JP2011230007A - Sewage treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewage treatment system capable of further reducing energy consumption by effectively utilizing methane gas generated in a biological treatment.SOLUTION: The sewage treatment system 100 includes: an acid generation reaction tank 106 generating an organic acid by decomposing organic matter included in sewage; a temperature adjustment tank 108 adjusting a temperature of the sewage after the treatment in the acid generation reaction tank; a methane generation reaction tank 110 decomposing the organic acid included in the sewage subjected to temperature adjustment to generate methane gas; a boiler 140 generating steam by combustion of the methane gas; and a heat pump 120 performing heat exchange between a refrigerant and the sewage after the treatment in the methane generation reaction tank. In the temperature adjustment in the temperature adjustment tank, heating by injecting the steam generated in the boiler and heating or cooling by the heat exchange with the refrigerant in the heat pump are utilized.

Description

  The present invention relates to a sewage treatment system for purifying sewage.

  Water discharged from factories and the like may contain organic substances that serve as nutrient sources for microorganisms. If such water (hereinafter referred to as sewage) flows into the sea, rivers, and lakes as it is, eutrophication of the water in the sea will progress and microorganisms will grow abnormally, causing phenomena such as red tide and blue sea bream. It will cause. For this reason, when flowing sewage into the sea or the like, purification treatment is performed in advance.

  Various sewage purification treatment technologies have been proposed in the past, and representative examples include biological treatments using microorganisms such as aerobic microorganisms and anaerobic microorganisms, chemical treatments utilizing chemical reactions, There are physical treatments using precipitation aggregation and filtration. Among them, for example, as a purification treatment technique using biological treatment, Patent Document 1 discloses an organic acid generator that anaerobically fertilizes sludge to generate an organic acid, and an organic acid obtained by the organic acid generator. A wastewater treatment facility including a biological treatment tank that biologically treats wastewater using a slag is disclosed. According to Patent Document 1, since the temperature adjusting means is provided in the organic acid generator, it is possible to improve the production rate of the organic acid serving as the organic source in the biological treatment method. In addition, the temperature adjusting means has a heat pump, and the heat pump uses the heat obtained from the treated water to heat and cool the sludge, so that the heat energy of the treated water can be effectively used for the temperature adjustment. Energy savings.

JP 2007-260604 A

  According to the above-mentioned Patent Document 1, although energy can be saved, there is room for further improvement. Specifically, in Patent Document 1, since sludge contains not only acid producing bacteria but also methanogenic bacteria, it is described that the organic acid generated in the reaction in the acid fermenter is changed to methane gas. Yes. Then, in order to suppress the change to the methane gas of an organic acid, in patent document 1, it adjusts so that the temperature of the sludge in an acid fermentation layer may be 18-23 degreeC.

  However, as a practical matter, even if the temperature is adjusted to the above temperature range, the change to methane gas cannot be completely suppressed, and methane gas is generated although the amount is small. On the other hand, this methane gas is a main component of natural gas and is a useful energy source. And depending on the component contained in sewage, generation | occurrence | production of a large amount of methane gas can be anticipated. However, in Patent Document 1, no consideration is given to its utilization. Therefore, there is a problem in terms of effective utilization of methane gas.

  In view of such problems, an object of the present invention is to provide a sewage treatment system capable of further reducing energy consumption by effectively utilizing methane gas generated in biological treatment.

  In order to solve the above problems, a typical configuration of a sewage treatment system according to the present invention is a sewage treatment system that purifies sewage containing organic matter, and decomposes the organic matter contained in the sewage to remove the organic acid. Producing acid generation reaction tank, temperature adjusting tank for adjusting the temperature of treated sewage in the acid generating reaction tank, and generating methane gas by decomposing organic acid contained in sewage whose temperature is adjusted in the temperature adjusting tank In the temperature adjustment in the temperature adjustment tank, a methane generation reaction tank, a boiler that generates steam by burning methane gas, and a heat pump that exchanges heat between sewage and refrigerant after treatment in the methane generation reaction tank are provided. , Using heating by injecting steam generated in a boiler and heating or cooling by heat exchange with a refrigerant in a heat pump

  According to the above configuration, not only temperature adjustment by heat exchange in the heat pump but also temperature adjustment of sewage in the temperature adjustment tank using the heat of steam generated by burning methane gas generated in biological treatment in a boiler. Is possible. In other words, the temperature can be adjusted with the methane gas generated from the sewage, and the amount of heat that is insufficient with the methane gas can be compensated by the heat pump using the sewage as a heat source. Therefore, it is possible to effectively use the energy of methane gas and consequently the entire system, and it is possible to further reduce the energy required for adjusting the temperature of sewage.

