JP2002355695A - Water treatment method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove dioxins, etc., contained in water to be treated still more sufficiently than before at the time of cleaning treatment of water to be treated such as leached water or the like. SOLUTION: A water treatment apparatus 100 is constituted by successively arranging a biological nitrification/denitrification tank 4, a sedimentation/ separation tank 5 and a flocculation/sedimentation tank 6 to the rear stage of a flocculation/sedimentation tank 50 connected to pretreatment tanks 20 and 30 to which leached water W containing dioxins is supplied. The leached water W to which a carbonate and a flocculant are added in the pretreatment tanks 20 and 30 is supplied to the flocculation/sedimentation tank 50 to be subjected to the separation treatment of flocculated sludge and subsequently treated with activated sludge in the biological nitrification/denitrification tank 4. The leached water W is introduced into the sedimentation/separation tank 5 to be separated from activated sludge and flocculated sludge is removed in the flocculation/sedimentation tank 6. Mixed sludge D of a part of activated sludge separated from the leached water W and flocculated sludge is subjected to nitrification treatment in a biological reaction tank 1 and dioxins in the mixed sludge D are decomposed accompanied thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water treatment method and apparatus, and more particularly to a water treatment method for treating water to be treated containing an organic chlorine compound and a water treatment apparatus therefor.

[0002]

2. Description of the Related Art Fly ash generated from waste incineration facilities, suspended solids contained in leachate from waste disposal sites, and soil contaminated with such fly ash and leachate are represented by dioxins. In some cases, organic chlorine compounds that are hardly decomposable are contained, which is a major social problem. On the other hand, as an effective method and apparatus for decomposing dioxins contained in water to be treated such as leachate to be treated, WO 00/58038 (WO 00/580) by the present applicant has been proposed.
38) A method and an apparatus for treating an organic chlorine compound described in a pamphlet have been proposed.

[0003] This method and apparatus is a method for subjecting treated water to nitrification treatment to simultaneously oxidatively decompose hardly decomposable organic chlorine compounds such as dioxins contained in the treated water. No complicated equipment is required, and no severe processing conditions such as high temperature and high pressure are required. As a result, as compared with the conventional dioxin processing technology, a useful effect such as high processing efficiency of dioxins can be achieved while reducing processing time and processing cost.

[0004]

By the way, the present inventors have applied the above-mentioned conventional method by the present applicant to the purification treatment of leachate or the like using activated sludge, and have examined its effects and applicability. After a detailed study, the following findings were obtained. That is, when activated sludge (excess sludge) subjected to water treatment is treated by the above-described conventional method, dioxins contained in the sludge can be removed with a sufficiently high efficiency. However, depending on the properties of the water to be treated and the like, the adsorption and transfer of dioxins contained in the water to be treated to excess sludge are not sufficient, and dioxins may not always be sufficiently removed from the entire treatment system.

Accordingly, the present invention has been made in view of such problems, and has been developed in purifying water to be treated.
It is an object of the present invention to provide a water treatment method and apparatus capable of removing more difficult-to-decompose organic chlorine compounds such as dioxins contained in the water to be treated than in the past.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have made intensive studies and as a result have obtained the following findings. Generally, in water treatment such as leachate,
Components such as dissolved substances and suspended substances originally contained in raw water are removed in advance prior to biological treatment with activated sludge, or the above components are further removed after separating excess sludge for improving water quality. Often. These components are generally agglomerated and removed as solids, but unlike activated sludge, which is partially recycled, is usually discarded after being stored. The present inventors have found that dioxins and the like that have not been transferred to excess sludge can be significantly contained in such recovered solids, and have completed the present invention.

That is, the water treatment method according to the present invention comprises:
(1) A method comprising a biological treatment step of biologically treating treated water containing an organic chlorine compound with activated sludge,
(2) an activated sludge separation step of solid-liquid separation of the activated sludge contained in the treated water subjected to the biological treatment, and (3) a solid-liquid separation of the aggregated sludge that has been aggregated by adding a coagulant to the treated water. Coagulated sludge separation step, and (4) adding reduced (or reduced) nitrogen to at least a part of each of activated sludge and coagulated sludge obtained by solid-liquid separation and performing aerobic treatment to reduce reduced nitrogen And a sludge treatment step for oxidizing the sludge.

