Comparative study of wastewater purification efficiencies of two emergent helophytes:: Typha latifolia and Juncus subulatus under arid climate

The aim of the present study is to assess wastewater purification efficiency of two higher aquatic plant, Typha latifolia and Juncus subulatus in an arid climate. The experiment was conducted from August 1994 to March 1996. The plots (capacity: 115 liters, diameter: 57 cm) were filled to 5 cm depth with gravel and 30 cm with soil (texture: 30% clay, 34% silt and 36% sand) and planted with young shoots of Typha and Juncus. The plots without plant were used as controls. The plots were weekly and exclusively irrigated by urban raw wastewater (25 liters). The influent was percolating through the substratum. Results revealed significant performances for reduction of organic load in all systems. Indeed, COD and TSS removal efficiencies were respectively 91% and 73% for Typha latifolia, 92% and 76% for Juncus subulatus, 83% and 73% for an unplanted system. Depletion of nutrients during the experimental period was low and even negative: 32% TP (total phosphorus) and 31% NH4 (ammoniacal nitrogen) in Typha system, 27% TP and 17% NH4 in Juncus system -10% TP and -22% NH4 in unplanted system. In addition, the presence of these helophytes maintained sufficient porosity in order to allow water percolation treatment. The unplanted system clogged in winter. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.