JP2004261698A

JP2004261698A - Cleaning method for seawater and brackish water and apparatus therefor

Info

Publication number: JP2004261698A
Application number: JP2003053737A
Authority: JP
Inventors: Ryosuke Hata; 良介秦; Sakae Komita; 栄小三田; Kenji Sawai; 賢司沢井; Taichi Yoshikawa; 太一吉川; Miki Akatsu; 美樹赤津; Kenichi Sasaki; 賢一佐々木
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2003-02-28
Filing date: 2003-02-28
Publication date: 2004-09-24
Anticipated expiration: 2023-02-28
Also published as: JP4302411B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method for seawater or brackish water and an apparatus therefor in which transmissivity is improved by high rate filtration, and further, effective sterilization can be performed by ultraviolet radiation. <P>SOLUTION: In the method of cleaning seawater and brackish water, the water to be treated containing suspended matter and microorganisms is subjected to biological membrane filtration treatment, and the filtered water to be treated is irradiated with ultraviolet rays, and is sterilized. Further, when the seawater and brackish water are subjected to the biological membrane filtration treatment, the biological membrane filtration is performed preferably in a state where oxygen is not fed to a filtration layer using a granular material with an effective grain size of ≥2 mm. The cleaning apparatus for seawater and brackish water is provided with a biological membrane filtration apparatus 16 having a filtration layer consisting of a granular filter media, and an ultraviolet radiation apparatus 20 sterilizing the water to be treated. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、海水浴場や釣り場、自然景観など親水空間を作ることを目的として、下水道からの流入水がある閉鎖性水域の被処理水をろ過し、紫外線照射装置で殺菌することによる海水及び汽水の浄化方法及びその装置に関する。
【０００２】
【従来の技術】
下水道の流入がある閉鎖性水域の海水や汽水は、降雨後に合流式下水道からの未処理放流水及びノンポイント汚濁などの影響によって汚染されることが知られている。また、赤潮や台風時の荒波による底泥の舞い上がりなどによっても汚染が生じる。処理対象を海水や汽水とした場合、その量は膨大であり、仕切りをした区域の浄化であっても、ろ過処理を行なう場合ろ過装置の大きさも大規模になる。
海水ろ過に関する技術は製塩業で古くから実用化され、１ｍｍ程度の砂やアンスラサイトによって浮遊物質を除去する目的で多くの実績を有している。最近では、この技術の延長として水族館の水処理に利用され、アンモニア性窒素の硝酸化も実施されていることが（非特許文献１）に記載されている。
一方、生物膜ろ過法は好気性ろ床法とも呼ばれ、活性汚泥に変わる下水処理方法として開発され、現在では排水処理分野で広く利用されているが、ＢＯＤやＳＳ、アンモニア性窒素の硝化などに用いられていることが（非特許文献２）に記載されている。
【０００３】
【非特許文献１】
高田正英，工業用水「水族館における水処理設備」，ｐ１３−ｐ２４（平成３年１２月）
【非特許文献２】
