JP5118722B2 - Wastewater treatment system - Google Patents

Description

  The present invention relates to a wastewater treatment system that decomposes organic matter contained in wastewater by utilizing the growth and metabolic activity of aerobic microorganisms.

  An adjustment tank, a reaction tank, a separation tank into which waste water flows in, a culture tank in which a part of the waste water extracted from the separation tank flows in and the waste water is brought into contact with humic substances, and a mixed water containing humic substances are used as culture tanks. There is a wastewater treatment system that includes a humic substance supply tank to be supplied and decomposes organic matter contained in wastewater using soil bacteria (see Patent Document 1).

  The wastewater supplied to the adjustment tank flows into the reaction tank from the adjustment tank, and further flows into the separation tank from the reaction tank. In the separation tank, the purified treated water is discharged to the outside, and the treated water is circulated to the adjustment tank and the reaction tank. A part of the treated water flows from the separation tank into the culture tank. A humic substance supply tank is connected to the culture tank via a water pipe, and mixed water containing humic substance is supplied from the humic substance supply tank. In the culture tank, the treated water and the mixed water are mixed and stirred together with the humic substances, and the soil bacteria contained in the treated water grow. The treated water and the mixed water mixed and stirred in the culture tank are circulated to the adjustment tank and the reaction tank.

JP 2002-233888 A

  The system disclosed in Patent Document 1 is based on the conditions of soil bacteria, the decomposition ability and decomposition time of soil bacteria for organic matter, the growth time of soil bacteria in wastewater, the temperature of wastewater suitable for the growth of soil bacteria, and the like. Because the amount of bacteria is different, the amount of soil bacteria contained in the treated water is not stable, and it is difficult to always have a certain amount of soil bacteria in the treated water and the mixed water circulating in the adjustment tank and the reaction tank. . In this system, if the amount of soil bacteria contained in the treated water or mixed water is small, even if the treated water or mixed water is circulated to the adjustment tank and the reaction tank, the organic matter in the adjustment tank, reaction tank, and separation tank Decomposition takes time and wastewater cannot be treated in a short time.

  In addition, this system cannot remove radioactive materials in wastewater even if radioactive materials are contained in the wastewater. Therefore, wastewater containing a small amount of radioactive materials discharged from nuclear facilities (including radioactive materials) Not suitable for treatment of highly contaminated water. Wastewater discharged from nuclear facilities such as conversion plants that concentrate and concentrate uranium ore to process nuclear fuel, enrichment plants, nuclear power plants, and reprocessing plants that convert spent nuclear fuel to plutonium It is a special wastewater containing substances that must be treated after mixing with the wastewater and diluting it, or treating the wastewater after it has been stored in the water tank for a long time to confirm the decrease in radioactivity. Takes time and effort.

  An object of the present invention is to provide a wastewater treatment system capable of treating wastewater in a short time. It is another object of the present invention to provide a wastewater treatment system that can remove radioactive substances contained in wastewater and is suitable for use in nuclear facilities.

Premise of the present invention to solve the above problems, a first container vent passage aqueous accommodating the filter medium to deposit the aerobic microorganisms on the surface, and allows water a predetermined amount of waste water discharged in nuclear power plants the Including a biological treatment process using a biological treatment apparatus having a first aeration tank capable of accommodating one container and a first air diffuser for supplying air to waste water in the first aeration tank, and aerobic in the biological treatment process This is a wastewater treatment system that decomposes organic matter contained in wastewater by utilizing the growth and metabolic activity of microorganisms.

The first aspect of the present invention is characterized in that the first container has a bottom wall, a cylindrical peripheral wall extending upward from the periphery of the bottom wall, and a top opening surrounded by a top edge of the peripheral wall, The peripheral wall has a mesh shape in which a large number of through holes penetrating the walls are formed, the bottom wall has a raised bottom hemisphere that is recessed toward the top opening, and the first aeration tank has a bottom wall and a bottom A cylindrical peripheral wall extending upward from the peripheral edge of the wall and a top opening surrounded by the top edge of the peripheral wall. In the biological treatment apparatus, when the first container is accommodated in the first aeration tank, the first container is Located at the approximate center of the 1 aeration tank, the raised bottom hemispherical bottom wall of the first container is spaced apart from the bottom wall of the first aeration tank by a predetermined dimension, and the top opening of the first container is the top of the first aeration tank Located below the opening, the first diffuser is located between the raised hemispherical bottom wall of the first container and the bottom wall of the first aeration tank. Are arranged, in the biological treatment process, the filter media is formed from a number of granular activated carbon for adsorbing organic substances have an average particle size of 1.3～2.0Mm, including ¹⁰ 7 ^{to 10 10} microorganisms per milliliter An inoculum solution and a nutrient source that promotes the growth of microorganisms are introduced into the first aeration tank together with waste water, and the microorganisms decompose organic substances while forming a biofilm on the surface of the activated carbon over time.

