An Upflow-Type Filtration Device Using Expanded Polypropylene Media (EPM) to Treat First Flush of Rainwater

The first flush of rainwater in urban areas is highly contaminated and causes adverse effects on both the water environment and ecosystem. In this study, a novel filtration device using expanded polypropylene media (EPM) was developed for efficient control of pollutants in first flush of urban runoff. The effect of foaming ratio on EPM for filtration efficiency and clogging potential was examined under various operating conditions. Experimental results using a laboratory-scale filtration device indicated that the removal efficiencies of suspended solids were initially high (>90% removal until 60 minutes) and decreased with filtration time (60% for EPM15 at 180 minutes and less than 10% for EPM45). Similarly, more than 90% of Cr, Pb, and Zn were removed for EPM15 within 30 minutes and decreased with filtration time. The surface area and specific hydraulic resistance of EPM were sensitive to foaming ratio. Optimum conditions for foaming ratio increased pollutant removal and minimized head loss. A simple model was derived and applied for theoretical analysis of the filtration device with EPM.