THE USE OF FLOATING MACROPHYTES AS A BIOLOGICAL ALTERNATIVE FOR WATER QUALITY IMPROVEMENT IN EUTROPHIC ENVIRONMENTS

The urban streams in the Amazon are experiencing eutrophication due to sewage discharge, which threatens the diversity and abundance of aquatic fauna, as well as human health. Macrophytes have the ability to absorb high nitrogen compounds from the water. Little is known about the decontamination effects of Amazonian macrophyte species. This study aims to evaluate the physicochemical variables of water from an urban stream after treatment with native macrophytes. The experiment was conducted at the Federal Institute of Amazonas, Tabatinga Campus. Two hundred liters of water were collected from the Buriti stream, near the municipal public landfill. The polluted water was transferred to 20-liter aquariums in duplicates, and the treatments used were four species of floating macrophytes: Pistia stratiotes, Salvinia auriculata, Azolla filiculoides, and Eichhornia azurea. The macrophyte density used in the aquariums was 20 ± 1 g l-1. Dissolved oxygen, pH, total ammonia, nitrite, conductivity, dissolved solids, and aquarium temperature were monitored over seven days. The eutrophic water treated with the four experimental macrophyte species showed a reduction in total nitrite and an increase in pH within 24 and 72 hours, respectively. Eichhornia azurea decreased electrical conductivity and total solids in the water within 24 and 48 hours, respectively. Pistia stratiotes was the macrophyte with the greatest reduction in total ammonia. Salvinia auriculata was the only experimental species that did not reduce total ammonia in the water. Overall, Eichhornia azurea, followed by Pistia stratiotes, were the most efficient macrophytes for water treatment, altering pH, electrical conductivity, total dissolved solids, ammonia, and total nitrite. In this sense, the macrophytes Eichhornia azurea and Pistia stratiotes can be biological alternatives for the treatment and improvement of the physicochemical variables of water in an eutrophic environment.