Wastewater treatment system and wastewater treatment method

Abstract

To provide a wastewater treatment device and a wastewater treatment method that can suppress clogging of a reverse osmosis membrane and reduce the amount of water taken in and the amount of water discharged.SOLUTION: There is provided a wastewater treatment system including: biological treatment means for biologically treating domestic wastewater; a raw water tank for storing the biologically treated wastewater, which is a raw water tank including first circulation means for transferring raw water from the raw water tank to the biological treatment means, and second circulation means for sterilizing the raw water from the raw water tank by first sterilization means and returning the sterilized raw water to the raw water tank; and membrane treatment means for separating the raw water in the raw water tank into concentrated water and permeated water.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wastewater treatment system and a wastewater treatment method.

Background Art

[0002] As interest in global environmental issues grows, off-grid houses (buildings designed to be able to independently secure life lines necessary for life, such as electricity, gas, and water supply, without relying on public infrastructure) that minimize the burden on the natural environment have attracted attention. The electricity used in off-grid houses utilizes natural energy, and the water uses natural-derived water such as well water, river water, and rainwater. However, in areas where there is no sewage system and it is difficult to take in and discharge water from wells, etc., it is impossible to use water that is essential for life, and as a result, people cannot live. Therefore, a mechanism that can achieve water self-sufficiency regardless of the conditions of the land, such as the availability of water intake and drainage, is required.

[0003] In Patent Document 1, assuming a self-circulating toilet, a biological treatment tank that treats wastewater discharged from consumers with microorganisms and a circulating wastewater treatment unit including an ozone generator for the purpose of deodorization, decolorization, and sterilization are proposed. In Patent Document 2, in a water treatment method for desalinating seawater by reverse osmosis membrane (hereinafter also referred to as "RO membrane") treatment, organic substances such as extracellular polymeric particles that cannot be completely removed by solid-liquid separation means contained in seawater are removed by a foam separation device, and the concentrated water separated by the reverse osmosis membrane is used for defoaming the foam generated by the foam separation device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a water treatment apparatus for recycling domestic wastewater such as washbasin water, shower water, kitchen water, washing machine water, etc., the ozone generator described in Patent Document 1 for deodorizing and sterilizing excrement and urine is over-specification, and the method described in Patent Document 2 regarding seawater desalination is also unnecessary for treating domestic wastewater that does not contain organic substances such as extracellular secretion polymer particles.

[0006] Even for raw water obtained by biologically treating domestic wastewater that does not contain excrement and urine, the organic substances contained in the domestic wastewater are not completely removed, and the microorganisms themselves in the biological treatment facility may remain in the raw water as SS (Suspended Solids: suspended substances of 2 mm or less that cause turbidity of water quality). The inventors faced the problem that the water quality deteriorates due to the inorganic substances contained in the raw water and the SS accumulated at the bottom of the raw water tank during the long-term continuous recycling of domestic wastewater. In addition, the growth of general bacteria in the raw water stored in the raw water tank is recognized, resulting in the deterioration of water quality and the generation of foul odors. There is also a problem that when the raw water with deteriorated water quality is treated by a reverse osmosis membrane, the amount of pure water produced decreases due to the blockage of the reverse osmosis membrane. Under such circumstances, a wastewater treatment system that suppresses the accumulation of inorganic substances and SS and the generation of miscellaneous bacteria in the raw water passed through the reverse osmosis membrane and does not impose a load on the reverse osmosis membrane is desired.

Means for Solving the Problems

[0007] The present invention provides a wastewater treatment system and a wastewater treatment method that can suppress the blockage of a reverse osmosis membrane and reduce the intake and discharge amounts of water.

