JP3726429B2

JP3726429B2 - Dephosphorization device

Info

Publication number: JP3726429B2
Application number: JP16256697A
Authority: JP
Inventors: 哲朗深瀬; 雅秀柴田
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 1997-06-19
Filing date: 1997-06-19
Publication date: 2005-12-14
Anticipated expiration: 2017-06-19
Also published as: JPH1110166A

Description

【０００１】
【発明の属する技術分野】
本発明は、下水、し尿、排水の汚泥脱水濾液、汚泥消化脱離液等のリン含有水中のリンを効率的に除去し、ＭＡＰ（リン酸アンモニウムマグネシウム）粒子として回収する脱リン装置に係り、特に、均一なＭＡＰ粒子を安定に得ることができる脱リン装置に関する。
【０００２】
【従来の技術】
下水、し尿、排水の嫌気、好気処理工程で得られる汚泥脱水濾液や汚泥消化脱離液等のリン含有水のリンを除去する脱リン装置として、従来、反応塔内にリン含有水を上向流で通水し、マグネシウムイオンを添加して、リン含有水中のリン及びアンモニアとマグネシウムイオンからＭＡＰを生成させ、塔上部から処理水を取り出すと共に、塔下部からＭＡＰ粒子を回収する脱リン装置がある。
【０００３】
【発明が解決しようとする課題】
従来の脱リン装置では、ＭＡＰを効率的に生成させることができるが、生成するＭＡＰ粒子の粒径が０．５〜５ｍｍ程度とバラツキが大きく、均一な粒径のＭＡＰ粒子を得ることができないという欠点がある。また、このようにＭＡＰ粒子の粒径のバラツキが大きいことにより、被処理水のリン濃度が変動したり、ＭＡＰ粒子の引き抜き量制御が不十分であったりすると、ＭＡＰの微細粒子が処理水中に流出したり、ＭＡＰ粒子の粗大化でＭＡＰ粒子の流動が損われ、リンの除去率が低下したりする場合があった。
【０００４】
本発明は上記従来の問題点を解決し、ＭＡＰ粒子の粒径の制御が容易で、所望の均一粒径のＭＡＰ粒子を安定に得ることができる脱リン装置を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明の脱リン装置は、塔下部にリン含有水の導入口、塔上部に処理水の取出口を有すると共に、小径部と、該小径部の上側の拡径部と、該拡径部の上側の大径部とを有する反応塔と、該反応塔外からリン酸アンモニウムマグネシウムの微細粒子を該反応塔内に添加する手段と、該反応塔の拡径部からリン酸アンモニウムマグネシウム粒子を抜き出して該反応塔の塔下部に循環する配管と、該反応塔の処理水の取出口から取り出した処理水の一部を該反応塔の塔下部に循環させる配管とを備えてなる脱リン装置であって、前記リン酸アンモニウムマグネシウムの微粒子が、ＭＡＰ微粒子生成槽に原水であるリン含有水、マグネシウム塩及びアルカリ剤の必要量を添加して、ｐＨ８〜１０の条件下、５〜６０分ゆっくり撹拌することにより製造した、粒径５０μｍ〜１ｍｍのリン酸アンモニウムマグネシウムの微粒子であることを特徴とする。
【０００６】
本発明者らは、従来の脱リン装置で得られるＭＡＰ粒子の粒径に大きな幅がある理由について検討した結果、次のような知見を得た。
【０００７】
即ち、ＭＡＰの生成反応は、リンとアンモニアとマグネシウムイオンとの反応によるＭＡＰの生成、不溶化と、不溶化したＭＡＰ同士の会合等によるＭＡＰ粒子の成長の繰り返しによるものであるが、単に被処理水を反応塔に上向流通水し、生成したＭＡＰ粒子を塔下部から引き抜くだけでは、ＭＡＰ粒子の粒径の制御はできない。
【０００８】
即ち、成長したＭＡＰ粒子を塔下部から引き抜いても、これを完全に引き抜くことは困難であり、塔内に残留したＭＡＰ粒子が徐々に大きくなり、遂には粒径１ｃｍ以上の粗大粒子となる。このため、粒径にバラツキが生じる。また、この粗大粒子によりＭＡＰ粒子の流動が損なわれ、リン除去率が低下する。
【０００９】
本発明では、反応塔外から別途ＭＡＰ微粒子生成槽で製造したＭＡＰ微粒子を種晶として反応塔内に添加することにより、ＭＡＰ粒子の粒径を制御する。即ち、ＭＡＰ微粒子を多量に添加すれば小粒径のＭＡＰ粒子を得ることができ、少量添加すれば大粒径のＭＡＰ粒子を得ることができる。
【００１１】
