Create near natural water plant, enjoy water purification park∣BEWG constructed wetland practice 2021-07-26
Wetland is the “kidney of the earth”, which is called the three ecosystems of the earth together with forests and oceans. As the "kidney of the city", constructed wetland plays an irreplaceable role in purifying water quality, storing rain and flood, protecting biodiversity, and building urban blue-green space. It is an important hub connecting social water cycle and natural water cycle, and also a microcosmic embodiment of China's ecological civilization construction.
BEWG has many years of exploration and experience in the practice of constructed wetland products and tail water wetland of sewage plant. A rich case is the successful practice of BEWG to help recycled water recycling through constructed wetland, accelerate the construction of beautiful countryside, and promote the establishment of new industrial towns. It also broadens the application scope of BEWG’s constructed wetland, and finally forms the BEWG constructed wetland solution with five characteristics.
Encyclopedia: what is wetland?
First, the definition of wetland is very broad. According to the definition of the International Convention on wetlands, A wetland refer to a marsh, wet plains, peatland or water areas, whether natural or constructed, permanent or temporary, with static or flowing, or fresh, brackish or salt water body, including water areas with a water depth of no more than 6 meters at low tide. Therefore, in a broad sense, constructed wetlands include not only wetland systems built to purify water quality, but also productive wetland systems such as paddy fields and fish ponds.
In a narrow sense, constructed wetlands are more focused on water purification function, and both ecological landscape value. According to the “Constructed Wetland Water Quality Purification technical Guide” issued by the Ministry of Ecological Environment this year, constructed wetlands, "Refers to batching of the low pollution water to the unique ecosystem constituted by filling material (including soil), aquatic plants, animals and microorganisms by simulating the structure and function of natural wetlands, through the synergistic effects of physical, chemical and biological to improve water quality engineering. Or use flood land, depressions and green land to improve the near natural system by optimizing water collection and distribution and other strengthening measures, so as to improve the water purification function and ecological quality ".
The Technical Outline of the 14th Five-Year Plan for Water Ecological Environment Protection in Key River Basins takes constructed wetlands as an important measure to improve the ecological environment of rivers and lakes. The opinions on promoting the sewage resource utilization and the opinions on the treatment of rural domestic sewage also take constructed wetlands as an important way for low-carbon sewage treatment and recycled water circulation.
It should be noted that as a natural purification system, constructed wetlands have faced problems such as large land occupation, insufficient effluent stability, and insufficient ecological landscape value in previous practice. Constructed wetlands technology needs to be further improved.
Five unique features -- originality manufacturing from BEWG
In recent years, combined with watershed water environment treatment, BEWG has built constructed wetlands in many places according to local conditions to purify the water quality of polluted water bodies such as sewage plant tail water, rural sewage, river and lake water, and based on long-term operation, it has continuously accumulated and optimized engineering parameters, gradually forming a full bandwidth, stable water quality, intensive, assembly and park five characteristics of BEWG constructed wetland solution. Next, let's learn about the practical achievements of BEWG constructed wetland by combining the typical cases of two sewage plants tail water wetlands.
Liaocheng has reached the standard class IV high load tail water wetland for 1600 consecutive days
Scientific design scheme
The construction of Shandong Liaocheng Qingquan River Wetland was started in 2015 and officially put into operation in December 2016. The combined process of horizontal subsurface flow + surface flow wetland is mainly used for the advanced purification of the tail water (class I A standard) of Guan County sewage treatment plant, and the effluent is discharged into Qingquan river. The project covers an area of about 15 hectares and has a treatment capacity of 80000 M³/d. The effluent reaches the quasi III- quasi IV level.
Among them, the horizontal subsurface flow wetland covers a total area of 80000m², with a design hydraulic load of 1.0 m³/(m²·D), which reaches the upper limit of the recommended value of Shandong landmark specifications. The total area of surface flow wetland is about 53000 m²，Design hydraulic load 1.51 m²/(m²·D), higher than the conventional value. Qingquan River Wetland needs to meet the strict requirements of third-party online monitoring and real-time assessment while operating at high load, which puts forward a very strict test for the engineering design, construction and subsequent operation and maintenance of the wetland.
