JPH08238B2 - Solid-liquid separation method for digested sludge - Google Patents
Solid-liquid separation method for digested sludgeInfo
- Publication number
- JPH08238B2 JPH08238B2 JP15925892A JP15925892A JPH08238B2 JP H08238 B2 JPH08238 B2 JP H08238B2 JP 15925892 A JP15925892 A JP 15925892A JP 15925892 A JP15925892 A JP 15925892A JP H08238 B2 JPH08238 B2 JP H08238B2
- Authority
- JP
- Japan
- Prior art keywords
- sludge
- solid
- digested sludge
- digested
- liquid separation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Landscapes
- Physical Water Treatments (AREA)
- Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
- Treatment Of Sludge (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は消化汚泥の固液分離方法
に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-liquid separation method for digested sludge.
【０００２】[0002]
【従来の技術】消化汚泥の固液分離方法としては、従来
から主として重力濃縮法が用いられてきた。ところがこ
の重力濃縮法は固液分離を十分に行えないため、次のよ
うな問題があった。 濃縮消化汚泥濃度が低く、次工程の脱水、乾燥工程
等の能力を低下させていた。 消化脱離液中に固形物等が混在するため、水処理系
への返流水として返流されると水処理系の負荷が高くな
る。 嫌気性の消化工程においてオルトリン態のリンが溶
出し、消化脱離液中のオルトリン態リンの濃度が高かっ
た。 また、重力濃縮法は固液分離速度が遅いために、固液分
離槽の大きさを嫌気性消化槽と同じほど大きくしなけれ
ばならないという問題もあった。2. Description of the Related Art Conventionally, a gravity concentration method has been mainly used as a solid-liquid separation method for digested sludge. However, since the gravity concentration method cannot sufficiently perform solid-liquid separation, it has the following problems. The concentration of concentrated digested sludge was low, and the ability of dehydration and drying processes in the next process was reduced. Since solid substances and the like are mixed in the digested and desorbed liquid, the load on the water treatment system increases when it is returned as return water to the water treatment system. In the anaerobic digestion process, ortholine phosphorus was eluted, and the concentration of ortholine phosphorus in the digestive desorbate was high. Further, the gravity concentration method has a problem that the size of the solid-liquid separation tank has to be as large as that of the anaerobic digestion tank because the solid-liquid separation speed is slow.
【０００３】一方、重力濃縮法の欠点を解消した固液分
離方法として、加圧浮上濃縮法と呼ばれる方法が知られ
ている。この方法は主として汚泥の濃縮工程で用いられ
るもので、圧力容器内で加圧し汚泥に空気等のガスを溶
解させた後、圧力を開放するとガスが気泡となって汚泥
に付着し、汚泥を浮上させる現象を利用した固液分離方
法である。しかしこの方法は汚泥に高い圧力を加えるた
めに多くの電力を必要とし、また設備も複雑化する欠点
があった。On the other hand, as a solid-liquid separation method that solves the drawbacks of the gravity concentration method, a method called pressure floating concentration method is known. This method is mainly used in the sludge concentrating process.When pressure is released in the pressure vessel to dissolve gas such as air and then the pressure is released, the gas becomes bubbles and adheres to the sludge, causing the sludge to float. This is a solid-liquid separation method that utilizes the phenomenon of causing. However, this method requires a lot of electric power to apply a high pressure to the sludge and has a drawback that the equipment is complicated.
【０００４】[0004]
【発明が解決しようとする課題】本発明は上記した従来
の問題点を解決して、多くの電力や複雑な設備を必要と
せず、消化汚泥を十分にかつ速い速度で固液分離するこ
とができる消化汚泥の固液分離方法を提供するために完
成されたものである。DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and is capable of solid-liquid separation of digested sludge at a sufficiently high speed without requiring a lot of electric power and complicated equipment. It has been completed to provide a solid-liquid separation method for digested sludge that can be obtained.
