JP3874635B2 - Sewage treatment method and treatment apparatus - Google Patents

Description

【００１７】
第１表に示すように、凝集反応槽２への原水流入量が１０ｍ³／ｄであり、無機凝集剤３として塩化第２鉄１００ｍｇ／リットルを連続注入した。反応槽２の凝集ｐＨを５．０になるように、常時Ｈ₂ＳＯ₄又はＮａＯＨの注入で制御を行った。反応時間は約２０分とした。
【００１８】
第２表にろ過分離槽８の処理条件を示す。本実施例では、通水性ろ過体として、有効面積０．４ｍ²の平面型織布ろ過体５枚を束ねて、ろ過体モジュール９としてろ過分離槽８に設置した。ろ過時の平均水頭圧を約１０ｃｍとした。ろ過水量は約１０ｍ³／ｄである。
【００１９】
【表２】

【００２０】
ろ過体に対する洗浄は、ろ過を一旦停止し、ろ過モジュール９に対する空洗及び水逆洗を行う。空洗は風量１３５リットル／ｍｉｎで３分間行った。水逆洗は、空洗後に水量５５リットル／ｍｉｎで約１分間行った。水逆時間は排泥弁１５を開放して、内部侵入汚泥が逆洗水の一部とともに１０ｃｍの水頭圧により排出した。水逆洗終了後もさらに排泥弁１５を約１〜３分間開放して、モジュール９内部の残留汚泥混合液を排出した。
【００２１】
図２に、第２表の処理条件で２ヶ月連続処理時のろ過フラックスの経過を示す。連続処理において、ろ過Ｆｌｕｘが常時５ｍ／ｄ程度であり、安定した処理が得られた。
このように約２ヶ月連続した時の、原水１及び処理水２０の平均値を第３表に示す。
【００２２】
【表３】