本発明では、別途、ＭＡＰ微粒子生成槽を設け、この槽で、リン含有水にマグネシウムイオンを添加して所定のｐＨ条件下、所定時間撹拌して、著しく均一な粒径のＭＡＰ微粒子を得ることができる。
【００１２】
【発明の実施の形態】
以下に図面を参照して本発明の実施の形態を詳細に説明する。
【００１３】
図１は本発明の脱リン装置の実施の形態を示す系統図である。
【００１４】
図中、１は頂部が開放した反応塔であり、下部にリン含有水（原水）の導入配管２が、上部に処理水の取出配管３が設けられている。この反応塔１は小径部１Ａ、拡径部１Ｂ及び大径部１Ｃで構成され、小径部１ＡはＭＡＰの造粒反応部、大径部１Ｃは沈殿部、拡径部１Ｂは移行部とされている。小径部１Ａの下部にはＭｇＣｌ₂等のマグネシウム塩溶液（マグネシウム塩を含有するものであれば良く、海水であっても良い。）の供給管４及びＮａＯＨ等のアルカリ剤の供給管５が設けられている。
【００１５】
取出配管３で取り出された処理水は処理水槽６に貯留され、一部は配管７より反応塔１下部に循環され、残部は配管８より系外へ排出される。
【００１６】
拡径部１Ｂには、ＭＡＰ粒子を抜き出して反応塔１下部に循環する配管１０が設けられている。１１は溢流堰、１２はＭＡＰ粒子の排出管、１３はｐＨ計である。
【００１７】
２０はＭＡＰ微粒子生成槽であり、原水の導入配管２１、ＭｇＣｌ₂等のマグネシウム塩供給管２２、ＮａＯＨ等のアルカリ剤供給管２３、撹拌機２４、ｐＨ計２５を備える。このＭＡＰ微粒子生成槽２０で生成したＭＡＰ微粒子は、配管２６より、反応塔１の上部から反応塔１に供給される。
【００１８】
なお、Ｐ₁，Ｐ₂，Ｐ₃，Ｐ₄はポンプ、Ｖはバルブであり、ＭはＭＡＰ粒子の流動層の界面を示す。
【００１９】
反応塔１では、ＭＡＰが析出するｐＨ条件、即ちｐＨ７．７〜９．０、好ましくはｐＨ８．１となるように、供給管５よりＮａＯＨ等のアルカリ剤が注入される。また、ＭＡＰの析出にマグネシウムが不足する場合には、供給管４よりＭｇＣｌ₂等のマグネシウム塩溶液を注入する。
【００２０】
小径部１Ａ、即ちＭＡＰ造粒反応部では、既に析出しているＭＡＰ粒子を種晶としてＭＡＰが造粒される。即ち、被処理水の流入とＭＡＰ粒子の循環によりＭＡＰ粒子が流動状態となり、このＭＡＰ粒子の表面に新たなＭＡＰが析出して、大粒のＭＡＰ粒子が造粒される。
【００２１】
このＭＡＰの析出において、原水のリン濃度が高いと、種晶の不存在下でＭＡＰの微小結晶が自己析出し、大粒のＭＡＰ粒子が得られないという不具合があるが、この脱リン装置では、反応塔１の処理水を処理水槽６より配管７及びポンプＰ₂により抜き出して循環することにより、反応塔１内のＭＡＰ造粒反応部のリン濃度を低下させることができる。これにより反応塔１内のＭＡＰの過飽和度が低下し、ＭＡＰは微小結晶として自己析出することなく、種晶のＭＡＰ粒子の表面でのみ析出してＭＡＰ粒子の大粒子化を促進する。この処理水の循環は、反応塔１内のＭＡＰ造粒反応部のリン濃度をリン酸塩濃度１００ｍｇ／Ｌ以下、特に４０〜８０ｍｇ／Ｌとなるように行うのが好ましい。
【００２２】
ＭＡＰの析出により、リン濃度が低下した液は反応塔１内を上昇して取出配管３より排出される。この際、ＭＡＰ粒子は大粒子化しているため、多量の汚泥固形物を含む原水を処理する場合においても、ＭＡＰ粒子が固形物と共に排出されることなく、良好に沈殿分離される。即ち、ＭＡＰ粒子は、汚泥固形物よりも十分に大きい比重、粒度であるため、良好な分離性にて沈殿分離し、汚泥固形物のみが処理水中に含有されて溢流堰１１を越流して排出される。
【００２３】
以上の処理は連続処理にて行われる。
【００２４】
小径部１Ａの反応造粒部で粒大化したＭＡＰ粒子は、反応塔１下部の排出管１２より間欠的に取り出される。
【００２５】
本発明では、このような脱リン処理に当り、ＭＡＰ微粒子生成槽２０で生成させたＭＡＰ微粒子を添加するため、このＭＡＰ微粒子の添加量を制御することにより、容易に所望の均一粒子のＭＡＰ粒子を回収することができる。特に、図１の脱リン装置では、ＭＡＰ粒子の循環を行うことで、より一層粒径の均一化を図ることができる。
【００２６】
このＭＡＰ微粒子の添加は間欠的に行っても、連続的に行っても良く、また、反応塔１からのＭＡＰ粒子の抜き出し毎に行っても良い。
【００２７】
また、ＭＡＰ粒子の循環量は、原水流量に対して１／１０〜１倍程度で行うのが好ましい。
【００２８】
