Tail water constructed wetland system and method for enhancing low-temperature denitrification of microorganisms

Abstract

The invention belongs to the technical field of sewage treatment systems, and particularly relates to a tail water constructed wetland system and method for enhancing microorganism low-temperature denitrification. The constructed wetland system comprises a water inlet pipe, a constructed wetland pool body and a drainage system, the constructed wetland pool body is divided into a water distribution area, a wetland filler area and a water collection area by perforated lattice walls; wetland plants are planted above the wetland filler area; a filler in the wetland filler area comprises a hydroxylated graphene coating porous mesh bubble filler; the drainage system is located in the water collecting area; a slow-release biomass carbon source is put into the water distribution area. The constructed wetland system provided by the invention can be used for a treatment process for deep denitrification and resource utilization of tail water of a sewage treatment plant under all climate, and has good denitrification efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment systems, and in particular relates to a tailwater artificial wetland system and method for enhancing low-temperature microbial denitrification. Background Art

[0002] Constructed wetlands are a key process for the advanced treatment and resource utilization of wastewater plant tailwater. However, due to climatic constraints, the activity of functional microorganisms in constructed wetlands decreases during low temperatures. In particular, microorganisms involved in nitrogen conversion are significantly affected by the temperature drop, resulting in reduced wastewater treatment efficiency and unstable tailwater quality and compliance with standards. Summary of the Invention

[0003] The purpose of the present invention is to provide a tailwater artificial wetland system and method for enhanced microbial low-temperature denitrification. The artificial wetland system provided by the present invention can be used for the treatment process of deep denitrification and resource utilization of sewage treatment plant tailwater in all climates, and has good denitrification efficiency.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a tailwater artificial wetland system for enhancing microbial low-temperature denitrification, comprising a water inlet pipe, an artificial wetland pool and a drainage system;

[0006] The artificial wetland pool is divided into a water distribution area, a wetland filling area and a water collection area by a perforated flower wall;

[0007] Wetland plants are planted above the wetland filling area; the filler in the wetland filling area includes a hydroxylated graphene coated porous mesh foam filler;

[0008] The drainage system is located in the water collection area; and a slow-release biomass carbon source is placed in the water distribution area.

[0009] Preferably, the effective depth of the wetland fill area is 130 to 200 cm;

[0010] From bottom to top, the wetland filling area includes a sedimentation filling layer, a functional filling layer and a planting filling layer.

[0011] Preferably, the depth of the sedimentation filler layer is 30 to 50 cm;

[0012] The filler in the sedimentation filler layer is one or more of pebbles, gravels and crushed stones with a particle size of 20 to 30 mm;

[0013] The depth of the functional filler layer is 90 to 130 cm; the filler of the sedimentation filler layer is a hydroxylated graphene coated porous cellular filler and a non-coated filler;

[0014] The depth of the planting filler layer is 10 to 20 cm; the filler in the planting filler layer is gravel and / or crushed stone with a particle size of 5 to 10 mm.

[0015] Preferably, the hydroxylated graphene coated porous reticulated foam filler is located in the region of 10 to 70 cm from the bottom to the top of the functional filler layer;

[0016] The volume percentage of the hydroxylated graphene coating porous cellular filler in the functional filler layer is 10 to 40%.

[0017] Preferably, the non-coated filler comprises one or more of rock debris, bioceramsite and zeolite;

[0018] The rock debris includes gravel or crushed stone; the particle size of the non-coated filler is 20 to 30 mm.

[0019] Preferably, the water level regulating drainage pipe is a drainage pipe provided with a rotating elbow; the water level regulating drainage pipe is a drainage pipe provided with a rotating elbow; the rotating elbow portion is located in the water collection area, and the other end passes through the side wall of the pool body.

[0020] Preferably, the water distribution holes of the perforated flower wall are located on the top of the sedimentation filler layer.

[0021] Preferably, the water inlet pipe is laid under the permafrost layer.