府中裕一，用水と排水「生物膜ろ過装置による有機性排水の処理」，Ｖｏｌ．２５，Ｎｏ．５，ｐ４７７−ｐ４８５（１９８３）
【０００４】
【発明が解決しようとする課題】
ところで、日本国内での自然海域が減少し、人口海浜などの親水空間の要求が高まっている。中でも、都市部での臨海地区では、合流式下水道による未処理水の流入などにより大腸菌が存在し、海水に触れることが好ましくない状況がある。
このような場合に、製塩業や水族館の水処理でのろ過では浮遊物質やアンモニア性窒素の除去に主眼があるため、細かい砂を用いて比較的ゆっくりとろ過するシステムになっている。言うまでもなく、ろ過速度が遅いということは同一処理水量を得るためには設備が大きくなることである。
同様に、従来の生物膜ろ過法ではろ過層に酸素を供給するための散気がなされているため、高速ろ過ができない。原水が下降流に流れる場合は、高速にすると上昇する空気を押さえつける形になり、ろ過速度の限界がある。上向流の場合は空気を原水が同伴する形になり、ろ過層を乱すことになり、これまた高速化は困難である。
本発明は、このような状況下で浮遊物質や有機物質を除去することを主眼とせず、高速ろ過により透過率を改善し、効果的なＵＶ消毒を行う、という観点から発明されたものである。又、コンパクトな設備を提供することが本発明の目的でもある。
【０００５】
【課題を解決するための手段】
本発明者らは、上記課題の解決のため、鋭意検討を重ね海水を対象としてろ過実験を行ない、通常時はＬＶ＝３００〜５００ｍ／日程度の高速運転を、降雨時や赤潮発生時や台風時の海水が汚れた時はＬＶ＝１００〜３００ｍ／日の低速運転を行なうことで、安定した処理水質と、省スペース、大流量処理が行なえることを見出し、本発明を完成するに至った。
【０００６】
すなわち、本発明は下記の手段により上記課題を解決した。
（１）海水及び汽水の浄化方法であり、浮遊物質と微生物とを含有した被処理水を生物膜ろ過処理し、ろ過された該被処理水に紫外線を照射して殺菌することを特徴とする海水及び汽水の浄化方法。
（２）該海水及び汽水を生物膜ろ過処理する際に、粒径が有効径２ｍｍ以上の粒状材を用いたろ過層に酸素を供給しない状態で生物膜ろ過することを特徴とする前記（１）記載の海水及び汽水の浄化方法。
（３）前記生物膜ろ過処理において、前記海水及び汽水の汚れ具合により、ろ過速度を１００〜５００ｍ／ｄの範囲で変化させることを特徴とする前記（１）又は（２）記載の海水及び汽水の浄化方法。
（４）前記ろ過層出口水の溶存酸素濃度が所定濃度よりも低い場合に、ろ過層に酸素を含有する気体を供給することを特徴とする前記（１）記載の海水及び汽水の浄化方法。
（５）粒状のろ材からなるろ過層を有する生物膜ろ過装置、及び被処理水を殺菌する紫外線照射装置を備えたことを特徴とする海水及び汽水の浄化装置。
【０００７】
【発明の実施の形態】
以下に、本発明の形態を図面に基づいて詳細に説明する。図１は本発明方法で用いる生物膜ろ過装置を示す概略説明図である。図２は本発明の海水の浄化方法を示すブロック図である。
各図毎に、その詳細を以下に述べる。
【０００８】
本発明方法で用いるろ過装置では、図１に示すように海水１は流入管２からバッフルプレート３を介して生物膜ろ過装置４の生物膜ろ過層５に導かれ、ろ材６の層を通過し、集水管９を経由して生物膜ろ過水８となる。ろ過装置４外部には上から排水管１１、中間排水管１２が取り付けてある。７は支持材であり、１０は空洗管である。生物膜ろ過の場合、ろ過処理中通気操作を行なう場合があるが、本発明では被処理水のＤＯを利用するため通気を必要としない。図１の場合、海水の流通方向を下降流ろ過としたが、上向流ろ過でも良い。
【０００９】
酸素を含有する気体（空気や酸素）の供給は、ろ過層の閉塞の原因となり、ろ過速度の上昇には不利である。このため、本発明では酸素を供給しない生物膜ろ過を基本とする。
しかし、ろ過層での酸素消費が大きくてろ過層内の下流域が貧酸素状態になる場合には酸素の供給を行い嫌気状態となるのを防ぐ。
【００１０】
生物膜ろ過層５を構成するろ材６としては、粒径は有効径２ｍｍ以上５ｍｍ以下が良く、好ましくは有効径３ｍｍ以上３．５ｍｍ以下で、比重１．５以上２以下で空洞のないものが良い。有効径が小さいと、ろ過層５のろ過抵抗が大きくなりやすく、ろ過の高速化は困難である。ろ材６の比重が２以上であると、後に説明する逆洗が十分行われず、ろ過層閉塞の危険がある。さらに、空洞のあるものであると、空洞に浮遊物質が滞留し、ろ過層内の均一な流れを妨げるため好ましくない。材質としては、無煙炭や無機焼結材、活性炭などが適切である。必ずしも細孔や孔がある必要はない。また、加圧状態を作らなくともろ過速度は３００ｍ／ｄ以上が可能である。通常、未使用のろ材を用いると、１週間、長いときで４週間程度は透過率の改善は見られない。
【００１１】
処理を開始すると、徐々に透過率の改善が見られる。これは、ろ材表面に生物膜が自生したことによって、生物膜の吸着作用が生じるためである。このようにして生物膜ろ過が進むと、海水の汚濁程度によるが、通常、１週間に一度、逆洗を行う。
逆洗は、逆洗ブロワと逆洗ポンプを使用するが、その一例を示すと第１表の通りであり、ろ過層の余剰生物膜を系外に排出する。
【００１２】
【表１】

