Abstract

ESPINOSA GUTIERREZ, Gabriela et al. Assessment of infiltrations to the sewer by comparison of pollutant concentrations on wastewater: Case study in Tepic, Mexico. Rev. Int. Contam. Ambient [online]. 2015, vol.31, n.1, pp.89-98. ISSN 0188-4999.

The infiltration of rain or groundwater into the sewer systems can negatively affect the hydraulic capacity of the sewer network as a consequence of the increment of the total volume of water. Furthermore, the composition of the wastewater in the pipelines may also be affected due to the dilution of its components in a larger volume. These effects may lead to important technical problems with an inherent economic cost. For instance, the overflow of the drain lines, operational problems at the wastewater treatment facilities, and an increase of pollutant emissions to the environment due to the lack of treatment. The evaluation of sewer infiltrations is a key factor in order to counteract these potential problems by means of preventive or corrective measures. Conventionally, the infiltration is assessed as the difference between the total flow of generated wastewater and the actual water flow in the pipelines. This strategy is not feasible when there are not flow measurement devices at the consumption or at the discharge points. This is the case in the city of Tepic, Nayarit in Mexico. In the present study, an alternative approach was used to evaluate the infiltrations into the domestic sewer in the city of Tepic during the rainy season. This approach is based on a comparative analysis of theoretical and measured nitrogen and phosphorus content in wastewater samples from the sewer. Evidence of high infiltration into the sewer was found. The dilution factor calculated for the wastewater at different locations and sampling days ranges from 30 to 500 %, indicating a potential problem for the sewer network and for the efficiency in the wastewater treatment.

Keywords : urban drainage system; rain; dilution; nitrogen; phosphorus; sampling; wastewater management.

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