JP2004209385A

JP2004209385A - Sludge filter aid and method for dehydrating sludge

Info

Publication number: JP2004209385A
Application number: JP2002382373A
Authority: JP
Inventors: Hiroki Ishibashi; 浩樹石橋
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 2002-12-27
Filing date: 2002-12-27
Publication date: 2004-07-29

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sludge filter aid capable of reducing the water content in a dehydrated cake produced by a sludge treatment, and a method for dehydrating sludge. <P>SOLUTION: The sludge filter aid contains 95-65 pts.wt. slaked lime per 5-35 pts.wt. porous material particle consisting essentially of silicon dioxide having ≤50% 45 μm plus sieve percentage and ≤10 mL float. In the method for dehydrating the sludge which includes a flocculation process for forming flocculated sludge by mixing a ferric chloride aqueous solution and slaked lime slurry with the sludge and a filtration process for filtering the flocculated sludge, the flocculation process includes a process for mixing porous material particle consisting essentially of silicon dioxide in the slaked lime slurry. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、汚泥濾過助剤及び汚泥の脱水方法に関するものである。
【０００２】
【従来の技術】
従来、下水処理においては、塩化第二鉄等の凝集剤と消石灰等の凝集助剤とによって下水処理によって生じた汚泥を凝集させて凝集汚泥とし、この凝集汚泥を濾過して脱水ケーキと脱水濾液とに分離している（例えば、特許文献１参照。）。
【０００３】
【特許文献１】
特開２０００−３０１２００号公報（第２−５頁、図１）
【０００４】
【発明が解決しようとする課題】
ところで、下水処理場においては、下水処理によって脱水ケーキが１日当たり数十トンから数百トン単位で発生する。このため、多量の脱水ケーキをコンポスト（堆肥）として利用したり、埋立て処理あるいは焼却処理したりするにしても、運搬に多大な経費を要している。このため、汚泥処理においては、運搬経費を削減するため、脱水ケーキにおける含水率を少しでも低減することが望まれていた。
【０００５】
この発明は、上述した従来技術による問題点を解消するため、汚泥処理によって生ずる脱水ケーキにおける含水率の低減が可能な汚泥濾過助剤及び汚泥の脱水方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上述した課題を解決し、目的を達成するため、請求項１の発明に係る汚泥濾過助剤は、４５μｍふるい上百分率が５０％以下、かつ、フロートが１０ｍＬ以下の二酸化ケイ素を主成分とする多孔物質の粒子５〜３５重量部に対し、９５〜６５重量部の消石灰を含むことを特徴とする。
【０００７】
