Water treatment apparatus and water treatment method

Abstract

To provide a water treatment apparatus and a water treatment method capable of efficiently using heat of underground water and suppressing corrosion of a liquid contact part of a heat exchange part.SOLUTION: A water treatment apparatus 20A includes a pumping piping L1 for pumping up underground water in a well 10 as water to be treated W1 and a heat exchange part 1 for heat-exchanging the water to be treated W1 pumped up by the pumping piping L1, wherein a first end part of the pumping piping L1 is connected to a pumping pump 9 and a second end part of the pumping piping L1 is directly connected to the heat exchange part 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water treatment apparatus and a water treatment method.

Background Art

[0002] The groundwater stored in the aquifer more than 10 m below the ground surface will reach a substantially constant water temperature regardless of whether the rain in summer seeps in or the snowmelt in winter seeps in. When this is pumped up as well water, the well water has substantially the same water temperature in both summer and winter, so it feels cold in summer and warm in winter.

[0003] In Japan, although it varies by region, in the Kanto Plain, the浓尾平野 (Nobi Plain), and the Osaka Plain, the water temperature of groundwater is 15 to 18°C, and it is common that the annual temperature difference of the fluctuating water temperature is within 1°C. Of course, in shallow wells with a depth of several meters, the annual temperature difference may be affected by the outside air. Conversely, in deep wells exceeding 100 m, due to the rise of the geothermal temperature, the water temperature of groundwater gradually increases as it gets deeper from the ground surface. The reason why the water temperature of groundwater increases as it gets deeper from the ground surface is that it is affected by the magma inside the earth. Although it varies by region, it rises by about 3 degrees per 100 m.

[0004] As groundwater, deep well water and shallow well water are generally easy to use. Deep well water is groundwater at a depth of 10 to 200 m pumped from a confined aquifer. Shallow well water is groundwater at a depth of 1 to 50 m pumped from above the confined aquifer. The deeper the water temperature, the closer it is to 15 to 18°C. The well water in this article refers to the water pumped from a deep well or a shallow well.

[0005] The thermal energy of the groundwater pumped from a deep well or a shallow well can also be utilized. For example, in Patent Document 1, a heat utilization system that utilizes the heat of groundwater has been proposed. The heat utilization system of Patent Document 1 includes a pretreatment means for treating groundwater using a separation membrane, and a heat exchanger provided downstream of the pretreatment means and performing heat exchange using the groundwater treated by the pretreatment means. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-113662 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in the heat utilization system described in Patent Document 1, heat exchange is performed downstream of the membrane separation device, so the heat of the groundwater pumped from the deep well is affected by the outside air through the piping, tanks, and devices. As a result, the heat of the groundwater that could have been used for heat exchange is lost, and the efficiency of heat recovery decreases.

[0008] In addition, as described in Patent Document 1, if heat exchange is performed downstream of the membrane separation device, dissolved oxygen is likely to be mixed into the groundwater. When producing purified water for domestic use or drinking water, disinfection is often performed with oxidizing agents such as hypochlorous acid. If water containing such dissolved oxygen and oxidizing substances comes into contact with the wetted parts (especially copper piping) of the downstream heat exchange section, the corrosion reaction of the wetted parts will proceed rapidly. As a result, water leakage from the heat exchange section or equipment damage may occur.

[0009] The present invention provides a water treatment apparatus and a water treatment method that can fully utilize the heat of groundwater and suppress corrosion of the wetted parts of the heat exchange section. [Means for solving the problem]

[0010] The present invention has the following aspects. [1] A water treatment device for purifying groundwater, A pumping pipe for drawing up the aforementioned groundwater as treated water, A heat exchange unit that performs heat exchange of the water to be treated, pumped up by the aforementioned water pumping pipe, Equipped with, A water treatment apparatus in which the first end of the water lifting pipe is connected to a water lifting pump, and the second end of the water lifting pipe is directly connected to the heat exchange section. [2] A storage tank for storing the heat-exchanged water produced when the water to be treated undergoes heat exchange in the heat exchange section, A heat exchange water supply pipe is provided for passing the heat exchange water from the heat exchange section to the storage tank, The water treatment apparatus described in [1] further comprises the following: [3] The water treatment apparatus according to [2], further comprising a raw water supply pipe that leads the heat-exchanged water from the storage tank to a downstream stage of the storage tank. [4] The water treatment apparatus according to [3], wherein a raw water pump for supplying the heat-exchanged water to a downstream stage is provided in the raw water supply piping. [5] The water treatment apparatus according to any one of [2] to [4], further comprising a circulation pipe for returning a portion of the heat-exchanged water stored in the storage tank to the heat exchange section. [6] The water treatment apparatus according to [5], wherein a circulation pump for returning a portion of the heat-exchanged water stored in the storage tank to the heat exchange section is provided in the circulation piping. [7] The water treatment apparatus according to any one of [3] to [6], further comprising a branch circulation pipe that returns a portion of the heat-exchanged water flowing through the raw water supply pipe to the heat exchange section. [8] The water treatment apparatus according to [7], wherein a circulation valve is provided in the branch circulation pipe for changing the return flow rate when a portion of the heat-exchanged water flowing through the raw water supply pipe is returned to the heat exchange section.

