JP2001129600A - Fermented sludge treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fermented sludge treatment method recovering energy in methane fermentation, suppressing the use amount of a polymer at a time of dehydration and capable of ensuring heat necessary for primary fermentation in composting. SOLUTION: Easily decomposable organic waste 1 such as garbage or livestock excretion is subjected to methane fermentation treatment in a membrane type methane fermentation tank 3 and the methane gas generated in the membrane type methane fermentation tank 3 is recovered as fuel and the membrane separation liquid and excessive methane fermentation sludge taken out of the membrane type methane fermentation tank 3 are subjected to biological nitrifying and denitrifying treatment along with highly concentrated organic waste 6 such as excretion or septic tank sludge in a water treatment process 8 and the excessive sludge 11 taken out of the water treatment process 8 is dehydrated and a dehydrated cake 14 is composted 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating fermented sludge using raw garbage, livestock manure and the like as raw materials.

[0002]

2. Description of the Related Art Conventionally, there is a methane fermentation treatment method as a method for treating garbage, livestock manure, and the like. Methane fermentation sludge generated by methane fermentation treatment is composted after dehydration treatment, or is stored and subjected to liquid fertilization. By using it as a treatment.

[0003]

In the above-described configuration, the methane fermentation sludge contains most of the biologically degradable organic substances already consumed by microbial degradation, and the primary methane fermented sludge that is usually seen when composting is used. Fermentation (a vigorous reaction with heat generation) did not occur, and it was necessary to constantly apply a large amount of heat from the outside.

[0004] The water content of the dewatered cake of methane fermented sludge is 7
5 to 85%, 70% water content before putting into fermenter
It is necessary to adjust the moisture to a certain degree. However, since methane fermentation sludge has high alkalinity, a large amount of polymer is required as a coagulant during dehydration. The present invention solves the above-described problems, and provides a fermentation sludge treatment method capable of recovering energy in methane fermentation, suppressing the amount of polymer used during dehydration, and securing the calorie required for primary fermentation in composting. The purpose is to do.

[0005]

In order to solve the above-mentioned problems, a method for treating fermented sludge according to the present invention uses a methane fermentation treatment system to convert easily decomposable organic wastes such as garbage and livestock manure into a membrane type. Methane fermentation treatment in the methane fermentation tank, recovers methane gas generated in the membrane methane fermentation tank as fuel, and supplies the membrane separation liquid and excess methane fermentation sludge taken out from the membrane methane fermentation tank to the water treatment system, and water treatment In the system, the membrane separation liquid, excess methane fermentation sludge is subjected to biological nitrification and denitrification in a water treatment process together with high-concentration organic waste such as human waste and septic tank sludge, and the excess sludge taken out of the water treatment process is dewatered. And to compost the dehydrated cake.

In the above-mentioned configuration, in the membrane type methane fermenter, only the easily decomposable organic waste such as garbage and livestock manure is subjected to the methane fermentation treatment, so that the fermentation period is shortened and the methane fermenter is greatly enlarged. It can be downsized,
The amount of methane gas recovered as fuel increases, and the efficiency of energy recovery increases. Methane fermentation in a membrane-type methane fermentation tank may be performed by any of mesophilic bacteria and thermophilic bacteria,
The membrane used is an immersion flat membrane, a rotating flat membrane, a tubular membrane, or the like.

On the other hand, high-concentration organic wastes, such as night soil and septic tank sludge, having low methane fermentation efficiency are treated in a water treatment system. In this water treatment process, the alkalinity of the methane fermentation sludge is consumed in the nitrification reaction process by subjecting the membrane separation liquid and excess methane fermentation sludge taken out of the methane fermentation tank to biological nitrification denitrification together with human waste and septic tank sludge. And
Insufficiency in alkalinity in the nitrification reaction process can be prevented, and anaerobicity can be easily maintained in the denitrification process by feeding digested sludge (methane fermentation sludge), so that denitrification can be performed smoothly.

[0008] By consuming alkalinity, it is possible to reduce the amount of polymer consumed when dewatering excess sludge. Since the tank capacity in the water treatment process is determined by the nitrogen load, it is not necessary to increase the BOD load even if the membrane separation liquid and the excess methane fermentation sludge increase the BOD load. Surplus sludge extracted from the water treatment process of biological nitrification and denitrification of methane fermentation sludge, night soil, and septic tank sludge simultaneously has a lower calorific value than methane fermentation sludge.
Primary fermentation easily occurs in composting, and less external heating is required. For this composting, a mechanical stirring type high-speed composting device or the like is used. Part of the surplus sludge is fed into the membrane methane fermentation tank.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, in the methane fermentation treatment system, easily decomposable organic waste 1 such as garbage and livestock manure is treated in the pretreatment step 2 and then methane fermentation treatment is performed in the membrane methane fermentation tank 3. The membrane type methane fermentation tank 3 has a membrane separation device (not shown), and the membrane to be used is an immersion type flat membrane, a rotary flat membrane, a tubular membrane, or the like. The methane fermentation in the membrane type methane fermentation tank 3 may be performed by any of mesophilic bacteria and thermophilic bacteria. Energy recovery 5 is performed using methane gas 4 generated in the membrane methane fermenter 3 as fuel.

