Modeling sewage leakage to surrounding groundwater and stormwater drains

Abstract

Underground sewage pipe systems deteriorate over time resulting in cracks and joint defects. Sewage thus leaks out and contaminates the surrounding groundwater and the surface water in stormwater drains. Many studies have investigated the problem of sewage leakage but no published studies, to the best knowledge of the authors, have examined the hydrologic interactions between leaky sewage pipes, groundwater and stormwater drains. This study numerically models such interactions using generic conditions in Singapore. It first develops accurate representations of weep holes and leaky sewage pipes, and further shows the long-term and short-term system responses to rainfall events. Some of the implications include: (1) quality of water seeping into the drains tends to be low in dry years; (2) complete contaminant attenuation after pipe rehabilitation takes several years; (3) responses to rainfall events at weep holes are immediate but the effects on sewage leakage might only show up a few days later. The simulation results allow us to better understand the local-scale migration of sewage leakage from a sewage pipe to nearby stormwater drains. With calibrations and verifications with local field data, the modeling framework would be applicable and beneficial to the sewage leakage monitoring and sewage pipe rehabilitation worldwide.

Sewer asset management – state of the art and research needs

“…Some existing models on exfiltrating of raw wastewater to the pipe surroundings (e.g. Ly and Chui 2012;Vizintin et al 2009) are primarily focused on the dynamics of the leakage point and typically require unavailable information on aspects such as leak location, leak size, thickness of clogged layer, and hydraulic conductivity of pipe bedding material thus precluding its practical application in most cases (Roehrdanz et al 2017). Consequently, recent research has proposed simplified methods that do not require prior knowledge of leaking defect locations, based on exfiltration probability scores (Lee et al 2015) to predict where pipes are likely leaking and contaminating groundwater, thus allowing implementation of water resource protection as planning criterion for sewer asset management (Roehrdanz et al 2017).…”

Unraveling the ecological processes modulating the population structure of Escherichia coli in a highly polluted urban stream network

“…Septic tanks are also known to contribute to non-point pollution through leakage, acting as a source of pathogens, dissolved nutrients and metals to groundwater and nearby streams 38 , 39 . Likewise, sanitary systems such as sewer networks, if present, cause pollution by leakage and subsequent exfiltration to water bodies 39 , 40 . Hence, ecological niche conditions and human-facilitated dispersal processes may also play an important role in modulating E. coli population structure in urban surface waters.…”

Unraveling the ecological processes modulating the population structure of Escherichia coli in a highly polluted urban stream network

“…Septic tanks are also known to contribute to non-point pollution through leakage, acting as a source of pathogens, dissolved nutrients and metals to groundwater and nearby streams 38,39 . Likewise, sanitary systems such as sewer networks, if present, cause pollution by leakage and subsequent ex ltration to water bodies 39,40 . Hence, ecological niche conditions and human-facilitated dispersal processes may also play an important role in modulating E. coli population structure in urban surface waters.…”