JPH10328693A - Biological treatment for waste liquid containing organic solid matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating waste liquid containing organic solid matter in which treated water of high quality is obtained by applying high-load anaerobic treatment to treatment of waste liquid containing the organic solid matter and efficiently performing treatment and also stabilization of organic sludge and volume reduction are enabled. SOLUTION: Waste liquid 11 containing organic solid matter is applied to solid-liquid separation in a first solid-liquid separator 1. Separated liquid 12 is introduced into a high-load anaerobic treatment device 2 and applied to high-load anaerobic treatment by a UASB method or the like. High-load anaerobically treated liquid 14 is introduced into an activated sludge treatment tank 3 and remaining soluble organic substance and a small amount of SS component are aerobically decomposed. Activated sludge treatment liquid 15 is applied to solid-liquid separation and separated liquid 16 is discharged as treated water 18 to the outside of the system. A part of separated sludge 17 is returned to the activated sludge treatment tank 3 as return sludge 19. The residue of separated sludge 17 is transferred to an aerobic digestion tank 21 as aerobic after- treatment sludge 22 and mixed with solid matter 13 separated in the first solid-liquid separator 1. Air is passed into the mixed solution and organic substance is aerobically digested.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biological treatment method for wastewater containing organic solids, and more particularly to a treatment method combining anaerobic treatment and aerobic treatment.

[0002]

2. Description of the Related Art Effluents from the food industry, such as effluents from beer production, contain organic solids, and anaerobic and aerobic treatments are used to treat such effluents containing organic solids. Are performed in combination.

Among anaerobic treatments, high-load anaerobic treatment such as a fixed bed method in which anaerobic bacteria are fixed and brought into contact with a liquid to be treated, a UASB (upflow anaerobic sludge blanket) method, etc., are efficient. This method is known as a method for treating soluble BOD, but cannot directly treat effluent containing suspended BOD, that is, organic solids. The reason for this is that in a high-load anaerobic treatment, the soluble BOD decomposes at a high rate, but the organic solids occlude the fixed bed and the sludge blanket, reducing the treatment efficiency.

For this reason, the waste liquid containing organic solids has been subjected to solid-liquid separation, and the separated liquid has been subjected to anaerobic treatment and aerobic post-treatment, and the separated solids have been separately treated. Since the separated solids are partially subjected to acid fermentation and have a strong odor, it is difficult to perform the dehydration treatment as it is.For this reason, it is usually sent to the aerobic post-treatment step to perform aerobic decomposition together with the anaerobic treatment liquid. I have.

FIG. 3 is a flow sheet showing a conventional method for treating wastewater containing organic solids. In FIG. 3, 1 is a first solid-liquid separator, 2 is a high-load anaerobic treatment device, 3 is an activated sludge treatment tank, 4 is a second solid-liquid separation device, and an activated sludge treatment tank 3 and a second Solid-liquid separator 4
Constitute the aerobic post-processing device 5.

In the processing method according to the flow shown in FIG. 3, a waste liquid 11 containing an organic solid is first solid-liquid separated into a separated liquid 12 and a separated solid 13 in a first solid-liquid separation device 1. The separated liquid 12 is introduced into the high-load anaerobic treatment device 2 and subjected to anaerobic treatment. Thereby, the soluble organic matter in the separation liquid 12 is decomposed into methane through the acid generation step and the methane generation step.
As the high-load anaerobic treatment device 2, a device that performs high-load anaerobic treatment by a fixed bed method, a fluidized bed method, a UASB method, or the like can be used. The high-load anaerobic treatment liquid 14 is introduced into the activated sludge treatment tank 3 of the aerobic post-treatment device 5, aerated with air from the diffuser, and flows out from the remaining soluble organic matter and the high-load anaerobic treatment device 2. Decompose small amounts of SS aerobically. The activated sludge treatment liquid 15 is solid-liquid separated into a separation liquid 16 and a separation sludge 17 by the second solid-liquid separation device 4, and the separation liquid 16 is discharged out of the system as a treatment water 18. Returned to the activated sludge treatment tank 3 as returned sludge 19,
The remaining part 20 is dewatered and then disposed of by a method such as incineration.

The separated solid 13 separated by the first solid-liquid separator 1 is introduced into the activated sludge treatment tank 3 of the aerobic post-treatment device 5 and mixed with the high-load anaerobic treatment liquid 14 to form an organic solid. Break down the minute.

