JP2005046697A - Activated sludge treatment method - Google Patents
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は活性汚泥処理方法に関する。
【０００２】
【従来の技術】
コークス炉から排出されるコークスス炉ガスの凝縮水等は、排水処理設備に流入させ、活性汚泥によって無害化している。通常、活性汚泥曝気槽内へ凝縮水等を流入させる際、汚泥への負荷軽減のために、希釈水を用いて希釈を行っているが、希釈水は主に海水を用いている（特開平９−２９０２９２号公報等）ため、この海水に含まれるＣａイオンが原水中に存在する炭酸イオン及び活性汚泥が有機物分解の際に排出する炭酸イオンと反応して炭酸カルシウムが析出する。
【０００３】
析出した炭酸カルシウムは曝気槽内に堆積し、曝気槽の有効容積を低減させてしまう。また、析出した炭酸カルシウムは散気装置のエアーノズルを目詰まりさせる原因にもなっている。更に曝気槽の後段工程の終末処理設備である脱色設備では、砂ろ過塔のろ材や吸着塔内の活性炭の固着を引き起こしている。
そこで、炭酸カルシウムの析出を防止するために、酸添加によるｐＨ調整が行われている（特開２０００−３２５９８１号公報）が、コークス炉排水等は一般にアルカリ度が高いため、多量の酸を添加する必要があった。また更には、酸添加による活性汚泥中の微生物への影響が懸念される。
希釈水を工水にすることも考えられるが、沈殿槽での汚泥の沈降速度低下が懸念される。
【０００４】
【特許文献１】特開平９−２９０２９２号公報 段落番号［００３５］等
【特許文献２】特開２０００−３２５９８１号公報 段落番号［００１１］等
【０００５】
【発明が解決しようとする課題】
ｐＨ調整用の酸やアルカリを添加することなく炭酸カルシウムの析出速度を抑制でき、かつ活性汚泥中の微生物への影響や汚泥の沈降速度への影響が小さい活性汚泥の処理方法が求められていた。
【０００６】
【課題を解決するための手段】
本発明者等は上記課題を解決すべく鋭意検討した結果、炭酸カルシウムの析出速度がカルシウム濃度に依存性が大きいことを見出し、本発明を完成するに至った。即ち本発明の要旨は、下記（１）〜（５）に存する。
（１） 原水を曝気槽に導入して活性汚泥処理する方法において、曝気槽中のカルシウム濃度が１１０〜１７０ｍｇ／リットルであることを特徴とする活性汚泥処理方法。
【０００７】
（２） 希釈水として工水と海水を用い、曝気槽中のカルシウム濃度が１１０〜１７０ｍｇ／リットルとなるように工水と海水を曝気槽に流入させる上記（１）に記載の活性汚泥処理法方。
（３） 曝気槽内が、好気性である上記（１）又は（２）に記載の活性汚泥処理法方。
【０００８】
（４） 曝気槽出口のｐＨが７．２以上である上記（１）〜（３）のいずれかに記載の活性汚泥処理方法。
（５） 原水がコークス炉排水である上記（１）〜（４）のいずれかに記載の活性汚泥処理法方。
【０００９】
【発明の実施の形態】
本発明の活性汚泥処理方法は、原水を曝気槽に導入して活性汚泥処理する方法において、曝気槽中のカルシウム濃度が１１０〜１７０ｍｇ／リットルであることを特徴とする。曝気槽中のカルシウム濃度が低すぎると汚泥沈降速度が低下し、高すぎると炭酸カルシウムの析出量が増加する。好ましくは１２５ｍｇ／リットル以上、１５５ｍｇ／リットル以下である。
【００１０】
