JPH03207494A - Biological treatment - Google Patents

Abstract

PURPOSE:To enhance the treating ability of bacteria and to reduce cost by using coke of 5-30mm diameter as a bacteria carrier when water to be treated such as sewerage is biologically treated by catalytic oxidation with blown air. CONSTITUTION:When water to be treated is biologically treated by catalytic oxidation with blown air, coke of 5-30mm diameter is used as a bacteria carrier so as to easily treat sewage, night soil, ordinary water, etc. A catalytic oxidation tank is divided into two or more tanks and function to degrade org. matter in water is rendered to the 1st tank. Coke of a large diameter, preferably 20-30mm is used as a filler in the 1st tank. Coke of 10-20mm diameter is preferably used in the 2nd tank so as to capture suspended solids flowing out of the 1st tank and to degrade the residual org. matter.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to sewage treatment, human waste and combined septic tanks, gray water supply,
This article relates to biological treatment methods useful for miscellaneous water reclamation treatment, general water treatment, etc.

[Conventional technology]

In general, water treatment can be broadly classified into physical treatment and biological treatment.

Physical treatment basically removes suspended solids (SS) suspended in wastewater through filtration with sand, etc.
Although it removes suspended solids, it cannot remove dirt (mainly organic matter) dissolved in water. Therefore, in order to remove such soluble dirt, aerobic microorganisms such as bacteria (hereinafter referred to as
Abbreviated as "bacteria". ) is required.

Biological treatment removes dirt by utilizing the power of bacteria to take in dissolved dirt in water and decompose it; one type of biological treatment is the catalytic oxidation method (fixed filter bed). There are various systems for this catalytic oxidation method, depending on what is used as a carrier for the bacteria.

For example, the carrier may be a string loop, an artificial stone, a natural stone, a sintered material (such as sintered volcanic ash), a honeycomb tube, or the like.

Among these, artificial stones, natural stones, sintered materials, etc. are particularly advantageous in terms of cost.

[Problem to be solved by the invention]

However, as long as conventional carriers are used, processability is not necessarily high and the cost of the carrier increases accordingly.

Therefore, the main object of the present invention is to provide a biological treatment method that has good processability and can reduce the cost of carriers.

[Means to solve the problem]

The above problem is that the particle size of
This can be solved by using coke of ~308.

In this case, catalytic oxidation is carried out at multiple locations, and the coke particle size in the first treatment section is set to 20 to 3
It is preferable to set the coke particle size to 0 mm, and set the coke particle size in the subsequent second processing portion to 10 to 20 noi.

By using coke as a filler in the tank, increasing its surface area per unit volume and increasing its affinity for bacteria, more bacteria can live in the treatment tank, improving treatment performance. This is an attempt to improve the results.

[For production]

In the present invention, coke is used as a carrier for bacteria in the catalytic oxidation treatment. Coke is less expensive and has a larger surface area per unit volume than conventional carriers. Therefore, the habitat area for bacteria is large, and processing capacity is improved. Furthermore, the present inventors have found that the processing capacity is higher even when compared with a carrier having the same surface area.

The reason for this is that coke has carbon as its main component.
This is thought to be due to its high affinity with bacteria.

On the other hand, in this type of biological treatment, the treatment capacity depends on the particle size. Conventionally, in many cases, one aeration tank (contact oxidation tank) is filled with a material having one type of particle size.

However, if carriers with small particle size are used to increase filling efficiency, etc., depending on the sludge load in the water, a lot of sludge will be generated, filling the spaces between the carriers, making it difficult for water to pass through, and causing problems in the tank. The flow rate increases, the sludge adhering to the carrier is peeled off, the SS content carries over, and the SS content of the treated water increases.

On the other hand, when a carrier with a large particle size is used, the surface area per unit volume becomes small, resulting in poor processing performance. Also, since the surface area is small, if some sludge adheres to the carrier,
This requires a step in which a larger amount of air and water than usual is introduced into the tank and some of the sludge adhering to the carrier is expelled from the tank.

Therefore, if you are trying to have two functions (biological treatment and filtration treatment) in one aeration tank, either one of the functions must be sacrificed, or both functions must function somewhat insufficiently. The current situation was that there was only one.

