Detection and quantification of lateral, illicit connections and infiltration in sewers with Infra-Red camera: Conclusions after a wide experimental plan

Abstract

Separate sewer systems are sensitive to illegal or mis-connections. Several techniques (including the Distributed Temperature Sensor) are now available to identify and locate those connections. Based on thermal fingerprints, DTS allows the localization of each lateral connection along a reach. The use of Infra-Red camera has been investigated with 748 laboratory experiments (artificial connections along a flume). The tested connections vary in diameters (from 75 to 200 mm), lengths of intrusion (from 0 to 200 m), shapes (circular or linear i.e. cracks), depths, discharge rates between the lateral connection and the main flume, and temperatures. IR frame analysis (for detection) and 2D temperature mapping (at the free water surface, for quantification) demonstrate that: i) the detection limit is very low (ratio between lateral and main discharges: 0.025) and ii) the quantification of the lateral discharge is impossible. Application of an IR camera seems to be a promising technique to detect lateral connections.

Pollution Source Localization in Wastewater Networks

“…In recent years, several project initiatives [6,7] and prototypes of sensor systems [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] for wastewater monitoring have been proposed and studied. These include the design of sensors (electrochemical sensors, optical sensors, mass spectrometry, ion spectrometry, etc.)…”

Sewer asset management – state of the art and research needs

“…Current research is focussing on the application and further development of tracer methods to detect and quantify exfiltration (Rieckermann et al 2007;Stegemann et al 2018). In lab-scale experiments, the application of Infra-Red cameras has been tested (Lepot, Makris, and Clemens 2017a). This method seems to be able to detect infiltration, but the detection limit is relatively high.…”

Performances and Uncertainty of Temperature Methods for Illicit Infiltrations and Inflows Assessment in Stormwater Sewers

“…At first, unknown variables are estimated from measured data through eqns (2) and 3for Case A1, eqns (7) and (8) for Case B1 and eqns (13) and (14) for Case C1:…”

“…To this aim, the first step is usually the identification of the most critical areas and network sections, where further investigations must be developed at a local scale. The first step consist, most of the times, in the analysis of the night-time minimum of dry weather flows; after that, a number of different methodologies and technologies can be applied for the next level of the survey, depending on site conditions and resources availability: visual inspections and progressive sampling at manholes [11], smoke test and dye test [12], closed-circuit television camera (CCTV) inspections, Infra-Red camera [13], stable isotopes, polluting flows analysis, punctual measures of temperatures. In last decades, Distributed Time Sensing (DTS) technique has been successfully applied to locate I&I in sewers [14], [15]; it is based, too, on temperature measurements, but continuous in time and space; it allows to identify illicit flows for large distances without requiring access to private properties.…”