The present invention has the following embodiments.
(1) An example embodiment of the present invention includes a microorganism culturing step of wastewater treatment systems to produce seed solution by culturing the microorganism, the microorganism culture step, aeration accommodating the filter medium to deposit the aerobic microorganisms on the surface A microorganism having a water-permeable second container, a second aeration tank capable of storing a predetermined amount of waste water and accommodating the second container, and a second aerator for supplying air to the waste water in the second aeration tank A culture apparatus is used , and the second container has a bottom wall, a cylindrical peripheral wall extending upward from the periphery of the bottom wall, and a top opening surrounded by a top edge of the peripheral wall, and the bottom wall and the peripheral wall are The bottom wall has a raised hemispherical shape that is recessed toward the top opening, and the second aeration tank has a bottom wall and a peripheral edge of the bottom wall. A cylindrical peripheral wall extending upward from the top, and a top opening surrounded by the top edge of the peripheral wall In the microorganism culture apparatus, when the second container is accommodated in the second aeration tank, the second container is positioned at the approximate center of the second aeration tank, and the raised bottom hemispherical bottom wall of the second container is the second aeration. The top opening of the second container is located below the top opening of the second aeration tank, and the second diffuser is disposed on the bottom wall of the raised bottom hemisphere of the second container. In the microorganism culturing process , microorganisms are inoculated and nutrient sources that promote the growth of microorganisms are introduced into the second aeration tank together with waste water, and the microorganisms are passed with time. And 10 ⁷ to 10 ¹⁰ per 1 ml of waste water in the second aeration tank.
Another exemplary embodiment of (2) The present invention includes a film processing step of wastewater treatment system for filtering treated water is located downstream of the microorganism culturing step has been purified through a microbial culture process, membrane treatment steps Then, the treated water inlet, the membrane that removes fine impurities, low molecules, ions, and radioactive substances contained in the treated water, the outlet that discharges the filtered water from which the treated water has been filtered, and the remainder other than the filtered water membrane device which have a and reflux inlet to circulate a microorganism culturing step the concentrated water is used, and in film processing step, is removed radioactive material traces contained in the treated water, the microbial culture process, contained in the concentrated water Organic matter is decomposed along with wastewater.
(3) Another example of the embodiment of the present invention includes a pretreatment process in which the wastewater treatment system is disposed upstream of the microorganism culture process to remove coarse flocs contained in the wastewater. 2. Description of the Related Art A filtration device having a waste water receiving tank for storing water and a filter installed in the tank is used .
(4) In another example of the embodiment of the present invention, a wastewater treatment system is arranged downstream of the membrane treatment process, and BOD (biochemical oxygen consumption), COD (chemical oxygen demand), SS of filtered water (Floating matter), including an inspection process for inspecting the amount of radioactivity. In the inspection process, the BOD (Biochemical Oxygen Consumption), COD (Chemical Oxygen Demand), SS (Floating Substance), and Radioactivity in filtered water If below the specified value, the filtered water is discharged, and the BOD (Biochemical Oxygen Consumption), COD (Chemical Oxygen Demand), SS (Floating Matter), and Radioactivity are the predetermined values. When the above is shown, the filtered water is returned to the biological treatment process and reprocessed in the biological treatment process .
(5) In another example of the embodiment of the present invention, the packing density of the activated carbon with respect to the volume of the first and second containers is in the range of 400 to 450 g / liter .
(6) In another example of the embodiment of the present invention, the air supply amount of the first and second diffusers is in the range of 0.05 to 0.1 liter / min per liter of waste water .
(7) In another example of the embodiment of the present invention, the first and second aeration tanks are provided with heaters for heating waste water in the tanks, and the waste water temperature in the tanks is maintained at 20 to 37 ° C. by the heaters. The
(8) In another example of the embodiment of the present invention, the first and second aeration tanks are provided with a pump for circulating the waste water in the tanks, and the flow rate of the waste water in the tanks is 1.2 to 3.2 cm / It is in the range of sec .
(9) In another example of the embodiment of the present invention, the ratio of the inoculum solution introduced into the first aeration tank is 0.05% or more with respect to the unit volume of waste water in the first aeration tank .
(10) In another example of the embodiment of the present invention, the amount of waste water stored in the first aeration tank is in the range of 200 to 1000 liters .
(11) Another example of the embodiment of the present invention is cleaning wastewater, laundry wastewater, kitchen wastewater, and bathroom wastewater for equipment from which wastewater is discharged within the nuclear power plant.

According to the wastewater treatment system according to the present invention, because the nutrients for promoting the growth of inoculum solution and microorganism containing 10 ⁷ to 10 ¹⁰ aerobic microorganisms per milliliter is injected into the first aeration tank with waste water The amount of microorganisms in the wastewater in the first aeration tank is stable, and a constant amount of microorganisms can be always propagated and activated in the first aeration tank, and the organic matter contained in the wastewater in a short time using the microorganisms. Can be disassembled. In the wastewater treatment system, organic matter is adsorbed on the granular activated carbon that forms the filter medium, and microorganisms create a biofilm on the surface of the activated carbon, so the organic matter and microorganisms in the wastewater concentrate on the activated carbon, and biological regeneration by the activated carbon and microorganisms is performed. While being utilized, the organic matter can be efficiently decomposed in a short time by the synergistic effect of the organic matter adsorption action of activated carbon and the biodegradation of microorganisms against the organic matter.

The wastewater treatment system has a culture device that cultivates aerobic microorganisms to produce a seed solution, and in the culture device, the microorganisms are grown to 10 ⁷ to 10 ¹⁰ per 1 ml of waste water in the second aeration tank. inoculum solution containing microorganisms can be stably produced Rutotomoni a certain amount of from microorganisms can be incorporated into the waste water in the first aeration tank, the waste water processing capacity of the system according to the quantitative instability of microorganisms Can be prevented. In the wastewater treatment system, it is possible to test the ability to decompose microorganisms into organic matter, the decomposition time, the growth time of microorganisms, the temperature of wastewater suitable for the growth of microorganisms, etc. The optimal growth conditions for the microorganisms can be determined and applied to the operating conditions of the first aeration tank. Since the waste water treatment system can put the selected microorganisms into the first aeration tank and can operate the first aeration tank under the optimum conditions for the growth of the microorganisms, the waste water treatment capacity in the first aeration tank is always maintained. Can be held constant.

Since the waste water treatment system has a membrane device that filters the treated water purified through the first aeration tank, fine impurities contained in the treated water can be removed through the membrane device. The wastewater treatment system returns the concentrated water separated through the membrane device to the first aeration tank, and the organic matter contained in the concentrated water is decomposed together with the wastewater in the first aeration tank. Therefore, a small amount of organic matter contained in the concentrated water Can be further reduced.

In the wastewater treatment system, the packing density of activated carbon with respect to the volume of the container is in the range of 400 to 450 g / liter, so that the activated carbon does not overlap densely in the first container, and oxygen in the air is contained in all the activated carbon in the container. Sufficiently supplied, it is possible to promote the growth and activation of microorganisms on the surface of the activated carbon, and the microorganisms form a biofilm on the surface of the activated carbon in a short time.

In the wastewater treatment system, since the air supply amount of the first and second diffusers is in the range of 0.05 to 0.1 liter / min per liter of wastewater, air is supplied to all the activated carbon in the first and second containers. Since oxygen in the inside can be sufficiently supplied and the growth and activation of microorganisms on the activated carbon surface can be promoted, the microorganisms form a biofilm on the surface of the activated carbon in a short time. In the wastewater treatment system, even if a swirl flow is generated in the wastewater in the container due to the floating of air in the wastewater, the activated carbon does not collide violently in the first and second containers. In addition, the biofilm formed on the surface of the activated carbon does not peel off.

