JP3854471B2

JP3854471B2 - Water purification equipment

Info

Publication number: JP3854471B2
Application number: JP2001064293A
Authority: JP
Inventors: 邦雄海老江; 友明宮ノ下
Original assignee: Organo Corp
Current assignee: Organo Corp
Priority date: 2001-03-08
Filing date: 2001-03-08
Publication date: 2006-12-06
Anticipated expiration: 2021-03-08
Also published as: JP2002263660A

Description

【０００１】
【発明の属する技術分野】
本発明は、無機凝集剤を混合後に有機高分子凝集剤（ポリマー）を混合し凝集沈殿処理を行う凝集沈殿処理装置と、凝集沈殿処理水について砂ろ過処理を行う砂ろ過装置を有する浄水処理装置に関する。
【０００２】
【従来の技術】
従来より河川水、湖沼水等の表流水を原水とする浄水処理において、凝集沈殿処理と砂ろ過を組み合わせた処理が広く採用されている。
【０００３】
この凝集沈殿処理では、アルミ系や鉄系の無機凝集剤が利用されているが、これら無機凝集剤に有機高分子凝集剤を併用する場合も多い。これは、ポリマーを利用することで、微細な無機凝集剤フロックや懸濁物質を容易に粗大化でき、沈降速度を上昇して良好な沈殿上澄み液を安定して得ることができるからである。
【０００４】
そこで、良好なフロックが形成されるように凝集条件を決定している。通常の場合、ポリマー添加後の急速撹拌強度をＧ値で３００ｓｅｃ^−１（以下ｓ^−１と記す）未満、急速撹拌時間を５分未満になるようにしている。これによって、フロックの最大成長径は１０ｍｍ前後あるいはそれ以上に達し、沈殿池におけるフロック沈降速度が上昇し、沈殿上澄み液の水質を向上することができる。
【０００５】
【発明が解決しようとする課題】
ところが、フロックの成長を優先させて、撹拌強度を３００ｓ^−１未満としたり、急速撹拌時間を５分未満になるようすると、沈殿池でのフロックの除去性は向上し、沈殿上澄み水の濁度やＳＳ（懸濁物質濃度）といった定量的指標でみるとその絶対値は小さくなる。しかし、このような凝集では微小な粒子がフロックに取り込まれず、これがろ過池に供給されてろ過抵抗が増加しやすいという問題があった。そして、ろ過抵抗が上昇しやすいと、逆洗頻度が増加し逆洗が遅れるとブレークスルーが発生し、処理水質が悪化してしまうという問題があった。
【０００６】
一方、ポリマー添加後の急速撹拌の撹拌強度を、Ｇ値で３００ｓ^−１以上とし、５分以上行うと、撹拌強度が比較的強いことにより、フロックの最大成長径が数ｍｍにとどまる。このため、フロックの沈降速度は、無機単独の場合に比べそれほど増加せず、沈殿処理水の濁度も攪拌強度を弱くした場合のようによくならない。このため、ポリマーを添加したにもかかわらず沈殿池を小さくできないという問題があった。
【０００７】
本発明は上記課題に鑑みなされたものであり、最終的な処理水水質を向上することができる浄水装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明は、無機凝集剤を混合後に有機高分子凝集剤を混合し凝集沈殿処理を行う凝集沈殿処理装置と、凝集沈殿処理水について砂ろ過処理を行う砂ろ過装置を有する浄水処理装置であって、前記有機高分子凝集剤の混和を撹拌強度Ｇ値で３００〜１０００ｓｅｃ^−１で５分以上行うとともに、前記砂ろ過装置の前段で繊維をろ材に用いた繊維ろ過装置による粗ろ過処理を行うことを特徴とする。
【０００９】