[0022] Preferably, the preparation of the hydroxylated graphene coated porous cellular filler comprises the following steps:

[0023] mixing a dispersion of graphene oxide with polybutylene glycol under alkaline conditions to perform hydroxylation to obtain hydroxylated graphene oxide;

[0024] hydrolyzing γ-glycidyloxypropyltrimethoxysilane to obtain hydrolyzed KH-560;

[0025] mixing the aqueous dispersion of hydroxylated graphene oxide, the hydrolyzed KH-560 and triethylamine to obtain an aqueous dispersion of modified graphene oxide;

[0026] The multilayer reticulated foam filler is immersed in the aqueous dispersion of the modified graphene oxide for modification to obtain a hydroxylated graphene coated porous reticulated foam filler.

[0027] The present invention also provides a method for treating sewage using the tailwater artificial wetland system with enhanced microbial low-temperature denitrification according to the above technical solution, comprising the following steps:

[0028] The tail water of the sewage plant is mixed with the slow-release biomass carbon source in the water distribution area and then enters the wetland filler area of the constructed wetland pool body for purification, and the purified water flows into the water collection area through the perforated flower wall and is discharged through the drainage system.

[0029] The application provides a tail water constructed wetland system for enhancing low-temperature denitrification of microorganisms, which comprises an inlet pipe, a constructed wetland pool body and a drainage system.

[0030] The application provides the constructed wetland system with the following advantages.

[0031] (1) The hydroxylated graphene coating porous net foam filler adopted in the application can change the structure of the denitrification functional microbial community in the low-temperature period, activate the growth of nitrogen metabolism functional microorganisms such as Pseudomonas, Glaciicola, Hymonad, Acinetobacter and Enterobacter, stimulate Pseudomonas to become the dominant genus, significantly improve the denitrification functional gene abundance of Pseudomonas, strengthen the denitrification process of the tail water constructed wetland in the low-temperature period, and improve the denitrification efficiency.

[0032] (2) The hydroxylated graphene coating porous net foam filler adopted in the application has higher pollutant adsorption performance and microbial affinity, changes the composition of the denitrification functional microorganisms, can activate Pseudomonas and Magnetospirillum at room temperature, improve the abundance of the denitrification functional genes, improve the denitrification reaction rate of the tail water constructed wetland, and guarantee the deep denitrification effect of the tail water.

[0033] (3) The hydroxylated graphene coating porous net foam filler adopted in the application can regulate the adaptability and denitrification process of the functional microorganisms at room temperature and low temperature, realize one-time addition, automatically regulate the functional microorganisms according to the temperature in the later period, and does not need to be operated again, thereby guaranteeing the effect of meeting the standard of the full-weather tail water deep treatment. DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0035] Figure 1Schematic diagram of the artificial wetland system provided by the present invention, wherein: 1 - artificial wetland pool; 2 - sedimentation filler layer; 3 - functional filler layer; 4 - planting filler layer; 5 - wetland plants; 6 - water inlet pipe; 7 - water level regulation drainage pipe; 8 - drainage pipe controlled by electromagnetic valve; 9 - perforated flower wall; 10 - slow-release biomass carbon source. DETAILED DESCRIPTION

[0036] The present invention provides an artificial wetland system, comprising a water inlet pipe, an artificial wetland pool and a drainage system;

[0037] The artificial wetland pool is divided into a water distribution area, a wetland filling area and a water collection area by a perforated flower wall;

[0038] Wetland plants are planted above the wetland filling area; the filler in the wetland filling area includes a hydroxylated graphene coated porous mesh foam filler;

[0039] The drainage system is located in the water collection area; and a slow-release biomass carbon source is placed in the water distribution area.

[0040] The artificial wetland system provided by the present invention comprises a water inlet pipe.

[0041] As an embodiment of the present invention, the water inlet pipe is preferably laid under the frozen soil layer; the water inlet pipe passes through the side wall of the artificial wetland pool, and the end thereof is located in the water distribution area.

[0042] The artificial wetland system provided by the present invention comprises an artificial wetland pool body, wherein the artificial wetland pool body is divided into a water distribution area, a wetland filling area and a water collection area by a perforated flower wall. Wetland plants are planted above the wetland filling area.

