Treatment of tannery wastewater in a pilot scale hybrid constructed wetland system in Arequipa, Peru

Abstract

Tannery wastewater is an industrial effluent characterized by high and variable concentrations of complex pollutants. These contaminants pose a high risk to the environment if discharged into a body of water without undergoing proper treatment. This study evaluated the performance of a pilot-scale hybrid constructed wetland system (horizontal subsurface flow + free water surface flow) for tannery wastewater treatment. The pollutant removal efficiency of the hybrid constructed wetland was determined, and the chromium bioaccumulation and growth and survival parameters of the macrophytes Isolepis cernua and Nasturtium aquaticum were evaluated. The 5-day biological oxygen demand, the chemical oxygen demand, total suspended solids, total dissolved solids and chromium reached maximum levels (98%, 97%, 97%, 33% and 98%, respectively) after treatment in the pilot-scale hybrid constructed wetland. The average concentrations of the 5-day biological oxygen demand, chemical oxygen demand, total suspended solids and chromium were within the discharge limits established by national and international organizations for surface water bodies. The macrophytes had low levels of chromium bioconcentration and translocation, with the growth and survival, especially of Isolepis cernua, revealing a high capacity to adapt to the variability and possible toxic effects of tannery wastewater. In general, the pilot-scale hybrid constructed wetland proved to be a feasible alternative for the treatment of tannery wastewater in an important industrial zone in Peru.