[0008] That is, the present invention is (1) A wastewater treatment system comprising: biological treatment means for performing biological treatment on domestic wastewater; a raw water tank for storing the biologically treated water; first circulation means for transferring the raw water in the raw water tank to the biological treatment means; and second circulation means for sterilizing the raw water in the raw water tank by means of a first sterilization means and returning it to the raw water tank, wherein the first sterilization means is ultraviolet irradiation; and membrane treatment means for separating the raw water in the raw water tank into concentrated water and permeated water. (2) The wastewater treatment system according to (1), further comprising: a permeated water tank for storing the permeated water separated by the membrane treatment means; second sterilization means for performing sterilization treatment on the permeated water in the permeated water tank; and a sterilized water tank for storing the sterilized water obtained by the sterilization treatment by the second sterilization means. (3) In the second sterilization means, the sterilization treatment is to make the sterilizing agent in the sterilizing agent tank contained in the permeated water. A flow meter for measuring the flow rate of the permeated water is arranged after the membrane treatment means, the measured value of the flow meter is taken into a control device, and the flow rate of a pump for pumping the sterilizing agent from the sterilizing agent tank is automatically controlled based on the measured value of the flow meter. The wastewater treatment system according to (2). (4) The wastewater treatment system according to (2), wherein the second sterilization means includes at least one selected from the group consisting of sodium hypochlorite treatment, chlorine treatment, bromine treatment, ultraviolet irradiation, ozone treatment, and metal ion treatment. (5) The wastewater treatment system according to (3), wherein the sterilizing agent includes at least one selected from the group consisting of sodium hypochlorite solution, chlorine water, bromine water, and metal ion water. (6) Further, a rainwater storage tank for storing rainwater, a water supply pump for transferring the rainwater in the rainwater storage tank to the biological treatment means, a solenoid valve for controlling the drainage of the raw water in the raw water tank, an electric conductivity meter for measuring the electric conductivity of any one selected from the group consisting of the raw water, the concentrated water, and the permeated water, and a control device capable of controlling the water supply pump and the solenoid valve according to the electric conductivity measured by the electric conductivity meter. The control device opens the solenoid valve to start the drainage of the raw water when the measured value of the electric conductivity meter exceeds the threshold value, and at the same time operates the water supply pump to start the transfer of the rainwater to the biological treatment means. When the measured value of the electric conductivity meter is below the threshold value, the solenoid valve is closed to stop the drainage of the raw water, and at the same time the water supply pump is stopped to stop the transfer of the rainwater to the biological treatment means. The wastewater treatment system according to (1) or (2), characterized in that. (7) Further, an ion exchange resin device, a water supply pump for transferring the raw water in the raw water tank to the ion exchange resin device, an electric conductivity meter for measuring the electric conductivity of any one selected from the group consisting of the raw water, the concentrated water, and the permeated water, and a control device capable of controlling the water supply pump according to the electric conductivity measured by the electric conductivity meter. The control device operates the water supply pump to start the transfer of the raw water to the ion exchange resin device when the measured value of the electric conductivity meter exceeds the threshold value, and stops the water supply pump to stop the transfer of the raw water to the ion exchange resin device when the measured value of the electric conductivity meter is below the threshold value. The wastewater treatment system according to (1) or (2), characterized in that. (8) Further, an ion exchange resin device, a conductivity meter for measuring the conductivity of any one selected from the group consisting of the raw water, the concentrated water, and the permeated water, a pipe for transferring the concentrated water to the ion exchange resin device, and a solenoid valve for controlling the switching of the pipe for transferring the concentrated water to the ion exchange resin device and the pipe for not transferring the concentrated water to the ion exchange resin device, and a control device capable of controlling the solenoid valve according to the conductivity measured by the conductivity meter, wherein the control device operates the solenoid valve to start the transfer of the concentrated water to the ion exchange resin device when the measured value of the conductivity meter exceeds a threshold value, and operates the solenoid valve to stop the transfer of the concentrated water to the ion exchange resin device when the measured value of the conductivity meter is below the threshold value. The wastewater treatment system according to (1) or (2). (9) A wastewater treatment method including a biological treatment step of performing biological treatment on domestic wastewater, a raw water storage step of storing the biologically treated biological treatment water as raw water in a raw water tank, and a membrane treatment step of separating the raw water into permeated water and concentrated water, the wastewater treatment method including a first circulation step of transferring the raw water to the biological treatment step and a second circulation step of sterilizing the raw water by a first sterilization means and transferring it to the raw water tank. is provided.

Effect of the Invention

[0009] According to the present invention, it is possible to provide a wastewater treatment system and a wastewater treatment method that can suppress the clogging of the reverse osmosis membrane, enable automation, and suppress the water intake and drainage volume in an off-grid environment.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail with reference to the drawings. Unless otherwise specified in the text, all technical terms and scientific terms used in this specification have the same meaning as those generally understood by those skilled in the technical field to which the present invention belongs. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. It should be noted that the following embodiments illustrate devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the structure, arrangement, etc. of the components as follows.

[0012] 1. Overall Configuration As shown in FIG. 1, the wastewater treatment system according to an embodiment of the present invention includes biological treatment means for biologically treating domestic wastewater discharged from a residential building, a raw water tank for storing the biologically treated water, membrane treatment means for separating the raw water supplied from the raw water tank into permeate water and concentrated water, a permeate water tank for storing the permeate water separated by the membrane treatment means, and a sterilization treatment water tank for storing the sterilized treated water after performing sterilization treatment on the permeate water in the permeate water tank. The sterilized treated water stored in the sterilization treatment water tank can be reused as domestic water in the residential building.

[0013] 2. Residential Building In the present invention, the "residential building" is a type of building or facility that provides housing or accommodation, and refers to a building designed for people to live and reside in. The residential building includes collective housing facilities such as one or more housing units or apartments, and provides facilities and equipment to support the lives of residents, such as the supply of electricity and domestic water. In the present invention, the wastewater discharged from the residential building is classified into domestic wastewater and toilet wastewater. "Domestic wastewater" is not particularly limited, but refers to wastewater from bathtubs, showers, washing machines, washbasins, kitchens, etc. "Toilet wastewater" refers to wastewater mainly containing excrement discharged from toilets. In the present invention, the combination of domestic wastewater and toilet wastewater is referred to as "domestic sewage".

[0014] 3. Biological treatment means In the present invention, the "biological treatment means" relates to methods and devices for efficiently removing or decomposing harmful substances in water. The biological treatment means can biologically decompose, convert, or remove pollutants such as organic substances, nitrogen compounds, and phosphorus compounds in water by utilizing microorganisms, enzymes, or other biological elements. The water in which harmful substances have been removed or decomposed by the biological treatment means is referred to as "biologically treated water".

[0015] 4. Raw water tank In the present invention, the "raw water tank" refers to a water tank for storing the biologically treated water treated by the biological treatment means. In the present invention, the water stored in the raw water tank is referred to as "raw water". The raw water is sent to the membrane treatment means, and impurities are further removed. Bacteria such as general bacteria grow during the storage of the raw water stored in the raw water tank, which may cause odors. Also, even though it is biologically treated raw water, organic substances are not completely removed by the biological treatment means, and microorganisms in the biological treatment means may accumulate in the raw water as SS (Suspended solids: suspended substances in water) at the bottom of the raw water tank or the like. If the water quality of the raw water deteriorates due to the growth of general bacteria and the remaining SS, the filter membrane of the membrane treatment means may be contaminated, which may interfere with stable operation. Therefore, in the present invention, the deterioration of the water quality of the raw water stored in the raw water tank is suppressed by using the following (1) first circulation means and (2) second circulation means.

