JPS61138592A - Method for removing bod componentand nitrogen component - Google Patents

Abstract

PURPOSE:To reduce a setting area and to stabilize a treatment by separating a packing material layer wherein microbes are implanted into two stages, inserting aerobes and anaerobes in the front-stage of the packing material layer in coexistence with each other, and implanting aerobes in the rear-stage of the packing material layer. CONSTITUTION:The packing material layer is separated into two stages, untreated water is brought into contact in series with the front-stage of the packing material layer 1 and the rear-stage of the packing material layer 2, and the part of water discharged from the layer 2 is circulated into an untreated water vessel 5 and mixed, when untreated water contg. BOD components and nitrogen components is brought into contact with the packing material layer wherein microbes are implanted to remove biologically the BOD components and nitrogen components. Moreover, the aerobes and anaerobes are implanted in the layer 1 in coexistence with each other by controlling the amt. of dissolved oxygen in the vicinity of the outlet of the layer 1 to oxidize and denitrify the BOD components in the layer 1. Besides, oxygen is sufficiently supplied into the layer 2 to implant aerobes, and the residual BOD components are oxidized and/or nitrated in the layer 2. Consequently, the setting area can be reduced, and the treatment can be stabilized.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention uses BOD components and nitrogen components in various industrial wastewater to be treated with microorganisms grown on the surface or voids of various fillers.
This relates to a method of biological treatment by bringing it into contact with a so-called microbial membrane.

<Prior art> Nitrogen and phosphorus have long been attracting attention as causative agents of eutrophication in lakes and marshes and red tide in closed sea areas, and various methods have been considered to remove these substances from wastewater. .

BACKGROUND ART Conventionally, when removing nitrogen components from wastewater, a method has been implemented in which BOD components are simultaneously removed along with nitrogen components from wastewater by an activated sludge method using the following reaction.

SOD component + Ot = COz + Hz O・-・(
1) Organic nitrogen +0□→CO□+N Ha ”+○H-
...(2) NH4"+3/20z-NOz-+HzO
+28"-(31Noz-+1/202-N O
ff-・-・(41NOff-+Organic carbon source-NO□-
+ 1/3 CO2 + 2/3 H, O... (5) N O2 - organic carbon source - 1/2 N 2 + 1/2
COz+OH...(6) In other words, the wastewater flows into the anaerobic tank and the aerobic tank in that order,
In addition, a part of the water flowing out from the aerobic tank is circulated to the anaerobic tank. In the aerobic tank, BOD components are removed using equations (11 to (4)), and organic nitrogen and ammonia nitrogen in the wastewater are removed. NO2- or N03- (nitrification), and NO1\NO,- is decomposed into nitrogen gas (denitrification) using equations (5) and (6) in an anaerobic tank.

<Problems to be solved by the invention> However, the conventional activated sludge method for removing BOD and nitrogen components is inefficient because it reacts with microorganisms in the form of a slurry, and has the disadvantage that the processing equipment is relatively large. There are also problems with processing stability, such as bulking.

The present invention aims to solve the conventional drawbacks in biologically removing BOD components and nitrogen components from wastewater, and to provide a method that can reduce the installation area and perform stable treatment.

<Means for Solving the Problems> The present invention divides the packing material layer on which microorganisms have grown into two stages, brings the raw water into contact with the former filling material layer in series, and prevents the outflow of the latter filling material layer. By circulating and mixing a portion of the water with the raw water and adjusting the dissolved oxygen in the outflow water near the outlet of the front filler layer to an appropriate value, aerobic microorganisms and anaerobic microorganisms can coexist in the front filler layer. By oxidizing and decomposing the BOD components in the water that comes into contact with the plant by aerobic microorganisms, NO and -1N Ox- are decomposed into nitrogen by anaerobic microorganisms, and by supplying sufficient oxygen to the subsequent filler layer. Aerobic microorganisms are grown on the filler layer to oxidize and decompose residual BOD components in the water that comes into contact with it, and/or to remove organic nitrogen and ammonia nitrogen.
It is nitrified to o, -.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram of a flow showing an example of an embodiment of the present invention, in which a first stage reaction tank 1 and a second stage reaction tank 2 filled with various fillers are arranged in series. These reaction vessels are conventionally known as microbial membrane devices, and allow microorganisms to grow on the surface or voids of the filler.

The filler for the reaction tanks 1 and 2 may be granular materials such as gravel, crushed stone, lightweight artificial stone, Raschig rings, net-like materials, etc.
There are molded products such as honeycomb tubes, but lightweight artificial stone has a porous surface that is effective for microbial colonization, and can be easily filled. When washing the attached microorganisms with rising water, it is preferable to use lightweight artificial stone as the filler because the filler can be floated at a relatively low flow rate.

In the present invention, first, the wastewater 3 containing nitrogen components and BOD components and a part of the outflow water 4 from the second stage reaction tank 2 are mixed in the raw water tank 5, and the mixed water is pumped by the pump 6 to the first stage reaction tank 1. At the same time, air from the blower 7 flows in from the lower part of the pre-stage reaction tank 1 to supply oxygen.