【０００５】[0005]
【課題を解決するための手段】上記の課題を解決するた
めになされた本発明は、密閉された嫌気性消化槽内で有
機性汚泥をpHが7.3 以上のアルカリ条件下で嫌気性消化
処理することにより、得られる消化汚泥中の炭酸イオ
ン、重炭酸イオン、溶存二酸化炭素濃度の総和を増加さ
せた後、消化汚泥のpHを低下させることによって二酸化
炭素ガスを放出させ、このガスを利用して消化汚泥を浮
上分離させて濃縮消化汚泥と消化脱離液とに固液分離す
ることを特徴とするものである。なお、塩化第二鉄また
はＰＡＣを使用して消化汚泥のpHを低下させることが好
ましく、また、この方法により得られた濃縮消化汚泥に
凝集剤を添加して脱水処理することにより、好ましい結
果を得ることができる。Means for Solving the Problems The present invention, which has been made to solve the above-mentioned problems, is directed to anaerobic digestion of organic sludge in a sealed anaerobic digestion tank under alkaline conditions having a pH of 7.3 or higher. By increasing the total amount of carbonate ions, bicarbonate ions, and dissolved carbon dioxide concentration in the obtained digested sludge, the carbon dioxide gas is released by lowering the pH of the digested sludge, and this gas is used. The method is characterized in that the digested sludge is floated and separated to perform solid-liquid separation into concentrated digested sludge and digested desorbed liquid. In addition, ferric chloride
Use PAC to lower the pH of digested sludge
Preferred, also, by dehydrated by adding an aggregating agent to the concentrated digested sludge obtained by this method, it is possible to obtain favorable results.
【０００６】[0006]
【実施例】以下に本発明を図示の実施例とともに更に詳
細に説明する。図１において、１は密閉された嫌気性消
化槽であり、有機性汚泥はそのままあるいは濃縮されて
２〜４％程度の濃度とされて嫌気性消化槽１へ投入さ
れ、嫌気的に消化処理されて消化汚泥となる。そしてこ
のときに嫌気性消化槽１において主として二酸化炭素や
メタンガスが発生する。The present invention will be described in more detail below with reference to the illustrated embodiments. In FIG. 1, 1 is a closed anaerobic digestion tank, and organic sludge as it is or concentrated to a concentration of about 2 to 4% is introduced into the anaerobic digestion tank 1 and anaerobically digested. And becomes digested sludge. At this time, carbon dioxide and methane gas are mainly generated in the anaerobic digestion tank 1.
【０００７】嫌気性消化槽１にはアルカリ貯留槽２から
アルカリが添加され、嫌気性消化槽１内をpHが7.3 以上
のアルカリ条件に保つ。アルカリの添加は嫌気性消化槽
１へ投入される有機性汚泥に対して行ってもよい。図２
は嫌気性消化槽１内のpHと発生ガス中の二酸化炭素とメ
タンガスの割合との関係を示すグラフであり、pHを高く
するとメタンガス割合の高い消化ガスが得られる。逆に
二酸化炭素はpHが７付近であった通常の消化よりも割合
が低くなり、pH８で約15％程度となる。これより、嫌気
性消化槽１内の二酸化炭素分圧は約0.15atm 程度とな
る。Alkali is added to the anaerobic digestion tank 1 from the alkali storage tank 2, and the inside of the anaerobic digestion tank 1 is maintained under alkaline conditions with a pH of 7.3 or higher. The addition of alkali may be performed on the organic sludge added to the anaerobic digestion tank 1. Figure 2
Is a graph showing the relationship between the pH in the anaerobic digestion tank 1 and the ratio of carbon dioxide and methane gas in the generated gas. When the pH is increased, a digested gas with a high methane gas ratio is obtained. On the contrary, the ratio of carbon dioxide is lower than that of the normal digestion where the pH is around 7, and it becomes about 15% at pH 8. From this, the partial pressure of carbon dioxide in the anaerobic digester 1 is about 0.15 atm.