[0011] [9] A water treatment method for purifying groundwater, The pumping process involves drawing up the aforementioned groundwater as water to be treated, A heat exchange step involves directly supplying the water to be treated to a heat exchange section that performs heat exchange of the water to be treated pumped up in the aforementioned pumping step, It has, A water treatment method in which the first end of a water pumping pipe used in the water pumping process is connected to a water pump, and the second end of the water pumping pipe is directly connected to the heat exchange section.

[10] The water treatment method according to [9], further comprising a circulation step of returning a part of the heat exchange water generated by heat exchange of the treated water in the heat exchange section to the heat exchange section, and performing heat exchange again in the heat exchange section using the returned heat exchange water.

[11] The water treatment method according to

[10] , further comprising a control step of controlling the return flow rate when returning a part of the heat exchange water to the heat exchange section based on the water temperature of the heat exchange water returned in the circulation step.

[12] A water treatment method using the water treatment apparatus according to any one of [1] to [8].

Advantages of the Invention

[0012] According to the present invention, there are provided a water treatment apparatus and a water treatment method capable of sufficiently utilizing the heat of groundwater and suppressing the corrosion of the liquid contact portion of the heat exchange section.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a schematic configuration diagram showing an example of a water treatment apparatus. [Figure 2] FIG. 2 is a schematic configuration diagram showing another example of the water treatment apparatus. [Figure 3] FIG. 3 is a schematic configuration diagram showing another example of the water treatment apparatus. [Figure 4] FIG. 4 is a schematic configuration diagram showing another example of the water treatment apparatus.

Embodiments for Carrying Out the Invention

[0014] The meanings of the terms are as follows. The "~" indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value.

[0015] The treatment target of the water treatment device and the water treatment method is groundwater. The groundwater is pumped up from, for example, deep wells and shallow wells. In the case of deep wells, for example, groundwater in the confined aquifer can be used. As the groundwater, for example, groundwater at a depth of 1 to 200 m underground can be used. The water temperature of the groundwater pumped up from deep wells and shallow wells is, for example, 15 to 18 °C.

[0016] The groundwater may contain anions such as organic matter, ammonia nitrogen, hydrogen carbonate ions, nitrate ions, sulfate ions, chloride ions; cations such as iron ions, manganese ions, calcium ions, magnesium ions; impurities such as bacteria, etc.

[0017] Hereinafter, some embodiments of the present invention will be described with reference to the drawings. However, the following description relates to representative examples, and the present invention is not limited to the following description. The dimensional ratios in the respective drawings are for convenience of explanation and are different from the actual ones. In the following drawings, the same components are denoted by the same reference numerals, and the description of overlapping components may be omitted.

[0018] [First Embodiment] (Water treatment device) First, a first embodiment regarding the water treatment device 20A illustrated in FIG. 1 will be described. The water treatment device 20A is for purifying the groundwater in the well 10. The water treatment device 20A includes a pumping pipe L1, a heat exchange unit 1, a heat exchange water supply pipe L2, a storage tank 2, a raw water supply pipe L3, a raw water pump 3, an oxidation treatment unit 4, a sand filtration treatment unit 5, an activated carbon treatment unit 6, a membrane treatment unit 7, and a disinfection treatment unit 8.

[0019] The pumping pipe L1 is for pumping up the groundwater in the well 10 as the water to be treated W1. The first end of the pumping pipe L1 is connected to a pumping pump 9 disposed in the well 10. The second end of the pumping pipe L1 is directly connected to a heat exchanger (not shown) of the heat exchange unit 1. The water pump 9 only needs to be able to pump up groundwater and is not particularly limited. Examples include submersible pumps and surface pumps.

[0020] Here, the direct connection between the second end of the pumping pipe L1 and the heat exchange section 1 means that the pumped water to be treated W1 is connected in such a way that it can be passed directly to the heat exchange section 1 without any water treatment. In such a water treatment apparatus, as illustrated in Figure 1, no processing units for various water treatments such as turbidity removal, chemical treatment, or purification are arranged between the pumping pipe L1 and the heat exchange section 1.