As shown in FIG. 3, when high-load anaerobic treatment is employed as anaerobic treatment, in order to decompose organic substances stably and efficiently, the high-load anaerobic treatment apparatus 2 is used as described above. The first stage is provided with the first solid-liquid separation device 1 and the drainage 11
It is necessary to previously separate solids such as organic solids therein as separated solids 13. Usually, the separation liquid 12
Solid-liquid separation is performed so that the SS in the effluent 11 is 10 to 20% or less of the COD _Cr in the drainage 11.

In the case where the high-load anaerobic treatment is the fixed bed method, clogging of the filter bed by the inflowing SS component is prevented by separating the solid content by the solid-liquid separator 1, and the anaerobic treatment is stably and efficiently performed. can do. In the case of the UASB method, the reduction of methane production activity due to the incorporation of organic solids into the granules and the floating of the granules due to cavitation inside the granules are prevented, and the anaerobic treatment is stably and efficiently performed. can do.

[0013] Separated solid content 13 separated by solid-liquid separation device 1
Since some have undergone acid fermentation and have a pronounced odor, dehydration and disposal may cause odor pollution,
The separated solid 13 is transferred to the activated sludge treatment tank 3 to perform aerobic treatment. By subjecting the separated solid 13 to aerobic treatment, generation of odor is prevented, and the amount of generated sludge can be reduced.

However, in the conventional processing method as shown in FIG.
There is a problem that high-quality treated water 18 cannot be obtained. That is, in the activated sludge treatment tank 3, since the amount of the solid organic matter is larger than the amount of the soluble organic matter, floc formation of the activated sludge becomes poor, so that fine SS leaks into the treated water 18 and becomes transparent. If the temperature decreases, the treated water 18
May become cloudy. In addition, in the conventional method, since the separated solids are decomposed by aerobic post-treatment, it is difficult to employ a processing method other than the activated sludge treatment such as biofilm filtration as the aerobic post-treatment. There is also a problem that it cannot be selected.

Further, in the aerobic treatment, in order to obtain the treated water 18 of high quality, the wastewater 11 containing organic solids may be directly introduced into the activated sludge treatment tank 3 to increase the ratio of soluble organic matter. However, in this case, there is a problem that the effect of the high-load anaerobic treatment is reduced by half, and the efficiency of the entire treatment is reduced.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to apply a high-load anaerobic treatment to the treatment of wastewater containing organic solids to efficiently treat the wastewater, and to obtain treated water of high water quality. An object of the present invention is to propose a method for treating wastewater containing organic solids, which can stabilize and reduce the volume of organic sludge.

The present invention provides a solid-liquid separation step of solid-liquid separation of a waste liquid containing an organic solid into a separated liquid and a separated solid, and an anaerobic treatment step of anaerobic-treating the separated liquid in the solid-liquid separation step. When,
Aerobic post-treatment step of aerobically treating the anaerobic treatment liquid of the anaerobic treatment step, sludge of the aerobic post-treatment step, and aerobic digestion by aerating a mixture of the solids separated in the solid-liquid separation step. And an aerobic digestion step.

The effluent to be treated in the present invention is an effluent containing organic solids. Specific examples include wastewater from the food industry, such as wastewater from beer production, wastewater from starch production, and potato processing wastewater, other industrial wastewater, human waste, and livestock manure. Of these, the food industry effluent is preferred. Inorganic solids may be contained in small amounts, but if they contain a relatively large amount of inorganic solids, such as sewage sludge or water treatment sludge, after separating the inorganic solids,
It can be subjected to the method of the present invention.

In the method of the present invention, the waste liquid containing organic solids is first solid-liquid separated into a separated liquid and a separated solid in a solid-liquid separation step. As the solid-liquid separation, methods such as spontaneous sedimentation, coagulation sedimentation, flotation under pressure, and centrifugation can be adopted.

The separated liquid separated in the solid-liquid separation step is introduced into an anaerobic treatment step and subjected to anaerobic treatment. This allows
The soluble organic matter in the separated liquid is decomposed through the steps of organic acid generation and methane generation. The anaerobic treatment can be performed in a separate reaction vessel for organic acid production and methane production, or can be performed in one reaction vessel.