【００２３】
第３表に示すように、原水１のｐＨが７．１、濁度３２０度、ＳＳ１５０ｍｇ／リットル、色度１２０度であるのに対し、ろ過後の処理水２０では、ｐＨ７．０、濁度５．０度以下、ＳＳ５ｍｇ／リットル以下、色度１０度となり、ろ過水が清澄であると認められた。また、ＣＯＤについては、原水１の１３０ｍｇ／リットルであるのに対し、処理水２０では、２０ｍｇ／リットルとなり、凝集処理で良好な水質が得られた。
【００２４】
【発明の効果】
本発明によれば、有機性汚水等の高度処理として用いられてきた、従来の凝集反応槽の後段にろ過分離槽を設置し、該ろ過分離槽に通水性ろ過体を浸漬し、凝集処理を受けた原水をろ過分離槽上部に供給すれば、ろ過分離槽内の通水性ろ過体により、少ない水頭圧で清澄なろ過水を得ることができる。
凝集汚泥混合液に対し、低い水頭圧で通水性ろ過体よりろ過を行うと、ろ過体表面に比較的均一であり、ろ過性能の高い凝集汚泥層が形成される。この汚泥ろ過層によってＳＳが完全に阻止され、清澄なろ過水を得ることができる。
【００２５】
凝集反応槽では、酸性凝集を行い、例えば、ｐＨを４．５〜６．５と設定すると、凝集処理後の汚泥フロックが大きく、透水性の良いものであるため、ろ過体表面に短時間で汚泥のダイナミックろ過層が形成できる。該汚泥ろ過層はろ過体への付着力が弱く、ろ過時間とともに汚泥ろ過層が肥大し、ろ過抵抗の増加を生じた時、ろ過モジュール下部の空気洗浄管による曝気、及びろ過体内部へ清水を用いた水逆洗を行うことで、容易に剥離することが可能である。さらに長時間無機凝集剤添加による凝集処理を行っても、ろ過体表面に無機質のスケールの生成がほとんどなく、ろ過体に対し、酸等の薬品による洗浄は不要である。
【図面の簡単な説明】
【図１】本発明の汚水の処理を実施する装置の概略説明図である。
【図２】本発明の実施例１のろ過水Ｆｌｕｘの経時変化を示すグラフである。
【符号の説明】
１ 流入原水
２ 凝集反応槽
３ 無機凝集剤
４ 酸またはアルカリ
５ 攪拌機
６ 凝集混合液供給ポンプ
７ 空洗用ブロワ
８ ろ過分離槽
９ ろ過モジュール
１０ 高分子凝集剤
１１ 濃縮汚泥
１２ 空洗用散気管
１３ 凝集混合液供給ライン
１４ ろ過水ライン
１５ 排泥弁
１６ 排出汚泥
１７ 処理水槽
１８ 逆洗ポンプ
１９ ろ過水弁
２０ 処理水[0001]
BACKGROUND OF THE INVENTION
The present invention relates to sewage treatment, a method for treating sewage that can be used for advanced treatment of organic sewage and sewage secondary treated water, dyeing wastewater, SS, COD, chromaticity, etc. of paper wastewater, and The present invention relates to a processing apparatus.
[0002]
[Prior art]
Conventionally, there is a coagulation precipitation method as a method for removing advanced treatment of sewage such as organic sewage (hereinafter referred to as “raw water”), in particular phosphorus, persistent COD, and chromaticity. In this case, an inorganic flocculant is injected into the raw water in advance to cause an agglomeration reaction, and then introduced into a mixing tank to which a polymer flocculant is added. After sludge flocs are formed, the raw water is further introduced into a sedimentation basin and solidified. Liquid separation must be performed. Usually, a method is used in which a mixed liquid of coagulated sludge is introduced into a sedimentation basin, and the supernatant liquid after sedimentation of the sludge by gravity sedimentation is discharged from the sedimentation basin as treated water.
[0003]
[Problems to be solved by the invention]
However, in order to settle the coagulated sludge, a polymer coagulant must be added to the mixing tank to increase the sludge floc. In addition, in order to sufficiently settle the coagulated sludge and obtain good treated water, a sedimentation basin having a wide sedimentation area necessary for it and providing a long residence time is required. It is an increase factor. Furthermore, since fine SS may be contained in the outflow water from the settling basin, a post-treatment by sand filtration or the like is required to obtain advanced treated water without SS.
In recent years, instead of a sedimentation basin, agglomerated membrane filtration combining membrane filtration and agglomeration reaction treatment has been used. In this case, a microfiltration membrane or an ultrafiltration membrane is generally used as the solid-liquid separation membrane.
[0004]
However, suction or pressurization by a pump is necessary as a filtration separation means, and since it is normally performed at a pressure of several + kPa to several hundred kPa, the power by the pump is large, and the running cost is increased. In addition, in the membrane separation, clear treated water without SS is obtained. On the other hand, the permeation flux is low, and it is necessary to periodically wash the medicine in order to prevent membrane contamination.
The present invention has been made in view of such conventional problems, and is a method and a method for treating sewage that can reduce the power requirement with a small device, can be operated for a long time with a stable flux at a low running cost. It is an object to provide an apparatus.
[0005]
[Means for Solving the Problems]
The above problem is solved by various means described below.
(1) After allowing sewage to flow into the flocculation reaction tank and performing an acidic flocculation treatment, the flocculated mixed liquid is supplied to the upper part of the filtration separation tank in which the aqueous filter is immersed, and the flocculated sludge is dynamically filtered on the surface of the water permeable filter. A method for treating sewage, characterized in that a layer is formed, and filtered water is obtained from the water-permeable filter at a water head pressure.
(2) The method for treating sewage as described in (1) above, wherein the pH of the coagulation reaction tank is 4.5 to 6.5.
(3) The method for treating sewage according to (1) or (2) above, wherein a polymer flocculant is injected into a line for supplying the flocculated liquid mixture to the filtration / separation tank.
[0006]
(4) A filtration module in which a sewage supply pipe is connected and a flocculation reaction tank in which sewage is introduced to cause agglomeration reaction, a supply pipe for agglomerated mixed liquid from the agglomeration reaction tank is provided in the upper part of the tank, and the filtration module is immersed in the tank. A filtration separation tank provided with an air-washing air diffuser below the filtration module, a filtrate water line that takes out the filtrate water connected to the top of the filtration module and supplies the treated water tank, and the treated water after pH adjustment is discharged. An apparatus for treating sewage, comprising a treated water tank to which a treated water discharge pipe is connected, wherein a supply pipe for a polymer flocculant is connected to the flocculated liquid supply line of the filtration / separation tank.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, a filtration separation tank has been installed after the conventional flocculation reaction tank, which has been used as an advanced treatment for organic sewage, etc., and a water-permeable filter is immersed in the filtration separation tank to perform the flocculation treatment. If the received raw water is supplied to the upper part of the filtration / separation tank, clear filtered water can be obtained with a small head pressure by the water-permeable filter in the filtration / separation tank. The required hydraulic head pressure is usually sufficient from several centimeters to several tens of centimeters.
