JP3684410B2 - Sewage sludge treatment method and treated sewage sludge - Google Patents
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【０００１】
【産業上の利用分野】
本発明は、産業排水及び一般家庭排水を処理して生じる有機性下水汚泥の処理に関するものである。
【０００２】
【従来の技術】
近年、下水道網の整備の拡大に伴い下水汚泥の発生量は増加の一途をたどっている。下水汚泥の処理法としては、従来、重油のような助燃用燃料を加えて焼却し、焼却灰を埋立て処分するのが一般的であったが、最終処分先の埋立地の確保が困難となりつつあり、下水処理産物の減容化あるいは有効利用法の開発が急務である。
焼却灰の減容化方法としては溶融ガラス化する方法が一部の処理場で試みられているが、エネルギーコストが高い上に排出される灰を処理する問題が残り根本的な解決法とはなっていない。また、焼却灰の有効利用法としては、レンガ製品の製造や有機肥料への使用等、多くの方法が試みられているが、新たに市場を開拓する必要があったり、既存の競合品と対抗するには品質的・コスト的になお問題があるなどの難点があり、汚泥の大量的かつ安定的な利用にはつながっていない。
【０００３】
このような中にあって汚泥を生石灰等と混合・脱水した上でセメント原料または製鉄用焼結原料として利用する技術（特開平 3-98700号、特開平3-207497号）が注目されている。セメント製造または製鉄では１０００℃以上の炉を用いて原料を焼結しており、汚泥をこれらの炉に投入すると、汚泥中の有機物は助燃用燃料を加えずに燃焼するので、助燃用燃料を必要とする従来の処理法と比較してエネルギ−的に有利である。しかも無機物は硅酸質材料や石灰質原料として有効利用され、また既存のセメント製造施設や製鋼施設をそのまま利用できる利点があり、さらに廃ガス対策も既存設備の廃ガス処理で足りる。また、これらの方法はセメントあるいは鉄鋼といった継続運転する産業用原料として用いるために汚泥の大量処理が可能であり、新商品開発に伴なう市場開拓努力なしに安定的に下水汚泥が処理できる点で画期的な解決法ともいえ、今後、この方向の利用法が普及することが望まれている。
【０００４】
【従来技術の課題】
一方、これらの方法には次のような課題が残っている。すなわち、現在の下水処理法の主流である活性汚泥法においては窒素分は汚泥に濃縮吸着させているため、処理場から排出される下水汚泥は多量の窒素分を含む。下水汚泥に生石灰類を添加する上記処理方法では、汚泥に生石灰を混合した際の発熱によって汚泥中の窒素分が分解し、多量のアンモニアガスが発生して揮散するため周囲に悪臭が拡散する。発生したアンモニアガスの大部分は生石灰との混合時に回収することができるが、一部は生石灰水和後の高比表面積の消石灰と乾燥汚泥の混合物（以下、“乾粉”と称す。）に吸着されて残存する。この残存アンモニア分は温度の上昇と共に揮散し、乾粉保管用サイロ内では気温が３０℃以上になると濃度数％以上のアンモニアガスが充満し、作業環境が劣悪になる。この乾粉を密閉保管しても、その出し入れや移送の際、あるいはセメント原料として炉に投入する際などにはアンモニアガスの漏出が避けられず、悪臭が漂う。
因みに、人間の臭覚は１ppm 程度のアンモニア濃度でも感知するため、これ以下にアンモニア濃度を除去する脱臭処理方法が求められている。
【０００５】
アンモニア臭気対策としては、ペット用砂等でよく行われているように、活性炭などの有機系高比表面積物質に吸着させる方法が知られている。しかし、この方法は乾粉の臭気対策には適さない。すなわち、活性炭などはアンモニアのほかに水やゴミ等を吸着して短期間に表面が飽和し、吸着力が急激に低下する欠点がある。また、多量に使用すると処理コストの増大を招き、少量の使用で効果を挙げるために微粉化すると、保管時あるいは移送時に空気中の酸素と結合し易くなり、いわゆる粉塵爆発の危険性を招く。
活性炭などを用いる方法に代えて、気相あるいは液相の酸を滴下することによりアンモニアを中和することも考えられるが、酸の保管自体が危険物の保管となり管理が面倒になる上、配管等の耐食対策が必要なため処理コストが相当に嵩む問題がある。
【０００６】
【発明の解決課題】
本発明は、以上のような従来の処理方法における問題を解決したものであり、大量に発生する下水汚泥の悪臭を除去し、下水汚泥を安定的に有効利用できる方法を提供することを目的とする。
本発明によれば、下水汚泥と生石灰の混合物の悪臭が低コストで除去されるので、該混合物をセメント原料あるいは製鉄原料として利用し易くなり、さらには従来利用されていない分野での新たな用途も可能になる。
【０００７】
【課題を解決するための手段】
本発明によれば、以下の構成からなる下水汚泥の処理方法と下水汚泥処理物が提供される。
（１） 下水汚泥に生石灰類を混合した後に、この混合物を熟成混合機に移して熟成を進行させ、この熟成混合物に硫酸アルミニウム含有粉体を添加して脱臭する処理方法において、含水率６０〜１００％の下水汚泥について、汚泥固形分１００重量部に対して５０〜１５０重量部の生石灰類を混合して水分量を低減した後に、この混合物を熟成混合機に移して熟成させることによってさらに水分量を低減して水分量３〜８％の乾粉とし、この熟成乾粉に硫酸アルミニウム含有量が５重量％以上の脱臭用粉体を上記乾粉１００重量部に対して０.１〜７０重量部混合して脱臭することを特徴とする下水汚泥の処理方法。
