JP4631169B2 - Method and apparatus for dephosphorization of water containing orthophosphoric acid - Google Patents
Method and apparatus for dephosphorization of water containing orthophosphoric acid Download PDFInfo
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【０００１】
【発明の属する技術分野】
本発明は、正リン酸イオンを含有する原水にカルシウムイオンを添加してリン酸カルシウムの不溶化物を生成させ、これを分離して処理水を得る正リン酸含有水の脱リン方法及び脱リン装置に係り、特に、処理水のｐＨ及びカルシウムイオン濃度に基いてｐＨ調整剤とカルシウムイオンの添加量を調整することにより、リン濃度やカルシウムイオン濃度、Ｍ−アルカリ度等の水質変動が激しい原水中のリンを確実に除去して、リン濃度の低い高水質の処理水を安定に得る脱リン方法及び脱リン装置に関する。
【０００２】
【従来の技術】
下水、し尿、排水等の嫌気、好気処理工程で発生する汚泥脱水濾液、消化脱離液等の正リン酸イオンを含有する原水からリンを除去する方法として、原水にカルシウムイオンを添加して、ｐＨアルカリ性でリン酸カルシウムの不溶化物を生成させ、これを分離することによりリンを除去する方法がある。この方法で用いられるカルシウムイオン源としては、水酸化カルシウム（Ｃａ（ＯＨ）２）、塩化カルシウム（ＣａＣｌ２）等があり、このうち、Ｃａ（ＯＨ）２を用いた場合には、ｐＨ調整のためのアルカリ剤を兼用することができる。ＣａＣｌ２を用いた場合には、別途、水酸化ナトリウム（ＮａＯＨ）等のアルカリを添加してｐＨ調整を行う。また、反応形態としては、反応槽で原水にカルシウム化合物と必要に応じてアルカリ剤を添加して反応させ、不溶化物を沈殿槽で分離する沈殿法と、原水を晶折槽に導入して種晶の表面にリン酸カルシウムを析出させる晶折法とがある。
【０００３】
従来、このような脱リン法において、薬注制御はｐＨの測定値に基いて行われており、原水に対して、ｐＨが一定となるように薬注制御が行われている。しかし、ｐＨ値に基く薬注制御では、リン濃度やカルシウムイオン濃度が変動する原水に対して、含有されるリンを確実にリン酸カルシウムとして不溶化して除去することができず、処理水のリン濃度が原水のリン濃度に対応して大きく変動するという欠点がある。
【０００４】
リン含有水にカルシウムイオンを添加して脱リン処理するに当たり、原水のリン濃度の変動に対応して確実に脱リン処理を行う方法として、特開平１０−７６２７８号公報には、反応により得られた反応液の残留カルシウムイオン濃度を測定し、添加したカルシウムイオン量と残留カルシウムイオン量とから計算により、原水の溶解性リン（ＰＯ４−Ｐ）濃度（消費されたカルシウムイオン量と反応してリン酸カルシウムを生成するリン量）を算出し、算出された原水のリン濃度からこれを処理するために必要なカルシウムイオン量を求め、この結果に基いて薬注を行う方法が記載されている。
【０００５】
【発明が解決しようとする課題】
しかし、特開平１０−７６２７８号公報記載の方法では、原水のリン濃度を確実に把握することはできず、このため、脱リン処理を安定に行うことができない場合があった。即ち、下水処理水等のリン含有水中のＰＯ４−Ｐイオンをカルシウムイオンと反応させて不溶化する場合、カルシウムイオンは原水中のＭ−アルカリや空気中の二酸化炭素との反応で炭酸カルシウム（ＣａＣＯ３）を析出させるため、添加したカルシウムイオン量と残留カルシウムイオン量とから、原水中のＰＯ４−Ｐ濃度を正確に求めることはできない。特に、Ｍ−アルカリ度等の水質変動の激しい排水処理の場合や開放系で運転されている脱リン処理系では、ＰＯ４−Ｐイオン以外の要因で消費されるカルシウムイオン量が多く、またその変動も激しいことから、添加したカルシウムイオン量と残留カルシウムイオン量との差に基いてＰＯ４−Ｐイオン量を求めることは妥当ではない。
【０００６】