[0016] (1) First circulation means In the present invention, the "first circulation means" refers to the water circulation in which the raw water in the raw water tank is transferred to the biological treatment means, the transferred raw water is treated again by the biological treatment means, and then transferred back to the raw water tank as biologically treated water. Whether to transfer the raw water in the raw water tank to the biological treatment means is determined by the quality of the raw water. The "quality of the raw water" refers to the degree of impurities contained in the raw water, and "poor quality of the raw water" means that the impurities contained in the raw water are relatively high. Examples of the impurities contained in the raw water include inorganic substances and silicic acid. The inorganic substances are not particularly limited, and examples thereof include calcium, sodium, potassium, and magnesium. The most important thing to note when performing the subsequent reverse osmosis membrane (hereinafter also referred to as "RO membrane") is the accumulation of inorganic substances, and the accumulation of inorganic substances contained in the raw water causes a decrease in the treatment efficiency of the reverse osmosis membrane. The degree of the quality of the raw water can be measured by the difference between the electrical conductivity of the raw water before passing through the membrane treatment means described later and the electrical conductivity of the permeated water after passing through the membrane treatment means. The first circulation means needs to be carried out regularly by comprehensively considering the difference in the measured value of the electrical conductivity, the total amount of water in the biological treatment means and the raw water tank, the amount of domestic wastewater flowing into the biological treatment means, etc. The implementation of the first circulation means may be manually switched according to the judgment of the administrator, or may be set to automatically switch based on the difference in the measured value of the electrical conductivity, etc. The raw water pumped up from the raw water tank may be discharged outside the system in addition to being transferred to the biological treatment means by the first circulation means.

[0017] (2) Second circulation means In the present invention, the "second circulation means" refers to the water circulation in which raw water pumped from the raw water tank is sterilized by the first sterilization means and the sterilized raw water is transferred back to the raw water tank. Whether or not to sterilize the raw water in the raw water tank by the second circulation means is determined by the water level in the raw water tank. The water level in the raw water tank is not particularly limited, but using a water level gauge can be mentioned. The transfer means is not particularly limited, but a method of pumping up the raw water containing proliferated general bacteria and the like with a pump and returning it to the raw water tank can be considered. The "first sterilization means" is not particularly limited, but examples include ultraviolet irradiation, ultrasonic treatment, ozone treatment, etc. In the present invention, ultraviolet irradiation is preferred as the first sterilization means. This is because the raw water in the raw water tank is membrane-filtered by the membrane treatment means, and ultraviolet irradiation will not have an adverse effect on the treatment membrane of the membrane treatment means.

[0018] 5. Membrane treatment means In the present invention, the "membrane treatment means" refers to means for separating the water to be treated into permeated water and concentrated water by a semipermeable membrane. In one embodiment of the present invention, the raw water pumped up by a pump or the like is separated into permeated water and concentrated water by the membrane treatment means. The semipermeable membrane used in the membrane treatment means of the present invention is not particularly limited as long as it can remove impurities contained in the raw water, and examples include reverse osmosis membranes, nanofiltration membranes (also referred to as "nanofiltration membranes", "NF membranes"), microfiltration membranes (also referred to as "microfiltration membranes", "MF membranes"), ultrafiltration membranes (also referred to as "ultrafiltration membranes", "UF membranes"), etc. From the perspective of recycling for domestic use, it is preferable to use a reverse osmosis membrane. The semipermeable membrane may be used alone, or the same type or different types of semipermeable membranes may be combined and used in multiple stages.

[0019] Before the raw water is sent to the semipermeable membrane, a pre-filtering device may be used. By using a pre-filtering device, particles and suspended substances in the water can be preliminarily removed, clogging of the semipermeable membrane can be reduced, and the maintenance interval can be extended. Also, by removing organisms such as microorganisms, viruses, and algae, the growth of microorganisms and the like and the deterioration of the membrane in the semipermeable membrane can be suppressed. The pre-filtering device is not particularly limited, but examples include activated carbon filters, sand filtration, particle filters, etc.

[0020] In the present invention, the water that has permeated through the semipermeable membrane is referred to as "permeated water", and the water that has not permeated through the semipermeable membrane is referred to as "concentrated water". The permeated water is stored in a permeate water tank, and the concentrated water is transferred back to the raw water tank. The transfer of the concentrated water may be sent back to the raw water tank, may be sent to the pipe that transfers from the raw water tank to the membrane treatment means, or may be discharged outside the system.

[0021] 6. Permeate water tank In the present invention, the "permeate water tank" refers to a water tank that stores the permeated water separated by the membrane treatment means. The water stored in the permeate water tank is pure water from which impurities have been removed by the membrane treatment means. However, if it is stored for a long time, there is a risk of the growth of general bacteria, so sterilization is necessary before it is used as domestic water. The transfer means of the permeated water is not particularly limited, but an example is a method of pumping up the permeated water in the permeate water tank with a pump. The permeated water pumped up from the permeate water tank is sterilized by the "second sterilization means" and transferred to the sterilization treatment water tank as sterilized treated water. The second sterilization means is not particularly limited, but examples include treatment with a bactericide, ultraviolet irradiation, ozonation, etc. The bactericide is not particularly limited, but examples include sodium hypochlorite solution, chlorine water, bromine water, and metal ion water. In the present invention, the second sterilization means is preferably sodium hypochlorite treatment or chlorine treatment. Also, in the present invention, the bactericide is preferably sodium hypochlorite solution or chlorine water. Sodium hypochlorite and chlorine are generally used to sterilize microorganisms in water. Sodium hypochlorite solution can be made by diluting a chlorine-based bleaching agent. Chlorine water can be made by adding chlorine gas or chlorine compounds (such as chlorine gas, chlorine salts, chlorine dioxins, etc.) to water. The amount of sodium hypochlorite or chlorine added to the permeated water is 0.01 ppm to 0.3 ppm, preferably 0.03 ppm to 0.2 ppm, more preferably 0.05 ppm to 0.15 ppm with respect to the permeated water, and a sufficient sterilization effect can be expected, and the impact on the human body can be reduced when used as domestic water.

