Method for removing nitrogen and phosphorus from wastewater in a sequencing batch reactor

Abstract

This invention provides a sequential batch process for treating nitrogen and phosphorus in wastewater. The method includes the following steps: (1) introducing wastewater into an electrochemical reaction device while adding sulfur-containing materials; (2) subjecting the wastewater to an electrochemical reaction under the action of a DC power supply, followed by sequential stirring and aeration; (3) repeating step (2) in a cycle, allowing the wastewater to settle before discharge. This invention achieves immediate start-up, extreme nitrogen and phosphorus removal, and rapid proliferation of sulfur-autotrophic bacteria in the wastewater treatment process by combining intermittent DC power supply with intermittent microaerobic aeration. Furthermore, it eliminates the need to adjust the pH during the wastewater treatment process and improves the service life of the anode.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a method for sequential batch processing of nitrogen and phosphorus in wastewater. Background Technology

[0002] Excessive nitrogen and phosphorus levels in wastewater effluent have become a challenging issue in water treatment in recent years. With increasingly stringent effluent quality standards, controlling nitrogen and phosphorus concentrations in the effluent is urgently needed. Biological treatment of wastewater has been widely used for denitrification, with heterotrophic denitrification being one of the most common methods and applied by the vast majority of wastewater treatment plants. However, the effluent from the biological treatment stage of wastewater treatment plants often lacks organic carbon sources, rendering conventional heterotrophic denitrifying bacteria and polyphosphate-accumulating bacteria unable to function effectively.

[0003] Currently, sulfur autotrophic technology is widely used in biological filters and constructed wetlands to treat wastewater with low C / N ratios, mainly due to its unique biochemical metabolic mechanism. Unlike traditional heterotrophic microorganisms, sulfur autotrophic microorganisms oxidize sulfides (such as H2S, S2S, etc.) 0 It obtains energy and uses inorganic carbon sources (such as CO2) for growth, which significantly reduces its dependence on organic carbon sources and is suitable for treating wastewater with low organic content.

[0004] While sulfur autotrophic technology has demonstrated numerous advantages in wastewater treatment, its drawbacks cannot be ignored. Firstly, sulfur autotrophic microorganisms grow slowly, requiring longer start-up and residence times and larger reactor volumes compared to heterotrophic microorganisms. This can impose space and economic limitations in practical engineering applications, leading to challenges such as large footprint and difficult start-up of sulfur autotrophic biofilters. Secondly, the sulfide oxidation reaction during sulfur autotrophy easily generates acidic byproducts, such as sulfuric acid, causing a decrease in the system's pH value. Additional alkaline substances are needed for neutralization to maintain a suitable microbial growth environment, increasing operating costs and complexity. Furthermore, sulfur autotrophic technology is sensitive to environmental conditions; fluctuations in factors such as temperature, oxygen concentration, and sulfide concentration can affect microbial activity and system stability. Finally, the sulfur autotrophic process may produce odorous gases (such as H2S), posing potential hazards to the surrounding environment and the health of operators, requiring corresponding gas treatment facilities, further increasing system complexity and operating costs. In summary, although sulfur autotrophic technology performs well under specific conditions, its application still requires comprehensive consideration of factors such as sulfur source supply, pH control, space requirements, environmental sensitivity, and gas treatment to ensure the system's economic viability and sustainability.

[0005] In summary, providing a wastewater denitrification and phosphorus removal method that is quick to start, low in cost, requires a small equipment footprint, and is easy to operate is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for sequential batch processing of nitrogen and phosphorus in wastewater. By combining intermittent DC power supply with intermittent micro-aerobic aeration, the method achieves immediate start-up and extreme nitrogen and phosphorus removal in the wastewater treatment process, without the need to adjust the pH during the wastewater treatment process, and improves the service life of the anode.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for treating nitrogen and phosphorus in wastewater using a sequencing batch process, the method comprising the following steps:

[0009] (1) Pass the wastewater into the electrochemical reaction device and add sulfur-containing materials at the same time;

[0010] (2) The wastewater is subjected to an electrochemical reaction under the action of DC power supply, and then stirring and aeration are carried out in sequence;

[0011] (3) Repeat step (2) to allow the wastewater to stand and then discharge it.

[0012] The sequencing batch method for treating nitrogen and phosphorus in wastewater provided by this invention combines intermittent DC power supply with intermittent microaerobic aeration, achieving immediate start-up, maximal nitrogen and phosphorus removal, and rapid proliferation of sulfur-autotrophic bacteria in the wastewater treatment process. Furthermore, it eliminates the need for pH adjustment during wastewater treatment and extends the lifespan of the anode. This method has low requirements for equipment and operation, is economical and efficient, and is beneficial for practical engineering applications.

[0013] It is worth noting that this invention, by employing intermittent DC power supply for the electrochemical reaction, not only promotes cell apoptosis and releases the endogenous carbon source from the inoculated sludge, thereby enhancing endogenous denitrification and achieving immediate start-up of maximal nitrogen and phosphorus removal, but also extends the lifespan of the anode. Furthermore, the use of intermittent microaerobic aeration not only promotes the hydrolysis of the endogenous carbon source and improves the heterotrophic denitrification utilization rate, but also provides additional oxygen electron acceptors for sulfur autotrophic bacteria, enabling higher ATP synthesis and rapid self-proliferation. This, in turn, promotes the rapid replacement of endogenous heterotrophic denitrification by sulfur autotrophic denitrification, resulting in highly efficient nitrogen removal. By combining intermittent DC power supply with intermittent microaerobic aeration, and through the "relay" behavior of endogenous denitrification and sulfur autotrophic denitrification, immediate start-up and maximal nitrogen and phosphorus removal are achieved without the need for additional pH adjustment during wastewater treatment.

