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“Green pearl” decorates the beautiful countryside --BEWG rural sewage constructed wetland practice 2021-08-17
In the first two series of articles, we introduced the cases of constructed wetlands with a treatment scale of more than 10000 tons. In this issue, we will introduce the case of "mini" wetlands to provide customers with green solutions suitable for rural domestic sewage treatment through collecting parts into a flat.
Rural domestic sewage treatment is not only an important part of improving rural living environment, but also an important step for implementing the Rural Revitalization Strategy. Rural sewage in China has the characteristics of "scattered distribution, small water volume and large fluctuation", which leads to three difficulties in rural sewage treatment: "high cost per ton of water, difficult on duty management and difficult stable discharge". As a natural sewage treatment technology with low energy and chemicals consumption and unattended daily, constructed wetland can well cope with the two difficulties of high cost per ton of water and difficult on-duty management, and integrate into the rural ecological landscape to resolve the Not in my back yard. However, due to the uneven construction and management level in the early stage of technological development, the stability of its effluent quality has been controversial.
BEWG combines the traditional sewage treatment operation experience with the ecological engineering theory to form a wetland solution for rural sewage treatment, presenting all the characteristics of stable water quality, intensification and parkization, achieving the stable compliance of hundreds of constructed wetland sites, and contributing to the writing of a new chapter of beautiful countryside. Among them, the two rural projects of BEWG in Heshan, Guangdong and Daxing, Beijing not only have their own characteristics, and the treatment mode is also quite representative.
"Combination of Gray-Green" treatment mode integrated into rural public space
"All green" treatment, long-term compliance
Heshan rural sewage treatment phase I Project
"Combination of Gray-Green" rural small wetland site group
Management of urban and rural integration to enhance residents' sense of fulfillment
Since 2016, BEWG has been entrusted by Heshan Water Bureau to carry out sewage treatment, water environment treatment and rural sewage treatment in Heshan City. Among them, Heshan rural sewage treatment phase I project covers 155 villages in 10 towns in the city, with 98 new sites, and the treatment scale of a single site is 5~80 M³/d. Total scale: 3040m³/d. It serves 48000 permanent residents.
In the process of improving the water environment of Heshan Water Affairs Bureau, Heshan Water Bureau and BEWG pay great attention to the principle of urban-rural integration of environmental protection, and comprehensively enhance the sense of fulfillment and happiness of urban and rural residents. The rural sewage treatment project in Heshan City is carried out synchronously with the treatment of the urban section of the Shaping River Basin in Heshan, which can effectively reduce the pollution load entering the Shaping river. More importantly, it protects the living environment of hundreds of villages and makes the streams and ponds behind the villagers' houses clear.
Combined with the characteristics of dense rural population in Guangdong, the small area of land for public facilities in the village, and residents like to gather in public areas, the sewage treatment site adopts the "Combination of Gray-Green" treatment mode. The process flow is "regulated hydrolysis + contact oxidation + constructed wetland". Through the reasonable configuration of plant and site space, as well as the optimization and fine configuration of wetland plants, the treatment site is compact and has high appearance value, ensuring the quality of public area.
The constructed wetland has the functions of deep purification, improving the stability of water discharge standards and optimize the site landscape. Wetland covers an area of 0.5~2m² per ton of water，adopts medium and high load horizontal subsurface flow wetland process. With the help of wetlands, the effluent quality of all sites of the project reaches 100% of the secondary standard of the Guangdong landmark "Rural domestic sewage treatment discharge standard" (db44/2208-2019), in which the indicators of COD and ammonia nitrogen can reach GB18918-2002 level A standard.
"Complementation of Gray-Green" flexible operation to ensure low-carbon operation of the system
"Complementation of Gray-Green" flexible operation to ensure low-carbon operation of the system
The "Combination of Gray-Green" process mode improves the flexibility of system operation, so as to realize the maximum low-carbon operation of the project. The amount of rural sewage production is affected by the flow of people, and there is often a seasonal low water volume. At this time, the aeration and pharmaceutical dosage of the site biochemical section can be appropriately reduced, so as to give more play to the purification role of the constructed wetland and reduce the carbon footprint of sewage treatment.
Taking Taiping Village site as an example, the design scale of the site is 25 M³/d. However, in the non holiday dry season, the average inflow is only 7.9 M³/d. For this reason, the operation team of BEWG developed a corresponding low-energy consumption operation strategy, water from the contact oxidation tank treatment, after processed by constructed wetland, the further removal rate of various indicators reaches more than 50%, and the ammonia nitrogen removal rate was 91%. Finally, all the indicators of the effluent reached the first-class A standard, of which the main indicators reached class IV, while the average water and electricity consumption per ton was less than 0.2 kilowatt, achieving a high standard discharge of rural sewage treatment under low-carbon operation.
