The development of tools and methods for the evaluation of the physical integrity of sewage networks. A focus on physicochemical and hydrological approaches.

The deterioration of sewage systems can result in the intrusion of extraneous water, affecting the capacity, performance, and environmental sustainability of sewage infrastructure. Consequently, accurately assessing extraneous water in sewage networks is crucial for achieving sustainable urban water management. This thesis explored methods for identifying and quantifying extraneous water in a sewage system through the analysis of stable isotope of oxygen (δ18O) and hydrogen (δ2H), electric conductivity (EC), chemical oxygen demand (COD), turbidity and temperature at a selected sampling point. The study validated the stable isotopes method for quantifying infiltration. Inflow and infiltration (I&I) were estimated over selected 24-hour periods in March, April, May, and September, during both low and high groundwater levels under dry and wet weather conditions. During dry weather, the contribution of sewage and groundwater to the total flow was analyzed using δ18O, EC, COD, turbidity, and continuous temperature monitoring, followed by the simulation of the network’s hydraulic and temperature profile. In the wet period, contributions from sewage, groundwater, and surface runoff were estimated using pairs of tracers (δ18O & EC and δ18O & COD). Finally, spatiotemporal analysis was performed to estimate I&I on a regional scale, encompassing 50 sampling points as well as the wastewater treatment plant. Overall, the contribution of extraneous water fluctuated both spatially and temporally, influenced by factors such as land use, geological conditions and seasonal changes. By addressing challenges in detection and quantification, this study offers valuable insights for improving the management and maintenance of sewer networks, ultimately helping to develop more targeted and efficient strategies for mitigating I&I and ensuring the sustainability of wastewater systems.