[0014] As a preferred technical solution of the present invention, the electrochemical reaction device in step (1) includes a sealed reaction tank;

[0015] The reaction tank is equipped with a cathode and an anode, and the cathode and the anode are independently connected to a power source.

[0016] The reaction tank is equipped with a stirring device;

[0017] The top of the reaction tank is independently equipped with an exhaust port and a sulfur-containing material inlet;

[0018] The side wall of the reaction tank is equipped with an aeration pipe;

[0019] The sidewall of the reaction tank is provided with an inlet pipe and an outlet pipe from top to bottom.

[0020] In this invention, the electrochemical reaction device has a simple structure, occupies a small area, and has a volume of approximately 1L. The exhaust port is only opened during aeration; the power source is an external DC power supply.

[0021] As a preferred technical solution of the present invention, the diameter to height ratio of the reaction tank is 1:(1.5 to 2.5), for example, it can be 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3 or 1:2.4, etc., but is not limited to the listed values, and other values ​​within the range are also applicable.

[0022] Preferably, the anode comprises an iron electrode.

[0023] Preferably, the cathode comprises a graphite electrode.

[0024] In this invention, the dimensions of the anode and cathode are 8cm × 4cm × 0.2cm (length × width × thickness), which can be enlarged or reduced according to the actual situation by those skilled in the art.

[0025] Preferably, the distance between the cathode and the anode is 2.5 to 3.5 cm, for example, it can be 2.6 cm, 2.7 cm, 2.8 cm, 2.9 cm, 3 cm, 3.1 cm, 3.2 cm, 3.3 cm or 3.4 cm, but is not limited to the listed values, and other values ​​within the range are also applicable.

[0026] Preferably, the aeration pipe is connected to a blower.

[0027] Preferably, the height of the water inlet pipe is 7 / 10 to 9 / 10 of the height of the reaction tank, for example, it can be 7 / 10, 4 / 5 or 9 / 10.

[0028] Preferably, the height of the outlet pipe is 1 / 5 to 3 / 10 of the height of the reaction tank, for example, it can be 1 / 5 or 3 / 10.

[0029] As a preferred technical solution of the present invention, in the wastewater described in step (1), the concentration of COD (chemical oxygen demand) is 5-50 mg / L, and the concentration of NO3 is... - The concentration of -N is 10–25 mg / L, PO4 3-The concentration of -P is 1–3 mg / L.

[0030] In this invention, all concentrations refer to mass concentrations.

[0031] In this invention, the wastewater in step (1) includes the effluent from the secondary sedimentation tank of a wastewater treatment plant or simulated nitrogen- and phosphorus-containing wastewater. When using simulated nitrogen- and phosphorus-containing wastewater, sodium acetate, glucose, and peptone are used as a composite carbon source, and potassium nitrate and potassium dihydrogen phosphate are used as N and P pollutants in simulated excessive domestic wastewater.

[0032] Preferably, the flow rate of the wastewater in step (1) is 100-150 mL / min, for example, it can be 105 mL / min, 110 mL / min, 115 mL / min, 120 mL / min, 125 mL / min, 130 mL / min, 140 mL / min or 145 mL / min, but is not limited to the listed values, and other values ​​within the range are also applicable.

[0033] Preferably, the sewage inlet time in step (1) is 4 to 7 minutes, for example, it can be 4.5 minutes, 5 minutes, 5.5 minutes, 6 minutes or 6.5 minutes, but is not limited to the listed values. Other values ​​within the range are also applicable.

[0034] Preferably, the concentration of the inoculated sludge in the electrochemical reaction device in step (1) is 3500-4500 mg / L, for example, it can be 3600 mg / L, 3700 mg / L, 3800 mg / L, 3900 mg / L, 4000 mg / L, 4200 mg / L, 4300 mg / L or 4400 mg / L, etc., but is not limited to the listed values, and other values ​​within the range are also applicable.

[0035] Preferably, the sulfur-containing material in step (1) includes sulfur.

[0036] Preferably, the initial addition amount of the sulfur-containing material in step (1) is 1 to 1.5 g / L, for example, it can be 1.05 g / L, 1.1 g / L, 1.15 g / L, 1.2 g / L, 1.25 g / L, 1.3 g / L or 1.4 g / L, but is not limited to the listed values. Other values ​​within the range are also applicable.

[0037] In this invention, the amount of sulfur-containing material added is the concentration of the sulfur-containing material.

[0038] Preferably, the time for replenishing the sulfur-containing material in step (1) is when treating wastewater, and the daily replenishment amount is 300-400 mg / L, for example, it can be 310 mg / L, 320 mg / L, 330 mg / L, 350 mg / L, 360 mg / L, 380 mg / L or 390 mg / L, etc., but is not limited to the listed values, and other values ​​within the range are also applicable.

[0039] As a preferred technical solution of the present invention, the voltage of the DC power supply in step (2) is 0.6 to 1V, for example, it can be 0.65V, 0.7V, 0.75V, 0.8V, 0.85V, 0.9V or 0.95V, but is not limited to the listed values. Other values ​​within the range are also applicable.

[0040] Preferably, the electrochemical reaction in step (2) is carried out under stirring.

[0041] In this invention, the stirring speed is 150-250 rpm.

[0042] Preferably, the electrochemical reaction time in step (2) is 25 to 35 minutes, for example, it can be 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes or 34 minutes, but is not limited to the listed values. Other values ​​within the range are also applicable.

