JPH10286565A - Water treatment plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment plant provided with a device for after- treating cleaned wastewater efficiently, and having a high water recovery ratio. SOLUTION: A water treatment plant is constituted of a membrane filtration equipment and a coagulating sedimentation device 40 attached to the membrane filtration equipment. The coagulating sedimentation device 40 is used for concentrating cleaned wastewater flowed out of the membrane filtration equipment and provided with a coagulant injection equipment constituted of cleaned wastewater tank 42 for storing a cleaned wastewater drained from the membrane filtration equipment, a cleaned wastewater pump 44 for transferring the cleaned wastewater from the cleaned wastewater tank 46 for storing a coagulant solution and a coagulant injection pump 48 for transferring the coagulant solution, and a chemical mixing tank 50 and also a coagulating sedimentation tank 52. Also the coagulating sedimentation device 40 is provided with an equipment for returning preliminarily returned water to an inlet of the membrane filtration equipment, a sludge water tank 54 for storing sludge water drained from the bottom of the coagulating sedimentation tank 52, a press type dehydrator 56 for dehydrating sludge water and separating sludge and a sludge water pump 58 for transferring the sludge into the dehyrator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment apparatus having a membrane filtration apparatus for obtaining permeated water as treated water by membrane filtration of raw water. A water treatment apparatus having a membrane filtration device that alternately performs a washing step and requires a post-treatment of washing wastewater flowing out of the washing step, and in particular, river water, lake water, dam water, and dam water containing a large amount of suspended matter. Since the raw water is used as industrial water, sewage treated water, etc., clogging of the filtration membrane proceeds quickly, and therefore, the frequency of the washing process is high, and the optimal water treatment apparatus is used when the amount of washing wastewater is large. Things.

[0002]

2. Description of the Related Art In a membrane filtration apparatus, water to be treated is permeated through a filtration membrane, and foreign matter, for example, fine particulate suspensions in the water to be treated is captured by the filtration membrane while the permeated water is treated. In recent years, since it is possible to obtain clean treated water relatively efficiently by reliably capturing even foreign matter which is fine solid particles, the method includes the turbidity treatment of clean water and wastewater. It is used in various fields. By the way, in the process of membrane filtration of the water to be treated, the filtration membrane is gradually clogged by the foreign matter in the water to be treated that has been captured, and the pressure difference in the passage of the water to be treated passing through the filtration membrane increases. Therefore, the filtration membrane is usually washed at the time when the pressure difference reaches a predetermined pressure difference, when the membrane filtration step is performed for a predetermined time, and when a predetermined amount of water to be treated is permeated. Thus, the membrane filtration function is restored.

[0003] In the washing step of the filtration membrane, contrary to the flow of water in the membrane filtration step, from the secondary side of the filtration membrane, ie, the permeate outflow side, to the primary side of the filtration membrane, ie, the inflow side of the water to be treated. The washing medium, for example, washing water is permeated, and thereby foreign substances adhering to the membrane surface on the primary side of the filtration membrane are separated from the filtration membrane. For the washing water, use mainly permeated water or sometimes a mixed fluid of permeated water and gas, and when permeating the permeated water through the filtration membrane, allow the permeated water to permeate while being pressed by gas such as air. There is also. The separated foreign matter is discharged to the outside as cleaning wastewater together with the water to be treated and / or the cleaning water.

Here, the configuration of the membrane filtration device will be described with reference to FIG. The membrane filtration device 10 includes a treated water tank 12 for storing the treated water, a treated water pump 14 for supplying the treated water, and a hollow fiber membrane module 16 having an ultrafiltration membrane (UF membrane) as a filtration membrane. And a treated water tank 18 for storing treated water, and a washing water pump 20 for sending washing water. The membrane module 16 is of a cross flow type,
A treated water pipe 22 for introducing treated water is provided at one end (lower end in FIG. 4) of the primary side of the filtration membrane, and a treated water flowing out to the treated water tank 18 as permeated water is treated on the secondary side. Water pipe 2
4 is connected to the other end of the primary side (the upper end in FIG. 4) of a concentrated water pipe 26 for returning non-permeated water, that is, concentrated water having a high concentration of suspended matter, to the treated water tank 12. . Further, a washing water pipe 28 is connected to the treatment water pipe 24 from the treatment water tank 18 via the washing water pump 20 to introduce washing water to the secondary side of the filtration membrane, and a washing drain pipe 30 for discharging washing waste water to the outside is provided. It branches off from the water pipe 22 to be treated.