In the water treatment method having such a configuration, at least a part of the activated sludge subjected to the biological treatment (biological nitrification and denitrification treatment) is sent to a sludge treatment step as excess sludge, and reduced nitrogen is added. Then, a nitrification reaction is caused by the aerobic treatment, and organic chlorine compounds such as dioxins contained in the excess sludge are oxidatively decomposed. At the same time, a coagulant is added to the water to be treated, and for example, coagulated (precipitated) sludge obtained by coagulation by the coprecipitation action is also introduced into the sludge treatment step.

In general, a polymer-based flocculant, an inorganic flocculant and the like can be used as the flocculant, and the flocculant contains an inorganic component. Some may also be included. Therefore, by treating these in the sludge treatment step, the organochlorine compounds contained in the aggregated sludge are also oxidatively decomposed. In particular, aerobic treatment with activated sludge sent to the biological treatment step as surplus sludge is more preferable because the efficiency of oxidative decomposition of the organochlorine compound is enhanced, and is particularly useful when the coagulated sludge contains a large amount of inorganic components. In this case, the device configuration is simplified.

As described above, according to the water treatment method of the present invention, surplus sludge and coagulated sludge are taken out of the system of the biological treatment step and subjected to biological nitrification treatment, whereby dioxins and the like concentrated and adsorbed on the sludge are removed. It oxidatively decomposes organic chlorine compounds. Although the decomposition mechanism of such a hardly decomposable organochlorine compound has not yet been sufficiently elucidated, the hardly decomposable organochlorine compound is involved in an enzyme reaction system involving an oxidase such as ammonia monooxygenase produced by nitrifying bacteria. It is presumed that oxidative decomposition of is promoted.

[0011] More specifically, the coagulated sludge separation step comprises:
(A) It is preferable to have a first coagulation separation step of solid-liquid separation of coagulated sludge by adding a coagulant to water to be treated before performing the biological treatment step.

Thus, in the first coagulation separation step,
Components such as dissolved substances and suspended substances originally contained in the water to be treated aggregate and are effectively removed from the water to be treated, so that the biological treatment in the biological treatment step can be performed more favorably. The coagulated sludge containing the solid content can contain organic chlorine compounds such as dioxins contained in the water to be treated and suspended substances before biological treatment, but they are sent to the sludge treatment step to be oxidatively decomposed.
When the coagulated sludge obtained in the first coagulation / separation step mainly contains an inorganic component, it is desirable to perform the oxidation (nitrification) treatment in the sludge treatment step together with the excess sludge as described above.

Alternatively, the coagulated sludge separation step is a step (b) in which a coagulant is added to the treated water from which the activated sludge has been separated after the activated sludge separation step has been carried out to perform solid-liquid separation of the coagulated sludge. It is also preferable to have a coagulation separation step.
In this case, in the second coagulation / separation step, a small amount of suspended solids, activated sludge, and other solids remaining in the water to be treated separated from the activated sludge are coagulated and separated. Agglomerated sludge containing such solids includes organic chlorine compounds that did not migrate to the activated sludge separated from the water to be treated, and organic chlorine compounds contained in the solids themselves remaining in the water to be treated. May be included. And such organic chlorine compounds are also oxidatively decomposed in the sludge treatment step.

Further, it is preferable that the method further comprises a membrane separation step for membrane-separating the activated sludge and coagulated sludge treated in the sludge treatment step from the treated liquid, and this membrane separation step is carried out after the sludge treatment step is performed. Alternatively, it may be performed while performing the sludge treatment step. This makes it possible to highly separate the treated liquid from the sludge from which the organochlorine compound has been decomposed and removed in the sludge treatment step. For example, when returning the treatment liquid to the biological treatment step, the sludge flows into the biological treatment step. Is prevented. Therefore, even if the organic chlorine compound slightly remains in the sludge, it is suppressed from being returned to the biological treatment system. In addition, since the sludge from which the organic linear compound has been sufficiently decomposed and removed can be efficiently recovered, subsequent discharge or recovery is easy.

Further, when treating leachate as the water to be treated, a salt capable of reacting with calcium (Ca) to form a poorly water-soluble salt is added to the leachate in the first coagulation separation step. It is suitable. In this case, the “salt” may be added in the form of a solution, or may be added as it is (solids such as powders and granules).

Further, HCl contained in exhaust gas from a waste incineration plant
Inexpensive slaked lime is often used to remove lime. Ca contained in slaked lime penetrates into soil over time and eventually migrates into leachate. In the first coagulation separation step, a salt capable of forming a hardly soluble salt by reacting with Ca, such as an alkali metal carbonate, is added to such leachate, and coagulated sludge coagulated by the coagulant is removed. Therefore, in addition to the decomposition and removal of the organic chlorine compound, a better biological treatment by removing Ca is performed.