In the wastewater treatment system, the first and second aeration tanks are provided with heaters that maintain the temperature of the wastewater in the tanks at 20 to 37 ° C., and an optimum temperature environment can be created for the growth of microorganisms in the aeration tanks. from the proliferation and activation of microorganisms in the first and second aeration tank can be reliably accelerated, it can be processed wastewater shorter time by using a microorganism.

In the waste water treatment system, the first and second aeration tanks are provided with pumps for circulating the waste water in the tanks, and the flow rate of the waste water in the tanks is in the range of 1.2 to 3.2 cm / sec . The stagnation of the waste water in the second aeration tank can be prevented, and all the waste water stored in the first and second aeration tanks can be reliably brought into contact with the activated carbon, and the organic matter can be adsorbed efficiently on the activated carbon. Since the wastewater treatment system has a wastewater flow rate in the range of 1.2 to 3.2 cm / sec, even if the activated carbon collides in the first and second containers, the impact is small and the activated carbon is damaged. No, the biofilm formed on the surface of the activated carbon does not peel off.

In the wastewater treatment system, the proportion of the inoculum solution introduced into the first aeration tank is 0.05% or more with respect to the unit volume of the wastewater in the first aeration tank. The amount of microorganisms is stable, and a constant amount of microorganisms can always be reliably grown and activated in the first aeration tank.

In the wastewater treatment system, the amount of wastewater stored in the first aeration tank is in the range of 200 to 1000 liters, so the system itself can be downsized and the system can be easily installed in a limited facility. . The wastewater treatment system can be operated and stopped freely according to the need for wastewater treatment, unlike the case where the volume of wastewater stored in the first aeration tank is large, and adapts to the wastewater discharge of the facility. However, wastewater can be treated in a short time.

Since the wastewater treatment system is installed in a nuclear power plant and the membrane device filters out radioactive materials contained in the wastewater, the wastewater can be removed while quickly removing the radioactive materials contained in the wastewater discharged from the nuclear power plant. It can be processed in a short time and discharged to the outside. The wastewater treatment system eliminates the need to mix and dilute wastewater with water and store wastewater in a water tank for a long time to confirm the decrease in radioactivity. The system is used to treat wastewater immediately. since it is possible to it is possible to save the time and cost for waste water treatment in nuclear power plants.

Process block diagram of a wastewater treatment system. The block diagram of the system shown as an example. The perspective view of an aeration tank. The perspective view which isolate | separates and shows an aeration tank and a container. The perspective view of a culture apparatus. The perspective view of the culture apparatus which isolate | separates and shows an aeration tank and a container. The conceptual diagram which shows the process of the organic substance by microorganisms. The schematic diagram which shows the principle of biological reproduction.

  The details of the wastewater treatment system according to the present invention will be described below with reference to the accompanying drawings.

  1 and 2 are a process block diagram of a wastewater treatment system and a system configuration diagram shown as an example. In FIG. 2, the flow of waste water, treated water, filtered water, and concentrated water in the system is indicated by arrows. 3 and 4 are a perspective view of the first aeration tank 5 and perspective views showing the first container 4 (container) and the aeration tank 5 separately, and FIGS. 5 and 6 are shown as an example. It is the perspective view of the culture apparatus 25, and the perspective view of the culture apparatus 25 which isolate | separates and shows the 2nd container 26 and the 2nd aeration tank 27. 3 and 5, the flow of waste water stored in the aeration tanks 5 and 27 is indicated by arrows. In this embodiment, a case where the system is installed in a nuclear power plant among the nuclear facilities will be described as an example. In addition to nuclear power plants, nuclear facilities that can use this system include conversion plants, concentration plants, reprocessing plants, and nuclear laboratories. However, this system does not limit the facilities that can use the system to nuclear facilities.

  This system uses the growth and metabolic activity of aerobic microorganisms to decompose organic matter in wastewater discharged from nuclear power plants and remove radioactive substances contained in wastewater. The treated water that has been subjected to the decomposition of organic matter and the removal of radioactive substances is discharged into the ocean and rivers. This system includes a pretreatment process 100, a biological treatment process 101, a microorganism culturing process 102, a filtration treatment process 103, a membrane treatment process 104, and an inspection process 105. Wastewater to be treated at nuclear power plants is waste water for washing equipment, laundry wastewater for work clothes, kitchen wastewater, bathroom wastewater, and other miscellaneous wastewater (excluding highly contaminated water) These wastewaters contain trace amounts of radioactive substances. Organic substances contained in miscellaneous wastewater include biodegradable organic substances and persistent organic substances. Nuclear power plants that do not use this system are usually treated after mixing and diluting miscellaneous wastewater, or after confirming that the radioactivity has decreased below the specified value by storing the wastewater in a storage tank for a long time. There must be.

In the pretreatment process 100, coarse flocs such as suspended suspended matters and oils and fats contained in the wastewater are removed. The pretreatment process 100 uses a filtration device formed from a wastewater receiving tank 1 and a filter 2 installed in the tank 1. Waste water is passed through the waste water pipe 3 to the filter 2, and after the coarse floc is removed by the filter 2, the waste water is stored in the tank 1. The waste water in the tank 1 is inspected for BOD (biochemical oxygen consumption), COD (chemical oxygen demand), SS (floating matter), and radioactivity as needed. Inside the filter 2, a wire mesh and a filter filter with a filter mesh of 0.1 to 0.2 mm are installed in sequence (not shown). The wire mesh and the bag filter are cleaned or replaced according to dirt. Waste water is sent from the tank 1 to the biological treatment process 101 according to the necessity of treatment.

In the biological treatment process 101, organic substances contained in the wastewater are decomposed using the growth and metabolic activity of aerobic microorganisms. As shown in FIG. 3, the biological treatment process 101 is disposed in the aeration tank 5, a first water-permeable first container 4 (container) that houses the filter medium, a first aeration tank 5 that houses the container 4, and the aeration tank 5. A biological treatment apparatus formed from the first air diffuser 6 and the heater 7 and a pump 8 that circulates waste water in the aeration tank 5 is used . The aeration tank 5 is connected to the waste water receiving tank 1 through a water distribution pipe 9. A valve 10 is attached to the water distribution pipe 9 to flow waste water to the aeration tank 5 or stop the flow of waste water. The waste water flowing in from the tank 1 is stored in the aeration tank 5, and the organic matter contained therein is decomposed by microorganisms, and then sent to the filtration process 103 as treated water.