In the membrane filtration step, the water to be treated is sent from the water tank to be treated 12 to the hollow fiber membrane module 16 by the water pump 14 to be treated, and the permeated water that has passed through the filtration membrane is treated as treated water to the treated water tank 18. The treated water other than the treated water used as the entering and washing water is sent to the outside. The water to be treated that has not passed through the filtration membrane returns to the raw water tank 12 as concentrated water having high turbidity. When the differential pressure of water passing through the hollow fiber membrane module 16 rises and reaches, for example, a predetermined pressure, the flow shifts from the membrane filtration step to the filtration membrane washing step. In the cleaning process,
The treated water is introduced as washing water from the treated water tank 18 by the washing water pump 20 and is permeated from the secondary side of the filtration membrane to the primary side, whereby foreign substances adhering to the primary membrane surface of the filtration membrane are removed. Peel from The peeled foreign matter is washed water and / or
Alternatively, the washing drain pipe 30 accompanies the water to be treated and serves as washing drainage.
Is discharged to the outside. The washing wastewater discharged to the outside has high turbidity, including foreign substances that have been separated from the filtration membrane.Therefore, except for the case where the discharge amount of the washing wastewater is extremely small, it is directly used for rivers, etc. without post-treatment. Discharging is undesirable from a safety and environmental point of view. For example, if the SS (solid suspension) of raw water per liter is about 10 mg, the water recovery rate is about 90% in a normal membrane filtration device, so that the SS of the washing wastewater is about 1 per liter.
00 mg, and the sludge concentration becomes about 0.01%. Therefore, conventionally, washing wastewater is separated into solid and liquid with low turbidity by sedimentation separation or mechanical dehydration, or sludge is concentrated by evaporating water by solar drying.

[0006]

By the way, the membrane filtration device of the conventional water treatment apparatus has the following problems regarding washing and drainage. First, there was a problem that post-treatment of the washing wastewater was technically difficult. In other words, the concentration of solids in the washing wastewater, that is, the sludge concentration, is too high to be discharged as it is, but too low for solid-liquid separation or evaporation, and dehydration or solar drying. Is very inefficient, and as a result, large equipment and a large site are required for solid-liquid separation, resulting in an increase in cost. Therefore, as a new method, a non-cake filtration method has been proposed in which a washing flat water is filtered while removing solids on the membrane so that solids are not deposited on the membrane by using a rotary flat membrane or an immersion membrane. ing. In this method, the treatment speed mainly depends on the membrane permeation speed of water, and the treatment speed (volume of dry solid matter / unit area of membrane / unit time) depends on the sludge concentration until the sludge concentration of the washing wastewater reaches about 10% or more. It is almost constant irrespective of the change of. Therefore, the method using the rotary flat membrane or the immersion membrane has a very low treatment efficiency when the sludge concentration is low as in the case of washing wastewater, and furthermore, energy is required to remove solids attached to the membrane. There is a problem that the consumption amount is larger than the treatment amount of the washing wastewater, and economical efficiency is low for practical use. The second problem is that the water recovery rate of the water treatment device is low. In the conventional cleaning process, permeated water is used as cleaning water, and is discharged to the outside as cleaning wastewater. The required amount of the washing water varies depending on the quality of the water to be treated, the type of the filtration membrane, and the like, but usually reaches 5 to 20% of the water to be treated, and accordingly, the water recovery rate of the water treatment apparatus decreases accordingly. .

[0007] In view of the above circumstances, an object of the present invention is to provide a water treatment apparatus having a device for efficiently post-treating washing wastewater and having a high water recovery rate.

