JP2003236558A - Water cleaning system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the recovery rate (water cleaning efficiency) of cleaning effluent of a sand filter basin by efficiently treating the cleaning effluent. <P>SOLUTION: The cleaning effluent 22 is admitted from a sand filtration basin 16 into the coagulation and sedimentation basin 20 of a cleaning effluent treatment facility 10 and is separated at a high speed to thick sludge 32 and supernatant 26. The thick sludge 32 is stored together with the withdrawn sludge 15 in a sludge basin 18 and is then admitted into a sludge membrane separator 40 and membrane separated water 44 is formed in a rotary flat membrane separator 50. The membrane separated water 44 is refluxed to a reception well 12. On the other hand, the supernatant 26 of the coagulation and sedimentation basin 20 is subjected to membrane filtration in a supernatant membrane separator 28 and is refluxed as treated water 30 to the reception well 12. The membrane separated water 44 subjected to the membrane filtration and the treated water 30 are refluxed to the reception well 12, by which the increase of the treatment load in the sand filtration basin 16 is prevented. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water purification system, and more particularly to a water purification system having a sand filter.

[0002]

2. Description of the Related Art Generally, water purification facilities use a flocculant (polyaluminum chloride: P) for raw water taken into a landing well from a river or the like.
(AC, etc.) and the like are injected, and after a suspended substance (hereinafter, SS) having relatively large particles is precipitated and removed in a sedimentation tank, further,
Fine sand SS is removed from the raw water in a sand filter, and a disinfectant is injected to make clean water.

In this case, the filter sand layer of the sand filter basin is clogged with fine particles, and therefore physical cleaning such as backwashing is regularly required for stable operation. By this physical cleaning, a large amount of cleaning waste water containing 10% or more of the amount of treated water in the purified water manufacturing facility is generated, and thereby the recovery rate of water is significantly reduced. In order to solve this problem, washing wastewater is returned to the landing well or sedimentation basin to prevent the water recovery rate from decreasing.

[0004]

However, since the cleaning waste water is reused as raw water, SS in the raw water of the sand filter basin remarkably increases, and the treatment load in the sand filter basin increases. As a result, protozoa such as Cryptosporidium that are difficult to sterilize stay in the sand filter for a long period of time, which raises a problem that epidemiological risk increases.

In order to solve this, it has been attempted to concentrate the washing wastewater in a concentrating tank before the reflux, and to recycle the gravity-separated supernatant water to a landing well or a sedimentation basin. However, for SS that could not be removed in the sedimentation tank before sand filtration,
Even if the precipitate is removed by the concentration tank, its settling property is poor.
In addition, sludge becomes anaerobic by staying in the thickening tank for a long period of time, the elution of manganese from the sludge, the deterioration of water quality of the reflux water due to the decomposition of organic matter, and the treatment load in the sedimentation basin and sand filtration basin further increases. There was a drawback that

The present invention has been made in view of the above circumstances and can efficiently treat the cleaning and drainage water of the sand filter basin, without causing the epidemiological risk of the treated water and the deterioration of the water quality. , Even if the treated water is returned to the purified water manufacturing facility,
An object of the present invention is to provide a water purification system capable of increasing the recovery rate (water purification efficiency) of cleaning wastewater without increasing the processing load in the sand filter.

[0007]

In order to achieve the above-mentioned object, claim 1 of the present invention comprises a water purification facility having a sand filter and a cleaning wastewater treatment facility for treating the cleaning wastewater of the sand filter. In the purified water system, the washing wastewater treatment facility comprises a coagulating sedimentation tank for separating the washing wastewater into supernatant water and concentrated sludge, and a sludge membrane separation device for subjecting the concentrated sludge to membrane separation treatment, and the supernatant water and the It is characterized in that the membrane-separated water that has been membrane-separated by the membrane separation device is refluxed to the inlet side of the purified water production facility.

According to the first aspect of the present invention, the washing wastewater of the sand filter basin is separated into the supernatant water and the concentrated sludge by using the coagulating sedimentation basin so that they can be efficiently separated in a short residence time. At the same time, the washing wastewater is separated into the supernatant water and the concentrated sludge to reduce the volume of the sludge, so that the concentrated sludge can be efficiently membrane-separated by the sludge membrane separator. As a result, the quality of the supernatant water from the coagulation sedimentation tank and the quality of the membrane separation water from the sludge membrane separation device are improved, so even if the water is recycled to the water purification facility, the treatment load in the sedimentation tank and sand filtration tank will not increase. It is possible to increase the recovery rate of cleaning wastewater.