If sufficient oxygen is supplied to the first stage reaction tank 1, aerobic microorganisms will grow in the filler layer, and if oxygen is not supplied, anaerobic microorganisms will grow. The dissolved oxygen concentration meter 8A installed in the upper part measures the dissolved oxygen in the outflow water near the outlet of the packing material layer, and by adjusting the value to an appropriate value, it is possible to provide a suitable solution to the filling material layer in the pre-stage reaction tank l. Aerobic microorganisms and anaerobic microorganisms are allowed to coexist and colonize, and the aerobic microorganisms remove the BOD component in the water according to the reaction formula +11 described above, and the anaerobic microorganisms remove the BOD component from the water according to reaction formulas (5) and (6). , NOZ in water, NO
It decomposes Z into nitrogen.

In the case of a microbial membrane device, unlike the activated sludge method in which microorganisms are present in the form of a slurry, the microorganisms are held in a membrane form in the filler, so oxygen can easily diffuse outside the microbial membrane. It becomes aerobic, and the inside tends to become anaerobic due to the diffusion of oxygen.

The present invention actively utilizes such properties of the microbial membrane, and the dissolved oxygen near the outlet of the filler layer is
By adjusting g as O/β, the outside of the microbial membrane is stably maintained as aerobic microorganisms, and the inside as anaerobic microorganisms. If the dissolved oxygen near the outlet of the filler layer is less than 092 mg as O/1, the growth of aerobic microorganisms will be inhibited, and if it is more than 2 mg as 071, the growth of anaerobic microorganisms will be inhibited, and both aerobic microorganisms and anaerobic microorganisms cannot be maintained stably, and the object of the present invention cannot be achieved.

In order to adjust the dissolved oxygen in the water flowing out near the outlet of the packing material layer of the first stage reaction tank 1 to 0.2 to 2 mg as O//l, for example, as shown in the figure, dissolved oxygen is added directly above the packing material layer. It is preferable that a densitometer 8A is attached and the amount of air supplied is adjusted by a valve 9 that is operated in response to a signal from the densitometer 8A. Note that if the water quality of drainage water 3 is stable, a manual valve may be used. Additionally, the amount of air can be adjusted by incorporating an inverter into the blower and varying the rotation speed.

In the present invention, the outflow water from the first stage reaction tank 1 then flows upwardly into the second stage reaction tank 2 from the lower part thereof, and at the same time, the air from the blower 7 flows from the bottom part of the second stage reaction tank 2 to supply oxygen.

In the second stage reaction tank 2 of the present invention, organic nitrogen and ammonia nitrogen in water are removed by aerobic microorganisms as described in (2) and (3) above.
), (4), if No. 2- and No. - binding and BOD components remain, they are oxidized and decomposed by aerobic microorganisms according to equation (1). Therefore, it is necessary to supply sufficient oxygen to the second stage reaction tank 2.
It is necessary to adjust the dissolved oxygen in the outflow water near the outlet of the filler layer to at least 2 mg as 071 or more. 2
If the amount of oxygen is less than mg as O/It, the above-mentioned reaction will not proceed efficiently, which is not preferable.

In addition, it is preferable to attach a dissolved oxygen concentration meter 8B to the upper part of the second stage reaction tank 2 in the same way as the first stage reaction tank 1, and to adjust the amount of air supplied by a valve 1O which is interlocked with the signal from the second stage reaction tank 8B. In the case of the second stage reaction tank 2, unlike the first stage reaction tank 1, there is no need to strictly control the amount of oxygen in the outflow water to keep it within a certain value range, and it is sufficient to keep it at 2 mg as 071 or more. In the case of supplying air such as air, the addition of the dissolved oxygen concentration meter 8B can be omitted.

The outflow water 4 from the latter stage reaction tank 2 is then fed to the distribution tank 11,
Here, the water is divided into effluent to be circulated to the raw water tank 5 and effluent to be taken out as treated water. The removal rate of nitrogen components in the waste water 3 increases as the circulation rate of the effluent water 4 increases, but on the other hand, the capacity of the pump 6 increases in proportion to the circulation rate, which is undesirable. It is appropriate that (flow rate of waste water + circulation flow rate/flow rate of waste water) be about 2 to 5.

FIG. 2 is an explanatory diagram of a flow showing another embodiment of the present invention, in which the reaction tank 12 is divided into front and rear parts, with the lower part serving as the former filling material layer 13 and the upper part serving as the latter filling material layer 14. .