[0008]

In order to economically post-process the washing wastewater, the present inventor concentrated the washing wastewater to take out sludge water having a high sludge concentration, and further separated the sludge from the sludge water. I thought it would be effective. By the way, conventional centrifugal concentrators and membrane concentrators have a relatively small installation area, but consume a large amount of energy, and conventional coagulation and sedimentation apparatuses require a large installation area. It is inconvenient. Further, in order to concentrate the washing wastewater on the basis of economical attractiveness using the above-mentioned rotary flat membrane or immersion membrane, a sludge concentration of several% is necessary,
Pretreatment of concentrating the washing wastewater to 100 times or more is necessary, which complicates the process and increases the cost.
These methods are also unsuitable as a method for concentrating washing wastewater. Therefore, the present inventor concluded that, instead of the usual coagulation and sedimentation method, the cleaning wastewater is concentrated by performing the sedimentation separation action and the coagulation action by the filler in a mutually complementary manner to efficiently concentrate the washing wastewater. Conceived to adopt a coagulating sedimentation device,
Through repeated experiments, the present invention has been completed.

In order to achieve the above object, a water treatment apparatus according to the present invention filters water to be treated with a filtration membrane, and obtains permeated water as treated water while capturing foreign substances in the water to be treated by the filtration membrane. Water provided with a membrane filtration device for alternately performing a membrane filtration step and a washing step of washing the filtration membrane with washing water to separate foreign matters trapped from the filtration membrane and further discharging a washing wastewater containing the separated foreign matters. In the treatment device, a water supply means for supplying the cleaning wastewater discharged from the membrane filtration device, an addition means for adding a coagulant to the cleaning wastewater, and a contact material accumulation layer formed by accumulating small piece contact materials having a large porosity. The washing wastewater to which the coagulant has been added is introduced, the water flows through the contact material accumulation layer in an upward flow, the suspended matter in the washing wastewater is coagulated and separated, and the washing wastewater is purified, and Sewage discharged as treated water and containing separated suspension It is characterized in that it comprises a coagulation-sedimentation device and a coagulation-sedimentation tank to flow out of water from the bottom.

The water to be treated by the present water treatment apparatus is river water, lake water, dam water, industrial water, sewage treated water, or the like. The membrane filtration device used in the present invention is a microfiltration membrane (M
F), a membrane filtration device of a type that uses a filtration membrane such as an ultrafiltration membrane (UF) as a filter medium and restores the filtration function of the filtration membrane by washing the filtration membrane with washing water.
The filtration type may be either a total filtration type or a cross flow type. The material of the filtration membrane may be any of inorganic materials such as ceramics or organic materials such as polyacrylonitrile and cellulose acetate. The structure of the filtration membrane may be tubular, hollow fiber, flat membrane, or spiral. Any of

The coagulating sedimentation apparatus used as the apparatus for concentrating the washing wastewater in the present invention is, for example, the coagulating sedimentation apparatus disclosed by the applicant in Japanese Patent Application Laid-Open No. 6-304411. I do. The main part of the present coagulation settling apparatus is a coagulation settling tank. The coagulating sedimentation tank has a sedimentation separation area and a layer height of several tens to several hundreds of centimeters formed by randomly accumulating a large number of small piece contact materials having a high porosity such as a short tube type contact material.
The washing wastewater first flows into the sedimentation / separation area, and then flows upward through the coagulation / sedimentation area. Before entering the coagulation sedimentation tank, a coagulant is added to the washing wastewater, and the suspension is coagulated.
First, large flocculated flocs are separated and settled in the settling separation area into which the washing wastewater flows. Next, a large number of small flow stagnation regions are formed in the downstream region of the contact material in the contact material accumulation layer as the washing wastewater passes through the coagulation sedimentation region. Due to the remarkable flocculation and sedimentation of the suspension in the flow stagnation region, a relatively large suspension (SS) contained in the washing wastewater precipitates, and the flocculation effect of the added flocculant is promoted. ,
The suspension agglomerates and precipitates forming flocs of the suspension. In addition, the suspension adheres and is trapped between the hollow portion of the short tube type contact material and the short tube, and solid-liquid separation is performed. The contact material is desirably an internal hollow contact material having a large porosity and surface area such that the surface area per 1 m ³ of the contact material volume is 200 m ² or more, preferably 300 m ² or more in an accumulated state. ~ 12mm and length 15
A short tube type contact material made of plastic having a size of about 20 mm, a spherical filler having a hollow spherical body and a large number of holes formed in a spherical surface, a teralet packing, or the like can be used.

