RELATED APPLICATIONS

This is a Continuation-In-Part application of International Patent Application serial No. PCT/JP00/01830 filed on Mar. 24, 2000, now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for processing organic chlorine compounds.

2. Related Background Art

There are cases where objects to be processed such as fly ash or main ash generated from waste incinerators, leachate from waste disposal facilities, suspended matters contained in the leachate, soils contaminated by inappropriately disposed wastes, and biological sludge subjected to leachate treatments contain a high concentration of hard-to-decompose organic chlorine compounds represented by dioxins. There are urgent social needs for eliminating or detoxifying the hard-to-decompose organic chlorine compounds. Recently, various methods for decomposing and processing materials containing such organic chlorine compounds have been proposed.

Among these methods, examples of physicochemical methods include high temperature incineration method, molten salt incineration method, active carbon adsorption method, gamma ray decomposition method, ozone decomposition method, wet type air oxidization method, catalyst incineration method, supercritical hydroxylation method, alkaline chemical decomposition method, alkaline catalyst decomposition method, thermal desorption method, and the like. On the other hand, as a biological method, Japanese Patent Application Laid-Open No. HEI 10-323646 and Japanese Patent Application Laid-Open No. HEI 10-257895 disclose methods using microorganisms having a lignin decomposing capability.

Also, literatures, e.g., Hiroyuki Nakagawa et al., “Bio-Remediation of Environment Contaminated with Aromatic Compounds,”

Water Purification and Liquid Wastes Treatment

, 39, 535-544 (1998), pp.539-540; Satoshi Takada, “Possibility of Decomposition of Dioxins by White-Rot Fungus,” the 23rd Lecture Meeting of Japan Society for Environmental Chemistry, Advanced Abstracts, 35-40 (1998); Tomohiko Ishiguro, “Decomposition and Elimination of Noxious Chemical Materials Such as Dioxins by Microorganisms,”

Journal of Water and Waste

, 33, 645-651 (1991); and the like generally describe methods using polychlorinated biphenyl (PCB) decomposing microorganisms, white-rot fungus, and the like. Further, a literature—C. Klimm et al.,

Chemosphere

, 37, 2003-2011 (1998)—reports an example of processing dioxins in a case where an object to be treated is kept under an anaerobic condition.

SUMMARY OF THE INVENTION

The inventors have studied the above-mentioned conventional methods and, as a result, have found the following problems. Namely:

(1) Conventional physicochemical methods often necessitate complicated, large-scale apparatus for fully decomposing organic chlorine compounds, such as dioxins, contained in the object to be processed. Among them, there are methods for which high temperature, high pressure, and the like are indispensable conditions. Therefore, if such methods are employed, then the processing tends to take time and labor, thereby raising the processing cost.

(2) Microorganisms employed in conventional biological methods tend to be hard to handle and collect. Also, there is a tendency that the kinds of dioxins fully decomposable thereby are limited, and the processing with a favorable stability and reproducibility is hard to carry out. As a result, the efficiency of decomposing dioxins may not always be sufficient.

(3) In the method in which the object to be processed is kept under an anaerobic condition, the effect of reducing dioxins with time cannot fully be obtained.

In view of such circumstances, it is an object of the present invention to provide a method and apparatus for processing organic chlorine compounds, which can decompose hard-to-decompose organic chlorine compounds such as dioxins by a treatment simpler than conventional ones, can remarkably improve the efficiency of decomposition, and can lower the processing cost.

For solving the above-mentioned problems, the inventors have repeated diligent studies, and have found that, if a specific microorganic body is caused to act on an object to be processed containing an organic chlorine compound such as a dioxin under a predetermined condition, the organic chlorine compound can be decomposed. Also, the inventors have found that the decomposing rate of organic chlorine compound can be enhanced if components inhibiting the decomposition of organic chlorine compound by the microorganic body are eliminated under a predetermined processing condition. The inventors have further repeated studies based on these findings, thereby accomplishing the present invention.

Namely, the method of processing an organic chlorine compound in accordance with the present invention is a method of decomposing and eliminating the organic chlorine compound in an object to be processed, the method comprising a biological treatment process of causing a first microorganic body capable of oxidizing reduced nitrogen to come into contact with the object to be processed, and biologically processing the object to be processed in a state containing the first microorganic body, so as to decompose the organic chlorine compound.

In such a method of processing an organic chlorine compound, if an aerobic treatment is carried out as the biological treatment, then a nitrifying reaction in which reduced nitrogen is oxidized by the first microorganic body is carried out. At this time, along with the nitrifying reaction, a reaction of decomposing the organic chlorine compound contained in the object to be processed proceeds, whereby the organic chlorine compound is decomposed, so as to turn into lower hydrocarbon, carbon dioxide, water, and the like.

Though the mechanism of decomposing the organic chlorine compound has not fully been elucidated, it is presumed that a conjugate reaction such as co-oxidation, for example, proceeds in an enzymatic reaction system in which an oxidase produced by the microorganic body involves, whereby the organic chlorine compound is oxidized and decomposed along with the oxidization (nitrification) of reduced nitrogen. However, the action is not restricted thereto. Such an enzymatic reaction does not necessitate severe reaction conditions such as high temperature and high pressure in particular, whereby hard-to-decompose organic chlorine compounds can be decomposed by very simple processing.

Preferably, a reduced nitrogen adding process for adding reduced nitrogen to the object to be processed is provided. As a consequence, an amount of reduced nitrogen sufficient for carrying out the aerobic treatment as the biological treatment can be supplied. Hence, the reaction of oxidizing reduced nitrogen by the first microorganic body and, consequently, the reaction of decomposing the organic chlorine compound can be caused to proceed reliably and sufficiently.

Thus, it is preferred that the biological treatment process comprises an aerobic treatment process of oxidizing reduced nitrogen contained in the object to be processed with the first microorganic body and decomposing the organic chlorine compound in an aerobic atmosphere. Here, as the first microorganic body, nitrite bacteria, nitrate bacteria, and the like which are easy to obtain and culture are preferably used. Examples of reduced nitrogen are those oxidized by such a first microorganic body, such as ammonium ion and urea, which may be originally contained in the object to be processed or be added thereto.

If the anaerobic treatment is carried out as the biological treatment, then the activity of first microorganic body for oxidizing reduced nitrogen tends to decrease. However, it has been verified that the organic chlorine compound in the object to be processed is favorably decomposed even in an anaerobic atmosphere in the state where the biological activity of the first microorganic body is maintained by way of a biologic treatment in an aerobic atmosphere (which may be the above-mentioned aerobic treatment process).

Though details of the mechanism of decomposing the organic chlorine compound have not been clear, it is presumed that, for example, an oxidase produced by the first microorganic body in the aerobic treatment is eluted as the first microorganic body is disassembled under the anaerobic condition, whereby the organic chlorine compound is oxidized and decomposed by an enzymatic reaction in which this oxidase involves. However, the action is not restricted thereto. As mentioned above, since such an enzymatic reaction does not necessitate severe reaction conditions such as high temperature and high pressure in particular, hard-to-decompose organic chlorine compounds can be decomposed by a very simple processing.

Thus, it will also be preferable if the biological treatment process comprises an anaerobic treatment process in which the object to be processed containing the first microorganic body keeping its biological activity by way of a biological treatment in an aerobic atmosphere is held in an anaerobic atmosphere. In addition, it is desirable that, in this anaerobic treatment process, supply of a gas including oxygen to the object to be processed is blocked, so as to form an anaerobic atmosphere, and this anaerobic atmosphere is maintained. In the anaerobic treatment process, it will be further preferable if the temperature of the object to be processed is held at 15° C. or higher, since the reaction of decomposing the organic chlorine compound is remarkably accelerated thereby.

It will be further preferred if the method further comprises an oxidized nitrogen eliminating process of reducing and eliminating oxidized nitrogen contained in the object to be processed with a second microorganic body capable of reducing oxidized nitrogen in an anaerobic atmosphere. If the object to be processed is one subjected to a nitrogen treatment of leachate or one with which the above-mentioned aerobic treatment process is carried out, for example, then oxidized nitrogen such as nitrate ion and nitrite ion generated upon oxidization of reduced nitrogen by the first microorganic body is contained in the object to be processed. Also, some of objects to be processed originally contain oxidized nitrogen. For such oxidized nitrogen, an environmental emission standard value has been defined, and there is a fear that the purified water or purified product obtained by processing the object to be processed may contain oxidized nitrogen by a nitrogen content exceeding its standard value in some cases.

