【発明の詳細な説明】
本発明は、廃水処理方法に関するものであり、
さらに詳しくは、廃水を活性汚泥処理する際、曝
気槽中に粉末活性炭を共存させる方法において、
曝気槽内の活性汚泥濃度と活性炭濃度との和（以
下、MLSSと記す）を従来一般に実施されてきた
値よりも著しく高い25000ppm以上とする廃水処
理方法であり、本発明方法により新規に添加する
活性炭量を著減させることが出来る。
廃水を活性汚泥処理するに当り、曝気槽中に粉
末活性炭を添加して処理効果を向上させる方法
は、公知（例えば特公昭44−5949号公報、特開昭
46−140号公報等）であり、既に活性汚泥処理設
備を有しているところでは、活性炭投入のための
簡単な設備を追加するだけで廃水の高度処理を実
現できるため、大いに注目を集めている方法であ
る。しかしながら、従来、添加した活性炭は使い
捨てにするか、湿式酸化方式や焙焼賦活方式の再
生炉で再生されているが、これ等には次の様な問
題点がある。
(1) 活性炭を使い捨てにした場合は、比較的多量
の活性炭を使用するため、そのコストが非常に
大きくなる。
(2) 再生炉を設置すると、その設備費、運転費が
膨大なものとなる。また、技術的には活性炭を
再生する際、活性汚泥が燃焼してしまい、汚泥
が減少すること、活性炭の再生ロス等の問題点
が挙げられる。
これらの諸問題点を克服するため鋭意検討を重
ねた結果、本発明者等は、次のような事実すなわ
ち活性汚泥法曝気槽に粉末活性炭を添加してゆく
と、老廃活性炭が槽内に蓄積して徐々にMISSが
上昇するが、これにともなつて同程度の水質
（COD、色度等）の処理水を得るために、添加す
る必要のある新活性炭量は、漸減していくという
驚くべき事実を発見し、本発明を完成するに至つ
た。
廃水の活性汚泥処理法におけるMLSS値（この
場合は活性汚泥のみで、活性炭は使用しない。）
は、通常5000ppm程度であり、その際曝気槽中
に粉末活性炭を添加する前記方法でも活性炭添加
量は、数十ないし、数百ppmが一般的であつ
て、この場合もMISS値は大略5000〜10000ppm
程度にとどまる。
本発明方法は、このような一般的な操作条件を
根本からくつがえし、活性汚泥法曝気槽に粉末活
性炭を添加していく過程で生じる老廃活性炭およ
び余剰汚泥の廃棄を少なくともMLSS値が
25000ppm（うち活性炭20000ppm程度）に達す
るまでは行なわず、さらにその後もこの高MLSS
値を維持しつつ操作を行なうことを最大の特徴と
するものであり、その結果、一度このような高
MLSS値に達したあとは、新たに添加する活性炭
の量を従来法に比べて著しく低減することができ
るのである。新規に添加すべき活性炭の量は、処
理すべき原廃水の水質、得らるべき処理水の水
質、さらにはMLSS値などによつて当然異なる
が、例えば一般的な産業廃水の処理の場合には、
10ppm前後で十分であることが多い。これは従
来の曝気槽中に活性炭を添加する活性汚泥処理法
で要する活性炭量の数分の一ないし、十数分の一
の値であり、使い捨てにしてもコスト的にはほと
んど問題にならず、したがつて、活性炭再生炉の
必要もなくなる。
本発明方法におけるMLSSは、25000ppm（う
ち活性炭は20000ppm程度）以上、通常30000な
いし、80000ppm（うち活性炭は25000ないし、
70000ppm程度）であるが、曝気槽内に老廃活性
炭が多く蓄積すればするほど効果を発揮するの
で、槽内での撹拌、スラツジ・ボリユーム
（VV）等に悪影響がない限り、高い方が望まし
い。
使用する粉末活性炭は、高MLSSで操作すると
いう本発明方法の特質上、活性汚泥とともに高濃
度に蓄積した時の流動性および沈降性が良く、か
つ原廃水中のCOD成分、BOD成分、着色成分等
を良く吸着するものが望ましいが、一般には廃水
処理用として市販されている粉末活性炭で十分で
ある。粉末活性炭の曝気槽への投入は、粉末のま
までも、スラリー状でも可能であるが、飛散の問
題等を考慮すれば、スラリー状にして投入する方
が望ましい。
また、曝気槽の運転管理については、従来の活
性汚泥処理法と同様にCODあるいは、BODで負
荷調整すればよいが、本発明方法の場合には曝気
槽内に多量の活性炭が蓄積するので、容積負荷
（Kg-COD/m3・dあるいはKg-BOD/m3・d）あるい
は、活性炭分を除去した汚泥負荷（Kg-COD/Kg
−ＭＬＳＳ・ｄあるいはKg-BOD/Kg-MLSS・d）を
運転管理の指標にするのが好都合である。
曝気槽内の水温、PH、溶存酸素等は従来の活性
汚泥処理法と同様に管理すればよい。こうして処
理水の水質が目標値に達するように粉末活性炭を
適宜曝気槽内に添加すればよく、その添加方式は
連続方式でも間歇方式でもよい。
以上の様に、廃活性炭を曝気槽に蓄積すればす
るほど新規に添加する活性炭量を減少させること
ができる理由は、明確ではないが、次の様に推測
される。すなわち、添加した活性炭表面には簡単
に生物分解が可能な物質（以下易分解性物質と記
す）と、通常の活性汚泥法では分解できない物質
（以下離分解性物質と記す）が吸着される。易分
解性物質は数時間から数十時間で分解され、それ
だけ活性炭は再生され、再び他の物質が吸着され
る。これが繰り返えされ、活性炭は難分解性物質
ばかりを吸着し、一応老廃活性炭となる。しか
し、難分解性物質も数十日から、数百日間活性汚
泥と接触すれば、ある程度分解されることは十分
考えられる。したがつて、難分解性物質が非常に
ゆつくりと分解されると仮定すれば、老廃活性炭
を大量に曝気槽内に蓄積しておけば、全体として
