Methods to reduce carbon emissions from wastewater treatment

Abstract

The present invention relates to a method for reducing carbon emissions in a sewage treatment process. It is applicable to environmental protection fields such as sewage treatment and pollution reduction and carbon reduction. The technical solution adopted by the present invention is: a method for reducing carbon emissions in a sewage treatment process, comprising: adding nano-ferroferric oxide in the sewage treatment process; introducing an anaerobic ammonia oxidation reaction in the sewage treatment process. Ferroferric oxide has electrical conductivity and can improve the electron transfer ability of microorganisms. In the biological denitrification process, the carbon source is quickly utilized by heterotrophic bacteria, and the electrons are transferred to N2O reducing functional bacteria through the interspecies electron transfer process, thereby promoting the conversion and utilization of organic matter and the reduction of N2O. At the same time, no carbon source consumption occurs during the denitrification process of the anaerobic ammonia oxidation reaction, which improves the carbon source utilization efficiency of heterotrophic bacteria and achieves the purpose of pollution reduction and carbon reduction. The present invention reduces the emissions of methane and nitrous oxide in the sewage treatment process by adding nano-ferroferric oxide in the sewage treatment process, thereby achieving a reduction in direct carbon emissions.

Description

Technical Field

[0001] The present invention relates to a method for reducing carbon emissions in a sewage treatment process, and is applicable to environmental protection fields such as sewage treatment and pollution and carbon reduction. Background Art

[0002] Rural sewage suffers from significant fluctuations in both volume and quality, and existing sewage treatment processes lack adaptability and stability. When water volume and influent organic matter concentrations are low, excessive aeration is common, leading to low total nitrogen removal rates, high energy consumption, and high carbon emissions. Therefore, it is necessary to explore a sewage treatment method and device with strong adaptability, stability, low energy consumption, and low carbon emissions, tailored to the specific characteristics of rural sewage volume and quality.

[0003] Wastewater treatment carbon emissions include both direct and indirect emissions. Direct greenhouse gases primarily include methane and nitrous oxide, while indirect emissions primarily include electricity consumed by aeration and recirculation equipment, as well as carbon emissions from chemical preparation and transportation. Therefore, reducing wastewater treatment carbon emissions requires addressing both direct and indirect emissions, achieving simultaneous reductions in both. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in view of the above-mentioned problems, a method for reducing carbon emissions in the sewage treatment process is provided.

[0005] The technical solution adopted by the present invention is: a method for reducing carbon emissions in a sewage treatment process, characterized by comprising:

[0006] Nano-ferroferric oxide is added during the sewage treatment process; anaerobic ammonia oxidation reaction is introduced during the sewage treatment process.

[0007] Ferroferric oxide is conductive, which improves the electron transfer capacity of microorganisms. During the biological denitrification process, the carbon source is rapidly utilized by heterotrophic bacteria, and electrons are transferred to N2O-reducing bacteria through interspecies electron transfer, thereby promoting the conversion and utilization of organic matter and the reduction of N2O. At the same time, the anaerobic ammonium oxidation reaction does not consume the carbon source during denitrification, improving the efficiency of carbon source utilization by heterotrophic bacteria and achieving the goal of reducing pollution and carbon emissions.

[0008] The sewage treatment process includes the following sewage treatment processes performed successively:

[0009] Anaerobic process, using glycogen-accumulating bacteria and phosphate-accumulating bacteria to convert internal carbon sources in an anaerobic environment, rapidly removing organic matter and simultaneously releasing phosphorus;

[0010] Aerobic I process: Under the environment where the dissolved oxygen concentration is controlled at a preset value, ammonia nitrogen is oxidized into nitrite nitrogen and nitrate nitrogen through nitrification reaction, and phosphorus is absorbed by phosphate-accumulating bacteria;

[0011] Anoxic I process, which removes nitrite nitrogen, nitrate nitrogen and ammonia nitrogen through denitrification and anaerobic ammonium oxidation reactions in an anoxic environment;

[0012] Anoxic II process, which removes nitrite nitrogen, nitrate nitrogen and ammonia nitrogen through denitrification and anaerobic ammonium oxidation reactions in an anoxic environment;

[0013] Aerobic I process, under the environment where the dissolved oxygen concentration is controlled at a preset value, removes ammonia nitrogen through nitrification oxidation and further removes organic matter.

[0014] The hydraulic retention times of the anaerobic, aerobic I, anoxic I, anoxic II and aerobic II processes are 1.5-2h, 2h, 2h, 2h and 0.5h respectively.

[0015] The anaerobic, aerobic I, anoxic I and aerobic II processes adopt activated sludge reactors, and the anoxic II process adopts a fixed-bed biofilm reactor.

