JP2002086156A - Waste water treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treating device for stably proceeding biological treatment without enlarging capacity of a biological treating tank, to improve quality of treated water at little addition rate of an inorganic fluculating agent and to reduce quantity of generated inorganic sludge. SOLUTION: The treating device is constituted so that at least one device of a clarifying filtration device 7 and an adsorption device 9 is connected to the stage after a solid-liquid separator 6, a back washing apparatus 11 conducts backwashing treatment for at least one of these devices 7 and 9, the waste water caused by backwashing is mixed with the first mixed liquid by returning it between a biologically treating tank 3 and a mixing tank 5 or to the mixing tank 5 through a returning line L2 of backwashing waste water, so that mixed liquor suspended solid(MLSS) concentration in the tank 5 and MLSS concentration flowing into the separator 6 from the tank 5 are reduced without changing MLSS concentration in the tank 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wastewater treatment apparatus for purifying wastewater.

[0002]

2. Description of the Related Art Conventionally, as a wastewater treatment apparatus disposed in a human waste treatment facility, for example, Japanese Patent Application Laid-Open No. 11-2164 is disclosed.
No. 94 is known. The wastewater treatment apparatus described in this publication removes the supplied human waste and septic tank sludge and then dehydrates it with a dehydrator to separate it into dehydrated sludge (dehydrated cake) and dehydrated filtrate. In a biological treatment tank), the dehydrated filtrate is subjected to biological nitrification and denitrification treatment to form a mixed liquid containing activated sludge and biologically treated water, and an inorganic flocculant is added to the mixed liquid in the mixing tank to form a coagulated sludge. And a mixed liquid containing coagulation-treated water and a high-speed sedimentation tank (solid-liquid separation device). The separated filtrate is filtered by a sand filtration tower, the separated filtrate of the sand filtration tower is subjected to activated carbon adsorption by an activated carbon adsorption tower, and the activated carbon adsorption treated water is discharged. .

[0003]

Here, in the above wastewater treatment apparatus, it is difficult to improve the quality of the treated water with a small addition rate of the inorganic coagulant.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a wastewater treatment apparatus capable of improving the quality of treated water with a small addition rate of an inorganic coagulant.

[0005]

The present inventor has studied the above-mentioned problems of the wastewater treatment apparatus. As a result, in the coagulation treatment at the latter stage of the nitrification denitrification tank, the MLSS
(Mixed Liquor Suspended Solids)
It has been found that the quality of treated water can be increased with a small addition rate of an inorganic coagulant. Therefore, in order to increase the treatment water quality with a small addition rate of the inorganic coagulant, it is conceivable to lower the MLSS concentration in the nitrification denitrification tank. Here, M of the nitrification denitrification tank
The LSS concentration is adjusted to, for example, 12000 to 20000 mg / L in order to stably perform the biological nitrification denitrification treatment. In order to stably perform the biological nitrification denitrification treatment by lowering the MLSS concentration, the capacity of the nitrification denitrification tank must be increased from the relation of MLSS × water tank capacity = total sludge amount, which is preferable. Absent.

Therefore, a wastewater treatment apparatus according to the present invention comprises a biological treatment tank for subjecting water to be treated to biological treatment to produce a first mixed solution containing activated sludge and biologically treated water,
A mixing tank for mixing a mixed solution of the above and an inorganic coagulant to produce a second mixed solution containing coagulated sludge and coagulated water, and solid-liquid separation of the second mixed liquid into solids and separated water Solid-liquid separation device, and a clarification filtration device that is connected to the subsequent stage of the solid-liquid separation device and clarifies and filters the water to be treated in the purification treatment unit provided with the filter medium, and the organic matter of the water to be treated in the purification treatment unit provided with the adsorbent. At least one of an adsorption device for adsorbing the water, a backwashing device for backwashing a purification treatment unit of the at least one device, and a backwash wastewater from the purification treatment unit by the backwashing device, as a first liquid mixture. And a backwash drainage return line between the biological treatment tank and the mixing tank or for returning to the mixing tank for mixing.

According to such a wastewater treatment apparatus, at least one of a clarifying filtration apparatus and an adsorption apparatus is connected downstream of the solid-liquid separation apparatus, and at least one of the apparatuses is subjected to backwashing by a backwashing apparatus. This is carried out, and the backwash wastewater is returned to the mixture tank or between the biological treatment tank and the mixing tank via the backwash wastewater return line to be mixed with the first mixed solution. Therefore, without changing the MLSS concentration in the biological treatment tank, the MLSS concentration in the mixing tank and the MLSS concentration flowing from the mixing tank to the solid-liquid separation device are reduced.