（２） 含水率６０〜１００％の下水汚泥について、汚泥固形分１００重量部に対して５０〜１５０重量部の生石灰類を混合して水分量を低減した後に、この混合物を熟成混合機に移して熟成させることによってさらに水分量を低減して水分量３〜８％の乾粉とし、この熟成乾粉に硫酸アルミニウム含有量が５重量％以上の脱臭用粉体を上記乾粉１００重量部に対して０.１〜７０重量部混合してなる脱臭下水汚泥処理物。
【０００８】
【具体的な説明】
（Ｉ）生石灰類による脱水工程
本発明で処理する下水汚泥は、主に下水処理場で発生する汚泥であるが、この他に、し尿、家庭用雑排水、産業用排水処理などによって発生した汚泥を含む。これらの汚泥は一般に含水率６０〜１００％程度まで脱水処理されており、本発明はこの下水汚泥を使用する。
下水汚泥に混合する生石灰類とは、ＣａＯを主成分とし、下水汚泥の水分を取り込んで消石灰類になるものを云い、具体的には、生石灰、仮焼ドロマイト、水滓、高炉スラグなどが含まれる。生石灰類の粒度は粒径７０mm以下、好ましくは３０mm以下であれば良い。
生石灰類の混合量は下水汚泥の含水率にもよるが、概ね、下水汚泥１００重量部に対して５０〜１５０重量部、好ましくは８０〜１３０重量部程度が用いられる。生石灰の添加量がこの範囲よりも少ないと汚泥が乾燥せず、セメント原料ないし製鉄原料として適さない。また生石灰の添加量が多すぎるとコスト高になるので好ましくない。含水率８０％の下水汚泥に同量程度の生石灰を混合したものは、含水率がほぼゼロの乾燥した粉体が得られる。
【０００９】
（ II ）硫酸アルミニウム含有粉体による脱臭工程
以上のように脱水処理された汚泥と石灰の混合物に硫酸アルミニウムを含む粉体を添加して脱臭する。
硫酸アルミニウムは、Al2 （SO4 ）3 で表わされる単塩、硫酸アルミニウムと他の塩からなる複塩およびその水化物（含水塩）を用いることができる。複塩には、例えば、硫酸アルミニウムカリウム［KAl(SO4 ) 2 、カリミョウバン］や硫酸アルミニウムナトリウム［ NaAl(SO4 ) 2 、ナトリウムミョウバン］などの、いわゆるミョウバンが含まれる。ミョウバンは一般式:XAl3 （SO4 ）2 (OH)6 で表されるが、ＸがＫ、Na，NH4 、(1/2)Pb 等であるものが有効に用いられる。さらにAlの部分をFe、Cu、Znで一部置換したものも用いられる。
【００１０】
硫酸アルミニウムは乾粉に添加混合されると乾粉中の水分と反応して加水分解する。加水分解物は硫酸を含むため強酸性を示す。本発明の脱臭作用は基本的には硫酸アルミニウム粉末の吸着作用と硫酸アルミニウムの加水分解によって生じた硫酸とアンモニアとの中和反応との相乗的な作用に基づくものと推察される。すなわち、従来、消臭剤として使用されているシリカゲル、ゼオライトおよび活性炭の消臭効果はこれらの表面吸着作用に専ら基づいており、乾粉のアンモニア成分のほかにも水蒸気を多量に吸着する。このため、吸着作用が飽和し、肝心のアンモニアガスを十分に吸着できず、消臭効果が低下する。一方、本発明の硫酸アルミニウム粉末は適度な湿分によって硫酸を生じるので、水蒸気を吸着してもこの硫酸によってアンモニアが中和される。従って、シリカゲルなどと異なり、水蒸気の吸着による吸着作用の飽和による消臭効果の低下をきたさず、高い消臭効果を発揮することができる。
【００１１】
硫酸アルミニウム粉末は粒度が細かいほど消臭効果が大きいが、過度の粉砕はコストアップにつながる上に、吸湿を招きやすいため好ましくない。具体的には３mm以下が適当であり、0.05〜１mm以下がより好ましい。
因みに、従来のシリカゲルなどの消臭剤も、吸着効果を高めるために比表面積が大きくなるよう微粉末のものが用いられるが、前述したように、多量の水分の吸着により短時間に吸着作用が飽和するので微粉化しても消臭効果はそれ程向上しない。一方、本発明の硫酸アルニミウム粉末は吸着作用と硫酸による中和作用の相乗的作用によって脱臭するので、粒度が細かいほど吸着能による消臭効果が大きいものの、後述する実施例および比較例に示すように、必要以上に微粉化しなくてもよい。
【００１２】
硫酸アルミニウムは、通常、結晶水を有する水和物として得られ、この結晶水は結晶中に拘束されているため特に悪影響を及ぼすことはないが、粒子（結晶）表面の過度な付着水分は乾粉と接触させる前に酸を生じて容器や管路を侵し、また硫酸アルミニウム粉末の凝集を招き管路やフィーダなどの閉塞を生じるなど流動性低下の原因となり、さらには粉末表面が水分で飽和されると吸着作用が低下する。従って、硫酸アルミニウム粉末は乾燥状態で用いることが好ましい。具体的には含水率５０％以下が好ましい。
【００１３】
硫酸アルミニウムは単独で使用してもよく、また、消臭作用を有する他の粉体と混合して使用してもよい。併用する粉体としては、例えば、シリカゲル、クリストバライト、ケイ藻土のような硅酸質粉体、各種の粘土類、活性白土、酸性白土、ゼオライト、タルク、セピオライト等のような硅酸塩鉱物粉や炭酸カルシウム等が挙げられる。これらのうち、ケイ藻土、酸性白土およびその加工品である活性白土が好適である。これらは、その粒子表面に酸基を保持するのでアンモニア分子を効果的に捕捉することができ、硫酸アルミニウム粉末の消臭効果と相俟って優れた脱臭効果が得られる。また、化学成分が SiO2 −Al2 O3 系であるので脱臭した下水処理物をセメント原料や製鉄原料あるいは土壌改良材などに利用するうえでも都合がよい。
【００１４】
