JPH0947786A - Biological filtration-type denitrifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the biological fitration-type denitifying method by which BOD for denitrification is not deficient even when backwashing is carried out, a denitrification reaction proceeds sufficiently, and the amt. of backwashing water is reduced. SOLUTION: A water-permeable supporting member 2 is horizontally set at the upper part of a tank 1, and a foldable filter medium bed 3 is provided below the member. A diffuser pipe 4 is furnished in the middle of the bed 3 in its height direction, and an aerobic nitrification part 5 is formed above the diffuser pipe and a denitifuing part 6 is formed below the pipe. A part of the nitrification soln. is circulated to the denitrifying part 6 through a pipeline 7. When the bed 3 is clogged, 3 times or above of weak backwashings are applied between strong backwashings.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は下水等の不溶性の有
機物を含む排水の窒素除去を行なう生物濾過式窒素除去
方法に係り、特に逆洗方法を改良した生物濾過式窒素除
去方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological filtration type nitrogen removal method for removing nitrogen from waste water containing insoluble organic matter such as sewage, and more particularly to a biological filtration type nitrogen removal method with an improved backwashing method.

【０００２】[0002]

【従来の技術】排水中の窒素を除去する方法では、微生
物による硝化・脱窒反応を利用した方式が多くの実績を
持つ。中でも小さな敷地面積で効率よく窒素を除去する
方法として、近年、生物濾過法が注目されている。その
一つにポリプロピレンやウレタン樹脂等を発泡させた比
重が極めて小さい浮上性の濾材で濾過槽内に脱窒濾層を
形成し、この濾層に上向流で原水を通水して、生物濾過
し、脱窒を行なう方法がある。2. Description of the Related Art As a method for removing nitrogen in waste water, a method utilizing a nitrification / denitrification reaction by microorganisms has many achievements. Among them, the biological filtration method has recently attracted attention as a method for efficiently removing nitrogen in a small site area. In one of them, a denitrifying filter layer is formed in the filter tank with a buoyant filter medium that has an extremely small specific gravity, such as polypropylene or urethane resin foamed, and raw water is passed through this filter layer in an upward flow to create a living organism. There is a method of filtering and denitrifying.

【０００３】この浮上性濾材は、発泡成形されているの
で小粒径であり、表面積が広いため、生物濾過の場合、
濾材に付着する生物膜の保持量は極めて大であり、その
結果、高負荷運転が可能となり、高度の処理水を得るこ
とができる。また、濾材表面に脱窒菌を付着させている
ため処理水の固液分離に沈殿池を必要とせず、小さな敷
地面積内に設置することができる。This floatable filter medium has a small particle size because it is foam-molded and has a large surface area. Therefore, in the case of biological filtration,
The amount of biofilm attached to the filter medium is extremely large, and as a result, high load operation becomes possible and a high level of treated water can be obtained. Moreover, since denitrifying bacteria are attached to the surface of the filter medium, a sedimentation basin is not required for solid-liquid separation of treated water, and it can be installed in a small site area.

【０００４】この生物濾過法では、濾過時間の経過と共
にＳＳの捕捉と余剰汚泥の発生により濾過層が閉塞して
くるため、定期的に洗浄が必要である。洗浄においては
捕捉ＳＳと余剰汚泥を確実に排出し、差圧を低減するこ
とが必要である。In this biological filtration method, since the filtration layer is clogged due to the trapping of SS and the generation of excess sludge with the lapse of filtration time, periodical cleaning is necessary. In cleaning, it is necessary to reliably discharge the trapped SS and excess sludge to reduce the differential pressure.

【０００５】洗浄が不十分になると、濾材間にスライム
状に微生物が付着し濾材を固着させて通水を妨げる恐れ
があるため、浮上性濾材を用いた上向流式脱窒方法で
は、以下のようなＳＳを十分に排出できる逆洗方法が一
般的である。If cleaning is insufficient, microorganisms may adhere between the filter media in the form of slime, and the filter media may be fixed to impede water flow. A backwashing method capable of sufficiently discharging SS as described above is generally used.