Here, when both the clarifying filtration device and the adsorption device are provided, specifically, the clarifying filtration device and the adsorption device are connected in this order, and the clarifying filtration device uses the separated treated water of the solid-liquid separation device. After performing the clarification filtration process, the adsorption device performs an adsorption process on the organic matter in the separated filtrate of the clarification filtration device, and the backwash device performs a backwash on at least one of the purification processing units of the clarification filtration device and the adsorption device.

The backwash drainage return line is interposed between the biological treatment tank and the mixing tank, stores the first mixed liquid in the biological treatment tank, and supplies the first mixed liquid to the mixing tank. It may be configured to be connected to the mixed liquid water tank, and the first of the biological treatment tanks.
May be connected to a line for supplying the mixed liquid to the mixing tank.

[0010] When a part of the treated water treated in the purification treatment section is used as the backwash water of the backwash apparatus, the backwash water and dilution water outside the system are not separately added. The treated water amount (discharged water amount) is reduced as compared with the case.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a wastewater treatment apparatus according to the present invention.

The wastewater treatment apparatus according to the present embodiment is disposed in a human waste treatment facility, and treats human waste and septic tank sludge whose carrying ratio is increasing with the recent spread of septic tanks. This wastewater treatment apparatus is generally arranged from upstream to downstream (from left to right in the figure) to remove debris 1a, 1
b, dehydrator 2, nitrification denitrification tank (biological treatment tank) 3, mixed liquid water tank 4, mixing tank 5, high-speed sedimentation tank (solid-liquid separation device) 6, sand filtration tower (clarification filtration device) 7, activated carbon raw water tank 8, an activated carbon adsorption tower (adsorption device) 9 and an activated carbon treatment water tank 10 are provided.

[0013] The debris removing device 1a removes contaminants of human waste supplied through the line L1, and the debris removing device 1b removes contaminants of septic tank sludge supplied through the line L2. The contaminants are removed by the debris removing device 1a, and the sludge water mainly composed of human waste is supplied to the dehydrator 2 via the line L3,
The contaminants are removed by the residue removing device 1b, and the sludge water mainly composed of the septic tank sludge is supplied to the dehydrator 2 via the line L4. A part of the coagulated sludge in the high-speed settling tank 6 is also supplied to the dehydrator 2 via the line L12.

The dewatering machine 2 performs a dewatering treatment on the sludge water and the coagulated sludge to generate a dewatered sludge and a dewatered filtrate. This dewatered sludge is discharged out of the system via the line L6. on the other hand,
The dehydrated filtrate is supplied to the nitrification denitrification tank 3 via a line L5 as water to be treated.

The nitrification denitrification tank 3 performs a biological nitrification denitrification treatment on the dehydrated filtrate to produce a first mixed solution containing activated sludge and biologically treated water. The nitrification denitrification tank 3 is provided with a part of the coagulated sludge of the high-speed sedimentation tank 6 via a line L11 in order to maintain a constant sludge concentration that is reduced by performing the biological nitrification denitrification treatment. Is supplied. When the concentration of the sludge in the nitrification denitrification tank 3 is kept constant by the supplied coagulated sludge, the surplus of the coagulated sludge is supplied to the dehydrator 2 through the line L12. The first mixed liquid generated in the nitrification denitrification tank 3 is supplied to the mixed liquid water tank 4 via a line L7 as a first mixed liquid supply line.

The mixed liquid water tank 4 stores a first mixed liquid, and the first mixed liquid in the mixed liquid water tank 4 is supplied to a line L7.
Is supplied to the mixing tank 5 via a line L8 as a first mixed liquid supply line.

The mixing tank 5 is provided with a line L13 for the first mixed liquid.
The inorganic flocculant is added to the mixture, and the mixture is stirred by a stirrer (not shown) to form a fine floc as coagulated sludge. The second mixing containing the coagulated sludge (fine floc) and coagulated water Generate a liquid. As the inorganic coagulant, for example, an iron-based or aluminum-based one is adopted, and as the iron-based inorganic coagulant, for example, polyiron sulfate, ferric chloride, or the like is used. As the aluminum-based inorganic coagulant, for example, Bansulfate, polyaluminum chloride and the like are used. In this mixing tank 5, a pH adjuster is added in order to adjust the pH lowered by the addition of the inorganic coagulant. When, for example, an iron-based inorganic coagulant is used as the inorganic coagulant, the pH is adjusted to about 5 to 5.5. The second mixed liquid generated in the mixing tank 5 is supplied to the high-speed sedimentation tank 6 via the line L9.

