A system and method for enhancing low-temperature denitrification of effluent water in a microbial wetland

Abstract

The application belongs to the technical field of sewage treatment systems, and particularly relates to a tail water artificial wetland system and method for enhancing microbial low-temperature denitrification. The artificial wetland system comprises a water inlet pipe, an artificial wetland pool body and a drainage system. The artificial wetland pool body is divided into a water distribution area, a wetland filler area and a water collection area by a perforated flower wall. Wetland plants are planted above the wetland filler area. The filler of the wetland filler area comprises a hydroxylated graphene coating porous net bubble filler. The drainage system is located in the water collection area. Slow-release biomass carbon sources are put into the water distribution area. The artificial wetland system provided by the application can be used for a treatment process for deep denitrification and resource utilization of tail water of a sewage treatment plant under all climates, and has good denitrification efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment systems, and particularly relates to a tail water constructed wetland system and method for enhancing microbial low-temperature denitrification. BACKGROUND

[0002] The constructed wetland is an important process for advanced treatment and resource utilization of tail water of a sewage plant. However, due to the climate condition, the activity of functional microorganisms is reduced in the low-temperature period, especially the functional microorganisms participating in nitrogen transformation are significantly affected by the temperature reduction, which leads to a decrease in sewage treatment efficiency, and problems such as unstable water quality and unstable standard reaching of the tail water in the advanced purification treatment. SUMMARY

[0003] The application aims to provide a tail water constructed wetland system and method for enhancing microbial low-temperature denitrification. The constructed wetland system provided by the application can be used for the process of advanced denitrification and resource utilization of tail water of a sewage treatment plant under all climates, and has good denitrification efficiency.

[0004] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0005] The application provides a tail water constructed wetland system for enhancing microbial low-temperature denitrification, comprising a water inlet pipe, a constructed wetland pool body and a drainage system.

[0006] The constructed wetland pool body is divided into a water distribution area, a wetland filler area and a water collection area by a perforated flower wall.

[0007] Wetland plants are planted above the wetland filler area. The filler of the wetland filler area comprises a hydroxylated graphene coating porous net foam filler.

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

[0009] Preferably, the effective depth of the wetland filler area is 130-200 cm.

[0010] From bottom to top, the wetland filler area comprises a settlement filler layer, a functional filler layer and a planting filler layer.

[0011] Preferably, the depth of the settlement filler layer is 30-50 cm.

[0012] The filler in the settlement filler layer is one or more of pebbles, gravel and broken stones with a particle size of 20-30 mm.

[0013] The depth of the functional filler layer is 90-130 cm. The filler of the settlement filler layer is a hydroxylated graphene coating porous net foam filler and a non-coating filler.

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

[0015] Preferably, the hydroxylated graphene coating porous net bubble filler is located in the 10-70 cm region from the bottom of the functional filler layer;

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

[0017] Preferably, the non-coated filler includes one or more of rock debris, biological ceramsite and zeolite;

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

[0019] Preferably, the water level adjusting drainage pipeline is a drainage pipeline provided with a rotating elbow; the water level adjusting drainage pipeline is a drainage pipeline provided with a rotating elbow; and the rotating elbow is partially located in the water collecting area and the other end penetrates through the side wall of the pool body.

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

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

[0022] Preferably, the preparation of the hydroxylated graphene coating porous net bubble filler includes the following steps:

[0023] The dispersion solution of graphene oxide is mixed with polybutylene glycol under alkaline conditions to perform hydroxylation to obtain hydroxylated graphene oxide;

[0024] The hydrolysis of γ-glycidyl ether propyltrimethoxysilane is carried out to obtain hydrolyzed KH-560;

[0025] The water dispersion solution of hydroxylated graphene oxide is mixed with hydrolyzed KH-560 and triethylamine to obtain a water dispersion solution of modified graphene oxide;

[0026] The multi-layer net bubble filler is immersed in the water dispersion solution of modified graphene oxide to obtain a hydroxylated graphene coating porous net bubble filler.

[0027] The application also provides a method for treating sewage by using the enhanced microorganism low-temperature denitrification tail water artificial wetland system according to the above technical solution, which includes 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, Psychromonas, Hymenobacter, 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 1The schematic diagram of the artificial wetland system provided by the present application, wherein, 1-artificial wetland pool body; 2-settling filler layer; 3-functional filler layer; 4-planting filler layer; 5-wetland plants; 6-water inlet pipe; 7-water level regulating drainage pipeline; 8-electromagnetic valve controlled drainage pipeline; 9-perforated flower wall; 10-slow-release biomass carbon source. DETAILED DESCRIPTION

[0036] The present application provides an artificial wetland system, comprising a water inlet pipe, an artificial wetland pool body and a drainage system.

