Designing and Evaluating the Performance of Full-scale Bioretention Cells in Indian Conditions

Abstract Urbanization leads to an increase in impervious area percentage and significantly alters the predevelopment hydrology. Bioretention cells are sustainable stormwater management techniques that mimic the natural soil system of an area and help in restoring the hydrological balance. Present study involved construction of full- scale bioretention cells and filling with engineered filter media derived from rice and maize residues. The filter media was derived from coarse sand and topsoil mixed with rice straw derived biochar and maize straw derived compost. The bioretention cells were planted with plant varieties- Thumbergia erecta, Haemelia patens and Tabernaemontana Divaricata. The bioretention cells were observed for pre and post plantation hydraulic conductivity and hydrologic performance. Full-scale bioretention cells reported a pre-plantation average hydraulic conductivity between 118 mm/hr-324 mm/hr. Post-plantation average hydraulic conductivity ranged between 341.6-562.0 mm/hr. The minimum and maximum pre-plantation hydraulic conductivity for bioretention cell 1 filled with compost were 112.5 and 136.5 mm/hr, respectively. The average hydraulic conductivity of 120.5, 211.1 and 241.4 mm/hr were observed for bioretention cells 1, 3 and 5 respectively. In the case of biochar-filled bioretention cells, the average hydraulic conductivity recorded for various rainfall events were 162.3, 175.5 and 190.3 mm/hr for bioretention cells 2, 4 and 6, respectively. Given the design parameters adopted for the field-scale bioretention cells, the time to empty based on minimum hydraulic conductivity values was 22 times faster than the recommended hydraulic conductivity for bioretention cells. The volume and peak flow reduction of the full-scale bioretention cells ranged between 82.95-90.28% and 86.1-92.3%, respectively. The total contribution of 6 bioretention cells to the groundwater recharge in three recorded events was 15.77 m3.