【０００８】嫌気性消化槽１内で発生した二酸化炭素
は、ヘンリーの法則により嫌気性消化槽１内の消化汚泥
に溶け込む。ヘンリー定数は温度によって異なるので、
溶解二酸化炭素濃度[CO2] は嫌気性消化槽１内の雰囲気
中の二酸化炭素分圧、嫌気性消化槽１内の温度により支
配される。また、溶存二酸化炭素は CO2 ＋H2O ⇔H + ＋HCO3 - ⇔２H + ＋CO3 2- の形で解離し、アルカリ側では [HCO3 -] や[CO3 -] が
増加して平衡状態となるが、pHが低下すると炭酸イオン
や重炭酸イオンは二酸化炭素に戻る。従って消化汚泥中
の炭酸イオン、重炭酸イオン、溶存二酸化炭素の濃度
は、嫌気性消化槽１内の二酸化炭素の分圧、嫌気性消化
槽１内の温度、pHにより支配されることとなる。図３に
分圧を0.15atm とした場合の清水中の炭酸イオン、重炭
酸イオン、溶存二酸化炭素の総和濃度がpHによりどのよ
うに変化するかを示した。この図３から分かるように、
pHが7.3 以上のアルカリ側では消化汚泥に溶け込んだ炭
酸イオン、重炭酸イオン、溶存二酸化炭素の総和濃度は
急激に増加する。The carbon dioxide generated in the anaerobic digester 1 dissolves into the digested sludge in the anaerobic digester 1 according to Henry's law. Henry's constant varies with temperature, so
The dissolved carbon dioxide concentration [CO 2 ] is controlled by the partial pressure of carbon dioxide in the atmosphere in the anaerobic digester 1 and the temperature in the anaerobic digester 1. Further, the dissolved carbon dioxide CO 2 + H 2 O ⇔H + + HCO 3 - ⇔2H + + CO 3 dissociates 2 form, an alkaline side is [HCO 3 -] and [CO 3 -] is increased equilibrium However, when the pH drops, carbonate ions and bicarbonate ions return to carbon dioxide. Therefore, the concentrations of carbonate ions, bicarbonate ions, and dissolved carbon dioxide in the digested sludge are governed by the partial pressure of carbon dioxide in the anaerobic digestion tank 1, the temperature in the anaerobic digestion tank 1, and the pH. Figure 3 shows how the total concentration of carbonate ions, bicarbonate ions, and dissolved carbon dioxide in clear water changes with pH when the partial pressure is 0.15 atm. As you can see from this Figure 3,
On the alkaline side where the pH is 7.3 or higher, the total concentration of carbonate ions, bicarbonate ions and dissolved carbon dioxide dissolved in the digested sludge rapidly increases.
【０００９】次に図１に示すように、嫌気性消化槽１か
ら出た消化汚泥は混和槽３に導かれpH低下剤貯留槽４よ
りpH低下剤が加えられる。この結果、消化汚泥中に溶け
込んでいた炭酸イオン、重炭酸イオン、溶存二酸化炭素
等が二酸化炭素ガスとなり、二酸化炭素ガスと消化汚泥
との混合液が固液分離槽５に投入される。なお二酸化炭
素ガスの発生量は、pHを８から７とした場合、理論上は
7333mg/Lとなる。Next, as shown in FIG. 1, the digested sludge discharged from the anaerobic digestion tank 1 is introduced into a mixing tank 3 and a pH lowering agent is added from a pH lowering agent storage tank 4. As a result, carbonate ions, bicarbonate ions, dissolved carbon dioxide, etc. dissolved in the digested sludge become carbon dioxide gas, and the mixed liquid of carbon dioxide gas and digested sludge is put into the solid-liquid separation tank 5. The amount of carbon dioxide gas generated is theoretically in the range of pH 8 to 7.
It becomes 7333 mg / L.
【００１０】固液分離槽５では、発生した炭酸ガスが消
化汚泥中の固形成分に付着し、見掛け比重を小さくして
固形成分を浮上させる。混和槽３における混合が完全で
あれば約30〜60分で浮上が完了し、濃度が２倍以上とな
った濃縮消化汚泥と清浄な消化脱離液とに分離される。
濃縮消化汚泥は凝集剤貯留槽６より凝集剤が添加されて
脱水機７で脱水され、消化脱離液は水処理系へ送られ
る。In the solid-liquid separation tank 5, the generated carbon dioxide gas adheres to the solid components in the digested sludge to reduce the apparent specific gravity and float the solid components. If the mixing in the mixing tank 3 is complete, the flotation is completed in about 30 to 60 minutes, and the digested sludge having a concentration twice or more and the clean digested desorbed liquid are separated.
A coagulant is added to the concentrated digested sludge from the coagulant storage tank 6 and dehydrated by the dehydrator 7, and the digested desorbed liquid is sent to the water treatment system.
【００１１】図４は浮上時間を30分とした場合に、固液
分離槽５中の気固比によって濃縮倍率及び濃縮消化汚泥
SS回収率がどのように変化するかを示したグラフであ
る。この図から分かるように、濃縮倍率を２以上とする
には気固比を0.1g-CO2/g-ss とする必要があるが、前記
のようにpHを８から７として7333mg/Lの二酸化炭素ガス
を発生させた場合には、気固比は0.36g-CO2/g-ssとなる
ので、高い濃縮倍率が得られることが分かる。FIG. 4 shows the concentration ratio and the concentrated digested sludge depending on the gas-solid ratio in the solid-liquid separation tank 5 when the floating time is set to 30 minutes.