Now, the rural sewage treatment in Heshan has been advanced to the third phase, and the water quality of many ponds and streams in the Shaping River Basin has been significantly improved. The revival of rural water ecological environment has driven the development of local water culture to be more prosperous. The constructed wetland with flowers blooming everywhere has also become a new landmark of rural living environment in Heshan.
Taking Taiping Village site as an example, the design scale of the site is 25 M³/d. However, in the non holiday dry season, the average inflow is only 7.9 M³/d. For this reason, the operation team of BEWG developed a corresponding low-energy consumption operation strategy, water from the contact oxidation tank treatment, after processed by constructed wetland, the further removal rate of various indicators reaches more than 50%, and the ammonia nitrogen removal rate was 91%. Finally, all the indicators of the effluent reached the first-class A standard, of which the main indicators reached class IV, while the average water and electricity consumption per ton was less than 0.2 kilowatt, achieving a high standard discharge of rural sewage treatment under low-carbon operation.
Now, the rural sewage treatment in Heshan has been advanced to the third phase, and the water quality of many ponds and streams in the Shaping River Basin has been significantly improved. The revival of rural water ecological environment has driven the development of local water culture to be more prosperous. The constructed wetland with flowers blooming everywhere has also become a new landmark of rural living environment in Heshan.
Rural sewage treatment project in former Anding village, Daxing District, Beijing
Rural domestic sewage wetland takes the lead
Different from Heshan' "Combination o Daxing former Anding village rural sewage treatment site adopts the "All green" treatment mode of constructed wetland. Based on the topographic conditions of the original ponds in the village, BEWG and its BHZQ adopted the treatment process of "pre-treatment + vertical subsurface flow wetland + surface flow wetland", with a design treatment scale of 40m³/d. Among them, pre-treatment unit and vertical subsurface flow wetland unit are mainly used for purification, covering an area of 600m²。
Sufficient residence time, reasonable process design and scientific operation mechanism jointly ensure the year-round non blocking and stable operation of this "All green" treatment site under the climate of North China. As the main treatment process of the site, the constructed wetland has been running steadily so far, and the average removal rates of COD, ammonia nitrogen and total phosphorus have reached 83%, 90% and 88% respectively. The project effluent implements Beijing Rural Sewage landmark standard IIA. In the presence of periodic high concentration impact of the influent, the daily compliance rate is 100%, and the daily compliance rate reaches more than 90% with reference to the national standard IA water quality standard.
No aeration, no dosing, low carbon benchmark
As the main process, the constructed wetland does not need aeration and dosing, and the daily operation only has one lifting pump station electricity equipment. In addition, the site is unattended and requires only low-frequency inspection and maintenance. This natural treatment mode not only saves costs, but also makes the site a real low-carbon sewage treatment site.
The lush reeds and yellow flag in the wetland, as well as the wet wild flowers with a wide variety of colors, form a delightful contrast with surrounding orchard scenery. If it were not for the tips of the popular science exhibition board, people would not notice the processing site when passing by. It is this wetland that silently guards the living environment of former Anding village and the environmental quality of surrounding water bodies.
Thousands of villages, thousands of households, thousands of shares of water, a wide range of and fluctuations; The constructed wetland is the main beam, with clear water and beautiful scenery, benefiting the people's livelihood. As a sewage treatment technology with low energy consumption, low cost, easy maintenance and high efficiency, constructed wetland provides a green option with low carbon footprint and high ecological value for the comprehensive treatment of rural living environment. Therefore, it has been advocated and promoted by the guiding opinions on rural domestic sewage treatment and other documents.
The advantages of BEWG rural sewage constructed wetland products, such as stable water quality, intensification and parks, have been tested in practice throughout the country. In the future, BEWG will continue to explore, optimize and practice rural sewage treatment, and provide customers with more high-quality rural sewage constructed wetland solutions. "Green pearl" decorates beautiful countryside -- BEWG rural sewage constructed wetland practice.
Thousands of villages, thousands of households, thousands of shares of water, a wide range of and fluctuations; The constructed wetland is the main beam, with clear water and beautiful scenery, benefiting the people's livelihood. As a sewage treatment technology with low energy consumption, low cost, easy maintenance and high efficiency, constructed wetland provides a green option with low carbon footprint and high ecological value for the comprehensive treatment of rural living environment. Therefore, it has been advocated and promoted by the guiding opinions on rural domestic sewage treatment and other documents.
The advantages of BEWG rural sewage constructed wetland products, such as stable water quality, intensification and parks, have been tested in practice throughout the country. In the future, BEWG will continue to explore, optimize and practice rural sewage treatment, and provide customers with more high-quality rural sewage constructed wetland solutions. "Green pearl" decorates beautiful countryside -- BEWG rural sewage constructed wetland practice.
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