上記混合粉体中の硫酸アルミニウム含有量は５重量％以上であり、内割で１０重量％以上含有するものが好ましい。また、混合粉末の使用量は乾粉１００重量部に対して０．１〜７０重量部、好ましくは１〜１０重量部が適当である。硫酸アルミニウムの含有量が１０重量％未満であると十分な脱臭効果を得るための混合粉末の使用量が増し、処理コストが嵩む。また、混合粉末の使用量が０．１重量％未満では消臭効果が乏しく、かつ混合が困難であり、使用量が７０重量％を超えても脱臭効果は変わらず、むしろ重量増およびコスト高になるので好ましくない。
【００１５】
(III) 本方法の処理工程例
本方法の処理工程例を図１に示す。図示する処理工程は、下水汚泥供給部１、生石灰供給部２、乾粉製造部３、排ガス排水処理部４およびこれらを結ぶ移送系から構成されている。
下水汚泥供給部１では、下水処理場でフィルタープレス等により含水率が７０〜８０％に脱水処理された汚泥ケーキが供給装置１１を通じて乾粉製造部３に所定量ずつ送られる。一方、生石灰供給部２には生石灰の計量手段１４が設けられており、一定量の生石灰が乾粉製造部３に送られる。
【００１６】
乾粉製造部３は原料混合機１２および熟成混合機１３から構成される。原料混合機１２では汚泥ケーキと生石灰供給部２から送られてくる一定量の生石灰が混合される。汚泥の固形分１００重量部に対して概ね５０〜１５０重量部の生石灰を添加して均一に混合した後に、この混合物を熟成混合機１３に移し、水分量が十分に低減した状態になるまで混合する。
これらの混合機１２、１３の排気系にはバッグフィルタ１５、排ガス冷却装置１６、スクラバ１７、中和槽１８、ミストセパレータ１９および活性炭吸着器２０からなる排ガス排水処理部４が付設される。
【００１７】
熟成が進行した時点で、熟成混合物に硫酸アルミニウムを含有する消臭用粉体を添加する。消臭用粉体の添加量は乾粉１００重量部に対して０．１〜７０重量部である。消臭用粉体を添加することにより、混合物のアンモニア残存量は人が臭気を感じる閾値の１ppm 以下に低減され、アンモニア臭が除去される。
【００１８】
本発明の処理方法によって無臭化した乾粉（処理物）は貯蔵タンクなどに保管され、セメントもしくは鉄鋼用原料、あるいは土壌改良剤または肥料および水処理材として用いられる。
具体的には、セメントの製造工程において、上記処理物を他のセメント原料と共に原料系に投入して用いることができる。上記処理物の消石灰と汚泥固形分の無機物はセメント成分となり、汚泥の有機物は焼成時の燃料となる。また、上記処理物は製鉄工程において焼結原料の一部として用いることができる。
土壌改良剤としては、単独で用いても良く、またはシリカ、石灰粉、フライアッシュなどの既知の土壌改良成分と共に用いても良い。肥料としては、単独であるいは他の栄養成分とともに用いる。水処理材としては、そのまま、あるいは成分調整して用いる。
【００１９】
【実施例】
以下に本発明の実施例および比較例を示す。なお本実施例は例示であり、本発明の範囲を限定するものではない。
【実施例１および比較例】
（１）使用材料
実施例・比較例で用いた材料は次のとおりである。
（イ）下水汚泥：活性汚泥処理した含水率８０％の下水汚泥。乾燥品の有機物含有率９４％。（ロ）生石灰：ＣａＯ含有量９４％以上の石灰石焼成品。（ハ）脱臭用粉体：実施例では市販の硫酸バン土、ナトリウムミョウバン、カリミョウバンおよび硫酸鉄を用い、併用成分として、ケイ藻土、活性白土および炭酸カルシウムを用いた。比較例では、ゼオライト、硅石粉、セピオライト、ベントナイト、鹿沼土および活性炭のみからなる粉体を用いた。各粉体の物性は表１（実施例）および表２（比較例）に示す通りである。
【００２０】
【表１】
【表２】
（２）脱水工程
ホバートミキサーに汚泥１kg、生石灰１kgを入れ、１５分間低速で混合した。生石灰の水和に伴い機内の温度は最高１７０℃に達し、水分は水蒸気となって揮散した。水分量１５％となった混合物（消石灰と脱水汚泥）を１２時間熟成し、その後、水分・アンモニア含有量が均一になるように混合した。この結果、水分量３％〜８％の乾燥混合物（乾粉）が得られた。
【００２３】
（３）アンモンモニア濃度の測定
予備試験として、水分量８％の上記乾粉を流速20cm/secで温度 100℃の容器内に流し、発生したアンモニアガスを水中に導いて補集し、ガスクロマトグラフを用いてその濃度を測定した。本発明の脱臭処理を行わない上記乾粉のアンモニア濃度は６０００ppm であった。因みに、悪臭防止法による臭気強度目安では、濃度１ppm で全ての人がアンモニア臭を感じるとしており、６０００ppm の濃度は極めて激しいアンモニア臭である。なお同様に他の悪臭成分を分析したところ、硫化水素１ppm 以下、トリメチルアミン０．０４ppm 以下、ノルマル吉草酸０．００１ppm 以下であった。
実施例および比較例は、実際の使用態様にあわせ、吸引式検知管を用いてアンモニア濃度を測定した。即ち、容量１００mlの捕集びん中に乾粉２０ｇを入れ、４０℃の温度に１６時間保持した後、上部空間に滞留するアンモニア蒸気を検知管で濃度測定した。この結果を表３および表４に示した。
【００２４】
（４）脱臭工程
上記捕集ビンに乾粉２０ｇと共に表１〜２に掲げた各試料粉末を入れ、発生するアンモニアガスの濃度を測定した。各試料の測定結果を粉体の添加量（０．１〜５％）ごとに表３および表４に示した。なお、表３は水分量３％の乾粉を使用したもの、表４は水分量８％の乾粉を使用したものである。
【００２５】
【表３】
【表４】
これらの結果に示されるように、本発明の処理方法によれば、脱臭用粉体の添加量が０．１％でもアンモニア濃度を概ね１〜数ppm 以下まで低減することができる。一方、本発明の脱臭用粉体に代えてゼオライトや活性炭等を混合したものは、最も脱臭効果が高い活性炭を用いた場合でも、アンモニア濃度を１ppm 以下にするには、水分量３％の乾粉に対して活性炭が３％以上必要であり、水分量８％の乾粉に対しては活性炭の量を増やしても良好な脱臭効果が得られない。しかも活性炭等を用いたものは混合状態も大きく影響し、良く混合しないものはアンモニア濃度が高く脱臭効果が低い。
