Retención de P y N en un wetland construido para tratamiento de efluentes cloacales.

MAINE, M. A.; SANCHEZ, G. C.; HADAD, H. R.; CAFFARATTI, S.; PEDRO, M. C.; SUÑÉ, N.

VI Congreso Iberoamericano de física y Química Ambiental

Congreso; VI Congreso Iberoamericano de física y Química Ambiental; 2011

Sociedad Iberoamericana de Física y Química Ambiental (SiFyQA).

This study aims to determine the removal efficiency of N and P from water and determine if they were retained by macrophytes or by sediment in an artificial wetland for sewage treatment. Water, sediment and macrophytes were sampled at different distances from the discharge point. The concentration of nutrients in water was periodically measured throughout the experiment (180 days). Total N and P concentrations were also analyzed in sediments and in the aerial and submerged tissues of the dominant plants (Eichhornia crassipes and, Typha domingensis). A sequential extraction of P of the sediment (Golterman, 1996) was also performed at the beginning and the end of the study. According to the soluble reactive phosphorus (SRP) concentration at the inlet and outlet of the wetland, it was found that the wetland carried out an efficient removal of nutrients until anoxia occurred in the outlet zone, which was resolved with forced aeration and the construction of a waterfall in the outlet area of the wetland. P was accumulated in both, sediment and macrophytes. PT increased in the inlet sediment, showing the fraction of P bound to ferric oxy-hydroxides the highest increase. Macrophytes accumulated P mainly in their aerial parts. Performing a mass balance, it was found that the sediment was the main P compartment. However, macrophytes carried out the highest P removal from water during the study period (approximately 80% of the P), being the floating species E. crassipes responsible for 50% of P removal, probably due to its high removal capacity and high productivity (70% plant cover). The advantage of macrophytes is the possibility of being harvested, which leads to important removal rates of P in short times. In contrast, if the mechanism of P uptake was based on the soil matrix, sites for P sorption could be saturated or P could be reversible desorbed for example under anoxic conditions In the case of nitrogen, the macrophytes retained 25% of this nutrient while the sediment showed no significant retention, so it can be proposed that denitrification is the main removal process.