【０００１】
【発明の属する技術分野】
本発明は凝集剤の添加方法および装置に関し、下水・廃水処理などで発生する汚泥に高分子凝集剤などの凝集剤を添加・混合し、凝縮させる技術に係るものである。
【０００２】
【従来の技術】
従来、下水・廃水処理等で発生する余剰汚泥は減容化を目的として濃縮される。濃縮対象汚泥としては、必ずしも１種類の汚泥だけでなく、最初沈殿池汚泥（初沈汚泥）、または余剰汚泥、最初沈殿池汚泥の双方を混合した混合汚泥も濃縮の対象となることがある。
【０００３】
汚泥の濃縮法には重力濃縮法、機械濃縮法があり、機械濃縮法には遠心濃縮法、常圧浮上法、加圧浮上法、造粒濃縮法がある。これら以外に機械濃縮法の技術としては、濾布を使用した走行式のベルトスクリーン型、ウェッジワイヤーやパンチングメタルを使用した回転ドラム式のドラムスクリーン型、ウェッジワイヤーを使用した固定式の傾斜スクリーン等がある。
【０００４】
しかし、近年では汚泥に含まれる有機物量の増加に伴って濃縮不良が生じ、汚泥の濃縮性が悪化し、後工程の汚泥処理に影響が出ている場合が増えている。このため、難濃縮性の汚泥に対しては濃縮促進剤として高分子凝集剤などを添加することもある。汚泥と凝集剤を反応させる方式にはドラム式、攪拌式などの様々な種類がある。
【０００５】
以下に、下水・廃水処理の一例を図４に示す。図４において、沈砂池１１にて流入する原水中の砂、砂利、粗大なごみを除去する。沈殿池１２にて浮遊する固形物を沈殿させて初沈汚泥として引き抜く。初沈汚泥は余剰汚泥と混合して後に混合汚泥として引き抜く場合もある。沈殿池１２の分離水は反応タンク１３で微生物の働きにより生物処理を行う。反応タンク１３の生物処理水は沈殿池１４で活性汚泥を沈殿させ、清澄な上澄水を消毒槽１５で消毒後に河川などへ放流する。沈殿池１４の沈殿汚泥は返送汚泥として反応タンク１３に送るほか、余剰汚泥として引き抜く。引き抜いた初沈汚泥、余剰汚泥は、凝集剤槽１６から凝集剤を添加して後に汚泥濃縮機１７に送って濃縮汚泥と脱離液に分離する。
【０００６】
【発明が解決しようとする課題】
ところで、汚泥と凝集剤を反応させる手段にはドラム式、攪拌式など従来からある優れた凝集方法があるが、対象となる汚泥の凝集反応に必要な滞留時間に適した槽容積を設計段階で決定する必要があり、全く異なる２種類の汚泥を同じ装置で凝集させることは想定されていない。また、これらの凝集装置には攪拌動力が必要である。
【０００７】
本発明は上記した課題を解決するものであり、濃縮対象汚泥の性状の変化に対して凝集反応時間を適切に調整することができ、攪拌のための動力を必要としない凝集剤の添加方法および装置を提供する。
【０００８】
【課題を解決するための手段】
上記課題を解決するために、請求項１に係る本発明の凝集剤の添加方法は、先端が汚泥濃縮手段に連通する所定管路長の給泥管路に、基端から給泥ポンプによって濃縮対象汚泥を供給し、先端側の複数箇所でそれぞれ薬液バルブを介して給泥管路に連通する薬液供給管路に、基端から薬液供給ポンプで凝集剤を供給し、任意の薬液バルブを開栓して凝集剤を給泥管路に供給し、凝集剤を投入した濃縮対象汚泥が給泥管路を流れて汚泥濃縮手段に達するまでの滞留時間において凝集剤を濃縮対象汚泥に混合して凝集反応を行わせるものであって、開栓する薬液バルブを適宜に選択することで滞留時間を調整して濃縮対象汚泥の性状に応じた凝集反応時間を確保するものである。
【０００９】
上記した構成により、濃縮対象汚泥を汚泥濃縮手段で濃縮して得られる濃縮汚泥において所定濃縮濃度および所定ＳＳ回収率を達成するのには、汚泥濃縮手段に投入する濃縮対象汚泥に所定の凝集効果が生じていることが必要である。
【００１０】
凝集剤が所定の凝集効果を発揮するために必要な凝集反応時間は、濃縮対象汚泥のＴＳ（総固形物量）が少ないほどに短くなり、ＴＳ（総固形物量）が多いほどに長くなる。一方、凝集剤の添加により濃縮対象汚泥中に発生する凝集フロックは給泥管路を流れる距離、換言すると滞留時間が長いほどに壊れ易くなる。したがって、過剰な滞留時間は凝集効果を減じて濃縮濃度およびＳＳ回収率を低下させる要因となる。よって、ＴＳに相応した凝集反応時間となるように滞留時間を制御する必要があるので、開栓する薬液バルブを適宜に選択することで滞留時間を調整して濃縮対象汚泥の性状に応じた凝集反応時間を確保する。
【００１１】
請求項２に係る本発明の凝集剤の添加装置は、先端が汚泥濃縮手段に連通し、基端が濃縮対象汚泥を供給する給泥ポンプに連通した所定管路長の給泥管路と、基端が凝集剤を供給する薬液供給ポンプに連通し、先端側の複数箇所でそれぞれバルブを介して給泥管路に連通する薬液供給管路とを備えたものである。