[0043] It is worth noting that, compared with continuous power supply, using intermittent DC power supply can not only save power consumption in electrochemical reactions, but also more than double the lifespan of the iron anode and alleviate the degree of cell apoptosis.

[0044] As a preferred technical solution of the present invention, the stirring speed in step (2) is 150 to 250 rpm, for example, it can be 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, 210 rpm, 220 rpm, 230 rpm or 240 rpm, but is not limited to the listed values, and other values ​​within the range are also applicable.

[0045] Preferably, the stirring time in step (2) is 25 to 40 minutes, for example, it can be 26 minutes, 28 minutes, 30 minutes, 32 minutes, 35 minutes, 36 minutes, 37 minutes or 38 minutes, but is not limited to the listed values. Other values ​​within the range are also applicable.

[0046] As a preferred technical solution of the present invention, during aeration in step (2), the concentration of DO (dissolved oxygen) in the wastewater is 1 to 1.5 mg / L, for example, it can be 1.1 mg / L, 1.2 mg / L, 1.3 mg / L or 1.4 mg / L, but is not limited to the listed values. Other values ​​within the range are also applicable.

[0047] It is worth noting that by introducing an intermittent microaerobic aeration process, not only is the oxidation rate of ammonia nitrogen improved, but the reduction rate of nitrate is also increased. Combined with intermittent DC power supply, this further ensures stable phosphorus removal efficiency.

[0048] Preferably, the aeration in step (2) is carried out under stirring.

[0049] Preferably, the aeration time in step (2) is 3 to 10 minutes, for example, it can be 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes or 9 minutes, but is not limited to the listed values. Other values ​​within the range are also applicable.

[0050] As a preferred technical solution of the present invention, the number of cycles in step (3) is ≥ 1 time, for example, it can be 2 times, 3 times or 4 times, etc.

[0051] It is worth noting that during the cyclical execution of step (2), the voltage of the DC power supply, stirring and aeration time and other parameters can be adjusted accordingly based on the actual situation.

[0052] As a preferred technical solution of the present invention, the settling time in step (3) is 25 to 35 minutes, for example, it can be 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes or 34 minutes, etc., but is not limited to the listed values, and other values ​​within the range are also applicable.

[0053] Preferably, the flow rate of the effluent discharge in step (3) is 100-150 mL / min, for example, it can be 105 mL / min, 110 mL / min, 115 mL / min, 120 mL / min, 125 mL / min, 130 mL / min, 140 mL / min or 145 mL / min, but is not limited to the listed values, and other values ​​within the range are also applicable.

[0054] Preferably, the time for water discharge in step (3) is 4 to 7 minutes, for example, it can be 4.5 minutes, 5 minutes, 5.5 minutes, 6 minutes or 6.5 minutes, but it is not limited to the listed values. Other values ​​within the range are also applicable.

[0055] As a preferred technical solution of the present invention, the method includes the following steps:

[0056] (1) The wastewater is fed into the electrochemical reaction device at a flow rate of 100-150 mL / min, and sulfur-containing materials are added at the same time.

[0057] The wastewater contained COD at a concentration of 5–50 mg / L and NO3. - The concentration of -N is 10–25 mg / L, PO4 3- The concentration of -P is 1-3 mg / L; the sewage influent time is 4-7 min; the concentration of inoculated sludge in the electrochemical reaction device is 3500-4500 mg / L;

[0058] The initial addition amount of the sulfur-containing material is 1-1.5 g / L; the replenishment time of the sulfur-containing material is when treating wastewater, and the daily replenishment amount is 300-400 mg / L.

[0059] The electrochemical reaction device includes a sealed reaction tank; a cathode and an anode are provided in the reaction tank, and the cathode and the anode are independently connected to a power source; a stirring device is provided in the reaction tank; an exhaust port and a sulfur-containing material inlet are independently provided at the top of the reaction tank; an aeration pipe is provided on the side wall of the reaction tank; and an inlet pipe and an outlet pipe are provided on the side wall of the reaction tank from top to bottom.

[0060] (2) The wastewater is subjected to an electrochemical reaction for 25 to 35 minutes under the action of stirring and a DC power supply with a voltage of 0.6 to 1V, then stirred for 25 to 40 minutes at a speed of 150 to 250 rpm, and then aerated for 3 to 10 minutes under stirring; during the aeration, the concentration of DO in the wastewater is 1 to 1.5 mg / L.

[0061] (3) Repeat step (2) at least once, let the sewage stand for 25 to 35 minutes, and finally discharge the sewage at a flow rate of 100 to 150 mL / min for 4 to 7 minutes.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The sequencing batch reactor (SBR) method for treating nitrogen and phosphorus in wastewater provided by this invention combines intermittent DC power supply with intermittent microaerobic aeration. Through the relay behavior of endogenous denitrification and sulfur autotrophic denitrification, it achieves immediate start-up, maximal nitrogen and phosphorus removal, and rapid proliferation of sulfur autotrophic bacteria in the wastewater treatment process. Furthermore, it eliminates the need for pH adjustment during wastewater treatment and extends the lifespan of the anode. After 10 days of operation, it ensures that the total nitrogen and total phosphorus in the effluent are less than 1 mg / L and 0.2 mg / L, respectively. This method has low requirements for equipment and operation, a short hydraulic retention time, a small footprint, and is economical and efficient, making it suitable for practical engineering applications. Attached Figure Description

[0064] Figure 1 A schematic diagram of the electrochemical reaction device provided by the present invention;