【００２８】
【実施例２】
水分量３％の上記乾粉に硫酸バン土、カリミョウバン、硫酸バン土＋活性白土混合物（１：１）をそれぞれ３％添加したものをセメント原料として用い、これを他のセメント原料（石灰石、粘土、銅カラミを所定量加え粉砕した調合原料）に内割り１０％となるように添加し、ペレット化したものを１４５０℃で焼成した。得られたセメントクリンカーをブレーン値３５００ｍ2 /gになるまで粉砕した。このポルトランドセメントをJIS R 5201により評価した。表５の結果に示すように、本発明の処理物を添加したものは、これを加えないセメントと比較して凝結時間およびモルタル強度に大差なく、上記処理物をセメント原料として使用できることが確認された。
【００２９】
【表５】
【実施例３】
実施例２と同様に水分量３％の乾粉に硫酸バン土、カリミョウバンを添加混合し、それぞれを高炉原料（鉄鉱石、石灰石、コークスを所定量加え所定の粒度に粉砕したもの）に内割り５％となるように添加し、ペレット化したものを１３８０℃のロータリーキルンで焼結させた。硫酸バン土、ミョウバン添加品とも焼結体の圧縮強度は無添加のものと比較して±５％の範囲内にあった。また、比重、流動性その他の特性も乾粉を添加したものとしないものでは有意の差は見られなかった。
【００３１】
【実施例４】
実施例２と同様に水分量３％の乾粉に硫酸バン土、カリミョウバンを添加混合し、それぞれｐＨ１．５の硫酸廃液に投入し、ｐＨ６．９〜７．４となるように中和した。生じた沈殿を回収したところ、純度９２％の石膏が得られた。か焼特性等について検討した結果、有効利用可能な水準であった。
【００３２】
【発明の効果】
本発明に係る下水汚泥の処理方法によれば、汚泥処理産物である乾粉が低コストで実質的に無臭化され、その取扱性が著しく改善される。従って、この乾粉を広い用途に利用し易い。また、本発明の処理方法により得られた処理産物はカルシウムおよび硫酸塩を主体として含むため、セメント・鉄鋼原料として有効かつ大量に処理することができる。さらに、この処理産物は、含有される有機成分およびカルシウムその他の無機養分並びに硫酸アンモニウムにより、脱硝効果、土壌改良効果および植物の肥育効果などが顕著であり、しかも無臭であるので地盤改良材・肥料・水処理材などとしても有用である。
【図面の簡単な説明】
【図１】本発明の処理工程図
【符号の説明】
１…下水汚泥供給部
２…生石灰供給部
３…乾粉製造部
４…排ガス排水処理部[0001]
[Industrial application fields]
The present invention relates to treatment of organic sewage sludge generated by treating industrial wastewater and general household wastewater.
[0002]
[Prior art]
In recent years, the amount of sewage sludge generated has been increasing with the expansion of the sewer network. Conventionally, sewage sludge has been incinerated by adding a fuel for auxiliary combustion such as heavy oil, and incineration ash is landfilled. However, it is difficult to secure a landfill site for final disposal. There is an urgent need to reduce the volume of sewage treatment products or develop effective utilization methods.
As a method of reducing the volume of incinerated ash, a method of melting glass has been tried in some treatment plants, but the energy cost is high and the problem of treating the discharged ash remains the fundamental solution. is not. In addition, many methods have been tried for effective use of incinerated ash, such as the manufacture of brick products and the use of organic fertilizers. However, there is a need to open up new markets and to compete with existing competitors. However, there are problems such as still having problems in terms of quality and cost, and this has not led to a large and stable use of sludge.
