JPS6352557B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a highly active wastewater treatment agent for microbiologically decomposing and removing organic substances in wastewater.

Conventional technology To decompose organic substances in wastewater, conventional methods include a floating activated sludge method in which flocs of microorganisms (Pseudomonas, Flavobacterium) are suspended in an aeration tank, or a contact aeration method in which microorganisms are used in the form of a membrane. The rotating disk method, the sprinkled bed method, etc. are used. In this method, since the microorganisms come into direct contact with the wastewater, the microorganisms are eaten by large organisms in the wastewater that feed on bacteria, such as threadworms, rotifers, and ringworms, and the amount of microorganisms is reduced. The drawback was that organic substances in wastewater could not be stably decomposed over a long period of time.

Recently, wastewater treatment agents have been proposed in which various bacteria are encased and immobilized in gels of synthetic polymers such as polyacrylamide, carrageenan, and alginic acid.

Problems to be Solved by the Invention These treatment agents in which bacteria are immobilized in gel solve the disadvantage that bacteria are eaten by relatively large microorganisms, but the activity of the immobilized bacteria decreases and the long-term Durability is an issue when used for wastewater treatment.

When a naturally occurring less toxic substance such as carrageenan or alginic acid is used as a gel, the activity of immobilized bacteria is only slightly reduced, but the gel has low physical strength and durability.

On the other hand, when polyacrylamide gel is used, it has high physical strength and good durability, but the acrylamide monomer used for immobilization,
Since the crosslinking agent, polymerization initiator, etc. exert a toxic effect on bacteria, there is a drawback that the activity tends to decrease.

Therefore, the present invention aims to minimize the toxic effects of monomers and additives used for entrapping immobilization inside synthetic polymer gels such as polyacrylamide gels, and to provide highly active processing agents. purpose.

Means for Solving the Problems The wastewater treatment agent according to the present invention is characterized in that activated sludge is flocculated into flocs using a flocculant, and the resulting flocs are encased and fixed inside a polymer gel. do.

The wastewater treatment agent of the present invention can be produced by adding a flocculant to activated sludge to flocculate it into flocs, and then encasing and fixing the resulting flocs inside a polymer gel.

The flocculant may be an inorganic or organic flocculant. As the inorganic flocculant, aluminum sulfate, ferric sulfate, or any known inorganic flocculant can be used. The organic flocculant may be any of cationic, anionic, and nonionic polymer flocculants. Examples of the cationic polymer flocculant include polyvinylpyridine hydrochloride and polyethyleneimine, and examples of the anionic polymer flocculant include sodium polyacrylate, maleic acid copolymer salt, and polyacrylamide partial hydrolyzate salt. etc. Furthermore, examples of the nonionic polymer flocculant include polyacrylamide, polyoxyethylene, and the like.

In the present invention, it is preferable to use the above-mentioned flocculant to flocculate activated sludge into a flocculant having a size of 100 μm or more.

In order to immobilize the aggregate thus obtained, the aggregated bacteria and a polymerization initiator are mixed in a solution containing a monomer such as acrylamide, a crosslinking agent, a polymerization promoter, etc., and a polymerization reaction is performed.

As the polymerization method, known methods such as radical polymerization, radiation polymerization, redox polymerization, etc. can be used depending on the properties of the monomer.

In the present invention, gels such as polyacrylamide and photocurable resin can be used as the polymer gel, and the case where polyacrylamide gel is used will be described below.

As a crosslinking agent for acrylamide, N,N'-
Methylenebisacrylamide, N,N'-propylenebisacrylamide, diacrylamide dimethyl ether, 1,2-diacrylamide ethylene glycol, N,N'-diacryltartaric acid diamide, etc. can be used.

As the polymerization accelerator, 3-dimethylaminopropionitrile, N,N,N',N'-tetramethylethylenediamine, etc. can be used. Further, as a polymerization initiator, potassium peroxodisulfate is usually used.

The gel obtained by polymerization is molded into the shape of a sphere, cylinder, plate, fiber, hollow fiber, etc. with a size of 0.5 mm to 5 mm.

In this way, if a floc of microorganisms is prepared in advance and then mixed with a monomer polymerization solution and polymerized, immobilized microorganisms that exhibit high activity over a long period of time, excellent strength, and high durability can be obtained. can get.