When the flocculated sludge mixed liquid is filtered with a water-permeable filter at a low water head pressure, a flocculated sludge layer having a relatively uniform and high filtration performance is formed on the surface of the water-permeable filter. This becomes one kind of dynamic filtration membrane, and SS is completely blocked by the sludge filtration layer on the surface of the filter body, and clear filtered water can be obtained in the flocculated mixed liquid.
[0008]
The present inventors perform acidic flocculation in the flocculation reaction tank. For example, when the pH is set to 4.5 to 6.5, the sludge floc after the flocculation treatment is large and water permeability is good. It was found that a sludge dynamic filtration layer can be formed on the body surface in a short time. The sludge filtration layer has weak adhesion to the filter body.When the sludge filtration layer enlarges with the filtration time and the filtration resistance increases, aeration by the air washing tube at the bottom of the filtration module and clean water inside the filter body It can peel easily by performing the water backwashing used. Further, even when the coagulation treatment is performed by adding an inorganic coagulant for a long time, almost no inorganic scale is generated on the surface of the filter body, and the filter body is not required to be washed with a chemical such as an acid.
[0009]
The same effect can be obtained by using any of nonwoven fabric, woven fabric, filter fabric, metal net, etc. as the water-permeable filter. Moreover, as a filter body shape, any of a plane type, a cylindrical type, and a hollow type can be used, and a plurality can be bundled and used as a filter body module.
As a result of the inflow of sludge as the upper part of the filtration separation tank, when the agglomerated sludge mixed liquid is solid-liquid separated from the filtration module, the agglomerated sludge mixed liquid forms a layered flow along the filtration surface of the filtration module. Dynamic filtration is performed, and sludge concentrated by the filtration settles in the lower part of the filtration separation tank. In addition, during regular backwashing, the sludge peeled off from the filtration surface settles in the lower part of the tank by gravity sedimentation to form concentrated sludge. If this concentrated sludge is regularly discharged from the lower part of the filtration separation tank, the concentration of the sludge mixed liquid inside the filtration separation tank will not increase, and a stable sludge dynamic filtration layer can be formed on the surface of the filter body at all times. it can. Dynamic filtration is filtration performed by an adhering layer of activated sludge particles formed on the filter cloth surface of the filter body as the filtration proceeds.
[0010]
By the time the sludge dynamic filtration layer is formed on the surface of the filter body, sludge intrusion occurs in the filtration module. For this reason, in order to eliminate the accumulation of sludge inside the module, it is necessary to periodically drain the mud. As this waste mud method, a waste pipe that penetrates from the lower part of the filtration module is provided, and installed so that the discharged sludge is introduced into the coagulation reaction tank. The discharge power is preferably natural flow due to water head pressure, and the water head pressure is approximately the same as the head pressure during filtration.
[0011]
【Example】
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment. However, the present invention is not limited to this example.
[0012]
Example 1
FIG. 1 is a flow sheet of an example of a treatment method according to the present invention for organic waste water.
As shown in FIG. 1, the influent raw water 1 flows into the agglomeration reaction tank 2, an inorganic flocculant 3 and an acid or alkali 4 for pH adjustment are added, and the agglomeration treatment is performed with constant stirring by the agitator 5. The sludge mixed liquid after the flocculation treatment is sent to the upper part of the filtration separation tank 8 from the flocculated mixed liquid supply pump 6. Here, the polymer flocculant 10 is injected into the flocculated liquid supply line 13 in accordance with the filtration properties of the flocculated sludge. The agglomerated liquid mixture that has flowed into the upper part of the filtration separation tank 8 flows down along the membrane surface of the filtration module 9 in the filtration separation tank 8, is filtered with a head pressure difference from the filtration module 9, and is obtained through the filtered water line 14. Water flows into the treated water tank 17 and is discharged after adjusting pH by adding NaOH as treated water 20.
[0013]
When the sludge filtration layer grows excessively on the surface of the filter body and the amount of filtered water decreases, the filtration module 9 is washed. As a washing method, the filtration water valve 19 is once closed and the filtration is stopped, and then aeration is performed from the air washing blower 7 through the air diffuser 12 below the filtration module 9 to peel off the sludge filtration layer on the surface of the filter body. After air washing by aeration, the filter surface adhering sludge was peeled off by a water backwashing operation in which filtered water was introduced from the backwash pump 18 through the filtrate water line 14 into the filtration module.
[0014]
Until the sludge dynamic filtration layer is formed, the sludge enters the filtration module 9. If the sludge valve 15 is opened at the time of back washing with water in order to discharge the intruding sludge inside the module 9 to the outside, a part of the introduced back washing drainage is discharged as sludge 16 together with the intruding sludge into the coagulation reaction tank 2. Can be discharged. Even after the end of the water backwash, the drainage valve 15 is further opened for several minutes to remove the discharged sludge.
[0015]
After obtaining filtered water from the filtration module 9 of the filtration / separation tank 8, the condensed sludge concentrated in the lower part of the filtration / separation tank 8 settles, and this is supplied as a concentrated sludge 11 to a sludge concentration tank or sludge dewatering equipment. Processing such as dehydration is performed.
Table 1 shows the processing conditions of the agglomeration reaction tank in this example. Moreover, the processing conditions of the filtration separation tank are shown in Table 2.
[0016]
[Table 1]

