JP2004358328A

JP2004358328A - Microorganism carrier

Info

Publication number: JP2004358328A
Application number: JP2003158494A
Authority: JP
Inventors: Tatsuya Yoshii; 達也吉井; Joji Ichihara; 譲治市原; Kaneo Mizuno; 金夫水野; Yoshiyuki Takashima; 良行高嶋
Original assignee: Denka Consultant and Engineering Co Ltd
Current assignee: Denka Consultant and Engineering Co Ltd
Priority date: 2003-06-03
Filing date: 2003-06-03
Publication date: 2004-12-24
Anticipated expiration: 2023-06-03
Also published as: JP3977775B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microorganism carrier for waste water treatment which is excellent in initial water wettability, and improves a biological treatment efficiency of waste water by reducing an acclimatization period and increasing the amount of sticking biomembrane. <P>SOLUTION: The microorganism carrier is made of thermoplastic resin foam containing 5-50 pts.wt. grain husk, especially wheat bran, with respect to 100 pts.wt. thermoplastic resin, and has a specific surface area of 5-50 m<SP>2</SP>/g dried carrier, The minimum particle diameter of the carrier is ≥2 mm, and the maximum particle diameter is ≤25 mm. The carrier has hardness of not being deformed by finger force, and is made by foam molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明が属する技術分野】
本発明は実用的廃水処理能力の高い微生物担体に関し、より詳しくは担体表面の水濡れ性が優れると共に、馴養期間が短縮され、定常運転時のＢＯＤ処理能力及び硝化脱窒素能力が高い廃水処理用微生物担体に関する。
【０００２】
【従来の技術】
従来、廃水処理、特に好気的手段による廃水ＢＯＤの積極的低減に関しては、活性汚泥法が採用されていた。活性汚泥法を更に効率化した方法として接触酸化法、流動性担体を充填した流動床法がある。例えば、特許文献１に開示された好ましい担体を用いて特許文献２に開示された流動床式廃水処理装置により処理した場合には、活性汚泥法の１０〜数１０倍の処理効率が得られている。
【０００３】
流動床式廃水処理装置の処理槽に充填される粒状微生物担体としては、ポリプロピレン、ポリエチレン、ポリビニルアルコール、ポリウレタン等の各種合成樹脂やセルロース誘導体が使用されている。これらは粒状、円筒状、円柱状等の形状に成形され、発泡により表面積を増加し、或いはフィラーの充填により適正な含水密度、１．０±０．１０に調整される。ここで、含水密度とは、水中で連通気泡に吸水させ密度が一定となったときの密度を言う。
【０００４】