In contrast, when coke is used as a carrier according to the present invention, the surface area per unit volume is large and the particle size of the coke itself obtained from the steel mill is suitable for biological treatment. As a result, when a single tank is filled with a coke carrier, both biological treatment properties and filtration properties are good.

According to a preferred embodiment of the present invention, the contact oxidation tank (aeration tank) is divided into two or more tanks, the first tank has a function of decomposing organic components in water, and most of the organic components in water are absorbed in this tank. Disassemble. Coke with a large particle size is used as the filling material for this tank. By doing this, even if a large amount of organic matter is decomposed and a large amount of sludge is generated in the tank, the sludge can be accumulated in the tank because there are relatively many gaps between the cokes. Thus, by using coke with a large particle size as a carrier in the first tank, it is possible to exhibit decomposition performance while maintaining the filtration performance of the tank.

In addition, because the particle size of the carrier in the first tank is large (and there are many gaps), some sludge may flow out from the first tank, but even in such cases, the next second tank handles the sludge that flows out. can be captured and decomposed by bacteria.

This second tank has the function of capturing the SS components flowing out from the first tank, as well as the function of decomposing and removing the remaining organic components in the water.

In this way, by dividing the contact oxidation tank into a plurality of zones or in one contact oxidation tank and varying the coke particle size in these zones, good treatment can be achieved.

[Specific structure of the invention]

The present invention will be explained in more detail below.

FIG. 1 is a treatment flow sheet for carrying out the biological treatment method according to the present invention.

The treated water 1 is introduced into an adjustment storage tank 3 after relatively coarse solid matter is removed by a screen 2 such as a bar type. In the adjustment storage tank 3, air from an air blower 4 is supplied from the bottom thereof to suspend the solid content, and then the solid content is removed by a mesh screen 6 via a flow meter 5. The treated water 7 containing a large amount of suspended matter overflowing from the adjustment storage tank 3 is once stored in a discharge tank 8 and then discharged 9.

The water from which suspended solids have been removed by the mesh screen 6 is introduced into the oil flotation tank IO, where most of the oil is floated, and the treated water is then introduced into the oil adsorption tank 11 where it is finely dispersed. The oil is separated by a two-stage adsorption membrane 11a,
The next treated water is temporarily stored in the pit 12.

The water after this treatment is then transferred to the first contact oxidation tank 13 arranged in series.
and is sent to the bottom of the second catalytic oxidation tank 14 and passes through the fixed packed beds 13a and 14a made of coke, where the biological treatment that is the main focus of the present invention is performed, and as described above, the soluble dirt is removed. is decomposed and removed.

From the bottoms of the first contact oxidation tank l3 and the second contact oxidation tank 14, air from blowers 13b and 14b (not shown) is blown through aeration nozzles 13c and 14c to increase the activity of aerobic bacteria and to increase the soluble Decomposes dirt. In this case, the particle size of the coke filled in the first catalytic oxidation tank l3 is preferably larger than the particle size of the coke in the second catalytic oxidation tank 14. Specifically, it is particularly preferable that the particle size of the filled coke in the first contact oxidation tank 13 is 20 to 30 mm, and the particle size of the filled coke in the second catalytic oxidation tank 14 is 10 to 20 mm.

The backwash wastewater discharged from the top of the first contact oxidation tank 13 and the second contact oxidation tank 14 passes through the pipe 22A to the sludge digestion tank 1.
The suspended water 15a is returned to the adjustment storage tank 3, while the settled water 15b is disposed of outside the system by a tank truck.

On the other hand, 2 discharged from the top of the second contact oxidation tank l4
The secondary treatment water system 6 is introduced into the secondary treatment water pit 17 and left standing. A part of this secondary treated water is used as backwash water for the first and second contact oxidation tanks 13 and 14.

On the other hand, the remainder of the secondary treated water is sent to a membrane separation filter l8 having a membrane for separation, and the remaining impurities are filtered out by the membrane.

This filtrate 19 is stored in a gray water storage tank 21 and provided for use. Further, concentrated water with a high impurity concentration is returned to the adjustment storage tank 3. As the membrane separation operation continues, the membrane separation effect decreases, so a membrane cleaning agent (for example, sodium hypochlorite NaCIO) is supplied from the membrane cleaning agent tank to the membrane separation filter 18, and the membrane is cleaned for a predetermined period of time. Concentrate into a liquid. Thereafter, the membrane cleaning agent is returned to the membrane cleaning agent tank 26 through the pipe line 22 for repeated use. Membrane cleaning agent with reduced cleaning effect is transferred to pipe 2.
2, the neutralizing agent is charged from the neutralizing agent tanks 24A and 24B, and after being neutralized, it is discharged from the system.