このように、比較的強い攪拌で、有機高分子凝集剤を混合することで、有機高分子凝集剤により、微細な懸濁物質を細くすることができる。一方、このような強い攪拌を行うと、フロック径が十分大きくならず、微細フロックが沈殿池より流出する可能性が高いが、これは繊維ろ過で除去することができる。繊維ろ過器はろ過速度を大きくとれるため、装置の全体としての大きさ（浄水装置全体）を小さくできる。そして、繊維ろ過器の処理水には、微細懸濁物質が非常に少ないため、砂ろ過供給水濁度が安定し、砂ろ過装置におけるろ過抵抗の低減が図れる。
【００１０】
また、前記凝集沈殿装置の表面負荷率（単位時間の処理水量／沈殿池の有効断面積）が３．５ｍ／時以上、前記繊維ろ過装置のろ過速度が１０ｍ／時以上であることが好適である。
【００１１】
また、前記繊維ろ過装置のろ材が長さ５０ｃｍ〜３００ｃｍの長繊維束であることが好適である。
【００１２】
【発明の実施の形態】
以下、本発明の実施形態について、図面に基づいて説明する。
【００１３】
河川水、湖沼水等の表流水からなる原水は、無機混和池１０に導入される。この無機混和池１０には、攪拌翼１２ａと、これを回転させるモータ１２ｂからなる攪拌機１２が配置されている。また、この無機混和池１０には、無機凝集剤タンク１４内の無機凝集剤がポンプ１６によって供給される。無機凝集剤としては、例えばＰＡＣ（ポリ塩化アルミニウム：Ａｌ_２Ｏ_３１０％含有）が利用される。なお、この無機混和池１０の急速攪拌強度は通常３００ｓ^−１未満、滞留時間は５分未満であるが、これに限定されない。
【００１４】
次に、無機凝集剤が混合された水は、高分子混和池１８に導入される。この高分子混和池１８には、攪拌翼２０ａと、これを回転させるモータ２０ｂからなる攪拌機２０が配置されており、また高分子凝集剤タンク２２内の高分子凝集剤ががポンプ２４によって供給される。高分子凝集剤としては、例えばノニオン性アクリルアミドポリマーが利用される。また、アニオン性アクリルアミドポリマーが好適な場合もあるが、これらに限定されるものではない。この高分子混和池１８の急速攪拌強度は３００ｓ^−１以上、滞留時間は５分以上に設定されている。
【００１５】
高分子混和池１８からの無機凝集剤および高分子凝集剤が混合された水は、凝集池２６に導入される。この凝集池２６には横軸パドル式の緩速攪拌機２８が設けられており、ここで緩速攪拌されフロックの粗大化が図られる。
【００１６】
そして、無機凝集剤および高分子凝集剤によりフロック形成された水が沈殿池３０に導入され、ここで固形物が沈殿される。この沈殿池３０で沈殿された固形物は汚泥として系外に排除され、上澄み水は繊維ろ過器３２に導入される。
【００１７】
この繊維ろ過器３２は、特公平５−１２００２号公報、特公平５−１１４８２号公報、特許第２７９９３７６号公報などに記載されている長繊維束を利用したものが好適である。この繊維ろ過器３２では、ろ過塔の底部近傍に支持体を設け、この上方に長さ５０ｃｍ〜３００ｃｍの長繊維束の下端を固定するとともに、上端を自由端とする。そして、この長繊維束をろ過塔内にほぼ直立状態を維持するように充填し、ろ過体を形成する。そして、ろ過塔内に下降流で水を通過させてろ過体により懸濁物質を捕捉除去する。このような繊維ろ過器３２は、比較的空隙率が高く、砂ろ過池などに比べろ過速度を十分大きくとれ、砂ろ過池に流入する水についての粗ろ過が行える。すなわち、砂ろ過において、ろ過抵抗上昇の原因となる微細なフロックを効果的に除去することができる。なお、長繊維束の場合、このようなろ過の際にその長さが上述のように５０ｃｍ〜３００ｃｍが好適である。
【００１８】
この繊維ろ過器３２のろ過処理水は、次に砂ろ過池３４に供給され、残留する懸濁物質がろ過処理される。この砂ろ過池３４は、例えばアンスラサイト、ケイ砂の二層で形成されており、比較的精密なろ過を行う。これによって、水道水として配水できる水質のろ過処理水が安定して得られる。
【００１９】
ろ過処理水は、処理水タンク３６に貯留され、消毒された後配水される。また、処理水タンク３６内の処理水は、逆洗ポンプ３８によって、砂ろ過池３４、繊維ろ過器３２の底部に供給できるようになっており、これによって砂ろ過池３４、繊維ろ過器３２を逆洗できる。また、砂ろ過池３４、繊維ろ過器３２の底部にはブロア４０からの空気も供給できるようになっており、これによって空気逆洗も行われる。