[0003]
In this situation, attention has been paid to the technology (JP-A-3-98700, JP-A-3-207497) that mixes and dehydrates sludge with quicklime and uses it as a raw material for cement or as a sintering material for iron making. . In cement manufacturing or iron making, raw materials are sintered using a furnace of 1000 ° C or higher. When sludge is put into these furnaces, organic matter in the sludge is burned without adding auxiliary fuel. It is energetically advantageous compared to the conventional processing methods required. In addition, inorganic materials are effectively used as oxalic materials and calcareous materials, and have the advantage that existing cement production facilities and steelmaking facilities can be used as they are, and waste gas treatment with existing facilities is sufficient. In addition, these methods can be used as industrial raw materials for continuous operation, such as cement and steel, so that sludge can be treated in large quantities, and sewage sludge can be treated stably without efforts to develop new markets for new products. This is an epoch-making solution, and it is hoped that usage in this direction will spread in the future.
[0004]
[Prior art issues]
On the other hand, these methods still have the following problems. That is, in the activated sludge method, which is the mainstream of the current sewage treatment method, nitrogen is concentrated and adsorbed on the sludge, so the sewage sludge discharged from the treatment plant contains a large amount of nitrogen. In the above treatment method in which quick lime is added to sewage sludge, the nitrogen content in the sludge is decomposed by the heat generated when the quick lime is mixed with the sludge, and a large amount of ammonia gas is generated and volatilized. Most of the generated ammonia gas can be recovered when mixed with quicklime, but part of it is adsorbed to a mixture of slaked lime with high specific surface area and dry sludge (hereinafter referred to as “dry powder”) after quicklime hydration. Remains. This residual ammonia content is volatilized as the temperature rises, and when the temperature reaches 30 ° C. or higher in the dry powder storage silo, ammonia gas with a concentration of several percent or more is filled, resulting in a poor working environment. Even if the dry powder is stored in a sealed state, leakage of ammonia gas is unavoidable when it is taken in and out, transferred, or put into a furnace as a cement raw material, and a bad odor drifts.
Incidentally, since human odor is sensed even at an ammonia concentration of about 1 ppm, a deodorizing treatment method that removes the ammonia concentration is required below this.
[0005]
As a countermeasure against ammonia odor, a method of adsorbing on an organic high specific surface area material such as activated carbon is known, as is often done with pet sand. However, this method is not suitable for measures against dry powder odor. That is, activated carbon or the like has a disadvantage that the surface is saturated in a short period of time by adsorbing water or dust in addition to ammonia, and the adsorptive power rapidly decreases. Further, when used in a large amount, the processing cost increases, and when pulverized to obtain an effect by using a small amount, it becomes easy to combine with oxygen in the air at the time of storage or transfer, so that there is a risk of so-called dust explosion.
Instead of using activated charcoal or the like, ammonia can be neutralized by dropping a gas-phase or liquid-phase acid, but the storage of the acid itself becomes the storage of hazardous materials and the management becomes troublesome. Therefore, there is a problem that the processing cost is considerably increased.
[0006]
[Problem to be Solved by the Invention]
The present invention solves the problems in the conventional treatment method as described above, and aims to provide a method capable of removing a bad smell of sewage sludge generated in a large amount and stably and effectively using the sewage sludge. To do.
According to the present invention, the bad odor of the mixture of sewage sludge and quicklime is removed at low cost, so that the mixture can be easily used as a cement raw material or an iron making raw material, and further, a new use in a field that has not been conventionally used. Is also possible.
[0007]
[Means for Solving the Problems]
According to the present invention, a sewage sludge treatment method and a sewage sludge treatment product having the following configurations are provided.
(1) After mixing quicklimes with sewage sludge, this mixture is transferred to an aging mixer and ripening proceeds, and an aluminum sulfate-containing powder is added to the aging mixture to deodorize it. For 100% sewage sludge, 50 to 150 parts by weight of quicklime is mixed with 100 parts by weight of sludge solids to reduce the amount of moisture, and then the mixture is transferred to an aging mixer to further age. Reduce the amount to dry powder with a moisture content of 3 to 8%, and mix 0.1 to 70 parts by weight of the deodorized powder with an aluminum sulfate content of 5% by weight or more with respect to 100 parts by weight of the dry powder. The method of processing sewage sludge characterized by carrying out deodorizing.
(2) For sewage sludge with a moisture content of 60 to 100%, 50 to 150 parts by weight of quicklime is mixed with 100 parts by weight of sludge solids to reduce the moisture content, and then the mixture is transferred to an aging mixer. By aging, the water content is further reduced to a dry powder having a water content of 3 to 8%. The deodorized powder having an aluminum sulfate content of 5% by weight or more is added to the dry powder with respect to 100 parts by weight of the dry powder. Processed deodorized sewage sludge by mixing 0.1 to 70 parts by weight.
[0008]
[Specific explanation]
(I) Dehydration process using quicklimes The sewage sludge to be treated in the present invention is mainly sludge generated at a sewage treatment plant. In addition to this, human waste, household wastewater, industrial wastewater treatment, etc. Including sludge generated by These sludges are generally dehydrated to a moisture content of about 60 to 100%, and the present invention uses this sewage sludge.
Quicklime that is mixed with sewage sludge means CaO as the main component, which takes in moisture from sewage sludge and becomes slaked lime, and specifically includes quicklime, calcined dolomite, water tank, blast furnace slag, etc. It is. The particle size of quicklime is 70 mm or less, preferably 30 mm or less.