なお、本発明において、反応塔に添加するＭＡＰ微粒子は、ＭＡＰ微粒子生成槽２０に原水であるリン含有水、ＭｇＣｌ_２等のマグネシウム塩及びＮａＯＨ等のアルカリ剤の必要量を添加して、ｐＨ８〜１０の条件下、５〜６０分ゆっくり撹拌することにより製造した、粒径５０μｍ〜１ｍｍのＭＡＰ微粒子である。
【００２９】
また、ＭＡＰ微粒子の添加量は前述の如く、所望とするＭＡＰ粒子の粒径により異なるが、一般的には、粒径５ｍｍ程度のＭＡＰ粒子を得る場合には引き抜いたＭＡＰ量の０．０１〜１重量％程度とし、粒径１ｍｍ程度のＭＡＰ粒子を得る場合には引き抜いたＭＡＰ量の０．０５〜５重量％程度とするのが好ましい。
【００３０】
なお、本発明においてＭＡＰ微粒子の添加箇所には特に制限はなく、図１に示す如く、反応塔１の上部から添加しても良く、また、ＭｇＣｌ又はＮａＯＨの供給管を利用して添加しても良い。更に、別途ＭＡＰ微粒子の供給管を増設しても良いが、既存の設備をそのまま利用できる点から、反応塔上部から添加するか、ＮａＯＨ，ＭｇＣｌ₂の供給管を利用するのが好ましい。
【００３１】
また、反応塔の型式には、制限はなく、プラグフローでも流動床でも良い。
【００３２】
なお、図示の例では、Ｍｇ塩及びアルカリ剤のみを添加しているが、ＭＡＰの生成にアンモニアが不足する場合には、反応塔、ＭＡＰ微粒子生成槽に更にアンモニアを添加する必要がある。
【００３３】
【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。
【００３４】
実施例１
図１に示す脱リン装置により、ＰＯ₄−Ｐ：３０ｍｇ／Ｌ，ＮＨ₄−Ｎ：５４ｍｇ／Ｌの合成排水を後述の運転条件で処理した。
【００３５】
なお、ＭＡＰ微粒子生成槽では、この合成排水流量１０ｍＬ／分（＝０．６Ｌ／時），滞留時間（ＨＲＴ）５０分，槽内ｐＨ８．８，ＭｇＣｌ₂添加量０．４ｍｇ−Ｍｇ／分で撹拌下ＭＡＰ微粒子の生成を行い、粒径０．１〜０．５ｍｍのＭＡＰ微粒子を生成させ、このＭＡＰ微粒子０．５ｍＬを１日に１回反応塔に添加した。
【００３６】
また、反応塔の大きさは次の通りである。
【００３７】
反応塔寸法
小径部１Ａの直径：３ｃｍ
小径部１Ａの高さ：１．７ｃｍ
大径部１Ｃの直径：４ｃｍ
大径部１Ｃと拡径部１Ｂの合計の高さ：０．３ｍ
塔容量：１．５８Ｌ

【００３８】
その結果、図２（ａ）に示す如く、得られたＭＡＰ粒子の平均粒径は、０．７〜０．９ｍｍの範囲に安定していた。また、処理水のＰＯ₄−Ｐ濃度も図２（ｂ）に示す如く８〜１０ｍｇ／Ｌで安定していた。
【００３９】
比較例１
実施例１において、反応塔のＭＡＰの循環を行わず、また、ＭＡＰ微粒子生成槽のＭＡＰ微粒子の添加を行わなかったこと以外は同様にして処理を行ったところ、図３（ａ），（ｂ）に示す如く、初期のリン除去は良好に行われるが、ＭＡＰ粒子の粒径が徐々に大きくなり、平均粒径が２ｍｍ程度にまで大粒子化した時点で処理水のＰＯ₄−Ｐ濃度は９ｍｇ／Ｌから１６ｍｇ／Ｌにまで悪化した。これは、ＭＡＰ粒子の粗大化によりＭＡＰ生成反応が起こる粒子の比表面積が小さくなると共に、ＭＡＰ粒子の流動が阻害されたために、ＭＡＰ生成反応速度が低下したことによると推定される。
【００４０】
【発明の効果】
以上詳述した通り、本発明の脱リン装置によれば、リン含有水からＭＡＰ粒子を生成させて脱リン処理するに当り、所望の均一粒径のＭＡＰ粒子を安定に得ることができる。このように、ＭＡＰ粒子の粒径が安定することから、ＭＡＰ微粒子の流出又はＭＡＰ粒子の粗大化による反応阻害が防止され、効率的な脱リン処理を行うことができ、長期に亘り、低リン濃度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】本発明の脱リン装置の実施の形態を示す系統図である。
【図２】実施例１の結果を示すグラフであり、図２（ａ）は得られたＭＡＰ粒子の平均粒径の経時変化を示し、図２（ｂ）は処理水のＰＯ₄−Ｐ濃度の経時変化を示す。
【図３】比較例１の結果を示すグラフであり、図３（ａ）は得られたＭＡＰ粒子の平均粒径の経時変化を示し、図３（ｂ）は処理水のＰＯ₄−Ｐ濃度の経時変化を示す。
【符号の説明】
１反応塔
７処理水槽