[0021] In one example, the length of the pumping pipe L1 extending from the ground surface of the well 10 to the inlet of the heat exchange unit 1 is preferably 100m or less, more preferably 50m or less, and even more preferably 30m or less, from the viewpoint of efficiently utilizing the heat of the groundwater. In another example, the pumping pipe L1 does not have to be exposed from the ground surface of the well 10, in which case the heat exchange unit 1 may be located below the ground surface of the well 10 (underground).

[0022] The heat exchange unit 1 is for performing heat exchange on the water to be treated W1, which is pumped up by the water pumping pipe L1. The heat exchange unit 1 may be used to heat the material to be heat exchanged, as in heating applications, or to cool the material to be heat exchanged, as in cooling applications.

[0023] As the heat exchanger (not shown) of the heat exchange section 1, for example, a groundwater cooler, an outdoor unit of an air conditioner, a heat pump, a fan coil, a chiller (cooling water circulation device), etc., can be used. As the heat exchanger, a heat exchanger used in an air conditioner is preferred. The heat exchanger performs heat exchange by utilizing the heat of the water to be treated W1.

[0024] The material of the wetted part of the heat exchange section 1 that contacts the second end of the water pumping pipe L1 is not particularly limited, but may be a metal material such as copper or stainless steel. In particular, since copper pipes are prone to corrosion, the technical significance of applying the water treatment apparatus and water treatment method of this embodiment is even greater.

[0025] When the water pump 9 is stopped for a certain period of time, the water to be treated W1 remains in the wetted part of the heat exchange section 1, and as the residence time lengthens, a higher concentration of copper dissolves than when the water pump 9 is operating. In advance, the copper concentration of the water remaining in the heat exchange section may be measured at each residence time, and a mechanism may be provided to measure the residence time during which the copper concentration does not exceed 1.0 mg / L, and to discharge the water remaining in the heat exchange section from the system if that residence time is exceeded. The standard for the copper concentration of heat-exchanged water W2 is not particularly limited as long as it does not exceed 1.0 mg / L, but it is preferably 1.0 mg / L or less, more preferably 0.5 mg / L or less, and even more preferably 0.2 mg / L or less.

[0026] In one example, a heat exchanger (not shown) can utilize the heat of the water to be treated W1 by exchanging heat between the water to be treated W1 and a heat transfer medium or refrigerant (e.g., air). After the heat of the water to be treated W1 is utilized, it becomes heat-exchanged water W2. Heat-exchanged water W2 is produced when the water to be treated W1 undergoes heat exchange in the heat exchange section 1.

[0027] The heat exchange water supply pipe L2 is for supplying heat exchange water W2 from the heat exchange section 1 to the storage tank 2. The first end of the heat exchange water supply pipe L2 is connected to the heat exchanger (not shown) of the heat exchange section 1, and the second end of the heat exchange water supply pipe L2 is connected to the storage tank 2. The storage tank 2 is for storing the heat exchange water W2.

[0028] If the material of the wetted parts of the heat exchanger 1 is copper, copper will dissolve in the treated water W1. For drinking water, it is necessary to operate the system within a range that does not exceed the drinking water quality standard of 1.0 mg / L for copper concentration. If the copper concentration of the treated water W1 and the heat-exchanged water W2 is measured in advance and there is a possibility that the copper concentration will exceed the drinking water quality standard, the modified example shown in Figure 4 is useful.

[0029] The water treatment device 1D shown in Figure 4 is equipped with a bypass pipe L6. The first end of the bypass pipe L6 is connected to the middle of the water pumping pipe L1, and the second end of the bypass pipe L6 is connected to the middle of the heat exchange water supply pipe L2. A valve V1 is provided in the water pumping pipe L1, and a valve V2 is provided in the bypass pipe L6. In addition, a drain pipe L7 is connected to the middle of the heat exchange water supply pipe L2, and a drain valve V3 is provided in the drain pipe L7.

[0030] The bypass piping L6 allows a portion of the water to be treated W1 to be supplied to the storage tank 2 without passing through the heat exchange section 1. The opening and closing of valves V1 and V2 can be changed to maintain the copper concentration of the heat-exchanged water W2 within a range not exceeding 1.0 mg / L.

[0031] Refer to Figure 1 again. The raw water supply pipe L3 is for guiding heat-exchanged water W2 from the storage tank 2 to the downstream section of the storage tank 2. The first end of the raw water supply pipe L3 is connected to the storage tank 2. The raw water supply pipe L3 is equipped with a raw water pump 3, an oxidation treatment section 4, a sand filtration treatment section 5, an activated carbon treatment section 6, a membrane treatment section 7, and a disinfection treatment section 8 in this order. The raw water pump 3 is for supplying heat-exchanged water W2 to the downstream oxidation treatment section 4, sand filtration treatment section 5, activated carbon treatment section 6, membrane treatment section 7, and disinfection treatment section 8.