The water treatment apparatus according to the present invention is an apparatus for effectively implementing the water treatment method of the present invention,
(1) Water to be treated containing an organic chlorine compound is supplied,
An activated sludge separating section in which the treated water is biologically treated with activated sludge, and (2) the treated water biologically treated in the biological treatment section and the activated sludge are separated into solid and liquid. (3) a coagulated sludge separation section to which water to be treated is supplied, a coagulant is added, and solid matter coagulated from the water to be treated is separated into coagulated sludge from the treated water by solid-liquid separation;
Connected to the activated sludge separation section and the coagulated sludge separation section,
Activated sludge and coagulated sludge are supplied, and reduced nitrogen is supplied, and reduced nitrogen is oxidized (ie, nitrified) under aerobic conditions, and (5) sludge treatment unit is connected. Alternatively, the method further comprises a membrane separation unit provided in the sludge treatment unit, wherein the activated sludge and the coagulated sludge are separated from the treated liquid by a membrane.

Further, a coagulated sludge separation section is provided in front of the biological treatment section, and a first coagulation separation section in which a coagulant is added to the water to be treated to separate coagulated sludge into solid and liquid. It is preferable to have Alternatively, the coagulated sludge separation unit
It is also useful to have a second coagulation / separation unit which is provided in front of the biological treatment unit and in which coagulation sludge obtained by adding a coagulant to the water to be treated is separated into solid and liquid.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted. Unless otherwise specified, the positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

FIG. 1 is a schematic diagram showing a first embodiment of a water treatment apparatus according to the present invention. Water treatment device 100
Is disposed downstream of the coagulation sedimentation tank 50 (first coagulation / separation unit) in which the pretreatment tanks 20, 30 and the post-treatment tank 70 to which the leachate water W containing dioxins is supplied are connected. , A biological nitrification denitrification tank 4 (biological treatment section), a sedimentation separation tank 5 (activated sludge separation section), and a coagulation sedimentation tank 6 (second coagulation separation tank) in which a pretreatment tank 30 and a post-treatment tank 71 are connected in series. ) Are sequentially arranged. Among these tanks, the coagulation sedimentation tanks 6, 50 function as a coagulation sludge separation unit.

A filtration tower 7, an adsorption tower 8, and a sterilization tank 9 are connected in series at the subsequent stage of the coagulation / sedimentation tank 6. Furthermore, the sedimentation separation tank 5 and the coagulation sedimentation tanks 6, 50 are connected to the biological reaction tank 1 (sludge processing unit) by a piping line, and the biological reaction tank 1 has a membrane separation device 2 (membrane separation unit).
The sludge dewatering machine 3 is connected via.

The pretreatment tank 20 contains sodium carbonate (Na).
A carbonate storage tank 21 in which a carbonate solution such as ₂ CO ₃ ) is stored.
The pretreatment tank 30 adjacent to the pretreatment tank 20 is connected to a flocculant storage tank 31 in which a flocculant is stored. The coagulant is not particularly limited, and for example, an ionic or nonionic polymer coagulant, an inorganic coagulant, or the like can be used. Of these, inorganic coagulants include calcium coagulants (calcium hydroxide, calcium oxide, etc.), iron coagulants (ferric chloride, polyiron sulfate, etc.), and aluminum coagulants (aluminum sulfate, polychloride). Aluminum and the like, and these can be used alone or as a mixture of two or more.

The coagulating sedimentation tank 50 is a so-called gravity sedimentation separation tank of the type that promotes sedimentation separation by utilizing a difference in specific gravity, and has a scraper M1 therein. This coagulation sedimentation tank 5
Leached water W is supplied to 0 through the pretreatment tanks 20 and 30. The post-treatment tank 70 is a pH adjustment tank (neutralization tank), and uses an acid such as nitric acid to adjust the liquid property of the leachate W to a pH suitable for biological treatment in the subsequent biological nitrification and denitrification tank 4. It is to adjust.

Further, the biological nitrification and denitrification tank 4 has activated sludge containing microbial cells such as nitrifying bacteria and denitrifying bacteria. Has become. The biological nitrification denitrification tank 4 is composed of an anaerobic treatment tank 41 provided with a stirrer M2 and an aerobic treatment tank 42 provided with an aeration stirrer K having an aeration tube connected to a blower B. It is.