【０００６】即ち、まず濾過層下部の排水管から水を抜
き、上部から水を供給して（例、流速：３０〜６０ｍ／
ｈ）水逆洗を行ない、次いで濾過層下部から空気を供給
して（流速１０〜２０ｍ／ｈ）空気逆洗を行なう、水逆
洗、空気逆洗を数回繰り返し、最後に濾過層を水でリン
スすることにより、濾過層に捕捉されたＳＳをほぼ完全
に濾過層から除去する。That is, first, water is drained from the drainage pipe at the lower part of the filtration layer, and water is supplied from the upper part (eg, flow velocity: 30-60 m /
h) Backwashing with water, then air is supplied from the lower part of the filter layer (flow rate 10 to 20 m / h) to backwash air, backwashing with water and backwashing with air are repeated several times, and finally the filter layer is washed with water. By rinsing with, the SS trapped in the filter layer is almost completely removed from the filter layer.

【０００７】このような逆洗において、水逆洗時に濾過
層の展開率を５〜２５％とし、逆洗水（排出水）のＳＳ
濃度変化がピークを超え、ピーク時の０〜２０％になる
まで洗浄する。In such backwashing, when the water is backwashed, the expansion rate of the filter layer is set to 5 to 25%, and the SS of the backwash water (discharged water) is
Wash until the change in concentration exceeds the peak and reaches 0 to 20% of the peak.

【０００８】[0008]

【発明が解決しようとする課題】ところが、従来の濾過
層の洗浄方法では、濾過層に捕捉されたＳＳを大量に排
出するので、逆洗後に脱窒反応に必要なＢＯＤの不足を
生じる問題がある。生物濾過法では微生物量を高濃度に
維持できるため高負荷運転が可能であるが、その反面、
滞留時間が短くなるため、可溶化に時間のかかる不溶性
有機物質の利用が困難で脱窒のためのＢＯＤが不足し易
い。濾過層内の捕捉ＳＳ量が増えるに従って不溶性有機
物質の可溶化が促進され、不足ＢＯＤを補うようになる
が、逆洗を行なうと捕捉ＳＳが流出してしまうためＢＯ
Ｄ不足を生じる。However, in the conventional method for cleaning the filtration layer, since a large amount of SS trapped in the filtration layer is discharged, there is a problem that a shortage of BOD necessary for the denitrification reaction occurs after backwashing. is there. The biological filtration method allows high load operation because the amount of microorganisms can be maintained at a high concentration, but on the other hand,
Since the residence time becomes short, it is difficult to use an insoluble organic substance that requires a long time to be solubilized, and the BOD for denitrification tends to be insufficient. As the amount of trapped SS in the filtration layer increases, the solubilization of the insoluble organic substance is promoted to compensate for the insufficient BOD, but when backwashing is performed, the trapped SS flows out, so that BO
D shortage occurs.

【０００９】また、逆洗水量が多く、原水量に対して３
０％を上回る場合があり、固液分離設備が大型化する問
題がある。Also, the amount of backwash water is large, which is 3 with respect to the amount of raw water.
There is a case where it exceeds 0%, and there is a problem that the solid-liquid separation equipment becomes large.

【００１０】本発明は、逆洗を行なっても脱窒のための
ＢＯＤが不足せず、十分に脱窒反応を行なわせることが
でき、しかも逆洗水量も少なくて済む生物濾過式窒素除
去方法を提供することを目的とする。According to the present invention, the BOD for denitrification is not deficient even when backwashing is performed, the denitrification reaction can be sufficiently performed, and the backwashing water amount is small, and the biological filtration type nitrogen removal method is required. The purpose is to provide.

【００１１】[0011]

【課題を解決するための手段】本発明の生物濾過式窒素
除去方法は、浮上性濾材を充填して形成した脱窒濾過層
に排水を上向流に通水して生物的に脱窒し、通水の継続
により脱窒濾過層が目詰まりしたときに該濾過層の逆洗
を行なう生物濾過式窒素除去方法において、該逆洗とし
て、捕捉懸濁物の大部分を排出する強逆洗と、それより
も弱い逆洗を施す弱逆洗とを、強逆洗の間に３回以上の
弱逆洗を行なうように実施することを特徴とするもので
ある。According to the method for removing nitrogen by biological filtration of the present invention, the denitrification filter layer formed by filling the buoyant filter medium is used to pass wastewater in an upward flow to biologically denitrify. In the biological filtration nitrogen removal method of backwashing the denitrification filter layer when the denitrification filter layer is clogged due to continuation of water flow, as the backwashing, strong backwashing for discharging most of the trapped suspension. And weak backwashing in which weaker backwashing is performed than this is performed so that weak backwashing is performed three or more times during strong backwashing.