本発明は上記従来の問題点を解決し、正リン酸イオンを含有する原水にカルシウムイオンを添加してリン酸カルシウム不溶化物を生成させ、これを分離して処理水を得るに当たり、リン濃度やカルシウムイオン濃度、Ｍ−アルカリ度等の水質変動が激しい原水中のリンを確実に除去して、リン濃度の低い高水質の処理水を安定に得ることができる正リン酸含有水の脱リン方法及び脱リン装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の正リン酸含有水の脱リン方法は、正リン酸イオンを含有する原水にカルシウムイオンを添加して生成するリン酸カルシウム不溶化物と処理水とを分離する正リン酸含有水の脱リン方法において、処理水のｐＨとカルシウムイオン濃度を測定し、それぞれの測定値が所定値となるように、原水にｐＨ調整剤とカルシウムイオンを添加する方法であって、ｐＨとリン酸カルシウムの溶解度積との関係から、処理水の正リン酸濃度の所定値を与えるｐＨとカルシウム濃度を演算し、該演算値となるようにそれぞれｐＨ調整剤の添加量及びカルシウムイオン添加量を制御することを特徴とする。
【０００８】
本発明の脱リン装置は、正リン酸イオンとカルシウムイオンを反応させてリン酸カルシウム不溶化物を生成させる反応槽と、該反応槽に正リン酸イオンを含有する原水を供給する原水供給手段と、該反応槽にカルシウムイオンを添加するカルシウム添加手段と、該反応槽にｐＨ調整剤を添加するｐＨ調整剤添加手段と、該反応槽のリン酸カルシウム不溶化物を含む反応液を汚泥と処理水とに固液分離する固液分離手段と、該処理水のｐＨを測定するｐＨ測定手段と、該処理水のカルシウムイオン濃度を測定するカルシウム濃度測定手段と、該ｐＨ測定手段の出力信号とカルシウム濃度測定手段の出力信号が入力され、ｐＨとリン酸カルシウムの溶解度積との関係から、処理水の正リン酸濃度の所定値を与えるｐＨとカルシウム濃度を演算し、ｐＨ調整剤添加手段及びカルシウム添加手段へそれぞれｐＨ調整剤の添加量及びカルシウムイオン添加量を制御する制御信号を出力する演算制御装置とを備えたことを特徴とする。
【０００９】
即ち、本発明者らは、原水の水質変動に影響されることなく、原水中のリンを確実に除去する薬注制御方法について鋭意検討を重ねた結果、原水から析出するリン酸カルシウムには特有の溶解度積が存在し、処理水のｐＨと処理水に残存するイオン濃度とから、得られる処理水の溶解性リン（ＰＯ４−Ｐ）濃度を求めることが可能であること、従って、処理水のＰＯ４−Ｐ濃度をどの程度にするかの目標値を定め、このＰＯ４−Ｐ濃度が達成される処理水のｐＨと残存カルシウムイオン濃度となるように、薬注制御を行えば、安定かつ確実な脱リン処理を行えることを見出し、本発明を達成させた。
【００１０】
例えば、原水にカルシウムイオンとアルカリ剤を添加してリン酸カルシウムを析出させる脱リン処理において、処理水のｐＨ、ＰＯ４−Ｐ濃度及びカルシウムイオン濃度を測定してその関係を調べると、図３（ａ）に示すような結果が得られる。この図３（ａ）の測定値から、処理水のｐＨと、処理水のリン酸カルシウム（Ｃａ３（ＰＯ４）２）の溶解度積（ｌｏｇ（［Ｃａ２＋］３［ＰＯ４ ３−］２））との関係を求めると、図３（ｂ）の通りであり、溶解度積の理論値に対して実測値から計算により求められた溶解度積は、約１０倍であることがわかる。即ち、溶解度積の理論値の１０倍に対して、処理水ｐＨと処理水の残存カルシウムイオン濃度を定めることにより、処理水ＰＯ４−Ｐ濃度を求めることができる。換言すれば、溶解度積の理論値の１０倍に対して、目標とするＰＯ４−Ｐ濃度を代入することにより、処理水ｐＨと処理水に残留させるカルシウムイオン濃度を定めることができ、このような処理水ｐＨ及びカルシウムイオン濃度となるように薬注制御を行うことにより、目標ＰＯ４−Ｐ濃度の処理水を安定かつ確実に得ることが可能となる。
【００１１】
【発明の実施の形態】
以下に本発明の実施の形態を詳細に説明する。
【００１２】
本発明においては、溶解性ＰＯ４−Ｐを含有する原水にカルシウム化合物と必要に応じてアルカリ剤等のｐＨ調整剤を添加してリン酸カルシウムの不溶化物を析出させることにより脱リン処理するに当たり、処理水のｐＨとカルシウムイオン濃度を測定し、この測定値が所定の値となるようにカルシウム化合物及びｐＨ調整剤の添加量を制御する。
【００１３】
即ち、前述の如く、このような脱リン処理に当たり、実測値から求められた処理水のリン酸カルシウムの溶解度積は、処理水ｐＨに対して所定の値となり、この溶解度積は、理論値の約１０倍である。従って、測定されたｐＨ値に対応する溶解度積（この値は理論値の約１０倍となる）に、目標とするＰＯ４−Ｐ濃度を代入することにより、このＰＯ４−Ｐ濃度を得るための処理水のカルシウムイオン濃度を算出することができるので、処理水のカルシウムイオン濃度が算出されたカルシウムイオン濃度となるように、カルシウム化合物の添加量を制御すれば良い。
