JPH02118B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluidized bed type sewage treatment apparatus.

Recently, biological treatment processes using biofilms have been attracting attention. Especially fixed bed contact aeration system,
The results of the rotating plate contact method are remarkable.

One of the common features of these biofilm methods is that there is no need to return sludge because living organisms are attached to the surface of the contact material or rotating plate.

Since sludge is not returned, the amount of activated sludge flocs floating in the mixed liquid in the biological treatment tank is very small (MLSS; 50 to 200 ppm or less), and the sludge is collected in the settling tank, which is the next treatment process after the biological treatment tank. Sedimentation separation is easy.

Therefore, for BOD removal and decomposition, we do not rely much on the activities of activated sludge flocs that are free and suspended in the mixed liquid in the biological treatment tank, but instead rely on the activities of living organisms attached to the contact material and the surface of the rotating plate. It's almost swaying.

Since the special bed method is also a biofilm method, there is no need for return sludge in principle. However, since the adhesion medium is fluid, if a separate hopper-type sedimentation tank is installed like the fixed bed contact aeration method and the rotating disk method, the fluidized bed method differs from the above two methods. Since the adhesion medium is advected to the settling tank together with the mixed liquid in the biological treatment tank, the need for return sludge arises.

However, if the sludge is returned, the advantage of the biofilm method will be lost because more floating activated sludge will be present.

Therefore, in the fluidized bed system, the structure must be such that the adhesion medium does not flow out from the biological treatment tank, so in the case of the internal circulation type, the structure of the sedimentation tank is as shown in Figure 7. A gravity return system is known for returning the adhesion medium in a one-piece single hopper type sedimentation tank.

In the case of this well-known structure, only the medium with attached organisms is separated by sedimentation. Since floating activated sludge flocs do not need to be separated by sedimentation after being returned, the design is designed to increase the water area load so that the rising speed of the liquid part is greater than the settling speed of activated sludge flocs that are not attached to the medium. There is.

Therefore, floating activated sludge flocs with a small density do not separate by sedimentation, so the treated water of the fluidized bed method contains SS, and a subsequent treatment step is required to remove this SS.

Possible bioadhesive media include sand, activated carbon, anthracite, plastic particles, etc., but media with low density have low sedimentation properties when organisms adhere to them, and the media flows out. In the case shown in Figure 7, sand with a high density is suitable.

In contrast to the above-mentioned well-known treatment methods, the present invention has a structure in which only floating activated sludge flocs (excess sludge) not attached to the medium can be constantly removed.

Therefore, the number of activated sludge flocs that are always floating freely in the mixed liquid in the biological treatment tank is extremely small, and even though the medium is returned by gravity, almost no SS is contained in the treated water. .

Therefore, it is not necessary to install a device for removing SS in the next treatment step, but if it is desired to obtain treated water of higher quality, an SS removing device may be installed afterwards.

A first example shown in the first and second figures, and a second example shown in the third and fourth figures, are methods for constantly removing activated sludge that does not adhere to the biofouling medium and exists in suspension from a biological treatment tank. The explanation is as follows.

First, to explain the structure of the device, the vertically long frame 1
is constructed by integrally connecting a large-diameter upper hollow body 101 with a small-diameter lower hollow body 102, and an air lift pipe 2 for ventilation is provided across the upper hollow body 101 and the lower hollow body 102. are shared.

In the upper hollow body 101 of the vertically long frame 1, an upper biological treatment tank 3 is constructed around the air lift pipe 2, and around the treatment tank, sedimentation using a gravity sedimentation method is provided via a gas-solid-liquid separation tank 5. A tank 4 and a surplus sludge storage tank 6 are defined. The gas-solid-liquid separation tank 5 is
This is a tank that separates air, fixed liquid, and liquid. Inside the upper hollow body 101, an advection device 8 consisting of an advection port is provided in the partition wall 7 facing the biological treatment tank 3, the biological treatment tank 3 is communicated with the gas-solid-liquid separation tank 5, and this advection device is connected to the air lift pipe 2. It is arranged at a position lower than the upper end of the tank so that air bubbles, biofouling media, floating activated sludge flocs, etc. can be advected to the gas-solid-liquid separation tank 5. In the upper hollow body 101, the gas-solid-liquid separation tank 5 is communicated with the surplus sludge storage tank 6 by a transfer device 9 having a transfer port located higher than the advection device 8.
This transfer device transfers and removes floating activated sludge flocs to the excess sludge storage tank 6. In the lower hollow body 102, the lower biological treatment tank 10 configured around the air lift pipe 2 is communicated with the upper biological treatment tank 3, the sedimentation tank 4, the gas-solid-liquid separation tank 5, etc. The biofouling medium in the gas-solid-liquid separation tank 5 is configured to be able to settle, and even if the biofouling medium accidentally flows into the sedimentation tank 4, it is configured to immediately settle. A sewage inflow pipe 11 is disposed at the bottom of the lower biological treatment tank 10, and an air supply pipe 201 is attached near the lower end of the air lift pipe 2, so that air is supplied by an air supply means (not shown).

Sand (not shown) is put into the lower biological treatment tank 10 as a bioadhesion medium, and this sand is mixed with activated sludge to cause bioadhesion. Note that the upper end of the upper hollow body 101 is open.

Next, to explain the operation, the method of mixing the biofouling medium and activated sludge is that when air is sent into the air lift tube 2, the upward force of the air and bubbles causes an upward flow inside the air lift tube 2 along with the medium. The water is pumped.