はかなりの吸着能を回復することができると推察
される。
本発明方法の具体的な実施方法の一例を図２に
したがつて説明する。処理すべき原廃水は、ポン
プ６により供給ライン５を通つて曝気槽１に入
る。槽内には活性汚泥および高濃度の老廃活性炭
が存在しており、ここで曝気処理を受けた処理水
はライン１０を経てクラリフアイアー２に入る。
処理水に伴なつてきた活性汚泥および活性炭の大
部分は、ここで沈降して底部から抜き出され、返
送ポンプ７および返送ライン８を経て曝気槽１に
戻される。クラリフアイアー２の上澄液中には、
まだ微量の活性炭（および活性汚泥）が懸濁して
いる場合が多いので、ライン１１によりサンドフ
イルター３に送つて過し、処理水放流ライン１
２より放流する。サンドフイルター３は、目詰り
を防止するために、時々逆洗ポンプ１３を用いて
処用水で逆洗する。逆洗水はライン１４を経て曝
気槽１に返送する。一方、新規に添加する粉末活
性炭はスラリー化槽４でスラリーとし、ライン１
２より放流される処理水の水質をチエツクしなが
ら、必要に応じてポンプ９およびライン１５を経
て、曝気槽１に添加する。
以上のように本発明方法によれば、曝気槽に蓄
積した活性炭を抜き出し再生せずに、長期間、高
濃度に活性汚泥と共存させることにより、難分解
性物質を吸着した活性炭の生物再生をはかり、新
規投入活性炭を著減することができるのであり、
その経済的意義は、極めて大きい。次に実施例を
挙げて、本発明方法を具体的に説明する。
なお、実施例中廃水のCOD、BODはJIS
K0102の方法に基づいて測定した。また、色度は
次に示す方法により測定した。すなわち、JIS
K0101に示されている色度標準液（塩化白金酸カ
リウム2.49ｇ、結晶塩化コバルト2.00ｇを塩酸
100mlに溶解し、さらに水を加えて１に希釈し
たもの）の可視部400〜700mm）における吸光度曲
線を画き、その吸光度曲線、波長軸（すなわち、
吸光度Ｏの直線）、400mmおよび700mmにおいて波
長軸に垂直に引いた直線の間に囲まれる面積を測
定し、それをＳとする。次に試料について、吸光
度曲線を画き、標準液の場合と同様に面積を求め
てそれをS′とし、試料の色度を次式より計算す
る。
色度（度）＝（S′／Ｓ）×1000
実施例
ある産業廃水（COD220ppm、BOD180ppm、
色度2100度）をCOD容積負荷0.25Kg-COD/m3・
ｄ、曝気槽滞留時間12hr、曝気槽水温25℃、曝気
槽PH6.5、曝気槽溶存酸素5.0ppm、
MLSS5000ppmで活性汚泥処理した時の処理水の
BODは5ppm、CODは82ppm、色度は1200度であ
つた。処理水のCODを40ppm以下、色度500度以
下にするために、曝気槽に粉末活性炭をスラリー
状にして添加していつたが、槽内に老廃活性炭が
ほとんど蓄積していない状態では、新規に添加す
る必要のある活性炭は、85ppm（対原水供給
量、以下も同じ）であつた。老廃活性炭が徐々に
蓄積し、MLSSが6000ppm（うち老廃活性炭約
1000ppm）に達した時に新規に添加する必要の
ある活性炭は、82ppmに減少した。これは従来
の活性炭添加活性汚泥法に相当する。さらに老廃
活性炭の蓄積量が増加し、MLSSが高くなるにし
たがつて、新規に添加すべき活性炭量は減少して
いつた。この間の状況を図１に示す。図１から明
らかなようにMLSSが25000ppm（うち老廃炭約
20000ppm）以上になれば、新たに添加すべき活
性炭は約10ppmあるいは、それ以下にとどま
る。本発明方法、従来の活性炭添加活性汚泥法、
および通常の活性汚泥法の差を明確にするため
に、三者の比較を表１に示す。
【表】[Detailed description of the invention] The present invention relates to a wastewater treatment method,
More specifically, in a method of coexisting powdered activated carbon in an aeration tank when treating wastewater with activated sludge,
This is a wastewater treatment method in which the sum of activated sludge concentration and activated carbon concentration (hereinafter referred to as MLSS) in the aeration tank is 25,000 ppm or more, which is significantly higher than the value that has been generally implemented in the past, and it is newly added by the method of the present invention. The amount of activated carbon can be significantly reduced. When treating wastewater with activated sludge, methods for improving the treatment effect by adding powdered activated carbon to the aeration tank are known (e.g., Japanese Patent Publication No. 44-5949, Japanese Patent Application Laid-Open No.
