Identifying the first flush in stormwater runoff using UV spectroscopy

Stormwater often contains a wide range of chemical pollutants. In stormwater harvesting, separation of the polluted first flush is a significant but important challenge. Current practices are generally empirical and provide very approximate estimates of the finish of the first flush period. Since the first flush is significantly more expensive to treat, it is essential to accurately separate the first flush from the rest of the runoff in order to treat only the required volume. This is only possible when a real-time monitoring method is applied. This paper evaluates the feasibility of using UV spectroscopic methods to rapidly characterize stormwater pollutants over time in order to provide enough information to separate the first flush from the remaining volume to be harvested. Three stormwater events are used to demonstrate that relative comparison of UV spectra over time can be used to readily identify the end point of the first flush. The findings from this study will enable urban stormwater planners and engineers to more reliably and rapidly separate and treat stormwater for reuse in real-time.