  The temperature adjustment tank may be adjusted so that the temperature of the sewage falls within a range of 25 ° C to 37 ° C. Thereby, generation | occurrence | production of methane gas can be accelerated | stimulated suitably. In addition, when the temperature of sewage will be less than 25 degreeC, the activity of methanogen will become inactive and the production | generation efficiency of methane gas will fall. If the temperature of the sewage exceeds 40 ° C., the methanogen may be killed, so it is preferable to control the temperature to about 37 ° C. or less in view of safety.

  The sewage treatment system further includes a second boiler that burns fossil fuel to generate steam, and the temperature adjustment in the temperature adjustment tank may also utilize heating by injecting steam generated in the second boiler. .

  This makes it possible to adjust the temperature of the sewage in the temperature adjustment tank even if, for example, the heat obtained by heat exchange in the heat pump and the heat of the steam generated by burning methane gas in the boiler are combined in winter, etc. When there is a shortage of heat, it becomes possible to appropriately compensate for the shortage of heat. Therefore, more reliable temperature adjustment is possible.

  ADVANTAGE OF THE INVENTION According to this invention, the wastewater treatment system which can aim at the further reduction of energy consumption can be provided by utilizing effectively the methane gas which generate | occur | produces in biological treatment.

It is a figure showing a schematic structure of a sewage treatment system concerning a 1st embodiment. It is a figure which shows schematic structure of the sewage treatment system concerning 2nd Embodiment. It is a figure which shows schematic structure of the sewage treatment system concerning 3rd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(First embodiment)
FIG. 1 is a diagram illustrating a schematic configuration of a sewage treatment system 100 according to the first embodiment. The sewage treatment system 100 purifies sewage containing organic matter. As shown in FIG. 1, sewage discharged from a factory or the like (not shown) has a flow rate provided on the uppermost stream side of the sewage treatment system 100 after foreign matters are removed by a screen, a strainer, a filter or the like (not shown). It is stored in the adjustment tank 102. In the flow rate adjustment tank 102, the temporarily stored sewage is supplied to the floating separation tank 104 after the supply amount is adjusted in accordance with the treatment capacity of the sewage treatment system 100.

  In the levitation separation tank 104, the sewage introduced from the flow rate adjustment tank 102 is pressurized to dissolve the air, and then released (depressurized) to atmospheric pressure. Then, fine bubbles are generated in the sewage and adhere to the suspended matter, and the apparent density of the suspended matter decreases (becomes lower than the density of water). Thereby, since the suspended solids float in the water (floating separation method), the suspended solids can be removed from the sewage.

  Then, the sewage from which suspended substances are removed is sent to the acid generation reaction tank 106 and subjected to anaerobic treatment. In the acid generation reaction tank 106, the organic matter contained in the sewage is decomposed to generate an organic acid. Specifically, the inside of the acid generation reaction tank 106 is set in an anaerobic state, and organic acids (lower fatty acids) such as acetic acid and propionic acid are generated by decomposing organic substances in the sewage by acid generating bacteria. In particular, acetic acid is useful as a raw material for methane gas described below.

  The sewage treated as described above is sent to the temperature adjustment tank 108. In the temperature adjustment tank 108, the temperature of the treated sewage in the acid generation reaction tank 106 is adjusted. Thereby, the temperature of sewage can be made into the temperature suitable for the process in the methane production | generation reaction tank 110 which is a next processing tank.