46-140, etc.), and in places that already have activated sludge treatment equipment, it is attracting a lot of attention because advanced treatment of wastewater can be achieved just by adding simple equipment to add activated carbon. This is the way to be. However, conventionally, the added activated carbon is either disposable or regenerated in a regeneration furnace using a wet oxidation method or a roasting activation method, but these methods have the following problems. (1) If activated carbon is made disposable, the cost will be very high because a relatively large amount of activated carbon will be used. (2) If a regeneration furnace is installed, the equipment and operating costs will be enormous. Further, technically speaking, when regenerating activated carbon, activated sludge is burned, resulting in a decrease in sludge, and there are problems such as regeneration loss of activated carbon. As a result of extensive studies to overcome these problems, the inventors of the present invention discovered the following fact: When powdered activated carbon is added to an activated sludge aeration tank, waste activated carbon accumulates in the tank. The surprising result is that the MISS gradually increases, but the amount of new activated carbon that needs to be added to obtain treated water with the same quality (COD, chromaticity, etc.) gradually decreases. This discovery led to the completion of the present invention. MLSS value in activated sludge treatment method for wastewater (in this case, only activated sludge is used and activated carbon is not used)
is usually around 5,000 ppm, and even with the method described above in which powdered activated carbon is added to the aeration tank, the amount of activated carbon added is generally tens to hundreds of ppm, and in this case, the MISS value is approximately 5,000 to 5,000 ppm. 10000ppm
It remains to a certain extent. The method of the present invention fundamentally overturns these general operating conditions, and allows the disposal of waste activated carbon and excess sludge generated during the process of adding powdered activated carbon to the activated sludge method aeration tank to at least a MLSS value.
We do not carry out this process until it reaches 25,000ppm (including about 20,000ppm of activated carbon), and even after that, we continue to use this high MLSS.