The inventors have also found that the decomposing efficiency of inorganic chlorine compound in the aerobic and anaerobic treatment processes decreases if such oxidized nitrogen exists in the object to be processed. In the anaerobic treatment process in particular, the organic chlorine compound tends to be insufficiently eliminated if the object to be processed contains a microorganic body, such as denitrifying bacteria, adapted to reduce oxidized nitrogen as in the case of biological sludge subjected to a biological treatment. It is presumed that, if oxidized nitrogen exists under an anaerobic condition, then the activity of the denitrifying bacteria is maintained and, under the influence thereof, the first microorganic body is restrained from being disassembled, whereby the elution of oxidase is stagnated. However, the action is not restricted thereto.

If the object to be processed containing such oxidized nitrogen is subjected to the oxidized nitrogen eliminating process, then a denitrifying reaction in which the second microorganic body reduces oxidized nitrogen by using oxidized nitrogen and nutrients is carried out. As a consequence, oxidized nitrogen can be eliminated under a mild condition of normal temperature and normal pressure by turning it into nitrogen, carbon dioxide, water, and the like. As a consequence, the decomposing efficiency of organic chlorine compound in the aerobic and anaerobic treatment processes can fully be prevented from decreasing. Here, denitrifying bacteria and the like which are easy to obtain and culture are preferably used as the second microorganic body. Preferably, the oxidized nitrogen eliminating process is carried out before the aerobic treatment process, after the aerobic treatment process, or before the anaerobic treatment process.

More preferably, the aerobic treatment process has a first microorganic body adding step of adding the first microorganic body to the object to be processed; a reduced nitrogen adding step of adding reduced nitrogen to the object to be processed; and a decomposing step of supplying a gas containing oxygen to the object to be processed, so as to form an aerobic atmosphere, and causing the first microorganic body to oxidize reduced nitrogen and decompose the organic chlorine compound.

If the object to be processed is one containing a sufficient amount of the first microorganic body and/or reduced nitrogen beforehand, as with sludge generated upon another biological treatment, for example, then the first microorganic body adding step and/or reduced nitrogen adding step may not be carried out. Also, the first microorganic body adding step and reduced nitrogen adding step may be carried out simultaneously, or any of them may be carried out earlier, whereas they can be carried out before or simultaneously with the decomposing step. Here, the reduced nitrogen adding step is substantially equivalent to the above-mentioned reduced nitrogen adding process.

In this manner, oxygen is supplied to the object to be processed, so that an aerobic atmosphere is formed favorably, whereby a nitrifying reaction in which the first microorganic body oxidizes reduced nitrogen and its accompanying reaction of decomposing organic chlorine compound proceed under a mild condition of normal temperature and normal pressure. As a consequence, hard-to-decompose organic chlorine compounds can be decomposed by a mild and simple treatment at normal temperature and normal pressure without necessitating severe reaction conditions such as high temperature and high pressure. Also, since reduced nitrogen is positively added, the nitrifying reaction caused by the first microorganic body can be maintained favorably.

More preferably, the oxidized nitrogen eliminating process has a second microorganic body adding step of adding the second microorganic body to the object to be processed; a carbon source adding step of adding to the object to be processed an organic carbon source which becomes a nutrient for the second microorganic body; and an eliminating step of blocking supply of a gas containing oxygen to the object to be processed, so as to form an anaerobic atmosphere, and causing the second microorganic body to reduce and eliminate oxidized nitrogen.

If the object to be processed is one containing a sufficient amount of the second microorganic body and/or organic carbon source beforehand, such as surplus sludge generated upon another biological treatment, then the second microorganic body adding step and/or carbon source adding step may not be carried out. Also, the second microorganic body adding step and carbon source adding step may be carried out simultaneously, or any of them may be carried out earlier, whereas they can be carried out before or simultaneously with the eliminating step. If such an oxidized nitrogen eliminating step is carried out, then the second microorganic body grows while using the organic carbon source (also referred to as carbon source or hydrogen donor) as a nutrient, during which a denitrifying reaction for reducing oxidized nitrogen is favorably carried out.

It will also be preferred if an object to be processed mixing process of adding to and mixing with the object to be processed in at least one of the aerobic treatment process, oxidized nitrogen eliminating process, and anaerobic treatment process another object to be processed, different therefrom, containing an organic chlorine compound. In this manner, the other object to be processed can be processed by use of the first microorganic body acclimatized to the environment of use in each process. As a consequence, the decomposing efficiency of the organic chlorine compound contained in the other object to be processed is enhanced.

More preferably, as the first microorganic body and/or second microorganic body, those in a dehydrated cake form whose moisture is at least partly eliminated or in a lyophilized powder form are used.

Microorganic bodies are often obtained in the form of biological sludge as being cultured and acclimatized in a liquid such as a culture liquid in general. If a dehydrated cake form of biological sludge whose moisture is at least partly eliminated is used as a microorganic body, then its volume can be lowered. Also, since it is not liquid, its handling such as transportation and storage and operations for adding it to the object to be processed become easier, and the space for its storage and stock can be reduced. Further, since the moisture necessary for growing microorganic bodies decreases, the growth of inutile microorganic bodies which carry out no nitrifying reaction or inhibit the nitrifying reaction is suppressed.

On the other hand, if microorganic bodies are in a lyophilized powder form, then their volume reduction ratio is high, their volume can further be lowered, handling upon transport and storage as well as operations of adding them to the object to be processed become further easier, and the space for storage and stock can further be reduced. Also, since the moisture is eliminated by lyophilization, the above-mentioned growth of inutile microorganic bodies is further suppressed. Further, long-term storage is facilitated.

It will be useful if the method comprises a slurry-forming process of causing at least one of the object to be processed, the first microorganic body, and the second microorganic body to become slurry. In this manner, even if the object to be processed is a solid having a low water content, such as fly ash or soil, for example, the object to be processed can be made easier to flow. As a consequence, it becomes easier to supply a gas including oxygen to the object to be processed, whereby an aerobic atmosphere is further favorably formed.

As a result, the nitrifying reaction caused by microorganic bodies becomes active, whereby the reaction decomposing of organic chlorine compound accompanying the nitrifying reaction is accelerated. Also, it becomes easier for the first microorganic body and the oxidase produced by the first microorganic body to come into contact with the organic chlorine compound. Therefore, the nitrifying reaction caused by the first microorganic body and its accompanying reaction of oxidizing and decomposing the organic chlorine compound are further accelerated. Further, it becomes easier for the second microorganic body and oxidized nitrogen to come into contact with each other, whereby the reaction of decomposing oxidized nitrogen is accelerated. Also, when the first microorganic body and/or second microorganic body is used in the form of dehydrated cake or powder, their fluidity increases, whereby their miscibility with the object to be processed improves. As a result, the decomposing efficiency of organic chlorine compound can further be improved.

It will further be preferred if the aerobic treatment process has a pH adjusting step of adjusting the pH of the object to be processed containing the first microorganic body and reduced nitrogen to a range of 5 to 9, and/or a desalting step of adjusting the salt concentration of the object to be processed to 4% or lower. If such a pH condition is attained, the growth of first microorganic body becomes active, and its activity can be kept high. Therefore, the nitrifying reaction caused by the first microorganic body and its accompanying reaction of decomposing the organic chlorine compound can improve their efficiency.

If the salt concentration of the object to be processed exceeds 4%, then the activity of oxidase produced by the first microorganic body tends to be suppressed, whereby it becomes harder to maintain the nitrifying reaction. As a result, the nitrifying reaction is stagnated, whereby the reaction of decomposing the organic chlorine compound, in which this oxidase is supposed to be involved, tends to be suppressed. Here, if the salt concentration of the object to be processed prior to the addition of the first microorganic body and reduced nitrogen is 4% or lower, then the salt concentration in the object to be processed in a later treatment can reliably become 4% or lower.