Further, the sedimentation / separation tank 5 and the coagulation / sedimentation tank 6 connected to the subsequent stage of the biological nitrification / denitrification tank 4 together constitute a gravity sedimentation / separation tank configured similarly to the coagulation / sedimentation tank 50. An aggregating agent storage tank 61 in which an aggregating agent is stored is connected to the aggregating and settling tank 6, and examples of the aggregating agent include those used in the above-described aggregating agent storage tank 31. In addition, the post-treatment tank 71 after the coagulation settling tank 6 includes:
It is a pH adjustment tank (neutralization tank) like the post-treatment tank 70 described above. Furthermore, the filtration tower 7 disposed downstream of the coagulation sedimentation tank 6 has a filter using various filtration materials such as sand, anthracite, activated carbon, and ceramics. On the other hand, the adsorption tower 8 has an adsorption layer filled with various adsorption media such as a carbonaceous adsorbent such as activated carbon.

On the other hand, the biological reaction tank 1 is supplied with sludge separated into solid and liquid in the sedimentation separation tank 5 and the coagulation sedimentation tanks 6 and 50, respectively, and has an aeration and agitation having an aeration tube connected to the blower B. A device K is provided internally. In addition, the biological reaction tank 1 contains ammonia water (NH ₄ O) as reduced nitrogen.
An ammonia water storage tank 13 storing H) is connected thereto. Examples of the membrane separation device 2 installed at the subsequent stage of the biological reaction tank 1 include an immersion type equipped with a membrane separation module having an immersion membrane, and a casing type. Examples of the immersion membrane include hollow fiber, tubular, and flat membranes. Usually, a microfiltration membrane,
It is preferable to use an ultrafiltration membrane or the like.

An example of the water treatment method according to the present invention using the water treatment apparatus 100 configured as described above will be described. First, while supplying the leachate W to the pretreatment tank 20,
A carbonate solution is added from the carbonate storage tank 21. Leachate W
Often contain Ca (ion: Ca ²⁺ ) originating from slaked lime or the like, as described above, reacting with carbonate ions (CO ₃ ^2- ) in a carbonate solution, and has poor water solubility. Calcium carbonate (CaCO ₃ ), which is a salt, is generated and precipitates in the leachate water W.

Next, the leachate W is allowed to flow into the pretreatment tank 30, and a coagulant (solution) such as ferric chloride (FeCl ₃ ) is added from the coagulant storage tank 31. It is introduced into the tank 50. In the coagulation sedimentation tank 50, the liquid properties such as pH are adjusted as needed, and CaC
Aggregate inorganic solids containing O ₃ . At this time, suspended solids (Suspended Solid) originally contained in the leachate W
s; hereinafter, referred to as “SS”. ) Can also aggregate together. In addition, since hardly decomposable organic chlorine compounds such as dioxins contained in the leachate W are also hardly soluble, they tend to adhere to SS or the like or disperse in a colloidal form. Also migrates to the coagulated portion together with SS and the like.

After operating the scraper M1 to promote coagulation, the coagulation component and the liquid component are separated into solid and liquid by gravity sedimentation separation, and the coagulated solid content is sent to the biological reaction tank 1 as coagulated sludge ( First coagulation separation step). On the other hand, the leachate W as the supernatant water is pH-adjusted (neutralized) in the post-treatment tank 70 and then introduced into the anaerobic treatment tank 41 of the biological nitrification denitrification tank 4. In the anaerobic treatment tank 41, only the stirring by the stirrer M2 is performed without supplying air or the like to the leachate W to perform the anaerobic treatment (denitrification treatment). Furthermore, the anaerobic treatment tank 41
The mixed liquid of leachate W and activated sludge treated in the above is introduced into the aerobic treatment tank 42, and the blower B is operated to operate oxygen (O) such as air.
₂ ) Aerobic treatment (nitrification treatment) while supplying gas containing
I do.

Next, a part of the mixed liquid of the leachate W and the activated sludge treated in the aerobic treatment tank 42 is supplied to the sedimentation separation tank 5, while the other part is returned to the anaerobic treatment tank 41, and the biological nitrification is performed. In the denitrification tank 4, the leachate W is circulated (biological treatment step). In this case, the anaerobic treatment tank 41, nitrite nitrogen contained in the mixed liquid is circulated back from the aerobic treatment tank 42 (NO ₂ ^- -N) and nitrate nitrogen (NO ₃ ^- -N) activated sludge The following formula (1) and / or formula (2) due to the action of denitrifying bacteria therein: 2NO ₂ ⁻ + 6H ⁺ → 2H ₂ O + 2OH ⁻ + N ₂ ... (1) 2NO ₃ ⁻ + 10H ⁺ → 4H ₂ O + 2OH ^- + N ₂ ... are denitrified by a reduction reaction represented by (2), nitrogen content is released removed becomes nitrogen gas (N _2).