Its main feature is that it performs operations while maintaining the value, and as a result, once such high
After reaching the MLSS value, the amount of newly added activated carbon can be significantly reduced compared to conventional methods. The amount of activated carbon that should be newly added will naturally vary depending on the quality of the raw wastewater to be treated, the quality of the treated water to be obtained, and the MLSS value, but for example, in the case of general industrial wastewater treatment. teeth,
Around 10ppm is often sufficient. This is a fraction or tenth of the amount of activated carbon required in the conventional activated sludge treatment method, which involves adding activated carbon to the aeration tank, and there is almost no problem in terms of cost even if it is disposable. , Therefore, there is no need for an activated carbon regeneration furnace. The MLSS in the method of the present invention is 25,000 ppm (of which activated carbon is about 20,000 ppm) or more, usually 30,000 to 80,000 ppm (of which activated carbon is about 25,000 to 80,000 ppm).
(approximately 70,000 ppm), but the more waste activated carbon accumulates in the aeration tank, the more effective it becomes, so a higher value is preferable as long as it does not adversely affect stirring in the tank, sludge volume (VV), etc. The powdered activated carbon used has good fluidity and sedimentation properties when accumulated in high concentration with activated sludge due to the characteristics of the method of the present invention, which is operated at high MLSS, and has good fluidity and sedimentation properties, and is highly effective against COD components, BOD components, and colored components in raw wastewater. It is desirable to use a carbon that can adsorb substances such as the like, but powdered activated carbon, which is commercially available for wastewater treatment, is generally sufficient. Powdered activated carbon can be charged into the aeration tank either as a powder or in the form of a slurry, but in consideration of the problem of scattering, it is preferable to charge it in the form of a slurry. In addition, regarding the operational management of the aeration tank, it is sufficient to adjust the load using COD or BOD as in the conventional activated sludge treatment method, but in the case of the method of the present invention, a large amount of activated carbon accumulates in the aeration tank, so Volume load (Kg-COD/m 3・d or Kg-BOD/m 3・d) or sludge load with activated carbon removed (Kg-COD/Kg
-MLSS・d or Kg-BOD/Kg-MLSS・d) is conveniently used as an indicator for operation management. The water temperature, pH, dissolved oxygen, etc. in the aeration tank can be managed in the same manner as in conventional activated sludge treatment methods. Powdered activated carbon may be appropriately added to the aeration tank so that the quality of the treated water reaches the target value, and the addition method may be continuous or intermittent. As mentioned above, the reason why the more waste activated carbon is accumulated in the aeration tank, the more the amount of newly added activated carbon can be reduced is not clear, but it is presumed as follows. That is, substances that can be easily biodegraded (hereinafter referred to as easily degradable substances) and substances that cannot be decomposed by the normal activated sludge method (hereinafter referred to as dissolvable substances) are adsorbed on the surface of the added activated carbon. Easily decomposable substances are decomposed within several hours to several tens of hours, and the activated carbon is regenerated accordingly, and other substances are adsorbed again. As this process is repeated, the activated carbon absorbs only the persistent substances and becomes waste activated carbon. However, it is quite conceivable that even hard-to-decompose substances will be decomposed to some extent if they are in contact with activated sludge for several tens to hundreds of days. Therefore, assuming that persistent substances are decomposed very slowly, by accumulating a large amount of waste activated carbon in the aeration tank, a considerable amount of adsorption capacity can be recovered as a whole. It is presumed that. An example of a specific implementation method of the method of the present invention will be explained with reference to FIG. The raw wastewater to be treated enters the aeration tank 1 through the supply line 5 by means of a pump 6 . Activated sludge and high-concentration waste activated carbon are present in the tank, and the treated water that has been aerated here enters Clarifier 2 via line 10.
Most of the activated sludge and activated carbon that have accompanied the treated water settle here, are extracted from the bottom, and are returned to the aeration tank 1 via the return pump 7 and return line 8. In the supernatant liquid of ClarifIre 2,
Since a small amount of activated carbon (and activated sludge) is often still suspended, it is sent to the sand filter 3 via line 11, and then passed through the treated water discharge line 1.
Release from 2. The sand filter 3 is sometimes backwashed with treated water using a backwash pump 13 to prevent clogging. Backwash water is returned to the aeration tank 1 via line 14. On the other hand, newly added powdered activated carbon is made into a slurry in slurry tank 4, and is made into a slurry in line 1.
