JPH02135200A - Treatment of organic waste water and device therefor - Google Patents

Abstract

PURPOSE:To reduce the treating time and to decrease the frequency of washings by passing org. waste water through a filter bed, and further injecting an oxygen-contg. gas. CONSTITUTION:The waste water 8 is passed through a screen, etc., and then introduced into a tank filter 2. Most of the suspended solids(SS) and SS-based oxygen demand (OD) are collected by a fibrous filter medium packed in the filter bed 1, and removed. The effluent water 22 from the tank filter 2 is sent to a biological-membrane tank filter 4, and fine SS, which has not been removed in the tank filter 2, is collected. The BOD component is biologically oxidized and decomposed by the oxygen in the air supplied from an air diffuser 10 and the microbes living in the filter bed 3, and the waste water is purified. By this method, the working rate of the filter is increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to BOD components such as urban sewage and industrial wastewater, SS (
The present invention relates to a method and apparatus for treating organic wastewater that incorporates biofilm filtration to treat organic wastewater containing (suspended solids).

[Prior Art] In the biofilm filtration method, wastewater is made to flow into a tank equipped with a biofilm filtration bed filled with granular filter media and equipped with an aeration means that blows air from the bottom of the filtration bed. This method biologically oxidizes and decomposes BOD components in wastewater by the action of aerobic microorganisms that grow on the surface. This method has high oxygen dissolution efficiency due to good gas-liquid contact within the filter bed, and also has the function of removing SS at the same time as removing BOD components. However, in this method, especially high BO
D. When treating wastewater with high SS, the filter bed becomes severely clogged, requiring frequent cleaning, and the removal operation must be interrupted each time.

A technique for alleviating the clogging of the filter bed and reducing the number of times of cleaning is proposed in Japanese Patent Application Laid-Open No. 58-49492. This technology divides the biofilm treatment process, which has both a biological treatment function and an SS capture function, into two stages, and each stage is responsible for removing SS and BOD components in wastewater. FIG. 4 is an explanatory diagram of this technique. In FIG. 4, in the apparatus of this technology, a first step treatment tank equipped with a submerged filter bed 41 and a second step treatment tank equipped with a deep filter bed 42 are arranged in series. Filter bed of each treatment tank 41.42
is filled with granular filter media, and the particle size of the filter media filled in the submerged filter bed 41 in the first step is equal to that of the deep filter bed 42 in the second step.
The particle size should be larger than that of the filter medium to be filled. Each treatment tank has an aeration device 43 at the bottom thereof for supplying oxygen to the microorganisms growing on the filter beds 41 and 42, respectively.
It is equipped with 44. However, the first step may include anaerobic biological treatment, and in this case, the air diffuser 43 is stopped.

When treating organic wastewater containing BOD components and SS by the above technique, the wastewater 8 is
1, part of the BOD component and part of ss are removed. SS and BOD remaining in the effluent water 4o from this first step
The components are removed in the next second step, a deep filtration bed 42, and are discharged as treated water 23.

And, in the examples, S S 160 to 260 mg/4
, the results of treating sewage with a BOD of 140 to 380 mg/β are shown. In this experiment, the first step was anaerobic biological treatment, and the experimental conditions were as follows.

1st step (anaerobic filter bed) Filter medium 10-15 stops plastic particle filling height
2m Water flow rate Residence time in filter bed 4 hours (12m/day) 2nd process (deep filter bed) Filter medium 3-4 am Anthracite filling height 1
．． 5m Water flow rate LOm/hour (240m 7 days) According to the experimental results, the removal rate of SS in the first step was 43-53%,
The BOD removal rate is 57-79%. In addition, the required frequency of filtering and unwashing is 48 to 60 times for the filtration bed in the first step.
It is stated that the filter bed in the second step was once every 30 to 40 hours.

[Problems to be Solved by the Invention] The above-mentioned conventional technology is a useful technology that can reduce the frequency of filtration and unwashing, but the processing time (residence time)
This requires a long time, resulting in a large-sized device, and there is also a need to further reduce the frequency of filtration and unwashing.

In other words, the conventional technology simply divides the biofilm treatment process, which has both a biological treatment function and an SS capture function, into two stages, and since all the removal of BOD components is done by biological oxidative decomposition, the treatment time is naturally becomes longer, and particularly the residence time in the filter bed in the first step requires a long time. Furthermore, in the first step, if high BOD and high SS wastewater is purified only by biological oxidative decomposition, it is inevitable that the filter bed will be clogged to a large degree and the frequency of filtering and unwashing will increase. The filtration bed in the first step is filled with granular filter media, or granular filter media has a large pressure loss and therefore has a high degree of clogging, so it is not a suitable filter media for high BOD and high SS treatment.

