BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a drinking water supply system that can supply drinking water containing minerals such as calcium.

2. Description of the Related Art
Conventionally, tap water or well water is used for drinking in general households, business establishments, etc., after removing chlorine and organic matter with active carbon using small-sized water filters.

Tap water supplied to general households, business establishments in emerging nations is sometimes unfit for drinking. Therefore, packaged drinking water (up to 20 liter) is bought from manufacturer for consumption.

Similarly, water supplied to schools and hostels in emerging nations is sometimes unfit for drinking. Therefore, packaged drinking water is bought from manufacturers for consumption.

Documents that describe the technology related to this patent application are Japanese Patent Application Laid-open No. 2009-74279 and Japanese Patent Application Laid-open No. H6-71249.

There is a new requirement of adding minerals, such as calcium, to cater to the demand for drinking water containing minerals, such as calcium, in water filters used in general households, business establishments, etc., for health benefits.

In case of general households and business establishments in emerging nations, microorganisms and germs develop in the water if the water is not consumed for a certain time after buying the packaged water for consumption. Sometimes the water contaminates after it is packed in the barrels. Similarly, if drinking water containing minerals, such as calcium, that is good for health, is desired, minerals need to be newly added.

SUMMARY OF THE INVENTION

In view of the above discussion, it is an objective of the present invention to provide a drinking water supply system that can supply drinking water containing minerals that is good for health.

According to an aspect of the present invention, a drinking water supply system that supplies drinking water prepared from water includes a water purification device that purifies the water. The water purification device includes at least one of an NF membrane and a UF membrane that filter the water.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of a drinking water supply system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a structure of a user pipeline according to the embodiment.

FIG. 3 is a diagram depicting in thick lines a flow of tap water in a regular mode in a regular state in the drinking water supply system according to the embodiment.

FIG. 4 is a diagram depicting in thick lines a flow of tap water in the regular mode when there is increased usage of water according to the embodiment.

FIG. 5 is a diagram depicting with thick lines a flow in a re-purification mode in which water is purified by stopping a water circulation in a supply block according to the embodiment.

FIG. 6 is a diagram depicting with thick lines a flow in a sand filtering device and an active carbon adsorber of a filter block in a cleaning mode according to the embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS Exemplary embodiments of the present invention are explained below with reference to the accompanying drawings.

FIG. 1 is a structural diagram of a drinking water supply system according to an embodiment of the present invention.

A drinking water supply system S according to the embodiment converts tap water that is unfit for drinking into drinking water containing minerals that is good for health, and supplies the drinking water containing minerals that is good for health to users (supply destination) such as schools and hotels.

It is assumed below that tap water that is unfit for drinking is supplied to the drinking water supply system S through a water pipeline Is.

The drinking water supply system S includes a filter block Sa that converts the tap water that is unfit for drinking and supplied from the water pipeline Is into drinking water that is fit for drinking, and a supply block Sb that circulates and supplies the drinking water obtained in the filter block Sa to a P. 0. U. (point of use) pipeline of the users such as schools and hotels. The drinking water supply system S is controlled by a not shown controlling device (monitoring device).

The filter block Sa of the drinking water supply system S includes first and second raw water tanks la and lb that store therein the tap water supplied via the water pipeline Is, a sand filtering device 2 that removes large foreign substances from the tap water, an active carbon adsorber 3 containing active carbon that adsorbs chlorine, organic matter, etc. from the tap water, an MF filter 4 having an MF membrane that removes minute foreign substances from the tap water, a treated water tank 5 that stores therein the treated water obtained in the above manner, a pre-filter 6 composed of an MF membrane (microfiltration membrane) that filters the treated water, and a membrane unit 7 including a first filter 7a and a second filter 7b. The MF membrane (microfiltration membrane) successfully separates suspensoid and colloidal particles contained in the water.

The first and second filters 7a, 7b include either an NF membrane (nanofiltration membrane) or a UF membrane (ultrafiltration membrane), or a combination of both.

The NF membrane (nanofiltration membrane) has selectivity for chemical elements and ions. That is, the NF membrane allows minerals to pass and cuts off microorganisms and impurities having low-molecular weight.

The UF membrane (ultrafiltration membrane) performs molecular level sifting based on the pore size of membrane and the size of the molecules of the matter to be removed from the water, while letting the minerals to pass.

In this way, the first and second filters 7a and 7b use a membrane that can perform filtration while leaving out minerals such as calcium (besides calcium (Ca), minerals such as phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (C12), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), iodine (I), selenium (Se), manganese (Mn), molybdenum (Mo), chromium (Cr), and cobalt (Co)) without using an RO membrane (reverse osmosis membrane) that is normally used and cause to retain the minerals for the health of the users who use the drinking water.

