Detection of leakage of domestic wastewater in urban stormwater drainage

Key points of this research results

  • The field research technique for finding the leakage from decrepit sewer pipelines into urban water area was established.
  • A possible leakage was found by this methodology in the central district in an urban area.
  • While the tracers used in this study were found to be applicable, the background level, i. e., the rain input was proved to be unignorable.


The decrepitude of social infrastructure facilities is one of the urgent issues facing developed countries like Japan. In urban areas, the aging of sewage pipes would become a major threatening issue coming the next ten years. Even minor cracks can cause leakage leading to contamination of surface and/or groundwater.

In this study, to examine the contamination of urban surface water due to leakage from household sewage in an urban district, the concentration distribution of household-originated chemicals (fragrance substances) in the rainwater pipes were explored for during dry days in an urban watershed having an old separated sewer system (over 40 years) and discovered two pollution hotspots. We found that one hotspot was due to direct discharge from households, while the other was due to double misconnections from old sewer pipe remnants to rainwater pipes from one or more households. On the other hand, by measuring the reference of rainwater before reaching the surface, we found that the target substance contained levels that could not be ignored in the analysis.

This study demonstrated the existence of leakage of domestic sewage due to the poor maintenance of aging domestic sewage networks, and showed that fragrance compounds are effective as tracers of leakage.

Source: N. Ozaki, M. Funaki, T. Kindaichi, A. Ohashi, Detection of domestic-use chemicals in urban storm drains during dry days, in as separated sewer area, Environmental Science: Water Research & Technology, 2023.