Impactos do Centro de Tecnologia em Pesca e Aquicultura (CTPA) no córrego Felizardo, Uruguaiana, RS

Abstract

Aquaculture is the fastest-growing animal food production in Brazil in recent years. Due to the intensification of production, fish farming has been considered as an impactful activity for the environment. Effluents from aquaculture are rich in nitrogen, phosphorus and organic matter that contribute to eutrophication of natural water bodies. In the Uruguaiana city, one of the main areas for the development of aquaculture is the Center for Technology in Fisheries and Aquaculture (CTPA) from Unipampa. However, the CTPA does not have any system for wastewater treatment. Thus, the aim of the present study was to verify if the effluents from CTPA are causing some environmental impact in the Felizardo stream, Uruguaiana. For this, the water was collected monthly in four distinct points located in Felizardo stream during the period from June/2017 to May/2018. The sampling points were: P01 - located upstream of the CTPA, being the physico-chemical reference for the analyzes comparing with other points; P02 – location of water abstraction to supply CTPA tanks; P03 - site of the launching of the fish farming effluents; and P04 - located downstream of the fish farming sector, with a distance of 500 meters from P03. The physical parameters analyzed were: water flow, temperature, electrical conductivity and turbidity. The analyzed chemical parameters were: dissolved oxygen, pH, hardness, alkalinity, total ammoniacal nitrogen, nitrite and orthophosphate. For air and water temperature, total ammoniacal nitrogen and nitrite, no statistical differences were observed among the points along the seasons. The dissolved oxygen was also very similar among the points throughout the year, except for the winter where P02 (4.33 ± 0.69 mg / L) presented values significantly lower than the other sampling points. The turbidity was higher in P03 (40.01  28.53 NTU) during the summer when compared to the other points. The same was observed for orthophosphate during the summer (0.08 ± 0.03 mg / L) and autumn (0.06 ± 0.01 mg / L) in which P03 presented values significantly higher than the other points. For conductivity, pH, alkalinity and hardness, significantly lower values were always observed in P02, when compared to other points, especially in spring, summer and autumn. These results indicate that especially during the summer when the management of tanks occurs more frequently, the CTPA effluents contribute punctually to the increase of orthophosphate and turbidity in the Felizardo stream. In addition, the results obtained with respect to pH, hardness and alkalinity indicate that the water of the dam must be used carefully for the supply of the CTPA tanks to avoid losses in production. With the exception of orthophosphate, the results of this study allow to include the Felizardo stream in the Class II, according to the National Council for the Environment (CONAMA) Resolution No. 357 of March 17, 2005.