The anaerobic treatment includes a fixed bed method, a fluidized bed
Load, anaerobic biological treatment such as UASB method
You. The high-load anaerobic treatment conditions include a temperature of 25 to 40.
° C, preferably 30 to 38 ° C, residence time 2 to 48 hours,
Preferably for 4 to 24 hours, COD _CrLoad 4 to 40kgC
OD_Cr/ M^Three/ Day, preferably 5-20 kg COD
_Cr/ M^Three/ Day is desirable.

The anaerobic treatment liquid subjected to the anaerobic treatment in the anaerobic treatment step is introduced into an aerobic post-treatment step, and is subjected to an aerobic treatment. As a result, soluble organic matter remaining in the anaerobic treatment and a small amount of SS flowing out from the anaerobic treatment step are aerobically decomposed. As the aerobic post-treatment, various aerobic biological treatments such as an activated sludge treatment method and a biofilm filtration method can be employed.
In the case of activated sludge treatment, the activated sludge treatment liquid is subjected to solid-liquid separation, and the separated liquid is discharged out of the system as treated water. In the case of biofilm filtration, the biofilm filtrate is discharged outside the system as treated water.

In the present invention, in the aerobic post-treatment step, only the anaerobic treatment liquid is subjected to the aerobic treatment, and the solids separated in the solid-liquid separation step are not mixed. There is no leakage and no turbidity of the treated water, and high-quality treated water can be obtained.

The separated solid in the solid-liquid separation step is introduced into an aerobic digestion step, and a part or all of sludge (hereinafter, referred to as aerobic post-treatment sludge) generated from the aerobic post-treatment step, for example, activated sludge Separated sludge from solid-liquid separation of treatment liquid,
In the case of the biofilm filtration method, the solution is mixed with a part or all of the biofilm washing solution, and air or oxygen is passed through the mixed solution to perform aerobic digestion. Thereby, the organic solids are mainly decomposed aerobically, the sludge is stabilized, and the odor component is also decomposed.

As the aerobic digestion, a method of introducing separated solids and aerobic post-treatment sludge into an aerobic digestion tank and aerobically treating microorganisms by aerating air or oxygen to the mixed solution is employed. be able to.

The residence time of the aerobic digestion tank varies depending on the quality and quantity of the separated solids, but by setting the residence time to about 1 to 5 days, the organic solid content in the separated solids is usually 50%.
Up to 70% can be mineralized. Aerobic digester M
The LSS concentration depends on the concentration of the organic solids in the separated solids and the like, but is usually about 3000 to 30000 mg / L, preferably 5000 to 10000 mg / L. For example, the volume of the separated solid obtained by solid-liquid separation of the beer production effluent in the solid-liquid separation step is about 5 to 10% of the volume of the beer production effluent. In this case, the capacity of the aerobic digestion tank is determined by (5 to 10% of the liquid volume of the beer production effluent) x (the number of staying days). The separated solid content of the beer production effluent is a sludge slurry having an organic solid content concentration of usually about 1 w / w%.

[0024]

According to the present invention, the method for biologically treating a wastewater containing an organic solid is anaerobic-treated for a separated liquid in a solid-liquid separation step, and the treated liquid is subjected to an aerobic post-treatment and a solid-liquid separation step. The aerobic digestion is performed by mixing the separated solid content and the sludge from the aerobic post-treatment process, so that high-load anaerobic treatment can be applied to the treatment of wastewater containing organic solid content to efficiently perform the treatment. As a result, it is possible to obtain treated water of high quality and to stabilize and reduce the volume of organic sludge.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 is a flow sheet showing a biological treatment method for a wastewater containing an organic solid content according to an embodiment, and the same reference numerals as those in FIG. 3 denote the same or corresponding parts. In FIG. 1, reference numeral 21 denotes an aerobic digestion tank.

In the processing method according to the flow shown in FIG. 1, a waste liquid 11 containing an organic solid is first solid-liquid separated into a separated liquid 12 and a separated solid 13 in a first solid-liquid separator 1. The separated liquid 12 is introduced into the high-load anaerobic treatment device 2 and subjected to anaerobic treatment. Thereby, the soluble organic matter in the separation liquid 12 is decomposed into methane through the acid generation step and the methane generation step.
As the high-load anaerobic treatment device 2, a device that performs high-load anaerobic treatment by a fixed bed method, a fluidized bed method, a UASB method, or the like can be used. The high-load anaerobic treatment liquid 14 is introduced into the activated sludge treatment tank 3 of the aerobic post-treatment device 5, aerated with air from the diffuser, and flows out from the remaining soluble organic matter and the high-load anaerobic treatment device 2. Decompose small amounts of SS aerobically. The activated sludge treatment liquid 15 is solid-liquid separated into a separation liquid 16 and a separation sludge 17 by the second solid-liquid separation device 4, and the separation liquid 16 is discharged out of the system as treated water 18. Separated sludge 17
Is returned to the activated sludge treatment tank 3 as return sludge 19, and the remainder is returned to the aerobic digestion tank 2 as aerobic post-treatment sludge 22.
Transfer to 1.