[0065] Among them, 1-reaction tank, 2-DC power supply, 3-stirring device, 4-exhaust port, 5-sulfur-containing material inlet, 6-aeration pipe, 7-water inlet pipe, 8-water outlet pipe;

[0066] Figure 2 NO3 in the effluent during operation of the methods provided in Example 1 and Comparative Examples 1-2 - Graph showing the relationship between -N concentration and time;

[0067] Figure 3 During the operation of the methods provided in Example 1 and Comparative Examples 1-2, the effluent NH4 content was... + Graph showing the relationship between -N concentration and time;

[0068] Figure 4 During the operation of the methods provided in Example 1 and Comparative Examples 1-2, the effluent PO4 3- Graph showing the relationship between -P concentration and time;

[0069] Figure 5 After running the methods provided in Example 1 and Comparative Examples 1-2 for 30 days, NO3 in the effluent was... - -N, NH4 + -N and PO4 3- Graph showing the average concentration of -P;

[0070] Figure 6 The methods provided for Example 1 and Comparative Examples 1-2 are NO3-free in wastewater. - After running with -N, add NO3 before letting it stand. — The results of COD concentration and denitrification rate after N2 are shown in the figure;

[0071] Figure 7 The relative abundance of each bacterium on day 15 and day 35 of the method provided in Example 1 and Comparative Examples 1-2;

[0072] Figure 8 This is a fluorescence staining result image of live and dead microorganisms in activated sludge in Example 1;

[0073] Figure 9 The image shows the fluorescence staining results of live and dead microorganisms in the activated sludge of Comparative Example 1.

[0074] Figure 10 The image shows the fluorescence staining results of live and dead microorganisms in the activated sludge of Comparative Example 2.

[0075] Figure 11The graph shows the intracellular ATP content of microorganisms in the activated sludge obtained by the methods provided in Example 1 and Comparative Examples 1-2. Detailed Implementation

[0076] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0077] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0078] This invention provides an electrochemical reaction device (structural schematic diagram shown in Figure 1). Figure 1 As shown), the electrochemical reaction device includes a sealed reaction tank 1; the diameter to height ratio of the reaction tank 1 is 1:2;

[0079] The reaction tank 1 is equipped with a cathode and an anode, which are independently connected to an external DC power supply 2. The anode is an iron electrode, and the cathode is a graphite electrode. The distance between the cathode and the anode is 3 cm. The dimensions of the anode and the cathode are both 8 cm × 4 cm × 0.2 cm.

[0080] The reaction tank 1 is equipped with a stirring device 3;

[0081] The top of the reaction tank 1 is independently equipped with an exhaust port 4 and a sulfur-containing material inlet 5;

[0082] The side wall of the reaction tank 1 is provided with an aeration pipe 6; the aeration pipe 6 is connected to a blower.

[0083] The side wall of the reaction tank 1 is provided with an inlet pipe 7 and an outlet pipe 8 from top to bottom; the height of the inlet pipe 7 is 4 / 5 of the height of the reaction tank 1; the height of the outlet pipe 8 is 1 / 5 of the height of the reaction tank 1.

[0084] The wastewater in the following examples and comparative examples is simulated nitrogen- and phosphorus-containing wastewater. The concentration of COD in the simulated nitrogen- and phosphorus-containing wastewater is 20 mg / L, and the concentration of NO3 is... - The concentration of -N is 20 mg / L, PO4 3-The concentration of -P is 1 mg / L; the concentration of the inoculated sludge in the electrochemical reactor is 4000 mg / L. All concentrations in the following examples and comparative examples are mass concentrations.

[0085] Example 1

[0086] This embodiment provides a sequencing batch reactor (SBR) method for treating nitrogen and phosphorus in wastewater, the method comprising the following steps:

[0087] (1) Simulated nitrogen- and phosphorus-containing wastewater is introduced into an electrochemical reaction device (e.g., at a flow rate of 120 mL / min) at a flow rate of 120 mL / min. Figure 1 Sulfur was added simultaneously to the contents shown in the diagram.

[0088] The wastewater is introduced for 5 minutes; the initial amount of sulfur added is 1.2 g / L; the sulfur is replenished at a daily rate of 350 mg / L when treating simulated nitrogen- and phosphorus-containing wastewater.

[0089] (2) The wastewater was subjected to a first electrochemical reaction for 30 minutes under the action of stirring at 200 rpm and DC power supply at 0.8V, then stirred for 35 minutes at 200 rpm, and then aerated for 10 minutes under stirring at 200 rpm; during the first aeration, the concentration of DO in the wastewater was 1.2 mg / L.

[0090] (3) The wastewater underwent a second electrochemical reaction for 30 minutes with stirring at 200 rpm and a DC power supply of 0.8V. Then, it was stirred for 30 minutes with stirring at 200 rpm and then aerated for 5 minutes with stirring at 200 rpm. During the second aeration, the concentration of DO in the wastewater was 1.2 mg / L. After the wastewater was allowed to stand for 30 minutes, it was finally discharged at a flow rate of 120 mL / min for 5 minutes.

[0091] Before the settling process, the process also includes: performing the second aeration once in steps (2) to (3).

[0092] Example 2

[0093] This embodiment provides a sequencing batch reactor (SBR) method for treating nitrogen and phosphorus in wastewater, the method comprising the following steps:

[0094] (1) Simulated nitrogen and phosphorus-containing wastewater was introduced into the electrochemical reaction device at a flow rate of 100 mL / min, and sulfur was added at the same time;

[0095] The wastewater is introduced for 7 minutes; the initial amount of sulfur added is 1.2 g / L; the sulfur is replenished at a daily rate of 320 mg / L when treating simulated nitrogen- and phosphorus-containing wastewater.