According to a second aspect of the present invention, in the first aspect, the supernatant water obtained by the coagulating sedimentation tank is subjected to membrane separation by a supernatant water membrane separator, and the membrane-separated water thus separated is used in a water purification facility. Since the water is refluxed to the inlet side, the quality of the supernatant water separated in the coagulation sedimentation tank can be further improved and the water can be recycled to the purified water production facility.

According to a third aspect of the present invention, in the second aspect, a rotary flat membrane separator is used as the sludge membrane separator, and an immersion flat membrane type membrane separator or a hollow fiber type membrane is used as the supernatant water membrane separator. Since the separation device is used, the characteristics of the rotary flat membrane separation device that is suitable for filtering a small amount of thick sludge such as concentrated sludge and the large-scale treatment of liquid with a thin sludge concentration such as supernatant water It is possible to effectively utilize the characteristics of the immersion flat membrane type membrane separator or the hollow fiber type membrane separator suitable for the above.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a water purification system according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a water purification system according to the present invention. The water purification system comprises a water purification facility 5 and a cleaning wastewater treatment facility 10.

The purified water production facility 5 mainly comprises the landing well 12,
It consists of a sedimentation basin 14 and a sand filtration basin 16.

In the landing well 12, the raw water supplied from a sand basin (not shown) is temporarily stored, and after stabilizing the fluctuation of the water level and adjusting the flow rate, the SS in the raw water is agglomerated and agglomerated. The agent is added to the raw water.

In the sedimentation basin 14, SS having relatively large particles is used.
Cause precipitation. The SS precipitated in the settling basin 14 is drawn out from the settling basin 14 and discharged as a drawn-out sludge 15 to a sludge basin 18 described later, while the treated water flowing out of the settling basin 14 flows into a sand filter basin 16.

In the sand filtration basin 16, the treated water from the sedimentation basin 14 is subjected to sand filtration to obtain sand filtration water 17. In this case, it is possible to filter the treated water at a high speed (about 5 to 10 m / h) by sand-filtering the treated water coagulated in the landing well 12. However, since the sand filter basin 16 is clogged with fine particles in the sand filter layer due to long-term operation, physical cleaning such as backwashing is regularly required for stable operation. As a result, the cleaning drainage 22 is generated. This cleaning drainage 22 is collected and introduced into the drainage basin 24. The sand filtered water 17 is discharged out of the system as clean water through an activated carbon adsorption basin (not shown).

The washing wastewater treatment facility 10 shown by the broken line portion in FIG. 1 is subjected to membrane filtration treatment of the drawn sludge and the washing wastewater discharged from the settling basin 14 and the sand filtration basin 16 and then to the above-mentioned purified water producing facility 5. It is a facility for reflux.

The cleaning wastewater treatment facility 10 is mainly composed of a coagulation sedimentation tank 20, a sludge membrane separation device 40, a supernatant water membrane separation device 28, and the like, and the cleaning wastewater 22 stored in the drainage tank 24 is the coagulation sedimentation tank 20. Is flowed into.

The coagulation sedimentation tank 20 has a water area load of 1000 m.
A high speed type of ³ / m ² · day or more is preferable, and for example, a slurry circulation type or a micro sand type can be used.

FIG. 2 shows a slurry circulation type coagulating sedimentation tank 20A.

As shown in the figure, the flocculation sedimentation tank 20A mainly comprises a stirring tank (coagulation reaction tank) 62 and a floc formation tank 6.
4 and a settling tank 66. The stirring tank 62 and the floc formation pond 64 are provided with stirring blades, and the cleaning wastewater 22 flowing into the stirring tank 62 from the drainage tank 24 (see FIG. 1) is stirred by the stirring tank 62 while PAC is added. Is stirred rapidly. As a result, the SS in the cleaning drainage 22
Are aggregated to form floc groups. In the floc formation pond 64, gentle stirring is performed as compared with the stirring tank 62, and a stable floc group is formed. These floc groups flow from the floc formation pond 64 into the settling tank 66 by the stirring force in the floc formation pond 64. The flocs flowing into the settling tank 66 are gravity-separated and settled at the bottom of the settling tank 66. With this, the supernatant water 26 obtained in the settling tank 66
Are collected and flowed into the supernatant water membrane separation device 28 described later. The inclined plate 70 is provided to improve the area efficiency of the settling tank 66, whereby the floc group is efficiently settled. Here, a part of the floc group is returned to the floc formation pond 64 (reference numeral 65), and the other floc group settled at the bottom is discharged to the drainage pond 18 (see FIG. 1) as the concentrated sludge 32.