During circulation, wastewater is purified through adsorption and oxidation by living organisms that adhere to the medium.

Most of the air fed into the air lift tube 2 is degassed when moving from the upward flow to the downward flow. but,
Fine bubbles have a downward flow of 30 cm/sec or more, so
Mixed into the circulating flow without being degassed. Most of the air bubbles in the upper biological treatment tank 3 are on the side of the partition wall 7 where the circulating flow is fastest, and by the advection device 8 of this partition wall, the air bubbles are immediately naturally transferred to the gas-solid-liquid separation tank 5 as shown in the second diagram, and the air bubbles are Simultaneously with the migration, the biofouling medium (double-dashed arrow) and floating activated sludge flocs (not shown) also migrate.

The biofouling medium (double-dashed line) that has migrated into the gas-solid-liquid separation tank 5 has a high specific gravity, so it settles naturally and is returned to the lower biological treatment tank 10, and the floating activated sludge flocs have a low specific gravity, so they are Sludge is lifted by the rising force of air bubbles.

The rising air bubbles are deaerated as they are, but the floating activated sludge flocs can be removed by installing the transfer device 9 near the water surface, that is, at the same height as the water surface, or at a position slightly lower than the water surface. Then, the sludge is naturally transferred from the transfer device 9 into the excess sludge storage tank 6 by the stirring flow generated by the upward flow. Therefore, the floating activated sludge flocs can be constantly transferred and removed, and the amount of sludge floating in the upper and lower biological treatment tanks 3, 10 can be minimized.

The purified liquid (dotted arrow) flows into the settling tank 4 to become treated water, and flows out of the system from the outlet 12 of the settling tank 4 via the water collection gutter 13 and the outflow pipe 14. Reference numeral 15 in FIGS. 3 and 4 indicates a scum prevention plate provided as necessary.

In the structure of the third example shown in FIGS. 5 and 6, a surplus sludge storage tank 6 is installed outside the vertically long frame 1, and an advection port is provided in the partition wall 7 facing the upper biological treatment tank 3 inside the frame. A transfer device 9 consisting of a transfer pipe is provided from the advection device 8 to the excess sludge storage tank 6,
This transfer device has the surplus sludge storage tank 6 side placed high,
The biofouling medium (two-dot chain arrow) in the upper biological treatment tank 3 is separated from the floating activated sludge flocs in the transfer device 9, and is returned to the lower biological treatment tank 10 through natural sedimentation, and the flocs are returned to the lower biological treatment tank 10. The sludge is naturally transferred to the surplus sludge storage tank 6 by the agitation flow generated. The purified liquid treatment is the same as in the previous example. The upper end of the upper hollow body 101 is open.

Therefore, according to the third example, the inclined transfer device 9 exhibits the same separation effect as the gas-solid-liquid separation tank 5 in the first and second examples, and the separation tank In addition to eliminating the need to separate the floating activated sludge flocs, the floating activated sludge flocs can be constantly transferred and removed, and the amount of sludge floating in the upper and lower biological treatment tanks 3 and 10 can be minimized. It has a similar effect.

Note that a baffle plate 15 is installed on the discharge side of the transfer device in the excess sludge storage tank 6 in FIGS. 5 and 6.

[Brief explanation of drawings]

1 and 2 show a first example of the sewage treatment apparatus of the present invention, in which FIG. 1 is a vertically sectional perspective view, FIG. 2 is a longitudinal sectional front view of the main part, and FIGS. Figure 4 shows an outline of the second example, Figure 3 is a front view, Figure 4 is a plan view, Figures 5 and 6 are outlines of the third example, and Figure 5 is a front view. FIG. 6 is a front view of the main part, FIG. 6 is a plan view thereof, and FIG. 7 is a schematic front view of a known example. In the figure, 1 is a vertically long body, 101 is an upper hollow body,
102 is a lower hollow fuselage, 2 is a vertical air lift pipe,
3 is an upper biological treatment tank, 4 is a settling tank, 5 is a gas-solid-liquid separation tank, 6 is an excess sludge storage tank, 7 is a partition wall, 8 is an advection device, 9 is a transfer device, 10 is a lower biological treatment tank, 1
1 is a wastewater inflow pipe.

Claims (1)

[Claims] 1. A vertically long airlift pipe for ventilation is installed in the center of a vertically long body consisting of an upper hollow body and a lower hollow body connected to each other, and an upper biological treatment tank is installed around the airlift pipe within the upper hollow body of the body. A sedimentation tank is defined around each of the treatment tanks, and a gas-solid-liquid separation tank is defined separately from both tanks, and an excess sludge storage tank is provided inside or outside the vertical frame, and an upper biological treatment The upper biological treatment tank is connected to the gas-solid-liquid separation tank by placing an advection device installed on the partition wall facing the tank at a position lower than the upper end of the vertical air lift pipe.
The upper biological treatment tank or gas-solid-liquid separation tank is connected to the excess sludge storage tank by a transfer device located higher than the advection device, and the lower biological treatment tank is constructed around the vertical air lift pipe in the lower hollow body of the vertically long frame. A fluidized bed type sewage treatment device in which the upper biological treatment tank, sedimentation tank, and gas-solid-liquid separation tank are connected to each other, and a sewage inflow pipe is provided at the bottom of the lower biological treatment tank.