Although the mixing amount of quicklime depends on the water content of sewage sludge, it is generally about 50 to 150 parts by weight, preferably about 80 to 130 parts by weight with respect to 100 parts by weight of sewage sludge. If the amount of quicklime added is less than this range, the sludge will not dry, making it unsuitable as a cement raw material or a steelmaking raw material. Moreover, since the cost will become high when there is too much addition amount of quicklime, it is not preferable. When sewage sludge with a moisture content of 80% is mixed with the same amount of quick lime, a dry powder with a moisture content of almost zero can be obtained.
[0009]
( II ) Deodorizing step with aluminum sulfate-containing powder The powder containing aluminum sulfate is added to the sludge and lime mixture dehydrated as described above to deodorize.
As aluminum sulfate, a single salt represented by Al 2 (SO 4 ) 3 , a double salt composed of aluminum sulfate and another salt, and a hydrate (hydrated salt) thereof can be used. Examples of the double salt include so-called alum such as potassium aluminum sulfate [KAl (SO 4 ) 2 , potassium alum] and sodium aluminum sulfate [NaAl (SO 4 ) 2 , sodium alum]. Alum is represented by the general formula: XAl 3 (SO 4 ) 2 (OH) 6 , and those having X of K, Na, NH 4 , (1/2) Pb or the like are effectively used. Furthermore, the Al part partially substituted with Fe, Cu, Zn is also used.
[0010]
When aluminum sulfate is added to and mixed with dry powder, it reacts with water in the dry powder and hydrolyzes. Since the hydrolyzate contains sulfuric acid, it shows strong acidity. The deodorizing action of the present invention is presumed to be basically based on a synergistic action of the adsorption action of aluminum sulfate powder and the neutralization reaction of sulfuric acid and ammonia generated by the hydrolysis of aluminum sulfate. That is, the deodorizing effect of silica gel, zeolite and activated carbon conventionally used as a deodorant is based solely on their surface adsorption action, and adsorbs a large amount of water vapor in addition to the dry powder ammonia component. For this reason, the adsorption action is saturated, the essential ammonia gas cannot be sufficiently adsorbed, and the deodorizing effect is lowered. On the other hand, since the aluminum sulfate powder of the present invention generates sulfuric acid by an appropriate moisture, ammonia is neutralized by this sulfuric acid even if water vapor is adsorbed. Therefore, unlike silica gel or the like, a high deodorizing effect can be exhibited without causing a decrease in the deodorizing effect due to saturation of the adsorption action due to the adsorption of water vapor.
[0011]
The finer the particle size of the aluminum sulfate powder, the greater the deodorizing effect. However, excessive pulverization leads to an increase in cost and is also not preferable because it tends to absorb moisture. Specifically, 3 mm or less is suitable, and 0.05-1 mm or less is more preferable.
Incidentally, conventional deodorizers such as silica gel are also used in the form of fine powder so as to increase the specific surface area in order to enhance the adsorption effect. However, as described above, a large amount of moisture can be adsorbed in a short time. Since it is saturated, the deodorizing effect is not improved so much even if it is pulverized. On the other hand, since the aluminum sulfate powder of the present invention deodorizes by the synergistic action of the adsorption action and the neutralization action with sulfuric acid, the finer the particle size, the greater the deodorization effect due to the adsorption ability, but as shown in the examples and comparative examples described later. Furthermore, it is not necessary to pulverize more than necessary.
[0012]
Aluminum sulfate is usually obtained as a hydrate with water of crystallization, and since this water of crystallization is constrained in the crystal, there is no adverse effect, but excessively adhering moisture on the particle (crystal) surface is dry powder. Before contact with the water, acid is generated and the container and pipe are eroded, and the aluminum sulfate powder is agglomerated to cause clogging of the pipe and feeder, resulting in fluidity deterioration, and the powder surface is saturated with moisture. As a result, the adsorption action decreases. Therefore, the aluminum sulfate powder is preferably used in a dry state. Specifically, the water content is preferably 50% or less.
[0013]
Aluminum sulfate may be used alone or in combination with other powders having a deodorizing action. Examples of the powder to be used in combination include oxalate powders such as silica gel, cristobalite, diatomaceous earth, various clays, activated clay, acid clay, zeolite, talc, sepiolite, etc. And calcium carbonate. Among these, diatomaceous earth, acid clay, and activated clay that is a processed product thereof are preferable. Since these retain acid groups on the particle surface, they can effectively trap ammonia molecules, and an excellent deodorizing effect is obtained in combination with the deodorizing effect of the aluminum sulfate powder. Moreover, since the chemical component is SiO 2 —Al 2 O 3, it is convenient to use the deodorized sewage treatment product as a cement raw material, an iron making raw material, a soil improvement material, or the like.
[0014]
The content of aluminum sulfate in the mixed powder is 5% by weight or more, and it is preferable to contain 10% by weight or more by internal percentage. Moreover, the usage-amount of mixed powder is 0.1-70 weight part with respect to 100 weight part of dry powder, Preferably 1-10 weight part is suitable. When the content of aluminum sulfate is less than 10% by weight, the amount of the mixed powder used for obtaining a sufficient deodorizing effect increases, and the processing cost increases. Further, if the amount of the mixed powder used is less than 0.1% by weight, the deodorizing effect is poor and mixing is difficult, and even if the amount used exceeds 70% by weight, the deodorizing effect does not change, but rather the weight increases and the cost increases. This is not preferable.
