Investigation of Water Quality and Aquatic Ecological Succession of a Nascent River Replenished by Reclaimed Water in Beijing

Abstract

There is a potential to create a new ecosystem in the river replenished by reclaimed water, but it is unknown what the longer-term effects are of using this water. Therefore, the water quality and aquatic ecological evolution of a nascent river (Jing River) replenished by reclaimed water in Beijing were investigated, and the conventional water quality, phytoplankton indicators and submerged plant growth conditions from October 2018 to December 2020 were analyzed. The Spearman correlation and redundancy analysis between possible influential environmental factors and algal indicators were conducted. The results showed that the major water quality indicators could meet the water quality standards of landscape water, and there were 7 phyla including 322 species of phytoplankton. The phytoplankton density showed an increase followed by a decreasing trend. Phytoplankton densities of each monitoring site achieved 10 to 25 million cells/L in 2019, then phytoplankton densities decreased in 2020, which ranged from 8 to 20 mil-lion cells/L. Phytoplankton growth was influenced by changes in water quality and ecosystems. Simultaneously, the submerged plant coverage rate gradually increased from 2018 (0%) to 2020 (26.27% - 37.06%), and the biodiversity increased as well. Through the implementation of eco-logical restoration measures in the Jing River, the reclaimed water environment evolved into a more natural water environment, which could provide some technical suggestions for similar areas to use reclaimed water as a water replenishment source.

Keywords: nascent river, reclaimed water, Water quality, phytoplankton, submerged plants, Restoration