  As the filter medium, granular activated carbon 11 that adsorbs organic substances in wastewater is used. The activated carbon 11 is accommodated in the container 4. The container 4 includes a bottom wall 12, a cylindrical peripheral wall 13 that extends upward from the periphery of the bottom wall 12, and a top opening 14 that is surrounded by the top edge of the peripheral wall 13. In the container 4, the bottom wall 12 has a raised bottom hemisphere that is recessed toward the opening 14. The bottom wall 12 and the peripheral wall 13 have a mesh shape in which a large number of through holes 15 penetrating the walls 12 and 13 are formed. The through hole 15 has an opening diameter smaller than the minimum particle diameter of the activated carbon 11 so that the activated carbon 11 does not pass through the walls 12 and 13 and leak to the outside of the container 4. In the container 4, waste water and air can pass through the through holes 15 in the walls 12 and 13, but the activated carbon 11 cannot pass through the through holes 15 in the walls 12 and 13.

The aeration tank 5 includes a bottom wall 16, a cylindrical peripheral wall 17 extending upward from the periphery of the bottom wall 16, and a top opening 18 surrounded by the top edge of the peripheral wall 17. The aeration tank 5 can accommodate the entire container 4. The peripheral wall 17 of the aeration tank 5 is formed with inlets 19 and 20 for waste water and concentrated water described later, and an outlet 21 for discharging treated water. When the container 4 is accommodated in the aeration tank 5, the container 4 is positioned substantially at the center of the aeration tank 5, and the raised bottom hemispherical bottom wall 12 of the container 4 is spaced apart from the bottom wall 16 of the aeration tank 5 by a predetermined dimension, The opening 14 of the container 4 is located below the opening 18 of the aeration tank 5. A space 22 is formed between the peripheral wall 13 and the peripheral wall 17. When waste water flows into the aeration tank 5, the entire container 4 is immersed in the waste water. The air diffuser 6 is disposed between the raised bottom hemispherical bottom wall 12 of the container 4 and the bottom wall 16 of the aeration tank 5. A blower (not shown) is connected to the air diffuser 6. The heater 7 is disposed on the bottom wall 16 of the aeration tank 5. A water supply pipe 23 extending from the pump 8 is connected to the bottom wall 16 and the peripheral wall 17 of the aeration tank 5.

In the biological treatment process 101, an inoculum solution containing 10 ⁷ to 10 ¹⁰ microorganisms per milliliter and a nutrient source that promotes the growth of the microorganisms are introduced into the aeration tank 5. In the biological treatment process 101, air 24 is supplied from the diffuser 6 to waste water in the aeration tank 5, the waste water in the aeration tank 5 is heated to a predetermined temperature by the heater 7, and in the aeration tank 5 by the pump 8. Wastewater circulates. The air 24 is released as bubbles from the diffuser 6 into the waste water, and floats in the waste water from the bottom wall 12 of the container 4 toward the opening 14. Waste water in the aeration tank 5 flows from the bottom wall 12 of the container 4 toward the opening 14 by the air 24 discharged from the diffuser 6 and the suction and discharge of the waste water by the pump 8, and from the opening 14 to the peripheral wall. It flows toward the bottom wall 16 of the aeration tank 5 through the space 22 between the wall 13 and the peripheral wall 17. In the container 4, the activated carbon 11 gently and repeatedly floats and sinks due to the flow of the wastewater and the rising of the air 24 in the wastewater.

  Organic substances contained in the wastewater are adsorbed by the activated carbon 11 while circulating in the aeration tank 5. The microorganisms gradually grow and activate in the wastewater while capturing organic substances and nutrients in the wastewater, and form a biofilm on the surface of the activated carbon 11 with the passage of time. The organic matter adsorbed on the activated carbon 11 is decomposed by microorganisms in the biofilm. The waste water is decomposed into microorganisms after the organic matter contained therein is converted into treated water, which is sent to the filtration process 103. The activated carbon 11 is exchanged or regenerated when its organic matter adsorption capacity is saturated.

  In the microorganism culturing step 102, an inoculum solution to be introduced into the aeration tank 5 is produced through a culture apparatus 25 for culturing microorganisms. As shown in FIG. 5, the culture apparatus 25 includes an aeration-permeable second container 26 that contains a filter medium, a second aeration tank 27 that contains the container 26, and a second air diffuser disposed in the aeration tank 27. And a pump 30 for circulating the waste water in the aeration tank 27. The aeration tank 27 is connected to the wastewater receiving tank 1 through a water distribution pipe 31. A valve 32 is attached to the water distribution pipe 31. The waste water flowing from the tank 1 is stored in the aeration tank 27. As the waste water, the same waste water treated in the aeration tank 5 is used. In the culture device 25, microorganisms grow to a predetermined amount. In the culturing step 102, the culturing apparatus 25 is used to test the ability of the microorganisms to decompose organic matter, the decomposition time, the growth time of the microorganisms, the temperature of the wastewater suitable for the growth of the microorganisms, and the like. Further, the BOD, COD, and SS of the waste water after a predetermined time has been inspected.

  For the filter medium, granular activated carbon 11 that adsorbs organic substances is used. The activated carbon 11 is accommodated in the container 26. The container 26 includes a bottom wall 33, a cylindrical peripheral wall 34 that extends upward from the periphery of the bottom wall 33, and a top opening 35 that is surrounded by the top edge of the peripheral wall 34. In the container 26, the bottom wall 33 has a raised bottom hemisphere that is recessed toward the opening 35. The bottom wall 33 and the peripheral wall 34 have a mesh shape in which a large number of through holes 36 penetrating the walls 33 and 34 are formed. The through hole 36 has an opening diameter smaller than the minimum particle diameter of the activated carbon 11 so that the activated carbon 11 does not pass through the walls 33 and 34 and leak to the outside of the container 26. In the container 26, waste water and air can pass through the through holes 36 of the walls 33 and 34, but the activated carbon 11 cannot pass through the through holes 36 of the walls 33 and 34.