[0017]
As shown in Table 1, the amount of raw water flowing into the agglomeration reaction tank 2 was 10 m ³ / d, and ferric chloride 100 mg / liter was continuously injected as the inorganic flocculant 3. Control was always performed by injecting H ₂ SO ₄ or NaOH so that the coagulation pH of the reaction tank 2 was 5.0. The reaction time was about 20 minutes.
[0018]
Table 2 shows the processing conditions of the filtration separation tank 8. In this example, five flat woven fabric filter bodies having an effective area of 0.4 m ² were bundled as a water-permeable filter body and installed in the filtration separation tank 8 as a filter body module 9. The average head pressure during filtration was about 10 cm. The amount of filtered water is about 10 m ³ / d.
[0019]
[Table 2]

[0020]
For the washing of the filter body, the filtration is temporarily stopped, and the filtration module 9 is washed with water and backwashed with water. The air washing was performed for 3 minutes at an air volume of 135 l / min. The water backwashing was performed for about 1 minute at a water volume of 55 liters / min after air washing. During the water reversal time, the mud valve 15 was opened, and the invading sludge was discharged with a head pressure of 10 cm together with a part of the backwash water. The drainage valve 15 was further opened for about 1 to 3 minutes after the end of the water backwashing, and the residual sludge mixed liquid in the module 9 was discharged.
[0021]
In FIG. 2, the progress of the filtration flux at the time of 2 months continuous processing on the processing conditions of Table 2 is shown. In the continuous treatment, the filtration flux was always about 5 m / d, and a stable treatment was obtained.
Thus, the average value of the raw water 1 and the treated water 20 when it continues for about two months is shown in Table 3.
[0022]
[Table 3]

