JP2010269255A - Sewage treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sewage treatment method increasing N<SB>2</SB>O treatment efficiency by selectively recovering exhaust gas with high N<SB>2</SB>O concentration, preventing lowering of the treatment efficiency due to treatment of whole gas volume even in a case of low concentration of N<SB>2</SB>O. <P>SOLUTION: In the sewage treatment method, a dissolved oxygen meter 8 set in a biological reactor 1 treating waste water with activated sludge, an exhaust gas recovering means 5 recovering aerated gas into the biological reactor 1, and a control means 7 controlling opening/closing of a control valve 6 set in the exhaust gas recovering means 5 are provided. The control means 7 recovers the aerated gas by controlling opening/closing of the control valve 6, when a current measurement of the dissolved oxygen meter 8 exceeds an average of measurements of the dissolved oxygen meter 8 for at least 6 hours. The N<SB>2</SB>O generation amount is predicted from the dissolved oxygen in the biological reactor, and the exhaust gas is treated when the N<SB>2</SB>O concentration in the exhaust gas is high. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a sewage treatment method for reducing greenhouse gases generated in the process of sewage treatment, particularly N ₂ O generated from an aeration tank of a biological reaction tank.

The sewage treatment method includes an activated sludge method in which biological treatment is performed with microorganisms called activated sludge. In the activated sludge method, nitrogen in the wastewater is removed by a nitrification process that oxidizes ammonia nitrogen to nitrate nitrogen and a denitrification process that reduces nitrate nitrogen to nitrogen gas. It is known that N ₂ O is generated as a byproduct of the nitrification process and the denitrification process. [Non-Patent Document 1] describes that N ₂ O in exhaust gas increases as the nitrification reaction proceeds. N ₂ O has a greenhouse effect 310 times that of CO ₂ and is an emission reduction target substance for preventing global warming.

As described in [Non-Patent Document 2], N ₂ O in denitrification is reduced to N _2. For this reason, it can be removed by dissolving N ₂ O in a reaction tank having a denitrification reaction. [Patent Document 1] describes a method in which exhaust gas containing N ₂ O is introduced into a reaction vessel to dissolve and remove N ₂ O.

JP 2007-075821 A

Matsubara Makoto, Mizuochi Motoyuki: Nitrous oxide emissions from sewage treatment plants, Environmental hygiene engineering research, Vol.8, No.3 (1994) Basic research on long-term sewerage technology development, New Sewerage Technology Promotion Organization (1996) http://www.jiwet.jp/result/annual/plan/1996a1-1-2m.htm

Since the inflow conditions fluctuate at the sewage treatment plant, the N ₂ O concentration in the exhaust gas changes. In the conventional technique described in [Patent Document 1], the entire amount of exhaust gas is always introduced into the reaction vessel. Even when N ₂ O is in a low concentration, the gas is processed in its entirety, which may reduce the processing efficiency.

An object of the present invention is to provide a sewage treatment method capable of improving N ₂ O treatment efficiency by selectively recovering exhaust gas having a high N ₂ O concentration.

  In order to achieve the above object, a sewage treatment method of the present invention includes a dissolved oxygen meter installed in a biological reaction tank, an exhaust gas recovery means for recovering a gas aerated in the biological reaction tank, and an exhaust gas recovery means. A control means for controlling the opening and closing of the provided control valve, the control means is an average value of at least 6 hours or more of the measured value of the dissolved oxygen meter, when the current value of the measured value of the dissolved oxygen meter exceeds, The control valve is controlled to open and close to recover the aerated gas, or the recovery gas flow rate from the exhaust gas recovery means is controlled according to the measured value of the dissolved oxygen meter.

  In addition, a sewage treatment method for aeration of a plurality of biological reaction tanks and treating wastewater with activated sludge, wherein a dissolved oxygen meter installed in each of the plurality of biological reaction tanks and a gas aerated in the biological reaction tanks Exhaust gas recovery means for recovery and an aerated gas by controlling the opening and closing of a control valve provided in the exhaust gas recovery means when the measured value of the dissolved oxygen meter exceeds the average value of the exhaust gas recovery means And a control means for obtaining a difference between the measured values of the dissolved oxygen meter on the upstream side and the dissolved oxygen meter on the downstream side, calculating an average value of at least 6 hours, and calculating the average value When the current value of the difference between the measured values of the oximeter exceeds, the control valve is controlled to open and close to recover the aerated gas, or the recovered gas flow rate of the exhaust gas recovery means is controlled by the current value of the difference Than is.