[0043] As an embodiment of the present invention, the effective depth of the wetland filling area is preferably 130 to 200 cm; as an embodiment of the present invention, from bottom to top, the wetland filling area includes a sedimentation filling layer, a functional filling layer and a planting filling layer.

[0044] As an embodiment of the present invention, the depth of the sedimentation filler layer is preferably 30 to 50 cm; the filler in the sedimentation filler layer preferably includes one or more of pebbles, gravels and crushed stones with a particle size of 20 to 30 mm;

[0045] As an embodiment of the present invention, the depth of the functional filler layer is preferably 90 to 130 cm; the filler of the sedimentation filler layer is preferably a hydroxylated graphene coated porous reticular filler and a non-coated filler; the non-coated filler preferably includes one or more combinations of rock fragments, bioceramic aggregate and zeolite; the rock fragments preferably include gravel or crushed stone.

[0046] As an embodiment of the present invention, the particle size of the non-coated filler is preferably 20 to 30 mm; the volume percentage of the hydroxylated graphene coated porous reticulated filler in the functional filler layer is preferably 10% to 40%; as an embodiment of the present invention, the hydroxylated graphene coated porous reticulated filler is preferably located in the 10 to 70 cm area from the bottom to the top of the functional filler layer.

[0047] As an embodiment of the present invention, the preparation of the hydroxylated graphene coated porous cellular filler comprises the following steps:

[0048] mixing a dispersion of graphene oxide with polybutylene glycol under alkaline conditions to perform hydroxylation to obtain hydroxylated graphene oxide;

[0049] Mixing γ-glycidyloxypropyltrimethoxysilane (KH-560) and an ethanol aqueous solution, and hydrolyzing the resulting mixture under acidic conditions to obtain hydrolyzed KH-560;

[0050] The aqueous dispersion of the hydroxylated graphene oxide and the hydrolyzed KH-560 are mixed, and coupled under triethylamine conditions to obtain an aqueous dispersion of modified graphene oxide;

[0051] The multilayer reticulated foam filler is immersed in the modified graphene oxide dispersion for modification to obtain a hydroxylated graphene coated porous reticulated foam filler.

[0052] The present invention mixes a dispersion of graphene oxide with polybutylene glycol under alkaline conditions and performs hydroxylation to obtain hydroxylated graphene oxide.

[0053] As an embodiment of the present invention, the concentration of the graphene oxide dispersion is preferably 2 mg / mL. As an embodiment of the present invention, the alkaline condition is preferably obtained by adjusting the graphene oxide dispersion to a pH of 10 using a NaOH solution and then ultrasonically treating it for 30 minutes.

[0054] As one embodiment of the present invention, the weight average molecular weight of the polybutylene glycol is preferably 1000-2000; the mass ratio of the graphene oxide to polybutylene glycol is preferably 1-2:5-10, specifically 1:5, 2:5, 1:6, 2:6, 1:7, 2:7, 1:8, 2:8, 1:9, 2:9, 1:10 or 2:10. As one embodiment of the present invention, the hydroxylation is preferably carried out under water bath shaking conditions; the hydroxylation temperature is preferably 80-90°C, and the time is preferably 6 hours. As one embodiment of the present invention, after the hydroxylation, the hydroxylation reaction solution is further freeze-dried to obtain hydroxylated graphene oxide.

[0055] The invention mixes gamma-glycidyloxypropyltrimethoxysilane (KH-560) and an ethanol aqueous solution, and hydrolyzes the obtained mixed solution under acidic conditions to obtain hydrolyzed KH-560.

[0056] As an embodiment of the present invention, the volume concentration of the ethanol aqueous solution is preferably 90%; the concentration of γ-glycidyloxypropyltrimethoxysilane in the mixed solution is preferably 2wt%; the acidic conditions are preferably provided by acetic acid, and the mass concentration of the acetic acid is preferably 0.1-0.5%.