【００２０】
このような浄水装置において、沈殿池３０からの沈殿処理水に微細なフロックが含まれても、この懸濁物質は繊維ろ過器３２において除去される。繊維ろ過器３２は、元々空隙率が高く、懸濁物質の保持容量が大きい。そこで、沈殿処理水中の懸濁物質量が増えても、その繊維ろ過水における処理水質の変動はあまりない。沈殿処理水が、砂ろ過池３４に直接供給される場合には、沈殿処理水中の懸濁物質量が増えるとすぐに目詰まり発生などの問題が生じるが、繊維ろ過器３２を設けることでこのような問題が生じない。
【００２１】
従って、本実施形態の浄水処理装置では、沈殿池３０の表面負荷率を比較的大きくすることにより沈殿池３０を小さくできる。また、繊維ろ過器３２は、ろ過速度を大きくとれるため、小型にできる。そして、本実施形態では、高分子混和池１８において、攪拌強度を３００ｓ^−１以上、滞留時間を５分以上に設定している。これによって、高分子凝集剤が無機混和池１０から供給される水と確実に混合される。そして、このような比較的強力な攪拌によって、フロックサイズは小さくなるが、高分子凝集剤に微細な懸濁物質が捕捉される。このような凝集処理によって沈殿池３０で得られる上澄み水は、比較的にＳＳの多いものとなる。しかし、これらの多くは繊維ろ過器３２において除去される。そして、砂ろ過池３４に供給される水には微細な懸濁質はほとんど含まれなくなり、砂ろ過池３４におけるろ過処理の負荷を減少して好適なろ過処理が行える。
【００２２】
すなわち、高分子凝集剤混合後の攪拌を弱くすると、フロックは粗大化するが、微細な懸濁物質が残り、砂ろ過池３４におけるろ過抵抗が大きくなる。本実施形態によれば、攪拌強度の強い高分子混和池１８と、繊維ろ過器３２と、砂ろ過池３４を組み合わせることによって、装置の全体としての大きさを小さくして、良好な最終処理水を得ることができる。
【００２３】
なお、本実施形態では、無機凝集剤にＰＡＣを用いているが、硫酸バンド、塩化第二鉄、硫酸第二鉄、ポリ硫酸アルミニウム・鉄等の鉄やアルミニウムを原料とするものであれば、特に限定する必要はない。また凝集助剤として、硫酸、塩酸、炭酸、水酸化ナトリウム、消石灰等を加えることも好ましい。
【００２４】
本実施形態では、凝集池２６の前でのみ高分子凝集剤の混和を行っているが、繊維ろ過器３２の前でも高分子凝集剤の混和を行っても良い。また、繊維ろ過器３２の前でのみ高分子凝集剤の混和を行っても良い。
【００２５】
【実施例】
（１）凝集沈殿ろ過法（比較例）
図１の構成から繊維ろ過器３２を省略した装置を用いて実験を行った。この実験条件を以下に示す。
【００２６】
「実験条件」
・原水流量：１，０００ｍ^３／時
・無機混和池：滞留時間３分、撹拌強度２００ｓ^−１
・高分子混和池：滞留時間５分、撹拌強度６００ｓ^−１
・凝集池：横軸パドル３段式、滞留時間４０分
・沈殿池：上向流式傾斜板付き沈殿池、滞留時間４０分、上昇速度３ｍ／時
・砂ろ過池：ケイ砂７００ｍｍ、有効径０．６ｍｍ、均等係数１．３、ろ過速度１２０ｍ／日
・原水濁度：３０度
・原水ｐＨ：７．２
・凝集剤：ＰＡＣ注入率２０ｍｇ／ｌ
・凝集助剤：高分子凝集剤（ノニオン性アクリルアミドポリマー）、注入率０．３ｍｇ／Ｌ
【００２７】
このように、濁度３０度の原水に、凝集剤としてＰＡＣ２０ｍｇ／Ｌを無機混和池１０で加え、急速撹拌をＧ値２００ｓ^−１で３分間行い、引き続き凝集助剤として高分子凝集剤を高分子混和池１８で加え、急速撹拌をＧ値６００ｓ^−１で５分間行い、凝集池２６にてフロック形成を行い、沈殿池３０にて沈殿分離を行って、砂ろ過池３４にてろ過処理を行い処理水を得る。砂ろ過池３４は４８時間に１回、空気逆流洗浄を通水速度６０ｍ／時×５分間を行った後、逆流水洗浄を通水速度３６ｍ／時×８分間行った。
【００２８】
この時の各工程での濁度は、原水３０度、沈殿処理水０．９度、ろ過水濁度０．０４度となっていた。また砂ろ過池の通水時間４８時間でのろ過抵抗は、１，５００ｍｍであった。
【００２９】