In the case of FIG. 1, since only the high-load anaerobic treatment liquid 14 is subjected to the activated sludge treatment in the activated sludge treatment tank 3, floc formation of the activated sludge is good.
The leakage of fine SS into the inside 8 is prevented, the visibility of the treated water 18 does not decrease, and the treated water 18 of high quality is obtained without becoming cloudy.

The separated solid 13 separated by the first solid-liquid separation device 1 and the aerobic post-treatment sludge 22 are converted into an aerobic digestion tank 21.
Then, air or oxygen is aerated from the air diffuser to the mixed solution in the tank to aerobically digest organic substances. In this case, the aerobic microbial cells contained in the aerobic post-treatment sludge 22 decompose the organic solids and odor components in the separated solids, and the sludge itself is self-digested.

The aerobic digestive juice 23 can be dehydrated after a concentration operation such as sedimentation concentration, or can be directly concentrated and dehydrated by a method such as granulation concentration after adding an agent. The desorbed liquid after dehydration can be discharged to the outside of the system as it is, or can be returned to the raw water tank to be mixed with the discharged liquid 11 or transferred to the activated sludge treatment tank 3. The dewatered sludge can be disposed of by a method such as incineration.

In the aerobic digestion tank 21, the organic solids in the separated solids 13 are decomposed, and a part of the aerobic post-treatment sludge 22 is decomposed by self-digestion due to excessive aeration. Reduces the volume. Further, since the generated sludge is in a state in which excess organic substances are decomposed by self-digestion, stabilized sludge is obtained and handling is easy.

This sludge can be disposed of in the same manner as in the conventional method by dehydration, incineration, etc., and further reduced in volume by solubilization by ozone treatment or the like and aerobic treatment in the activated sludge treatment tank 3 or the aerobic digestion tank 21. It is also possible to increase the degree of conversion.

FIG. 2 shows an embodiment using an aerobic post-treatment device 5 comprising a biofilm filtration device 6 and a backwash wastewater concentration tank 7. The processing method according to the flow of FIG. 2 introduces the high-load anaerobic treatment liquid 14 into the biofilm filtration device 6 and aerobically removes the remaining soluble organic matter and a small amount of SS flowing out of the high-load anaerobic treatment device 2. Decompose. The filtrate 25 is discharged as treated water 18 out of the system.

The biofilm filtration device 6 has a filter layer on which a biofilm is formed. The high-load anaerobic treatment liquid 14 is passed through the filter layer, and air is diffused from the lower part of the filter layer. An apparatus capable of removing impurities such as organic substances and SS can be used.

The filter layer is formed of a floating carrier such as a granular foamed resin, or a sedimentable carrier such as a resin, activated carbon, sand, etc., having a particle size of 0.5 to 20 mm, preferably 1 to 5 mm. A film formed is preferable, but a block shape,
A biofilm may be formed on a collection of linear or planar carriers, or on a carrier that is three-dimensionally continuous as a whole. The biofilm is formed spontaneously by passing the liquid to be treated through these filter layers and performing the same operation as the treatment operation. The biofilm is formed by the propagation of activated sludge containing microorganisms that decompose organic substances and the like in the liquid to be treated on the carrier. The filter layer is formed so that the liquid can be passed while such a biofilm is formed. The height of the filter layer, the size of the gap and the like are arbitrarily determined within the range required for the treatment.

As the treatment proceeds, the amount of sludge in the filter layer increases due to the capture of SS and the growth of the biofilm, and the pressure loss increases. Therefore, the filter layer is backwashed and washed. After the backwash wastewater 26 is concentrated in the backwash wastewater concentration tank 7, the concentrated sludge 27 is removed from the aerobic digestion tank 2.
Introduce to 1 for aerobic digestion. The separation liquid 28 is mixed with the high-load anaerobic treatment liquid 14 and introduced into the biofilm filtration device 6 for aerobic treatment. Other operations are the same as those in FIG.