During a regular mode, based on a control exerted by the controlling device, the first filter 7a is mainly used, while the second filter 7b is controlled by a not shown valve so as to allow a minimum (least) flow amount. Meanwhile, the functions of the first filter 7a and the second filter 7b can be interchanged periodically, or after a desired random period, based on the control exerted by the controlling device.

The first and second raw water tanks la and lb, the sand filtering device 2, the active carbon adsorber 3, the MF filter 4, the treated water tank 5, the pre- filter 6, and the membrane unit 7 are arranged in this order on a pipeline I through which the tap water flows. The first raw water tank la stores therein the tap water supplied from the water pipeline Is. The second raw water tank lb serves as a buffer, or a backup tank, for the first raw water tank la.

First and second raw water pumps pi and p2 are arranged between the first and second raw water tanks la and lb and the sand filtering device 2. The first and second raw water pumps pi and p2 supply the tap
water flowing in the water pipeline Is and stored in the first and second raw water tanks la and lb to the sand filtering device 2.

The first raw water pump pi is a pump that is operated when supplying water from the first raw water
tank la to the sand filtering device 2 during the regular mode. The second raw water pump p2 is used as a backup pump for the first raw water pump pi, or for causing a backward flow (see arrows (31 and (32 in
FIG. 6) when performing cleaning of the sand filtering device 2 and the active carbon adsorber 3.

That is, the second raw water pump p2 supplies, when performing cleaning of the sand filtering device 2, the tap water to the sand filtering device 2 through pipelines II and 12 as shown by the arrow pi in FIG. 6.

The second raw water pump p2 supplies, when performing cleaning of the active carbon adsorber 3, the tap water to the sand filtering device 2 through pipelines I1 and 13 as shown by the arrow (32 in FIG. 6.
First and second high pressure pumps p3 and p4 are arranged between the treated water tank 5 and the pre-filter 6. The second high pressure pump p4 is used as a backup pump for the first high pressure pump p3. That is, the second high pressure pump p4 is operated when the first high pressure pump p3 is out of order. Meanwhile, the first and second high pressure pumps p3 and p4 can be interchanged alternately for operation and backup.

Other reference symbols shown in the filter block Sa are explained below.

Reference symbols dl to d20 represent valves that are opened/closed to allow/stop a flow inside the pipeline I.

Reference symbols gl to g4 represent check valves that allow a flow in an arrow-direction of the pipeline I, and prevent a flow in an opposite direction to the arrow-direction.

A reference symbol nl represents a check valve, or an inspection hole, for monitoring a backward flow when the sand filtering device 2 is being cleaned using the backward flow (see the arrow (31 in FIG. 6) .

A reference symbol n2 represents a check valve, or an inspection hole, for observing the backward flow when the active carbon adsorber 3 is being cleaned using the backward flow (see the arrow (32 in FIG. 6)

A reference symbol cl represents a control valve that acts as a closing valve for preventing a reflux flow of water from the supply block Sb to the treated water tank 5 when the water of a supply block Sb satisfies predetermined water quality conditions as drinking water, and acts as an opening valve for allowing a reflux flow of water from the supply block Sb to the treated water tank 5 when the water of the supply block Sb does not satisfy the predetermined water quality conditions as drinking water.

The filter block Sa includes pressure gauges tl to t4 arranged inside the pipeline I for measuring the pressure of flow of water in the pipeline I as flow sensors, and a flowmeter rl for measuring a flow amount of the flow of water in the pipeline I.

Next, the supply block Sb of the drinking water supply system S is explained.

The supply block Sb is connected to the filter block Sa with the pipeline I.

The supply block Sb includes a first purification tank 8a and a second purification tank 8b that respectively store therein the drinking water obtained in the filter block Sa, an ozonizer 9 that supplies ozone (03) to the drinking water flowing in the pipeline I, a UV (ultraviolet) sterilization device 10 that sterilizes the drinking water, a filter 11 having an MF membrane (microfiltration membrane) that removes foreign substances mixed in the drinking water that goes out from a user pipeline Sc for circulation, and a mineral replenishing device 13 that adds minerals. A fluorine adding device 14 that adds fluorine (F) to the drinking water can be arranged behind the membrane unit 7 as shown by a dashed two-dotted line in FIG. 1.

The first purification tank 8a is a tank that stores therein the drinking water supplied from the filter block Sa, while the second purification tank 8b is a buffer, or a backup tank, for the first purification tank 8a.
Inverter-controlled first and second feed pumps p5 and p6 are arranged between the first and second purification tanks 8a and 8b and the UV sterilization device 10.

The inverter-controlled first feed pump p5 is a pump that supplies the drinking water in the first purification tank 8a to the UV sterilization device 10 and the user (supply destination) pipeline Sc. The inverter controlled second feed pump p6 is a pump used as a backup pump for the first feed pump p5.