FIG. 3 shows a microsand type coagulating sedimentation tank 20.
B is shown.

The coagulating sedimentation tank 20B is a stirring tank (quick stirring tank).
74, injection stirring tank 76, floc formation pond 78, precipitation tank 8
0, a micro sand recovery device 82, and the like.
The cleaning wastewater 22 flows from the drainage pond 24 into the stirring tank 74,
In the stirring tank 74, PAC is added and rapidly stirred.
Further, the micro sand and the polymer coagulant are added in the injection stirring tank 76. At this time, the addition of microsands increases the interfacial area required for aggregation, and the aggregation speed and the aggregation effect are increased. The effect in the floc formation basin 78 and the settling tank 80 is the same as that of the slurry circulation type described above, so the description thereof will be omitted. It is press-fitted (reference numeral 83). The microsand recovery device 82 is composed of a liquid cyclone, and the concentrated sludge 32 press-fitted into the microsand recovery device 82 is given a swirling motion by the liquid cyclone, and is separated into microsand and sludge by centrifugal force by this, and the microsand is separated. Be recovered. The collected microsands are reused.

Then, as shown in FIG. 1, both the concentrated sludge 32 from the high-speed type coagulating sedimentation tank 20 and the drawn-out sludge 15 from the sedimentation tank 14 are used as the original sludge 42 in the drainage pond 18
Store in. The drainage pond 18 may be provided with an air diffuser 34 or the like that prevents the raw sludge 42 from being anaerobicized. Sludge pond 18
The raw sludge 42 stored in is temporarily stored in the sludge tank 43 provided in the sludge membrane separation device 40, and then flows into the rotary flat membrane separation device 50.

In the rotary flat membrane separation device 50, a plurality of parallel hollow rotary shafts 52, 52 are rotatably arranged side by side, and each hollow rotary shaft 52 has a communication hole formed at a predetermined interval in the axial direction thereof. The rotating flat membranes 54, 54 ... Are attached at positions (not shown). The rotary flat membrane 54 is formed by coating a water-permeable spacer such as a disc-shaped non-woven fabric or a net in a disk shape with a membrane such as a microfiltration membrane or an ultrafiltration membrane. . As the material of this film, a polyolefin-based, polyethylene-based, polyolefin-based organic polymer film, metal film, ceramic film or the like can be used. The hollow rotary shaft 52 is rotated in the same direction by a motor (not shown). In addition, by sucking the hollow portion of the hollow rotary shaft 52 with a suction pump (not shown), the rotary flat membrane 5
The membrane-separated water 44 is sucked from the raw sludge 42 through 4.
It should be noted that the concentrated sludge 58 discharged by the rotary flat membrane separation device 50
Is discharged from the sludge membrane separation device 40, subjected to sludge treatment such as mechanical dehydration and sun drying, and then discarded.

The membrane separation water 44 treated by the sludge membrane separation device 40 is stored in the return water tank 56 and is returned to the landing well 12 of the purified water production facility 5.

As described above, by the two-stage treatment of the coagulation sedimentation tank 20 and the sludge membrane separation device 40, the supernatant water 26 and the membrane separation water 44 can be efficiently recovered from the washing waste water, and can be effectively used as reflux water.

On the other hand, the supernatant water 26 separated by the coagulating sedimentation tank 20 is subjected to a membrane filtration treatment by a supernatant water membrane separator 28. Although a microfiltration membrane or an ultrafiltration membrane can be used as the filtration membrane in the supernatant water membrane separation device 28, it is desirable that the supernatant water membrane separation device 28 can process a large amount of water at low pressure. A filtration membrane is more preferred. Further, as the type of the filtration device of the supernatant water membrane separation device 28, it is preferable to use a hollow fiber membrane or a submerged flat membrane, which has good volume efficiency and can process a large amount of thin sludge (low-concentration sludge). The treated water 30 obtained by subjecting the supernatant water 26 to membrane filtration by the supernatant water membrane separator 28 is returned to the landing well 12. Here, the treated water 30 is returned to the landing well 12, but in the landing well 12, mainly the stabilization of the water level fluctuation and the addition of PAC are only performed, and therefore the amount of the treated water 30 refluxed and the PAC. It may be refluxed to the settling basin 14 depending on the addition amount of.

