Avaliação da influência da precipitação na rede de esgotamento sanitário do tipo separador absoluto - Feira de Santana - BA

Abstract

The objective of this study was to evaluate the influence of stormwater on the energy consumption in the pump stations of the urban sewage system of Feira de Santana city. Data concerning the energy consumption in the pump stations, the water consumption in the area, and the precipitation rate were collected for the time period of 2008-2011. Statistical tests were performed by applying the Spearman’s rank correlation, the Anderson-Darling goodness-of-fit test, the Student’s test t, and the Ljung-Box test. The results showed that, regarding a potential influence of the effective precipitation rate on the energy consumption in the pumps, the correlation not significantly different from zero with a 95% confidence level for all the 19 pump stations. Similar results were obtained for the case of the potential influence of the public water consumption on the energy consumption in the pump stations. However, considering the total energy consumption in the pump stations, the correlation with the effective precipitation is significant, although weak (R=0.30). Thus, it was estimated that 9% of the total energy consumption in the pump stations is explained by the precipitation. By analyzing the correlation between the energy consumption of all the pump stations, it was found that the all possible correlations are weak, and only in 12% of the cases the correlation is significantly different from zero with a 95% confidence level. Moreover, such correlation was not observed in pumping stations installed in series. In addition, seasonality tests applied to the time series precipitation and water consumption revealed seasonality with a one year lag, suggesting good quality of data concerning these parameters. These results point to the hypothesis of potential errors or inconsistency with our study in the data collecting process regarding the energy consumption in the pump stations. A possible explanation lies in the fact that the energy consumption times series was made available in a monthly basis, thus potentially not reflecting precipitation peaks measured in a daily basis. The results of this study, as a preliminary conclusion, point that the impact of precipitation on the overall energy consumption in the wastewater treatment system of Feira de Santana is not significant.