【００１４】
本発明の好適な実施形態としては、処理水のｐＨ測定手段の測定値に基いて、処理水のｐＨが一定となるようにアルカリ剤等のｐＨ調整剤の添加量を制御すると共に、このｐＨ値に対応する溶解度積から、目標とする処理水ＰＯ４−Ｐ濃度を得るためのカルシウムイオン濃度を算出し、カルシウムイオン濃度測定手段の測定値がこのカルシウムイオン濃度となるように、カルシウム化合物の添加量を制御する方法が挙げられる。
【００１５】
なお、本発明では、このように、ｐＨとカルシウムイオン濃度とを個別に制御することから、カルシウム化合物としては、アルカリ性のＣａ（ＯＨ）２を用いるよりも、中性のＣａＣｌ２を用い、ｐＨ調整のためにＮａＯＨ等のアルカリ剤を添加することが好ましい。
【００１６】
このような本発明の正リン酸含有水の脱リン方法及び脱リン装置で処理する原水としては、下水処理水、下水汚泥集約処理で発生する排水が挙げられ、本発明は、このような原水を反応槽でカルシウム化合物と必要に応じてアルカリ剤を添加して反応させ、不溶化物を沈殿槽で分離する沈殿法に対しても、原水を晶折槽に導入して種晶の表面にリン酸カルシウムを析出させる晶折法に対しても有効に適用可能である。
【００１７】
【実施例】
以下に実施例及び比較例を挙げて本発明をより具体的に説明する。
【００１８】
実施例１
図１に示す装置により合成排水の処理を行った。
【００１９】
まず、合成排水（ＰＯ４−Ｐ：１０ｍｇ／Ｌ，Ｃａ：３９ｍｇ／Ｌ，Ｍ−アルカリ：８８ｍｇ／Ｌ）を原水槽１に導入し、この原水槽１において、正リン酸塩（リン酸二水素一ナトリウム：ＮａＨ２ＰＯ４）水溶液を添加し、このときの注入ポンプＰ１の稼動時間や回転数を変えることにより、原水のＰＯ４−Ｐ濃度を１０〜５０ｍｇ／Ｌの範囲で変動させた。
【００２０】
この合成排水にＣａＣｌ２水溶液を注入した後、攪拌装置を備える第１反応槽２及び第３反応槽３に順次送給して反応させた後、沈殿槽４で固液分離した。なお、第１反応槽２では、アルカリ剤としてＮａＯＨ水溶液を添加してｐＨ調整した。沈殿槽４の分離汚泥は、一部を第１反応槽２に返送し、残部を系外へ排出した。また、分離液は処理水槽５を経て系外へ取り出した。
【００２１】
本実施例では、この処理水槽５にｐＨ計６とＣａイオンセンサ７を設け、ｐＨ計６の測定値が９．０となるように、ＮａＯＨ水溶液の注入ポンプＰ３の稼動を制御すると共に、Ｃａイオンセンサ７の測定値が３５〜４０ｍｇ／ＬとなるようにＣａＣｌ２水溶液注入ポンプＰ２の稼動を制御した。
【００２２】
このとき、ＣａＣｌ２水溶液の添加量は２５〜９５ｍｇ−Ｃａ２＋／Ｌの範囲で変動した。
【００２３】
原水のＰＯ４−Ｐ濃度と処理水のＰＯ４−Ｐ濃度の経時変化は図２に示す通りであり、原水のＰＯ４−Ｐ濃度の変動にも係わらず、処理水のＰＯ４−Ｐ濃度を約５ｍｇ／Ｌ程度に安定に維持することができた。
【００２４】
比較例１
実施例１において、Ｃａイオンセンサを設けず、ｐＨ計による制御のみで、ＣａＣｌ２水溶液の添加は、５０〜５５ｍｇ−Ｃａ２＋／Ｌで一定としたこと以外は実施例１と同様にして処理を行った。その結果、原水のＰＯ４−Ｐ濃度変動に応じて処理水のＰＯ４−Ｐ濃度は、図２に示す如く大きく変動し、安定な処理を行うことはできなかった。
【００２５】
【発明の効果】
以上詳述した通り、本発明の正リン酸含有水の脱リン方法及び脱リン装置によれば、正リン酸イオンを含有する原水にカルシウムイオンを添加してリン酸カルシウム不溶化物を生成させ、これを分離して処理水を得るに当たり、リン濃度やカルシウムイオン濃度、Ｍ−アルカリ度等の水質変動が激しい原水中のリンを確実に除去して、リン濃度の低い高水質の処理水を安定に得ることができる。
【図面の簡単な説明】
【図１】実施例１で用いた脱リン装置を示す系統図である。
【図２】実施例１及び比較例１の結果を示すグラフである。
【図３】（ａ）図は、処理水のｐＨとカルシウムイオン濃度及びＰＯ４−Ｐ濃度との関係を示すグラフであり、（ｂ）図は、処理水のｐＨと溶解度積との関係を示すグラフである。
【符号の説明】
１ 原水槽
２ 第１反応槽
３ 第２反応槽
４ 沈殿槽
５ 処理水槽
６ ｐＨ計
７ Ｃａイオンセンサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dephosphorization method and dephosphorization apparatus for water containing normal phosphate, in which calcium ion is added to raw water containing normal phosphate ions to produce an insolubilized product of calcium phosphate, and this is separated to obtain treated water. In particular, by adjusting the addition amount of the pH adjuster and calcium ions based on the pH of the treated water and the calcium ion concentration, the raw water is subject to significant fluctuations in water quality such as phosphorus concentration, calcium ion concentration, and M-alkalinity. The present invention relates to a dephosphorization method and a dephosphorization apparatus that reliably removes phosphorus and stably obtains high-quality treated water having a low phosphorus concentration.
[0002]
[Prior art]
As a method of removing phosphorus from raw water containing normal phosphate ions such as sewage, human waste, wastewater and other anaerobic and sludge dehydrated filtrates generated during aerobic treatment, digestion and desorption liquid, calcium ions are added to the raw water. There is a method in which phosphorus is removed by forming an insolubilized calcium phosphate with an alkaline pH and separating it. Calcium ion sources used in this method include calcium hydroxide (Ca (OH) 2 ), calcium chloride (CaCl 2 ), etc. Among these, when Ca (OH) 2 is used, pH adjustment is performed. Therefore, the alkali agent can also be used. When CaCl 2 is used, pH adjustment is performed by separately adding an alkali such as sodium hydroxide (NaOH). Moreover, as a reaction form, a calcium compound and an alkali agent are added to the raw water in the reaction tank to react, and a precipitation method in which the insolubilized product is separated in the precipitation tank, and the raw water is introduced into the crystallizing tank and seeded. There is a crystal folding method in which calcium phosphate is precipitated on the crystal surface.