In addition, it is desirable that, in the reduced nitrogen adding process and/or reduced nitrogen adding step, reduced nitrogen be added to the object to be processed such that the content of reduced nitrogen with respect to 1 ng of the organic chlorine compound becomes 0.01 to 10.0 g-N. If this adding ratio is less than 0.01 g-N, then the amount of nitrifying reaction becomes insufficient, whereby the reaction of decomposing the organic chlorine compound would not proceed sufficiently. If the adding ratio exceeds 10.0 g-N, by contrast, then the nitrifying reaction remarkably lowers the pH in the object to be processed. As a result, the amount of alkali agent injected for adjusting the pH increases, which is uneconomical. Also, there is a fear that the pH adjustment may raise the salt concentration and inhibit the nitrifying reaction. Here, the unit “g-N” indicates that it is the weight of nitrogen.

The apparatus for processing an organic chlorine compound in accordance with the present invention is aimed at effectively carrying out the method of processing the organic chlorine compound in accordance with the present invention, which is an apparatus for decomposing and eliminating the organic chlorine compound in an object to be processed, the apparatus comprising a biological treatment section in which a first microorganic body capable of oxidizing reduced nitrogen and the object to be processed come into contact with each other, and the object to be processed in a state containing the first microorganic body is biologically processed, so as to decompose the organic chlorine compound. Here, it will be preferable if a reduced nitrogen adding section for adding reduced nitrogen to the object to be processed is further provided.

Further, it is preferred that the biological treatment section comprises an aerobic treatment section, formed with an aerobic atmosphere, in which reduced nitrogen contained in the object to be processed is oxidized by the first microorganic body, and the organic chlorine compound is decomposed; and/or an anaerobic treatment section, formed with an anaerobic atmosphere, for holding in the anaerobic atmosphere the object to be processed containing the first microorganic body keeping a biological activity by way of a biological treatment in an aerobic atmosphere.

More preferably, in the anaerobic treatment section, the object to be processed is supplied, supply of a gas containing oxygen to the object to be processed is blocked, so as to form an anaerobic atmosphere, and this anaerobic atmosphere is maintained. Further, it will be useful if the anaerobic treatment section has a temperature adjustment section capable of adjusting the temperature of the object to be processed.

It is desirable that an oxidized nitrogen eliminating section in which oxidized nitrogen contained in the object to be processed is reduced and eliminated by a second microorganic body capable of reducing this oxidized nitrogen be further provided.

Specifically, it is further preferred that the aerobic treatment section comprises a first microorganic body adding section for adding the first microorganic body to the object to be processed; a reduced nitrogen adding section for adding reduced nitrogen to the object to be processed; a diffuser section for sending a gas containing oxygen to the object to be processed; and a first reaction treatment section in which the object to be processed is supplied, and the first microorganic body oxidizes reduced nitrogen and decomposes the organic chlorine compound.

It is also preferred that the oxidized nitrogen eliminating section have a second microorganic body adding section for adding a second microorganic body to the object to be processed; a carbon source adding section for adding to the object to be processed an organic carbon source which becomes a nutrient for the second microorganic body; and an eliminating section in which the object to be processed is supplied, supply of a gas containing oxygen to the object to be processed is blocked, and oxidized nitrogen is reduced and eliminated by the second microorganic body.

Further, it is preferred that an object to be processed mixing section for adding to and mixing with the object to be processed in at least one of the aerobic treatment section, oxidized nitrogen eliminating section, and anaerobic treatment section another object to be processed, different therefrom, containing an organic chlorine compound be provided.

It is further preferred that a slurry-forming section in which a liquid is added to and mixed with at least one of the object to be processed, first microorganic body, and second microorganic body, so as to cause at least one of the object to be processed, first microorganic body, and second microorganic body to become slurry be provided. In addition, it is further preferred that the aerobic treatment section have a pH adjustment section for adjusting the pH of the object to be processed containing the first microorganic body and reduced nitrogen, and/or a desalting section for adjusting the salt concentration of the object to be processed.

In the present invention, dioxins refer to at least one kind of or a mixture of at least two kinds (including homologues) of polychlorinated dibenzoparadioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs).

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a block diagram showing a first embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention;

FIG. 2

is a block diagram showing a second embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention;

FIG. 3

is a block diagram showing a third embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention;

FIG. 4

is a block diagram showing a fourth embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention;

FIG. 5

is a block diagram showing a fifth embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention;

FIG. 6

is a block diagram showing a sixth embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention;

FIG. 7

is a block diagram showing a seventh embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention;

FIG. 8

is a graph showing a homologue concentration distribution of dioxins contained in a mixture after oxidized nitrogen is eliminated in Example 4; and

FIG. 9

is a graph showing a homologue concentration distribution of dioxins contained in an analysis sample collected after the anaerobic atmosphere in Example 4 has been maintained for 30 days.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be explained with reference to the accompanying drawings. Here, constituents identical to each other will be referred to with numerals or letters identical to each other without repeating their overlapping explanations.

FIG. 1

is a block diagram showing a first embodiment concerning the apparatus for processing an organic chlorine compound in accordance with the present invention. The processing apparatus

1

(apparatus for processing the organic chlorine compound) is configured such that a pretreatment bath

20

, a solid-liquid separating bath

23

, an ammonia storage bath

24

, a nitrifying bacteria storage bath

25

, an off-gas system

26

, and an alkali storage bath

27

are connected to a reaction treatment bath

22

(first biological treatment section).

In the pretreatment bath

20

, fly ash K (object to be processed) containing organic chlorine compounds such as dioxins is subjected to pretreatment. For example, the fly ash K is powder-like ash obtained when burnable wastes are incinerated in waste incinerating facilities. A water supply line

50

for transferring water L

1

is connected to the pretreatment bath

20

, whereas the latter is further provided with a stirrer

60

for stirring and mixing the fly ash K and water L

1

, so as to desalt and wash the fly ash K.

Further connected to the pretreatment bath

20

is a drain line (not depicted) for partly letting out the water L

1

in which a salt is dissolved upon mixing the fly ash K and water L

1

. The fly ash K desalted and washed here becomes slurry S

1

. Thus, the pretreatment bath

20

, water L

1

, water supply line

50

, stirrer

60

, and drain line constitute a desalting section and a slurry-forming section.

Examples of dioxins include polychlorinated dibenzoparadioxins (PCDDS), polychlorinated dibenzofurans (PCDFS), and coplanar polychlorinated biphenyls (coplanar PCBS) represented by the following formulae (1), (2), and (3), respectively. They are quite hard to dissolve and quite hard to decompose among organic chlorine compounds, and are compounds which are quite hard to process by conventional methods, thereby being considered as materials which are problematic in terms of environmental conservation, reduction of influence to organisms, and the like.

[Here, p and q in formula (1) and r and s in formula (2) each indicate an integer from 0 to 4, where 1≦p+q≦8, and 1≦r+s≦8. Also, t and u in formula (3) each indicate an integer from 0 to 5, where 1≦t+u≦10.]

The ammonia storage bath

24

is used for storing aqueous ammonia R as a biologically utilizable reduced nitrogen, and is provided with a transfer line

54

for supplying the aqueous ammonia R to the biological treatment bath

22

. Thus, the ammonia storage bath

24

and transfer line

54

constitute a reduced nitrogen adding section. Strictly speaking, reduced nitrogen is nitrogen within ammonia molecule or ammonia ion contained in the aqueous ammonia R, whereas the aqueous ammonia R acts as a source for supplying reduced nitrogen.

Further, the nitrifying bacteria storage bath

25

is used for storing nitrifying bacteria N (first microorganic body) having a capability of oxidizing reduced nitrogen. A water supply line

55

for supplying culture solution L

2

which can culture the nitrifying bacteria N is connected to the nitrifying bacteria storage bath

25

, whereas the latter is provided with a stirrer

65

for stirring and mixing the nitrifying bacteria N and culture solution L

2

, so as to yield slurry. Thus, the nitrifying bacteria storage bath

25

, culture solution L

2

, water supply line

55

, and stirrer

65

constitute a slurry-forming section.

Also connected to the nitrifying bacteria storage bath

25

is a transfer line

56

for transferring to the biological treatment bath

22

highly fluid slurry S

2

obtained upon mixing the nitrifying bacteria N and culture solution L

2

. Thus, the bacteria storage bath

25

and the transfer line

56

constitute a first microorganic body adding section.

