Water Quality Rehabilitation of the Tiankeng Drainage Canal

The water quality rehabilitation scheme of the Tiankeng Drainage Canal in Hengli Town, Dongguan, Guangdong, China was proposed by low impact development concept. The total length of the Tiankeng Drainage Canal is 4.538 km, of which the length of main drainage canal is 3.23 km and the total length of four branch drainage canals is 1.309 km. The drainage area of the Tiankeng Drainage Canal is 4.49 km², and river slope is 0.08%. The water quality of the 1.559 km culvert section from Hengtian Drainage Station to South Ring Road and Zhongshan Middle Road is worse than Class V of the Environmental quality standards for surface waterGB3838-2002, and the average width of the culvert is 14.4 m. The section from the intersection of South Ring Road and Zhongshan Middle Road to Xincheng South Road is an open canal section with a length of about 1.670 km and the width of the canal is 8–20 m. The main ecological treatment facilities include (1) ecological gully for removing suspended solids, (2) advance bioretention system to treat the polluted canal water during dry season and stormwater during the rainy season, (3) floating contact oxidation reactors for aeration and plant absorption and landscape projects. The improved low impact techniques were used to treat the polluted water and stormwater in placement of the traditional sewer treatment plant. The total investment is lower than the traditional treatment scheme. The construction of the Tiankeng water quality rehabilitation project is planned to start in January 2019, and will be completed in December 2019.