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Updated: Jul 8, 2026

Vegetated Treatment Systems for Removing Contaminants Associated with Surface Water Toxicity in Agriculture and Urban Runoff
Published on: May 15, 2017
First flush in a combined sewer system
Janet Barco1, Sergio Papiri, Michael K Stenstrom
1Department of Civil and Environmental Engineering, University of California Los Angeles, 5714 Boelter Hall, Los Angeles, CA 90095-1598, USA.
Abstract:
Pollutant first flush was examined in an urban catchment with area of 12.7 ha and drained by a combined sewer system located in northern Italy. A total of 23 rainfall-runoff events were monitored and 281 samples were analyzed. The selected quality parameters were biochemical oxygen demand, chemical oxygen demand, suspended solids, settleable solids, total phosphorus, total nitrogen, ammonium nitrogen, lead, and zinc, specific conductivity and hydrocarbons. A subset of representative storms was selected for first flush analysis. The catchment presented a strong first flush for almost all storms and most constituents. The analysis shows that treating the maximum amount of the early part of the runoff is a better strategy than treating a constant flow rate. Best management practices that can treat or store the first runoff are favored in this kind of system for these water quality parameters.
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