Estimation and spatial analysis of water pollution loads from towns in China

More than 95% of towns in China have no sewage treatment facilities at present. Increasing domestic sewage discharge from towns has greatly threatened not only the local environment and drinking water safety, but also the national water environment and sustainable development. However, there is no systemic investigation and data on sewage discharge and pollution loads from towns, which is necessary in order to plan and arrange sewage treatment in towns at the national scale. In order to estimate sewage discharge and pollution loads and to clarify its spatial distribution, we conducted two nationwide investigations of water use and sewage discharge in towns. Combined with investigation data from the Ministry of Housing and Urban–Rural Development of the People's Republic of China (MOHURD), domestic sewage discharge and pollution loads were calculated and spatial distribution and influent factors were analysed. The results showed that (1) in 2008, the total amount of domestic sewage discharge from towns of 398 prefectural-level cities was 2.64 billion tons, which had a chemical oxygen demand (COD) of 3.99 million tons, total nitrogen (TN) of 623,000 tons and total phosphorus (TP) of 56,000 tons; (2) the national average intensity of sewage discharge was 76,100 ton/km²/year, and the average intensities of COD, TN and TP emission were 74.06 ton/km²/year, 14.81 ton/km²/year and 1.04 ton/km²/year, respectively. In South and East China, including Shanghai, Jiangsu, Zhejiang, Guangdong, Fujian, Guangxi and Sichuan Provinces, the contaminant emission intensity was much higher and was also relatively high in the Beijing–Tianjin–Hebei region and in northeast China. These regions will be the focus of town-level domestic sewage treatment efforts. The results provide scientific support for rational planning of sewage treatment in towns in China.