A wastewater denitrification device based on electrochemical assisted anaerobic ammonia oxidation

Abstract

The application discloses a wastewater denitrification device based on electrochemical auxiliary anaerobic ammonia oxidation, which comprises a reactor cylinder body, a water inlet is arranged at the bottom of the reactor cylinder body, and a water outlet is arranged at the top of the reactor cylinder body; an anode layer and a cathode layer are sequentially arranged in the reactor cylinder body in a longitudinal direction from bottom to top; the cathode layer and the anode layer are net bags made of stainless steel, and the net bags are filled with carbon fillers; and the anode layer and the cathode layer are connected with an external power source through wires. + -N, NO2 ‑ -N and NO3 ‑ -N can be simultaneously removed, and NH4 ‑ -N can be efficiently oxidized even under the condition that the NO2 + -N content in the water inlet of the reactor is low; thus, the denitrification efficiency of the whole reaction device is effectively improved; in addition, the device can fully play the role of anaerobic ammonia oxidation bacteria in the denitrification process, so that the denitrification reaction is more thorough, and thus the production amount of the byproduct nitrous oxide is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to a wastewater denitrification device based on electrochemical assisted anaerobic ammonia oxidation. BACKGROUND

[0002] The traditional anaerobic ammonia oxidation process has low growth rate of anaerobic ammonia oxidation bacteria, slow reactor start-up, and extremely harsh requirements for environmental conditions, so the above process has large performance fluctuation in actual operation, and cannot guarantee stable treatment efficiency. In order to overcome the above shortcomings, anaerobic ammonia oxidation microbial fuel cell and anaerobic ammonia oxidation microbial electrolysis cell are used to replace the traditional anaerobic ammonia oxidation process. However, in actual operation, the above two processes still have the defects of large operation difficulty, complex device structure and high investment cost. The reason is that the device of the above process needs two independent chambers to realize stable reaction, and needs special membrane material, electrode material and the like to make the device stable. At the same time, the anaerobic ammonia oxidation microbial fuel cell has insufficient anode and cathode potential difference during operation, and it is difficult to improve the denitrification effect of the whole system without external voltage to make up the potential difference. SUMMARY

[0003] The purpose of the present application is to provide a wastewater denitrification device based on electrochemical assisted anaerobic ammonia oxidation, which can improve the oxidation efficiency of NH4 + -N in the anode area of the system (promote fast electron transfer), thereby effectively improving the denitrification efficiency of the device; at the same time, the device can also eliminate the dependence of ammonia nitrogen and nitrite nitrogen on external NO2 - -N in the process of anaerobic ammonia oxidation, and can make the denitrification reaction more complete in the denitrification process, thereby reducing the production amount of byproduct nitrous oxide.

[0004] Technical scheme: The wastewater denitrification device based on electrochemical assisted anaerobic ammonia oxidation provided by the present application comprises a reactor cylinder, a water inlet is arranged at the bottom of the reactor cylinder, and a water outlet is arranged at the top of the reactor cylinder; an anode layer and a cathode layer are sequentially arranged in the reactor cylinder in a longitudinal direction from bottom to top; the cathode layer and the anode layer are net bags made of stainless steel, and the net bags are filled with carbon fillers; the anode layer and the cathode layer are connected with an external power source through wires.

[0005] The depth of the net bags of the anode layer and the cathode layer is not greater than 50 mm.

[0006] The net bags of the anode layer and the cathode layer are fixedly connected with the clamping groove on the inner side wall of the reactor cylinder through the net bag buckle.

[0007] The vertical height between the upper end surface of the anode layer net and the bottom of the reactor cylinder is not less than 200 mm; and the vertical height between the upper end surface of the cathode layer net and the bottom of the reactor cylinder is not more than 600 mm.

[0008] The vertical distance between the upper end surface of the anode layer net and the bottom of the cathode layer net is 100-350 mm. The inner side wall of the reactor cylinder is provided with a plurality of buckle grooves in the longitudinal direction, and the interval between the cathode layer and the anode layer is adjusted to be 100-350 mm by changing the position of the anode layer net.

[0009] The carbon filler is a carbon material such as biochar, activated carbon or graphite particles.