２０ＭＡＰ微粒子生成槽[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dephosphorization apparatus that efficiently removes phosphorus in phosphorus-containing water such as sewage, human waste, drainage sludge dehydrated filtrate, sludge digestion and desorption liquid, and recovers it as MAP (ammonium magnesium phosphate) particles. In particular, the present invention relates to a dephosphorization apparatus that can stably obtain uniform MAP particles.
[0002]
[Prior art]
As a dephosphorization device that removes phosphorus in phosphorus-containing water such as sludge dewatered filtrate and sludge digestion and desorption liquid obtained in anaerobic and aerobic treatment processes of sewage, human waste, and wastewater, conventionally, phosphorus-containing water has been added to the reaction tower. A dephosphorization device that passes water countercurrently, adds magnesium ions, generates MAP from phosphorus and ammonia and magnesium ions in phosphorus-containing water, removes treated water from the upper part of the tower, and recovers MAP particles from the lower part of the tower There is.
[0003]
[Problems to be solved by the invention]
In the conventional dephosphorization apparatus, MAP can be generated efficiently, but the generated MAP particles have a large variation in particle size of about 0.5 to 5 mm, and MAP particles having a uniform particle size cannot be obtained. There is a drawback. In addition, due to the large variation in the particle size of the MAP particles as described above, if the phosphorus concentration of the water to be treated fluctuates or the amount of MAP particles to be extracted is insufficiently controlled, the fine particles of MAP will be in the treated water. In some cases, the MAP particles flow out, the flow of the MAP particles is impaired, and the phosphorus removal rate decreases.
[0004]
An object of the present invention is to solve the above-mentioned conventional problems, and to provide a dephosphorization apparatus that can easily control the particle size of MAP particles and can stably obtain MAP particles having a desired uniform particle size.