Effect The flocculant used to form the floc envelops the microorganisms, and as a result, the toxicity of the monomer and polymerization initiator does not penetrate into the inside of the floc during the polymerization reaction, which significantly reduces the rate of microorganisms being killed. yields immobilized microorganisms with activity.

Furthermore, the polymer gel protects the microorganisms entrapped and immobilized therein from being eaten by relatively large microorganisms, and also acts as a carrier with excellent physical durability.

Examples Next, the present invention will be described in detail based on examples.
The present invention is not limited to this.

Example 1 Activated sludge from Matsudo City K sewage treatment plant was 40,000mg/
Anionic polymer flocculant Prestol 444K (manufactured by Nu-Metals & Chemicals) was added at 0.5% based on the dry weight of the bacteria to produce flocculated bacteria. Separately, acrylamide monomer 32
% and N,N'-methylenedisacrylamide 2
%, mix this solution and flocculated bacteria in the same volume ratio, then add 3-dimethylaminopropionitrile as a polymerization accelerator to 0.5%, and further add peroxo as a polymerization initiator. Potassium disulfate was added to a concentration of 0.25%, and the flocculated bacteria were immobilized by polymerization. The diameter of the polyacrylamide gel containing the aggregated bacteria that has been comprehensively fixed in this way is
It was molded into a cylinder with a length of 2.6 mm and a height of 2.6 mm.

The waste water treatment agent thus obtained was filled into the aeration tank 1 shown in FIG. 1 at a filling rate of 40%. The aeration tank 1 shown in FIG. 1 consists of an ascending pipe 2 and a descending pipe 3, and wastewater is injected from a wastewater inlet 4 and flows out from a treated water outlet 5. Air is sent from the air pipe 6, and bubbles are sent from the riser pipe 2.
is raised, the wastewater treatment agent 7 is made to flow due to the air lift effect, and brought into contact with the wastewater to decompose organic substances. Figure 2 shows the results of treating sewage with a BOD of 60 to 220 mg for a residence time of 3 hours.

For comparison, as a conventional method, a contact aeration method was carried out by filling a 40% plastic corrugated plate and forming a microbial film on the surface of the corrugated plate. The results of treating the same wastewater as the above using this contact aeration method were
As shown in the figure.

As can be seen from Figure 2, with the conventional method, a large number of threadworms appeared after the 25th day of operation, the amount of microorganisms decreased, and the quality of the treated water deteriorated. On the other hand, when the wastewater treatment agent of the present invention was used, the quality of the treated water was stable and good even if threadworms were generated in the wastewater.

Example 2 Microorganism flocs were prepared in the same manner as in Example 1, but various flocs with different diameters were manufactured, each was fixed encirclingly in the same manner as in Example 1, and formed into a cylinder with a diameter of 3 mm and a length of 3 mm. The activity of the obtained wastewater treatment agent was measured and the results are shown in FIG.

Activity was measured by oxygen uptake rate (mgO ₂ /h).
The residual rate of activity is the ratio of the oxygen uptake rate before comprehensive fixation to the oxygen uptake rate after comprehensive fixation.

As is clear from Figure 3, the floc diameter is 100μm.
The residual activity of the wastewater treatment agent that comprehensively immobilized microorganisms (no flocculant added) was less than 15%;
The residual activity of the wastewater treatment agent in which a flocculant was added and flocculates were fixed to a flocculate diameter of 100 μm or more was 25 to 45%, and the activity was significantly improved.

In the above examples, Prestol was used as the flocculant.
Although 444K was used, similar results can be obtained using other organic or inorganic flocculants.

Effects of the Invention According to the present invention, a reduction in the amount of microorganisms due to ingestion by relatively large microorganisms can be prevented, and a wastewater treatment agent with high microbial activity, high physical strength, and excellent durability can be obtained. .

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of the aeration tank used in the example of the present invention, Figure 2 is a diagram of the daily change in BOD concentration of wastewater and treated water in Example 1, and Figure 3 is a graph of floc diameter and activity. It is a relationship diagram with a residual rate. 1...Aeration tank, 2...Rising pipe, 3...Downcomer pipe, 7...Wastewater treatment agent.

Claims (1)

[Scope of Claims] 1. A wastewater treatment agent that microbiologically decomposes organic substances in wastewater, which uses a flocculant to flocculate activated sludge into flocs and enclose the resulting flocs inside a polymer gel. A wastewater treatment agent characterized by being fixed. 2. The treatment agent according to claim 1, which contains fixed activated sludge flocs with a size of 100 μm or more.