[0016] The nano-ferroferric oxide is added corresponding to the anaerobic process.

[0017] The nano-ferroferric oxide is added corresponding to the anoxic I process and the anoxic II process.

[0018] The dosage of the nano-ferroferric oxide is 3-5 g / L.

[0019] The dissolved oxygen concentration in the aerobic I process is 0.2-0.5 mg / L; the dissolved oxygen concentration in the aerobic II process is 4.0-5.0 mg / L.

[0020] The beneficial effect of the present invention is that the present invention reduces the emission of methane and nitrous oxide during the sewage treatment process by adding nano-ferroferric oxide during the sewage treatment process, thereby reducing direct carbon emissions.

[0021] The present invention introduces anaerobic ammonium oxidation reaction into the sewage treatment process, utilizes the characteristic of anaerobic ammonium oxidation reaction that has low oxygen demand, reduces aeration energy consumption in the sewage treatment process, and thus achieves reduction of indirect carbon emissions.

[0022] The hydraulic retention times (HRTs) for the anaerobic, aerobic I, anoxic I, anoxic II, and aerobic II processes in this invention are 1.5-2 hours, 2 hours, 2 hours, 2 hours, and 0.5 hours, respectively. Compared to conventional anaerobic-anoxic-aerobic wastewater treatment processes, the aerobic process in this invention has a smaller proportion of aerobic tanks, while the anoxic process has a larger proportion of anoxic tanks, effectively reducing aeration fan energy consumption. This eliminates the backflow of nitrification solution from the aerobic tank to the anoxic tank in conventional anaerobic-anoxic-aerobic wastewater treatment processes, saving energy consumed by the reflux pump.

[0023] In the present invention, the anaerobic, aerobic I, anoxic I and aerobic II processes use activated sludge reactors, and the anoxic II process uses a fixed-bed biofilm reactor. The biofilm can proliferate and enrich long-sludge-age microorganisms, such as autotrophic bacteria and archaea. These microorganisms can utilize low-concentration substrates, have strong substrate affinity, and convert low-concentration pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart in the embodiment.

[0025] Figure 2 These are the control test results in the examples, nitrate removal and greenhouse gas emission flux (a without adding nano-ferroferric oxide; b with adding nano-ferroferric oxide).

[0026] Figure 3 This is the sewage treatment system in the embodiment.

[0027] 1. Inlet tank; 2. Anaerobic unit; 3. Aerobic I unit; 4. Anoxic I unit; 5. Anoxic II unit; 6. Aerobic II unit; 7. Secondary sedimentation tank unit; 8. Outlet tank. DETAILED DESCRIPTION

[0028] Example 1: This embodiment is a method for reducing carbon emissions in a sewage treatment process. The method introduces an anaerobic ammonium oxidation reaction into the sewage treatment process by adding nano-ferrous oxide.

[0029] This example uses nano-ferroferric oxide to improve sludge stability, accelerate nitrate reduction, and reduce direct emissions of methane and nitrous oxide, two greenhouse gases, from the sewage pool, thereby reducing direct carbon emissions. This example also utilizes the low oxygen consumption of the anaerobic ammonium oxidation reaction to reduce aeration energy consumption, thereby reducing indirect carbon emissions.

[0030] like Figure 1 As shown, the sewage treatment process in this embodiment includes the following sewage treatment processes performed in sequence:

[0031] S1. Anaerobic process is used to remove organic matter from sewage. In an anaerobic environment, saccharin-accumulating bacteria and phosphate-accumulating bacteria are used to convert the internal carbon source, quickly removing organic matter and releasing phosphorus simultaneously.

[0032] S2, Aerobic I process, is used for aerobic phosphorus removal and ammonia nitrogen oxidation reaction. It increases the dissolved oxygen in the sewage through aeration, further removes organic matter in an environment where the dissolved oxygen concentration is higher than the preset value, oxidizes ammonia nitrogen into nitrite nitrogen and nitrate nitrogen through nitrification reaction, and uses polyphosphate bacteria to achieve excessive phosphorus absorption under aerobic conditions.

[0033] S3, Anoxic I process, is used for the removal of nitrate, residual ammonia nitrogen and residual phosphate. It uses the internal carbon source generated by the anaerobic unit to undergo denitrification in an anoxic environment, and uses the anaerobic ammonium oxidation reaction to achieve the simultaneous removal of nitrite nitrogen, nitrate nitrogen and residual ammonia nitrogen. At the same time, denitrification and phosphorus removal reactions can occur to further remove nitrate and phosphate.