As the hydrogen (H ⁺ ) donor (hydrogen donor) used in the denitrification reaction, the BOD component (substance) contained in the leachate W is used. If the BOD component is insufficient due to the properties of the water W or the progress of the treatment, the anaerobic treatment tank 41 uses an organic substance such as an alcohol such as methanol or an organic acid such as acetic acid as a hydrogen donor.
May be added.

In the aerobic treatment tank 42, sufficient agitation is performed by aeration of air or the like from an aeration / agitator K provided at the bottom of the tank. Thereby, a favorable aerobic atmosphere is formed, and the BOD component remaining in the mixed solution from the anaerobic treatment tank 41 is oxidized and decomposed. At the same time, the ammonia nitrogen (NH ₄ ⁺ -N) contained in the mixed solution is converted into the following formula (3) and / or formula (4) by the action of nitrifying bacteria in the activated sludge; 2NH ₄ ⁺ + 3O ₂ → 2NO ₂ ^- + 2H ₂ O ^{+ 4H + ... (3) 2NO} 2 - + O 2 → 2NO ₃ ^- ... is nitrified by the oxidation reaction represented by (4), nitrite nitrogen (NO ₂ ^- -N) and nitrate nitrogen (NO ₃ ^- -N) is generated.

In this way, both the treatment of the BOD component in the leachate W and the treatment of the nitrogen content in the biological nitrification denitrification tank 4 are realized. At this time, some of the hardly decomposable organic chlorine compounds such as dioxins contained in the leachate W can be oxidatively decomposed, but the remaining part is adsorbed by the activated sludge and moves to the sludge side. Next, the mixed liquid containing such activated sludge and leachate W is separated into solid and liquid by gravity sedimentation in the sedimentation separation tank 5 (activated sludge separation step). Then, a part of the settled activated sludge is returned to the anaerobic treatment tank 41 and used for biological treatment, while the remaining part is sent to the biological reaction tank 1 as surplus sludge. On the other hand, the leachate W, which is the supernatant water after the nitrification and denitrification treatment, is sent to the coagulation sedimentation tank 6.

Here, according to the findings of the present inventors, the content of dioxins among the hardly decomposable organic chlorine compounds contained in general leachate W is, for example, approximately 0.2 to 50.
pg-TEQ / l ("TEQ" indicates the toxic equivalent number;
“L” indicates liter. The same applies hereinafter. ), And the concentration of dioxins contained in the supernatant water supplied to the coagulation sedimentation tank 6 is, for example, about 0.1 to 10 pg-TEQ / l. In addition, surplus sludge sent to the biological reaction tank 1 includes:
About 15 pg-TEQ / g-dry ("g-dry" is
Indicates that the weight per dry sludge. The same applies hereinafter. )
Dioxins.

Next, in the coagulating sedimentation tank 6, the coagulant (solution) is transferred from the coagulant storage tank 61 to the leachate W as the supernatant water obtained in the sedimentation separation tank 5 in the same manner as in the coagulation sedimentation tank 50 described above. Is added. Fine suspended solids remain in the leachate W sent out from the sedimentation separation tank 5, but are aggregated into relatively large particles by the addition of a coagulant. As a result, the fine suspended solids are liable to settle, and are separated into solids and liquids by gravity sedimentation, and dioxins and the like contained in the supernatant water are adsorbed and transferred to the flocculated component. At this time, the activated sludge, SS component and other solids remaining in the supernatant water are also coagulated and separated from the liquid.

Next, the coagulated solids are sent to the biological reaction tank 1 as coagulated sludge, and leachate W as supernatant water is introduced into the filtration tower 7 to perform a filtration treatment. After removing the particulate matter by a sterilization treatment in the sterilization tank 9, the water is discharged out of the system as treated water Ws. The concentration of the hardly decomposable organic chlorine compound such as dioxins in the treated water Ws is generally 0.01 to 1%.
The level is reduced to about pg-TEQ / l, which is a level at which discharge to a river or the like is sufficiently possible.