[0032] The oxidation treatment unit 4 is for oxidizing the heat-exchanged water W2 using an oxidizing agent. Examples of oxidizing agents include, but are not limited to, sodium hypochlorite and other hypochlorite salts. The heat-exchanged water W2 becomes oxidized water W3 upon addition of the oxidizing agent.

[0033] The oxidation treatment unit 4 can oxidize impurities such as iron and manganese in groundwater. In the water treatment device 20A, the oxidation treatment unit 4 is installed downstream of the heat exchange unit 1 in order to suppress corrosion of the wetted parts of the heat exchange unit 1.

[0034] The sand filtration unit 5 is an example of a turbidity removal unit. The sand filtration unit 5 is a sand filtration device filled with sand as a filter medium. The sand filtration unit 5 removes turbidity components (e.g., solids) from the oxidized water W3. The oxidized water W3 that has passed through the sand filtration unit 5 becomes sand-filtered water W4.

[0035] The activated carbon treatment unit 6 is also an example of a turbidity removal treatment unit. The activated carbon treatment unit 6 is an adsorption device filled with activated carbon as a filter material. The activated carbon treatment unit 6 removes organic and inorganic substances (residual chlorine, metals, metal compounds, etc.) from the sand-filtered water W4 by adsorption. The sand-filtered water W4 that has passed through the activated carbon treatment unit 6 becomes activated carbon treated water W5.

[0036] The membrane treatment unit 7 performs membrane treatment on activated carbon treated water W5. The membrane treatment unit 7 obtains membrane-treated water W6 by treating the activated carbon treated water W5 using a separation membrane. Membrane-treated water W6 is the permeate that has passed through the separation membrane. As the separation membrane, ultrafiltration membranes (UF membranes), microfiltration membranes (MF membranes), nanofiltration membranes (NF membranes), reverse osmosis membranes (RO membranes), etc., can be used. Examples of filtration membrane forms include spiral membranes, hollow fiber membranes, tubular membranes, and flat membranes. Examples of separation membrane materials include polyamide, polysulfone, cellulose acetate, and polyacrylonitrile.

[0037] The disinfection treatment unit 8 is for disinfecting the membrane-treated water W6 using a disinfectant. Examples of disinfectants include, but are not limited to, sodium hypochlorite and other hypochlorite salts. The membrane-treated water W6 becomes treated water W7 upon the addition of the disinfectant.

[0038] (Water treatment method) Next, we will describe an example of a water treatment method using the water treatment device 20A described above. First, groundwater is pumped up from well 10 as treated water W1 (pumping process). Next, the treated water W1 pumped up in the pumping process is directly supplied to heat exchange unit 1 (heat exchange process).

[0039] Here, directly supplying the water to be treated W1 pumped up in the pumping process to the heat exchange section 1 means that the pumped water to be treated W1 is passed through the heat exchange section 1 without any water treatment. In this water treatment method, as illustrated in Figure 1, no processing units for various water treatments such as turbidity removal, chemical treatment, or purification are placed between the pumping pipe L1 and the heat exchange section 1.

[0040] The first end of the water pumping pipe L1 is connected to the water pumping pump 9 of the well 10, and the second end of the water pumping pipe L1 is directly connected to the heat exchange section 1. Therefore, heat loss of groundwater W1 (water to be treated W1) during the time it is supplied to the heat exchange section 1 can be minimized.

[0041] The temperature difference between the groundwater temperature in well 10 and the treated water W1 at the inlet of the heat exchange unit 1 is not particularly limited, but may be 2.0°C or less, 1.0°C or less, or 0.5°C or less. To reduce this temperature difference, the outer surface of the pumping pipe L1 may be wrapped with insulating material.

[0042] The dissolved oxygen concentration of the treated water W1 at the inlet of the heat exchange section 1 is preferably 2.0 mg / L or less, more preferably 1.0 mg / L or less, and even more preferably 0.5 mg / L or less. The dissolved oxygen concentration of groundwater is often almost 0 mg / L. Therefore, the lower the dissolved oxygen concentration of the treated water W1 at the inlet of the heat exchange section 1, the better.