[0057] After obtaining the hydrolyzed KH-560, the present invention mixes the aqueous dispersion of the hydroxylated graphene oxide and the hydrolyzed KH-560, and couples them under triethylamine conditions to obtain an aqueous dispersion of modified graphene oxide.

[0058] As an embodiment of the present invention, the concentration of the aqueous dispersion of hydroxylated graphene oxide is preferably 1 mg / mL, and the pH value is preferably 6.0 to 7.0. As an embodiment of the present invention, the mass ratio of the hydrolyzed KH-560 to the aqueous dispersion of hydroxylated graphene oxide is preferably 2 to 4:1 to 2.

[0059] In one embodiment of the present invention, the aqueous dispersion of hydroxylated graphene oxide and the hydrolyzed KH-560 are preferably mixed by ultrasound, and the ultrasound duration is preferably 30 minutes. In another embodiment of the present invention, the coupling is preferably performed under shaking conditions, and the shaking temperature is preferably 40-50°C, and the shaking duration is preferably 1-2 hours.

[0060] After obtaining the modified graphene dispersion, the present invention immerses the multilayer reticulated foam filler into the aqueous dispersion of the modified graphene oxide for modification to obtain a hydroxylated graphene coated porous reticulated foam filler.

[0061] As an embodiment of the present invention, the modification temperature is preferably 80-90°C, and the time is preferably 3 hours. As an embodiment of the present invention, after the modification, the modified multilayer reticulated filler is further washed with ethanol and then dried; the drying temperature is preferably 50-60°C.

[0062] As one embodiment of the present invention, the depth of the planting filler layer is preferably 10 to 20 cm; the filler in the planting filler layer is preferably gravel and / or crushed stone with a particle size of 5 to 10 mm. As one embodiment of the present invention, the wetland plants are planted in the plant filler layer; the wetland plants are preferably native wetland plants with well-developed root systems, specifically Iris pumila.

[0063] As an embodiment of the present invention, the water distribution holes of the perforated flower wall are located on the top of the sedimentation filler layer.

[0064] The artificial wetland system provided by the present invention includes a drainage system.

[0065] As an embodiment of the present invention, the drainage system preferably includes a double drainage pipe. Specifically, the drainage system preferably includes a water level regulating drainage pipe and a drainage pipe controlled by an electromagnetic valve; the water level regulating drainage pipe is a drainage pipe provided with a rotating elbow; the rotating elbow portion is located in the water collection area, and the other end passes through the side wall of the pool body.

[0066] As one embodiment of the present invention, one end of the drainage pipe controlled by the solenoid valve is laid in the sedimentation filler layer, and the other end passes through the side wall of the artificial wetland pool. As one embodiment of the present invention, the drainage pipe controlled by the solenoid valve is periodically opened, and the periodic opening time is 2 to 4 times the hydraulic retention time of the wetland, thereby achieving rapid drainage of the wetland and promoting the reoxygenation function of the wetland.

[0067] The present invention also provides a method for treating sewage using a tailwater artificial wetland system with enhanced microbial low-temperature denitrification as described in the above technical solution, comprising the following steps:

[0068] The tail water from the sewage treatment plant is introduced into the water distribution area from the water inlet pipe and mixed with the slow-release biomass carbon source, and then enters the wetland filling area of ​​the artificial wetland pool for purification. The purified water flows into the water collection area through the perforated flower wall and is then discharged through the drainage system.

[0069] In the present invention, after the tail water of the sewage treatment plant enters the water distribution area, it preferably enters the wetland filling area evenly through the bottom perforated flower wall.

[0070] In the present invention, when the tail water flows through the functional filler layer during the low temperature period, the hydroxylated graphene coated porous mesh filler can regulate the structure and abundance of the microbial community, activate the denitrification functional microorganisms, significantly improve the abundance of the denitrification functional genes, make full use of the available carbon source released by the slow-release biomass carbon source, promote the denitrification and denitrification efficiency of the artificial wetland during the low temperature period, improve the nitrate removal rate in the tail water, and, assisted by the tidal flow operation mode, effectively solve the problem of low denitrification efficiency of the artificial wetland during the low temperature period, and achieve standard discharge of the tail water of the artificial wetland during the low temperature period.