To the biological treatment bath

22

, slurries S

1

, S

2

are supplied from the pretreatment bath

20

and the nitrifying bacteria storage bath

25

, respectively, and the aqueous ammonia R is supplied from the ammonia storage bath

24

. The biological treatment bath

22

has a stirrer

62

for stirring and mixing these supplied products, whereby the slurries S

1

, S

2

and aqueous ammonia R are stirred and mixed, so as to become a mixture W (object to be processed). Installed within the biological treatment bath

22

is a diffuser tube

21

(diffuser section), connected to a blower

30

, for sending air as a gas containing oxygen into the mixture W. As will be explained later, a nitrifying treatment for decomposing the organic chlorine compounds in the object to be processed is performed within the biological treatment bath

22

.

The alkali storage bath

27

is used for storing alkali C to be added to the mixture W for adjusting the pH thereof to a value suitable for the biological treatment, and has a transfer line

57

for supplying the alkali C to the biological treatment bath

22

. Thus, the alkali storage bath

27

and transfer line

57

constitute a pH adjustment section.

The off-gas system

26

is used for letting out gases or gaseous components occurring within the biological treatment bath

22

from the processing apparatus

1

by way of an exhaust line

58

, and processing these gases if necessary. Examples of such gaseous components include the excess of air supplied to the reaction treatment bath

22

, ammonia gas evaporating from the aqueous ammonia R, carbon dioxide gas which is a reaction product, and NOx gas and nitrogen gas though in a trace amount.

The biological treatment bath

22

further comprises a pH meter

40

for monitoring the pH of mixture W and the change in pH, and a sampling line for sampling a part of the mixture W within the biological treatment bath

22

and yielding an analysis sample A.

The solid-liquid separating bath

23

is used for separating the processed mixture w by gravity sedimentation into a processed liquid Fw, which is a supernatant, and a processed solid Fs. Connected to the solid-liquid separating bath

23

are a transfer line

53

for letting out the processed liquid Fw, a transfer line

59

for letting out a part of the processed solid Fs as surplus sludge, and a transfer line

79

for returning the remnant of processed solid Fs as thickened sludge to the biological treatment bath

22

.

A first embodiment concerning the method of processing an organic chlorine compound in accordance with the present invention carried out by use of the processing apparatus

1

constructed as mentioned above will now be explained.

First, fly ash K containing dioxins is supplied to the pretreatment bath

20

and, while water L

1

is supplied thereto by way of the water supply line

50

, the fly ash K and water L

1

are fully mixed by the stirrer

60

. Consequently, the fly ash K is desalted and washed(desalting step). Subsequently, water L

1

in which a salt is dissolved is separated from the fly ash K by sedimentation, filtration, or the like. A part of the water L

1

is let out of the pretreatment bath

20

by way of a drain line (not depicted), and the desalted and washed fly ash K is formed into slurry S

1

(slurry-forming process).

Preferably, the water L

1

injected into the pretreatment bath

20

here is in an amount which can desalt and wash the fly ash K such that the salt concentration in the mixture w having been formed from the object to be processed within the biological treatment bath

22

or the salt concentration in the slurry S

1

becomes 4% or lower. If their salt concentration is 4% or lower, then a nitrifying reaction in which nitrifying bacteria are involved, which will be explained later, can be carried out favorably.

In the case where the fly ash K contains foreign matters and contaminants, it is desirable that these foreign matters and contaminants to be eliminated by sieving (sizing) or the like, and they may be eliminated by sedimentation or the like in the pretreatment bath

20

.

The solid content in the slurry S

1

, i.e., the content of fly ash K, is adjusted to such a content range within which stirring is possible and gases can easily be supplied. For example, it is preferably adjusted to about 0.5% to 10% by mass if water L

1

is used as a mixing medium for slurry S

1

.

If the solid content is less than 0.5% by mass, then the fluidity of slurry S

1

is enhanced, so that the gas supply is carried out favorably, but the volume of the pretreatment bath

20

and biological treatment bath

22

increases, so that the apparatus becomes larger, which is uneconomical. If the solid content exceeds 10% by mass, by contrast, then the pretreatment bath

20

and biological treatment bath

22

can be made smaller, but the fluidity of slurry S

1

tends to deteriorate, whereby uniform stirring and gas supply gradually become difficult.

On the other hand, while nitrifying bacteria N are introduced into the nitrifying bacteria storage bath

25

, culture solution L

2

for the nitrifying bacteria N is supplied thereto by way of the water supply line

55

. Then, they are stirred and mixed by the stirrer

65

, so that the nitrifying bacteria N are formed into slurry S

2

(slurry-forming process).

Here, it will be preferred if the nitrifying bacteria N are cultured and acclimatized in the nitrifying bacteria storage bath

25

such that MLVSS (Mixed Liquor Volatile Suspended Solids) becomes preferably 100 mg/l or higher, more preferably 1000 mg/l or higher, and that their nitrifying capability attains an active state of preferably 0.01 kg-N/kg-SS/day or higher, more preferably 0.05 kg-N/kg-SS/day or higher. Here, the units “kg-N” and “kg-SS” refer to masses of nitrogen and suspended matters (SS: Suspended Solids), respectively (ditto in the following).

As the form of nitrifying bacteria N, those in a state where water is eliminated as much as possible from sludge formed like a floc after being cultured and acclimatized beforehand in a culture liquid under a natural or synthetic environment, or in a state in which water is partly eliminated therefrom can be used favorably. An example of the former is sludge lyophilized into powder. An example of the latter is a dehydrated cake preferably having a moisture content of about 70% by mass or higher obtained after the moisture content in sludge is eliminated by about 30% by mass or less. If the moisture content in the dehydrated cake is less than about 70% by weight, then the cell water of nitrifying bacteria N tends to be eliminated as well.

Such a form of nitrifying bacteria N with lowered moisture content can yield a smaller volume as compared with their original state where they exist as a mass in the culture liquid, and can be handled as a solid. Therefore, the handling of nitrifying bacteria N at the time of transfer and at the time of storage and stock is easy. Also, the space for storage and stock can be reduced. Further, since the moisture content necessary for growing microorganic bodies is small, biological reactions can be prevented from being effected before the microorganic bodies are added to the object to be processed, or the growth of inutile microorganic bodies which effect no desirable biological reactions or inhibit such reactions can be suppressed. Also, the powder obtained by lyophilization can easily be stored for a long period.

Aqueous ammonia R is supplied to and stored in the ammonia storage bath

24

. As the aqueous ammonia R, one whose concentration has been adjusted beforehand may be supplied to the ammonia storage bath

24

or its concentration may be adjusted after it is supplied to the ammonia storage bath

24

.

Subsequently, a predetermined amount of slurry S

1

is transferred from the pretreatment bath

20

to the biological treatment bath

22

by way of the transfer line

51

. Also, a predetermined amount of nitrifying bacteria N is added to the slurry S

1

within the biological treatment bath

22

from the nitrifying bacteria storage bath

25

by way of the transfer line

56

(first microorganic body adding step). Further, a predetermined amount of aqueous ammonia R is added to the slurry S

1

from the ammonia storage bath

24

by way of the transfer line

54

(reduced nitrogen adding process or reduced nitrogen adding step).

Then, they are stirred and mixed by the stirrer

62

, so as to yield the mixture W. Subsequently, while stirring is carried out, the blower

30

is driven, so as to send out air to the diffuser tube

21

, thereby causing the diffuser tube

21

to jet out fine bubbles of air to the mixture W.

These fine bubbles form a gas/liquid multiphase flow, which sends air to the whole mixture W, so that oxygen is distributed throughout the mixture W, whereby a favorable aerobic atmosphere is formed. Here, it will be preferred if the amount of air supplied from the blower

30

is such that the dissolved oxygen content in the mixture W is preferably 0.5 mg/L or higher. Also, at least one dissolved oxygen content meter may be installed in the biological treatment bath

22

, so as to monitor the dissolved oxygen content in the mixture W.

Once the aerobic atmosphere is formed, oxidization of ammonium ion, i.e., nitrifying reaction, is effected by the nitrifying bacteria N. Here, as the nitrifying bacteria N, those including nitrite bacteria and/or nitrate bacteria can be used. Nitrite bacteria, also referred to as ammonium oxidizing bacteria, have a capability of oxidizing ammonium ion (NH

4

+

) into nitrite ion (NO

2

) and carry out a reaction represented by the following expression (4):

NH

4

+

+1.5O

2

→NO

2

−

+H

2

O+2H

+

  (4)

Such nitrifying bacteria N include genera of Nitrosomonas, Nitrosococcus, Nitrosospira, Nitrosocystis, and the like, which are contained in soil and are easy to obtain and culture.