The first feed pump p5 restricts the flow amount of the drinking water to the minimum (least) at night time using an inverter control; because, the usage amount of drinking water drastically drops down at the night time. In this way, a constant control of flow does not lead to "dead water". This leads to a decrease in power consumption.

A control valve c2 is arranged in the supply block Sb. The control valve c2 performs a control by acting as a closing valve that allows a reflux flow from the supply block Sb to the treated water tank 5 when the drinking water circulating in the supply block Sb does not satisfy the predetermined water quality conditions. In contrast, the control valve c2 acts as an opening valve for continuing the circulation of the drinking water in the supply block Sb when the drinking water circulating in the supply block Sb satisfies the predetermined water quality conditions.

Reference symbols bl to bl2 represent valves that are opened/closed to allow/stop the flow inside the pipeline I.

Reference symbols g5 to g7 represent check valves that allow a flow in an arrow-direction of the pipeline and prevent the flow in the opposite direction of the arrow-direction.

The supply block Sb includes pressure gauges t5 and t6 that respectively measure a pressure of the flow of the drinking water in the pipeline I.

The supply block Sb includes, as sensors, a Ph meter s1 that measures the Ph of the drinking water flowing through the pipeline I to the user (supply destination) pipeline Sc as a forward path, a conductivity meter s2 that measures the conductivity of the drinking water in the pipeline I as the forward path, a residual chlorine meter s3 that measures the residual chlorine in the drinking water in the pipeline I as the forward path, a particle counter s4 that counts the number of particles in the drinking water in the pipeline I as the forward path, and a conductivity meter s5 that measures the conductivity of the drinking water returning in the pipeline I from the user (supply destination) pipeline Sc as a return path.

Because pure water has low conductivity, contamination of the drinking water in the pipeline I of the supply block Sb can be determined by the controlling device by judging whether the difference between the conductivity of drinking water in the pipeline I measured using the conductivity meter s5 arranged in the return path and the conductivity of drinking water in the pipeline I measured using the conductivity meter s2 arranged in the forward path is indicative of a degree of contamination greater than or equal to a permissible value.

When the controlling device determines that the measurement result of the particle counter 4 is greater than a permissible value representing a degree of contamination, thereby indicating increased particles in the drinking water, or when the controlling device determines that the difference between the conductivity of drinking water in the pipeline I as a return path and the conductivity of drinking water in the pipeline I as the forward path is greater than the permissible value showing the degree of contamination, the controlling device opens a valve b3 and/or a valve b5 to supply ozone (03) and cause bubbling from below in the first purification tank 8a and/or the second purification tank 8b.

Supply of minerals such as calcium is performed by the mineral replenishing device 13 by supplying a mineral solution to the drinking water or by dissolving solid minerals in the drinking water.

With regards to the timing of supplying minerals such as calcium, the minerals are replenished in the drinking water (tap water) when upon deciding insufficiency of the minerals. The minerals are judged to be insufficient when the conductivity measured by the conductivity meter s2 in the forward path and/or the conductivity measured by the conductivity meter s5 in the return path is less than or equal to respective
permissible values, or when the mineral measurement result of the mineral replenishing device 13 is less than or equal to a permissible value.

The mineral replenishing device 13 is illustrated as arranged after the membrane unit 7 of the filter block Sa; however, the mineral replenishing device 13 can be arranged in the supply block Sb, which is a circulation line. Meanwhile, the mineral replenishing device 13 can be arranged at any location as long as the minerals can be added to the drinking water. Similarly, the fluorine adding device 14 illustrated with a dashed-two dotted line in FIG. 1 can be arranged in the supply block Sb, which is a circulation line. Meanwhile, the fluorine adding device 14 can be arranged at any location as long as fluorine can be added to the drinking water.

FIG. 2 is a schematic diagram showing a structure of the user pipeline Sc.

The pipeline I as the forward path coming from the supply block Sb of the drinking water supply system S is connected to an inlet Iin (see FIG. 1) of the user pipeline Sc. Thus, the drinking water of the supply block Sb enters into the user pipeline Sc through the inlet Iin. On the other hand, the pipeline I as the return path of the supply block Sb is connected to an outlet lot (see FIG. 1) of the user pipeline Sc. Thus, the drinking water from the user pipeline Sc enters into the pipeline I as the return path through the outlet lot.

The user pipeline Sc is arranged in single or multiple levels. Moreover, not shown taps for drinking the water are arranged at predetermined single or multiple locations on the user pipeline Sc.