[0034] S4, anoxic II process, removes nitrite nitrogen, nitrate nitrogen and ammonia nitrogen through denitrification and anaerobic ammonium oxidation reactions in an anoxic environment, and removes the remaining small amount of nitrate and ammonia nitrogen.

[0035] S5, Aerobic I process, removes ammonia nitrogen and oxygen through nitrification reaction when the dissolved oxygen concentration is higher than the preset value, and is used for further oxidation and removal of residual ammonia nitrogen and organic matter to ensure that the ammonia nitrogen and COD concentrations in the effluent meet the emission standards.

[0036] In this embodiment, the hydraulic retention times of the anaerobic, aerobic I, anoxic I, anoxic II, and aerobic II processes are 1.5-2 hours, 2 hours, 2 hours, 2 hours, and 0.5 hours, respectively. The anaerobic, aerobic I, anoxic I, and aerobic II processes employ activated sludge reactors, while the anoxic II process employs a fixed-bed biofilm reactor.

[0037] Testing revealed that in the anaerobic-aerobic-anoxic-aerobic treatment process, the pre-anaerobic process is the primary greenhouse gas emission unit, with CH4 and N2O emissions accounting for over 70% of the entire treatment process. This embodiment reduces greenhouse gas emissions by adding nano-ferroferric oxide during the anaerobic treatment process. The dosage of nano-ferroferric oxide is determined by the volume of the wastewater to be treated, preferably 3-5g / L.

[0038] In this embodiment, different dissolved oxygen concentrations are controlled in the aerobic I and aerobic II units. The dissolved oxygen concentration in the aerobic I unit is 0.2-0.5 mg / L; the dissolved oxygen concentration in the aerobic II unit is 4.0-5.0 mg / L.

[0039] Example 2: This example is a method for reducing carbon emissions in a sewage treatment process, which is basically the same as Example 1. The only difference is that in this example, nano-ferroferric oxide is added during the anaerobic process, the anoxic I process, and the anoxic II process to achieve simultaneous reduction in methane and nitrous oxide emissions.

[0040] The test results are as follows Figure 2As shown, the nitrate reduction rates of the control group and the nano-ferroferric oxide addition group (dosage of 5g / L) were 1.54 and 1.75gN / (gVSS h), respectively, and the nitrate removal rate increased by 14%. The methane (CH4) emission factors of the control group and the nano-ferroferric oxide addition group were 0.02% and 0.007%, respectively. The emission factors of nitrous oxide (N2O) of the control group and the nano-ferroferric oxide addition group were 0.1% and 0.07%, respectively. The addition of nano-ferroferric oxide reduced CH4 and N2O emissions by 65% ​​and 30%, respectively. Therefore, the addition of nano-ferroferric oxide can simultaneously increase the nitrate reduction rate and reduce greenhouse gas emissions.

[0041] Example 3: This example is a sewage treatment system that can implement the methods of Examples 1 and 2. The sewage treatment system includes an inlet tank, an anaerobic unit, an aerobic I unit, an anoxic I unit, an anoxic II unit, an aerobic II unit, a secondary sedimentation tank unit, and an outlet tank, etc., which are arranged in sequence along the flow direction of the sewage (see Figure 3 ).

[0042] In this example, the inlet pool is used to collect the sewage to be treated; the anaerobic unit is used to provide an anaerobic environment to remove organic matter in the sewage, and utilize saccharin-accumulating bacteria and phosphate-accumulating bacteria to convert the internal carbon source, so that the organic matter is quickly removed and phosphorus is released simultaneously.

[0043] In this embodiment, the aerobic unit I is used to provide an aerobic environment with a dissolved oxygen concentration higher than a preset value to facilitate aerobic phosphorus removal and ammonia nitrogen oxidation reactions. The dissolved oxygen in the sewage is increased through aeration, organic matter is further removed, and ammonia nitrogen is oxidized into nitrite nitrogen and nitrate nitrogen. In addition, polyphosphate bacteria are used to achieve excessive phosphorus absorption under aerobic conditions.

[0044] In this example, the anoxic I unit is used to provide an anoxic environment to remove nitrate, residual ammonia nitrogen and residual phosphate. The internal carbon source generated by the conversion in the anaerobic unit is used to undergo denitrification under anoxic conditions, and the anaerobic ammonium oxidation reaction is used to achieve the simultaneous removal of nitrate and residual ammonia nitrogen. At the same time, denitrification and phosphorus removal reactions can occur to further remove nitrate and phosphate.

[0045] In this example, the anoxic II unit is used to provide an anoxic environment to remove the remaining small amount of nitrate and ammonia nitrogen. Unlike the anoxic I unit, further removal of pollutants can occur under lower substrate concentration conditions.