[0003]
Conventionally, in such a dephosphorization method, chemical injection control is performed based on a measured value of pH, and chemical injection control is performed so that the pH is constant with respect to raw water. However, in the chemical injection control based on the pH value, it is not possible to reliably insolubilize and remove the contained phosphorus as calcium phosphate with respect to the raw water whose phosphorus concentration and calcium ion concentration fluctuate, There is a drawback that it varies greatly according to the phosphorus concentration of the raw water.
[0004]
Japanese Patent Laid-Open No. 10-76278 discloses a method for performing dephosphorization treatment by adding calcium ions to phosphorus-containing water to ensure dephosphorization treatment in response to fluctuations in the phosphorus concentration of raw water. The residual calcium ion concentration of the reaction solution was measured and calculated from the amount of added calcium ion and the amount of residual calcium ion, and the concentration of soluble phosphorus (PO 4 -P) in the raw water (reacted with the amount of consumed calcium ion) A method is described in which the amount of phosphorus that produces calcium phosphate is calculated, the amount of calcium ions required to treat this is calculated from the calculated concentration of phosphorus in the raw water, and drug injection is performed based on this result.
[0005]
[Problems to be solved by the invention]
However, in the method described in Japanese Patent Laid-Open No. 10-76278, the phosphorus concentration of raw water cannot be ascertained with certainty, and therefore dephosphorization treatment may not be performed stably. That is, when PO 4 -P ions in phosphorus-containing water such as sewage treated water are reacted with calcium ions to insolubilize, calcium ions are reacted with M-alkali in raw water or carbon dioxide in the air to generate calcium carbonate (CaCO Since 3 ) is precipitated, the PO 4 -P concentration in the raw water cannot be accurately determined from the added calcium ion amount and the residual calcium ion amount. In particular, in the case of wastewater treatment with drastic fluctuations in water quality such as M-alkalinity or in a dephosphorization treatment system operated in an open system, the amount of calcium ions consumed due to factors other than PO 4 -P ions is large. Since the fluctuation is severe, it is not appropriate to obtain the PO 4 -P ion amount based on the difference between the added calcium ion amount and the residual calcium ion amount.
[0006]
The present invention solves the above-mentioned conventional problems, adds calcium ions to raw water containing normal phosphate ions to produce calcium phosphate insolubilized materials, and separates them to obtain treated water. Dephosphorization method and dephosphorization of normal phosphoric acid-containing water that can reliably remove phosphorus in raw water with high water quality fluctuations such as concentration and M-alkalinity, and can stably obtain high-quality treated water with low phosphorus concentration An object is to provide a phosphorus device.
[0007]
[Means for Solving the Problems]
The dephosphorization method for normal phosphoric acid-containing water according to the present invention is a method for dephosphorizing normal phosphoric acid-containing water by separating calcium phosphate insolubilized product produced by adding calcium ions to raw water containing normal phosphate ions and treated water. In this method, the pH of the treated water and the calcium ion concentration are measured, and a pH adjusting agent and calcium ions are added to the raw water so that each measured value becomes a predetermined value . From the relationship, the pH and calcium concentration giving a predetermined value of the normal phosphoric acid concentration of the treated water are calculated, and the addition amount of the pH adjuster and the calcium ion addition amount are controlled so as to be the calculated values, respectively. .
