Abstract: The technical design of small-scale plots (SSPs) of constructed wetland (CW) was described along with details of some associated wastewater purification effects in winter. Plots were comprised of two chambers. One chamber induced downward-flow,while the other created upward-flow. During Oct. 1997～Jan. 1998,the average plot removal rates for COD_Cr,BOD₅ and total suspended solids were 53.6%,78.7% and 80.2%,respectively. Reductions of bacteria,total coliforms (TC),fecal coliforms (FC) and algae were 99.4%,85.9%,89.7% and 97.7%,respectively. The mean removal rates of Kjeldahl nitrogen (KN),ammonium (NH₄⁺-N) and total phosphorus (TP) were 39.2%,16.5% and 25.8%. The treatment effects were not significantly different from each other. Concentrations of nitrate (NO₃^--N) in effluents were higher than those of the influent,and nitrate concentrations in the effluents of plant-systems were higher than those of the control. This indicated that presence of macrophytes enhanced nitrification in the CW. The downward followed by upward flow CWperformed better in removing contaminants and microorganisms from polluted surface water. It is an improved technology to purify water quality and rehabilitation of aquatic ecosystems.

Key words: Constructed wetland, Vertical flow, Downflow-upflow, Wastewater purification, drought resistance, relationship between root and leaf, spring drought stress, physiological characteristics.