A sewage treatment method for realizing water purification and synergistic greenhouse gas reduction based on alkalization

Abstract

The present invention discloses a sewage treatment method for realizing water purification and synergistic greenhouse gas emission reduction based on alkalization of alkaloids, comprising the following steps: After mixing domestic sewage with water containing sulfate, it enters a sulfate reduction reactor, where organic matter is oxidized to CO2 and sulfide is generated, and CO2 is fixed in the water body in the form of HCO3 ‑ ; The effluent of the sulfate reduction reactor enters a selective sulfur oxidation reactor, where sulfide is oxidized to elemental sulfur while partially reducing nitrate nitrogen; The effluent of the selective sulfur oxidation reactor enters a sulfur sedimentation tank to recover elemental sulfur; The effluent of the sulfur sedimentation tank enters a nitrification reactor for ammonia oxidation and nitrification, while consuming the remaining organic matter; The effluent of the nitrification reactor and the elemental sulfur recovered from the sulfur sedimentation tank enter a deep denitrification and nitrogen removal reactor to conduct deep nitrogen removal of the sewage. The method of the present invention has a small CO2 emission, a small sludge production emission, and a relatively high effluent pH value.

Description

Technical Field

[0001] The present invention relates to a sewage treatment method, and particularly to a sewage treatment method for realizing water quality purification and synergistic greenhouse gas emission reduction based on alkalization of alkaloids. Background Art

[0002] In current mainstream sewage treatment processes, organic matter is mainly removed through aerobic oxidation. A part is oxidized to CO by endogenous respiration of heterotrophic bacteria. 2 Since the aerobic oxidation process of organic matter does not increase the alkalinity and pH of the water body, and the solubility of CO in the water body is limited, most of it is directly released into the air. Another part of anabolism enables the growth of heterotrophic bacteria, which is converted into excess sludge and finally converted into CO during the sludge disposal process. 2 and CH. 2 This increases the indirect emission of greenhouse gases. At the same time, aerobic oxidation requires high-power aeration, and the energy consumption of this process also increases the indirect emission of greenhouse gases. The denitrification process depends on heterotrophic denitrification of organic matter. This process not only has direct emission of N. 4 O, but also often has the need to strengthen denitrification with an external carbon source. The additional dosing of organic matter agents also means more indirect emissions of greenhouse gases. 2 Summary of the Invention

[0003] In order to overcome the above-mentioned disadvantages and deficiencies of the prior art, the purpose of the present invention is to provide a sewage treatment method for realizing water quality purification and synergistic greenhouse gas emission reduction based on alkalization of alkaloids, with small CO emissions, small sludge production, and ensuring that the pH of the effluent is maintained at a relatively high level. 2

[0004] The purpose of the present invention is achieved by the following technical solutions:

[0005] The present invention provides a sewage treatment method for realizing water quality purification and synergistic greenhouse gas emission reduction based on alkalization of alkaloids, comprising the following steps:

[0006] Inoculate sulfate-reducing bacteria in the first reactor to obtain a sulfate-reducing reactor; inoculate sulfur-oxidizing bacteria in the second reactor to obtain a selective sulfur-oxidizing reactor; inoculate ammonia-oxidizing bacteria and nitrifying bacteria in the third reactor to obtain a nitrification reactor; inoculate sulfur autotrophic denitrifying bacteria in the fourth reactor to obtain a deep denitrification and nitrogen removal reactor;

[0007] Mix domestic sewage with water containing sulfate and then enter the sulfate-reducing reactor. Among them, the C / S mass ratio of the influent of the sulfate-reducing reactor is 0.2 - 2.0, and the influent sulfate concentration is 40 - 400 mg S / L. In the sulfate-reducing reactor, sulfate-reducing bacteria use sulfate as an electron acceptor to oxidize organic matter in the sewage to CO. 2 and produce sulfide, CO.2 Fixed in the water body in the form of HCO 3 - ; The sulfide includes H 2 S, HS - , S 2- At least one of;