The type of the coagulant is not limited, but an inorganic coagulant, for example, an aluminum coagulant is used from the viewpoint of economy and harmlessness. The addition rate of the aluminum-based flocculant is suitably in the range of 0.001 to 0.05 in terms of the ALT ratio (the ratio of the injection amount (mg / liter) of aluminum to the washing turbidity).

The water supply means for supplying the washing wastewater discharged from the membrane filtration device to the coagulation sedimentation device is not limited. For example, a pump, direct injection from the membrane filtration device, or natural inflow due to a height difference from the membrane filtration device, etc. It is. A washing and drainage tank may be provided to temporarily store water. The adding means for adding the coagulant to the washing wastewater is a known means, for example, a coagulant solution may be added to a washing drainage water pipe for sending water to the coagulating sedimentation apparatus, or a mixing tank is provided, where the washing drainage is provided. And a coagulant solution. If necessary,
A means for promoting coagulation or aggregation of the suspension, for example, a line mixer, a rapid mixing tank with a stirrer, or the like may be provided between the means for adding a flocculant and the apparatus for coagulation and precipitation. When the water treatment apparatus is provided with a concentration means for treating the sludge water and further concentrating the sludge water, there is no restriction on the concentration means, and the conventional concentration means, for example, a centrifuge, a press-type dehydrator, a rotary flat membrane A mechanical dehydrator such as a immersion type membrane, a solar drying method, a heat drying method, or the like can be used.

The upward flow rate of the washing wastewater in the coagulating sedimentation tank is 200 m / day to 800 m / day (8 to 33 m ³ / m ^2).
/ Hr), preferably from 300 m / day to 500 m / day. The size of the suspension in the primary treatment water flowing out of the coagulation sedimentation tank is about 100 μm or less. Conversely, all suspensions of 100 μm or more in the washing wastewater are captured in the coagulation sedimentation tank. The present coagulating sedimentation apparatus can concentrate the washing wastewater with a remarkably high load, compared with a conventional high-speed coagulating sedimentation basin or the like with a water flow rate of about ^{2 to 5} m ³ / m ² / hr. The installation area is also small.
Further, since almost no power is required, the operation cost is not increased as compared with the conventional concentrator.

In the present invention, the primary treated water flowing out of the coagulation and sedimentation device is introduced into the membrane filtration device together with the water to be treated, whereby the water is recovered from the washing wastewater which has conventionally been discharged to the outside, and the water treatment device is used. Water recovery can also be increased.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings by way of examples. Embodiment This embodiment is one of embodiments of a water treatment apparatus according to the present invention, and FIG. 1 is a flow sheet showing a configuration of a coagulation / sedimentation apparatus 40 constituting a main part of the water treatment apparatus of this embodiment. It is. In the water treatment apparatus of the present embodiment, the membrane filtration device 10 shown in FIG.
And a coagulation / sedimentation device 40 attached to the membrane filtration device 10. The configuration of the membrane filtration device 10 is as described above, and the description is omitted here. Coagulation sedimentation device 4
Reference numeral 0 denotes a device for concentrating the washing wastewater flowing out of the membrane filtration device 10, a washing drainage tank 42 for storing the washing wastewater flowing out of the membrane filtration device 10, and a washing drainage pump for feeding the washing wastewater from the washing drainage tank 42. 44, a coagulant injecting facility including a coagulant solution tank 46 for accommodating a coagulant solution and a coagulant injecting pump 48 for feeding the coagulant solution, a chemical mixing tank 50, and a coagulating sedimentation tank 52. Further, the coagulation / sedimentation apparatus 40 includes a sludge water tank 54 for storing the sludge water discharged from the bottom of the coagulation / sedimentation tank 52, a press-type dehydrator 56 for dewatering the sludge water to separate and concentrate solids, and A sludge water pump 58 for feeding sludge water from the tank 54 to the dehydrator 56 is provided.

The coagulant solution is injected from the coagulant tank 46 storing the coagulant solution into the washing wastewater in the chemical mixing tank 50 by the coagulant injection pump 48. Chemical mixing tank 50
Is a container provided with a stirrer 60 and installed at a higher position than the coagulation sedimentation tank 52, in which washing wastewater is temporarily retained, and the washing wastewater and the flocculant are rapidly mixed while the washing wastewater is stirred by the stirrer 60. The washing wastewater mixed with the coagulant is caused to flow into the coagulation sedimentation tank 52 via the inflow pipe 62 at a height difference.

