DUAL FILTRATION FOR STORMWATER TREATMENT: EFFECTIVENESS OF GRAVEL PACKED FILTER MEDIA FOR DECONTAMINATION OF STORM RUNOFF

Abstract

Elevation of suspended solids (SS) and dissolved inorganic contaminants (DIC) is increasingly limiting the utility of stormwater runoff. This work presents results from gravel-packed dual porosity filtration experiment in effort to remove SS and DIC from stormwater runoff. The objective was to assess the efficiency of modified dual porosity filter (DPF) using graded gravels as filter media. The filter consisted of two gravel layers in a trench: the convictive layer (25mm gravels) at the top and receiving layer (19mm gravels) at the bottom, each 25cm thick. The flow (gravity) was maintained at 1000mL per minute and the trench slope was 2%. The filter influent and effluent were monitored for TSS and heavy metals (Pb, Cu and Zn). Results indicated that the filter is able to attenuate TSS and DIC concentration in stormwater runoff. On average TSS was minimized by 70% while heavy metals concentration was reduced by 43.68%, 50.14% and 54.16% for Pb, Cu, and Zn respectively. It was further observed that higher TSS removal efficiency increases the removal of heavy metals in stormwater runoff. Depending on type and concentration of contaminants in runoff catchments, this study demonstrates that modified DPF may be useful in polishing stormwater for non-portable water uses.

Keywords: runoff treatment, water purification, rainwater use.