JPH04197493A - Method and apparatus for filtering sewage - Google Patents

Abstract

PURPOSE:To continuously perform the filtering of various sewages such as raw sewage or the like at high speed for a long time by providing a bed packed with small porous bodies having elasticity in a tank and arranging sewage supply parts over many stages in the height direction of the packed bed. CONSTITUTION:A bed 3 packed with small porous bodies having elasticity is provided in a treatment tank 2 and sewage supply parts 10-12 are arranged over many stages in the height direction of the packed bed 3 and sewage is distributed and supplied to take out filtered treated water from the treated water outflow pipe 4 provided to the lower part of the packed bed 3. As a result, various sewages such as raw sewage or the like can be continuously filtered at high speed for a long time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a novel filtration system that can purify various types of wastewater, such as river water, lake water, human waste, sewage, and wastewater, extremely quickly and highly with only a single treatment tank. METHODS AND APPARATUS. Note that filtration here includes not only normal filtration but also a filtration treatment method in which air is supplied while filtration is performed, as in the case of biochemical treatment.

[Conventional technology]

Aerobic biological filter bed devices have been known for some time. This device supplies organic sewage in a downward flow to a fixed bed immersed in granular materials such as sand, activated carbon, anthracite, chamotte, natural lightweight aggregate, and artificial lightweight aggregate, while air bubbles are pumped out from the bottom of the fixed bed. BOD is biologically removed by the biofilm on the surface of the filter medium while SS is filtered out while being brought into countercurrent contact with wastewater.

This device (BAF: Biological Aerat
(abbreviated as ed Filter) is rational because biological treatment and SS filtration are performed simultaneously in the same tank, and it has attracted a lot of attention, and actual devices are becoming widespread at a considerable speed.

However, when the present inventor retested the performance of BAF of this conventional technology, SS and BOD were 100% like raw sewage.
■It was confirmed that when organic wastewater with a rating of 1 or more is passed through at a high concentration, severe clogging occurs in the surface layer of the packed bed due to SS and biofilm growth and enlargement, and the filtration resistance increases rapidly. That is, even if the sewage is passed through at a low filtration rate (LV) of 25 m/day, filtration cannot be continued for 5 hr L.

As a result, the filter bed must be frequently backwashed, the amount of backwash wastewater becomes large, and the production efficiency of treated water is extremely poor, which is a serious drawback.

[Problem to be solved by the invention]

The object of the present invention is to develop a method and device that fundamentally solves the serious drawbacks of the conventional BAF, and is capable of continuously filtering various types of wastewater such as raw sewage at a high filtration rate for a long period of time. The purpose of this project is to provide a revolutionary new type of BAF.

[Means to solve the problem]

As a result of examining the causes of the shortcomings of conventional BAF, we discovered that conventional BAF has serious problems with its filter media composition.We adopted a new filter media that had not been considered before, and improved the raw water supply method. The present invention was completed based on the discovery that this provides a fundamental solution.

That is, the present invention is based on a new concept of forming a packed fixed bed using elastic porous bodies and supplying wastewater in a multi-stage manner in the height direction of the packed bed. ) A packed bed of elastic porous bodies is provided in the tank, and sewage supply sections are installed in multiple stages in the height direction of the packed bed to distribute and supply the sewage, and filtered water is supplied to the packed bed. A filtration method for sewage characterized by taking it out from the bottom, and (2) a packed bed of elastic porous bodies is provided in the tank, and sewage supply parts are installed in multiple stages in the height direction of the packed bed. The wastewater is distributed and supplied, filtered water is taken out from the lower part of the packed bed, and oxygen-containing bubbles are intermittently or continuously supplied into the packed bed from a position below the lowest stage of the wastewater supply section. (3) A packed bed of elastic porous bodies is provided in the tank, and a multi-stage supply section for distributing and supplying wastewater in the height direction of the packed bed is provided. A sewage filtration device, characterized in that it is installed in the shape of a tank and is equipped with a treated water outflow section for taking out the filtered water from the lower part of the packed bed, and (4) a packed bed of elastic porous bodies in the tank. A supply section for distributing and supplying sewage in the height direction of the packed bed is installed in a multi-stage manner, and a treated water outflow section takes out the filtered water from the lower part of the packed bed and oxygen-containing bubbles are added to the sewage water. This problem can be solved by using a biological filtration device for wastewater, which is characterized in that a feeding device is provided for feeding into the packed bed from a position below the lowest stage of the feeding section.