Excellent effluent index
According to the daily monitoring data of COD at the inflow and outflow and ammonia nitrogen at the inflow and outflow for a total of 55 months and more than 1600 days from December 2016 to July 2021, the effluent of the tail water wetland can stably reach the quasi class IV design goal (increased by 1-2 grades), the average removal rates of COD and ammonia nitrogen can reach 39.24% and 76.30% respectively, and the effluent compliance rate is 100%, and the wetland effluent can still meet the standard in winter.
Ideal ecological effect
The construction and operation of Qingquan River tail water wetland not only greatly improved the water quality of Qingquan River, but also created a smart wetland ecological landscape for Guan County. The wetland plants such as cattails, Acorus calamus, barracuda grass, shallots, iris flavescens, Canna, Chelidonium, lotus, etc. bloom competitively. The main indicators of water quality reach class IV, and more than 80% of the days reach class surface III. It has become an indispensable "Instagram-Worthy Location" for citizens' life.
Constructed wetland water purification landscape park with stable operation in Urumqi Alpine Region
Innovative design according to local conditions
ShiQiHu wetland is the pilot project of Urumqi “water into the city" project - river lake water system connection project, which was officially put into operation in 2019. The project covers an area of about 75 hectares and has a treatment capacity of 80000 m³/d. The effluent meets the quasi class IV standard, and the treatment processes such as plunge forebay, horizontal subsurface flow, wetland and ecological pond are adopted.
The terrain of the project is high in the southeast and low in the northwest, with three hills in the middle and a total height difference of about 30 meters. The overall topographic characteristics pose a certain challenge to the water distribution scheme design of the wetland. In the first version of the plan, the design unit proposed to completely level the site, and this plan will cause serious damage to the natural ecological base of the site.
In order to comply with the regional topographic characteristics and make full use of the rich topographic height difference changes, the design of the ShiQiHu wetland is different from the flat site and regular unit arrangement used in the traditional layout. The multi-level water distribution system is used according to local conditions to realize the uniform water distribution on the slope. At the same time, the curvilinear unit design is carried out to integrate the subsurface flow wetland unit into the site texture, realize the superposition of the site ecological wetland texture, mountain grass slope texture and Yulin meadow texture, and create a multi-level landscape and space.
Tackling challenges to forge fine products
Urumqi is covered with ice and snow in winter. The average temperature is -15.2 ℃, the average freezing line is -1.4m, and the snow thickness is as high as 30cm. Therefore, in winter, the urban water system does not need to be replenished, and ShiQiHu wetlands do not run. The severe cold climate and the working condition of discontinuous water supply not only pose a challenge to the insulation and antifreeze of wetland pipelines, but also pose difficulties to the survival of wetland plants. Before large-scale construction, BEWG set up a construction method test area to test different insulation methods, winter water level regulation, plant species and plant planting methods, and finally ensured the normal operation of ShiQiHu wetland in winter and the natural growth of perennial wetland plants.
ShiQiHu wetland mainly serves as an ecological landscape function in the near future, making ecological use of the water of Hongyanchi reservoir, and in the long term, purifying and regenerating the tail water of urban sewage treatment plants, so as to protect the ecological base flow of water system in water scarce cities. It is a representative of large-scale constructed wetlands in the northwest alpine region.
For a long time, the constructed wetlands created by BEWG have been like pearls on the urban and rural water environment governance map. Some have reduced the pollution load from the source, and some have completed the "last mile" of improving the ecological health of rivers and lakes, realizing the recycling of regional recycled water, building a good ecosystem, and creating a new style of beautiful urban and rural landscapes, It provides a good place for urban and rural residents to relax and exercise.
During the 14th Five Year-Plan period, China has put forward higher requirements for the comprehensive benefits of green infrastructure. Relying on the "Two Mountains" theory, BEWG will continue to improve the product power of constructed wetlands, create near natural plants, enjoy water purification parks, and continue to contribute professional power to promote the construction of ecological civilization.
Accompany with the wetlands in summer
Start a romantic journey with nature
More beautiful wetlands created by BEWG
Please look forward to the next episode......