The coagulation sedimentation tank 52 is a tank for sedimenting and separating and coagulating and separating fine flocculants generated in the washing wastewater by the addition of the coagulant. As shown in FIG.
The cleaning drain water inflow zone 64, the contact material accumulation zone 66, and the water collecting zone 68 are sequentially formed. The contact material accumulation zone 66 is defined by eyelet-shaped outflow prevention plates 70 and 72 provided at the upper and lower portions of the zone,
In the area between them, a large number of small-sized plastic contact members 74 having a relatively small specific gravity in the form of a short tube having a large porosity as shown in FIG. The contact material accumulation layer 76 is formed. The water collecting zone 68 is a contact material collecting zone 6
6 is a region for collecting the treated water that has passed through and treated, the water collecting portion 78 provided immediately above the outflow prevention plate 70 in the contact material accumulation zone 66, and an overflow from the upper end of the water collecting portion 78. It comprises a collecting trough 80 for collecting the flowing treated water, and an outflow pipe 82 connected to the collecting trough 80 and allowing the treated water to flow out. The treated water that has flowed out is returned to the raw water tank 12.

The washing drainage from the chemical mixing tank 50 flows into the inflow zone 64 via the inflow pipe 62. Inflow pipe 6
2 penetrates the center of the inflow zone 64 and has a downward opening at the tip. Below the opening of the inflow pipe 62, a current changing plate 84 having an inverted umbrella is provided in order to change the direction of the washing drainage that has flowed downward upward. Further, an alkali agent injection pipe 86 is connected to the inflow pipe 62, and an alkali solution is injected as needed to adjust the pH of the washing wastewater. The bottom of the inflow zone 64, that is, below the current plate 84, is configured as a sludge storage zone 88 formed in an inverted cone shape for accumulating sludge, and a sludge water pipe 90 for discharging sludge water is connected to the lowermost portion. Have been. Further, an air supply pipe 92 provided with a large number of air nozzles for injecting air upward is provided above the inflow zone 64. The air supply pipe 92 blows out the air fed in by the air blower 94 to form the contact material accumulation zone 66. Of the contact material 74 is stirred and washed.

The washing wastewater to which the coagulant has been added first flows into the inflow zone 64 of the coagulation / sedimentation tank 52. In the inflow zone 64, relatively large flocs of flocs formed by agglomeration of suspended matter in the washing wastewater first settle and separate. Next, the washing wastewater flows into the contact material accumulation zone 66. There, the remaining fine flocs in the washing wastewater are coagulated and settled in the flow stagnation region, adhere to the contact material by contact with the contact material, or are trapped in the gap between the contact materials. And separated from the washing wastewater. The clarified treated water flows out from the upper water collection zone. In particular, in the contact material accumulation zone 66, a large number of flow stagnation regions are formed in the downstream region of the contact material 74, and remarkable flocculation and sedimentation of the suspension proceeds in the flow stagnation region. Flock that adheres to or is trapped between contact materials,
As the floc grows gradually due to the contact with the subsequent fine floc, etc., and the floc diameter increases and flocs whose sedimentation velocity is higher than the rising flow velocity of the cleaning drainage are formed, the floc separates from the contact material by the flow of the cleaning drainage. ,
Sludge is settled against the flow of washing wastewater, and sludge storage zone 8
8 is deposited. In this way, the suspended matter in the washing drainage is accumulated as flocs in the sludge storage zone 88, and the sludge water pipe 9
Discharged by 0.

