Nutrient removal fromdomestic wastewater by waterhyacinths: the importance of plant growth, detritus production anddenitrification

In recent years, the aquatic macrophyte Eichhornia crassipes (waterhyacinth) has shown promise in its ability to remove nutrients and other contaminants from wastewaters (1,2). This floating species has achived widespread use in macrophyte-based wastewater treatment systems because of its high productivity (3,4), rapid nutrient assimilation capacity (5) and ease of harvest. Continuous plant harvesting is usually practiced in waterhyacinth treatment ponds in order to keep the plants at an optimum standing crop for growth, and to provide an ultimate means of removing nutrients form the wastewater. Recent small-scale studies have suggested, however, that there exist other biological, chemical, and physical nutrient sinks in waterhyacinth ponds which supplement the N and P removal obtained through plant harvest (6). The goal of the present study, conducted in a large-scale treatment system, was to evaluate the importance of such nutrient sinks relative to plant standing crop and detritus nutrient immobilization. These data should be useful in formulating management strategies for waterhyacinth-based treatment systems.