The operation of the water purification system configured as above will be described.

In FIG. 1, the raw water coagulated in the landing well 12 flows into the sedimentation basin 14 from the landing well 12, and SS is precipitated in the sedimentation basin 14. The precipitated SS is withdrawn from the settling basin 14 and discharged as sludge 15 to a drainage basin 18. The treated water flowing out from the settling basin 14 is a sand filter basin 1.
6, and sand filtration water 17 is obtained in the sand filtration pond 16. The cleaning drainage 22 from the sand filtration basin 16 is a drainage basin 24.
The water is stored in and is flowed into the coagulation sedimentation tank 20.

In the coagulation sedimentation tank 20, the supernatant water 26 and the concentrated sludge 32 are separated at high speed, and the concentrated sludge 32 is the sedimentation tank 1
Along with the sludge 15 drawn out from No. 4, it is stored as the original sludge 42 in the drainage pond 18. This raw sludge 42 is passed through the sludge tank 43 of the sludge membrane separation device 40 to the rotary flat membrane separation device 5
It is flowed into 0 and separated into membranes. By membrane separation, protozoa such as SS and Cryptosporidium, Escherichia coli, etc. are removed from the membrane separation water 44. The membrane separation water 44 is stored in the return water tank 56 and then returned to the landing well 12 or the settling basin 14.

On the other hand, the supernatant water 26 separated in the coagulation sedimentation tank 20 is subjected to membrane filtration treatment in the supernatant water membrane separation device 28 and is returned to the landing well 12 or the sedimentation tank 14 as treated water 30.

In this way, the cleaning drainage 22 of the sand filtration pond 16
In a high-speed type coagulation sedimentation tank 20 with supernatant water 26 and concentrated sludge 3
Since the concentrated sludge 32 is subjected to membrane separation by the sludge membrane separation device 40, the sludge membrane separation device 40
The volume of sludge before membrane separation can be reduced. As a result, the membrane separation efficiency in the sludge membrane separation device 40 can be increased, so that the membrane separated water 44 with good water quality can be efficiently recovered from the sludge contained in the cleaning wastewater and returned to the purified water production facility 5. be able to. In addition, the cleaning drainage 22
Since the high-speed type coagulating sedimentation tank 20 was used as a device for separating the supernatant water 26 and the concentrated sludge 32, the S
S can also be settled at high speed, and the residence time in the flocculation settling tank 20 is shortened, so that the treatment efficiency can be improved. Paradoxically, the sludge membrane separation device 4 is provided after the coagulation sedimentation tank 20.
Since 0 is reserved, the coagulation sedimentation basin 20 does not require strict treatment, and high-speed treatment can be the first to improve treatment efficiency. Therefore, the sludge does not become anaerobic during the treatment in the coagulation sedimentation tank 20, and the quality of the supernatant water does not deteriorate due to the elution of manganese from the sludge and the decomposition of organic matter.

Therefore, the recovery rate (cleaning efficiency) of the cleaning wastewater 22 can be increased without increasing the processing load on the settling basin 14 and the sand filtration basin 16. In addition, since the processing load on the sand filter 16 does not increase, protozoa such as Cryptosporidium that are difficult to sterilize do not stay in the sand filter 16 for a long period of time, thus eliminating the epidemiological risk. Further, by reducing the volume of the sludge before the membrane separation by the sludge membrane separation device 40, the sludge membrane separation device 40 can be made compact.

Further, the supernatant water 26 obtained by the coagulating sedimentation tank 20 is subjected to membrane separation by a supernatant water membrane separator 28, and the treated water 30 subjected to membrane separation is refluxed to the inlet side of the purified water production facility 5. It is possible to further improve the quality of the supernatant water 26 separated in the coagulation sedimentation tank 20 and to recirculate it to the purified water manufacturing facility.

Further, since the rotary flat membrane separation device 50 is used as the sludge membrane separation device 40, and the immersion flat membrane type membrane separation device or the hollow fiber type membrane separation device is used as the supernatant water membrane separation device 28, Characteristics of the rotary flat membrane separation device 50 suitable for filtering a small amount of thick sludge such as concentrated sludge, and an immersion flat membrane type membrane suitable for treating a large amount of a liquid having a low sludge concentration such as supernatant water. The characteristics of the separation device or the hollow fiber membrane separation device can be effectively utilized.