[0022] 7. Sterilization treatment water tank In the present invention, the "sterilization treatment water tank" refers to a water tank that stores the permeated water sterilized by the second sterilization means as sterilized treatment water. In the present invention, the water transferred from the sterilization treatment water tank is referred to as "domestic water". The domestic water is transferred to the residential building and can be used as domestic water for toilet flushing, bathing, showering, washing, dishwashing, etc. Also, the domestic water can be used as drinking water. The transfer means of the domestic water is not particularly limited, and an example is a method of pumping up the domestic water in the sterilization treatment water tank with a water supply pump. The domestic water may be transferred directly to the residential building, or may be transferred to a water heater and supplied to the residential building as hot water.

[0023] 8. Rainwater storage tank In the present invention, the "rainwater storage tank" refers to a water tank that stores rainwater. In places where it is difficult to obtain water from a water supply or a well, obtaining water from rainwater is also one of the options. The rainwater may be collected from the rain gutters of the building. The rainwater may be sent to the raw water tank or may be sent to the domestic wastewater treatment tank which is a biological treatment means. By sending the rainwater to the domestic wastewater treatment tank, general bacteria and the like that have grown while the rainwater is stored in the rainwater storage tank can be removed. A drain port is provided in the raw water tank, and it can be set to automatically drain by electric control with a solenoid valve.

[0024] The opening and closing of the solenoid valve provided at the drain port can be set, for example, to automatically drain from the raw water tank by time control by determining the amount of drainage per day. At the same time, it can be set to supply the same amount of rainwater as the amount of drainage per day from the rainwater storage tank to the domestic wastewater treatment tank or the raw water tank. By performing a fixed amount of water supply and drainage every day in this way, the deterioration of the RO membrane can be suppressed.

[0025] An electrical conductivity meter is installed in the pipes through which raw water, concentrated water, and permeated water pass, and a control device capable of controlling a water supply pump and a solenoid valve according to the electrical conductivity measured by the electrical conductivity meter is used, so that water supply and drainage can be automatically controlled. When the electrical conductivity measured by the electrical conductivity meter exceeds the threshold value, the control device opens the solenoid valve provided at the drainage port, and at the same time activates the water supply pump to start the transfer of rainwater to the biological treatment means. When the electrical conductivity measured by the electrical conductivity meter is below the threshold value, the control device closes the solenoid valve provided at the drainage port, and at the same time stops the water supply pump to stop the transfer of rainwater to the biological treatment means. With this method, water can be taken only when the water quality deteriorates, so rainwater can be saved even in seasons and places with little precipitation. The threshold value of the electrical conductivity for opening the solenoid valve provided at the drainage port of the raw water tank and activating the water supply pump connected to the rainwater storage tank is not particularly limited, but is 500 to 3,000 μS / cm, preferably 800 to 2,500 μS / cm, more preferably 1,000 to 2,000 μS / cm, which can suppress the deterioration of the RO membrane and save the intake of rainwater.

[0026] 9. Ion Exchange Resin Device In the present invention, the "ion exchange resin device" refers to a container filled with ion exchange resin. The ion exchange resin is a synthetic resin having an ion exchange group, and its shape is mainly spherical with a diameter of about 1.0 mm. In addition to the spherical shape, the ion exchange resin also has fibrous and liquid forms. The ion exchange groups of the ion exchange resin are not particularly limited, and examples include strong acidic ion exchange groups, weak acidic ion exchange groups, strong basic ion exchange groups, weak basic ion exchange groups, and the like. By utilizing the difference in adsorption between the fixed ions contained in the ion exchange resin and the counter ions contained in the solution, each ion contained in the solution can be separated.

[0027] A strongly basic anion exchange group is a functional group of an anion exchange resin having a quaternary ammonium group on a crosslinked styrene skeleton. It has a strong basicity and dissociates not only in acidic solutions but also in alkaline solutions, enabling ion exchange with inorganic acids, neutral salts, weak acids, etc. Strongly basic anion exchange resins include type I with a trimethylammonium group and type II with a dimethylethanolammonium group, and they have different basicities. Type I has the highest basicity and can strongly adsorb anions, so it is used when high-purity demineralized water is desired. On the other hand, type II has a lower basicity than type I, so the quality of the obtained demineralized water is inferior, but the amount of regenerant used can be reduced. The strongly acidic ion exchange group is not particularly limited, but examples include a sulfonic acid group (-SO3H). Strongly acidic ion exchange resins are used in a wide range of fields such as water treatment for the production of pure water and soft water, purification of pharmaceuticals and foods, and catalysts. The weakly acidic ion exchange group is not particularly limited, but examples include a carboxyl group. There are two types of weakly acidic ion exchange groups: acrylic acid type and methacrylic acid type. The acrylic acid type is used for the treatment of water with high carbonate hardness, and the methacrylic acid type is used for the purification of antibiotics and amino acids, etc.

[0028] By periodically passing the raw water in the original water tank or the concentrated water separated by the reverse osmosis membrane device through the ion exchange resin device, the impurity ions contained in the raw water or the concentrated water can be removed. An electrical conductivity meter is installed in the pipes through which the raw water, concentrated water, and permeate water pass, and by using a control device capable of controlling the water supply pump and the electromagnetic valve according to the electrical conductivity measured by the electrical conductivity meter, the passage of the raw water or the concentrated water to the ion exchange resin device can be automatically controlled. When the electrical conductivity measured by the electrical conductivity meter exceeds the threshold value, the control device activates the water supply pump to start transferring the raw water to the ion exchange resin device, and when the electrical conductivity measured by the electrical conductivity meter falls below the threshold value, the control device stops the water supply pump to stop transferring the raw water to the ion exchange resin device. When the electrical conductivity measured by the electrical conductivity meter exceeds the threshold value, the control device activates the electromagnetic valve to start transferring the concentrated water to the ion exchange resin device, and when the electrical conductivity measured by the electrical conductivity meter falls below the threshold value, the control device activates the electromagnetic valve to stop transferring the concentrated water to the ion exchange resin device. With these methods, the use of the ion exchange resin can be minimized and the deterioration of the ion exchange resin can be suppressed.