請求項１の発明によれば、多孔物質の粒子が汚泥中に空隙を形成し、この空隙が濾液の通路となって脱水ケーキにおける含水率が低減される。
【０００８】
また、請求項２の発明に係る汚泥濾過助剤は、上記の発明において、前記粒子が、パーライトあるいは珪藻土のいずれかであることを特徴とする。
【０００９】
一方、上述した課題を解決し、目的を達成するため、請求項３の発明に係る汚泥の脱水方法は、汚泥に塩化第二鉄水溶液と消石灰スラリーとを混和して凝集汚泥とする凝集工程と、前記凝集汚泥を濾過する濾過工程とを含む汚泥の脱水方法において、前記凝集工程は、前記消石灰スラリー中に二酸化ケイ素を主成分とする多孔物質の粒子を混合する工程を含むことを特徴とする。
【００１０】
請求項３の発明によれば、消石灰スラリー中に多孔物質の粒子を混合することによって、濾過工程において多孔物質の粒子が汚泥中に空隙を形成し、この空隙が濾液の通路となって脱水ケーキにおける含水率が低減される。
【００１１】
【発明の実施の形態】
以下、図面を参照して、この発明に係る汚泥濾過助剤と汚泥の脱水方法の好適な実施の形態について説明する。
【００１２】
（実施の形態１）
先ず、この発明の汚泥濾過助剤と汚泥の脱水方法に係る実施の形態１について説明する。この発明の実施の形態１では、汚泥濾過助剤における多孔物質の粒子と消石灰との混合比と、用いる多孔物質の粒子の大きさとに関する目安をつけるために行った机上試験における汚泥の脱水方法について説明する。
【００１３】
先ず、汚泥２０００ｍＬをビーカーに取り、この中に濃度３７．５％の塩化第二鉄水溶液を５．７ｇ（塩化第二鉄固形分約２．１ｇ）添加して３０秒間攪拌した。攪拌後、ビーカーに多孔物質の粒子と消石灰とを加え、１分間攪拌した。このとき、多孔物質の粒子は、二酸化ケイ素を主成分とする天然火山ガラスである真珠岩，松脂岩，黒曜岩を粉砕し、焼成炉で急速に加熱、膨張させた後、所定の粒度に粉砕分級した３種類のパーライトを用いた。但し、多孔物質の粒子は、二酸化ケイ素を主成分とする多孔物質であれば、パーライトの他、珪藻土であってもよく、粉砕粒子の他、未粉砕の粒子であってもよい。これら３種類のパーライトは、４５μｍふるい上百分率がそれぞれ０％，９％，４９％であり、フロートがそれぞれ１ｍＬ以下，４ｍＬ以下，１０ｍＬ以下である。これら３種類のパーライトを以下に述べる混合比で消石灰と混合し、５種類の消石灰スラリー（実施例１〜５参照）とし、各混合比の消石灰スラリー毎に汚泥を脱水処理した。
【００１４】
ここで、４５μｍふるい上百分率Ｒ（％）は、ＪＩＳＺ８８０１「試験用ふるい」に規定する目開き４５μｍ、直径２００ｍｍのふるいにＴ（ｇ）の試料を入れ、ふるいを通過する水が透明になるまで流水で試料を洗浄した後、ふるい上に残留した試料を１００〜１０５℃で乾燥し、その質量を測定してふるい上質量ｍ（ｇ）とし、次式によって算出される。
Ｒ＝（ｍ／Ｔ）×１００
【００１５】
一方、フロートは、メスシリンダーに試料（多孔物質の粒子）を１０ｇ入れ、水を２００ｍＬの目盛りまで注入して攪拌した後、シリンダー内壁面に付着した試料を水洗しながら２５０ｍＬに希釈する。このメスシリンダーを５分間静置後、水面付近に浮遊する試料の容量（ｍＬ）を読み取ってフロートとする。
【００１６】
次いで、綾織りされたポリプロピレン製の濾布（５００ｇ／ｍ^２）をセットした加圧式濾過試験機（米国，グレフコ社製、ＬＡＢＯＲＡＴＯＲＹＰＲＥＳＳＵＲＥＦＩＬＴＥＲ）を用い、前記汚泥を４．０ｋｇ／ｃｍ^２の条件で２０分間加圧して濾過した。濾過終了後、ケーキを濾布と共に加圧式濾過試験機から取り出し、濾布から厚さ約１ｃｍの部分のケーキを切り取った。このケーキを圧搾機（株式会社丸東製、圧縮試験機）の前記と同じ素材からなる濾布に載せ、０．５ｋｇ／ｃｍ^２で３０秒間、２．０ｋｇ／ｃｍ^２で３０秒間、４．０ｋｇ／ｃｍ^２で３分間と順次圧搾し、脱水ケーキとした。
【００１７】
このようにして得た脱水ケーキを濾布から剥離し、含水率（％）を赤外線水分計（株式会社ケット科学研究所製、ＦＤ−６００）を用いて測定した。その結果を、実施例１〜５として加圧式濾過試験機による前記汚泥の２０分間濾過後における濾液量（ｍＬ）及び濾布の状態と共に表１に示した。また、比較のため、粉砕粒子を含まない消石灰１９．３ｇを添加した汚泥について、同様にして測定した含水率等に関する結果を表１に比較例１として併せて示した。
