Temporal and spatial trends of a floating islands system's efficiency.

Floating Treatment Systems (FTWs) are known to be an efficient means to treat eutrophic surface waters, but most of the studies are related to the use of FTWs at the laboratory, microcosm or mesocosm level. It is necessary to expand these studies to larger surface areas and to introduce new supporting materials, substrates and plants adapted to the different regional conditions. This study aimed to evaluate the efficiency of temporal and spatial remediation of a floating island system, set up in a 400m experimental area delimited in an urban reservoir located on the main campus of the Federal University of Campina Grande-PB, Brazil. The experiment was carried out in three stages and 16 physicochemical and biological variables were monitored at thirteen sampling points regularly distributed in the study area, for a period of eight months. Temporally, the variables turbidity, electrical conductivity and total, fixed and volatile dissolved solids tended to decrease. Spatially, considering the 13 sampling points in sequence, the trend of reductions were found in the total dissolved solids, volatile dissolved solids and electrical conductivity. The trend of elevation was more substantial for the concentrations of ammonia-nitrogen and orthophosphate. In addition, occasional substantial reductions was found in variables that did not show statistical trends, such as chemical oxygen demand and total phosphorus. This study demonstrated the importance of expanding the scale of evaluation of floating island systems, finding significant results in terms of reduction of pollutants and adaptation of new structures and plants to adverse environmental conditions.