【００１２】本発明において、脱窒濾過層に付着した大
部分の懸濁物（ＳＳ）を除去する逆洗が強逆洗であり、
懸濁物の一部を除去する洗浄が弱逆洗である。弱逆洗に
おいては、新たに捕捉したＳＳの２０〜９０％相当量を
排出する。In the present invention, the backwash for removing most of the suspension (SS) adhering to the denitrification filter layer is the strong backwash,
The wash that removes part of the suspension is a weak backwash. In the weak backwash, 20 to 90% of the newly captured SS is discharged.

【００１３】かかる本発明では、ＳＳの排出量が少な
く、差圧の低減効果の大きい弱逆洗を強逆洗の間に行な
うことで、濾過層内の平均ＳＳ保持量を高く維持し、不
溶性有機物の可溶化を促進してＢＯＤの不足を補うこと
ができる。In the present invention, by performing weak backwashing, which has a small SS discharge amount and a large effect of reducing the differential pressure, during the strong backwashing, the average SS retention amount in the filtration layer is kept high and the insoluble matter is insoluble. The solubilization of organic substances can be promoted to compensate for the lack of BOD.

【００１４】本発明では、強逆洗２回の間に弱逆洗を３
回以上、例えば３〜３０回行なう。このように弱逆洗を
行なうことにより、逆洗水量も少なくなる。In the present invention, 3 times of weak backwash are carried out between 2 times of strong backwash.
Repeat more than once, for example 3 to 30 times. By performing the weak backwash in this way, the amount of backwash water also decreases.

【００１５】[0015]

【発明の実施の形態】図１は本発明方法が適用される硝
化脱窒装置の一例を示す概略的な縦断面図であり、槽体
１の上部に透水性支持部材２が水平に設置され、その下
側に浮上性濾材層３が設けられている。浮上性濾材層３
の高さ方向の途中に散気管４が設けられ、それよりも上
側が好気的な硝化部５とされ、下側が嫌気的な脱窒部６
とされている。硝化液の一部は配管７によって脱窒部６
へ循環される。８は逆洗排水管、９は弁、１０は凝集剤
添加手段を示す。1 is a schematic vertical sectional view showing an example of a nitrification / denitrification apparatus to which the method of the present invention is applied, in which a water-permeable support member 2 is horizontally installed above a tank body 1. The floatable filter medium layer 3 is provided on the lower side thereof. Floating filter medium layer 3
A diffusing pipe 4 is provided midway in the height direction, the upper side is an aerobic nitrification section 5, and the lower side is an anaerobic denitrification section 6.
It has been. A part of the nitrification liquid is denitrifying part 6 through pipe 7.
Circulated to 8 is a backwash drain pipe, 9 is a valve, and 10 is a coagulant adding means.

【００１６】浮上性濾材としては、例えば、ポリスチレ
ン、ポリプロピレンやウレタン樹脂等を直径１〜１０ｍ
ｍの球体や不定形状に発泡成形した、比重が水より小さ
い、好ましくは０．１以下の濾材が用いられる。As the floatable filter material, for example, polystyrene, polypropylene, urethane resin or the like having a diameter of 1 to 10 m is used.
A m-shaped sphere or a filter material having a specific gravity smaller than water, preferably 0.1 or less, which is foam-molded into an indefinite shape, is used.

【００１７】このような浮上性濾材を生物反応槽に充填
し、適当な位置に配置される透水性の濾材支持部材２に
よって上向流通水された際に、支持部材下方に浮上性濾
材層よりなる生物濾過層が形成される。A biological reaction tank is filled with such a buoyant filter medium, and when water is circulated upward by a water-permeable filter medium support member 2 arranged at an appropriate position, the buoyant filter medium layer is placed below the support member from the buoyant filter medium layer. A biofiltration layer is formed.

【００１８】本発明は、この生物濾過層を脱窒菌が付着
した脱窒濾過層として使用する場合に適用されるもので
あり、この浮上性濾材層が脱窒層のみからなる場合にも
適用でき、また、図１のように脱窒部６の上側に硝化部
５を形成した場合にも適用される。The present invention is applied when this biological filter layer is used as a denitrifying filter layer to which denitrifying bacteria are adhered, and is also applicable when this buoyant filter medium layer is composed only of the denitrifying layer. Further, it is also applied to the case where the nitrification section 5 is formed above the denitrification section 6 as shown in FIG.

【００１９】本発明における強逆洗は、捕捉ＳＳ中の微
生物がスライム状に濾材を固着させることを防ぐために
定期的に行なわれる。The strong backwash in the present invention is carried out periodically in order to prevent the microorganisms in the trapped SS from sticking the filter medium in the form of slime.

