JPS58150496A - Process for methane fermentation of waste liquid highly contg. nitrogen - Google Patents

Abstract

PURPOSE:To dilute a raw waste liquid for lowering the concentration of nitrogen, by subjecting the waste liquid highly contg. nitrogen to denitrification with circulating dilution, methane fermentation and digestion in order, and returning the part of a digested liquid as circulatory diluting water. CONSTITUTION:A raw waste liquid is mixed and agitated with the part of a digested liquid contg. NO2<-> and NO3<-> as circulatory diluting water, to perform dilution and denitrification. The diluted denitrified liquid is transferred to the step of methane fermentation, to mainly perform mesophilic fermentation. On this occasion, it is necessary to heat a fermenting tank with steam or the like. However, the amount of the steam for heating fermenting tank can be lowered, since the temp. of the digested liquid as diluting water is higher than that of industrial water. In order to suppress the formation of ammonia gas, the adjustment of pH is performed by HCl or the like. The treated liquid is further digested, and NH4<+> remaining in the treated liquid is converted into NO2<-> and NO3<->.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a methane fermentation treatment process for high nitrogen content waste liquids.

Anaerobic digestion, that is, reduction and stabilization of organic wastewater by methane fermentation, is generally effective for treating concentrated wastewater and sludge.

In meth/fermentation, most of the carbon dioxide and methane are dissipated, but some of the NH4-N in the effluent remains in the sludge in the form of alkaline stationary ammonium NH4-HCO5, and the methane is released into the sludge. Creates a slightly alkaline environment necessary for survival.

However, when nitrogen-containing waste liquids such as human waste, livestock feces, and fishery processing waste liquids are subjected to methane fermentation treatment, there are certain problems.

For example, if the image concentration in the fermenter is too high, fermentation is inhibited by NHs gas), and the high-load escape becomes 'Al&. In addition, it is important to remove a large amount of nitrogen from wastewater by meta/fermentation, and high f! If 11A-containing substances are released, it will promote g-nutrient enrichment in lakes and marshes.

This rounded high nitrogen-containing waste liquid must be denitrified before being fed to the pump to reduce its concentration.

Conventionally, raw waste liquid is converted into nitrogen by using P1 water for industrial cultivation.
A method of lowering the temperature by 11 degrees is known.

However, this method requires a large amount of industrial water, which results in a large amount of effluent water, which becomes insufficient if there is a limit to the amount of effluent water.

Other methods include biological oxidation current and ammonia slipping, but the former requires a large area, and the latter has drawbacks such as high equipment costs and running costs.

The purpose of the present invention is to provide an economically advantageous methane fermentation process that does not require industrial water or the like, especially in a methane fermentation process that includes a step of diluting raw waste liquid to lower the nitrogen concentration. As a result of intensive study, the inventors have completed the present invention.

That is, the present invention is to sequentially perform denitrification treatment, methane fermentation treatment, and digestion treatment on a high nitrogen-containing waste liquid using circulating dilution water, and return a portion of the digested treated liquid for use as the circulation dilution water. This is a method for methane fermentation of high nitrogen-containing waste liquid, which is characterized by the following: No separate dilution water is required, and the amount of effluent water can be reduced to the same level as the original waste liquid.
Denitrification and methane fermentation are effectively carried out.

Hereinafter, the present invention will be explained in detail based on the accompanying drawings.

The figure shows a flow sheet of 11 processes for methane fermentation of high nitrogen-containing wastewater of the present invention.

The raw waste liquid (flow rate Qs (ze/muy)) is digested as circulating dilution water and is treated as 9 NO! - and a portion of the treatment solution containing NOr (flow rate Qm (m''/m1)) is mixed and stirred to perform diluted denitrification treatment.

NOj and NOj in the dilution water are reduced and removed to N1 gas as shown in the following formula using the organic matter of the SM liquid as a hydrogen donor.

2NOs" + 3 (HJ→N1↑1201-+2H
Fable 0 (1) 2NOa-+5(Hl) → N, ↑+2ou
-+a) IIo (2) The amount of diluted water to be mixed with the raw waste liquid may be appropriately determined depending on the nitrogen concentration of the raw waste liquid so that the concentration can be treated by methane fermentation (approximately 2000 ppm or less). The volume of the denitrification treatment tank is such that the amount supplied to the treatment tank (Qs + Qs) can be perfused for 2 to 6 hours,
It is preferable that the NOx''-N load is 0.1 to 0.2 kl-N/ze·mu 18i degrees.

Next, the diluted and denitrified liquid is sent to a methane fermentation process, where it is mainly subjected to medium temperature generation.

At this time, it is necessary to heat the fermenter with steam, etc.
Since the temperature of the dilution water is higher in the digestion solution than in industrial water, the amount of steam used to heat the fermenter can be reduced.

Further, in order to suppress the generation of ammonia gas, it is recommended to adjust the pH to 4 (pH 8 or less) using H (J, etc.).

- After the treatment liquid is digested, the NH remaining in the treatment liquid is
4 becomes NOi and No,'' as shown in the following formula.

NH4" + "/2 false → NO, -+H, 0+2H"
(3) No1-1- /20m+ No=-(4)
Equation (3) above is for nitric acid digestion, and equation (4) is for nitric acid digestion, and both can achieve the purpose of the present invention, but the amount of oxygen that should be supplied to the nitrification process and the amount of oxygen that should be supplied to the denitrification process are Nitrite digestion is more economical because both amounts of hydrogen donors are smaller than in nitrite digestion and the rate of reduction by denitrifying carbon dioxide is faster.

A portion of the treatment liquid containing N01- and NOs'''' is returned to the dilution denitrification process as dilution water, as described above.

Regarding the actual treatment of high nitrogen-containing waste liquid according to the present invention,
Place 1! Although it is necessary to appropriately select the deterioration of the device, since it is not directly related to the essence of the present invention, the explanation will be omitted, and the effects of the present invention will be clarified by the following examples.

EXAMPLE A high nitrogen-containing waste liquid was treated with livestock manure according to the process shown in the figure. The processing conditions are as follows: 1) Dilution denitrification treatment process treatment tank volume so wl retention time
4 hours 2) Methane fermentation treatment process Fermentation tank volume 3700 - medium temperature fermentation approximately 37°C 3) Digestion treatment process Treatment tank volume 1800 ℃) The obtained results are shown in the following table along with the properties of the raw waste liquid.

From this, it can be seen that since the present invention does not charge dilution water separately, the amount of discharged water can be reduced to about 4 times the amount of raw waste liquid, and dilution can be effectively carried out, which is very advantageous in terms of cost. It became clear. Further, even after continuous operation for 150 days, fermentation was not inhibited by ammonia gas.

[Brief explanation of drawings]

The figure is a 70-sheet of the methane fermentation treatment process of nitrogen-containing waste liquid for the present invention. %lFFSumitomo Heavy Industries Empirotic Co., Ltd.

Claims (1)

[Claims] 1. High nitrogen content waste liquid is denitrified by circulating dilution111
A methane fermentation treatment process for high nitrogen-containing waste liquid, characterized in that methane fermentation treatment and digestion treatment are performed sequentially, and a portion of the digested treated liquid is returned and used as the circulation dilution water.