On the other hand, in the biological reaction tank 1, a mixture of excess sludge (activated sludge) and coagulated sludge (hereinafter referred to as “mixed sludge D”) sent from the sedimentation separation tank 5 and the coagulation sedimentation tanks 6, 50, respectively, Ammonia water is added from the ammonia water storage tank 13, and a gas containing oxygen such as air from the blower B is supplied from the aeration and stirring device K. This allows
Ammonia nitrogen (NH ₄ ⁺ −) added to mixed sludge D
N) is nitrified by the oxidation reaction represented by the above formula (3) and / or formula (4) by the action of nitrifying bacteria in the sludge.

The excess sludge sent from the sedimentation separation tank 5 has been subjected to the denitrification treatment in the biological nitrification denitrification tank 4, that is, the content of reduced nitrogen has been reduced by denitrification. By the addition, the concentration of reduced nitrogen is increased, and the above-mentioned nitrification reaction proceeds favorably. As described above, when the biological nitrification reaction is forcibly caused in the biological reaction tank 1, the decomposition of the hardly decomposable organic chlorine compounds such as dioxins contained in the mixed sludge D is remarkably promoted. Lower hydrocarbons, carbon dioxide,
It is converted into water and made harmless (sludge treatment step).

Although the decomposition mechanism of dioxins and the like has not been sufficiently elucidated yet, oxidation of dioxins and the like in an enzyme reaction system involving an oxidase such as ammonia monooxygenase produced by nitrifying bacteria is not considered. It is considered that they occur at the same time. Possibly, ammonia monooxygenase or the like acts on dioxins or the like, and a co-oxydation reaction in which dioxins are oxidized in parallel with the nitrification reaction shown in formula (3) and / or formula (4). It is presumed that a kind of conjugation reaction is in progress.

Next, after performing nitrification treatment in the biological reaction tank 1 for a predetermined time, the mixed sludge D is introduced into the membrane separation device 2 and separated into a liquid component and a solid component by membrane filtration (membrane separation step). ). Since the obtained liquid separation membrane separation liquid contains a large amount of oxidized (or oxidized) nitrogen such as nitrate nitrogen, it is returned to the anaerobic treatment tank 41 of the biological nitrification denitrification tank 4.
On the other hand, the treated mixed sludge D, which is a solid content, is sent to the sludge dewatering machine 3 to be dewatered, and then discharged out of the system as dewatered sludge Ds for disposal. In addition, the dewatered separated liquid separated from the dewatered sludge Ds in the sludge dewatering machine 3 also returns to the anaerobic treatment tank 41 because it contains nitrate nitrogen and the like.

According to the water treatment apparatus 100 configured as described above and the water treatment method using the same, the nitrification reaction is caused by adding ammonia water, which is reduced nitrogen, to the mixed sludge D in the biological reaction tank 1. Thereby, even the hardly decomposable organic chlorine compounds such as dioxins contained by being adsorbed to the mixed sludge D are oxidized and decomposed to be harmless. The mixed sludge D contains not only the activated sludge used for the biological nitrification and denitrification treatment of the leachate W, but also the agglomerated sludge agglomerated from the leachate W. Most of dioxins are recovered.

Accordingly, the concentration of the hardly decomposable organic chlorine compounds such as dioxins contained in the treated water Ws can be sufficiently reduced, and most of the dioxins recovered from the leachate W can be rendered harmless. Therefore, the possibility that dioxins and the like are discharged out of the water treatment apparatus 100 is extremely low. On the other hand, although a large amount of agglutinated components have been conventionally recovered from the water to be treated such as the leachate W, they are usually stored or managed and disposed of thereafter. That is, according to the present invention, emission of dioxins and the like to the outside of the system can be significantly suppressed as compared with the conventional method.

The coagulated sludge contains little or no microbial cells, such as surplus sludge that is a part of activated sludge. May need to be added separately. Although the decomposition treatment of dioxins and the like in the coagulated sludge can be performed in this manner, improvement is desired from the viewpoint of reducing labor and man-hours and simplifying the apparatus configuration. On the other hand, if the water treatment apparatus 100 is used, the coagulated sludge is mixed with the surplus sludge and the nitrification treatment is performed in the single biological reaction tank 1.
It is possible to prevent an increase in labor and man-hours and a complicated device configuration.
Furthermore, there is an advantage that the scale of the apparatus can be reduced in comparison with the above-described conventional apparatus configuration in which coagulated sludge is stored.