Embodiment

[0029] <First Embodiment> Hereinafter, embodiments of the wastewater treatment system will be described in detail with reference to the drawings. In the drawings for explaining the embodiments, the same reference numerals are generally given to the same components, and the repeated description thereof is omitted. Note that the present invention is not limited to the following embodiments.

[0030] Figure 2 shows the first embodiment of the wastewater treatment system of the present invention. The wastewater treatment system shown in Figure 2 includes a domestic wastewater treatment tank 10 (manufactured by DAIKI AKSHIS CO., LTD., capacity 700L) into which domestic wastewater 1 from a residential building is introduced, a raw water tank 20 (manufactured by TAKUMINA CO., LTD., capacity 200L) into which the biologically treated water 2 flowing out of the domestic wastewater treatment tank 10 is introduced, a circulation pump 31 (manufactured by IWAKI CO., LTD., MD-15R) that pumps up the raw water 3 in the raw water tank 20, a pre-filter 32 and activated carbon 33 for performing pre-filtration treatment, and a permeate water tank 40 (manufactured by TAKUMINA CO., LTD., capacity 100L) into which the permeate water 4 separated by a reverse osmosis membrane device 30 (RO membrane: XLE-2549, high-pressure pump 20FHD5-04-S-V) is introduced. The permeate water 4 pumped up from the permeate water tank 40 by a circulation pump 42 (manufactured by IWAKI CO., LTD., MD-15R) and sodium hypochlorite 6 pumped up from a disinfectant tank 41 (manufactured by TAKUMINA CO., LTD., capacity 30L) by a solenoid-driven metering pump 43 (manufactured by TAKUMINA CO., LTD., CLPW-30W) are mixed to form a disinfected treated water 7 that is introduced into a disinfected treated water tank 50 (manufactured by TAKUMINA CO., LTD., capacity 200L). The domestic water 8 in the disinfected treated water tank 50 is pumped up by a pressurized water supply pump 51 (manufactured by KAWAMOTO SEISAKUSHO CO., LTD., NR205S) and reused in the residential building. The concentrated water 5 separated from the permeate water 4 by the reverse osmosis membrane device 30 is basically transferred to the raw water tank 20 through pipes 301, 303 and 304, but it is also possible to transfer it to the pipe 201 in front of the pump 31 through pipes 301 and 302 and to drain it outside the system through pipes 301, 303 and 305.

[0031] The domestic miscellaneous wastewater treatment tank 10 shown in Fig. 2 will be described in detail. The domestic miscellaneous wastewater 1 discharged from the residential building is first introduced into the impurity removal tank 101 of the domestic miscellaneous wastewater treatment tank 10. In the impurity removal tank 101, the air supplied by the blower 11 (manufactured by AEYA Air Pump Co., Ltd., AP30P) is diffused by the diffuser pipe 14, and the domestic miscellaneous wastewater 1 is stirred together with the filter material by the bubbles 17. In the impurity removal tank 101, most of the solids (suspended matters) contained in the domestic miscellaneous wastewater 1 are removed by the plastic filter material, and the organic matters contained in the domestic miscellaneous wastewater 1 are decomposed by the anaerobic microorganisms attached to the surface of the filter material. The domestic miscellaneous wastewater 1 from which solids have been removed and organic matters have been decomposed in the impurity removal tank 101 is introduced into the aerobic filter bed tank-1 (102) by the circulation pump 12 (manufactured by Iwaki Co., Ltd., MD-15R). In the aerobic filter bed tank-1 (102), the air supplied by the blower 11 (manufactured by AEYA Air Pump Co., Ltd., AP-30P) is diffused by the diffuser pipe 15, and the organic matters contained in the domestic miscellaneous wastewater 1 are decomposed by the aerobic microorganisms attached to the surface of the filter material. The aerobic filter bed tank-1 (102) and the aerobic filter bed tank-2 (103) are connected at the bottom of the tank, and the domestic miscellaneous wastewater 1 that has passed through the aerobic filter bed tank-1 (102) is introduced into the aerobic filter bed tank-2 (103). In the aerobic filter bed tank-2 (103), the air supplied by the blower 11 is diffused by the diffuser pipe 16, and the organic matters contained in the domestic miscellaneous wastewater 1 are decomposed. The sedimentation tank 104 is connected to the aerobic filter bed tank-2 (103) at the bottom of the tank, and the domestic miscellaneous wastewater 1 purified by the aerobic filter bed tank-1 (102) and the aerobic filter bed tank-2 (103) is stored. The domestic miscellaneous wastewater 1 stored in the sedimentation tank 104 is transferred to the raw water tank 20 as raw water 2 by the overflow from the sedimentation tank 104. Here, the solids contained in the sedimentation tank 104 settle to the bottom of the tank, and the settled solids are transferred to the impurity removal tank 101 by the air lift pump 13.

[0032] The circulation means of the raw water 3 shown in Fig. 2 will be described. The raw water tank 20 is provided with a pipe 201 connected to the reverse osmosis membrane device 30, a pipe 304 for returning the concentrated water 5 transferred from the reverse osmosis membrane device 30 to the raw water tank 20, a pipe 202 for transferring the raw water 3 to the second circulation means, a pipe 203 for transferring the raw water to the raw water tank by the second circulation means, and a water level gauge 24.

