JPS632679B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for decolorizing and purifying human waste, in which activated sludge treated water obtained from microbial treatment of human waste is decolorized and purified by ozone oxidation.

Conventionally, human waste has been treated with a combination of anaerobic microbial treatment called digestion and aerobic microbial treatment called activated sludge, or directly treated with activated sludge, and then discharged as a precipitated supernatant. This biological treatment alone could not remove the brownish-brown bile oxides and humic compounds that are unique to human waste, and the colored substance was released into rivers and the sea.However, from the perspective of environmental conservation and water reuse, In recent years, coagulation treatment, ozone treatment, etc. have been added after biological treatment to further purify the treated effluent.

Ozone is a gas with strong oxidizing power that can be continuously generated using only electricity from air as a raw material, and it not only decolorizes and deodorizes wastewater and oxidizes pollutants, but also sterilizes pathogenic bacteria and inactivates viruses. Let's do it.
In addition, unlike chlorine, it can be easily generated in the required amount by changing the discharge voltage or discharge frequency of an ozone generator without having to handle and store it in a high-pressure container, making it an indispensable device for human waste treatment equipment. It's summery. Generally, a flocculant is added to biologically treated water of human waste, suspended matter is removed by pressure flotation or coagulation sedimentation, and the treated water is brought into contact with ozone-containing gas to decolorize, deodorize, and
COD and BOD levels are also reduced, and the water is discharged as colorless treated water.

Human excrement, human waste, has relatively constant chemical properties, and even with activated sludge treatment, it is possible to operate more stably than urban sewage, which is contaminated with toxic substances such as industrial wastewater. However, since human waste is manually collected and processed, the processing load for the activated sludge method fluctuates greatly, often on weekends, at the end of the month, and at the end of the year. Conversely, in periods other than this, the amount of treatment is small and aeration is continued while the BOD load of the activated sludge is low, resulting in an over-aerated state and an abnormal increase in nitrite ion concentration. This increase in nitrite ions will not be a problem in the next coagulation process, but when performing ozone decolorization purification, nitrite ions react preferentially with ozone, so the speed of decolorization decreases significantly, and complete decolorization is This is done after the ions are gone. Therefore, during overaeration when the amount of human waste to be processed is small, a situation occurs in which almost no decolorization is possible with the normally required amount of ozone injection.

The present invention has been made in order to eliminate the drawbacks of the conventional methods described above, and an object of the present invention is to provide a method for decolorizing and purifying human waste that can eliminate the abnormal generation of nitrite ions and perform the most efficient ozone treatment. With the goal.

In other words, regarding the method of decolorizing and purifying treated human waste water using ozone, measures must be taken to avoid producing over-aerated treated water that abnormally contains nitrite ions from the front aeration tank, such as reducing the amount of aeration air and reducing the amount of returned sludge. Adjust operating operations to keep the dissolved oxygen concentration at the aeration tank outlet below 2ppm, and avoid over-aerated conditions.
The sludge separated in the settling tank is sufficiently aerated in the re-aeration tank to be aerobically activated, and then used as return sludge in the activated sludge aeration tank for continuous, stable ozone decolorization and purification.

Embodiments of the present invention will be described below with reference to the drawings. Human waste desorbed liquid A undergoing activated sludge treatment is mixed with diluted water B such as river water, groundwater, or seawater in a mixing tank 1 and activated return sludge C sent from an aeration tank 13.
The activated sludge is mixed with the activated sludge aeration tank (hereinafter referred to as aeration tank) 2, where it is aerated with air sent from the blower 3 to the left and injected from the differential user 4. The treated water treated with aerobic microorganisms is sent to a sedimentation tank 5 where sludge is separated by sedimentation, suspended matter E is removed by the next coagulation sedimentation device or pressurized flotation device 6, and the water enters an ozone reaction tower 7. The water is decolorized and purified by contact with the ozonized gas injected from the ozone generator 8 through the differential user 9, and is discharged as treated water F.
The exhaust gas G containing a trace amount of unreacted ozone passes through the ozone decomposition unit 10, becomes harmless, and is released into the atmosphere.