[0071] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0072] Example 1

[0073] Preparation of hydroxylated graphene coated porous cellular filler:

[0074] Graphene oxide (GO) dispersion (2 mg / mL) was adjusted to pH 10 with 1 mol / L NaOH solution and ultrasonicated for 30 min. Then, polybutylene glycol (MW 2000) (GO:PTMG=1:5) was added to the GO dispersion, shaken in an 80°C water bath for 6 h, and freeze-dried to obtain hydroxylated graphene oxide.

[0075] KH-560 was added to a 90 vol.% ethanol aqueous solution, and the resulting mixture (the concentration of KH-560 in the mixture was 2 wt%) was adjusted to pH 5.0 with 0.5 wt.% acetic acid and shaken for 60 minutes to obtain hydrolyzed KH-560;

[0076] The hydrolyzed KH-560 was added to an aqueous dispersion of hydroxylated graphene oxide (1 mg / mL, pH = 6.0-7.0, the mass ratio of the hydrolyzed KH-560 to the aqueous dispersion of hydroxylated graphene was 1:1) and ultrasonicated for 30 min. Triethylamine (the mass of triethylamine was 0.1% of the mixed solution) was added to the resulting mixture, and the mixture was shaken at 50° C. for 2 h to obtain an aqueous dispersion of modified graphene oxide;

[0077] The multilayer reticulated foam filler (made of polyurethane) was immersed in the above-mentioned mixed solution and maintained at 90°C for 3 hours; then washed with ethanol three times and dried at 60°C to obtain a hydroxylated graphene coated porous reticulated foam filler.

[0078] like Figure 1 The constructed wetland system includes a constructed wetland pond, a wetland filler system, a wetland plant system, a water inlet system, and a drainage system. The wetland pond measures 0.8m x 0.4m x 1.6m and consists of, from bottom to top, a sedimentation filler layer, a functional filler layer, and a planting filler layer. The sedimentation filler layer is 20-30mm pebbles with a depth of 20cm. The functional filler layer is composed of 10-20mm hydroxylated graphene-coated porous mesh filler, 10-20mm gravel, and 10-20mm bioceramic aggregate in a volume ratio of 2:4:4, with a depth of 90cm. The planting layer is 5-10mm gravel with a depth of 20cm. The wetland plants are yellow iris.

[0079] The constructed wetland system was used to treat simulated sewage plant tailwater at a temperature of 9.2-12.4°C and a hydraulic retention time of 36 hours. The average COD and TN concentrations in the wetland influent were 48.69 mg / L and 16.54 mg / L, respectively. After passing through the constructed wetland system, the effluent temperature was 9.1-11.8°C, and the average COD and TN concentrations in the effluent were 21.87 mg / L and 5.25 mg / L, respectively.

[0080] The results of microbial analysis in the functional layer filler showed that the abundance of denitrification functional genes increased significantly at low temperatures, and Pseudomonas was the dominant genus in the wetland microbial community.

[0081] Example 2

[0082] The constructed wetland system comprises a constructed wetland pool, a wetland filler system, a wetland plant system, an inlet water system and a drainage system. The wetland pool is 30m x 30m x 1.5m, with an effective depth of 1.3m, and comprises a settlement filler layer, a functional filler layer and a planting filler layer from bottom to top, wherein the settlement filler layer is 20-30mm pebbles with a depth of 20cm; the functional filler layer is composed of 10-20mm hydroxylated graphene coating porous mesh foam filler, gravel, zeolite and biological ceramsite, with a volume ratio of 1:4:2:3, and a depth of 90cm; the plant planting layer is 5-10mm gravel with a depth of 20cm. The wetland plant is Acorus calamus. The inlet water system uses a sewage lifting pump for lifting, and the inlet water pipeline into the wetland unit is DN100. The water level regulating drainage pipe is a DN150 drainage pipe, and the electromagnetic valve controlled drainage pipe is a DN300 drainage pipe. During winter operation, the inlet water temperature is 7.2-11.3℃, the hydraulic retention time is 54h, and the main pollutants of the tail water of the sewage plant, COD, NH3-N, TN and TP, are 44-56mg / L, 0.92-1.48mg / L, 9.15-17.18mg / L and 0.42-0.45mg / L, respectively. After the constructed wetland system, the water temperature of the wetland effluent is 8.2-9.4℃, and the main pollutants of the effluent, COD, NH3-N, TN and TP, are 32-38mg / L, 0.65-1.14mg / L, 5.38-9.81mg / L and 0.25-0.29mg / L, respectively.

