Detection of domestic-use chemicals in urban storm drains during dry days in a separated sewer area

Abstract

The decrepitude of infrastructures currently threatens developed countries, including Japan. Thus, the development of effective management and maintenance techniques is important. In this respect, the leakage and destruction of separated domestic sewer pipelines are worsening in urban areas because of poor maintenance, as they have existed for over 60 years. Even minor cracks could cause sewer leakage and severe potential subsurface and surface water pollution. Thus, in order to examine the urban stormwater pollution due to leakages of domestic sewers in urban areas, the concentrations of domestic-use chemicals (fragrance compounds) and polycyclic aromatic hydrocarbons (PAHs) were measured in storm drains on no-rain days in an urban watershed area with old separated sewers developed over 40 years back. From the measurements, the concentrations of the domestic-use chemicals were higher at the final outlet of the storm drain than those in rainfall and puddle waters. On the other hand, the PAH concentration was similar to or higher for rainfall and puddle waters. The high concentration of the domestic-use chemicals in the discharge was mostly attributed to chemical inputs during subsurface water transfers, rather than solid/liquid/air partition changes. By measuring concentrations in the storm drain networks in the area, two hot spots were found. One was suggested to be from direct discharge from a household, and the other could be due to double misconnection from one or more households (unrevealed) to a vestige of an old sewer pipeline and from the vestige to a storm pipeline. The stable high concentration at the final discharge was suggested to be due to the loading from these hot spots. The study pointed out the possibility of leakages of domestic sewages due to poor maintenance in old domestic sewer networks, which can increase the risks for public health and indicated the effectiveness of fragrance compounds as tracers for the leakages.