CN106830343A - The method that the unbalance tail water wetland nitrogen removal rate of carbon nitrogen is improved using water plant - Google Patents

Abstract

The present invention is a method for improving the total nitrogen removal rate of carbon-nitrogen unbalanced tail water wetland by utilizing aquatic plants, constructing a composite treatment system, including four subsystems of stable pond-surface flow wetland-ecological aqueduct-horizontal subsurface flow wetland, each subsystem The process is sequentially connected in series. Advantages: 1) Reduce the competition between different species in the aquatic plant community, improve the stability of the aquatic plant community, and avoid the secondary pollution caused by the centralized decomposition of aquatic plant residues; 2) Reduce the cost of talents, and the decomposed organic matter can provide wetland denitrification Carbon source, improve nitrogen removal rate; 3) Alternate anaerobic and aerobic environments in different subsystems and different regions within the subsystem, balance nitrification and denitrification, and increase total nitrogen removal rate; 4) Reduce wetland purification projects The ubiquitous lack of purification capacity in winter alleviates the lack of carbon sources in summer in tailwater wetlands 5) The purpose of providing efficient, sustainable and stable carbon sources is achieved.

Description

The method of using aquatic plants to improve the removal rate of total nitrogen in tail water wetland with carbon and nitrogen imbalance

technical field

The invention relates to a method for improving the total nitrogen removal rate of carbon-nitrogen unbalanced tail water wetlands by using aquatic plants, and belongs to the technical field of advanced treatment of tail water structure wetlands of sewage treatment plants.

Background technique

For nitrogen, removal mechanisms in wetlands include volatilization, ammonification, nitrification/denitrification, plant uptake, and substrate adsorption. Many studies have shown that the main nitrogen removal mechanism in wetlands is microbial nitrification/denitrification, and the amount of nitrogen removal by nitrification/denitrification accounts for more than 70% of the total nitrogen removal. Sewage treatment plants often use the A/O process, which consumes a large amount of COD, especially BOD, which causes a serious imbalance in the carbon-nitrogen ratio of the tail water, resulting in insufficient carbon sources in the denitrification process, inhibiting denitrifying microorganisms, and reducing nitrogen removal efficiency. In addition, similar to general wetlands, tailwater wetlands are plagued by large seasonal fluctuations in purification capacity and insufficient purification capacity in winter, and cannot meet the purification requirements of tail water from sewage treatment plants with relatively balanced seasonal water output.

Aiming at the low nitrogen removal efficiency of carbon and nitrogen imbalance tail water wetlands, various solutions have been developed at home and abroad. However, these methods still have obvious deficiencies in the actual application process, and the method of adding high C/N raw sewage is reasonable. It is difficult to control the feeding ratio, it is easy to reduce the quality of effluent water, and the effect is limited by the insufficient content of low-molecular organic matter in raw sewage; the method of adding low-molecular carbohydrates has disadvantages such as high operating costs and low effective utilization of carbon sources; while the method of adding plant straw At present, it is mainly in the research and development stage of the technology, and there are still disputes about the dosing method, dosing amount, dosing timing, etc., and it is difficult to meet the requirements of large-scale applications.

Reed, wild rice, calamus, Zailihua, etc. are the most commonly used aquatic plant species in constructed wetland ecological engineering; because the vigorous growth period of these aquatic plants overlaps almost completely with the vigorous activity period of denitrifying bacteria, it is difficult to select aquatic plants in The period of high demand for microbial carbon sources (spring and summer) provides sufficient carbon sources; the types of aquatic plants currently selected and their configurations tend to exacerbate seasonal fluctuations in wetland purification capacity.

Contents of the invention

The invention proposes a method for improving the total nitrogen removal rate of carbon-nitrogen unbalanced tailwater wetlands by utilizing aquatic plants, and aims to effectively solve the problem of insufficient nitrogen removal efficiency in carbon-nitrogen unbalanced tailwater wetlands existing in the prior art.

