Nutrient and metal removal in a constructed wetland for waste-water treatment from a metallurgic industry.

MAINE, M. A.; SUÑE, N.; HADAD, H. R.; SÁNCHEZ, G.; BONETTO, C.

Avignon, Francia

Conferencia; 9th International Conference on Wetlands Systems for Water Pollution Control.; 2004

International Water Association (IWA)-Association Scientifique et technique pour l´eau et l’environnement (ASTEE).

The following contribution summarizes the nutrient and metal removal in a constructed wetland for treating wastewater from a tool industry. The wetland was 50 m length by 40 m width, with a central baffle dividing it in two identical sections. Water depth was 0.5-0.8 m and the water residence time ranged from 7 to 12 days. The wetland was rendered impermeable by means of a bentonite layer covered with a layer of the surrounding soil. Several locally available macrophyte species were transplanted into the wetland. Eichhornia crassipes (water hyacinth), showed fast growth and soon became dominant attaining 80% cover of the wetland surface. Typha dominguensis (cattail) and Pontederia cordata (pickerelweed) developed as accompanying species attaining 14 and 6 % cover. The wetland removed 85 % of Cr and 64 % of the incoming Ni. Zn concentrations were below 50 µg.l-1 in most samplings. The presence of metals in plant tissue was more significant in the roots than in the leaves. Metal concentration in the bottom sediments did not increase. An increased concentration in the macrophyte tissue represented the main retention mechanism. The outcoming water was anoxic in most samplings. Phosphorus and ammonium were not retained within the wetland being higher at the outlet on several occasions. On the other hand, 81 and 88% of the incoming nitrate and nitrite were removed. Large denitrification losses are suggested.