The high-speed sedimentation tank 6 is disclosed in JP-A-11-21649.
No. 4 discloses a high-speed sedimentation tank, and a polymer flocculant is added to the second mixed solution via a line L14, and the mixture is stirred by a stirrer (not shown). Is coarsened to form coarse flocks as coagulated sludge, and the second mixed liquid is subjected to solid-liquid separation into coagulated sludge (coarse flocs: solids) and separation treatment water. As the polymer flocculant, for example, an anionic polymer flocculant is used. The coagulated sludge separated by solid-liquid separation in the high-speed sedimentation tank 6 is supplied to the nitrification denitrification tank 3 via the line L11, and the surplus is supplied to the dehydrator 2 via the line L12, as described above. You. On the other hand, the separation treatment water in the high-speed sedimentation tank 6 is supplied to the sand filtration tower 7 via the line L10.

The sand filtration tower 7 is provided with sand as a filter medium, and the separation treatment water is clarified and filtered in a purification processing section provided with the filter medium to capture fine solids such as SS (Suspended Solids). In some cases, only sand is used as the filter medium of the sand filtration tower 7, but in other cases, for example, a combination of sand and anthracite is used. The separated filtrate of the sand filtration tower 7 is supplied via a line L15 to an activated carbon raw water tank 8 for storing the separated filtrate.
And the separated filtrate from the activated carbon raw water tank 8 is supplied to the activated carbon adsorption tower 9 via a line L16.

The activated carbon adsorption tower 9 is provided with activated carbon as an adsorbent, and in a purification treatment section provided with the activated carbon, the separated filtrate is subjected to activated carbon adsorption treatment to capture organic substances such as COD (Chemical Oxygen Demand). The activated carbon adsorption treated water of the activated carbon adsorption tower 9 is supplied via a line L17 to an activated carbon treated water tank 10 for storing the activated carbon adsorption treated water, and the activated carbon adsorption treated water of the activated carbon treated water tank 10 is appropriately supplied via a line L18. Released outside.

Here, the present embodiment is provided with a backwashing device 11 for backwashing the sand filtration tower 7 and the activated carbon adsorption tower 9. The backwashing device 11 includes a backwash water supply line L20 that connects the activated carbon raw water tank 8, the activated carbon treatment water tank 10, the sand filtration tower 7, and the activated carbon adsorption tower 9, and is interposed in the backwash water supply line L20. And a pump capable of supplying the treated water stored in the activated carbon raw water tank 8 and the activated carbon treated water tank 10 to the purification section of the sand filtration tower 7 and the activated carbon adsorption tower 9 via the backwash water supply line L20. 12 are provided.

In the present embodiment, in particular, the sand filtration tower 7, the activated carbon adsorption tower 9 and the mixed liquid water tank 4 are connected to each other.
A backwash wastewater return line L2 that guides backwash wastewater from the purification section of the sand filtration tower 7 and the activated carbon adsorption tower 9 back to the mixed solution tank 4
1 is provided. In addition, conventionally, the backwash wastewater of a sand filtration tower and an activated carbon adsorption tower is generally sent to a backwash wastewater receiving tank and stored.

According to the wastewater treatment apparatus configured as described above, in order to prevent clogging of the purification section of the sand filtration tower 7 and the activated carbon adsorption tower 9, the sand filtration tower 7 (for example, once to twice).
/ Frequency of one day, for example, once in the activated carbon adsorption tower 9 / (2
The backwashing is performed by the backwashing device 11 at a frequency of about one week to one month.

At this time, the pump 12 is driven, and a part of the treated water stored in the activated carbon raw water tank 8 and the activated carbon treated water tank 10 is transferred to the sand filtration tower 7 through the backwash water supply line L20. Are supplied to the purification processing section of the activated carbon adsorption tower 9, respectively.
Backwashing of the purification processing unit is performed. This sand filtration tower 7,
Selection of the inflow of the backwash water to the purification processing section of the activated carbon adsorption tower 9 is performed by opening and closing a valve (not shown) provided in the backwash water supply line L20. With this backwash,
The purification unit of the sand filtration tower 7 and the activated carbon adsorption tower 9 can be used for a long time.

The backwash wastewater from the purification section of the sand filtration tower 7 and the activated carbon adsorption tower 9 is returned to the mixed liquid water tank 4 at the subsequent stage of the nitrification denitrification tank 3 via the backwash wastewater return line L21. The first mixed liquid mixed with the first mixed liquid and containing the backwash wastewater is supplied to the mixing tank 5.