[0015]
(III) Example of processing steps of this method FIG. 1 shows an example of the processing steps of this method. The illustrated treatment process includes a sewage sludge supply unit 1, a quicklime supply unit 2, a dry powder production unit 3, an exhaust gas wastewater treatment unit 4, and a transfer system connecting them.
In the sewage sludge supply unit 1, a sludge cake dehydrated to 70 to 80% by a filter press or the like at a sewage treatment plant is sent to the dry powder production unit 3 through the supply device 11 by a predetermined amount. On the other hand, the quicklime supply unit 2 is provided with a quicklime measuring means 14, and a certain amount of quicklime is sent to the dry powder production unit 3.
[0016]
The dry powder production unit 3 includes a raw material mixer 12 and an aging mixer 13. In the raw material mixer 12, a certain amount of quicklime fed from the sludge cake and the quicklime supply unit 2 is mixed. After adding approximately 50 to 150 parts by weight of quicklime to 100 parts by weight of the sludge solid content and mixing uniformly, the mixture is transferred to the aging mixer 13 and mixed until the water content is sufficiently reduced. To do.
An exhaust gas waste water treatment unit 4 including a bag filter 15, an exhaust gas cooling device 16, a scrubber 17, a neutralization tank 18, a mist separator 19 and an activated carbon adsorber 20 is attached to the exhaust system of the mixers 12 and 13.
[0017]
When aging has progressed, a deodorizing powder containing aluminum sulfate is added to the aging mixture. The addition amount of the deodorizing powder is 0.1 to 70 parts by weight with respect to 100 parts by weight of the dry powder. By adding the deodorizing powder, the amount of ammonia remaining in the mixture is reduced to 1 ppm or less, which is a threshold value at which people feel odor, and the ammonia odor is removed.
[0018]
The dry powder (treated product) that has not been brominated by the treatment method of the present invention is stored in a storage tank or the like and used as a raw material for cement or steel, or as a soil conditioner or fertilizer and water treatment material.
Specifically, in the cement manufacturing process, the treated product can be used together with other cement raw materials in a raw material system. The slaked lime and sludge solid matter inorganic matter in the above treated product becomes a cement component, and the sludge organic matter becomes a fuel for firing. Moreover, the said processed material can be used as a part of sintering raw material in an iron manufacturing process.
As a soil improvement agent, you may use independently, and may use it with known soil improvement components, such as a silica, a lime powder, and a fly ash. As a fertilizer, it is used alone or with other nutritional components. As a water treatment material, it is used as it is or after adjusting its components.
[0019]
【Example】
Examples of the present invention and comparative examples are shown below. In addition, a present Example is an illustration and does not limit the scope of the present invention.
Example 1 and Comparative Example
(1) Materials used The materials used in Examples and Comparative Examples are as follows.
(I) Sewage sludge: Sewage sludge treated with activated sludge and having a water content of 80%. 94% organic content of the dried product. (B) Quicklime: A calcined limestone product with a CaO content of 94% or more. (C) Powder for deodorization: In the examples, commercially available vanadium sulfate, sodium alum, potassium alum and iron sulfate were used, and diatomaceous earth, activated clay and calcium carbonate were used as the combined components. In the comparative example, a powder composed only of zeolite, meteorite powder, sepiolite, bentonite, Kanuma soil, and activated carbon was used. The physical properties of each powder are as shown in Table 1 (Examples) and Table 2 (Comparative Examples).
[0020]
[Table 1]
[Table 2]
(2) Dehydration step 1 kg of sludge and 1 kg of quicklime were put into a Hobart mixer and mixed at a low speed for 15 minutes. Along with the hydration of quicklime, the temperature inside the machine reached a maximum of 170 ° C., and the water was evaporated as water vapor. The mixture (slaked lime and dehydrated sludge) having a moisture content of 15% was aged for 12 hours, and then mixed so that the moisture and ammonia contents were uniform. As a result, a dry mixture (dry powder) having a moisture content of 3% to 8% was obtained.
[0023]
(3) Measurement of ammonia concentration As a preliminary test, the above dry powder with a moisture content of 8% was flowed into a container at a temperature of 100 ° C at a flow rate of 20 cm / sec, and the generated ammonia gas was introduced into water and collected. The concentration was measured using a gas chromatograph. The ammonia concentration of the dry powder not subjected to the deodorizing treatment of the present invention was 6000 ppm. By the way, according to the standard of odor intensity according to the malodor control method, all people feel ammonia odor at a concentration of 1 ppm, and the concentration of 6000 ppm is extremely intense ammonia odor. Similarly, other malodorous components were analyzed and found to be 1 ppm or less of hydrogen sulfide, 0.04 ppm or less of trimethylamine, and 0.001 ppm or less of normal valeric acid.
In the examples and comparative examples, the ammonia concentration was measured using a suction type detection tube in accordance with the actual usage. That is, 20 g of dry powder was put into a 100 ml capacity collection bottle and kept at a temperature of 40 ° C. for 16 hours, and then the concentration of ammonia vapor staying in the upper space was measured with a detector tube. The results are shown in Tables 3 and 4.
[0024]
(4) Deodorizing step Each sample powder listed in Tables 1 and 2 together with 20 g of dry powder was put into the collection bottle, and the concentration of the generated ammonia gas was measured. The measurement results for each sample are shown in Tables 3 and 4 for each amount of powder added (0.1 to 5%). Table 3 uses dry powder with a moisture content of 3%, and Table 4 uses dry powder with a moisture content of 8%.