It is a graph showing how the SS recovery rate changes. As can be seen from this figure, it is necessary to set the gas-solid ratio to 0.1g-CO 2 / g-ss in order to increase the concentration ratio to 2 or more. When carbon dioxide gas is generated, the gas-solid ratio is 0.36 g-CO 2 / g-ss, which means that a high concentration factor can be obtained.
【００１２】なお、前記したpH低下剤として塩化第二鉄
(以下塩鉄と略す) やＰＡＣ等を使用すれば、図５に示
すように消化脱離液中のオルトリン態リンの濃度を低下
させることができる。図５に示すように、理論上はFe/P
O4-Pの比が１となるように塩鉄を添加すればオルトリン
態リンを100 ％除去できるはずであるが、現実にはこれ
より過剰量の添加が必要となる。例えば図５に示すよう
に、塩鉄添加率が1.62[Fe/PO4-P]の場合、PO4-P 除去率
は64％程度となる。Ferric chloride is used as the above-mentioned pH lowering agent.
By using (hereinafter abbreviated as salt iron) or PAC, the concentration of ortholine phosphorus in the digestive desorbed liquid can be reduced as shown in FIG. As shown in Fig. 5, theoretically Fe / P
If salt iron is added so that the O 4 -P ratio becomes 1, it should be possible to remove 100% of orthophosphorus phosphorus, but in reality it is necessary to add an excessive amount. For example, as shown in FIG. 5, when the salt iron addition rate is 1.62 [Fe / PO 4 -P], the PO 4 -P removal rate is about 64%.
【００１３】上記のようにして得られた濃縮消化汚泥
は、通常行われている凝集剤の添加量より少量の添加で
フィルタープレス脱水機による場合にも、ベルトプレス
脱水機による場合にも優れた脱水性を示す。その結果を
表１と表２に示す。本発明の濃縮消化汚泥はフィルター
プレス脱水機、ベルトプレス脱水機ともに脱水能力を大
きく向上させるとともに、ケーキ水分も低下させること
ができ、濾布からの剥離性も向上させることができる。The concentrated digested sludge obtained as described above is superior to the filter press dehydrator and the belt press dehydrator when it is added in a smaller amount than the commonly used coagulant. Shows dehydration. The results are shown in Tables 1 and 2. The concentrated digested sludge of the present invention can greatly improve the dewatering ability in both the filter press dewatering machine and the belt press dewatering machine, reduce the water content of the cake, and improve the releasability from the filter cloth.
【００１４】[0014]
【表１】 [Table 1]
【００１５】[0015]
【表２】 [Table 2]
【００１６】[0016]
【発明の効果】以上に説明したように、本発明の消化汚
泥の固液分離方法によれば、嫌気性消化槽内で有機性汚
泥をpHが7.3 以上のアルカリ条件下で嫌気性消化処理し
た後、pHを低下させることによって放出される二酸化炭
素ガスを利用して消化汚泥を浮上分離させるようにした
ので、従来の加圧浮上濃縮法とは異なり、多くの電力や
複雑な設備を必要とせず、消化汚泥を十分にかつ速い速
度で固液分離することができる。また本発明によれば、
脱水工程における能力を向上させることができるととも
に、pH低下剤として塩鉄やＰＡＣ等の凝集剤を使用する
ことにより、水処理系に返流される消化脱離液中のオル
トリン態リン濃度を低下させることができる。As described above, according to the method for solid-liquid separation of digested sludge of the present invention, organic sludge is anaerobically digested in an anaerobic digester under alkaline conditions of pH 7.3 or higher. After that, the digested sludge is floated and separated by using the carbon dioxide gas released by lowering the pH, so unlike the conventional pressure flotation method, it requires a lot of power and complicated equipment. Therefore, the digested sludge can be solid-liquid separated at a sufficiently high speed. According to the invention,
The capacity in the dehydration process can be improved, and the concentration of orthophosphorus phosphorus in the digested and desorbed liquid returned to the water treatment system can be reduced by using a coagulant such as iron salt or PAC as a pH lowering agent. Can be made.
【図１】本発明の工程を示すフローシートである。FIG. 1 is a flow sheet showing the steps of the present invention.
【図２】嫌気性消化槽内のpHと、発生ガス中の二酸化炭
素とメタンガスとの割合の関係を示すグラフである。FIG. 2 is a graph showing the relationship between pH in the anaerobic digester and the ratio of carbon dioxide and methane gas in the generated gas.