【００１３】
図２におけるブロック図では原水１を海から取水し、原水槽１３に貯留する。貯留した原水を原水ポンプ１５によってろ材を充填した生物膜ろ過装置１６に流入させ、下向流にてろ過する。生物膜ろ過水１７は処理水槽１８に貯留され、処理水ポンプ１９によってＵＶ消毒装置２０に導入され紫外線殺菌される。その処理水は処理対象区画に放流する。逆洗ポンプ２２及び逆洗ブロア２３によって定期的に逆洗を施した後の逆洗排水は逆洗排水槽２４に貯留し、逆洗排水ポンプ２５によって排水処理設備に移送する。
なお、照射する紫外線の波長は２００ｎｍ〜３００ｎｍの範囲、好ましくは２５０ｎｍ〜２６０ｎｍの範囲である。
【００１４】
【実施例】
以下に、海水を実際に組み込んだ浄化試験での運転結果を示す実施例に基づいて本発明をさらに詳しく説明するが、本発明の範囲はそれらにより限定されるものではない。
【００１５】
実施例１
図３に本発明の方法による処理フローと従来方法（比較例）を行なう処理フローを併せて示す。
水深２．５ｍの海辺において海底から高さ１ｍの地点で取水した海水（原水）１を、海水取水ポンプ１３によって取水し、原水槽１４に貯留して、本発明方法としてろ過装置に生物膜ろ過装置１６を、従来方法（比較例）として砂ろ過装置２７を用いるフローを並列にて設け、９月から１１月までの２ヶ月間運転した。各々のろ過処理水をＵＶ消毒装置２０によって紫外線殺菌処理を施し、５０ｍ四方を区画した海へ放流した。
【００１６】
（実験装置）
この実験に使用した生物膜ろ過装置１６及び砂ろ過装置２７は、各ろ過装置の高さが２５００ｍｍ、直径が３００ｍｍで、各ろ過層の高さが２０００ｍｍであり、使用した各ろ材は第２表に示すとおりであり、ＵＶ消毒装置２０は消費電力が３３０Ｗの紫外線ランプを有するものであり、滞留時間が０．６分のものであった。
本発明方法では、通常ＬＶ＝４００ｍ／日で運転し、赤潮発生時や強度の高い降雨が発生した後など原水濁度が高まった時にＬＶ＝２００ｍ／日で運転した。従来方法（比較例）では実験期間を通じてＬＶ＝２００ｍ／日で運転した。第２表に本発明方法と従来方法（比較例）の処理条件を示す。
（実験結果）
本発明方法と従来方法（比較例）の実験結果を第３表にまとめて示す。
【００１７】
【表２】

