has been found that a deacetylation ratio of chitin / chitosan is preferably 80% or more in order to efficiently exert the flocculating effect when used in combination with a microbial flocculant. This point does not overlap with the above-mentioned 67 to 75%, and is the first discovery by the present inventors. Therefore, among the KOYO chitosans, SK-10 (85% or more), SK-50 (80% or more), SK-200 (80% or more), SK-400 (8
0% or more) can be applied to the present invention. The figures in parentheses indicate the deacetylation rate.

As the microorganism-producing coagulant which is one component of the present invention, a known microorganism-producing coagulant can be used. The microorganism-producing coagulant is produced by a microorganism-producing bacterium extracellularly or intracellularly during the growth process. The term "extracellular" refers to production in a medium. For example, in the case of a liquid medium, that is, a culture solution, the liquid itself becomes a flocculant solution. When produced in cells, it is necessary to release the flocculant from the cells into the medium. For example, a means such as rupture of the cells or elution of the cells with a specific agent is used. The cells may be aggregated and separated from the culture solution, or the cells may be killed with a drug. If the cells are not toxic, they may remain in the culture solution as they are.

[0022] Gram-positive bacteria that produce flocculants include:
Rhodococcus erythropolis, Nocardia restricta, Nocardia calcarea, Nocardia rhodny, Corynebacterium, Aureobacterium, Oerskovia and the like can be used. Examples of gram-negative bacteria include Alcaligenes ratus, Alcaligenes cupidus, Pseudomonas, Acinetobacter, Enterobacter and the like.

In particular, Gram-positive bacteria that can be used in the present invention include:
Rhodococcus erythropolis KR-S-1 strain (FE
RM BP-4913), Aureobacterium KYM
-6 strain (FERM P-11357), Oerskovia KYM-7 strain (FERM P-11358) and the like.
The numbers in parentheses are the deposit numbers with the National Institute of Bioscience and Human-Technology, National Institute of Advanced Industrial Science and Technology, and strains can be obtained under predetermined conditions. As represented by Rhodococcus erythropolis, some gram-positive bacteria produce glycoproteins as microbial aggregating agents. In particular, Rhodococcus erythropolis produces a glycoprotein named NOC-1,
This NOC-1 is used as a microorganism-producing coagulant in Examples described later.

These microorganism-producing coagulants have not yet been marketed as commercial products. Then, the inventor obtained various strains, cultured them in a liquid medium or solid medium under predetermined conditions, and produced a microorganism-producing flocculant in the medium. Microbial culture methods have a strong aspect common to various microorganisms. For example, in order to produce NOC-1, a method of culturing Rhodococcus erythropolis KR-S-1 is described. A liquid medium is inoculated with a seed bacterium and cultured at 30 ° C. with shaking for 2 to 4 days. The NOC-1 is accumulated in the culture solution.

Lord Coccus erythropolis KR-S
Since the -1 strain is produced extracellularly, that is, while excreting NOC-1 in the culture solution, the culture solution itself can be used as a microorganism-producing flocculant.

As another microorganism-producing bacterium, the aforementioned strain of the genus Aureobasidium (FERM P-1422) is used.
8) is available and the coagulant produced is an acidic polysaccharide. It is extremely rare that a microorganism-producing coagulant is commercialized, but this acidic polysaccharide is sold by Sophie Co., Ltd. under the trade name Amy. Amy is an acidic polysaccharide culture, and the unpurified culture itself is sold as a commercial product. Therefore, when used in the present invention, the culture solution itself or a diluted solution thereof is used.

In the present invention, the combined weight ratio represented by the fractional ratio of the microorganism-producing coagulant / chitin / chitosan is from 1/9 to
It is desirable to be in the range of 5/5. Within this range, a high aggregation effect can be obtained. In addition, the microbe-produced coagulant and chitin / chitosan are simultaneously coagulated and dehydrated.
It may be added to hydrous sludge or may be added sequentially.
In the sequential addition, the microorganism-producing coagulant may be added first, or chitin / chitosan may be added first, and the coagulation / dehydration effect can be exhibited as a synergistic effect of both agents regardless of the order of addition.

