JPH09122626A - Pretreatment method for fermentation raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use waste containing heavy metals effectively by fermentation. SOLUTION: In advance of fermentation, a positive electrode and a negative electrode are inserted into a fermentation raw material 1 to pass direct current continuously or intermittently to remove heavy metals from the raw material 1. The electrophoresis of the heavy metals takes place by the energization of the raw material with a high water content, and the heavy metals can be removed easily by catching them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pretreating a fermented raw material for separating and removing heavy metals from the fermented raw material before fermenting the internal organs of shellfish, sewage sludge and the like for composting. is there.

[0002]

Conventionally, the internal organs of scallops, sewage sludge, etc. are mainly incinerated and then disposed of in a special landfill site. However, there is a demand for a treatment method that does not rely on incineration due to the problem of carbon dioxide generated during incineration. For example, it is considered that the above materials are fermented to be composted, and the fermentation device is similar to leftover food and animal excrement. Attempts have been made to stir and ferment in. However, heavy metals such as Cu, Cd, and As are easily accumulated and concentrated in the internal organs of shellfish and sewage sludge. When these are fermented and composted using these as raw materials for fermentation, the fermented product obtained has a high concentration of heavy metals. Remains. If this fermented product is used as compost, the soil will be contaminated with heavy metals and cause environmental problems. It is also possible to reduce the volume of these raw materials by fermentation to dispose of them, but as described above, since heavy metals are contained in high concentrations, there are many restrictions on the disposal site and disposal method, and the effect of volume reduction. Can't get enough. From these circumstances, it is conventionally considered that it is practically difficult to ferment the above-mentioned shellfish internal organs and sewage sludge for effective use or volume reduction.

The present invention has been made in view of the above circumstances. Fermentation processing of shellfish internal organs and sewage sludge, etc., where heavy metals are easily accumulated and concentrated, is utilized as compost, or volume is reduced as waste. It is an object of the present invention to provide a pretreatment method for a fermented raw material, which can reliably and easily separate and remove heavy metals so that they can be easily treated.

[0004]

In order to solve the above problems, the method for pretreatment of a fermentation treatment raw material according to the first aspect of the present invention is a continuous or intermittent direct current to the fermentation treatment raw material prior to the fermentation treatment. It is characterized in that heavy metals are separated and removed from the raw material for fermentation treatment by electrifying electricity. The pretreatment method of the fermentation treatment raw material of the second invention is characterized in that the energization treatment in the first invention is performed before the dehydration step. A pretreatment method for a fermentation raw material according to a third aspect of the invention is the first or second aspect of the invention, which utilizes a dehydration action that is performed at the same time as the separation of heavy metals by an electric current treatment to reduce the dehydration treatment in a subsequent step. It is characterized by

The present invention is optimally applied to the case of performing fermentation treatment for the purpose of composting, but is not limited to this and can be applied to the case of reducing the volume. is there. Further, the raw material to be treated in the present invention includes, as described above, the internal organs of shellfish (scallop, etc.) and sewage sludge, but is not limited to this, and contains many heavy metals. It can be used for other fermentative raw materials which are difficult to treat after the fermenting treatment and for fermentative raw materials for which the content of heavy metals is positively reduced, although the amount of heavy metals is not so large.

This energization treatment is performed before the fermentation treatment step, but it is desirable to perform it before the dehydration step as shown in the second aspect of the invention. This dehydration step is a step of reducing the water content of the fermentation treatment raw material having a high water content before the fermentation treatment in order to increase the fermentation efficiency. In this case, the energization treatment may be performed immediately before the dehydration step, and other treatments (for example, a raw material crushing step) can be interposed.

In the energization treatment, at least one positive electrode and at least one negative electrode are prepared, and these electrodes are placed in contact with the fermentation treatment raw material or embedded in the raw material. When disposing the electrodes, it is desirable to dispose a plurality of electrodes at equal intervals so that the treatment can be performed efficiently. The material of the electrode is not particularly limited, but it has good durability,
Further, it is desirable that the metal component does not elute into the raw material. In addition, when a direct current is applied, since heavy metals and raw material solids move through moisture, moisture may be dropped or around the electrode to prevent electrodeposition of the raw material on the positive electrode so that the separation efficiency does not decrease. It is desirable to dispose an adsorbing film, an ion exchange film or the like around the negative electrode so as to dispose the raw material blocking material in the above and to facilitate separation of heavy metals. Further, it is desirable to provide a hole or the like near the electrode for water intake. In addition, the current to be applied is a weak current that does not electrolyze water. When the direct current to be applied is large, a large amount of hydrogen gas is generated, and even if an electric shock occurs, it may lead to a serious accident, which increases the risk of working, which is not preferable.

When a direct current is continuously applied,
Continue energizing for a predetermined time. At this time, the energization amount may be constant, or the energization amount may be variously changed over time. Further, in the case where the energization is continuously performed, the energization can be performed in a predetermined cycle or according to a predetermined time table, and further, the energization can be optionally performed. The fermented raw material that has been subjected to the electric current treatment is desirably subjected to dehydration treatment immediately after or after performing necessary treatment (crushing treatment or the like), and then subjected to fermentation treatment.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings. In order to ferment the fermented raw material and use it as compost, the fermented raw material is subjected to the following energization treatment to remove heavy metals. Fermentation raw material 1
Are housed in a predetermined container 2, and a plurality of positive electrodes 3, ... And negative electrodes 4 ,. Among them, the positive electrode 3 has a structure in which a raw material blocking material 3b that blocks the movement of the raw material 1 is arranged so as to surround the positive electrode portion 3a, and the negative electrode 4 has heavy metals around the negative electrode portion 4a. The electrode unit 4 has a structure in which a filter 4b for collecting is provided.
A water intake hole 4c is provided between a and the filter 4b.