[0008] The effluent of the sulfate reduction reactor enters the selective sulfur oxidation reactor; in the selective sulfur oxidation reactor, the oxidation-reduction potential ORP of the water body is controlled to be -400 mV to -200 mV, and sulfur-oxidizing bacteria use oxygen and / or oxidized nitrogen as electron acceptors to oxidize sulfide to elemental sulfur, while reducing part of the nitrate nitrogen;

[0009] The effluent of the selective sulfur oxidation reactor enters the sulfur sedimentation tank to separate and recover elemental sulfur;

[0010] The effluent of the sulfur sedimentation tank enters the nitrification reactor, and ammonia-oxidizing bacteria and nitrifying bacteria carry out complete ammonia oxidation and nitrification, while consuming the remaining organic matter in the sewage;

[0011] The effluent of the nitrification reactor and the elemental sulfur recovered from the sulfur sedimentation tank enter the deep denitrification reactor, and sulfur autotrophic denitrifying bacteria use elemental sulfur as an electron acceptor to deeply denitrify the sewage.

[0012] Preferably, the effluent of the nitrification reactor is divided into two parts, one part enters the deep denitrification reactor, and the other part is refluxed to the selective sulfur oxidation reactor.

[0013] Preferably, the effluent of the deep denitrification reactor, after sedimentation and separation, the sludge is divided into two parts, one part enters the sludge treatment system, and the other part is refluxed to the selective sulfur oxidation reactor.

[0014] Preferably, the pH values of the influent of the sulfate reduction reactor, the effluent of the sulfate reduction reactor, and the effluent of the selective sulfur oxidation reactor increase from 6 to 7.5 to 7.5 to 8.9 and 7.8 - 9.5 in sequence, and finally the effluent pH is increased to 7.5 - 9, so that more CO 2 dissolves in water, thereby reducing the direct emission of CO 2 .

[0015] Preferably, the residence time of the sewage in the sulfate reduction reactor is 8 - 14 hours.

[0016] Preferably, the residence time of the sewage in the selective sulfur oxidation reactor is 0.5 - 3 hours.

[0017] Preferably, the residence time of the sewage in the nitrification reactor is 3 - 5 hours.

[0018] Preferably, the residence time of the sewage in the deep denitrification and nitrogen removal reactor is 1.5 to 4.5 hours.

[0019] Preferably, the domestic sewage is the domestic sewage of a coastal city; the sulfate-containing water is seawater.

[0020] Preferably, the deep denitrification of the sewage is specifically: reducing NO 3 - 、NO 2 - to N 2 step by step.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] The sewage treatment method for realizing water quality purification and synergistic greenhouse gas emission reduction based on alkalization in the present invention, through sulfate reduction reaction and sulfur oxidation reaction, while removing organic matter and partial nitrate nitrogen, improves the alkalinity and pH of the water body, and then increases the solubility of CO 2 and reduces the direct emission of CO 2 ; The elemental sulfur recovered by the sulfur sedimentation tank is used for enhanced denitrification by sulfur autotrophic denitrification, avoiding the indirect emission of CO 2 caused by the additional addition of organic matter due to insufficient carbon source in the heterotrophic denitrification process. Compared with the current mainstream sewage treatment process of aerobic oxidation and heterotrophic denitrification of organic matter, it not only has lower energy consumption and smaller sludge production, but also ensures that the pH of the effluent is maintained at a relatively high level, making the effluent water body of the sewage treatment method of the present invention have stronger carbon sequestration ability and smaller CO 2 emissions, and is particularly suitable for the treatment of domestic sewage in coastal cities. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic flow chart of the sewage treatment method for realizing water quality purification and synergistic greenhouse gas emission reduction based on alkalization in one embodiment of the present invention.

[0024] Figure 2 is a graph showing the change of the physical and chemical indexes of the effluent of the embodiment simulated in the activated sludge mathematical model over time.

