Method for promoting denitrification to remove nitrate nitrogen in water by magnetic resins

Abstract

In view of the current pollution to sewage by nitrate nitrogen, the present invention discloses a method for promoting denitrification to remove nitrate nitrogen in water by magnetic resins. In the method disclosed by the present invention, magnetic anion exchange resins are in contact with and mixed with sewage, and nitrate nitrogen in the sewage is removed quickly and efficiently by both the ion exchange between the magnetic anion exchange resins and the nitrate nitrogen in the sewage and the denitrification enhanced by the magnetic material. Meanwhile, the regeneration and recycle of the magnetic anion exchange resins are realized by the denitrification of microorganisms.

Claims

1. A method for promoting denitrification to remove nitrate nitrogen from water by magnetic resins, comprising the following steps of: (1) adsorption using the magnetic resins: feeding nitrate-laden wastewater into a vessel A, mixing the nitrate-laden wastewater with the magnetic resins in the vessel A, and removing nitrate nitrogen from the nitrate-laden wastewater by contacting the magnetic resins to the nitrate-laden wastewater for a period of time from 5 to 60 min, wherein the magnetic resins are anion exchange resins; (2) separation: passing the nitrate-laden waste-water from the vessel A into a reactor B wherein the magnetic resins are separated from the nitrate-laden wastewater by hydrocyclone separation, returning 0% to 70% of the separated magnetic resins to the vessel A, and putting the remaining magnetic resins into a denitrification reactor C; (3) denitrification: adding electron donors to the reactor C, incubating the magnetic resins in the reactor C for 0.5 h to 8 h at the temperature from 15° C. to 38° C.; and (4) resin recycling: returning the magnetic resins on the bottom of the reactor C to the vessel A for recycling by gravitational setting.

2. The method according to claim 1, wherein, in step (1), the ratio of the magnetic resins to the nitrate-laden wastewater is 1:3-200 by volume.

3. The method according to claim 1, wherein, in step (1), the magnetic resins are nanoscale/microscale Fe.sub.3O.sub.4-supported strong base anion exchange resins, nanoscale/microscale Fe.sub.2O.sub.3-supported strong base anion exchange resins or magnetic strong base anion exchange resins prepared by copolymerization.

4. The method according to claim 1, wherein, in step (3), the electron donor is one or more selected from the group consisting of methanol, sodium acetate, glucose, starch, lactic acid, lactate, sulfur, divalent iron salt and ferrous sulfide.

5. The method according to claim 1, wherein a volatile solid is added to the reactor C, the volatile solid is one or more selected from the group consisting of activated sludge, denitrifying bacteria and anaerobic sludge.

6. The method according to claim 5, wherein the concentration of volatile solid is 0.1 to 20 g/L.

7. The method according to claim 1, wherein, in step (3), the electron donors are added in the reactor C in such an amount that the C/N ratio in a solution is 5.5 to 7.5.

8. The method according to claim 1, wherein, in step (3), incubating the magnetic resins in the reactor C for 1 hour at the temperature 30° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart of a process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins.

DETAILED DESCRIPTION OF THE INVENTION

(2) The process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided by the present invention will be further described by the following embodiments.

Embodiment 1

(3) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(4) The concentration of nitrate nitrogen in sewage was 115 mg/L, and the sewage was treated by the following steps. (1) The sewage was fed into a pool A, and was then in contact with and mixed with magnetic anion exchange resins and non-magnetic anion exchange resins (Purolite®A520E), respectively, wherein the flow ratio of the resins to the water was 1:100 and the contact time was 40 min. The used magnetic anion exchange resins were strong base anion exchange resins formed by supporting nanoscale/microscale Fe.sub.3O.sub.4 on Purolite®A520E.

(5) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 30% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(6) (3) Electron donors were added in the reactor C, the temperature was maintained at 35° C., and the magnetic resins were retained in the pool C for 5 h, wherein the electron donors were sodium acetate. At the start of the process, denitrifying bacteria was added in the reactor C.

(7) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(8) The device continuously operated for 10 days, and the sewage was in contact with and mixed with the magnetic anion exchange resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 95%±4%. When the sewage was in contact with and mixed with common strong base anion exchange resins (Purolite®A520E), the removal rate of nitrate nitrogen in the discharged water was only 83%±6%.