【００２０】強逆洗は、通常の生物濾過で使用される逆
洗方法を使用することができ、濾過層に捕捉された懸濁
物の大部分を除去できるものであれば良い。例えば、前
述したように水逆洗（例、２分間）と空気逆洗（例、２
分間）の組み合わせを数回（例、３回）とリンス（例、
５分）を行なう方法、水逆洗のみを多量の水で行なう方
法、脈動流を与える水逆洗方法等が使用できる。The strong backwash can use the backwash method used in ordinary biological filtration, and may be any one that can remove most of the suspension trapped in the filtration layer. For example, as described above, backwashing with water (eg, 2 minutes) and air backwashing (eg, 2 minutes)
Min) combination several times (eg 3 times) and rinse (eg,
5 minutes), a method in which only backwashing with water is performed with a large amount of water, and a backwashing method in which a pulsating flow is applied can be used.

【００２１】なお、この水逆洗は、通水を停止し、濾過
層下方の逆洗排水管８に設けた弁を開として、濾過層内
の水を排出すると共に濾材支持部材上の処理水を支持部
材を通して供給することにより行なわれる。In this backwashing with water, the flow of water is stopped and the valve provided in the backwash drain pipe 8 below the filter bed is opened to discharge the water in the filter bed and to treat the treated water on the filter medium support member. Is supplied through the support member.

【００２２】例えば、流速３０〜６０ｍ／ｈで供給する
と、濾過層は下方に向かって１０５〜１２５％展開する
（展開率５〜２５％）。濾過層の展開により濾過層が緩
み、また、水の流れによる濾材の流動、衝突により、捕
捉されたＳＳは剥離され、水と共に排出される。For example, when supplied at a flow rate of 30 to 60 m / h, the filtration layer expands 105 to 125% downward (expansion rate 5 to 25%). The filter layer is loosened due to the expansion of the filter layer, and the captured SS is separated due to the flow and collision of the filter medium due to the flow of water, and the SS is discharged together with the water.

【００２３】空気逆洗するには、逆洗水の供給を停止し
て濾過層の下方から散気する。これにより、気泡流によ
って激しく濾材が流動、衝突を繰り返し、濾材に強く付
着していたＳＳも剥離される。To carry out backwashing with air, supply of backwashing water is stopped and air is diffused from below the filter layer. As a result, the filter medium vigorously flows and repeatedly collides with the bubble flow, and the SS strongly adhered to the filter medium is also peeled off.

【００２４】このような強逆洗によって、濾過層に捕捉
された大部分のＳＳを除去するが、予め定めた逆洗工程
を一通り行なうことにより終了とする。The strong backwash removes most of the SS trapped in the filtration layer, but the process is completed by repeating a predetermined backwash step.

【００２５】弱逆洗は、強逆洗を１回行なった後、３〜
３０回、特に好ましくは３〜１０回行なう。弱逆洗の実
施時期は所定の濾過差圧に達したときに行なっても良い
し、所定時間毎に行なっても良い。For weak backwashing, after performing strong backwashing once, 3 to
It is carried out 30 times, particularly preferably 3 to 10 times. The weak backwash may be performed when a predetermined filtration differential pressure is reached, or may be performed at predetermined intervals.

【００２６】弱逆洗は、濾過層に新たに捕捉されたＳＳ
の２０〜９０％相当量を除去し、残りを濾過層内に残留
する方法なら任意の方法で良い。例えば、逆洗水を濾過
層上部から供給して下部から排出する水逆洗を１回のみ
行なう。弱逆洗は予め設定した洗浄水量を供給するか、
予め設定した時間水を供給することにより行なう。例え
ば、流速３０〜６０ｍ／ｈで、１〜６分間、好ましくは
１〜３分間水を供給することにより行なう。The weak backwash is performed by the SS newly trapped in the filtration layer.
Any method may be used as long as it is a method of removing 20 to 90% of the above amount and leaving the rest in the filtration layer. For example, backwashing water is supplied only once from the top of the filter layer and discharged from the bottom. For weak backwash, supply a preset amount of wash water, or
This is done by supplying water for a preset time. For example, it is performed by supplying water at a flow rate of 30 to 60 m / h for 1 to 6 minutes, preferably 1 to 3 minutes.

【００２７】また、逆洗排水中のＳＳ量を測定し、所定
ＳＳ濃度になったときに弱逆洗を終了しても良い。Alternatively, the amount of SS in the backwash drainage water may be measured, and the weak backwash may be terminated when the SS concentration reaches a predetermined value.

