JP2572334B2 - Method and apparatus for microbiological reduction of excess sludge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a bacteriolytic action in which excess sludge generated in the process of microbiologically treating wastewater such as human waste, sewage and / or organic wastewater is widely distributed and inhabits in nature. The present invention relates to a method for microbiologically reducing excess sludge reduced by slime bacteria.

[0002]

2. Description of the Related Art Conventionally, the excess sludge generated from the biological treatment of human waste, sewage and / or organic wastewater, particularly aerobic biological treatment, is enormous,
Large amounts of energy and resources are being consumed for their processing and disposal.

At present, there are about 1,2 human waste treatment sites in Japan.
00 places, sewage treatment plant (urban sewage) 800-1,000
There are 0 places, and the amount of excess sludge to be treated and disposed of is enormous even if the organic wastewater treatment is separated. Although some of these excess sludges are effectively used, most of the excess sludge is concentrated in its entirety, and an auxiliary for dehydration is added thereto. And then
It is treated and disposed of by inputting large amounts of energy and resources for incineration. However, as the amount of excess sludge increases, the facilities for concentration and dewatering must be enlarged, and the dewatering rate is limited, so that incinerators are also required to process large volumes. For this reason, not only are local governments struggling with the economic burden required for treatment and disposal, but also from the perspective of technical response to secondary pollution such as air pollution and water pollution, and global warming. Solutions.

For this reason, a method for reducing the amount of excess sludge generated has been sought. For example, in sewage treatment, excess sludge and first sedimentation basin (hereinafter referred to as “first sedimentation”) sludge are concentrated, then mixed at a generation ratio, and treated by methane fermentation (anaerobic digestion) to reduce excess sludge. Have been. However, since the excess sludge is a surplus of activated sludge microorganisms, the degradation rate of the cell wall and cell membrane of the bacterial cells is poor in the ordinary methane fermentation treatment, and the digestion time of about 20 to 30 days is required. Requires excessive investment in maintenance.

On the other hand, microbiological methods for destroying cell walls and cell membranes of bacterial cells without using digestion have been studied. For example, Japanese Patent Application Laid-Open No. 112998/1986 proposes a method of adding bacteriophage to sludge generated by biological treatment of wastewater and reducing the amount of sludge by bacteriolysis. However, bacteriophages have extremely high host specificity, and certain bacteriophages are parasitized and lysed only by certain bacteria. Therefore, in order to reduce the amount of multi-bacteria mixed culture sludge such as activated sludge by bacteriophage, the same number of bacteriophages as the number of bacterial species that actually inhabit the activated sludge are screened from nature and formulated. It is difficult to apply this method to sludge reduction.

[0006] In addition, the destroyed bacterial contents are released into the water, resulting in new organic pollution. In the patent publication, the released organic matter seems to be bacteriophage, but viruses containing bacteriophage are very small particles, such as colloids, as they were called filterable pathogens in the old days. Removal is not easy. In this patent publication, the separated water subjected to solid-liquid separation is discharged, and it is clear that a large number of bacteriophages are contained in the separated water, which becomes new pollutants. On the other hand, it is easy to think about introducing a purifying device,
Returning to the biological treatment step would inoculate the activated sludge with a bacteriophage solution having a very high lytic power at that time, which may hinder the treatment.

Therefore, it is necessary to provide a means for treating bacteriophage. However, as described above, the virus has a colloidal level and, as a matter of course, cannot be separated by ordinary sedimentation. Separation is difficult,
It is necessary to separate by ultrafiltration or reverse osmosis filtration equipment. Alternatively, inactivation / sterilization means must be provided, and in some cases, a disinfectant abatement device used for the device is required. Thus, the number of incidental facilities has become enormous, making it hardly practical for practical use.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to develop a sludge reduction method and a sludge reduction apparatus suitable for the method, which do not require special auxiliary equipment, by bacteriolysis and recycling of microorganisms. .