The technical solution of the present invention: a method of using aquatic plants to improve the total nitrogen removal rate of carbon and nitrogen imbalance tail water wetlands, and construct a composite treatment system, which includes stabilization ponds - surface flow wetlands - ecological aqueducts - —Four subsystems of the horizontal subsurface flow wetland, and each subsystem is connected in sequence through each process;

Each of the processes described is to plant a large number of aquatic plants. The area ratio of cold-season and warm-season aquatic plants is 2:1. The aquatic plants are not harvested throughout the year. The organic matter secreted by the roots of the aquatic plants and the decomposition of residues are used to gradually improve the water quality. The carbon and nitrogen imbalance can further improve the nitrogen removal rate, and due to the configuration of cool-season and warm-season aquatic plants, secondary pollution caused by the decomposition of aquatic plants can be avoided.

Advantages of the present invention:

1) Interplanting between cool-season and warm-season types can not only reduce the competition among different species in the aquatic plant community, improve the stability of the aquatic plant community, but also avoid the centralized decomposition of aquatic plant residues and the formation of secondary pollution;

2) The aquatic plants in this treatment system are not harvested throughout the year, which can reduce the cost of labor, and at the same time, the decomposed organic matter can provide carbon sources for wetland denitrification, which can increase the nitrogen removal rate while reducing labor costs;

3) The treatment system includes stabilization ponds, ecological aqueducts, surface flow wetlands, and horizontal subsurface flow wetland composite treatment systems. Due to the differences in water depth, water disturbance degree, and aquatic plant types in different systems, different subsystems and subsystems Anaerobic and aerobic environments appear alternately in different regions, balancing nitrification and denitrification, and improving the removal rate of total nitrogen;

4) The present invention puts more emphasis on the planting of cool-season aquatic plants, which not only helps to alleviate the common problem of insufficient purification capacity in winter in wetland purification projects, but also helps to alleviate the acute problem of carbon source shortage in tailwater wetlands in summer.

Description of drawings

Accompanying drawing 1 is the schematic diagram of embodiment of the present invention.

In the attached picture It is a floating bed plant, are floating plants, are emergent plants (cool-season), It is an emergent plant (warm season type), are submerged plants (cool-season type), It is a submerged plant (warm season type).

detailed description

A method of using aquatic plants to improve the total nitrogen removal rate of carbon-nitrogen unbalanced tail water, constructing a composite treatment system in series of stable pond-surface flow wetland-ecological aqueduct-horizontal subsurface flow wetland technology, through the absorption of aquatic plants, Microbial nitrification/denitrification, physical sedimentation and natural volatilization can gradually remove nitrate nitrogen and ammonia nitrogen from the water body. The core lies in the large number of aquatic plants planted in each process. The ratio of cold-season and warm-season aquatic plants is 2 : 1. Aquatic plants are not harvested throughout the year. Through the secretion of organic matter from the roots of aquatic plants and the decomposition of residues, the carbon and nitrogen imbalance in the water body can be gradually improved, and the nitrogen removal rate can be further improved. configuration to avoid secondary pollution caused by the decomposition of aquatic plants.

The stabilization pond—surface flow wetland—ecological aqueduct—horizontal subsurface flow wetland process is connected in sequence; the depth of the stabilization pond is 3.0-4.0 m, the deepest ecological aqueduct is no more than 1.5 m, and the depth of the surface flow wetland is 0.3-1.5 m; (Stable pond + ecological aqueduct + surface flow wetland) and horizontal subsurface flow wetland area ratio > 5:1, hydraulic retention time 2-4 days.

The composite treatment system includes a large-area aquatic plant community, the average coverage of aquatic plants is not less than 50%, and the carbon-nitrogen ratio of the water body is gradually increased through the decomposition of organic matter secreted by aquatic plant roots, litter and dead residues, Improve nitrogen removal rate.

The aquatic flora is interplanted with cool-season and warm-season plants, and the total area ratio is 2:1. Specific configuration of suitable aquatic plant communities: Emergent plants in the shallow water area on the bank of the stable pond are mainly reeds, reeds, cattails and aquatic iris; floating leaf plants are mainly water hyacinth; floating bed plants are mainly cool-season aquatic Celery is dominant, and the overall coverage of plants is greater than 20%. The aquatic plant community of the ecological aqueduct includes submerged plants and emergent plants. Bamboo, cattails and aquatic iris are the main species, and the coverage of aquatic plants on the water surface is 30-50%; aquatic plants in surface flow wetlands include reeds, reeds, cattails and aquatic iris; aquatic plant communities in horizontal subsurface flow wetlands are dominated by reeds and aquatic iris host.