[0025] Figure 3 is a graph showing the change of the greenhouse gas emission indexes of the embodiment simulated in the activated sludge mathematical model over time. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following is a further detailed description of the present invention in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0027] Embodiment

[0028] The sewage treatment method for realizing water quality purification and synergistic greenhouse gas reduction based on alkalization in the embodiments of the present invention includes the following steps:

[0029] Inoculate sulfate-reducing bacteria in the first reactor to obtain a sulfate reduction reactor; inoculate sulfur-oxidizing bacteria in the second reactor to obtain a selective sulfur oxidation reactor; inoculate ammonia-oxidizing bacteria and nitrifying bacteria in the third reactor to obtain a nitrification reactor; inoculate sulfur autotrophic denitrifying bacteria in the fourth reactor to obtain a deep denitrification and nitrogen removal reactor;

[0030] After mixing domestic sewage with water containing sulfate, it enters the sulfate reduction reactor. Among them, the C / S mass ratio of the influent water of the sulfate reduction reactor is 0.2 - 2.0, and the influent sulfate concentration is 40 - 400 mg S / L; in the sulfate reduction reactor, the sulfate-reducing bacteria use sulfate as an electron acceptor to oxidize the organic matter in the sewage to CO 2 and produce sulfide. CO 2 is fixed in the water body in the form of HCO 3 - ; The sulfide includes at least one of H 2 S, HS - , S 2- ;

[0031] The effluent of the sulfate reduction reactor enters the selective sulfur oxidation reactor; in the selective sulfur oxidation reactor, the oxidation-reduction potential ORP of the water body is controlled to be -400 mV - -200 mV, and the sulfur-oxidizing bacteria use oxygen and / or oxidized nitrogen as electron acceptors to oxidize sulfide to elemental sulfur and simultaneously reduce part of the nitrate nitrogen;

[0032] The effluent of the selective sulfur oxidation reactor enters the sulfur sedimentation tank to separate and recover the elemental sulfur in the reducing sulfur;

[0033] The effluent of the sulfur sedimentation tank enters the nitrification reactor, and the ammonia-oxidizing bacteria and nitrifying bacteria perform complete ammonia oxidation and nitrification, while consuming the remaining organic matter in the sewage;

[0034] The effluent of the nitrification reactor and the elemental sulfur recovered from the sulfur sedimentation tank enter the deep denitrification and nitrogen removal reactor, and the sulfur autotrophic denitrifying bacteria use elemental sulfur as an electron acceptor to perform deep nitrogen removal on the sewage.

[0035] In some embodiments of the present invention, the effluent of the nitrification reactor is divided into two parts. One part enters the deep denitrification and nitrogen removal reactor, and the other part is refluxed to the selective sulfur oxidation reactor to provide an electron acceptor mainly composed of nitrate nitrogen for the sulfur oxidation reaction.

[0036] In some embodiments of the present invention, after the effluent of the deep denitrification reactor is separated by sedimentation, the sludge is divided into two parts. One part enters the sludge treatment system, and the other part is refluxed to the selective sulfur oxidation reactor.

[0037] In some embodiments of the present invention, the treatment method of the present invention is applied to the domestic sewage treatment in coastal cities, and seawater can be used for the water containing sulfate.

[0038] In some embodiments of the present invention, the sulfate reduction reactor is an upflow reactor, and packing is installed for the attachment and growth of sulfate-reducing bacteria.

[0039] In some embodiments of the present invention, the residence time of the sewage in the sulfate reduction reactor can be set to 8 - 14 hours.

[0040] In some embodiments of the present invention, the residence time of the sewage in the selective sulfur oxidation reactor can be set to 0.5 - 3 hours.

[0041] In some embodiments of the present invention, the residence time of the sewage in the nitrification reactor can be set to 3 - 5 hours.

[0042] In some embodiments of the present invention, the residence time of the sewage in the deep denitrification reactor can be set to 1.5 - 4.5 hours.

[0043] In the sulfate reduction reactor of the above embodiments, sulfate-reducing bacteria (SRB) dominate the dissimilatory sulfate reduction process. Using sulfate as an electron acceptor, organic substances such as glucose and acetic acid are oxidized to CO 2 and sulfide is produced. During this process, along with the consumption of sulfate ions, alkalinity is generated in the water body, and the pH increases significantly. The CO 2 produced during the degradation of organic substances is fixed in the water body in the form of HCO 3 - , greatly reducing the direct emission of CO 2 . At the same time, due to the low yield coefficient of SRB for the utilization of organic substances, the sludge production is small, further reducing the CH 4 emission during the sludge disposal process. Taking acetic acid as an example of organic substances, the reaction formula of this process is as follows:

