JP2535744B2 - Treatment method for wastewater containing phosphate ions - Google Patents
Treatment method for wastewater containing phosphate ionsInfo
- Publication number
- JP2535744B2 JP2535744B2 JP2274338A JP27433890A JP2535744B2 JP 2535744 B2 JP2535744 B2 JP 2535744B2 JP 2274338 A JP2274338 A JP 2274338A JP 27433890 A JP27433890 A JP 27433890A JP 2535744 B2 JP2535744 B2 JP 2535744B2
- Authority
- JP
- Japan
- Prior art keywords
- phosphate
- hydroxyapatite
- reaction
- phosphate ions
- ions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は排水中のリン酸イオンを石灰により除去する
際に、石灰使用量が少なく、ろ過し易い水酸アパタイト
沈殿を生成させる方法に関する。Description: TECHNICAL FIELD The present invention relates to a method for producing a hydroxyapatite precipitate that is easy to filter and uses a small amount of lime when removing phosphate ions in wastewater with lime.
石灰によるリンの一般的な除去法は、水酸化カルシウ
ムを添加し、pH10〜12の条件下に、リンを水酸アパタイ
トの沈殿として除去する凝集沈殿法である。A general method for removing phosphorus with lime is a coagulation sedimentation method in which calcium hydroxide is added and phosphorus is removed as a precipitate of hydroxyapatite under conditions of pH 10 to 12.
この沈殿生成のためのpHが高いことから、次のような
問題が生じている。Since the pH for producing this precipitate is high, the following problems occur.
沈殿がアルカリ性で、再利用が困難。Alkaline precipitate makes it difficult to reuse.
沈殿生成量が多く、ろ過が困難。A large amount of precipitate is formed, making filtration difficult.
石灰使用量が多い。A large amount of lime is used.
処理水を中性にするための酸の添加が必要。It is necessary to add an acid to make the treated water neutral.
これらの欠点を解消し、ろ過し易い沈殿を生成させる
従来技術としては、pH4.5〜７で沈殿を生成させる方法
（特開昭53−107151）及び第１槽でpH5.5〜6.5でリン酸
イオン沈殿物として、さらに凝集剤を添加して、沈殿物
を凝集沈降させて分離し、上澄液に石灰を加えてpH10以
上として凝集剤を添加し、生成する沈殿を脱水すること
なく全量、第１槽へ返送する方法（特開昭57−187092）
がある。しかしながら、前記特開昭53−107151号に記載
されている方法は、pHが6.5程度の条件下に行うもので
あり、その際の処理水中のリン酸イオン濃度は100ppm以
上と高濃度であり、リン酸イオンの除去は不十分であ
る。また、前記特開昭57−187092号の方法ではpH10以上
で沈殿させるので、石灰使用量が多くなることは避けら
れない。これらの方法では排水処理方法として満足する
結果を得ることができない。As a conventional technique for eliminating these drawbacks and producing a precipitate that is easy to filter, there is a method of producing a precipitate at pH 4.5 to 7 (Japanese Patent Laid-Open No. 53-107151) and phosphorus at pH 5.5 to 6.5 in the first tank. As an acid ion precipitate, a coagulant is further added to precipitate and separate the precipitate, and lime is added to the supernatant liquid to adjust the pH to 10 or more, and the coagulant is added. , Method of returning to the first tank (JP-A-57-187092)
There is. However, the method described in JP-A-53-107151 is carried out under the condition that the pH is about 6.5, and the phosphate ion concentration in the treated water at that time is as high as 100 ppm or more, Removal of phosphate ions is inadequate. Further, in the method disclosed in JP-A-57-187092, since precipitation is performed at pH 10 or higher, an increase in the amount of lime used cannot be avoided. With these methods, satisfactory results cannot be obtained as wastewater treatment methods.
石灰によるリン酸イオンの沈殿生成は、次の反応によ
り水酸アパタイトを生成させるものである。The precipitation of phosphate ions by lime produces hydroxyapatite by the following reaction.