[0009]

Means for Solving the Problems In order to achieve the object of sludge reduction, the present inventors have found that sludge bacterium, which is extremely commonly distributed and inhabiting the natural world, has surplus sludge produced by lytic enzymes produced outside the cells. The present invention has been achieved by focusing on the action of lysing bacterial cells such as BOD-utilizing bacteria, which are the main constituent bacteria, and assimilating into self-cell construction. That is, the above object is achieved by the development of the method and apparatus for microbiologically reducing excess sludge of the present invention. 1) Microbial weight loss of surplus sludge characterized by inoculating surplus sludge discharged from a biological treatment process of sewage with a single strain or multiple strains of myxobacteria having a bacteriolytic action and allowing them to act under aerobic conditions. Method. 2) Excess sludge discharged from the biological treatment process of sewage is inoculated with a single strain or multiple strains of lytic bacteria having a bacteriolytic action, and is reduced under aerobic conditions; A method for microbiologically reducing excess sludge, comprising a step of solid-liquid separation of reduced sludge and circulating and returning a part of the separated sludge subjected to solid-liquid separation to the reduction step. 3) Excess sludge discharged from the biological treatment process of sewage is inoculated with a single strain or multiple strains of myxobacteria having a bacteriolytic action, and is reduced under aerobic conditions, and discharged from the reduction process. Microorganisms of excess sludge having a step of solid-liquid separation of the reduced sludge, circulating a part of the separated sludge solid-liquid separated back to the reduction step, and leading the separated liquid to a biological treatment step Biological weight loss method. And 4) a sludge reduction tank having means for introducing an oxygen-containing gas,
A solid-liquid separation device for solid-liquid separation of the reduced sludge discharged from the sludge reduction tank, means for leading a part of the separated sludge separated into solid and liquid to the sludge reduction tank, An apparatus for microbiologically reducing excess sludge, comprising means for leading to an apparatus. It is.

(Functions of the Invention) The excellent functions and effects of the present invention will be described below with reference to FIG. However, embodiments of the present invention are not limited to this. In FIG. 1, the excess sludge 4 from the biological treatment tank 1 to be reduced is introduced into the excess sludge concentration tank 2 and the excess sludge concentration is set to 20,0.
After concentrating to about 00 to 30,000 mg / liter, it is transferred to the sludge reduction tank 3. On the other hand, as for myxobacteria used for the reduction of surplus cells, it is preferable to increase and culture one or more kinds of unique strains from the natural world and use them as seeds for sludge reduction. It is also possible to select a strain having an excellent lytic action from the stocks of a preservation institution and use it.

Myxobacteria 12 to be inoculated into the sludge reduction tank 3
A liquid mixed culture may be used, or a so-called dry cell obtained by culturing myxobacteria in a liquid medium and / or a solid medium, separating and concentrating the cells by ordinary means, and freeze-drying the cells. May be used. Furthermore, the combined use of both types of cells does not hinder the present invention. These inoculum cells 12 are inoculated and mixed into the sludge reduction tank 3 by any means such as shower, spray, injector or simple piping.
Thus, it is usually allowed to act under aerobic conditions at about 25 ° C. for 3 to 5 days to lyse excess sludge, assimilate and reassemble into myxobacteria, and reduce the amount of sludge due to loss accompanying respiration and the like. .

[0012] The remaining sludge is a residue of decomposition of activated sludge and a regrowth of slime bacteria. These are led to a concentration device 7, concentrated to an appropriate concentration, and if necessary, an organic and / or inorganic coagulant is injected. Then, the remaining sludge is dewatered by a commonly used dehydrator 8, and the dewatered cake is dried. obtain. As the concentrating device 7 and the dehydrating device 8, any conventional device for biologically treated sludge can be used. Further, it is effective to mix the concentrated sludge 14 and / or the coagulated sludge 15 and then dehydrate the remaining sludge before dehydrating the remaining sludge. The solid-liquid separation means can be of course another means.

In this separated liquid 10 (spill water), some mucous bacteria and the cell content in excess sludge lysed by the mucus bacteria are dissolved without being partially utilized. Since the cell content is mainly an easily decomposable organic substance and becomes a BOD component, it is taken out of the system through the residual water pipe 9 and is combined with the biological treatment apparatus 1 for night soil, sewage or organic waste water to be treated. Efficient and preferred. Alternatively, the BOD is introduced into the biological treatment step 11 provided separately and independently,
The components may be decomposed and then discharged to the outside. As these biological treatment steps 1 and 11, existing biological treatment methods such as ordinary activated sludge treatment and fluidized-bed type biofilm treatment with a carrier input can be appropriately applied. In addition, the treatment of the separation liquid 10 by a method not based on biological treatment is not prevented.

