Citrus waste hydrochar performance as soil amendment in constructed wetlands for the treatment of wastewater from the sugarcane industry

Resumen

Objective: This study evaluated the performance of citrus waste hydrochar as a soil amendment in constructed wetlands for treating sugarcane industry wastewater, assessing its impact on organic matter removal and plant development.

Design/Methodology/Approach:  Two horizontal subsurface flow constructed wetlands were compared: C1 (amended with orange waste hydrochar) and C2 (control). The systems treated diluted sugarcane wastewater (1 g COD/L) with a 72-hour hydraulic retention time over 150 days. Three plant species (Canna indica, Spathiphyllum wallisii, Typha latifolia) were monitored in triplicate for stem growth, leaf count, leaf length, and leaf width. Statistical analysis included Shapiro-Wilk normality tests and Mann-Whitney U comparisons.

Results: The hydrochar system showed initial negative removal efficiencies (-31.5% COD, -39.4% soluble COD) due to leaching phenomena, but outperformed the control during maturation (69.3% vs 65.5% COD removal). Strong linear correlations between total and soluble COD were observed (R²=0.997 C1, R²=0.983 C2). Plant responses were species-specific: Typha latifolia showed 142.0% greater leaf length (p=0.0124), Spathiphyllum wallisii increased stem length by 31.9% (p=0.0088), while Canna indica exhibited trade-offs between stem growth and leaf production.

Limitations/Implications:  Single-replicate wetland design limits statistical power for system-level comparisons. Initial hydrochar leaching requires pre-treatment strategies. Findings support circular-economy approaches through the valorization of agricultural waste.

Conclusion:  Citrus waste hydrochar enhances constructed wetland performance after stabilization, particularly improving soluble COD removal and promoting selective plant growth, making it a promising amendment for wastewater treatment applications.