  In the present embodiment, the temperature adjustment tank 108 adjusts the temperature so that the temperature of the sewage falls within the range of 25 ° C to 37 ° C. In general, in anaerobic treatment, when the temperature of sewage is less than 25 ° C., the methane-producing bacteria that contribute to the generation of methane gas become inactive, so the generation of methane gas is suppressed and the generation efficiency of methane gas decreases. It is because it ends. If the temperature exceeds 40 ° C., the methanogen may be killed. Therefore, it is preferable to control the temperature to about 37 ° C. or less in view of safety. Therefore, the adjustment temperature is preferably in the above range. In the temperature adjustment tank 108, the temperature is adjusted by being heated by the heat pump 120 and the boiler 140 or being cooled by the heat pump 120. The details of the temperature adjustment of the sewage in the temperature adjustment tank 108 will be described later.

  The sewage whose temperature has been adjusted as described above is sent to the methane production reaction tank 110. In the methane production reactor 110, the organic acid contained in the sewage after temperature adjustment is decomposed to produce methane gas. Specifically, an assembly of methanogenic bacteria is formed below the methanogenic reaction tank 110. And by making the inside of the methane production | generation reaction tank 110 into an anaerobic state, this methane production microbe decomposes | disassembles the organic acid in wastewater, and methane gas is produced | generated. In particular, in this embodiment, since the temperature of sewage is optimized in the temperature adjustment tank 108 as described above, the methane production reaction is favorably promoted.

  Furthermore, in this embodiment, a methane recovery device 112 is connected to the methane generation reaction tank 110. The methane recovery device 112 is also connected to a boiler 140 described later, and the recovered methane gas is supplied to the boiler 140. Thereby, methane gas can be used in the boiler 140.

  The sewage treated in the methane generation reaction tank 110 is sent to the nitrification tank 114. In the nitrification tank 114, ammonia (NH4) in sewage is oxidized to generate nitric acid (NO3). Specifically, when the inside of the nitrification tank 114 is in an aerobic state, ammonia in the sewage is first oxidized by ammonia oxidizing bacteria to become nitrous acid (NO2). The nitrous acid is converted into nitric acid by being oxidized by the nitrite oxidizing bacteria. The sewage subjected to such treatment is then sent to the denitrification tank 116.

  In the denitrification tank 116, the nitric acid in the sewage generated in the nitrification tank 114 is reduced to nitrogen (N2). When the denitrification tank 116 is in an anaerobic state, the denitrification bacteria decompose organic substances in the sewage using bound oxygen of nitrate molecules. As a result, nitric acid is reduced, nitrogen gas is generated, and nitrogen is removed from the sewage. The sewage thus nitrified and denitrified passes through a filtration membrane (not shown) in the membrane separation tank 118 to filter sludge. As the filtration membrane, a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane) can be used. Thereafter, treatment such as disinfection is performed as necessary, and the treated water is purified and discharged out of the system.

  In this embodiment, the tanks for performing the nitrification / denitrification process are arranged in the order of “nitrification tank 114 and denitrification tank 116”, but the present invention is not limited to this. For example, if the above tanks are arranged in the order of “denitrification tank 116 and nitrification tank 114” and a circulation path (not shown) for circulating sewage is provided in these tanks, the same effects as in this embodiment can be obtained. . In addition, sewage may be circulated in the three tanks of the methane production reaction tank 110, the denitrification tank 116, and the nitrification tank 114.

  The flow of the sewage purification process in the sewage treatment system 100 has been described above. Next, the temperature adjustment of the sewage in the temperature adjustment tank 108 that is a feature of the sewage treatment system 100 of the present embodiment will be described. In order to adjust the temperature of sewage in the temperature control tank 108, the sewage treatment system 100 is provided with a heat pump 120 and a boiler 140.

  In the heat pump 120, a primary refrigerant (such as chlorofluorocarbon gas) circulates inside, and waste water after treatment in the methane generation reaction tank 110 (sewage after treatment in the membrane separation tank 118 in this embodiment) and primary refrigerant (refrigerant). And the sewage in the temperature control tank 108 is heated using the heat obtained in the heat exchange. Further, as will be described later, the sewage in the temperature control tank 108 can be cooled by the heat pump 120. Thus, since the heat pump 120 uses the heat exchange cycle, it is possible to save energy and reduce carbon dioxide emissions. Therefore, the environmental load of the sewage treatment system 100 can be reduced.