一方、各種資材の運送時に資材と容器、資材と資材との間の空隙を埋めるバラ緩衝材として、ポリプロピレン等のポリオレフィン系樹脂にコーンスターチ、オカラやふすま等を混合し、押出機で押し出して得られた高発泡率の樹脂成形体が使用されている。この緩衝材は樹脂の比率が約３０重量％、コーンスターチ、オカラ、ふすま等の比率が約７０重量％を占めるため物理的衝撃に弱く、手指で押さえると直ちに変形し、廃水処理槽に投入した場合約１〜３か月で微生物分解され、物理的に破壊され、廃水処理用の担体としては使用できない。
【０００５】
【発明が解決しようとする課題】
流動床式廃水処理装置の一般的な長所として、処理効率が高く処理槽容積が少ないこと、流入廃水流量の変動による汚泥の流出がないこと等が挙げられる。流動床式廃水処理装置には種々の種類の粒子状担体が用いられるが、中でも、担体の外見上の表面だけでなく、担体内部にも微生物生息域を有する連通気泡率の高い担体は、担体あたりの微生物量の多さによる活性の高さと共に、廃水水質、水量の変動に対する安定性が高いので実用的に優れた担体として使用されている。ここで、連通気泡とは、担体内部の気泡の気相部が互いに繋がっていると共に、その気相部が担体外部に開いている気泡である。
【０００６】
ところが、連通気泡は直径が通常０．１ｍｍ以下の細孔であるため水の進入が難しく、水が連通気泡に完全に進入するまでは、担体は水面に浮上状態であったり、水面近くに偏在したりして水中に均一に分散せず、その機能を充分に発現しない。
そこで、流動床式廃水処理装置に新しい担体を装入し、短期間で槽内を均一に流動させ、微生物膜を付着させ、定常の処理能力を発現せしめる迄に要する期間（馴養期間）を短くすること及び廃水処理効率を高めることが従来からの課題であった。
【０００７】
【特許文献１】
特許第２７１１６２５号公報
【特許文献２】
実公平６−３４８８０号公報
【０００８】
【課題を解決するための手段】
本発明は上記課題を解決することを目的とし、その構成は、硬質熱可塑性樹脂に穀物殻、特にふすまを含有する熱可塑性樹脂発泡体からなる微生物担体であって、比表面積が５〜５０ｍ^２／ｇ乾燥担体で、担体１つの粒子の最小径と最大径がそれぞれ２ｍｍ以上、２５ｍｍ以下であり、手指の力で変形しない硬度を有し、化学発泡剤、液化ガス発泡剤及びガス発泡剤のいずれも用いることなく発泡成形されていることを特徴とする。
更に、流動床式廃水処理装置の担体として使用するため、適正な硬度を保つ必要上穀物殻の配合量は、樹脂１００重量部に対し５〜５０重量部である。
【０００９】
すなわち、本発明はＢＯＤ増加因子であるため、従来担体に配合しなかった穀物殻を敢えて配合することにより、微生物の栄養源として微生物の着床を促し、馴養期間を短縮し、定常運転後は微生物の生育を活発化して処理効率を高める事実を見出して完成したものである。また、本発明の穀物殻の配合により、担体の連通気泡中への水の進入速度を著しく加速し、含水飽和までの時間を著しく短縮することができる。
【００１０】
【発明の実施の形態】
本発明においては、連通気泡とは気泡が一方の面或いは二方以上の面に開口している気泡であり、発泡担体の表面積は発泡担体の乾燥重量あたりの表面積、すなわち、比表面積＝ｍ^２／ｇ乾燥担体で表す。比表面積は粒子表面の凹凸を含めた表面積の他、連通気泡の細孔内の表面積も加算される。本発明においては４ｎｍ〜４００μｍの径の気泡孔の表面積測定に適した水銀圧入式細孔分布測定装置により測定した数値を用いる。
なお、製造時に水で冷却される担体の場合には、水を含んでいるので完全に乾燥した後に測定する。
【００１１】
本発明で使用する穀物殻としては籾殻、オカラ、小麦殻であるふすま等が挙げられる。これら穀物殻は嵩比重０．２〜０．４が好ましく、粒度は１８〜２６タイラーメッシュである。穀物殻の配合量は樹脂１００重量部に対し５〜５０重量部、好ましくは１０〜４０重量部、より好ましくは２０〜３５重量部である。これら穀物殻はそれ自体水分を結合水として含有しているため特に発泡剤を添加しなくとも発泡し、適正な発泡率が得られる。
【００１２】
一般的に、流動床式廃水処理装置においては、処理槽の出口に網目状の分離手段を設け処理槽からの微生物担体の流出を防いでいる。担体はスクリーン等の分離手段の開口部に詰まったり、処理槽の壁面に衝突することもあり、物理的な衝撃に耐えることを要する。したがって、本発明に使用される熱可塑性樹脂は硬質樹脂であることを要し、ポリプロピレン、高密度ポリエチレン、ポリスチレン、硬質ポリ塩化ビニル等の硬質汎用樹脂及びこれらの樹脂の混合物が好ましい。