Inflow condition management means having information on the flow rate and concentration flowing into the biological reaction tank, plant condition management means having information on the current specifications of the plant specifications and operating conditions, inflow condition management means and plant condition management means and N ₂ O concentration calculation means for calculating the N ₂ O concentration containing based on information on the aeration of the exhaust gas, and an exhaust gas recovery means for recovering the aeration gas to the bioreactor, provided in the exhaust gas collection means Control means for controlling the opening and closing of the control valve, and the control means controls the opening and closing of the control valve when the calculated value of the N ₂ O concentration calculating means is equal to or greater than the set value, or the exhaust gas from the exhaust gas collecting means with the calculated value The recovery flow rate is controlled.

  Also, a nitrogen measuring means for measuring one or more of nitrate nitrogen concentration, nitrite nitrogen, and ammonia nitrogen in the reaction liquid of the biological reaction tank, and for recovering the gas aerated in the biological reaction tank Exhaust gas recovery means and a control means for controlling the opening and closing of a control valve provided in the exhaust gas recovery means. The control means controls the opening and closing of the control valve according to the measurement value of the nitrogen measurement means, or from the exhaust gas recovery means with the measurement value The exhaust gas recovery flow rate is controlled.

According to the present invention, to predict the N ₂ O emissions from the dissolved oxygen, or nitrogen concentration in the bioreactor, when the N ₂ O concentration in the exhaust gas high, it is possible to process the exhaust gas, the N ₂ O performance It can be improved.

It is a block diagram of the waste water treatment apparatus which shows Example 1 of this invention. It is a block diagram of the waste water treatment apparatus which shows Example 2 of this invention. It is a block diagram of the waste water treatment apparatus which shows Example 3 of this invention. It is a block diagram of the waste water treatment apparatus which shows Example 4 of this invention. It is a block diagram of the waste water treatment apparatus which shows Example 5 of this invention. It is a block diagram of the waste water treatment apparatus which shows Example 6 of this invention. It is a block diagram of the waste water treatment apparatus which shows Example 7 of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the reaction tank of this embodiment is composed of a biological reaction tank 1 and a sedimentation tank 2.

  Inflow water flows into the biological reaction tank 1, and treated water flows out from the sedimentation basin 2. The biological reaction tank 1 is mixed with activated sludge inhabited by a plurality of microorganism groups. The aeration means 4 connected to the blower 3 aerates the biological reaction tank 1 and supplies dissolved oxygen in the air to the activated sludge by aeration. In FIG. 1, the biological reaction tank 1 is shown as one tank, but the biological reaction tank 1 may be divided into a plurality of aerobic tanks that are aerated and anaerobic tanks that are not aerated.

  An exhaust gas recovery means 5 for recovering the aerated exhaust gas is installed in the upper part of the biological reaction tank 1. The exhaust gas recovery means 5 is provided with a control valve 6. In order to recover the exhaust gas by the signal of the control means 7, the control valve 6 is controlled to be opened and closed by an on-off signal, and the exhaust gas recovery amount is controlled. The control valve 6 is connected to the exhaust gas treatment device. The biological reaction tank 1 is provided with a dissolved oxygen meter 8 for measuring dissolved oxygen in the reaction solution, and the measurement signal is input to the control means 7. Note that the wastewater treatment performance of the biological reaction tank 1 is not affected by the presence or absence of exhaust gas recovery by the exhaust gas recovery means 5.

  A sedimentation basin 2 for solid-liquid separation of the reaction solution and activated sludge is installed downstream of the biological reaction tank 1. Part of the activated sludge that has settled in the sedimentation basin 2 circulates in the biological reaction tank 1 as return sludge, and a part is discharged as excess sludge.

The wastewater that has flowed into the biological reaction tank 1 is treated with activated sludge. The organics in the influent water are oxidized and decomposed, it is finally removed as CO _2. Most of the nitrogen components in the inflow water are ammonia nitrogen and organic nitrogen, but the organic nitrogen becomes ammonia nitrogen by the activated sludge, and the ammonia nitrogen is oxidized to nitrite nitrogen and nitrate nitrogen.

