Full-scale ornamental constructed wetlands for caffeine removal from rural wastewater and coffee-processing effluents
Abstract
The coffee agroindustry is one of the main economic activities in rural communities of developing countries. However, its processing generates wastewater with high organic loads and emerging contaminants such as caffeine. In the absence of proper sanitation infrastructure, these discharges are often combined with municipal wastewater, increasing the risk of water pollution and threatening both environmental and community health. In this context, sustainable and low cost treatment alternatives are requerid to mitigate these impacts, particularly in rural settings. This study evaluated the performance of a full-scale hybrid system consisting of a settler tank followed by constructed wetland cells (SF-CW and SSF-CW) planted with ornamental species (Eichhornia crassipes, Alocasia odora, Hedychium coronarium, Heliconia psittacorum and Zantedeschia aethiopica). Monitoring was carried out from February to July 2024, including caffeine analysis by UV-Vis spectrophotometry during both the coffee harvesting and processing season and periods when only rural domestic wastewater was treated. The system achieved an average caffeine removal efficiency of over 99% during the coffee processing season. The ornamental plants adapted well to the operational conditions, showing high resilience and stable growth, as well as potential ornamental and commercial value. This work provides full-scale operational evidence of the potential of ornamental constructed wetlands as a practical and replicable solution for treating rural wastewater mixed with coffee-processing effluents, while simultaneously delivering environmental protection, social benefits, and local economical opportunities for rural communities.