【００２８】例えば、洗浄時の濾過層の展開率が５〜２
５％となる逆洗流速において、逆洗水ＳＳ濃度変化がピ
ークに達する前の所定濃度で終了すると、濾過差圧が著
しく減少するにもかかわらずＳＳ分が多量に残留するの
で好ましい。For example, the development rate of the filter layer during washing is 5 to 2
At a backwash flow rate of 5%, it is preferable to finish at a predetermined concentration before the SS concentration change of the backwash water reaches a peak because a large amount of SS remains even though the filtration differential pressure is significantly reduced.

【００２９】弱逆洗により、ＳＳの捕捉量を多く保ち、
かつ差圧を低減できる理由は以下である。強逆洗後ＳＳ
の捕捉により差圧が上昇したときのＳＳ捕捉量の分布は
図３のように濾過層入口付近に集中している。弱逆洗で
はこの入口付近のＳＳの一部を排出させるとともに、濾
過層の内部に分散させる効果がある。弱逆洗時には、濾
材が一度展開するため、濾材を離れたＳＳが濾過層内で
一部混合される。従って、逆洗排水ＳＳ濃度がピークに
達する前に洗浄を停止すると、一度濾材から離れたＳＳ
が通水の再開とともに濾過槽上部へ移動して捕捉され
る。排出されるＳＳが少量でも、入口付近に集中してい
たＳＳが上層へ分散されることにより差圧は大きく低下
する。A weak backwash keeps a large amount of captured SS,
The reason why the differential pressure can be reduced is as follows. After strong backwash SS
The distribution of the amount of trapped SS when the differential pressure rises due to trapping is concentrated in the vicinity of the inlet of the filtration layer as shown in FIG. The weak backwash has the effect of discharging a part of the SS near the inlet and dispersing it inside the filtration layer. During weak backwashing, the filter medium develops once, so that the SS that has left the filter medium is partially mixed in the filter layer. Therefore, if washing is stopped before the backwash drainage SS concentration reaches a peak, the SS once separated from the filter medium
The water moves to the upper part of the filter tank and is captured as the water flow resumes. Even if a small amount of SS is discharged, the SS concentrated in the vicinity of the inlet is dispersed to the upper layer, so that the differential pressure is greatly reduced.

【００３０】また、弱逆洗の継続により、捕捉ＳＳの分
布が次第に上層へ広がってゆくため、層全体のＳＳ保持
量が次第に増加してゆく。効果は継続回数の増加ととも
に向上し、弱逆洗一回の排出量を新たに捕捉したＳＳの
５０％とすると、３回の継続で平均ＳＳ保持量は従来法
（強逆洗のみを行なう）の３０％以上向上する。Further, by continuing the weak backwash, the distribution of trapped SS gradually spreads to the upper layer, so that the SS retention amount of the entire layer gradually increases. The effect improves as the number of continuations increases, and assuming that the discharge amount of one weak backwash is 50% of the newly captured SS, the average SS retention amount after three consecutive times is the conventional method (only strong backwash is performed). Of 30% or more.

【００３１】図２に展開率５〜２５％となる逆洗流速に
おける逆洗水量と逆洗水ＳＳ濃度、洗浄後の差圧の関係
の例を示す。逆洗開始後逆洗水ＳＳ濃度は次第に増加
し、濾過層容積の０．５〜１．５倍量でピークに達す
る。その後次第に濃度は低下し、２〜４倍量で逆洗用水
と同等となる。一方、差圧の回復率は０〜０．２倍量で
急激に上昇し、その後の変化は小さい。これは差圧の上
昇に対して、逆洗初期に排出される濾過層入口付近のＳ
Ｓの影響が大きいことを示している。FIG. 2 shows an example of the relationship between the backwash water amount, the backwash water SS concentration, and the differential pressure after washing at a backwash flow rate at a development rate of 5 to 25%. After the start of backwashing, the SS concentration of backwashing water gradually increases and reaches a peak at 0.5 to 1.5 times the volume of the filter bed. After that, the concentration gradually decreases, and becomes 2 to 4 times that of the backwash water. On the other hand, the recovery rate of the differential pressure sharply increases at 0 to 0.2 times the amount, and the change thereafter is small. This is because the S near the inlet of the filter layer, which is discharged in the initial stage of backwashing, is increased by the increase of the differential pressure
It shows that the influence of S is great.