[0025]
[Table 3]
[Table 4]
As shown in these results, according to the treatment method of the present invention, the ammonia concentration can be reduced to approximately 1 to several ppm or less even when the addition amount of the deodorizing powder is 0.1%. On the other hand, in the case where zeolite or activated carbon or the like is mixed instead of the deodorizing powder of the present invention, even if activated carbon having the highest deodorizing effect is used, in order to make the ammonia concentration 1 ppm or less, dry powder with a moisture content of 3% On the other hand, 3% or more of activated carbon is necessary, and a good deodorizing effect cannot be obtained even if the amount of activated carbon is increased with respect to dry powder having a moisture content of 8%. Moreover, those using activated carbon or the like greatly affect the mixing state, and those that do not mix well have high ammonia concentration and low deodorizing effect.
[0028]
[Example 2]
3% each of the above dry powder with a moisture content of 3% each of a mixture of 1% of sulfated soil, potassium alum, sulfated soil + activated clay mixture (1: 1) is used as a cement material, and this is used as another cement material (limestone, clay) The mixture was crushed by adding a predetermined amount of copper calami to a blended raw material) so as to be 10%, and the pelletized product was fired at 1450 ° C. The obtained cement clinker was pulverized to a brane value of 3500 m 2 / g. This Portland cement was evaluated according to JIS R 5201. As shown in the results of Table 5, it was confirmed that the treated product of the present invention can be used as a cement raw material with no significant difference in setting time and mortar strength compared to cement to which this is not added. It was.
[0029]
[Table 5]
[Example 3]
As in Example 2, 3% moisture dry powder was added to and mixed with sulfite and potash alum, and each was internally divided into blast furnace raw materials (iron ore, limestone and coke added to each other and ground to a predetermined particle size). The pellets were added to 5% and pelletized, and sintered in a rotary kiln at 1380 ° C. The sintered compact and the alum-added product had a compressive strength within the range of ± 5% compared to the non-added one. Moreover, the specific gravity, fluidity, and other characteristics were not significantly different between those with and without dry powder added.
[0031]
[Example 4]
In the same manner as in Example 2, vane sulfate soil and potassium alum were added to and mixed with dry powder having a water content of 3%, and each was added to a sulfuric acid waste solution having a pH of 1.5, and neutralized to a pH of 6.9 to 7.4. When the resulting precipitate was recovered, a gypsum having a purity of 92% was obtained. As a result of examining the calcination characteristics, etc., it was a level that could be used effectively.
[0032]
【The invention's effect】
According to the method for treating sewage sludge according to the present invention, dry powder, which is a sludge treatment product, is substantially non-brominated at low cost, and its handleability is remarkably improved. Therefore, it is easy to use this dry powder for a wide range of applications. Moreover, since the treatment product obtained by the treatment method of the present invention contains calcium and sulfate as main components, it can be treated effectively and in large quantities as a cement / steel raw material. In addition, this processed product has remarkable denitration effect, soil improvement effect, plant fattening effect, etc. due to the organic components and calcium and other inorganic nutrients and ammonium sulfate contained, and it is odorless, so ground improvement material, fertilizer, It is also useful as a water treatment material.
[Brief description of the drawings]
FIG. 1 is a processing process diagram of the present invention.
DESCRIPTION OF SYMBOLS 1 ... Sewage sludge supply part 2 ... Quicklime supply part 3 ... Dry-powder production part 4 ... Exhaust gas waste water treatment part
Claims (2)
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| JP02757595A JP3684410B2 (en) | 1995-01-24 | 1995-01-24 | Sewage sludge treatment method and treated sewage sludge |
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| JP02757595A JP3684410B2 (en) | 1995-01-24 | 1995-01-24 | Sewage sludge treatment method and treated sewage sludge |
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| CN102815853A (en) * | 2011-06-10 | 2012-12-12 | 湖北中科博策新材料研究院 | Harmless mud processing method for sewage treatment plant |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100757360B1 (en) * | 2005-11-25 | 2007-09-11 | 주식회사 서울암면 | Retreat method of organic or inorganic waste resources |
| KR100704735B1 (en) * | 2005-12-06 | 2007-04-06 | 주식회사 서울암면 | Method for removing malodor of organic waste resources |
| CN102320080B (en) * | 2011-06-16 | 2014-03-19 | 温州圣平泥浆固化有限公司 | Deep dewatering, solidifying and brick making device for municipal domestic sludge and building pile sludge and processing method thereof |
| CN102616951B (en) * | 2012-03-28 | 2013-10-09 | 李明琛 | Method for comprehensively treating and utilizing sewage and sludge produced during silica gel production |
| CN103435250B (en) * | 2013-07-11 | 2016-01-20 | 北京师范大学 | A kind ofly add the method that microbial flocculant improves activated sludge dehydration performance |
| CN104649563B (en) * | 2013-11-25 | 2016-08-17 | 中国石油化工股份有限公司 | A kind of advanced treatment process of sludge containing oil |
| CN103964657B (en) * | 2014-04-30 | 2016-06-22 | 湖南子宏生态环保科技有限公司 | A kind of processing method of residual sludge reduction |
| CN104445863A (en) * | 2014-12-31 | 2015-03-25 | 梁毅 | Method for achieving deep sludge dehydration and energy utilization on plate-and-frame filter press |
-
1995
- 1995-01-24 JP JP02757595A patent/JP3684410B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102815853A (en) * | 2011-06-10 | 2012-12-12 | 湖北中科博策新材料研究院 | Harmless mud processing method for sewage treatment plant |
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|---|---|
| JPH08197095A (en) | 1996-08-06 |
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