[0005]
[Means for Solving the Problems]
The dephosphorization apparatus of the present invention has an inlet for phosphorus-containing water at the lower part of the tower and an outlet for treated water at the upper part of the tower, a small diameter part, an enlarged diameter part on the upper side of the small diameter part, A reaction tower having an upper large-diameter portion, means for adding fine particles of ammonium magnesium phosphate from the outside of the reaction tower, and extraction of the magnesium magnesium phosphate particles from the enlarged diameter portion of the reaction tower A dephosphorization apparatus comprising: a pipe that circulates to the lower part of the reaction tower; and a pipe that circulates a part of the treated water taken from the treated water outlet of the reaction tower to the lower part of the reaction tower. The ammonium magnesium phosphate fine particles are slowly stirred for 5-60 minutes under the condition of pH 8-10 by adding necessary amounts of phosphorus-containing water, magnesium salt and alkaline agent as raw water to the MAP fine particle production tank. Manufactured by And, wherein the Oh Rukoto in microparticles of magnesium ammonium phosphate particle size 50Myuemu～1mm.
[0006]
As a result of examining the reason why the particle size of MAP particles obtained by a conventional dephosphorization apparatus has a large range, the present inventors have obtained the following knowledge.
[0007]
In other words, the MAP production reaction is based on repeated production of MAP by the reaction of phosphorus, ammonia and magnesium ions, and insolubilization, and the growth of MAP particles by association of the insolubilized MAPs. It is not possible to control the particle size of the MAP particles by simply flowing upward water into the reaction tower and drawing the generated MAP particles from the bottom of the tower.
[0008]
That is, even if the grown MAP particles are pulled out from the lower part of the tower, it is difficult to pull out the MAP particles completely, and the MAP particles remaining in the tower gradually increase to finally become coarse particles having a particle diameter of 1 cm or more. For this reason, the particle size varies. Moreover, the flow of the MAP particles is impaired by the coarse particles, and the phosphorus removal rate is lowered.
[0009]
In the present invention, the particle size of the MAP particles is controlled by adding the MAP fine particles produced separately from the outside of the reaction tower in the MAP fine particle production tank into the reaction tower as seed crystals. That is, MAP particles having a small particle size can be obtained by adding a large amount of MAP fine particles, and MAP particles having a large particle size can be obtained by adding a small amount.
[0011]
In the present invention, a separate MAP fine particle production tank is provided, in which magnesium ions are added to phosphorus-containing water and stirred for a predetermined time under a predetermined pH condition to obtain MAP fine particles having a remarkably uniform particle size. There kill in.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 1 is a system diagram showing an embodiment of the dephosphorization apparatus of the present invention.
[0014]
In the figure, reference numeral 1 denotes a reaction tower whose top is open, and is provided with an introduction pipe 2 for phosphorus-containing water (raw water) in the lower part and a discharge pipe 3 for treated water in the upper part. This reaction tower 1 is composed of a small diameter part 1A, an enlarged diameter part 1B, and a large diameter part 1C. The small diameter part 1A is a MAP granulation reaction part, the large diameter part 1C is a precipitation part, and the enlarged diameter part 1B is a transition part. ing. Below the small-diameter portion 1A, there are provided a supply pipe 4 for a magnesium salt solution such as MgCl ₂ (so long as it contains magnesium salt, or seawater) and a supply pipe 5 for an alkaline agent such as NaOH. It has been.
[0015]
The treated water taken out by the take-out pipe 3 is stored in the treated water tank 6, a part is circulated from the pipe 7 to the lower part of the reaction tower 1, and the remaining part is discharged from the pipe 8 to the outside of the system.
[0016]
The expanded diameter portion 1B is provided with a pipe 10 that extracts MAP particles and circulates them to the lower part of the reaction tower 1. 11 is an overflow weir, 12 is a discharge pipe for MAP particles, and 13 is a pH meter.
[0017]
Reference numeral 20 denotes a MAP fine particle production tank, which includes a raw water introduction pipe 21, a magnesium salt supply pipe 22 such as MgCl ₂ , an alkali agent supply pipe 23 such as NaOH, a stirrer 24, and a pH meter 25. The MAP fine particles generated in the MAP fine particle generation tank 20 are supplied to the reaction tower 1 from the upper part of the reaction tower 1 through the pipe 26.