中でも、高密度ポリエチレン、ポリプロピレンが好適に使用されるが、これらの樹脂にポリスチレンを２〜１０重量％配合するとより高い硬度を付与することができる。
【００１３】
担体の硬度は手指で押さえた程度の力で変形或いは破損するようなものであってはならない。具体的には、乾燥担体を内径５０ｍｍ、深さ１２０ｍｍの円筒形容器に入れ、嵩体積で２００ｃｍ^３充填する。その上から直径４８ｍｍの円盤状ピストンを３０ｍｍ／分の速度で下げ、荷重とピストンの変位を、オリエンテック社製の圧縮引張試験機ＲＴＣ−１２１０Ａを用いてを測定する。この測定結果から１０Ｎから４０Ｎまで荷重が変化する際のピストンの変位が１〜３ｍｍ程度であることが好ましい。
【００１４】
本発明の発泡担体は、硬質樹脂、穀物殻及びフィラーを配合混練して押出成形して得られる。穀物殻自体が含有する水分に由来して発泡し、表面が粗面となり表面積が拡大する他、表面に開口部を有する多くの連通気泡を有し、担体粒子表面よりはるかに大きい担体内部の表面積を有する。
【００１５】
本発明においては、発泡担体は連通気泡と独立気泡を有し、このため担体の含水密度は樹脂及び樹脂配合物の真比重よりも小さくなる。そこでタルク、石灰石、活性炭、木粉、焼却灰、ペーパースラッジ焼却灰等の真比重が１より大きい無機及び有機の粉状物質をフィラーとして充填配合して水中安定後の見掛け比重を１±０．１０、好ましくは１±０．０５の範囲に調整する。
フィラーには担体比重の調節の他、発泡の核剤として、微生物との親和性の向上、コスト低減等の効果もある。
【００１６】
担体粒子の形状は立方体、直方体、円柱状、円筒形又はこれらの基本型を変形した形状、不定型等、特に限定はないが、その大きさは２〜２５ｍｍの範囲である。円筒形のように明らかな貫通孔を有する場合でも、貫通孔を無視して外寸法で判断する。流動床用担体にあっては、使用状態における担体の機能が担体の表面積にほぼ比例するため２５ｍｍを越える担体はその嵩容積あたりの表面積が減少して好ましくない。また、処理槽から処理水が流出する際に、担体を処理水と分離するためにスクリーン分離法、浮上分離法、沈降分離法等があり、いずれの方式にあっても極度に小さい担体は分離が困難であり、最小径２ｍｍ以上の担体が好ましい。
【００１７】
本発明微生物担体を製造する方法は特に限定しない。穀物殻を含有するため発泡剤、液化ガス発泡剤、ガス発泡を使用せずに充分に発泡させることができる。例えば、ポリオレフィン樹脂、ポリスチレン等の原料樹脂に穀物殻、フィラー等を配合し、通常のプラスチック押出機を用いてダイスから１本或いは２本以上のストランドとして押出すことができる。発泡ストランドを水槽にて冷却固化し、所定の長さに切断する方法等がある。
本発明の微生物担体は流動床式廃水処理装置に好ましく使用される。使用にあたっては本発明担体を流動床式廃水処理槽に、処理槽の水槽容積あたり１０〜６０％の嵩容積になるように充填すると高い廃水処理効率を発現する。
【００１８】
【実施例】
実施例１
活性炭１重量部
ポリスチレン６重量部
ポリプロピレン９４重量部
タルク１５重量部
ふすま３０重量部
界面活性剤１重量部
上記原料を上記割合で混合し、６５ｍｍφスクリュー押出機にて、５ｍｍφの孔１２個を有するストランドダイより押出して発泡ストランドを得た。このストランドを水槽にて冷却固化後、ペレタイザーカッターにて５ｍｍ長さに切断して５ｍｍφ、高さ５ｍｍの本発明円柱状発泡担体を得た。
なお、使用したふすまの嵩比重は０．３０であり、粒度は２２タイラーメッシュ篩で４３％篩上、５７％通過のふすまであった。
【００１９】
この担体粒子の含水密度は１．０３（ｇ／ｍｌ）であり、水銀圧入法による比表面積は４５ｍ^２／ｇ乾燥担体であった。担体中の水銀圧入法による空隙率は４２％であった。これらの結果を表１に示した。
【００２０】
実施例２〜４及び比較例１
ふすまの量を表１に示すように代えた以外は実施例１と同様にして微生物担体を製造し、実施例２〜４とした。又、比較例１としてふすまを添加せず、発泡剤としてアゾジカルボンアミド１重量部を配合した以外は実施例１と同様にして担体を製造した。
