| Summary: | The present study aims to contribute to the sustainability of swine production by evaluating usage of the aquatic macrophyte Lemna valdiviana in the tertiary treatment of pig waste. Five assays (1 to 5) in triplicate were conducted using swine effluent with different COD (Chemical Oxygen Demand) concentrations: 400, 550, 700, 850 and 1,000mg.L-1, respectively. The trial lasted for 21 days and the evaluated variables were: (a) pollutant removal efficiency, (b) biomass production and (c) plant protein content under the different detention times of 7, 14 and 21 days. In general, assays 1 and 2 (CODs of 400 and 550mg.L-1) presented the best removal efficiencies under a detention time of 21 days. Regarding the purpose of both nutrient removal and production of high protein biomass, assay 3 (COD of 700mg.L-1) showed the best results under 14 days’ detention time (36.81% crude protein). It was established that the use of duckweeds in the tertiary swine waste treatment was able to provide a sustainable alternative regarding its advantages such as effluent polishing, minimization of environmental impact, and production of high protein feed.
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