The aeration tank 27 includes a bottom wall 37, a cylindrical peripheral wall 38 extending upward from the periphery of the bottom wall 37, and a top opening 39 surrounded by the top edge of the peripheral wall 38. The aeration tank 27 can accommodate the entire container 26. A wastewater inlet 40 is formed in the peripheral wall 38 of the aeration tank 27. When the container 26 is accommodated in the aeration tank 27, the container 26 is positioned substantially at the center of the aeration tank 27, and the raised bottom hemispherical bottom wall 33 of the container 26 is spaced apart from the bottom wall 37 of the aeration tank 27 by a predetermined dimension, The opening 35 of the container 26 is located below the opening 39 of the aeration tank 27. A space 41 is formed between the peripheral wall 34 and the peripheral wall 38. When the wastewater flows into the aeration tank 27, the entire container 26 is immersed in the wastewater. The diffuser 28 is disposed between the raised bottom hemispherical bottom wall 33 of the container 26 and the bottom wall 37 of the aeration tank 27. A blower (not shown) is connected to the air diffuser 28. The heater 29 is disposed on the bottom wall 37 of the aeration tank 27. A water supply pipe 42 extending from the pump 30 is connected to the bottom wall 37 and the peripheral wall 38 of the aeration tank 27.

  In the culturing step 102, seeds of microorganisms and nutrient sources that promote the growth of microorganisms are introduced into the aeration tank 27. In the culturing step 102, the bubble-like air 24 is supplied from the diffuser 28 to the waste water in the aeration tank 27, and the waste water in the aeration tank 27 is heated to a predetermined temperature by the heater 29 and at the same time by the pump 30. The waste water inside circulates. Waste water in the aeration tank 27 flows from the bottom wall 33 of the container 26 toward the opening 35 by the air 24 discharged from the diffuser 28 and the suction and discharge of the waste water by the pump 30, and from the opening 35 to the peripheral wall. The fluid flows toward the bottom wall 37 of the aeration tank 27 through the space 41 between the peripheral wall 34 and the peripheral wall 38. In the container 26, the activated carbon 11 gently and repeatedly floats and sinks due to the flow of the wastewater and the rising of the air 24 in the wastewater.

Organic substances contained in the wastewater are adsorbed by the activated carbon 11 while circulating in the aeration tank 27. Microorganisms grown from the inoculum gradually grow and activate in the wastewater while capturing organic substances and nutrient sources in the wastewater, and form a biofilm on the surface of the activated carbon 11 with the passage of time. The organic matter adsorbed on the activated carbon 11 is decomposed by microorganisms in the biofilm. In the culturing step 102, microorganisms grow to 10 ⁷ to 10 ¹⁰ per 1 ml of waste water in the aeration tank 27, and an inoculum solution containing a certain amount of microorganisms is produced. The inoculum solution produced in the culturing step 102 is put into the aeration tank 5 and used for decomposing organic substances in the wastewater.

  In addition, the culture apparatus 25 may be formed from the second aeration tank 27 and the second diffuser 28 excluding the second container 26 and the pump 30 and the activated carbon 11 accommodated in the container 26. In this case, an inoculum of microorganisms and a nutrient source that promotes the growth of microorganisms are introduced into the aeration tank 27, and bubbled air 24 is supplied from the diffuser 28 to the waste water in the aeration tank 27 to culture the microorganisms. . In the culture step 102, desalted water can be used instead of waste water.

  The containers 4 and 26 and the aeration tanks 5 and 27 are made of synthetic resin or metal. As the diffusers 6 and 28, a diffuser plate, a circular diffuser plate, a porous diffuser cylinder, or a disk diffuser can be used. As the microorganism, Bacillus subtilis (Bacillus bacteria) such as Tulee Gensis subtilis and Purmis is used. Glucose, amino acids, nucleic acids, nitrogen, potash, vitamins, chitosan, minerals, etc. are used as nutrient sources. As minerals, potassium, calcium, magnesium, sodium, silicon, phosphorus, boron, sulfur, manganese, iron, zinc, germanium, etc. are used. The kind and amount of the nutrient source to be introduced into the aeration tank 5 are appropriately determined according to the test result in the culture apparatus 25.

  The activated carbon 11 has an average particle size in the range of 1.3 to 2.0 mm. If the average particle diameter of the activated carbon 11 is less than 1.3 mm, depending on the specific gravity of the activated carbon 11, the activated carbon 11 easily rises toward the openings 14 and 35 of the containers 4 and 26 due to the flow of the waste water. In some cases, the air may leak into the aeration tanks 5 and 27 from the openings 14 and 35 of the holes 4 and 26. When the average particle size of the activated carbon 11 exceeds 2.0 mm, the activated carbon 11 stops in the containers 4 and 26 and the activated carbon 11 comes into contact with each other, and when the microorganisms form a biofilm on the surface of the activated carbon 11, activated carbon As a result of 11 being connected to each other by a biofilm, the degree of freedom is further lost. As a result, the organic matter adsorption capacity of the activated carbon 11 is lowered, and the wastewater treatment function in the aeration tanks 5 and 27 is lowered.

  The packing density of the activated carbon 11 into the containers 4 and 26 is in the range of 400 to 450 g / liter. When the packing density of the activated carbon 11 is less than 400 g / liter, the amount of the activated carbon 11 is small, and most of the organic matter in the waste water cannot be adsorbed on the activated carbon 11, and the organic matter remains in the waste water at a high concentration. Decomposition of organic substances due to biological regeneration with microorganisms becomes insufficient. When the packing density of the activated carbon 11 exceeds 450 g / liter, the activated carbon 11 settles on the bottom walls 12 and 33 of the containers 4 and 26 and closely overlaps in the containers 4 and 26. Insufficient oxygen in the air can be supplied to the surface of the activated carbon 11, and the growth and activation of microorganisms on the surface of the activated carbon 11 is insufficient. In the aeration tanks 5 and 27 in which the activated carbon 11 is accommodated in the containers 4 and 26 at the filling density, oxygen is sufficiently supplied to all the activated carbons 11 in the containers 4 and 26, and the growth and activation of microorganisms on the surface of the activated carbon 11 are performed. It can be promoted, and microorganisms form a biofilm on the surface of the activated carbon 11 in a short time.

  The air supply amount of the diffusers 6 and 28 is in the range of 0.05 to 0.1 liter / min per liter of waste water. When the air supply rate is less than 0.05 liter / min per liter of wastewater, sufficient oxygen is not supplied to the microorganisms in the wastewater, and the growth and activation of the microorganisms are insufficient, and it takes a long time to decompose organic matter. . When the air supply amount exceeds 0.1 liter / min per liter of wastewater, the swirling flow more than necessary occurs in the wastewater in the containers 4 and 26 due to the floating of the air 24 in the wastewater, and the bottom wall 12 of the containers 4 and 26 , 33 may collide violently with each other, the activated carbon 11 may be damaged, or the biofilm formed on the surface of the activated carbon 11 may be peeled off. In the aeration tanks 5 and 27 in which the air supply amount is in the above range, oxygen can be sufficiently supplied to all the activated carbons 11 in the containers 4 and 26, and the growth and activation of microorganisms on the surface of the activated carbon 11 can be promoted. Therefore, microorganisms form a biofilm on the surface of the activated carbon 11 in a short time. Furthermore, since the activated carbons 11 do not collide violently in the containers 4 and 26, the activated carbon 11 is not damaged, and the biofilm formed on the surface of the activated carbon 11 does not peel off.