In the treatment method according to the flow of FIG. 2, since the biofilm filtration device 6 is used as the aerobic post-treatment device 5, the treated water 18 having high water quality can be obtained efficiently. Further, as in the case of FIG. 1, the sludge is reduced in volume and stable sludge is obtained.

COMPARATIVE EXAMPLE 1 The wastewater containing organic solids was biologically treated according to the flow shown in FIG. As the high-load anaerobic treatment device 2, a device based on the UASB method was used. As the drainage 11, general wastewater from a beer factory was used. Table 1 shows the water quality.

[0038]

[Table 1]

As the activated sludge treatment tank 3, a 5-liter aeration tank was used, and as the solid-liquid separator 4, a 3-liter settling tank was used. While maintaining the volume ratio of the UASB treatment liquid 14 to the separated solid 13 at 9: 1, the water quality of the treated water 18 was examined while the residence time was reduced stepwise. Table 2 shows the results.

Example 1 In the flow of FIG. 1, the same drainage 11 as in Comparative Example 1 was subjected to biological treatment. A 4-liter aeration tank was used as the activated sludge treatment tank 3, a 3-liter settling tank was used as the solid-liquid separator 4, and a 1-liter aeration tank was used as the aerobic digestion tank 21. The sludge concentration in the activated sludge treatment tank 3 was extracted to about 3000 mg / L, and the entire amount of the extracted sludge was supplied to the aerobic digestion tank 21. Table 2 shows the results.

Example 2 In the flow of FIG. 2, the same effluent 11 as in Comparative Example 1 was biologically treated. As the biofilm filtration device 6, floatable spherical beads (specific gravity 0.05) made of expanded polystyrene having a particle diameter of 3 mm are used.
Packing height 76 in a column with 50mm inner diameter x 120cm length
A device packed to a volume of 1.5 cm (1.5 liter) was used. A sedimentation tank was used as the backwash wastewater concentration tank 7. The biofilm filtration device 6 was backwashed once a day with a stream of water and air. After the backwash wastewater 26 is concentrated in the sedimentation tank,
The S component was mixed with the separated solid 13 and supplied to the aerobic digestion tank 21. The aerobic digestion tank 21 has the same volume of 1 l as in the first embodiment.
Iter's aeration tank. Table 2 shows the results.

[0042]

[Table 2] Note in Table 2) Each run was operated for 2 weeks for 2
Average week values

As can be seen from the results shown in Table 2, the aeration tank of Comparative Example 1 was 5 liters, and the volume of the aeration tank + digestion tank of Example 1 was 5 liters.
liter, and the total aeration tank capacity is the same, but the treated water quality is clearly superior in Example 1. Further, in the treatment of Example 2 using biofilm filtration, it is clear that the quality of treated water is improved with a more compact configuration. The amount of generated excess sludge was almost the same between Comparative Example 1, Example 1 and Example 2, and the conversion ratio of excess sludge to SS was about 30% with respect to the raw water BOD ₅ load.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a processing method according to an embodiment.

FIG. 2 is a flowchart illustrating a processing method according to another embodiment.

FIG. 3 is a flow sheet showing a conventional processing method.

[Explanation of symbols]

 1, 4 solid-liquid separation device 2 high-load anaerobic treatment device 3 activated sludge treatment tank 5 aerobic post-treatment device 6 biofilm filtration device 7 backwash wastewater concentration tank 11 wastewater 12, 16, 28 separated liquid 13 separated solid Min 14 High-load anaerobic treatment liquid 15 Activated sludge treatment liquid 17 Separated sludge 18 Treated water 19 Returned sludge 20 Remaining 21 Aerobic digestion tank 22 Aerobic post-treatment sludge 23 Aerobic digestion liquid 25 Filtrate 26 Backwash wastewater 27 Concentration Sludge

Claims (1)

[Claims] 1. A solid-liquid separation step of solid-liquid separation of an effluent containing an organic solid content into a separated liquid and a separated solid, an anaerobic treatment step of anaerobic-treating the separated liquid in the solid-liquid separation step, An aerobic post-treatment step of aerobically treating the anaerobic treatment liquid of the anaerobic treatment step; aerobic digestion by aerating through a mixture of the sludge of the aerobic post-treatment step and the solid separated in the solid-liquid separation step. A biological treatment method for a wastewater containing organic solids, which comprises an aerobic digestion step.