Impacto da sazonalidade climática em estações de tratamento de esgoto localizadas na cidade de Fortaleza-CE

Abstract

A lot of Wastewater Treatment Plants in Brazil have both structural and operational problems, which can be detrimental to the discharge into the water resources where the effluents from these units are discharged. Therefore, it is really important to study their reliability and the environmental particularities in which these plants are inserted. The purpose of this work is to investigate the relationship between the seasonality characteristic of the climate of the city of Fortaleza and the behavior of the effluent from 23 Wastewater Treatment Plants through the evaluation of reliability and percentage of Targets of compliance with the legislative standards of these plants and using six water quality parameters for this evaluation. The results showed that the Chemical Oxygen Demand (COD) and Total Suspended Solids (TSS) parameters are the most affected by the climatic seasonality where, for coefficients of determination between 0.40 and 0.83, showed that the greater the rainfall the greater the dilution of these parameters. For the parameters Total Coliforms and Escherichia Coli coefficients of determination were found between 0.16 and 0.63. Although these values are a little lower, and we still see that there is also a correlation between rainfall and quality, however, contrary to what develops with the parameters Chemical Oxygen Demand and Total Suspended Solids, higher rainfall volumes contribute to higher concentrations of Total Coliforms (TC) and Escherichia Coli (EC), which is attributed mainly to leaching. The parameters pH and Free Residual Chlorine already showed very low values of coefficient of determination compared to the previous parameters showing no influence of leaching on these parameters. From these last results, the study proceeded to develop semi-annual evaluations. The box-plots produced and the descriptive statistics also corroborate the results cited above. The calculations obtained by percentage of attendance targets again confirms that the performance of most stations changes according to seasonality. In the first half of the year the goals are easier to meet for most stations with respect to the parameters COD and TSS. This situation is inverted when it refersto the TC and EC parameters, where the goals are more easily met in the second half of the year. It is important to investigate the environmental situations in which both the Wastewater Treatment Plants and the Sanitary Sewage Systems that conduct the sewage are found.