【００１２】
上記した構成により、開栓する薬液バルブを適宜に選択することで滞留時間を調整して濃縮対象汚泥の性状に応じた凝集反応時間を確保できる。
請求項３に係る本発明の凝集剤の添加装置は、給泥管路が九十九折状もしくは螺旋状の管路をなすものである。
【００１３】
上記した構成により、狭いスペースに長い管路長の給泥管路を配置することができ、給泥管路が九十九折状もしくは螺旋状をなすことで管路内での流れが乱流となって濃縮対象汚泥と凝集剤の攪拌効果が高まり、凝集反応の効率が向上する。よって、攪拌のための特別な動力を必要としない。
【００１４】
請求項４に係る本発明の凝集剤の添加装置は、給泥管路が途中に複数の攪拌手段を有するものである。
上記した構成において、攪拌手段は給泥管路を構成する管継手や管路内に配置する固定翼であり、攪拌手段を通過する際に濃縮対象汚泥と凝集剤の攪拌効果が高まるので、攪拌のための特別な動力を必要とせずに凝集反応の効率の向上を図ることができる。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。図１〜図３において、給泥管路１は先端が汚泥濃縮機（例えばベルト型濃縮機）２に連通しており、基端が濃縮対象汚泥を供給する給泥ポンプ３に連通し、給泥ポンプ３の吸込側が汚泥貯留槽４に連通している。給泥管路１は所定管路長を有しており、九十九折状もしくは螺旋状、あるいは直線状の管路に形成することができるが、本実施の形態では単管５を管継手６で９０°に接続して幾重にも屈曲する九十九折状に形成しており、狭いスペースに必要な長さの管路長の給泥管路１を効率良く配置している。管継手６は後述するように攪拌手段として作用するが、給泥管路１の途中に必要に応じて、流路断面積が拡縮する管路、管内スクリュー、オリフィス形状、邪魔板、ピン類等の攪拌手段を設ける。
【００１６】
薬液供給管路７は基端が凝集剤を供給する薬液供給ポンプ８に連通しており、薬液供給ポンプ８の吸込側が凝集剤槽９に連通している。薬液供給管路７は先端側の複数箇所で分岐してそれぞれ薬液バルブ１０、１１、１２、１３を介して給泥管路１に連通している。薬液供給管路７の各接続位置から給泥管路１の先端までの管路長は予め実験等で求めたものであり、給泥管路１に対する薬液供給管路７の接続位置を濃縮対象汚泥の汚泥種毎に異なる位置に設定している。
【００１７】
以下、上記した構成における作用を説明する。汚泥貯留槽４には濃縮対象汚泥として最初沈殿池汚泥（以後、初沈汚泥と称す）や余剰汚泥、もしくはそれらの混合物を貯留する。凝集剤槽９には高分子凝集剤等の凝集剤を貯留する。
【００１８】
濃縮対象汚泥は給泥ポンプ３を駆動することで給泥管路１を通して汚泥濃縮機２に供給する。この際に、何れかの薬液バブル１０、１１、１２、１３を開栓した状態において薬液供給ポンプ８を駆動することで薬液供給管路７を通して給泥管路１に凝集剤を供給する。
【００１９】
凝集剤を投入した濃縮対象汚泥は給泥管路１を流れて汚泥濃縮機２に達するまでに、給泥管路１を流動する間の管壁との摩擦に由来する乱流、管路が９０°に屈曲することに由来する乱流、管継手６における流路断面積の変化や継ぎ目の抵抗要素に由来する乱流、固定翼等の攪拌手段に由来する乱流によって攪拌作用を受ける。この乱流によって攪拌効果が高まり、凝集剤と濃縮対象汚泥との混合を促進することで凝集反応の効率が向上する。
【００２０】
この凝集剤を投入した濃縮対象汚泥が給泥管路１を流れて汚泥濃縮機２に達するまでの管路長および滞留時間は、開栓する薬液バブル１０、１１、１２、１３を適宜に選択することで調整でき、濃縮対象汚泥の性状に応じた凝集反応時間を確保できる。
【００２１】
ところで、濃縮対象汚泥を汚泥濃縮機２で濃縮して得られる濃縮汚泥には所定濃縮濃度（濃縮汚泥中の固形物量の割合）および所定ＳＳ回収率（濃縮対象汚泥中の固形物量に対する濃縮汚泥中の固形物量の割合）が求められる。このために、汚泥濃縮機２に投入する濃縮対象汚泥には所定の凝集効果が生じていることが必要である。
【００２２】
図２は粘性の高い初沈汚泥（ＴＳ２．４Ｗｔ％）に凝集剤（０．４Ｗｔ％）を添加する場合における凝集剤の添加位置と濃縮汚泥の濃縮濃度の関係を示すものである。図２より明らかなように、給泥管路１の先端に最も近いバルブ１０を開栓して凝集剤を添加する場合、つまり最も滞留時間が短い場合に濃縮濃度およびＳＳ回収率がともに低くなり、先端から最も遠いバルブ１３を開栓して凝集剤を添加する場合、つまり最も滞留時間が長い場合に濃縮濃度およびＳＳ回収率がともに高くなる。
【００２３】