[0096] (2) The wastewater was subjected to an electrochemical reaction for 35 minutes under the action of stirring at 150 rpm and DC power supply at 0.6V, then stirred at 150 rpm for 38 minutes, and then aerated at 150 rpm for 8 minutes; during the aeration, the concentration of DO in the wastewater was 1.5 mg / L.

[0097] (3) Repeat step (2) 3 times, let the sewage stand for 30 minutes, and finally discharge the sewage at a flow rate of 100 mL / min for 7 minutes.

[0098] Example 3

[0099] This embodiment provides a sequencing batch reactor (SBR) method for treating nitrogen and phosphorus in wastewater, the method comprising the following steps:

[0100] (1) Simulated nitrogen and phosphorus-containing wastewater was introduced into the electrochemical reaction device at a flow rate of 150 mL / min, and sulfur was added at the same time;

[0101] The wastewater is introduced for 4 minutes; the initial amount of sulfur added is 1.2 g / L; the sulfur is replenished at a daily rate of 350 mg / L when treating simulated nitrogen- and phosphorus-containing wastewater.

[0102] (2) The wastewater was subjected to a first electrochemical reaction for 25 minutes under the action of stirring at 250 rpm and DC power supply at 1V, then stirred for 32 minutes at 250 rpm, and then aerated for 5 minutes under stirring at 250 rpm; during the first aeration, the concentration of DO in the wastewater was 1 mg / L.

[0103] (3) The wastewater was subjected to a second electrochemical reaction for 25 minutes under the action of stirring at 250 rpm and DC power supply of 1V, then stirred for 28 minutes at 250 rpm, and then aerated for 6 minutes under stirring at 250 rpm. During the second aeration, the concentration of DO in the wastewater was 1 mg / L. After the wastewater was allowed to stand for 30 minutes, it was finally discharged at a flow rate of 150 mL / min for 4 minutes.

[0104] Before the settling process, the process also includes: performing the second aeration once in steps (2) to (3).

[0105] Example 4

[0106] This embodiment provides a method for sequential batch treatment of nitrogen and phosphorus in wastewater. Except that the first electrochemical reaction and the second electrochemical reaction in steps (2) and (3) are not carried out under stirring, the other conditions are the same as in Example 1.

[0107] Example 5

[0108] This embodiment provides a method for sequential batch treatment of nitrogen and phosphorus in wastewater. Except for the DC power supply voltage of 0.3V in the first electrochemical reaction and the second electrochemical reaction in steps (2) and (3), all other conditions are the same as in Example 1.

[0109] Example 6

[0110] This embodiment provides a method for sequential batch treatment of nitrogen and phosphorus in wastewater. Except for the DC power supply voltage of 1.5V in the first electrochemical reaction and the second electrochemical reaction in steps (2) and (3), all other conditions are the same as in Example 1.

[0111] Example 7

[0112] This embodiment provides a sequential batch method for treating nitrogen and phosphorus in wastewater. Except that the first aeration and the second aeration in steps (2) and (3) are not carried out under stirring, the other conditions are the same as in embodiment 1.

[0113] Example 8

[0114] This embodiment provides a sequential batch method for treating nitrogen and phosphorus in wastewater. Except that the concentration of DO in the wastewater is 0.5 mg / L in the first aeration and the second aeration in steps (2) and (3), all other conditions are the same as in Example 1.

[0115] Example 9

[0116] This embodiment provides a sequential batch method for treating nitrogen and phosphorus in wastewater. Except that the concentration of DO in the wastewater is 3 mg / L in the first aeration and the second aeration in steps (2) and (3), all other conditions are the same as in Example 1.

[0117] Comparative Example 1

[0118] This comparative example provides a sequential batch method for treating nitrogen and phosphorus in wastewater. Except for adjusting steps (2) to (3) to: electrochemically reacting the wastewater for 280 min under stirring at 200 rpm and DC power supply at 0.8 V, letting the wastewater stand for 30 min, and finally discharging the wastewater at a flow rate of 120 mL / min for 5 min, all other conditions are the same as in Example 1.

[0119] Comparative Example 2

[0120] This comparative example provides a sequential batch method for treating nitrogen and phosphorus in wastewater. Except for adjusting steps (2) to (3) to: stirring at 200 rpm for 280 min, letting the wastewater stand for 30 min, and finally discharging the wastewater at a flow rate of 120 mL / min for 5 min, all other conditions are the same as in Example 1.

[0121] Comparative Example 3

[0122] This comparative example provides a method for sequential batch treatment of nitrogen and phosphorus in wastewater. Except for the absence of the first and second stirring in steps (2) and (3), all other conditions are the same as in Example 1.

[0123] After running the methods provided in the above examples and comparative examples for 1 day and 10 days respectively, the concentrations of nitrate nitrogen, ammonia nitrogen and phosphate in the water were determined by ion chromatography, and the results are shown in Table 1.

[0124] Table 1

[0125]

[0126] As shown in Table 1:

[0127] (1) The method provided in Examples 1-3 of the present invention can achieve immediate start-up and extreme nitrogen and phosphorus removal in wastewater treatment by combining intermittent DC power supply with intermittent micro-aerobic aeration. After 1 day, the concentrations of total nitrogen and total phosphorus in the effluent are less than 0.8 mg / L and 0.3 mg / L, respectively; after 10 days, the concentrations of total nitrogen and total phosphorus in the effluent are less than 0.8 mg / L and 0.2 mg / L, respectively.

