Temporal and spatial variation of phosphate distribution in the sediment of a free surface water constructed wetland.

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

Ghent, Bélgica

Simposio; International Symposium on Wetland Pollutant Dynamics and Control.; 2005

Universiteit Gent, Faculty of Bioscience Engineering, WETPOL.

This study  is aimed at determining the spatial and temporal variation of the P distribution in sediments of an artificial wetland for sewage and industrial effluent treatment, and the fraction that is potentially involved in the exchange processes. The water and sediment samples were taken at the inlet, middle and outlet areas del wetland during 30 months.The P-fractionation in sediment was performed following the EDTA method, proposed by Golterman (1996) A significant increase in the concentration of the fraction of Fe(OOH)»P can be observed at the inlet, mainly that of CaCO3»P. The high pH, Ca2+ and CO3-2 concentrations in the inlet water suggest that P would co-precipitate together with CaCO3 . Therefore, it seems that CaCO3»P represents the main precipitating mechanism. However, mineralization of organic matter maintained the sediment at a pH range lower than the high values prevailing in the inlet wastewater. CO3-2 would undergo partial dissolution and the released SRP would be readsorbed onto the Fe(OOH)»P fraction. Since the environment for P retention (high pH and Fe, Ca and ionic concentrations) is largely provided by the inlet wastewater, the wetland would be expected to continue retaining P as far as the composition of the inlet solution is maintained and there are available adsorption sites in the sediment.