本発明において原水とは、活性汚泥処理にて処理する物質を含有している水であり、具体的には一般下水、有機物を含有する廃水、コークス炉で発生する安水、及びこれにプラントで発生する廃水等が含まれる。コークスプラントから発生する原水には、コークス原料の石炭に由来するＮＨ４ＳＣＮ等の活性汚泥への被毒物質や、フェノール類等のＣＯＤ成分が含まれていおり、カルシウム濃度は２ｍｇ／リットル程度である。
【００１１】
本発明において工水とは、河川水等から得る工業用水であり、一般的にはカルシウム塩類やマグネシウム塩が溶解している。カルシウム濃度は０〜２０ｍｇ／リットルの工水を用いることが好ましい。カルシウム濃度が高すぎると、本発明の効果が発現しないので好ましくない。
曝気槽中のカルシウム濃度を１１０〜１７０ｍｇ／リットルとする手段としては、イオン交換やキレート法でＣａを除去する、または工水にＣａを添加するか、あるいはカルシウムを高濃度に含む水や廃水等が挙げられ、また、簡易に濃度を調整できる観点から、原水の希釈水として工水と海水を用いている系で、工水と海水を、曝気槽中のカルシウム濃度が１１０〜 １７０ｍｇ／リットルとなるように曝気槽に流入させる方法が挙げられる。
【００１２】
希釈水として工水と海水を用い、工水と海水を、曝気槽中のカルシウム濃度が１１０〜 １７０ｍｇ／リットルとなるように曝気槽に流入させる方法について具体的に説明する。
曝気槽内のカルシウム濃度は、原水と原水中に含まれる被毒物質を希釈するための海水及び工水の各カルシウム濃度の加重平均から求める。まず、原水中及び工水中に含まれるカルシウム濃度を測定する（海水中のカルシウム濃度は３９５ｍｇ／リットルである）。カルシウム濃度の測定方法としては、滴定法、原子吸光法、イオンクロマト分析法等が挙げられる。原水中のカルシウム濃度をＡｍｇ／リットル、工水中のカルシウム濃度をＢｍｇ／リットル、海水中のカルシウム濃度をＣｍｇ／リットル、曝気槽へ流入させる原水量をＤｍ３／ｈ、原水の希釈倍率をＸ倍とすると、工水流入量をＥｍ３／ｈ、海水流入量をＦｍ３／ｈ、曝気槽中のカルシウム濃度Ｇｍｇ／リットル（１１０≦Ｇ≦１７０）とすると、曝気槽への各々の流入量は下記の通りとなる。
【００１３】
【式１】
原水と希釈工水及び希釈海水の総量 ＝ Ｘ＊Ｄ ｍ３／ｈ ＝ Ｄ＋Ｅ＋Ｆ ・・・（１）
ここで、曝気槽中のカルシウムを濃度Ｇｍｇ／リットルとすると、Ｇの濃度は下記式で表される。
【００１４】
【式２】
Ｇ ＝ （Ａ＊Ｄ＋Ｂ＊Ｅ＋Ｃ＊Ｆ）／（Ｄ＋Ｅ＋Ｆ） ・・・（２）
上記式（１）及び式（２）より、
【００１５】
【式３】
Ｅ ＝ Ｄ＊（Ｇ＊Ｘ−Ａ−Ｃ＊Ｘ＋Ｃ）／（Ｂ−Ｃ） ・・・（３）
【００１６】
【式４】
Ｆ ＝ Ｄ＊（Ｇ＊Ｘ−Ａ−Ｂ＊Ｘ＋Ｂ）／（Ｃ−Ｂ） ・・・（４）
となる。原水中のカルシウム濃度Ａ、工水中のカルシウム濃度Ｂ、海水中のカルシウム濃度Ｃ、曝気槽へ流入させる原水量Ｄ、原水の希釈倍率Ｘは任意に決まるので、曝気槽中のカルシウム濃度Ｇを１１０〜１７０ｍｇ／リットルの中から設定すると、上記式（３）及び（４）より、工水流入量Ｅｍ３／ｈ及び海水流入量をＦｍ３／ｈが決定できる。
【００１７】
より具体的に説明すると、原水中のカルシウム濃度を２ｍｇ／リットル、工水中のカルシウム濃度を８ｍｇ／リットルとし、海水中のカルシウム濃度を３９５ｍｇ／リットル、曝気槽へ流入させる原水量を１３０ｍ３／ｈ、原水の希釈倍率を３．３とし、曝気槽中のカルシウム濃度Ｇを１５０ｍｇ／リットルと設定すると、上記式（３）及び（４）より、工水の曝気槽への流量は１４０ｍ３／ｈ、海水の曝気槽への流量は１５９ｍ３／ｈとすればよい。
【００１８】