  The waste water temperature in the aeration tanks 5 and 27 is maintained at 20 to 37 ° C. by the heaters 7 and 29. If the waste water temperature is less than 20 ° C. or the waste water temperature exceeds 37 ° C., the growth and activation of microorganisms become insufficient, and it takes a long time to decompose organic substances. In the aeration tanks 5 and 27 in which the wastewater temperature is maintained in the above range, the growth and activation of microorganisms are promoted under an optimum temperature environment, and wastewater can be treated in a short time using microorganisms.

  The flow rate of the wastewater in the aeration tanks 5 and 27 is in the range of 1.2 to 3.2 cm / sec. If the flow rate of the waste water is less than 1.2 cm / sec, the waste water stagnates in the aeration tanks 5 and 27, and the waste water stored in the aeration tanks 5 and 27 cannot be brought into sufficient contact with the activated carbon 11 and is included in the waste water. The organic matter to be absorbed cannot be efficiently adsorbed on the activated carbon 11. When the flow rate of the waste water exceeds 3.2 cm / sec, the activated carbons 11 collide violently due to the swirling flow generated in the containers 4 and 26 and the activated carbons 11 are damaged or the biofilm formed on the surface of the activated carbon 11 is peeled off. Resulting in. In the aeration tanks 5 and 27 in which the flow rate of the waste water is in the above range, the stagnation of the waste water in the aeration tanks 5 and 27 can be prevented, and all the waste water stored in the aeration tanks 5 and 27 is reliably brought into contact with the activated carbon 11. The organic matter can be efficiently adsorbed on the activated carbon 11. Furthermore, even if the activated carbons 11 collide with each other in the containers 4 and 26, the impact is small, the activated carbon 11 is not damaged, and the biofilm formed on the surface of the activated carbon 11 is not peeled off.

  The ratio of the inoculum solution introduced into the aeration tank 5 is 0.05% or more with respect to the unit volume of waste water flowing into the aeration tank 5. If the proportion of the inoculum solution is less than 0.05%, the amount of microorganisms per unit volume of waste water is small, the microorganisms cannot be grown in a short time, and it takes a long time to decompose organic substances in the waste water. In the aeration tank 5 in which the inoculum solution is introduced at the above-mentioned ratio, the amount of microorganisms in the wastewater in the aeration tank 5 is stable, and a constant amount of microorganisms can always be reliably grown and activated in the aeration tank 5.

  The amount of waste water stored in the aeration tank 5 is in the range of 200 to 1000 liters. If the amount of wastewater stored exceeds 1000 liters, the system itself will become large, and not only can the system be installed in a limited location within the nuclear power plant, but the system will be able to meet the needs of wastewater treatment at the nuclear power plant. Operation and shutdown cannot be performed freely, and wastewater cannot be treated in a short time while adapting to the amount of wastewater discharged from nuclear power plants.

  In the filtration process 103, the fine clock contained in the treated water is removed. The filtration process 103 is formed from three filters 43, 44, and 45 into which treated water sequentially flows. The filter 43 is connected to the aeration tank 5 through a water distribution pipe 46. A valve 47 and a water supply pump 48 for forcibly supplying treated water to the filter 43 are attached to the water distribution pipe 46.

  In the filtration processing step 103, fine clocks in the treated water are gradually removed from the filter 43 toward the filter 45. In these filters 43, 44, and 45, a hollow paper membrane filter and a porous flat membrane filter are installed (not shown). The filter 43 has a filter mesh of 15 to 30 microns, and the filter 44 has a filter mesh of 5 to 10 microns. The filter 45 uses a filter with a filter mesh of 1 to 3 microns. The treated water that has passed through the filters 43, 44, 45 is sent to the membrane treatment step 104. The filter is replaced in response to dirt.

  In the membrane treatment step 104, the treated water is divided into filtered water and concentrated water through the membrane device 49. The membrane device 49 has a membrane installed therein (not shown), removes fine impurities of 10 μm to 1 nm contained in the treated water by the membrane, and is low in the treated water by the reverse osmosis principle of the membrane. Remove molecules and ions. Furthermore, radioactive materials contained in the wastewater are removed. The membrane device 49 is formed with an inlet 50 for treated water, an outlet 51 for discharging filtered water, and a circulation port 52 for circulating concentrated water to the aeration tank 5. The membrane device 49 is connected to the filter 45 via the water distribution pipe 53. A valve 54 and a water supply pump 55 that forcibly supplies treated water to the membrane device 49 are attached to the water distribution pipe 53. The membrane device 49 is connected to the aeration tank 5 through a water distribution pipe 56. A valve 57 is attached to the water distribution pipe 56.

  As the membrane device 49, at least one of a flat membrane type module, a rotating flat membrane type module, a tubular type module, a spiral type module, and a hollow fiber type module is used. The concentrated water is sent to the aeration tank 5 through the water distribution pipe 56. In the aeration tank 5, a small amount of organic matter contained in the concentrated water is decomposed together with the waste water through the microorganisms. The filtered water is sent to the filtered water receiving tank 58.

Microfiltration membrane (MF: Micro Filtration Membrane), ultrafiltration membrane (UF: Ultra)
At least an ultrafiltration membrane and a reverse osmosis membrane are used among Filtration Membrane), Reverse Osmosis Membrane (RO), and Nano Filtration Membrane (NF). The membranes are made from cellulose acetate, polyamide, polyacrylonitrile, polysulfone, polyvinylidene fluoride, Teflon (registered trademark), and polypropylene. The membrane is replaced in response to performance degradation.

In the inspection step 105, the BOD, COD, SS, and the amount of radioactivity of the filtered water stored in the filtered water receiving tank 58 are inspected. The tank 58 is connected to the membrane device 49 via the water distribution pipe 60. A valve 61 is attached to the water distribution pipe 60. As a result of the inspection, if the BOD, COD, SS, and the amount of radioactivity of the filtered water are below predetermined values, the filtered water is discharged into the sewer or river. As a result of the inspection, if the BOD, COD, SS, and the amount of radioactivity of the filtered water show a predetermined value or more, the filtered water is returned to the tank 1 ( returned to the biological treatment process) and reprocessed in the aeration tank 5. Is done.