[0014] The myxobacteria slightly contained in the sewage are:
It does not hinder the operation of activated sludge at all due to the fact that its growth rate is much slower than that of BOD-utilizing bacteria in activated sludge. Should be removed with. A particularly preferable system can be constructed by applying the method to a membrane separation type activated sludge method which has remarkably progressed in recent years.

On the other hand, since the separated sludge contains concentrated myxobacteria, it can be used repeatedly if it is returned to the reduction tank via a return pipe. If this becomes stable as a seed, inoculation of new myxobacteria is not possible. It becomes unnecessary. However, in order to prepare for the initial enrichment culture or the reduction of myxobacteria due to some accident, it is preferable to provide a myxobacterium culture facility near the facility of the present invention, or to prepare an external transfer means, It does not prevent this.

(Action) The method of the present invention for reducing excess sludge using microorganisms is carried out by using microorganisms such as Myxococcus (Myxococcus).
genus or Stigmate
lla) genus, Cystobacter
r) genus, Melittangium
Myxobacteria including the genus secrete lytic enzymes outside of the cells under aerobic conditions, lyse other viable cells around the myxobacteria, and use them as their own nutrient sources for growth This is a completely new method of reducing excess sludge, which focuses on doing so. The characteristics of the slime bacteria used in the present invention have low specificity regarding predation,
The lytic enzyme produced outside the bacteria acts on and dissolves a wide range of microorganisms present in the sludge, so that the sludge can be reliably reduced.

The bacteria in other surplus sludge cannot be proliferated due to the depletion of organic substances available to the outside. However, the slime bacteria used in the present invention cannot be grown under the above-mentioned conditions even under such conditions. Grow as a source of organic matter. In addition, since slime bacteria have a complicated life cycle, their energy efficiency is low, and the conversion rate of used food sources is low. Therefore, the yield when organic matter is reconstructed as mycelial bacteria is poor, and the effect of weight reduction is large. According to the present invention, the final excess sludge amount can be reduced to half or less, and the conventional troublesome sludge treatment is released.

[0018]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1) The lytic activity and function of each of the six strains of the myxobacteria shown in Table 2 below were confirmed. Excess activated sludge (sludge concentration of about 7,000 mg / liter) discharged from the nitrification and denitrification process of night soil was placed in a 0.5-liter round-bottom flask, and increased in volume in the two-membered culture medium in Table 1 to Table 2. 3 cc / liter of a liquid culture of each of the myxobacteria shown in (1) was added and allowed to act.
After shaking culture at a culture temperature of 25 ° C. and a culture time of 5 days,
Although there was a slight difference between each strain, it was found that the cell walls of the cells of the excess activated sludge were almost completely lysed, and the bacterial cell liquid discharged to the liquid side was assimilated by the slime bacteria. Was.

[0020]

[Table 1]

* Escherichia coli (Escherichia coli) may be used as a live bacterium added to the above-mentioned medium, or a bait bacterium may be obtained from a biological treatment step.

[0022]

[Table 2]

(Example 2) Excess activated sludge discharged from a nitrification liquid circulation type nitrification denitrification process was used as an object of weight reduction by slime bacteria. Table 3 shows the general composition of the excess sludge.

[0024]

[Table 3]

On the other hand, myxococcus xanthus myxococ is a slime bacterium that lytically reduces excess sludge.
cus xanthus ATCC 25232 was selected. Commercial baker's yeast was used as a dietary bacterium of the bacteria obtained from the Microbial Strain Conservation Agency (ATCC), and the medium for two-member culture shown in Table 1 was placed in a 1-liter round bottom flask.
0 cc, inoculate the bacteria into two platinum loop cultures,
Shaking culture (aerobic increasing culture) was performed at 5 ° C. for 5 days.

Further, a sample (1) shown in Table 3 was selected as a test excess activated sludge, and two 1-liter round bottom flasks (A,
B) were filled with 500 cc each, and 5 cc of the culture solution of Myxococcus xanthus was used for A, and B was shake-cultured at 25 ° C. (normal temperature) for 5 days as a control. After 5 days, the shake culture solution (A), ( Regarding B), the concentration of organic matter in the excess sludge and the reduction rate thereof were determined. Table 4 shows the results.

[0027]

[Table 4]

As can be seen from Table 4, the reduction of the excess activated sludge of the human waste system by the myxobacterium Myxococcus xanthus was extremely remarkable.