The aquatic plants are not harvested throughout the year, and the secondary pollution caused by the simultaneous decomposition of a large number of plant residues is avoided through the configuration of cool-season and warm-season aquatic plants.

The horizontal subsurface flow wetland filler is gravel with a particle size of 3.0-5.0cm and a depth of 1.2-1.5m; the second upper layer is a tile sheet with a diameter of 1.0-2.0cm and a depth of 10.0cm; the uppermost layer is a coarse sand layer with a maximum particle size of 2.0mm, depth 5.0cm.

The surface flow wetland adopts a furrow structure, the furrow is 80.0-100.0m long, 10.0m wide, 0.3-0.5m deep, 7.0-8.0m wide, and 1.5-2.0m deep.

The slope coefficient of the ecological water delivery channel is 1-2, the bottom width is 1.0-3.0 m, the length is adjusted to local conditions, and the total length should be greater than 2.0 km.

Below in conjunction with accompanying drawing, the present invention will be further described,

The experimental treatment object is the tail water of a certain urban sewage treatment plant. The annual average concentration of main pollutants is: COD = 113.4mg/L, total nitrogen = 50.6mg/L, total phosphorus = 2.16mg/L, ammonia nitrogen = 12.6mg/L , BOD/TN=1.88.

The designed aeration pond is 40,000m ² , the surface flow wetland is 150,000m ² , the total length of the ecological aqueduct is 2.5km, the water surface is 10,000m ² , and the subsurface flow wetland is 40,000m ² . In the aeration pond, there are 400 m ² reeds, 300 m ² mosaic reeds, 500 m ² oriental cattails, 700 m ² aquatic iris, and 5000 m ² cress floating beds.

Tail water is removed through absorption by aquatic plants, microbial nitrification-denitrification, physical settlement and natural volatilization; at the same time, through the secretion of plant roots, the decomposition of litter and dead residues, the carbon and nitrogen imbalance in the target water body is gradually eliminated. Improvement, from 1.88 (BOD: TN) before entering the system to >2.5 (BOD: TN) after flowing out of the system, and the TN removal rate of the system is > 85%.

The specific arrangement of aquatic plant communities: the emergent plants in the shallow water area of the stable pond bank are reed ( P.australis (Cav.) Trin. ex Steud.), mosaic reed bamboo ( A.donax var. versicolor ), cattail ( T. orientalis Presl.) and aquatic iris ( I. pseudacorus ), water hyacinth ( E. crassipes ) was the main floating leaf plant, and cool-season cress ( O.javanica (B.)DC.) was the main floating bed plant. Mainly, the overall coverage of plants is greater than 20%; the aquatic plant community of the ecological aqueduct includes submerged plants and emergent plants, among which, submerged plants include P.cripus and M. spicatum , The water plants are mainly reed ( P.australis (Cav.) Trin.ex Steud.), mosaic reed ( A.donax var. versicolor ), cattail ( T.orientalis Presl.) and aquatic iris ( I. pseudacorus ) , the water surface aquatic plant coverage is between 30-50%; the surface wetland aquatic plants include reed ( P.australis (Cav.) Trin. ex Steud.), mosaic reed bamboo ( A.donax var. versicolor ), cattail ( T.orientalis Presl.) and aquatic iris ( I. pseudacorus ); the aquatic plant community in horizontal subsurface wetlands is dominated by reed ( P.australis (Cav.) Trin. ex Steud.) and aquatic iris ( I. pseudacorus ).

