JPS596991A - Disposal of flithy water - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This invention relates to an improvement in a wastewater treatment method using anaerobic bacteria.

A conventional method for treating sewage or sludge (herein referred to as sewage) using anaerobic bacteria is as shown in FIG.
Sewage is introduced into the tank from step 3, and the anaerobic bacteria previously introduced into the tank decomposes organic matter in the wastewater and generates gas, and the treated liquid, that is, the desorbed liquid, is discharged from the draw pipe 14. The generated gas is sent to a gas holder from a gas discharge pipe 15, and the digested sludge is pulled out from a digested sludge drawing pipe 16 at the bottom of the tank.

When using this conventional method, the anaerobic bacteria in the tank 11 tend to flow out of the tank from the outflow pipe 14 together with the desorbed liquid, so there is a limit to increasing the concentration of anaerobic bacteria in the tank 1. As a result, the rate of decomposition of organic matter within the 11 was also limited, and as a result, it could only be used for the purpose of treating highly concentrated wastewater such as human waste over a long period of time.

The present invention aims to provide a wastewater treatment method that increases the concentration of anaerobic bacteria in the digestion tank and increases the treatment rate per volume.In the wastewater treatment method using anaerobic bacteria, fly ash is is introduced into the digestion tank to kill anaerobic bacteria, sewage is sent from the bottom of the digestion tank to create an upper surface flow in the tank, and the desorption liquid is drawn out through a desorption liquid withdrawal pipe provided at the upper part of the side wall of the digestion tank. The present invention relates to a wastewater treatment method for suppressing the outflow of anaerobic bacteria from the tank.

The invention will now be described in detail with reference to embodiments shown in the accompanying drawings. FIG. 2 schematically shows the structure and embodiment of a digester suitable for carrying out the present invention. A sewage supply pipe 2 is provided at the bottom of the digestion tank 1, and a desorbed liquid drawing pipe 4 is provided at the top of the side wall 3 of the digestion tank. Further, a digested sludge drawing pipe 5 is provided at the lower part of the side wall 30 so that the digested sludge can be pulled out without pulling out the fly ash put into the tank as much as possible.

A fly ash input lower is provided on the ceiling 6 of the digestion tank 1, and an agitator 9 equipped with stirring blades 8 is provided in the center of the ceiling to agitate the fly ash settling at the bottom of the tank and supply sewage from the bottom of the tank. This is done in such a way that it rides on the upward flow generated by the The gas generated in the tank is led to a tank (not shown) through a gas discharge pipe 10.

Sewage is pumped into the digester with this structure through the sewage supply pipe 2 at the bottom, and fly ash is introduced into the tank from the fly ash input lower. The fly ash adheres to the inside of the tank and settles in the tank.The fly ash is stirred by the stirring blade 8 of the stirrer 9 and floats in the tank, and the sedimentation is repeated to concentrate the anaerobic bacteria in the tank and remove the desorbed liquid. Since the outflow of anaerobic bacteria from the drawn pipe 4 is suppressed, the volume of the tank can be reduced or the processing capacity per unit volume can be increased.

In order to prevent the fly ash from settling at the bottom of the tank, it is stirred by stirring blades 8, and the sewage is raised and floated by the upward flow of the sewage sent into the tank from the sewage supply pipe 2 at the bottom of the tank. As with the conventional method, there is a risk of short-circuiting and flowing out of the tank before it is digested, but in this method, when wastewater is supplied from the bottom of the tank and repeatedly floated up and down inside the tank, the above-mentioned There is no need to worry about water leaking out without sufficient digestion.

The effects of the method of the present invention can be numerically illustrated using experimental examples as follows.

Table 1 shows the results of measuring the effect of fly ash input on the activated sludge sedimentation rate (SV30) and the suspended solids (SS) of the liquid in the digester in a laboratory scale digester. Ta. EM is the sewage test method (197
The method described in the 4th edition, published by the Japan Sewage Works Association) was used. In addition, the evaporation residue (TS
) and loss on ignition (VTS) are TSL for sample 1.
, 06%, VTSo, Section 52, TSl for sample 2
, 62, VTS O, 79%.

Table 1 From Table 1, the addition of fly ash is effective in concentrating the sludge and therefore anaerobic bacteria in the filter and digester, and also reducing the amount of suspended matter in the desorbed liquid, thus suppressing the outflow of anaerobic bacteria. I understand that.

Furthermore, an experimental example in which the method of the present invention is applied to dilute wastewater such as sewage is shown below. Biochemical oxygen demand: l: (Bo
D) t6omg/, of artificial sewage in addition to digested sludge1
Continuously flowed into a 12 volume digester containing 80g of fly ash, water temperature 22-28℃, residence time 2.4
When treated for ~2.8hr, BOD17~43mg
/ of effluent water can be obtained, and the method of the present invention has made it possible to digest sewage using anaerobic bacteria, which has been considered difficult in the past.

As explained above, by putting fly ash into the anaerobic digestion tank, the anaerobic bacteria in the tank are concentrated, and
Since the outflow can be suppressed and the concentration of anaerobic bacteria can be increased, the reaction rate per unit response volume of the digester can be increased. It can now be applied to the treatment of dilute wastewater such as sewage, which previously could not be treated, or the reaction rate will be faster, making it possible to downsize the equipment used to treat human waste and sewage sludge. The particle size of the fly ash used is 200μ! It is preferable to set the temperature to η or less; if the particle size becomes large, it tends to settle at the bottom of the tank and create a dead space, so it is not preferable.

It also has the secondary effect of expanding the effective uses of fly ash generated from coal-fired boilers and helping to solve processing problems, so its practical effects are extremely significant.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet centered on a digestion tank for explaining a conventional treatment method, and FIG. 2 is a longitudinal sectional view schematically showing an embodiment of the method of the present invention. ■...Digestion tank, 2...Sewage supply pipe, 3...Side wall,
4... Desorption liquid drawing pipe, 5... Digested sludge drawing pipe, 6...
...Tank ceiling, 7...Fly ash inlet, 8...
Stirring blade, 9... Stirrer, 10... Gas discharge pipe.

Claims (1)

[Claims] In the wastewater treatment method using anaerobic bacteria, fly ash is poured into the digester from the top of the tank to attach anaerobic bacteria, and the sewage is sent from the bottom of the tank and upward into the tank. A sewage treatment method for suppressing anaerobic bacteria from flowing out of the tank, characterized by generating a flow and drawing the desorbed liquid from a desorbed liquid drawing pipe provided at the upper part of the side wall of the digestion tank.