  Specifically, the heat pump 120 includes an evaporator 122, a compressor 124, a condenser 126, and an expansion valve 128 provided on the primary refrigerant circulation path 120a.

  The evaporator 122 exchanges heat between the primary refrigerant circulating in the primary refrigerant circulation path 120a and the treated sewage in the membrane separation tank 118 (treated water after all treatments are completed) via the secondary refrigerant. Do. As a result, the primary refrigerant can absorb heat from the treated sewage in the membrane separation tank 118 and obtain heat for heating the sewage in the temperature adjustment tank 108.

  In the present embodiment, an evaporator-side secondary refrigerant circulation path 122a is provided in the evaporator 122, and the secondary refrigerant is circulated through the evaporator-side secondary refrigerant circulation path 122a using the pump 122b as power. A first heat exchanger 132 is provided on the evaporator-side secondary refrigerant circulation path 122a. Since the first heat exchanger 132 is arranged on the downstream side of the membrane separation tank 118 on the sewage treatment system, the sewage after the treatment in the membrane separation tank 118 passes through the first heat exchanger 132. With such a configuration, the treated sewage in the membrane separation tank 118 exchanges heat with the secondary refrigerant circulating in the evaporator-side secondary refrigerant circulation path 122a in the first heat exchanger 132. Then, the secondary refrigerant after heat exchange exchanges heat with the primary refrigerant in the evaporator 122, and the heat of the secondary refrigerant (heat of sewage after treatment in the membrane separation tank 118) is transferred to the primary refrigerant. That is, the primary refrigerant of the heat pump 120 indirectly exchanges heat with the treated sewage in the membrane separation tank 118 via the secondary refrigerant circulating in the evaporator-side secondary refrigerant circulation path 122a.

  As the secondary refrigerant flowing through the evaporator-side secondary refrigerant circulation path 122a, for example, water or antifreeze can be used. By not using the treated water directly for the evaporator 122, the heat pump and the treated water system can be separated. Thereby, inflow of sewage into the heat pump 120 can be avoided, and the heat pump can be unitized.

  The compressor 124 compresses the primary refrigerant using electric power. Thereby, the primary refrigerant becomes a high-temperature and high-pressure gas.

  The condenser 126 performs heat exchange between the primary refrigerant compressed by the compressor 124 and having a high temperature and the sewage in the temperature adjustment tank 108 via the secondary refrigerant. Thereby, the temperature adjustment can be performed by heating the sewage in the temperature adjusting tank 108 using the heat of the primary refrigerant.

  In the present embodiment, the condenser 126 is provided with a condenser-side secondary refrigerant circulation path 126a, and the secondary refrigerant is circulated through the condenser-side secondary refrigerant circulation path 126a using the pump 126b as power. A second heat exchanger 134 is provided on the condenser-side secondary refrigerant circulation path 126a. The temperature adjustment tank 108 is connected to the second heat exchanger 134 via a sewage circulation path 134a, and the sewage in the temperature adjustment tank 108 is circulated using the pump 134b as power. With such a configuration, the primary refrigerant compressed by the compressor 124 exchanges heat with the secondary refrigerant circulating in the condenser-side secondary refrigerant circulation path 126a in the condenser 126. Then, the secondary refrigerant after the heat exchange exchanges heat with the sewage in the temperature adjustment tank 108 in the second heat exchanger 134, and the heat of the secondary refrigerant (heat of the primary refrigerant) moves to the sewage in the temperature adjustment tank 108. To do. That is, the primary refrigerant of the heat pump 120 indirectly exchanges heat with the sewage in the temperature adjustment tank 108 through the secondary refrigerant circulating in the condenser-side secondary refrigerant circulation path 126a.

  As the secondary refrigerant flowing through the condenser-side secondary refrigerant circulation path 126a, for example, water or antifreeze can be used. By not using the treated water directly for the evaporator 122, the heat pump and the treated water system can be separated. Thereby, inflow of sewage into the heat pump 120 can be avoided, and the heat pump can be unitized.

  The expansion valve 128 expands and cools the primary refrigerant in a reduced pressure state. Thereby, in the evaporator 122, it becomes possible for the primary refrigerant to absorb the secondary refrigerant and thus the heat of the sewage after the treatment in the membrane separation tank 118 again, and the primary refrigerant can be reused.