[0044]

[0045] In the sulfur oxidation and denitrification reactors of the above embodiments, the effluent of the sulfate reduction reactor containing sulfide enters the selective sulfur oxidation reactor for selective sulfur oxidation. Sulfur-oxidizing bacteria (SOB) use oxygen (O 2 ) and oxidized nitrogen (NO 3 - , NO 2- , NO, N 2 O) and other electron acceptors. By regulating the water body redox potential ORP between -400 mV and -200 mV, H 2 S is selectively oxidized to elemental sulfur, and at the same time, part of the nitrate nitrogen is reduced to nitrogen gas or other nitrogen oxides. Through the consumption of weak acids such as H 2 S, the pH value of the water body can be further increased, strengthening the fixation of CO 2 . The generated elemental sulfur can be recycled as an electron donor for subsequent advanced denitrification of sewage, further reducing the indirect greenhouse gas emissions from chemical agent dosing in the denitrification process. The reaction formula in this process is as follows:

[0046]

[0047] In the advanced denitrification reactor of the above embodiment, sulfur autotrophic denitrifying bacteria use reducing sulfur such as elemental sulfur S 0 as an electron acceptor, and use the elemental sulfur recovered from the effluent of the sulfur sedimentation tank for advanced denitrification, reducing NO 3 - , NO 2 - etc. to N 2 step by step. Compared with the chemical agent dosing of adding external organic carbon sources in the traditional process, the indirect greenhouse gas emissions of elemental sulfur S 0 are lower. At the same time, there is no need to worry about the problem of secondary pollution caused by excessive addition of organic matter. In this process, the reaction formula is as follows:

[0048]

[0049] To better illustrate the effects of the embodiments of the present invention, a mathematical model of activated sludge based on matlab is used to simulate the effects of the sewage treatment solution of the present invention:

[0050] Water samples from the primary sedimentation tanks of several water purification plants in Zhuhai were collected on-site, and their physical and chemical indexes were measured. The average values are shown in Table 1, representing the influent water quality of the water purification plants.

[0051] Table 1 Average values of influent physical and chemical indexes of several water purification plants in Zhuhai

[0052] The seawater sulfate concentration is about 900 mg S / L. Seawater and domestic sewage are mixed at a ratio of 1:13 to increase the sulfate concentration to about 80 mg S / L, and the C / S mass ratio is 1.96.

[0053] Using a mathematical model of activated sludge based on matlab, as Figure 1The shown treatment process is operated with the process parameters shown in Table 2 to simulate the water quality purification efficiency and greenhouse gas emissions of the embodiments of the present invention. The predicted results of the physicochemical indexes of the stable effluent and the predicted results of the greenhouse gas emission indexes are shown in Tables 3 to 4 respectively. The variations of the effluent physicochemical indexes and the greenhouse gas emission indexes with time are respectively as Figures 2 - 3 shown.

[0054] The results show that the embodiments of the present invention can achieve a gradual increase in pH, from 7.46 of the influent of the sulfate reduction reactor to 8.69 of the effluent of the sulfate reduction reactor and 9.06 of the effluent of the selective sulfur oxidation reactor, and can effectively resist the pH drop during the nitrification process, and finally achieve a high-pH effluent with a pH equal to 8.42.

[0055] Table 2 Process operation parameters

[0056]

[0057] Table 3 Predicted results of the physicochemical indexes of the process effluent

[0058]

[0059] Table 4 Predicted results of the process greenhouse gas emissions (global warming potential of 100)

[0060]

[0061] To further illustrate the effects of the embodiments of the present invention, the activated sludge mathematical model based on matlab is used and operated with the process parameters shown in Table 5 to simulate the water quality purification efficiency and greenhouse gas emissions of the traditional A2 / O process. The predicted results of the physicochemical indexes of the stable effluent and the predicted results of the greenhouse gas emission indexes are shown in Tables 6 to 7 respectively.

