JP4618937B2 - How to remove phosphorus from wastewater. - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、化学工業、食品工業、医薬工業、肥料工業等の各種工場から出る排水や、下水処理場、し尿処理場等の処理施設から出る排水の処理に関し、より詳しくは、排水中にオルトリン酸イオン、ポリリン酸イオン、有機リン酸イオン等の形態で含まれているリンの除去方法の技術分野に属する。
【０００２】
【従来の技術】
従来、排水中のリンを除去するには、凝集剤として硫酸アルミニウム（硫酸バンド）、ポリ塩化アルミニウム（ＰＡＣ）等のアルミニウム塩や、硫酸第１鉄、塩化第２鉄等の鉄塩を用い、リンを凝集沈殿させる方法が一般的であるが、多量の凝集剤を連続して使用するため、処理コストが高く付き、また凝集剤から大量の沈殿物が汚泥として発生し、汚泥の再資源化も困難であったため、近時、排水を膜分離処理し、次にジルコニウム・フェライトを構成材料とするリン吸着剤でリンを吸着処理する排水のリン除去方法が、特開平11-147088号公報として提案され、処理コストが少なくてすみ、厄介な凝集沈殿物の発生がないリン除去方法として知られている。
【０００３】
【発明が解決しようとする課題】
上記の特開平11-147088号公報の先行技術は、吸着剤からのリン酸を脱離させるために苛性ソーダ(水酸化ナトリウム)を注入させて排出させるが、この排出した脱着液からリン酸を回収するときは、さらに苛性ソーダを注入してリン酸を常温で晶出させて回収していたが、回収率は50%前後と必ずしも高くはなかった。しかも、着脱液に更に大量の苛性ソーダを使用するため、処理液の処分もやっかいな問題であった。
また、吸着剤を蒸発固化する方法もあるが、熱管理がやっかいで経費も嵩むとう問題点があった。
【０００４】
本発明は、上記の問題点に鑑みて為されたもので、その課題は、排水のリン除去方法において、脱着液から過剰な薬剤を用いることなく、極めて効率よくリン酸を回収することであり、回収したリン酸が肥料等に再利用できるようにすることである。
【０００５】
【課題を解決するための手段】
上記の課題を解決するために、請求項１に記載の発明は、排水のリン除去方法において、膜分離法により処理された排水を吸着剤を充填した吸着塔に注入してリン酸を吸着剤に吸着させ、吸着剤の吸着飽和に達した場合には逆洗滌し、次にリン酸を吸着させた吸着塔に水酸化ナトリウム水溶液を注入してリン酸を脱着し、最初の逆洗滌分は前記吸着塔の処理工程前段の排水原液に戻し、以後の脱着液は冷却してリン酸を晶出させて回収するとともに液体分は処理工程前段の排水原液に戻すことを特徴とする排水のリン除去方法である。
【０００６】
削除
【０００７】
請求項２に記載の発明は、請求項１に記載の排水のリン除去方法において、前記脱着液の冷却温度を５から１０℃の範囲に制御することを特徴とする排水のリン除去方法である。
【０００８】
請求項３に記載の発明は、請求項１又は２のいずれかに記載の排水のリン除去方法において、排水をジルコニウム・フェライトの吸着剤を充填した二連の吸着塔のいずれか一方に注入してリン酸を吸着剤に吸着させ、吸着剤の吸着飽和に達した場合には吸着剤に水酸化ナトリウム水溶液を吸着塔の底部から注入してリン酸を脱着することを特徴とする排水のリン除去方法である。
【０００９】
削除
【００１０】
【発明の実施の形態】
次に、本発明に好適な実施の形態について、図面に基づいて本発明の排水のリン除去システムの実施例を説明する。
[実施例１]
第１の実施例を図１に沿って説明する。
図１において、化学工業、食品工業、医薬工業、肥料工業等の各種工場から出る排水や、下水処理場、し尿処理場等の処理施設から出る排水原液は、まず、原水調整槽(1)に一時貯留され、次に膜分離装置(2)に送られる、 膜分離装置(2)の槽内には、平膜モジュールを備えた濾過膜ユニット(2a) が配置されている。図示は省略するが、前記各平膜モジュールは、対向状に配置された２枚の平膜と、両平膜の周縁部間に配置された額縁状スペーサとよりなる。各平膜モジュールに、その中空部内と連通するように吸引管が接続され、すべての吸引管が１つの吸引ポンプ(3a) に接続されている。
濾過膜ユニット(2) の下には複数の散気管(4) が配され、散気管(4) にブロワにより空気が送り込まれる。
上記構成の膜分離装置(1) によって排水を処理し夾雑物や活性汚泥等を除いた後、この膜透過水を原水流入ラインＡに通過して、吸引ポンプ(3a)により二連の内のいずれか一方のリン吸着塔(7)に送る。
ここで、この膜透過水からの原水流入ラインＡの流量は、通常、リン吸着塔(7) 内の通水条件がＬＶ＝約４．４(m/h)、ＳＶ＝約２.２(1/h)となるように、一定流量でリン吸着塔(7) に供給されるが、リン吸着塔入口の膜分離処理水のｐＨは７前後でとしている。
【００１１】
リン吸着塔(7) には、塔底から約２/３の高さまでリン吸着剤(8)が充填され、底部に脱リン処理水ラインＢが配されていて、通常の運転状態では、処理水は脱リン処理水ラインＢによりｐＨ調整装置(9)に送られ、水酸化ナトリウム(苛性ソーダ)の添加等により許容範囲のｐＨとして最終処理水となって放流される。