10Ca2+＋６HPO4 2-＋８OH-＝Ca10(0H)2(PO4)6＋６H2O 石灰によるリン酸イオンの凝集沈殿反応をpH10〜12の
条件下に行うと水酸アパタイトの沈殿の容積が大きくな
る原因は、水酸イオンやカルシウムイオンの濃度が高い
ために微細な結晶の成長が急速に起り、水を取り込んだ
沈殿が生成することによるものと考えられる。そこで、
水酸化カルシウムの添加を徐々に行うことにより、理論
上必要とするカルシウムイオン及び水酸イオンの濃度よ
り低いカルシウムイオン及び水酸イオンの濃度の状態で
上記の反応を行うことを検討した結果、リン酸イオン濃
度がカルシウムイオン濃度より高い場合には、pH9程度
で、上記の反応の水酸アパタイトの理論必要量Ca/Pのモ
ル比5/3に達しないにもかかわらず、大部分のリン酸イ
オンが除去されることを本発明者らは見いだした。10Ca 2+ ＋ 6HPO 4 2 ＋ 8OH − ＝ Ca 10 (0H) 2 (PO 4 ) 6 ＋ 6H 2 O When agglomeration and precipitation reaction of phosphate ion by lime is carried out under the condition of pH 10 to 12, the volume of precipitation of hydroxyapatite It is considered that the cause of the increase in water content is that the concentration of hydroxide ions and calcium ions is high, so that the growth of fine crystals occurs rapidly and a precipitate containing water is generated. Therefore,
As a result of studying performing the above reaction at a concentration of calcium ion and hydroxide ion lower than the theoretically required concentration of calcium ion and hydroxide ion by gradually adding calcium hydroxide, phosphorus When the acid ion concentration is higher than the calcium ion concentration, most of the phosphoric acid is present at a pH of about 9 even though the theoretical required amount of hydroxyapatite for the above reaction, Ca / P, does not reach 5/3. The inventors have found that the ions are removed.
この反応においてカルシウムイオンを増加させると、
生成する水酸アパタイトは増加し、リン酸イオンの除去
率は高くなるが、反応速度も大きくなるため、沈殿の容
積も大となり、水を取り込んだ沈殿が生じ、この沈殿を
ろ過することは困難である。したがって、ろ過しやすい
沈殿を生成させるためには、反応系中に存在させるカル
シウムイオンの添加量をできるだけ抑え、少なくともそ
の理論必要量以下にする事が必要であることが判明し
た。従来の技術では、リン酸イオンの除去率の向上に注
目し、リン酸イオンに比較してカルシウムイオンを過剰
に添加しており、そのため、ろ過しにくい沈殿が生成
し、固液分離やスラッジの取扱が困難となっている。Increasing calcium ion in this reaction
The amount of hydroxyapatite produced increases and the removal rate of phosphate ions increases, but the reaction rate also increases, so the volume of the precipitate also becomes large, and a precipitate containing water is generated, and it is difficult to filter this precipitate. Is. Therefore, in order to form a precipitate that is easy to filter, it has been found that it is necessary to suppress the addition amount of calcium ions present in the reaction system as much as possible, and at least to make the amount equal to or less than the theoretical required amount. In the conventional technology, attention is paid to the improvement of the removal rate of phosphate ions, and calcium ions are added in excess compared to phosphate ions, so that precipitates that are difficult to filter are generated, and solid-liquid separation and sludge It is difficult to handle.
カルシウムイオンが少ないと、沈殿生成反応は遅くな
り、容積が小さく、ろ過しやすい沈殿ができるが、逆
に、リン酸イオンの除去率は低下する。この場合、リン
酸イオンの除去率を高めるには、反応槽内の水酸アパタ
イトの沈殿濃度を高くすればよいことがわかった。濃度
の異なるリン酸イオンを含有する排水に対し、同一のモ
ル比の水酸化カルシウムを添加した時、リン酸イオン濃
度が高いほど、リン酸イオン除去率は高くなった。これ
は、リン酸イオン濃度が高いほど沈殿生成量が多く、生
成する沈殿が水酸アパタイトの結晶成長の核になること
により、反応速度を上昇させるためである。したがっ
て、反応槽中に予め沈殿を懸濁させることは、リン酸イ
オンの除去率を高めるために有効な手段である。When the amount of calcium ions is small, the precipitation formation reaction becomes slow, the volume is small, and the precipitates can be easily filtered, but conversely, the phosphate ion removal rate decreases. In this case, it was found that in order to increase the removal rate of phosphate ions, the precipitation concentration of hydroxyapatite in the reaction tank should be increased. When calcium hydroxide having the same molar ratio was added to wastewater containing phosphate ions having different concentrations, the phosphate ion removal rate was higher as the phosphate ion concentration was higher. This is because the higher the phosphate ion concentration, the larger the amount of precipitate produced, and the produced precipitate becomes the nucleus of crystal growth of hydroxyapatite, thereby increasing the reaction rate. Therefore, suspending the precipitate in the reaction vessel in advance is an effective means for increasing the removal rate of phosphate ions.