In order to obtain treated water with less nitrite ions, the dissolved oxygen concentration is monitored using a dissolved oxygen detector 11 and a dissolved oxygen meter 12 placed near the outlet of the aeration tank 2 for activated sludge treatment, and based on this dissolved oxygen concentration, The amount of return sludge C sent from the re-aeration tank 13 to the mixing tank 1 can be adjusted by adjusting the amount of air fed from the blower 3 or by adjusting the excess sludge withdrawal valve 14 through the sludge withdrawal valve regulator 15. .

In other words, as is known as the principle of the activated sludge biosorption method, BOD components are adsorbed by microbial cells during the initial contact between the returned sludge C and the urine desorbed fluid A. After that, the COD in the water only gradually decreases as the BOD components inside the bacteria are digested. In addition, unless the aeration air volume and sludge concentration are adjusted, nitrite ions in the aeration tank 2 will be generated from a dissolved oxygen concentration of about 1 PPm, and will accumulate at such a high concentration that it will interfere with the subsequent ozone decolorization and purification. For this reason, BOD is greatly reduced, and if sludge is separated before nitrite ions are generated, relatively treated water can be obtained.

In this example, in activated sludge treatment, the aeration air volume is adjusted so that the point at which BOD is removed and nitrite ions begin to increase is aligned with the outlet of the aeration tank 2.
The amount of ozone is adjusted to maintain the dissolved oxygen concentration at the outlet of the aeration tank 2 at a maximum of 2.0 ppm or less, preferably about 1.0 ppm, so that maximum ozone decolorization and purification can be achieved with the minimum amount of ozone consumption.

If long-term operation is performed with the dissolved oxygen concentration low in this way, the sedimentation properties of the sludge will deteriorate and a large amount of suspended matter will come out of the sedimentation tank 5, but as shown in the figure, generally the sludge will be flocculated or precipitated in the stage before ozone decolorization. Since pressure flotation is performed, the amount of sludge discharged from here increases somewhat, but there is no problem if the amount of excess sludge H to be drawn out is reduced.

However, if the sludge is operated for a long time with a low dissolved oxygen concentration, the overall activity of the sludge decreases, and the sludge tends to become anaerobic and its properties change. Therefore, if the sludge sedimented and separated in the sedimentation tank 5 is sufficiently aerated in the re-aeration tank 13 to completely digest the BOD components incorporated into the microorganisms, there will be no difference from the general activated sludge method. In the figure, air is sent to the reaeration tank 13 through a reaeration tank blower 16 and a reaeration tank diffuser 17. Furthermore, this reaeration tank 13
No matter how many nitrite ions and nitrate ions are generated, so-called denitrification will occur in the initial state when they are mixed with human waste desorbed liquid A in the aeration tank 2, and the effect of nitrogen removal will appear as a whole. Furthermore, if excess sludge H is removed from the reaerated sludge, sludge with better dewatering properties than usual can be obtained.

The present invention is not limited to this embodiment, and may be operated manually if the load fluctuation is small. Furthermore, instead of using a dissolved oxygen meter, aeration can be performed using a nitrite ion electrode or manual analysis to detect nitrite ions. It goes without saying that the air volume or the amount of returned sludge may be adjusted.

As explained above, the present invention enables optimal operation of ozone decolorization purification by adding a reaeration tank and adjusting the aeration air volume or the amount of returned sludge in the existing activated sludge aeration tank.

[Brief explanation of the drawing]

The figure is a system diagram showing one embodiment of the present invention. 2...Activated sludge aeration tank, 7...Ozone reaction tower, 8...
Ozone acid generator, 11... Dissolved oxygen detector, 12... Dissolved oxygen meter, 13... Re-aeration tank, A... Human waste desorbed liquid, C
... Returned sludge, E... Suspended matter.

Claims (1)

[Claims] 1. In the case where activated sludge treated water is decolorized with ozonized gas after removing suspended matter, the aeration air volume of the activated sludge aeration tank is lowered or the amount of returned sludge is reduced, and the outlet of the activated sludge aeration tank is In addition to obtaining activated sludge treated water with a dissolved oxygen concentration of 2.0 ppm or less, the sedimented and separated sludge is re-aerated in a re-aeration tank to make it sufficiently aerobic, and then returned as return sludge from the activated sludge aeration tank. A distinctive method for decolorizing and purifying human waste.