本発明は、コークス炉から排出させる廃水（凝縮水）のように、活性汚泥に対する被毒性物質が多く含まれており、これを希釈するために海水や水を用いる必要のある原水の場合に特に効果的である。
本発明における活性汚泥処理方法としては、例えば図１に示すように、 ６．曝気槽、７．沈殿槽を配置した構成からなる。該構成からなる本発明の活性汚泥処理方法では、原水は、曝気槽１で活性汚泥により生物処理されたあと、沈殿槽７で固液分離され分離水は処理水として系外へ排出される。分離汚泥は返送汚泥として６．曝気槽へ返送され、分離汚泥の一部は余剰汚泥として系外へ抜き出される。
【００１９】
活性汚泥の生物処理には、例えば原水がコークス炉から排出された廃水である場合は、フェノール、ＳＣＮ、ＮＨ４等を含むコークス炉廃水で培養（馴致）した菌を用いる。菌種としてはチオシアン資化菌、亜硝酸菌等が存在する。また、コークス廃水以外では、その原廃水流入下で培養した菌を用いればよい。
一般に、コークス炉から排出される原水やその他の廃水で、活性汚泥法により生物学的処理技術を用いる排水処理設備では、廃水中に含まれるアンモニア、シアン、ＣＯＤ成分等、活性汚泥中の菌体に高負荷あるいは処理を妨げる成分を含むので、曝気槽へ流入させる際、負荷軽減のため希釈水により希釈を行う。原水の希釈に用いる希釈水と原水の比率（容量比）は、通常、希釈水／原水で１／１〜４／１の範囲で運用される。希釈水には、海水、工水、河川水などの水を用い、これらを１種類あるいは２種類以上を混合している。希釈水に海水と工水を用いている場合には、一般に希釈水中の海水／工水の比率（容量比）は、５／１〜０．５／１のように任意の範囲で用いる。
【００２０】
曝気槽内の温度は、３０〜３５℃であることが好ましい。温度が低すぎたり高すぎたりすると、活性汚泥中の菌の活性度が低下し、原水中に含まれるＣＯＤ成分やＳＣＮの分解性に影響が及ぶことが懸念される。曝気槽内の温度を３０〜３５℃にする方法としては、原水、海水、工水の各温度を調節する方法や、曝気槽中に冷却あるいはヒーター等の温調装置を設置すること等が挙げられる。
【００２１】
曝気槽内においては、活性汚泥中の菌が有機物を分解してＣＯ２を発生させる。このＣＯ２が液中で反応し、炭酸カルシウム（ＣａＣＯ３）の炭酸源となる。この他、原水中にＣＯ２を有する廃液についても同様に有効な手段である。曝気槽内は、嫌気性でも好気性でもよいが、菌の特性から、好気性の方が好ましい場合が多い。
【００２２】
曝気槽に硫酸等の酸を添加して曝気槽内のｐＨ調整を行う場合い、曝気槽出口のｐＨを７．１以下にすれば、炭酸カルシウムの結晶は十分に析出しない。このため曝気槽出口のｐＨが７．２以上である場合に本発明は特に有効な手段である。
【００２３】
【実施例】
以下本発明を実施例によりより詳細に説明する。
実施例１
図１の設備からなる活性汚泥設備において、ベンチスケールの実験装置（１９２Ｌ）を用いて、コークス炉排水を活性汚泥処理で、希釈水に海水及び工水を用い、希釈水中の海水比率を変えて、曝気槽内のカルシウム濃度を調整した場合の汚泥中の炭酸カルシウム（Ａｓｈ）に与える影響を確認した。また、希釈水中の海水比率を変更することによる炭酸カルシウム（Ａｓｈ）の析出量の増減による汚泥沈降性への影響を確認した。
【００２４】
＜運転条件＞
原水流量：４．０Ｌ／ｈ
海水流量：１．０〜７．０Ｌ／ｈ
工水流量：１．０〜７．０Ｌ／ｈ
希釈倍率：３倍
ＭＬＶＳＳ：５０００〜７０００ｍｇ／Ｌ
ｐＨ：９．０〜９．５
温度：３３〜３５℃
返送汚泥量：１２Ｌ／ｈ