【００１８】
【表１】

ここで、表１に示す濾布の状態とは、圧搾後の脱水ケーキを濾布から剥離する際の剥離性に関する評価であって、濾布の状態が二重丸（◎）であるとは、脱水ケーキを濾布から非常に剥離し易く、目視観察したときに濾布の目詰まりが殆ど見られず、従って濾布の汚れが少ないことを意味する。また、濾布の状態が丸（○）であるとは、脱水ケーキを濾布から剥離し難く、目視観察したときに濾布に目詰まりが見られ、従って濾布の汚れが多いことを意味する。
【００１９】
また、表１においては、粉砕粒子である３種類のパーライトに関し、４５μｍふるい上百分率が、それぞれ０％のものをＮｏ．１（実施例１，２）、９％のものをＮｏ．２（実施例３，４）、４９％のものをＮｏ．３（実施例５）と表示した。このとき、Ｎｏ．１，Ｎｏ．２のパーライトと消石灰との混合比は、それぞれ３：７と２：８の２通りに設定し、Ｎｏ．３のパーライトは同じく３：７に設定した。
【００２０】
表１に示す結果から、この発明の汚泥濾過助剤は、消石灰のみを添加して汚泥を濾過した場合に比べると、消石灰に粉砕粒子、即ち、パーライトを上述の割合で添加することにより、脱水ケーキにおける含水率が小さくなり、汚泥から排出される濾液量も多く、濾布の目詰まり等が少なくなって濾布の状況が良好になることが分かった。但し、この発明の汚泥濾過助剤は、実施例１，２の結果から明らかなように、４５μｍふるい上百分率が０％のパーライトでは、消石灰との混合比を３：７とすると、２：８とした場合よりも脱水ケーキにおける含水率が少なかった。一方、実施例３，４の結果からは、４５μｍふるい上百分率が９％のパーライトでは、消石灰との混合比を２：８とすると、３：７とした場合よりも脱水ケーキにおける含水率が少なかった。
【００２１】
一方、この発明の汚泥濾過助剤は、パーライトの大きさとして実施例１，２に記載した４５μｍふるい上百分率が０％のＮｏ．１のものを使用すると脱水ケーキにおける含水量が最も少なくなる。但し、濾液量は、実施例３，４に記載した４５μｍふるい上百分率が９％のＮｏ．２が最も多くなる。従って、表１に示す結果から、この発明の汚泥濾過助剤は、粉砕粒子として４５μｍふるい上百分率が０％と９％のパーライトを用いると好ましいことが分かった。但し、４５μｍふるい上百分率が９％のパーライトは、４５μｍふるい上百分率が０％のパーライトより安価で経済的なことから、粉砕粒子としてより好ましい。
【００２２】
（実施の形態２）
次に、この発明の汚泥濾過助剤と汚泥の脱水方法に係る実施の形態２について説明する。この発明の実施の形態２では、上記机上試験の結果に基づき、二酸化ケイ素を主成分とする粉砕粒子として４５μｍふるい上百分率が９％のパーライト２０重量部を消石灰８０重量部に混合した汚泥濾過助剤を用い、汚泥処理設備において実機試験を行った。図１は、この発明の実施の形態２であり、この発明による汚泥濾過助剤を用いた実機による汚泥の脱水方法を説明する模式図である。
【００２３】
汚泥処理設備１は、図１に示すように、濃縮汚泥槽２、溶解槽３、塩化第二鉄溶液槽４、凝集汚泥槽５及びフィルタプレス６を備えている。
【００２４】
濃縮汚泥槽２は、下水処理によって生じた汚泥が貯留され、汚泥には凝集汚泥槽５で塩化第二鉄水溶液（濃度３７．５％）と消石灰スラリーが添加される。
【００２５】
溶解槽３は、消石灰とパーライトとを水で溶解して消石灰スラリーとする。ここで、本発明の濾過助剤を汚泥処理設備において使用する場合、汚泥処理設備に新たな粉砕粒子受入槽と計量器並びに粉砕粒子の搬送設備を設ける必要が生じ、その分の設備投資が必要となる。そこで、予め消石灰とパーライトとを所定割合に混合して所定量袋に入れたものを商品としておき、汚泥処理設備に搬入して使用できるようにしておく。このようにすると、ユーザーは、汚泥処理設備における既存の消石灰受入槽を活用して消石灰スラリーを調整することができるので、新たな設備投資をする必要がないという利点がある。
【００２６】
塩化第二鉄溶液槽４は、濃度３７．５％の塩化第二鉄水溶液を貯留したタンクである。
【００２７】