The sludge treatment method according to the present invention means that the suspended sludge, which is a suspended substance, is coagulated and settled from the target water to be subjected to solid-liquid separation, and the separated sludge having a high water content is dewatered. To reduce the water content. The water to be treated covers a very wide area, including urban sewage, agricultural settlement drainage, livestock drainage, factory drainage, civil engineering and construction drainage. More specifically, it covers a wide range of fields, such as the water freshening field of water supply and middle water supply, the separation of fermented liquid and cultured cells in the fermentation industry, and the clarification treatment in the food industry and civil engineering dredging. The wet sludge to be dehydrated includes raw sludge, surplus sludge, digested sludge and mixed sludge thereof, and the present invention can be applied to sludge in general.

As can be seen from the specific examples of the above-mentioned sludge treatment liquid, the sludge according to the present invention includes inorganic sludge, organic sludge, and mixed sludge thereof. Inorganic sludge is a sludge made of an inorganic substance, for example, muddy water formed on the ground, dispersed colloids of metals and sulfur, and associated colloids such as iron hydroxide. Organic sludge is a sludge made of organic substances, and includes a wide range of organic substances such as human waste and sewage in sewage, and cultured cells in fermentation liquor.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the novel flocculant according to the present invention and a sludge treatment method using the same will be described below.

Example 1 Combination of Acidic Polysaccharide Amy and Chitin / Chitosan In this example, surplus sludge obtained by treating agricultural settlement wastewater by the activated sludge method was used as raw material sludge, and the surplus sludge was suspended. The water to be treated was coagulated and precipitated. As the properties of the water to be treated, the solid content in 1 liter of the water to be treated (mg), that is, MLSS was 17000 mg / L, and its PH was 6.2.

As the microorganism-producing flocculant, a flocculant sold by Sophie Co. under the trade name Amy is used. This flocculant is cultured by a strain of the genus Aureobasidium (FERM P-14228), a kind of black yeast. It is an acidic polysaccharide produced in liquid. Since the Amy of the product is provided as a culture solution of unknown concentration, the stock solution at the time of receipt of this culture solution or a dilution of the same with water (hereinafter abbreviated as Amy and distinguished by the degree of dilution) is used for the production of microorganisms according to the present invention. Used as an agent.

As the chitin / chitosan, standard SK-400 from Koyo Chitosan sold by Koyo Chemical Co., Ltd. was used. This SK-400 is a pale yellowish white powder and is a high molecular weight chitin / chitosan having a deacetylation ratio of 80% or more. 0.5% of this SK-400
An aqueous acetic acid solution was prepared, and this 0.5% aqueous solution or a diluted solution thereof with water (hereinafter, abbreviated as chitosan and distinguished by dilution) was used as chitin-chitosan.

As shown in FIG. 1, the experimental method of the coagulation and sedimentation was as follows: 500 mL glass beaker 2 (98 mmφ × 12 mm).
At 0 mmh), 300 mL of the sludge treatment liquid 4 is introduced, and at this time, the liquid depth becomes 60 mm. Predetermined amounts of Amy and chitosan were simultaneously or sequentially added to this beaker 2 with a pipette. In Table 1, when Amy and chitosan are listed in two stages, this means simultaneous addition, and when described as first (stage) and second (stage), it means that they were sequentially added in that order. After the addition of the amy and / or chitosan, a cooking egg whisk was manually inserted almost vertically into the beaker liquid as a stirrer 6 and stirred for a predetermined time. The speed change switch and the transformer 8 are manually adjusted, and about 1
It was adjusted so as to be 00 rpm and about 60 rpm with slow stirring.