The user pipeline Sc has a reverse-return pipe structure. That is, the length starting from the inlet Iin and reaching the outlet lot through a main pipeline ScO, a first pipeline Scl, and a main pipeline Sc9 is equal to the length starting from the inlet Iin and reaching the outlet lot through the main pipeline ScO, a second pipeline Sc2, and the main pipeline Sc9. Taps for supplying drinking water are arranged in the first pipeline Scl and the second pipeline Sc2.

In other words, with regards to the user pipeline Sc, the flow resistance of a pipe starting from the inlet Iin and reaching the outlet lot through the first pipeline Scl, and the flow resistance of a pipe starting from the inlet Iin and reaching the outlet lot through the second pipeline Sc2, that is, the flow resistance of the first pipeline Scl and the second pipeline Sc2 are equal or substantially equal.

Therefore, the drinking water inflowing to the user pipeline Sc from the inlet Iin flows uniformly through both the user pipelines Sc (first pipeline Scl and second pipeline Sc2) without getting stagnated (so to speak, becoming dead water). As a result, quality of the drinking water flowing in the user pipeline Sc can be maintained.

The user pipeline Sc has been explained using two branched pipes, that is, the first pipeline Scl and the second pipeline Sc2; however, the user pipeline Sc can either have a single pipe or any desired number of reverse-return branched pipes.

The user pipeline Sc need not have the reverse-return pipe structure if stagnation (occurrence of dead water) of drinking water in the pipeline can be prevented. If the flow resistance of each of the branched pipes (the first pipeline Scl and second pipeline Sc2) can be maintained equal or substantially equal by, for example, appropriately adjusting the diameters of each of the branched pipes branching from the main pipeline ScO (the first and second pipes Scl and Sc2) to appropriately control the flow resistance of the flow in each branched pipeline starting from the inlet Iin and reaching the outlet lot, stagnation of drinking water in the pipeline can be prevented. However, the reverse-return pipe structure has a simple framework and is more advisable owing to its easy installation.

Operation of drinking water supply system S

Next, an operation of the drinking water supply system S is explained.

First, a regular mode in an operating condition when the drinking water supply system S is in a regular state is explained.

FIG. 3 is a diagram depicting in thick lines a flow of the tap water in the regular mode at the regular state in the drinking water supply system S.

When in the regular state, the controlling device opens the valves dl, d2, d5, d7, dll, dl3, dl6, dl7, and dl9 of the filter block Sa, and starts the first raw water pump p1 and the first high pressure pump p3.

Furthermore, other valves, such as the control valve cl of the filter block Sa, are closed. The valve d2 is closed when the second raw water tank lb is filed with the drinking water, or when it is already full.

As a result, the drinking water from the water pipeline Is is stored in the first and second raw water tanks la and lb. The second raw water tank lb is used as a buffer, i.e., as a backup tank. The water stored in the first raw water tank la flows to the sand filtering device 2 after passing through the valves d5 and d7, the first raw water pump p1, and the check valve gl, and foreign substances are removed by the sand filtering device 2. The water filtered by the sand filtering device 2 flows to the active carbon adsorber 3 after passing through the valve dll, and chlorine (C12), organic matter, etc. are adsorbed in the active carbon in the active carbon adsorber 3. The water in the active carbon adsorber 3 then flows to the MF filter 4 after passing through the valve dl3 where the minute particles are removed by filtration.

The water in the MF filter 4 then flows to the treated water tank 5 after passing through the valve dl6 and is stored there. The water in the treated water tank 5 then flows to the pre-filter 6 after passing through the valve dl7, the first high pressure pump p3, the check valve g3, and the valve dl9, where the water is filtered. The water passed through the pre-filter 6 is filtered by the membrane unit 7 (7a and 7b) and flows to the first purification tank 8a and/or the second purification tank 8b of the supply block Sb, after passing through the mineral replenishing device 13 and the fluorine adding device 14.

When in the regular state, the second purification tank 8b of the supply block Sb is used as a buffer tank and the second feed pump p6 is not used.

The controlling device opens the valves bl, b2, b4, b7, blO, bll, bl2, and the regulating valve c2, and starts the first feed pump p5.

The controlling device closes the other valves of the supply block Sb.

The water supplied from the filter block Sa is stored in the first purification tank 8a and/or the second purification tank 8b. FIG. 3 illustrates a situation where the water has been stored in the first purification tank 8a and the second purification tank 8b. Meanwhile, when in the regular state, the second purification tank 8b acts as a buffer tank, i.e., a backup tank.

The water in the first purification tank 8a flows to the UV sterilization device 10 after passing through the valve b4, the first feed pump p5, the valve b7, the check valve g5, and the valve blO, and is sterilized using ultraviolet rays in the UV sterilization device 10.

The sterilized water in the UV sterilization device 10 passes through the valve bll and the check valve g7, and flows to the user pipeline Sc as drinking water from the inlet Iin.