Therefore, for example, 12000 to 20000 m
Without changing the MLSS concentration of the nitrification denitrification tank 3 adjusted to g / L, the MLSS concentration flowing into the mixing tank 5 is reduced by the amount of the backwash wastewater flowing. Therefore, the MLSS concentration flowing into the high-speed sedimentation tank 6 is also reduced. As a result, it is possible to enhance the quality of the treated water with a small addition rate of the inorganic flocculant. Further, since the addition rate of the inorganic flocculant is reduced in this manner, it is possible to reduce the amount of generated inorganic sludge. Furthermore, since there is no need to change the MLSS concentration in the nitrification denitrification tank 3, it is possible to stably perform the biological nitrification denitrification processing without increasing the capacity of the nitrification denitrification tank 3. .

In the present embodiment, the backwashing device 1
Part of the treated water (the treated water stored in the activated carbon raw water tank 8 and the activated carbon treated water tank 10) that has been treated in the purification section of the sand filtration tower 7 and the activated carbon adsorption tower 9 is used as the backwash water 1. Since the backwash water and dilution water outside the system are not separately added, the amount of treated water (the amount of discharged water) is reduced as compared with the case where these are added, and the sand filtration tower 7 and the activated carbon adsorption tower 9 can be downsized. Have been. Therefore, cost reduction can be achieved.

Further, since the MLSS concentration flowing into the high-speed settling tank 6 at the subsequent stage of the mixing tank 5 is also reduced, sufficient floc is formed to perform stable solid-liquid separation even with a small addition rate of the polymer flocculant. It is possible to do.

As described above, the present invention has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments. 4, but may be returned to the line L7 or the line L8 as the first mixed liquid supply line. In this case, the mixed liquid tank 4 may or may not be provided.

In the above embodiment, the biological treatment tank is a nitrification denitrification tank 3 for performing a biological nitrification denitrification treatment. However, for example, when treating wastewater containing no nitrogen, The biological treatment tank uses BOD (Biochemical Oxyg
en Demand) and an aeration tank for oxidizing COD.

The present invention is also applicable to a wastewater treatment apparatus in which an inorganic coagulant is added to the line L8 and a polymer coagulant is added to the line L9. In this case, it is preferable to return the backwash wastewater to the upstream side from the inorganic coagulant supply position.

In the above embodiment, the solid-liquid separation device is the high-speed settling tank 6, but the present invention is also applicable to a wastewater treatment device having a membrane separation tank, for example. In this case, there is no need to add a polymer flocculant.

In the above embodiment, in order to reduce the size of the sand filtration tower 7 and the activated carbon adsorption tower 9, a part of the treated water is used as backwashing water for the sand filtration tower 7 and the activated carbon adsorption tower 9.
However, for example, backwash water may be supplied from outside the system.

In the above embodiment, a part of the treated water stored in the activated carbon raw water tank 8 and the activated carbon treated water tank 10 is supplied to the sand filtration tower 7 and the activated carbon adsorption tower 9 as backwash water. But the line L1 for supplying the separated filtrate
5, L16, line L1 for supplying activated carbon adsorption treated water
7, L18, the sand filtration tower 7 and the activated carbon adsorption tower 9 can be connected, and part of the treated water flowing through these lines can be supplied to the sand filtration tower 7 and the activated carbon adsorption tower 9 as backwash water. is there.

In the above embodiment, the backwash wastewater from both the sand filtration tower 7 and the activated carbon adsorption tower 9 is returned between the biological treatment tank 3 and the mixing tank 5. The backwash drainage of either the tower 7 or the activated carbon adsorption tower 9 may be returned between the biological treatment tank 3 and the mixing tank 5.

Further, in the above embodiment, the application to the wastewater treatment apparatus having both the sand filtration tower 7 and the activated carbon adsorption tower 9 is described, but any one of the sand filtration tower 7 and the activated carbon adsorption tower 9 is provided. The present invention is also applicable to a wastewater treatment apparatus. In this case, one of the backwash wastewater is returned between the biological treatment tank 3 and the mixing tank 5. For example,
When the solid-liquid separation device is a membrane separation tank, fine solids such as SS are trapped in the membrane separation tank. Therefore, the sand filtration tower 7 for trapping fine solids such as SS is eliminated. In this case, only the activated carbon adsorption tower 9 is provided. In this case, the backwash wastewater of the activated carbon adsorption tower 9 is returned between the biological treatment tank 3 and the mixing tank 5.

The backwash wastewater is returned to the biological treatment tank 3.
Is not limited to between the mixing tank 5 and the mixing tank 5.
And mixed with the first liquid mixture. In this case, it is desirable to return the backwash wastewater to the upstream side (front side) of the line L13 for supplying the inorganic flocculant.