[0043] The heat-exchanged water W2 generated in the heat exchange section 1 is temporarily stored in the storage tank 2 before flowing through the raw water supply pipe L3. The raw water pump 3 sequentially supplies the heat-exchanged water W2 to the oxidation treatment section 4, sand filtration treatment section 5, activated carbon treatment section 6, membrane treatment section 7, and disinfection treatment section 8. During this process, the heat-exchanged water W2 sequentially becomes oxidized water W3, sand filtered water W4, activated carbon treated water W5, membrane treated water W6, and treated water W7.

[0044] The uses of treated water W7 are not particularly limited, but for example, it can be used as drinking water or purified water. The water treatment device 20A can perform heat exchange in conjunction with the production of purified water or drinking water. Therefore, heat exchange will also stop when the water supply is shut off, such as at night. Such a water treatment device 20A is suitable for use in places where water supply and heating / cooling are used simultaneously, such as shopping malls.

[0045] According to the water treatment device 20A, the process from groundwater from well 10 to producing drinking water or purified water can be carried out in a single pass without branching or merging of pipes, passing through the heat exchange unit 1, oxidation unit 4, sand filtration unit 5, activated carbon unit 6, membrane unit 7, and disinfection unit 8 in that order. Therefore, a simple structure can be achieved while simultaneously producing drinking water or purified water and utilizing the heat from groundwater.

[0046] It is preferable to monitor the water temperature of the heat exchange water W2 and treated water W7 using a thermometer or the like. Water temperature monitoring may be done remotely or on-site. For example, when the heat exchange unit 1 is used for heating, an alarm may be issued when the water temperature of the heat exchange water W2 falls below the lower limit of a preset allowable temperature range. When the heat exchange unit 1 is used for cooling, an alarm may be issued when the water temperature of the heat exchange water W2 rises above the upper limit of a preset allowable temperature range. When an alarm is issued, the heat exchange can be stopped by stopping the water pump 9.

[0047] The "allowable temperature range" is the usable temperature range of the separation membrane in the membrane processing unit 7, that is, the temperature range of the membrane feed water in which the performance of the separation membrane (e.g., rejection rate) can be maintained. The permissible temperature range of the membrane processing unit 7 can be determined by measuring the relationship between the temperature of the membrane supply water and the treatment water, and the rejection rate of the membrane processing in the membrane processing unit 7. For example, the permissible temperature range of the membrane processing unit (operating temperature range of the separation membrane) can be determined from the following perspectives.

[0048] i) Correlation between membrane feed water temperature and rejection rate as specified by the separation membrane manufacturer, ii) The temperature of the membrane feed water corresponding to the rejection rate obtained according to the water quality of the treated water when applied to the water treatment apparatus, iii) A temperature set considering the practical problems when supplying treated water.

[0049] Regarding points i) and ii) mentioned above, when the water temperature is within the allowable temperature range of the membrane processing unit 7, the pore size of the separation membrane is within the appropriate range. The viscosity of the water becomes relatively low. Therefore, the water flow resistance of the separation membrane becomes low. Thus, the water to be treated can be properly treated with the membrane. On the other hand, when the water temperature of the water to be treated falls below the allowable temperature of the membrane processing unit 7, the pore size of the separation membrane becomes smaller. The viscosity of the water increases. Therefore, the water flow resistance of the separation membrane becomes higher. When the water temperature of the water to be treated exceeds the allowable temperature of the membrane processing unit 7, the pore size of the separation membrane becomes larger, and the performance in removing impurities decreases.

[0050] Regarding iii) mentioned above, considering the water quality of the treated water, it is preferable to set the tap water temperature to the upper limit so that the treated water meets the 51 standard values ​​for tap water. Also, to prevent freezing problems, it is preferable to set the lower limit of the allowable temperature range of the membrane treatment unit to 5°C.

[0051] (Mechanism of action) According to the first embodiment described above, the second end of the water pumping pipe L1 is directly connected to the heat exchange section 1. Therefore, heat loss of groundwater (water to be treated W1) during the period until the groundwater is supplied to the heat exchange section 1 can be minimized. In addition, it is easier to prevent the mixing of oxygen from the atmosphere into the water to be treated W1 during the period until the groundwater is supplied to the heat exchange section 1. As a result, the dissolved oxygen concentration of the water to be treated W1 supplied to the heat exchanger of the heat exchange section 1 can be easily reduced, thus suppressing corrosion of the wetted parts of the heat exchange section.

[0052] [Second Embodiment] The water treatment apparatus 20B shown in Figure 2 differs from the water treatment apparatus 20A shown in Figure 1 in the following two respects. The water treatment device 20B is further equipped with a circulation pipe L4 that returns a portion of the heat-exchanged water W2 stored in the storage tank 2 to the heat exchange unit 1. A circulation pump 11 is provided in the circulation piping L4 to return a portion of the heat-exchanged water W2 stored in the storage tank 2 to the heat exchange section 1. • Valve V4 is provided in the circulation piping L4.

