Can the removal efficiency of a constructed wetland be affected by an event of plant depredation?

MAINE, M. A.; HADAD H. R.; SANCHEZ, G.C.; CAFFARATTI, S.E.; PEDRO, M.C.; DI LUCA, G. A.; MUFARREGE, M. M.

Venecia

Conferencia; 12th International Conference on Wetland Systems for Water Pollution Control.; 2010

12th International Conference on Wetland Systems for Water Pollution Control.

A 2,000 m2 free water surface wetland was constructed to treat wastewater containing metals (Cr, Ni, Zn and Fe) and nutrients from a tool factory in Argentina. Typha domingensis became the dominant species and covered 80 % of the wetland surface since 2005.  In June 2009, a population of approximately 30 capybaras (Hydrochoerus hydrochaeris), pig-sized tailless South American amphibious rodents, caused the complete depredation of the aerial part of macrophytes. However, the roots and rhizomes of T. domingensis were not damaged. In November 2009, to allow the recovery of the vegetation, a simple perimeter protection system was installed to stop the approaching of capybaras. Subsequently, T. domingensis showed a luxuriant growth that was also enhanced by the growth season, reaching a cover of 60 % after 30 days. Wetland efficiency was compared considering the stage without aboveground parts in plants and the previous normal operation. Removal efficiencies did not present significant differences between the two periods, being 49.0-66.5 % Cr, 48.1-53.0 % Ni, 74.8-82.4 % Fe, 81.7-86.1 % NO3-, 82.0-86.4 % NO2-. BOD and COD decreased 65.0-67.8 % and 64.4-68.3 %, respectively. This work proves the importance of the rhizosphere system in the dynamics of the wetland.