JPS631116B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating organic wastewater with a biofilm.

Conventionally, in the treatment of organic wastewater using immersed bed equipment, granular solids with a specific gravity greater than 1.0, such as anthracite, sand, and PVC pipes, or flat members such as honeycomb tubes are immersed in a treatment tank, and air lift aeration is performed. Therefore, oxygen is supplied to the immersed bed and liquid is circulated.

However, such a method has the following drawbacks.

Since oxygen is supplied using an air lift, the residence time of air bubbles in the processing tank is extremely short. This is because an upward flow of the liquid occurs in the air lift section, and the rising speed of the air bubbles is accelerated by this upward flow. Therefore, the oxygen supply power efficiency is only about 1 Kg.O ₂ /KWH at most, which is not energy-saving.

When granular solids are used as a material, the floor frequently becomes clogged, so each time the raw water supply has to be stopped and treated water is used to backwash and drain the floor, operation management becomes extremely difficult. This is troublesome, and moreover, stable processing effects cannot be obtained.

In order to speed up biological treatment, it is necessary to increase the amount of microorganisms in the treatment tank, and for this purpose it is necessary to increase the specific surface area of the material. However, if a material with a large specific surface area and a small particle size is used, the aforementioned bed clogging occurs in an extremely short period of time, so it has been practically impossible to use a material with a small particle size.

The present invention appropriately solves these drawbacks of the conventional method, saves energy in aeration, and effectively prevents troubles such as clogging of the immersion bed.
The purpose is to provide a new biological treatment method using a immersed bed.

That is, the present invention provides an immersion system in which an immersion packed bed is formed using a particulate microbial film-adhesive material that floats on water, and an air lift pipe is provided in the vertical direction of the immersion packed bed to generate a circulating flow. In the floor device, raw water is caused to flow downward into the immersed packed bed, and air is supplied from within or below the immersed packed bed for biological treatment, and the amount of air supplied into the air lift pipe is intermittently controlled. This is a biological treatment method for organic wastewater characterized by increasing and decreasing the amount of organic wastewater. In addition, in this specification, the above-mentioned "increase/decrease"
means both the start/stop (on/off) of air supply and the increase/decrease of the air supply amount during supply.

To explain the embodiment of the present invention with reference to the drawings, the upper part of the tank includes foamed polypropylene, wood chips, sawdust,
Specific gravity such as perlite and glass glass balloons
An immersed bed section 1 made of any floating granular solid of 1.0 or less is provided, and an aeration pipe 3 connected to a blower 10 is provided directly below the immersed bed section 1, and an aeration pipe 3 connected to the blower 10 is installed between the upper part of the tank and the immersed bed. The raw water 2 is treated by a treatment device in which an air lift pipe 4 is arranged vertically so as to communicate with the lower part of the section 1. That is, the raw water 2 is aerated with the air 5 from the aeration tube 3 while flowing downward through the immersion bed 1, and then is discharged to the outside of the system as treated water 11 through the outflow section 7. Since the raw water 2 and the air 5 are brought into contact with each other in a countercurrent manner within the immersion bed 1 as described above, air bubbles do not immediately escape into the atmosphere as in conventional devices. Since the air bubbles are trapped in the voids between the floating materials, the residence time of the air bubbles in the immersed bed section 1 is lengthened, and the benefit of significantly improving oxygen absorption efficiency is obtained.

However, as this treatment continues, SS accumulates in the material and the resistance increases. Here, the cleaning treatment of the immersed bed section 1 is carried out as follows. That is, air 5 is placed at the bottom of the air lift pipe 4.
When supplying or increasing the supply amount, a circulating flow by the airlift pipe 4 is generated or increased, and the downward flow velocity of the submerged bed section 1 increases significantly, and the downward expansion rate of the bed height increases. At this time, the SS and excess microbial slime that had been trapped in the gaps between the materials are peeled off, ascend the outflow section 7, and flow out of the system, leading to subsequent solid-liquid separation devices such as sedimentation basins, filters, and screens. At 8, sludge 13 is removed.

At this time, the effect of removing the SS and microbial slime can be increased by intermittently turning on and off the air supply to the air lift tube 4, or by intermittently increasing and decreasing the air supply. Moreover, if the amount of air supplied is increased further and the material is circulated along with it, a peeling effect within the air lift tube 4 can also be expected.