25 is a gray water disinfectant tank.

Next, in the contact oxidation treatment applied to the above-mentioned treatment examples, in the case of the first contact oxidation treatment, a liquid (or water) with a high concentration of impurities (nutrients) enters, so for example, the same The removal rate also increases the amount of sludge generated.

Therefore, in the first catalytic oxidation treatment, it is necessary to increase the diameter of the filler to provide more space for storing sludge.
Coke is preferably used because it is porous and carbon materials are generally optimal as a habitat for bacteria.

When the sludge increases to a certain extent, it is necessary to perform backwashing, but the apparent specific gravity of coke is about 0.8 to 0.9, and when it enters the water, water enters the pores and sinks in the water, but the specific gravity at the time of backwashing is is appropriate, so when backwashing is performed by blowing air up from the aeration nozzles 13c and 14c using the blowers 13b and 14b, the coke will float in the tank 13 or 14, so the backwashing will not be possible. High cleaning effect.

On the other hand, in particular, the coke particle size in the second catalytic oxidation tank can be made smaller than the coke particle size in the first catalytic oxidation tank. This is because most of the impurities are removed in the first catalytic oxidation tank, so the amount of impurities that must be decomposed by bacteria in the second catalytic oxidation tank is small. Additionally, excess sludge generated in the first catalytic oxidation tank flows into the second catalytic oxidation tank, so it is necessary to treat this as well. For this purpose, the second aeration tank is required to perform the following two roles: (1) capture and digest the sludge flowing out, and (2) decompose the impurities (in the water). For this purpose, it is necessary to make the coke particle size smaller than that in the first contact oxidation tank and create an environment where bacteria can easily live, and coke with relatively small particle size and porousness is ideal for this purpose. It is. but,
If the coke particle size is too small, there is a risk that it will flow out of the tank during backwashing, so a certain particle size is required. For the above reasons, the first aeration tank is 20-30mm.
, it is preferable that the second aeration tank uses coke having a particle size of 10 to 20 m/m.

〔Example〕

Next, an example will be described.

The wastewater was purified using the biological treatment equipment shown in FIG. In this case, the conditions for the Examples and Comparative Examples were as follows.

Example 1: When the particle size of the coke used in the first catalytic oxidation tank 13 and the second catalytic oxidation tank 14 is the same in both tanks, 25 m.

Example 2: The coke particle size in the first contact oxidation tank 13 was set to 25
m, when the particle size in the second contact oxidation tank 14 is 15.

Conventional example; Comparative example using sintered volcanic ash as a carrier:
When coke with a particle size outside the above numerical range is used.

Biological treatment is performed under each of the above conditions, and the concentration of each impurity in the raw water and the corresponding impurity concentration of the treated water (
mg/l) was measured, and the results shown in Table 1 were obtained.

From the table above in Table 1, it is clear that according to the present invention, impurities in raw water can be reliably removed.

〔Effect of the invention〕

As described above, the present invention provides advantages such as good processability and the ability to reduce the cost of the carrier.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of processing according to the present invention. 1...Water to be treated, 3...Adjustment storage tank, 8...Discharge tank, IO...Oil flotation tank, 1l...Oil adsorption tank, 12.
... Primary treated water pit, 13... First contact oxidation tank tank,
14...Second contact oxidation tank, 15...Sludge digestion tank, l
7... Secondary treated water pit, 18... Membrane separation filter,
2l... Gray water storage tank, 23... Neutralization tank.

Claims (2)

[Claims] (1) As a carrier for bacteria in the catalytic oxidation method in which treated water is treated under air blowing, the particle size is 5 to 30.
A biological treatment method characterized by using mm coke. (2) Catalytic oxidation is carried out at multiple locations, and the coke particle size in the first treatment area is 20 to 30 m.
m, and the coke particle size in the subsequent second treatment section is 10
2. The method of claim 1, wherein the length is ˜20 mm.