Impacts of sanitation improvement on reduction of nitrogen discharges entering the environment from human excreta in China

Identifying the sanitation efficacy in reducing contaminations entering the environment is an important step for water pollution controls and developing management strategies to further improve sanitation conditions. With continuous efforts in sanitation improvement during the past decade, reductions in discharges of aquatic nutrients are expected in China. In this study, we estimated the aquatic nitrogen discharges from human excreta in 31 provinces in China during 2006–2014. The results indicated that the nitrogen discharges entering the environment from human excreta are largely determined by both local population and sanitation conditions. In 2014, the nitrogen discharges from human excreta in the rural areas (2118(1219–3140) Gg per year) (median and 95% confidence interval) are higher than those in the urban areas (1485(626–2495) Gg per year). The significant relationship (R2=0.38, n=29) between the total nitrogen concentrations in lakes and corresponding local nitrogen discharges indicated that, the lakes might be potentially affected by the contaminant inputs from human excreta. The further calculations under two policy scenarios showed that through sanitation improvement, further reduction of nitrogen discharges from human excreta in the developed regions might be limited. The sanitation improvement in the less-developed regions, such as Tibet, Qinghai, and Ningxia, should be considered a priority due to the larger reduction potentials. [Display omitted] •Nitrogen discharges entering environment from human excreta are determined by local population and sanitation conditions.•The total nitrogen concentration in China’s lakes might be potentially affected by local nitrogen inputs from human excreta.•For further nitrogen control, the sanitation improvement in less-developed regions should be considered a priority.