The drinking water flowing through the outlet lot from the user pipeline Sc flows to the filter 11 after passing through valve bl2, and is filtered there, after which the drinking water is refluxed to the first purification tank 8a after passing through the regulating valve c2.

In this way, the water supplied from the filter block Sa is circulated by being supplied to the first purification tank 8a, and after flowing to the user pipeline Sc; it is refluxed to the first purification tank 8a.
Next, cases of increased usage of water from the regular state of FIG. 3 are explained using FIG. 4. FIG. 4 is a diagram showing a flow of tap water in the regular mode during increased usage of water, depicted using thick lines.

In the regular state of FIG. 3, when the flow amount measured using the flow meter rl increases and the amount of water used increases, the controlling device additionally uses the second raw water tank lb as the buffer tank for the filter block Sa, and the second purification tank 8b as buffer tank for the supply block Sb. In this case, since the flow amount is high, the controlling device starts the second raw water pump p2 and the second high pressure pump p4 used as the backup pump for the filter block Sa, as well as the second feed pump p6 used as the backup pump for the supply block Sb.

The controlling device opens the valves d6, d8, d8a, dl8, and d20 of the filter block Sa and the valves b6 and b8 of the supply block Sb, to be in the state shown in FIG. 4.

Although FIG. 4 illustrates the use of the second raw water tank lb, the second purification tank 8b, the second raw water pump p2, the second high pressure pump p4, and the second feed pump p6, the controlling device can make any selection appropriate for the usage and situation.

Regulation of Minerals
During the regular mode (including when amount of the water used is high), as mentioned earlier, the minerals are replenished to the drinking water (tap water) that has been filtered in the membrane unit 7 (7a and 7b) upon deciding insufficiency of the minerals. Insufficiency of the minerals is judged when the conductivity measured by the conductivity meter s2 arranged in the forward path and/or the conductivity measured by conductivity meter s5 arranged in the return path is found to be less than or equal to the permissible value, or when the measured value of minerals in the mineral replenishing device 13 is less than or equal to the permissible value. Moreover, as mentioned above, a suitable quantity of fluorine can be added to the drinking water by arranging the fluorine adding device 14.

When the measured value of minerals is less than or equal to the permissible value and the minerals are to be replenished to the drinking water by the mineral replenishing device 13, or when fluorine is to be added by the fluorine adding device 14, the controlling device notifies the administrator using an abnormality notifying device by contacting the administrator of the drinking water supply system S on cell phone or by sending an email to a terminal device, setting off an alarm, switching an warning lights, etc.

Maintenance of quality of drinking water

To maintain the water quality at the prescribed level during the regular mode (including when volume of water used is high), the circulating water (drinking water) is sterilized in the UV sterilization device 10 during circulation; in addition, the circulating water is filtered by the filter 11 after the circulating water returns from the user pipeline Sc.

Quality of the circulating water is measured by measuring its Ph with the Ph meter s1, measuring the conductivity with the conductivity meters s2 and s5, and measuring the residual chlorine with the residual chlorine meter s3. Minute particles in the circulating water are counted with the particle counter s4.
When the controlling device determines the residual chlorine measured by the residual chlorine meter s3 to be higher than the prescribed permissible value, the active carbon adsorber 3 is cleaned as described later, and adsorption function of active carbon is reinforced. Until the value of the residual chlorine reaches the permissible value, the water stored inside the first and second purification tanks 8a and 8b can be discarded and it can configured such that the water having the permissible value of residual chlorine is only circulated.

When the count of the minute particles measured by the particle counter s4 deviates from the permissible values, or/and when the difference between the conductivities measured by the conductivity meters s2 and s5 deviates from the permissible value, the controlling device activates the ozonizer 9, while opening the valves b3 and b5 to supply ozone (03) to the water stored in the first and second purification tanks 8a and 8b, thereby removing microorganisms and breaking down organic matter using ozone.

When the residual chlorine measured by the residual chlorine meter s3, the count of the minute particles measured by the particle counter s4, as well as the difference between the conductivities measured by the conductivity meters s2 and s5 deviates from their respective permissible values, the controlling device notifies the administrator using the abnormality notifying device by contacting the administrator of the drinking water supply system S on cell phone or by sending an email to the terminal device, setting off the alarm, switching on the warning lights, etc.

Purification using reflux flow of circulating water
When the count of the minute particles measured by the particle counter s4 deviates from the permissible value despite of supplying ozone (03), or/and when the difference between the conductivities measured by the conductivity meters s2 and s5 deviates from the permissible values, the controlling device notifies the administrator using the abnormality notifying device by contacting the administrator of the drinking water supply system S on cell phone or by sending an email to the terminal device, setting off the alarm, switching on the warning lights, etc.