実施例２〜４及び比較例１の比表面積、含水密度及び担体中の空隙率を測定して表１に併記した。
なお、比表面積は島津製作所社製ＡＵＴＯＲＯＰＥＩＩ９２２０により水銀圧入法で測定した。
【００２１】
【表１】

【００２２】
実施例５及び比較例２
水槽有効容積１リットルの曝気槽Ａ、Ｂの２槽を用い、その容積の２０％にあたる２００ｍｌの嵩容積の担体を充填した。曝気槽Ａには実施例１の担体を、曝気槽Ｂには比較例１の担体をそれぞれ充填し、実施例５及び比較例２とした。両曝気槽共、下水処理場の活性汚泥２００ｍｌを種汚泥として入れ、原水はグルコースを水に溶解してＴＯＣ＝５００ｐｐｍの模擬原水を８０ｍｌ／時間で連続的に供給し、曝気槽底部の多孔質散気装置より５リットル／分の空気を供給し、２０〜２５℃の範囲の水槽温度で連続運転した。この運転では返送汚泥を行わなかった。曝気槽出口には目開き２．５ｍｍのスクリーンを設けた。
各曝気槽出口の処理水をＮｏ．６濾紙でろ過後ＴＯＣの分析を行い、その結果を表２に示した（以下、ろ過後のＴＯＣをｓ−ＴＯＣとする）。
【００２３】
【表２】

【００２４】
実施例１の担体を用いた実施例５の場合、処理水のｓ−ＴＯＣ濃度は２４日以降９０ｐｐｍ以下で実質一定となり、馴養期間が完了した。比較例１の担体を用いた比較例２の場合、４０日以降実質１２０ｐｐｍ以下で一定となり、馴養期間が完了した。
表２より馴養期間は実施例１の担体を用いた実施例５の方が、比較例１の担体を用いた比較例２より短く、処理水のｓ−ＴＯＣ濃度も実施例５の方が低く、処理効率も実施例５が優れていることが明らかである。
【００２５】
実施例５において、運転日数８４日目の担体全量を取出し、超音波洗浄機で６０分間振動させて付着生物膜を剥離させ、乾燥重量（以下、ＤＳと略す）を測定したところ、付着生物膜量は３．８８ｇ−ＤＳであった。
一方、比較例２についても運転日数８４日目の担体全量を取出し、実施例５と同様にして付着生物膜量を測定したところ、１．６７ｇ−ＤＳであった。
【００２６】
実施例６及び比較例３
水槽有効容積１リットルの曝気槽Ａ、Ｂの２槽を用いて、その２０％にあたる２００ｍｌの嵩容積の担体を充填した。曝気槽Ａには実施例１の担体を、曝気槽Ｂには比較例１の担体をそれぞれ２００ｍｌ充填し、それぞれ実施例６及び比較例３とした。両曝気槽共に、下水処理場の活性汚泥５００ｍｌを種汚泥として入れた。
原水はＮＨ_４Ｃｌ２２．９ｇ、ＫＨ_２ＰＯ_４５ｇ、Ｋ_２ＨＰＯ_４１０ｇ、
ＮａＨＣＯ_３５６ｇ、メタノール２４ｇを水に溶かして３リットルとしたものを用いた。この原水のＢＯＤは７９００ｐｐｍ、全窒素は１８１０ｐｐｍ、であった。この原水を各曝気槽に０．５リットル入れ、各曝気槽を５リットル／分の空気で１２時間曝気後、１２時間曝気を停止するサイクルを３日間続けた。
３日間経過後、各槽の液をＮｏ．６ろ紙でろ過後溶存全窒素を測定したところ、曝気槽Ａは１１６ｐｐｍであり、一方、曝気槽Ｂは３５４ｐｐｍであった。
【００２７】
【発明の効果】
本発明の微生物担体を流動床式廃水処理装置に使用すれば、初期の水濡れが良好となり、馴養期間の短縮と、付着生物膜量の増加によって廃水の生物処理効率が改善される。更に硝化／脱窒素の担体としても使用される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a microorganism carrier having a high practical wastewater treatment capability, and more specifically, to a wastewater treatment having a high water wettability on the surface of the carrier, a short acclimation period, and a high BOD treatment capability and a high nitrification and denitrification capability during steady operation. It relates to a microbial carrier.