  When organic matter and nitrogen are oxidized, dissolved oxygen in the reaction solution is consumed. When the oxygen supply rates are equal, the dissolved oxygen concentration increases when the concentration of these substances to be treated in the reaction solution decreases, that is, when the treatment is completed. In general, since the amount of inflow water and the concentration of inflow water change in sewage, the concentration of dissolved oxygen often increases or decreases. That is, when the dissolved oxygen concentration rises, it can be seen that the oxidation is finished and the nitrate nitrogen concentration is increased.

The N ₂ O concentration in the exhaust gas increases in proportion to a decrease in ammonia nitrogen and an increase in nitrate nitrogen. The control means 7 can selectively process the exhaust gas containing N ₂ O at a high concentration by controlling the control valve 6 based on the measurement signal of the dissolved oxygen meter 8.

  A control method of the control means 7 will be described. The control means 7 stores the measured value of the dissolved oxygen meter 8 for a set period. For example, the control means 7 calculates the average value of the measured values of the dissolved oxygen meter 8 up to 6 hours ago. The average value and the current measured value of the dissolved oxygen meter 8 are compared. If the measured value is equal to or greater than the average value, the control valve 6 is controlled to introduce the exhaust gas into the processing apparatus. An upper limit value may be provided instead of the average value or higher, and the control valve 6 may be controlled when the measured value of the dissolved oxygen meter 8 is equal to or higher than the upper limit value. In this case, the upper limit value is preferably about 1 mg / L. Moreover, the control means 7 may control the control valve 6 based on the measured value of the dissolved oxygen meter 8, and may increase the collection amount of exhaust gas in proportion to the measured value.

Information on the amount of air supplied from the blower 3 may be input to the control means 7, and as the amount of air increases, the measured value of the dissolved oxygen meter 8 also increases. By controlling the valve 6, the prediction accuracy of the N ₂ O concentration can be improved, so that the N ₂ O recovery efficiency can be improved.

Thus, according to the present embodiment, by measuring the dissolved oxygen concentration, the exhaust gas having a high N ₂ O concentration can be selectively recovered, and the N ₂ O treatment efficiency can be improved.

  A second embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment shown in FIG. 1 is that in the second embodiment, the biological reaction tank 1 is divided into two dissolved oxygen concentration meters 8-1 and 8-2. A densitometer is installed. The biological reaction tank 1 may not have a partition wall. In this embodiment, the exhaust gas recovery means 5 is installed in the reaction tank in which the downstream dissolved oxygen concentration meter 8-2 is installed. Good. Signals from both the upstream dissolved oxygen concentration meter 8-1 and the downstream dissolved oxygen concentration meter 8-2 are input to the control means 7. When the amount of air diffused by the air diffuser 4 is uniform, the upstream biological reaction tank has more ammonia versus nitrogen and organic matter than the downstream biological reaction tank, and the dissolved oxygen concentration meter may have a lower value. Many.

  A control method by the control means 7 will be described. The control means 7 calculates | requires the difference of the measured value of the downstream dissolved oxygen concentration meter 8-2 and the upstream dissolved oxygen concentration meter 8-1. The control means 7 calculates the average value of differences up to 6 hours ago. The calculated average value is compared with the difference between the measurement values. If the difference between the measurement values is equal to or greater than the average value, the control valve 6 is controlled to introduce the exhaust gas into the processing apparatus. Moreover, the control means 7 may control the control valve 6 and introduce exhaust gas into a processing apparatus, when the difference of a measured value exceeds a setting value. In this case, the set value is preferably 0.5 mg / L or more.

The control means 7 may control the control valve 6 to increase the exhaust gas recovery amount in proportion to the magnitude of the difference between the measured values. The set value may be changed based on the data on the amount of air supplied from the air diffuser 4 to the biological reaction tank 1, and the set value is decreased when the amount of air is small and set when the amount of air is large. Increase the value. The nitrification reaction proceeds in the biological reaction tank in which the downstream dissolved oxygen concentration meter 8-2 that is equal to or higher than the set value is installed, the nitrate nitrogen concentration increases, and the N ₂ O content in the exhaust gas is high.

