Model of a Pilot Constructed Treatment Wetland in Uganda

In this paper a model of a pilot constructed treatment wetland in Uganda is described. Fishes (Nile tilapias) are being cultured in order to recover the cost of the construction and maintenance. The purpose of the model is to assist in the management of constructed wetlands. The pilot constructed wetland is modeled as two modules, the first describing wastewater treatment ponds and the second module describing the ponds for fish culture. The model has been validated with data from literature and an experiment. The predictions of the modules are analyzed under several conditions that can be influenced by the designer of treatment wetlands. The factors determined as major influences on the treatment efficiency and fish growth are the nutrient load applied to the constructed wetland, the availability of dissolved oxygen and photosynthesis. The design of future CTW should be based on the amount of nutrients in the wastewater and the volume of wastewater that is available on a regular basis. For the design and maintenance of fish culture ponds the open surface area and measures to prevent excessive algal growth should be considered.