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 m² 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 P₁ (0.9–2.0 mm), P₂ (2.0–5.0 mm), and P₃ (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 P₁: 259, P₃: 204, P₂: 193, T: 146 stems/m². Removal efficiencies (%) for TSS, BOD₅, COD, NH₄⁺/NH₃, and TP were: P₁ (88, 93, 87, 76, 49), P₃ (80, 88, 82, 61, 37), P₂ (77, 87, 78, 63, 34), and T (77, 80, 79, 62, 50). The P₁ 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.