Characteristics and applications of hybrid constructed wetlands for low-polluted water: Cased in Bagong River of the Yellow River Watershed, China

Abstract

Low-polluted waters treated by traditional constructed wetlands were usually difficult especially because of restricted available land use. A hybrid constructed wetlands (CWs) could be applied to remediate low-polluted rivers, which can realize steps complementary to each other that exploit the specific advantages of the individual systems and achieve higher treatment effects. The hybrid CWs covering a total area of 99647m2, was developed to treat the polluted Bagong River, one of tributary to the Yellow River, have been in operation since the end of 2020. This paper introduced the specific construction method of the hybrid CWs, and the water quality of the river could be improved 1–2 grades after flowing through the CWs (according to the Chinese standard GB3838-2002). The treatment capacity was designed to be 65,000 m3·d−1, and the obtained results showed a satisfactory pollutant removal capacity of the hybrid system, with mean removal rates of 57.00%, 20.00%, 48.00%, and 29.00% for ammonia nitrogen, total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD), respectively. Meanwhile, >12 species of aquatic birds were attracted to inhabited in the hybrid CWs. The results of correlation analysis concluded that temperature and plant growth were the dominant factors affecting the removal of pollutants in the hybrid CWs system, and the porous concrete as substrate also has obvious phosphorus removal effect. The results showed that the system had relatively stable impact resistance and good ecological benefits under different influent loads, and can better improve water quality and biodiversity. Thus, the hybrid CWs would be a promising and feasible treatment method for low-polluted waters, as adapted to the local context.