（２）凝集沈殿ろ過法（実施形態）
図１の装置を用いて実験を行った。実験条件を以下に示す。
【００３０】
［実験条件］
・原水流量：１，０００ｍ^３／時
・無機混和池：滞留時間３分、撹拌強度２００ｓ^−１
・高分子混和池：滞留時間５分、撹拌強度６００ｓ^−１
・凝集池：横軸パドル３段式、滞留時間４０分
・沈殿池：上向流式傾斜板付き沈殿池、滞留時間２０分、上昇速度６ｍ／時
・繊維ろ過器：アクリル製長繊維ろ材、ろ材長１５０ｃｍ、充填密度１００ｋｇ／ｍ^２、ろ過速度４８０ｍ／日（２０ｍ／時）
・砂ろ過池：ケイ砂７００ｍｍ、有効径０．６ｍｍ、均等係数１．３、ろ過速度２４０ｍ／日
・原水濁度：３０度
・原水ｐＨ：７．２
・凝集剤：ＰＡＣ注入率２０ｍｇ／ｌ
・凝集助剤：高分子凝集剤（ノニオン性アクリルアミドポリマー）、注入率０．３ｍｇ／Ｌ
【００３１】
濁度３０度の原水に、凝集剤としてＰＡＣ２０ｍｇ／Ｌを無機混和池１０で加え、急速撹拌をＧ値２００ｓ^−１で３分間行い、引き続き凝集助剤として高分子凝集剤を高分子混和池１８で加え、急速撹拌をＧ値６００ｓ^−１で５分行い、凝集池２６にてフロック形成を行い、沈殿池３０にて固液分離を行って、さらに繊維ろ過器３２にて粗ろ過を行った後、砂ろ過池３４にてろ過処理を行い処理水を得る。繊維ろ過器３２は２４時間に１回、水・空気逆流洗浄を水通水速度１００ｍ／時、空気通水速度３００ｍ／時で６分間行っている。砂ろ過池３４は４８時間に１回、空気逆流洗浄を通水速度６０ｍ／時×５分間行った後、逆流水洗浄を通水速度３６ｍ／時×８分間行った。
【００３２】
この時の各工程での濁度は、原水３０度、沈殿処理水１．２度（比較例０．９度）、繊維ろ過処理水濁度０．１度、砂ろ過水濁度０．０３度（比較例０．０４度）となっていた。沈殿処理水濁度で比べると、比較例よりも高い値となっているが、繊維ろ過処理水つまり砂ろ過供給水では、比較例よりも低い値となっている。また砂ろ過池の通水時間４８時間でのろ過抵抗は、ろ過速度が従来法の２倍であるにも拘わらず７００ｍｍと比較例のろ過抵抗１，５００ｍｍの半分以下であった。
【００３３】
比較例の各設備の設置面積を１００とした場合の設置面積を比較すると、表１の様に沈殿池で５０％、ろ過池（本発明では繊維ろ過器＋砂ろ過池）で７５％に縮小できている。
【表１】

【００３４】
【発明の効果】
以上説明したように、本発明によれば、比較的強い攪拌で、有機高分子凝集剤を混合することで、有機高分子凝集剤により、微細な懸濁物質を捕捉することができる。一方、このような強い攪拌を行うと、フロック径が十分大きくならず、微細フロックが沈殿池より流出する可能性が高いが、これは繊維ろ過で除去することができる。繊維ろ過器はろ過速度を大きくとれるため、装置の全体としての大きさ（浄水装置全体）を小さくできる。そして、繊維ろ過器の処理水には、微細懸濁物質が非常に少ないため、砂ろ過供給水濁度が安定し、砂ろ過装置におけるろ過抵抗の低減が図れる。
【図面の簡単な説明】
【図１】実施形態の装置の全体構成を示す図である。
【符号の説明】
１０無機混和池、１８高分子混和池、２０攪拌装置、２６凝集池、３０沈殿池、３２繊維ろ過器、３４砂ろ過池。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water purification apparatus having a coagulation sedimentation treatment apparatus that performs an aggregation precipitation process by mixing an organic polymer flocculant (polymer) after mixing an inorganic flocculant, and a sand filtration apparatus that performs a sand filtration process on the coagulation precipitation treated water. About.
