Biomass production of papyrus (Cyperus papyrus) in constructed wetland treating low-strength domestic wastewater.

In this study, the pilot-scale constructed wetlands were fed with low-strength domestic wastewater to investigate the energy-capturing efficiency and plant productivity. Papyrus was a selected emergent macrophyte planted in the systems. The wastewater was intermittently fed to the systems, corresponding to the organic loading rates of 10, 16, 31, and 63 kg BOD/ha-d. With abundant sunshine in the tropical-climate area, papyrus converted solar radiation to biomass of about 2200-3100 g dry weight/m(2) from the two-month period of the experiments. Furthermore, the energy contents of papyrus are 16.2, 17.2, and 16.8 MJ/kg for culms, umbels, and total above-ground parts, respectively. From the plant productivity and the energy contents of papyrus obtained from this study, the energy capturing efficiencies can be estimated to be in the range of 4.4-6.0%, which are relatively high, compared with those of other plants.