  FIG. 7 is a conceptual diagram showing processing of organic matter by microorganisms. As shown in FIG. 7, the biodegradable organic matter is captured by the microorganisms in the biofilm, then undergoes biodegradation of the microorganisms to become decomposition products, is decomposed into inorganic substances (carbon dioxide), and is discharged from the microorganisms. The Intermediates (organic substances) that have not been decomposed to inorganic substances are discharged from microorganisms and mixed in wastewater or adsorbed on activated carbon. If the biofilm on the surface of the activated carbon is not sufficiently formed, the microorganisms in the biofilm capture the maximum amount of organic matter, and the microorganisms are in a state of capturing the organic matter as much as free by decomposition and discharge. Then, the organic matter passes through the biofilm without being decomposed by microorganisms and is adsorbed on the activated carbon. Since activated carbon has an adsorption and desorption action on organic matter, the organic matter desorbed from the activated carbon is again captured and decomposed by microorganisms. This is called biological regeneration.

  FIG. 8 is a schematic diagram showing the principle of biological regeneration. In FIG. 8, the biodegradable organic substance 61 is indicated by a white circle, and the hardly decomposable organic substance 62 is indicated by a black circle. When the adsorption and desorption functions of the activated carbon 11 with respect to the organic matter are substantially balanced, as shown in FIG. 8A, the biodegradable organic matter 61 and the hardly degradable organic matter 62 are similarly pores of the activated carbon 11. Enter 63. As shown in FIG. 8B, the microorganism grows on the surface of the activated carbon 11 while capturing the biodegradable organic matter 61 adsorbed on the activated carbon 11, and forms a biofilm 64 on the surface of the activated carbon 11. When the microorganisms form the biofilm 64 on the surface of the activated carbon 11 and the biodegradable organic matter 61 is actively decomposed by the microorganisms, the biodegradable organic matter 61 in the liquid phase decreases as shown in FIG. Since the adsorption amount of the activated carbon 11 is governed by the equilibrium relationship, when the concentration of the biodegradable organic substance 61 in the liquid phase is decreased, it is adsorbed in the pores 63 of the activated carbon 11 as shown in FIG. The biodegradable organic substance 61 is desorbed from the activated carbon 11, and the desorbed biodegradable organic substance 61 enters the biofilm 64 and is captured and decomposed by the microorganism. By this action, the entire activated carbon adsorption seat is vacant, so that the activated carbon 11 can adsorb new organic matter as shown in FIG. Finally, as shown in FIG. 8F, the adsorption function of the activated carbon 11 is saturated in a state where the hardly decomposable organic substance 62 is adsorbed. The biodegradable organic substance 61 is decomposed by microorganisms, and the adsorption amount of the activated carbon 11 depends on the hardly decomposable organic substance 62. In the biological regeneration, the biodegradable organic matter 61 contained in the wastewater is treated with microorganisms, and the hardly degradable organic matter 62 contained in the wastewater is removed by the activated carbon 11.

  The COD in the wastewater in the aeration tank 5 was 120 mg / liter immediately after the wastewater was allowed to flow into the aeration tank 5 (elapsed time 0). The COD value after 30 minutes was 73 mg / liter, the COD value after 1 hour was 35 mg / liter, and the COD value after 2 hours was 22 mg / liter. The COD value after 3 hours was 14 mg / liter, the COD value after 6 hours was 9 mg / liter, and the COD value after 24 hours was 8 mg / liter. In the aeration tank 5, the COD in the wastewater decreased with the passage of time, and the COD in the wastewater could be significantly reduced in about 6 hours.

  This system can always grow and activate a certain amount of microorganisms in the aeration tank 5, and can decompose organic substances contained in wastewater in a short time using the microorganisms. In the system, organic substances are adsorbed on the granular activated carbon 11 forming the filter medium, and microorganisms form a biofilm on the surface of the activated carbon 11. Therefore, organic substances and microorganisms in the wastewater are concentrated on the activated carbon 11, and the organisms by the activated carbon 11 and the microorganisms. While utilizing regeneration, the organic matter can be efficiently decomposed in a short time by the synergistic effect of the organic matter adsorbing action of activated carbon and the biodegradation of microorganisms with respect to the organic matter.

Since this system can grow 10 ⁷ to ¹⁰ 10 microorganisms per milliliter of waste water in the aeration tank 27 using the culture device 25, a certain amount of microorganisms are mixed into the waste water in the aeration tank 5. It is possible to prevent a reduction in wastewater treatment capacity of the system due to microbial instability. In the system, the culturing device 25 can be used to test the ability to decompose microorganisms into organic matter, the decomposition time, the growth time of microorganisms, the temperature of wastewater suitable for the growth of microorganisms, etc. It is possible to determine the optimum growth conditions of the aeration tank 5 and apply them to the operating conditions of the aeration tank 5. The system can put the selected microorganisms into the aeration tank 5 and can operate the aeration tank 5 under the optimum conditions for the growth of microorganisms, so that the wastewater treatment capacity in the aeration tank 5 is always kept constant. Can do.

  This system can remove fine impurities contained in the treated water via the membrane device 49, and returns the concentrated water separated via the membrane device 49 to the aeration tank 5, so that the organic matter contained in the concentrated water can be obtained. Can be decomposed together with the waste water in the aeration tank 5, so that a trace amount of organic substances contained in the concentrated water can be reduced.

  This system can remove radioactive substances contained in waste water discharged from nuclear power plants through the membrane device 49, so that the waste water can be mixed with water and diluted, or the waste water can be stored in the storage tank for a long time. It saves the trouble of storing and confirming the decrease in radioactivity, and saves the time and cost for treating the wastewater at the nuclear power plant.