リン吸着塔(7)としては、２塔(7a)(7b)を並列に設置して、一定期間毎に三方弁(5a.5b)で切替えて、交互に稼働させて装置全体としては連続して操業できるようにし、休んでいるリン吸着塔(7a)(7b)側は、この間に後述するように洗滌や吸着剤の活性化等のメンテナンス、および、リン酸を晶出させるための脱着水の回収を行う。
吸着剤(8)としては、ジルコニウム・フェライト(水和物)をベースとする武田薬品工業（株）製の「セブントールＰ」(登録商標)を使用する。この吸着剤は平均粒径約0.7mmの造粒品である。
【００１２】
ここで、ジルコニウム・フェライトをベースとする吸着剤(8)は、ｐＨ約１〜７の範囲でリン酸イオンをより多量に選択的に吸着する。この吸着剤を用いてｐＨ１〜８.６の酸性から中性域の液中でリン酸イオンの吸着操作を行った後、アルカリ性水溶液でリン酸イオンを脱離させ、ついでこの吸着剤を酸性水溶液で処理することにより、再生することができる。例えば、リン酸イオンを吸着させた本吸着剤を７重量％の水酸化ナトリウム水溶液中に数時間浸すことにより、吸着したリン酸イオンは脱着する。これを水洗して、１％の硫酸水溶液に数時間浸すことにより、本吸着剤は再活性化され初期の吸着性能を回復する。脱着に用いるアルカリ性水溶液は、水酸化カリウムや水酸化カリューム含む水溶液であって、アルカリ性水溶液のアルカリ濃度は０.１〜２０重量％程度であればよい。活性化に用いる酸性水溶液は塩酸、硝酸などの酸を含む水溶液であってよく、酸の濃度は０.１〜１０重量％程度であればよい。
【００１３】
この一連の脱着、活性化操作は、カラムに吸着剤を充填したまま行うことができ、吸着剤の吸着飽和に達した場合には、吸着操作終了させアルカリ性水溶液、酸性水溶液を順番にカラムに通水することにより、後述するように容易に再生を行うことができる。
この一連の脱着、活性化操作を行うのが、主に、硫酸循環・アルカリ供給ラインＣと、逆洗排水・硫酸循環ラインＤであり、アルカリ供給ラインＣには、洗滌のためのブロワ(10a)と洗滌水槽(10b)と水酸化ナトリウム水溶液槽(11)と硫酸水溶液槽(12)とが配備され、付随するポンプ（3c〜3b)と各種の二方弁(6a〜6d)が配備され、逆洗排水・硫酸循環ラインＤには三方弁(5d)と二方弁(6e,6f)が配備されている。
メンテナンスとともにリン酸を晶出させるための脱着水の回収を、脱着液ラインＥで行うが、この脱着液ラインＥには脱着液分離槽(13)と冷却装置(14)とこれに付随する三方弁(5c)と二方弁(6a,6c)が配設されている。
第１の実施例の特徴の１つは、排水処理の脱着液において、リン酸ナトリウム塩の晶出が、脱着液の水温を１０℃以下にすると著しく増加することを見出した点にある。これにより従来の水酸化ナトリウムを増量しなくても済むようにした点である。
【００１４】
次に、このリン酸の吸着剤から脱着、および、吸着剤の活性化操作の手順(イ)から(ル)を説明する。
[脱リン処理工程]
（イ）原水調整槽(1)および膜分離装置(2)により処理された排水を、ポンプ(3a)により連続的に吸着塔(7)に供給するが、先ず、リン吸着塔(7a)を稼働させる場合には、上流側の三方弁(5a)はリン吸着塔(7a)側に解放し、リン吸着塔(7b)側を閉じるとともに、下流側の三方弁(5b)はリン吸着塔(7a)側に解放し、リン吸着塔(7b)側を閉解放状態とし、膜透過水を吸引ポンプ(3a)でリン吸着塔(7a)に供給する。
そして、排水を吸着剤(ジルコニウム・フェライト)(8)に接触させ、排水中のリンを吸着剤に吸着させ、リンを除去した処理水として連続して放流させる。
なお、この状態では吸着塔(7b)は休止状態である。
（ロ）リン吸着塔(7a)でのリンの吸着剤の吸着飽和に達し吸着能力が低下すると、上流側の三方弁(5a)はリン吸着塔(7b)側に解放し、リン吸着塔(7a)側を閉じるとともに、下流側の三方弁(5b)はリン吸着塔(7a)側を閉じリン吸着塔(7b)側を解放状態とし、膜透過水を吸引ポンプ(3a)でリン吸着塔(7b)に供給し、吸着塔(7b)が稼働状態となり、吸着塔(7a)が休止状態となる。
【００１５】
[洗滌工程]
（ハ）休止状態にある吸着塔(7a)の内部を洗滌するが、硫酸循環・アルカリ供給ラインＣを用いて、洗滌のためのブロワ(10a)と洗滌水槽(10b)から二方弁(6b)を介して、吸着塔(7a)の底から塔内の閉塞防止のためエアーと水とを噴射して、通常の処理水の流れとは逆方向の洗滌を行っている。
この際、洗滌水は吸着塔(7a)に満杯になるが、この洗滌水は吸着塔(7a)の上部に設けられた逆洗排水・硫酸循環ラインＤによって、二方弁(6e)および三方弁(5d)を介して、処理工程前段である原水調整槽等に戻される。
（ニ）所定時間・所定量の逆洗滌が終了すると、エアーと水の噴射を止め、吸着塔(7a)に残っている洗滌水は、脱着液ラインＥを利用し、二方弁(6a)および三方弁(5c)を介して処理工程前段である排水原液の原水調整槽等に戻される。
【００１６】
[吸着剤リン脱着活性化工程]
（ホ）ポンプ(3b)を稼働させアルカリ水溶液槽(11)から水酸化ナトリウムを吸着塔(7a)の底から注水し、吸着剤からリン酸を離脱させて脱着液として排出する。
（へ）所定時間・所定量のアルカリ水溶液を吸着塔(7)が満水になるまで注入した後、三方弁(5c)を脱着液分離槽(13)側に開き、脱着水を脱着液分離槽(13)に排出する。