Embodiment 2

(9) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(10) The concentration of nitrate nitrogen in sewage was 112 mg/L, and the sewage was treated by the following steps.

(11) (1) The sewage was fed into a pool A, and was then in contact with and mixed with magnetic microsphere resins (the resins disclosed in Chinese Invention Patent 201110327637.8), wherein the flow ratio of the resins to the water was 1:200 and the contact time was 60 min.

(12) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 20% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(13) (3) Electron donors were added in the reactor C, the temperature was maintained at 38° C., and the magnetic resins were retained in the pool C for 7 h, wherein the electron donors were glucose. At the start of the process, activated sludge was added in the reactor C.

(14) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(15) The device continuously operated for 15 days, and the sewage was in contact with and mixed with the magnetic microsphere resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 91%±2%.

Embodiment 3

(16) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(17) The concentration of nitrate nitrogen in food wastewater was 82 mg/L, and the food wastewater was treated by the following steps.

(18) (1) The food wastewater was fed into a pool A, and was then in contact with and mixed with magnetic acrylic strong base anion exchange microsphere resins (the resins disclosed in Chinese Invention Patent 201010017687.1), wherein the flow ratio of the resins to the water was 1:50 and the contact time was 45 min.

(19) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 45% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(20) (3) Electron donors were added in the reactor C, the temperature was maintained at 30° C., and the magnetic resins were retained in the pool C for 8 h, wherein the electron donors were methanol. At the start of the process, anaerobic sludge was added in the reactor C.

(21) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(22) The device continuously operated for 7 days, and the food wastewater was in contact with and mixed with the magnetic acrylic strong base anion exchange microsphere resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 94%±3%.

Embodiment 4

(23) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(24) The concentration of nitrate nitrogen in petrochemical wastewater was 45 mg/L, and the petrochemical wastewater was treated by the following steps.

(25) (1) The petrochemical wastewater was fed into a pool A, and was then in contact with and mixed with magnetic strong base anion exchange resins (Song H, et al. Journal of Industrial & Engineering Chemistry, 2014, 20(5):2888-2894.), wherein the flow ratio of the resins to the water was 1:20 and the contact time was 10 min.

(26) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 60% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(27) (3) Electron donors were added in the reactor C, the temperature was maintained at 20° C., and the magnetic resins were retained in the pool C for 1 h, wherein the electron donors were starch. At the start of the process, activated sludge was added in the reactor C.

(28) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(29) The device continuously operated for 8 days, and the food wastewater was in contact with and mixed with the magnetic strong base anion exchange resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 96%±2%.

Embodiment 5

(30) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(31) The concentration of nitrate nitrogen in experimental water was 150 mg/L, and the experimental water was treated by the following steps.

(32) (1) The experimental water was fed into a pool A, and was then in contact with and mixed with magnetic anion exchange resins (Wu Xuehui, et al. Journal of Guangxi University (Natural Science Edition), 1999, 24(2):163-166.), wherein the flow ratio of the resins to the water was 1:3 and the contact time was 5 min.

(33) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 70% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(34) (3) Electron donors were added in the reactor C, the temperature was maintained at 18° C., and the magnetic resins were retained in the pool C for 0.5 h, wherein the electron donors were lactic acid. At the start of the process, denitrifying bacteria was added in the reactor C.

(35) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(36) The device continuously operated for 7 days, and the experimental water was in contact with and mixed with the magnetic anion exchange resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 87%±5%.

Embodiment 6

(37) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(38) The concentration of nitrate nitrogen in food wastewater was 75 mg/L, and the food wastewater was treated by the following steps.

(39) (1) The food wastewater was fed into a pool A, and was then in contact with and mixed with magnetic anion exchange resins, wherein the flow ratio of the resins to the water was 1:150 and the contact time was 50 min. The used magnetic resins were strong base anion exchange resins formed by supporting nanoscale/microscale Fe.sub.2O.sub.3 on Purolite®A520E.

(40) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 5% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(41) (3) Electron donors were added in the reactor C, the temperature was maintained at 35° C., and the magnetic resins were retained in the pool C for 6.5 h, wherein the electron donors were sodium acetate and glucose. At the start of the process, activated sludge was added in the reactor C.

(42) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(43) The device continuously operated for 12 days, and the food wastewater was in contact with and mixed with the magnetic anion exchange resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 92%±2%.

Embodiment 7

(44) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(45) The concentration of nitrate nitrogen in sewage was 68 mg/L, and the sewage was treated by the following steps.

