Potential for the use of duckweed-based pond systems in Zimbabwe

Duckweed systems are a form of natural wastewater treatment method that is ideal for developing countries. They demand less in terms of financial resources for construction and maintenance, manpower sophistication, electricity requirements, and machinery. This paper looks at the duckweed technology as a new phenomenon in Zimbabwe, reviews its requirements and problems, and finally explores its potential in the Zimbabwean environment. A simple spreadsheet model was developed to assess a water and nutrient balance of an ideal duckweed system. It was concluded that under ideal or optimum operating conditions, duckweed systems could achieve the required Zimbabwean nutrient standards of 10 mg·l-1 total nitrogen and 1 mg·l-1 total phosphorus. Duckweed systems would suit areas of moderate to high water consumption to avoid toxicity problems and also to increase the surface area available for duckweed growth. It was recommended that further experiments be carried out locally to improve and validate the model developed and used in this paper.