Further, the coagulated sludge obtained by coagulation treatment in the coagulation sedimentation tank 50 prior to the biological nitrification denitrification treatment of the leachate W is obtained by coagulation treatment in the coagulation sedimentation tank 6 after the bionitrification denitrification treatment. Since both of the coagulated sludge and the coagulated sludge are introduced into the biological reaction tank 1 and collectively treated, it is possible to further suppress the discharge of dioxins and the like removed from the leachate W to the outside of the system.

Furthermore, since the mixed sludge D after the decomposition treatment of the hardly decomposable organic chlorine compounds such as dioxins is separated into solid and liquid by the membrane separation device 2, the separation between the membrane separation liquid and the solids (sludge) is high. Separation can be performed, and it is possible to sufficiently prevent sludge from being mixed into the membrane separation liquid returning to the anaerobic treatment tank 41.

In addition, a pretreatment tank 20 is provided to add carbonate to the leachate W to aggregate the generated calcium carbonate and remove it from the leachate W before the biological nitrification and denitrification treatment. Not only is the efficiency of decomposing and removing organic chlorine compounds improved, but also the purification performance is improved, and the quality of the treated water Ws can be further improved.

FIG. 2 is a schematic diagram showing a second embodiment of the water treatment apparatus according to the present invention. Water treatment device 200
Is a biological reaction tank 15 provided with a membrane separation module 25 (membrane separation unit) instead of the biological reaction tank 1 and the membrane separation device 2.
It is configured similarly to the water treatment apparatus 100 shown in FIG. 1 except that it has a (sludge treatment section). Although not particularly limited, the membrane separation module 25 is preferably an immersion type module having a plurality of flat membranes, hollow fiber membranes, and the like.

The water treatment apparatus 200 having such a configuration
In, ammonia water is added to the mixed sludge D of the excess sludge and the coagulated sludge introduced into the biological reaction tank 15, and the membrane is separated by the membrane separation module 25 while supplying a gas such as air while stirring and aerating. (Membrane separation step). Thereby, the membrane separation liquid can be continuously returned to the anaerobic treatment tank 41 while decomposing dioxins and the like by the nitrification reaction of the mixed sludge D. Therefore, more efficient biological treatment of the mixed sludge D can be achieved. Note that the other processing procedures and operational effects are the same as those in the water treatment apparatus 100 described above, and a description thereof will be omitted.

FIG. 3 is a schematic diagram showing a third embodiment of the water treatment apparatus according to the present invention. Water treatment device 300
Is a water treatment apparatus 1 shown in FIG. 1 except that an anaerobic treatment tank 60 is installed between the biological reaction tank 1 and the membrane separation apparatus 2.
It has a configuration equivalent to 00. This anaerobic treatment tank 60 is an anaerobic treatment tank 4 that constitutes the biological nitrification denitrification tank 4.
As in 1, the stirrer M2 is provided inside.

In the water treatment apparatus 300 having such a configuration, the mixed sludge D that has been nitrified in the biological reaction tank 1 is introduced into the anaerobic treatment tank 41, and the anaerobic treatment is performed by operating only the stirrer M2. The mixed sludge D that has undergone nitrification treatment contains oxidized nitrogen such as nitrate nitrogen, and the anaerobic treatment in the anaerobic treatment tank 41 causes a reduction reaction by the action of denitrifying bacteria, thereby performing denitrification. .

When the anaerobic state is further maintained in this state, microbial cells such as nitrifying bacteria contained in the mixed sludge D are disintegrated, and accordingly, dioxins and the like remaining in the mixed sludge D in a small amount remain. Decomposition can occur. Although the details of this mechanism of action are unclear, oxidizing enzymes such as monooxygenase produced by nitrifying bacteria are eluted by disintegration of the bacterial cells, and this enzyme-mediated co-oxidation reaction causes oxidative degradation of organic chlorine compounds. It is presumed to be promoted.

Therefore, according to the water treatment apparatus 300 and the water treatment method of the present invention using the water treatment apparatus 300, in both the biological reaction tank 1 and the anaerobic treatment tank 60, the poorly soluble dioxins and the like contained in the mixed sludge D are mixed. Since the decomposition of the organic chlorine compounds is performed, their harmlessness can be further enhanced.
In addition, regarding the processing procedure and operation effects other than these,
Since this is the same as in the water treatment apparatus 100 described above, the description here is omitted.

[0053]

As described above, according to the water treatment apparatus and the water treatment method of the present invention, in the purification treatment of the water to be treated such as leachate, it is difficult to decompose dioxins and the like contained in the water to be treated. It is possible to remove organic chlorine compounds more sufficiently than before, improve the harmless performance of the collected and removed organic chlorine compounds, and significantly reduce the amount of organic chlorine compounds emitted outside the system. Become.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a first embodiment of a water treatment apparatus according to the present invention.

