Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2002-02-19
2004-10-19
Barry, Chester T (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S611000
Reexamination Certificate
active
06805797
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of treating the incineration ash containing the heavy metal and the wastewater sludge, and more particularly, to a method comprising the steps of making the heavy metals existing in the incineration ashes insolulable, stabilizing the organic materials and separating from the ashes, and burying them in the conventional structure used for burying the plants. And such process is based on the reasonable plan considering the mutual relations between the properties.
BACKGROUND ART
The method of disposing the solid wastes recently causes an additional problem of city life since the method depends mainly on burying them under the ground. However, it is scarcely possible to secure a vast area of ground enough to bury the wastes even in the countries having the small territory in area such as Korea. Therefore, as an alternative plan, a method of treating the wastes by combusting them has been proposed for extending the effective life of the ground to bury in.
In case that the wastes are incinerated and buried in the ground, an advantage that the effective life of landfill may be extended by reducing the volume of trash to be buried may be achieved.
Generally, there have been proposed two types of methods of treating the incineration ash, one of which is the conventional solidification method carried out by mixing the solidifier and the incineration ash together with the additional water in a mixer, and then solidifying the mixture. And a chemical method of solid stabilization by adding a certain chemical agent to the incineration ash to stabilize the heavy metals existing in the ash.
However, the conventional solidification method has several defects as follows:
1) The effect of reducing the volume of incineration ash is not significant, 2) since the heavy metal in the cement may be eluded out depending pH value, the possibility of elution of the heavy metal is great, and 3) the cost for treatment is also high. The chemical method also has the defects that: 1) the expensive chemicals (chelating agents) should be used; 2) another possible problem causing another contamination may be caused due to using those chemicals (chelating agents); and 3) the possibility of elution of the heavy metal depending on pH is still high.
It is shown in the
FIGS. 1 and 2
attached herein that the defects of the prior art, depict the amount of heavy metal contained in the incineration ash and the amount of elution, respectively. And
FIG. 2
shows the result of elution test carried out by TCLP method.
FIG. 1
shows the amount of total contents of heavy metal, which the heavy metal contained in the incineration ash comprises 15.936 mg/kg of Pb, 620 mg/kg of Cd, 1.662 mg/kg of Cu, 20.311 mg/kg of Zn and so forth, which is relatively great amount.
Furthermore, as a result of analyzing the elements of incineration ash, it was detected that the incineration ash contained little nitrogen (N) and up to 3.997% of sulfur.
FIG. 2
shows the amount of elution of heavy metal, which the heavy metal eluded from the incineration ash comprises 12.51 mg/l of Pb, 17.03 mg/l of Cd, 5.90 mg/l of Cu, 302.19 mg/l of Zn etc., which significantly exceeds the current standard allowed by the government.
As mentioned above, a little amounts of heavy metals incinerated is not essentially removed from the ash during the incineration process but it is just being concentrated and still existing in the incinerated ash (as being the fly ash as well as the ash lain on the bottom). And if entrapped by the dust collector, its concentration becomes much higher than that has not gone through the incineration. The heavy metals contained in the fly ash and the ash lain on the bottom may be eluded by the rain water when filled in the landfill, and become the leachate, which may cause the secondary contamination of soil and underground water Therefore, a suitable control and/or treatment are required in order to avoid such contamination.
DISCLOSURE OF INVENTION
It is therefore the object of the present invention to provide an essential method for treatment of the incineration ash, which may solve above problems
The present invention provides a method of treating the incineration ash and the wastewater sludge (hereinafter, called as “incineration ash”), both of which contain a certain amounts of heavy metals, which comprises the steps of converting the heavy metals contained in the incineration ash into an insoluble state, using a safe manner, in order to prevent the exuding of the heavy metals from the incineration ash outwardly when eluded.
The present invention also provides a method for treatment of the incineration ash by burying together with together with organic wastes, which comprises treating the incineration ash with sulfate-reducing bacteria, which may be provided by the organic wastes containing the sulfate-reducing bacteria.
To accomplish above object, the present invention provides a method for treatment of the incineration ash and the wastewater sludge, wherein a mutual relations in using nutrients exists between the incineration ash containing the heavy metal and the organic wastes containing the wastewater sludge and sulfate-reducing bacteria, which comprises: burying the incineration ash together with the organic wastes under the ground, in which the bacteria reduce the sulfates existing in the incineration ash to form the sulfides, and binding the formed sulfides with the heavy metal to form the insoluble metal sulfides, in order to prevent the heavy metal from exuding out of the incineration ash as eluate.
The present invention also provides a method for treatment of the incineration ash and the wastewater sludge, comprising: burying the incineration ash together with the organic wastes containing the sulfate-reducing bacteria under the ground, and covering them with a depth of soil, so that the said sulfate-reducing bacteria promote the heavy metal to precipitate in the form of insoluble metal sulfides, in order to prevent the heavy metal from exuding out of the incineration ash as eluate.
The present invention further provides a method for treatment of the incineration ash and the wastewater sludge, which comprises: collecting and mixing the aqueous eluate exuding out of the incineration ash and the aqueous eluate exuding out of the organic waste containing the said sulfate-reducing bacteria in a disposal plant, and reacting both the aqueous eluates so that the said sulfate-reducing bacteria existing in the aqueous eluate exuding out of the organic waste deposits the heavy metals from the aqueous eluate exuding out of the incineration ash as the insoluble metal sulfides, resulting in the disposal of the aqueous eluate exuding out of the incineration ash and the aqueous eluate exuding out of the organic waste.
Furthermore, according to an aspect of the invention, the said organic wastes may comprise the sewage sludge containing the said sulfate-reducing bacteria.
The present invention will be described hereinafter by referring to attached drawings.
The present invention provides a method for treatment of the incineration ash and the wastewater sludge, which is carried out by reducing the large amount of sulfates in the inclination ash into the sulfides, binding the sulfides with the heavy metals from the inclination ash, and precipitating and removing the insoluble metal sulfides as formed.
FIG. 3
shows the result of analysis for the elements of the incineration ash by use of element analyzer. As seen from the
FIG. 3
, a large amount of sulfur element exists in the incineration ash.
The element sulfur binds with oxygen in the incineration ash, and exists in the form of sulfate (SO
4
−2
) in the solution containing the incineration ash.
The mechanism of binding the heavy metal with sulfur in the incineration ash by the sulfate-reducing bacteria will be explained hereinafter referring to FIG.
4
.
FIG. 4
shows the pathway through which the sulfate (SO
4
−2
) is to be reduced into sulfides (S
−2
) by the sulfate-reducing bacteria.
The sulfate (SO
4
&m
Barry Chester T
Birch & Stewart Kolasch & Birch, LLP
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