（ト）脱着液を排出し終わると三方弁(6a)を閉じ、硫酸水溶液槽(12)からポンプ(3c)を稼働し、硫酸水溶液を吸着塔(7a)の底から、逆洗排水・硫酸循環ラインＤ
を用いて循環注水させ、吸着剤を中和して活性化させる。
なお、(ホ)〜(ト)において、アルカリ水溶液や硫酸水溶液を吸着塔(7a)の底から注入することで、確実にこれらの水溶液が吸着剤(ジルコニウム・フェライト)(8)に接触し、リン酸の脱着を促進し、中和を促進させる。
（チ）吸着剤を中和して活性化させた後バルブ(6e)を開き、三方弁(5d)を硫酸水溶液槽(12)に硫酸水溶液にに戻すか、或いは、吸着塔(7a)の底から排出する。
【００１７】
[リン酸晶出工程]
（リ）一方、脱着水を脱着液分離槽(13)に排出するが、脱着液分離槽(13)は、冷却装置(14)により常に５℃から１０℃になるように制御装置(図示せず)に制御されている。
（ヌ）脱着液が５℃から１０℃に冷却されることにより、脱着液分離槽(13)内にはリン酸が晶出し、８０％以上晶出した時点で、フィルターで固液を分離し、晶出たリン酸を個体物として回収し、液体分である水酸化ナトリウム水溶液体も回収するが、バルブ(6g)によりＰＨ調整(図示せず)を行い、処理工程前段である排水原液の原水調整槽等に注入する。
なお、この水酸化ナトリウム水溶液体は、水酸化ナトリウム水溶液槽(11)に循環させてもよい。
【００１８】
[連続切替工程]
（ル）以上の[洗滌工程]と[吸着剤リン脱着活性化工程]と[リン酸晶出工程]が終了し、リン吸着塔(7b)でのリンの吸着剤の吸着飽和に達し吸着能力が低下すると、再び、(イ)の状態に戻し、連続して脱リン処理された処理水が放流される。
上記のような構成および操作であるので、上記のポンプや三方弁や二方弁は自動制御されるようにして、連続操業を自動化することも可能である。
【００１９】
ここで、前記[リン酸晶出工程]でのリン酸塩の回収率について、図２を用いて説明する。
図２は、次の表１、表２をグラフにしたもので、横軸は脱着液の水温で縦軸はリン酸のリン回収率である。
表１での試験は、PO4 3- 濃度27200(mg/L),NaOH(水酸化ナトリウム) 濃度19000(mg/l)の着脱液に７％になるようにNaOHを添加、溶解後所定の水温に調整、水温が安定した後に５Aろ紙で固液分離し、ろ液の分析結果から回収率を算出した。
【００２０】
[表１:ろ液分析結果]
水温 pH NaOH PO4 3- 回収率
℃ (mg/L) (mg/L) ％
５ 12.4 62600 2600 90.4
８ 12.4 61800 2660 90.2
10 12.2 60000 2700 90.1
20 12.9 58200 9400 65.4
30 13.1 62000 18200 33.1
【００２１】
図２に示されるように、２０℃以上では回収率は約６６％以下である。これは、冷却装置(14)による温度制御がない場合には、水酸化ナトリウムによる化学反応が生じているため、通常は冬場でも１５℃以上であって、２０℃前後では回収率は６０％程度である。したがって、５℃から１０℃になるよおに制御するのが好ましく、更に好ましくは、８℃から１０℃に制御するのが効率的である。
本実施例では、薬品である水酸化ナトリウムを極力使用しないようにするため、脱着液には水酸化ナトリウムを添加していない。
次の表２は、PO4 3- 濃度27200(mg/L)の着脱液に水酸化ナトリウム(NaOH)を添加せず、同様の方法で水温調整のみで結晶出を行ったものである。
【００２２】
[表２:ろ液分析結果]
水温 pH PO4 3- 回収率
℃ (mg/L) ％
５ 12.4 4488 83.5
８ 12.3 4760 82.0
10 12.3 5413 80.1
20 12.5 14797 45.6
30 13.0 21461 21.1
【００２３】
本実施例では、前記（４）の工程もあって、ほぼ８０％以上の回収率であった。 表２および図２から判るように、１０℃以下から急激に回収率が向上するが、５℃以下にしても回収率の向上は見られず、冷却するエネルギーを浪費するので、５℃から１０℃になるよおに制御するのが好ましく、更に好ましくは、８℃から１０℃に制御するのが効率的である。
このようにして、水酸化ナトリウムで脱着したリン酸イオンは、過剰な水酸化ナトリウムを使用することがなく、リン酸ナトリウムの結晶で回収することが可能であって、貴重なリン資源として再使用することができる。
【００２４】
削除
【００２５】
なお、本発明の特徴を損なうものでなければ、上記の実施例に限定されないことは勿論であり、例えば、断続的操業になるが、吸着塔を一つとしてもよい。
【００２６】
【発明の効果】
以上説明したように、請求項１及び２に記載の発明によれば、着脱液の晶出に水酸化ナトリウム水溶液を補充する必要がなく、従来に比べて水酸化ナトリウム水溶液の使用量が格段に少なくなり、かつ、極めて効率がよくリン酸を回収することであり、回収したリン酸が肥料等に再利用できる。
請求項３に記載の発明によれば、アルカリ水溶液や硫酸水溶液を吸着塔の底から注入することで、確実にこれらの水溶液が吸着剤に接触し、リン酸の脱着を促進し、吸着剤中和を促進させて、吸着剤のリン脱着活性化が一層促進される。
【図面の簡単な説明】