[0002]
[Prior art]
Conventionally, an activated sludge method has been employed for wastewater treatment, particularly for aggressive reduction of wastewater BOD by aerobic means. As methods for further improving the activated sludge method, there are a catalytic oxidation method and a fluidized bed method filled with a fluid carrier. For example, when the treatment is performed by the fluidized bed wastewater treatment apparatus disclosed in Patent Document 2 using the preferred carrier disclosed in Patent Document 1, a treatment efficiency 10 to several tens times that of the activated sludge method is obtained. I have.
[0003]
Various synthetic resins such as polypropylene, polyethylene, polyvinyl alcohol, and polyurethane, and cellulose derivatives are used as the granular microbial carrier to be filled in the treatment tank of the fluidized bed wastewater treatment apparatus. These are formed into a shape such as a granular shape, a cylindrical shape, or a cylindrical shape, and the surface area is increased by foaming, or the water content is adjusted to an appropriate value of 1.0 ± 0.10. Here, the water-containing density refers to the density when the communicating bubbles absorb water in water and the density becomes constant.
[0004]
On the other hand, corn starch, okara, bran, etc. are mixed with polyolefin resin such as polypropylene as a buffer material to fill voids between materials and containers, materials and materials during transportation of various materials, and extruded with an extruder. A resin molded article having a high foaming rate is used. This buffer material is vulnerable to physical impact because the ratio of resin is about 30% by weight and the ratio of corn starch, okara, bran, etc. is about 70% by weight. It is biodegraded in about 1 to 3 months, physically destroyed, and cannot be used as a carrier for wastewater treatment.
[0005]
[Problems to be solved by the invention]
The general advantages of a fluidized-bed wastewater treatment system include high treatment efficiency and small treatment tank volume, and no sludge outflow due to fluctuations in the flow rate of inflow wastewater. Various types of particulate carriers are used in a fluidized bed type wastewater treatment apparatus. Among them, a carrier having a high open-cell bubble rate having a microbial habitat not only on the outer surface of the carrier but also inside the carrier is a carrier. It is used as a practically excellent carrier because of its high activity due to the large amount of microorganisms per unit and high stability against fluctuations in wastewater quality and water volume. Here, the communicating bubbles are bubbles in which the gas phase portions of the bubbles inside the carrier are connected to each other and the gas phase portion is open to the outside of the carrier.
[0006]
However, since the communicating bubbles are usually pores having a diameter of 0.1 mm or less, it is difficult for water to enter, and the carrier floats on the water surface or is unevenly distributed near the water surface until the water completely enters the communicating bubbles. It does not disperse evenly in water and does not exhibit its function sufficiently.
Therefore, a new carrier is charged into the fluidized-bed wastewater treatment equipment, and the time required for the fluid to uniformly flow in the tank in a short period of time, adhere the microbial membrane, and develop a steady treatment capacity (acclimation period) is shortened. And improving the efficiency of wastewater treatment have been conventional issues.
[0007]
[Patent Document 1]
Japanese Patent No. 2711625 [Patent Document 2]
Japanese Utility Model Publication No. 6-34880
[Means for Solving the Problems]
An object of the present invention is to solve the above-mentioned problems, and a structure thereof is a microorganism carrier comprising a thermoplastic resin foam containing cereal hulls, particularly bran in a hard thermoplastic resin, having a specific surface area of 5 to 50 m ^2. / G dry carrier, the minimum diameter and the maximum diameter of one particle of the carrier are 2 mm or more and 25 mm or less, respectively, and have a hardness not deformed by the force of a finger, and a chemical foaming agent, a liquefied gas foaming agent and a gas foaming agent. It is characterized by being foamed without using any of them.
Furthermore, in order to use as a carrier of a fluidized bed type wastewater treatment apparatus, the blending amount of cereal husk is 5 to 50 parts by weight with respect to 100 parts by weight of resin in order to maintain appropriate hardness.
