Utilização de microalgas na remoção de nutrientes de uma lagoa eutrofizada da cidade de Manaus - AM

Abstract

The disposal of domestic effluents without an adequate treatment may increase nitrogen and phosphorus levels in natural water bodies. We tested whether the microalgae Scenedesmus acuminatus, Chlorella vulgaris and Planktothrix isothrix unevenly reduced dissolved nutrient concentrations in different dilutions of eutrophicated water with domestic effluent. We used eutrophicated water from an urban and subjected it to three conditions: undiluted water, diluted by 50%, and diluted by 90%. We added microalgae biomass to these different conditions. C. vulgaris and S. acuminatus reached their peak growth on the 7th and 9th day, respectively. C. vulgaris had higher biomass production and higher specific growth rate at PW0 (10.4 ± 9.4 mg L-1 and 0.96 d-1) and at PW50 (10 ± 8.5 mg L-1 and 0.85 d-1). The growth of P. isothrix was low compared to that of green microalgae. The three species were equally efficient in removing ammonia in PW0. Nitrate removal rate was highest for Chlorella vulgaris in PW0, and higher for C. vulgaris and P. isothrix in PW50 and PW90. Orthophosphate removal efficiency was higher for S. acuminatus and C. vulgaris in PW0, equally efficient for the three species in PW50, and higher for C. vulgaris and P. isothrix in PW90. We conclude that water eutrophicated by undiluted domestic effluent is the best option as an alternative medium for growing planktonic green microalgae. We concluded that the three species of microalgae tested are efficient in removing ammonia. Scenedesmus acuminatus was not an ideal species for nitrate removal. Planktothrix isothrix was efficient in removing nutrients when domestic wastewater is diluted. Chlorella vulgaris was efficient in removing nutrients from domestic wastewater whether diluted or not.