[0002]
[Prior art]
Conventionally, in water purification treatment using surface water such as river water and lake water as raw water, a treatment combining a coagulation sedimentation treatment and sand filtration has been widely adopted.
[0003]
In this coagulation-precipitation treatment, an aluminum-based or iron-based inorganic coagulant is used, but an organic polymer coagulant is often used in combination with these inorganic coagulants. This is because by using the polymer, fine inorganic flocculant flocs and suspended substances can be easily coarsened, the sedimentation rate can be increased, and a good sediment supernatant can be stably obtained.
[0004]
Therefore, the aggregation conditions are determined so that good flocs are formed. Normally, a rapid stirring strength after adding the polymer (hereinafter referred to as ^{s -1)} 300 sec ^-1 in G value less than, is set to be rapid stirring time less than 5 minutes. As a result, the maximum growth diameter of floc reaches about 10 mm or more, the floc sedimentation rate in the sedimentation basin is increased, and the water quality of the sediment supernatant can be improved.
[0005]
[Problems to be solved by the invention]
However, if priority is given to floc growth and the stirring intensity is set to less than 300 s ^-1 or the rapid stirring time is set to less than 5 minutes, the floc removal in the sedimentation basin is improved, and the turbidity of the sediment supernatant water. The absolute value is small when viewed with quantitative indicators such as SS and suspended solids (SS). However, in such agglomeration, there is a problem that minute particles are not taken into the floc and are supplied to the filtration basin, and the filtration resistance tends to increase. If the filtration resistance is likely to increase, the frequency of backwashing increases, and if backwashing is delayed, breakthrough occurs and the quality of the treated water deteriorates.
[0006]
On the other hand, when the stirring intensity of the rapid stirring after the addition of the polymer is set to 300 s ^-1 or more in G value and is performed for 5 minutes or more, the stirring strength is relatively strong, and thus the maximum growth diameter of flocs is only a few mm. For this reason, the sedimentation rate of flocs does not increase so much as compared with the case of inorganic alone, and the turbidity of the precipitated treated water is not as good as when the stirring intensity is weakened. For this reason, there was a problem that the sedimentation basin could not be made small despite the addition of the polymer.
[0007]
This invention is made | formed in view of the said subject, and it aims at providing the water purifier which can improve final treated water quality.
[0008]
[Means for Solving the Problems]
The present invention is a water purification apparatus having a coagulation sedimentation treatment apparatus that performs an aggregation precipitation process by mixing an organic polymer flocculant after mixing an inorganic flocculant, and a sand filtration apparatus that performs a sand filtration process on the coagulation precipitation treated water. In addition, the organic polymer flocculant is mixed at a stirring strength G value of 300 to 1000 sec ⁻¹ for 5 minutes or more, and is subjected to a coarse filtration process using a fiber filtration device using fibers as a filter medium in the previous stage of the sand filtration device. It is characterized by.
[0009]
In this way, by mixing the organic polymer flocculant with relatively strong agitation, the fine suspended substance can be thinned by the organic polymer flocculant. On the other hand, when such strong stirring is performed, the floc diameter is not sufficiently large, and there is a high possibility that the fine floc flows out from the sedimentation basin, but this can be removed by fiber filtration. Since the fiber filter can increase the filtration speed, the overall size of the device (the entire water purification device) can be reduced. And since the fine suspended substance is very few in the treated water of a fiber filter, sand filtration supply water turbidity is stabilized and reduction of the filtration resistance in a sand filtration apparatus can be aimed at.
[0010]
Moreover, it is preferable that the surface load factor (the amount of treated water per unit time / the effective sectional area of the settling basin) of the coagulation sedimentation apparatus is 3.5 m / hour or more, and the filtration speed of the fiber filtration apparatus is 10 m / hour or more. is there.
