The Feasibility Research On The Treatment Project For Dagu Drainage River

Dagu drainage river course is one of the drainage river courses for the polluted water in the south of Tianjin, playing a crucial role in the draining of Tianjin. Built in 1958, the river course is 83.63 kilometers, and has never been treated since the reformation in 1965.As far as the current situation of the river course concerned, the cross section of it decreases, the mud under it badly accumulates, and the structure along it is damaged seriously with an inadequate scale. These often cause the overflow of the polluted water in the flood season, affecting the normal draining of the downtown area and the rural enterprises along the river. In addition, according the test report, the mud under Dagu Drainage River is full of heavy metal elements with the water and the bottom mud seriously polluted. The serious pollution has resulted in the reduction of the water's use value and the environmental deterioration in the area along the river course.With the total water demand of 81.316 million tons per year or approximately 450 thousand tons per day, Dagu Drainage River crosses three suburban districts– Xiqing, Jinnang and Tangdu, and is mainly used for agriculture along it. According to the draining plan and the future use function of Dagu drainage river in the fifteenth five-year development plan of Tianjin's public service, and considering the current draining situation of Dagu drainage river, after the comprehensive consideration and the overall analysis of its design water quantity, the treatment plan for Dagu drainage river was determined segment by segment, which includes the removal of the mud, the repair of the dyke, the protective laying, the disposal of the mud, the reformation of the structure along the river, the reconstruction of the pump station for Dagu drainage river, Ji Village drainage river and Pioneer drainage river. In this treatment project, the cutting– off of the pipelines for the polluted water is an important part in the treatment for the river course. Along each of the three Drainage Rivers - the upper reaches of Dagu Drainage River, Ji Village Drainage River and Shuanglin Drainage River are some draining pipelines, which are directly connected to Dagu River. These drainage outlets are from the pipelines for the polluted water in the nearby residential area and factories and enterprises about them. In order to guarantee that the river course will not be polluted by the untreated polluted water discharged into it after the treatment for the river course, it is very necessary to cut all the drainage outlets from the pipelines for the polluted water along the river course off it.The inverse trapezium cross section of the original river course is maintained in the design plan for the river course. Dagu River is the main drainage river to the south of Haihe River and the overall removal of the mud has never been conducted for some ten years, so a large quantity of mud will be dug out in this treatment. A well– arranged disposal of the deposit is an important part in the treatment for Dagu River.In accordance with the test report, 1,284,358 m3 mud meet the standard for agricultural use, which takes up 55.8% of the total mud quantity. Only the hygienic land filling is suitable for the deposit in such a large quantity. The land filling site is different from the ordinary drying site. In order to prevent the underground water and the surrounding environment from the secondary pollution by the mud, the inner liners will be used on the land filling site to avid the outflow of the percolate. The sealing treatment will be conducted on the land filling site after the land filling of the mud.The treatment of Dagu Drainage River is a systematic project with relatively long engineering period, so the reinforcement of the administrative work in the construction period is needed. As important as it is the administration and maintenance of the river course, which is a work demanding longer period of time.