[0018]
P ₁ , P ₂ , P ₃ , P ₄ are pumps, V is a valve, and M is the fluidized bed interface of MAP particles.
[0019]
In the reaction tower 1, an alkaline agent such as NaOH is injected from the supply pipe 5 so that the pH condition for precipitation of MAP, that is, pH 7.7 to 9.0, preferably pH 8.1. Further, when magnesium is insufficient for precipitation of MAP, a magnesium salt solution such as MgCl ₂ is injected from the supply pipe 4.
[0020]
In the small-diameter portion 1A, that is, the MAP granulation reaction portion, MAP is granulated using the already precipitated MAP particles as seed crystals. That is, the MAP particles become fluidized by the inflow of the water to be treated and the circulation of the MAP particles, and new MAP is deposited on the surface of the MAP particles, and large MAP particles are granulated.
[0021]
In the precipitation of MAP, if the phosphorus concentration of the raw water is high, MAP microcrystals are self-precipitated in the absence of seed crystals, and large MAP particles cannot be obtained. By removing the treated water from the reaction tower 1 from the treated water tank 6 by the pipe 7 and the pump P ₂ and circulating it, the phosphorus concentration in the MAP granulation reaction section in the reaction tower 1 can be lowered. As a result, the supersaturation degree of MAP in the reaction tower 1 is reduced, and MAP does not self-precipitate as fine crystals, but only precipitates on the surface of the seed crystal MAP particles, thereby promoting the enlargement of the MAP particles. This treatment water is preferably circulated so that the phosphorus concentration in the MAP granulation reaction section in the reaction tower 1 is a phosphate concentration of 100 mg / L or less, particularly 40 to 80 mg / L.
[0022]
The liquid whose phosphorus concentration has decreased due to the precipitation of MAP rises in the reaction tower 1 and is discharged from the extraction pipe 3. At this time, since the MAP particles are large, even when the raw water containing a large amount of sludge solids is processed, the MAP particles are well precipitated and separated without being discharged together with the solids. That is, since the MAP particles have a specific gravity and particle size sufficiently larger than the sludge solids, they are precipitated and separated with good separability, and only the sludge solids are contained in the treated water and overflow the overflow weir 11. Discharged.
[0023]
The above process is performed in a continuous process.
[0024]
The MAP particles enlarged in the reaction granulation part of the small diameter part 1A are intermittently taken out from the discharge pipe 12 at the lower part of the reaction tower 1.
[0025]
In the present invention, the MAP fine particles produced in the MAP fine particle production tank 20 are added in such dephosphorization treatment. Therefore, by controlling the addition amount of the MAP fine particles, the desired uniform MAP particles can be easily obtained. Can be recovered. In particular, in the dephosphorization apparatus of FIG. 1, the particle size can be further uniformed by circulating the MAP particles.
[0026]
The addition of the MAP fine particles may be performed intermittently or continuously, or may be performed every time the MAP particles are extracted from the reaction tower 1.
[0027]
Further, it is preferable that the circulation amount of the MAP particles is about 1/10 to 1 times the raw water flow rate.
[0028]
In the present invention, MAP particles added to the reaction column, a phosphorus-containing water is raw water M AP microparticle generation tank 20, by adding the required amount of alkaline agents, such as magnesium salts and NaOH of MgCl ₂ and the like, pH 8 10 under the conditions of, was prepared by stirring for 5 to 60 minutes Slowly, Ru Oh by the MAP particles having a particle size of 50μm~1mm.
[0029]
Further, the amount of MAP fine particles added varies depending on the desired particle size of the MAP particles as described above. Generally, when obtaining MAP particles having a particle size of about 5 mm, the amount of MAP extracted is 0.01 to When MAP particles having a particle diameter of about 1 mm are obtained, the amount is preferably about 0.05 to 5% by weight of the extracted MAP.
[0030]
In the present invention, there are no particular restrictions on the location of addition of the MAP fine particles, and as shown in FIG. 1, it may be added from the top of the reaction tower 1 or may be added using a supply pipe for MgCl or NaOH. Also good. Further, although a MAP fine particle supply pipe may be additionally provided, it is preferable to add from the upper part of the reaction tower or use a NaOH / MgCl ₂ supply pipe from the viewpoint that the existing equipment can be used as it is.
[0031]
Moreover, there is no restriction | limiting in the type of a reaction tower, A plug flow or a fluidized bed may be sufficient.