[0009]
That is, since the present invention is a BOD increasing factor, by intentionally blending grain husks that were not previously blended with the carrier, it promotes implantation of microorganisms as a nutrient source for microorganisms, shortens the acclimation period, and after steady operation. It was completed by finding the fact that the growth of microorganisms was activated and the treatment efficiency was improved. In addition, the blending of the cereal husk of the present invention can significantly accelerate the rate of entry of water into the open cells of the carrier, and can significantly shorten the time until saturation with water.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the open cells are cells in which the cells are open on one side or two or more sides, and the surface area of the foamed carrier is the surface area per dry weight of the foamed carrier, that is, the specific surface area = m ² / G expressed as dry carrier. The specific surface area includes not only the surface area including the irregularities on the particle surface but also the surface area in the pores of the communicating bubbles. In the present invention, numerical values measured by a mercury intrusion-type pore distribution measuring apparatus suitable for measuring the surface area of pores having a diameter of 4 nm to 400 μm are used.
In the case of a carrier that is cooled with water at the time of production, it is measured after being completely dried because it contains water.
[0011]
Grain husks used in the present invention include rice husk, okara, and wheat husk bran. These grain husks preferably have a bulk specific gravity of 0.2 to 0.4 and a particle size of 18 to 26 Tyler mesh. The blending amount of the cereal husk is 5 to 50 parts by weight, preferably 10 to 40 parts by weight, more preferably 20 to 35 parts by weight based on 100 parts by weight of the resin. Since these cereal husks themselves contain moisture as bound water, they are foamed without adding a foaming agent, and an appropriate foaming rate can be obtained.
[0012]
Generally, in a fluidized-bed type wastewater treatment apparatus, a mesh-like separation means is provided at an outlet of a treatment tank to prevent outflow of microorganism carriers from the treatment tank. The carrier may clog the opening of the separation means such as a screen, or may collide with the wall surface of the processing tank, and must withstand physical impact. Therefore, the thermoplastic resin used in the present invention needs to be a hard resin, and a hard general-purpose resin such as polypropylene, high-density polyethylene, polystyrene, or hard polyvinyl chloride, and a mixture of these resins are preferable.
Among them, high-density polyethylene and polypropylene are preferably used, but when these resins are blended with 2 to 10% by weight of polystyrene, higher hardness can be imparted.
[0013]
The hardness of the carrier must not be such that it is deformed or broken by the force of the finger. Specifically, the dry carrier is placed in a cylindrical container having an inner diameter of 50 mm and a depth of 120 mm, and is filled with a bulk volume of 200 cm ³ . A disk-shaped piston having a diameter of 48 mm is lowered from above at a speed of 30 mm / min, and the load and the displacement of the piston are measured using a compression / tensile tester RTC-1210A manufactured by Orientec. From this measurement result, it is preferable that the displacement of the piston when the load changes from 10 N to 40 N is about 1 to 3 mm.
[0014]
The foamed carrier of the present invention is obtained by compounding and kneading a hard resin, a grain hull, and a filler, and extruding the mixture. Foamed by the moisture contained in the cereal husk itself, the surface becomes rough and the surface area increases, and in addition to many open cells with openings on the surface, the surface area inside the carrier that is much larger than the surface of the carrier particles Having.
[0015]
In the present invention, the foamed carrier has open cells and closed cells, so that the water density of the carrier is smaller than the true specific gravity of the resin and the resin compound. Therefore, an inorganic or organic powdery substance having a true specific gravity of more than 1 such as talc, limestone, activated carbon, wood flour, incinerated ash, paper sludge incinerated ash and the like is filled and blended as a filler to give an apparent specific gravity of 1 ± 0. It is adjusted to 10, preferably 1 ± 0.05.
The filler not only regulates the specific gravity of the carrier, but also has an effect as a foaming nucleating agent, such as an improvement in affinity with microorganisms and a reduction in cost.
