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This project is located in Dongguan City, Guangdong Province, Dasha River, 6.3 km long, in the new urban center of Humen Town, Dongguan City, which is a tributary of the Eastern Diversion Canal. The harnessing section starts at Humen fairy tale kindergarten and ends at Changde Road Bridge. The river is 1.7 kilometers long and the water area is about 4200 square meters. The average width of the river is 23 meters, the average velocity is 0.1 meters, and the depth of the inrush is uneven, and the depth is between 0.1 and 0.4 meters. The main project content is to restore the water ecology of the river in situ, and to carry out three-year operation and maintenance services at the same time. Preliminary objectives: to eliminate black and odor, the ultimate goal: to achieve the main surface water quality standards of V-type water.

Short-term objectives

In order to eliminate the black odor, the water body indexes of monitoring section reached the following standards (transparency > 25cm, dissolved oxygen > 2mg/L, redox potential > 50mV, ammonia nitrogen < 8mg/L).

Long-term objectives

At the same time, the black odor can be eliminated and the V-type water in the surface water environmental quality standard (GB3838-2002) can be reached. Dissolved oxygen > 2 mg/L, ammonia nitrogen < 2 mg/L, total phosphorus < 0.4 mg/L, chemical oxygen demand (CODcr) < 40 mg/L.

Current situation of water quality

（1）Existing problems：

There are a large number of residential and industrial districts around the upper reaches of the harnessing section. When the sewage in this area is not completely intercepted, it enters the river, resulting in serious siltation of the river bed in the current harnessing section. Mud is rich in a large number of organic matter, withered branches, leaves, dead weeds, dormant algae, garbage and other debris, and has been anaerobic. The slope of the harnessing reach is small, the upstream recharge flow is not large, the flow of water body is slow, the ability of oxygen self-purification is insufficient, and it is easy to form black odor. There are a small number of incomplete sewage interception rainwater outlets along the coast, and the drainage is not large, but the water quality and sensory quality are poor, which has an impact on the recovery of water quality control process.

（2）River pollution：

Regulation of Upper Reach Water

Harnessing River Bed Siltation

Imperfect Sewage Interception of Rainwater Gate in Harnessing Reaches