Myriophyllum aquaticum-Based Surface Flow Constructed Wetlands for Enhanced Eutrophic Nutrient Removal—A Case Study from Laboratory-Scale up to Pilot-Scale Constructed Wetland

Water pollution caused by various eutrophic nutrients such as nitrogen (N) and phosphorus (P), such as outbreaks of eutrophication in rivers and lakes, has become a serious environmental problem in China. Such problems have spurred extensive studies aiming at finding environmentally friendly solutions. Various constructed wetlands (CWs), planted with different macrophytes, have been considered as environmentally safe technologies to treat various wastewaters for several decades. Due to their low energy and operational requirements, CWs are promising alternative solutions to water eutrophication problems. Within the CWs, macrophytes, sediments, and the microbial community are indispensable constituents of such an ecosystem. In this study, a laboratory-scale surface flow CW (LSCW) was constructed to investigate the effects of two different plants, Eichhornia (E.) crassipes (Mart.) Solms and Myriophyllum (M.) aquaticum, on the removal of eutrophic N and P. The results showed that both plants could significantly reduce these nutrients, especially ammonium (NH4+), and LSCW planted with M. aquaticum performed better (82.1% NH4+ removal) than that with E. crassipes (66.4% NH4+ removal). A Monod model with a plug flow pattern was used to simulate the relationship of influent and effluent concentrations with the kinetic parameters of this LSCW. Based on the model, a pilot-scale surface flow CW (PSCW) was designed, aiming to further enhance N and P removal. The treatment with M. aquaticum and polyethylene materials showed the best removal efficiency on NH4+ as well as on total nitrogen and phosphorus. In general, the enlarged PSCW can be a promising solution to the eutrophication problems occurring in aquatic environments.