【００３２】これらの関係からＳＳの流出が少なく差圧
低減効果の大きい弱逆洗方法の条件は、逆洗初期より逆
洗水ＳＳ濃度がピークまでの範囲、好ましくはピーク前
の１０〜９０％程度の濃度の時に洗浄を中断することと
なる。濾過層上部に分散、捕捉されたＳＳは、逆洗初期
には排出されないため、ピーク以前で洗浄を中断すれば
排出されるＳＳは新たに捕捉されたＳＳが主で、排水濃
度も比較的安定している。従って、洗浄を中断する方法
は、逆洗水のＳＳ濃度を連続的に測定して洗浄水量を制
御する方法でも良いが、予め逆洗時間と逆洗水ＳＳ濃度
の概略の関係を求めて、洗浄時間又は洗浄水量を設定す
る方法が平易である。From these relationships, the condition of the weak backwashing method in which the outflow of SS is small and the effect of reducing the differential pressure is large is that the SS concentration of the backwashing water is from the initial stage of the backwashing to the peak, preferably 10 to 90% before the peak. The washing will be interrupted when the concentration is about the same. SS dispersed and captured on the upper part of the filtration layer is not discharged in the initial stage of backwashing, so if the washing is interrupted before the peak, the discharged SS is mainly newly captured SS, and the concentration of wastewater is relatively stable. are doing. Therefore, the method of interrupting the cleaning may be a method of continuously measuring the SS concentration of the backwash water to control the amount of wash water, but previously obtaining a rough relationship between the backwash time and the SS concentration of the backwash water, The method of setting the cleaning time or the amount of cleaning water is simple.

【００３３】排出するＳＳ量は新たに捕捉したＳＳの２
０〜９０％相当量が好ましい。２０％未満では濾過層入
口付近のＳＳが除去されないため、洗浄後の差圧の上昇
が極端に早くなり、弱逆洗を続けた運転ができなくな
る。従って、すぐに強逆洗を行わねばならず、結局平均
保持ＳＳ量が従来法と変わらない。９０％超では捕捉Ｓ
Ｓ量の増加が小さく、従来法との差は小さい。The amount of SS discharged is 2 times that of the newly captured SS.
The equivalent amount of 0 to 90% is preferable. If it is less than 20%, the SS in the vicinity of the inlet of the filtration layer is not removed, so that the differential pressure after cleaning rises extremely quickly, and the operation in which the weak backwashing is continued cannot be performed. Therefore, strong backwash must be performed immediately, and the average retained SS amount is not different from the conventional method. Captured S above 90%
The increase in the amount of S is small and the difference from the conventional method is small.

【００３４】弱逆洗は、濾過層入口付近のＳＳを排出す
ることで差圧低減効果が大きいが、層内部にＳＳを多く
残すため、繰り返す毎に濾過継続時間が短かくなる。ま
た、捕捉ＳＳがスライム化し易く、逆洗間隔が長くなり
すぎると、ＳＳが強く付着して、通常の逆洗でも剥離し
にくくなるので、３〜１０回程度で強逆洗を行なうのが
好適である。The weak backwash has a great effect of reducing the differential pressure by discharging SS in the vicinity of the inlet of the filtration layer, but since a large amount of SS is left inside the layer, the filtration continuation time becomes shorter each time it is repeated. Further, if the trapped SS is easily slimed and the backwashing interval becomes too long, the SS adheres strongly and is difficult to be peeled off even in the normal backwashing. Therefore, it is preferable to perform the strong backwashing about 3 to 10 times. Is.

【００３５】強逆洗後はＳＳの流出によりＢＯＤ不足を
生じるが、弱逆洗の実施によりＢＯＤが補われ脱窒率の
高い時間が延長されるため、平均値で従来法（強逆洗の
みを行なう。）より脱窒率が向上する。また、水量の少
ない弱逆洗の併用により逆洗水量が低減される。After strong backwash, BOD becomes insufficient due to outflow of SS, but since weak backwash is supplemented with BOD and the time of high denitrification rate is extended, the average value of the conventional method (strong backwash only The denitrification rate is improved. In addition, the amount of backwash water is reduced by using weak backwash with a small amount of water.

【００３６】排水中に窒素と共にリンが含まれていると
きは、生物濾過層に通水して脱窒を行なう際に、流入排
水に無機凝集剤を添加するのが好ましい。When the drainage contains phosphorus together with nitrogen, it is preferable to add an inorganic coagulant to the inflowing drainage when water is passed through the biological filtration layer for denitrification.