[0033] The raw water 3 pumped up by the pump 21 is introduced into the impurity removal tank 101 of the domestic wastewater treatment tank 10 through the pipes 202 and 204. This is an example of the first circulation means, and the suspended matter, solids, and inorganic substances contained in the raw water that have settled at the bottom of the raw water tank 20 are transferred to the domestic wastewater treatment tank 10 and are subjected to biological treatment again. Note that the raw water 3 pumped up by the pump 21 can also be drained out of the system through the pipes 202 and 205.

[0034] The raw water 3 pumped up by the pump 21 is transferred to the raw water tank 20 through the pipes 202 and 203. The pipe 203 made of a transparent material is irradiated with ultraviolet rays 23 at 6W by a UV germicidal lamp 22 (manufactured by K.K. Kankyo Technos, UV-6W unit), and the raw water 3 is sterilized by the ultraviolet rays 23 in the process of flowing through the pipe 203. In this embodiment, the pump 21 operates when the water level gauge 24 detects that the raw water 3 in the raw water tank 20 is above a certain water level. This is an example of the second circulation means, and it is possible to sterilize the general bacteria that have propagated in the raw water tank 20.

[0035] The raw water 3 pumped up from the raw water tank 20 by the pump 31 is passed through the pipes 201, and after the impurities are removed by the pre-filter 32 and the activated carbon 33, it is separated into permeated water 4 and concentrated water 5 by the reverse osmosis membrane device 30. A flow meter 34 and an electrical conductivity meter 36 are installed in the pipe 206 between the activated carbon 33 and the reverse osmosis membrane device 30. A flow meter 35 and an electrical conductivity meter 37 are installed in the pipe 306 through which the permeated water 4 that has passed through the reverse osmosis membrane device 30 is transferred to the permeated water tank 40. The permeated water 4 is stored in the permeated water tank 40. There are three routes through which the concentrated water 5 is transferred. The first is a route in which the concentrated water 5 is transferred from the pipe 301 through the pipe 302 to the pipe 201, pumped up by the pump 31, passed through the pre-filter 32 and the activated carbon 33, and then separated into permeated water 4 and concentrated water 5 again by the reverse osmosis membrane device 30. The second is a route in which it is transferred from the pipe 301 through the pipes 303 and 304 to the raw water tank 20. The third is a route in which it is drained out of the system from the pipe 301 through the pipes 303 and 305.

[0036] The permeated water 4 stored in the water tank 40 is pumped up by the pump 42 at a flow rate of 4 L / min and transferred to the sterilization treatment water tank 50 through the pipe 401. In this process, the sodium hypochlorite solution 6 pumped up from the disinfectant tank 41 by the pump 43 is mixed with the permeated water 4 to form the sterilization treatment water 7. The pump 43 is set to operate in conjunction with the pump 42 so that the sodium hypochlorite solution 6 is supplied at a flow rate such that the concentration of sodium hypochlorite contained in the sterilization treatment water 7 is 0.1 ppm (0.4 mg / L in the case of 4 L / min) with respect to the permeated water 4.

[0037] The sterilization treatment water 7 stored in the sterilization treatment water tank 50 is pumped up by the pressurized water supply pump 51 as domestic water 8 according to demand and supplied to the residential building.

[0038] <Second Embodiment> Next, the second embodiment will be described with reference to FIG. 3. In this description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 3 is a diagram showing the control of the operation of the pump 42 based on the flow rate of the permeated water 4.

[0039] As shown in FIG. 3, in the second embodiment, the flow meter 35 and the pump 43 are connected to the control device 39. Since the flow rate of the permeated water 4 transferred by the pump 42 is determined by the amount of water in the water tank 40, the flow rate of the sodium hypochlorite solution 6 to be transferred by the pump 43 is determined by the flow rate of the permeated water 4 that has permeated through the reverse osmosis membrane device 30. Since the flow rate of the permeated water 4 is determined by the transfer amount of the pump 31, in the second embodiment, the value of the flow rate of the permeated water 4 measured by the flow meter 35 is taken in, and the flow rate of the pump 43 is controlled.

[0040] By configuring as in the second embodiment, the flow rate of the sodium hypochlorite solution 6 supplied by the pump 43 can be appropriately controlled.

[0041] <Third Embodiment> Next, the third embodiment will be described with reference to FIG. 4. In this description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. FIG. 4 is a diagram showing a wastewater treatment system to which a device for automatically supplying and discharging water is added in order to alleviate the deterioration of the quality of raw water and reduce the burden of the drainage and water intake operations.

[0042] As shown in FIG. 4, in the third embodiment, the rainwater storage tank 60 is connected to the domestic wastewater treatment tank 10 via the water supply pump 61. The water supply pump 61, the electromagnetic valve 62, and the electric conductivity meter 36 are connected to the control device 63. The rainwater in the rainwater storage tank 60 is transferred to the domestic wastewater treatment tank 10 by the water supply pump 61. The amount of the raw water 3 drained through the pipe 205 is electrically controlled by a valve opened and closed by the electromagnetic valve 62. When the electric conductivity of the raw water 3 measured by the electric conductivity meter 36 exceeds a certain threshold value, the electromagnetic valve 62 is opened by the control device 63, and a certain amount of the raw water 3 is drained. Simultaneously with the opening of the electromagnetic valve 62, the water supply pump 61 is operated by the control device 63, and the supply of rainwater from the rainwater storage tank 60 to the domestic wastewater treatment tank 10 is started. When the electric conductivity of the raw water measured by the electric conductivity meter 36 falls below a certain threshold value, the electromagnetic valve 62 is closed by the control device 63, and the drainage of the raw water 3 is stopped. Simultaneously with the closing of the electromagnetic valve 62, the water supply pump 61 is stopped by the control device 63, and the supply of rainwater from the rainwater storage tank 60 to the domestic wastewater treatment tank 10 is stopped. The control of the water supply pump 61 and the electromagnetic valve 62 by the control device 63 may be performed according to the electric conductivity of the permeated water 4 measured by the electric conductivity meter 37. The control of the water supply pump 61 and the electromagnetic valve 62 by the control device 63 may be performed according to the electric conductivity of the concentrated water 5 measured by the electric conductivity meter 38. By performing the drainage of the raw water 3 and the intake of rainwater simultaneously in this way, the water supply and drainage can be automatically performed.