【図１】 本発明を使用するのに好適な排水のリン除去システムの第１の実施例の排水処理システムの概略図である。
【図２】 本件発明の第１の実施例の晶出の実験値のグラフの図である。
【符号の説明】
Ａ…原水流入ライン、Ｂ…処理水ライン、Ｃ…硫酸循環・アルカリ共通ライン、Ｄ…逆洗排水・硫酸循環ライン、Ｅ…脱着液ライン
１…原水調整槽(処理工程前段)、２…膜分離装置、2a…濾過膜ユニット、
3a,3b,3c…ポンプ、４…散気管、5a,5b.5c,5d…三方弁、
6a,6b,6c,6d,6e,6f…二方弁、(7),7a,7b…リン吸着塔、
８…吸着剤(ジルコニウム・フェライト)、９…ｐＨ調整装置、
10…放流槽、10a…ブロワ、10b…洗滌水槽、
11…水酸化ナトリウム水溶液槽、12…硫酸水溶液、13…脱着液分離槽、
14…冷却装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the treatment of wastewater from various factories such as the chemical industry, food industry, pharmaceutical industry, fertilizer industry, and wastewater from treatment facilities such as sewage treatment plants and human waste treatment plants. The present invention belongs to the technical field of a method for removing phosphorus contained in the form of acid ions, polyphosphate ions, organic phosphate ions, and the like.
[0002]
[Prior art]
Conventionally, in order to remove phosphorus in waste water, aluminum salts such as aluminum sulfate (sulfuric acid band) and polyaluminum chloride (PAC), and iron salts such as ferrous sulfate and ferric chloride are used as flocculants. The method of coagulating and precipitating phosphorus is common, but since a large amount of coagulant is used continuously, the processing cost is high, and a large amount of precipitate is generated from the coagulant as sludge, and sludge is recycled. since it is also difficult, recent, draining the membrane separation process, phosphorus removal methods wastewater adsorption treatment phosphorus in phosphorus adsorbent then the zirconium ferrite as the constituting materials, JP-a-11-147088 JP Is known as a phosphorus removal method that requires less processing costs and does not generate troublesome aggregated precipitates.
[0003]
[Problems to be solved by the invention]
Prior art of the above-mentioned Japanese Patent Application Laid-Open No. 11-147088 is injecting and discharging caustic soda (sodium hydroxide) in order to desorb phosphoric acid from the adsorbent, and recovering phosphoric acid from this desorbed liquid when, which had been recovered phosphate was cold in crystallized by further injection of caustic soda, recovery was not always higher around 50%. Moreover, since a larger amount of caustic soda is used for the detachable liquid, disposal of the processing liquid is also a troublesome problem.