[0083] Although the above embodiments have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which are within the protection scope of the present application.

Claims

1. A tailwater artificial wetland system for enhanced microbial low-temperature denitrification, characterized in that: Including water inlet pipes, artificial wetland pools and drainage systems; The artificial wetland pool is divided into a water distribution area, a wetland filling area and a water collection area by a perforated flower wall; Wetland plants are planted above the wetland filling area; the filler in the wetland filling area includes a hydroxylated graphene coated porous mesh foam filler; The drainage system is located in the water collection area; and a slow-release biomass carbon source is placed in the water distribution area.

2. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 1, characterized in that: The effective depth of the wetland fill area is 130 to 200 cm; From bottom to top, the wetland filling area includes a sedimentation filling layer, a functional filling layer and a planting filling layer.

3. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 2, characterized in that: The depth of the sedimentation filler layer is 30 to 50 cm; The filler in the sedimentation filler layer is one or more of pebbles, gravels and crushed stones with a particle size of 20 to 30 mm; The depth of the functional filler layer is 90 to 130 cm; the filler of the sedimentation filler layer is a hydroxylated graphene coated porous cellular filler and a non-coated filler; The depth of the planting filler layer is 10 to 20 cm; the filler in the planting filler layer is gravel and / or crushed stone with a particle size of 5 to 10 mm.

4. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 3, characterized in that: The hydroxylated graphene coated porous reticulated foam filler is located in the region of 10 to 70 cm from the bottom to the top of the functional filler layer; The volume percentage of the hydroxylated graphene coating porous cellular filler in the functional filler layer is 10 to 40%.

5. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 1, characterized in that: The non-coated filler includes one or more of rock debris, bioceramsite and zeolite; The rock debris includes gravel or crushed stone; the particle size of the non-coated filler is 20 to 30 mm.

6. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 1, characterized in that: The water level regulating drainage pipe is a drainage pipe provided with a rotating elbow; the rotating elbow is located in the water collection area, and the other end passes through the side wall of the pool body.

7. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 1, characterized in that: The water distribution holes of the perforated flower wall are located on the top of the sedimentation filler layer.

8. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 1, characterized in that: The water inlet pipe is laid under the frozen soil layer.

9. The tailwater artificial wetland system for enhancing low-temperature microbial denitrification according to claim 1 or 4, characterized in that: The preparation of the hydroxylated graphene coating porous reticulated foam filler comprises the following steps: mixing a dispersion of graphene oxide with polybutylene glycol under alkaline conditions to perform hydroxylation to obtain hydroxylated graphene oxide; hydrolyzing γ-glycidyloxypropyltrimethoxysilane to obtain hydrolyzed KH-560; mixing the aqueous dispersion of hydroxylated graphene oxide, the hydrolyzed KH-560 and triethylamine to obtain an aqueous dispersion of modified graphene oxide; The multilayer reticulated foam filler is immersed in the aqueous dispersion of the modified graphene oxide for modification to obtain a hydroxylated graphene coated porous reticulated foam filler.

10. A method for treating sewage using the tailwater artificial wetland system for enhanced microbial low-temperature denitrification according to any one of claims 1 to 9, comprising the following steps: The tail water from the sewage treatment plant is introduced into the water distribution area from the water inlet pipe and mixed with the slow-release biomass carbon source, and then enters the wetland filling area of ​​the artificial wetland pool for purification. The purified water flows into the water collection area through the perforated flower wall and is then discharged through the drainage system.

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