Thereafter, the air supply to the air lift tube 4 is stopped or reduced, and the steady processing state is restored again. Note that 6 is the water surface of the immersed floor portion 1, and the increase in resistance can be detected by the rise of this water surface 6. 9 is a porous water-permeable body (such as a net) for preventing floating granular solids from flowing out of the system. Further, 14 is a variable flow valve for adjusting the amount of air 5 supplied to the air lift pipe 4;
6 is a switching valve for directly converting the effluent from the outflow portion 7 into treated water 11 or feeding it to the solid-liquid separator, and 12 is solid-liquid separated water.

It is most preferable that the supply of air 5 to the air lift tube 4 is usually stopped in a steady state or kept at an amount that does not cause the immersion bed 1 to expand, but the immersion bed 1 may expand slightly. A method of constantly supplying a certain amount can also be adopted.

In any case, during routine biological treatment,
The expansion coefficient of the immersed bed section 1 (the bed height H at the time of expansion divided by the bed height h in the fixed bed state, that is, H/
It is important to operate with h) set to 2.0 or less, so that the rise of air bubbles from the air diffuser pipe 3 can be effectively suppressed. The cross-sectional area of the outflow part 7 is SS
It is also possible to use the outflow section 7 as a sedimentation separation section by setting it in accordance with the sedimentation speed of . Furthermore, during steady-state treatment, the treated water 11 flowing out from the lower part of the immersed bed section 1 contains almost no SS, so it can be discharged as is without flowing into the solid-liquid separator 8. In addition, air diffuser 3
The installation position is directly below the floor or preferably at the lowest level in the floor, and it is not very preferable to install it at the bottom of the tank like in a normal aeration tank. The reason for this is that the required discharge pressure of the blower 10 increases as the aeration water depth increases.

Note that since dissolved oxygen is supplied to the microbial membrane even when the air lift tube 4 is activated, the biological treatment continues, and as a result, there is no need to stop the supply of raw water during floor cleaning as in the conventional method.

As described above, the method of the present invention aerates from an aeration device installed inside or below a immersed bed made of floating granular material, and allows raw water to flow downward into the immersed bed while introducing air bubbles into the immersed bed. The liquid circulation rate is changed intermittently using an air lift to increase or decrease the layer height of the immersed bed. This method is fundamentally different from the method in which oxygen supply and liquid circulation are carried out only by air lift aeration, and all the drawbacks of the conventional submerged bed method can be overcome. In other words, even if a material with a small particle size and a large specific surface area is used, it will not become impossible to move due to bed clogging, and furthermore, backwashing is not required and the raw water supply can be processed without having to be stopped. Furthermore, since materials with small particle sizes can be used, the amount of microorganisms in the treatment tank can be maintained at a high concentration, making it possible to speed up biological treatment.In addition, the residence time of oxygen-containing bubbles such as air in the tank is long, so oxygen can be absorbed. The efficiency is high, the blower air flow is small, and the blower discharge pressure is also small, making it possible to save energy during aeration. Furthermore, since air lift aeration is performed intermittently or as a secondary operation, the power for aeration is reduced. It also improves consumption efficiency and has the benefit of being able to process at a lower cost.

[Brief explanation of the drawing]

The drawings are system explanatory diagrams showing embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Immersed floor part, 2... Raw water, 3... Air diffuser pipe, 4... Air lift pipe, 5... Air, 6... Water surface, 7... Outflow part, 8... Solid-liquid separator, 9... …
Porous water permeable body, 10... blower, 11... treated water, 12... solid-liquid separated water, 13... sludge, 14-
16...Valve.

Claims (1)

[Scope of Claims] 1. A immersed packed bed is formed using particulate microbial film adhering material that floats on water, and an air lift pipe is provided in the vertical direction of the immersed packed bed to generate a circulating flow. In the immersed bed device, raw water is allowed to flow downward into the immersed packed bed, and air is supplied from below the upper end of the immersed packed bed for biological treatment, and the amount of air supplied into the air lift pipe is intermittently controlled. A biological treatment method for organic wastewater characterized by increasing or decreasing the amount of organic wastewater. 2. Claim 1, wherein the operation of increasing and decreasing the air supply amount is performed by turning on and off the air supply.
The method described in section. 3. The method according to claim 1 or 2, wherein the air supply amount is increased or decreased so that the material is entrained in water.