JP2007301515A - Electrolysis device of sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolysis device of sludge which can prevent a deterioration of electrolysis efficiency by scraping scales deposited and adhering to the surface of a negative plate and removing sludge scum which is apt to accumulate in the upper part between electrode plates. <P>SOLUTION: In the electrolysis device of sludge which electrolyzes surplus sludge, generated by biological treatment of organic waste water with chlorides contained to sterilize the surplus sludge, a metal film element is used as at least the negative plate, and gas or liquid is injected from the inside of the metal film element for backwashing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to sludge solubilization technology for sterilizing the sludge by electrolytic treatment with respect to surplus sludge generated by biological treatment of organic wastewater. The present invention relates to a processing apparatus.

Conventionally, in sewage treatment plants, sewage and rainwater containing organic pollutants and the like are mixed, stirred and aerated with the activated sludge microorganisms held in the biological reaction tank, so that the activated sludge microorganisms absorb and decompose the pollutants. In the subsequent stage, the activated sludge microorganisms are solid-liquid separated to obtain clean supernatant water.
Activated sludge microorganisms obtained by solid-liquid separation are generally called surplus sludge, but it is necessary to carry out appropriate treatment and disposal such as landfill after dehydration or incineration.
However, since these treatment costs are high and there is not enough land to landfill, in recent years, solubilization treatment technology for excess sludge has attracted attention.

Solubilization technology is a chemical, physical or biological treatment of surplus sludge that kills activated sludge microorganisms that make up surplus sludge and returns it to the bioreactor. A system that breaks down microorganisms.
As one method for killing activated sludge microorganisms, there is a chemical method in which a chlorine compound such as chlorine molecules or hypochlorous acid is added.

In addition to adding chlorine molecules and hypochlorous acid directly, they can be generated by adding a chloride salt such as sodium chloride to sludge and electrolyzing it.
That is, sodium chloride or the like is added to excess sludge and electrolyzed to generate hypochlorous acid and chlorine molecules or hypochlorite ions, thereby killing activated sludge microorganisms (Patent Document 1). .
Alternatively, when there is sufficient chloride in the target excess sludge, electrolysis can be performed without adding chloride salt, thereby generating chlorine molecules and killing activated sludge microorganisms ( Patent Document 2).

In this way, chlorine molecules and hypochlorous acid can be generated by electrolyzing a chloride-containing solution or sludge. However, magnesium, calcium, etc. contained in the sludge during the electrolysis process are cathodic. It precipitates on the side and adheres to the electrode as a scale.
Since the electrical resistance increases at the portion where the scale is attached, only a part of the surface of the electrode is used effectively, and the efficiency is lowered.

Moreover, oxygen gas, hydrogen gas, and chlorine gas are generated by electrolyzing excess sludge.
In normal electrolysis, these gases become bubbles and most of them disappear when they rise to the surface of the water. However, in sludge, sludge containing these gases becomes highly viscous bubbles and does not disappear easily.
The foamed sludge accumulates over time as sludge scum, and when it reaches not only the part on the liquid level of the electrode but also below the liquid level that contributes to the electrolytic reaction, the electrode area decreases and efficiency increases. There is a problem that the remarkably decreases.

As a countermeasure, air bubbles are blown between the electrode plates through the air diffused holes of the cleaning pipe provided below the electrode plates, generating an air stirring water flow, etc., and stirring and cleaning between the electrode plates, and adhesion and accumulation of sludge. There is a method for preventing this (Patent Document 3).
On the other hand, in order to perform electrolysis with less energy consumption, it is effective to make the electrode plate interval as narrow as possible. However, if the electrode plate interval is about 10 mm or less, the resistance increases, and the stirring air is used as the electrode. It may become difficult to enter between the plates, and only a part between the electrodes may be stirred.
Therefore, in order to prevent the adhesion and accumulation of sludge, it is necessary to leave an interval of a certain value or more, and wasteful energy consumption occurs.
JP 2002-126782 A Japanese Patent Laid-Open No. 2003-062592 JP 2005-305389 A

  In view of the problems of the conventional sludge electrolytic treatment apparatus, the present invention peels off the scale deposited and adhered to the surface of the cathode plate and removes sludge scum that tends to accumulate in the upper part between the electrode plates, It aims at providing the electrolytic treatment apparatus of the sludge which can prevent the efficiency fall of electrolytic treatment.