【００１８】
【表３】

【００１９】
本発明法ではろ過速度を従来方法の２倍に設定しているため、処理水量も２倍となる。晴天時と降雨直後の日において大腸菌群数は大きく異なる。晴天時は２〜６ｍｇ／リットルを推移し、この時、ろ過処理水のＳＳは本発明法では０．２〜０．９ｍｇ／リットル、従来方法（比較例）では０．２〜０．５ｍｇ／リットルとなった。紫外線透過率は原水が８６〜８９％であったのに対し、本発明法では９２〜９４％、従来法では９２〜９５％となった。ろ過処理水のＳＳでは従来法の方が明らかに本発明法より優れているが、ＵＶ消毒に最も重要な因子である紫外線透過率ではほとんど同じ値である。つまり、ＳＳ除去効果では劣るが、処理水量が２倍であるにもかかわらず、紫外線透過率では同等という結果が得られた。大腸菌群数は原水において３６〜９３００個／１００ｍＬに対し、本発明方法、従来法共に検出下限値３．６以下〜１５個／１００ｍＬとなり、本発明方法は従来法に比して遜色が無かった。
【００２０】
一方、降雨直後の原水の水質は悪化し、原水のＳＳが１０〜１５ｍｇ／リットルまで上昇した。この時、ろ過処理水のＳＳは、本発明法では０．９〜１．５ｍｇ／リットル、従来方法では０．７〜１．１ｍｇ／リットルとなった。紫外線透過率は原水が５５〜７８％であったのに対し、本発明法では８５〜９２％、従来法では８７〜９３％となった。
大腸菌群数は、原水において１５０００〜４６００００個／１００ｍＬに対し、本発明方法、従来法共に検出下限値３．６以下〜７４個／１００ｍＬとなり、晴天時と同様本発明方法は従来法に比して遜色が無かった。
【００２１】
【発明の効果】
本発明によれば、従来の砂ろ過法―ＵＶ消毒による処理方法に比して、省スペース、大流量処理が可能となるとともに、紫外線透過率について従来法とほぼ同程度まで高めることができるので、ＵＶ消毒においても遜色のない消毒効果が得られる。
ＵＶ消毒の前処理である本発明による生物膜ろ過処理方式を採用する海水浄化設備において通常時はＬＶ＝３００〜５００ｍ／日程度の高速運転を行なうことが可能であり、また、従来法では処理不能であるような赤潮発生時や台風通過後の海水が著しく汚れた場合でもＬＶ＝１００〜３００ｍ／日の低速運転を行なうことも可能であるので、実用的である。
【図面の簡単な説明】
【図１】本発明の海水浄化方法に用いるろ過装置である。
【図２】本発明の海水浄化方法の処理フローのブロック図である。
【図３】実施例の処理フローと従来法（比較例）の処理フローを並列して示すブロック図である。
【符号の説明】
１海水
２流入管
３バッフルプレート
４生物膜ろ過装置
５生物膜ろ過層
６ろ材
７支持材
８生物膜ろ過水
９集水管
１０空洗管
１１排水管
１２中間排水管
１３海水取水ポンプ
１４原水槽
１５原水ポンプ
１６生物膜ろ過装置
１７生物膜ろ過水
１８処理水槽
１９処理水ポンプ
２０ＵＶ消毒装置
２１生物膜ろ過水
２２逆洗ポンプ
２３逆洗ブロア
２４逆洗排水槽
２５逆洗排水ポンプ
２６逆洗排水
２７砂ろ過装置
２８ろ過水
２９ろ過水槽[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention aims at creating a hydrophilic space such as a beach, a fishing ground, and a natural scenery, by filtering the water to be treated in a closed water area having inflowing water from a sewer and sterilizing it with an ultraviolet irradiation device. The present invention relates to a purification method and an apparatus therefor.
[0002]
[Prior art]
It is known that seawater and brackish water in closed water areas where sewer flows in are contaminated after rainfall by the effects of untreated effluent from combined sewers and non-point pollution. Pollution is also caused by the rising of the bottom mud due to the red tide and the rough waves during a typhoon. When the processing target is seawater or brackish water, the amount is enormous, and even when purifying a partitioned area, the size of the filtration device becomes large when performing the filtration treatment.
The technology related to seawater filtration has been practically used in the salt industry for a long time, and has many achievements for removing suspended solids with sand or anthracite of about 1 mm. Recently, it has been described in Non-Patent Document 1 that this technique is used as an extension of water treatment in aquariums and nitrification of ammonia nitrogen is also performed.
On the other hand, the biofilm filtration method, also called the aerobic filter method, was developed as a sewage treatment method replacing activated sludge, and is now widely used in the wastewater treatment field. (Non-Patent Document 2).
[0003]
[Non-patent document 1]
Masahide Takada, Industrial Water “Water Treatment Facilities in Aquariums”, p13-p24 (December 1991)
[Non-patent document 2]
Yuichi Fuchu, Water and Wastewater “Treatment of Organic Wastewater by Biofilm Filtration Device”, Vol. 25, no. 5, p477-p485 (1983)
[0004]
[Problems to be solved by the invention]
By the way, the natural sea area in Japan is decreasing, and the demand for a hydrophilic space such as an artificial beach is increasing. In particular, in coastal areas in urban areas, coliforms are present due to inflow of untreated water due to combined sewerage, and there are situations in which it is not preferable to touch seawater.
In such a case, since filtration in the salt industry or aquarium water treatment mainly focuses on the removal of suspended solids and ammonia nitrogen, the system is configured to filter relatively slowly using fine sand. Needless to say, the slow filtration rate means that the equipment becomes large to obtain the same amount of treated water.
Similarly, in the conventional biofilm filtration method, high-speed filtration cannot be performed because air is diffused to supply oxygen to the filtration layer. When raw water flows in a downward flow, a high speed will suppress the rising air, and there is a limit to the filtration speed. In the case of an upward flow, the air is accompanied by raw water, which disturbs the filtration layer, and it is difficult to increase the speed.
The present invention has been invented from the viewpoint of improving transmittance by high-speed filtration and performing effective UV disinfection without focusing on removing suspended substances and organic substances under such circumstances. . It is also an object of the present invention to provide compact equipment.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and conducted a filtration experiment on seawater. Normally, high-speed operation with an LV of about 300 to 500 m / day was performed during rainfall, when a red tide occurred, or during a typhoon. When the seawater at the time becomes dirty, it has been found that by performing low-speed operation at LV = 100 to 300 m / day, stable treated water quality, space saving and large flow rate treatment can be performed, and the present invention has been completed. .