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

[0038] Wetland plants are planted above the wetland filler area; the filler of the wetland filler area comprises a hydroxylated graphene coated porous net bubble filler.

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

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

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

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

[0043] As an embodiment of the present application, the effective depth of the wetland filler area is preferably 130-200 cm; as an embodiment of the present application, from bottom to top, the wetland filler area comprises a settling filler layer, a functional filler layer and a planting filler layer.

[0044] As an embodiment of the present application, the depth of the settling filler layer is preferably 30-50 cm; the filler in the settling filler layer preferably comprises one or more of pebbles, gravel and broken stones with a particle size of 20-30 mm;

[0045] As an embodiment of the present application, the depth of the functional filler layer is preferably 90-130 cm; the filler of the settling filler layer is preferably a hydroxylated graphene coated porous net bubble filler and a non-coated filler; the non-coated filler preferably comprises one or a combination of several of rock debris, biological ceramsite and zeolite; the rock debris preferably comprises gravel or broken stones.

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

[0047] As an embodiment of the present application, the preparation of the hydroxylated graphene-coated porous reticular bubble filler comprises the following steps:

[0048] The dispersion liquid of graphene oxide is mixed with polybutylene glycol under alkaline conditions to perform hydroxylation, thereby obtaining hydroxylated graphene oxide.

[0049] γ-glycidyl ether propyltrimethoxysilane (KH-560) is mixed with an aqueous ethanol solution, and the obtained mixture is hydrolyzed under acidic conditions, thereby obtaining hydrolyzed KH-560.

[0050] The aqueous dispersion liquid of the hydroxylated graphene oxide is mixed with the hydrolyzed KH-560, and coupling is performed under triethylamine conditions, thereby obtaining an aqueous dispersion liquid of modified graphene oxide.

[0051] The multilayer reticular bubble filler is immersed in the dispersion liquid of the modified graphene oxide to perform modification, thereby obtaining a hydroxylated graphene-coated porous reticular bubble filler.

[0052] The dispersion liquid of graphene oxide is mixed with polybutylene glycol under alkaline conditions to perform hydroxylation, thereby obtaining hydroxylated graphene oxide.

[0053] As an embodiment of the present application, the concentration of the dispersion liquid of graphene oxide is preferably 2 mg / mL. As an embodiment of the present application, the alkaline conditions are preferably obtained by adjusting the pH value of the graphene oxide dispersion liquid to 10 using a NaOH solution and then performing ultrasonic treatment for 30 min.

[0054] As an embodiment of the present application, the weight average molecular weight of the polybutylene glycol is preferably 1000-2000; the mass ratio of the graphene oxide to the polybutylene glycol is preferably 1-2:5-10, and can be 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 an embodiment of the present application, the hydroxylation is preferably performed under water bath oscillation conditions; the temperature of the hydroxylation is preferably 80-90°C, and the time is preferably 6 h. As an embodiment of the present application, after the hydroxylation, the hydroxylated graphene oxide is obtained by freeze-drying the hydroxylation reaction liquid.

[0055] The present application mixes gamma-glycidoxypropyltrimethoxysilane (KH-560) and an aqueous ethanol solution, and hydrolyzes the mixture under acidic conditions to obtain hydrolyzed KH-560.

[0056] As an embodiment of the present application, the aqueous ethanol solution has a volume concentration of 90%; the concentration of gamma-glycidoxypropyltrimethoxysilane in the mixture is preferably 2 wt%; and the acidic conditions are preferably provided by acetic acid, which has a mass concentration of 0.1-0.5%.

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

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

[0059] As an embodiment of the present application, the mixing of the aqueous dispersion of hydroxylated graphene oxide and the hydrolyzed KH-560 is preferably performed by ultrasonic treatment, and the ultrasonic treatment is preferably performed for 30 min. As an embodiment of the present application, the coupling is preferably performed under shaking, and the shaking is preferably performed at a temperature of 40-50℃ for 1-2 h.

[0060] After obtaining the dispersion of modified graphene, the present application modifies the multilayer mesh foam filler by immersing it in the aqueous dispersion of modified graphene oxide to obtain a hydroxylated graphene-coated porous mesh foam filler.