(Example 3) Excess activated sludge was prepared by treating the groundwater that had substantially no industrial wastewater by the standard activated sludge method, and inoculated with two kinds of slime bacteria to reduce the amount. First, 1 volume of the activated sludge mixture was supplied from the aeration tank of the standard activated sludge facility.
0 liter was collected, and left standing for 1.5 hours by a normal gravity sedimentation method, and activated sludge precipitated and concentrated at the bottom was used as a test sample.
Table 5 shows the analysis values of this sample.

[0030]

[Table 5]

The concentrated excess sludge was dispensed into two 1-liter round bottom flasks (A) and (B) in 500 cc increments.
In (A), the following two types (a) and (b) were selected from the myxobacteria described above, and 2.5 cc of the increased culture solution was inoculated, respectively, and (B) was not added with the strain liquid as a control ( a) Myxococcus xanthus (Myxococc)
us xanthus ATCC25232) (b) Myxococcus fulbus
s fulbus ATCC 23093) The medium, culture conditions, and culture method used for increasing culture of each myxobacterium are the same as those in Example 2.

Further, the reduction of the concentrated activated sludge by the myxobacteria was carried out in the same manner as in Example 2. Table 6 shows the results.

[0033]

[Table 6]

As shown in Table 6, the sludge reduction was remarkable even in the test for reducing the amount of activated sewage sludge using the mixed bacterial body liquid of the two types of myxobacteria, Myxococcus xanthus and Myxococcus fulbus. Thus, it has been proved that the present invention has a sufficient possibility of practical use.

[0035]

According to the present invention, as detailed above,
This is an invention from a completely different point of view from the prior art, and has the following operational effects. (1) To reduce the amount of waste sludge, sewage treatment or organic wastewater biological treatment, especially the large amount of excess sludge discharged from the biological oxidation treatment process, which is extremely difficult to treat, by almost half. Can be. (2) By adopting the present invention, the sludge treatment facility can be reduced and the treatment cost can be significantly reduced.

(3) Of the various types of sludge discharged from the biological treatment step, since the amount of surplus sludge which is most difficult to treat is reduced by half, sludge treatment as a total process, particularly dewatering, becomes extremely easy. (4) The amount of myxobacteria to be inoculated can be significantly reduced by the operation of circulating and returning a part of the separated sludge from the concentration step and the dehydration step to the sludge reduction tank. Bacterial inoculation can be omitted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a method and an apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Biological treatment tank 2 Excess sludge concentration tank 3 Sludge reduction tank 4 Excess sludge 5 Sludge return piping 7 Concentrator 8 Dehydrator 9 Excess water piping 10 Separation water 11 Biological treatment process 12 Mucus bacteria 13 Air 14 Concentration primary sludge 15 Concentration Coagulated sludge 16 Residual water piping 17 Separated water

Claims (4)

(57) [Claims] 1. A microorganism for surplus sludge characterized by inoculating surplus sludge discharged from a biological treatment step of sewage with a single strain or a plurality of strains of lytic bacteria having a bacteriolytic action, and allowing them to act under aerobic conditions. Biological weight loss method. 2. A reduction step of inoculating surplus sludge discharged from a biological treatment step of sewage with a single strain or a plurality of strains of myxobacteria having a bacteriolytic action, and acting under aerobic conditions.
A microbiological method of surplus sludge characterized by having a step of solid-liquid separation of the reduced sludge discharged from the reduction step, and circulating and returning a part of the separated sludge subjected to the solid-liquid separation to the reduction step. Weight loss method. 3. A weight-reducing step in which a surplus sludge discharged from a biological treatment step of sewage is inoculated with a single strain or a plurality of strains of myxobacteria having a bacteriolytic action and allowed to act under aerobic conditions;
It has a step of solid-liquid separation of the reduced sludge discharged from the weight reduction step, and circulates and returns a part of the separated sludge subjected to the solid-liquid separation to the weight reduction step, thereby leading the separated liquid to the biological treatment step. Characteristic method for microbiological reduction of excess sludge. 4. A sludge reduction tank having means for introducing an oxygen-containing gas, a solid-liquid separation device for solid-liquid separation of reduced sludge discharged from the sludge reduction tank, and a solid-liquid separated sludge. A means for guiding a part of the sludge to the sludge reduction tank, and a means for guiding the separated liquid to the biological treatment apparatus.