[0008]
The dephosphorization apparatus of the present invention comprises a reaction tank for reacting normal phosphate ions and calcium ions to produce a calcium phosphate insolubilized product, raw water supply means for supplying raw water containing normal phosphate ions to the reaction tank, A calcium addition means for adding calcium ions to the reaction tank, a pH adjuster addition means for adding a pH adjuster to the reaction tank, and a reaction liquid containing calcium phosphate insolubilized material in the reaction tank in sludge and treated water as a solid liquid A solid-liquid separation means for separating; a pH measuring means for measuring the pH of the treated water; a calcium concentration measuring means for measuring the calcium ion concentration of the treated water; an output signal of the pH measuring means; and a calcium concentration measuring means. An output signal is input, and from the relationship between pH and the solubility product of calcium phosphate, the pH and calcium concentration giving a predetermined value of the normal phosphate concentration of the treated water are calculated, Characterized in that an arithmetic control unit for outputting a control signal for controlling the amount of calcium ions added amount of each pH adjusting agent to the H adjusting agent addition means and calcium addition means.
[0009]
That is, as a result of intensive studies on a chemical injection control method that reliably removes phosphorus in raw water without being affected by fluctuations in the quality of raw water, the present inventors have determined that the solubility of calcium phosphate precipitated from raw water is unique. It is possible to determine the soluble phosphorus (PO 4 -P) concentration of the resulting treated water from the pH of the treated water and the ion concentration remaining in the treated water, and thus the PO of the treated water If the target value for the 4- P concentration is determined and the chemical injection control is performed so that the PO 4 -P concentration becomes the pH of the treated water and the residual calcium ion concentration, stable and reliable The present invention has been achieved by finding that it can perform a dephosphorization process.
[0010]
For example, in a dephosphorization treatment in which calcium phosphate and an alkaline agent are added to raw water to precipitate calcium phosphate, the pH, PO 4 -P concentration, and calcium ion concentration of the treated water are measured and the relationship is examined. ) Results as shown in FIG. From the measured value of FIG. 3 (a), the pH of the treated water and the solubility product of the treated water calcium phosphate (Ca 3 (PO 4 ) 2 ) (log ([Ca 2+ ] 3 [PO 4 3− ] 2 )) 3 is as shown in FIG. 3B, and it can be seen that the solubility product obtained by calculation from the actual measurement value is about 10 times the theoretical value of the solubility product. That is, the treated water PO 4 -P concentration can be obtained by determining the treated water pH and the remaining calcium ion concentration of the treated water for 10 times the theoretical value of the solubility product. In other words, by substituting the target PO 4 -P concentration for 10 times the theoretical value of the solubility product, the treated water pH and the calcium ion concentration remaining in the treated water can be determined. By performing chemical injection control so that the treated water pH and calcium ion concentration can be adjusted, treated water having a target PO 4 -P concentration can be obtained stably and reliably.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention are described in detail below.
[0012]
In the present invention, the dephosphorization treatment is performed by adding a calcium compound and a pH adjuster such as an alkaline agent as necessary to the raw water containing soluble PO 4 -P to precipitate an insolubilized calcium phosphate. The pH of the water and the calcium ion concentration are measured, and the addition amount of the calcium compound and the pH adjuster is controlled so that the measured value becomes a predetermined value.
[0013]
That is, as described above, in such dephosphorization treatment, the solubility product of the calcium phosphate of the treated water obtained from the actually measured value becomes a predetermined value with respect to the treated water pH, and this solubility product is about 10 theoretical values. Is double. Therefore, to obtain this PO 4 -P concentration by substituting the target PO 4 -P concentration into the solubility product corresponding to the measured pH value (this value is about 10 times the theoretical value). Since the calcium ion concentration of the treated water can be calculated, the addition amount of the calcium compound may be controlled so that the calcium ion concentration of the treated water becomes the calculated calcium ion concentration.
[0014]
As a preferred embodiment of the present invention, the addition amount of a pH adjusting agent such as an alkaline agent is controlled based on the measured value of the pH measurement means of the treated water so that the pH of the treated water is constant, and this pH From the solubility product corresponding to the value, the calcium ion concentration for obtaining the target treated water PO 4 -P concentration is calculated, and the measured value of the calcium ion concentration measuring means becomes the calcium ion concentration so that the calcium ion concentration becomes the calcium ion concentration. A method for controlling the amount added is mentioned.