[0053] The same mechanism of action as that of the water treatment device 20A in Figure 1 operates in the water treatment device 20B. In addition, the water treatment device 20B has the following features.

[0054] The first end of the circulation pipe L4 is immersed in the heat-exchanged water W2 in the storage tank 2, and the second end of the circulation pipe L4 is connected to the heat exchanger (not shown) of the heat exchange unit 1. According to the water treatment device 20B, heat exchange can be performed by circulating a portion of the heat-exchanged water W2 stored in the storage tank 2 between the storage tank 2 and the heat exchange unit 1. More specifically, a portion of the heat-exchanged water W2 is returned to the heat exchange unit 1, and heat exchange can be performed again in the heat exchanger (not shown) of the heat exchange unit 1 using the returned heat-exchanged water W2 (circulation process). Using the storage tank 2 as a cushion tank in this way is also useful for effectively utilizing the heat of groundwater or water to be treated W1.

[0055] According to the water treatment device 20B, heat exchange can be performed by operating the circulation pump 11 between the storage tank 2 and the heat exchange unit 1. Therefore, even if the raw water pump 3 is stopped during water outages such as at night, heat exchange can be performed at any time by operating the circulation pump 11, independently of the production operation of drinking water or purified water. Thus, the water treatment device 20B is suitable for use in hospitals, welfare centers, apartment buildings, detached houses, etc.

[0056] In the water treatment apparatus 20B, it is preferable to monitor the water temperature of the heat-exchanged water W2 and treated water W7 using a thermometer or the like, but it is also useful to control the return flow rate when a portion of the heat-exchanged water W2 is returned to the heat exchange unit 1 based on the water temperature of the returned heat-exchanged water W2' (control step).

[0057] The return flow rate of the heat-exchanged water W2' can be changed by the output of the circulation pump 11. In a preferred example, the circulation pump 11 can be used to control the return flow rate when a portion of the heat-exchanged water W2' is returned to the heat exchange unit 1 based on the water temperature of the heat-exchanged water W2' flowing through the circulation pipe L4.

[0058] For example, if the temperature of the heat-exchanged water W2' is within the allowable temperature range of the membrane processing unit 7 (for example, 5°C or higher and less than 25°C), a portion of the heat-exchanged water W2 in the storage tank 2 can be returned to the heat exchange unit 1 for heat exchange. On the other hand, if the temperature of the heat-exchanged water W2' falls outside the allowable temperature range of the membrane processing unit 7 (for example, less than 5°C or 25°C or higher), the circulation of the heat-exchanged water W2' using the storage tank 2 and the heat exchange unit 1 will not be performed. Additionally, if the temperature of the heat-exchanged water W2' matches the ambient temperature, the circulation of the heat-exchanged water W2' using the storage tank 2 and the heat exchange unit 1 will not be performed.

[0059] For example, when the heat exchange unit 1 is used for heating, it is useful to increase the return flow rate of heat exchange water W2 from the storage tank 2 by changing the output of the circulation pump 11 so that the flow rate of heat exchange water W2' increases when the water temperature of heat exchange water W2' falls below the lower limit of the preset allowable temperature range. When the heat exchange unit 1 is used for cooling, it is useful to decrease the return flow rate of heat exchange water W2 from the storage tank 2 by changing the output of the circulation pump 11 so that the flow rate of heat exchange water W2' decreases when the water temperature of heat exchange water W2 rises above the upper limit of the preset allowable temperature range.

[0060] In the water treatment device 20B, it is preferable to monitor the dissolved oxygen concentration of the heat-exchanged water W2' flowing through the circulation pipe L4. This is to manage the corrosion status of the wetted portion between the second end of the circulation pipe L4 and the heat exchanger (not shown) of the heat exchange section 1.

[0061] [Third Embodiment] The water treatment apparatus 20C shown in Figure 3 differs from the water treatment apparatus 20A shown in Figure 1 in the following two respects. The water treatment device 20C is further equipped with a branch circulation pipe L5 that returns a portion of the heat-exchanged water W2 flowing through the raw water supply pipe L3 to the heat exchange unit 1. A circulation valve V5 is provided in the branch circulation pipe L5 to change the return flow rate when a portion of the heat-exchanged water W2 flowing through the raw water supply pipe L3 is returned to the heat exchange section 1.

[0062] The same mechanism of action as that of the water treatment device 20A in Figure 1 operates in the water treatment device 20C. In addition, the water treatment device 20C has the following features.