＜実験方法＞
実験に使用する１．原水には、コークス原料の石炭に由来するＮＨ４、ＳＣＮ等や、フェノール類等のＣＯＤ成分が含まれる実液を採取して用いた。（原水のカルシウム濃度は２ｍｇ／リットル）と希釈水である２．海水（カルシウム濃度３９５ｍｇ／リットル）及び３．工水（カルシウム濃度８ｍｇ／リットル）を６．曝気槽に流入させ、４．エアー曝気による好気性条件の下、活性汚泥処理を行った。原水の希釈倍率を３．０倍に固定し、希釈水中の海水比率を変化させることで曝気槽内のカルシウム濃度を調整した。
【００２５】
＜曝気槽内カルシウム濃度の調整＞（原水と希釈水比率）
希釈水中の海水比率を１０％〜９０％の範囲で段階的に海水と工水の比率を変え、各々の海水比率における曝気槽内の汚泥に含まれる炭酸カルシウム濃度（Ａｓｈ比率）及び汚泥沈降性を測定するための沈降テストを実施した。
＜結果＞
実験の結果を図３に示す。図３からわかるように、曝気槽内の汚泥が含有する炭酸カルシウム量（Ａｓｈ）はカルシウム源である海水比率が高いほど多く、海水比率が低くなるに従って少なくなる。よって、炭酸カルシウムの析出量を抑制するには、希釈水中の海水比率をできるだけ低くすれば良い。一方、汚泥沈降性（ＳＶ６０）については、希釈水中の海水比率が４０％以下では、炭酸カルシウムの析出量低減にともなって沈降性が低下することがわかる。この結果から、曝気槽内の炭酸カルシウムの析出を抑制でき、かつ汚泥の沈降性に影響しない程度の炭酸カルシウム量を維持できる運転条件として、希釈水中の海水比率が４０％〜６０％、即ち曝気槽中のカルシウム濃度が１１０〜１７０ｍｇ／リットルより好ましくは希釈水中の海水比率が４５％〜５５％即ち曝気槽中のカルシウム濃度が１２５〜１５５ｍｇ／リットルであることが確認できた。
【００２６】
試験例
ビーカーテストにおいてカルシウム濃度と炭酸カルシウムの析出速度の関係を求めるための実験をおこなった。
＜実験条件と装置＞
炭酸源としてＣＯ３ ２−を含むコークス炉から排出される安水を原水として約６７０ミリリットル用い、これとカルシウム源としてカルシウム３９５ｍｇ／リットルを含む希釈用海水、及び希釈用工水（カルシウム濃度８ｍｇ／リットル）とを密閉容器に入れ、スターラーで連続攪拌しながら、任意の時間毎にサンプル溶液中のカルシウム濃度を測定し、下記に示す３種類の海水：工水比率での経時変化を求めた。
【００２７】
今回の実験に用いたサンプルのカルシウム濃度は、原水の希釈倍率を３．０にし、希釈水中の海水比率を変化させることで調整した。
実験の結果を図２に示す。図２から、炭酸カルシウムの析出速度は、排水中のカルシウム濃度の影響を大きく受け、カルシウム濃度が高いほど析出速度が速く、カルシウム濃度が低くなるに従って析出速度が低下することが確認できた。
【００２８】
【発明の効果】
ｐＨ調整用の酸やアルカリを添加することなく炭酸カルシウムの析出速度を抑制でき、かつ活性汚泥中の微生物への影響や汚泥の沈降速度への影響が小さい活性汚泥の処理方法を提供できる。
【図面の簡単な説明】
【図１】本発明の活性汚泥処理法方の構成を示す図である。
【図２】実施例１の結果を示す図である。
【図３】実施例２の結果を示す図である。
【符号の説明】
１ 原水
２ 海水
３ 工水
４ エアー
５ 処理水
６ 曝気槽
７ 沈殿槽
８ 返送汚泥
９ 余剰汚泥[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an activated sludge treatment method.