【図３】二酸化炭素分圧を0.15atm としたときの清水の
pHと、炭酸イオン、重炭酸イオン、溶存二酸化炭素の総
和濃度との関係を示すグラフである。[Fig. 3] Fresh water when the carbon dioxide partial pressure is 0.15 atm
3 is a graph showing the relationship between pH and the total concentration of carbonate ions, bicarbonate ions, and dissolved carbon dioxide.
【図４】気固比と、濃縮倍率及び濃縮消化汚泥SS回収率
との関係を示すグラフである。FIG. 4 is a graph showing a relationship between a gas-solid ratio, a concentration ratio, and a concentrated digested sludge SS recovery rate.
【図５】pH低下剤である塩鉄の添加量と、消化脱離液中
のオルトリン態リンの除去率との関係を示したグラフで
ある。FIG. 5 is a graph showing the relationship between the amount of iron salt, which is a pH-lowering agent, and the removal rate of ortholine phosphorus in the digestive desorption solution.
１ 嫌気性消化槽 ２ アルカリ貯留槽 ３ 混和槽 ４ pH低下剤貯留槽 ５ 固液分離槽 ６ 凝集剤貯留槽 ７ 脱水機 1 Anaerobic digestion tank 2 Alkali storage tank 3 Mixing tank 4 pH lowering agent storage tank 5 Solid-liquid separation tank 6 Coagulant storage tank 7 Dehydrator
Claims (3)
をpHが7.3 以上のアルカリ条件下で嫌気性消化処理する
ことにより、得られる消化汚泥中の炭酸イオン、重炭酸
イオン、溶存二酸化炭素濃度の総和を増加させた後、消
化汚泥のpHを低下させることによって二酸化炭素ガスを
放出させ、このガスを利用して消化汚泥を浮上分離させ
て濃縮消化汚泥と消化脱離液とに固液分離することを特
徴とする消化汚泥の固液分離方法。1. A digestion sludge obtained by subjecting an organic sludge to an anaerobic digestion treatment in an enclosed anaerobic digestion tank under alkaline conditions having a pH of 7.3 or more, carbonate ions, bicarbonate ions, and dissolved dioxide. After increasing the total carbon concentration, the pH of the digested sludge is lowered to release carbon dioxide gas, and the digested sludge is floated and separated by using this gas to solidify the digested sludge and the digested desorbed liquid. A solid-liquid separation method for digested sludge, characterized by liquid separation.
汚泥のpHを低下させる請求項１に記載の消化汚泥の固液
分離方法。 2. Digestion using ferric chloride or PAC
The solid-liquid digested sludge according to claim 1, which lowers the pH of the sludge.
Separation method.
汚泥に凝集剤を添加して脱水処理することを特徴とするCharacterized by adding a coagulant to sludge for dehydration treatment
消化汚泥の固液分離方法。Solid-liquid separation method for digested sludge.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15925892A JPH08238B2 (en) | 1992-06-18 | 1992-06-18 | Solid-liquid separation method for digested sludge |
| US08/040,609 US5360546A (en) | 1992-04-01 | 1993-03-31 | Method for treating organic sludge |
| EP19930302610 EP0564298B1 (en) | 1992-04-01 | 1993-04-01 | Method for treating organic sludge |
| DE1993619270 DE69319270T2 (en) | 1992-04-01 | 1993-04-01 | Processes for the treatment of organic sludges |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15925892A JPH08238B2 (en) | 1992-06-18 | 1992-06-18 | Solid-liquid separation method for digested sludge |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0671296A JPH0671296A (en) | 1994-03-15 |
| JPH08238B2 true JPH08238B2 (en) | 1996-01-10 |
Family
ID=15689833
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15925892A Expired - Lifetime JPH08238B2 (en) | 1992-04-01 | 1992-06-18 | Solid-liquid separation method for digested sludge |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH08238B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109574434B (en) * | 2018-12-13 | 2020-07-14 | 上海交通大学 | Method for producing methane by enhancing anaerobic digestion of excess sludge by using alkaloids |
| CN110835220A (en) * | 2019-11-28 | 2020-02-25 | 天津凯英科技发展股份有限公司 | Sludge anaerobic digestion method and application |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57144099A (en) * | 1981-02-28 | 1982-09-06 | Hitachi Plant Eng & Constr Co Ltd | Anaerobic digestive method for organic sludge |
| JPS586560A (en) * | 1981-06-30 | 1983-01-14 | Fujitsu Ltd | Magnetic disk device |
-
1992
- 1992-06-18 JP JP15925892A patent/JPH08238B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0671296A (en) | 1994-03-15 |
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