Innovative low-tech approach for domestic wastewater treatment using vertical constructed wetlands with sugarcane bagasse substrate and Canna indica in tropical climates

Vertical flow constructed wetlands are increasingly adopted for domestic wastewater treatment due to their effective contaminant removal and low energy use. However, availability of conventional filter media can limit implementation in some communities. This study evaluates sugarcane bagasse as an alternative filter medium during the first 10 months (start-up phase) of operation. Four pilot units (0.26 m 2 each), planted with four Canna indica seedlings, were studied under controlled tropical conditions and fed synthetic domestic wastewater. Three units contained a transition layer of bagasse fragments (5.0–10.0 mm) and retention layers consisting of P 1 (0.9–2.0 mm), P 2 (2.0–5.0 mm), and P 3 (1.2–5.0 mm). A control unit (T) included a 20 cm transition layer of gravel (5.0–10.0 mm), and a 30 cm retention layer of sand (2.0–5.0 mm) was also monitored. Each unit featured a 20 cm drainage layer of stones (19.0–45.0 mm). Results showed 43–46 % compaction of bagasse filter media height. Media size and nature affected plant growth and density, crucial for performance. After 300 days, plant densities were P 1 : 259, P 3 : 204, P 2 : 193, T: 146 stems/m 2 . Removal efficiencies (%) for TSS, BOD 5 , COD, NH₄ + /NH₃, and TP were: P 1 (88, 93, 87, 76, 49), P 3 (80, 88, 82, 61, 37), P 2 (77, 87, 78, 63, 34), and T (77, 80, 79, 62, 50). The P 1 unit, featuring the finest bagasse retention layer, demonstrated promising potential for community-scale potential applications in low-income tropical areas. Increasing the heights of the transition and retention layers is recommended to offset compaction and improve performance further. • Units with finer bagasse particles (unit P 1 ) show enhanced contaminant removal efficiency compared to coarser media. • Plant growth is more robust in units with finer filter media, indicating better physical and biological conditions. • Fine particle size contributes to improved removal of suspended solids, organic matter, and nutrients. • Bagasse is a sustainable filter medium performing as well as conventional materials for wastewater treatment.