This study, conducted in Kenya, gives the first insight into the performance of a constructed treatment wetland receiving pulp and paper mill wastewater in the tropics. The wetland effectively removed organic matter, suspended solids, phenols and nutrients. BOD and phenols reduction rates are reported for the first time. Design parameters and guidelines for the set-up and maintenance of a full-scale wetland are recommended. The study concludes that integrating a full-scale wetland, as a tertiary stage with the existing treatment ponds would significantly improve the quality of water in River Nzoia downstream of the effluent discharge. This is a valuable resource book for scientists, managers and students in the field of wetland ecology, water and environmental management.