このように、凝集剤が所定の凝集効果、例えば図２中に一点鎖線で示す設定値の基準を満たす所定濃縮濃度および所定ＳＳ回収率を発揮するためには、濃縮対象汚泥のＴＳ（総固形物量）が多いほどに凝集反応時間を長く必要とし、少ないほどに凝集反応時間が短くてすむ。
【００２４】
一方、図３は粘性の低い余剰汚泥（ＴＳ０．３Ｗｔ％）に凝集剤（０．３Ｗｔ％）を添加する場合における凝集剤の添加位置と濃縮汚泥の濃縮濃度の関係を示すものである。図３より明らかなように、給泥管路１の先端に最も近いバルブ１０を開栓して凝集剤を添加する場合、つまり最も滞留時間が短い場合に濃縮濃度およびＳＳ回収率がともに高くなり、先端から最も遠いバルブ１３を開栓して凝集剤を添加する場合、つまり最も滞留時間が長い場合に濃縮濃度およびＳＳ回収率がともに低くなる。
【００２５】
これは凝集剤の添加により濃縮対象汚泥中に発生する凝集フロックが給泥管路を流れる距離、換言すると滞留時間が長いほどに壊れ易くなるためであり、過剰な滞留時間は凝集効果を減じて濃縮濃度およびＳＳ回収率を低下させる要因となるので、凝集剤が所定の凝集効果、例えば図３中に一点鎖線で示す設定値の基準を満たす所定濃縮濃度および所定ＳＳ回収率を発揮するためには、ＴＳに相応した凝集反応時間となるように滞留時間を制御する必要がある。
【００２６】
よって、汚泥種毎に異なる濃縮対象汚泥の性状に応じて開栓する薬液バルブを適宜に選択することで滞留時間を調整して適切な凝集反応時間を確保する。
【００２７】
【発明の効果】
以上のように本発明によれば、開栓する薬液バルブを適宜に選択することで滞留時間を調整して汚泥種毎に異なる濃縮対象汚泥の性状に応じた適切な凝集反応時間を確保でき、複数種類の汚泥種に柔軟に対応することができる。よって、従来のように対象となる汚泥の凝集反応に必要な滞留時間に適した槽容積を設計段階で決定する必要がなくなり、全く異なる２種類の汚泥を同じ装置で凝集させることが可能となる。
【００２８】
給泥管路が九十九折状もしくは螺旋状の管路をなすことで、狭いスペースに長い管路長の給泥管路を配置することができるとともに、管路内での流れが乱流となって濃縮対象汚泥と凝集剤の攪拌効果が高まり、攪拌のための特別な動力を必要とせずに凝集反応の効率を向上させることができる。管継手や管路内に配置する固定翼等の攪拌手段によって攪拌効果を高めて凝集反応の効率をさらに向上させることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態における凝集剤の添加装置を示す平面図である。
【図２】同実施の形態において添加位置が濃縮濃度とＳＳ回収率に与える影響を示すグラフ図である。
【図３】同実施の形態において添加位置が濃縮濃度とＳＳ回収率に与える影響を示すグラフ図である。
【図４】従来の下水・廃水処理の一例を示すフローシート図である。
【符号の説明】
１ 給泥管路
２ 汚泥濃縮機
３ 給泥ポンプ
４ 汚泥貯留槽
５ 単管
６ 管継手
７ 薬液供給管路
８ 薬液供給ポンプ
９ 凝集剤槽
１０、１１、１２、１３ バルブ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for adding a flocculant, and relates to a technique for adding, mixing, and condensing a flocculant such as a polymer flocculant to sludge generated in sewage / wastewater treatment or the like.
[0002]
[Prior art]
Conventionally, excess sludge generated in sewage / wastewater treatment or the like is concentrated for the purpose of volume reduction. As the sludge to be concentrated, not only one kind of sludge but also sludge mixed with first settling tank sludge (first settled sludge) or surplus sludge and first settled tank sludge may be subjected to concentration.
[0003]