In addition, the controlling device stops the circulation of water in the supply block Sb by closing the regulating valve c2 as shown in FIG. 5, while opening the control valve cl for a reflux flow of water
circulating in the supply block Sb to the treated water tank 5 of the filter block Sa through the control valve cl. FIG. 5 is a diagram depicting with thick lines a flow in a re-purification mode in which water is purified by stopping a water circulation in the supply block Sb.

The water refluxed to the treated water tank 5 is filtered by the pre-filter 6 and filtered by the membrane unit 7, and then supplied to the first and second purification tanks 8a and 8b. At this time, the first raw water pump p1 is turned off and the valve dl6 is closed to shut the supply of tap water from the first raw water tank la to the treated water tank 5.

Meanwhile, the supply of tap water from the first raw water tank la to the treated water tank 5", can be
continued while the valve dl6 is closed. However purification of water circulating in the supply block
Sb can be done quickly if the supply of tap water from the first raw water tank la to the treated water tank
is stopped, therefore it is preferable to stop the supply of tap water from the first raw water tank la to
the treated water tank 5.

Furthermore, when the count of the particles measured by the particle counter s4 and the difference• between the conductivities measured by the conductivity-meters s2 and s5, respectively, are within the permissible values, the control valve cl is closed and the regulating valve c2 and the valve dl6 are opened, and the first raw water pump p1 is operated to return to the regular mode shown in FIG. 3 or FIG. 4.

Detection of clogging of purifiers and subsequent cleaning
Next, removal of dirt from the sand filtering device 2, the active carbon adsorber 3, the MF filter 4, the pre-filter 6, and the membrane unit 7 that are purifying devices arranged in the filter block Sa, as well as removal of dirt from the filter 11 that is a purifying device arranged in the supply block Sb is explained.
With regards to dirt of the sand filtering device 2 and the active carbon adsorber 3, in the regular mode shown in FIG. 3, when the difference between a pressure value measured by the pressure gauge tl and a pressure value measured by the pressure gauge t2 is greater than or equal to the permissible value, the controlling device determines that the sand filtering device 2 and/or the active carbon adsorber 3 is/are clogged up with dirt.

Whether the sand filtering device 2 and/or the active carbon adsorber 3 is/are clogged up with dirt can be determined by judging whether the difference between a flow amount of water measured by an upstream flow meter trl of the sand filtering device 2, and a flow amount of water measured by a not shown downstream flow meter of the active carbon adsorber 3 is greater than or equal to a permissible value.

FIG. 6 is a diagram depicting with thick lines a flow in the sand filtering device 2 and an active carbon adsorber 3 of the filter block Sa in a cleaning mode.

The controlling device closes the valves d7 and d8a, while stopping the first raw water pump p1, the first high pressure pump p3, and the first feed pump p5 to pause the regular mode. In addition, the controlling device opens valves d5, d8, d9, dlO, dl2, and dl4, and operates the second raw water pump p2 to switch to a purification mode.

As a result, water in the first raw water tank la flows to the pipelines I1 and I2 after passing through the second raw water pump p2 and a check valve g2, and flows back in the opposite direction of that in the
regular mode shown in FIG. 3 FIG. 3 (the arrow (31 shown in FIG. 6) to the sand filtering device 2 from the valve d9. Such a backward flow of water removes the dirt from the sand filtering device 2, and the dirt in the sand filtering device 2 is thrown out from the pipeline 12 and the valve dlO.

Simultaneously, water in the first raw water tank la flows to the pipes II and 13 after passing through the valves d5 and d8, the second raw water pump p2, and the check valve g2, and then flows back in the opposite direction of that in the regular mode shown in FIG. 3 (the arrow (32 shown in FIG. 6) to the active carbon adsorber 3 from the valve dl2. Such a backward flow of water removes the dirt from the active carbon adsorber 3, and the dirt of the active carbon adsorber 3 is thrown out from pipe 13 and valve dl4.

In the above explanation, the dirt of the sand filtering device 2 and dirt of the active carbon adsorber 3 were detected together and cleaned by simultaneously backwashing the sand filtering device 2 and the active carbon adsorber 3. However, the dirt in the sand filtering device 2 and the active carbon adsorber 3 can be detected separately by the upstream and downstream pressure, flow amount, etc., and can be cleaned separately.

Similarly for the MF filter 4, when pressure values measured by its upstream pressure gauge t2 and a downstream pressure gauge t3 are greater than or equal to their respective permissible values, or when the difference between the flow amount levels measured by the not shown flow meters arranged upstream and downstream is greater than or equal to a permissible value, the controlling device decides that clogging up of the MF filter 4 has occurred. In this case, the controlling device pauses the regular mode shown in FIG. 3, and the MF filter 4 is cleaned by generating a backward flow in the opposite direction of that in the regular mode.