The nitrate bacteria, also referred to as nitrite oxidizing bacteria, have a capability of oxidizing nitrite ion (NO

2

−

) into nitrate ion (NO

3

−

) and carry out a reaction represented by the following expression (5):

NO

2

−

+0.5O

2

→NO

3

−

  (5)

Such nitrifying bacteria include genera of Nitrobacter, Nitrocystis, and the like, which are contained in soil and are easy to obtain and culture.

According to the reaction shown in the above-mentioned expressions (4) and(5), ammonium ion derived from the aqueous ammonia R contained in the mixture W is nitrated in the aerobic atmosphere after forming nitrite. Here, a reaction of oxidizing and decomposing dioxins contained in the fly ash K in the mixture W proceeds simultaneously, whereby the dioxins are decomposed into lower hydrocarbon, carbon dioxide, water, and the like (decomposing step).

Though such a mechanism of decomposing dioxins has not fully been elucidated, it is presumed that dioxins are oxidized and decomposed in an enzymatic reaction system in which oxidases such as ammonia monooxygenase produced by nitrifying bacteria N are involved. It is inferred that ammonia monooxygenase probably acts on dioxins, so that a kind of conjugate reaction such as a co-oxidation reaction in which dioxins are oxidized in parallel with the nitrifying reaction shown in expressions (4) and (5) occurs. However, the action is not restricted thereto.

Here, the pH and changes in pH of the mixture W within the biological treatment bath

22

are monitored by the pH meter

40

installed in the biological treatment bath

22

. If the above-mentioned nitrifying reaction is carried out while air is diffused into the mixture W from the diffuser tube

21

, then the pH of mixture W shifts toward the acidic side as the reaction proceeds.

Therefore, according to the actually measured value of pH, alkali C is added to the biological treatment bath

22

from the alkali storage bath

27

by way of the transfer line

57

so as to attain an optimal pH for activating the growth of nitrifying bacteria N, i.e., such that the pH becomes preferably 5 to 9, more preferably 7 to 8. Further, it will be preferred if the temperature of mixture W in the nitrifying reaction is 10 to 40° C.

As alkali C, alkaline solutions such as sodium hydroxide solution can be used. At a pH near 7, various buffer solutions may be used, and aqueous ammonia R may also be used as alkali C. If the pH value of mixture is adjusted to the above-mentioned preferable range, then the nitrifying bacteria N are actively grown, and the state where the activity of nitrifying bacteria N is enhanced is maintained. As a result, the decomposing efficiency of dioxins can be kept high.

Preferably, the amount of addition of aqueous ammonia R, which is a supply source of reduced nitrogen, is such a ratio that nitrogen (reduced nitrogen) in aqueous ammonia R is 0.01 to 10.0 g-N with respect to 1 ng of dioxins contained in the fly ash K in slurry S

1

.

If this ratio of addition is less than 0.01 g-N/1 ng of dioxins, then the amount of nitrifying reaction caused by nitrifying bacteria N tends to be insufficient, whereby the decomposing reaction does not proceed sufficiently. If the ratio of addition exceeds 10.0 g-N/1 ng of dioxins, by contrast, then the decrease of pH becomes remarkable along with the nitrifying reactions, whereby the amount of injection of alkali C for adjusting the pH increases, which is uneconomical. In this case, there is a fear of the pH adjustment raising the salt concentration of mixture W, whereby the nitrifying reaction caused by nitrifying bacteria N may be inhibited.

Therefore, if aqueous ammonia R is added such that the amount of nitrogen in the aqueous ammonia R is 0.01 to 10.0 g-N/1 ng of dioxins, then the nitrifying reactions caused by nitrifying bacteria N are carried out in an optimal state, whereby the dioxins can be decomposed effectively and economically. Also, it is desirable that the concentration or total amount of dioxins in fly ash K is analyzed beforehand such that aqueous ammonia R attains such a preferable ratio of addition, or a part of slurry S

1

may be collected and analyzed. Here, aqueous ammonia R may be added continuously or intermittently.

Then, while carrying out the nitrifying reaction of mixture W, a part of the mixture W is sampled periodically, and thus obtained analysis sample A is analyzed, so as to quantitatively determine the concentration of dioxins in the mixture W. After it is verified that the concentration of dioxins has become a target value or lower, the supply of air from the diffuser tube

21

is stopped, so as to terminate the processing for decomposing dioxins along with the nitrifying reactions.

Thereafter, the mixture W is transferred to the solid-liquid separating bath

23

by way of the transfer line

52

. The gases generated during the processing of mixture W within the biological treatment bath

22

are introduced into the off-gas system

26

by way of the exhaust line

58

, so as to carry out exhaust processing.

In the solid-liquid separating bath

23

, the mixture W is separated into the processed liquid Fw, which is a supernatant, and the processed solid Fs. By way of the transfer line

53

, the processed liquid Fw is sent out to a drain system which is not depicted. On the other hand, a part of the processed solid Fs is let out as surplus sludge from the solid-liquid separating bath

23

by way of the transfer line

59

. This surplus sludge can finally be dumped for landfill, or be reused as a resource. On the other hand, the remnant of processed solid Fs is returned to the biological treatment bath

22

as thickened sludge by way of the transfer line

79

.

According to the method of processing an organic chlorine compound using the processing apparatus

1

, such as the one explained in the foregoing, dioxins can fully be decomposed by a simple treatment in which aqueous ammonia R and nitrifying bacteria N are added to and mixed with slurry S

1

of fly ash K, and then air is sent thereto under normal temperature and normal pressure, so as to form an aerobic atmosphere. Thus, without necessitating a severe reaction condition such as high temperature and high pressure in particular, dioxins can fully be decomposed by a treatment remarkably simpler than conventional ones, whereby the processing cost can drastically be lowered.

Since the processing method of this embodiment is wet type processing, the fear of dioxins diffusing to the outside and causing a secondary contamination can fully be prevented from occurring as compared with conventional methods using incineration processing represented by a high temperature incinerating method. Also, employed nitrifying bacteria N, aqueous ammonia R, and alkali C are inexpensive general-purpose products which are easily available, and conventional complicated, large-size processing apparatus are unnecessary, whereby the spending on equipment and the like can be cut down, so as to further lower the cost.

Further, since the fly ash K and nitrifying bacteria N are used in the form of slurry, it becomes easier for air to be uniformly supplied to their mixture W, and nitrifying bacteria N and oxidases, such as ammonia monooxygenase, produced by the nitrifying bacteria N are more likely to come into contact with dioxins. Hence, the nitrifying reactions caused by nitrifying bacteria N become further active, and the decomposition of dioxins can be accelerated.

FIG. 2

is a block diagram showing a second embodiment of the apparatus for processing an organic chlorine compound in accordance with the present invention. The processing apparatus

2

(apparatus for processing the organic chlorine compound) comprises a denitrifying bacteria storage bath

35

, a methanol storage bath

34

, and an acid storage bath

37

which are connected to the biological treatment bath

22

in addition to the processing apparatus

1

shown in FIG.

1

. In this embodiment, the biological treatment bath

22

acts as the aerobic treatment section, anaerobic treatment section, first reaction treatment section, oxidized nitrogen eliminating section, and second reaction treatment section.

The denitrifying bacteria storage bath

35

is used for storing denitrifying bacteria (denitrification bacteria) M (second microorganic body) having a capability of reducing oxidized nitrogen (or nitrogen in ions in a strict sense) such as nitrate ion (NO

3

−

) and nitrite ion (NO

2

−

) generated upon the nitrifying reaction caused by the nitrifying bacteria N within the biological treatment bath

22

.

A water supply line

75

for supplying culture solution L

3

which can culture denitrifying bacteria M is connected to the denitrifying bacteria storage bath

35

, whereas the latter is provided with a stirrer

85

for stirring and mixing the denitrifying bacteria M and culture solution L

3

, so as to yield slurry. Thus, the denitrifying bacteria storage bath

35

, culture solution L

3

, water supply line

75

, and stirrer

85

constitute a slurry-forming section.

Also connected to the denitrifying bacteria storage bath

35

is a transfer line

76

for transferring highly fluid slurry S

3

obtained upon mixing the denitrifying bacteria M and culture solution L

3

to the biological treatment bath

22

. Thus, the denitrifying bacteria storage bath

35

and transfer line

76

constitute a second microorganic body adding section.