In addition, there is a method of evaporating and solidifying the adsorbent, but there is a problem that heat management is troublesome and cost increases.
[0004]
The present invention has been made in view of the above-mentioned problems, and its problem is to recover phosphoric acid very efficiently without using excessive chemicals from the desorption liquid in the phosphorus removal method of waste water. In other words, the collected phosphoric acid can be reused as fertilizer.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention described in claim 1 is a method for removing phosphorus from wastewater by injecting the wastewater treated by the membrane separation method into an adsorption tower filled with an adsorbent, so that phosphoric acid is adsorbed. When the adsorption saturation of the adsorbent is reached, backwashing is performed, and then sodium hydroxide aqueous solution is injected into the adsorption tower on which phosphoric acid is adsorbed to desorb phosphoric acid. Returning to the waste water stock solution before the treatment step of the adsorption tower, cooling the subsequent desorption solution to crystallize and recovering phosphoric acid, and returning the liquid content to the waste water stock solution before the treatment step. It is a removal method.
[0006]
Delete [0007]
The invention according to claim 2 is the method for removing phosphorus from waste water according to claim 1 , wherein the cooling temperature of the desorption liquid is controlled in the range of 5 to 10 ° C. .
[0008]
The invention described in claim 3 is the phosphorus removal process of waste water according to claim 1 or 2, drain the zirconia c adsorbents beam ferrite in one of the adsorption tower of duplicate filled Drainage characterized by adsorbing and adsorbing phosphoric acid to the adsorbent, and when adsorbing saturation of the adsorbent is reached, a sodium hydroxide aqueous solution is injected into the adsorbent from the bottom of the adsorption tower to desorb phosphoric acid. This is a phosphorus removal method.
[0009]
Delete [0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, the preferred embodiment of the present invention will be described with reference to the drawings and examples of the wastewater phosphorus removal system of the present invention.
[Example 1]
A first embodiment will be described with reference to FIG.
In Fig. 1, wastewater from various factories such as chemical industry, food industry, pharmaceutical industry, and fertilizer industry, and wastewater stock solution from treatment facilities such as sewage treatment plants and human waste treatment plants are first put into the raw water adjustment tank (1). A filtration membrane unit (2a) having a flat membrane module is disposed in a tank of the membrane separation device (2) that is temporarily stored and then sent to the membrane separation device (2). Although not shown, each of the flat membrane modules is composed of two flat membranes arranged opposite to each other and a frame-like spacer arranged between the peripheral portions of both flat membranes. A suction pipe is connected to each flat membrane module so as to communicate with the inside of the hollow portion, and all the suction pipes are connected to one suction pump (3a).
A plurality of diffuser tubes (4) are arranged under the filtration membrane unit (2), and air is sent to the diffuser tubes (4) by a blower.
After the wastewater is treated by the membrane separation device (1) having the above configuration to remove impurities and activated sludge, the membrane permeated water is passed through the raw water inflow line A, and the suction pump (3a) Send to either phosphorus adsorption tower (7).
Here, the flow rate of the raw water inflow line A from this membrane permeated water is usually LV = about 4.4 (m / h), SV = about 2.2 ( 1 / h), it is supplied to the phosphorus adsorption tower (7) at a constant flow rate, and the pH of the membrane separation treated water at the phosphorus adsorption tower inlet is about 7.
[0011]
The phosphorus adsorption tower (7) is filled with a phosphorus adsorbent (8) to a height of about 2/3 from the bottom of the tower, and a dephosphorization treatment water line B is arranged at the bottom. water is sent to p H adjusting device (9) by dephosphorylation treated water line B, it is discharged to a final treated water as p H tolerance by addition of a sodium hydroxide (caustic soda).
As the phosphorus adsorption tower (7), two towers (7a) and (7b) are installed in parallel, switched by a three-way valve (5a.5b) at regular intervals, and operated alternately, so that the entire system is continuous. The rest of the phosphorus adsorption towers (7a) and (7b) that are resting are operated during this period, as described later, for maintenance such as washing and adsorbent activation, and desorption water for crystallizing phosphoric acid. To collect.
The adsorbent (8), using the zirconium-ferrite (hydrate) the base to Takeda Chemical Industries Co., Ltd. "Seven Thor P" (registered trademark). This adsorbent is a granulated product having an average particle size of about 0.7 mm.