[0128] (2) A comparison of Examples 1 and 4 shows that when the electrochemical reaction is not carried out under stirring, the microorganisms cannot fully contact the pollutants, resulting in the ineffective removal of nitrate nitrogen in the effluent. A comparison of Examples 1 and 5-6 shows that when the voltage of the external DC power supply is too low, the electrochemical reaction is insufficient and the release of endogenous carbon sources is limited, resulting in poor removal of total nitrogen and total phosphorus in the effluent. When the voltage of the external DC power supply is too high, the microbial mortality rate is too high, resulting in significant release of ammonia nitrogen in the effluent and a decrease in the removal rate of nitrate nitrogen.

[0129] (3) A comparison of Examples 1 and 7 shows that when aeration is not carried out under stirring, the ammonia nitrogen removal rate in the effluent is reduced because the microorganisms cannot fully contact the pollutants. A comparison of Examples 1 and 8-9 shows that when the DO concentration of the wastewater is too low during aeration, the total nitrogen removal rate in the effluent is poor because the hydrolysis process of endogenous organic matter is hindered and the ammonia nitrogen oxidation process is limited. When the DO concentration of the wastewater is too high during aeration, the nitrate nitrogen concentration in the effluent is higher than 15 mg / L in 1 day because the hypoxic environment cannot be stably provided for denitrification.

[0130] (4) Comparison of Example 1 and Comparative Examples 1-2 shows that when a continuous external power supply is used for nitrogen and phosphorus removal, the ammonia nitrogen dissolution phenomenon is very obvious due to cell apoptosis and rupture caused by electrical stimulation, and the total nitrogen removal rate in the effluent is low. When the wastewater is stirred only throughout the process, not only does the removal of nitrate nitrogen show the characteristic of difficult start-up of sulfur autotrophic denitrification, but it also shows the phenomenon of cell apoptosis and ammonia nitrogen dissolution and nitrate dissimilatory reduction to ammonium (DNRA). In addition, due to the lack of iron electrode, the phosphorus removal effect is extremely poor.

[0131] (5) Comparing Example 1 and Comparative Example 3, it can be seen that when there is no interval between electrochemical reaction and aeration, the nitrate nitrogen removal rate in the effluent is less than 50% due to the loss of the hypoxic environment.

[0132] Performance testing and mechanism

[0133] (I) Instant Startup Effect

[0134] To determine the effectiveness of immediate startup over 1-10 days, the methods provided in Example 1 and Comparative Examples 1-2 were run for 10 days. The concentrations of nitrate nitrogen, ammonia nitrogen, and phosphate in the water were then measured using ion chromatography. The results are as follows: Figure 2-4 As shown.

[0135] Depend on Figure 2-4 It can be seen that in Example 1, the concentrations of nitrate nitrogen in the effluent after 10 days were all below 0.5 mg / L, ammonia nitrogen concentrations were all less than 0.5 mg / L, and phosphate concentrations were less than 0.2 mg / L, achieving immediate and extreme nitrogen and phosphorus removal effects at the wastewater treatment plant. However, the method provided in Comparative Example 1 showed poor nitrate nitrogen removal efficiency in the first ten days, ranging from 50% to 80%, and ammonia nitrogen dissolution was very significant, exceeding 7 mg / L, surpassing the limits of outdoor drainage standards. Although the lowest ammonia nitrogen dissolution concentration reached around 2 mg / L after about 10 days, this was due to cell apoptosis and rupture caused by electrical stimulation. Comparative Example 2 exhibited difficulties in initiating sulfur autotrophic denitrification, with effluent concentrations far exceeding those of Example 1. This system also exhibited cell apoptosis-induced ammonia nitrogen dissolution and nitrate dissimilatory reduction to ammonium (DNRA) phenomena, although slightly better than Comparative Example 1. Because Comparative Example 2 did not introduce an iron electrode, its phosphorus removal rate was less than 20%, relying solely on biological assimilation.

[0136] Furthermore, it is shown that in terms of the start-up of extreme nitrogen and phosphorus removal in wastewater, Example 1 exhibits the characteristic of immediate start-up. The present invention can significantly avoid the problem of ammonia nitrogen backlash caused by cell apoptosis or DNRA process due to the power supply or sulfur autotrophic system through intermittent aeration, thereby achieving effective ammonia oxidation and denitrification. Combined with stable phosphorus removal through intermittent DC power supply, it makes up for the problem of excessively rapid anode electrode wear, and further ensures the immediate start-up of extreme nitrogen and phosphorus removal function.

[0137] (II) Extreme nitrogen and phosphorus removal effect

[0138] To determine the ultimate nitrogen and phosphorus removal efficiency, when both Example 1 and Comparative Examples 1-2 reached stable effluent conditions (i.e., each reaction unit operated for ≥30 days), the concentrations of nitrate nitrogen, ammonia nitrogen, and phosphate in the effluent from multiple groups after 30 days of operation were measured using ion chromatography. The results are as follows: Figure 5 As shown.

[0139] Depend on Figure 5 It can be seen that, after the method provided in Example 1 achieves effluent stabilization, the average concentration of ammonia nitrogen in the effluent is less than 0.3 mg / L, the average concentration of nitrate nitrogen is 0.7 mg / L, the average concentration of phosphate is 0.19 mg / L, the total nitrogen removal rate is 95.0%, and the total phosphorus removal rate is 81.0%. In contrast, after the method provided in Comparative Example 1 achieves effluent stabilization, the average concentration of ammonia nitrogen in the effluent is 1.8 mg / L, the average concentration of nitrate nitrogen is 0.8 mg / L, the average concentration of phosphate is 0.17 mg / L, the total nitrogen removal rate is 87.0%, and the total phosphorus removal rate is 83.0%. Furthermore, after the method provided in Comparative Example 2 achieves effluent stabilization, the average concentration of ammonia nitrogen in the effluent is 0.9 mg / L, the average concentration of nitrate nitrogen is 2.7 mg / L, the average concentration of phosphate is 0.87 mg / L, the total nitrogen removal rate is 82.0%, and the total phosphorus removal rate is 13.0%.