Claims (9)

1. A method for improving the total nitrogen removal rate of carbon-nitrogen imbalance tailwater wetlands by using aquatic plants, characterized in that a composite treatment system is constructed, which includes stabilization ponds—surface flow wetlands—ecological aqueducts— There are four subsystems in the horizontal subsurface flow wetland, and each subsystem is connected in series through each process; Each of the processes described is to plant a large number of aquatic plants. The area ratio of cold-season and warm-season aquatic plants is 2:1. The aquatic plants are not harvested throughout the year. The organic matter secreted by the roots of the aquatic plants and the decomposition of residues are used to gradually improve the water quality. The carbon and nitrogen imbalance can further improve the nitrogen removal rate, and due to the configuration of cool-season and warm-season aquatic plants, secondary pollution caused by the decomposition of aquatic plants can be avoided. 2. A method of utilizing aquatic plants to improve the total nitrogen removal rate of carbon-nitrogen imbalance tailwater wetland according to claim 1, characterized in that, the water depth of the stable pond is 3.0-4.0 m, and the ecological aqueduct is no more than 1.5 m , the water depth of the surface flow wetland is 0.3-1.5 m. 3. a kind of method utilizing aquatic plants to improve carbon-nitrogen imbalance tail water wetland total nitrogen removal rate according to claim 1, it is characterized in that, described each subsystem constructs suitable aquatic plant communities, and the average coverage of aquatic plants is less than If it is lower than 50%, through the decomposition of organic matter secreted by aquatic plant roots, litter and dead residues, the carbon-nitrogen ratio of the water body will be gradually increased, and the nitrogen removal rate will be increased. 4. A method of utilizing aquatic plants to improve the total nitrogen removal rate of carbon-nitrogen imbalance tailwater wetlands according to claim 1, wherein said horizontal underflow wetland filler is gravel, with a particle size of 3.0-5.0cm and a depth of 1.2-1.5m, the next upper layer is a tile sheet, with a diameter of 1.0-2.0cm and a depth of 10.0 cm; the uppermost layer is a coarse sand layer with a maximum particle size of 2.0mm and a depth of 5.0cm. 5. A method of utilizing aquatic plants to improve the total nitrogen removal rate of carbon-nitrogen imbalance tail water wetland according to claim 1, characterized in that, the surface flow wetland adopts a furrow structure, and the furrow length is 80.0-100.0m, The width of the ridge is 10.0m, the water depth of the ridge is 0.3-0.5m, the width of the ridge is 7.0-8.0m, and the depth is 1.5-2.0m. 6. A method of utilizing aquatic plants to improve the total nitrogen removal rate of carbon-nitrogen imbalance tailwater wetland according to claim 1, characterized in that, the slope coefficient of the ecological water delivery channel is 1-2, and the bottom width is 1.0-3.0 m, the length should be adjusted according to local conditions, and the total length should be greater than 2.0 km. 7. A method of using aquatic plants to increase the total nitrogen removal rate of carbon-nitrogen imbalance tailwater wetlands according to claim 2, characterized in that, the area of the stable pond + ecological aqueduct + surface flow wetland and horizontal subsurface flow wetland Ratio>5:1, hydraulic retention time 2-4 days. 8. a kind of method utilizing aquatic plants to improve the total nitrogen removal rate of carbon-nitrogen imbalance tail water wetlands according to claim 3, is characterized in that, described suitable aquatic plant communities, its cool-season type and warm-season type aquatic plants The implementation of interplanting, the total area ratio of 2:1. 9. A method of utilizing aquatic plants to improve the total nitrogen removal rate of carbon-nitrogen imbalance tailwater wetlands according to claim 8, characterized in that, the specific configuration of the suitable aquatic plant communities: stabilizing pond banks in shallow water areas The water plants are mainly reeds, mosaic reeds, cattails and aquatic iris, the floating leaf plants are mainly water hyacinth, the floating bed plants are mainly cool-season cress, and the overall coverage of plants is greater than 20%. The plant community includes submerged plants and emergent plants. Among them, the submerged plants include Aphrodisiac spica and P. spicaculata, and the emergent plants are mainly reeds, reeds, cattails and aquatic iris. The coverage of aquatic plants on the water surface is 30 -50%; Aquatic plants in surface flow wetlands include reeds, Phragmites mosaicus, cattails and aquatic iris; aquatic plant communities in horizontal subsurface flow wetlands are dominated by reeds and aquatic iris.