[0012]
Here, zirconium ferrite-based adsorbing agent (8) is more heavily selectively adsorbing phosphate ions in the range of p H of about 1-7. Using this adsorbent, phosphate ions are adsorbed in an acidic to neutral range of pH 1 to 8.6, and then the phosphate ions are desorbed with an alkaline aqueous solution. Can be played back by processing. For example, the adsorbed phosphate ions are desorbed by immersing the adsorbent adsorbed with phosphate ions in a 7% by weight sodium hydroxide aqueous solution for several hours. This is washed with water and immersed in a 1% sulfuric acid aqueous solution for several hours, whereby the present adsorbent is reactivated and the initial adsorption performance is restored. The alkaline aqueous solution used for desorption is an aqueous solution containing potassium hydroxide or potassium hydroxide, and the alkaline concentration of the alkaline aqueous solution may be about 0.1 to 20% by weight. The acidic aqueous solution used for the activation may be an aqueous solution containing an acid such as hydrochloric acid or nitric acid, and the acid concentration may be about 0.1 to 10% by weight.
[0013]
This series of desorption and activation operations can be performed while the column is filled with an adsorbent. When the adsorption saturation of the adsorbent is reached, the adsorption operation is terminated and an alkaline aqueous solution and an acidic aqueous solution are sequentially passed through the column. The water can be easily regenerated as described later.
This series of desorption and activation operations is mainly performed in the sulfuric acid circulation / alkali supply line C and the backwash drainage / sulfuric acid circulation line D. The alkali supply line C includes a blower for washing (10a ), Washing water tank (10b), sodium hydroxide aqueous solution tank (11) and sulfuric acid aqueous solution tank (12), and accompanying pumps (3c-3b) and various two-way valves (6a-6d) The backwash drainage / sulfuric acid circulation line D is provided with a three-way valve (5d) and a two-way valve (6e, 6f).
The desorption water for crystallizing phosphoric acid together with maintenance is collected in the desorption liquid line E. The desorption liquid line E has a desorption liquid separation tank (13), a cooling device (14), and the three sides associated with it. A valve (5c) and a two-way valve (6a, 6c) are provided.
One of the features of the first embodiment is that it has been found that the crystallization of sodium phosphate salt increases significantly when the water temperature of the desorption liquid is 10 ° C. or less in the desorption liquid of the waste water treatment. As a result, the amount of conventional sodium hydroxide need not be increased.
[0014]
Next, procedures (i) to (l) for the operation of desorbing the phosphoric acid from the adsorbent and activating the adsorbent will be described.
[Dephosphorization process]
(B) The wastewater treated by the raw water adjustment tank (1) and the membrane separator (2) is continuously supplied to the adsorption tower (7) by the pump (3a). First, the phosphorus adsorption tower (7a) When operating, the upstream three-way valve (5a) is released to the phosphorus adsorption tower (7a) side, the phosphorus adsorption tower (7b) side is closed, and the downstream three-way valve (5b) is a phosphorus adsorption tower ( 7a) is released, the phosphorus adsorption tower (7b) side is closed, and the membrane permeate is supplied to the phosphorus adsorption tower (7a) by the suction pump (3a).
Then, the waste water is brought into contact with the adsorbent (zirconium U-time ferrite) (8), the phosphorus in the wastewater is adsorbed on the adsorbent, it is discharged continuously as treated water to remove phosphorus.
In this state, the adsorption tower (7b) is in a dormant state.
(B) When the adsorption capacity of the phosphorus adsorbent reaches the phosphorus adsorption tower (7a) and the adsorption capacity decreases, the upstream three-way valve (5a) is released to the phosphorus adsorption tower (7b) side and the phosphorus adsorption tower ( 7a) side is closed and the downstream three-way valve (5b) closes the phosphorus adsorption tower (7a) side and opens the phosphorus adsorption tower (7b) side, and the membrane permeated water is sucked into the phosphorus adsorption tower by the suction pump (3a). (7b), the adsorption tower (7b) becomes active, and the adsorption tower (7a) becomes inactive.
[0015]
[Washing process]
(C) The inside of the adsorption tower (7a) in the resting state is washed, but using the sulfuric acid circulation / alkali supply line C, the two-way valve (6b) from the washing blower ( 10a ) and the washing water tank ( 10b ) In order to prevent clogging in the tower from the bottom of the adsorption tower (7a), air and water are jetted to perform washing in the direction opposite to the flow of normal treated water.
At this time, the washing water fills the adsorption tower (7a), but this washing water is fed back to the two-way valve (6e) and three-way by the backwash drainage / sulfuric acid circulation line D provided at the upper part of the adsorption tower (7a). Via the valve (5d), it is returned to the raw water adjustment tank or the like, which is the previous stage of the treatment process.
(D) When the predetermined amount of backwashing is completed for a predetermined time, the air and water injection is stopped, and the washwater remaining in the adsorption tower (7a) is removed from the two-way valve (6a) using the desorption liquid line E. And it is returned to the raw water adjustment tank etc. of the drainage raw solution which is a front | former stage of a process through a three-way valve (5c).
[0016]
[Adsorbent phosphorus desorption activation process]
(E) The pump (3b) is operated, sodium hydroxide is poured from the bottom of the alkaline aqueous solution tank (11) from the bottom of the adsorption tower (7a), phosphoric acid is released from the adsorbent and discharged as a desorption liquid.