[0010] As described above, in the membrane type methane fermentation tank 3, only the easily decomposable organic waste such as garbage and livestock manure is subjected to methane fermentation, so that the fermentation period is shortened and the membrane type methane fermentation tank 3 is reduced. Can be significantly reduced in size, the amount of methane gas recovered as fuel increases, and the efficiency of energy recovery increases. The membrane separation liquid and excess methane fermentation sludge taken out from the membrane type methane fermentation tank 3 are supplied to a water treatment system for treating high-concentration organic waste such as human waste and septic tank sludge.

On the other hand, in the water treatment system, high-concentration organic wastes 6 such as human waste and septic tank sludge, which have poor methane fermentation efficiency, are pretreated in a pretreatment step 7 together with a membrane separation liquid and excess methane fermentation sludge. In the water treatment process 8, biological nitrification and denitrification treatment is performed. In this way, by subjecting the membrane separation liquid and excess methane fermentation sludge taken out from the membrane type methane fermentation tank 3 to biological nitrification denitrification treatment together with human waste and septic tank sludge, the alkalinity of the methane fermentation sludge is reduced in the nitrification reaction process. It can be consumed and prevent alkalinity shortage in the nitrification reaction process. In addition, by introducing digested sludge (methane fermented sludge), anaerobic can be easily maintained in the denitrification process, and the denitrification treatment can be performed smoothly. Since the tank capacity in this water treatment process 8 is determined by the nitrogen load, it is not necessary to increase the BOD load even if the membrane separation liquid and the excess methane fermentation sludge increase the BOD load.

The secondary treatment water 9 taken out of the water treatment process 8 is subjected to an advanced treatment 10 and then discharged or used for diluting an inhibitor of membrane methane fermentation. A part of the surplus sludge 11 taken out from the water treatment process 8 is put into the membrane type methane fermentation tank 3, and the rest is dewatered in a dewatering step 12. The dewatered filtrate 13 is separately treated, and the dewatered cake 14 is composted 15 by a mechanical stirring type high-speed composting device or the like.

The excess sludge 11 extracted from the water treatment process 8 for simultaneously biologically nitrifying and denitrifying the methane fermented sludge, night soil and septic tank sludge has a lower heating value than the methane fermented sludge. Primary fermentation is more likely to occur and less external heating is required.

[0014]

As described above, according to the present invention, the membrane separation liquid and excess methane fermentation sludge taken out of the methane fermentation tank are subjected to biological nitrification and denitrification together with human waste and septic tank sludge in a water treatment process. As a result, the alkalinity of the methane fermentation sludge can be consumed in the nitrification reaction process, the lack of alkalinity in the nitrification reaction process can be prevented, and the digestion sludge (methane fermentation sludge) can be introduced to facilitate the anaerobicity of the denitrification process. Nitrogen treatment can be performed smoothly, and consumption of polymer during dehydration can be reduced due to consumption of alkalinity. Excess sludge removed from the water treatment process has a lower calorific value than methane fermentation sludge, so that primary fermentation is likely to occur in composting and less external heating is required.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a fermentation sludge treatment method according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 easily decomposable organic waste 3 membrane methane fermenter 6 high concentration organic waste 8 water treatment process 11 excess sludge 12 dehydration step 15 composting

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C05F 7/00 C05F 9/00 9/00 17/00 17/00 B09B 3/00 CD (72) Inventor Toshiyuki Shibata 4F004 AA02 AA03 BA03 BA04 CA18 CA19 CB44 4D040 BB22 BB52 4D059 AA01 AA02 AA05 AA07 BA01 BA12 BA21 BA48 BE00 BE42 BE49 CA22 CA28 CC01 4H061 AA02 CC36 CC39 CC51 CC55 GG35 GG50 GG55 GG70

Claims (1)

[Claims] In a methane fermentation treatment system, easily decomposable organic wastes such as garbage and livestock manure are subjected to methane fermentation in a membrane methane fermentation tank, and methane gas generated in the membrane methane fermentation tank is used as fuel. The collected and separated methane fermentation sludge and excess methane fermentation sludge taken out from the membrane methane fermentation tank are supplied to a water treatment system.In the water treatment system, the membrane separation liquid and excess methane fermentation sludge are converted to high concentration of human waste, septic tank sludge, etc. A method for treating fermented sludge, comprising biologically nitrifying and denitrifying in a water treatment process together with organic waste, dehydrating excess sludge taken out from the water treatment process, and composting a dewatered cake.