凝集汚泥槽５は、塩化第二鉄水溶液と消石灰スラリーとが添加され、攪拌により汚泥を凝集させる。このとき、凝集汚泥槽５は、塩化第二鉄水溶液と消石灰スラリーと汚泥との混合物のｐＨが１１．３〜１２．５程度である。
【００２８】
フィルタプレス６は、凝集汚泥槽５で凝集された凝集汚泥を濾過し、脱水ケーキと脱水濾液とに分離する。得られた脱水ケーキは、コンポストや埋立て資材として利用したり、焼却等によって処分したりするために搬送される。一方、脱水濾液は、排水されたり、この汚泥処理設備で再利用されたりする。但し、上述のような濾過が可能であればフィルタプレス６に限定されるものではなく、例えば、ベルトプレス，遠心脱水機，スクリュープレス，回転式真空脱水機等を使用することも可能である。
【００２９】
汚泥処理設備１において、４４ｋｇの消石灰に４５μｍふるい上百分率が９％のパーライト１１ｋｇを混合してなる５５ｋｇの濾過助剤（消石灰８０重量部：パーライト２０重量部）を溶解槽３で４９５ｋｇの水に混合した消石灰スラリーと、濃縮汚泥（６７００ｋｇ）と、塩化第二鉄水溶液（３７．５％）４３．５ｋｇを、凝集汚泥槽５に添加し、攪拌・混和により凝集させてフィルタプレス６で濾過し、脱水ケーキと脱水濾液とに分離した。このようにして４種類の汚泥について脱水処理を実行し、得られた脱水ケーキの含水率と平均値、脱水濾液における浮遊物質（ＳＳ：ｓｕｓｐｅｎｄｅｄｓｏｌｉｄｓ）の量（ｍｇ／Ｌ）に関する測定結果を表２に実施例６として示した。同様に、４０ｋｇの消石灰に４５μｍふるい上百分率が９％のパーライト１０ｋｇを混合してなる５０ｋｇの濾過助剤（消石灰８０重量部：パーライト２０重量部）を溶解槽３で４５０ｋｇの水と混合した消石灰スラリーと、濃縮汚泥（６７００ｋｇ）と、塩化第二鉄水溶液（３７．５％）４３．５ｋｇを、凝集汚泥槽５に添加し、同様の処理をした４種類の汚泥について脱水ケーキの含水率と平均値、脱水濾液における浮遊物質（ＳＳ：ｓｕｓｐｅｎｄｅｄｓｏｌｉｄｓ）の量（ｍｇ／Ｌ）を測定過した。その結果を表２に実施例７として示した。
【００３０】
【表２】

一方、比較のため、溶解槽３においてパーライトを加えることなく５５ｋｇの消石灰のみを４９５ｋｇの水と混合して消石灰スラリーを調整し、これを４３．５ｋｇの塩化第二鉄水溶液（３７．５％）と共に濃縮汚泥に添加し、前述と同様にして比較例２〜４としてそれぞれ４種類の汚泥について脱水処理を行った。得られた複数の脱水ケーキの含水率と平均値、脱水濾液における浮遊物質の量（ｍｇ／Ｌ）に関する測定結果を併せて表２に示した。
【００３１】
表２に示す実施例６，７と比較例２〜４の結果から明らかなように、消石灰８０重量部に４５μｍふるい上百分率が９％のパーライト２０重量部を混合した濾過助剤を用いると、消石灰単独の場合に比べて脱水ケーキの含水率が平均値で１．６〜２．０％減少していた。また、脱水濾液においても浮遊物質の量（ｍｇ／Ｌ）も顕著に減少していた。このように、本発明の汚泥濾過助剤及び汚泥の脱水方法によれば、汚泥処理によって生ずる脱水ケーキにおける含水率が低減され、脱水ケ−キの運搬に要する経費を削減することができる。
【００３２】
【発明の効果】
以上説明したように、この発明の汚泥濾過助剤によれば、４５μｍふるい上百分率が５０％以下、かつ、フロートが１０ｍＬ以下の二酸化ケイ素を主成分とする多孔物質の粒子５〜３５重量部に対し、９５〜６５重量部の消石灰を含み、また、この発明の汚泥の脱水方法においては、汚泥に塩化第二鉄水溶液と消石灰スラリーを混和して凝集汚泥とする凝集工程と、当該凝集汚泥を濾過する濾過工程とを備えた汚泥の脱水方法において、前記凝集工程は、前記消石灰スラリー中に二酸化ケイ素を主成分とする多孔物質の粒子を混合する工程を含むので、汚泥処理によって生ずる脱水ケーキにおける含水率を低減することができるという効果を奏する。
【図面の簡単な説明】
【図１】この発明の実施の形態２であり、この発明の汚泥濾過助剤を用いた実機による汚泥の脱水方法を説明する模式図である。
【符号の説明】
１汚泥処理設備
２濃縮汚泥槽
３溶解槽
４塩化第二鉄溶液槽
５凝集汚泥槽
６フィルタプレス[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sludge filter aid and a method for dewatering sludge.