[0063] The first end of the branch circulation pipe L5 is connected to the middle of the raw water supply pipe L3, and the second end of the branch circulation pipe L5 is connected to the heat exchanger (not shown) of the heat exchange unit 1. According to the water treatment device 20C, heat exchange can be performed by circulating a portion of the heat-exchanged water W2 flowing through the raw water supply pipe L3 in the order of heat exchange unit 1, storage tank 2, and raw water supply pipe L3. More specifically, a portion of the heat-exchanged water W2 can be returned to the heat exchange unit 1, and heat exchange can be performed again in the heat exchanger (not shown) of the heat exchange unit 1 using the returned heat-exchanged water W2 (circulation process). Using the storage tank 2 as a cushion tank in this way is also useful for effectively utilizing the heat of groundwater and water to be treated W1.

[0064] The first end of the branch circulation pipe L5 is connected to the raw water supply pipe L3 downstream of the raw water pump 3. According to the water treatment device 20C, the heat-exchanged water W2 is sequentially supplied to the oxidation treatment unit 4, sand filtration treatment unit 5, activated carbon treatment unit 6, membrane treatment unit 7, and disinfection treatment unit 8 by the action of the raw water pump 3, and a portion of the heat-exchanged water W2 can be returned to the heat exchange unit 1. Therefore, the raw water pump 3 can be used for both the production of drinking water and purified water and heat exchange in the water treatment device 20C. As a result, the number of pumps to be installed can be reduced.

[0065] In the water treatment apparatus 20C, it is preferable to monitor the water temperature of the heat-exchanged water W2 and treated water W7 using a thermometer or the like, but it is also useful to control the return flow rate when a portion of the heat-exchanged water W2 is returned to the heat exchange unit 1 based on the water temperature of the returned heat-exchanged water W2' (control step).

[0066] In the water treatment apparatus 20C, the flow rate of the returned heat-exchanged water W2' can be changed by the opening of valve V5. In a preferred example, the return flow rate when a portion of the heat-exchanged water W2' is returned to the heat exchange section 1 based on the water temperature of the heat-exchanged water W2' flowing through the branch circulation pipe L5 can be controlled using valve V5.

[0067] For example, if the temperature of the heat-exchanged water W2' is within the allowable temperature range of the membrane processing unit 7 (e.g., 5°C or higher, but less than 25°C), a portion of the heat-exchanged water W2 flowing through the raw water supply pipe L3 can be returned to the heat exchange unit 1 for heat exchange. On the other hand, if the temperature of the heat-exchanged water W2' falls outside the allowable temperature range of the membrane processing unit 7 (e.g., less than 5°C or 25°C or higher), the circulation of the heat-exchanged water W2' using the raw water supply pipe L3, heat exchange unit 1, and storage tank 2 will not be performed. Additionally, if the temperature of the heat-exchanged water W2' matches the ambient temperature, the circulation of the heat-exchanged water W2' using the raw water supply pipe L3, heat exchange unit 1, and storage tank 2 will not be performed.

[0068] For example, when the heat exchange unit 1 is used for heating, it is useful to increase the return flow rate of heat exchange water W2 from the raw water supply pipe L3 by changing the opening of valve V5 so that the flow rate of heat exchange water W2' increases when the water temperature of heat exchange water W2' falls below the lower limit of the preset allowable temperature range. When the heat exchange unit 1 is used for cooling, it is useful to decrease the return flow rate of heat exchange water W2 from the raw water supply pipe L3 by changing the opening of valve V5 so that the flow rate of heat exchange water W2' decreases when the water temperature of heat exchange water W2' rises above the upper limit of the preset allowable temperature range.

[0069] In the water treatment apparatus 20C, it is preferable to monitor the dissolved oxygen concentration of the heat-exchanged water W2' flowing through the branch circulation pipe L5. This is to manage the corrosion status of the wetted portion between the second end of the branch circulation pipe L5 and the heat exchanger (not shown) of the heat exchange section 1.

[0070] [Other embodiments] Although one embodiment has been described above with reference to an example of an embodiment, the present invention is not limited to the example of an embodiment disclosed herein and can be implemented with appropriate modifications without changing the essence of the invention. The embodiment disclosed herein can be implemented in various other forms, and various omissions, substitutions, and modifications are possible without departing from the spirit of the invention. [Industrial applicability]

[0071] The present invention provides a water treatment apparatus and a water treatment method that can fully utilize the heat of groundwater and suppress corrosion of the wetted parts of the heat exchange section. [Explanation of symbols]

[0072] 1 Heat exchange section 2 Storage tank 3. Raw water pump 4. Oxidation treatment 5. Sand filtration treatment section 6. Activated carbon treatment section 7. Membrane Processing Unit 8. Disinfection treatment area 9. Water pump 10 wells 11. Circulation pump L1 Water pumping piping L2 Heat Exchange Water Supply Piping L3 Raw Water Supply Piping L4 Circulation piping L5 Branch circulation piping