The present invention solves the above-mentioned problems, and provides a method and apparatus for treating organic wastewater that can continue treatment for a long time by shortening the treatment time and further reducing the frequency of cleaning the filter bed. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the method of the present invention includes a method in which water-resistant fibers are formed into a non-woven material and filled with a fiber filter medium whose porosity does not substantially change when water is passed through. A filtration step in which organic wastewater is passed through a filtration bed filled with organic waste water to capture SS and SS BOD components, and the effluent from this filtration step is passed through a filtration bed filled with granular filter media and oxygen-containing It consists of a biological treatment process in which gas is introduced and mainly BOD is removed.

Further, the device of the present invention includes a filtration tank equipped with a filtration bed filled with a fibrous filter medium made of non-woven water-resistant fibers and whose porosity does not substantially change during water passage; It consists of a biofilm filtration tank connected by a flow path, equipped with a filtration bed filled with granular filter media, and equipped with means for supplying an oxygen-containing gas below or inside the filtration bed. As the water-resistant fibers forming the fibrous filter medium, plastic fibers such as polyvinylidene chloride or metal wires such as stainless steel are used. Further, as the granular filter medium, anthracite, granular activated carbon, plastic particles, lightweight aggregate, expanded shale, etc., in any shape can be used.

[Function] The present invention is effective against SS in wastewater and BOD components contained in SS and whose purification rate by microorganisms is relatively slow (SS BOD components).
Filtration that physically or physicochemically captures fine SS
This is a method and apparatus for treating organic wastewater that combines biofilm filtration that mainly removes BOD components, and after removing most of SS and SS-based BOD components in the wastewater in the previous stage filtration treatment, this effluent water is is processed by biofilm filtration. Therefore, the functions for each processing step are clearly divided, and each processing step can be performed efficiently. That is, in the first-stage filtration process, only the filtration function is performed efficiently to prevent SS and SS-related BOD from being brought into the second-stage biofilm filtration process as much as possible. At this time, since the first-stage filtration treatment does not involve any biological treatment operation, the treatment time may be short, and the degree of clogging of the filtration bed is small, so that filtration can be continued for a long time. In biofilm filtration treatment, runoff water from which most of the SS and SS-related BOD have been removed through filtration treatment is treated, so the BOD load is significantly reduced. Therefore, the clogging of the filter bed is reduced, and the treatment can be continued for a long time.

The reason why the treatment can be carried out in a short time, the degree of clogging of the filter bed is small, and the treatment can be continued for a long time is because the filtration treatment in the first stage has excellent characteristics. In the filtration process of the present invention, a special filter medium is used.

This filter medium is a fibrous filter medium in which the above-mentioned water-resistant fibers are formed in a non-woven manner, and the porosity does not substantially change when water is passed through it, and was discovered based on the results of many tests.

The requirements for the filter medium listed by the present inventors are as follows, and the fiber filter medium used in the present invention satisfies all of these requirements.

■Filtration speed can be increased.

■High SS removal efficiency.

■Low pressure loss.

■ Filtration can be continued for a long time.

(Hard to get clogged) ■A large amount of SS is captured.

This fibrous filter medium has a much larger porosity than granular filter media.
Therefore, the pressure loss of the filter bed filled with this fibrous filter medium is extremely small, and as described later, it has the characteristic that it does not impair the removal efficiency of SS.

The fibrous filter medium used has a porosity of about 80% to 99.5%. This porosity is such that the pressure drop does not increase due to compression during water flow, and the degree of clogging is not large, and the SS
The decision was made on the assumption that the removal rate was good. Generally, the porosity of granular filter media is 45~
Approximately 55%, molded products such as Raschig rings 65-75%
Although the fibrous filter medium used in the present invention has a larger porosity than these granular filter media, it is possible to obtain high SS removal efficiency. A porosity of 80% is the lower limit at which the degree of clogging is small even when filtering wastewater with a high SS concentration, and if the porosity exceeds 99.5%, the removal rate of SS will be insufficient and the function as a filter medium will be insufficient. .

The granular filter medium used in the biofilm filtration process is selected to have an appropriate particle size depending on the SS concentration and particle size distribution in the wastewater, and is usually about 2 to 10 liters.