Thus, according to Example 2, exhaust gas with a high N ₂ O concentration can be selectively recovered by measuring the dissolved oxygen concentration, and the N ₂ O treatment efficiency can be improved.

  A third embodiment of the present invention will be described with reference to FIG. The difference between Example 3 and Example 1 is the difference between the dissolved oxygen meter 8 and the nitrogen concentration meter 9. The nitrogen concentration meter 9 can measure at least one of ammonia body nitrogen, nitrite nitrogen, and nitrate body nitrogen. The measured value of the nitrogen concentration meter 9 is input to the control means 7, and the control means 7 controls the control valve 6 according to the measured value.

  A control method by the control means 7 will be described. When the measurement item is ammonia nitrogen, when the measurement value is less than or equal to a preset setting value, the control means 7 determines that the measurement value is greater than or equal to the preset value when the measurement item is nitrite nitrogen or nitrate nitrogen. In this case, the control valve 6 is controlled to introduce the exhaust gas into the processing apparatus. The set values are preferably 10 mg / L for ammonia nitrogen, 0.5 mg / L for nitrite nitrogen, and 5 mg / L for nitrate nitrogen.

  Moreover, the control means 7 calculates the average value of the measured values of the nitrogen concentration meter 9 up to 24 hours ago. Compare the average value with the current value. If the measurement item is ammonia nitrogen, the measurement value is less than the average value. If the measurement item is nitrite nitrogen and nitrate nitrogen, the measurement value is greater than the average value. In addition, the control valve 6 may be controlled to introduce the exhaust gas into the processing apparatus.

  Further, the control means 7 may control the control valve 6 to increase the exhaust gas recovery flow rate as the ammonia body nitrogen concentration decreases, and as the nitrite nitrogen and nitrate nitrogen increase.

As described above, according to Example 3, the progress of the nitrification reaction can be understood by directly measuring the nitrogen concentration, and the exhaust gas having a high N ₂ O concentration in which the nitrification reaction has progressed can be selectively recovered, and the N ₂ O treatment efficiency can be recovered. Can be improved.

A fourth embodiment of the present invention will be described with reference to FIG. The difference between the fourth embodiment and the third embodiment is that, instead of the nitrogen concentration meter 9 of the third embodiment, in the fourth embodiment, an N ₂ O concentration calculation means 10, an inflow condition management means 11 and a plant condition management means 12 are provided. This is the point. The control means 7 controls the control valve 6 based on the calculation result of the N ₂ O concentration calculation means 10 when the calculation result exceeds the set value.

A calculation method of the N ₂ O concentration calculation means 10 will be described. The N ₂ O concentration calculation means 10 receives inflow water amount and inflow water quality information from the inflow condition management means 11 and plant specifications and current operation information from the plant condition management means 12. Although not shown, the inflow condition management means 11 stores inflow water amount, inflow water quality database, inflow water amount measuring device, and measured values from the inflow water quality measuring device. Although not shown, the plant condition management means 12 has a database of information such as the water temperature of the biological reaction tank 1, the amount of air blown from the aeration means 4, and the concentration of activated sludge, and these information are sequentially updated. Yes.

In the N ₂ O concentration calculation means 10, an activated sludge model that models the reaction of activated sludge, for example, an IWA (International Water Association) model is recorded. In the activated sludge model, the nitrification reaction is modeled, and the ammonia body nitrogen concentration and nitrate body nitrogen concentration in the biological reaction tank 1 can be calculated according to the inflow conditions and the plant operating conditions. The amount of nitrification is obtained from the difference between the concentration of the influent water in the inflow condition management means 11 and the concentration in the reaction tank, and the N ₂ O concentration is estimated from the amount of nitrification. The N ₂ O concentration contained in the exhaust gas aerated in the biological reaction tank is calculated from the estimated N ₂ O concentration. The control means 7 controls the control valve 6 when the N ₂ O concentration is equal to or higher than a set value. The control means 7 may control the exhaust gas recovery flow rate of the exhaust gas treatment device according to the calculated value of the N ₂ O concentration.

Thus, according to the fourth embodiment, the N ₂ O gas concentration can be predicted by the model, and the exhaust gas having a high N ₂ O concentration can be selectively recovered, so that the N ₂ O treatment efficiency can be improved.