[0011]
In addition, it is preferable that the filter medium of the fiber filtration device is a long fiber bundle having a length of 50 cm to 300 cm.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
Raw water composed of surface water such as river water and lake water is introduced into the inorganic mixing basin 10. The inorganic mixing basin 10 is provided with a stirrer 12 including a stirring blade 12a and a motor 12b for rotating the stirring blade 12a. In addition, an inorganic flocculant in the inorganic flocculant tank 14 is supplied to the inorganic mixing basin 10 by a pump 16. As the inorganic flocculant, for example, PAC (polyaluminum chloride: containing Al ₂ O ₃ 10%) is used. In addition, although the rapid stirring intensity | strength of this inorganic mixing basin 10 is usually less than 300 s- ¹ , and a residence time is less than 5 minutes, it is not limited to this.
[0014]
Next, the water mixed with the inorganic flocculant is introduced into the polymer mixing basin 18. In the polymer mixing pond 18, a stirrer 20 including a stirring blade 20 a and a motor 20 b that rotates the stirring blade 20 a is disposed. The polymer flocculant in the polymer flocculant tank 22 is supplied by a pump 24. The As the polymer flocculant, for example, a nonionic acrylamide polymer is used. Moreover, although an anionic acrylamide polymer may be suitable, it is not limited to these. The rapid mixing strength of the polymer mixing basin 18 is set to 300 s ^-1 or more, and the residence time is set to 5 minutes or more.
[0015]
Water mixed with the inorganic flocculant and the polymer flocculant from the polymer mixing pond 18 is introduced into the flocculent pond 26. The agglomeration pond 26 is provided with a horizontal axis paddle type slow agitator 28, which is agitated at a slow speed to increase the floc size.
[0016]
Then, water flocked by the inorganic flocculant and the polymer flocculant is introduced into the settling basin 30 where the solid matter is precipitated. The solid matter precipitated in the settling basin 30 is excluded from the system as sludge, and the supernatant water is introduced into the fiber filter 32.
[0017]
The fiber filter 32 is preferably one using a long fiber bundle described in Japanese Patent Publication No. 5-12002, Japanese Patent Publication No. 5-11482, Japanese Patent No. 2799376, and the like. In the fiber filter 32, a support is provided in the vicinity of the bottom of the filtration tower, the lower end of the long fiber bundle having a length of 50 cm to 300 cm is fixed above, and the upper end is a free end. And this long fiber bundle is filled so that a substantially upright state may be maintained in a filtration tower, and a filter body is formed. Then, water is passed through the filtration tower in a downward flow, and suspended substances are captured and removed by the filter body. Such a fiber filter 32 has a relatively high porosity and can take a sufficiently high filtration rate as compared with a sand filter basin or the like, and can perform rough filtration on water flowing into the sand filter pond. That is, in sand filtration, fine flocs that cause an increase in filtration resistance can be effectively removed. In the case of a long fiber bundle, the length is preferably 50 cm to 300 cm as described above during such filtration.
[0018]
The filtered water from the fiber filter 32 is then supplied to the sand filtration basin 34 where the remaining suspended material is filtered. The sand filtration basin 34 is formed of, for example, two layers of anthracite and silica sand, and performs relatively precise filtration. As a result, water-treated filtered water that can be distributed as tap water is stably obtained.
[0019]
The filtered treated water is stored in the treated water tank 36 and distributed after being disinfected. Further, the treated water in the treated water tank 36 can be supplied to the bottom of the sand filter basin 34 and the fiber filter 32 by the backwash pump 38, thereby allowing the sand filter pond 34 and the fiber filter 32 to be supplied. Can be backwashed. In addition, air from the blower 40 can be supplied to the bottoms of the sand filtration basin 34 and the fiber filter 32, whereby air backwashing is also performed.
[0020]
In such a water purifier, even if fine flocc is contained in the sedimentation water from the sedimentation basin 30, this suspended substance is removed by the fiber filter 32. The fiber filter 32 originally has a high porosity and a large suspended substance retention capacity. Therefore, even if the amount of suspended solids in the precipitated treated water increases, there is not much variation in the quality of the treated water in the fiber filtrate. When the sedimentation water is supplied directly to the sand filtration basin 34, problems such as clogging occur as soon as the amount of suspended substances in the sedimentation water increases. Such a problem does not occur.