[0015]
In the present invention, since the pH and the calcium ion concentration are individually controlled as described above, neutral CaCl 2 is used as the calcium compound rather than alkaline Ca (OH) 2. It is preferable to add an alkaline agent such as NaOH for adjustment.
[0016]
Examples of the raw water to be treated by the method for removing phosphoric acid-containing water and the dephosphorization apparatus of the present invention include sewage treated water and wastewater generated by sewage sludge intensive treatment. In the precipitation method in which the calcium compound and an alkali agent are added and reacted in the reaction tank, if necessary, and the insolubilized material is separated in the precipitation tank, the raw water is introduced into the crystallizing tank and calcium phosphate is added to the surface of the seed crystal. The present invention can also be effectively applied to a crystal folding method for precipitating.
[0017]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0018]
Example 1
The synthetic waste water was treated by the apparatus shown in FIG.
[0019]
First, synthetic waste water (PO 4 -P: 10 mg / L, Ca: 39 mg / L, M-alkali: 88 mg / L) is introduced into the
[0020]
After injecting CaCl 2 aqueous solution into this synthetic wastewater, it was sequentially fed to the first reaction tank 2 and the
[0021]
In this embodiment, the
[0022]
At this time, the addition amount of the CaCl 2 aqueous solution varied in the range of 25 to 95 mg-Ca 2+ / L.
[0023]
Aging of PO 4 -P concentration in the treated water and PO 4 -P concentration of the raw water is as shown in FIG. 2, despite variations in the PO 4 -P concentration of the raw water, PO 4 -P concentration of treated water Was stably maintained at about 5 mg / L.
[0024]
Comparative Example 1
In Example 1, the Ca ion sensor was not provided, and the treatment was performed in the same manner as in Example 1 except that the addition of the CaCl 2 aqueous solution was made constant at 50 to 55 mg-Ca 2+ / L only by control with a pH meter. went. As a result,
[0025]
【The invention's effect】
As detailed above, according to the dephosphorization method and dephosphorization apparatus of normal phosphoric acid-containing water of the present invention, calcium ions are added to the raw water containing normal phosphate ions to produce calcium phosphate insolubilized product, When separating and obtaining treated water, phosphorus in raw water with a large fluctuation in water quality such as phosphorus concentration, calcium ion concentration, M-alkalinity, etc. is surely removed to stably obtain high-quality treated water with low phosphorus concentration. be able to.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a dephosphorization apparatus used in Example 1. FIG.
FIG. 2 is a graph showing the results of Example 1 and Comparative Example 1.
FIG. 3A is a graph showing the relationship between the pH of treated water and the calcium ion concentration and PO 4 -P concentration, and FIG. 3B shows the relationship between the pH of the treated water and the solubility product. It is a graph to show.
