Sewage Exfiltration As a Source of Storm Drain Contamination during Dry Weather in Urban Watersheds

Separating storm drains and sanitary sewers is expected to control sewage pollution, for example, from combined sewer overflows, and to reduce excessive stormwater flow to wastewater treatment plants. However, sewage contamination has been found in such separated storm drain systems in urban areas d...

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Bibliographic Details
Published in:Environmental science & technology 2011-09, Vol.45 (17), p.7151-7157
Main Authors: Sercu, Bram, Van De Werfhorst, Laurie C, Murray, Jill L. S, Holden, Patricia A
Format: Article
Language:English
Subjects:
Applied sciences
Bacteria
Buildings. Public works
California
Characterization of Natural and Affected Environments
Contamination
Environmental Monitoring - methods
Environmental Pollution
Exact sciences and technology
Feces - microbiology
Humans
Methanobrevibacter smithii
Other wastewaters
Pollution
Rhodamines - chemistry
Risk assessment
Sewage - analysis
Sewage - microbiology
Sewage disposal
Sewerage. Sewer construction
Stormwater
Urban areas
Urban Population
Wastewaters
Water Movements
Water Pollutants, Chemical - analysis
Water treatment and pollution
Watersheds
Weather
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Summary:Separating storm drains and sanitary sewers is expected to control sewage pollution, for example, from combined sewer overflows, and to reduce excessive stormwater flow to wastewater treatment plants. However, sewage contamination has been found in such separated storm drain systems in urban areas during dry-weather flow. To determine whether transmission of sewage is occurring from leaking sanitary sewers directly to leaking separated storm drains, field experiments were performed in three watersheds in Santa Barbara, CA. Areas with high and low risks for sewage exfiltration into storm drains were identified, and rhodamine WT (RWT) dye pulses were added to the sanitary sewers. RWT was monitored in nearby storm drain manholes using optical probes set up for unattended continuous monitoring. Above-background RWT peaks were detected in storm drains in high-risk areas, and multiple locations of sewage contamination were found. Sewage contamination during the field studies was confirmed using the human-specific Bacteroidales HF183 and Methanobrevibacter smithii nifH DNA markers. This study is the first to provide direct evidence that leaking sanitary sewers can directly contaminate nearby leaking storm drains with untreated sewage during dry weather and suggests that chronic sanitary sewer leakage contributes to downstream fecal contamination of coastal beaches.
ISSN:0013-936X
1520-5851
DOI:10.1021/es200981k