A modular wastewater treatment system has been installed for the Colombian Coffee Growers Federation (FEDERACAFE) at the Fundacion Manuel Mejia residential training centre. This system was designed by the University of Portsmouth, UK, and based on previous experience with the Gravel Bed Hydroponic (GHB) constructed wetland system. The steep topography of the site posed constraints on the design and a modular system composed of a rock filter in gabions for primary treatment, GBH beds for secondary treatment and a pond for tertiary treatment was selected. This system was designed to follow the contours of the site and maximise treatment. The GBH reed bed was planted with Typha angustifolia in early 1997. The system is being monitored by CENICAFE, the research division of FEDERACAFE. Monitoring of the system has shown large BOD removals from more than 350 to less than 20 mg/l. Initial results have also suggested 4 log cycle reductions in indicator bacteria. It is hoped that the success of this system will result in the replication of the treatment process at many villages in the Colombian coffee growing region where conventional sanitation technologies are impractical.