Hereinafter, the membrane filtration device 10 and the coagulation / sedimentation device 4
An operation method of the water treatment apparatus according to the present embodiment, which is 0, will be described. First, the membrane filtration device 10 is operated, the membrane filtration process is performed in the same manner as in the conventional membrane filtration device, and the process shifts to the washing process when the pressure difference in water passing through the filtration membrane rises to a predetermined pressure.
The washing wastewater that has flowed out in the washing process is temporarily stored in the washing wastewater tank 42. Next, the coagulant solution is injected into the chemical mixing tank 50 at a predetermined addition rate by the coagulant injection pump 48 while the cleaning drainage is supplied from the cleaning drain tank 42 to the chemical mixing tank 50 by the cleaning drain pump 44. The washing wastewater is stirred and mixed for a predetermined time in the chemical mixing tank 50, and then the inflow pipe 6
After that, it flows into the coagulation sedimentation tank 52. In the coagulation sedimentation tank 52, the suspension in the washing wastewater including the suspension agglomerated by aggregation is separated, and the washing wastewater contains only a relatively fine suspension, for example, a small amount of only a suspension of 100 μm or less. It returns to the raw water tank 12 through the outflow pipe 82 as treated water. On the other hand, the sludge water discharged from the sludge water pipe 90 is once stored in the sludge water tank 54 and sent to the press type dehydrator 56 by the sludge water pump 58 to be dewatered. After dewatering, sludge with a low moisture content is obtained. Instead of the mechanical dehydrator such as the press dehydrator 56, the sludge water may be subjected to solar drying.

When operated for a long time, the coagulation settling tank 5
Since the suspended matter accumulates on the second contact material 74 and the coagulation sedimentation function is reduced, the coagulation sedimentation tank 52 needs to be washed. In order to wash the coagulation sedimentation tank 52, the supply of the washing wastewater to the coagulation sedimentation tank 52 is stopped, and first, the air blower 94 is activated,
For a predetermined time, air is jetted from the nozzle of the air supply pipe 92 to stir and flow the contact material of the contact material accumulation layer 76.
Thereby, the suspension adhered to the contact material and the suspension trapped between the contact materials are separated from the contact material. Then, the injection of air is stopped, and the suspension is settled and left to accumulate in the sludge storage zone 88. Next, the sludge water pipe 9
0 is released, and the accumulated sludge is discharged together with the water in the coagulation sedimentation tank 52. When the effluent contains suspended matter at a high concentration, it is treated in the same manner as ordinary sludge water. When the effluent has a low suspended matter concentration, the discharged water pipe 9 branched from the sludge water pipe 90 is used.
It is sent to the raw water tank 12 by 6.

EXPERIMENTAL EXAMPLE An experimental apparatus basically having the same configuration as the water treatment apparatus of the present embodiment, comprising the membrane filtration apparatus 10 and the coagulation / sedimentation apparatus 40, was manufactured according to the following specifications. The treatment and concentration treatment of the washing wastewater were performed under the following conditions. Membrane filtration device 10 modules: Hollow fiber membrane module Number of modules: 1 Effective filtration membrane area per module: 50 m ² Filtration membrane: UF membrane with a cut-off molecular weight of 150,000 and membrane material of cellulose acetate Water flow : 1.2 m ³ / m ² / day

Coagulating sedimentation device 40 Washing drainage tank 42 Material: polyethylene tank Effective volume: 1.5 m ³ Residence time of washing drainage: 6 hours Rapid mixing tank 50 Material: polyethylene tank Effective volume: 0.1 m ³ Washing drainage and flocculant Residence time of the solution: 7.2 minutes Coagulation sedimentation tank 52 Diameter: 150 mm Cross-sectional area: 0.0177 m ² Layer height of the filler accumulation layer: 1.0 m Water flow rate: 14.1 m / h Water flow: 0.25 m ³ / h Sludge water tank 54 Material: Polyethylene tank Effective volume: 0.1 m ³ Dehydrator 56 Model: Single-sided diaphragm type pressure dehydrator Filter cloth area: 0.0209 m ² Press-in pressure: 0.7 Mpa Press-in time: 60 minutes Pressing Pressure: 1.5Mpa Pressing time: 40 minutes

Raw water Water source: river water Average SS: adjusted to 22 mg / l SS by adding kaolin Operating conditions of membrane filtration device 10 Filtration method: cross flow Water recovery: 90%, therefore, the amount of washing water is of 10% corresponds coagulating sedimentation apparatus 40 coagulant type was used in the water: PAC (polyaluminum chloride) addition rate: 18 mg of PAC / liter - detergent drain (however, the concentration of Al ₂ O ₃ of 10% PAC solution)