In the above-described embodiment, the clarifying filtration device is the sand filtration tower 7 and the adsorption device is the activated carbon adsorption tower 9 assuming that the function is sufficiently exhibited. Any device can be used as long as it can clarify and filter the water to be treated, and any adsorbing device can be used as long as it can adsorb organic matter in the water to be treated using an adsorbent.

Further, in the above embodiment, the application to the wastewater treatment apparatus into which human waste and septic tank sludge is introduced is described. However, the application to the wastewater treatment apparatus into which either human waste or septic tank sludge is introduced is described. The present invention is also applicable to other wastewater.

[0040]

In the wastewater treatment apparatus according to the present invention, at least one of a clarifying filtration apparatus and an adsorption apparatus is connected downstream of the solid-liquid separation apparatus, and at least one of these apparatuses is backwashed by a backwashing apparatus. To carry out the backwash wastewater between the biological treatment tank and the mixing tank via the backwash wastewater return line or back to the mixing tank and mix with the first mixed solution to change the MLSS concentration in the biological treatment tank. MLSS concentration in the mixing tank and the MLSS concentration flowing from the mixing tank into the solid-liquid separation device are reduced, so that the biological treatment can be carried out stably without increasing the capacity of the biological treatment tank. In addition, it is possible to increase the quality of treated water and reduce the amount of inorganic sludge generated with a small addition rate of the inorganic flocculant.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a wastewater treatment apparatus according to the present invention.

[Explanation of symbols]

3: Nitrification denitrification tank (biological treatment tank) 4: Mixed liquid tank 5
... mixing tank, 6 ... high-speed sedimentation tank (solid-liquid separation device), 7 ... sand filtration tower (clarification filtration device), 8 ... activated carbon raw water tank, 9 ... activated carbon adsorption tower (adsorption device), 10 ... activated carbon treatment water tank, 11 ... Backwashing device, 12 ... Pump, L7, L8 ... First mixed liquid supply line, L20 ... Backwash water supply line, L21 ... Backwash drainage return line.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 9/00 501 C02F 9/00 501A 501H 502 502D 502H 502P 503 503C 504 504A 504E F-term (reference) 4D015 BA19 BA24 BA25 BB09 BB12 CA02 CA03 CA12 DA04 DA05 DA13 DA16 DC08 EA06 EA13 EA19 EA32 EA37 FA01 FA02 FA03 FA11 FA16 FA22 FA26 4D024 AA04 AB01 AB02 BA02 CA01 DA03 DA08 DB02 DB03 DB12 DB15 DB16 DB21 4D028 AC01 AC09 CC00 BB14 BE02 BB24 BB25 BB54 BB63 BB91 4D062 BA19 BA24 BA25 BB09 BB12 CA02 CA03 CA12 DA04 DA05 DA13 DA16 DC08 EA06 EA13 EA19 EA32 EA37 FA01 FA02 FA03 FA11 FA16 FA22 FA26

Claims (4)

[Claims] 1. A biological treatment tank for subjecting water to be treated to biological treatment to produce a first mixed liquid containing activated sludge and biologically treated water, and mixing the first mixed liquid with an inorganic flocculant. A mixing tank for producing a second mixed liquid containing coagulated sludge and coagulated water, a solid-liquid separator for solid-liquid separating the second mixed liquid into solids and separated water, At least one of a clarification filtration device connected to the subsequent stage of the device and clarifying and filtering the water to be treated in a purification treatment unit provided with a filter medium and an adsorption device for adsorbing and treating organic matter in the water to be treated in a purification treatment unit provided with an adsorbent. A backwashing device for backwashing the purification treatment unit of the at least one device; and the biological treatment tank for mixing backwash wastewater of the purification treatment unit by the backwashing device with the first mixed solution. Backwashing between and mixing tank or returning to mixing tank Wastewater treatment apparatus comprising a water return line, a. 2. The clarifying filtration device and the adsorption device are both provided, and the clarifying filtration device and the adsorption device are connected in this order, and the clarifying filtration device clarifies the separation water of the solid-liquid separation device. Performing a filtration process, the adsorption device performs an adsorption process on the organic matter of the separated filtrate of the clarification filtration device, and the backwash device performs backwashing of the purification processing unit of at least one of the clarification filtration device and the adsorption device. The wastewater treatment device according to claim 1, wherein 3. Between the biological treatment tank and the mixing tank,
A mixed solution tank for storing the first mixed solution in the biological treatment tank and supplying the first mixed solution to the mixing tank; and the backwashing drain return line is connected to the mixed solution tank. The wastewater treatment device according to claim 1 or 2, wherein: 4. The wastewater treatment according to claim 1, wherein a part of the treated water treated in the purification treatment section is used as the backwash water of the backwash device. apparatus.