  A fifth embodiment of the present invention will be described with reference to FIG. Example 5 is configured in the same manner as Example 3. However, in Example 5, the nitrogen concentration meter 9 is not installed, and the biological reaction tank 1 is divided into a preceding anaerobic tank and a subsequent aerobic tank. The exhaust gas treatment device 13-1 is installed on the upstream side of the biological reaction tank 1 and connected to the control valve 6.

The inflow water flows into the biological reaction tank 1 through the exhaust gas treatment device 13-1. The exhaust gas is introduced into the exhaust gas treatment device 13-1, and the N ₂ O gas is dissolved in the inflowing water. N ₂ O dissolved in the inflow water flows into the biological reaction tank 1. The inflow water of the biological reaction tank 1 flows into an anaerobic tank (also called an oxygen-free tank). The anaerobic tank is a tank substantially free of dissolved oxygen, and N ₂ O is reduced to N ₂ gas by a denitrification reaction with activated sludge in the anaerobic tank. The exhaust gas treatment device 13-1 requires power such as a pump to dissolve the exhaust gas into the influent water. However, in this embodiment, the exhaust gas having a high N ₂ O concentration can be selectively recovered, and the amount of exhaust gas to be processed is small. Therefore, N ₂ O treatment efficiency can be improved.

  A sixth embodiment of the present invention will be described with reference to FIG. The sixth embodiment is configured in the same manner as the first embodiment, but in the sixth embodiment, the dissolved oxygen meter 8 is not installed, and the exhaust gas treatment device 13-2 is installed on the downstream side of the settling basin 2, and the control valve is used. 6 is connected.

In the exhaust gas treatment device 13-2, treated water is retained. The exhaust gas is introduced into the exhaust gas treatment device 13-2, and the N ₂ O gas is dissolved in the treated water. In the exhaust gas treatment device 13-2, when the exhaust gas is dissolved in the influent water, power such as a pump is required. However, in this embodiment, the exhaust gas having a high N ₂ O concentration can be selectively recovered, and the amount of exhaust gas to be processed is small. Therefore, N ₂ O treatment efficiency can be improved.

A seventh embodiment of the present invention will be described with reference to FIG. Example 7 is configured in the same manner as Example 6, but in Example 7, an exhaust gas pyrolysis device 14 for thermally decomposing N ₂ O in the exhaust gas is installed, and the control means 7 is an exhaust gas. It is connected to the thermal decomposition apparatus 14.

Examples of the exhaust gas thermal decomposition apparatus 14 to be applied include a catalyst-filled one, a generator, and a sludge incinerator. Since N ₂ O can be decomposed by heat, for example, in a sludge incinerator, N ₂ O can be reduced by raising the combustion temperature of the free board to 850 ° C. or higher.

If the amount of exhaust gas is large, the load on the exhaust gas pyrolysis device 14 increases. However, exhaust gas with a high N ₂ O concentration can be selectively recovered, and the amount of exhaust gas is reduced, so that energy consumption can be reduced. In this embodiment, exhaust gas having a high N ₂ O concentration can be selectively recovered, and the amount of exhaust gas to be processed can be reduced, so that N ₂ O treatment efficiency can be improved.

1 bioreactor 2 sedimentation tank 3 blower 4 diffuser means 5 gas collecting means 6 control valve 7 controlling unit 8 the dissolved oxygen meter 9 nitrogen concentration meter 10 N ₂ O concentration calculating means 11 flows condition management unit 12 plant condition management means 13 1, 13-2 Exhaust gas treatment device 14 Exhaust gas pyrolysis device

Claims (11)

