JP2001029997A - Treating equipment for organic waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both of the dewaterability of digested sludge and the degradability of organic materials by digesting organic waste in a methane fermentation tank, concentrating the sludge, which is drawn from the methane fermentation tank, in a concentrator, and returning a part of the sludge concentrated with the concentrator to the methane fermentation tank. SOLUTION: An organic waste to be treated is fed to the methane fermentation tank 1 to be subjected to a digestion treatment, and the digested sludge is fed to a concentrator 3 through a sludge tank 2 to be concentrated. A part of the concentrated sludge is returned to the methane fermentation tank 1, and the remainder is subjected to a dewatering treatment in a dehydrator 4. The dehydrated cake of a low moisture content, obtained from the dehydrator 4, is recycled in the form of compost or the like, and the separated liquid after the concentration, obtained from the concentrator 3, and the separated liquid after the dehydration, obtained from the dehydrator 4 are discharged out of a system to be subjected to a water treatment separately. As a result, the return of methane bacteria to the methane fermentation tank can improve the degradability of organic materials in the methane fermentation tank, and the lengthened retention time of solid substances can improve the degradability of solid organic materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for treating organic waste, and more particularly to an organic waste such as human waste, livestock manure, septic tank sludge, garbage, excess sludge, primary sludge, food waste and the like. An apparatus for digesting and concentrating and dewatering digested sludge,
The present invention relates to an organic waste treatment apparatus in which digested sludge has improved dehydration and organic matter decomposability.

[0002]

2. Description of the Related Art Conventionally, organic waste such as night soil, livestock manure, septic tank sludge, garbage, surplus sludge, primary settled sludge, food waste, and the like are separated into apparatuses as shown in FIGS. 2 (a) and 2 (b). Has been processed.

In the apparatus shown in FIG. 2A, first, organic waste is charged into a methane fermentation tank 1 for digestion. If necessary, a coagulation aid is added to the digested sludge drawn from the methane fermentation tank 1 to the sludge tank 2, and preconcentration is performed by the concentrator 3. As the concentrating device 3, a gravity belt filter, a screen, a centrifugal concentrator, or the like can be used. The concentrated sludge is further subjected to a dehydration treatment by a dehydration device 4 after adding a coagulation aid as necessary.

As described above, by providing the concentrating device 3 and the dewatering device 4 and dewatering the digested sludge in two stages, a dewatered cake having a low water content of about 75% can be obtained. The dehydrated cake having a low water content from the dehydration device 4 is recycled in the form of compost or the like. The concentrated separated liquid of the concentrating device 3 and the dehydrated separated liquid of the dehydrating device 4 are separately treated with water.

In the apparatus shown in FIG. 2 (b), first, organic waste is put into a methane fermentation tank 1 for digestion treatment, and a part of digested sludge extracted from the methane fermentation tank 1 to a sludge tank 2 is required. The coagulation aid is added accordingly and the mixture is concentrated by the concentration device 3. As the concentrator 3, a gravity belt filter, a screen, a centrifugal concentrator, or the like can be used.
The sludge of about 7% is concentrated to a solid concentration of about 8 to 12%. This concentrated sludge is returned to the methane fermentation tank 1. . By returning the concentrated sludge to the methane fermentation tank 1 in this way, methane bacteria can be returned to the methane fermentation tank 1,
Organic matter decomposability in the methane fermenter 1 can be improved. In addition, since the residence time of the solid can be lengthened, the decomposability of the solid organic substance can be improved. On the other hand, the remainder of the digested sludge in the sludge tank 2 is added with a coagulation aid as needed, and then dewatered by the dewatering device 4 to obtain a dewatered cake. The concentrated separated liquid of the concentrating device 3 and the dehydrated separated liquid of the dehydrating device 4 are separately treated with water.