[0006]
That is, the present invention has solved the above problems by the following means.
(1) A method for purifying seawater and brackish water, wherein the water to be treated containing suspended substances and microorganisms is subjected to biofilm filtration treatment, and the filtered water to be treated is sterilized by irradiation with ultraviolet rays. How to purify seawater and brackish water.
(2) When the seawater and brackish water are subjected to biofilm filtration treatment, biofilm filtration is performed without supplying oxygen to a filtration layer using a granular material having an effective particle size of 2 mm or more. ).
(3) The seawater and brackish water according to (1) or (2), wherein in the biofilm filtration treatment, a filtration speed is changed in a range of 100 to 500 m / d depending on a degree of contamination of the seawater and brackish water. Purification method.
(4) The method for purifying seawater and brackish water according to (1), wherein when the dissolved oxygen concentration in the outlet water of the filtration layer is lower than a predetermined concentration, a gas containing oxygen is supplied to the filtration layer.
(5) A seawater and brackish water purifier, comprising: a biofilm filtration device having a filtration layer made of granular filter media; and an ultraviolet irradiation device for sterilizing water to be treated.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing a biofilm filtration device used in the method of the present invention. FIG. 2 is a block diagram showing a method for purifying seawater of the present invention.
The details are described below for each figure.
[0008]
In the filtration device used in the method of the present invention, as shown in FIG. 1, seawater 1 is guided from an inflow pipe 2 to a biofilm filtration layer 5 of a biofilm filtration device 4 via a baffle plate 3 and passes through a layer of a filter medium 6. , And becomes the biofilm filtered water 8 via the water collecting pipe 9. A drain pipe 11 and an intermediate drain pipe 12 are attached to the outside of the filtration device 4 from above. 7 is a support material, and 10 is an empty washing tube. In the case of biofilm filtration, ventilation may be performed during the filtration process, but in the present invention, ventilation is not required because DO to be treated is used. In the case of FIG. 1, the flow direction of the seawater is downflow filtration, but may be upflow filtration.
[0009]
Supply of oxygen-containing gas (air or oxygen) causes blockage of the filtration layer, and is disadvantageous for increasing the filtration rate. For this reason, the present invention is based on biofilm filtration without supplying oxygen.
However, when oxygen consumption in the filtration layer is large and the downstream region in the filtration layer is in a poor oxygen state, oxygen is supplied to prevent the anaerobic state.
[0010]
As the filter medium 6 constituting the biofilm filtration layer 5, those having an effective diameter of 2 mm to 5 mm, preferably an effective diameter of 3 mm to 3.5 mm, a specific gravity of 1.5 to 2 and no cavities are preferable. good. If the effective diameter is small, the filtration resistance of the filtration layer 5 tends to increase, and it is difficult to increase the filtration speed. When the specific gravity of the filter medium 6 is 2 or more, backwashing described later is not sufficiently performed, and there is a risk of clogging of the filtration layer. Furthermore, it is not preferable that the hollow material has a cavity because suspended matter stays in the cavity and prevents uniform flow in the filtration layer. Suitable materials include anthracite, an inorganic sintered material, and activated carbon. It is not always necessary to have pores or holes. Also, the filtration speed can be 300 m / d or more without creating a pressurized state. Usually, when an unused filter medium is used, the transmittance is not improved for one week or as long as about four weeks.
[0011]
When the process is started, the transmittance is gradually improved. This is because the biofilm adsorbs on the surface of the filter medium due to the natural growth of the biofilm on the surface of the filter medium. When biofilm filtration proceeds in this way, backwashing is usually performed once a week, depending on the degree of seawater contamination.
The backwashing uses a backwashing blower and a backwashing pump. One example is shown in Table 1, and the surplus biofilm of the filtration layer is discharged out of the system.
[0012]
[Table 1]