【００３７】無機凝集剤の添加によりリンを不溶化し、
生物濾過層で除去でき、窒素、リンを同時に除去でき
る。ただし、凝集剤の添加によりＳＳ分が増加する。
（従って、従来の逆洗方法を採用すると逆洗回数が増加
することになる。本発明方法によると、次の通り、弱逆
洗により凝集フロックを比較的容易に除去できる。）生
物濾過層内の濾材の固着は、主に微生物の粘質物による
ものと考えられる。無機凝集剤の添加により、原水中の
ＳＳは水酸化物フロックを介在した凝集フロックとなっ
て濾過層内に捕捉され、水酸化アルミニウム等の水酸化
物の介在により粘質物による結合が弱まり、固着しにく
くなる。そのため、脱窒率の高い弱逆洗の継続時間を延
長することが可能で平均脱窒率が向上する。無機凝集剤
を添加する場合は、５〜３０回程度の弱逆洗の継続が可
能である。The addition of an inorganic coagulant insolubilizes phosphorus,
It can be removed with a biological filtration layer, and nitrogen and phosphorus can be removed at the same time. However, the addition of the coagulant increases the SS content.
(Therefore, if the conventional backwashing method is adopted, the number of backwashing is increased. According to the method of the present invention, the floc of flocs can be relatively easily removed by the weak backwashing as follows.) It is considered that the fixation of the filter medium is mainly due to the viscous substance of microorganisms. By adding an inorganic coagulant, SS in the raw water becomes coagulated flocs with hydroxide flocs intervening and is trapped in the filtration layer, and due to the interposition of hydroxides such as aluminum hydroxide, the bond by viscous substances weakens and sticks. Hard to do. Therefore, it is possible to extend the duration of weak backwashing, which has a high denitrification rate, and the average denitrification rate is improved. When an inorganic coagulant is added, weak backwashing can be continued about 5 to 30 times.

【００３８】無機凝集剤としては、公知のものが使用で
き、例えば、アルミニウム塩、鉄塩、カルシウム化合物
等が使用できる。添加量は特に制限はないが、０．１〜
５ｍｇ／Ｌ（リットル）あるいはリン濃度を目安にして
設定すれば良い。As the inorganic coagulant, known ones can be used, for example, aluminum salt, iron salt, calcium compound and the like can be used. The addition amount is not particularly limited, but 0.1 to
It may be set using 5 mg / L (liter) or phosphorus concentration as a guide.

【００３９】[0039]

【実施例】【Example】

（実施例１）図１に示す硝化脱窒装置の容量等を次の通
りとし、都市下水処理場の初沈越流水の処理を行なっ
た。（なお、凝集剤は添加せず。） 浮上性濾材：直径３．５ｍｍのポリプロピレン 脱窒部容積：５００Ｌ（リットル） 硝化部容積：１０００Ｌ 原水通水量：８Ｌ／ｍｉｎ 循環比：３ 逆洗は、濾過差圧が２ｍ−Ｈ₂ Ｏに達する度に行なっ
た。強逆洗と弱逆洗との組み合わせは、強逆洗１回の後
に弱逆洗を５回行なうようにした。強逆洗はＬＶ５０ｍ
／Ｈの水逆洗を１０分間行なうものとし、弱逆洗は同流
速の水逆洗を２分間だけ行なうものとした。(Example 1) The capacities of the nitrification / denitrification equipment shown in FIG. (The coagulant is not added.) Floating filter medium: polypropylene with a diameter of 3.5 mm Denitrification part volume: 500 L (liter) Nitrification part volume: 1000 L Raw water flow rate: 8 L / min Circulation ratio: 3 The filtration differential pressure was performed every time the pressure reached 2 m-H ₂ O. In the combination of the strong backwash and the weak backwash, the strong backwash was performed once and then the weak backwash was performed five times. Strong backwash is LV50m
/ H was backwashed with water for 10 minutes, and weak backwash was carried out with water at the same flow rate for only 2 minutes.

【００４０】その結果、表１に示す水質の処理水が得ら
れた。なお、逆洗水比率を表２に示す。As a result, treated water having the water quality shown in Table 1 was obtained. The backwash water ratio is shown in Table 2.

【００４１】（比較例１）弱逆洗の代わりに強逆洗のみ
を行なうようにした他は実施例１と同様にして同一の排
水の処理を行なった。処理水水質を表１に示す。(Comparative Example 1) The same wastewater treatment was carried out as in Example 1 except that only strong backwashing was carried out instead of weak backwashing. Table 1 shows the treated water quality.