[0010] The filling rate of the carbon filler in the net of the anode layer and the cathode layer is 30%-50%, and the filling height of the carbon filler in the net is lower than the depth of the net.

[0011] The aperture of the net of the anode layer and the cathode layer is not more than 2 mm; the aperture of the net is smaller than the particle size of the carbon filler; and the porosity of the carbon filler is 85%.

[0012] The upper surface of the cathode layer net is exposed to air and directly contacts with air, the height of the upper surface of the cathode layer net is higher than the height of the water outlet of the reactor cylinder, and the lower part of the cathode layer net is immersed in the water body.

[0013] The voltage applied by the external direct current power supply is 0.6-0.8 V.

[0014] The reactor cylinder is wrapped with a silicone rubber sleeve, heating and heat preservation and light shielding are realized through the silicone rubber sleeve, and the water temperature in the reactor cylinder is maintained at 32-38 ℃.

[0015] Beneficial effects: Compared with the prior art, the device has the following remarkable advantages: the device can simultaneously remove NH4 + -N, NO2 - -N and NO3 - -N, and can efficiently oxidize NH4 - -N under the condition that the content of NO2 + -N in the water inlet of the reactor is low; thereby effectively improving the denitrification efficiency of the whole reaction device; in addition, the device can fully play the role of anaerobic ammonia oxidation bacteria in the denitrification process, so that the denitrification reaction is more thorough, thereby reducing the production amount of the byproduct nitrous oxide. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the device;

[0017] Figure 2 It is a flow direction diagram of water flow in the device;

[0018] Figure 3 The connection diagram of the net bag buckle and the buckle slot (bolt slot) on the inner wall of the reactor cylinder is fixed and connected by bolts;

[0019] Figure 4 The column chart of nitrite nitrogen effluent concentration and the removal rate line chart of the blank group and the experimental group after reaching stable operation;

[0020] Figure 5 The column chart of ammonia nitrogen effluent concentration and the removal rate line chart of the blank group and the experimental group after reaching stable operation;

[0021] Figure 6 The column chart of nitrate nitrogen effluent concentration of the blank group and the experimental group after reaching stable operation;

[0022] Figure 7 The column chart of nitrous oxide gas emission flux of the blank group and the experimental group after reaching stable operation;

[0023] Figure 8 The column chart of nitrite nitrogen effluent concentration and the removal rate line chart of the blank group and the experimental group after reaching stable operation under the condition of insufficient influent nitrite nitrogen concentration;

[0024] Figure 9 The column chart of ammonia nitrogen effluent concentration and the removal rate line chart of the blank group and the experimental group after reaching stable operation under the condition of insufficient influent nitrite nitrogen concentration;

[0025] Figure 10 The column chart of nitrate nitrogen effluent concentration of the blank group and the experimental group after reaching stable operation under the condition of insufficient influent nitrite nitrogen concentration;

[0026] Figure 11 The column chart of nitrous oxide gas emission flux of the blank group and the experimental group after reaching stable operation under the condition of insufficient influent nitrite nitrogen concentration. DETAILED DESCRIPTION

[0027] As Figures 1-3 shown, the application is based on an electrochemical assisted anaerobic ammonia oxidation wastewater denitrification device, which comprises a reactor cylinder 1, the bottom of the reactor cylinder 1 is provided with a water inlet 17, the water inlet 17 is connected with an external water collecting pool 11, the top of the reactor cylinder is provided with a water outlet 16, the water outlet 16 is connected with an external water storage pool 12; the reactor cylinder 1 is provided with an anode layer 3 and a cathode layer 2 in sequence from bottom to top along the longitudinal direction; the cathode layer 3 and the anode layer 2 are nets made of stainless steel, the nets are filled with carbon fillers 4; the anode layer 3 and the cathode layer 2 are connected with an external direct current power supply 5 through wires respectively, forming a closed loop. The voltage applied by the external direct current power supply 5 is 0.6V-0.8V, and the power supply is continuous for 24 hours a day.