The experimental apparatus was operated under the above conditions, and samples of raw water, primary treated water (treated water of the coagulation sedimentation apparatus), washing wastewater, etc. were collected, and pH, water temperature, SS (mg / l), sludge concentration were measured. (%), The following results were obtained. Sample source pH Water temperature (° C) SS (mg / l) Sludge concentration (%) Raw water 7.7 18 20-Washing wastewater 7.3 18 200 0.021 Primary treated water 7.1 196-Sludge water 7.1- 9.1 Dewatered sludge---32.6

In the present embodiment, the concentration of the sludge in the washing wastewater is increased to a concentration that enables economical mechanical dehydration or solar drying by concentrating the washing wastewater with a specific coagulating sedimentation apparatus. The coagulating sedimentation device 40 of the present embodiment
Is effective in complementing the coagulation sedimentation action and the re-agglomeration action due to the filler, so that the apparatus can be miniaturized, and
Since no power is required, the concentration of the washing wastewater can be performed more economically than in the conventional method. In addition, since the addition rate of the coagulant is low, it is economical.

[0028]

According to the present invention, the use of a specific coagulation / sedimentation apparatus, which complementarily performs the sedimentation / separation action and the coagulation / sedimentation action, as a concentrator for the washing wastewater flowing out of the membrane filtration device, enables a mechanically efficient operation. The washing wastewater can be concentrated to a sludge concentration at which sludge can be economically separated by a dehydration method or a solar drying method. Further, the specific coagulation / sedimentation apparatus has a high concentration efficiency, so that the apparatus can be downsized and the installation area can be small. By introducing the primary treated water flowing out of the coagulation and sedimentation device together with the raw water into the membrane filtration device, the water recovery rate of the water treatment device can be increased. In addition, since the amount of the coagulant used is small, even when the primary treated water is introduced into the membrane filtration device,
The effect on the membrane filtration device is negligible.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a configuration of a coagulation / sedimentation apparatus.

FIG. 2 is a schematic diagram showing a configuration of a coagulation sedimentation tank.

FIG. 3 is a perspective view of a contact material.

FIG. 4 is a flow sheet showing a configuration of a membrane filtration device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Membrane filtration apparatus 12 Treated water tank 14 Treated water pump 16 Hollow fiber membrane module 18 Treated water tank 20 Wash water pump 22 Treated water pipe 24 Treated water pipe 26 Concentrated water pipe 28 Wash water pipe 30 Wash drain pipe 40 Coagulation sedimentation apparatus 42 Cleaning Drain tank 44 Cleaning drain pump 46 Coagulant solution tank 48 Coagulant injection pump 50 Chemical mixing tank 52 Coagulation sedimentation tank 54 Sludge water tank 56 Press dehydrator 58 Sludge water pump 60 Stirrer 62 Inflow pipe 64 Inflow zone 66 Contact material accumulation zone 68 Water collecting zone 70, 72 Outflow prevention plate 74 Contact material 76 Contact material accumulation layer 78 Water collecting part 80 Water collecting trough 82 Outflow pipe 84 Current changing plate 86 Alkaline agent injection pipe 88 Sludge storage zone 90 Sludge water pipe 92 Air supply pipe 94 Air blower

Claims (2)

[Claims] 1. A membrane filtration step in which water to be treated is subjected to membrane filtration by a filtration membrane, and foreign matter in the water to be treated is captured by the filtration membrane to obtain permeated water as treatment water, and the filtration membrane is washed with washing water for filtration. In a water treatment apparatus provided with a membrane filtration device that alternately performs a washing step of alternately performing a washing step of detaching foreign matter trapped from the membrane and further discharging a washing wastewater containing the detached foreign matter, supplying the washing wastewater discharged from the membrane filtration apparatus And a contact material accumulation layer formed by accumulating a small piece of contact material having a large porosity, and introducing the washing wastewater to which the flocculant is added. Sludge that flows through the contact material accumulation layer in an upward flow, agglomerates and separates suspended matter in the washing wastewater, cleans the washing wastewater, flows out as primary treatment water, and contains the separated suspended matter. Coagulation settling tank having coagulation settling tank for discharging water from bottom A water treatment device comprising a sedimentation device. 2. The water treatment apparatus according to claim 1, wherein the primary treatment water flowing out of the coagulation / sedimentation apparatus is introduced into the membrane filtration apparatus together with the water to be treated.