(F) After injecting a predetermined amount of alkaline aqueous solution for a predetermined time until the adsorption tower (7) is full, open the three-way valve (5c) to the desorption liquid separation tank (13) side, and remove the desorption water from the desorption liquid separation tank. Discharge to (13).
(G) When the desorbed liquid has been drained, the three-way valve (6a) is closed, the pump (3c) is operated from the sulfuric acid aqueous solution tank (12), and the sulfuric acid aqueous solution is fed back from the bottom of the adsorption tower (7a). Circulation line D
Use water to circulate water and neutralize and activate the adsorbent.
The contact in (e) - in (g), the adsorption tower of an alkali aqueous solution or aqueous sulfuric By injecting from the bottom of (7a), ensures these aqueous solutions adsorbent (zirconium U-time ferrite) (8) And promotes desorption of phosphoric acid and promotes neutralization.
(H) After neutralizing and activating the adsorbent, the valve (6e) is opened, and the three-way valve (5d) is returned to the sulfuric acid aqueous solution tank (12) or returned to the sulfuric acid aqueous solution, or the adsorption tower (7a) Drain from the bottom.
[0017]
[Phosphate crystallization process]
(L) On the other hand, the desorbed water is discharged to the desorbed liquid separation tank (13). The desorbed liquid separating tank (13) is always controlled by the cooling device (14) so that the temperature is kept at 5 to 10 ° C. Control).
(N) When the desorption liquid is cooled from 5 ° C. to 10 ° C., phosphoric acid is crystallized in the desorption liquid separation tank (13). The crystallized phosphoric acid is recovered as a solid, and the sodium hydroxide aqueous solution, which is a liquid component, is also recovered, but the pH is adjusted (not shown) by a valve (6 g), Inject into raw water adjustment tank.
The sodium hydroxide aqueous solution may be circulated in the sodium hydroxide aqueous solution tank (11).
[0018]
[Continuous switching process]
(L) The above [washing process], [adsorbent phosphorus desorption activation process] and [phosphoric acid crystallization process] have been completed, and the adsorption capacity of the phosphorus adsorbent in the phosphorus adsorption tower (7b) has been reached. Is lowered, the state is returned to the state (a) again, and the treated water that has been continuously dephosphorized is discharged.
Because of the configuration and operation as described above, the continuous operation can be automated by automatically controlling the pump, the three-way valve, and the two-way valve.
[0019]
Here, the phosphate recovery rate in the [phosphoric acid crystallization step] will be described with reference to FIG.
FIG. 2 is a graph of the following Tables 1 and 2. The horizontal axis represents the water temperature of the desorption liquid, and the vertical axis represents the phosphorus recovery rate of phosphoric acid.
In the test in Table 1, NaOH was added to a detachable solution of PO 4 3- concentration 27200 (mg / L) and NaOH ( sodium hydroxide ) concentration 19000 (mg / l) so that it might become 7%. After adjusting to the water temperature and stabilizing the water temperature, solid-liquid separation was performed with 5A filter paper, and the recovery rate was calculated from the analysis result of the filtrate.
[0020]
[Table 1: Results of filtrate analysis]
Water temperature pH NaOH PO 4 3- Recovery ℃ (mg / L) (mg / L)%
5 12.4 62600 2600 90.4
8 12.4 61800 2660 90.2
10 12.2 60000 2700 90.1
20 12.9 58 200 9400 65.4
30 13.1 62000 18200 33.1
[0021]
As shown in FIG. 2, the recovery rate is about 66% or less at 20 ° C. or higher. This is because, when there is no temperature control by the cooling device (14), a chemical reaction is caused by sodium hydroxide, so it is usually 15 ° C or higher even in winter, and the recovery rate is around 60% at around 20 ° C. It is. Therefore, it is preferable to control the temperature from 5 ° C. to 10 ° C., and more preferably from 8 ° C. to 10 ° C.
In this embodiment, sodium hydroxide is not added to the desorption liquid in order to minimize the use of sodium hydroxide as a chemical.
The following Table 2 shows the crystallization by adjusting the water temperature in the same manner without adding sodium hydroxide ( NaOH) to the removable solution having a PO 4 3− concentration of 27200 (mg / L).
[0022]
[Table 2: Filtration analysis results]
Water temperature pH PO 4 3- Recovery ℃ (mg / L)%
5 12.4 4488 83.5
8 12.3 4760 82.0
10 12.3 5413 80.1
20 12.5 14797 45.6
30 13.0 21461 21.1
[0023]
In this example, the recovery rate was approximately 80% or more due to the step (4). As can be seen from Table 2 and FIG. 2, the recovery rate is drastically improved from 10 ° C. or lower. However, even if the temperature is 5 ° C. or lower, the recovery rate is not improved, and energy for cooling is wasted. It is preferable to control the temperature so that the temperature becomes 0 ° C., and it is more efficient to control the temperature from 8 ° C. to 10 ° C.