The cleaning wastewater treatment facility 10 used in the water purification system according to the present invention is not limited to the above embodiment. For example, the supernatant water membrane separation device 28
Since the thickened sludge is also generated by the above, it may be combined with the thickened sludge 32 from the coagulating sedimentation basin 20, as shown by reference numeral 29 in FIG.

[0038]

[Examples] The following description will be made by comparing the case where the coagulation sedimentation tank 20 is provided in the cleaning wastewater treatment facility 10 and the case where it is not provided.

Water purification scale of water purification facility 5 6000
0 m ³ / day, raw water turbidity 10 degrees, PAC injection rate 30 mg /
Assuming that L water purification equipment is designed, if the concentration of the drawn sludge 15 in the settling basin 14 is 0.7%,
The amount of drawn sludge 15 is 126 m ³ / day. on the other hand,
Assuming that the backwash flow rate is 0.9 m / min, the surface wash flow rate is 0.2 m / min, and the time required for each wash is 6 minutes in the sand filtration basin 16, the amount of water in the wash drainage water 22 is 3700 m ³ / d, which is very large. In order to directly filter this with the sludge membrane separation device 40, the sludge membrane separation device 40 requires a large-scale facility. However, as shown in the present invention, when the cleaning wastewater 22 is treated in the coagulation sedimentation tank 20 before being subjected to membrane filtration in the sludge membrane separation device 40, the sludge recovery rate is 90%, and the cleaning wastewater 22 is discharged. Assuming that the concentration is 0.4%, it will be 168 m ³ / day, and the scale of the sludge membrane separation device 40 can be greatly reduced to about 1/13.

[0040]

As described above, according to the present invention,
The wastewater from the sand filtration pond can be efficiently treated, and there is no risk of epidemiologic risk or deterioration of the quality of the treated water. The treatment load on the pond does not increase, and the recovery rate of cleaning wastewater (water purification efficiency) can be increased.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a water purification system according to the present invention

FIG. 2 is a schematic diagram showing a slurry circulation type coagulating sedimentation tank used in the water purification system according to the present invention.

FIG. 3 is a schematic diagram showing a microsand type coagulation sedimentation basin used in the water purification system according to the present invention.

[Explanation of symbols]

5 ... Purified water production facility, 10 ... Washing wastewater treatment facility, 16 ... Sand filtration basin, 20 ... Coagulation sedimentation basin, 20A ... Coagulation sedimentation basin (slurry circulation type), 20B ... Coagulation sedimentation basin (micro sand type), 26 ... Top Clear water, 28 ... Supernatant water membrane separator, 32 ...
Concentrated sludge, 40 ... Sludge membrane separator, 50 ... Rotating flat membrane separator

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 1/44 C02F 1/44 K 11/12 11/12 EF term (reference) 4D006 GA06 GA07 HA01 HA41 HA84 HA93 JA01 JA55Z JA56Z JA67Z KA01 KA52 KA54 KA57 KB13 KB15 MA01 MA03 MC02 MC03 MC22 PA01 PA02 PB08 PB15 PB24 4D015 BA19 BA23 BB05 DA04 EA32 FA01 FA02 FA03 FA16 FA17 4D059 AA03 BE06 BE42 BE51 CA28

Claims (3)

[Claims] 1. A water purification system comprising a purified water production facility having a sand filter and a cleaning wastewater treatment facility for treating the cleaning wastewater of the sand filter, wherein the cleaning wastewater treatment facility uses the cleaning wastewater as supernatant water. A coagulation sedimentation tank for separating concentrated sludge into a sludge, and a sludge membrane separation device for performing a membrane separation treatment on the concentrated sludge, and the supernatant water and the membrane separation water membrane-separated by the sludge membrane separation device A water purification system that recirculates to the entrance side of. 2. The cleaning wastewater treatment facility is characterized in that the supernatant water obtained by the coagulation sedimentation tank is subjected to membrane separation by a supernatant water membrane separator, and then returned to the inlet side of the purified water production facility. The water purification system according to claim 1. 3. The sludge membrane separation device is a rotary flat membrane separation device, and the supernatant water membrane separation device is an immersion flat membrane type membrane separation device or a hollow fiber type membrane separation device. The water purification system described in 2.