[0061] As an embodiment of the present application, the modification is preferably performed at a temperature of 80-90℃ for 3 h. As an embodiment of the present application, after the modification, the modified multilayer mesh foam filler is cleaned with ethanol and dried; and the drying is preferably performed at a temperature of 50-60℃.

[0062] As an embodiment of the present application, the depth of the filler layer is preferably 10-20 cm; and the filler in the filler layer is preferably gravel and / or crushed stone with a particle size of 5-10 mm. As an embodiment of the present application, the wetland plants are planted in the plant filler layer; and the wetland plants are preferably native wetland plants with developed root systems, and can be specifically Acorus gramineus.

[0063] As an embodiment of the present application, the water distribution holes of the perforated flower wall are located at the top of the settlement filler layer.

[0064] The artificial wetland system provided by the application comprises a drainage system.

[0065] As an embodiment of the application, the drainage system preferably comprises double drainage pipes, in particular, the drainage system preferably comprises a water level regulating drainage pipe and an electromagnetic valve controlled drainage pipe; the water level regulating drainage pipe is a drainage pipe provided with a rotary elbow; one end of the rotary elbow is located in the water collecting area, and the other end penetrates through the side wall of the pool body.

[0066] As an embodiment of the application, one end of the electromagnetic valve controlled drainage pipe is laid in the settlement filler layer, and the other end penetrates through the side wall of the artificial wetland pool body. As an embodiment of the application, the electromagnetic valve controlled drainage pipe is a regularly opened drainage pipe, and the regularly opening time is 2-4 times of the hydraulic retention time of the wetland, so as to realize rapid drainage of the wetland and promote the reoxygenation function of the wetland.

[0067] The application also provides a method for treating sewage by using the enhanced microorganism low-temperature denitrification tail water artificial wetland system.

[0068] After 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 artificial wetland pool body for purification, the purified water flows into the water collecting area through the perforated flower wall and is then discharged through the drainage system.

[0069] In the application, the tail water of the sewage plant enters the water distribution area and is preferably uniformly introduced into the wetland filler area through the bottom perforated flower wall.

[0070] In the application, when the tail water flows through the functional filler layer during the low-temperature period, the hydroxylated graphene coating porous net bubble filler can regulate the microbial community structure and abundance, activate the denitrification functional microorganisms, significantly improve the abundance of denitrification functional genes, fully utilize the available carbon source released by the slow-release biomass carbon source, promote the denitrification and nitrogen removal efficiency of the artificial wetland during the low-temperature period, and improve the removal rate of nitrate in the tail water. In combination with the tidal flow water flow operation mode, the problem of low denitrification efficiency of the artificial wetland during the low-temperature period is effectively solved, and the tail water artificial wetland during the low-temperature period can meet the discharge standard.

[0071] In order to further illustrate the application, the schemes of the application are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the protection scope of the application.

[0072] Example 1

[0073] Preparation of the hydroxylated graphene coating porous net bubble filler:

[0074] The graphene oxide (GO) dispersion solution (2 mg / mL) was adjusted to pH = 10 with 1 mol / L NaOH solution, ultrasonically treated for 30 min, then polytetramethylene glycol (molecular weight 2000) (GO:PTMG = 1:5) was added to the GO dispersion solution, oscillated in a water bath at 80℃ for 6 h, and freeze-dried to obtain hydroxylated graphene oxide;

[0075] KH-560 was added to a 90 vol.% aqueous ethanol solution, 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 oscillated for 60 min to obtain hydrolyzed KH-560;

[0076] The hydrolyzed KH-560 was added to the 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 oxide was 1:1), ultrasonically treated for 30 min, then triethylamine (the mass of triethylamine was 0.1% of the mixture) was added to the resulting mixture, and oscillated at 50℃ for 2 h to obtain an aqueous dispersion of modified graphene oxide;

[0077] The multi-layer mesh foam filler (made of polyurethane) was immersed in the above mixture, and kept at 90℃ for 3 h; then washed with ethanol for 3 times, and dried at 60℃ to obtain a hydroxylated graphene-coated porous mesh foam filler.