【００４２】[0042]

【表１】 [Table 1]

【００４３】[0043]

【表２】 [Table 2]

【００４４】（実施例２）原水に凝集剤として硫酸バン
ドを８ｍｇ−Ａｌ／Ｌ添加し、且つ弱逆洗の回数を強逆
洗１回に対して１０回とした他は実施例１と同様にして
同一の排水の処理を行なった。結果を表１，２に示す。Example 2 Similar to Example 1 except that 8 mg-Al / L of sulfuric acid band was added to the raw water as a coagulant, and the number of weak backwash was 10 times for 1 strong backwash. The same waste water was treated. The results are shown in Tables 1 and 2.

【００４５】（比較例２）原水に凝集剤として硫酸バン
ドを８ｍｇ−Ａｌ／Ｌ添加した他は比較例１と同様にし
て同一の排水の処理を行なった。結果を表１，２に示
す。(Comparative Example 2) The same wastewater treatment was carried out as in Comparative Example 1 except that 8 mg-Al / L of sulfuric acid band was added to the raw water as a coagulant. The results are shown in Tables 1 and 2.

【００４６】表１より明らかな通り、本発明方法による
と、窒素除去法（実施例１）、窒素・リン除去法（実施
例２）のいずれにおいても従来法（比較例１又は２）よ
り脱窒率が向上し、ＮＯ₃ −Ｎ濃度が低下した。また、
表２の通り、本発明によると逆洗水比率も低減し、特に
実施例２の低減効果が大きい。As is clear from Table 1, according to the method of the present invention, in any of the nitrogen removal method (Example 1) and the nitrogen / phosphorus removal method (Example 2), the removal from the conventional method (Comparative Example 1 or 2) was performed. The nitriding ratio was improved and the NO ₃ —N concentration was decreased. Also,
As shown in Table 2, according to the present invention, the backwash water ratio is also reduced, and the reduction effect of Example 2 is particularly large.

【００４７】[0047]

【発明の効果】以上の通り、本発明の生物濾過式窒素除
去方法によると、逆洗後においても脱窒に必要なＢＯＤ
が濾材層中に十分に存在するようになり、排水を十分に
脱窒処理することが可能となる。また、この逆洗として
洗浄水量の少ない弱逆洗を強逆洗の間に施すようにして
いるため、洗浄水量も少なくて足りるようになる。As described above, according to the biological filtration type nitrogen removal method of the present invention, the BOD required for denitrification even after backwashing.
Is sufficiently present in the filter medium layer, and the wastewater can be sufficiently denitrified. Further, since the weak backwash with a small amount of wash water is performed between the strong backwashes as the backwash, the amount of wash water can be small.

【図面の簡単な説明】[Brief description of drawings]

【図１】実施例方法に用いられる硝化脱窒装置の構成図
である。FIG. 1 is a configuration diagram of a nitrification denitrification apparatus used in an example method.

【図２】運転データを示すグラフである。FIG. 2 is a graph showing operation data.

【図３】捕捉ＳＳ量の分布例を示すグラフである。FIG. 3 is a graph showing an example of distribution of trapped SS amount.

【符号の説明】[Explanation of symbols]

１ 槽体 ３ 浮上性濾材層 ４ 散気管 ５ 硝化部 ６ 脱窒部 1 Tank 3 Floating filter medium layer 4 Air diffuser 5 Nitrification part 6 Denitrification part

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 浮上性濾材を充填して形成した脱窒濾過
層に排水を上向流に通水して生物的に脱窒し、通水の継
続により脱窒濾過層が目詰まりしたときに該濾過層の逆
洗を行なう生物濾過式窒素除去方法において、 該逆洗として、捕捉懸濁物の大部分を排出する強逆洗
と、それよりも弱い逆洗を施す弱逆洗とを、強逆洗の間
に３回以上の弱逆洗を行なうように実施することを特徴
とする生物濾過式窒素除去方法。1. When the denitrification filter layer formed by being filled with a floatable filter medium is biologically denitrified by passing drainage in an upward flow, and the denitrification filter layer is clogged due to continuous water flow. In the biological filtration nitrogen removal method in which the filtration layer is back-washed with, a strong back-wash that discharges most of the trapped suspension and a weak back-wash that performs a weaker back-wash are used as the back-wash. The method for removing nitrogen by biological filtration is characterized in that weak backwashing is performed three or more times during strong backwashing.