JPS5836698A - Treatment for sewage - Google Patents

Abstract

PURPOSE:To assure a sufficient residense time even in an aerating tank of small capacity by separating SS with a centrifugal concentrator prior to supplying of sewage to be treated to the aerating tank, aerating the liquid contg. SS to decompose the org. SS to soluble SS and supplying the same to the aerating tank. CONSTITUTION:Sewage to be treated is first supplied to a centrifugal concentrator 1 to separate the SS in the sewage. The sewage removed of SS is fed to an aerating tank 2 and the liquid contg. SS is fed into a high SS aerating tank 5. After the org. SS in the liquid contg. SS is aerated until it has solubility in the high SS aeration tank 5, the liquid is supplied into the tank 2. The liquid aerated in the tank 5 is removed of solids with a centrifugal concentrator 4, and the separated liquid is supplied to the tank 2. The solids are disposed as excess sludge or in some cases they are recirculated to the tank 5.

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, SS in wastewater is first removed by sedimentation treatment, which is widely practiced, but only in small-scale treatment facilities.

Since a sludge treatment system such as a dewatering machine is not installed, a sedimentation tank is often not installed at first, and in such cases, the SS mostly flows directly into the aeration tank.

Here 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 aerates it in a separate aeration tank, thereby making it possible to ensure sufficient residence time even in a small-capacity aeration tank. The purpose is to provide a processing method for

Next, an example of the steps of the method of this invention will be explained using drawings. In the process shown in FIG. 1, wastewater to be treated is first introduced into a centrifugal concentrator 1, where 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 concentrator 4 is for further concentrating the settled sludge, and the concentrated sludge is transferred to the high SS aeration tank 5, and the separated liquid is transferred to the aeration tank 2 described above. On the other hand, the first
The SS concentrated in the centrifugal concentrator 1 is introduced into a high SS aeration tank 5. That is, the high SS aeration tank 5 performs an aeration process on the liquid containing SS at a high concentration concentrated in the first and second centrifugal concentrators 1 and 4, respectively. The aerated liquid is sent to the aeration tank 2 and subjected to aeration again.

Alternatively, as shown in Fig. 2, the liquid atomized in the high SS aeration tank 5 is concentrated in the second centrifugal concentrator 4, the f liquid is sent to the aeration tank 2, and a part of the thickened sludge is returned. High SS as sludge
It may be returned to the aeration tank 5. In addition, if necessary, the excess sludge taken out from the settling tank 3 can be concentrated in the second centrifugal thickener 4.In addition, in the example shown in Fig. 3, the fume tank 2 is The second centrifugal concentrator 4 is filled with filter media to retain microorganisms, and the entire amount of the settled sludge from the settling tank 3 and the high SS
The entire amount of liquid from the aeration tank 5 is supplied. 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 surplus sludge.

Figure 4 shows S separated from wastewater by centrifugal concentrator 1.
This graph shows the temporal change in BOD when S-type organic substances are aerated. From this graph, it can be seen that in order to decompose S-type organic substances, they must first be decomposed to soluble K by aeration for a predetermined time t. It can be seen that the subsequent decomposition is carried out with high efficiency. In this invention, the SS organic matter separated in the centrifugal concentrator 1 is decomposed into soluble K by being aerated in the high SS aeration tank 5, and then aerated together with microorganisms in the aeration tank 2. 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 a decanter type, an example of a particularly preferred specific structure is shown in FIG. A basket 13 supported by a vertical rotating shaft 12 is housed in a housing designated by the reference numeral 11 in FIG.

The basket 13 and the r-cloth 14 are rotated at high speed by power supplied to the rotating shaft 12 via an external pulley 15. Then, the wastewater to be treated is supplied to the supply pipe 16
It is supplied to the center of the F cloth 14 through. The rotating basket 13 and the f-cloth 14 have an upside-down truncated cone shape,
Since it is rotating at high speed, the liquid content in the wastewater is
The solids pass through the indicator holes of the basket 13 under the action of centrifugal force and are released into the rtiii 17 in the radial direction, and the solid content moves away from the center of rotation (upward in FIG. 5) on the P cloth 14 under the action of centrifugal force. After moving, W is discharged into a concentrated liquid chamber 19 separated from the f liquid chamber 17 by a partition wall 18 .

As a result, SS in wastewater is efficiently separated, and S
The concentrated liquid containing a large amount of S and the f liquid are taken out separately through 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 wastewater is treated with a fine-mesh screen, initial sedimentation tank, etc., a very fine-mesh centrifugal concentration Ia10F cloth can be used, and SS organic matter can be removed very effectively.

As described above, according to #4, SS in wastewater is separated by a centrifugal concentrator before the aeration tank, and after being decomposed to a soluble state in the high SS aeration tank, the remaining wastewater is Along with this, they will be subjected to the usual embarrassment treatment. Therefore, compared to the case of treating wastewater that still contains SS, the aeration tank needs to have a small capacity because the residence time is short (
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 process of this invention method. Figures 2 and 3 are flow sheets showing other steps, Figure 4 is a graph showing temporal changes in BOD in SS due to ventilation, and Figure 5 is centrifugal filtration suitable for carrying out the method of this invention. FIG. 2 is a schematic vertical cross-sectional view of a concentration-like state. 1... Centrifugal concentrator, 2... Aeration tank, 3... Sedimentation tank, 4... Centrifugal concentrator, 5-... High SS aeration tank. 11-...Housing, 13-...Basquera), 14-
...f cloth, 16...supply pipe, 17...f liquid chamber,
19...Concentrate chamber. Patent applicant Nishihara Environmental Health Research Institute 111
Figure 112 Figure 3 Figure 4 Figure t is! Qi time figure 5

Claims (2)

[Claims] (1) Before supplying the sewage to the aeration tank to be treated, the SS contained in the sewage is separated using a centrifugal concentrator,
By aerating this SS-containing liquid, organic S
A method for treating wastewater, which comprises decomposing S to soluble K and then supplying it to the aeration tank. (2) Remove solid content from the aerated liquid in the high SS aeration tank using a centrifugal concentrator.1. A method for treating wastewater according to claim 1, characterized in that the separated liquid is supplied to the aeration tank.