The methanol storage bath

34

is used for storing methanol S (organic carbon source) which becomes a nutrient for the denitrifying bacteria M, and is provided with a transfer line

74

for supplying the methanol S to the biological treatment bath

22

. Thus, the methanol storage bath

34

and transfer line

74

constitute a carbon source adding section.

To the biological treatment bath

22

, slurries S

1

, S

2

, S

3

are supplied from the pretreatment bath

20

, nitrifying bacteria storage bath

25

, and denitrifying bacteria storage bath

35

, respectively, whereas aqueous ammonia R and methanol S are supplied from the ammonia storage bath

24

and methanol storage bath

34

, respectively. In the biological treatment bath

22

, thus supplied products are stirred and mixed, so as to yield the mixture W (object to be processed).

The acid storage bath

37

is used for storing an acid D to be added for adjusting the pH of mixture W to a value suitable for the biological treatment, and has a transfer line

77

for supplying the acid D to the biological treatment bath

22

. Namely, the acid storage bath

37

, alkali storage bath

27

, and transfer lines

57

,

77

constitute a pH adjustment section.

A second embodiment concerning the method of processing an organic chlorine compound in accordance with the present invention carried out by thus configured processing apparatus

2

will now be explained.

First, fly ash K containing dioxins is supplied to the pretreatment bath

20

and, while water L

1

is supplied thereto by way of the water supply line

50

, the fly ash K and water L

1

are fully mixed by the stirrer

60

. Consequently, the fly ash K are desalted and washed (desalting step). Subsequently, water L

1

in which a salt is dissolved is separated from the fly ash K by sedimentation, filtration, or the like. A part of the water L

1

is let out of the pretreatment bath

20

by way of a drain line (not depicted), and the desalted and washed fly ash K is formed into slurry S

1

(slurry-forming process).

Preferably, the water L

1

injected into the pretreatment bath

20

here is in an amount which can desalt and wash the fly ash K such that the salt concentration in the mixture W having been formed from the object to be processed within the biological treatment bath

22

or the salt concentration in the slurry S

1

becomes 4% or lower.

The solid content in the slurry S

1

, i.e., the content of fly ash K, is adjusted to such a content range within which stirring is possible and gases can easily be supplied. For example, it is preferably adjusted to about 0.5% to 10% by mass if water L

1

is used as a mixing medium for slurry S

1

.

On one hand, while nitrifying bacteria N are introduced into the nitrifying bacteria storage bath

25

, culture solution L

2

for the nitrifying bacteria N is supplied thereto by way of the water supply line

55

. Then, they are stirred and mixed by the stirrer

65

, so that the nitrifying bacteria N are formed into highly fluid slurry S

2

(slurry-forming process). It will be preferred if nitrifying bacteria N are cultured and acclimatized in the nitrifying bacteria storage bath

25

such that MLVSS becomes preferably 100 mg/l or higher, more preferably 1000 mg/l or higher, and that their nitrifying capability attains an active state of preferably 0.01 kg-N/kg-SS/day or higher, more preferably 0.05 kg-N/kg-SS/day or higher.

On the other hand, while denitrifying bacteria M are introduced into the denitrifying bacteria storage bath

35

, culture solution L

3

for the denitrifying bacteria M is supplied thereto by way of the water supply line

75

. Then, they are stirred and mixed by the stirrer

85

, so that the denitrifying bacteria M are formed into highly fluid slurry S

3

. It will be preferred if denitrifying bacteria M are cultured and acclimatized in the denitrifying bacteria storage bath

35

such that MLVSS becomes preferably 100 mg/l or higher, more preferably 1000 mg/l or higher, and that their nitrifying capability attains an active state of preferably 0.01 kg-N/kg-SS/day or higher, more preferably 0.05 kg-N/kg-SS/day or higher.

As the form of nitrifying bacteria N and denitrifying bacteria M, those in a state where water is eliminated as much as possible from sludge formed like a floc after being cultured and acclimatized beforehand in a culture liquid under a natural or synthetic environment, or in a state in which water is partly eliminated therefrom can be used favorably.

An example of the former is sludge lyophilized into powder. An example of the latter is a dehydrated cake preferably having a moisture content of about 70% by mass or higher obtained after the moisture content in sludge is eliminated by about 30% by mass or less. If the moisture content in the dehydrated cake is less than about 70% by weight, then the cell water of nitrifying bacteria N tends to be eliminated as well.

Also, aqueous ammonia R and methanol S are supplied to and stored in the ammonia storage bath

24

and methanol storage bath

34

, respectively. As the aqueous ammonia R and methanol S, those whose concentrations are adjusted beforehand may be supplied to the aqueous ammonia bath

24

and methanol storage bath

34

, respectively, or their concentrations may be adjusted after they are supplied to their respective baths

24

,

34

.

Subsequently, a predetermined amount of slurry S

1

is transferred from the pretreatment bath

20

to the biological treatment bath

22

. Also, predetermined amounts of nitrifying bacteria N, denitrifying bacteria M, aqueous ammonia R, and methanol S are added to the slurry S

1

within the biological treatment bath

22

(first microorganic body adding step, second microorganic body adding step, reduced nitrogen adding step, and carbon source adding step, respectively). Then, they are stirred and mixed by the stirrer

62

, so as to yield the mixture W. Thereafter, while stirring is carried out, the blower

30

is driven, so as to send out air to the diffuser tube

21

, thereby causing the diffuser tube

21

to jet out fine bubbles of air to the mixture W.

These fine bubbles form a gas/liquid multiphase flow, which sends air to the whole mixture W, so that oxygen is distributed throughout the mixture W, whereby a favorable aerobic atmosphere is formed. Here, it will be preferred if the amount of air supplied from the blower

30

is such that the dissolved oxygen content in the mixture W is preferably 0.5 mg/L or higher. Also, one or more dissolved oxygen concentration meter may be installed in the biological treatment bath

22

, so as to monitor the dissolved oxygen concentration in the mixture W.

Once the aerobic atmosphere is formed, oxidization of ammonium ion, i.e., nitrifying reaction represented by expressions (4) and (5), is effected by the nitrifying bacteria N. As a consequence of such a nitrifying reaction, ammonium ion derived from the aqueous ammonia contained in the mixture W is nitrated in an aerobic atmosphere after forming nitrite. Here, a reaction of oxidizing and decomposing dioxins contained in the fly ash K in the mixture W proceeds simultaneously, whereby the dioxins are decomposed into lower hydrocarbon, carbon dioxide, water, and the like (decomposing step).

Here, the pH and changes in pH of the mixture W within the biological treatment bath

22

are monitored by the pH meter

40

installed in the biological treatment bath

22

. If the above-mentioned nitrifying reaction is carried out while air is diffused into the mixture W from the diffuser tube

21

, the pH of mixture W shifts toward the acidic side as the reaction proceeds. Therefore, according to the actually measured value of pH, alkali C is added to the biological treatment bath

22

from the alkali storage bath

27

by way of the transfer line

57

so as to attain an optimal pH for activating the growth of nitrifying bacteria N, i.e., such that the pH becomes preferably 5 to 9, more preferably 7 to 8. Further, it will be preferred if the temperature of mixture W in the nitrifying reaction is 10 to 40° C.

Preferably, the amount of addition of aqueous ammonia R, which is a supply source of reduced nitrogen, is such a ratio that nitrogen (reduced nitrogen) in aqueous ammonia R is 0.01 to 10.0 g-N with respect to 1 ng of dioxins contained in the fly ash K in slurry S

1

. Here, aqueous ammonia R may be added continuously or intermittently.

Then, while carrying out the nitrifying reaction of mixture W, a part of the mixture W is sampled periodically, and thus obtained analysis sample A is analyzed, so as to quantitatively determine the concentration of dioxins in the mixture W. After it is verified that the concentration of dioxins has become a target value or lower, the supply of air from the diffuser tube

21

is stopped, so as to terminate the processing for decomposing dioxins along with the nitrifying reaction.