[0032]
In the illustrated example, only the Mg salt and the alkali agent are added. However, when ammonia is insufficient for the production of MAP, it is necessary to further add ammonia to the reaction tower and the MAP fine particle production tank.
[0033]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0034]
Example 1
With the dephosphorization apparatus shown in FIG. 1, synthetic wastewater of PO ₄ -P: 30 mg / L, NH ₄ -N: 54 mg / L was treated under the operating conditions described below.
[0035]
In the MAP fine particle production tank, the synthetic waste water flow rate is 10 mL / minute (= 0.6 L / hour), the residence time (HRT) is 50 minutes, the pH in the tank is 8.8, and the MgCl ₂ addition amount is 0.4 mg-Mg / minute. The MAP fine particles were generated with stirring to generate MAP fine particles having a particle size of 0.1 to 0.5 mm, and 0.5 mL of the MAP fine particles was added to the reaction tower once a day.
[0036]
The size of the reaction tower is as follows.
[0037]
Reaction tower dimensions Diameter of small diameter part 1A: 3 cm
Height of small diameter part 1A: 1.7cm
Diameter of large diameter part 1C: 4cm
Total height of the large diameter part 1C and the enlarged diameter part 1B: 0.3 m
Tower capacity: 1.58L

[0038]
As a result, as shown in FIG. 2A, the average particle diameter of the obtained MAP particles was stable in the range of 0.7 to 0.9 mm. Also, the PO ₄ -P concentration of the treated water was stable at 8 to 10 mg / L as shown in FIG.
[0039]
Comparative Example 1
In Example 1, when the MAP was not circulated in the reaction tower and the MAP fine particles were not added in the MAP fine particle production tank, the same processing was performed. As shown in FIGS. As shown in FIG. 4), the initial phosphorus removal is performed well, but the PO ₄ -P concentration of the treated water is increased when the particle size of the MAP particles gradually increases and the average particle size is increased to about 2 mm. It worsened from 9 mg / L to 16 mg / L. This is presumably because the specific surface area of the particles in which the MAP generation reaction occurs due to the coarsening of the MAP particles is reduced and the flow of the MAP particles is inhibited, so that the MAP generation reaction rate is reduced.
[0040]
【The invention's effect】
As described above in detail, according to the dephosphorization apparatus of the present invention, MAP particles having a desired uniform particle diameter can be stably obtained when MAP particles are generated from phosphorus-containing water and dephosphorized. As described above, since the particle size of the MAP particles is stabilized, the reaction inhibition due to the outflow of the MAP fine particles or the coarsening of the MAP particles can be prevented, and an efficient dephosphorization treatment can be performed. Concentrated treated water can be obtained stably.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a dephosphorization apparatus of the present invention.
2 is a graph showing the results of Example 1, FIG. 2 (a) shows the change over time in the average particle size of the obtained MAP particles, and FIG. 2 (b) shows the PO ₄ -P concentration of treated water. Shows the change over time.
3 is a graph showing the results of Comparative Example 1, FIG. 3 (a) shows the change over time in the average particle size of the obtained MAP particles, and FIG. 3 (b) shows the PO ₄ -P concentration of treated water. The time-dependent change of is shown.
[Explanation of symbols]
1 reaction tower 7 treated water tank 20 MAP fine particle production tank

Claims

It has an inlet for phosphorus-containing water at the lower part of the tower and an outlet for treated water at the upper part of the tower, and has a small diameter part, an enlarged diameter part above the small diameter part, and a large diameter part above the enlarged diameter part. A reaction tower, means for adding fine particles of ammonium magnesium phosphate from the outside of the reaction tower, and extraction of the magnesium magnesium phosphate particles from the diameter-expanded portion of the reaction tower. A dephosphorization device comprising a circulating pipe and a pipe for circulating a part of the treated water taken out from the treated water outlet of the reaction tower to the lower part of the reaction tower ,
By adding the necessary amounts of phosphorus-containing water, magnesium salt and alkaline agent as raw water to the MAP fine particle production tank, the ammonium magnesium phosphate fine particles are slowly stirred for 5 to 60 minutes under the condition of pH 8-10. production was, dephosphorization and wherein the Oh Rukoto in microparticles of magnesium ammonium phosphate particle size 50Myuemu～1mm.