[Explanation of symbols]
DESCRIPTION OF
Claims (2)
処理水のｐＨとカルシウムイオン濃度を測定し、それぞれの測定値が所定値となるように、原水にｐＨ調整剤とカルシウムイオンを添加する方法であって、
ｐＨとリン酸カルシウムの溶解度積との関係から、処理水の正リン酸濃度の所定値を与えるｐＨとカルシウム濃度を演算し、該演算値となるようにそれぞれｐＨ調整剤の添加量及びカルシウムイオン添加量を制御することを特徴とする正リン酸含有水の脱リン方法。In the dephosphorization method of normal phosphate-containing water that separates the calcium phosphate insolubilized product produced by adding calcium ions to raw water containing normal phosphate ions and the treated water,
A method of measuring the pH and calcium ion concentration of treated water, and adding a pH adjuster and calcium ions to raw water so that each measured value becomes a predetermined value ,
From the relationship between the pH and the solubility product of calcium phosphate, the pH and calcium concentration giving a predetermined value of the normal phosphate concentration of the treated water are calculated, and the added amount of the pH adjuster and the added amount of calcium ions are respectively set to the calculated values. A method for dephosphorization of water containing orthophosphoric acid, wherein
該反応槽に正リン酸イオンを含有する原水を供給する原水供給手段と、
該反応槽にカルシウムイオンを添加するカルシウム添加手段と、
該反応槽にｐＨ調整剤を添加するｐＨ調整剤添加手段と、
該反応槽のリン酸カルシウム不溶化物を含む反応液を汚泥と処理水とに固液分離する固液分離手段と、
該処理水のｐＨを測定するｐＨ測定手段と、
該処理水のカルシウムイオン濃度を測定するカルシウム濃度測定手段と、
該ｐＨ測定手段の出力信号とカルシウム濃度測定手段の出力信号が入力され、ｐＨとリン酸カルシウムの溶解度積との関係から、処理水の正リン酸濃度の所定値を与えるｐＨとカルシウム濃度を演算し、ｐＨ調整剤添加手段及びカルシウム添加手段へそれぞれｐＨ調整剤の添加量及びカルシウムイオン添加量を制御する制御信号を出力する演算制御装置とを
備えたことを特徴とする脱リン装置。A reaction vessel for reacting normal phosphate ions and calcium ions to produce calcium phosphate insolubilized material,
Raw water supply means for supplying raw water containing normal phosphate ions to the reaction vessel;
Calcium addition means for adding calcium ions to the reaction vessel;
PH adjusting agent addition means for adding a pH adjusting agent to the reaction vessel;
Solid-liquid separation means for solid-liquid separation of the reaction liquid containing the calcium phosphate insolubilized material in the reaction tank into sludge and treated water;
PH measuring means for measuring the pH of the treated water;
Calcium concentration measuring means for measuring the calcium ion concentration of the treated water;
The output signal of the pH measuring means and the output signal of the calcium concentration measuring means are input, and from the relationship between the pH and the solubility product of calcium phosphate, the pH and calcium concentration giving a predetermined value of the normal phosphate concentration of the treated water are calculated, A dephosphorization apparatus comprising: an arithmetic control device that outputs a control signal for controlling the addition amount of the pH adjustment agent and the addition amount of calcium ions to the pH adjustment agent addition means and the calcium addition means, respectively.
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| JPS58223479A (en) * | 1982-06-21 | 1983-12-26 | Kurita Water Ind Ltd | Device for treating water containing phosphate |
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| JPH1076278A (en) * | 1996-09-03 | 1998-03-24 | Unitika Ltd | Apparatus for controlling addition of phosphorus removing agent |
| JPH1085761A (en) * | 1996-09-13 | 1998-04-07 | Japan Organo Co Ltd | Method and apparatus for treating drainage containing fluorine |
| JPH10128344A (en) * | 1996-11-06 | 1998-05-19 | Japan Organo Co Ltd | Apparatus and method for treating fluorine-containing drainage |
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Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58223479A (en) * | 1982-06-21 | 1983-12-26 | Kurita Water Ind Ltd | Device for treating water containing phosphate |
| JPS60202788A (en) * | 1984-03-22 | 1985-10-14 | Kurita Water Ind Ltd | Treating apparatus for waste water containing fluorine and phosphorus |
| JPS60225692A (en) * | 1984-04-23 | 1985-11-09 | Hitachi Plant Eng & Constr Co Ltd | Method and apparatus for controlling contact crystallization phosphorization process |
| JPS61153191A (en) * | 1984-12-26 | 1986-07-11 | Ebara Infilco Co Ltd | Catalytic dephosphorizer |
| JPS62250990A (en) * | 1986-04-25 | 1987-10-31 | Ataka Kogyo Kk | Treatment of waste water containing phosphate ion |
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| JPH1076278A (en) * | 1996-09-03 | 1998-03-24 | Unitika Ltd | Apparatus for controlling addition of phosphorus removing agent |
| JPH1085761A (en) * | 1996-09-13 | 1998-04-07 | Japan Organo Co Ltd | Method and apparatus for treating drainage containing fluorine |
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