[0140] Example 1, by introducing an intermittent micro-aerobic aeration process, not only improved the oxidation rate of ammonia nitrogen but also the reduction rate of nitrate, resulting in a higher total nitrogen removal rate than Comparative Example 1. Furthermore, the intermittent DC power supply ensured stable phosphorus removal efficiency.

[0141] (III) Initial nitrogen removal during endogenous denitrification

[0142] To determine the initial endogenous denitrification process, Example 1 and Comparative Examples 1-2 were first tested under conditions where there was no nitrate nitrogen in the influent. Before settling, an equal amount of nitrate nitrogen was added to assess the nitrogen removal efficiency. The results are as follows: Figure 6 As shown.

[0143] Depend on Figure 6 It can be seen that the COD concentrations in Example 1, Comparative Example 1, and Comparative Example 2 were 73.2 mg / L, 66.4 mg / L, and 10.1 mg / L, respectively; and the denitrification rates in Example 1, Comparative Example 1, and Comparative Example 2 were 2.2 mgN / (gMLSS·h), 1.7 mgN / (gMLSS·h), and 0.13 mgN / (gMLSS·h), respectively.

[0144] An external DC power supply can significantly promote the release of intracellular carbon sources. Compared with Comparative Example 2, the COD release of Comparative Example 1 increased by 56.3 mg / L. The release of these carbon sources can significantly increase the endogenous denitrification rate, making the denitrification rate of Comparative Example 1 8 times higher than that of Comparative Example 2. In Example 1, due to the introduction of intermittent microaerobic aeration, on the one hand, the endogenous COD is further released into the extracellular space (more than 10% higher than the COD release in Comparative Example 1), providing more potential organic electron donors for denitrification. On the other hand, intermittent microaerobic aeration can increase the hydrolysis process of these released CODs, thereby increasing their bioavailability. As a result, the endogenous denitrification rate of Example 1 is more than 29% higher than that of Comparative Example 1. Moreover, Example 1 has a more continuous endogenous carbon source supply and conversion capacity than Comparative Example 1, which keeps the wastewater treatment rate stable and efficient in the first 10 days.

[0145] (iv) Targeted regulation of microbial communities

[0146] To determine the directional regulation of microbial communities, the genus-level community structure of Example 1 and Comparative Examples 1-2 was tested on days 15 and 35 of operation. The results are as follows: Figure 7 As shown.

[0147] Depend on Figure 7 It was observed that on day 15, denitrifying bacteria and hydrolytic fermenting bacteria such as Ferruginibacter and Thermomonas significantly proliferated in Example 1 and Comparative Example 1, providing metabolic support for the release and utilization of endogenous carbon sources. In Example 1, the denitrifying bacteria Terrimonas were significantly enriched with a relative abundance of 3.8%, and the relative abundance of bacteria related to endogenous denitrification and hydrolytic acidification functions reached 22.5%. This allowed for the effective biotransformation of endogenous carbon sources during the process of enhancing intracellular carbon source release with external DC power, and provided the system's heterotrophic denitrifying bacteria with the carbon sources required for synthesis and decomposition metabolism. This further explains the reason for the immediate initiation of extreme denitrification in Example 1.

[0148] Furthermore, the ultimate nitrogen removal performance of Example 1 is also attributed to the rapid proliferation of sulfur autotrophic denitrification. The enhanced endogenous denitrification process provided crucial support for the proliferation of sulfur autotrophic denitrifying bacteria. Due to the introduction of oxygen electron acceptors, the proliferation rate of sulfur autotrophic bacteria (Thiobacillus and Sulfurimonas) was significantly increased in Example 1, reaching a relative abundance of 21.4% on day 15, compared to only 2.0% and 0.8% in Comparative Examples 1 and 2, respectively. Therefore, sulfur autotrophic denitrification rapidly replaced endogenous denitrification, enabling Example 1 to achieve a seamless transition in ultimate nitrogen removal. During the system community stabilization period (day 35), the relative abundance of Thiobacillus in Example 1 reached 37.5%, while Comparative Examples 1 and 2 only reached 16.9% and 11.3%, respectively. The higher sulfur autotrophic bacterial community abundance in Example 1 ensured its higher nitrogen removal efficiency and lower effluent total nitrogen concentration.

[0149] (V) Microbial proliferation protection and energy supply

[0150] To further explain the balance between endogenous carbon source release and sulfur autotrophic bacteria proliferation, dead microorganisms (red), live microorganisms (green), and damaged microorganisms (yellow) were identified by fluorescent staining. The results are as follows: Figure 8-10 As shown.

[0151] Depend on Figure 8-10 It is known that applying an external DC power supply can cause cell damage and apoptosis, thereby releasing intracellular COD into the extracellular space. In Example 1, not only does intermittent DC power supply greatly alleviate the degree of cell apoptosis, but intermittent microaerobic aeration also significantly enhances the metabolism of residual organic matter (such as DNA) and the decomposition of apoptotic microorganisms, achieving maximum bioavailability of endogenous carbon sources.