The sludge concentration method includes a gravity concentration method and a mechanical concentration method, and the mechanical concentration method includes a centrifugal concentration method, a normal pressure flotation method, a pressure flotation method, and a granulation concentration method. In addition to these technologies, mechanical concentrating methods include traveling belt screen type using filter cloth, rotating drum type drum screen type using wedge wire or punching metal, and fixed inclined screen using wedge wire. There is.
[0004]
However, in recent years, poor concentration has occurred due to an increase in the amount of organic matter contained in sludge, and the concentration of sludge has deteriorated, and the sludge treatment in the subsequent process has been increasingly affected. For this reason, a polymer flocculant or the like may be added as a concentration accelerator to hardly condensable sludge. There are various types of methods for reacting sludge with a flocculant, such as a drum type and a stirring type.
[0005]
An example of sewage / wastewater treatment is shown below in FIG. In FIG. 4, sand, gravel, and coarse dust in the raw water flowing into the sand basin 11 are removed. The solid matter floating in the sedimentation basin 12 is settled and pulled out as primary sludge. The primary sludge may be mixed with surplus sludge and then withdrawn as mixed sludge. Separation water from the sedimentation basin 12 is subjected to biological treatment in the reaction tank 13 by the action of microorganisms. The biologically treated water in the reaction tank 13 causes activated sludge to settle in the sedimentation basin 14, and clear supernatant water is disinfected in the disinfection tank 15 and discharged to a river or the like. The settled sludge in the settling basin 14 is sent to the reaction tank 13 as returned sludge, and is extracted as surplus sludge. The extracted initial settled sludge and excess sludge are added with a coagulant from a coagulant tank 16 and then sent to a sludge concentrator 17 to be separated into a concentrated sludge and a desorbed liquid.