Similarly, when pressure values or/and a difference between the flow amount values measured by a not shown pressure gauge or/and a flow meter (filter-dirt detecting device) arranged upstream and downstream of each of the pre-filter 6, the first and second filtration filters 7a and 7b of the membrane unit 7 of the filter block Sa, and the filter 11 of the supply block Sb is/are greater than or equal to their respective permissible values, it is decided that clogging has occurred, and cleaning is performed by generating a backward flow in the opposite direction of that in the regular mode shown in FIG. 3 using a not shown pump (filter dirt removing means).

If the clogging is not restored despite of the above cleaning up, the controlling device notifies the administrator using the abnormality notifying device by contacting the administrator of the drinking water supply system S on cell phone or by sending an email to the terminal device, setting off the alarm, switching on the warning lights, etc.

Meanwhile, clogging in the pre-filter 6, the first and second filters 7a and 7b of the membrane unit 7 of the filter block Sa, and the filter 11 of the supply block Sb can also be detected and cleaned either separately or in appropriate combinations.

Maintenance of the mineral replenishing device 13
Despite of replenishing minerals in drinking water (tap water) using the mineral replenishing device 13, when the conductivity measured with the conductivity meter s2 arranged in the forward path and/or the conductivity measured with the conductivity meter s5 arranged in the return path is not within their respective permissible values, or when the measured value of minerals in the mineral replenishing device 13 is not within the permissible value, the controlling device notifies the administrator using the abnormality notifying device by contacting the administrator of the drinking water supply system S on cell phone or by sending an email to the terminal device, setting off the alarm, switching on the warning lights, etc.

Similarly, when the fluorine adding device 14 has been arranged, and when, despite of addition of fluorine to the drinking water (tap water) by the fluorine adding device 14, prescribed levels of fluorine are not detected by a fluorine detector of the fluorine adding device 14 or a fluorine detection device arranged in the circulation line, the controlling device notifies the administrator using the abnormality notifying device by contacting the administrator of the drinking water supply system S on cell phone or by sending an email to the terminal device, setting off the alarm, switching on the warning lights, etc.

According to the drinking water supply system S of the present embodiment, because the first and second filters 7a and 7b of the membrane unit 7 include any of the NF membrane and the UF membrane, or a combination of these, minerals good for human body can be allowed to pass through along with removing germs from the water. Therefore, by using the NF membrane or/and the UF membrane, the minerals contained in water are retained and are not completely removed, and the drinking water containing minerals can be desalinated. Moreover, by monitoring the water quality, minerals can be regulated by adding them when found to be insufficient after membrane filtration.
Accordingly, the drinking water that is good for health containing minerals that are generally essential for the human body can be supplied.

Furthermore, cavity protection can be achieved by introducing fluorine to the teeth and making teeth stronger to withstand acid by adding fluorine to the drinking water (tap water).

When the mineral replenishing device 13 is unable to supply minerals to the drinking water (tap water)
and when the fluorine adding device 14 is unable to add fluorine to the drinking water (tap water), this fact can be notified to the administrator.

Furthermore, even when there are microorganisms and rust in a water supply pipeline (user pipeline Sc) of the users (supply destinations) such as schools and hotels, the water quality can be maintained at the prescribed level by monitoring the circulating water. Moreover, a low-priced and precise system can be constructed by using conductivity sensors (conductivity meters s2 and s5) as first and second water-quality detecting device.

Furthermore, by arranging the active carbon adsorber 3 containing active carbon filter before the membrane unit 7, chlorine, organic matter, etc. can be removed.

Even if germs are contaminating the circulating water returning from the users (supply destination) such as schools and hotels, it can be sterilized by removing the germs using the ozonizer 9, the UF sterilization device 10, and the filter 11, and safe water can be supplied to the users.

Furthermore, if water quality gets deteriorated, circulation is stopped and impurities can be removed again using the pre-filter 6 and the membrane unit 7. Thus, safe water, untouched by human hands can be supplied to the users. Moreover, in case of deterioration of water quality, the administrator can be notified through cell phone, email, alarm, warning lights, etc., and the administrator can immediately identify and resolve the problem regarding water quality for highly safe drinking water.

Furthermore, because the drinking water supply system S is connected to reverse-return type of the user pipelines Sc, the circulating water flows smoothly without getting stagnated, and generation of microorganisms, mixing of rust in the pipeline Sc can be controlled.

Therefore, a drinking water supply system that can control mixing of microorganisms and rust, etc., and can supply good quality drinking water containing minerals, such as calcium, that are good for human body can be realized.