After the diffusion of air, i.e., supply of air, to the mixture W is stopped, the dissolved oxygen remaining in the mixture w is consumed by the nitrifying bacteria N, whereby the mixture W attains therein an anaerobic atmosphere in which the dissolved oxygen concentration is nearly zero. Once the anaerobic atmosphere is thus formed, the denitrifying bacteria M added to the mixture W consume methanol Sand carry out a denitrifying reaction for reducing the nitrite ion (NO

2

−

) and nitrate ion (NO

3

−

) generated upon the nitrifying reaction caused by the nitrifying bacteria N. Here, it is preferred that an inert gas such as nitrogen gas is supplied to the gaseous phase section of the biological treatment bath

22

, so as to replace air. As a consequence, the supply of oxygen from the gaseous section to the mixture W is blocked, whereby the anaerobic atmosphere can be maintained favorably.

Here, the denitrifying bacteria M have a capability of reducing oxidized nitrogen such as nitrite ion (NO

2

−

) and nitrate ion (NO

3

−

); and examples thereof include genera of Pseudomonas Achromobacter, Bacillus, and Micrococcus. These denitrifying bacteria M perform respiration by using oxygen in the above-mentioned aerobic atmosphere. In the anaerobic atmosphere, by contrast, they grow by using oxidized nitrogen and nutrients and, at that time, carry out one or both of reactions (referred to as nitrite respiration and nitrate respiration, respectively) represented by the following expressions (6) and/or (7):

NO

2

−

+3H

+

→0.5N

2

+H

2

O+OH

−

  (6)

NO

3

−

+5H

+

→0.5N

2

+2H

2

O+OH

−

  (7)

In this embodiment, methanol S is used as a nutrient, whereby a denitrifying reaction represented by the following expression (8) and/or (9):

NO

2

−

+½CH

3

OH→½N

2

+½CO

2

+½H

2

O+OH

−

  (8)

NO

3

−

+⅚CH

3

OH→½N

2

+⅚CO

2

+{fraction (7/6)}H

2

O+OH

−

  (9)

is carried out. As a consequence of these reactions, the nitrite ion (NO

2

−

) and nitrate ion (NO

3

−

) generated upon nitrification are reduced so as to produce nitrogen, carbon dioxide, water, hydroxyl ion, and the like, thereby eliminating the nitrite ion (NO

2

−

) and nitrate ion (NO

3

−

) (eliminating step).

The pH and changes in pH of the mixture W within the biological treatment bath

22

are monitored by the pH meter

40

during the denitrifying reaction as well. As mentioned above, the pH of mixture W shifts toward the alkali side as the denitrifying reaction proceeds. Therefore, according to the actually measured value of pH, acid D is added to the biological treatment bath

22

from the acid storage bath

37

by way of the transfer line

77

so as to attain an optimal pH for activating the growth of denitrifying bacteria M, i.e., such that the pH becomes preferably 5 to 9, more preferably 6 to 8 (pH adjusting step). Further, it will be preferred if the temperature of mixture W in the denitrifying reaction is 10 to 40° C.

As the acid D, generally employed inorganic acids, organic acids, and the like can be used. Also, various kinds of buffer solutions may be used at a pH near 7. If organic acids such as acetic acid are used as a nutrient in place of methanol S, these organic acids may also be used as the acid D. If the pH value of mixture W is thus adjusted to the above-mentioned preferable range, then the denitrifying bacteria M are actively grown, and the state where the activity of denitrifying bacteria M is enhanced is maintained. As a result, the decomposing efficiency upon reduction of oxidized nitrogen such as nitrite ion (NO

2

−

) and nitrate ion (NO

3

−

) can be kept high.

Preferably, the amount of addition of methanol S, which is a nutrient for the denitrifying bacteria M, is such a ratio that it becomes at least 0.5 mg with respect to 1 mg-N (NO

2

−

, NO

3

−

) contained in 1 L of mixture W. If this adding ratio is less than 0.5 mg, then the nitrite respiration or nitrate respiration of the denitrifying bacteria M tends to be carried out insufficiently.

Also, it is desirable that an equivalent is determined beforehand such that methanol S attains the above-mentioned preferable adding ratio. Alternatively, a part of the mixture W may be collected, so as to analyze nitrite ion, nitrate ion, and other nitrogen-containing components. Here, methanol S may be added continuously or intermittently.

The reaction of denitrifying the mixture W is carried out for a predetermined time, so as to terminate the biological treatment of mixture W, and the mixture W is transferred to the solid-liquid separating bath

23

by way of the transfer line

52

. In this case, the mixture W may be transferred to the solid-liquid separating bath

23

after the concentration of nitrite ion, nitrate ion, and other nitrogen-containing components in the mixture W is quantitatively determined and seen to be a target value or lower upon analyzing an analysis sample A obtained by periodical sampling of a part of the mixture W.

The gases generated during the processing of mixture W within the biological treatment bath

22

are introduced into the off-gas system

26

by way of the exhaust line

58

, so as to carry out exhaust processing. Examples of such gases include the excess of air supplied to the biological treatment bath

22

, ammonia gas evaporating from aqueous ammonia R, and carbon dioxide gas, nitrogen gas, and the like which are reaction products.

In the solid-liquid separating bath

23

, the mixture W is separated into the processed liquid Fw, which is a supernatant, and the processed solid Fs. By way of the transfer line

53

, the processed liquid Fw is sent out to a drain system which is not depicted. On the other hand, a part of the processed solid Fs is let out as surplus sludge from the solid-liquid separating bath

23

by way of the transfer line

59

. This surplus sludge can finally be dumped for landfill, or be reused as a resource. On the other hand, the remnant of processed solid Fs is returned to the biological treatment bath

22

as thickened sludge by way of the transfer line

79

.

According to the method of processing an organic chlorine compound using the processing apparatus

2

such as the one explained in the foregoing, as in the method of processing an organic chlorine compound using the above-mentioned processing apparatus

1

, dioxins can fully be decomposed, without necessitating a severe reaction condition such as high temperature and high pressure in particular, by a processing operation remarkably simpler than conventional ones, whereby the processing cost can drastically be lowered.

Also, since it is wet type processing, the fear of dioxins diffusing to the outside and causing a secondary contamination can fully be prevented from occurring. Also, employed nitrifying bacteria N, denitrifying bacteria M, aqueous ammonia R, methanol S, acid D, and alkali C are inexpensive general-purpose products which are easily available, and conventional complicated, large-size processing apparatus are unnecessary, whereby the spending on equipment and the like can be cut down, so as to further lower the cost.

Further, since the fly ash K, nitrifying bacteria N, and denitrifying bacteria M are used in the form of slurry, it becomes easier for air to be uniformly supplied to their mixture W, and nitrifying bacteria N and oxidases, such as ammonia monooxygenase, produced by the nitrifying bacteria N are more likely to come into contact with dioxins. Hence, the nitrifying reaction caused by nitrifying bacteria N becomes further active, and the decomposition of dioxins can be accelerated.

Furthermore, by a simple processing operation in which methanol S and denitrifying bacteria M are added to and mixed with fly ash K, and then air is blocked under normal temperature and normal pressure, so as to form an anaerobic atmosphere, nitrate ion and nitrite ion which are generated secondarily by the nitrifying reaction upon decomposing dioxins can fully be reduced and can be processed as harmless nitrogen gas. Therefore, the nitrogen concentration of processed liquid Fw can be lowered to such a level that it can be released to the environment.

Also, since the concentration of nitrate ion and nitrite ion in the thickened sludge to be returned is remarkably lowered, the activity of nitrifying bacteria N can be restrained from being lowered by these ions. Therefore, the nitrifying reaction caused by the nitrifying bacteria N can be maintained favorably. As a result, the reaction of decomposing dioxins along with the nitrifying reaction is maintained more favorably, whereby the decomposing efficiency of dioxins can be improved.

FIG. 3

is a block diagram showing a third embodiment of the apparatus for processing an organic chlorine compound in accordance with the present invention. The processing apparatus

3

(apparatus for processing the organic chlorine compound) comprises a nitrifying bath

32

for carrying out nitrification processing of a mixture X in which slurry S

2

of nitrifying bacteria N and aqueous ammonia R are mixed with slurry s of fly ash K, and a denitrifying bath

33

for carrying out denitrification processing of a mixture Y in which slurry

53

of denitrifying bacteria M and methanol S are mixed with the mixture X transferred from the nitrifying bath

32

. Thus, the nitrifying bath

32

and denitrifying bath

33

form a reaction treatment section.