  A dissolved oxygen meter installed in a biological reaction tank that treats wastewater with activated sludge, an exhaust gas recovery means for recovering the gas aerated in the biological reaction tank, and a control valve provided in the exhaust gas recovery means is opened and closed Control means for controlling, and the control means controls the opening and closing of the control valve when the measured value of the dissolved oxygen meter exceeds an average value of at least 6 hours or more of the measured value of the dissolved oxygen meter. And collecting the aerated gas.   A dissolved oxygen meter installed in a biological reaction tank that treats wastewater with activated sludge, an exhaust gas recovery means for recovering the gas aerated in the biological reaction tank, and a control valve provided in the exhaust gas recovery means is opened and closed Control means for controlling, and when the measured value of the dissolved oxygen meter exceeds a preset upper limit value, the control valve is controlled to open and close to recover the aerated gas Sewage treatment method.   A sewage treatment method for aeration of a plurality of biological reaction tanks to treat wastewater with activated sludge, wherein a dissolved oxygen meter installed in each of the plurality of biological reaction tanks and a gas aerated in the biological reaction tanks An exhaust gas recovery means for recovering and a control means for controlling opening / closing of a control valve provided in the exhaust gas recovery means, the control means measuring the dissolved oxygen meter on the upstream side and the dissolved oxygen meter on the downstream side The difference between the values was calculated and an average value of at least 6 hours or more was calculated, and when the difference between the current values of the measured values of the dissolved oxygen meter exceeded the average value, the control valve was controlled to open and close and aerated A sewage treatment method characterized by recovering gas.   A sewage treatment method for aeration of a plurality of biological reaction tanks to treat wastewater with activated sludge, wherein a dissolved oxygen meter installed in each of the plurality of biological reaction tanks and a gas aerated in the biological reaction tanks Exhaust gas recovery means for recovery, and control means for controlling the opening and closing of a control valve provided in the exhaust gas recovery means, the control means of the value of the dissolved oxygen meter on the upstream side and the value of the dissolved oxygen meter on the downstream side A sewage treatment method characterized by controlling the control valve with a difference to control the flow rate of the recovered gas. A sewage treatment method for treating wastewater with activated sludge, inflow condition management means for storing flow rate and concentration information flowing into a biological reaction tank, and plant conditions for storing information on the current values of plant specifications and operating conditions a management unit, and N ₂ O concentration calculation means for calculating the N ₂ O concentration contained in the exhaust gas information based on the aeration of the inflow condition management unit and the plant condition management unit, which is aerated in the bioreactor An exhaust gas recovery means for recovering gas and a control means for controlling opening and closing of a control valve provided in the exhaust gas recovery means, wherein the control means has a calculated value of the N ₂ O concentration calculating means equal to or greater than a set value In this case, the control valve is controlled to open and close to recover the aerated gas. A sewage treatment method for treating wastewater with activated sludge, inflow condition management means for storing flow rate and concentration information flowing into a biological reaction tank, and plant conditions for storing information on the current values of plant specifications and operating conditions a management unit, and N ₂ O concentration calculation means for calculating the N ₂ O concentration contained in the exhaust gas information based on the aeration of the inflow condition management unit and the plant condition management unit, which is aerated in the bioreactor An exhaust gas recovery means for recovering gas and a control means for controlling opening and closing of a control valve provided in the exhaust gas recovery means, the control means controlling the control valve with a value calculated by the N ₂ O concentration calculation means And controlling the exhaust gas recovery flow rate.   A sewage treatment method for treating wastewater with activated sludge, a nitrogen measuring means for measuring one or more of nitrate nitrogen concentration, nitrite nitrogen, and ammonia nitrogen in a reaction solution of a biological reaction tank; An exhaust gas recovery means for recovering the gas aerated in the biological reaction tank, and a control means for controlling opening and closing of a control valve provided in the exhaust gas recovery means, the control means depending on the measured value of the nitrogen measurement means A sewage treatment method characterized in that the aerated gas is recovered by opening and closing the control valve.   A sewage treatment method for treating wastewater with activated sludge, a nitrogen measuring means for measuring one or more of nitrate nitrogen concentration, nitrite nitrogen, and ammonia nitrogen in a reaction solution of a biological reaction tank; An exhaust gas recovery means for recovering the gas aerated in the biological reaction tank, and a control means for controlling opening and closing of a control valve provided in the exhaust gas recovery means, the control means is a measurement value of the nitrogen measurement means A sewage treatment method, wherein the exhaust gas recovery flow rate is controlled by controlling the control valve.   The sewage treatment method according to any one of claims 1 to 8, wherein the exhaust gas recovered from the exhaust gas recovery means is processed by being injected into inflow sewage.   The sewage treatment method according to any one of claims 1 to 8, wherein the exhaust gas recovered from the exhaust gas recovery means is injected into the treated water.   The sewage treatment method according to any one of claims 1 to 8, wherein the exhaust gas recovered from the exhaust gas recovery means is thermally decomposed and processed.

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