Hunan Wastewater Treatment Plant, Sangzhi County, Hunan, China

The Hunan wastewater treatment plant is located in Sangzhi County, part of Zhangjiajie city in Hunan province, China. It serves a population of approximately 110,000 people, placing it in the medium-to-large agglomeration category for Chinese municipal wastewater infrastructure. As a plant of this scale in China, it is expected to comply with the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002), which mandates secondary treatment as a minimum. For larger plants serving over 100,000 people, more stringent nutrient removal requirements may apply, especially if the receiving water body is in a sensitive area. The plant discharges into the local watershed, which ultimately drains into the Lishui River, a tributary of the Yuan River, and then into Dongting Lake and the Yangtze River system. This downstream chain supports diverse aquatic life and provides water for agriculture and communities in the region.

The plant's treated effluent enters the Lishui River, which flows into the Yuan River and then into Dongting Lake, one of China's largest freshwater lakes. Dongting Lake is an ecologically important wetland that supports migratory birds and fish species. The lake connects to the Yangtze River, a major waterway with significant biodiversity and economic importance. Proper treatment is essential to prevent eutrophication and protect downstream ecosystems.