While checking the quality of the treated water discharged from 2, it is added to the aeration tank 1 via the pump 9 and line 15 as necessary. As described above, according to the method of the present invention, activated carbon accumulated in an aeration tank is not extracted and regenerated, but is allowed to coexist with activated sludge at a high concentration for a long period of time, thereby achieving biological regeneration of activated carbon that has adsorbed persistent substances. It is possible to significantly reduce the amount of newly added activated carbon,
Its economic significance is extremely large. Next, the method of the present invention will be specifically explained with reference to Examples. In addition, the COD and BOD of wastewater in the examples are JIS
Measured based on the method of K0102. Moreover, chromaticity was measured by the method shown below. In other words, JIS
The color standard solution shown in K0101 (2.49 g of potassium chloroplatinate, 2.00 g of crystalline cobalt chloride) was added to hydrochloric acid.
Draw an absorbance curve in the visible range (400 to 700 mm) of the solution (dissolved in 100 ml and diluted to 1 with water), and draw the absorbance curve, wavelength axis (i.e.
The area surrounded by the straight line drawn perpendicular to the wavelength axis at 400 mm and 700 mm is measured, and this is defined as S. Next, draw an absorbance curve for the sample, find the area in the same way as for the standard solution, use it as S', and calculate the chromaticity of the sample using the following formula. Chromaticity (degrees) = (S'/S) x 1000 Example: Certain industrial wastewater (COD 220ppm, BOD 180ppm,
chromaticity 2100 degrees) and COD volume load 0.25Kg-COD/ m3 .
d, aeration tank residence time 12hr, aeration tank water temperature 25℃, aeration tank PH6.5, aeration tank dissolved oxygen 5.0ppm,
Treated water when activated sludge treated with MLSS5000ppm
BOD was 5ppm, COD was 82ppm, and chromaticity was 1200 degrees. In order to keep the COD of treated water below 40 ppm and the chromaticity below 500 degrees, we have been adding powdered activated carbon in the form of a slurry to the aeration tank, but with almost no waste activated carbon accumulated in the tank, it is necessary to add new activated carbon to the aeration tank. The amount of activated carbon that needed to be added was 85 ppm (relative to the amount of raw water supplied; the same applies hereinafter). The waste activated carbon gradually accumulates, and the MLSS reaches 6000 ppm (of which the waste activated carbon
The amount of activated carbon that needs to be newly added when it reaches 1000ppm has been reduced to 82ppm. This corresponds to the conventional activated sludge method with activated carbon added. Furthermore, as the accumulated amount of waste activated carbon increased and the MLSS became higher, the amount of newly added activated carbon decreased. The situation during this time is shown in Figure 1. As is clear from Figure 1, the MLSS is 25,000 ppm (of which approximately 25,000 ppm of waste coal
20,000ppm) or more, the amount of activated carbon that needs to be added remains at about 10ppm or less. The method of the present invention, the conventional activated sludge method with activated carbon added,
In order to clarify the differences between the activated sludge method and the conventional activated sludge method, a comparison of the three methods is shown in Table 1. 【table】
【図面の簡単な説明】[Brief explanation of the drawing]
図１はMLSSと処理水の色度を500度以下、
CODを40ppm以下にするために必要であつた新
活性炭の添加率との関係を示すもので、横軸は
MLSS（ppm）を縦軸は新活性炭添加率（ppm）
を示す。図２は、本発明方法を実施するための装
置の具体的な例を示すものである。
１……曝気槽、２……クラリフアイアー、３…
…サンドフイルター、４……活性炭スラリー化
槽、６……原水供給ポンプ、７……返送汚泥ポン
プ、９……活性炭スラリー供給ポンプ、１３……
サンドフイルター逆洗ポンプ。
Figure 1 shows the chromaticity of MLSS and treated water below 500 degrees.
It shows the relationship with the addition rate of new activated carbon that was necessary to reduce COD to 40ppm or less, and the horizontal axis is
MLSS (ppm) and vertical axis is new activated carbon addition rate (ppm)
shows. FIG. 2 shows a specific example of an apparatus for carrying out the method of the present invention. 1...Aeration tank, 2...Clarifia, 3...
... Sand filter, 4 ... Activated carbon slurry tank, 6 ... Raw water supply pump, 7 ... Return sludge pump, 9 ... Activated carbon slurry supply pump, 13 ...
Sand filter backwash pump.