  In order to achieve the above object, the sludge electrolysis apparatus of the present invention is a sludge electrolysis process in which surplus sludge generated by biological treatment of organic waste water is sterilized by electrolytic treatment in a state containing chloride. In the apparatus, at least a metal film element is used as a cathode plate, and gas or liquid is back-washed and injected from the inside of the metal film element.

  In this case, a metal film element is used for both the cathode plate and the anode plate, and gas or liquid can be back-washed and injected from the inside of the metal film element.

  According to the sludge electrolytic treatment apparatus of the present invention, a metal film element is used as at least a cathode plate of the electrolytic treatment apparatus, and gas or liquid is back-washed and injected from the inside of the metal film element. It is possible to remove the adhering scale and keep the electrode surface clean, and to prevent the adhesion and accumulation of highly viscous sludge scum generated during electrolytic treatment even when the electrode plate interval is narrowed. As a result, sludge can be sterilized efficiently by effectively utilizing the entire surface of the electrode during electrolysis.

  In this case, surplus sludge adheres and accumulates between the electrode plates during the electrolytic treatment by using metal film elements for both the cathode plate and the anode plate and back-injecting gas or liquid from the inside of the metal film element. And can be easily removed.

Embodiments of the sludge electrolytic treatment apparatus of the present invention will be described below based on the drawings.
In the present invention, a metal film element is used for the cathode of the electrode used for the electrolytic treatment.
The metal membrane element is a flat membrane element of a thin metal filter membrane used for separation of a solid and a liquid as used in a membrane filtration device or the like.
In a membrane filtration device, a plurality of flat membrane elements (also referred to as “membrane modules”) are arranged inside a filtration tank in parallel with a predetermined gap, and a suction pipe is connected to each hollow flat membrane element. At the same time, the flat membrane element is immersed in the sewage water in the filtration tank and the inside of the flat membrane element is sucked, so that only the liquid in the sewage is filtered and sucked to separate the liquid and solids in the sewage water. And configured to process.

When separating the liquid and solid matter by sucking the inside of the flat membrane element, the solid matter may accumulate on the surface or inside of the membrane and cause clogging. There are reverse cleaning method and chemical cleaning method.
In the present invention, the principle of the reverse cleaning method and chemical cleaning method is used for peeling off scales, sludge scum, and sludge that adhere to and accumulate on the surface of the electrode plate.

During the electrolytic treatment, calcium, magnesium, etc. are deposited on the cathode side of the electrode, but a metal film element is used for the cathode, and air, water, chemical solution or gas is sent continuously or intermittently, and the metal film electrode is reversed. By washing, scales such as calcium and magnesium deposited on the electrode surface can be peeled off, and the electrode surface can always be kept clean.
In addition, the highly viscous foamy sludge scum adhering to the electrode surface can be easily peeled off, and a reduction in electrolytic efficiency can be prevented.
Note that a normal electrode such as a metal electrode or a carbon electrode may be used for the anode. By using a metal film element for the anode, sludge that gradually adheres and accumulates on the anode side can be easily removed. it can.

  FIG. 1 shows an embodiment in the case where a metal membrane element is used for the cathode plate and air is used as a cleaning means for the electrode surface in the sludge electrolytic treatment apparatus of the present invention.