Connected to the nitrifying bath

32

are a pretreatment bath

20

, a nitrifying bacteria storage bath

25

, an ammonia storage bath

24

, and an alkali storage bath

27

. Connected to the denitrifying bath

33

, on the other hand, are a denitrifying bacteria storage bath

35

, a methanol storage bath

34

, an acid storage bath

37

, and a solid-liquid separating bath

23

. The nitrifying bath

32

and denitrifying bath

33

are connected to each other by way of a transfer line

52

, through which the mixture X is supplied from the nitrifying bath

32

to the denitrifying bath

33

. While the nitrifying bath

32

has a diffuser tube

21

, the denitrifying bath

33

is provided with no diffuser tube.

A third embodiment concerning the method of processing an organic chlorine compound in accordance with the present invention will now be explained. First, in the nitrifying bath

32

, addition of aqueous ammonia R and pH adjustment are effected while air is diffused into the mixture X from the diffuser tube

21

, and the nitrifying reaction of the above-mentioned expressions (4) and (5) is carried out in an aerobic atmosphere with stirring caused by a stirrer

62

. As a consequence, dioxins are sufficiently decomposed along with the nitrification processing.

Subsequently, the mixture X containing nitrate ion and nitrite ion (oxidized nitrogen), subjected to the nitrifying reaction, is transferred to the denitrifying bath

33

, and denitrifying bacteria M are added thereto, so as to yield the mixture Y. While the supply of air is blocked, addition of methanol S and pH adjustment are performed, and the denitrifying reaction of the above-mentioned expressions (8) and (9) is carried out in an anaerobic atmosphere with stirring caused by a stirrer

83

. As a consequence, nitrate ion and nitrite ion are reduced, whereby the nitrogen concentration in the mixture Y is greatly lowered.

The nitrogen gas and carbon dioxide gas generated upon the denitrifying reaction are sent to an off-gas system

26

by way of an exhaust line

78

. On the other hand, new slurry S

1

of fly ash K is supplied to the nitrifying bath

32

from the pretreatment bath

20

, and nitrification processing in the nitrifying bath

32

is carried out in parallel with the denitrification processing in the denitrifying bath

33

.

Subsequently, after the completion of denitrification processing, the mixture Y is transferred to the solid-liquid separating bath

23

. If the nitrification processing in the nitrifying bath

32

has ended by this time, the mixture X is transferred to the denitrifying bath

33

from the nitrifying bath

32

, and new slurry S

1

of fly ash K is transferred from the pretreatment bath

20

to the nitrifying bath

32

. Then, the nitrification processing, denitrification processing, and solid-liquid separation processing are carried out in parallel in the nitrifying bath

32

, denitrifying bath

33

, and solid-liquid separating bath

23

, respectively. A part of the processed solid Fs isolated by the solid-liquid separating bath

23

is returned as thickened sludge to the nitrifying bath

32

by way of a transfer line

79

.

The method of processing an organic chlorine compound using such a processing apparatus

3

enables continuous processing of fly ash K as the object to be processed, so as to improve the processing efficiency, whereby the processing amount (throughput) can be enhanced. Also, the decomposing efficiency of dioxins can be made as high as or higher than that in the method of processing an organic chlorine compound using the processing apparatus

1

.

FIG. 4

is a block diagram showing a fourth embodiment of the apparatus for processing an organic chlorine compound in accordance with the present invention. The processing apparatus (apparatus for processing the organic chlorine compound) is configured such that a solid-liquid separating bath

43

is disposed between the nitrifying bath

32

and denitrifying bath

33

in the processing apparatus

3

shown in FIG.

3

.

In the processing apparatus

4

, the mixture X having been subjected to nitrification processing in the nitrifying bath

32

is transferred to the solid-liquid separating bath

43

by way of a transfer line

52

. The mixture X is separated into the processed liquid Fz and processed solid Ft by gravity sedimentation or the like. At this time, nitrification processing of new slurry S

1

of fly ash K can be carried out in the nitrifying bath

32

in parallel therewith. Subsequently, the processed liquid Fz is supplied to the denitrifying bath

33

by way of a transfer line

70

. On the other hand, a part of the processed solid Ft is let out as surplus sludge, whereas the remnant of processed solid Ft is returned as thickened sludge to the nitrifying bath

32

.

The processed liquid Fz contains the nitrate ion and nitrite ion (oxidized nitrogen) generated upon the nitrifying reaction. In the denitrifying bath

33

, denitrifying bacteria M are added to the processed liquid Fz, so as to yield the mixture Z, in which addition of methanol S and pH adjustment are carried out, and denitrification processing is effected in an anaerobic atmosphere with stirring. At this time, the nitrification processing of new slurry S

1

of fly ash K and solid-liquid separation of new mixture X can be carried out in parallel therewith in the nitrifying bath

32

and solid-separating bath

43

, respectively.

Thereafter, the mixture Z having been subjected to the denitrification processing is sent to the solid-liquid separating bath

23

by way of a transfer line

73

, so as to be separated into the processed liquid Fw and processed solid Fs. A part of the processed solid Fs is returned as thickened sludge to the denitrifying bath

33

.

The method of processing an organic chlorine compound using thus configured processing apparatus

4

also enables continuous processing of fly ash K, so as to improve the processing efficiency, whereby the processing amount (throughput) can be enhanced.

FIG. 5

is a block diagram showing a fifth embodiment of the apparatus for processing an organic chlorine compound in accordance with the present invention. The processing apparatus

5

(apparatus for processing the organic chlorine compound) is configured in the same manner as the processing apparatus

3

shown in

FIG. 3

except for lacking the pretreatment bath

20

, ammonia storage bath

24

, nitrifying bacteria storage bath

25

, alkali storage bath

27

, and processed solid (return sludge) transfer line

79

. Also connected to the denitrifying bath

33

(reaction treatment section) is a transfer line

81

for transferring biological sludge P (object to be processed) containing nitrifying bacteria subjected to an aerobic treatment of waste water containing nitrogen, such as leachate, whereas a sampling line for analysis sample A is further provided therewith.

A fifth embodiment concerning the method of processing an organic chlorine compound in accordance with the present invention using this processing apparatus

5

will now be explained. First, biological sludge P from a biological treatment process is supplied into the denitrifying bath

33

, a predetermined amount of methanol S is added thereto (carbon source adding step), denitrifying bacteria M are further added thereto if necessary (second microorganic body adding step), and they are mixed. The biological sludge P often contains oxidized nitrogen, such as nitrate ion and nitrite ion, which are originally contained in waste water and the like or generated due to activities of nitrifying bacteria in the preceding biological treatment under an aerobic condition.

Subsequently, the pH of thus obtained mixture E is adjusted, and the denitrifying reaction of the above-mentioned expressions (8) and (9) is carried out in an anaerobic atmosphere with stirring caused by the stirrer

83

. Consequently, the oxidized nitrogen contained in the biological sludge P is reduced and eliminated (eliminating step). As a result, the nitrogen concentration in the mixture E is greatly lowered (oxidized nitrogen eliminating process). Here, the nitrogen gas and carbon dioxide gas generated upon the denitrifying reaction are sent to the off-gas system

26

by way of the exhaust line

78

.

Then, the supply of methanol S is stopped, so as to maintain an anaerobic atmosphere within the denitrifying bath

33

(anaerobic treatment process). As a consequence, the nitrifying bacteria contained in the biological sludge S of mixture E are disassembled. Here, the biological sludge P often contains organic chlorine compounds, such as dioxins, contained in the waste water in the preceding biological treatment process. In this embodiment, dioxins are decomposed as nitrifying bacteria are disassembled.

Though details of the mechanism of decomposing dioxins have not been elucidated, it is presumed that, for example, an oxidase, such as oxygenase, produced by nitrifying bacteria in the aerobic treatment is eluted from the nitrifying bacteria as the latter are disassembled under the anaerobic condition, whereby the dioxins are oxidized and decomposed by an enzymatic reaction in which this oxidase involves. Also, it is presumed that, if oxidized nitrogen remains or exists in the biological sludge P, then the activity of denitrifying bacteria contained in the biological sludge P is maintained, so that the disassembling of nitrifying bacteria is suppressed under the influence thereof, whereby the elution of oxidase is stagnated. However, the action is not restricted thereto.

The processing temperature of mixture E in the anaerobic treatment process is held preferably at 15° C. or higher, more preferably at 18° C. or higher. If this processing temperature is lower than 15° C., then the decomposition of organic chlorine compound tends to be harder to proceed. Preferably, the denitrifying bath

33