Enhanced removal methods for nitrate nitrogen and organic matter in reclaimed water from constructed wetlands

Abstract

This invention belongs to the field of constructed wetland reclaimed water treatment technology, specifically relating to an enhanced removal method for nitrate nitrogen and organic matter in constructed wetland reclaimed water sources. This invention involves adding glucose, manganese ions, and copper ions to the reclaimed water source, enriching heterotrophic bacteria and loading them with metal ions within the constructed wetland's packing bed, and generating extracellular active enzymes through the stress response of the heterotrophic bacteria to the metal ions. This process achieves enzymatic hydrolysis of recalcitrant humic organic matter, improving the biodegradability of the reclaimed water, and ultimately enhancing the removal of nitrate nitrogen and organic matter.

Description

Technical Field

[0001] This invention belongs to the field of constructed wetland reclaimed water treatment technology, specifically relating to an enhanced removal method for nitrate nitrogen and organic matter in constructed wetland reclaimed water sources. Background Technology

[0002] Reclaimed water, the treated wastewater discharged from urban sewage treatment plants, is characterized by its large volume and stable quality, serving as a reliable "second water source" for cities. Currently, using reclaimed water as a supplementary water source is a crucial measure to address water scarcity and ecological degradation. Among these measures, constructed wetland water purification projects play a key role in improving the quality of reclaimed water.

[0003] Constructed wetlands purify pollutants through the synergistic effects of microorganisms, substrate materials, and aquatic vegetation. However, due to the unique characteristics of reclaimed water, the purification efficiency of constructed wetlands for nitrate nitrogen and organic matter is limited. After undergoing a "secondary biological treatment + tertiary advanced treatment" process, the nitrogen remaining in the reclaimed water from urban domestic sewage is mainly in the form of nitrates, while the organic matter is primarily humic organic matter. On the one hand, humic organic matter has a complex molecular structure and a large molecular weight, making it difficult to remove through microbial degradation, substrate adsorption, and vegetation absorption within constructed wetlands. On the other hand, nitrate nitrogen removal mainly relies on denitrification, but due to the scarcity of bioavailable carbon sources, denitrification processes cannot be effectively constructed within constructed wetlands. Furthermore, while substrate materials and vegetation are effective at removing ammonia nitrogen and phosphate, their removal capacity for nitrate nitrogen is limited. Therefore, exploring a method for removing nitrate nitrogen and organic matter is of great significance. Summary of the Invention

[0004] This invention discloses an enhanced removal method for nitrate nitrogen and organic matter in reclaimed water from constructed wetlands. By using humic organic matter in the reclaimed water as an organic carbon source for denitrification, simultaneous removal of organic matter and nitrate nitrogen can be achieved. This is accomplished by adding glucose, manganese ions, and copper ions to the reclaimed water, enriching heterotrophic bacteria and loading them with metal ions within the constructed wetland's packing bed, and generating extracellular active enzymes through the stress response of the heterotrophic bacteria to the metal ions. This process then achieves the enzymatic hydrolysis of recalcitrant humic organic matter, improving the biodegradability of the reclaimed water, and ultimately enhancing the removal of nitrate nitrogen and organic matter.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] Enhanced removal methods for nitrate nitrogen and organic matter in reclaimed water from constructed wetlands include: using humic organic matter in the reclaimed water as an organic carbon source for denitrification to achieve simultaneous removal of humic organic matter and nitrate nitrogen.

[0007] Preferably, in the method, glucose, manganese ions, and copper ions are added to the reclaimed water source, and heterotrophic bacteria are enriched and loaded with metal ions in the constructed wetland packing bed. The heterotrophic bacteria produce extracellular active enzymes through the stress response to metal ions, thereby realizing the enzymatic hydrolysis process of humic organic matter that is difficult to biodegrade, improving the biodegradability of the reclaimed water source, and ultimately enhancing the removal process of nitrate nitrogen and humic organic matter.

[0008] Preferably, the method includes the following specific steps:

[0009] (1) Lay manganese ore sand in the bottom layer area of ​​the artificial wetland at a filling rate of 35%-50%;

[0010] (2) During the process of purifying reclaimed water by the construction wetland, nitrate nitrogen is used as the water quality indicator. When the removal effect of nitrate nitrogen by the construction wetland reaches a stable state, a glucose solution with a COD equivalent concentration of 3 mg / L is added to the influent.

[0011] (3) After the constructed wetland continues to operate for 40-50 days, stop adding glucose solution and add divalent copper ion solution to the influent to make the concentration of divalent copper ions in the influent 0.02 mg / L;

[0012] (4) When the concentration of divalent copper ions in the effluent of the constructed wetland is greater than 0.01 mg / L, stop adding divalent copper ions and start adding divalent manganese ions to make the concentration of divalent manganese ions in the influent 3 mg / L.