[0023]
As shown in Table 3, the raw water 1 has a pH of 7.1, a turbidity of 320 degrees, an SS of 150 mg / liter, and a chromaticity of 120 degrees, whereas the treated water 20 after filtration has a pH of 7.0 and turbidity. It became 5.0 degrees or less, SS5 mg / liter or less, and chromaticity 10 degrees, and it was recognized that filtered water was clear. The COD was 130 mg / liter for the raw water 1, whereas it was 20 mg / liter for the treated water 20, and good water quality was obtained by the coagulation treatment.
[0024]
【The invention's effect】
According to the present invention, a filtration separation tank has been installed after the conventional flocculation reaction tank, which has been used as an advanced treatment for organic sewage, etc., and a water-permeable filter is immersed in the filtration separation tank to perform the flocculation treatment. If the received raw water is supplied to the upper part of the filtration / separation tank, clear filtered water can be obtained with a small head pressure by the water-permeable filter in the filtration / separation tank.
When the flocculated sludge mixed liquid is filtered from the water-permeable filter at a low water head pressure, a flocculated sludge layer that is relatively uniform and has high filtration performance is formed on the surface of the filter. SS is completely blocked by the sludge filtration layer, and clear filtered water can be obtained.
[0025]
In the flocculation reaction tank, acidic flocculation is performed. For example, if the pH is set to 4.5 to 6.5, the sludge floc after the flocculation treatment is large and has good water permeability. A sludge dynamic filtration layer can be formed. The sludge filtration layer has weak adhesion to the filter body.When the sludge filtration layer enlarges with the filtration time and the filtration resistance increases, aeration by the air washing tube at the bottom of the filtration module and clean water inside the filter body It can peel easily by performing the water backwashing used. Further, even when the coagulation treatment is performed by adding an inorganic coagulant for a long time, almost no inorganic scale is generated on the surface of the filter body, and the filter body does not need to be cleaned with chemicals such as acid.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic explanatory diagram of an apparatus for carrying out wastewater treatment according to the present invention.
FIG. 2 is a graph showing a change with time of filtered water Flux of Example 1 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inflow raw water 2 Coagulation reaction tank 3 Inorganic flocculant 4 Acid or alkali 5 Stirrer 6 Coagulation liquid mixture supply pump 7 Air-washing blower 8 Filtration separation tank 9 Filtration module 10 Polymer flocculant 11 Concentrated sludge 12 Air-washing air diffuser 13 Coagulated liquid supply line 14 Filtration water line 15 Drainage valve 16 Drainage sludge 17 Treated water tank 18 Backwash pump 19 Filtration water valve 20 Treated water

Claims (4)

After the sewage is introduced into the flocculation reaction tank and subjected to acidic flocculation treatment, the flocculated mixture is supplied to the upper part of the filtration separation tank in which the aqueous filter is immersed, and a dynamic filtration layer of flocculated sludge is formed on the surface of the water permeable filter. A method for treating sewage, characterized in that filtered water is obtained at a water head pressure from the water-permeable filter. 2. The method for treating sewage according to claim 1, wherein the pH of the coagulation reaction tank is 4.5 to 6.5. The method for treating sewage according to claim 1 or 2, wherein a polymer flocculant is injected into a line for supplying the flocculated liquid mixture to the filtration separation tank. A flocculation reaction tank for connecting a sewage supply pipe and causing sewage to flow into the flocculation reaction, a flocculation mixture supply pipe from the flocculation reaction tank is provided at the upper part of the tank, and a filtration module immersed in the tank is provided, A filtration / separation tank in which an air diffusing pipe for air washing is disposed below the filtration module, a filtrate water line that takes out the filtrate water connected to the top of the filtration module and supplies the treated water tank, and treated water that releases the treated water after pH adjustment An apparatus for treating sewage, comprising a treated water tank to which a discharge pipe is connected, wherein a supply pipe for a polymer flocculant is connected to the aggregated liquid supply line of the filtration / separation tank.

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