[0013]
In the block diagram in FIG. 2, raw water 1 is taken from the sea and stored in a raw water tank 13. The stored raw water flows into a biofilm filtration device 16 filled with a filter medium by a raw water pump 15, and is filtered by a downward flow. The biofilm filtered water 17 is stored in a treated water tank 18, introduced into a UV disinfection device 20 by a treated water pump 19, and sterilized by ultraviolet rays. The treated water is discharged to the section to be treated. The backwash drainage after the regular backwash by the backwash pump 22 and the backwash blower 23 is stored in the backwash drain tank 24 and transferred to the wastewater treatment facility by the backwash drain pump 25.
The wavelength of the ultraviolet light to be irradiated is in the range of 200 nm to 300 nm, preferably in the range of 250 nm to 260 nm.
[0014]
【Example】
Hereinafter, the present invention will be described in more detail based on examples showing operation results in a purification test in which seawater is actually incorporated, but the scope of the present invention is not limited thereto.
[0015]
Example 1
FIG. 3 shows a processing flow according to the method of the present invention and a processing flow performing the conventional method (comparative example).
Seawater (raw water) 1 which is drawn at a height of 1 m from the seabed at a seaside with a depth of 2.5 m is taken by a seawater intake pump 13 and stored in a raw water tank 14. The apparatus 16 was operated for two months from September to November by providing a flow using a sand filtration device 27 in parallel as a conventional method (comparative example). Each of the filtered waters was subjected to an ultraviolet sterilization treatment by the UV disinfection device 20, and was discharged into the sea divided into 50m square.
[0016]
(Experimental device)
The biofilm filtration device 16 and the sand filtration device 27 used in this experiment had a height of each filtration device of 2500 mm, a diameter of 300 mm, and a height of each filtration layer of 2000 mm. The UV disinfection apparatus 20 had an ultraviolet lamp with a power consumption of 330 W, and the residence time was 0.6 minutes.
In the method of the present invention, the vehicle was normally operated at LV = 400 m / day, and was operated at LV = 200 m / day when the raw water turbidity increased, such as when red tide was generated or after strong rainfall occurred. In the conventional method (comparative example), the operation was performed at LV = 200 m / day throughout the experimental period. Table 2 shows the processing conditions of the method of the present invention and the conventional method (comparative example).
(Experimental result)
Table 3 summarizes the experimental results of the method of the present invention and the conventional method (comparative example).
[0017]
[Table 2]

[0018]
[Table 3]