Conventionally, the biological treatment method itself using sponge granules has been known (Reference: Fuchu et al., "Fluidized bed biofilm treatment using urethane foam", Water and Wastewater, Vol. 132.
No.5. pp17-24 (1990)).

This technology uses biofilm attached to the surface and inside of sponge particles instead of floating activated sludge in the activated sludge method.

That is, a large number of sponge particles are put into an aeration tank, and aeration air is used to make the sponge particles float and fluidize to remove BOD.
This is a technique that precipitates S and microbial flocs.

The idea of using sponge particles as a microbial adhesion carrier while floating and flowing is well known, but as in the present invention, it is immobilized by forming a packed bed with elastic porous bodies, and raw water is transferred in multiple stages. Previously, engineers and researchers had never come up with the idea of simultaneously removing SS filtration and BOD in the same tank by supplying air bubbles in a downward flow and bringing them into countercurrent contact with air bubbles. be.

The reason for this is that when a packed bed is formed using sponge particles, the porosity of the packed bed becomes as large as 95%, creating a packed bed full of gaps, making it impossible to effectively remove SS. If air bubbles are supplied from the bottom of such a packed bed, turbulence will occur due to the upward movement of the bubbles, making it impossible to effectively filter SS, and most of the SS will pass through the packed bed. This is probably because it was thought that

However, the inventor of the present invention overcame this preconception or fixed idea and conducted an actual experiment, which revealed that, contrary to the conventional preconception, SS and BOD were removed simultaneously extremely effectively, and the filtration resistance increased. It was found that this was significantly less than the conventional BAF.

This experimental fact is a remarkable finding discovered for the first time by the present invention, and is a phenomenon that forms the basis of the present invention.

The present invention has the following advantages: a fixed bed filled with immersion is formed using elastic porous bodies, raw water is passed through it in a downward flow, and raw water is distributed and supplied in multiple stages in the height direction of the packed bed. It is an original idea.

When the elastic porous bodies used in the present invention (hereinafter, elastic porous bodies are simply referred to as porous bodies) are compressed under atmospheric pressure, they expel internal air, contract, and stop being compressed. It is a small porous body with elasticity that can be restored to its original state by absorbing air inside it, and any shape, material, pore structure, etc. can be used as long as it has water absorbing properties.

The material for the porous body is not particularly limited as long as it has the above-mentioned properties, and known materials such as organic polymers and inorganic compounds can be used. A material having the following properties is preferable, and a urethane resin or the like is particularly preferable.

For example, porous bodies such as polyurethane foam are produced by foaming plastics such as urethane resin using a foaming method that creates open cells, and are used as is or after being cut into desired shapes and sizes.

The size of the porous bodies is 10 to 30 mm, preferably 1
The diameter is 5 to 20 mm, and the shape can be square, spherical, or various other shapes, but square is preferred. The specific gravity is usually preferably about 0.8 to 1.2.

The pore size of the porous body has a distribution, but a maximum of several mm is acceptable as long as the porosity of the entire porous body is 90% or more.

The most preferred embodiment of the present invention is to maintain aerobic conditions by supplying oxygen-containing bubbles to the packed bed filled with the porous bodies, thereby allowing microorganisms to adhere and propagate, thereby forming a biofilm on the surface of the packed bed. This method is used to biologically remove wastewater components that can be formed and can be treated at least aerobically, such as BOD, NH2-N, etc., and to physically remove SS. It's okay<NO-N
It may also have functions such as denitrification. Furthermore, it goes without saying that only physical removal of the SS may be performed.

In the present invention, it is sufficient to have at least one packed bed in a single tank, and a plurality of packed beds with different types of microorganisms, porous bodies, etc. can be provided in a single tank. For example, a plurality of aerobic packed beds made of porous bodies having different particle sizes and specific gravity, or an aerobic packed bed and an anaerobic packed bed can be provided in a single tank. In this case, the present invention provides, in addition to the packed bed made of porous bodies, a known filter medium other than the porous bodies, such as sand,
A packed bed made of granular solids such as anthracite, lightweight aggregate, and activated carbon may be used in combination.

In the present invention, organic sewage is supplied from a supply section provided in multiple stages in the height direction of the packed bed made of porous bodies, or the supply section is installed in multiple stages here. This means that the supply parts are arranged at a plurality of locations where the initial position (i.e., the supply part) at which the fluid flows down to the packed bed differs at least in the vertical direction, and the details of the configuration are not particularly limited.