In the above embodiment, two units of the first and second raw water tanks la and lb and the first and second purification tanks 8a and 8b are arranged as an example; however, three or more units can also be arranged. Moreover, one unit of each of the raw water tank and the purification water tank can also be arranged.

Furthermore, in the above embodiment, the first and second purification tanks 8a and 8b are arranged as an example; however, a drinking water supply system can be constructed without the purification tank.

Furthermore, by arranging the active carbon adsorber 3 containing active carbon filter before the membrane unit 7, chlorine, organic matter, etc. can be removed.

Furthermore, in the above embodiment, the tap water is used as an example; however, the present invention can be applied to water other than the tap water, such as well water or warm water from hot
springs. Meanwhile, the water in the scope of claims also provides warm water.

A drinking water supply system according to a first aspect of the present invention is drinking water supply system that supplies drinking water prepared from water. The drinking water supply system includes a water purification device that purifies the water and includes at least one of an NF membrane and a UF membrane that filter the water. According to the first aspect of the present invention, drinking water containing minerals such as calcium is made available by arranging at least one of the NF membrane and the UF membrane which can remove the target impurities such as microorganisms, germs, while retaining the minerals such as calcium, in the water.

A drinking water supply system according to a second aspect of the present invention, in the drinking water supply system according to the first aspect, further includes a first water-quality detecting device that detects minerals contained in the water filtered using at least one of the NF membrane and the UF membrane; and a mineral supplying device that supplies minerals to the water based on detection result obtained at the first water-quality detecting device. According to the second aspect of the present invention, extra minerals can be added when the minerals, such as calcium, in the drinking water are judged to be insufficient, or when the minerals are to be replenished.

A drinking water supply system according to a third aspect of the present invention, in the drinking water supply system according to the first and second aspects, further includes an active carbon filter arranged upstream of at least one of the NF membrane and the UF membrane. According to the third aspect of the present invention, the active carbon filter can remove chlorine, organic matter, etc.

A drinking water supply system according to a fourth aspect of the present invention, in the drinking water supply system according to any one of the first to third aspects, further includes a circulation line arranged downstream of the water purification device to supply purified water to a supply destination pipeline.

According to the fourth aspect of the present invention, provision of the circulation line for circulating the purified water in the supply destination pipeline enables immediate supply of drinking water to the supply destination pipeline.

A drinking water supply system according to a fifth aspect of the present invention, in the drinking water supply system according to the fourth aspect, further includes a purification tank that stores therein the purified water, wherein the circulation line circulates the purified water between the supply destination pipeline that supplies the drinking water and the purification tank. According to the fifth aspect of the present invention, arranging the purification tank in the circulation line for storing water can deal with sudden fluctuation of drinking water flow amount.

A drinking water supply system according to a sixth aspect of the present invention, in the drinking water supply system according to the fourth or fifth aspect, further includes a second water-quality detecting device that detects water quality of water flowing through the circulation line; and a monitoring device that maintains the water quality at a prescribed level. According to the sixth aspect of the present invention, microorganisms, rust, etc. can be removed from the drinking water and the water quality can be maintained at the prescribed level.

A drinking water supply system according to a seventh aspect of the present invention, in the drinking water supply system according to any one of the first to sixth aspects, further includes a fluorine supplying device that supplies fluorine to the water. According to the seventh aspect of the present invention, fluorine can be added to the drinking water for cavity protection.

According to the present invention, a drinking water supply system that can supply drinking water containing minerals that is good for health can be realized.

Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.

We Claim:

1. A drinking water supply system that supplies drinking water prepared from water, the drinking water supply system comprising:

a water purification device that purifies the water and includes at least one of an NF membrane and a UF membrane that filter the water.

2. The drinking water supply system according to Claim 1, further comprising:

a first water-quality detecting device that detects minerals contained in the water filtered using at least one of the NF membrane and the UF membrane; and

a mineral supplying device that supplies minerals to the water based on detection result obtained at the first water-quality detecting device.

3. The drinking water supply system according to Claim 1 or 2, further comprising an active carbon filter arranged upstream of at least one of the NF membrane and the UF membrane.

4. The drinking water supply system according to any one of Claims 1 to 3, further comprising a circulation line arranged downstream of the water purification device to supply purified water to a supply destination pipeline.

5. The drinking water supply system according to Claim 4, further comprising a purification tank that stores therein the purified water, wherein

the circulation line circulates the purified water between the supply destination pipeline that supplies the drinking water and the purification tank.

6. The drinking water supply system according to Claim 4 or 5, further comprising:
a second water-quality detecting device that detects water quality of water flowing through the circulation line; and

a controlling device that provides a control to maintain the water quality at a prescribed level.

7. The drinking water supply system according to any one of Claims 1 to 6, further comprising a fluorine

supplying device that supplies fluorine to the water.