Infiltration/Inflow Assessment and Detection in Urban Sewer System

Abstract

Infiltration and inflow (I/I) of non-sewer water into the urban sewer system is a critical problem in the long term for sustainable urban water management and water infrastructural asset management, with serious environmental, social and economic impacts on cities and sewer systems. I/I of unwanted stormwater, groundwater and other extraneous sources in sewer systems decrease availability and increase the risk of hydraulic overloading of the wastewater network, which may lead to local flooding or sanitary sewer overflows. Furthermore, it has negative impacts on performance and efficiency of wastewater treatment plants and increases pumping costs, energy consumption and maintenance requirement. There is no standard and specific operational procedure for investigating and detecting illicit connections and I/I in sewer systems. This study discusses commonly used and advanced methods of localizing and quantifying I/I level in sewer systems, and identifies advantages and limitations of each method. A combination of these techniques can provide sewer operators possibilities to compare different technologies and reducing assumptions and uncertainties in assessing and localizing I/I in the sewer system in a standardized way and support the decision-making in maintenance and rehabilitation plans with more accurate and reliable data about location and magnitude of I/I in the sewer system.