JP2000079399A - Treatment of highly concentrated waste solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly conc. waste soln. treatment method capable of integrally treating excretions and capable of performing solid-liquid separation after methane treatment in a sedimentation tank. SOLUTION: In a highly conc, waste soln. treatment method for digesting an org. waste soln. containing a suspending solid in high concn. such as livestock excretions in an anaerobic digesting process 7 to subject the digested soln. 8 flowing out of the digesting process 7 to solid-liquid separation 12 and treating the primary separated water 13 obtained by separating a suspending solid 17 in an aerobic treatment process 14 and subjecting this treated soln. to solid-liquid separation to obtain the secondary separated water 15, the solid-liquid separation 12 of the outflown digested soln. 8 is performed after a part 15' of the secondary separated water is injected, and all of known solid-liquid separation techniques can be adapted to the solid-liquid separation 12, but a gravity sedimentation simple in maintenance and operation is pref. used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating high-concentration waste liquid, and more particularly, to a method for biologically treating an organic waste liquid containing high-concentration suspended solids such as livestock manure.

[0002]

2. Description of the Related Art Conventionally, livestock manure is mainly subjected to aerobic treatment, but aerobic treatment of a high-concentration waste liquid in which feces and urine are mixed requires a great deal of energy for aeration.
For this reason, pig houses have a structure in which feces and urine are separately discharged, and in many cases only urine having a relatively low concentration of contamination is subjected to aerobic treatment. The feces that are separately discharged are often sprayed directly on the fields or composted by a composting device. As described above, in the manure treatment, the conventional aerobic treatment requires a large amount of energy, and thus the methane fermentation treatment is also known as an effective means. Methane fermentation is energy-saving because organic matter is decomposed only by stirring, but water temperature must be maintained at about 38 ° C., and thus usually requires heating. The methane generated in the methane fermentation treatment is used for heating. Since urine treatment alone cannot generate a sufficient amount of methane for warming, when performing methane fermentation treatment, manure is mixed to increase the concentration and improve the amount of methane generated.

The liquid after the methane fermentation treatment still has a high concentration of pollutants. For this reason, further aerobic treatment is required, but a large amount of suspended substances having a high BOD requires a large amount of aeration energy. For this reason, the digestion / desorption liquid is subjected to aerobic treatment by removing suspended substances using a mechanical solid-liquid separator such as a centrifugal dehydrator, but the mechanical solid-liquid separator has a large power consumption and a large amount. Requires chemicals for sludge flocculation and requires regular maintenance.
On the other hand, the gravity sedimentation method using a sedimentation tank does not have the drawbacks of the mechanical solid-liquid separation device, but it is practically difficult to separate the digestion / elimination liquid into treated water and suspended solids. In addition, separation of manure in a livestock barn requires separation equipment and work, and there is a demand for integrated treatment of manure.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and can treat feces and urine integrally, and can perform solid-liquid separation after methane treatment in a sedimentation tank. It is an object to provide a method.

[0005]

In order to solve the above-mentioned problems, according to the present invention, an organic effluent containing a high concentration of suspended solids is digested in an anaerobic digestion step, and effluent digestion from the digestion step is performed. The liquid is solid-liquid separated, the primary separated water obtained by separating the suspended solids is treated in an aerobic treatment step, and the treated liquid is subjected to solid-liquid separation to obtain a secondary separated water. In the treatment method, the solid-liquid separation of the outflow digestion liquid is performed after a part of the secondary separation water is injected. Solid-liquid separation performed in the present invention, precipitation, coagulation sedimentation, flotation, centrifugation,
Any known solid-liquid separation technology such as membrane separation can be applied, but gravity sedimentation by sedimentation with a simple maintenance operation is preferred. Known digestion means can be applied to the digested sludge settled by the gravity settling method. At this time, the digested sludge can be economically and easily dewatered because fine suspended solids are not contained therein.

[0006]

Next, a processing method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a process chart showing an example of the treatment method of the present invention. An example in which this process chart is applied to the treatment of pig manure will be described. The swine manure 1 is, for example, a press-type contaminant removal device 2 such as a screw press dehydrator.
Then, impurities 3 such as biologically inactive hair and straw in manure are separated,
The soft solids in the feces that have been dehydrated and removed are screwed together with urine by a screw press 2 and squeezed out as a squeezed liquid 4.
Is stored in The stored liquid 6 is introduced into a methane fermentation tank 7 adjusted to about 38 ° C., and organic matter in the water is decomposed into methane gas and carbon dioxide gas.
0, stored in the gas tank 11 and used for boilers, generators, etc. The residence time of the methane fermentation tank 7 may be 10 to 20 days, but it is desirable that the residence time is long within an allowable range in order to gasify organic matter as much as possible.