FIG. 2 is a configuration diagram schematically showing a second embodiment of the water treatment apparatus according to the present invention.

FIG. 3 is a configuration diagram schematically showing a third embodiment of the water treatment apparatus according to the present invention.

[Explanation of symbols]

1, 15: biological reaction tank (sludge processing unit), 2: membrane separator (membrane separation unit), 3: sludge dehydrator, 4: biological nitrification denitrification tank (biological processing unit), 5: sedimentation separation tank (activated sludge) Separation section),
6 ... coagulation sedimentation tank (second coagulation separation section), 13 ... ammonia water storage tank, 20, 30 ... pretreatment tank, 21 ... carbonate storage tank, 25 ... membrane separation module (membrane separation section), 31, 61
... Coagulant storage tank, 41,60 ... Anaerobic treatment tank, 42 ... Aerobic treatment tank, 50 ... Coagulation sedimentation tank (first coagulation separation section),
100, 200, 300: water treatment device, D: mixed sludge,
W: Leachate (water to be treated).

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 3/12 C02F 3/12 V ZAB ZABD 9/00 501 9/00 501C 502 502P 502Z 503 503C 504 504A 504E (72) Inventor Kohei Miki 63-30 Yuyugaoka, Hiratsuka-shi, Kanagawa F-term in Hiratsuka Works of Sumitomo Heavy Industries, Ltd. (Reference) 4D015 BA23 BB05 CA02 DA17 DB01 EA12 EA32 FA01 FA12 FA17 FA22 FA26 4D028 AB00 AC01 BB07 BD16 BE04 BE08 4D038 AA08 AB59 BB06 BB13 BB17 BB18 BB19 4D059 AA05 AA06 AA18 BA01 BA31 BE55 BE56 CA28 DA41

Claims (7)

[Claims] 1. A water treatment method comprising a biological treatment step of biologically treating treated water containing an organic chlorine compound with activated sludge, wherein the activated sludge contained in the treated water subjected to the biological treatment is solid-liquid separated. An activated sludge separating step, a flocculant is added to the water to be treated, and a coagulated sludge is separated into solid and liquid. A sludge treatment step of oxidizing the reduced nitrogen by adding a reduced nitrogen to at least a part thereof and performing aerobic treatment,
A water treatment method comprising: 2. The method according to claim 1, wherein the coagulated sludge separating step comprises the steps of: prior to performing the biological treatment step, performing a solid-liquid separation on the coagulated sludge that has been formed by adding a coagulant to the water to be treated;
The water treatment method according to claim 1, further comprising a coagulation separation step. 3. The coagulated sludge separating step, after performing the activated sludge separating step, adds a coagulant to the water to be treated from which the activated sludge has been separated, and solid-liquid separates the coagulated sludge. The water treatment method according to claim 1, further comprising a second coagulation separation step. 4. A leachate is treated as the water to be treated, and a salt capable of reacting with calcium (Ca) to form a poorly water-soluble salt is added to the leachate in the first coagulation separation step. The water treatment method according to claim 1, wherein: 5. A water treatment apparatus comprising: a biological treatment section to which water to be treated containing an organic chlorine compound is supplied, and wherein the water to be treated is biologically treated by activated sludge, wherein the biological treatment is performed by the biological treatment section. Activated sludge separating section for solid-liquid separation of the treated water and the activated sludge, the treated water is supplied, a coagulant is added, and the solid content agglomerated from the treated water is treated as coagulated sludge. An agglomerated sludge separating section for solid-liquid separation from water, connected to the activated sludge separating section and the agglomerated sludge separating section, wherein the activated sludge and the agglomerated sludge are supplied, and reduced nitrogen is supplied. A sludge treatment section in which the reduced nitrogen is oxidized under aerobic conditions. 6. The first coagulated sludge separating section is provided in front of the biological treatment section, and a coagulant is added to the water to be treated to perform coagulation sludge solid-liquid separation. The water treatment device according to claim 5, further comprising an aggregating / separating unit. 7. The second method, wherein the coagulated sludge separation section is provided in front of the biological treatment section, and a coagulant is added to the water to be treated, and coagulated coagulated sludge is subjected to solid-liquid separation. The water treatment device according to claim 5, further comprising an aggregating / separating unit.