(46) (1) The sewage was fed into a pool A, and was then in contact with and mixed with magnetic anion exchange resins, wherein the flow ratio of the resins to the water was 1:80 and the contact time was 30 min. The used magnetic resins were magnetic strong base anion exchange resins prepared from macroporous anion exchange resins D201 by copolymerization.

(47) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 10% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(48) (3) Electron donors were added in the reactor C, the temperature was maintained at 25° C., and the magnetic resins were retained in the pool C for 5.5 h, wherein the electron donors were ferrous sulfide. At the start of the process, denitrifying bacteria was added in the reactor C.

(49) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(50) The device continuously operated for 9 days, and the sewage was in contact with and mixed with the magnetic anion exchange resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 92%±2%.

Embodiment 8

(51) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(52) The concentration of nitrate nitrogen in experimental water was 100 mg/L, and the experimental water was treated by the following steps.

(53) (1) The experimental water was fed into a pool A, and was then in contact with and mixed with magnetic acrylic strong base anion exchange microsphere resins (the resins disclosed in Chinese Invention Patent 201010017687.1), wherein the flow ratio of the resins to the water was 1:60 and the contact time was 20 min.

(54) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 35% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(55) (3) Electron donors were added in the reactor C, the temperature was maintained at 30° C., and the magnetic resins were retained in the pool C for 3.5 h, wherein the electron donors were sodium acetate, glucose and starch. At the start of the process, denitrifying bacteria and anaerobic sludge were added in the reactor C.

(56) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(57) The device continuously operated for 10 days, and the experimental water was in contact with and mixed with the magnetic acrylic strong base anion exchange microsphere resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 90%±3%.

Embodiment 9

(58) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(59) The concentration of nitrate nitrogen in sewage was 92 mg/L, and the sewage was treated by the following steps.

(60) (1) The sewage was fed into a pool A, and was then in contact with and mixed with magnetic strong base anion exchange resins (the resins disclosed in Journal of Industrial & Engineering Chemistry, 2014, 20(5):2888-2894.), wherein the flow ratio of the resins to the water was 1:30 and the contact time was 35 min.

(61) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 50% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(62) (3) Electron donors were added in the reactor C, the temperature was maintained at 25° C., and the magnetic resins were retained in the pool C for 2 h, wherein the electron donors were divalent iron salt and ferrous sulfide. At the start of the process, activated sludge and anaerobic sludge were added in the reactor C.

(63) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(64) The device continuously operated for 15 days, and the sewage was in contact with and mixed with the magnetic strong base anion exchange resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 90%±3%.

Embodiment 10

(65) As shown in FIG. 1, the process for promoting denitrification to remove nitrate nitrogen in water by magnetic resins provided in this embodiment includes the following steps.

(66) The concentration of nitrate nitrogen in experimental water was 120 mg/L, and the test water was treated by the following steps.

(67) (1) The experimental water was fed into a pool A, and was then in contact with and mixed with magnetic strong base anion exchange resins (the resins disclosed in Journal of Industrial & Engineering Chemistry, 2014, 20(5):2888-2894.), wherein the flow ratio of the resins to the water was 1:40 and the contact time was 50 min.

(68) (2) The water from the pool A was treated by hydrocyclone separation (reactor B), 0% of the separated magnetic resins were returned to the pool A, and the remaining magnetic resins were put into a denitrification reactor (reactor C).

(69) (3) Electron donors were added in the reactor C, the temperature was maintained at 15° C., and the magnetic resins were retained in the pool C for 3 h, wherein the electron donors were divalent iron salt and ferrous sulfide. At the start of the process, activated sludge and anaerobic sludge were added in the reactor C.

(70) (4) The magnetic resins on the bottom of the pool C were returned to the pool A for recycling by natural deposition.

(71) The device continuously operated for 13 days, and the sewage was in contact with and mixed with the magnetic strong base anion exchange resins. In the water finally discharged from the device, the removal rate of nitrate nitrogen was 88%±3%.

(72) In the foregoing embodiments, the flow ratio is obtained by uniformly mixing a certain amount of water with the resins so that the resins become a fluid, i.e., a ratio of the volume of the resins to be fed into the reactor A per hour to the volume of sewage to be treated.

(73) Other aspects involved in the present invention, which are not explained here, are the same as those in the prior art.