[0013] (5) Stop adding divalent manganese ions when the concentration of divalent manganese ions in the effluent of the constructed wetland is greater than 0.10 mg / L, and the constructed wetland continues to operate normally thereafter.

[0014] The beneficial effects of the enhanced removal method for nitrate nitrogen and organic matter in reclaimed water from constructed wetlands according to the present invention are as follows:

[0015] 1. Based on the water quality characteristics of reclaimed water, glucose solution was used as an electron donor for heterotrophic microorganisms to increase the microbial enrichment on the surface of manganese ore sand in constructed wetlands.

[0016] 2. By loading divalent copper ions and divalent manganese ions onto the surface of manganese ore, microorganisms use divalent copper ions as active sites and divalent manganese ions as inducers to produce extracellular reactive enzymes.

[0017] 3. According to the current standards for reclaimed water discharge, the COD concentration in reclaimed water is generally less than 30 mg / L. This invention can reduce the COD concentration to below 15 mg / L and remove more than 3 mg / L of nitrate nitrogen.

[0018] In summary, this invention improves the biodegradability of reclaimed water by adding glucose, manganese ions, and copper ions to the reclaimed water source, enriching heterotrophic bacteria and loading them with metal ions in the constructed wetland packing bed, and generating extracellular active enzymes through the stress response of heterotrophic bacteria to metal ions. This process enables the enzymatic hydrolysis of humic organic matter that is difficult to biodegrade, thereby enhancing the removal of nitrate nitrogen and humic organic matter. Attached Figure Description

[0019] Figure 1 Schematic diagram of an artificial wetland purification and reclaimed water device (in the diagram, 1. reclaimed water source; 2. water pump; 3. purified water; 4. aquatic plants; 5. manganese ore sand layer; 6. support layer; 7. quartz sand layer).

[0020] Figure 2 The purification effect of constructed wetlands on nitrate nitrogen in reclaimed water sources.

[0021] Figure 3 The purification effect of constructed wetlands on COD in reclaimed water sources. Detailed Implementation

[0022] The following description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0023] The following embodiments can be understood as illustrating a part of the structure or method of the present invention individually, or as combining the embodiments to explain the broader structure or method of the present invention.

[0024] Example 1

[0025] Enhanced removal methods for nitrate nitrogen and organic matter in reclaimed water from constructed wetlands include: using humic organic matter in the reclaimed water as an organic carbon source for denitrification to achieve simultaneous removal of humic organic matter and nitrate nitrogen.

[0026] On the one hand, humic organic matter has a complex molecular structure and a large molecular weight, making it difficult to purify and remove in constructed wetlands through microbial degradation, adsorption by filler materials, and absorption by vegetation. On the other hand, nitrate nitrogen removal is mainly achieved through denitrification, but due to the scarcity of bioavailable carbon sources, denitrification processes cannot be effectively constructed in constructed wetlands. Furthermore, while filler materials and vegetation are effective in removing ammonia nitrogen and phosphate, their ability to remove nitrate nitrogen is limited. Based on the above problems, this invention uses humic organic matter in reclaimed water as an organic carbon source for denitrification to achieve simultaneous removal of humic organic matter and nitrate nitrogen.

[0027] Example 2

[0028] Based on Example 1, this example discloses:

[0029] In the method described, glucose, manganese ions, and copper ions are added to the reclaimed water source. Heterotrophic bacteria are enriched and loaded with metal ions in the constructed wetland packing bed. Extracellular active enzymes are generated through the stress response of heterotrophic bacteria to metal ions, thereby realizing the enzymatic hydrolysis process of humic organic matter that is difficult to biodegrade, improving the biodegradability of the reclaimed water source, and ultimately enhancing the removal process of nitrate nitrogen and humic organic matter.

[0030] Example 3

[0031] Based on Example 2, this example discloses:

[0032] The method includes the following specific steps:

[0033] (1) Lay manganese ore sand in the bottom layer area of ​​the artificial wetland at a filling rate of 35%-50%;

[0034] (2) During the process of purifying reclaimed water by the construction wetland, nitrate nitrogen is used as the water quality indicator. When the removal effect of nitrate nitrogen by the construction wetland reaches a stable state, a glucose solution with a COD equivalent concentration of 3 mg / L is added to the influent.

[0035] (3) After the constructed wetland continues to operate for 40-50 days, stop adding glucose solution and add divalent copper ion solution to the influent to make the concentration of divalent copper ions in the influent 0.02 mg / L;

[0036] (4) When the concentration of divalent copper ions in the effluent of the constructed wetland is greater than 0.01 mg / L, stop adding divalent copper ions and start adding divalent manganese ions to make the concentration of divalent manganese ions in the influent 3 mg / L.

[0037] (5) Stop adding divalent manganese ions when the concentration of divalent manganese ions in the effluent of the constructed wetland is greater than 0.10 mg / L, and the constructed wetland continues to operate normally thereafter.