[0002]
[Prior art]
The coke oven gas condensate discharged from the coke oven flows into the waste water treatment facility and is rendered harmless by activated sludge. Usually, when condensed water or the like is allowed to flow into an activated sludge aeration tank, dilution water is used for dilution to reduce the load on the sludge. Therefore, Ca ions contained in the seawater react with carbonate ions present in the raw water and carbonate ions discharged when the organic sludge is decomposed to precipitate calcium carbonate.
[0003]
The precipitated calcium carbonate accumulates in the aeration tank and reduces the effective volume of the aeration tank. In addition, the precipitated calcium carbonate also causes clogging of the air nozzle of the diffuser. Furthermore, in the decolorization equipment which is the final treatment equipment in the latter stage process of the aeration tank, the filter medium of the sand filtration tower and the activated carbon in the adsorption tower are stuck.
Therefore, in order to prevent precipitation of calcium carbonate, pH adjustment by acid addition is performed (Japanese Patent Laid-Open No. 2000-325981). However, coke oven drainage and the like generally has a high alkalinity, so a large amount of acid is added. There was a need to do. Furthermore, there is a concern about the influence on the microorganisms in the activated sludge by the acid addition.
Although it is conceivable to use dilution water as industrial water, there is a concern that the sedimentation rate of sludge in the settling tank may decrease.
[0004]
[Patent Document 1] Japanese Patent Laid-Open No. 9-290292, paragraph number [0035], etc. [Patent Document 2] Japanese Patent Laid-Open No. 2000-325981, paragraph number [0011], etc.
[Problems to be solved by the invention]
There has been a need for a method for treating activated sludge that can suppress the precipitation rate of calcium carbonate without adding acid or alkali for pH adjustment, and that has little effect on microorganisms in activated sludge and on sedimentation rate of sludge. .
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the precipitation rate of calcium carbonate is highly dependent on the calcium concentration, and have completed the present invention. That is, the gist of the present invention resides in the following (1) to (5).
(1) An activated sludge treatment method, wherein the raw sludge is introduced into an aeration tank and the activated sludge treatment is performed, and the calcium concentration in the aeration tank is 110 to 170 mg / liter.
[0007]
(2) The activated sludge treatment method according to the above (1), wherein the working water and seawater are used as dilution water, and the working water and seawater are flowed into the aeration tank so that the calcium concentration in the aeration tank is 110 to 170 mg / liter. Way.
(3) The activated sludge treatment method according to (1) or (2), wherein the inside of the aeration tank is aerobic.
[0008]
(4) The activated sludge treatment method according to any one of (1) to (3), wherein the pH of the aeration tank outlet is 7.2 or more.
(5) The activated sludge treatment method according to any one of (1) to (4), wherein the raw water is coke oven wastewater.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The activated sludge treatment method of the present invention is characterized in that the raw water is introduced into the aeration tank and the activated sludge treatment is performed, and the calcium concentration in the aeration tank is 110 to 170 mg / liter. If the calcium concentration in the aeration tank is too low, the sludge settling rate decreases, and if it is too high, the amount of precipitated calcium carbonate increases. Preferably they are 125 mg / liter or more and 155 mg / liter or less.
[0010]
In the present invention, raw water is water containing a substance to be treated by activated sludge treatment, specifically, general sewage, waste water containing organic matter, low water generated in a coke oven, and this in a plant. This includes wastewater that is generated. The raw water generated from the coke plant contains poisonous substances to activated sludge such as NH 4 SCN derived from coke raw material coal and COD components such as phenols, and the calcium concentration is about 2 mg / liter. is there.
[0011]
In the present invention, industrial water is industrial water obtained from river water or the like, and generally calcium salts and magnesium salts are dissolved therein. It is preferable to use 0 to 20 mg / liter of industrial water for the calcium concentration. If the calcium concentration is too high, the effect of the present invention is not exhibited, which is not preferable.