[0019]
In the method of the present invention, the filtration rate is set to be twice that of the conventional method, so that the amount of treated water is also doubled. The number of coliform bacteria differs greatly between fine weather and the day immediately after rainfall. In fine weather, it changes from 2 to 6 mg / l. At this time, SS of the filtered water is 0.2 to 0.9 mg / l in the method of the present invention, and 0.2 to 0.5 mg / l in the conventional method (comparative example). Liters. The UV transmittance was 86-89% for raw water, 92-94% for the method of the present invention, and 92-95% for the conventional method. In the SS of the filtered water, the conventional method is clearly superior to the method of the present invention, but has almost the same value in the ultraviolet transmittance, which is the most important factor for UV disinfection. That is, although the SS removal effect was inferior, the result that the UV transmittance was the same was obtained despite the doubled amount of treated water. The number of Escherichia coli groups was 36 to 9300 cells / 100 mL in raw water, but the lower limit of detection was 3.6 to 15 cells / 100 mL in both the method of the present invention and the conventional method, and the method of the present invention was comparable to the conventional method. .
[0020]
On the other hand, the quality of the raw water immediately after the rain deteriorated, and the SS of the raw water rose to 10 to 15 mg / liter. At this time, the SS of the filtered water was 0.9 to 1.5 mg / L in the method of the present invention and 0.7 to 1.1 mg / L in the conventional method. The UV transmittance of raw water was 55 to 78%, whereas the UV transmittance was 85 to 92% in the method of the present invention and 87 to 93% in the conventional method.
The number of coliform bacteria in the raw water is 15,000 to 460000 cells / 100 mL, and the lower limit of detection is 3.6 or less to 74 cells / 100 mL in both the method of the present invention and the conventional method. There was no inferiority.
[0021]
【The invention's effect】
According to the present invention, compared with the conventional sand filtration method-a processing method using UV disinfection, space saving and large flow rate processing can be performed, and ultraviolet transmittance can be increased to about the same level as the conventional method. Also, a disinfection effect comparable to UV disinfection can be obtained.
In a seawater purification facility employing the biofilm filtration treatment system according to the present invention, which is a pretreatment for UV disinfection, it is possible to normally operate at a high speed of about LV = 300 to 500 m / day. Even when the red tide is impossible or the seawater after passing the typhoon is extremely contaminated, the low-speed operation of LV = 100 to 300 m / day is possible, so that it is practical.
[Brief description of the drawings]
FIG. 1 is a filtration device used in the seawater purification method of the present invention.
FIG. 2 is a block diagram of a processing flow of the seawater purification method of the present invention.
FIG. 3 is a block diagram showing a processing flow of an embodiment and a processing flow of a conventional method (comparative example) in parallel.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Seawater 2 Inflow pipe 3 Baffle plate 4 Biofilm filtration device 5 Biofilm filtration layer 6 Filter medium 7 Supporting material 8 Biofilm filtration water 9 Water collection pipe 10 Empty washing pipe 11 Drain pipe 12 Intermediate drain pipe 13 Seawater intake pump 14 Raw water tank 15 Raw water pump 16 Biofilm filtration device 17 Biofilm filtration water 18 Treatment water tank 19 Treatment water pump 20 UV disinfection device 21 Biofilm filtration water 22 Backwash pump 23 Backwash blower 24 Backwash drainage tank 25 Backwash drain pump 26 Backwash drain 27 sand filtration device 28 filtered water 29 filtered water tank

Claims

A method for purifying seawater and brackish water, comprising subjecting treated water containing suspended substances and microorganisms to biofilm filtration, and irradiating the filtered treated water with ultraviolet rays for sterilization. Purification method.

The seawater according to claim 1, wherein, when the seawater and the brackish water are subjected to biofilm filtration treatment, biofilm filtration is performed without supplying oxygen to a filtration layer using a granular material having an effective particle size of 2 mm or more. And brackish water purification method.

The method for purifying seawater and brackish water according to claim 1 or 2, wherein in the biofilm filtration treatment, a filtration speed is changed within a range of 100 to 500 m / d depending on a degree of contamination of the seawater and brackish water.

The method for purifying seawater and brackish water according to claim 1, wherein when the dissolved oxygen concentration in the outlet water of the filtration layer is lower than a predetermined concentration, a gas containing oxygen is supplied to the filtration layer.

A purification device for seawater and brackish water, comprising: a biofilm filtration device having a filtration layer made of a granular filter material; and an ultraviolet irradiation device for sterilizing water to be treated.