[0006]

In the treatment apparatus shown in FIG. 2 (a), the sludge is treated in consideration of the improvement of the dewatering property of the digested sludge.
Although staged dewatering is employed, no consideration is given to improving the organic matter decomposition characteristics in the methane fermentation tank. For this reason, organic matter decomposability is 30% like excess sludge of activated sludge.
For example, when methane fermentation treatment is applied to organic waste having a low degree, about 70% of organic matter has a drawback that it is extracted without being decomposed.

In the treatment apparatus shown in FIG. 2B, the digested sludge is drawn out, concentrated and returned in consideration of the improvement of the organic matter decomposition characteristics in the methane fermentation tank. Since no particular consideration is given to the improvement, there is a disadvantage that the water content of the obtained dehydrated cake is relatively high.

The present invention solves the above-mentioned conventional problems, and in an apparatus for digesting organic waste and dewatering digested sludge, an organic material capable of improving both the dehydrating property of digested sludge and the decomposability of organic substances. It is an object of the present invention to provide a wastewater treatment device.

[0009]

SUMMARY OF THE INVENTION An organic waste treatment apparatus according to the present invention comprises: a methane fermentation tank for digesting organic waste; a concentrator for condensing sludge drawn from the methane fermentation tank; An organic waste treatment device having a dewatering device for dewatering the sludge concentrated by the concentrating device, comprising a return means for returning a part of the sludge concentrated by the concentrating device to the methane fermentation tank. Features.

According to the present invention, the two-stage dewatering of the sludge and the return of the concentrated sludge to the methane fermentation tank can simultaneously improve the dewaterability of the digested sludge and the organic matter decomposability.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of an organic waste treatment apparatus according to the present invention.

In the present invention, human waste to be treated,
Livestock manure, septic tank sludge, garbage, surplus sludge, first settling sludge,
First, methane fermentation tank 1
For digestion. The digestion treatment conditions are preferably a temperature of 35 to 40 ° C. and a residence time of about 15 to 30 days for medium temperature methane fermentation, and 50 to 6 days for high temperature methane fermentation.
The residence time at 0 ° C. is preferably about 7 to 15 days.

The digested sludge passes through the sludge tank 2 and is concentrated in the concentration device 3. In this concentration, if necessary, a cationic polymer flocculant such as dimethylaminoethyl acrylate or dimethylaminoethyl methacrylate may be used. About 0.3 to 1.0% (based on dry solids) may be added.

As the concentrating device 3, a gravity belt filter, a screen, a centrifugal concentrator, or the like can be used.
Concentrate to ~ 12%. A part of the concentrated sludge is returned to the methane fermentation tank 1, and the remaining part is dewatered by a dehydrator 4. Here, if the ratio of the concentrated sludge returned to the methane fermentation tank 1 is excessively small, the effect of improving the organic matter decomposability by returning the sludge cannot be sufficiently obtained. For this reason, the amount of sludge returned to the methane fermentation tank 1 among the concentrated sludges is preferably 30 to 80%, particularly preferably 50 to 60%.

As the dewatering device 4 for dewatering the remaining portion of the concentrated sludge, a centrifugal separator, a belt press dehydrator, a screw press dehydrator, or the like can be used, and the concentrated sludge is further dewatered by the dehydration device 4. The water is dehydrated into a dehydrated cake having a low water content of about 72 to 75%.

In the dewatering of the concentrated sludge, if necessary, a cationic polymer flocculant, for example, a flocculant such as dimethylaminoethyl acrylate or dimethylaminoethyl methacrylate, may be used in an amount of 1.0 to 1.5%. (Based on dry solids) may be added.

The dewatered cake having a low water content obtained from the dewatering device 4 is recycled in the form of compost or the like.

On the other hand, the concentrated separated liquid obtained from the concentrating device 3 and the dehydrated separated liquid obtained from the dehydrating device 4 are discharged out of the system and separately subjected to water treatment.