[0002]
[Prior art]
Conventionally, in sewage treatment, sludge generated by sewage treatment is agglomerated into flocculated sludge by a flocculant such as ferric chloride and a flocculating aid such as slaked lime, and the flocculated sludge is filtered to obtain a dewatered cake and a dewatered filtrate. (See, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP-A-2000-301200 (pages 2-5, FIG. 1)
[0004]
[Problems to be solved by the invention]
By the way, in a sewage treatment plant, dewatered cake is generated in tens of tons to hundreds of tons per day due to sewage treatment. For this reason, even if a large amount of dehydrated cake is used as compost (compost) or landfilled or incinerated, transportation requires a great deal of expense. For this reason, in sludge treatment, it has been desired to reduce the water content in the dewatered cake as much as possible in order to reduce transportation costs.
[0005]
An object of the present invention is to provide a sludge filtration aid capable of reducing the water content in a dewatered cake generated by sludge treatment and a method for dewatering sludge in order to solve the above-mentioned problems caused by the conventional technology.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, a sludge filtration aid according to the invention of claim 1 is characterized in that a 45 μm sieve upper percentage is 50% or less, and a float mainly composed of silicon dioxide having a float of 10 mL or less. It is characterized in that it contains 95 to 65 parts by weight of slaked lime for 5 to 35 parts by weight of particles of the substance.
[0007]
According to the first aspect of the invention, the particles of the porous material form voids in the sludge, and the voids serve as passages for the filtrate, thereby reducing the water content in the dewatered cake.
[0008]
The sludge filtration aid according to the invention of claim 2 is characterized in that, in the above invention, the particles are either pearlite or diatomaceous earth.
[0009]
On the other hand, in order to solve the above-mentioned problems and achieve the object, a method for dewatering sludge according to the third aspect of the present invention includes a flocculation step of mixing an aqueous ferric chloride solution and slaked lime slurry with the sludge to form a flocculated sludge. And a filtration step of filtering the agglomerated sludge, wherein the aggregating step includes a step of mixing particles of a porous substance containing silicon dioxide as a main component in the slaked lime slurry. .
[0010]
According to the invention of claim 3, by mixing the particles of the porous substance in the slaked lime slurry, the particles of the porous substance form voids in the sludge in the filtration step, and the voids serve as passages for the filtrate to form a dewatered cake. , The moisture content is reduced.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a sludge filter aid and a method for dewatering sludge according to the present invention will be described with reference to the drawings.
[0012]
(Embodiment 1)
First, a first embodiment of a sludge filtration aid and a method for dewatering sludge according to the present invention will be described. In the first embodiment of the present invention, a method for dewatering sludge in a desk test conducted to provide a guide regarding a mixing ratio between particles of porous material and slaked lime in a sludge filter aid and a size of particles of porous material to be used. explain.
[0013]
First, 2000 mL of sludge was placed in a beaker, and 5.7 g of a 37.5% aqueous ferric chloride solution (solid ferric chloride solid content: about 2.1 g) was added thereto, followed by stirring for 30 seconds. After the stirring, the porous substance particles and slaked lime were added to the beaker, and the mixture was stirred for 1 minute. At this time, the particles of the porous material are crushed from natural volcanic glass composed mainly of silicon dioxide, such as perlite, pinestone, and obsidian, and rapidly heated and expanded in a firing furnace. Three types of pearlite that were pulverized and classified were used. However, the particles of the porous material may be diatomaceous earth other than pearlite as long as the porous material contains silicon dioxide as a main component, and may be unground particles in addition to ground particles. These three types of pearlite have 0%, 9%, and 49%, respectively, on the 45 μm sieve, and the floats are 1 mL or less, 4 mL or less, and 10 mL or less, respectively. These three types of pearlite were mixed with slaked lime at a mixing ratio described below to form five types of slaked lime slurries (see Examples 1 to 5), and sludge was dewatered for each slaked lime slurry of each mixing ratio.