The formation state of the flocculated floc was performed after the completion of the flocculating and sedimentation operation, and after standing for 20 minutes while continuing to observe with the naked eye. As a first judgment, the content was subjected to natural filtration using No. 2 filter paper, and judgment was made from the filtration speed and the clarity of the filtrate. For the examples in which the primary state was considered to be good in the primary determination, a secondary determination was performed. That is, 5A filter paper was spread on a water-jet pump and Nutsche and filtered under reduced pressure, and the water content of the remaining water-containing sludge cake was measured using an infrared moisture meter FD-600 manufactured by Kett Science Laboratory Co., Ltd. The measurement was performed by heating the sample at 105 ° C. for 1 hour. The determination results of the example and the comparative example are shown in Table 1, and are described as “real 1” and “ratio 1”, respectively.

[0036]

[Table 1]

Example 1-1 and Example 1-2 show the case where Amy and chitosan are sequentially added to the water to be treated,
Regardless of the order of addition, flocculation and floc formation of sludge and filtration thereof have been successful. Examples 1-3 to 1-8 show the case where Amy and chitosan were added to the water to be treated at the same time, irrespective of rapid or slow stirring, and even if the amount of both coagulants was considerably reduced, Large flocs are formed throughout. In addition, the filtrate was transparent because of good filterability, and the water content of the dewatered sludge cake was relatively low. On the other hand, as shown in Comparative Examples 1-1 and 1-2, when Amy or chitosan is used alone, cake does not coagulate or has a very small floc, so that the cake has good filterability. It can be seen that the water content of the.

As can be seen from Table 1, the coagulation effect is higher when diluting the amy or chitosan to the water to be treated than when adding it undiluted. When diluted, the viscosity is reduced and the water is easily mixed with the water to be treated. Therefore, the amount of the coagulant used can be reduced, which is extremely economical. In addition, the stirring time can be shortened by the lower viscosity, and the higher the dilution ratio, the more effective in many respects.

[Example 2: Combined use of glycoprotein NOC-1 and chitin / chitosan] Rhodococcus erythropolis KR deposited at the Institute of Biotechnology and Industrial Technology, National Institute of Advanced Industrial Science and Technology
The same strain as that of -S-1 (FERM BP-4913) was obtained and cultured by the present inventors in a liquid medium, and only the undiluted culture solution was used as NOC-1 of a microorganism-producing coagulant.

The composition of this liquid medium is as follows:
This liquid medium was inoculated with a seed bacterium and cultured with shaking at 30 ° C. for 2 days. Glucose and fructose were used as carbon sources. NOC-1 is accumulated in this culture solution Carbon source 10 g / L K2HPO4 5 g / L KH2PO4 2 g / L MgSO4 0.2 g / L Urea 0.5 g / L Yeast extract 0.5 g / L NaCl 0.1 g / L purified water 1L (liter)

The culture solution of NOC-1 had a pH of 7.0 to 8.0 and an agglutinating activity of 1.0 to 1.5. This activity value is 1 / OD550 sample-1 / OD5
Given in 50 blanks, it is obtained from the kaolin flocculation properties of inorganic sludge.

The method for measuring the above activity value is as follows. Take 1 mL of the cultured NOC-1 in a 100 mL graduated cylinder and add 9 mL of pure water for dilution. to this,
80m of suspension water containing kaolin at a concentration of 5000ppm
Add L and 10 mL of a 10% aqueous solution of calcium chloride to make a total of 100 mL. This solution is slowly stirred upside down three times, and then allowed to stand for 10 minutes. afterwards,
1 mL of the liquid in the measuring cylinder is sampled from a position 10 cm below the liquid surface as a sample, and sealed in a cell for measuring absorbance. With a spectrophotometer manufactured by Shimadzu Corporation, wavelength 55
The absorbance OD550 at 0 nm is measured. A blank in which the NOC-1 portion of the above operation was replaced with pure water was separately prepared, and the absorbance was measured for the blank.

As chitin / chitosan, standard SK-400 from Koyo Chitosan (trade name, sold by Koyo Chemical Co., Ltd.) was used. In the same manner as in Example 1, a 0.5% aqueous solution of SK-400 in acetic acid was prepared, and this 0.5% aqueous solution or a diluent thereof (hereinafter abbreviated as chitosan and distinguished by the degree of dilution) was used. Used as chitin and chitosan. In practice, no chitosan diluent was used.