The digested liquid 8 flowing out of the methane fermenter 7
Next, is introduced into the solid-liquid separation tank 12 together with the recirculated portion 15 ′ of the secondary separation water 15 from the aerobic treatment device 14, and is separated into primary separation water 13 and digested sludge 17. Primary separation water 1
The BOD material remaining in 3 is oxidized by a conventional aerobic treatment device 14 such as an activated sludge method or an oxidation ditch, and a part of the secondary separation water 15 is discharged as treated water 16. The surplus sludge 18 generated from the digested sludge 17 and the aerobic treatment device 14 may be directly sprayed on farmland, but it is preferable to mix it with the screw press contaminants 3 after dehydration to form compost. When dewatering digested sludge 17 and surplus sludge 18, the same dehydrator as described above may be used.

[0008]

The present invention will be described below in more detail with reference to examples. Example 1 According to the process diagram of FIG. 1, the treatment of pig manure was performed under the following processing conditions. (Treatment conditions) Swine manure amount: about 1.3 m ³ / day, squeezed liquid treatment amount: 1 m ³ / day, pressing type foreign matter removal device: screw press dehydrator, dehydrated foreign matter moisture content: 63%, storage tank, Volume: 3.0 m ³ ,

Methane fermentation tank, volume: 20 m ³ , water temperature: 37-39 ° C., residence time: 20 days, gas generation: 28 m ³ / day, gas tank: 20 m ³ , solid-liquid separation tank (gravitational sedimentation tank), volume : 5 m ³ , digestion fluid 8 inflow: 1 m ³ / day, secondary separation water 15 ′ inflow: 1 m ³ / day, solid-liquid separation time: 12 hours, solid-liquid separation tank separation water: 1.5 m ³ / day ,

Aerobic treatment device, (oxidation pond), effective volume: 10 m ³ , primary separated water 13 inflow: 1.5 m ³ , secondary separated water 15 outflow: 1.5 m ³ / day, residence time: 6, 7 days, Processed water 16 outflow: 0.5 m ³ / day, Digested sludge 17 outflow: 0.5 m ³ / day, For comparison, digestion liquid alone was introduced into the solid-liquid separation tank 12, Separation was performed for 24 hours, and the amount of separated water was only 0.2 m ³ . Table 1 shows the water quality after each treatment as a treatment result.
In the table, the squeezed liquid showed an average value, and the solid-liquid separation tank separation water and the oxidation pond treated water showed a fluctuation range.

[0011]

[Table 1]

[0012]

According to the present invention, the following effects can be obtained. (1) The solid-liquid separation of digestive juice can be performed by an economical and simple gravity sedimentation method without using a mechanical device. (2) Since it is not necessary to separate livestock dung and urine, the structure of the livestock barn can be simplified, and troublesome sorting work can be omitted.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a processing method of the present invention.

[Explanation of symbols]

1: pig manure, 2: impurity removing device, 3: foreign material, 4: squeezed liquid, 5: storage tank, 6: storage liquid, 7: methane fermentation tank,
8: digestion liquid, 9: biogas, 10: desulfurizer, 11: gas tank, 12: solid-liquid separation tank, 13: primary separated water, 1
4: aerobic treatment device, 15: secondary separated water, 15 ': return water, 16: treated water, 17: digested sludge, 18: surplus sludge,

Continued on the front page (72) Inventor Naoaki Kataoka 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa F-term in Ebara Research Institute, Ltd. (Reference) 4D040 AA01 BB01 4D059 AA01 BA01 BA12

Claims (1)

[Claims] 1. An organic effluent containing a high concentration of suspended solids is digested in an anaerobic digestion step, and the digested effluent from the digestion step is solid-liquid separated to separate suspended solids. One
A method for treating a high-concentration waste liquid in which the next separated water is treated in an aerobic treatment step and the treated liquid is subjected to solid-liquid separation to obtain a second separated water. A method for treating high-concentration waste liquid, which is performed after a part of water is injected.