[0014]
Here, the percentage R (%) on the 45 μm sieve is determined by placing a T (g) sample in a sieve having a mesh size of 45 μm and a diameter of 200 mm specified in JIS Z 8801 “Test sieve”, and water passing through the sieve becomes transparent. After the sample has been washed with running water until it is completely dry, the sample remaining on the sieve is dried at 100 to 105 ° C., and its mass is measured to obtain the mass on the sieve m (g), which is calculated by the following equation.
R = (m / T) × 100
[0015]
On the other hand, for the float, 10 g of a sample (particles of a porous substance) is put into a measuring cylinder, water is poured to a scale of 200 mL, and the sample is stirred. After that, the sample attached to the inner wall surface of the cylinder is diluted to 250 mL while being washed with water. After the graduated cylinder is allowed to stand for 5 minutes, the volume (mL) of the sample floating near the water surface is read to obtain a float.
[0016]
Next, the sludge was 4.0 kg / cm ² using a pressurized filtration tester (LABORATORY PRESSURE FILTER, manufactured by Glefco, USA) set with a twill-woven polypropylene filter cloth (500 g / m ² ). For 20 minutes and filtered. After the completion of the filtration, the cake was taken out of the pressurized filtration tester together with the filter cloth, and a cake having a thickness of about 1 cm was cut out from the filter cloth. This cake was placed on a filter cloth made of the same material as described above of a pressing machine (manufactured by Maruto Co., Ltd., compression tester), and was placed at 0.5 kg / cm ² for 30 seconds and at 2.0 kg / cm ² for 30 seconds. It was squeezed sequentially at 0 kg / cm ² for 3 minutes to obtain a dehydrated cake.
[0017]
The dehydrated cake thus obtained was peeled from the filter cloth, and the water content (%) was measured using an infrared moisture meter (FD-600, manufactured by Kett Science Laboratory Co., Ltd.). The results are shown in Table 1 as Examples 1 to 5 together with the amount of filtrate (mL) and the state of the filter cloth after filtering the sludge for 20 minutes using a pressure filtration tester. Further, for comparison, the sludge to which 19.3 g of slaked lime containing no pulverized particles was added, the results regarding the water content and the like similarly measured are shown in Table 1 as Comparative Example 1.
[0018]
[Table 1]

Here, the state of the filter cloth shown in Table 1 is an evaluation regarding the releasability when the dewatered cake after pressing is peeled from the filter cloth, and the state of the filter cloth is a double circle (で). The dewatered cake is very easily peeled off from the filter cloth, and when visually observed, almost no clogging of the filter cloth is observed, which means that the filter cloth is less stained. In addition, the state of the filter cloth being a circle (○) means that the dewatered cake is hard to peel off from the filter cloth, and the filter cloth is clogged when visually observed, and thus the filter cloth is much soiled. I do.
[0019]
Further, in Table 1, regarding the three types of pearlite as pulverized particles, those having a top percentage of 45 μm on a sieve of 0% each were Nos. No. 1 (Examples 1 and 2), 9% No. 2 (Examples 3 and 4), 49% 3 (Example 5). At this time, No. 1, No. The mixing ratios of the pearlite and slaked lime of No. 2 were set to two types of 3: 7 and 2: 8, respectively. Perlite No. 3 was also set at 3: 7.
[0020]
From the results shown in Table 1, the sludge filter aid of the present invention is more dewatered by adding ground particles, that is, pearlite, to slaked lime in the above-described ratio, compared to the case where sludge is filtered by adding slaked lime alone. It was found that the water content in the cake was reduced, the amount of filtrate discharged from the sludge was large, the clogging of the filter cloth was reduced, and the condition of the filter cloth was improved. However, as is clear from the results of Examples 1 and 2, the sludge filter aid of the present invention has a mixing ratio of 2: 7 with slaked lime in the case of pearlite having an upper percentage of 45% on a sieve of 45 μm. The moisture content in the dehydrated cake was lower than in the case of On the other hand, the results of Examples 3 and 4 show that, in the case of pearlite having an upper percentage of 9% on a 45 μm sieve, when the mixing ratio with slaked lime is 2: 8, the water content in the dehydrated cake is smaller than that of 3: 7. Was.
