Distribution of Mn, Al, Cu and Zn in a constructed wetland receiving municipal sewage

Abstract

A constructed wetland at Nucice near Prague, Czech Republic, has been in operation since 1996 and the system is designed to treat sewage from 650 PE together with stormwater. The total area of the beds planted with Phalaris arundinacea and Phragmites australia is 3,224 m2 (two beds 62 x 26 m each). Pea gravel (8/16 mm) is used as a filtration material. During the period 1998-1999, removal of Mn, Al, Cu and Zn from wastewater and distribution of the metals in sediments and plants were studied. Metals were measured in three vertical profiles of the filtration bed (0-15, 15-30 and 30-60 cm) and at four locations along the longitudinal profile of the bed (5, 16, 32, 48 m from the inlet). Metal concentrations in plant tissues (roots, stems, leaves) of Phalaris arundinacea were measured along the longitudinal profile of the bed at the same locations as for sediments. The results showed that the retention of metals is high (up to 98%) with the major decrease in metal concentrations within the first 5 metres of the bed. The major decrease in metal concentration in the filtration material was observed in the inlet zone between 5 and 16 metres. In Phalaris tissue, metal concentrations decreased in the order roots > stems > leaves but statistically significant differences varied among the studied metals.