Means for setting the calcium concentration in the aeration tank to 110 to 170 mg / liter include removing Ca by ion exchange or a chelate method, adding Ca to industrial water, water containing high concentration of calcium, waste water, etc. In addition, from the viewpoint that the concentration can be easily adjusted, the working water and seawater are used as dilution water of the raw water, and the calcium concentration in the aeration tank is 110 to 170 mg / liter. The method of making it flow into an aeration tank is mentioned.
[0012]
A method of using industrial water and seawater as dilution water and causing the industrial water and seawater to flow into the aeration tank so that the calcium concentration in the aeration tank is 110 to 170 mg / liter will be specifically described.
The calcium concentration in the aeration tank is obtained from the weighted average of each calcium concentration of seawater and industrial water for diluting raw water and poisonous substances contained in the raw water. First, the calcium concentration contained in raw water and industrial water is measured (the calcium concentration in seawater is 395 mg / liter). Examples of the method for measuring the calcium concentration include titration, atomic absorption, and ion chromatography analysis. The calcium concentration in the raw water is Amg / liter, the calcium concentration in the industrial water is Bmg / liter, the calcium concentration in the seawater is Cmg / liter, the amount of raw water flowing into the aeration tank is Dm 3 / h, and the dilution rate of the raw water is X times Assuming that the inflow of industrial water is Em 3 / h, the inflow of seawater is Fm 3 / h, and the calcium concentration in the aeration tank is Gmg / liter (110 ≦ G ≦ 170), each inflow to the aeration tank is It becomes as follows.
[0013]
[Formula 1]
Total amount of raw water, diluted industrial water and diluted seawater = X * D m 3 / h = D + E + F (1)
Here, when the calcium in the aeration tank is Gmg / liter, the concentration of G is expressed by the following formula.
[0014]
[Formula 2]
G = (A * D + B * E + C * F) / (D + E + F) (2)
From the above formula (1) and formula (2),
[0015]
[Formula 3]
E = D * (G * X-A-C * X + C) / (B-C) (3)
[0016]
[Formula 4]
F = D * (G * X−A−B * X + B) / (C−B) (4)
It becomes. Since the calcium concentration A in the raw water, the calcium concentration B in the industrial water, the calcium concentration C in the sea water, the raw water amount D flowing into the aeration tank, and the dilution rate X of the raw water are arbitrarily determined, the calcium concentration G in the aeration tank is 110. When set from ˜170 mg / liter, Fm 3 / h can determine the industrial water inflow amount Em 3 / h and seawater inflow amount from the above formulas (3) and (4).
[0017]
More specifically, the calcium concentration in the raw water is 2 mg / liter, the calcium concentration in the industrial water is 8 mg / liter, the calcium concentration in seawater is 395 mg / liter, and the amount of raw water flowing into the aeration tank is 130 m 3 / h. When the dilution ratio of the raw water is 3.3 and the calcium concentration G in the aeration tank is set to 150 mg / liter, the flow rate to the aeration tank of the working water is 140 m 3 / h from the above formulas (3) and (4). The flow rate of the seawater to the aeration tank may be 159 m 3 / h.
[0018]
The present invention contains a lot of toxic substances for activated sludge, such as waste water (condensed water) discharged from a coke oven, and particularly in the case of raw water that needs to use seawater or water to dilute it. It is effective.
As an activated sludge treatment method in the present invention, for example, as shown in FIG. 6. Aeration tank, It consists of a configuration with a settling tank. In the activated sludge treatment method of the present invention having such a configuration, the raw water is biologically treated with activated sludge in the
[0019]
For biological treatment of activated sludge, for example, when the raw water is wastewater discharged from a coke oven, bacteria cultured (acclimated) in coke oven wastewater containing phenol, SCN, NH 4 and the like are used. Examples of the bacterial species include thiocyan assimilating bacteria and nitrite bacteria. In addition to the coke wastewater, bacteria cultured under the inflow of the raw wastewater may be used.