Therefore, as long as the above conditions are satisfied, the structure of the supply section at the same horizontal position is not particularly limited, and the spout section of the organic wastewater of the supply section may be at one point or at multiple points, and may be linear or planar. Further, the supply section may be provided on the wall of the tank, or preferably, it may be provided inside the tank to achieve the advantage of the present invention, that is, S
This is desirable because it is possible to effectively exhibit a high filtration rate and high filtration continuity while maintaining a high removal rate of S and BOD.

The installation position of the supply section is, for example, in the case of a 3 m packed bed, above the packed bed surface, 100 cm from the packed bed surface,
The 200 cm point can be mentioned.

In addition, the present invention is applicable to the treatment of organic wastewater with a BOD of 100 to 400 ■/l and an SSS of 120 to 500
m/day, the filtration duration is 12 hours or more, and the amount of cleaning wastewater generated per 1rTi of sewage water is 0.05 to 0.
．． Since 15rd can be achieved, extremely efficient processing is possible.

Further, the amount of ejection from the supply section may be set to be constant or different in each supply section, and can be set as appropriate. It is possible to adjust the SS so that it is distributed more uniformly throughout the packed bed without being biased, and it is also possible to improve the filtration duration, the actual amount of water to be treated, and the removal efficiency.

When biological filtration is performed in the present invention, oxygen-containing bubbles are supplied to the packed bed in order to maintain at least aerobic conditions, or the position of the oxygen-containing bubble supply section is controlled by the organic filter provided in the packed bed. It is disposed at least below the lowest stage of the wastewater supply section, and can uniformly supply oxygen from the lower part of the packed bed to the upper part. The detailed structure of this oxygen-containing bubble supply device is not particularly limited, and conventionally known devices can be used.

Further, a packed bed made of granular solids other than porous bodies may be provided below the packed bed made of porous bodies, and when the device of the present invention is an aerobic biological filtration device, the latter packed bed Preferably, an oxygen-containing bubble supply section is provided within the chamber.

Furthermore, an anaerobic packed bed may be provided below the oxygen-containing bubble supply section.

In the present invention, the treated water is obtained from the treated water outflow part provided at the bottom of the tank, but the structure of this treated water outflow part can be any known device, and there are no particular restrictions, and it may be provided separately. The structure may also be a combination of the oxygen-containing bubble supply section of the packed bed and the packed bed cleaning means described below, such as a block structure.

In the device of the present invention, the packed bed must be washed after the filtration can be continued for a period of time, but the means for cleaning is not particularly limited (any conventionally known means can be applied). In this case, even if the oxygen-containing bubble supply device is also used for cleaning, a dedicated means such as an air supply device for air cleaning, a water supply device for water cleaning, etc. can be provided separately. In this case, water treated by the apparatus of the present invention is usually used as the washing water, but other water may be used in combination, if desired. Furthermore, in place of the cleaning air, any non-toxic gas that does not contain oxygen, such as nitrogen gas, may be used in combination, and such gas is particularly suitable when an anaerobic packed bed is provided, and is particularly suitable for this purpose. It is preferable to arrange the supply device at a position where the packed bed can also be commonly washed.

Further, it is preferable to provide an outflow prevention device on the packed bed to prevent the porous bodies from flowing out of the seed yarn during processing, washing, etc. As the outflow prevention device, a porous member such as a net can be used.

Washing water containing SS and the like generated by washing the packed bed with the washing device is discharged from a washing wastewater outlet provided at the upper part of the treatment tank. A known configuration can be applied to the outflow portion, but when the above-mentioned outflow prevention device is provided, the outflow portion may be provided at the upper part of the device.

〔Example〕

Hereinafter, specific examples in which the present invention is used as an aerobic biological filter bed will be described with reference to the accompanying drawings, along with its structure and operation, but the present invention is not limited thereto.
Needless to say, it can be applied as normal SS filtration.

Example 1 First, the description will be made with reference to FIG.

The biological filtration device 1 to which the method of the present invention is applied has a small porous body (preferably one having open cells, such as a rectangular parallelepiped piece of polyurethane foam with a size of 1 to 3 cm) in the treatment tank 2.
It has a filling layer 3 of. The height of the packed bed is not particularly limited, but is preferably about 2 to 4 m. Further, the packed bed 3 is not forcibly filled in a compressed state, but is filled in a natural state.

