JPH0243558B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for anaerobic digestion of human waste. Conventionally, when human waste is subjected to anaerobic digestion, the digestion tank is divided into two tanks, each of which is retained for 15 days, for a total of 30 days. For this reason, anaerobic digestion treatment methods are disadvantageous in that they require higher construction costs than aerobic treatment methods. However, the anaerobic digestion method requires less electricity than other methods, and the amount of electricity required is 5000 ~ 5000 per ^1Nm3 .
Methane-containing digestion gas with a calorific value of 6000 Kcal is produced as a by-product and has the advantage of being able to be used effectively. For this reason, in recent years there has been a growing momentum to review anaerobic digestion processing methods. In this case, instead of conventional methods, methods such as a fluidized bed method, a high temperature fermentation method, a packed column method, a two-phase method, etc. that make the digestion reaction more efficient are being considered. The present invention relates to a two-phase system among the above. As is well known, the anaerobic digestion reaction consists of an acid generation phase in which high molecular weight organic matter passes through low molecular weight organic matter to generate volatile organic acids, and a methane generation phase in which volatile organic acids generated in the acid generation phase are converted into methane gas and carbon dioxide gas. It is a two-step reaction. The microorganisms involved in each phase are facultative anaerobes, and obligate anaerobic methanogens. The optimal environmental conditions for these bacteria are shown in Table 1.
It is different as follows.

[Table] The conventional method is to conduct these two-stage reactions with different optimal environmental conditions in the same tank under the same environmental conditions. For this reason, it was not necessarily efficient. The two-phase system corrects this drawback. The two-phase method is a method in which the acid production phase and the methane production phase are separated and independent, and the process is carried out efficiently under optimal environmental conditions. According to the two-phase system, the residence time is only about 10 days, and the amount of digested gas generated is about 20% higher. Although the two-phase method is an excellent method, some of the human waste undergoes acid fermentation while it remains in the toilet tank for one to two months, and the organic components of the liquid are volatile organic acids. is the main thing. Therefore, it is not necessary to pass the liquid portion of human waste through an acid production process, and it is unreasonable to pass the entire amount of human waste through an acid production process and a methane production process. The present invention is a method that improves this unreasonable point. That is, after separating human waste into solid matter and liquid, the liquid containing 500 to 2000 mg/volatile organic acid is passed through the acid production process and entered into the methane production process.
Approximately 2% of the solid content in human waste is put into the acid production process to be decomposed to volatile organic acids and then led to the methane production process, which is more efficient than the method of passing the entire amount through the acid production process and methane production process. good. Next, an embodiment of the present invention will be explained with reference to FIG. The human waste 9 is led to a solid-liquid separation device 1 such as a screen, a concentrator, a dehydrator, etc., and solid-liquid separation is performed. The solid content is put into an acid fermentation tank 3 after converting the high molecular weight organic matter into low molecular weight by a hydrolysis device 2 using any means such as acid, alkali, or heating. In this case, the acid treatment conditions include adding hydrochloric acid and setting the pH to 2 and stirring for about 1 hour, and the alkali treatment conditions include adding caustic soda and setting the pH to 12 and stirring for about 1 hour, and the heat treatment conditions include temperature Heating time is 30 at around 120℃.
Quantiles are preferred. In an acid fermenter, the gas generated in the tank is circulated, mixed, and brought into contact with facultative anaerobes to decompose it into volatile organic acids such as acetic acid and propionic acid. Next, the human waste liquid and the effluent from the acid fermentation tank are introduced into the methane fermentation tank 4, and the gas generated from the methane fermentation tank is circulated and mixed, and brought into contact with methane-producing bacteria to produce volatile organic acids. Converts into methane gas, carbon dioxide gas, etc. Digestion gas generated from the acid fermentation tank and the methane fermentation tank is stored in a gas holder 6 after hydrogen sulfide is removed by a desulfurization device 5. Digestion gas is about methane gas
Since it contains 60%, it can be used as fuel for the heating device 7 that heats the acid fermenter and methane fermenter.
The surplus can be effectively used as other fuel. On the other hand, the desorbed liquid from the methane fermentation tank has BOD and SS concentrations.
Since the amount is 1000 to 3000 mg/, it is usually treated in the activated sludge treatment device 8. In short, the present invention uses a two-phase method, which is more efficient than conventional anaerobic digestion methods, to separate human waste into liquid and solid content, and the liquid content is directly sent to the methane fermentation tank to solidify the waste. The aim is to reduce the tank capacity and increase the amount of digested gas generated by guiding the methane fermenter from the acid fermenter to the methane fermenter for treatment. In the above embodiments, the treatment of human waste has been described, but the present invention is also applicable to human waste wastewater in general.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet illustrating an embodiment of the human waste treatment method according to the present invention. 1: Solid-liquid separation device, 2: Hydrolysis device, 3: Acid fermentation tank, 4: Methane fermentation tank, 5: Desulfurization device, 6:
Gas holder, 7: Warming device, 8: Activated sludge treatment device, 9: Human waste.

Claims (1)

[Claims] 1 Separate human waste into solid matter and liquid, and the liquid is directly put into the methane production process for treatment.The solid matter is hydrolyzed by acid, alkali treatment, heat treatment, etc., and then introduced into the acid production process, followed by methane production. A human waste disposal method characterized by processing through a process.