4 First container (container)
5 First Aeration Tank 6 First Air Diffuser 7 Heater 8 Pump 11 Granular Activated Carbon 25 Culture Device 26 Second Container 27 Second Aeration Tank 28 Second Air Diffuser 29 Heater 30 Pump 49 Membrane Device 50 Inlet 51 Outlet 52 Reflux port 64 Biofilm

Claims (12)

An aeration-permeable first container containing a filter medium for adhering aerobic microorganisms to the surface; a first aeration tank capable of storing a predetermined amount of waste water discharged from a nuclear power plant and capable of accommodating the first container; It includes a biological treatment process using biological treatment device having a first air diffuser for supplying air to the waste water of the first aeration tank, using the growth and metabolic activity of aerobic microorganisms in the biological treatment process In a wastewater treatment system that decomposes organic matter contained in the wastewater,
The first container has a bottom wall, a cylindrical peripheral wall extending upward from a peripheral edge of the bottom wall, and a top opening surrounded by a top edge of the peripheral wall, and the bottom wall and the peripheral wall are: It has a mesh shape in which a large number of through holes penetrating the walls are formed, the bottom wall has a raised bottom hemisphere that is recessed toward the top opening, and the first aeration tank has a bottom wall and the bottom A cylindrical peripheral wall extending upward from the peripheral edge of the wall, and a top opening surrounded by a top edge of the peripheral wall;
In the biological treatment apparatus, when the first container is accommodated in the first aeration tank, the first container is positioned substantially at the center of the first aeration tank, and the raised bottom hemispherical bottom wall of the first container is the first aeration tank. The top opening of the first container is located below the top opening of the first aeration tank, and the first diffuser is a hemispherical bottom wall of the first container. And the bottom wall of the first aeration tank,
In the biological treatment step, the filter medium is formed from a number of granular activated carbons having an average particle diameter of 1.3 to 2.0 mm and adsorbing the organic matter, and 10 ⁷ to 10 ¹⁰ microorganisms per milliliter. An inoculum solution containing and a nutrient source that promotes the growth of the microorganism are introduced into the first aeration tank together with the wastewater, and the microorganisms form the organic matter while forming a biofilm on the surface of the activated carbon over time. The wastewater treatment system, wherein the wastewater treatment system is decomposed. The wastewater treatment system includes a microorganism culturing step of producing the inoculum solution by culturing the microorganism, the said microorganism culturing step, the second container vent water permeability which accommodates the filter medium to deposit aerobic microorganisms on the surface And a second aeration tank capable of storing a predetermined amount of waste water and accommodating the second container, and a second aerator for supplying air to the waste water in the second aeration tank is used. And the second container has a bottom wall, a cylindrical peripheral wall extending upward from a peripheral edge of the bottom wall, and a top opening surrounded by a top edge of the peripheral wall, and the bottom wall and the peripheral wall However, the bottom wall has a raised hemispherical shape that is recessed toward the top opening, and the second aeration tank has a bottom wall, A cylindrical peripheral wall extending upward from the peripheral edge of the bottom wall A top opening surrounded by the top edge of the peripheral wall, and in the microorganism culture apparatus, when the second container is accommodated in the second aeration tank, the second container is positioned substantially at the center of the second aeration tank. The raised bottom hemispherical bottom wall of the second container is spaced apart from the bottom wall of the second aeration tank by a predetermined distance, and the top opening of the second container is located below the top opening of the second aeration tank, A second air diffuser is disposed between the raised hemispherical bottom wall of the second container and the bottom wall of the second aeration tank. In the microorganism culturing step , the microorganism seeds and the growth of the microorganisms are promoted. The nutrient source to be fed is input to the second aeration tank together with the waste water, and the microorganisms grow to 10 ⁷ to 10 ¹⁰ per 1 ml of the waste water in the second aeration tank over time. Wastewater treatment system. The wastewater treatment system includes a film processing step of filtering the treated water is arranged downstream has been purified through the microbial cultivation process of the microorganism culturing step, and in the film processing step, and the treated water inlet A membrane that removes fine impurities, low molecules, ions, and radioactive substances contained in the treated water, a discharge port that discharges filtered water obtained by filtering the treated water, and a remaining concentrated water other than the filtered water. membrane device which have a and reflux inlet to circulate the microbial cultivation process is used, in the film processing step, the radioactive substance traces contained in the treated water is removed, in the microorganism culturing step, contained in the concentrated water The wastewater treatment system according to claim 2, wherein organic matter is decomposed together with the wastewater. The wastewater treatment system includes a pretreatment step that is disposed upstream of the microorganism culturing step and removes coarse floc contained in the wastewater. In the pretreatment step, a wastewater receiving tank that stores the wastewater; and The wastewater treatment system according to claim 2 or 3, wherein a filtration device having a filter installed in the tank is used . The wastewater treatment system is disposed downstream of the membrane treatment process and inspects BOD (Biochemical Oxygen Consumption), COD (Chemical Oxygen Demand), SS (Floating Matter), and Radioactivity in the filtered water. Including an inspection process, where the BOD (Biochemical Oxygen Consumption), COD (Chemical Oxygen Demand), SS (Floating Substances), and Radioactivity in the filtered water are below a predetermined value. When the filtered water is discharged and the filtered water has a BOD (biochemical oxygen consumption), COD (chemical oxygen demand), SS (floating matter), and radioactivity exceeding a predetermined value, The wastewater treatment system according to claim 3 or 4, wherein the filtered water is returned to the biological treatment step and retreated in the biological treatment step . The wastewater treatment system according to any one of claims 2 to 5 , wherein a packing density of the activated carbon with respect to a volume of the first and second containers is in a range of 400 to 450 g / liter . The wastewater treatment system according to any one of claims 2 to 6 , wherein an air supply amount of the first and second diffusers is in a range of 0.05 to 0.1 liter / min per liter of the wastewater. The said 1st and 2nd aeration tank is equipped with the heater which heats the wastewater in these tanks, The wastewater temperature in these tanks is hold | maintained at 20-37 degreeC with the said heater, The any one of Claim 2 thru | or 7 The wastewater treatment system described in 1. Wherein the first and second aeration tank, a pump for circulating the waste water in their tank, the flow rate of the waste water in their tank is claims 2 to the range of 1.2~3.2cm / sec The wastewater treatment system according to any one of 8. Waste water according to the ratio of the inoculum solution put into the first aeration tank, any claims 1 to 9 is 0.05% or more of the unit volume of waste water of the first aeration tank Processing system. The wastewater treatment system according to any one of claims 1 to 10, wherein an amount of wastewater stored in the first aeration tank is in a range of 200 to 1000 liters . The wastewater treatment system according to any one of claims 1 to 11, wherein the wastewater is cleaning wastewater, laundry wastewater, kitchen wastewater, or bathroom wastewater for equipment discharged in the nuclear power plant .

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