In the present invention, by returning a part of the concentrated sludge to the methane fermentation tank 1 as described above, it is possible to return the methane bacteria to the methane fermentation tank 1 to improve the organic matter decomposability in the methane fermentation tank 1. Also, by increasing the residence time of the solid, the decomposability of the solid organic substance can be improved. In addition, since the digested sludge is dehydrated in two stages, a dewatered cake having a low moisture content is obtained.

[0021]

The present invention will be described more specifically below with reference to examples and comparative examples.

The properties of the organic waste (excess sludge for concentrated human waste treatment) treated in the following Examples and Comparative Examples are as follows.

[Properties of Organic Waste] TS: 30000 mg / L SS: 22000 mg / L Example 1 The apparatus of the present invention shown in FIG.
Treated at m ³ / day.

First, the organic waste is supplied to the methane fermenter 1
At 40 ° C. for a residence time of 20 days, and the digested sludge was fed to the concentration device 3 via the sludge tank 2. A centrifugal separator was used as the concentrator 3 to concentrate digested sludge having a solid concentration of 2% to a solid concentration of 4%.

A part of the concentrated sludge was returned to the methane fermentation tank 1 by 60%, and the remaining part was dehydrated by the dehydrator 4. A screw press dehydrator was used as the dehydrator 4.

The decomposition rate of SS by methane fermentation and the water content of the dehydrated cake were as shown in Table 1. In addition, in concentrating, a cationic polymer coagulant, Crifix CP984 (Kurita Kogyo Co., Ltd.) was added as a coagulating aid in an amount of 0.5% (based on dry solids). Crifix CP984 (Kurita Kogyo Co., Ltd.) as a coagulation aid
% (Vs. dry solids).

Comparative Example 1 Organic waste was treated with the conventional apparatus shown in FIG. 2 (a). The processing conditions of the methane fermentation tank 1, the equipment used as the concentrating device 3 and the dehydrating device 4, the processing conditions, and the addition conditions of the coagulation aid were the same as in Example 1.

The decomposition rate of SS by methane fermentation and the water content of the dehydrated cake were as shown in Table 1.

Comparative Example 2 Organic waste was treated with the conventional apparatus shown in FIG. 2 (b). The processing conditions of the methane fermentation tank 1, except that 60% of the digested sludge in the sludge tank 2 was fed to the concentrator 3 and the remainder was fed to the dehydrator 4, were used as the concentrator 3 and dehydrator 4. The equipment, processing conditions, and addition conditions of the coagulation aid were the same as in Example 1.

The decomposition rate of SS by methane fermentation and the water content of the dehydrated cake were as shown in Table 1.

[0031]

[Table 1]

As is evident from Table 1, the organic waste treatment apparatus of the present invention can provide a dewatered cake having a low water content because of its good organic matter decomposition efficiency and dewatering efficiency of digested sludge. The amount of dewatered cake discharged is also small.

[0033]

As described above in detail, according to the apparatus for treating organic waste of the present invention, when the organic waste is digested and the digested sludge is dehydrated, the dewaterability of the digested sludge and the organic matter are reduced. Degradability can be improved together, and efficient processing can be performed.

The organic waste treatment apparatus of the present invention can be easily realized simply by adding a line for returning the concentrated sludge to the methane fermentation tank from the existing apparatus of the enrichment apparatus, and is extremely industrially possible. It is advantageous.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of an organic waste treatment apparatus of the present invention.

FIG. 2 is a system diagram showing an embodiment of a conventional organic waste treatment apparatus.

[Explanation of symbols]

 1 Methane fermentation tank 2 Sludge tank 3 Concentrator 4 Dehydrator

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Claims (1)

[Claims] 1. An organic apparatus comprising: a methane fermenter for digesting organic waste; a concentrator for concentrating sludge drawn from the methane fermenter; and a dehydrator for dewatering the sludge concentrated by the concentrator. An apparatus for treating organic waste, comprising: a return means for returning a part of the sludge concentrated by the concentrator to the methane fermentation tank.