Análises quantitativa e qualitativa das águas superficiais da Bacia Hidrográfica do Riacho Doce/AL para avaliação das cargas de poluição

Abstract

In a scenario where water availability for human consumption is increasingly compromised, it is extremely important to conserve water and adopt measures that mitigate the degradation of rivers, seas and lakes, in order to guarantee the quality of water resources. In this sense, the objective of this work was to analyze the influence of polluting sources on the quality of surface waters in the Riacho Doce/AL Hydrographic Basin. The methodology began with the delimitation of the area, the determination of a water quality-monitoring plan and flow measurements to obtain the pollutant load, with monthly collections carried out from March 2022 to January 2023, in the dry and rainy seasons, along the Riacho Doce River to the mouth. On-site measurements were taken at four points using the HORIBA U53 probe, which evaluate pH, water temperature, ORP, conductivity, turbidity, DO and salinity. A water sample for each point was stored so that the quality variables could later be obtained using laboratory methodologies, namely: BOD5, total coliforms, total ammonia nitrogen and phosphorus. Finally, the flow rate was measured from the use of the windlass, with the purpose of calculating the pollutant load at each collection point. Based on the results obtained, it is possible to conclude that the characteristics of land use and occupation directly affect water quality, considering that, for all physical-chemical and biological parameters analyzed, concentrations were found above those permitted by legislation when the proximity of areas with large accumulation of solid waste, which was the case of study points P1 (Bowl head), downstream of the Sewage Treatment Station) and P2 ("Grota da Esperança"), areas with disorderly occupation, in addition to the Points P3 (District "Riacho Doce") and P4 (Mouth of "Riacho Doce"), which are respectively in areas of pasture and urban occupation, where in the rainy season they presented an average DBO load of 505.29 kg/day and 305.06 kg/day, except for the turbidity parameter that met the legislation. This situation reinforces the importance of efficient public policies that can prevent pollution of water bodies used to supply the population. Sewage treatment, solid waste collection and effective drainage of rainwater are essential to prevent environmental degradation and preserve the quality of surface water sources.