Identifying sources of infiltration and inflow in sanitary sewers in a northern community: comparative assessment of selected methods

Abstract

Infiltration and inflow (I/I) into sanitary sewers causes numerous negative effects on the whole wastewater management system and ultimately, on the receiving waters. Consequently, a number of methods have been developed to analyse the performance of sewer systems with respect to I/I, including: distributed temperature sensing (DTS), closed-circuit television (CCTV) inspections, flow and conductivity measurements, automatic or grab sampling of ammonium, smoke testing, and visual inspection of manholes. Such methods were compared in an application to sanitary sewers in a small community and assessed with respect to their accuracy and ability to identify locations of sources of I/I, as well as temporal and spatial resolutions of the obtained results. Furthermore, different approaches to ammonium sampling during I/I monitoring campaigns were discussed. It was concluded that among the methods tested in this study, DTS had the highest temporal and spatial resolution, while ammonium grab sampling showed promise for initial screening of large catchments. HIGHLIGHTS Number of methods to analyse I/I in sewer system were compared.; CCTV and visual inspection provided many locations with a potential risk of I/I but were not confirmed by other methods.; Advantages and practical limitations of different ammonium sampling strategies were discussed.; Combination of two to three methods is recommended depending on the main focus of an I/I monitoring programme.;

Keywords

• ammonium
• closed-circuit television inspection
• conductivity
• distributed temperature sensing
• infiltration and inflow
• wastewater