Yitong River is the mother river of Changchun City. It originates from the northern foot of Qingding mountain in hadaling mountain range in Yitong County, Jilin Province. It flows into the second Songhua River about 20km after it joins with Yinma River 5km under the Baoshan bridge in Baoshan Town, Nong'an county.

The natural length of Yitong River in Changchun City is about 47.14km, and the middle section is about 15.88km (from sihuazha to nanraocheng). The average width of the river is 140m, and the narrowest part is 110m. The average gradient of the middle section is about 0.5 ‰, the average water depth is about 2.5m, and the total water capacity is about 6.3 million m3. The circulating contact oxidation project on the upstream side of Sihua bridge is located in the downstream of the middle section of Yitong River, in the flood land to the east of Diding Road, adjacent to Sihua bridge in the north and railway bridge in the south, covering an area of 2.4ha, which is one of the important guarantee measures for the water section in the middle section of Yitong River to reach the standard.

1. Water quality characteristics and target analysis
Water source: the main river of Yitong River;
Treatment scale: 26880m 3 / D;

Water quality objective: the effluent from the side circulating contact oxidation project meets the class V standard for surface water, and the main indicators include CODCr, ammonia nitrogen and TP.

2. Process flow

Biological contact oxidation process is adopted in the upstream side circulating contact oxidation project of Sihua bridge.

3. Overall plan

The circulating contact oxidation project on the upstream side of Sihua bridge mainly uses the existing auxiliary river channel and beach pool to design the water inlet and outlet system to transport the river water of Yitong River to the bubble pond for water purification. After purification, the water body flows back to the Yitong River to achieve the purpose of water purification. The treatment measures mainly include artificial aquatic grass treatment unit and floating wetland unit, constructing three-dimensional microbial purification system, nano aeration system, gravel filtration system, aquatic animal and plant ecological restoration system, and integrating water treatment facilities with landscape nodes to achieve water treatment objectives, at the same time, improve the regional ecological landscape and beautify the environment.


4. Node design
1) Qingyu diequan (water inlet)
Qingyu butterfly spring is the water inlet of the purification pond. The landscape treatment method is adopted to combine the water inlet with the falling water, and at the same time, it plays the function of natural aeration. The pinnate Island planting pool is used to decorate the plant landscape to form the landscape node of Qingyu butterfly spring.
Green leisure Pavilion -- connect with the shore site through the steps and footpaths, step up and step into the scenery Pavilion in the pond. Lean on the fence, have a leisurely view, and grow with water and grass. It becomes a landscape and a beautiful viewing place, and forms the landscape node of the green leisure Pavilion in seeing and being watched.

2) Cuidao Fuyao (floating wetland unit)
In terms of form, design elements are extracted from the wings of flying birds. After abstract evolution, the layout form of water landscape island is formed. Through the occlusion and interleaving of landscape Island, the requirements of water treatment process can be met, and the landscape form problems of ecological floating island can be solved. The water model, bird's paradise, plump wings and whirlwind wings dance, which means that the ROC can spread its wings, soar and flourish.

3) Jade Bird playing with wild rice (floating wetland unit)
Jade birds play with wild rice. The ecological floating island is covered with green plants to purify the water quality. Combined with exquisite water bird sculpture pieces, white jade bird landscape sculpture pieces are interspersed among the ten thousand green trees, which enlivens the landscape atmosphere and adds landscape interest. Standing on the existing landscape tower, you can overlook the whole picture of the purification pond, and enjoy the beautiful scenery of the opposite Yitong River, forming a landscape node of jade bird playing with Zizania in the purification pond.


5. Conclusion
The circulating contact oxidation project on the upstream side of Sihua bridge is one of the important guarantee measures for ecological treatment of Yitong River. The landscape method is used in the design project to show the water treatment facilities, purify the water quality, improve the landscape, and realize the integration of ecological landscape and water quality improvement.