[0021]
On the other hand, the sludge filter aid of the present invention has a pearlite size of No. When one is used, the water content in the dewatered cake is minimized. However, the amount of the filtrate was the same as that described in Examples 3 and 4 when the percentage on the 45 μm sieve was 9%. 2 is the most. Therefore, from the results shown in Table 1, it was found that the sludge filter aid of the present invention preferably uses pearlite having 0% and 9% on 45 μm sieve as pulverized particles. However, pearlite having a 45% sieving percentage of 9% is more preferable as pulverized particles because it is cheaper and more economical than pearlite having a 45% sieving percentage of 0%.
[0022]
(Embodiment 2)
Next, a second embodiment according to the sludge filtration aid and the method for dewatering sludge of the present invention will be described. In the second embodiment of the present invention, based on the results of the above-mentioned desk test, sludge filtration aid obtained by mixing 20 parts by weight of pearlite having a percentage of 9% on a 45 μm sieve as crushed particles containing silicon dioxide as a main component with 80 parts by weight of slaked lime. An actual machine test was performed in a sludge treatment facility using the agent. FIG. 1 is a second embodiment of the present invention, and is a schematic diagram illustrating a method of dewatering sludge by an actual machine using a sludge filtration aid according to the present invention.
[0023]
As shown in FIG. 1, the sludge treatment facility 1 includes a concentrated sludge tank 2, a dissolution tank 3, a ferric chloride solution tank 4, a coagulated sludge tank 5, and a filter press 6.
[0024]
The concentrated sludge tank 2 stores sludge generated by sewage treatment, and an aqueous ferric chloride solution (concentration: 37.5%) and slaked lime slurry are added to the sludge in a coagulated sludge tank 5.
[0025]
The dissolving tank 3 dissolves slaked lime and perlite with water to form slaked lime slurry. Here, when the filter aid of the present invention is used in a sludge treatment facility, it is necessary to provide a new pulverized particle receiving tank, a measuring device, and a facility for transporting the pulverized particles in the sludge treatment facility, which requires a corresponding capital investment. It becomes. Therefore, slaked lime and perlite are mixed in a predetermined ratio in advance and put in a predetermined amount bag to prepare a product, which is carried into a sludge treatment facility so that it can be used. In this way, the user can adjust the slaked lime slurry by utilizing the existing slaked lime receiving tank in the sludge treatment facility, so that there is an advantage that it is not necessary to make a new capital investment.
[0026]
The ferric chloride solution tank 4 is a tank that stores an aqueous solution of ferric chloride having a concentration of 37.5%.
[0027]
In the coagulation sludge tank 5, an aqueous ferric chloride solution and slaked lime slurry are added, and the sludge is coagulated by stirring. At this time, the pH of the mixture of the ferric chloride aqueous solution, the slaked lime slurry, and the sludge in the coagulation sludge tank 5 is about 11.3 to 12.5.
[0028]
The filter press 6 filters the aggregated sludge aggregated in the aggregated sludge tank 5 and separates the aggregated sludge into a dehydrated cake and a dehydrated filtrate. The obtained dehydrated cake is transported for use as compost or landfill material, or for disposal by incineration or the like. On the other hand, the dehydrated filtrate is drained or reused in this sludge treatment facility. However, it is not limited to the filter press 6 as long as the above-described filtration is possible, and for example, a belt press, a centrifugal dehydrator, a screw press, a rotary vacuum dehydrator, or the like can be used.