[Example] FIG. 2 is an explanatory diagram schematically showing a fiber filter medium used in the present invention. This fiber filter medium 30 has water-resistant fibers 31
It is made into an elastic body by bending, and the processed water-resistant fibers 31 are coated and bonded with a binder to form a three-dimensional mesh-like structure into a non-woven material. The diameter of the water-resistant fibers 31 constituting the fiber filter medium 30 is 100 denier (approximately 0.0911
1 m) to 10,000 denier (approximately 0.91+u). The porosity of the fiber filter medium 30 is selected within the range of 80% to 99.5% as described above.

The diameter of the water-resistant fibers 31 constituting the fiber filter medium 30 was determined as follows based on the results of a filter medium selection experiment.

If the filled fiber filter medium 30 is compressed and reduced in volume during water passage, the porosity will decrease and the processing performance will change, which is undesirable.For this reason, the water-resistant fibers 31 are Sometimes, it is necessary to have a strength that is not substantially compressed, and the diameter of the water-resistant fiber 31 that meets this condition needs to be about 100 deniers or more. However, if it becomes too thick, the effective surface area of the filter medium per unit volume of the filter medium decreases, and the filtration efficiency deteriorates. Thus, in consideration of the relationship with filtration efficiency, it is desirable that the diameter of the water-resistant fiber 31 is 10,000 deniers or less.

FIG. 1 is an explanatory diagram schematically showing a cross section of an embodiment of the device according to the present invention.

In FIG. 1, a filter tank 2 equipped with a filter bed 1 filled with a fibrous filter medium shown in FIG. 2 and a filter bed 3 filled with a granular filter medium are shown.
A biofilm filtration tank 4 equipped with a filtration tank 4 is connected by a pipe 5. A wastewater inflow pipe 6 is connected to the filtration tank 2, a treated water discharge pipe 7 is connected to the biofilm filtration tank 4, and a treatment flow path for the wastewater 8 is formed. The biofilm filtration tank 4 is equipped with an air supply means 9, which is an oxygen-containing gas, consisting of an aeration diffuser 10, piping 11, and a blower 12 provided below the filtration bed 3.
is made to flow in to supply oxygen to the microorganisms growing on the filter bed 3. In addition, the filtration tank 2 and the biofilm filtration tank 4 are equipped with a mechanism for supplying air and washing water for washing the filter bed 1.3 and for discharging washing waste water. The cleaning air 14 is sent to the filtration tank 2 by a cleaning blower 15, piping 16, and a diffuser 17, and can also be supplied to the biofilm filtration tank 4 through the piping 18.11 and the diffuser 10 line. The cleaning water 19 is branched from the pipe 20 and
It can be made to flow into the filtration tank 2 through 0a, and into the biofilm filtration tank 4 through piping 20b. Washing water discharge pipes 21a21b are provided above the sides of the filtration tank 2 and the biofilm filtration tank 4, respectively.

The embodiments of the present invention are not limited to the above-mentioned examples, and for example, the material of the fibers constituting the fiber filter medium is not limited to polyvinylidene chloride, but may also be plastics such as polyethylene or polypropylene, or metals such as stainless steel. It may be. In addition, the filter bed 1 of the filter tank 2 is not only formed by laying fiber filter media formed into a cube or rectangular parallelepiped as shown in Fig. 2, but also formed into a cube or sphere of an appropriate size. It may be formed by filling an amorphous fibrous filter medium, or the fibrous filter medium may be packed into a basket-like container and a plurality of bags may be filled therein to form a filtration bed.

A wastewater treatment method using the apparatus configured as described above will be explained. The waste water 8 that has passed through a screen or the like is made to flow into the filter tank 2. Most of the SS and SS BOD in the waste water 8 are removed by the trapping function of the fiber filter medium filled in the filter bed 1. The filter bed 1 filled with the fiber filter medium has the property of trapping SS in all layers, so the increase in pressure drop is small and filtration can be continued for a long time, and a large amount of SS can be collected. can be captured. Effluent water 22 leaving the filtration tank 2 is sent to the biofilm filtration tank 4. In the biofilm filtration tank 4, fine S that could not be removed in the filtration tank 2 is
While capturing S, BOD components are biologically oxidized and decomposed by the oxygen in the air supplied from the diffuser 10 and the microorganisms living in the filter bed 3, and the wastewater is discharged as purified treated water 23. do.