[0016]
The shape of the carrier particles is not particularly limited, such as a cube, a rectangular parallelepiped, a columnar shape, a cylindrical shape, a shape obtained by deforming these basic shapes, an irregular shape, and the like, but the size is in a range of 2 to 25 mm. Even in the case where there is a clear through-hole such as a cylindrical shape, the judgment is made based on the outer dimensions ignoring the through-hole. In the case of a carrier for a fluidized bed, since the function of the carrier in use is almost proportional to the surface area of the carrier, a carrier exceeding 25 mm is not preferable because the surface area per bulk volume is reduced. In addition, when the treated water flows out of the treatment tank, there are screen separation method, flotation separation method, sedimentation separation method, etc. to separate the carrier from the treated water. Is difficult, and a carrier having a minimum diameter of 2 mm or more is preferable.
[0017]
The method for producing the microorganism carrier of the present invention is not particularly limited. Since it contains cereal husks, it can be sufficiently foamed without using a foaming agent, a liquefied gas foaming agent, or gas foaming. For example, grain hulls, fillers, and the like can be blended with a raw resin such as a polyolefin resin or polystyrene, and can be extruded from a die as one or more strands using a normal plastic extruder. There is a method of cooling and solidifying the foamed strand in a water tank and cutting it into a predetermined length.
The microorganism carrier of the present invention is preferably used for a fluidized bed type wastewater treatment apparatus. In use, when the carrier of the present invention is filled in a fluidized bed type wastewater treatment tank so as to have a bulk volume of 10 to 60% per tank capacity of the treatment tank, high wastewater treatment efficiency is exhibited.
[0018]
【Example】
Example 1
Activated carbon 1 part by weight Polystyrene 6 parts by weight Polypropylene 94 parts by weight Talc 15 parts by weight Bran 30 parts by weight Surfactant 1 part by weight The above-mentioned raw materials are mixed in the above ratio, and a strand having 12 holes of 5 mmφ with a 65 mmφ screw extruder. It was extruded from a die to obtain a foamed strand. After cooling and solidifying this strand in a water tank, it was cut into a length of 5 mm with a pelletizer cutter to obtain a columnar foamed carrier of the present invention having a diameter of 5 mm and a height of 5 mm.
The bulk specific gravity of the bran used was 0.30, and the particle size was 43% on a 22 Tyler mesh sieve, up to 57% passing bran.
[0019]
The water content of the carrier particles was 1.03 (g / ml), and the specific surface area by a mercury intrusion method was 45 m ² / g dry carrier. The porosity of the carrier obtained by the mercury intrusion method was 42%. Table 1 shows the results.
[0020]
Examples 2 to 4 and Comparative Example 1
Microbial carriers were produced in the same manner as in Example 1 except that the amount of bran was changed as shown in Table 1, and Examples 2 to 4 were made. In Comparative Example 1, a carrier was produced in the same manner as in Example 1 except that bran was not added and 1 part by weight of azodicarbonamide was added as a foaming agent.
The specific surface area, the water content density and the porosity in the carrier of Examples 2 to 4 and Comparative Example 1 were measured and are shown in Table 1.
The specific surface area was measured by a mercury intrusion method using AUTOROPE II 9220 manufactured by Shimadzu Corporation.
[0021]
[Table 1]

[0022]
Example 5 and Comparative Example 2
Two tanks, aeration tanks A and B, each having an effective volume of 1 liter, were filled with a carrier having a bulk volume of 200 ml or 20% of the volume. The aeration tank A was filled with the carrier of Example 1, and the aeration tank B was filled with the carrier of Comparative Example 1, respectively, to obtain Example 5 and Comparative Example 2. In both aeration tanks, 200 ml of activated sludge from a sewage treatment plant is put in as seed sludge, glucose is dissolved in water, and raw water with a TOC of 500 ppm is continuously supplied at a rate of 80 ml / hour. Air was supplied from the air diffuser at 5 L / min, and the operation was continuously performed at a water bath temperature in the range of 20 to 25 ° C. This operation did not return sludge. A screen with an aperture of 2.5 mm was provided at the outlet of the aeration tank.
The treated water at the outlet of each aeration tank was no. After filtering through 6 filter papers, the TOC was analyzed, and the results are shown in Table 2 (hereinafter, TOC after filtration is referred to as s-TOC).