本発明は、当初の第１段階反応を、あらかじめ水酸ア
パタイトを懸濁させた反応槽に連続的にリン酸イオン含
有排水を導入し、pH7〜10.5の範囲内で一定のpHで水酸
アパタイトを沈殿させて行うものである。このときのカ
ルシウム塩の添加量は、理論必要量以下である。pHの上
昇につれてリン濃度は対数的に減少するが、このpHとリ
ン酸イオン濃度の関係は予備テストで求めることができ
る。第１段階反応の処理水中のリン酸イオン濃度が目標
値以下の値にすることができれば、第２段階反応は不要
である。The present invention is the first stage reaction, the phosphate ion-containing wastewater is continuously introduced into the reaction tank in which the hydroxyapatite is suspended in advance, and the hydroxyapatite is maintained at a constant pH within the range of pH 7 to 10.5. Is performed by precipitating. The amount of calcium salt added at this time is not more than the theoretically required amount. Phosphorus concentration decreases logarithmically with increasing pH, but the relationship between this pH and phosphate ion concentration can be determined by preliminary tests. If the phosphate ion concentration in the treated water of the first-step reaction can be set to a value below the target value, the second-step reaction is unnecessary.
第１段階反応のみでリン酸イオン除去率が不十分であ
る場合には、固液分離することなく、第２段階反応へ送
り、理論必要量のカルシウム塩を添加する。第１段階の
反応では、pH7.0〜10.5の範囲の任意のpHに対し残存リ
ン濃度はほぼ一定の値となるので、第２段階反応で添加
するカルシウム塩の量は容易に決定できる。カルシウム
塩としては、塩化カルシウム、硫酸カルシウムなどが使
用できる。When the phosphate ion removal rate is insufficient only in the first-step reaction, the solution is sent to the second-step reaction without solid-liquid separation, and a theoretically required amount of calcium salt is added. In the reaction of the first step, the residual phosphorus concentration has a substantially constant value for any pH in the range of 7.0 to 10.5, so the amount of calcium salt added in the second step reaction can be easily determined. As the calcium salt, calcium chloride, calcium sulfate or the like can be used.
第１段階反応の懸濁状の水酸アパタイトの量を維持す
るために、第２段階反応で生成する水酸アパタイトの沈
殿の一部を第１段階反応槽へ循環する。懸濁させる水酸
アパタイトの量は1g/1（乾燥重量）以上が必要である。In order to maintain the amount of suspended hydroxyapatite in the first-step reaction, a part of the precipitate of hydroxyapatite produced in the second-step reaction is circulated to the first-step reaction tank. The amount of hydroxyapatite to be suspended must be 1 g / 1 (dry weight) or more.
また、排水中のリン酸イオンがリン酸ナトリウムの形
の場合には、処理に先だってナトリウムと当量の酸、あ
るいは塩化カルシウムを添加することにより、排水を酸
性にすればよい。When the phosphate ion in the waste water is in the form of sodium phosphate, the waste water may be acidified by adding an acid equivalent to sodium or calcium chloride prior to the treatment.
実施例１ 水酸アパタイト2g/1を含む排水を、容積200mlの反応
槽に移送し、リン酸イオン濃度200ppmのリン酸を含む溶
液を400ml/hの流速で連続的に反応槽に導入し、反応槽
内のpHを9.5にコントロールしながら５％の石灰乳を添
加した。処理水のリン濃度は6.2ppm、沈殿容積は10mlで
あった。この沈殿を含む処理水100mlにCa/P＝1.7になる
ように塩化カルシウムを添加し、10分間かくはんした。
その結果、pHは8.7に下がり、リン酸イオン濃度は0.5pp
mに低下した。沈殿の容積は6.5mlであった。Example 1 Wastewater containing 2 g / 1 of hydroxyapatite was transferred to a reaction tank having a volume of 200 ml, and a solution containing phosphoric acid having a phosphate ion concentration of 200 ppm was continuously introduced into the reaction tank at a flow rate of 400 ml / h, 5% lime milk was added while controlling the pH in the reaction tank to 9.5. The phosphorus concentration of the treated water was 6.2 ppm, and the precipitation volume was 10 ml. Calcium chloride was added to 100 ml of treated water containing this precipitate so that Ca / P = 1.7, and the mixture was stirred for 10 minutes.
As a result, the pH dropped to 8.7 and the phosphate ion concentration was 0.5pp.
fell to m. The volume of precipitation was 6.5 ml.
比較例１ あらかじめリン酸溶液に塩化カルシウムを添加し、Ca
/P＝1.7になるようにして、実施例１と同様な条件で操
作した。反応槽のpHは9.0で、リン酸イオン濃度は4.4pp
mであったが、得られた沈殿の容積は38mlであり、沈殿
の容積は大きいものとなった。Comparative Example 1 Calcium chloride was added to the phosphoric acid solution beforehand, and Ca
The operation was performed under the same conditions as in Example 1 such that /P=1.7. PH of the reaction tank is 9.0, phosphate ion concentration is 4.4pp
However, the volume of the obtained precipitate was 38 ml, and the volume of the precipitate was large.