[0006]
[Problems to be solved by the invention]
Means for reacting the sludge with the flocculant include conventional excellent flocculation methods such as a drum type and a stirring type.At the design stage, a tank volume suitable for the residence time required for the target sludge flocculation reaction is determined. It is necessary to determine, and it is not assumed that two completely different types of sludge are coagulated by the same apparatus. Further, these aggregating devices require stirring power.
[0007]
The present invention has been made to solve the above-mentioned problems, and can appropriately adjust the coagulation reaction time with respect to the change in the properties of the sludge to be concentrated, and a method of adding a coagulant that does not require power for stirring and Provide equipment.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method for adding a flocculant according to the present invention according to claim 1 is characterized in that a tip is concentrated by a sludge pump from a base end to a sludge supply pipe having a predetermined pipe length communicating with a sludge concentration means. The target sludge is supplied, and a coagulant is supplied from the base end to the chemical supply pipe communicating with the mud supply pipe via the chemical valve at a plurality of points on the distal end side by a chemical supply pump, and an arbitrary chemical valve is opened. Plug and supply the flocculant to the sludge supply line, and mix the flocculant with the sludge to be concentrated during the residence time until the sludge to be concentrated into which the flocculant is charged flows through the supply line and reaches the sludge concentration means. The coagulation reaction is performed, and the residence time is adjusted by appropriately selecting the chemical liquid valve to be opened to secure the coagulation reaction time according to the properties of the sludge to be concentrated.
[0009]
According to the above-described configuration, in order to achieve a predetermined concentration and a predetermined SS recovery rate in the concentrated sludge obtained by concentrating the sludge to be concentrated by the sludge concentrating means, a predetermined coagulation effect is applied to the sludge to be concentrated supplied to the sludge concentrating means. Needs to occur.
[0010]
The coagulation reaction time required for the coagulant to exhibit a predetermined coagulation effect becomes shorter as the TS (total solid content) of the sludge to be concentrated is smaller, and becomes longer as the TS (total solid content) is larger. On the other hand, the flocculated floc generated in the sludge to be concentrated due to the addition of the flocculant is more likely to be broken as the flow distance in the sludge supply line, in other words, the residence time is longer. Therefore, an excessive residence time is a factor that reduces the aggregation effect and lowers the concentration and SS recovery. Therefore, it is necessary to control the residence time so that the coagulation reaction time corresponds to the TS. Therefore, the residence time is adjusted by appropriately selecting the chemical solution valve to be opened, and the aggregation time is adjusted according to the properties of the sludge to be concentrated. Allow reaction time.
[0011]
The coagulant addition device of the present invention according to claim 2, wherein the leading end communicates with the sludge concentrating means, the base end communicates with a sludge pump that supplies sludge to be concentrated, and a sludge supply pipe having a predetermined pipe length, The base end is provided with a chemical solution supply pump for supplying a flocculant, and a chemical solution supply line communicating with a mud supply line via a valve at each of a plurality of points on the distal end side.
[0012]
According to the above-described configuration, the residence time can be adjusted by appropriately selecting the chemical liquid valve to be opened, and the coagulation reaction time according to the properties of the sludge to be concentrated can be secured.
In the apparatus for adding a flocculant of the present invention according to claim 3, the mud feed pipe forms a 99-fold or spiral pipe.
[0013]
With the above-described configuration, it is possible to arrange a mud feed pipe having a long pipe length in a narrow space, and the flow in the pipe is turbulent due to the 99/99 folded or spiral shape. As a result, the effect of stirring the sludge to be concentrated and the flocculant is enhanced, and the efficiency of the flocculation reaction is improved. Therefore, no special power for stirring is required.