[0043] The electrical conductivity of the raw water 3 flowing in from the domestic wastewater treatment tank 10 is in the range of 200 to 300 μS / cm. Since the electrical conductivity of tap water is 100 to 200 μS / cm, an electrical conductivity of 200 to 300 μS / cm indicates relatively good water quality. On the other hand, by repeating the use and treatment of water, it was confirmed that within about one to one and a half months, the electrical conductivity of the raw water deteriorated to a level approximately 10 times or more, and the treated water volume of the RO membrane also dropped from 1.6 Lpm to about half, 0.8 Lpm. Therefore, as an example, the threshold value of the electrical conductivity of the raw water 3 measured by the conductivity meter 36 can be set to 1,000 μS / cm, and when a value exceeding this value is measured, the water supply and drainage can be automatically performed. By doing so, the electrical conductivity of the raw water 3 can be suppressed to about 3 to 5 times the electrical conductivity of the raw water 3 flowing in from the domestic wastewater treatment tank 10, and the reduction of the treated water volume of the RO membrane can also be prevented.

[0044] <Fourth Embodiment> Next, the fourth embodiment will be described with reference to FIG. 5. In this description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. FIG. 5 is a diagram showing a wastewater treatment system in which an ion exchange resin device for removing only impurities and the like in the concentrated water is added in order to suppress the deterioration of the raw water quality and the deterioration of the RO membrane.

[0045] As shown in FIG. 5, in the fourth embodiment, pipes 204 and 205 are provided in the raw water tank 20, and the pipes 204 and 205 are connected to the ion exchange resin device 70. A water supply pump 72 is installed in the pipe 204. The water supply pump 72 and the electrical conductivity meter 36 provided in the pipe 204 are connected to the control device 73. When the electrical conductivity of the raw water 3 measured by the electrical conductivity meter 36 exceeds a certain threshold value, the water supply pump 72 operates and the transfer of the raw water 3 to the ion exchange resin device 70 is started. When the electrical conductivity of the raw water 3 measured by the electrical conductivity meter 36 falls below a certain threshold value, the water supply pump 72 stops and the transfer of the raw water to the ion exchange resin device 70 stops. The control of the water supply pump 72 by the control device 73 may be performed according to the electrical conductivity of the permeated water 4 measured by the electrical conductivity meter 37. The control of the water supply pump 72 by the control device 73 may be performed according to the electrical conductivity of the concentrated water 5 measured by the electrical conductivity meter 38. By doing so, the use of the ion exchange resin can be minimized.

[0046] <Fifth Embodiment> Next, the fifth embodiment will be described with reference to FIG. 6. In this description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 6 is a diagram showing a wastewater treatment system in which an ion exchange resin device for removing only impurities and the like in the concentrated water is added to suppress the deterioration of the raw water quality and the deterioration of the RO membrane, and is a modification of the fourth embodiment.

[0047] As shown in FIG. 6, in the fifth embodiment, pipes 306 and 307 are provided in pipe 303, and pipes 306 and 307 are connected to the ion exchange resin device 70. A solenoid valve 74 provided in pipe 303, a solenoid valve 75 provided in pipe 306, and an electric conductivity meter 36 are connected to the control device 73. When the electric conductivity of the raw water 3 measured by the electric conductivity meter 36 exceeds a certain threshold value, the control device 73 closes the solenoid valve 74, and at the same time opens the solenoid valve 75, thereby starting the transfer of the raw water 3 to the ion exchange resin device 70. When the electric conductivity of the raw water 3 measured by the electric conductivity meter 36 is below a certain threshold value, the control device 73 opens the solenoid valve 75 and at the same time closes the solenoid valve 75, thereby transferring the raw water 3 to the raw water tank 20 via pipes 303 and 304. The control of the solenoid valve 74 and the solenoid valve 75 by the control device 73 may be performed according to the electric conductivity of the permeated water 4 measured by the electric conductivity meter 37. The control of the solenoid valve 74 and the solenoid valve 75 by the control device 73 may be performed according to the electric conductivity of the concentrated water 5 measured by the electric conductivity meter 38. By doing so, the use of the ion exchange resin can be minimized.

[0048] <Sixth Embodiment> Next, the sixth embodiment will be described with reference to FIG. 7. In this description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 7 is a diagram showing a wastewater treatment system in which an ion exchange resin device 70 for removing impurities in the concentrated water 5 is added to suppress the deterioration of the quality of the raw water 3 and the deterioration of the reverse osmosis membrane device 30, and is a modification of the fourth and fifth embodiments.

[0049] As shown in Fig. 7, in the sixth embodiment, pipes 306 and 307 are provided in pipe 303, and pipes 306 and 307 are connected to the ion exchange resin device 70. A three-way valve with a solenoid valve 76 is installed at the branch point between pipe 303 and pipe 306. When the conductivity of the concentrated water 5 measured by the conductivity meter 38 exceeds a certain threshold, the solenoid valve 76 is actuated by the control device 73, and the transfer of the concentrated water 5 to the ion exchange resin device 70 is started. When the conductivity of the concentrated water 5 measured by the conductivity meter 38 is below the threshold, the solenoid valve 76 is actuated by the control device 73, and the concentrated water 5 is transferred to the raw water tank 20 via pipes 303 and 304. The control of the solenoid valve 76 by the control device 73 may be performed according to the conductivity of the raw water 3 measured by the conductivity meter 36. The control of the solenoid valve 76 by the control device 73 may be performed according to the conductivity of the permeated water 4 measured by the conductivity meter 37. By doing so, the use of the ion exchange resin can be minimized.