A treated water outflow pipe 4 is provided at the bottom of the packed bed 2.
The treated water outflow level 5 rises to the same level as the interface 6 of the packed bed. 7 represents the water level in the tank at the start of water flow.

Reference numeral 8 denotes a pipe for supplying oxygen-containing gas (air, etc.) necessary for respiration of microorganisms growing on the surface and inside of the filled filter medium.

9 is organic wastewater such as sewage, and 10 is a supply section that distributes and supplies the organic wastewater 9 in a multi-stage manner in the height direction of the packed bed 3.
11.12 and 1. They are each provided with a spout 13, 14, 15. The ejection part may have a structure in which a simple pipe is opened upward or downward, and may be a normal supply mechanism. 13 is located above the packed bed, and 14.15 is located within the packed bed.

Therefore, organic wastewater such as sewage is supplied to the supply section 10.11.1.
2, the oxygen-containing gas supply pipe 8 is distributed in a multi-stage manner in the height direction of the packed bed 3, and is passed through the packed bed 3 in a downward flow.
The bubbles are brought into countercurrent contact with the ascending flow of bubbles discharged from the oxygen-containing gas supply section 16 through the oxygen-containing gas supply section 16.

In addition, it is suitable that the position of the oxygen-containing gas supply section 16 is set at a position 1 to 2 m below the lowest stage of the raw water distribution section.

As the wastewater 9 flows down the packed bed 3 of porous bodies, the SS in the wastewater is filtered and removed, and the soluble B in the raw water is removed.
Decomposed and removed by OD or microbial membrane into 002 and LO,
The treated water becomes clear and flows out from the treated water outflow pipe 4. In this case, it is also possible to cause nitrification of NH and -N.

Surprisingly, as sewage passes through the packed bed 3, which is made up of porous bodies made of a sponge-like material with a porosity of over 90% and is full of gaps, it grows on the surface and inside of the filter material. The packed bed forms a stable filtration layer due to the microbial membrane, and the SS and colloid adsorption effect of the microbial membrane effectively removes SS in wastewater, and the increase in filtration resistance is also lower than that of conventional anthracite. It was observed that this amount was significantly lower than that of a BAF device using granular materials as a filter medium.

In other words, even if the porosity of the packed bed of the present invention is much larger than that of conventional BAF equipment (porosity is as small as about 50%), microbial membranes propagate in the porous filter medium, thereby reducing the SS in wastewater. It was confirmed for the first time that the removal effect of BAF was significantly increased, and that using a general filter medium with a small porosity like the conventional BAF device is inappropriate because the filtration resistance increases rather quickly.

In other words, conventional BAFs have only been able to treat wastewater while leaving major problems in the selection of filter media.

Moreover, since conventional BAF equipment supplies organic wastewater only from above the upper end of the filter bed, a large amount of SS is captured only near the upper end interface of the filter bed, and the microbial film is concentrated in this area. Due to the proliferation, an undesirable phenomenon was observed in which the filtration resistance near the upper interface of the filter bed increased very quickly.

In order to solve the drawbacks of the conventional BAF, the present invention has conducted various studies, and by distributing and supplying organic wastewater in a multi-stage manner in the height direction of the packed bed of porous bodies, the SS in the packed bed is
It was discovered that the distribution of supplementary amounts can be averaged. This method prevents SS capture and microbial film growth from being concentrated only near the upper interface of the packed bed.
It was confirmed that it was possible to disperse the material throughout the height of the packed bed. As a result, it was found that the increase in filtration resistance of the packed bed could be significantly reduced compared to conventional BAF.

In summary, the present invention improves the conventional B by the following two concepts.
The shortcomings of AF have been fundamentally solved.

(2) Construct an aerobic biological filter bed using porous bodies that have not been applied to conventional BAF.

■ Organic wastewater is distributed and supplied in multiple stages in the height direction of the packed bed.

The above two concepts made it possible to significantly reduce the growth rate of the aerobic biological filter bed.

According to the present invention, organic sewage can be treated at a high filtration rate (LV).
) Even if water is passed through the filter, the filtration resistance increases or decreases, so the frequency of cleaning the filter bed is reduced, and as a result, the amount of cleaning wastewater generated is lower than that of the conventional BA.
It decreases significantly from F.

The cleaning of the packed bed 3, which is the biological filter bed in the present invention, is easy, and when cleaning the filter bed, the cleaning water supply pump 17 is driven,
And by supplying cleaning air 18, simultaneous water and air cleaning is performed.
If this is carried out for ~10 minutes, the SS trapped in the filter bed of the packed bed 3 can be effectively washed out.