That is, a part of the waste water 3 and the outflow water 4 from the latter filler layer 14 is received in the raw water tank 5, and the mixed water flows upwardly from the lower part of the reaction tank 12, and the air from the blower 7 is sent to the reaction tank 12.
The aerobic microorganisms and anaerobic microorganisms that are supplied from the lower part of the water and grown on the front filler layer 13 oxidize and decompose the BOD component in the water, decompose NO□-1N Os- into nitrogen, and then decompose the BOD component in the water. The effluent is directly transferred to the latter filler layer 14.
The aerobic microorganisms grown on the latter filler layer 14 convert the organic nitrogen and ammonia nitrogen in the water into NO, -1N Ox-, and if BOD components remain. This is oxidized and decomposed. The dissolved oxygen concentration meter 8A and valve 9 are used to measure dissolved oxygen in the outflow water near the outlet of the pre-stage filler layer 13 to 0.2 to 2 mg as O.
Needless to say, the pressure is adjusted to 7N, and air is additionally supplied from the lower part of the rear filling material layer 14 to
4, to supply sufficient oxygen.

Note that in both FIGS. 1 and 2, water is passed through the filler layer in an upward flow, but the present invention is not limited to upward flowing water, and in some cases, downward flowing water may be used. be able to.

<Effects of the Invention> As explained above, in the present invention, unlike the conventional activated sludge method, the BOD component and nitrogen component in wastewater are removed by the microbial membrane method, so it is possible to increase the biomass retained. As a result, the installation area of the equipment can be reduced, and problems such as bulking do not occur at all.
Can be processed stably. Furthermore, unlike the conventional activated sludge method, the present invention does not clearly distinguish between anaerobic tanks and aerobic tanks, but allows aerobic microorganisms and anaerobic microorganisms to coexist and grow in the pre-filling material layer. This means that the system is effectively used, and this also allows the installation area of the device to be reduced.

The present invention will be explained in detail below.

<Example> Two reaction tanks with a diameter of 0.25 m and a height of 2.5 m were prepared, and both tanks were filled with lightweight artificial stones with an average particle size of 12 m to a height of 2 m, as shown in Figure 1. One side was used as a first-stage reaction tank, and the other side was used as a second-stage reaction tank.

BOD 200mg as O/l, total nitrogen 30
mgasNil, ammonia nitrogen is 10mg as
N//l of wastewater is treated as water to be treated, and the wastewater is treated as 45 J/l of wastewater.
At the same time, the water was supplied to the raw water tank with H, and the outflow water from the rear reaction tank was circulated and mixed with 9017H, and the mixed water of 13M/H was flowed into the front reaction tank in an upward flow.

In addition, air is introduced from the lower part of the first reaction tank at a rate of 1.5 m/H to adjust the dissolved oxygen in the outflow water near the outlet of the packing material layer of the first reaction tank to 1.8 mg as O/l, and A sufficient amount of air is introduced from the bottom of the tank to reduce the amount of dissolved oxygen in the outflow water near the outlet of the packing material layer of the latter stage reaction tank.
The g as was set to 0714 or higher.

When such operation continues for a long time and the treatment becomes stable, the BOD in the outflow water from the front and rear reaction tanks
When each nitrogen was measured, the results were as shown in Table 1, 8.

Next, reduce only the amount of air supplied to the first stage reaction tank, and reduce the dissolved oxygen in the outflow water near the outlet of the packing material layer to 0.2 mg.
As O/(l) or less, the BOD and each nitrogen in the outflow water from each tank when the treatment was stabilized were as shown in Table 1.

Furthermore, the dissolved oxygen supplied to the first stage reaction tank is 2 mgsO/
When it was set to 1 or more, the BOD and each nitrogen in the outflow water from each tank when the treatment was stabilized resulted in the results shown in C in Table 1.

? As shown in B in Table 1, when the amount of air in the front reaction tank is insufficient, the activity of aerobic microorganisms in the front reaction tank is inhibited, resulting in a decrease in the amount of BOD components removed. As a result, the nitrification reaction is inhibited and the amount of total nitrogen removed also decreases. Furthermore, as shown in C of Table 1 (if the amount of air in the front reaction tank is excessive, the denitrification reaction in the front reaction tank is inhibited and the amount of total nitrogen removed is reduced).

Dissolved oxygen near the outlet of the packing material layer in the first stage reaction tank was reduced to 0°2~2
．． BOD in A adjusted to 0 mg as O/l range
and nitrogen components are effectively removed.

[Brief explanation of the drawing]

FIG. 1 is a flow explanatory diagram showing an example of an embodiment of the present invention, and FIG. 2 is a flow explanatory diagram showing another embodiment of the present invention.

Claims (1)

[Claims] In order to biologically remove BOD and nitrogen components by bringing raw water containing BOD and nitrogen components into contact with the filler layer on which microorganisms have grown, the filler layer is divided into two stages, and the raw water is added to the first stage. Bringing the filler layer into series contact with the latter filler layer, circulating and mixing a portion of the outflow water from the latter filler layer with the raw water, and adjusting the amount of dissolved oxygen in the outflow water near the outlet of the first filler layer. By allowing aerobic microorganisms and anaerobic microorganisms to coexist and grow on the filler layer, oxidation and denitrification of BOD components are performed in the first filler layer, and sufficient oxygen is supplied to the second filler layer. By doing so, aerobic microorganisms are allowed to grow on the filler layer, and residual BOD is removed in the filler layer.
B, characterized by oxidizing and/or nitrifying components
How to remove OD and nitrogen components.