[0062] The results show that compared with the comparative example, the pH of the effluent of the embodiment is increased by 0.83 units, the TIC is increased by 11.21 mgC / L, and for every 10,000 m 3 of sewage treated, the direct emission of CO 2 is reduced by 1.45 t of CO 2 equivalent, the indirect emission of greenhouse gases is reduced by 12.13 t of CO 2 equivalent, and the total emission is reduced by 13.58 t of CO 2 equivalent.

[0063] Table 5 A2 / O process operation parameters

[0064]

[0065] Table 6 Predicted results of the physicochemical indexes of the A2 / O process effluent

[0066]

[0067] Table 7 Prediction Results of Greenhouse Gas Emissions from A2O Process (Global Warming Potential of 100)

[0068] The above embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A sewage treatment method based on biological alkalization to achieve water purification and greenhouse gas emission reduction, characterized in that: The following steps are involved: Sulfate-reducing bacteria are inoculated in the first reactor to obtain a sulfate-reducing reactor; sulfur-oxidizing bacteria are inoculated in the second reactor to obtain a selective sulfur-oxidizing reactor; ammonia-oxidizing bacteria and nitrifying bacteria are inoculated in the third reactor to obtain a nitrification reactor; sulfur-autotrophic denitrifying bacteria are inoculated in the fourth reactor to obtain a deep denitrification reactor; After the domestic sewage is mixed with the sulfate-containing water, it enters the sulfate reduction reactor, wherein the inlet C / S mass ratio of the sulfate reduction reactor is 0.2-2.0, and the inlet sulfate concentration is 40-400 mg S / L; in the sulfate reduction reactor, the sulfate-reducing bacteria use sulfate as an electron acceptor to oxidize the organic matter in the sewage into CO2 and produce sulfide, and CO2 is converted into HCO3 - The sulfides include H2S, HS - , S 2- At least one of; The effluent from the sulfate reduction reactor enters the selective sulfur oxidation reactor; in the selective sulfur oxidation reactor, the water redox potential (ORP) is controlled to be -400mV to -200mV, and the sulfur oxidizing bacteria use oxygen and / or oxidized nitrogen as electron acceptors to oxidize sulfide into elemental sulfur and reduce part of the nitrate nitrogen at the same time; The effluent from the selective sulfur oxidation reactor enters the sulfur precipitation tank to separate and recover elemental sulfur; The effluent from the sulfur precipitation tank enters the nitrification reactor, where ammonia oxidizing bacteria and nitrifying bacteria carry out complete ammonia oxidation and nitrification, while consuming the remaining organic matter in the sewage; The effluent from the nitrification reactor and the elemental sulfur recovered from the sulfur precipitation tank enter the deep denitrification reactor. The sulfur autotrophic denitrifying bacteria use elemental sulfur as an electron acceptor to deeply denitrify the wastewater.

2. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The effluent from the nitrification reactor is divided into two parts, one part enters the deep denitrification reactor, and the other part flows back to the selective sulfur oxidation reactor.

3. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The effluent from the deep denitrification reactor is separated by sedimentation, and the sludge is divided into two parts, one part enters the sludge treatment system, and the other part flows back to the selective sulfur oxidation reactor.

4. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The pH values ​​of the inlet water of the sulfate reduction reactor, the outlet water of the sulfate reduction reactor, and the outlet water of the selective sulfur oxidation reactor are respectively 6-7.57.5-8.9 and 7.8-9.5, and finally the outlet pH is increased to 7.5-9, so that more CO2 is dissolved in water, thereby reducing the direct emission of CO2.

5. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The residence time of the sewage in the sulfate reduction reactor is 8 to 14 hours.

6. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The residence time of the sewage in the selective sulfur oxidation reactor is 0.5 to 3 hours.

7. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The residence time of the sewage in the nitrification reactor is 3 to 5 hours.

8. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The residence time of the sewage in the deep denitrification and denitrification reactor is 1.5 to 4.5 hours.

9. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The domestic sewage is domestic sewage from coastal cities; the sulfate-containing water is seawater.

10. The sewage treatment method for achieving water purification and greenhouse gas emission reduction based on biological alkalization according to claim 1 is characterized in that: The deep denitrification of sewage is specifically: NO3 - 、NO2 - Gradually reduced to N2.

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