[0028] The reactor body 1 has an inner diameter of 200 mm and a height of 600 mm, with a height-to-diameter ratio of 3:1. Multiple locking slots (bolt slots) 15 are longitudinally provided on the inner sidewall of the reactor body 1. The mesh bags of the anode layer 3 and cathode layer 2 are equipped with locking clips 8 corresponding to the locking slots 15. Bolts 13 pass through the locking clips 8 and are fixedly connected to the locking slots 15, thus securing the mesh bags to the reactor body 1. A sampling port 9 is also provided on the sidewall of the reactor body 1.

[0029] Starting from a position 200mm from the bottom of the reactor cylinder 1, a locking groove 15 is set every 50mm, for a total of 6 locking grooves; the inner diameter of the locking groove 15 is 3mm and the depth is 10mm; a 3mm diameter circular hole is reserved on the net bag, and the net bag is fixedly connected to the locking groove 15 on the inner side wall of the reactor cylinder 1 by bolts with a diameter of 3mm and a length of 10mm; by adjusting the position of the net bag of the anode layer 3 relative to the net bag of the cathode layer 2, the internal resistance between the anode and cathode can be adjusted, thereby controlling the voltage in the water.

[0030] The depth of the anode layer 3 and cathode layer 2 mesh is 50 mm; the vertical height between the anode layer 3 mesh clip 8 and the bottom of the reactor shell is not less than 200 mm; the vertical height between the cathode layer 2 mesh clip 8 and the bottom of the reactor shell 1 is not less than 600 mm. The upper surface of the cathode layer 2 mesh is exposed to the air and in direct contact with it, and the height of the upper surface of the cathode layer 2 mesh is higher than the height of the reactor shell outlet 16; the lower part of the cathode layer 2 mesh is immersed in the water.

[0031] The carbon filler 4 is at least one of biochar, activated carbon, or graphite particles, such as activated carbon. The activated carbon filling rate in the mesh bags of the anode layer 3 and cathode layer 2 is 30% to 50%, and the filling height of the activated carbon in the mesh bags is lower than the depth of the mesh bags.

[0032] A comparative experiment was conducted, setting up a blank group (no power supply) and an experimental group (powered for 24 hours a day and maintained at 0.6V). Both groups were inoculated with the same amount of sludge (MLSS of 0.7g / L) and used the same high-concentration nitrogen influent (initial concentration of nitrite nitrogen of 670mg / L and initial concentration of ammonia nitrogen of 560mg / L). The influent was pumped by a peristaltic pump, and the hydraulic retention time was 3 days for both groups.

[0033] like Figures 4-6 As shown: After the unit was started up and reached stable operation (nitrite and ammonia nitrogen removal rates fluctuated by less than 5%), the effluent concentrations of nitrite, ammonia, and nitrate nitrogen were measured every two days from day 1 to day 29. The nitrite oxide emission flux was measured on days 9, 19, and 29. The results are as follows:

[0034] The average removal rate of nitrite nitrogen in the control group was 94.7%, while that in the experimental group was 97.6%. The average concentration of nitrite nitrogen in the effluent was 35.4 mg / L in the control group and 15.6 mg / L in the experimental group. The average removal rate of ammonia nitrogen in the control group was 94.3%, while that in the experimental group was 97.4%. At the corresponding removal rates, the average effluent concentration of ammonia nitrogen in the control group was 32.2 mg / L, while that in the experimental group was 14.7 mg / L. This indicates that the device of the present invention (experimental group) can guarantee a higher ammonia nitrogen removal efficiency. Regarding nitrate nitrogen in the effluent, the average effluent concentration of nitrate nitrogen in the control group was 25.3 mg / L, while that in the experimental group was 18.7 mg / L.

[0035] like Figure 7 As shown, the emission flux of nitrous oxide gas in the blank group was higher than that in the experimental group, with an average increase of 0.16 g / m³. 2 / day.