[0014]
In the apparatus for adding a flocculant of the present invention according to claim 4, the mud feed pipe has a plurality of stirring means in the middle.
In the above-described configuration, the stirring means is a pipe joint constituting the mud feed pipe or a fixed blade disposed in the pipe, and when passing through the stirring means, the effect of stirring the sludge to be concentrated and the flocculant is increased. It is possible to improve the efficiency of the agglutination reaction without requiring special power for the reaction.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIGS. 1 to 3, the sludge supply line 1 has a leading end communicating with a sludge concentrator (for example, a belt-type concentrator) 2 and a base end communicating with a sludge pump 3 for supplying sludge to be concentrated. The suction side of the mud pump 3 communicates with the sludge storage tank 4. The mud feed pipe 1 has a predetermined pipe length and can be formed in a 99-fold, spiral, or straight pipe. In the present embodiment, the single pipe 5 is connected to a pipe joint. 6 is formed in a ninety-nine-fold shape which is connected to 90 ° and bent multiple times, and the mud feed pipe 1 having a pipe length of a necessary length is efficiently arranged in a narrow space. The pipe joint 6 functions as a stirring means as described later. However, as required, a pipe having a passage cross-sectional area expanding and contracting, a screw in a pipe, an orifice shape, a baffle plate, pins, etc. Is provided.
[0016]
The chemical solution supply pipe 7 has a base end communicating with a chemical solution supply pump 8 for supplying a coagulant, and a suction side of the chemical solution supply pump 8 communicates with a coagulant tank 9. The chemical supply pipe 7 branches at a plurality of points on the distal end side and communicates with the mud supply pipe 1 through chemical liquid valves 10, 11, 12, and 13, respectively. The pipe length from each connection position of the chemical supply pipe 7 to the tip of the mud supply pipe 1 is obtained in advance through experiments or the like. Different positions are set for each type of sludge.
[0017]
Hereinafter, the operation of the above configuration will be described. The sludge storage tank 4 stores first settling tank sludge (hereinafter, referred to as first settled sludge), excess sludge, or a mixture thereof as sludge to be concentrated. The flocculant tank 9 stores a flocculant such as a polymer flocculant.
[0018]
The sludge to be concentrated is supplied to the sludge concentrator 2 through the sludge supply line 1 by driving the sludge pump 3. At this time, the coagulant is supplied to the mud supply pipe 1 through the chemical supply pipe 7 by driving the chemical supply pump 8 in a state where any of the chemical bubbles 10, 11, 12, 13 is opened.
[0019]
Before the sludge to be concentrated into which the coagulant is introduced flows through the sludge supply line 1 and reaches the sludge concentrator 2, the turbulent flow resulting from friction with the pipe wall while flowing through the sludge supply line 1 causes A stirring effect is caused by turbulence caused by bending at 90 °, turbulence caused by a change in the cross-sectional area of the flow passage in the pipe joint 6, turbulence caused by a resistance element at the seam, and turbulence caused by stirring means such as fixed blades. This turbulence enhances the stirring effect, and promotes the mixing of the flocculant with the sludge to be concentrated, thereby improving the efficiency of the flocculation reaction.
[0020]
The length of the pipeline and the residence time until the sludge to be concentrated into which the coagulant has been introduced flows through the sludge supply line 1 and reaches the sludge concentrator 2 are appropriately selected from the chemical liquid bubbles 10, 11, 12, and 13 to be opened. The coagulation reaction time according to the properties of the sludge to be concentrated can be secured.
[0021]
By the way, the concentrated sludge obtained by concentrating the sludge to be concentrated by the sludge concentrator 2 has a predetermined concentrated concentration (the ratio of the amount of solids in the concentrated sludge) and a predetermined SS recovery rate (the amount of solids in the concentrated sludge with respect to the amount of solids in the sludge to be concentrated). Is determined. For this reason, it is necessary that the sludge to be concentrated to be introduced into the sludge concentrator 2 has a predetermined coagulation effect.