[0046] In this embodiment, the aerobic II unit is used to provide an aerobic environment with a dissolved oxygen concentration higher than a preset value to further oxidize and remove residual ammonia nitrogen and organic matter, ensuring that the ammonia nitrogen and COD concentrations in the effluent meet the discharge standards.

[0047] In this embodiment, the secondary sedimentation tank unit is used to separate mud and water, the clarified water is sent to the effluent tank, and the bottom sludge is returned to the anaerobic unit.

[0048] In this example, the tank volumes for anaerobic, aerobic I, anoxic I, anoxic II, and aerobic II are 1:2:2:2:2:0.5, respectively. Compared to traditional anaerobic-anoxic-aerobic wastewater treatment processes, this method utilizes a smaller aerobic tank and a larger anoxic tank, effectively reducing aeration fan energy consumption. This eliminates the backflow of nitrification solution from the aerobic to the anoxic tanks in traditional anaerobic-anoxic-aerobic wastewater treatment processes, saving energy consumed by the return pump.

[0049] In this example, the anaerobic, aerobic I, anoxic I, and aerobic II reactors are activated sludge reactors, while the anoxic II reactor is a fixed-bed biofilm reactor. Biofilms enable the proliferation and enrichment of long-lived microorganisms in sludge, such as autotrophic bacteria and archaea. These microorganisms can utilize low-concentration substrates and have strong substrate affinity, enabling the conversion of low-concentration pollutants. The anoxic II reactor uses a combination of fillers, including polypropylene plastic, polyurethane sponge, and fiber, with a fill rate of 60-80%. It is secured to the reactor tank by a metal frame.

[0050] In this example, the reactors were inoculated with conventional activated sludge, while Anoxic I and Anoxic II were inoculated with a small amount of anammox sludge. After inoculation, the sludge concentration in the reactors was 3-5 g mlss / L. The anammox sludge accounted for approximately 30%-50% of the mass in Anoxic I and Anoxic II.

[0051] In this embodiment, the dissolved oxygen concentrations in the aerobic I and aerobic II units are controlled to be different, with the dissolved oxygen concentration in aerobic I being 0.2-0.5 mg / L and the dissolved oxygen concentration in aerobic II being 4.0-5.0 mg / L. In this embodiment, the sludge return ratio of the secondary sedimentation tank is 30%-50%.

Claims

1. A method for reducing carbon emissions in a sewage treatment process, characterized in that: include: Adding nano-ferroferric oxide during sewage treatment; introducing anaerobic ammonium oxidation reaction during sewage treatment; The sewage treatment process includes the following sewage treatment processes performed successively: Anaerobic process, using glycogen-accumulating bacteria and phosphate-accumulating bacteria to convert internal carbon sources in an anaerobic environment, rapidly removing organic matter and simultaneously releasing phosphorus; Aerobic I process: Under the environment where the dissolved oxygen concentration is controlled at a preset value, ammonia nitrogen is oxidized into nitrite nitrogen and nitrate nitrogen through nitrification reaction, and phosphorus is absorbed by phosphate-accumulating bacteria; Anoxic I process, which removes nitrite nitrogen, nitrate nitrogen and ammonia nitrogen through denitrification and anaerobic ammonium oxidation reactions in an anoxic environment; Anoxic II process, which removes nitrite nitrogen, nitrate nitrogen and ammonia nitrogen through denitrification and anaerobic ammonium oxidation reactions in an anoxic environment; Aerobic II process, in an environment where the dissolved oxygen concentration is controlled at a preset value, removes ammonia nitrogen through nitrification oxidation and further removes organic matter; The anaerobic, aerobic I, anoxic I and aerobic II processes use activated sludge reactors, and the anoxic II process uses a fixed-bed biofilm reactor; The nano-ferroferric oxide is added corresponding to the anaerobic process.

2. The method for reducing carbon emissions in a sewage treatment process according to claim 1, characterized in that: The hydraulic retention times of the anaerobic, aerobic I, anoxic I, anoxic II, and aerobic II processes are 1.5-2 h, 2 h, 2 h, 2 h, and 0.5 h, respectively.

3. The method for reducing carbon emissions in a sewage treatment process according to claim 1, characterized in that: The nano-ferroferric oxide is added corresponding to the anoxic I process and the anoxic II process.

4. The method for reducing carbon emissions in a sewage treatment process according to claim 1 or 3, characterized in that: The dosage of the nano-ferroferric oxide is 3-5 g / L.

5. The method for reducing carbon emissions in a sewage treatment process according to claim 1, characterized in that: The dissolved oxygen concentration in the aerobic I process is 0.2-0.5 mg / L; the dissolved oxygen concentration in the aerobic II process is 4.0-5.0 mg / L.

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