Reference numeral 19 indicates a cleaning drainage outflow portion, and reference numeral 20 indicates a porous member (such as a net) for preventing the outflow of porous bodies.

Embodiment 2 Another preferred embodiment of the present invention includes a biological filtration device 21 shown in FIG.

This shows that if a fixed layer 22 of granular solids such as anthracite, zeolite, granular activated carbon, or chamotte is provided under the packed bed 3 of porous bodies shown in FIG. 1, even better treated water quality can be obtained. A filtration device can be configured. In this case, the position of the oxygen-containing gas supply section 16 shown in FIG. 1 is preferably provided within the fixed layer 22. Note that the symbols used in FIG. 2 have the same meanings as in FIG. 1.

It is important that the particle size of the granular solid of the fixed layer 22 is smaller than the size of the porous bodies, and that the specific gravity is larger than that of the porous bodies.゛Example 3 Using the device shown in Fig. 1 of the present invention (diameter 20 cmφ), performance comparison was made with a conventional BAF device (diameter 20 cmφ). Raw water includes underground water (5S100~130■/II,
BOD 120-150/1) was used.

Table 1 shows the experimental conditions and results. -Table 1 As is clear from Table 1, compared to the conventional BAF device, the present invention can continue filtration for 16 hours at the same raw water and the same filtration rate.
It can be extended to double the length of time, resulting in remarkable effects that can be called technological innovations, and the quality of the treated water is the same as that of conventional equipment. However, the conventional device can only filter for 3 hours, making it impractical.

As a result, the washing wastewater generation ratio of the present invention is significantly reduced compared to conventional devices, and disposal is easy, and the production efficiency of treated water is also very high.

〔Effect of the invention〕

■ Since the continuous filtration time can be significantly longer than that of conventional BAF, the frequency of cleaning can be significantly reduced.

■ It is necessary to consume treated water to clean the filter bed, but
The present invention can significantly reduce the consumption of treated water compared to conventional devices. In contrast, in conventional BAF, most of the treated water must be consumed as cleaning water, which is extremely unreasonable.

■ Since it is possible to achieve a high LV that cannot be achieved with conventional BAF, the installation area and construction cost of the device can be greatly reduced.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views for explaining an example of a specific embodiment of the present invention. l: Biological filtration device 2: Treatment tank 3: Filled bed 4: Treated water outflow pipe 5: Treated water outflow water level 6: Interface 7: Water level in tank 8: Oxygen-containing gas supply pipe 9: Organic sewage 10.11.12 : Supply section 13, 14.
15: Spout part 16: Oxygen-containing gas supply part 17: Cleaning water supply pump 18: Cleaning air 19: Cleaning wastewater outflow part 20: Porous member 21: Biological filtration device 22: Fixed layer

Claims (4)

[Claims] (1) A packed layer of elastic porous bodies is provided in the tank, and sewage supply sections are installed in a multi-tiered manner in the height direction of the packed layer, and the sewage is distributed and supplied, and the filtered water is poured into the filling layer. A method of filtration of sewage characterized by taking it out from the bottom of the layer. (2) A packed layer of elastic porous bodies is provided in the tank, and a sewage supply section is installed in a multi-tiered manner in the height direction of the filled layer, and the sewage is distributed and supplied, and the filtered water is poured into the filling layer. A method for filtrating sewage, characterized in that oxygen-containing bubbles are taken out from the bottom of the layer and intermittently or continuously supplied into the packed bed from a position below the lowest stage of the sewage supply section. (3) A packed bed of elastic porous bodies is provided in the tank, and a supply section for distributing and supplying wastewater in the height direction of the packed bed is installed in a multi-tiered manner, and the filtered water is transferred to the packed bed. A sewage filtration device characterized in that it is equipped with a treated water outflow section that is taken out from the bottom of the sewage filtration device. (4) A packed bed of elastic porous bodies is provided in the tank, and supply sections for distributing and supplying wastewater in the height direction of the packed bed are installed in a multi-tiered manner, and the filtered water is transferred to the packed bed. Biological filtration of wastewater, characterized in that it is equipped with a treated water outflow section taken out from the lower part of the wastewater supply section and a supply device for supplying oxygen-containing bubbles into the packed bed from a position below the lowest stage of the wastewater supply section. Device.