In general, in wastewater treatment facilities that use biological treatment technology by the activated sludge method with raw water and other wastewater discharged from coke ovens, fungal cells in activated sludge such as ammonia, cyanide, COD components contained in the wastewater Since it contains components that impede high load or treatment, when it is introduced into the aeration tank, it is diluted with dilution water to reduce the load. The ratio (volume ratio) of dilution water and raw water used for dilution of the raw water is normally operated in a range of 1/1 to 4/1 with dilution water / raw water. As dilution water, water such as seawater, industrial water, and river water is used, and one or two or more of these are mixed. When seawater and industrial water are used as dilution water, the ratio of seawater / engineering water (volume ratio) in the dilution water is generally used in an arbitrary range such as 5/1 to 0.5 / 1.
[0020]
The temperature in the aeration tank is preferably 30 to 35 ° C. If the temperature is too low or too high, the activity of the bacteria in the activated sludge is lowered, and there is a concern that the degradability of COD components and SCN contained in the raw water may be affected. Examples of the method for adjusting the temperature in the aeration tank to 30 to 35 ° C. include a method for adjusting each temperature of raw water, seawater, and industrial water, and a temperature control device such as cooling or a heater in the aeration tank. It is done.
[0021]
In the aeration tank, the bacteria in the activated sludge decompose organic substances and generate CO 2 . This CO 2 reacts in the liquid and becomes a carbonate source of calcium carbonate (CaCO 3 ). In addition, the waste liquid having CO 2 in the raw water is also an effective means. The inside of the aeration tank may be anaerobic or aerobic, but aerobic is often preferred from the characteristics of the bacteria.
[0022]
When adjusting the pH in the aeration tank by adding an acid such as sulfuric acid to the aeration tank, if the pH at the outlet of the aeration tank is set to 7.1 or less, the calcium carbonate crystals are not sufficiently precipitated. Therefore, the present invention is a particularly effective means when the pH of the aeration tank outlet is 7.2 or higher.
[0023]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
In the activated sludge facility consisting of the facility of FIG. 1, using a bench scale experimental device (192L), the coke oven wastewater is treated with activated sludge, seawater and industrial water are used as dilution water, and the seawater ratio in the dilution water is changed. The effect of adjusting the calcium concentration in the aeration tank on the calcium carbonate (Ash) in the sludge was confirmed. Moreover, the influence on the sludge settling property by the increase / decrease in the precipitation amount of calcium carbonate (Ash) by changing the seawater ratio in dilution water was confirmed.
[0024]
<Operating conditions>
Raw water flow rate: 4.0L / h
Seawater flow rate: 1.0-7.0 L / h
Industrial water flow rate: 1.0-7.0 L / h
Dilution factor: 3 times MLVSS: 5000 to 7000 mg / L
pH: 9.0-9.5
Temperature: 33-35 ° C
Return sludge volume: 12L / h
<Experiment method>
Used for experiments In the raw water, an actual liquid containing COD components such as NH 4 and SCN derived from coke raw material coal and phenols was collected and used. (The calcium concentration of the raw water is 2 mg / liter) and diluted water. 2. seawater (calcium concentration 395 mg / liter) and 5. Add industrial water (calcium concentration 8mg / liter). 3. flow into the aeration tank; Activated sludge treatment was performed under aerobic conditions by air aeration. The calcium concentration in the aeration tank was adjusted by fixing the dilution rate of the raw water to 3.0 times and changing the seawater ratio in the diluted water.
[0025]
<Adjustment of calcium concentration in the aeration tank> (Rate of raw water and diluted water)
The ratio of seawater to industrial water is changed stepwise in the range of 10% to 90% in the dilution water, and the concentration of calcium carbonate (Ash ratio) and sludge settling in the sludge in the aeration tank at each seawater ratio A sedimentation test was performed to measure the.
<Result>
The result of the experiment is shown in FIG. As can be seen from FIG. 3, the amount of calcium carbonate (Ash) contained in the sludge in the aeration tank increases as the seawater ratio as the calcium source increases, and decreases as the seawater ratio decreases. Therefore, in order to suppress the precipitation amount of calcium carbonate, the seawater ratio in the diluted water should be as low as possible. On the other hand, as for the sludge settling property (SV60), it can be seen that when the seawater ratio in the diluted water is 40% or less, the settling property is lowered as the precipitation amount of calcium carbonate is reduced. From this result, as an operating condition that can suppress the precipitation of calcium carbonate in the aeration tank and maintain the amount of calcium carbonate that does not affect the sedimentation property of sludge, the seawater ratio in the diluted water is 40% to 60%, that is, aeration It was confirmed that the calcium concentration in the tank was 110 to 170 mg / liter, more preferably the seawater ratio in the diluted water was 45% to 55%, that is, the calcium concentration in the aeration tank was 125 to 155 mg / liter.