(Example 1) An urban sewage treatment experiment was conducted using the apparatus having the configuration shown in FIG.

The experimental conditions were as shown in Table 1, and air of 10 to 15 N per kg of inflow BOD was supplied to the biofilm filtration tank. The water quality of the sampled wastewater was as shown in Table 2. The results are shown in Table 2 and Figure 3.

Table 2 Experimental Results Figure 3 compares the particle size distributions of waste water and ss of the filtration tank outflow water. The particle size of SS contained in runoff water is mostly less than 37μ, and purification by microorganisms is relatively slow3.
Most of the ss of 7 μ or more is removed in the filtration tank.

In other words, the BOD in the effluent sent to the biofilm filtration tank
The ingredients are only those that are quickly purified by microorganisms,
The BOD load on the biofilm filtration tank is significantly reduced.

In Table 2, when calculating the removal rate of ss and BOD in the filtration tank, the removal rate of ss is 70 to 85%,
This value is the removal rate of the treatment tank in the first step in the conventional technology.
This is an extremely high value compared to 3% to 53%. And B.O.
Regarding the removal of D, the conventional technology using biological treatment is
Whereas the removal rate was 7 to 79%, a removal rate of 50 to 60% was obtained by simple filtration.

The frequency of cleaning the filter bed was once every 48 to 96 hours for the filtration tank, and once every 48 to 72 hours for the biofilm filtration tank. This cleaning frequency is also significantly reduced compared to the conventional technology.

Table 3 shows the results of a comparison between the present invention and the conventional activated sludge technology based on the above experimental results, based on trial calculations by the inventors.

In Table 3, the filtration tank of the present invention replaces the initial settling tank of the activated sludge process, and the biofilm filtration tank replaces the activated sludge aeration tank. Further, according to the present invention, a final settling tank is not required. As is clear from Table 3, the present invention requires only 30% of the space ratio and 35% of the energy ratio compared to the activated sludge method, resulting in significant space and energy savings.

[Effects of the Invention] The present invention is based on a combination of filtration treatment and biofilm filtration treatment, in which organic wastewater is filtered through a filter bed filled with a fiber filter medium having excellent characteristics, and then biofilm filtration is performed. The structure has the following effects:

The fiber filter media used in filtration treatment has low pressure loss and
Since the amount of SS trapped is large, filtration processing can be continued for a long time, increasing the operating rate of the filtration device.

Furthermore, since the filtration process can be performed at a high filtration rate and with a short residence time, the scale of the filtration apparatus can be small.

Most of the SS and Ss-based BOD components in wastewater are removed by filtration, and the load on biofilm filtration is significantly reduced. As a result, high BOD and high SS wastewater can be efficiently treated, and the scale of the apparatus can be reduced.

Furthermore, since the BOD load is reduced, the amount of air to be diffused can be reduced, and the blowing power can be saved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram schematically showing a cross section of an embodiment of the device according to the present invention, Fig. 2 is an explanatory diagram schematically showing a fiber filter medium used in the present invention, and Fig. 3 is an explanatory diagram schematically showing a cross section of an embodiment of the device according to the present invention. The fourth figure is an explanatory diagram of a conventional biofilm filtration device. 1.3... Filter bed, 2... Filter tank, 4... Biofilm filtration tank, 5... Piping, 6... Wastewater inflow pipe, 7...
Treated water discharge pipe, 8... Drainage, 9... Air supply means,
DESCRIPTION OF SYMBOLS 10... Diffuser, 12... Blower-513... Air, 22... Outflow water, 23... Treated water, 30...
Fiber filter medium, 31... Water resistant fiber.

Claims (2)

[Claims] (1) Organic wastewater is passed through a filter bed filled with a fibrous filter material made of non-woven water-resistant fibers and whose porosity does not substantially change during water passage to remove SS and SS BOD components. A method for treating organic wastewater consisting of a filtration step for capturing, and a biological treatment step for mainly removing BOD by passing the effluent from this filtration step through a filter bed filled with granular filter media and introducing an oxygen-containing gas. . (2) a filtration tank equipped with a filtration bed filled with a fibrous filter medium made of non-woven water-resistant fibers and whose porosity does not substantially change when water is passed through; connected to this filtration tank by a flow path; A treatment device for organic wastewater comprising a biofilm filter tank equipped with a filter bed filled with granular filter media and a means for supplying oxygen-containing gas below or inside the filter bed.