[0021]
Therefore, in the water purification apparatus of this embodiment, the sedimentation basin 30 can be made small by making the surface load factor of the sedimentation basin 30 comparatively large. Further, the fiber filter 32 can be made small because the filtration rate can be increased. In this embodiment, in the polymer mixing basin 18, the stirring intensity is set to 300 s ⁻¹ or more, and the residence time is set to 5 minutes or more. This ensures that the polymer flocculant is mixed with the water supplied from the inorganic mixing basin 10. Such relatively strong agitation reduces the floc size but traps fine suspended matter in the polymer flocculant. The supernatant water obtained in the sedimentation basin 30 by such a coagulation treatment is relatively rich in SS. However, many of these are removed in the fiber filter 32. The water supplied to the sand filtration basin 34 contains almost no fine suspended matter, and a suitable filtration process can be performed by reducing the load of the filtration process in the sand filtration basin 34.
[0022]
That is, if the stirring after mixing the polymer flocculant is weakened, the flocs become coarse, but fine suspended substances remain, and the filtration resistance in the sand filtration basin 34 increases. According to the present embodiment, by combining the polymer mixing basin 18 having a strong stirring strength, the fiber filter 32, and the sand filtration basin 34, the overall size of the apparatus is reduced, and good final treated water is obtained. Can be obtained.
[0023]
In this embodiment, PAC is used as the inorganic flocculant. However, if the raw material is iron or aluminum such as sulfate band, ferric chloride, ferric sulfate, polyaluminum sulfate / iron, There is no particular limitation. It is also preferable to add sulfuric acid, hydrochloric acid, carbonic acid, sodium hydroxide, slaked lime, etc. as an agglomeration aid.
[0024]
In this embodiment, the polymer flocculant is mixed only before the aggregation pond 26, but the polymer flocculant may be mixed before the fiber filter 32. Further, the polymer flocculant may be mixed only in front of the fiber filter 32.
[0025]
【Example】
(1) Coagulation precipitation filtration method (comparative example)
Experiments were performed using an apparatus in which the fiber filter 32 was omitted from the configuration of FIG. The experimental conditions are shown below.
[0026]
"Experimental conditions"
・ Raw water flow rate: 1,000 m ³ / hour ・ Inorganic mixing pond: Residence time 3 minutes, stirring strength 200 s ⁻¹
-Polymer mixing pond: Residence time 5 minutes, stirring strength 600 s ^-1
・ Coagulation basin: 3-stage horizontal paddle type, residence time 40 minutes ・ Sedimentation basin: sedimentation basin with upward flow type inclined plate, residence time 40 minutes, ascending speed 3 m / hour ・ Sand filtration basin: silica sand 700 mm, effective diameter 0.6 mm, uniformity coefficient 1.3, filtration rate 120 m / day, raw water turbidity: 30 degrees, raw water pH: 7.2
-Flocculant: PAC injection rate 20 mg / l
-Coagulation aid: Polymer flocculant (nonionic acrylamide polymer), injection rate 0.3 mg / L
[0027]
In this way, PAC 20 mg / L as a flocculant was added to the raw water with a turbidity of 30 degrees in the inorganic mixing basin 10 and rapid stirring was performed at a G value of 200 s ⁻¹ for 3 minutes. It is added in the molecular mixing basin 18 and is rapidly stirred at a G value of 600 s ⁻¹ for 5 minutes. The flocs are formed in the coagulation basin 26, the precipitate is separated in the sedimentation basin 30, and the sand filtration basin 34 is filtered. To obtain treated water. The sand filtration basin 34 was subjected to air backwashing at a flow rate of 60 m / hour × 5 minutes once every 48 hours, and then backwashed at a flow rate of 36 m / hour × 8 minutes.
[0028]
The turbidity in each process at this time was 30 degrees of raw water, 0.9 degree of precipitation treated water, and 0.04 degree of filtered water turbidity. Moreover, the filtration resistance in the sand filtration pond at the time of water flow of 48 hours was 1,500 mm.
[0029]
(2) Coagulation precipitation filtration method (embodiment)
Experiments were performed using the apparatus of FIG. Experimental conditions are shown below.