Industrial Applicability

[0050] The present invention can provide a wastewater treatment apparatus and a wastewater treatment method that can suppress clogging of the reverse osmosis membrane, enable automation, and reduce the water intake and drainage volume in an off-grid environment.

Explanation of Signs

[0051] 1 Domestic wastewater 2 Biologically treated water 3 Raw water 4 Permeated water 5 Concentrated water 6 Sodium hypochlorite solution 7 Sterilized treated water 8 Domestic water 10 Domestic wastewater treatment tank 20 Raw water tank 30 Reverse osmosis membrane device 40 Permeated water tank 50 Sterilized treated water tank 60 Rainwater storage tank 70 Ion exchange resin device

Claims

1. A biological treatment means for biologically treating the domestic wastewater; A raw water tank for storing the biologically treated water, A first circulation means for transferring raw water from the raw water tank to the biological treatment means; A second circulation means for sterilizing the raw water in the raw water tank by a first sterilization means and returning the raw water to the raw water tank; Equipped with The raw water tank, wherein the first sterilization means is ultraviolet light irradiation; A membrane treatment means for separating the raw water in the raw water tank into concentrated water and permeated water; A wastewater treatment system comprising:

2. Further, a permeate tank for storing the permeate separated by the membrane treatment means; A second sterilization means for sterilizing the permeated water in the permeated water tank; A sterilization water tank for storing sterilized water sterilized by the second sterilization means; The wastewater treatment system according to claim 1 .

3. 3. The wastewater treatment system according to claim 2, wherein in the second sterilization means, the sterilization treatment is to cause a bactericide in a bactericide tank to be contained in the permeate, and a flow meter for measuring the flow rate of the permeate is disposed downstream of the membrane treatment means, the measurement value of the flow meter is input into a control device, and the flow rate of a pump for pumping the bactericide from the bactericide tank is automatically controlled based on the measurement value of the flow meter.

4. 3. The wastewater treatment system according to claim 2, wherein the second sterilization means includes at least one selected from the group consisting of sodium hypochlorite treatment, chlorine treatment, bromine treatment, ultraviolet irradiation, ozone treatment, and metal ion treatment.

5. 4. The wastewater treatment system according to claim 3, wherein the bactericide comprises at least one selected from the group consisting of sodium hypochlorite solution, chlorine water, bromine water, and metal ion water.

6. In addition, a rainwater storage tank for storing rainwater; A water supply pump that transfers the rainwater in the rainwater storage tank to the biological treatment means; an electromagnetic valve for controlling discharge of the raw water from the raw water tank; an electrical conductivity meter for measuring the electrical conductivity of any one selected from the group consisting of the raw water, the concentrated water, and the permeated water; a control device capable of controlling the water supply pump and the solenoid valve in accordance with the electrical conductivity measured by the electrical conductivity meter; Equipped with The control device includes: When the measured value of the electrical conductivity meter exceeds a threshold value, the solenoid valve is opened to start discharging the raw water, and at the same time, the water supply pump is operated to start transporting the rainwater to the biological treatment means; When the measured value of the electrical conductivity meter falls below a threshold value, the solenoid valve is closed to stop the discharge of the raw water, and at the same time, the water supply pump is stopped to stop the transfer of the rainwater to the biological treatment means.

3. The wastewater treatment system according to claim 1 or 2.

7. Further, an ion exchange resin device; a water supply pump that transfers the raw water in the raw water tank to the ion exchange resin device; an electrical conductivity meter for measuring the electrical conductivity of any one selected from the group consisting of the raw water, the concentrated water, and the permeated water; a control device capable of controlling the water supply pump in accordance with the electrical conductivity measured by the electrical conductivity meter; Equipped with The control device includes: When the measured value of the electrical conductivity meter exceeds a threshold value, the water supply pump is operated to start transferring the raw water to the ion exchange resin device; When the measured value of the electrical conductivity meter falls below a threshold value, the water supply pump is stopped to stop the transfer of the raw water to the ion exchange resin device.

3. The wastewater treatment system according to claim 1 or 2.

8. Further, an ion exchange resin device; an electrical conductivity meter for measuring the electrical conductivity of any one selected from the group consisting of the raw water, the concentrated water, and the permeated water; an electromagnetic valve for controlling switching between a pipe for transferring the concentrated water to the ion exchange resin device and a pipe for not transferring the concentrated water to the ion exchange resin device; a control device capable of controlling the solenoid valve in accordance with the electrical conductivity measured by the electrical conductivity meter; Equipped with The control device includes: When the measured value of the electrical conductivity meter exceeds a threshold value, the solenoid valve is operated to start transferring the concentrated water to the ion exchange resin device; When the measured value of the electrical conductivity meter falls below a threshold value, the solenoid valve is operated to stop the transfer of the concentrated water to the ion exchange resin device.

3. The wastewater treatment system according to claim 1 or 2.

9. A biological treatment process for biologically treating the domestic wastewater; A raw water storage step of storing the biologically treated water in a raw water tank as raw water; A membrane treatment step of separating the raw water into a permeate and a concentrate; A wastewater treatment method comprising: A first circulation step of transferring the raw water to the biological treatment step; a second circulation step of sterilizing the raw water by a first sterilization means and transferring the raw water to the raw water tank; The wastewater treatment method comprises the steps of:

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