[0023]
[Table 2]

[0024]
In the case of Example 5 using the carrier of Example 1, the s-TOC concentration of the treated water became substantially constant at 90 ppm or less after 24 days, and the acclimatization period was completed. In the case of Comparative Example 2 using the carrier of Comparative Example 1, it became constant at substantially 120 ppm or less after 40 days, and the acclimatization period was completed.
From Table 2, the acclimatization period of Example 5 using the carrier of Example 1 was shorter than that of Comparative Example 2 using the carrier of Comparative Example 1, and the s-TOC concentration of the treated water was lower in Example 5 than in Example 5. It is clear that Example 5 is excellent in processing efficiency.
[0025]
In Example 5, the entire amount of the carrier on the 84th operating day was taken out, the adhered biofilm was peeled off by vibrating with an ultrasonic cleaner for 60 minutes, and the dry weight (hereinafter abbreviated as DS) was measured. The amount was 3.88 g-DS.
On the other hand, also in Comparative Example 2, the total amount of the carrier on the 84th operating day was taken out, and the amount of the attached biofilm was measured in the same manner as in Example 5. The result was 1.67 g-DS.
[0026]
Example 6 and Comparative Example 3
Using two tanks, aeration tanks A and B, each having an effective volume of 1 liter in a water tank, a carrier having a bulk volume of 200 ml corresponding to 20% of the tank was filled. The aeration tank A was filled with the carrier of Example 1 and the aeration tank B was filled with 200 ml of the carrier of Comparative Example 1, respectively, to obtain Example 6 and Comparative Example 3, respectively. In both aeration tanks, 500 ml of activated sludge from a sewage treatment plant was introduced as seed sludge.
Raw water was 22.9 g of NH ₄ Cl, 5 g of KH ₂ PO ₄ , 10 g of K ₂ HPO ₄ ,
A solution prepared by dissolving 56 g of NaHCO ₃ and 24 g of methanol in water to make 3 liters was used. The BOD of this raw water was 7900 ppm and the total nitrogen was 1810 ppm. 0.5 L of this raw water was put into each aeration tank, and each aeration tank was aerated with air at 5 L / min for 12 hours, and then the cycle of stopping the aeration for 12 hours was continued for 3 days.
After 3 days, the liquid in each tank was When the total dissolved nitrogen was measured after filtration with 6 filter papers, the aeration tank A was 116 ppm, while the aeration tank B was 354 ppm.
[0027]
【The invention's effect】
When the microbial carrier of the present invention is used in a fluidized-bed wastewater treatment apparatus, the initial water wetting becomes good, and the acclimatization period is shortened, and the biological treatment efficiency of wastewater is improved by increasing the amount of attached biofilm. It is also used as a carrier for nitrification / denitrification.

Claims

A thermoplastic resin foam mainly composed of a hard thermoplastic resin and a cereal shell, having a specific surface area of 5 to 50 m ² / g dry carrier, wherein the minimum diameter and the maximum diameter of one carrier particle are 2 mm or more and 25 mm, respectively. A microbial carrier for wastewater treatment, which has the following hardness, which does not deform under the force of fingers.

The microorganism carrier for wastewater treatment according to claim 1, wherein the cereal hull is contained in an amount of 5 to 50 parts by weight based on 100 parts by weight of the resin.

3. The waste water treatment according to claim 1, wherein the hard thermoplastic resin is high-density polyethylene, polypropylene, a mixture of high-density polyethylene and polypropylene, or a resin containing 10% by weight or less of polystyrene. Microbial carrier.

The microorganism carrier for wastewater treatment according to any one of claims 1 to 3, wherein the cereal husk is covered with bran.

100 parts by weight of the hard thermoplastic resin is blended with 5 to 50 parts by weight of cereal hulls, and foamed without using any of a chemical blowing agent, a liquefied gas blowing agent and a gas blowing agent. A method for producing a microorganism carrier for wastewater treatment having a hardness of 2 mm or more and 25 mm or less and not deformed by the force of a finger.