  As described above, according to the sewage treatment system 100 of the present embodiment, the sewage in the temperature adjustment tank 108 using heat of the sewage after treatment in the membrane separation tank 118 by heat exchange with the primary refrigerant in the heat pump 120. Can be heated. For this reason, it is possible to effectively use the heat of the treated sewage in the membrane separation tank 118, and it is possible to reduce the energy required for adjusting the temperature of the sewage in the temperature adjusting tank 108. In addition, since heat is absorbed from the treated sewage in the membrane separation tank 118, facilities for cooling the sewage discharged to the river are not required, and the system can be simplified and the equipment cost can be reduced. it can.

  Furthermore, in this embodiment, the four-way valve 120b is provided on the primary refrigerant circulation path 120a, and if the four-way valve 120b is switched, the circulation direction of the primary refrigerant in the primary refrigerant circulation path 120a can be reversed. As a result, when the temperature of the sewage in the temperature adjustment tank 108 exceeds a predetermined range, the four-way valve 120b is switched to reverse the direction of circulation of the primary refrigerant, and the heat of the sewage is absorbed by the primary refrigerant, thereby separating the membrane. It becomes possible to exhaust heat to the treated sewage in the tank 118. That is, according to the sewage treatment system 100 of the present embodiment, the sewage in the temperature adjustment tank 108 can be cooled by heat exchange with the primary refrigerant in the heat pump 120. This eliminates the need for equipment such as a cooling tower that has been provided for cooling the sewage in the temperature control tank 108 in the related art, thereby reducing costs.

  Further, in the sewage treatment system 100 of this embodiment, a boiler 140 is further provided as a sewage temperature adjusting means in the temperature adjusting tank 108 in addition to the heat pump 120 described above. The boiler 140 is supplied with the methane gas recovered from the methane generation reaction tank 110 by the methane recovery device 112 and burns it to generate steam. A steam pipe 140a is connected to the boiler 140, and the generated steam is injected into the temperature adjustment tank 108 through the steam pipe 140a. Thereby, it becomes possible to heat the sewage in the temperature adjustment tank 108 using the steam generated in the boiler 140 and perform temperature adjustment.

  When methane gas is burned as described above, carbon dioxide is generated. Such methane gas is a biogas generated by decomposing organic substances by microorganisms as described above. For this reason, the carbon dioxide produced | generated here does not affect the increase / decrease in a carbon dioxide, ie, carbon neutral. Therefore, compared with the case where fossil fuel is burned in a boiler, an environmental load can be reduced. In addition, since the greenhouse effect of methane gas is said to be about 21 times that of carbon dioxide, the influence of the greenhouse gas on the environment can be further suppressed by burning methane gas into carbon dioxide.

  As described above, according to the sewage treatment system 100 according to the present embodiment, not only temperature adjustment by heat exchange in the heat pump 120 but also heat of steam generated by burning methane gas generated in biological treatment in a boiler. By utilizing this, the temperature of the sewage in the temperature adjustment tank 108 can be adjusted. Thereby, methane gas and by extension, the energy of the whole system can be used effectively, and it becomes possible to further reduce the energy required for adjusting the temperature of sewage. Also, by burning methane gas, it is possible to reduce the load on the global environment.

(Second Embodiment)
Next, the sewage treatment system according to the second embodiment will be described. FIG. 2 is a diagram illustrating a schematic configuration of a sewage treatment system 200 according to the second embodiment. In addition, about the element which shows the substantially same function and structure as the component of the sewage treatment system 100 of 1st Embodiment mentioned above, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 2, the sewage treatment system 200 according to the second embodiment is different from the sewage treatment system 100 of the first embodiment in that it further includes a second boiler 240 as temperature control means for sewage in the temperature adjustment tank 108. . Specifically, the second boiler 240 provided in the sewage treatment system 200 burns fossil fuel to generate steam. As such fossil fuels, city gas, natural gas, petroleum, coal and the like can be suitably used.