[0022]
FIG. 2 shows the relationship between the addition position of the flocculant and the concentration of the concentrated sludge when the flocculant (0.4 Wt%) is added to the highly viscous primary sludge (TS 2.4 Wt%). As is apparent from FIG. 2, when the valve 10 closest to the end of the mud feed pipe 1 is opened and the coagulant is added, that is, when the residence time is shortest, both the concentration and the SS recovery rate become low. When the valve 13 farthest from the tip is opened and the coagulant is added, that is, when the residence time is longest, both the concentration and the SS recovery rate increase.
[0023]
As described above, in order for the flocculant to exhibit a predetermined flocculation effect, for example, a predetermined concentration concentration and a predetermined SS recovery rate that satisfy the criteria of the set value indicated by the dashed line in FIG. The larger the amount, the longer the agglutination reaction time is required, and the smaller the amount, the shorter the agglutination reaction time.
[0024]
On the other hand, FIG. 3 shows the relationship between the addition position of the flocculant and the concentration of the concentrated sludge when the flocculant (0.3 Wt%) is added to the excess sludge having a low viscosity (TS 0.3 Wt%). As is clear from FIG. 3, when the valve 10 closest to the end of the mud feed pipe 1 is opened and the coagulant is added, that is, when the residence time is shortest, both the concentrated concentration and the SS recovery rate increase. When the valve 13 farthest from the tip is opened and the coagulant is added, that is, when the residence time is longest, both the concentrated concentration and the SS recovery rate become low.
[0025]
This is because the flocculation floc generated in the sludge to be concentrated due to the addition of the flocculant becomes more susceptible to breakage as the distance flowing in the sludge supply line, in other words, the longer the residence time, the excessive residence time reduces the flocculation effect. Since the concentration concentration and the SS recovery rate are reduced, the flocculant is required to exhibit a predetermined flocculation effect, for example, a predetermined concentration concentration and a predetermined SS recovery rate satisfying the criteria of the set value indicated by the dashed line in FIG. It is necessary to control the residence time so that the coagulation reaction time corresponds to the TS.
[0026]
Therefore, by appropriately selecting a chemical liquid valve to be opened according to the properties of the sludge to be concentrated which differs for each type of sludge, the residence time is adjusted to secure an appropriate coagulation reaction time.
[0027]
【The invention's effect】
As described above, according to the present invention, it is possible to adjust the residence time by appropriately selecting a chemical liquid valve to be opened, to secure an appropriate coagulation reaction time according to the properties of the sludge to be concentrated, which differs for each type of sludge, It is possible to flexibly cope with plural kinds of sludge types. Therefore, it is not necessary to determine the tank volume suitable for the residence time required for the target sludge coagulation reaction at the design stage as in the related art, and two completely different types of sludge can be coagulated by the same apparatus. .
[0028]
By forming a 99-fold or spiral pipe, the mud supply pipe can arrange a long pipe length in a narrow space, and the flow in the pipe becomes turbulent. As a result, the effect of stirring the sludge to be concentrated and the flocculant is enhanced, and the efficiency of the flocculation reaction can be improved without requiring any special power for stirring. Stirring effect such as a fixed wing or the like arranged in a pipe joint or a pipe can enhance the stirring effect, thereby further improving the efficiency of the agglutination reaction.
[Brief description of the drawings]
FIG. 1 is a plan view showing an apparatus for adding a flocculant according to an embodiment of the present invention.
FIG. 2 is a graph showing the effect of the addition position on the concentration and SS recovery in the same embodiment.
FIG. 3 is a graph showing an influence of an addition position on a concentration concentration and an SS recovery rate in the same embodiment.
FIG. 4 is a flow sheet diagram showing an example of conventional sewage / wastewater treatment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sludge supply line 2 Sludge concentrator 3 Sludge supply pump 4 Sludge storage tank 5 Single pipe 6 Fitting 7 Chemical supply line 8 Chemical supply pump 9 Coagulant tank 10, 11, 12, 13 Valve