本発明によれば、反応槽中に水酸アパタイトの懸濁状
の沈殿を生成させ、それを核として排水中のリン酸イオ
ンを水酸アパタイトとして晶析させるため、微細な結晶
が多発するのを防止することができ、又得られる沈殿の
容積が小さく、沈殿はろ過しやすい状態のものが得るこ
とができる。本発明の方法は、反応の自動制御が可能で
あり、又操作は簡単な連続処理である。反応により生成
する沈殿も主に水酸アパタイトで、再利用も可能であ
る。According to the present invention, a suspension-like precipitate of hydroxyapatite is generated in the reaction tank, and phosphate ions in the wastewater are crystallized as hydroxyapatite using the precipitate as a nucleus, so that fine crystals frequently occur. Can be prevented, the volume of the obtained precipitate is small, and the precipitate can be easily filtered. The method of the present invention allows automatic control of the reaction and is a simple continuous operation. The precipitate generated by the reaction is mainly hydroxyapatite and can be reused.
Claims (3)
で生成した水酸アパタイトを懸濁させた反応槽内にリン
酸イオンを含む排水を導入後、リン酸イオンに対するカ
ルシウムイオンが、その理論必要量（Ca/P＝5/3）より
も低い値となるように水酸化カルシウムを添加し、リン
酸イオンと水酸化カルシウムの反応のpHを7.0〜10.5の
条件下に、リン酸イオンを結晶性沈殿として沈殿させる
ことを特徴とするリン酸イオン含有排水の処理方法。1. After introducing wastewater containing phosphate ions into a reaction vessel in which hydroxyapatite produced by the reaction of phosphate ions and calcium hydroxide is suspended, calcium ions with respect to phosphate ions have the theory of Add calcium hydroxide to a value lower than the required amount (Ca / P = 5/3), and adjust the pH of the reaction between phosphate ion and calcium hydroxide to 7.0 to 10.5 under conditions of phosphate ion A method for treating wastewater containing phosphate ions, which comprises depositing as a crystalline precipitate.
ンを含む状態で得られる水酸アパタイトが懸濁する排水
に、前記リン酸イオン濃度に対応するカルシウム塩の理
論必要量を添加し、かつ、リン酸イオンと水酸化カルシ
ウムの反応をpH8.0〜10.0の条件下に行うことにより、
前記残存するリン酸イオンを水酸アパタイトの沈殿とす
ることを特徴とするリン酸イオン含有排水の二段階処理
方法。2. The theoretically required amount of calcium salt corresponding to the phosphate ion concentration is added to the wastewater in which the hydroxyapatite obtained in the state containing phosphate ions obtained by the treatment method of claim 1 is suspended. And, by carrying out the reaction of phosphate ions and calcium hydroxide under the conditions of pH 8.0 to 10.0,
A method for treating phosphate ion-containing wastewater in a two-step process, wherein the remaining phosphate ions are precipitated hydroxyapatite.
の一部を請求項１の水酸アパタイトとして循環使用する
ことを特徴とするリン酸イオン含有排水の処理方法。3. A method for treating a phosphate ion-containing wastewater, characterized in that a part of the precipitation of hydroxyapatite obtained in claim 2 is reused as hydroxyapatite of claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2274338A JP2535744B2 (en) | 1990-10-12 | 1990-10-12 | Treatment method for wastewater containing phosphate ions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2274338A JP2535744B2 (en) | 1990-10-12 | 1990-10-12 | Treatment method for wastewater containing phosphate ions |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04150996A JPH04150996A (en) | 1992-05-25 |
| JP2535744B2 true JP2535744B2 (en) | 1996-09-18 |
Family
ID=17540268
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2274338A Expired - Lifetime JP2535744B2 (en) | 1990-10-12 | 1990-10-12 | Treatment method for wastewater containing phosphate ions |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2535744B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3977757B2 (en) * | 2003-02-12 | 2007-09-19 | 日本化学工業株式会社 | Dephosphorization method of waste water |
| JP4223334B2 (en) * | 2003-06-18 | 2009-02-12 | アタカ大機株式会社 | Phosphorus recovery equipment |
| JP4759989B2 (en) * | 2004-11-18 | 2011-08-31 | 栗田工業株式会社 | Treatment method for wastewater containing phosphoric acid |
| JP4600865B2 (en) * | 2005-03-31 | 2010-12-22 | 株式会社日立プラントテクノロジー | Method for crystallizing phosphorus-containing water |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62250990A (en) * | 1986-04-25 | 1987-10-31 | Ataka Kogyo Kk | Treatment of waste water containing phosphate ion |
| JP2598456B2 (en) * | 1988-05-09 | 1997-04-09 | 川崎製鉄株式会社 | Treatment method for phosphate-containing water |
-
1990
- 1990-10-12 JP JP2274338A patent/JP2535744B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04150996A (en) | 1992-05-25 |
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|---|---|---|---|
| EXPY | Cancellation because of completion of term |