title: Field validation of a new low-cost method for determining occurrence and duration of combined sewer overflows.
abstract: Combined sewer overflow (CSO) events produced in combined sewer systems (CSS) during wet weather conditions are a threat for the receiving water bodies. The large number of CSO structures normally present in a CSS makes that the monitoring of the complete CSO network in a simultaneous way would drastically increase the investment costs. In this paper, a new methodology is presented aiming to characterize the occurrence and duration of CSO events by means of low-cost temperature sensors. Hence, a large number of CSO structures can be simultaneously monitored and the system can be characterized as a whole. The method assumes temperature differences between the overflowing mix of wastewater and stormwater and the sewer gas phase, so the temperature shift produced during a rainfall episode is related to a CSO event occurrence. The method has been tested and validated in La Garriga CSS (Spain) where the temperature at 13 CSO weirs was monitored for a period of 1 year (57 rainfall episodes). For the whole set of CSO events, occurrence and duration were successfully determined in 80% of cases. Advantages, limitations and potential applications of the method are discussed at the end of the paper.
authors.affiliation: Catalan Institute for Water Research, Scientific and Technological Park of the University of Girona, H2O Building, Emili Grahit 101, 17003 Girona, Spain. Electronic address: amontserrat@icra.cat.
authors.forename: A
authors.initials: A
authors.lastname: Montserrat
authors.forename: O
authors.initials: O
authors.lastname: Gutierrez
authors.forename: M
authors.initials: M
authors.lastname: Poch
authors.forename: Ll
authors.initials: L
authors.lastname: Corominas
keywords: CSO; CSS; Monitoring; Sewer system; Temperature; Wastewater