| Summary: | The urban stormwater runoff carries significant amount of sediments and nutrients and discharges into the nearby water bodies. Among the best management practices (BMPs), catch basin insert (CBI) is a promising technology that can remove stormwater pollutants at source. We have investigated the one-stage CBI to remove gross pollutants from stormwater but it was unable to remove dissolved pollutants. Next, we have tested a mix-medium of biochar and alum sludge in batches to remove nutrients from water. In this study, a modified two-stage CBI was experimented in a laboratory column using non-woven geotextile and a mix-medium of biochar and alum sludge. A synthetic stormwater composed of sediments (0-300µm) and nutrients (NH3-N, NO3-N, NO2-N, PO4-P) (1-5mg/L) was pumped into the column at flowrate of 5-10 mL/min. The column effluent was collected at predefined time interval and measured for total suspended solid (TSS) and nutrient concentrations. The results revealed that TSS removal was higher (>90%) in coarse sediments (>150 µm) and the nutrient removal was significant except for NO3-N. The PO4-P removal (98-100%) was found highest followed by NH3-N (97-98%) and NO2-N removal (94-96%). However, the flow rate did not show significant effect on nutrient removal using the mix-medium.
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