JPS648600B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for aerobic biological treatment of wastewater.

Prior to aerobic biological treatment such as activated sludge treatment, it is widely practiced to remove SS from wastewater through initial precipitation treatment, but in small-scale treatment facilities, sludge treatment systems such as dehydrators are not installed. In many cases, a sedimentation tank is not provided at the beginning because the SS is not oxidized.In such cases, most of the SS flows directly into the aeration tank where it is oxidized. Furthermore, even if a settling tank is provided initially, the removal rate of organic SS is not so high, and much of it still flows into the aeration tank. However, since SS organic substances have a slow oxidation rate, it is necessary to use an aeration tank with a large capacity.

This invention separates SS in wastewater using a centrifugal concentrator and atomizes it in a separate aeration tank.
It is an object of the present invention to provide a method for treating sewage that can ensure sufficient residence time even in a small-capacity aeration tank.

Next, an example of the steps of the method of this invention will be explained with reference to the drawings. In the process shown in Figure 1,
The wastewater to be treated is first introduced into the centrifugal concentrator 1, where the SS is separated. The sewage from which SS has been removed is sent to an aeration tank 2 for normal activated sludge treatment, and after being subjected to a predetermined aeration treatment, it enters a settling tank 3, where the activated sludge is separated by precipitation.
The supernatant liquid separated in the settling tank 3 is discharged outside the system as treated water, and the settled sludge is transferred to another centrifugal concentrator 4.

The second centrifugal thickener 4 is for further concentrating the settled sludge, and the thickened sludge is sent to the high SS aeration tank 5.
In addition, the separated liquid is transferred to the aeration tank 2 described above. On the other hand, the SS concentrated in the first centrifugal concentrator 1 is introduced into the high SS aeration tank 5. In other words, the high SS aeration tank 5 contains high concentration SS concentrated by the first and second centrifugal concentrators 1 and 4, respectively.
Perform aeration treatment on liquids containing. The aerated liquid is then sent to the aeration tank 2 and subjected to aeration again.

Alternatively, as shown in Figure 2, the liquid aerated in the high SS aeration tank 5 is concentrated in the second centrifugal concentrator 4, the liquid is sent to the aeration tank 2, and a part of the concentrated sludge is used as return sludge. It may be returned to the high SS exposure tank 5. Moreover, if necessary, the excess sludge taken out from the settling tank 3 can be concentrated by the second centrifugal concentrator 4.

Furthermore, in the example shown in FIG. 3, the aeration tank 2 includes:
The second centrifugal concentrator 4 is filled with contact filter media and is supplied with the entire amount of settled sludge from the settling tank 3 and the entire amount of liquid from the high SS aeration tank 5 to retain microorganisms. . The separated liquid is then sent to the aeration tank 2, a part of the concentrated liquid is returned to the high SS aeration tank 5, and the rest is discharged as excess sludge.

Figure 4 shows the results when SS organic matter separated from wastewater by centrifugal concentrator 1 is aerated.
This graph shows the change in BOD over time. From this graph, it is clear that the decomposition of SS organic matter requires a certain amount of time t.
It can be seen that if the substance is first decomposed to a soluble state through exposure, subsequent decomposition can be carried out with high efficiency. In this invention, the SS organic matter separated in the centrifugal concentrator 1 is decomposed into a soluble state by being aerated in the high SS aeration tank 5, and then is aerated together with microorganisms in the aeration tank 2. Ru. Therefore, BOD removal in the aeration tank 2 is performed with high efficiency, and even if the aeration tank 2 has a small capacity, a sufficient treatment effect can be obtained.

Although the centrifugal concentrators 1 and 4 may be of decanter type, an example of a particularly preferred specific structure is shown in FIG. A basket 13 supported by a vertical rotation shaft 12 is accommodated within the housing designated by the reference numeral 11 in FIG. 5, and a cloth 14 is disposed along the inner surface of the basket 13. The basket 13 and the cloth 14 are rotated at high speed by power supplied from the outside to the rotating shaft 12 via the pulley 15. The wastewater to be treated is then supplied to the center of the fabric 14 via the supply pipe 16. Rotating basket 13 and cloth 14
has an upside-down truncated conical shape and rotates at high speed, so the liquid in the waste water passes through the cloth 14 and the small holes in the basket 13 under the action of centrifugal force, and radially enters the liquid chamber 17. The solid content moves on the cloth 14 in the direction away from the center of rotation (upward in FIG. 5) due to centrifugal force, and then moves into the liquid chamber 17.
The concentrate is discharged into a concentrate chamber 19 separated from the concentrate by a partition wall 18. As a result, the SS in the wastewater is efficiently separated, and the concentrated liquid and liquid containing a large amount of SS are separately taken out through the pipes 20 and 21, respectively.

Note that the reference numeral 22 indicates a cleaning pipe provided with a large number of nozzles 23, which is used when the work is interrupted and cleaning is performed when the cloth 14 or the like becomes clogged.

In addition, if the wastewater is treated with a fine-mesh screen, initial sedimentation tank, etc., a very fine-mesh cloth can be used as the cloth for the centrifugal concentrator 1.
SS organic matter can be removed very effectively.

As described above, according to this invention, SS in wastewater
is separated by a centrifugal concentrator before the aeration tank, is decomposed to a soluble state in the high SS aeration tank, and then undergoes normal aeration tank treatment along with the rest of the wastewater. Therefore, compared to the case of treating wastewater that still contains SS, the aeration tank only needs to have a small capacity because the residence time is short, and moreover, a stable treatment effect can be obtained. In addition, since the amount of inflow water in the high SS aeration tank is small, the capacity may be very small even if sufficient residence time is provided. In other words, according to this invention, the entire facility can be made compact.

[Brief explanation of drawings]

Figure 1 is a flow sheet showing an example of the steps of the method of this invention, Figures 2 and 3 are flow sheets showing other steps, and Figure 4 is a
Graph showing temporal changes in BOD during SS, 5th
The figure is a schematic longitudinal sectional view of a centrifugal superconcentrator suitable for carrying out the method of the invention. 1... Centrifugal concentrator, 2... Aeration tank, 3... Sedimentation tank,
4...Centrifugal concentrator, 5...High SS aeration tank, 11...Housing, 13...Basket, 14...Cloth, 16
...supply pipe, 17...liquid chamber, 19...concentrate liquid chamber.

Claims (1)

[Claims] 1. SS contained in the wastewater is separated using a centrifugal concentrator before the wastewater to be treated is supplied to the aeration tank, and this SS-containing liquid is subjected to aeration treatment. Therefore, a method for treating sewage characterized by decomposing organic SS to a soluble state and then supplying it to the aeration tank. 2. The method according to claim 1, characterized in that a centrifugal concentrator removes solid content from the liquid aerated in the high SS aeration tank, and the separated liquid is supplied to the aeration tank. How to treat sewage.