Granulometry, chemistry and physical interactions of non-colloidal particulate matter transported by urban storm water

Abstract

Urban rainfall-runoff is a major source of anthropogenic pollutions to the natural water bodies. Particulate matter generated from anthropogenic environments and activities is a constituent of environmental concern as well as a carrier substrate for reactive contaminants such as metals. Partitioning, transport and transformation of particulate-bound contaminants are determined by the granulometry, physical and geochemical properties of the particulate carriers. Previous research emphasized in the transport of colloidal and suspended particles in rainfall-runoff. The settleable and sediment material were ignored though they are a major granulometric fraction which may contain most of the sorbed or transported constituents such as metals, organics or inorganics. In this research the entire flow section of rainfall-runoff was captured. Particulate matters in the catchment were analyzed for solid fractions, metal partitioning and distribution, fractal nature, morphology, chemical composition, and settling characteristics. Unsteady hydrodynamic conditions and short residence time determine coagulation and flocculation is still a dynamic mechanism in urban rainfall-runoff. Natural coagulation and flocculation (C/F) as well as coagulants/flocculants assisted C/F was studied for particles in urban rainfall-runoff. A C/F model incorporating fractal geometry and sedimentation mechanism was applied to simulate the particle size distribution in a 2-m settling column test. The overarching objective is to facilitate decision-making with respect to urban runoff management, regulations, treatment and potential disposal of runoff sediment residuals