  A steam pipe 240a is connected to the second boiler 240, and the generated steam is injected into the temperature adjustment tank 108 through the steam pipe 240a. Therefore, in the sewage treatment system 200, in addition to the heat exchange in the heat pump 120 and the steam generated in the boiler 140, the steam generated in the second boiler 240 is also used to heat the sewage in the temperature adjustment tank 108 to adjust the temperature. Can be done. As a result, for example, in the winter, the heat required for the temperature adjustment of the sewage in the temperature adjustment tank 108 is insufficient even if both the heat obtained by heat exchange in the heat pump 120 and the heat of the steam generated in the boiler 140 are combined. In such a case, the shortage of heat can be compensated suitably, and more reliable temperature adjustment is possible.

(Third embodiment)
Next, the sewage treatment system according to the third embodiment will be described. FIG. 3 is a diagram illustrating a schematic configuration of a sewage treatment system 300 according to the third embodiment. In addition, about the element which shows the function and structure substantially the same as the component of the sewage treatment system 100 of 1st Embodiment mentioned above and the sewage treatment system 200 of 2nd Embodiment, the same code | symbol is attached | subjected and description is given. Omitted.

  As shown in FIG. 3, the sewage treatment system 300 according to the third embodiment mainly includes a third heat exchanger 334 that performs heat exchange between the sewage in the nitrification tank 114 and the secondary refrigerant, and the third heat exchange. It differs from the sewage treatment system 100 of 1st Embodiment and the sewage treatment system 200 of 2nd Embodiment in the point provided with the sewage circulation path 334a which circulates a secondary refrigerant | coolant to the container 334. FIG.

  Specifically, switching valves 322a and 322b are provided between the evaporator 122 and the first heat exchanger 132 in the evaporator-side secondary refrigerant circulation path 122a. The secondary refrigerant circulation path 122a is branched to provide a branch circulation path 334c. A third heat exchanger 334 is provided on the branch circulation path 334c. Thus, by switching the switching valves 322a and 322b, the secondary refrigerant circulates in the branch circulation path 334c and eventually the third heat exchanger 334 using the pump 122b as power. The third heat exchanger 334 is connected to the nitrification tank 114 by a sewage circulation path 334a, and the sewage in the nitrification tank 114 circulates in the sewage circulation path 334a using the pump 334b as a power and flows to the third heat exchanger 334.

  With the above configuration, the sewage in the nitrification tank 114 and the secondary refrigerant circulating in the evaporator-side secondary refrigerant circulation path 122a can exchange heat in the third heat exchanger 334. Therefore, even if the temperature of the sewage rises due to the aerobic treatment (nitrification reaction) in the nitrification tank 114, the heat of the sewage is transferred to the secondary refrigerant to cool the sewage to a temperature suitable for the aerobic treatment. It can be carried out. As a result, a cooling facility such as a cooling tower required for cooling the nitrification tank 114 becomes unnecessary, and the facility cost can be reduced.

  The secondary refrigerant that has exchanged heat with the sewage in the nitrification tank 114 in the third heat exchanger 334 exchanges heat with the primary refrigerant in the evaporator 122. For this reason, the heat transferred from the sewage in the nitrification tank 114 to the secondary refrigerant is finally used for temperature adjustment of the sewage in the temperature adjustment tank 108. Therefore, it is possible to effectively use the heat of the sewage in the nitrification tank 114 that has conventionally been exhausted to the cooling facility, and at the same time, it is possible to reduce the energy required for temperature adjustment in the temperature adjustment tank 108.

  In the configuration of the first embodiment, power control of the heat pump 120 is performed based on the temperature of the temperature adjustment tank 108, whereas in the configuration of the third embodiment, power control of the heat pump 120 is performed in the nitrification tank 114. Based on the temperature. For this reason, when there is little heat which the secondary refrigerant obtained by heat exchange with the sewage of the nitrification tank 114, there is a possibility that the amount of heat for heating the sewage in the temperature adjustment tank 108 by the heat pump 120 may be insufficient. However, in the configuration of the third embodiment, the temperature of the temperature adjustment tank 108 can be appropriately adjusted by including the boiler 140 using the recovered methane gas and the second boiler 240 using fossil fuel. Further, as described in the second embodiment, the second boiler 240 can be effectively used even in a situation where heat tends to be insufficient, such as in winter.

