Temporal and spatial variation of phosphate distribution in the sediment of a free water surface constructed wetland.
This study was aimed at determining the spatial and temporal variation of P distribution in sediment of an artificial wetland for sewage and industrial wastewater treatment, and the fraction that is potentially involved in the P exchange processes. Influent, effluent, macrophytes and sediment at the inlet, middle and outlet areas were sampled over 24 months. The P-fractionation in sediment was performed following the EDTA method. Eichhornia crassipes and Typha domingensis removed P efficiently when cover was high, but E. crassipes caused anoxic conditions. The increase in cover of T. domingensis may contribute to attain oxic conditions and to improve P removal. When macrophytes are not present or when cover is low, sediment seems to increase removal efficiency. A significant increase in the concentration of the fraction of Fe(OOH) approximately P and mainly that of CaCO(3) approximately P can be observed at the inlet. High pH, Ca(2+) and CO(3)(-)(2) concentrations in the influent suggest that P co-precipitates together with CaCO(3). Therefore, it seems that CaCO(3) approximately 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 influent. CO(3)(-)(2) could undergo partial dissolution and the released i-P(diss) could be readsorbed onto the Fe(OOH) approximately P fraction. Since the environment for P retention (high pH, Fe, Ca and ionic concentrations) is largely provided by the influent, the wetland may be expected to continue retaining P as far as the composition of the influent is maintained and there are available adsorption sites in the sediment.
Maine
M A
MA
Química Analítica, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santiago del Estero 2829 (3000), Santa Fe, Argentina. amaine@fiqus.unl.edu.ar
Suñe
N
N
Hadad
H
H
Sánchez
G
G
D000327:Adsorption; D001118:Argentina; D001673:Biodegradation, Environmental; D018533:Biomass; D019015:Geologic Sediments / Q000737:chemistry*; D017553:Phosphorus Compounds / Q000032:analysis* / Q000378:metabolism; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry; D014871:Water Microbiology; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
D017553:Phosphorus Compounds; D014874:Water Pollutants, Chemical; D014867:Water