In this way, phosphate ions desorbed with sodium hydroxide can be recovered in the form of sodium phosphate crystals without using excess sodium hydroxide and reused as a valuable phosphorus resource. can do.
[0024]
Delete [0025]
It should be noted that the present invention is not limited to the above-described embodiment as long as the characteristics of the present invention are not impaired. For example, although intermittent operation is performed, one adsorption tower may be used.
[0026]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, it is not necessary to replenish the detachable liquid with the sodium hydroxide aqueous solution, and the amount of the sodium hydroxide aqueous solution used is remarkably higher than before. This is to reduce the amount of phosphoric acid with extremely high efficiency, and the collected phosphoric acid can be reused as a fertilizer.
According to the invention described in claim 3 , by injecting an aqueous alkali solution or an aqueous sulfuric acid solution from the bottom of the adsorption tower, these aqueous solutions are surely brought into contact with the adsorbent, thereby promoting the desorption of phosphoric acid. by promoting the sum, phosphorus desorption activation of adsorbent Ru is further promoted.
[Brief description of the drawings]
FIG. 1 is a schematic view of a wastewater treatment system according to a first embodiment of a wastewater phosphorus removal system suitable for using the present invention.
FIG. 2 is a graph of experimental values for crystallization according to the first embodiment of the present invention.
[Explanation of symbols]
A ... Raw water inflow line, B ... Treatment water line, C ... Sulfuric acid circulation / alkali common line, D ... Backwash drainage / sulfuric acid circulation line, E ... Desorption liquid line 1 ... Raw water adjustment tank (front stage of treatment process), 2 ... Membrane Separator, 2a ... filtration membrane unit,
3a, 3b, 3c ... pump, 4 ... diffuser, 5a, 5b.5c, 5d ... three-way valve,
6a, 6b, 6c, 6d, 6e, 6f ... two-way valve, (7), 7a, 7b ... phosphorus adsorption tower,
8 ... adsorbent (zirconium U-time ferrite), 9 ... p H adjusting device,
10 ... Release tank, 10a ... Blower, 10b ... Washing water tank ,
11 ... Sodium hydroxide aqueous solution tank, 12 ... Sulfuric acid aqueous solution, 13 ... Desorption liquid separation tank,
14 ... Cooling system
Claims (3)
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| JP2001181971A JP4618937B2 (en) | 2001-06-15 | 2001-06-15 | How to remove phosphorus from wastewater. |
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| JP2010197945A Division JP2010264457A (en) | 2010-09-03 | 2010-09-03 | Method of removing phosphorus in waste water |
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| JP4657680B2 (en) * | 2004-11-05 | 2011-03-23 | 悠平 稲森 | Recovery method of phosphorus component |
| JP2010069413A (en) * | 2008-09-18 | 2010-04-02 | Cosmo Oil Co Ltd | Organic waste water treatment method |
| JP5443059B2 (en) * | 2009-05-29 | 2014-03-19 | 株式会社東芝 | Water treatment equipment |
| JP5518372B2 (en) * | 2009-05-29 | 2014-06-11 | 株式会社東芝 | Water treatment equipment |
| JP5020397B1 (en) * | 2011-06-28 | 2012-09-05 | 株式会社アサカ理研 | Water treatment system and water treatment method |
| JP6989840B2 (en) * | 2017-06-30 | 2022-01-12 | ▲高▼橋金属株式会社 | Phosphoric acid recovery method |
| JP7061452B2 (en) | 2017-12-04 | 2022-04-28 | 活材ケミカル株式会社 | Phosphoric acid production method and purification method |
| CN112978845A (en) * | 2021-04-14 | 2021-06-18 | 南京简迪环境工程有限公司 | Recycling treatment process for 1, 3-cyclohexanedione wastewater |
| CN113185022A (en) * | 2021-04-20 | 2021-07-30 | 福建省芝星炭业股份有限公司 | Emission reduction method for recycling phosphorus-containing wastewater of activated carbon by phosphoric acid method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62289288A (en) * | 1986-06-10 | 1987-12-16 | Kubota Ltd | Treatment of phosphorus-containing waste liquid |
| JPH07256274A (en) * | 1994-03-22 | 1995-10-09 | Nippon Chem Ind Co Ltd | Treatment of sodium phosphate-containing waste fluid and recovery of sodium phosphate |
| JPH11147088A (en) * | 1997-09-11 | 1999-06-02 | Hitachi Zosen Corp | Dephosphorization of waste water |
-
2001
- 2001-06-15 JP JP2001181971A patent/JP4618937B2/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62289288A (en) * | 1986-06-10 | 1987-12-16 | Kubota Ltd | Treatment of phosphorus-containing waste liquid |
| JPH07256274A (en) * | 1994-03-22 | 1995-10-09 | Nippon Chem Ind Co Ltd | Treatment of sodium phosphate-containing waste fluid and recovery of sodium phosphate |
| JPH11147088A (en) * | 1997-09-11 | 1999-06-02 | Hitachi Zosen Corp | Dephosphorization of waste water |
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