The experimental method and the method of judging the coagulation and sedimentation are the same as those in Example 1, and the description thereof will be omitted. The results of the examples and comparative examples are shown in Table 2 and show the results of the actual 2 and the ratio 2
It is represented as

[0045]

[Table 2]

From Comparative Examples 1 and 2, chitosan alone aggregated sludge, but the floc was small and the filterability was poor. Further, from Comparative Example 3, it was not possible to coagulate and settle sludge even if NOC-1 alone was added in a sufficiently large amount. On the contrary, as can be seen from Example 1, NOC-
When 1 and chitosan are sequentially added, the cohesiveness is improved. Examples 2 to 6 show the case where NOC-1 and chitosan were added at the same time. In any case, irrespective of the rapid stirring or the slow stirring, coagulation and sedimentation were observed and the filterability was good. Example 1
5 does not neutralize the sludge treated water, and Example 6 neutralizes the sludge treated water in advance. That is, regardless of the presence or absence of neutralization, the co-addition enhances the aggregation effect. In addition, even if the addition amount was reduced, a large floc was formed by stirring for a very short time, the filterability was good, and the water content of the hydrous sludge cake was also good.

The present invention is not limited to the above-described embodiment, but includes various modifications and design changes within the technical scope thereof without departing from the technical concept of the present invention.

[0048]

As described in detail above, the present invention efficiently purifies sludge treated water such as urban sewage, agricultural settlement drainage, livestock drainage, factory drainage, civil engineering and construction sludge which has increased rapidly in recent years. can do. In addition, since the coagulant uses a coagulant produced by microorganisms and a chitin-chitosan complex obtained from biomass resources, it is safe for living organisms, including humans, and without polluting the natural environment. It has the effect of efficiently coagulating and settling sludge from water. Accordingly, a coagulant that has been used in large quantities in the past, that is, a coagulant that replaces an acrylamide polymer in which an aluminum salt or monomer that is a causative substance of Alzheimer's disease is called a carcinogen or neurotoxin, has been provided. In the near future, the effect of the present invention to protect soil from environmental pollution is extremely large.

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining a novel aggregating test method for an aggregating agent according to the present invention.

[Explanation of symbols]

2 is a beaker, 4 is a sludge treatment liquid, 6 is a stirrer, and 8 is a transformer.

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Claims (6)

[Claims] 1. A flocculant comprising a combination of a microorganism-producing flocculant and chitin / chitosan. 2. An agglutinating agent mainly containing a glycoprotein produced by a Gram-positive bacterium containing Rhodococcus erythropolis as the microorganism-producing flocculant or an acidic polysaccharide produced by a strain of Aureobasidium genus as a main component. The flocculant according to claim 1, wherein a chitin / chitosan obtained by deacetylating chitin to 80% or more is used as the chitin / chitosan. 3. The coagulant according to claim 2, wherein the combined weight ratio of the microorganism-produced coagulant and chitin / chitosan is 1: 9 to 5: 5. 4. A method for treating sludge, comprising adding a microorganism-producing coagulant and chitin / chitosan as coagulants to water to be treated to coagulate and settle sludge, or adding it to hydrous sludge to dewater sludge. . 5. An agglutinating substance mainly composed of a glycoprotein produced by a Gram-positive bacterium including Rhodococcus erythropolis as the microorganism-producing flocculant or an acidic polysaccharide produced by a strain of the genus Aureobasidium. 5. The sludge treatment method according to claim 4, wherein a chitin / chitosan obtained by deacetylating chitin to 80% or more is used as the chitin / chitosan. 6. The combined weight ratio of the microorganism-producing coagulant and chitin / chitosan is 1: 9 to 5: 5, and both agents are added simultaneously or sequentially, and the order of addition is not limited in the sequential addition. 6. The method for treating sludge according to 5.