Uso de calcários para remoção de fosfato da água e mitigação da eutrofização de açudes do semiárido brasileiro

Abstract

The eutrophication of dams in the Brazilian semi-arid region is the main problem responsible for the loss of water quality in these environments. Eutrophication is caused by increased ex-ternal and internal loads of nutrients, especially phosphorus, from domestic and agropastoral effluents, especially in the Brazilian semi-arid region. Several techniques have been proposed to mitigate the eutrophication of lakes and reservoirs and generally involve the control of ex-ternal and internal phosphorus loads. The objective of this study was to evaluate the phos-phate sorption potential of two types of limestone commercially exploited in Rio Grande do Norte for future use of the product in improving the water quality of the dams. In a first ex-periment, the phosphate sorption potential in deionized water of dolomite and beige calcitic limestones was evaluated using the Langmuir model. Different concentrations of FSR (: 0; 1; 2.5; 5; 10; 20; 40; 60; 80 and 100 mg L) were used for a single dose of limestone (0.1g). How-ever, in a second experiment, different doses (0, 1, 2, 4 and 8 mg.mL-1) of both limestones were applied to water samples from two eutrophic ponds. The results of the first experiment demonstrated a low Maximum Adsorption Capacity (Q) of both limestones (1.17 white and 0.13 yellow). The results for the second experiment showed high phosphate adsorption effi-ciency regardless of the type of limestone used. The results also showed that the pH of the water did not increase after the application of limestone in the hard water of the dams. More research is needed to evaluate the phosphate adsorption potential of limestones under differ-ent environmental conditions, but the preliminary results presented here are promising and suggest that limestones can be effective in removing phosphate from the water of the investi-gated eutrophic reservoirs.