[0036] With reduced influent nitrite nitrogen, the initial nitrite nitrogen concentration was reduced to 450 mg / L, while the ammonia nitrogen concentration remained unchanged. All other experimental conditions were maintained. After reaching stable operation, the effluent concentrations of nitrite nitrogen, ammonia nitrogen, and nitrate nitrogen were measured every two days from day 1 to day 29. The nitrite oxide emission flux was measured on days 9, 19, and 29. The results are as follows:

[0037] like Figures 8-10 As shown: the average removal rate of nitrite nitrogen in the control group was 98.0%, while that in the experimental group was 99.0%. When the concentration of nitrite nitrogen in the influent is lower than that of ammonia nitrogen, the consumption of nitrite nitrogen as a reaction substrate increases, and the corresponding removal rate also increases. In the effluent, the average concentration of nitrite nitrogen in the control group was 8.9 mg / L, while that in the experimental group was 4.5 mg / L. The average removal rate of ammonia nitrogen in the control group reached 93.0%, while that in the experimental group was 97.0%. At the corresponding removal rates, the average effluent ammonia nitrogen concentration in the control group was 39.2 mg / L, while that in the experimental group was 16.8 mg / L. Even with insufficient nitrite nitrogen in the influent, the device of this invention can ensure a higher ammonia nitrogen removal efficiency. Regarding nitrate nitrogen in the effluent, the average effluent nitrate nitrogen concentration in the control group was 23.2 mg / L, while that in the experimental group was 17.5 mg / L.

[0038] like Figure 11 As shown, the emission flux of nitrous oxide gas in the blank group was higher than that in the experimental group, with an average increase of 0.15 g / m³. 2 / day. The device of this invention achieves better denitrification while reducing nitrous oxide greenhouse gas emissions. Therefore, the device of this invention can achieve better denitrification with lower nitrite nitrogen in the influent and less greenhouse gas emissions, realizing low-carbon denitrification.

Claims

1. A wastewater denitrification device based on electrochemical-assisted anaerobic ammonia oxidation, characterized in that: The reactor includes a reactor shell with an inlet at the bottom and an outlet at the top. An anode layer and a cathode layer are arranged longitudinally from bottom to top within the reactor shell. Both the anode and cathode layers are stainless steel mesh bags filled with carbon filler. The anode and cathode layers are connected to an external power source via wires. Multiple locking grooves are provided longitudinally on the inner wall of the reactor shell. The mesh bags of both the anode and cathode layers are fixedly connected to these grooves by mesh bag locking mechanisms. The upper surface of the cathode layer mesh bag is exposed to air, and its height is not lower than the height of the reactor shell outlet. The lower part of the cathode layer mesh bag is immersed in water.

2. The wastewater denitrification device based on electrochemical-assisted anaerobic ammonium oxidation according to claim 1, characterized in that: The depth of the anode and cathode mesh is no more than 50 mm.

3. The wastewater denitrification device based on electrochemical-assisted anaerobic ammonium oxidation according to claim 1, characterized in that: The vertical distance between the upper end face of the anode layer mesh and the bottom of the reactor cylinder is not less than 200 mm; the vertical distance between the upper end face of the cathode layer mesh and the bottom of the reactor cylinder is not greater than 600 mm.

4. The wastewater denitrification device based on electrochemical-assisted anaerobic ammonia oxidation according to claim 1, characterized in that: The vertical distance between the upper end face of the anode layer mesh bag and the bottom of the cathode layer mesh bag is 100~350mm.

5. The wastewater denitrification device based on electrochemical-assisted anaerobic ammonium oxidation according to claim 1, characterized in that: The carbon filler is at least one of biochar, activated carbon, or graphite particles.

6. The wastewater denitrification device based on electrochemical-assisted anaerobic ammonium oxidation according to claim 1, characterized in that: The carbon filler in the mesh pockets of the anode and cathode layers has a filling rate of 30% to 50%, and the filling height of the carbon filler in the mesh pockets is lower than the depth of the mesh pockets.

7. The wastewater denitrification device based on electrochemical-assisted anaerobic ammonium oxidation according to claim 1, characterized in that: The pore size of the mesh bags in the anode and cathode layers is no greater than 2 mm; the pore size of the mesh bags is smaller than the particle size of the carbon filler.

8. The wastewater denitrification device based on electrochemical-assisted anaerobic ammonium oxidation according to claim 1, characterized in that: The voltage applied by the external DC power supply is 0.6V~0.8V.

Images