Abstract: Constructed wetlands have been being used more and more extensively in treatment of rural domestic sewage. The plants used in constructed wetlands are mostly alien garden plants, which might pose threats to rural ecological environment. Environmental risks of eight exotic plants used for this purpose were analyzed for comprehensive evaluation, using a modified Australian weeds risk assessment system and a Chinese alien plants invasion risk assessment index system. Eichhornia crassipes and Pistia stratiotes have been defined as invasive plants, which are very risky and should be used sparingly; Myriophyllum aquaticum and Thalia dealbata have a high potential risk of invasion and should be used with caution; Cyperus alternifolius, Canna indica, Pontederia cordata and Cyperus papyrus are relatively lower in invasion risk and may be appropriately used in constructed wetlands. Analysis of the above-mentioned exotic wetland plants, except the first two for suitable distribution shows that all the wetland plants are suitable to grow in South China, where paddy fields, rivers, lakes, reservoirs and fish ponds are extensively distributed. These wetland ecosystems are vulnerable to threats. It is, therefore, essential to intensify the management of constructed wetlands and wetland plants, by adopting measures likes use of native substitutes, site selection, growth management, isolation and re-use of biomass, etc. so as to reduce the risk of exotic wetland plants, to make better use of them in treating rural domestic sewage and to improve ecological environment of the rural areas.

Key words: rural sanitary sewage, constructed wetlands, wetland plants, environmental risk, management measures