[0152] By intermittently introducing oxygen electron acceptors, ATP synthesis was also enhanced (e.g. Figure 11 As shown in the figure, the intracellular ATP content in Example 1 was 7.6 μmol / g MLSS, while that in Comparative Examples 1 and 2 was only 7.1 μmol / g MLSS and 7.0 μmol / g MLSS, respectively. Example 1 was 7.0% and 8.6% higher than Comparative Examples 1 and 2, respectively. The higher ATP accumulation due to higher catabolism provides sufficient energy for the anabolic metabolism of sulfur-autotrophic bacteria. In other words, Example 1 achieved a stable transition from extracellular electron acceptor supply to intracellular energy supply, which further explains the rapid proliferation of sulfur-autotrophic bacteria in Example 1 to meet the ultimate denitrification requirements.

[0153] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for treating nitrogen and phosphorus in wastewater using a sequencing batch process, characterized in that, The method includes the following steps: (1) The wastewater is fed into the electrochemical reaction device, and sulfur-containing materials are added at the same time; the concentration of the inoculated sludge in the electrochemical reaction device is 3500~4500 mg / L; (2) The wastewater is subjected to an electrochemical reaction for 25-35 minutes under the action of stirring and a DC power supply with a voltage of 0.6-1V, then stirred for 25-40 minutes at a speed of 150-250rpm, and then aerated for 3-10 minutes under stirring; during the aeration, the concentration of DO in the wastewater is 1-1.5mg / L. (3) Repeat step (2) to allow the sewage to stand and then discharge it.

2. The method according to claim 1, characterized in that, The electrochemical reaction apparatus in step (1) includes a sealed reaction tank; The reaction tank is equipped with a cathode and an anode, and the cathode and the anode are independently connected to a power source. The reaction tank is equipped with a stirring device; The top of the reaction tank is independently equipped with an exhaust port and a sulfur-containing material inlet; The side wall of the reaction tank is equipped with an aeration pipe; The sidewall of the reaction tank is provided with an inlet pipe and an outlet pipe from top to bottom.

3. The method according to claim 2, characterized in that, The diameter to height ratio of the reaction tank is 1:(1.5~2.5).

4. The method according to claim 2, characterized in that, The anode includes an iron electrode.

5. The method according to claim 2, characterized in that, The cathode includes a graphite electrode.

6. The method according to claim 2, characterized in that, The distance between the cathode and the anode is 2.5~3.5cm.

7. The method according to claim 2, characterized in that, The aeration pipe is connected to a blower.

8. The method according to claim 2, characterized in that, The height of the inlet pipe is 7 / 10 to 9 / 10 of the height of the reaction tank.

9. The method according to claim 2, characterized in that, The height of the outlet pipe is 1 / 5 to 3 / 10 of the height of the reaction tank.

10. The method according to claim 1, characterized in that, In step (1), the concentration of COD in the wastewater is 5~50 mg / L, and NO3... - The concentration of -N is 10~25 mg / L, PO4 3- The concentration of -P is 1~3 mg / L.

11. The method according to claim 1, characterized in that, The flow rate of the wastewater in step (1) is 100~150mL / min.

12. The method according to claim 1, characterized in that, The sewage inlet time in step (1) is 4 to 7 minutes.

13. The method according to claim 1, characterized in that, The sulfur-containing material in step (1) includes sulfur.

14. The method according to claim 1, characterized in that, The initial addition amount of the sulfur-containing material in step (1) is 1~1.5g / L.

15. The method according to claim 1, characterized in that, The time for adding sulfur-containing materials in step (1) is when treating wastewater, and the daily addition amount is 300~400mg / L.

16. The method according to claim 1, characterized in that, The number of cycles in step (3) is ≥ 1.

17. The method according to claim 1, characterized in that, The settling time in step (3) is 25~35 minutes.

18. The method according to claim 1, characterized in that, The flow rate of the effluent discharged in step (3) is 100~150mL / min.

19. The method according to claim 1, characterized in that, The time for discharging water in step (3) is 4 to 7 minutes.

20. The method according to claim 1, characterized in that, The method includes the following steps: (1) The wastewater is fed into the electrochemical reaction device at a flow rate of 100~150mL / min, and sulfur-containing materials are added at the same time; The wastewater contained COD at a concentration of 5-50 mg / L and NO3. - The concentration of -N is 10~25 mg / L, PO4 3- The concentration of -P is 1~3 mg / L; the sewage influent time is 4~7 min; the concentration of inoculated sludge in the electrochemical reaction device is 3500~4500 mg / L; The initial addition amount of the sulfur-containing material is 1~1.5g / L; the replenishment time of the sulfur-containing material is when treating wastewater, and the daily replenishment amount is 300~400mg / L; The electrochemical reaction device includes a sealed reaction tank; a cathode and an anode are provided in the reaction tank, and the cathode and the anode are independently connected to a power source; a stirring device is provided in the reaction tank; an exhaust port and a sulfur-containing material inlet are independently provided at the top of the reaction tank; an aeration pipe is provided on the side wall of the reaction tank; and an inlet pipe and an outlet pipe are provided on the side wall of the reaction tank from top to bottom. (2) The wastewater is subjected to an electrochemical reaction for 25-35 minutes under the action of stirring and a DC power supply with a voltage of 0.6-1V, then stirred for 25-40 minutes at a speed of 150-250rpm, and then aerated for 3-10 minutes under stirring; during the aeration, the concentration of DO in the wastewater is 1-1.5mg / L. (3) Repeat step (2) at least once, let the sewage stand for 25-35 minutes, and finally discharge the sewage at a flow rate of 100-150 mL / min for 4-7 minutes.

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