Excess sludge A generated in the water treatment system is guided to the electrolytic cell 1.
The electrolytic cell 1 is provided with electrodes used for electrolytic treatment. The electrode plate includes a metal film cathode 2 using a metal film element and an anode 3 using a general electrode such as a carbon electrode or a metal electrode.
Electrolytic chemical solution B supplied from electrolytic chemical tank 4 is added to electrolytic cell 1. In this embodiment, sodium chloride as a chloride source and pH in electrolytic cell 1 are set to about 5 as the liquid. An example of combining hydrochloric acid as an acid for the purpose is shown below.
In addition to the above, the combination of chloride and acid may be sodium chloride and sulfuric acid, potassium chloride and nitric acid, or hypochlorous acid itself may be used.
These chlorine molecules and hypochlorous acid generated by the electrolytic treatment are strong oxidizing agents and can sterilize sludge microorganisms contained in the excess sludge A.
That is, the cell wall and cell membrane of the microorganism can be damaged, and the function as a living body can be stopped, whereby the microorganism becomes an inanimate organic substance.

  The excess sludge subjected to the electrolytic treatment flows out from the electrolytic cell 1 as electrolytic sludge C, but the sludge is returned to the biological reaction tank (not shown) in the water treatment system, and the activated sludge retained in this tank. Degraded by microorganisms.

On the other hand, the metal film cathode 2 installed in the electrolytic cell 1 is provided with an air supply pipe 5 for blowing air, and air D is blown by a blower 6 such as a blower or a compressor.
When the air blown into the metal film cathode 2 is ejected as fine bubbles E from countless holes in the metal film cathode 2, precipitates and scale F such as magnesium and calcium adhering to the electrode surface are removed. In addition to peeling, adhesion and accumulation of highly viscous foamy sludge scum G containing hydrogen gas generated by electrolysis can be prevented or easily peeled off.

Further, in the conventional method, the stirring flow generated from below the electrode plates is taken into consideration, and the electrode plate interval is set to about 10 mm. However, in this embodiment, even if the electrode plate interval is 10 mm or less, the gap between the electrode plates is Stirring is performed without any problem by the air ejected from the inside of the metal film electrode.
Therefore, the distance between the electrode plates can be further narrowed, and the power consumption can be reduced.
The fluid back-injected into the metal film element may be water, chemicals, gas, or the like in addition to air.
Further, by using a metal film element for the anode, it is possible to more effectively prevent sludge from adhering to and depositing on the electrode plate.

  The sludge electrolysis apparatus of the present invention has been described based on the examples thereof. However, the present invention is not limited to the configurations described in the above examples, and the configurations described in the examples are appropriately combined. The configuration can be changed as appropriate without departing from the spirit of the invention.

  The sludge electrolysis apparatus of the present invention uses a metal film element as at least a cathode plate, and removes scales and sludge scum adhering to the cathode by backwashing gas or liquid from the inside of the metal film element. Since it has the characteristic, it can be used suitably for the use of the cleaning of the electrode of an electrolytic treatment apparatus.

1 shows an embodiment of the sludge electrolysis apparatus of the present invention, (a) is a sectional view of an electrolytic cell, (b) is a side view showing an electrode plate made of a metal film element, and (c) is an enlarged view of the electrode plate. It is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolysis tank 2 Metal film cathode 3 Anode 4 Electrochemical tank 5 Air supply piping 6 Air blower A Excess sludge B Electrochemical C Electrolytic sludge D Air E Fine bubble F Scale G Sludge scum

Claims (2)

  In a sludge electrolysis apparatus for sterilizing surplus sludge generated by biological treatment of organic wastewater by electrolytic treatment in a state containing chloride, at least a metal film element is used as a cathode plate, and the metal film element The sludge electrolytic treatment apparatus is characterized in that gas or liquid is back-washed and injected from the inside of the inside.   2. The sludge electrolysis apparatus according to claim 1, wherein a metal film element is used for both the cathode plate and the anode plate, and gas or liquid is back-washed and injected from the inside of the metal film element.

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