[0026]
Test Example An experiment was conducted to determine the relationship between the calcium concentration and the precipitation rate of calcium carbonate in the beaker test.
<Experimental conditions and equipment>
About 670 milliliters of low water discharged from a coke oven containing CO 3 2- as a carbonic acid source is used as raw water, seawater for dilution containing 395 mg / liter of calcium as a calcium source, and industrial water for dilution (calcium concentration of 8 mg / liter) ) Was measured, and the calcium concentration in the sample solution was measured every arbitrary time while continuously stirring with a stirrer, and the change with time in the following three types of seawater: working water ratio was determined.
[0027]
The calcium concentration of the sample used in this experiment was adjusted by changing the dilution ratio of the raw water to 3.0 and changing the seawater ratio in the diluted water.
The result of the experiment is shown in FIG. From FIG. 2, it was confirmed that the precipitation rate of calcium carbonate was greatly influenced by the calcium concentration in the waste water, and the higher the calcium concentration, the faster the precipitation rate, and the lower the calcium concentration, the lower the precipitation rate.
[0028]
【The invention's effect】
It is possible to provide a method for treating activated sludge that can suppress the precipitation rate of calcium carbonate without adding acid or alkali for pH adjustment, and that has little effect on microorganisms in activated sludge and on the sedimentation rate of sludge.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an activated sludge treatment method according to the present invention.
FIG. 2 is a diagram showing the results of Example 1.
3 is a graph showing the results of Example 2. FIG.
[Explanation of symbols]
1 Raw water 2
Claims (5)
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| JP2003204944A JP2005046697A (en) | 2003-07-31 | 2003-07-31 | Activated sludge treatment method |
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| JP2003204944A JP2005046697A (en) | 2003-07-31 | 2003-07-31 | Activated sludge treatment method |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1884497A2 (en) * | 2006-07-24 | 2008-02-06 | Siemens Aktiengesellschaft | Wastewater purification facility |
| JP2008207064A (en) * | 2007-02-23 | 2008-09-11 | Petroleum Energy Center | Treatment method of organic wastewater |
| JP2008307459A (en) * | 2007-06-13 | 2008-12-25 | Shibaura Institute Of Technology | Polluted seawater purification method by microorganism derived from seawater |
| JP2014028366A (en) * | 2012-06-29 | 2014-02-13 | Nippon Rensui Co Ltd | Treatment apparatus for water discharged from coke oven and treatment method for water discharged from coke oven |
| JP2020081976A (en) * | 2018-11-27 | 2020-06-04 | 三菱ケミカル株式会社 | Waste water treatment facility |
-
2003
- 2003-07-31 JP JP2003204944A patent/JP2005046697A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1884497A2 (en) * | 2006-07-24 | 2008-02-06 | Siemens Aktiengesellschaft | Wastewater purification facility |
| EP1884497A3 (en) * | 2006-07-24 | 2008-09-10 | Siemens Aktiengesellschaft | Wastewater purification facility |
| JP2008207064A (en) * | 2007-02-23 | 2008-09-11 | Petroleum Energy Center | Treatment method of organic wastewater |
| JP2008307459A (en) * | 2007-06-13 | 2008-12-25 | Shibaura Institute Of Technology | Polluted seawater purification method by microorganism derived from seawater |
| JP2014028366A (en) * | 2012-06-29 | 2014-02-13 | Nippon Rensui Co Ltd | Treatment apparatus for water discharged from coke oven and treatment method for water discharged from coke oven |
| JP2020081976A (en) * | 2018-11-27 | 2020-06-04 | 三菱ケミカル株式会社 | Waste water treatment facility |
| JP7139913B2 (en) | 2018-11-27 | 2022-09-21 | 三菱ケミカル株式会社 | Wastewater treatment facility |
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