[0029]
In the sludge treatment facility 1, 55 kg of a filter aid (80 parts by weight of slaked lime: 20 parts by weight of pearlite) obtained by mixing 44 kg of slaked lime with 11 kg of pearlite having a 45 μm sieving percentage of 9% on a sieve is dissolved in 495 kg of water in the dissolution tank 3. The mixed slaked lime slurry, concentrated sludge (6700 kg), and 43.5 kg of an aqueous ferric chloride solution (37.5%) are added to the flocculation sludge tank 5, aggregated by stirring and mixing, and filtered with a filter press 6. , And separated into a dehydrated cake and a dehydrated filtrate. The dewatering process was performed on the four types of sludge in this manner, and the measurement results regarding the water content and the average value of the obtained dewatered cake and the amount (mg / L) of suspended solids (SS: suspended solids) in the dewatered filtrate were shown. Example 2 is shown in FIG. Similarly, 50 kg of filter aid (80 parts by weight of slaked lime: 20 parts by weight of perlite) obtained by mixing 40 kg of slaked lime with 10 kg of pearlite having a percentage of 9% on a 45 μm sieve is mixed with 450 kg of water in the dissolving tank 3. The slurry, concentrated sludge (6700 kg), and 43.5 kg of an aqueous ferric chloride solution (37.5%) were added to the coagulated sludge tank 5, and the water content of the dewatered cake was determined for the four types of sludge treated in the same manner. The average value and the amount of suspended solids (SS: suspended solids) in the dehydrated filtrate were measured (mg / L). The results are shown in Table 2 as Example 7.
[0030]
[Table 2]

On the other hand, for comparison, in the dissolution tank 3, 55 kg of slaked lime alone was mixed with 495 kg of water without adding perlite to prepare a slaked lime slurry, and this was mixed with 43.5 kg of an aqueous ferric chloride solution (37.5%). Together with the concentrated sludge, and dewatering treatment was performed on four types of sludge as Comparative Examples 2 to 4 in the same manner as described above. Table 2 also shows the water content and the average value of the obtained plural dehydrated cakes and the measurement results regarding the amount (mg / L) of the suspended substance in the dehydrated filtrate.
[0031]
As is apparent from the results of Examples 6 and 7 and Comparative Examples 2 to 4 shown in Table 2, when a filter aid obtained by mixing 80 parts by weight of slaked lime with 20 parts by weight of pearlite having a 9% on-screen percentage of 45%, The water content of the dehydrated cake was reduced by an average of 1.6 to 2.0% as compared with the case of slaked lime alone. In addition, the amount of suspended substances (mg / L) was also significantly reduced in the dehydrated filtrate. As described above, according to the sludge filter aid and the sludge dewatering method of the present invention, the water content of the dewatered cake generated by the sludge treatment is reduced, and the cost required for transporting the dewatered cake can be reduced.
[0032]
【The invention's effect】
As described above, according to the sludge filtration aid of the present invention, the percentage of the 45 μm sieve on the sieve is 50% or less, and the float is 10 mL or less. On the other hand, it contains 95 to 65 parts by weight of slaked lime, and in the sludge dewatering method of the present invention, an aggregating step of mixing an aqueous ferric chloride solution and slaked lime slurry into sludge to form an agglomerated sludge; In the method of dewatering sludge provided with a filtration step of filtering, since the agglomeration step includes a step of mixing particles of a porous substance containing silicon dioxide as a main component in the slaked lime slurry, in the dewatered cake generated by the sludge treatment This has the effect of reducing the water content.
[Brief description of the drawings]
FIG. 1 is Embodiment 2 of the present invention, and is a schematic diagram illustrating a method of dewatering sludge by an actual machine using the sludge filtration aid of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sludge treatment equipment 2 Thickened sludge tank 3 Dissolution tank 4 Ferric chloride solution tank 5 Coagulated sludge tank 6 Filter press

Claims

A sludge characterized by containing 95 to 65 parts by weight of slaked lime with respect to 5 to 35 parts by weight of particles of a porous substance containing silicon dioxide as a main component, the percentage of which is not more than 50% on a 45 μm sieve and the float is not more than 10 mL. Filter aid.

The sludge filter aid, wherein the particles are either pearlite or diatomaceous earth.

In an agglomeration step of mixing an aqueous ferric chloride solution and slaked lime slurry with the sludge, and a dewatering method of the sludge including a filtration step of filtering the agglomerated sludge,
The method for dewatering sludge, characterized in that the coagulation step includes a step of mixing particles of a porous substance containing silicon dioxide as a main component in the slaked lime slurry.