[0038] Example 4

[0039] Based on the above embodiments, this embodiment discloses:

[0040] The constructed wetland packing bed device built in the embodiment is as follows: Figure 1As shown, the reactor is constructed using transparent acrylic sheets, and its dimensions (length × width × height) are 0.9 × 0.3 × 0.5 m. The reactor packing bed is filled from bottom to top with pebbles (10 cm), manganese ore (20 cm), and quartz sand (20 cm), with the manganese ore filling rate being 40%. The reactor operates under the condition that the hydraulic retention time is 3 days. According to the technical solution of the present invention, the operation stages of the example constructed wetland device include: a start-up and stable operation stage, a glucose addition stage, a copper ion addition stage, and a manganese ion addition stage.

[0041] like Figure 2 As shown, during the stable operation phase (0-54 days), the removal effect of constructed wetlands on nitrate nitrogen reached a stable state, with the nitrate nitrogen removal amount maintained at around 0.4 mg / L and the removal rate at approximately 11%.

[0042] like Figure 2 , 3 As shown, within 55-99 days, only a glucose solution with a COD equivalent concentration of 3 mg / L was added to the influent of the constructed wetland. The average removal of nitrate nitrogen by the constructed wetland was 1.05 mg / L, with an average removal rate of 25%; the average removal of COD was 14.5 mg / L, with an average removal rate of 43%.

[0043] like Figure 2 , 3 As shown, within 100-125 days, only a 0.02 mg / L divalent copper ion solution was added to the influent of the constructed wetland. The average removal of nitrate nitrogen by the constructed wetland was 1.77 mg / L, with an average removal rate of 38%; the average removal of COD was 13.5 mg / L, with an average removal rate of 53%.

[0044] like Figure 2 , 3 As shown, within 125-134 days, only a 3 mg / L divalent manganese ion solution was added to the influent of the constructed wetland. The average removal rate of nitrate nitrogen by the constructed wetland was 3.65 mg / L, with an average removal rate of 86%; the average removal rate of COD was 16.3 mg / L, with an average removal rate of 67%. The nitrate nitrogen concentration removal was above 3 mg / L, and the COD effluent concentration was below 15 mg / L.

[0045] like Figure 2 , 3 As shown, within 135-160 days, after stopping the addition of divalent manganese, the constructed wetland can still operate stably, with nitrate nitrogen removal of more than 3 mg / L and COD effluent concentration below 15 mg / L.

[0046] Working principle of the invention:

[0047] 1. Based on the water quality characteristics of reclaimed water, glucose solution was used as an electron donor for heterotrophic microorganisms to increase the microbial enrichment on the surface of manganese ore sand in constructed wetlands.

[0048] 2. By loading divalent copper ions and divalent manganese ions onto the surface of manganese ore, microorganisms use divalent copper ions as active sites and divalent manganese ions as inducers to produce extracellular reactive enzymes.

[0049] 3. According to the current standards for reclaimed water discharge, the COD concentration in reclaimed water is generally less than 30 mg / L. This invention can reduce the COD concentration to below 15 mg / L and remove more than 3 mg / L of nitrate nitrogen.

Claims

1. An enhanced removal method for nitrate nitrogen and organic matter in reclaimed water from constructed wetlands, characterized by: include: Using humic organic matter in reclaimed water as an organic carbon source for denitrification, so as to achieve the simultaneous removal of humic organic matter and nitrate nitrogen; In the method described, glucose, manganese ions, and copper ions are added to the reclaimed water source. Heterotrophic bacteria are enriched and loaded with metal ions in the artificial wetland packing bed. Extracellular active enzymes are generated by the stress response of heterotrophic bacteria to metal ions, thereby realizing the enzymatic hydrolysis process of humic organic matter that is difficult to biodegrade, improving the biodegradability of the reclaimed water source, and ultimately enhancing the removal process of nitrate nitrogen and humic organic matter. The method includes the following specific steps: (1) Lay manganese ore sand in the bottom layer area of ​​the constructed wetland at a filling rate of 35%-50%; (2) During the process of purifying reclaimed water by the construction wetland, nitrate nitrogen is used as the water quality indicator. When the removal effect of nitrate nitrogen by the construction wetland reaches a stable state, a glucose solution with a COD equivalent concentration of 3 mg / L is added to the influent. (3) After the constructed wetland continues to operate for 40-50 days, stop adding glucose solution and add divalent copper ion solution to the influent to make the concentration of divalent copper ions in the influent 0.02 mg / L; (4) When the concentration of divalent copper ions in the effluent of the constructed wetland is greater than 0.01 mg / L, stop adding divalent copper ions and start adding divalent manganese ions to make the concentration of divalent manganese ions in the influent 3 mg / L. (5) Stop adding divalent manganese ions when the concentration of divalent manganese ions in the effluent of the constructed wetland is greater than 0.10 mg / L, and the constructed wetland continues to operate normally thereafter.

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