Claims

1. A water treatment device for purifying groundwater, A pumping pipe for drawing up the aforementioned groundwater as treated water, A heat exchange unit that performs heat exchange of the water to be treated, pumped up by the aforementioned pumping pipe, A storage tank for storing the heat-exchanged water produced when the water to be treated undergoes heat exchange in the heat exchange section, A heat exchange water supply pipe is provided for passing the heat exchange water from the heat exchange section to the storage tank, A circulation pipe for returning a portion of the heat exchange water stored in the storage tank to the heat exchange section, Equipped with, A water treatment apparatus in which the first end of the water lifting pipe is connected to a water lifting pump, and the second end of the water lifting pipe is directly connected to the heat exchange section.

2. A water treatment apparatus for purifying groundwater, A pumping pipe for drawing up the aforementioned groundwater as treated water, A heat exchange unit that performs heat exchange of the water to be treated, pumped up by the aforementioned pumping pipe, A storage tank for storing the heat-exchanged water produced when the water to be treated undergoes heat exchange in the heat exchange section, A heat exchange water supply pipe is provided for passing the heat exchange water from the heat exchange section to the storage tank, A raw water supply pipe is provided to guide the heat-exchanged water from the storage tank to the downstream section of the storage tank, A branch circulation pipe that returns a portion of the heat-exchanged water flowing through the raw water supply pipe to the heat exchange section, Equipped with, A water treatment apparatus in which the first end of the water lifting pipe is connected to a water lifting pump, and the second end of the water lifting pipe is directly connected to the heat exchange section.

3. The water treatment apparatus according to claim 1, further comprising a raw water supply pipe for guiding the heat-exchanged water from the storage tank to a downstream stage of the storage tank.

4. The water treatment apparatus according to claim 3, wherein a raw water pump for supplying the heat-exchanged water to a downstream stage is provided in the raw water supply piping.

5. The water treatment apparatus according to claim 1, wherein a circulation pump for returning a portion of the heat-exchanged water stored in the storage tank to the heat exchange section is provided in the circulation piping.

6. The water treatment apparatus according to claim 5, further comprising a mechanism for controlling the return flow rate when a portion of the heat exchange water is returned to the heat exchange section based on the water temperature of the heat exchange water flowing through the circulation piping, using the circulation pump.

7. The water treatment apparatus according to claim 2, wherein a circulation valve for changing the return flow rate when a portion of the heat-exchanged water flowing through the raw water supply pipe is returned to the heat exchange section is provided in the branch circulation pipe.

8. The water treatment apparatus according to claim 2, wherein a raw water pump for supplying the heat-exchanged water to a downstream stage is provided in the raw water supply piping.

9. The water treatment apparatus according to claim 7, further comprising a mechanism for controlling the return flow rate when a portion of the heat exchange water is returned to the heat exchange section based on the water temperature of the heat exchange water flowing through the branch circulation pipe, using the circulation valve.

10. A water treatment method for purifying groundwater, The pumping process involves drawing up the aforementioned groundwater as water to be treated, A heat exchange step involves directly supplying the water to be treated to a heat exchange section that performs heat exchange of the water to be treated pumped up in the aforementioned pumping step, A circulation process is performed in which a portion of the heat-exchanged water generated when the treated water undergoes heat exchange in the heat exchange section is returned to the heat exchange section, and heat exchange is performed again in the heat exchange section using the returned heat-exchanged water. It has, A water treatment method in which the first end of the water pumping piping used in the water pumping process is connected to a water pump, and the second end of the water pumping piping is directly connected to the heat exchange section.

11. The water treatment method according to claim 10, further comprising a control step of controlling the return flow rate when a portion of the heat exchange water is returned to the heat exchange unit based on the water temperature of the heat exchange water returned in the circulation step.

12. The water treatment method according to claim 11, wherein in the control step, if the water temperature of the heat-exchanged water returned in the circulation step is within the allowable temperature range of the membrane processing unit located downstream of the heat exchange unit, a portion of the heat-exchanged water is returned to the heat exchange unit and heat exchange is performed again.

13. The water treatment method according to claim 11, wherein in the control step, if the water temperature of the heat-exchanged water returned in the circulation step falls outside the allowable temperature range of the membrane processing unit located downstream of the heat exchange unit, the return of a portion of the heat-exchanged water to the heat exchange unit is stopped.

14. A water treatment method using a water treatment apparatus according to any one of claims 1 to 9.

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