  Furthermore, in the configuration of the third embodiment, in addition to performing power control of the heat pump 120 based on the temperature of the temperature adjustment tank 108 as described above, the flow rates of the switching valves 322a and 322b based on the temperature of the nitrification tank 114 Control may be performed. That is, the switching valves 322a and 322b are controlled based on the temperature of the nitrification tank 114, and the amount of secondary refrigerant flowing into the third heat exchanger 334 (nitrification tank 114 side) and the first heat exchanger 132 (treated water). The amount that flows to the side) may be adjusted. Accordingly, the secondary refrigerant can obtain heat from the sewage in the nitrification tank 114 in the third heat exchanger 334 and can also obtain heat from the treated water in the first heat exchanger 132. Therefore, it is possible to efficiently heat the sewage in the temperature adjustment tank 108 without deficient in the heat obtained by the secondary refrigerant, in other words, without reducing the amount of heat of the heat pump 120.

  In the present embodiment, the third heat exchanger 334 is connected to the nitrification tank 114, but the present invention is not limited to this, and the third heat exchanger 334 may be connected to the denitrification tank 116 ( Denitrification reaction is also exothermic reaction). Moreover, you may provide on the path | route between arbitrary two tanks. Moreover, although it was set as the structure which provides the 2nd boiler 240 in the sewage treatment system 300 in this embodiment, it is not limited to this, The 2nd boiler 240 does not necessarily need to be provided.

  Moreover, although not illustrated in the first to third embodiments described above, a process (process) that is not included in these embodiments, for example, a dephosphorization process may be added to the sewage treatment system. However, the dephosphorization process is not necessarily required because the presence or absence is determined by the quality of the factory effluent and the discharge standards of the treated water (river or lake).

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used as a sewage treatment system for purifying sewage.

DESCRIPTION OF SYMBOLS 100 ... Sewage treatment system, 102 ... Flow control tank, 104 ... Flotation separation tank, 106 ... Acid production reaction tank, 108 ... Temperature adjustment tank, 110 ... Methane production reaction tank, 112 ... Methane collection | recovery apparatus, 114 ... Nitrification tank, 116 Denitrification tank, 118 ... Membrane separation tank, 120 ... Heat pump, 120a ... Primary refrigerant circulation path, 120b ... Four-way valve, 122 ... Evaporator, 122a ... Evaporator side secondary refrigerant circulation path, 122b ... Pump, 124 ... Compressor 126 ... Condenser, 126a ... Condenser side secondary refrigerant circulation path, 126b ... Pump, 128 ... Expansion valve, 132 ... First heat exchanger, 134 ... Second heat exchanger, 134a ... Sewage circulation path, 140 ... Boiler, 140a ... steam piping, 200 ... sewage treatment system, 240 ... second boiler, 240a ... steam piping, 300 ... sewage treatment system, 322a ... switch valve, 32 b ... changeover valve, 334 ... third heat exchanger, 334a ... sewage circulation path, 334b ... pump, 334c ... branch circulation route

Claims (3)

A sewage treatment system for purifying sewage containing organic matter,
An acid generation reaction tank for decomposing organic substances contained in the sewage to generate an organic acid;
A temperature adjustment tank for adjusting the temperature of the treated sewage in the acid generation reaction tank;
A methane generation reaction tank that decomposes an organic acid contained in sewage whose temperature is adjusted in the temperature adjustment tank to generate methane gas;
A boiler that generates steam by burning the methane gas;
A heat pump for exchanging heat between the sewage and the refrigerant after the treatment in the methane generation reaction tank;
With
In the temperature adjustment in the temperature adjustment tank, a sewage treatment system using heating by injecting steam generated in the boiler and heating or cooling by heat exchange with the refrigerant in the heat pump is used.   The sewage treatment system according to claim 1, wherein the temperature adjustment tank adjusts the temperature so that the temperature of the sewage falls within a range of 25 ° C. to 37 ° C. A second boiler that burns fossil fuel to generate steam;
The sewage treatment system according to claim 1, wherein heating by injecting steam generated in the second boiler is also used for temperature adjustment in the temperature adjustment tank.

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