Constructed wetlands for rehabilitation and reuse of surface waters in tropical and subtropical areas ? first results from small-scale plots using vertical flow beds

Abstract

The application of constructed wetlands is seen to be a valuable way to treat polluted surface waters for rehabilitation of the water body (shallow lakes) and for reuse as irrigation and drinking water. In a first step a construction and operation design was worked out for small-scale plots which have been operated in Europe and at a site in China. The small-scale plots are designed as subsurface flow systems with a downflow and upflow compartment in series. The different layers consist of sand and gravel with a minimum hydraulic conductivity of about 10⁻⁴ m/s. Several small-scale plots, planted with different species, have been tested in parallel. During almost one year of operation the monitoring of the systems aimed at: checking the effectiveness of different plant species, variation of loading rates and intervals and variation of recirculation to the system. The results for some relevant parameters (BOD₅, NH₄-N, N, P) show a high overall efficiency – strongly depending on operation conditions such as feed rate, alternate feeding and resting time. As a result the construction design has been modified for the construction of pilot systems in China. The whole project was carried out within the INCO-DC programme of EC with partners from Germany and China.