Assessing the characteristics of different-sized particles in the first flush of roof runoff

Abstract

The first flush occurs during urban runoff events. In this study, we aimed to assess the characteristics of different-sized particles in the first flush of roof runoff, and runoff was collected from an asphalt roof (AR), metal roof (MR), and cement roof (CR) for analysis. There were no clear patterns in the particle size distributions in the runoff from the three roofs and were affected by several factors. The strength of the first flushes differed significantly for particles in different size categories in AR, MR, and CR runoff and were very different from suspended solids (SS). The comparison showed that it would be possible to meet the SS control design expectation required by the Chinese national standard for runoff pollution control (VFF = 3 mm) for particles 45 μm. The methods presented provide an alternative for assessing the ability to control the transport of different-sized particles in runoff. HIGHLIGHTS First flushes of SS, chemical oxygen demand, total nitrogen, and total phosphorus in runoff were stronger for an AR, followed by an MR, and weakest for a CR.; First flushes of different-sized particles were different from those of SS.; First flushes of particles in the different size ranges were influenced by the rainfall characteristics and roof types.; Requirements of the Chinese national standards can be met for particles 45 μm.;

Keywords

• first flush
• particle size distribution
• roof runoff
• runoff pollution
• stormwater management