Biological and chemical oxygen demand in the Uraim River and the urbanization process. Paragominas-Pará

Abstract

The preservation and reuse of water resources require the adequacy of the physical-chemical and biological parameters of the water to the current environmental legislation. In this sense, this research aimed to quantitatively analyze the biological oxygen demand - BOD and the chemical oxygen demand - COD, in an extension equivalent to 4,250 meters, from the point of water collection in the Water Treatment Station (area of less urbanization) to the left side of the PA 125 bridge (area of greater urbanization), Paragominas-PA, as well as relating the variation of these parameters to the number of inhabitants in these two places. The methodology employed was observational, systematic, direct, and laboratory analysis protocols established for Brazilian waters were observed. Statistical analysis of data after laboratory analysis was performed using the BioEstat 5.3 software, based on descriptive statistics (calculations for: mean, standard deviation and coefficient of variation) and use of Pearson's linear correlation. The data obtained and analyzed indicated that both BOD (≤ 20, unpolluted waters) and COD (< 200, polluted waters) remained within the maximum permitted limits, in the two guidelines used in the six points analyzed (BOD = 0 .9±1.1; COD =1.7±0.3). However, the BOD, between P3 (0.9mg/L of O2) and P6 (1.1 mg/L of O2), more urbanized places, there was a variation for more, in the two analyzed parameters, which indicated the entry of organic matter from domestic effluents, which is harmful to aquatic ecosystems, due to the absence of adequate basic sanitation in the municipality, which could determine a higher cost for the treatment of water captured in the Uraim river, which will increase the cost of cubic meter to the community that is supplied with water distributed by the company SANEPAR.