When a direct current is passed between the positive electrode 3 and the negative electrode 4 by the power source 6, an electrophoretic phenomenon occurs. In systems with high water content, heavy metal components are in the positive ion state or non-ionic colloid (slightly positively charged), and the solid content of the raw material is in the anionic state or slightly negatively charged. It is a colloid, and the heavy metals 7a and the water 7b attached thereto move positively and move to the negative electrode 4 side, while the solid content 8a of the fermentation raw material 1 and the water 8b attached thereto show negative. Attempts to move to the positive electrode 3 side. However, since the raw material blocking material 3b is disposed on the positive electrode 3, the solid content 8a and the adhering moisture 8b are slightly moved. On the other hand, the heavy metals 7a and the adhering water 7b actively move to the cathode 4 side, and the heavy metals 7a are captured by the filter 4b of the cathode 4. The adhered water 7b passes through the filter 4b and is taken out from the water intake hole 4c.

By continuing the energization, the heavy metals 7a in the fermentation raw material 1 are gradually removed and collected in the filter 4b, and the water in the fermentation raw material 1 is also gradually removed as adhered water, thereby containing water. The rate drops. The fermented raw material 1 from which heavy metals have been removed and the water content has been reduced by the end of the energization treatment is subjected to fermentation treatment by removing the positive electrode 3 and the negative electrode 4, and performing a crushing step, a dehydration step, and the like.
The fermentation treatment raw material 1 has a reduced water content due to the energization treatment, and the burden of the dehydration step is reduced. Next, a predetermined fermentation process is performed, and a compost containing no heavy metals is obtained.

[0012]

[Examples] Examples in which sewage sludge is used as a raw material for fermentation will be described below. This sewage sludge contains 12 ppm of As as heavy metals and has a water content of 95%.
Met. The sewage sludge was energized by the device described in the above embodiment. Specifically, a direct current of 8 mA was continuously applied for 6.5 hours. As a result, As in the sewage sludge was reduced to 0.01 ppm or less, and the water content was 7
It fell to 5%. The sewage sludge was dehydrated to reduce the water content to 70% and then subjected to fermentation treatment to reduce the volume.
Heavy metal content of the obtained fermented material is 0.01 pp
Since it was less than m, the disposal process could be easily performed.

Next, an example in which the internal organs of scallops are used as a raw material for fermentation will be described. This raw material contained 5 ppm of Cd as a heavy metal and had a water content of 90%. After this raw material was crushed to a size of several mm, an electric current treatment was carried out in the same device as above. When energized, a direct current of 10 mA was applied intermittently at 25 Hz for 10 hours. As a result, the Cd in the raw material was 0.01 ppm or less, and the water content was 80.
%. This material was dehydrated to adjust the water content to 70%, and then fermented to obtain compost. The content of heavy metals in the obtained compost was 0.01 ppm or less, and the soil was not contaminated even when it was added to the soil as compost.

[0014]

As described above, according to the method for pretreatment of a fermentation treatment raw material of the present invention, a DC current is continuously or intermittently applied to the fermentation treatment raw material before the fermentation treatment, so that Since the heavy metals are separated and removed from the raw material, the heavy metals can be removed from the raw material by a simple method, and the fermentation treatment raw material containing the heavy metals can be effectively used and the treatment can be facilitated.

Further, if the energization treatment is carried out before the dehydration step, the heavy metals can be efficiently separated and removed by utilizing the water contained in the fermentation treatment raw material. Generally, the raw material used for the fermentation treatment has a high water content (70% or more), and an electrophoretic phenomenon can be caused by applying electricity as it is without adding water. Such an effect cannot be obtained when the fermented material is electrically treated. Because of fermentation, the water content of the processed material is 30%.
This is because the water content has been reduced to a certain degree, and it is necessary to add water to obtain a smooth electrophoretic phenomenon. Further, there is also an effect that the water content of the fermentation treatment raw material can be reduced by energizing before the dehydration step, so that there is also an effect that the burden of the dehydration step can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an apparatus used for energization processing.

FIG. 2 is a plan view of the same.

FIG. 3 is an enlarged front view of a positive electrode and a negative electrode.

FIG. 4 is a schematic diagram for explaining a state of heavy metals and a raw material solid content in a raw material during energization.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fermentation processing raw material 3 Positive electrode 3a Positive electrode part 3b Raw material blocking material 4 Negative electrode 4a Negative electrode part 4b Filter 4c Water intake hole 6 Power source 7a Heavy metal 7b Adhesion moisture 8a Treatment raw material solid content 8b Adhesion moisture

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C05F 7/00 2115-4H C05F 17/00 17/00 B09B 3/00 A (72) Inventor 9 Eken Uen, 1-3, Takanodai, Yotsukaido, Chiba Stock Company Japan Steel Works (72) Inventor Takeshi Fukushima 1-3, Takanodai, Yotsukaido, Chiba Stock Company Japan Steel Works (72) Inventor Yoshiaki Oda Tokyo Fuchu No. 1 Nikkocho, Ichi, Japan Steel Works Ltd.

Claims (3)

[Claims] 1. A pretreatment of a fermentation treatment raw material, characterized in that, prior to the fermentation treatment, a direct current is continuously or intermittently applied to the fermentation treatment raw material to separate and remove heavy metals from the fermentation treatment raw material. Method 2. A method for pretreatment of a raw material for fermentation treatment, wherein the energization treatment according to claim 1 is performed before the dehydration step. 3. A pretreatment of a fermented raw material, characterized in that by carrying out the energization treatment according to claim 1 or 2, dehydration is carried out at the same time as the separation of heavy metals, and the dehydration treatment in the subsequent step is reduced. Method