[0030]
[Experimental conditions]
・ Raw water flow rate: 1,000 m ³ / hour ・ Inorganic mixing pond: Residence time 3 minutes, stirring strength 200 s ⁻¹
・ Polymer mixing pond: residence time 5 minutes, stirring strength 600 s ⁻¹
・ Coagulation basin: 3-stage horizontal paddle, residence time 40 minutes ・ Sedimentation basin: sedimentation basin with upward flow type inclined plate, residence time 20 minutes, rising speed 6 m / hour ・ Fiber filter: acrylic long fiber filter medium, Filter medium length 150cm, packing density 100kg / m ² , filtration speed 480m / day (20m / hour)
・ Sand filtration pond: Silica sand 700mm, effective diameter 0.6mm, uniformity coefficient 1.3, filtration rate 240m / day ・ Raw water turbidity: 30 degrees ・ Raw water pH: 7.2
-Flocculant: PAC injection rate 20 mg / l
-Coagulation aid: Polymer flocculant (nonionic acrylamide polymer), injection rate 0.3 mg / L
[0031]
PAC 20 mg / L as a flocculant is added to the raw water with a turbidity of 30 degrees in the inorganic mixing basin 10 and rapid stirring is performed at a G value of 200 s ⁻¹ for 3 minutes. In addition, rapid stirring was performed at a G value of 600 s ⁻¹ for 5 minutes, floc formation was performed in the aggregation pond 26, solid-liquid separation was performed in the sedimentation basin 30, and coarse filtration was further performed in the fiber filter 32. Thereafter, filtration is performed in the sand filtration pond 34 to obtain treated water. The fiber filter 32 performs water / air backwashing once every 24 hours for 6 minutes at a water flow rate of 100 m / hour and an air flow rate of 300 m / hour. The sand filtration basin 34 was subjected to air backwashing at a flow rate of 60 m / hour × 5 minutes once every 48 hours, and then backwashed at a flow rate of 36 m / hour × 8 minutes.
[0032]
The turbidity in each step at this time is 30 degrees of raw water, 1.2 degrees of precipitated treated water (comparative example 0.9 degrees), fiber filtered treated water turbidity 0.1 degree, sand filtered water turbidity 0.03. Degree (comparative example 0.04 degree). When compared with the sedimentation water turbidity, the value is higher than that of the comparative example, but the fiber filtration treated water, that is, the sand filtration supply water, is lower than the comparative example. Further, the filtration resistance of the sand filtration basin with a water passage time of 48 hours was 700 mm, which is less than half of the filtration resistance of 1,500 mm in the comparative example, even though the filtration rate was twice that of the conventional method.
[0033]
Comparing the installation area when the installation area of each facility in the comparative example is 100, as shown in Table 1, it is reduced to 50% in the sedimentation basin and 75% in the filtration basin (in the present invention, fiber filter + sand filtration basin). is made of.
[Table 1]

[0034]
【The invention's effect】
As described above, according to the present invention, fine suspended substances can be captured by the organic polymer flocculant by mixing the organic polymer flocculant with relatively strong stirring. On the other hand, when such strong stirring is performed, the floc diameter is not sufficiently large, and there is a high possibility that the fine floc flows out from the sedimentation basin, but this can be removed by fiber filtration. Since the fiber filter can increase the filtration speed, the overall size of the device (the entire water purification device) can be reduced. And since the fine suspended substance is very few in the treated water of a fiber filter, sand filtration supply water turbidity is stabilized and reduction of the filtration resistance in a sand filtration apparatus can be aimed at.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration of an apparatus according to an embodiment.
[Explanation of symbols]
10 Inorganic mixing pond, 18 Polymer mixing pond, 20 Stirrer, 26 Coagulation pond, 30 Sedimentation basin, 32 Fiber filter, 34 Sand filtration pond

Claims

A water purification apparatus having a coagulation sedimentation treatment apparatus that performs an aggregation precipitation process by mixing an organic polymer coagulant after mixing an inorganic flocculant, and a sand filtration apparatus that performs a sand filtration process on the coagulation precipitation treated water,
While mixing the organic polymer flocculant at a stirring intensity G value of 300 to 1000 sec ⁻¹ for 5 minutes or more,
The water purification apparatus characterized by performing the rough filtration process by the fiber filtration apparatus which used the fiber for the filter medium in the front | former stage of the said sand filtration apparatus.

The apparatus of claim 1.
The water purification apparatus characterized in that the surface load factor of the coagulation sedimentation apparatus is 3.5 m / hour or more, and the filtration speed of the fiber filtration apparatus is 10 m / hour or more.

The apparatus according to claim 1 or 2,
The water purification apparatus characterized in that the filter medium of the fiber filtration device is a long fiber bundle having a length of 50 cm to 300 cm.