[0078] As shown in Figure 1 , the constructed wetland system comprises a constructed wetland tank, a wetland filler system, a wetland plant system, a water inlet system, and a drainage system. The wetland tank is 0.8 m x 0.4 m x 1.6 m in size, and comprises a settlement filler layer, a functional filler layer, and a planting filler layer from bottom to top. The settlement filler layer is composed of pebbles with a particle size of 20-30 mm and a depth of 20 cm. The functional filler layer is composed of hydroxylated graphene-coated porous mesh foam fillers with a particle size of 10-20 mm, gravel with a particle size of 10-20 mm, and biological ceramsite with a particle size of 10-20 mm, and the volume ratio of the three is 2:4:4, and the depth is 90 cm. The planting filler layer is composed of gravel with a particle size of 5-10 mm and a depth of 20 cm. The wetland plant is Acorus calamus.

[0079] The constructed wetland system was used to treat simulated wastewater plant effluent, the water temperature was 9.2-12.4℃, the hydraulic retention time was 36 h, and the average concentrations of COD and TN in the wetland influent were 48.69 mg / L and 16.54 mg / L, respectively. After the treatment by the constructed wetland system, the water temperature of the wetland effluent was 9.1-11.8℃, and the average concentrations of COD and TN in the wetland effluent were 21.87 mg / L and 5.25 mg / L, respectively.

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

[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 constructed wetland system for enhanced microbial low-temperature denitrification of wastewater, characterized in that, Includes inlet pipes, constructed wetland pools, and drainage systems; The artificial wetland pool is divided into a water distribution area, a wetland filler area, and a water collection area by a perforated flower wall; The wetland filler area is planted with wetland plants; the filler material in the wetland filler area includes hydroxylated graphene-coated porous mesh foam filler. The drainage system is located in the water collection area; the water distribution area is provided with a slow-release biomass carbon source. The preparation of the hydroxylated graphene-coated porous mesh filler includes the following steps: A dispersion of graphene oxide was mixed with polybutanediol under alkaline conditions and hydroxylated to obtain hydroxylated graphene oxide. Hydrolyzing γ-glycidoxypropyltrimethoxysilane yields hydrolyzed KH-560. Aqueous dispersions of hydroxylated graphene oxide were mixed with hydrolyzed KH-560 and triethylamine to obtain aqueous dispersions of modified graphene oxide. The porous mesh filler was immersed in an aqueous dispersion of the modified graphene oxide to obtain a hydroxylated graphene-coated porous mesh filler.

2. The constructed wetland system for enhanced microbial low-temperature denitrification of tailwater as described in claim 1, characterized in that, The effective depth of the wetland filler zone is 130~200cm; From bottom to top, the wetland filler zone includes a settling filler layer, a functional filler layer, and a planting filler layer.

3. The constructed wetland system for enhanced microbial low-temperature denitrification of tailwater as described in claim 2, characterized in that, The depth of the settling filler layer is 30~50cm; The filler in the settling filler layer is one or more of pebbles, gravel and crushed stone with a particle size of 20-30mm; The depth of the functional filler layer is 90~130cm; the filler in the functional filler layer is a hydroxylated graphene-coated porous mesh filler and an uncoated filler. The depth of the planting filler layer is 10-20cm; the filler in the planting filler layer is gravel and / or crushed stone with a particle size of 5-10mm.

4. The constructed wetland system for enhanced microbial low-temperature denitrification of tailwater as described in claim 3, characterized in that, The hydroxylated graphene-coated porous mesh filler is located in the 10-70cm region from bottom to top of the functional filler layer; The volume percentage of the hydroxylated graphene-coated porous mesh filler in the functional filler layer is 10-40%.

5. The constructed wetland system for enhanced microbial low-temperature denitrification of tailwater as described in claim 3, characterized in that, The uncoated filler includes one or more of rock debris, bio-ceramic particles, and zeolite; The rock fragments include gravel or crushed stone; the particle size of the uncoated filler is 20~30mm.

6. The constructed wetland system for enhanced microbial low-temperature denitrification of tailwater as described in claim 1, characterized in that, The water distribution holes of the perforated flower wall are located at the top of the settling filler layer.

7. The constructed wetland system for enhanced microbial low-temperature denitrification of tailwater as described in claim 1, characterized in that, The water inlet pipe is laid beneath the frozen soil layer.

8. A method for treating wastewater using the constructed wetland system for enhanced microbial low-temperature denitrification of tailwater as described in any one of claims 1 to 7, comprising the following steps: The wastewater from the sewage treatment plant is introduced into the water distribution area through the inlet pipe and mixed with the slow-release biomass carbon source. Then, it enters the wetland filler 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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